E L E M WN TW C HEMIS TEt, IN WHICH THK RECENT DISCOVERIES IN THE SCIENCE ARE INCLUDED AND ITS DOCTRINES FAMILIARLY EXPLAINED. Illustrated by numerous Engravings, AND DESIGNED FOR THE USE OF SCHOOLS AND ACADEMIES. BY J. L. COMSTOCK, M. D. Mom. Con. M. S. ; Hon. Mem. R. t. M. S. ; Author of Notes to Conv. on Chemistry, Author of Gram, of Chemistry; Elem. Mineralogy;.Natural History of Quadrupeds and Birds; Natural Philosophy, &c. ' PUBLISHED BY PRATT, WOODFORD & CO., No. 63 WALL STREET. 1844. DISTRICT OF CONNECTICUT, s. It. S. Be it Remembered, That on the second day of March, in the fifty-fifth year a, the Independence of the United States of America, J. L. Comstock, of the said District, hath deposited in this office the title of a Book, the right whereof he claims as Author, in tho words following, to wit: " Elements of Chemistry, in which the recent Discoveries in the Science are included, and its Doctrines familiarly explained. Illustrated by numerous Engravings, and designed for the use of Schools and Academies. By J. L. Comstock, M. D. Mem. Con. M. S.; Hon. Mem. R. I. M. S. ; Author of Notes to Conv. on Chem.; Author of Gram. Chem.; of Elem. Mineralogy; of Nat. Hist, of Quad, and Birds; of Syst. Nat. Philosophy, &c." In conformity to the act of Congress of the United States, entitled, " An act for the encouragement of learning, by securing the copies of Maps, Charts, and Books, to the authors and proprietors of such copies, during the times therein mentioned."—And also to the act, entitled, "An act supplementary to an act, entitled, ' An act for the encouragement of learning, by securing '"e copies of Maps, Charts, and Books, to the authors and proprietors of such copies, during the times therein mentioned,' and extending the benefit* thereof to the arts of designing, engraving, and etching historical and other prints." CHARLES A. INGERSOLL, Clerk of the District of Connecticut A true copy of Record, examined and sealed by me, CHARLES A. INGERSOLL, Clerk of the District of Cv+cctieu . PREFACE It is hardly necessary for the author of the following volume to make any excuses for its publication, since, notwithstanding the multiplicity of books on the same subject, there seems to be none, which are exactly adapted to the object for which this is principally designed. The Conversations on Chemistry, and the works of Parke and Joyce, besides the interlocutory form in which they are written ? are objectionable, in not containing the recent discoveries and improvements in the science; and the volume of Dr. Turner, though free from these objections, is too large for the use of schoors and academies. In this volume, it has been the intention of the author, not only to avoid these objections, but, at the same time, to explain the elements and doctrines of the science in sufficient detail, to give a competent knowledge of its several parts, and in such language as can be understood by those who will but read the book attentively and pursue the subject in course. It appears to the writer, that in teaching Chemistry to youth, its elementary parts have not been sufficiently insisted on at the beginning. Of all the sciences, this is the most complete, in respect to its language—the order of its arrangement, the succession of its subjects, and consequently in the facility with which it may be learned. But from these perfections, arises the absolute necessity of becoming well acquainted with its first principles, before the student can derive and retain any useful knowledge from its study. The nomenclature of chemistry, the laws of affinity, and the doctrine of proportions, are far more necessary to a proper knowledge of this science, than is a knowledge of ma thematics to the study of Astronomy. The cause of an eclipse or the reason why the complicated motions of the earth shorjuc produce a change of seasons, can be fully understood without the use of mathematics. But without a knowledge of affinity, and proportions, the decomposition of a salt, or the formation of a definite compound, are absolutely incomprehensible phenomena; nor can they be explained without a previous acquaintance with the peculiar language of chemistry. It is from a conviction of the importance of first principle:? m learning this science, that the author has devoted so much attention to the imponderable agents, attraction, affinity, and galvanism, and to the explanation of definite proportions and chemical equivalents. 4 PREFACE. The doctrine of definite proportions, being now universally adopted, forms one of the lundamental principles of chemical science. And whether the theory of atoms, which accounts for the facts on which this doctrine is founded, be true, or false, the doctrine itself will ever maintain its integrity, its elements being nothing more than the expression of facts which experiment and analysis have developed. The subject of proportions, independently of its relation to the theory or practice of Chemistry, is highly curious and of uncommon interest, both to the naturalist and the moral philosopher. To the first it shows that the laws of nature are equally inherent and efficient, in dead and in animated matter, and that the effects of these laws are as peculiar and distinctive in the formation of chemical compounds, as they are in the production and habitudes of the different races of animals. To the moralist, this subject teaches, that nothing has been formed by the fortuitous concurrence of atoms, but that even the "stocks and stones" bear the impress of creative agency and design—that the air he breathes and the water he drinks, are formed of invariable proportions of certain elements, and that these compounds are so precisely adapted to his nature and wants, that the least change in the proportion of their constituents "would inevitably effect his destruction. Besides the charms which this subject presents to the reflecting student, the composition of compound bodies, in recent books ol chemistry, is expressed in equivalent numbers, and therefore cannot be understood without a knowledge of the doctrine of proportions. The author, therefore, before the description of each element and compound, has affixed to its name, at the head of the sections, its combining number, or atomic weight. By this ar rangement, the pupil, at a single glance, becomes acquainted, not only with the scientific, and common names, but also with the composition, and proportions of all the compounds described. In respect to the authorities which have been consulted in the composition of this work, the principal are Dr. Thomson, Dr. Henry, Sir H. Davy, Mr. Gray, Dr. Ure, Mr. Accum, Mr. Faraday, the Library of Useful Knowledge, the Journal of the Royal Institution, Silliman's Journal, and Dr. Turner. Of the work of the latter author, free use has been made, his arrangement of subjects, with some variations, having been adopted, and his exposition of the doctrine of proportions carefully consulted. The work now offered, is not however to be considered as a servile compilation; the former experience of the author as a lecturer, and his habit, for many years, of analysing various substances, having given him opportunities, not only of verifying the deductions of others, but occasionally of making new experi ments for himself. Hartford, November 15, 1831. CONTENTS. PART L PART II. ¦ Phosphorus - - . - 160 Sulphur and oxygen * 155 Sulphur ... 154 Carbon and oxygen - - 149 Carbon- - 147 Ammonia - - - 146 Nitrogen and hydrogen - 146 Nitric acid - - - 144 Nitrous acid ... 143 Nitric oxide - - - 141 Nitrous oxide - 138 Nitrogen and oxygen - - 138 The atmosphere - - 135 1* Nitrogen - - - - 134 Oxygenized water - - 133 Properties of water - - 131 Compound blow-pipe - 129 Water - 127 Hydrogen ... 122 Oxygen - - - - 115 Non-metallic substances - 115 Inorganic chemistry - - 115 Explanations - - - 112 Ponderable Bodies - - 112 ! J Nomenclature - - - 110 Specific gravity - 107 I Portable balance - 107 • Lamp furnace - - - 106 i Gas apparatus ... 104 Chemical apparatus - - 100 r Theory of atoms 98 ! Wollaston's scale - - 96 I portional numbers 95 i Method of ascertaining the pro- Chemical equivalents - 93 Combination by volumes - 91 1 Definite proportions 86 ¦ Indefinite proportions - 84 l Force of chemical affinity - 83 i Changes produced by chemical combinations - 79 i Gravity .... 79 Quantity of matter 77 Cohesion - 76 Double elective affinity » 74 Single elective affinity 73 Simple affinity - - - 72, Affinity .... 71 Chemical attraction - 70 Attraction 69 Heating effects of galvanism 68 Chemical effects of galvanism 61 Galvanism ... 54 Chemical effects of electricity 53 Electricity ... 48 Phosphorescence 45 Light • - 44 Sources of caloric 41 Cold .... 39 Thermometer 35 Specific caloric - - - 32 Expansive power of heat - 25 Conductors of caloric - 22 Evaporation 18 Steam .... 15 Combined caloric 13 Caioric .... 11 fcSlirONDEHABLE AGENTS - - 10 6 CONTENTS. Phosphorus and oxygen - 166 Barium - 225 Chlorine .... 163 Barium and oxygen - • 225 Chlorine and hydrogen - 166 Strontium ... - 226 Calcium - 227 Chlorine and oxygen - 167 Chlorine and nitrogen - - 168 Calcium and oxygen - - 22S Lime and chlorine - • 229 Iodine .... 169 Phosphuret of lime - - 234 Iodine and hydrogen - - 171 Order 2d. -Metals, which are supposed to be analogous to order 1st. Properties of the earths - - 236 Bromine - 172 Fluoric acid - 173 Combinations op simple non-metallic substances with each other. Carbon and hydrogen - - 175 Magnesia - 236 Alumina .... 237 Safety lamp - 181 Glucina - 238 Gaslights - - - - 183 Ittria 238 Zirconia ... 238 Hydrogen and sulphur - 187 Hydrogen and phosphorus - 189 Silica 239 Nitrogen and carbon - 190 Order 3d. -Metals which decompose water at a red heat. Manganese - - - - 241 Cyanogen and hydrogen - 191 Carbon and sulphur - - 195 Metals - - - - 196 Manganese and oxygen - 241 General remarks - 196—202 Arrangement of the metals - 203 Iron - - - - • - 242 Iron and oxygen - - 243 Sulphuret of Iron - 245 CLASS I. Metals, the oxides of which arc decomposed by heat alone. Zinc .... 246 Zinc and oxygen - - - 246 Mercury ... - 204 Cadmium - 247 Mercury and oxygen - 206 Tin 248 Mercury and chlorine - - 206 Tin and oxygen - - 248 Mercury and sulphur - 207 Order 4th — Metals which do not decompose water at any temperature. Arsenic .... 249 Silver 208 Gold .... 210 Platinum - - - - 212 Arsenic and oxygen - - 250 Palladium and rhodium - 215 Arsenic and sulphur - - 251 Iridium and osmium - - 216 Chromium ... 251 Chromium and oxygen - - 252 CLASS II. Metals, the oxides of which arc not reducible to the metallic state by heat alone. Order 1st. — Metals which decom- Molybdenum ... 253 Tungsten .... 253 Columbium ... 254 Antimony .... 254 pose water at common temperatures. Potassium - - - - 217 Antimony and oxygen 255 Antimony and sulphur - 25f Uranium .... 256 Potassium and oxygen - 220 Cerium - - ¦ 256 Sodium - 221 Cobalt .... 257 Sodium and oxygen - - 222 Nickel .... 258 Sodium and chlorine - - 223 Bismuth 259 Lithium 224 Bismuth and oxvgen - • 259 7 CONTENTS. PART III. PART IV. Analytical Chemistry - 332 . Analysis of the mixed gases 332 i A nalysis of minerals - - 335 Analysis of mineral waters - 341 Chemical equivalents - • 340 Animal heat 328 Respiration ... - 325 Blood. 323 Oil 323 Gelatine .... 322 Albumen - 322 Fibrin ... 321 General remarks - 321 Animal Chemistry. Quinia 321 Narcotine - 320 Morphia - - - - 319 Vegetable alkalies - - 318 Ether 316 Alcohol ... 315 Fermentation - 313 Resins - 312 Vegetable oils - - - 311 Gluten 3081 Extractive matter - - 309; Colouring matter - 309' Tannin .... 310! Starch .... 308 Sugar - - - - -307 Gum .... 306 Ingredients of plants - - 306 Composition of vegetables - 304 Citric acid - - - - 304 Tartar emetic ... 303 Tartaric acid ... 302 Oxalic acid ... 301 Vegetable acids ... 299 Recapitulation - - - 298 Veuetable Chemistry. General remarks - - 290 Organic Chemistry. Hydrosulphureis ... 288 Muriates - 286 Carbonates - 284 Fluates .... 283 Borates - - - - 282 Phosphates 282 Chlorates - - - - 279 Nitrates .... 275 Sulphates .... 2G9 General remarks - 265—269 Sulphuret of lead - - 264 Salts. Lead and oxygen - - 263 Lead 262 Copper and oxygen - - 261 Copper 260 Tellurium ... 260 Titanium .... 260 CHEMISTRY. Chemistry is that science which investigates the composition and properties of bodies, and by which we are enabled to explain the causes of the natural changes which take place in material substances. Natural Science has been divided into two great branches, the one comprehending all those natural changes which are accompanied by sensible motions; the other, including all those natural changes accompanied by insensible motions. The first science is called Natural Philosophy; including also the Philosophy of Mechanics, and the laws of motion. The second is known under the name of Chemistry, or Chemical Philosophy. As a science, Chemistry is of the highest importance to mankind, since by its investigations, the practical arts are constantly improving. All chemical knowledge is founded on analysis and synthesis* that is, the decomposition of bodies, or the separation of compounds into their simple elements, or the recomposition of simple bodies into compounds. When water is passed through a red hot iron tube, in the form of steam, it is decomposed; its oxygen uniting with the iron, while its hydrogen passes away in a state of freedom, or may be collected and retained. This is called analysis; and the bodies *o separated from each other, if they cannot again be decomposed, are called elements. Thus hydrogen and oxygen are the elements of water. When oxygen, which may be obtained pure, as will be seen in another place, is burned with hydrogen, a quantity of water will be formed. This is called synthesis, or the recomposition of water from its elements. Thus all knowledge of this science is obtained by experiment. What is Chemistry 1 How is science divided 1 What is the foundation of all choraleal knowledge t What is analysis J What is synthesis J 10 IMPONDERABLE AGENTS. As a science, chemistry is intimately connected with a great variety of natural phenomena. All satisfactory explanation of the causes of rain, hail, dew, wind, earthquakes, and volcanoes, have been given by the aid of chemical knowledge. The phenomena of respiration, the decay and growth of plants, and the functions of the several parts of animals, are also explained in a satisfactory manner, only by the aid of chemistry. As an art, chemistry is connected, more or less intimately with nearly every branch of human industry, and particularly with agriculture and manufactures. In its application to agriculture, chemistry furnishes the most direct and certain means of ascertaining what a barren soil wants to make it a fruitful one, and also what ingredient any soil requires to best adapt it to any given kind of produce. Many of our most common and useful articles are manufactured entirely by chemical processes. The making of soap, glass, bleaching salts, the several kinds of acids, and almost every kind ol medicine, depend wholly on the manipulations of chemistry. The art of the potter, iron-smith, tanner, sugar-maker, distiller, brewer, ¦winter, paper-maker, and painter, are also connected in various degrees with chemistry. Natural objects may be separated into two great divisions, or classes, viz.; Imponderable agents and Ponderable bodies, PART I. Imponderable agents. The imponderable agents are Light, Caloric, or Heat, Electricity, and Galvanism, These are called th© imponderable agents, because they possess no appreciable weight. The investigation of many of the properties of these agents, and particularly those of light and attraction, belong to the several departments of Natural Philosophy, but they each possess properties also, which are strictly chemical, and it is these properties only, which it is proposed here to examine., What are among the natural phenomena which chemistry explains? What are among the most important arts which derive advantage from chemistry 1 How are natural objects divided 1 What are the imponderable agents 1 Why are these agents called imponderable 1 11 CALORIC. CALORIC. Heat is the sensation which one feels when he touches a body hotter than the hand; and this sensation is caused by the passage of caloric from the hot body to the hand. Thus caloric is the cause of the sensation which we call heat, and heat is the effect of the passage of caloric into the hand. Caloric, then, is the matter, or principle of heat, while heat is the sensation produced by the transfer of this principle to the living system, from some body hotter than itself. Caloric is imponderable; that is, there is no appreciable difference in the weight of a body, whether it is hot or cold. This principle seems to be present in all bodies, nor is there any known process by which it can be separated from any substance. For since heat constantly passes from the hotter to the colder body, until every thing in the same vicinity becomes of an equal temperature, so if we take a substance at a temperature however low, and carry it to a place where the temperature is still lower, this substance will give out heat until its temperature becomes the same with that of the surrounding air. For instance, if a piece of ice at 32 degrees of temperature, could be transported to any place, as in Siberia, where the temperature is 60 degrees below 32, then this piece of ice will continue to emit caloric until its temperature becomes only equal to that of the surrounding atmosphere, and it would therefore give out GO degrees of heat. It will be quite obvious to any one, that if a piece of iron, or any other substance, be carried from the cmen air on a summer's day, where the heat is 92, to an idfilouse, where the heat is only 32, that the iron will continue to part with its heat until it becomes of the same temperature with the ice, and therefore that it will in a short time, lose 60 degrees of heat, as indicated by the thermometer. Heat and cold are therefore merely relative terms, and so far as our sensations are concerned, depend on circumstances. Thus we call a body cold when its temperature is lower than our own, and it has at the same time, the power of conducting heat rapidly. That the sensation of cold, which we When one touches a body hotter than his hand, why does lie feel the sensation of heat? What is caloric ? What is heat ? How is it proved that caloric is imponderable ? Uow is it shown that caloric is present in all bodies ? What illustrations show that ice will emit caloric * How are heat and cold relative terms? How is it shown that the utu. •ation of cold often depends on the conducting power of the body ? 12 CALOli^ experience, when touching another body with the hand, depends greatly on the conducting power of the body touched, is easily proved by the following e. A enment. A piece of woollen cloth, or fur, and a vessel of quicksilver, being placed in the same room, will both indicate the same temperature, when the bulb of a thermometer is wrapped in the one, or plunged into the other. And yet if the experiment be made in the warmest day of summer, the mercury will feel cold to the hand, while no sensation will be produced on touching the cloth or fur. Now both articles touched, bfcmg of the same temperature, it is certain that the different sensations must depend on the power of the mercury to absorb, or conduct away the heat of the hand more rapidly than the fur or cloth. On the contrary, we say a body is warm, or hot, Avhen it imparts heat to the hand, more or less rapidly. But this sensation, to a certain degree, also depends on circumstances, and is connected with the relative temperature of the hand, and the conducting power of the substance touched. Thus if one hand be placed in water, at 32 degrees, and the other in water at 130 degrees, and then both hands be plunged into water at 90 degrees, one hand will feel cold, and the other warm, though the temperature to which both are exposed is the same, j This principle is illustrated by the different sensations which men and animals experience, when transported from a cold or hot climate, to one which is temperate. A Russian would consider the coldest New England winter, a pleasant and comfortable season, while an inhabitant of Sumatra, or Borneo, would tremble with the cold of our September, wwhite bear from Greenland, or a dog from Kamtschatka, would constantly suffer from the heat, while an elephant, or a naked dog from Africa, would require protection from the cold. One of the most obvious properties of caloric,) is, its ten dency to an equilibrium, that is, its disposition to pass from the hotter body to that which is colder. Thus if several bodies of different temperatures be placed in the same room, the warmer body will continue to impart its heat to those which are colder until they all indicate the same temperature by When do we say a body is warm or hot? How is it shown that the sensations of heal and cold depend on circumstances? What illustrations are given of this principle ? What is one of the most obvious properties of caloric ? What is meant by equilibrium 1 How is it shown that caloric tends to an equilibrium ? 13 ORIC the thermometer. This distribution is so equal and general, that two thermometers, graduated exactly alike, and placed under the same cirq; instances in the open air, will indicate the same degrees of heat though placed miles apart. Thus zoloric ihas the power of pervading all substances, and of equalizing their temperatures.! Caloric exists in two different states, viz. in a state of combination, and in a state of freedom. It has already been stated, that all bodies are supposed to contain caloric, but tha all bodies do not contain sensible heat, or are not warm to the touch requires no proof. Common occurrences, however, as we have already seen, are sufficient to show, that to a certain extent, the sensation of heat depends on circumstances, and that it is only necessary that a body touched, should be of a higher temperature than the hand, for us to perceive the sensation of warmth. But it by no means proves, that because the thing touched does not feel warm, that it contains no caloric. I It follows, therefore, that when the body touched, conveys the sensation of heat, that caloric passes from the body to the hand, and this is called free, or uncombined caloric; but that when no sensation follows, the heat is combined, or latent, in the body touched, and therefore is not imparted to the hand. Combined or latent Caloric. This is also sometimes called caloric of fluidity, because in the conversion of solids into fluids, a quantity of heat is absorbed which is not indicated by the thermometer, v.n i which, therefore, becomes latent in the fluid. The experiments of Dr. Black, in relation to this subject, are highly curious and interesting. These experiments prove, that if a pound of water at 32 degrees be mixed with a pound of water at 172 degrees, the temperature of the mixture will be intermediate between them, and therefore 102 degrees. But if a pound of ice at 32 degrees be mixed with a pound of water at 172 degrees, the ice will soon be dissolved, and then on applying the thermometer to the water thus formed, it will be found at the same temperature that the ice was before the addition of the Avarm water, and there What conclusions is drawn from the fact that caloric is equally distributed? What are the two states in which caloric exists ? Is it a proof that a body contains no heat because it does not fee! warm? If every body contains heat, whydoes it not. always feel warm? What Is free heat? What is latent heat 7 How many decrees of heal oecome latent during the conversion of ice into water ? 2 CALORIC. fore at 32 degrees instead of 102 degrees, as before. In this experiment, therefore, the pound of hot water lost 140 degrees of caloric which is employed in melting the ici', and which is not appreciable by the thermometer, but remains latent in the water. It follow, then, that a quantity of caloric becomes insensible during the melting of ice, which, were it free, or uncombined, would raise the temperature ol the same weight of water 140 degrees; for, the ice being at 32 degrees, and the water at 172 degrees at the beginning ol the experiment, and the whole being at 32 degrees at the end, the water loses 140 degrees, being the excess of 172 degrees above 32. It is well known that >if a piece of ice be exposed to the rays of the hottest sun in the summer, or if it is placed in a vessel over a fire, the temperature of the ice, or of the water flowing from it, will not be raised above 32 degrees, until the ice is all melted, when the thermometer placed in the vessel will instantly begin to rise.? Those Avho have melted snow, or ice for culinary or other purposes, are well aware how much more time and fuel it takes to obtain a vessel of boiling water from ice, than it does from the liquid itself. But this fact is readily accounted for by Dr. Black's experiment, since we have seen above, that 140 degrees of heat ~~ n first employed merely in converting the ice into water, and that this caloric does not raise the water one degree above the freezing point, or 32 degrees, until all the ice is melted. This principle is of vast consequence to the world, and particularly to the inhabitants of cold climates, where the ground is covered with snow and ice, a part or the whole of the vear. In some northern climates, and particularly in Russia, the transition from the cold of winter to the heat of summer, takes place within a few days, the ground being covered several feet deep with the accumulated snow of the winter. Now were it not for the fact above explained, and did the snow and ice follow the same law in respect to temperature, that Ave observe in some other bodies, thisAvhole mass Avouldbe turned into Avater nearly as soon as the temperature of the atmos- IIow is this shown by experiment 1 What common fact shows that the temperature of water cannot be raised as long as it contains ice 7 What circumstances are mentioned under which the great quantity of caloric absorbed by melting ice, is a blessing to mankind ? When the temperature of the atmosphere is above the freezing point, why d'jef not the snow and ice instantly return to water! 15 STEAM. phere became above 32 degrees, and consequently the whole country would be inundated and destroyed by the flood. But in consequence of the quantity of caloric employed in the liquefaction of the snow, the melting is gradual, and no such accident ensues. This is a striking instance of the wisdom and mercy of Providence towards man, though to most of the world it is unseen and unknown. We have mentioned the melting of ice, as be: ng the most familiar example, in most parts of our country, of the conversion of a solid into a fluid. But the same piinciple holds with respect to the conversion of other solids into liquids, though the quantity of caloric required for this purpose varies with the substance. From the experiments of Dr. Irvine, it appears that the following named substances vary in this re?pect very widely and also very unexpectedly. Equal weights of each substance are supposed to be employed in the experiments: The degrees indicate the extent to which each would have been heated by the caloric of fluidity, proper to it. Spermaceti 145 degrees; Lead 162 deg.; Bees-wax 175 deg.; Zinc 493 deg.; Tin 500 deg.; Bismuth 550 deg. Steam. When water, or other liquids, are converted into steam, a large quantity of caloric is absorbed, Avhich is not indicated by the thermometer, and which therefore becomes latent in the steam. If a thermometer be placed, in an open vessel of water, over a lire, there will be indicated a gradual increase of heat until me water boils, after which, no increase of the fire will raise me temperature of the water another degree; nor does the ateam, arising from a vessel of water which boils violently, indicate a greater degree of heat than the water itself, or of the steam arising from another vessel which boils moderately. The steam conveys away all the heat above 212 degrees of Fahrenheit's thermometer, which is the temperature of boiling water under the ordinary pressure of the atmosphere. The quantity of caloric which combines with the water to form steam, is nearly 1000 degrees greater than that of the same weight of boiling water. In other terms, the caloric of fluidity in steam surpasses that of an equal weight of boiling water by nearly 1000 degrees. Consequently there is nearly In melting, do other solids besides ica absorb a quantity of calorie not appreciable by the thermometer'! Why cannot water in an open vessel be heated higher thai. 3*2 degrees 'f How many degrees of heat does steam contain, which is not indicated by the thermometer 1 .6 STEAM 1000 degrees of heat in steam which is not indicated by th> thei mometer, and is therefore latent. Various methods have been adopted by different philosophers in order to ascertain correctly the exact quantity of latent heat in steam. Among these, one of the latest and most simple is that of Dr. Ure, of Glasgow. His apparatus consisted of a small glass retort, with a short neck, inserted into a globular receive* - of the same material, made very thin, and about three inches in diameter. This globe was surrounded with a certain quantity of water, at a known temperature, in a glass basin. A quantity of water, or other liquid to be examined, amounting to 200 grains, was put into the retort, and rapidly distilled into the globe, by the heat of an Argand lamp. The heat imparted by the condensation of the steam in the globe, to the water contained in the dish, by which it was suirounded, was indicated by a very delicate thermometer kept constantly moving through it. By means of this contrivance, Dr. Ure found the latent heat of the steam of water to be 1000 degrees. That of alcohol, of the sp. grav. 825, to be 457, and that of ether about 303. We have stated that the temperature of boiling water, and of steam, is. 212 degrees, under the ordinary pressure of the atmosphere. The cause of ebullition, or boiling, is the formation of vapor, or steam, at the bottom of the vessel, in consequence of the application of heat there. The steam being lighter than the water, or other fluid from which it is made, constantly ascends in bubbles, and escapes from the surface into the open air. The process of boiling, when conducted in a tall glass vessel, over an Argand lamp, may be minutely examined, and is both interesting and instructive. It is found by experiment, that different fluids at the surface of the earth boil at different temperatures, depending generally on the specific gravity of the fluid, and also, that the same fluid boils at various temperatures, depending on the degrees of atmospheric pressure. Thus, under the same pressure of the atmosphere, or on.the level of the sea, water boils at 212 degrees. Ether at 100 degrees, alcohol 173 degrees, nitric acid, of the specific gravity of 1450, at 240 degrees, and water, saturated with sea salt, 216 degrees. We may observe, that in these instances, the boiling of a Describe the apparatus of Dr. Ure, to ascertain the quantity of caloric in steam 1 What is f ;ie cause of ebullition or boiling ? On what docs the boiling temperature of fluids generally depend 7 Why is the boiling temperature of water saturated with salt, higher than that of pure water? What is said concerning the influence of specific gravity on the boiling temperature ol liquids 7 17 STEAM. fluid seems to follow a general law depending on its specific gravity. This is strictly the case in respect to the boiling point of sulphuric acid, which always requires a temperature for its ebullition in a direct proportion to its specific gravity. Thus, according to Dr. Dalton, sulphuric acid sp. gr. 1,408, boiled at 240 degrees, while that of sp. gr. 1,670 boiled ai 360 degrees; that of 1,780, at 435 degrees, and that of 1,850 at 620 degrees. The boiling point of a fluid is not, however, in all cases, to be estimated by its specific gravity, the fixed oils requiring much higher temperatures for their ebullition than other fluids of the same density. Thus, linseed oil boils at 640 degrees, though its specific gravity is less than that of water, and mercury boils at about 660, though its specific gravity is about 14 times that of water. That water, or any other fluid, Avill boil with a less degree of heat, in proportion as the weight of the atmosphere is removed, may be readily proved by means of the air pump, or by ascending up a mountain, where the air is less dense than it is on the level of the sea. The most simple illustration of this subject, with the air pump, may be made by means of a small vessel of ether; for if this be placed under the receiver, and the air exhausted, the fluid will boil, or turn to vapor, during ordinary temperatures of the atmosphere. If a vessel of hot water, instead of the ether, be placed under fhe receiver, and the air withdrawn from it, the water will coninue to boil until its temperature is reduced down to 70 degrees. Fig. 1. In the absence of an air pump, the same principle may be strikingly illustrated as follows. Adapt a good cork to the glass flask, Fig. 1, so as to make it air tight; put a gill or two of water into it, and apply the heat of a lamp until it boils. After it has boiled for a short time, introduce the cork, and at the same time take the flask from the fire. It will continue to boil for a tew minutes after its removal. When the ebullition has ceased, it will boil again violently on plunging the flask into a jar of cold water, as seen in the Under what circumstances will water boil at a less temperature than 212 degrees! At what temperature does water boil when the pressure of the atmosphere is removed 1 How may the pressure of the atmosphere be removed from a vessel of water, without the u*e of an air pump'! 2* 18 EVAPORATION. figure. On taking it out of the water, the ebullition wil> cease, but will instantly recommence if again plungea inio the water, and this may be continued until the flask is nearly cold. In this experiment, the boiling is continued in consequence of the partial vacuum which is occasioned by the condensation of the steam with which the flask was at first filled. Li the flask be taken from the vessel of cold water, and plunged into one of hot water, the boiling will instantly cease, because the heat will convert a portion of the water in the flask, which had been condensed, into steam, and thus the partial vacuum which had been formed will be filled with vapor, the pressure of which will prevent f urther ebullition. This principle is beautifully illustrated by the fact, that the higher we ascend from the surface of the earth, the lower will be the temperature at which water boils. The reason is obvious ; (the pressure of the atmosphere diminishes in proportion to the ascent, and the boiling temperature sinks in pro portion as the pressure is removed, f Upon this principle is constructed the thermom cleric barow.c ier, which indicates the elevation of any place above the level of the sea, by the temperature at which water boils at that elevation. By experiment it has been found that a difference in elevation, amounting to nearly 520 feet, makes a difference of one degree in the boiling point of water. A traveller therefore who ascends a high mountain may ascert hi nearly his elevation, by the temperature at which ne finds his teakettle to boil. Thus Saussure found that at a certain station on Mount Blanc, water boiled when heated to 187 degrees. This being 25 degrees less than its boiling point at the level of the sea, allowing 520 feet for every degree, would give an elevation of 13,000 feet. This method cannot however be very accurate, since the weight of the atmosphere at the same place varies at different times about three inches of the barometric guage. [See Natural Philosophy, article Barometer.^ Evaporation. During the process of ebullition, there is a rapid formation cf vapor, attended by more or less commotion in the liquid. Why will the water in a vessel, fig. 1, be made to boil by cold and cease to boil by h«at? Why does water boil at a lower temperature on a high mountain than on the level of the sea 1 What instrument is constructed on this principle? How may a traveller who ascends a high mountain ascertain nearly his elevat ion by the boding cf a tea-kettle ? What is Rv«poration ? EVAPORATION. 19 Evaporation aiso consists in the formation of vapor without heat, but the process is so slow as not to occasion any visible commotion in the fluid. Evaporation takes place, even during the coldest seasons, while ebullition requires various degrees of heat, or at least the removal of atmospheric pressure. To prove that evaporation takes place at ordinary temperatures, nothing more is necessary than to expose a quantity of water to the open air in a shallow vessel, when the fluid will be found gradually to diminish, and finally to disappear entirely. There is, however, a great difference in the rapidity with which different fluids evaporate, and in general it is found that those whose boiling points are lowest, disappear most rapidly. Thus, ether, and alcohol, evaporate much more rapidly than water. The chief circumstances which influence evaporation are, Extent of surface, and the state of the atmosphere in respect to temperature, moisture, and dryness. \ As evaporation takes place only from the surfaces of fluids, it is obvious that its rapidity must, under equal circumstances, be in proportion to this extent of surface. Thus, a given quantity of water will evaporate four times as soon from a vessel two feet square, as it will from a vessel of one foot square. In respect to temperature, it hardly need to be remarked, that fluids evaporate more rapidly in warm, than in cold situations, and that the process is hastened in proportion to the degree of heat employed. Fluids evaporate much more rapidly in a dry, than in a damp atmosphere. Even when the season is cold, if the air be dry, this process goes on rapidly, while it is comparatively slow, during the warmest season, if the air is already saturated with moisture. As evaporation consists in the formation of vapor, and the subsequent removal of successive portions of the evaporating fluid, by the air which comes into contact with its surface, it is obvious that the process must be more rapid in a current of air, than it is in a place where the air is still. And hence we find by experience, that evaporation is more rapid in the open How is it shown that evaporation takes place without the aid of heat 7 What, relation ¦toes there seem to be between the boiling point of a fluid and its evaporation? What *re the chief circumstances which influence evaporation 1 Is evaporation most rapid 'n hot or cold weather 1 In what does evaporation consist 7 Why is evaporation more -apid in 'ho ipen air, titan in the house? 20 EVAPORATION. air than in the house, and that under equal circumstances is most speedily effected during a strong wind. We have already explained, that one of the peculiar circumstances attending the formation of steam, is the large quantity of caloric which it absorbs, and carries away. Now it appears by experiment, that the conversion of fluids into vapor always requires large quantities of caloric, which becomes latent in the vapor, however slowly the process is carried on, and hence under ordinary circumstances, evapora tion, by conveying off the heat, has the effect of generating cold. To make this fact sensible by experiment, we havt only to pour a little ether on the hand, when a strong sensa tion of cold will be felt during its evaporation. When ou clothes are wet by a shower of rain, we feel cold for the same reason, but the sensation is less strong, because the evapora lion of water is not so rapid as that of ether. It has been explained that water boils at a lower temperature in proportion as the pressure of the atmosphere is removed. For the same reason, evaporation under equal circumstances, is most rapid when the weight of the atmosphere is removed, as under the exhausted receiver of the air pump. The cooling effects produced by the evaporation of water in the open air are not strikingly apparent, because the pro cess is comparatively slow, and therefore the quantity of caloric carried away from a body in any given time, is but little more than it receives from surrounding objects. But whei water is placed in a vacuum, its evaporation is very rapid, and did not the vapor from it fill the vacuum, and thus prevent farther evaporation, the heat would be carried away so rapidly as soon to turn the water to ice. Fig. 2. This curious effect is produced by means of an instrument invented by Dr. Wollas'on, and called the Cryophorus, or Frost bearer, Fig. 2. It consists of two glass balls as free from air as possible, and joined together by a glass tube. One of the balls What is said concerning the latent of vapor 7 How is cold produced by evapora tion? Does the pressure of the atmospi.ire influence this process 1 Why does not the evaporation of water from the surface of the earth produce intense cold ? How may he evaporation of water be made so rapid as to turn itself into ice? What is tlu nstrument, Fig. 2, called? EVAPORATION. 21 contains a portion of distilled water, while the other parts of the instrument, which appear empty, are full of aqueous vapor, which prevents the farther evaporation of the water by the pressure the vapor exerts on it. But when the empty ball is plunged into a freezing mixture, all the vapor within it is condensed; and then the evaporation becomes so rapid from the water in the other ball, as to freeze it in a few minutes. To make this experiment succeed, the tube should be a yard long, the balls holding about a quart each. The same effect on water Avill be produced by the evaporation of ether under the exhausted receiver of an air pump. This experiment may be conveniently made by placing a little water in a glass cup, and covering it with ether, after Fig. 3. which suspend the cup within the receiver of the air pump, as shown at Fig. 3. On exhausting the receiver, the ether will boil, in consequence of its rapid evaporation, and in a few minutes the water will be frozen. Evaporation takes place constantly, from the surfaces of our bodies, and it is owing to this circumstance that men are enabled to undergo exercise during the heat of summer. In general, the more violent the exercise, the greater is the quantity of perspiration arising from the surface, and consequently the greater the quantity of heat carried away. In this manner nature regulates the heat of the system, and during health sustains the equilibrium of animal temperature. Whenever this exhalation from the skin is suppressed, which only results from disease, the temperature of the system rises, and fever succeeds. In some cases of this kind, the heat of the human body exceeds that of the standard oj health by seven or eight degrees. The natural temperature of the human body in health, is about 98 degrees, and whenever the heat of summer is equa to that of the body, it becomes exceedingly oppressive. Th least exertion then brings on copious perspiration, which, in deed, prevents the immediate consequence of a higher am How may water be frozen by the evaporation of ether? From what provision of na ture are we enabled to use violent exercise in warm weather ? How does perspiratio relieve us from tlm effects of excessive heat ? Wliat is the effect of suppressed perspir* tion on the temperature of our system 7 22 CONDUCTORS OF CALORIC. mal temperature, but which is generally succeeded by lan< guor and debility. It is a wonderful fact, that the living animal has the power of resisting both heat and cold, and of maintaining its o\w> temperature, whatever may be the temperature of the air or water in which it is immersed. Sir Joseph Banks, and Sir Charles Blagden, found by experiment that they could endure for a short time the heat of a room, the temperature of which was 264 degrees, that is, 52 degrees hotter than boiling water. These gentlemen found that their hands, could not bear the heat of their watch-chains, or metallic buttons, but that their chests felt cold, and that the temperature of their bodies was not elevated above 98 degrees. In this room, eggs placed in a tin frame, were roasted in twenty minutes, and beef-steak was well cooked in about the same time Conductors of Caloric Some bodies have the power of conducting caloric much more rapidly than others. Thus one can hardly hold a brass pin for a moment, in the flame of a lamp, without burning his fingers, while a piece of glass of the same size, may have one of its ends melted with heat, without warming the other. Bodies which are most dense are generally the best conductors. Thus the metals conduct better than stones; stones better than earth; earth better than wood; and wood better than charcoal, cloth, or paper. But in particular cases there is no relation between the density of the body, and its power to conduct caloric. Thus platina is the most dense of the metals, and still it is one of the worst conductors among them; and glass is a worse conductor, than many substances of less than half its density. The conducting powers of different substances, are ascertained by making rods of the same length and size, of each substance; one end of which being coated with wax, the other end is placed in a vessel of hot water, and the state ol the wax on each, at the end of a given time, will show its comparative conducting power. What is said of the power of animals to resist heat as well as cold 1 What striking illustration is given of the power of men to resist heat 1 What bodies are generally tl best conductors of heat 1 Are the most dense bodies always the best conductors ol heat How are the conducting powers of different bodies ascertained 1 CONDUCTORS OF CALOilIC. 23 Solid substances, such as the metals, conduct caloric m all iirections, whether upwards, downwards, or sideways, with learly equal facility. Of all solids, those which are most porous, conduct heat with the least facility. It is on this account that flannel is warmer in the winter, than silk or linen. It does not so readily conduct away the animal heat. It is owing to the air, which loose spongy substances involve, that they resist the passage of heat better than those of a closer texture. — Thus eider down, and fur, make the warmest clothing, because they contain the most air among their parts, and for the same reason cotton batting is much warmer than the same weight of cotton cloth. The imperfect conducting power of snow, also arises from this cause. When newly fallen, a great proportion of its bulk consists of the air which it contains, as may be readily proved by the comparatively small quantity of water it makes when melted. Such a provision was designed for the benefit of man, in preventing the destruction of various products of the earth during the cold of winter. Farmers, in cold climates, always lament the nakedness of the earth during the winter, because many of their crops are in consequence injured by its severity. So great is the protecting effect of snow, that in Siberia, it is said, when the temperature of the air has been 70 degrees below the freezing point, that of the earth under the snow has seldom been colder than 32 degrees. Our ordinary sensations every day convince us of the different powers of various substances to conduct heat. In the winter, the different articles in a cold room convey very different sensations to the hand. A pair of tongs will conduct away so much heat from the hand as to give a sensation of pain, while a piece of fur, or flannel, scarcely feels cold, and yet both are of the same temperature, when tested by the thermometer. * Liquids communicate heat with considerable rapidity, though they conduct it so imperfectly that Count Rumford, What kind of solids are the worst conductors of caloric? Why do loose spongy bodies conduct heat more slowly than others? Why is cotton batting warmer than the same weight of cotton cloth 7 In what manner does snow protect the earth from the cold of winter? What is said to have been the difference between the temperature of the air, and the earth covered with snow, in Siberia? Why does a pair of tongs feel cold, when a piece of flannel or fur. at the same temperature gives no sensation? How do liquid* eonvcy caloric. 24 CONDUCTORS OF CALORIC. after many experiments, concluded that they were absolutely non-conductors. Liquids convey heat chiefly by a change of place among their particles. When a vessel of water is placed over the fire, that portion of the fluid nearest the heat having imbibed a portion of caloric, becomes lighter than before, and rises upward, communicating a part of its heat to the portions above. At the same time, that which is above sinks to the bottom of the vessel, and having obtained its portion of caloric, again rises, giving out a share to the surrounding fluid, .ike the former. In this manner does the water in the different parts of the vessel exchange places until the whole gains the temperature of 212 degrees. But though fluids convey heat chiefly by exchanging the places of their particles, yet they are not wholly Avithout the poAver of conducting it in any direction. Count Rumford, Ave have already stated, decided from his experiments that liquids AA r ere perfect non-conductors of heat; but Dr. Murray, and since him, other experimenters, have established the contrary doctrine. Dr. Murray's apparatus consisted of a vessel of ice, at the bottom of Avhich was placed a delicate thermometer. The vessel was then partly filled Avith oil, at the temperature of 32 degrees, so as to cover the bulb of the thermometer; and nearly touching the oil, AA r as suspended an iron cup, into Avhich Avas poured a quantity ol boiling Avater. In seven and a half minutes the heat from the water had raised the thermometer from 32 degrees to degrees, Avhen it became stationary, and then gradually began to fall. Dr. Hope placed we'er in a vessel of eleA r en inches in dia meter, and so contrived his apparatus, that a stream of cold water should circulate around this vessel, to prevent its conducting power from affecting the result. He then applied heat to the upper surface of the water in the vessel, and found by the indications of a thermometer placed in it, that the fluid conducted the caloric downwards. By such nice experiments only, has it been ascertained, that fluids conduct heat downwards; while under all ordinary circumstances, they may be considered perfect nonconductors. Are fluids wholly without the power of conducting caloric? By what method did Or. Murray determine that fluids were conductors of caloric? In what manner diO Dr. Hope ascertain the same fact. EXPANSION BY HEAT. 25 V Expansive Power of Heat. One of the most remarkable properties of heat arises from ihe mutual repulsion of its particles, so that when it enters into other substances it overcomes the cohesive attraction oi their parts, making them less dense than before, and thus enlarging their dimensions. In general terms, therefore, heat expands ail bodies. The ratio of this expansion, however, differs greatly in different substances. Thus, with the same increments of heat, fluids expand more than solids, and aeri form bodies more than fluids. There is also a considerable difference in the expansibility of different solids and different liquids; but the aeriform fluids, as air and the gases, all expand equally, with the same increase of temperature. The expansion of a solid is readily proved, by adapting a piece of metal, when cold, to an orifice, or notch, and then heating it, when it will be found too large for its former place. The cylindrical piece of brass, attacheG to the handle a, fig. 4, is exactly fittea to the notch in the plate b, and also to the aperture through the plate, so that it will enter the notch, and pass through the aperture, when cold; but when heated, even below redness, it will neither enter the notch, nor pass through the aperture. This proves that heat enlarges, or expands the dimensions of solids in every direction. The relative degrees of expansion which different solids undergo, at low degrees of heat, are shown by an mstru- ment called the pyrometer, one form of which is seen at Fig. 5. Flow docs heat operate tj enlarge the dimension* of bodies J 3 A rod of any metal,«,is laid on the rests, and one end made to touch the immoveable screw, b, while the other end touches the index \t. The rod Fig. 5. 26 EXPANSION BY HEAT. is then heated by the spirit lamps d, and its comparative cx- is shown by the multiplied motion of the index e along the graduated scale. In comparing different substances by means of this instrument, it will be necessary that all the rods should be of the same size and length, and that the heat of the lamps should be applied the same length of time. From experiments made with this instrument, it appears, that in most instances, there is a relation between the expan sion of the metals, and their fusibility, and in general, that those which are most easily fusible, expand most with equal increments of heat. Thus lead, tin, and zinc, expand much more by the same degrees of heat, than copper, silver, and iron, and the former are much more easily fusible than the latter. The expansion of the metals by heat, is often turned to advantage by certain mechanics and artizans in their business. In constructing large cisterns for brewers, or other manufacturers, the hoops are made too small for the circumference of the vessel. They are then heated, and in this state driven on the vessel, and as they contract in cooling, the vessel is thus bound together more firmly than could be done by any other means. Carriage-makers, by heating the iron band, or tire, which surrounds the wheels of carriages, and putting it in its place while hot, bind these parts together, with the greatest possible firmness. The great force with which metals contract on cooling, was strikingly illustrated some years since in Paris. The two sides of a large building in that city, having been pressed out by the weight of its contents and the roof, M. Molard proposed to remedy the evil, by making several holes in the two walls, opposite to each other, through which, strong iron bars should be introduced, so as to cross the inside of the building, from one wall to the other. On the projecting ends of the bars, on the outside of the building, were screwed strong plates of iron. The bars were then heated, by which their What bodies expand least, and what most, by heat 7 What is said of the equal ex pansion of air and the gases by heat 1 How is the expansion of a piece of mete shown by fig. 4 7 How are relative degrees of expansion which solids undergo ascertained 7 Explain fig. 5 What relation is there between the expansion of metals and their fusibilities? In what mechanical arts is the expansion of the metals, by heat, turned to advantage? In what manner were the wails of a building in Paris drawn towards each other by means of heat' 27 EXPANSION BY HEAT. ends w ere made to project further beyond the walls, thus permitting the plates to be advanced, until they again touched the walls, which might be an inch, or more. The bars, then, on cooling, contracted, and drew the walls as much nearei each other as the bars expanded in heating. There were two sets of these bars, so that, while one set was contracting and drawing the wall to its place, the other set was heating, and prepairing to retain what was thus gained. In this manner, a force was exerted, which the power of man could scarcely have applied by any other means, and by which the walls of an immense building were made to resume their perpendicular position. The expansion of a liquid by heat, may be strikingly shown by means of a glass ball, with a long small tube attached to it. When the ball, and a part of the neck, are filled with a liquid, and heat applied to the ball, the liquid expands, and continues to rise up the tube with considerable rapidity, until the liquid boils, when it will be thrown out with great force by the steam. The different expansibilities of different fluids by the same increase of heat may be shown by two such vessels as that iust described. ' Fig. 6. On the tube of each, fix a mark at the same height and fill one up to the mark with alcohol, and the other with water. Then plunge the bulbs of both into the same vessel of boiling hot water, thus making the heat applied to each, exactly equal.— Both the fluids will expand, and rise up the tubes, but the alcohol will be found to rise about twice as high as the water. It has already been remarked, that the ratio of expansion in all aeriform fluids, is equal, with equal increments of heat. If therefore, the ratio of expansion for one gas, as for instance, oxygen, be known, then the ratio for all the other gases, as well as that for the common air, which we breathe, will be indicated. From the experiments of several philosophers, it is proved, :hat this rate of expansion is equal to the -rHth part of the In what manner is the expansion of a fluid most strikingly shown ? How are the -'iflferent expansibilities of different fluids shown? Explain Fig. 6. How much more •a-joansible s alcohol than water? What is the ratio of expansion in aeriform bodies I 28 RADIATION OF HEAT. volume which the gas occupied, for every degree of heit's scale, at 32° and upwards. This" calculation is made from the experiments of Gay Lussac, Avho found that 100 parts, or volumes of air, at 32°, expanded to 137.5 parts, when heated to 212°. The increase of bulk for 180 degrees, that is, from the freezing to the boiling point, is therefore 37£, which, by calculation, will be found nearly rirth part for each degree. The expansion of air by heat may readily be shown by blowing up a bladder, and securing the mouth by a string, so that none can escape, and then holding it towards the fire. As the air becomes rarefied by the heat, the bladder will become more and more tense, until it bursts with an explosive report. Fig. 7. A more elegant experiment is, to take a glass tube, terminated by a bulb, and put in so much water as to about half fill the tube, and then, having immersed it in a vessel ol water, as represented in Fig. 7, apply the heat of a lamp to the bulb. As the heat rarefies the air in the bulb, the water will be forced down the tube, but will slowly rise again to its former place, by the pressure of the atmosphere on the fluid, when the heat is removed, and the air in the ball allowed to contract. Radiation of Heat. When we approach a heated body we become sensible that it emits caloric without touching it, and if a thermometer be cacried near, this will indicate an increase of temperature. — The caloric thus flowing from a heated body, is called radiant caloric, because it radiates, or is thrown off in all directions, like the rays of light from a radiant point. If the hand be held under the heated body, a sensation of warmth will still be perceived, which proves that this effect is produced without the intervention of a stream of heated air, which is felt only above the hot body, and never below it. Neither ?.s this effect produced by the gradual conduction of the caloric by the air, for the heat from a hot ball may be felt in the What is the difference in the bulk of 100 parts of air at the freezing and boiling points of water 7 What simple experiments show the expansion of air by heat 7—Explain Fig . What is meant by radiant heat 7 How is it proved that radiant heat is not conducted oy the air ? 29 RADIATION OF HEAT. open air, at a distance from it and in the direction contrary to that of the wind. It is found also, that caloric radiates equally well through all the gases, and better through a vacuum than any medium; and hence we may infer that no medium at all is necessary for the passage of radiant caloric. When radiant caloric falls upon a solid or liquid, its rays are either reflected from it, and thus receive a new direction, or they lose their radiant form entirely by absorption into the body. Thus, a substance highly polished will throw the heat back, towards the radiating body, and remain cold itself; while another substance, with a rough surface, will become warm at the same distance, because it absorbs, but does not reflect the heat. Radiant heat, and light, follow exactly the same laws in their passage to and from polished surfaces, the angles of incidence and reflection being equal. Fig. 8. a Thus the ray a, c, Fig. 8, is the ray of incidence, and c, d, is the ray of reflection. The angles which a c make with the perpendicular line e c, and the plane of the mirror, are exactly equal to those made by c, d, with the same and plane surface. {See Optics in Nat. Philosophy.) Hence with a concave mirror, the rays of heat, like those of light, may be concentrated, or collected to a focus, and by .3 of two "such mirrors, very interesting experiments may be made, illustrating the Jaws of radiant heat, in several respects. Provide a pair of concave metallic mirrors, about ten or twelve inches in diameter, and two in concavity. They may be made of common tinned iron, or of brass, which is better, but much more expensive, These mirrors may be supported by stands made of wood on which they slide up and down, a nd are fixed by thumbscrews as represent ed in Fig. 9 Fig. 9. How is it shown that no medium a: all is necessarv to convey radiant caloric? 3* 30 RADIATION OF HEAT. Place the mirrors at the same height, on a bench or table exactly facing each other, and from ten to twenty feet apan. as they are less or more perfect, and place a screen of papei or other substance between them. Then in the focus of one mirror place a cannon ball, heated a little below redness, and in the other focus place a thermometer. When every thing is thus prepared, remove the screen, and the thermometei will instantly begin to rise, and will finally indicate a degree of temperature depending on the size and perfection of the mirrors, their distance apart, and the heat of the ball. The focus of a twelve inch mirror of the ordinary shape, is about four and a half inches distant from the centre of concavity. By placing the mirrors near each other, and using a red hot ball, a much more striking experiment may be made, for on removing the screen, powder will flash in the focus as if by magic, since the eye cannot detect the cause on which its inflammation depends. The dotted lines in the drawing, Fig. 9, show the course of the rays of heat from the hot ball to the thermometer. The ball being placed in the focus of the mirror, the caloric radiates to all parts of its surface, and being reflected under the same angles at which it falls, the rays are thrown into parallel lines, and thus become incident rays to the second mirror. By the same hwof incident and reflection, the second mirror conveys the rays to a focus at the same distance before it, that the hot ball is placed before the first mirror, because their focal distances are just equal. The heat of the ball is therefore concentrated on the bulb of the thermometer, which is placed in the focus of this mirror. If a burning lamp be placed in the focus of the first mirror, and a piece of paper, or the hand, in the focus of the second, there will be seen a bright luminous spot on the paper or hand, showing that light follows the same laws of reflection that heat does. There is however a remarkable difference between the sub stances of which mirrors are commonly made, with respect to their powers of reflecting heat and light. A concave glass mirror, covered in the usual manner with amalgam, when placed before a red hot cannon ball, will reflect the light. Does heat raJiate through solid bodies? Explain Fig. 8, and show which is the ray of incidence and which that of reflection. Explain Fig. 9 ; show the direction ol the rays of heat from the heated ball to the mirrors, and from the mirvor to the the:. mometer. How is it shown by the mirror that heat and light follow the same laws at reflection? 31 RADIATION OF HEAT. out not the heat, the mirror itself absorbing the radiant caoric, and soon growing warm. But a well polished metallic mirror reflects both the heat and light, and although held so near an ignited body, as were it combustible, to be inflamed, it still remains cold. For the same reason, andirons, which are kept highly polished, will remain cold though near a winter's fire. Any one who has undertaken to boil water in a silver cup before the fire, will be convinced of the power of a bright metallic surface to resist the penetration of caloric. The nature or colours of the surfaces of bodies have also an important influence over their power of radiating caloric. When other circumstances are equal, the rate at which bodies cool appears to be in an inverse ratio to the polish, or brightness of their surfaces. Thus, the surfaces of bodies are found to radiate heat more rapidly when they are rough than when smooth, and most rapidly when their surfaces are both rough and dark coloured. Mr. Leslie covered one side of a cubical tin vessel with lamp black, another side with writing paper, a third with glass, and left the fourth uncovered. The vessel was then filled with hot water, and placed before a concave mirror, in the focus of which was placed an air thermometer, as represented by Fig. 10. On turning the black side towards the reflector, the fluid in the thermometer indicated a rise of temperature equal to 100°; the papered side being turned towards the reflector, the thermometer sunk to 98° ; the glass side indicated 90° ; and the metallic side only 12°. The radiating power Fig. 10. of these surfaces, therefore, are respectively to each other as the numbers 100, 98, 90, and 12. What is the difference between a mirror of glass and one of metal, in their powers to reflect heat and light? Why do polished andirons remain cold when near the Are? Why is it difficult to boil water in a bright mstallic vessel? What effect does the nature, or color of a surface, have on its radiating power ? Describe Fig. 10, and explain how Ihe different surfaces affect the thermometer 32 SPECIFIC CALORIC. Various practical uses may be made of this principle to the common concerns of life. A close stove, intended to warm a room by radiating its heat to the objects surrounding it, should be dark coloured, with a rough surface; while one intended to warm with hot air passing through it, should have a bright metallic surface A dark, rough stove pipe, passing through a room, might render it comfortably warm; while a polished tin pipe, of the same length and dimensions, would hardly change its temperature perceptibly. For the same reason, a highly polished metallic coffee pot will keep.its contents hot, while the contents of one made of dark earthen ware would become nearly cold. Specific Caloric. . Equal weights of the same substance, at the same temperature, contain equal quantities of caloric, but equal weights of different substances at the same temperature, contain unequal quantities of caloric. The quantity peculiar to each body, or substance, is called specific caloric. When one body of the same weight is found to contain more caloric than another, that containing the most, is said to possess the greatest capacity for caloric. When equal quantities of the same fluid at different tern peratures are mingled together, the resulting temperature ia a medium between these temperatures. Thus, if a quart of water at 100°, be mixed with another quart of water at 40°, the temperature of the mixture will be 70°. The same result will occur when any other liquid is mixed in equal proportions, but at different temperatures, as oil, alcohol, or mercury. But when equal quantities of different fluids are mingled together, at different temperatures, the resulting temperature is not a medium, but is either above or below it. We should expect without experiment, that quicksilver would possess a greater capacity for caloric than the same bulk of water, and therefore that when equal quantities of these two fluids at different temperatures are mixed, the What practical uses may be made on the principles established by Mr. Leslie's experiment 1 Why does a bright coffee pot keep its contents warm longer than one that is tarnished 1 What is meant by specific caloric 1 What is meant by capacity for caloric 1 Nuppose equal quantities of the same fluid at different temperatures are mixed, wha •will be the rosidting temperature 1 33 SPECIFIC CA10RIC. resulting temperature would be above the arithmetical mean. But in this we are disappointed; for if we mix a quart of water at 40° with a quart of quicksilver at 100°, the temperature of the mixture will not be 70°, as in the experiment with the water alone, but only 60°. This proves that a quart of quicksilver, although it weighs about fourteen times as much as a quart of water, still contains less caloric, and therefore that water has a greater capacity for caloric than quicksilver. For, in the first experiment, a quart of water at 100° raised the temperature of another quart at 40° to 70°; but here a quart of quicksilver at 100° raises the heat of the same bulk of water to only 60°. The quicksilver, then, loses 40°, which nevertheless raises the temperature of the water only 20°. The relative capacities of water and quicksilver for heat, may be shown by mixing equal weight? of the two fluids at different temperatures, and then ascertaining how much the resulting temperature differs from the arithmetical mean. Mix a pound of water at 100° with the same weight of mercury at 40°, and the heat of the mixture will be 98°; that is, 28° above the arithmetical mean, because when equal weights of water were mixed at these temperatures, the resulting temperature was only 70°; but here it is 98. The water, then, has lost only 2°, while the same weight of mercury has gained 58°, for the temperature of the mercury before the mixture was only 40°, while that of the water was 100°. The capacity of water for heat, is therefore to the capacity of mercury for the same, in the proportion of 58 to 2, or as 29 to 1. It appears from a great variety of experiments made by different philosophers on this curious subject, that whatever may be the cause of the different capacities of bodies for heat, the effect is greatly influenced by the state of density in which bodies exist, and that in general their capacities increase, in a ratio to the decrease of their specific gravities. In the above experiment, the capacity of water is to mercury as 29 to 1, while their specific gravities are as 1 to 14. Various methods have been employed by philosophers to ascertain the capacities of the several gases for heat. When fluids of different kinds are mixed under the same circumstances, will the result Ing temperature be a medium 7 Which fluid has the greatest capacity ibr caloric, water or quicksilver 7 How is this shown 7 If a pound of mercury at 40° be mixed with a pound of water at lfXP, what will be the resulting temperature? 34 SPECIFIC CALORIC. To determine and compare the relative capacities of these bodies in this respect, Gay Lussac contrived an apparatus, by means of which, a hot current of one gas met a cold current of another gas, in the centre of a small reservoir, containing a thermometer. A thermometer was also placed in ihe cuirent of each gas before they met. Thus by knowing their temperatures before their mixture, and afterwards, it was easy to infer their respective capacities for caloric. Bernard, in order to determine the specific caloric of elastic fluids, caused them to pass through a pipe inclosed in a larger pipe, the latter being constantly filled with steam. In this manner he was enabled to know precisely the temperature of the gas under experiment, and also to raise the temperaure of each to the same degree. Having thus determined its temperature, the gas was then made to pass into a spiral tube immersed in cdW water, and the specific caloric of each gas was inferred by the quantity of heat it imparted to the water. By these and similar experiments, it has been ascertained that the aeriform fluids differ greatly in the quantities of their specific caloric, —thus, the capacity of hydrogen for caloric is more than 12 times greater than the capacity of an equal bulk of atmospheric air, though the air weighs about 13 times as much as the hydrogen. It is also ascertained that out of nine gases on which experiments were made, none except hydrogen has a capacity for heat equal to that of water, but that they all have greater capacities than any of the metals. Hydrogen, the lightest of all bodies, has the greatest capacity for heat, while the metals, the most ponderous of all bodies, have the least. The same substance by having its bulk enlarged, and consequently its density decreased, acquires an increased capacity for caloric. Thus water, when thrown on the bulb of a thermometer, sinks the mercury, because, in assuming the form of vapour, its capacity for caloric is increased, and it consequently absorbs and carries away the heat from the mercury. Some philosophers have accounted in part, for the intense cold in the upper regions of the atmosphere, on the What are the proportionate capacities of mercury and water for heit 1 In general, do the capacities of bodies for heat increase, or decrease, with their densities 1 By whal method did Gay Lussac determine the capacities of the gases for caloric? By what ma thod did Bernard determine tne capacities of the gases for caloric? What gas lias tl greatest capacity for heat ? In general, what class of bodies have the greatest, and wh) the least capacity for heat ? THERMOMETER. 35 supposition of the increased capacity of the air for heat as the pressure of the incumbent atmosphere is removed. On the contrary, we know, that by increasing the density of air, its capacity for caloric is diminished, and that under certain circumstances sufficient heat may be set free in this manner to produce ignition. Fig. 11. This effect may be produced by the little instrument represented by Fig. 11. It consists of a metallic tube ten, or twelve inches long, the bore of which is less than half an inch in diameter. To this is fitted a rod and piston, moving air tight, the lower end of the piston being excavated to receive a little tinder. When the pis-ton is suddenly forced down, nearly to the bottom of the tube, the condensation of the air it contains, evolves so much heat, as to set fire to the tinder in the end of the piston, ana in this way a fire may conveniently be kindled. Thermometer. The thermometer is an instrument founded on the principle, that the expansion of matter is proportional to the augmentation of temperature, and is designed to measure the varia tions of heat and cold. The first attempt to measure such variations on this principle was made by Sanctorius, an Italian physician, in the seventeenth century. He employed a glass tube blown into a ball at one extremity, and open at the other. After expelling a small part of the air by heating the ball, the open end was plunged into a vessel of colored fluid, and as the air in the ball cooled, the fluid ascended up the tube. Any variation of temperature by expanding, or contracting the air in the ball, would then cause the liquid in the tube to rise or fall. An arrangement of this kind is represented at Fig. 7 If a body has its bulk enlarged, is its capacity for heat increased or diminished thereby 1 How has the intense cold of the upper regions been accounted for on tins principle! How is it proved that the air has less capacity for heat when condensed that; otherwise 1 On what principle is the thermometer constructed ? Who first constructed thermometers ? What fluid was first employed to indicate the variations o! temperature 1 36 THERMOMETER. Fig. 12. A better construction for an air thermometer is represented at Fig 12. It consists of a thin glass bottle, containing a small quantity of a colored liouid, and stopped closely by a cork. Through the cork is passed a broken thermometer tube, open at both ends. This tube descends, nearly to the bottom of the bottle, and dips into the fluid. There is, therefore, a quantity of air above the fluid which cannot escape, and when this expands by the application of heat, the fluid is forced up the tube. Thus the height of the fluid will indicate the expansion of the air, and consequently, the degree of heat to which the instrument is exposed. There are, however, two objections to the employment of air for this purpose. Its expansions and contractions are so great even by changes of temperature, that a tube, several feet in length would be required to measure them; and as air suffers condensation by pressure, the variation of the barometer would affect its height, at the same temperature. For these reasons, the air thermometer, for common purposes, is both inconvenient and inaccurate, and therefore has long since been laid aside. There is, however, a modification of this instrument, invented by Mr. Leslie, and called the differential thermometer, which for certain purposes is a very elegant and useful instrument. Fig. 13. A drawing of this instrument is represented by Fig. 13, and it is designed, as its name imports, to shew the difference of temperature between two places at short distances from each other. It consists of a glass tube terminated at each end by a bulb, and bent as shown in the figure. The tube is partly filled with some colored fluid, as sulphuric acid, tinged with carmine, or alcohol, colored by cochineal, the bulbs and other parts of the tube being filled with air. It will be obvious, from the construction of this instrument, that it cannot indicate the temperature of the atmosphere, since an equal expansion of the air in both bulbs would press equally on the fluid in both legs of the tube, and consequently it would rise in neither. But if one bulb is ex- Describe the construction of an air thermometer. What are the objections to a'r thermometers? How is the differential thermometer constructed, and for what puqioscs is t useful. THERMOMETER. 37 posed to a higher temperature than the other, then the expansion of the air in this, will be greater than in the other, and consequently the fluid will rise towards the bulb where the air-is least expanded. The use of this thermometer, then, consists in showing the difference of temperature to which the two bulbs are exposed, as in experiments on the radiation of heat, already described. The scale affixed to one of the legs, shows the rise in degrees, and is divided into 100 parts. The legs are six inches long, and the bulbs an inch or a little more in diameter. The stand may be of glass or wood. Some of these instruments are so delicate as to be affected by the approach of the hand. Air, being inapplicable to the construction of thermometers for the purpose of measuring the absolute temperature of places or things, for the reasons already noticed, solid bodies are equally so from a contrary defect; their expansion by heat being so small as not to be appreciated without the adaptation of complicated machinery. A perfect substance for this purpose, would be a fluid, which would expand uniformly with equal increments .of heat, and which would neither freeze nor boil at any temperature to which it might be exposed Mercury approaches nearer to these conditions than any other substance, and therefore this is the fluid now almost universally employed. The blowing of the best thermometer tubes requires much experience and skill in the workmen, and is performed only by particular artists. This is the most difficult part of its construction. The mercury is introduced by heating the bulb, and thus rarefying the air within it, and then dipping the open end of the tube into a vessel of the fluid. As the air contracts within by cooling, the pressure of the external atmosphere forces the mercury to enter the tube to supply its place. When the bulb is nearly filled in this way, the mercury is boiled, to expel the air. Having filled about one third of the tube, the open end is sealed hermetically, that is, by melting the glass. This is done while the mercury in the bulb is heated nearly to its boiling point, so as to exclude all the air. Having sealed the end of the tube, the next step in the Why will not the differential thermometer indicate the temperature of the atmosphere 1 Why are not solid bodies proper for the construction of thermometers 1 What would be a perfect substance for the construction of thermometers'? What is the most perfect fluid in our possession for this purpose ? How are thermometer tubes filled! 4 38 THERMOMETER. construction of the thermometer, is its graduation. This is done by ascertaining two fixed and invariable points on the tube, which are the same in every thermometer, and then by making a scale of equal divisions between these two points These are the freezing and boiling points. The freezing point is found by immersing the bulb o the thermometer in melting snow or ice, for it has been as certained, that the temperature of water flowing from melting snow or ice, is every where the same, whatever may be the heat of the atmosphere where the experiment is made. The boiling point is slightly affected by the pressure of the atmos phere; but the thermometer will be sufficiently accurate foi all ordinary purposes, when this point is ascertained by im mersing the bulb in pure boiling water, open to the air, and on the level of the sea, during pleasant weather. (See Ba rometer, in Nat. Philosophy.) Fig. 14. The freezing - and boiling points are marked with a diamond or file, on the tube; and on the scale to be afterwards affixed, the freezing point, is marked 32, and the boiling point, 212. The interval between these two points is then accurately divided into 180 equal parts. This i3 the division of Fahrenheit's scale, the thermometer generally employed in this country, and is the only scale referred to in this work. The commencement of this scale is 32 degrees below the freezing point, and is called zero, being marked with the cipher 0, to signify the total absence of heat. This degree of cold, it is supposed, Fahrenheit obtained by mixing snow and common salt, and it was probably the greatest de gree of cold known in his time, though at the pre sent day certain mixtures produce much greater, and at a future period, the progress of science may show the means of abstracting heat, so as to solidify even the air we breathe. The absolute zero must therefore be considered an imaginary point. Besides the Zero and the freezing and boiling points, marked on Fahrenheit's scale, Fig. 14, there are also noted the temperature of the blood, and the heat of summer, and sometimes other points, as fever heat, &c. Hr'/ is the freezing point of the thermometer ascertained 1 How is the boiling point mm gained? 39 COLD Cold. Cold is a negative condition, and depends on the absence, or privation of heat. Intense artificial cold may be produced by the rapid absorption of heat during the conversion of solids into liquids. Dr. Black long s»ace discovered the Erinciple, that when bodies pass from a denser to a rarer state, eat is absorbed and becomes latent in the body so transformed, and consequently cold is produced. And also that when bodies pass from a rarer to a denser state, their latent heat is evolved, and becomes sensible. It is known to almost every one, that dissolving common salt in water, particularly if the salt is fine, will render the water so cold, even in summer, as to be painful to the hand. The salt, as it passes from the solid to the liquid state, absorbs caloric from the water, and thus the heat that was before sensible, becomes latent, and cold is produced. On the contrary, when a piece of lead or iron, is beaten smartly with a hammer, it becomes hot, because the metal, in consequence of the hammering, has its capacity for caloric reduced, and thus the heat which was before latent, now becomes sensible. For the same reason, when air is compressed forcibly in a tube, or as it is sometimes called, in a Jire!mmp, as already explained, the heat, which was before latent, )ecomes sensible, because the condensation lessens its capacity for caloric. The principle on which all freezing mixtures act, is therefore the change of state, which one or more of the articles employed undergo, during the process, and this change consists in an enlarged capacity for caloric. The degree of cold will then depend on the quantity of caloric which passes from a free to a latent state, and this again will depend on the quantity of substance liquefied, and the rapidity of the liquefaction. What numbers are marked on the scale at the freezing and boiling points ? What is the number of degrees between these two points ? What does zero signify 7 How far below the freezing point is the zero of Fahretdieit 7 Is the point of the absolute zero known! What is cold I How may intense artificial cold be produced I When bodies pass from a denser to a rarer state, is heat or cold produced 7 How is the temperature of water generally known to be affected by dissolving common salt in it? How is this change of temperature accounted for 7 Why does a piece of iron become hot 'by hammering 7 How do you account for the heat evolved, where air is compressed ? What is Hie principle on which freezing mixtures act 7 On wliat circumstance will the degree of colli produced by freezing mixtures dejiend ? 40 COLD, .The substances most commonly employed for this purpose are those originally used by Fahrenheit, to produce the zero of his thermometric scale; viz. common salt and snow, »r pounded ice. For this purpose the salt should be fine, and the ice, which must always be used in summer, is to be reduced to small particles in a cold mortar. Fig. 15. The vessel to contain the substance to be frozen, may be made of tin, and of the shape represented by Fig. 15. It is simply a tall vessel, holding a few pints, with a close cover, and a rim round the top, for the convenience ol handling it. For common purposes, this may be set into any convenient wooden vessel, (having first introduced the substance to be frozen,) and then surrounded by the freezing mixture. The only care to be taken in this part of the process is, to see that the freezing mixture in the outside vessel reaches as high as the con- tents of the internal one. With two or three pounds of line common salt, and double this weight of pounded ice, three or four pints of iced cream may be mllde in this way, during the warmest days of summer. The process requires two or three hours, and while it is going on, the vessel should be set in a cellar, or covered with a flannel cloth, as a bad conductor of the external heat. When the thermometer is at 32°, the cold generated by the above process, sinks it down to zero, as above stated. By this method, two solids are changed into liquids, and both during the change, absorb caloric from the contents of the inner vessel. The salt melts the ice in consequence of the avidity with which it imbibes moisture, or by reason of its affinity to water, and the water in its turn dissolves the salt. Other substances having a stronger affinity (see affinity) for water than common salt, will produce the same effects still more powerfully. Thus, muriate of lime (see this article) five parts, and ice four parts, will sink the thermometer from 32° to 40° below zero, that is, in the whole, 72 degrees. At this temperature, mercury freezes. A still more effective mixture is four parts of fused potash, and three parts of snow. Whit are the substances most commonly used as freezing mixtures') Explain Fig. .5, anl show how it is to be used. How far below 32 degrees will a mixture of ice a»»tf common salt sink the thermometer 1 Why does the salt melt the ice 1 What substance sinks the thermometer from 32 to 40 degrees below zen»1 SOURCES OF CALORIC. 41 This is said to sink the mercury from 32° to 50° below zero, thai is, 82 degrees. In these experiments the thermometers are rilled with alcohol, instead of mercury. Freezing mixtures are also made of a solid and a fluid. One of the most effectual of this kind is composed of diluted sulphuric acid and snow, or pounded ice. This sinks the mercury from 32° to 23" below zero. Though ice or snow is commonly employed foi this purpose, still powerful frigioric effects may be produced without either, the absorption of caloric being caused by the rapid solution of a salt in a fluid. One of the most common and cheap among these is a mixture of sulphate of soda or Glauber's salt, and diluted sulphuric acid. This sinks the mercury from 50° to 3° above the freezing point, that is 47°. In describing experiments of this kind, it should always be noted from what point the thermometer begins to descend, otherwise no judgment of the power of the freezing mixture can be formed. If, for instance, a mixture would cause the depression of the thermometer from, and below any given point, then by repeating the process continually, Ave should be able to find the absolute zero. Thus, by means of muriate of lime and snow, the thermometer is made to sink 82°, that is, from 32° above, to 50° below zero. Noav if the same cause Avould again produce the same effect, by its re-application, the thermometer AA r ould sink to 132° beloAv zero, a degree of cold never yet produced by any means. But an unlimited degree of cold can never be produced by the art of man ; for it is found on experiment, that Avhen the temperature produced by the freezing mixture is greatly below that of the air, the caloric is so rapidly communicated, as to prevent any effect by repeating the process. Mr. Walker, who made a great number of experiments on this subject, was never able to produce a greater degree of cold than that of 100° beloAv the zero of Fahrenheit. Sources of Caloric. The sources of caloric may be reduced to six, viz. The In these experiments, why ia alcohol used to fill the thermometer, Instead of mercury 1 What is said of sulphuric acid and snow, as a freezing mixture 1 What substances form a freezing mixture without the use of ice or snow ? In making experiments with freezing mixtures, why is it necessary to state the degree from which the thermometer begins to (all 1 Wlmt is the reason that an unlimited degree of cold cannot be produced by an I What is the greatest degree of cold ever produced 1 What are the sources ot caloric ? 