AN ELEMENTARY TREATISE ON PRACTICAL CHEMISTRY AND QUALITATIVE INORGANIC ANALYSIS, SPECIALLY ADAPTED FOR USE IN THE LABORATORIES OF COLLEGES AND SCHOOLS, AND BY BEGINNERS. FRANK CLOWES, D.Sc., Lond., FELLOW OF THE CHEMICAL SOCIETIES OF LONDON AND BERLIN ; FELLOW OF THE INSTITUTE OF CHEMISTRY ; SENIOR SCIENCE MASTER AT THE HIGH SCHOOL, NEWCASTLE-UNDER-LYME; LATE SCIENCE MASTER AT QUEENWOOD COLLEGE. WITH ILLUSTRATIONS. LKOM THE THIRD ENGLISH EDITION. PHILADELPHIA: HENRY C. LEA’S SON & CO. 1881. PREFACE. This little treatise was commenced to supply a course of Practical Chemistry to my own classes. I was encour- aged to proceed with it by finding that a want of a suffi- ciently elementary and explanatory Laboratory Text- book was very widely felt. It has been my aim throughout to give all necessary directions so fully and simply as to reduce to a minimum the amount of assistance required from a teacher. The language employed has been rendered simple and intel- ligible by avoiding the unnecessary use of scientific terms, and by explaining or paraphrasing in ordinary words any such terms when introduced for the first time. The directions howto work, and the descriptions of the prepa- ration and use of apparatus, have been given more fully than is usual, since my own experience, confirmed by that of other teachers, convinces me that one of the most seri- ous hindrances to the utility of many of the smaller Text- books on Practical Chemistry is the too great conciseness of the language employed, which frequently renders it unintelligible to the student unless supplemented by very copious verbal explanation from the teacher. Whilst making the very desirable amplifications above referred to, the book has been kept within small dimen- sions, partly by the omission of all such higher instruc- tion as is not required by a student of elementary chem- PREFACE. istry, and partly by the insertion of the supplementary or merely explanatory portions in smaller type. The text has been supplemented by appendices containing matter suited to more advanced students. I have also thought it best to avoid entering into any lengthy theoretical ex- planations. The modern teaching of chemistry is in prac- tice very appropriately divided into two departments— namely, theoretical instruction imparted by lectures or by the study of textbooks of theoretical chemistry, and prac- tical instruction imparted in a chemical laboratory by working according to the directions of a practical text- book. Since by this system the student has time and opportunity afforded him for the study of the theoretical and descriptive portions of the science, it is as unneces- sary as it is undesirable that his Practical Textbook should tempt him to bestow valuable time in the labora- tory upon the study of matters of theoretical—not prac- tical—importance. The analytical reactions and methods have been care- fully worked through from the text by myself and by the members of my classes; the accuracy and intelligibility of their descriptions have thus, I hope, been secured. Only those reactions and methods which are commonly em- ployed for analytical purposes have been entered. I have naturally, in selecting analytical methods for an elementary treatise, felt it desirable that those chosen should be as simple and easy of execution as possible; in some cases, however, methods which are most eligible on these grounds have proved on trial to be so inferior in accuracy and delicacy, that they have been abandoned in favor of others which are recommended by their trust- worthiness rather than by their simplicity. In such cases, however, I have also described the more simple methods, PREFACE. since they may be employed in analyses in which minute quantities of a substance have not to be tested for. The reactions given in an elementary textbook must necessa- rily be limited as to number, and I have felt it advisable to introduce such reactions as are useful in general analy- sis rather than those which claim to be merely interest- ing and instructive. The book has been divided into seven sections, the contents of which are fully stated on pages ix-xv. The first six contain a good practical course for senior students; this may, however, be modified to suit junior students, or those working with a special object, as is shown in the Introduction. The seventh section contains full lists of all apparatus, reagents, and chemicals required in working through the different sections; there is also added a list of general apparatus, with a description when necessary of its con- struction and use. In this section there will also be found full and systematic descriptions of the most simple methods for preparing the different solutions required in analysis, with a statement of the strength most appropri- ate for each. Experience has proved that these are mat- ters which merit more attention than is usually bestowed upon them. The methods of preparing pure chemicals are omitted, since they may now be readily and cheaply purchased ; before using purchased chemicals their purity should, however, always be ascertained by the tests given in this section. Symbolic notation has been employed, instead of the full chemical names, throughout the sections on analyti- cal chemistry. In its most concise form this chemical shorthand conduces so much to brevity in writing down results that no other plea is required for its use. The PREFACE. simple plan of labelling each bottle in the laboratory with the chemical formula as well as the name of its con- tents, will prevent any difficulty arising from this gen- eral employment of chemical formulae. Special features in the book are the arrangement of all tables across instead of along the pages; the turning of the book is thus rendered unnecessary—a conveni- ence which will be appreciated by all students of Practi- cal Chemistry. The “Tables of Differences/’ which contain for each Analytical Group a summary of the differences of be- havior of its members with reagents, are also special— being an extension of the system employed in Galloway’s “ Manual of Qualitative Analysis.” It is almost superfluous to mention that free use has been made of the standard works of Fresenius and Rose; much valuable information has been introduced from these sources. I have also frequently adopted the very conve- nient tabular form of entering analytical methods which is employed in Valentin’s “Textbook of Practical Chemistry,” and with the author’s permission have tran- scribed, with a few trivial alterations, the excellent Phos- phate Table devised by him. My acknowledgments are also due to Dr. W. A. Tilden, of Clifton College, and to the Rev. T. N. Hutchinson, of Rugby, and to many other teachers who have suggested valuable improvements. The book is especially intended to furnish a course of instruction in practical chemistry in the laboratories of our public and other schools. It will thus supply a de- mand which is rapidly increasing, as the value of a sound elementary instruction in practical science is becoming more widely appreciated, both as a means of mental training and as a preparation for the chemical and medi- PREFACE. cal professions, as well as for many branches of manu- facturing industry and enterprise. The fifth section has been inserted for the use of those who are preparing for practical examinations in which proficiency in the analy- sis of simple salts only is required of the candidate. This is the standard fixed for the Preliminary Scientific (M.B.) Examination of the London University, and for the more elementary examinations conducted by the Oxford and Cambridge Universities, such as those for school certificates. The sixth section and appendices, however, contain additional details suited for the analytical work of ad- vanced students, and will be found sufficient to qualify a student for the higher University examinations in qualitative analytical chemistry. The present edition has been subjected to a careful re- vision, and the analysis of simple salts in Section V has been recast in a more simple and systematic form. F. C. Newcastle-under-Lyme, January, 1880. CONTENTS. Paragraph Page SECTION I. Experiments illustrating the Prepara- tion and Properties of Gases, etc. I. Oxygen, — 19 II. Hydrogen, ..... — 25 III. Carbon dioxide, .... — 29 III a. Nitric oxide, ....#. — 34 IV. Ammonia, — 34 V. Carbon monoxide, .... — 37 V a. Chlorine, — 39 V b. Hydrochloric acid gas, ... — 40 VI a. Distillation of water, ... — 40 VI b. Preparation of nitric acid, . . — 42 SECTION II. Preparation and Use of Apparatus re- quired in Analysis, 1-19 43 Bunsen burner, 1, 2 43 Spirit-lamp, 3 45 Blowpipe, 4 45 Glass tubes, cutting, ..... 5 46 “ bending, 6 47 drawing out, .... 7 47 Boring corks, 8 47 Making sulphuretted hydrogen tube, . . 9 48 Making ignition-tubes, .... 10 49 “ stirring-rods, . . . . 11,11a 49 Mounting platinum wires, .... 12 50 Making wash-bottle, 13 50 Cleaning glass and porcelain apparatus, . 14 52 Cleaning platinum foil and wire, . . 15 53 Putting away apparatus, .... 16 53 Heating glass and porcelain: . . . 17 54 Porcelain dishes, 18 54 Glass vessels, 19 54 X CONTENTS. Paragraph Page SECTION III. Analytical Operations, Descriptions il- lustrated by Experiments, . . . 20-356 56 Solution, 20 56 Evaporation, 21 58 Precipitation, 22 59 Filtration and decantation, ... 23,23a 60 Decantation, 236 63 Washing precipitates on the filter, . . 24,24a 63 by decantation, . 246 64 Drying precipitates, 25 64 Removing precipitates from the filter, . 26 65 Ignition, 27 67 Sublimation, 28 68 Fusion, 29 68 The Use of the Blowpipe: . 30 69 Borax beads, 31 70 Flame colorations, 32 71 Ignition on charcoal in the blowpipe flame, 33 73 Levigation of residue, .... 33a 74 The Use of Test-pope?^: .... 34 75 Making neutral, acid, and alkaline, . . 35, 35a 77 Turmeric-paper, 356 78 Fractional solution, crystallization and dis- tillation, ...... — 79 SECTION IV. Analytical Reactions, .... 36-329 80 Introductory remarks on analytical classifi- cation and on the analytical course which follows, ....... — 80 Analytical classification, .... 36 83 Analytical groups, ..... 37 84 Method of trying the reactions, ... 38 84 Entry in the Note-book:..... 39 86 Chemical notation, 40 86 Chemical equations, ..... 41 87 Rules for drawing out an equation, . . 42 87 Contractions to be employed, ... 43 88 Examples showing method of entry in the note-book, ...... 44 89 Rules to be observed whilst working,. . 45 89 Reactions for Metals: Group V (Potassium Group): 40-67 91 Potassium, ...... 47-50 92 Ammonium, ...... 51-55 94 Sodium, 56, 57 95 CONTENTS. XI Paragraph j Page Magnesium, 58-63 96 Table of differences and its use, ... 64, 65 97 Principles of separation, .... 66 98 Table for separation and detection, . . 67 100 Group IV (Barium Group) : .... 68-89 101 Barium, 69-74 101 Strontium, 75-79 102 Calcium, 80-86 103 Table of differences, .... 87 103 Principles of separation and detection, . 88 104 Table for separation and detection, . . 89,438 104 Group III a (Iron Group) : . . . . 90-109 105 Aluminium, j 91-94 105 Iron, 95-101 106 Chromium, 102-106 108 Table of differences, 107 109 Principles of separation and detection, . 108 110 Table for separation and detection, . . 109,436 110 Group III b [Zinc Group): .... 110-141 110 Zinc, 111-114 111 Manganese, 115-120 112 Nickel 121-128 113 Cobalt, 130-137 115 Detection of members separately, . . 138 117 Table of differences, . . . . . 139 117 Principles of separation and detection, . 140 118 Table for separation and detection, . . 141,437 118 Group II a (Copper Group): .... 142-176 119 Mercuricum, 143-148 119 Lead, 149-153 121 Bismuth, 154-159 122 Copper, • . 160-168 123 Cadmium, 169-172 125 Table of differences, ..... 173 125 Detection of members separately, . . 174 125 Principles of separation and detection, . 175 125 Table for separation and detection, . . 176-435a 126 Group II b (Arsenic Group): . . . . 177-210 128 Arsenic, 179-190 128 Antimony, 191-200 136 Tin, 201-205 138 Table of differences, 206 140 Principles of separation and detection, . 207 140 Table for separation and detection, . . 208-4356 141 A second method of separation and detec- tion, 209 141 A third, 210 142 Group I (Silver Group): .... 211-222 143 Lead, [149-153] [121] Silver, 212-216 144 Mercurosum, 217-219 144 CONTENTS. Paragraph Page Table of differences, ..... 220 145 Principles of separation and detection, . 221 145 Table for separation and detection, . . 222, 433 145 Reactions for gold, . .... 223-224a 146 Reactions for platinum, .... 225, 226 146 Reactions for Acid-radicles : 227-329 147 Group I (Sulphate Group), .... 227,228 148 Group II (Carbonate Group) : . . . 229-246 149 Carbonates, ...... 229 149 Sulphides, ...... 230-235 150 Sulphites, 236-238 152 Theiosulphates, 239-240a 152 Hypochlorites, ..... 241,242 153 Nitrites, . . . . . . 243-245 154 Detection of the members when mixed, . . 246 154 Group III (Nitrate Group): .... 247-256 155 Nitrates, 247-251 155 Chlorates, 252-255 157 Detection when mixed, .... 256 158 Group IV {Chloride Group): .... 257-274 158 Chlorides, 257-260 158 Bromides, ...... 261-264 161 Iodides, 265-270 162 Detection of separate members, . . • 271 164 Separation and detection, .... 272-274 165 Group V (Phosphate Group) : 275-282 167 Phosphates, ...... 275-278a 167 Arsenates, . . . . . • 279 169 Detection, ....... 280-28la 169 Separation and detection, .... 282 170 Ungrouped Acid-radicles: .... 283-302 170 Borates, ....... 283-285 170 Chromates, ...... 286-289 171 Silicates, ...... 290-293 173 Fluorides, ...... 294-298 174 Fluosilicates, ...... 299-302 176 Organic Acid-radicles: . . . . . 303-329 178 Cyanides, ...... 303-306 178 Ferrocyanides, ..... 307-310 180 Ferricyanides, ..... 311-314 181 Sulpliocyanides, ..... 315,316 181 Oxalates, ...... 317-319 182 Tartrates, ...... 320-325 183 Acetates, ...... 326-328 185 SECTION Y. Analysis of Simple Substances for one Metal and one Acid-radicle, . . . 330-369 187 Introductory remarks, and tabular classifi- cation of metals, ..... 330 187 CONTENTS. Paragraph Page Preliminary examination of a solid for the metal, 331-333 190 Solution of a solid substance, . . . 332 191 Preliminary examination of a liquid for the metal, ....... 334 196 Preliminary examination for the acid- radicle, ...... 335-338a 198 Examination for the metal, .... 339-348 200 General table and notes thereon, . . 339-343 200 Table I (Silver Group), .... 344 202 Table II (Copper and Arsenic Groups), . 345 203 Table III A (Iron Group), .... 346 204 Table III b (Zinc Group) 347 204 Table IV (Barium Group), . . . 348 205 Examination for the acid-radicle, . . . 349-356 205 Examination of Group III, .... 357-361 209 Examination of a substance with metallic ap- pearance, ....... 366 214 Examination of an insoluble substance, . . 367-369 215 Examples of entry of analyses, . . . . — 219 SECTION VI. Full Analytical Course and Tables, . 370-487 228 Introductory: Separation of metals into groups by group reagents, ...... 370 228 Addition of reagents in excess, ... 371 229 Evaporation before precipitating Group III, 372 229 General remarks, . . . . . 373,374 230 Preliminary examinations, their use, . . 375-378 230 General analytical course: Preliminary examination of a liquid, . . 380, 381 233 Solution of a non-metallic solid, . . . 383-3866 234 Preliminary examination of solids for the metals present, ..... 387-409 236 Preliminary examination of solids for acid- radicles, ...... 410-418 242 Examination for metals: 419-439 246 General table and notes thereon, . . 419-432 246 Table I (Silver Group) and Table G, . . 433, 434 251 Table II (Copper and Arsenic Groups), . 435 252 Table III A (Iron Group), .... 436 254 Table III B (Zinc Group), .... 437 255 Table IV (Barium Group), . . . 438 256 Table V (Potassium Group), . . . 439 259 Examination for acid-radicles, .... 440-454 261 Table showing solubility of substances in water and acids, ...... 455-458 266 Remarks on the precipitation of Group III, . 459-462 269 Ilules for the precipitation and examination of Group III, 463 272 XIV CONTENTS. Paragraph Page Table III Cj (Iron and Zinc Groups mixed), ...... 464 273 Table III c2 (Iron and Zinc Groups mixed), ...... 465 274 Table III D (Phosphates in Group III), . 466 276 Examination of substances with metallic appear- ance, . ...... 467-471 278 Separation and detection of gold and platinum, . 472-474 281 Examination of substances insoluble in water and acids, 475-479 283 Analysis of silicates, ..... 480,481 287 Analysis of substances containing cyanogen, . 482-487 289 Example showing how to enter analytical results,. 488-493 290 SECTION VII. Apparatus and Chemicals required for the preceding Course, .... 494-539 301 List of apparatus for each student, ■ . . 494 301 List and, description of general apparatus: . 495-506 304 Indigo-prism,'cobalt-glass, cork-borers, . 496-498 304 Sulphuretted hydrogen apparatus, . . 499,500 304 Passing sulphuretted hydrogen, . . . 500a 307 Agate mortar, leaden or platinum crucible, . 501, 502 308 Steam-oven, water-bath, tubulated flasks, . 503-505 308 Distillation of water, . . . . . 506 311 Recovery of the metals from silver and plat- inum residues, ..... 507,508 314 Directions for preparation of reagents and solu- tions: ....... 509-517 316 Introductory remarks, .... 509,510 316 Dilution of liquids, ..... 511 316 Solution of solids, ..... 512-515 317 Preparation of solutions for the reactions, . 516,517 320 Lists of the reagents, solutions, and chemicals, stating their condition or strength and special processes of preparation: .... 518-533 321 Introductory and explanatory remarks, . 518-521 321 Labelling and varnishing, .... 522,523 322 List of reagents for each bench, . . . 524 324 List of reagents, for general use, ‘ . . 525, 526 326’ Preparation of saturated solutions of solids,. 527 330 “ “ “ of gases, . 528 : 331 Lists of solutions required for Section IV, . 529, 530 j 334 List of chemicals required for Section I, . 531 j 338 List of chemicals required for Section III, . 532 j 339 List of sundry other requisites, . . . 533 | 340 Examples of substances to be given for analysis, . , 534-539 j 341 CONTENTS. Paragraph Page Appendix I.—Reactions and detection of tlie rarer elements, 540-554 345 Group I (Silver Group): 540, 541 345 Thallium, 540 345 Tungstates, 541 346 Group II a (Copper Group): . . . . 542 346 Palladium, 542 347 Group IIb (Arsenic Group): . . . 543-545 347 Molybdates, 543 347 Selenium, 544 348 . Tellurium 545 348 Group III (Iron and Zinc Groups) : . . 546-550 349 Uranium, 546 349 Indium, 547 349 Beryllium, 548 350 Titanium, 549 350 Vanadium, 550 351 Group V (Potassium Group): ... 551, 552 352 Lithium, 551 352 Rubidium and Ca?sium, . . . 552 352 General table for detection of the rarer elements, | 553 354 Table for examination of Group III for the rarer elements, .... 554 356 Appendix II.—The spectroscope, its use in analysis, 555,556 358 Spectrum-chart, 557 360 Appendix III.—List of chemical elements with symbols and atomic weights, . . 558 362 Thermometric scales, .... 559 362 Weights and measures—French and Eng- lish, 560,561 363 PRACTICAL AND ANALYTICAL CHEMISTRY. INTRODUCTION. The course of practical chemistry which should be pur- sued by a student depends partly upon his object in studying the science, and partly upon the time and means which he has to devote to the study. The first four sections and the sixth furnish a good general course for a senior student who wishes to obtain a training in practical and analytical chemistry; but for younger students, after completing the first three sections, the most suitable an- alytical course consists in trying through the reactions in Section IV, and as the reactions for each group are com- pleted, testing several substances containing only one member of the group for the metal present by the table of differences. The analysis of simple substances by Section V may then be worked through, and, after be- coming familiar with this, separations of the mixed mem- bers in each group are done, leading thus to Section VI. The modification which should be made in the student’s course to suit individual cases will, perhaps, be most readily understood by stating the objects of each section in the book: Section I is adapted to impart experience in chemi- cal manipulation, and to afford practical illustra- tions of the elementary portions of theoretical or descriptive chemistry ; it may be omitted when in- struction iti analysis only is required. Section II is indispensable, and must be carefully perused. 18 introduction. Section III is also indispensable to the student of analytical chemistry, but if the time at his dis- posal is very limited, he may omit the performance of the experiments described in this section, and merely read through the text. Section IV must be carefully worked through. A student whose time is limited may, however, simply try the reactions and omit the performance of analyses at the end of each group. Section V is intended for students whose object is to learn only the analysis of simple salts, such as is required in many modern examinations on practical chemistry. This section may also be used as an easy begin- ning in analysis, and as an introduction to more complicated analyses to be made by Section VI, or it may be passed over by the student who is in- tending to learn general analysis. Section VI is not required by a student who is learning only the analysis of simple salts, but should be carefully worked through by the student of gen- eral analysis, who may, after becoming thoroughly conversant with its contents, pass on to quantita- tive analysis, or to any special branch of practical chemistry he may require. SECTION I. EXPERIMENTS ILLUSTRATING THE PREPARATION AND PROPERTIES OF GASES, ETC. Introductory Remarks.—In this section full directions are given for the preparation of five gases (viz., oxygen, hydrogen, carbon dioxide, ammonia, and carbon monoxide) and for certain interesting and in- structive experiments which may be made with them. The processes of preparation and manipulation required for these gases are more or less typical of those employed for all other gases, and the student will, therefore, from the experience obtained by performing the experi- ments with the above-named gases, easily prepare and experiment upon the three other gases (nitric oxide, chlorine, and hydrochloric acid) by following the directions inserted in small print, and any other gas by the account given of it in a treatise on chemistry. Those gases which are in small type may be omitted in the practical course. Two examples of the process of distillation are also appended. The reference numbers inclosed in brackets refer to the para- graphs which commence with Section II (p. 43); the numbers will be found in thick type in the text, and at the head of each page the numbers of the paragraphs are also placed in square brackets. A full list of the apparatus required for this section is given in par. 494, and its use is explained in pars. 1-10 and 14-19; a list of chemicals and certain other requisites will be found in par. 531. Note.—The student must carefully read through the whole descrip- tion of each experiment before beginning to perform it, and after its successful performance should enter a brief description of it in his note-book. I. Oxygen Gas.—When iron is for some time exposed to moist air its surface becomes covered with rust; many other metals undergo a similar change in moist air, but the alteration produced in their appearance is not usually so noticeable as in the case of iron. The liquid metal mercury does not rust as iron does in moist air, but it be- comes slowly covered with red mercury rust when strongly heated for some time in a flask open to the air; this mercury rust has received the name of mercuric oxide. The fact that metals become heavier by rusting proves that something is added during the process. 20 PREPARATION OF OXYGEN. [Exp. 1. Exp. 1.—Place in a clean and perfectly dry test-tube sufficient mercuric oxide to cover the bottom ; heat the powder (1, 19) as shown in Fig. 1, loosely stopping the end of the tube with the thumb. As soon as small drops of mercury form on the sides of the tube, remove the thumb and quickly place inside the top of the tube the burning end of a slip of wood (e. g., the uncoated end of a wooden lucifer match); the flame will be seen to burn more brightly. If, after again heating the powder for some time in the way just de- scribed, the slip be introduced into the mouth of the tube immediately after blowing out the flame and whilst there is a spark at its end, the glowing end will be caused to burst into flame. This behavior with a burning or glowing slip of wood is one of the most remarkable properties of oxygen gas, and we frequently make use of this property as a “test” for its presence. The chemical change which has occurred is thus represented by an equation : Fig. 1. Since by heat, then, we can separate from mercuric oxide mercury and oxygen, we learn that the process of rusting consists in the metal taking oxygen gas"from the air, and the increase of weight above referred to is thus accounted for; if all metal rusts could be decomposed by heat we might obtain oxygen from them just as from mercuric ox- ide. This method of making oxygen is interesting, since it was the first means known of preparing the gas; it is never used nowadays to prepare large quantities of oxygen, since other substances are known which contain a larger pro- portion of oxygen, and give it off, when they are heated, more easily than mercuric oxide does—substances which are also preferable on account of their greater cheapness. Potassium chlorate is most frequently employed : I-IgO = Hg + 0. KC10S = KC1 + O,. Exp. 2-4.] preparation of oxygen. 21 Exp. 2.—Place in a clean dry test-tube a little potas- sium chlorate, and heat it as in Exp. 1. The white salt, after “decrepitating ” or crackling, “ fuses ” or melts, and when further heated appears to boil; the small bub- bles which are given otf consist of oxygen gas, as may readily be proved by holding in the mouth of the test- tube a burning or glowing splinter of wood as described in Exp. 1. Potassium chlorate gives off oxygen gas much more readily than does mercuric oxide; but if it is mixed with small quantities of certain other substances, which them- selves appear to undergo no change, its oxygen is driven off by heat with extreme facility; of these substances, manganic oxide or black oxide of manganese is the one usually chosen. Exp. 3.—Powder some potassium chlorate (about as much as would fill a watch glass) finely in a mortar, mix with it, by rubbing them together in a mortar, about one- fifth as much powdered manganic oxide, and heat a small quantity of the mixture in a test-tube; the oxygen will begin to come off as soon as the mixture is heated, and a comparatively gentle heat will cause the gas to be rapidly evolved. In the preceding experiments the oxygen was detected in the tube in which it was prepared, and was allowed to pass away freely into the air. When the gas has to be collected in a vessel unmixed with air, it is made to pass through a bent glass tube (the delivery-tube), which is fitted by means of a cork air-tight into the mouth of the test-tube; the end of this tube dips into some water, and the bubbles of gas are allowed to rise into a vessel full of water and inverted over the end of the delivery-tube. This process of “collecting” oxygen is fully described in the following experiment; in the performance of which two students may advantageously work together, one at- tending to the regulation of heat to the mixture, the other to filling the gas-jars. Exp. 4.—Select a sound cork, of such a size that, after having been softened by being squeezed or by being rolled with gentle pressure on the floor under the foot, it fits 22 PREPARATION OF OXYGEN. [Exp. 4. tightly into the mouth of the test-tube to be employed. Then bend (6) a piece of hard glass tubing, about 14 inches in length, into the form shown in the figure; so adapting the bends by trial that when the apparatus is fitted to- gether the bottom of the test-tube may be at a convenient height in the flame, the end of the delivery-tube at the same time dipping about an inch under water. Make a hole through the centre of the cork (8), of such a size that the glass tube fits tightly into it. Then test whether the apparatus is air-tight by fitting the glass tube into the cork, and the cork into the test-tube, and blowing down the open end of the delivery-tube; no air must be heard to escape, or must be seen to bubble out on moistening Fig. 2. the cork; if air does escape, a fresh cork must be taken. Now pour into the perfectly dry test-tube the oxygen mixture (see Exp. 3) off a piece of paper folded into a trough, or scoop up the mixture from the mortar with the mouth of the test-tube, until the tube is about one- third full, and tit in the cork and delivery-tube. Before heating the tube fill the jar in which the oxygen is to be collected with water, close it with a stopper or ground-glass plate or with the hand, invert its mouth in water three or four inches in depth, contained in an earthenware pan or bowl, and carefully remove the stopper or plate. If this operation has been performed with proper precaution the jar will be entirely filled with water, and no air-bubble will remain. Next proceed to heat Exp. 4.] PREPARATION OF OXYGEN. 23 the upper part of the oxygen mixture, holding the tube in one hand and keeping the lamp slowly moving with the other hand, in order to prevent any part of the glass from being suddenly and strongly heated, which would be liable to crack it. Oxygen gas will soon be evolved, but will not at once appear at the end of the delivery-tube, since it has first to drive out the air which filled the ap- paratus ; as soon as a slip of wood glowing at its end is kindled when held at the mouth of the delivery-tube, the oxygen has driven out the air and is beginning to escape; the end of the delivery-tube is then at once dipped under water beneath the mouth of the jar, and the stream of bubbles rising into it will rapidly displace the water. As soon as the jar is full of gas, close its mouth under water with the stopper or glass plate, and remove it for experiment. The jar may also be removed by slipping under its mouth a small dish or saucer; the water taken out in the saucer then closes the mouth of the jar air-tight. Precautions.—The water must be removed from the pan, when it rises inconveniently high, by means of a small porcelain dish; if at any time the gas should be given off too rapidly, the flame should be removed until the current slackens; the lower portions of the mixture should be heated only after the upper parts refuse to yield any more gas: when the process is to be stopped, the end of the delivery-tube must be removed from the water before the gas has ceased to bubble out, and the test-tube must not be allowed to touch cold or wet ob- jects, which would cause the hot glass to crack. Several bottles filled with oxygen will be required for the following experiments, or the same bottle may, if necessary, be refilled with the gas according to the above directions, after the completion of each experiment. Note.—The use of ground-glass plates, which must close the mouth of the jar perfectly air-tight, is much easier than that of stoppers. An earthenware “ beehive shelf,” which may be used in a common earthen pan, or a “ pneumatic trough,” is also convenient, since it supports the jar during the process of collection. Oxygen gas is remarkable for the energy with which COMBUSTIONS IN OXYGEN. [EXP. 5, 6. it combines with or burns many substances; three ex- amples are given of this property in Exps. 5, 6, and 7. Exp. 5.—Select a splinter of wood charcoal or a small piece about the size of a nut; the experiment is more brilliant if the surface of the charcoal formed originally part of the bark of the tree. Bind this upon a “ defla- grating spoon” with a little fine iron or copper wire; then adjust the wire handle of the spoon in the brass cap, so that when held beside the bottle of oxygen with the cap on a level with the mouth of the jar, the little metal cup is about an inch from the bottom of the bottle. Now heat the charcoal in the Bunsen flame, or better in the blowpipe flame (4), until a part of its surface glows when held in the air, and quickly place it in the bottle of oxygen, with the brass plate covering the mouth of the bottle. (See Fig. 7, p. 33.) The charcoal will burn much more brilliantly than in air, throwing off sparks if its surface was “ barky c + o2 = co2. When it ceases to burn, pour into the bottle a little clear lime-water from a small beaker or test-tube, quickly close the bottle, and shake the liquid round inside it; the clear liquid becomes milky, indicating the presence of carbon dioxide gas, as will be hereafter explained. Exp. 6.—Remove the charcoal from the deflagrating spoon and replace it by a piece of sulphur as large as a pea; heat the spoon in the flame until the sulphur melts and begins to burn with a pale-blue almost invisible flame. Then place the spoon in a fresh jar of oxygen; the sulphur will at once burn with a much brighter flame, which emits a beautiful violet light: S + 02 = so2. Sulphur dioxide or sulphurous anhydride gas remains in the bottle; its presence is proved by its suffocating smell, also by pouring a little water into the bottle and shaking it round. Sulphurous acid is thus formed, and is recog- nized by dropping into the water a piece of blue litmus- paper, which is immediately reddened, and by pouring Exp. 7.] 25 COMBUSTIONS IN OXYGEN. in a few drops of red potassium dichromate solution, the color of which changes to green. Exp. 7.—Cleanse the deflagrating spoon from any re- maining sulphur, and put into it a small piece of phos- phorus no larger than a pea. The phosphorus may be cut with a knife; it must be touched only with wet fingers, and should be handled as little as possible, since it is liable to catch fire by the heat of the hand; it is always kept under water, being dried only immediately before being used by pressing it between filter-paper or blotting-paper, or with a dry cloth. Set fire to the phos- phorus by holding the spoon in the flame, and notice how it burns in the air; then place the spoon in a jar of oxygen—the phosphorus will burn most brilliantly, pro- ducing a white substance called phosphorus pentoxide, or phosphoric anhydride: p,+o. = p2o#. When the phosphorus has ceased to burn, pour in a little water and shake it round in the jar, the white substance dissolves, yielding phosphoric acid : P205 + 3Ht0 = 2H,P04, and the water may now be proved to be acid by drop- ping into it a piece of blue litmus-paper, which will be immediately reddened. Tests for Oxygen.—A convenient test for oxygen is to introduce into the gas a slip of wood with a spark at the end, which is caused to burst into flame. Only one other gas possesses this property, and it is readily distinguished from oxygen by other means. This test only detects oxygen when it is in a pretty pure condition. II. Hydrogen Gas.—The liquid substance water consists of oxygen gas combined with another gas called hydrogen; several processes are known for preparing hydrogen from water. This gas is, however, most readily obtained from another liquid containing it, called hydro- chloric acid, by the action upon it of the metal zinc. 26 PREPARATION OF HYDROGEN. Exp. 8. Exp. 8.—Fit a two-necked Woulffe’s bottle1 (a, Fig. 3) with air-tight, perforated corks, bearing a thistle funnel (b), whose end reaches nearly to the bottom of the bottle, and a tube bent, as shown at c, and terminating just below the cork; join to this, by means of a short piece of tightly fitting india-rubber tube, a bent deliv- ery-tube, d. Pour into the bottle sufficient granulated Fig. 3. zinc to cover the bottom, replace the corks, and, after ascertaining that the apparatus is air-tight by closing the end of the delivery-tube and blowing down the thistle funnel, pour in through the funnel sufficient water to cover the zinc and the end of the funnel-tube; then add strong hydrochloric acid gradually until, after mixing the acid and water by shaking the bottle, the hydrogen is seen to rise from the zinc in numerous small bubbles: Zn + 2HC1 = 2H + ZnCl2. Then dip the end of the delivery-tube under water con- tained in the pan or trough, and allow the gas to bubble out through the water for at least five minutes. This delay is necessary in order to give the hydrogen time to entirely remove the air which filled the bottle, and which, 1 A wide-necked bottle may be used instead, being fitted as shown in Fig. 5 (p. 30). Exp. 9, 10:] preparation of hydrogen. 27 when mixed with hydrogen, produces a dangerously ex- plosive mixture. Before collecting larger quantities of the gas for experiments ascertain that the hydrogen is no longer mixed with air by inverting a test-tube filled with water over the end of the delivery-tube. As soon as the tube is full of gas close its mouth with the thumb and hold it to a flame; if the gas burns with a slight explosion, the tube is again similarly filled with the gas and tried in the same way. As soon as the gas burns quietly with a pale flame, a small thick glass cylinder or tube may be filled with it in the same way as was directed for oxygen. If during the preparation of gas for the following ex- periments the gas comes off' too slowly, it is only neces- sary to pour in a little more strong acid through the funnel and mix it with the liquid in the bottle by gently shaking the latter. Exp. 9.—Hold the vessel filled with hydrogen with its mouth open and directed upwards for a short time, the gas will entirely escape; the absence of the gas may be shown by holding a lighted taper in the vessel, when no flame will be seen at the mouth. If the cylinder be refilled with hydrogen and held for a short time mouth downwards, the hydrogen will remain in it, and its pres- ence may be shown by the gas burning with a pale flame when a lighted taper is introduced. These results prove that hydrogen is much lighter than air, since its tendency to rise prevents it from passing out downwards through the open mouth, whilst it readily escapes upwards from the erect cylinder. Since hydrogen is so much lighter than air, it is possible to collect the gas without using water by a process called “ displacement.” The delivery- tube of the hydrogen apparatus is passed up to the top of the inverted jar containing air, the hydrogen rises to the upper part of the jar and gradually pushes out the heavier air downwards. Exp. 10.—Fill a jar with hydrogen by “ displace- ment.” For this purpose fit upon the india-rubber joint of the hydrogen apparatus a delivery-tube bent as shown in Fig. 4, and when a brisk effervescence of gas has been 28 COMBUSTION OF HYLROGEN. [EXP. 11. caused by pouring in some strong hydrochloric acid, pass this tube up to the top of an inverted jar and allow the jar to remain in this position for several minutes; it is best to loosely close the mouth of the jar during this process by letting it rest upon a perforated disk of cardboard, or upon the round brass cap of a deflagrat- ing spoon, supported upon a retort stand ring, or upon an iron tripod stand, since the en- trance of air by “diffusion” is thus almost entirely pre- vented. Remove this jar, keeping it mouth downwards, and push up inside it a burning wax taper five or six inches in length. The hydrogen will be lighted and will burn with a pale flame at the mouth of the jar, but the flame of the taper will be seen to be extinguished by the gas. The taper may, however, be rekindled by holding it in the hydrogen flame burning at the mouth of the jar. Exp. 11.—Cover the bottle and funnel-tube with a cloth, to prevent accident in case of an explosion, and light the hydrogen at the end of the delivery-tube used in the last experiment. Hold over the flame a perfectly clean, dry, and cool tumbler or beaker; the inside will become dimmed with moisture, showing that hydrogen gas burning in the air produces water: Fig. 4. H2 + O = H20. Note.—Since all gases which have been in contact with water con- tain more or less vapor of water, or are “ moist,” it is usual to employ for this experiment a stream of hydrogen gas which has been freed from moisture or “dried.” A gas is dried or “ desiccated” by pass- ing it through some substance which readily absorbs moisture. Strong sulphuric acid (oil of vitriol), calcium chloride, and quick- lime are the desiccating agents most commonly employed. The gas may he made to bubble through strong sulphuric acid contained in a bottle, B (Fig. 10, p. 38), connected, as shown in the figure, with the generating apparatus. It may he also dried by passing it through a tube containing fragments of calcium chloride, or of quicklime Exp. 12,13. PREPARATION OF CARBON DIOXIDE. 29 (Fig. 10 a), or pieces of pumice-stone moistened with strong sulphuric acid. The moistened pumice may be contained in a U-tube (Fig. 106), or in the bottle b (Fig. 10, p. 38). Exp. 12.—Measure the height of a short, thick glass cylinder, and divide it into three equal parts by small pieces of gum-paper stuck upon the outside. Fill the cylinder with water, and, after inverting it in water, fill one-third with oxygen (Exp. 4), and the remainder with hydrogen (Exp. 8); let the jar stand with its mouth under water for five or six minutes to allow the gases to mix; then apply a lighted taper to the mouth of the jar directed downwards, taking care not to place the fingers beneath it: the gases combine to form water with a loud ex- plosion. Test for Hydrogen.—Hydrogen gas is recognized by burning with a pale flame in air or oxygen, the flame de- positing water on any cold object held above it. III. Carbon Dioxide Gas, or Carbonic Anhy- dride.1—When carbon was burnt in oxygen (Exp. 5) a gas called carbon dioxide remained in the jar; the gas may be prepared in this way, but a much more easy method consists in pouring hydrochloric acid upon some pieces of marble. CaC03 + 2HC1 = C02 + II20 + CaCl2. Chalk or limestone may be substituted for marble, but these do not answer so well. Exp. 13.—Rinse out the apparatus used for preparing hydrogen, and place in it some small pieces of marble; fit into the india-rubber joint a delivery-tube bent at right angles, as shown iy Fig. 5; then pour through the funnel-tube sufficient water to cover the marble and the end of the funnel-tube, and then strong hydrochloric acid until gas comes off with brisk effervescence. Place the delivery-tube in a jar, with its end nearly touching the bottom; cover the mouth of the jar with a small disk of 1 Formerly called carbonic acid, a name which is incorrect, since all acids contain hydrogen. 30 PREPARATION OF CARBON DIOXIDE. [EXP. 14, 15. cardboard which has had a slit cut m it tor the delivery- tube, or pass the delivery-tube through the brass cap of a deflagrating spoon, and allow the ap- paratus to stand for several minutes. Carbon dioxide being much heavier than air will soon fill the jar by “dis- placement ; ” that is to say, it will col- lect in the lower part of the jar, and, by gradually rising in it, will lift out the air. Since this gas has the property of extinguishing a burning taper, it is easy to ascertain when the jar is full by holding a lighted taper just inside its mouth; if the flame is extinguished, the carbon dioxide has reached the top. Carbon dioxide gas, being very largely dissolved by water, is rarely collected over water, the process of “displacement” being preferable. Exp. 14.—Allow this jar of carbon dioxide to stand uncovered and with its mouth upwards for a few minutes; then place in the jar a burning taper; the carbon dioxide is shown to be stiil present in the vessel by the immediate extinction of the flame. Then hold the jar for several minutes, with its mouth downwards; on testing with a lighted taper only air will be found in the vessel. These experiments prove that carbon dioxide is heavier than air, since it remains in a vessel which is open above, and falls out of one which is open below. Exp. 15.—Since this gas is so much heavier than air, it can be poured from vessel to vessel like water. This may be shown by pouring carbon dioxide from a bottle tilled with the gas into a jar full of air, the latter being somewhat the smaller. The bottle is gradually tilted a little beyond the horizontal position, with its mouth over that of the jar. After holding it in this position for a short time it may be proved by a lighted taper that the gas has left the bottle and is present in the jar. Fig. 5. Fig. 6. Exp. 16,17.; PROPERTIES OF CARBON DIOXIDE. 31 Exp. 16.—Pour a little lime-water from a test-tube or small beaker into ajar of carbon dioxide and shake the liquid round in the jar. The lime-water will at once become milky, owing to the lime which is dissolved in the water being converted by the carbon dioxide into chalk (calcium carbonate), which, being an insoluble sub- stance, remains mixed as a white powder or “precipi- tate ” with the water: Exp. 17.—Carbon dioxide gas readily dissolves in cold water, forming a liquid which probably contains carbonic acid: CaH A + C02 = CaC03 + H20. C02+II20 = II2C03. The solubility of the gas in water may be proved by displacing the air front a bottle, previously half filled with cold water, by carbon dioxide; then tightly closing the mouth of the bottle with the wetted palm of the hand, and shaking vigorously for a short time; the bottle will adhere to the hand, owing to a partial vacuum being produced by the absorption of the gas by the water. A further proof is afforded by dipping the end of the deliv- ery-tube (Fig. 5) to the bottom of a beaker containing water, so as to cause the gas to bubble through the liquid. After the bubbles have passed for several minutes the water may be shown to contain carbonic acid by pouring some of it into a test-tube and adding a little lime-water, which will cause a milkinessalso, By adding to another part of the carbonic acid solution several drops of blue litmus solution, or dipping into it a piece of blue litmus- paper, which will become red, indicating the presence of an acid ; keep this liquid. If this liquid containing car- bonic acid be tasted it will be found to possess a taste re- sembling that of soda-water, and in fact soda-water is merely water which contains a large quantity of carbonic acid, as may be proved by examining it with lime-water and litmus. If some of the water containing; carbonic acid be boiled in a test-tube, the carbon dioxide gas is driven off again; the bubbles of gas are seen rising in 1 Sometimes the milkiness disappears, for reasons explained in Exp. 18, unless much lime-water is added. 32 PROPERTIES OF CARBON DIOXIDE. [EXP.18,19 the water long before the latter boils, and after the liquid has been boiled briskly for several minutes it may be proved to be free from carbonic acid by giving no milki- ness on addition of lime-water, and by not changing the color of bine litmus-paper or solution. The red liquid prepared by adding bine litmus to the carbonic acid solu- tion will also become blue when it is boiled. Exp. 18.—Dilute some lime-water, contained in a small beaker, with an equal quantity of distilled water, and allow the carbon dioxide gas to bubble through it as in Exp. 17; a milkiness will be produced owing to the formation of chalk (Exp. 16); but if the gas is allowed to bubble for several minutes through the liquid, the milkiness will gradually disappear, since the chalk dis- solves entirely in the carbonic acid which is formed by the carbon dioxide dissolving in the water. On boiling some of this clear liquid it again becomes milky, since the carbon dioxide is driven out of the water by heat, and therefore the chalk can no longer remain dissolved. It will be found, on pouring out the water, that part of the chalk remains adhering to the inside of the tube, whence it may be removed by pouring in a few drops of hydrochloric acid. The above experiment explains the origin of the coating or “incrustation” of chalk inside kettles and steam-boilers in which chalk-water is boiled. Such water contains chalk dissolved by carbon dioxide gas present in the water; this gas is driven off when the water is boiled, and a great part of the chalk separates upon the sides of the vessels. Tests for Carbon Dioxide.—It is evident that the pres- ence of carbon dioxide gas is shown by its properties of extinguishing a burning taper, and turning lime-water milky; these are the ordinary “ tests” for carbon dioxide. AVe may now proceed to employ them to prove that car- bon dioxide is evolved from our lungs during the pro- cess of respiration, and also that it is produced by a burn- ing candle. Exp. 19.—Invert a bottle full of water in a pan of water, and fill it with air from the lungs by blowing the breath out through a glass tube, one end of which is dipped into the water and held beneath the mouth of the Exp. 20.] tests for carbon dioxide. 33 bottle. In order to obtain air from the lungs a full breath should be drawn, and the nose then closed by pinching it with the finger and thumb. Before allowing any breath to pass up into the bottle, the greater portion should be breathed out through the tube so as to replace the air contained in the windpipe, mouth, and tube by air from the lungs; the remainder of the breath is then allowed to bubble up into the bottle. Close the bottle, remove it from the pan, and introduce into it a lighted taper; the flame will be immediately extinguished. Now blow air from the lungs, obtained as just de- scribed, through a glass tube into lime-water contained in a small beaker; the lime-water will become milky. Exp. 20.—Fasten a small piece of candle or wax taper upon the deflagrating spoon, and place it alight in a bottle of air, the mouth of which is closed by the brass plate (Fig. 7). After burning for a short time the flame will be extinguished, and if re- lighted will be again extinguished when placed in the jar. Now pour in some lime-water from a small beaker, and shake it round in the bottle; the liquid will be rendered milky. A similar experiment may be per- formed, substituting for the candle the flame of coal-gas which is burnt from a jet inside the inverted bottle, and closing the mouth of the bottle with a glass plate, as soon as the flame is extinguished. The extinction of the flame, and the milkiness then produced by shaking the lime-water in the bottle, will prove the production of carbon dioxide by the combustion. Hence carbon dioxide gas is constantly being intro- duced into the air by respiration and combustion, and we should therefore expect to be able to detect its pres- ence in air by the above tests: It is manifestly not present in sufficient quantity to extinguish a burning taper, but the presence of carbon dioxide in air may be shown by lime-water in the following way: Fig. 7. 34 PREPARATION OF AMMONIA. [EXP. 21-23. Exr. 21.—Pour some clear lime-water into a watch glass, or better a clock glass, and allow it to stand for a few minutes in the air; a him of chalk will gradually form on the surface, and will be seen as white flakes when the water is stirred. III. a. Nitric oxide gas may be prepared in the apparatus used for making carbon dioxide (Fig. 5, p. 30). Exp. 22.—The pieces of marble are removed and the apparatus washed out. Some scraps of copper (copper clippings or turnings) are then placed in the flask, and nitric acid diluted with an equal measure of water poured in: 3Cu + 8HN03 = 2N0 + 3Cu(NOs)2 + 4H20. A reddish-brown gas soon fills the inside of the vessel, and should be allowed to bubble off for a time through water; it may then be collected over water as was directed for hydrogen gas. Nitric oxide is colorless, but it forms a reddish-brown gas (chiefly nitrogen tetroxide) when mixed with free oxygen. This is shown by filling a jar with the gas over water, and then allowing it to stand with its mouth open in the air ; the entrance of the oxygen of the air at once produces red fumes. The appearance of red fumes in the preparation ‘ vessel is thus explained, since the vessel is at first filled with air, with which the first portions of the gas mingle. IV. Ammonia Gas.—The familiar smell of common “smelling salts” is due to ammonia gas, which is con- stantly being given off from the solid “carbonate of ammonia” contained in the bottle. The gas is thus evolved only very slow- ly ; it may be made to come off much more rapidly if the “car- bonate of ammonia” is mixed with lime and the mixture is then gently heated. Sal ammo- niac is usually employed instead of the carbonate of ammonia: Fig. 8. 2NH4C1 + CaH202 = 2NH3 + CaCl2 + H.20. Exp. 23.—Powder some am- monium chloride or sal ammo- niac in a mortar, and mix with it thoroughly on a sheet Exp. 24.] PROPERTIES OF AMMONIA. 35 of paper about an equal quantity of slaked lime in fine powder. Pour some of this mixture into a small flask (Fig. 8) until it is about one-third filled, and close the neck of the flask with a tightly fitting perforated cork, into which is inserted a straight piece of glass tube eight or nine inches long. Heat the mixture gently by placing the flask upon a piece of wire gauze on a tripod stand and putting underneath it a lighted rose-burner. Am- monia gas will soon be smelt issuing from the end of the tube, and, since it is much lighter than air, may be col- lected by “ displacement,” as seen in Fig. 8. To ascer- tain when the vessel is filled with the gas it is only neces- sary to hold at the mouth of the jar a piece of moistened red litmus or yellow turmeric paper; since ammonia gas changes the color of the former to blue and of the latter to reddish-brown, it is easy to see whether it has reached the mouth of the jar by observing whether any change is produced in the color of the paper. A more easy way to prepare ammonia gas for the fol- lowing experiments consists in heating a little “ Liquor Ammonise Fortissima ” in the flask (Fig. 8) instead of the solid substances. Ammonia gas does not burn continuously in air at the ordinary temperature, but ,jt burns readily either in strongly heated air or when lighted in oxygen gas. Show this by holding the end of the delivery-tube, from which a stream of gas is issuing, in the top of a Bunsen flame; a pale yellowish-green flame of burning ammonia will be seen; and if the end of the tube is dipped into a jar of oxygen, the ammonia maybe inflamed as it issues into the oxygen gas. Ammonia should always be collected by displacement, since it is extremely soluble in water, and therefore its collection over that liquid would lead to great waste of the gas. For this reason, also, the vessels in which am- monia is to be collected should always be perfectly dry inside. Exp. 24.—Place a jar full of ammonia mouth down- wards in a vessel of water, and gently shake the jar so as to agitate the water at its mouth ; the water rapidly absorbs 36 [Exp. 25. PROPERTIES OF AMMONIA. the gas and rises in the jar to fill the space formerly oc- cupied by the gas. If a little water be rapidly poured into a jar of ammo- nia by momentarily partly opening it and at once cover- ing it again with a glass plate or with the hand, and the water be then shaken in the jar, the water, owing to its having absorbed the gas, will, when poured out, be found to have acquired the smell and behavior with litmus and turmeric papers which characterize the gas. This liquid is in fact weak “ Liquor Ammoniae,” a solution prepared in large quantities by letting ammonia gas bubble for some time through cold water. When this solution is boiled the ammonia gas is in great part expelled. Exp. 25.—Pour into a glass jar a little strong hy- drochloric acid, close the jar with a glass plate, and shake the acid about inside the jar,— hydrochloric acid gas will thus be liber- ated ; the liquid may then be allowed to run out by slipping aside the glass plate for a moment. Place this jar in an in- verted position over a jar containing ammonia gas, and covered with a glass plate (Fig. 9 a), then withdraw the glass plates, so that the mouths of the jars are in contact (Fig. 9 b), and the hydrochlo- ric acid and ammonia gases can freely intermingle. Dense white fumes of solid ammonium chloride will immediately be formed : Fig. 9. NH3 + HC1 = NH4C1. This experiment may also be performed by dipping a glass rod into some strong hydrochloric acid, and holding it in ammonia gas as it issues from the delivery-tube of the apparatus, or in a jar previously filled with the gas; the same white fumes will at once appear. Tests for Ammonia Gas.—-Ammonia gas may be readily recognized by its pungent smell, by turning moistened red litmus-paper blue and moistened turmeric-paper Exp. 26.] PREPARATION OF CARBON MONOXIDE. 37 reddish-brown, and also by giving white fumes with a glass rod moistened with strong hydrochloric acid. Gases are frequently made to pass through certain liquids, in order to free them from impurities before they are collected; this is termed “ washing” a gas. In some cases gases are purified by causing them to pass over pieces of a solid substance, which absorbs the impurities. The preparation of carbon monoxide gas from oxalic acid will serve to show how these processes are performed. V. Carbon Monoxide.—This gas is produced when carbon dioxide gas is made to pass over red-hot char- coal : C02 + C = 2CO. It is often thus formed in open grates, and is seen burn- ing at the top with its characteristic blue flame. Carbon monoxide-is usually prepared by heating solid oxalic acid with strong sulphuric acid, when a mixture of carbon monoxide and carbon dioxide is given off: H2GA-2H20 + h2so4 = CO + co2 + H2S04.3H20. Exp. 26.—Place a little solid oxalic acid in a test-tube; pour upon it strong sulphuric acid1 sufficient to cover it to a depth of at least half an inch, and heat the mixture. After a short time effervescence will be noticed, owing to gases being evolved ; hold in the mouth of the tube a glass rod freshly dipped into lime-water; the drop of lime-water hanging upon its end will become milky, showing that carbon dioxide is one of the gases evolved. Hold a burning taper to the mouth of the test-tube; a blue flame will be seen, caused by the carbon monoxide gas burning in the air. 1 Strong sulphuric acid is a very corrosive liquid, and great care must be taken not to get any upon the skin or clothes; should any of this acid or of any other acid get upon the skin it must be at once washed off’; if it should accidentally be spilt upon the clothes, the part must be rubbed with ammonia solution. If the acid has remained for some time on the clothes it will produce a red stain, which will be removed by ammonia solution, unless it has been caused by nitric acid. 38 PROPERTIES OF CARBON MONOXIDE. [Exp. 27. In order to get rid of the carbon dioxide gas which is mixed with the carbon monoxide, the mixed gases are “washed” with solution of caustic soda, or passed over pieces of sol id caustic soda; the soda absorbs the carbon dioxide readily, but allows the carbon monoxide to pass on: CO+C02 + 2NaHO = CO + Na2C03 + H20.' Exp. 27.—Heat the mixture of oxalic acid and strong sulphuric acid in a flask (a) fitted as shown in Fig. 10, and pass the gases either into a wash-bottle (a small Wouiffe’s bottle, or a broad-necked bottle), fitted as shown in B, and containing caustic soda solution; or through a tube (a) containing fragments of quicklime, or a U-tube (6) filled with fragments of caustic soda or soda-lime or with fragments of pumice-stone or broken tobacco-pipe stem Fig. 10. moistened with strong caustic soda solution. If the carbon dioxide is to be completely removed, the gases must be passed through two or more such tubes or bottles. The car- bon monoxide gas thus more or less perfectly freed from carbon dioxide may be collected over water, and will be found to give either no milkiness with lime-water or a slight milkiness if the stream of gas has been so rapid that the caustic soda has not been able to absorb the car- bon dioxide completely. By heating a formate with strong sulphuric acid carbon monoxide alone is given off, and is thus readily obtained free from carbon dioxide. Carbon monoxide resembles hydrogen in being inflam- Exp. 28, 29.] PREPARATION OF CHLORINE. 39 mable and in extinguishing a burning taper; it also ex- plodes when mixed with oxygen or air, hence before collecting a cylinder of the gas for experiment, ascertain that the gas coming off from the apparatus is free from air by collecting a small test-tube full and proving that it burns quietly. Exp. 28.—Push a burning taper up into a cylinder filled with carbon monoxide; the gas will burn with a blue flame at the mouth of the jar but the taper will be extinguished. As soon as the gas has ceased to burn in- side the cylinder, pour in a little lime-water and shake it about; the liquid becomes milky, showing that by the combustion of carbon monoxide in the oxygen of the air carbon dioxide gas is produced: CO + o = co2. Tests for Carbon Monoxide.—Carbon monoxide is recog- nized by burning with a pale-blue flame in the air, pro- ducing carbon dioxide, which renders lime-water milky. V. a. Chlorine gas may be made in the apparatus employed for the preparation of carbon monoxide. The washing-bottle may either be dispensed with or mav be used containing a little water to free the chlorine from hydrochloric acid gas. Exp. 29.—Place some manganic oxide powdered, or better in small lumps, in the flask A (Fig. 10, p. 38), pour upon it some strong hydrochloric acid, mixed with about one-third its measure of water, and heat gently in a draught-cupboard or in the open air. A greenish-yellow gas is evolved, which may be collected by displace- ment, like carbon dioxide, since it is much heavier than air: The gas has a very destructive action on the lungs, and must on no account be inhaled; it is usually recognized by its yellowish-green color, its peculiar smell, and by its property of bleaching moist vege- table colors. This last property is shown by placing in a jar of the gas a piece of moistened litmus-paper or fabric dyed with madder (“Turkey red”)- The colors of both will be destroyed. A burning wax taper plunged into a jar containing chlorine continues to burn with a very smoky flame. Oil of turpentine, introduced into the gas by moistening a strip of filter-paper with the warm liquid, catches fire of itself and gives rise to dense smoke. A piece of dutch-foil or copper-leaf also burns when dropped into chlorine. Tests for Chlorine.—Chlorine gas is recognized by its yellow color, its smell, and its power of bleaching moistened litmus-paper. Mn02 + 4HC1 = Cla + MnCl2 + 2H20. 40 DISTILLATION OF WATER. [EXP. 30, 31. ‘ V. b. Hydrogen chloride, or hydrochloric acid gas. Exp. 30.—Place in the cleansed Hask a (Fig. 10), which was used for the preparation of carbon monoxide, some lumps of sodium chlo- ride (common salt) obtained by breaking up a mass of melted table salt, or by breaking a piece of rocksalt; pour upon it strong sulphuric acid and heat gently. Hydrochloric acid gas is evolved : and being heavier than air may be eolleeted by displacement, in the same way as carbon dioxide. The gas fumes strongly in moist air, turns moistened blue litmus-paper red, dissolves easily in water (Exp. 24), giving an “acid” liquid (hydrochloric acid), which, like the gas, turns blue litmus red. Tests for Jlydrochloric Acid.—This gas is known by fuming in theair, turning moistened blue litmus-paper red, giving white fumes with ammonia gas, and yielding when dissolved in water a milky liquid on addition of silver nitrate solution, which does not become clear on adding nitric acid. NaCl + II2S04 = HC1 + NaHS04, VI. Distillation.—This process is employed to sep- arate liquids which boil at a comparatively low temper- ature, either from solids, or from other liquids which are not converted into vapor at all or only at much higher temperatures. It consists in boiling the liquid and cool- ing or “condensing” the vapor, which is thus given oif, again into a liquid—the “distillate;” the non-volatile solid or liquid substances present are thus left behind in the vessel in which the liquid is boiled. As examples of this process, the purification of common spring-water from thewsolid substances dissolved in it, and the prepa- ration of nitric acid, may be performed. Exp. 31. Distillation of Water.—Pour into a clean re- tort, a (Fig. 11), some tap-water through a funnel placed in the mouth, or in the “tubulure” (i. e., the opening for the stopper or cork) if a tubulated retort is employed. Support the retort, whose bulb has been about half filled with water, in a retort-stand or upon a tripod, with its neck sloping downwards and dipping into a small clean flask or bottle, b, which is partly immersed in cold water contained in an evaporating basin. Cover the bulb of the flask with a broad strip of filter-paper, whose ends dip inio the water contained in the dish; or, instead of cooling the flask cool the neck of the retort, by wrapping Exp. 31.1 DISTILLATION OF WATER. 41 round the lower part of it a piece of filter-paper, c, and round this a piece of wet string or tow, d; then arrange a funnel, e, with its mouth partly stopped so as to drop cold water on the upper part of the filter-paper; this water will be drained off by the string, d, and must not be allowed to run into b. On carefully boiling the water in the retort steam passes into the flask and is there condensed to “distilled water.” The first few drops should be thrown awav, as they are apt to be impure from rinsing the retort neck and flask. Whilst this pro- cess of distillation is going on, add to some tap-water, contained in a test-tube, several drops of nitric acid and Fig. 11. some silver nitrate solution, and notice that the water be- comes milky. A separate portion in another test-tube will also be found to become milky on addition of some ammonia and ammonium oxalate solution. These changes are due to the presence in the water of certain solid substances dissolved in it. If the distilled water from the flask be examined in the same way it will remain clear, showing that these substances have been removed by distillation. Tests for Distilled Water.—Good distilled water should remain quite clear when to separate portions of it are 42 PREPARATION OF NITRIC ACID. [EXP. 32. added solutions of ammonium oxalate, silver nitrate, barium chloride, and ammonium sulphide; these tests prove the absence of calcium, chlorides, sulphates, lead, and iron respectively. It should also leave no residue when evaporated. Exp. 32.—Nitric Acid.—Clean the retort from Exp. 31 by rinsing out the bulb with a little dilute hydro- chloric acid, and then thoroughly with water; let it drain for a few minutes, and place in it some solid potassium nitrate (nitre); then pour upon this, through a funnel placed in the neck or tubulure, a quantity of strong sul- phuric acid about equal in weight to the nitre used, and allow the acid to drain off the neck, in case a non-tubu- lated retort is employed, by supporting it for some time in an upright position. Proceed to distil just as in the preceding experiment; a yellow oily liquid will trickle down the neck of the retort into the flask; this liquid is somewhat impure nitric acid, and will be found to fume strongly in the air : kno3 + h2so4 = iino3 + khso4. Test for Nitric Acid.—Place some small pieces of cop- per in a test-tube, pour upon them a little of this nitric acid; on warming gently reddish-brown fumes will ap- pear in the tube, and a blue solution will remain (see Exp. 22, p. 34). This property of giving red fumes when treated with copper is often used as a test for nitric acid. SECTION II. PREPARATION AND USE OF APPARATUS REQUIRED IN ANALYSIS. JSotes.—Keier to the list in paragraph (494)*, which shows what apparatus is required for each student, and mark all apparatus as directed in the note at the end of the list. 1. The Bunsen Burner.—By far the most useful lamp for general heating purposes is the Bunsen burner (Figi 12). It is a gas lamp so constructed that coal-gas entering th rough the tube a is mixed with a proper proportion ol air which flows in through the holes at the foot of the burner, and the mixture of gas and air is burnt at the top of tube h. The oxygen of the air, which is thus mixed with the gas, burns the carbon in the interior of the flame. Accordingly the luminosity, which is believed to depend upon the ex- istence in the flame of unburnt carbon or carbon compounds, is destroyed. The Bunsen flame is therefore useful because it deposits no soot upon a cool object which is being heated in it, and also because it is much hotter, owing to the more complete combustion of the gas, than any of the ordinary flames. Its high temperature, non-lumi- nosity, and colorless appearance also render it very val- uable for producing flame colorations, as will be seen hereafter. The lamp should be provided with some means for partly or entirely closing the air-holes when requisite; this is usually effected either by a loose per- forated ring which is slipped over them, or by making flip fillip h fnrn round on ifs loner ‘iyn. Wlipn a small Fig. 12. 1 Numbers occurring in the text which are inclosed in brackets refer to the paragraphs commencing in this section. For con- venience in reference, paragraph numbers are printed in thick type ; and at the head of each page the numbers of the paragraphs it con- tains will be found inclosed in square brackets. 44 THE ROSE BURNER. 2. flame is being employed, the air must be partly shut off*, else the flame “ burns below.” When the lamp is to be used, a piece of tightly fitting india-rubber tubing T5gths of an inch in diameter is pushed over the end of the tube a, and the other end of the tubing is slipped over the tube which supplies gas to the working bench, the gas tap is turned on, and as soon as the gas is distinctly smelt issuing from the tube b, it is lighted. The flame should be almost perfectly color- less, and give scarcely any light. Occasionally the gas will burn at the bottom instead of the top of the tube b ; this usually happens when the flame is turned down very low, or the supply of gas is insufficient; also when the quantity of air admitted through the holes is too great, or the burner is lighted too soon after turning on the gas tap. It may be at once detected by looking through the holes in the base of the lamp, when the luminous flame will be seen burning from the small gas-jet inside; the flame produced whilst the gas is “ burning below” is also characterized by being long and somewhat luminous, and by emitting a very unpleasant smell. In such a case the flame should be at once extinguished by pinching the india-rubber tubing close to the burner, and the gas should be relighted after escaping for a few seconds. The momentary stoppage of the gas stream by suddenly striking the india-rubber tube upon the bench with the hand will also frequently cause the flame to rise to the top of the burner without extinguishing it. Closure of the air-holes serves the same purpose, but this must be done with care, as after the flame has burned below for a short time the metal becomes too hot to be touched. The risk of the gas burning below is prevented by slip- ping upon the top of the burner a tightly fitting thimble, with a hole in its top somewhat less in diameter than that of the burner. 2. For diffusing heat over a large surface, the “ rose burner ” is very useful; it is a small perforated metal cap c (Fig. 12), which, when placed upon the top of the tube b, yields a small circle of flames; the rose burner is put on and removed by grasping it with crucible tongs; 3,4: USE OF THE BLOWPIPE. 45 it is of course very hot after being removed, and should never be handled, or placed upon wood, until it is cool. 3. The flame of a spirit-lamp is occasionally employed instead of the Bunsen flame, but for general purposes the spirit- lamp should only replace the Bunsen burner where coal-gas cannot be obtained. The spirit-lamp (Fig. 13) con- sists of a glass vessel containing methylated spirit, into which dips a cotton wick, supported by means of a brass or, better, a stoneware wick holder. When not in use the wick should be always covered with the glass cap to prevent evaporation of the spirit. If the spirit is tolerably free from resin- ous matter its flame will be non-luminous, and will de- posit no soot upon a cold object. 4. The blowpipe is frequently used to produce a small but very hot flame from the flame of a gas-lamp, spirit- lamp, or candle, by blowing through it a fine stream of air from the mouth. In order to obtain the “blowpipe flame” from the flame of a Bunsen bur- ner, the blowpipe is held by the right hand, with its finely pierced tip a (Fig. 14) resting on the edge of the burner, and just inside the flame (Fig. 15); the mouth- piece b is then taken be- tween the lips, and after blowing out the cheeks to their full extent, the air contained in them is forced out through the jet a, and causes a small pointed tongue of flame to issue from the side of the gas flame. The (Fief difficulty in learning to use the blowpipe properly is experienced in acquiring Fig. 13. Fig. 15. Fig. 14. GLASS TUBE CUT AND BENT. [5. the habit of keeping up the blast of air for some time uninterrupted by the breathing. A little patient trial will, however, soon remove this difficulty, if it is borne in mind that the cheeks must be kept constantly inflated with air, and that the air must be forced through the blowpipe by the pressure of the cheeks alone, and not by the action of the lungs, breathing being carried on mean- while through the nose, and the mouth being occasionally replenished with air from the throat just before breathing out the air from the lungs through the nose. It is frequently necessary to have both hands free whilst using the blowpipe; this may be secured by rest- ing the jet a on the top of the burner, and supporting the other end, b, by the lips alone, as shown in Fig. 15; or the blowpipe may be rested on a support of convenient height, such as the ring of a retort-stand properly adjusted. The bright flame obtained by nearly closing the air- holes of the burner is much better suited for use with the blowpipe than the ordinary non-luminous flame. A bur- ner with an elliptical orifice which gives a flat flame is commonly substituted for the ordinary round flame of the Bunsen burner; it is easily obtained by slipping a brass tube down the tube of the burner. A further account of the uses of the blowpipe is given in par. 30. 5. Glass tube or rod is cut by laying it upon a flat sur- face, and making a deep scratch with the edge of a three-cor- nered file at the point to be cut. The glass is then held with both hands, one on either side of the scratch and close to it, and a gentle pressure is exerted upon the glass as if trying to break it across (Fig. 16). If the file-mark has been made sufficiently deep, the glass will readily break at the scratch; the sharp edges of a rod or tube should always be at once rounded by holding them in the Bunsen or blowpipe flame Fig. 16. 6-8.] 47 BORING CORKS. until they are partly melted, or by rubbing them with the face of a file. 6. Glass tube is bent by holding the part to be bent in the upper edge of a common fish- tail gas flame, so as to heat at least two inches of the glass (Fig. 17). The Bunsen flame must never be employed for bending glass tub- ing ; it produces a most unsatis- factory bend. The tube is sup- ported by holding it with both hands, one on either side of the flame, and whilst being heated it is constantly turned slowly round on its axis so as to heat all sides equally. As soon as the glass is felt to be soft and pliable it is taken out of the flame and quickly bent to the required angle. The heated part must not be allowed to touch anything until it is cold; the soot is then removed from it by a cloth or piece of paper. A bend, if properly made, should be a curve, and should not alter the bore of the tube (Fig. 17a); if a sharp angle is made the bore will be narrowed, and the bend, besides being unsightly,is very liable to break under a small strain (Fig. 17 6). Glass rod may be bent in the Bunsen or blowpipe flame. 7. Glass tube is drawn oat by holding it with both hands as for bending; and, whilst turning it constanly round on its long axis, the part to be drawn out is strongly heated in the Bunsen or, better, in the blowpipe flame (see Fig. 15); when the glass is well softened, the two ends are slowly pulled asunder in opposite directions. 8. Corks are bored usually by means of brass cork- borers, which are used as punches. A borer is selected of the same size as the glass tube which is to be inserted Fig. 17. Fig. 17 a. Fig. 17 b. 48 SULPHURETTED HYDROGEN TUBE. "9. into the cork, rather less than greater; the cork is then pressed against a wooden surface (best against the upright edge of a thick bench or table), and the per- foration made in it by gently pushing the borer through whilst constantly turning it upon its axis (Fig. 18). Caution and practice will enable the student to make a clean straight hole without damaging the surrounding parts of the cork. In boring a single hole through a cork the easiest way to make it straight is to bore from the centre of one end halfway towards the other, then reverse the cork and bore a hole to meet this from the centre of the opposite end. A perforation may also be made by pushing a sharply pointed round tile carefully through the cork. The round file is required for smoothing the interior of holes made by the cork-borer, or for slightly enlarging them when they are too small; whilst doing this great care must be taken to leave the hole round in shape, and not to enlarge it so much that the glass tubing when in- serted tits loosely. In perforating india-rubber stoppers the borer used must be sharp, and must be kept well wetted with water, or better with solution of caustic soda or potash. The edge of the cork-borer is sharpened when neces- sary by rubbing the outer part of the edge obliquely with the face of a fine-toothed three-cornered or flat file. 9. Sulphuretted Hydrogen lube.—A tube of the requi- site shape will have been used for the experiments in Sec- tion I; it is seen as a bent delivery-tube in Fig. 5 (p. 30). If not already made bend a piece of glass tubing (6) ten or twelve inches in length at right angles into the shape shown in Fig. 17 a, the shorter limb being about two inches long. This tube is to be kept for passing sulphuretted hydrogen gas through liquids. Fig. 18. 10, 11.] GLASS STIRRING RODS. 49 10. Small Ignition-tubes.—A piece of hard glass tubing,1 perfectly dry inside and out, and not much less than the eighth of an inch in internal diameter, is drawn out at its middle point by heating it strongly in the blowpipe flame, as shown in Fig. 15, p. 45. The narrowed portion of the tube (Fig. 19) is then cut across (5) at its middle Fig. 19. point, and by heating the conical part a, the narrow tube may be drawn off and- a small closed tube is obtained (Fig. 19 a). If the closed end is strongly heated in the blowpipe flame and blown into whilst hot, it may be expanded into a small bulb, such as that seen in Fig. 36. Small test-tubes, three inches long by half an inch in diameter, serve well for ignition-tubes. 11. Glass Stirring-rods.—Three or four glass rods are made by cutting (5) a length of solid glass rod into pieces, some about seven inches long, others of about half that length. Any small projections are filed or chipped off, and both ends of each rod are then rounded by holding them in the upper part of the Bunsen flame, or better in the tip of the blowpipe flame, and turning the rod constantly round on its lon«; axis until it be- comes red-hot at the end (see Fig. 20); the sharp edges are thus partially melted. Fig. 19 a. Fig. 20. 