ARMY MEDICAL LIBRARY WASHINGTON Founded 1836 Section.- Number LllALf... Fobm 113c, W. D., S. G. O. -10643 (Revised June 13, 1936) t*ti£g£ £Jb, *1 PRINCIPLES OF CHEMISTRY. THE PRINCIPLES OF CHEMISTRY, ILLUSTRATED BY SIMPLE EXPERIMENTS. Dr. JULIUS ADOLPH STOCKHARDT, PROFESSOR IN THE ROYAL ACADEMY OF AGRICULTURE AT THARAND, AND ROYAL INSPECTOR OF MEDICINE IN SAXONY. TRANSLATED BY C. H. PEIRCE, M. D. THIRD AMERICAN, FROM THE HIFTfl GERMAN EDITION., u*GE0N GENERAL'S OFFICE I'M 1 •' - ftyP Us... * >'■ ' •"■•"' CAMBR IDGE :( f (f " ® ' PUBLISHED B Y—J"©" If N " IT A U fLEf,T. f BOSTON: PHILLIPS, SAMPSON, & CO. PHILADELPHIA: LIPPINCOTT, GRAMBO, & CO. 1851. Entered according to Act of Congress, in the year 1851, by John Bartt.ktt, in the Clerk's Office of the District Court of the District of Massachusetts. W TVTY-y. /?57 s CAMBRI DGE: STEREOTYPED AND PRINTED BY METCALF AND COMPANY, PRINTERS TO THE UNIVERSITY. The following corrections, intended for this edition, were received too late for insertion in the text: — Page 36, line 19, for " quantity," read " measure." " 68, " 30, for " 12 5," read " 12.5." " 548, " 17, for "cotton-factories," read "print-works." " 553, " 10, for "fragile," read "rigid." " 591, for "pigments," read "dyes." " 658, line 20, before " § 197," insert " Oxalate of lime." PREFACE. The following work has been translated, at the rec- ommendation of Professor Horsford, as a good intro- duction to the study of chemistry. Such alterations only have been made in the text, as were required to adapt it to use in this country. Other changes might have been desirable, such as sub- stituting the hydrogen for the oxygen scale of equiva- lent weights, the Fahrenheit instead of the Centigrade thermometrical scale,* the adoption in every instance of a scientific instead of a popular nomenclature, &c.; but, after due deliberation, it was concluded not to depart from the original, except when absolutely ne- cessary to do so. Where alterations in modes of ex- pression, &c, have been made, the meaning of the author has been carefully retained. In some few instances, the scientific nomenclature usually adopted in our chemical books has been de- parted from; but this could not well be avoided with- out somewhat marring the character of the original * It is highly probable that the Centigrade thermometer will in a few years be generally adopted in this country for scientific purposes a* PREFACE. work. The changes, however, that have been intro- duced, will in no way confuse the more advanced student, even if they do not assist the learner. There has been in many cases great difficulty in rightly translating terms used in the arts and man- ufactures, for the obvious reason that there must be many peculiar technical terms in use in Germany, where arts and manufactures, such as porcelain-mak- ing, metallurgy, brewing, wine-making, &c, are so extensively cultivated. An important part of the labor of translating has been performed by a friend, whose familiar knowledge of the German language has been to me of much value and assistance. I am also under great obligations to the Rev. Dr. Francis, for his kindness in looking over the pages as they issued from the press, and for many valuable suggestions. C. H. p. Cambridge, Sept. 1, 1850. NOTE TO THE THIRD AMERICAN EDITION. The first American edition of Stockhardt's " Princi- ples of Chemistry," translated from the third German edition, has been thoroughly revised with the fifth, re- cently published, and many alterations and additions have been made; among which are those that refer to Dobereiner's lamp, the section giving a Synopsis of Chemical Tests, and the Index. For the sake of convenience, we have also added a table of the symbols and equivalents of the chemical elements, from the " Annual Report of the Progress of Chemistry, &c, No. V., by Justus Liebig, M. D., &c." In this table the equivalent numbers are in accordance with the hydrogen instead of the oxygen scale, the lat- ter, having oxygen as 100, being employed in the body of the work, as in the original, while the scale with hydrogen as 1 is that generally adopted by English and American chemists. C. H. P. Cambridge, January 1, 1851. INTRODUCTION. The rapid progress of experimental science during the last twenty-five years is to be ascribed, in great measure, to the fact that pupils, as well as instructors, have become experimenters. This is especially true with respect to chemistry. For every contemporary of Davy, engaged in experimental researches in this de- partment, there are probably, at present, scores of per- sons occupied in the same field. The fruits of this la- bor are to be seen in the improved condition of manu- factures ; in the more substantial scientific basis upon which many processes, formerly altogether empirical, are now securely fixed; in the progress of agriculture, and the arts generally; and, to some extent, in the progress of medicine. The course of instruction to which this greatly in- creased experimental investigation is chiefly to be at- tributed, namely, the practical or experimental course, bears the same relation to the study of text-books on chemistry that anatomical dissections do to the perusal X INTRODUCTION. of essays on operative surgery, or the solutions of problems in celestial mechanics to lectures on the ar- chitecture of the heavens. It is, beyond question, the most efficient method to secure a sound and available knowledge of the science, either elementary or more comprehensive. Works designed to teach chemistry by experiment are already in use, both here and abroad, but most of them take for granted the possession of expensive ap- paratus, and a laboratory; scarcely any are designed to bring the practical study of the science within the means of the more elementary schools; — and none are to be found suited to the winter-evening firesides all over the country, where the younger and the more advanced of both sexes would delight in chemical ex- periments, did not the apparently necessary expense of apparatus forbid them. It is to meet the latter two wants, as well as those of a general text-book, that the work of Professor Stock- hardt, edited by my late assistant, Dr. Peirce, is em- inently suited. The apparatus necessary for many of the most in- structive and interesting chemical experiments would cost but a few dimes, and as many dollars would fur- nish the requisites for all, or nearly all, the most impor- tant experiments, if performed in the simple manner laid down in this book. A few tubes and flasks, a spirit-lamp, some corks, india-rubber and reagent bot- tles, almost complete the list. In consequence of the INTRODUCTION. XI extensive adoption of this as an introductory work in the schools of Germany, sets of apparatus to accom- pany it are advertised by manufacturers. The qualifications of this work, as a text-book for schools, are such as to leave little, if any thing, to be desired. The classification is exceedingly convenient. The elucidation of principles, and the explanation of chemical phenomena, are admirably clear and concise. The summary, or retrospect, at the close of each chap- ter, presenting at a glance the essential parts of what has gone before, could scarcely have been more happily conceived or expressed for the wants of a pupil or an instructor. The book is also well adapted to the wants of teach- ers who desire to give occasional experimental lectures at a moderate expense, — and of those who design to commence the study of chemistry, either with or with- out the aid of an instructor. E. N. HORSFORD, Rumford Professor in the University at Cambridge. CONTENTS. PART I. INORGANIC CHEMISTRY. SECTION Chemical Action,..........1 Weighing and Measuring,........ 