4* 42 SOURCES OF CALORIC. Sun, Combustion, Electricity, the bodies of living* want blooded animals, Chemical action, and Mechanical action. The Sun constantly radiates caloric to the earth, and fj the great fountain of heat to us and to the -whole solai system. Combustion. This supplies the heat employed in the arts, and for culinary purposes. In this process the caloric is ex tricated from the oxygen of the atmosphere, as it unites with the burning body and supports its combustion. The light h supposed to be furnished by the burning body. Electricity. Whenever two bodies in opposite electrical states are made to approach each other, so as to produce a discharge through the air, or along a nonconductor, there appears a flash of light attended by heat. By the action oi Galvanism, which is a modification of electricity, the most intense heat hitherto known has been produced. When the electric fluid passes through a piece of metal, or other conductor, of sufficient size, no phenomena are produced ; but in its passage through a nonconductor, or through a conductor which is too small to adniit of a free passage, heat is produced. (See Electricity, in Nat. Philosophy.) Vital action. The bodies of air breathing animals are a continual source of heat. The numerous theories which have been invented to account for the cause of animal heat cannot here be investigated. That it however depends en the oxygen of the atmosphere which we breathe, seems to 1 e proved by the fact, that animal warmth cannot for any length of time be sustained without it. Chemical action. Chemical action without combustion is capable of producing considerable degrees of heat. If water be thrown on unslacked quicklime, in small quantities at a time, its heat will be gradually augmented to nearly 1000 deg., or so as to ignite wood. The heat in this experiment is accounted for, on the law already explained, that when bodies pass from a rarer to a denser state, caloric is evolved. The slacking lime absorbs the water and retains it as a part of its substance, and thus a fluid is converted into a solid, with the evolution of much caloric. What is the great fountain of heat 7 How is heat extricated by combustion ? When does electricity produce heat? What is the cause of electrical heat, according to Sir 11 Davy ? What is said of vital action, as a cause of heat ? What is said of chemical ac ticn as the cause of heat 7 How is the heat produced by throwing water on Quicklime, wxountcd for? 43 SOURCES OF CALORIC. If three parts of strong sulphuric acid and one of water bo suddenly mixed together, a degree of heat considerably, above that of boiling water will be produced. In this case ihe heat is also accounted for on the principle of condensation, for if the two fluids be measured before and after mixture, it will be found that their union has occasioned a loss of bulk, and probably also a loss of capacity for caloric. The inflammation of Spirit of Turpentine by nitric acid is a case of intense chemical action, in which 1000 degrees of heat are evolved. About an ounce of the turpentine with the same weight of nitric, mixed with a little sulphuric acid, are the proportions. The acid should be poured on the turpentine from a vessel tied to a line several feet long, as the explosion sometimes throws the burning matter to a considerable distance. Mechanical action. This includes percussion, friction, and condensation. Caloric is evolved by the percussion of hard bodies against each other. This is owing to the condensation of the body struck, in consequence of which its latent heat becomes sensible. If a piece of soft iron be struck smartly several times with a hammer, on an anvil, it becomes hot, and even red hot, if ihe experiment be well conducted. When a piece of steel and a flint are struck together, the condensation produces so much heat as to set fire to the small particles of steel which at the same time are struck off by the blow. Friction. Caloric is evolved, or produced by friction. The friction of machinery Avhen the motion is rapid, frequently causes so much heat as to set the wood on fire. The inhabitants of various nations obtain fire by rubbing pieces of dry wood together. The friction of carriage wheels sometimes sets them on fire. Th« principle on which caloric is produced by friction has not been demonstrated. It cannot be referred to condensation, since the rubbing of two soft bodies together, such as When sulphuric acid and water are mixed, what is the cause of the heat produced t How may spirits of turpentine be inflamed by chemical action 1 What does mechanical action as a source of heat include 1 How is the evolution of heat by percussion accounted for 7 When a piece of stee\ is struck by a flint, how is the fire produced J How is the heat produced by friction accounted fori How does condensation produce heat 1 44 LIGHT Jit? hand against the coat sleeve, or the two hands against each other, causes heat. Count Rumford, who made a laborious and varied course of experiments on this subject, was led to the conclusion that the heat produced by friction could not be connected with the decomposition of oxygen gas, nor with the increase ol density, nor could it be caused by any change in the specific caloric of bodies. Others have also made experiments with a view to determine this question, but as yet no one has pre tended to give any satisfactory explanation of its cause. The Condensation of an elastic fluid by sudden pressure causes heat, as has already been explained, and illustrated by Fig. 11. The heat evolved in this case arises simply from the diminished capacity of the air for caloric, in consequence of its increased density. Light. The next imponderable agent which falls under our notice,, is light. The investigation of the properties of light,—its laws of reflection and refraction, and its effects on the sense of vision, and subjects belonging to the science of Optics. (Sec Optics in Nat. Philosophy.) Some of the effects of light are however properly considered here, since they produce chemical phenomena. Light may be decomposed by means of a prism, into seven primary colours. The succession of these colors, beginning with the uppermost, is violet, blue, green, yellow, orange, red. The decomposition of light, only requires that a ray should be admitted through a small aperture into a room, and made to pass through a triangular prism, as represented by Fig 16. The direction of the ray towards the point c will be changed bv ithe refractive power ol the prism, and at the same time it will be decomposed into the col- Fig. 16. To what science does the investigation of the properties of light, with its efTects or the sense of vision, belong 1 Why do some of the effects of light properly belong to th< ¦nvestigations of chemistry! Into how many primary colors may light be divided What is the succession of these colors, beginning with the uppermost T How may thi lecomposition of be light effected 1 45 liotit. ors already named, the violet corresponding with L, and the red with 7. It may be observed by the figure, that the red is refracted least, and the violet 'most, from the direction of the original ray, these two colours terminating the under ana the upper parts of the spectrum. These seven, are called the primary colours, since they cannot by any known means be again decomposed, or separated into other colours. The whole seven are called the solar spectrum. The heating poAvers of these several colours are different. Take a sensible air thermometer (fig. 13) and move the bulb in succession through all the coloured rays, waiting at each for the fluid to rise, or fall. The thermometer will be found to indicate the greatest heat in the red ray, next in the green, and so on in a diminishing ratio to the violet. When the thermometer is moved a little beyond the red ray, but in a line Avith the spectrum, the heat is still greater than in the ray itself. These heating rays are invisible to the eye, and hence it is concluded that there exists in the solar beam, a distinct ray Avhich causes heat, but no light. The illuminating poAA r er of each primary ray in the solar spectrum, is different from the other. This is proved by permitting the spectrum to fall on a large printed sheet, of the same sized type, Avhen it Avill be found, that at the same distance, the parts illuminated by some of the rays can be read, Avhile those illuminated by others are indistinct. Light is capable of being absorbed by certain substances; of remaining in them for a time, and then of being extricated unaltered. Such bodies are called solar phosphori. Phosphorescence. Phosphorescence may be defined, the emission of l.'ght Avithout sensible heat, or Avithout combustion. A considerable number of substances haA r e the poAA-er of absorbing a quantity of light when exposed to the rays of the sun, and of emitting it again, so as to become luminous in Which ray is most, and which is least refracted, from the direction of the original ray 1 What are these seven colours called 1 What are the whole called ? What is said of the heating powers of the different rays? Is the greatest heating power in the red ray, or beyond it? Are the heating rays visible, or invisible? How is it proved that the illuminating powers of the different rays differ ? AVhat is phosphorescence ? AVhat are solar phosphori ? AVhat is s»iid of the power of bodies to absorb anil emit •ight? 46 PHJSPHDRESCENCE. the dark. Most substances lose thi*3 property in a snort lime, but acquire it again by another exposure to the sun, and thit may be repeated any number of times. Several substances by this treatment become so luminous as to render minute objects visible in the dark. Canton's phosphorus is of this kind, and may be prepared as follows: Calcine common oyster shells in the fire for an hour; then select the purest and whitest parts, and reduce them to fine powder. Mix three parts of this powder with one of sulphur, and having pressed the mixture into a crucible, keep it red hot for one hour. Then let the crucible cool, and select the brightest and purest parts, which cork up in a dry vial for use. When this composition has been exposed for a few minutes to the light of the sun, and then carried into the dark, k will be sufficiently luminous to show the hour by a watch dial. The same property is possessed by compositions called Homberg's and Baldwin's phosphorus. The diamond, also, possesses this property, as shown by the celebrated experiment of Dufay, who, having exposed a diamond to the light, immediately covered it with wax, and on removing the wax several months afterwards, found that it shone in the dark. Some substances phosphoresce by friction ; some by scratching, and others by heat. That variety of carbonate of lime called dolomite, gives light on being rubbed. Loaf sugar mixed with whites of eggs and dried, as is done for the frosting of cake, emits a streak of light on being scratched with a sharp point. Several varieties of fiuate of lime, and of marble, emit light when coarsely powdered and thrown on a hot plate of iron, so as to be seen in the dark. A piece of tobacco pipe, or a piece of quicklime, when heated by the compound blowpipe, or by other means to a degree which would only make other bodies red, give out a brilliant phosphorescent light, which is so intense as to be come intolerable to the eyes. Another kind of phosphorescence may be observed during the decomposition of certain animal substances. Thus, if a small piece of fresh herring, or mackerel, be put into a two What is Canton's phosphorus ? How is Canton's phosphorus prepared 1 What i necessary in order to make this substance Bhine in the dark 1 How did Dufay conrin* the light in a diamond? What is said of the phosphorescence of other substances 1 What is said of the phosphorescence of a piece of tobacco pipe, or quicklime ? How may i piece of tub. b J made to exhibit phosphorescence ? PHOSPHORESCENCE. 47 ounce vi.il of sea water, or into pure water, with, a little common salt, and the vial be kept in a warm place for two or three days, there will then appear a luminous ring on the surface of the water, and if the vial be shaken, the whole will give a phosphorescent light. Light produces very material effects on the growth of all vegetables, from the most humble plant, to the tallest tree of the forest. Plants, vegetating in the dark, are white, feeble, almost tasteless, and contain but little combustible or carbonaceous matter. On exposing such plants to the light of the sun, their colours become green, their tastes become much more intense, and the quantity of their combustible matter becomes greatly increased. These changes are strikingly obvious, and beyond all doubt depend on the agency of light. Light not only affects the natural, but in many instances, the artificial colours of things. In this respect, hoAvever, its effects appear not to be reducible to any general kw, for in some instances it destroys, and in others it augments, or even creates, the colours of bodies. On exposing bees AA r ax to the sun and moisture, its coloui is discharged, and it becomes white; it is also Avell lyiOAvn that the colours of printed goods, and of carpets, are changed or faded, by the same influence; and that the former mode of bleaching, consisted in exposing the cloth to the united influence of light, air, and moisture. On the contrary, the colours of plants appear to be exclusively owing to their exposure to light, and various chemical preparations, such as phosphorus, and the nitrate and chloride of silver, become dark coloured, and even black, by the influence of light. Light has also an important and curious influence on the crystallization of salts. Make a strong solution of the sulphate of iron, in Avater, and place it in a shalloAV dish. Cover one half of the dish with a black cloth, and set it in a darkened room, permitting only a single ray of light to enter, so as to strike upon the solution in the uncovered part of the dish. Thus one half of the solution will be exposed to the light, Avhile the other half will be in darkness. After the dish has stood in this situation for a day or two, it will be found that no How are plants affected by growing in the dark! What changes are effected by the light of the sun on plants which have grown in the dark 1 How are the artificial colours of thing* affected by light! To what do the colours of plants appear to be entirely owL" i what substances become dark coloured by tho influence of light! 48 ELECTRICITY. signs of crystallization are to be seen in that part of ihe soli) tion which has been kept in the dark, while that part which lias been exposed to the light will be completely crystallized. Another curious fact connected with this subject, is, that fkants emit oxygen gas, through the influence of the sun's ight. To make this obvious, fill a tall glass vessel, such as a bell glass, with water, and invert it into another vessel 01 water. Then introduce into the bell glars some sprigs of mint or any other plant of vigorous growth, m i expose the whole to the action of the sun. Small bubbles of air will soon appear, as though issuing from the leaves of the plant. These will, one after another, detach themselves and arise to the upper part of the vessel, and on examination, the air thus extricated will be found to consist of very pure oxygen gas. (See Oxygen.) In this experiment, the water serves only as the means of collecting the oxygen ; the water itself not being decomposed by the plant, but only the air which it contains. The air which we breathe contains a quantity of carbonic acid, which is decomposed by the organs of the plant, the carbon being retained, while the oxygen is emitted. (See Vegetation.) Electricity. The third imponderable agent is Electricity, including Galvanism. The ancients knew nothing of electricity as a science. They knew indeed that amber and glass, when rubbed, would attract light substances; and about the beginning of the eighteenth century, it was discovered that a certain stone called tourmaline, would attract feathers and hair when heated, and that some precious stones would do the same when rubbed. As an important science, electricity can claim no higher date than the age of Franklin. Galvanism is of much more recent date than electricity. This science owes its name and origin to an accidental discovery made by Galvani, an Italian, in 1791. Galvani was professor of anatomy at Bologna, and his great discovery seems to have been owing indirectly to the sickly condition of his wife. This lady being consumptive, was advised to How Is it shown that light has an influence on the crystallization of salts 1 How is it demonstrated that plants emit oxygen gas through the influence of the sun's light ? De scribe the chemical changes by which plants extricate oxygen gas. Was electricity known to the ancients as a science 1 What is the date of electricity as a science 1 To what circumstance does galvanism owe its origin 1 ELECTRICITY. 49 lake soup made of the flesh of frogs, as the most delicate nti trnrient. One of these animals, ready skinned, happened to lie on a table in the professor's laboratory, near which stood an electrical machine, with which a pupil was making experiments. While the machine was in action, the pupil chanced to touch one of the legs of the frog with a knife which he held in his»hand, when suddenly the dead animal, was thrown into violent convulsions. This singular circumstance excited the attention of the sick lady, who was present, and it was communicated to her husband, who was out of the room at the time. Galvani immediately repeated the experiment, and soon found that the convulsions took place only when a spark was drawn from the electrical machine, the knife at the same time touching the nerve of the frog. He also ascertained from further investigations, that the same contractions were excited without the agency of an electrical machine, provided he employed two metals, such as zinc and silver, one of which was made to touch the nerve, while the other touched the muscle of the frog. [See Gtdvanism.] It is from such a beginning that the now important science of Galvanism had its origin. Electricity, as an agent* is considered as an exceedingly subtle fluid, so light as not to affect the most delicate balances —moving with immeasurable velocity, and pervading all substances. It is therefore its effects on other bodies, only, or its phenomena, which it is in our power to examine. The simple facts on which the whole science of electricity is founded, may be stated in a few words. If a piece of glass, amber, or sealing wax, be rubbed with the dry hand, or with flannel, silk, or fur, and then held near 3mall light bodies, such as straws, hairs, or threads, these, bodies will fly towards the glass, amber, or wax, thus rubbed, and for a moment will adhere to them. The substances having this power of attraction, are called electrics, and the agency by which this power is exerted is called electricity. Some bodies, such as certain crystals, exert the same power when heated, and others become electric by pressure.' Although these are simple facts on Avhich the science is based, yet electricity exhibits a vast number of curious and What is said of electricity as an agent ? Is it in our power to examine electricity as a substance 1 How are we enabled to examine the properties of this agent? Describe the simple phenomena of electricity. Wiiat are electrics? What is electricity 7 By whul process besides friction, do some bodies become electric? 5 50 ELECTRICITY. Fig. 17. interesting phenomena, depending on the variety and kind of machinery, and the quantity of the electrical influence employed. When a piece of glass, or other electric, lias been rubbed, so as to attract other bodies, it is said to be excited, and it it is found that most substances 'are capable of this excitement when managed in a peculiar manner. The most common are, amber, glass, rosin, sul- phur, wax, and the fur of animals. I When an excited electric is presented towards a small ball, made of pith, or cork, and suspended by a string - , Fig. 17, the ball is attracted to the electric, and adheres to it for a moment. And if two such balls be suspended so as to touch each other, and the excited Fig. is. electric be made to touch one of them, ; the ,1 mi • :. .l j r .i . • ." other will instantly recede from the one so touched, that is, they will mutually repel each other,!and remain for a short time in the position shown by Fig. 18. If while they are in this position, one of them be touched with the finger, or a piece of metal, :they will again instantly attract each other, and come together, and if suspended apart, will forcibly approach each other, as represented by Fig. 19. Fig. 19. In the explanation of these phenomena, we sup ipose that all bodies are pervaded with the electric fluid, but that when in equilibrium, l ike air and water, it produces no obvious effects, and that it is only when this equilibrium is disturbed, or when some bodies contain more of the fluid than others, that electrical effects can be produced. When an electric is rubbed with the hand, or other exciting substance, it receives a portion of the electric fluid from that substance, consequently the electric, then, has a greater portion of electricity than is natural, while the hand, or other substance, has less. When two bodies are in different When is an electric said to be excited! What are the mo?t common electrics 1 What effect does an excited electric produce on a suspended pith ball 1 What is the effect on two pith balls in contact! When the balls are thrown apart by repulsion, what effect is produced by touching one of them with the finger ? Explain these phenomena. Are all bodies supposed to be pervaded by the electrical fluid ! SnU pose an electric is rubbed by the hand, does it in consequence contain more or less electricity than before? Whence docs the electric obtain this additional quantity O; electricity 1 51 ELECTRICITY. ik'clrical states, that is, when one has more, or less than th° natural quantity, they attract each other. This is illustrated 6y Fig. 17. where the ball is represented as moving towards the excited electric. But when two bodies have each more or less than the natural quantity, they repel each other. This is illustrated by Fig. 18, where the repulsion is caused by the communication of an uncommon share of the fluid from the excited electric to one ball, and from this ball to the other, and thus the two balls have more than their ordinary quantity of electricity, and are in the same electrical state. On touching one of the balls with the finger, they again attract each other, because the finger deprives this ball of a part of its electricity, Avhile the other ball is not affected, and thus the two bails are thrown into different electrical states. This is illustrated by Fig. 19. To account for electrical phenomena, Dr. Franklin supposed, as above stated, that all terrestrial things had a natural quantity of that subtle fluid, but that its effects became apparent, only when a substance contained more or less than the natural quantity, which condition is effected by the friction of an electric, Thus, when a piece of glass is rubbed by the hand, the equilibrium is lost, the electrical fluid passing from the hand to the glass, so that now the hand contains less, and the glass more, than their ordinary quantities. These two states he called positive and negative, implying the presence and absence of the electrical fluid. If now a conductor of electricity, such as a piece of metal, be made to touch the positive bod}?-, or is brought near it, the accumulated fluid will leave this body and pass to the conductor, which wiL then contain more than its natural quantity of the fluid. But if the conductor be made to touch a negative body, then the conductor will impart a share of itis own natural quantity of the fluid to that body, and consequently will contain less than ordinary. Also, when one body, positively, and the other negatively electrified, are connected by a conducting substance, then the fluid rushes from the negative to the positive side, and the equilibrium is restored. When do bodies attract each other through the influence of electricity! When do bodies repel each other through this influence? When the balls are thrown apart by repulsion, why do they attract each other on touching one of them with the finger 7 How arc these phenomena accounted for on Dr. Franklin's i**eory ? What are the pci live and negative electrical states? 52 ELECTRICITY. This theory, originally invented by Dr. Franklin, will account satisfactorily for nearly every electrical phenomenon. There is, however, another theory, that of Dufay, which is still embraced by some writers. This theory supposes that there are two kinds of electricity, which are termed the vitreous and resinous, corresponding with the positive and negative of Franklin. This theory is founded on the fact, that when two pith balls, or other light bodies, near together, are touched by an excited piece of glass, or sealing wax, they repel each other. But if one ol the balls be touched by the glass, and the other by the wax, they will attract each other. Hence Dufay concluded that electricity consists of two distinct fluids, which exist together in all bodies: that these two fluids attract each other, but that they are separated by the excitation of an electric, and that when thus separated, and transferred to non-electrics, as to the pith balls, the mutual attraction of the two electricities, causes the balls to rush towards each other. The electricity corresponding with the positive of Franklin, is called vitreous, because it is obtained from glass; while the other is called resinous, because it is obtained from wax and resin. In respect to the merit of those two theories, we can only say here, that Franklin's is by far the most simple, and accounts equally well for nearly every electrical phenomenon. Somebodies permit the electrical fluid to pass through them without difficulty. These are called conductors. They are the metals, water, and other fluids, except the oils, steam, ice, and snow. The best conductors are gold, silver, platina, brass, and iron. The conductors are non-electrics, that is, they show no signs of excitement when rubbed, under common circumstances. The electrics are non-conductors, that is, they will not conduct the electric fluid from a negative to a positive substance, and when excited, this fluid accumulates on their surfaces, because they have not the power of co:i- Does Dr. Franklin's theory account for most of the phenomena observed I What do the positive and negative states imply I How does Dufay's theory differ from Franklin's! How do the vitreous and resinous electricities of Dufay correspond with tlie positive and negative of Franklin 7 Why is one kind of electricity called vitreous and the othet resinous 7 Which theory is said to be the most simple, and therefore to be preferred 1 What bodies permit electricity to pass through them without difficulty, and what are they called 7 What arc the best conductors? What is the difference between conductors and tion-conductors 7 ELECTRICITY. 53 ducting it away. A body is said to be insulated, when it is supported by a non-conductor. A man standing on a stool supported by glass legs, or standing on a cake of wax, is insulated. When one body, or system of bodies, is in the positive state, the other part, or system, being contiguous, is invariably in the negative state. If one end of a stick of sealing-wax, or glass rod, be positive, the other end will be negative, and if one side of a plate of glass be positive, the other side will be negative. (Sec Electricity in Nat. Philosophy.) Chemical Effects of Electricity. The chemical effects of electricity are most conspicuous in that form of this agency known under the name of Galvanism, but there are many instances in which common electricity produces important chemical changes. When powerful electrical discharges are passed through a glass tube containing pure water, by means of a gold or platina conductor, the water is decomposed, and resolved into its two elements, hydrogen and oxygen (see these articles,) which immediately assume the gaseous form. If afterwards the gaseous mixture thus obtained be submitted to electrical shocks, the re-union of these elements will again be effected, the hydrogen will be inflamed, while its combustion will be supported by the oxygen; the gaseous mixture will entirely disappear, and water will be formed. Fig. 20. The method of performing this experiment is shown by Fig. 20, where a represents a glass tube containing the two gases, and b, c, the two electrical conductors, the points of which approach so near, as to permit the fluid to pass through the gases, from one point ro the other. To explain the phenomena of the decomposition of the water by electrical agency, we have to suppose that the two gases are naturally in opposite states of electricity, but that Why does electricity accumulate, when a non-conductor is excited 7 When is a body said to be insulated'! When one side of a body is positive, in what electrical state will the other side be 1 What arc the effects of powerful electrical shocks on water 1 What are the effects of the same on a mixture of hydrogen and oxygen 7 Explain Fiff. 20, and show how the latter experiment is performed. What is it necessary to suppose, in order to explain the decomposition of water by electrical agency 7 5* 54 GALVANISM. vyhcn united to form water, the electricity is in a state of equi librium. When therefore Avater is submitted to the power of this agent, this equilibrium is destroyed, the negative gas or oxygen passing to the positive conductor, Avhile the hydrogen being in a positive state, passes to the negative conductor. Thus the fluid is decomposed, and assumes the gaseous form of its constituents. , ( The union of the two gases, and the consequent recompo 'sition of AArater, is simply in consequence of the heat eA'olveo by the electrical shock, as it passes through them. A degree of heat by any other means, sufficient to inflame the hydro gen, AA'ould produce the same effect. Precisely the same phenomena, are produced by gakanism, both in respect to the decomposition of Avater, and the re union of its elements. When sulphate of copper is submit ted to the action of a poAA'erful electrical machine, the salt is decomposed, and the metal is revived around the negative Avwe. Other metallic salts undergo the same decomposition. These effects arise from the different electrical states of the elements of Avhich the salts are composed, the positive element being attracted to the negative conductor, and the contrary. It will be seen directly, that the indentity of gabvanism and electricity is proved by many similar results. Galvanism. It has already been stated, that the science of galvanism had its origin from an accidental discovery made by a pupil of Galvani, an Italian professor. This subject was afterwards prosecuted by Galvani, Avith the most untiring ardor and with great success; and as his discoveries were made knoAvn, from time to time, to the scientific Avorld, philosophers in all parts of Europe vied with each other in repeating his experiments, in varying them in all possible Avays, and in making neAV experiments to account for the cause of the novel and surprising phenomena they observed. An account of these researches belong to the history of Galvanism, and cannot be included in this concise epitome of the science. How dose electricity act to recompose water from its two elements 1 What ! s said 1* respect to galvanism, as producing the same results as electricity 1 AVhen sulphate ol copper is submitted to the action of electricity, what phenomena ensue? How is tl.it effect on the salts accounted for? What 13 said of the interest excited among philoeo pliers by the discovery of galvanism ? 55 GALVANISM. II must suffice here, to state that the discoveries of Professor Volta of Pavia, have contributed more towards the progress and development of the true principles of this science, than the united researches of all his co-labourers. The discovery and invention of the Galvanic, or Voltaic pile, the entire merit of which belongs to the Professor of Pavia, removed all doubt respecting the identity of electricity and galvanism, and is said to have been the result of deep meditation and reasoning. Volta's discovery was published in 1800, and since that time several modifications, and many improvements in the mode of extricating the galvanic influence, have been made; they all, however, appear to be founded on his original invention. * To make this subject plain, it is necessary to state, that Galvani found that when the different parts of a recent animal, as the nerves and muscles, were made to touch each other, and then the opposite ends of this series made to communicate by means of two different metals, signs of electricity were always apparent. Hence Galvani concluded that the different parts of animals were in opposite states of electricity, and that the metals only served to restore the equilibrium. On the contrary, Volta maintained that the electrical excitement was owing to the contact of the two metals, and that the animal substances only served to conduct the fluid from the positive to the negative metal. And to show that this was the true theory of the phenomena, he proved by direct experiment, that when a piece of zinc, and a piece of silver, are placed in contact, and moistened, they are both excited, the zinc positively and the silver negatively. Thus, when a piece of silver, as a dollar, is placed on the tongue, and a piece of zinc under the tongue, and then their two edpes made to touch each other, electricity will pass from the zinc to the silver, of which the person will be sensible, not only by a peculiar metallic taste, but by the perception of a slight flash of light, particularly if the eyes be closed. The quantity of electricity evolved by two pieces of metal, oemcr exceedingly small, Volta tried the experiment of adding What philosopher next to Galvani, ha«i made the most successful researches on the aoture of galvanism? Who discovered the galvanic pile ? What is said concerning the identity of electricity and galvanism? From what experiment did Galvani conclude that the different parts of animals are in different electrical states? By what simple ex- Dtriment is it shown that when moistened zinc and silver touch each other, electricity passes from one to the other? 56 GALVANISM. nany pieces, arranging them in pairs, with a conductor be tvveen them, and found that the galvanic influence was increased in proportion to the number of plates thus combined. Such attempts led him finally to construct the Voltaic pile already mentioned. This pile consists of a multiplied number of galvanic series, terminating at one extremity by a positive, and at the other by a negative conductor. The conditions necessary for galvanic excitation are entirely different from those under which common electricity is obtained. We have seen that electricity is accumulated when an electric or non-conductor is rubbed with the dry hand, or with another non-conductor, as a piece of silk or fur. In ordinary galvanic excitation, suck substances as are called electrics are not concerned. These substances are all conductors of the electric fluid; one of them a simple conductor, the other two having each the additional power of different degrees of electrical, or gal vanic excitement. These three substances are usually zinc, water, and copper, and these, arranged in the order named, compose a simple galvanic circle. The water, which is mixed with a small quantity of acid, not only serves as a conductor of the galvanic fluid, from the positive to the negative metal, but also by acting slightly on the metals, is the efficient cause of the galvanic excitation. Fig. 21. This arrangement, together with the course of the electrical agent from one metal to the other, and through the water to the first metal again, will be understood by Fig. 21. Suppose c to be a plate of copper, and z a plate of zinc, touching each other at the top, and placed in a vessel of acidulated water. Then the action of the acid will produce an evolution of electri- city from both metals, that from the zinc being positive, and that from the copper negative. The electrical fluid will therefore pass from the zinc through the Avater to the copper, and from the copper by contact to the zinc, and so in a perpetual circuit in the direction of the arrows. What is the principle on which the Voltaic pile is constructed ? What is the difference between the substances used to collect electricity, and galvanism 1 Wtiai tnreo substances usually compose a simple galvanic circle 1 What is the use of the water and acid omployed in the extrication of galvanism? Explain Fig. 21, an;l show the course vf tKe galvanic fluid 57 GALVANISM. It is a multiplication of this principle, that is, by forming a series of simple galvanic circles, which composes the galvanic pile, or pile of Volta, already mentioned. This compound galvanic circle is constituted by a series of simple circles, so united, as to concentrate the influence of the whole at a given point. It may be constructed as follows: Provide three glass rods, say of two feet \n length each, and fix these in an angular direction from each other in a base of wood. Provide also circular plates of copper and zinc, two or three inches in diameter, about the eighth or tenth of an inch thick, and in number proportionate to the power of the intended pile. Next cut out the same number of circular pieces of card paper, or of Avoollen clcth, that there are pieces of either metal, but less in size. Having thus obtained the elements of the pile, its construction consists in placing first on the base, or board within the rods, a plate of copper, then on this a plate of zinc, and next, on the zinc, a piece of the paper, or cloth, dipped in salt water, or acidulated water, thus forming a single galvanic circle. The same arrangement is observed throughout the whole series, that is, copper, zinc, paper; copper, zinc, paper; except in the last circle,- or top of the pile, which ends with the zinc. Fig. 22, represents such a pile, a, b, being the glass rods and z, x, the pieces of wood, the upper piece having holes to admit the rods in order to make them secure. Fig. 22. Such a series, affords a constant stream of the galvanic influence, but is always most powerful when first constructed, or before the plates become oxidated. On this account, after having been some time in use, it re quires to be taken in pieces, the plates cleaned from rust, and then again reconstructed, when it regains its original energy. A pile composed of two dozen plates of each metal, will give a small shock, which, when taken by the hands, may be felt to the elbows. The mode of receiving the shock, is by wetting the hands, and then having placed one of them in IIcw is tlie pile of Volta constructed? After the frame is made, and the plates ot metal and paper prepared, how is the pile then constructed? When does the pile operate most powerfully ? How may the pile, after the plates have become oxidated, be mad" as powerful as at first 1 What is the mode of receiving the shock from the galvanic pile? 58 GALVANISM. contact with the zinc plate, which terminates one end of the pile, touch with the other hand, the copper plate which terminates the other end of the pile. Or these two plates may be touched with a wire, wound with a wet rag and held in the palm of each hand. When experiments are to be made by passing the galvanic influence through any substanc c, this is done by connecting a wire with each terminating plate : the two moveable ends of the wire being then brought near each other, and the substance placed between them, the fluid passes from the positive to the negative side, and so through the substance. These wires are called the poles of the Voltaic pile. Any number of these piles may be connected together by making a metallic communication from the last plate of the one, to the first plate of the other, always observing to preserve the order of succession from the zinc to the copper, and from the copper to the zinc. In this manner a gaivanic battery is constructed, the power of which will be proportionate to the number of plates employed. The galvanic fluid, it ought to have been observed, is extricated only on condition that one of the metals employed be more easily oxidated, or more readily dissolved in an acid, than the other. Any two metals will form an effective galvanic apparatus on this condition, and it is always found that the metal having the strongest affinity for oxygen is positive, while the other is negative. Thus, any metal, except that which has the least affinity for oxygen, of all, may form tne positive or negative side, by having another metal more or less oxidable than itself, placed in contact with it. Copper, in contact with zinc, is negative, because zinc is most easily dissolved, or has the strongest affinity for oxygen of the two. But when copper is in contact with silver, it becomes positive, while the silver is negative; and for the same reason silver becomes positive when in contact with gold, or platina. The greatest effect is produced, other circumstances being equal, when two metals are placed together, one having the greatest, and the other the least affinity for oxygen, as zinc and platina. When it is required to pass the electricity through a substance, how is this donel What are the wires or conductors called ? How is a galvanic battery constructed 1 How must the metals differ, in respect to their affinity for oxygen, in order to evolve In what electrical state is the metal which has the strongest affinity for oxygen 1 What will be the state of copper when in contact with zinc 1 What will be the state of copper when in contact with silver or gold 7 What metals will produce the greatest effect on this account 1 59 GALVANISM. Since the invention of Volta. a great variety of different Methods have been devised, in order to extricate the galvanic ftttid with greater convenience, or with greater power; and also to modify its action for different purposes. Among these inventions, the galvanic trough is one of the most convenient and common in this country, though by far less powerful in proportion to the surface of the metal employed, than several others. In this arrangement, the plates of copper and zinc are placed with their flat surfaces in contact, and are, soldered together on'the edges. These plates are then fixed in'grooves, cut in the opposite sides of a long narrow mahogany box, leaving between them narrow intervals. The box of course is open on one side, the ends and bottom being made water '.ight, and also the cells between the plates, by cement. In fixing the plates, it is obvious that all the zinc surfaces must be on one side, or face in the same direction, and all the cop- per surfaces on the other side. Fig. 23. Fig. 23 represents such a trough, furnished with conductors of brass wire, iv, u\ which are fastened to the two end plates, or merely dipped into the cells. The latter is the most convenient method, on account of its allowing the operator to graduate the shock at pleasure, by including between the poles a greater or less number of the plates. The conductors pass through the glass tubes, a, a, so as to allow the operator to handle them without receiving the shock himself, and then pass to a glass plate on which the subject of experiment is laid. When this trough is to be used, the cells between the plates are filled Avith water containing in solution a quantity of common salt, or made slightly sour by muriatic, sulphuric, or nitric acid. If the Avater is made Avarm, the action will be much increased. Care must be taken that too much acid be not used, for if the action on the zinc plates is such as to AVhat method of extricating the galvanic power is said to lie a mong the most convenient 7 Describe the construction of the galvanic trough. In what order must the plates of zinc and copper be placed 7 Which is said to be most convenient, to connect the poles to the plates, or merely to dip them into the cells 7 AVhat are the nses of the glass tubes a a 7 When the trough is to be used, with what are tne cells Slled 7 60 GALVANISM. occasion ihe emission of bubbles of hydrogen, ihe galvanic action ceases almost entirely. After the trough is filled with the water, its edges, and also those of the plates, must be wiped dry, and care must be taken that it does not leak, otherwise the electric fluid will be conducted away by the water. Want of attention to these circumstances, will sometimes occasion an entire failure of n galvanic experiment. Another mode of arranging the galvanic apparatus, is by means of a row of glasses, each containing solution of common salt, or a dilute acid. In each glass is placed a plate of copper and another of zinc, not in contact, but so connected by slips of metal, or by wires, that the zinc in one cup shall be connected with the copper of the next cup; the zinc in the second cup with the copper of the third, and the copper of the third with the zinc of the fourth, and so on through the series; except the terminating cups, which contain only a single plate each, one of copper and the other of zinc. This arrangement will be understood by Fig. 24, where Fig. 24. a, a, a, are the glasses, z the zinc, x the copper, and w the wires by whicn they are connected The advantage of this method consists in the exposure of the two sides of the plates to the action of the acid ; Avhile by soldering the plates, as in the construction of the trough just described, one of the surfaces of each metal is protected from the acid, and contributes nothing to the effect. But the bulk of this apparatus, and the danger of breaking the glasses in case of transportation, prevents its general adoption. A convenient and more compendious modification of this principle has therefore been contrived, and is called the trough battery. In this arrangement, the zinc and copper plates are united in pairs, as just described, by means of slips of metal, which are soldered to each other. Twelve pairs of these plates are then fastened to a piece of baked wood, being placed at such a distance apart as to fit the cells of a trough which contains the water and acid. The trough may be made of baked mahogany, with partitions of glass, or What caution is necessary In respect to the quantity of acid, and also in respect to dry jig the edges of the trough 1 Describe the mode of extricating galvanism by means ol glass cups. Why is the apparatus made with cups objectionable 7 In what is cai/eu the trough battery, how are the plates united ? 61 GALVANISM. what is better, the whole may be made of earthen, or Wedgewood's ware. When this battery is to be used, the cells in the trough aic partly filled with water, containing an acid or salt in solution, and then the plates being connected with the slip of wood, are all let down into the cells at the same instant, by means of a pulley, each cell containing one plate of zinc and another of copper. Where great power is wanted, any number of these troughs may be connected together, by passing a slip of copper from the positive end of one, to the negative end of the other trough. For the use of a laboratory, this is by far the most convenient, as well as the most powerful means of ob- Lnining large quantities of the galvanic fluid, yet devised. When an experiment is finished, the operator, in a few minutes, can raise all the plates from their troughs by means of pullies, and thus they are suspended, ready to be let down again when wanted. The power also, with the same extent of surface, is double that of the galvanic trough, where the plates are soldered together, since with the present method, the entire surface of each metal is exposed to the action 01 the acid. The plates can likewise be more readily cleaned, and the whole apparatus more easily kept in repair. The Galvanic Battery of the Royal Institution of Great Britain, is constructed on the above plan. It is of immense power, consisting of 200 troughs of Wedgewood's ware, each containing ten cells, and receiving ten double plates of copper and zinc, each plate containing a surface of 32 square inches. The whole number of double plates is therefore 2000, and the whole metallic surface exposed to electrical excitation at the same instant, is equal to 128,000 square inches. It was by means of this apparatus that Sir Humphrey Davy performed his brilliant experiments, and succeeded in decomposing the alkalies, and showing their metallic bases. (See potash and soda.) Chemical effects of Galvanism. It is a singular, and, per- In the trough battery, how are the plates of metal brought into contact with the ac'ul 1 What are said to be the advantages of this method 1 Why is this battery more powerful than the galvanic trough in which the plates are soldered together 1 What peculioi conveniences has this arrangement 7 What number of double plates does the battery ol die Royal Institution consist of? What important discoveries did Sir II. Davy make by means of this battery ? G 62 GALVANISM. Gaps, unaccountable fact, that the extent of the continuous surface of the metals, from which the galvanic fluid is obtained, has an influence over its effects, when employed for various purposes. We should suppose, both from reasoning and analogy, that the amount of galvanic action would, in every case, be proportioned to the number of square inches of metallic surface, and that it could make no difference in the result, whether the individual pieces of metal were large or small. But experience shows that this is not the case. The effect of a battery composed of large plates, and one o. small plates of the same extent of surface, is quite different. That composed of the large plates having the most intense chemical, or heating power, while that consisting of small ones has the greatest effect on the animal system. Thus, a man can bear with little inconvenience the shock from Mr. Children's battery, composed of plates six feet long and two feet and a half wide; while he would be stunned, or per haps killed, by the shock from the same amount of surface, were it divided so as to proceed from plates of only two 01 three inches in diameter. And yet Mr. Children's battery gives the most intensely brilliant caloric effects, while the caloric agency of the small plates is comparatively slight and insignificant. The decomposing chemical effects of galvanism have been much more extensively employed than those of common electricity. Indeed, the decomposing power of electricity was little known before the brilliant discoveries of Sir H. Davy, by means of galvanism; but since that time, Dr. Wollaston has shown that most, if not all of the chemical effects of the galvanic battery, may be produced by electricity. The decomposition of water by means of electricity, was effected by the Dutch chemists long before the discovery oi galvanism. A description of the method of doing this has already been given, while treating of electricity. This seems to have been the most important chemical decomposition effected by electricity, before the discoveries of Galvani and Volta. Since that period, the science of chemistry has owed to Is there any difference in the effect of a battery composed of large or small plates, whes the extent of their surfaces is the same 1 What is the difference between the effects ol large and small plates 1 Will electricity produce the same chemical effects as galvanism * Was the decomposition of water effected by electricity before the discovery of galva.'iisml Of what use has galvanism been to cherr' try 1 63 GALVANISM. .hat of galvanism some of the most magnificent and important discoveries ever made in that science, viz. the decomposition of the alkalies, and as a consequence of this, other discoveries of great interest and value. One of the most extraordinary facts belonging to the agency of galvanism, is the discovery that the elements of decomposed bodies follow an invariable law in respect to the electrical sides on which they arrange themselves. Thus, in decomposing water, or other compounds containing its elements, the hydrogen escapes at the negative pole, and the oxygen at the positive. In the decomposition of the salts (see salts) and other compounds, this law is in every instance observed, the same kind of element being always disengaged at the same pole of the battery. When a compound consists of two gaseous elements, they may be readily separated, and each gas obtained separate by placing the compound in a bent tube, and then exposing it to the galvanic action. This simple arrangement is represented by Fig. 25 Fig. 25. Il consists of a glass tube bent as in the figure, a small orifice being ground at the angle so as to let in the water, or instead of this, two tubes may be used with their lower ends placed in contact The tubes being filled with water, and their lower ends placed in a dish of the same fluid, the two platina wires proceeding from the two sides of the battery are passed through corks in the upper ends of the tubes, and pushed down, so as to come within about the eighth of an inch of each other. Care must be taken that the adjustment be such as to allow the gases as they ascend to come within the orifices of the tubes. The battery being now set in action, small bubbles of gas vvill be seen to arise from the ends of the wires, but in different quantities. The tube from the negative wire will soon be filled with hydrogen gas, while the other in the same time will be only half filled with oxygen. This circumstance arises from the fact, that in forming water, these two In the decomposition of water by galvanism, at which pole of the battery does hydro eon always escape 1 Describe the method of decomposing water by galvanism, and ot retaining the two gases in a separate state. In perfuming this experiment, why is tho •ube on the negative side first filled with gas J 64 GALVANISM. gases combine in the proportion of two volumes of hydrogen to one of oxygen. Of course, therefore, when water is decomposed, the volume of oxygen is only half that of hydrogen. In this experiment, the poles of the battery must be of platina, or gold, otherwise, if they are made of iron, or other oxidable metal, the oxygen combines with the metal instead of being extricated and rising up the tube. When neutral salts, whether alkaline, metallic, or earthy, such as common salt, blue vitrol, or alum, are exposed to the action of a powerful battery, the same law is observed; the acid, which contains the oxygen, goes to the positive wire, while the bases being alkalies, metals, or earths, are transferred with the hydrogen (for these salts always contain water) to the negative wire. But the most surprising effects of the power of this principle is exhibited when the compound is placed in cups connected with the two sides of the battery, and the two constituents of the compound are transferred from one cup to the other. If the solution of any saline compound, such as Glauber's salt, be made in water, and placed in two cups, one connected with the positive, and the other with the negative side of the battery, then, by making a communication between the cups, by means of some moistened asbestos, or cotton, and setting the battery in action, the two constituents of the salt will be transferred from one cup to the other. Fig. 26. Fig. 26 will show the situation Fig. 26 will show the situation 'of the cups, the asbestos, and the galvanic poles for this experiment. Both cups contain a solution oi Glauber's salt. This salt is composed of sulphuric acid, soda, and water. The cup P is connected to the positive side of the battery, by a wire, passing into the fluid, and the cup N, with the negative side, in the same manner. The cups are connected by the moistened asbestos passing from the fluid of one to that of the other. When this arrangement is completed, and the battery has been some time in action, it will be found that the water in the positive In decomposing the sails, what law is observed in respect to the poles, at which theii elements are extricated 1 Explain Fig. 20, and describe how the elements of the salt are transferred from one cup to the other. In which cup is the acid, and in which is tho alkali found < 65 GALVANISM cup will have an acid taste, while that :n the negative cup will have an dkaline taste; and if the action be continued a sufficient time, all the acid contained in the salt will be found in one cup, and all the soda in the other. Nor does it appear to make any difference in the result, at what part of the fluid circuit the salt to be decomposed ia placed This is proved by placing three cups m line, and connecting them together by moistened asbestos, as shown by Fig. 27. If the Glauber's salt, or any other saline compound be put Fig. 27. into the middle cup, and water into the others, and the two galvanic poles be connected with the other cups, P being the positive, and N the negative side, then all the acid will be transferred to the positive, and all the alkali to the negative cup, while the water in the middle cup will remain nearly in a state of purity. If the two outer cups be filled with an infusion of red cabbage, instead of simple water, the operator can see the progress of his experiment, since the contents of one cup will be turned red by the acid, and the contents of the other green by the alkali. A phenomenon of a still more extraordinary kind occurred to Sir H. Davy, during his experiments on this subject. For it was proved that the galvanic action was capable of sus pending the laws of affinity, so that an acid might be conveyed through an alkaline substance, or an alkali through an acid, without any combination taking place between them, or either might be passed through a cup of infusion of cabbage, without changing its colour. The three cups being arranged as in the last experiment, and connected iogether by films of moistened cotton, or asbestos, there was put into the negative cup, N, a solution of sulphate of soda, and into the other two cups, Describe Fig. 27, and show into which cup the salt is placed, and into which its different elements are transferred by the galvanic action. What is the advantage of filling the iwo outside cups with infusion of red cabbage 1 \V*hat extraordinary phenomenon is observed in respect to the suspension of the laws of affinity by galvanic action i Desciibe the experiment by which it was found that an acia oran alkali was made to pass through a cup of infusion of cabbage without changing its colour 6* 66 GALVANISM. an infusion of red cabbage in water ; this infusion being one of the most delicate tests of the presence of an acid or an alkali. After these cups, so arranged, had been for a short time placed in the galvanic circuit, the infusion in the positive cup became red, and afterwards strongly acid, while that in the middle cup continued of the same colour as at first. Thus, as the salt was decomposed, its acid passed through the middle cup without mixing in the least with the water it contained, otherwise ts colour would have been changed. On reversing the connections, with the poles of the battery, the alkali of the salt was transferred to the opposite cup, the solution of which it tinged green, without in the least affecting the colour of that in the middle cup. On placing an alkaline solution in the middle cup, the acid was transferred through it, without combination ; and when an acid Avas placed in that cup, an alkali passed through it in like manner. To account for these singular phenomena, Sir Humphrey Davy supposed that the elements of compound bodies were in different and opposite states of electricity, but that durinp their chemical union, an equilibrium existed in these electri cal states. This theory we have already mentioned, in ac counting for the decomposition of water by common electri city. .But Sir H. Davy believed it to extend in general t< all chemical compounds. To explain how the elements o bodies may be in this state, he supposed that each element if naturally possessed with a portion of electricity, whether il is in a state of combination or not; and that the elements, in this respect, naturally divide themselves into two classes, one of which is endowed with positive, and the other with negative electricity. In proof of this, it is found as an experimental fact, that oxygen, chlorine, iodine, (see the latter article,) and acids in general, are naturally negative, while hydrogen, the metals, and the metallic oxides, and the alkalies, are naturally positive. Thus it appears that bodies having the strongest attraction or chemical affinity for each other, arc naturally in opposite states of electricity, and that the supporters of com- What are the other proofs galvanic action suspends the action of affinity t How does Sir H. Davy account for these phenomenal In what state of electricity are oxygen, chlorine, iodine, and the acids generally t In what state arc hydrogen and the metals 1 Are bodies having the strongest chemical affinity for each other, ir. ti * same 01 n opposite states of electricity 1 67 GALVANISM. bustion, oxygen, chlorine, and iodine, are all negatively electrified. From such considerations, Sir H. Davy not only accounts lor the chemical agency of the galvanic fluid, but also for that force called affinity, or chemical attraction, which impels bodies of different kinds to unite, and form compounds. Thus, oxygen being naturally negative, and hydrogen naturally positive, they unite with a force or energy proportional to the difference of their electrical states. The decomposing force of the galvanic battery may readily be accounted for on the same principle ; for if water be presented to any substance of a higher state of positive electricity than its hydrogen, then a decomposition would ensue, because the oxygen would leave the hydrogen, and attach itself to that substance for which it had the strongest attraction. The voltaic battery produces this effect, by offering to the two constituents of water stronger opposite electrical energies than these two substances have for each other. Thus, supposing the electrical force of hydrogen for oxygen to be equal to 3, and that of oxygen to hydrogen to be equal to 3, then they would combine with a force equal to 6. But if we suppose the galvanic battery to offer to the oxygen a positive electrical energy equal to 4, and at the same time to the hydrogen a negative energy equal to 4, then it is obvious that their combining force would be overcome, and that the oxygen w«uld fly to the positive, and the hydrogen to the negative poles of the battery, and thus that compound would be reduced to its original elements; and we find that this is exactly what happens as a fact, when the water is exposed to the galvanic circle. This, it must be acknowledged, is one of the most beautiful theories ever invented, and at the same time agrees with the phenomena observed in most energetic chemical changes. But there are still some facts for which it does not satisfactorily account; nor is it absolutely certain, that in any case, chemical attraction is owing to the different electrical states of the combining bodies, so that in the present state of knowledge, this theory must be taken only as a probable and high ¦ !y ingenious hypothesis. How is the decomposing force of galvanism accounted for 1 What is said in rettion to the truth, or probability, of the electrical theory advanced by Sir II. Davy 1 it certain that in any case chemical attraction is caused by opposite eicctrics H» «s? 68 GALVANISM Healing effects of Galvanism. One of the effects of galvj> nic action is the evolution of heat; and where the action is strong, it is accompanied with light, but not otherwise. There is a remarkable difference between the conditions necessary to the evolution of heat by galvanic action, and by common electricity. In common electricity, there is no production of heat, where the fluid moves through a perfect conductor, and Avithout obstruction. When it moves along a rod of metal, no sensible heat, or light, is evolved, unless the conductor is too small for the quantity. But in its passage through non-conducting substances, as air, or dry Avood, both heat and light are a consequence. But when gah'anism passes through a perfect conductor, and the circuit remains entire, and Avhen no light is evolved, there is still an elevation of temperature caused by its passage. This is readily proved, by making the tAvo poles of the battery meet in a vessel of Avater containing a thermometer, w r hen it will be found that the temperature of the water will soon be raised, and if the experiment be continued, the fluid Avill boil by the heat evolved. If the battery consists of an extensive series of electrical circuits, very powerful calorific effects are produced by the passage of the fluid through metallic Avires. Iron Avire is melted and falls down in globules, and steel Avire burns, with corruscations too brilliant for the unprotected eye. The heating effects of galvanism seem to deprihd on the conducting power of the metal employed, the heat being in an inverse ratio to the poAver of the conductor. This is curiously illustrated by passing the fluid through a wire, or chain, composed of alternate portions, or links, of platina and silver, soldered together, when it will be found that the silver will scarcely be warmed, Avhile the platina will be intensely ignited. It appears from some experiments made Avith Mr. Children's great battery, that the heat excited by Voltaic action is more intense than that produced by any other means. What is said of the heating effects of galvanism? What are the different conditions under which heat and light is evolved by electricity and galvanism? When galvanism is passed through a perfect conductor, what effect is produced ? What is the effect when t is passed through water ? How are metallic wires affected by powerful galvanic action ? When galvanism is passed through a chain, the links of which are alternately silver and platina, what is the effect on oach metal J What is said of the power of Mr Children' oaltery ? 69 ATTRACTION. Many substances were fused by it, which were exposed to the best wind furnaces without any impression. A piece of platina wire, one thirtieth of an inch in diameter, and eighteen inches long, became instantly red, then white hot, with a brilliancy insupportable to the eyes, and in a few se conds was fused into globules. Still this battery had little effect on water, or on the human frame, the shock being felt no higher than the elbows. But still more brilliant effects were produced by the battery of the Royal Institution, when pieces of charcoal were attached to its poles and then brought near each other. This battery, when the cells were filled with a mixture of GO parts of water, and one part of nitric, and one of sulphuric acid, afforded the most splendid and impressive results. When pieces of charcoal about one inch long and the sixth of an inch in diameter, were placed in the circuit, and made to approach each other, a bright spark was seen to issue from one to the other, and in a moment the charcoal became ignited to whiteness. Then by widening the space between the charcoal points, a constant discharge continued when they were four inches apart, affording a most brilliant ascending arch of light, broad in the middle, and terminating in points i t the charcoal, resembling in shape, two cones, applied base Tig. 28. to base. The shape of this brilliant phenomenon is represented at Fig. 28, where a and b are the poles of the battery with pieces of char- coal attached to them, and between these the ascending arch of light. When any substance Avas held in this arch, it became instantly ignited; platina, one of the most infusible of all the metals, melted in it as readily as Avax in a candle; quartz, sapphire, magnesia, and lime, all entered into fusion; and points of diamond and plumbago, rapidly disappeared, seeming to evaporate Avith the heat. Attraction. By attraction is meant that property in bodies Avhich gives What effect does this battery have on the human frame 1 AVhat are the effects when pieces of charcoal are placed near each other, in a powerful galvanic circuit? Tdescribe p ig. 28. What substances were fusod by the battery of the Royal Institution 1 AVhat is »he fourth imponderable agent belonging to our list! 70 ATTRACTION. them a tendency to approach each other, whether they exist in atoms, or masses. Attraction has received various names, according to the circumstances .under which it is observed to act. Thus, that kind of attraction which extends to all kmds and quantities of matter, and to all distances, is called ath action of gravitation. This attraction extends reciprocally from one planet to another, and from all the planets to the fixed stars, and is the cause of the orbicular motion of the heavenly orbs. It also extends to all terrestrial masses o.' matter, and is the cause of their weight, or tendency to approach the centre of the earth. » The force of gravitation is directly as the quantity of matter, and inversely as the square of the distance. The quantity of matter being given, and the attracting force at a certain distance, say four feet, being known, then this force will increase, or diminish, as the square of the distance. Thus, if one body attracts another, at the distance of two feet, with a force of 36 pounds, then at the distance of four feet, its force of attraction will be only i as much, or 9 lbs., and so in this ratio whatever the distance may be. (See Natural Philo sophy.) By attraction of cohesion, or aggregation, is meant that force which tends to preserve bodies in masses by acting on the particles of which they are composed. This attraction is supposed to act only at insensible distances, as when the atoms of bodies touch each other, and only when the particles of matter are of the same kind. Chemical Attraction is that power which forces the particle* of bodies of different kinds to combine and form a compotind. This force is also called affinity, because this kind of union takes place only between particular substances. Like the attraction of cohesion, it acts only at insensible distances, that is, the particles of bodies must be brought into the immediate vicinity of each other before they will combine. But it differs from cohesive attraction in taking place only between heterogeneous atoms, or among particles of different kinds ol matter. Several other kinds of attraction are described, (See What Is meant by attraction 7 What is attraction of gravitation 7 What are the raws of attractive force 7 Suppose a body is attracted with a force of 3(5 pounds, at the distance of two feet, wha' wi.l the force be at the distance of four feet? What is meant by attraction of cohesion 7 What is chemical attraction 7 How do cohesive and chemicai attractions differ? In what respect is a knowledge of chemical attraction important? 71 ATTRACTION. Natural Philosophy,) but it is chemical attraction, or affinity, which must more immediately occupy our attention here. Affinity. Chemical attraction is a subject of the highest importance in the study of chemistry, since a knowledge of the whole science includes little more than an acquaintance with the laws and effects of affinity, that is, of chemical attraction and repulsion. We have already noticed that this science is founded on experiment, and from deductions arising from facts thus discovered. Now chemical experiments are only the means 01 discovering chemical affinities, and a knowledge of these affinities are the facts on Avhich the whole science is founded. By experiment we know that some bodies have an affinity to each other; that is, we know that on presenting them to each other under certain circumstances, they will combine, and form a third substance, which differs from either of the first. We know also by the same means, that other substances, when presented together in the same manner, will repel each other; that is, they will not combine, nor can they : e made to unite so as to form a third substance. This kind of knowledge it is impossible for man to acquire without actual experiment; for by no process of reasoning could he ever determine before hand, whether two bodief; would attract or repel each other, any more than he could tell what they were composed of by mere inspection. We know, for instance, that when we mix acid and water, the two liquids unite, or blend together; now, by reasoning from analogy, we should have the same grounds for believing diat any other fluid would unite with water, that we had for believing that an acid would, and therefore that oil and water would combine, as well as acid and water. But experiment shows, that on this subject, neither reason nor analogy lends us the least aid, for, on mixing the oil and water, Ave find that they mutually repel each other, and though blended together by force, they again separate as soon as the force is removed. It is then only by actual experiment that we can decide In what docs a knowledge of the science of chemistry chiefly consist? What ars the tacts on which the science of chemistry is founded 7 How is it known that some Qodies attract, while others repel each other 7 Is it possible to gain any knowledge o. chemistry, except by experiment 7 What reason would there be to svppose, without experiment, that oil and water would not combine? What is the first ecuuVKH! necessary to eflect chemical union? 72 AFFINITY. whether two bodies have an affinity for each other, and con sequently whether they are capable of forming a chemical compound, or not. There are several circumstances which affect the results of chemical affinity, or conditions on which its action depends, which will be mentioned in their turn. There are also several kinds of affinity, which have received different names, depending on the conditions under which its action takes place. These appellations and conditions will also claim at tention as they occur. With a few exceptions, the first condition necessary to effect chemical combination is, that one or both the bodies should be in a fluid state, since however strong the affinity of two bodies may be to each other, their particles cannot unite unless they are free to move. Hence, to effect the combination of solids, their cohesion must first be destroyed either by solution in a fluid, or by means of heat. The acids and alkalies have a strong affinity for each other, but on mixing them, even when in the finest poAvder, no chemical combination ensues, because in all chemical compounds the union takes place betAvecn theatoms of the combining substances. But on pouring a quantity of water upon such a mixture, chemical action instantly ensues, and a third substance, differing entirely from the alkali or the acid, is the result of the combination. This compound is called a salt. In like manner, if zinc and copper be reduced to the fines) poAvder, and mixed ever so intimately by mechanical force there will still be no intimate union betA\ r een their particles But if heat be applied so as to reduce them to a fluid state they combine Avith considerable energy, and form a yelloAV alloy, called brass, Avhich differs greatly from the zinc 01 copper of Avhich it is formed. Simple Affinity. The most simple cases of affinity art afforded by the mixture of tAvo substances Avhich have the poAver of combining Avith each other, in any proportion. Water and sulphuric acid, or Avater and alcohol, form such combinations. What are termed neutral salts, Avhich are formed by the union of a pure acid, and a pure alkali, are instances of the same kind, only that they do not combine in all proportions. In a great variety of instances, after two AVhat is necessary, in order to eflect the chemical combination of solids 1 Why will not solids combine as well as fluids 1 In what manner may copper and asinc be made to combine! What are the most simple cases of affinity 1 Give an illustration of thia affinity. AFFINITY. substances have combined, when mixed alone, or without the admixture of any other substance, this first union may be destroyed by the intervention of another, or a third sub stance, having a stronger attraction for one of these substances than they have for each other. This forms an instance of what has been termed by Bergman, Elective Affinity. Single Elective Affinity, is exercised when one composi tion is destroyed, and at the same time another is formed. There are many familiar examples of this kind of decomposition, some of which we witness almost every day. Camphor dissolved in alcohol or in strong spirits, makes a transparent solution ; but if water be poured into this solution, it instantly becomes turbid, and the camphor separates from its connection with the alcohol, and rises to the surface of the fluid. This separation takes place because the alcohol has a 'stronger affinity for the water than for the camphor, and the turbidness is caused by the insolubility of the camphor in water, in consequence of which it takes the solid form. Soap is composed of oil, an alkali, and water. The oil and water have no affinity for each other, but the alkali has a strong affinity both for the oil and water, and consequently the three substances unite and form a compound. But if an acid be mixed with a solution of soap, the compound is decomposed, for the alkali has a stronger attraction for the acid than for the oil and water, and consequently the oil is rejected and rises to the surface, while the acid and the alkali form a new compound. This affinity is called elective, because when one substance is mixed with several others it seems to manifest a choice between them, and elects one with which it unites, to the rejection of the others. It is most probable that every substance has an affinity for many other substances. We know indeed that this is true in a great variety of instances, since experiment shows that one substance will form several compounds with other substances, in succession, and that these compounds may in succession What is single elective affinity? Give an example of the exercise of this kind of affinity. When water is poured into a solution of camphor in spirit, why is the camphor separated ? What is the composition of soap ? When an acid is mixed with a solution of soap why does the oil rise to the surface ? Why is this kind v» ere the Avater soon becomes saturated, and Avill dissolve no more; but if the water be agitated, the whole Avill soon dissolve. It is found, also, that metals differing Avidely in their specific gravities, when melted together, do not mix eq .tally, unless they are stirred, because the heavier metal settles to the bottom. Changes produced by Chemical Combinations. By chemical combination is meant a union between two or more substances of different kinds, so intimate that they can not again be separated by mechanical means. Thus, if clay or chalk and water be mixed, the mixture Avill for a time be turbid, or opake, but if suffered to stand for a day or tAvo, the clay or chalk will settle to the bottom of the vessel, and the water above will become transparent. But if water be mixed with an acid, or with a salt, or Avi'.h sugar, the union becomes permanent, nor will rest, or filtration, or any other mechanical means, separate either of these ingredients from the waer. Hence, the distinction between mechanical mixture and How docs caloric act to separate a volatile from a fixed principle 1 How is the decomposition of a fluid effected by heat 1 What is said of gravity in opposing chemical union 1 How does common salt, in water, illustrate this principle 1 What is said of the combination of metals in this respect 1 What is meant by chemical combination I What is the distinction between mechanical mixture and chemical union t Why will not chalk and water combine permanently 1 When water and sugar are mixed, why does not the sugar settle to the bottom of the vessel 1 80 CHEMICAL CHANCES. chemical union. In the first, no affinity between the sub stances exists, and therefore no union takes place, and th* chalk or clay falls to the bottom of the vessel. In the second, there is a combination between the particles of which the substances are composed, owing to the affinity existing between them, and hence they are not separated, except by a stronger force than that of the existing affinity. The changes that accompany chemical action, are in some proportion to its intensity. In the instances above named, where water is mixed with a small quantity of acid or salt this action is feeble, and the sensible changes produced in considerable, being only a slightly acidulous, or saline taste, given to the water. But in cases where the chemical action is intense, the changes produced in the combining substances are often great in proportion. Thus, when the two gases, oxygen and hydrogen, are burned together, their combination is attended with most intense chemical action, by which the highest degrees of heat are evolved, and at the same time the change produced is no less than the condensation of two elastic gases into the fluid water. Many substances which are highly corrosive, in a sepa rate state, become mild, and lose all their acrid qualities by combination with each other. Sulphuric acid and potash, for example, are highly caustic substances. They both act with great energy on animal and vegetable bodies, producing decomposition and total destruction of texture. The acid turns the blue colors of vegetables to red, and the alkali turns these colors to green. But on mixing these substances together, they entirely destroy the caustic qualities of each other, and there results a solid compound, called sulphate oj potash, which is mild to the taste, and neither acts on animal or vegetable bodies, nor changes the colors of the latter. This is called a neutral salt, because the substances of which it is composed, thus neutralize the active properties of each other. When the opposing properties of chemical agents are thus destroyed by combination, they are said to saturate each other, and it is found that the acrid and caustic qualities of all Is there any proportion between the intensity of chemical action and the changes pro tluced thereby 1 What illustrations of this law are given 1 What effect does combination sometimes have on the corrosive properties of bodies 1 Give an illustration of this effect 1 What is the composition of sulphate of potash 1 What is a neutral salt 1 When are substances said to saturate each other 1 81 AFFINITY. the acids and akalies are weakened in proportion as one is added to the other, until the point of saturation is attained, when the compound becomes neutral, and is not affected by a further addition of the acid or alkali, Avhich forms a part of its composition. A change of bulk is also in many instances the result of chemical union, so that the two bodies after combination, do not occupy the same space as before. Thus, when a pint of sulphuric acid is mixed with a pint of water, the chemical action is so great as to raise the thermometer above the boiling point, and the resulting compound will not measure two pints as before the mixture, but considerably less. When zinc and copper are fused together, the resulting alloy has a specific gravity greater than the medium specific gravities of the two metals, showing that their bulks are diminished by the union. The same happens when alcohol and water are mixed; and in general it is found that the rei/ulting body after chemical combination has a greater specific gravity than the mean of its components. Another change often produced by the exercise of affinity, :s that of colour. The alloys of any two metals do not exhibit the medium of their two colours. Thus the white metal, zinc, and the reel one, copper, when melted together, form the yellow compound, brass. The colours of the metallic ox ides differ according to the quantities of oxygen they contain. The black oxide of mercury contains 200 parts of the metal and 8 parts of oxygen, while the same quantity of the metal combined with 1G parts of oxygen, forms the red, oxide of mercury. We have already had occasion to notice, that blue. vegetable colours are changed to red by acids, and to green Dy alkalies ; and in addition to this, Ave may state generally, that all vegetable colours are changed, more or less, by the application of these agents. There is still another change, Avhich is the effect of chemical affinity, and is often highly important; this is the change of form. Of this change chemistry exhibits a great variety of examples, many of Avhich are highly curious and interest- What is said of change of bulk as a result of chemical action 7 Suppose a quantity o* water and sulphuric acid are mixed, will they occupy the same btdk that they did before he mixture 7 Will the bulk be greater or less than before 7 In chemical combinations, s the resulting body more or less dense than the medium density of its components 7 What is said of the change of colour produced by chemical combinations 7 Is change ot *orm ever effected by chemical combinations ? 82 Ai'FINll Y. mg. Thus, if a saturated solution of muriate of lime in wa ter, be mixed with a small quantity of sulphuric acid, the two fluids immediately become a solid. . This change is produced by the exercise of affinit)\ The muriate of lime ia composed of lime and muriatic acid, and of this salt, water will dissolve a large quantity and still remain fluid. The sulphuric acid has a stronger attraction for lime than the muriatic has, and the sulphate of lime is nearly insoluble in water. When therefore the former acid is added to the solution, a sulphate of lime is formed, which in a spongy form occupies the whole vessel. On the contrary, if equal parts of alum and acetate, or sugar of lead, be rubbed forcibly together in a mortar, they form a compound mass which is nearly fluid. The cause of this change from the solid to the semi-fluid state, is also easily explained. The alum and sugar of lead contain a quantity of water, called the water of crystallization. When they are forcibly rubbed together, the elements of which they are composed, unite in consequence of mutual affinity, and thus the water of crystallization is set free, and occasions the partial fluidity of the mixture) The great changes which the two gases undergo in the formation of water, have already been mentioned. Similar changes, so far as respects the condensation of elastic fluids and liquids, are phenomena which are frequently witnessed in experimental chemistry. Thus, water absorbs about 500 time its own bulk of the gas, called ammonia, which is in this manner condensed, and forms a part of the liquid. The compound thus formed is known by the name of spirit of hartshorn. Quicklime, in the process of slacking, absorbs a large quantity of water, which by this combination becomes solid, and forms a part of the dry lime. In the formation of the gases, on the contrary, there is an immense increase of bulk. When water is decomposed and made to assume its elementary gaseous form, there is an increase of bulk nearly equal to 2000 volumes. That is, a cubic inch of water contains 662 cubic inches of oxygen, and 1325 cubic inches of hydrogen; thus the volume is increased 1987 times by the decomposition. The expiosion How is the change of form accounted for when sulphuric acid and muriate of lime are mixed 1 How is the change of form explained, when alum and acetate of lead are forcibly mixed 1 What is said-of the condensation of ammonia by water, and the condensation of water by slacking lime 1 How many times more bulky are the gases of vhicb water is composed, than water itself I 83 AFFINITY. 