1 To distinguish hard glass from soft (lead) glass, hold the tube towards the light with one end near the eye ; with hard glass the ring of glass will appear green or colorless, with soft glass black or dark. 50 THE WASII-BOTTLE. [lla-13. The end of the rod must not be allowed to touch any- thing until it is cool. 11 a. Sometimes a very thin glass rod is required; this may be made from a stouter rod by softening it in the blowpipe flame (Fig. 15, p. 45), and then drawing it out until the required fineness is produced. 12. Mounted Platinum Wires.—The platinum wire used must not persistently color the flame green. Draw Fig. 21. out a piece of glass tube, six or seven inches in length, at its middle point (Fig. 15, p. 45) into the shape shown in Fig. 19. Cut it across at the middle of the narrow portion. Each piece of glass thus obtained serves for the handle to a wire. Break off the narrow part of the tube until it extends only about a quarter of an inch from the shoulder (a, Fig. 19), and into the narrow opening insert the end of a piece of platinum wire about two inches in length and bent round at its other end into a circle about the eighth of an inch across by rolling it round a piece of thick wire; then hold the end of the wire surrounded by glass in the Bunsen or blowpipe flame until the glass melts and thick- ens around it, fixing it firmly when cold (Fig. 21). At least two wires should be mounted in this way. They are then rendered less liable to be lost and much more easy to handle. The wire may also be mounted by soften- ing the end of a short piece of glass rod in the blowpipe flame, and stick- ing the wire into it. 13. Wash-bottle.—A thin flat-bot- tomed flask is chosen, best of the tri- angular shape shown in Fig. 22, and of 16 or 18 ounces capacity; the neck must not be less than an inch in Fig. 22. 13.; THE WASH-BOTTLE. 51 diameter. Procure a sound cork which is slightly too large to enter the neck, soften the cork by placing it upon the floor and rolling it backwards and forwards under the foot with gentle pressure; when thus softened the cork must fit tightly into the flask. A vulcanized india-rub- ber stopper is much more durable for this and most other chemical purposes; it is perforated by a sharp well- wetted cork-borer, or by a wetted round file. Two pieces of glass tubing rather longer than would be required for the tubes a and b are then bent (6) into the form shown in Fig. 22. The ends of the tubes are, if necessary, cut off to the right length, and their sharp edges are rounded by holding them in the Bunsen flame or in the tip of the blowpipe flame, or by rubbing them with the face of the file. Two parallel holes are then bored in the cork by means of a round file or with a proper-sized cork-borer (8); the holes must be somewhat smaller than the glass tubes, and must not run into one another or to the outside of the cork. They are slightly enlarged, if necessary, by the round file. Into these holes the tubes a and b are then gently pushed with a twisting motion ; if the holes have been made of the proper size the tubes must enter some- what stiffly, but without requiring much pressure. If the holes have been carelessly made too large, the tubes may often be made to fit by slipping upon them little pieces of narrow india-rubber tubing, or by putting the pieces of india-rubber tubing into the holes in the cork before fit- ting in the glass tubes. Upon the upper end of a is fitted a piece of small india-rubber tubing about an inch in length, into the other end of which is pushed a short jet (c) made by draw- ing out a piece of glass tubing in the flame (Fig. 15, p. 45); its opening may be contracted, if necessary, by holding it perfectly dry in the flame for a short time. The neck of the flask should then be bound round with twine like the handle of a cricket bat, or tightly covered with a piece of flannel; this prevents the fingers from being burnt when water has been boiled in the flask and its neck has become heated by the steam. 52 CLEANING APPARATUS. [14. The wash-bottle, when thus fitted up, is filled about two-thirds with distilled water. Tap-water should never be kept in the wash-bottle. A fine stream of water may then be obtained from the jet (c) by blowing down the tube (6); this stream serves for washing precipitates and for other purposes. A larger stream is obtained by inverting the bottle, when the water will flow out from the end of the tube (6), air entering meanwhile by the tube (a). Hot water is frequently required for washing precip- itates ; to obtain this the wash-bottle is placed upon a piece of wire gauze supported on a tripod-stand, and is heated by the Bunsen flame, as shown in Fig. 10 (p. 38). 14. Cleaning Apparatus.—It is indispensable to the success of an analyst that all glass and porcelain appa- ratus should be scrupulously clean before being used. Test-tubes, beakers, and porcelain dishes are washed in a stream of tap-water by using the test-tube cleaner (Fig. 23 6). A little hot hydrochloric acid will remove most stains, but occasionally it is necessary to heat a little strong sulphuric or nitric acid in a vessel in order to cleanse it; hot caustic potash or ammonia solu- tion may also often be used with advantage to re- move grease. In fact, in removing a substance from a vessel to which it strongly adheres, the student should always consider what the sub- stance is, and then remove it by a liquid in which it is easily soluble. Each article after having been well washed and rinsed with tap- water should be placed upside down in the small wicker-basket to drain, or if required for immediate use it should be rinsed out with a little distilled water. It should be borne in mind that apparatus must be washed as soon as possi- ble after use, as after standing the surface is usually much more difficult to cleanse. The brush must be cautiously moved as it reaches the bottom of a test-tube, since the glass is very thin and the brush is easily pushed through it. Test-tube Brush.—It will be found that the piece of sponge at the end of the test-tube cleaner (Fig. 23 «) is Fig. 23. 15-16.] CLEANING APPARATUS. 53 not well adapted to cleanse the bottom of test-tubes and boiling-tubes. A much more efficient end is given to the brush by removing the sponge and bending back the end of the wire stem upon itself at a point just above where the hairs commence (Fig. 23 b). By slightly curv- ing the part of the stem carrying hairs, the brush will better adapt itself to curved surfaces such as those of porcelain dishes. Test-tubes whilst in use are placed in the test-tube stand; boiling-tubes may be supported in the wicker-basket, or in a specially made stand. When washed they should be placed to drain mouth downwards in the wicker-basket. Glass funnels should have their narrow stems cut off to within about half an inch from the shoulder; the sharp outer edge must then be removed by rubbing it with the face of a triangular tile. The inside of the narrow neck is best cleaned by washing it with a common tobacco- pipe cleaner, inserted from the shoulder of the funnel so as not to cut the hairs by the edge at the other end of the neck. 15. Platinum foil and wire are cleansed, by boiling them in hydrochloric acid and rinsing off the acid with water; the wire should then be strongly heated for some time in the blowpipe flame until, on being dipped into pure strong hydrochloric acid, it no longer colors the Bunsen flame. If the tip of the wire cannot be thus cleansed it should be cut off. Commercial platinum often contains barium, and the wire made from it therefore gives a green color to the flame ; such wire is useless for flame coloration tests and for spectrum analysis. It is best to keep the foil or wire in a small beaker or dish containing strong hydrochloric acid diluted with sufficient water to prevent it from fuming ; the platinum will thus be ready for use after having been rinsed with water. 16. Before putting by apparatus it should be made a rule to wash all glass and porcelain which is not in actual use, and place it in the wicker-basket to drain ; the basket is put away with its contents. HEATING GLASS VESSELS. [17-19. All iron apparatus should be carefully dried, and must be kept in a dry place to prevent rusting. On no account mud metal apparatus be kept in the wicker draining-basket. 17. Heating Glass and Porcelain.—A few general pre- cautions should be observed in heating glass and porce- lain vessels, to guard against cracking them. A vessel containing a liquid must never be heated by the flame above the level of the liquid inside. A dry hot vessel must be allowed to cool before pour- ing in any liquid, or placing it on a cold surface. See also (18, 19). 18. Porcelain dishes are generally used for boiling liquids; they are supported on a tripod or retort stand, and may be safely heated by the naked flame. Porcelain crucibles are used for containing solid bodies which are to be strongly heated; they are supported on a pipe- clay triangle placed upon the ring of a retort-stand or upon a tripod-stand : the flame should not be allowed to play steadily at once upon the bottom of the crucible so as to heat it suddenly, but should be constantly shifted by moving the burner, until the porcelain is hot. The crucible should also be allowed to cool slowly on the tri- angle, as contact with a cold body is very apt to crack it; the crucible and its cover whilst hot are handled by the crucible tongs. 19. Glass vessels require to be heated more cautiously than porcelain ; a large naked flame must never be al- lowed to play for any length of time on any one part of the glass surface. In heating a test-tube or boiling-tube, this “local heating ” is prevented by holding the tube obliquely with the lower part in the flame (Fig. 1), and moving it gently up and down, or by constantly turning it round on its axis. Test-tubes are too narrow for boil- ing liquids, in the liquid being very apt to boil over. Small quantities may be boiled and larger quantities heated short of boiling in a test-tube, but the broader “ boiling-tubes ” are best suited for this purpose. Large glass flasks, such as the wash-bottle, are most safely heated by placing them on a piece of wire gauze on a tri- pod-stand (Fig. 10, p. 38) and heating with a rose burner; HEATING GLASS VESSELS. 55 in some laboratories a sand-bath is available; the flask is then heated by being placed on the surface of hot sand. Test-tubes, if not full of liquid, can be held by the neck whilst being heated, if the tube be held obliquely so that the fingers are not over the flame. All risk of burning the fingers is avoided by bending round the neck of the tube a slip of folded paper or of leather, and pinching the ends together close to the tube. SECTION III. ANALYTICAL OPERATIONS. The student, before commencing the analytical reac- tions, must become familiar with the operations which are constantly employed in analytical chemistry. The processes will be most readily and perfectly understood by reading the following descriptions, and performing the experiments given in illustration of them. 20. Solution.—Many solid substances, if stirred or shaken with water, gradually “dissolve” in that liquid; salt and alum may be mentioned as examples. Other liquids may be employed instead of water, and if they cause the solid substance immersed in them to become partially or entirely liquid and mingle uniformly with the liquid, they are said to “dissolve” the solid, the liquid thus obtained being called a “solution” of the solid, and the liquid which dissolves the solid being termed the “solvent.” Thus water, when shaken with sodium chloride (common salt), dissolves it, yielding solu- tion of sodium chloride; and water is therefore called a solvent for sodium chloride. Further, a solid which dis- solves in a liquid is said to be “soluble” in that liquid; if it does not dissolve it is said to be “ insoluble.” The process of solution is more rapid when the solid substance is employed in the state of powder than when it is in large lumps, since a larger surface of the sub- stance is exposed to the solvent by the powder; it is also much hastened by heating the solvent, which causes a more rapid circulation of the liquid over the solid, and also frequently increases the solubility of the substance. Two kinds of solution may be distinguished. “Simple solution” occurs when a substance dissolves in a liquid without alteration in composition, the solution possessing therefore the taste, color, and other general properties of 2o; SOLUTION. 57 the solid, and yielding the solid substance again when the solvent is removed by “evaporation.” Solution of sodium chloride in water is an example of a “simple solution.” “Chemical solution,” on the other hand, is always at- tended by a chemical change in the substance to be dis- solved; and since the solution therefore contains a sub- stance differing in composition from the undissolved solid, the properties of the solution are usually not the same as those of the undissolved solid, and on removing the solvent by evaporation the original substance is not ob- tained. In dissolving solid substances in liquids, test-tubes, porcelain basins, or small glass flasks are generally em- ployed. Exp. 33.—Place a piece of potassium nitrate (nitre) in a small clean beaker, till the beaker one-third with water,1 and stir the solid about in the water with a glass rod ; the potassium nitrate will slowly dissolve in the water; if the liquid be heated the solution will be much more rapidly effected. Powder another piece of potassium nitrate by crushing it and then rubbing it in a mortar with the pestle; place this powder in a test-tube, pour in water, and heat the bottom of the test-tube; the potas- sium nitrate will dissolve much more rapidly than before, showing that solution is accelerated by powdering the solid and employing heat. Keep these solutions. Exp. 34.—Powder a little copper sulphate (blue vitriol) in a mortar, place it in a small porcelain dish, half till the dish with water, and heat it on a tripod or retort stand. The blue copper sulphate dissolves, yielding a blue solution. Keep this solution. These two experiments are both examples of “simple solution.” Exp. 33 shows that a colorless solid gives a colorless solution. Exp. 34 proves that a colored solid gives a colored solution. This is generally true, and hence we can often infer the presence or absence of a colored substance in a solution by merely noting the ' Here and in all subsequent cases water must be understood to signify dinfilled water. 58 EVAPORATION. [21. color of the liquid. Moreover, if a drop of the potassium nitrate solution be tasted, it will be found to possess the same taste as the solid; chemists occasionally rely upon taste, as well as upon color, when examining “ simple solutions.” Exp. 35.—Place in a test-tube a small piece of calcium carbonate (marble or chalk), pour upon it a little water, and heat the tube. The calcium carbonate will be found to be “insoluble” in water. Add to the water some hy- drochloric acid : “ effervescence,” or escape of numerous small bubbles of gas, will occur; the piece of calcium carbonate will meanwhile slowly diminish in size, and will at last entirely disappear in the liquid if sufficient acid is added. Exp. 36.—Place in a test-tube a small piece of cop- per ; on warming this with a little water it remains un- dissolved, but on adding to the water some nitric acid and heating, the copper slowly dissolves, giving off red fumes, and will be entirely dissolved if sufficient nitric acid is employed. Experiments 35 and 36 are examples of “chemical solution;” the calcium carbonate is changed by the hy- drochloric acid into calcium chloride, and this substance, not the calcium carbonate, remains in solution. The cop- per is changed into copper nitrate, which is then dissolved by the water. It will be noticed that in both these cases a gas is given off; this is a very usual, but not a uni- versal, effect during “chemical solution;” the distin- guishing fact is that the solid substance which is to be dissolved has undergone a chemical change in the act of passing into solution. 21. Evaporation.—When it is wished to obtain a substance, which is dissolved in a liquid, in the solid condition, the liquid is boiled away as a vapor, or “evaporated;” the solid substance is then left behind in the vessel. Exp. 37.—Pour the potassium nitrate solution from Exp. 33 into a porcelain evaporating-basin, place the basin on a tripod-stand, and boil it over the Bunsen flame until the water has been nearly boiled away; then 22. PRECIPITATION. 59 make the flame smaller and continue heating; until the water has disappeared. The solid potassium nitrate is left in the dish. In evaporating a solution, a small flame or a rose burner should always be used towards the end of the process, and the flame should be moved about, if neces- sary, else some of the substance will spirt out of the dish. Often' a part only of the liquid is evaporated for the purpose of “concentrating” the solution, i. e., making it stronger by removing a portion of the solvent. A solu- tion, when .sufficiently concentrated, will often form “crystals” of the dissolved substance if allowed to stand till cold. Exp. 37 a.—Concentrate the copper sulphate solution made in Exp. 34, and allow it to cool; if sufficient water has been evaporated it will form crystals. Keep the copper sulphate in the dish. 22. Precipitation.—Two perfectly clear and transparent solutions, on being mixed together, often become more or less turbid and opaque, owing to a solid insoluble sub- stance being formed in the liquid. A solid substance so formed in a liquid is called a “precipitate.” Exp. 38.—Pour into a test-tube some barium chloride solution, and then some ammonium carbonate solution; a white precipitate is formed owing to the production of insoluble solid barium carbonate. Keep this test-tube with the precipitate. In the above instance barium chloride and ammonium carbonate separately dissolve easily in water, but if their solutions are mixed they yield by a chemical change two different substances,—ammonium chloride and barium carbonate. The former of these dissolves in water, but the latter (like marble) is insoluble, and therefore re- mains free as a powder in the liquid. Substances are very frequently removed or separated in analysis byeafising them to form insoluble compounds or precipitates with other substances which are added for the purpose. 'In producing a precipitate, care must be taken that 60 FILTRATION. [23, 23 a. the two solutions are well mixed; this mixture may be effected by closing the mouth of the test-tube with the thumb and several times inverting is, or often by simply warming the bottom of the test-tube in the flame; mix- ture may also be effected by stirring with a glass rod, or by pouring the liquid from one vessel to another. The last three methods are to be used when the liquid present is corrosive, and therefore must not be allowed to touch the skin. A precipitate which does not form readily is often caused to appear more rapidly on thoroughly mix- ing or agitating the liquid by the above means, or by heating it. Precipitates produced with different substances differ much in appearance and properties; hence a precipitate is frequently formed to show the presence of a substance or to separate one substance from another. Substances thus added to produce precipitates are called “reagents.” The appearance of a precipitate is usually described by its color and its condition: it is “flocculent” if it forms in flocklike masses, “crystalline” if in small par- ticles which are seen to be crystals under a lens or mi- croscope, “gelatinous” if jellylike, etc. A slight pre- cipitate causes only a “ turbidity” in a liquid. The color of a precipitate or liquid is often invisible or falsified by gaslight; if the color is to be seen at night, it should be examined with the light produced by a piece of burning magnesium ribbon. Occasionally solid substances are used to produce pre- cipitates; thus one metal is not unfrequently precipitated from its solution by immersing in the liquid another metal. Exp. 39.—Dip a clean penknife blade into some of the copper sulphate solution left from Exp. 37 a, to which a few drops of sulphuric acid have been added; after a short time the metal copper is precipitated from its solu- tion and covers the iron as a red film. 23. Filtration and Decantation.—It is frequently nec- essary to separate a precipitate from the liquid in which it is suspended. This is effected either by filtration or decantation. 23 a. Filtration is performed by pouring the liquid 23 a.] 61 FILTRATION. containing the precipitate upon some porous paper; the liquid itself runs through the pores of the paper, but the solid particles of the precipitate cannot pass through, and remain on the surface of the paper. The paper employed is called “ filtering-paper,” and the liquid which runs through is termed the “ filtrate.” A filtrate may fre- quently be colored by some substance dissolved in it, but it must always be perfectly clear and free from turbidity caused by solid particles suspended in it. Exp. 40.—Measure a glass funnel from its shoulder to its edge along the sloping side (Fig. 24), cut a square of filter-paper whose edge is rather less than double this length, fold it across first along the dotted line (Fig. 25 a), then again as shown by the dotted line in Fig. 25 b. This gives a square (Fig. 26 c) which at one angle has four free corners; these are removed by cutting with a pair of scissors along the curved dotted line shown in Fig. 25 c. The “ filter” is now made and merely requires to be opened; by sepa- rating the edges, formed by cutting oft' the corners, so that they form a circle, three remaining on one side of Fig. 24. Fig. 25. the circle anti one on the other, a little closed pointed paper bag is formed (Fig. 25 d); this is gently pressed with dry fingers into the dry funnel, and the folding altered if necessary till it fits tightly into the glass; it is [23 a. 62 FILTRATION. then moistened all over with a little water from the wash- bottle, and is ready for use. The preliminary moistening of the filter-paper must not be neglected, since if the liquid and precipitate are poured upon a dry filter, some particles of the precipitate get between the fibres, which then swell by the wetting, inclosing the solid particles and stopping the pores of the filter. As an example of the process of filtration, the barium carbonate precipitate obtained in Exp. 38 may be fil- tered off. Pour the liquid containing the precipitate upon the filter, the funnel being placed with its neck in a Jest- tube, and the test-tube being supported in a test-tube stand (Fig. 26); care must betaken that the inside of the upper part of the test- tube is not wetted, else the space between the neck of the funnel and the inside ot the tube is liable to become filled with liquid, and the egress of air being thus prevented the filtration is stopped. The tunnel might also be supported upon the ring of a wooden filter-stand, and the filtrate be received in a small beaker in- stead of in a test-tube. Take great care not to let the level of the liquid in the funnel reach the upper edge of the filter-paper. If the above directions have been car- ried out, and no hole has been made in the paper whilst preparing the filter, the filtrate will run through perfectly clear, leaving the barium carbonate on the filter. Keep the funnel, filter, and precipitate. Circular filters can be purchased ready cut, and only requiring to be folded twice to be ready for use. The filter must always be of such size that when placed in the funnel its edge is below the rim. Sometimes the fil- trate runs through turbid; it can then usually be made quite clear by passing the whole, or the first portions, of the filtrate once or twice again through the same filter; but with many precipitates a double filter should be used, a double filtration being thus performed in one operation. It should be borne in mind that hot liquids run through Fig. 26. 23 6-24 a.] WASHING PRECIPITATES. 63 a filter much more quickly than cold ; hence, if not in- admissible for other reasons, a solution should always be boiled before being: filtered. O Note.—Common filter-paper contains a little calcium carbonate, which is of no importance in ordinary analyses, and is only objection- able when a substance has to be examined for traces of calcium. To remove this impurity, in special analyses, the filters are moistened in a funnel with dilute hydrochloric acid, and then well washed with distilled water. 23 b. Decantation.—Precipitates which settle rapidly ind completely in the liquid in which they are formed may frequently be separated from that liquid without the use of a filter. The vessel is allowed to stand at rest until the precipitate has completely settled, and the liquid is then care- fully poured off or “ de- canted/’ by allowing it to run gently down a wet- ted glass rod which is pressed against the edge or lip of the vessel (Fig. 27), the precipitate being left in the vessel. This process, if carefully performed, effects a fair separation of heavy precipitates. The pre- cipitate obtained by adding sulphuric acid to some boil- ing solution of barium chloride may be separated by de- cantation. Keep the precipitate in the test-tube. 24. Washing Precipitates.—A precipitate which has been filtered from the liquid in which it was suspended has often to be washed until it is perfectly free from the adhering liquid. This “ washing” is performed as de- scribed under 24 a if the precipitate has been separated by filtration, and by 24 b if by decantation. 24 a. Exp. 41.—Support the funnel, which contains the filter and barium carbonate precipitate from experi- ment 40, with its neck in a beaker or flask, and blow in a fine stream of hot distilled water from the wash-bottle, so directed by moving the jet with the fingers as to stir up the precipitate well; in this way fill the filter to Fig. 27. 64 DRYING PRECIPITATES. [246, 25. within a short distance from its edge; let this water run through perfectly, then nearly fill the filter again in the manner just described ; repeat this process two or three times, letting the liquid run through perfectly each time before putting in afresh quantity; the water running through from the third or fourth washing will usually be quite tasteless, and the precipitate and filter will be freed from everything soluble in water. Boiling, or at least hot, water should always be used for washing purposes, as the process is thus rendered much more rapid. 24 b. Washing by Decantation.—Heavy precipitates, after having been separated from liquids by decantation, are washed also by the same process. The precipitate is shaken or stirred with distilled water, and allowed to settle; when the water has become quite clear it is poured off (Fig. 27). By several times repeating this washing process with addition of fresh portions of dis- tilled water, the precipitate may be entirely freed from adhering solutions. The precipitate of barium sulphate, remaining in the test-tube from the experiment at the end of 23 b, may be thus washed by decantation. 25. Drying Precipitates.—A precipitate is often re- quired in a dry condition after it has been filtered off and washed. It is dried by placing the funnel in a hollow tin cone or cylinder, the filter-dryer (Fig. 28), and support- ing this on a piece of wire gauze upon a tripod-stand over the flame of a rose burner turned very low; or the filter- dryer may be placed on a gently heated sand-bath. The funnel is thus heated by the current of hot air, and rapidly dries the filter and precipitate. Great care must be taken to regulate the heat and watch the process, so as not to char the filter. A more rapid method of drying a precipitate, after it has drained for a time, consists in spreading the filter upon a piece of wire gauze supported on a tripod-stand ; a small flame from a rose burner is then placed beneath Figs. 28. 26.] 65 the gauze, and the filter carefully watched to avoid charring it. A precipitate is partially dried by opening out the filter upon several dry filter-papers; this process may precede those already mentioned. 26. Removing Precipitates from the Filter.—When a small quantity of a moist precipitate has to be taken from a filter to test its behavior or closely examine its appearance, it is most readily removed by dipping the end of a glass rod into the precipitate; by touching a watch glass or the interior of a test-tube with the end of the rod, a small quantity of the precipitate is deposited for examination. If the precipitate is to be removed from the filter as completely as possible, several methods are available; one or other must be chosen according as circumstances render it suitable. a. The bottom of the filter may be pushed out through the neck of the funnel with a glass rod, which is small enough to pass easily through the neck (11 a), and the precipitate may then be washed down into a vessel be- neath with a fine stream of water or other liquid from the wash-bottle. h. Without breaking the filter the funnel may be held with its neck horizontal, and the rim just inside the edge of a porcelain dish (Fig. 29); the precipitate is then washed out by directing a fine stream of water from a wash-bottle against the sides of the filter. c. The filter and precipitate are allowed to stand for some time, so as to drain off* as much water as possible; the filter is then carefully taken out of the funnel, partially dried if neces- sary by laying it upon several folds of filter-paper, and after removing the portions of the paper which contain no precipitate, together with the empty fold,1 it is spread out inside a porce- REMOVAL OF PRECIPITATES. Fie. 29. 1 Filters may be made without this fold, by cutting one of the round papers (Fig. 25 d) through across one of the folded diameters, 66 REMOVAL OF PRECIPITATES. [26. lain dish; the liquid with which it is to be treated is poured upon it, and by shaking the dish so as to cause the liquid to move round and round, and occasionally carefully stirring the precipitate with a glass rod, the precipitate is washed off the paper without tearing the latter to pieces. The paper is then carefully removed by a glass rod. d. If it is undesirable to add a liquid to the precipi- tate upon the filter, the filter and precipitate, after drain- ing for a short time, are removed from the funnel; the filter is spread out upon a flat piece of glass and the pre- cipitate carefully scraped off with a glass rod or a small spatula. If the precipitate is required dry, the filter, after removal from the funnel, may be carefully opened and spread upon several thickness of filter-paper to drain. When there is a large quantity of the precipitate a sufficient quantity may be removed on the end of a glass rod or spatula, without taking the filter out of the funnel. This method is usually the most imperfect, but is frequently the best for other reasons. e. A precipitate has sometimes to be dissolved off the filter; the hot liquid used as a solvent may then be poured upon the precipitate; it will run through the filter into a vessel below, taking with it the precipitate in solution. The liquid, after it has run through, should be heated again, and once more poured upon the precipitate, if the latter is not entirely dissolved; this re-heating and re- turning of the liquid to the filter should be continued as long as anything is dissolved; any remaining portion of the precipitate must then be removed by a little fresh solvent. /. A precipitate, if small in quantity, may also be rinsed off the filter with the liquid with which it is to be treated or dissolved. The funnel is placed with its neck in a test-tube, the liquid is poured into the filter from another test-tube, and the precipitate is quickly stirred up with the liquid with a glass rod thin enough to pass down bringing the cut edges together, and sharply folding them over several times, pressing them with the nail; if properly made, such a filter is perfectly impervious to the precipitate. 27.; IGNITION. 67 through the neck of the funnel; the bottom of the filter is then pushed out through the neck by the glass rod, and the liquid carrying most of the precipitate will run through ; if some of the precipitate remains on the filter, the same liquid is poured through the filter again into the other tube, and by thus pouring backwards from one tube to another all the precipitate may be removed. Note.—The greater part of a precipitate may often be removed by a clean knife or spatula, and the remainder by some one of the foregoing methods. Exp. 42.—Remove the precipitate of barium carbonate remaining from Exp. 41 from the filter by one of the above processes, using hydrochloric acid as a solvent for method e. 27. Ignition.—Solid substances occasionally require to be heated strongly or “ ignited.” This process of ignition is employed with various objects. 1 d. In order to see what effect strong heat has upon a substance, since by this means we can frequently detect its composition. For this purpose we use small tubes made from hard glass tubing (10), or small test-tubes. Exp. 43.—Heat a little mercuric oxide in a small tube of hard glass; after a short time minute shining drops of the metal mercury will be seen on the upper part of the tube; if then a small splinter of wood with a spark at its end be held in the tube it will burst into flame. The behavior of this red powder on being “ignited,” there- fore, shows it to contain the elements mercury and oxygen. Substances are often heated on platinum foil with the same object. Thus a little charcoal powder when heated on platinum foil burns away. 2d. Ignition is also used as a means of separating from a solid mixture substances which are “ volatile,” or which change entirely into vapor when heated ; these are driven off by heat from other substances which are “non- volatile,” or can be strongly heated without changing into vapor, and which therefore remain behind. Exp. 44.—Heat a small piece of ammonium chloride on a strip of platinum foil held in the flame by crucible 68 FUSION. [28-29. tongs; the ammonium chloride being volatile will give off white fumes, which are best seen by removing it from the flame for an instant, and the solid substance will slowly disappear or “ volatilize.” Heat in the same way a small piece of potassium chlo- ride; this will melt, but will not disappear, since it is only slightly volatile. It will become solid again on cooling. Hence, if from a mixture of ammonium chloride and potassium chloride the potassium chloride is to be ob- tained alone, the mixture would l>e strongly heated for some time, when the ammonium chloride would be re- moved as vapor, leaving the potassium chloride behind. 28. Sublimation is the process of heating solid sub- stances and converting them into vapor, then cooling this vapor so as to “condense” it, or render it solid again. A volatile substance may thus be obtained free from other substances which are not volatile or only slightly so. Exp. 45.—Heat a small piece of ammonium chloride in a tube of hard glass closed at one end and two or three inches in length; it changes into vapor, which again cools into solid ammonium chloride in the upper part of the tube. This is an example of the process called “ sublimation,” and the solid substance at the upper part of the tube is a “ sublimate.” 29. Fusion.—Substances are often melted or “fused” together to cause certain chemical changes to occur be- tween them. Melting or “fusion” is performed some- times on platinum foil, but often in porcelain or plati- num crucibles. For fusion in a crucible an intense heat is often recjuisite; this may be obtained by using the blowpipe flame, but the Bunsen flame will usually suffice if the crucible be surrounded by the conical filter-dryer (Fig. 28, ]). 64) which steadies the flame and increases the draught. Exp. 46.—Place upon a slip of platinum foil a mix- ture of powdered sodium carbonate and potassium nitrate, then a very small quantity of manganese oxide; hold the foil with crucible tongs in the top of the Bunsen flame, or heat the under surface of the foil with the blowpipe 30.] USE OF THE BLOWPIPE. 69 flame. The mass will melt or fuse; it is kept in a melted state for a short time and then allowed to cool, when a bluish-green mass is obtained. The production of this color is due to the presence of sodium manganate formed by the fusion; this color on fusion with sodium carbonate and potassium nitrate is produced only when manganese is present, and is therefore a test for that element. 30. Use of the Blowpipe.—The blowpipe is used, as has been already explained (4), to obtain an intensely hot flame which may be made to play in a convenient direc- tion upon any substance to be heated; it is very useful for analytical purposes, since by its skilful use the com- position of an unknown substance, when ascertained by other means, can usually be confirmed; and with many substances (especially minerals) a complete, or at any rate sufficient, analysis can he made by the blowpipe alone. The way in which the flame is obtained has been already explained (4). In a well-formed blowpipe flame two parts may be distinguished: the “inner flame,” which is blue and pointed, and around and beyond this an almost colorless flame, “ the outer flame.” The inner flame is often called the “reducing” or “deoxidizing flame,” because it sepa- rates or “ reduces ” metals from their oxides and com- pounds, and in general “deoxidizes” substances; the outer flame is also known as the “ oxidizing flame,” be- cause it changes metals into their oxides, and “ oxidizes” many other substances. These two flames also produce other distinctive effects. The “inner flame” is best obtained of large size by placing the tip of the blowpipe nozzle only in the very edge of the flame, or even just outside it; the “outer flame” is best obtained by putting the nozzle much fur- ther into the gas flame. It may also be noted that the “reducing flame” is furnished most readily by the lu- minous gas flame; the “oxidizing flame” is most easily and perfectly formed from a Bunsen flame which con- tains some air, and which is obtained by either leaving the air-holes at the foot of the burner entirely open or by only partially closing them. [31. 70 BORAX BEAD. There are several purposes for which the blowpipe is employed in analytical chemistry with which the student should become familiar; the following experiments will exemplify the most important of them. 31. E xp. 47.—Borax Bead.—Place a little borax, which has been finely powdered in a mortar, upon a watch glass; moisten the loop of a piece of mounted platinum wire (12) with water or in the mouth, and dip it into the powdered substance, then hold the loop with the adhering powder in the blowpipe flame until the bo- rax melts; if this is insufficient when melted to form a bead which fills the loop, dip the loop with the melted substance upon it again into the powder,—more powder will adhere and may be melted in the flame; in this way powder is to be constantly added until when held in the flame a liquid drop or bead is produced which completely fills the loop. This bead must be perfectly colorless and transparent on cooling. Keep the bead on the wire. If the melted bead easily drops from the wire, either the loop or the bead is too large and must be lessened in size. The most convenient-sized loop is one which is rather less than one-eighth of an inch across; it is best made by rolling the tip of the wire round a piece of stout wire. If the bead is too large, remove a portion whilst it is in a fused condition by giving the wire a sudden jerk. Certain substances when melted in this bead color it, and as a rule the color produced by each of these sub- stances has some characteristic tint or peculiarity. The color of the bead should be examined after it has been heated, first in the outer and then in the inner flame, and must be noted both hot and cold. If the bead appears opaque, on account of too much of the coloring substance having been introduced, it can generally be made trans- parent by shaking off some of the fused borax, or by flat- tening the fused bead by gently squeezing it between a small pair of pincers. Exp. 48.—Moisten the clear cold borax bead and dip it into some powdered ferrous sulphate, thus taking up very little of the powder upon it; then heat the bead and substance for a short time in the tip of the outer blow- 32.] FLAME COLORATIONS. 71 pipe flame, and examine the color of the bead by looking through it at a piece of white paper or at a window light; it will be reddish-brown whilst hot, but the color will become lighter on cooling; now heat the bead again for some time in the tip of the inner blowpipe flame; its color will be changed to green. These two colors, shown by the borax bead in the outer and inner blowpipe flames respectively, characterize the metal iron. The fused borax bead is detached by giving the wire a sudden jerk ; it may also be removed after cooling by crushing it on a hard flat surface by a sharp blow with the pestle. The wire when not in use should be kept in dilute hydrochloric acid. Should it not be perfectly clean after washing off the acid, the simplest method of cleansing it is to make a fresh bead upon the loop and jerk it off whilst melted; this will usually remove all impurity. A borax bead must never be used for these purposes until it has been found to be perfectly colorless, both hot and cold, when heated in the outer blowpipe flame. If the first bead which is made in the loop is tinted with any color, it must be jerked off whilst fused and another bead formed with fresh borax, this being also thrown off and replaced if not quite free from color; this process is to be repeated until the bead is obtained perfectly clear and colorless. 32. Flame Colorations.’—Many substances give a char- acteristic color to the flame. The blowpipe flame is often employed to obtain these colors; an ordinary Bunsen flame, however, although it does not give the colors quite so promptly and intensely, answers the purpose well. The flame best suited for this purpose is obtained by surrounding the Bunsen flame with a conical chimney, reaching about two-thirds of the height of the flame (Fig. 30), and then so regulating the sup- ply of air entering into the air-holes that a small luminous point appears near the top Fig. 30. 1 For a more detailed and exact description of flame tests, see Bun- sen’s paper in the Philosophical Magazine for 1867. 72 FLAME COLORATIONS. ;32. of the flame; the platinum wire is held either in this luminous tip or just above it. A filter-dryer also forms a very good chimney, being supported just above the foot of the burner on a wire tripod, which may be made by bending down the ends of a pipe-clay triangle. Exp. 49.—Hold a loop of platinum wire in the inner blowpipe flame; if the wire is clean it will become red- hot without coloring the flame. If it colors the flame, clean the wire by boiling it with hydrochloric acid in a test-tube, and then rinsing well with water; or by moist- ening with strong hydrochloric acid, and heating strongly in the blowpipe flame until it no longer colors the flame. If it cannot be thus cleansed, cut off the end. Now moisten the wire and dip it into a little powdered sodium chloride, or dip the loop into some sodium chloride dis- solved in water, so that when removed a drop of the solu- tion remains in the loop, then hold the loop at the tip of the inner blowpipe flame; the outer flame will be col- ored bright yellow. Repeat the experiment, placing the moistened loop in the upper and outer part of the Bun- sen flame; the same yellow tint will be obtained. This yellow color is given only by sodium and its compounds. Remove all sodium chloride from the platinum wire loop by heating it strongly in the tip of the blowpipe flame until it ceases to impart any color to the flame. Then dip the wire into some potassium nitrate solution; this will give to the flame a pale-violet color, which is characteristic of potassium and its compounds. As will be seen subsequently, the examination of flame colorations, aided by the use of colored glasses, and of a hollow glass prism filled with indigo solution, is of great use in ordinary analysis. Exp. 49 a.—Look at the yellow flame coloration pro- duced by sodium chloride through a piece of cobalt glass or through the indigo prism; no yellow color will be visible. Now dip the wire loop into a mixture of a few drops of sodium chloride and potassium chloride solu- tions; when held in the flame only the sodium coloration is seen, but through the blue glass or prism the potas- sium is seen to produce a red flame coloration. By means 33.; IGNITION OP CHARCOAL. 73 of the blue glass or prism then potassium is discoverable in the presence of sodium, by which its presence is other- wise masked. By far the most perfect method of examining flame colorations, more especially for the rarer elements or for mere traces of the more common ones, is by the use of the spectroscope; every advanced student should make himself familiar with the use of this instrument, at least in its simplest and smallest form. A paper on the use of the spectroscope for qualitative analysis will be found in the appendix; this is well worthy of the attention of senior students. Two platinum wires should be kept in readiness, one to be used for borax beads and the other for flame colora- tions, since a loop which has been used for borax colors the flame yellow. 33. Ignition on Charcoal in the Blowpipe Flame.— Wood charcoal forms a very useful support for substances which are to be heated in the blowpipe flame. It cannot itself be melted, it conducts heat very badly, and posessess other properties which render it peculiarly adapted for ignitions. It is, if necessary, sawn into small pieces of the required shape and size with a fine-toothed saw. Ignition on charcoal serves chiefly to detect the pres- ence of metals; the substance for this purpose is heated either alone or mixed with certain other substances (usu- ally sodium carbonate and potassium cyanide) in the inner blowpipe flame; globules or scales of the metal are thus frequently produced, also in many cases the oxide of the metal forms a characteristic coating or “ incrustation” on the charcoal; an examination of the color and prop- erties of the metal or incrustation, or of both, will fre- quently lead to the detection, or confirm the presence, of some metal. Charcoal is apt to leave a white ash when heated alone in the blowpipe flame; this must not be mistaken for an incrustation. A powder frequently re- quires to be moistened with water before being heated by the blowpipe flame, in order to prevent the flame from blowing it off the charcoal. 74 IGNITION ON CHARCOAL. [33 a. Exp. 5Q.—Choose a piece of wood charcoal free from large cracks, scoop out a small hollow near one end with a knife, and place in the hollow a small quantity of a mixture of powdered lead acetate and sodium carbon- ate or potassium oxalate. Heat this mixture in the inner blowpipe flame, hold- ing the charcoal in such a way that the rest of the flame plays over its surface (Fig. 31). After heating for some time bright globules of lead will be seen in the cavity, and on removing the charcoal from the flame the surface round the cavity will be found to be colored with *a yellow “incrustation.” If one of the little globules of metal be then taken off the charcoal with the point of a penknife, and be struck smartly with a pestle on the bottom of a mortar turned upside down, it will flatten out into a cake, showing that the metal is “ malleable” not “ brittle.” The metal lead is the only metal which gives a yellow incrustation and malleable globules; this test therefore serves to detect its presence. 33 a. The melted mass left on the charcoal after fusing a metallic salt with sodium carbonate is best examined for metallic powder or scales by detaching it from the charcoal with the point of a penknife, then crushing it in an agate mortar or in a watch glass with a little water; on stirring and quickly decanting the water down a wet glass rod or pestle held against the edge of the vessel (Fig. 32), the metallic powder, if present, will be left; by repeating this process of “ levigation,” the metal is ob- tained free from soluble substances and charcoal; it may then be further examined by a lens or magnet. A mix- ture of copper sulphate with sodium carbonate, when heated on charcoal and “ levigated ” as directed above, will furnish little red scales of copper; a mixture of fer- Fig. 31. »4.] 75 USE OF TEST-PAPERS. rous sulphate and sodium carbonate will yield a gray powder consisting of metallic iron, which, when touched with the point of a magnetized knife, will become at- tached to it. Fig. 32. 34. Use of Test-papers.—Certain vegetable colors undergo remarkable changes when acted upon by chem- ical substances. Some of these are used for analytical purposes; the following experiment will explain how they are made use of. Exp. 51.—Boil some pieces of a common red pickling cabbage-leaf in water; a blue liquid will be produced. Pour some of this liquid into a test-tube and add several drops of hydrochloric acid, the color will change to bright red; to another portion of the blue liquid add several drops of ammonia, the color changes to. green; to a third portion of the blue liquid add a little ammonium chloride solution, the color remains unchanged. Mix in a test-tube a little ammonia solution with three times as much distilled water, and add this weak ammo- nia gradually to the liquid reddened by several drops of hydrochloric acid; by careful addition the blue color may be exactly restored, the acid previously added being “neutralized” by the ammonia. Exp. 52.—Pour some blue litmus solution (made by boiling solid litmus in water and filtering) into three test-tubes; to the first add hydrochloric acid drop by drop until it turns distinctly red, preserve this liquid ; to the second add ammonia solution, the liquid remains blue; to the third add ammonium chloride solution, the color will not be affected. 76 USE OF TEST-PAPERS. [34. Divide the reddened liquid into three parts; to one part add ammonia solution, the original blue color is restored ; to another part add hydrochloric acid, the red color is unchanged; to the other part add ammonium chloride, the red color remains unaltered. These experiments may also be made with litmus test- papers, which are prepared by soaking paper in the blue and red liquids respectively, and allowing it to dry. Exp. 53.—Repeat the preceding experiment, using the litmus-papers instead of the solution, and moistening them with the liquid by dipping a glass rod into it and then touching the paper with the moistened end; the results mentioned in Exp. 52 will be obtained. It will be seen then that the three substances employed differ in their action on litmus test-papers, as follows: Hydrochloric acid reddens blue litmus does not affect red litmus. Ammonia does not affect “ blues “ Ammonium chloride... * does not affect “ Each of these substances is a sample of a whole class, the members of which resemble it in their action on litmus. The class of acid substances, including sulphuric acid, nitric acid, etc., and many metallic salts, resemble hy- drochloric acid in reddening blue litmus and not affecting red. The class of alkaline substances, including potassium hydrate, sodium hydrate, etc., and many salts of the al- kalies, resemble ammonia in bluing red litmus and not affecting blue. The class of neutral substances, including potassium chloride, sodium chloride, etc., resemble ammonium chlo- ride in not affecting either blue or red litmus. Hence in analysis we use red and blue litmus-papers to test whether a liquid is “ acid,” “ alkaline,” or “ neu- tral.” The red cabbage liquid, as will be seen, is better suited for a test-paper than litmus, since one paper shows both 35.; 77 NEUTRALIZING AN ACID. alkalies and acids; but the color is very apt to spoil with keeping. Sometimes a liquid in which a colored precipitate is suspended has to be tested by litmus-paper; the precipi- tate then frequently hides the color of the paper when a drop of the liquid is placed upon it. In such a case moisten the paper with a drop of liquid, and wash the liquid off after a short time with a stream of distilled water from the wash-bottle; the color of the paper is then distinctly seen. 35. Making Neutral, Acid, and Alkaline.—An acid substance by being mixed with a proper proportion of an alkaline substance becomes “neutral;” similarly an alka- line substance is rendered “ neutral ” by mixture with a proper quantity of an acid. Thus by mixing hydro- chloric acid and ammonia in the proper proportions, the neutral substance ammonium chloride is formed; the acid is then said to be “neutralized” by the alkali, or the alkali by the acid. It is often required to “neutralize” an acid with an alkali or vice versa. The following experiment will show how this process of neutralizing an acid is per- formed. Exp. 54.—Pour a little hydrochloric acid into a por- celain dish, add to it ammonia, several drops at a time, keeping the liquid constantly stirred with a glass rod, and occasionally touching a slip of blue litmus-paper with the end of the rod moistened by the well-stirred liquid ; as soon as the paper is only faintly reddened by the liquid, the ammonia is added very carefully, stirring well after the addition of each drop, and trying the ac- tion of the liquid by touching the wet glass rod against first blue and then red litmus-paper, waiting a short time to give the liquid time to act on the paper. When the colors of both blue and red paper remain unaffected, the process of “ neutralization ” is completed. It is well to add dilute ammonia towards the end of the process; this is prepared by mixing a little ammonia with three or four times as much distilled water in a test-tube. 78 ANALYTICAL OPERATIONS. [35 a, 35 b. The process of neutralizing may often be simplified, when the liquid is clear and colorless, by dropping into it a small piece of blue litmus-paper, the color of which is noted after each addition of ammonia; the condition of the liquid should, however, even in this case be proved towards the end by moistening with it both red and blue paper. The process of neutralizing an alkali with an acid is precisely similar to that of neutralizing an acid with an alkali, except that red litmus is at first used instead of blue. 35 a. It will be readily understood from what has been said above, that if an alkaline or neutral liquid is to be “acidified,” acid is added gradually, as was de- scribed in the preceding experiment, until a drop of the well-mixed liquid reddens blue litmus-paper. If an acid or neutral liquid has to be made alkaline, the alkali is added until a drop of the liquid turns red litmus blue. These processes are often termed adding acid or alkali “ in excess.” 35 h. Yellow turmeric-paper is occasionally employed instead of red litmus to test for alkalies, which turn it reddish-brown; it is unaffected by acids, with the ex- ception of boracic acid. The most important use for tur- meric-paper is to test for boracic acid, the solution of which, if dried on the paper at a gentle heat, turns it orange-red. Exp. 55.—This may be shown by stirring a little borax upon a watch glass with dilute hydrochloric acid until it is dissolved, then moistening the lower part of a slip of turmeric-paper with this liquid, and holding it some distance above the flame, or, better, placing it in a steam oven until dry; the portion of the slip which was moistened will now appear reddish-brown, the color being well seen by contrast with the light-yellow upper portion of the paper. FRACTIONAL SOLUTION, ETC. 79 FRACTIONAL SOLUTION, CRYSTALLIZA- TION, AND DISTILLATION. 1. Fractional Solution. — Since different substances show differences in solubility in water and acids, it is often possible by means of solvents to separate the con- stituents of a mixture. This process is termed separa- tion by “fractional solution.” Illustrate this by making a mixture of powdered ferrous sulphate (FeS04.7H20) and ferric oxide (Fe203); on warming a portion of this with water, FeS04.7H20 alone dissolves, leaving Fe2Os: if another portion is warmed with HC1, both substances dissolve. 2. Fractional Crystallization. — If a solution of two different salts be boiled down in an evaporating basin, one salt will usually furnish crystals before the other does, and by this process of “fractional crystallization” a separation of the salts may often be effected. Boil down a solution of sodium chloride (NaCl) and nitre (KN03): NaCl will crystallize out of the boiling liquid in hollow cubes, and on cooling prisms of nitre will separate. 3. jFractional Distillation.—Liquids which boil at dif- ferent temperatures may often be separated by distilla- tion (p. 40); that part of the mixture which first distils over consisting chiefly of the liquid with the lowest boil- ing-point, and the successive portions of the distillate becoming richer in the liquids of higher boiling-points. The process of “fractional distillation” may be illus- trated by distilling a mixture of alcohol and water; since alcohol boils at a lower temperature than water, the first part of the distillate contains the greater part of the alco- hol, as is shown by its burning and by its dissolving camphor or iodine in quantity. The last portion of the distillate does not give these tests for alcohol, and is I proved to be water by turning dry CuS04 blue and dis- solving it. SECTION IV. ANALYTICAL REACTIONS. Course of Practical Analysis to be Pursued by the Student.—The text is so arranged that two main courses may be framed from it in this and the following sections. The one is suited to senior students, and dispenses with the training in the detection of simple substances, which, although useful as a stepping-stone to the full analytical method, is in itself of only small importance. The other course is suited to junior students, and forms an easy approach to the more difficult complete methods of an- alysis; it teaches the plan of analyzing simple substances which may contain one acid-radicle and one metallic- radicle. This course is therefore also suited to those who are learning analytical chemistry with the view of preparing themselves for examinations in which the can- didate is not required to detect more than one acid-radicle and one metal lie-radicle. These courses are described below as the “senior course” and “junior course.” The senior course consists in working through the ana- lytical reactions in Section IV; as those for each group are completed, several substances whose composition is unknown to the student are tested for one member only by the “table of differences” at the end of the group: as soon as these are detected with readiness, substances which may contain two or more of the members mixed together are analyzed by the group-table in Section VI: a reference to the “table of differences” will show at a glance on what principles these group-tables are founded, and this is further explained by a statement following the “ table of differences.” This plan of working with each group-table before going on to the reactions for the next group is to be recommended, since, whilst the differ- ANALYTICAL REACTIONS. 81 ences upon which the separation and special tests of the elements in the groups are fresh in the student’s memory, they are practically applied. The analytical tables are thus gradually rendered intelligible one after another, whilst the student is proceeding through the reactions. The book is so arranged, however, that the analytical tables may be left until the reactions for all the groups have been finished. When all the groups have been worked through in this manner, the analysis of substances is commenced which may contain any members of any of the different analytical groups; the directions for the systematic method of analysis required for this purpose being contained in Section VI. The Junior Course.—Since this is intended to teach only the detection of one metallic and one acid radicle, the student, whilst working through Section IV, omits all those paragraphs marked “s” after the number, re- lating to the separation and detection of the mixed mem- bers of a group; and, after finishing the reactions for each group, he proceeds to detect the members occurring singly in several substances of unknown composition by the table of differences, and by reference to the reac- tions. After working in this way through Section I V, he at once proceeds to analyze simple substances by Sec- tion V. As stated above, this junior course may occasionally be made to precede the senior with advantage; that is to say, the student, after working through the junior course, and learning how to detect simple substances, may analyze mixtures containing two or more members of each group by the directions given at the end of each of the groups in Section IV, and may then proceed to the full method of analysis contained in Section VI. 82 INTRODUCTORY REMARKS ON INTRODUCTORY REMARKS ON ANALYTI- CAL CHEMISTRY. The science of chemistry reveals to us the fact that every substance on this earth, and probably in the uni- verse, consists either of one kind of matter only, or of two or more different kinds which we cannot further separate. Those substances which contain only one kind of matter are called “chemical elements;” their number at present amounts to a little over sixty. A list of them is given in paragraph 558 at the end of the book. It is not often that these elements occur singly; two or more of them are commonly found together either in a state of mere “ mixture,” or united in a much more intimate manner by the force of “ chemical affinity ” to form a “ chemical compound.” Analytical chemistry or analysis (literally meaning an unloosening or separation) teaches us how to discover what element, elements, or sometimes what groups of elements, any substance of unknown composition contains; it also enables us to ascertain whether any particular element or group of elements is present in a given substance. In order to become a thorough analyst, it is necessary to be intimately acquainted with the properties of every element and of the compounds it forms with other elements, and therefore efficiency in analysis depends in a large measure upon the knowledge of what is usually termed “ theo- retical,” or more appropriately, perhaps, “ descriptive chemistry.” But, although we recognize a substance by its properties, still a knowledge of all its properties is not requisite to enable us to detect its presence; for or- dinary analytical purposes certain marked properties of each element or group of elements are selected, and by these properties, called “ tests ” or “ reactions,” we detect its presence. The “ tests ” or “ reactions ” most frequently selected are the following: 1st. The behavior of a substance when heated under various conditions; and 2d. Its behavior when mixed with certain liquid or solid substances; such 36.] ANALYTICAL CLASSIFICATION. 83 substances, added for analytical purposes, are called reagents. Some reagents serve for detecting one ele- ment or compound only, and are therefore called special reagents; others separate or detect a group of elements or compounds, and are called group reagents or general reagents; these latter reagents serve to separate sub- stances into “ analytical groups,” as will be more fully explained hereafter. The student must bear in mind that, although an ac- quaintance with the most important reactions of sub- stances is indispensable to success as an analyst, caution, skill, and neatness in manipulation are not less necessary, and the most scrupulous attention must be paid to all directions bearing on these matters. 36. Analytical Classification.—The chemical elements are frequently divided into two classes, viz., metals and non-metals. These classes form, with a slight modification, convenient divisions for analytical purposes. In the class of “ metals ” must be included the hypothetical metallic- radicle ammonium (NH4), also the element hydrogen. The class of “ non-metals,” either singly, or in groups formed by their combination inter se or less frequently with a metal, unite with hydrogen and with metals form- ing “salts;” the hydrogen salts of these radicles are usually called “ acids.” Thus Cl,1 S04, P04, Mn04 form the hydrogen salts or acids, HC1, H2S04, H3P04, HMn04, and the metallic salts, KC1, MgS04, Na3P04, KMn04; metal-hydrogen salts or acid salts, such as NaHS04, Na2HP04, are also known. The general name, “ acid-radicle,” is conveniently applied to Cl, S04, P04, Mn04, etc., it being understood that although most of these are unisolated compound radicles,—i. e., groups containing more than one element,—some of them are elements; their common property is that of forming, in combination with hydrogen and with metals, salts. For analytical purposes, then, we may separate the substances 1 The meaning and use of chemical symbols will be briefly ex- plained hereafter (40) ; but the student is presumed to be already acquainted with them. In par. 558 will be found a list of the symbols of the different elements. 84 METHOD OF TRYING [37, 38. we have to detect into the groups of Metals and Acid- radicles. In trying the reactions for these substances it is usual to employ, not the substances themselves, but certain compounds—usually salts—which contain them. For convenience in hasty writing it is not uncommon to employ abbreviations for the compound radicles, es- pecially for such as are constantly met with or are of unusual complexity. In the text the only such abbre- viations employed are: Am for (NH4), the metallic-radicle ammonium. T “ (C4H406), the acid-radicle of tartaric acid and the tartrates. A “ (C2H302), the acid-radicle of acetic acid and the acetates. Cfy “ (FeCy6), the acid-radicle of ferro- and ferri-cy- anides. Ho “ (HO), the radicle hydroxyl, occurring in hy- drates, etc. 37. Analytical Groups.—The metals are separated by their behavior with certain general reagents into five principal groups, two of these being further subdivided into two sub-groups. Each of these groups receives a dis- tinctive name,—either a number from its place in the system, or a name from some conspicuous or important member of the group, or from the general reagent used to precipitate the group. Thus we speak indifferently of the 4th Group, the Barium Group, or the Ammon- ium-carbonate Group. On pages 190 and 191 will be found a table showing the analytical groups with their distinctive numbers, names, and group reagents placed at the head of each column ; the names and symbols of the elements contained in the group are arranged vertically beneath. It is, perhaps, well to avoid referring to a group by its number, as different analysts number the groups differ- ently, and the name thus given is therefore apt not to denote the group with certainty. 38. Method of Trying the Analytical Reactions in Sec- tion 1F.—In order to become fully acquainted with the 38.] THE ANALYTICAL REACTIONS. 85 behavior of different substances with “reagents,” and thus to be able to detect them by their “ reactions,” each of these reactions should be performed with the substance itself or with one of its compounds, and the appearance presented carefully observed, so that the substance would be easily recognized in a body of unknown composition by means of those tests. The following general rules must be carefully attended to in trying the reactions; they may be read through before commencing the reactions (par. 47): 1. A solution of the substance which is directed to be used must always be employed, unless it is specially stated that the solid is required. Solid substances are required as a rule only for blowpipe reactions. A solution can be readily made from the solid, if necessary, by warming it with water, or in some cases with dilute acid (529). This is often called the “ original solution.” 2. Commence by taking in a test-tube or small beaker a small quantity (about 15-20 cc.) of the solution of the substance. If the solid substance is also required, take some of it upon a Avatch glass. 3. Pour a small portion of the solution into a perfectly clean test-tube, and add the first-mentioned reagent to it. The reagent must ah\rays be added in small quantity at first; more can be employed aftenvards if excess is re- quired. The student must from the first acquire the habit of Avorking with small quantities both of solutions and reagents. For each of the reactions a separate portion of the “original solution” is thus poured into a clean test-tube and the required reagent added to it. 4. Before trying each reaction the student must care- fully read through the Avhole of the description of the results he is to obtain ; he must then perform the experi- ment, literally following out the directions given. lie must consider it a necessary condition of after-success that each result is obtained precisely as stated in the text, and must never on any account pass on until he has consci- entiously satisfied himself that the statements of the book are true, and that he could at any time repeat the test successfully. 86 CHEMICAL NOTATION. [39, 40. 39. Entry in Note-book.—Each reaction as soon as it has been satisfactorily tried, should be neatly entered in the note-book in a short form. Since nothing so much aids brevity as the symbolic notation commonly used by chemists, the student should invariably adopt this chem- ical shorthand in entering results. A full account and explanation of chemical notation may be found in any work on theoretical chemistry, and merely a few hints will therefore be given here which will be of special use for the purpose of briefly entering reactions. 40. Chemical Notation.—Each element has its cor- responding symbol, consisting of one or two letters; thus S stands for sulphur, Cl for chlorine. These symbols also stand for one atom of each element; by being writ- ten one after another they give the formula of a com- pound substance, showing what elements, and how many atoms of each of these elements, its molecule contains; thus KC1 stands for one molecule of potassium chloride, a compound of one atom of potassium and one atom of chlorine ; PtCl4 stands for one molecule of platinic chlo- ride, which consists of one atom of platinum combined with four atoms of chlorine, the small figure placed below a symbol to the right denoting how many atoms of that element are present. A number placed before a formula multiplies each symbol in that formula, thus 2PtCl4 signifies two molecules of platinum chloride, containing altogether two atoms of platinum and eight atoms of chlorine. If two or more symbols are included in brackets any number placed outside, either before or below the brackets, multiplies each symbol contained in the brackets; thus both Sr(NOa)2 and Sr2(NOs) stand for SrN2Og, and this may also be written Sr2NOs. In paragraph 558 will be found a list of the elements, with their symbols and atomic weights; paragraphs 524, 525, 526, 529, and 530 contain a list of the names and cor- responding formulae of all. the most common compound substances mentioned in the course of the book. Sym- bols and formuhe are always used in the text instead of names, but the student can readily find the correspond- 41, 42.] 87 CHEMICAL EQUATIONS. ing names by reference to the above tables, or to the labels on the bottles which should contain both names and formulae. 41. Chemical Equations.—On adding a “reagent” to a substance some change usually occurs which gives rise to ail alteration of color, or very frequently to the forma- tion of a precipitate having a certain color, appearance, or behavior with other liquids, which are characteristic of that particular substance, or of some element or group of elements contained in it; this change should be briefly described in the note-book in words, and then represented by a chemical equation. The rules for drawing out an equation may be found in any treatise on chemistry; a few general directions only are given here, which will be of service for the special object in question. 42. Rules for Writing Down an Equation.—Write down the formulae of the two substances which are mixed together for the reaction, with the sign of addition ( + ), between them; then write the sign of equality ( = ), fol- lowed by the formula of the precipitate produced. In a complete equation the formulae written on the left-hand side of the sign (=) are usually called the “ left-hand side ” of the equation ; those to the right the “ right-hand side.” Since most of the following reactions are cases of “ double decomposition,”—i. e., cases where a mutual ex- change of certain elements or groups of elements occurs between the two compounds,—a little consideration will usually show how many molecules of the substances on the left-hand side of the equation are required to yield the formula for the precipitate, and also whether any other, and if so what other, substance is at the same time formed. It is always necessary that the number of atoms of any one element on both sides of the equation should be equal. The following are dissected examples: The first test for K (47): KC1 + PtCl4 = K2PtCJ6. This is simply placing together the substances mixed and the precipitate formed; the equation thus formed is evi- 88 CHEMICAL EQUATIONS. '43. dently not correct, since we have two atoms of K on the right-hand side and only one on the left, also 6 atoms of Cl on the right and only 5 on the left; but this inequal- ity is at once removed if we place 2 before the KC1, thus: Evidently if the above equation is correct the precipitate is here the only substance formed, since the number of atoms in the substances on the left-hand side is exactly equal to that in the substance on the right. Take now the first test for Ba (69): 2KC1 + PtCl4 = K2PtC]g. This represents the substances mixed and the precipitate formed, but evidently the left-hand side of the equation contains more than the right (viz., Am2 and Cl2); hence we write it fully thus: BaCl2 + Am2COs =BaC03 + BaCl2 + Am2C03 = Ba0O3 -f 2AmCl, which states that on mixing together barium chloride (BaCl2)and ammonium carbonate (Am2C03), we obtain ba- rium carbonate (BaC03) and ammonium chloride (AmCl). In writing out these equations a systematic method should be observed. Write down on the left-hand side of the equation first the substance whose reaction is being tried, then the reagent added; and on the right-hand side write first the formula for the precipitate with a line drawn over it by way of distinction, then any substance or substances which may be formed with it. In the reactions which follow, the formulae of the sub- stance used, of the reagent added, and of the precipitate produced will always be given, these being sufficient data to enable the student to form the equation ; only where the equation is exceptionally difficult or compli- cated will it be given in full. 43. The following contractions are recommended: expt. for experiment. pp. “ precipitate. ppn. “ precipitation. ppd. “ precipitated. sol. “ soluble. insol. for insoluble. soln. “ solution. crystne. “ crystalline. col'K “ coloration. 44, 45.] RULES FOR WORKING. 89 44. Examples are given below showing how the reac- tion should be entered in the note-book; they should be referred to as soon as the student commences the reactions for the metals: 1st. [See pars. 47-50.] Potassium (K).—Used KC1. PtCl4: stirred on watch-glass: yellow crystne pp., sol. in much water and in KHO, insol. in alcohol: 2KC1 + PtCl4 = KaPtClg. NalJT: well shaken in a test-tube: white crystne pp., sol. in water, KHO, and HC1: KC1 + NaHT = KHT + NaOl. Flame coln : pale violet, crimson-red through the indigo-prism or cobalt glass. Heated in tube or on platinum foil, solid KC1 melted, but gave no fumes; hence not volatile. 2d. [See pars. 69-74.] Barium (Ba).—Used BaCl2. Am2C03 : white pp., sol. in HA : BaCl2 + Am2C03 = BaC03 2AmCl. CaSOi : heavy white pp., insol. in boiling HC1 : BaCl2 + CaS04 = BaS04 + CaCl2. K2CrOi : light yellow pp., sol. in IIC1, insol. in IIA : BaCl2 + K2Cr04 = BT(Jr04 + 2KC1. Flame coln : on loop of Pt-wire, yellowish-green color. 45. General Rules to be Observed whilst Working.—The student should attend carefully to the following precau- tions, which will most materially aid the progress and accuracy of his work; if they are observed from the commencement they will not be felt irksome: 1. Before commencing work look through the reagent bottles belonging to the working bench (524); replace any which are absent, and arrange the bottles, if neces- sary, in the order indicated on an accessible list, or 90 RULES FOR WORKING. [45. shown by the number on the labels of the bottles, or by the labels on the edge of the shelf. Then proceed to fill any which are empty and to re-label any whose labels are imperfect or loose. If any of the liquid reagents are not quite clear when shaken they must be filtered before use. 2. Arrange the apparatus required for use, on the hinder part of the bench, so as to leave the front free to work upon; this will lessen the risk of upsetting anything. 3. Before commencing work, all glass and porcelain which is not in use should be carefully cleansed, if not already clean ; but it is best never to put apparatus away dirty. 4. In using a reagent bottle take it in the right hand, remove the stopper by taking hold of it between any two of the fingers, or between the fourth finger and palm, of the left hand; hold the stopper in this way and replace it immediately after the bottle has been used. Pour the liquid out at the side opposite to that bearing the label, and prevent the last drop from run- ning down the outside by touching the lip of the bottle either with the stopper or against the clean edge of the vessel. Solid reagents should be taken out of the bottle on a clean knife-blade or spatula, or with a spoon of wood or horn; or a small quantity should be turned out upon a piece of paper or upon the palm of the hand. The bottle must be re-stoppered and replaced on the shelf in its proper place with the label outwards immediately after use, and must never be left standing on the working bench. 5. If any solution or precipitate has to be put by for some time, always label it with a piece of gummed paper bearing an inscription or a reference number which is explained in the note-book and is sufficient to recall to mind what the solution or precipitate consists of; never trust to memory in this matter. 6. Brass crucible tongs must never be employed for holding hot evaporating-basins containing acids, as some of the brass is apt to be dissolved and thus introduced 46.] REACTIONS FOR THE METALS. 91 into the solution. A hot dish may be moved either by holding it with a cloth or by lifting the stand upon which the dish is placed. 7. Liquids only are to be poured down the sinks; all solid refuse, such as soiled filters, broken glass, pieces of charcoal, etc., which would tend to stop the holes in the sink, must be thrown into a box placed in any accessible position in the laboratory, or into a small earthenware jar or vessel placed upon each working-bench. 8. When a student is examining a substance to detect its composition, he must fully write down in his note- book each test or process, with the result obtained, as soon as it is completed. The analysis is thus written out gradually as it progresses; on no account must the entry of the results he left until the completion of the analysis. This rule cannot be too strongly enforced, as neglect of it is always attended with loss to the beginner. The most convenient form of entry is that of the analytical tables. *** Cleanliness and neatness in analytical work can- not be too carefully attended to; more confusion and error may be caused by using dirty test-tubes, beakers, dishes, and funnels than would be thought possible by the beginner. REACTIONS FOR THE METALS. Note.