8 Specific Gravity (Areometer, &c),.......11 The Ancient Division of the Elements, . . . . . 18 Water and Heat,..........21 Expansion by Heat, and Thermometer. Expansion of Liquids,.........22 Thermometer,..........24 Expansion of Solids..........27 Expansion by Cold,.........28 Melting of Solids,..........30 Latent Heat,..........32 Boiling and Evaporation. Boiling of Water,..........34 Steam,...........35 Aqueous Vapor,..........37 Distillation,..........41 Diffusion of Heat. Conduction of Heat,.........42 Radiation of Heat,.........43 Formation of Dew,.........44 Solution and Crystallization. Solution,...........45 Crystallization,..........50 Composition of Water,.........55 b XIV CONTENTS. Non-Metallic Elements, or Metalloids. First Group: Organogens. Oxygen (oxides, acids, bases, salts, neutralization, &c.), ... 56 Hydrogen (spongy platinum, explosive gas, formation of water, chem- ical symbols and formulas),........82 Air (barometer, safety-tube, Spritz-bottle, influence of the air on boil- ing, current of air, gases, vapors, composition of air), ... 90 Nitrogen or Azote,.........101 Carbon (charcoal, soot, coke, graphite, diamond, carbonic acid, car- bonic oxide gas),..........103 Combustion (conditions of combustion; rapid and slow, complete and incomplete combustion, flame, &c.),.....Ill Retrospect of the Organogens. Second Group: Pyrogens. Brimstone, Sulphur (amorphous and dimorphous bodies, flowers of sulphur, precipitated sulphur, sulphuret of iron), . . . .123 Sulphuretted Hydrogen,........132 Selenium,............137 Phosphorus,...........138 Phosphuretted Hydrogen (predisposing affinity, water-bath, &c), . 145 Retrospect of the Pyrogens. Tldrd Group: Halogens. Chlorine (nascent state, degrees of oxidation, of sulphuration, of chlorination, &c),..........150 Iodine,............155 Bromine, Fluorine,..........156 Cyanogen,...........157 Retrospect of the Halogens. Fourth Group: Hyalogens. Boron and Silicon,..........153 Retrospect of the Metalloids. Acids. First Group: Oxygen Acids. Nitric Acid (acids, bases, neutralization, &c),.....159 Nitrous Acid, Nitric Oxide, Nitrous Oxide, . . . . \q\ CONTENTS. XV Carbonic Acid (diffusion, mineral water, &c),.....164 Sulphuric Acid (anhydrous, Nordhausen, common, &c), . . 168 Sulphurous Acid,..........174 Phosphoric Acid,..........176 Phosphorous Acid, Oxide of Phosphorus,.....177 Chloric Acid, Hypochlorous Acid, &c, . . . . . 178 Cyanic Acid, Fulminic Acid,........179 Boracid Acid (glass, blow-pipe, volatilization of fixed substances, &c ), 180 Silicic Acid,...........183 Retrospect of the Oxygen Acids. Second Group: Hydrogen Acids. Hydrochloric Acid or Muriatic Acid (haloid salts, &c), . . . 185 Aqua Regia, or Nitro-muriatic Acid, . . . . . 188 Ilydrobromic and Hydriodic Acids,.......189 Hydrofluoric Acid (etching on glass),......190 Hydrocyanic or Prussic Acid,........191 Retrospect of the Hydrogen Acids. Retrospect of the Combinations of the Metalloids with Oxygen and Hydrogen. Third Group : Organic Acids. Tartaric Acid (tartar, formation of organic acids, &c), . . .194 Oxalic Acid,...........196 Acetic Acid,...........198 Retrospect of the Vegetable Acids. Radicals,............199 Capacity of Neutralization,........200 Light Metals. First Group: Alkali Metals. Potassium (carbonate of potassa, lye, nitre, gunpowder, chlorate of potassa, matches, tartar, liver of sulphur, &c), . . .201 Sodium (common salt, Glauber salts, carbonate of soda, borax, solder- ing, glass, &c), ..........215 Ammonia (dry distillation, chloride of ammonium, carbonate of am- monia, &c),...........227 Lithium,...........236 Retrospect of the Alkalies. XVI CONTENTS. Second Group : Metals of the Allcaline Eartlis. Calcium (chalk, quicklime, burning of lime, mortar, gypsum, chloride of lime, &c),...........237 Barium and Strontium (heavy spar, &c),.....248 Magnesium (Epsom salt, white magnesia, &c), .... 249 Retrospect of the Alkaline Earths. Third Group: Metals of the Earths. Aluminum (clay and loam, Artesian wells, arable soil, earthen-ware, alum, &c),...........252 Glucinum, Yttrium, Zirconium, &c,......266 Retrospect of the Earths. Retrospect of the Light Metals. Laws of Chemical Combination (classification of chemical combina- tions, chemical proportions, equivalents, atoms, amorphism, dimor- phism, isomorphism, atomic weights),......267 Heavy Metals. First Group of the Heavy Metals. Iron (oxide of iron, and ores, cast-iron, wrought-iron, steel, salts of iron, green vitriol, &c, Prussian blue, prussiate of potassa, sulphu- ret of iron, &c),..........275 Manganese (black oxide of manganese, salts of manganese, &c), . 297 Cobalt and Nickel (smalt, German silver, &c), .... 303 Zinc (granulated zinc, white vitriol, distillation of zinc, &c), . 309 Cadmium,............315 Tin (tinning, salts of tin, mosaic gold, &c),.....316 Uranium,............328 Retrospect of the First Group of Heavy Metals. Second Group of the Heavy Metals. Lead (litharge, sugar of lead, white-lead, lead-tree, sulphuret of lead, &c),............329 Bismuth (fusible metal, oxide of bismuth, &c.), .... 344 Copper (oxide of copper, colors of copper, reduction of metals, salts of copper, blue vitriol, verdigris, sulphuret of copper, alloys of copper, brass, &c),..........343 Mercury (oxide of mercury, salts of mercury, cinnabar, amalgams, &c), 365 Silver (alloys, lunar caustic, &c),.......379 Gold (alloys, solution of gold, &c),......3gg CONTENTS. XV11 Platinum (solution of platinum, spongy platinum, &c), . . 390 Palladium, Iridium, Rhodium, Osmium,......395 Retrospect of the Second Group of Heavy Metals. Third Group of the Heavy Metals. Tungsten, Molybdenum, Tellurium, Titanium, &c, .... 396 Chromium (salts of chromium, chrome yellow, chromic acid, &c), 397 Antimony (tartar emetic, Kermes mineral, golden sulphuret, type- metal, &c.),...........402 Arsenic (fly-poison, white arsenic, Schweinfurth green, orpiment, Marsh's arsenical test, &c),........410 Retrospect of the Third Group of Heavy Metals. Retrospect of all the Metals (metals, metallic oxides, sulphurets, chlorides, oxygen salts, occurrence of the metals, &c). Classification of the more common Chemical Elements. PART II. ORGANIC CHEMISTRY. Vegetable Matter. Vegetable Life (constituents of plants, organic radicals, &c), . . 419 I. Vegetable Tissue (germination, woody tissue, linen, cotton, bleaching, &c),........426 Changes of the Vegetable Tissue by Acids (gun-cotton, &c), 433 Changes of the Vegetable Tissue by Alkalies, . . . 434 Changes of the Vegetable Tissue by Heat with free Access of Air,..........435 Changes of the Vegetable Tissue by Heat without Access of Air (charcoal, illuminating gas, wood-vinegar, creosote, wood-spirit, wood-tar, pit-coal tar, tar-water, coke, &c), . 