0/ gun powder is another example of the vast increase 0/ volume by chemical decomposition. Force of Chemical Affinity. Although it is ascertained, ny means already described, that the affinity of one body for a number of others, is not of equal force, yet we are ignorant how much difference there is in the forces of these different degrees of affinity. The only means of deciding this question is to observe the tendency which several substances have to unite with the same substance, under similar circumstances. Oxygen, for instance, as a universal agent, might be selected as a standard, and the force of affinity between this and other bodies be estimated by their degrees of oxidation under the same circumstances. We know that there is an immense difference between the forces with which different bodies attract this principle. Some of the metals, for instance, absorb oxygen with such avidity, that they cannot be preserved in their metallic state when exposed to the even for a short time; while others have so little affinity for this principle, that they cannot be oxidated without the most ener getic means) Thus, potassium (see this word) attracts oxy gen with e;.xh force as to decompose water, at common temperatures, by absorbing it from the hydrogen ; Avhile the affinity of platina or gold for this principle is so weak as not to attract it at all, except at the highest degrees of heat, or from acids which impart it most easily. We may constantly observe the effect of the different forces with which several metals attract oxygen in the common affairs of life. Thus, iron and lead, when exposed to the moisture of the atmosphere, soon tarnish, and after a time, by the absorption of oxygen, their surfaces become covered with rust, or the oxides of iron and lead. But silver and gold when exposed in the same manner, continue bright and untarnished for years, as may be observed in the points <*f lightning rods, and the gilded vanes and balls of church steeples. This difference can only arise from the different forces with which these metals attract the oxygen of the atmosphere. There is no department in chemistry, either as a science, Hew might the force of affinity be ascertained ? How do we know that there is a great Jifl'erence between the forces with which bodies attract oxygen 1 How is this difference illustrated 1 How is it shown that iron and lead attract oxygen with greater force than silver and gold 1 84 PROPORTIONS. ir an art, which so much needs the investigation of able men as this. Tables of affinity, showing at once the force of attraction between different chemical elements, would enable the inquirer, without further experiment, to decide what substance would decompose any given compound, and therefore how to separate, or combine, the different principles of bodies for a vast variety of purposes. Tables to a very limited extent have already been constructed for such purposes, but the difficulty and magnitude of this subject seems to have deterred the more modern chemists from engaging in this exten sive department of the science. Indefinite and Definite Proportions. It is ascertained by experiment that some bodies unite in unlimited, or indefinite proportions, while others combine in proportions which are always limited, or definite. of the laws of definite proportions is one of the mol>important and wonderful among the great and brilliant achievements in modern chemistry. It is sufficient of itself to convince any reasoning mind, that order and system pervade the universe, and that the minutest atoms of matter, and the vast orbs that move round the heavens, are equally under the control of the invariable laws of the Creator. Indefinite proportions. When we mix 'water and alcohol, or water and any of the acids, they unite in any proportion. Thus, a drop of acid will combine with any quantity of water, and water will unite in the same manner with alcohol, or acid. This principle may be tested by direct experiment; for if a gallon of water be tinged blue by a vegetable colour, a few drops of sulphuric acid will turn every drop in the gallon to a red colour, thus proving, that this small quantity of acid has diffused itself through the whole mass. By similar experiment it can be shown that a small quantity of water will diffuse itself through a large quantity of acid. These examples prove that some bodies combine in unlimited proportions on both sides. Other combinations appear to be limited on one side, and unlimited on the other. Thus, common salt, and other saline substances, will dissolve in water in any proportion short of What would be the use of tables, showing the force of attraction between different chemical elements 7 What is said of the discovery of the laws of definite proportions 7 What substances are mentioned, which combine in unlimited proportions? 85 proportions. Ine point of saturation, after which, if more he aoVted, it wili fall to the bottom of the vessel and remain solid. The greatest proportions in which water and common salt combine, are those of 100 of the former, with 40 of the latter; but the smallest quantity of salt will diffuse itself through the largest quantity of water, and the probable reason why salt does not unite with water in every proportion, is, that its cohesion resists the feeble affinity of the fluid after it becomes saturated. In all cases where bodies combine with each other in every proportion, or where the proportions are limited on one side, and indefinite on the other, the force of affinity by Avhich such compounds are formed is feeble, and the compounds themselves often differ but little from the original ingredients. Thus, alcohol and water-combine in all proportions, but the union produces only a modification of the qualities of each, the degrees of which depend on the proportions of the mixture, and the force of affinity between them is so weafc, that distillation, by a gentle heat, entirely destroys their union. Solutions of the salts, sugar, acids, and many other principles, are examples of the same kind; a moderate heat, and sometimes evaporation, Avithout heat, will dissipate the AA'ater and leave the other ingredients in their former state. In these, and a great variety of other -instances, although the force of affinity is slight, still there is a Avide difference between such compounds, and mere mechanical mixtures, since the latter are separated by rest, while the ingredients of the former are not separated by rest, filtration, or any other mechanical means. These solutions, or combinations, formed by feeble affini ties, resemble mixtures in respect to the slight changes which their ingredients undergo by uniting, Avhile they resemble chemical compounds in respect to the inseparable nature of me union, by mechanical means. The writer of the article Chemistry, in the Library of How is it proved that a few drops of acid will difTtrse itself through a large quantity ?f water 1 What bodies combine in limited proportions on one side, and unlimited proportions on the other f In what proportions do Water and common salt combine 1 In cases where bodies unite in all proportions, is the force of affinity strong or weak 1 Whal arc the substances mentioned, which unite in all proportions 1 In what respect do com frictions, formed by feeble affinities, resemble mixtures, and in what respect do they rest ml ilc chemical compounds'? What are these slight combinations called in the Licra; j of Useful Knowledge 1 8 86 PROPORTIONS. Useful Knowledge, has called such slight combinations Ch& mical mixtures, in order to distinguish them from compounds formed by energetic affinities, and which come within the law of definite proportions. But as the student will find in most books on this subject, that mixtures are distinguished from compounds only by the means necessary to separate their ingredients, we have thought best, at present, to continue the same division; at the same time, having it distinctly understood, that the um versality of definite proportions, applies only to energetic combinations. Definite Proportions. By definite proportions in chemistry, it is meant that the ingredients, or elements of chemical compounds, unite with each other in certain proportions only ; and that these proper tions in the same compound, are under all circumstances invariably the same, The proofs of this doctrine are established by experiments conducted with the most rigid exactness, and it is true, beyond all controversy. The subject of definite proportions may be conveniently treated of, under three several propositions or laws, it being understood that the proportion of hydrogen in water represents unity or 1, and that this is the common unit to which all the other numbers refer. First, The composition of all chemical compounds is fixed, and invariable. Experiment shows that some bodies combine in only one proportion. Thus, there is only one compound of zinc, and oxygen, called the oxide of zinc. Other bodies combine in two proportions. Thus, there are two oxides of copper, one of which is composed by weight of 1 proportion of oxygen, and 8 of copper, and the other, 2 of oxygen, and 8 of copper. Other bodies again combine in three, four, five, or even six proportions, the latter being the greatest number of compounds What is meant by definite proportions in chemistry 1 What is the first law of definit< proportions 1 What two substances combine only in one proportion 1 What two sub stances are mentioned which combine in two proportions, and what are tliese prcpor tions 1 What number of compounds tire known to be formed by two elements 1 Th« (iroportions of any chemical compound 'joint, d(*inite, what would be tho effect of charvi ing these proportions 1 87 PROPORTIONS. known to have been formed by any two substances, within the limits of definite proportions. The proportions of any given compound being invariably the same, it follows that its characteristic properties depend on these proportions, and tha0f these proportions are changed, the compound will contain new properties, and therefore a new substance is formed. As an example of the change produced on the compound, by a different proportion of one of its constituents, we will cite mercury and chlorine, (see chlorine.) These two substances unite in two proportions, the first of which is composed of mercury 200, and chlorine 36. This forms the well known medicine called calomel, and is sometimes given in doses of a tea-spoonful at a time, without injury. The other is composed of mercury 200, and chlorine 72, being one more proportion of chlorine, than is contained in the calomel. But the two compounds in their sensible qualities are entirely different, the latter being one of the most active and fatal of poisons, and is known by the name of corrosive sublimate. (Thus two substances uniting in one proportion, form a compound which is comparatively inert, while in another proportion they form one of the most virulent poisons known. Nor is there any medium, or half way union between these bodies ; they combine in these two proportions or not at all. For, suppose 200 parts of mercury should be exposed to the action of 40 parts, by weight, of chlorine, then the mercury would combine with 36 parts of the gas, and no more, leaving the other 4 parts remaining untouched. And so, on the contrary, if 210 parts of the meta. be exposed to the action of 36 parts of the gas, then the gas will combine with 200 parts of the mercury, while the 10 parts would remain uncombined. In all energetic combinations the proportions of the combining substances are limited in the same manner, though the proportions themselves are exceedingly various. Indeed, it appears that the law of limited proportions, is as universal and as permanent as the law of gravitation itself, and that its doctrines, so far from being founded on the theoretical opinions of men, are in truth based the number er equivalent, of carbonate of potash 70 1 CHEMICAL EQUIVALENTS. 95 of potash, 48, avid two of carbonic acid, 44, and its number is therefore 92. Again, having in the memory the numbers representing carbonic acid, we can readily apply them to the composition of other compounds, with which this acid is united. Thus, the number for carbonate of soda, is 54, and we know from its name (see Nomenclature,) that it contains only one proportion of carbonic acid. Now by recollecting the combining proportion of sodium, we know, in a moment, the composition of the carbonate of soda. The combining number for carbonic acid being 22, this substracted from 54, leaves 32, for the other combining proportion, and knowing that 24 is the number for sodium, and that soda is composed of sodium and oxygen, and that the combining number of oxygen is 8, we ascertain the composition of the salt in question, viz. sodium 24, oxygen 8 ,=€2 soda; carbonic acid 22=54, carbonate of soda. By the same law of proportions, suppose it is required to find the composition of sulphate of soda. The composition and number of soda being known, we have only to remember that the combining proportion of sulphur is 16, and that sulphuric acid is composed of one proportion of sulphur and 3 of oxygen, and the composition of this salt and its number is ascertained. Soda 32, sulphur 1G; oxygen 3 proportions, 24, 16=40 added to 32=72. Therefore the number for sulphate of soda is 72, and its composition 32 of soda and 40 of sulphuric acid. Thus by the application of this law to the combining numbers, or the equivalents of chemical bodies, a table of which may be found at the end of this work, the composition of most compounds may be readily ascertained. Method of ascertaining the proportional nu m hers of compounds. The combining numbers of all the elementary bodies, as already stated, represent the smallest proportions in which they are severally found in union with any other body. But it is obvious that all these numbers must have one common unit from which they are calculated, otherwise there would exist no proportions between them. For this purpose, hydro- Why ta bi-carbonate of potash represented by 02? Why is caibonate of soda represent, (d by 54 ! By the same law of proportion, show why the equivalent for sulphate of soda is 72? What are the units or data from which the combining numbers, or equivalent* are calculated ? 96 CHEMICAL EQUIVALENTS. gen, as uniting in the West possible proportion, is employ ed. Thus, hydrogen unites with oxygen in one proportion, by weight to form water, and the weight of hydrogen being 1, the weight of oxygen in water is 8, which is also the small est proportion in which the latter body is found in union. These two elements having an extensive range of affinity and therefore being found in combination with a great variety of other substances, are made the data, or points of comparison from which all the other numbers are calculated. Afterwards, other compounds were examined which contained the smallest proportions of these elements united to other substances. Among these it was found that the gas called carbonic oxide, contained the smallest combining proportion of carbon, united with the smallest proportion of oxygen, these proportions being as 6 to 8. And also, that the gas called sulphuretted hydrogen, contained the smallest pro portion of hydrogen united to the smallest of sulphur, these proportions being 1 of hydrogen and 16 of sulphur. Thus, the numbers for carbon and sulphur were found to be 6 for the former and 16 for the latter, the numbers for hydrogen and oxygen being 1 and 8. On examination of the different oxides of iron, it was found that the least proportion with which that metal combined with oxygen, was that of 28 of the former, and 8 of the latter. The number for iron is therefore 28, and that of this oxide of iron 32. In this manner the proportional numbers of each compound has been ascertained, and from these, tables of chemical equi valents have been constructed. WollastorCs scale of Chemical Equivalents. Dr. Ure says, that this scale of chemical equivalents has contributed more to facilitate the general study and practice of chemistry than any other invention of man. The description of this instrument was published by the inventor in 1814. It consists of a piece of mahogany board two or three inches wide, and of a length proportionate to the extent of the scale it contains, or of the size of the type in which it is printed. Running through the middle of the board there is a sliding Having the numbers for hydrogen and oxygen as data, how are the numbers for other bodies found? What are the equivalent numbers for carbon and sulphur? Explain iiow the number for iron was found. Describe the construction of Wollaston's scale 01 chemical equivalents ? 97 CHEMICAL EQUIVALENTS. rule, containing the proportionate numbers of all the most common chemical compounds, and on each side of the rule are printed the names of the compounds corresponding with these numbers. The divisions of this scale are laid out logometrically, after the manner of the common Gunter's scale, and consequently the ratios between the numbers are found, by the juxtaposition of the several lines, on the sliding and fixed parts, with the greatest accuracy. T he arrangement of this instrument is such, that the weigh of any ingredient in a compound, or its definite proportion, ana also the equivalents of the acids and alkalies, may be at once seen by merely moving the sliding part. On this scale, instead of taking hydrogen for unity, Dr. Wollaston has taken oxygen, which he calls 10; but if we. slide down the middle rule so that 10 on it stands opposite to 10 hydrogen on the left hand, then every thing on the scale will be in accordance with Sir H. Davy's system of proportions, taking hydrogen for unity, and also in accordance with the theory of definite gaseous combination, by volume. The principle on which this instrument works, may be learned in a few minutes; and after a little practice, it becomes one of the most efficient and beautiful of labor-saving machines, to both the practical and theoretical chemist. Nothing but actual practice with the instrument, will con vey to the mind of the learner a knowledge of its practical usefulness ; we will however give an example, by which the principle of its construction may perhaps be comprehended. We have already stated, that on this scale oxygen is the unit from which all the other proportions are calculated, and that this clement is marked 10. When therefore, 10 on the sliding rule is against this number, the weights of the other bodies are in due proportion to this number. Thus carbonic acid being 27.54, and lime 35.46, carbonate of lime being the sum of these numbers, is placed at 62. Then if the sliding rule be drawn upwards, so that the number 100, on it, corresponds with carbonate of lime, the other numbers will correspond with carbonic acid and lime, and will show the proportions in which these ingredients unite to form 100 What principle does Dr. Wullaston call unity, and what is its number on the scale o chemical equivalents'! On what evidence is the truth of the doctrine of definite propor tons founded 1 9 98 ATOMS. parts of carbonate of lime. Thus, the number 56 conns ponds with lime, while 44 corresponds with carbonic acid, these two numbers making 100 Theory of Atoms. That chemical bodies unite in definite proportions, by weight, and also by volume, and that where one body unites with another in more than one proportion, the second is a multiple of the first, are facts resting on the evidence of experiment alone. These facts, in themselves so wonderful, and in their relation to science so important excited the inquiry and speculations of many philosophic minds, as to their cause. Among these inquirers, Mr. Dal ton, of Manchester, seems to have been the most successful, having proposed a theory which accounts, with few, if any exceptions, for all the phenomena observed, and which therefore explains satisfactorily, the reasons why bodies com bine in such proportions. As the basis of this theory, Mr Dalton assumes that the union of bodies in their smallest pro portions, always takes place between the atoms of which they are composed; that is, one atom of one body combines with one atom of the other body. Thus, water is formed by the combination of one atom or particle of oxygen combined with one particle or atom of hydrogen. This theory supposes also that the ultimate atoms of matter are indivisible; that they are always of the same shape and size in the same body, and that their weights are different in the different bodies. Thus, the weight of an atom of oxygen is 8 times that of an atom of hydrogen, these being the proportions in which these gases form water. But when bodies unite in several proportions, then it is 2 or 3 atoms of one, to one atom of the other. Thus, sulphurous acid is composed of 2 atoms of oxygen united to 1 atom of sulphur, and sulphuric acid is composed of 1 atom of sulphur and 3 atoms of oxygen, these being the relative weights of their elements. But as it is found that the lowest proportion in which sulphur unites with any other body, is in the proportion of 16 by What is said of Mr. Dalton's theory of atoms? What does Mr. Dalton assume ns the basis of his theory of atoms ? On this theory what is water composed of 1 What docs this theory suppose, in respect to the divisibility, shape, and weight, of the atoms of bodies ? Why is an atom of oxygen supposed to be eight times as heavy as one of hydrogen 1 Why is an atom of sulphur supposed to be twice as heavy as one of oxygen t Why is it supposed that sulphurous acid contains 1 atom of sulphur united to two atoms of oxygen 1 That sulphuric acid is composed of 1 atom of sulp]. til and 3 atoms of oxygen 1 Why is the equivalent number of oxygon 8 Why is tnat for sulphur 16 1 99 ATOMS. weight, hydrogen being 1, so it is assumed that a particle of sul phur is sixteen times as heavy as one of hydrogen, and twice as heavy as one of oxygen. And as in sulphurous acid the weight 01 oxygen is found to be exactly double that in water, it is reasonable to suppose that sulphurous acid consists of 1 atom of sulphur united to 2 atoms of oxygen, and for the same reason, since sulphuric acid contains three times the weight of oxygen that water does, that this acid is composed of 1 atom of sulphur and 3 atoms of oxygen. All this, whether true or false, exnlains in the most satisfactory manner, why bodies combine with each other in definite proportions, and why these proportions are expressed by the numbers attached to each. Thus, hydrogen is unity, or the prime equivalent, and is expressed by I, because by weight this gas is found to form water by uniting with 8 parts of oxygen. Oxygen is expressed by 8, because its proportion in water weighs eight time as much as the hydrogen. The number for sulphur is 16, because this is the smallest proportion in which it unites with any substance, and the number for the oxygen in sulphurous acid is 16, because in this acid the sulphur and oxygen are of equal weights, and therefore iust twice the weight of the oxygen in water ; and the number for the oxygen in sulphuric acid is 24, because its weight is three times that in water. Now by supposing that one atom of oxygen is 8 times as heavy as one of hydrogen, and that an atom of sulphur is twice as heavy as one of oxygen, or 16, times as heavy as one of hydrogen, the whole mystery of the law of definite proportions is reduced to simple arithmetical calculation, for the proportional numbers are in fact nothing more than the relative weights of the atoms of which the several bodies are composed. In respect to the truth or falsity of this theory, it is obviously without the bounds of demonstration, for we never can ascertain whether the proportions on which it is founded are the smallest in which bodies combine, nor whether, if so, they combine atom to atom, as is supposed. But whether it be true or false, it does not in the least affect the truth of the aw of definite proportions, which, as already stated, is founded on experiment alone, and is therefore purely an expression Why is the number or oxygen in sulphuric acid 24 1 What is said of the proportionate numbers in relation to the weights of the atoms of bodies ? What is said in respect to the truth of this theory 1 100 CHEMICAL APPARATUS. of facts. The atomic theory, however, must always be considered an elegant arid probable hypothesis, and while it displays uncommon ingenuity, and great chemical research, has the advantage of agreeing, in general, perfectly with the facts obtained by analysis. Chemical Apparatus. Before proceeding to treat of ponderable bodies, and the description of particular agents, it is proposed to describe some of the most common, and necessary utensils, used in the manipulations of chemistry. Fig. 29. A crucible, Fig. 29, is a deep conical cup, of a triangular shape at the top, and round at the bottom. Crucibles are made of this shape for the convenience of pouring out their fluid contents at either angle. They are made of clay and sand baked hard, ana will withstand very high degrees of heat without melting, but are liable, to crack when suddenly cooled. They are chiefly manufactured at Hesse, in Germany, and hence are called Hessian crucibles. Fig. 30. A melting pot, Fig. 30. These pots are made of various sizes and materials. Those used in glass houses are made of clay, and are of large size. Chemists employ those made of silver or platina, as well as of black lead, but of small dimensions. Metallic crucibles are used for particular purposes, when the substance to be experimented on would destroy the common crucible, in consequence of its corrosive quality. A matrass, Fig. 31, is a glass vessel, in the shape of an egg, with a long neck. It is employed in effecting the solution of such substances as require heat, and long continued digestion, for that purpose. When used, they are commonly placed in a sand bath, that is, in sand moderately heated. Whether it is true or false, does it in the least affect the truth of the doctrine o f definite and multiple proportions 1 What is a crucible, and for what purpose is It v»*J 1 Of what are crucibles made 1 How do melting pots dilfer from crucibles ? Of wha> «ub stances are melting pots made 1 Ol what arc matrasses made 7 For what purpose r« these vessels used 1 101 CHEMICAL APPARATUS. A retort and receiver is repre sented at Fig. 32. Retorts, a, are egg shaped vessels, with the neck turned on one side. These vessels are of various capacities, from a gill to a bar- rel, or more. They are made of glass, metal, or earthen ware, but most commonly of glass. No vessel is so much used in experimental chemistry as the retort. In the process of distillation, in collecting the gases, in concentrating the acids, and in a great variety of other operations, this vessel is universally employed. The receiver, b, is a necessary appendage to the retort, and ij destined to receive whatever comes over from it, during the process of distillation. For common purposes, these vessels are made of glass, but in the manufacture of various articles they are made of wood or metal. Fig. 33. Fig. 33, represents a tubulated retort. It differs from the plain Fig. 33, represents a tubulated retort. It differs from the plain retort, figured above, in having a tubulure, or opening, as seen in the figure, to which is fitted a glass ground stopper. This opening saves the trouble of detaching the retort from the receiver when any additions are to be made to its contents, after they are connected, as in Fig. 32. It is also necessary for the introduction of a safety tube, a part of this apparatus, absolutely necessary in some processes, and which will be described in another place. Fig. 34. The alembic, Fig. 34, is used for the distil- The alembic, Fig. 34, is used for the distil- lation or sublimation of solid, volatile substan- ces. It consists of two parts, the head a, which is ground on, so as to be perfectlytight, and the body b, which is set into a sand bath, when in use. The product of sublimation rises into the head, where it is condensed, and then runs down the spout into a receiver. What is a retort 1 How large are retorts 1 Of what are retorts made 1 What are the uses of retorts ? What is a receiver, and what is its use 1 Of what are recevers made 1 How does a tubulated, differ from a plain retort 1 What is the use of the of opening, in this retort 1 What is an alembic 1 What is the use of the alembi", ? 9* 102 CHEMICAL APPARATUS. Fig. 35. Evaporating dish, Fig. 35. Every chenu cal apparatus must have among its utensil* shallow dishes for evaporating fluids. The best are made of Wedgewood's ware, and com* packed in nests containing several sizes each The heat is applied by means of heated sand or ashes, and these vessels are used to evaporate solutions of salts, in order to obtain crystals, and for various other purposes. Fig. 36. Fig. 36, a Florence flask, furnished with a Fig. 36. Fig. 36, a Florence flask, furnished with a tube, to be used instead of a retort. Students will save considerable expense, by employing these flasks in the room of retorts. The cork is pierced with a burning iron, and through the aperture is passed a tube of glass or lead, bent as in the figure. In obtaining oxygen, by means of oxide of manganese and sulphuric acid, and for many other purposes, this arrangement will serve instead of the best retort, while, if broken, the expense is only a few cents. Fig, 37. The common bloio pipe, Fig. 37, is a little instru- merit by means of which the most violent heat of a furnace may be produced. It is a pipe of brass, about the third of an inch in diameter at the largest end, and thence tapering, gradually, to a point, and bent, as in the figure. To use it, place the curved end in the flame of a lamp, or candle, and apply the lips to the other end, then blow gently and steadily, giving the jet of flame a horizontal direction. To keep up a constant stream of air for a length of time, the inspiration must be made by the nostrils, while the cheeks are used as bellows. The art of doing this is soon learned by practice. The small fragments of ore, or other substance, on which the flame is thrown, must be laid on a piece of charcoal, which is held by small foreceps. When a very intense heat is required, and the fragment is so light as to be blown away by the air, it may be confined by making a small cavity in the charcoal support, into which the substance is put, and anothei piece of charcoal is placed partly over this. Of how many parts does the alembic consist 7 For what purposes are evaporaiion dishes employed ? What does Fig. 36 represent? What are the advantages of twine. Florenco flasks instead of retorts 7 What is the common blow pipe 7 What is the ua« of this instrument 7 Describe the mode of using it. CHEMICAL APPARATUS. 103 Fig. 38. GahiCs Blowpipc,Fig. 38, is a much more convenient form than the common one above described. In the common form, the flame is sometimes nearly extinguished, and the process stopped, by the condensed moisture from the breath. In Gahn's instrument this is prevented by the chamber a, Avhich retains the condensed moisture, and Avhich may be taken off from the main pipe for its removal. The tip of the small pipe through which the air passes to the flame, fits to a socket, so that those of different sized orifices can be used. The dropping tube, Fig. 39, is a small glass tube, bloAvn into a ball in the middle, and ending Avith a fine orifice at the loAver end. It is filled by dipping the small end into the fluid, and exhausting the air by sucking at the upper end with the mouth. The thumb is then placed on the upper end, Avhich keeps the liquid from running out. On rig. 39. raising the thumb, the contents will descend in drops, but is instantly restrained on replacing it. This little instrument is highly useful for various purposes, and particularly when it is required to introduce one fluid under another, as Avater under alcohol, or sulphuric acid under water. The simple arrangement, Fig. 40, is designed to collect and retain for the purpose of temporary examination, such gases as are lighter than the atmosphere, Fig. 40. and at the same time are absorbab'e by water. These gases, for more thorough examination, require the aid of a mercurial bath, but most of their properties may be examined by the apparatus represented by the figure. The flask a, is to contain the materials for extricating the gas, and into the mouth of this, there is inserted a tube a foot or more long. The tall bell glass b, or a large tube closed at the upper end, is inverted over this tube, as seen in the figure. As an example of the use of this apparatus, suppose we desire to make some experiments on ammonia, a gas which is rapidly absorbed by water and specifically lighter than atmospheric air. The materials for separating this gas are muriate of am How does Gahn's blowpipe differ from the coivjaon one 1 What are the peculiar ad 104 CHEMICAL ArfARAItS. monia, called also sal ammoniac, and slacked quick-lime. These being separately reduced to powder, equal parts are then mixed, and introduced into the flask a, and the, tube put into its pla:e. On application of a gentle heat, the gas will De set free in consequence of the combination which takes place between the lime and the muriatic acid of the muriate ol ammonia. The ammonia is thus set at liberty, and being lighter than the air, ascends and gradually displaces the air from the vessel b, and takes its place. This experiment affords an instance of the chemical action of two solids on each other. Fig. 41. Fig. 41 is designed as a simple illustration of a gas apparatus. The method of making experiments with the permanently elastic fluids, such as common air, and tho gases, and of transferring them from one vessel to another, though sufficient- ly simple, requires some directions for the beginner. The gases are none of them sufficiently dense, to be retained in vessels open to the air for any considerable time; and some of them being lighter than the atmosphere, instantly ascend, and are lost, when the vessels containing them are opened. All the gases, therefore, when open to the air, mix with it more or less rapidly, according to their densities, and thus escape us entirely, being diffused in the atmosphere. Hence, to retain a gas in a state of purity, it must be kept from contact with the atmosphere, and hence also the necessity of first filling the vessel with a fluid instead of air, before the gas is introduced, and of transferring it under a fluid from one vessel to another. The figure represents a wooden vessel or tub, a, with a shelf k, k, fixed a few inches from the brim. When the apparatus is to be used, the tub is to be filled with water, vantages of this blowpipe ? Describe the construction of Gahn'3 blowpipe. What is the Bhape of the dropping tube? What is the use of this instrument? Describe the manner of using the dropping tube. For what purposes is the dropping tube useful ? What is the use of the apparatus represented by Fig. 40 ? Describe, Fig. 40, and explain an example of its use. How may ammonia be obtained and examined by means of this appa ratus? What is represented by Fig. 41 ? Why cannot the gas be poured from one vet •el to another, and be retained in an jpen vessel like water 7 CHEM CAL APPARATUS. 105 bo as to rise a few inches above the shelf. Now wnen a glass jar, or any other vessel, open only at one end, is filled with water, by being plunged into the fluid, it will retain its contents when raised above the fluid, provided its mouth be kept under it; for the water is sustained in the vessel by the pressure of the atmosphere, on the same principle that the mercury is sustained m the barometer tube. (See Barometer in Natural Philosophy.) The vessels b, g, /, represent jars filled with water, and inverted on the shelf, their necks passing through an aperture in it, so as to preserve their uprigh'; positions. The vessels e, c, and i, are retorts, with their necks inserted into the mouths of the inverted jars. Now when common air, or any gas, is introduced into the mouth of a vessel so inverted, the air will rise to the upper part of the vessel, and will displace the water, and occupy its place. If a tumbler, or cup, in the state which we usually call empty, but which is really full of air, be plunged into water with its mouth downwards, very little water will enter it, because the admission of the fluid is opposed by the included air ; but if the mouth of the vessel be turned upwards, it immediately fills with water, while the air is displaced, and rises to the surface of the fluid in one or more bubbles. Suppose this is done under the mouth of a jar filled with water, the air will ascend as before, but instead of escaping, it will be detained in the upper part of the jar. In this manner, therefore, air may be transferred from one vessel into another, by an inverted pouring, and the first portions, instead of occupying the bottom of the vessels, like water, ascend to the top, the air, instead of running from a higher to a lower vessel, rising from the lower to the higher one. This is owing to the pressure of the water on the air, or to the lightness of air when compared Avith Avater. For the same reason, lead being lighter than quicksilver, if a bullet of the former be sunk in a vessel of the latter, it will rise to the surface. On this principle balloons ascend; the hydrogen with Avhich they are charged being 13 times lighter than the Explain the reason why a vessel filled with water may be raised above the fluid, provided its mouth be kept under it. When a tumbler is forced into the water with its mouth downwards, why does not the fluid rise in it? When air is introduced under a vessel, inverted and filled with water, why does it rise to the highcsi part of the veese. flow does the rise of a balloon illustrate this principle 1 106 CHEMICAL APPARATUS. atmosphere, the former is forced upwards by the pressure of the latter. Fig. 42. tutes for bell glasses. Fig. 43. A bell glass receiver, Fig. 42, is employed in making experiments on air, or the gases. It is a glass vessel, of the shape represented in the figure, and of various sizes, from the capacity ol a pint to that of several gallons. The knob at the upper part, is the handle by which it is moved. It is used for the temporary confinement of elastic fluids, on which experiments are to be made. Large tumblers are good substi- A lamp furnace, Fig. 43, is one ol the most indispensable articles in a chemical apparatus. It consists of a rod of brass, or iron, about half an inch in diameter, and three or four feet long, screwed to a foot of the same metal, or to a heavy piece ol wood. On this rod, slide three or four metallic sockets, into which are screwed straight arms terminated with brass or iron rings of different diameters. The screws cut on the ends of the arms where they enter the sockets are all of the same size, so that the rings may be changed from one socket to another, as convenience requires. These rings are for the support of retorts, receivers, evaporating dishes, &c, as repre rented in the figure, and may be moved up, or down, or turned aside, and then fixed in their places, by means of thumb screws passing through the sockets and acting on the rod. The lamp by which the heat is given for distillation, or other purposes, is also fixed with a thumb screw, so that the heat can be regulated by moving it up or down. Specific Gravity. The specific gravity of a body is its re What does Fig. 42 represent'! What is the use of the bell glass receiver 1 Descnbs tlie lamp furnace, Fig. 43. What are the uses of the rings on the ends of the arms 1 What are the uses of the thumb screws with which the sockets and lamp are furnished What is the specific gravity of a body 7 107 CHEMICAL APPARATUS. lative weight when compared with the same bulk of another body. For solids and liquids, water is the substance to which .he weight of other bodies are compared; and for elastic fluids, the atmosphere is the standard of comparison. When a body weighs twice as much as the same bulk of water, it is said to have the specific gravity of 2; and if it weighs three, four, or five times as much as the same bulk of water, it has the specific gravity of 3, 4, or 5. Water, therefore, is the unit, or standard of comparison, and has in this respect the specific gravity of 1. When a body is weighed in water, its weight will be diminished by exactly the weight of a quantity of water equal to its own bulk, and thus the difference between its weight m air and in water being known, its specific gravity is readily found. Fig. 44. The most simple mode of taking the specific gra vity of a solid, is by means of Nicholson's Portable Balance, represented by Fig. 44. The body is a hollow cylinder of tinned iron, terminated at each end by a cone. From the vertex of the upper cone rises the small stem a, of copper or brass, bearing a small tin cup. This cup slips on, and may be removed when the instrument is not in use. From the point of the lower cone is suspended the tin cup e, at the bottom of which is attached a cone of lead so heavy as to sink the whole instrument in water nearly to the base of the upper cone. Before this balance is used, it is placed in a vessel of water, and the upper cup loaded with weights until it sinks so far that a mark on the stem at a, coincides exactly with the surface of the water. The weights so added are called the balance weights, and their amount may be marked on the cup as a given quantity for future use : suppose this is 900 grains. The specific gravity of a solid may then be taken as follows. First place it in the upper cup, and add weights until the mark on the stem coincides with the water; suppose this With what substance are solids and liquids compared to And their specific gravities 1 What is the standard of comparison for clastic fluids? Suppose a body weighs twice as much as the same bulk of water, what is its specific gravity ? What does Fig. 44 represent 1 Describe this balance. What preparati on is necessary before the balance is used * What are the balance weights? After the balance weight is known, how will you pr»» teed to find the specific gravity of a body ! 108 CHEMICAL APPARATUS. to be 400 grains; subtract this from the balance weight, and we have 500 grains for its weight in air. Then remove the subject of experiment to the lower cup, and the stem will rise above the mark, because it weighs less in water than in air; weights must therefore be placed in the upper cup until the mark again coincides with the surface of the water; sup pose this to be 100 grains, which will be exactly the weight of the water displaced by the mineral or other solid. The specific gravity is now found by a very simple rule, namely, Divide the weight in air by the loss in water, and the quotient will be the specific gravity. In the present instance, Ave ha\ r e 500 grains for the Aveight m air, and 100 for the loss in AA'ater; therefore 100 :: 500=~ 5, the specific gravity. The most simple method of taking the specific gravity of iquids, is by means of a graduated bottle holding 1000 grains of water, which is taken as the unit or standard for other liquids. Fig. 45. Take a small bottle Avith a long narrow neck, as represented by Fig. 45, and having weighed it accurately, introduce into it exactly 1000 grains of pure water, and mark the level of the water with a file on the neck of the bottle. The bottle thus prepared will serve to ascertain the specific gravity of any fluid, for since water is the standard by which the comparative weights of all other fluids are known, the same bulk of any other fluid, weighed at the same temperature, will be its specific gravity. Thus, suppose that when the bottle is filled with sulphuric acid up to the mark at which the water weighed 1000 grains, it should be found to weigh 1800 grains; then the specific gravity of the acid would be 1800, water being 1000. If filled to the same mark with alcohol it might weigh 800 grains. The specific gravity of alcohol would therefore be 800, water being 1000. But as it is understood that water is the standard of comparison, the specific gravities of bodies are expressed merely by the numbers signifying their relation to this standard. Thus the specific gravity of After finding the weight of a body in air, and its weight in water, what is the rule for finding its specific gravity? What are the most simple means of finding the specific gravity of a liquid? How does a tottle filled With 1000 grains of water, become the standard for other liquids ? Suppose a given bulk of water weighs 1000 grains, and .he same bulk of another fluid 1600 grains, what would be the specific gravity of the fltter? 109 CHEMICAL APPARATUS lead is 11, that is, it is 11 times as heavy as water, bulk for bulk; while the specific gravity of ether is 750, that is, a given bulk of ether will weigh 750 grains, ounces, or pounds, while the same bulk of water weighs 1000 grains, ounces, or pounds. (See spec. grav. in Nat. Philosophy.) To determine accurately the specific gravity of the gases, is an operation of great delicacy, and requires not only very nice apparatus, but much experience. The method by which it is done is, however, easily explained, and will be readil understood. We have already said that atmospheric air is the standard of comparison for the gases. In the first place, therefore, it is necessary to ascertain the weight of a given volume of air. This is done by weighing very accurately, a light glass vessel furnished with a good stop-cock, when full of air, or in its ordinary state. Then having withdrawn the air, by means of an air pump, and closed the stop-cock, the vessel is again weighed, and the difference will show the weight of air which the vessel contained. On making this experiment, it is found that 100 cubic inches of air weigh 30.5 grains, and by the same method, the weight of a given portion of any elastic fluid may be ascertained. In all these experiments, it is understood that the thermometer stands at 60° and the barometer at 30°. Suppose, then, that the glass globe a, Fig. 46 Fig. 40. is of sufficient capacity to contain 100 cubic T inches of air weighing 30.5 grains, and it is found on filling it with oxygen that the same quantity of this gas weighs 34 grains. Then to find the specific gravity of the latter gas we say, "as the weight of the air is to that of the oxygen, so is unity, or the specific gravity of the atmosphere to the specific gravity of oxygenP Thus, 30.5. 34:: 1=1.1147. gives 1.1147 for the specific gravity of oxygen gas. But since it is inconvenient in practice to experiment on just 100 cubic inches of gas, the graduated vessel b, has been invented, to show once what quantity of gas in cubic inches is weighed in the globe a. The globe being first exhausted of air, and its stop-cock closed, is then connected with the receiver b, containing the gas, and both cocks How is tlio specific gravity of a gas ascertained 1 10 110 NOMENCLATURE being opened, the gas passes from the receiver to the globe The receiver being open at the bottom, and set over water, or mercury, the rise of the fluid will show the quantity of gas which passes into the globe, and on weighing the globe both before and after connecting it with the receiver, the differ ence will show the weight of the air thus transferred. Nomenclature. The nomenclature of Chemistry, now universally employed, was invented by the French chemists about 1784. Before that period, the names of chemical substances were entirely arbitrary, that is, each substance had an independent name, the signification of which had nothing to do with its composition, or often gave an erroneous idea concerning it. Thus, solution of muriate of lime was called liquid shell, ana afterwards oil of lime. Liquid ammonia was called bom spirit, and sulphuric acid was called oil of vitriol. It is true, at that time the substances known to chemists were few in number, when compared with the immense list of the present day. But even then, their number was such as to make it difficult for the memory to retain them, and at the same time to remember their origin or composition, when this was known. At present, were the substances mentioned in any chemical book merely designated by arbitrary names or names inexpressive of their composition, the student would necessarily spent more time in learning and remembering them, than is now required to obtain a knowledge of the whole science of Chemistry. The general diffusion o) chemical knowledge, therefore, is in a great measure owing to the present nomenclature, —its perfect simplicity, its copiousness of meaning, and the ease with which it is learned and retained. Each term in this nomenclature designates the composi tion of the compound substance to which it is applied; ana What is the weight of 100 cubic inches of common air ? Suppose it is found that 100 cubic inches of oxygen gas weighs 31 grains, how is its specific gravity found? Explair Fig. 46, and show the design of each vessel, and the manner of using them. When was the chemical nomenclature invented, and by whom? Before this invention, how won chemical substances designated ? What is said concerning improper names before tint invention? At present, were the substances known to chemists designated only by arbitrary names, what would be the consequence to the learner? What effect has this no menclature had on the diffusion of chemical knowledge ? By this nomenclature what do the names of the substances designate? NOMENCLATURE. 111 as the simple substances are comparatively few, the composition of most chemical substances are known only by these names. The names of the acids are derived from those of their bases, that is, from the names of the substances to which oxygen unites in such proportions as to form acids. Thus, sulphur is the base of sulphuric acid, and carbon is the base of carbonic acid. Some of these bases unite with several proportions of oxygen, and form acids of different degrees of strength. These proportions are designated by the different terminations of the name of the acid, the smaller proportion being signified by ous and the larger by ic. Thus, sulphurous and sulphuric, and nitrous and nitric acids, mean that these acids contain single and double proportions of oxygen. The salts, that is, the compounds which the acids form with alkalies, earths, and metallic oxides, also indicate by their names the substances they contain. Thus, the salts ending in ile consist of a base, united to an acid ending in ous; and a salt ending in ate contains an acid ending in ic Sulphite and phosphite of potash are formed of potash and sulphurous and phosphorous acids, while sulphate and phosphate of potash denote compounds of sulphuric and phosphoric acids, united to the same base. The names of all the salts, of which there are nearly 2000, denote their composition in the same manner, and thus we know the ingredients of their compositions by merely seeing their names. The termination urel denotes the union of simple non-metallic bodies with a metal, a metallic oxide, or with each other. Thus, sulphuret and carburet of iron, indicate a combination between sulphur or carbon with iron. As oxygen combines with several of the metals in different proportions, but not always sufficient in quantity to form acids, the compounds so formed, though derived from the same metal, differ from each other. These compounds are called oxides, and are distinguished from each other by the Greek derivatives, prot, dent, From what are the names of the acids derived 1 What is the base of sulphuric acid 1 What is the base of carbonic acid? By what termination in the word is a weak acid designated 1 By what termination is the strong acid indicated ? What arc the compounds jailed which the acids form with different bases'! If an acid ends in ous, what is the termination of the salt of which it composes a parti If the acid ends In ic, how does the salt end ? How will you know the composition of a salt by merely hearing its name 1 What does the termination vret denote? What is the composition of a carbttrei ol Mdphur ? Wliat are oxides 1 112 NOMENCLATURE. trit, and per. Protoxide signifies the first degree of oxidn tion; deutoxide, the second; tritoxide, the third; and peroxide the highest. In some of the salts, it was formerly supposed that the acid prevailed, or that more acid was present than necessary to saturate the alkali, and in others that the alkali prevailed. The first of these were called supe.rsa.lts, and the second subsalts, while those in which the acid and alkali were in due proportion, were called neutral salts. These names are now regulated by the atomic constitution of the salt. If it is a compound of one atom of acid and one of alkali, the generic name is employed, as carbonate of potash. But if two or more atoms of the acid be combined with the same base, a numeral is prefixed to indicate its composition in this respect. Thus, when the acid is in two proportions, or there are two atoms of acid to one of potash, it is called oi-carbonate of potash. The three salts of oxalic acid and potash are called the oxalate, oinoxalate, and quadroxa\ate of potash, the first consisting of one atom of each, the second of two atoms of acid to one of potash, and the third of four itoms of acid to one of potash. PART II. PONDERABLE BODIES. Explanations. A ponderable body, is one which has ap preciable weight. A simple body, is one which has not been decomposed These are also called elements, or elementary bodies. It is possible that all the substances now called elementary, may still be in reality compounds, for our knowledge on this subject is entirely negative, that is, all bodies which the art of chemistry has been unable to separate into parts, or to decompose, are called simple, in order to distinguish them from By what terms are the different oxides denoted 7 What is a deutoxide 7 What is a trt7oxide7 What is a peroxide 7 What is said of supersalts and awtaalts J What are carbonate and Wcarbonate of potash 7 What is a ponderable body 7 What is a simole body 7 What is the difference between a simple and an elementary body 7 Whet- do chemists call a body simple 7 113 PONDERABLE BODIES. Known compounds. Before the refinements of chemical analysis were known, it was believed that nature afforded only four elements, viz. fire, air, earth, and water. Analysis has however shown, that fire, or heat, is the result of chew cal union; that air is a compound of nitrogen and oxygen ; that there are many earths, and that water is composed cf hydrogen and oxygen. The number of simple bodies now enumerated amount to about fifty, or perhaps fifty-two. They consist of about 40 metals, three, or perhaps four supporters of combustion, viz. oxygen, chlorine, and iodine, and probably also bromine, and seven non-metallic combustibles, viz. phosphorus, carbon, hydrogen, sulphur, boron, selenium, and nitrogen. Only a few years since, potash, soda, and several other substances, now found to be compounds, were supposed to be elementary bodies ; and it is highly probable, that many substances, now arranged as simple, will soon be found to be compounds. Before proceeding to describe the properties of the gases, it might be thought necessary to detail more particularly than has been done, the modes of confining and transferring them from one vessel to another. But it is thought that such directions are better understood by the student, and much more readily followed when given in connexion with the particular subjects or cases, to which they immediately apply. The method, for instance, of transferring the nitrous oxide from the retort to the gasometer, and from the gasometer to the gas bag, will be best understood if given in connexion with an account of the properties of the gas, or immediately after it. The same, it is thought, may be said of confining and transferring the other gases. As several different methods are required, depending on the nature of the gas, its absorption by water, its specific gravity, and other properties, these different modes can be best explained and understood in immediate connexion with the description of the peculiar properties of each gas. As the doctrine of definite proportions is not only highly interesting as a subject of philosophy, but is also intimately connected with chemistry, both as a science, and a practical How many elements were formerly supposed to exist ? What is said concerning fire, air, earth, and water? How many elements are now supposed to exist, and what *re they ? What is said of the probability that some bodies now arranged as elemerta will be found to be compounds'? 10* a 14 art, we shall attach to the name of each substam i*t 'he hood of sections, its equivalent number, so thai the roadn- may at once observe its combining proportion. And it is earnestly recommended to the pupil, that he should not only rep;ard this subject as one of great importance in a scientific relation, but also, when viewed in a different light, as one that tends directly to impress the mind with the most serious conviction, that nothing in nature has been left to chance, but that the Almighty Creator has left a witness of himself, even in the proportions, and arrangement of the atoms of matter. Nothing, perhaps, even the sublimest works of nature, are more calculated to elicit the wonder and astonishment of a reflecting mind, than the fact that substances combine Avith each other in exact, and definite quantities, and that these quantities or proportions, are the same in relation to the same substance throughout the world, and have been so ever since the creation. This discovery may be considered as a neAV proof, directed expressly to the present age, that the most minute works of Avhat Ave call nature, do indeed bear the most indubitable marks of divine agency and design. But while the discovery itself is an evidence of the profound philosophy of the present age, the developement of its principles, by the constant accession of new ideas, is calculated rather to humble the pride of human knowledge, by as constant a conviction, that after all our acquirements, Ave knoAV comparatively nothing of the laAvs and operations of nature. The very fact, that the laAvs of proportions, now comparatively just known to man, have existed ever since the creation of matter, and have been in perpetual exercise all over the universe, Avithout a suspicion of their existence, is of itself a sufficient proof of the almost entire ignorance of man even of the phenomena of nature, and a still stronger proof of his ignorance of her laws. And if facts, in themselves so simple, yet so wonderful, and when once known, so obvious, have escaped the observation of man for thousands of years, is it not What is said of the doctrine of definite proportions, in relation to philosophy and chemistry 1 In what other respects is this subject recommended to the particular attention of the pupil? What is said of divine agency and design in the minute works of nature 1 After all human acquirements, how much do we know of the laws and operations of nature ? What is proved by the fact, that die law of definite proportions, though existing ever since the creation of matter, have, until lately, remained unknown 1 What is said of the probability that wonderful phenomena are constantly going on before our cyw" 115 INORGANIC CHEMISTRY. probable that phenomena are constantly going on before our eyes, which, could we understand them, would astonish us still more, and at the same time affoid a still stronger conviction of our ignorance, and want of penetration ? These considerations, while they are calculated to humble the pride of human intellect, by showing how little we know of the laws which govern even the ordinary operations of nature, ought, by the conviction of ignorance, to prove an incentive to constant observation on natural phenomena, that, if possible, we might arrive at the knowledge of their true causes. INORGANIC CHEMISTRY. NON-METALLIC SUBSTANCES. Oxygen —8. The name oxygen is derived from two Greek words, and signifies the former, or generator of acids, because it enters into the composition of most acid substances, and was formerly considered the universal and only acidifying principle in nature. It was discovered by Dr. Priestley in 1774, and named by him dephlogisticated air. Its specific gravity is 1.11, air being 1. It is a non-conductor of electricity, like common air. Its electrical state is always negative, and when suddenly and forcibly compressed, as in the fire-pump, already described, it emits light and heat. Oxygen may be obtained from many substances. The peroxides of lead, or manganese, and the nitrate and chlorate of potash, all yield it in abundance, when merely exposed to a dull red heat. The cheapest and most convenient substance for this pur* pose is black, or peroxide of manganese, in the state of fine powder. This, when heated in an iron bottle or gun-barrel, will yield upwards of 120 cubic inches of the gas to an ounce of the oxide. For small experiments, a gun-barrel may be used; but where considerable quantities are wanted, a wrought iron bottle, with a neck 18 inches long, is the best instrument. What does the term oxygen signify 7 Who discovered this gas 7 What is the specific gravity of oxygen gas 7 What are the substances from wh ich it can be obtained 7 What is the cheapest and most convenient mode of obtaining it? How many cubic inches of this gas will an ounce of the black oxide of manganese yield 7 What are the methods described of extricating this gas from manganese 7 116 OXYGEN. Fi(t. 47. The shape is represented at Fig. 47, with the addition of a piece of gun-barre], fitted to the mouth of the bottle by grinding. A tube, leading from the gun-barrel to the gas holder, conveys away the oxygen as it is extricated from the manganese. In the absence of such a bottle, oxygen may be conveniently obtained by mixing, in a proper vessel, one part of sulphuric acid, and two parts of the oxide of manganese, and applying the heat of a lamp. The cheapest and most convenient vessels for this purpose are Florence flasks, fitted with corks and tubes, as represented by Fig. 36. This, and the lamp furnace, ' Fig. 43, together with an inverted vessel filled with water, constitute the apparatus necessary for the extrication and confinement of oxygen. With respect to the theory of these processes, it is necessary to state, that there are three oxides of manganese, each of course containing different proportions of oxygen. These oxides are thus constituted, the combining proportion of man ganese being 28, and that of oxygen 8. Protoxide manganese, 28, added to oxygen, 8=36 Deutoxide 28, " " 12=40 Peroxide 28, " " 16=44 When the peroxide is exposed to a red heat, it parts with half a proportion of oxygen, that is, 4 parts, the number for oxygen being 8, and is therefore reduced to a deutoxide, whose number, it will be observed, is 40. The number for the peroxide being 44, and the loss by a red heat being 4, we obtain 4 grains of oxygen for every 44 grains of the oxide, which in bulk is nearly 12 cubic inches, making about 128 cubic inches for each ounce of the oxide. When oxygen is obtained by means of sulphuric acid, the. theoretical expression is different. In this case the peroxide loses a whole proportion of oxygen, and is thus converted into a protoxide, which then combines with the acid, forming What apparatus is necessary for obtaining this gas from manganese by means of sulphuric acid 1 How many oxides of manganese are there, and what are the projiortionp of oxygen in each ? What proportion of oxygen does the peroxide part with at a red heat? To what oxide is the peroxide reduced by parting with a portion of its oxygen ? What docs deutoxide mean ? Explain the chemical changes which take place when the •xygen is obtained by means of sulphuric acid. OXYGEN. 117 a sulphate of manganese, Avhich remains in the retoit. By this process, therefore, the peroxide yields 8 grains of oxygen to every 44 grains employed; but in practice it is found that the first method is the best and cheapest. It will be observed, that the weight of oxygen for the deutoxide, expressed above, is only 12, being a proportion and a half, instead of 2 proportions of that element. The oxides o. lead and iron afford examples of precisely the same kind. These facts were at first supposed to afford exceptions to the law of definite proportions, or rather to the atomic theory by which the cause of definite quantities is explained. But it will be remembered, as already stated, that the smallest proportions in which bodies have been found to combine by weight, are those by which they are represented in numbers. Now the smallest proportion in which oxygen has hitherto oeea known to combine, is in water, this proportion being as S to 1. The number, therefore, for oxygen is 8. But if it should be hereafter found, in the course of analysis, that oxygen unites in half this proportion, in any instance, then this apparent anomaly will be completely explained, for then its union with hydrogen, to form water, will be in two proportions, and its union with manganese, forming the deutoxide, will be in three proportions, &c. The fact, therefore, that oxygen unites in the proportion of 12 is not considered a valid objection to the universality of the law of definite and multiple proportions, but only a proof that the smallest combining proportion of oxygen may not yet have been discovered. This digression seemed necessary, in order to explain, once for all, this apparent anomaly. Oxygen gas is an invisible transparent fluid, like common air, and has neither taste nor smell. It is sparingly absorbed by water, 100 cubic inches of which, take up three or four cubic inches of the gas. Oxygen has the most universal affinity of any known substance, there being not one of the simple substances witn which it may not be made to combine. It unites with all the metals, forming a very extensive class of compounds, known under the name of oxides. With some of them it combines What is said concerning the weight of oxygen for the deutoxide of manganese 1 Why does not the discovery, that oxygen sometimes combines in the proportion of 12, tend to invalidate the atomic theory 1 What is said of (lie taste and smell of oxygen 1 In what proportion is this gas absorbed by water 1 What is said concerning the extensive affinity if oxygen 1 118 OXYGEN in such proportions as to form acids. Such is tne case Willi arsenic, molybdena, and others. With the simple combustibles, sulphur, carbon, &c, it also combines in various proportions, forming- oxides and acids. With the metals sodium and potassium, it enters into combination to form the alkalies soda and potash. Thus the acids and alkalies, though in most of their properties so entirely opposed to each other, are composed of oxygen united to different bases, the base ol sulphuric acid being sulphur, and that of potash being potassium. The process of oxidation sometimes takes place very slowly, as in the rusting of iron exposed to the atmosphere. In this case, the affinity of the iron for the oxygen contained m the atmosphere, though constantly exerted, produces its effects very gradually, particularly if the iron is kept in a dry state; but the oxidation is greatly facilitated if the iron is moistened with water, since then the meta, absorbs oxygen from the water, as well as from the air. In ordinary combustion, which is nothing more than a rapid oxidation, with the extrication of heat and light, the strong affinity between the combustible and the oxygen is caused by the great elevation of temperature. The combustible requires, in the first place, to be heated to a certain degree, before it will attract oxygen with sufficient force to emit heat and light, after which, the elevation of its temperature is continued by the absorption of oxygen, and thus the combination of one portion of oxygen with the burning body causes the aosorption of another. A combustible is any substance, capable of uniting with oxygen, or any other supporter of combustion, with such rapidity, as to cause the disengagement of heat and light. In this sense, iron, steel, and many other bodies, though they will not burn in the open air, are strictly combustibles, as they conform to the above definition, when heated in oxygen gas. In this gas, all combustibles burn with greatly increased What are the compounds of oxygen and the metals called 1 Does it ever form acid* by combining with the metals? When combined with the metals potassium and sodimn, what are formed? What is said of the spontaneous oxidation, or rusting of iron 1 Wl'«t inordinary combustion? In combustion what causes the strong affinity between ttM burning body and oxygen? In kindling a fire, why is it necessary to raise the tempera ture of the wood, in order to make it burn? What is a combustible body? In wnal sense are iron, steel, and otner metals, combustibles 7 119 OXYGEN. splendor ; and many substances which, before the discovery of this gas, could not, in any sense, belong to this class, are now strictly combustibles. The combustion of various substances in oxygen gas, affords experiments of the most brilliant and instructive kind. Among these, the combustion of iron, steel, and zinc, are highly interesting, not only because we are not in the habit of seeing metals burn, but because the first give out the most splendid corruscations of light, while the zinc burns with a light peculiar to itself. To exhibit the combustion of iron or steel, in this gas, procure a piece of wire of small size, or what is better, a watch spring, and wind it round a slender rod of wood, so as to coil it in a spiral form, the turns of the wire being about the fourth of an inch apart. Then withdraw the rod, and fix to the lower end of the coil a small piece of thread dipped in melted bees-wax, or sulphur, or what is better, a little piece of spunk. The other end of the wire, for a few inches, is to be left straight, and fixed to the cork fitting the mouth of the bottle in which the experiment is to be made. Next, fill a clear glass bottle of a quart or more capacity with oxygen gas, and having set it upright, cover the mouth with a plate of glass, or otherwise. Then inflame the combustible on the end of the wire, and having removed the cover from the bottle, introduce the coil, and fix the cork in its place, as represented by Fig. 47. Flo- 47 .ng the least fracture. the eyes to bear, throwing out the most brilliant corruscations in every direction. Noav and then a globule of the melted metal will fall, and if the vessel contains Avater, it will leap on its surface for an instant or Iavo, being throAvn up by the steam into Avhich it converts the fluid. If the vessel contains no water, the intense heat of the globule Avill cause it to melt the glass and sink into its substance, and if the glass be thin, it will fuse a path quite through it, Avithout caus- The wire will burn Avith a light too vivid for What is said of the brilliancy of the combustion of some of the metals ? How is the tron wire prepared for combustion in oxygen gas? Describe Fig. 47. What causes thn globules of melted iron to leap on the surface of the water ? What is said of the action of die globules of metal on tho glass 1 120 OXYGEN. To witness the combustion of zinc in oxygen, first prepare the metal by melting, and pouring it while fluid into the water. Then place some thin pieces in a spoon prepared with a cork on its handle, as represented by Fig. 48, and put in the i midst of the zinc a small piece of phosphorus. Having a bottle of the gas prepared as in the last experi ment, inflame the phosphorus by holding the spoon over a lamp, and instantly introduce it into the hot tie, fixing the cork in its place. The metal will burn with a beautiful white light, often tinged with green, owing to a small quantity of copper which the zinc contains. FigA9. If a lighted candle be blown out and then plunged into a vessel of this gas, while a spark of fire remains in the wick, it will be relighted with a slight explosion. The best way of making this experiment, is, to place a short piece of candle in a socket, fixed to a wire, as in Fig. 49. In this manner a candle may be blown out and again set on fire by dipping it into a bottle of oxygen, twenty or thirty times, and perhaps oftener. During combustion in oxygen gas, the oxygen combines with the burning body, and produces remarkable changes, not only on the combustible, but also on the gas. The combustible, on examination, will be found to have sensibly increased in weight, by the combination, while the oxygen entirely loses the power of again supporting combustion, so that if a lighted candle be plunged into it, instead of burning with splendor as before, it is now instantly extinguished. FigA9. These changes are readily explained by the analysis of the body burned, and of the gas. The iron loses its brilliancy, and is converted into a dark brittle substance, easily pulverised in a mortar. This is an oxide of iron, and consists of the iron itself united to the ponderable portion of the gas. If the iron is weighed before the combustion, and afterwards, it will be found to have increased in weight in the proportion of 8 parts to the 28. Describe the method of preparing and burning zinc in oxygen gas. What is the effect when a candle is blown out, and then instantly plunged into the gas t What effect does combustion produce on oxygen gas 1 What change is produced on the iron burned in it 1 Why does the oxide of iron weigh more than the metal before it was burned 7 Suppose the iron and oxygen are both accurately weighed before and after the experiment, what effect on their weights will be produced by the combustion? 121 OXYGEN. The gas on the contrary loses in weight what is gained by the iron, and if the vessel in which the experiment is made, be open at the bottom, and stands in a dish of water, the diminution of the gas in volume will be indicated by the rise of the water in the vessel. If the gas and iron are both accu rately weighed before the experiment and afterwards, the sum of their weights will be found precisely the same, proving that nothing has escaped, and that what has been lost by the oxygen has been gained by the iron. When other combusti bles are submitted to the action of this gas, though they may entirely change their appearance by the process, or seem to be dissipated and consumed, yet nothing is lost by the burning, there being in all such instances merely a change of form. Thus, when charcoal or diamond is burned in a confined portion of this gas, instead of losing as in the former experiment, the gas increases in weight, that is, it is converted into carbonic acid gas, by a union between the oxygen of the gas, and the carbon of the diamond or charcoal, so that what is lost by the charcoal is gained by the gas. In every instance, the gaseous matter which remains in the vessel after combustion, is unfit to support animal life. If a bird or any other animal be confined in a limited portion of atmospheric air, it soon dies, because it destroys the oxygen the air contains, by converting it into carbonic acid, thus leaving another portion of the atmosphere called nitrogen, both of which are destructive to life. (See Nitrogen.) If a bird be confined in a portion of oxygen, it will live longer than in the same quantity of atmospheric air, because it is the oxygen alone which supports the respiration ; but it dies when the oxygen is consumed, or converted into carbonic acid. But if any animal be introduced into a portion of air after its oxygen has been destroyed, or absorbed by a burning body, it dies in a few seconds, unless like the frog it has the power of suspending its respiration. Finally, it is proper to remember, that no animal can live u an atmosphere which will not support combustion. Is any thing lost by combustion 1 When charcoal is burned in a confined portion »! oxygen gas, what effect is produced on each? Into what gas is the oxygen converted by the process 1 Will the gas left after combustion ever sustain animal life? Why will a bird or any other animal soon die when confined in a limited portion of common air? Why will an animal live longer in oxygen gas, than in the sam» portion of common air ? Will an animal live in air which will not support combustion ? u 122 HYDROGEN. Were this fact more generally known and remembered we should not every year hear of instances where lives are lost by descending into old wells or cisterns. The cause of such accidents is the presence of carbonic acid, in -he bottoms of such cavities; and were the precaution taken to let down a burning candle, before the descent of the person, all danger might be avoided; for if the flame is extinguished the air will not support animal life. It has been recently reported, that throwing buckets of water into a well, where two persons had fallen down by suffocation with carbonic acid gas, had been the means of saving their lives. (See Carbonic Acid.) Hydrogen. —1. The name of this gas is derived from two Greek words, signifying the generator of water, because it enters largely into the composition of that fluid. It was discovered by Mr. Cavendish in 1766. Its specific gravity is 0.694, air being 1.—100 cubic inches weigh 2.11 grains, while the same bulk of air weighs 30.5 grains; it is therefore about 14 times lighter than atmospheric air. Compared with oxygen, it is just 16 times lighter than that gas; being indeed the lightest of all known ponderable bodies. It refracts light more powerfully than any other body, its refraction being in the ratio of 6.6, air being 1. Its electricity is positive. Hydrogen may be obtained by several processes, but in no instance without the presence of water, it being evolved only by the decomposition of that fluid. The most convenient method, is to put fragments of iron or zinc into a proper vessel, and pour on them two parts by weight of sulphuric acid, diluted with 5 or 6 parts of water. The hydrogen will immediately ascend through the water in abundance. Will air which is unfit for respiration support combustion? What precaution ought always to be taken, before a person goes into a well rr old cistern 1 What ia the derivation of the word hydrogen? What is the weight of 100 cubic inches ol this gas? What is its weight when compared with air? How much lighter is hydrogen than oxygen ? What substance is lighter than hydrogen gas 7 What is said of its power to refract light 1 What is the electrical state of this gas? Can this gas bo obtained without the presence of water? Why? What is the best method of obtaining this gas 1 123 HYDROGEN. Where only small quantities of the gas are wanted, the simple apparatus represented at Fig. 50, is all that is required. It consists of a Florence flask into which the zinc and acid are put, with a tube leading under a bell glass, or large tumbler filled with water, and inverted in a dish of the same fluid 'Zinc for this purpose is better than Fig. 50. iron, and is easily prepared by melting,, and while fluid, pouring it into water. The production of the hydrogen depends on the decomposition of the water which is effected by the united action of the metal and acid. The metal having an attraction for oxygen, obtains it from the water; this forms an oxide of the metal which is instantly dissolved by the acid ; the surface o the metal is thus left clean, and exposed to the water, from which it attracts another portion of oxygen, which is dissolved as before. Meanwhile the hydrogen being thus detachca from the oxygen, absorbs caloric, and is evolved in the form of hydrogen gas. Hydrogen may also be obtained by passing the vapor o water through a hot iron tube. In this case, the oxygen of the water combines with the iron, while the hydrogen is set free. Place a gun barrel across a furnace so as to heat it red hot. Connect to one end of the barrel, by means of a tube, a retort containing water, and placed over an Argand lamp: and to the other end of the barrel fix a tube, leading under a vessel of water, inverted in a water bath. Then make the water in the retort boil, so that its steam may pass into the gun barrel, and hydrogen will be evolved, and will pass into the inverted vessel. Hydrogen, when obtained by either of these methods, is not quite pure, but contains a little sulphur or carbon. For particular purposes it may be purified by passing it through a solution of pure potash in water. In this state hydrogen is without colour, taste, or smell. It On what does the production of hydrogen depend 1 Explain the chemical changes which take place during the production of this gas. By what other method may this gas be obtained'? How does the red hot gun barrel decompose the water? Is hydrogen a compound or an elementary body HYDROGEN. •s, so lar as is known, an elementary body, having lesisted all attempts to resolve it into more simple parts. It is inflammable, but not a supporter of combustion. If a lighted candle be introduced into a vessel of this gas, the flame is instantly extinguished, but in passing into the gas, it inflames that portion which is in contact with the atmosphere. This shows that the combustion of hydrogen requires the aid of oxygen which it absorbs from the atmosphere as a supporter. This experiment may be made by inverting the vessel containing the hydrogen in the open air, its levity preventing it from escaping downwards. In this state it will be seen to burn only on the lowest surface. But if the vessel containing it be turned upright, the whole will escape in a volume of flame. Hydrogen is the gas with which balloons are charged, and being about fourteen times lighter than common air, if the balloon is large, it ascends with great force. The principle on which balloons ascend, is the difference of specific gravity between the balloon as a whole, consisting of hydrogen, and the apparatus containing it, and the same bulk of atmospheric air. It is the same principle that makes a cork rise through water, or a leaden bullet through quicksilver. The principle of balloons may be illustrated thus. Fill a bladder, or a gas bag, furnished with a stop-cock, with hy- Irogen gas; attach to the stop-cock a tobacco pipe, or what is better, one of metal. Then dip the bowl of the pipe into a solution of soap, and form bubbles by pressing the bladder. These bubbles being detached from the pipe, will rise rapidly through the air. When hydrogen is mixed with oxygen and inflamed, the mixture detonates violently. The best proportions are two parts of the hydrogen and one of oxygen by volume. If soap bubbles of this mixture are touched with a candle when floating in the air, they give a report as loud as a pistol, but much more sharp and stunning. A loud report is also given when the hydrogen is mixed When a lighted candle is plunged into this gas, does it continue to burn, or is it extin guished 1 As the candle passes into the gas, what part of it is set on fire 1 How is this experiment best made? Why does the hydrogen burn only on the surface? With what gas are balloons filled ? On wha' principle do balloons ascend ? How may the principle of balloons be illustrated 7 What is the consequence of firing a mixture of hydrogen an* oxygen 1 What proportions of each make the loudest report ? 125 HYDROGEN. with common air, instead of oxygen. The best proportions are about three of the air to one of the hydrogen. Fig.b\. This experiment may be varied by means of the hydrogen gun, Fig. 51. It consists of a tin vessel, holding about a pint, the lower end being closed, and the upper end left open and fitted with a cork, a small orifice being made toward the lower end, as seen in the figure. Having filled this vessel about one third with water close the small orifice with the thumb, and let in hydrogen until the water is displaced. Thus, the vessel will contain three parts of air, and one of hydrogen. The cork being put rather loosely in its place, the mixture is fired by raising the thumb, and applying a lighted taper to the orifice. The cork will be driven out with- violence, attended with a loud report. When a jet of hydrogen is burned at the end of a tube with a fine bore, and with a large tube of glass, porcelain, or metal, musical tones are produced, which are grave or acute in proportion to the size or kind of tube employed. Fig. 52. This pleasing experiment may be performed by placing the materials for making hydrogen, in a convenient vessel, furnished with a tube, as in Fig. 52. Or the tube may be connected with a reservoir of gas already collected. The manner of holding the large tube to produce the musical tones is shown in the figure. Hydrogen cannot be breathed without deleterious effects, though it is not immediately fatal to animai life. The action of platinum sponge on hydrogen is singular, and highly curious. When a jet of this gas is directed on a few grains of the sponge, both being cold, and in the open air, the latter immediately becomes hot, and in a moment glows with a red heat, seiiing fire to the hydrogen. Platinum sponge is prepared by dissolving the metal m What arc the best proportions for mixing hydrogen and air for the same purpose 1 Describe the method of using the hydrogen gun, Fig. 51. How are musical tones produce.* by the burning of hydrogen 1 Explain Fig. 52. Is hydrogen a respirable gas What effects does it produce when breathed 1 What phenomena are produced when hy dr igen is thrown in a stream upon piatina sponge 1 How is platina sponge prepared 1 11* 126 HYDROGEN. nilro-muriatic acid, that is, a mixture of one part of nitric to 2 parts of muriatic acid. Ammonia, or muriate of ammonia, is added to this solution, which produces a yellow precipitate When this precipitate is exposed to a red heat in a crucible, the acids and ammonia are driven off, and there remains pure platinum, in the form of a delicate spongy mass. Another method of obtaining the sponge, is to throw the yellow precipitate on filtering paper, and when the liquid has passed through, to dry the paper, and introduce it, with the adhering precipitate, into the crucible. This curious effect of the action between platina sponge and hydrogen, was discovered by Professor Dobereiner, Oi Jena, who invented the following method of producing an instantaneous light by its means. Fig. 53. The two vessels, a and b, Fig. 53, are of glass ; a is prolonged in the form of a tube, and is fitted to the mouth of b, by grinding, or cement, so as to be air tight. The lower part of a reaches nearly to the botjtom of Z>, and is encompassed with a strip of zinc. Sulphuric acid, diluted with five or six parts of water, being placed in b, a is fixed in its place, as seen in the figure. Hydrogen is evolved by the action of the acid on the zinc, and pressing upon the fluid, (which must fill only about one half of b,) drives it up the tube into a. The stopper of a, is conical, and rises to let the air from that vessel escape. When so much gas has been evolved as to press most of the acid up into a, and consequently to remove it from the zinc, the chemical process will cease, leaving b nearly filled with hydrogen. The brass tube d, is cemented to the neck c, and furnished with a stop-cock. The box e, contains the platina sponge at the end of the tube. When a light is wanted, nothing more is necessary than to Explain Fig. 53, and show how hydrogen is produced, and in what manner it is throwr upon the sponge. Why does not the acid constantly act upon the isincl HYDROGEN. 127 open the stop cock d, and let a jet of the gas blow upon the sponge, which becoming immediately red hot, a match, and ihen a candle may be lighted. By permitting the hydrogen to escape, the acid again comes in contact with the zinc, and thus another portion of the gas is formed, and retained until wanted. Protoxide of Hydrogen 9. 