—In trying through the reactions for the metals, the usual analytical order of the groups has been reversed, because the most simple reactions occur in the last groups, and they are therefore bet- ter suited for a beginner. GROUP V.—POTASSIUM GROUP. 46. This group includes K, Na, Mg. The first three metals (K, NH4, Na) are known as the “alkali metals.” The members of this group are not precipitated by any of the five group reagents. 1 A hypothetical metal-radicle, “ Ammonium.” 92 GROUP V.—POTASSIUM. [47, 48. Potassium (K).—Use KC1. Refer if necessary to paragraphs 38 and 44 for directions how to work. 47. PtCl4 added after a drop of dilute HC1 to some of the KC1 solution on a watch-glass and stirred with a glass rod, gives a yellow crystalline precipitate (K2PtCl6), forming first along the lines where the rod has rubbed the glass. Stir up the precipitate and pour off the liquid with the precipitate into three test-tubes; to one add much dis- tilled water and heat, the precipitate dissolves; to another part add alcohol, the precipitate does not dissolve. Hence this precipitate is soluble in water, insoluble in alcohol. By warming the third portion with solution of KHO, the precipitate is also shown to be soluble in that liquid. Remarks.—The following remarks are of great im- portance in using the above test for K. Since this pre- cipitate is soluble in alkalies the liquid should always be neutral or only faintly acid before adding PtCl4; and since it is more insoluble in alcohol than in water, addi- tion of alcohol causes the precipitate to form more rapidly in dilute solutions; owing to the solubility of the pre- cipitate in water, very dilute solutions must however be evaporated nearly to dryness before applying the test. It is always well to add several drops of HC1 before the PtCl4, and to make sure by test-paper that the liquid is acid in reaction. These remarks apply also to the pre- cipitate produced by PtCl4 with ammonium salts (52). 48. IT T (or better NaHT) mixed with some of the solution in a test-tube gives a white crystalline precipitate (KHT); usually this precipitate appears only when the mouth of the test-tube is closed with the thumb, and the tube is well shaken for some time. KC1 + NaHT = KHT + NaCl. KC1 + H2T = KHT + HC1. Shake up and pour some of the liquid and precipitate into four test-tubes; add to these portions, water,1 KHO, 1 By “ water ” is always meant “ distilled water,” unless otherwise stated. 49, 50.] GROUP V.—POTASSIUM. 93 and HC1 respectively; on being shaken and warmed the precipitate will dissolve in each of these liquids. Hence this precipitate is soluble in HX), KHO, and HC1. To the fourth portion add alcohol; the precipitate does not dissolve, since it is insoluble in alcohol. Remarks.—In using the above test for the detection of K, the precipitate is not obtained at once in dilute solu- tions, but its formation is much hastened by the addition of alcohol; very dilute solutions must first be concentrated by evaporation. The solution to be tested should be neutral or only feebly alkaline; if acid in reaction, the acid should be neutralized by Na2C03 or boiled off' if volatile; feebly acid solutions may, however, be at once mixed with NaHT; to an alkaline solution II2T should be added till the reaction is strongly acid. Note.—Tn the following reactions when a precipitate is stated to be soluble or insoluble in certain liquids, it must be proved to be so in the manner described in (47, 48), unless different directions are given. 49. Flame Coloration (32).—Hold a loop of platinum wire in the flame and see that it gives no color to the flame; then dip it into some KC1 solution, or. better still, moisten it and dip it into some powdered KC1, and again hold the loop in the upper part of the flame. A pale- violet color will be imparted to the flame if the KC1 is pure;1 but whatever color is thus seen, the flame-color will always appear pale blue or violet through the thinner portions of an indigo-prism, and deep crimson-red through the thickest parts. The light of a Bunsen flame itself usually appears pale blue through the indigo-prism ; this color should be noted before using the prism for examining a flame coloration. The flame coloration due to potassium shows in the spec- troscope a red line (a) and an indigo-blue line (/3) (557). Note.—A piece of blue cobalt glass may be used instead of the indigo-prism, but is by no means to be recommended, as the color of different specimens is somewhat variable in shade and in intensity, whereas the color of the indigo can be obtained of an invariable tint, by dissolving indigo-carmine in water. 50. Heat a little solid KC1 in a small dry test-tube, or better on a piece of platinum foil; the KC1 will melt 1 KN03 usually gives a purer potassium coloration. 94 GROUP V.—AMMONIUM. [51-53. but will not pass into vapor and produce white fumes unless heated very strongly, since K-salts are non-vola- tile at a moderate heat. The fused residue is often trans- parent and invisible if in small quantity; its presence is shown by a slight crackling being heard during cooling. Ammonium (NH4, or Am).—Use NII4C1 (AmCl). Note.—The symbol Am is often written for NII4; it is very con- venient, as it does away with the necessity of using brackets; e. g., Am2S = (NH4)2S. 51. KIIO1 (or NaHO) poured into some of the solu- tion, or upon the solid, in a test-tube and heated gives off JSII3 gas: NH4C1 + KIIO = NH3 + KC1 + II20. This gas is known by the following properties: a. Its pungent smell—that of common smelling salts. b. By turning moistened red litmus-paper blue. A small piece of red litmus-paper is wetted with distilled water and placed upon a clean glass rod, and is then held in the test-tube, taking great care not to touch with it the liquid or the sides of the tube; the paper becomes blue. c. A glass rod dipped into strong HC1 or strong HA, and held over the mouth of the test-tube, produces dense white fumes. 52. PtCl4, when stirred on a watch-glass with some AmCl solution, gives a yellow crystalline precipitate (Am,PtCl6); this precipitate is soluble in water and in KIIO, but insoluble in alcohol. The remarks at the end of par. 47 apply here also. This precipitate, if boiled with KHO, evolves NH3 (difference from K2PtCl„). 53. H2 T (or better NaHT), shaken for some time in a test-tube with AmCl solution, gives a white crystalline precipitate (AniHT), soluble in H20, KHO, and HC1, insoluble in alcohol. The remarks in par. 48 apply here also. 1 In all cases where KIIO is to be used NaHO may be substituted, and either KHO or NaHO may be used unless it is specially stated that “pure NaHO” is to be employed. 54-57.] GROUP V.—SODIUM. 95 Note.—This precipitate is more soluble than the KHT precip- itate, and therefore does not form so readily. Indeed with II./T a precipitate rarely forms unless alcohol is added, in which the pre- cipitate is less soluble than in water. With NallT a precipitate is obtained on shaking the liquid well for some time unless it is very dilute. 54. Flame Coloration.—AmCl, if pure, gives on pla- tinum wire no color to the flame. 55. Heat a little solid Am Cl in a small dry test-tube, or on a piece of platinum foil; it will be converted into vapor producing white fumes, which are seen if platinum foil is used by removing the foil for a moment from the flame ; hence AmCl is volatile. If the experiment is performed in a dry test-tube, a white coating or “sublimate” forms on the upper part of the tube. Sodium (Na).—Use NaCl. 56. Flame Coloration.—NaCl gives an intense yellow color to the flame; the color is almost invisible or appears pale blue when viewed through the indigo-prism, and never shows the slightest tinge of red or purple, even when seen through the thickest parts of the prism. A crystal of red K2Cra07 appears colorless if illuminated by this yellow flame. Examined by a small spectroscope, the sodium coloration gives a single yellow line (a) (557). The yellow color of the sodium flame is always readily seen, since it overpowers that of K; its production is the most reliable, and often the only possible, test for sodium. Note.—If both K and Na are present, the K colora- tion is unseen and the yellow coloration of Na is alone visible; but on examining this flame through the indigo- prism or cobalt glass, the crimson coloration of the K is at once seen; prove this by mixing together KOI and NaCl and trying the flame coloration without and with the indigo-prism. The spectroscope also shows the lines of Na and K quite distinct from one another. 57. Some solid NaCl heated in a dry test-tube, or better on platinum foil, melts without producing white fumes unless heated very strongly, since NaCl is not volatile at a moderate heat. 96 GROUP V.—MAGNESIUM. [58-63. Magnesium (Mg.)—Use MgS04.7H20 solution. 58. Na2lIPO4* added after AmCl and AmHO gives a white crystalline precipitate (MgAmP04); if much water is present this precipitate forms only when the liquid is warmed and well stirred or shaken ; it is soluble in acids (use HC1 or HNOs), insoluble in AmHO. MgS04 + AmCl + AmHO + Na2HP04 = MgAmPO, + Na2S04+ AmCl + H20. 59. KHO gives a white precipitate (MgHo2),2 soluble in acids. 60. AmllO gives a white precipitate (MgHo2); but if AmCl is added to the MgS04 solution before the AmHO, no precipitate is produced. 61. Am2C03 gives a white precipitate (MgCOs), but only in strong solutions and on standing for some time; AmCl prevents the formation of this precipitate. 62. Flame Coloration.—MgS04.7H20, if pure, gives no color to the flame. 63. Blowpipe Test.—A little solid MgS04.7H20 placed in a small cavity on a piece of wood-charcoal and then heated in the tip of the outer blowpipe flame, shines brightly and gives a white unmelted mass of MgO; no white fumes are given off since MgO is not volatile. If this white mass after cooling is moistened with several drops of cobalt-nitrate solution and again strongly heated for some time3 in the outer blowpipe flame, it becomes delicate pink in color; this color is best seen when the mass is quite cold, by comparison with a white piece of paper held near the residue on the charcoal. 1 NaAmllPO* is better than Na2HP04, since it produces the precipitate more readily than does Na2HP04 in dilute solutions, and always in a crystalline condition. 2 This convenient symbol (Ho) for the group hydroxyl, first pro- posed by Frankland, will be employed throughout in the formulae for all hydrates containing more than one atom of hydroxyl; it pre- vents the necessity of using brackets, as a number placed below the symbol multiplies both H and O, thus IIo2 equals (HO)2 or Il202; and Ho3 equals (HO)3 or 1I303. 3 It is necessary to heat strongly after moistening with Co(N03)2, else blue Co(N03)2 remains. 54.] GROUP V.—TABLE OP DIFFERENCES. 97 64. Group Y.—Table of Differences. Note.—A blank (thus ) signifies that no marked characteristic change occurs. For the method of using the table see par. 65. Tests. K—salts. NH4—salts. Na—salts. Mg—salts. 1. a. For solutions. 1. Boil with IvHO solution: NHj gas given off: known by its smell and by turning moist red litmus blue; it also gives dense white fumes with strong HC1. White precipitate. Pale violet flame, which appears crimson Hi rough the indigo- prism. Intense yellow flame, which shows notinge of red through the indigo- prism. on clean plati- num wire: 3. Add ArnCl, Am Ho and Na,IIP04: White crystalline precipitate. 4. Add Pt014, Yellow crystal- line precipitate, forms only in strong solu- tions. Yellow crystal- line precipitate, forms only in strong solu- tions. and a drop of dilute HC1, and stir vigorously; 5. Add H2T (or better NaHT) and shake well: White crystalline precipitate in strong solu- tions. White crystalline precipitate in strong solu- tions. b. For solids only. 6. Heat to red- ness in a dry i test-tube, or on platinum foil: Non-volatile, un- less heated to bright redness. Volatile; white fumes are given off aud the sub- stance passes into vapor (at least partially) forming a sub- limate on the upper part of the tube. Non-volatile un- less heated to bright red- ness. Non-volatile. 7. Heat strongly on charcoal in the outer blow- pipe flame: Melt easily and sink into the charcoal, col- oring the flame pale violet. (See 20 Are volatile, giv- ing off white fumes. Melt easily and sink into the charcoal, col- oring the flame intense yellow. (See 2.) Leave ultimately a white infusible residue which shines brightly, and which if moistened with Co(N02)2 solu- tion and re- heated becomes pink. i 1 In using these tests for tlie detection of a single memher of the group in solution, only the first lour need be employed ; the fifth test may be substituted for the fourth. Tests 6 and 7 are used only for the examination of solids. They may be supplemented, however, by tests 1 and 2. 98 GROUP V. [65, 66. 65. The method of using the foregoing table may be explained in a few words. Suppose a solution to be given which is known to contain one member of this group, the first five tests in the table (four and five being alter- native) will enable us to decide which member is present. It is simply necessary to examine separate portions of the solution by these tests until a result is obtained which conclusively proves the presence of one of the four sub- stances. Tests 1, 2, 6, and 7 are similarly employed for examination of a solid substance. The student should never rest content with one test only when a second can be tried in confirmation, and he should always consider the tables of differences as mere sumnuyies, and should refer back to the separate reactions for fuller accounts of the tests when required. The results of these analyses, and of all analyses sub- sequently made by using the tables of differences, are best entered in three parallel columns, as shown in the upper part of the table in par. 67. The statement of the experiment or test performed is entered in the first col- umn, the result observed being placed beside it in the second column, whilst beside this in the third column is stated the conclusion inferred from the result obtained. At the end of each analysis state the result thus: “ Found K.” 66. (s)1 Detection of Members Mixed.—We can also devise from the above table a plan for detecting the mem- bers of this group when mixed together. It is evident— 1. ThatNH4 can always be detected by boiling with KHO solution. 2. That Na can always be detected by its yellow-flame coloration. 3. That Mg can always be detected by giving a white precipitate on addition of AmCl, AmHO, and Na2HP04 to its solution. 1 Paragraphs marked with an (s) are intended for a student using the senior course, and are passed over in the junior course. 66.] GROUP V. 99 4. That K may always be detected by giving a flame coloration which appears crimson through the indigo- prism. 5. That the confirmatory test for Iv by stirring with PtCl4, may be tried if no XH4 is present; but it cannot be employed when NH4 has been found, since NH4 gives a yellow precipitate exactly like that given by K. Hence NH4 is first removed by evaporating some of the solution to dryness, and strongly heating the solid substance thus obtained on platinum foil as long as white fumes come off; the residue (if any) on the foil will then be free from jNTH4, and can be dissolved and tested for K by PtCl4. The above remark concerning the PtCl4 test applies also to the H2T test for K, since NH4 gives a precipitate with H2T precisely similar to that yielded by K. The following scheme, which embodies the above tests, must be used to test for Mg, K, Xa, and NH4, when they may be present together. The student should examine several substances by this table for the four .members of Group V, writing down the results he obtains fully in the form adopted in the table; that is to say, three columns are ruled; in the first is described the test performed, in the second the result observed, in the third what substance is inferred from that result to be present or absent. After writing out the tests the metals which have been found in the solu- tion are stated thus: “ Found K and Na.” *** Experiment IV in the following table may be omitted by a beginner, K being tested for by the flame coloration alone (Exp. II). 100 [67. TABLE FOR GROUP V. 67. (s) Table for Testing for Mg, K, Na, NH4, IN A SOLUTION WHICH MAY CONTAIN ONE OR ALL OF THEM. (See note at the top of page 101.) Experiment. Observation. Inference. I. Add to a small part of the solution AmCl, then AmHO and Na»HP04, shake well and allow to stand if no precipitate appears at once. 1. A white precipitate forms. [2. No precipitate appears.] Presence of Mg. [Absence of Mg.] II. Dip a small loop of clean platinum wdre into the solution, and hold it near the top of the Bunsen flame. 1. A yellow flame.1 Look at the yellow flame through the indigo- prism ; a crimson-red color is seen. Presence of Na, possibly also of K. Presence of K. 2. A pale-violet flame, ap- pearing crimson red when seen through the indigo-prism. Presence of K and absence of Na. [3. No color is imparted to the flame.] [Absence of K and Na.] III. Boil some of the solu- tion in a test-tube with KHO solution, and try whether NH3 is given off by smelling; or if it cannot be smelt, by test- ing with moistened red litmus-paper or strong HC1. 1. NIIj gas is smelt, or the red litmus becomes blue, and white fumes are ob- tained with HC1. [2. No NH3 is smelt, and moist red litmus-paper is not blued, neither are white fumes obtained with HC1.] Presence of NH4. [Absence of NH4.] IV. A confirmatory test for K may be made by adding PtCl« or NallT. If Exp. Ill lias shown that N1I4 is present, proceed to test forK by column A ; if NH( is absent, test for K by column B (66, 5). A. B. Boil some more of the solution down to dryness in a porcelain dish; scrape out tiie white substance left in the dish, and heat it strongly on a piece of plati- num foil as long as any white fumes are seen to be given off' when the foil is taken out of the flame for an instant. Place the foil w'heu cold in a test-tube, and boil it with very little water, to which a drop of dilute HC1 has been added, and evaporate to several drops; cool the liquid, and pour it out upon a watch-glass, add a little PtCl4,3 and stir well : A yellow precipitate : Presence of K. Pour a little of the solution upon a watch-glass, add PtCI4, and stir well: a yellow precipitate : Presence of K. If no precipitate forms, K may never- heless be present, the solution heingtoo dilute to allow the precipitate to form ; therefore pour some of the solution into a porcelan dish, boil down nearly to dryness, cool and test this liquid by --tirring it with Ptf'l4Q on a watch-glass, adding alcohol if the precipitate does not appear at once: a yellow precipitate: Presence of K. Note.—Addition of alcohol will fre- quently produce the precipitate without evaporation. 1 Almost all substances contain traces of Na, and therefore when heated in the Bunsen flame tinge it more or less yellow ; hence, unless the yellow coloration is very intense, enter in the results “ No trace.” 2 In this and all subsequent places where PtCl4 is directed to be used as a test for K, the NaHT test may be substituted for economical reasons. 68-73.] GROUP IV.—BARIUM. 101 Note.—Separate portions of the solution are to be used for each of these experiments. It must be understood that only one of the num- bered results in the second column can be obtained in each experiment, but one or other of these must invariably be observed. In subsequent tables that result only is stated in the second column which indicates the presence of the substance, and the absence of that result proves the absence of the substance ; the portions in brackets will therefore be omitted in future. GROUP IV.—BARIUM GROUP. 68. This group includes Ba, Sr, Ca. The members of this group differ from those of Group V by being precipitated as carbonates by Am2C03, even in the presence of AmCl.1 They are not precipitated by any other of the group reagents. Barium (Ba).—Use BaCl2.2H20.2 69. Am2COs added after some AmCl: white precipi- tate (BaC03) which is at first flocculent, but if heated and allowed to stand slowly shrinks in bulk and becomes crys- talline. Pour a little of this into another test-tube and add to it some IIA, the precipitate dissolves entirely if sufficient HA is added. 70. CaSOi or HJ30i: heavy white precipitate (BaSO,), insoluble in HC1 even on boiling. 71. KiCrOi added after some HA : yellow precipitate (BaCr04), soluble in warm HC1, insoluble in warm HA. (Diff. from Sr.) 3 72. IT2SiFfi: semi-transparent precipitate (BaSiF6) : The precipi- tate often does not appear in dilute solution until after some time, or until the liquid is boiled, or alcohol is added. Shaking or stirring the liquid hastens its formation. 73. Am2C2Oi-. white precipitate (BaC204l. 1 On boiling with Am Cl solution, however, the precipitates are more or less perfectly dissolved. 2 These two molecules of water are termed “ water of crystalliza- tion,” and are always present in crystallized barium chloride. 3 A reaction in small type is comparatively unimportant, and may be read through and omitted by beginners. 102 GROUP IV.—STRONTIUM—CALCIUM. [74-82. 74. Flame Coloration: BaCl2 gives a yellowish-green color to the flame, visible through the indigo-prism. The spectrum consists of a number of lines, the most characteristic of which are three green lines, a, /?, y (557). Strontium (Sr). Use Sr (N03)2.4H20. 75. Am2C03 added after someAmCl: white precipi- tate (SrCOg), soluble in HA. This precipitate is floccu- lent at first, but if heated it quickly becomes crystalline and shrinks very considerably. 75 a. CaSOt or : white precipitate (SrS04), this precipitate does not usually form at once in a cold solu- tion, but only after standing for some time. The precipi- tate, however, appears at once on boiling the liquid. 76. K;tCr()i added after some HA: no precipitate, since SrCr04 is soluble in IIA. 77. H2SiF6: no precipitate. 78. Am2C2Oi: white precipitate (SrCr2Oi). 79. Flame Coloration: crimson red ; this color appears intense red through the indigo-prism unless the flame coloration is very faint. The strontium spectrum contains many lines; the most characteristic are the orange line (a), the red lines (/?, y), and the blue line (5) (557). Calcium (Ca).—Use CaCl2.6H20. 80. AmiC03 added after AmCl: white precipitate (CaCOs) soluble in HA. This precipitate is flocculent at first, but on standing for some time or on being gently heated it shrinks considerably and becomes crystalline. 81. CaSOi: no precipitate, even on standing or on being boiled. 82. HJSOi: white precipitate (CaS04) forms at once in strong solutions, and often in weak solutions on being boiled; but since CaS04 is not cpiite insoluble in water, some of it will always remain dissolved; prove this by boiling the liquid containing the precipitate and filtering 83-87.] GROUP IV.—TABLE OF DIFFERENCES. 103 it, then keep adding AmHO to the filtrate and stirring it until a drop of the solution turns red litmus blue and the liquid smells of NH3, then add Am2C204, a white precipitate will form, showing the presence of Ca (85), which must have been dissolved as CaS04. 83. K.2CrOi: no precipitate. 84. Il2SiF6: no precipitate. 85. Am2C2Oi: white precipitate (CaC204), soluble in most acids except IIA and H2C204. 86. Flame Coloration: yellowish red; this color viewed through the indigo-prism does not appear red but dingy green, thus differing from that given by Sr. In the calcium spectrum the most characteristic lines are the green line (/?), and the intense orange line (a) (557). 87. Group IV.—Table of Differences. The first three tests only need he used for the detection of a member of this group occurring by itself in solution; test 1 serves also for solids. Tests. |! Ba—salts. Sr—salts. ,Ca—salts. 1. Flame coloration: Greenish-yel- | j low. Intense crimson ap- pears red through the indigo-prism. Yellowish red, ap- pears dingy green through the in- digo-prism. 2. CaS04 added to the An immediate cold solution: precipitate. 3. K2Cr04 added after Light yellow precipitate. A precipitate ap- pearing only after a short time or immediately on boiling. [4. H2SiF6 added: White precip- i itate. 5. H2SO, added in ex- j 'Entirely pre- cess and boiled: cipitated as j llaSO, 11 Entirely precipitated as SrSO« Partially precipi- tated as CaS04; hence the filtrate from the precipi- tate contains Ca, which may be de- tected by" adding AmliO in excess, and then Am2' '204; a white precipitate forms. [88,89. GROUP IT.—TABLE OF DIFFERENCES. When analyzing a solution which is known to contain only one member of this group, its detection by the iirst three of the above tests will be exceedingly simple. 88. (s) The separation and detection of Ba, Sr, and Ca, when mixed, depends upon the following differences: 1. The flame colorations, examined if necessary through the indigo-prism, or by means of the spectroscope. 2. The difference in behavior with CaS04, which at once indicates the presence or absence of Ba. 3. The separation of Ba, if present, by K2Cr04 in the presence of HA. 4. The precipitation of Sr by CaS04 on being boiled, which will indicate the presence of Sr in the absence, or after the separation, of Ba. 5. The precipitation of Sr, if present, by boiling with H2S04; sufficient CaS04 then remaining in the solution to give, after making the filtrate alkaline with AmllO, a precipitate with Am2C204. 89. (s) A solution which has to be examined for Ba, Sr, and Ca, and can contain only these substances, is made alkaline, if not already so, by addition of AmHO ; then Am2C03 is added as long as it is seen to cause any precipitate after the liquid has been stirred well and allowed to settle. The liquid is then filtered, and a little more Am2COs added to the clear filtrate; if any further precipitate forms, more Am2C03 is added and the liquid is again poured through the same filter, pouring the first portion of the filtrate once more through the filter as it is sure to come through turbid. As soon as the filtrate gives no further precipitate with Am2C03, all the mem- bers of this group which were present in the solution have been precipitated as carbonates, and on filtration are obtained on the filter. The precipitate is then examined by Table IV (438). Note.—In using the group tables in Section YI, it must be under- stood that they are drawn out to meet the case of all the members of the group being present. If, therefore, in any case no precipitate forms on addition of a reagent, the substance or substances whose presence would have been indicated by the formation of the precipi- tate must be absent. lienee a filtration which is directed to be made is often unnecessary, and the solution itself is treated as is directed for the filtrate. 90-94.] GROUP III A.—ALUMINIUM. GROUP III a.—IRON GROUP. 90. This group includes Al, Fe, Cr. The members of this group differ from those of groups III b, IV, and V by being precipitated by AmHO after addition of AmCl; they are not precipitated, how- ever, by the group reagents for Groups II and I. This group is also precipitated by Am2S, or by II2S added to the alkaline solution. Group III A further differs from Group III b in being completely precipitated by adding BaCOs shaken up with water; this reagent affords the most perfect means of sepa- rating the two groups. The members of this group show no characteristic flame colorations; but with the exception of Al, they give borax beads of characteristic color. Aluminium (Al).—Use A1 Am(S04)2.12H20 ammonia- alnm, or A1K(S04)2.12H.20 potash-alum. 91. AmllO: white flocculent precipitate (Al2Ho6), which is seen best on boiling the liquid; soluble in HC1 and in HA; slightly soluble in AmHO, especially in the absence of AmCl: 2AlAm(S04)2 4- GAmHO = Al2IIo6 + 4Am2S04. 92. KHO added in very small quantity: same pre- cipitate as AmHO; soluble in excess of KHO. If to a part of the KHO solution HC1 be added gradually until it is neutral, the Al2Ho6 is reprecipitated ; if more acid is added the precipitate dissolves, but is reprecipitated by adding AmHO in excess. From another portion of the KHO solution the Al2Ho6 may be reprecipitated by ad- dition of sufficient AmCl. 93. Am2S: same precipitate (Al2Ho6), II2S gas coming off or remaining dissolved in the liquid: 2AlAm(S04)2 + 3Am2S + 6II20 = Al2Ho6 + 4Am2S04 4- 3H2S. 94. Blowpipe Reaction. — Some solid AlAm(S04).2. 12H./J heated on charcoal in the outer blowpipe flame, 106 GROUP III A.—IRON. [95-98. then moistened, after cooling, with Co(N03)2 solution, and again heated in the outer flame, gives a fine blue mass. 95. Ikon (Fe).—Two classes of iron compounds are known, which differ in appearance and properties and behave differently with reagents ; they are distinguished as ferrous and ferric compounds respectively, the former being supposed to contain the metal ferrosum (Fe"),1 the latter ferricum (Fe"'). It is usual in stating analytical results to mention in which state of combination the iron exists, and therefore some distinctive tests are described below (101). The whole of the reactions of ferrous com- pounds are not given, because Fe, if present, is always separated and detected in the course of analysis as fer- ricum, and ferrosum is tested for by special reactions in the original substance. Ferrous are readily converted into ferric compounds by boiling for a short time with a lit- tle strong HN03, or with HC1 and a crystal of KC103. Ferricum (Fe'").—Use Fe2CJ,. Ferric salts are usually yellow or reddisli-yellow; ferrous salts usually pale green, or white if perfectly dry. 96. AmllO or KHO: reddish-brown flocculent pre- cipitate (Fe2Ho6); insoluble in KHO, soluble in HC1. 97. Am./8: a black precipitate (FeS), mixed with white S : soluble in boiling acids, insoluble in KHO : Fe2Cl6 + 3Am2S — 2FeS + S + tJAmCl. In a very dilute solution of Fe a green color is pro- duced at first by Am2S, and the black precipitate sepa- rates only after a time. 98. IfiS:2 same black precipitate in alkaline solutions: in neutral or acid solutions S is precipitated and the ferric is changed to a ferrous salt, the color of the solution 1 This distinction of the two conditions of Fe and other elements by dashes or roman numbers placed above the symbol, hrst proposed by Odling, is very convenient for brevity. 2 1I2S may be added as a solution of the gas in trying the reactions ; in the course of analysis the gas is usually passed into the liquid. 99-101. GROUP III A.—IRON. 107 changing from yellow to pale green, as is seen after boil- ing and filtering: Fe2Cl6 + H2S = 2FeCI2 + 2HC1 + S. 99. Blowpipe Beaetions.—These are the same for fer- rous as for ferric compounds. Fused with Na2COs on charcoal in the inner flame a gray magnetic powder is left (33 a); this is shown to be magnetic by being at- tracted when touched under water by the end of a mag- net, or of a magnetized knife-blade. Outer flame: reddish-brown while hot; yellow when cold. Inner “ greenish bead, the color of green bot- tle-glass. 100. Boi •ax bead: 101. Distinctive Tests foe Feerous and Fer- ric Salts. For these tests several drops of dilute IIC1 should be first added to the Fe solution. Reagents to be added. Ferric salts. (Use Fe2C)6 solution.) Ferrous salts. (Use FeS04 solution.) 1. KtFeCye added in small quantity: Dark-blue precipitate, “ Prussian blue;” insoluble in HC1,1 solu- ble in H3C204, and slightly sol- uble in K4FeCys added in ex- cess; turned brown by KllO. Light-blue precipitate, be- comingdark blue in the air, or on addition of HN03 or Br-water. 2. !Ts(FeCyah : No precipitate: the solution darkens, but on dilution with water is seen to contain no precipitate. Dark-blue precipitate “Turnbull’s blue:” in- soluble in HC1. In very dilute solution only a dark bluish-gray color is produced. 3. KCyS: Blood-red coloration : no precipi- tate is produced, the liquid be- ing perfectly clear on dilution; the color is immediately de- stroyed when several drops are poured into some HgCl2 solu- tion ; its production is hin- dered by HNO» and by HA. No red coloration unless small quantities of fer- ric salts are present. 4. KI10 : Reddish-brown precipitate. Dingy-green precipitate, turning brown in tin air. 1 The solubility and insolubility of this precipitate must be shown by warming separate portions of the blue liquid containing the pre- cipitate with HC1, II2C2O4, and KrFeCys, then separately filtering each; if the precipitate has been dissolved the filtrate will be dark blue. GROUP III A.—CHROMIUM. [102-106. Chromium (Cr.)—Use CrK(S04)2.12IIa0, chrome- alum. Chromic salts are usually green or violet in color. 102. AmHO: pale bluish-green precipitate (Cr2Ho6): if AmHO is added in large quantity and the liquid is heated some of the precipitate is dissolved, producing a beautiful violet-red solution whose color is best seen after filtering; but from this solution the Cr2IIo6 is reprecip- itated on boiling the liquid for several minutes in a por- celain dish. 103. KIIO added in small quantity gives the same precipitate (Cr2Ho6); if more cold KHO is added the precipitate is entirely dissolved to a green fluid; on di- luting this liquid with water and boiling for several minutes the Cr2IIo6 is reprecipitated and the liquid be- comes colorless. AmCl added to the KHO solution also reprecipitates the Cr2Ho6. 103 a. If to some of the green liquid, obtained by adding KHO in excess to the chromium solution, a little red-lead or lead-peroxide (Pb02) is added and the liquid is then boiled, a yellow liquid is obtained from which a yellow precipitate (PbCrOJ is thrown down by addition of HA in excess. 104. AnyS precipitates Cr2IIo6, H2S gas being given off’ or remaining dissolved. The reaction is similar to that with AlAm(S04)2 par. 93. 105. Blowpipe Reaction.—If Na2C03 and KNOs be mixed with any solid substance containing Cr, and the mixture be fused on a piece of platinum foil or in a por- celain crucible or lid, or in a loop of platinum wire as was directed for the borax bead (31), a yellow mass is formed colored by Na2Cr04. If this yellow mass is dis- solved by boiling it with water, a yellow solution is ob- tained ; this solution, if made acid with HA and boiled for a few minutes to drive off C02, gives with PbA2 solu- tion a yellow precipitate of PbCr04. 106. Cr forms two classes of compounds; in one class Cr in com- bination with oxygen functions as an acid-radicle; this class includes the chromates, such as KiCrCh and K2CY2O7, they are usually yellow or reddish in color; but Cr also forms a series of salts in which it 91.] GROUP III A.—TABLE OF DIFFERENCES. acts as a metallic-radicle; these are usually green or violet, and give the above reactions for Cr. The latter compounds pass by oxidation into the former, as in reactions (103) and (105), where the oxidation is caused by Pb02 and KXO-. respectively. Chromates pass by re- duction into the green compounds; examples of this change will be found under the tests for chromic acid (286). This reduction of chromic acid causes it to be detected in the course of analysis as a base, and a special experiment has to be performed to ascertain whether the Cr was present originally as a metallic or as an acid radicle. 107. Group III a.—Table of Differences. Tests. Al—salts. Fe"'—salts. Fe"—salts. Cr—salts. a. For liquids. 1. AddAinHO: White flocculent precipitate. Reddish - brown flocculent pre- cipitate. Dingy - green pre- cipitate, rapidly turning brown when left ex- posed to the air. Pale-green floccu- lent precipitate, color unaltered by exposure to air. 2. Add KHO: While flocculent precipitate, easily soluble in excess of KHO. Reddish - brown flocculent pre- cipitate, insolu- ble in excess of KUO. The same precipi- tate as with Am HO, insoluble in excess of KUO. Pale-green precipi- tate, soluble in excess of cold KUO, but repre- cipitated on dilut- ing and boiling for some time. 3. Add KCyS | and a few drops of HC1: Deep blood - red coloration, de- stroyed by pouring into HgCl2 solution. No coloration less Fe"' is present. un- also b. Blow-pipe j tests for solids. 4. Fuse with NiuCOg and KNOg on pla- tiuuui foil: On cooling a white mass of Na2COg re- mains, with dark - brown particles of FejO*. Same as Fe'". On cooling a yel- low mass re- mains, easily sol- uble in water; the solution, af- ter having been boiled with ex- cess of HA, gives a yellow pre- cipitate with PbA2. 5. Heated on charcoal: 6. Fused in bo- rax bead: In the outer flame { when cool if moistened with Co(NOs)2 solu- tion and re- heated strongly gives a fine blue mass. In inner flame mixed with Na,COa gives a gray magnetic powder. (33 a. Reddish - yellon in outer flame. Greenish-yellow in inner flame. Same as Fe'". Same as Fe'". Green both in outer and inner flames. 110 GROUP III B.—ZINC GROUP. [108-110. Members of this group occurring singly are easily distinguished by one or other of the above tests, the first three serving for liquids, the last three for solids; tests 2 and 5 are the best for Al, 2, 4, and 6 for Cr, and 1, 3, or 6 for Fe. 108. (s) The separation and detection of these three substances when mixed depend upon the following dif- ferences : 1. The solubility of Al2Hofi in boiling KHO, in which Fe2Ho6 and Cr2IIo6 are insoluble. 2. The conversion of Cr2Ho6 by fusion with Na2C03 and KN03 into soluble Na2Cr()4; Fe2Ho6 remaining as Fe203, which is insoluble in water. 3. The yellow color of the solution of Na2Cr04 in water, and production of a yellow precipitate by acidify- ing it with HA and adding PbA2. 4. The blood-red coloration obtained by adding IvCyS to the Fe2Os dissolved in IIC1. 109. (s) A solution which may contain Al, Fe, Cr, is examined in the following manner: To a few drops of the solution acidified with HC1 add a little K4FeCy6; if a blue precipitate is produced Fe is present; this portion is rejected. Two other small por- tions of the acidified solution are then tested; one with K6(FeCy6)2, which by giving a dark-blue precipitate shows the presence of Fe"; the other with IvCyS, which if it gives a blood-red color proves the presence of Fe'". Boil the rest of the solution for several minutes, add- ing a few drops of strong IIN03 if Fe" is present ; add some AmCl, then AmHO until the liquid after being well stirred is alkaline and smells of NH3; boil, filter, and examine the precipitate by Table III a (436), disre- garding all the appended notes. GROUP III b.—ZINC GROUP. 110. This group includes Zn, Mn, Ni, Co; its mem- bers differ from those of Groups IV and V, by being precipitated by Am2S in neutral or alkaline solution, and by H2S in alkaline solution; they are not precipitated by 111-112.] GROUP III B.—ZINC. the group reagents for Groups III A, II, and I. Mn is, however, liable to be precipitated by AmHO, even in the presence of AmCl, if the solution stands exposed to air for some time. The members of this group show no characteristic flame colorations, but with the exception of Zn give character- istic colors to a borax bead. BaCOs does not precipitate this group as it does Group III a, unless its members are present as sulphates. Zinc (Zn).—Use ZnS04.7H20. Zinc salts are usually colorless. 111. Am2S: white precipitate (ZnS): the precipitate often appears yellow from the presence of excess of yel- low Am2S in the liquid; its true color is seen in the next reaction, or by letting the precipitate produced by Am2S settle, or by filtering it. For the solubility of this pre- cipitate see the end of the next reaction. 112. H2Swhite precipitate (ZnS): the Zn is only partly precipitated from a neutral solution, since H2S04 is separated and dissolves the ZnS: ZnS04 + H2S = ZnS + H2S04; but if NaHO or AmHO be added to neutralize the H2S04 when it is set free, the Zn may be entirely pre- cipitated ; addition of NaA also causes complete pre- cipitation, since HA replaces H2S04 in the solution, and ZnS is insoluble in HA: Add H2S to some ZnS04 solution to which AmCl has been first added and then AmHO until it is alkaline, and show by adding to separate portions of this liquid HC1, HA, and Am2S, that ZnS is soluble in HC1, and insoluble in HA and in Am2S.2 ZnS04 + II2S + 2NaA = ZnS + ATa2S04 + 2HA. ' II2S may be used in this group as sulphuretted hydrogen water. 2 The tests which show the solubility of the sulphides of this group are best tried on the precipitate obtained by adding Am Cl, AmHO, 112 GROUP III B.—MANGANESE. [113-117. 113. KUO added in small quantity gives a white pre- cipitate (ZnHo2); if more KHO is added, this precipitate dissolves; the ZnHo2 is, however, reprecipitated as such by adding much water to this solution and boiling it, or as Z11S by passing H2S gas into it. 114. Solid ZnS04.7H20 powdered with Na2COs in a mortar, then heated on charcoal in the inner blowpipe flame, gives an incrustation on the charcoal, which is yel- low whilst hot and white when cold. It cannot be driven away by the outer blowpipe flame, but is easily removed by the inner flame. If this incrustation on cooling is moistened with cobalt-nitrate solution and strongly heated in the outer blowpipe flame it becomes green. The above changes of color are more distinctly obtained by igniting a little solid ZnSCh in the outer blowpipe flame on charcoal; it is yellow whilst hot, and white when cold; if moistened with Co(NO:i)2 solution and reheated in the outer flame, it becomes green. Manganese (Mn).—Use MnCl2 or MnS04. Manganous salts are usually of a pale-pink color. Alkaline man- ganates are green, permanganates purple. 115. Am28: flesh-colored or pale-pink precipitate (MnS): the liquid should be filtered, since the precipitate often appears discolored by the yellow Am2S, the color of the precipitate on the filter is then easily seen; the color of the moist precipitate changes to dark brown on standing in the air upon the filter. For the solubility of this precipitate see (116). 116. 1I2S precipitates MnS partly from neutral solu- tions, entirely from alkaline solutions, but not at all in presence of free IICl or HA; show with separate por- tions of the MnS precipitate, obtained by adding AmCl, AmHO, and then H2S solution to the liquid, that MnS is soluble in HC1 and in HA, but insoluble in Arn2S. 117. jKHO: white precipitate (MnHo2), quickly turned brown by pouring the liquid containing the pre- and II2S, unless freshly prepared colorless Am2S can be obtained, since from yellow Am2S acids precipitate sulphur. 118-121.] GROUP III B.—NICKEL. 113 cipitate into a white porcelain dish or upon a filter: the precipitate is insoluble in excess of KHO. 118. ArriTIO gives the same precipitate, but if suffi- cient AmCl is first added, AmliO produces no imme- diate precipitate; the solution, however, on standing exposed to the air turns brown and the Mn is gradually precipitated as brown Mn2HOg. 118 a. Pour a little MnS04 (notMnCl2) solution upon some red or brown lead oxide (Pb02), add HN03, which must be quite free from Cl; boil the mixture and allow the powder to settle ; the clear-liquid is colored deep red by the formation of permanganic acid (HMn04). The production of this color is prevented by the presence of even a minute quantity of chlorine. 119. Blowpipe Tests.—If any solid substance contain- ing Mn be fused in the outer flame with a mixture of Na2C03 and a little KN03 upon platinum foil, a bluish- green mass is obtained on cooling ; the mixture should be fused by heating the lower surface of the foil with the blowpipe flame. The test may be also made by fusing a mixture of Na2C03 and KN03 into a bead in a loop of platinum wire, and then fusing the substance into this bead by heating it in the extreme tip of the outer flame. 119 a. Fused with Na2C03 on charcoal in the inner flame, a gray magnetic powder is obtained (33 a). 120. Borax Bead.—Use very little Mn0211 In the outer flame Violet-red bead whilst hot. Amethyst-red on cooling. In the inner flame.—A colorless bead. Nickel (Ni).—Use NiS04.7H20. Nickel salts are usually bright green iu color. 121. AmJS : black precipitate (NiS); add more-yellow Am2S,2 boil and filter, a brown filtrate runs through, 1 A borax bead is often opaque from the use of too much sub- stance. If such is the case fuse the bead in the blowpipe flame, then by a sudden jerk throw some of the fused mass off’ and fuse again the remaining portion with fresh borax ; repeat this if necessary. The fused bead often becomes transparent when flattened by squeez- ing with small pincers. 2 The Am2S must be yellow; colorless Am2Sdoes not dissolve NiS. 114 GROUP III B.—NICKEL [122-127. colored by NiS dissolved in the excess of Am2S; pour this filtrate into a porcelain dish and boil for some time, adding distilled water if necessary to prevent the dish becoming dry; the black NiS will be precipitated and may be filtered off, giving a colorless filtrate. If HA. is added to the dark filtrate until it is acid, the NiS is also precipitated from it. 122. IJ2S: black precipitate (NiS) in neutral solu- tions or in solutions acid with IIA (112), but HC1 pre- vents the precipitation ; show with portions of the liquid containing NiS, obtained by adding H.2S to NiS04 solu- tion to which a little AmCl and AmHO have been added, that NiS is insoluble in cold dilute HC1 and in HA, but soluble when heated with HC1 after adding a crystal of KCIO,. 123. KHO : light-green precipitate (NiHo2). 124. AmHO added in very small quantity : bluish- green precipitate (NitIo2), soluble in excess of AmHO to a violet-blue liquid, soluble also in AmCl. If AmCl be first added, AmHO causes no precipitate. 125. KCy solution1 added in small quantity gives a yellowish-green precipitate (NiCy2); by further addition of KCy this precipitate is dissolved, but HC1 reprecipi- tates NiCy2 from the solution. 128. If some NiS04 solution is made acid with several drops of HCl,then KCy solution gradually added, whilst stirring or shaking the liquid, until the precipitate is re- dissolved, and the solution thus obtained is boiled for a short time, then cooled and divided into two parts: HC1 added in excess to one part will produce a precipitate of NiCy2, often only appearing after a time : Na2Cl20, or Br-water after excess of NaHO, added to the other part will give on warming a black precipitate (Ni2Ho6). Blowpipe Reactions: 127. Solid NiS04.7II20 powdered with Na2C03 in a mortar and then fused on charcoal in the inner blowpipe ilame, leaves a gray powder which is attracted by the magnet. (33 a). 1 KCy solution must always be prepared immediately before use; it is decomposed by keeping. 128-135.] GROUP III B.—COBALT. 115 128. Borax head: Violet or sherry-red bead whilst hot. Pale yellow on cooling. In outer flame In inner flame, after being heated for some time. ■ Black or opaque bead. Cobalt (Co).—Use Co(N03)2.6H20. Cobalt salts are usually reddish-pink in color. 130. Am2S: black precipitate (CoS); on adding much Am2S, boiling and filtering, the filtrate is colored yellow by Am2S and is not dark colored, since CoS is insoluble in Am2S (difference from NiS). For the solubility of CoS see Exp 131. 131. dl/S: black precipitate (CoS), only forms in al- kaline solutions or in solutions acid with HA(112); HC1 prevents the precipitation. Add AmCl, then AmHO in excess, and then H2S-water to some Co(N()3)2 solution, and pour into separate portions of this liquid HC1 and HA, the precipitate does not dissolve; to the portion containing HC1 add a crystal of KC103 and heat, the precipitate dissolves readily. 132. KILO: blue precipitate (CoHo2), turning green if poured out upon a watch-glass and allowed to stand in the air, and becoming pale red on being boiled ; the red color is, however, frequently more or less masked by a brown cobalt hydrate precipitated at the same time. 133. AmHO: bluish-green precipitate, having the same properties as that given by IvHO; soluble in AmCl, hence if AmCl is added before AmHO no precipitate is produced. 134. KCy solution added in small quantity gives a reddish-brown precipitate (CoCy2); add more KCy solu- tion slowly and whilst shaking the liquid, the precipi- tate dissolves ; now add HC1, the CoCy2 is reprecipitated. 135. If some Co(NOs)2 solution is made acid with a few- drops of IIA, then KCy solution added slowly until the precipitate at first formed just redissolves, and the 116 GROUP III B. [136, 139. liquid is boiled until no further smell of HCy is evolved, then cooled and divided into three parts, it will be found that neither HC1, nor Na2Cl2G, nor Br-water with excess of NallO solution, produces a precipitate on warming the liquid. [Difference from Ni (126).] The difference of behavior of the Ni and Co solutions which have been boiled with excess of KCy, is due to the fact that NiCy2 forms with KCy a feeble compound (NiCy2.2KCy), which is soluble in water, but is easily decomposed ; whereas CoCy2 forms with KCy in the air the very stable soluble compound lv6(CoCy6)2, “ Potassium cobalticyanide.” Blowpipe Reactions: 136. Fused with Na2CC>3 on charcoal in the inner flame Co(NOs)2 gives a gray metallic powder attracted by the magnet (33 a). 139. Group III Tests. Za—salts. Mn—salts. a. For liquids. 1. Add AnioS, or better, While precipitate: soluble in Pink precipitate: soluble i AuiCl, AinllO in excess, cold dilute HC1: insoluble cold dilute HC1: soluble ii and H2S-water: in HA. III. 2. Add KHO : While precipitate: soluble in White precipitate: turnin 3. Add KCy, solution : This test need oil ly be tried when a black precipitate has been obtained by Test No. 1. excess of KHO. brown in the air: insolubl in KHO. b. Blowpipe tests for solids. 4. Fused with Na2C03: On charcoal in the inner On charcoal in the innei 5. Borax bead: flame: gives a white incrus- tation,which,if moistened with Co(NOa)o and heated in the outer flame, turns green. The substance itself when strongly heated after having been moist- ened with Co(N03)2 also becomes green. flame: a gray magnetic powder (33 a). On platinum foil in outei flame: a bluish-green mass showing more rapidly if a little KNOabe mixed with the Na2C03 before fusing.! Outer flame.—Amethyst-red.\ Inner flame.—Colorless. 137-138.] TABLE OF DIFFERENCES. 137. Borax bead: strong solution may be employed, the bead being dipped into it; fine blue bead in both in- ner and outer flames ; opaque if too much Co(N03)2 has been used. 138. When a solution is to tie examined for only one member of this group, its detection by one or more tests in the table (139) will be very easy. The precipitate with Am2S is distinctive, ZnS and MnS being equally recognized by their different colors ; NiS and CoS, which differ from ZnS and MnS by being black, are distin- guished from one another by the solubility of NiS in ex- cess of Am,S, the liquid therefore giving a brown fil- trate. KHO also gives characteristic precipitates with lble of Differences. Ni—salts. Co—salts. Hack precipitate: soluble in boiling yellow to a dark solution : insoluble in cold dilute HC1 and in HA, Black precipitate: insoluble in boiling yellow in cold dilute HC1, and in HA. Ireen precipitate: insoluble in KIIO. Blue precipitate: insoluble in KHO. Idded in excess to the slightly acid solu- tion and boiled for some time, then Na«- CloO (or Br-water and excess of NallO) added, gives a black precipitate on lieat- iug. Added in excess to slightly acid solution and boiled for some time, Na2('l20(or Br- water and excess of NaHO) gives no pre- cipitate on heating. )n charcoal in the inner flame, a gray mag- netic powder (33 a). Same as Ni. )uter flame -f Vio,el or Vel,ow while hot- juter name. | yellow when cold. 'nner flame.— Gray or opaque bead. Outer and inner flames—Fine blue bead. order to ascertain whether the precipitate has been dissolved, filter and observe er the filtrate is dark in color. 118 GROUP III B.—DETECTION. [140,141. each of these substances. The most distinctive tests for Ni and Co are 3 and 5 ; for Zn and Mn, 2, 4, and 5. 140. (s). The method for separating and detecting Zn, Mn, Ni, Co, when mixed, depends on : 1. The solubility of NiS in yellow Am2S ; ZnS, MnS and CoS being insoluble.1 NiS is precipitated from this solution by boiling or by addition of HA, and the pres- ence of Ni is then confirmed by fusion in a borax bead. 2. The solubility of ZnSand MnS in cold dilute HC1, NiS and CoS being almost insoluble. (Note 1, below.) 3. The solubility of ZnIIo2 in cold KHO, in which MnIIo2 is insoluble; white ZnS is then precipitated from this solution by II2S. 4. The production of a bluish-green mass by fusing MnHo,2 with Na2COs and KN()3. 5. The difference of behavior of the KCy solution of Ni and Co with Na2Cl20, or with Br-water and excess of NaHO ; and the marked difference in their borax beads. (Note 2, below.) Note 1.—Mn may also be separated from Ni and Co by passing H2S into the solution containing NaA (112); Mn remains in solution, NiS and CoS are precipitated. Note 2.—A modification by Henry of Rose’s method for separating Ni and Co is also to be recommended ; it depends upon the fact that, whilst Co is precipitated as C02H06 by BaCO* in presence of Br, Ni remains in solution. The sulphides are dried and then strongly ig- nited in an open porcelain crucible; the metals remaining as oxides are dissolved by boiling with a little strong HC1, carbon is filtered off if necessary, and to the clear solution, after being cooled and mixed with Br-water, excess of BaCOs is added in a small corked flask : the flask is then well shaken and allowed to stand for about half an hour ; on filtering, Co if present is detected in the precipitate by the borax bead ; Ni is precipitated from the filtrate by heating it with KHO; on filtering, the presence of Ni in the precipitate may be confirmed by fusing a portion of it in the borax bead. 141. (s). A solution is examined for Z11, Mn, Co, Ni, by adding AmCl to it in a boiling-tube, then AmHO if necessary until it is alkaline, and then Am2S until, after being well stirred or shaken, the liquid smells of it. The liquid is then boiled, a few drops are poured upon a til- 1 In order to ascertain whether the precipitate has been dissolved, filter and observe whether the filtrate is dark in color. 142-144.] GROUP II A.—MERCURY. ter and the color of the filtrate noted ; if it is colorless, sufficient Am2S has not been added; more Am2S is then to be poured in, and the liquid again boiled. When a few drops run through the filter brown or yellow in color, AnijS has been added in excess; the whole is boiled and filtered and the precipitate examined by Table III B (437); the filtrate if yellow is rejected, if brown it is examined for Ai according to (431). GROUP II a.—COPPER GROUP. 142. This group includes Hg", Pb, Bi, Cu, Cd; its members differ from those of Groups III A, III b, IV and V, in being precipitated by H,S in acid solutions. With the exception of Pb, which in a strong solution is partially precipitated by HC1, the members of this group are not precipitated by HC1. The sulphides differ from those of Group II b, by being insoluble in Am2S or KHO. If very much acid is present, H2S does not precipitate the members of this group readily or completely; they are precipitated how- ever on dilution. Mekcuricum (Hg").—Use IIgCl2- 143. Hg forms two series of compounds distinguished as mercuric and mercurous; the mercury in these two states behaves differently with reagents, and may be distinctively called mercuricum and mercu- rosum ; in the latter state it is classed under Group I. 144. Ji2Sblack precipitate (HgS): if the H2S solu- tion is added slowly, the precipitate is first white, then brown or orange, and ultimately becomes black: these changes of color during the addition of II2S are char- acteristic of mercuric salts. Filter and wash the precipi- tate: place portions of it in three test-tubes: boil one portion with strong HN03 and another with strong HC1, the precipitate is not dissolved by either acid; mix the contents of the two tubes and warm again, the precipi- 1 A test-tube half full of the solution must be used in order to get sufficient precipitate for the experiments below. This remark ap- plies also to the liquid used for obtaining the IGS-precipitate with the other members of this group. 120 GROUP II A.—MERCURY. [145—147. tate will now dissolve: boil the third portion with Am,S, the precipitate does not dissolve. Hence HgS is in- soluble in hot strong IIN03, in hot strong IIC1, and in Am2S, but is easily soluble in a mixture of IIN03 and HC1 or “ aqua regia.” 145. SnCl2: white precipitate (Hg2Cl2): if more SnCl2 is added and the liquid boiled, the white precipitate be- comes gray and consists of fine particles of Hg; if the liquid be decanted and the gray precipitate be then boiled with strong IIC1, the Hg particles unite to globules visible by a lens or frequently by the naked eye. 2HgCl2 + SnCl2 = Hg2Cl2 + SnCl4. Hg2Cl2 + SnCl2 = 2Hg + SnCI4. 146. Cu: if a small strip of copper sheet or a copper coin, whose surface has been polished and cleansed by rubbing it with sandpaper, be immersed in some HgCl2 solution made acid with a drop or two of HC1, it will soon become coated with a gray film of Hg: If the surface of the Cu, after having been immersed for several minutes, is dried and rubbed hard with a cloth or piece of wash-leather, it will appear more or less whitened like silver, the liquid metal Hg having “amalgamated” the Cu. The Hg may be readily driven off by heating the Cu strongly; if this heating is performed in a test-tube, or better in a small hard glass tube sealed at one end (10), a sublimate of globules of Hg forms upon the cool sides of the tube. 147. Mix a little solid HgCl2 intimately with about three times as much Na2C03, by powdering them together in a mortar, or with a pestle on a watch-glass. Pour some of this dried mixture into a perfectly dry small test-tube (see note below), and cover the mixture with a small layer of Na2C03; now heat strongly first the layer of Na2C03, then gradually the mixture: Hg will sublime, condensing in globules on the sides of the tubes. Sometimes the globules are so small that the layer appears as a gray film ; they may be united into HgCl2 + Cu = Hg + CuCl2. 148-151.] GROUP II A.—LEAD. 121 visible globules by rubbing the film with a splinter of wood or with a thin glass rod (11 a), or the separate globules may be seen by means of a poeket lens. Note.—The powdered mixture is best dried by spreading it out upon a watch-glass and placing it in a stream or water oven ; it may be dried also by supporting it on the filter-drver (25) at some height above a small flame. A powder such as the above is most easily placed in a narrow closed tube by alternately scooping the powder up with the mouth of the tube, and tapping the tube so as to shake the power to the bottom, or by turning the powder out upon a piece of note-paper folded over into a trough and pouring it thence into the tube, holding both over the watch-glass to catch any substance which falls. Both the inside of the tube and the powder must be perfectly dry, else some powder obstinately adheres to the sides of the tube and obscures the sublimate. The heating must never be commenced until the sides of the tube are perfectly clean ; they are cleansed if necessary with a twisted slip of filter-paper or a wooden match; also if any drops of water condense on the inside of the tube during the first stage of the heating they must be removed by a twisted piece of filter-paper, or by a small piece of filter-paper rolled round a wooden match or a thii\ piece of wire. 148. Heat a little solid HgCl2 in a tube closed at one end ; the substance sublimes in white fumes, since Hg- compounds are volatile. Lead (Pb).—Use PbA2.3H20 dissolved in water to which a little HA has been added. 149. II, S: black precipitate (PbS): this precipitate is red if much hydrochloric acid is present in the solution, but becomes black on diluting with water and passing H2S, or on adding more H2S-solution. Filter or decant, and show with separate portions of the precipitate that PbS is insoluble in KHO or Am„S, soluble in boiling dilute HNOs, but converted by boiling strong IIN03 into insoluble PbS04. 150. I1CI: white precipitate (PbCl2), forms only in cold and strong solutions : on boiling, the precipitate dis- solves,1 but the PbCl2 separates again in beautiful crys- tals on cooling. 151. II2SO4: white precipitate(PbS04): this precipi- tate is much less soluble in dilute H2S04 than in water, 1 If the precipitate does not entirely dissolve add a little water and boil again. 122 GROUP II A.—BISMUTH. [152-156. hence H2S04 should be added in excess to a pretty strong solution of Pb: pour off into two test-tubes and let the liquid stand; decant the liquid from the precipitate, and show that the precipitate may be dissolved by pouring upon it HAorIl2T, then AmHO in excess,and boiling; show also that it dissolves in boiling strong HC1. 152. KlCrOi or K2Cr./)7: yellow precipitate (Pb CrOj; pour off into two tubes and show that the pre- cipitate is soluble in KHO, but insoluble in HA. 153. Blowpipe Reaction.—Mix well some powdered PbA2.3lf20 with about twice as muchbTa2C03; heat the mixture in a cavity on apiece of charcoal in the inner flame; a yellow incrustation will form around the cavity and small bright white-globules of Pb will be seen within it. The incrustation is readily removed when heated in the inner blowpipe flame, coloring the flame azure-blue. Detach one of the globules with the point of a knife, place it on the bottom of a mortar turned upside down, and give it a smart blow with the pestle; it flattens out without breaking into powder, because Pb is malleable, not brittle. If one of the globules be fixed upon the point of a penknife, it will be found by gentle friction on paper to mark it as a black-lead pencil does. Bismuth (Bi).—Use Bi(K03)3.5H20 dissolved in di- lute HC1. 154. IfS: brownish-black precipitate (Bi2S3): let stand and decant most of the water; then pour some of the precipitate into three test-tubes, and show that it is insoluble in Am2S, and in KHO, but soluble in strong IIN03. 2Bi(N 03)3 + 3Hj3 = Bi2S3 + 6IIN03. 155. A mHO or KHO: white precipitate (BiITo3): pour off a small quantity of the liquid and precipitate into a tube, add much AmllO and warm, the precipitate is undissolved; filter off the rest of the precipitate and dissolve it by pouring upon the filter a few drops of, hot dilute HC1; keep this solution. 156. II20: pour the 1JC1 solution obtained from the 157-160.] GROUP II A.—COPPER. 123 last reaction, or some of the original solution, into a large quantity of distilled water contained in a beaker; on stirring and letting stand a milkiness appears, due to the formation of BiOCl. BiClg + H20 = BiOCl + 2IIC1. Pour a little of the milky liquid into two test-tubes; warm one portion after adding to it a little strong HC1, the precipitate dissolves; to the other add H2T and warm, the milkiness remains (difference from SbOCl). If but little Bi is present this milkiness often only appears after stirring and letting the liquid stand for five or ten min- utes. 157. K1CrOi or K2Cr.,07 (see note below) : yellow floeculent precipitate [Bi2(Cr04)3] : add KHO, the pre- cipitate does not dissolve (difference from PbCrOJ; it dissolves completely in HC1 or HNOa added in excess. Note.—Since this precipitate is soluble in HC1, and IIC1 is present in the Bi-solution used, the free IICl must first be removed by dis- solving in a little of the Bi-solution a sufficient quantity of solid NaA ; the free HC1 is thus replaced by HA, which does not dissolve the precipitate: NaA + IIC1 = NaCl + HA. 158. IIjdOi: no precipitate. 159. Blowpipe Reaction.—A mixture of powdered Bi(N03)3 and Na2COs, heated on charcoal in the inner flame, gives an incrustation orange-red whilst hot, yellow when cold; also white globules of Bi, which are very brittle, being crushed to powder by a sharp blow with a pestle (153). Copper (Cu).—Use CuS04.6H20. Copper salts are usually blue, sometimes green in color ; their color commonly becomes very pale, or disappears when the salts are thoroughly freed from water of crystallization. 160. H2S: brownish-black precipitate (CuS): filter, keeping the funnel carefully covered with a glass plate, as air quickly oxidizes CuS to CuS04, which dissolves and runs through with the filtrate. Place some of the precipitate in five test-tubes, and show that it is insoluble in KHO, in Am2S, and in boiling dilute H2S04, but dis- 124 GROUP II A. COPPER. [161-167. solves in boiling HN03, dilute or strong, and in KCy solution. 161. AmllO added in very small quantity: a greenish- blue precipitate: if more AmIIO is added this precipi- tate dissolves, yielding an intensely blue liquid containing (N2Cux4m4H2)S04, which becomes again light blue on adding an acid in excess. 162. R2SOa: no precipitate. 163. KiFeCy6: reddish-brown precipitate (Cu",, FeCyfi), insoluble in HA; the color is best seen by trying the reaction in a white porcelain dish. In very dilute solution only a reddish color is produced. 164. Fe: a bright strip of steel or iron, such as the blade of a penknife, freed from grease by rubbing with sandpaper, or by boiling in a dilute KHO and washing, when dipped into CuS04 solution made acid with a few drops of H2S04, is covered with a red film of Cu after a time. 165. Zn and Pt.: Zn if placed upon a piece of plati- num foil or wire in some CuS04 solution contained in a porcelain dish or watch-glass, causes a red film of Cu to deposit on the platinum. The CuS04 solution should he first made acid with a few drops of H2S04. Blowpipe Reactions: 166. A mixture of powdered CuS04.6H20 and Na2C03, if heated on charcoal in the inner blowpipe flame, gives red scales of Cu, which are best seen by separating them as directed in (33 a). In outer flame: Green whilst hot, blue when cold. Red or colorless bead when cold; obtained only when very little * Cu is present, and the bead is long heated in a good re- ducing flame.1 167. Borax bead. In inner flame: ' The red head is much more easily and rapidly obtained by fusing a fragment of Sn or Zn into the bead ; the former gives a clear, the latter a turbid bead. 168-175.] GROUP II A.—CADMIUM. 125 168. Flame coloration: a loop of platinum wire dipped into CuS04 solution, and held in the inner blowpipe flame, or in the Bunsen flame, gives a green coloration ; the flame shows a blue centre after the loop has been moistened HC1. Cadmium (Cd).—Use CdS04.4H20. 169. HjS: bright-yellow precipitate (CdS): boil off the H2S, and pour the liquid into several tubes; show with these separate portions that the precipitate is insol- uble in Am2S, in KHO, and in KCy solution, but solu- ble in boiling dilute HN03and in boiling dilute H2S04; dilute the H2S04 solution with much water and pass II2S for a short time, yellow CdS is reprecipitated. 170. AmHO added in small quantity, best by using AmHO much diluted: white precipitate (CdIIo2); on adding more AmHO the precipitate readily dissolves. 171. H.iSOi: no precipitate. 172. Blowpipe Reaction.—Powdered CdS04 mixed with Na2C03 and heated on charcoal in the inner blow- pipe flame, gives a brown incrustation. 173. Group II a.—Tap,le of Differences.—(See pp. 126, 127.) 174. The color of the H2S precipitate, and its behavior with strong HNO;i, enable the analyst to detect one mem- ber of this group when present alone : the most charac- teristic special tests for each member of this group will be found under its reactions. 175. (s). The separation of Hg, Pb, Bi, Cu, Cd, de- pends upon the following differences: 1. The solubility of Bi2S3, CuS, CdS in strong boiling HN03; HgS and PbS being insoluble, and remaining as HgS and PbS04. 2. The solubility of PbS04 in HA and excess of AmHO; HgS being insoluble. 3. The solubility of CuHo2 and CdHo2, and insolu- bility of BiHo3, in excess of AmHO. 4. The solubility of CdS and insolubility of CuS in boiling dilute H2S04. The insolubility of CdS in KCy GROUP II A. 176. solution, in which CuS easily dissolves, furnishes another means of separation. After having been separated, the presence of each metal is confirmed by some special test. 176. (s). A solution which may contain Pb, Ilg, Bi, Cu, Cd, mixed, is first made acid, if not already so, with a little HC1;1 II2S is then passed in a rapid stream through the solution for about five minutes; the precipitate is fil- tered off, the filtrate mixed with H2S water, or diluted with a little water and II2S again passed for a short time, Group II a. Tests. Ilg—salts. Pb—salts. a. For liquids. 1. Pass ELjS, or add HoS water: Black precipitate ; when fil- tered and well washed, in- soluble in boiling strong HNOa, and unchanged by it. Black precipitate; almoi insoluble in boiiingstron UNO,, changed by it iut white PbSO<. 2. Add II,S0 except for (187). dissolved in H20. 187. AgN03, Light-yellow 'precipitate Brown precipitate several drops (Ag2HAs03or Ag3As03): (Ag3As04): show are added to this precipitate forms only that it is soluble a solution of on adding carefullv, drop in AmHO and in As203in water. by drop, a little dilute HN03. For this reaction Am HO:1 show that it is As203 dissolved dissolved by AntHO and in boiling water is employed, because HC1 would yield by HN03. It is also appreciably soluble in a precipitate of AmN03: hence, if too AgCl. much AmllO has been added,the precipitate does not always form on neu- ' 188. CuSO„ tralizing with HN03. Yellow Oh-green precipitate Pale-green precipitate several drops: (Cu"HAs03) : this precip- (CuHAs04) : soluble itate forms only on adding dilute AmHO carefully, drop by drop :2 show that it is soluble in AmHO and in HN03. in AmHO and in hno3. 189. CuSO„ The above yellowish-green No clear blue solution two drops: precipitate is first pro- is obtained, and no then KHO duced, but on addition of Cu20 is produced on added: more KHO this dissolves boiling the liquid. to a clear blue liquid, which on being boiled deposits red Cu20. 190. AmCl, No precipitate. VVhite crystalline pre- AmH 0, and cipitate(MgAmAs04): My SO,: if filtered off and moistened with AgN03 solution on the filter it becomes brown. 1 AsoOs when dissolved in water yields H,AsOs, which cannot give with AgNO, the AgjAsOj precipitate, because this decomposition would liberate IINOj, in which AgsAs03 is soluble; hence the addition of AruHO is necessary to neutralize the free acid ; but since the precipitate is also soluble in AmHO, the latter must be added carefully in only just sufficient quantity to neutralize the acid. This is best effected by using some very dilute AmHO, made by pouring a few drops into a test-tube, filling the tube two-thirds with distilled water, then closing it with the thumb, and inverting it for a moment. The dilute AmHO is to be added drop by drop, shaking or stirring the test solution after each addi- tion until the precipitate is obtained. 3 The precipitate produced by CuSO, is soluble in acids, hence the IIC1 present in the solution must be neutralized by careful addition of AmHO before the precipitate will appear. 136 GROUP II B. ANTIMONY. [191-194. Antimony (Sb).—UseSbCls, or 2KSb0T.H20 “Tar- tar emetic,” dissolved in dilute HC1. Antimonic compounds give results ultimately identical with anti- monious in the following eight reactions, except in (192). After these reactions, which are common to Sb in both its sets of compounds, are given two which are distinctive; they are, however, rarely used and may be neglected by the student. 191. H2S: orange-red precipitate (Sb2S3): pour into two tubes and show that the precipitate is dissolved when warmed with pure NaHO or with but is repre- cipitated from these solutions on addition of IIC1 in excess. 192. If poured into much water, SbCl, solution yields a white precipitate or turbidity (SbOCl); this precipitate redissolves on adding HC1 and warming, and is also readily soluble in H/f; in this latter respect it differs from the similarly formed BiOCl precipitate (156). 193. If a few drops of acid SbCl3 solution be poured upon a piece of platinum foil,1 and a piece of Zn be dropped into it, a black deposit of Sb will rapidly form on the foil. If the foil be rinsed with water, and then boiled with HC1, the stain remains undissolved, but it is rapidly removed by boiling HNOs. Tests depending on the formation of SbH3: SbII3 differs from Asll3 in not being poisonous, and in being free from smell. 194. If Sbtl3 gas, formed by the action of acid SbCl3 solution on Zn, is passed into AgNOs solution in a pre- cisely similar way to that described for AsHg (181), a black precipitate (SbAgs) forms: SbH3 + 3AgNOs = SbAg3 + 3HN03. This precipitate is to be filtered off, and the filtrate, which will contain no Sb, rejected. Wash the precip- itate four or five times with boiling water upon the filter; then pour upon it boiling dilute H2T solution, which will 1 A slip of platinum foil laid in a watch-glass or porcelain dish, or with turned-up edges, may be employed; the inverted lid of a plati- num crucible is very convenient for this purpose. 195-198.] GROUP II B.—ANTIMONY. 137 dissolve the Sb, and receive the liquid in a test-tube; boil it, and pour it once more upon the filter; add HC1 to the liquid, filter if necessary, and pass H2S into it; orange-red Sb2S3 will be precipitated. 195. A stain produced by Sb on porcelain, in the manner already described (182), differs from the As stain in presenting a dead surface and in being insoluble in Ha2Cl20; also when the stain is dissolved by warming with Am2S, the solution if gently evaporated leaves orange-red Sb2S3. 196. The Sb mirror, obtained as described in (183), differs from the As mirror by being formed much nearer to the flame, and on both sides of the heated part of the tube; it may further be distinguished by the tests given in (195). This mirror, after oxidation, is also insoluble in boiling water; and if dissolved in a little boiling HC1 the solution gives an orange-red precipitate (Sb.,S3) when H2S is passed into it, whereas the As203 solution gives yellow As2S3. 196 a. SbII3 if allowed to act on filter-paper moistened with IJgCl2 solution as described in 183 a for AsH3, yields a grayish-brown stain. 197. Boiled with Zn or A1 and KHO, no SbH3is evolved. [Dif- ference from As (184.)] 198. If a little solid KSbOT or Sb203, or any sub- stance containing Sb, be mixed in a cavity on wood char- coal with and KCy, and the mixture be heated in the inner blowpipe flame, a white incrustation forms on the charcoal, and white globules of metallic Sb are obtained which are extremely brittle. The flame is col- ored pale green. If the melted Sb be allowed to stand aside on the charcoal the globule emits a white smoke, and coats itself with sharp white crystals of the oxide. The two distinctive tests (199, 200) for antimonious and antimonic compounds given in the following table are seldom used; they may be read through without try- ing the reactions, and may be referred to hereafter if re- quired for analytical purposes. 138 GROUP II B.—TIN. 199-203. Distinctive tests for antimon/oks and antimon/c COMPOUNDS. Keagent. AntimomcuM. (Use the above solution of SbCl3 in dilute HC1.) Antimonic. (Use KsSbaO, solution, ob- tained by boiling some “ Potassium metantimo- nate” with H20.) 199. Add excess of KHO, then AgN 03 solution. A dart-colored precipitate which when shaken after addition of Am 110 leaves black Ag«0 undissolved. A brown precipitate,which dissolves entirely on ad- dition of AmHO. 200, Add excess of 1IC1 and warm; then pour in a little KI solu- tion : No iodine is set free; proved by the liquid not turning brown and giving no color after being cooled and mixed with freshly pre- pared starch solution. Iodine is liberated, giving a brown color to the liquid and yielding a deep-blue color when starch solu- tion is added to the cold liquid. Tin (Sn).—Stannosum and Stannicum. Distinctive reactions for stannOKS and stannic COMPOUNDS. Test. Stannous Compounds. Use SnCl2-2H20 dissolved in dilute HC1. Stan me Coin pounds. Use SnCl4 in dilute HC1. 201. PassPLjS: Dark-brcnon precipitate (SnS): pour off two por- tions and show that the precipitate is soluble in KHOand in yellow Am2S on heating ; and is precip- itated again by HC1, from the KHO solution as brown SnS, from the AnijS solution as yellow SnSj. SnS differs from SnS2 in being insoluble in colorless Am2S, which readily dissolves SnS2. Yellow precipitate (SnS2), often form- ing only when the liquid is heated; pour off portions and show that the pre- cipitate is soluble in (both yellow and colorless) and in KHO on heating, and is precipitated again by HC1 as yellow SnS2 from both solutions. 202. IIgCl3 r A white precipitate (Hg2Cl2): turns gray on being boiled if the SnCl2 is in excess (145). 203. AuC13 : added after a few drops of SnCl4 solution or of Cl water: Purple or dark-brown pre- cipitate, “ Purple of Cas- sius.” 204, 205.; GROUP II B.—TIN. 139 Reactions common to Stannous and Stannic Compounds. 204. Zn in presence of HC1 precipitates from Sn so- lutions a spongy mass of Sn ; the Zn and solution should be allowed to stand together for some time in a small porcelain dish; the action is much hastened by gentle heat. If this test is done on platinpm foil the Sn is de- posited in a spongy state on the Zn and does not stain the Pt (difference from Sb). SnCl4 is not so readily acted upon by Zn as SnCl2is; from SnCl2 the Sn is often pre- cipitated in beautiful crystals. 205. A solid Sn-compound, SnCl2 or Sn02, mixed with powdered Na2C03 and KCy, and heated on charcoal in the inner blowpipe flame, gives a slight white incrusta- tion and white particles of metallic Sn, which are with difficulty fused into globules. The globules of Sn differ from those of Pb by not marking paper (153). 140 GROUP II B.—DIFFERENCES. ;206, 207. 206. Group II b.—Table op Differences. The following tests answer for these elements in both sets of com- pounds ; for distinctive tests see the preceding reactions. Tests. As. • Sb. Sn. a. For liquids. 1. Pass IPS into the solution acidified with HC1 and heat; if no precipi- ' tate forms, heat to boiling, and again passH2S: Yellow precipi- tate, insoluble in boiling strong HC1. Orange-red pre- cipitate, soluble in boiling strong HC1. ( SnS — Brown J precipitate, j SnS5 — Yellow I precipitate. Both soluble in boiling strong HC1. 2. Zn and HC1: AsH3 gas is evolved, which if passed into AgNOs solution gives a black precipitate of Ag, H3AsU3 be- ing left in solu- tion ; on adding dilute AmllO to this solution yellow Ag3As03 precipitates. SbJTs gas is evolved, which if passed into AgN03 solution gives a precipi- tate of Ag3Sb, from which hot H2T solution dissolves Sb; H3S gives in this solution after adding HC1 orange-red Sb3S3. Sn is deposited on the Zn strips. 3. Zn and HC1 on platinum: AsH3 evolved, no stain on the plat- inum. Black slain of Sb on the platinum. Sn deposited on the zinc, no stain on the plat- inum. 6. For solids. 4. Heated with Na2C03 and KOy on char- coal in the in- ner blowpipe flame: 5. Heated with solid Na2C03 and KCy in a bulb-tube: No metallic glob- ules ; smell of garlic. Black mirror and smell of garlic. Brittle metallic globules, white incrustation, Malleable metallic globules, white incrustation. The detection of anyone member of this group is sim- ple ; the color of the precipitate with H2S, confirmed by special tests, is quite sufficient to identify it with ease. 207. (s) Many methods have been proposed for the sep- 208, 209.] GROUP II B.—DETECTION. 141 aration and detection of As, Sb, and Sn, when mixed ; two of the most trustworthy are those introduced by Hof- mann (208) and by Fresenius (210); a method more simple, though less trustworthy, is given in (209). 