436 Changes of the Vegetable Tissue by Air and Water, or Pu- trefaction and Decay (humus, marsh gas, pit-coal, brown coal, peat, &c),.........443 II. Starch, or Fecula (starch from potatoes, wheat, and peas; al- buminous substances; sago, inuline, &c), . . . 450 Changes of Starch into Gum and Sugar (starch-gum, dex- trine, starch-syrup, malt, diastase, mashing, &c), . . 458 m. Gum and Vegetable Mucus (gum Arabic, tragacanth, cerasine, pectine),.........464 c -Will CONTENTS. IV. Sugar (grape-sugar, cane-sugar, liquid sugar, sugar of milk, mannite),..........469 Changes of Sugar by Heat and Acids.....475 Retrospect of the Vegetable Tissue, Starch, Gum, and Sugar. V. Albuminous Substances (albumen, caseine, gluten), . .477 Changes of the Albuminous Substances by Decay and Putre- faction (formation of ammonia and nitre), . . . 479 Retrospect of the Albuminous Substances. VI. Conversion of Sugar into Alcohol (alcoholic fermentation), 482 Wine,...........484 Beer (surface fermentation, bottom fermentation, yeast, &c), 487 Brandy (rectification, fusel oil, &c),.....491 Spirit of Wine, or Alcohol (tinctures, cordials, &c), . 498 VTI. Conversion of Alcohol into Ether (olefiant gas, sulphuric ether, ether, naphtha, &c),.......502 Organic Radicals (ethyle),......508 VELI. Conversion ofAlcolwl into Vinegar (vinegar from brandy, wine, beer, starch, and sugar. Quick method of making vinegar. Aldehyde, acetyle, &c),.......509 Conversion of Sugar into Lactic and Butyric Acids (muci- laginous fermentation), .......515 Formation of Alcohol, Acetic Acid, and Lactic Acid, on the Baking of Bread,........516 Retrospect of the Changes of Sugar and Alcohol. IX. Fats and Fat Oils (oil, lard, tallow, emulsion, &c), . . 520 Changes of Fat by Heat (olefiant gas, illumination, &c), . 528 Composition of Fats (stearine, oleine, &c), .... 532 Vegetable Fats (drying oils, unctuous oils, &c), . . 534 Animal Fats (tallow, butter, fish oil, spermaceti, wax, &c), . 536 Fats and Alkalies, Soaps (hard soap, soft soap, fat acids, oxide of glyceryle, &c),.......540 Properties of Soaps ; Insoluble Soaps (plaster), . . 548 X. Volatile or Ethereal Oils (preparation of them, varieties of vol- atile oils),..........551 Composition and Properties of the Volatile Oils (burning fluids, perfumed distilled water, oleo-saccharum, conversion of the volatile oils into resin, &c), ..... 556 XI. Resins and Gum-Resins ("turpentine and balsams, prepara- tion of the resins, kinds of resins, &c), . . . 563 Composition and Properties of the Resins (sealing-wax, lamp- black, lac-varnish, resin soap, &c),.....573 Gum-Resins,..... . 5g2 CONTENTS. XIX Caoutchouc (gum elastic, gutta percha), .... 584 Retrospect of the Fats, Volatile Oils, and Resins. XII. Extractive Matter (extracts, crystallizable and uncrystallizable extractive matter, &c),.......585 XDX Coloring Matter, or Pigments,......590 XIV. Organic Bases or Alkaloids (morphine, quinine, &c), . . 596 Retrospect of the Extractive and Coloring Substances, and of the Vegetable Bases. XV. Organic Acids (racemic acid, citric acid, "malic acid, tannic acid, &c ),..........598 XVI. Inorganic Constituents of Plants (ashes), arable soil, . . 607 XVIJ. Nourishment and Growth of Plants,.....613 Uncultivated Plants, Food of Plants, .... 614 Cultivated Plants,........615 Retrospect of Vegetable Matter in General. Animal Matter. Animal Life. Constituents of the Animal Body, &c, . . . 619 I. The Egg (white of eggs, yolk of eggs, egg-shells), . . 622 II. The Milk (butter, caseine, milk-sugar, &c), .... 625 Digestion,..........635 III. The Blood (fibrine, blood corpuscles, albumen, &c), . . 636 Respiration and Means of Nourishment, .... 639 IV. The Flesh (juice of flesh, muscular tissue, boiling of meat, prep- aration of broth and soup, salting of meat), . . . 640 V. The Bile,..........645 VI. The Skin (gelatine, glue, leather, horny substance, &c), . . 646 VII. Tlie Bones (bone-earth, animal coal, bone-dust, &c), . . 654 Vin. Tlie Solid Excrements and Urine (urea, uric acid, guano, &c.), . 659 Retrospect of Animal Matter in General. A Synopsis of the Most Important Chemical Tests, . . 657 Chemical Symbols and Equivalents,.....666 Index,............667 PART FIRST. INORGANIC CHEMISTRY. (mineral chemistry.) INORGANIC CHEMISTRY. CHEMICAL ACTION. 1. Every one knows that iron, heated to redness, changes into scales or cinders, and that, exposed to moist air or earth, it is converted into rust; that the expressed juice, of the grape gradually turns to wine, and this, again, to vinegar; that wood in a stove, or oil in a lamp, disappears in burning; and that animal and vegetable substances in time putrefy, disintegrate, and finally disappear. Iron cinders and rust are iron altered in constitution; iron is hard, tenacious, of a grayish-white color, and brilliant; by heating to redness it becomes black, dull, and brittle; on exposure to moisture it is converted into a powder of a yellowish-brown color. Wine is altered must, in which nothing of the sweet taste peculiar to the grape-juice can be perceived ; but it has acquired a spirituous flavor, together with a heating and intoxicat- ing power, which was not in the must. Vinegar is altered wine; it has an acid smell and taste, and has lost its spirituous flavor, as well as its exhilarating 4 CHEMICAL ACTION. properties, its tendency being rather cooling and seda- tive. Search must be made in the air for the oil and wood which have disappeared during combustion ; both these substances are converted into vapor or gas, and warmth and light are thereupon evolved with the phenomenon of fire. Of a similar nature are the changes which animal and vegetable substances under- go, if kept for a sufficient length of time; they are gradually converted, as they putrefy or decay, into vari- ous kinds of gas, some of which emit a very disagree- able odor. Such processes, by which the weight, form, solidity, color, taste, smell, and action of the substances become changed, so that new bodies with quite different prop- erties are formed from the old, are called chemical pro- cesses, or chemical action. 2. Wherever we look upon our earth, chemical action is seen taking place, on the .land, in the air, or in the depths of the sea. The hard basalt, the glass-like lava, become gradually soft, their dark color passes into lighter, they crumble to smaller and smaller pieces, and are finally changed to earth. A potato placed in the earth grows soft, loses its mealy taste, becomes sweet, and finally decays. The bud, that sends forth a sickly pale shoot in a dark cellar, when exposed to the light and air grows up a vigorous, firm, and green plant, which, imbibing its nourishment from the moist air and soil, forms from their elements new bodies, not to be found previously in the water or the air. A delicate network of cells and tubes pervades the whole plant, imparting to it firmness; these we call vegetable tissue, or woody fibre. We find in the sap, which passes up and down through these cells, albumen and other vis- cous substances; in the leaves and in the stalks a chemical action. 