AN ELEMENTARY TREATISE ON PRACTICAL CHEMISTRY AND QUALITATIVE INORGANIC ANALYSIS, SPECIALLY ADAPTED FOR USE IN THE LABORATORIES OF SCHOOLS AND COLLEGES, AND BY BEGINNERS. BY' FRANK CLOWES, D.Sc. Lond. FELLOW OF THE CHEMICAL SOCIETIES OF LONDON AND BERLIN ; SENIOR SCIENCE MASTER AT THE HIGH SCHOOL, NEWCASTLE-UNDER-LYME; LATE SCIENCE MASTER AT QUEENWOOD COLLEGE. wITH ILLUSTRATIONS. FROM THE SECOND ENGLISH EDITION. PHILADELPHIA: HENRY C. LEA. 1 8 7 7. SHERMAN & CO., PRINTERS, PHILADELPHIA. PREFACE TO THE SECOND EDITION. This little treatise was commenced to supply a course of Practical Chemistry to my own classes. I was en- couraged to proceed with it, by finding that the want of a sufficiently 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 in- telligible 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 how to work, and the description of the preparation 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 serious hindrances to the utility of many of the smaller Text-books on Practical Chemistry is the too great conciseness of the language employed, which fre- quently renders it unintelligible to the student unless supplemented by copious verbal explanation from the teacher. Whilst making the very desirable amplifications above referred to, the book has been kept within small dimen- IV PREFACE. sions, partly by the omission of all such higher instruc- tion as is not required by a student of elementary chem- istry, and partly by the insertion of the supplementary or merely explanatory portions in smaller type. I have also thought it best to avoid entering into any lengthy theoretical explanations. The modern teaching of chem- istry is in practice very appropriately divided into two departments, namely, theoretical instruction imparted by lectures or by the study of text-books of theoretical chemistry, and practical instruction imparted in a chem- ical 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 unnecessary as it is undesirable that his Practical Text-book should tempt him to bestow valuable time in the laboratory upon the study of matters of theoretical, not practical, 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 intelli- gibility of their descriptions have thus, I hope, been secured; only those reactions and methods which are commonly employed 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 recom- mended by their reliability rather than by their sim- plicity. In such cases, however, I have also described PREFACE. V the more simple methods, 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 text-book have necessarily been limited as to number, and I have felt it in general advisable to introduce such reactions as are useful in general analysis, rather than those which claim to be merely interesting 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 stu- dents; 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 gen- eral apparatus, with a description when necessary of its construction 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 ap- propriate for each. Experience has proved that these are matters 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 chem- icals, their purity should, however, always be ascer- tained 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 VI PREFACE. results that no other plea is required for its use. The simple plan of labelling each bottle in the laboratory with the chemical formula as well as the name of its contents, will prevent any difficulty arising from this general employment of chemical formulae. The “Tables of Differences,” which contain for each Analytical Group a summary of the differences of be- havior of its members with reagents, are special—being an extension of the system employed in Galloway’s Manual of Qualitative Analysis. lt 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 convenient tabular form of entering analytical methods which is employed in Valentin’s Text-book of Practical Chemistry, and with the author’s permis- sion have transcribed, with a few trivial alterations, the excellent Phosphate Table devised by him. My ac- knowledgments 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 demand which is rapidly increasing, as the value of a sound elementary instruction in practical science is be- coming more widely appreciated, both as means of mental training and as a preparation for the chemical and medical professions, as well as for many branches of manufacturing industry and enterprise. The fifth sec- tion has been inserted for the use of those who are spe- PREFACE. VII cially preparing for practical examinations in which proficiency in the analysis of simple salts only is re- quired of the candidate. This is the standard fixed for the Preliminary Scientific (M. B.) Examination of the London University, and for the more elementary exam- inations in the Oxford University, such as those for school certificates and open scholarships. The sixth section, however, contains additional details suited for the higher analytical work of advanced stu- dents, and will be found sufficient to qualify a student for the higher examinations in analytical chemistry, such as the B. Sc. Honors Examination in the London University. The introduction as appendices into this edition of the reactions and methods of detection of the rarer elements, and of the use of the spectroscope with a spectrum chart, will, it is believed, render the book more useful to advanced students. F. C. Newcastle-under-Lyme, November, 1876. CONTENTS. SECTION I. Paragraph. Page. Experiments illustrating the Methods of Preparation and Properties of Gases, Etc. I. Oxygen, 15 II. Hydrogen, ...... 22 III. Carbon dioxide, ..... 25 Ilia. Nitric oxide, ..... 30 IV. Ammonia, ...... 31 Y. Carbon monoxide, .... 33 V a. Chlorine, ...... 36 Y b. Hydrochloric acid gas, 36 VI a. Distillation of water, .... 36 VI 6. Preparation of nitric acid, . 38 SECTION II. Preparation and Use of Apparatus re- quired for Chemical Analysis. 1-19 40 Bunsen burner, ...... 1, 2 40 Spirit-lamp, ...... 3 42 Blowpipe, ....... 4 42 Glass tubes, cutting, 5 43 “ bending, ..... 6 44 “ drawing out, .... 7 44 Boring corks, ...... 8 45 Making sulphuretted hydrogen tube, 9 45 Making ignition tubes, .... 10 46 “ stirring-rods, .... 11 46 Mounting platinum wires, .... 12 47 Making wash-bottle, ..... Cleaning glass and porcelain apparatus, 13 47 14 49 Cleaning platinum-foil and wire, 15 50 Putting away apparatus, .... 16 50 Heating glass and porcelain : 17 51 Porcelain dishes, ..... 18 51 Glass vessels, 19 51 X CONTENTS. Paragraph. Page. SECTION III. Analytical Operations, Descriptions illus- TRATED BY EXPERIMENTS, .... 20-35b 53 Solution, ....... 20 53 Evaporation, 21 55 Precipitation, ...... 22 56 Filtration and decantation, 23, 23a 58 Decantation, 236 60 Washing precipitates on the filter, 24, 24a 61 “ “ by decantation, 246 61 Drying precipitates, ..... 25 62 Removing precipitates from the filter, 26 62 Ignition, ....... 27 64 Sublimation, 28 65 Fusion, ....... 29 66 The Use of the Blowpipe : ... 30 66 Borax-beads, ...... 81 67 Flame colorations, ..... 32 69 Ignition on charcoal in the blowpipe flame, 33 70 Levigation of residue, .... 33a 72 The Use of Test-papers: . 34 72 Making neutral, acid, and alkaline, . 35 74 Turmeric-paper, 35a, 356 75 Fractional solution, crystallization and dis- tillation, ....... 76 SECTION IV. Analytical Reactions, .... 36-329 78 Introductory remarks on analytical classifica- tion and on the analytical course which follows. Analytical classification, .... 36 81 Analytical groups, ..... 37 82 Method of trying the reactions (rules), 38 83 Entry in the Note-book: . 39 84 Chemical notation, ..... 40 84 Chemical equation, ..... 41 85 Rules for drawing out an equation, . 42 85 Contractions to be employed, 43 87 Examples of showing method of entry in the note-book,...... 44 87 Rules to be observed whilst working, 45 87 Reactions for Metals: Group V (Potassium, Group): . . . 46-47 89 Potassium, 47-50 90 Ammonium, ...... 51-55 92 CONTENTS. XI Paragraph. Page. Sodium, ....... 56,57 93 Magnesium, ...... 58-63 94 Table of Differences and its use, Principles of separation and detection, 64,65 96 66 97 Table for separation and detection, . 67 99 Group IV (Barium Group): .... 68-80 100 Barium, ....... 69-74 100 Strontium, ...... 75-79 101 Calcium, ....... Table of Differences, ..... 80-86 101 87 102 Principles of separation and detection, 88 102 Table for separation and detection, . 89,438 103 Group IIIx (Iron Group): .... 90-109 103 Aluminium, 91-94 104 Iron, ....... 95-101 104 Chromium, ...... 102-106 106 Table of Differences, ..... 107 108 Principles of separation and detection, 108 109 Table for separation and detection, . 109,436 109 Group IIIb (Zinc Group): .... 110-141 109 Zinc, 111-114 110 Manganese, ...... 115-120 111 Nickel, 121-128 112 Cobalt, ....... 130-137 114 Table of Differences, 138 116 Detection of members separately, 139 117 Principles of separation and detection, 140 117 Tuble for separation and detection, . 141,437 118 Group IIA (Copper Group): ... 142-176 118 Mercuricum, ...... 143-148 118 Lead, ....... 149-153 120 Bismuth,. ...... 154-159 122 Copper, ....... 160-168 123 Cadmium, ...... 169-172 125 Table of Differences, 173 126 Detection of members separately, 174 126 Principles of separation and detection, 175 126 Table for separation and detection, . 176-435n 126 Group IIB (Arxenic Group) : ... 177-210 127 Arsenic, ....... 179-190 128 Antimony, ...... 191-200 135 Tin, ....... 201-205 137 Table of Differences, ..... 206 139 Principles of separation and detection, 207 139 Table for separation and detection, . A second method of separation and detec- 208-4356 140 tion, ....... 209 140 A third, 210 141 CONTENTS. Paragraph. Page. Group I (Silver Group) : . 211-222 143 Lead, ....... r149-1531 120 Silver, . . . 212-2lb 143 Mercurosum, .... 217-219 143 Table of Differences, ..... 220 144 Principles of separation and detection, 221 144 Table for separation and detection, . 222,433 145 Reactions for gold, ..... 223,224a 145 Reactions for platinum, .... 225,226 145 Reactions for Acid Radicles: 227-329 147 Group I. Sulphate Group : .... 227,228 147 Group III. Carbonate Group: 229-240 148 Carbonates, .... 229 148 Sulphides, ...... 230-235 149 Sulphites, 236-238 151 Theiosulpbates, . . ... 239,240« 151 Hypochlorites, ..... 241,242 152 Nitrites, ...... 243-245 153 Detection of the members when mixed, 246 153 Group III (Nitrate Group): . 247-256 154 Nitrates, ....... 247-251 154 Chlorates, .... 252-255 156 Detection when mixed, .... 256 157 Group IV {Chloride Group): 257-274 157 Chlorides, .... 257-260 157 Bromides, ..... 261-264 159 Iodides, 265-270 161 Detection of separate members,. 271 163 Separation and detection, .... 272-274 164 Group V (Phosphate Group) : 275-282 166 Phosphates, 275-278a 166 Arsenates, ..... 279 167 Detection, ....... 280-281« 168 Separation and detection, .... 282 168 Ungrouped Acid Radicles (Inorganic): 283-302 169 Borates, ...... 283-285 169 Chromates, 286-289 170 Silicates, ...... 290-293 172 Fluorides, 294-298 173 Fluosilicates, ...... 299-302 175 Organic Acid Radicles: . 303-328 177 Cyanides, ...... 303-306 177 Ferrocyanides, ..... 307-310 179 Ferricyanides, ..... 311-314 179 Sulphocyanides, 315, 316 180 Oxalates,....... 317-319 180 Tartrates, ...... 320-325 181 Acetates, 326-328 183 CONTENTS. Paragraph. Page. SECTION y. Analysis of Simple Substances for one Metal and one Acid Radicle, 330—3696 185 Introductory remarks, .... 330 185 Preliminary examination of a solid for the metal, 331, 333 188 Solution of a solid substance, 332 189 Preliminary examination of a liquid for the metal, 334 194 Actual examination for the metal in a neu- tral or acid liquid, .... 335-345 196 Examination of a solid or liquid for the acid radicle: ...... 346-3586 207 Introductory remarks, .... 346-347 207 Preliminary examination, 348-351 209 Actual examination, .... 352-3586 211 Examination of an alkaline liquid, . 359-360« 214 Examination of a substatice with metallic ap- pearance, ....... 366 217 Examination of an insoluble substance, . 367-3696 218 Examples of entry of analyses, 222 SECTION VI. Full Analytical Course and Tables, 370-493 232 Introductory : Separation of metals into groups by group reagents, ...... 370 232 Addition of reagents in excess, . 371 233 Evaporation before precipitatiug Group 111 372 233 General remarks, 373,374 234 Preliminary examinations for their use, . 375-378 234 General analytical course: Preliminary examination of a liquid, 380,381 237 Solution of a non-metal lie solid, 382-385 238 Preliminary examination of solids for the metals present, ..... 387-409 240 Preliminary examination of solids for acid radicles, 410-418 246 Actual examination for metals: 419-439 249 General table and notes thereon, 419-432 349 Table 1 (Silver Group) and Table G, 433,434 254 Table 11 (Copper and Arsenic Groups), 435 255 Table III a (Iron Group),. 436 257 Table III B (Zinc Group), . 437 259 Table IV (Barium Group), 438 261 Table V (Potassium Group), 439 263 XIV CONTENTS. Paragraph. Page. Actual examination for acid radicles, Table showing solubility of substances in 440-454 265 water and acids, ..... 455 271 Explanation and use of the table, . 456-458 272 Remarks on the precipitation of Group III, Rules for the precipitation and examination 459-462 273 of Group III, ..... Table III Cj (Iron and Zinc Groups 463 275 mixed), Table IIIc2 (Iron and Zinc Groups 464 276 mixed), . . . . . . 465 278 Table III d (Phosphates in Group III), Examination of substances with metallic 466 279 appearance, ...... 467-471 281 Separation and detection of gold and plati- ¥ num, ....... Examination of substances insoluble in wa- 472-474 285 ter and acids, ..... 475-479 286 Analysis of silicates, ..... 480,481 482-487 290 Analysisof substances containing cyanogen, Example showing how to enter analytical 291 results, SECTION VII. Apparatus and Chemicals required for the 488-493 296 PRECEDING COURSE, List of apparatus for each student, 494-539 303 494 303 List and description of general apparatus: . 495-506 306 Indigo-prism, cobalt-glass, cork-borers, 496-498 306 Sulphuretted hydrogen apparatus, 499,500ra 306 Passing sulphuretted hydrogen,. 500a 309 Agate mortar, leaden or platinum crucible, 501,502 310 Steam-oven, water-bath, tubulated flasks, . 503-505 310 Distillation of water, .... Recovery of the metals from silver and 506 313 platinum residues, .... Directions for preparation of reagents and 507,508 316 solutions: ...... 509-517 318 Introductory remarks, .... 509,510 318 Dilution of liquids, ..... 511 318 Solution of solids, ..... 512-515 319 Preparation of solutions for the reactions, Lists of the reagents, solutions, and chemicals, stating their condition or strength and 516, 517 323 special processes of preparation: 518, 533 323 Introductory and explanatory remarks, 518-521 323 Labelling and varnishing, .... 522,523 324 List of reagents for each bench, 524 326 List of reagents for general use, 525,526 328 CONTENTS. XV Paragraph. Page. Preparation of saturated solutions of solids, 527 332 “ “ “ of gases, 528 332 List of solutions required for Section IV, . 529,530 336 List of chemicals required for Section I, . List of chemicals required for Section III, 531 339 532 340 List of sundry other requisites, .... Examples of substances to be given for analysis) 533 341 534-539 341 Appendix I.—Reaction and detection of the Rarer Elements, ..... Group I. (Silver Group): . Thallium, 540-554 346 540,541 540 346 346 Tungstates, ...... 541 347 Group II A. (Copper Group): . . . 542 348 Palladium, 542 348 Group II b. (Arsenic Group): 543-515 348 Molybdates, ...... 543 348 Selenium, ...... 544 349 Tellurium, Group III. (Iron and Zinc Groups): 545 349 546-550 350 Uranium, 546 350 Indium, 547 351 Beryllium, 548 351 Titanium, ...... 549 351 Vanadium, ...... 550 352 Group V (Potassium Group): 551,552 352 Lithium, 551 352 Rubidium and Caesium, .... General Table for detection of the rarer 652 353 elements, ...... 553 354 Table for examination of Group III, for the rarer elements, ..... 554 356 Appendix II.—The spectroscope, its use in analysis, ....... 555 357 Spectrum-chart, ...... 557 359 Appendix III.—List of chemical elements with symbols and atomic weights, . 558 361 Thermometric scales, ..... 559 361 Weights and measures, French and English, 560,561 362 PRACTICAL AND ANALYTICAL CHEMISTRY. INTRODUCTION. The course of practical chemistry which should be pursued 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 sec- tions and the sixth furnish a good general course for a senior student who wishes to obtain a training in prac- tical and analytical chemistry; but for younger students the most suitable analytical course consists in trying through the reactions in Section IY, and, as the reac- tions for each group are completed, testing several sub- stances 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 becoming familiar with this, separa- tions of the mixed members in each group are done, lead- ing 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 chem- ical manipulation, and to afford practical illustra- tions of the elementary portions of theoretical or descriptive chemistry; it may be omitted when instruction in analysis only is required. 14 introduction. Section II is indispensable and must be carefully perused. Section III is also indispensable to the student of analytical chemistry, but if the time at his disposal 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, sim- ply try the reactions and omit the performance of analyses at the end of each group. Section V is intended specially for students whose object is to learn only the analyses 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 intending 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 general analysis, who may, after becoming thoroughly conversant with its contents, pass on to quantitative analysis or to any special branch of practical chemistry he may require. PREPARATION OF OXYGEN. 15 SECTION I. PREPARATION OF GASES, ETC. In this section full directions are given for the prep- aration of five gases (viz., oxygen, hydrogen, carbon dioxide, ammonia, and carbon monoxide), and for certain interesting and instructive experiments which may be made with them. The processes of preparation and ma- nipulation 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 perform- ing the experiments with the above-named gases, easily prepare and experiment upon the three other gases (nitric oxide, chlorine, and hydrochloric acid) by follow- ing 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, if desired. Two examples of the process of distillation are also appended. The reference numbers inclosed in brackets refer to the paragraphs which commence with Section II (p. 40); 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. The student must carefully read through the whole description of each experiment before beginning to per- form 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 ex- posed to moist air its surface becomes covered with rust; 16 [Exp. 1. PREPARATION OF OXYGEN. 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 becomes 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. 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 described, 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. HgO = Hg -f- O. 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 EXP. 2, 3.] PREPARATION OP OXYGEN. 17 heat we might obtain oxygen from them just as from mercuric oxide. This method of making oxygen is in- teresting since it was the first means known of preparing the gas ; it is never used nowadays to prepare large quan- tities of oxygen, since other substances are known which contain a large proportion 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 fre- quently employed: kcio3=kci + o3. 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 (crackling), fuses (or melts) and when further heated, appears to boil; the small bubbles which are given off* consist of oxygen gas, as may readily be proved by holding in the mouth of the test-tube a burn- ing 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 themselves appear to undergo no change, its oxygen is driven off by heat with extreme facility; of these sub- stances manganic oxide (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 the 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 de- tected 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 18 PREPARATION OF OXYGEN. [Exp. 4. 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” oxy- gen is fully described in the following experiment; in the performance of which two students may advantage- ously work together, one attending 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 tightly into the mouth of the test-tube to be employed. Then bend (6) a piece of hard glass tubing about fourteen inches in length, into the form shown in the figure; so adapting the bends by trial that when the apparatus is fitted together 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 deliv- ery-tube ; no air must be heard to escape, or must be seen to bubble out on moistening 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) Exp. 4.] PREPARATION OF OXYGEN. 19 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 fit in the cork and delivery-tube. Before heating the tube fill the jar in which the oxy- gen is to be collected with water, close it with a stopper or ground-glass plate (or with the hand), invert its mouth into water three or four inches in depth, con- tained in an earthenware pan or bowl, and carefully re- move 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 the upper part of the oxygen mixture, holding the tube in the right hand; keep the lamp slowly moving with the left, 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 apparatus; as soon as a slip of wood glowing at its end is kindled, when held at the mouth of the deli very-tube, the oxygen has driven out the air, and is beginning to escape; the end of the de- livery-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 he 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 20 COMBUSTIONS IN OXYGEN. [EXP. 5, 6. test-tube must not be allowed to touch cold or wet objects, 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 con- venient, since it supports the jar during the process of collection. Oxygen gas is remarkable for the energy with which it combines with or burns many substances; three ex- amples are given of this property in Expts. 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 “ de- flagrating 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 bot- tle. Now heat the charcoal in the Bunsen flame, or better the blowpipe flame (4), until a part of its surface glows when held in the air, and quickly place it into the bottle of oxygen, with the brass plate covering the mouth of the bottle. (See Fig. 7, p. 30.) The char- coal will burn much more brilliantly than in air, throw- ing off sparks if its surface was “ barky C -(- Oa — C02. 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 Exp. 7.] 21 COMBUSTIONS IN OXYGEN. and begins to burn with a pale-blue almost invisible flame. Then place the spoon into a fresh jar of oxygen, the sulphur will at once burn with a much larger flame, which emits a beautiful violet light: s + o2 = so2, Sulphur dioxide (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 recognized by dropping into the water a piece of blue litmus-paper, which is immediately reddened, and by pouring 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 place into it a small piece of phos- phorus no larger than a pea. The phosphorus may be cut with a knife, but 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): P2 05 — P2Os. When the phosphorus has ceased to burn pour in a little waiter and shake it round in the jar, the white substance dissolves, yielding phosphoric acid : P205 + 3H20 = 2JI3P04, and the water may now be proved to be acid by dropping into it a piece of blue litmus-paper, which will be imme- diately reddened. Test for Oxygen.—A convenient test for oxygen is to introduce into the gas a slip of wood with a spark at the 22 PREPARATION OF HYDROGEN. [Exp. 8. end, which is caused to burst into flame. Only one other gas possesses this property, and it is readily distin- guished 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 hy- drogen from water. This gas is, however, most readily obtained from another liquid containing it, called hy- drochloric acid, bv the action upon it of the metal zinc. Exp. 8.—Fit a two-necked Woulffe’s bottle* (a, Fig. 3), with air-tight perforated corks bearing a thistle fun- Fig. 3. ncl (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 delivery- tube d. Pour into the bottle sufficient granulated zinc to cover the bottom, replace the corks, and after ascer- taining that the apparatus is air-tight by closing the end of the delivery-tube and blowing down the thistle-fun- * A wide-necked bottle may be used instead, being fitted as shown in Fig. 5 (p. 2(5). Exp. 9.] preparation of hydrogen. 23 nel, 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 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 fube is full of gas close its mouth with the thumb, and hold it to a flame; if the gas burns with a slight ex- plosion, 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 jar (or 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 jar 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 jar, when no flame will be seen at the mouth. If the jar be refilled with hydrogen and held for a short time mouth down- wards, the hydrogen will remain in it, and its presence 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 ten- dency to rise prevents it from passing out downwards 24 PREPARATION OF HYDROGEN. [EXP.10, 11. through the open mouth, whilst it readily escapes up- wards 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 hy- drogen 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 deli very-tube bent as shown in Fig. 4, and when a brisk effervescence of gas has been 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 let- ting it rest upon a perforated disk of card-board (or the round brass cap of a deflagrat- ing spoon), supported upon a retort-stand ring, or upon an iron tripod-stand, since the entrance 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 Fig. 4. Exp. 12.] preparation of carbon dioxide. 25 become dimmed with moisture, showing that hydrogen gas burning in the air produces water: h2 + O = H20. Note.