208. (s) Hofmann’s method consists in pouring the solution into a flask in which H is being generated by the action of HC1 upon Zn; Sn remains as a spongy mass on the Zn, As and Sb are evolved as AsH3 and SbII3; these gases, if passed into AgNO., solution, yield soluble H3As03and insoluble Ag3Sb, which are separated by filtration ; the three members of this group thus sep- arated are then detected by special tests. As, Sb, Sn, occurring together in a solution, are tested for by precipitating them with H2S, filtering, and testing the filtrate by passing H2S through it as was directed for precipitating Group II A. The precipitate is then ex- amined by Table II (435 b, Arsenic Group), using only the right-hand side of the table. The H2S precipitate may also be examined by the sim- pler method given in (209), or by the very accurate, but less simple method, in (210). 209. (s) The following method of examining a pre- cipitate produced by II2Sfor As, Sb, Sn is recommended by its comparative simplicity ; it is sufficiently accurate for ordinary analyses where traces of these metals have not to be looked for. It depends upon the insolubility of As2S3 in hot strong IIC1, in which SnS, SnS„ and Sb2S3 are soluble; the further separation of Sb and Sn is effected either by adding Zn alone to the acid solution, when Sb is evolved as SbII3 and Sn is deposited upon the Zn, or by adding Zn and Pt, wffien Sn is deposited on the Zn and Sb on the Pt. The precipitate produced by H2S is filtered off and al- lowed to drain for some time upon the filter in the funnel; it is best to drain it still further by carefully taking the filter out of the funnel, opening it out, and spreading it upon a piece of filter-paper folded several times upon itself; the precipitate is then removed to a small porcelain dish and heated for some time nearly to boiling with strong fuming HC1; the liquid is cooled and filtered: [210. 142 GROUP II B.—DETECTION. The residue will The filtrate may be examined for Sb and Sn by consist chiefly of either I or II below: As2S3, which is I. Place a piece of platinum foil in a porcelain almost insoluble dish and pour the acid filtrate upon it, then in strong HC1. touch the foil with a piece of Zn; II will Dry the washed re- come off witli effervescence, and if either at sidue on the filter at a gentle heat, then mix it with once or after a few minutes a black stain ap- pears upon the platinum, the presence of Sb is indicated.1 three or four times The platinum foil is removed and pieces of as much powdered Zn are placed in the liquid; as soon as the KCy and Na2C03, bubbles of II cease to be given off', Zn still re- and heat the mix- maining undissolved, remove the pieces of ture in a small Zn, rubbing and rinsing any dark deposit bulb-tube, remov- back into the dish; let this deposit settle, de- ing any drops of cant the liquid and heat the solid deposit water inside the Avith strong IIC1 for several minutes in a test- tube by a twisted tube, dilute with a little water, filter if neces- piece of filter- paper ; a black mirror (185): Presence of As. sary, and add to the solution a few drops of IIgCl2 solution; a white or gray precipitate (204, 202) indicates the presence of Sn. II. The acid filtrate is poured into a little hy- Note.—The As2S3 may also be dis- drogen flask (Fig. 34, p. 132), in which II has solved by heating been coming off' briskly for about five min- with a little fuming utes, being produced by the action of a little HN03. The excess strong HC1 upon some pieces of Zn. The H of IIN03 is boiled is lighted at the jet, and the inside of a small off and As detected porcelain dish or crucible lid pressed down as H3As04 by add- upon the flame; a black stain not dissolved by ing Am Cl excess of hot Na20120 solution shows the presence ofSb. AmllO and MgS04; or by addition of The residue in the flask is tested for Sn, as directed in the latter part of I (above). AgN03, and then cautiously neutral- izing with AmHO. 210. (s) The following method of detecting As, Sb, Sn, described by Fresenius, is very delicate and trust- worthy. It depends upon the fact that fusion with Na2C03 and NaN03 converts As2S3 into soluble Na2 HAs04, Sb2S3 into insoluble Na2H2Sb207, and SnS2 into insoluble Sn or Sn02. The precipitated sulphides are dried on the filter and 1 The Sb thus deposited on the Pt may, after rinsing the foil, be dissolved by heating the Pt in a'test-tube with a little very dilute HN03; on cooling, diluting, and passing H2S, an orange-red pre- cipitate will form, confirming the presence of Sb. 211.] GROUP I.—SILVER GROUP. the precipitate1 mixed well on a watch-glass or in an agate-mortar with equal weights of powdered Na.2C03 and VaNO..; this powder is dropped in small quantities at a time into some NaNOs kept melted in a small por- celain crucible over a Bunsen flame. When the powder has all been added the crucible is heated sufficiently to keep the substance melted for a few minutes, and the melted mass is then poured into a small dry porcelain dish; as soon as the substance has cooled cold water is poured upon it in the dish and also upon the residue ad- hering to the inside of the crucible, and the solid sub- stance is allowed to soak for some time, with occasional stirring, crushing it by pressure with a pestle if it does not easily fall to pieces ; it is then filtered : The residue is washed on the filter with a mix- Filtrate: HN03 is ture of equal measures of water and alcohol, added until the to prevent solution of the jSTa2H2Sb207, the solution is just washings are rejected. The precipitate is acid after being then rinsed into a small porcelain dish, using boiled, then as little water as possible; a few drops of AgNO:j solution strong HC1 are added and the dish is heated, is poured in as more HC1 being added, if necessary, to make long as it causes the liquid acid to litmus-paper. Whether the any precipitate, residue has dissolved or not, place in the liquid and very dilute a piece of clean platinum foil, and upon the AmllO is added foil a piece of pure Zn. If a black stein forms little by little.3 after a time upon the platinum, it proves the A brown precipi- presence of Sb.2 When the Zn ceases to be tate, readily dis- acted upon, Sn if present will remain as a solving in excess spongy deposit. This is to be washed by de- of AmllO, shows cantation, dissolved by boiling with HC1 in a the presence of As. test-tube, and HgCl2 added immediately to the solution; a white precipitate (202) shows the presence of Sn. GROUP I.—SILVER GROUP. 211. This group includes Pb, Ag, Hg' (Mercurosura); its members differ from those of all the other analytical 1 If the quantity of the precipitate is very small the part of the paper containing the precipitate is cut up into small pieces and treated as the precipitate. 2 See the footnote on p. 142. 3 Instead of mixing dilute AmHO with the liquid, it may be care- fully poured upon the top of the liquid ; a brown color is then seen at the surface of contact. 144 [212-217. GROUP I.—MERCUROSUM. groups by being precipitated as chlorides by HCl: since, however, PbCl2 is rather soluble in water, Pb is not en- tirely precipitated by HCl, and is usually found also in Group II a as PbS. Lead (Lb).—Reactions already given in Group II A (149-153). Silver (Ag).—Use AgN03 solution. 212. HCl: white precipitate (AgCl), becomes curdy on being shaken or heated: pour off into four tubes; filter one, wash the precipitate and let it stand for some time exposed to sunlight or common daylight, it will become blackish-purple; show with the other portions that AgCl dissolves readily when heated with AmHO or with KCy solution, and is precipitated again from these solutions on adding HNOs in excess; also that it is insoluble in HNOj even on boiling. 213. II2S or Am2S: black precipitate (AgaS), insoluble in Am2S or KIIO, soluble in boiling dilute HNOs. 214. KIIO: brown precipitate (AgHO), insoluble in excess. 215. AmHO: light-colored precipitate, produced only when very dilute AmHO is added drop by drop, easily soluble in excess of AmHO. 216. A mixture of a solid Ag-compound and powdered Na2C03 heated on charcoal, gives white malleable globules or scales of Ag and no incrustation. Mercurosum (Ilg').—Use Hg'2(N03)2.H20 dissolved in dilute HNOa. Reactions (145, 146,147, and 148) given under Mercuricum (Ilg'') yield precisely similar results with Mercurosum (Hg'), and may be repeated with Hg/2(N03)2 solution. In reaction (146), however, it is not necessary to add acid, since the Hg/2(IST03)2 solution is already acid. 217. HCl: a white precipitate (Hg'2Cl2), insoluble in dilute acids unless warmed with both HCl and HNOa, which convert it into soluble Hg"Cl2: becomes black when AmHO is poured upon it, but does not dissolve. 218-221.] GROUP I.—DIFFERENCES. 145 218. AmHO or KIIO: black precipitate, insoluble in excess. 219. It2S: black precipitate (Hg/2S): this precipitate, like IIg//S (144), is insoluble in Am2S, in hot strong HC1, and in hot strong HXOo, but is easily dissolved when heated with a mixture of HNO3 and HC1. 220. Group I.—Table of Differences. Tests. Pb. Ag. Hg'. a. For liquids. 1. Add HC1: White precipitate soluble in boiling water; AmHO neither dissolves the precipitate nor changes its color. White curdy pre- cipitate, insolu- ble in boiling water, easily soluble in warm AmHO, repre- cipitated from this solution by adding HN03 in excess. White precipitate insoluble in boiling water, and insolu- ble in AmHO but blackened by it. 2. Add AmHO: White precipitate, insoluble in ex- cess. Brawn precipitate, readily soluble in excess. Black precipitate, insoluble in ex- cess. 3. Add KaCr04: Bright-yellow pre- cipitate. Chocolate-red pre- cipitate. Scarlet-red precip- itate. b. For solids. 4. Fused with Na2C03 on char- coal in t he inner blowpipe flame: 5. Heated in a bulb-tube mixed with Na2C03: While malleable globules of metal which mark pa- per; yellow in- crustation on the charcoal. White malleable globules or scales which do not mark paper; no incrustation. Ho metallic glob- ules. Gray sublimate, consisting of globules of me- tallic mercury. By the above differences any one member of this group is readily distinguished. 221. (s) The separation and detection of Pb, Ag, and w, when mixed, depend upon : 1st. The solubility of PbCl2 in boiling water, in which AgCl and Hg'2Cl2 are insoluble. 2d. The solubility of AgCl in AmHO, in which Hg'2Cl2 is insoluble. 146 GOLD—PLATINUM. [222-226. The presence of each member, when tints separated, is then confirmed by one of its special tests. 222. (s) A solution which is to be examined for Pb, Ag, Hg', is precipitated by HC1 added in excess, then filtered, and the clear filtrate is tested with more HC1 to ascertain that no further precipitate is produced. The precipitate is then examined by Table I (433). The foregoing reactions only include those for the metals of com- mon occurrence. For information concerning the detection and sep- aration of the rarer metals, which will only be required by a some- what advanced student, the appendix must be consulted. The metals gold and platinum, however, are briefly noticed here on account of their frequent employment for chemical and other purposes. These two metals are dissolved only by a mixture.of IIC1 and I4N03: their most important reactions are given below. Gold (Au).—Use AuC13 solution. Gold solutions are usually bright yellow in color. 223. SnCl2 containing a little SnCl4: purple or dark-brown pre- cipitate (“ Purple of Cassius”), best seen by performing the experi- ment in a white porcelain dish. 224. FeSOi produces either at once, or on heating the solution, a very finely divided precipitate of Au: the liquid usually appears bluish by transmitted light; always copper-red by reflected light: 2AuC13 + 6FeSO, = 2Au + 2Fe2(S04)3 -f- Fe2Cl6. 224 a. II2S03 produces on boiling a similar precipitate of Au: by boiling the liquid for some time in a porcelain dish, the Au settles in small black masses, and the solution loses its color. Platinum (Pt).—Use PtC'l4 solution. 225. AmCl added to a strong solution produces on standing for some time, or more quickly on being stirred, a yellow precipitate (Am2PtCl6): rather soluble in hot water. 226. SnCI2 gives a reddish-brown color in the solution acidified with HC1, owing to the formation of PtCl2 : The method of separating and detecting An and Pt is fully stated in paragraphs 472-474. PtCI4 + SnCl2 = PtCla + SnCl4. REACTIONS FOR ACID-RADICLES.—GROUP I. 147 *** Note.—Before commencing the reactions for acid-radicles the student may with advantage analyze several substances which are lia- ble to contain any one or more of the members of the metallic groups. If only one metal has to be looked for (see column 1, paragraph 539), the directions given in paragraphs (330-369) may be followed, omit- ting those portions which relate to the detection of acid-radicles. If two or more metals may be present (see columns 2, 3, paragraph 539), full directions for ascertaining to which analytical group or groups they belong will be found in the General Table (419); and the group precipitate or precipitates thus obtained may be then examined by the group tables (433-439), with which the student will probably al- ready be familiar. REACTIONS FOR ACID-RADICLES. In the course of analysis acid-radicles are usually de- tected by special tests; they cannot advantageously be precipitated in groups and the members of each group then separated and identified, as is done in the case of metals. Accordingly the arrangement here adopted con- sists in simply placing together in a group such acid-rad- icles as in some respects resemble one another in their reac- tions, and at the end of each group stating upon what differences the detection of its members when occurring together depends. The reactions for acid-radicles are worked through in a manner similar to that employed for the reactions of the metals,—a compound (usually a salt) containing the radicle being employed. At the end of each group the student may with advantage detect one or more of its members, as was done with the metals. GROUP 1.—SULPHATE GROUP. Sulphates are the only commonly occurring salts which give with BaCl2 a precipitate insoluble in boiling HC1. Fluosilicates resemble sulphates in this respect, but differ in so many other reactions that they are considered here- after (299-302) in connection with fluorides and silicates, to which they are more closely related. 148 GROUP I.—SULPHATES. [227, 228. Sulphates (- "S04).—Use Na2SO4.10H2O. 227. BaCt2 or Ba(N03)2: white precipitate (BaSOJ, insoluble when boiled with dilute HC1 or HNOs. Tf BaCla or Ba(NOn)2 be added to a solution containing much strong IIC1 or IINO3, a white precipitate may be produced consisting of BaCh or Ba(NOs)2, which however is readily distinguished from the precipitate of BaSOi by being dissolved when boiled with water. Sr(NOo)2 and Bh(N0d9 give also white precipitates (SrS04 and PbS04). 228. Blowpipe Test.—Solid Na2SO4.10H2O or any solid sulphate, if mixed with solid Na2C03‘ and fused on charcoal in the inner blowpipe flame produced from a spirit flame, yields Na2S: Na2S04 + 4C = Na2S + 4CO. The Na2S is readily detected by detaching the solid mass, after it has cooled, from the charcoal with the point of a knife; placing a portion of it upon a bright silver coin, then moistening it with a drop of water and crushing it by pressure with a knife-blade. After the moistened mass has remained upon the coin for a short time rinse it off, a black stain will then be seen upon the silver where the substance had rested (231). Another portion of the cool mass may be moistened with a drop of HC1, when the fetid smell of H2S will be observed, and a piece of paper moistened with PbA2 solu- tion and held above it, will be blackened (230). This test for a sulphate is reliable only when it is known that sul- phur in no other form is present in the substance to be tested ; it is also necessary that no sulphur should be introduced in the Na2C03, or by the flame. Now coal-gas sometimes contains sufficient sulphur to give the above reaction with pure Na2CC>3, hence it is always ad- visable to employ a spirit rather than a gas-flame. Hydrogen sulphate, or sulphuric acid (H2S04), may be detected by producing black charred stains on paper which lias been dipped into it and dried by heat; it also has a strong acid reaction to litmus, and evolves hydro- 1 Addition of NaaB-tOT is useful in preventing tlie fused mixture from sinking into the charcoal. 229.] GROUP II.—CARBONATES. 149 gen with Zn, properties shown however by some metallic and acid sulphates. GROUP II.—THE CARBONATE GROUP. The five following classes of salts give off characteris- tic gases when acted upon by HC1. *** The systematic tables of differences, such as are given for each group of the metals, are not drawn out for the acid-radicle groups; the student should have no difficulty in constructing such tables for himself, either mentally or on paper, by looking through the reactions. Carbonates (-"C03).—UseNa2C03, or white marble (CaCOs). 229. HCl or HA or almost any other acid, if poured upon some Na2C03 in a test-tube, causes carbon-dioxide gas (C02) to come off with effervescence ; this gas is rec- ognized by its property of turning lime- or baryta-water milky by the production in them of insoluble CaCOs or BaCOs. The test may be tried in several ways: 1. The acid is poured upon the carbonate in a test- tube. A glass rod which has been dipped into some per- fectly clear lime-water1 and has a small drop adhering to its end is then introduced into the test-tube, carefully avoiding touching the liquid or the sides of the tube; the drop will quickly become milky. 2. The acid is poured upon the Na2C03 in a small beaker, and this is immediately covered with a watch- glass placed with its convex face downwards, having a drop of clear lime-water1 adhering to the middle of the face; the drop becomes milky. 3. Since C02 gas is much heavier than air, on adding acid the gas evolved from the carbonate will remain in the test-tube if the tube is held erect and its mouth loosely 1 Baryta-water gives a much more decided result than lime-water. 150 GROUP II.—CARBONATES. f229. closed with the thumb; by gradually sloping the tube the heavy gas is poured into another test-tube containing lime-water1 without allowing any liquid to flow out; on closing this tube with the thumb and well shaking it the lime-water will become milky; or if the inside of the tube has been rinsed with lime-water the sides become white. 4. The C02, if it is given off in considerable quantity, may also be made to pass into some lime-water through a doubly bent tube fitted air-tight by a perforated cork or india-rubber stopper into the tube in which the C02 is generated, as shown in the Fig. 37; or the ap- paratus shown in Fig. 38 may be em- ployed. Of the above methods 1 and 3 are the most simple ; by method 4 the C02 is not found unless given off in somewhat large quantity. The following precautions must be attended to. Since the milki- ness at first caused by CO2 disappears gradually when more CO2 is absorbed, if the lime-water does not at once become milky, it must be constantly watched to avoid the risk of its becoming milky and again clear before being seen. Also if the addition of the first few drops of acid does not cause an effervescence of CO2 more acid should be added, as many carbonates retain the first portions of CO2 by forming acid carbonates : Fig. 37. Fig. 38. A solid substance which is being tested by HC1 for CO2 should be first moistened so as to drive out the air-bubbles entangled in it, which, in coming oflj might make one suspect effervescence of CO2. Hydrogen carbonate, or carbonic acid (II2C03), can only exist in dilute aqueous solution ; addition of lime-water to its solution causes milkiness; but, since other sub- stances in solution behave in a similar way, it is best found by boiling the liquid and passing the steam with the C02 which accompanies it into lime-water; the lime- water becomes milky. NaaCOs + CO2 + II2O = 2NaHCOs. I Baryta-water gives a much more decided result than lime-water. 230-235.] GKOUP II.—SULPHIDES. 151 Sulphides (- "S).—Use FeS for solid, and Am2S for liquid. 230. HCl or IJ,SOi poured upon a small fragment of FeS causes H2S-gas to come otf with effervescence; this gas is detected by its fetid smell, resembling that of rotten eggs, and by its property of blackening PbA2-solution by the formation of PbS. The gas may be made to act upon the PbA2-solution by the methods given for C02 (229), or better by placing a piece of filter-paper moist- ened with PbA2-solution on the end of a glass rod so that one-half of the slip adheres to the glass rod and the other hangs free, and holding the rod in the gas as in the test for C02 (229, 1). This test is made much more delicate if the paper is moistened with a solution prepared by adding KHO to boiling PbA2-solution until the precipitate first formed dissolves; a test-paper thus pre- pared becomes intensely blackened by H2S. 231. Solutions of soluble sulphides, if dropped upon a bright silver coin, produce a black stain (Ag2S); this may be removed by rubbing the coin with moist lime. 232. Insoluble sulphides, which give off II2S with HCl (e. g., FeS) produce a black stain when placed on a silver coin and moistened with a drop of HCl. 233. P5A2-solution gives with soluble sulphides a black precipitate (PbS). The solution produced by add- ing KIIO in excess to PbA2-solution is more delicate than PbA2 alone. 234. Many sulphides (e.g., FeS2, “Iron Pyrites”), and also free S, if strongly heated in a tube open at both ends, and held obliquely in the flame, or in the tube shown in Fig. 35 (p. 132), give off S02-gas, recognized by its pungent smell and by turning paper moistened with K2Cr207 green. 235. Reaction (306), given under HCy, may be em- ployed also as a very delicate test for soluble sulphides. Test (228) for a sulphate, also answers for a sulphide. Hydrogen sulphide, or hydrosulphuric acid (H2S), in aqueous solution, is easily recognized by (231) or (233), and, unless the solution is very dilute, also by its smell, 152 GROUP II.—THEIOSULPHATES. )236-239. and by suspending lead-paper over the liquid: H2S-gas is detected by (230). Sulphites (-"S03).—Use Na2S03. 236. HCl, or H2SOv poured upon Na2SO:! and warmed, gives off SO,2-gas, known by its pungent smell and by turning K2Cr207 solution green; the K2Cr2Or solution may be exposed to the gas by the methods described under (229), preferably by introducing a glass rod with a drop hanging upon its end into the gas; or by moisten- ing a small strip of filter-paper with the K2Cr207 solu- tion and making it adhere by one-half of its length to the rod (230), the other half hanging freely, and intro- ducing it into the gas as in (229, 1). 237. BaClp. white precipitate (BaS03): entirely sol- uble in HCl, unless some Na2S04 is present, when BaS04 remains undissolved; on adding Cl- or Br-water to the HCl solution, BaS04 is formed and precipitated: BaSOs + 2HC1 = BaCl2 + H2S03. BaCl2 + H2SOs + H20 + 2C1 = BaS04 + 4HC1. 238. Na2S03, added to a mixture of HCl and Zn, which is giving off pure H, immediately causes an evo- lution of H2S with the II; the H2S is detected by it? smell, or by blackening a piece of filter-paper moistened with solution of PbO in excess of KHO (230). Hydrogen sulphite, or sulphurous acid (H2S03), can be found in aqueous solution by adding a drop of K2CraO, solution, which will at once become green; S02-gas is found as directed under (236). Theiosulpiiates1 ( -"S,03).—Use Na2S,03.5H20. 239. HCl or II.,SOi causes no immediate change in the cold; but the liquid on standing, or on being warmed, deposits a precipitate of yellow S, and S02 is given off; 1 Formerly known as hyposulphites. 210-242.] GROUP II.—HYPOCHLORITES. 153 the S02 is recognized by its pungent smell and by chang- ing the color of K2Cr207 solution (236). 240. Fe,Ck ■ gives a reddish-violet color, which vanishes after a short time, or immediately when heated, the Fe2Cl6 solution at the same time loses its yellow color, owing to the change of Fe2Cl6 into FeCl2. 240 a. AgN0.3: a white precipitate (Ag2S203), becom- ing black after standing for a short time, or immediately upon being heated, owing to the formation of Ag2S: Ag2S203 + H20 = Ag2S + H2S04. The above precipitate (Ag2S203) dissolves very readily in excess of the Na2S203 solution, lienee it is most easily obtained by dropping the latter into some AgNOa solu- tion. Hydrogen theiosidphate, or theiosulphuric acid (H2S2Os), is extremely unstable, rapidly separating into S + H2S03. Hypochlorites (-'CIO).—Use NaClO.NaCl, or Na2Cl20 solution. Hypochlorites give off a faint smell of Cl in the air if solid or in strong solution. 241. HCl, or Il.JSOi, or even H20 in the cold, or when gently warmed, if much water is present, sets free Cl-gas, which may be recognized by its smell, its yellowish color, and by bleaching a piece of moistened litmus-paper, which is held for a short time in the tube without touching the liquid or the sides of the tube. A piece of litmus-paper shaken up with the solution, without addition of acid, is also bleached, the C02 in the air probably liberating the Cl; on addition of a drop of any acid the bleaching is very rapid: Xa2Cl20 + 2HC1 = 2C1 + 2NaCl + H20. 242. Pb(N03)2, or PbA2 solution, added in large quan- tity gives a white precipitate, becoming reddish, and then dark brown (Pb02) when boiled for a short time. MnCl2 likewise gives a dark-brown precipitate on heating. 154 GROUP II.—nitrites. [243-246. Hydrogen hypochlorite, or hypochlorous acid (HCIO), is a yellow liquid with sweetish smell, which if strong is very unstable; it bleaches litmus, and evolves Cl when warmed with HC1. Cl2()-gas is of a deep yellowish- green color, and has an irritating smell; it dissolves easily in water to form the above acid. Nitrites (-'NOa).—Use KN02. 243. Warmed with dilute II2S04, reddish-brown “nitrous fumes,” with a characteristic smell, are given off; they are best seen by looking down the tube at some white object. 244. If cold FeS04 solution is added to KN02 solu- tion it becomes brown ; on adding cold dilute H2S04the color becomes much more intense: it is produced by the combination of NO with FeS04; this color is destroyed by boiling, red fumes being given off (243). 245. If solution of KI and several drops of starch solution (par. 526, remark 35) are added to KN02 solu- tion, and the liquid is then made acid with HA, an in- tense blue color will be produced, owing to the combina- tion of iodine, set free by the HN02, with the starch; the experiment is best done in a white porcelain dish, the liquid, which often appears black at first, being diluted, if necessary, till its blue color becomes visible. This is a most delicate test, and is rather characteristic if the color is not produced till the HA is added. Hydrogen nitrite, or nitrous acid (HN02) is extremely unstable, decomposing into HN()3, NO, and HzO. *** The student will have no difficulty in detecting any one of the above acid-radicles occurring singly in a liquid or solid : warming with HC1 will usually indicate which of them is present, and its presence may then be confirmed by a second test. 246. (s) Most of the acids formed by the salts of Group II on addition of HC1, react upon one another; e.g., IICIO destroys HN02, H2S, and II2SOs; and H2S destroys HjjSOj. The analyst may often by skilful use of the 247.] 155 GROUP III.—NITRATES. above reactions detect these acids when mixed, but their detection in certain mixtures is a problem only soluble by careful consideration, and not unfrequently insoluble. S02, if evolved, may be detected by K2Cr207 paper; H2S by PbA2 paper ; Cl by bleaching moist litmus- paper ; N203 by its brown color. But C02 can only be detected in presence of much S02 by passing the gases through hot K20r2O7 solution, which absorbs S02,C02 passing on and being detected by lime-water. GROUP III.—NITRATE GROUP. The two classes of salts which follow resemble one another in many respects, more particularly in the fact that no member of them is insoluble in water; hence no method of precipitating them is known. Nitrates (-'N03).—Use KNOs. 247. Add to some KN03 solution contained in a rather broad test-tube about an equal bulk of strong H2S04; cool the liquid by letting a stream of cold water run upon the tube from the tap; then hold the tube in a slanting posi- tion, and pour some strong cold FeS04 solution in a gentle stream down the inside of the tube. If this solution is poured in with proper care it will form a distinct layer resting on the surface of the acid liquid, and at the sur- face of contact of the two layers a dark-brown film or ring will appear, sometimes extending upwards towards the surface of the liquid. The color is most easily seen by holding a piece of filter-paper between the tube and a bright flame or window, and looking through the tube at the light. A mere yellow color is often produced in the absence of a nitrate and may be disregarded. The test is made more delicate by letting the tube stand in a small beaker of cold water for a few minutes, since heat prevents or destroys the brown color. If much nitric acid is present, on mixing the acid and FeS04 solution by shaking, the brown color extends upwards, 156 GROUP III.—ACID-RADICLES. [248-251 a. until by the heat evolved by dilution of the acid the NO is expelled, forming brown fumes in the test-tube, and the liquid loses its dark-brown color (244). 248. Place some small scraps of Cu in some KNOs solution, and add strong II2S04; brown nitrous fumes appear at once or on warming the tube; they are best seen, if small in quantity, by looking down the tube at a white surface. The liquid at the same time becomes blue from the presence in it of Cu(N03)2: 8HN03 + 3Cu = 2NO + 3CuN2Oe + 4H20. NO is itself a colorless gas, but yields on mixture with air N2Os and N2G4 which are reddish-brown. 249. If some cold dilute indigo solution be poured into cold KNOs solution until it is decidedly blue, and then H2SOg be added, the blue color remains unchanged (dif- ference from chlorates). 250. If any solid nitrate be fused for some time at a red heat with fusion mixture on platinum foil, oxygen gas is given off slowly with effervescence1 and KNOz is formed; if the foil, after cooling, be boiled in water, a portion of the solution may be proved to contain KNOz by the test in paragraph (245); another portion, if acidi- fied with HNOj, will be found to give no precipitate with AgN03 (difference from chlorates). A solution of a nitrate may also be reduced to nitrate by nascent H. Add to a little KNOs solution some dilute II2S04 and starch paste with KI; no color will be pro- duced, but on dropping in a fragment of Zn a deep-blue color is seen (245). 251. Solid KNOs fused on charcoal in the blowpipe flame “ deflagrates,” that is to say, the surface of the charcoal burns rapidly like gunpowder. 251 a. Many metallic nitrates [e. g., Pb(N03j2] when heated in a glass tube closed at one end, evolve reddish-brown fumes with a characteristic smell (N204) and oxygen—PbN206 = N204 + 0+ PbO. 1 If this experiment is performed in a small hard-glass tube as described in (254), the oxygen can rarely be detected, since it is evolved very slowly ; lienee the student may perform the ignition on platinum foil and neglect the test for oxygen. 252-254. 157 GROUP III.—CHLORATES. The fumes are recognized by their color and smell, the O by its in- flaming a glowing splinter of wood. Hydrogen nitrate, or nitric acid (HN03), lias a strong acid reaction; it gives with FeS04 solution a brown ring (247), and with Cu brown fumes (248) without addition of H2S04. Evaporated with quill-clippings, it stains them bright yellow. Chlorates (-'C103).—Use KC103. 252. If to a cold solution of XC103 some cold dilute indigo solution be added drop by drop till the liquid is colored faintly but distinctly blue, then some H2S03 or NaIIS03 be poured in and the mixture shaken, the blue color of the indigo is at once destroyed (difference from nitrates). 253. Strong poured upon a little solid KC103 becomes orange-red in color, and evolves when shaken a bright-yellow gas (CIA): 3KCios + h2so4 = ci2o4 + kcio4 + k2so4 + h a This gas has a smell somewhat resembling that of chlorine; it explodes readily when gently heated, hence on warm- ing the mixture in the tube crackling sounds or small explosions will be produced. This experiment may be dangerous, unless the KC103 is used in very small quan- tity, and heated gently with the mouth of the test-tube turned away from the operator. 254. AgN03 produces no precipitate with KCIO, solu- tion if it is free from KC1. But if some solid KCIO31 be heated in a test-tube, or better in a small ignition-tube (10), after melting it begins to give oil' oxygen with effervescence; this gas may be recognized by placing in the tube a slip of wood with a spark at its end, which is easily obtained by kindling a match and suddenly blow- ing out the flame,—the spark is caused to burst into a flame. If the tube is then allowed to cool and the resi- 1 If the chlorate used for this test does not yield a soluble chloride, fusion mixture must be mixed with it before heating, in order to ob- tain a soluble chloride in the residue. 158 GROUP IV.—ACID-RADICLES. [255-257. due dissolved by boiling with some water, a portion of the solution will be found to give no reaction for HN02 (245); but another portion will give a white precipitate (AgCl) with AgNOa, which does not dissolve in HNO„ even on boiling, but is easily soluble in AmHO (differ- ence from a nitrate); this precipitate is caused by KC1: KC10S = KC1 + 03. 255. Blowpipe Test.—KC103 if heated on charcoal in the blowpipe flame, causes the charcoal to “ deflagrate.” Hydrogen chlorate, or chloric acid (HC103), is a color- less, odorless liquid, which first reddens and then bleaches litmus-paper; on being kept for some time it changes into O, Cl, IIC104 and II20; the same change occurs rapidly when it is heated. 256. As will be seen, there is little difficulty in dis- tinguishing a nitrate from a chlorate. W hen present together they more or less interfere with one another’s reactions ; but they may be detected, in the absence of chlorides and nitrites, by heating strongly for a short time and testing the residue for nitrite and chloride (250 and 254). GROUP IV.—CHLORIDE GROUP. Chlorides, bromides, and iodides closely resemble one another; they are all precipitated by AgN03 from solu- tions to which HNOs has been added in excess; in this respect they differ from all salts except cyanides, ferro- cyanides, and ferricyanides, and these are easily distin- guished by other means. Chlorides (-'Cl).—Use NaCl. 257. AgN03 added to a little NaCl dissolved in water, gives a pure white precipitate (AgCl), which collects into curdy masses when heated or shaken, and quickly turns violet in sunlight or more slowly in daylight. Decant the water; to one portion of the precipitate add HN03 and warm, it does not dissolve; to one other portion add AmHO, it readily dissolves. Decant the liquid from 258-260. CHLORIDES. 159 a portion of the precipitate after shaking and letting the precipitate settle, and warm the precipitate with a little strong H2S04, the acid remains colorless and no colored vapor is given off. 258. Solid NaCl warmed with strong H2S04 gives off colorless HCl-gas, which is recognized by fuming in the air, reddening moistened blue litmus-paper, and making a drop of AgNOg solution on the end of a glass rod milky. 259. If solid NaCl be powdered and mixed with finely powdered Mn02, then strong II2S04 added, and the mix- ture warmed, chlorine gas comes off*: 2NaCl + MnO, -f 3II2S04 = 2C1 + MnS04 + 2NaHS04+2H2Q. This gas is recognized by its property of bleaching a piece of moist blue litmus-paper, introduced into the tube on a glass rod. The most delicate way of testing is to warm the mixture in a small beaker covered with a watch- glass which bears on its under surface a piece of moist litmus-paper, and let the apparatus stand for some time. Moist starch is not colored when held in the air in the tube. Many samples of commercial Mn02 evolve Cl when heated with H2S()4; hence the MnOa, unless specially prepared by precipitation, must be carefully tested before using it for tins reaction ; or the Mn02 and II2S04 may be first boiled together as long as any bleach- ing action is produced when moist litmus is held in the tube, then the substance to be tested is added and Cl again tested for whilst heating the mixture. 260. If an intimate mixture of solid INfaCl with three or four times as much K2Cr2Or in fine powder be made by rubbing the two substances together in a mortar, and this mixture be then poured into the tubulated flask shown in Fig. 38/ page 150, and mixed with strong H2S04 by pouring in the acid and shaking it round 1 The test-tube fitted as shown in Fig. 37 is much less suitable. 160 ACID-RADICLES.—GROUP IV. ;260. in the flask, on warming the flask reddish-brown vapor (CrO2012) will be evolved: 4NaCl + K2Cr207 + 6H2SO, = 2Cr02Cl2 + 4NaIIS04 + 2KHS04 + 3H20. If the neck of the flask be closed by an india-rubber or a glass stopper, and the delivery-tube be made to dip into water in a test-tube, the vapor on passing into the water will impart to it a reddish-yellow color owing to the formation of H2Cr04: Cr02Cl„ + 2H20 = II2Cr04 + 2HC1. On adding to this yellow liquid excess of AmHO, the color becomes pale yellow; on now adding excess of IIA the original reddish-yellow color is reproduced, and in this liquid the presence of'H2Cr04, and therefore indi- rectly that of HC1, may be shown by the formation of a yellow precipitate on addition of PbA2 solution. Since by this method the detection of a chloride depends on the formation of H2Cr04 in the liquid in the test-tube from the vapor of Cr02Cl2, great care must he taken that no H2Cr04 is introduced into that liquid from any other source. Now, since the mixture in the flask contains a chromate, the greatest precaution must he taken that none of it is allowed to get into the bent delivery-tube, and thence into the test-tube. In transferring the powder to the flask, it must he poured down the side of the perfectly dry neck opposite to that at which the delivery-tube enters; also, whilst heating the mixture it must not he allowed to rise or splash into the neck of the flask. If these precautions are not taken, and H2Cr04 as such is introduced into the water in the test-tube, the test is worthless as an indication of the presence of a chloride. Care must also he taken that the liquid is not sucked hack from the test-tube into the flask. This is prevented hv raising the delivery- tube out of the water in the test-tube as soon as the heating is stopped. Hydrogen chloride, or hydrochloric acid(IIC1), is a color- less gas which fumes in the air, and dissolves very readily in water; both the gas and its solution render AgNOs solution, which has been acidified with UNO.,, milky. Heated with Mn02 the liquid acid evolves chlorine gas. 261-2G3.] 161 BROMIDES. Bromides (- 'Br).—Use KBr. 261. AgN03 added to a little KBr solution gives a yellowish-white precipitate (AgBr), which is easily coagu- lated by heating or shaking the liquid; it is insoluble in IIXO,, but rather soluble in AmIIO, thus somewhat re- sembling the AgCl precipitate, from which it is distin- guished by its color. By shaking well, allowing to settle, decanting the liquid, and heating the precipitate with strong H2S04, no violet vapor is evolved, the precipitate thus differing from Agl. 262. Solid KBr when heated with strong H2S04 gives off reddish-brown vapor of Br,1 which somewhat resembles Cl in smell, but differs by its color and by turning moist starch orange-red, the color disappearing by heat. This last test is best performed by dipping the wetted end of a glass rod into some powdered starch, and then moistening the adhering starch by breathing upon it several times. If Mn02 be mixed with KBr powder before adding H2S04, the Br is evolved in greater quantity and more readily. 263. Cl-waier, added carefully drop by drop to a little KBr solution whilst shaking it, liberates Br, which gives the solution an orange-red color; excess of Cl-water must be carefully avoided, as it destroys the color: KBr + Cl = Br + KC1. On warming a part of this solution in a dish, brown fumes are given off which color orange-red some starch held in the vapor as described in the preceding reaction. If CS2 be added to another portion and the liquids are then well shaken together, the Br is dissolved by the CS2, and on standing the reddish-brown CS2 solution sinks to the bottom; on adding a little KHO solution and shaking well, the color of the Br again disappears from the CS2, owing to the formation of the colorless salts KBr and KBrOs: 6Br + 6KHO = 5KBr + KBr03 + 3H20. 1 KBr solution does not so easily give off Br vapor, but the liquid becomes colored reddish-brown. 162 ACID-RADICLES—GROUP IV. [264-266. 264. A mixture of solid KBr and K2Cr207 heated with strong II2S04 as in (260), gives off reddish-brown vapor of Br: GKBr + K2Cr A + 11 H*S04 = 3Br2 + Cr2(S04)3 + 8KHSO, + 7H20. This vapor, if received in a little water, imparts its color to the water; if the liquid is shaken up with CS2, however, the Br is dissolved away from the water by the CS2, which forms a brown layer at the bottom of the water; by shaking well, after addition of AmHO or KHO, the color of the solution is destroyed (difference- from a chloride). Hydrogen bromide, or hydrobromic acid (IIBr), is a gas resembling IIC1; its solution differs by evolving Br when heated with Mn02. Iodides (-'I).—Use KI. 265. AgNOz added to a little KI solution, gives a yellow precipitate (Agl), which is easily coagulated by heating or shaking the liquid; it is insoluble in HN03, and very slightly soluble in AmHO. This precipitate differs from AgCl and AgBr by its color and its slight solubility in AmHO, but more par- ticularly by its behavior when heated with strong H2S04. If the precipitate, coagulated by heating or shaking the liquid, is allowed to settle and the liquid decanted, then strong H2S04 poured in and heated with the precipitate, the acid becomes colored red, and violet vapors of iodine are seen especially on looking down the tube; the color is particularly distinct after the tube has been allowed to cool for a short time. This vapor of iodine may be de- tected when almost invisible by holding in the air of the tube a glass rod previously dipped into freshly made starch solution, which will become colored blue. 266. CuSOi mixed with II2S03 or FeSO,} solution, which reduces it to Cu2S04, gives a white precipitate 267, 268.] IODIDES. (Cu2I2); warming, or the addition of a single drop of Am HO, causes this precipitate to form more quickly: 2CuS04 + H2S03 + H,0 = Cu2S04 + 2H2S04 2KI + Cu2S04 = Cu2I2 + K2S04. If this precipitate is allowed to settle and the water poured off, or if it be filtered, and the precipitate is then warmed with strong H2S04, the liquid becomes violet and gives off violet fumes of I. Solutions of chlorides and bromides are not precipi- tated thus by Cu.2S04. 267. Solid KI if warmed with strong H2S04, gives off violet vapor of I,1 which, if in large quantity, cools on the sides of the tube to black solid: this vapor colors starch solution blue, as may be proved by dipping a rod moistened with freshly made starch solution2 into it, or by pouring the heavy fumes out into a white porcelain dish whose inside has been wetted with starch solution, or by dipping into the vapor a slip of filter-paper moist- ened with starch solution. The I is more readily and plentifully evolved, if some Mn02 be mixed with the KI before adding H2S04. 268. Cl-water added drop by drop, carefully avoiding excess which would form colorless IC13, sets free I, which dissolves in the water giving a brown liquid ; divide this into three parts: 1. Heat one part; violet vapor of I is given off and is best seen by lookingdown the mouth of the tube at a white surface. The color is most distinctly seen if, before heat- ing, some strong II2S04 is added to the liquid. If a glass rod is dipped into starch solution and held in the vapor, the starch becomes blue. 2. To another portion starch solution is added, which gives an intense blue color often appearing black unless much starch is added and the liquid largely diluted; on 1 KI solution does not so easily give ofi’ purple vapor, but the liquid becomes reddish-brown or red. 2 The starch solution must always be freshly made (par 526, re- mark 35), as after being kept it loses the property of yielding a blue color with iodine. 164 [269-271. ACID-RADICLES. GROUP IV. warming the solution the color disappears, but often re- appears when the liquid is cooled. To insure the dis- appearance of the color on being heated, the solution must be diluted and the starch added in excess. 3. To the third portion add a drop of CS2 and shake well; the CS2 dissolves the I, and gradually settles to the bottom having a beautiful violet color. Add a little KHO solution and shake well, the violet color of the CS2 will disappear owing to the formation of the colorless salts KI and KI03. The last two methods of testing for the free I are by far the most delicate known; but Cl-water is by no means the best reagent for setting I free from its compounds, because if added in excess it com- bines with the I and prevents its detection. The reagents described in (269) are much better suited for liberating I from its compounds. 269. If a little KN02 is added to the KI solution, and then any dilute acid (IIA, IIC1 or poured in, IIN02 is produced and liberates I. A solution of N204 in dilute 1I2SC)4, made by heating Pb(X03)2 strongly and passing the red fumes into dilute II2S04 (528, 5), also sets free I from KI. The I thus liberated in solution may be identified by the three methods described in (268), of which the third is the most delicate. These two reagents for liberating I do not hinder its detection if they are added in excess, and they are also useful because they do not liberate Br from its com- pounds. 270. JIgCl2 gives with a solution of iodide a scarlet precipitate, with a solution of bromide or chloride it gives no precipitate; PbA2 gives with iodide solution a bright-yellow precipitate, with bromide or chloride a white precipitate. Hydrogen iodide, or hydriodio acid (III), is a gas re- sembling HC1 and Hbr ; its solution differs by evolving I when heated with Mn02. 271. A chloride, bromide, or iodide is easily detected by the foregoing tests. The reactions given in para- graphs (259) and (260) are perhaps the most character- istic tests for a chloride, those described in (262), (263) 272, 273.] ACID-RADICLES.—GROUP IV. 165 and (264) for a bromide, whilst an iodide is detected with the greatest ease and certainty by reaction (269). The color of the precipitate produced by AgNOa in the solution made acid with HN03, and its behavior with Am HO, though less reliable than the above tests, serve to indicate which of these acid-radicles is present, AgCl being pure white and very easily soluble in AmHO, AgBr being pale yellow and not readily soluble in AmHO, whilst Agl is primrose-yellow and almost insoluble in AmHO. See also the distinctive action of hot strong H2SO, on Agl, described in paragraph (265). 272. (s) The detection of a chloride, bromide, and iodide when occurring together. The method of examination varies according to whether an iodide is present or absent; since a chloride cannot be detected in the presence of an iodide, the latter, if present, must be separated before proceeding to examine for the chloride (273). In paragraph (274) is given a process for detecting an iodide and bromide; it is of value only when a chloride has not to be tested for. 273. (s) To a small portion of the solution, made just acid if necessary by addition of dilute II2S04, add a little cold freshly prepared starch solution and then strong HNOs, or either of the reagents mentioned in (269), drop by drop; a dark-blue coloration1 shows the presence of an iodide. The remainder of the solution is examined for a chloride and bromide by the directions given below under A or B according as an iodide is present or ab- sent : A. An Iodide is Present.—Add to the solution a rea- gent consisting of a mixture of CuS04 solution with half its measure of strong H2S03 solution, and warm gently for a short time ; Cu2I2 will be precipitated (266). In order to be sure that the iodide is entirely precipi- tated, a small quantity of the liquid must be filtered and warmed with a little more of the above reagent; if any further precipitate is caused, the filtered portion is returned 1 Black, unless the starch solution has been added in sufficient quantity to the dilute solution. [273. 166 ACID-RADICLES. GROUP IV. to the unfiltercd liquid, more of the reagent is added to the whole, which is then warmed for a time and again tested as above, to see if the precipitation is complete; these trials are repeated until a small portion, on filtra- tion, gives no further precipitate when warmed with more of the reagent. The whole is then filtered till clear, pure NaHO is added in excess to the filtrate and the liquid boiled. The precipitate thus produced is filtered off, and the filtrate, now free from iodide, is tested for bromide and chloride by the directions given under B. B. No Iodide is Present.—Make the solution alkaline, if not already so, by addition of pure NaHO, then evap- orate it to dryness in a porcelain dish, scrape the residue off the sides of the dish and mix it with three or four times as much powdered K2Cr207 by rubbing the two substances together in the dish with a pestle (260). Trans- fer this mixture into the small tubulated flask (Fig. 38, p. 150) by pouring it down the perfectly dry neck on the side opposite to that at which the tube enters, and taking the greatest care to let none of the powder enter the delivery-tube. Then pour into the flask strong H2S04 sufficient to cover the powder to the depth of about a quarter of an inch, at once close the neck with an india- rubber or glass stopper, and dip the end of the delivery- tube into water contained in a test-tube. Mix the con- tents of the flask by cautious shaking, and warm the mixture gently, carefully guarding against allowing any of the mixture to get into the delivery-tube and thence into the water in the test-tube.1 As soon as no more reddish-brown vapor is visible in the flask or its deliv- ery-tube, discontinue the heating, and immediately with- draw the test-tube. If no colored vapor has been evolved and the water in the test-tube is colorless, chloride and bromide are absent. If the water is colored, pour into it CS2 sufficient to forma layer at the bottom of the tube about as large as a small nut; close the mouth of the tube with the thumb, and shake vigorously; if the CS2 on 1 See the precautions in the note at the end of par. 260. 273a-275. GROUP V.—PHOSPHATES. 167 settling shows a brown color, the presence of Br from a bromide is shown. Separate the water from the CS2 by pouring it through a wetted til ter, add to the filtrate AmHO in excess, then HA in excess, and PbA2 solution. A yellow precipi- tate indicates the presence of a chromate, which proves indirectly that a chloride was present. 273 a. (s) The above method will also serve for the examination for chloride, bromide, and iodide in the AgNOs precipitate. The precipitate is dried, and fused for about ten minutes in a porcelain crucible with three or four times as much fusion mixture; the cool mass is boiled with H20 for some time and filtered, the filtrate being examined as directed above (273). 274. (s) If only an iodide and a bromide have to be tested for, the following method may be employed. Pour into the solution CS2 sufficient to form a large drop at the bottom; add Cl-water drop by drop, shaking thor- oughly after each addition: an iodide, if present, shows first by its liberated iodine coloring the CS2 purple, but on continuing the addition of Cl-water this color is de- stroyed ; a bromide is then detected by a brown coloration of the CS2, which, however, is also destroyed if too much Cl-water is added. GROUP V.—PHOSPHATE GROUP. Phosphates and arsenates resemble one another closely in many reactions; the points of difference they present from one another and from other salts will, however, if carefully attended to, render their detection a simple matter. Phosphates (-'"P04).—Use Na2HP04.12II20 solu- tion. 275. Mc/80i solution to which some AmCl lias been added and then a little AraHO, gives with Na2HP04 a white crystalline precipitate (MgAmPO*): this precipi- 168 ACID-RADICLES.—GROUP V. [276-278tf. tate is almost insoluble in AmHO, but easily soluble in acids. If very little Na2HP04 is present, the precipitate appears only on warming, stirring, or shaking well, and letting stand. 276. Fe2Cl6 dropped in after a little HA. and some NaA solution gives, especially when warmed, a yellowish- white precipitate of Fe///P04. 277. AmHMoOi dissolved in IPSTO, gives a yellow precipitate if a drop of Na2HP04 solution is added to it; the formation of the precipitate is hastened by gentle warming, stirring, or shaking, but it often appears only after a time. Pour off a part of the liquid and show that the precipitate is soluble in KHO, NallO, and AmHO; and insoluble in acids, especially in HNOs. This reaction (277), if properly performed, is the most delicate test known for a phosphate, but careful attention must be paid to the fol- lowing precautions: The AmtlMoO* solution must be prepared ac- cording to the directions given in (52G, remark 40). The solution to be tested must not be alkaline to test-paper; it is best made dis- tinctly acid with HNO3; it is then to be added in small quantity only to some of the AmHMo04 solution in a test-tube, more of the liquid being added if after gently warming and stirring or shaking well no yellow precipitate forms after a few minutes. This last precaution must be particularly observed, as an excess of phosphate altogether prevents the formation of the precipitate: show that this is the case by pouring into some Na2HP04 solution, contained in a test-tube and made acid with HNO3, a few drops of AmHMo04 solution ; it will be found that no precipitate will form even on heating and shaking the liquid, since the phosphate is present in large quantity compared with the AmHMoOi; but on adding a few drops of this liquid to some fresh AmIIMo04 solution the precipitate appears. It must also lie re- membered that HC1 retards or prevents the formation of this precip- itate, and therefore an HN03 solution should always be used when possible. 278. AgNOs: yellow precipitate (Ag3P04): pour off a portion, and show that the precipitate is soluble in AmHO and in IIN03. 278 a. A very delicate test for the presence of P in the form of a phosphate or otherwise, consists in strongly heating the dry solid sub- stance with a small piece of Na in a little tube of hard glass closed at one end: on breaking the tube and breathing upon the powdered substance a smell of onions, due to HSP, is perceived. A phosphate made into a paste with strong H2S04 and heated strongly at the tip of the inner blowpipe flame, gives a bluish-green color to the flame. 279-281.] ARSENATES. 169 Hydrogen phosphate, or phosphoric acid (H,P04), is a colorless crystalline substance; its solution is strongly acid, but does not char paper and organic substances (difference from II2S04). It yields reactions (275 and 277). Arsenates (-r//As04).—Use Na2HAs04.12H20 solu- tion. 279. The precipitates formed in reactions (275, 27G, 277) for phos- phates are precisely similar in appearance and general properties to those formed with the same reagents by arsenates. The precipitate, however, which is formed by an arsenate with AgN03 differs from that given by a phosphate by being broivn in color; also AmliMoOt gives with an arsenate a precipitate only on boiling. 280. The following differences serve to detect and separate a phosphate and an arsenate: 1. The fact that an arsenate yields a precipitate with AmHMoOj only when the liquid is boiled, whereas the corresponding precipitate with a phosphate is produced by gentle heat. 2. An arsenate solution, if boiled with strong HC1, gives when II2S is passed into the hot liquid, first a white precipitate of S, then yellow As2S3; a phosphate solution, under the same circumstances, gives no precipitate. 3. In a perfectly neutral solution, AgNOs gives with an arsenate solution a brown precipitate, with a phosphate a canary-yelloio precipitate. Hence, if occurring separately, a phosphate and ar- senate may be distinguished by one or more of these differences. 281. The simplest method of ascertaining which of these two acid-radicles is present is to throw the precip- itate yielded by AmCl, AmHO, and MgS04 upon a filter, wash it with a little cold water, and drop AgN03 upon it; if the precipitate consisted of MgAmAs04 it will become brown, if of MgAmP04 canary-yellow (280, 3). Or the precipitate produced by AmCl, AmHO, and MgSO} may be examined for arsenate by dissolving a part of it in dilute HN03, adding AgNOs as long as it 170 ;282, 283. UNGROUPED ACID-RADICLES. causes any white precipitate, and then very dilute AmllO gradually drop by drop; if arsenate is present a broivn precipitate will form just before the liquid becomes alka- line to test-paper; phosphate gives a yellow precipitate. Instead of mixing the dilute AmllO it may be poured upon the top of the acid liquid, when the color appears at the surface of contact. 282. If both arsenate and phosphate have to be tested for, AraCl, AmHC), and MgS04are added as long as any further precipitate is caused; the precipitate is filtered off1 and dissolved in a little boiling strong HC1, II2S is passed for several minutes into this hot HC1 solution, when the presence of arsenate is shown as above (280, 2); the precipitate, if any has formed, is filtered off and H2S passed into the boiling filtrate; if any further precipitate is produced, the gas must be passed again until it no longer causes a precipitate; the clear filtrate from this precipitate is then evaporated just to dryness, dissolved in a little dilute HNOs, and tested for phosphate by add- ing a few drops of it to AmHMoO, solution and gently warming. Arsenite, if present, may be detected by H2S in the filtrate from the Mg precipitate, acidified with HC1; yellow As2S3 is precipitated at once. UNGROUPED ACID-RADICLES. The salts of the following acid-radicles present in their reactions no marked resemblances to one another or to other salts, and are usually detected by special tests. Borates (-'BO,, or -'"BO.,).—-Use Na,B4O7.10H2O. 283. If some powdered Na2B407 be stirred with a little dilute HC1 on a watch-glass and a strip of turmeric-paper 1 A small portion of the precipitate may be filtered off upon another filter and tested at once for arsenate by dropping upon it AgN03 solution. If the precipitate turns brown, arsenate is present and must be separated in the other part of the Mg precipitate before test- ing for phosphate; if the precipitate turns yellow, phosphate alone is present. 284, 285.] BORATES—CHROMATES. 171 be half immersed in the liquid, then dried on a watch- glass in the steam-oven or on a water-bath,1 the part which was moistened appears reddish-brown, and becomes bluish-black when moistened with AmHO. This is a most useful test for a borate. 284. If some methylated spirit be poured upon a little solid Na2B407 in a test-tube or porcelain dish, some strong H2S04 added, and the mixture be heated and set fire to, the spirit burns with a green-edged flame, seen best by blowing the flame out after it has burnt for a time and then relighting it. This test is not quite a characteristic, since some chlorides yield a somewhat similar green flame. 285. A mixture of CaF2, Na2B4()72 and KHS04, if finely powdered, moistened, and heated on a loop of platinum wire in the inner blowpipe flame, colors the outer flame momentarily green after being heated, for a short time. This test is not always decisive, since many phosphates and Cu-salts give the same coloration, and it is besides liable to be masked by the flame colorations of other sub- stances. Hydrogen borate, or boydc acid (HB02), is a white porous mass; when combined with 2H20 it forms a crys- talline scaly hydrate; when strongly heated these yield a fusible glass consisting of B„03. The solution of the acid reddens litmus-paper and colors turmeric reddish- brown, especially on drying the paper. The acid is soluble both in 1I20 and in alcohol; on evaporating these solu- tions, the acid passes off’ with the vapor of the liquid. Reactions (283, 2.84, 285) will serve to detect boric acid. Chromates (-"CrOJ.—Use K2Cr207 (or K2Cr04. CrOs) solution. All chromates are more or less yellow or red in color. The yel- 1 The paper inay also be dried over a small flame, if it is not heated above steam-heat (100° C.). 2 Boric acid is better, since the Na flame coloration tends to con- ceal the green coloration caused by BF3. 172 UNGROUPED ACID-RADICLES. '286-288. low solution of an alkaline chromate becomes orange-red on addition of an acid, owing to formation of a dichromate. 286. Various substances, which readily combine with oxygen, deoxidize acid K2Cr207 solution to a solution of a chromic salt, the color of the solution at the same time changing from orange-red to a bright green. To show this, add HC1 or H2S04 to some K2Cr2Or solution, divide the orange-red solution into five parts and deoxidize each of these portions by one of the following methods: a. Pass H2S into the hot solution: white S separates. b. Add some NaHS03 or H2SOs and warm. c. Add alcohol and boil. d. Boil for some time, after adding much strong HC1. e. Add some Zn to the acidified liquid and warm: the change of color is in this case slow. In each case the change in composition is shown by the liquid becoming green ; the following equations show the decomposition occurring with H2S and with HC1, the others may be drawn out by the student: K2Cr207 + 3H2S + 8HC1 = Cr2Cl6 + 2KC1 + 7H20 + S3. K2Cr207 + 14HC1 = Cr2Cl6 + 2KC1 + 7H20 + 3C12. This green solution gives all the reactions for Cr (102-104). Note.—Since chromic acid is thus reduced by boiling with HC1 and by II2S to a chromic salt, a chromate leads to precipitation of Cr2IIo6 in Group III in the ordinary course of analysis. Hydrogen peroxide (H202), if added after some ether to an acid solution of a chromate, on well shaking the liquids cause the ether to assume a blue color; addition of a few drops of strong HN03 is useful. The H202 may be produced by adding BaO,2 to the cold acid liquid. This reaction is exremely delicate and characteristic. 287. AgNO,purple-red precipitate (Ag2Cr04): sol- uble in AmHO and in HN03. 288. PbA2: yellow precipitate (PbCr04): soluble in KHO, insoluble in HA. 289-291/ SILICATES. 173 289. yellowish-white precipitate (BaCrOJ: insoluble in HA, soluble in HCl. Hydrogen chromate, or chromic acid (H2Cr04?). Cr03 dissolves in water to a reddish-yellow liquid, with a strongly acid reaction. The liquid evolves Cl and be- comes green if it is boiled with HCl; when neutralized by an alkali it becomes yellow, the solution yielding the reactions in pars. 287, 288, 289. Use Na2SiC)3 solution for liquid; for solid, finely ground sand or solid Na2Si03. Silicates. 290. IICl added slowly drop by drop to a solution of Na2Si03 whilst stirring or shaking it, will usually, unless the solution is very dilute [see Note 2 below], give a gelatinous precipitate of H4Si04; but this precipitate is very apt to remain dissolved, hence its non-appearance is no proof of the absence of II4Si04. 290 a. Small quantities of H4Si04, or II4SiO in dilute solution, may be detected by evaporating the solution, made acid with HC1, to dryness in a porcelain dish, and heating the residue to 100° as long as acid fumes come off': on stirring and warming the dry residue with strong IICl, Si02 remains undissolved as a white powder. Note 1.—During the last part of the evaporation the silica often separates as a gelatinous mass, and unless the heat is lessened and the residue stirred with a glass rod it will spirt: spirting is best avoided by finishing the evaporation, as soon as the liquid becomes thick, upon a water-bath. The undissolved Si02, left on treating with HCl, is best seen by pouring out the liquid into a test-tube: it is sol- uble in hot KHO solution. Note 2—The solution of Na2Si03 used for these reactions is made of such a strength that acids do not precipitate II4Si04 from it, but by boiling some of it down to a quarter its volume before adding the acid the precipitate is usually obtained. 291. AmCl or Am2C03 causes a gelatinous precipitate of Il4Si04, which usually forms only after a time. [292-295. UNGROUPED ACID-RADICLES. Blowpipe Jests. 292. A little solid SiO,2, or a silicate, if fused into a bead of Na20O3, causes frothing from C02 escaping: Na2C03 + SiO = 0O2 + NaaSi03. 293. Fused in a bead of NaAm HP04 the Si02 is not dissolved, but floats about in transparent particles, and on cooling remains as little opaque masses in the bead. The particles of Si02 are usually best seen in the bead whilst fused. Hydrogen silicate, or silicic acid (H4Si04), is a white gelatinous substance with no reaction to litmus; it is insoluble in water, and but very slightly soluble in acids, but dissolves as an alkaline silicate in solutions of the alkalies or alkaline carbonates. On ignition it forms a white insoluble powder (Si02), which yields reactions (292) and (293). Fluorides (- 'F).—Use finely powdered CaF2. The most useful tests for a fluoride depend upon setting free hydro- fluoric acid and allowing this to act upon a glass surface, which it “etches” or corrodes, causing it to appear dim when perfectly dry. 294. Strong IIlSOv if warmed with a little CaF2 in a test-tube, liberates HF, which causes the glass to behave towards the liquid as if it were greasy. The HF etches the glass, and on washing away the cooled mixture, and perfectly drying the inside of the tube, it will be found to be dimmed and roughened. This test is often performed by gently warming the substance, upon which several drops of strong H2S04 have been poured, upon a watch-glass for some time; on wash- ing off the substance and drying the glass thoroughly it will be found to be dimmed and roughened where the substance and acid rested ; this is best seen, if only very slight, by holding the glass so as to see the reflection from its surface. 295. A less simple, but more delicate plan, consists in placing the CaF2 in a platinum crucible, or in a small leaden cup made by bending a piece of sheet-lead, and 296, 297.] FLUORIDES. 175 pouring upon it some strong II.,S04. The crucible is then covered with a watch-glass, with its hollow upwards, and filled with cold water to keep the glass cool; the crucible is placed in a porcelain dish containing sufficient hot water to reach half way up the sides of the crucible, the water being occasionally heated if necessary by a small flame ;l on removing the watch-glass after ten minutes or more, washing and then thoroughly drying it, the part of the surface covering the crucible will be found to be dimmed by the action of the HF vapors. The delicacy of this method is much increased by the modification described in (296). 296. The convex surface of a watch-glass is covered with a thin film of beeswax or solid paraffin by carefully heating the glass held by crucible-tongs at some distance above a flame, then rubbing its convex side with a piece of wax or paraffin ; it is thus covered with a melted layer, which may be made uniform by once more heating the glass, allowing any excess of wax to drop off, and keep- ing the glass moving whilst it cools; the coating is finally hardened by immersion for a short time in cold water. Lines or characters are then traced on the glass towards its centre by gentle pressure with the point of a penknife, the object being simply to remove the wax from these parts and not to scratch the glass. The glass thus pre- pared is exposed as in (295) to the HF vapor for about twenty minutes or half an hour, the wax being prevented from melting by cold water in the hollow of the glass. The watch-glass is then removed and cleansed from wax by holding it with crucible-tongs above the flame and quickly wiping off the wax when melted : a clean bright surface will be thus obtained on which the traced lines will usually be visible at once on holding the glass up to the light; but if mere traces of a fluoride were present they will be made visible by breathing upon the cold surface. 297. The presence of SiO, or a silicate prevents the 1 Or the crucible may be heated gently over a very small flame or ou a sand-bath. 176 FLUOSILICATES. [298, 299. liberation of HF by H2S04, SiF4 being given otf in- stead : this gas possesses no etching power, and there- fore if Si02 or a silicate is present, the methods given above do not serve for the detection of a fluoride. SiF4, however, produces white fumes in air, and if passed into dilute AmHO yields a colorless flocculent precipitate of II4Si04 and gives AmF in solution : the formation of the flocculent precipitate of H4Si04 is sufficient proof of the presence of a fluoride, but the AmF itself may be detected in the filtrate from this precipitate by adding CaCl2, filtering off the precipitate of CaF2, and drying and examining it by (296). By mixing Si02 with any substance to be tested for a fluoride the above method may be employed for its de- tection ; use for the reaction a mixture of CaF2 and SiCk. A small piece of marble may be dropped into the tube in which the SiF4 is evolved, to carry that gas over into the AmHO solution. The changes which occur are thus expressed : 2CaF2 + Si02+ 2H2S04 = SiF4 + 2H20 + 2CaS04. " SiF4 + 4AmHO = H4Si04 + 4AmF. 298. CaCl2 added to NaF solution1 gives a gelatinous almost transparent precipitate (CaF2), which becomes more visible on heating or adding AmHO : slightly soluble in HC1, almost insoluble in HA. Hydrogen fluoride, or hydrofluoric acid (HF), is a colorless gas, which fumes in the air, etches glass, and dissolves easily in water. The solution of HF is acid in reaction, and ditfers from all other acids in dissolving SiO and attacking insoluble silicates. Fluosilicates (-"SiFe).—Use H2SiF6. 299. BaCl2: white precipitate (BaSiF6), which usually appears only on gently warming the solution, and thus 1 Prepared by boiling in water the mass obtained by fusing for several minutes on platinum foil some powdered CaF2 and fusion mixture, filtering the solution, and acidifying the filtrate with IIA. 300-302. FLUOSILICATES. 177 differs from BaS04: it is somewhat soluble in boiling HC1, but insoluble in alcohol. Put by some of this precipitate for reaction (301). This precipitate differs from the precipitate of BaS04, which it somewhat resembles in being rather insoluble in JIC1, by being more or less transparent and crystalline; but fluosilicates differ from sulphates also in giving no precipitates with Sr(N03)2 or Pb(N03)2, and in giving, when heated with excess of Am HO, a fiocculent pre- cipitate of II4Si04, and AmF in solution (297); fluosilicates differ also by the following very distinctive reactions. 300. KCl, on warming, gives a very transparent ge- latinous precipitate (K2SiF„), which is visible only after being allowed to settle for a time; it is insoluble in alcohol. 301. By evaporating H2SiF6 solution, or heating a fluosilicate, with strong H2S04, HF is given off, and may be detected by its etching action on glass (294 et seq.). Evaporate a little H2SiF6 or BaSiF6 from (299), after adding strong H2S04, upon a watch-glass to dryness; on washing off the residue the glass will be found to be etched. • 301 a. A solid substance (e. g., the precipitate of BaSiF6 or K2SiF6) may also be examined by any of the methods given above for HF, the most delicate being (296). This method is particularly useful for proving a precipitate produced by BaCl2 to consist of BaSiFg.1 302. The above reactions readily distinguish between sulphates and fluosilicates, both of which give precipitates with BaCl2, which are insoluble in boiling HC1. There is only one other class of salts —the selenates—which give with BaCl2 a white precipitate insoluble 1 The readiest means of producing an etch with this precipitate is to pour it off into a watch-glass, decant the water, and warm the precipitate for some time with strong H2S04; on washing the glass and drying it, it will be found to be corroded. When the more deli- cate process (296) has to be employed, the precipitate should be shaken up with the liquid, poured off into a platinum crucible or leaden cup, the liquid decanted, and the precipitate warmed with strong H2S04 as described in (296). ORGANIC ACID-RADICLES. [303. in IICl, and this precipitate (BaSe04), if boiled with strong HC1 for some time, evolves Cl and gradually dissolves as BaSe03, thus differ- ing from BaS04 and BaSiF6; further, this HC1 solution, if warmed with II2S03, yields a reddish precipitate of Se. Hydrogen fluosilicate, or hydrofluosilicic acid (H2SiF6), is a strongly acid liquid, volatilizing entirely as 2HF + SiF4 when heated in platinum. By evaporating it in glass the glass is etched. It is precipitated by KC1 and by BaCl2. REACTIONS OF ORGANIC ACID-RADICLES. The following acid-radicles are included here, although the first four are frequently, and the other three always, classed amongst organic compounds, because they are of such frequent occurrence, and their detection is usually a matter of so little difficulty that they may reasonably be appended even to an elementary treatise on inorganic analysis. Cyanides (-'Cy).—Use KCy solution. IlCy smells of bitter almonds; the alkaline cyanides also smell faintly of the same. 303. AgNOz: white precipitate (AgCy), most easily obtained by pouring a drop of the KCy solution into the AgNOa solution : show with three separate portions that this precipitate is soluble in KCy solution added in ex- cess, and in AmHO, but insoluble in dilute HN03. If some of the precipitate be filtered off and well washed with hot water until free from AgNCb (shown by HC1 causing no milkiness with the last few drops of the washing water), then dried, scraped from the filter into a porcelain crucible, and heated strongly, Ag is left; if this residue on cooling be warmed with a little dilute HNO3, it dissolves, giving oft' red fumes; anfl a drop of IIC1 added to this solu- tion gives a curdy precipitate of AgCl. This reaction distinguishes AgCy from AgCl, AgBr, and Agl, which like it are precipitated by 301-306.] CYANIDES. 179 AgN03, and are insoluble in IINO3, but which, when dried and strongly heated, melt without decomposing; lienee, after cooling, if IINO3 be warmed with them it dissolves out no Ag, and HC1 added to the HNO3 gives either no precipitate or a mere milkiness due to imperfect washing of the precipitate. This method is somewhat tedious and need seldom be used, cyan- ides being readily detected by the following reactions. 304. If some FeS04 solution, mixed with several drops of Fe2Cl6, is added to KCy solution and the liquid is then made strongly alkaline with KHO and boiled, then cooled and TIC1 added to acid reaction, “ Prussian blue” (Fe'^Cfy,,1) remains as a deep-blue precipitate; or, if in small quantity, it dissolves, giving a bluish-green solution. If no cyanide had been present, the addition of HC1 would have given a nearly colorless liquid. 305. If to some KCy solution, contained in a test-tube fitted as shown in Fig. 37 (p. 150), dilute II2S04 is added, then a small piece of marble dropped in and the liquid boiled, allowing the steam to pass off into some AtmS solution, AmCyS is formed. This substance gives with Fe2Cl6 a blood-red coloration, which may be obtained by pouring the Am2S solution out into a porcelain dish, boiling it, allowing it to cool, making acid with HC1 (see Note 1, p. 180), and adding several drops of Fe2Cl6; a blood- red color, only faintly seen when but little KCy is used, shows that HCy has passed into the Am2S, producing AmCyS, and therefore proves the presence of a cyanide. A little of this red liquid should be added to some HgCl2 solution ; if the red color is destroyed it was certainly due to the presence of AmCyS. The marble is used to cause evolution of C0.2-gas, which lessens the risk of the Am2S being sucked hack during the reaction. 306. The former test can often be more simply per- formed by boiling the solution of KCy or HgCy2 with Am2S, which must be added until the yellow color re- mains after boiling for a short time. If a dark-colored precipitate forms, this must usually be filtered off before 1 The symbol Cfy conveniently represents the group (FeCy6); it is used here to avoid brackets. 180 FERROCYANIDES. [307. the color of the filtrate can be seen. Then filter if neces- sary, acidify with HC1 in a porcelain dish (see Note 1, below), and add Fe2Cl6 in small quantity; a blood-red color is produced in the liquid, which is not removed by heat or addition of HC1, but may be destroyed by add- ing a few drops of the liquid to some HgCl2. Note 1.—On adding IICl to the Am2S (305, 306), white S separates unless the yellow liquid has been previously boiled in a porcelain dish until it becomes colorless, tilling in distilled water as it evapo- rates ; but this separation of S is advantageous, since it helps to show by its whiteness even a faint reddish tint in the liquid. Methods (304, 305, 306) are exceedingly delicate tests for a cyanide. Methods (305) and (306), if less readily performed than (304), exceed it in delicacy. Method (306) is the more easy of the two to perform, and (305) is only used in cases where, after boiling with excess of Am2S, the filtrate is dark-colored, and therefore the red coloration would be invisible. Note 2.—IIgCy2 does not show tlie reactions for a cyanide by methods (303, 304, and 305) ; but by boiling with according to method (306), AmCyS is obtained in the filtrate from the black HgS precipitate, and will give the red coloration with Fe2Cl6. (Solid HgCy2 heated in a small tube closed at one end also gives off cyanogen gas, which burns with a peachblossom-colored flame. Hydrogen cyanide, or hydrocyanic (“Prussic”) acid. (HCy), is a colorless, volatile, inflammable liquid, smelling like bitter almonds: it is highly poisonous, both when in- haled as vapor and swallowed as liquid : it readily mixes with water. The acid is easily detected by AgNOa (303), also by (304), or by formation of AmCyS when the liquid is boiled with AnizS (306). \ Ferrocyanides (—""FeCyJ or ~""Cfy.)—Use K4FeCy6.3H20 (or K4Cfy.3H20) solution. 307. Fe2Cl6: dark-blue precipitate, “Prussian blue” (Fe4Cf‘y3): insoluble in HC1, soluble in H2C204 to a dark- blue liquid : changed by KHO into brown Fe2Ho6. 1 This part of the formula of a ferroeyanide is conveniently written Cfy to avoid using brackets. 308-315.] FERRI-, SULPHO-CYANIDES. 181 The solubility in H20 and insolubility in IICl are shown by pour- ing off portions, heating them with HC1 and H20 respectively, fil- tering and noting whether the filtrate is blue: a third portion is mixed with KHO, and becomes brown. 308. FeSOi: light-blue precipitate (Fe"K2Cfy), which quickly becomes darker on standing in the air, or immediately on addition of Cl-water or Br-water, or on warming with HN03: it is insoluble IICl. 309. OuSOi- a chocolate-colored precipitate insoluble in HA. 310. AgN03: white precipitate (Ag4Cfy), insoluble in IINO3 and in AmHO. If heated with HN03 this pre- cipitate changes to orange-red Ag6Cfy2, soluble in Am 110. Ferricyanides [ - vi(FeQ/6)2, or -viQfy2].— Use K6(FeCy6)2 (or Iv6Cfy2) solution. 311. Fe2C/6: dark-green or brown coloration; no pre- cipitate is formed, as may be seen by adding much water to the liquid. 312. FeSOi: dark-blue precipitate, “ Turnbull’s blue,” (Fe"3Cfy2): insoluble in acids: blue color destroyed by KHO. 313. OuSOi: yellowish precipitate. 