5 green coloring matter, — chlorophyll; and in the ripe tubers, a mealy substance, — starch. None of these sub- stances are injurious to health; but if the potatoes grow in the dark and without soil, for instance, in the cellar, there is produced in their long pale shoots a very poisonous body, solanine. The potato forms one of our most important articles of food. The starch contained in it is not soluble in water, but when received into the stomach quickly undergoes such a change that it can be dissolved or di- gested, and then introduced as a liquid into the blood. The blood comes in contact in the lungs with the in- haled air; the blood changes its color, the air changes its constitution, and the heat which we feel in our bodies is developed. We must conclude, from these changes, that chemical action is going on in our own bodies. 3. As long as a plant or an animal lives, the chemical processes are under the guardianship of a higher mys- terious power, which is called the vital force, and by which they are constrained to furnish the materials for the structure of the animal or vegetable bodies. The vital force is, as it were, the architect who plans the building, and sees that the requisite materials are pro- cured by the chemical processes, and worked up accord- ing to his will. Hereupon arise innumerable new bod- ies, which cannot be artificially imitated, as, for exam- ple, wood, sugar, starch, fat, gelatine, flesh, &c. They are called organic compounds, or animal and vegetable substances, in opposition to inorganic or mineral bodies, which may be artificially imitated by putting together their constituent parts. When life in an animal or veg- etable ceases, the chemical powers obtain the mastery, and these, as if they were the grave-diggers of nature, fulfil the old motto, — "Earth to earth, and dust to 1* 6 CHEMICAL action. dust." The leaves of the potato plant become yellow, and then brown; they fall off, and are gradually con- verted into a dark powdery substance, — humus. In the course of time even this disappears, with the excep- tion of a little ashes, which cannot take flight with the rest. What here it takes years to bring to pass, happens in minutes if we throw the dry leaves into the fire. The chemical action is in both cases quite similar,—the only difference consists in the time in which it occurs; it goes on rapidly, as combustion, under a strong heat, and slowly, as a process of decay, at a moderate tempera- ture. But what appears to us annihilation is only change. The substances which have been, not an- nihilated, but only rendered invisible by combustion or decay, we find again under another form, with exactly the same weight, in the air; from the air, they are again drawn down to the earth by the chemical processes going on in living plants. 4. We see from this how the inscrutable power of the Almighty appointed the chemical processes for his servants, in order, by their agency, to produce the eternal vicissitude which we daily observe around us in all nature, and to call forth evermore, in uninterrupted succession, new life from death; thus it is self-evident how improving and instructive for every thinking man must be that science which explains to him this vicissi- tude, and opens to him a clearer insight into the won- ders of creation. This deeper insight will not only lead the mind of man to higher improvement and perfection, but must also fill it with greater admiration and profounder rev- erence for Him, who revealed to us in these wonders his unsearchable omnipotence and wisdom. In another point of view, the interest in chemical CHEMICAL ACTION. 7 knowledge will be most powerfully excited by the use- ful application which can be made of it in every-day life. Chemistry teaches the apothecary how to com- pound and prepare his medicines; it teaches the physi- cian how to cure maladies by means of these medi- cines; it not only shows the miner the metals con- cealed in rocks, but aids him also in smelting and working them. Chemistry, in connection with physics, has been the principal lever by which so many arts and trades have been brought to such a degree of per- fection within the last few decades, and by its means we have been supplied with the numberless conveniences of life that were not enjoyed by our fathers. It can- not be doubted that the farmer must at once regard chemistry as his indispensable friend, for it is this alone which acquaints him with the constituent parts of his soil, with the proper nutriment of the plants he wishes to cultivate, and with the means whereby he can en- hance the fruitfulness of his fields. 5. Chemical Force or Affinity. — If a ball of iron be heated to redness, till a thick crust of scales is formed around it, and then weighed, it will be found to have increased in weight; consequently, it must have been supplied with something ponderable from the air. This ponderable substance is a species of gas, called oxygen; by its union with the iron it has become fixed, yet by other chemical processes it can be reconverted into its gaseous form. If this crust of iron is now exposed for a time to moisture, it will gradually become rust, and again weigh more than before; it has attracted and united to itself water, and more oxygen from the air. Accordingly, the crust consists of iron and oxy- gen, the rust, of iron, oxygen, and water, which have become most closely united with each other; — 8 CHEMICAL ACTION. they are chemically combined. There is a peculiar power, which is considered the cause of this intimate union, as, in general, of all chemical changes; it is called chemical power or affinity, and bodies that possess this capacity of uniting with each other are said to have an affinity for each other. Accordingly, iron at a red heat has an affinity for the oxygen of the air, and at an ordinary temperature it has also an affinity for water. A ducat changes neither its color nor its weight, whether at a glowing heat, or exposed to moisture; we con- clude that gold possesses no affinity for oxygen or for water. 6. A force cannot be seen or grasped; we notice it only in the effects which it produces. If we would know whether a piece of steel possesses magnetic power, we apply a needle, and try whether this is attracted by it or not; we then conclude from its be- haviour as to the absence or presence of magnetism. Precisely the same course, that of experiment, must be taken, in order to become acquainted with the chemi- cal forces, the affinities of bodies for each other. Every experiment is a question put to a body, the answer to which we receive through a phenomenon, that is, through a change which we observe, sometimes by the sight or the smell, sometimes by the other senses. The question has just been put to iron and gold, whether they have an affinity for oxygen; the iron, converted in- to black oxide, gave an answer to this question, the un- changeable gold did not. Every change which we per- ceive, every new property which we observe in a body, is a letter in the language of chemistry. To learn this easily and thoroughly, it is above all things useful for the beginner to exercise himself in spelling, that is, in mak- ing experiments. To give directions for this is the ob- CHEMICAL ACTION. 