—Since all gases which have been in contact with water contain more or less vapor of water, or are “ moist,” it is usual to employ for this Exp. a stream of hydrogen gas which has been freed from moisture or “dried.” Agasis dried (or desiccated) by passing 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 be made to bubble through strong sulphuric acid con- tained in a bottle, b (Fig. 10, p. 35), connected, as shown in the figure, with the generating apparatus. It may be also dried by passing it through a tube containing fragments of calcium chloride, or of quicklime (Fig. 10a), or pieces of pumice-stone moistened with strong sulphuric acid : the moistened pumice may be con- tained in a U-tube (Fig. 10 6), or in the bottle b (Fig. 10, p. 35). 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 explosion. Test.—Hydrogen gas is recognized by burning with a pale flame in air or oxygen, the flame depositing water on any cold object held above it. III. Carbon Dioxide Gas (Carbonic Anhy- dride).*—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 * Formerly called carbonic acid, a name objectionable on chem- ical grounds. 26 PREPARATION OF CARBON DIOXIDE. [Exp. 13,14. method consists in pouring hydrochloric acid upon some pieces of marble: ‘ CaC03 + 2HC1 = C02 + HzO + CaCl2. Chalk or limestone may be substituted tor marble, but it does 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 deli very-tube bent at right angles, as shown in 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 cardboard which has had a slit cut in it for the de- livery-tube (or pass the delivery-tube through the brass cap of a deflagrating spoon), and allow the apparatus to stand for several minutes. Carbon dioxide being much heavier than air, will soon fill the jar by “displacement,” that is to say, it will collect 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 taper is extin- guished, 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 very preferable. Exp. 14.—Allow this jar of carbon dioxide to stand uncovered, and with its mouth upwards for a few min- utes, then place in the jar a burning taper; the carbon dioxide is shown to be still present in the vessel by the immediate extinction of the taper. Then hold the jar Fig. 5. Exp. 15-17.] properties of carbon dioxide. 27 for several minutes with its mouth downwards; on test- ing 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 only 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. Exp. 16.—Pour a little lime-water from a test-tube or small beaker into a jar 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 common chalk (calcium carbonate), and this, being an insoluble substance, remains mixed as a white powder (“ precipitate ”) with the water : Fig. 6. CaH202 + C02 = CaC03 + II20. Exp. 17.—Carbon dioxide gas readily dissolves in cold water, forming a liquid which probably contains car- bonic acid : C02 + H20 = H2C03. The solubility of the gas in water may be proved by displacing the air from a bottle, previously half filled with cold water, by carbon dioxide ; then tightly closing the mouth of the bottle with the wet hand, and shaking vigorously for a short time: the bottle will adhere to 28 PROPERTIES OF CARBON DIOXIDE. [EXP. 18. 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 delivery-tube em- ployed in Exp. 13 to the bottom of a beaker containing water, so as to cause the gas to bubble up through the liquid. After the bubbles have passed for several min- utes, 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 milkiness;* also, by add- ing 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. If this liquid containing carbonic acid be tasted, it will be found to possess a taste resem- bling 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 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 milkiness on addition of lime-water, and by not changing the color of blue litmus-paper or solution. 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 dissolves entirely in the carbonic acid which is formed by the carbon dioxide dissolving in the water. On boil- ing some of this clear liquid it again becomes milky, since the carbon dioxide is driven out of the water by * Sometimes the milkiness disappears, for reasons explained in Exp. 18, unless much lime-water is added. Exp. 19, 20.] 29 TESTS FOR CARBON DIOXIDE. heat, and therefore the chalk can no longer remain dis- solved. 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 ex- plains 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 the greater part of the chalk separates upon the sides of the vessels. Tests jor 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. We may now proceed to employ them, to prove that carbon dioxide is evolved from our lungs during the process of respiration, and also that it is produced by a burning 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 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 air to pass up into the bottle, a portion should be breathed out through the tube, so as to replace the air contained in the mouth and in the 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 (Eig. 7). After burning for a short time the flame 30 TESTS FOR CARBON DIOXIDE. [Exp. 21, 22. will be extinguished, and if relighted 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 liquor will be rendered milky. A similar experiment may be per- formed, substituting the flame of coal- gas which is burnt from a bent tube for that of a candle, and closing the mouth of the bottle with a piece of cardboard. The extinction of the flame, and the milkiness then pro- duced by shaking 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 pres- ent 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: Exp. 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 film 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. 26). 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(N03)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 directed for hydrogen gas Nitric oxide is colorless, but it forms a reddish-brown gas (chiefly nitrogen tetrox- ide) when mixed with free oxygen. This is shown by filling ajar with the ga» over water, and then allowing it to stand with its Exp. 23.] properties oe ammonia. 31 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- stant])' being given otf from the solid “carbonate of ammo- nia” contained in the bottle. The gas is thus evolved only very slowly ; it may be made to come off' much more rapidly if the “carbonate of ammonia” is mixed with lime and the mix- ture is then gently heated ; sal ammoniac is usually employed instead of the carbonate of am- monia : 2NH4C1 + CaH A = 2NHa + CaCl2 + HA Ekp. 23.—Powder some ammonium chloride(sal am- moniac) in a mortar, and mix with it thoroughly on a sheet 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 8 or 9 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 collected by “ displacement,” as described in Exp. 10. To ascertain when the vessel is filled with the gas it is only necessary to hold at the mouth of the jar a piece of moist red litmus or yellow turmeric paper; since am- monia gas changes the color of the former to blue and of the latter to reddish-brown, it is easy to see whether Fig. 8. 32 PROPERTIES OF AMMONIA. [EXP. 24, 25. it has reached the mouth of the jar by observing whether any change is produced in the color of the paper. Ammonia gas does not burn continuously in air at the ordinary temperature, but it 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 the 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 NH3 may be 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 the gas and rises in the jar to fill the space for- merly occupied by the gas. If a little water be rapidly poured into a jar of am- monia by momentarily partly opening it and at once covering 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 Ammonite,” a solu- tion prepared in large quantities bv letting ammonia gas bubble for some time through cold water. Exp. 25.—Pour into a glass jar a little strong hydro- chloric acid, close the jar with a glass plate, and shake the acid about inside the jar, hydrochloric acid gas will thus be liberated; the liquid may then be allowed to run out by slipping aside the glass plate for a moment. Place this jar in an inverted position over a jar contain- ing ammonia gas, and covered with a glass plate (Fig. 9, Exp. 26.] preparation of carbon monoxide. 33 a), then withdraw the glass plates, so that the mouths of the jars are in contact (Fig. 9, 6), and the hydrochloric acid and ammonia gases can freely intermingle. Dense white fumes of solid ammonium chlo- ride will immediately be formed : NH3 + HC1 = NH4C1. This experiment may also be per- formed 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. Fig. 9. Tests for Ammonia Gas.—Ammonia gas may be read- ily recognized by its pungent smell; by turning moist- ened red litmus-paper blue, and moistened turmeric-paper 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. The preparation of carbon monoxide gas from oxalic acid will serve to show how this process is 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 car- bon monoxide and carbon dioxide is given off’: H2C204.2H20 + H2S04 = CO + C02 + H2S04.3H20. Exp. 26.—Place a little solid oxalic acid in a test- 34 PROPERTIES OF CARBON MONOXIDE. [EXP. 27. tube; pour upon it strong sulphuric acid* sufficient to cover it to a depth of at least half an inch, and heat the mixture. After a short time effervescence will be no- ticed, 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 iras burnina: in the air. 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; this liquid ab- sorbs the carbon dioxide readily, but allows the carbon monoxide to pass on : CO + C02 + 2NaIIO = CO + Na2COs + H20. The way in which this washing: is effected is explained in Exp. 27. 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 Woultfe’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 (b) filled with fragments of caustic soda or with fragments of pumice-stone moistened with strong caustic soda solution. The carbon 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 * 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 caused by nitric acid. Exp. 28.] tests for carbon monoxide. 35 not been able to absorb the carbon 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- mable and in extinguishing a burning taper; it also explodes when mixed with oxygen or air, hence before Fig. 10. 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 = cor Tests for Carbon Monoxide. — Carbon monoxide is recognized by burning with a pale-blue flame in the air, producing carbon dioxide, which renders lime-water milky. 36 DISTILLATION OF WATER. [Exp. 29,30. Y. 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 may be used containing a little water. Exp. 29.—Place some manganic oxide, powdered, or better in small lumps, into the flask a (Fig. 10, p. 35), pour upon it some strong hydrochloric acid mixed with about one-third its measure of water, and heat gently in a draught-cupboard or out of doors in the open air. A greenish-yellow gas is evolved, which may be collected by displacement like carbon dioxide, since it is much heavier than air: Mn02 + 4IIC1 = Cl, + MnCl, + 2H20. The gas has a very destructive action on the lungs, and must on no account be inhaled ; it is usually recognized bv its yellowish- green color, its peculiar smell, and by its property of bleaching moist vegetable colors. This last property is shown by placing in ajar of the gas a piece of moistened litmus-paper or fabric dyed with madder (“Turkey red”); the colors of both will be de- stroyed. A burning wax taper plunged into a jar containing chlorine continues to burn with a very smoky flame; oil of tur- pentine, 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. V. b. Hydrogen Chloride, or Hydrochloric Acid Gns. Exp. 30.—Place in the cleansed flask a (Fig. 10), which was used for the preparation of carbon monoxide, some lumps of sodium chloride (common salt), obtained by breaking up a mass of the melted powder, or by breaking a piece of rock-salt; pour upon it strong sulphuric acid and heal gently. Hydrochloric acid gas is evolved: NaCl + II.2S04 = HC1 + NhHS04. and being heavier than air, may be collected by displacement in the same way as carbon dioxide. The gas fumes strongly in moist air, turns moist blue litmus-paper red, dissolves easily in wa'er (Exp. 24) giving an “ acid ” liquid (hydrochloric acid), which, like the gas, turns blue litmus red. Tests for Hydrochloric Acid.—This gas is known by fuming in the air, turning moist blue litmus 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. VI. Distillation.—This process is employed to separate liquids which boil at a comparatively low tem- Exp. 31.] DISTILLATION OF WATER. 37 perature, 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 cooling (“condensing”) the vapor, which is thus given off, again into a liquid (the “distillate”), the non- volatile solid or liquid substances present being thus left behind in the vessel in which the liquid is boiled. As examples of this process, the purification of common spring-water from the solid substances dissolved in it, and the preparation of nitric acid, may be performed. A. Distillation of Water.— Exp. 31.— Pour into a clean retort a (Fig. 11) some tap-water through a funnel placed in the mouth, or in the tubulure (i.e., the open- ing for the stopper or cork) if, as is better, a tubulated Fig. 11 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 dip- ping into a small, clean flask or bottle b, which is partly immersed in cold w'ater contained in an evaporating basin. Cover the bulb of the flask with a broad strip of filter-paper, whose ends dip into the water contained in the dish; or instead of cooling the flask cool the neck PREPARATION OF NITRIC ACID. [EXP. 32. of the retort, by wrapping 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. 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 away, as they are apt to be impure from rinsing the retort neck and flask. Whilst this process of dis- tillation is going on, add to some tap-water contained in a test-tube several drops of nitric acid and some sil- ver nitrate solution, and notice that the water becomes 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 sub- stances 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 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. B. Nitric Acid.—Exp. 32.—Clean the retort from Exp. 31 by rinsing out the bulb with a little dilute hydrochloric 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 sulphuric acid about equal in weight to the nitre used, and allow the acid to drain off the neck (in case a non-tubulated retort is employed), by supporting it for some time in an upright position. Proceed to distil just as in the preceding experiment; a thick yellow oily Exp. 32.1 PREPARATION OF NITRIC ACID. 39 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 = hno3 + 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. (See Exp. 22, p. 30.) This property of giving red fumes when treated with copper is often used as a test for nitric acid. 40 THE BUNSEN BURNER. [1. SECTION II. PREPARATION AND USE OF APPARATUS REQUIRED IN ANALYSIS. Notes.—Refer 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 (Fig. 12). It is a gas lamp so constructed that coal gas entering through the tube a may be burnt mixed with a proper proportion of air which flows in through the holes at the foot of the burner; 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 existence in the flame of unburnt carbon or carbon compounds, is destroyed. The Bunsen flame is therefore useful, because it de- posits no soot upon any 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-luminosity, and colorless appearance also render it very valuable for producing flame colora- tions, 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 Fig. 12. * Numbers occurring in the text which are inclosed in brackets refer to the paragraphs commencing in this section. For conve- nience in reference, paragraph numbers are printed in thick type, and at the head of each page will be found, inclosed in square brackets, the numbers of the paragraphs it contains. 2-] THE BUNSEN BUHNER. 41 either by a loose perforated ring which is slipped over them, or by making the tube b turn round on its long axis. When a small 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 ,5gths 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 pinch- ing 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 burnt 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 cap c (Fig. 12) made of iron, which, when placed upon the [3,4. 42 USE OF THE BLOWPIPE. top of the tube b, yields a small circle of flames ; the rose-burner is put on and removed by grasping a small iron peg in its centre with crucible-tongs; 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 ob- tained. The spirit-lamp (Fig. 13) consists of a glass vessel con- taining methylated spirit, into which dips a cotton wick sup- ported 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 resinous matter, its flame will be non-luminous, and will deposit no soot upon a cold object. 4. The bloicpipe 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 burner, 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 between the lips, and after blow- ing out the cheeks to their full extent, the air Fig. 13. Fig. 15. Fig. 14. 5.] GLASS TUBE CUT AND BENT. 43 forced out through the jet a, and causes a small-pointed tongue of flame to issue from the side of the gas-flame. The chief difficulty in learning to use the blowpipe properly is experienced in acquiring the habit of keep- ing 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 meanwhile 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 ad- justed. The bright flame obtained by closing the air-holes of the burner is much better suited for use with the blow- pipe than the ordinary non-luminous flame. A burner with an elliptical orifice which gives a flat flame is com- monly 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 surface, and making a deep scratch with the edge of a three-cornered 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 Fig. 16. 44 GLASS TUBE DRAWN OUT. [6, 7. 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 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-tubing; it pro- duces a most unsatisfactory bend. The tube is supported by hold- ing 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. 17 a); if a sharp angle is made, the bore will be nar- rowed, and the bend, besides being un- sightly, is very liable to break under a small strain (Fig. 17 b). Glass rod may be bent in the Bunsen or blowpipe flame. 7. Glass tube is drawn out by holding it with both hands as for bending; and whilst turning it constantly round on its long axis, the part to be drawn out is strongly heated in the Bunsen, or better, in the blowpipe Fig. 17. Fig. 17 a. Fig. 17 6, 8, 9.] 45 BORING CORKS. 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 ol the same size as the glass tube which is to be inserted 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 pushing the borer through whilst constantly turning it upon its long axis (Fig. 18). Caution and practice wili 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 file carefully through the cork. The round file is required for smoothing the interior of holes made by the cork-borer, or for slightly enlarg- ing 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 inserted fits 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 Tube.—A tube of the requi- site shape will have been used for the experiments in Section f; it is seen as a bent delivery-tube in Figs. 4 Fig. 18. 46 GLASS STIRRING RODS. [10,11, and 5 (pp. 24, 26). 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. 10. Small Ignition-Tubes.—A piece of hard glass tub- ing,* perfectly dry inside and out, 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. 42. The narrowed por- tion of the tube (Fig. 19) is then cut across (5) at its Fig. 19. middle point, and by heating the conical part a, the narrow tube may be drawn oil, 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 ex- panded into a small bulb. (See Fig. 36, p. 133.) 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 bet- ter in the tip of the blow- pipe flame, and turning the rod constantly round on its long axis until it Fig. 19 a. Fig. 19 a. Fig. 20. * To distinguish hard glass from soft (lead) glass, hold the tube toward 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. 11 a-13.] THE WASH-BOTTLE. 47 becomes red hot at the end (see Fig. 20); the sharp edges are thus partially melted. The end of the rod must not be allowed to touch anything 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. 42), and then quickly drawing it out until the required fineness is produced. 12. Mounted Platinum Wires.—The platinum wire used here must not persistently color the flame green. Fig. 21. Draw out a piece of glass tube six or seven inches in length at its middle point (Fig. 15, p. 42) into the shape shown in Fig. 19. Cut it across (5) at the middle ot the narrow portion. Each piece of glass thus obtained serves for the handle to a wire. Break otf the narrow part of the tube until it extends only about a quarter ot 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 au 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 thickens 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 softening the end of a short piece of glass-rod in the blowpipe flame, and sticking the wire into it. 13. Wash-bottle.—A thin flat-bot- tomed flask is chosen (best of the trian- gular shape shown in Fig. 22) and of 16 or 18 ounces ca- pacity; the neck must not be less than an inch in diameter. Procure a sound cork which is slightly too large to enter Fig. 22. THE WASH-BOTTLE. [13. 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-rubber 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 re- quired 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 (5) to the right length, and their sharp edges 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 rather 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 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 fitting in the glass tubes. Upon the upper end of a is fitted a piece of small india-rubber tubing about an inch and a half in length, into the other end of which is pushed a short jet (c) made by drawing out a piece of glass tubing in the flame (Fig. 15, p. 42); its nozzle may be contracted, if neces- sary, 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. The wash-bottle, when thus fitted up, is filled about 14.] 49 CLEANING APPARATUS. 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 (b); 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 precipi- tates; 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 issuing from a rose-burner, as shown in Fig. 10 (p. 35). 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). Sometimes a little hot hydrochloric acid is requisite to remove stains, and occasionally it is neces- sary to heat a little strong sulphuric acid in a vessel in order to cleanse it from grease or other impurities; a little hot caustic potash or ammonia may also often be used with advantage. In fact in removing a substance from a vessel to which it strongly adheres, the student should always consider what the substance 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 im- mediate use, should be rinsed out with a little distilled water. It should be borne in mind that apparatus must be washed as soon as pos- sible 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 as the glass is very thin 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 Fig. 23. 50 CLEANING PLATINUM FOIL AND WIRE. [15,16. cleaner (Fig. 23 a) is 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 curving 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 file. The inside of the narrow neck is best cleaned by washing it with a com- mon 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 aiul porcelain which is not in 17-19. HEATING GLASS VESSELS. 51 actual use, and place it in the wicker basket to drain ; the basket is put away with its contents. All iron apparatus should be carefully dried, and must be kept in a dry place to prevent rusting. On no account must metal apparatus be kept in the wicker drain- ing basket. 17. Heating Glass and Porcelain.—A few general precautions should be observed in heating glass and por- celain 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. Porce- lain 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 triangle, 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 allowed 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 boiling liquids in, the liquid being very apt to boil over. Small quantities may be boiled and larger quan- tities heated short of boiling in a test-tube, but the broader “ boiling tubes ” are best suited for this purpose. 52 [19. HEATING GLASS VESSELS. Large glass flasks, such as the wash-bottle, are most safely heated by placing them on a piece of wire gauze on a tripod-stand (Fig. 10, p. 35), and heating with a rose-burner; in some laboratories a sand-bath is avail- able, 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. 20.] ANALYTICAL OPERATIONS. 53 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 sugar may be mentioned as examples. Other liquids may be employed instead of water, and if they cause the solid substance immersed in them to partially or entirely become 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 solution of sodium chloride, and water is therefore called a solvent for sodium chloride. Further, a solid which dissolves 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 thus 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. “Sim- 54 SOLUTION. [20. pie 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 the solid, and yielding again the solid sub- stance 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 attended by a chemical change in the substance to be dissolved, and since the solution therefore contains a substance 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 obtained. 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, fill the beaker one-third with water,* 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 in the Bunsen flame, 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 bot- tom of the test-tube; the potassium nitrate will dissolve much more rapidly than before, showing that solution is accelerated by powdering the solid and employing heat. Keen these solutions. Exp. 34.—Powder a little copper sulphate (blue vitriol) in a mortar, place it in a small porcelain dish, half fill the dish with water, and heat it on a tripod or retort-stand. The blue copper sulphate dissolves, yield- ing a blue solution. Keep this solution. These two experiments are both examples of “simple * Here, and in all subsequent cases, water must be understood to signify distilled water. 