314. AgN03: orange-colored precipitate (Ag6Cfy2), in- soluble in HNOs, soluble in AmHO. Frequently a white residue is left on adding AmHO, consisting of Ag4Cfy, and showing that K4Cfy was present in the K6Cfy2 solu- tion. Sulphocyanides (- 'CyS).—Use KCyS solution. 315. Fe2Cl6: blood-red coloration, but no precipitate: the color is destroyed by HgCla solution, but not by HC1. 182 ORGANIC ACID-RADICLES. '316-318. 316. Cyanides are usually detected in analysis by methods (304, 305, 306). Ferro- andferricyanides can be found and distinguished by their first three tests, or by the precipitate given by AgNOsin the solution acidified with IINO3; this precipitate, if a ferricyanide is present, will have a more or less decided orange-red color ; on filter- ing, or decanting, and warming the precipitate with AmHO, white, Ag4Cfy will be left if a ferroeyanide was present, and on acidifying the filtrate with IIN03 orange-red Ag6Cfy2 will be precipitated. A sulphocyanide is found by (315). The three following acid-radicles and their salts differ from the foregoing by being charred and emitting a smell of burning when heated in the solid state; oxalates, how- ever, do so only to a slight extent. If the salt be one of the alkalies or of the alkaline earths, the residue left after ignition contains a carbonate, which effervesces with an acid, whereas the original substance did not do so. Oxalates (-"C204, or - "O).—Use Am2C204.2H20, (or Am20.2Ui0). 317. Strong HfiOi heated with solid Am20.2H20 causes an effervescence of gas consisting of a mixture of CO and C02: Am2C204 + 2H2S04= CO + CO,2 +Am2S04+ H2S04.H20. The CO is detected by burning with a blue flame when a light is applied, the CO2 by rendering a drop ot lime- water on a glass rod milky. No blackening or charring is produced by strong H2S04; oxalates differ in this respect from the salts of all other organic acids. 318. CaCl.,, CaSO4, or lime-water, added to Am2C204 solution (made by diluting some of the reagent solution in a test-tube with an equal quantity of water), gives a white precipitate (CaC204), insoluble in AmHO and in HA, soluble in HC1 or HNOs. 318a-320.1 TARTRATES. 183 318 a. If this precipitate is filtered off, a portion placed on a watch-glass will not effervesce with dilute HC1; but if the remainder is dried and heated to dull redness on platinum foil, it is converted without blackening into CaC03, which effervesces with dilute HC1. This is a general test for oxalate of K, Na, Ba, Sr, or Ca; oxalates of these metals leave carbonates on ignition which effervesce with an acid. 319. Heated with MnO, and IT SO,, solid oxalates give off 0O2: Am2C204 + Mn02 + 2H2S04 = 2CO, + MnS04 + Am2S04 + 2H20. Since commercial Mn02 usually contains some carbonate, it will give off CO2 when treated with 1I‘2S()4. If the Mn02 to be used is not known to be free from carbonate the best way to make the test is to add to some of the Mn02 in ar test-tube a little H2S04, and heat to boiling; if C02 is found in the tube by a glass rod with a drop of lime-water on its end, continue to boil, occasionally drawing fresh air into the test-tube by pushing down a glass tube near to the surface of the liquid and sucking out the air; as soon as no CO2 is detectable in the tube after boiling for a short time, and the liquid is distinctly acid, the Am2C204 is added and the mixture again heated, CO2 will be rapidly given off, and may be detected by the ordinary methods. If the Mn02 gives no C02 with II2S04, proceed at once to add the Am2C204, heat and test for C02. Hydrogen oxalate, or oxalic acid (H2C204, or H2C204. 2H20 if crystallized), when heated in a glass tube closed at one end partly sublimes unaltered, and is partly de- composed, yielding vapors which cause coughing; it yields reactions (317) and (319). It dissolves in water to an acid, poisonous liquid. Tartrates (- "C4H4Ob, or -"'T). For a neutral tartrate use Na2T.2H20 or KNaT; for an acid tartrate use ILT or NaHT. 320. A solid tartrate or solid IT2T, when heated strongly in a tube, chars, giving off a smell of burnt sugar. 184 [321-324. ORGANIC ACID-RADICLES. 321. A solid tartrate or solid H2T heated with strong H2S04 blackens, giving off a mixture of CO, C02, and 322. AgN03 gives with solution of a neutral tartrate a white curdy precipitate (Ag2T), soluble in AraHO and in HNOa. Allow some of the above precipitate (AgzT) to settle in a test-tube, and pour off as much of the liquid from above it as possible; then pour very dilute AmHO drop by drop into the tube, until the precipitate, after being shaken up with the liquid, is nearly but not quite dissolved; then heat the test-tube gradually and gently by immersing it in a beaker of cold water and slowly raising its temperature to 60°, a brilliant mirror of Ag will form on the interior of the tube. If the liquid, in- stead of being slowly heated to 60°, be quickly boiled, the Ag deposits as a black precipitate, which is not so characteristic. 323. CaCli precipitates from a neutral tartrate solu- tion white or crystalline CaT : the precipitate often sepa- rates only after shaking the liquid well and letting it stand for a time; it is soluble in acids and its formation is retarded by AmCl and other Am-salts. This precipi- tate is soluble in strong cold KHO,1 is reprecipitated by boiling, but dissolves again more or less completely on cooling. Decant the liquid from the precipitate and pour upon the precipitate a little very dilute AmHO in a test-tube, drop in a small crystal of AgN03and warm carefully as in (322). A silver mirror forms on the part of the glass on which the AgNOs rests. 324. KCl, or better KA, if added to solution of H2T or an acid tartrate, gives on stirring or shaking a white crystalline precipitate (KHT). If IIA is added at the same time, the precipitate may also be obtained with neutral tartrates. Addition of alcohol assists the forma- tion of the precipitate, which is soluble in alkalies and in mineral acids. 1 A milkiness remains, however, if the potash solution contains carbonate. 325-328.] 185 ACETATES. 325. If a few drops of Fe.Cl6 solution be added to H2T or KNaT solution, then KHO or AmHO until the liquid is strongly alkaline, no precipitate forms. The precipitation of several other metals (e. g., Al, Mn, Cu) by alkalies is similarly prevented by H2T: this is owing to the formation of a double tartrate of the alkali and the other metal, which salt is not decomposed by an alkali. Hydrogen tartrate, or tartaric acid (H2T), occurs in colorless crystals which do not alter in the air; they taste pleasantly acid, and dissolve in water and in alcohol: they are detected by heating them alone or with strong H2S04 (320, 321): if dissolved and neutralized they also yield the reactions in (322, 323). Acetates. (-'C2H302, or -'A).—Use NA.3H20.1 326. Solid NaA if strongly heated blackens, giving off a peculiar smell and a vapor (acetone) which burns with a bright flame when kindled. 327. Heated with strong H2S04, vapor of HA is given off, recognized by its pungent smell of vinegar. If alco- hol is first added to the NaA then strong II,)S04, and the mixture is warmed, a fragrant smell of ethyl-acetate (EtA) is emitted; it is most decided when the liquid is shaken after cooling for a short time. 328. Fe2Cl6 added in small quantity to a little NaA dissolved in water, gives a deep-red color: on boiling the solution, made neutral but not alkaline with AmtlO (if necessary), all the Fe separates as a light-brown precipi- tate and the liquid becomes colorless. The red color of the solution before being boiled is changed to yellow by addition of HC1 (difference from the coloration due to sulphocyanide). Hydrogen acetate, or acetic acid (II A).—“ Glacial acetic acid” is at 17° C. a colorless crystalline substance, emit- ting when heated a very pungent and inflammable vapor : it is strongly acid. It dissolves in water readily, impart- ORGANIC ACID-RADICLES. r329. ing its peculiar smell to the liquid in a mild degree* The acid is completely volatile without decomposition. 329. The above organic acid-radicles may be specially tested for by any of their reactions; (318) being generally used to test for an oxalate in solution, (317) or (319) when it is solid; a tartrate is best detected in solution by reac- tion (322) or (323), or if solid by (320); an acetate is found by (326) or (327). *** After completing the reactions for the acid-radicles the student may proceed to Section VI, unless he is in- tending to learn the analysis of simple salts, when he pro- ceeds to Section V. SECTION Y. ANALYSIS OF SIMPLE SUBSTANCES CONTAINING ONE METAL AND ONE ACID-RADICLE.1 Note.—This section may be neglected by a student who is proceed- ing through the senior analytical course. 330. The ordinary method of proceeding to detect the metal or acid-radicle or both in a simple substance, is to make a few preliminary experiments, which will usually give some idea as to what substance is present, and will occasionally even detect metal or acid-radicle, or both of them, with certainty. AVhether the composition of the substance has been satisfactorily proved by this prelimi- nary examination or not, the next process is to endeavor to dissolve the substance, if it is not already in the liquid form, in water or acids; then by adding to the solution certain group-reagents in the proper order of succession, it is found to which analytical group the metal present belongs. The following table gives the analytical groups for metals, each group being headed by its distinctive number, name, and group-reagent: 1 Two metals may occasionally be present, as when an alnm, or tartar-emetic [K(SbO)T], is given for analysis; also there may be two acid-radicles in the liquids given for analysis, since a salt insolu- ble in water is occasionally dissolved in an acid; but the student should always be informed of this if it in any way complicates the analysis. It will not usually do so, since in the most commonly oc- curring case, that of an alkaline earth phosphate dissolved in HC1, the Pt\ is detected in Group III, and accordingly no other acid- radicle is looked for. TABLE OF ANALYTICAL Table showing the Analytical I ■1 Note. — It will be observed that there are two divisions of Groups II and III. In analysis it is usual to separate tbe two divisions of Group II from one another, after having sepa- rated the whole group from the remaining groups; the two divi- sions of Group III are by some analysts precipitated together and subsequently sep- arated ; they are, however, often pre- cipitated separately, and treated as dis- tinct groups. Metals whose chlorides are insoluble in water and dilute acids, and which are therefore precipitated from their solutions by hydro- chloric acid. Metals whose sulphides are insoluble , dilute acids, and which are therefii precipitated from acid solutions I sulphuretted hydrogen. Group I. Hydrochloric Acid, Silver Group. or Group II. Sulphuretted Hydrogen Group, j f Group II a. j Copper Group. Sulphides insoluble in NaHO and in AmaS. | Group II b. j Arsenic Groii| Sulphides solul in NaHO and AnioS. [Lead, Silver, Mercurosum, . 1 pb] Ag Hg' Mercuricum, Hg'' [Lead, . . Pb] Bismuth, . Bi Copper,. . Cu Cadmium, . Cd 2 Tin, . Arsenic, . Antimony,. 3 1 After discovering to which of the above analytical groups the metal present belongs, it is identified by the properties or appearance of the group-precipitate, and its presence confirmed, if necessary, by special tests made on the precipitate or on another portion of the “ original solution.”1 The acid-radicle, if it has not been already detected during the examination for the metal, is tested for in a less systematic manner. A few preliminary experiments are first performed, and if these do not detect the acid- radicle, it is found, partly by a systematic examination, including that described above for the detection of the metal, but more commonly by special tests. A substance insoluble in water and in acids is examined according to the special directions in (367-369). Since in these analyses only one metal and one acid- radicle are to be looked for, the examination for the metal is carried no further when one metal has been detected with certainty, and the examination for the acid-radicle 1 By the “original solution ” is meant the solution of the substance, or the substance itself, if a liquid is under analysis, to which no re- agent has been added. CLASSIFICATION OF METALS. Classification of the Metals. itals which are precipitated as hy- rates from their solutions contain- ig ammonium chloride when made kaline with ammonia, or as sul- liides or hydrates when ammonium dphide or sulphuretted hydrogen is ibsequently added. Metals whose carbon- ates are precipi- tated by addition of ammonium carbon- ate in the presence of ammonium chlo- ride. Metals whose solutions are not precipitated by any of the fore- going group-reagents in the presence of ammonium chloride. Group III. \mmonia and Ammoniam-su!phide Group. Group IV. A mmonium-carbo note or Barium Group. Group V. Potassium Group. Group III A. mmon ia or Iron [ Group. Group III b. (Ammonium, sul- -< phide or Zinc ( Group. iminium, . A1 n, . . Fe :omium, . Cr 4 Zinc, . . Zn Manganese,. Mn Nickel,. . Ni Cobalt, . . Co 5 Barium, . . Ba Stroi tium, . . Sr Calcium, . . Ca 6 Ammonium, . NH, Potassium, . K Sodium, . . Ma Magnesium, . Mg 7 is similarly at an end when the presence of one such radicle has been satisfactorily proved. It must, however, be understood that substances given for analysis are liable to contain impurities, which will yield only slight indi- cations; if in the course of analysis, therefore, only a slight result is obtained, proceed until some substance is detected in larger quantity, entering against the slight result “ Trace of The separation and washing of a precipitate by “ decan- tation” (23 b, 24 b) is recommended wherever it is possi- ble, as this process is more easily performed than that of filtration (23 a); if a precipitate, however, refuses to settle after heating and shaking the liquid, filtration must usually be resorted to. Caution.—In every analysis each result must be fully entered in the note-book as soon as the experiment has been performed, the form of entry being the same as that adopted for the directions in the text. For examples of substances to be given for analysis by Section V, see par. 537. *** The numbers in brackets refer to the paragraphs in the text, in which tests or processes to be employed by the student are fully described. 190 ANALYSIS OF A SOLID SUBSTANCE. [331. DIRECTIONS FOR THE ANALYSIS OF A SIMPLE SUBSTANCE. The substance given for analysis may be either a solid or a liquid. If it is a solid examine by (331 et seq.) omitting (334), if a liquid is to be analyzed begin at (334). THE SUBSTANCE GIVEN FOR ANALYSIS IS A SOLID. 331. Make a careful examination of the properties of the substance, noting down its color,1 its smell, if it pos- sesses any, also its form—whether it is in powder, crystals, or non-crystalline pieces ; note carefully also any appear- ance or property which may strike you on examining the substance with the naked eye or with the assistance of a lens; after noting down the results of this examination, the substance is powdered as finely as possible. If the substance possesses a metallic lustre or appear- ance, work as directed under (366) ; if it is not metallic in appearance, proceed to ascertain its solubility by the directions contained in (332), and, according to the result thus obtained, conduct the further analysis of the sub- stance by (333) or by (367). 1 The salts of the following metals are colored: Cu, blue; Fe///, brownish-yellow; Fa", pale green ; Ni, Cr, CuCl2, green; Mn, delicate pink; Co, reddish-pink. Chromates, light yellow ; dichromates, orange- red; Sb2S3, CuO, Mii02, black; HgO, Pb304, red; Pb02, dark brown; PbO, light brown ; Cr203, green. 332.] SOLUBILITY OF THE SUBSTANCE. Solubility of the Substance. 332. Since the method of examination of a solid sub- stance depends upon whether it is soluble or insoluble in water or acids, the following experiments are tried. Place a small quantity of the finely powdered substance in a broad test-tube or a boiling-tube, fill the tube about one-third with water, and heat to boiling: . 7Tie substance dissolves. ifter examining aportionof the solid substance by the prelimi- nary tests (333) and (335-338 a) proceed to ex- amine the color The substance does not dissolve: heat a fresli portion with dilute HC1 to boiling; if it does not dissolve, decant and boil the residue with strong HC1: 2. The substance dissolves. Absence of Group I., except pos- sibly Pb. The substance does not dissolve: put aside the test-tube containing the substance with HC1. and stir a fresh portion of the substance with a little dilute HN03; if it is not dissolved, boil. If dilute HN03 does not dissolve it, heat with a little strong HN03: the liquid to litmus by (334, I, II), and, re- fer to (339) for directions for analysis. After examining a portion of the solid substance by the prelimi- nary tests (333) and (335-338 a) proceed to ex- amine the HC1 solution (after noting its color, see 334, 1) for the metal by (339). 3. The substance dissolves. After examining a portion of the solid substance The substance does not dissolve: mix together the contents of the two tubes in which the substance was heated with HCI and with HNOs, and heat the mixture: by the prelimi- nary tests (333) and (335-338 a) examine the HN03 solution (after noting its color, see 334, I) for the metal by (339), taking care after testing for Group I by HC1 to boil down consider- ably in a porce- lain dish after adding a little strong HCI,1 and then add dilute HCI be- fore testing for Group II by HaS. 4. The substance dissolves. After examining a portion of the solid substance by the prelimi- nary tests (333) and (335-338 a) examine the so- lution in HNOa and HCI mixed as directed in the preceding column (332, 3) for the metal by (359). 5. The substance does not dis- solve. Examine a fresh portion of the substance by (367 et seq.). 1 This method of proceeding removes HNOa, which would cause with H3S a deposit of S. 192 PRELIMINARY EXAMINATION [333. Preliminary Examination of a Soluble Solid. 333. The table is thus arranged: In the first column is placed the experiment to be made; in the second a list of the results, any one or more of which may be observed; and in the third the inferences to be drawn from the re- sults. Confirmatory or supplementary experiments are occasionally entered; they are, however, only to be tried when the result preceding them in the second column has been noticed. A more complete preliminary examination will be found in (387-408). Experiment. Observation. Inferences. I. Heat a portion of I. The substance does not change, Absence of volatile, the substance in an ignition-tube, or in a small dry test- fusible and organic substances, and of water. tube, first gently and at last to red- ness. II. The substance changes : 1. Drops of water condense in the top of Presence of HoO. the tube. 2. The substance fuses easily, . . Probable presence of a salt of Naor K, or of Ba, Sr, Ca, Mg. 8. The substance sublimes, .... Presence of a salt of NH4, As, or Hg: possibly also of II2C2O4, of S (yel- low), and of I Confirmatory. — Boil (purple vapor). A smell of NHS is evolved and white Presence of NH,. another portion of fumes appear when a rod moistened Confirm by PtCl4 the substance with with strong HC1 is held to the mouth (52), and proceed KHO solution. of the tube. to (335). Confirmatory. — Mix A gray sublimate of minute metallic glob- Presence of Hg. Pour another portion of ules, best seen by a lens. upon the original the substance with substance a few about three times as much powdered drops of AmllO, if it blackens Hg' is Na2COj and KCy present, if not, Hg" and heat in an ig- is present. nition-tube. A black mirror-like sublimate, . Presence of As. 4. The substance blackens, and gives off Presence of an or- C02, which makes a drop of lime-water ganic acid-radicle, on a glass rod milky. probably A, 0 or T : the last is known by a smell of burnt If the cool residue in the tube effervesces with HC1, whereas the original sub- sugar. The organic acid- stance did not. with Iv, Na, Ba, Sr, Ca, or Mg. 333.; OF A SIMPLE SOLUBLE SOLID. 193 Experiment. Observation. Inference. 5. Gas or vapor is g vapor: Bed nitrous fumes smell. S02, known by its sn K2Cr20, solution g Cl, Br, I, known by and I by action on by bleaching mois A slip of wood with glows brightly or The gas can be light mouth of the tut the flame: Pale greenish-yellow plosively, and niti Bright while, the un garlic. Peachblossom-colored mate of Hg. 6. The substance cha Yellow, hot. Yellow-brown, “ Bark red or 1 „ brown, J iven off; smell the recognized by their uell and by turning reen. smell and color: Br starch-paste, and Cl t litmus. a spark at its end Hirsts into flame. ed and burns at the e; note the color of the gas burns ex- ous fumes are seen. burnt gas smells of flame, gray subli- nges color: White, cold. Yellow, “ Bed-brown, “ From nitrate of a heavy metal. From combustion of free S or a sulphide: possibly also from a sulphate, sulphite, or theiosulphate. From certain chlo- rides, bromides, or iodides, also free I. 0 from chlorate or nitrate, or N20 from decomposi- tion Of NH4NO3. Presence of FfH3, from strongly heat- ed NH4NO3. Presence of PHS,pro- bably from a hypo- phosphite. Presence of Cy, from HgCy2. ZnO. PbO, Sn02 or Bi203. F e203. II. Dip into the pow- 1. The flame is not colored, .... Probable absence of dered substance a moistened loop of platinum wire, and 2. The flame is colored: the substances enu- merated below. Presence of Na. the Bunsen flame; Intense yellow,1 moisten with strong HC1, and again hold Pale violet, appearing crimson-red 1 “ K. in the flame. through the indigo-prism, . . j ( Appearing green through the) “ Ca. R j J indigo-prism, ... 1 Kea •< Appearing intense red through) “ Sr. L the indigo-prism, . . j r Yellowish-green, . “ Ba. r, ] Bright green with blue centre 1 Green-t after moistening with HC1, f “ Cu. L Green, B2O3. f Pale blue (livid) Presence of As,Sb,Pb. Juwe \ Vivid blue, “ CuCl2. 1 If the coloration for Na or K is intense, no further examination for the metal is necessary, hut the presence of K should be confirmed by stirring with PtCl4 (47). Proceed to (335).' If the coloration is slight, a trace only of the metal is present, and the examina- tion for another metal is continued. 194 PRELIMINARY EXAMINATION ;333. Experiment. Observation. Inference. III. Heat a portion 1. The charcoal “deflagrates,” or burns Presence of a nitrate of the substance in rapidly. or chlorate. a cavity scooped on 2. A white mass is left in the charcoal Presence of Ba, Sr, charcoal, in the which does not fuse, and shines brightly Ca, Mg, Al, or Zn. blowpipe flame. when strongly heated. Confirmatory. — De- The red paper becomes blue in a short time Presence of Ba, Sr, tach a small portion where the substance rests. Ca, or possibly of of the white mass, place it on red lit- Mg. . mus paper and moisten it with a drop of water. Confirmatory.—If the A blue residue, . Presence of Al, or moist residue is not possibly of a phos- alkaline to test- phate, silicate, or paper, moisten the borate. remainder on the charcoal with Co(N03)2 solution A pink residue,. Presence of Mg. and heat again strongly in the blowpipe flame. A green residue, “ Zn. 3. The residue is not white and does not consist of globules of metal, neither is there any incrustation formed upon the charcoal; proceed to Exp. IV. 4. The residue contains metallic globules or an incrustation forms on the char- coal : proceed to Exp. V, omitting Exp. IV. IY. Fuse a small The bead is colorless when heated in both Absence of the met- quantity1 of the substance into a flames. als below. clear colorless borax bead, first in the inner, then The bead is colored In outer flame. In inner flame. in the outer flame, Blue, hot;green, cold. Red or colorless. Presence of Cu. noting in both cases Blue, hot and cold. Blue, hot and cold. “ Co. the color of the bead whilst hot and Broun or dingyI purple, hot; light > Gray or black, hot 1 and cold, . j “ Ni. when cold. brown, cold. j Brown, hot: yellow, I Bottle-green, hot) “ Fe.» cold. f and cold,. . ( Green,'2 hot and cold. Green, hot and cold. “ Cr. Purple, hot and cold. Colorless, hot and! cold, . . ; “ Mn. Confirmatory. — The A yellow mass on cooling, “ Cr. presence of Cr or Mn may be eon- Armed by fusing a A bluish-green mass on cooling, . “ Mn. portion of the sub- stance on platinum foil or wire with Na2COs and KN03. 1 It is necessary to adjust carefully the quantity of substance fused into the bead ; if too much is used, the bead will often appear opaque; if too little is employed, one of the metals may escape detection. It is best at first to fuse only a minute quantity into the bead, add- ing more if no color, or but a faint color, is produced. 2 Cr if present as a chromate gives a bead brown whilst hot, after having being fused in the outer blowpipe flame; but this brown color is not reproduced in the case of Cr when the bead, after becoming green by being heated in the inner flame, is again heated in the outer flame. 333. 195 OF A SIMPLE SOLUBLE SOLID. Experiment. Observation. Inference. Y. Mix the substance Metallic scales or globules are obtained, or an in a small cavity on incrustation on the charcoal: wood-charcoal with NaoCO, and KCy, Globules. Incrustation. and heat strongly in White and brittle. White, .... Presence of Sb. the inner blowpipe White and brittle. Yellow, .... “ Bi. llame for several Red and malleable. None, . . “ Cu. minutes. White and malleable, 1 marking paper Yellow, .... “ Pb. easily. If metallic globules White and malleable, are obtained, detach not marking paper, >> None, .... “ Sn. one and strike it sharply on the bot- and readily fusible. Wkite and malleable, not marking paper, tom of an inverted None, “ Ag. mortar with the pes- fusible only with . tie, and note whether difficulty. it is crushed to pow- ( Yellow whilst hot, der {brittle) or merely white when cold; flattened out into a becomes green cake (malleable). None, .... ■ when moistened with Co(N03)2 “ Zn. If the globules are solution and re- white and malle- heated in the able, take one upon outer flame. the point of a pen- None, .... Brown, .... “ Cd. knife and see if it None, .... White; on smelling! will mark paper as the charcoal a ( “ As. a black lead-pencil smell of onions is j does. perceived. J After the completion of the preliminary tests for the metal, a solution of the substance is made according to the directions in (332), and this solution is examined as there directed. preliminary examination [334. 334. Preliminary Examination of a Liquid. Experiment. Observation. Inference. I. Note the color of the liquid. Note.—If the color has to be observed by night it should be examined by the white light obtained by burning a piece of magnesium ribbon. Delicate tints are best seen by looking through some thick- ness of the liquid at a sheet of perfectly white paper. (Very delicate, .... Pink. •< (intense, f Very delicate, .... Green, -j ( Intense, (Reddish-yellow, .... Yellow. •< (Light yellow Blue, Violet or purple, The liquid is colorless, .... Presence of • Mil or dilute Co solution. Presence of Co. “ Fe", or Ni or Cr in dilute solu- tion. “ Ni, Cr, or Cu. “ Fe"' or a bi- chromate. “ neutral chro- mate. “ Cu. “ Cr or a perman- ganate. Absence of Co, Ni, Cr, Cu, etc. II. Dip pieces of red and blue litmus- paper into the li- quid. It is neutral, (Not affecting the color of either paper.) Absence of free acids and alkalies, and of all salts but some of those of Am, Na, K, Mg, Ba, Sr, Ca, Ag. It is acid (Turning blue paper red.) If, on adding Na2C03 to a part of the solu- tion and warming, no effervescence occurs, free acid and acid salt are absent. Presence of a free acid, of an acid salt, or of a salt with acid reaction. It is alkaline, (Turning red paper blue.) If the color of the paper becomes only slightly changed it indicates, probably, the presence of an alkaline salt. Presence of a hydrate of K, Na, Am, Ca. Sr, or Ba, or of a salt with alkaline reaction. 334; OF A SIMPLE LIQUID. 197 Experiment. Observation. Inference. III. Evaporate (21) some of the liquid upon a thin watch glass1 heated very gently by support- ing it some inches aboveasmall flame upon a piece ol wire gauze, or by means of a sand or water bath. If a residue remains on the glass bring this gradually into the flame and heat it more strongly. A residue is left, On being strongly heated the residue black- ens and emits a smell of burning, The smell resembles that of burning sugar. Note.—If the cold residue after ignition ef- fervesces with a drop of IICl, whereas the un- ignited residue did not, the organic acid-rad- icle is united with Ba, Sr, Ca, Mg, Na, or K. The results iu Exp. I, par. 333, may be here ohserved and should be noted. Keep this residue for Exp. VI. No residue is left If the liquid is also colorless, tasteless, and without action on litmus-paper, it must con- sist only of distilled water, and no further examination of it need be made. If the liquid is alkaline, NIT3 must be looked for; if it is acid, H2CO» H2S03, HC1, HN03, IKSO,. and other volatile acids only need be tested for. Presence of some dis- solved solid. Pres, of A, 0, or T. Pres, of T. Absence of any dis- solved solid. IV. Add excess of strong NallO or KHO solution and boil (51). A smell of NIT3; moist red litmus is turned1 Presence of NH4. blue, and a rod moistened with strong H( 1 No further test need produces white fumes when held in thejbe tried for a metal, mouth of the test-tube. j Proceed to (335). V. Experiment II (page 193) is then tried by dipping the platinum wire into the liquid, concentrated, if necessary, by evaporation. VI. Experiment IY (page 194) is tried by fusing some of the (above) in the borax bead. residue from Exp. Ill 1 A piece of thin glass from the side of a broken flask is a cheap and useful substitute for a watch-glass. PRELIMINARY EXAMINATION r335- Pbeliminary Examina- 335. Pour dilute II2S04 in excess upon the substance in a test- 336. A gas is evolved, shown by effervescence or by a cliarac- 1. Colorless gas 2. Gas smelling of burning 3. Gas with a most 4. Yellow gas smell-] without smell. A drop of lime sulphur. A drop of K2Cr20, solution held fetid smell. A slipof filter-paper ing of Cl. A slip of moist! or baryta water, held in the tube in the tube upon the end of a moistened with al- litmus-paper heldi glass rod, becomes green : kaiine solution of in the tube is upon the end of a glass rod becomes milky : Presence of a car- bonate. Presence of a sulphite. 2 a. The S02 gas is given off only after standing for a time or on warming, and yellow 8 separates; Presence of a theiosulphate. PbA2 and held in the tube, is blackened: Presence of a sul- phide. bleached: Presence of a hypo- chlorite. 337. Add strong H.2S04 in small quantity to a fresh portion of any of the results enumerated below occurs;1 if none of them is] 1. Fumes are evolved with pungt to litmus-paper, the liquid is not Presence of a chloi Confirmatory. — Hold in the fumes a glass rod moistened with a solution of AgN03 acidified with UNO,; the solution on the rod becomes milky: Presence of a chloride. Confirm by (351). nt smell and acid reaction colored: ide or nitrate. Confirmatory .—Drop into the acid some small pieces of Cu ; reddish-brown gas is evolved : Presence of a nitrate. 2. The liquid becomes yellow or red, and a chlorous smell is given off; on warming the tube a crackling noise or slight explosion is pro- duced : Presence of a chlorate. Confirmatory.—To a portion of the cold solution of the substance in water add a few drops of dilute in- digo solution, then some the blue color of the indigo is destroyed. 338. After heating the tube containing the strong H2S04 and porcelain dish for (338 a); rinse out the tube, and dry the inside of a fluoride is shown. The presence of a fluoride, if decisively 338 a. Add to the liquid in the porcelain dish alcohol, mix by a greenish tinge it shows: Presence of a borate (confirm by 353). 1 If Pb, Ba, Sr, or Ca is present the addition of H2S04 causes a 338 FOR THE ACID-RADICLE. TION FOR THE ACID-RADICLE. tube, and observe the effect produced;1 then heat to boiling: teristic smell; see below : 5. Reddish-brown fumes are 6. Smell of HCy. evolved, best seen by looking! Test for a cyanide and a down the tube at white ferro-, ferri-j and sulpho- paper. cyanide in the original On adding a little cold dilute substance by (351). II2SO4 and FeS04 solution No gas is evolved : Absence of carbonate sul- phite, theiosulphate, sulphide, hypochlorite, nitrite. Pass on to (337). brown liquid: Presence of a nitrite. 7. Smell of vinegar. Refer to (337,4) below. the substance, mix well by shaking, heat the liquid and note whether noticed proceed to (338) and (338 a): 3. A reddish-brown or violet color 4. A smell of 5. A mixture of 6. The substance is produced in the acid, and no vinegar is no- CO and CO» blackens and explosion or crackling occurs on ticed: gases is given evolves gases, warming: Presence of an off: found by a amongst which Presence of a bromide or iodide. acetate. drop of lime- SO.> is recog- water held in nized by its If on heating the mixture, colored Confirmatory. — the tube being smell and its ac- vapor is evolved (see note), hold in Add to a fresh turned milky, tion on KjCraO* the vapor the end of a glass rod portion of the and by the CO solution; covered with moist starch powder; substance some burning with a Prob. presence of the starch becomes brown: alcohol, then blue flame when a tartrate. Presence of a bromide. strong HoSOi: kindled: a fragrant smell Presence of an Confirm by The starch becomes bluish-black : proves an ace- oxalate. (354). Presence of an iodide. tate. Note.—The vapor is much more easily obtained by mixing the sub- stance with Mn(), powder, before adding HS3—orange. As2s3—yellow. Examine for the metal by Table II (345). To a fresh portion of the solu- \CautUm. ■— If a tartrate or evaporating the liquid must dilute HC1, and tested by If AmCl and AmHO produce and warmed. Should a (343) or fluoride (338) have The precipitate may be: ] , a i Wn f colorless and 9 2 6 ( transparent. Cr2fIoB—pale green. F<'qIIo6—reddish-brown. 1 f dingy green turn- FeIIo2—■< ing brown in thej t air. Examine for the metal by Table III a (346). If the precipitate is opaque or white and has none of the; above appearances refer toj (357). If no metal can be found, the substance is probably an acid (see 334, II). ISOTES TO THE GENEBAE TABLE. 340. If the liquid is neutral or alkaline, a portion of it is made just acid by slowly dropping in dilute IINO.3; if this produces no precipi- tate, or a precipitate which dissolves on adding more IELNO3, another portion of the liquid is examined by the above table. If a precipitate forms which is not dissolved by adding more ITNOs, it may consist of colorless, gelatinous H4Si04 from a silicate, or finely divided S, which is precipitated white from a polysulphide, and yellow from a theiosulphate; or of Sn02, or metastannic acid, or Sb205 (all white); it may also possibly be SnS2, AS2S3 (both yellow), Sb2S3 (orange-red), these sulphides being precipitated from a sulphostan- nate, sulpharsenite, or sulphantimonite. If H4Si04 separates, it is best to evaporate the acidified solution quite to dryness, then heat the residue with dilute HC1; any insolu- 343/ GENERAL TABLE FOR THE METAL. EXAMINATION FOR THE METAL. ruination, it is most rapidly found by ascertaining to which Denial tests for each member of the group. ly precipitate forms, more IIC1 is added and the liquid heated: ater is added to it (343), the liquid is then diluted, and if no precipitate has formed it on AmCl is added, then AmTIO in excess : ;alate has been found by (337), some of the solid substance or the residue obtained by i strongly heated on apiece of porcelain, the residue on cooling is then dissolved in mCl and excess of Am 110.] precipitate, a few drops of the original solution are added to some AmHMo04 dlow precipitate torm, indicating the presence <>f a phosphate, or should a chromate ien found refer to (357) for the examination of the Group III a precipitate. ) the same portion add a few drops of or H9S-water: [Note—Before adding Ann>S the liquid may be blue, showing presence of Ni, or violet Bin dissolved Cr2Ho8; the latter must be precipitated by long boiling in a porcelain sh before adding Am.^S.] ie precipitate may be: ! ZnS—white. 1 MnS—pink. 1 NiS—black. 1 CoS— “ f [FeS— “ xamine for the metal by Table III b (347). To the same portion add Am2CO,: The precipitate may be: BaC03—white. SrC03— “ CaCO*— “ Examine for the metal by Table IV (348). To the same portion add Na2HP04, warm gently and shake well; A white crystal- line precipitate proves presence of My. The metal still pre- sent may be NIf4, Na, K; it should have been detected already in the pre- liminary examina- tion by Tests I or II (333). ble residue confirms the presence of a silicate, it is filtered off, and the filtrate tested for the metal by the above general table. Any other substance insoluble in dilute HNO3 is filtered off, and may generally be known by its appearance; further, Sn02 becomes yellow and Sb205 orange when moistened with II2S-water; metastannic acid becomes golden-yellow if moistened with SnCl2 solution. 341. Make a note of any changes which occur on the addition of HC1; gases may be evolved (336), or a yellow solution may become reddish-yellow, which renders probable the presence of a neutral chro- mate. 342. Before H2S is added, the liquid must be heated, and if any smell of Cl or of S02 or brown nitrous fumes should be perceived, the solution must be boiled down nearly to dryness, then dilute HC1 added and HZS added at once. During evaporation gelatinous If4Si04 may separate (340). 343. The following changes occurring on the gradual addition of II 2S are of importance. If the precipitate is white at first-, then broivn, and at last black, the presence of IIg/r is shown; if the solution is 202 TABLE I.—SILVER GROUP. A44. strongly acid and gives a red precipitate becoming black on dilution witli H2S-water Pb is present. A separation of white S may occur accompanied by the following changes of color, which are characteristic and should be noted down: A reddish-yellow solution changing to pale, green indicates a ferric salt. A reddish-yellow “ “ bright green “ chromate. A green “ “ colorless “ manganate. A purple “ “ colorless “ permanganate. The precipitate of S is known by being perfectly white and running through a filter; it need not be further examined. A yellow precipitate which forms only on boiling the liquid may be As2S3 from an arsenate, or SnS2 from a stannic salt. 344. TABLE I.—SILVER GROUI5. A white 'precipitate forms on addition of HC1, and is either not dissolved when boiled with HC1, or it dissolves and reappears in crystals on cooling, the liquid showing the presence of Pb. The precipitate may consist of AgCl, PbCb, Hg,Cl2. Let the precipitate settle and decant the liquid: boil the precipitate in the test-tube with AmliO: 1. The precipitate dissolves, at least in part (see note below): Presence of Ag. Confirm by adding excess of HNOsto the Am HO solution; a milkiness appears. Note.—Coagulated AgCl often dissolves only slowly in AmHO, 2. The precipitate does not dissolve : The color of the precipitate is unchanged: Presence of Pb. Confirm by decanting the liquid, dissolving the precipitate in HA, and adding KaCr04 to the solution; a yellow pre- cipitate forms. The precipitate becomes black : Presence of Hg' (Met curosum). Confirm by immersing a bright slip of copper in a portion of the orig- inal solution, made acid with a few drops of HNOa; a gray deposit forms on the Cu, which becomes white and bright when rubbed. 345.] COPPER AND ARSENIC GROUPS. 345. TABLE II.—COPPER AND ARSENIC GROUPS. Note the color of the precipitate yielded by H2S: 1. The precipitate is dark brawn or black; it may consist of SuS, CuS, IlgS, Bi2S3, PbS. Add pure NaHO in excess to a small quantity of the liquid and precipitate, or of the recipitate alone after decanting the liquid if possible, and boil: 'he precipitate dis- solves: to a portion of the NaHO solu- tion add IK 1 in excess; brown SnS is reprecipitated, toil another portion of the precipitate after adding a little yellow AnioS, then add HC1 in excess; a yellow precipi- tate of SnS2: Presence of Sn" [ (Stannosum). 'he presence of Sn" should be con- firmed by adding HgCl2 to a part of the original HC1 solution, a white precipitate shows presence of Sn". The precipitate does not dissolve: it may consist of CuS, IlgS, B:9S3, PbS. a. The original solution is blue or green, and becomes intensely blue on additiou of excess of AmHO : Presence of Cu. Confirm by adding a few drops of H2S04 to the original solution, and dipping into it a bright knife-blade or piece of steel; a red film of Cu deposits. The original solution is colorless. Test in separate portions for Hg, Bi, Pb by the following special tests: Immerse in the acid solution a bright strip of Cu ; a gray film is slowly de- posited, which be- comes brilliant white when rubbed: Presence of Hg" (Mercuricum). Caution.—A salt of Hg' may have been converted into an Hg" salt during solution in IIN03. The original sub- stance should therefore be treated with AmHO; if it blackens Hg' is present, if not Ilg" was originally in the substance. Pour another portion of the original solution into much cold distilled water; a white precipi- tate or milkiness: Presence of Pi. Note.—If Bi is suspected and no milkiness appears, add excess of AmHO to the liquid; Bi if present falls as hydrate; filter, pour one or two drops of boiling HC1 upon the pre- cipitate, and let them drop through into large excess of water; a milkiness on stirring shows presence of Bi. To a portion add HaS04, a white precipitate: Presence of Pb. The presence of Pb should be confirm- ed by adding to a part of the original solution AmHO in excess, then IIA in excess, then K2Cr04: a yellow precipitate shows presence of Pb. 2. The precipitate is yellow: it may consist of CdS, SnS2. Boil the precipitate with NaHO in excess, after decanting the liquid if possible : 'he precipitate does not dissolve: it is bright yellow and pulverulent; ; Presence of Cd. The presence of d may be con- rmed by showing iat the precipitate rod need by I f._»S issolves on being ■led with dilute l«so4. The precipitate dissolves: it may consist of AsaS3 or SnS2 ; examine por- tions of the original solution as directed below: Acidify a portion with HC1, and place in it a piece of Zn resting on a piece of platinum foil; Sn is deposited on the Zu: Presence of Sri1' (Stannicum). The deposit of Sn should be detached from the Zn, and dissolved by boiling it in a test-tube with a little strong HC1, then HgCl2 added ; a white precipitate confirms the presence of Sri"- Acidify a portion with strong HC1, immerse in it some pieces of bright Cu and boil'; a black film is de- posited on the Cu : Presence of As. Note.—If the yellow pre- cipitate formed by II2S ap- peared at once in the cold, the As is present as Arseno- snm; if it formed only on boiling, Arsenicum is present. 3. The precipitate is orange-red: it may consist of Sb2S3. Confirm by acidifying a portion of the original solution with HOI, and immersing in it a ece of Zu resting on a slip of platinum foil ; a black stain on the platinum (133): Presence of Sb. Note.—It occasionally happens, if the solution has not been sufficiently diluted, that. II9S ves a reddish precipitate with Pb solution; such a precipitate, however, becomes black on Iding more ll^S-water. 204 IRON GROUP—ZINC GROUP. [346, 347. 346. TABLE III a.—IRON GROUP. The color of the precipitate produced by addition of AmCl and AmHO will usually indicate whether it con- tains Fe, Al, Cr; the following tests may be made in confirmation. To a portion of the original solution add KIIO gradu- ally until a precipitate has formed (see note below table), then add KHO in excess and stir well, one of the follow- ing results will be obtained: 1. A colorless ge- 2. A pale-green 3. A reddish- 4. A dingy green latinous preeipi- gelatinous pre- brown preeipi- precipitate tate is produced, cipitate forms, tate forms, insol- forms, insoluble which dissolves which dissolves tible in excess in excess of in excess of KHO in excess of of KHO. Add KHO; the pre- to a colorless so- K H O to a green KCyS to the cipitate if filter- Iution: the pre- solution ; when original HC1 ed off and ex- cipitate reap- Pb02is added to solution, a blood- posed to the air pears on gradual this green solu- red coloration: gradually be- addition of HC1 to the KHO solu- tion : Presence of Al. tion and the liquid is boiled and then acidi- fied with HA, a yellow precipi- tate is pro- duced : Presence of Cr. Presence of Fe'". comes brown: Presence of Fe”. Note.—If a colorless gelatinous precipitate has been produced by AmCl and AmHO, and is not produced by addition of KHO, a sili- cate is probably present. Its presence is confirmed bv fusing the solid substance in a bead of NaAmHP04 (293); or by evaporating the acid solution to dryness, a residue insoluble in acid is Si02, and may be tested by the bead as directed above. 347. TABLE III b.—ZINC GROUP. The color of the precipitate produced by addition of Am2S or of H2S to the alkaline solution will distinguish Zn or Mn from Ni, Co, and Fe, and will usually distinguish Zn and Mn also from one another. See a and b below: a. If the precipitate is light in color, add to some of the original solution KHO gradually until a precipitate forms, then add KHO in excess. A white precipitate, dissolving in excess of KHO and repre- 348,349. EXAMINATION FOR ACID-RADICLE. cipitated by addition ofllaS proves presence of Zn. A white or brownish precipitate, insoluble in excess of KIIO and gradually turning dark brown when filtered off and exposed to the air shows presence of Mn. b. If the precipitate is black it will consist of either CoS or NiS or possibly of FeS ; the distinction of the metals Ni and Co by the color of their solutions—Ni being green, Co pink—and by the colors they impart to the borax bead is quite simple. FeS is only precipitated here from a dilute solution of a ferrous salt; Fe// is best detected by (346). 348. TABLE IV.—BARIUM GROUP. Dip a loop of platinum wire into the original solution or into the HC1 solution of the precipitate produced by Am2COs, and hold the wire in the Bunsen flame. If the flame coloration thus obtained is not decisive, employ the tests placed at the foot of each column as confirmatory : A yellowish-green flame : Presence of Ba. Confirmatory.-Add CaS04 to a perfectly cold por- tion of the IICl solu- i ion; a precipitate forms immediately. Note.—A brilliant green coloration may be pro- duced by II3HO3. A crimson flame, appear- ing deep red through the indigo-prism : Presence of Sr. Confirmatory-AAA CaS04 to a perfectly cold por- tion of the HC1 solu- tion ; no precipitate is produced, but a pre- cipitate appears im- mediately on boiling. A red flame, appearing dingy-green through the indigo-prism: Presence of Ca. Confirmatory.-AAA CaS04 to part of the HOI solu- tion and hoil; no pre- cipitate. To the rest add AmHO in excess, and AinsCsO,; a white precipitate forms. EXAMINATION FOR THE ACID-RADICLE. 349. If the acid-radicle has not been found already in the preliminary examinations (335-338 a), or during the examination for the metal (341, 343) or elsewhere, it must be tested for as directed below. Since the'solu- bility of the substance (332) and the metal it contains are known, much trouble is usually saved by referring to the “Table of Solubilities” (455-458). Thus a salt of the metal found, which is insoluble in water, cannot be present if the substance is soluble in water or is a neu- tral liquid ; and an insoluble salt cannot be present in an acid solution or in a substance which is soluble in acids. 206 EXAMINATION OF A SUBSTANCE [350,351. For the tests given below, use separate portions of the original substance; try the tests in succession until an acid-radicle is found. 350. Acidify a portion of the liquid, or if a solid dis- solve it, with dilute HC1 and add BaCl2. It Pb, Hg', or Ag has been found acidify with HNOs and add Ba(N03)2, since HC1 and chlorides would precipitate the above metals as chlorides. A white precipitate forms which does not disappear on boiling : Presence of a sulphate. 351. Acidify a portion of the liquid, or if a solid is being examined dissolve the solid with dilute IIN03; filter off any precipitate or residue which may form, and add AgNO:i solution ; a precipitate forms, which does not disappear on warming. Note the color of the precipitate ; and according as it is white, yellow, or orange, examine it by 1, 2, or 3: 1. The precipitate is white; it may consist of AgCl, AgCy, Ag4FeC.ve, or AgCyS. Make a portion of the original solution just acid with IIC1, then add Fe2ClB: A deep-blue precipitate: Presence of aferrocydnide. A blood-red coloration : Presence of a sulphocyanide. If Fe2Cl6 has yielded neither a precipitate nor coloration, indicating absence of a ferro-and sulphocyanide, decant the liquid from the precipitate caused by AgNOa, pour upon the precipitate some strong HXOa and boil. The precipitate remains undissolved: Presence of a chloride. The precipitate dissolves: Presence of a cyanide. Confirm the presence of a cyanide in a portion of the original solution by boiling it with FeS04, Fe2018, and KHO, and acidifying with HC1; a blue precipitate: Presence of a cyanide. 2. The precipitate is yellow, and may consist of AgBr or Agl. Test some of the original solution for an iodide by adding to it starch solution and KN02 solution, then acidifying (if not acid) with HC1; a deep-blue coloration: Presence of an iodide. If an iodide is not thus detected, add to another por- tion of the original solution several drops of Cl- water; if the liquid becomes yellow, and on being shaken with CS2 colors that liquid reddish-brown, • it shows: Presence of a bromide. 3. Orange-red precip- itate. Make a portion of the original solu- tion just acid with HC1, then add FeS04 solution; a deep-blue precipi- tate shows: Presence of a ferro- cyanide. 352-355. FOR THE ACID-RADICLE. 207 Note.—If Hg lias been found, HgCy2 may be present, notwithstand- ing the formation of no precipitate with AgN03. If not already de- tected in (333, I), refer to (306, Note 2, p. 180). 352. Acidify some of the original liquid, or if it is a solid dissolve it with dilute HN03; filter if necessary, add a small quantity of this acid solution to some AmHMo04 solution, stir well and warm gently: A yelloiv precipitate shows: Presence of a phosphate. If no precipitate forms heat to boiling; the formation of a yel- ’ low precipitate shows: Presence of an arsenate. The presence of a phosphate or arsenate may be confirmed by dis- solving the yellow precipitate, separated by filtration or decantation, by pouring upon it a little AmHO ; on adding to this solution AmCl and MgS04, a crystalline precipitate will form, which is to be filtered off and washed with a little cold water: several drops of AgN03 solu- tion are poured upon this precipitate on the filter; if it becomes yel- low a phosphate is present, if brown an arsenate is present. The pres- ence of an arsenate is further confirmed by a yellow precipitate (AS2S3) appearing with H2S when the liquor is boiled. 353. Acidify a portion of the original liquid, or if a solid stir it with HC1; dip into this solution a piece of turmeric-paper, and dry the paper at a gentle heat; if the paper becomes reddish-brown when dry, and changes to dingy green or blue-black when moistened with AmliO, the presence of a borate is shown. 354. The acid-radicles, one of which may still be pres- ent, are ;/T, and 'F. If the metal found belongs to Groups I, II, III, or IV, the examination for one of these radicles must be begun at (356); if the metal pres- ent is K, Na or NII4 examine by (355). 355. Make the solution just alkaline with AmHO, then add Ca012 solution in some quantity, shake well and let stand if no precipitate forms at once: the pre- liminary examination (337) will usually have indicated which of these acid-radicles is present, and thus show EXAMINATION FOR THE ACID-RADICLE. [356. according to which of the three columns below the precipi- tate is to be further tested : I. A crystalline precipitate, ap- II. A while pulverulent pre- III. A gelatinous floe- pearing after some lime, shows cipitate shows probable culent precipitate probable presence of a tartrate. Confirm by 1 or 2 below : presence of an oxalate. shows probabl z pres- ence of a fluoride. 1. Decant the liquid from the The presence of an oxalate, Confirm by filtering precipitate, add a little water already indicated by the and warming some and a single drop of AniHO, test in (337, 5), must be of the precipitate, drop in a small crystal of confirmed either by warm- or of the substance AgN03 and warm very care- ing some of the original if solid, in a small fully; a mirror is formed substance with MnO, and cup of lead or plat- below the crystal, presence of II»S04, and testing for ilium with strong a tartrate. This test may be COo-gas (319); or by the HjSO,; fumes will be evolved which tried also with the original more tedious method of solution by (322). filtering off and drying etch a'properly pre- 2. On acidifying some of the some ot the above preeip- pared watch-glass neutral original solution with it ate of CaOoOj, then (296). HA and adding alcohol and igniting it and testing KA (unless K or NH4 has for a carbonate with HC1 (318 a). been detected in the sub- stance), and stirring or shak- ing well, the formation of a crystalline precipitate shows presence of a tartrate. 356. An oxalate or fluoride of Ba, Sr, Ca or Mg will have been already detected. A tartrate of any one of these metals is found by gently heating the finely pow- dered substance if it is solid, or the neutral solution if a liquid, with very dilute AmHO and a crystal of AgNO,: the formation of a mirror shows 'presence of a tartrate. If a metal of Groups I, II, or III has been found, the metal must be separated before testing for the acid- radicle. If the metal belongs to Group I or II, make the original solution just acid with HC1, and add H2S solu- tion or pass II2S (500 a) into the liquid for about five minutes; filter off the precipitate and add more II2S to the filtrate; if no more precipitate forms,1 boil in a por- celain dish until the liquid ceases to smell of H2S, and examine by (355). 1 If any further precipitate forms add more of the reagent, filter, and test again by adding more of the reagent; this addition of re- agent, filtration, and testing the filtrate is repeated until no further precipitate forms on addition of the reagent to the filtrate. 357, 358.] EXAMINATION OF GROUP III A. If the metal belongs to Group III add AmCl, AmHO till alkaline, then Am2S: boil and filter, add to the fil- trate Am.jS if no more precipitate forms (see footnote, page 208), add HA in excess, boil, filter off S if neces- sary, and examine by (355). Note.—If no acid-radicle can be found in any quan- tity and the substance is not metallic in appearance, it is probably an oxide or a sulphide; most sulphides yield a sulphate or sulphuric acid when boiled with strong HN03, which may be detected after dilution by (350); an oxide may often be known by its color (see footnote, page 190) or by some other special property or test, e. g., Mn02 by evolving Cl when heated with HC1, Pb304 by leaving brown Pb02 when treated with dilute HN03. EXAMINATION OF GROUP III a. 357. The precipitate formed by addition of AmCl and AmHO to the solution of a substance insoluble in water may consist of Al2Ho6, Fe2Ho6, Cr2Ho6; or of Fe, Al, Cr, Zn, Mn, Ni, Co, Ba, Sr, Ca, Mg as phosphate or oxalate; or of Ba, Sr, Ca as chromate or fluoride. The systematic examination of a precipitate in Group III A for these substances is a difficult matter; such an exam- ination is, however, only necessary when an oxalate (337, 5), a chromate (343), or a fluoride (338) have been already detected, or when a phosphate is found. If a precipitate forms in Group III A, and the above acid- radicles are absent, proceed as directed in (346); if the above acid-radicles are present, the metal, unless cer- tainly detected during the preliminary examination, must be tested for as directed below. 358. Note the appearance of the precipitate caused by AmCl and AmHO, then add Am2S to the liquid and precipitate, stir well, and note again the appearance of the precipitate: examine further by 1 or 2 (page 210). 210 EXAMINATION OP A SIMPLE SUBSTANCE. [358. 1. The precipitate after addition of Am.JS is black; it may consist of FeS, CoS, or NiS; the means of distinguish- ing these three metals is given below. Note first the color of the original solution (334, 1). The color of the original b. The color of c. The color of the original solution was solution was yellow the original green: Presence of Ni or Fe". or reddish-brown: solution teas Presence of Fe'". pink, or pos- Note the effect which was produced by (Ferricum.) sibly blue, be- the ad lition of ArnCl and AmHO: coming pink This is confirmed by on dilution: the precipitate pro- Presence of Co. A blue solution was A dingy-green pre- duced by ArnCl and produced : cipitate, which, AmHO in the origi- The presence Presence of Ni. when shaken mil solution having of Co may be been pale-yellow or confirmed by The presence of celain dish and reddish-brown, and adding ex- Ni may be con- left for several becoming black on cess of KHO firmed*bv adding minutes exposed addition of Am9S. to the origi- to the air, be- As a confirmatory nal solution ; to a part of the comes brown : test add to a portion a blue precip- of the original solu- itate turning a light-green pre- (Ferrosum.) tion, acidified with red on boil- cipitate shows the HC1 if necessary, a ing shows the presence of Ni. Confirm by adding few drops of KCyS presence of Co. solution ; a blood-red Ni will also have ot the original coloration is pro- Co will also been detected by solution, acidi- duct'd. have been its borax bead detected by (333, IV). if necessary; a bead (333, cipitate is pro- IV). duced. 2. The precipitate, after addition of Am.fi, is white or light-colored.—It may consist of Cr2Ho6, A1„H06, ZnS, MnS; [or of BaCr04, or Ba, Sr, Ca, Mg, as phosphate, oxalate, fluoride, silicate, or possibly borate.] The substances in brackets can, however, only be present if the liquid given for analysis was acid in reac- tion, or if a solid was given which was insoluble in water. To a small portion of the original solution add KIIO drop by drop until a precipitate is produced. (See note below the table.) Note the color and ap- pearance of this precipitate, then add a larger quantity of KHO and stir or shake well; one of the following results (a or 6) will be noticed: 358. PHOSPHATE, ETC., IN GROUP III A. 211 a. The precipitate at first produced by KIIO redissolves when the KHO is added in larger quantity ; indicating the presence of Al, Zn, or Cr. Note the appearance of the precipitate: A pale-green flocculent precipi- A while precipi- 'A white flocculent precipitate, not late: tnte, which is re- reprecipitated from the KHO Presence of Or. precip Hated from the KHO solu- solution by addition of a few drops of H2S-water or by boil- Confirm bv boiling some of the tion, by addi- ing, but reprecipitated immedi- green KIIO solution with lead- tion of a few atelv if sufficient AtnCl solu- peroxide (I’b< V); a yellow liquid drops of HoS- tion is added : is obtained, which, if decanted, yields a vellow precipitate on water, but is not repreeipi- Presence of Al (see note). addition of HA in excess. tated by addi- tion of AmCl: Note.—A1P04 is precipitated here aho, and is soluble in KIIO, The color of the solution and of Presence of Zn. but differs from AI2Ho6 in being reprecipitated from the KHO detected Cr. Confirmed by no precipitate hav- solution by addition of excess of HA ; if P04 has beeu detected Note.—If the Or was present as ing been pro- the analysis is finished. A1P04 a chromate, AmCl and Am MO duced by AmCl is soluble onlv in acids, hence will have Yielded no precipitate ; and AihHO, but the original liquid must have but there will have been a green been acid or the original solid precipitate on addition of Am,S and heating. itate by addi- tion of AnioS, or of H2S after A m 110. substance insoluble in water. Note.—Sometimes a flocculent precipitate is produced on adding AmCl and Am HO to the original solution, and yet no precipitate is produced byKHO; this renders probable the presence of an alka- line silicate. In this case evaporate a portion of the solution to dryness with HC1; warm the residue with HC1: if any insoluble residue is left, the presence of a silicate is proved ; filter and test the filtrate for K or Na. b. The precipitate at first produced by KHO does not re- dissolve on addition of more KHO; the precipitate will have one of the following appearances : A white or divgy-yellow pre- cipitate, rapidly darkening when shaken in the air: Presence of Mn. Confirmed in the prelimi- nary examination by pro- ducing a green mass when fused with Na2C03 and KNOa, and by no precipi- tate having been produced on addition of AniCI and AmHO, unless the solution was exposed for some time to the air. A pale-yellow precipitate, not darkening in the air: this precipitate will also have been produced by AmCl and AmHO and its color will not have been altered by addition of Am2S: Presence of BaCrOi. Ba has been already con- firmed by the flame colora- tion (333, II), and a chro- mate by the change of color of the orange-red liquid to green on adding H2S (343). A white precipitate, not dark- ening in the air: Presence 0" Ba, Sr, Ca, or Mg as phosphate, oxalate, Pass on to (359). Note.—This precipitate can only be formed if theorigi- narsolution was acid. EXAMINATION OF A PHOSPHATE. [359,360. 359. The precipitate may consist of Ba, Sr, Ca, or Mg as phosphate, oxalate, borate,1 fluoride, or silicate. Examine for the metal and acid-radiele as directed below, working through the columns from left to right, unless the presence of a phosphate (339), oxalate (333, I, 4, or 337, 5), borate (334, V, or 333, II, or 338 a), or fluoride (338) has been already proved, in which case proceed at once to examine according to (3G0), or by column 1, or 2, or 3 below. If this precipitate is proved to contain a phosphate, oxalate, borate, fluoride, or silicate, the further examina- tion for an acid-radicle becomes unnecessary. 1. Add AmHO in 2. Stir some of 3. Place another 4. If phosphate, ox- excess to a por- the precipitate portion of the alate, borate and tion of the origi- produced by precipitate pro- fluoride have nal solution,2 fil- AmHO,2 column duced byAmllO,2 been prov d to ter, dry the pre- 1, on a watch- glass,with a little column 1, in a be absent, sili- cipitate and heat leaden cup or cate is probably a portion of it to water to which platinum cruei- present. a dull red heat a few drops of ble, add strong for several min- IT Cl have been IIoSO, and warm Test for it utes on plati- added, until the geutlv, covering par. 361 num foil. precipitate isdis- the vessel with Place the foil in solved. Hip into a watch-glass, a test-tube and the liquid a slip which has been pour a few drops of turmeric-pa- coated with a of dilute HC1 per, and dry at film of wax and upon it; if the steam heat; the has had charac- residue dissolves slip appears red- ters traced with with efferves- cence, it shows th e presence of an dish-brown, and becomes dingy a sharp point through the wax green when (296); the glass oxalate. moistened with is etched ; Test this HC1 so- lution for Ba, Sr, AmHO: Presence of a borate. Presence of a fluoride. Ca, Mg, by (339f, using it as the original solu- tion. If the ignited pre- Examine for the metal present by (361). Examine for the metal present by (361). cipitate does not dissolve with ef- If a borate is not If no fluoride is fervescenee, pass found, proceed found, proceed on to column 2. to column 3. to column 4. 360. Examination of a Phosphate—Explanation of Method— In order to detect Ba, Sr, Ca, or Mg present as phosphates the IJ04 1 Borates of Ba, Sr, and Ca, are rarely precipitated in Group III, since they are soluble in the AmCl formed on adding AmHO to the HC1 solution. 2 If a solid is being examined, a portion of the original solid is employed for this test, instead of the precipitate produced by AmHO in the IIC1 solution. 36i.; EXAMINATION FOR PHOSPHATES, ETC. 213 must be removed from the solution and the metal left as chloride. This is effected by neutralizing all HC1 and leaving the solution acidified only by free HA ; by gradual addition of Fe2Cl6 and boiling all P04 is precipitated as FePOt, which, though soluble in HC1, is perfectly insoluble in HA. On filtering, FeP04 remains upon the filter, and the filtrate contains the metal (Ba, Sr, Ca, or Mg) as chlo- ride, and is perfectly free from phosphate. Method.—Add to a portion of the cold original solu- tion AmHO drop by drop, whilst constantly shaking the liquid, until a slight precipitate is formed which does not disappear by shaking; then add HA and NaA solution, and drop in Fe2Cl6 until the liquid, after being well shaken, has a brown or red color; boil and filter im- mediately. The precipitate is thrown away. To the fil- trate AmCl is added, then AmHO until it is just in excess, boil and filter; the liquid or filtrate, which must smell strongly of NH3, is then tested for Ba, Sr, Ca, and Mg by (339), this liquid taking the place of the original solution. If any precipitate is formed by it must be wrell washed several times with boiling water to remove Na, since else the intense yellow coloration of Na would mask that ofBa, Sr, or Ca. 361. A portion of the original substance is placed in an evaporating basin, which is then nearly filled with dilute HC1, and the liquid is entirely boiled away; the dish is once more filled with acid, and again evaporated to dryness; the residue in the dish is then warmed with dilute HC1, and filtered if any residue is left: Solution: the HC1 solution is examined Residue: if any resi- for Ba, Sr, Ca, Mg bv (339), this so- due remains in- lution being treated as is there di- soluble in IIC1, it rected for the original solution. proves: Presence of a silicate. The evaporation to dryness with HC1 removes H3BO3 and IIF, which volatilize, whilst Si02 is left insoluble in HC1, and therefore remains as an insoluble powder on afterwards warming with HC1; tli is residue of SiC>2 also remains, however, if HF was present, being caused by the corrosion of the dish; since, however, HF if present has already been found, no notice will then be taken of the residue. 214 ANALYSIS OF A SIMPLE SUBSTANCE. '366. THE SUBSTANCE POSSESSES METALLIC LUSTRE. 366. This shows the probable absence of an acid- radicle. The only non-metallic elements likely to be present are free carbon as graphite, free iodine, or com- bined sulphur, since several sulphides are decidedly me- tallic in appearance.1 The presence of the metals Ni, Co, Ee in the free state, and of Fe304, may be shown by the substance being attracted by a magnet. Pb, or graphite, will be recognized by marking paper when rubbed upon it, as a black-lead pencil does; the mark due to Pb dis- appears if wetted with dilute HNOs. Preliminary Examination. Experiment. Observation. Inference. I. Heat a portion of the substance in a small ig- nition-tube (10). 1. A black lustrous mirror forms, 2. A yellow sublimate forms, melting, when heated, to brown drops,. 3. Violet vapor is given off, condens- ing to black scales on the sides of the tube, If the substance sublimes entirely in violet vapors Presence of As. Presence of S. Presence of I. Iodine alone is present. II. Heat a portion in the inner blowpipe flame in a cavity scooped on a piece of wood- charcoal. 1. Smell of garlic, 2. If an incrustation forms, refer to par.(333,V),where in the second and third column will be found the ap- pearance of the incrustation and the metal whose presence it indicates. 3. Smell of burning sulphur, 4. A green flame coloration, Presence of As. Presence of S, Presence of Cu. III. Place a por- tion of the sub- stance in a piece of hard glass tube open at both ends, and heat it strongly in the Bunsen flame, and afterwards in the blowpipe flame if neces- sary. 1. A gas is evolved from the upper end which smells of burning sul- phur and turns a piece of filter- paper moistened with K,/>o01 solu- tion green, . . . .* . 2. The substance burns completely but slowly away, glowing when strongly heated.' This effect is best seen by heating it strongly on Pt- foil by directing the blowpipe flame on the under surface of the foil, Presence of S. Presence of C. 1 The most common sulphides which possess metallic lustre are “ copper pyrites” and “ iron pyrites,” which resemble brass in ap- pearance ; and “ galena,” resembling lead. 367, 368/ INSOLUBLE SUBSTANCES. 215 After completing the preliminary examination proceed as directed under (332). No acid-radicle need be tested for except S; a portion of the substance is dissolved in strong IINO„ and after diluting with water II2S04 is tested for by BaCl2; if a white precipitate forms insoluble on boiling, it confirms the 'presence of S. THE SUBSTANCE IS INSOLUBLE BOTH IN WATER AND IN ACIDS. 367. It may consist of any one of the following sub- stances, those included in brackets being less likely to occur than the others, since they are soluble in sufficient water or.acid on heating. As will be seen below the color serves to give some notion as to what substance is present. 1. White: BaS04, SrS04, (CaS04b PbS04, (PbCl)2, AgCl,1 Si02, (Al2Os ignited), Sn02, Sb2Os, Sb204, CaE2. 2. Bark-colored: ignited Fe203 (dark-brown or black), ignited Cr20:i (dark green), FeCr,04, and ignited PbCr04 (dark brown), C (black). 3. Yellow : S, AgBr,1 Agl,1 (Pbl2). An insoluble silicate may also be present. For a fuller description of these substances see (475). According to the color of the substance examine it by (368 or 369). 368. The substance is white. If sufficient substance is at hand try the following preliminary tests, if not, pro- ceed at once to (368 a). Pour upon a small portion a drop of Am2Sif it blackens the presence of Pb or Ag is probable, if it becomes yellow or orange-red the presence of Sn or Sb is probable; pass to Test III in the follow- ing table. If no change of color is produced by Am2S, try Tests I and II. 1 Darkens quickly in sunlight, and slowly in ordinary daylight. ANALYSIS OF A SIMPLE SUBSTANCE. [368. 216 Experiment. Observation. Inference. I. Moisten a clean loop of platinum wire, im- merse it in the powdered substance, and heat the A yellowish-green flame. Presence of Ba. Test for adhering powder for a short time strongly in the inner blowpipe flame; moisten the loop A crimson flame, appear- Presence of Sr. [ SO, by ing deep red through the indigo-prism. Presence of Ca. Exp. II. with a drop of strong HC1, and hold it in the Bunsen flame. A reddish flame, appear- ing dusky green through the indigo-prism. IT. Fuse a portion of the substance, mixed with The cooled mass, if de- Presence of a sulphate. tached from the char- Note.—If S()4 is not Na»C03in fine powder, coal, placid upon a found, test for r by (338 in a cavity scooped upon bright silver coin, and or 296), or examine the a piece of wood-char- coal, in the inner blow- pipe flame, produced from a spirit-lamp flame. moistened with water, gives, when crushed with the blade of a knife, a black stain. substance by (368 a). III. Mix some of the White metallic malleable Presence of Pb as chloride, finely powdered sub- globules, which mark sulphate, or chromate. stance with powdered paper, and if dissolved Refer to the note below Na20O3and KCy, on a small cavity made in a piece of wood-charcoal, and heat the mixture in the inner blowpipe flame. If metallic globules form, detach one and strike it smartly with the pestle on the inverted mortar. Also take a globule on in HN03 give a white precipitate with HaS04; a yellow incrustation is also formed on the charcoal. White metallic malleable globules which do not mark paper; they dis- solve in HC1. the solu- tion giving a white pre- cipitate with HgCl2- tins table. the point of a penknife and try if it marks pa- per as black lead does. White metallic brittle globules, which if dis- solved in boiling HC1, give an orange-red pre- cipitate with H2S: white incrustation. Presence of SnO 2* White scales, no incrus- tation : the metal is insoluble in IICl, and if dissolved in HN03gives no precipitate with H2S04 but a white pre- cipitate with IIC1; the original subslance is instantly blackened by a drop of AmsS, and is Presence of Sb»0 or Sb«Ov dissolved on being warmed with AmHO. Presence of AgCl. [See also (368 a).] Note.—Boil some of the substance with much water, add HNO3 and AgNO.s; a white precipitate shows presence of PbCI2- Test for chromate by fusing in a porcelain crucible with Na2C03 -j- K2CO3; a yellow mass on cooling shows presence of PbCrOi. The presence of PbSCh may be proved by Test II, and by pouring upon the original substance HA, then excess of AmHO, and boiling; 368 a." ANALYSIS OF INSOLUBLE SUBSTANCES. 217 the substance will dissolve; acidify a portion of the solution with IIA, and add K2Cr04; a yellow precipitate : Presence of Pb. Acidify an- other portion with IIC1, and add BaCl2; a white precipitate insoluble on boiling: Presence of SO4. If none of the substances mentioned in the above table have been detected, test for Ab03 by heating the sub- stance strongly on charcoal in the outer blowpipe flame after moistening it with Co(N03)2 solution; a blue mass shows presence of Al2Or If A1203 is not found fuse some of the substance in a clear bead of NaAmHPCh; it floats undissolved: Pres- ence of Si02, or a silicate. Proceed to (368 a). 368 a. Fuse a portion of the finely powdered sub- stance, mixed with two or three times as much fusion mixture, for several minutes on a piece of platinum foil (or if Pb or Ag is present, in a porcelain crucible) in the blowpipe flame; boil the cool mass with water, filter and wash the residue. Examination of the TJndissolved Residue.—Heat the residue with dilute HN03; if it is not dissolved in a short time, decant and keep the HN03, and heat the residue with a small quantity of dilute HNOa and HC1 mixed ; if the residue is still undissolved it has been insufficiently fused. The acid solution is then examined for the metal by (339). Examination of the Water Solution.—When the metal present has been detected, it will usually be possible to limit the number of acid-radicles which need be tested for by referring to the list in (367). Tests are given be- low for all acid-radicles likely to occur in insoluble sub- stances. Separate portions of the water solution are to be used. Sulphate: acidify a portion with HC1 and add BaCh; a white precipitate. Chloride: acidify a portion with HN03 and add AgNOs, a white precipitate easily soluble in AmHO. If the precipitate has a yellow tinge and is not easily soluble in Am HO, add to a fresh portion of the water solution dilute Cl-water drop by drop, shaking well between each 218 ANALYSIS OF A SIMPLE SUBSTANCE. [369. addition; a brown coloration of the CS2 shows a bromide, a violet coloration an iodide. Silicate: make a portion acid with IIC1 and evapo- rate to perfect dryness; if on warming with dilute 1101 an insoluble residue is left, this proves the presence of silica or a silicate. Fluoride: acidify with HA and add CaCk; a gelatin- ous white precipitate forms. Confirm by tests (338 or 296) tried on some of the original substance. 369. The substance is dark-colored. (See 367, 2.) Place some of the substance on a piece of platinum foil and heat the foil strongly on its under surface by the blowpipe flame: The, substance burns away The, substance does not burn away; place upon it slowly but completely: three or four times as much powdered Na2C03 Presence of C. and KXOj, and fuse for some time: 1. The substance dissolves, forming a yellow mass when cold : Presence of O20*. 2. The substance remains undissolved as a dark- brown powder, and the mass on cooling is white: Presence of Fe^03.' Confirm by boil- ing the mass with water, filtering and fusing the brown residue into a borax bead (100). The substance is yellow (367, 3). Heat a portion of it strongly in a small ignition-tube; one of the following results will occur: It fuses and sublimes, the subli- It fuses but does not sublime mate being yellow and melt- Examine a portion of the sub- ing to reddish-brown drops stance for Ag and Pb and for when heated: Hr and I by (368 a). Presence of S. Note.—If the substance sublimes en- tirely it consists only of sulphur. 1 FeCr204 shows both reactions 1 and 2, since it contains Loth Fe and (Jr. EXAMPLES OF ENTRY. ANALYSES OF SIMPLE SALTS, SHOWING HOW TO ENTER RESULTS. A. Liquid given for analysis. Preliminary Examination for the Metal. Experiment. Observation. Inference. 1. Noted the color of the liquid. Blue. Presence of Cu. 2. Dipped into it a piece of blue litmus-paper. The paper was turned red, hut on addition of no etferves- ceuce occurred. Presence of a salt with acid reaction. 3. Evaporated a few drops slowly upon a watch-glass. Ignited the residue strongly. Pale-blue residue left. Blackened without smell of burning. Presence of some dis- solved solid. Absence of organic acid- radicles. 4. Added KHO solution and boiled. No smell of Nil,. Absence of NH4. 5. Dipped a loop of plat- inum wire into the solution and held it in the flame. 6. Dipped a clear borax bead into a portion of theresiduefrom 3.and fused in the ou' er a nd inner blowpipe flames. Bright green flame; on moistening the wire with strong HC1 and again boiling it in the flame it gave a blue coloiation. In outer flame the bead") was green whilst hot, blue when cold. [ In inner flame it be- | came colorless. Presence of Cu. Presence of Cu. Preliminary Examination for the Acid-radicle. Experiment. Observation. Inference. 1. Added dilute IIaS04 No gas was evolved. Absence of carbonate, and warmed. sulphite, sulphide, and nitrite. 2. Added strong H2S04 No gas was evolved. Absence of chlorate. and warmed. And no red fumes on adding Cu clippings. Absence of nitrate. 220 EXAMPLES OP ENTRY Examination for the Metal. To a portion of the liquid added 1IC1: No precipitate. Absence of Group I. Added strong H2S-water: A brownish-black precipitate. Presence of Sn", Hg" Bi, Pb, or Cu. Allowed the precipitate to settle, poured off' as much of the liquid as possible, and boiled the precipitate with excess of JiallO ; it remained undissolved. Since the original solution was blue, a clean knife-blade was dipped into a portion of it acidified with II2S04; red copper was deposited on the steel: Presence of Cu. Examination for the Acid-radicle. Added HC1 and BaCh; a white precipitate was pro- duced which did not disappear on boiling: Presence of Sulphate. t-t 7 /—. r> 1 Lound wu. Sot. B. Liquid given for analysis. Preliminary Examination for the Metal. Experiment. Observation. Inference. i. Noted the color of the liquid. Light yellow. Presence of a neutral chromate. 2. Dipped red litmus- paper into the liquid. It was turned faintly blue. Probable presence of an alkali-salt. 3. Evaporated a few drops to dryness upon a watch-glass. Ignited the residue strongly. A yellow residue re- mained. No blackening. Presence of some dis- solved solid. Absence of organic acid- radicle. 4. Boiled a portion with excess of KHO. No smell of NIT,. Absence of NH«. 5. Dipped a loop of plat- inum wire into the solution, and held it in the Bunsen flame. A pale-violet flame, ap- pearing crimson through the indigo- prism. Presence of K. 6. Dipped a clear borax bead into the residue from 3, and fused iu the outer and inner blowpipe flames. Outer flame: brown,' hot; green, cold. Inner flame: green, hot and cold. Brown color not reappear- ing in the outer flame. Presence of Cr as a chromate. OF A SIMPLE ANALYSIS. 