1 p. Oxygen 8-j-l p. Hydrogen I. Water. It is only necessary to remark in respect to the above abbreviations, that the number for water, as already explained, is , being composed of 1 proportion of oxygen 8, and 1 proportion of hydrogen 1. The same method being observed with respect to the other substances to be described, the student has only to notice the numbers affixed to the names of each substance, and he at once becomes acquainted with the proportions and composition of each compound, and the number by which the compound itself is represented. This method, it is thought will not only be found highly convenient, but will also greatly facilitate the acquirement of a proper knowledge of chemical equivalents, a subject, as formerly remarked, of great importance to the student in the present state o, the science. It has been stated that water, by analysis, is composed of two parts of hydrogen, and one of oxygen, by volume, and 1 part hydrogen, and 8 oxygen by weight. Having described the properties of these two gases separately, it now remains to demonstrate by synthesis, that is, by the combination of these gases, that water is the product. It may be seen by a very simple experiment, that when nydrogen is burned, water is formed. When one portion of the gas escapes, in what manner is another portion generated 1 What is signified by the numbers affixed to water, oxygen and hydrogen 7 With what does the student become acquainted by observing the numbers affixed to names of tho elements, and of their compounds 7 By analysis, what is the composition of water, by weight and measure 7 By what simple experiment may be snown that when hydrogen to burned, water is formed 7 128 WATER Fig. 54. Fill with hya'rogen a blad der, furnished with a stop cock, and small tube. In flame the hydrogen at the end of the tube, and intro duce the flame into a dry f v ' y glass globe with two open- ings, as represented at Fig 54. As the gas burns, the rarefied and vitiated air will pass DfT at one of the openings, while the other admits fresh air to support the combustion. In a few minutes the inside of the globe will be covered with moisture, and by continuing the experiment, water will run down its sides, which may be tasted or otherwise examined. The same experiment may be made with a large glass tube instead of a globe. In this experiment, it is supposed that the combustion of the hydrogen is supported by the oxygen of the atmosphere, and therefore nothing can be known of the proportions in which they unite. Nor would it be absolutely certain by this experiment that it was the oxygen of the atmosphere which combined with the hydrogen, and supported its combustion. But when the two gases are confined, each in a separate gasometer, and burned together in an exhausted vessel, the result will not only demonstrate to the senses that water is the product, but will also show the exact proportions of each element by weight and measure. For this purpose two graduated gasometers contain the two gases, each being furnished with a tube, leading to the glass globe, Fig. 55. Before the experiment begins, this globe is connected with an air pump by the scre w c, and completely exhausted of air, and then accurately weighed. Ic is then connected with the two gasometers which contain the gases by the pipes d and e. When every thing is thus prepared, the stop-cock d is opened, and a small stream of hydrogen let in, which is instantly inflamed by an electrical spark from the conductor a, this being of course connected with an electrical Is it absolutely certain by this experiment, that it is the oxygen of the atmosphere which unites with the hydrogen to form water 1 How may it be demonstrated that the combustion of hydrogen and oxygen form water 1 Describe the apparatus represented by Fig. 55, and explain how the two gases are brought together, and how inflamed 1 129 WATER. machine. The oxygen is then admitted, by turning the stopcock, e, and thus the combustion of the hydrogen is supported At the end of the process, the graduated gasometers shew exactly the volume of each gas consumed, and as the weight of 100 cubic inches of these gases are known, it is easy to compute the weight of the volumes consumed, and by weighing the globe to compare it with the weight of water produced. By such experiments made with every attention to accuracy, together with that before described, of weighing the gases by means of exhausted vessels, Fig. 45, it is proved, that hydrogen and oxygen unite in the proportions of two of the first, to one of the last, by volume; and in the proportions o* 1 and 8, by weight; that the sole product of the combustion of the two gases is water, and that the weight of the water is just equal to the combined weights of the two gases. In this manner has the constitution of water been demonstrated beyond all doubt or controversy. Compound Blowpipe. When hydrogen and oxygen are burned together, in the proportions in which they form water, a most intense heat is produced. The compound blowpipe, the instrument by means of which the combustion of the two gases is regulated for this purpose, was invented by Professor Hare, of Philadelphia, in 1801. The apparatus consists of two pipes, which convey the gases from two gas-holders, to another tfhort pipe, at the end of which their combustion takes place. Fig. 56. The principle of the compound blowpipe will be understood by Fig. 56. The two brass pipes c and d, are connected with the gas-holders a and b, by coupling screws, which fix their lower ends to short tubes furnished with stopcocks, as seen in the figure. These stop-cocks are for the convenience of confining the gas in the gas-holders, when the blowpipe is not in use, and At the end of the process, how is it ascertained what proportion of each gas has been consumed, and how much water formed 1 What has been proved by such experiments in respect to the quantities and proportions of the gases consumed, and quantity ot water formed t What is said of the intense heat produced by the combustion of hydrogen and oxygen 1 What is the instrument called by which the combustion r/ the two gases is 130 COMPOUND BLOWPIPE. for other purposes connected with the pneumatic cistein. The two upper stop-cocks are designed to regulate the quantity of gas from each pipe, so as to produce the greatest heat, and also to stop it entirely while making experiments. The gas-holdert'i a and b, are two boxes of painted tin, open at the bottom, and made to fit a cistern of wood, about fiv« feet long, containing water. These boxes are fixed in theii places, at each end of the cistern, by buttons, so that they cannot rise when filled with gas. They may be two and a half, or three feet deep, and two feet wide, or of any other size, according to the extent of the experiments proposed. The cistern must be several inches deeper than the boxes, so that the water will rise above them. The two pipes convey the two gases separately to the point e, where they are soldered together, and on their united points is screwed a platina* or silver tip, having a single orifice, at the end of which their combustion is effected. If the tip is of silver, it should be large, and care taken not to include il in the cavity of the charcoal support, while making experiments, otherwise it will be melted. Having such an apparatus ready, the gas-holders are put in their places, (the blowpipe being removed, until every thing is prepared for experiment,) and water is poured into the cistern, the stop-cocks being open for the escape of the air. When the cistern and boxes are full of water, the stop-cocks are closed, the blowpipe screwed on, and the two gases are conveyed under the boxes by tubes, coming from the vessels where the gases are evolved. One of the boxes being filled with hydrogen and the other with oxygen, the blowpipe is set in action by turning the stop-cock connected with the hydrogen, and setting the gas on fire as it issues from the tip. The oxygen is then admitted, when the flame of the hydrogen will become less, being reduced to a small blue flame, which gives little light, and to the eye appears insignificant, and regulated for this purpose 1 Explain Fig. 56, and show the uses of the two tubes, th stop-cocks, and the platina tip, &c. In filling the cistern, why are the stop-cocks let open 1 What is said of the smallness of the flame, and the intensely heating powei o J lis blowpipe 1 131 PROPERTIES OF WATER. totally incapable of the calorific effects attributed to this celebrated machine. But the student who had never witnessed its powers, will be struck with astonishment, when he finds that a piece of iron, or copper wire, held in this little flame, burns with nearly the same facility, that a cotton thread consumes in a candle; and that a piece of tobacco pipe not larger than a kernel of corn, will give a light, from which he will instantly be forced to cover his eyes. The compound blowpipe melts the most refractory substances, and even dissipates in vapor those which are infusible by the best furnaces. No means hitherto discovered, with the exception of the galvanic battery, produce calorific effects so intense as this blowpipe. Fig. 57. The pneumatic cistern above described is represented at Fig. 57, with the blowpipe in its place. For schools or private experiments, perhaps this is as cheap and convenient a form as can be constructed; since it serves the purpose of gasometers for the blowpipe, and a cistern for experiments on all the gases where a water bath is employed. It is believed, after having had occasion to direct the construction of several cisterns for the above named purposes, that the following dimensions are sufficient. Length of the cistern, 5£ feet; depth, 2} or 3 feet; width, 2 feet; gas-holders or boxes, 2 feet square. The cistern to be made of pine boards, and well painted on both sides before it is used. The frame and legs on which it stands, must be separate from the cistern, about 18 inches high, and furnished with rollers. Such an apparatus, including the blowpipe and boxes, costs about 14 dollars. Properties of Water. It is unnecessary to describe the common properties of a fluid which is so universally knowu, that neither man nor animal can exist without it. The purest water not having undergone distillation, is that which falls from the clouds.—It Is there any means of producing a more intense heat than that produced by the com Hound blowpipe ? Explain Fig. 57. What water is purest without distillation 1 132 PROPERTIES OF WATER. is transparent, and without either taste or smell; and being perfectly bland and neutral, it is to all animals, whose tastes have not been vitiated, the most agreeable of drinks. The weight of water, as already shown, is the standard by which the weight or gravities of all solids and liquids are estimated. The weight of a cubic foot of pure water is 1000 avoirdupois ounces. A cubic inch of this fluid weighs, at the temperature of 60°, 252.52 grains, and consists of 28.00 grains of hydrogen, and 224.46 grains of oxygen. By dividing 224.46 by 28.06, it maybe seen how nearly these gases unite in the proportions of 1 and 8 to form water. The weight of water, when compared with that of air, is as 828 to 1. The effect of temperature upon liquid water is distinguished by a peculiarity of a very striking kind, and exhibits a departure from the general laws of nature, for a purpose so obviously wise and beneficent, as to afford one of the strongest and most impressive of those endless proofs of design and omniscience in the frame of creation, which it is the most exalted pleasure of the chemist, no less than of the naturalist, to trace and admire. " All liquids, except water, contract in volume, as they cool down to their points of congelation; but the point of the greatest density in water is about 40°, its freezing point being 32 0 . 1 ' As its temperature deviates from this point, either upwards or downwards, its density diminishes ; or in other words, its volume increases. This peculiar law is of much greater importance in the economy of nature than might at first be supposed. The cold air which rushes from the polar regions progressively abstracts the heat from the great natural basins of water, or lakes, till the whole mass is reduced to 40°; but at this point, by a wise Providence, the influence of the atmosphere no longer has this effect; for the superficial stratum, by farther cooling, becomes specifically lighter, and instead of sinking to the bottom, as before, and displacing the warmer water, it now remains at the surface, becomes converted into a cake of ice, and thus preserves the water under it from the influence of farther cold. To what animals is water the most agreeable of all drinks 1 What is the weight of & cubic foot of pure water ? What is the weight of a cubic inch of water 1 How may it be proved that the weights of hydrogen and oxygen in water are in the proportions of 1 to 8 t What is the weight of water when compared to that of air ? At what temperature is water at its greatest density 1 When water is above or below the temperature o< 40 degrees, how is its bulk affected 1 In what respect is the expansion of water iti freezing, if great consequence to man 1 133 OXYGENIZED WATER. If, like mercury, water continued to increase in density to :*s freezing point, the cold air would continue to rob the mass of water of its heat, until the whole sunk to 32°, when it would immediately congeal into a solid mass of ice to the hot torn, and thus every living animal it contained would perish. In the northern or southern temperate zones, such masses of ice would never again be liquefied; a striking proof of the beneficence and design of the Creator in forming water with such an exception to the ordinary laws of nature. Water, in its natural state, always contains a quantity o. air. This may be shown by placing it under the receiver of an air pump, for as the air is removed from the receiver, bubbles will be seen to rise from the water. The air in water is found to contain a larger proportion of oxygen than the common air of the atmosphere. The lives of all such fishes as live entirely under the water, depend on the quantity of oxygen it contains, for no animal can live and move where oxygen does not exist. Deutoxide of Hydrogen. —17. 2 p. Oxygen 16+1 p. Hydrogen, 1. Oxygenized Water. Water, in the scientific language of chemistry, is the protoxide of hydrogen; being composed of hydrogen, with one proportion of oxygen. (Sec Nomenclature.) It was supposed that hydrogen was incapable of a farther degree of oxygenation', until 1818, when Thenard, a French chemist, showed that by a certain intricate process, hydrogen could be made to combine with another dose of oxygen, and thus a new compound was formed, called deutoxide of hydrogen. This compound is formed in precise accordance to the law of definite and multiple proportions, and consists of 2 proportions of oxygen and 1 of hydrogen, as stated at the head of this section. It is a highly curious and interesting compound. In some of its properties, it exactly resembles water, being inodorous and colourless; Tn.it in others, it is remarkably different. It is corrosive to the skin, which it turns white, and to If water, like mercury, had its density increased by cold to 32 degrees, what would be the consequence, on large bodies of this fluid 1 What is said of the beneficence and design of forming water with this exception to the ordinary laws of nature 7 How's i shown that water always contains air t How does the air in water differ from common air? What is the scientific name of water 1 What is deutoxide of hydrogen? What are the properties of oxygenized water ? How does this compound differ from commcm water 1 134 NITROCEN. the tongue it is sharp and biting, and leaves a peculiar metallic taste in the mouth. At the temperature of 58°, it is decomposed, oxygen gas being evolved in abundance. It is therefore necessary, in the summer season, to keep it surrounded with ice. It is also decomposed and turned into common water by nearly all the metals, and most rapidly by those which have the strongest attraction for oxygen. Some of the metallic oxides produce the same effect, without passing into a higher degree of oxidation, a fact which has not been satisfactorily explained. The metals, silver and platinum, in a state of fine division, decompose this water, when thrown into it, with such energy as to produce explosions. The same effect is produced by the oxides of silver, gold, mercury, manganese, and several other metals. Nitrogen. —14. This gas was formerly called azote, which signifies lijk destroyer, because no animal can live Avhen confined in it. But the same epithet might be applied to several other gases, with equal propriety; and therefore, being the basis of nitric acid, it is more properly called nitrogen. As the atmosphere is composed of fourfifths of nitrogen, this gas may be obtained by placing a mixture of iron filings and sulphur, a little moistened, in a confined portion of air, as under a bell glass, over water. The mixture will absorb the oxygen from the air, and leave the nitrogen nearly pure. It may also be obtained by burning a piece of phosphorus in a vessel of air, inverted over water. The phosphorus forms phosphoric acid with the oxygen of the air, which acid is absorbed by the water, thus leaving the nitrogen remaining in the vessel. Nitrogen is transparent, and without taste or smell, like common air. It is arranged as a simple body, though there are reasons for believing that it is a compound. It is destructive to animal life, and is a non-supporter of combustion. A lighted candle plunged into it, is instantly extinguished, and any animal soon dies when confined in it At what temperature is this compound decomposed 7 Why do the metals decompose this kind of water; and what do they absorb fiom it 1 What was the former name of nitrogen 7 What does azote signify 7 Why is it now called nitrogen 7 How may nitrogen be obtained 7 How is gas.obtained by means of iron filings and su'phur 7 Howl* nitrogen obtained by means of phosphorus 7 What are the i iropcrties of thi t gas7 135 ATM 38PM ERA. Vet it exerts no injurious influence on the lungs, the privation of oxygen being the soie cause of death. Its specific gravity is a little less than that of atmospheric air, nitrogen being 0.9722, air being 1000. One hundred cubic inches weigh 29.7 grains. When combined with oxygen in certain proportions, it forms nitric acid. Nitrogen exists in all animal substances, and in such plants as putrefy with an animal odour, as cahtage and mushrooms. The Atmosphere. The air which we breathe is composed of 20 parts of oxygen, and 80 parts of nitrogen, to every 100 by volume. These proportions are found never to vary, except from local causes. Gay Lussac, in an aerial voyage, carried with him an exhausted bottle, closely corked, and when at the height of nearly 22,000 feet from the earth, he uncorked his bottle, and let in the air. It was then closely corked again, and brought to the earth. On examination, this air was found to contain precisely the same proportions of the two elements as that taken from the surface of the earth. Specimens of air have also been brought from Chimborazo, Mount Blanc, from the deserts of Africa, and from the midst of the oceans, and on analysis, they have all been found to contain the same proportions of the two gases. These proportions are found by experiment to form the most agreeable air for respiration, and to be best fitted for the support of animal life. Animals confined in air, containing more than the ordinary proportion of oxygen, have their respiration hurried, and become feverish, by over excitement; while those confined to air which contains a less proportion of that gas, become languid and faint, from the want of its stimulating effects. Besides these two gases, the atmosphere contains variable portions of carbonic acid gas, and aqueous vapor. The car- In what manner docs nitrogen destroy life 1 Is the specific gravity of nitrogen greater, or less, than that of atmospheric airl With what substance does nitrogen form nitric acid 1 In what vegetables is this gas found 1 What is the composition bf atmospheric air 1 What is said of the constancy of these proportions 1 From what parts of the world have specimens of air been analysed, and found to contain the same proportions of the two gases 1 What is the effect of a greater proportion of oxygen than common air contains on the animal system t What is the effect of a less proportion on the system 7 l>oes the atmosphere contain #llier gases besides oxygen and tmgen 1 136 ATMOSPHERE. bonic acid seems always to be present, since Saussure [ouiA it in the air of Mount Blanc, taken from the height of 16,000 feet above the level of the sea. Its proportion never exceeds one part in a 100, in freely circulating air ; and it generally amounts to only 1,1000th or 1,2000th part of the whole. The proportion of aqueous vapor is also exceedingly variable, but seldom exceeds 1 part in 100. The air of particular situations, is also found to contain small quantities of carburetted hydrogen, or inflammable gas, and of ammonia; but these are not constant. It has been a question among chemists, whether the two gases composing the atmosphere are simply in a state of mixture, or whether they exist in a state of chemical combination. Mixture has commonly been distinguished from combination, by the spontaneous separation of the ingredients ot the former. But, although oxygen is specifically heavier than nitrogen, no such instance has been found to occur. Air, confined in a long tube standing vertically for many months, was found to contain the usual proportion of oxygen in its upper part. The proportions of its constituents are also definite, like those of energetic combinations. By weight, there are two proportions of nitrogen 28, with 1 of oxygen 8. And by volume 4 parts of the first, 80, to one of the latter, 20, in the 100, thus making the simple proportions of 4 to 1. It has, however, been found that other gases of different specific gravities mix with entire uniformity where it is known that no chemical union exists between them. Thus, if one vessel be filled with carbonic acid gas, and another with hydrogen gas, the latter being placed over the former, with a tube communicatingbetween them, the two gases will mix with perfect uniformity in a few hours. In this instance, a part of the carbonic acid, though 22 times as heavy as the hydrogen, is found to have ascended into the upper vessel, while a part ol the hydrogen, though 22 times lighter than the acid gas, descends into the loAver one. The cause of such an intimate mixture, under such circumstances, and without the influence What other gas is always found in the air ? AVhat gases are occasionally found, their presence depending on local circumstances? What reasons are there to believe that air is a chemical compound? A\ r hat singular fact is mentioned in respect to the mixture of carbonic acid and hydrogen, through a tube ? What does this fact show with respect U he uniform mixture, of the elements of the atmosphere Without a chemical union? What iies the fat titty with which oxygen is abstracted from the atmosphere tend to show in >ect to this chemica, inionl ATMOSPHERE. 137 of chemical attraction, has not been explained. But the facf is sufficient to show, that the uniform mixture of the const) tuents of the atmosphere may be accounted for, without a chemical union. The facility, also, with which oxygen is abstracted from the atmosphere is against a chemical union. Thus, rain water contains a considerable portion of oxygen, besides a portion of atmospheric air. But the attraction of water for oxygen, is not supposed sufficient to overcome a chemical combination, and therefore did such a combination exist in the atmosphere, oxygen would not be found in water under such circumstances. On the Avhole, it is most probable, that the constituents of the atmosphere exist in a state of mixture, and not in a state of chemical union. The oxygen of the atmosphere being the principle which supports life, and flame, it is obvious that large quantities of this gas must be consumed every day, and therefore that its quantity must diminish, unless there exists some source from which it is replaced. The quantity consumed, however, must be exceedingly small, in a definite period of time, when compared with the whole; for the atmosphere not only entirely surrounds the earth, but extends above it, at every point, about 45 miles. Now, when we consider how small a proportion of this immense mass, comes into contact with ani mals or fires at any one time, and that it is only tlese small portions that become vitiated, we may suppose that ages would elapse before any difference could be detected in the quantity of oxygen, even were there no means of replenishment provided. But the wisdom and design of Deity which the study of nature every where detects, and which as constantly seems ordained for the benefit and comfort of man, has not left so important a principle as that of vital air to be consumed, without a source of regeneration. It appears from experiments, that vegetation is the source from which the atmosphere is replenished with oxygen, and so far as is known, this is the only source. Growing plants, during the day, absorb carbonic acid from the atmosphere, On the whole, is it most probable that the elements of the atmosphere exist in a state of mixture, or in that of a chemical union 1 What is said of the quantity of oxygen consumed by animals, and flame, when compared with the whole, which exists in the atmosphere 1 From what source is the atmosphere replenished wit! oxygen 1 38 ATMOSPHERE. decompose the gas, emit the oxygen of which it is in pan composed, and retain the carbon to increase their growth. — (See Vegetation.) We have seen, under the article Oxygen, that when wood or carbon is burned, that oxygen is thereby converted into carbonic acid gas, and a greater or less propoition of this gas contained in the atmosphere may be attributed to this source. Here, then, we are able to trace another instance of the wonderful order and design of Omnipotence. The destruction of plants by burning, while the process absorbs the oxygen from the air, furnishes carbonic acid, which in its turn, is decomposed by growing vegetables, the carbon being again converted into wood, while the oxygen goes to replenish the loss created by the burning, and to purify the atmosphere lor the use of man. NITROGEN AND OXYGEN. In addition to the reasons formerly assigned for supposing the atmosphere not to be a chemical compound, may be adduced the fact, that most other combinations of nitrogen and oxygen produce corrosive or noxious substances. Five such compounds are known to chemists, and they all admirably illustrate the changes produced by chemical combinations, as already noticed under the article Affinity. They also confirm the truth of the doctrine of multiple proportions, having been adduced, as illustrations of this principle, under the same article. Some of the most material properties ol each of these compounds will be stated, beginning with that containing the least proportion of oxygen, and ending with that containing the most. Protoxide of Nitrogen. —22. 1 p. Nitrogen 14X1 p. Oxygen 8. Nitrous Oxide. The best method of obtaining this gas is by fusing a salt called nitrate of ammonia. This salt may readily be formed How do plants obtain the oxygen which they emit'? Whence comes the carbonic acid gas which plants decompose 1 What is said of the wonderful order and evident design of Providence, in making the destruction of plants the means of replenishing the air with oxygen 7 What is said of the compounds of nitrogen and oxygen in reference to the chemical nature of the atmosphere? What do these compounds illustrate? What is the signification of protoxide ? What other name is there for protoxide of nitx.-gen 1 How is this gas obtained ? 139 NITROGEN AND OXYGEN. *-y mixing carbonate of ammonia with nitric acid (aquafortis) diluted with four or rive parts of water, and then evaporating the solution by a gentle heat. The ammonia should be added in small lumps until the effervescence ceases ; and the evaporation continued until a drop of it, placed on glass, cpn cretes. Having prepared the salt, the nitrous oxide or exhilarating gas may be procured from it, and its effects by respiration tried by the following simple means, when no better apparatus can be obtained. Prepare a Florence flask, as shown at Fig. 36, and into this put four or five ounces of the nitrate of ammonia. For a gas holder, fit to a large stoneware jug a cork pierced with two apertures with a burning iron; into one of the apertures pass a tube of glass or tin, so that it shall reach nearly to the bottom when the cork is in its place, and stop the other orifice with a cork. For a pneumatic cistern, take a common wash tub, and fit to it a strip of board passing through the middle, and about four inches from the top, so that when the tub is filled with water, the board will be covered. Through the board cut a hole to receive the neck of the jug, so that it will stand inverted. Having prepared things in this manner, fill the jug with water, and invert it in the tub, also previously filled with water. Then bend the tube belonging to the flask, so that it will enter the mouth of the jug, while the flask itself stands on a ring of the lamp furnace, and apply a gentle heat. If no lamp furnace is at hand, the flask maybe suspended by a wire or string, and heated by a common lamp, or a few coals. The salt will soon melt and become fluid and transparent, when the gas will be extricated in abundance. When the jug is nearly full, which will appear by the sound of the bubbles, slip the hand under its mouth, and having set it upright, immediately put the cork with the tube through it, in its place. As the nitrous oxide sometimes contains a mixture of nitric oxide, or deutoxide of nitrogen, which is dangerous to respire, but which is absorbed by water, it is safest How is nitrate of ammonia formed 1 Having prepared the salt, in what manner is the gas extracted from it 1 In what manner may a temporary gas holder and water bath ba prepared 1 Having prepared the gas holder, or jug, and the water bath, or tut., how will you proceed to All the jug with gas? How will you know when the jug is full of" gas What gas is sometimes mixed with the nitrous oxide I 140 NITROGEN AND OXYGEN. before the gas is respired to let it stand an hour or two, /vith the water remaining in the jug. To respire the gas, prepare a bladder, or oiled silk bag, by attaching to it a tube which fits closely to the second aperture in the large cork, and having squeeztd all the air out o. the bladder, or bag, remove the small cork and pass in the tube. Next pour such a quantity of water into the jug through the long tube as it is desired to obtain gas in the bag. Now the gas cannot escape through the long tube, because its lower end is in the water, nor can it escape through the mouth of the jug, this being closed by the cork ; it therefore passes into the bag. When this is full, withdraw the tube from the jug, and having expired, or thrown the air from the lungs, close the nose with one hand, and with the other apply the tube to the lips and breathe the gas from the bag into the lungs, and from the lungs to the bag. Sir H. Davy respired 12 quarts, but the medium dose is from 4 to 8 quarts for an adult. On some persons this gas has a highly exhilarating or intoxicating effect, and produces the most agreeable sensations, often attended by momentary mental hallucinations, and corresponding actions. On others it produces mental depression, and melancholy forebodings. Its action commonly continues only for a few moments, and its effects seldom or never produce a state of languor or debility, which might be expected to follow such a degree of excitement. The composition of the protoxide of nitrogen by volume, is nitrogen 100, and oxygen 50. 100 cubic inches of this gas weighs 46.5 grains, and its specific gravity is therefore 1.5, air being 1. It is transparent, and colorless, has a sweetish taste, and an agreeable aromatic smell. It is a supporter of combustion, and many substances burn in it with far greater energy than in atmospheric air. The burning body absorbs the oxygen from the nitrous oxide and thus the nitrogen remains in the vessel. Why is it safest to let the gas stand over water awhile before it is breathed 1 After having prepared a bladder, or gas bag, how is this filled with the gas from the jug 7 How is the gas respire'' ? What is the medium dose for an adult 1 What effect is the respiration of this gas said to produce on the human feelings 1 What is the composition of the n j-ous oxide 1 Wliat is its specific gravity 1 Does this gas support combustion 1 NITROGEN AND OXYGEN. 141 Deutoxide of Nitrogen.—30. 1 p. Nitrogen 14+2 p. Oxygen 16. Nitric Oxide. Nitrous Gas. Deutoxide oi nitrogen, as expressed above, and as its name, •signifies, contains two proportions of oxygen to one of nitrogen. It was formerly called nitric oxide, and nitrous gas, but analysis having shown its composition, its name is fixed in accordance. This gas is formed by the action of nitric acid on copper. Having introduced some copper turnings or filings into a retort, pour on them a quantity of strong nitric acid or aqua fortis. A violent effervescence will ensue, and the gas will escape in abundance. At first it will appear of a deep red colour, which is owing to the presence of atmospheric air in the retort; but on passing it through water the red fumes are absorbed, and the nitrous gas remains pure and colorless. To understand the chemical changes by which this gas is formed, it is necessary to state that nitric acid is composed of 40 parts of oxygen and 14 parts of nitrogen, and that this acid is decomposed by the process. A part of the oxygen of the acid unites with the copper, and forms an oxide of the metal, while another part of the oxygen continues in union with the nitrogen, forming a deutoxide of nitrogen, which, as already seen, contains only 16 parts of oxygen. The gaseous form of the deutoxide is owing to the absorption of a quantity of caloric at the instant of its formation. The evolution of this gas is therefore owing to the abstraction of a part of the oxygen from nitric acid, by the copper. Other metals, and particularly quicksilver, will produce the same effect. Nitrous gas, when pure, is sparingly absorbed by water. It is a little heavier than atmospheric air, 100 cubic inches weighing 31.7 grains, while the same quantity of air weighs 30.5 grains. It cannot be respired, even in small quantity, without a sense of suffocation, and violent coughing. It instantly extinguishes the flame of most substances, when plunged into it, but if charcoal, or phosphorus, in a state of What docs deutoxide signify ? What is the composition, and what the equivalent numbers for deutoxide of nitrogen ? What was the former name of this gas 1 How is nitric oxide obtained ? Why do the first portions of this gas appear red 1 What are the chemical changes by which this gas is formed? What causes the gaseous form of this acid ? To what is the evolution of this gas owing? What is the weight of this gasl What are its effects on respiration and flame ? 142 NITROGEN AND OXYGEN. vivid combustion, be immersed in it, its oxygen is absoibtd ami they burn with increased energy. When mixed with atmospheric air, red fumes are generated, as already noticed. This is owing to th# union of the oxygen of the atmosphere with the nitrous gas. When pure oxygen is added to a portion of this gas, the red becomes still deeper, and there is formed nitrous acid, Avhich is entirely absorbed by water. Thus these two gases, nitrous gas and oxygen, are a delicate test for each other, the smallest quantity ol the one being detected by introducing a quantity of the other. From the property of the nitrous gas above stated, it has been employed in Eudiometry, that is, to ascertain the purity of the atmosphere, or the quantity of oxygen it contains. The method by which this is done, is to confine a certain portion of air in a graduated tube, and then to introduce into the tube, a sufficient quantity of the gas to unite with all the oxygen it contains. Then as the compound formed between the oxygen and the nitrous gas is entirely absorbed by water, it is readily seen by the graduated tube what proportion ol air has disappeared, after agitating the mixture with water, and consequently how much oxygen it contained. The composition of deutoxide of nitrogen has been accurately ascertained by burning charcoal in it, which absorbs all the oxygen, amounting to exactly one half the volume of the whole, and leaves the nitrogen, which amounts to the other half. By this analysis, it is found that 100 parts of this gas lose 50 parts of oxygen, and that 50 parts of nitrogen remain. 50 cubic inches of oxygen weigh 16.8 grains, 50 cubic inches of nitrogen weigh 14.9 grains, The 100 parts therefore weigh 31.7 grains. The equivalent composition therefore is 1 atom, or equivalent of nitrogen 14 2 do. do. oxygen 16 30 What acid is formed when this gas combines with an additional portion of oxygen gas 1 By what fluid is this gas absorbed 1 In what manner is the nitrous gas employed to ascertain the quantity of oxygen in the atmosphere 1 In what manner has the composition of this gas been ascertained 1 What is the composition of this gas 1 What is -ts cqu ¦ valent number 1 What are the equivalent numbers of its elements 1 NITROGEN AND OXYGEN. 143 Nitrous Acid —46. 1 p. Nitrogen 14-f-4 p. Oxygen 32. The next compound of nitrogen and oxygen which we shall.notice is nitrous acid. This acid is formed by adding oxygen to the compound '.ast described, in consequence of which, the nitrogen of that compound combines with another portion of oxygen equal to that which it before contained. The deutoxide contained 2 proportionals of oxygen, 16. The nitrous acid contains 4 proportionals of oxygen, 32. Between these, there is a hypothetical compound, containing 3 proportions of oxygen, but which has not been obtained in a free state. This is called hyponitrous acid, and by some subnitrous acid, because it contains less oxygen than nitrous acid. . Nitrous acid may also be obtained by the distillation of nitrate of lead, in a retort. (See Nitrate of Lead.) During the distillation, the receiver should be kept cold, by surround ing it with ice. By either of these methods, there is obtained a vapour, or gas, of a deep orange red colour, which is the nitric acid in a gaseous state. To obtain it pure, it is, however, necessary that the receiver should be first exhausted by the air pump, because the gas is instantly absorbed by water, and a mercurial bath cannot be employed, because the gas acts upon that metal. By volume this acid is composed of, Nitrogen 100 By weight, Nitrogen 14 Oxygen 200 Oxygen 32 300 46 Nitrous acid, in its fuming state, is totally irrespirable; but supports the combustion of phosphorus or charcoal, when these are introduced into it in a state of combustion. Water absorbs this gas in large quantities, and acquires thereby, first a green and afterwards a blue tint. If still more be added, it becomes yellow, or colourless, and forms a solution of nitrous acid in water. What are the processes by which nitrous acid may be obtained? What is the compoeition of this acid ? In what does Uiis acid occur, and what is its colour t How is this acid obtained in its pure state ? Why cannot a mercuiial or water bath be employed to confine this gas? What are the definite proportions of the elements of this acid by volume ana weight? Docs this gas support combustion or animal life 1 What is said d us absorption by water and the colours prodiucd thercbv 7 144 NITRIC ACID. Nitric Acid —54. 1 p. Nitrogen 14+5 p. Oxygen 40. Aqua Fortis If a mixture of oxygen and nitrogen be confined in a glass tube containing a little water, and powerful electrical shocks be passed through this mixture, the water, after a continued succession of such shocks, will possess acid properties. By this process, the two gases are made to combine and form nitric acid, which is absorbed by the water. This experiment is designed merely to prove mat the acid in question is formed of oxygen and nitrogen. The usual mode of forming this acid, is by the distillation of the nitrate of potash, more commonly called nitre, or saltpetre, with sulphuric acid. The proportions are four parts of nitre, in coarse powder, with three parts of the acid by weight The receiver must be large, and kept cold, otherwise much of the acid will escape before it is condensed. The strongest acid is formed when no water is placed in the receiver, that already combined with the sulphuric acid being sufficient tc condense the nitric acid vapor as it is formed. The strongest nitric acid is without color, and has a specific gravity of 1.5, that is, this acid is by one half heavier than water. In this state it contains 25 per cent, of water. The dry nitric acid, which is formed by the condensation of its constituent gases, contains no water, and is composed, as stated at the head of this section, of 1 proportion of nitrogen, 14, and 5 proportions of oxygen, 40. The combining number of the dry acid is, therefore, 54. The acid obtained by distillation contains the same elements as the dry acid, and in the same proportions, but with the addition of two proportions of water. Now, the combining proportion of water being 9, that is, oxygen 8 and hydrogen 1, it is easy, by the above data, to find the combining or equivalent number for liquid nitric acid. It may be stated thus : What is the composition of nitric acid, and what its combining number 7 What ear periment shows that this acid is formed of nitrogen and oxygen 7 What is the usual mode of obtaining this acid? In what manner is the strongest nitric acid formed? Whence comes the water to absorb the acid vapor when none is placed in the receiver 7 What is the specific gravity of the strongest acid ? What proportion of water does it contain 7 How is the dry nitric acid formed 7 Does the acid obtained by distillation (entain he same elements as the dry 7 NITRIC ACID. 145 1 prop, of Nitrogen 14 5 prop, of Oxygen 40 54 dry acid. 2 prop, water 18 72 liquid acid. The acid in this state is called hydro nitric acid, from Greek word signifying Avater, to denote its combination with that fluid. When this acid combines iwith other substances it abandons the Avater, which therefore is not reckoned in its equivalent number. In this state it is called anhydrous nitric acid, denoting that it contains no Avater. Nitric acid is an exceedingly acrid and corrosive substance. It stains the sk in and nails of a permanent yelloAv, and is an active Doison Avhen swalloAved. It parts Avith its oxygen Avith great facility, and hence is decomposed by nearly every combustible body. It combines with most of the metals, and decomposes all vegetable and animal substances. As a proof of the slight degree of force Avith which this acid retains its oxygen, take some Avarm, dry, and finely pow dered charcoal, and pour on it a few drachms of strong nitric acid. The charcoal will be ignited, Avith the emission of immense volumes of red fumes. By this process the acid is decomposed, and parts Avith 2 or 3 portions of its oxygen to the charcoal, in consequence of Avhich it is converted into nitrous acid, and deutoxide of nitrogen, Avhich pass off in the form of red fumes. If an ounce of the spirit of turpentine be placed in a cup, and on it there be poured suddenly, about half an ounce of this acid, the turpentine will be inflamed with an explosion, sending forth a great quantity of black smoke, and often throwing the acid and fire to a considerable distance. In both these cases, the acid parts with its oxygen Avith so What are the constituents of liquid nitric acid 7 Wli.it is the chemical name for the liquid nitric acid 7 When this acid combines with other substances, what becomes of its water 1 What is the chemical name for the dry acid 7 What are the properties of nitric acid 7 How is it shown that this acid holds its oxygen with a slight force 7 What effect Joes the action of the charcoal have on this acid 7 What are the red fumes which pass off during this experiment 7 How may spirit of turpentine be inflamed by this acidl Why are the combustibles set on fire by this acid 7 13 146 ntuch freedom, aud the combustibles absort with such avidity, as to set them on fire. In making the latter experiment, the vial containing the acid should be tied to a long stick, otherwise the operator will be in danger from the explosion. Nitric acid forms a great number and variety of salts, when combined with the different metals, earthr, and alkalies. Most of these salts scintillate when thrown on burning charcoal. This is in consequence of the oxygen which the salt emits when exposed to heat, and by which the combustion oi the charcoal is rendered more vivid. This scintillation is a sure proof that the salt is a nitrate. All the nitrates are soluble in water, and many of them furnish oxygen gas of more or less purity when heated in a retort. NITROGEN AND HYDROGEN. Ammonia 17. 1 p. Nitrogen 14+3 p. Hydrogen 3 Hartshorn. There is a substance well known to artists, and others, by the name of sal-ammoniac. In chemistry its name is muriate of ammonia. If some of this substance be pulverized by itself, and then mixed with an equal portion of unslaked quicklime, also in powder, and then introduced into a retort, upon the application of a gentle heat, there will arise an extremely pungent gas, which is ammonia. Water absorbs this gas with great avidity, and in large quantities, and consequently it cannot be collected like most other gases, by means of the water bajth. In the absence of a mercurial bath, therefore, its properties can be examined by receiving it in a bladder attached to the retort, or by means of a tall bell glass, and the appa ratus described at Fig. 40. This gas is transparent, and colorless. In its pure state it cannot be respired. An animal cannot live in it, and it extinguishes the flame of burning bodies. What is said of the salts formed by the combinations of nitric acid I Why do the raltt I this acid scintillate when thrown on burning charcoal 7 What is said of the solubility Of the nitrates? How is ammonia obtained? Why cannot this gas be collected under T*ttt I How may its properties be examined without a mercurial bath % CARBON. 147 This gas is composed of 1 equivalent or atom of nitrogen 14 3 do. do. hydrogen 3 Its combining weight is therefore 17 It is much lighter than atmospheric air, 100 cubic inches weighing only 18 grains. When this gas is absorbed by water, which will take up more than 500 times its own bulk of it, there is formed the well known pungent liquid called spirit of sal ammoniac, or spirit of hartshorn, and by the apothecaries, liquid ammonia. When ammoniacal gas is submitted to the pressure of 6 or 7 atmospheres, equal in the whole to about 100 or 120 pounds to the square inch, it is condensed into a clear colorless liquid, but when the pressure is removed, it again expands, and assumes its former gaseous state. Ammonia is called the volatile alkali, by which it is distinguished from the fixed alkalies, soda and potash. It possesses, fully, all the properties of an alkali, having an acrid taste, a strong affinity for water, and being capable of neutralizing the corrosive qualities of the acids. The article used in smelling bottles, and called volatile salts, and salt of hartshorn, is a carbonate of ammonia. The salts of ammonia, and particularly the muriate and carbonate, are articles of considerable importance in commerce, in the arts, and in medicine. Carbon. —6. Nature furnishes carbon in its purest state, in the form ol that precious gem, the diamond. That the diamond is nothing but pure carbon, is proved by direct analysis. If in a glass vessel containing oxygen gas, a piece of diamond be placed, and then exposed to the intense heat of a large convex lens, or burning glass, the diamond entirely disappears, and there remains in the vessel carbonic acid, instead of oxygen. Thus the diamond, like other com- What are the most obvious properties of ammonia 1 What is the composition of am monia, and what is its equivalent number? What is the weight of 100cubic inches ol his gas? How is liquid ammonia formed? What quantity of this gas will water ab wrb? What is said of the condensation of ammonia into a liquid ? What is the article Tailed volatile salts ? What is said of the alkaline properties of ammonia 7 How is it ..roved that the diamond is composed of p-re carbon 1 148 CARBON bustibles, forms carbonic acid by being burned, or by uniting with oxygen. When charcoal, or carbon from wood, is burned in pure oxygen gas, exactly the same result is produced, the charcoal entirely disappears, and the oxygen is converted into carbonic acid. Charcoal may be obtained for experiments, by burying wood under sand, in a crucible, and exposing it to an intense heat for an hour or two. By this process, the water and other ingredients of which Avood is composed are driven off, and the carbon remains. Both diamond and charcoal sustain the most intense de grees of heat, Avithout change, provided oxygen is entiiely excluded from them. Charcoal, when neAvly prepared, possesses the property of absorbing large quantities of air, or other gases, at common temperatures, and of yielding the greater part of them again Avhen heated. There is, hoAvever, a great difference in respect to the quantity absorbed, depending on the kind of gas Avith Avhich the experiment is made. Ammoniacal gas is taken up in the largest quantity, this being 90 times the bulk of the charcoal. Muriatic acid gas is absorbed in the proportion of 85 times the bulk of the charcoal. Other gases are absorbed only in small proportions, nitrogen being only 7f times, and hydrogen 1.75 times the bulk of the charcoal. The greatest absorption takes place in charcoal made from the most compact kinds of Avood, and the amount is much diminished when the charcoal is reduced to powder. Charcoal, recently prepared, has the property of resisting putrefaction in animal substances, and of rendering such substances sweet, after they are tainted. The most offensive stagnant water, loses its odor and becomes perfectly SAveet by being filtered through poAvdered charcoal. It also destroys the color of many substances. Vinegai loses its color, and becomes transparent like AA'ater, by being boiled with charcoal, and red wines, or colored brandy, are bleached by passing through it. The best charcoal for these When diamond, or charcoal, is burned in oxygen gas, what is the product 7 How may charcoal be obtained from wood in a pure state 1 What peculiar property docs newly prepared charcoal possess 7 What difference is there in respect to the quantity of the different gases absorbed by charcoal 1 AVhat gases are absorbed in the greatest, and what in the least quantity 7 What effect does newly prepared charcoal have on putrefying animal substances 7 What effect docs charcoal have on the color of particular substar coal What kind of charcoal is best for the above purposes 7 149 CARBON AND OXYGEN. purposes is prepared by calcining animal substances in close vessels. In the present state of knowledge, charcoal is a simple substance, having resisted all attempts to decompose, or separate it into other elements. Its atomic weight or combining numoer is 6, this being the proportion in which it is found to unite with oxygen, to form carbonic acid, and in no instance has it been detected in a less proportion in combination. CARBON AND OXYGEN. Carbonic Acid —22. 1 p. Carbon 6+2 p. Oxygen 16. Fixed Air. It has just been stated, that when diamond or charcoal is Durned in oxygen, the latter is changed into carbonic acid. By this process the volume of oxygen is not changed, but its weight is increased by exactly the amount of the diamond, or charcoal, consumed. Carbonic acid, therefore, consists of oxygen, with a quantity of charcoal dissolved in, or combined wiih it. This acid can, however, be obtained by a much cheaper, and more direct method, than by the combustion of diamond, or even of charcoal, in oxygen gas. Carbonic acid exists in a fixed state, in vast abundance, as a part of the composition of limestone or marble. This che mica! compound, so abundant in nature as to form immense mountains, is composed of 22 parts of carbonic acid, and 28 of lime. Carbonic acid may therefore be obtained most readily, by exposing carbonate of lime to the action of some acid which has a stronger affinity to the lime th°n the acid has with which it is naturally combined, thus by forming a new compound between the lime and the stronger acid, the carbonic acid will be set at liberty. Is charcoal a simple, or a compound body 1 What is the combining number, or atomic weight, of carbon 1 When diamond, or charcoal, is burned in a confined portion •)f oxygen gas, what efFect does the combustion have on the volume and weight of the gas 1 In what natural compound is carbonic acid contained in great abundance 1 What proportion of carbonic acid does marble contain 1 What are the chemict principles on which carbonic acid may be obtained from limestone, o. marble 1 13* 150 CARBON AND OXYGi.N. For this pur pose, introduce pure white mar ble, in small frag ments, into the two necked bottle a, fig. 58. having the bent tube c, connected with one of the necks and passing under the jar d, filled with water and inverted in the water bath. "—Then pour through the funnel b, some sulphuric acid, diluted with five, or six parts of water. Effervescence will immediately ensue, in consequence of the escape of the gas, which in a few minutes will be seen to rise in bubbles through the water in the jar. The chemical changes during this process illustrate the law of simple affinity, formerly explained, viz., that one substance may have an attraction for several others, but with different degrees of force. Thus lime has an affinity for carbonic acid, with which it combines and forms carbonate of lime. But sulphuric acid having a still stronger attraction for the lime, when this is added, the carbonate is decomposed, the sulphuric acid and lime unite and form sulphate of lime, while the carbonic acid being thus rejected, escapes in the form ol gas. This gas is inodorous, colourless, and elastic. It extinguishes burning substances of all kinds, and is so poisonous, that a small quantity of it mixed with atmospheric air animal life. It is this gas which Jestroys the lives of many persons everj winter, in consequence of warming close rooms with open vessels of burning charcoal. In such cases the air becomes Explain Fig. 58, and describe the process of obtaining carbonic acid gas from marble Explain how this process illustrates the law of simple affinity. What new salt is iormeo when sulphuric acid is poured on marble 1 What is the effect of tiii3 gas on Same, and animal life 1 When ch trcoal is burned in an open vessel, in a close room, *hat is tin effect on the air of the .-oom 1 CARBON AND OXYGEN. noxious from two causes; the charcoal, by abstracting the oxygen from the atmosphere, would leave only the nitrogen, which, as we have already seen, will not support animal life. The mere absence of the oxygen would, therefore, be the negative means of destroying life. But this is not the most active cause of destruction. The air is not only deprived of its oxygen, by the burning charcoal, but the oxygen, by uniting with the charcoal, becomes an absolute poison; this is indeed of so deleterious a nature, that when pure, it causes death by producing a spasm of the glottis, thus closing entirely the passage to the lungs, and when mixed with atmospheric air, in such a proportion as to be taken into the* lungs, it then acts as a narcotic poison, producing dimness of sight, loss of strength, difficulty of breathing, then entire suspension of respiration, and finally, insensibility, apoplexy, and death. When limestone is exposed to heat, this gas is driven off] and in consequence of this loss, the limestone is converted into quicklime, a substance Avell known as the basis of mortar for building. The gas, thus extricated, being quite pure, is exceedingly deleterious, and sometimes proves fatal to the workmen and others in the vicinity of the kiln, where the burning is perrormed. M. Foder states, that in the year 1806, a family residing at Marseilles, consisting of seven persons, were all rendered apoplectic, in consequence of breathing carbonic acid, which \yas extricated from an oven in the yard of the house, where limestone was burning. The gas had come into the house through the door and windows, and by some means it was found, during the night, that the family were in danger, and the alarm was given, but not in time for any one to escape. In the morning all the seven were found in different places, one on the stairs, one on the step of the door, &c, with lamps in their hands, in the attitude of flight; but the deleterious gas had taken away their strength, and put out their lights. They all appeared to have fallen down of apoplexy, while attempting to escape death by flight. Five Avere dead beyond recovery, but the two others Avere brought to life. Some people, who are perfectly aA\ r are of the poisonous How does pure carbonic acid cause death 1 When mixed with air, so as to be respired, how does it cause deatli 1 When limestone is exposed to a red heat, what changes are produced on it 1 What were the circumstances under which a family at Marseilles were -endered apoplectic by this gas 1 Is there any difference between the poisonous effects o! harcoal prepared in a coal-pit, and that taken from the hearth 1 152 CARBON AND OXYGEN. * effects of the air arising from ignited charcoal, which has been prepared in coal-pits, still unaccountably believe, that the coals from a common fire are innocent. This opinion has probably arisen from the circumstance, that coals from the fire are taken up with a quantity of ashes, in which they are chiefly covered, so that their combustion is made less rapid, than when charcoal alone is used. But that there is no difference in respect to the poisonous property of this gas, whether the charcoal has been prepared in a coal pit, or on the hearth, is proved by the fact, that a respectable citizen and his wife, a short time since, had nearly fallen victims to this mistaken opinion. Water absorbs carbonic acid from the atmosphere, and it is owing to its presence in spring and well water, that we are indebted to their pleasant flavour. Boiling causes this gas to escape in consequence of the heat, and whoever has tasted ol water immediately from a fountain, and of another portion of the same water, which has been boiled, will observe a remarkable difference. Water which has been recently boiled, will absorb its own bulk of carbonic acid, when agitated with it. The smart and agreeable taste peculiar to soda water, to lively beer, champaigne, cider, and porter, is owing to the presence of this gas. This shows that, though a deadly poison when taken into the lungs, it may be taken into the stomach, not only Avith impunity, but Avith pleasure. The poisonous quality of this gas is a striking instance ol the change produced on bodies by chemical combination. Charcoal alone is so inert as to be taken into the stomach in any quantity, Avithout other deleterious effects, than Avhat might arise from over distention, and in fine poAvder it is so far from being injurious to the lungs, that the coalmen consider their business as of the most healthy kind. Oxygen, as it exists in the atmosphere, is the very pabulum of animal life, and when perfectly pure, may be respired Avithout any other ill effects, except what arise from over excitement. But when these tAvo substances are chemically united, they form, as already described, a compound of the most deleterious kind, What is said of the absorption of this gas by water, and the lively taste given the fluid n consequence ? Why does water which has been boiled taste flat and insipid 1 To what liquids does this gas give their smart and lively taste 1 What does this prove i» respect to the poisonous quality of this gas 1 How do the. poisonous qualities of tnis gas illustrate the changes produced on bodies by chemical combinations 1 153 CARBON AND OXYGEN. a poison which, according to M. Halle, destroys animal life in the space of two minutes. The specific gravity of this gas is 1.52, air being 1 ; so that it is about one half heavier than air. It may be poured from one vessel to another like water, and as it instantly ex'inguishes.flame, lights may be put out with it, in a manner which will puzzle and astonish those who are not in the secret. If a short piece of candle be lighted and set in a tumbler, and then a jar of this gas, which in appearance contains nothing, be held so that its contents run into the tumbler, the light will be as effectually extinguished, as though the tumbler had been filled with so much water. One of the best tests of the presence of this acid is lime water, which though perfectly transparent before, instantly becomes cloudy, or turbid, when the smallest quantity of this gas is blown into it. The small quantity of carbonic acid which is generated in the lungs at every inspiration, is sufficient to form a precipitate in lime water. (See Respiration.) The cause which renders lime water turbid by being mixed with carbonic acid is easily understood. Water dissolves a small quantity of lime which it holds in solution; but carbonate of lime is insoluble in water. When carbonic acid is blown into a vessel of lime water, the lime instantly combines with it, forming a carbonate of lime, which, being insoluble, is seen in the form of a white cloud. The carbonate thus formed, being heavier than water, sinks to the bottom, or is precipitated. The large quantities of this acid which are formed by combustion and respiration, it might be supposed, would increase the quantity in the atmosphere, particularly in crowded manufacturing cities, so as to make the air poisonous. But as already explained, the wisdom of Omnipotence has prevented the accumulation of this gas in particular places, in consequence of its specific gravity, for experiment shows, that not withstanding the great difference existing among the gases in this respect, they all mix uniformly. Hence, by this wonderful provision, or exception to the general law of gravity, What is the specific gravity of this gas"! How may lights be extinguished by this gas in a manner to puzzle those who are not in the secret 1 } What is a good test for carbonic aciJ 7 What effect is apparent when a little of this gas is blown into lime water! Why does lime water become turbid by the presence of carbonic acid ? Why is the atmosphere seldom rendered \ Visonous by the accumulation of this gas? 154 SULPHTR. this gas, though extricated in immense volumes in the free open air, soon diffuses itself on all sides, and mixes with the surrounding atmosphere, so as seldom to prove deleterious by local accumulation. The composition of this gas has been determined with ac curacy, and as seen at the head of this section, it is composed of 2 proportions of oxygen 16, and 1 proportion of carbon 6; hence its combining weight is 22. Carbonic Oxide. —14. 1 p. Carbon 6-J-l p. Oxygen 8. When two parts of chalk, and one of iron filings, are mixed together and heated in a gun-barrel, carbonic oxide gas is obtained. The student will readily understand the principle of its formation. An oxide contains too small a proportion of oxygen to form an acid.. When lime or chalk is heated, carbonic acid is extricated, and when iron is heated, it has a strong attraction for oxygen. When therefore the chalk and iron filings are heated together, we may suppose, in the first place, that the carbonic acid is extricated, as usual, but that the iron instantly absorbs one half of its oxygen, thus converting the acid gas into an oxide. This gas possesses the mechanical properties, color, and transparency of carbonic acid. Like that gas, it extinguishes the flame of burning bodies, but is itself inflammable, the light which it puts out, setting it on fire at the surface, where it burns quietly, with a pale, lambent flame. The combining proportion of carbon has been determined from this compound, its elements, carbon and oxygen, having never been found to combine in smaller proportions than 6 of carbon and 8 of oxygen by weight. SULPHUR 16. Sulphur is found in the vicinity of volcanoes in large quantities, being sublimed, or brought up from the depths below, by the heat of the volcano, where it existed in combination with the metals. It is also found combined with various metals, What is the composition of thiB gas, and what its combining number ? How is carbonic oxide formed 7 What are the chemical changes which take place in forming this gas by means of chalk and iron filings! What are the properties of this gas? What is its composition and combining number 7 In what situation is sulphur chiefly found 1 Whence comes the sulphur found in the vicinity of volcanoes? 155 SULPHUR AND OXYGEN. forming sulphurels, a class of compounds hereafter to be examined ; nor is it entirely wanting in the animal and vegetable kingdoms, many substances in each containing it in small quantities. Sulphur is a well known brittle solid, of a greenish yellow color, which has little or no taste, but which emits, a peculiar odour when heated, or rubbed. Its specific gravity is nearly 2, water being 1. When heated to a temperature a little above boiling water, it melts, and becomes completely fluid. In this state it is cast into moulds, and is known in commerce under the name of roll brimstone. If the heat is raised to 300°, it loses its fluidity, oecomes viscid, and acquires a reddish color. If in this state it be poured into water, it becomes ductile, and is then employed to take the impressions of medals and seals. The color and texture of these false medals have the appearance of some metallic alloy, and those who are unacquainted with their composition, taking them for such, are at first surprised at their lightness. When sulphur is heated to 500° in a close vessel, it rises in vapor, or sublimes, and is condensed unchanged, except in form, which is that of an impalpable powder, well known under the name of flowers of sulphur. In this manner it is purified. Sulphur combines with the earths, alkalies, the metals, and with several proportions of oxygen. Its compounds are therefore numerous, and some of them interesting. It has not been found combined with any substance in a less proportion than 16, with which it forms an acid, called the hyposulphurous, when united to 8 parts of oxygen. Sulphur, so far as known, is a simple body; all attempts to decompose it, having proved fruitless. SULPHUR AND OXYGEN. Sulphurous Acid —32. 1 p. Sulphur 16+2: p. Oxygen 16. When sulphur is burned in pure oxygen gas, the latter How is sulphur described 1 What is its specific gravity 1 At what degree of heat k«s sulphur melt 1 What is roll brimstone 1 How is sulphur prepared to take the impvaasions of medals and seals 1 How are flowers of sulphur prepared t With what sther bodies does sulphur combine 1 What is the lowest proportion in which sulphur ia known t» combine 1 Is it an element or a compound I 156 SULPHUR AND OXYGEN. suffers no change of volume, but acquires a most suffocating tind pungent odour, and many new properties, entirely different from those of oxygen. The compound so formed is sulphurous acid gas. It is colourless and transparent; extinguishes flame and animal life; and first turns vegetable blue colours to a red, and then destroys them. When diluted with a large proportion of atmospheric air, it is still so acrid as to produce a sense of suffocation and violent coughing on those who attempt to breathe it. It is the same gas which is formed when sulphur is burned in the open air, but when burned with oxygen it is pure and undiluted. It possesses the property of bleaching linen, silk, straw, &c, and hence is employed by milliners and others for this purpose. Its specific gravity is more than double that of atmospheric air, and hence it may be kept for some time in jars by merely covering them with a piece of glass. Its equivalent composition is 16 sulphur and 16 oxygen. Its bleaching property may be shown, by introducing a red rose, or other coloured flower, into ajar containing it, which will soon become white. The rose must first be moistened, otherwise the experiment will not succeed. The colour may again be restored by an alkali. This gas has a strong disposition to unite with anothei proportion of oxygen, and hence it will revive some metallic oxides, by depriving them of their oxygen. This property may be used as the means of making an interesting experiment. Make a solution of acetate (sugar) of lead in pure water, and with it moisten a piece of ribbon, or a small plant, such as a sprig of mint. The thing moistened of course presents no other appearance than if wet with common water, but when plunged for a moment into a jar of this gas, it comes out completely covered with a coat of brilliant metallic lead. This chemical change is thus explained. The acetate of lead is an oxide of the metal, dissolved in the acetic acid, or vinegar. The sulphurous acid having a stronger attraction How is sulphurous acid gas produced 7 What effect does this gas produce on flame, animal life, and vegetable colors? How does this gas differ from that produced by burning sulphur in the air 7 What is the specific gravity of this gas 7 What is its equivalent composition 7 How may the bleaching property of this gas be shown 7 How may the color of the rose again be restored 7 How may a ribbon, or small plant, be covered with metallic lead by means of this gas? What are the chemical changes which take Jace in reviving the lead by this acid? 157 SULPHUR AND OXYGEN. for oxygei. than the lead has, the acetate is decomposed by being deprived of its oxygen by the acid, and is thus revived or brought to its metallic state. According to Mr. Faraday, the sulphurous acid is condensed and brought into the liquid state, by being submitted to the pressure of two atmospheres, which is equal to that of 30 pounds to the square inch. This acid unites with metallic oxides, and forms salts, called sulphites. Sulphuric Acid —40. 1 p. Sulphur 16-f3 p. Oxygen 24 Oil of Vitriol. Sulphuric acid is an article of considerable consequence in commerce and the arts, and is prepared in large quantities in Europe and America. It was formerly obtained by the distillation of a well known substance called green vitriol or copperas, and was therefore called oil of vitriol. The composition of this acid as above seen, gives it the name of sulphuric acid; and green vitriol, therefore, which is composed of this acid and iron, is the sulphate of iron. By distilling this substance at a high heat, it is decomposetl, and the acid is obtained in the form of a dense, colorless, liquid, of an oily appearance, which emits copious white fumes in the air. If this liquid be again distilled at a lowei degree of heat, into a receiver surrounded with ice, there will pass over a colorless vapor, which will condense in the receiver, in the form of a white crystalline solid. This solid is dry, or anhydrous sulphuric acid, so called, because it contains no water. The sulphuric acid of commerce, is this solid dissolved in water. This acid is prepared by the combustion of 8 parts of sulphur mixed with 1 part of nitre, in large chambers lined with sheet lead. The acid is formed in the state of gas, and is absorbed by a thin stratum of water placed on the floor of the chamber. The following is the theory of this pro- How may this acid be condensed to a liquid state ? What are the salts called which this acid forms with metallic oxides ? How w;is sulphuric acid formerly obtained 1 What is the chemical name of copperas! How is the dry, or anhydrous sulphuric acid procured! Of what does the liquid sulphuric acid of commerce consist! Describe the manner in which the sulphuric acid of commerce is prepared. 4 158 SULPHUR AND OXYGEN. cess. The sulphurous acid, formed by the burning sulp.hu i takes a portion of oxygen from the nitre, and is conveusi into sulphuric acid. This acid then combines with the potash of the nitre, and displaces nitrous and nitric acids in vapor These vapors are decomposed by the sulphurous acid into nitrous gas, or deutoxide of nitrogen. This gas, suddenly expanded by the heat, rises to the roof of the chamber, where there is an aperture communicating with the open air. There it absorbs a portion of oxygen from the atmosphere and is converted into nitrous acid vapor, which, being a heavy aeriform body, immediately falls down upon the sulphurous flame, and imparting a portion of its oxygen to the sulphurous acid vapor, converts it into sulphuric acid, which is then absorbed by the water. The nitrous acid vapor, being thus reconverted into nitrous gas, again ascends to the roof of the chamber for another dose of oxygen, with which it descends as before, and thus the process continues. 100 parts of ni tre, and 800 of sulphur, will produce 2000 parts of tht acid. From Dr. Ures' paper on this subject, we learn that the common acid of the shops contains from 3 to 4 per cent, of foreign matter, consisting chiefly of sulphate of potash, and sulphate of lead, and that it often contains much more than these proportions, in consequence of the introduction of nitre, to remove the brown color, accidentally given the acid by bits of wood, or straw. The purest sulphuric acid obtained by the usual process has a specific gravity of about 1845, water being 1000. If it is much heavier than this, adulteration by means of some ponderous substance may be suspected, and if much lighter, its strength will probably be found deficient in consequence of dilution with water. In consequence of the strong attraction of this acid for water, with which it unites in all proportions, it absorbs moisture from the air with avidity, and thus when vessels containing it are left open, they gain in weight, instead of losing by evaporation. If carboys of this acid are permitted to stand in a damp place, as in a cellar, with the stoppers left out, there will probably be a gain in weight, What impurities does the sulphuric acid of commerce always contain 1 What pro portion of these substances does the common sulphuric acid of the shops contain 1 How may the quantity of foreign matter in this acid be ascertained 1 What is the specific gravity of the best sulphuric acid, obtained by the usual process 1 What is said of thft absorption of water by this acid, when left open 1 159 SULPHUR AND OXYGEN. which will amount to much more than the interest of the it oney the acid cost. It therefore becomes honest dealers, as well as careful buyers, to see that this acid is well secured from contact with the air. This acid is one of the most caustic and corrosive of all substances. When mixed in the proportion of four parts of acid with one of water, the temperature of the mixture rises to 300°. Its extreme activity as a caustic seems to depend on its avidity for moisture, and the heat occasioned by the union. On the entire skin, when this is dry, it produces no immediate effect, but if there is the smallest erosion or scratch, it operates on that part instantly, and with the most intense and painful energy. The flesh appears to be first burned, and then dissolved by its action. In case of any accident, where the concentrated acid is hrown upon the clothes or skin, as it is generally known that this acid burns, the spectators run for water, which is thrown on, with the intention of diluting the acid, and thus to prevent its farther action. This, though meant in kindness to the sufferer, might be the means of his destruction ; for the degree of heat, thus raised, would be sufficient to destroy his skin, without the farther action of the acid. In such cases, there is much less danger in waiting until some potash, chalk, or even ashes, can be procured, and thrown on the part. Meantime, the sufferer should be stripped of the clothing on which the acid has fallen, and the acid absorbed from the skin with a moistened sponge, or cloth, or even a handful of dry clay, thrown upon the part. Strong sulphuric acid boils at 620°, and freezes at 15° below zero. The dry acid is composed of 1 equivalent of sulphur 16 3 do of oxygen 24 40 The common or hydro-sulphuric acid contains, in addition In what proportions does a mixture of this acid and water produce the greatest degree of heat 7 On what does the causticity of this acid seem to depend 7 In case this acid is accidentally thrown upon a person, what is said to be the best method of neutralizing its effec's 7 What is the composition of the dry acid 7 What quantity of water does the strongest common acid contain 7 What is the equivalent number for the hydrosulphunc acid 7 160 PHOSPHORUS. to the above one proportion of water, making its equivalent number 49. phosphorus—12. Phosphorus is a yellowish, inflammable solid, which in the open air emits white fumes, and at common temperatures is luminous in the dark. This substance has never been found in a simple state, but is combined with animal substances, in considerable quantities, and is occasionally found in minerals. It is obtained from bones by the following process. It? the first place, the bones are calcined, or burned in an oper fire, and then pulverized, and digested for two or three days with half their weight of sulphuric acid, to which water i« occasionally added. This solution is then mixed with twice its bulk of hot water, and the liquid separated by straining through a cloth. By this process, the bones, which are composed of phosphoric acid and lime, are decomposed, and two new salts, viz., the sulphate of lime, and the biphosphate of lime, are formed. The sulphate of lime is insoluble in water, and therefore the filtrated solution contains only the biphosphate, which is soluble. Thus, the bones, which are a phosphate of lime, mixed with animal matter, are first deprived of this matter by burning, and then converted, in part, into the biphosphate by the sulphuric acid. We have, then, in this stage of the process, a solution of the biphosphate, or acidulous phosphate of lime in water. This solution is then evaporated to the thickness of syrup, mixed with one fourth of its weight of charcoal in powder, and distilled with a strong heat, in an earthen retort. The charcoal combines with the oxygen of the biphosphate, which being thus decomposed, the phosphorus distils over, and is obtained in a vessel of water, into which the mouth of the retort is placed. Phosphorus, thus obtained, is of a yellowish, or flesh color, but may be made colorless and transparent by re-distillation. This substance is exceedingly inflammable, so that at common temperatures, it is necessary to preserve it under water, in well stopped bottles. It may be set on fire by slight friction, or even by the heat of the hand. It is in- Wliat is phosphorus 1 In what state is phosphorus "found, in a simple or combmeo state 7 By what progress is phosphorus obtained 1 Describe the different chemica, changes which take place in the process of its preparation. What is said of the inflam mobility of phosphorus ? In what manner must it be preserved from the air 1 161 PHOSPHORUS AND OXYGEN. fiOiuble in water, but is soluble in other or oils, to which it communicates the property of shining in the dark. Put a piece of phosphorus into a vial half filled with olive oil, then keeping the thumb on the mouth of the vial, warm the bottom, shaking it now and then, until the phosphorus is melted. This forms liquid phosphorus, and a vial thus prepared, may be occasionally useful to show the hour of the night by a watch. All that is necessary for this purpose is to hold the vial in the hand for a few minutes, until it becomes warm, then take out the cork, and the union of the oxygen of the air with the phosphorus, will evolve sufficient light to see the hour. That the light is owing to the combination of oxygen with the phosphorus, or to its slow combustion, in the above instance, is proved by the fact, that phosphorus may be melted, and sublimed in pure nitrogen, without the least appearance of light. Its combustion in oxygen gas is exceedingly vivid, and affords a striking and splendid experiment for a public lecture room. When taken into the stomach, phosphorus proves a virulent and deadly poison, though in minute doses, it has been used as a medicine, when dissolved in ether. phosphorus and oxygen. Phosphoric Acid —28. 1 p. Phosphorus 12-f2 p. Oxygen 16. Phosphorus, as above stated, unites with oxygen with great lapidity, and affords an instance of intense chemical action, attended with the most brilliant phenomena. During this combustion, copious white vapors are produced, which fall to the bottom of the vessel in which the experiment is made, like flakes of snow. This white vapour is the dry, or anhydrous phosphoric acid. If exposed to the air, it soon attracts moisture in sufficient quantity to dissolve it, and thus becomes liquid phosphoric acid. How is liquid phosphorus prepared 1 For what purpose may a vial of this mixture be useful 1 How is it proved that the luminous appearance of phosphorus is owing to the absorption of oxygen 1 What is said of the poisonous quality of this gas when taken into the stomach 1 What is said of the union of phosphorus and oxygen 1 In what form does the dry phosphoric acid appear 7 Why does this acid become liquid on exposure to the air 1 By what other method may this acid be formed 1 14* 162 phosphorus and oxvge-n This acid may also be formed by the action of nitric acid on phosphorus. The union is made by dropping pieces of phosphorus into the strong acid. The phosphorus absorbs one proportion of oxygen frbm the acid, thus converting this acid into the deutoxide of nitrogen, or nitrous gas, which escapes in immense volumes during the process. The phosphorus is thus converted into phosphoric acid, which is obtained in the solid form by evaporating the solution to dryness. Phosphoric acid unites with water in all proportions, and produces a small degree of heat during the solution. Its taste is intensely sour, but it is not corrosive. When heated in contact with charcoal, the latter absorbs its oxygen, and the phosphoric acid is converted into phosphorus. This acid combines with various bases, and forms a class of compounds called phosphates. Its composition is 1 proportion of phosphorus 12 2 do. of oxygen 16 Consequently its equivalent is 28 Phosphorous Acid —20. 1 p. Phosphorus 12-f-l p. Oxygen 8. This acid is obtained by exposing pieces of phosphorus to .he open air, in consequence of which it spontaneously ab sorbs oxygen, and undergoes a slow combustion. If two or three sticks of phosphorus be thus exposed in a glass funnel, set into the mouth of an empty bottle, the acid will be formed, and by attracting moisture from the air, will be dissolved, and pass down into the bottle, where at first may be found a quantity of liquid phosphorous acid. This acid combines with different bases, and forms salts which are called phosphites. Phosphorous acid, when exposed for some time to the air, absorbs another proportion of oxygen, and is then converted into phosphoric acid. Indeed the acid formed by this method, is probably always mixed with the phosphoric acid. There are several other compounds of phosphorus and oxygen, but these are the most important. The phosphates will be described in their proper place. When phosphorus is thrown into nitric acid, what are the chemical changes which ensue t In what manner does charcoal convert phosphoric acid into phosphorus? Whai b the composition and what the combining number of this acid ? How is phosphorous cid obtained 7 What are the salts called which this acid formB with the different bases 163 BORON BORON —8. There is a solid substance, resembling alum in appearance, which is used in medicine and the arts, under the name of borax. From borax there is extracted an acid, called the boracic acid. When boracic acid is heated in contact Avith the metal called potassium, the metal, having a strong affinity for oxygen, deprives the acid of that principle, and thus its base, called boron, is set free. This, so far as is knoAvn, is an element. Boron is insoluble in AA r ater, alcohol, or oil. It may be exposed to the strongest heat in a close without change, but Avhen heated to about 600° in the open air, it takes fire, burns vividly, and by the absorption of oxygen, ;s again converted into boracic acid. Boracic Acid. —This is the only known compound of boron and oxygen. It is a natural product, occasionally found in springs, and also in several salts, of Avhich borax, or the borate of soda is the principal. The acid may be obtained from the borate of soda, by dissolving that substance in hot Avater, and then adding sulphuric acid until the solution becomes sour. Sulphuric acid combines with the soda, forming sulphate of soda, or Glauber's salt, Avhile the boracic acid thus set free, is formed Avhen the water cools, in small crystals. It is not readily soluble in water, but alcohol dissolves it freely, Avhich being set on fire, burns Avith a beautiful green flame. This green flame is a good test of the presence of boracic acid in any composition. This acid is composed of Boron 1 proportion 8 Oxygen 2 do. 16 The combining p. of this acid is therefore 24 chlorine —36. Oxymuriatic Acid. This highly important and useful gas is obtained by the action of muriatic acid on black, or peroxide of manganese. The most convenient mode of preparing it is by mixing strong How is boron obtained 1 Is boron a compound, or an elementary body 1 What ara the properties of boron! What is boracic acid! How may boracic acid be obtained 1 What is the common name for borate of soda! What is the best test for the presence of Doracic acid ! What are the elements of boracic acid, and what is its combining numoerl How is chlorine obtained! 164 CJU0R1NE. muriatic acid, contained in a retort, with half its weight of the black oxide of manganese in fine powder, and then applying a gentle heat. The gas may be received in glass bottles filled with water, and inverted in the pneumatic cistern, in the usual way. The water should be warmed, to prevent absorption. A cheaper mode of obtaining this gas, is to mix three parts of sea-salt, powdered with one of the manganese, in a tubulated retort, (Fig. 33,) and then to pour in two parts of sulphuric acid, diluted with an equal quantity of water. By the heat of a lamp, the gas will be extricated in abundance. This gas is of a yellowish green color, the name, chlorine, in Greek, signifying green. It has an astringent taste, and is so exceedingly suffocating, that a bubble or two let loose in a room, will excite coughing and a sense of strangulation. Cold water, recently boiled, will absorb twice its volume of chlorine, which it gives out again on being heated. The specific gravity of this gas is 2.5, so that it is more than twice as heavy as atmospheric air. 100 cubic inches weigh 76.25 grains, while the same quantity of common air weighs only 30.5 grains. Chlorine was formerly called oxymuriatic acid, from the opinion that it was composed of muriatic acid and oxygen. But according to the logic of chemistry, it is now universally considered a simple body, having never been decomposed, though repeatedly submitted to the most active decomposing agents known to chemists. Sir H. Davy submitted it to the most powerful effects of gah'anism, and to charcoal heated to whiteness, without decomposition, and without separating the least trace of oxygen from it. Hence, according to the present state of knowledge, it is an elementary body. Chlorine is a supporter of combustion. When a lighted taper is plunged into this gas, it burns with a small red flame, emitting a large quantity of smoke. Phosphorus takes fire in it spontaneously, and so do several of the metals. Fill a deep bottle, or large tube, with this gas, and set it upright, with the mouth covered by a plate of glass. Have some antimony prepared, by being pounded in a mortar; What are the two processes, described, of obtaining it 7 What is said of the color and suffocating effects of this gas? What is its specific gravity? What was the former name of this gas ? Does this gas contain any oxygen ? What is said of tha experiments of Sir II. Davy on chlorine ? Is this an elementary, or a compound body I Is chlorine a supporter of combustion 7 What substances take fire in this gas spontane•usly ? !65 CHLORINE AND HYDROGEN. then slide off the cover and pour in the metal. It will ta»ce fire before it reaches the bottom, and afford a beautiful shower of white flame. This affords an elegant and striking experiment. The metals, tin, zinc, copper, arsenic, and even gold, when in the state of powder, or thin leaves, will be inflamed in the same manner. Chlorine has a very strong attraction for hydrogen, but it is through the mysterious influence of light that the combination between the two substances seems spontaneously to be effected. Thus, when a mixture of these two gases is kept in the dark, no combination ensues, but if exposed to the direct light of the sun, they combine suddenly, and with a violent detonation. This gas, though formerly called an acid, does not appear to possess any acid properties. It is not sour to the taste, nor does it redden vegetable blue colors, properties nearly universal in the acids. But the most important property of chlorine, is its bleaching power, all vegetable and animal colors being discharged by its action. For this purpose, it is combined with quicklime, forming chloride of lime, or bleaching powder, an article very extensively employed at the present time, and which will be described, and its properties examined, in its proper place. Another very important property of chlorine is its disinfecting power, any infectious or disagreeable odor being almost instantly destroyed by it. For this purpose, the chloride of lime is also chiefly employed. The compounds of chlorine which are not acid, are called chlorides, or chlorurels. When chlorine, united to oxygen, combines with a base, and forms a salt, it is called a chlorate. These were formerly called hyperoxymuriates. They possess no bleaching properties. In what manner may a shower of flame be made by this gas and a metal ! What is said of the union between this gas and hydrogen! Does chlorine contain any of the properties of an acid 1 What is the most important property of chlorine 1 What does chio rine form, when combined with quicklime 1 What other important and useful property has this gas! What are the compounds of chlorine, which are not acid, called! 