21.] EVAPORATION. 55 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 color of the liquid. Moreover, if a drop of the potas- sium nitrate solution be tasted, it will be found to possess the same taste as the solid ; chemists occasionally rely upon taste, as upon color, when examining “simple solu- tions.” Exp. 35.—Place in a test-tube a few small pieces of calcium carbonate (marble or chalk), pour upon them a little water and heat the tube; the calcium carbonate will be found to be “insoluble” in the water. Add to the water some hydrochloric acid, “effervescence,” or escape of numerous small bubbles of gas, will occur; the pieces 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 few small pieces of copper; on warming these with a little water they remain undissolved, 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 emnloved. 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 dis- solved 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 universal, effect during “chemical solution;” the distinguishing 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 vapor, or “evap- 56 [22. PRECIPITATION. orated;” 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 make the flame smaller, and heat until the water has quite 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 solution, 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 trans- parent solutions, on being mixed together, often become more or less turbid and opaque, owing to a solid insolu- ble substance being formed in the liquid. A solid sub- stance 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 22.] PRECIPITATION. 57 the latter (like common marble) is insoluble, and there- fore remains as a fine powder in the liquid. Substances are very frequently removed or separated in analysis by thus causing them to form insoluble com- pounds or precipitates with other substances which are added for the purpose. In producing a precipitate care must be taken that 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 it, 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 we frequently form a precipitate 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 microscope, “gelatinous” if jelly-like, etc. A slight precipitate causes only a “ turbidity” in a liquid. Tiie 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 58 FILTRATION. 23, 23 a. 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 precipi- tated from its solution, and covers the iron as a red film. 23. Filtration and Decantation.—It is fre- quently necessary 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 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, they 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 frequently 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 Fig. 24. Fig. 25. 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. 23 a. FILTRATION. 59 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 re- quires to be opened; by separating the edges, formed by cutting off the corners, so that they form a circle, three remaining on one side of the circle and 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 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 precipi- tate get between the fibres, which then swell by the wet- ting, 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 filtered off. Pour the liquid containing the precipitate upon the filter, the funnel being placed with its neck in a test- tube, and the test-tube being supported in a test-tube stand (Fig. 26); care must be taken 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 of the tube is liable to become filled with liquid, and the egress of air being thus prevented the filtration is stopped. The funnel might also be sup- ported upon the ring of a filter-stand, and the filtrate be received in a small beaker instead 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 carried out, and no hole has been made in the paper whilst preparing the filter, the filtrate will run Fig. 26. 60 DECANTATION. [23 b. 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 a filter much more quickly than cold, hence, if not inadmissible for other reasons, a solution should always be boiled before being filtered. Note.—Common filter-paper contains a little calcium-carbonate, which is of no importance in ordinary analyses, and is only objec- tionable when a substance has to be examined for traces of calcium. To remove this impurity in special analyses, the filters are moist- ened in a funnel with dilute hydrochloric acid, and then well washed with distilled water. 23 6. Decantation.—Precipitates which settle rapidly and 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 precipi- tate has completely set- tled, and the liquid is then carefully poured otf (“decanted”) by allow- ing it to run gently down a wetted 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 per- formed, effects a fair separation of heavy precipitates. Fig. 27. 24, 24 a, 6. 61 WASHING PRECIPITATES. The precipitate obtained by adding sulphuric acid to some boiling solution of barium chloride may be sepa- rated by decantation. 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 perfectly free from the liquid adhering to it; this “ washing” is performed as described under 24 a if the precipitate has been separated by fil- tration, and by 24 6 if by decantation. 24 a. Exp. 41.—Support the funnel, which contains the filter and barium carbonate precipitate from Exp. 40, with its neck in a beaker or flask, and with the wash-bottle blow in a fine stream of hot distilled water, so directed by moving the jet with the fingers as to stir up the precipitate well; in this way fill the filter to within a short distance from its edge; let this water run through perfectly, then nearly fill the filter again in the manner just described, and repeat this process two or three times, letting the.liquid run through perfectly each time before putting in a fresh quantity; the water run- ning through from the third or fourth washing will usu- ally be quite tasteless, and the precipitate and filter will be freed from everything which dissolves 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 6. 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, then allowed to settle; when the water has become quite clear it is poured off (236). By several times repeating this wash- ing process with addition of fresh portions of distilled water, the precipitate may be entirely freed from adher- ing solutions. The precipitate of barium sulphate remaining in the test-tube from the experiment at the end of 23 6 may be thus washed by decantation. 62 REMOVAL FROM THE FILTER. 25, 26. 25. Drying Precipitates.—A precipitate is often re- quired in a dry condition after it lias been filtered off and washed. It is dried on the filter and in the funnel by placing the funnel in a hollow tin cone or cylinder (filter-dryer, Fig. 28), and supporting 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 burn the filter. A more rapid method of drying the precipitate consists in spreading the filter, after having allowed it to drain for a time, upon a piece of wire gauze supported on a tripod-stand; a small flame from a rose-burner is then placed beneath the gauze, and the filter carefully watched to avoid burning it. 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 appear- ance, 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 examina- tion. 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 with a fine stream of water or other liquid from the wash-bottle into a vessel beneath. b. Without breaking the filter the funnel may be held Fig. 28. 26 REMOVAL FROM THE FILTER. 63 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 (more particularly the empty fold)* it is spread out inside a porcelain 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 occa- sionally carefully stirring the precipitate with a glass rod, the precipitate is washed off the paper without tear- ing the latter to pieces. The paper is then carefully re- moved 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 draining for a short time, are removed from the funnel, the filter is spread out upon a flat piece of glass and the precipitate carefully scraped off with a knife, or better with a small spatula. If the precipitate is required dry, the filter after removal from the funnel may be care- fully opened and spread upon several thicknesses 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 spatula or knife 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 Fig. 29. * Filters may be made without this fold, by cutting one of the round papers (Fig- 25d) through across one of the folded diame- ters, 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. 64 26, 27. IGNITION. poured upon the precipitate; it will run through the filter into a vessel below, taking with it the precipitate in solu- tion : the liquid should be heated again and once more poured upon the precipitate, if the latter is not entirely dissolved ; this reheating and returning of the liquid to the filter should be continued as long as anything is dis- solved ; any remaining portion of the precipitate must then be removed by a little fresh solvent. / /. A precipitate, if in small 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 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 the precipitate may often be'removcd by a clean knife or spatula, and the remainder by some one of the foregoing methods. Exp. 42.—Remove the precipitate of barium carbo- nate 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 igni- tion is employed with various objects. 1 st. 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). 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, and if then a small splinter of wood with a spark at its end be held in the tube, it will burst 28/ 65 SUBLIMATION. into flame. The behavior of this red powder on being “ ignited,” therefore, shows it to contain the elements of mercury and oxygen. Substances are often heated on platinum foil with the same object. 2d.—Ignition is also used as a means of separating from a solid mixture certain substances which are “vol- atile,” or which, when heated, change entirely into vapor; these are driven off by heat from other sub- stances, which are “non-volatile” (i. e., can be strongly heated without changing into vapor), and which, there- fore, remain behind. Exp. 44.—Heat a small piece of ammonium chloride on a strip of platinum foil held in the flame by crucible 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 chloride; this will melt, but will not disappear, since it is oidy slightly volatile. It will become solid again on cooling. Hence, if we had a mixture of ammonium chloride and potassium chloride, and wanted to obtain the potas- sium chloride alone, we should strongly heat the mix- ture for some time, when the ammonium chloride would be removed 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 on the upper part of the tube. This is an example of the process 66 FUSION—USE OF THE BLOWPIPE. [29, 30. 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. This melting or “fusion” is performed sometimes on platinum foil, but often in porcelain or platinum crucibles. For fusion in a crucible an intense heat is often requisite; 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, p. 62) which steadies the flame and creates a draught. Exp. 46.—Place upon a slip of platinum foil with bent-up edges, a mixture of powdered sodium carbonate and potassium nitrate, then a very small quantity of manganese chloride; hold the foil with crucible-tongs in the top of the Bunsen flame, or heat the under surface of the foil with the blowpipe 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 ob- tained. The production of this color is due to the pres- ence of sodium manganate formed by the fusion ; this peculiar color on fusion with sodium carbonate and po- tassium 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 already explained (4), to obtain an intensely hot flame, which may be made to play in a convenient direction upon any substance to be heated ; it is very useful for analytical purposes, since by its skilful use the composi- tion 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 be 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 31. BORAX BEAD. the “ reducing or deoxidizing flame,” because it separates or “reduces” metals from their oxides and compounds, and in general “deoxidizes” substances; the outer flame is also known as the “ oxidizing flame,” because it changes metals into their oxides, and “ oxidizes ” many other substances. These two flames also produce other dis- tinctive effects. The “innqr 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 further into the gas flame. It may also be noted that the “reducing flame” is furnished most readily by the luminous 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. There are several purposes for which the blowpipe is employed in analytical chemistry with which the stu- dent should become quite familiar; the following ex- periments will exemplify the most important of them. 31. Exp. 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 borax 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 com- pletely fills the loop. This bead must be perfectly col- orless 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 68 BORAX BEAD. '31. 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 iron wire. If the bead is too large, remove a por- tion 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 ap- pears opaque, on account of too much of the coloring substance having been introduced, it can generally be made transparent by shaking off some of the fused borax, or by flattening 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- 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; nowheat 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 blow- pipe flames respectively, characterize the metal iron. The borax bead is best detached from the wire whilst it is melted 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 32, FLAME COLORATIONS. 69 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 re- peated until the bead is obtained perfectly clear and colorless. 32. Flame Colorations.* — Many substances give a characteristic 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 pur- pose well. The flame best suited for this purpose is obtained by surrounding the Bunsen flame with a coni- cal chimney, reaching about two-thirds of the height of the flame (Fig. 30), and then so regulating the supply of air enter- ing into the air-holes that a small lumin- ous point appears near the top of the flame; the platinum wire is held either in or just above this luminous tip. Afllter- 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 bend- ing down the ends of a pipeclay 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 so- lution remains in the loop; then hold the loop at the tip Fig. 30. * For a more detailed and exact description of flame-tests, see Bunsen’s paper in the Philosophical Magazine for 1867. 70 IGNITION ON CHARCOAL. 33. 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 Bunsen flame, the same yellow tint will be obtained. This yel- low 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 chloride 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 of the blue glass or prism then potassium is discoverable in the presence of sodium, bv 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 him- self 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. It is well to keep two platinum wires, one to be used for borax beads and the other for flame colorations, since a loop which has been used for borax colors the flame yellow. 33. Ignition on Charcoal in the Blowpipe Flame.— Common wood charcoal forms a very useful support for 33. IGNITION ON CHARCOAL. 71 substances which are to be heated in the blowpipe flame. It cannot itself be melted, it conducts heat very badly, and possesses 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 ox- ide of the metal forms a characteristic coating or “ in- crustation ” on the charcoal; an examination of the color and properties of the metal, or incrustation, or of both, will frequently lead to the detection, or confirm the pres- ence, 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 fre- quently requires to be moistened with water before being heated by the blowpipe flame, in order to prevent the flame from blowing it off the charcoal. Exp. 50.—Choose a piece of wood-charcoal free from large cracks, scoop out a small hollow near one end with a knife, and in the hollow place a small quantity of a mixture of powdered lead acetate and sodium carbo- nate (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 continuing the 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 Fig. 31. 72 USE OF TEST-PAPERS. 33 a, 34. be then taken off the charcoal with the point of a pen- knife, 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 Fig. 32. 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 obtained free from soluble substances and charcoal; it may then be further examined by a lens or magnet. A mixture 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 ferrous-sulphate and sodium carbonate will yield a gray powder consisting of metallic iron, which, when touched with the pole of a magnet, will become attached to it. 34. Use of Test-papers.—Certain vegetable colors un- dergo remarkable changes when acted upon by chemical substances. Some of these are used for analytical pur- poses; the following experiment will explain how they are made use of. 34. USE OF TEST-PAPERS. 73 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 ammo- nium 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 ammonia 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. 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 moisten- ing them with the liquid by dipping a glass rod into it, and then touching the paper with the moistened end. It will be seen then that the three substances employed differ in their action on litmus test-papers. Hydrochloric acid . . reddens blue litmus does not affect red litmus. Ammonia does not affect “ “ blues “ “ Ammonium chloride . “ “ “ “ U docs not affect “ “ NEUTRALIZING AN ACID. [35. 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 hydro- chloric 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 alkalies, resemble ammonia in bluing red litmus, and not affecting blue. The class of neutral substances, including potassium chloride, sodium chloride, etc., resemble ammonium chloride 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 “ neutral.” The red cabbage liquid, as will be seen, is better suited for a test-paper than litmus, since one paper shows both 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 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. An acid substance by being mixed with a proper proportion of an alkaline substance becomes “ neutral;” similarly an alkaline substance is rendered “neutral” by mixture with a proper quantity of an acid. Thus by mixing hydrochloric 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 performed. 35 a, 35 b. ANALYTICAL OPERATIONS. 75 Exp. 54.— Pour a little hydrochloric acid into a porcelain 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 red- dened by the liquid the ammonia is added very carefully, stirring well after the addition of each drop, and trying the action 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 un- affected, 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 ammo- nia with three or four times as much distilled water in a test-tube. 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, and after each addition of ammonia noting its color; the condition of the liquid should, however, even in this case be proved towards the end by moistening 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, save 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. 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 b. 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 excep- tion of boracic acid. The most important use for tur- 76 FRACTIONAL SOLUTION, meric paper is to test for boracic acid, 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, moistening the lower part of a slip of turmeric paper with this liquid, and drying it by hold- ing it at some distance above the flame, or better by placing it in a steam-oven ; 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, CRYSTALLIZATION, 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 Fe2()3: 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. Fractional Distillation.—Liquids which boil at dif- ferent temperatures may often be separated by distillation (p. 36); that part of the mixture which first distils over consisting chiefly of the liquid with the lowest boiling- point, and the successive portions of the distillate be- CRYSTALLIZATION AND DISTILLATION. 77 coming 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 alcohol, 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 proved to be water by turning dry CuS04 blue and dis- solving it. 78 ANALYTICAL REACTIONS. 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 artificial importance. The other course is suited to junior students, and forms an easy approach to the more difficult complete methods of analysis: it teaches the plan of analyzing simple sub- stances which may contain one acid and one metal. This course is therefore also suited to those who are learning analytical chemistry with the view of preparing themselves for examinations in which the candidate is not required to detect more than one acid and one metal. These courses are described below as the “ Senior Course ” and “Junior Course.” The Senior Course consists in working through the analytical reaction in Section IV; and as those for each group are completed, several substances whose composi- tion is unknown to the students are tested for one mem- ber only by the Table of Differences at the end of the group; as soon as these are detected with readiness, sub- stances which may contain two or more of the members mixed together are analyzed by the group table in Sec- tion 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 work- ing with each group table before going on to the reac- tions for the next group is to be recommended, since, ANALYTICAL REACTIONS. 79 whilst the differences 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 intelligi- ble one after another, whilst the student is proceeding through the reactions. The book is so arranged, how- ever, that all 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 con- tain 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 metal and one acid, the student whilst working through Section IV omits all those para- graphs marked “s” after the number, relating to the separation and detection of the mixed members 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 reactions. After working in this way through Section IV, he at once proceeds to analyze simple substances by Section 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 mem- bers 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. 80 INTRODUCTORY REMARKS. INTRODUCTORY REMARKS OK ANALYTICAL 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.” Analytic chemistry or analysis (literally meaning an unloosing 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 ele- ment 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 “Theoretical,” or more appropriately perhaps “Descrip- tive, Chemistry.” But although we recognize a sub- stance by its properties, still a knowledge of all its prop- erties is not requisite to enable us to detect its presence: for ordinary 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 be- 36.; ANALYTICAL CLASSIFICATION. 81 havior when mixed with certain liquid or solid sub- stances. Such substances, added for analytical purposes, are called reagents. Some reagents serve for detecting one element 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 substances 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 reaction 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 modifica- tion, convenient divisions for analytical purposes. In the class of “metals” must be included the hypothetical metallic radicle ammonium (NHJ, also the element hy- drogen. 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 forming “salts;” the hydrogen salts of these radi- cles being often called “acids.” Thus Cl,* S04, P04, Mn04 form the hydrogen salts (acids), HC1, II2S04, H3P04, HMn04, and the metallic salts, KC1, MgS04, Na3P04, KMn04: metal hydrogen salts (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., contain 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 * The meaning and use of chemical symbols will briefly be ex- plained hereafter (40); but the student is presumed to be already acquainted with them. In par. 540 will be found a list of the symbols of the different elements. 82 ANALYTICAL GROUPS. 37. purposes, then, we may separate the substances 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 com- pounds—usually salts—which contain them. For convenience of 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- cyanides. 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 distinctive name—either a number from its place in the systematic course, or a name from some conspicuous or important member of the group, or from the general re- agent used to precipitate the group. Thus we speak indifferently of the 4th Group, the Barium Group, or the Ammonium-carbonate Group. In sec. v, par. 330 will be found a table showing the analytical groups with their distinctive numbers, names, and group reagents placed at the head of each column ; and the names and symbols of the elements contained in the group 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. TRYING ANALYTICAL REACTIONS. 83 33. Method of Trying the Analytical Reactions in Sec- tion IV.—In order to become fully acquainted with the 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 sub- stance itself or with one of its compounds, and the ap- pearances presented carefully observed, so that the sub- stance 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 so- lution 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 c.c.) of the solution of the substance. If tffe solid substance is also required, take some of it upon a watch-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 always be added in small quan- tity at first; more can be employed afterwards if excess is required. The student must from the first acquire the habit of working with small quantities both of solu- tions 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 description of the results he is to obtain ; he must then perform the experiment literally following out the directions given. He 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 conscientiously sat- 84 CHEMICAL NOTATION. 