221 Examination for the Metal. Since the liquid was alkaline in reaction, added to a small portion of it a few drops of HN03 until it became acid; this produced no precipitate. To another portion added HC1; the liquid turned from yellow to orange-red, indicating presence of a neutral chromate: No precipitate Absence of Group I. Then added IT2S-watfr and wanned: The liquid be- came green, and white S was de- posited : Presence of a chromate. To another portion of the original solution added AmCl, then AmHO; no precipitate formed: then added Am2S and boiled: No precipitate in the cold, but on boiling a green floccnlent precipitate gra- dually formed, evidently consisting of Cr2Ho6 re- duced from the chromate. Added to another portion of the solution AtnCl, AmHO, and AmaC03: No precipitate. Absence of Group IV. Added to the same portion Na2HIJ04 and stirred : No precipitate. Absence of Mg. Since K was found by the flame coloration in the pre- liminary examination, its presence was confirmed by stirring a portion of the solution, to which a few drops of HC1 had been added, with PtCl4 on a watch-glass; a yellow crystalline precipitate forming on the lines rubbed by the rod : Presence of K. Found K, Cr()4. C. A white crystalline substance given for analysis. Boiled a small portion with water; it dissolved com- pletely. Preliminary Examination for the Metal. Experiment. Observation. Inference. t. Heated in small dry test-tube. 1. Dipped a loop of moistened plat- inum wire into the powdered substance, moistened with strong The substance gave off'red fumes and oxygen gas, which inflamed a glow- ing splinter of wood. It left a yellow residue. Presence of a nitrate of a heavy metal. Presence of Pb, Sn, or Bi. IIC1 and held in the Bunsen flame. A pale-blue flame. Presence of As, Sb, Pb. 5. Heated a small portion in a cavity Deflagration occurred. Presence of a nitrate or on wood-charcoal in the inner blow- pipe flame. Awhite malleable globule remained which easily marked paper. A yellow incrustation. chlorate. Presence of Pb. 4. Fused on charcoal in the inner blowpipe flame with Na2C03and KCy. Same result as with 3. Presence of Pb. 222 EXAMPLES OF ENTRY Examination for the Metal in Solution. Boiled a portion of the powdered substance with water, cooled, added HC1 to a part of the clear solution ; a white precipitate was formed, which disappeared on boiling, but appeared again in the crystalline form on cooling the liquid (probable presence of Pb). Confirmed the presence of Pb by decanting the liquid and boiling the precipitate with AmHO, it remained white and did not dissolve; decanted the ammoniacal liquid, dissolved the precipitate in a little HA, and added K2Cr04, a yellow precipitate: Presence of Pb. Since a nitrate was found in the preliminary examina- tion, its presence was confirmed by adding strong H.2S04 to the aqueous solution of the substance, and pouring solution of PeS04 carefully upon the cooled liquid in a test-tube; a brown ring formed on the surface of the acid : Presence of NO,t. Also some of the solution when heated with Cu and strong II2S04, evolved reddish-brown fumes: Presence of NOs. Found Pb, NOz. r>. A white powder, emitting no smell, given for analysis. Boiled some of the powdered substance with water, it did not dissolve: added a few drops of strong HC1 and boiled, the substance dissolved completely (absence of Group I) without effervescence. Preliminary Examination for the Metal. Experiment. Observation. Inference. 1. Heated in a small dry test-tube. No change. Absence of volatile and fusible substances and of water of crystalliza- tion, etc. 2. Dipped a moistened loop of plat- inum wire into the powdered sub- stance, moistened the powder with strong HC1, and held it in the Bun- sen flame. No flame coloration. Probable absence of K, Na, Ba, Sr, Ca, Cu, etc. 3. Heated a portion of the powder strongly on charcoal in the inner blowpipe flame. Thesubstance did not fuse A white luminous resi- due, which when moist- ened on red litmus- paper showed an alka- line reaction. Absence of alkali salt. Presence of Ba, Sr, Ca, Mg. OF A SIMPLE ANALYSIS. 223 Examination of the Solution. To a portion of the HC1 solution added H„S-water • no precipitate : Absence of Group II. To another portion of the HC1 solution added AmCl and Am HO in excess, a white flocculent precipitate: then added Am2S, the color of the precipitate was un- changed. To a few drops of the HC1 solution added IvHO drop by drop until a white flocculent precipitate formed, then added excess of KHO and boiled; the precipitate did not dissolve, and it did not become discolored in the air: Presence of Ba, Sr, Cu, Mg as phosphate, oxalate, etc. Added a few drops of the original HC1 solution to some AmIIMoOt solution in a test-tube, and warmed gently ; a yellow precipitate: Presence of POv To another portion of the cold HC1 solution added AmliO drop by drop until a precipitate formed which did not dissolve when shaken, then added HA and NaA solution until this precipitate dissolved when the liquid was well shaken. Fe2Cl6 was added until the liquid appeared red; it was then boiled and immediately filtered. To the filtrate Am HO was added in excess and the precipitate filtered off, then Am2COs was added; a white precipitate formed: Presence of Ba, Sr, or Ca. Filtered and dissolved the precipitate by pouring upon it a few drops of HC1; dipped a loop of platinum wire into the solution, and held it in the Bunsen flame; a red- dish flame appearing dingy green through the indigo- prism : Presence of Ca. A few drops of the solution boiled with CaS04 gave no precipitate: absence of Ba and Sr, therefore the pres- ence of Ca was confirmed by adding to the rest of the solution excess of AmHO, then Am2C204; a white pre- cipitate : Presence of Ca. Found Ca, POv E. A white odorless 'powder given for analysis. Boiled a portion of the substance with water, it did not dissolve: added IIC1 and heated again, it dissolved completely (absence of Group I) without effervescence. 224 EXAMPLES OF ENTRY Preliminary Examination. Experiment. Observation. Inference. 1. Heated a portion in a small dry test-tube. The substance blacken- ed slightly ; it evolved C02, which turned a drop of lime-water milky. The residue in the test-tube effer- vesced with HC1, whereas the original substance did not. Presence of an organic salt of K, Na, Ba, Sr Ca, or Mg. 2. Held a portion of the substance on a loop of platinum wire in tlie Bunsen flame; then moistened with HC1 and again held in the flame. A red coloration, appear- ing dusky green through the indigo- prism. Presence of Ca. 3. Heated on charcoal in inner blowpipe flame. A white luminous mass remained, which wThen moistened on red lit- mus-paper turned it blue. Presence of Ba, Sr, Ca, or Mg. Examination for the Metal. Added to a portion of tlie HC1 solution strong H2S- water. No precipitate: To another portion of the HC1 solution added Absence of AmCl, then AmHO in excess, a white precipi- Group 11. tateformed ; added Am2S, tlie color of the pre- cipitate remained unaltered. To another portion of the solution added KIIO drop by drop until a precipitate formed, then more KHO and boiled; a white precipitate in- soluble in KHO, and not darkening in the air : Presence of oxalate, phosphate, etc., of alkaline earths. Since the presence of an oxalate of an alkali- or alkaline earth-metal was indicated in the pre- liminary examination, a portion of the original substance was heated on platinum foil, then dissolved in HC1 (effervescence), and to the so- lotion excess of A ml 10 and of Am./Xte was added. The liquid was warmed and put aside till the precipitate subsided, then the liquid was decanted and the precipitate dissolved in a few drops of HC1. A platinum wire dipped into this IIC1 solution gave a red flame coloration, appearing dusky green through the indigo-prism: Presence of Ca. [Confirmed by another portion of this HC1 solution giving a white precipitate with excess of AmHO and Am2C204.] OF A SIMPLE ANALYSIS. 225 The presence of 02O4 was confirmed by heating some of the original substance with strong H2S04; gases were evolved which rendered milky a drop of lime-water, and burnt with a blue fiame, showing presence of C02 and CO : Presence of C.2Or Found Ca, C204. F. A yellow metallic-looking substance given for analysis. Preliminary Examination. Experiment. Observation. Inference. I Heated a portion of the substance strongly in a small tube closed at one end. A yellow sublimate formed which melted into brown drops; a smell of burning S was evolved, and a piece of paper dipped into K2Cr20*solution when placed in the mouth of the tube became green. A brown residue left Presence of S. Probable presence of Fe. 2. Heated strongly on charcoal in the inner blowpipe flame. Srong smell of burning S. The resit! lie fused into a dark-colored glo- bule, which when cold was strongly attracted by the magnet. Presence of S. Probable presence of Fe. 3. Heated a fragment strongly in a glass tube open at both ends, and held obliquely in the flame. A gas was evolved with a suffocating smell, and which turned K2Cr20i paper green. SOg from combust ion of S Solution, of Substance. Warmed the powdered substance with a mixture of strong HN03 and HOI, it dissolved completely; boiled down in an evaporating-dish, adding strong JIC1 several times; when nearly dry, diluted with water. Examination of the Solution for the Metal. Since the substance dissolved entirely in HC1, Group I is absent; to a portion of the solution added H2S- water: 226 EXAMPLES OF ENTRY The solution be- To another part of the solution added AmCl, came colorless, then excess of AmHO, a brown flocculent pre- and white S was cipitate formed, presence of Fe'" ; then added precipitated. Am2S, and heated ; the precipitate became Probable presence black, and on settling left a yellow solution : of a ferric salt. Absence of Ni. Confirmed the presence of Fe by adding to a fresh part of the original solution K4FeCy6solu- tion, a dark-bine precipitate: Presence of Fe'". Confirmed the presence of S by adding to a part of the original solution BaCl2; a white precipitate formed which did not disappear on boiling: Presence of SOi derived from oxidation of sulphur. Found Fe, S. G. A white powder given for analysis. Boiled a small portion with water, it did not dissolve. Boiled another portion with HC1, it did not dissolve: added HNOs and heated again, the substance was not dissolved. Hence the substance is insoluble in water and in acids, and, since it is white, it can only be BaS04, SrS04, (CaSOJ, PbS04, (PbCl), AgCl, Si02, Al2Os, Sn02, Sb2()„ or CaF2. Poured Am2S upon some of the substance, its color was unchanged ; probable absence of Pb, Ag, An, Sb. Preliminary Examination. Experiment. Observation. Inference. 1. Took some of the powder up with a loop of moist platinum wire, ignited it strongly in the inner blowpipe flame, moist- ened it with HC1, and held iu the Bun- sen flame. A yellowish-green color- ation. Presence of Ba. 2. Fused a portion with Na2C03on charcoal in the inner blowpipe flame, placed the cooled mass on a bright shill- ing, and moistened it with a drop of water. A black stain on the coin. Presence of S. OF A SIMPLE ANALYSIS. Examination of the Solution. Fused some of the powder with fusion mixture on platinum foil; boiled the cold mass with water, filtered. Filtrate, made acid with HC1 and added BaCl,; a white precipitate, which did not disappear on boiling the liquid : Presence of SOr The residue on the filter was well washed with boiling water, and boiling dilute HC1 poured upon it; it dissolved completely : Absence of Group I. To a portion added strong HoS-water and heated : No precipi- tate. Absence of Group II. To another portion added AmCl, then AmllO in ex- cess, then AnijS, and boiled: No precipi- tate. Absence of Group III. To another portion of the original solu- tion added AmCl, AmHO, and Am2C03: A white precipitate: Presence of Ba, Sr, or Ca. A platinum-wire loop dipped into the original solution gave a yellowish-green tint to the Bunsen flame: Presence of Ba. Found Ba, $04. SECTION VI. FULL ANALYTICAL COURSE AND TABLES. After having tried the reactions of the analytical groups and learned for each group how to detect its mem- bers occurring singly or two or more together, solutions containing a single member belonging to any of the groups, or members of two or more of these groups mixed, will readily be analyzed. 370.) It is necessary first to separate the metals present into groups by adding the group reagents successively in such an order that each precipitates its own group only, leaving in solution the members of all other groups which may be present. This is effected by adding the group reagents- in, the order directed in the general table (419); refer to this and to the group table on pp. 188, 189. HC1, which is the first reagent added, precipitates only Group I, leaving Groups II, III, IV, and V in solu- tion ; hence if a precipitate is obtained on adding excess of HC1, after filtering it off* any member or members of Group I present will be obtained upon the filter, whilst the members of all other groups remain in the filtrate. On passing H2S into the heated filtrate,1 members of Group II alone will be precipitated and may be filtered off; the filtrate,1 after removal of H2S and oxidation of any Fe present by boiling with IIN03, may be mixed with AmCl and excess of AmHO ; the AmHO will pre- cipitate any members of Group III a, Group III b, and Mg remaining dissolved by the AmCl; the addition of Am2S to the filtrate1 will separate Group III b as sul- phides. Group IY is precipitated from the filtrate1 by 1 Or solution, supposing no precipitate to have been obtained, and filtration therefore to have been unnecessary. 371,372.] ADDITION OF REAGENTS IN EXCESS. 229 the last group reagent Am2COs, and the filtrate1 is ex- amined for Group V, the members of which not being precipitated by any group reagent will now remain in solution if they were originally present. Since each group must be entirely precipitated by its own group reagent it is necessary, if any precipitate is formed, to add each group reagent in “ excess ” before proceeding to add the next; unless the presence of the reagent in excess is ascertained before proceeding, much confusion may be caused. 371. Addition of Reagents in Excess.—The most gen- eral method for ascertaining the presence of a reagent in excess is to add a few drops more of the reagent to the clear liquid obtained either by letting the precipitate settle or by filtering off a small quantity of it; if any further precipi- tate is formed the filtered portion must be returned, more of the reagent must be added, and the clear liquid again tried with a few additional drops of the reagent, this pro- cess being repeated until-no further precipitate is caused. In certain cases this method of proceeding is rendered unnecessary, the excess of a reagent being detectable by its smell after thoroughly mixing up the solution and blowing out the air above it; this is the case for example with TI2S and AmHO. In other cases the excess is seen by the color of the filtrate, as with yellow Am2S. 372. Evaporation before Precipitating Group III.— Since certain organic substances hinder or prevent the precipitation of the members of Group III a by AmHO, it is necessary, if the preliminary examination has shown the presence of organic matter, to destroy it by evaporation and ignition before proceeding to precipitate Group III; evaporation to dryness and gentle ignition are also neces- sary to separate Si02, which if remaining in solution might be mistaken for Al2Ho6. But if it is known that neither organic substances nor Si02 are present, a consid- erable saving of time may be effected by boiling the II2S filtrate until it no longer smells of H2S, then continuing 1 Or solution, supposing no precipitate to have been obtained, and filtration therefore to have been unnecessary. 230 preliminary examination [373-375. to boil for several minutes after adding a few drops of strong HN03; this process may replace the evaporation to dryness and ignition. 373. General Remarks.—The ordinary method of analysis drawn out in the general table and in the ta- bles for examination of the group precipitates will pre- sent little difficulty if the directions therein given are strictly complied with. Table III c will perhaps be found rather more difficult, and should not be attempted until some proficiency has been obtained by practice on the other group tables. Table III d, which must be employed under conditions fully explained in (460), should not be used until considerable proficiency has been attained. 374. It will be seen that the full course of analysis is arranged so as not only to prove what is present, but also that all else is absent; this, except in special cases, is the object in view. The process of analysis is much hastened by using separate portions of the solution instead of carrying on the examination throughout with one part of the solution; the plan in the general table is however preferable, since it gives at once a notion of the relative quantities of the different substances present. For an example of how to write out the results see pars. (488-493); it will be seen that the form adopted is that of the analytical tables. Preliminary Examination of Solid Substances. 375. Before proceeding to employ the full course of analysis for substances of complex composition, the stu- dent will do well to examine a few solid substances for metals and acid-radicles by the tables given in paragraphs (387—418).1 For the full account of how to try these tests for any particular substance the student must refer back to the preceding reactions in Section IV. 1 For example of substances to be analyzed by the preliminary examinations see paragraph (538). 376-379.] OF COMPLEX SOLIDS. 231 The results of these analyses are entered in the form of the table as shown in the examples in paragraphs (488) and (489). The entries must be made during the progress of the analysis. 376. Preliminary Examination for Metals.—A little study of this table (387 et seq.) will show that it contains three main tests, marked Exps. I, II, and III; these stand in the first column; in the second column are placed the results which may be noticed on trying these experi- ments; the student should glance through these so as to be forewarned of what he has to look for. The main classification of the results which may be observed is in- dicated by large-type letters, the subsidiary divisions are marked by small numbers and italics, and the individual results are simply placed in succession in a vertical column. Occasionally an observation is made which it is advisable to confirm by an additional experiment: this “ confirmatory ” test is then entered in the first column, just below the ob- servation to be confirmed, and is marked “confirnA” to distinguish it from the main experiment, its results are placed beside it in the second column; the student must understand that any one or more of the results noted in the second column may be looked for. A few salts and mixtures such as those mentioned in (538) should be subjected to a careful preliminary exami- nation by the student, and the results obtained carefully entered. 377. Preliminary Examination for Acid-radicles.— This table (410-418) exactly resembles in arrangement the table for metals which precedes it, and no explanation is therefore necessary. The student should examine by it some solid substances (538) for acid-radicles only. 378. A few solid substances may now be tested for both metals and acid-radicles by the two preliminary tables. Detection of Acid-radici.es and Metals by Preliminary Tests and by Examination of the Solution. 379. After having become familiar with the prelimi- 232 ANALYSIS OF COMPLEX SUBSTANCES. '379. nary examination of solid substances the student may analyze some easy substances containing only one or two metals and acid-radicles. The analytical course drawn out for the examination of complex substances may be at once employed for these more simple analyses, as the student is thus enabled to prove not only the presence of any particular metals or acid-radicles, but also the ab- sence of all others. He will by this means be gradually introduced to the analytical course, and after satisfactorily analyzing some simple substances, may proceed to mixtures of gradually increasing difficulty or complexity. At first no mixture should be attempted which will yield a precipitate containing a phosphate in Group III, and members of Groups III A and III B should not be present together in the same solution, also substances con- taining organic matter and Si02 should be avoided; the examination of the filtrate after passing II2S is thus very much simplified. The following is a description of the course to be pur- sued in making the complete analysis of a complex sub- stance. GENERAL COURSE OF ANALYSIS FOR SOLID AND LIQUID SUBSTANCES. The substance given for analysis1 will be either a liquid or a solid, since the analysis of gases forms a de- partment which is best studied by itself. Unless it is known that cyanogen is not present in the substance, it must be tested for in a small portion by the “ Prussian blue” or AmCyS test (304 or 306); but if found, refer to (482 et seq.) for the preparation of the solution and the method of analysis: if cyanogen is not present the substance is examined by (380, 381) or by (382 et seq.), according as it is liquid or solid. Silicates may also be tested for by fusing some of the finely powdered substance in a bead of microcosmic salt (293). THE SUBSTANCE IS A LIQUID. 380. Test it with both blue and red litmus-papers, one of the following results will be obtained : It is neutral It is acid It is alkaline (not changing either paper). (turning blue litmus red). (turning red litmus blue). Absence of acids and al- Presence of an acid, or Presence of a hydrate of kalies and of salts with acid or alkaline reac- tion. The salts of Ag and Mg and certain salts of Am, Na, K, Ba, Sr, and Ca are the only neutral soluble salts. salt with acid reaction. Am, N'a, K, Ba, Sr, or Ca, or of a salt with alkaline reaction. 381. Evaporate a few drops of the liquid upon a piece of platinum foil or a piece of thin glass or porce- lain,2 smelling it occasionally: 1 For examples of substances to be analyzed see par. (539). 2 A piece of the side of a broken flask will serve well. 234 ANALYSIS OF COMPLEX SOLIDS. [382, 383. No residue is left: The liquid must A residue is left: Examine the liquid consist of some volatile substance, by the further preliminary tests in probably of water, either pure or (334) or evaporate a portion of the containing certain gases or volatile solution to dryness in a porcelain substances dissolved in it (e. <7., NH3, dish, avoiding heating the substance HU1, Br, etc.) which are detected by after it is dry ; examine the residue their smell, by the action of the by the preliminaty tables for metals liquid on litmus-paper,or by special and acid-radicles (387-418). Exam- tests. If the liquid has no action on ine the larger part of the solution litmus, no smell, and leaves no resi- for metals by the general table (419) due on evaporation, and is tasteless, paying attention to (420), and the it is pure water. rest of the solution for acid-radicles by (440 et seq ). THE SUBSTANCE IS A SOLID. 382. If the substance is metallic in appearance refer to (467) for the method of analysis, or if it is non- metal lie proceed as is directed below. Finely powder some of the substance in a mortar, using an agate mortar if it is very hard. A part of this powder is first examined by the preliminary tables for metals and acid-radicles (387-418). Process of Solution. 383. A large part of the remainder is boiled in a flask or boiling-tube with distilled water; if it dissolves entirely see (384): if the powder does not dissolve, allow the liquid to stand still until the undissolved portion has in great part settled, then decant through a filter: the filtrate is Solution I: Residue in flask: Boil with dilute HC1 (386), allow any residue to settle, decant through the filter used above (386 a); repeat this process and finally boil the residue with strong HC1, let settle, decant through the filter: Filtrate is Residue: Heat with dilute, then with strong HNOa '386 6) as was directed above for HC1; decant through the filter: Filtrate is Residue may he warmed for a short time with a mixture of strong UNO, (386 b) with three times as much HC1; if this does not dissolve it, dilute and decant the acid mixture through the filter: Solution II. Solution III. Filtrate is Solution IV. Residue: Wash well with water,dry, and examine as directed (475 el seq.) for substances insoluble ii: water and acids. 384-3866.' SOLUTION OF A SOLID. 235 384. If at any of the preceding stages the substance dissolves entirely, proceed at once to examine the solu- tion by the general table (419), paying attention to (420) if the substance is entirely soluble in water. 385. The Solutions I, II, III, IV need rarely be examined separately; a general method is to add to I some HN03 (see 420) and then some HC1 to the clear liquid; add also to the IIN03 solution (III) some HC1. Any precipitate thus caused by HC1 is examined by Table I, and any precipitate caused then on mixing the Solutions I, II, III, IV is examined by (475) as an in- soluble substance. It is best to boil down the Solutions III and IV considerably before mixing them with I and II, in order to get rid of the HNOs as much as pos- sible ; they are then mixed with dilute HC1, and any precipitate thus caused is examined by Table I. 386. Any changes which occur on adding IIC1 should be noted down ; notice especially whether any gases are given off. Many of these gases may be detected by their smell, but a closer examination of them may be neglected, as they are obtained in the preliminary examination for acid-radicles (411). If the gases come off from the aque- ous solution on adding IIC1, or on mixing the IIC1 and aqueous solutions, they must have been present com- bined with metals as salts soluble in water, probably salts of alkalies; if they are evolved on treating the residue insoluble in water with HC1, they were present as salts insoluble in water. 386 a. On cooling the hot HC1 solution crystals often separate; these consist probably of PbCl2; they may be filtered off and dissolved in a little boiling water; if on addition of K2Cr04 to this solution a yellow precipitate forms, it shows the presence of Pb. 386 6. IIHOj seldom requires to be used in dissolv- ing a substance, and when necessary should be employed only in small quantity, since it is liable to cause a pre- cipitate of S from II2S (423). Note.—If a complex solid mixture is given for analysis, and the only object is to obtain a solution as rapidly as possible, it may be 236 PRELIMINARY EXAMINATION [387. at once boiled with aqua regia for a few minutes, then diluted and filtered: the residue is examined as a substance insoluble in water and acids (475 et seq.), and the filtrate is evaporated nearly to dry- ness : dilute IICl is added, and the solution examined by the gen- eral table (419). PRELIMINARY EXAMINATION FOR METALS. 387. The substance is required in the solid state for this examination; hence if a solution is being analyzed, some of it must be evaporated to dryness and the dry residue employed (see 381). Carefully note down the appearance and physical properties of the original substance: whether it is crys- talline or amorphous;1 its hardness,2 color,3 smell, and anything which strikes you on a careful examination aided by a pocket lens. The following three experiments (388, 397, 398), to- gether with some confirmatory ones when necessary, are then to be tried on small quantities of the finely pow- dered substance, and the results obtained noted down. For a fuller explanation of the form of the table, see paragraph 376. 1 A body, if crystalline, consists of particles which have a definite and similar shape; the particles are amorphous if they show no similar and definite shape. '2 The hardness of a substance may be roughly tested by trying to scratch it with the point of a penknife: if very easily scratched, it is soft; if the knife will not scratch it, but simply marks it as a lead- pencil would do paper, it is very hard (e. g., Quartz). 3 The salts of the following metals are colored: Cu, blue; Fe///, brownish-yellow; Fe//, pale green; Ni, Cr, CuCl2, green; Mil, delicate pink ; Co, reddish-pink. Chromates, light yellow; dichromates, orange- red ; Sb2S3, CuO, M11O2, black; HgO, Pb304, red; Pb02, dark brown; PbO, light brown ; Cr203, green. 388, 389.; FOR METALS IN COMPLEX SUBSTANCES. 237 Experiment. Observation. Inference. 388. Exp. I.—Heat a small quantity of the substance in a small test-tube or piece of hard glass tubing drawn off at one end. a. The substance does not change. Absence of organic substances which blacken aud give off a smell of burning; of volatile sub- stances which sub- lime; of substances which are altered by ignition; and of water combined with or absorbed by the substance, which would be evolved as steam and form drops on the side of the tube. b. The substance changes. 1. It changes color : Yellow, hot. white, cold. Yellow, brown “ yellow, “ Yellow-brown “ yellow, “ Dark red or | „ red- 1 « black ( brown j The substance blackens— a. Emitting a smell of burn- ing. The black carbon may be burnt off' by strongly heating on plat- inum foil with the blow- pipe flame. ZnO. PbO. Sn02 or Bi2Os. FcjOj. Presence of organic matter. Smell of acetone. Smell of burning sugar. b. Emitting no smell of burn- ing. The color is not removed by ignition as under a. An acetate. A tartrate. Probable presence of Co or Cu salts. Confirmatory.—The subli- mate is carefully exam- ined, if necessary, with the aid of a lens. 2. It fuses and becomes solid again on cooling. 3. It sublimes. White, crystaline (sparkling) sub- limate. White, non-crystalline sublimate. Black sublimate, becomes red when rubbed. Yellow sublimate. Salts of alkalies or cer- tain salts of the alkaline earths. Compounds of Am, As, Hg; or free S or I. HgCl2, As2Oa. Probably Am-salt. HgS. f AsaS,. •< HgTj, becomes scar- (. let when rubbed. Sublimate of reddish drops, 1 which are yellow when cold, j Violet vapor, cooling to blackish crystals. S free or from certain polysulphides. Presence of I. 389. Confirmatory. — Heat another portion of the substance, mixed with about three times as much Ha2COs in fine dry powder and a little KCy, in a tube closed at one end (147). Gray mirror, which, when rubbed with a splinter of wood or a glass rod, or when examined by a lens, is seen to consist of glob- ules of Hg. Blackish-brown shining mirror, and smell of garlic; no globules. Presence of Hg. Presence of As. [390-396. 238 PRELIMINARY EXAMINATION Experiment. Observation. Inference. 390. Confirmatory. — Pour a little strong KHO solu- tion upon some of the substance and heat to boiling; or mix some of the substance with soda- lime in a mortar, and moisten and heat. NIIj is given off, known by its smell and by turning moist red litmus-paper blue or turmeric- paper brown; the change in color is only a trustworthy indi- cation, if it occurs very soon, as the NH3 in laboratory air often causes it to occur after a time. Presence of NII4. 391. Confirmatory.—Exam- ine the drops of water on the sides of the tube with blue and red litmus- papers. ' 4. The substance gives off water. It fuses first, then gives off water, and again becomes solid if the heat is continued. It swells up considerably whilst giving off its water. The water is alkaline. The water is acid. 5. Gas or vapor is given off.1 a. It is without smell. Presence of water, ab- sorbed or combined. Water of crystalliza- tion. Borax and certain borates, alums, and phosphates. Probably Nil, com- pounds. Presence of volatile acids, e. g., HNO,, HC1, H2S04. 392 Confirmatory.—Intro- duce a burning splinter of wood into the tube. It burns more brightly, and if in- troduced with a spark at the end is inflamed. The flame is extinguished. 0 from chlorates, nitrates, peroxides, etc.; orpossibly N20. C02 or N. 393. Confirmatory. — Intro- duce a glass rod moist- ened with lime-water, into the tube. The lime-water turns milky. The lime-water does not turn milky, but the flame was ex- tinguished (392). COa from carbonates, oxalates, etc. N, from AmNOj prob- ably. 6. The gas or vapor has a smell. 394. Confirmatory.—Intro- duce a glass rod or slip of paper moistened with K2Cr20„ Smell of burning S. The KjCraO, turns green; moist blue litmus is also reddened by the gas. Reddish-brown nitrous fumes are given off, known by their pecu- liar smell, and by not eoloring starch paste orange-red. S02 from combustion of free S, or from acid sulphites, hyposul- phites, reduction of sulphates or oxida- tion of sulphides. Nitrates of heavy metals (e. g, of Pb, Bi, Hg, etc.). Smell resembling Cl: 395. Confirmatory.—Intro- duce a glass rod carry- ing a piece of moist lit- mus. Yellowish gas, which bleaches moist litmus. Cl from certain chlo- rides. 396. Confirmatory.—Intro- duce a glass rod with moist starch powder on its end. Brown vapor, which colors the moist starch powder orange-red. Violet vapor, which colors starch solution blue. Br from certain bro- mides. I, free or from certain iodides. 1 This will usually be shown by effervescence of the substance; if the gas or vapor is not detected by its color or smell, it can only be found on testing for it specially by (392) and (393). 397-399.] FOR METALS IN COMPLEX SUBSTANCES. 239 Experiment. Observation. Inference. c. The gas can he ignited, and burns at the mouth of the tube with a: Pale yellowish-green flame, more or NH, probably from less explosive. strongly heated Nil, NO,. Bright-white flame, producing PH, probably from a white fumes; the uuburnt gas smells of garlic. liypophosphite. Peachblossom-colored flame. Cv from a cyanide, probably from HgCyo. 397, Exp. II. — Dip a a. The substance colors the moistened loop of plat- inum wire, which gives flame: no color to the Bunsen 1. Intense yellow. Na. flame, into the sub- Examine the flame through stance, and hold the the indigo-prism; a crimson K or Sr, or both, are loop with the adhering powder near the top of color is seen. present. the Bunsen flame, or in 2. Pale violet, crimson through 1 K. the inner blowpipe flame. Then moisten the indigo-prism. j with a drop of strong HC1 and heat again. 3. Yellowish-green. Ba probably. Continue the heating until no further change occurs in the color of 4. Crimson, same through the) Sr. the flame. indigo-prism. / Note.—If silicic acid is 5. Orange-red, dingy-green 1 Ca. present, the colorations for K and Na usually show through the indigo-prism. / only after ignition of the 6. Bright green. Cu or B«03. pow’dered substance with A blue color is seen after powdered CaSO,. moistening with strong HCi. Ou. 7 Blue iIntense i. mue. -yLivid CuCE, CuBr». As, Sb, Pb. ‘ b. The substance does not color Probable absence of the flame. the above. 398. Exp. III.—Ileat the a. The substance decrepitates, or NaCl and certain other substance in a small crackles. crystalline salts. cavity scooped in a piece b. The substance deflagrates, or Chlorates, nitrates, etc. of wood-charcoal, in the blowpipe flame. causes charcoal to burn rapidly, c. The substance fuses easily, and Salts of alkalies and is absorbed by the charcoal, or certain salts of the forms a liquid bead. d. An infusible residue is left on alkaline earths. the charcoal. 1. The residue is white and very Probably BaO, SrO, luminous. OaO, MgO, AEO„ ZnO (or SiO.,). 399. Confirmatory. — De- The paper turns blue, showing the BaO, SrO, CaO, and possibly MgO. tach a portion of the cool residue from the char- residue to be alkaline. coal, place it upon a piece of red litmus- paper, and moisten with a drop-of water. 240 PRELIMINARY EXAMINATION [400-404. Experiment. Observation. Inference. 400. Confirmatory. — Mois- A blue residue, the color of which A1203, and some phos- ten the residue on the does not disappear with intense phates, silicates, and charcoal when cool with heat. borates. several drops of Co (N03')2 solution, and heat again A pink residue. MgO. strongly in the outer blowpipe flame. A green residue ZnO. 2. The residue is colored. 401. Confirmatory. — Heat Color of bead. a small quantity of the In outer flame. In inner flame. substance in a clear col- Green, hot. Colorless or red, \ Cu. orless borax bead, first Blue, cold. Blue, hot and cold. J in the outer, then in the Blue, hot and 1 Co. inner blowpipe flame. cold. cold. j Violet, hot. Yellow, cold. Gray or opaque. Ni. Brown-red, hot. Green, hot and 1 Fe. Yellow, cold. cold. [ Green, hot and Green, hot and ) Cr. ) '►See (402). Mn.) cold. Reddish-purple, cold. i (olorless, hot \ hot and cold. and cold. j 402. Confirmatory. — The Light-yellow mass on cooling. Cr. presence of Mn and Cr, may be confirmed by fusing the substance Blue-green mass on cooling. Mn. (See 406.) with Na2COs and KN03 on platinum foil. 3. The residue is colored, or metallic scales or globules are seen. 403. Confirmatory. — Heat The substance is reduced to the Au, Ag, Cii, Pb, Sn, Sb, also some ot the sub- metallic state. (See 407.) Hi [Co, Ni, Fe, Mn, stance, mixed or covered form gray powders]. with powdered KCy and a. Without incrustation. Au, Ag, Cu, Co, Ni, Fe, Na2('<)3 or K2C204, on Mn. charcoal in the inner Brilliant while metal. Ag. blowpipe flame. Yellow metal. Au. Red scales or globules. Gray powder, attracted bv a mag- Cu. netized knife-blade (407). Fe, Co, Ni, Mn. b. With incrustation. Globules. Incrustation. 404. Confirmatory. — De- White, malleable, None or very Sn. tach several of the glob- not marking slight. ules with the point of a knife, and strike them paper. on the bottom of an in- While, brittle. Orange, hot. I Bi. •verted mortar with the Yellow, cold. 1 pestle; if they flatten to a cake they are malleable, While, malleable, Yellow, hot and Pb. marking paper. cold. if crushed to a powder they are brittle. Try also White, brittle, White, close to Sb. if a globule, fixed on the giving white substance. point of a knife, marks fumes. paper. White or none. Yellow, hot. ) Zn. Note. — The appearance White, cold. j and malleability of one re- While or none. Red-brown,easily Cd. duced metal is frequently volatilized. much altered by the pres- None. White, and white As. ence of another. fumes: smell of garlic. 105-409. FOR METALS IN COMPLEX SUBSTANCES. 241 Experiment. Observation. Inference. 405. Exp. IV.— Fuse some of the substance, mixed with Na2COs, on charcoal in the inner blowpipe dame produced Jrom a spirit-lump; re- move the fused mass when cold, place it on a bright-silver coin, mois- ten with a drop of water, and let stand for several minutes. On rinsing off the substance, the coin is found to be stained black (408). Also, if a drop of HC1 be placed upon the mass, a smell of is perceived, and lead-paper is blackened. Presence of S, free or combined. Note. — Since this reaction serves to de- tect S and sulphur acid-radicles, it more properly belongs to the preliminary ex- amination for acid- radicles : it is, however, best tried here. Notes to the preceding Preliminary Table. 406. The green color produced by Mn conceals the light yellow- due to Cr; on boiling the residue with water it gives a pink or pur- ple solution, the color of which is best seen on filtering; this color is due to the formation of KMn04, and shows Mn to be present. On acidifying this solution with HA and boiling again for several min- utes, the purple color is destroyed; and on filtering, the yellow color due to Cr is seen: the presence of Cr may he further confirmed by the formation of a yellow precipitate in the acid solution on addition of PhA2. 407. The metal is best separated and examined by detaching the mass when cold from the charcoal, and powdering it by crushing in a mortar or on a watch-glass with a little water, letting stand for a short time, and then quickly pouring oft' the water down a glass rod or pestle which is wetted and pressed against its edge; by several times repeating this operation, the heavier metallic particles alone are left in the mortar or watch-glass (33 a). 408. This stain is removed by rubbing the coin with a little lime made into a paste with water. 409. Note.—When the substance to be examined contains several bodies, they frequently more or less mask one another’s reactions: thus Co if mixed with Fe will give a bead green whilst liot and blue w hen cold, thus resembling Cu, but differing in remaining blue in the inner flame: hence the composition of many complex mixtures is only roughly indicated by the preliminary examination, and must be confirmed and established in the wet way. Many substances, more particularly minerals, however, can be completely analyzed by a careful preliminary examination. 242 PRELIMINARY EXAMINATION 410,411. PRELIMINARY EXAMINATION FOR ACID- RADICLES. 410. The substance is required for this examination in the state of powder or of strong solution. If the substance given for analysis is a solution, part of it may be evaporated to dryness: the dry residue is then finely powdered and subjected to the following tests. If several acid-radicles and metals are present, the reac- tions may be more or less perfectly concealed or altered, hence failure in obtaining a certain reaction does not in all cases necessarily prove the absence of an acid-radicle. Experiment. Observation. Inference. 411, Exp. T.—Treat some of the sub- stance with dilute HC1 and note the result, then heat moderately (416). One or more of the following gases may be envolved : A colorless gas without smell, which turns milky a drop of lime-water on the end of a glass rod. C02 from a carbonate. A gas of suffocating smell which turns a drop of KiCr20, solution green. Yellow S is precipitated at the same time. S02 from a sulphite. S02 and S from a theio- sulphate.1 A gas with fetid odor, which blackens a drop of PbA2 solution, or a piece of lead-paper (417). IIjS from a sulphide; or possibly from a sulphite or hyposulphite, if Zn orother reiueing agent be present. Reddish fumes. H203 from a nitrite. A yellowish-green gas, of suffocating smell, and which bleaches moist lit- mus-paper, is envolved: a. In the cold ; and also evolved on adding HA. Cl from hypochlorites. 6. Only when heated. Cl from action of HC1 on oxidizing substances, e. g., MnOa, chromates, ni- trates, chlorates, etc. A colorless gas, smelling of bitter almonds. HCy from a cyanide. 1 Formerly called a “ hyposulphite.” 412-414.; FOR ACID-RADICLES. 243 Experiment. Observation. Inference. 412. Exp. II. — Heat another portion gen- tly with strong H2S04. Note.—No attention need be paid to gases evolved in Exp. I (411). 1. A gas is evolved with pungent smell, which fumes in the air, and renders milky a drop of AgNO, solution made acid with HN03. HC1, HBr, HI, HF* from chloride, bromide, iodide, or fluoride. Confirmatory. — Mix some of the substance with MnOj free from chloride, add strong H2S04 and warm. A yellow gas is given off with strong smell, and which bleaches moist litmus-paper (418). Brown vapor is given off, which colors a little moist starch powder orange-red. Violet vapor is given off, which colors a drop of starch paste blue. Probably Cl from a chloride. Br from a bromide. I from an iodide. 2. A heavy fumingsuffo- cating gas is evolved, and the liquid behaves as if the glass were greasy ; on rinsing out the tube, and drying it thoroughly, the in- side is seen to be cor- roded and dimmed. HF from a fluoride. Note.—The HF acting upon the silica of the glass evolves Si F4.which is detected by holding a moistened glass rod in the gas; Si02 is deposited as a gelatinous film upon it. 413. Confirmatory. — Drop into the hot liquid a few small pieces of copper. 414. Confirmatory.—Boil some of the substance with water, or take some of the solution if a liquid ; cool, add about twice as much strong HaSO* cool, and pour cold solution of FeS04 carefully in upon the top of the acid liquid. 8. The acid fumes are reddish, usually seen only on heating after adding a few frag- ments of Cu. A dark-brown ring or layer forms upon the surface of the acid, best obtained on cool- ing the liquid by im- mersing the test-tube in cold water. 4. Greenish-yellow gas, smelling like Cl, and exploding when warmed. Confirm by adding indigo solution and HjjSOjto the color- less aqueous solution of the substance (252). For detection of a ni- trate and chlorate when mixed, see (256). Presence of a nitrate. Note.—If iodide is present it must usually be separated by Cu2S04 (266) before a nitrate can be detected. Presence of a nitrate. Presence of a chlorate. 5. The substance changes from yellow to green, 0 being evolved as is shown by a glowing taper. Presence of a chromate. 1 HF would also render the drop milky by depositing Si02 from SiF4, formed by its action on the glass, but it is distinguished by corroding the glass. (See 412, 2, note.) 244 EXAMINATION FOR ACID-RADICLES. "415-418 Experiment. Observation. Inference. 6. Yellowish-green gas, with suffocating smell, which bleaches moist litmus. 7. The same gas as in 6, but colored reddish- brown by nitrous fumes: Cl from a hypochlorite (detected already in 411), or from a chlo- ride in presence of Mn02, etc. A chloride in presence of a nitrate or nitrite. 8. Or colored reddish- brown by CrOCl2. A chloride in presence of a chromate. 9. Substance does not blacken, but evolves CO, which burns with a blue flame, and COa, which turns a drop of lime-water milky. Presence of an oxalate. 10. Substance blackens, and SOa is smelt. Presence of a tartrate. 11. A smell of acetic acid or vinegar is noticed. HA from an acetate. 415. Confirmatory.—Add a little alcohol to the substance and heat with II2S04. Strong fragrant odor. Ethyl-acetate from an acetate. Notes on the Preceding Table. 416. If HC1 has been employed in dissolving the substance, the acid-radicles detected by the action of HC1 will have been already noticed in preparing the solution for metals (383). 417. The S present in sulphides which are not decomposed by dilute HC1, is detected bv fusing the powdered substance with two or three times as much fusion mixture (Na2C03 + K2CO3) in a covered crucible, boiling with a little water, and placing a drop upon a bright silver coin, when a dark stain will be produced; or by adding excess of an acid to the solution, when II2S will be evolved. Smaller quan- tities of S may be detected by the formation of a black color or pre- cipitate on adding PbA2 to the solution. 418. Chlorides treated in this manner evolve Cl, recognized by its color, smell, and bleaching action on litmus-paper; but this test for chlorides is reliable only if the precautions stated in (259) are attended to, since many samples of MnC>2 evolve Cl when warmed alone with H2SO4. EXAMINATION FOR METALS. EXAMINATION FOR METALS. After the preceding preliminary examinations have been made, a solution of the substance is made as directed in (383 et seq.), and this solution is further examined in a more systematic manner. This is often called “ The Ex- amination in the Wet Way/’ See next page. GENERAL TABLE FOR A19. 419. GENERAL TABLE FOR SEPARATION 01 If the substance for analysis is a liquid with neutral or alkaline reaction,! examined as directed below. In this table, and also in the group tables which follow, it has been sup precipitate will be produced when the reagent is added for its detection; an! Add to the greater part of the “original solution’’1 HC1; if any precipitate is produced, The precipitate may con- tain— PbClj—while. A " Cl—white. Hg2Cl2—white. (See 422.) Examine the precipitate by Table I (433). The filtrate or solution, which must give no further precipi- then diluted with water (425), unless it is already dilute warmed gently (426, 426 a) and filtered : The precipitate may con- tain— Phf-ihlnet 1 Insoluble Pbo—black 1 ■ Bi*S ,-black Knnd PuS—black \ . s CaS—yellow J 2 SnS—brown - SnS2—yellow ) Soluble Sb2S3—orange (_ in KHO As2K3—yellow i and in rAuaSa—black] ) Am*8. [PtSa—black] J The solution or filtrate isdi- cipitated : as soon as H2S dish until it ceases to smell and the residue gently ig- and heated, then water is Add a few drops of the acid tate shows the presence of a Add to the rest of the HC1 solo- once any precipitate which (429): if a phosphate is pliates are absent proceed ai [Note.—Kefer to Examine the precipitate by Table II (435). The precipitate may contain- Note.—The absence of Pb is not proved if it is not precipitated in this group, as PbCla is somewhat sol- uble, and Pb may there- fore be found only in Group II. Note 1.—This precipitate should not be examined at once, as possibly a precipi- tate may be formed on boiling the filtrate, and this would have to be added to the above. Note2.—Unless theliquid has been sufficiently di- luted some of the above metals may be afterwards precipitated by AmaS in Group III, and cause much confusion. A12IIob—almost colorless. S Cr2Hos—light green. Ee2lIos~reddish-brown. 1 Examine the precipitate by ble III a (436). Notes to the General Table. 420. If the liquid under examination is alkaline or neutral in reaction, before commencing the examination by the general table, IINO3 must be added in slight excess; if no precipitate forms, pro- ceed at once to examine the liquid by the general table ; if a precipi- tate is produced, more 11X03 is to be added, and the liquid heated ; 1 By the “ original solution ” is meant the solution of the substance if a solid, or the substance itself if a liquid, to which no reagent has been added. 420: SEPARATION OF METALS INTO GROUPS. METALS INTO GROUPS BY GROUP REAGENTS. requires special treatment (420); if its reaction is acid, it may be at once posed that all metals are present; if a metal or group of metals is absent, no hence no filtration is necessary, the solution being then treated as a filtrate. continue to add IIC1 as long as it causes any further precipitate (421), warm and filter: fate on addition of several drops of HC1, is hoiled down if necessary (423), and is it is then saturated with by passing the gas through the solution' (500 a), and luted and HoS is passed again into it, to make sure that Group II is completely pre- produces no" further precipitate the clear solution or filtrate is boiled In a porcelain of HoS (427), a little strong HN03 is then added, and the liquid is evaporated to dryness nited in the dish. When the dish is cool, a little strong IICl is poured upon the residue added; any undissolved residue is filtered off (428;. solution to some AmHMoO,solution in a test-tube, and warm gently ; a yellow precipi- phosphate; if no precipitate is formed with AmHMoO«,phosphates are absent. tion Am Cl, heat it to boiling, then add AmHO in excess, boil again and filter off al, may form as quickly as possible, keeping the funnel closely covered with a glass plate present anil a precipitate is produced by AmHO refer to Table ill D (466), if pilos- is directed below: (463 et seq.), for full directions for precipitating Groups III a and III b.] Add to the filtrate or solution, which may be colored (430), Am2S in excess, boil and filter; The precipitate may contain— | ZnS—white. 1 MnS—light pink. 1 CoS—black. | NiS—black. Examine this precipitate at Wonce by Table III b (437). Add to the filtrate or solution, which must be dis- tinctly yellow or brown (431), Am2COj, warm gently and filter: The precipitate (432) may contain— BaCOj—white. SrCO g—white. CaCOj—white. Examine the precipitate by Table IV (438). The filtrate may contain Mg, K, IS'a. Examine by Table V (439). should a precipitate still remain, it is filtered off and the filtrate ex- amined by the general table, commencing with the addition of HC1. The precipitate caused and not dissolved by IINO3 may be finely divided sulphur, separated as a white powder from a sulphide, or yellow from a theiosulphate ;2 this precipitate is recognized by its color, and by not being separable by standing or filtration, it may be disregarded; there may also be precipitated if4Si04 (gelatinous, 1 Instead of diluting and passing the gas, II2S solution may be added 2 Often called a “ hyposulphite.” 248 NOTES TO THE [420a-425. almost colorless), Sn02 or metastannic acid (see 420 a), Sb205, AgCl (all three white), S11S2, As2Ss (both yellow). Sb2S3 (orange). Hence a full examination of this precipitate for all that it may contain will involve boiling the precipitate with aqua regia, diluting and filtering; the insoluble residue is examined as a substance insoluble in water and acids (475), and the aqua regia solution is added to the filtrate from the precipitate caused by IINO,), any precipitate caused on thus mixing the solutions being examined by Table I (433). 420 a. Metastannic acid is precipitated from a solution of an alkaline metastannate by addition of an acid; it forms a white pre- cipitate which becomes golden-yellow when moistened with SnCl2 solution; it is further recognized by its dissolving in the washing- water whilst being washed, but being reprecipitated when the wash- ings run into the acid filtrate. 421. Even if IIC1 has been used in dissolving the substance, it is advisable to add a few drops of the acid to make sure that no member of Group I remains. 422. It must be remembered that HC1 also precipitates strong Ba solutions; this precipitate, however, disappears as PbCl2does on dilut- ing with water and heating, thus differing from AgCl and IIg2Cl2. 423. If IIN03 or aqua regia has been used in dissolving the sub- stance, or if the solution smells of Cl or S02, it should be boiled down considerably until after adding HC1 and boiling, neither of the above gases is smelt; it is then diluted, and II2S passed at once whether the dilution has caused any precipitate or not. If As has been detected in the preliminary examination, H2S03 should be added until the liquid smells of S02 after having been boiled for a short time, and the liquid is then heated for some time short of boiling, until it no longer smells of S02. This treatment re- duces arsenic and stannic compounds to the arsenioas and stannous condition. In the case of As this reduction is to be recommended, since arsenic compounds are not easily precipitated by H2S; it is also very desirable to reduce stannic compounds, since SnS2 unlike SnS readily runs through the filter, and being yellow in color may be mistaken for 8. It will of course be necessary to ascertain by special tests (187-190, and 201-203), made on the original solution, in which state As and Sn were originally present. If any precipitate is pro- duced by boiling with II2S03 other than white sulphur, refer to (424). 424. Whilst boiling with H2S03 some II2S04 is usually formed, which may partially or completely precipitate Pb, Ba, Sr as white sulphates; H2S03 will also possibly precipitate Au, which causes the cool liquid to appear blue by transmitted and red by reflected light, and on boiling separates as a black powder. Examine any precipi- tate formed by H2S03 by Table G (434). 425. On addition of water, Bi, Sb, Sn may give white precipitates of their oxychlorides ; these precipitates may be disregarded, since 1I2S readily converts them into sulphides. 426. II2S often causes a fine white precipitate of S, owing to the presence of certain oxidizing substances, such as Cl, IIN03, IIC103, II2Cr04, II2Mn04, HMn04, II2S03, Fe2Cl6, etc.; this precipitate is known by its perfect whiteness, and by not being separable by stand- ing or filtration, it may be neglected; great care must however be 426 a-430. GENERAL TABLE. 249 taken not to mistake SnS2 for S; it resembles S in running through filter-paper, but is distinctly yellow in color; it may often be coagulated by being shaken or heated. 426 a. Certain changes may be observed whilst H2S is being passed ; they should be carefully noted. Thus Pb and Hg during precipitation by II2S show characteristic colors (149, 144); a solution colored reddish-yellow by II2Cr04 becomes green ; and a solution colored green by H2Mn04 or purple by HMn04 becomes colorless. 427. if on boiling the filtrate or solution after passing H2S a yel- low precipitate forms, this shows the presence of an arsenic or a stannic compound; in this case pass H2S into the boiling liquid as long as it causes any further precipitate, filter off and add this pre- cipitate to any precipitate already obtained by H2S to be examined by Table II. 428. Si02 and other substances may be present in this residue, but Si02 is distinguished from them all by readily dissolving in hot KIIO solution. The other substances which may remain undissolved by IIC1 are A1203, Fe203, Cr203, rendered difficultly soluble by the ignition to which the residue has been subjected ; they are dissolved by long- continued heating with strong HC1, and the solution is added to the other solution which is to be examined for Group III A. BaS04 and SrS04 may also remain undissolved ; they are detected by heating some of the residue strongly for a short time in the inner blowpipe flame upon a loop of platinum wire, then moistening the loop with a drop of strong HC1 and holding it in the outer part of the Bunsen flame; crimson-red flashes appearing red through the indigo-prism prove the presence of Sr; a yellowish-green flame color- ation shows Ba. A less ready method of detecting Ba and Sr is to dry the insoluble residue, fuse it on platinum foil with three or four times as much fusion mixture; allow it to cool, then boil with water until the mass is disintegrated, filter, wash the residue well upon the filter, and ex- amine it by Table IV (438) for Ba and Sr only. 429. Mn and Zn are very liable to be precipitated with Fe2IIoe, A1211o6, Cr2Ho6. The precipitation of Mn is partly prevented by keeping the liquid from exposure to the air after adding AmHO: but the further precaution should be taken of dissolving the precipi- tate produced by AmHO in IIC1 and reprecipitating it by AmHO, then filtering and adding the filtrate to the original filtrate from the Group III a precipitate : this treatment of the precipitate should be repeated several times, if small quantities of Zn or Mn have to be looked for in presence of A1 or Fe ; or better still Groups III A and III b may be precipitated together (459) and the precipitate exam- ined by Tables III c (464, 465). See rules (463). 430. The filtrate or solution, after adding AmCl and AmHO, may be colored blue by Ni, or reddish-violet by Cr2IIo6 which is dissolved in the excess of AmHO. The Cr2IIo6 must be removed before proceeding to examine for the three remaining groups ; it is readily separated as a pale-green floc- culent precipitate by boiling the liquid for a short time in a procelain NOTES TO THE GENERAL TABLE. 431, 432. dish, adding a little more AmllO if the liquid does not smell of NII3 alter being boiled for a short time; this precipitate is filtered off, and the filtrate, which is colorless if the Cr has been entirely removed by boiling the liquid sufficiently long, is further examined for Groups III B, IV, and Y by the general table. The coloration due to Ni differs from that caused by Cr2Ho6 in not being thus removed by boiling the liquid. 431. A broivn or dark-colored filtrate shows that Ni is present,1 some of the NiS precipitated by Ain2S having been dissolved in the excess of Am2S and giving the filtrate its dark color. If this coloration is noticed the filtrate should be poured into a porcelain dish and boiled, occasionally adding water if necessary, until on removing the lamp for a short time the black NiS settles, leaving a colorless liquid. The liquid is then run through a small filter, and the black precipitate tested for Ni by fusing a portion of the filter-paper stained by the NiS in a colorless borax bead: if a bead is .obtained, which when heated in the outer flame is violet or brown whilst hot, and yellow when cold, and which becomes gray or opaque in the inner flame, Ni is certainly present and need not be further tested for in Table III B. The colorless filtrate is examined by the general table for Groups IV and V. 432. Part of the precipitate produced by Am2C03 often adheres firmly to the inside of the vessel in which it has been produced ; in this case rinse the tube out several times with distilled water and then dissolve the precipitate by pouring in some hot HA, causing it to run over the inside of the tube, and add this solution to the HA solution of the Am2C03 precipitate made in Table IV. 1 If Groups III A and III b have been precipitated together by AmCl, AmllO, and Am2S added in succession (459) the brown color- ation of the filtrate may also be due to Cr2IIo6: on boiling the filtrate colored by Cr2Ho6 in a porcelain dish for several minutes, pale-green Cr2I4o6 is precipitated, which cannot be mistaken for black NiS. 433, 434.] TABLE I.—SILVER GROUP. 251 433. TABLE I.—SILVER GROUP. The precipitate produced by HC1 may consist of PbCl2, AgCl, and Hg'2Cl2: the precipitate on the filter is washed five or six times with boiling water, the first portions of the washings being kept apart: The first portions of the Residue: pour upon the precipitate on the filter washings may contain some hot AinHO ; when this has run through, PbCl2 in solution, heat it again, and pour it once more upon the which if present in any quantity will be de- filter. Filtrate: add HNOs Residue on the filter is posited in brilliant crystals on cooling. until the liquid is black: dry at a gentle Test for, or confirm the acid : a white pre- heat, best in a steam-bath : presence of, Pb, by cipitate uniting scrape the precipitate off adding to the washings into curdy parti- the filter, mix with some KoCr04; a yellow pre- cles when shaken dry NaoC03, and heat in a cipitate readilv soluble or boiled shows: small ignition-tube (147). in KHO shows: Presence of Ag. Globules of Hg form on Presence of Pb. the sides of the tube, often appearing only when the inside of the tube is rubbed or examined with a lens; Presence of Ilg' (Mereu- rosum). 434. Table G.—Examination of the Precipitate formed on Boiling the IIC1 Solution with H2S03. (See par. 424.) The precipitate produced by H,SO, may contain An, PbS04, BaS04, and SrS04; the last three substances are perfectly white, and An, if present, is therefore usually seen by coloring the precipitate brown or black ; the Au is also usually visible during precipitation by HoSO*. or after the white sulphates have subsided, since it colors the liquid blue by transmitted and reddish by reflected light. Ba and Sr can often be at once detected, if present, by taking a little of the moist precipitate on a loop cf platinum wire, heating in the inner blowpipe flame for some time, moistening with HC1, and examining the flame coloration; but a more trustworthy method of proceeding is the following: Rinse the precipitate into a small porcelain dish, using as little water as pos- sible; dissolve in the liquid a small crystal of II2T or add a few drops of strong HA; then add AmllO until it is just in excess, and boil for a short time; let stand and decant through a filter ; Solution may con- tain I’bSOi; add HA in excess, then K2Cr04; a yellow precipi- tate soluble in KHO shows: Presence of Pb. Residue: pour upon the residue in the dish a little HC1 and a few drops of HNOs, heat to boiling, let stand, de- cant into a porcelain dish: Solution: boil until the smell of Cl is removed; add several drops of fresh FeSO, solution; a blue coloration and red- dish precipitate show: Presence of Au. Residue: dry by gently heating the dish, fuse with fusion mixture on platinum foil, and exam- ine the massfforBa and Sr as directed in the last part of (428). TABLE II. COPPER >35. The precipitate produced by H2S in the HC1 solution, afte of the washing-water, collected in a test-tube, give no preeipitat from the filter and boiled with KIIO or a small quantity of Amj,S 435. TABLE II.—COPPER ANI GROUP II a.—COPPER GROUP. 435 a. The residue may contain HgS, I’bS, CuS, CdS. After having washed the pre- cipitate and allowed it to drain, remove it from the filter into a porcelain dishi2Gd), pour upon it strong HNOa sufficient to cover it completely, and heat gently as long as any red fumes come off, adding more strong H N03 if necessary to prevent evaporation to dryness. Boil off nearly all the acid, add a little water and dilute II0SO4, let stand for some time. stirring occasionally, and filter ; Residue may contain HgS Filtrate mav contain Bi, Cu, Cd. (black), PbS04 (white), see Add Am HO in excess, boil and filter: Note 1. [Note.—A blue coloration shows presence of Cu.l 1 porcelain dish, using as little Precipitate (not easily Filtrate: add HC1 until the liquid water as possible; add a little seen in dark-blue so- is acid, then pass to satura- HA. then AmHO in excess. lutions); wash with tion, filter and wash quickly, keep- boil and filter; hot water, dissolve off the filter by pouring upon it a few drops of ing the filter covered with a glass plate; rinse the precipitate into a test-tube, pour upon it some di- the filter at a gentle heat, best in _ the Add HA in excess, boiling dilute HC1, pour this solution into a large quanti- ty of cold distilled lute II.2S04, boil and filter through a covered filter (Note 3): thenKaCr04 a yellow precipitate: Residue: dissolve Filtrate: add Scrape the water, a milkiness ap- pearing at once or by pouring a little boiling much water and pass II«? Presence of Pb. after stirring aud let- HNOjupon the for some time ting stand for some filter, add to the (or add much heat it, mixed time, shows: solution AmHO H,S-water), s with dryNajCO, in a small igni- Presence of Bi. in excess, then HA in excess, yellow precipi- tate shows: ; tion-tube; glob- Note.—A precipitate and a few drops Presence of Od. ules of Hg form produced by AmHO of K4FeCys: a Note. — If thi« on the sides of must always be tested chocolate - red precipitate I the tube, which as above for Bi, since precipitate dark - colored, become visible Pb and Hg might pos- shows: CuS is present when rubbed sibly appear here as (see Note 3:: or when looked white precipitates and Presence of Chi. filter it off, boil for by a lens ; be mistaken for Bi. it once more Presence of Hg" , (Mercuricum). with HjjSQ* fil- ter and test the filtrate by H./ as above, for Cd. Note 1.—A white residue does not necessarily show the absence ofHg. Note 2.—If the amount of the residue is too small to be removed the portion of the paper containing it may be cut up and mixed with Na2CO:s. For the precautions requisite in performing this test see (147). Note 3.—Unless this precipitate is filtered in a covered funnel, washed quickly, and examined at once, CuS is liable to be oxidized and to pass into the filtrate as CuS04; it then discolors the CdS pre- cipitate, or may be entirely overlooked if present in small quantity. 1 If traces of Cu have to be tested for, should be substituted for Am2S, since CuS is somewhat soluble in Am2S; but and Au2S3 are much more readily soluble in AnijS. 435 6.1 AND ARSENIC GROUPS. RSENIC GROUPS. tving been well washed with hot water until the last few drops only a very slight milkiness on addition of AgNOs, is removed id filtered: GROUP II b.—ARSENIC GROUP. 'he filtrate may contain As?S,, SbsSlt SnS,, SnS, [Au,S3, PtSa]. Add to it IIC1 until it is acid, and pass H2S unless the liquid smells strongly ; the above sulphides if present will be re- precipitated ; a mere milkiness due to precipitati >n of S may be disregarded. The precipitate is filtered off and examined as directed in 435 6 (see Note 4. below): 35 h. Remove the precipitate from the filter into a porcelain dish, using as little water as possible; add a little strong HC1 and heat, occasionally dropping in a crystal of KC103 «ntH the precipitate dissolves entirely, or leaves onlv a slight residue of sulphur. Heat this solution just short of boiling (Note 5) until it ceases to smell of ('1 (Note 6), then cool it and pour it, through a filter if necessary, into a small flask (181) containing pieces of pure Zn: if the gas does not come off readily, add a little strong HC1, and cause the gas after passing through some PbA2 solution (see caution 181) to bubble through some AgNO- solution contained in a broad test-tube. As soon as the evolution of gas slackens, drop in more Zn, unless some remains undissolved in the flask, and as soon as the gas ceases to come on, some Zn still remaining undissolved, remove the test-tube containing the AgNO* solution; if any black precipitate has formed in this solution it must be examined as kelow ; if the liquid has remained clear and colorless it may be rejected, since As and Sb are aosent. 'esidue in the flask may con- sist of Su (Pt, Au), and excess of Zn ; remove any deposit of Su by shaking the pieces of Zn well with the liquid and quickly pouring off into a dish, decant the liquid and wash the Sn by decantation in the dish; hoil the residue with a little strong HC1 in a test-tube, then quickly dilute, decant (Note 7), and add HgCI2 to the solution; a white precipitate, becoming black with AmHO, shows: Presence of Sn (Note 8). To the liquid in the test-tube add several drops of AgNOs solution, filter: Precipitate: wash well with boiling water until HC1 gives no milkiness with the last few drops of the washing-water, then pour upon the filter a little boiling dilute H2T so- lution, boil it and pour it again through the filter; re- peat this several times, then add to the solution HC1 and pass ; an orange-red pre- cipitate shows: Presence of Sb. Note. — This precipitate is often only seen -on settling from the yellow liquid. Filtrate: dilute several drops of AmHO largely in a test-tube and add this liquid drop by drop to the filtrate : a light- yellow precipitate which settles in flocks on shak- ing the liquid shows: Presence of As (Note 8). It is well to pour a few drops of H2S-water into the funnel with each fresh addition of washing-water. Note 4.—The detection of As, Sb, Sn by the method given in (435 b) is very trustworthy and delicate (208); it is excelled in these respects by tire method in (210). For beginners, however, the process (209) is recommended by its greater simplicity. Note 5.—The solution must not be heated to boiling, else SbCl5 or SnCl4 might be volatilized if present. Note 6.—In this solution As and Sn will be present as stannicam, and arsentcwm, and in this state are not well suited for detection: the following modification makes their detection much more rapid and certain, especially when they are present only in small quantity. After 254 TABLE III A. IRON GROUP. )436. warming until the liquid ceases to smell of Cl, add H2SOs drop by drop, until the liquid after being warmed for a short time smells of S02; then heat it short of boiling until the smell of SO2 is removed, and pour, through a filter if necessary, into the IT apparatus. Great care must be taken to remove the SO2 entirely, else Sb and As may remain as sulphides in the II apparatus. Note 7.—A residue here will contain An or Pt if they are present; if they are to be tested for refer to (473, 474). Note 8.—The precipitation by H2S in the general table will often show in what condition As or Sn were present (427); further dis- tinctive tests may be tried on the original solution by (187-190) and (201-203). 436. TABLE III a.—IRON GROUP. The precipitate produced by boiling, after addition of AmCl and of AmHO in excess, may contain Al2Ho6, Cr2IIo6, Fe2IIo6: the color of the precipitate will usually show whether it contains any quantity of Fe2ITo6 (red- dish-brown), or Cr2Ho6 (pale green), since A121Io6 is colorless. Dissolve the precipitate by pouring upon the filter a little bailing dilute 11 Cl, add to the solution pure KHO or NaHO until the precipitate remains after stirring, then add KIIO or NaHO in considerable excess, boil for some time and filter : 1. Filtrate may contain 2. Precipitate may contain Cr„IIoB and FeoHo,. Dry upon Al2Ho,j dissolved in ex- the filter, carefully avoiding charring the paper; when cess of NaHO; it it is sufficiently dried the substance will have shrunk con- green, CraHo6 is also in siderably into small, hard, dark-colored pieces; detach solution and must be pre- these from the filter and lose them with a little solid cipitaled by further boil- Na2CO» and KNO, upon a piece of platinum toil, either ing in a porcelain dish supported upon a pipeclay triangle or held in the Bun- and then removed by sen flame Jay crucible-tongs. Continue the fusion by filtration. beating the under surface of the foil in the blowpipe Add strong IIC1 gradually flame as long as any frothing occurs, then allow to cool; to the liquid drop by drop; a colorless gelatin- ous precipitate will form, should Al be present. If a yellow mass indicates the presence of Cr (Note 1). Boil the platinum foil in a small porcelain dish with water until the substance is entirely dissolved or only a dark-brown powder (Fe20,) remains undissolved ; take acid is added in excess out the foil, allow the powder to settle, and decant the this precipitate dissolves, but reappears on adding liquid through afilter: 3. Filtrate will be yellow if Cr 4. Residue in porce- AmHO in excess. The appearance of this pre- is present (Note 1 a). Add HA lain dish ; dissolve by cipitate shows: gradually until it is in excess, pouring in a little Presence of Al. which is shown by the color be- MCI and boiling, add Foie.—Sodium and po- coming reddish, boil for several some water, then a tassium hydrates are very liable to contain Al2Hos: the analyst must ascertain that the Al does not come minutes, then add PbA2solution; a yellow precipitate shows: Presence of Cr (Note 2). fewT dropsof KCyS so- lution ; a blood-red coloration shows : Presence of Fe (Note 3). from this source. 437.] TABLE III B.—ZINC GROUP. 255 Note 1.—If Mn was present in the original substance, it is often precipitated more or less completely with the Fe, and will be detected by imparting to the fused mass a bluish-green color; this should be noted, as the Mn may possibly be entirely precipitated in this group, and will then not be detected in the next group. Note 1 a.—The green color, due to the presence of Mn, conceals the pale-yellow color due to Or; but on dissolving the cool mass in water and boiling with HA, the manganese coloration is destroyed; and, on filtering from any dark-colored precipitate, the yellow color due to Cr becomes evident. Note 2.—Cr may have been present as a chromic salt, Cr replacing H in an acid; or as a chromate, Cr being united with O to form an acid-radicle. Ascertain in which state it was present by boiling some of the original substance with Na2C03 solution and filtering; a yellow filtrate, which on being acidified with HA gives a yellow precipitate with PhA2, shows that Cr was present as a chromate ; Cr, previously combined with an acid as a chromic salt, remains undissolved as green Cr2Ho6, and does not color the filtrate: it is found by 2 in the above table. Note 3.—Fe is always detected here in the ferric condition, since, even if originally present as ferrosum, it will have been oxidized by boiling with HNO3 as directed in the general table. To ascertain in which condition the Fe was present, boil some of the original sub- stance with HC1, and divide the HC1 solution, after filtering, if neces- sary, into two parts: to one portion add Iv6Fe2Cyi2, a dark-blue pre- cipitate shows presence of Fe" (Ferrosum): to another portion add KCyS, a blood-red color shows presence of Fe"' (Ferricum). 437. TABLE III b.—ZINC GROUP. The precipitate produced by Am2S in the solution or in the filtrate from Group III A, may contain ZnS, MnS, NiS, CoS. The color of the precipitate will usually show whether it contains any quantity of NiS or CoS which are black, or consists only of MnS (pink) or ZnS (white). The presence of Hi, indicated by the filtrate after boiling with Ami 10 in the general table being blue in color, and also by a dark- brown filtrate being obtained after boiling with Ara,S, will usually have been proved to a certainty by the examination in the borax bead of the black NiS, precipitated by boiling the dark-brown filtrate from Am2S (431); if Ni has been thus found its further detection in the ArnnS precipitate, as directed below, will be unnecessary. TABLE III B.—ZINC GROUP. '438. Remove the precipitate from the filter with cold dilute IIC1 in the liquid to stand, occasionally stirring it well. The precipitate milky liquid may be at once examined by 2 (below), or a black (below), the filtrate being examined by 2: 1. Residue (black) may contain NiS, CoS. Examination by the borax bead: Fuse a small quantity in a clear borax bead in the extreme tip of the ouler blowpipe flame, note its color; then fuse the bead for some time in the inner blowpipe flame, and again observe its color. Any one of the following observations may be made: Bine bead in both flames shows : Presence of Co. Co need not be further tested for, but if any doubt exists as to the presence of Ni the rest of the residue must be examined as below. Brown or yelloivbead, when cold after fusing it in the outer flame, which becomes gray or opaque, in the inner flame, shows presence of Ni, absence of Co. Unless mere traces of Co have to be tested for, no further ex- amination need be made. A bead which is neither brown nor\ blue, but of some intermediate hue on cooling Irom the outer flame, indicates the probable presence of both Co and Ni. | Examine the remainder of the; black residue as directed below for Ni and Co, or for Co alone] if Ni has been already detected j by (431). Further Examination of the Residue.—Rinse the residue from the filter into a porcelain dish, using as little water as possible ; pour in a little strong HC1 and boil for some time, adding occasionally a small crystal of KC103, until the black residue is entirely dissolved or only a small quantity of dark sulphur remains; then boil down nearly to dryness, a blue liquid shows presence of Go; dilute with a little water, filter if necessary into a boiling-tube and pour in KCy solution slowly until the precipitate formed at first is just redissolved ; boil briskly for several minutes, and add much strong Na2,'l20, or make decidedly alkaline with NallO and add much ltr-water; heat nearly to boiling, and allow the liquid to stand at least ten minutes, filter (Note 1, page 257): 3. Precipitate (black): wash and confirm the presence of Ni by fusing some of the precipitate, or the paper stained with the precipitate, in a borax bead in the outer and inner blowpipe flames; a bead yellow when cold, becoming black in the inner flame shows: Presence of Ni. 4. Filtrate must be warmed with more Na2Cl20 or Br- water, and filtered from any additional precipitate which may form, then evaporated to dryness and strong HNOs poured upon the residue as long as any frothing is caused; this is then evaporated just to d ry ness, the residue dissolved in water, excess of KHO added to it, and any precipitate filtered otf and fused into a borax bead, taking the paper stained by the precipitate if the precipitate is not easily removed; a blue bead shows : Presence of Co. 438. TABLE IV.—BARIUM GROUP. The precipitate produced by Am2C03 may contain BaCOs, SrCO„ CaCOs; it is to be well washed with boil- ing water. Before dissolving the precipitate off the filter much may usually be learnt by an examination of the flame coloration yielded by the HC1 solution (see 1 below). The results thus obtained are afterwards con- firmed in the wet way (see 2 below). 438; TABLE IV.