9 ject of the present little work. Those experiments only have been introduced, which, on the one hand, can be performed easily, safely, and without great expense, and, on the other hand, seem best adapted to illustrate the chemical doctrines and laws, and to imprint them on the memory. 7. There are four leading questions which the chem- ist puts to the different natural bodies. a.) Of what are they composed ? Take, for instance, a piece of bone. How is it affected when strongly heat- ed in a furnace ? It becomes whiter, lighter, and less solid than before (bone-ashes). But how is it affected when heated in a covered vessel 1 It becomes lighter, and black (bone-black). If exposed to boiling water, or to steam, how is it affected ? It becomes lighter, and re- mains white; but in the water is dissolved glue. How in muriatic acid ? It becomes transparent; the bone- earth is dissolved, and a gristly mass remains, which, when boiled with water, turns to glue. What is the action of fire upon the glue ? In a covered vessel it is converted into coal, in an open one it burns and dis- appears. These few experiments show that the bone contains a glue which is combustible, and an earth which is not so; they show, at the same time, that it is the carbonized glue which, in the second experiment, colors the bone-earth black, and makes it bone-black; that this glue is dissolved in water, but not in muri- atic acid, &c. Glue and bone-earth are called the proximate constituents of bone, but by continued chemi- cal processes these can be resolved still further, that is, separated into simpler constituents. In bone-earth are found phosphorus, a metal (calcium), and oxygen; in the glue, besides carbon, three other bodies, — oxygen, hydrogen, and nitrogen. These bodies can be de- 10 CHEMICAL ACTION. composed no further by any known method of analysis, and are therefore called simple bodies, or chemical ele- ments. There are now about sixty known elements, and almost every year adds to their number; but this in- crease is of little importance to chemical science or its applications, for it consists of elements which but very seldom occur. This separating of compounded bodies into simple ones is designated by the name of analysis. b.) Wliat changes do bodies undergo, when placed in contact with other bodies ? Phosphorus, which is ob- tained from bones, is luminous in the air, and is grad- ually converted into an acid liquid; it unites with the oxygen of the air, as the iron did on being heated to redness. If the phosphorus is gently heated, this union is attended with a vivid combustion, and there is formed an acid body which is different from the former; to which, if chalk be added, a new body is formed, very similar to bone-ashes; it is in fact artificial bone-ashes. The number of new bodies which may be produced by the union of the elements with each other, or with com- pound bodies, is infinite, and entirely different sub- stances are often formed, according as the combination takes place under the influence of cold or heat, in water or in air, in greater or smaller quantities. This is combination or synthesis. c.) Wliat useful applications can be made of chemical theory and practice? When the chemist discovers a new body, or a new property in one already known, or a new method of synthesis or analysis, he imparts his discovery to the apothecary, the physician, the farmer, the manufacturer, and the tradesman, that ex- periments may be instituted for the purpose of ascer- taining whether any advantage, facility, or improve- ment can be derived for pharmacy, medicine, agricul- CHEMICAL ACTION. 11 ture, or the arts. Phosphorus ignites spontaneously at a gentle heat; it is used in friction-matches. Taken into the stomach it acts as a violent poison; it is at present the most common means for the extirpation of rats and mice. Bone-ashes and gluten are the constitu- ents universally found in the seeds of different kinds of grain ; the chemist concludes from this, that pulverized bones must yield an excellent manure for grain; the agriculturist demonstrates this by experiments on a large scale. In bone-black the property has been dis- covered of attracting many substances held in solution in liquids, and of condensing them in itself: on account of this property, it is used for making impure water potable; the sugar-refiner employs it to make brown syrup colorless; with it the distiller purifies brandy from forisel oil. This is applied or practical chemistry. d.) What are the causes of chemical changes, and according to what laws do they take place? If chemical experiments are performed, as they should be, with the balance in the hand, it will soon be observed, that when two different bodies which can unite with each other are brought together, sometimes a part of the one, sometimes a part of the other, remains free. Further experiments will show how much of one body, in weight, can be united with the other. If all bodies are tested in the same manner, the certainty is finally attained, that all chemical combinations take place only in fixed, unchangeable proportions, and that to every individ- ual body is assigned a definite weight, with which it always enters into any combination whatever. (§ 268.) This certainty is called a natural law. Many such laws of nature have already been ascertained, and they serve as a certain guide to the chemist in his labors, since they cannot, like human laws, be arbitrarily evaded or 12 WEIGHING AND MEASURING. changed. By them alone we attain to a scientific in- sight into the chemical processes, and to the capability of putting direct questions to bodies by experiment, and of testing the truth of the answers received. An explanation of the chemical processes based on natural laws, which presents a clear idea of the subject to the mind, is called a Theory. WEIGHING AND MEASURING. 8. Weighing. — The balance is to the chemist what the compass is to the mariner. The ocean was indeed navigated before the discovery of the compass; but not till after this could the sailor steer with confidence to a certain place, and recover his proper course, however often lost. And so, in chemistry, no systematic method of study could be pursued before the introduction of the balance. The balance is the standard, as well as the test, of chemical experiments; it teaches us how to ascertain the true composition of bodies, and shows us whether the questions put, the answers received, or the conclusions drawn from them, are correct or false. Hence it cannot be too strongly recommended to those commencing the study of chemistry to use the balance even in simple experiments. For the experiments de- scribed in this book, a common apothecaries' balance is all that is requisite. Such a balance consists of a brass beam, with arms of equal length, through the centre of which passes a steel wedge-shaped axis, resting on a hardened plate, so that the beam, to the extremities of which the pans are attached, may easily vibrate. It is essential WEIGHING AND MEASURING. 