166 CHLORINE AND HYDROGEN. CHLORINE AND HYDROGEN. Muriatic Acid —37. I p. Chlorine 36-f-1 p. Hydrogen I. We have just seen that chlorine has a strong affinity for hydrogen, hut that no union takes place between them, without the influence of light. When the light is entirely excluded, a mixture of these gases remains without change. When the mixture is made in a glass vessel, and exposed to the light of day in the shade, the gases, if of equal volumes, slowly combine, and form muriatic acid gas. But when the mixture is exposed to the direct rays of the sun, the union is sudden, and attended by an explosion. This combination does not change the volume of the original mixture, but the properties of the two gases are greatly changed. If the vessel in which the experiment has been made is unstopped under water, the fluid will in a few moments entirely absorb its contents, and fill the vessel in its place, while the two gases, before combination, were absorbed by water only in small proportions. The peculiar odor of chlorine, and its prompt bleaching property, are also destroyed, and other change of properties will become apparent on further examination. The compound formed by the union of chlorine and hydrogen is called muriatic acid gas. This gas is composed by weight of I equivalent of chlorine 36 1 do. of hydrogen 1 Combining weight of muriatic acid gas 37 The production of muriatic acid by the combination of its elements, is designed to prove its constitution, and combining proportions. This acid is, however, much more readily prepared, by the action of sulphuric acid on common salt. If the salt be pulverized and mixed with an equal weight of the acid, and then the heat of a lamp applied, muriatic acid When a mixture of hydrogen and chlorine is kept in the dark, what change takes place 1 When placed in the shade, what is the effect'? When the mixture is placed in the sun, what effect is produced 1 What are the changes produced on these gases by this combination 1 What is the name of the new gas 1 What is said of the absorption by water of chlorine, and hydrogen, and also of muriatic acid gas 1 What is the composition of muriatic acid gas, and what is its combining number 1 How is this gas most readily and conveniently prepared 1 167 Cni-ORINE AND OXYGEN. gas will be disengaged. But it must not be received over water, which will absorb several hundred times its own bulk of this gas. Muriatic acid gas is a transparent, elastic fluid, of a very pungent smell, and intensely acid taste. Its attraction for water is so great, that when it escapes in the open air, even LB the dryest season, it instantly forms a white cloud, in consequence of combining with the moisture of the atmosphere. Water, at the temperature of 40°, absorbs 480 times its bulk of this gas, and the solution is known under the name of muriatic acid, or spirit of sea salt, and is largely employed for chemical and manufacturing purposes. This acid is prepared, in the large way, by extricating the gas from sea salt, by sulphuric acid, as above described, and then passing a current of it into water, as long as any is absorbed. It forms, with the different bases, a class of salts, called muriates. When this gas, in a pure state, is submitted to the pressure )f 40 atmospheres, that is, 600 pounds to the square inch, it /s condensed into a liquid. CHLORINE AND OXYGEN. There are four compounds of chlorine and oxygen, formed *f the union of as many different proportions of the oxygen «* the same proportions of chlorine. These compounds are known only to chemists, and with the exception, perhaps, of chloric acid, possess no value in the art They are all formed by the action of an acid on the chlorate of potash, or the chlorate of barytes. The chief interest which these substances possess, in a chemical relation, is their strict conformity to the laws of definite and multiple proportions. Their names and constituents are as follow: Protoxide of chlorine, 36 chlorine -J- 8 oxygen. Peroxide of chlorine, 36 " -j-32 " Chloric acid, 36 " -j-40 Perchloric acid, 36 •« -j-56 Wity does muriatic acid gas firm a white cloud in the open air? How many times Its own bulk of this gas will water absorb? Under what name is this solution of gas in water known ? How is the muriatic acid of commerce prepared ? Under what pressure s this gas condensed into a liquid ? How many compounds of chlorine and oxygen are Known ? Do tbe compounds of chlorine and oxygen possess any value in the arts? Id what relation arc the compounds of chlorine and oxygen interesting 7 168 CHLORINE AN<> NITROGEN. T; us, the first is composed of 1 proportion of chlorine combined to 1 of oxygen. The second, I of chlorine and 4 of oxygen. The third, 1 of chlorine and 5 of oxygen. The fourth, 1 of chlorine and 7 of oxygen. The equivalent numbers, therefore, for the first, is 36+8— 44; the second, 36+32=68; for the third, 36-4-40=76; and for the fourth, 36+56=92. CHLORINE AND NITROGEN. Chloride of Nitrogen —158. 4 p. Chlorine 144+1 p. Nitrogen 14. This curious compound was discovered by Dulong, a French chemist, in 1811. Chlorine and nitrogen have but a very slight affinity for each other, but they may be made to combine, by passing a current of the first through a solution of nitrate of ammonia. (Nitric acid, it maybe remembered, consists of the two elements, oxygen and nitrogen, and ammonia is composed of hydrogen and nitrogen. By the union of these two compounds, nitrate of ammonia is formed.) To prepare chloride of nitrogen, dissolve an ounce or two of the nitrate of ammonia, in 14 or 16 ounces of hot water, and when ihe solution has cooled to about 90 degrees, invert in the solution a glass jar, with a wide mouth, filled with chlorine. The solution gradually absorbs the chlorine, and consequently, rises in the jar, at the same time acquiring a yellow color. In about half an hour, minute globules, of a yellow fluid, like oil, are seen floating on its surface. These, by,uniting, acquire the size of small peas, when they sink to the bottom of the vessel. These globules are the chloride of nitrogen. They are formed by the decomposition of the ammonia, in the solution ; the chlorine combining with its nitrogen, and thus forming the compound in question. A cup of lead, or glass, should be placed at the bottom of the solution, and under the mouth of the jar, to receive the product. The chloride of nitrogen is the most violently explosive substance yet discovered, and should not be experimented What is the atomic weight, or chemical equivalent of chlorine 7 What are the names, and what the combining numbers, of the four compounds of chlorine and oxygen 7 What is said of the affinity between chlorine and nitrogen 7 What is the composition of nitrate of ammonia 1 How is the chloride of nitrogen prepared 7 What chemical changes take place in the formation of chloride of nitrogen 7 What cautions are given with respect to experimenting on this compound 1 169 IODINE. upon by the student, m quantities larger than a mustard-seed at a time, and even in this quantity, with great caution. Both its discoverer and Sir H. Davy, notwithstanding their expe rience and caution as chemical experimenters, were seriously injured by its violence. At the temperature of about 200 degrees, it explodes, and at common temperatures, when thrown on some combustible. When a small globule is thrown into olive oil, or spirit of turpentine, it explodes with such violence as to shatter any vessel of glass in pieces. The violence of its detonation is owing to the great vo lume of the products which are formed at the instant. The compound consists wholly of the two gases, chlorine and nitrogen, condensed, and combined with each other. When, therefore, the explosion takes place, these two elements assume their gaseous forms, thus, in an instant, occupying a vast space, when compared to their former state. Chloride of nitrogen consists of 1 equivalent of nitrogen 14 4 do. of chlorine 144 Making its number, 158 IODINE 124. The next simple substance we shall examine, is iodine. Its name signifies, in Greek, "violet colored," because, when in the state of vapor, it is of a most beautiful violet color. Iodine was discovered at Paris by a manufacturer of nitre, in 1812. This substance is obtained from the ley made of the ashes of marine vegetables, or from the substance called kelp or barilla, which is an impure alkali, made during the manufacture of soda. The process is as follows : Dissolve the soluble part of kelp, or the ashes of sea-weeds in water ; concentrate the solution by evaporation, when crystals of carbonate of soda will appear, which must be separated. Then pour the remaining liquor into a clean vessel, and mix with it an excess of sulphuric acid. Boil this liquid for some time, and then strain it through a cloth. Put this At what temperature does this compound explode! What combustible substances cause it to explode at common temperatures! Explain the cause of its violent explosion. What art the combining numbers for its constituents, and also for the compounu! What does the name iodine signify, and from what circumstance has it derived Its name! By what process is iodine prepared 1 What is the appearance of iodin* 1 15 170 IODINE. liquid into a small flask, and mix with it as much black oxide of manganese by weight, as there was sulphuric acid; then attach to the mouth of the flask a glass tube, closed at the upper end, and apply the heat of a lamp to the flask. The iodine will be sublimed, and will attach itself to the tube in small brilliant scales resembling black lead. Iodine thus obtained is a friable solid, with a brilliant metallic lustre, and bluish gray color. Its taste is hot and acrid, and it is sparingly soluble in water. It corrodes the cork o( the vial in which it is kept, and escapes—is a strong poison when taken in large doses: but in solution with alcohol, which dissolves it freely, has been considerably used as a medicine. When heated in a retort to about 250 degrees, it evaporates, and fills the vessel with an exceedingly rich violet colored gas. As the retort cools, it again condenses in fine brilliant points resembling frost on the glass. If exposed to the open air it slowly evaporates, and if handled, it leaves a brown stain on the fingers. Iodine resembles chlorine in smell, and in some of its properties, particularly in destroying vegetable colors. Like oxygen and chlorine, it is a non-conductor of electricity, and is a negative electric. So far as is known it is a simple body. It has a strong attraction for the pure metals, and the simple non-metallic substances, such as sulphur and phosphorus. These compounds are called iodides. From experiments made by Dr. Thompson, the atomic weight of iodine is 124. The best test for iodine in its free state is starch, with which it forms an insoluble compound in water, of a deep blue color. This test is so delicate as to indicate the most minute portion of starch in solution. Iodine combines with hydrogen, oxygen, and chlorine, forming hydriodic acid, iodic acid, and chloriodic acid. Among these, the hydriodic acid, only, is of any importance or use. What are its sensible properties? What are its uses? What is the effect when it U heated in a retort? When exposed to the open air what is the consequence? In what respects does iodine resemble chlorine ? What is its electrical state ? Is iodine a simple or a compound body ? For what substances has iodine a strong attraction 7 What m the atomic weight of iodine ? What is the most delicate test for iodine 7 171 IODINE AND HYDROGEN. IODINE AND HYDROGEN, Hydriodic Acid —125. 1 p. Iodine 124-f-l p. Hydrogen 1. When iodine is heated in a porcelain tube with hydrogen gas, the two substances combine and form a compound in the form of a gas, which has acid properties, and which is rapidly absorbed by water. This is the hydriodic acid. This gas is without color, is very sour to the taste, reddens the blue colors of vegetables, and has an odor similar to muriatic acid gas. It combines with alkalies, forming salts, called hydriodales. The discovery of iodine was one of the means of subverting the former doctrine, that oxygen was the universal acidifying principle, the above instance showing that compounds, having all the properties of acids, are formed by the combination of hydrogen with iodine. Several other instances of similar nature have been discovered, as in the case of muriatic acid. These instances appear, however, to be only exceptions to a universal principle, oxygen being still the acknowledged agent by which most acids are formed. Hydriodate of Potash. This is given a place here, instead of among the salts, because it is the only salt of the kind to be described, and because, in manufacturing this compound, the method of obtaining the hydriodic acid is different from that stated above. It is the only hydriodate of any use or importance, and does not exist as a salt in a separate state, but only in solution. In preparing hydriodate of potash for medicinal use, the preliminary labor of forming the acid may be dispensed with, and the salt in solution, may be formed by a very simple process, as follows: Add to a hot solution of pure caustic potash in water, as much iodine as it is capable of dissolving. This will form a solution of a reddish brown color, consisting of the iodate How may hydriodic acid be formed 1 What are its sensible properties 1 What are the salts called which this acid forms with alkalies 1 How does this acid demonstrate that exygen is not the universal acidifying principle ? Are there any other instances in which an acid is formed without oxygen 1 What is said relative to these exceptions to a general principle ? How is the hydriodate of potash formed? What does the reddish brown solu ion consist of ? 172 BROMJNE. and hydriodate of potash, together with an excess of free iodine. Through this solution, a current of sulphuretted hydrogen gas is transmitted, until the free iodine and iodic acid are converted into hydriodic acid, changes which may be known to be accomplished by the appearance of the liquid, which will gradually lose its brown color, and become colorless and transparent. The solution is then heated to expel the remaining sulphuretted hydrogen, and after being filtered, is pure hydriodate of potash, in aqueous solution. This solution is considerably employed, as a medicine, in scrofula, and other glandular diseases. BROMINE 75. The name bromine is from the Greek, and signifies a # " strong, or rank odor." Bromine, after undergoing various and multiplied tortures, by means of the most powerful decomposing agents, is arranged as an elementary body, having endured fire, galvanism, &c, without loss of integrity. It was discovered by Balard, of Montpelier, in 1826, and like iodine, exists in the ashes of marine vegetables, and also in sea water. The process of extricating it is too intricate to be detailed in this work, nor would it ever be undertaken by pupils in chemistry, for which this book is designed. Bromine is a fluid of a hyacinth red color, when viewed by transmitted light; but of a blackish red, when seen in the ordinary manner, or by reflected light. Its odor resembles that of chlorine, but is much more disagreeable. Like iodine, it corrodes wood or cork, and stains the fingers of a yellowish hue. Its specific gravity is 3. It is a strong poison. It is volatile at common temperatures, and emits red vapors similar to those of nitrous acid. A. lighted taper is soon extinguished by it, but before going out it burns with a flame which is green at the base and red at the top. How is it known when a sufficient quantity of sulphuretted hydrogen has been passed through the solution of iodine f What is the use of the hydriodate of potash 1 What loes the name bromine signify 1 Is it an element, or a compound ? In what substanca does it exist'} What is the appearance of bromine 1 In what respects is it slnvlar to toJinel 173 FLUORIC ACID. Bromine does not turn blue vegetable colours red, but like chlorine, destroys them. From these properties it will be observed, that this new substance has many characters in common with iodine and chlorine. Bromine combines with oxygen, hydrogen, and chlorine, but these compounds are little known, and of no interest except to professed chemists. Its equivalent number, as seen at the head of this section is 75. Fluoric Acirl —10. It is a singular circumstance in chemistry, that the base of the fluoric acid has never been detached from the acid itself, notwithstanding every effort has been made on the part of the chemists to effect a separation. It will be remembered, that all the other acids consist of a base united to an acidifying principle, and that the two elements have been examined in separate states. Thus, sulphuric acid consists of sulphur and oxygen; carbonic acid, of carbon and oxygen, &c. The base of this acid, however, has been named fluorine, but whether this is united to oxygen, as the acidifying principle, or whether such a base exists or not, is unknown. Fluoric acid must, therefore, at present, be examined as a simple body, or in connection with substances to which it unites. This acid exists in nature in considerable quantities, being found combined with lime, forming the salt called fiuate of lime, but more commonly known under the name of Derbyshire spar. This latter substance is found crystallized, and of various colors intermixed, forming, when polished, one of the most beautiful productions of the mineral kingdom. It is in common use, for vases, candlesticks, snuff-boxes, &c. To obtain fluoric acid, a quantity of fiuate of lime is powdered, and submitted to the action of twice its weight of strong sulphuric acid, in a retort of lead. On the application of a gentle heat to the retort, the acid distils over, and must be received in a leaden vessel. In what respect does it resemble chlorine in properties 1 What is the equivalent number of bromine 1 Has the base of fluoric acid ever been detached from the acid itself 1 Is the same true of any of the other acids'? What is the base of fluoric acid called 1 la it known that any such base exists 1 What natural substance contains fluoric acidl How is fluoric acid obtained from fiuate of lime 1 15* 174 FLUORIC ACID T<\g. 59. The retort, and receiver, Fig 59, made of sheet lead, and soldered together on the edges, and the juncture between them stopped with a lute of clay, Avill answer very well. The white fluor must be selected for this purpose, as being most pure. It is first put into the retort, the acid poured in, and then connected with the receiver, which must be surrounded with a mixture of common salt and snow, or powdered ice. Fluoric acid, at the temperature of 32°, or the freezing point, is a colourless liquid, and will retain its liquid state, if preserved in well stopped vessels, when the temperature i3 60°. But if exposed to the air when the temperature is above 32°, it flies off in dense white fumes, which consist of the acid, and the moisture of the air with which it combines. No substance with which we are acquainted has so strong an affinity for water as fluoric acid. Its liquid state appears to be owing to the water which is distilled over from the sulphuric acid during the process of obtaining it, and no process yet devised has succeeded in freeing it entirely from moisture. When a single drop is let fall into water, a hissing noise is produced, like that occasioned by the plunging of a red hot iron into the same fluid, such is the heat produced by its combination with water. In experimenting with this fluid, the utmost caution is necessary ; for no substance so instantly and effectually disorganizes the flesh, and produces such deep and obstinate ulcers, as this. The least particle would inevitably destroy an eye, or create an obstinate ulcer on any other part. Fluoric acid has the singular property of corroding glass, and may be used for this purpose in the fluid state, as above described, or in the gaseous form, the latter of Avhich is commonly the most convenient. Any design may be etched on glass, by the following simple method: First, cover the glass with a coat of bees wax, or engravers' What is the appearance of fluoric acid at the temperature of 32 degrees'? What is it* appearance when exposed to the open air, at a temperature above 32 degrees 1 What is said of the affinity of this singular acid for water? What is said of the action of this acid on the flesh t What is said of the action .if fluoric acid on glass 1 Describe the method of making designs on glass. CARBON AND HYDROGEN. 175 varnish. If wax is used, it must be spread over the surface as thin as possible. This is done by heating the glass over a lamp, and at the same time rubbing it with wax. A thin and even coat may thus be obtained. Next draw the design by cutting the wax with a sharp pointed instrument, quite down to the glass, so that every line may leave its surface naked; otherwise the design will be spoiled, since the acid will not act through the thinnest film of the wax. A large needle answers for a graver for this purpose. Having made the design, the etching is done by placing the glass in a horizontal position and pouring on the liquid acid. But a simpler method is the temporary extrication of the gas from the fiuor spar, for the occasion. For this purpose, take a lead or tin cup, large enough to include the figures on the glass, the lower the better, and having placed on its bottom a table spoonful of powered spar, pour on it a quantity of strong sulphuric acid sufficient to form a paste. Then place the glass on the cup, as a cover, with the etching downwards, and set the cup in a dish of hot water, or apply to it the gentle heat of a lamp, taking care not to melt the wax. In twenty or thirty minutes the etching will be finished, and the wax may be removed with a little spirit of turpentine. In this manner, figures of any kind may be permanently and beautifully done on glass. COMBINATIONS OF SIMPLE NON-METALLIC COMBUSTIBLES WITH EACH OTHER, CARBON AND HYDROGEN. Carburcited Hydrogen —8 1 p. Carbon 6-f-2 p. Hydrogen 2. Light Carburetted Hydrogen. This gas has also been called hydro-carburet, and heavy inflammable air. It exists in every stagnant pool of water, especially during he warm season, being generated by the decomposition of vegetable products. To obtain it from such places, fill a glass jar with water, After the design is formed, in what manner is the etching done 1 What are the names under which carburetted hydrogen has been known T In what place has this gas been formed by the operation of nature 1 176 CARBON AND HYDROGEN. and invert it in a stagnant pool or ditch; then stir the mud under it with a stick, and the gas will rise and displace the water in the jar. To preserve it for examination, slide a dish under the mouth of the jar while in the water, and then carefully raise, and carry the whole to the place of experi ment. The gas so obtained is found to contain a proportion of carbonic acid gas, which may be removed by passing it through lime water. This gas is composed by weight of 1 equivalent of carbon 6 2 do. of hydrogen 2 8 It is immediately destructive to animal life, and will not support combustion. It is highly inflammable, and burns with a yellowish blue flame, but owing to the carbon it contains, it gives- considerably more light than pure hydrogen. Mixed with atmospheric air, like hydrogen, it detonates powerfully when inflamed. When burned with oxygen, the product of the combustion is water and carbonic acid. There appears to be several varieties of light carburetted hydrogen, or perhaps the difference may depend on a mixture of the light and heavy kinds. If a volume of steam be sent through a red hot gun barrel filled with charcoal, the gas obtained differs little in its illuminating powers from that obtained from stagnant pools. Nor is there any material difference between these and that evolved by the burning of common wood, such as maple or beech, in a gun barrel. But if pine wood containing turpentine, be heated in the same manner, the gas obtained has much greater illuminating powers, the brilliancy of the flame being nearly equal to that of oil gas. Now as by analysis there appears to be only two kinds, or varieties, of carburetted hydrogen; in the first ol Avhich there is but one proportion, and in the second two proportions of carbon, it is most probable that these different powers of illumination depend on a mixture of the two gases. How may it be obtained from stagnant pools of water! What gas is commonty found mixed with this t What is the atomatic composition of carburetted hydrogen ? How does it affect animal life and combustion 1 When burned, why does this gas gire a atronger light than pure hydrogen 7 What is said concerning the several varieties of car tmretted hydrogen. 177 CARBON AND HYDROGEN. This gas sometimes exists in large quantities in coal mince, and is known by the miners under the name of fire-damp. The most shocking accidents have often occurred in consequence of the explosion of this gas in the mines, when mixed with atmospheric air. In some mines, this gas flows from the coal beds in vast quantities, being obviously the product of the decomposition of water by the coal. But in what manner the water is decomposed, is unexplained. Did the process consist in the formation of sulphuric acid, in consequence of the oxygenation of the sulphur, and the subsequent action of this acid on the iron, of the sulphuret of iron, there would be formed sulphuretted, instead of carburetted hydrogen. There arc no facts, it is believed, which warrant the supposition, that in ordinary cases, the decomposition is consequent upon the heat, or ignition of the coal. Possibly in such vast bodies of coal as are found to exist in some mines, the water is slowly decomposed, by gradually imparting its oxygen to the carbon, without the aid of heat. We have already stated, that when carburetted hydrogen is mixed with atmospheric air, and inflamed, a violent explosion is the consequence. In the coal mines of England, the mixture of atmospheric air and the gas in question, often produces such an exp.osive compound. It appears that the miners have no certain means of ascertaining the presence of this gas, probably because, being much lighter than the atmospheric air, it at first rises to the roof of the mine, and then gradually descends towards the floor. As the miners work entirely by the light of lamps, one of which is sufficient to set fire to the explosive compound existing throughout the whole cavern, it is obvious, that as soon as the hydrogen has mixed with the air near the floor of the mine in the exploding proportions, it must inevitably take fire. It can readily be imagined, particularly by those who have witnessed the detonation of a pint or two of this compound, that a quantity covering many acres of surface, and extending upwards in some places, at least, several hundred feet, must produce the most awful consequences. Under what name is this gas known, when it occurs in coal mines'? In what manner I this gas formed in coal beds? What are the remarks on this subject 1 What is the onsequence, when this gas is mixed with atmospheric air and inllamed 1 In what situa-4ons is it said that explosive compounds are thus formed ? What is the reason that the tuners are not aware of the existance of this compound until the whole takes fire 1 178 CARBON AND HYDROGEN. Such explosions have often taken place in the coal-mines in different parts of England. That which happened in a mine called Felling colliery, in Northumberland, on the 25th of May, 1812, was attended with the loss of 92 lives, and spread poverty and wretchedness throughout the whole district. Most of these men had wives and children, who depended entirely on their daily labor for support, and who, in addition to the loss of their husbands and fathers, by so sudden and awful a death, were in a moment deprived of the means of subsistence. This mine had been wrought a century or more, and only a single accident from fire-damp had before happened, and this was so trifling, as only to slightly burn two or three workmen. Twenty-five acres of coal had been excavated in this mine, and the number of men employed under at the time of the accident, was 128. The explosion took place between the hours of 11 and 12 in the morning. The fire was seen to issue from two shafts leading to the mine, and called William and John, and at the same instant, the noise of the explosion, which was heard three or four miles, and the trembling of the earth, showed that an awful accident had happened there. The force of the expanded gas was such as to throw from the two shafts immense clouds of dust, and small coal, which rose high in the air, and also pieces of wood and working implements, which fell back near the shafts. As soon as the explosion was heard, the wives and "children of the colliers came by hundreds to the place. But not a single person who was in the mine during the accident, was to be seen. Terror and dismay was pictured on every countenance; soma were crying out for a father, some for a son, and others for a husband. The machinery for entering the mine, being shattered by the blast, it was at first impossible to go down, but the urgency of the occasion soon impelled those present to find the means of entering the shaft; and in about half an hour from the time of the explosion, 32 persons, all who remained alive out of 121, who were in the mine, were brought out. It appeared that of the whole number of the workmen, seven had come up, on different occasions, before the explosion, and were unhurt. The wives and children of those who were What number oflives were destroyed by such an explosion at Felling colliery in 18121 179 CARBON AND HYDROGEN. known to be still in the mine, waited in a most heart-rending state of anxiety, and those who had their friends seemed to suffer nearly as much from excess of joy, as they had before done from suspense and grief. These hurried away with their friends from the dismal scene, while those who were still in suspense, or whose hopes ended in the dreadful certainty that their husbands or fathers were indeed among the dead, still lingered about the place, silently enduring the torture of a forlorn hope, and uttering cries of agony and despair. As the fate of many of the men was still uncertain, because tney were in different parts of the mine, from those who had been found alive, the exertions of those above were unremitted, and in the course of an hour or two, many hundred people had collected around the shafts, all anxious to do every thing in their power for the sufferers. But it was soon found that the pit in some places was still on fire, the gas probably continuing to burn as it was extricated from the coal. It was also found by those who attempted to descend, that where the mine was not on fire, it was filled with carbonic acid gas, the product of combustion, and that therefore it was impossible for any person to make further examination without inevitable death. Consequently all hope of finding any of the unfortunate persons alive, who were still in the mine, was abandoned, and it was proposed that the shafts should be closed, in order to extinguish th'e fire. But the wives and children of the sufferers, distracted at the idea of seeing their friends buried alive, and still entertaining hopes of their recovery, made the most pitiful importunities against such a course, while others became frantic with rage, and accused those of murder who proposed it. The owners of the mine, therefore, in mercy to the feelings of these distracted widows and orphans, waited until all were satisfied that no hopes remained of ever again seeing their friends alive, when the two' shafts were closed with earth. To insure the extinguishment of the fire, the mine was kept, closed from the 27th of May until the 8th of July, on which day it was again opened and ventilated. On this occasion, the lamentations of the widows and orphans was again reuewed, and such was the crowd of people that assembled on the spot, some urged by feeling, and others by curiosity, that constables were in attendance to preserve order. Those who descended to search for the remains of these unfortunate sufr'-rers, found no difficulty in breathing the air of the mine. 180 SAFETY LAMP. rmt were struck with horror at the scene of destruction and mutilation which the explosion had occasioned. The search continued until the 19th of September, when 91 bodies had been found, brought up, and interred, but the 92d never was found. We have been thus particular in describing a single instance of the awful effects of the fire damp in mines, that the reader might fully appreciate the safety-lamp, an invention made by Sir Humphrey Davy, expressly for the purpose o, preventing such explosions, and which has proved completely successful. Before the invention of this lamp, such explosions were more or less common, and all the mines were subject to them, though none has been attended Avith such destruction to human life, as that of Felling colliery. In 1815, such an occurrence happened in a mine at Durham, and destroyed 57 persons, and in another mine, 22 persons were killed in the same manner. The invention of the safety-lamp was not owing to accident, but is the result of inquiries undertaken and pursued expressly for the purpose of protecting the miners from such horrible accidents as we have described above. Sir Humphrey Davy commenced his inquiries, by determining the proportions in which carburetted hydrogen and atmospheric air, in mixture, produce explosions; and found, that when the gas is mixed' with three or four times its vol ume of air, it does not explode at all. When mixed with five or six times its bulk of air, it detonates, feebly, but when the air is in the proportion of seven or eight times the bulk of the gas, the explosion is most powerful; and with fourteen times its volume of air, it still explodes, though slightly. He also found that the strongest explosive mixture would not take fire when in contact with iron heated to redness, or even to whiteness; while the smallest point of flame, owing to its higher temperature, caused an instant explosion. What other accidents of the same kind are noticed 1 Does it appear that all excavated coal mines arc liable to such accidents 1 Who invented the safety-lamp, which protects the miners from such accidents 1 Was this invention accidental, or was the safety-lamp the result of inquiry and experiment 1 In what proportions did Sir H. Davy find that carburetted hydrogen and common air exploded with the least force, and in what proportions with the greatest force 1 What did Sir II. Davy discover in respect to the communication of flame through narrow tubes 1 181 SAFETY LAMP. But the most important step in this inquiry was deducea from the foot that flame cannot be communicated through a narrow tube. The fact itself was known before, but Sir H. Davy discovered, that the power of tubes, in this respect, is not necessarily connected with their lengths, and that a short one is as efficacious in preventing the transmission of flame, as a long one, provided its aperture be reduced in proportion to its length. Pursuing this principle, he found that fine wire gauze, which may be considered as an assemblage o exceedingly short tubes, was totally impermeable to flame j and on making the experiment, it was found that a lighted 'amp, when completely surrounded with such gauze, might be introduced into an explosive mixture, without setting it on fire. Thus the means of preserving- the miners, a most useful and laborious class of people, from the dreadful effects of the fire-damp, was at once developed. It only became necessary to surround their lamps with a fine net Avork of brass wire, to insure their safety from explosion. This lamp also indicates the existence of danger ; for when the fire-damp in the mine is in a highly explosive state, it takes fire within the gauze, and burns there, Avhile the light of the lamp itself is unseen. When the miners observe this indication of danger, they instantly leave the mine, for although the flame within the gauze will not communicate Avith the explosive mixture on the outside, Avhile the gauze is entire, yet as a high degree of Fig. 60. heat would be kept up by the combustion within the lamp, the wire would soon become oxidated, and perhaps fall in pieces, when an instant explosion would be the consequence. The safety lamp is represented by Fig. 60. The cistern a holds the oil, and is in all respects a complete lamp, Avith a spout at the side, for feeding it. On the top of this is set the cylinder of Avire gauze, b, supported by three iron or brass rods, to Avhich is connected the disc, or cover c, and to the cover, the ring, or handle by Avhich the Avhole is carried. The draAAung d, is a On pursuing this inquiry, what did Sir II. Davy discover with respect to wire gauze 1 3n this principle, how was it discovered that the miners might be protected from explev •ions 1 In what manner do these lamps indicate the presence of danger 1 • 16 182 OAS LIGHTS. p;ece of wire passing through a tube, showing the manner m which the lamp is trimmed, and the wick raised, without making any dangerous communication between the outside and inside of the lamp. This tube passes through the cistern containing the oil. The reason why the wire gauze obstructs the communication of flame is easily explained. We have already stated, that according to the experiments of Sir H. Davy, the heat of flame is greater than that of a metal heated to whiteness, for the former occasioned a mixture of air and gas instantly to explode, while the iron, though Avhite hot, produced no effect. Now the metals are all rapid conductors of heat; when, therefore, the flame comes in contact with the wire, its temperature is so reduced by the conducting power of the metal, as to be incapable of setting fire to the gas which is on the outside. Any one may illustrate this principle, by holding a piece of wire gauze over the flame of a lamp, and then bringing his hand over this, as near the lamp as he can bear. Now on removing the gauze, he will find that he cannot for an in stant bear the additional heat. Bicarburetted Hydrogen —14. 2 p. Carbon 12+2 p. Hydrogen 2. Olefiant Gas. To prepare this gas, mix in a capacious tubulated retort, three measures of alcohol, with eight measures of undiluted sulphuric acid, and then apply the heat of a lamp. This mixture turns black, swells, and emits bubbles of gas in abundance, which may be collected over water, in the same manner as described for hydrogen. Alcohol is composed of carbon, hydrogen, and oxygen. During this process, the oxygen of the sulphuric acid appears to combh e with a part of the carbon of the alcohol, in consequence of which, sulphurous acid gas is evolved, and the hydrogr a is set free. At the same time, the hydrogen combines w;th another portion of the carbon, and escapes in the Why does it become necessary for the men (o leave the mine, when the explosive mixture burns within the gauze 1 Describe the safety lamp, as -epresented at Fig. CO, and po.'nt ov.t the uses of its several parts. Explain tlis reason way the flame is not communicated through the wire gauze. How may this principle bei lustrated by holding a pieo» of w're ga I7.e and the hand over a candle 1 How is olefiatf or bicarburetted bydrogea V* ooiame '1 What is the composition of alcohol? 183 GAS LIGHTS. form of bicarburetted hydrogen. Or perhaps the evolution of the defiant gas is owing to the strong attraction which the sulphuric acid has for the water which the alcohol contains, and by combining with which, the hydrogen and carbon are liberated. Olefiant gas is colorless and elastic. It possesses no taste, and when pure, little smell, though, when not purified, it has a faint odor of ether. When mixed with oxygen and inflamed, it explodes with violence. This gas is a little lighter than atmospheric air, 100 cubic inches weighing 29.64 grains. The weight of carbon in this composition is 25.41 grains, and the weight of hydrogen 4.23 grains. Olefiant gas, therefore, consists of Grains. Carbon, by weight 24.31, or two atoms, 12 Hydrogen, do 4.23, or two atoms, 2 29.64 14 This gas may be decomposed, by passing it through a red not porcelain tube, one proportion of carbon being deposited, in consequence of which, it is converted into light carburetted hydrogen, which, as we have already seen, contains only 1 proportion of carbon to 2 of hydrogen. Gas Lights. The olefiant gas, when pure, (with perhaps a single exception) gives the most brilliant and intensely luminous flame of any known substance. The illuminating powers of other gases depend chiefly, if not entirely, on the olefiant gas they contain. In all cases, the light of any inflammable gas is in exact proportion to the quantity of carbon it contains. The flame of pure hydrogen scarcely gives sufficient light to show the hour on a watch dial. When combined with one proportion of carbon, forming carburetted hydrogen, its light is greatly increased, and when combined with another pro- What are the chemical changes which take place during the production or olefiant gas 1 What are the sensible properties of this gas? Does it explode when mixed with oxygen and inflamed? What is the weight of carbon, and what the weight of hydrogen, in this gas? What is the atomic composition and what the combining number of this gasl How is olefiant gas decomposed and resolved into carburetted hydrogen 7 What is said ol the brilliant light of the olefiant gas ? On what does the brilliancy of gas lights depend 1 184 GAS LIGHTS. portion, its light becomes perfectly fitted for the purposes of illumination. Gas light, for the purpose of illumination, was first made and employed by Dr. Clayton, an Englishman, in 1739, but from some unknown cause, was given up, and neglected for sixty years afterwards. At length, Mr. Murdock instituted a series of experiments on the subject, and the gas distilled from coal, began to be used, on a small scale, for lighting different factories in the vicinity of London. From that period, which was about 30 years since, gas lights obtained from coal, or oil, have gradually come into use, for the purpose of lighting streets, shops, and manufactories, in all parts of Great Britain, and is, at the present time, in common use on the continent of Europe, and in several parts of America. For many years, the gas lights of London, and other parts of England, were supplied entirely by the distillation of bituminous coal; but more recently, many of the gas works, in different parts of that kingdom, obtain their lights from oil In this country, also, oil gas is chiefly employed. In respect to the advantages of gas, on the morals of soci ety, in great cities, Mr. Gray, in his Operative Chemist, says, "From the more brilliant manner in which our streets (those of London) are lighted by gas, than they ever were or could be, by oil or tallow, there is a greater degree of security, both in person and property, for every class of honest men. Crimes cannot now be committed in darkness and secrecy: and as the risk of detection increases, the temptation to guilt is diminished, and thus coal gas, by the brilliant light it sheds on our streets, has worked, and is now working, a moral reformation. The house-breakers and pick-pockets dread the lamps more than the watchmen, and a more efficacious measure of police was never introduced into society, than that from gas lights." Oil gas is obtained by distilling impure whale or other oil, in large cylindrical cast iron retorts. From four to six such retorts, which, in appearance, resemble 24 pound cannon, are placed across a furnace built of brick, and are all heated by When were gas lights, for the purpose of illumination, first employed 1 From wha* substance was gas lights first obtained 1 What is the substance now employed in this country, and in some parts of England, for this purpose 1 What is said of the influence of gas lights on the morals of'Londonl How is oil gas manufactured 1 Describe the furnace and retorts. 185 OAS LIGHTS. the same fire. These art half filled with pieces of orick, or iron, in order to increase the surface, and thus to effect the decomposition of a greater proportion of the oil. The oil is contained in a reservoir placed so high as to run to the retorts through a tube, of which each retort has a separate branch. The oil is admitted into the retorts on the outside of the furnace, the quantity being regulated by a stop-cock, with which each is furnished. On the opposite side of the furnace, the gas is conducted from each retort by separate tubes, which afterwards join in a common tube of larger size, and thence is conveyed to the gasometer. The oil is admitted into the retorts in a very small stream, or sometimes only by drops, and is decomposed, and converted into gas as fast as it runs in. In large works, the gasometer is of immense size, being 30 or 40 feet in diameter, and 15 or 20 feet high, and capable of containing from 12, to 20,000 cubic feet of gas. This is made of sheet iron, suspended by a chain, over a pulley, and counterbalanced by weights on the other side. This falls into a tank, or cistern, held together by iron hoops, which are drawn with great force around it by means of screws. The tank being filled with water, the gasometer is let down into it, while the air escapes by opening a valve in its top. When the air is all excluded the gas is conducted into the gasometer by a pipe coming from the retorts, and opening under the water. As the gas rises through the water, the gasometer is buoyed up, and rises also, and thus the vessel h filled with inflammable gas instead of air. From the gasometer, which is the great fountain, the gas is conducted by one large iron pipe, laid under ground to the place or street where it is burnt. It is then conducted in smaller pipes through the different streets, and from these pipes it is conveyed to the houses and shops by small tubes; and tubes of still smaller size convey it to the burners where the lights are wanted. Rosin has lately been used instead of oil, and is said to yield a gas fully equal in quality to that of oil, and at a much less expense. As the burners are stationary, in the ordinary mode o" light- How is the oil admitted into the retorts 1 In large works, what is the size o iae gwrmeter 1 How is the gas conveyed into the gasometer ? How is the gas oonrq fc«« the gasometers to the gas burners 7 What inconvenience is experienced In i llki o> ordinary gas lights! 16* 186 GAS LIGHTS. ing with gas, there exists an inconvenience in its employment for the purpose of common household illumination, where the lights are often necessarily carried to different parts of • room, or from one room to another. There is also another inconvenience, which arises from the expense of laying con ductors through streets where the houses are scattered, and consequently, where but a small quantity of the gas is wanted. To remedy these defects in the ordinary method of lighting with gas, it has, within a few years been proposed to condense the gas in strong copper, or brass lamps, at- the gas works, and then transport them thus filled, to the houses, to supply the place of common lamps. This is distinguished by the name portable gas, and has been, and it is believed is still extensively, employed in London and its vicinity. To fill these lamps, there is provided a long iron pipe, at one end of which is a forcing pump, which is also connected with another pipe leading from the gasometer, to the pump through which the gas is conveyed. The long pipe is furnished with short tubes placed at convenient distances apart, and communicating Avith its inside. These tubes are cut with screw threads, which fit the screws at the bottoms of the lamps, and on which these vessels are screwed, to be filled. Thus by working the forcing-pump, the gas is brought from the gasometer, forced into the pipe, and from the pipe into the lamps, so that many are filled at the same time. There is a mercurial gauge connected with the pump, by which its pressure is shown, and consequently by which the amount of condensation of the gas in the lamps is indicated. The flame, in bui ning the gas, is regulated by turning a small screw, and the gas is prevented from escape at the bottom by a valve, and another screw. The gas obtained from oil, is much purer than that obtained from coal. The latter cannot be burned until it is purified by being passed through lime water, in order to deprive it of the carbonic acid, and other impurities ; but the oil gas does not require any such process, being fit for use as it passes from the retort. The illuminating power of the oil gas is also much greater How has it been pr posed to remedy this defect 1 Under what name is this condensed gas known 1 In v nat manner are the portable gas lamps filled 1 How is it ascertained with what degree of force the gas is condensed in the lamps 1 Which is most pure, th« gas obtained from oil, or that from coal 1 Which gas has the ,reatest illuminating pow«Jr that from the coal, or that from oil 1 187 HYDIOGEN AND SULPHUR. jhan that of coal gas. According to the experiments of Mr. Accum, two cubic feet of coal gas will burn one hour, and give a quantity of light equal to three tallow candles, eigh f . of which weigh a pound. But according to the experiment:? of Mr. Dewey, superintendent of the gas works of New- York, one cubic foot of oil gas will give light for one hour, equal to 8 candles, 6 to the pound. This agrees very nearly with the result of Mr. Ricardo's experiments, who found that a given quantity of oil gas was equal in illuminating power to four times the same quantity of coal gas. One gallon of clean whale oil will make 100 cubic feet of gas, which, according to the above statement will burn 100 hours, and give as much light as 8 mould candles, 6 weighing a pound. Such an immense difference between the cost of gas, and other lights, would seem to indicate the propriety of establishing gas works in every village. But the expenses of erecting and tending small establishments of this kind, are such as not to yield any considerable profit to the owners. In this country, where 2,000, or 2,500 lights are wanted in a compact town, perhaps gas works, might be maintained. The ex{>enses of erecting such works would be not far from the folowing, viz. 2} miles, 3 inch main pipe, $7,500 Gasometer and tank, 3,000 Refrigerator and connections, 1,500 One bench retorts, 6 in number, 3,000 Labour to erect the works 3,000 17,500 HYDROGEN AND SULPHUR. Sulphuretted Hydrogen. 17. 1 p. Sulphur 16+1 p. Hydrogen 1. This gas may be procured by placing in a retort some sulphuret of antimony, or iron, and pouring on it sulphuric or muriatic acid. The sulphurets of these metals may be prepared by heating either of them, in filings or powder, with What is said to be the comparative difference between the illuminating power of ceal and oil gas 1 What quantity of gas is it said one gallon dT oil will make, and how long will this gas burn 1 The cost of oil gas being much less than other lights, why are the* tot universally used 1 How may sulphuretted hydrogen be procured 1 188 HYDROGEN AND SULPHUR. sulphur; or the natural sulphurets may be employed. Thp chemical changes concerned in the formation of this gas, are as follows. The oxygen of the water which the acid contains unites with the metal of the sulphuret, which metal is then dissolved by the acid. Thus, the hydrogen of the water, and the sulphur of the sulphuret, are both set at liberty, and having an affinity for each other, they combine, and escape in the form of sulphuretted hydrogen. Sulphuretted hydrogen, is a transparent, elastic gas, which ooth to the taste and smell, is exceedingly unpleasant and nauseous, its odor being similar to that of putrefying eggs. Under a pressure of 17 atmospheres, that is, under a weight equal to 255 pounds to the square inch, this gas is condensed into a colorless liquid, but again assumes its gaseous form, when the pressure is removed. This gas is instantly fatal to animal life, when pure, and even when diluted with 1500 times its bulk of air, has been found so poisonous as to destroy a bird in a few seconds Like hydrogen, it instantly extinguishes flame, but is itself inflammable and burns with a pale blue flame. The products of its combustion are water and sulphuric acid. The composition of this gas being hydrogen and sulphur, the water formed during its combustion is the product of the union between the hydrogen, and the oxygen of the atmosphere, during the act of combustion ; while the sulphuric acid is formed, by the union of the oxygen of combustion with the sulphur. Sulphuretted hydrogen tarnishes silver, and even gold, and blackens paint, made with preparations of lead. This gas is often generated curing the decomposition of animal products, in sink drains and ditches, and hence the paint of white lead, about such places often becomes black in consequence. Eggs contain a small quantity of sulphur, which on boiling is converted into sulphuretted hydrogen, and hence a silver spoon is instantly tarnished by coming in contract with a boiled egg. What chemical changes take place by which this gas is evolved ? What are the sensible properties of this gas ? Under what pi assure may this gas be condensed into a liquid ? Does it remain liquid when the pressure is removed 1 What is said of the poisonous effects of this gas? What are the effects of plunging a burning candle into this gas? When this gas is burnejj, what are the products of combustion? Whence come the water and sulphuric acid 1 What is its effects on the metals 7 189 HYDROGEN AND PHOSPHORUS. The composition of sulphuretted hydrogen by weight, is C5 follows: .100 cubic inches of this gas weigh 36 grains. This is composed of sulphur, 33.89 do. do. do. of hydrogen, 2.11 do. 36.00 HYDROGEN AND PHOSPHORUS. Phosphuretted Hydrogen —13. 1 p. Phosphorus 12+1 p. Hydrogen 1. This compound consists of hydrogen, in which is dissolved a small quantity of phosphorus. It may be formed in several ways. One of the most simple is the following: Into five parts of water put 15 or 20 grains of phosphorus, cut into small pieces. It must be cut under Avater to prevent its taking fire. Then add one part of granulated zinc, and pour in three parts of sulphuric acid. The gas will instantly rise through the water in small bubbles, and will take fire spontaneously on coming in contact with the air. Each bubble as it takes fire will form a horizontal ring of white smoke, which will gradually enlarge a* it rises, until lost in the air. The cause of this curious appearance is owing to the formation of a small quantity of phos phoric acid by the combustion of the phosphorus, and which having a strong affinity for moisture, attracts it from the atmosphere, and thus forms a little ring of dew, which is visible to the eye. Phosphuretted hydrogen may also be obtained by placing some pieces of phosphuret of lime in water, when the gas will be extricated, and will rise through the water as above described. [See Phosphuret of Lime.] This gas detonates with great violence when mixed with oxygen, and forms a dangerous explosive compound with atmospheric air; consequently much caution is required in making experiments with it. When a bubble of phosphuretted hydrogen is allowed to mix with oxygen, a flash of the most vivid light is spontane- What is the composition of 100 cubic inches of this gas by weight 7 How is phosphuretted hydrogen formed? What singular property does this gas possess7 How is the ring of white smoke accounted for, which rises after the combusti n of a bubble of tins gas 7 With what substances does phosphuretted hydrogen afford jangerous detona ing compounds 7 190 NITROGEN AND CARBON. ously proauced, which, in a darkened room, resemoles lightning. The safest method of performing tnis beautiful experiment, is to let up into a small strong bell glass, or a thick glass tube, a few ounces of oxygen gas. Then, having collected a little of the phosphuretted hydrogen in a small vial, hold the bell glass in the left hand, with its mouth under water, and with the right hand manage the vial, so as to et only a single bubble at a time escape into the oxygen. The detonation of each bubble will produce a considerable reaction on the bell glass, which will be felt by the hand. But if the experiment be performed as described, there will be no danger of an explosion. The gas above described is called per-phosphureiied hydrogen, denoting, as already explained, the highest degree with which one body unites with another. It is so called to distinguish it from the proto-phosphuretted hydrogen, which contains only half the quantity of phosphorus, and is a much less interesting compound. Per-phosphuretted hydrogen consists of 1 equivalent of phosphorus, 12 1 do. hydrogen, 1 13 NITROGEN AND CARBON. Carburet of Nitrogen —20. 2 p. Carbon 12-}-1 p. Nitrogen 14. Cyanogen. By boiling together red oxide of mercury and prussian blue. in poAvder, Avith a sufficient quantity of AA'ater, there may be obtained a compound Avhich shoots into crystals, and Avhich was formerly called prussiate of mercury, but is noAv knoAvn by the name of cyanuret of mercury. When this salt is heated in a retort, it turns black, the cyanogen passes over in the form of a gas, and the mercury is revived, or assumes its metallic form. This gas has a pungent, disagreeable odor, burns with a purplish blue flame, extinguishes burning bodies, and is reduced to a liquid under the pressure of about three and a half atmospheres. This gas must be collected over mercury. What directions are given for admitting bubbles of this gas into oxygen? What is the equivalent composition of per-phosphuretted hydrogen ? How may cyanuret of mercury be formed ? How is cyanogen procured ? What are the properties o.' this gas ? 191 PRUSSIC ACID. 100 cubic inches of this gas weigh 55 grains, and is found o be composed of 2 equivalents of carbon, 12 1 do. nitrogen, 14 26 its combining number. Cyanogen, ihough a compound gas, has the singular property of combining with other substances, in a manner perfectly similar to the simple gases, such as oxygen and hydrogen. The term cyanogen, comes from two Greek words signifying to form blue, because it is an ingredient in Prussian blue. Hydrocyanic Acid —27. 1 p. Cyanogen 26-f-l p. Hydrogen 1. Prussic Acid. Cyanogen is obtained by simply heating cyanuret, or prussiate of mercury, as above described. Hydrocyanic, or prussic acid, is composed of cyanogen and hydrogen. It may be obtained, by heating in a retort a quantity of prussiate of mercury with two thirds of its weight of muriatic acid. During this process, there takes place an interchange of elements. The cyanogen of the cyanuret of mercury unites with the hydrogen, forming hydrocyanic acid, while a muriate of the peroxide of mercury remains in the retort. But a more common method of making prussic acid is the following: Mix together, hi a convenient vessel, four ounces of finely powdered Prussian blue, two and a half ounces of red oxide of mercury, and twelve ounces of water. Boil the mixture for half an hour, now and then stirring it. The blue color will disappear, and the solution will become yellowish green. Filter the solution, and wash the residuum, by pouring on boiling water, in quantities sufficient to make up the loss bv evaporation, and let this also pass through the filter. Put this solution, which is a prussiate of mercury, into a retort containing two ounces of clean iron filings, then connect the retort with a receiver, and place them on a lamp fur- What is the equivalent composition of this gas, and what is its combining number? Whence comes the name of this gas? How may hydrocyanic, or prussic acid, be formed by means of prussiate of mercury and muriatic acid? What are the interchanges of elements which take place during this process? What is the more common method decr.bed for making Prussic acid? 192 PRUSSIC ACID. nace, as represented by Fig. 61, taking care that the juncture be made air tight, which may be done by winding a wet rag around the neck of the retort. Next, pour into the retort one ounce of sulphuric acid, diluted with three or four parts of water, and stop its tubulure by passing in a straight glass tube, which had been ready prepared by being passed through a cork. Then light the lamp, and distil with a slow heat, until three ounces of prussic acid is obtained. The receiver must be kept cold, and also from the light, by being covered with a wet cloth. Fig. 61. The fumes of this acid are exceedingly poisonous, and therefore the lamp furnace should be set in a fire-place during the process, so that they may escape up the chimney. There is a complicated interchange of principles which take place in this process, which Scheele explained thus. In prussian blue the prussic acid exists in combination with iron. The red oxide of mercury, having a stronger attraction for this acid than the iron has, the prussian blue is decomposed, and a prussiate of mercury is formed, which is soluble in water. On the addition of the iron filings and sulphuric acid to this solution, the iron absorbs the oxygen from the mercury, which is then precipita ted in the metallic form, and at the same instant the iron is thus oxidized, it is dissolved by the sulphuric acid forming the sulphate of iron. Thus, the prussic acid is liberated, because it does not combine with the metals, but only with their oxides, and as the iron deprives the prussiate of mercury of it& oxygen, the prussic acid remains free in the solution of the sulphate of iron, and being volatile, readily passes over into the receiver, by a gentle heat. The hydrocyanic acid thus obtained, is a perfectly color less, limpid fluid, and cannot be distinguished by the eye from distilled water. It has a strong odor, resembling that ol peach blossoms, and when much diluted has the taste of bit- Jer almonds. Prussic acid is the most active and powerful of all known What is said of the poisonous quality of the fumes of this acid, and of the precautions to avoid them 1 Explain carefully the complicated interchange of chemical principles that take place by this process. What is the appearance of the acid thus obtained 1 W'hat is the smell of this acidl What eases are mentioned of its poieonoua effect* 193 PRUSSIC ACID. poisons. A single drop placed on the tongue of a dog causes his death in a few seconds, and a servant girl who swallow ed a small glass of it, diluted with alcohol, fell down instant ly, as though struck with apoplexy, and died in two minutes. A professor at Vienna, having prepared some of this acid in its most concentrated state, by way of experiment, diffused some of it on his naked arm, and was killed thereby in a short time. These instances not only show the terrific and mysteriou effect which this substance has on the animal economy, but they also show what extreme caution is necessary in preparing and using it. When much diluted, it has, however, been considerably employed as a medicine, in cases of consumption, and often with good effect. Although the investigations of chemistry have developed this substance, than which, even lightning itself is scarcely more prompt, or sure, in destruction, still the wisdom of Omniscience has connected circumstances with its production and nature, which, in a great measure, will always prevent its employment for criminal purposes. The process by which it is made, requires more chemical skill than generally falls to the lot of unprincipled and vicious persons; and when obtained, its active properties are so evanescent, as never to remain more than a week or two, without peculiar treatment; and sometimes it becomes nearly inert in a few days. The odor, also, which is distinguished in animals destroyed by it, is often the sure means of detection. The commencement of its decomposition is marked by the reddish brown color of the liquid, and, in a short time after, it becomes black, and deposits a thick carbonaceous substance, at the same time it loses its peculiar smell, and emits that of ammonia. In this state, the prussic acid has none of its former properties, but becomes entirely inert and worthless. This substance possesses the sensible qualities of an acid only in a very slight degree, being hardly sour to the taste, and producing but very little change in the blue colors of vegetables. It however performs the office of an acid in For what purposes is this acid employed when much diluted 1 What circumstances are connected with the production and nature of this acid, which it is said will prevent its employment for wicked purposes'! How does the acid appear while decomposing 1 Does this substance possess the sensible qualities of an acid 1 In what respect do*»« U perform the office of an acid J 17 194 PRUSSIC ACID. combining with alkaline bases, forming salts, called prussiates or hydrocyanates. The following is an example, by which the composition o< a substance may be found, when one of its elements can be made to combine with a third body, in a known proportion. By a previous experiment it was ascertained how much cyanogen would combine with a given portion of potassium, the basis of potash. Then, Gay Lussac exposed to the action ol 100 measures of prussic acid, heated so as to be in the state of vapor, a quantity of potassium precisely sufficient to absorb 50 measures of cyanogen. By this process, cyanuret oi potassium Avas formed, and exactly 50 measures of the vapor of prussic acid Avas absorbed, lea\*ing 50 measures of pure hydrogen remaining in the vessel in Avhich the experiment was made. From this experiment, it appears that prussic acid is composed of equal volumes of cyanogen and hydrogen, and therefore that they combine in the ratio of their specific gravities, that is, the Aveight of the vapor of prussic acid must be the combined Aveights of cyanogen and hydrogen, of an equal bulk. Noav the specific gravity of hydrogen is known to be 0.0694, and cyanogen gas, 1.8044, air being 1000. Cyanogen, therefore, is 26 times as heavy, bulk for bulk, as hydrogen, and since they combine in equal proportions, by volume, to form prussic acid, it follows that this acid consists of an atom of hydrogen united to an atom of cyanogen, and therefore, that an atom of cyanogen gas is 26 times as heavy as an atom of hydrogen. Thus, the atomic Aveight of cyanogen is 26, that of hydrogen being 1, and the specific gravity of the vapor of prussic acid being the medium betAveen them, is 0.9369, because 0.0694, the specific gravity of hydrogen, added to 1.8044, the specific gravity of cyanogen, makes How did Gay Lussac know that exactly 50 measures of cyanogen were absorbed by the potassium 1 [Cyanogen combines with metals in the same manner that oxygen does. See Cyanogen.] What was the quantity of hydrogen which remained after this absorption'! From this experiment, what appears to be the composition of prussic acid, by volume ; and therefore, the vapor of prussic acid consists of the combined weights of what 1 How does it appear - that cyanogen is 26 times as heavy as hydrogen"! Multiply 0.0694 by 26. How does it appear that an atom of cyanogen is 26 times as heavy as one of hydrogen 1 [Because they combine in equal volumes, but cyanogen weighs 26 times the most.] What then is the weight of an atom of cyanogen, that of hydrogen being 195 CARBON AND SULPHUR. 1.8738, the medium, or half of which is 0.9369, the specific gravity of the vapor of prussic acid. The composition of prussic acid may therefore be stated thus: Byvo'ume. By weight. Cyanogen 50 1.8044 26, one atom, Hydrogen 50 0.0694 1, one atom. 100 Tcid vapor. 27 atomic weight. Thus the atomic weight, or equivalent number for cyanogen is 26, and that for prussic acid is 27. The above will serve as a practical example of the method of finding the atomic weight of a constituent, under similar circumstances. CARBON AND SULPHUR. Sulphuret of Carbon —38. 1 p. Carbon 6+2 p. Sulphur 32. This singular compound may be made by the following process. Place an earthen tube, of about an inch and a half in diameter, a little inclined across a chaffing dish, previously nearly filled with small pieces of newly burned charcoal. To the higher end of this tub; adapt another tube of glass, filled with small pieces of sulphur. The end of this tube, not connected with the one of earthen, must be stopped with a cork, through which passes a wire,.the whole being made air tight. To the opposite end of the earthen tube, another glass tube must be connected, and so bent as to pass under the surface of some water, contained in a bottle. When every thing is thus prepared, the charcoal in the chafhngdish is set on fire, and when the centre of the tube becomes red hot, the sulphur must be pushed forward with the wire, so as to come in contact with the charcoal. The combination instantly ensues, and the vapor of sulphuret of carbon will condense under the water in the vessel. In this state it is of \ yellowish color, but may be purified by redistilling in a What is the specific gravity of the vapor of prussic acid, it being the medium between those of cyanogen and hydrogen 7 From these data, what is the composition of prussic »cid, by volume and weight 7 What is the equivalent number for prussic acid 7 Describe the process for making sulphuret of carbon. What is the color of the compound so prepared 1 How may it be purified, so as to become colorless and transparent 7 196 METALS. retort containing a little muriate of lime, to absorb the water The heat, during this process, must not be over 110°, and therefore, is best applied by a vessel of water over a lamp, in which the retort is placed. The neck of the retort is dipped under water, as before. The compound, thus obtained from two solids, the one black and the other yellow, is a perfectly transparent and colorless liquid. Its taste is acrid and pungent, and its smell exceedingly fetid and disagreeable. Its specific gravity is 1.27, water being 1.00. It does not mix with water, but sinks through that fluid, as water does through the lightest oil. It possesses very high refractive powers, (see Nat. Philosophy,) and is so volatile as to produce an intense degree of cold by evaporation, when exposed to the open air. It is highly inflammable, and burns with a blue flame, emitting copious fumes of sulphuric acid. It dissolves phosphorus and iodine, the solution of the latter being of a beautiful pink color. It was stated a year or two since in Paris, and republished in the journals of this country, that when this substance is mixed with phosphorus, and allowed to stand under water for six or eight months, the phosphorus combines with the sulphur, thus, leaving the carbon to crystallize, and form real diamonds. Having left such a mixture, undisturbed, for a much longer period than the recipe directs, Ave have as yi t discovered no appearance of this precious gem. Sulphuret of carbon is composed of 1 equivalent, or atom, of carbon, 5 2 do. * do. sulphur, 32 Its combining number, 38 METALS. The metals form the most numerous class of undecomposed. or elementary bodies. They possess a peculiar lustre, called the metallic, which continues in the streak, or when they art In what respect does this compound show the mysterious effects of chemical combina lion 1 What are the sensible properties of sulphuret of carbon t What is its speciflt gravity 1 What is said of its refractive powers, its volatility, and its inflammability 1 What has been published concerning the method of making diamonds from this sub stance 1 What is the equivalent composition of sulphuret of carbon 1 What is its equi valent number 1 Have any of the metals been decomposed 1 What is the peculiar lu» tre of the metals called 7 197 METALS. reduced to small fragments. They are ail conductors of electricity and caloric. They are fusible, at different temperatures, and in fusion retain their lustre and opacity. They are, in general, good reflectors of light, and with the exception of gold, which, in the thinnest leaves transmits a green light, they are perfectly opaque. Many of the metals may be extended under the hammer, and are hence called malleable, or under the rolling press, and are called laminable, or may be drawn into wire, and are called ductile. Others can neither be draAvn into wire, nor hammered into plates, but may be ground to powder in a mortar; these are called brittle metals. The metals are capable of combining with each other, in any proportion, when melted together, and such compounds are called alloys. With a few exceptions, the metals have the greatest specific gravity of all bodies. Potassium and sodium swim on water, but with these exceptions, the lightest among them, cerium, is about 5£ times the weight of water; platinum is more than 20 times heavier than the same bulk of water. The metals differ in respect to brilliancy, color, density, hardness, elasticity, ductility, tenacity, conductility for caloric and electricity, fusibility, expansibility by heat, stability, odor, and taste. When combined with oxygen, chlorine, iodine, or sulphur, and the resulting compounds submitted to the action of galvanism, the metals without exception are revived, and appear at the negative side of the battery, hence all the metals are positive electrics. The malleable metals, such as gold, silver, and iron, in whatever manner their surfaces are increased, if this is done rapidly, grow hot, and crumble under the hammer, or press, and finally refuse to be extended any further. It then becomes necessary, if their surfaces are to be farther extended, to anneal them, which is done by exposure to a red heat, when they become soft and malleable as before. It is pro- What imponderable agents do all the metals conduct? Are all the metals opaque? What are malleable, laminable, and ductile metals ? What are brittle metals ? What is an alloy ? What is said of the specific gravity of the metals 7 What are the properlies in respect to which the metals differ ? What is the electrical state of the metals % When the surfaces of the malleable metals are suddenly increased, what effect is thereby produced on their temperature 7 When is it necessary to anneal a metal 7 17* 198 METALS. bable that this change is produced by a quantity of caloric which the metal retains in its latent state, and by which its particles are prevented from forming so compact a mass as before. When the metal is again drawn under the hammer or press, it grows hot, and at the same time is increased in density and specific gravity, the caloric before absorbed being given out, and the metal is again rendered brittle by the process. All the metals are converted into a fluid state by sufficient degrees of heat. In this respect there is a vast difference m the different metals. Mercury is a fluid at all common temperatures, and does not assume the solid form unless exposed to a temperature nearly 40° below the freezing point, while platina and columbium continue solid under the highest heat of a smith's forge, and only become fluid under the heat ol the compound blowpipe, or the action of the most powerful galvanic battery. With several exceptions, these bodies suffer a singular change on exposure to air and moisture, or on exposure to air and heat. They lose their tenacity, brilliancy, and othei qualities peculiar to the metals, soil the fingers, and crumble to powder, but at the same time increase in weight. This change is termed oxidation, and in this state they are termed metallic oxides. This increase in weight and loss of metallic splendor, does not happen when the metal is placed in a vacuum, or when it is protected from the air by varnish or other means, but is found to be the consequence of the union between the metal and the oxygen of the air, or water, or both. Thus, iron, when exposed to air and moisture, spontaneously absorbs oxygen and is converted into a brown friable matter called rust. This is an oxide of iron. The increase of weight is caused by the solid oxygen which thus combines with the metal. Metals, in the language of chemistry, are termed combustibles, because they are capable of combining with oxygen, How is the process of annealing supposed to affect the metal, so as to restore its malleaoility 7 By what means may all the metals be rendered fluid t What is said of the dif ferent temperatures at which the metals become fluid 1 The metals, with the exception of platina, gold, and silver, are said to suffer a peculiar change, when exposed to heat, or to air and moisture. To what is this change owing, and what are the resulting compounds called ? What causes iron arid other metals to rust, when exposed to tlie air Why are the metals termed combustible in the language of chemistry 1 199 METALS. and thus passing through the process of oxidation, or combustion. In ordinary combustion there is an extrication o* heat and light, and under favorable circumstances, several of the metals exhibit these phenomena. Zinc burns with a brilliant flame when heated, and exposed to the open air ; and iron, when heated in oxygen gas, emits the most vivid scintillations, attended with intense heat. Gold and platina, the metals which have the least affinity for oxygen, are still capable of uniting with it so rapidly, as to produce scintillations when heated with the flame of the compound blowpipe. In all cases the metals combine with oxygen most rapidly when exposed to the highest degrees of heat. Hence, at common temperatures, their oxidation proceeds so slowly as not to emit sensible light or heat; and some of them, such as gold, silver, and platina, do not combine with it at all at such temperatures. Some of the metals combine with oxygen in only one proportion, while others combine with it in three or four proportions. Thus, there is only a single oxide of zinc, but there are three or four oxides of iron. After the metals are converted into oxides, they may again oe reduced, that is, brought back to their metallic states, by depriving them of their oxygen. This may be done by several methods, depending on the nature of the metal, or the force by which it retains the oxygen. The reduction of many of the metals from their ores, is nothing more than depriving them of their oxygen. For this purpose, a common method is to heat the oxide with some combustible, which has a stronger affinity for the oxygen than the metal has. Thus, the oxide parts with its oxygen, and assumes the metallic form, while the combustible absorbs that which the oxide before contained, and is itself consumed or converted into an oxide. As an example, carbon when heated has a stronger affinity for oxygen than iron, and therefore, when carbon and oxide of iron are strongly heated together, the iron is reduced while the char- Under what circumstances do several of the metals exhibit the ordinary phenomena of combustion t Under what circumstances do all the metals combine most rapidly with oxygen? What metals do not combine at all with oxygen at common temperatures 7 Do the metals all combine with the same proportion of oxygen 1 After a metal has been converted into an oxide, how may it again be reduced, or brought again to its metallic state? By what method can the metals be deprived ol their oxygen ? What is one of the most •oramon methods of reducing iron from its ores ? 200 METALS. coal is converted into an oxide, or an acid, and passes into the air, or in common language, is burned up. This is the method of reducing iron from its ores. In some instances, heat alone drives away the oxygen and reduces the metal; but in such cases the metal has only a weak affinity for oxygen. The oxides of gold, mercury, and platina, are thus reduced. Metals having stronger affinities for oxygen, resist such methods of reduction, and require the more powerful agency of galvanism. When metallic oxides are exposed to this influence, the reduced metal is found at the negative side of the battery, while the oxygen rises through the water at the positive side. None of the metals are soluble in an acid, in their metallic states, but when first combined with oxygen they are readily dissolved. Gold will not dissolve in muriatic acid alone, because this acid does not part with its oxygen with such facility as to form an oxide of the metal. But if a quantity of nitric acid be added to the muriatic, the gold instantly begins to enter into solution, and a chloride of the metal is formed. If a piece of zinc be thrown into sulphuric acid, it will remain undissolved, but if three or four parts of water be poured in, the metal is attacked with great violence, and soon dissolved. In this case the water furnishes the oxygen, by which the zinc is oxydized, and it is then dissolved by the acid. By this method hydrogen is obtained ; the metal decomposing the water by absorbing its oxygen, while the hydrogen is set at liberty. The metals combine with phosphorus, sulphur, and carbon, forming compounds called phosphurets, sulphurets, and carburets. Of all the inflammable bases, sulphur appears to possess When iron is reduced by heating its oxide with charcoal, what becomes of the oxy gen? In what instances does heat alone reduce the metallic oxides? When metallic oxides are reduced by means of galvanism, at which pole of the battery is the oxygen extricated ? Are any of the metals soluble in the acids, while in their metallic states 7 Why is it necessary to add nitric acid to the muriatic acid before it will dissolve gold? Why does not zinc dissolve in strong sulphuric acid 7 Why is hydrogen evolved when the zinc is dissolved in diluted sulphuric acid? When a metal combines with phosphorus, what is the resulting compound called ? What is the composition of a sulphuret 7 What is the composition of a carburet? What combustible body appears to possess the strongest affinity for the metals ? METALS. 201 .he strongest affinity for the metals, and its combination with some of them is attended with remarkable phenomena. This affinity is shown by the following interesting experiment. Introduce into a Florence flask, three parts of iron, or copper filings, and one part flowers of sulphur, well mixed together. Then stop the flask with a cork, and place it over a lamp, so as to heat it slowly, and as soon as any redness appears, remove the flask from the fire. The chemical action thus begun, will be continued by the heat evolved by the combination between the sulphur and the metal, and the whole mass in succession will become red hot, which, in the dark, will produce a very beautiful appearance. We have stated, in a former part of this work, that when bodies pass from a rarer to a denser state, caloric is evolved. The heat and light, in this experiment, seems to be the consequence of this general law of condensation, for the sulphuret, formed by the union of the two bodies, occupies much less space than the metal and sulphur did before. Many of the metallic sulphurets are very abundant in nature, forming the ores of the metals. Several metals are extracted entirely from such ores. The most abundant sul phurets are those of lead, antimony, copper, iron, and zinc. The phosphurets are seldom found as natural products, but may be formed, by bringing phosphorus into contact with the metal, at a high temperature. Carbon unites with iron in several proportions. Unrefined jron, steel, and black lead, are all carburets of iron, the latter containing 95 per cent, of carbon. When the oxide of a metal is dissolved in an acid, there is a compound formed, which differs entirely from either of /hese two substances, and when the liquor is evaporated there remains a crystalline solid, called a metallic salt. These salts differ materially from each other, according to the kind of acid and metal of which they are composed. Some of them, such as the sulphate of iron, and acetate of lead, are of great importance to the arts. The oxides of the metals readily unite by fusion with glass, What experiment is stated,|illustrating the affinity between iron and sulphur 1 Whence does the heat arise in this experiment! What are the most abundant sulphurets in na'tire ? Are the phosphurets often found native 1 What carburets are mentioned ? What A a metallic salt 1 What particular salts are mentioned, as being of great importance to ae arts t What is said of the uni>»< oetween the metallic oxides and glass 1 202 METALS, and it is by such means that this substance is made to resemble gems and precious stones. The stained glass, so celebrated among the ancients, and used in the windows 01 churches, was prepared in this manner. This art was said to have been lost, but stained glass is still made in many parts of Europe, and in this country. (See Glass.) Compounds, made by fusing two or more metals together, are called alloys. In these cases there is a chemical union between the metals ; and hence such compounds differ greatly from the metals of which they are composed. In general, the specific gravity of the alloy is greater than the medium specific gravity of the two metals, and of consequence, the bulk of the alloy is less than that of the two metals taken separately. As an example, if two bullets of copper and two of tin, of equal bulk, be melted together, they will form little more than three bullets of the same size. This diminution ol bulk is accounted for, by supposing that the particles of the two metals enter into a closer union with each other, when combined, than those of either did in a separate state. The alloys of the metals are also more easily fusible than the metals of which they are composed; that is, the melting point of an alloy is below the medium temperature at which the metals composing it are fusible. An alloy, made of 8 parts bismuth, 5 lead, and 3 tin, is a curious instance of this fact. In a separate state, the melting point of lead is 500°, bismuth, 490°, and tin, 430°, and yet, when these are fused together, the compound melts at 212°. Amusing toys, in the form of tea-spoons, have been made of this alloy. Such spoons, in the hand of those who know no thing of their composition, have excited great astonishment, by coming out of a cup of hot tea with their bowls melted off The number of metals, and the variety of properties which they possess, render it necessary to throw them into classes and orders, that a knowledge of these properties may be more easily obtained. The following arrangement is that originally proposed by Thenard, and adopted by Henry and others. We have already stated, that some of the metals are reduced from the state of oxides by heat alone, such metals hav- What are alloys 1 In what respect do alloys diner from the metals of which they ar« composed 1 How is the increased specific gravity of the alloys accounted for 1 What i» said of the fusibility of alloys 1 What curious illustration of the fusibility of an alloy mao>. of bismuth, lead, and tin, is given ? 203 METALS. .ng only a slight affinity for oxygen. Others, it was also stated, have so strong an attraction for oxygen, that they cannot be reduced by this method, but require the presence of a combustible, or some other means, for their reduction. The arrangement into classes is founded on this distinctive difference, The orders of the second class are founded on the powers of tne metals to decompose water. Class I.—Metals, the oxides of which are reducible to the metallic state, by heat alone. These are Mercury, Platinum, Osmium, Silver, Palladium, and Gold, Rhodium, Iridium. Class II.—Metals, the oxides of which are not reducible to the metallic state by the action of heat alone. Order 1.—Metals which decompose water at common temperatures. These are, Potassium, Lithium, Strontium, Sodium, Barium, Calcium. Order 2.—Metals which are supposed to be analogous to Order 1, but whose properties are but little known. These are, Magnesium, Ittrium, Zirconium, Glucinum, Aluminum Silicium. Order 3.—Metals which decompose water at a red heat These are, Manganese Iron, and Zinc, Tin, Cadmium. Order 4.—Metals which do not decompose water at any temperature. These are, Arsenic, Uranium, Titanium, Molybdenum, Columbium, Bismuth, Chromium, Nickel, Copper, Tungsten, Cobalt, Tellurium, Antimony, Cerium, Lead. Of the first class, there are S metals; of the second, there are 32; making 40 in all. What is the distinctive difference between the metals, on which is founded the arrangemen*, into classes ? What are the peculiar properties on which the orders of the second ascare founded? How are the classes and orders defined, and what are the names ot the metals belonging to each 1 How many metals belong to the first class and how many to the second. 