—BARIUM GROUP. le way described in par. 26 c; take out the paper and allow ill either dissolve, leaving only white sulphur, in which case the !sidue will be left which must be filtered off and examined by 1 . Solution or filtrate may contain Zn, Mn. Boil in a porcelain dish until it ceases to smell of then drop in a small crystal of KUO*, and boil for several minutes. After cooling the liquid add pure NaHO until after stirring the liquid it turns red litmus-paper blue, then add more NaHO, stir well and filter: [Precipitate is white at first, but rapidly darkens in the air. Fuse a portion of it with solid Na2C03 and KNOs on platinum foil; a bluish-green mass is ob- tained on cooling showing; Presence of Mn. Note.—Mn may have been origi- ally present either replacing 11 1 an acid, or combined with 0 i an acid-radicle. Its presence i an acid-radicle is indicated by le color of the original solution, nee in the form of manganate is green, and as permanganate is purple ; these colors disap- ear on boiling the HCI solution ir some time, or on passing IlaS. 6. Filtrate: pass H,S, a white precipitate forms, often somewhat discolored, showing; Presence of Zn. Note.—From a dilute solution of ZnHo2 in NaHO the ZuHoj is precipitated on boiling; hence after adding NaHO, as directed above, the liquid must not be boiled, else Zn might be precipitated with the MnHo2 and escape detection. But by diluting and boiling the above filtrate it is usually possible to cause any ZnHo2 it holds in solution to precipitate, especially if the alkalinity of the liquid be somewhat reduced by cautious addition of HCl in quantity insufficient to make the liquid acid. If this precipitate be separated by pouring the liquid through a double filter and then be dissolved otf the filter and the sides of the boiling-tube by a little boiling HA, ZnS may he precipitated perfectly white from this solution by H2S, showing; Presence of Zn. Note 1.—If this precipitate adheres to the sides of the boiling-tube, it is [ssolved, after the liquid has been emptied out, by pouring in a little boiling [Cl; from this solution the Ni is precipitated by addition of KIIO, and the recipitate filtered off and tested by the borax bead for Ni. 1. Examination by Flame Coloration.—Take a small quantity of the precipitate off the filter upon the end of a glass rod, and dissolve it by moving the end of the rod about in several drops of HC1 on a watch-glass; dip into this solution a loop of platinum wire which imparts no color to the flame, then hold the loop for some time in the Bunsen flame, repeating the process if the coloration is not satisfactorily observed at first. Ca will impart to the flame a yellowish-red color, Sr a crimson-red, Ba a yellowish-green. The red colorations yielded by Ca and Sr are distinguished by viewing the flame through the 258 TABLE IV.—BARIUM GROUP. [439. indigo-prism ; the Ca coloration then appears dingy green, whilst its coloration remaining after the others have disappeared. When interfere with one another ; but if at any time a red color is visi- coloration is visible without using the prism, the presence of Ba 2. Examination in the Wet Way.—The rest of the precipitate again boiling the liquid, and pouring it once more through the the solution is acid, and if it is not, add HA whilst stirring acid solution into a test-tube,and put by the larger portion (B). lower part of the tube in cold water or holding it in a stream from precipitate forms refer to Column I (below); if no immediate then forms refer to Column II; if no precipitate forms even I. An immediate precipitate is produced by CaSOt in the cold, shovnng: Presence of Ba. Portion (B) must then be tested for Sr and Ca which may also be present; examine it as directed below : Add K.2Cr04 solution until the color of the liquid is reddish-yellow; heat, and filter through a double filter-paper, pouring the filtrate through the same filter repeatedly if necessary until the liquid is quite clear; then add to the liquid, which must be orange-red in color, AmllO until the color changes to pale yellow, then add Am2C03 solution : No precipitate forms, showing: Absence of Sr and Ca. A precipitate forms, showing Sr, Ca, or both of them, to be present. Add to the liquid Am2C03 in excess, filter, reject the filtrate and dissolve the precipitate off the filter in as little boiling HA as possible; pour off a small part (A') of this solution, reserv- ing the larger portion (B'). To (A/) add CaS04 solution and boil: No precipitate forms: Absence of Sr. Examine portion (B') for Ca as directed at (C) in Column III. A precipitate forms: Presence of Sr. Examine portion (B') for Ca as directed at (C), Column II. 439. TABLE V.— The filtrate, after addition to the original solution of all the NH4. Since, however, NH4-salts have been added as group re- detected by boiling a portion of the original substance with KHOj would be recognized by its smell or its action on moistened red NH4, since it will have been already tested for in the preliminary 439. TABLE V.—POTASSIUM GROUP. the Sr coloration still appears crimson ; Ba is usually found by all three metals are present together their colorations are apt to hie through the indigo-prism, Sr is certainly present; if a green is proved. is dissolved off the filter by pouring upon it a little boiling HA, filter if the precipitate is not entirely dissolved. Test whether until the liquid is acid, then pour off a small portion (A) of the To the portion (A), after it has been cooled by immersing the the tap, add several drops of CaS()4 solution; if an immediate precipitate forms heat the liquid to boiling, and if a precipitate after several minutes refer to Column III. II. A precipitate is not formed at once on the III. No precipitate is produced addition of CaSOv but appears on boiling the by CaSOi even on boiling, liquid, showing: showing: Absence of Ba and presence of Sr. Absence of Ba and, Sr, and presence of Ca. C. Portion (7?) is then examined for Ca as C. Confirm the presence of directed below: Ca by making portion (B) Add dilute H2S04 in excess, boil and filter, reject the precipitate; add to the filtrate sev- alkaline with AmHO (35 a), then add Am2C204 solution ; eral drops more II2S04 and boil; if this a white precipitate forms, causes any precipitate boil and filter, and sliowing: again test the filtrate by addition of H2S04 Presence of Ca. and boiling; repeat this process if neces- sary. To the clear filtrate, which gives no (See. note below.) Note.—If mere traces of Ca further precipitate on addition of II2S04 have to be tested for, the filter- and boiling, add gradually AmHO until paper used in the analysis after mixing the liquid by thorough stir- must first be freed from any ring or shaking, it turns red litmus-paper traces of Ca it may contain blue, then add Am2C204 solution and warm by wetting it with dilute HC1, gently; a white precipitate, often appear- and then thoroughly washing ing only after a time, shows: it with distilled water, as Presence of Ca. described in the note to par. (See note, Column III.) 23 a (p. 63). POTASSIUM GROUP. group reagents in succession, may still contain Mg, K, Na, and agents, it is useless to test for NH4 in this filtrate; NH4 must be solution,and ascertaining whether any NH3 gas is evolved, which litmus-paper. It is, however, usually unnecessary to test here for examination (390). Proceed to examine for Group V as di- 260 TABLE V.—POTASSIUM. 439. rected below. Evaporate the filtrate from Group IV to dryness in a porcelain dish, scrape out the solid resi- due and heat it to redness upon a piece of platinum foil in the Bunsen flame as long as any white fumes are seen to be given off on removing the foil for an instant from the flame (Note I). All NH4 compounds are thus entirely removed. If any residue remaihs (Note 2) it is to be dis- solved by boiling the foil in a test-tube with a small quantity of water to which several drops of dilute IIC1 have been added. Divide this solution into two equal parts: Examination fob Mg. Examination for K and Na. Before testing for Mg in one portion of this solution it is necessary to remove from it any traces of Ba, or Ca which it may possibly con- tain,1 and which might else he mistaken for Mg. Add, therefore, several drops of H2S04 to the liquid, boil for a short time and let stand; then, whether a pre- cipitate has formed or not, add a little AmCl, then AmHO in excess, then sev- eral drops of Am2C2<>4, and warm gently; if any pre- cipitate has formed proceed to filter at once as quickly as possible. To the liquid in which the addition of II2SO4, AmCl, AmHO in ex- cess, and AiUoC204 causes no further precipitate add Na2HP04, and if no precip- itate forms at once warm gently, shake or stir the liquid violently and let it stand for some time; a white crystalline precipi- tate shows: Presence of Mg. In the other port ion proceed to test for K and Na as directed below. The presence of Mg in no way interferes with the detection of K and Na, and hence if it has been detected its removal is unnecessary. Flame Coloration.—Dip into the solution a loop of platinum wire which has been proved when held in a Bunsen flame not to impart any color to it. Hold the loop in the Bunsen dame ; one of the following results will he observed ; A bright-yellow flame color- ation, indicating the pres- ence of Na (Note 3). Examine this coloration through the indigo- prism ; it appears red, indicating presence of K; if no red color is visible K is probably absent or present only in very minute quantity. A pale-violet color- ation, appear- ing crimson-red through the indi- go-prism, shows: Presence of K, and absence of Na. It is usual to confirm the results of the exami- nation of the flame coloration by pouring the remainder of the solution upon a watch- glass, adding to it several drops of PtCl4 (Note 4) and stirring well for some time: the formation of a yellow precipitate shows: Presence of K. See “ Remarks (47),” and Note 5, page 261. Note 1.—If the residue is small in amount it may be ignited in the dish; but this is not to be generally recommended, as the porcelain dish is liable to be cracked by the heat, and it is also difficult to get entirely rid of the JSdI4 salts by heating only in porcelain. 1 Traces of Ba, Sr, Ca may remain unprecipitated by Am2COa in Group IV. 440.; EXAMINATION FOR ACID RADICLES. 261 Note 2.—It is not safe to place much reliance upon an examination of the foil for the detection of a small quantity of residue, but it may usually be detected by its producing a crackling noise whilst the foil is cooling immediately after its removal from the flame. Should there be any doubt, the foil must be boiled with water and a drop of HC1, and the solution examined for Mg, K, and Na, as directed above. Note 3.—A yellow coloration, more or less intense, will almost always be obtained here, since nearly all substances and reagents contain small quantities of Na; hence the student must note the in- tensity of the coloration, and judge from it whether the quantity of Na is small or large; he must then enter accordingly, either “ Presence of Na,” or “ Presence of trace of Na.” Note 4.—If iodine is present, PtCl4 will produce an intense red coloration; hence if iodine is suspected to be present, before adding PtCl4 the above solution should be evaporated to dryness with a little strong HN03, the residue dissolved in a few drops of dilute HC1 and tested with PtCl4 for K. This is of course unnecessary if, before precipitating Group III in the general table, the solution has been evaporated to dryness with HNG3. In case of uncertainty, add PtCl4 to a drop only of the above solution; and if iodine is found to be present proceed as directed above. Note 5.—Mere traces of K and Na may be detected by adding Pt014, and evaporating the liquid to dryness in a porcelain dish upon a water-bath (504); then pouring absolute alcohol into the dish and stirring; any yellow residue shows presence of K, the solution giving the pure Na coloration if Na is present. By Altering off the yellow residue and washing it with absolute alcohol, it will yield the pure K flame coloration. EXAMINATION FOR ACID-RADICLES. 440. Several acid-radicles will probably have been already detected for certain, if present, by the preliminary examinations. Such are C03, S03, S, NO.,, CIO, NOs, C103, A: their reactions are so characteristic, that unless interfered with by the presence of other substances, their presence or absence will have been proved to a certainty: in case any uncertainty is felt, the analyst should refer to the reactions given in Section IV for the particular acid- radicle in question and select a reaction which will be decisive. The examination for metals also frequently yields proof of the presence of certain acid-radicles. Thus on passing II2S into the 1IC1 solution: [441. EXAMINATION FOR A reddish-yellow solution, becom- ing green and depositing white sulphur, shows . . . Presence of CrOi A green solution, becoming color- less, shows .... Presence of (MnOi)" A purple solution, becoming color- less, shows . . . . Presence of (MnO?)' A yellow precipitate of A.s2S3, ap- pearing only when the liquid is boiled, shows .... Presence of As04 An insoluble residue of Si02, after evaporating to dryness the fil- trate from the II2S-group, shows Presence of Si03 And a yellow precipitate obtained with AmIIMo04 before precipi- tating Group III, shows . . Presence of POi The presence of any of these acid-radicles thus detected will require no further confirmation. 441. Of the acid-radicles which remain to be tested for, some can be detected by the plan drawn out below (442-445); others are best detected by special tests made on the original substance (446-454). Much time and trouble may usually be saved by con- sidering what acid-radicles can possibly be present. A careful preliminary examination will usually have limited this number considerably, and it may be further reduced 443. I. Portion acidified with IICl. Present. On addition of BaCl2 solution a white precipitate insol-1 uble on boiling (444, 1), j (SO,)" On addition of RaCl2 solution, a semi-transparent pre-) cipitate insoluble on boiling (444, 2), . . . j (Sii'e)" On addition of AruCl and Am2C03, a semi-transparent) precipitate, J (SiO,)" On addition of FeS04 solution, a dark-blue precipitate, (Fe2Cyi2,v* On addition of Fe2n6 solution, a dark-blue precipitate: ) FeS04 yielding a light-blue precipitate, . . . j (FeCys,w On addition of Fe2Cl„ solution, a red coloration de-1 stroyed by pouring into HgCl2 solution, . . . j (CyS)' 9 . 1 F will be readily detected in this precipitate, or better 442, 443.] ACID-RADICLES. 263 by the knowledge already obtained as to the solubility of the substance under analysis, and the metals it contains. A reference to the table of solubilities (455), and the explanatory paragraphs 456, 457, and 458 will show how this knowledge is applied. General Examination for Certain Acid- radicles. 442. Before employing the liquid tests it is advisable to separate from the substance any metals other than K, Na, and NH4, which it may contain, since some of these are liable to be precipitated by the reagents added for the detection of the acid-radicles. If alkali-metals alone are present this separation is unnecessary, since they are not precipitated by any of the reagents. This separation of the metals may usually be effected by boiling a portion of the substance with Na20O3 solu- tion, which must be added as long as it causes any pre- cipitate. Filter from the precipitate, and divide the clear filtrate into five equal portions. Reserve one of these portions in case of accident and a second for the tests for organic acid-radicles, and acidify the others whilst they are hot by addition of HC1, HN03, and IIA respectively: examine these portions as directed below, using a sepa- rate part for each test : II. Portion acidified Present. Present. with //A 03 Reter to (414,3). with 11 A. On addition of AgN03, \ O11 addition of PbA^) (CrO 4)" a pure white precipi- ! tate, easilv soluble in f A111HO (444, 1), . . ) Cl' solution a yellow pre- > cipilate, . . . j On addition of AgN03, 4 F',1 probably. Br' lution a white gelat- V a light-yellow precipi- ! tate, with difficulty sol- [ iuotts precipitate, . J uble in AniHO, . . J On addition of CaCl2 a I (CoO,)",1 probably. On addition of AgNO,, 4 white pulverulent pre- ) cipitate, . . . ) a yellow precipitate, [ I' almost insoluble in [ AmllO J (P04)'", or (As04)'". yellowish-white p> e- V Refer to (445). cipitate (449, 450), . j in the original substance by (452), (C30 )" by (453). 264 SPECIAL tests [441-448. Notes on the Preceding Table. 444. 1. Unless the Na2C03 solution used in preparing the solu- tion for these tests was pure, (SOi)// and (Cl)', if detected, may have been present only as impurities in theNa2COs; portions of the origi- nal substance should then be tested by (44(3) and (447). 2. The presence of (SiF6)// should be continued by other tests, such as adding KC1 (300), or evolving HF by strong 1I2S04 (301); the IIF is most readily evolved from the BaSiF6 precipitate (301 a). 3. Should AgN03 yield a black precipitate, this proves the presence of a sulphide, or possibly a theiosulphate; add HNOs, and boil; the black Ag2S will thus be decomposed, leaving a milky liquid, in which any other precipitate is readily seen after being coagulated by heat- ing or shaking. 445. It must be remembered that (Cy)/, (FeCy jiv, (Fe2Cv]2)Ti, and (CvS) are also precipitated by AgNOs, and therefore if these acid-radicles have been already found, a precipitate produced by AgNC>3 does not prove the presence of (Cl)', (Br)', or (I)', which acid-radicles must be specially examined for, as directed below. If chloride, bromide, and iodide have all to be tested for, a portion of the Na2CC>3 solution must be examined by (273); or the precipitate obtained by AgN03 (see 443, II) may be tested by (273 a) for Cl, Br, I. If only bromide and iodide have to be tested for, use par. 274. Special, Tests for Acid-radicles to be made on the Original Substance. 446. Sulphate.—A portion of the original substance is boiled with HC1, the liquid decanted or filtered if not clear, and BaCl2 added to it: a white precipitate shows presence of S04. 447. Chloride.—A portion of the original substance is warmed with IIN03, the solution decanted or filtered if necessary, and AgNOs solution added to it, a perfectly white precipitate, easily dissolved by warm AmHO, shows presence of chloride. 448. Cyanide if present will have been detected by its special test and by the smell of bitter almonds, which is given off by the substance, after adding H2S04 (411). Add to some of the substance Am2S in excess and boil; filter from any dark-colored precipitate, boil the filtrate for a short time, acidify with HC1 and add Fe,Cl6; a red coloration, not destroyed by heat but removed by addition to HgCl2, shows presence of Cy, possibly as (FeCy6)iv, 449-452.] FOE ACID-RADICLES. 265 (Fe2Cy12)vi, or (CyS), if these acid-radicles have been found (443, 1). 449. Arsenate.—This acid-radicle cannot be present unless As was detected during the examination for metals; the presence of (As04)/r/ is there rendered prob- able by the precipitation of yellow As2S3 occurring only when the liquid saturated with H2S is boiled. If As has been found amongst the metals, proceed to test for (As04)'" by adding to a portion of the Na2C03 solution (442) IIC1 until it is acid, then AmCl, AmHO in excess, and MgS04; filter off any precipitate which forms on warming and shaking the liquid, and pour a few drops of AgN03 solution upon the white precipitate on the filter; a change of color to brown shows presence of {AsOy. 450. Phosphate.—Boil some of the original substance with dilute IIN03, add a little of this clear solution, fil- tered if necessary, to some AmHMo04 solution, shake and stir the liquid well, and if no precipitate forms warm very gently ; a yellow precipitate shows presence of (POi)'". If (AsCh)"' has been detected (449) this test for (P04)/// is only trustworthy when the yellow precipitate has been obtained either in the cold or by employing a very gentle heat. If any doubt is felt con- cerning the presence of (POAA boil some of the substance with strong HC1, and examine for (P04)/// after having entirely separated the (As04)/// by passing II2S into the boiling HC1 solution. A doubtful precipitate with AmHMo04 may be proved to contain phos- phate by dissolving it in AmHO, adding AmCl and MgSO-t, filtering and dropping AgNOa upon the precipitate; if phosphate is present it turns yellow, if arsenate brown. 451. Borate.—Warm a portion of the substance with a little dilute HC1, dip into the solution a strip of turmeric- paper and dry it in a steam-oven or at a gentle heat; if the slip is reddish-brown and becomes blue-black when moist- ened with AmHO, the presence of (BOA" is shown. 452. Fluoride.—Pour upon a portion of the powdered substance strong H2S04; and warm the mixture in a leaden or platinum crucible covered with a watch-glass, which has been coated with wax or paraffin, and has then had characters traced through the film with the point of a penknife: the characters are etched upon the glass, showing the presence of F. 266 table op solubility [453, 453 a. If SiO,2 is known to be present, the test must be made by conducting the gas, evolved on heating the substance with strong 112S04, into dilute AmHO, when a deposit of gelatinous II4Si04 proves the presence of F. 453. Oxalate.—The precipitate produced by CaCl2 in III (443), or the original substance if it contains no car- bonate, is mixed on a watch-glass with MnO, free from carbonate, and strong II2S04, and gently warmed: C02 is evolved and detected by holding over the bubbles which rise from the mixture a rod moistened with lime- water, or by inverting another watch-glass containing on its under surface a drop of lime-water over the glass con- taining the mixture. 453 a. Tartrate.—The presence of T will probably have been indicated in the preliminary examination (388 or 412). In order to confirm its presence, any metals of Groups I, II, and III must be separated by H,S or Am2S, and CaT is then precipitated from the liquid, made just alkaline with AmHO and mixed with a little AmCl, by adding excess of CaCl2, shaking well and let- ting stand for some time. A precipitate may consist of 455. TABLE SHOWING THE SOLUBILITY OF A blank signifies that the solubility K. Na. Am. Mg. Bci. Sr. Ca. Fe". Fe"'. Al. Or. Zn. Mn Ni. 1. Oxide . . w. w. w. a. w. w. w-a. a. a. a.i. a.i. a. a. a. 2. Sulphide . w. w. w. w-a. w. w. w-a. am- a. — — a. a. amn. 3. Chloride . w. w. w. w. w. w. w. w. w. w. a.i. w. w. W. 4. Iodide w. w. w. w. w. w. w. w. w. — — w. w. — 5. Sulphate . w. w. w. w. i. i. w-a“—i. w. w. w. w.a. w. w. w. 6. Nitrate . w. w. w. w. w. w. w. w. w. w. w. w. w. w. 7. Phosphate w. w. w. a. a. a. a. a. a. a. a. a. a. a. 8. Carbonate w. w. w. a. a. a. a. a. — — — a. a. a. 9. Borate w. w. w. a. a. a. a. a. a. a. a. a. a. a. 10. Arsenite . w. w. w. a. a. a. a. a. a. a. a. a. a. a. 11. Arsenate. w. w. w. a. a. a. a. a. a. — — — — a. 12. Chromate w. w. w. w. a. a. a. — w. a. a. w. i. a. 13. Fluoride . w. w. w. a. a-i. i. a-i. — — — — — — — 14. Oxalate . w. w. w. a. a. a. a. a. a. a. w-a. a. w.a. a. Only the most commonly occurring compounds are contained in this table; the solubility of other substances may be obtained by refer- ence to Storer’s “ Dictionary of Solubilities.” 456. The table is thus arranged: in a horizontal line at the head 454-456. IN WATER AND ACIDS. CaT, Ca3(P04)2, or CaO. By shaking this precipitate with cold KHO solution, CaT is dissolved and may be reprecipitated from the solution or filtrate by diluting and boiling for some time: the liquid is decanted and the precipitate is then gently warmed with a little very dilute AmHO and a crystal of AgNOa; a metallic mirror shows the presence of T. 454. Sulphide.—Very small quantities of S may be detected by boiling the substance with KIIO for some time, and adding to the clear solution alkaline RbA2 so- lution, when a black precipitate or coloration will appear. The above directions must only be considered as afford- ing examples of how the principal acid-radicles are de- tected. By reference to the individual reactions in Section IV and to the directions there given for the detection of similar acid-radicles when occurring together, this method will serve for the detection of all the commonly occurring acid-radicles. SUBSTANCES IN WATER AND ACIDS. is unknown or unimportant. THC‘|COTt'lOtCI>GOC50T-iC^CO^ . o^joi4§ .4 CmOH'j3Z,MOS<1 Ag. cs s•« — £ j- Is a | a as > cs % 5 a ► 1 l l 1 I l l l l l l 1 •5 S. ► ► 1 1 1 1 1 1 1 ► s’ £ fe 1 * 1 « 1 1 ! 1 A Is a 1 * 1 1 1 1 « * A | d 3 | | | CS 3 « « £ 1 fs -s cs « s d ci £ | cs s* a os 'p | 1 1 =« 1 « § .„• a c5o3^fjc$fcioSaSc5o5cc’n^5Sc3 c« a £ cs’T*'? cS C5 | 03 cC j3 > c3 cJ £ p£ a *1*1 ££««*«* | |c« are placed the more commonly occurring metals, which yield salts or basic oxides; in the vertical column on the left is a list of that por- tion of the names of the compounds thus formed, which corresponds to the acid-radicle; the same are also placed in chemical symbols in a 268 THE TABLE OF SOLUBILITY. [457,458. vertical column on the right. The solubility of a compound is de- noted by letters: w. Signifies soluble in water. a. Soluble in acids; the term standing for ITC1, HNO3, and aqua regia. . am. Soluble in muriatic, or hydrochloric acid. an. Soluble in nitric acid. anm. Soluble in a mixture of muriatic and nitric acids, or aqua regia, but not in either separately. i. Insoluble in water and acids. w.a. Letters thus placed together with a stop between, signify that in different states the substance shows these different solu- bilities. w-a. Letters connected by a hyphen indicate that the substance is only slightly soluble in the first solvent, and may therefore partially fall under the class denoted by the second letter. w.b. Decomposed more or less by much water with formation of a basic salt which is insoluble in water but soluble in acid. 457. To find the solubility of any compound of one of the metals placed at the top of the table, glance down the vertical column which is headed by this element; the letter indicating the solubility of the compound will be found in a horizontal line with the acid-radicle portion of the name. Thus to find the solubility of zinc sulphate, it is only necessary to glance down the vertical column with Zn at its head : on a horizontal line with “sulphate” (SO4) stands the letters, showing the zinc sulphate is soluble in water. 458. The way in which this table is used after ascertaining the solubility of a substance under analysis, and detecting the metals present in it, may be explained by an example. In a substance which was entirely soluble in water, the metals found were K, Ba, Ag. We glance down the columns headed by these three metals, and can thus see at once which acid-radicles may be present: all acid-radicles might be present combined with K since all its salts are soluble in water, but the presence of Ba in a substance soluble in water shows that SO4, P04, CO3, BOs, AsOa, AsCb, CrOi, and F cannot be present, since these acid-radicles form compounds with Ba which are insoluble in water; Ag excludes in addition S, Cl, Br, and I; hence amongst the more commonly occurring acid-radicles only NO3 need be tested for. This example shows how much we may often simplify the examina- tion for acid-radicles, when the metals present in a substance and also its solubility are known, by referring to the above table. 459.] REMARKS ON GROUP III. 269 REMARKS ON THE PRECIPITATION OF GROUP III. 459. In the general table (419) it is assumed that in the absence of (P04)r// the two Sub-groups III a and III B can be separated from one another by adding first AmCl and then excess of AmHO to the solution ; Group III A alone being thus precipitated, and Group III b being afterwards precipitated by adding Am2S to the fil- trate. Now although AmCl entirely prevents the pre- cipitation of Group III b by AmHO, if the solution is kept covered from the air, still if the members of Group III A are present at the same time in the solution they are precipitated by AmHO, and the presence of AmCl will not prevent Mn arid Zn from being precipitated with them in smaller or larger quantity, Mn particularly showing a tendency to be precipitated with Fe, and Z11 with Cr. Hence if either Mn or Zn, especially the former, be present in small quantity only, it may be en- tirely precipitated in Group III A: this is not a serious matter in the case of Mn, since it is readily detected in the ordinary examination of the precipitate by Table III A by yielding a green mass on fusion with Na2COs and KNOs; but Zn may be entirely passed over, since if precipitated with Cr2Ho6 its presence would certainly not be detected in Table III a. The method of dis- solving the precipitate several times in HC1 and re- precipitating with AmHO, to some extent meets this difficulty; but it is preferable whenever a precipitate is produced on adding AmCl and AmHO, and traces of Mn, and more particularly of Zn, have to be tested for, to precipitate Groups III A and III b together by add- ing in succession AmCl, AmHO, and Am2S, and boiling. The precipitate is then examined by Table III c (464, 465) for Groups III a and III b, the filtrate being examined, as directed in the general table, for Groups IV and V. It must, however, be understood that if no precipitate is produced by AmCl and AmHO, Am2S may be added, and the precipitate, if any, examined by 270 REMARKS ON THE [460,461. Table III b, since in the absence of Group III A the members of Group III b are not precipitated by AmIIO in the presence of AmCl. 460. The presence of (POi)'" in ihe HCl solution which is to be examined for Groups III, IV, and V involves no special procedure if AmllO added after Am Cl produces' no precipitate, since the phosphates of Groups III and IV and of Mg must be absent. If, however, on adding AmCl and AmllO a precipitate is formed, the directions given at the head of Table III D (466) must be followed, and the precipitate must be ex- amined by that table. The reason for this departure from the ordinary course of analysis is that, whereas Al, Cr, Ba, Sr, Ca, and Mg, if present as phosphates, are completely precipitated by Am HO, the phosphates of Ni, Co, Mn, Zn, and Fe are only partially precipitated by Am HO; their metals are, however, entirely precipi- tated by Am2S. The filtrate from Am2S is then exam- ined as directed in the general table for Groups IV and V. The principle on which the method drawn out in Table III d is founded are: 1. The insolubility of the phosphates of Al, Fe, and Cr in III in the presence of an alkaline acetate, the other portions of the precipitate being soluble. 2. The separation of all the (P04)r// which is in the HA solution combined with Ba, Sr, Ca, or Mg, by Fe2Cl6 in an HA solution. The further separation of Al, Fe, and Cr phosphates is somewhat complicated by the fact that A1P04 is only decomposed by fusion mixture when Si02 is also present, and this Si02 has to be removed after the fusion by methods which will be intelligible on reference to (290,-291). 461. The reason why, in obtaining the precipitate for Table III d, the precipitates produced by AmHO and Am.,S are filtered and washed separately, is that phos- phates of Fe, Zn, Mn, Ni, and Co are converted by AmaS into sulphides, forming at the same time ammo- 462.] PRECIPITATION OF GROUP III. 271 nium phosphate which remains in solution, and this would precipitate Ba, Sr, Ca, Mg as phosphates from the solution, even if they were not originally present in that condition. Now this besides complicating the pro- cess of analysis, would also render it impossible to state whether Ba, Sr, Ca, and Mg were originally present as phosphates or not. Hence the phosphates of Groups III and IV and of Mg are first precipitated by AmCl and AniHO, then any members of Group III b and any remaining traces of phosphates of Group III are precipi- tated from the filtrate by Am2S. The two precipitates are mixed and treated with Am2S, which will dissolve away the (POJ'" from Fe, Zn, Mn, Ni, Co phosphates if present, leaving the other phosphates undecomposed; hence, if on filtering and testing the filtrate with AmCl, AniHO, and MgS04 a white crystalline precipitate is obtained, this indicates the presence of (P04)"', and indi- rectly establishes the presence in the original precipitate of phosphate of some one or more of the metals Fe, Zn, Mn, Ni, Co. 462. Oxalates, borates, fluorides, and silicates of Ba, Sr, Ca, Mg would likewise be precipitated by AmHO in Group III A; but by the evaporation of the HC1 solution after passing H2S, IT3B03 and HF are usually volatilized, and IIaSi03 becomes insoluble; oxalates are also decomposed by a gentle ignition after evaporation. *** The best course to be pursued in precipitating and examining Group III will be found in (463). 272 PRECIPITATION OF GROUP III. [463. 463. RULES FOR THE PRECIPITATION AND EXAMINATION OF GROUPS III a AND III b. Refer to pars. 459-462 for the explanation of these rules. The following rules may be laid down for precipi- tating and detecting members of Groups III A and III B in the HC1 solution, a small portion of which has been tested for (P04)"' by AmHMo04: I. If the addition of AmllO after AmCl causes no pre- cipitate, showing the absence of Al, Fe, Cr and of their phosphates, and of phosphates of Ba, Sr, Ca, and Mg, Am2S is at once added, the liquid boiled, and the pre- cipitate, if any, examined for members of Group III b by Table III b (437): this course is pursued whether (P04)"' is present or absent, since even if phosphate is present, metals of Groups III and IV and Mg are not present as phosphates. II. If the addition of Am HO after AmCl causes a precipitate, showing the presence of Al, Fe, Cr, and cpor is not present, the plan of precipitation depends upon the object of the analysis. If small quantities of Zn need not be tested for, the method given in the general table (419) may be fol- lowed. If traces of Zn have to be tested for in the solution, add AmCl, then AmHO and Am,S in excess, boil, filter, and examine the precipitate by Table III cx (464) or III c2 (465). The method described in Table III cx gives trustworthy results, and is to be used for very careful analysis; the method in Table III c2 is, however, much more simple, and is sufficiently accurate for general use. III. If the addition of AmHO after AmCl causes a precipitate, and {FOf" is present, the method of precipi- tation to be adopted will be found in par. 466, together with the table for the examination of the group pre- cipitate. 464.] TABLE IIICj FOR GROUP III. 273 464. TABLE III q.—THE SEPARATION OF GROUPS III a AND III b BY BaCOs. The precipitate may contain Fe, Al, Cr, Zn, Mn, Ni, Co. Rinse it off the filter into a porcelain dish, using as little water as possible, add some strong HC1 and boil, adding at intervals a small crystal of KC103 until all is dissolved but a small quantity of yellow sulphur. Evap- orate very nearly to dryness, dilute with a little water, and pour, through a filter if necessary, into a small flask. Cool, pour in a small quantity of BaCOs suspended in water, cork the flask tightly and shake well; repeat the addition of BaC03 and agitation until the precipitate is distinctly whitened by the excess of BaCOs; then shake well and allow the flask to stand by corked for at least fifteen minutes, occasionally shaking it vigorously. Let the precipitate subside, filter; wash the precipitate with a little cold water, allowing the washings to run through into the filtrate, then wash thoroughly, rejecting the washing-water: 1. Precipitate may contain Fe, Al, Cr, and BaCO*; dissolve it in as little boiling HC1 as possible; remove Ba from the boiling solution by adding dilute 1I2S04 gradually, until after allowing the precipitate to settle, a few additional drops of acid cause no further precipitate (Note 1, below); filter, add pure NaHO in excess to the filtrate, boil and filter: 2. Filtrate may contain Zn, Mn, Ni, Co, and BaCl2. Remove Ba by adding to the boiling liquid dilute H2S04 gradually, until the last few drops produce no further precipitate in the clear liquid from which the BaS04 has been allowed to settle; filter, add pure NaHO in excess to the cold filtrate, stir well and filter. Precipitate may contain Mn, Ni, Co; rinse off the filter into a porcelain dish with as little water as possible, add some strong HC1 and boil; evapo- rate nearly to dryness, add a little strong solution of NaA to the liquid, pass HaS to saturation, filter: Filtrate: pass a white precipitate indicates: Presence of Zn. Precipitate,: ex- amine for Fe and Cr by col- umn 2, Table III a (436). Filtrate: exam- ine for Al by column 1, Table III a (436). Note. 1.—The separation of Ba may be neglected here, the precipi- tate being at once boiled witli NaHO: in this case much white BaCOa will remain with the Fe203 after fusion to separate Cr ; it will however dissolve with the Fe and cause no complication. Precipitate: ex- amine for Ni and Co ac- cording to Table III b, column 1(437). Filtrate: add AmHO in excess; a flesh-colored precipitate shows: Presence of Mn. 274 TABLE IIIC2 FOR ANALYSIS ;465. 465. TABLE III c2.—FOR EXAMINATION OF Remove the precipitate produced by AmCl, AmHO, and dish, pouring in dilute HC1, and gently stirring and shaking residue is left, filter (see Note 1): Residue if black may contain NiS and CoS; examine it as directed in Table III B, column 1 (437). Filtrate may contain Al, Fe, Cr, Zn, Mn. Carefully note its result of this observation, examine the liquid by column I. The liquid is perfectly colorless : Absence of Cr. Boil the liquid in the dish for a few minutes until it no longer smells of II2S, then add a small crystal KCIO* and boil down to a small bulk; cool, add NallO in excess, stir well and filter : Precipitate may contain Fe, Mn. Dry and fuse it on platinum foil with NaaC03 and KNOa; a blue-green mass shows: Presence of Mn. Boil the foil in a porcelain dish with water for some time, and if any undis- solved residue is left, de- cant the liquid, boil the residue with HC1, and add KCyS; a blood-red colora- tion shows: Presence of Fe (Note 3, 436). Filtrate may contain Zn, Al. Divide into two equal parts (Note 2). Into one portion pass H2S; a white precipitate forms at once: Presence of Zn. To the other portion add di- lute HC1 gradually whilst stirring; if no precipitate forms, add HC1 in excess, then Am HO in excess, and heat; a colorless floccu- lent precipitate: Presence of Al. Note 1.—A mere milkiness, due to the separation of sulphur, shows the Note 2.—A1 and Zn may also be detected without dividing the filtrate by a colorless flocculent precipitate shows Presence of Al: this is filtered off and 4o5. OF GROUPS III A AND III B. 275 GROUPS III a AND III b, WHEN MIXED. Am2S from the filter by opening the filter out inside a porcelain the liquid: take out the filter-paper, stir well, and if any black color, which is best seen by pouring it into a white porcelain dish, and according to the I or II. II. The liquid has a violet or bright-green color: Presence of Or. Boil the liquid in the dish until II3S is no longer smelt, drop in a small crystal of KC103 and boil down nearly to dryness; dilute with a little water, pour into a small flask and add BaC< >3 suspended iu water gradually while constantly shaking the liquid until the excess of BaCG3 whitens the precipitate ; cork the flask and allow it to stand for not less than fifteen minutes, occasionally shaking it well; filter, wash first with cold water, letting the washings run into the filtrate, then with boiling water, rejecting the washings: Precipitate may contain Fe, Al, Cr; examine it by column 1, Table III c, (464). Filtrate may contain Zn, Mn ; boil, and whilst boiling, add dilute 1I2S0« gradually until the last few drops cause no further precipitate, filter from BaS03; cool, add pure NaHO in excess, stir well and filter; Precipitate: dry and fuse with Na2C03and KNOa on plati- num foil; blue-green mass: Presence of Mn. Filtrate: pass H2S; white precipitate: Presence of Zn. absence of Ni and Co, and does not render filtration necessary. adding to it HC1 gradually until it becomes acid, then AmHO until alkaline; II2S passed into the filtrate; a white precipitate shows Presence of Zn. 276 PRECIPITATION AND EXAMINATION [466. TABLE III d.—FOR EXAMINATION 466. If (P04)'" is found in the HC1 solution in the general tate forms on addition of AmCl and excess of AmHO, the liquid the precipitate is washed well with hot water. To the filtrate and the filtrate examined for Groups IV and V (419, 431). The a porcelain disli and stirred well with a little Am2S, then filtered, be examined for (PO,)'" by adding MgS04; if this is present, The residue left after stirring with Am2S may contain Ba, Sr, Ca, Or as hydrates. Remove it from the filter and heat it with drop in several small crystals of KC103, and evaporate very nearly tion of HA and NaA (526. 84), as long as any precipitate is pro- Filtrate: Add Fe2Cl6 (Note 2) drop by drop as long as a precipitate forms, and until the liquid, after being well stirred or shaken, remains reddish; addition of Fea('ls in large excess must be carefully avoided. Warm gently for some time, filter whilst hot, and wash with hot water: Filtrate: Add AmCl, AmHO (Note 3), and AmtS: filter: Precipitate con- taining FePO« may be neg- lected. Filtrate: Add AmaC08: filter: Precipitate: examine by table III c (464, 465) for Zn, Mn, Ni, Co, also for A1 and Cr. Test a portion of the original solution, or the solution of the substance in IIC1, for Fe" and Fe"' by Note 3 (436). Precipitate may con- tain BaCOa, SrCOa, CaC03. Examine this precipitate by Table IV (438,). Ba, Sr, Ca, if found in this precipi- tate, were present in the solution as phosphates. Filtrate may contain Mg; add Na4HPO«, warm and shake well; white crys- talline precipitate: Presence of Mg as phosphate. Note 1.—An insoluble residue here may contain SrS04 and BaS04, and must originally as phosphates. Note 2.—A few drops of Fe2Cl6 may be added to a small part only of the fil- med at once for Groups III and IV and for Mg, without adding Fe2C)6. Note 3.—Since this filtrate has to be tested for Groups III a and III B, it ing the precipitate by Table 111 c, or by precipitating Groups III a and III B cipitates by Tables III A and III b (436, 437). Note 4.—Since CrP04 is rarely present, this precipitate may generally be solution, and is detected by acidifying with HC1 and adding AmHO in ex- and is detected by dissolving in HC1 and adding KCyS. 466.] OF PHOSPHATES IN GROUP III. 277 OF PHOSPHATES IN GROUP III. table (419) after precipitating Groups I and II, and a precipi- containing the precipitate is gently heated, filtered quickly, and Am2S is added in excess, and the solution boiled, then filtered, two precipitates yielded by AmHO and by Am2S are transferred to and the residue on the filter is washed well. The filtrate should Fe, Zn, Mn, Ni, Co, one or more were present as phosphates. Mg as phosphates; Fe, Zn, Mn, Ni, Co as sulphides; and Al, dilute HC1 in a porcelain dish. If this does not dissolve it, to dryness. Filter off' S if necessary (Note 1) ; then add a solu- duced. Heat gently, and filter while hot: Precipitate may consist of FeP04, A1P04, CrP04 (Note 4). Dry the precipitate on the filter, and fuse it for a short time in a platinum crucible or on platinum foil with a mixture of finely powdered SiOo, Na2CO,, and KNOa. When cold dissolve by boiling with a little distilled water, add Atu2COs; allow to stand for a short time, stirring occasionally ; let the precipitate subside, filter : Filtrate: add IIA until the solu- tion is acid, boil for a short time, then add PbA2; yellow precipi- tate of PbCr04: Presence of Or as phosphate. Note.—A white precipitate on addition of PbA3 may be disre- garded. Precipitate may contain H4Si04, Fe and A1 as silicates, and FeaHos. Acidify with HC1, evaporate to dryness, and heat the dry residue gently. Warm with a few drops of strong HC1, add hot water, and filter: Filtrate: add pure NaHO in excess, boil and filter: Residue is Si02 and may be neglected. Filtrate: acidify with HC1, and add AmHO in excess, boil: white, gelatinous precipitate: Presence of Al as phosphate. Precipitate is brown Fe2HoB: dissolve by boiling with HC1, and add KCyS: blood-red coloration: Presence of Fe as phosphate. be examined by the latter part of (428): Ba or Sr, if found here, were present trate and heated; if it causes no precipitate the other portion may be exam- may be examined either by adding AmCl, AmHO,and Am2S together and analyz- separately by AmCl and AmHO, and then Am2S, and by examining the pre- tested by boiling with excess of NaHO, and filtering; A1P04 will be in cess, which gives a gelatinous precipitate; Fe2IIo6 remains as a precipitate, EXAMINATION OF A [467-469. 467. ANALYSIS OF METALS AND ALLOYS. After making the preliminary examination given be- low either of the two methods (470 or 471) may be adopted. The first method is by far the most ready and certain for the examination of a metal or alloy of un- known composition, since all metals, even when present in small quantity only, may thus be detected. In making the solution by the second method, Sn, Sb, Au, and Pt are left undissolved, all other metals passing into solution; it is not, however, to be recommended as a general process for examination of metals and alloys, since the following complications are apt to occur. If As is present with Sn, a part or the whole of the As may remain in the residue; Pt, if present with a sufficient quantity of Ag, may pass entirely into solution; and Sb will always partly dissolve. The process, however, is useful in cases where an alloy, known to contain a large proportion of Sn or Sb, has to be examined for other metals, since these are dissolved away at once from the bulk of the Sn or Sb; but care must be taken that As is not passed over in the presence of Sn. Pkeliminaky Examination. Note the color, and also if any smell is given off when the substance is rubbed with the hand; also whether it is crystalline or not, and if it is attracted by a magnet (Fe, Ni, Co, etc.). Note also the hardness of the metal; by seeing if it can be scratched or cut by a steel knife; also whether on being struck smartly with a hammer it breaks to powder (brittle), or flattens out (malleable); then try the following experiments: Experiment. Observation. Inference. 468. I.—Heat a small portion on charcoal in the inner blowpipe flame. 469. II-—Heat a portion in a small tube closed at one end. Note.—As and S can frequently only he detected as arsenate and sulphate by fusion with KNO, and Na2C03, dissolving in water, and testing the solution by (449) or (446). The results obtained hy (403) and (404) in the preliminary table may be here noiiced. A metallic sublimate forms. The sublimate consists of small liquid globules. A yellow sublimate melting to reddish-yellow drops; the substance when heated slowly in a tube open at both ends evolves SOa (417). The inference will be found stated in (403) and (404). Presence of Hg, Cd, As; the two latter are de-| tected by (468). Presence of Hg. Presence of S from a sul- phide. 470,471.] METAL OR ALLOY. 279 Processes for Solution and Examination of a Metal or Alloy. 470. Method I.—Pour some rather dilute HC1 upon the powdered metal in a small flask covered with a watch- glass with its concave surface upwards, and heat for some time just short of boiling; if the metal dissolves readily, continue heating until the metal is completely dissolved, and examine the IIC1 solution according to the general table (419). Frequently HC1 alone does not effect complete solu- tion; two or three drops of strong HN03 should then be poured in, and more HN03 and HC1 added occasionally when the action ceases or when red fumes are no longer given off* on heating. When the metal has entirely dis- appeared, add a little more strong HC1 and boil as long as any Cl or reddish fumes are given off*; then dilute with a little water, heat to boiling, and cool; filter if there is any white residue: Residue, if crystalline, is proba- Filtrate (Note 1): dilute largely bly PbCl2, and will be found to with II20 (see Note 2), and dissolve entirely if washed with whether this causes a precipi- sufficient boiling water. tate or not, pass II2S to satura- In this solution the presence tion into the solution ; examine of Pb is confirmed by adding any precipitate thus produced K2CrOi, which gives a yellow by Table II (435), and proceed precipitate soluble in excess of to examine the filtrate for KHO, showing presence of Pb. Groups 111, IV, and V, as di- rected in the general table (419). If any residue is left after washing well with boiling water, it is probably AgCl; confirm the Note 1.—If Au and Pt may be present, they must be tested for in presence of Ag by pouring upon the II2S precipitate, according to the directions in (472-474). the residue hot AmllO : it dis- solves completely but is repre- Note 2.—A white precipitate ap- cipitated on adding HNO3 in pearing on dilution is due to the excess: Presence of Ag. presence of Bi, Sb, or Sn. 471. Method II.—Pour upon the finely divided metal some strong HNOj,1 and heat in a small flask, 1 If Ilg is found in the preliminary examination and small quan- tities of Ag have to be tested for, the Ilg should be expelled by heat- ing the substance strongly in a porcelain crucible before dissolving in acid, as Hg(N03)i tends to prevent the precipitation of Ag by HC1 in Group I. 280 EXAMINATION OF A METAL. [471. covered with a watch-glass, as long as any red fumes appear: one of two results will occur : I. II. The substance dis- solves completely with or without ad- dition of water. Absence of Pt, Au, Sb, Sn, (Note 1). Examine the solu- tion, after boiling nearly to dryness and diluting with water(Note 2), by the general table (419;. A residue is left: adfl some hot water and boil, then filter and wash the residue on the filter well with boiling water(Note 2;. The residue may present the following appearances: 1. Entirely metallic or black powder: probably Pt or Au. Dissolve by heating in a small flask covered with a watch-glass, with a little HC1 to which a few drops of HN03 have been added. When completely dissolved add more HC1, and boil down in au evaporating-basin nearly to dryness; examine the so- lution for Au and Pt by (474), com- mencing with the addition of KC1 and using only the left-hand side of the table, since Sn will be absent. 2. White powder may contain Sn, Sb, As, possibly also Pt and Au concealed in it (Note 3). Note 1.—The solution is liable to contain small quantities of these metals, which must always be tested for in a careful analysis. Note 2.—BiOOi will often precipitate on dilution, but the precipi- tate will disappear on adding HC1 and boiling, being thus easily dis- tinguished from the Group 1 precipitate. Note 3.—If much residue is obtained a small quantity of it may be heated in a test-tube with 1IC1 adding KC103; if it dissolves entirely dissblve the whole of the residue, then examine the solution by Table II, commencing at (435 b); if it refuses to dissolve proceed with the rest of the residue as directed below. If the residue is small in quan- tity examine it at once as directed below. Examination of the Non-metallie Residue Insoluble in HNOz.—Dry the residue on the filter at a gentle heat, mix it thoroughly with about an equal quantity of pow- dered Na2C03 and NaNO.„ and add the mixture grad- ually to some NaNO, in fusion in a porcelain crucible; then pour the melted substance out into a porcelain dish; allow it to cool, then pour upon it cold water and let it stand for some time. After crushing the mass with a pestle and stirring it occasionally, filter, and wash the residue on the filter with dilute alcohol, throwing away the washings: 472.] DETECTION OF GOLD AND PLATINUM. 281 Residue may contain Sn, Sb, Pt, Au. Filtrate may contain Place it in a small porcelain dish, pour (AsG4)/// : add HNOs in a little HC1 and heat, then add until the solution is water; whether the residue has dis- acid and boil, evapo- solved or not place in the liquid a strip rating the liquid ill a of Pt-foil and drop upon it a piece of dish if very bulky. pure Zn; 11 is given off; wait until Pour into half this so- this ceases, taking care that there is lution AgNOs as long some Zn left undissolved, and adding as it gives any precipi- more Zn if the first piece has entirely tate, and add gradu- ally AmHO diluted dissolved. Now remove the platinum strip; if it is stained black Sb is present. with 10 or 12 times its The residue in the dish may consist of bulk of water; a brown Sn, Au, and Pt; remove the Zn, rins- precipitate shows: ing off any substance adhering to it Presence of As. into the dish, stir the liquid in the dish well, then pour off the liquid carefully, To the other half of the leaving the residue; pour in water, stir well, and again pour off'carefully. acid solution add AmHO in excess, then Boil the residue for some time with MgS04, and rub the inside of the vessel strong HC1 in a test-tube, dilute, de- cant, add HgCl2; a white precipitate with a glass rod; a forms: Presence of Sn. white crystalline pre- Residue: dissolve by warming with HC1 cipitate, often appear- and HN03 and examine the solution ing only after some for Au and Pt by (474), using only the time, shows: left-hand portion of the table. Presence of As. SEPARATION AND DETECTION OF Au AND Pt. 472. Au and Pt will, in the ordinary course of analy- sis, be entirely precipitated as sulphides in the second group, if II2S is passed for some time into the hot IIC1 solution ; and since these sulphides are soluble in KHO and in Am2S, on examining the H2S precipitate by Table II (435), the Au and Pt will pass into the filtrate when the precipitate is boiled with KHO or Am2S. No modi- fication of the process described in Table II is required for the detection of these two metals until the examina- tion of the residue in the hydrogen flask is commenced. The Au and Pt will be present in this residue, associated 282 DETECTION OF GOLD AND PLATINUM. [473,474. with Sn if it be present, and usually also with at least a part of the Sb (if present), since Zn and Pt in contact in an acid liquid cause the separation of metallic Sb (193). Accordingly, when Au and Pt have to be tested for, the ordinary course of analysis is to be followed until the residue in the hydrogen flask is obtained; and this is examined as directed in (473). 473. After washing the residue left in the hydrogen flask by decantation in a porcelain dish, and removing any excess of Zn, boil it with a little strong HC1 in a test-tube for several minutes, allow the residue to settle, and decant the liquid : 474. Residue:1 pour upon the residue in the dish a little Solution: to one HC1, add several drops of HNOa. and boil gently very part add HtrCU; nearly to dryness; add some KC1 solution and evaporate a white pre- once more very nearlv to dryness. Pour some absolute cipitate, which alcohol into the cool dish and stir well for a time, allow does not appear the precipitate to settle and decant the liquid, wash the at once if only precipitate by stirring it with a little more alcohol and traces of Sn are decant the liquid when the precipitate has settled; present; Presence of Sn. Precipitate will consist of Solution will be yellow if Au is yellow K3Pt('ls and ex- present; evaporatecarelully Pour the other cess ot KC1; dissolve it in on a water-bath just to dry- part of this so- a little boiling water, pour ness, dissolve in a little water lution into a it into a white dish, add and add a few drops of freshly porcelain dish, several drops of HCI, then prepared FeSO« solution. Au immerse it in a SnCl2; an orange-red col- will be precipitated in a fine strip of Pt and oration confirms the powder, causing the liquid to drop a piece of Presence of Pt. appear reddish by reflected Zn on the Pt; a and blue by transmitted black stain on light: the Pt shows: Presence of Au. Presence of Sb. 1 If Sb lias not been detected already in the precipitate produced by the gases in AgNC>3 solution (435 b) this residue should be exam- ined for Sb, as the Sb, instead of having been given off as SbH3, may have been deposited on the Pt or An. Boil it once more for some time with strong I Id to remove all Sn, wash the residue well by de- cantation and boil it in the dish with H2T adding a fewr drops of IINO3, decant, and test the liquid for Sb by adding IIC1 and passing II2S: the residue is then examined as above (474). 475/ INSOLUBLE SUBSTANCES. 283 EXAMINATION OF SUBSTANCES INSOLU- BLE IN WATER AND ACIDS. 475. An insoluble substance may consist of one or more of the following substances, all of which are white except Ee2Oa, Cr203, FeCr2Ot, PbCrO*, S, C, and AgCl which has been exposed to light. In the following list those substances which are embraced in brackets ( ) may possibly be present, those in square brackets [ ] improbably, because they are soluble in water. 1. PaSOi Insoluble in water and acids. 2. SrSOi “ “ “ 3. [CaSO,] 4. (PbSOt) Not perfectly insoluble in water, soluble in hot HC1; hence it should pass into the acid so- lution. 5. PbCrOi Insoluble after being strongly heated. 6. [PbCQ Soluble in boiling water, and should therefore have been removed if the residue was well washed with boiling water. This may have been originally present as such, or may have been derived from the use of HC1 in making the solution, or by the action of aqua regia on the insoluble substances AgBr, Agl, AgCv, Ag6Fe2Cy12, Ag4EeCy6. 7. AgCl 8. Si02 Either uncombined, or as a silicate. 9. (A/,/),) ) 10. (Fe203) l 11. (Gr203) j Insoluble after being strongly ignited, but these are usually dissolved by long boiling with strong HC1. 12. FeCr2Oi Chrome iron ore, native. 13. (Sn02) Native or ignited. 14. Sb20s,Sb20< 15. CrF2 Also a few other fluorides, and some meta- phosphates and arsenates. Yellow, slowly soluble in strong 1IN03, giving red fumes, and yielding PI2S04. Black, and quite insoluble. 16. S ■ 17. C If sufficient of the substance is at disposal, the preliminary exami- nation (476) may be made on a portion of it. In case the quantity of substance is small, however, the whole of the substance must be employed for the examination by fusion (477). 284 EXAMINATION OF 476. PRELIMINARY EXAMINATION. The substance must be in the state of dry powder. Make a careful examination of it with a pocket lens. Experiments I and II need only he made if the substance is light in color. Experiment. Observation. Inference. I. Observe whether the substance darkens when allowed to stand in the light for some time. The color changes to vio- let or black. Presence of AgCl. II. Pour a little Am2S upon a portion of the substance on a watch- glass. The substance blackens; pass on to III. The substance does not blacken; pass on to V, omitting ill and IV, since Pb and Ag must be absent. Presence of Pb or Ag. III. Heat some of the sub- stance with a little water and a small piece of KCy ; filter off, keeping the residue; to the fil- trate add AmgS. A brownish precipitate. Presence of AgCl. Confy. On warming some of the substance with AmliO, filtering, and adding excess ot HNOato the filtrate, a white pre- cipitate forms, which, when shaken well or heated, coagulates into flocks. IV. Wash the residue from Exp. Ill well upon the filter: a. It is white-, drop upon it. h. It is dark-colored; pour The residue blackens. Presence of PbS04 or PbCl2. in a little HA, and boil after adding AmliO in excess; filter, to the fil- trate add HA in excess and K20rO4. A yellow precipitate, sol- uble in 1CHO. Presence of PbS04 or PbCl*. V. Take up some of the substance upon a moist- ened loop of platinum wire ; heat it for a short time in the inner blow- pipe flame, then moisten with a drop of strong HC1, and hold in the outer part of a Bunsen flame. A reddish-yellow colora- tion, dusky-green when seen through the indigo- prism. A crimson-red coloration appearing deep red through the indigo- prism. A yellowish-green colora- tion. Note.—If all these are pre- sent, the colorations may often be seen in succession. Presence of Ca' • as Presence of Sr sulphate. Presence of Ba J VI. Heat in a small test- tube or ignition-tube, then strongly on a piece of porcelain or broken glass, or on platinum foil. A yellow sublimate forms on. the sides of tube. When strongly heated the substance smoulders and ultimately burns away. Presence of S. Presence of C. 477, 478.] INSOLUBLE SUBSTANCES. Experiment. Observation. Inference. VII. Heat with strong H2S04in a platinum cru- cible or leaden cup cov- ered with a watch-glass (296); or if a silicate is present, examine by pa-sing the gas into Am HO (297). The glass is etched. A gelatinous precipitate is obtained in the AmHO. Presence of F. Presence of F. VIII. Fuse some of the substance in a bead of NaAmHPO, first in the outer then in the inner blowpipe flame. Particles are seen floating undissolved in the melt- ed bead. Green-colored bead. Reddish-brown bead, col- orless when cold, and hecom i ng greenish i n the inner flame. Presence of SiO.> (480). Presence of Cr. Presence of Fe. Examination of Insoluble Substances. 477. Mix the finely powdered substance1 with three or four times its weight of fusion mixture, and heat the mixture in a small covered porcelain crucible2 until it melts; keep it in fusion for at least ten minutes. Allow the crucible to cool, then pour some water into it and allow to stand or boil until the solid mass is loosened from the crucible; boil this in a porcelain dish with dis- tilled water, crushing the mass by pressure with a pestle if it does not quickly fall to pieces. Allow the residue to settle, pour off the solution through a filter, and boil the residue with a little more water; pour off through the same filter, adding this filtrate to the former one. For the examination of the undissolved residue see (478), for the filtrate (479). 478. Residue on the filter; wash well with boiling water, then make a hole in the bottom of the filter, wash 1 Which, if it is found by Exp. VI to contain free S or C, must first be heated strongly for some time in an open porcelain crucible. 2 If Pb and Ag have been proved to be absent by the preliminary tests, or if they have been first removed by boiling the substance with KCy solution, then with IIA and excess of AmHO and washing well, a platinum crucible may be used. The use of a platinum crucible is preferable, since after fusing in porcelain small quantities of A120:j and Si02 will always be found, being derived from the action of the Na2C03 on the glaze of the porcelain. 286 INSOLUBLE SUBSTANCES. [479. the residue through into a test-tube by pouring upon it a little boiling dilute UNO., (see Note 1 below), and boil; the residue dissolves entirely if the fusion has been con- tinued sufficiently long (see Note 2). Filter if necessary, and examine the solution by the general table (419), bearing in mind that only the metals enumerated in (475) are likely to be present (Note 3). Note 1.—If Ag and Pb are known to be absent by the preliminary experiments, IIC1 may be used for dissolving the residue and is preferable; if effervescence is produced by these acids the presence of P>a, Sr, Ca, or Mg is proved. Note 2.—A residue here may consist of chrome iron ore; this may be dissolved by heating with IIN03 and KC103, and the solution tested by the general table, when Cr and Fe will be found. Note 3.—It is best to evaporate t he solution quite to dryness before testing for Group III, using a water-bath towards the end if the sub- stance spirts. This is always necessary if Si02 is present in the sub- stance, since it is sometimes obtained in the acid solution, and is by this means at once separated. 479. Aqueous Solution of the Fused Mass.—Divide into two parts, A and b. a. Add HC1 until the liquid is distinctly acid, and evaporate in a porcelain dish to dryness, finishing the process on a water-bath if necessary to avoid spirting; then continue to heat the dish gently until the residue is quite dry; pour in a little strong HC1 and warm, dilute and heat again; an insoluble residue shows presence of SiOr Filter, and examine the filtrate by the general table (419) more particularly for Al, but other bases should also be tested for, which being soluble in alkalies may pass into this solution, such as Cr, Mn, Zn, Sn. B. Test separate portions for the following acid-rad- icles as described below: 1. Chloride: acidify with IIN03 and add AgN03; white precipitate easily soluble in AmHO. 2. Sulphate: acidify with HC1 and add BaCl2; white precipitate insoluble on boiling. Note.—Unless the fusion mixture employed was free from chloride and sulphate, Tests 1 or 2 are worthless. 480.] ANALYSIS OF SILICATES. 287 3. Chromate: acidify with HA and add PbA2; yellow precipitate; a chromate is seen also by the yellow color of the solution. Cr thus detected may have been present acting as a metal or as a constituent of an acid-radicle. 4. Phosphate: acidify with HN03, add a few drops to AmIIMo04 solution and warm gently. A yellow precipitate forms, often only after a time, or on gently heating. If As has been found on passing HJ3 into the hot HC1 solution, must be tested for in a portion of the filtrate after boiling off H2S, else the above yellow precipitate may be due to (As04)"'. 5. Fluoride: add IIC1 in excess to a part of the solu- tion, stir well, and let stand until the C02 has escaped, then add AmHO in excess, then CaCl2 as long as it produces any precipitate, and let stand for a time; filter off, dry the precipitate and examine it for F by pouring strong H2S04 upon it in a plat- inum crucible covered with a watch-glass (296). ANALYSIS OF SILICATES. 480. The presence of silica is shown by Exp. VIII in the preliminary examination of insoluble substances (476); when it has been found it becomes necessary to examine for all metals, since many silicates which are soluble when alone, become insoluble when mixed or combined with insoluble silicates. The ordinary analytical course requires but slight modification to adapt it to the examination of silicates. Many silicates are entirely decomposed by heating with strong HC1 for some time just .short of boiling ; if this decomposition has been effected, only a colorless residue of silicic acid will remain, which may be identi- fied by its solubility in hot Na2C03 solution. 288 CYANOGEN COMPOUNDS. [481, 482. If the silicate is not completely decomposed by hot strong HC1, some of it must be fused with fusion mix- ture as directed in (477), and the cool residue boiled with water; the solution and residue are then examined by (478) and (479), remembering, however, that all metals may be present. 481. Since Na and K cannot be tested for in the solu- tion obtained after fusion, a separate portion must be examined for K and Na by one of the following pro- cesses : I. Evaporate the powdered substance several times in a platinum dish or crucible either with hydrofluoric acid and subsequently with strong H2S04, or with five times its weight of calcium fluoride mixed into a paste with strong II2S04, in either case heating finally until no more white fumes are evolved. Boil the cool residue with water, add BaCl2 solution as long as it causes any precipitate, then add AmHO in excess and Am2CO;j as long as it causes any precipitate, filter and examine the filtrate for K and Na by Table Y (439). II. Mix the powdered substance intimately with four times its weight of barium hydrate, and heat strongly in a platinum crucible for about half an hour; dissolve the cool mass in dilute HC1, add AmHO in excess and then Am2C03 in excess, filter, rejecting the precipitate; evap- orate the filtrate to dryness, ignite the residue, then boil it with water; add a little HC1 to the solution and test for K and Na by Table Y (439). 482. ANALYSIS OF SUBSTANCES CONTAIN- ING CYANOGEN. If a small quantity of the substance to be analyzed, when examined by (304) or (306), is found to contain cyanogen, the usual course of analysis must be somewhat modified, since the presence of cyanogen would produce confusing results. The cyanogen may be present as a 483. PRELIMINARY EXAMINATION. 289 cyanide, sulphocyanide, ferrocyanide, ferricyanide, or co- baltieyanide, rarely as a manganocyanide or chromicy- anide. Since the method to be adopted when a cyanide or sulphocyanide only is present is much more simple than that rendered necessary by the presence of the other cyanogen compounds above mentioned, it is advisable first to ascertain in what form the cyanogen occurs, by the following preliminary experiments made on a small portion of the substance ; according to the results yielded by these experiments the further examination of the sub- stance is made by Method I (484) or by Method II (485). Preliminary Examination. 483. Boil a portion of the substance for several min- utes with KHO solution, then add some Na2COs solution as long as it causes any precipitate, and boil again for several minutes; filter, make the cold filtrate just acid with IICl, filter if necessary, and test separate portions as follows : Reagent added. Result. Inference. ’ Blue precipitate, . Presence of (FeCys)iT 1. FeSO« solution, (FeCysV‘ White precipitate,. Probable presence of (CoCy8V 2. Fe2Cl, solution, Blue precipitate, . Presence of (FeCys)ir Blood-red coloration Presence of (CyS/. 3. ZnS04 solution as long as it Light-brown preci- pitate, . [ White precipitate,. j- Presence of (FeCysV! eauses any precipitate, . Confirmatory.—Filter off the \ Presence of (FeCye)lv, (CoCys)2,‘- precipitate, add ZnS04 solu- tion to the filtrate, and if it causes any precipitate, pour again through the filter, re- peating this process until no A blue bead is pro- ) duced, . . i Presence of (CoCys)'1 further precipitate is produced by ZnSO,. Fuse some of the precipitate in a clear borax bead 290 [484, 485. ANALYSIS OF If these preliminary tests show the presence of (FeCy6)iT, substance by Method II (485). If the absence of these acid-radi- whicli indicate their presence, proceed according to Method I If none of the above acid-radicles are found in the prelimi- analytieal course is to expel HCy by boiling after adding IIC1 484. Method I.—If (CyS)' is present, boil the portion of HN03 for some time, dilute a little and boil again. If any resi- solve the residue as directed at the end of (420), any undissolved IINO3 solution is evaporated nearly to dryness and examined Another portion of the substance is examined for acid-radicles 485. Method II. (Fresenius).—Boil the substance with washings to the filtrate : Filtrate: examine this for metals, more es- pecially the alkalies, and for acid-radicles according to the directions given for analyzing a liquid (380). The acid-radicles should be first tested for in a portion of the solution and if (FeCyty\ (FetCyn)’’, (Co*Cyl2)Ti, one or more be found, the solution must be evaporated to dryness with IINOs, and the residue strongly heat- ed (see general table) after filtering from the HoS precipitate, in order to destroy these cyanogen radicles. The Fe, Co, etc., in the cyanogen acid-radicles will then be detected in the general table. Ilexidue.: boil with KI10 solution for several minutes, then add and boil again ; filter and wash the residue : Filtrate: pass 11, S, audit' it causes any precipitate continue KHO,' heat and filter : Precipitate: wash well with boiling water, and boil the precipitate with strong HN03, a black residue of HgSmay remain ; filter this off after diluting the acid, and confirm the presence of Hg in the precipitate by heating it with Na,CG3 in a bulb- tube (147). The filtrate (or solution if HgS is absent) is evaporated to dryness, the residue is then dissolved in a little hot strong HC1, the solution is much diluted, saturated with H<>S, and filtered : Filtrate: add dilute saturation and filter: Precipitate: boil with K1K), filter off any black precipitate and examine it for Hg by heating it with Na,C<)3 in a bulb-tube (147). Add to the filtrate or solution HC1 until it is acid, pass I12S to saturation, and examine for As, Sb, Sn (Pt, Au , by Table II (435), commencing at (435 b). Precipitate: exam- ine for Pb and Cu by Table 11 (435 a). Filtrate: add Am Cl, AmHO in excess, and AntjS, and examine for Zu, Mn, Ni, Co, etc., by Table III c, (465). 1 If H2S causes a precipitate to form, N:i IIS or KIIS may be added, drop by this may be done instead of passing II2S to saturation and then adding KIIO. 485.1 CYANOGEN COMPOUNDS. (FeCy6)2vi, (CoCy6)2Ti. one or more, examine tlie remainder of the cles is indicated by not obtaining the results in the second column (484). nary experiments, the only modification requisite in the ordinary in preparing the solution (383) or in testing for Group I (419). the substance which is to be examined for metals with strong due remains decant the solution and proceed to endeavor to dis- residue being then examined according to (475 et seq.). The y (419). in the usual way. water, filter, and wash the residue with boiling water, adding the some Na2CC3 solution as long as it causes any precipitate in the solution or the filtrate, to pass the gas until the liquid is saturated, then add more Residue: dissolve and examine for metals in the usual manner (383). Fe, Co, Mn, Cr, if found in this residue, were not present as (FeCy»),T, (FegCyia)’1, (Co2Cy12),i, etc. HN03, gradually until the liquid is just acid, pass II2S to Filtrate : Divide into two parts, *, /8 : Examine for acid-radi- cles in the usual way, testing for (CoaCyH)Vi by adding excess of ZuSOi, filtering and try- ing whether the precipi- tate gives a blue bead with borax. fi. Evaporate to dryness and fuse the residue: when cold, boil it with water and filter: Residue: dis- solve in HC1, and test for Al, Ee, Mn, Co (4H5); the last three if found were present as cyanogen acid-radicles. Filtrate: acidify a portion if yellow with IIA and add PbAa; a yel- low precipitate shows (Cr04)", the Cr having been present as cyanogen acid-radicle. Test another part for Al by adding HC1 in excess, then Am HO in ex- cess. drop, until it no longer gives any precipitate in the liquid or in the filtrate ; 292 CYANOGEN COMPOUNDS. [486,487. 486. The advantage of employing this somewhat com- plicated and tedious method of Fresenius is that it usually enables the analyst to ascertain whether Fe, Co, Mn, Cr, when present, form a part of a complex cyanogen acid- radicle or simply act as metals combined with acid-radi- cles. For if Fe, Co, Mn, Cr, are found in the residue left after boiling with KHO and Na2C03, they were present in the latter form ; if found in the alkaline filtrate they were present as cyanogen acid-radicles ; if they were detected as cyanogen acid-radicles in the aqueous solution they were entirely present in that solution in that form, although they will also be detected in the examination for metallic-radicles ; if they were detected only as me- tallic-radicles and not as cyanogen acid-radicles, they were present as metallic-radicles in the aqueous solution. 487. The following two processes have been proposed for removing cyanogen from a substance before analysis, after which the substance may be examined for metals in the usual way (382 et seq.); but these methods, though much more easy and rapid, are less perfect than the pre- ceding ones, since Fe, Co, Mn, Cr, if detected, may have been present either as cyanogen acid-radicles, or as metals united with an acid-radicle, or in both forms. 1. Pour upon the powdered substance strong H.2S04 in a porcelain crucible, evaporate to dryness, and ignite the residue strongly ; when cold dissolve it by heating with a little strong HC1, adding water and heating again. (Rose.) 2. “ Cyanogen compounds are best destroyed by fusion in a porcelain crucible with 3 or 4 times their weight of a mixture of 3 parts of Am2S04 and 1 part of AmX03.” The residue left in the crucible is dissolved and examined for metals in the usual way. 488. EXAMPLE OF ENTRY. EXAMPLE SHOWING HOW TO ENTER THE RESULTS OF ANALYSIS OF A COMPLEX SUBSTANCE. The substance given for analysis consisted of a powder containing pink, blue, white, and black particles. It smelt faintly of ammonia. 488. Preliminary Examination for Metals. Experiment. Observation. Inference. Expt. I.—Heated in a small dry test-tube. Confy.—Held in the Water given off which turned red litmus- paper blue. Strong smell of NHrgas. Substance blackened, no smell of burning. Slight white sublimate. The lime-water became Pres, of II20. Pres, of NH4. Pres, of Nil, Prob. pres, of Co, Cu, and abs. of T and A. Pres, of As, NII4, Hg. upper part of the tube a glass rod with a drop of lime-water hanging on milky. Brown nitrous fumes evolved, recognized by COj evolved. its end. Confy.—Boiled a portion of the substance with KHO solution. their smell. Cl-gas evolved, found by smell and bleaching litmus. NHj-gas was evolved, re- cognized by its smell, and by giving white fumes with strong HC1. Pres, of nitrate. Pres, of Cl. Pres, of Nil,. Confy.—Heated strongly another portion of the dried substance with Jia2C03in a bulb-tube. No mirror formed. Abs. of Hg and As. Expt. II.—Heated a por- tion of the substanceon a loop of platinum wire Bright-yellow flame. The flame appeared crimson through the Pres, of Na. in the Bunsen flame, moistened with IIC1 and heated again in the flame. Heated for some time in the tip of the inner indigo-prism. Crimson col” appearing intense red through the Pres, of K. blowpipe flame, moist- ened with HC1, and indigo-prism. Bright-green col“ with Pres, of Sr. again held in the Bunsen flame. blue core. Pres, of Cu. 294 EXAMPLE OF ENTRY Experiment. Observation. Inference. Expt. III.—Heated a portion of t he substance on charcoal in the inner The greater part of the substance fused readily, and was absorbed by blowpipe flame. the charcoal. Pres, of a salt of K, Na. Confy.—Fused in a clear borax bead in the outer and inner blowpipe Deflagration occurred. A red metallic residue remained. In the outer flame a“| bead green whilst hot, 1 blue when cold. V Pres, of chlorate, nitrate. Pres, of Cu. Pres, of Cu. flames. Confy.—Fused on plat- inum foil with Na3C03 I11 the inner flame red and nearly opaque. ) No bluish-green or yellow mass on cooling. Abs. of Mn and Cr. KN03. Confy.—Fused on char- Red metallic residue. Pres, of Cu. coal in the inner blow- pipe flame with Na3C03. A portion placed on a sil- ver coin and moistened gave no black stain. Abs. of S. 489. Preliminary Examination for Acid- radicles. Experiment. Observation. Inference. Expt. I.—Added dilute HC1 without heating. Heated to boiling. A colorless gas was evolved, which was free from smelt, and turned a drop of lime-water milky. Cl was evolved, recog- nized by its smell and by bleaching moist lit- mus-paper. Pres, of carbonate. Abs. of sulnhite, hypo- chlorite, etc. Pres, of nitrate, chlorate, or some other oxidizing substance. Expt. II.—Added strong HaS04. Confy.—Dropped in cop- per turnings and heated. Heated strongly, cooled, and rinsed out. Confy.—Boiled a portion of the substance with water, added strong HaS04, cooled and poured in FeS04 solu- tion carefully. A bright-yellow chlorous gas evolved, which crackled when warmed. Reddish-brown fumes evolved. The tube when dry was seen not to be etched. A biown ring formed on the surface of the acid. Pres, of chlorate. Pres, of nitrate. Abs. of fluoride. Pres, of nitrate. OF A COMPLEX ANALYSIS. 490. Examination for Metals in the Wet Way. Boiled a portion of the substance with Fe2Cl6, FeS04 and KIIO, added IIC1 in excess, no blue pp.: Absence of Gy. Proceeded to dissolve the substance and examine the solution by the general table. (Continued on page 296.) 