13 that the axis should be in the right place of the beam, a little above its centre of gravity, as in Fig. 1, a. The centre of gravity can be found by balancing the beam on its flat side, with the index attached to it, on a needle, and when the beam rests b. horizontally, the point of the needle desig- nates the centre of gravity. If the axis be placed too low, beneath the centre of gravity, as in Fig. 1, b, the beam will over- set, if one of the pans is more heavily loaded than the other. If placed directly in the centre of gravity, the balance itself will cease to vibrate when the beam is in an oblique position. When the axis is too high above the centre of gravity, the balance loses much of its sensibility. This latter defect occurs most frequently, but is easily remedied by lowering the axis. 9. The apothecaries' weight and the French decimal weight are those commonly used. The following is the table of the apothecaries' weight, wrhich will an- swer for all the experiments given in this book: — Pound. Ounces. Drachms. Scruples. Grains. 1 = 12 = 96 = 288 = 5760 1 = 8 = 24 = 480 1 = 3 = 60 1 = 20 10. The new French system of weights and meas- ures, which is now almost universally adopted by chemists, is characterized by great simplicity, all its divisions being made by ten; hence the name decimal 2 14 WEIGHING AND MEASURING. weight and measure. Its unit is derived from the size of our globe. In order to define tlie different localities on this globe, imaginary circles, as is well known, have been drawn around it. Those which pass round the earth from east to west, the largest of which is the equator, are called parallels of latitude (circles of latitude); those which pass round the earth lengthwise, intersect- ing at the poles, meridians (circles of longitude). The parallels of latitude grad- Fig.2. ually become smaller to- wards the poles ; the me- ridians, on the contrary, are all of equal size. The circle, N E S W N repre- sents a meridian or circle of longitude. The fourth part of this circle, or, what is the same thing, the fourth part of the cir- cumference of our earth, as N E, is the basis of the French system. This quadrant was divided into ten million parts, one of which was taken as the unit, under the name of meter. A meter is about three feet and a quarter in length. The smaller measures are produced by dividing by ten, and are designated by Latin terms; the larger ones by multiplying by ten, and are designated by Greek terms. Smaller Measures. Meter. Decimeter = ^ meter. Centimeter = jj3 " Millimeter =,,?«„ " Larger Measures. Meter. Decameter = 10 meters. Hectometer = 100 " Kilometer = 1,000 " Myriameter =10,000 " SPECIFIC GRAVITY. 15 The system of weights was derived from the measure of length, in the following manner. A cubical box was taken, measuring exactly one centimeter in each direction, and this was filled with water at its greatest density (at the temperature -f-4° C.); the weight of this quantity of water was called a gramme. This is taken as the unit of the decimal weights, and is multi- plied or divided by ten. Smaller Weights. Larger Weights. Gramme. Gramme. Decigramme = ^ gramme. Decagramme = 10 gr. Centigramme = IOg " Hectogramme = 100 " Milligramme =I0,S0 " Kilogramme = 1,000 " Myriagramme =10,000 " One gramme is equal to 15.44579grs. Troy. One kilogramme is equal to 21b. 3oz. 4.17dwt. Av. It is well enough known that the body whose weight is to be ascertained must be put into one scale, and in the other weights sufficient to restore the index to its original perpendicular position. The weight of a body thus determined is, in scientific language, called its ab- solute weight. Thus, a piece of sugar weighing two ounces has an absolute weight of two ounces; or, if a vessel be filled with two pounds and one ounce of water, this water has an absolute weight of two pounds and one ounce. SPECIFIC GRAVITY. 11. Ice floats in water, iron sinks in it, because the former is lighter, the latter heavier, than water. But if we put a piece of ice in spirit it sinks, or if we put a piece of iron upon quicksilver or mercury it floats; conse- quently, ice is heavier than spirit, iron lighter than quick- 16 SPECIFIC GRAVITY. silver. It also follows that spirit is lighter than water, since it can support less weight, and quicksilver heavier than water, as it can bear a greater weight. The terms heavier and lighter, in this sense, correspond to what in scientific language is called specifically heavier or specif- ically lighter, and equal bulks are always to be under- stood in speaking of the comparative weights of bodies. The expression, ice is lighter than iron, means, therefore, that, taking equal bulks of each, the former weighs less than the latter; and when we say that quicksilver is heavier than water, we mean that in equal volumes, as a pint, for instance, the quicksilver has a greater weight than the water. But in absolute weight, no regard is paid to the volume of substances. In order to ascertain how many times heavier quick- silver is than water, or iron than ice, it is only ne- cessary to weigh equal volumes or portions of each, and to compare their weights. If, for example, we take five vessels, each of which would contain exactly 100 grains of water, and fill them respectively with spirit, ice, water, iron, and quicksilver, the following differences of weight will be found: the vessel filled with spirit would weigh 80 grains; with ice, 90 grains; with water, 100 grains; with iron, 750 grains; with quicksilver, 1,350 grains. To facilitate the comparison of the numbers which denote how much greater the specific gravity of one body is than that of another, water has been fixed upon as the standard or unit. Therefore, in the above case, the question is, How much lighter than water are spirit and ice, and how much heavier are iron and quick- silver ? or, in other words, How many times is 100 con- tained in 80, 90, 750, and 1,350 ? The other numbers, then, are to be divided by 100, the weight of water, and there is found for SPECIFIC GRAVITY. 17 Spirit, -nrd", or, in decimals, 0.80; it is therefore 3- lighter than water. Ice, -nfo or, in decimals, 0.90; it is therefore -jV lighter than water. Iron, y!£, or, in decimals, 7.50; it is therefore 7^- times heavier than water. Quicksilver, -WoS or> in decimals, 13.50; it is therefore 13y times heavier than water. These numbers represent the specific weights (sp. gr.). Thus, according to calculation, spirit having a specific gravity of 0.80, 80 parts of it would occupy the same space as 100 parts of water; therefore it is only four fifths as heavy as water, or, what is the same thing, one fifth lighter than water. The specific gravity of quick- silver being 13.5, that is, 13^ parts of quicksilver do not take up more space than one part of water; since it is 13y times heavier than water. 