204 MERCURY CLASS I. Metals, the oxides of .vhich are decomposed by the actloi of heat alone. mercury—200 Mercury, or quicksilver, is found native, or in its pure state, only in small quantities, the mercury of commerce being chiefly extracted from cinnabar, which is a sulphuret of the metal. The metal is extracted from this ore, by heating it in iron retorts, mixed with iron filings or lime. By this process, the sulphur combines with the lime or iron, forming a sulphuret of lime or iron, while the mercury is volatilized, and is distilled into a receiver, where it condenses in its pure form. This metal is distinguished from all others by preserving its fluidity at common temperatures. Its specific gravity is 13.5. At the temperature of 600° it boils, rises in vapor, and may be distilled from one vessel into another. At 40° below zero it becomes solid, and is then malleable, and may be hammered into thin plates. When pure, this metal is not readily oxidized in the open air at common temperatures, but Avhen mixed with other metals, such as tin, or zinc, there is commonly a film of oxide on its surface; hence this is an indication that the mercury is impure. When mercury is triturated with an equal quantity of sulphur, there is formed a black powder, called ethiops mineral. Mercury readily combines with gold, silver, tin, bismuth, and zinc; but not so readily with copper, arsenic, and anti mony, and with platina and iron scarcely at all. The resulting compounds between mercury and the other metals, are called amalgams. Mercury has such an affinity for gold and tin as to dissolve these metals in small pieces, at common temperatures. In the mines of South America, a great proportion of the gold What is the definition of class fust? From what substance is the mercury of commerce extracted 1 What is the composition of cinnabar, and what its chemical name 1 What is the method of obtaining the mercury from its sulphuret t What striking distinction is there between mercury and oilier metals 1 What is the specific gravity of mercury 1 At what temperature does mercury boil, and at what temperature does it freeze? When solid, what property common to many other metals does it nossesal What are the obvious indications of impurity in this metal 1 What is ethiops mineral 1 When mercury combines with other metals, what is the compound called 7 205 MKHCURY. was formerly procured by amalgamation. Sand containing particles of gold, was agitated in a close vessel with mercury and the two metals thus brought in contact, united and formed an amalgam. This was then distilled in an iron vessel, by which the mercury was driven away, while the gold remained. At the present time, the gold-beaters make use of the same means to obtain the small particles of the metal contained in the sweepings of their shops. The sweepings being placed in a close vessel, and agitated with mercury, an amalgam i form.ec. The gold is then separated by pressing the amalgam in a buckskin bag, which forces the mercury through the pores of the leather, while the gold is retained. Mercury is applied to many other uses in the arts, and is a constituent in several important medicines. The silvering on the backs of looking-glasses, is an amai gam of tin, and is put on in the following manner: A sheet of tin foil is laid perfectly smooth on a slab of marble, and on the tin foil, mercury is poured, until it is about the eighth of an inch thick; the attraction of the metals for each other, keeping the mercury from running off When the mercury is spread equally over the surface, the glass plate is run or slid on. This is so managed, by partly immersing the end of the plate in the edge of the mercury, and pushing it forward, a? to entirely exclude the air from between the metal and the glass. Weights are then laid on the plate, to press out the mercury which does not amalgamate with the tin. In about 24 or 36 hours, the amalgam adheres to the plate in the manner we see it on looking-glasses. The glass, therefore, merely serves to keep the amalgam in its place, and being transparent, to transmit the image which is reflected from the surface of the metal. Could the mercury be kept from oxydalion, and be retained in its place without the glass plate, such mirrors would be much more perfect, since the glass prevents some of the rays of light from passing to and from the metal. IIow is cold obtained by mercury 7 How do gold-beaters obtain the small particles of jold from among the sweepings of tneir shops 7 What is the composition sailed the silvi.ring, on the backs of looking-glasses'! Describe the process of silvering a plate of glhss. In forming a looking-glass, what is the use of the glass plate I 18 206 MERCURY MERCURY AND OXYGEN. Peroxide of Mercury —216. 1 p. Mercury 200+2 p. Oxygen 16. Red Precipitate. This compound is commonly formed by dissolving mercury in nitric acid, and then exposing the nitrate to such a degree of heat as to expel all the acid. It is in the form of small, shining crystalline scales, of a red color. When exposed to a red heat, this oxide is reduced, and converted into oxygen, and metallic mercury, a circumstance on which its arrangement in the present class depends. When long exposed to the action of light, the same effect is produced. Red precipitate is employed in medicine chiefly as an escharotic. It will be observed at the head of this section, that the per oxide of mercury is composed of 200 parts of the metal combined with 16 parts or two equivalents of oxygen. The protoxide of this metal consists of 200 mercury, and 8 oxygen, these compounds conforming precisely to the doctrine of definite and multiple proportions, as formerly explained. The reason Avhy so large a number as 200 is taken for the equivalent of mercury, and some other metals, will be understood, when it is recollected, that the data from which all the proportional numbers are estimated, is the proportions of hydrogen and oxygen forming water. The proportion of oxygen in this compound being 8, and this number for oxygen being fixed, that for mercury is 200, because it is found by experiment, that these are the smallest proportions in which thesr wo bodies combine. MERCURY AND CHLORINE. Protochloride of Mercury —236.. I p. Mercury 200+1 p. Chlorine 36 Calomel. When chlorine, a gas formerly described, is brought in contact with mercury, at common temperatures, a combination takes place between them, amounting to one proportion of each, forming a protochloride of the metal. This, however is not the common method of preparing calomel; the What is the composition of peroxide of mercury 1 By what simple process is it ob taincd 1 How may this oxide be decomposed 7 What is the use of red pre.-ipitate 7 Ei plain the reason why the combining number for mercury is 200. 207 MERCURY. two constituents being more conveniently combined in their proper proportions, by mixing the bichloride of this metal with an additional quantity of mercury. The bichloride of mercury contains, as its name signifies, two proportions of chlorine and one of the metal. This compound is known under the name of corrosive sublimate. It contains mercury 200, and chlorine 72 parts by weight. When this salt is triturated with mercury, the metal absorbs a part of the chlorine, and the whole is converted into a protochloride, or calomel. The proportions are 272 parts, or 1 equivalent of the corrosive sublimate, and 200 parts, or 1 equivalent of the mercury. This process affords a beautiful illustration of the truth of the doctrine of definite proportions; for when these equivalents are mixed in a mortar, and then sublimed by heat, 36 parts, or 1 proportion of the chlorine is transferred from the bichloride to the metallic mercury, thus converting the whole into 472 parts of protochloride of mercury, or calomel. This process also shows, in a striking manner, the effects of different proportions of the same principles, on the qualities of bodies. Corrosive sublimate is one of the most active and virulent of all metallic poisons, and in doses of only a few grains, occasions the most agonizing symptoms, which commonly end in death. But calomel is a mild and safe medicine, which maybe taken in doses of 60, or even 100 grains, without injury. And yet the only chemical difference between these two substances is, that the calomel is a compound of 1 atom of chlorine combined with one of mercury, while corrosive sublimate consists of 2 atoms of the first and 1 of the metal. MERCURY AND SULPHUR, Sulphuret of Mercury —216. 1 p. Mercury 200+1 p. Sulphur 16, Cinnaba*. Cinnabar is prepared by fusing mercury and sulphur together, and afterwards subliming the compound. When this compound is reduced to a fine powder, it forms the well What is said of the combination between mercurv ano the gas chbrna nt common temperatures 1 What common name has the protoclnorme of mercury 7 How does tho nrotochloride differ from the bichloride of mercury I What is the common name for the bichloride of mercury 1 What is the common mode of making calomel 1 What proportions of corrosive sublimate and mercury comoine and form catomeJl What two principles are strikingly illustrated by this combination What is the composition or sulphuret of mercury 1 208 SILVER. known pigment vermilion. Cinnabar occurs in nature, in large quantities, and is the substance, as already stated, fron* which mercury is chiefly obtained. SILVER 110. Silver is found native in small quantities. It also occurs mixed with several other metals, as copper, antimony, arsenic, and sometimes with gold, but is chiefly found in combination with sulphur, forming a sulphuret of silver. This metal, when pure, admits of a lustre only inferior to hat of polished steel. Its specific gravity is I I, being about half that of platina. In malleability and ductility it excels all the other metals except gold and platina. Silver is fused by the heat of a common furnace, and by a long continued and high degree of heat it may be volatilized, or turned into vapor. By slow cooling, this metal may be obtained in regular crystals. It is not oxidated by exposure to the combined action of heat and moisture, but is readily tarnished by sulphureous vapor. Sulphuric acid dissolves this metal, when assisted by heat, but its proper solvent jS nitric acid, with which it readily combines, and when the solution is evaporated, forms nitrate of silver, a substance known under the name of lunar caustic. Silver is precipitated from its solutions, by several of the ather metals, in its metallic form. This happens when any other metal, having a stronger affinity for oxygen than silver, is placed in a solution of this metal. If a quantity of nitrate of silver, or lunar caustic, be dissolved in water, and a slip of clean polished copper be dipped into it, the copper will be covered with a coat of silver. Diana's silver tree is made by precipitating silver from its solution by means of mercury. This interesting experiment may be performed in the following manner. Mix together six parts of a solution of nitrate of silver, and four parts Oi a solution of nitrate of mercury, both completely saturated. Add a small quantity of rain water, and put the mixture into What is the more common name for this compound 1 What is vermilion ? In what states does silver occur? What, is the substances with which it is chiefly found combined' What is its specific gravity ? What is said of its malleability and ductility ? How mav stiver be obtained in crystals? What vapor readily tarnishes silver ? What is the proper solvent of this metal ? What is the salt formed when silver is dissolved in nitric acid? How is lunar caustic formed? How mav silver be precipitated in its metadie form? What is the process for forming Diana's silver tiee i SILVER. 209 ii glass decantei, containing six parts of amalgam, made of seven parts of mercury, by weight, and six parts of silver leaf. In the course ol some hours, there will appear small shining scales of metallic silver on the amalgam, which will increase, and shoot out in tne form of a silver tree, producing a very beautiful appearance. Silvering powder may be prepared in the following mam ner. Precipitate silver from its solution in nitric acid, by dropping into it some plates of clean copper. Take 20 grains of this powder, and mix with it two drachms of cream of tar tar, the same quantity of common salt, and half a drachm of alum. These articles must be finely pulverized, and intimately mixed in a mortar. If a little of this powder be moistened, and rubbed on a clean surface of brass or copper the silver will be precipitated, and the surface of the metal will be covered with it. In this way the silvering of candlesticks, or other articles, where it is worn off, may be replaced. The addition of the other articles to the precipitated silver, probably serves no other purpose than to keep the surface of the brass perfectly clean, and free from oxide, as the powder is rubbed on. Silver may also be precipitated on ivory, and then revived by the action of solar light. Into a dilute solution of nitrate of silver immerse a slip of polished ivory, and let it remain until it acquires a yellow color, then place it in a tumbler of pure water, and expose it to the direct rays of the sun for a few hours, or until it turns black. If now, it be gently rubbed, the surface will be changed into a bright metallic one, and the slip of ivory will, in appearance, be transmuted into one of silver. This change is caused by the deoxidizing power of the solar rays, in consequence of which, the oxygen is separated from the silver, and the metal reduced to its former state. A very useful solvent of silver is made by dissolving one part of nitre with about eight parts of strong sulphuric acid. This solvent, when heated to about the temperature of boil- alkalies ? 223 SODIUM AND CHLORINE. soda All the salts of soda are soluble in water, and are not precipitated by any other substances. SODIUM AND CHLOJUNE. Chloride, of Sodium —60. 1 p. Sodium 24+1 p. Chlorine 36. Common Salt. When sodium is exposed to chlorine, or is heated in muri atic acid gas, the salt is formed, lately known under the name of muriate of soda, or common salt. This is an abundant product of nature, and exists, ready formed, in Spain, England, Poland, and other countries, in large quantities. In these countries it is dug out of the earth, and is known by the name of rock salt. Sea water and certain springs also contain this salt in solution. When common salt is dissolved in water, and the solution is evaporated rapidly, it crystallizes in the form of hollow four-sided pyramids ; but if allowed to evaporate spontaneously, it occurs in regular cubes. Thus, the crystals show in what manner the salt has been manufactured. In England, vast quantities of salt are annually raised from the mines, chiefly of Cheshire, and purified for sale. The impurities consist chiefly of clay and oxide of iron, besides which, it contains various proportions of sulphate of magnesia, or Epsom salt, sulphate of lime, and muriate of lime. It is purified by being dissolved in sea-water, and subsequently evaporated. Formerly, all the English salt was evaporated by artificial heat, the brine being boiled until it was ready to shoot into crystals. Its crystals were, therefore, always in the form of hollow pyramids. But it has been supposed, by victuallers and others, that this salt is far less efficacious, as a preserver of animal food, than that prepared by the spontaneous evaporation of sea-water in hot climates. Hence, salt from the West Indies, which is crystallized in solid cubes, has been preferred for curing provisions for long voyages, or for summer use. What is chloride of sodium ? What the sources of common salt 7 When a solution of common salt is evaporated rapidly, what is the form of its crystals ? When evaporated slowly, in what form are the crystals? Where are the salt mines of England! What impurities exist In the Cheshire rock salt ? How is this salt purified ? Why were, the crystals of this salt always in the form of hollow pyramids? What salt was formerly supposed best for the preservation of animal substances ? 224 li rmu lu- ll) this country, although immense quantities of common salt jre manufactured, by the evaporation of water from salt springs and from the sea, and a sufficient supply for our con sumption might be made, yet we annually import large quantities from the West Indies, there having been, until lately, an opinion that no other kind of salt would preserve animal substances through the hot season. Dr. Henry, for the purpose of ascertaining the difference between English salt, crystallized by heat, and that from the West Indies, crystallized by spontaneous evaporation, analyzed many specimens of each. The result showed the presence of sulphate of magnesia and sulphate of lime in both, but the difference in the quantity of muriate of soda, in several specimens of each kind, was so trifling, as to make no possible difference in respect to their preserving qualities. It is presumed, therefore, that the prejudices in favor of foreign salt ought to be discarded as imaginary, and that equal weights of fine or coarse salt, whether made by artificial or spontaneous evaporation, are equally efficacious for all purposes. Common salt contains no water of crystallization, but decripitates remarkably when heated, owing to the conversion of the water into steam, which is mechanically confined within its crystals. Its solubility is not, like most other salts, increased by heat, and it requires two and a half times its weight of water for solution, whether hot or cold. LITHIUM 18. Lilhia is an alkaline substance, discovered by M. Arfwedson, a Swedish chemist, in 1818. It exists in the minerals called spodumenc, and lejridolite, and also in some varieties ol mica. This alkali is distinguished from potash and soda, by its power of neutralizing larger quantities of the different acids, and by its action on platinum, when melted on that metal. In respect to its metallic base, called lithium, Sir H. Davy succeeded, by means of galvanism, in obtaining a white metal What is said of the real difference between salt made by rapid or slow evaporation? Does common salt contain any water of crystallization 1 Why does common salt decripitate, or fly in pieces, when thrown upon a fire? Is the solubility of this salt increased ny heat 1 What quantity of water does it require for solution 1 What is lithia 1 In what minerals is this alkali found 1 How is lithia distinguished from potash and soda 1 225 METALS. tiom lithia, similar m appearance to sodium, but it was oxidized so rapidly, and reconverted into the alkali, that it could not be collected. From the experiments of several chemists on the sulphate of -lithia, it is inferred that the alkali, lithia, is composed of the metal lithium 10, combined with oxygen 8, making the combining number for lithia 18. Lithia has been procured only in very small quantities and has never been applied to any useful purpose. barium —70. There is a substance, called sulphate of barytes, which is found abundantly in nature. By the decomposition of this substance, an alkaline earth is obtained, called baryta or barytes. When barytes, in the form of paste mixed with water, is exposed, in contact with mercury, to the action of a powerful galvanic battery, its decomposition is effected, and the metal barium, its base, amalgamates with the mercury. The amalgam being exposed to heat, the mercury is driven off, and pure barium remains. The metal thus obtained, is of a dark gray color, with a lustre inferior to cast iron. It fuses at a heat below redness, and at a red heat is converted into vapor, which acts violently upon glass. The specific gravity of barium is four or five times that of water. When exposed to the air, it falls into a white powder, which is found to be an oxide of barium, or barytes. When heated in oxygen, it burns with a deep red light, and when thrown into water, the fluid is decomposed, hydrogen being extricated. BARIUM AND OXV EN. Protoxide of Bariw, —78. 1 p. Barium 70-f-1 p. Oxygen 8. Barytes. When the metal barium, is exposed to the air, it falls into a powder, which was formerly called pure barytes, or baryta, but which Sir H. Davy has proved by the above stated ex- What is known concerning the metallic base of this alkali % What are the equivalent numbers of lithium, and lithia 1 How is baryta obtained! By what process is barium separated from baryta ? What is the color of barium 1 At what temperature is barium fusible 1 What is the specific gravity of barium 1 When barium is exposed to the uit what compound is formed 1 226 METALS. Deriment, to consist of a metal and oxygei. This substance is therefore called oxide of barium. Oxide of barium may also be obtained by a different process from that above described, viz. by exposing the carbonate of baryta to an intense heat, mixed Avith charcoal. The carbonate of barytes is found native in small quantities, but maybe obtained from the sulphate of barytes by a simple process. Mix sulphate of barytes in fine powder, with three times its weight of carbonate of potash, (pearlash), and a proper quantity of water. Let the mixture boil for an hour, now and then breaking the lumps into which it is apt to run, with a pestle. By this means the two salts will decompose each other, and there will be formed carbonate of barytes, and sulphate of potash. The carbonate may now be exposed to a high heat, or it may be dissolved in nitric acid, and this decomposed, which is effected by a moderate heat, when protoxide of barium, or barytes, will be obtained. This substance is of a white color, has a sharp caustic taste; changes vegetable blue colors to green ; neutralizes acids, with which it forms salts, and is a strong poison. When water is thrown on it, it falls into fine powder, like quicklime, but with a greater evolution of heat. Barytes is composed of I equivalent, or atom of barium, 70 1 do. of oxygen, 8 The equivalent combining number for barytes, 78 Barytes is soluble in about twenty parts of water, at com mon temperatures, and this solution forms a delicate test for the presence of carbonic acid. The carbonate of barytes being insoluble in water, a white cloud is instantly formed by the union. STRONTIUM —44. The sulphate and carbonate of strontian, or strontia, are native salts. They consist of pure strontian, combined with sulphuric and carbonic acids. From the sulphate, the car- When thrown into water, what effects are produced 1 By what process may barium oe obtained without the agency of galvanism 7 How may carbonate of barytes be ex traded from the sulphate 7 What are the properties of barytes, or protoxide of barium What is the composition of barytes 7 In what quantity of water is barytes soluble 1 Why is barytes a test for carbonic acid 1 How is the carbonate of strontian produced from the sulphate 7 227 METALS. boi ate may be procured by precisely the same means as already described for barytes, and the pure oxide may also be obtained, and the metal strontium separated from it, by the same process as that described for barytes. Strontia resembles baryta in most respects. It slakes in water, causing an intense heat, and possesses distinct alkaline properties. The metal strontium is similar to barium in appearance, and when exposed to the air quickly attracts oxygen, and in converted into strontia. Perhaps the principal difference between these two substances, which has been detected, is their different combining proportions with oxygen, and the inertness of the oxide of strontium on animals. The protoxide of strontium connsists of Strontium, 1 equivalent 44 Oxygen. 1 do. 8 52 The oxides of barium, as already stated, are strong poi sons, but those of strontium are inert. CALCIUM 20. When carbonate of lime, or white marble, is exposed to a . ed heat, the carbonic acid is expelled, and there remains a white caustic substance, well known under the name of quicktime. When this substance is exposed to the action of galvanism, in the same manner as already described for the decomposition of barytes, calcium, the metallic base of lime, is separated. This metal is of a whiter color than barium, and has a lustre like silver. When exposed to the air, it absorbs oxygen, and is converted into quicklime, and when thrown into water, the fluid is decomposed, its oxygen being absorbed, while hydrogen is given off, and a solution of lime remains How is the pure earth strontia obtained from the carbonate ? By what process is the meta. strontium separated from strontia 7 What is the appearance of this metal 7 What is the composition of strontia, or the protoxide of strontium 7 What is the combining number of strontia? What is the difference between strontia and baryta! What is quick•ime 7 How may quicklime be decomposed, and calcium, its metallic base, oe separated 7 What, is the appearance of calcium 7 How is calcium converted into quicklime ! What •fleet is produced when calcium is thrown into water? 228 METALS CALCIUM AND OXYGEN. Oxide of Calcium —28. 1 p. Calcium 20+1 p. Oxygen 8. Quicklime. From the quantity of hydrogen evolved by the action o. calcium on water, it has been determined that lime is com posed of Calcium, 1 equivalent 20 Oxygen, 1 do. 8 Making the equivalent for lime, 28 Carbonate of lime exists in great abundance as a natural product, under the names of limestone, marble, and chalk. Quicklime, the pure earth, is obtained by exposing the carbonate to heat, and is a substance of great importance in the arts, and particularly in building. Mortar is composed of this substance combined with water, and mixed with a proportion of sand. Quicklime absorbs water with remarkable avidity, and at the same time a high degree of heat is produced. This process is called slaking, and the heat is caused by the condensation of the water into a solid state, in consequence of which caloric is evolved. The lime will remain perfectly dry after having absorbed one third of its weight of water, which therefore forms a part of the slaked lime, or hydrate of lime. Hydrate of lime is composed of 28 parts or 1 proportion of lime 9 parts, or 1 do. of water 37 is therefore its combining number. Lime is very sparingly soluble in water, and it is a singular fact, that it is more soluble in cold, than in hot water. Thus. Mr. Dalton found that one grain of lime, at the temperatura of 212° required 1270 grains of water for its solution, while at the temperature of 60°, the same quantity was dissolved in How is the combining proportion of oxygen with calcium determined ? What is the composition of lime, or oxide of calcium? What is the equivalent number for Hme" What causes the heat, when water is thrown on quicklime ? What is the scientific name for slaked quicklime? What is the composition of hydrate of lime? What singular fact is mentioned concerning the solubility of lime in cold, and hot water? 229 CHLORIDE OF LIME. 778 grains of water. By other experiments, it has been found that water, at the freezing point, will take up just twice the quantity of lime that it will at the boiling point. Consequently, on heating lime water, which has been prepared in the cold, a deposition of the lime will ensue. Lime water, therefore, when used for medicinal purposes, should be prepared in cold, instead of hot water, as commonly directed, and should also be kept in a cool place. It should likewise be closely stopped from the air, for, as the lime has a strong attraction for carbonic acid, of which the atmosphere always contains a small portion, if left open, it is soon converted into carbonate of lime, as shown by the production of a thin pellicle on its surface. Lime water is a delicate test for the presence of carbonic acid, with which it forms a white insoluble compound, the carbonate of lime. The air from the lungs contains a small quantity of carbonic acid, and hence, on blowing into a vessel of clear lime water, it instantly becomes cloudy, or turbid. LIME AND CHLORINE. Chloride of Lime —92. 2 p. Lime 56-f-l p. Chlorine 36. Oxymuriate of Lime. Bleaching Powder. The gas called chlorine, as already shown, possesses strong bleaching or whitening powers; but as it would be inconvenient to manufacture this gas at every place where it is wanted, and as its application is more convenient when combined with some other substance, it is found that in practice, these purposes are best answered by first combining it with lime. The manufacture of bleaching powder is a business of great importance, and is carried on in large establishments prepared for the purpose. The retorts, in which the gas is extricated, are made of lead or platina. If of lead, they must be of new metal and cast, for the gas acts on tin, a part of the composition of solder, How much more lime will water dissolve at the freezing than at the boiling point ? Had lime water, for medicinal purposes, ought to bo made with hot or cold water ? Why 7 Why should l : me water be closely stopped from the air 1 Why does lime water become cbudy when air from the lungs is blown into it? What is the chemical name for bleach Ing powder ? Does the bleaching property exist in the lime or in the chlorine What are the advantages of combining the chlorine with the lime for this purpose Why must new lead be used for retorts in making chlorine? 20 230 CHLORIDE OF LIME. and since old lead generally contains a portion of this metal, owing to its having formerly been soldered, it is soon destroyed. These retorts are placed in iron vessels of water, to which the heat is applied. In large manufactories, each retort is capable of containing 10 cwt. of common salt, ground with from 10 to 14 cwt. of black oxide of manganese, in proportion as the latter contains more or less oxygen. This being introduced, there is added from 16 to 18 cwt. of sulphuric acid, of the specific gravity of 1650. The lime, recently slaked, is contained in trays, or shallow boxes of wood, placed in a large chamber, built of granite,'or siliceous sandstone, or lined on the inside with lead. This chamber has two windows of glass opposite to each other, through which the workmen are enabled to see how the process goes on. Every part of this chamber is made air tight, the door being secured by fat lute, and strips of cloth. In order to get rid of the remaining gas, after the absorp tion of the lime is completed, there are three trap doors, one in the roof, and two in the floor or sides of the chamber. These are opened by means of ropes and pullies, so that the workmen may avoid the vapor that passes out. The lime being placed in the boxes, the gas is let in to the chamber from the retorts, under which a fire is afterwards kindled, in order to hasten the process, and obtain more chlorine. The gas, being heavier than air, is let in at the upper part of the room, and gradually descends, while the air in part mixes with it, and in part rises above it. The lime absorbs the chlorine with great avidity, its condensation causing the evolution of a large quantity of caloric ; the latter circumstance is, however, to be avoided, as too high a heat partly decomposes the chloride of lime, by expelling the-oxygen, and thus forming a chloride of calcium instead of a chloride of lime. The gas is, therefore, admitted slowly, in order to avoid this consequence. The process continues four days, before the absorption is considered sufficient to make the best bleaching powder, for its quality depends entirely on the quantity of chlorine which the lime contains* Describe the chamber in which the lime, for making the chlorde of lime, is pluced. Wllft contains the lime, when placed in the chamber ? Into what part of the room is the chlorine admitted? Why must the chlorine be admitted slowly ? If the heat rises too high, why is there a muriate instead, of a chloride of lime, formed? How long a tiino i» required for making the best bleaching powder? 231 CHLORIDE OF LIME. In some manufactories, the lime is stirred by means of rakes, with long handles passing through the sides of the room, the passages being made close, by means of milk of lime, or lime moistened, so as to be about the consistence of cream, and contained in boxes through which the handle passes. In others, the traps above described, are opened at the end of two days from the beginning of the process, and when the gas has subsided, the workmen enter and rake over the lime, so as to present a new surface to the action o the gas. The doors and traps are then closed, and the gas admitted for two days more, at the end of which time the process is finished, and the doors are again opened, and the chloride of lime removed, and put into close casks for use. In general, according to Mr. Gray, a ton and a half of good bleaching powder is considered the average product of each ton of the salt employed. It is said that the principal difficulty in the manufacture of this article, is the production of chloride of calcium, by decomposition, instead of the chloride of lime. To understand the cause of this difficulty, it must be remembered, that calcium and chlorine have a stronger affinity for each other than calcium and oxygen. Lime is composed of calcium and oxygen; and chloride of lime is therefore composed of oxygen, calcium, and chlorine. Now these three elements being present, there is formed a chloride of calcium, in consequence of the cause just stated; and in proportion as this is formed, the bleaching property of the salt is destroyed, this property being possessed only by the chloride of lime. The same effect is produced when the temperature is raised too high during the manufacture of this compound, for then the oxygen of the lime or base is expelled, and the calcium and chlorine form chloride of calcium. The only mode of avoiding this difficulty, appears to consist in admitting the chlorine slowly, as already stated. This salt is also subject to decomposition from other causes. When mixed Avith Avater, and exposed to the action of the In what manner is the lime stirred, in order to hasten its absorption of the chlorine 7 What proportion does the bleaching powder formed bear to the quantity of salt employed J What is said to be the principal difficulty in the manufacture of bleaching powder? What is the difference in composition between muriate of lime and chloride of lime 7 Explain tne chemical changes which take place when chloride of lime is decomposed by neat, and converted into muriate of lime. 232 CHLORIDE OF LIME. atmosphere, carbonic acid unites with the lime, while the chlorine is expelled, and thus a carbonate instead of a chloride remains, or by decomposition of the water, a muriate of lime is formed, which is also without bleaching properties. As the goodness of bleaching powder depends entirely on the quantity of chlorine it contains, it is a matter of great consequence to the purchaser to ascertain its quality in this respect, by actual experiment. According to the experiments of Dr. Ure, lime, under a slight pressure, is capable of condensing nearly its own weight of chlorine; but according to the same author, the bleaching powder of commerce always contains a considerable proportion of the muriate of lime, while the chloride itself often does not contain more than one half or one third the quantity of chlorine which the lime is capable of absorbing. Hence the consumers of this article are often cheated out of one half or two thirds of the price they pay for it, besides the delay and vexation incident upon the failure of the process in Avhich it is used. The manufacturers of paper and cotton goods are often sensible of this fact, by experience. It appears, on experiment, that when bleaching powder is kept for a considerable time, even in properly secured vessels, such as glass bottles well corked, that it still slowly undergoes the same change, which is immediately effected by heat, as described above. This seems to be in consequence of the superior affinity of chlorine for the calcium, or the metallic basis of the lime, by which the oxygen is slowly disengaged, and a chloride of calcium, or muriate of lime, is 'ormed, and thus the bleaching power is in process of time entirely destroyed. The principal expense of manufacturing chloride of lime, being that of the chlorine itself, and there being no method of ascertaining its quantity, except by experiment, the purchaser generally has to depend chiefly on the honesty of the manufacturer, for the goodness of the article, even when re ' In what manner is chloride of lime decomjrosed, when it is exposed to the atmosphere i On what does the bleaching property of the chloride depend 1 What quantity of chlorine is lime capable of absorbing 1 According to Dr. Ure, what does the bleaching powder ol commerce contain besides the chloride of lime 1 What kind cf decomposition does bleaching powder slowly undergo when confined in close vessels? CHLORIDE OF LIME. 233 ftently made. But as there are several causes of decomposition, even when it is honestly and carefully made, the buyer is still liable to be deceived, unless he makes his experiment before the purchase Under such circumstances, the English chemists have devised several simple methods of testing the quality of bleaching powder, in order that the buyer might judge of its good ness without actual trial at home. One of these methods is, to expose the salt to a sufficien' degree of heat to expel the oxygen from the lime, and by measuring its quantity, to judge of the quantity of the chlo ride of lime. The quantity of oxygen thus expelled, indicate? the quality of the bleaching powder, so far only as regards the quantity of muriate of lime with which it is mixed; for as above stated, the base of the chloride contains oxygen, while the muriate contains none. But in addition to the imperfection of this method in not indicating the actual quantity of chlorine present, there is much difficulty in ascertaining the quantity of oxygen by it, since various proportions of chlorine might also be disengaged by the heat, along with the oxygen. This method cannot therefore be readily or generally employed. It has also been proposed, to analyze the powder by nitrate of silver. But this test only indicates the quantity of muriate of lime, by forming with the muriatic acid an insoluble chloride of silver. This test is therefore useless. Several other methods have been tried, and among them, that of destroying the color of a certain quantity of indigo has been most employed. A known quantity of indigo being in solution, a certain number of grains of the powder is added, and the strength of the latter ascertained by the amount of coloring matter destroyed, or by the number of grains required to discharge, entirely, the color of a certain quantity of indigo. This method has the advantage of simplicity, but is defective in other respects, and particularly so in regard to the difference in the quantity of coloring matter in different kinds or specimens of indigo. The most accurate method is to decompose the chloride On what principle has it been proposed to ascertain the goodness of bleaching powdet by the quantity of oxygen it contains? How is the goodness of bleach'ng powdei tested frv means of a solution of indigo ? What is the defect in this method ? 20* 234 PHOSPUUllET OP LIME. of lime confined in a glass tube, over mercury, by means of muriatic acid. The chloride by this means would only be decomposed, and converted into the muriate of lime, Avhile the muriate already formed, would remain as before. By this process the chlorine of the chloride is set free, unmixed, and its quantity readily measured by the tube in which the experiment is made. There being no standard of the quantity of chlorine which the best bleaching powder ought to contain, it is by the comparison of different specimens only, that the purchaser can be guided. Experiments have long since shown, that chlorine has the power of combining with, or in some other manner, neutralizing, or destroying, the fetid exhalations arising from putrifying substances, and of preventing their deleterious effects. In cases of infectious disease, therefore, it is highly useful. For this purpose, a table spoonful or two of the pcwder is mixed with a pint of water, and placed in the sick room, and sprinkled in the rooms adjoining. The fetid effluvia from putrid water, from sink drains, or from any other source, is immediately destroyed by the application of a quantity of the chloride. By placing a sheet, wet with the chloride of lime water, in the bottom of the coffin, and afterwards often sprinkling the shroud with the same, the bodies of the dead may be preserved without offence for many days in the hottest season. Phosphuret of Lime. This compound is formed by passing the vapor of phosphorus over fragments of quicklime, at a red heat. The experiment may be performed in the following manner. Having procured a tube of green glass about a foot and a half long, and half an inch in diameter, stop one end Avith a cork, or otherwise, and place in it a drachm of phosphorus, letting it occupy the closed end. Then holding the tube in a horizontal position, push into it with a Avire, or rod, pieces of fresh burned quicklime about the size of peas, until they rill the middle part of the tube, taking care that the lime does not reach the phosphorus by tAA r o inches. Then stop the What is said to be the most accurate method of ascertaining the quantity of chloride ¦n bleaching powder 1 Is there any standard of the strength of bleaching powder 1 What is said of the disinfecting power of chlorine 1 What is phosphuret of lime? Describe the process of making the phosphuret of lime. 235 METALS, mouth of the tube loosely, to prevent the free access of the air, but leaving room for that in the tube to pass out as it expands. Next, heat that part of the tube containing the lime red hot, by means of a chafing dish of coals, at the same time keeping the phosphorus cool by a wet rag passed round the end of the tube. When the lime is seen to be at a red heat, bring a hot iron or lamp under the phosphorus, which will soon be turned into vapor, and passing over the lime, the two substances combine, and form the phosphuret of lime. When phosphuret of lime is thrown into water, mutual decomposition ensues, and there rises bubbles of yb .sphuretted hydrogen through the fluid, which take fire oni eaching the air. The phosphorus absorbs the oxygen from the water, thus liberating the hydrogen, which combines with a portion of phosphorus, forming the gas above named. Order 2.—Metals which are supposed to be analogous to order 1st, but whose properties are but little known. These are, Magnesium Ittrium and Glucinum Aluminum Zirconium Magnesia, glucina, ittria, alumina, and zirconia, before the galvanic experiments of Sir H. Davy, have been known under the general name of earths, and were considered pure elementary substances. When these earths are submitted to the action of a powerful galvanic battery, they all give more or less evidence that their bases are metals combined with oxygen. Magnesia, for instance, when exposed for a long time to the action of a powerful battery, in contact with mercury, appears to be decomposed; for the mercury becomes enlarged in bulk, and losing its fluidity, shows signs of having formed an amalgam with the metallic base of the magnesia. When this amalgam is heated in a close vessel out of contact with the air, the mercury is driven off, and there remains a dark gray film, of a metallic appearance, which, Avhen exposed to the action of oxygen, is converted When phosphuret of lime is thrown into water, what are the chemical changes produced ? What is the definition of order 2d. ? Whai are the names of the substances belonging to order 2d. ? Under what names were these substances known before the experiments of Sir H.Davy? Were they formerly considered compound, or elementary Bodies? What is the reason for supjwsing that magnesia has a metallic base! 236 EARTHS. into a white powder, having the properties of It is therefore concluded, that magnesia has a metallic base, though the metal itself has never been separated in such quantities as to allow any further examination of its properties than those above stated. When the earth alumina, which is the base of alum, is brought into contact with the vapor of potassium at a while heat, and in a close vessel, the potassium is converted into potash. Now, as potassium is converted into potash only by the absorption of oxygen, and as the oxygen could have been derived from no other source except the alumina, such an experiment show's that alumina contains oxygen, and therefore by analogy, there is reason to suppose that alumina is composed of the metal aluminum and oxygen. The other earths above named, when submitted to similar experiments, have each shown that they contained oxygen; and as potash, soda, and lime, are known to be metallic oxides, that is, to consist of a metal combined with oxygen, it is inferred that the earths, possessing similar properties, are also composed of a metal united with oxygen. It is therefore agreed among writers on chemistry, that the bases of these earths should be arranged as metals, under the names above specified; though their existence, wich perhaps the exception of magnesium, has never been directly proved. In consequence of the discovery, or the inference, that thes earths possess metallic bases, their names, in conformity Avith the language of chemistry, are changed from words denoting simple bodies, to such as denote compounds. Thus, the earth formerly called magnesia, is now known under the name ol oxide of magnesium, and the'simple term alumina, is changed to oxide of aluminum, the same language being adopted with respect to all the other earths above named. Properties of the Earths. Magnesia, or oxide Magnesium. Pure magnesia is well known as a medicine, under the name of calcined magnesia. This is obtained by exposing the carbonate of magnesia to a red heat. It is white, tasteless, and inodorous, but possesses What is the reason for supposing that alumina has a metallic base 7 On what grounds w it believe' 1 that the other earths belonging to this order have metallic bases 7 What are the scientific imes of magnesia and alumina, supposing them to be the oxides of meta'al How is pure m gnesia obtained 7 What effect does magnesia have on vegetable colors 7 237 METALS. slight alkaline properties, being capable of changing the blue colors of vegetables to green, and of neutralizing the acids, with which it forms various saline compounds. One of these, the sulphate of magnesia, or Epsom salt, is a well known medicine. Magnesia, in a few instances, has been found in the native state, but always in small quantities only. That sold by apothecaries is obtained from certain springs, as that of Epsom, where it exists, in combination with sulphuric acid, forming Epsom salt, which is dissolved in the Avater. Calcined or pure magnesia, if exposed to the air, absorbs carbonic acid, and is converted into a carbonate. Hence, a large proportion of that used in medicine, and sold for calcined, is in truth the carbonate, the change being effected by carelessness, in exposing the calcined to the air. Alumina, or Oxide of Aluminum. The earth alumina is one of the most abundant productions of nature, every description of clay being an aluminous earth, of a greater or less degree of 'purity. The clay, of Avhich bricks, pipes, and earthen ware are made, consists chiefly of this earth. The ruby and the sapphire, two of the hardest and most beautiful of gems, are also composed of alumina. Pure alumina, for experiment, is most easily obtained from alum, Avhich is a sulphate of alumina and potassa. To obtain the earth, dissolve one part of alum in six parts of boiling Avater, and when the solution is cold, add one part of carbonate of potash. By this process the sulphate of alumina is decomposed, in consequence of the strong affinity existing between the potash and sulphuric acid, and two neAV salts are formed, viz. sulphate of potash and carbonate of alumina, the latter being precipitated to the bottom of the vessel. This precipitate being Avashed, and then exposed to. a red heat, to expel the carbonic acid, is pure alumina. The substance, thus procured, is Avhite, inodorous, soft to the touch, and tasteless. Mixed Avith Abater, it forms a mass What is the most common salt of which magnesia is the base ? How is pure mag. nes ; a convened into a carbonate ? How is the uncertainty of magnesia, as a medicine, accounted for? What is the earth of which clay is chiefly composed ? What common articles and what precious stones are composed of alumina ? How may pure alumina be obtained ? AVhat chemical changes take place when alum, in solution, is mixed w ith carbonate of potash 7 What is the appearance of pure alumina? 238 METALS. which is exceedingly plastic, and may be worked into ah shapes. The tenacity of every kind of clay is owing to the alumina it contains. Alumina, being insoluble in water does not affect the colors of vegetables. It, however, performs the part of an alkali in neutralizing the acids, and forming with them saline compounds. Glucina, or Oxide of Glucinum. The earth called glucina has been discovered but in small quantities, being known to exist only in the minerals, emerald, beryl, and euclase. Its name comes from a Greek Avord signifying sweet, because some of its combinations are sweet to the taste. In some of its properties it resembles alumina, and in others it differs from all the other earths. One of its distinctive properties is that above mentioned, of forming a compound, when dissolved in sulphuric acid, which is sweet to the taste. Ittria, or Oxide of Ittrium. Ittria resembles alumina and glucina in most of its chemical properties, but differs from them both, in being insoluble in a solution of pure potash. This earth has been found only in a single rare mineral, in Sweden. It forms peculiar salts, when combined with the acids, and is thus known to differ from all the other earths. Zirconia, or Oxide of Zirconium. This earth is also exceedingly rare, having been detected only in the zircon, a precious stone found in Ceylon, and the hyacinth of France. It resembles alumina and the other earths in being a white soft powder. Its salts are distinguished by being precipitated from their solutions by all the pure alkalies. Zirconium, the base of this earth, was separated from its oxygen, by the Swedish chemist, Berzelius, in 1824. It wa> in the form of a black powder, which took fire in the opei air at a temperature far below a red heat, and burned with ; bright flame. The product of the combustion was zirconia But whether this base is of a metallic nature, has not been decided. It is wanting in one property common to all metals, being a non-conductor of electricity. Silica, or Oxide of Silicium. Sir H. Davy's experiments In what minerals does the oxide of glucina exist 7 What is the meaning of the word glucina, and why is this earth so named 1 How does ittria differ from alumina and glucina 1 In what minerals has the earth zirconia been found 1 How are the salts of zirconia distinguished 1 What is said of the metallic base of zirconia 7 What is said of the metallic base of silica I 239 METALS. :m silica lead him to suppose, that in common with the earths above described, it had a metallic base, and it was arranged with them, in conformity to this opinion. But more recently, Berzelius has succeeded in decomposing this earth, and has given an account of the properties of its base. From this we learn that siliciumis of a dark brown color without the least trace of metallic lustre. That it is incombustible in the open air or in oxygen gas, and that it may even be exposed to the flame of the blowpipe without fusion, and without suffering the least change. It is not dissolved by any of the acids, except a mixture of the nitric and fluoric, with which it readily enters into solution. It is not a conductor of electricity. These properties, and particularly its want of metallic lustre, and of power to conduct electricity, prove that the base of silica is not of a metallic nature. Silica, orsilex, is a very abundant natural product. It forms a large part of all granitic, or primitive rocks, and mountains, and is the chief ingredient m sandstones, and earthy formations. Rock crystal, or quartz, flint, chalcedony, agate, cornelian, and all other substances of this kind, are composed almost entirely of silex. Silica may be obtained in sufficient purity, for most purposes by heating transparent rock crystal to redness and plunging it into water while hot, and then reducing it to powder. In this state, silex is a white powder, which feels harsh when rubbed between the fingers, and has neither tastenor smell. It is exceedingly infusible, but may be melted with the compound blowpipe. It resists the action of all the acids, except the fluoric, which dissolves it with considerable facility. It is dissolved by the fixed alkalies, and hence it would appear that its properties are rather of an acid, than of an alkaline nature. On this account several chemists have called silica an acid, and the compounds which it forms with the alkalies, have been termed silicates. From what has been said, the student will infer that there is yet considerable doubt and uncertainty, in respect to the real nature of silica. Dr. Thompson, being convinced of its non-metallic nature, Is the base of silica of a metallic nature 1 What substances are mentioned of which «ilica forms the principal part 1 How may pure silica be obtained 1 What are the pro forties of silica 1 What is said of the compound nature of silica? 240 METALS. arranges it with the simple bodies carbon and boron There is no doubt, however, from the experiments of Davy and Berzelius, of its compound nature; and that it consists of a base combined with oxygen, has been proved by direct experiment. But that its base is not a metal is proved from its want of lus tre, and power to conduct the electric fluid, these two proper ties being essential to all metallic bodies. Silex in the form of sand, is a principal article in the manufacture of glass. The common dark colored, or green glass, is composed of impure sand, which contains oxide ol iron, melted with kelp, wood ashes, or impure potashes. Crown glass, for windows, is composed of white sand, fused with a purer alkali. Plate glass, for looking glasses, is made of still purer materials; and what is known by the name of flint glass, of which decanters, and other ornamental or cut glassware is made, is composed of the purest sand and alkali, with the addition of a considerable portion of lead, which is added in the form of litharge, or red lead. This is the softest and heaviest kind of glass. It cuts more easily, and withstands the changes of temperature much better than glass containing no lead. Order 3.—Metals which decompose water at a red heat These are, Manganese, Iron, and Zinc, Tin, Cadmium. .The power of a metal to decompose water, depends on its affinity for oxygen. In some instances, as in those of potassium and sodium, already given, the metals have so strong an affinity for oxygen, as to absorb it from Avater, at common temperatures. Other metals do not decompose this fluid at any temperature, such being the 4th order of the present class. Those now to be examined, have an affinity for oxygen, Avhich they sloAvly absorb from the atmosphere, and a part of \A r hich they retain at high degrees of heat. But their attraction for oxygen is not in sufficient force to decompose Avater, except AA r hen heated to redness, when the combination is effected Avith considerable rapidity. What use is made of silex in the arts 1 Explain the difference between green glass, crown glass, and plate glass. AA'hat is the composition of cut glass 7 What is the definition of order 3d 7 What metals belong to order 3d 7 On what property of a metal does its power to decompose water depend 1 241 METALS. MANGANESE 28. This metal always occurs in nature in combination with oxygen, and which it holds with such force as to require the most intense heat for its removal. The metal may, however, be obtained in a pure state, by exposing the black, cr peroxide, mixed with a combustible, to the highest heat of a smith's forge. The combustible, which may be pitch or powdered charcoal, with which the oxide is mixed, is thus made to absorb the oxygen, and the metal is found at the bottom of the crucible. Manganese is of a dusky white color, with a specific gravity of 8. When exposed to the air it absorbs oxygen, and soon falls into powder, which afterwards changes its color from gray to brown, and from brown to black, according to its grade of oxidation. When this metal is exposed to a red heat, and the steam of water is passed over it, decomposition takes place, the oxygen of the water combines with the man ganese, and the hydrogen is disengaged. MANGANESE AND OXYGEN. Peroxide of Manganese —44. 1 p. Manganese 28-f-2 p. Oxygen 16. Black Oxide of Manganese. This compound occurs abundantly in nature, and is known under the name of black oxide of manganese. It is found in amorphous masses, of a dark gray or nearly black color, and is commonly mixed with various proportions of sand, oxide of iron, carbonate of lime, or other impurities. In its pure state, it occurs in the form of prismatic crystals of a dark color, and slightly metallic lustre. In this state the metal contains its full proportion of oxygen, and undergoes no change on exposure to the air, or to a moderate heat. When heated to redness, it parts with one proportion of oxygen, and is converted into a deutoxide. In this manner oxygen gas may be obtained. The peroxide of manganese is of considerable consequence in the arts, and In what state does manganese occur in nature? By what process may metallic manganese be obtained from the oxide 1 What is the appearance and specific gravity of r.umganese? Under what circumstances does manganese decompose water ? What is the scientific name for black oxide of manganese'! When peroxide of manganese is heated to redness, what chemical change does it undergo? Of what use is peroxide of manganese in the arts ? 21 242 METALS. particularly in the formation of chlorine for the manufacture of bleaching powders, and also in furnishing oxygen gas for other chemical uses. The methods for obtaining these gases have already been described. The peroxide of mercury is composed of 1 proportion of manganese, 28 2 proportions of oxygen, 16 44 There are two other oxides of manganese, viz. the protox ide, and the deutoxide. There is also reason to believe that manganese is capable of combining with such proportions of oxygen as to form acids; but the subject has not been sulticiently investigated to determine the composition or nature of these compounds. Manganese combines with the acids, and forms a variety of salts, which are either colorless, or of a reddish or pink hue. These salts are found only in the laboratory of the chemist, and are of no use in the arts. At a red heat this metal decomposes water. iron—28. This well known metal has a gray color, and a strong metallic lustre, which is much improved by burnishing. Iron is at once the most useful, the most abundant, and the most universally diffused of all the metals. It is found in the mineral, the vegetable, and the animal kingdoms, and in some countries it exists in such quantities as to form mountains of considerable size. When heated, it becomes soft and malleable, and in this state two pieces may be incorporated, or welded together, by hammering. Its specific gravity is about 8. It is attracted by the magnet, and may itself be made permanently magnetic. This property is of vast consequence to the world, being possessed by no other metals except nickel, and cobalt, and by these in a much inferior degree. Iron has a strong affinity for oxygen, and when exposed to air and moisture, soon rusts or oxidates on its surface. In a perfectly dry atmosphere, however, it undergoes little or no change, a proof that it absorbs oxygen with more facility What is the composition of the peroxide of manganese 7 What is said of the o manganese 7 What is tiie combining number for iron? What is said of the abundance and usefulness of iron 7 What is said of the affinity of iron for oxygen 7 243 METALS. from wate* ihan from the air. When heated, it attracts oxygen both from air and water, with great rapidity. When tho iceam of water is passed over iron, at a red heat, the wa- Cdr is decomposed, its oxygen combining with the metal, while the hydrogen is set at liberty. When heated to redness, in oxygen gas, it burns with intense brilliancy. Iron is exceedingly ductile, and may be drawn into wire not exceeding the thousandth part of an inch in diameter; but it cannot, like gold and silver, be hammered into thin leaves, and therefore is not highly malleable. The ores of this metal are very numerous, and some of them highly beautiful and interesting. They are chiefly sulphurets and oxides, but the oxides are the only ores from which the metal is obtained. Iron has, in a few instances, been found in its native state, mixed with lead and copper, or with some earthy substance. It has also been found in large masses, alloyed with five or six other metals, and called meteoric iron, from an opinion that these masses fell from the clouds. Native iron is soft and malleable as it occurs, and does not differ from that which has been reduced from its ores and purified. Cast iron contains variable proportions of carbon and oxygen, and in this state it is hard and brittle. These impurities are detached by the process of refining, and then the iron becomes soft and malleable. Steel is made by heating pure iron with carbon, or charcoal, by which it is rendered exceedingly hard and brittle. This change is produced in consequence of the absorption of a portion of carbon by the iron. Steel, therefore, is composed of iron and carbon, and its scientific name is carburet of iron. IRON AND OXYGEN. Oxide of Iron. Rust of Iron. Iron combines with oxygen in two proportions, forming the blue and red oxides of this metal. Under what circumstances does iron decompose water 1 In what does this decomposition consistf What is said of the ductility and malleability of iron ? In what state does iron occur as a natural product 1 What is the ore from which iron is extracted 1 Wh&t is meteoric iron 1 What are the impurities contained in cast iron 1 How is steel made l What is the composition of steel 1 What is the scientific name of steel ? 244 METALS Protoxide of Iron. The black or protoxide of this meta is formed by passing dry hydrogen over the red oxide, at n temperature a little below redness. This oxide is composed of 1 equivalent of iron 28, and 1 equivalent of oxygen 8. Its combining number, therefore, is 36. The Black Oxide of Iron, which occurs in the form of scales, Avhen iron is heated and hammered in the open air, is not a definite compound, but a mixture of the black oxide and metallic iron. Peroxide of Iron. This is the red oxide, and is known to mineralogists as a native compound, under the name of red hematite. The same article is known to button makers, and other artists, under the name of blood stone, and is employed to polish their work. The peroxide may be prepared by art, by dissolving iron in nitric acid, then precipitating it with ammonia, and heating the precipitate to a little below redness, to drive off the acid. Its color and other properties are like those of the native red oxide. The peroxide of iron is composed of iron 28, and oxygen 12. The Brown Oxide of Iron is composed of precisely the same proportions of the metal and oxygen as the red oxide, but in addition to these ingredients, it contains one proportion, or 9 parts of water. The other oxides of iron are either mixtures of the red and blue oxides, or one or both of these oxides containing various impurities. The great number of oxides of this metal, described in books of mineralogy, and differing from each other in color, hardness, and form, arise from such mixtures Thus, the magnetic oxide of iron, or native magnet, is composed of peroxido of iron 71, and protoxide 29 to the 100. The brown oxides of iron all contain water, and are, therefore, called hydrates. The ochres are of this kind. Iron combines with carbon, sulphur, iodine, phosphorus, and the different acids. Its compounds are, therefore, exceedingly various, in respect to form, color, and properties. We shall, however, examine only two or three of these compounds here, the salts being reserved for another place. Carburet of Iron. Steel, Ave have already said, is a carouret of iron. This important metal is manufactured from In how many proportions does oxygen combine with iron? What are the names of these oxides? What is the composition of the protoxide 7 AVhat iB the composition ot the peroxide of iron ? How does the brown differ from the red oxide of iron ? What is the composition of the native magnet ? What substances are mentioned with which iroD combines» 245 PETALS. the iron, by exposing the latter to a long continued red heat, m contact with charcoal. For this purpose, the purest malleable iron, in bars, is employed, and is found to gain in weight, one pound in 150, by the process. Steel, therefore, consists of iron combined with a 150th part of its weight of carbon, which it absorbs from the fire. When iron is perfectly enclosed, and heated with a fragment of diamond, it is converted into steel, in the same manner as when heated with charcoal. This experiment shows the identity of carbon and diamond, the only difference being the color and crystalline form of the latter. It also proves that the hardness of steel is owing to the particles of diamond which it contains. The native carburet of iron, commonly known under tne name of black lead, or plumbago, contains 95 parts of carbon and 5 of iron. This substance is infusible at the highest heat of a furnace, and hence is employed in making crucibles and melting pots. It is also used in making black lead pencils. Sulphuret of Iron. This compound occurs as a natural product, and is known to mineralogists and others, under the name of iron pyrites. It is a yellow brittle substance, often crystallized in the form of cubes, or octohedrons, with their surfaces highly polished. These specimens are generally taken for gold, by those who are ignorant of such matters, and the places where they are found, are sometimes kept a profound secret for years, for fear the owner of the soil should claim a part of the wealth. Every mineralogist, on pronouncing such specimens of no value, has occasionally witnessed the fallen countenance of the applicant, whose hopes and expectations he had thus blasted. Sulphuret of iron may also be formed by touching a bar of iron, at a glowing red heat, with a roll of brimstone. The compound will fall down in drops. The natural and artificial sulphurets are composed of precisely the same definite proportions, viz. iron 28, and sulphur 16. In what proportion is the weight of iron increased by being converted into steel? What Is said of converting iron into steel by mean3 of the diamond 7 What does this experiment prove? What is the composition and the proper name of black lead ? What are the uses of black lead ? Is sulphuret of iron a natural, or artificial compound 7 What is the appearance of the native sulphuret of iron? What precious metal is this compound sometimes taken for 7 How may sulphuret of iron be formed artificially ? What is the composition of sulphuret of iron 7 21* 246 METALS. ZINC 34 Zinc, when pure, is of a bluish white color, and of a stri ated fracture, presenting the result of a confused crystallization. When rubbed with the fingers it imparts to them a peculiar metallic taste and smell. When cold, this metal is not malleable, but when heated to between 200° and 300°, it becomes both malleable and ductile. If its temperature be raised to 400°, it becomes so brittle as to be readily reduced to powder, in a mortar. Zinc melts at 680 degrees, and if this temperature be increased, it burns with a bluish flame in the open air. When melted with copper it forms the alloy, well known under the name of brass. This metal never occurs in the native, or pure state, but is always found combined either with sulphur, carbonic acid, or oxygen. The sulphuret of this metal, called zinc blende,and the carbonate, called calamine, are the ores from which zinc is obtained. The sulphuret being roasted, that is, submitted to a low red heat in the open air, to drive off the sulphur, and oxidize the metal, is then melted with charcoal, by which the oxygen is absorbed, and the metal reduced. The calamine is first roasted to drive off the carbonic acid, and is then distilled in iron retorts, by which means the pure metal is obtained. This latter process is said to have been learned of the Chinese, and that a man was sent from Europe to China on purpose to obtain the secret. Pure zinc, when exposed to a white heat in a close vessel, will, in the same manner sublime, and again condense, unchanged. ZINC AND OXYGEN. Oxide of Zinc —42. 1 p. Zinc 34-f-l p- Oxygen 8. Flowers of Zinc. When zinc is exposed to a red heat in the open air, it burns with a white flame, and at the same time an oxide of the metal is formed, which rising by the heat, falls around the What is the color of pure zinc? Under what circumstance is zinc malleable? In wha; temperature does zinc melt ? What is the composition of brass 7 Is zinc ever found in the native state? What are the names of the ores of zinc, and of what are they comnosed ? How is zinc reduced from its sulphuret ? How is calamine reduced? How is he oxide of zinc formed? 247 CADMIUM. place of combustion in the form of white flakes. This substance was formerly called flowcts of zinc, and sometimes philosophical wool. It is an oxide of the metal, and the only one known. When this oxide is collected, and again submitted to the fire, it does not rise, as before, but melts into a clear glass. When the vapor of water is brought into contact with metallic zinc at a red heat, the water is decomposed, the zinc combining with its oxygen, and forming an oxide, in the same manner as is done in the open air. Both these oxides are composed by weight, of 1 atom, or equivalent of zinc, 34 1 do. do. oxygen, 8 Combining number for oxide of zinc, 42 cadmium —56 Cadmium is one of the new metals, having been discoverea in certain ores of zinc, in 1817. This metal in color and lustre resembles tin, but is harder and more tenacious. It is both ductile and malleable to a considerable degree. Its specific gravity is nearly 8.5. It fuses at a temperature somewhat less than 500 degrees, and at a little higher heat it rises in vapor, and condenses in globules like mercury. When cadmium is heated in the open air, like many other metals, it absorbs oxygen, and is converted into an oxide. It is readily dissolved by the nitric acid. When heated in contact with the vapor of water, the fluid is decomposed, and an oxide of the metal is formed. Cadmium combines, so far as is known, with only one proportion of oxygen. This oxide is composed of Cadmium, 1 equivalent 56 Oxygen, 1 do. 8 64 Cadmium, like the other metals, forms salts by combination with the acids. But these compounds are little known, and of no value. What was tliia oxide formerly called 1 How may zinc be made to decompose water 1 What is the composition of oxide of zinc, and what is its combining number 1 What is tadmium ? What other metals does cadmium resemble 7 Is this a brittle or a malleable metal t What is the specific gravity of cadmium 1 What is the composition of oxide of iadmiuml 248 tin TIN 59. Tin must be examined in the state of grain, or block tin ; what is commonly called tin, being sheets of iron, merely eovered with this metal. Tin is procured from its native oxides, by heat and charcoal, on the same principle that has already been described for iron and several other metals. The ores of tin are only two, viz. an oxide, and a sulphuret. This metal is not readily oxidizea by exposure to the atmosphere, though the brilliancy of its surface is soon tarnished. It is highly malleable, but not equally ductile, its tenacity not being sufficient to allow its being drawn into fine wire. Its specific gravity is 8. When heated to whiteness, it takes fire in the open air, and burns with a white flame, being at the same time converted into an oxide; at a red heat it decomposes water. Tin is a highly useful metal, being employed for many valuable purposes in the arts and conveniences of life. Thin sheets of iron, being dipped into melted tin, receive a coat ol the metal, and are thus prevented from rusting. This is called sheet tin, and is the article of which the common tin ware is made. Tin foil, that is, tin rolled into thin sheets, is used for many purposes. Electrical jars are coated with it, and the backs of looking-glasses are formed of an amalgam oi tin foil and mercury. Block tin forms a part of Britannia ware, of princes' metal, of pewter, speculum metal, &c. TIN AND OXYGEN. Tin combines with oxygen in two proportions: The first, or the protoxide, is formed when the metal is kept for some time in fusion in the open air. At this temperature it absorbs oxygen from the atmosphere, and is converted into a gray powder. This powder is the protoxide, and is composed of 1 equivalent, or atom of tin 59 1 do. do. oxygen 8 07 This oxide is soluble in acids and in ammonia. The se Of what metal is the sheet tin chiefly composed ! How is tin procured from its oxide! What are the only ores of tin ? Is tin readily oxidized by exposure to the air or not? What is said of the malleability and ductility of tin ? What is the specific gravity of tin 1 Into what is this metal converted when burned in the open air? How is sheet tin made? Wnat are the principal uses of tin? In how many proronions does tin combine with oxygen? How is the protoxide of tin formed I 249 ARSENIC cond, er peroxide of tin, is prepared by dissolving the metal in nitric acid, slightly diluted with water. It is a powder of a yellow color, and is composed of 1 equivalent of tin, 59 2 do. of oxygen, 16 75 This oxide, when melted with glass, forms white enamel. Tin combines with sulphur, chlorine, and the acids, form«ng a variety of compounds, some of which are occasionally used in the arts. Order 4.—Metals which do not decompose water at any temperature. These are, Arsenic Uranium Titanium Molybdenum Columbium Bismuth Chromium Nickel Copper Tungsten Cobalt Tellurium Antimony Cerium Lead The last order includes all such metals as attract oxygen tvith sufficient force, when heated to redness, to decompose water. The present division absorb and retain oxygen at high temperatures, but none of them attract that principle, even at the highest temperatures, with sufficient force to decompose water. arsenic—38. There are no mines worked merely for the purpose of obtaining arsenic, the arsenious acid, the only form in which it is used, being procured by the process of roasting the ores of cobalt. The ores of the latter metal, being heated in furnaces with long chimneys, the acid rises and attaches itself to the sides of the chimney, in layers, or cakes. After a considerable quantity has been accumulated in this manner, it is scraped off, and purified by a second sublimation, when What ie the composition of the protoxide of tint How is the peroxide of this metal prepared 1 What is the quantity of oxygen contained in the peroxide of tin 1 What is the definition of order 4th 7 What are the names of the metals arranged under the 4th order 7 Are any mines worked merely to obtain arsenic 7 How is the oxide of arsenic procured ? 250 ARSENIC aND OXYGEN. it forms the well known poison, called white, arsenic, or oxide of arsenic. From the white oxide the metallic arsenic is procured, by Heating this with a combustible. In legal investigations, where there is a suspicion of poisoning with arsenic, it sometimes happens that justice will depend on the decision of the chemist, whether arsenic might not have been the cause of death. In such cases, very minute portions of arsenic may be detected by means of a combustible and a glass tube, in the following manner: Let the matter suspected to contain the poison, be well dried at a low heat; then mix it with five or six times its weight o* powdered charcoal, and put the mixture into a thin glasf tube, closed at one end. If now heat be gradually applied to the tube until it becomes red, the metal, if arsenic be present, will rise and coat its inside, showing a brilliant metallic lustre, similar to that of steel. If it is found that, on heating a small piece of this metal, it rises in white vapor and gives the smell of garlic, it is arsenic beyond doubt. The structure of metallic arsenic is crystalline, and its specific gravity about 8. When heated to about 360° it sublimes, without fusion, its melting point being far above that at which it becomes volatile. If the metal is heated in the open air, it is converted into the arsenious acid, and again becomes "toisonous as before; but, while in the metallic form, arsenic has no action on the system, and, therefore, is not a poison. ARSENIC AND OXYGEN. Arsenious Acid —54. 1 p. Arsenic 38-f-2 p. Oxygen 16. White Arsenic. Oxide of Arsenic. We have stated above, that when metallic arsenic is heated in the open air, it is converted into a white substance, called oxide of arsenic. This is the arsenious acid of chemists. It differs from the oxides of metals in possessing acid properties. It is slightly soluble in water, reddens vegetable blue colors, and combines with alkalies, forming salts How may arsenic be reduced from its oxide to the metallic state 7 What is the a * peurance of pure arsenic 7 What is the specific gravity of arsenic 7 Is metallic arsei a poison 7 How is arsenious acid formed 7 251 METALS. called a 1 ) seniles. The arsenite of potash, usually called Fowle,'s solution of arsenic, has been long employed in medicine as> a remedy for eruptive, and other diseases. ARSENIC AND SULPHUR. Sulphurets of Arsenic. Sulphur combines with arsenic in two proportions, form rxygen does the deutoxide contain ? How is the peroxide of lead formed? What are til* -properties of 'he peroxide of lead ? How is lead reduced from the sulphuret ? METALS. 265 the sulphuric acid, which is formed by the union of the sulphur of the metal, the oxygen of the air, and the water of the wood, and forms a sulphate of lime. Meantime, the metallic lead, thus reduced, runs down into the lower part of the furnace, where it is drawn off into proper vessels. All the salts of lead act as poisons, with the exception of the sulphate, which Orfila has proved is not deleterious. The same author has shown that the acetate, or sugar of lead, is decomposed in the stomach by sulphate of magnesia or Epsom salt, and that the inert sulphate is thus formed. Hence, Epsom salt, or Glauber's salt, which is a sulphate of soda, becomes an antidote to the poisonous effects of sugar of lead when taken soon after it. SALTS. The compound resulting from the union of any acid with nn alkali, an earth, or a metallic oxide, in definite proportions, is called a salt. The substance which combines with the acid to form the salt, is called the base. Thus, lime is the base of carbonate of lime. Any substance capable of combining with an acid to form a salt, is called a salifiable base. The salifiable bases, therefore, are the alkalies, the earths, and metallic oxides. Any compound, which is capable of uniting in definite proportions with a salifiable base, or which in solution is sour to the taste, or reddens vegetable blues, is an acid. From this definition, it will be observed that acids are not necessarily sour to the taste. This, in many instances, arises from their insolubility, for an insoluble acid neither tastes sour, nor changes the color of vegetable blues. Other acids, which, though soluble, do not taste sour, and have little, if any action on colors, still have the property of neutralizing alkalies, and combining with salifiable bases in definite proportions ; such is the prussic acid. It was formerly supposed that all the acids contained oxy- What are the uses of charcoal and lime in the reduction of lead ? What compound ot lead is said to he poisonous ? What antidote is mentioned to the poisonous effects of sugar of lead ? How does Epsom salt act to neutralize the poisonous effects of the salts of lead! What is a salt ? What is the base of a salt ? What ts a salifiable base? What is an acid? Are all acids sour to the taste? Do all acids contain oxygen ? 23 266 SALTS gen, as the acidifying principle, but we have already had occasion to remark, that there are several known exceptions to this truth. Since the discovery of the compound nature of the alkalies, and the simple nature of chlorir.e, it is found that some compounds, in which oxygen exists as an element are alkalies, and that others, containing no oxygen, are acids Thus, the metal potassium, combined with oxygen, forms the alkali potassa, and chlorine, united to hydrogen, forms muriatic acid. The alkalies are supposed to possess characters exactly opposite to those of the acids. Their tastes are pungent; they neutralize the acids, and change vegetable blue colors to green. There are, however, many compounds, capable of forming salts, and of neutralizing acids, which do not possess the latter characters. Thus magnesia, though a powerful neutralizing substance, excites no taste, and produces little change on vegetable colors. This want of action obviously depends on its insolubility in water. Thus, a salifiable base does not necessarily contain sensible alkaline properties, but is any substance which forms a definite compound with acids, or which being soluble, has the alkaline taste, and changes vegetable blues to green. Ah the metallic oxides are salifiable bases. In speaking of the solution of a metal in an acid, it mus"i always be understood, that it is the oxide of the metal which is soluble, for no metal combines Avith an acid in its metallic state. The action of the acid is first to oxidate the metal; which it does, either by imparting to it a portion of its own oxygen, or by assisting it to obtain this principle from the Avater with Avhich the acid is mixed. When copper dissolves in nitric acid, the metal is rim oxidated at the expense of one proportion of the oxygen which the acid contains, and hence the fumes of nitrous gas Avhich escape. But Avhen zinc dissolves in dilute sulphuric acid, the metal is oxidated by the decomposition of the Avater, and then dissolved by the acid, and hence the escape of hydrogen during this process. Do the alkalies contain oxygen? Give an instance where oxygen, combined with a metal forms an alkali. Give an instance in which chlorine and another simple substance, united, form an acid. Why is magnesia tasteless 1 Are the metallic oxides salifiable Dasesl What change do the metals undergo before they are soluble in the acids 1 In what manner do the metals become oxides before they are dissolved t When zinc i* thrown into diluted sulphuric acid, why does hydrogen escape 1 267 SALTS. It is said that at least 2000 salts are known, but this is a small number when compared with those which might be formed ; for supposing each acid to be capable of forming a different compound with each salifiable base, and each base a distinct compound with every known acid, the salts would be numberless. It may be supposed, from the variety of properties pos sessed by the acids, that the salifiable bases, with which they are known to combine, that the resulting compound must present a great variety of different qualities, colors, and shapes, and in this we are not disappointed. Some of the salts are corrosive poisons, others are perfectly inactive on the animal system; some are used as medicines, others as paints, others in coloring, &c. It is obvious that in this epitome of the science, only a limited number of these compounds can be described. These we shall arrange in groups, or classes, each group consisting of the same acid, united to different salifiable bases. Most of the salts are capable of being crystallized, that is of forming dry solid figures of determinate shapes. During the act of crystallization, many of them combine chemically with a definite portion of water, which therefore '* called the water of crystallization. Some salts contain more than half their weight of wate* ¦ this is the case with sulphate of soda, or Glauber's salt, whicL consists of 72 parts of the dry sulphate, and 90 parts of water. Other salts, as muriate of soda, or common salt, contain no water of crystallization. But these salts sometimes con tain particles of water included mechanically within theii substance, and hence when heated they decrepitate, or fly in pieces, in consequence of the conversion of this water into steam. From this cause, common salt decrepitates violently when thrown on the fire. Salts containing a large quantity of the water of crystal' lization, when heated, undergo the aqueous fusion; that is .hey dissolve in the water they contain. Anhydrous salts, or such as are not chemically united with water, when heat What number of salts are said to be known 1 On what principle are the salts thrown part sulphur, and one of charcoal. These ingredients being first finely powdered separately, are then mixed into the form of a paste, with water, and beaten together with a wooden pestle, until they become very intimately incorporated. This paste is then granulated, by passing it through sieves, and carefully dried in the sun. Fulminating powder is made by mixing in a mortar three parts of nitre finely powdered, two parts of carbonate of potash, and one part of sulphur. The whole being thoroughly mixed by grinding, forms the powder in question. When a quantity of this mixture is placed on a shovel, and heated gradually, until the sulphur begins to inflame, it explodes, giving a loud and stunning report, and leaving the ears hardly in a state to hear any thing more for hours, or if the quantity be considerable, even for days. Not more than 15 or 20 grains of this powder should be exploded at once, unless in the open air. Nitrate of Ammonia. —The mode of preparing this salt, jvas described under the article nitrons oxide. This salt is composed of one proportion of nitric acid 54, and one proportion of ammonia 17=71. It also contains one proportion of Water=9. In what country is nitre formed spontaneously 1 When nitre is heated, what gases are expelled, and what substance remains in the fire 1 What are the uses of nitre T What is the composition of gunpowder I How is fulminating powder prepared 7 How is this powder used 1 24 278 NITRATES. Nitrate of Silver —164. 1 p. Nitric Acid 54-f-l p. Silver 110. Lunar Caustic. When silver is thrown into nitric acid, the metal is dissolved, with a copious disengagement of red fumes, which consist of the deutoxide of nitrogen, formerly described. The solution, if allowed to evaporate, will form large regular crystals in the shape of flat rhombs. These, if the metal is unalloyed, are pure nitrate of silver. They contain no water of crystallization. They undergo the igneous fusion at a very moderate heat, and in this state, being cast into small cylindrical moulds, form the substance so well known, and so universally employed in surgery, and for other purposes, under the name of lunar caustic. A solution of this salt in water, being applied to animal or vegetable substances, stains them, after exposure to light, of a permanent black color. The skin or hair may be made black in this manner, and there is no doubt but persons have colored their faces and hands with this substance, as preparatory to the commission of the worst of crimes. No washing, or any other means, will whiten the skin, once stained with this solution, until the scarf-skin itself wears off, or is removed, which requires several weeks. The solution itself is perfectly transparent, and in appearance cannot be distinguished from pure water. Indelible Ink is a solution of nitrate of silver in water, and is well known as the only substance in use, with which cotton and linen may be marked in a permanent manner. Nitrate of silver, in solution, is decomposed by a variety of substances, having a stronger attraction for oxygen than the silver has. By the action of such substances, the silver is revived, and appears in its metallic form. Thus, a stick of phosphorus placed in this solution, is soon covered with metallic silver; and if the solution be heated to the temperature of boiling water, with a little charcoal in it, the metal will be .educed, and maybe obtained in the form of crystals. The composition of the nitrate of silver is seen at the head of this section. When silver is thrown into nitric acid, what gas escapes'? What is the composition of nitrate of silver? What is the common name of nitrate of silver? What is lunar caustic ? What effect does a solution of nitrate of silver have on the skin, or hair ? What is indelible ink? What substances are mentioned, which decompose nit rats of silver 1 279 CHLORATES. There are many other nitrates, but none of them are of fulficient use, or interest, to require a description in this book. CHLORATES. The chlorates resemble the nitrates in many of their characters. These salts were formerly called oxymuriates. Most of them are decomposed at a red heat, with the evolution of pure oxygen gas, and are converted into metallic chlorides. The pupil may find some difficulty in pointing out the dis tmction between the chlorates and chlorides. The chlorates are composed of chlorine united to oxygen, forming chloric acid, which acid v being combined with the metallic oxides, forms chlorates. The chlorides are composed of uncombined chlorine, either united to the metals themselves, or their oxides. Thus, chloride of lime is composed of lime, or oxide of calcium, and chlorine. But chloride of calcium is composed of the two simple bodies, chlorine and the metal calcium, consequently contains no oxygen. When the chlorates are decomposed by heat, as above stated, and converted into chlorides, the change is produced by the expulsion of the oxygen which the compound contained, and the subsequent union between the chlorine and the base of the alkali, or the metal itself. Thus, when chlorate of potassa is heated, its oxygen escapes, while the chlorine remains, and combines with the base of the alkali, forming chloride of potassium. In producing the chlorates, it is not necessary that the chloric acid should first be formed, and then combined with the salifiable base, since the same result is produced by merely passing the chlorine through a solution of the alkali. This will be explained under the chlorate of potassa. The chlorates are all of them artificial compounds, none of them having been discovered in the native state. Most of them yield their oxygen to combustibles with such facility as to produce explosion. Thus, when chlorate of potash is rubbed in a mortar with phosphorus, or struck in contact with sulphur, violent detonations are produced. What were the chlorates formerly called 1 What is said of the decomposition of the chlorates by heat 7 What is the difference between the chlorates and the chlorides 7 What are the chemical changes by which the chlorates are converted into the chlorides 7 In producing the chlorates, is the chloric acid first formed, or is it only necessary to pass .he chlorine through the alkaline solution 7 Do any of the chlorates occur in nature 7 What is said of the facility y ith which the chlorates yield their oxygen to combustibles! 