296 EXAMPLE of entry 491. Roiled a portion of the substance with water; as it did noi IIC1 poured upon the undissolved residue; effervescence occurred, as long as any smell of Cl was perceived; the substance was water soln- which had been proved previously to give no pp. No pp. Abs. of Oroup I. Hg', Ag, and prob. Pb. Diluted with water and passed IJ2S until the liquid smelt strongly A black pp. Exaind by Table II. Filtrate which gave no further pp. with Boiled until it no longer smelt of IDS, on addition of HNG3 (prob. pres, of IF), of the HC1 sol" to some AinHMoO* boiled; filtered: A brown pp. Exam' by Table III A. 491. Examn. of pp. in Group II. Removed from the filter into a porcelain dish and boiled with KIIO filtered: Filtrate: Acidified with HC1, a white, milky liquid only; A bs. of Group II b. Pp. removed from fitter by a glass rod into a porcelain dish and boiled with strong HNOs as long as any red fumes came off, added dilute II2SO4 and stirred well: No. pp.: Abs. of Hg and Pb. Added to sol” excess of AmHO; blue solution {pres. ofCu): No pp. Abs. of Bi. Acidified the blue sol" with I1C1 and satu- rated with II2S; filtered off the black pp. rapidly and boiled it with dilute H2S04: Pp.: dissolved in a little boiling dilute 1IN0S, added AmHO in excess, then excess of HA, then K2FeCy„; choco- late-red pp.: Pres, of Cu. Filtrate: diluted much and passed II2S; no pp.; A bs. of Cd. Examn. of pf. ix Group III a. Dissolved in a little boiling dilute HC1, added pure NaHO in excess, boiled and filtered: Filtrate: added IIC1 gradually till the liquid became acid Pp.: dried and fused on platinum foil with Na4COa and KNOa, boiled the colorless [abs. of (P) mass when cold with water; decanted from the undissolved residue: in excess; no pp. Abs. of Al. Residue in the dish dissolved by boiling with a little HC1, added several drops of KCyS ; a blood-red colora- tion : Pres, of Fe. Soln. being colorless proved abs. of Cr. Acidified with HA, boiled, and added PbAa; no yellow pp.: Abs. of Cr. 491.’ OF A COMPLEX ANALYSIS. completely dissolve, the sol"- was decanted, and a little dilute and on boiling, Cl was smelt. Added a little strong HC1, boiled completely dissolved. Cooled this sol”- and mixed it with the on addition of a little dilute HN03: of the gas, Altered : HoS was pink (prob. pres, of Co). added some strong HNO* and boiled to dryness (the color of the sol" changed to light-brown warmed the residue with HC1, it dissolved completely (abs. of H«SiOa). Added a small portion warmed; no pp.: Abs. of (POt)"'. To the remr added AuiCl, then excess of AmHO, and Filtrate was again pink (presence of Co); added much Aid2S and boiled, Altered : A black pp. Exam4 by Table III b. Filtrate was yellow (absence of Ni): added Am2COs, Altered : A white pp. Filtrate. Examd by Table IV. Fxam1 by Table V. Exam51- of pp. in Group III b. Rinsed the pp. off the filter with some cold dilute HC1, stirred well, filtered : Pp. was black and had already been proved to contain no Ni; fused a portion into a clear borax bead, bead blue in both flames: Pres, of Co. Filtrate: boiled until it no longer smelt of HjS, added a crystal of KOIO,, boiled until the smell of "Cl ceased, cooled and added pure NaHO in excess; No pp. Abs. of Mn. Passed II2S into the sol°; no pp.: Abs. of Zn. Examn of pp. in Group IV. 1. Exam71■ by Flame coln-—Dissolved a small quan- tity of the pp. in a few drops of HC1 upon a watch- glass, dipped a loop of Pt-wire into the sol’1- and held it in the Bunsen flame; a crimson-red color was imparted to the flame, which appeared intense red through the indigo-prism: Pres, of Sr. This coloration was followed by a yellowish-green very persistent coln-: Pres, of Pa. 2. Examn■ in the Wet Way.—Dissolved the rest of the pp. in as little boiling IIA as possible; to a small part of the sol11-, perfectly cold, added 0aSO4 sol”-; an immediate pp. formed: Pres, of Ba. 298 EXAMPLE OF ENTRY [491. To the remainder of the IIA soln-, proved to be acid to litmus, added K2Cr04 until the liquid appeared yellow, warmed and poured through a double filter: P/i., which con- tained all the Ba present, was rejected. To the clear filtrate, which was orange-red in color, added AmHO until the color changed to light yellow, then added Ama(JOa in excess and filtered; Filtrate was re- jected. Pp.: dissolved in as little boiling HA as possible; added to a small por- tion ofthesolnCaSO«sol“ and boiled, a pp. formed, showing pres, of Hr. To the remainder of the HA solution added boiled, filtered, and to the filtrate, which gave no pp. after being boiled with more H2S04, added AmHO in excessand Am2,; on heating, a slight pp. formed; filtered, and added to the clear filtrate Naalll’O,; a white crystalline pp.: Into the smaller portion dipped a loop of platinum wire, and held it in the Bunsen flame; an intense yellow coin: Pres, of Na, appearing crimson through the indigo-prism: Pres, of Mg. Pres, of K. Confirmed the pres, of K by stirring a fresli portion of tbe sol“ with PtCl« on a watch-glass; a yellow pp. formed. Metals found: Cu, Fe, Co, Ba, Sr, Mg, Na, K, XII4. 492.1 OF A COMPLEX ANALYSIS. 492. Examn- for Acid-radicles. The following acid-raclicles have already been detected: (CO,)", (NO,)', (CIO,)'. By reference to the table of solubilities (455), under the columns corresponding to the above metals, the only salt insoluble in acids is found to be BaS04; since Ba is present, and the substance is entirely soluble in acids, (S04) is absent. The following acid-radicles have also been proved to be absent in the general examination for metals: (Cr04)", by the HOT solution not becoming green on passing H2S. (AsOg)'" and (As04);//, by no pp. forming in Group II B. (SiO.,)" and (SiF8)", by no residue insoluble in HC1 remaining on evaporating to dryness with HC1 for Group III A. (P04)r//, by testing with AmHMo04 in the HC1 soln* for Group III a. The organic acid-radicles A and T are absent, since there was no smell of burning on heating the substance. The only commonly occurring acid-radicles remaining to be specially tested for are therefore Cl, Br, I, (C204)", and (BO:j)///; and of these Br and I are probably absent, since no violet fumes of I or brown fumes of Br were evolved with strong II2S04. 300 EXAMPLE OF ENTRY. [493. Boiled a portion of the substance with pure Xa2C03 sol11- and filtered; acidified portions of the filtrate with— hno3 HA Added A gN(h; a perfectly white Added CaSOi; no pp.: pp., easily sol. in AmHO: Pres, of Cl. Abs. of (G Moistened a piece of turmeric-paper with HC1 soln- of the sub- stance and dried at 100° ; no brown stain produced. Abs. of (.BOs 493. Found Metallic-radicles: Cu, Fe, Co, Ba, Sr, Mg, Na, K, NH4. Acid-radicles: C03, N03, C103, Cl. SECTION VII. APPARATUS, REAGENTS, ETC., REQUIRED FOR THE FOREGOING COURSE. LIST OF APPARATUS REQUIRED BY EACH STUDENT. 494. The following list is so arranged that: Division I contains all apparatus which is required only for the experiments given in Section I. Division II is apparatus required both for Section I and for the Sections on Analysis. Division III is apparatus used only in analysis. Hence a student intending only to perform the experi- ments in Section I will require the apparatus in Divisions I and II. If he is omitting this portion and intends only to work through the Sections on Analysis, he must be furnished with the apparatus in Divisions II and III, and will not require that in Division I. Note.—Apparatus contained in large brackets [ ] is useful but not indispensable; the asterisk marks apparatus which may be kept for general use, and need not then be supplied to each student. Division I. (See note at end of list, page 303.) *1 Wide-mouthed, stoppered, white-glass gas-jar; about 24 oz. capacity, and 2 inches inside across the neck, whose upper edge should be ground so as to be closed with a ground-glass plate. *1 Small-flanged cylinder, 6 inches in height, 1J inches internal diameter, ground at the edge. *1 Deflagrating spoon, brass cap 2J inches across. *1 Small two-necked Woulffe’s bottle, not less than 4 oz. capacity; or a small wide-necked bottle of not less capacity. 302 LIST OF APPAKATUS. [494. *1 Small retort, best tubulated with stopper, about 4 to 6 oz. capacity. Division II. G Test-tubes, 5 or G inches long, and from to £ inch in diameter. 1 Test-tube cleaner. 2 Lengths of hard glass tubing, rather more than |th inch internal diameter. *1 Thistle funnel. *[1 Clock glass, about 4 inches across.] 1 Bound ground-glass plate, 3 inches across. 2 Porcelain dishes, one 2} inches across, one 3 inches across. 2 Watch-glasses, about 2 inches across. 1 Small flask, about 4 oz. capacity. *Bed or black india-rubber tubing; one piece 18 inches long and T6g inch internal diameter,1 one piece 6 inches long and ,3g inch internal diameter. *1 Bunsen burner1 with separate rose-top. 1 Small pestle and mortar. 1 Iron tripod-stand. 1 Piece of wire gauze, 5 inches square. *1 Round file. *1 Triangular file. *1 Small set of cork-borers. *1 Small retort-stand, 12 inches in height, and fitted with 3 brass rings. Division III. 4 Glass funnels, two 2 inches across at the top, two 2\ inches across at the top. [2 Tobacco-pipe cleaners, for cleaning glass tubes.] 2 Boiling tubes, 6 or 7 inches long, from 1£ to 1| inch across. 1 The Bunsen burner and gas-tubing may be fixtures on each working bench, and will not then be purchased by each student. 494.] LIST OF APPARATUS. 303 1 Test-tube stand with at least 12 holes. 1 Nest of 3 or 4 small-sized beakers. 1 Length of glass rod. *1 Small porcelain crucible, about 1| inch across, and lid. 1 Strip of platinum foil, 2 inches by 1 inch. 2 Pieces of platinum wire,1 each 1J to 2 inches long. 1 Black’s blowpipe. 1 Pipe-clay triangle, 2 inches in the side. *1 Pair of brass crucible-tongs. 1 Large flask for wash-bottle, 18 oz. capacity, and from 1 to inch across the neck. *1 Wooden filtering-stand. *1 Tin filter-dryer. 1 Small wicker-basket for draining test-tubes and other glass and porcelain apparatus after they have been washed. Little toilet baskets, 12 inches in length by 5J and inches high, serve well. Note.—For the experiments with gases the student will also require: *A pneumatic trough, or earthenware pan as a substitute for it (see note, p. 23). A small piece of candle. A wax taper, or slips of wood. A few sound corks of such a size as to fit test-tubes or small flasks. Caution.—In a laboratory where many students are working, it is best to mark at once each piece of appa- ratus with initials, number, or with some private mark, so as to be able to recognize it if mislaid. Glass, metal, or porcelain apparatus may be notched with the edge of the three-cornered file, or characters may be scratched upon it with the sharp points made by breaking off the tip of a three-cornered file. Wooden apparatus can be written upon with pen and ink, or scratched with the tip of a penknife. 1 Platinum wire containing Ba is not uncommon; it is known by giving a persistent green color to the Bunsen flame, and is useless for flame colorations. 304 LIST OP GENERAL APPARATUS. [495-499. APPARATUS FOR GENERAL USE. 495. The following apparatus need not be purchased by each student, but should be kept in constant readiness for general use: 496. An Indigo-prism.—A hollow glass prism, having an extremely small angle at its extremity, with ground- glass stopper fitting water-tight into the neck, is pur- chased ; this is to be very nearly filled with solution of indigo, and the stopper then tied in securely with fine copper wire. The indigo solution is made either by diluting a solution of indigo in strong sulphuric acid until it has the required intensity of color,1 or by dissolving indigo-carmine in water; the liquid is then allowed to stand for several days to give time for any sediment which may form to settle completely, and when quite clear is decanted into the prism. In the thicker part of the prism the blue must be so intense as to arrest the passage of the light from a flame colored yellow with a sodium compound, and to cause the potassium flame coloration to appear crimson-red. 497. Several Small Slips of Cobalt Glass.—This glass is used for the same purpose as the indigo-prism, but the prism is to be preferred, more especially for the examina- tion for Sr. 498. Set of Cork-borers.—These are used for perforat- ing a cork into which a piece of glass tubing has to be inserted (8). NestS of borers containing the three or four smallest sizes will be sufficient. 499. Sulph uretted Hydrogen Apparatus.—It is advis- able to employ a large apparatus which will supply this gas to all who are working in the laboratory. The use of a small private apparatus by each student not only causes unnecessary waste of materials and time, but vitiates the air of the laboratory whilst it is being washed out. Many forms of apparatus have been devised to supply the gas in a constant stream ; probably the following, the 1 The addition of the indigo solution to ten times its measure of acid will usually give the required shade. 500.] SULPHURETTED HYDROGEN APPARATUS. simplicity, efficiency, and cheapness of which render it very satisfactory, will be found the most generally useful. FlO. 39. Note.—The level of the liquids in the vessels is shown by dotted lines; the vessel A when lowered from its stand is also shown in dotted outline. The whole is drawn in section. 500. Sulphuretted Hydrogen Apparatus.—Two large bottles, A and B, with wide necks, and tubulures near the bottom, and of at least two quarts capacity, are fitted as shown in section in Fig. 39.1 India-rubber stoppers should be used instead of corks, as the latter soon be- come sodden with acid and rotten, and also lose their elasticity and permit leakage. The vessel B is laid upon its side to prevent breaking the bottom, and lumps of ferrous sulphide are dropped into it: the cork is then inserted, the clamp at E being closed. The glass tube fixed in the lower tubulure of B should be bent down- wards, so that its end nearly touches the bottom of the vessel. This drains the acid out of B to the lowest pos- sible level Avhen A is lowered. Strong commercial 1 This apparatus may be purchased completely fitted from Messrs. Mottershead, of Manchester, and from most apparatus sellers. 306 SULPHURETTED HYDROGEN APPARATUS. [500. hydrochloric acid1 is poured into A, then an equal bulk of water is added, and the liquids are mixed by shaking the vessel. When the gas is required, the vessel A is raised by being placed on a stand of suitable height, the acid runs into B, generates the gas by acting on the ferrous sul- phide, and by the pressure of the liquid in A the gas is forced through a little water in the washing-bottle C, and thence through a bent tube at D into the liquid which is to be saturated with sulphuretted hydrogen. When the flow of the gas is to be stopped, the screw- clamp on the india-rubber joint at E is tightened; by proper management of this screw-clamp the stream of gas can be either totally arrested or controlled to any required extent; this clamp must always be so regulated as to permit of as little waste of gas as possible whilst using the apparatus. During working hours the vessel A should be kept raised, as shown in the figure; when laboratory work ceases it should be lowered to the position shown in dotted outline. The vessel B is always kept slightly raised by being placed on a wooden block or a brick, so as to encourage the flow of the last portions of acid out of it into A when A is lowered. When the acid is spent, it is easily poured out of A and replaced by fresh; lumps of ferrous sulphide are added as required through the neck of B. The removal of the spent acid and the cleansing of the apparatus should be performad in the open air, or at a sink in a cupboard provided with a good draught. The neck of A may be kept stopped with a cork car- rying a bent funnel whose bend is filled with oil or glycerin ; this lessens the escape of gas dissolved in the acid, and tends to prevent the apparatus from causing a smell. If several students require to use the gas at the same time, the broad stopper of B is perforated and 1 The use of H2S04 instead of IIC1 is objectionable, since FeS04 crystallizes in the apparatus, impeding or preventing the action of the acid and its flow through the connecting tube ; also, it does not produce such an easy and rapid evolution of the gas. 500 a. PASSING SULPHURETTED HYDROGEN. 307 fitted with additional tubes and wash-bottles, or a system of distributing pipes or T-pieces connected with the tube from the cork in B may be employed. An apparatus for private use may be fitted as shown in Fig. 40. The larger bottle contains pieces of snlnViiOo nnnn wlnVli HC1, diluted with an equal measure of water, is poured through the thistle-fun- nel ; the gas bubbles through a little water in the smaller bottle, and thence into the solution to be saturated. The sulphuretted hydrogen ap- paratus should stand in a cupboard with a glass front and small doors, which is not used for any other purpose; the cupboard must be furnished with a flue in which a strong draught is created by an ar- gand or ring gas-burner, made of fire-clay or steatite and not of metal; if the cupboard doors are kept closed as much as possible, and students when using the gas are careful to prevent its unnecessary escape, the atmosphere of the laboratory may be kept tolerably free from this badly smelling gas. The cupboard should have within it a drain into which are emptied the spent acid and washings of the apparatus. 500 a. Passing Sulphuretted Hydrogen into a Liquid.— Each student should keep a bent glass tube (I), Figs. 39 and 40), made according to the directions in par. 9 : when the gas has to be passed into a liquid, the shorter end of this tube is fitted into the india-rubber joint E, and the other end is passed nearly to the bottom of the liquid; on slightly opening the clamp E, a stream of the gas will bubble up through the liquid and may be regu- lated by the clamp; when the gas has passed for about five minutes the liquid will generally be saturated; if this is the case it will smell of the gas strongly after the air above the liquid has been blown out of the vessel and the vessel has been well shaken. Great care must be taken to close the clamp at E completely when the gas is stopped. The tube D must be thoroughly cleansed after use, employing a tobacco-pipe cleaner if necessary for its inside. Fig. 40. 308 STEAM-OVEN. [501-503. 501. A Small Agate Pestle and Mortar (Fig. 32, p. 75). —This is required for powdering very hard substances, more particularly minerals. The substance must have been already broken into small fragments, and these are then crushed to powder by pressure and “ trituration/71 until a powder is produced in which no particles or grains are felt when it is pressed or rubbed with the pestle or the finger; such a powder is commonly termed an “ impalpable powder.77 On no account must a sub- stance be broken by placing it in the mortar and striking it blows with the pestle, as this is very liable to cause the fracture of the mortar. 502. Several small leaden sups or a platinum crucible should be kept in readiness for testing for F by para- graph (295) or (296). The leaden cups are easily made by beating out thick sheet lead into the required shape, the mouth being of such a size as to be readily oovered by a watch-glass; the small leaden inkpots often employed in school-desks serve well for this purpose. 503. A Steam-oven.—This is a small oven of sheet Fig. 41, copper, heated to the temperature of boiling water (100° C.) by water contained in the space between the exterior of the oven and a copper casing which surrounds it (Fig. 41); the outer casing often has a circular open- ing cut in the top, covered by a lid when not in use, 1 Eubbing round and round under the pestle. 504.] WATER-BATH. 309 which serves as a water-bath (504). The level of water in the jacket is maintained constant by a little contriv- ance shown in section at c: a small reservoir communi- cating by a lateral tube with the space between the oven and its jacket is constantly replenished by wrater which drops into it from the supply-tube (cl); the overflow of this reservoir is a tube rising in its centre whose end terminates inside above the level of the lateral tube. The outlet for steam (/) may be turned downwards, so that any water formed by the condensation of the steam drops into the reservoir (c), or it may be made to communicate with the worm of the still (506), the escape steam being thus condensed into distilled water. The steam-oven should always be supplied with distilled water, as this prevents the formation of a troublesome incrustation in the interior. A vessel of distilled water may be con- nected with the oven by a siphon, having a bulb or ver- tical closed tube at its bend, to prevent the air boiled out from the water from stopping the action of the siphon; or the escape-pipe (/) may be turned upwards and con- nected with a long vertical or oblique tube, which, if the flame is small, will condense the escaping steam, and obviate the necessity of a constant supply of water. The steam-oven is employed to drive off the moisture from solid substances which require to be dried at a gentle heat. 504. Several Copper Water-baths.—The water-bath con- sists of a hemispherical copper dish with its edges turned over inwards ; a series of flat copper rings of gradually diminishing diameters are made to rest upon the edges of the bath or upon one another’s edges, so that the opening at the top can be made as small as may be desired. The bath is about two-thirds filled with water, and is heated on a tripod-stand until the water boils, the excess of steam escaping by a small hole made just below the edge of the bath; the flame should be so regulated that the water is kept gently boiling. A small-sized saucepan is a homely substitute for the copper water-bath. Any liquid requiring to be evaporated at a gentle heat is placed in an evaporating-basin upon this bath, its tem- 310 WATER-BATH. [504 a, 505. perature during evaporation cannot then exceed the tem- perature of boiling water (100° C.). The top of the water-oven is frequently made to serve as a water-bath, see (503). If the water-bath requires to be used for any considerable length of time, it may l)e supplied with water in the same way as the steam-oven (503). 504 a. The following cheap and simple device serves the purpose of both water-bath and steam-oven on a small scale. Two circular plates of sheet zinc are ob- tained,1 about four inches in diameter, so as to cover the larger-sized porcelain dishes used by each student; in one of these a circular hole concentric with the edge of the plate and two and three-quarters inches in diameter is cut, in the other a similar hole is made one and a half inches across. These covers, when placed on one of the larger porcelain dishes, nearly tilled with water and boiled by a lamp, convert it into a water-bath, a small dish containing the liquid to be evaporated being sup- ported in the hole of the plates; small quantities of liquid may be evaporated or solid substances may be dried by placing them on a watch-glass supported on the smaller perforated plate. In a large laboratory, however, steam-ovens and water- baths are usually kept constantly heated by steam or boiling water, and are used in common by all students. The steam from a large water-bath may advantageously be condensed to distilled water by connecting the escape- pipe of the bath with a long tube or the still-worm. 505. Several Small Tubulated Flasks.—The small flask shown in Fig. 38 (p. 150) is very convenient for the reac- tions described in pars. 260, 264, and 273. It is the form of apparatus best suited for the test for a chloride described in (260) because the K2Cr207 powder is not introduced through the same tube as the Cr02Cl2 escapes by, and the risk of the mixture in the flask spirting into the delivery-tube is rendered very small. Its neck should be closed by an india-rubber or glass stopper. 1 Any working tinman will make them to order. 506.] DISTILLATION OF WATER. 311 DISTILLATION OF WATER. As has been already shown (Ex. 31, p. 40) water or- dinarily contains certain solid substances dissolved in it which render it in a chemical sense impure; such water is therefore unfit to be employed for the process of solu- tion and washing, since any impurity thus introduced into a substance during analysis would be considered when detected to have been present in the original sub- stance. The quantity of these impurities present in any particular water-supply will depend upon the nature of the soil with which the water has been in contact previous to its collection. The water supplied in some districts will be found when subjected to the tests given in [(526) Remark 41] to be almost perfectly pure; carefully col- lected rain-water will invariably yield no indication of dissolved impurity; the water supplied to the majority of laboratories will, however, be found to be unfit for analytical purposes, until it has been freed from the solid substances dissolved in it by being subjected to the process of distillation. In most towns distilled water can be purchased, but it is preferable to distil in the laboratory or its immediate neighborhood all the water required for use. For this purpose the steam obtained either from a steam-boiler or from a copper still heated by a furnace or gas-burner, or from the water-baths and steam-ovens in the laboratory, is condensed by a tin worm-pipe immersed in a tub through which a constant stream of cold water runs. 506. The following constant apparatus has proved most serviceable in the author’s laboratory, and may be used wherever gas and water are laid on in a suitable way. Its advantage lies in the fact that the still is con- stantly supplied with the hottest portion of the water from the condenser through a lateral tube. When the apparatus has been properly fitted up and the supply adjusted, it requires no attention whatever except light- ing and extinguishing the gas under the still, and turn- ing the water-supply on and off when distillation is started and stopped; it is advisable occasionally to re- move from the interior of the still, and from the supply- 312 DISTILLATION OF WATER. [506. tube connecting it with the condensing vessel, the deposit which accumulates by evaporation of the water. The accompanying sketch (Fig. 42) renders a length- ened description of the apparatus unnecessary ; it repre- sents the apparatus in section. A copper still (A) is heated by the flame of a large-sized Bunsen burner or by Fig. 42. a ring gas-burner, the steam passing off from the top of the still through a tin tube bent into a spiral form in the condensing-tub (B) which is made of copper or galvan- ized iron; from this condenser the distilled water flows into a large stoneware vessel (C), with a tap below from which the water is drawn when required. A long siphon- tube (C D) serves as a gauge. The condensing-tub (B) has three tubes let into the side facing the still; one of these (d), placed about an inch above the bottom of the vessel, is the inlet for' cold water from a cistern whose water level must be higher than that maintained in A 506.; 313 DISTILLATION OF WATER. and B ; this level is marked by the single dotted line, and is kept constant by the overflow-tube e, which is con- nected with a pipe leading to a sink or drain. Just be- low this overflow-tube is a short tube (/), which is on a level with another (g), opening into the side of the still; by connecting these two tubes with an india-rubber joint, a supply of warm water from the upper part of the con- denser is furnished to the still, keeping the level of water in it constant ; a small glass jet drawn out from a piece of glass tubing is fitted into this connecting-tube, and has been found sufficient to prevent a too free circu- lation of water between the still and condenser. The still is supported on an iron ring, projecting as a bracket from the condenser. By having two taps in the inlet- tube (cl), or by using two clamps on the india-rubber joint which connects it with the supply-pipe from the cistern, much time is economized, as the flow of water may be regu- lated once for all by one tap or clamp, the other being used only for stopping and starting the stream. The copper still should be furnished with a lid screwing upon its mouth for convenience in removing the deposit which collects within, and into this lid should be fastened a brass tribe carrying a screw-union by which the tin con- densing-pipe may be fastened steam-tight to the still. The wooden stand for the still and storing-jar is conve- niently fitted with shelves and doors to serve as a cup- board. Such a copper still, 23 inches in circumference below and 8 inches in height, when filled to a height of 4 inches and heated by. the largest-sized Bunsen burner, yields 2 liters of distilled water per hour. In laboratories where a larger supply of distilled water is required, a copper still of several gallons capacity may be set in masonry and heated by a small furnace fed with coal or gas. The overflow from the still-tub should then pass into a small cistern whose overflow-pipe keeps its water surface level with that required in the still; and the still and cistern are connected by a tube bent down- wards in its middle to prevent the passage of water from the still to the cistern. For tests of purity see Remark 41 (526). 314 SILVER RESIDUES. [507. RECOVERY OF THE METALS FROM SIL- VER AVI) PLATINUM RESIDUES. When AgN03 or PtCl4 has been added to a solution the liquid is not to be thrown into the sink. 507. Silver Residues.—If AgNOs has been added to a liquid it must be emptied into a vessel,1 labelled “Silver Residues,” containing strong HC1, which precipitates AgCl. When the vessel is full, the AgCl is allowed to settle, and the liquid decanted from the AgCl; more HC1 is then poured in, and the vessel is again ready for use. When a sufficiently large quantity of AgCl has been formed, let it settle, decant off the liquid, and wash the precipitate well by decantation; pour it upon a filter, and dry upon the filter. One of the two following methods may then be employed to obtain metallic Ag from the AgCl: 1. Mix the AgCl with twice its weight of a mixture in equal proportions by weight of Na2C03 and K2C03; place this in a clay crucible of such a size that the mix- ture only half fills it, and heat in a furnace until the mass becomes liquid; maintain it in a fused condition for about five or ten minutes, remove the crucible, and tap its bottom several times gently upon a brick to cause the fused particles of Ag to unite. Allow the crucible to cool, break it up, and wash the button of Ag, which will be found at the bottom, until it is quite free from adhering salts. This button is then dissolved by heating it in a flask with pure strong HN03 previously diluted with about half its measure of water; the solution is evaporated to dryness, the residue dissolved in a little water and once more evaporated to complete dryness. The AgNOs is then dissolved in the right proportion of water to furnish reagent No. 48 (525). 2. A readier method for decomposing the AgCl con- sists in placing it in a dish with a little water acidified 1 Most conveniently a large bottle, with a funnel in its neck. 508.] PLATINUM RESIDUES. 315 with dilute H2S04, and laying upon the AgCl some strips of Zn free from Pb; after some hours the Ag will be separated as a black spongy mass. This is well washed by decantation with hot dilute H2S04, and then washed also by decantation with boiling distilled water till free from the H2S04; the Ag is dissolved in HNOs as di- rected in the first process, the solution evaporated to dry- ness, and the AgN03 used for preparing the reagent. Any residue insoluble in HNOs will be unreduced AgCl; this may be filtered off and added to the silver residues for subsequent reduction. 508. Platinum Residues.—Liquids to which PtCl4 has been added are poured into a vessel1 labelled “Platinum Residues;” when a sufficient quantity has been obtained the liquid and precipitate are poured into a porcelain dish, evaporated to dryness, and heated strongly for some time; as soon as the dish is cool the residue is boiled with water, which is decanted, and upon the residue some so- lution of oxalic acid is poured; this is evaporated to dry- ness and the residue strongly ignited. The residue of metallic Pt is once more washed with boiling water, and is then dissolved by heating it with IIC1 to which one- third its measure of 11X (X has been added; the solution is evaporated to dryness, the last part of the process being performed over a water-bath. HC1 is then poured in, and it is once more evaporated to dryness and heated for some time on the water-bath; this residue when dissolved in water forms the reagent Ao. 28 (525). Any waste scraps of platinum foil and wire should be carefully pre- served, and after having been cleansed by boiling them with HNOs and washing well with water, they may be dissolved in IIC1 and HNOs and solution of PtCl4 pre- pared as is described above. 1 Conveniently a large glass bottle, with a funnel in its neck. 316 preparation of reagents. [509-511. DIRECTIONS FOR PREPARATION OF REAGENTS. Note.—The reagents required for chemical analysis are much more readily obtained at the present time than they were in former years. They can usually be purchased in a pure state, and therefore processes of preparation, which formerly of necessity occupied a large portion of Manuals of Practical Chemistry, are here omitted. It will he found usually more economical to purchase pure chemicals than to prepare them. 509. Many reagents are required in a dissolved or diluted state; it is a matter of much importance that these solutions should be made of a proper strength, and that the methods of preparing them should be as rapid and simple as possible. The strength of the solutions is chosen somewhat arbi- trarily; indeed, the strength of a solution may be varied with advantage according to the different purposes for which the reagent is to be employed. It is found, how- ever, that in practice a solution of one strength may usu- ally be made to serve all analytical purposes. The pro- portions of liquid or solid to be mixed with or dissolved in a certain quantity of water, which are given hereafter, are those (or very nearly those) recommended in standard works on analysis. It is not intended, however, to assert that they are for all purposes the best, but merely that they are generally suitable. 510. A good and economical store-bottle for liquid reagents is the “Winchester quart” bottle, a stock of which generally accumulates in a laboratory, being con- tinually introduced filled with strong acids. The follow- ing methods of filling these have been found simple and easy of execution. The process of preparing solutions divides itself natur- ally into the “dilution of liquids” (511), and the “solu- tion of solids” (512). 511. Dilution of Liquids. In the following lists the proportions by measure are stated in which the liquid and distilled water are to be 512, 513.] SOLUTION OF SOLIDS. 317 mixed; these proportions are roughly, but sufficiently accurately, obtained by measuring with a foot-rule the height of the bottle outside from the bottom to the pro- jecting ridge at the shoulder, then dividing this height in the required proportions, and marking the point of division by a line scratched upon the bottle with a three- cornered hie. Thus dilute HC1 (No. 2, 524) is made by mixing strong HC1 with three times its measure of water; supposing, then, the measured height of the “ Winchester ” to the shoulder to be 8 inches, a file-mark is made 2 inches from the bottom, and on filling the bottle to this mark with strong HC1, then up to the shoulder with dis- tilled water, stoppering and shaking up, a dilute acid of the required strength is obtained. This method serves for numbers 2, 3, 4, 6, and 7 (524). For the prepara- tion of No. 1 see column of remarks in the same para- graph. 512. Solution of Solids. For dissolving solids two methods are here described ; the former (514) is useful when the solution has to be rapidly prepared; the latter (515) requires less atten- tion, and may be used when the solution is not required at once. 513. Against each reagent prepared from a solid there is placed in paragraph (524) a number, signifying the number of grams (see 560 et seq.) to be dissolved in one Winchester quart of water, and in all the lists will be found the proportion by weight of solid to water. The former number is obtained from the proportion stated in the next column, by considering that an average-sized “Winchester,” filled an inch above the ridge round its shoulder, holds about 2400 cc., and since each cc. (560 et seq.) of water weighs approximately 1 gram, we have at once the weight of water (2400 grams) contained in the bottle, from knowing its capacity; and, the weight of water being known, the weight of solid to be dissolved in it is readily cal- culated from the proportion given.' Thus the proper strength of AmCl solution (No. 5, 524) is 1 of solid AmCl dissolved in 8 of water, as shown in the fifth column, or a given This method may also be employed when smaller quantities of the reagent are to be prepared. Measure the number of ce. required to fill the bottle, count the number as grams, and calculate the pro- portion of solid required as above. 318 PREPARATION OF REAGENTS. [514,515. weight of water must have dissolved in it Jth its weight of AmCl; since a “ Winchester” holds 2400 grams of water, we must then dis- solve -5-° —300 grams of AmCl in it to obtain a solution of proper strength. 514. Method I.—Weigh out the required quantity of the solid substance, dissolve by heating it with dis- tilled water in a large-sized porcelain dish placed on a tripod-stand over a rose-burner; this solution would often crystallize on cooling, hence it should be at once poured into some cold distilled water contained in a large beaker marked to show the quantity of liquid required to fill the “ Winchester.” Whilst pouring off the liquid press a wet glass rod, held vertically, against the lip of the dish, and let the bottom of the dish touch the inside of the top of the beaker. These directions will, with proper care, prevent the liquid from running down outside the beaker. Dilute this up to the “ Winchester” mark with distilled water, stir well, and if turbid let stand covered from dust until clear; then pour off into the store-bottle, carefully leaving the sediment behind. If the liquid is wanted in haste, it may be filtered into the bottle. The coarse brown French filter-paper is useful for this pur- pose, being strong and porous. It is best to filter the liquid before diluting it to the full extent, as the quan- tity to be passed through the filter is thus lessened and time economized. The above method is of general application in the solution of solids. 515. Method II.—The following method is advan- tageous, because the process of solution once started pro- ceeds continuously without further attention. It de- pends on the fact that the specific gravity of water be- comes higher the greater the quantity of solid dissolved in it; hence if the solid is immersed in the water, and supported near the surface, a circulation of the liquid is produced by the constant sinking of the water which has been in contact with the solid, and by dissolving some of it has increased in specific gravity, this being replaced by the comparatively lighter liquid from below. The circulation of water over the solid gradually dissolves it 515.] SOLUTION OF SOLIDS. 319 without the use of heat, and without requiring any atten- tion after the process has once been started. A glass cylinder (A, Fig. 43) open at both ends, has one end covered with a piece of muslin, shown by a fine dotted line, which is fastened on by an india-rubber ring, embracing its edges: this cylinder, with a muslin bottom, is supported in a large beaker by means of two pieces of glass rod or tube, bent as shown at ccc; the cylin- der stands at such a height that the muslin bottom is about two inches below the mark made on the beaker to show the Win- chester quart measure. Distilled water is then poured into the beaker until it buries the muslin to the depth of about half an inch ; the weighed substance, best in small pieces, is placed in the cylinder, and the whole allowed to stand until the solid.has been dissolved; with large quantities of substance this will usually require several hours, with smaller quantities about twenty minutes or half an hour. The processes of solution and filtration are performed simultaneously by laying a piece of filter-paper upon the muslin before fastening it on the cylinder; the filter- paper will retard the process, but the coarse gray kind referred to above will do so least. Perhaps the most advantageous way of using this pro- cess, especially for dissolving large quantities of sub- stance, is to start it over night; the solution will then be completed by the morning. In this case the filter-paper will be unnecessary, as any fine particles which have passed through the muslin will have settled, and the liquid can be decanted from them. It must be borne in mind that the solution of many salts in water, especially such salts as contain water of crystallization, increases the volume of the water; hence the quantity of water placed in the beaker must be less than the Winchester quart measure, and the liquid is made up to the required volume, if necessary, after solu- tion has been effected. Fig. 43. 320 PREPARATION OF REAGENTS. [516,517. As a convenient substitute for the glass cylinder, A, with muslin bottom, an earthenware colander may be employed (Fig. 43 a), filtration being effected when necessary by laying a piece of filter-paper inside the colander before placing in it the fragments of the substance. Should the beaker be able to contain more than the Winchester quart of water, a stop- pered bottle of suitable size may be immersed in it to raise the water-level sufficiently to reach the substance. Fig. 43 a. Preparation of Solutions required for try- ing the Reaction of Metals and Acid-radi- cles, Section IV. 516. The solutions required for trying these reactions should be prepared of a strength suited to yield them in a characteristic manner; it is therefore advisable that solutions of the requisite strength should be kept in readi- ness, since, if the student has to dissolve some of the solid substance himself, he is liable not to obtain satisfactory results, either because his solution is made inconveni- ently strong, or because it is too dilute. The plan of keeping these solutions in stock is also recommended by the consideration that it economizes the student’s time and tends to prevent waste of chemicals. 517. In paragraphs (529) and (530) are lists of the solutions which are required for the complete series of reactions in Section IV : the first column gives the num- ber, the second the name, and the third the formula of each substance; in the fourth is stated the number of grams which are to be dissolved in one Winchester quart of water or acid; in the fifth column the proportion by weight of solid to water, from which the number in col- umn 4 was derived; and in the sixth column will be found special remarks relating to the preparation of par- ticular solutions. The general methods of preparing 518-520.] LIST OF THE REAGENTS. 321 solutions have already been given in paragraphs (514) and (515). Pure solid chemicals are almost invariably sold in the crystalline condition, since they have been as a rule puri- fied by the process of crystallization. The weights given below are therefore weights of the crystalline sub- stance; in a few cases the substance was weighed in the uncrystalline condition—these are marked by an (a) placed after the name in the first column, signifying “amorphous.” Directions for labelling the store-bottles of these solutions will be found in paragraphs (522) and (523). LIST OF THE REAGENTS. 518. Paragraphs (524), (525), and (526) contain lists of the reagents, solid and in solution, which should be kept in readiness in the laboratory; they are dissolved in distilled water unless it is otherwise stated. The reagents are here divided into two classes. The first (524) being in constant use and comparatively inex- pensive, should be contained in small bottles placed above each working bench, or one complete set should be pro- vided for the use of each student. The second class (525, 526) are less frequently required, or are of a more costly nature, and one set may be placed in an accessible part of the laboratory for the use of many students. 519. Each reagent is numbered in the following lists; this number is a convenient means of reference and also serves to keep the reagent bottles always standing in the same order, which much facilitates finding any bottle when wanted ; the student is recommended to keep his bottles arranged in the order indicated by these numbers. The full name and chemical formula accompany each number, and every label in the laboratory should carry legibly the number, name, and formula of the reagent it contains. 520. In the last column of eacli list are placed re- marks as to the preparation and the condition of the re- 322 LABELLING. [521, 522. agent. The numbers found in the last column but one express the strength of the solution of the reagent if a liquid, by stating the proportion of the strong liquid or solid as purchased to the water with which it is mixed or in which it is dissolved, the proportion being expressed as a ratio in which the water always stands last; in the case of liquids the numbers express proportion by meas- ure (m.), in the case of solids the proportion by weight (w.). A number is also placed in the fourth column op- posite each reagent prepared by dissolving a solid sub- stance, which denotes the weight in grams of the solid to be dissolved in a Winchester quart bottle of water. Thus No. 2 (524), hydrochloric acid, is prepared by mixing strong HC1 with 3 times its measure of distilled water. No. 5, ammonium chloride, is made by dissolv- ing solid AmCl in 8 times its weight of water, or by dis- solving 300 grams of solid AmCl in one Winchester quart of water. Full descriptions are given in para- graphs (511), (514), and (515) of the methods used for making these solutions. 521. The special reagents which stand on shelves above the bench are kept in small bottles ; the solids, Nos. 18-21 (524), in 4-oz. wide-mouthed stoppered bottles, which are filled when necessary from the store-jars (stone- ware jars with ground clasp-covers),1 the liquids (Nos. 1— 8) in narrow-necked 6-oz. bottles, and (Nos. 9-17) in 4- oz. bottles supplied from the Winchester quart bottles in which the store-solutions are kept. The general rea- gents (525, 526) should be kept in bottles of not less than 12 oz. capacity. 522. Labelling.—Bottles intended to contain strong acids or alkalies should have labels etched upon the glass; such bottles are easily obtained; an ordinary pa}>er label, however, protected by paraffin varnish, which is applied according to the directions given below (523), will last for a considerable length of time. The paper labels required for reagents and store-bot- 1 Powdered solids are conveniently removed from large store-jars by means of wooden spoons. 523.] 323 REAGENT BOTTLES. ties are most conveniently kept ready gummed in the form of sheets either separate or stitched together into the form of a book. They must be stored in a dry place. They should bear in bold legible type at least the full name and formula of the substance, the number, if not already printed, being written upon each.1 Great care should be bestowed on making the moistened label ad- here over its whole surface by gentle pressure with a clean cloth. Names or formulae painted upon the clean glass with “ Brunswick black ” paint are very permanent, resisting ordinary wear and the action of chemicals perfectly. 523. Varnishing Labels.—It is advisable to varnish each paper label, which is intended to be permanent, as soon as it is perfectly dry; the label is thus protected against being soiled or wetted. The ordinary process consists in first sizing the label by brushing over it a so- lution of isinglass in water, and then, as soon as this has perfectly dried, applying a thin coat of label varnish ; the bottle must not be used until this varnish is quite hard. A much more simple process of varnishing consists in melting some solid paraffin, which must not be heated so strongly as to cause it to emit vapor, and brushing this rapidly over the dry label with an ordinary varnishing brush ; after a little practice a uniform film can be ap- plied which does not soak into the paper, hardens imme- diately, and resists the action of water, acids, and alka- lies. The chief precaution to be observed is to heat the paraffin as little as possible above its melting-point, as, if it is too hot, it greases the paper. 1 A book of labels (“ A Series of Chemical Labels for use in Lab- oratories”) is sold by Messrs. Mottershead, of Manchester, which contains the name of each substance in full, printed in clear type, space being left to insert formula and number. Messrs. Mottershead also supply gummed sheets of labels, printed especially for use with this book, containing all the numbers, names, and formula in the lists in pars. 524, 525, 526, 529, 530, 531, and 532. 324 REAGENTS REQUIRED [524. 524. Reagents Required 1. Reference number. 2. Name. [The numbers in brackets refer to marks corre- spondingly numbered in the sixth column.] 3. Formula. Liquids. 1. Sulphuric acid (*) H2SO« 2. Hydrochloric acid (“) HC1 3. Nitric acid (3) HN03 4. [HA. or ( 5. Ammonium chloride (s) (HL2Hs02 ) NH4C1 6. Ammonia, or Ammonium hydrate (s) NHJIO 7. . Ammonium sulphide C) (NH.)»S 8. Ammonium carbonate (8) (NH4)2C03 9. Ammonium oxalate (NH4I0C004.2HO0 10. Potash, or Potassium hydrate KHO 11. Potassium chromate, K«CrO« 12. Potassium ferrocyanide K4FeCye.3H20 13. 'Potassium ferricyanide (9) K„Fe2Cyl2 14. , r “Sodium phosphate (l0), or J Hydric disodic phosphate, or y Na2TIP04.12H»0 15. V. Hydrogen disodium phosphate, j Sodium carbonate Na2COs.10H2O (crystals) 1G. CaSO, 17. BaCl2.2HoO Solids. 18. Sodium carbonate (“) Na2COs 19. Borax (13i ‘ NaaB4OT 20. KCIO3 21. 1 This reagent undergoes decomposition by exposure to light and must not be kept near a 8 Hydrogen sodium ammonium phosphate (N.iAmHPO)«solution serves better for precipi- or NasHPO«. 524. FOR EACH BENCH. for each Bench. 4. Weight of solid in grams to be dis- solved in one “Win- chester” of water. 5. Proportion of solid by weight (w.) and liquid by measure (m.) to water. 6. [The small numbers refer to corresponding numbers in the second column.] 1 : 5 m. 1. Pure strong H3S04 must be poured in the proper proportion into water contained in a 1:3“ large thin beaker or an earthen jar, con- stantly stirring the water all the time; the 1:3“ right proportions are obtained by measure- ment of the height of the vessel (511). The hot liquid is cooled by immersing the vessel in cola water, and is then poured into the store-bottle. If the acid is pure, no white pre- 300 1 : 8 w. cipitate (PhS04) forms on dilution. 2. Must be colorless, and give after dilution no 1 : 3 m. precipitate with either BaCI2 or H2S. 3. Must give no precipitate atterdilution, with 1:1“ BaCl2or AgN03 added to separate portions. 4. Must give no precipitate with BaCI2. 400 1 : 5 w. 5 Must give no precipitate or coloration with AiiuS. 100 1 : 24 “ 6. Must give only a very slight precipitate with lime-water, no coloration with Am2S, 300 1:8“ and separate portions acidified with HN03 must give no precipitates with Ba013 and AgNOa. “Liquor ammonite fortissima,” of 880° specific gravity, is bought. 200 1 : 12 “ 200 1 : 12 “ 7. Must be yellow, and give with acids H2S and a white precipitate of S; it must give no 200 1 :12 “ precipitate with solutions of Ca or Mg salts. 8. The solid Atn2C03 is dissolved by being heated with water in a porcelain dish (514); in diluting, one-fourth of the “ Winchester” 200 1 : 12 “ must be filled with strong AmllO. 9. Must give no blue precipitate with Fe2C)e solution. 10. Must yield no precipitate with AmllO. 600 1:4“ 11. Dry finely powdered solid. It must, after having been dissolved in excess of HN03, Saturated solution (527). give no precipitate with BaCI3 or AgNOa, or AmHMo04 (277), and if evaporated with ex- 200 1 :12 “ cess of HC1 must leave no residue insoluble in dilute HC1 (290 a). 12. The borax is best dried by heating in a platinum or porcelain dish until after melt- ing it has again become solid; this solid mass is then finely powdered in a mortar and kept in a stoppered bottle. In small crystals. Blue and red litmus and turmeric papers in small strips. window. tation of Mg than does NaaHP04 solution; it is prepared of the strength given the above 326 '525. GENERAL REAGENTS 525.—Reagents for General Use, Note.—Lxcept in large laboratories it will be unnecessary to keep these I in the laboratory may be made up to the right strength as soon as they are 2. 3. Name. Reference [The small numbers in brackets refer to remarks Formula. number. correspondingly numbered in the fifth column.] 25 Sulphuric acid (”) HjjSO* 26 Hydrochloric acid (V HC1 27 Nitric acid (3)* HN03 28 “Platinum chloride PtCl, 29 Alcohol, Rectified spirit (l8) C2llsO 30 Tartaric acid (*9) HoT or H204H40g 31 Acid sodium tartrate, Hydric sodic tartrate (”) f NaHT.H20 32 Slaked lime (-1) * NaHC4H408.HjO 33 Caf 1I0)2 34 Cobalt nitrate i22) HA or HC2H302 35 Hydrofluosilicic acid i23) Oo(N 03)2 -6H 2O 36 f Sulphuretted hydrogen solution 1 1 Hydrogen sulphide j' ' Hjsih, H2S solution 37 Oxalic acid f H0O.2H0O 1 t H2C„04.2H30 / 38 Potassium sulphoeyanide KCyS 39 Potassium nitrate KNOj 40 Lead acetate (25) f PbA2.3H20 1 1 Pb(C2Hs0,)2.3H20 > 41 Sodium acetate f NaA.3HaO 1 t NaC2HtOj 3H20 i 42 Potassium cyanide v28) 43 Bromine water (21,* Br-water SnCla.2If30 44 Stannous chloride (*) 45 Copper t29) Cu 46 Zinc ,30) 47 Steel (31) Fe 48 Silver nitrate A NaAmIIPO,.4HoO 76 77 Calcium chloride CaCl2 6H„0(crystals)... 78 Potassium chloride KC1 79 Marble CaCOj 80s Distilled water (41) HaO 81 Pure sodium hydrate (42), pure soda NaHO 82 Fusion mixture (43) Na2CO,+ KoCOj 83 Barium carbonate (44) BaCOs 84 Solution of sodium acetate in dilute acetic acid (4S) NaA+lIA 85 Sodium nitrate (4B) (solid) NaN03 86 Silica, or finely powdered white sand. (See 548, 4) SiOo 87 Hydrofluoric acid (41) HF 88 Barium hydrate (in crystals) Ba(HO'o 8HaO 89 Zinc sulphate. (See No. III.) ZuS04.7II20 Refer to note under 1 Nos. 80-89 are certain special 526.; DETECTION OF ACID-RADICLES. rOR the Detection of Acid-radicles. the heading of(525). 4. Proportion by weight of solid to water; and weight in grams for a 12-oz. bottle in square brackets. 5. Remarks. [The numbers in this column refer to corresponding numbers in the second column.] See (527). 1 : 24 [20 grams]. See (528, 3). Solid. 1 : 60 [8 grams]. Solid. Solid. See (528, 5). In powder. In small pieces. In pieces as large as a pea. 32. To some of the PbA2 solution (No. 40) KIIO solution is added until, on warming, the precipitate at first formed is just re- dissoived; paper dipped into this liquid is a very delicate test for H2S (230). 33. The solution should not contain any free acid: to remove acid AmHO is added until the further addition of a single drop gives a reddish-brown precipitate of Fe2HOs in the solution. 34. FeSO, solution rapidly oxidizes in the air, hence the FeSO, should be kept in the solid state as small green crystals, which should not show a yellow coating in any part; these are dis- solved when required by crushing and shaking with cold water. 35. Starch solution rapidly changes; it is best therefore to keep the starch as a powder. Starch solution is made by stirring 2 grams of this powder, which has heen made into a paste with 10 cc. of cold water, into 100 cc. of boiling water and cooling. 36. Made by dissolving indigo carmine in water. 37. Should be kept in fine powder; it must not evolve Cl or CO2 when warmed with strong H3SO«. 38. In small pieces, or in powder. 39. The solution is prone to change, and should be made in small quantity only; it must evolve copious red fumes when mixed with IUSD,, 40. Make the solution with the following proportions: 1 gram of Am3Mo04 is dissolved in 12.5 cc. of strong AmHO which lias been previously mixed with an equal quantity of water; the solution is allowed to stand (if necessary) till clear, then poured off into 25 cc. of strong HN03; the liquid will become hot, and should be allowed to stand until it is cool before being used. 40 a. The IIN03 solution of this salt must yield no precipitate with AgN03. 41. Must leave no residue on evaporation; in separate portions no precipitates must be caused by BaCI*, AgN03, or Ain2C20«, neither must any precipitate or even dark coloration be produced by addition of Am,S. 42. The proportion by weight should be 1 : 10 of water; it is best kept in green glass bottles, as it slowly dissolves Pb from white flint glass. The solution must not become dark in color when mixed with ITaS, nor give a gelatinous precipitate (AljHo,) when mixed with excess of Amt'l solution. 43. Dry linely powdered Na3C03 and K3CG3 are intimately mixed in the proportion of 53 : 69 by weight, and kept in a stoppered bottle. 44. Pure powdered BaCOs is either purchased, or is made by precipitating BaCl2 so- lution completely with AnijCO, or Na3C03 solution, and washing the precipitate well by decantation. This powder is then mixed with distilled water to the con- sistency of thin cream. 45. Dissolve 20 grams of NaA in 60 cc. of distilled water, and add to the solution 40 cc. of strong HA. 16. By neutralizing strong hot Na3C03 solution with HN03and evaporating to dry- ness. Sold also as Chili saltpetre. 47. Purchased and kept in gutta-percha bottles. reagents entered apart. 330 PREPARATION of [527. PREPARATION OF SATURATED SOLUTIONS. By a “saturated solution” is meant a solution containing the maxi- mum quantity of the substance which the solvent can dissolve ; this quantity varies with the temperature of the solution; the solutions spoken of in this book are saturated at the ordinary temperature. Preparation of Sat crated Solutions of Solids. 527. The method described in (515) may be used, or the substance in powder may be constantly shaken up with the solvent for some time, and the solution then separated from excess of the solid by decantation or filtra- tion. The most ready method of preparing a saturated solution of Ca(HO)2, or of CaS04, is to pour some of the powder into a Winchester quart, then fill it up to the shoulder with water, and mix the powder thoroughly with the water by shaking the bottle; the shaking is re- peated at intervals during half an hour or more; the bot- tle is then allowed to stand until the excess of powder lias settled and the liquid above it is quite clear, when the liquid is poured off into another “ Winchester," leaving the powder behind; fresh water is poured upon this powder and more solution made as above by constant shaking, the bottle being allowed to stand by until the fresh supply is required. By thus making a fresh stock of solution whenever one lot is decanted, time is allowed for the freshly prepared solution to become perfectly clear before it is required for use. 1. Lime-water as made in the above manner by shaking slaked lime in powder with common tap-water. 2. Calcium sulphate solution is prepared by saturating distilled water by the above means with gypsum or plaster of Paris in powder. 528.] SATURATED solutions. 331 Preparation of Saturated Solutions of Gases. 528. The gas is made to bubble in a constant stream from the end of a glass tube which dips nearly to the bot- tom of the liquid (Fig. 44); the liquid must be kept cold, and be contained in a bottle which is fitted with an accu- rately ground stopper. In order to ascertain whether the solution is saturated, the bubbles of the gas are occa- sionally watched to see whether they diminish in size as they rise through the liquid ; if they do not, the bottle, after being closed tightly by the thumb or by inserting the stopper, is violently shaken; if this causes a pressure and escape of gas from the bottle into the air on unclosing its mouth, the liquid is saturated; if, on the contrary, it causes a pressure of air into the bottle, the gas must be passed again for some time, and the trial repeated, until on shaking, as directed above, an outward pressure is noticed. Note.—All the preparations mentioned below should be made in a draught cupboard, as the gases are injurious to the lungs if inhaled. 1. Sulphuretted hydrogen solution is made by fitting the bent tube a h (Fig. 44), by means of the india-rubber joint c, upon either of the apparatus described in (500) for the preparation of H2S; the gas is thus made to bubble through the distilled water (best recently boiled to ex- pel air, and cooled) until it is saturated. The solution should not be made in large quantities at a time, as it gradually decom- poses, depositing sulphur and losing its smell; it is then unfit for use. 2. Sulphurous acid solution is prepared by passing sulphur dioxide gas into dis- tilled water until it is saturated. The gas is made by heating scraps of copper with strong H2S04 in a glass flask fitted as is shown in A (Fig. 45). The gas passes from the flask through some water contained in a washing- bottle as shown at B (Fig. 45), and from this bottle into the distilled water (Fig. 44) through the tube a b, which is connected with the outlet tube of the washing-bottle Fig. 44. 332 PREPARATION OF [528. by means of the india-rubber joint c. The solution must be kept in a well-stoppered bottle. Fig. 45. 3. Chlorine-water.—Chlorine gas is made in the ap- paratus shown in Fig. 45, by gently heating manganic oxide in lumps or powder in the flask A with some strong commercial hydrochloric acid, previously mixed with a third of its volume of water. The gas bubbles through a little water in the washing-bottle B, and thence through the bent tube a b into the distilled water (Fig. 44). This solution must be kept in a dark place, or in a bottle which is coated with black paper, as it undergoes altera- tion by light. 4. Iiydrofluosilicic acid is made by passing silicon fluoride gas into water. The gas is prepared in a flask fitted as shown in A, Fig. 45. Into this flask there is first poured an intimate mix- ture of 50 grams of dry, pure, finely pow- dered fluor-spar with 50 grams of fine white sand; 300 grams of strong H.jS04 are then poured info the flask through the funnel-tube, and the acid is mixed with the powder by shaking it round in the flask; the gas is caused to be evolved by gently heating the flask, and is made to pass first through the bottle B (Fig. 45), which must be empty and dry inside; thence it escapes through a bent tube a b (Fig. 46), which is fitted upon the outlet tube of B by an india-rubber joint; the end of Fig. 46. 528.] SATURATED SOLUTIONS. 333 the tube, a b, is made to dip into mercury contained in a small beaker cl (Fig. 46), which stands in a large beaker containing 400 cc. of water. As soon as the silicon fluoride gas conies into the water, after escaping from the mercury, it is decomposed into hydrofluosilicic acid, which dissolves in the water, and silica, which remains suspended in the water as a gelatinous mass; the silica very soon closes the end of the delivery-tube a b unless it is kept immersed in the mercury. As the current of gas slackens, the heat is raised, until white fumes of H2S04 begin to appear in the preparation-flask; the process is then arrested and the gelatinous silica is separated from the solution by squeezing the latter through fine muslin and afterwards filtering it if not quite clear. The silica may be dried, heated strongly in a porcelain dish, and put by in a stoppered bottle as reagent No. 86 (526), for which it serves admirably. 5. Nitrogen-tetroxide Solution.—Lead nitrate in dry pieces is heated in a test-tube fitted with cork and delivery- tube (Fig. 47), and the red fumes which es- cape are passed into di- lute H2S04. Care must be taken to maintain the heat uniformly after the fumes begin to be evolved, else the liquid maybe sucked back into the hot tube by the con- traction of the gas on cooling; also the de- livery-tube must be removed from the liquid as soon as the heating is stopped. Fig. 47. 334 SOLUTIONS FOR TIIE REACTIONS [529. 529. Solutions for the Note.—Each bottle should bear on its label the number, name, and formula the solutions, containing the powdered solid of each of those substances on their label the name, number, and formula of the substance. 1. Reference number. 2. Name. [The numbers in brackets refer to similarly numbered remarks in the last column.] 3. Formula. 100 s. Potassium chloride KC1 lOl.s. Ammonium chloride AmCl 102.S. Sodium chloride NaCl 103.S. Magnesium sulphate MgS04.7H„0 BaCL.2H,6 104. Barium chloride 105. Strontium nitrate Sr(N03).>.-l IToO 106. Calcium chloride CaCl2.6H30 107.S. f Alum, or 1 [Aluminium potassium sulphate j AlK(S04'a 12II20 108.s. Ferric chloride (a)' 109.S. Ferrous sulphate (“] FeS04.7Ha0 llO.s. f Chrome alum, or [ j Chromium potassium sulphate CrK(S04)g.l2Ha0 111.8. Zinc sulphate ZnS04 711.,O 112.S. Manganese chloride (a) MnCl2 113.S. Nickel sulphate NiS04.7HJD 114.S. Cobalt nitrate Co(N( >3)2.6 fljO 115.8. Mercuric chloride HgCl3 116 s. Lead acetate (,9) PbA2.3HoO 117.s. Bismuth nitrate (w) BilNOaA.olToO 118.S. Copper sulphate (a) CuS046H.,0 119.S. Cadmium sulphate (a) CdS04.4Ha0 120.S. f Arsenious oxide (a) (51) [ [ Solution in dilute HC1 f As2Oj 120. 121.s. j Arsenious oxide (a) (Mj [ Solution in water Sodium arsenate NaaTI A s04. 12 II.,0 122.S. Antimonious chloride (“j3 SbClj 123.S. Stannous chloride (S4)..- SnCl2.2H20 124. Stannic chloride (5S) SnCl4 125. Silver nitrate AgNC3 126. Mercurous nitrate (“) Hg2(NG3)2.H20 1 a signifies that the solid substance is not 2 Solid Sb208 or K(SbO)T (Tartar emetic) 529.' OP THE METALS. 335 Reactions of the Metals. of the substance. Small 4-ounce wide-mouthed bottles should he kept near whose number has a small (s) affixed to it; these bottles should also carry 4. 5. G. Weight of solid in grains to tie dissolved in one “ Winchester.” Proportion by weight of solid to water. Remarks. [These numbers correspond to the small reference numbers in brackets in the second column.] • 100 200 50 50 25 100 100 (in crystals) 200 25 25 50 25 25 50 50 50 50 25 50 25 10 50 25 25 25 25 1 : 25 1 : 12 1 : 50 1 : 50 1 : 100 1 : 25 1 : 12 1 : 12 1 : 100 1 : 100 1 : 50 1 : 100 1 : 100 1 : 50 1 : 50 1 : 50 1 : 50 1 : 100 1 : 50 1 : 100 1 : 250 1 : 50 1 : 100 1 : 100 1 : 100 1 : 100 48. The solution must lie made acid with a little HjS04, and some clean iron nails kept in it, or better, a small quantity is freshly prepared when required (p. 329, 34, col. 5). 49. A little HA must be added to tbis solution to make it clear. 50. 25 grams of Bi(N03)3 must be dissolved by heat- ing with 25 cc. of strong HC1 diluted with 25 of water; this solution is cooled and poured into the bottle, and the measure made up by pouring in dilute HC1 containing one-twen- tieth of its volume of strong HOI. 51. Dissolve 10 grants of As,03 by heating it with 50 cc. of strong HC1 mixed with 50 cc. of water, and dilute to the Winchester quart. 52. Boil excess of As203 for several minutes with 200 cc. of water, filter and dilute to the quart.® 53. 28 grains of crystallized SbCl3 are dissolved in 25 cc. of strong HC1 mixed with 25 cc. of water, and diluted to the quart® with HC1 mixed with four times its measure of water. 54. Boil 25 grams of SnCl2 with 50 cc. of strong HC1 mixed with 50 cc. of water; as soon as it has dissolved to a clear solution dilute to the quart.® scraps of Sn must be kept in the bottle. 55. Heat 25 grams of SnCI2 with- 25 cc. of strong HOI and 100 cc. of water ; whilst constantly stirring, add KC103 to the hot solution until the liquid turns yellow and Cl is smelt, boil off the Cl and dilute to the quart.® 56. Dissolve by warming 25 grams of Hg2(N03)2 with G cc. of strong HNG3 diluted with 114 cc. of water, then pour water into this solu- tion until it is diluted to a quart.® Keep Hg in the bottom of the bottle. in the crystalline condition. may be used for the blowpipe reaction. 3 Winchester quart. SOLUTIONS FOR THE 530. 530. Solutions for the Note.—Refer to note at the head of the preceding table (529), which is pared amongst the reagents (524, 525, 526), and the solutions for reactions 1. Keference Number. 2. Name. [The small numbers in brackets refer to the corre- sponding numbers in the sixth column.] 3. Formula. 130 131.5. 132.5. 133.5. 134. 135. 136.5. 137.5. 138 .s. 139.5. 140.5. 141.5. 142. 143. 144.5. 145. 146.5. 147.5. 148. 149.5. 150. 151. 152. 153.8. 154.8. 155.5. NaaSO4.l0H2O Na2CO* CaCO, FeS AmaS NaHSOs NaaS2( )35H20 Na2Cl20 Kin02 KNO KC10a NaCl Natir K1 NaaHP04 12 IT./) Na2HAsO4.12Hj0 Na2B4(),.10H,O K2CraOT Na«SiU3 Sid2 CaFs HjSil’g KCv K4FeCv6.3fT20 K8Fe2C) I3 KtlyS AmlCj0a.2IJ20 H2T Na,T.2H20 NaA.3HjO Borax (ra) 530.; REACTIONS OF THE ACID-RADICLES. Keactions of the Acid-radicles. also applicable to this. Many of the solutions in this list are already pre- fer metals (529). 4. Weight of solid in grams to be dissolved in one Winchester quart 5. Proportion by weight of solid to water. 6. Remarks. [The numbers correspond to the small reference numbers in brackets in the second column.] 25 1 100 57. The Na2C03 is required only in the solid form, and can be taken from the reagent bottle on the working bench, No. 18(524). The marble is kept in small pieces as large as a pea; it is found in reagent bottle No. 79 100 1 25 (526). 100 1 25 58. The FeS is kept as a solid in small pieces as large as a pea. 100 1 25 The Am2S can be taken from reagent bottle 100 1 25 No. 7, on the working bench. 50 1 50 59. Strong “ Liquor Sodee Chlorinatse,” diluted 50 1 50 with an equal measure of water. 50 1 50 60. No. 102, paragraph 529. 12 1 200 61. No. 121, paragraph 529. 50 1 50 62. No. 19, paragraph 524. 50 1 50 63. The solution is made by dissolving 100 grams of the thick svrup, sold as “soluble glass,” 25 In fine powder. 1 100 in water, and diluting to the Winchester quart. The solid substance to be used is sand finely ground. 64. No. 35, paragraph 525. 65. No. 42, paragraph 525. The solution decorn- 50 1 50 poses by keeping; a little solid is dissolved 25 1 100 when required. 25 1 100 66. No. 9, paragraph 524. 25 1 100 67. No. 30, paragraph 525. 100 1 1 25 10 68. 123 grams of HaT are dissolved by heat in 500 ec. of water, the hot solution is exactly neu- tralized with solid NaaCOs, and then diluted to a Winchester quart. 69. A little of the solid substance (see No. 41, 525) is dissolved, when required, in water. 338 CHEMICALS FOR SECTION I. [531. 531. Chemicals Required for Section I. In the following list those substances which are used for Section I only are marked by letters of the alphabet. The bottles containing these substances should be arranged apart in alphabetical order. Against others a number is placed; this indicates that the substance is used for ana- lytical purposes, and will therefore be found, together with any necessary descriptive remarks, in one of the foregoing lists (524, 525, 526, 529, 530). Note.—All numbers below 22 refer to bottles standing on the shelves above the working bench. If a substance is required for more than one experiment, its entry is not repeated. Letter or number of refer- ence. Name. Formula. Remarks. A. 20. Mercuric oxide, Potassium chlorate, HgO. KC10,. The orange-colored precipitated oxide is best. B. Manganese dioxide, Mn02. Commercial oxide in powder. C. Wood-charcoal, C. In pieces as large as a hazelnut. 57. Lime-water, . Ca(HO)2. — D. 21. 59. Sulphur /Litmus and turmeric) | papers, . . / Potassium dichromate, . S. K2Cr20,. Pieces of roll sulphur as large as a pea. E. Phosphorus, P. Pieces as large as half a pea, kept in a stoppered bottle under water. F. Granulated zinc, Zn. Not necessarily pure. G. Hydrochloric acid, . HC1. Strong, commercial. H. Marble, .... CaC03. In pieces not larger than a hazelnut. I. Copper Cu. Turnings, clippings, or filings. Strong, commercial. ,T. Nitric acid, HNO„. K. 32. Ammonium chloride, Slaked lime, . NH,Cl. Ca(HO)a. Solid, commercial. L. Oxalic acid, HoCjA 2HoO. Solid, in crystals. M. Sulphuric acid, tl.,so4. Strong, commercial. N. Sodium hvdrate, NailO. Strong solution in water. 0. “Turkey red,” — In strips. P. Sodium chloride, . NaCl. In pieces as large as a hazelnut broken lrom a lump of rock-salt. 3. Nitric acid, HNOs. 48. Silver nitrate, . AgNOa. 6. Ammonium hydrate, NH4 HO. 9. Ammonium oxalate, (NH4)2C,04. 17. Barium chloride, . . BaCl2. 7. Ammonium sulphide, . (NH4/S. 39. Potassium nitrate, . KN03. 532. CHEMICALS FOR SECTION III. 532. Chemicals Required for the Experiments on Analytical Operations (Section III). All the substances, with those exceptions1 only which are named in this list, are required either for analytical purposes (see lists in paragraphs 524, 525, 526, 529, 530), where they may be found by the number placed in the first column; or they are already entered on the list of substances required for experiments on the gases (531), where they may be found by the reference letter in the first column. A letter (s) affixed to the number of refer- ence indicates that the substance is required in the solid condition; see note at heading of (529). Number or letter of reference. Name. Formula. 39. Potassium nitrate kno3 118.s. Copper sulphate CuS04.6H20 79. Marble CaC03 2. Ilvd rochloric acid IIC1 45. Copper Cu 3. Nitric acid HN03 17. Barium chloride BaCL.2HoO 8. Ammonium carbonate Am2C03 161.* Filter-paper In sheet, or cut. 1. Sulphuric acid HaSO, A. Mercuric oxide HgO K. Ammonium chloride NH4C1 100.S. Potassium chloride KCT 18. Sodium carbonate Na,C03 112. s. Manganese chloride MnClo 19 Borax Na2B40, 62.8. Ferrous sulphate FeS04.7H,0 102. Sodium chloride NaCl 160.* Wood-charcoal C 116.8. Lead acetate PbA„3H20 — Bed cabbage leaves 6. Ammonium hydrate NH.HO 5. Ammonium chloride N 11,01 21. f Litmus-paper — | Turmeric-paper 1 The exceptions are Nos. 160 and 161, which numbers refer to paragraph 533; also the red cabbage leaves, which are readily ob- tainable. 340 OTHER REQUISITES. [533. 533. Sundry other Requisites not included in THE PRECEDING LlSTS. Reference number. Name and description. 160. Wood-charcoal.—'This may be purchased in small pieces commonly used for fuel. If required for blowpipe experiments (33), the charcoal should be tolerably free from cracks and from bark. It may be sawn into convenient shape and size by a fine-toothed saw. 161. Filter-paper may be bought in sheets which are cut into squares of the required size; these are folded and cut as directed in experiment 40 (p. 61). Ready cut circular filters can also be purchased, which only require to be folded. 162. Corks.—These should be obtained as free as possible from holes or cracks; they must be sound and easily softened by pressure. All sizes between 1 j inch and 2 inch in diameter should be kept in stock. For wash-bottles and other permanently fitted apparatus in which the cork is not subjected to much heating, the india-rubber stoppers are much to be preferred to corks, since they are almost imperishable and retain their elasticity very much longer than corks do. 534, 535.] SUBSTANCES FOR ANALYSIS. 341 SUBSTANCES TO BE GIVEN FOR ANALYSIS BY THE PRECEDING TABLES AND DIREC- TIONS. 534. It must be understood that the substances men- tioned below are merely brought forward as examples of what may be given to the student for analysis; the teacher will use his own judgment in adopting and extending the list. 535. Substances for Analysts whilst trying THOUGH THE REACTIONS FOR METALS AND ACID- RADICLES. If the student, after working through the reactions for each of the metallic groups, intends to analyze substances containing one member only, or any two or more mem- bers, of that group, it is a good plan to analyze first a few substances containing only one member and to grad- ually increase the number present in those subsequently given. It is well to keep these substances in the dis- solved state1 as a rule, as they are intended mainly to afford practice in separation and detection according to the group tables, and the time spent by the student in preparing the solution is therefore wasted. Occasionally, however, a solid substance may be given in which the metal or acid-radicle present is to be detected by blow- pipe tests or other tests made on the solid substance. As examples of the substances to be given, in the order best suited to the gradual advance in difficulty, the fol- lowing, selected for Groups V, IV, and III B, will serve: Group V. Group TV. Group III b. Solution of NaCI Solution of BaCl2.2H»0 Solution of ZnS04.7H20 “ “ NH4C1 “ “ Sr(N0,\4H90 “ “ MnCU “ “ KCI “ “ CaCl„.6H20 “ “ NiSO, 7H20 “ “ NaCI + KCI “ “ Sr(N03V4H«0 “ “ Co(NO,)2.6H20 “ “ NaCl + NH4C1 + + Cat l2 f>H„0 “ “ MnCl2 + ZnS04.7H90 KCI “ “ BaCl,.2H20 + “ “ Co(N03)2 gh2o + “ “ NaCI + NH4C1 Sr(N03V4Ho0 NiS04.7Ho(> 4- “ “ MgS04 7HoO + + CaCi3.fiIloO ZnS04.7H20 NaCI + KCI “ “ BaCl2.2H20 + etc., etc., etc. Solids: NaCI, NII4C1, KCI, AmCl + NaCI, etc. Sr(N0a)2.4H»0 Solids: MnCl2, NiSO« 7H20, Co(N05)2.6H20. ZoS04.7tT20, etc. 1 The solutions already made for the reactions (529, 530) will serve very well for this purpose, being given either singly or mixed. 342 [536, 537. EXAMPLES OF 536. Substances are given to be tested for the members of an acid-radicle group in the same order (535),1 the first substances containing one member only, those subse- quently given containing two or more members of the group. 537. Substances . for Analysis by the direc- tions CONTAINED IN SECTION V. Any one of the solutions named in paragraphs 529 and 530 may be given for analysis by Section V, some of them being neutral, some acid, and others alkaline in reaction. The following more difficult solutions with acid or alkaline reaction may also be added to the list: Acid. Alkaline. Ca/P()4lo, “ Bone-ash ” dissolved in dilute HC1. BaC304 dissolved in dilute HC1. Mg(B03}22 “ “ HC1. BaCrO, “ “ HC1. KSbOa dissolved in water. Na2Si03, solution of “ soluble glass.” Na2Sn03, “ preparing salt ” of the dyer. Any of the solid salts which were dissolved in order to prepare the solutions in paragraphs 529 and 530, may be given for analysis as solid substances by (331 et seq.). As examples of substances possessing metallic appear- ance (366), the following may be mentioned as suitable for analysis: Zn, in pieces or filings. NiAs, Kupferniekel. Pb Graphite, or Black lead. FeS2, Iron Pyrites. Iron filings. As insoluble substances which require to be examined by (367 et seq.), the following may be given for analysis : BaSO,. CaF3, Fluor spar. PbS04. I'e('r.,()4, Chrome Iron Ore. AgCI. S, as pieces of roll sulphur. Sn02, Tinstone. C, as powdered wood-charcoal or plumbago. 1 See footnote on page 341. Made by mixing hot solutions of Na2B4C>T and Mg(N03)i. 538, 539. SUBSTANCES FOR ANALYSIS. 343 538. Solid Substances to be Analyzed by the Preliminary Examinations. For the Preliminary Examination for Metals (387): Simple. Complex. NH4C1 HgCls As203 KNOa p. may contain in addition to AgCI, Hg„C/2, PbCl2: TICI (white). J/tWOti “ ). TICI will usually be readily detected by a spectroscopic examination of tlie group pp. It may be removed from the group pp. by boiling with a little water, and ppd. from the cold filtrate by KI (Pi) is also thus ppd.): the pp. is yellow, and gives the thal- lium spectrum. If«IV04: a white pp. becoming yellow on boiling. Its presence is con- firmed by dropping a piece of Zu into a portion of the acid liquid and pp., when a deep-blue color will be obtained. Also by fusion of the pp. in a rai- crocosmic bead, which will be color- lessor yellow in the outer flame, blue (or with FeSO«, blood-red) in the inner flame. The group pp. may contain as sulphides, in addition to Ilg, Pb, Bi, Cu, Cd: Pd (black-brown) \ Insoluble in Tl (black; p),a. wdh As2S*i >• Am S [Os, Ilh, Ru ]‘ J ? And in addition to SnS, SnS%, As7Sa, A«2