39, 40. isfied himself that the statements of the book are true, and that lie could at any time repeat the test successfully. 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 chemi- cal 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 here given which will be of special use for the purpose of briefly entering reactions. 40. Chemical Notation.—Each element has its corre- sponding 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 written one after another they give the formula of a compound 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 stand for one molecule*>f platinic chlor- ide, 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 together 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(N03)2 and Sr2(N03) stand for SrN2()6, and this may also be written Sr.2NOa. In paragraph 540 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 formulae are always used in the text instead of 41, 42. 85 CHEMICAL EQUATIONS. names, but the student can readily find for these corre- sponding names by reference to the above tables, or to the labels on the bottles, which should contain both names and formulae. 41. On adding a “reagent” to a substance some change usually occurs which gives rise to an alteration of color, or very frequently to the formation of a precip- itate having a certain color, appearance, or behavior with other liquids, which are characteristic of that par- ticular substance, or of some element or group of ele- ments 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 here given, 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 to- gether for the reaction, with the sign of addition ( -f- ) between them ; then write the sign of equality ( = ), followed by the formula of the precipitate produced. In a completed 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 reac- tions are cases of “double decomposition”—i.e., cases where an exchange of certain elements or groups of ele- ments occurs between the two compounds,—a little con- sideration will usually show how many molecules of the substances oil 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): This is simply placing together the substances mixed KC1 + PtCl4 = K,PtCl6. 86 CHEMICAL EQUATIONS. [42. and the precipitate formed ; the equation thus formed is evidently 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 inequality is at once removed if we place 2 before the KOI, thus : 2KC1 + PtCI4 = K2lJtCl6 Evidently if the above equation is correct the precipi- tate 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): This represents the substances mixed and the precipitate formed, but evidently the left-hand side of the equation contains more than the right (viz., Am2and Cl2); hence we write it fully thus : BaCl2 -f AmaC03 = BaC03 -f- BaCl2 -f AiUjCOj = BaCQ3 + 2AmCl, which states that on mixing together barium chloride (BaCl2) and ammonium carbonate (Am2C03), we obtain barium carbonate (BaCO,) 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 formulse 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. 43-45. 87 EXAMPLES OF ENTRY. 43. The following contractions are recommended : expt. for experiment. pp. “ precipitate. ppn• “ precipitation. ppd- “ precipitated. sol. “ soluble. insol. for insoluble. soln- “ solution. crystne■ “ crystalline. coln- “ coloration. 44. Examples are given below showing how these re- actions should be entered in the note-book ; they should be referred to as soon as the student commences the reac- tions for the metals: 1st. [See pars. 47-50.] PtCl4: stirred on watch-glass: yellow crystne pp , sol. in much water and in KHO, insol. in alcohol: Potassium (K).—Used KC1. NaHT: well shaken in a test-tube: white crystne pp., sol. in water, KHO, and HCL : 2KC1 + PtCl4 = K2PtCI6. Flame coln: pale violet, violet-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. KC1 + NaHT = KHT + NaCl. 2d. [See pars. 69-74.] Barium (Ba).—Used BaCl2. Am2Co3: white pp., sol. in UA: BaCl2 + Am2C03 = BaCO, + 2AmCl: CaSOi: heavy white pp., insol. in boiling HC1: BaCl2 + CaS04 = BaS04 + CaCl2. K2CrOi: light yellow pp., sol in HC1, insol. in HA: BaCl2 + K2Cr04 = BaCr04 + 2KC1. Flame eoln : on loop of platm 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 88 RULES FOR WORK TNG. [45. bottles belonging to the working bench ; replace any which are absent, and arrange the bottles, if necessary, in the order indicated on an accessible list, or 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 relabel 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 any- thing. 3. Before commencing work, all glass and porcelain which is not in use should be carefully cleansed, if not already clean ; Jjut 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 running dowTn 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 knifeblade 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 restoppered 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 o»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 46. REACTIONS FOR THE METALS. 89 of the brass is apt to be dissolved and thus introduced into the solution. A hot dish may be moved either bv holding it with a clpth or by taking hold of 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 be left until the completion of the analy- sis. This rule cannot be too strongly enforced, as neg- lect of it is always attended with loss to the beginner. The most convenient form of entry is that of the Ana- lytical 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 better suited for a beginner. GROUP V.—POTASSIUM GROUP. 46. Tliis group includes K, NH4,* Na, Mg. : The first three metals (K, NII4, Na) are known as the “ alkali metals.’7 The members of this group are not precipitated by any of the five group reagents. * A hypothetical metal radical, “Ammonium.’ 90 ]47, 48. GROUP V. — POTASSIUM. Refer if necessary to paragraphs 38 and 44 for directions how to work. Potassium (K).—Use KC1. 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 distilled water and heat, the precipitate dissolves ; to the other part add alcohol, the precipitate does not dissolve. Hence this precipitate is soluble in water, insoluble in alcohol. Bv warming the other portion with solution of KHO the precipitate is also shown to be soluble in that liquid. Remarks.—The following remarks are of great impor- tance in using the above test for K. Since this precipi- tate 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 rap- idly in dilute solutions; owing to the solubility of the precipitate in water, very diluted solutions must, how- ever, 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 precipitate produced by PtCl. with ammonium salts (52). 48. H/T (or better NaHT) mixed with some of the solution in a test-tube gives a white crystalline precipi- tate (KHT); usually this precipitate appears only when the mouth of the test-tube is closed with the thumb and the tube well shaken for some time. KC1 + NaHT = KHT + NaCl, KC1 + H2T = KHT + HC1. Shake up and pour some of the liquid and precipitate 49.' GROUP V. POTASSIUM. 91 into four test-tubes; add to these portions water,* KHO, and HC1 respectively ; on being shaken and warmed the precipitate will dissolve in each of these liquids. Hence this precipitate is soluble in H20, KHO, and HCI. 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 in dilute solutions at once, but its formation is much hastened by the addi- tion of alcohol; very dilute solutions must first be con- centrated by evaporation. The solution to be tested should be neutral or only feebly alkaline; if acid in re- action, the acid should be boiled off (if volatile) or neu- tralized by Na2C03; feebly acid solutions may, however, be at once mixed with NallT; to an alkaline solution H2T should be added till the reaction is strongly acid. Note—In 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 above manner 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 ;f 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 purple- 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 spectroscope a red line (a) and an indigo-blue line (/?). Note.—A piece of blue cobalt glass may be used instead of the * By “ water” is always meant “distilled water,” unless other- wise stated. f KNOj usually gives a purer potassium coloration. 92 GROUP V. — AMMONIUM. 50-52. indigo-prism, but is by no means to be recommended, as the color of different specimens is somewhat variable in shade and in in- tensity, whereas the color of the indigo can be obtained of an invariable tint. 50. Heat a little solid KC1 in a small, dry test-tube, or better on a piece of platinum foil; the KC1 will melt, but will not pass into vapor producing white fumes un- less heated very strongly, since K-salts are non-volatile 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 NH4C1 (AmCl). Note.—The symbol Am is often written for NH4; it is very convenient, as it does away with the necessity of using brackets; e g., Am2S = (NH4)2S. 51. KHO* (or NaHO) poured into some of the solu- tion, or upon the solid, in a test-tube and heated gives off NHS gas: NH4C1 + KHO = NH3 + KC1 + H20. This gas is known by the following properties: a. Its pungent smell—that of common smelling salts. b. By turning moist 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. PtCli stirred on a watch-glass with some AmCl solution gives a yellow crystalline precipitate (Am.2PtCl6), soluble in water and in KHO, insoluble in alcohol. The * In all cases where KHO 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. 53-56. GROUP V. — SODIUM. 93 remarks at the end of par. 47 apply here also. This precipitate if boiled with KHO evolves NH3 (difference from K2PtCl6). 53. H2T (or better NallT) shaken for some time in a test-tube with AmCl solution gives a white crystalline precipitate (AmHT), soluble in H20, KHO, and HC1, insoluble in alcohol. The remarks in par. 48 apply here also. Note.—This precipitate is more soluble than the KHT precipi- tate, and therefore does not form so readily. Indeed with H2T a precipitate rarely forms unless alcohol be added, in which the pre- cipitate is less soluble than in water. With NaHT 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 AmCl 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 plati- num 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 pale bine when viewed through the indigo-prism, and never shows the slightest tinge of red and purple, even when seen through the thickest parts of the prism. A crystal of red K2Cr2Or appears colorless if illuminated by this yellow flame. Examined by a small spectroscope, the sodium coloration gives a single yellow line (a). The yellow color of the sodium flame is always readily seen, since it overpowers that of K ; its pro- duction is the most reliable, and often the only possible, test for sodium. 94 GROUP V. MAGNESIUM. 57-62. Note.—If both K and Na are present, the K coloration is unseen and the yellow coloration of Na is alone visible; but on examin- ing this flame through the indigo prism or cobalt glass, the purple coloration of the K is at once seen ; prove this by mixing together KC1 and NaCl and trying the flame coloration without and with the indigo prism. The spectroscope also shows the lines of Na and X quite distinct from one another. 57. Some solid NaCl heated in a dry test-tube, or bet- ter on platinum foil, melts without producing white fumes, unless heated very strongly, since NaCl is not volatile at a moderate heat. Magnesium (Mg).—Use MgS04.7H20 solution. 58. Na2HPO* 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. This pre- cipitate is soluble in acids (use HC1 orHNOs), insoluble in AmHO. MgS04 -f- AmCl + AmHO + Na2HP04 == MgAmP04 + Na2S04 -j- AmCl + H20. 59. KHO gives a white precipitate (MgHo2),f soluble in acids. 60. Flame Coloration.—MgS04.7H20, if pure, gives no color to the flame. 61. AmllO gives a white precipitate (MgHo2); but if AmCl is added to the MgS04 solution before the AmHO, no precipitate is produced. 62. Am2C03 gives a white precipitate (MgCOs), but only in strong solutions, and on standing for some time. AmCl prevents the formation of this precipitate. * NaAmHP04 is better than Na2HP04, since it produces the precipitate more readily than does Na2HP04 in dilute solutions, and always in a crystalline condition f This convenient symbol (Ho) for the group (Hydroxyl), first proposed by Frankland, will he employed throughout in the for mulse for all hydrates containing more than one atom of Hy- droxyl; it prevents the necessity of using brackets, as a number placed below the symbol multiplies both H and O, thus Ho2 equals (HO)2 or H202; and Ho3 equals (HO)s or H303. 63." GROUP V. — MAGNESIUM. 95 63. Blowpipe Test.—A little solid MgS04.7II20, 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 time* 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. * It is necessary to heat strongly after moistening with Co(N03)2, else blue Co(NC>3).2 remains. 96 GROUP V. TABLE OP DIFFERENCES *64. 64. Group V.—Table of Differences Note.—A blank (thus )signifies that no marked or characteristic change occurs. For the method of using the table see par. 63. Tests. K—Salts. NH4—Salts. Na—Salts. Mg—Salts. *a. For Solutions. 1. Boil with KHO solution. NIT, gas given off: known by its smell and by turning moist red lit- mus blue; it also gives dense white fumes with strong HC1. White precipi- tate. 2. Heat in flame on clean pla- tinum wire. Pale violet flame, which appears pale violet or purple red, through the indigo-prism. Intense yellow flame, which shows notinge of red through the indigo- prism. 3. Add ArnCl, AmHO, and Na„HP04. — — — White crystal- line precipi- tate. 4. Add PtCl4 and a drop of dilute HC1, and stir vigor- ously. Yellow crystal- line precipi- tate, forms only in strong solutions. Yellow crystal- line precipi- tate, forms only in strong solutions. 5. Add Haf (or better NaHT) and shake well. White crystal- line precipi- tate in strong solutions. White crystal- line precipi- tate in strong solutions. b.For Solids only. 6. Heat to red- ness in a dry test-tube, or on platinum foil. Non-volatile, unless heated to bright red- ness. Volatile; white fumes are given off and the substance passes into va- por (at least partially) for- ming a subli- mate on the upper part of the tube. Non-volatile, unless heated to bright red- ness. Non-volatile. 7. Heat strong- ly on charcoal in the outer blowpipe flame. Melt easily and sink into the charcoal, eol- oringtheflame pale violet. (See 2.) Are volatile,giv- ing off white fumes. Melt easily and sink into the charcoal, col- oring the flame intense yellow. (See 2.) Leave ultimate- ly a white in- fusible residue which shines brightly, and which if moist- ened with Co (NO, ,solution and reheated becomes pink. * In using these tests for the detection of a single member of the group in solution, only the first four need he 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 supple- mented, however, by tests 1 and 2. 65, 66.] group v. 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 alternative) 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 substances. Tests 1, 2, 6, and 7 are simi- larly 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 summaries, and should refer back to the separate re- actions 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 column, 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.)* 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. That NH4 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 * Paragraphs marked with an (s) are intended for a student using the senior course, and are passed over in the junior course. 98 GROUP V. ;66. white precipitate on addition of AmCl, AmHO, and Na2HP04. 4. That K may always be detected by giving a flame coloration which appears pale violet through the indigo- prism. 5. That the confirmatory test for K, by stirring with PtCl4, may be tried if no KH4 is present; but it can- not be employed when NH4 has been found, since NH4 gives a yellow precipitate exactly like that given by K. Hence we first get rid of NH4 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 oft'; the residue (if any) on the foil will then be free from NH4, and can be dissolved and tested for K by PtCl4. The above remark concerning the PtCl4 test applies also to the H/f test for K, since NH( gives a precipitate with H/T precisely similar to that yielded by K. The following scheme, which embodies the above tests, must be used to test for Mg, K, Na, and NII4, 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 rilled; in the first is described the test performed, in the second the result observed, in the third what substance is in- ferred to be present or absent from that result. 67. TABLE FOR GROUP V. 99 67. (s.) Table for Testing for Mg, Iv, Na, NH4, in A SOLUTION WHICH MAY CONTAIN ONE OR ALL OF THEM. (See note at the end of the Table.) Experiment. Observation. Inference. I. Add to a small part of the solution AinCl.then AmllO and Na.jHP04, 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 wire into the solution, and hold it near the top of the Bunsen flame. t. A yellow flame.* Look at the yellow flame through the indi- go-prism ; if a reddish- purple color is seen. 2. A pale violet flame ap- pearing reddish-purple when seen through the indigo-prism. [3. No color is imparted to the flame.] Presence of Na, pos- sibly also of JK. Presence of K. Presence of K and absence of Na. [Absence of K and Na.] III. Boil some of the solu- tion in a test-tube with KUO solution, and try whether NH3 is given off by smelling; or if it cannot besmeit.by test- ing with moist red lit- mus paper (51 b), or strong HC1. 1. NH3gas is smelt, or the red litmus becomes blue, and white fumes are obtained with HC'l. [2. No NIIj is smelt, and moist red litmus paper is not blued, neither are white fumes ob- tained with HC'l.] Presence of NH4. [Absence of NH4.] IV. A confirmatory test for K may be made by adding Pt(')4 or NallT. If Exp. Ill has shown that Nll4 is present, proceed to test for K as under A ; if Nll4 is absent, test for K as under B. (See 66, 5.) A. Boil some more of the solution down to dryness in a porcelain dish ; scrape out the white solid substance left in the dish, and heat it strongly on a piece of platinum foil with turned-up edges 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 when cold in a test-tube, and boil it with very little water, to which two or three drops of dilute HC1 have been added; cool the liquid, and pour it out upon a watch-glass, add a little Pt< l4lf and stir well. A yellow precipitate forms:—Pres- ence of K. B. Pour a little of the solution upon a watch-glass, add PtCl4, and stir well: A yellow precipitate:—Presence of K. If no precipitate forms,K may never- theless be present, the solution being too dilute to allow the precipitate to form; therefore pour some of the so- lution iuto a porcelain dish, boil down nearly to dryness, cool and test this liquid by stirring it with PtC)4+ on a watch-glass, adding alcohol if the pre- cipitate does not appear at once: A yellow precipitate:—Presence of K. Note.—Addition of alcohol will fre- quently produce the precipitate with- out evaporation. * Almost all substances contain traces of Na, and therefore tvhen heated in the Bunsen flame tinge it more or less yellow: hence, unless the yellow coloration is very intense, enter in the results “ Na trace.” f 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. 100 GROUP IV. BARIUM. '68-74. Note.—Separate portions of the solution are to be used for each of these experiments. It must be understood that only one of the numbered 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 col- umn which indicates the presence of a substance, and the absence of that result proves the absence of the substance; the portions in brackets will therefore be omitted in future. Exp. IV may be omitted by a beginner, K being tested for by the flame coloration alone (Exp. II). After writing out the tests tried in the above form, state at the end what has been found in the solution: thus—“Found, K and Na.” This is to be done after writing out each analysis. 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 AniCl.* They are not precipitated by any other of the group reagents. Barium (Ba).—Use BaCl2.2H20. 69. Am.fiOz added after some AmCl: white precipi- tate (Ba C03), which is at first flocculent, but if heated and allowed to stand slowly shrinks in bulk and be- comes crystalline. Pour a little of this into another test-tube and add to it some HA, the precipitate dissolves entirely if suffi- cient HA is added. 70. CaSOi (or H2SOt): heavy white precipitate (Ba S04): insoluble in HC1 even on boiling. 71. KfirOt added after some HA: yellow precipitate (BaCrOJ, soluble in warm HC1, insoluble in warm IIA. (DifF. from Sr.). 72.f H2SiF6: semi-transparent precipitate (BaSiFJ: the pre- cipitate often does not appear in dilute solution until after some time, or until the liquid is boiled, or alcohol is added. Shaking or stirring this liquid hastens its formation. 73. Am2GiOi: white precipitate (BaC204). 74. Flame Coloration: BaCl2 gives a yellowish-green color to the flame, visible through the indigo-prism. * On boiling with ArnCl solution, however, the precipitates are more or less perfectly dissolved. f A reaction in small type is comparatively unimportant, and may be omitted by beginners. 75-82. GROUP IV. — STRONTIUM CALCIUM. 101 The spectrum consists of a number of lines, the most characteristic of which are three green lines («, /3, y). Strontium (Sr).—Use Sr (N03)2.4H20. 75. Am2C03 added after some AmCl: white precipi- tate (SrC03): soluble in HA. This precipitate is floccu- lent at first; but if heated it quickly becomes crystalline and shrinks very considerably. 75 a. CaS04(or HjS04): white precipitate (SrSOJ : this precipitate does not usually form at once in a cold solution, but only after standing for some time. The precipitate, however, appears at once on boiling the liquid. 76. K.20r04 added after some HA: no precipitate, since SrCr04 is soluble in HA. 77. i/2N«F6: no precipitate. 78. Am2C.2Oi: white precipitate (SrCr204). 79. Flame coloration: crimson-red; this color ap- pears 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 (4 added to the cold solution. 3. KaCi04 added after HA. An immediate pre- cipitate. bight yellow pre- cipitate. A precipitate ap- pearing only after a short time or immedi- ately on boiling. [4. HaSiFs added. White precipitate. 5. 1T.jS04 added in excess and boiled. Entirely precipi- tated as BaS()4. Entirely precipi- tated as SrS04. Partially precipi- tated as CaS04; hence the filtrate from the precipi- tate contains Ca, which may be de- tected by adding AinHO in excess, and then Am,'',04; a white precipitate forms. When analyzing a solution which is known to con- tain only one member of this group, its detection by the first 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 : 89, 90.] 103 GROUP III A. — IRON. 1. The flame colorations, examined if necessary through the indigo-prism, or better by means of the spectroscope. 2. The difference in behavior with CaS04, winch 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 H.,S04; sufficient CaS04 then remaining in the solution to give, after making the filtrate alkaline with AmHO, 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; the liquid is then filtered (23), and a little more Am2C03 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 Am2COa, all the mem- bers of this group which were present in the solution have been precipated 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 VI it must be un- derstood that they art; drawn out to meet the case of all the mem- bers of the group being present. If therefore in any case no pre- cipitate forms on addition of a reagent, the substance or substances whose presence would have been indicated by the formation of the precipitate must be absent. Hence a filtration which is directed to be made is often unnecessary, and the solution itself is treated as is directed for the filtrate. 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 AmllO after addition of AmCl; they are not precipitated how- ever by the group reagents for Groups II and I. 104 91-95. GROUP III A. — ALUMINIUM. This group is also precipitated by Am2S, or by H2S 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 separating 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 AlAm(S04)2.12H20 or AIK (S04)2.12H20, ammonia- or potash-alum. 91. AmHO: white flocculent precipitate (Al2Ho6), which is seen best on boiling the liquid : soluble in HOI and in HA; slightly soluble in AmHO, especially in the absence of Am Cl. 2AlAni(S04)2 + GAraHO = Al2Ho6 -f- 4Am2S04. 92. KHO added iii 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 precipitated again; if more acid is added the precipitate dissolves, but is precipitated again by adding AmHO in excess. From another portion of the KHO solution the Al2Ho6 may be reprecipitated by addition of sufficient AmCl. 93. Am2S: same precipitate (Al2Ho6), H2S gas coming off’ or remaining dissolved in the liquid : 2AlAm(S04)2 + 3Am2S + GII20 = AUIo6 -f 4A.maS04 + 3H2S. 94. Blowpipe Reaction. — Some solid AlAm(S04)2. 12H20 heated on charcoal in the outer blowpipe flame, then moistened, after cooling, with Co(N03)2 solution and again heated in the outer flame, gives a fine blue mass. 95. Iron (Fe). Note.—Two classes of iron compounds are known, which differ in appearance and properties, and behave differently with reagents; they are distin- guished as ferrous and ferric compounds respectively, the former being supposed to contain the metal ferrosum 96-99. 105 GROUP III A. — IRON. (Fe"),* the latter ferricum (Fe"'). It is usual in stating analytical results to mention in which state of combina- tion the iron exists, and therefore some distinctive tests are described below (101). The whole of the reactions of ferrous compounds are not given, because Fe, if pres- ent, is always separated and detected in the course of analysis as ferricum, 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 little strong HNO,, or with HC1 and a crys- tal of KC103. Ferricum (Fe'").—Use Fe2Cl6. Ferric salts are usually yellow or reddish-yellow; ferrous salts usually pale green, or white, if perfectly dry. 96. AmHO (or KHO): reddish-brown, flocculent pre- cipitate Fe2Ho6: insoluble in KHO, soluble in HC1. 