12. Determination of Specific Gravity. — Experiment. — To determine the specific gravity of a fluid, a vial is weighed, filled with water, and then again weighed. This gives the weight of the water. Now pour out the water, and refill the vial either with spirit, syrup, lye, beer, or some other liquid, and ascertain by the balance the weight of each. Then divide the weight of each of these fluids by the weight of the water, and the quotient indicates the specific weight. It is very convenient to use a vial made to contain exactly 1,000 grains of water, as then, without any calculation, the number of grains which such a vial contains of any liquid expresses its specific weight. 13. Experiment. — Weigh a flask filled with water; then place a half-ounce weight on the pan which holds the weights, and by the side of the flask nails enough to adjust the beam. Remove both nails and 2* 18 SPECIFIC GRAVITY. flask from the pan, and put the nails into the flask. A bulk of water will be displaced equal to that of the nails; to determine its amount, replace the flask, after it has been thoroughly wiped on the outside, upon the pan, and remove weights from the other pan until the equi- poise is restored. The weights taken away (about 32 grains) form the divisor, and the half-ounce, or 240 grains, the dividend; the quotient -^ = 7.5, is the specific gravity of iron, of which the nails were made. 14. Experiment.— If we have to determine the specific grav- ity of a piece of iron, or of any other body which cannot be put into a flask, it must be fastened by a piece of fine thread to the pan of a com- mon balance, (Fig. 3, b,) the cords of this pan having been previously shortened. Weigh the body first in air, and then in water, immers- ing it an inch deep. As it sinks, the opposite pan falls; consequently iron must be lighter in the water than in air. If the iron in the air weighed half an ounce, then, in order to restore the equilibrium, it will be necessary, as in the former experiment, to remove from the pan a 32 grains, equal to the weight of the bulk of water displaced by the iron. The loss of weight is the same, whether the water be removed from the vessel or mere- ly displaced within it. This forms the divisor, and 240, SPECIFIC GRAVITY. 19 the weight of the iron in the air, the dividend, giving the quotient \-2- = 7.5. 15. Every substance becomes lighter in water in pro- portion to the amount of water displaced; this is a law of nature. If it displaces less water than its weight in the air, it sinks; if more, it floats. Even very heavy bodies can be made to float by increasing their volume; ships are constructed of iron, although it is eight times heavier than water; a tumbler floats upon water, and yet the specific gravity of glass is from three to four times greater than that of water. A thick piece of iron, weighing half an ounce, loses in water nearly one eighth of its weight; but if it is hammered out into a plate or a vessel of such a size that it occupies eight times as much space as before, it then loses its whole weight in water, and will float, sinking just to the brim. If made twice as large, it will displace one ounce of water, — consequently twice its own weight; it will then sink to the middle, and can be loaded with half an ounce weight before sinking entirely. 16. Areometer, or Hydrometer. — The same body will sink to a greater or less depth in different liquids, — deeper in the lighter ones, and not so deep in those which are denser. This has suggested a very conven- ient instrument for determining the spe- t00 's - cific gravity of liquids, the hydrometer 1 ^a- or areometer. This instrument consists of a hollow glass tube, made as repre- sented in Fig. 4. The interior is hol- low, and blown out into a bulb at the lower end, to cause it to float; the under part is loaded with quicksilver or shot, to give it a vertical position. The main tube serves to denote the depth to 20 SPECIFIC GRAVITY. which it sinks in any liquid, by means of a scale of degrees, with which it is furnished. There are vari- ous instruments of this kind, especially adapted for determining the density of spirits, brandy, oil, lye, syrup, &c. If a hydrometer for weighing spirits is put into water, it sinks only to the lowest point on the scale 0° (Fig. 4, a); but in the strongest alcohol, which is much lighter than water, it sinks to the highest point, 100°. A scale for testing lye (Fig. 4, b) must, on the contrary, have the 0° point at the top of the scale, to which it would sink in pure water; for lye being heavier than water, the instrument would be more or less buoyed up in it, according to its strength. In hydrometers for lighter liquids, the degrees proceed from the bottom to the top, in those for heavier liquids from the top down- wards. . In most of these scales the degrees are arbi- trary ; and in order to convert them into the correspond- ing specific numbers, tables, constructed for the pur- pose, must be referred to. 17. Experiment. — Pour brandy into a cylindrical jar, and observe the degree which it marks on the hydrometer; then put it in a warm place, and, when lukewarm, again note the degree, which will be higher than before, as the heat has expanded the liquid, made it lighter, and consequently apparently stronger than it really is. (§ 22.) The specific gravity of all bodies, when warmed, is less than when cold. On this account, in determining the density of bodies, regard should be paid to their temperature, and it has been agreed to consider 15° C. (§ 24) as the mean temperature. In the more accurate hydrometers, the mercury serving as the counterpoise has been ingeniously con- trived also to indicate the degree of heat of the liquid, by connecting with it a graduated tube. The small THE ANCIENT ELEMENTS. 21 scale, a, (Fig. 5,) denotes the temperature, the long scale, b, the density. The small scale is frequently so constructed, that the degrees cor- respond to those on the long scale, and in order to guard against error it is only necessary to add the degrees below the mean temperature to the density, or to subtract from the density those above. Gold is nineteen times, and silver ten times, heavier than water; gold alloyed with silver must, therefore, have a less specific weight than pure gold. The specific weight of brass is only = 8. Alcohol and ether are lighter in propor- tion to their purity and strength, while lye, syrup, the acids, &c, increase in density according to their purity. Hence it is evident how important it is, in many cases, to know the specific gravity of a body in order to judge of its quality. THE ANCIENT DIVISION OF THE ELE- MENTS. 18. Matter and Forces. — As we discern in ourselves the visible body, and its ruler, the invisible spirit, so we recognize in external nature bodies which we can handle and weigh, and forces or powers ruling these bodies a^d Jaaving no weight. 19. Aggregation. — The innumerable natural bodies which we meet with on the earth may be divided into three great classes; they are either solid, liquid, or aeri- form, and each of these states in which bodies exist is called its state of aggregation. 