280 CHLORATES Chlorate of Potash —124. 1 p. Chloric Acid 76+1 p. Potash 48. Oxymuriate of Potash. The chlorate of potash is formed by passing 1 chlorine gas .hrough a solution of the pure caustic alkali in water. The pure potash is readily prepared in the following man ner. Make a solution of the carbonate of potash in its own weight of hot water, in an iron vessel, and add to this as much quicklime by weight as there was potash, and let the mixture boil for about ten minutes. Then strain the solution ihrough a linen cloth, and it will be fit for use. Tlje lime absorbs the carbonic acid from the potash, forming'with it an insoluble compound, thus leaving the alkali in its mire, or caustic state. The caustic potash being placed in a proper vessel, the chlorine is passed into it as long as any of the gas is absorbed. The apparatus for this purpose is represented at Fig-. 64. Fig. 64. The solution is contained in the three necked bottle. The chlorine may be evolved by first introducing into the retort two ounces of finely powdered black oxide of manganese, and after every thing is arranged, as in the figure, pouring on this, through the safety tube, four ounces of muriatic acid, and then applying a gentle heat. When the solution is saturated, the gas will pass off by the bent tube into the open air. To obtain the salt, the solution is evaporated with a gentle heat, and on cooling, small shining crystals of chlorate ol potash will be deposited. The first product only must be reserved for use, as the solution will afterwards form crystals of muriate instead of chlorate of potash. In the production of this salt, by the above process, the chloric acid is formed by the decomposition of the water, the oxygen of which unites with one portion of the chlorine What is the composition of chlorate of potash 1 How is caustic potash prepared 1 What is the use of the lime in preparing caustic potash 1 Explain the process by whh'.h rhlorate of potash is formed. How is the chloric acid formed by !his process 'I 281 CHLORATES. to form the acid, while the hydrogen thus disengaged, unites with another portion of the chlorine, forming muriatic acid. Hence the solution, as above intimated, contains both muriate and chlorate of potash. When chlorate of potash is heated, it gives off oxygen gas nearly pure, and chloride of potassium remains. If two grains of this salt are mixed with one grain of sulphur, and the mixture is struck, or pressed suddenly, a loud detonation is produced. When struck in contact with powdered charcoal, a similar effect results. If a grain of the chlorate and half a grain of phosphorus be rubbed together in a mortar, very violent detonations will be the effect. In making this experiment, the hand should be covered with a glove, and the face protected by a mask, or averted, as the inflamed phosphorus is sometimes projected several feet by the explosion. If a little of this salt be mixed with twice its weight of white sugar, and on the mixture a few drops of strong sulphuric acid be poured, a sudden and vehement inflammation will be produced. These phenomena are owing to the facility with which the chlorate of potash parts with its oxygen to combustible sub stances. This salt forms the base of th.3 red French matches, by which a light is instantly obtained. The chlorate being finely pulverized by itself, is then mixed with twice its weight of white sugar, moistened so as to prevent explosion, and afterwards made into a paste with mucilage of gum arabic. A little of this paste is fixed on the ends of brimstone matches, so that when it is inflamed, first the sulphur ana then the wood is set on fire. These matches require only to be touched with a drop of sulphuric acid, when they instantly burst into flame. The acid, for convenience, is contained in a small vial, and is prevented from escaping by some fibres of asbestos. Attempts are said to have been made in France, on a large scale, to substitute the chlorate of potash for nitre in the manufacture of gunpowder. But it was found that the workmen could not mix the ingredients, under any circum- Whence comes the muriate of potash which the solution contains'? Mention some 01 the experiments which may be made with this salt, and a combustible. How are the red matches prepared from this salt ? What is said of the attempts made to substitute the chlorate of potash for nitre, in the preparation of gunpowder 1 24* 282 PHOSPHATES. stances without the greatest danger, and that in many in stances explosions took place after the powder was prepared ; the attempt was therefore abandoned. Attempts have also been made to use mixtures of this salt for percussion priming, but it was found that the chlorine acted so readily on the iron, as soon to injure the gun, and it was therefore laid aside, for the fulminating mercury, which is now generally used for this purpose. PHOSPHATES. The phosphates of the metals are converted into phospurets by heat and charcoal. . Some of the alkaline and earthy phosphurets undergo a partial decomposition by the same means, while others are not changed. A number of phosphates are found in the native state, such as those of iron, lime, copper and lead. Phosphate of Soda —60. 1 p. Acid 28+1 p. Soda 32. This salt is prepared on a large scale in chemical manufactories, by neutralizing with carbonate of soda, the superphosphate of lime, procured by the action of sulphuric acid on burned bones. The phosphate of lime which the solution contains, is separated by filtration, and the liquid containing the phosphate of soda is then evaporated until crystals of the salt are deposited. The phosphate of soda is composed of one proportion of the acid 28; one proportion of soda 32; and twelve proportions of water 108. It is employed in medicine, and in chemistry as a re-agent. BORATES The borates are few in number, and being most of them of no use, are little known. They are distinguished by imparting a green color to the flame of alcohol, when dissolved in it. Any borate, being first digested in sulphuric acid, then evaporated to dryness, and the residue What are the phosphates which occur in the native state 1 What is tl} plumula ? What is the radicle 1 What are the circumstances necessary to healthy germination 1 Will seeds grow, when exposed to air and moisture, under 32 degrees 1 How is it shown that seeds will not vegetate without air 1 What was Mr. Ray's experiment on the growth of seeds 7 What gas is absolutely necessary to tha growth of seeds 1 25* 294 VEGETATION. rishment, has been a matter of doubt and controversy. It ia certain, however, that they will not grow without the presence of heat, air, and moisture. It also seems necessary for their vigorous growth, that their roots should be placed in the earth, but whether this is requisite for their nourishment, or whether the ground serves merely to give them support, was a question long in dispute. Van Helmont planted a willow which weighed 5 pounds, in a pot containing 200 pounds of earth. This he watered lor the space of five years, and, at the end of that time, the tree was found to weigh 169} pounds, while the earth in which it had 3tood, being dried as at first, was found to have lost only two ounces. Here, then, was an increase of 164 pounds weight, and yet the food of the plant had been water only. This experiment was supposed to settle all controversy, and to decide that the sole food of plants was water. But Mr. Boyle afterwards showed, that the water with which the tree was moistened, contained earth, from which the willow derived at least a part of its nourishment. After a great variety of curious, and many elaborate experiments, on this subject, it has been ascertained, that plants will germinate in pure water, and that the young plant, for a time, will grow with no other aliment; but that it finally grows sickly, and does not come to maturity and produce seed, without other nourishment. A proof that plants do not thrive on water alone, is drawn from the well known fact, that soils become sterile by a long succession of crops, but are again made productive by the addition of new ingredients. Nor does it appear that the simple earths, or clay, without some additional ingredients, are sufficient to support the growth of vegetables. On making an experiment, by planting seeds in pure silica, alumina, or magnesia,, moistened with pure water, and exposed to proper degrees of heat, it was found that, although germination was effected, the young plants did not grow, until supplied with water, which contained vegetable or animal remains in solution. What are the agents necessary for the vigorous growth of a plant 1 What was the experiment of Van Helmont, and what was it supposed to decide 1 How did Mr. Boyle show that the willow did not live on water alone 1 What has been ascertained with respect to the growth of plants in pure water 1 What common fact, concerning soim, ¦hows that plants will not thrive on water alone t What is said of the growth of vegetables in the pure earths ? 295 VEGETATION. It is for this reason, that earth, taken from a depth below the surface, never forms a productive soil. The soils best adapted to the growth of plants, always contain a proportion of vegetable mould, that is, the remains of decayed vegetables. This mould contains a quantity of matter which is soluble in water, and it is probable that the fertility of a soil depends in a degree on the quantity of soluble matter it contains, and that in this manner the aliment of plants is prepared for absorption by the roots. The sap which is prepared from the fluid absorbed by the roots, is constantly ascending up the vessels of the plant during its growth, until it arrives at the leaves. Here it undergoes a considerable change, the watery parts being thrown off by the perspiration of the leaves, while that which remains is converted into a peculiar juice, called the true sap, which, like the blood of animals, is afterwards employed in forming the various substances found in plants. The leaves of plants are not only their perspiratory organs, but they also serve the purpose of respiration, that is, they alternately absorb carbonic acid and emit oxygen at their surfaces. Plants constantly throw off moisture from their surfaces by perspiration, but the quantity is much larger during the day than during the night. Dr. Hales found that a cabbage transmitted daily a quantify of water nearly equal to half its weight. The office of transpiration is performed entirely by the under side of the leaf, and may be almost entirely stopped by spreading varnish on that surface. The fact that plants absorb carbonic acid was first observed by Dr. Priestley. Having suffered a sprig of mint to vegetate for ten days in a quantity of this gas, which would instantly extinguish a candle, he found, at the end of that time, that the candle was not extinguished by it as before, but that the. flame continued for a while. Subsequent experiments have shown, that pure carbonic acid stops the growth of plants, Why does not the earth, taken from a considerable depth below the surface, form a productive soil ? On what does the fertility of a soil appear to depend ! What changes does the sap undergo in the leaves! What is the true sap, and what its use! What office do the leaves perform besides that of perspiration 1 What proportion of water did Dr. Hales find a cabbage to transmit! What part of the leaf throws off moisture ! What wai Dr. Priestley's experiment with a sprig 'if mint and carbonic cid* 296 VEGETATION. out that a small quantity is absolutely necessary to hoalthuvegetation. Jn Dr. Priestley's experiment, the sprig of mint could not have qualified the air in which it was confined, for the support of combustion, merely by the absorption of the carbonic acid. Jt must be inferred, therefore, from this experiment, that the plant not only absorbed carbonic acid, but that it gave out oxygen, or that it converted the carbonic acid into oxygen gas, and this inference has been confirmed by experiment. Plants, while growing in the light, absorb carbonic acid from the atmosphere, which they decompose; the oxygen, of which this acid is in part composed, being emitted, while the carbon is retained by the plant. If a growing plant, as a sprig of mint, be exposed to the sun, in a glass vessel filled with water, it constantly emits from its leaves small bubbles of air, which on examination are found to be oxygen gas. Now water, under ordinary circumstances, always contains a quantity of atmospheric air, and the atmosphere always contains a proportion of carbonic acid, and hence it may be inferred, that the water furnishes the air which the plant decomposes in this experiment; that this is the case, is proved directly by making the experiment with water, deprived of its air by the air pump, or by boiling, when not a particle of oxygen is obtained. That it is the carbonic acid which the plant decomposes, and from Avhich the oxygen is derived, is proved by two facts. The first is, that vegetables are found not to emit oxygen, unless carbonic acid be present. The other is, that if the plant be confined in a mixture of carbonic acid and oxygen, tne quantities of which are known, the proportion of oxygen will be increased, while that of the acid will be diminished. From these facts Ave arrive at the AA'onderful conclusion, that plants absorb carbonic acid from the atmosphere, and that they retain the carbon for their OAA*n nourishment, but return the oxygen to purify the air. And from all that is knoAvn, it is most probable that a great proportion, if not all In Dr. Priestley's experiment, what change did the mint produce on the carbonic acid ? When a plant is exposed to the sun in a vessel of water, whence comes the carbonic acid which it decomposes 1 What two facts prove that plants emit oxygen in cones quence of the decomposition of carbonic acid 1 When plants decompose carbonic acVt, what becomes of the carbon? From what source is it probable that plants derin? mo* ¦>( their carbon 1 297 VEGETATION. the carbon which wood contains is derived from the atmosphere in this manner. On the contrary during the night, or when the light of the sun is withdrawn, plants absorb oxygen, and form with it carbonic acid, a part of which they emit, and a part is retained. It appears from experiment, that vegetables not only cease to thrive, but that they actually die, if deprived of this nightly inspiration of oxygen. Thus, if a plant be confined during the day in a portion of carbonic acid, it decomposes a part of this gas, which is replaced by the emission of an equal volume of oxygen. But at night a part of this oxygen is absorbed and converted into carbonic acid, which is again emitted. Thus, ultimately, the plant decomposes all the carbonic acid, because it emits more oxygen during the day than it absorbs during the night. But if the oxygen which is formed during the day is withdrawn at evening, that is, if the plant has a new supply of pure carbonic acid every day, it soon droops, and dies for the want of its oxygdn. The leaves of plants absorb water, as well as carbonic acid and oxygen. The great effect which the dew of night, or sprinkling with water, has on a drooping flower, is a proof that the leaves imbibe moisture. Experiments also prove, that detached leaves often live for weeks when swimming on the water, and that a plant which is dying for want of moisture at the root, will revive and grow, when a branch with its leaves is placed in a vessel of water. It is most probable, therefore, that during dry seasons, and when there is a defect of moisture at the root, that the plant is in part sustained by the absorption of water from the air and particularly from the dew as it falls at night. In addition to heat, moisture, oxygen, and carbonic acid, healthy vegetation requires a certain quantity of light. It is well known that plants which grow in the dark are always nearly colourless, and that they appear weak and unhealthy. The disposition of plants to enjoy the light Js expressed by .neir inclination towards it, when it is stronger in one direction than in another. When do plants absorb oxygen from the amospherc 1 How is it shown that plants droop and die, when deprived of oxygen 7 How is it shown that the leaves of plants absorb water! What agent does healthy vegetation require in addition to heat, oxygen, water, and carbonic acid 7 How do plants show their disposition to enjoy the light 7 298 VEGETATION. Thus, bean, or potato vines growing in a dark cellar, wjfl always run towards the light, and if possible, will creep oat into the open air. And flowers, growing in pots placed near a window, will always lean towards the light, so tha, to keep them in a vertical position the pots must often be turned. In thick forests, the trees grow tall for the same reason j they stretch upwards to enjoy the light and heat of the sun. Plants which grow in the dark contain more water, and less carbon, than those which grow in the sun. A plant which grew in the dark, on analysis of one of its branches, was found to contain only one ninetieth part of carbon; but on allowing the same plant to stand for thirty days in the sun, it was found to contain one twenty-fourth part of carbon. This is readily accounted for, by the fact, that plants growing in the dark, emit no oxygen, but give out carbonic acid, and hence the defect of carbonaceous matter which they contain. This also accounts for the circumstance, that when a hoalthy plant is placed in the dark, it not only ceases to form carbon, but actually loses a part of that which it before con tairied, by the constant emission of carbonic acid. Recapitulation. I. Vegetable substances are chiefly composed of carbon, hydrogen, and oxygen, but sometimes contain portions o[nitrogen. 2. During the process of germination, the farinaceous substance of the seed, become sweet, and affords nourishment to the young plant. 3. Healthy germination does not proceed without the com bined presence of heat, water, and oxygen. 4. Seeds will not germinate in a vacuum, or in any gas which does not contain oxygen, though heat and moisture be 1 resent. Plants receive nourishment from the air, as well as from the earth. 6. Plants nourished by pure water, and having access tc the air, grow for a time, but do not produce seeds. 7. The nourishment which plants receive by the roots, is probably in a state of solution in water. Why do the trees in thick forests grow tall 1 What is the difference in composition be tween ilants growing in the dark, and in the light 1 How is the small quantity of carbo* conui.ned in plants growing in the dark accouri.ed for 1 The student should oe ablo tt> answet all the questions involved in this recapitulation. 299 VEGETABLE ACID?. 8. The sap undergoes a change in the leaves, where it parts with a portion of water, and is thus fitted to form the various substances found in vegetables. 9. In the day time, plants absorb carbonic acid, retain the carbon, and emit the oxygen. 10. In the night they absorb oxygen, and give out carbonic acid. 11. Plants do not live unless they are permitted to absorb oxygen during the night; nor will they live unless they absorb a portion of carbonic acid during the day. 12. Vegetation will continue for some time in either carbonic acid, or oxygen gas; because when confined in carbonic acid, plants emit a quantity of oxygen during the day, which they absorb at night; and when confined in oxygen r hey give out a quantity of carbonic acid at night, which again serves them during the day. 13. Healthy vegetation absolutely requires the agency of liq-ht. 14. Plants which grow in the dark, are white. They show their propensity to enjoy the light, by leaning, or creeping towards it. 15. Plants, growing in the dark, do not absorb, and decompose, but emit carbonic acid, and hence they contain a deficiency of carbon. VEGETABLE ACIDS. The vegetable acids are generally less liable to spontaneous decomposition than other vegetable products. They form salts when combined with the salifiable bases. Most of them are decomposed by hot nitric acid, being converted into carbonic acid and water. All of them suffer decomposition when exposed to a red heat. These acids are numerous, but a large proportion of them are of little consequence, ind therefore we shall describe only the most useful. S Acetic Acid —50 4 p. Carbon 24. 3 p. Oxygen 24. 2 p. Hydrogen 2. Vinegar. The acetic acid, or vinegar, exists ready formed in the sap What is said of tne tendency of vegetable acids to decomposition 7 How may the vege tab.e acids be decomposed 7 What is the composition of acetic acid 7 What is the com jtion "ame of acetic acid 7 300 VEGETABLE ACIDS. of some plants, either in a free state, or combined with hW, or potash. It may be formed artificially either by the acetous fermentation, or by the destructive distillation of wood. In the first case, it is made by exposing wine, cider, beer, or any other liquid capable of passing through the acetic fermentation, to the action of the air. This last condition is absolutely requisite, for no liquid will form vinegar if prevented from the access of air, that is, from the presence of oxygen The liquid must also be exposed to certain degrees of tem perature, for the acetic fermentation does not proceed, wher the thermometer is at 32 degrees, and but very slowly when it is near this point. In this process, little or no gas is evolved, but on the contrary the oxygen of the atmosphere is absorbed, so that the liquid undergoes a slow oxidation. The vinegar obtained by the distillation of wood is called pyroligneous acid, that is, the acid of burned wood. When first made, it is very impure, and of a dark colour, holding in solution carbon, soot, tar, and volatile oil, which gives it a strong smell of smoke. It is purified by a second distillation, and is largely employed for manufacturing purposes, and particularly in the preparation of white lead. The acetic acid is distinguished from all other acids by its peculiar flavor, odor, and volatility. Its salts are called acetates. These salts are all of them decomposed at a reo heat, or by the action of sulphuric acid. Acetate of head —172. 1 p. A. Acid 50+1 p. Oxide Lead 112. Sugar of head. This salt is prepared by dissolving either litharge, or white lead, in distilled vinegar. The solution is sweet to the taste and hence its common name. It occurs in small shining crystals, which contain 27 parts, or 3 atoms of water. This salt is partially decomposed when abandoned to the ac- Is vinegar ever found ready formed in plants 1 How may this acid be formed by art 1 What liquids form this acid by fermentation 1 What conditions are necessary to the production of vinegar by fermentation 1 What gas is absorbed from the air by the forming vinegar 1 What is the vinegar from distilled wood called 1 How is the acetic acid distinguished from all other acids 1 What is the composition ol acetate of lead 1 What is the common name for acetate of lead ? How is this salt prepared'! In what manner i :. thie salt decomposed when exposed to the air, and what new salt is formed I 301 VEGETABLE ACIDS tion of the atmosphere. It parts with its water of crystallization, and absorbs carbonic acid from the atmosphere, thus being changed into a carbonate, or into white lead. We have stated in another place, that in the manufacture of white lead, the same change is effected ; the lead being first dissolved by the acetic acid, and afterwards changed into a carbonate by the action of the atmosphere. The acetate of lead is largely employed in the process of colouring, and as a sedative and astringent in surgery. Acetate of Copper —130. 1 p. Acetic Acid 50-f-l p. Oxide of Copper 80. Verdigris. This salt may be prepared by exposing metallic copper to /he vapor of vinegar. The process appears to consist in the absorption of oxygen from the atmosphere by the metal, after which it is dissolved in the acetic acid. Verdigris is manufactured largely in the south of France, by placing plates of copper between the refuse of grapes after the juice is pressed out, for the making of wine. The fluids which the grapes still contain, pass through the acetic fermentation, by exposure to the atmosphere, and after several weeks, the plates acquire a coat of the acetate, which being scraped off, they are again exposed to the same process. The acetate is afterwards purified by solution, and crystallization. Oxalic Acid —36. 2 p. Carbon 12-f-3 p. Oxygen 24. Acid of Sorrel. The oxalic acid exists ready formed in several plants, and particularly in the oxalis acetosella, or wood sorrel, and also in common sorrel. It is readily prepared artificially, by digesting Avhite sugar in five or six times its weight of nitric acid, and evaporating the solution to the consistence of syrup. On cooling, crystals of oxalic acid will be deposited; but they should be purified by solution in water, and again crystallized by evaporation. What are the uses of acetate of lead 1 What is the composition fo acetate of copper I What is the common nftne of this salt 7 By what chemical process is this salt formed 7 How is verdigris made in the large way 7 What is the oxalic acid com|*iseil of 7 In what plants is this acid ready formed 7 26 302 VEGETABLE ACIDS. Oxalic acid crystallizes in slender, flat prisms, which have an exceedingly sour taste, and which in solution combine with the salifiable bases, and form a class of salts called oxalates. These crystals contain half their weight of water of crystallization. This acid is easily distinguished from all others, by the form of its crystals, and by its solution giving with lime water a white precipitate, which is not dissolved by adding in ex cess of the same acid. Oxalic acid is one of the most prompt and fatal poisons known, when taken in large doses. Fatal accidents have many times happened, in consequence of mistaking this acid for Epsom salts. This acid is employed by calico printers, for the purpose of discharging certain colors. It is also used in families, for taking out spots of iron mould, and other stains. The oxylates are none of them of much importance. The oxalates of potash, like the acid itself, is sold under the name of essential salt of lemons, for removing stains from linen. Tartaric Acid. 4 p. Carbon 24+5 p. Oxygen 40+2 p.»Hydrogen 2. Tartaric Acid —66. Cream of tartar is the purified lees, or deposits of wine casks. From cream of tartar the tartaric acid is produced, by mixing the former with chalk in fine powder, and throwing the mixture into boiling water, by which the cream of tartar, which .is a tartrate of potash, is decomposed, and a tartrate of lime is formed. The tartrate of lime is then washed, and decomposed by dilute sulphuric acid, which, combining with the lime, sets the tartaric acid at liberty, where it remains in solution. This solution being evaporated, the tartaric acid is obtained in white crystals. This acid is employed by calico printers, to discharge false prints, and by tallow chandlers to whiten their goods. It is also used, when dissolved in a large quantity of water, as a cooling beverage in the hot season. When mixed with car- IIow is this acid formed by art 1 What are the salts called, which the salifiable bases form with oxalic acid 7 He w is this acid distinguished from others 1 What is said of its poisonous effects'! What are the uses of oxalic acid! What is the tartaric arid composed of 1 What is the substance from which tartaric acid is obtained 1 By what process -, as in potatoes ? How are spirituous liquors obtained 1 316 ETHER. mentative solution, and which gives it a flavor. Thus, brandy, rum, and whiskey, have each a flavor of their own, which arises from this circumstance. These are called spirituous liquors. When a spirituous liquor is distilled, the alcohol is obtained in a state of much greater purity, the oil which it contained and most of the water being left in the retort, or still. In this state it is colorless, highly inflammable, produces cold by evaporation, and occasions a considerable augmentation of temperature by admixture with water. Common alcohol contains a portion of water, and has a specific gravity of from 850 to 875, water being 1000. It may be further purified, or freed from water, by adding to it warm carbonate of potash, or muriate of lime, which combines with the water, and sinks to the bottom of the vessel, after which the alcohol may be poured off Very pure alcohol may also be procured, by putting it into a bladder, which being suspended in a warm place, the water will slowly pass through the coats, while the pure alcohol is retained. The stronges' alcohol which can be procured by either of these methods, has a specific gravity of 800, or 796, at the temperature ol 60 degrees. Pure alcohol has never been frozen, though exposed to the lowest temperature which art has ever produced. It is a powerful solvent, being capable of dissolving camphor, resins, soap, volatile oils, sugar, balsam, &c. Pure alcohol has precisely the same properties, from whatever substances it is obtained. Ether. The name ether was originally applied to a highly fragrant and volatile liquid, obtained by the distillation of alcohol with sulphuric acid. But it has been found that the same substance, when distilled with other acids, affords a liquid possessing in some respects similar properties, and therefore these compounds are now distinguished by prefixing the name of the acid employed. What gives the peculiar flavor to distilled liquors, as brandy, rum, and whiskey 1 How is alcohol obtained 1 Do spirituous liquors yield pure alcohol on distillation 1 What » the specific gravity of common alcohol 1 How may pure alcohol be obtained 1 What a the specific gravity of the purest alcohol 7 What is said of the freezing of pure alco uol 1 What is said of the solvent powers of alcohol 1 How is ether obtained 1 317 ETHER. Sulphtsric Ether. To make sulphuric ether, pour into a tubulated retort a certain quantity of alcohol by weight, and add, in small portions at a time, the same weight of strong sulphuric acid, allowing the mixture to cool after each addition. Then connect the retort with a receiver, and, by means of a lamp, make the mixture boil. The receiver must be kept cold by the application of ice, or wet cloths. The ether will pass over and be condensed in the receiver. The ether thus obtained, contains a portion of alcohol, and commonly a little sulphuric acid, from which it is purified by agitation with potash, and redistillation. In respect to the chemical changes which take place between the alcohol and acid, to form the new product ether, it is found, on analysis, that the latter substance is composed of two proportions of olefiant gas, and one proportion of water. The number for olefiant gas being 14, and that for water being 9, the equivalent number for ether is 37. Now olefiant gas consists of 2 atoms of carbon 12, and 2 atoms of hydrogen 2=14, to which 1 atom of water 9, being added, makes the composition of ether. Alcohol is composed of, or contains the elements of, 1 atom of olefiant gas, and 1 atom of water, and therefore alcohol contains double the proportion of water that ether does. Now if 1 proportion or atom of water be abstracted from two of alcohol, the exact proportions constituting ether will remain. Thus, the number for alcohol being 23, double this number is 46, from which one atom of water, 9, being taken, there remains 37, the number representing ether. It will be seen, on comparing these several numbers, that they exactly correspond with the constituents above named, and it is supposed that this is the precise mode in which sulphuric acid operates to convert alcohol into ether. In consequence of the affinity of sulphuric acid for water, it abstracts one atom of that fluid from the alcohol, and thus the elements of ether remain. Sulphuric ether is a light, odorous, transparent fluid, of a hot and pungent taste. Its specific gravity, when most pure, is about 700, water being 1000 ; but that of the shops is 740, or 750, owing to the presence of alcohol. When exposed to What is the process of obtaining sulphuric ether 1 What is the composition of sulphuric ether 1 Explain the difference between alcohol and ether, and describe the change oy which the former is converted into the latter. What is the specific gravity of ether when most pure 1 How does ether occasion an intense degree of cold? 27* 318 VEGETABLE ALKALIES the open air, it evaporates with great rapidity, and occasions an intense degree of cold. This is in consequence of the principle already explained, that when a substance passes from a denser to a rarer state, caloric is absorbed. Ether is exceedingly combustible, and burns with a blue flame, the product of its combustion being water and carbonic acid. Ether is employed as a medicine in nervous fevers, and as a solvent in the arts. When pure, or when that of the shops is agitated with water, and, after standing a while, is poured off, it is a solvent of India rubber, one of the most insoluble of vegetable products. Nitrous Ether is prepared by distilling alcohol with nitric acid, in a manner similar to that described for sulphuric ether, to which its leading properties are similar. It is, however, still more volatile, and is subject to decomposition by keeping. Vegetable Alkalies. Potash and soda were formerly called vegetable alkalies, in order to mark their origin, and to distinguish them from the other alkaline substances. These alkalies, as stated in their proper places, are obtained chiefly by the incineration of land and sea plants, though they both exist ready formed by nature. They are found to be metallic oxides, and have been described under the names of oxide of potassium and oxide of sodium. The vegetable alkalies now to be descri bed, are strictly vegetable products, and are obtained, not by incineration, but by the digestion, or maceration, of certain vegetable substances in water. The following is an outline of the method by which they are obtained. In the first place, the substance containing the alkali is digested in a large quantity of very pure water, which dissolves the salt, the base of which is the alkali On adding some salifiable base, such as potash, or ammonia, which has a strong affinity for the acid of the vegetable salt, in the watery solution, this salt is decomposed, its acid combining with the potash, or ammonia, and thus leaving the vegetable alkali in the solution. This being insoluble, while Why does the evaporation of ether occasion cold 1 What are the uses of sulphuric ether 1 How is nitrous ether procured 1 How does the nitrous differ from the sulphuric ether 1 How do the oxides of potassium and sodium differ from the vegetable alkalies 1 How are the vegetable alkalies obtained 1 Give an outline of the process by which these substances are procured. 319 MORPHIA. .he new salt is soluble in water, is collected and washed on a filter. The vegetable alkali thus obtained, is however impure, and requires to be dissolved in alcohol, with the addition of some animal charcoal, which deprives it of its color —then filtered, and the alcohol evaporated, when the pure alkali will be obtained. The most important vegetable alkalies are, Morphia, Cinchonia, and Quinia. Morphia. Morphia is the narcotic principle of opium. Opium, be sides morphia, contains meconic acid, narcotine, gum, resin ous, extractive, and colouring matter, and a small quantity of caoutchouc, or India rubber. Morphia exists in the opium, combined with meconic acid, forming meconate of morphia. To obtain it, therefore, it is necessary to decompose this salt, by which the morphia is liberated, and afterwards obtained by the evaporation of some fluid in which it is soluble. This is done by boiling a solution of opium in water, with magnesia, by which the meconate of morphia is decomposed, and a meconate of magnesia is formed. The morphia being thus precipitated, is obtained in an impure state by filtration, and afterwards purified by solution in alcohol. On evaporating the alcohol, the pure alkali is deposited in crystals. Pure morphia occurs in small rectangular white prisms, of considerable lustre. It is insoluble in water, but alcohol, especially by the aid of heat, dissolves it freely. In its pure state, this substance is nearly tasteless, owing to its insolubility in water, but when it is rendered soluble by combining with an acid, or when dissolved in alcohol, it is intensely bit ter. From the same cause, in its pure and solid state, morphia is nearly inert on the living system, Orfila having given twelve grains to a dog, without any sensible effects. On the contrary, when in a state of solution, it acts on the system with great energy, Orfila having seen alarming effects from half a grain. What are the most important vegetable alkalies 1 What is morphia 1 What are the Ingredients in opium besides morphia! In what state does morphia exist in the opium 1 What is the process for obtaining morphia 1 What is the use of the magnesia in this process 1 What are the solvents of morphia 1 In what state is morphia used in medicine! 320 CINCHONIA AND QUINIA. The best method of using morphia in medicine, is to form with it an acetate, or a citrate, both of which are soluble in water, and alcohol. In either of these states, it is given in those cases where opiates are required, and it produces all the soothing effects of opium, without the disagreeable consequences which often follow the administration of that drug. Narcotine. This substance, though not an alkali, is con tained in opium, and is therefore properly noticed here. Narcotine is obtained by digesting opium in water, and evaporating the solution to the consistence of extract, and then digesting this with sulphuric ether. The water, as shown above, will hold in solution meconate of morphia, as well as narcotine, but the meconate is insoluble in ether, which only takes up the narcotine. On evaporation, the ether so treated will deposit small particles of narcotine. This substance is little soluble in water, either cold or hot. but dissolves in oil and alcohol. The unpleasant properties of opium as a medicine, are attributed to this substance, and perhaps the different effects of the salts of morphia from opium, are only owing to their not containing narcotine. Cinchonia and Quinia. It has been fully established, that the efficacy of cinchonia, or Peruvian bark, in the cure of fevers, resides in the alkalies, called cinchonia and quinia. These two principles, though quite analogous in many respects, are distinct substances, and appear to bear the same relation to each other as potash and soda. Cinchonia exists in the pale bark, quinia in the yellow, and both are present in the red bark. They are obtained from these substances by a process similar to that already described for separating morphia from opium. Cinchonia appears in white crystalline grains, which are nearly insoluble in water, but which are readily taken up by Why is it not used in its pure state 1 What advantage has morphia over opium as a medicine 1 How is narcotine obtained 1 Is narcotine soluble In water 1 What are the solvents of narcotine 1 What effects of opium are imputed to narcotine 1 What is said of the efficacy of cinchonia and quinia in the cure of fevers 1 What relation do cinchonia and quinia appear to bear to each other 1 In what species of bark do these alkalies exist 1 By what process are these substances obtained} What is the appearance o cinchonia 1 321 ANIMAL CHEMISTRY. boiling alcohol. Its alkaline properties are well marked by its power of neutralizing acids. It forms nitrates, muriates, sulphates, acetates, &c, all of which are soluble in water. Quinia is a white, porous substance, of a flocculent appearance. It does not, like cinchonia, form crystals. It is also nearly insoluble in water, but dissolves freely in alcohoi, affording an intensely bitter solution. Like cinchonia, it has strong alkaline powers, and forms salts with the several acids. Its febrifuge effects are much more decisive than those of cinchonia, and it is now extensively employed in the practice of medicine, in the form of the sulphate of quinia This salt crystallizes in delicate white needles. It contains 90 parts of the quinia combined with 10 of the acid. The composition of cinchonia and quinia is thus stated by Pelletier and Dumas. Cinchonia. Carbon 76.97 Oxygen 7.97 Hydrogen 6.22 Nitrogen 9.02 100.18 Quinia. Carbon 74.14 Oxygen 6.77 Hydrogen 8.80 Nitrogen 10.76 100.47 The composition of these alkalies, therefore, consist of the .ame elements, and nearly in the same proportions. ANIMAL CHEMISTRY. In relation to chemistry, the circumstances which distinguish animal from vegetable substances, are the large quantity of nitrogen which the former always contain, their strong tendency to putrefaction, and the offensive products which they exhale during decomposition. Animal substances are essentially composed of carbon, hydrogen, oxygen, and nitrogen; and in addition to these, they sometimes contain sulphur, phosphorus, iron, and small quantities of saline matter. Fibrin. —The lean parts of animals consist chiefly of fibrin How do the alkaline properties of cinchonia appear! What salts does it form with acids 1 What is the appearance of quinia 1 What is the solvent of quinia 1 In what form is quinia employed in medicine! What is the appearance of sulphate of quinia, and what its composition 1 In relation to chemistry, what are the circumstances which distinguish animal from vegetable substances! What is the essential composition of animal subs'ancesl 322 ANIMAL CHEMISTRY. This may he separated and observed in its pu-e state, by removing the soluble parts of lean beef, cut into small pieces, by repeated washing, and digestion in cold water. Fibrin thus obtained, is nearly white, and is insipid and inodorous. It readily passes into the putrefactive fermentation, but in thin pieces, suspended in a dry place,-its fluid parts evaporate, and it becomes hard, brittle, and translucent. Alcohol converts fibrin into a fatty substance, which is soluble in the same fluid and in ether, but is precipitated by the addition of water. This substance is decomposed by all the strong acids, and is dissolved by caustic potash. Fibrin is composed of 18 parts of carbon, 14 of hydrogen, 5 of oxygen, and 3 of nitrogen. Albumen. —Albumen enters largely into the composition of animals. Their solid, as well as fluid parts, contain it in greater or less proportion. Liquid albumen is nearly pure in the whites of eggs. Its appearance, and many of its properties, in this state, are well known. It is coagulated, and converted into a soft solid, by heat, by alcohol, and by the stronger acids. The character of being coagulated by heat, distinguishes albumen from all other animal fluids. It is completely soluble in cold water, and it is said that when this fluid contains only -nnnr P art °f albumen, it becomes opalescent by boiling. On this property is founded the clarifying effects of albumen. As it coagulates, by the heat of the water, it entangles any insoluble particles the fluid contains, and rises with them to the surface. Gelatine. —This substance forms a proportion of all the solid parts of animals, and is particularly abundant in the skin tendons, membranes, and bones. It is soluble in boiling water, and forms a bulky, semi-transparent, tremulous mass, when cold. By evaporation, it becomes a solid, brittle, hard, and semi-transparent substance, known in commerce and the arts, under the name of glue. This is chiefly prepared from the cuttings of skins, and the ears and hoofs of animals. Isin~ glass, which is the purest variety of gelatine, is prepared from certain parts of fish, and especially the sturgeon. The gela What is fibrin ? How may fibrin be obtained ? What are the propertiea of fibrin 1 What is the composition of fibrin 1 Where is albumen found nearly in a pure state' By what agents is albumen coagulated 1 By what property is albumen distinguished from all other animal fluids'? How does albumen clarify liquids? In what paris of ani mals is gelatine most abundant ? Under what name is dry gelatine known? What l» isinglass ? ANIMAL CHEMISTRY 323 line called calves foot jelly, is prepared by boiling the feet of that animal in water. Gelatine is precipitated by tannin. This is so delicate a irsi for gelatine, that it is said, an infusion of nut galls, which contains a large quantity of tannin, will show the presence of gelatine when mixed with 5000 times its weight of water. The three ingredients, fibrin, albumen, and gelatine, form the most bulky parts of all animals, that is, the flesh, tendons eartilages, and skin Oleaginous Substances. The fat of animals is very analogous, in its composition and proportions, to the fixed, vegetable oils, its ultimate principles being carbon, hydrogen, and nitrogen. There is a considerable variety in the appearance and qualities of the fatty principle contained in different animals. The solid fat of land animals is called tallow, while the corresponding substance from fish, which is fluid at common temperatures, is called oil. All these substances agree very nearly in respect to composition, the principal difference being in respect to form and appearance. Their uses, for making soap, giving light, &c are well known. Blood. The blood of animals obviously consists of two parts, cal .ed serum and crassamentum. In healthy blood, these two parts separate spontaneously on standing. The crassamentum coagulates, and forms a red, solid mass, while the serum surrounds it, in form of a yellowish fluid. The serum contains a small quantity of soda in a free state, and is 29 parts in 1000 heavier than water. It consists, in part, of albumen, and is coagulated by heat, acids, and alcohol. The crassamentum consists of two parts, the fibrin and the colouring matter. The fibrin does not differ, except in form, from that obtained from lean flesh, which has already been described. By what substance is gelatine precipitated from its solutions 1 What parts of animals are formed by fibrin, albumen, and gelatine 1 What are the ultimate principles of animal tatol What difference is there between animal fats and animal oils f In blood what is the serum and what the crasKimentv ra 1 Wha' is serum composed of ? Whit does crassamentum consist of? 324 ANIMAL CHEMISTRY. The coloring matter of the blood consists of distinct pai tides, which in birds and cold-blooded animals, are elliptical in form, but in man and other mammiferous animals, they are globular. These facts have been acsertained by means of the microscope. The globules are insoluble in the serum, but their color is dissolved by water acids, and alcohol. It has been suppossed that the crassamentum contained a portion of iron, but recent analysis has shown that this metal does not belong to the crassamentum as a whole, but only to the coloring matter ; for when the fibrin is carefully separated from the coloring principle, it does not contain a trace of iron, while iron is always found in the red globules. From the presence of iron in the globules, and its total absence in the other parts of the blood, it is inferred that the red color of the globules depend on the presence of this metal, though its quantity is found to be only half a grain to a hundred grains of the globules. It is found that during the coagulation of blood, heat is evolved, and consequently its temperature is raised. This is owing to its passage from a rarer to a denser state, in consequence of which its capacity for caloric is diminished. We have had frequent occasions to refer to this principle. The increase of temperature from this cause, is however very slight, perhaps not more than two or three degrees, but its cooling is considerably retarded by the caloric thus evolved. The blood presents several phenomena, which neither the principles of chemisty nor physiology have been able to ex plain. The cause of its coagulation, for instance, has never been satisfactorily accounted for. It does not arise for want of heat or motion, for if blood be drawn when the temperature of the air is equal to that of the animal from which it is taken, and then kept constantly in motion, its coagulation is not prevented, or even retarded. Indeed, neither moderate heat, nor cold, a vacuum, nor pressure, nor even dilution with water, seem to have any influence on the coagulation of the blood. On the contrary, its coagulation is pre- What does the coloring matter of blood consist of 1 On what metal does the coloring matter depend t What proportion of iron is contained in the red globules of the blood 1 What to said concerning the heat evolved by the coagulation of the blood ? What is said concerning the cause of the blood's coagulation 1 what circumstances are said not to affect the coagulation of the blood 1 325 ANIMAL CHEMISTRY. vented by certain causes, the effects of which could not be supposed to influence this circumstance. Thus, the blood of persons who have been destroyed by some kinds of poison, and by mental emotions, has been found uncoagulated, and in a fluid state. How causes so unlike should produce the same effects, or why either of them should affect the blood at all, are equally unknown. Respiration. Respiration is the act of breathing, and consists in the alternate drawing into, and throwing out of the lungs, a quantity of atmospheric air. And it appears that this process, or an equivalent one, is necessary to support the lives of all animals. The atmosphere, as formerly shown, is composed of 80 parts of nitrogen, and 20 parts of oxygen, and it is found by experiment, that no other gaseous compound can be substituted for respiration, nor can these proportions be varied without injury to its qualities. The immediate effect of respiration, is to produce a change in the color of the blood as it passes through the lungs, thus indicating that it suffers some change in its properties at the same time. The necessity of respiration to all warm blooded animals requires no proof; and the necessity that the blood should be brought into contact with the air inspired, is equally obvious from the organization of their lungs. Such animals are provided with two kinds or classes of blood vessels, called veins and arteries. The arteries, particularly the large ones, are deeply seated within the animal, and convey the blood to all parts of the living system. The veins, on the contrary, especially the small ones, are situated near the surface, and are destined to convey the blood back to the heart, which had been thrown out by the arteries. What circumstances are said to prevent the coagulation of the blood 1 What is respination 1 What is the composition of the atmosphere 1 What effect does a cnange in the composition or proportion of the elements of the atmosphere produce on respiration What is the immediate effect of respiration on the color of the blood 1 What is s&'A of me necessity of respiration 1 What are the two kinds of blood vessels called t Where jtre the veins atd arteries situated with respect to each other 1 What is the use of the m leries 1 What part of the circulation do the veins perform 1 28 326 RESPIRATION But besides these two great systems of blood vessels, there is another system called the pulmonary, which is des tined expressly to convey the blood to the lungs, where it undergoes the change above mentioned, and then back again to the heart. The entire circulation will now be readily understood.— The blood being thrown to all parts of the body, is returned to the right side of the heart by the great system of veins. From the right side of the heart it is sent to the lungs, by the pulmonary artery, and being there changed into arterial blood, is returned by the pulmonary veins to the left side of the heart, the left side of the heart, it is thrown to all parts the body by the great system of arteries, to be returned to the right side by the veins, as before. venous blood, fresh drawn, is suffered to stand a few minutes in a confined portion of atmospheric air, it is found that the air loses a part of its oxygen, which is replaced by the same volume of carbonic acid gas, and at tho same time the color of the blood, from being of a dark pur pie, becomes florid red. This is the same change of color which the blood undergoes in its passages through the lungs. The cause of the change in the lungs might therefore be inferred to be the absorption of oxygen by the blood, and the subsequent emission of carbonic acid. That this change of colour in venous blood, when out of he lungs, is owing to the contact of oxygen, is shown by the more immediate production of the same effect when oxygen is substituted for atmospheric air, and also by the fact that no change of color is produced when the oxygen is entirely excluded. Hence the inevitable conclusion, that fresh drawn venous blood emits a quantity of carbon in consequence of its coming in contact with oxygen, and that its change of color is caused by this emission. The same change thus proved to take place in the atmosphere, is constantly going on in the lungs. The venous blood, which, as above explained, is sent to the lungs through the pulmonary artery, is charged with carbon, to which it What is the office of the pulmonary system 7 Explain the entire circulation. From whifo side of the heart do the great arteries convey the blood to all parts of the body 7 How is the blood conveyed from the right to the left side of the heart 7 What effects do the contact of atmospheric air and venous blood produce on each 7 How is it proved that ths chanre of color in the blood is produced by the oxygen of the air 7 What is the cause ol die change o' color in venous blood 7 RESPIRATION. 327 owes its dark color. The oxygen of the atmosphere, by inspiration, fills all the air vessels of the lungs, and is thus brought nearly into contact with the blood, being separated from it only by the thinnest membrane. It appears that through this membrane, the oxygen of the atmosphere is absorbed, and having combined with a portion of the carbon of the blood, it is again emitted in the form of carbonic acid gas, and to this process is owing the change ."rom venous to arterial blood. In proof of this, experiment shows that when any living tnimal is confined in a portion of air containing a known. quantity of oxygen gas, the oxygen gradually disappears, .tnd is replaced by the same quantity of carbonic acid. In ordinary respiration, the air from our lungs always contains a portion of carbonic acid. This is proved by merely blowing into a glass vessel containing a solution of lime in water, or what is commonly called lime water, when the clear water will instantly become turbid, because the carbonic acid from the lungs unites with the lime of the water, and forms an insoluble carbonate. It does not appear that the oxygen is absorbed, and retained by the blood, for the absolute quantity of air, though many times respired by a confined animal, remains the same. 1 his also proves that the nitrogen of the atmosphere is not absorbed. It is well known by experiment, that the conversion of oxygen gas into carbonic acid, does not in the least change its volume, but only adds to its weight. This accounts for the reason why the volume of air is not changed by respiration, or by convertion into carbonic acid, provided no absorption take place. Thus the change from venous to arterial blood, seems to be produced entirely by the loss of carbon, which the former suffers while passing through the lungs. It appears also, from numerous experiments, that not only waim blooded animals, but also fish, and cold blooded reptiles of ihe lowest order, absolutely require the presence o. To what is the dark colour of venous blood owing 1 What change does the blood undergo in the lungs? How is it proved that oxygen is converted into carbonic acid in the lungs ? How is it proved that we emit carbonic aciil at every expiration ? In respiration, is the oxygen absorbed and retained by the blood, or not? How does it appeal that neither Ihe nitrogen nor the oxygen of the atmosphere is retained in the process o. respiration 7 In what does the change from venous to arterial blood consist ? What if 6**1 of the necessity of oxygen to support the lives of cold blooded reotilcs 1 328 ANIMAL HEAT. oxygen in order to sustain life. Water, it has already b» :* stated, always contains a portion of this gas in a free state, a.»d although the quantity is small, it is sufficient to sustain the lives of its inhabitants. That fish, frogs, and other animals of tnis kind, cannot sustain life without oxygen gas, is proved by the fact, that they die in a short time, if the water in which they are placed is covered with a film of oil, so that no oxygen is admitted. Frogs, though capable of suspending their respiration for a long time, die in less than an hour, if the small quantity of water in which they are confined is covered wilh oil. Aquatic insects and worms exhibit the same phenomena when treated in the same manner. In these cases, experiment has shown that oxygen is converted into carbonic acid, the effect being the same as that produced by the respiration of warm blooded animals. Indeed, the experiments of Spallanzani prove that animals produce this change by the action of their skin. Thus, serpents, lizards, and frogs, during their torpid state, and when their respiration is suspended, still require small portions of oxygen, which they constantly convert into carbonic acid by means of their skin, and it is probable, that in this manner, the blood of these animals parts with a little car bon. Animal Heat. During combustion there is an absorption of oxygen, and a suDsequent emission of carbonic acid gas, and in the act of respiration, oxygen disappears, and is replaced by the same acid gas. Combustion and respiration are therefore supported by the same principle, and yield the same product. This analogy led Dr. Black to conclude that the changes which take place on the air, and on the blood in the lungs, was the cause of animal temperature ; and several circumstances relative to the structure of animals and the quantity of oxygen they consume by respiration, seem to show that the heat of their blood depends, in a measure at least, on the quantity of this principle thus consumed. Animals having ihe power to maintain their temperatures above the media in which they live, are provided with capacious lungs, and consume large quantities of oxygen. Birds, the temperature How is it proved that fish and frogs require oxygen 7 What effect does the skin of tor pid animals have upon oxygen? What analogy is there between combustion and respi-ation? What is said concerning the quantity of oxygen consumed by warmblooded am male 1 329 ANIMAL HEAT. of whose blood is higher than that of man, and quadn peds, have lungs still more capacious, according to the'Y size, and consequently, most probably consume more vital air. On the contrary, fish, frogs, and other animal of this tribe, which consume only very minute portions of oxygen, do not, sustain their temperature above the media in which they live. ft appears also, that the temperature of an animal, when made to respire pure oxygen gas, is raised above the natural standard, but when the quantity of this gas consumed is small, the temperature of the animal falls, and the circulation of the blood is sluggish and languid. From these considerations, it would appear that the heat of the animal is sustained by its respiration, and that its temperature is proportionate, in some degree, to the quantity of oxygen it consumes, or converts into carbonic acid. Dr. Crawford, pursuing this idea, supposed that the carbonic acid discharged by the breath, being generated in the lungs, and accompanied with the loss of oxygen, extricated heat during its formation, and that the temperature of the animal might thus be explained. But as the heat of the lungs was found to be no greater than that of other internal parts, there must be some mode of accounting for its distribution to other parts of the system, otherwise this .heory could not for a moment be supported. It is obvious that, in whatever manner this distribution is effected, the heat must be latent, or insensible; for supposing it to be in a free state, the lungs, or part where it is generated, would still be at a higher temperature than the parts to which it is distributed. Accordingly, on comparing the capacities of venous and arterial blood for heat, Dr. Crawford found, that arterial blood had the greatest capacity, and therefore, that at the same temperature, it contained a quantity of latent heat, which the venous blood did not. He therefore supposed that this latent heat was conveyed by the arterial blood, to all parts of the system, and as the arterial is gradually converted into venous blood, so the latent heat gradually be- What is said of the quantity of oxygen consumed by fish and frogs ? Does it appear lhat there is any proportion between the heat of the animal and the quantity of oxygen it consumes by respiration 1 How did Dr. Crawford explain the cause of animal temperatur« 1 Suppose arterial blood to have a greater capacity for heat than venous blood, on what circumstance could animal temperature be explained t 28* 330 ANIMAL HEAT. came sensible, in all parts of the system, and that in this manner, animal ten pcrature is maintained. This beautiful th eory was supposed to be founded on thf true principles of chemistry and physiology, and being so received, it accounts: very satisfactorily for animal tempera ture. But Dr. Davy has since shown that the principal fact on which it is founded, the difference of the capacities of venous and arterial blood for heat, is not true, but that in this respect there is little or no difference between the two kinds of blood. If Dr. Davy has maintained the truth, it is obvious that Dr. Crawford's theory must fall to the ground. Although the facts stated above, in respect to the capacity of the lungs, in warm blooded animals, and the quantity of oxygen which they consume, when compared with cold blooded animals, would seem to show almost beyond a doubt, that animal temperature is connected with the quantity of oxygen consumed, and the changes which the blood undergoes in the lungs ; still some physiologists deny the agency of either of these causes in producing such effects, and ascribe the evolution of animal heat entirely to the influence ol the nervous system. The foundation of this doctrine, is an experiment of Mr Brodie, Avho found that on keeping up an artificial respiration in the lungs of a decapitated animal, the colour of the blood was changed from purple to red, and carbonic acid emiited as usual; but that this animal grew cold more rapidly than another decapitated animal of the same kind which lay untouched. It is obvions that this result would follow unless heat was evolved by the artificial respiration, because the air forced into the lungs would abstract the heat of the animal. "Were these experiments rigidly exact, says Dr. Turner, they would lead to the opinion that no caloric is evolved by the mere process of arterialization. This inference cannot, however, be admitted, for two reasons :—First, because other physiologists, in repeating the experiments of Brodie, have found that the prrcess of cooling is retarded by artifi- How did Dr. Da ry show that Dr Crawford's theory was untenable 7 What is the toun dation of the theo-y that animal h at is evoived by the nervous system 1 If heat were not evolved by artificial respirati n, why should this process cool the animal rapidly 1 What are Dr. Turner's two reasor for supposing that Mr. Brodie's experiments are not conclusive, that heat is not evolvei by respiration 1 ANIMAL HEAT. 33. t,ral respiration; and, secondly, because it is difficult tc conceive why the formation of carbonic acid, which uniformly gives rise to increase of temperature in other cases, should not be attended within the animal body with similar results It may hence be inferred, that this is one of the sources of animal heat." In respect to the influence of the nervous system over the development of animal temperature, there is no doubt but considerable effects may be safely attributed to this cause. But in what manner the heat is evolved, is perhaps uncertain. In conclusion, we may remark, that the subject of animal temperature has excited the attention, and has been made an object of experiment and research among philosophers and physiologists in all ages, and that many ingenious and some plausible theories have been invented and detailed, in order to give satisfactory explanation of its cause. The theory of Dr. Crawford, among these, wa3 perhaps the most plausi ble, and certainly the most philosophical and beautiful. Bu we have seen, that the leading facts on which it was found ed, have been proved by his successors not to be true, ana therefore the theory itself cannot be maintained. That the oxygen of the atmosphere is one of the causes of animal heat cannot be doubted, from the facts, that no animal can live without it, and that the heat of animals is in some proportion to the quantity of this principle consumed. But as this principle can have no effect, except through the lungs, if it is admitted that heat is evolved by its action there, there is still much difficulty in explaining either why the lungs are not constantly at a higher temperature than the other parts of the system, or if they were, how the heat could be conveyed to the other parts, from its fountain. On the whole, it appears that the cause of animal heat is one of the arcana of nature, into which man has not yet been permitted to look, and therefore, we must be contented at present to attribute it to the vital principle. Ia it probab'e that the nerves affect the tempeiature of the animal 1 What is said in conclusion on mis subject ? Has there been a.iy theory proposed which accounts satisfactorily for the cause of animal heat? To what is it said must we at ?««nt attribute the cause of anneal heat ? 332 ANALYSIS OF GASES PART IV. ANALYTICAL CHEMISTRY. To enter into a detailed account of experimental and ana tytical chemistry, is altogether inconsistent with the design and limits of the present work. My sole object in this cle oartment is to give a few concise directions /or conducting some of the more common analytical processes; and in or aer to render them more generally useful, I shall give exam pies of the analysis of mixed gases, of minerals, and of mine ral water?. ANALYSIS OF MIXED gIsES. Analysis of air, or of gaseous mixtures containing oxygen Of the various processes by which oxygen gas may be with drawn from gaseous mixtures, and its quantity determined, none are so convenient and precise as the method by means of hydrogen gas. In performing this analysis, a portion ol atmospheric air is carefully measured in a graduated tube, and mixed with a quantity of hydrogen, which is rather more than sufficient for uniting with all the oxygen present. The mixture is tnen introduced into a strong glass tube called Volta's eudiometer, and is inflamed by the electric spark, the aperture of the tube being closed by the thumb at the moment of detonation. The total diminution in volume, divided by three, indicates the quantity of oxygen originally contain ed in the mixture. This operation may be performed in a trough either of water or mercury. Instead of electricity, spongy platinum (page 126) may be employed for causing the union of oxygen and hydrogen gases; and, while its indications are very precise, it has the advantage of producing the effect gradually and without detonation. The most convenient mode of employing it with this intention is the following. A mixutre of spongy platinum and pipe-clay, in the proportion of about three parts of the former to one of the latter, is made into a paste with water, and then rolled between the fingers into a globular form. In order to preserve the spongy texture of the platinum, a little muriate of ammonia is mixed with the paste; and the ball has become dry, it is cautiously ignited at the flame of a spirit-lamp. The sal-ammoniac, escaping from all parts of the mass, gives it a degree of porosity which is peculiarly favorable to its action. The ball, thus preparea, should be protected from dust, and be heated to redness just 333 ANALYSIS OF GASES. before being used. To insure accuracy, the hydrogen employed should be kept over mercury for a few hours in contact with a spongy platinumball and a piece of caustic potash. The first deprives it of traces of oxygen which it commonly contains, and the second of moisture and sulphuretted hydrogen. The analysis must be performed in a mercurial trough. The time required for completely removing the oxygen depends on the diameter of the tube. If the mixture is contained in a very narrow tube, the diminution does not arrive at its full extent in less than twenty minutes or half an hour; while in a vessel of an inch in diameter me effect is complete in the course of five minutes. Mode of determining ihe quantity of nitrogen in gaseous mixtures. —As atmospheric air, which has been deprived of moisture and carbonic acid, consists of oxygen and nitrogen only, the proportion of the latter is of course knoAvn as soon as that of the former is determined. The only method, indeed, by which chemists are enabled to estimate the quantity of this gas, is by withdrawing the other gaseous substances with which the nitrogen is mixed. Mode of determining the quantity of carbonic acid in gaseous mixtures. —When carbonic acid is the only acid gas which is present, as happens in amospheric air, in the ultimate analysis of organic compounds, and in most other analogous researches, the process for determining the quantity of carbonic acid is exceedingly simple; for it consists merely in absorbing that gas by lime water or a solution of caustic potash. This is easily done in the course of a few minutes in an ordinary graduated tube; or it may be effected almost instantaneously by agitating the gaseous mixture with the alkaline solution in Hope's eudiometer. This apparatus is formed of two parts; a bottle capable of containing about twenty drachms of fluid, and furnished with a well-ground stopper; and a tube of the capacity of one cubic inch, divided into 100 equal parts, and accurately fitted by grinding to the neck of the bottle. The tube, full of gas, is fixed into the bottle previously filled with lime water, and its contents '.re briskly agitated. The stopper is then withdrawn under Avater, when a portion of liquid rushes into the tube, supplying the place of the gas Avhich has disappeared; and the process is afterwards repeated, as long as any absorption ensues. The eudiometer of Dr. Hope Avas originally designed for analyzing air or other similar mixtures, the bottle being fi' H «ed 334 ANALYSIS OF GASE3. with a solution of the hydro-sulphuret of potassa or Line, 01 some liquid capable of absorbing oxygen. To th« employment of this apparatus it has been objected, that the absorption is rendered slow by the partial vacunm which is continually taking place within it, an inconvenience particularly felt towards the close of the process, in consequence of the eudiometric liquor being diluted by the admission of water. To remedy this defect, Ur. Henry has substituted a bottle of elas tic gum for that of glass, by which contrivance no vacuum can occur. From the improved method of analyzing air, however, this instrument is now rarely employed in eudiometry; but it may be used with advantage for absorbing carbonic acid of similar gases, and is particularly useful for the purpose of demonstration. Mode of analyzing mixtures of hydrogen and other inflammable gases. —When hydrogen is mixed with nitrogen, air, or other similar gaseous mixtures, its quantity is easily ascertained by causing it to combine with oxygen either by means of platinum sponge or the electric spark. If, instead of hydrogen, any other combustible substance, such as carbonic oxide, light carburetted hydrogen, or olefiant gas, is mixed with nitrogen, the analysis is easily affected by adding a sufficient quantity of oxygen, and detonating the mixture by electricity. The diminution in volume indicates the quantity of hydrogen contained in the gas. and from the carbonic acid, which may then be removed by an alkali, the quantity of carbon is inferred. vVhen olefiant gas is mixed with other inflammable gases, its quantity is easily determined by an elegant and simple process proposed by Dr. Henry. It consists in mixing 100 measures, or any convenient quantity of the gaseous mixture, with an equal volume of chlorine in a vessel covered with a piece of cloth or paper, so as to protect it from light; and after an interval of about ten minutes, the excess of chlorine is removed by lime water or potassa. The loss experienced by the gas to be analyzed, indicates the exact quantity of olefiant gas which it had contained. In mixtures of hydrogen, carburetted hydrogen, and carbonic oxide, the analytic process is exceedingly difficult and complicated, and requires all the resources of the most refined chemical knowledge, and all the address of an experienced analyst. The most recent information on this subject will be found in Dr. Henry's Essay in the Philosophica Transactions for 1824. 335 ANALYSIS OF MINERALS. ANALYSIS OF MINERALS As the very extensive nature of this departmen* of analytical chemistry renders a selection necessary, I shall confine my remarks solely to the analysis of those earthy minerals with which the beginner usually commences his labours. The most common constituents of these compounds are silica, alumina, iron, manganese, lime, magnesia, potassa, soda, and the carbonic and sulphuric acids; and I shall, therefore, endeavor to give short directions for determining the quantity of each of these substances. In attempting to separate two or more fixed principles from each other, the first object of the analytical chemist is to bring them into a state of solution. If they are soluble in water, this fluid is preferred to every other menstruum, but if not, an acid or any convenient solvent may be employed. In many instances, however, the substance to be analyzed resists the action even of the acids, and in that case, the following method is adopted :—The compound is first crushed, by means of a hammer, or a steel mortar, and is afterwards reduced to an impalpable powder in a mortar of agate; it is then intimately mixed with three, four, or more times its weight of potassa, soda, baryta, or their carbonates ; and lastly, the mixture is exposed in a crucible of silver or platinum to a strong heat. During the operation, the alkali combines with one or more of the constituents of the mineral; and, consequently, its elements being disunited, it no longer resists the action of the acids. Analysis of Marble or Carbonate of Lime. —This analysis is easily made by exposing a known quantity of marble, for about half an hour, to a full white heat by which means the carbonic acid gas is entirely expelled, so that by the loss in weight the quantity of each ingredient, supposing the marble to have been pure, is at once determined. In order to ascertain that the whole loss is owing to the escape of carbonic acid, the quality of this gas may be determined by a comparative analysis. Into a small flask, containing muriatic acid, diluted with two or thrte parts of water, a known quantity o* marble is gradually added, the flask being inclined to one side in order to prevent the fluid from being flung out of the vessel during the effervescence. The diminution in weigh; experienced by the flask and its contents, indicates the quantity of carbonic acid which has been expelled. Should the carbonate suffer a greater loss in the fire thac 336 ANALYSIS OF MINERALS. when decomposed by an acid, it will most p- 'jably be found to contain water. This may be ascertained by heating a piece of it to redness, in a glass tube, the sides of which will be bedewed with moisture, if water is present. Its quantity may be determined by causing the watery vapour to pass through a weighed tube filled with fragments of the chloride of calcium, (muriate of lime,) by which the moisture is absorbed. Separation of Lime and Magnesia. —The more common kinds of carbonate of lime frequently contain traces of silicious and aluminous earths, in consequence of which, they are not completely dissolved in dilute muriatic acid. A very frequent source of impurity is the carbonate of magnesia, which is often present in such quantity that it forms a peculiar compound called magnesian limestone. The analysis of this substance, so far as respects carbonic acid, is the same as that of marble. The separation of the two earths may be conveniently effected in the following manner. The solution of the mineral in muriatic acid is evaporated to perfect dryness, in a flat dish or capsule of porcelain, and after re-dissolving the residuum, in a moderate quantity of distilled water, a solution of the oxalate of ammonia is added as long as a precipitate ensues. The oxalate of lime is then allowed to subside, collected on a filter, converted into quicklime by a white heat, and weighed; or the oxalate may be decomposed by a red heat, the carbonate resolved into the sulphate of lime by sulphuric acid, and the excess of acid expelled by a temperature of ignition. To the filtered liquid containing the magnesia, an excess of carbonate of ammonia, and then phosphate of soda is added, when the magnesia in the form of the ammoniaco-phosphate is precipitated. Of this precipitate heated to redness, 100 parts correspond to 40 of pure magnesia. (Murray.) Earthy Sulphates. —The most abundant of the earthy sulphates, is that of lime. The analysis of this compound is easily effected. By boiling it for fifteen or twenty minutes with a solution of twice its weight of the carbonate of soda f double decomposition ensues; and the carbonate of lime after being collected on a filter and washed with hot water, is either heated to low redness, to expel the water, and weighed or at once reduced to quicklime by a white heat. Of the dr s 1 carbonate, fifty parts correspond to twenty-eight of lime. The alkaline solution is acidulated with muriatic acid, and the sulphuric acid thrown down by the muriate of baryta. 337 ANALYSIS OF MINERALS. From the sulphate of this earth, collected and dried at a rea heat, the quantity of acid may easily be estimated. The method of analyzing the sulphates of strontia and baryta is somewhat different. As these salts are difficult of decomposition in the moist way, the following process is adopted. The sulphate, in fine powder, is mixed with three times its weight of the carbonate of soda, and the mixture is heated to redness in a platina crucible, for the space of half an hour. The ignited mass is then digested in hot water, and the insoluble earthy carbonate collected on a filter. The other parts of the process are the same as the foregoing. Mode of analyzing compounds of Silica, Alumina, and Iron. Minerals, thus constituted, are decomposed by an alkaline carbonate, potash, or soda, at a red heat, in the same manner as the sulphate of baryta. The mixture is afterwards digested in dilute muriatic acid, by which means all the ingredients of the mineral, if the decomposition is complete, are dissolved. The solution is next evaporated to dryness, the heat being carefully regulated towards the close of the process, in order to prevent any of the chloride of iron, the volatility of which is considerable, from being dissipated in vapor. By this operation, the silica, though previously held in solution by the acid, is entirely deprived of its solubility; so that on digesting the dry mass in water, acidulated with muriatic acid, the alumina and iron are taken up, and the silica is left in a state of purity. The siliceous earth, after subsiding, is collected on a filter, carefully edulcorated, heated to redness, and weighed. To the clear liquid containing iron and alumina, a considerable excess of a solution of pure potassa is added; so as not only to throw down these oxides, but to dissolve the alumina. The peroxide of iron is then collected on a filter, edulcorated carefully until the washings cease to have an alkaline reaction, and is well dried on a sand bath. Of this hydrated peroxide, forty-nine parts contain forty of the anhydrous peroxide of iron. But the most accurate mode of determining its quantity is by expelling the water by a red heat. This operation, however, should be done with care; since any adhering particles of paper, or other combustible matter, would bring the iron into the state of black oxide, a change which is known to have occurred by the iron being attracted by a magnet. To procure the alumina, the liquid in which it is dissolved is boiled with sal-ammoniac, when the muriatic acid unites 29 338 ANALYSIS OF MINERALS. with the potassa, the volatile alkali is dissipated in vapor. ar.J the alumina subsides. As soon as the solution is thus rendered neutral, the hydrous alumina is collected on a filter, dried by exposure to a white heat, and quickly weighed after removal from the fire. Separation of Iron and Manganese. —A compound of these metals or their oxide may be dissolved in muriatic acid. If the iron is in a large proportion compared with the manganese, the following process may be adopted with advantage. To the cold solution, considerably diluted with water, and acidulated with muriatic acid, carbonate of soda is gradually added, and the liquid is briskly stirred with a glass rod, during the effervescence, in order that it may become highly charged with carbonic acid. By neutralizing the solution in this manner, it at length attains a point at which the peroxide ol iron is entirely deposited, leaving the liquid colourless ; while the manganese, by aid of the free carbonic acid, is kept in solution. The iron, after subsiding, is collected on a filter, and its quantity determined in the usual manner. The filtered liquid is then boiled with an excess of the carbonate ol soda; and the precipitated carbonate of manganese is collected, heated to low redness in an open crucible, by which it is converted into the broAvn oxide, and weighed. This method is one of some delicacy; but in skilfui hands, it affords a very accurate result. It may also be employed for separating iron from magnesia and lime as well as from manganese. But if the proportion of iron is small, compared with that of manganese, the best mode of separating it is by the succinate of ammonia or soda, prepared by neutralizing a solution of succinc acid with either of those alkalies. That this process should succeed, it is necessary that the iron be wholly in the state of peroxide, that the solution be exactly neutral, which may easily be insured, by the cautious use of ammonia, and that the reddish-brown coloured succinate of iron be washed with cold water. Of this succinate, well dried at a temperature of 212° F., 90 parts correspond to 40 of the peroxide. From the filtered liquid, the manganese may be precipitated at a boiling temperature by carbonate of soda, and its quantity determined in the way above mentioned. The benzoate may be substituted for the succinate of ammonia in the preceding process. It may be stated as a general rule, that whenever it is in.ended to precipitate iron by means of the alkalies, the succinates, or benzoates, it is essential that this metal be in the ANALYSIS OF MINERALS. 339 n.iximum of oxidation. It is easily brought into this stale by digestion with a little nitric acid. Separation of manganese from lime and magnesia. —I r the quantity of the former be proportionally small, it is precipitated as a sulphuret by the hydrosulphuret of ammonia or potassa. This sulphuret is then dissolved in muriatic acid, and the manganese thrown down as usual by means of an alkali. But if the manganese be the chief ingredient, the best method is to precipitate it at once, together with the two earths, by a fixed alkaline carbonate at a boiling temperature. The precipitate, after being exposed to a low red heat and weighed, is put into cold water, acidulated with a drop or two of nitric acid, when the lime and magnesia will be slowly dissolved with effervescence. Should a trace of the manganese be likewise taken up, it may easily be thrown down by the hydrosulphuret of ammonia. Mode of analyzing an earthy mineral containing silica, iron, alumina, manganese, lime and magnesia. —The mineral, reduced to a fine powder, is ignited with three or four times its weight of the carbonate of potassa or soda, the mass is taken up in dilute muriatic acid, and the silica separated in the way already described. To the solution, thus freed from silica and duly acidulated, carbonate of soda is gradually added, so as to charge the liquid with carbonic acid, as in the analysis of iron and manganese. In this manner the iron and alumina are alone precipitated, substances which may be separated from each other by means of pure potassa. The manganese, lime, and magnesia, may be determined by the processes already described. Analysis of minerals containing a fixed alkali. —When the object is to determine the quantity of a fixed alkali, such as potassa or soda, it is necessary to abstain from the employment of these reagents in the analysis itself; and the beginner will do well to devote his attention to the alkaline ingredients only. On this supposition, he will proceed in the following manner. The mineral is reduced to a very fine powder, mixed intimately with six times its weight of the artificial carbonate of baryta and exposed for an hour to a white heat. The ignited mass is dissolved in dilute muriatic acid, and the soution evaporated to perfect dryness. The soluble parts are .aken up in hot water ; an excess of the carbonate of ammonia is added; and the insoluble matters, consisting of silica, carbonate of baryta, and all the constituents of the mineral, excepting the fixed alkali, are collected on a filter. The 340 ANALYSIS OF MINERALS. clear solution is evaporated to dryness in a porcelain capsule, and the dry mass is heated to redness in a crucible of platinum, in order to expel the salts of ammonia. The residue is the chloride of potassium or sodium. In this analysis, it generally happens that traces of manganese, and sometimes of iron, escape precipitation in the first part of the process; and, in that case, they should be thrown down by the hydrosulphuret of ammonia. If neither lime nor magnesia is present, the alumina, iron, and manganese, may be separated by pure ammonia, and the baryta subsequently removed by the carbonate of that alkali. By this method the carbonate of baryta is recovered in a pure state, and may be reserved for another analysis. The baryta may also be thrown down as a sulphate by sulphuric acid, in which case, the soda or potassa is procured in combination with that acid. The analysis is attended with considerable inconvenience, when magnesia happens to be present, because this earth is not completely precipitated, either by ammonia or its carbonate ; and, therefore, some of it remains with the fixed alkali. The best mode with which I am acquainted for effecting its separation, is the following. The carbonate of ammonia is first added, and the phosphoric acid is dropped into the liquid, until all the magnesia is thrown down in the form ol the ammoniaco-magnesian phosphate. The excess of phosphoric acid is afterwards removed by the acetate of lead, and thai of lead by sulphuretted hydrogen. The acetate of the alkali is then brought to dryness, ignited, and by the addition of sulphate of ammonia is converted into a sulphate. In the preceding account, several operations have been alluded to, which, from their importance, deserve more particular mention. The process of filtering, for example, is one on which the success of analysis materially depends. Filtration is effected by means of a glass funnel, into which a filter, made of white bibulous paper, is inserted. For researches of delicacy, the filter, before being used, is macerated for a day or two in water, acidulated with nitric acid, in order to dissolve lime and other substances contained in common paper, and it £ afterwards washed with hot water, till every trace of acid is removed. It is next dried at 212°, or any fixed temperature insufficient to decompose it, and then carefully weighed, the weight being marked upon it with a pencil. As dry paper absorbs hygrometic moisture rapidly from the atmosphere, the filter, while being weighed, should be inclosed in a light ANALYSIS OF MINERAL WATERS. 