97. AmjS: a black precipitate (FeS), mixed with white S: soluble in boiling acids; insoluble in KHO: Fe2Cl6 + 3Am„S = 2FeS + S + 6AraCl. In a very weak solution of Fe a green color is pro- duced at first by Am2S, and the black precipitate sep- arates only after a time. 98. H/S.'f same black precipitate in alkaline solutions: in neutral or acid solutions S precipitates, and the ferric is changed to a ferrous salt, the color of the solution changing from yellow to pale-green as is seen after boil- ing and filtering. Fe2Cl6 + H2S — 2FeCl2 + 2HC1 + S. Blowpipe Reactions.—These are the same for ferrous as for ferric compounds. 99. Fused with Na2COs on charcoal in the inner flame, a gray magnetic powder is left (see 33a); this is shown to be magnetic by being attracted when touched under * This distinction of the two conditions of Fe and other elements by dashes or Roman numbers placed above the symbol, first pro- posed by Odling, is very convenient for brevity. f II2S may be added as a solution of the gas in trying the reac- tions; in the course of analysis the gas is usually passed into the liquid. 106 GROUP III A. — CHROMIUM. 100-102. water by the end or pole of a magnet, or by a magnet- ized knife-blade. Outer flame: reddish-brovm while hot: yellow when cold. Inner “ greenish bead (the color of common green bottle glass). 100. Borax Bead 101. Distinctive Tests for Ferrous and Ferric Salts. Note.—For these tests several drops of first added to the Fe solution. dilute HOI should be Reagents to be added. Ferric Salts. Ferrous Salts. (For Ferrous Salt use FeSO«.7HaO solution.) 1. KtFeCys added in small quan- tity. Dark-blue precipitate (“ Prussian blue”): insoluble in HC1,* sol- uble in H/'30«, and slightly soluble in K4KeCys added in excess: turned brown by KHO. IAght-blne precipitate, be- eomiugdark-blue in the air, or on addition of HNOs or Cl-water. 2. Kn[FeOyt\ No precipitate: the solution darkens, but on dilution with water is seen to contain no precipitate. Dark-blue precipitate (‘‘Turt bull’s Blue”); insoluble in HC1. In very dilute solution only a dark bluish-gray color is produced. 3. KCyS. Blood-red coloration: no pre- cipitate is product d, the liquid being perfectly clear on dilu- tion ; the color is imm di- ately destroyed by adding Hg( la solution in sufficient quantity; its production is also hindered by HN03 and by HA. No red coloration unless small quantities of fer- ric salts are present. Chromium (Cr). Use CrK(S04)2.12H20. 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 * The solubility and insolubility of this precipitate must be shown by warming separate portions of the blue liquid containing the precipitate with HCI, H2C204 and K4FeCy6, then separately filtering each : if the precipitate has been dissolved, the filtrate will be dark-blue. 103-106. GROUP III A. — CHROMIUM. 107 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 Cr2Ho6 is precipi- tated again on boiling the liquid for several minutes in a porcelain dish. 103. KHO added in small quantity gives the same precipitate (Cr,Ho6): if more cold KIIO is added the precipitate is entirely dissolved to a green fluid; on diluting this liquid with water and boiling for several minutes, the Cr2Ho6 is precipitated again, and the liquid becomes colorless: AmCl added to the KHO solution also precipitates again 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. Am.,S precipitates Cr2Ho6: 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 some solid CrK(S04)2 or with the dried pre- cipitate produced by AmHO or KHO, and the mixture be fused on a piece of platinum foil or in a porcelain 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 dissolved by boiling it with water, a yellow solution is obtained : this solution, if made acid with HA and boiled for a few minutes to drive off C02, gives with PbA2 solution a yellow precipitate of PbCr04. 106. Note.—Cr forms two classes of compounds: in one class Cr in combination with oxygen functions as an acid radicle: this class includes the chromates such as K2(.’r()4 and K2Cr2(J7, they are usually yellow or reddish in color; but Cr also forms a series of salts in which it acts as a base; 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 a) and (105) where the oxidation is caused by Pb02 and KNO, respectively. Chromates pass by reduction into the green compounds ; examples of this change will be found under the tests for chromic acid (286). 108 GROUP III A. — TABLE OF DIFFERENCES. ;i07. 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 Or was present originally as a base or as an acid radicle. Tests. A1—Salts. Fe"'—Salts. Fe"—Salts. Cr—Salts. a. For liquids. 1. Add Am IIO. White floccu- lent precipi- tate. Reddish-brown flocculent precipitate. Dingy - green precipitate, rapidly turn- ing brown when left ex- posed to the air. Pale-green ft Oc- cident pre- cipitate, col- or unaltered by exposure to air. 2. Add KIIO. 3. Add KCyS and a few drops of 11 Cl. White floccu- lent precipi- tate, easily soluble in ex- cess of KIIO. Reddish - brown flocculent precipitate, insoluble in excess of KUO. Deep blood-red coloration, destroyed by HgCl* solu- tion. The same pre- cipitate as with AraHO, insoluble in excess of KUO. No coloration unless Fe'" is also present. Pale-green pre- cipitate, solu- ble in excess of cold KUO, but reprecipitated on diluting and boiling for some lime. 6. Blowpipe tests for solids. 4. Fuse with Nua< Oj and KNOson pla- tinum foil. On cooling, a white mass of NaaCO* re- mains with dark - brown particles of FeaOj. Same as Fe'". On cooling, a yellow mass remains, ea- sily soluble in water; the solution, af- ter having been boiled with excess of HA, gives a yellow pre- cipitate with PbAa. 5. Heated on charcoal. 6. Fused in bo- rax bead. In the outer flame when cool if moist- ened with Co (NO,', solu- tion and re- heated strongly gives a fine blue mass. In inner flame mixed with Na„C03 gives a gray mag- netic pow- der. (33a.) Reddish-yellow in outer flame. Green- ish-yellow in inner flame. Same as Fe'". Same as Fe'". Green both in outer and in- ner flames. 107. Group III a.—Table of Differences. 108-110.; 109 GROUP III B.—ZINC GROUP. Members of this group occurring singly are easily dis- tinguished hy 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 differ- ences : 1. The solubility of Al2Hofi in boiling KHO, in which Fe2Ho„ and Cr2Ho6 are insoluble. 2. The conversion of Cr2Ho6 by fusion with Na.,C03 into soluble Na2Cr04: 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 KCyS to the Fe„03 dissolved in HC1. 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 K4FeCyB; if a blue precipitate is produced Feis present; this portion is rejected. Two other small por- tions of the solution also acidified are then tested ; one with K6(FeCy6)2, which by giving a dark-blue precipi- tate shows the presence of Fe"; the other with KCyS, which if it gives a blood-red color proves the presence of Fe'",. Boil the rest of the solution for several minutes, after adding a few drops of strong HNOs if Fe" is present; add some AmCl, then AmHO until the liquid after being well stirred is alkaline and smells of IMHg; boil, filter, and examine the precipitate by Table III a (436), disregarding all the appended notes. GROUP III b.—ZINC GROUP. 110. This group includes Zn, Mu, Ni, Co; its mem- bers differ from those of Group IV and V, by being precipitated by Am2S in neutral or alkaline solution, and 110 Ill, 112. GROUP III B. — ZINC. by H2S in alkaline solution ; they are not precipitated by 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 characteristic colors to a borax bead. BaC03 does not precipitate this group as it does Group III A, unless its members are present as sulphates. Zinc (Zn).—Use ZnS04.7H20. 111. Am./S: 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. H2S:* white precipitate (ZnS): the Zn is only partly precipitated from a neutral solution since H2S04 is separated and dissolves the ZnS: but if an alkali (IvHO or AmHO) be added to neutralize the H2S04 when it is set free, the Zn may be entirely precipitated: addition of NaA also causes complete pre- cipitation, since it replaces II2S04 in the solution by HA, and ZnS is insoluble in HA: ZnS04 + H2S = ZnS + H2S04; ZnS04 + H2S + 2NaA = ZnS + Na2S04 + 2HA. Add H2S to some ZnS04 solution made alkaline with a few drops of AmHO, and show by adding to separate portions of this liquid HC1, IIA and Am2S, that Z11S is soluble in HC1, insoluble in HA and in Am2S.f * H2S niiiy be used in this group as sulphuretted hydrogen water, j- The tests which show the solubility of the sulphides of this group are best tried on the precipitate obtained by AmHO and H2S, unless freshly prepared colorless Am2S can be obtained, since from yellow Am2S acids precipitate sulphur. 113-117. GROUP III B.— MANGANESE. 113. KHO added in small quantity gives a white precipitate (ZnHo2): if more KHO is added, this pre- cipitate dissolves; the ZnHo2 is however precipitated again as such by adding much water to this solution and boiling it, or as ZnS by passing H2S gas into it. 114. Solid ZnS04.7H20 powdered with Na.2CO:t in a mortar, then heated on charcoal in the inner blowpipe flame, gives a white incrustation on the charcoal, which is yellow whilst hot. It cannot be driven away bv 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. Note.—The above changes of color are more distinctly obtained by igniting a little solid ZnSOt in the outer blowpipe flame on charcoal, it is yellow whilst hot, and white when cold: if moist- ened with Co(N03)2 solution, and reheated in the outer flame, it becomes green. Manganese (Mn).—Use MnCl2 or MnSO*. Manganous salts are usually of a pale pink color. Alkaline manganates are green, permanganates purple. 115. Am2S: flesh-colored or pinkish precipitate (MnS): the liquid should be filtered, since the precip- itate 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 darkens to brown on standing in the air upon the filter. For the solubility of this precipitate see Exp. (116). 116. U2S precipitates MnS partly from neutral solu- tions, entirely from alkaline solutions, but not at all in presence of free IICl or IIA: show with separate por- tions of the MnS precipitate, obtained by adding II.2S solution to the liquid after some AmHO, that MnS is soluble in HC1 and in HA, but insoluble in Atn2S. 117. KHO: white precipitate (MnHo2), quickly turned brown by pouring the liquid containing the pre- cipitate into a white porcelain dish or upon a filter: the precipitate is insoluble in excess of KHO. 112 118-121. GROUP III B.—NICKEL. 118. AmllO gives the same precipitate, but if suffi- cient AmCl is first added, AmHO produces no imme- diate precipitate, the solution, however, on standing exposed to the air turns brown, and the Mn is gradually precipitated as brown Mn2Ho6. 118 a. Pour a little MnS04 (not MnCl2) solution upon some red or brown lead oxide (Pb02), add 1IN03, 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 the color is prevented by the presence of chlorine in any soluble form of combination. 119. Blowpipe Tests.—If some solid MnCl2 be fused in the outer flame with a mixture of Na2Co3 and a little KNOa, a bluish-green mass is obtained on cooling. The mixture may be fused on a piece of platinum foil by heating the lower surface of the foil with the blowpipe flame; or a bead of the Na2C03 and KNOs mixed may be made in a loop of platinum wire, and the experiment tried just as with a borax bead, 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 (33a). 120. Borax Bead.—Use very little* solid MiiC12: 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 pale bright green in color. 121. Am.2S: Black precipitate (NiS); add more yel- * Borax beads are often opaque from the use of too much sub- stance; in such a case fuse the bead in the blowpipe flame, then bv a sudden jerk throw some of the fused mass oft','and fuse again the remaining portion with fresh borax ; repeat this if necessary. The fused bead may also be flattened by squeezing with small pin- cers. 122-127. GROUP III B. NICKEL. 113 low Am2S,* boil and filter; a brown filtrate runs through, colored bv 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. H2S: black precipitate (NiS) in neutral solutions or in solutions acid with HA, but HC1 prevents the pre- cipitation; show with portions of the liquid containing NiS, obtained by adding HJS to NiS04 solution to which a little AmHO has been added, that NiS is insoluble in cold dilute HC1 and in IIA, but soluble when heated with HC1 after adding a crystal of KC103. 123. KHO: light-green precipitate (NiHo,2). 124. AmHO added in very small quantity; bluish- green precipitate (NiHo2); 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 added in small quantity gives a yellowish- green precipitate (NiCy2); by further addition of KCy this precipitate is redissolved, but HC1 again precipitates NiCy2 from this solution. 126. If some nickel sulphate solution is made acid, with several drops of HC1, then KCy gradually added, whilst stirring or shaking the liquid, until the precipi- tate is redissolved, 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 short time; Na2Cl20, or Br-water after excess of NaHO, added to the other part will give on warming a black precipi- tate (Ni2Hofl). 127. Blowpipe Reactions.—Solid NiS04.7H20 pow- dered with Na2C03 in a mortar and then fused on char- * The Am»S must be yellow; colorless AmsS does not dissolve NiS. 114 GROUP III B. COBALT. ;i28-l£5. coal in the inner blowpipe flame, leaves a gray powder which is attracted by the magnet. (See 33 a.) 128. Borax Bead. Violet or sherry-red bead whilst hot. Pale yellow on cooling. In outer flame In inner flame, after being heated for some time. Blackish or opaque bead. Cobalt (Co).—Use Co(N03)2.6H20. Cobalt salts are usually reddish-pink in color. 130. Am.j3: black precipitate (CoS); on adding much Ain2S, 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. HZS: black precipitate (CoS), only forms in alka- line solutions or in solutions acid with HA; HC1 pre- vents the precipitation. Add H2S-water to some Co(NOs)2 solution, first made alkaline with a few drops of AmHO, 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. KHO: 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 KHO, soluble in AinCl; hence if AmCl is added before AmHO no precipitate is produced. 134. KCy added in small quantity gives a reddish- brown precipitate (CoCy2); add more KCy slowly and whilst shaking the solution the precipitate dissolves; now add HO, the CoCy2 is precipitated again. 135. If some Co(N03)2 solution is made acid with a few drops of HA, then KCy added slowly until the pre- 136, 137. GROUP III B.—COBALT. 115 cipitate at first formed just redissolves, and the liquid is boiled until no smell of HCy is evolved, then cooled and divided into three parts, it will be found that neither HC1, nor Na2Cl20, nor Br-water with excess of NaHO solution, produces a precipitate on warming the liquid. [Difference from Ni, see (126).] Note.—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 K6(CoCy6)2 “ Potassium Cobalti cyanide.” 136. Blowpipe, Reactions.—Fused with Na2C03 on charcoal in the inner flame, Co(b)03)2 gives a gray metallic powder attracted by the magnet (83 a). 137. Borax Bead.—Strong solution may be employed, the bead being dipped into it. Fine blue bead in both inner and outer flames, opaque if too much Co(N03)2 has been used. 116 GROUP III B. — TABLE OF DIFFERENCES. 188. Tests. Zn—Salts. Mn—Salts. Ni—Salts. Co—Salts. a. For liquids. 1. Add Am,S, or better H*S, and a few drops of AmHO. White precipitate: soluble in cold dilute HC1: insol- uble in HA. Pink precipitate: soluble in cold dilute HC1; soluble in HA. Black precipitate: soluble in boiling yellow to a dark solution : insoluble in cold dilute HC1 and in HA. Black precipitate: insoluble in boiling yellow Am7S,* in cold dilute HC1, and in HA. 2. Add KHO. White precipitate: soluble in excess of KHO. White precipitate: turning brown in the air : insolu- ble in KHO. Green precipitate: insoluble in KHO. Blue precipitate: insoluble in KHO. 3. Add KCy. [Note.—This test being employed to distin- guish between Ni and Co, need only be tried when a black precipitate has been i obtained by Test No. !•] Added in excess to the slightly acid solution and boiled forsome time, then NaaClaO (or Br-water, and excess of NaHO) added, gives a black precipitate on heating. Added in excess to slightly acid solution and boiled for some time, NaaClaO (or Br-water and excess of NaHO) gives no pre- cipitate on heating. b. Blowpipe tests for solids. i 4. Fused with Na„C03. 5. Borax bead. On charcoal in the inner flame: gives a white in- crustation, which, if moistened with Co(N03,'a and heated in the outer flame, turns green. The substance itself when strongly heated after having been moistened with Co(N032 also be- comes green. On charcoal in the inner flame: a gray magnetic powder (33 a). On platinum foil in outer flame: a bluish-green mass, showing more rap- idly if a little KN03 be mixed with the Na3C03 before refusing. Outer flame—Amethyst-red. Inner flame—Colorless. On charcoal in the inner flame, a gray magnetic powder (33 a.) A . f Violet-red or yellow while hot. uuter. | yellow when cold. Inner.—Gray or black opaque bead. Same as Ni. Outer and inner flames— fine blue bead. * In order to ascertain whether the precipitate has been dissolved, filter and observe whether the filtrate is dark in color. 138. Group III b.—Table of Differences. 139, 140. GROUP III B. — DETECTION. 117 139. When a solution is to be examined for only one member of this group, its detection by one or more tests in the above table will be very easy. The precipitate with Am2S is distinctive; ZnS and MnS being easily recognized bv 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 excess of Am2S, the liquid therefore gives a brown fil- trate. KHO also gives characteristic precipitates with 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.* NiS is precipitated from this solution by boiling or by addition of HA, and its pres- ence confirmed by fusion in a borax bead. 2. The solubility of ZnS and MnS in cold dilute ITC1, NiS and CoS being almost insoluble. (Note 1.) 3. The solubility of ZnHo2, in cold KHO, in which MnHo2 is insoluble; white ZnS is then precipitated from this solution by H2S. 4. The production of a bluish-green mass by fusing MnHo2 with Na2COs and KNOs. 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.) Note 1.—Mn may also he separated from Ni and Co by passing H2S into the solution containing free HA; Mn remains in solu- tion. NiS and CoS are precipitated. Note 2.—A modification by Henry of Rose’s method for sepa- rating Ni and Co is also to be recommended ; it depends upon the fact that, whilst Co is precipitated as Co2Ho6 by BaC03 in presence of Br, Ni remains in solution. The sulphides are dried and then strongly ignited in an open porcelain crucible ; the metals remain- ing 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 BaCO, is added * In order to ascertain whether the precipitate has been dis- solved, filter and observe whether the filtrate is dark in color. 118 GROUP II A. COPPER GROUP. "141-143. in a small corked flask; the flask is then well shaken and allowed to stand for about half an hour; on filterinsr, Co if present is de- tected in the precipitate by the borax bead ; Ni is precipitated from the filtrate by heating it with KHO, filtering and confirming the presence of Ni in the precipitate by fusing a portion of it in the borax bead. 141. (,$.) A solution is examined for Zn, Mn, Co, Ni, by adding AmCl to it in a boiling tube, then AmHO, if necessary, until it is alkaline; 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 filter and the color of the filtrate noted ; if it is color- less sufficient AmaS 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, Am2S has been added in excess, the whole is boiled and filtered, and the precipitate examined bv Table III B (437); the filtrate if yellow is rejected, if brown it is examined for Ni 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, HI b, IV, and V, in being precipitated by HjS 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. Mercuricum (-"Hg").—Use HgCl2. 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 dis- tinctively called Mercuricum and Mercurosum; in the latter state it is classed under Group I. 144-146.] GROUP II A. — MERCURY. 119 144. H,S: * black precipitate (HgS); if the H2S so- lution is added slowly, the precipitate is first white, then brown or orange, and ultimately becomes black; these changes of color during the addition of H,S are charac- teristic of mercuric salts. Filter and wash the precipi- tate; place portions of it in three test-tubes; boil one portion with strong HNOa, and another with strong HC1; the precipitate is not dissolved by either acid; mix the contents of the two tubes and warm again, the precipitate will now dissolve; boil the third portion with Am.2S; the precipitate does not dissolve. Hence HgS is insoluble in hot strong I1N03, in hot strong IIC1, and in Am2S, but is easily soluble in a mixture of HNOs and HC1 (“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 HC1, the Hg particles unite to globules visi- ble by a lens or frequently to the naked eye. 2HgCl2 + SnCl2 = Hg2Cl2 + SnCl4. HgaCls -f SnCl2 = 2Hg + SnCl4. 146. Cu: If a small strip of copper sheet or a copper coin, whose surface has been polished and cleansed by rubbing it with sand-paper, 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: HgCl2 + Cu = Hg + CuCl2. 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 per- * A test-tube half full of the solution must be used in order to i;et sufficient precipitate for the experiments below. This remark applies also to the liquid used for obtaining the II2S precipitate with the other members of this group. 120 GROUP II A. — LEAD. 147-149. formed in a test-tube, or better in a small hard-glass tube sealed at one end (10), globules of Hg are sublimed upon the cool sides of the tube. 147. Mix a little solid HgCl2 intimately with about three times as much Na2C03, by powdering them to- gether in a mortar, or with a pestle on a watch-glass. Pour some of this dried mixture into the bottom of a piece of perfectly dry hard-glass tubing closed by being drawn out (10) at one end (see note below), and cover the mixture with a small layer of Na2CO:3; now heat strongly first the layer of Na2C03, then gradually the mixture; Hg will sublime, condensing in globules on the sides of the tube. Sometimes the globules are so small that the layer appears as a gray film; they may be united into visible globules by rubbing the film with a splinter of wood or with a thin glass rod (11a), or the separate globules may be seen by the use of a pocket lens. Note.—The powdered mixture is best dried by spreading it out upon a watch-glass and placing it in a steam or water-oven ; it may be dried also by supporting it on the filter dryer (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 powder 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 Hg sublimate. The heat- ing must never be commenced until the sides of the tube are per- fectly 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 re- moved by a twisted piece of filter-paper, or by a small piece of filter-paper rolled round a wooden match or a thin piece of wire. 148. Heat a little solid HgCl, in a tube closed at one end ; the substance sublimes in white fumes, since Hg compounds are volatile. Lead (Lb).—Use PbA2.3H20 dissolved in water to which a little HA has been added. 149. HjS: black precipitate (PbS); this precipitate is 150-153.] GROUP II A. — LEAD. 121 red if much hydrochloric acid is present in the solution, but becomes black on diluting with water and passing PI2S, 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.jS, soluble in boiling dilute HN03, but converted by boiling strong HNOs into insoluble PbS04. 150. IICl: white precipitate (PbCl2), forms only in cold and strong solutions; on boiling, the precipitate dissolves,* but the PbCl2 separates again in beautiful crystals on cooling. 151. HjS04: white precipitate (PbS04) ; this precipi- tate is much less soluble in dilute H2S04 than in water, hence H,,S04 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 HA or H2T, then Am HO in excess, and boil- ing; show also that it is dissolves in boiling strong HC1. 152. K20r04 {or K2Cr.20-,); 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 PbA2.3H20 with about twice as much Na2COs; heat the mixture in a cavity on a piece 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. * If the precipitate does not entirely dissolve, add a little water and boil again. 122 GROUP II A. — BISMUTH. 154-159. Bismuth (Bi).—Use Bi(N03)3.5H20 dissolved in dilute HC1. 154. H28: 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 hno3. 155. AmITO (or KHO): white precipitate (BiIIo3); pour off a small quantity of the liquid and precipitate into a tube, add much AtnHO and warm, the precipi- tate 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. H.,0: pour the HC1 solution obtained from the 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: 2Bi(NOa)3 + 3H2S = Bi2S3 + 6HNOs. BiCJ3 + H20 = BiOCl + 2HC1. Pour a little of the milkv liquid into two test-tubes; warm one portion after adding to it a little strong HC1, the precipitate dissolves: to the other add H,Tand 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. K2CrOi or K2Cr207 (see note below): yellow flocculent. precipitate [Bi2(Cr04)3] : add KHO, the pre- cipitate does not dissolve (difference from PbCrOj; it dissolves completely in HC1 or HN03 added in excess. Note.—Since this precipitate is soluble in HC1, and HC1 is present in the Bi solution used, the free HC1 must first be removed bj dissolving 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 HOI = NaCl + HA. 158. U2SOi: no precipitate. 159. Blowpipe Reaction.—A mixture of powdered Bi 160-165. GROUP II A.—COPPER. 123 (XOjtg and Xa2CO:! 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 either blue or green in color; their color commonly becomes very pale or disappears when the salts are thor- oughly freed from water of crystallization. 160. H/S: 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 insolu- ble in KIIO, in Am2S, and in boiling dilute II2S04, but dissolves in boiling HX03 (dilute or strong), and in KCy solution. 161. Am HO added in very small quantity : a greenish- blue precipitate; if more AmHO is added this precipi- tate dissolves, yielding an intensely blue liquid contain- ing (N2CuAm4H2)S04, which becomes again light-blue on adding an acid in excess. 162. //2*S'04: no precipitate. 