2° THE ANCIENT ELEMENTS. Cohesion. — To divide a piece of ice into smaller fragments, a greater force is requisite than to separate water into minute portions; whence we infer that the particles of the solid ice adhere more strongly than those of the fluid water. A certain attracting power is regarded as the cause of this difference; it acts on the very smallest particles of matter, and is called cohesion or homogeneous attraction. In solid bodies, cohesion is stronger than in liquids, and in aeriform bodies hard- ly a trace of it can be perceived. The Ancient Elements, so called. — Of solid bodies, the most widely diffused is earth; of liquids, water; and of the aeriform bodies, air. From this the ancient phi- losophers concluded that all solid matter was formed of earth, all liquids of water, and aeriform bodies of air; on this account they called them elements, or pri- mary matter. They cannot now be regarded as such in a chemical point of view, since they have been decom- posed into still more simple bodies; but they may be viewed as physical elements, that is, as types of the three aggregate states of bodies. 20. We have no absolute knowledge of the forces of nature, they having as it were a spiritual existence. We are nevertheless as firmly convinced of their reality as we are of the reality of our own spirit, for we know them by their phenomena and effects. A piece of iron, on being thrown into the air, falls to the ground, which is ascribed to the power of gravitation; if exposed to a moist atmosphere, it rusts, that is, it unites with the oxygen of the air. This is the result of chemical force; and the force of electricity can free the iron again from this union. By the force of magnetism, a piece of iron, when balanced on a pivot, takes a direction from north to south; by the force of heat it can be WATER AND HEAT. 23 melted, &c, &c. From this it appears that there are various forces, but it is not improbable that they have one common origin, in the same way that all the differ- ent powers of the mind, will, imagination, judgment, &c, are all referred to one single spirit. Fire, the fourth of the old elements, may be regarded as the symbol of these forces. This also has lost its place among the chemical elements, since it is merely a phenomenon of chemical processes affording light and heat. Of these old elements, fire (heat), water, and air play an important part in most chemical experiments; heat being influential in promoting chemical changes, and water being the most usual solvent of solid and aeriform bodies. The air deserves consideration in all cases, for almost all chemical experiments are per- formed in it, and it may exert injurious or beneficial effects upon the*m. These three so-called chemical ele- ments will therefore first be more particularly con- sidered. WATER AND HEAT. 21. Water covers about three quarters of the sur- face of the globe; it exists sometimes solid, as at the poles, and sometimes fluid, as in warmer regions. In the form of rivers it intersects the land in all directions; while it rises in vapor into the air, and, forming clouds, returns in rain to the earth. Thus we find it in nature in its three aggregate forms, and it is obvious that these external differences have been effect- ed by the agency of heat. Hence water is peculiarly 24 WATER and heat. well adapted to serve as a study of the most impor- tant effects of heat. EXPANSION BY HEAT, AND THERMOMETER. 22. Expansion of Liquids. — Experiment.— Take the tare of a flask, —that is, place it on one of the pans of a balance and equipoise it by weights put into the opposite pan; — then fill it with water, and ascertain the weight of the latter. Warm the flask on a tripod over a simple spirit-lamp, moving it round gently at first, that the flask may heat gradually. The water will soon rise, and part of it run over. When it begins to boil, remove the lamp and let the vessel cool, and the water will then sink deeper than it stood before. How much has been displaced is found by its loss in weight; it will amount to about ^ of the first weight. The burning spirit, or alcohol, heats the bottom of the glass vessel, which in turn communicates heat to the water. The heat expands the water, consequently it occupies a greater space than before, and part of it must run over. Hence it follows that warm water must be lighter than cold water. If a pitcher filled with two pounds of ice-cold water be afterwards filled with boiling water, it will weigh about an ounce and a half less. As it cools, it contracts again to its former density. The same occurs with all other liquids, and indeed also with solids and gases: hence, it may be stated as a natural law, that all bodies expand by heat, and con- EXPANSION by heat, and thermometer. 25 tract on cooling. But the amount of expansion is very different in different bodies at the same temperature; alcohol, for example, expands two and a half times more, mercury two and a half times less, than water. When fluids are to be bought and sold by measure, an advantageous application may be made of this prin- ciple. If a hundred measures of brandy or alcohol are purchased in hot, and sold in cold weather, there will be a loss of four or five measures; therefore we should gain by buying in winter and selling in summer. 23. Experiment. — In order to observe more accurate- ly the expansion of water by heat, adapt to a flask a cork, rendered so soft by gentle pounding that it may be exactly fitted to the opening by mere pressure; perforate the cork with a round file, and make the hole just large enough to admit a glass tube. Fill the flask with water, so that, when the cork is firmly pushed in, the water shall stand at about a, (Fig. 7,) and heat it as in the former experiment. The water, which in the former experi- ment was displaced from the flask, in this case rises in the tube, and the higher in proportion to the smallness of its bore. By this means very slight changes of space are rendered visible, and these de- viations may be applied to the measurement of heat. This is done by particular instruments called ther- mometers. 24. Thermometer. — Water might be employed for measuring heat, by marking the boiling and freezing points, and graduating the intervening space; but mercury is far better adapted to the purpose, as it boils and freezes at greater extremes of temperature, 3 26 WATER AND HEAT. and more rapidly denotes the variations of heat and cold. The vessel containing the mercury may also be regarded as consisting of a flask and tube, but which, instead of being joined by a cork, are composed of one entire piece. Having introduced into it a sufficient quantity of mercury, and sealed the open end by fusion, it is immersed in melting snow, and the point to which the quicksilver falls is marked freezing point; that to which it rises in boiling water, boiling point. The space between these two points can now be divid- ed into degrees, to form the scale. The degrees below the freezing point are of the same dimensions as those above. There are several scales in use, though it is to be regretted that more than one has been adopted. The most common are the three following: — Reaumer's (R.), divided into eighty degrees; the centigrade of Celsius (O), into one hundred; and Fahrenheit's (F.), into one hundred and eighty degrees. The difference between these can be easily seen in the annexed figure. According to R. water freezes at 0° and boils at 80°; according to C. it freezes at 0°, and boils at 100°; ac- Fi