341 oox made for the purpose. When a precipitate is collected on a filter, it is washed with pure water until every trace of the original liquid is removed. It is subsequently dried and weighed as before, and the weight of ihe paper subtracted from the combined weight of the filter and precipitate. The trouble of weighing the filter may sometimes be dispense! with. Some substances, such as silica, alumina, and lime, which are not decomposed when heated with combustible matter, may be put into a crucible while yet contained in the filter, the paper being set on fire before it is placed in the furnace. In these instances, the ash from the paper, thb average weight of which is determined by previous experiments, must be subtracted from the Aveight of the heated mass. The tests commonly employed in ascertaining the acidity or alkalinity of liquids are litmus and turmeric paper. The former is made by digesting litmus, reduced to a fine powder, in a small quantity of Avater, and painting with it white paper which is free from alum. The turmeric paper is made in a similar manner ; but the most con\ _ enient test of alkalinity is litmus paper reddened by a dilute acid. ANALYSIS OF MINERAL AVATERS. Rain AA r ater collected in clean vessels in the country, or freshly fallen snoAV, when melted, affords the purest kind of AA r ater Avhich can be procured without having recourse to distillation. The water obtained from these sources, however, is not absolutely pure, but contains a portion of carbonic acid and air, absorbed from the atmosphere. It is remarkable that this air is very rich in oxygen. That procured from snoAv-Avater by boiling, was found by Gay Lussac and Humboldt to contain 34.8 and that from rain Avater 32 per cent, of oxygen gas. From the powerfully solvent properties of water, this fluid no sooner reaches the ground and percolates through the soil, than it dissolves some of the substances which it meets with in its passage. Under common circumstances, it takes up so small a portion of foreign matter that its sensible properties are not materially affected, and in this state it gives lise to spring, well, and river Avater. Sometimes, on the contrary, it becomes so strongly impregnated with saline and other substances, that it acquires a peculiar flavor, and is thus rendered unfit for domestic uses. It is then known by the name of mirieral 'water. 29* 342 ANALYSIS OF MINERAL WATERS. The composition of spring water is dependent on the natura of the soil through which it flows. If it has filtered through primitive strata, such as quartz rock, granite, and the like, it is in general very pure ; but if it meets with limestone or gypsum in its passage, a portion of these salts is dissolved, and communicates the property called hardness. Hard water is characterized by decomposing soap, the lime of the former yielding an insoluble compound with the oil of the latter If this defect is owing to the presence of the carbonate of lime, it is easily remedied by boiling, when free carbonic acid is expelled, and the insoluble carbonic of lime subsides. If sulphate of lime is present, the addition of a little carbonate of soda, by precipitating the lime, converts the hard into soft water. Besides these ingredients, the muriates of lime and soda are frequently contained in spring water. Spring water in consequence of its saline impregnation, is frequently unfit for chemical purposes, and on these occasions distilled water is employed. Distillation may be performed on a small scale by means of a retort, in the body of which water is made-to boil, while the condensed vapor is received in a glass flask, called a recipient, which is adapted to its beak or open extremity. This process is more conveniently conducted, however, by means of a still. The different kinds of mineral water may be conveniently arranged for the purpose of description in the four divisions of carbonated, chalybeate, sulphurous, and saline springs. The carbonated springs of which those of Seltzer, Spa, Pyrmont, Ballston and Carsbad, are the most celebrated, are distinguished by containing a considerable quantity of free carbonic acid, owing to the escape of which they sparkle when poured from one vessel into another. They commucate a red tint to litmus paper before, but not after being boiled, and the redness disappears on exposure to the air. Mixed with a sufficient quantity of lime water, they become turbid from the deposition of carbonate of lime. They frequently contain the carbonate of lime, magnesia, and iron, in consequence of the facility with which these salts are dissolved by water charged with carbonic acid. The best mode of determining the quantity of carbonic acid is by heating a portion of the water in a flask, and receiving the carbonic acid by means of a bent tube, in a graduated iai filled with mercury. The chalybeate waters are characterized by a strong styptic inky taste, and by striking a black colour with the infu- 343 ANALYSIS OF MINERAL WATERS. sion of Gallnuts. The iron is sometimes combined with the muriatic or sulphuric acid ; but most frequently it is in the form of a car bonate of the protoxide, held in solution by free carbonic acid. On exposure to the air, the protoxide is oxidized, and the hydrated peroxide subsides, causing the ochreous deposit, so commonly observed in the vicinity of chaly beate springs. To ascertain the quantity of iron contained in a mineral water, a known weight of it is concentrated by evaporation, and the iron brought to the state of peroxide by means of nitric acid. The peroxide is then precipitated by an alkali and weighed; and if lime and magnesia are present, it may be separated from those earths by the process described in the last section. Chalybeate waters are by no means uncommon ; but the most noted in Britain are those of Tunbridge, Cheltenham, and Brighton. The Bath water also contains a small quantity of iron. The sulphurous waters, of which the springs of Aix la Chapelle, Harrowgate, and Moffat afford examples, contain sulphuretted hydrogen, and are easily recognized by their odor, and by causing a brown precipitate with a salt of lead or silver. The gas is readily expelled by boiling, and its quantity may be inferred by transmitting it through a solution of the acetate of lead, and weighing the sulphuret which is generated. Those mineral springs are called saline Avhich do not belong to either of the preceding divisions. The salts which are most frequently contained in these waters, are the sulphates, muriates, and corbonates of lime, magnesia, and soda. Potassa sometimes exists in thern, and Berzelius has found lithia in the spring at Carlsbad. It has lately been discovered that the presence of hydriodic acid in small quantity is not unfrequent. As examples of saline water may be enumerated the springs of Epsom, Cheltenham, Bath, Bristol, Bareges, Buxton, Pitcaithly, Toeplitz, Ballston, and Saratoga. The first object in examining a saline spring is to determine the nature of its ingredients. Muriatic acid is detected by the nitrate of silver, and the sulphuric acid by muriate 01 baryta; and if an alkaline carbonate be present, the precipitate occasioned by either of these tests will contain a carbonate of silver or baryta. The presence of lime and magnesia may be discovered, the former by the oxylate of lime, and the latter by carbonate of ammonia and phosphoric acid. Po- 344 ANALYSIS OF MINERAL WATERS. tassa is known by the action of the muriate of platinum. T« detect soda, the water should be evaporated to dryness, the deliquescent salts removed by alcohol, and the matter insoluble in that menstruum taken up by a small quantity of water, and be allowed to crystallize by spontaneous evaporation The salt of soda may then be recognized by the rich yellowcolour which it communicates to flame. If the presence of hydriodic acid is suspected, the solution is brought to dryness, the soluble parts dissolved in two or three drachms of a cold solution of starch, and strong sulphuric acid gradually added. Having thus ascertained the nature of the saline ingredients, their quantity may be determined by evaporating a pint of water to dryness, heating to low redress, and weighing the residue. In order to make an exact analysis, a given quantity of the mineral water is concentrated in an evaporating basin as far as can be done without causing either precipitation or crystallization, and the residual liquid is divided into two equal parts. From one portion the sulphuric and carbonic acids are thrown down by the nitrate of baryta, and after collecting the precipitate on a filter, the muriatic acid is precipitated by the nitrate of silver. The mixed sulphate and carbonate is exposed to a low red heat, and weighed ; and the latter is then dissolved by dilute muriatic acid, and its quantity determined by weighing the sulphate. The chloride of silver, of which 146 parts correspond to 37 of muriatic acid, is fused in a platinum spoon or crucible, in order to render it quite free from moisture. To the other half of the concentrated mineral water, oxalate of lime is ad- for the purpose of precipitating the lime ; and the magnesia is afterwards thrown down as the ammoniaco-phosphate, bv means of the carbonate of ammonia and phosphoric acid. Having thus determined the weight of each of the fixed ingredients, excepting the soda, the ioss of course gives the quantity of that alkali; or it may be procured in a separate stale by the process described in the foregoing section. The individual constituent of the water being known, it remains to determine the state in which they were originally combined. In a mineral water containing sulphuric and muriatic acids, lime, and soda, it is obvious that three cases are possible. The liquid may contain sulphate of lime and muriate of soda, muriate of lime and sulphate of soda, or each arid may be distributed between both the bases. It was at one time supposed that the lime must be in combination with 345 ANALYSIS OF MINERAL WATERS. sulphuric acid, because the sulphate of that earth is left when the water is evaporated to dryness. This, however, by no means follows. In whatever state the lime may exist in the original spring, gypsum will be generated as soon as the concentration reaches that degree at which sulphate of lime cannot be held in solution. The late Dr. Murray,* who treated this question with much sagacity, observes, that some mineral waters, which (jpntain the four principles above mentioned, possess higher medicinal virtues than can be justly ascribed to the presence of sulphate of lime and muriate of soda. He advances the opinion, that alkaline bases are united in mineral waters with those acids with which they form the most soluble compounds, and that the insoluble salts obtained by evaporation are merely products. He therefore proposes to arrange the substances determined by analysis according to this supposition. To this practice there is no objection ; but it is probable that each acid is rather distributed between several bases, than combined exclusively with one of them. Sea water may be regarded as one of the saline mineral waters. Its taste is disagreeably bitter and saline, and its fixed constituents amount to about three per cent. Its specific gravity varies from 1.0269 to 1.0285 ; and it freezes at about 28.5° F. According to the analysis of Dr. Murray, 10,000 parts of water from the Firth of Forth contain 220.01 parts of common salt, 33.16 of sulphate of soda, 42.08 of muriate of magnesia, and 7.84 of muriate of lime. Dr. Wollaston has detected potassa in sea water, and it likewise contains small quantities of the hydriodic and iodic and hydrobromic acids. The water of the Dead Sea has a far stronger salino impregnation than sea water, containing one fourth of its weight jf solid matter. It has a peculiarly bitter, saline, and pungent taste, and its specific gravity is 1.211. According to the analysis of Dr. Marcet, 100 parts of it are composed of muriate of magnesia 10.216, muriate of soda 10.36, muriate of lime 3.92, and sulphate of lime 0.054. In the river Jordan, which flows into the Dead Sea, Dr. Marcet discovered the same principles as in the lake itself.— Turner's Chemistry. * Philosophical Transactions of Edinburgh, vii. 346 CHEMICAL MINERALOGY PART V. CHEMjjpAL MINERALOGY. By Chemical Mineralogy, we mean the application ol th« principles of chemistry to the examination of mineral substances. In this short treatise on the subject, we shall be confined chiefly to the examination of the most common mineral bodies, and hope to give such plain directions as will enable the student to assay the most important metalic ores of our country. Instruments and preparatory steps necessary for the analysis of mat all ic ores. —Before we proceed to show the methods by which ores are analysed, it will be necessary to describe a few simple instruments which are required for this purpose ; and also to point out what preliminary steps are necessary in order to prepare the ores for analysis. 1. A Balance, or pair of small scales, in order to ascertain the weight of the ore to be examined. Also to take the specific gravities of minerals. The latter may be done by the method and instrument described at p. 107 of this volume. 2. Blow-pipe. For a description of this, and the manner of using it, see p. 103. 3. Supports. In order to use the blow-pipe, it is necessa ry to employ a support, on which the substance to be heat ed, rests. In ordinary cases, a piece of charcoal answers for this purpose, but in others it is necessary to use a small platina spoon, or piece of platina foil, instead of the charcoal. 4. Magnet. This is used in order to ascertain whether the ore contains metallic iron. The best form is that of a small needle suspended on a fine point of copper, or brass The ore should be tried both before and after being heated by the blow-pipe ; because, although the ore may conttin iron it may not be magnetic until it is reduced. 5. Mortar and Pestle. A common wedgewood mortar is sufficient for most purposes. All substances to be analysed must be levigated as finely as possible. In most instances, the action of the solvents will he incomplete without this preparation 347 CHEMICAL MINERALOGY. t). A Flask for digesting the ore after levigation, is necessary. This has already been described at p. 102. 7. Test Tubes. These are of glass, five, or six inches long, and of various sizes. They may be made by taking pieces of glass tube, already broken, and closing them at one end by means of the blow-pipe, or alcohol lamp. They arc employed to subject small portions of the clear filtered solution of any substance to the action of various tests, and are among the indispensable instruments of analysis. 8. Glass plates. In many instances, when the quantity of matter is small, a drop in solution, placed on a glass plate, and then the test applied by means of a point of glass, or piece of platina wire, will decide all the operator wishes to know before he proceeds to further trials. Where the solution contains neutral, or other salts, by allowing the drop to dry we may decide what the solution is, by the forms of the crystals on the glass. (For crystalline forms, see the authors Mineralogy.) Processes necessary before the chemical examination of metallic substances. Roasting. This consists in keeping the ore at a moderate heat for a considerable length of time, in order to drive off all the volatile matter it contains, as water, carbonic acid, sulphur, &c. Roasting in the large way is performed by placing alternate layers of the ore, and wood or coal, in a chimney erected for this purpose, and then setting the fuel on fire at the bottom of the pile. Some ores consume days, or weeks, in this process. In the small way, what is called a muffle, or a common crucible, will answer all purposes, first breaking the ore into small fragments. A dull red heat is a sufficient temperature for most ores. Reduction. That is, reducing the ore to its metallic state, is generally performed in the small ways by means of powdered charcoal, or black flux, in a crucible, or black lead pot. Where the compound is the oxide of a metal, the charcoal at a high degree of heat, absorbs the oxygen from it, and thus the metal is revived, or reduced to its pure metallic form. For this purpose, the ore, as well as the charcoal, must be in powder, and mixed together, and the heat, in most cases, raised to whiteness. Cupellation. This process is applicable only to gold and silver. When either of these metals are in an impure 348 CHEMICAL MINERALOGY state, they are further alloyed with two or three times their weight, of lead, by melting them together. This mass is then placed in a kind of dish made of bone ashes, and in this state subjected to a sufficient heat to melt it, when the lead, together with the impurities, sink down into the cupel, and thus leave the gold or silver pure in the dish. Muffle. This is a small pot of clay arched over the top in the form of an oven, the upper part of which has several Fig. 68. apertures near the bottom a, to admit the air. Fig. 68. In this the cupel is placed by the door b, before the heat is applied. The muffle is then surrounded with coal, and the heat raised to whiteness. The use of the muffle is to protect the contents of the cupel from the contact of the coal, and other impurities. Fluxing. This process is necessary when the ore contains any considerable quantity of silicious, or stony matter. The chemical action concerned in the process, consists in the union of the silicious matter of the ore, with the flux employed. As an example, mix together a given quantity of lead or iron ore, with four times its weight of caustic potash, the ore being pulverized, and put the mass into a crucible of silver, and having put on the cover, subject it to a low red heat for half an hour. Then remove the crucible and pour in water, which will dissolve the potash which has combined with the silex. The water being carefully decanted, and the process repeated with hot water, the silex and other earthy matters will be washed away, and the metal left in the crucible. In most instances, it is necessary to grind the mass in a mortar, and wash it through a filter before the potash and metal are entirely separated. The ore which remains on the filter then becomes in a state to be dissolved in an acid, and is to be treated according to circumstances. Fusion. This is the conversion of solids into fluids by heat. It is usually called melting. Fusion is effected in different ways, according to the kind of ore to be acted upon, or its quantity. Minute fragments are melted by the blow-pipe, while for larger quantities the crucible, and forge, ">r furnace, are employed. Many substances which are inidsible alone, readily enter into fusion when surrounded with another substance which acts upon it chemically, or which merely serves to main the heat. 349 ANALYSIS OF METALLIC SUBSTANCES- In making - experiments on ores with the blow-pipe, tne glass of borax is commonly employed. This is the common borate of soda, previously exposed to such a degree ot heat as to drive off the water of crystallization. What is termed the black flux is also much employed to assist in melting refractory bodies. This is made by mixing two parts of the cream of tartar with one part of nitre, and deflagrating the mixture in a ladle, or other vessel. When the ores of metals are fused in a crucible, the pure metal is found at the bottom, in the form of a button. Elutriation. By this term is meant the repeated washing of any substance, as a precipitate, in order to free it from any remains of its solvent. In the analysis of ores, these washings must, in certain cases, be retained, and added to the filtered solution. When this is important, it will be mentioned when the description of the analysis is given. Evaporation. This is a process by which the fluid, or volatile parts of a solution are separated from those which are solid.. In some instances heat is employed for this purpose, while in others the process is suffered to go on by the natural action of the atmosphere. When the object is merely to find the weight of the solid portion of the mixture, or compound, a gentle heat facilitates the process, but when we wish to obtain fine crystals from a saline solution, the action of the atmosphere only is much the best. In either case, shallow dishes of porcelain, or wedgevvood ware, called evaporating dishes, are commonly used, though common white earthern ware dishes answer most purposes. ANALYSIS OF METALLIC SUBSTANCES. The tests, and re-agents required for the analysis of each metallic body, will be mentioned in connection with their uses, and in describing the several processes by which each metal, or its alloy is to be detected. Gold. This metal is always found in the reguline, or native state, but is seldom or never found perfectly pure, being 30 350 ANALYSIS OF METALLIC SUBSTANCES. alloyed with various metals, but most commonly with silver and copper. Tests for Gold, Proto-sulphate of Iron gives Metallic Gold. . Recent muriate of Tin " Purple precipitate. Potash and Soda " Yellow du. Hydro-sulphurets " Black do. Tests, or re-agents, are substances generally in the liquid form, by which certain other substances are indicated by the color, or appearance of the precipitates which the mutual action of the two bodies produce. Thus a solution of iron is instantly turned black by an infusion of nut galls. This infusion is therefore a test for the presence of iron in solution, and the muriate of tin is a test for gold, by throwing down a purple precipitate, and so of the other re-agents. Assay. Assay, or trial, is the means by which the quantity of precious or valuable metals is found to exist in a small quantity of ore, or alloyed metal. The practical difference between the assay and the analysis of an ore, consists in this : The analysis determines the nature and quantity of all the substances which the ore, or metallic mixture, contains; whereas the object of the assay is to find how much of the particular metal in question is contained in a given quantity of the compound under examination. Thus in the assay of gold, or silver, the baser metals they contain, are considered of no value, the object of trial on a small quantity being merely to find the per centage of precious metal contained in the whole, of which this is a sample. Assay of Gold. There are two or three methods by which the quantity of gold dispersed through the stony matrix in which it is found, is determined. The first is, by dissolving the metal in its proper solvent, then by a precipitate to throw the metal down, and afterwards melt it in a crucible. This is called assaying in the moist way. The other is, to melt the gold with lead, in a cupel, when the lead, combining with the other metals the gold contained, sinks into the substance of the cupel, leaving the gold 351 ANALYSIS OF METALLIC SUBSTANCES. on the surface. This is called assaying ii the dry way, or hy cupellation. Gold dust is assayed by this method. The last method is by amalgamation with quicksilver, and afterwards driving off this by heat, and thus leaving the gold in a nearly pure state. The assay in the moist way, the only one it is nesessary here to describe, is extremely simple and easily performed. Take a certain quantity of the stony matter containing the gold, say 400 grains, and having reduced it to a fine powder, mix it intimately with four times its weight of dry caustic potash, to which a little borax may be adder Place this mixture in a crucible, (this should be of silver, and expose it to a dull red heat for an hour. In most cases at the end of this time, the metal will have melted and run into the bottom of the crucible. Sometimes, however, from the imperfect fusion of the mass, or the small quantity of metal it contains, the metal is found in globules dispersed in it, and not united in a button at the bottom. In this case, the whole mass, crucible and all, may be placed in an iron vessel and boiled, until the flux is entirely dissolved, and thrown away. The small globules, together with the other matter which the water did not dissolve, may now be digested with eight or ten times its weight of nitro-muriatic acid, in a moderate heat, until the whole is dissolved, and all action has ceased. Then pour off the clear liquor, elutriate any residue that may remain with warm water, and add the washings to the first solution. The gold is now in solution with dilute nitro-muriatic acid, and must be precipitated by means of a solution of proto-sulphate of iron, which is to be added until no more precipitate falls. The whole is next to be thrown on a filter, elutriated, and the moisture suffered to pass, while that which remains is to be mixed with half its weight of nitre, and a little borax, and melted in a crucible as before, when a button of pure gold will be found at the bottom. Analysis of native Gold. Native gold, or gold as it occurs in its natural state, is usually alloyed with various proportions of metallic silver, and copper. The proportions of each are found by the following method. Proce, ¦? 1. Digest a given quantity of the metal, say 100 352 ANALYSIS OF METALLIC SUBSTANCES grains, witli so much nitro-muriatic acid as to dissolve the whole. During this process, a white flocculent precipitate will fall to the bottom of the vessel, which is the silver in the form of a chloride of that metal. The clear liquor must be decanted, leaving this to be collected, washed, and dried on a filter, and then weighed. The proportion ol pure silver may be estimated at three quarters the weight ol the chloride. Process 2. The remaining solution to which the washings of the precipitated silver was added, contains the solutions of gold and copper. On adding a solution of the proto-sulphate of iron, the gold will be precipitated, when the clear liquor must be decanted, and the precipitate washed and dried, and afterwards reduced to the metallic state by fusion with potash and borax, as above directed. Process 3. The liquor now remaining contains the copper, and the littte iron, which was added for the separation of the gold. Of the iron no account is to be taken, but the copper is to be precipitated by inserting in the liquor clean plates of iron, and heating the solution, when the plates will be covered with metallic copper, the weight of which may be ascertained by first weighing the plates, and then finding how much they have gained. If any of the copper falls to the bottom of the vessel, this must, after washing and drying, be added to that on the plates. The weight of each metal thus obtained, will, of course, show the proportions in the mass. Silver. The ores of this metal are considerably numerous, and are found in greater or less quantities in nearly every country. The most important are the following : Native Silver, composed of Silver and a little Antimony Auriferous Silver, —Silver and Gold. Sulphuretted Silver, —Silver and Sulphur. Red Silver, —Silver, Sulphur, Antimony and Oxygen. White Silver, —Sulphus, Antimony and Lead. Bismuthic Silver, —Silver, Sulphur, Bismuth and Lead. Carbonate of Lilver, —Silver, Carbonic Acid and Anti mony. Muriate of Silver, —Silver and Muriatic Acid. 353 ANALYSIS OF METALLIC SUBSTANCE?. Tests for Silver. Alkalies give Dark Olive precipitate. Plate ol* Copper " Metallic Silver. Muriatic Acid, f" "> White precipitate, which is and salts of, S f soluble in ammonia. Tincture of Galls, " Brown precipitate. The solution of silver gives a permanent black stain to the skin and hair, and also to cloth and silk. Indellible ink for marking is a solution of nitrate of silver. Assay of Silver. The proper solvent of silver is nitric acid, and for the purpose in question it should be quite pure. This metal is not acted upon by the fixed alkalies. To ascertain its purity, the ore must be first roasted to drive off any sulphur, or arsenic it may contain. It is then levigated, and mixed with three or four times it£> weight of cuastic potash, and the whole fused in a crucible, when the metal will be found at the bottom. If the metal thus obtained is found to be impure, it must be mixed with lead, and subjected to the process of cupellation in the manner directed for gold. Or, it may be assayed in the moist way, by dissolving it in pure nitric acid, precipitated with common salt, the precipitate collected, dried, and mixed with carbonate of potash, and fused ; the button of metal thus obtained, will be pure silver, and its weight compared with that of the ore, will give the per centage. Analysis of Silver ores. To give the analysis of all the silver ores, would be incompatible with the object of this work. An example or two must therefore suffice. Auriferous Silver. Process 1. 100 grains of crystallized auriferous silver, which, upon trial, was found to contain only gold, silver, and copper, were put into a flask with two ounces of nitromuriatic acid, and heat applied. Nitrous gas in red fumes was disengaged, and a white curd floated in the solution in consequence of the precipitating effects of the muriatic acid on the dissolved silver. When cold, the whole was 30* 354 ANALYSIS OF METALLIC SUBSTANCES. thrown upon a filter, and what remained after washing, waf» dried ; this being chloride of silver, was afterwards reduced to the metallic state, with a little black flux, in a crucible. Process 2. The washings of the silver being added to the filtered liquor, a solution of proto-sulphate of iron was poured in, until'no further precipitation followed. By this the gold was thrown down in the metallic form, which was afterwards, washed, dried, and reduced to a button, by means of nitre, and weighed. Process 3. Having thus obtained the gold and silver, the washings of the last process were added to the solution which now contained the copper only. This was precipitated by a clean plate of iron, and afterwards dried and weighed. The number of grains each metal weighed, showed their proportions in the ore, and the sum of the whole indicated the loss of less than a grain. Antimo?iial Silver. Process 1. Of Antimonial Silver-, 100 grains were pulverized and digested, with ten times its weight of nitric acid. A portion being undissolved, was washed and dried, and found to be silex. Process 2. The washings of the silex being added to the filtered solution, occasioned a turbidness, and on pouring in more water, a precipitate fell down, which was oxide of bismuth, contained in the ore. Process 3. Muriate of Soda being now added the whole of the silver was precipitated, which, being washed and dried, amounted to three fourths of the metal examined. Muriate of Silver. This is the richest of the silver ores, sometimes yielding 75 per cent, of the metal. It is known to the miners by the name of horn silver. Its composition is silverand mil* riatic acid, with generally some foreign impurities. Process 1. Mix the powdered ore with four times its weight of carbonate of potash, or soda, and flux in a crucible. When the fusion is complete, dissolve the mass with boiling water, elutriate what remains undissolved, and then digest it in nitric acid. This portion must be kept sepa* ANALYSIS OF METALLIC SUBSTANCES. 355 reiic, and the silver it contains precipitated with muriate of soda, and reduced with black UuX in a crucible. Process 2. The alkaline liquor, or the washings of the fused mass containing the muriatic acid of the ore, combined with the soda, is to be brought to the point of saturation, with distilled vinegar. This will throw down the alumine, which this ore usually contains, in the form of a white powder, which must be washed, dried, and weighed. Process 3. The remaining solution now contains the muriatic acid of the ore, and probably some portion of the soda, in which it was fluxed. This is to be evaporated to dryness, and the mass then digested for several days in alcohol. This will take up the uncombined soda, while the other portion of soda will have combined with the muriatic acid of the ore, forming muriate of soda. The liquor is then to be evaporated, and the muriate of soda weighed, 58 parts of which, are equal to 24 of muriatic acid. Process 4. If the ore contains sulphuric acid, which is often the case, the salt remaining after the third process, is to be dissolved in water, and tested with acetate of barytes, by which it will be precipitated. This acid is generally in very small quantities, and will hardly vary the result. Mercury. This metal is sometimes found in the native state, but the source whence the greater portion is obtained, is from the sulphuret of mercury, or native cinnabar. The ores of this metal are, Cinnabar, composed of Mercury and Sulphur. Native Amalgam,—Mercury and Silver. • Horn Mercury.—-Mercury Oxygen, Muriatic and Sulphuric Acids. Tests for Mercury. The presence of this metal in solution, may be detected as follows ; the re-agents being on the left, and their effects on the right. A plate of copper, Metallic Mercury. A plate of iron, Dark powder. Fresh lime water, Orange precipitate. Ferro-prussiate of potash, White do. Hydro-sulphurets, Black do. Gallic acid, Orange yellow 356 ANALYSIS Of METALLIC SUBSTANCES. In the large way, mercury is obtained by mixing the sulphuret, or native cinnabar, with iron tilings, or lime, and distilling the mixture in iron retorts. The sulphur of the mercury combines with the iron, or lime, and leaves the metal free, which being volatilized by the heat, is condensed in a cold vessel in the metalic form. An example of this process may be made in a glass tube, by means of a blow-pipe, by placing at the bottom, or sealed end of the tube, a piece of cinnabar, and inserting also a bright slip of copper. On applying the heat of the blow-pipe carefully to the ore, through the tube, the metal will sublime and attach itself to the copper. Analysis of the ores of Mercury. The analysis of these ores is simple, as they seldom contain many foreign ingredients. Native Cinnabar. This ore, as we have already seen, is composed of mercury and sulphur. Its analysis may be thus effected. Process 1.—Take 100 grains of the ore reduced to powder, and digest it with 8 or 10 times its weight of muriatic acid, adding now and then a few drops of nitric acid, to make the solution more perfect. When all action ceases, pour off the clear liquor, wash the residue, and dry it with a gentle heat. This will contain the sulphur, and such other matter as was insoluble in the acid. Process 2.—The insoluble matter after drying, is to be heated in a platina crucible, or in the absence of this, in the bowl of a tobacco-pipe, until all the sulphur is burned away, when, on re-weighing, the loss of weight will indicate the quantity of sulphur in the 100 grains. Process 3.—The clear liquor poured off in process 1, is now to be tested by placing a little in a test tube, and adding tinct. of nut-galls, when, if it contains iron, a dark precipitate will fall. Then insert a slip of clean iron, and if i* contains copper, a coat of the metal will cover the slip. If the solution is found to contain only copper and iron, in addition to the mercury, the whole must be evaporated to dryness, taking care not to employ so much heat as to decompose the muriate of mercury. Process 4.—The dry mass obtained by the last process must be dissolved in pure water, which will dissolve the 357 ANALYSIS OF METALIC SUBSTANCES. salts of mercury and copper, but will leave the iron behind in the state of a per-oxide. Process 5. —Immerse into the watery solution a clear p.ate of iron, and gently heat it, when both the copper and metcury will fall down. This being thrown on a fdter, and well washed, must be dried and weighed, and then exposed to a red heat, Avhich will drive off the salt of mercury, leaving the copper behind. Then on weighing the copper, the amount of the salt of mercury will be indicated, and the weight of the metal may be readily known, as the salt, which is the proto-chloride of mercurv, contains 84 parts mercury, and 16 chlorine. Arsenic. The form under which this metal is best known, is that of the white oxide, which is the arsenious acid. The metal from this is readily obtained by mixing it with a little black flux, or powdered chalcoal, placing the mixture at the bottom of a thin glass tube, and applying the heat of a candle, or lamp. The charcoal will absorb the oxygen, and the metal will rise, and be condensed on the inside of the tube, coating it with a brilliant white metal. No mines are worked for the purpose of obtaining arsenic, a sufficient supply of its oxides being obtained in the process of working the cobalt mines of Saxony and Germany. The ores of arsenic present the following varieties. Native arsenic, Arsenic with iron. Pharmacolite, Arsenic, lime and oxygen. Arsenical pyrites, Arsenic, iron and sulphur. Orpirnent, > Arsenic and sulphur. Kealger, ) r "White arsenic, Arsenic and oxygen. The presence of arsenic in any substance is readily known by the strong smell of garlic which it emits when exposed to heat. It will hardly be necessary to go through the processes of assaying, or analysing the ores of arsenic, since the metal in the pure state is of no value, as it turns to an oxide by mere exposure to the atmosphere. The best niethods of ascertaining the presence of this metal, are by the garlic odor above noticed, and the reduction of it in a glass tube, by means of the black flux above 358 ANALYSIS OF METALLIC SUBSTANCES. described. It is said, however, that where the metal is in the state of an oxide, or acid, no garlic odor is emitted, the presence of metallic arsenic being necessary for the pretence of this test. But if the oxide be heated in contact with charcoal, or any other reducing agent, the metal will always be present, as above explained. Still the most sure test is the reduction of the metal, since the garlic odor may possibly be so nearly imitated by some other substances, as to occasion mistakes, a matter which may in some instances, as in suspicion of poisoning, jeopardize human life. In such cases, if the chemist is called on to examine the contents of the stomach, or a portion of the vehicle in which it is supposed the arsenic was given, the fluid may be evaporated to dryness, and then mixed with black flux, and distilled in a common retort, with the heat of a lamp. The arsenic, if any be in the mixture, will rise and coat the in side of the neck of the retort, giving it a metallic lustre nearly resembling quicksilver. A little of this detached, and heated on charcoal, if it emits the garlic odor, will decide the question beyond any doubt, that it is arsenic. Cobalt. Most of the cobalt used in the arts comes from the Saxon mines, under the name of zaffree. This consists chiefly of solicious matter containing a small portion of the oxide of the metal. The ores of cobalt, which are found in many countries, are chiefly the following. , lL .. ( Cobalt, arsenic, sulphur, and some Cobalt pyrites, \ • i tJ ' ( times iron and copper. Red cobalt, Cobalt and arsenic acid. Earthy cobalt, Oxide of cobalt, iron and arsenic. Sulphate of cobalt, Oxide of cobalt, and sulphuric acid Tests of Cobalt. The solutions of the salts of this metal are either red, green, or blue, depending on the quantity of cobalt they contain. Potash and soda, Blue precipitate. Ferro-prussiate of potash Green precipitate. Carbonates, lied precipitate 359 ANALYSIS ( F METALLIC SUBSTANCES. All the ores of cobalt when melted with borax, give a deep blue bead. This is the readiest and most certain method of ascertaining the presence of that metal. Analysis of Cobalt. The cobalt pyrites, or arsenical cobalt, not only contains the two substances from which its scientific name is derived, but is often mixed with copper, iron, nickel, and bismuth also. Hence the analysis of this variety is considerably complicated. Process 1.—Mix one part of finely powdered arsenical cobalt, with three parts of nitre, in a crucible, and submit it to a red heat for one hour. A chemical interchange of elements will ensue, and the arseniate of potash will be the result. Dissolve this in nitric acid, and if any residue remains undissolved, mix it with nitre, and heat in a crucible as before ; then digest in nitric acid and filter. Process 2.—Evaporate the nitric acid solution with heat, in order to drive off any excess of acid, and then dilute with a large quantity of water. This will separate the bismuth, which will fall down in form of a white powder, which is to be separated by decantation, dried and weighed. Process 3.—Immerse in the solution from which the bismuth has been separated, a slip of clean iron of known weight. This will precipitate the copper in the metallic form on the iron, which must be weighed again to find the weight of copper. Then evaporate the remaining liquor to dryness, with heat. Process 4.—Digest the dry mass of process 3, in a solution of caustic ammonia. This will dissolve the cobalt and nickel, but not the iron. Process 5.—Drive off the excess of ammonia by heat, taking care not to continue the evaporation so as to produce any precipitate, then add caustic potash to the solution, and throw the whole on a filter, by which the nickel will be separated, while the clear liquor passes the filter. Process 6.—Boil the clear liquor, which has passed the filter, and oxide of cobalt will fall, and continue the evaporation to dryness. Process 7.—Mix the oxide obtained by the last process with charcoal powder in a covered crucible, and submit it to a strong heat for half an hour, or until reduction is effected. A button of cobalt will be found at the bottom of the era cible. At first, the metal fs bluish grey, but turns redt 1 ;;!: 360 ANALYSIS OF METALLIC SUBSTANCES. grey by exposure to the air. It is brittle, difficult of fusion, and has a specific gravity of about 8. The result of each process being weighed, will show, nof only the comparative quanty of each, but the sum of the whole will determine the per centage of the cobalt in the ore. Bisviuth. The ores of bismuth are rare, and in general it is found only in small quantities at a place. Most of the bismuth used in the arts, is obtained in the processes for making smalt from the ores of cobalt. The ores of cobalt being roasted and broken into small pieces, are mixed with certain quantities of potash and ground flints. This mixture is put into large clay crucibles, and fused with a strong heat for 12 hours, at the end of which, the blue glass, or smalt, will be perfectly formed. At the bottom of the crucibles, the bismuth and nickel, (more or less of which are contained in the cobalt ores,) are found reduced to their metallic states, These are readily separated, in consequence of the low degree of heat required to melt the bismuth. Bismuth is found under the following forms, viz: Native bismuth, The pure metal. Sulphuret of bismuth, Bismuth and sulphur. Oxide of bismuth, Bismuth and oxygen. The ores of the metal are very easily reduced, the process requiring only a blowpipe, and a piece of charcoal. The ore being fused, the charcoal absorbs the oxygen, and the metal instantly appears. Tests for Bismuth. The solutions of this metal are white, and water alone throws down a fine white oxide. Gallic acid. Greenish yellow. Ferro-cyanate of potash, Light yellow. Alkalies, "White precipitate. Assay. The assay of the ores of bismuth is easily effected. A given portion of the ore is to be digested in the form of povv- 361 ANALYSIS OF METALLIC SUBSTANCES. der, in nitric acid, and the solution filtered, and washed with water, containing a little of the same acid, by pouring this on the filter. The solutions being mixed, pour in 8 or 10 times their quantity of pure water, when a copious white precipitate will fall, which is easily reduced to the metallic state with a little black flux, or charcoal in a crucible. The heat for this purpose must be gentle, and the crucible covered, otherwise the metal after its reduction, will be lost by sublimation. If the bismuth is mixed with other metals, which dissolve in nitric acid, they still remain in the solution, not being precipitated by the mere addition of water, as in the case of bismuth. Analysis. Supposing the ore to be composed of bismuth, lead, iron, sulphur, and silex. Process 1. Pulverize the ore, and digest in nitric acid with heat until nothing more is dissolved ; silex and sulphur will remain, while the metals will be dissolved. Throw the whole on a filter, and wash by pouring on dilute acid, —the sulphur and silex will remain, and must be collected, dried, and weighed. Process 2. The clean liquor which passed through the filter, being diluted largely with water, the oxide of bismuth will fall, and after descanting the liquor, is to be dried, and reduced with black flux as above directed. Process 3. The solution is now supposed to contain only lead and iron, both in the form of nitrates. On the addition of sulphate of soda, the lead will be thrown down in the form of an insoluble heavy, white precipitate. This is to be collected by passing through the filter, dried and weighed. Process 4. To the remaining solution, add caustic am monia in excess, by which the oxide of iron will be thrown down, (while the liquor will assume a fine blue color,) and must be separated by the filter, and washed by more ammonia. The oxide being dried, may be reduced to the magnetic state by heating in a covered crucible with some unctuous substance, as linseed oil. Process 5. The ammoniacal solution of the last process must be a little more than saturated with some acid, and on immersing a slip of iron or zinc, the copper which it con 31 362 ANALYSIS OF METALLIC SUBSTANCES. tains will be obtained in the metallic form. For this pur pose the slip must be previously weighed, as already directed Reduction. The methods of reducing the ores of bismuth, are very simple, it being only necessary that they should be broken into fragments, and thrown upon burning charcoal or wood. In some instances the workmen seek out a hollow tree, or stump, and having filled it with alternate layers of brush wood and ore, set the whole on fire, and when the fuel is consumed, and the place cold, they find the bismuth among the ashes. Uses. The only use of bismuth in its metallic form is that of forming a very fusible solder, when alloyed with other metals. The oxide of bismuth is prepared by precipitating it from a solution in nitric acid by means of water as already directed. When a little muriatic acid is added to the nitric solution, the precipitate is composed of small glittering scales, and in this state is sold by perfumers under the name of pearl powder, and is used as a cosmetic; but it is well known that the application of such substances soon render their use absolutely necessary, as the skin soon becomes permanently darkened thereby. Antimony. This metal occurs under the following forms: Native antimony, Antimony, arsenic, silver, iron. Sulphuret of antimony, Antimony and sulphur. Red antimon \ Antimony, sulphur, and oxy«T. T , vr .. \ Antimony, arsenic, nickel, sul- Nickeliferous antimony, < p nur White antimony, Antimony, oxygen, and silex. Before the blow-pipe, the ores of antimony are easily reduced, generally with the emission of a sulphureous, and arsenical odor. By continuing the heat, the reduced metal is entirely dissipated in the form of a white oxide. Tests for Antimony. The solutions of antimony in muriatic acid are thrown 363 ANALYSIS OF METALLIC SUBSTANCES. down by mere dilution with water. The precipitate is a white suDmuriate. A plate of iron, Black powder of the metal. Sulphuretted hydrogen, Orange precipitate. Assay. The method of assaying the ores of this metal, will be understood by the following analysis : Process 1. A portion of the ore reduced, as usual, to r]ne powder, was digested with heat in a mixtute of 4 parts of muriatic, and 1 of nitric acid, until every thing soluble was dissolved. The liquor being filtered, there remained a residue of sulphur and silica. This being dried, was placed in a spoon, and held over the flame of a spirit lamp, until the blue flame ceased, and consequently the sulphur had burned out. The loss of weight thus gave the proportion of sulphur and silex. Process 2. The filtered solution being now diluted with pure water, the submuriate of antimony fell down, which being dried, was reduced to the metallic state, with a little black flux, in a crucible. In doing this, the heat must not be strong, lest the metal should be sublimed. Process 3. The remaining liquor, reduced by evaporation, was diluted with water, when another portion of the antimony was obtained, and added to the former quantity. Process 4. The solution being now tested in small por tions, in a test tube, was found to contain iron and lead. The iron was precipitated with caustic ammonia, and the lead afterwards, by sulphate of soda, both of which were reduced by means of charcoal powder in a crucible. Some of the ores of antimony contain silver, which may be known by the fall of an insoluble muriate of the metal, during the first process, and therefore mixed with the sulphur and silica. In order to separate it, the first residue must be digested in liquid ammonia, which will dissolve the muriate of silver. On saturating this with muriatic acid, and immersing a slip of copper, the silver will be obtained in the metallic state. It isand in most cases, the ores named are mixed with each other, so that the muriate, or carbonate, will perhaps contain both these ores, with the addition of chromate, sulphate, &c. Most of these ores, however, may be reduced to the metallic state with tho blowpipe, on charcoal. 365 ANALYSIS OF METALLIC SUBSTANCES. Tests for Lead. Sulphate of soda. Ferro-cyanate of potash, Infusion of galls, Sulphuretted hydrogen, White precipitate. Do. do. Do. do. Black precipitate. Assay. Notwithstanding the complicated admixture of these ores, their assay is sufficiently simple. Reduce a given weight of the ore to powder, and place it on a muffle, and apply a degree of heat just sufficient to volatilize the arsenic and sulphur, or until, on moving the muffle from the fire, the smell of these substances are no longer emitted. Having thus finished the roasting, the ore is to be levigated—mixed with two or three times its weight of black flux, and a litt'e muriate of soda, and exposed in a crucible to a strong heat. When the crucible is cold, a button of lead will be found at the bottom, which on being weighed and compared with the weight of the ore, will shew the percentage. If the ore to be assayed is galena, its own weight of black flux will be sufficient to effect is reduction, it first being roasted as above directed, and pulverized. In the roasting of lead ores, care must be taken not to fuse them, as it is much more difficult to dissipate their volatile parts, after fusion, than before. Analysis. Supposing the ore to be the carbonate of lead, mixed with green oxide of copper, and oxide of lead, its analysis may be performed as follows : Process 1. Having roasted the ore, put 100 grains into a flask, the weight of which had been previously ascertained, and pour on it by degrees a quantity of nitric acid, diluted by its own weight of water, the weight of the acid being 100 grains. Effervescence will instantly begin, which having subsided, the comparative weight of the bottle and its contents will shew the weight of the carbonic acid which escaped. Process 2. The clear liquor being decanted into a tall glass jar, drop in a solution of sulphate of soOa. unvil a white powder ceases to fall. The sulphate of leav5 tfcya separated must be washed, dried, and reduced with blacl*. ilux, or the 31* 366 ANALYSIS OF METALLIC SUBSTANCES. quantity of lead maybe readily estimated by the proportions of the metal and acid in the salt. Process 3. The copper now remaining in the solution, may be obtained by immersing in it a plate of iron, or zinc, and suffering it to remain at rest for 24 hours ; the copper will thus fall in the metallic state. If on testing the solution with ammonia, a blue tint is given it, copper still remains, and a gentle heat must be applied, the metallic plate remaining in its place, when the whole of the copper will fall, and being collected may be melted into a button, or by finding the addition to the weight of the plate of iron, or zinc, its weight is known. Reduction. The great quantities in which the ores of lead are found, together with its cheapness, and the facility with which it is reduced, render it unnecessary to observe that care and nicety in its reduction that are observed with respect to the more scarce and valuable metals. Galena is the only ore, which is worked for the express purpose of obtaining this metal. This is selected as free as possible from stony matter, and after being broken, is roasted in large furnaces, built for the purpose. By this process the sulphur and arsenic, if it contains the latter, is driven off, and the ore is brought to a proper state for the smelting furnace, where it is thrown in, mixed with charcoal. The heat of the furnace is urged by bellows, and is kept red until the ore melts, and running through the charcoal, is reduced to the metallic state. It is let out at the bottom of the furnace, and cast into pigs for market. Most of the lead of commerce contains a small quantity of silver, and in some instances the ores of this metal contain a quantity sufficient to pay the expence of extracting it. When the silver amounts to 12 or 14 ounces to the ton of lead, the former is separated by exposing the lead to a high degree of heat, in a furnace so constructed that the air shall constantly pass over the heated metal, and by which it is oxidated, or converted into litharge, while the silver remaining unchanged, is collected and refined. The litharge is afterwards reduced to the metallic state, by the simple process of melting it with charcoal in a close furnace, by which the oxygen is absorbed by the bur ring fuel. ANALYSIS OF METALLIC SUBSTANCES 367 Copper. Copper is often found in the native state, but more generally in small quantities. That which is used in commerce and the arts, is chiefly extracted from its ores, which are very numerous, it being found combined with oxygen, sulphur arsenic, carbonic acid, sulphuric acid, muriatic acid, &c. The following are among the most important species of this ore, Sulphuret of copper, Copper, sulpher and. iron. Grey copper, Copper, sulphur, iron and arsenic. Red oxide of copper, Copper and oxygen, and iron, Carbonate of copper, Copper and carbonie acid. Muriate of copper, Copper, muriatic acid, and water. Phosphate of copper, Copper and phosphoric acid. Sulphate of copper, Copper and sulphuric acid. Arseniate of copper, Copper and arsenic acid. Like the ores of lead, those of copper are variously intermixed, and often contain several more ingredients than are mentioned as belonging to their composition. For the description of these ores, the author must refer to his treatise on Mineralogy, where an account of each will be found. Tests for Copper. It is understood of course, that the metal is dissolved in some acid, to saturation, before the application of the test. Plate of iron, Potash, Metallic copper. Green precipitate. Azure blue color, Ammonia, Ferro-cyanate of potash, Reddish brown precipitate. Infusion of galls, Brown precipitate. Sulphuretted hydrogen, Brownish black precipitate. Action of the Blowpipe on Copper ores. The oxides of copper may be reduced on charcoal by the blowpipe. The carbonates are infusible without addition, but with borax form a green glass, and yield a metallic globule. The varieties containing sulphur and arsenic, yield white fumes, and give the odor of these substances respectively 368 ANALYSIS OF METALLIC SUBSTANCES Assay of Copper ores. As nearly all the ores of copper contain sulphur or arse nic, or both, they must in the first place be roasted with & gentle heat, in order to expel these substances. After this is done, the ore is to be pulverized, and mixed with twice its weight of black flux in a crucible, and exposed to a strong heat, as that of a smith's forge, for about half an hour. Should the globules of revived metal not readily form a button at the bottom, a little common salt thrown in, will render the fusion more complete. The little mass of pure copper will show the percentage of metal in the ore. Analysis of Copper ores. Process 1. Having roasted a specimen of the sulphuret of copper, previously weighed, on weighing it again, the amount of sulphur will be known. Then pulverize and digest in nitric acid, which will dissolve the copper, and iron it may contain. Filtrate the solution, which will separate the silex and any sulphur which the roasting did not expel. These being dried and weighed, the sulphur may be burned away in a spoon. The weight of silex will thus be known. Process 2. Precipitate the copper from the solution with a slip of clean iron, suffering the whole to remain at rest for 24 hours. The iron being weighed before, and after immersion, will show the weight of copper. Process 3. Add caustic ammonia to the remaining solution, which will throw down the iron in the state of an oxide. Then filter, and collect the iron, estimating the weight of the metal by that of the oxide, as shown by the table of equivalents. Process 4. If the liquid is colored blue by the ammonia it still retains copper, and must be acidified with nitric acid, and the bar of iron again immersed, and the action assisted by a gentle heat, when all the copper will fall on the iron, and its weight must be added to the former. Considerable experience is necessary, in order to make a satisfactory analysis of a copper ore, especially when it contains but a small quantity of the metal, mixed as these ores often are, with a variety of foreign ingredients. In making the assay also, a good deal of patience is often required, and the process several times repeated, before the 369 ANALYSIS OF METALLIC SUBSTANCES. result can be depended upon, unless the operator has nad much experience in the art of analysis. In Germany, where the art of smelting and refining the metals are carried to a high degree of perfection, every parcel of copper ore is assayed by three several persons before its reduction. Reduction of Copper Ores. The sulphuret of copper is one of the most abundant ores, and it is from this species that most of the copper of commerce is obtained. The processes are lengthy, requiring several months before the metal is ready for market. The ore, which is often contained in slate stone, is first broken into small pieces, and roasted in kilns with wood. A small quantity of fuel is, however, only required for this purpose, for the quantity of sulphur is such, that after it is once set on fire, the mass continues to burn, when the quantity of ore is great, for four, or five months, without further addition of fuel. When the ore ceases to burn, this part of the process is finished, and the sulphur which has sublimed by the heat, and is retained in long chimneys, is removed. The ore is then transferred to a reverberatory furnace, and mixed with charcoal, where it is submitted to a white heat for several hours, when the copper in the metallic state, but mixed with many impurities, is obtained. It is afterwards refined, by being repeatedly melted with charcoal, and granulated by pouring it into water, when it becomes malleable copper. In those ores of copper which contain arsenic, the slow roasting above described is omitted, the ore being at once thrown into the furnace, and the sulphur and arsenic dissipated in a few hours. In some establishments the refining is done by mixing the impure copper with a portion, say 6 per cent of lead, and stirring the melted metals together, by which means, the lead unites with the impurities, and both are skimmed off together. The workmen consider the process finished, when on dipping in an iron rod, and then plunging it into water, the copper with which it is coated, readily separates from the iron. Tin. The ores of tin have been found in but a few localities. They are always found in primitive rocks, generally in 370 ANALYSIS OF METALLIC SUBSTANCES granite, and are associated with copper, and iron. Jts chiei varieties are— Oxide of tin, Tin, oxygen, iron, and silex, Wood tin, Oxides of tin, and iron, Sulphuret of tin, Tin, sulphur, copper and iron. The oxide of tin occurs disseminated, massive, and in crystals, often of regular, and beautiful forms. Wood tin is of a light brown color, and when broken, sometimes resembles in texture, the grain of wood, or root of a tree, hence the name wood tin. It is a purer oxide than the above variety, which is called tin stone. Sulphuret of tin is the most impure variety, being mixed with copper, iron, and often other impurities. Action of the blowpipe on the ores of Tin. The oxides of tin, before the blowpipe, decripitate' strongly, but when in powder and mixed with charcoal, are reduced to the metallic state, though with considerable difficulty The sulphuret, treated in the same manner, melts into a dark scoria, but is not reduced. Tests for Tin. The salts of tin are uncolored, or white, The tests for solutions holding the metal in the state of protoxide, are as follows: Muriate of gold, Muriate of platina, Ferro-cyanate of potash, Per-chloride of mercury, Plate of lead, Purple precipitate. Orange do. White do. Black do. Metallic tin. Metallic tin has a silvery lustre, not readily tarnished by exposure. It always may be known from other metals by the peculiar crackling noise it makes on being bent. Assay of Tin. In the dry way, the assay of tin ores is sufficiently simple. Having reduced 100 grains of the ore to powder, place it in a crucible, and expose it to a low red heat, by which the sulphur and arsenic, if it contain any, will be dissipated. The ore is then to be mixed with charcoal, moistened with a little linseed oil, and exposed to a bright red heat, in a 371 ANALYSIS OF METALLIC SUBSTANCES. covered crucible. A button of the metal will be found at Ihe hottem, which, on being weighed, will show the percentage the ore contained. Analysis of the ore. Process 1. Mix the ore, being reduced to powder, with five or six times its weight of caustic potash, and submit the mixture to a red heat for half an hour in a silver crucible. Digest the grey mass thus formed, in hot water, and if any insoluble matter still remains, it must be mixed with more alkali, and again heated as before. Process 2. Filter the alkaline solutions, and if any thing remains, dissolve it in muriatic acid, and add this to the alkaline solution, which must be super-saturated with muriatic acid, and then evaporated to dryness. The dry mass must now be digested in hot water, which will take up all except the silex, which will remain after filtration. Process 3. The tin and copper, if the ore contained any, will now be contained in the muriatic solution, which is to be saturated with carbonate of potash, when a precipitate will fall. If this is white, it is to be collected, and the process ended by reducing it with charcoal powder, and a little oil or resin. But if it has a greenish appearance, it contains copper, and the precipitate must be re-dissolved in muriatic acid, when on the immersion of a slip of tin of known weight, the copper will cover it in the metallic state, and the difference of weight will show that of the copper. Process 4. The solution being now deprived of the copper, a plate of zinc immersed in it will throw down the tin in its metallic state, which, when dried and fused, will indicate the per centage contained in the ore. Reduction of Tin Ores. The reduction of what is called mine tin, that is, ore which is extracted from the mines at Cornwall in England, is reduced in the following manner. The ore is first stamped or pounded, and at the same time washed by a running stream, which carries away much of the earthy matter. It is then sent to the furnace to be roasted, after which it is again washed in order to purify it as much as possible. The ore thus prepared, is mixed with coal and a portion of slacked 372 ANALYSIS OF METALLIC SUBSTANCES. lime, and smelted in a reverberatory furnace, which is about seven feet long, five broad, and fifteen inches deep. The usual charge of ore is 7 cwt. which yields about two thirds of its weight of tin. To obtain 100 pounds of tin, there is consumed in the roasting, 38 pounds of coal, and in the smelting, 170 pounds of coal, in all 208 pounds, or a little more than twice the weight of the tin obtained. Refined Block Tin. The tin obtained by the above process, is afterwards refined by melting it with a gentle heat, in a reverberatory furnace, and allowing it to run off as fast as it becomes liquid, into an iron kettle, with a small fire under it. Thus the least fusible substance with which the metal is alloyed, are left behind. The tin in the kettle is kept fluid, and is further purified by taking it up in small quantities at a time, and pouring back again, by which the more oxydable parts are made to SAvim on the surface, and are skimmed off. Zinc. The ores of this metal are not numerous, nor are they very universally diffused, though in small quantities, they often occur among the ores of lead. The principal varieties of zinc are the following : Sulphuret of zinc, Zinc, sulphur, and iron. Red oxide of zinc, Zinc, oxygen, ire* and manganese. Electric calamine, Zinc, oxygen, silex. Sulphate of zinc, Zinc, sulphuric acid, and water. Carbonate of zinc, Zinc, and carbonic acid. Action of the blowpipe on Zinc ores. Before the bloAvpipe, on charcoal, the ores of zinc first evolve their volatile parts, as sulphur, and by continuing the heat, some of them become Avhite, or form scoria, Avhile oth-. ers emit white fumes, Avhich is an oxide of the metal. With glass of borax, they form a kind of translucent enamel, or if copper is present, the enamel is green. In the dry way, therefore, the tests of this metal are not satisfactory. 373 ANALYSIS OF METALIIC SUBSTANCES. Tests for Zinc. This metal is readily dissolved in all the mineral, and in several of the vegetable acids. The tests for its presence in solutions, are by no means decisive, many substances throwing down merely a white precipitate. The best method therefore, to detect its presence, is to have recourse to distillation, in the manner described for arsenic, only that more heat is required for the zinc. This method is as follows : Assay of Zinc ores. The ore in the first place, is to be roasted with a gentle heat. If the heat is carried to redness, the metal will be sublimed ; the roasting is only intended to get rid of the sulphur and arsenic. After roasting, the ore must be reduced to fine powder, and mixed with lamb-black, or charcoal powder, and introduced into a green glass retort, and exposed to a red heat. The meU.l will rise by sublimation, and will be condensed in the neck of the retort, which must be loosely stopped, or dipped into a snail quantity of water. The weight of the metal may be known by weighing the ore and charcoal, both before and after the process. Analysis of Zinc ores. Process 1. Reduce a given weight to fine powder, and as some varieties are hydrates, submit to the temperature of boiling oil, or mercury ; this will drive off the water, the loss of which must be estimated. Process 2. Digest the ore without heat, for two or three days, in dilute nitro-muriatic acid ; if any caloric is generated in the process, it should be kept down'by immersing the vessel containing it in cold water ; stir the mixture occasionally with a glass rod, and pour off the clear liquor; repeat the. process of immersion, and well wash with hot water. The residue after this will be sulphur and silex ; separate by burning over the flame of a spirit lamp. Estimate the quantity of sulphur thus lost. Process 3. Examine the residue, supposed to be silex ; it may have a portion of sulphate of lead intermixed ; if this i3 the case, digest the whole in sulphuric acid ; this will take up the lead, which is to be separated from the undissolved silex, and the former may be decomposed at a boiling tem-32 374 ANALYSIS 01 METALLIC SUBSTANCES perature in a solution of carbonate of potash. Carbonate of lead will fall, which should be collected, dried, and reduced to the metallic state. To ascertain the quantity of sulphur acidified by the nitric acid, and which was combined with the lead, but now with the potash, note the difference in the weight of the residues, before and after digestion with the sulphuric acid ; this will give the quantity of sulphate of lead, from which the equivalent quantities of acid and lead may be estimated. Process 4. The solution, No. 1, may now be tested for any free sulphuric acid, and acetate of barytes added, until no further precipitation ; this is to be collected, dried, and its equivalent of sulphur obtained and added to the former quantities; this method will give the whole of the sulphur contained in the ore. Process 5. Or, the residual solution may be tested for lead, and, if it contains any, which will be the case if any sulphate of this metal was found in the residue, it may be thrown down by the sulphate of soda. Process 6. Test a drop of the liquor with caustic ammonia, and if a blue tinge is perceptible, it contains copper, which is to be thrown down by inserting into the acid solution, a clean plate of iron, of known weight, as before mentioned. Process 7. Decompose the solution now holding zinc and iron, by carbonate of soda ; the carbonate of zinc, and oxide of iron, will be thrown down. Digest the precipitate in ammonia, the zinc will be dissolved, while the iron remains, and which may be reduced to the magnetic state by heating in a crucible with charcoal. Process 8. The ammonical solution may now be slightly super saturated with muriatic acid, and carbonate of soda added; the carbonate of zinc will thus be obtained pure, and may be brought to the metallic state with a little charcoal, or black flux in a retort, or close crucible, heated to redness.— Joyce's Chemical Mineralogy. Reduction. The method of reducing the ores of zinc, is said to have been introduced into Europe from China, and that a person was sent to that country expressly for the purpose of obtaining the secret. For this purpose, the ore is broken into small pieces and submitted to a gentle heat in a reverberatory 375 ANALYSIS OF METALLIC SUBSTANCES furnace until the carbonic acid, sulphur, and other volatile substances, are driven off. This being done, the ore is removed and placed in large jars made of ciay, on which airtight covers are luted. Each jar has an iron pipe which passes down through the floor of the furnace, and dips into water. The furnace is of sufficient length to contain eight or ten of these jars. The jars being filled with ore, and the covers luted on, a fire is kindled in the furnace, the heat of which, raises the zinc by sublimation, and passing through the open pipes, it falls down, and is condensed in the metallic form, in the water below. The whole process, therefore, is merely a dry distillation. Zinc is a cheap and abundant metal. It is not only employed in the form of sheets to cover the roofs of buildings, and other purposes, but also forms a component part of brass, one of the most useful of alloys. In making this composition, metallic zinc is not employed, since the heat necessary to melt the copper, would raise the zinc by sublimation, and drive it away without effecting the object. The copper, therefore, in sheets, is placed between layers of calamine, (native carbonate of zinc,) in melting pots, and on the application of fire, the zinc sublimes from the ore, and combines with the copper, now at a red heat, the whole afterwards running down to the bottom of the pot, in the state of brass. It is a curious fact, that brass was known and employed in the arts, for a long time before it was even suspected that any such metal as zinc existed. It was known by experience, that a certain earth, as it was thought, called Calamine, when heated with copper, changed that metal to a yellow color, and added considerably to its weight. But the ancient manufacturers of brass, it appears, never had a thought that the earth they employed was the ore of a metal, until the metal itself happened by accident to be produced. Iron. This metal, in one form or another, is much more universally diffused than any other, there being no mineralizing substance with which it is not found in combination. The ores of iron, are, therefore, very numerous. For a description of the forms, colors, and composition of these ores, the author must refer the student to his " Introduction to Mineralogy," where the distinctive characters, and defi- 376 ANALYSIS OF METALLIC SUBSTANCES. mte analysis of each species is given. The general composition of the principal species of iron ore, are the following : Native iron, Iron, lead and copper. Meteoric iron, Iron and nickel. Arseniate of iron, Iron, oxygen, and arsenic. Sulphuret of iron, Iron and sulphur. Oxide of iron, Iron and exygen. Red iron ore, Iron, oxygen, silex and lime. Brown iron ore, Iron, oxygen, manganese and silex. Bog iron ore, Iron, oxygen, clay and manganese. Specular oxide of iron, Iron and oxygen. Spathose iron ore, Iron oxygen, and carbonic acid. Phosphate of iron, Iron and phosphoric acid. Chromatc of iron, Iron and chromic acid. These are the principal ores of iron, though the list is far from containing the names of all the varieties known and enumerated. The ores of iron which furnish most of the metal, arc the oxides, and the bog ore. Action of the blowpipe on Iron ores. Several of the ores of iron are magnetic in their native states, and this in general may be considered a sufficient test of the presence of the metal. These ores contain at least some particles of iron in the native state. The oxides of iron do not move the magnet, until submitted to the action of the blowpipe, when most of them, if this is done in contact with charcoal, or some other combustible matter, become distinctly magnetic. Some of these ores, after a long application of the heat, are reduced to a sort of cast iron, but more generally they form a shapeless slag, of a black color, which has no other indication of iron, than that of being lifted by the magnet. Tests for Iron. Infusion of galls, Black precipitate. Ferro-prussiate of potash, Blue do. Sulphuretted hydrogen, Black do. The most ready test for iron, in any saturated, or dilute solution, is nflision of galls, or a little piece of the nutgall 377 ANALYSIS OF METALLIC SUBSTANCES. itself, suspended in the solution. In either case, a dark precipitate will gradually fall. Assay of Iron ores Before attempting the assay, the ore should be roasted with a strong red heat, as long as any vapor, or smell arises. After this, two parts of the mineral are to be intimately mixed by trituration, with one of fluor spar, one of charcoal, and four of common salt, by weight. This mixture is to be put into a covered and exposed to a white heat for an hour after which, if the operation has been well performed, a button of cast iron will be found at the bottom of the crucible, and by which the per centage of metal in the ore may be found. If the ore contains much stoney matter, one part of black flux should be added to the above mixture. The common salt, and fluorspar in the above process, act as fluxes, while the charcoal absorbs the oxygen from the metal. Analysis of Iron ores. There is, in general, no great difficulty in the analysis of the ores of iron. The pitchy ore, which is a sulphuric oxide of the metal, often containing manganese, may be treated as follows : Process 1. Pulverize the ore, and introduce a given weight into a flask, and pour on such a quantity of dilute muriatic acid as will take up every thing soluble, then filter, and wash the residue with water. Process 2. Add together the solution and washings of the above process, and drop in solution of muriate of ba rytes until no further precipitation takes place. The precipitate will be sulphate of barytes, formed by the mutual decomposition of the muriate of barytes added, and the sulphate of iron in the solution. To separate these, the solution must again be filtered, washed, dried, and weighed, and the quantity of sulphuric acid in the sulphate of barytes, estimated by the scale of chemical equivalents. Process 3. The filtered liquor now contains the iron and manganese. This is to be concentrated by evaporation, and a small quantity of nitric acid added, in order to render the iron a peroxide, and make it more readily separable. Caustic ammonia in solution must now be poured in, in excess, by which the iron will be precipitated, and can be 32* 378 ANALYSIS OF METALLIC SUBSTANCES. obtained by decanting the liquid, after which it may be Drought to the magnetic state, by heating in a crucible, with resin, or linseed oil. Process 4. The excess of ammonia must be driven off by heat, after which the oxide of manganese will fall, and after being dried, its weight found. In this manner the weight of iron in a given quantity of the ore is determined. In cases where much silex is mixed with the ore, as in the specular and magnetic oxides, where the acids have little effect in their native state, these are to the fluxed with three or four times their weight of potash, after which the muriatic acid will readily effect a solution of the whole of the iron, and which is then to be precipitated with ammonia, and after drying, brought to the magnetic state as above directed. Reduction of the ores of Iron. The ore is broken into small pieces by the aid of the stamping mill, which consists of several beams of wood, shod with iron, which are alternately lifted up, and let fall on the ore contained in a strong box. The machinery for this purpose is moved by means of water or steam. After the ore is broken, it is roasted to drive off the sulphur and other volatile matters. It is then transferred to the smelting furnace, where it is mixed with charcoal and lime, or sometimes with oyster shells, and melted, and thus becomes impure cast iron, or when cast into moulds, is known by the name of pig iron. The pig iron is next broken in pieces and removed to another furnace where, in England, it undergoes the process called puddling, for which, many years ago, a patent was obtained. This operation consists in placing the broken pigs in a reverberatory furnace, and when in fusion, stirring it with iron bars, so that every portion may be exposed to the air and flame. After a time the mass swells, emits a blue flame, and gradually becomes tenacious and less fusible, and at length is granulated or converted into small separate pieces. The fire is then urged so that these particles again agglutinate, and at a welding heat are again brought into masses. In this state of intense heat, the masses are passed in succession between iron rollers, by which a large quantity of extraneous matter is pressed out, and the iron becomes 379 ANALYSIS OF METALLIC SUBSTANCES. malleable. The sheets thus formed are then cut into bars, and again heated and hammered by means of a great, mass of iron lifted by machinery, and thus become the malleable iron of commerce. For a detailed account of the processes of working iron, the reader is referred to " Aikin's Dictionary of Chemistry," and for the construction of furnaces for the smelting of this and other metals, to " Gray's Operative Chemist." Chrome. The color of this metal is between tin white aud steel gray. It is obtained from the chromate of iron which is found native in various places. The metal is of no use in the arts, but its salts, especially the chromate of lead is employed extensively as a pigment. The ores of chrome are the following : Oxide of chrome, Chromate of iron, Chromate of lead, Chrome and oxygen. Chromic acid and iron. Chromic acid and lead. Action of the Blo wpipe. The green color of the oxide of chrome is changed to yellow by the blowpipe. With borax it forms a green glass. The chromate of iron is infusible alone, but with borax fuses into a bead of a rich and lively green. The native chromate of lead, also forms a green bead with borax. Tests for Chrome. The solutions of chrome are readily and strikingly distinguished by the fine yellow precipitate they form with nitrate of lead, which when dried, is known under the name of chrome yellow. With other nitrates the solutions of chrome form precipitates as follows. Nitrate of mercury, Rich cinnabar precipitate. Nitrate of silver, Nitrate of copper, Carmine, changing to purple. Chestnut precipitate. Assay of the ores of Chrome. As metallic chrome is useless, and difficult to obtain on account of the intense heat necessary for its fusion, all that 380 ANALYSIS OF METALLIC SUBSTANCES. is necessary in the assay, is to ascertain the quantity of oxide the ore contains. Process 1. Reduce a known portion of the chromate of iron, to a tine powder, and mix it with half its weight of nitre, and expose to a red heat in a crucible, for an hour, or until all the nitrous gas is expelled. By this process the chromic acid is absorbed by the potash of the nitre, and a chromate of potash is formed, while the oxide of iron remains free. Process 2. Dissolve the chromate of potash with hot water, and separate the oxide by filtering through cloth. Test the liquor with sulphuric acid, when if there arise the fumes of nitric acid, it shows that undecomposed nitre still remains, and probably chromic acid, and chromate of iron also. If it contains the latter, the solution must be evaporated to dryness, again mixed with nitre and fused, and the chromate of potash dissolved out as before, and this liquor added to the former. Process 3. The whole liquid must now be saturated with nitric acid, which generally throws down some earthy matter; filter this, and pour in solution of nitrate of mercury until no further precipitation takes place; throw the whole on a paper filter, collect and dry the red chromate of mercury thus obtained. Process 4. In order to obtain the oxide of chrome, the chromate of mercury obtained above must be placed in a retort, or muffle, and a moderate heat applied ; the mercury will thus be expelled, and the green oxide of chrome will remain, from which can be estimated the per centage of chromate of iron in the ore. Analysis of the Chromate of Lead. The color of the native chromate of lead is various tints of red, often very beautiful. Its composition is oxide of lead 64, chromic acid 36. Process 1. A given weight of the powdered ore is placed in a clean iron, or unglazed earthen vessel, and on it poured a solution of 3 or 4 parts of carbonate of potash in water; boil with a gentle heat until the chromate of lead is decomposed, when there will be in solution, carbonate of lead and chromate of potash : pour the whole on a filter, and having washed, dry the residuum, which will be carbonate of lead Should any yellowness remain, this powder must again be 381 ANALYSIS OF METALLIC SUBSTANCES boiled with potash as before, and the whole added together, filtered, and reduced to metallic lead by fusion with charcoal or black flux. Process 2. The chromic acid may be readily obtained from the remaining solution, thus, —Acidulate the solution with nitric acid, and then add muriate of barytes until no further precipitate falls ; collect the chromate of barytes thus formed on a filter. Process 3. The chromate of barytes of the last process is to be digested in dilute nitric acid, in quantity just sufficient to dissolve it; then add sulphuric acid, and the sulphate of barytes will be precipitated, leaving the chromic acid in solution. Process 4. The solution must now be evaporated, when crystals of red chromic acid will form, the weight of which will show by estimation the per centage of the chromate of lead the ore contained. Uranium. In the metallic state uranium is of no use, but some of its oxides are used as a coloring matter for porcelain. Its ores are rare, and generally occur only in small quantities. Black oxide of uranium, ms of water which the crystals contain. O. means oxygen. EQUIVALENTS. AcM, chlorocyanic (chl. 63-f-cyan. 26) 62 chromic, (chr. 28-f-o. 24) - 52 citric G8 c. 2w. 76! columbic ... . 152 fluoboric, (bor. a. 24+fl. a. 10) 34! fluoric 101 formic 37! fluosilicic, (fl. a. 10-f-siI. 16) - 26 gallic 1 62 hydriodic, (iod. 124-f-hyd. 1) - 125 hydrocyanic, (cyan. 26-j-hyd. 1) 27 hyposulphurous, (s. 16-f-o. 8) - 24 hyposulphuric, (s. 32-j-o. 40) 72 iodic, (iod. 124-j-o. 40) - - 164 malic , 70 manganeseous 1 . - - 62 manganesic? ... 60 molybdous .... 64 molybdic .... 72 muriatic, (chl. 36-f-hyd. 1) - 37 nitric, dry (nit. 14+0-40) - 64 nitric, liquid (sp. gr. 1. 5) 2 w. 72 nitrous (nit. 14-f-o. 32) - 46 oxalic 36 c. 4 w. 72 perchloric, (chl. 36-j-o. 56) - 92 phosphorous, (p. 12-f-o. 8) - 20 phosphoric, (p. 12-|-c. 16) - 28 saccholactic .... 104 selenic, (sel. 40+0. 16) - . 56 succinic .... 50 sulphuric, dry, (s. 16-f-o. 24) - 40 liquid, (sp. gr. 1. 8438) 1 w. - 49 sulphurous, (s. 16-f-o. 16) - 32 tartaric .... 66 c. 1 w. 75 titanic 48 tungstic, (t. 96-f-o. 24) - - 120 uric • 72 Alcohol, (olef. gas 14-f-aq. Tap. 9) - 23 Alum, anhydrous .... 262 j c. 25 w. 487 Alumina 18 sulphate 68 Aluminum .... 10 Ammonia, (nit. 14-f-hyd. 3) - 17 Antimony 44 chloride, (ant. 44-f-chI. 36) - 80 iodide, (ant. 44-(-iod. 124) - 168 oxide, (ant. 44-f-o. 8) - 52 deutoxide .... 55' peroxide - - . -60 sulphuret .... 60' trsenic 381 sulphuret, (realger) - - 541 Arsenic, sesquisulphuret,* (orpiment) 62 Barium 79 chloride, (b. 70-|-chl. 36) . 106 iodide, (b. 70-f-iod. 124) . i94 oxide, (baryta) ... 78 jieroxide? .... 86 phosphuret 82 sulphuret .... 86 Bismuth 72 chloride, (b. 72-)-chl. 36) - 108 oxide 80 iodide, (b. 72-f-iod. 124) - 196 phosphuret, (b. 72+p. 12) • 84 ! sulphuret, (b. 72-f-s. 16) - 88 Boron 8 < Cadmium 56 chloride, (cad. 56-f-chl. 36) . 92 oxide 64 iodide 144 phosphuret .... 68 sulphuret 72 Calcium 20 chloride, (cal. 20-f-chl. 36) - 7j6 iodide 144 oxide, (lime) 28 phosphuret .... 32 sulphuret .... 3* Carbon 6 bisulphuret, (c. 6-f-s. 32) - 38 chloride .... 42 perchloride • • • -120 oxide ..... 14 phosphuret 18 Cerium ...... 50 oxide 58 peroxide 62 Chlorine 30 hydrocarburet, (chl. 36-f-olef. gas 14) 50 oxide, (chl. 36-|-o. 8) - -44 peroxide .... 68 Chromium 28 oxide 36 deutoxide .... 44 Cobalt 26 chloride, (cob. 26-f-chL 36) - 62 iodide 150 oxide ..... 34 peroxide .... 33 phosphuret 38 sulphuret .... 42 jColumbium 144 I Copper 64 chloride, (cop 64-(-chl. 36) . 100 bichloride, (c. 64+chl. 72) J36 I iodide, (c. 64+iod. 124) - 138 • 1 proportion of arsenic, and 1 1-2 sulphur. EQUIVALENTS. Ooppei, Htide, (c. 64-J-o. 8) - - 72 preoxide, (c. 64-f-o. 16) - 80 phosphuret ... 76 sulphuret .... 80 bisulphuret .... 96 Cyanogen, (carb. 12—{—nit. 14) - 26 Cyanuret of sulphur, (cy. 26-f-s. 32) 58 Ether, (olef. gas. 28+wat. Tap. 9) • 37 Fluorine ..... 18 Glucinum 18 Glucina 26 Gold 200 chloride, (g. 200+chl. 3o) - 236 bichloride, (g. 200+chl. 72) - 272 iodide, (g. 200+iod. 124) - 324 oxide, (g. 200+0. 8) - 208 peroxide, (g. 200+O. 24) • 224 sulphuret, (g. 200+s. 48) - 248 Hydrogen 1 arseniuretted, (a. 38+h. 1) - 39 carburetted, (c. 6+h. 2) • 8 bicarburetted, (olefiant gas)(c. 12+h. 2) ... 14 seleniuretted, (s. 40+h. 1) • 41 sulphuretted, (s. 16+h. 1) • 17 bisulphuretted, (s. 32+h. 1) - 33 Hydruret of phosphorus - 13 Bihydruret of phosphorus - • 14 Iodine 124 Iridium 30 Iron 28 chloride, (i. 28+chl. 36) • -64 perchloride, (i. 28+chl. 54) 82 iodide, (i. 28+iod. 124) • 152 oxide, (i. 28+o. 8) - - - 36 peroxide, (i- 28+o. 12) . 40 sulphuret, (i. 28+s. 16) - 44 bisulphuret, (i. 28+s. 32) . 60 Lead 104 chloride, (1- 104+chl. 36) • 140 oxide, (I. 104+O. 8) ' - -112 deutoxide, (1. 104+0.12) . 116 peroxide, (1- 104+o. 16) - • 120 phosphuret,