163. KiFeCy6: reddish-brown precipitate (Cu2FeCy6), insoluble in IIA; the color is best seen by doing the reaction in a white porcelain dish. In very dilute solu- tion 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 sand-paper or by boiling in a little dilute KHO and washing, when dipped into CuS04 solution made acid with a few drops of Ii.2S()4, is covered with a red film of Cu after a time. 165. Zn and Pt: a strip of bright Zn if placed upon a piece of platinum foil or wire in some CuS()4 solution contained in a porcelain dish or watch-glass, causes a red film of Cu to deposit on the platinum : the CuS04 solu- tion should be first made acid with a few drops of h2so, GROUP II A. — CADMIUM. 166-173. 166. Blowpipe Reactions.—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 par. 33 a. In outer flame: Green whilst hot, blue when cold. 167. Borax bead. Red or colorless bead when cold, obtained only when very little Cu is present, and the bead is long heated in a good reducing flame.* In inner flame: 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 having been moist- ened with HC1. Cadmium (Cd).—Use CdS04.4H20. 169. H,S: bright yellow precipitate (CdS): boil off the H2S, and pour into several tubes; show with these separate portions that the precipitate is insoluble in Am2S, in KHO, and in KCy solution, but soluble in boiling dilute HN03, and in boiling dilute H2S04: di- lute the H2SOt solution with much water and pass II3S for a short time, yellow CdS is again precipitated. 170. AmHO added in small quantity, best by using AmHO much diluted: white precipitate (CdHo2); on adding more AmHO the precipitate readily dissolves. 171. jH2SOt: no precipitate. 172. Blowpipe Reaction. — Powdered CdS04, mixed with NasCO, and heated on charcoal in the inner blow- pipe flame, gives a brown incrustation. 173. Group II a.—Table of Differences.—(See opposite page.) * The red bead 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. 173. GROUP II A. TABLE OF DIFFERENCES. 125 Tests. Hg—Salts. Pb—Salts. Bi—Salts. Cu—Salts. Cd—Salts. a. For liquids. 1. Pass HaS or add water. Black precipitate, when filtered and well washed, insoluble in boiling strong HNOa, and.uuchanged by it. Black precipitate, al- most insoluble in boiling strong HN03, changed by it into white PbSU4. Black precipitate; sol- uble in boiling strong HNOjto form a colorless solution. Black precipitate; solu- ble in boiling concen- trated II NO, to form a blue solution; insolu- ble in boiling dilute IiaS04. IWiotcprecipitate; soluble iu boil- ing HNOj and in boiling di- lute HaS04. 2. Add HaS04. — White precipitate. — — — 3. Add AmHO. White precipitate, in- soluble in excess. White precipitate, in- soluble in excess. White precipitate, in- soluble in excess. Blue precipitate easily soluble in excess to a deep blue liquid. White precipitate, easily solublein excess. 6. Blowpipe reactions for solids. 4. Borax bead. — — — Jo„, |ln„„ — 5. Flame coloration. — — — Green when moistened with HC1 shows blue centre. — 6. Heated with NaaCO,, a. In a tube, closed at one end. Sublimate of Hg. — — — — 6. On charcoal in theinnerblow- pipe flame. Yellow incrustation; white malleable glob- ules. Orange-red incrusta- tion ; white brittle globules. No incrustation; red me- tallic scales. Brown incrusta- tion ; no glob- ules. Group II a.—Table of Differences. 126 GROUP II A.—DETECTION. 174-176. 174. The color of the II2S precipitate, and its be- havior with strong HN03, enable .the analyst to detect one member of this group when present alone: the most characteristic 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 HNO.t; HgS and PbS being insoluble. 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 BiHoa, in excess of AmHO. 4. The solubility of CdS and insolubility of CuS in boiling dilute H2S04. The insolubility of CdS in KCy 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, Hg, Bi, Cu, Cd, mixed, is first made acid, if not already acid, with a little HC1 ;* H2S-water is then added, or the gas is passed in a rapid stream through the solution for about five minutes; the precipitate is filtered off, the filtrate mixed with more H2S-water, or diluted with a little water aud H2S again passed for a short time, to ascertain whether all the above metals have been completely precipitated: if no further precipitate is produced, the filtrate may be rejected ; but in case H2S causes further precipitation more H2S solution must be added, or the gas must be passed for some time longer, and the liquid poured again through the filter, the filtrate only being rejected when PI2S no longer produces any precipitate in it; the pre- cipitate is then examined by Table II (435), commencing at Group II A (Copper Group), and using only the left- hand side of the table. * A white precipitate of PbCl2, which may form if the solution is very strong, being neglected, since it is readily converted into PbS by H2S. 177, 178. GROUP II B. — ARSENIC. 127 GROUP II b.—ARSENIC GROUP. 177. This group includes As, Sb, Sn ; its members differ from those of Groups III A, III b, IY, and V by being precipitated by HjS in a solution made acid with HC1; they differ from those of Group I, in not being precipitated by HC1. The sulphides of this group, which are precipitated by II2S, differ from those of Group II a, by being solu- ble in Am2S or KHO. 178. Each member of this group forms two series of compounds which resemble each other in many re- actions, but also present several differences. The two classes are distinguished conveniently by the termina- tions -ic and -ous; thus we speak of arsenic and arseni- ous acid. Arsenic (As), For arsenions compound use HC1 solution of As203. For Arsenic compound use water solution of Na2HAs04.12H20. a. Tests which give ultimately the same RESULT WITH BOTH SETS OF COMPOUNDS. The two solutions should be taken in separate test- tubes, and a portion of each tried in succession with each reagent; the difference of behavior is thus more easily appreciated and remembered. Arsenic compounds are converted into arseniows by boiling with HC1; this explains reactions 179 and 180 with arsenic solutions. 128 GROUP II B. ARSENIC. 179, 180. Reagent. Arsenioai solution. Arsenic solution (Na9HAs04.12Ha0). 179. HjS. In neutral solutions only a yellow No precipitate color is produced, but if the so- is produced lution is acid with HC1 a light in the cold yellow flocculent precipitate solution aci- (As2S3) forms immediately even in the cold. Shake up and pour some of the liquid into another dified with HC1 ; but if theacid solu- test-tube and show that KHO tion is boiled, and Am2S, added to the sepa- rate portions drop by drop, dis- H2Scauses in the hot solu- solve the precipitate, which, tion, first a milky pre- however, is thrown down again on addition of HC1 in ex- cipitate of S, cess.* then yellow As2S3. 180. Cu: three Reinsch’s Test.—If boiled in the The same depo- or four nar- solution to which some dilute sit is obtain- row slips HC1 has been added, Cu be- ed as with brightly pul- comes coated with a black film As2C3 but ished with (As2Cu5); if the Cu slips are only when sand-paper. carefully dried by being pressed strong HC1 between filter-paper, and are is added and heated near the lower end of a the liquid piece of hard-glass tube open at both ends and 4 and 5 inches in length, which is held somewhat obliquely in the flame or bent as seen in Fig. 85 (p. 182), a white sublimate of As203 forms in the upper part of the tube; on being examined with a lens this is seen to consist of white octohe- dral crystals. This sublimate may be dissolved when cold in boiled. a little hot water, and the pres- ence of As confirmed by tests 179 and 187. The presence of As in the deposit should always be confirmed in this way, since other metals besides As are de- posited on Cu as a black film. * The KHO solution of the precipitate and the As2S3 precipitated from it by HC1 are often discolored by black sulphides formed by the action of H2S upon Pb or Fe present as an impurity in the KHO : this discoloration may be almost entirely prevented by boil- ing the liquid before adding KHO, the free H2S is thus expelled. 181 GROUP II B.—ARSENIC. 129 Tests depending on the Formation of AsH3. Note 1.—As AsH3 is a very poisonous gas, the following ex- periments with it should be performed in a cupboard provided with a good draught, or in the open air. Note 2.—Arsenic compounds give these reactions less readily than arseniows, but by being boiled with HC1 for a short time they are converted into arseniows compounds, which then readily answer to the following reactions. 181. Hofmann’s Method.—If some scraps of Zn and some dilute HC1, both free from As, be placed together in a small flask fitted with a funnel-tube dipping below the liquid and a de- livery-tube, as shown in Fig. 33,* H gas will be given off*either at once or on adding a little strong IIC1; Zn + 2HC1 = 2H + ZnCl, The hydrogen can be made to bubble through some PbA2 solution contained in a second small flask connected with the first by a piece of india-rubber tubing; the gas, thus freed from any H2S with which it might possibly have been mixed, is then allowed to bubble through some AgNOs solution contained in a test-tube which is supported in a small beaker; if the Zn and acid were free from As, no precipitate or color is produced in the AgN03 solution. If a little As2Os solution be now poured into the larger flask through the funnel, a black precipitate (Ag) will Fig. 33. * Tn order to be sure that the corks and tubes fit air-tight, moisten the outside of the cork after it has been placed in the neck of the flask, and having closed one tube, blow down the other. No air-bubbles must be seen or heard to escape. Several of these apparatus may be kept ready fitted in the laboratory for general use. 130 181. GROUP II B.— ARSENIC. begin to form in the AgNOs solution ; this is produced by the AsH3 evolved by the action of the II upon the As203: As203 f 12H = 2AsH3 + 3H20. The AsII3 on passing into the AgNOs solution, reacts thus: AsHg + 6AgNOs + 3H20 = 6Ag + H3As03 + 6HN03. Hence Ag is precipitated, and H3As03 remains in solution. As soon as a copious precipitate has been obtained the test-tube is removed. It will be best to put by the test-tube with its contents to be examined afterwards as directed below, and whilst the gas is coming off to pro- ceed at once to use it for reactions 182 and 183. The liquid in the test-tube is filtered, the precipitate rejected, and several drops of AgNOs solution are added to clear the filtrate. On mixing with this liquid drop by drop some very dilute Am HO (made by pouring several drops of AmHO solution into a test-tube, then nearly filling up with distilled water and shaking the tube) and stirring or shaking after each addition, a light yellow precipitate (Ag3AsOs or Ag„HAsOs) will be obtained. The formation of this precipitate on ad- dition of AmHO, is explained by the fact that H3AsOs is in the solution in the presence of AgNOa and also of HN03 (see last equation); now AgNOa forms with H3As03 a yellow precipitate (Ag3AsOa) if no free acid is present in the liquid (see reaction 187); hence on neutralizing with AmHO the free HN03 already pres- ent, and that which is formed by the action of AgNOs on H3AsOs, the precipitate appears : H3As03 + 3AgNOs + 3AmH0 = Ag3As03 3AmNOs -j- 3H20. This precipitate is also readily soluble in AmHO; 182, 183. 131 GROUP II B. — ARSENIC. hence great caution is requisite to use very dilute iVrnHO, and to add it gradually. Caution.—Both flasks should be rinsed out each time after use, else some of the AsH3 may remain in it and be driven out in a future operation. 182. Disconnect the larger flask from the smaller, and slip into the india-rubber joint a tube of hard glass about four inches in length whose end is drawn out to a fine jet and supported on the ring of the retort-stand, as shown in Fig. 34; if the gas is not coming off briskly pour in through the funnel-tube a little strong HC1, and light the gas as it issues from the jet.* The flame will differ from that of pure H by burning with a bluish tinge, and by giving off white fumes of As203.f Press down upon the flame the inside of a porcelain crucible lid or of a porcelain crucible or dish, a dusky black film of As will be de- posited upon the cool surface; pour upon this some Na2Cl20 solution, the stain is rapidly dissolved. Warm also a stain of As, obtained inside a porcelain dish with Am2S, it will dissolve and on gentle evapora- tion will leave yellow As2S3. 183. Add a little more strong HC1 if necessary to Fig. 34. * If the experiment is performed as here directed, the H will have been evolved for some time before being lighted, and there is no fear of an explosion occurring ; but if the H is being pro- duced for the first time, allow it to escape briskly for four or five minutes, and ascertain that a test-tube full of the gas burns quietly (see Exp. 8, p. 2J) before adding the liquid to be tested for As and lighting the gas at the jet. f If these appearances are not noticeable, pour a little more As2Og solution into the flask through the funnel and mix by gentle shaking. 132 GROUP II B.—ARSENIC. 183 a, 184. cause the gas to come off rapidly, light it at the jet and heat a point near the middle of the tube strongly (see Fig. 34); a black mirror of As will form just beyond the part heated by the flame, and the flame burning at the jet will meanwhile be- come colorless, showing that the arsenic has been thus removed from the hy- drogen. Heat another point in the tube, so as to produce a second mirror; then divide the tube between the mir- rors, and show by warming one portion when cold with some Na2Cl20; solu- tion in a test-tube, that the mirror is soluble in Na2Cl20; show that the other, when heated in the tube held ob- liquely in the flame, or bent as shown in Fig. 35, gives a sublimate of As2Os. Dissolve the sublimate when cool in a little hot water, and confirm the presence of As by reactions 179 and 187. Note.—Tests 182 and 183 were first suggested by Marsh; the former is usually known as Marsh's test. 183 a. AsH3 produces a characteristic color with HgCl2 solution. Remove the cork from the larger flask and place a stopper of cotton-wool in its neck to stop any spirting from the liquid in the flask, then cover the mouth of the flask with a small piece of filter- paper moistened with HgCl2 solution. The paper becomes colored first yellow then brown. 184. If some pieces of Zn or A1 be boiled in KHO solution, H-gas is evolved which is free from odor, but if a little As203 solu- tion be now added and the liquid be again boiled, a garlic odor is evolved owing to the formation of AsHa: Fig. 35. J Zn + 2KH0 = H2 + ZnK202 \ As203 + 12H = 2AsH3 4. 3H20. If a small slip of filter-paper moistened with AgN03 solution and placed on the end of a glass rod,* be held in the gas in the mouth of the tube whilst the liquid is being boiled, the paper will be stained black by the separation of Ag (see reaction 181). This reaction does not succeed with arsenic compounds unless they are first reduced by boiling with HC1. It is not given by any Sb compounds (difference between As and Sb). * A simple method of getting a moistened piece of paper on the rod is to dip the rod into AgN03 solution ; then gently press the paper slip upon it whilst the rod is wet. 185, 186. 133 GROUP II B. — ARSENIC. 185. If some solid As2Oa or any As compound, be mixed with powdered Ka2COa and KCy (or with Fig. 36. K.CA) a mortar, and a small quantity of the mix- ture, after having been dried for some time at a gentle heat on a watch-glass, be introduced into a little bulb- tube of hard glass (Fig. 36) at least three inches in length; and if the substance be then heated, observing the precautions stated in the note under (147), a black mirror of As forms in the cooler part of the tube and frequently a smell of garlic may be detected at the mouth of the tube. If the bulb be cut off and the mirror be heated by holding the tube obliquely in the flame (Fig. 35), the mirror is converted into a sublimate of As203 crystals. 186. Blowpipe Reaction.—A mixture of any solid As compound with Na2CO., if heated on charcoal in the inner blowpipe flame emits a smell of garlic, which is noticed if the charcoal is removed from the flame and smelt. The flame is colored livid blue. A little solid As203 heated in a small hard-glass tube closed at one end is readily “sublimed,” and the sub- limate is seen under a microscope or a powerful lens to consist of octohedral crystals. 134 GROUP II B. — ARSENIC. [187-190. B. DISTINCTIVE TESTS FOR ARSE'S 10US AND ARSEN/C COMPOUNDS. Reagent. Arseniovs compound. Use As303 dissolved in HC1 except for (187). Arsenic compound. Use NaaHAs04.12Hi0 dissolved in HaO. 187. AgNOv several drops: Note.—For this reaction AsaOa dis- solved in boiling water is to be em- ployed, since HC1 would yield a pre- cipitate of AgCl. 188. CuS04, several drops: 189. CuSOv two drops: then KHO added. 190. AtnCl, AmHO, and MgS04. Light-yellow precipitate. (AgjH As03 or Ag3As03.) This precipitate forms only on adding carefully, drop hy drop, a little dilute AmHO.* Show that it is dissolved by AmHO and by HN03. It is also appreciably soluble in AmN03: hence, if too much AmHO has been added, the precipitate does not al ways form on neutral- izing with HN03 Yellowish-green precipitate (Cu//HAs03). This precipitate forms only on adding dilute AmHO carefully, drop by drop :f show that it is soluble in AmHO and in HN03 The above yellowish-green precipitateis firstproduced, but on addition of more KHO this dissolves to a clear blue liquid, which on being boiled deposits red CUgO. No precipitate. Brown precipitate. (AggAsOJ: show that it is soluble in AmHO and in HNOg. Pale-green precipitate, (CuHAs04) : soluble in AmHO and in HNOg. No clear blue solution is obtained, and no Cu20 produced on boil- ing the liquid. White crystalline pre- cipitate (MgAmAs04): if Altered off and moist- ened with AgNOg so- lution on the filter be- comes brown. * As203 when dissolved in water yields H3As03, which cannot give with AgN03 the Ag3As03 precipitate, because this decomposition would liberate HNO.,in which Ag3As03is soluble; hence the addition of Am HO 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 suffi- cient 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 closinsr it with the thumb and inverting it for a moment. This dilute AmHO is to he added drop by drop, shaking or stirring the test solution after each ad- dition until the precipitate is obtained. f The precipitate produced by CuS04 is soluble in acids; hence the HC1 present in the solution must be neutralized by careful addition of AmHO before the precipitate will appear. 191-194.] 135 GROUP II B. — ANTIMONY. Antimony (Sb). — Use SbCl3, or 2(KSb0T).H20 (“ Tartar Emetic”), dissolved in dilute HC1. Note.—Antimomc compounds give results ultimately identical with antimomot, and KCv on char- coal in the inner blowpipe flame. 5. Heated with solid NaaC03 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 metal- lic globules, white incrus- tation. The detection of any one member of this group is simple; 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- aration and detection of As, Sb, and Sn, when mixed; two of the most trustworthy are those introduced by 140 GROUP II B.—DETECTION. 208, 209. Hofmann (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 II 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 SbH:i; these gases, if passed into AgNOs solution, yield soluble H3As03and insoluble Ag3Sb, which are separated by filtration ; the three members of this group thus sepa- rated are then detected by special tests. As, Sb, Sn, occurring together in a solution, are tested for by precipitating them with H2S, filtering, and test- ing the filtrate by passing H2S through it as was directed for precipitating Group II a. The precipitate is then examined 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 simpler 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 H2S, for 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 in hot strong HC1, in which SnS, SnS2, and Sb2S3 are soluble; and the further separation of Sb and Sn is effected either by adding Zn alone to the acid so- lution, when Sb is evolved as SbH3 and Sn is deposited upon the Zn, or by adding Zn and Pt, when Sn is de- posited on the Zn and Sb on the Pt. The precipitate produced by H2S is filtered and allowed 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 por- celain dish and heated for some time nearly to boiling with strong fuming HC1; the liquid is cooled and filtered: 210.' GROUP II B. — DETECTION. 141 The Residue will The Filtrate may be examined for Sb and Sn consist chiefly of by either I or II below : As2S3, which is I. Place a piece of platinum foil in a porce- almost insoluble lain dish and pour the acid filtrate upon it, then touch the foil with a piece of Zn; H in strong HC1. Dry the washed res- will come off with effervescence, and if idue on the filter either at once or after a few minutes a black at a gentle heat, stain appears upon the platinum the Pres- then mix it with ence of Sb is indicated.* three or four times The platinum foil is removed and pieces as much powdered of Zn placed into the liquid : as soon as the KCyand Na2CU3, bubbles of H cease to be given off, Zn still and heat the mix- remaining undissolved, remove the pieces of ture in a small Zn, rubbing and rin-ing any dark deposit back into the dish; let this deposit settle, decant the liquid and heat the solid deposit bulb-tube, rernov- ing any drops of water inside the with strong HC1 for several minutes in a tube bv a twisted test-tube, dilute with a little water, filter if piece of filter- necessary, and add to the solution a few paper; a black drops of HgCl2 solution. A white or gray mirror (185): precipitate (204, 20-’) indicates the Pres- ence of Sn. Presence of As. 11. The acid filtrate is poured into a little Note.—The As2S3 hydrogen flask (Fig. 34, p. 131), in which II may also bedissolv- has been coming off briskly for about five ed by heating with a minutes, being produced by the action of a little fuming HNG3, little strong HCl upon some pieces of Zn. boiling off excess of The H is lighted at the jet, and the inside HN 03and detecting of a small porcelain dish or crucible lid the As as H3 As04 by pressed down upon the flame: a black stain adding AmCl ex- not dissolved by hot Na2Cl20 solution shows cess of AmHO and the Presence of Sb. MgS04; or bv ad- The residue in the flask is tested for Sn, dition of AgNOs. and then cautiously neutralizing with AmHO. as directed in the latter part of I (above). 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 Na2CG3 and NaNOs converts As2S8 into soluble Na2HAs04, Sb2S3 into * The Sb thus deposited on the Pt may, after rinsing the foil, be dissolved by heating the Pt in a test-tube with a very dilute HNOs; on cooling, diluting, and passing H2S, an orange-red pre- cipitate will form, confirming the Presence, of Sb. 142 GROUP II B. — DETECTION. ;2io. insoluble Na2IT2Sb207, and SnS2 into insoluble Sn or Sn02. The precipitated sulphides are dried on the filter, and the precipitate* mixed well on a watch-glass or in an agate mortar with equal weights of powdered Na2C03 and NaN03; this powder is dropped in small quantities at a time into some NaNO;i 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 adhering 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- ture of equal measures of water and alco- hol; the precipitate is then rinsed into a small porcelain dish, using as little water as possible; a few drops of strong HC1 are added, and the dish is heated. Whether the residue has dissolved or not, place in the liquid a piece of clean platinum foil, and upon the foil a piece of pure Zn. If a black stain forms after a time upon the platinum, it proves the Presence of Sb.f When the Zn ceases to be acted upon, Sn, if present, will remain as a spongy deposit. This is to be washed by decantation, dissolved by boiling with HC1 in a test-tube, and Hg(JI2 added immediately to the solution ; a white pre- cipitate (202) shows the Presence of Sn. Test 203 may be substituted for 202. Filtrate: HN03 is added until the solution is just acid after be- ing boiled; then AgNOs solution is poured in as long as it causes any precipitate, and very dilute Am HO is added little by little;J a brown precipi- tate readily dis- solving in excess of ArnHO shows the Presence of As. * 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, f See foot-note on p. 141. % Instead of mixing the dilute ArnllO with the liquid, it may be carefully poured upon the top of it: a brown color is then seen at the surface of contact. 211-217. GROUP I. — SILVER — MERCUROSUM. 143 GROUP I.—SILVER GROUP. 211. This group includes Pb, Ag, Pig' (Mercurosurn); its members differ from those of all the other analytical groups by being precipitated as chlorides by HCl: since, however, PbCl2 is rather soluble in water, Pb is not entirely precipitated by HCl, and is usually found also in Group II a as PbS. Lead (Pb).—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 HN03 in excess; also that it is insoluble in HN03 even on boiling. 213. H2S (or Am2S): black precipitate (Ag2S): insoluble in AnijS or KHU; soluble in boiling dilute HN03. 214. KHO: 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. 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 (Hg').—Use Hg'2(N03)2.Ha0 dissolved in dilute HN03. Note.—Reactions 145,146,147, and 148 given under mercuricum (Hg//) yield precisely similar results with Mercurosum (Hg') and may be repeated with the (N03)2 solution. In reaction 146 however it is unnecessary to add acid since the Hg/2(N03)2 solution is already acid. 217. HCl: a white precipitate (Hg'2Cl2): insoluble in dilute acids unless warmed with both HCl and IIN03, 144 GROUP I. TABLE OF DIFFERENCES. 218-221. which convert it into soluble Hg"Cl2; becomes black when AmHO is poured upon it, but does not dissolve. 218. AmHO (or KHO); black precipitate, insoluble in excess. 219. ; black precipitate (Hg^S); this precipitate, like Hg^S (144), is insoluble in Atn2S, in hot strong HC1, and in hot strong HNO,, but is easily dissolved when heated with a mixture of HNO, and HCl. 220. Group I.—Table of Differences. Test. Pb. Ag. Hg'. a. For liquids. 1. Add HC1. White precipitate: soluble in boiling water; A mill) neither dissolves the precipitate nor changes its color. White curdy pre- cipitate: insoluble in boiling water, easily soulile in warm Am HO, re- precipitated from this solution by addiug HNOa in excess. White precipi- tate : insoluble in boiling water, and insoluble in A m HO, but blackened by it. 2. Add AniliO. White precipitate : insoluble in ex- cess. Brown precipitate: readily soluble in excess. Black precipitate: insoluble in ex- cess. 3. Add KaCr04. Bright yellow pre- cipitate. Chocolate-red pre- cipitate. Scarlet-red pre- cipitate. b. For solids. 4. Fused with on charcoal in the in tier blowpipe flame. 5. Heated in a bulb-tube, mixed with Na/X)3. White 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. No 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 PbCl2in boiling water, in which AgCl and Hg'2Cl2 are insoluble. 2d. The solubility of AgCl in A111HO, in which Hg'„Cl, is insoluble. 222-226. GOLD —PLATINUM. 145 The presence of eacli member, when thus separated, is then confirmed by one of its special tests. 222. (s.) A solution which may contain Pb, Ag, Hg' is examined by first precipitating by HC1 added in ex- cess, then filtering and adding more HC1 to the clear filtrate to ascertain that no further precipitate is pro- duced. The precipitate is then examined by Table I (433). The foregoing reactions only include the metals of common oc- currence. For information concerning the detection and separa- tion of the rarer metals, which will only be required by a some- what advanced student, the appendix or larger analytical treatises 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 metals are dissolved only by a mixture of HC1 and HNOs; 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 ex- periment 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: 2AuCls + 6FeS04 = 2Au + 2Fea(S04)3 + Fe2Cl„. 224 n. H2S03 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 it color. Platinum (Pt).—Use PtCl4 solution. 225. AmCl added to a strong solution produces on standing for some time, or more quickly on being stirred or evaporated, a yel- low precipitate (Am2PtCI6); rather soluble in hot water. 226. SnCI2 gives a reddish-brown color in the solution acidified with HOI, owing to the formation of PtCI2: The method of separation; and detecting Au and Pt is fully stated in paragraphs 472-474. PtCl4 4- SnCl2 = PtCI2 + SnCl4. 146 REACTIONS FOR ACID RADICLES. — GROUP I. *** Note.—Before commencing the reactions for acids the stu- dent may with advantage analyze several substances which are liable 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, para- graph 539), the directions given in paragraphs 330-369 may be followed, omitting those portions which relate to the detection of acid radicles. If two or more metals maybe present (see columns 2, 3, paragraph 539), full directions for ascertaining to which ana- lytical group or groups they belong will be found in the General Table (419); and the group precipitate or precipitates thus ob- tained maybe then examined by the Group Tables (433-439), with which the student will probably already 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 radicles as in some respects resemble one another in their reactions, 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 containing the radicle (usually a salt) 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 I.—SULPHATE GROUP. The sulphates are the only commonly occurring salts which give with BaCl2 a precipitate insoluble in boiling HC1. Hydrofluosilicates resemble sulphates in this re- spect, but differ in so many other reactions that they are considered hereafter (299-302) in connection with fluor- ides and silicates, to which they are more closely related. 227, 228. GROUP I. SULPHATES. 147 Sulphates (-"S04).—Use Na2SO4.10H2O. 227. BaCl2 [or Ba(N03 : white precipitate (BaS04), insoluble when boiled with HC1 or HNOa. Note.—IfBaCl2 or Ba(N03)2 be added to a solution containing much strong HC1 or HNU3, a white precipitate may be produced consisting of BaCl2 or Ba(N03)2, which, however, is readily dis- tinguished from the precipitate of BaS04 by being dissolved when boiled with water. Sr(N03)2 and Pb(N03)2 give also white precipitates (SrS04 and PbS04). 228. Blowpipe Test.—Solid Na2S04 or any solid sul- phate, if mixed with solid Na2CC)3* and fused on char- coal in the inner blowpipe flamc produced from, a spirit- fiame, yields Na2S: 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. 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 solution and held above it, will be blackened (230). Note.—This test for a sulphate is reliable only when it is known that sulphur 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 Nh2C03, hence it is always advisable 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- Na2S04 -(- 4C — ]NajS -j- 4CO. * Addition of Na2B407 is useful in preventing the fused mix- ture from sinking into the charcoal. 148 GROUP II. — CARBONATES [229. gen with Zn, properties shown by some metallic and acid sulphates. GROUP II.—THE CARBONATE GROUP. The five following classes of salts give off character- istic gases when acted upon by HCl. *** 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 (-"CO,).—Use Na2C03, or white mar- ble (CaC03). 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 recognized by its property of turning lime or baryta- water milky by the production in them of insoluble CaC03 or BaC03. 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 perfectly clear lime-water* and has a small drop adher- ing to its end is then introduced into the test-tube, care- fully 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-water adhering to the middle of the face; the drop becomes milky. 3. Since 0O2 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 closed with the thumb; by gradually sloping * Baryta-water gives a much more decided result than lime- water. 230.] GROUP II. — CARBONATES—SULPHIDES. 149 the tube the heavy gas is poured into another test-tube containing lime-water 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 CO,2 if it is given off in con- siderable 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 gen- erated, as shown in Fig. 37; or the apparatus shown in Fig. 38 may be employed. 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. Note.—The following precautions must be attended to. Since the milkiness at first caused by C02 disappears gradually when more C02 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 C02 more acid should be added, as many car- bonates retain the first portions of C02 by forming acid carbonates : Na2C03 + C02 4- H20 =2NaHC03. A solid substance which is being tested by HC1 for C02 should be first moistened so as to drive out the air-bubbles entangled in it, which, in coming off, might make one suspect effervescence of CU2. . Hydrogen carbonate or carbonic acid (H2C03), can only exist in dilute aqueous solution ; addition of lime- water to its solution causes milkiness; but, since other substances 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. Ftg. 37. Fig. 38. Sulphides (-"S).—Use FeS for solid, and Am,S for liquid. 230. HCl (or HJ30t) poured upon a small fragment 150 GROUP II.—SULPHIDES. [231-235. of FeS causes H2S gas to come off 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 moistened 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). Note.—This test is made much more delicate if the paper is moist- ened with a solution prepared by addins; KHO to boiling PbA2 solution until the precipitate first formed dissolves; a test-paper thus prepared 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 H2S with HC1 (e. g., FeS) produce a black stain when placed on a silver coin and moistened with a drop of HC1. 233. PbA2 solution gives with soluble sulphides a black precipitate (PbS). The solution produced by add- ing KHO in excess to PbA2 solution is much more deli- cate 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 K2Cr2G7 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 (H„S), in aqueous solution, is easily recognized by (231) or (233), and, unless the solution is very dilute, also by its smell, and, by suspending lead-paper over the liquid ; H2S gas is detected by (230). 236-240. GROUP II. — THEIOSULPHATES. 151 Sulphites (-"S03).—Use Na2SOs. 236. HCl (or H.28 04) poured upon Xa2SO, and warmed gives off' SO., gas, known by its pungent smell and by turning K2Cr207 solution green; the K2Cr207 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 moist- ening a small strip of filter-paper with the K2Cr207 solution and making it adhere by one-half of its length to the rod (230), the other half hanging freely, and in- troducing it into the gas as in (229, 1). 237. BaCl2: white precipitate (BaSOs), entirely solu- ble 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. BaSO, + 2HC1 = BaCl2 + H2SOr BaCl2 + H2S03 + H20 + 2C1 = BaS04 + 4HC1. 238. Na2S03 added to a mixture of HCl and Zn which is giving off pure H, immediately causes an evolution of H2S with the H; the II2S is detected by its smell or by blackening a piece of filter-paper moistened with solu- tion of PbO in excess of KHO, see note (230). Hydrogen sulphite, or sulphurous acid (H2S03), can be found in aqueous solution by adding a drop of K2Cr207 solution, which will at once become green; SO,2 gas is found as directed under (236). Theiosulphates* (= "S203).—Use Na2S203.5H20. 239. HCl (or H2S04) causes no immediate change in the cold, but the liquid on standing or on being warmed deposits a precipitate of yellow S, and SO,2 is given off; the SO,2 is recognized by its pungent smell and by chang- ing the color of K2Cr207 solution (236). 240. Fe.2Cf6: 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. * Formerly known as Hyposulphites, 152 group 11. — hypochlorites. [240 a-242. 240 a. AgN03; a white precipitate (Ag2S203), becom- ing black after standing for a short time, or immediately upon being heated, owing to the formation of Ag2S: Ag2S2Os + H20 — AgjS + H2S04. The above precipitate (Ag2S203) dissolves very readily in excess of the Na2S2Os solution, hence it is most easily obtained by dropping the latter into some AgNOa solu- tion. Hydrogen theiosulphate, or theiosulphuric acid (H2S203), is extremely unstable, rapidly separating into S + H2SG3. Hypochlorites (-'CIO).—Use NaClO.NaCl (Na2 C120), solution. Hypochlorites give off h faint smell of Cl in the air if solid or in strong solution. 241. HCl( or H.lSOi or even 11,0) in the cold, or when gently wanned 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 touch- ing the liquid or the sides of the tube A piece of litmus shaken up with the solution, with- out 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: Na2Cl20 + 2HC1 = 2C1 + 2NaCl + H20. 242. Pb (AtO,)2 (or PbA2) solution added in large quantity 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. 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. C120 gas is of a deep yel- lowish-green color, and has an irritating smell, it dis- solves easily in water to form the above acid. 243-246. GROUP II.—NITRITES 153 Nitrites (= 'NO,).—Use KX02. 243. Warmed with dilute H2S04, 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 be added to KN02 solution, it becomes brown; on adding cold dilute H2S04 the color becomes much more intense; it is pro- duced 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 (made by boiling starch in water, and cooling it) be added to KN02 solution and the liquid be then made acid with HA, an intense blue color will be produced, owing to the combination 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 HN03 and NO. *** 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 indi- cate which of them is present, and its presence may then be confirmed by a second test chosen from amongst its reactions as stated above. 246. (s.) Most of the acids formed by the salts of Group II on addition of HOI, react upon one another; e.g., HCIO destroys HNOa, H2S, and H2S03, and H2S destroys H2S03. The analyst may often by skilful use of the 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; 154 GROUP III.—NITRATES. [247, 248. H2S by PbA2 paper; Cl by bleaching moist litmus- paper; N2Os by its red color. But C02 can only be detected in presence of much S02 by passing the gases through K20r2O7 solution which absorbs S02, C02, pass- ing 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 no member of them being insoluble in water; hence no method of precipitating them is known. Nitrates (-'N03).—Use KNOs. 247. Add to some KNOs solution contained in a rather broad test-tube about an equal bulk of strong H.2S04; cool the liquid by letting a stream of cold water run upon the tube from the tap; then hold the tube in a slanting position, 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 surface of contact of the two layers a dark-brown film or ring will appear, sometimes extend- ing 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, until by the heat evolved by dilution of the acid the NO is expelled, forming brown hues in the test- tube, and the liquid loses its dark-brown color (244). 248. Place some small scraps of Cu in some KN03 249-251.] GROUP III. — NITRATES. 155 solution, and add strong H2S04; reddish nitrous fumes appear at once or on wanning 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 0u(NO3)2: 8HNOs + 3Cu = 2NO + 3CuN2Os + 4H20. NO is itself a colorless gas, but yields on mixture with air N203 and N204, which are reddish-brown. 249. If some cold dilute indigo solution be poured into cold KN03 solution until it is decidedly blue, and then H2SOs be added, the blue color remains unchanged. (Difference 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 effervescence,* and KN02 is formed; if the foil after cooling be boiled in water, a portion of the solution may be proved to contain KN02 by the test in paragraph (245); another portion, if acidi- fied with HNO.„ will be found to give no precipitate with AgX03. (Difference from chlorates.) A solution of a nitrate may also be reduced to nitrite by nascent H. Add to a little KNOa solution some dilute II2S04 and starch paste with KI, no color will be produced, but on dropping in a fragment of Zn a deep blue color is seen (245). 251. Solid KNO.j fused on charcoal in the blowpipe flame “deflagrates,” that is to say, the surface of the charcoal burns rapidly like gunpowder. Note.—Many metallic nitrates [e g , Pb(N03)2] when heated in a glass tube closed at one end, evolve reddish-brown fumes with a characteristic smell (N204) and oxygen—PbN2Oa =N204 -f- O + PbO. The fumes are recognized by their color and smell, the O by its inflaming a glowing splinter of wood. Hydrogen nitrate, or nitric acid (HNOs), has a strong acid reaction, it gives with FeS04 solution a brown ring * 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; hence the student may perform the ignition on platinum foil and neglect to test for O. 156 [252-254. GROUP III. — CHLORATES. (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 KC10g some cold dilute indigo solution be added drop by drop till the liquid is colored faintly but distinctly blue, then some H2S03 or NaHS03 be poured in and the mixture shaken, the blue color of the indigo is at once destroyed. (Difference from nitrates.) 253. Strong H.,SOi poured upon a little solid KC103 becomes orange-red in color, and evolves when shaken a bright yellow gas (Cl2Oj : 3KC103 + H2S04 = CIA + kcio4 + k2so4 + h2o. This gas has a smell somewhat resembling that of chlo- rine; it explodes readily when gently heated, hence on warming 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 quantity, and heated gently with the mouth of the test- tube turned away from the operator. 254. AgN03 produces no precipitate with KC103 solution if it is free from KC1. But if some solid KC103* be heated in a test-tube or better in a small ignition-tube (10), after melting it begins to give off oxygen with effer- vescence ; 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 blowing out the flame, the spark is caused to burst into a flame. If the tube is then allowed to cool, and the residue dis- solved 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 AgNOs, which does not dissolve in HNOa * If the chlorate used for this test is not an alkaline chlorate, fusion mixture must he mixed with it before heating, in order to obtain a soluble chloride in the residue. 255-257.] CHLORIDES. 157 even on boiling, but is easily soluble in AmHO (differ- ence from a nitrate): this precipitate is caused by KC1: kcio3=kci + o3. 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 0,0, HC104 and H20; 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. When 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 IINOjj has been added in excess; in this respect they differ from all salts except cyanides, ferro- cy an ides, and ferricyanides, and these are easily distin- guished by other means. Chlorides ( - 'Cl).—Use NaCl. 257. AgNO3 added to a little NaCl dissolved in wa- ter, 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 HJN03 and warm, it does not dissolve; to another por- tion add AmllO, it readily dissolves. Decant the liquid from a portion of the precipitate after shaking and let- ting the precipitate settle, and warm the precipitate with a little strong H2S04, the acid remains colorless, and no colored vapor is given off. 8 158 ACID RADICLES.—GROUP IV. 258-260. 258. Solid NaCl warmed with strong H2S04 gives off colorless HC1 gas, which is recognized by fuming in the air, reddening moistened blue litmus-paper, and making a drop of AgNOa solution on the end of a glass rod milky. 259. If solid NaCl be powdered and mixed with finely powdered Mn02, then strong H2S04 added and the mix- ture warmed, chlorine gas comes off': 4NaCl + MnO, + 4H2S04 = 2Cl + MnCl2 + 4NaHS04 + 2H20. 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 to let the apparatus stand for some time. Moist starch is not colored when held in the air in the tube. Note.—Msiny samples of commercial Mn02 evolve Cl when heated with H2S04 ; hence the MnG2, unless specially prepared by precipitation, must be carefully tested before using it for this re- action; or the Mn02 and H2SC)4 may be first boiled together as long as any bleaching action is produced when moist litmus is held in the tube, then the substance to be tested is added, and 01 again tested for whilst heating the mixture. 260. If an intimate mixture of solid NaCl with three or four times as much K2Cr207 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* (229) (see note below), and mixed with strong H2S04 by pouring in the acid and shaking it round in the flask, on warming the flask reddish- brown vapor (Cr02Cl2) will be evolved: 4NaCl + K2Cr207 + 6H2SG4 = 2Cr02Cl2 + 4NaIIS04 + 2KHS04 + 3H80. If the neck of the flask be closed bv an india-rubber or a glass stopper, and the delivery-tube be made to dip * The test-tube fitted as shown in Fig. 87 is much loss suitable 261.] BROMIDES. 159 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: CrOaCl2 + 2H20 = H2004 + 2IIC1. On adding to this yellow liquid excess of AmHO, the color becomes pale yellow; on now adding excess of HA, the original reddish-yellow color is reproduced, and in this liquid the presence of H2Cr04, and therefore indirectly that of HC1, may be shown by the formation of a yellow precipitate on addition of PbA2 solution. Note.—Since bv this method the detection of a chloride depends on the formation of H2Cr04 in the liquid in the test-tube from the vapor or Cr02Cl2, great care must be taken that no H2Cr04 is in- troduced into that liquid from any other source. Now, since the mixture introduced into the flask contains a chromate, the greatest precaution must be taken that none of it is allowed to get into the bent delivery-tube, and thence into the test-tube. In introducing the powder into the flask, it must be 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 be 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 be taken that the liquid is not sucked back from the test-tube into the flask: this is prevented by raising the de- livery-tube out of the water in the test-tube as soon as the heating is stopped. Hydrogen chloride or hydrochloric acid (HC1) is a colorless 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 HNOa, milky. Heated with Mn02 the liquid acid evolves chlorine gas. Bromides (-'Br).—Use KBr. 261. AgN03 added to a little KBr solution gives a yellowish-white precipitate (AgBr), which is easily co- agulated by heating or shaking the liquid; it is insol- uble in HNOj, but rather soluble in AmHO, thus some- what resembling the AgCl precipitate, from which it is 160 ACID RADICLES. GROUP IV. [262-264. distinguished by its color. By shaking well, allowing to settle, decanting the liquid, and heating the precipi- tate with strong H2S04, no violet vapor is evolved, the precipitate thus differing from Agl. 262. Solid KBr when heated with strong II2S04 gives off reddish-brown vapor of Br,* which somewhat resem- bles 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 the KBr powder before adding H2S04, the Br is evolved in greater quan- tity and more readily. 263. Cl-water, 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. 264. A mixture of solid KBr and K2Cr207 heated with strong II2S04 as in (260), gives off reddish-brown vapor of Br: 6KBr + K2Cr207 + 11H2S04 = 3Br2 + Cr2(S04)3 + 8KHS04 + 7H20. * KBr solution does not so easily give off Br vapor, but the liquid becomes colored reddish-brown. 265, 266.] IODIDES. 161 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 bv CS2, which forms a brown layer at the bottom of the water: by shaking well after addition of AmHO or KHOthe color of the solution is destroved. (Difference from HC1.) Hydrogen bromide, or hydrobromic acid (HBr), is a gas resembling HC1; its solution differs by evolving Br when heated with Mn02. Iodides (-'I).—Use KI. 265. AgN03 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 IIN03, 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 liquor decanted, then strong IIaS04 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 detected 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 H2SOs or FeSO, solution, which reduces it to Cu2S04, gives a white precipitate (Cu2I2); warming, or the addition of a drop of AmHO, causes this precipitate to form more quickly: 20uSO4 + II2S03 + II20 = 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 162 ACID RADICLES. GROUP IV. [267, 268. warmed with strong II2S04, the liquid becomes violet and gives off* violet fumes of I. Solutions of chlorides and bromides are not precipi- tated thus by CuzS04. 267. Solid KI if warmed with strong H2S04 gives off violet vapor of I,* which, if in large quantity, cools on the sides of the tube to black solid I : this vapor colors starch solution blue, as may be proved by dipping a rod moistened with freshly made starch solutionf 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 moistened with starch solution. The I is more readily and plenti- fully evolved if some Mn02 be mixed with the KI be- fore adding the H2S04. 268. Cl-water added drop by drop (carefully avoiding excess, which would form colorless ICl3),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 looking down the mouth of the tube at a white surface. The color is most distinctly seen if, be- fore heating, some strong H2S04 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 warming the solution the color disappears, but often re- appears when the liquid is cooled. To insure the disap- pearance 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 * KI solution dups not so easily give off purple vapor, but the liquid becomes reddish-brown or red. f The starch solution must always be freshly made, as after being kept, it loses the property of yielding a blue color with iodine. 269-271.] ACID RADICLES. — GROUP IV. 163 KHO solution and shake well, the violet color of the CS2 will disappear owing to the formation of the color- less salts KI and KI03. Note.—The last two methods of testing for the free T are by far the most delicate known ; but Cl-water is by no means the best reagent fur setting 1 free from its compounds, because if added in excos it combines 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 (HA, HC1 or H2S04) poured in, HN02 is produced which liberates I. A solution of N204 in dilute H2S04, made by heating Pb(KOs)2 strongly and passing the red fumes into dilute H2SG4, 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. HgCl.2 gives with KI solution a scarlet precipi- tate, with KBr or NaCl it gives no precipitate; PbA2 gives with KI solution a bright yellow precipitate, with KBr or NaCl a white precipitate. Hydrogen iodide, or hydriodic acid (HI), 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 characteris- tic tests for a chloride, those described in (263) 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 AgXOa solu- tion in the solution made acid with HN03, and its beha- vior with AmHO, 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 164 ACID RADICLES. — GROUP IV. [272, 273. in AmHO, AgBr being pale yellow and not readily solu- ble in AmHO, whilst Agl is primrose-yellow and almost insoluble in AmHO. See also the distinctive action of hot strong H2S04 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 (see 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 H2S04, add a little cold freshly prepared starch solution and then strong HN03, or either of the reagents mentioned in (269), drop by drop ; a dark-blue coloration* 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 absent: A. An iodide is present.—Add to the solution a re- agent consisting of a mixture of CuS04 solution with half its measure of strong H2S03 solution, and warm gently for a short time; Cu2I2will 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 re- turned to the unfiltered 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 filtration, 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 * Black, unless the starch solution has been added in sufficient quantity to the dilute solution. 273.] ACID RADICLES. — GROUP IV. 165 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 in column B. B. No iodide is present.—Evaporate the solution (made alkaline, if not already so, by the addition of pureNaHO) 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). Transfer this mixture into the small tubulated flask (Fig. 38, p. 149) 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 H.2S04 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 an inch 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.* As soon as no more reddish-brown vapor is visible in the flask or its de- livery-tube, discontinue the heating, and immediately withdraw the test-tube. If no colored vapor has been evolved and the water in the test-tube is colorless, chlor- ide and bromide are absent. If the water is colored pour into it CS.2 sufficient to form a 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 vigor- ously; the CS.2 on settling shows a brown color, indi- cating the presence of Br from a bromide. Separate the water from the CS.2 by pouring it through a wetted filter, add to the filtrate AmHO in excess, then HA in excess, and PbA.2 solution. A yellow precipitate indicates the presence of a chromate, which proves indi- rectly that a chloride was present. * See the precautions in the note at the end of par. 260. 166 273 a-277. ACID RADICLES.—GROUP V. 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 destroyed; a bromide is then detected by a brown color- ation 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 NHP04.12H20. 275. 3fgS04 solution, to which some AmCl has been added, and then a little AraHO, gives with Na2HPO+ a white crystalline precipitate (MgAmP04): this precipi- tate is almost insoluble in AmllO, 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. Fe2Cln (a few drops only) added after a little HA and some NaA solution gives, especially on being heated, a yellowish-white precipitate of Fe'"P04. 277. AmHMoOv dissolved in HNO,. gives a yellow precipitate if a drop of Na3HP04 solution is added to it; the formation of the precipitate is hastened by gentle 278-279.] ARSENATES. 167 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 alkalies (KHO, NaHO, AmHO), and insoluble in acids, especially in HNOs. Note.—This reaction, if properly performed, is the most delicate test known for a phosphate, hut careful attention must he paid to the following precautions: The AmHMo04 solution must be pre- pared according to the directions given in par. 526, remark 40; the solution to be tested, must not be alkaline to test-paper; it is best made distinctly acid with HN03; it is then to be added in small quantity only to some of the AmHMoOt solution in a test- tube, more of the liquid being added only 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 Na2IiP04 solution, contained in a test-tube and made acid with HN03, 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 AmHMo04; but on adding a few drops of this liquid to some fresh AmHMo04 solution the precipitate appears. It must also be remembered that HC1 retards or prevents the formation of this precipitate, and therefore an HNOs solution should always be used when possible. 278. AgNOs; yellow precipitate (Ag3P04): pour off a portion and show the precipitate to be soluble in AmHO and in HN03 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 substance 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 H3P, 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. Hydrogen phosphate, or phosphoric acid (H3P04), is a colorless crystalline substance; its solution is strongly acid, but does not char paper and organic substances. (I)iff. from H2S04.) It yields reactions (275 and 277). Arsenates (-'"AsOJ.— Use Na2HAs04.12H20 solution. 279. The precipitates formed in reactions (275, 27-6, 277) for phosphates are precisely similar in appearance and general proper- ties to those formed with the same reagents by arsenates. The 168 ACID RADICLES. — GROUP V. [280-282. procipitate, however, which is formed by an arsenate with AgN03 differs from that given by a phosphate by being brovm in color; also AmHMo04 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 only yields a precipitate with AmHMo04 when the liquid is boiled, whereas the corresponding precipitate with a phosphate is produced by a gentle heat. 2. An arsenate solution, if boiled with strong HC1, gives when H2S is passed into the hot liquid, first a white precipitate of S, then yellow As2S3; a phosphate solution, under the same circumstances, gives no pre- cipitate. 3. In a perfectly neutral solution, AgNOs gives with an arsenate solution a brown precipitate, with a phos- phate a canary-yellow precipitate. 281. Hence, if occurring separately, a phosphate and arsenate may be distinguished by oue or more of these differences. 281 a. The simplest method of ascertaining which of these two acids is present is to throw the precipitate 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 (difference 3). Or the precipitate produced by AmCl, AmHO, and MgS04 may be examined for arsenate by dissolving a part of it in dilute HNOs, adding AgNOs as long as it causes any white precipitate, and then very dilute Am HO gradually drop by drop; if arsenate is present a brown precipitate will form just before the liquid becomes alkaline to test-paper; phosphate gives a yellow precipi- tate. Instead of mixing the dilute AmHO 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, AmCl, AmHO, and MgS04 are added as long as any further precipitate is caused; the precipitate is 283, 284.] BORATES. 169 filtered off* and dissolved in a little boiling strong HC1, H2S is passed for several minutes into this hot HC1 solution, when the presence of arsenate is shown as above (par. 280, 2); the precipitate is filtered off if any has formed, 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 adding a few drops of it to AmHMo04 solution and gently warming. Arsenite, if present, may be detected by H2S in the filtrate from the Mg precipi- tate, acidified with HC1; yellow A.s2S3 is precipitated. UNGROUPED ACID RADICLES (INORGANIC). The salts of the following acid radicles present no marked resemblances in their reactions to one another or to other salts, and are usually detected by special tests. Borates (- 'B02, or - '"BO*).—Use Na2B,O7.10H2O 283. If some Na2B407 be stirred with a little dilute HC1 on a watch-glass and a strip of turmeric paper be half immersed in the liquid, then dried on a watch-glass in the steam-oven or on a water-bath,f the part which was moistened appears reddish-brown, and becomes bluish-black when moistened with AmllO. This is a most useful test for a borate. 284. If some methylated spirit be poured upon a little solid Na2B4Or in a test-tube or porcelain dish, some strong H2S04 added, and the mixture be heated and set * A small portion of the precipitate may be filtered off upon another filter and tested at once for arsenate by dropping upon it AgNOg solution. If the precipitate turns brown, arsenate is pres- ent and must be separated in the other part of the Mg precipitate before testing for phosphate; if the precipitate turns yellow, phosphate alone is present. f The paper may also be dried over a small flame, if it is not heated above steam heat (100° C.). 170 UNGROUPED ACID RADICLES. [285, 286. 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 characteristic, since some chlorides yield a similar green flame. 285. A mixture of CaF2, Na2B407,* 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 substances. Hydrogen borate, or boric acid (HBOa), is a white porous mass; with 2H20 it forms a crystalline scaly hydrate; when strongly heated these yield a fusible glass consisting of B203. The solution of the acid reddens litmus-paper and colors turmeric reddish-brown, espe- cially on drying the paper. The acid is soluble, both in HaO and in alcohol; on evaporating these solutions, the acid passes off with the vapor of the liquid. Reactions 283, 284, and 285 will serve to detect boric acid. Chromates (- "Cr04).—Use K2Cr207. All chromates are more or less yellow or red in color. The yellow 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 K2Cr207 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 NaFTS03 or H2SOa and warm. * Boric acid is better, since the Na flame coloration tends to conceal the green coloration of BP3. 287-289.] SILICATES. 171 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 ease slow. In each case the change in composition is shown by the liquid becoming green: the following equations show the decomposition occurring with II,S and with HC1, the others may be drawn out by the student: K2Cr,07 + 3H2S + 8HC1=Cr2Cl6 + 2KC1 + 7H20 + S3. K2Cr207 + 14HC1 = Cr2Cl6 + 2KC1 + 7H20 + 3C12.' This green solution gives all the reactions for Cr (102-105). Note.—Since chromic acid is thus reduced by boiling with HC1 and by H2S to a chromic salt, a chromate leads to precipitation of Cr2tt°6 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 causes the ether to assume a blue color; addition of a few drops of strong HNOs is useful. The H202 may be produced by adding Ba02 to the cold acid liquid. This reaction is extremely delicate and charac- teristic. 287. AqNOn: purple-red precipitate (Ag2CrO.): solu- ble in Am'IIO and in UNO,* 288. PbA., : yellow precipitate (PbCr04): soluble in KHO, insoluble in HA. 289. BaCI2: yellowish-white precipitate (BaCr04): insoluble in HA, soluble in HC1. 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 HC1 ; when neutralized by an alkali it becomes yellow, the solution yielding the reactions in pars. 287, 288, 289. Use Na2Si03 solution for liquid ; for solid, finely ground sand or solid Na2Si03. Silicates. 172 UNGROUPED ACID RADICLES. [290-203. 290. HCl 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 pre- cipitate is very apt to remain dissolved, hence its non- appearance is no proof of the absence of H4Si04. 290 a. Small quantities of H4Si04, or H4Si04 in dilute solution, may be detected by evaporating the solution, made acid with HCl, 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 HCl, 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 soluble 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 H4Si04 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 causes a gelatinous precipitate of H4Si04, which usually forms only after a time. 292. Blowpipe Tests.—A little solid Si02 (or most silicates), if fused into a bead of Na2C03 causes frothing from CO escaping; Na2COs -f- Si02 = C02 r Na2SiOs. 293. Fused in a bead of NaAmHPO, 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 SiO,2 are usually best seen in the fused bead. Hydrogen silicate, or silicic acid (II4Si04), is a white flocculent 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. 294-296. 173 FLUORIDES. Fluorides (- 'F).—Use CaF2, finely powdered. Note.—The most useful tests for a fluoride depend upon setting free the acid and allowing it to act upon a surface of glass, which it ‘etches ” or corrodes, causing it to appear dim when perfectly dry. 294. Strong H.iSOi if warmed, with a little CaF2 in a test-tube, liberates HF, which causes the glass to be- have towards the liquid as if it were greasy. The HF etches the glass, and, on washing away the cooled mix- ture 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 washing off the substance and drying the glass thor- oughly, 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 pouring upon it some strong H2S04. The crucible is then covered with a watch-glass with its hollow up- wards and filled with cold water to keep the glass cool; the crucible is placed in a porcelain dish containing suf- ficient hot water to reach half way up the sides of the crucible, the water being occasionally heated, if neces- sary, by a small flame;* 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 bv the action of the HF vapors. The delicacy of this method is much increased by the modification described in par. 296. 296. The convex surface of a watch-glass is covered with a thin film of beeswax or solid paraffin by care- fully heating the glass held by crucible tongs at some * Or the crucible may be heated gently over a flame or on a sand-bath. 174 UNGROUPED ACID RADICLES. [297. 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 keeping the glass moving whilst cooling; 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 re- move the wax from these parts and not to scratch the glass. The glass thus prepared is exposed (as in par. 295) to the HF for about twenty minutes or half an hour, the wax being prevented from melting by cold water kept 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 the etched lines will be made visible by breathing upon the cold surface. 297. The presence of SiO,2, or a silicate, prevents the liberation of HF by H2S04, SiF4 being given off' 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 AtnHO yields a colorless flocculent precipitate of H4Si04 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 par. (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 Si02. 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. 298-301.] FLUOSILICATES. 175 The changes which occur are thus expressed : 2CaF2 + SiO,2 + 2H2S04 = SiF4 + 2H20 + 2CaS04. SiF4 4AmHO = H4Si04 + 4AmF. 298. CaCl2 added to NaF solution* gives a gelatinous almost transparent precipitate (CaF2), which becomes more visible on heating or adding AmHO; slightly solu- ble in HCI, 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 differs from all other acids in dissolving Si02 and insoluble silicates. Fluosilicates (-"SiFe).—Use H,SiF6. 299. BaC/2: white precipitate (BaSiF6\ which usually appears only on gently warming the solution, and thus 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 BhS04, which it somewhat resembles in being rather insoluble in HCI, 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 AmHO, a flocculent precipitate of H4Si04 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 (K2SiF6), 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). Evaporate a little H2SiF6 [or BaSiF6 from (299)], * Prepared by boiling in water the mass obtained by fusing for several minutes on platinum foil some powdered CaP2 and fusion- mixture, filtering the solution and acidifying the filtrate with HA. 176 ORGANIC ACID RADICLES. [301 a, 302. after adding strong H2S04, upon a watch-glass to dry- ness ; 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 BaSiF6.* 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 in HC1; and this precipitate (Ba8eOi), if boiled with strong HC1 for some time, evolves Cl and gradually dissolves as BaSeOj, thus differing from BaSOt and BaSiP6; further, this HC1 solution, if warmed with H2SOs, yields a reddish precipitate of Se. Hydrogen fluosilicatc, or hydrofluosilieic acid (H2SiF6), is a strongly acid liquid, volatilizing entirely when heated in platinum as 2HF -f- SiF4; bv evaporating it in glass the glass is etched. It is precipitated by KOI 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. HCy smells of hitter almonds, the alkaline cyanides smell only faintly of the same. * 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 delicate 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). 303-305.] CYANIDES. 177 303. AgNOz', white precipitate (AgCy): show with three separate portions that this precipitate is soluble in KCy solution added in excess, and in AmHO, but in- soluble in dilute 1IN03. If some of the precipitate be filtered off and well washed with hot water until free from AgN03 (shown by HC1 causing no milkiness with a 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 off red fumes; and a drop of HOI added to this solution gives a curdy precipitate of A«rCl. This reaction dis- tinguishes AgCy from AgCl, AgBr and Agl, which, like it, are precipitated by AgNOs, and are insoluble in HN03, since these three precipitates when dried and strongly heated melt without decomposing; hence, after cooling, if HNOa be warmed with them, it dissolves out no Ag, and HC1 added to the HN03 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, cyanides being readily detected by the following reactions. 304. If some FeS04 solution, mixed with several drops of Fe2Cl6, be added to KCy solution, and the liquid be then made strongly alkaline with KIIO and boiled, then cooled, and HC1 added to acid reaction, “ Prussian Blue” 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. 119), dilute H2S04 is added, then a small piece of marble dropped in and the liquid boiled, allowing the steam to pass off into some Am2S solution, AmCyS is formed. This sub- stance 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 1IC1, and adding several drops of Fe2Cl„: a blood-red color, only faintly seen when but little KCy is used, shows that HCy has passed into the Am2S, pro- * The symbol Cfy conveniently represents the group (FeCy6) ; it is used here to avoid brackets. 178 CYANIDES. [306. ducing AmCyS, and therefore proves the presence of a cyanide. Note.—The marble is used to cause evolution of C02 gas, which lessens the risk of the Am2S being sucked back during the reac- tion. A little HgCl2 solution should be added to a few drops of the red solution ; if the red color is destroyed it was certainly due to the presence of AmCyS. 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 be filtered off before the color of the filtrate can be seen.] Then filter if neces- sary, acidify with HC1 in a porcelain dish, 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 adding to a few drops of the liquid some HgCI2. Note 1.—On adding HC1 to the Am2S (305, 306), white S sepa- rates, unless the yellow liquid has been previously boiled in a porcelain dish until it becomes colorless (filling in distilled water as it evaporates); 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 AmsS, the filtrate is dark-colored, and there- fore the red coloration would be invi-ible. Note '2. — llgCy2 does not show the reaction for a cyanide by methods (303, 304, and 305); but by boiling with Am2S, 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 peach blossom-colored flame. Hydrogen cyanide, or hydrocyanic (“Prussic”) acid, 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 AgNOs (303), also by (304), or by formation of AmCyS when the liquid is boiled with Am2S (306). 307-314.] FERROCYANIDES. 179 Ferrocyanides ( - ""FeOy6,* or - "" Cjy). — Use K4FeCy6.3H90, (K4Cfy.3H20). 307. Fefif6: dark-blue precipitate, “Prussian Blue” (Fe4Cty3); insoluble in HC1, soluble in H2C204 to a dark- blue liquid; changed by KHO into brown Fe2Ho6. Note.—The solubility in H20 and insolubility in HC1 are shown by pouring off portions, heating them with HC1 and H2U respec- tively, filtering, 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 im- mediately on addition of Cl-water or Br-water, or on warming with HNOs. It is insoluble in HC1. 309. CuSOi: a chocolate-colored precipitate (Cu"2Cfy), insoluble in HA. 310. AgN03: white precipitate (Ag4Cfy), insoluble in HX03 and in AmHO. If heated with HNOs this precipitate changes to orange-red Ag6Cfy2, soluble in AmHO. Ferricyanides [- fiFeCyfi, or - ylCfy2~]. — Use K6(FeCy6)2, (K#Cfyt). 311. Fe.fil6: dark-greenish or brown coloration; no precipitate 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 de- stroyed by KHO. 313. CuSOi: yellowish precipitate. 314. AgNOz: orange-colored precipitate (Ag6Cfy2), insoluble in HN03, soluble in AmHO. Frequently a white residue is left on adding AmHO, consisting of Ag4Cfy, and showing that K4Cfy was present in the KsCfy2 solution. * The latter part of this formula is conveniently written Cfy to avoid using brackets. 180 ORGANIC ACID RADICLES. [315, 318. Sulphocyaniles (-'CyS).—Use KCyS. 315. Fe2Cl6: blood-red coloration, but no precipitate; the color is destroyed by HgCl2 solution, but not by HC1. 316. Cyanides are usually detected in analysis by methods (304, 305, 306) Ferro- and ferricyanides can be found and distinguished by their first three tests, or by the precipitate given by AgN03 in the solution acidified with HN03; this precipitate, if a ferricvanide is present, will have a more or less decided orange-red color ; on filtering, or decanting, and warming the precipitate with AmHO, white Ag4Cfy will be left if a ferrocyanide was present, and on acidifying the filtrate with HN03 orange-red Ag6Cfy2 will pre- cipitate. 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, however, 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, (Am,0.2H,0). 317. Strong II.1SOi heated with solid Am20.2H20 causes an effervescence of gas consisting of a mixture of CO and C02: Am2C204 + H2S04 = CO + C02 + A m 2S04 + H20. The CO is detected by burning with a blue flame when a light is applied, the CO,2 by rendering a drop of 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.2 (CaSOi} 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 AinHO and in HA, soluble in HC1 or HN03. 318 ci-321. TARTRATES. 181 318 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 a platinum foil, it is converted without blackening into 0aCO3, which effervesces with dilute HC1. Note.—This is a general test for oxalate of K, Na, Ba, Sr, or Ca; oxalates of these metals leave carbonates on ignition which effer- vesce with an acid. 319. Heated with Mn02 and H2S04, solid oxalates give off* C02: Am2CA + MnO„ + 2H2S04 = 2CO, + MnSO, + Am2S04 + 2H20. Note.—Since commercial Mn02 usually contains some carbonate, it will give off C02 when treated with II2S04 If the MnU2 to be used is not known to be free from carbonate the best way to per- form the test is to add to some of the Mn02 in a 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, occasion- ally drawing fresh air into the test-tube by pushing down a glass tube near to tbe surface of the liquid and sucking out the air ; as soon as no C02 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, C02 will be rapidly given off, and may be detected by the ordinary methods. If the Mn02 gives no C02 with H2S04 proceed at once to add the Am2C204, heat and test for C02. Hydrogen oxalate, or oxalic acid (H2C204, or crystal- lized H2C204.2H20), 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 in pars. (317) and (319). It dissolves in water to an acid, poisonous liquid. Tartrates. (- "C4H406, or - "T). For a neutral tartrate useNa2T. 2H20 or KNarJ\ For an acid tartrate use H./P or NaHT. 320. A solid tartrate or solid H2T when heated strongly in a tube chars, giving off a smell of burnt sugar. 321. A solid tartrate or solid H2T heated with strong 182 TARTRATES. [322-324. H2S04 blackens, giving off a mixture of CO, C02 and so2. 322. AyNOs gives with solution of a neutral tartrate a white curdy precipitate (Ag2T), soluble in AraHO and in HNOs. Allow some of the above precipitate (Ag2T)2 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 (best 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, instead of being slowly raised to 60°, be quickly boiled, the Ag deposits as a black precipitate, which is not so characteristic. 323. CaCl2 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 pre- cipitate is soluble in strong cold KHO,* is reprecipi- tated by boiling, but dissolves again more or less com- pletely 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 crystal of AgN03 and warm carefully as in par. (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 HA is added at the same time, the precipitate may also be obtained with neutral tartrates. Addition of alcohol assists the for- mation of the precipitate, which is soluble in alkalies and in mineral acids. * A milkiness remaining, however, if the potash solution con- tains carbonate. 325-328.] ACETATES. 183 325. If a few drops of Fe2Cl6 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 alco- hol. They are detected by heating them alone or with strong H.2S04 (320, 321): if dissolved and neutralized, they also yield the reactions in (322, 323). Acetates (- 'C,H302, or - 'A).—Use NaA.3H20. 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 (that of vinegar). If alcohol be first added to the NaA then strong H2S04, and the mixture warmed, a fragrant smell of ethyl-ace- tate (Et A) is emitted ; it is most decided when the liquid is shaken after cooling for a short time. 328. Fe.fil6 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 AmHO (if necessary), all the Fe separates as a light-brown pre- cipitate 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 (HA).—“ Glacial acetic acid ” is at 17° C. a colorless crystalline substance, pos- sessing (especially when heated) a very pungent smell, 184 ACETATES. [329. and giving inflammable vapor: it is strongly acid. It dissolves in water readily, imparting 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 gener- ally used to test for an oxalate in solution, (317) or (319) when it is solid; a tartrate is best detected in so- lution by reaction (322) or (323), or if solid by (320); an acetate is found by (326) or (327). *** After completing the reactions for the acid rad- icles the student may proceed to try the preliminary ex- aminations of solid substances for metals and acid rad- icles, as directed in paragraphs (375—377), unless he is intending only to learn the analysis of simple salts, when he proceeds to Section V (330 et seq.). 330.] ANALYSIS OF SIMPLE SALTS, ETC. 185 SECTION V. ANALYSIS OF SIMPLE SUBSTANCES CONTAINING ONE METAL AND ONE ACID RADICLE * Note.—This section may be neglected by a student who is pro- ceeding 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. If the composition of the sub- stance has not been satisfactorily proved by this prelim- inary examination, 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: * Two metals may occasionally be present, as when an alum, or tartar emetic [K(SbO)T], is given for analysis ; also there may be two acid radicles in the liquid, given for analysis, since a salt insoluble in water is occasionally dissolved in an acid; but the student should always be informed of this if it in any way com- plicates the analysis. It will not usually do so, since in the most commonly occurring case, that of an alkaline earth phosphate dissolved in HCI, the (-///P04) is detected in Group III, and accordingly no other acid radicle is looked for. 186 analysis of simple salts, etc. [330 tt It.wl11 be notlRed that there are two divisions of Groups II and III. In analysis it is usual to separate the two divisions of Group ii> af,ter having separated the whole group from the remaining groups; the two divisions of Group III are by some analysts precipitated together and subsequently separated ; they are, however, often precipitated separately, and treated as distinct groups Metals whose chlorides are insoluble in water and dilute acids, and which are there- fore precipitated from their solutions by hydrochloric acid. Metals whose sulphides are insolu- ble in dilute acids, and which are therefore precipitated from acid solutions by sulphuretted hydro- gen. Metals which are precipitated, either as hydrates or as sulphides, from their solutions made alka- line with ammonia, by ammoni- um sulphide or sulphuretted hy- drogen. Metals whose car- bonates are pre- cipitated by ad- dition of ammo- nium carbonate. Metals whose solutions are not precipitated by any of the fore- going group-reagents in the presence of ammonium chloride. f Group I. J Hydrochloric Acid Group. [Silver Group. f Group II. (. Sulphuretted Hydrogen Group. ( Group III. < Ammonia and Ammonium- [ Sulphide Group. ( Group IV. J Ammonium Carbo- j nate Group. [ Barium Group. ( Group V. -< Potassium ( Group. f Group II a. ( Copper Group. Sulphides insol- uble in NaHO and in Am^. f Group II b. j Arsenic Group. Sulphides solu- ble in NaHO and in Am2S. f Group III a. J Ammonia | Group. [Iron Group. ( Group III b. A mmoniumSul- ( phide Group. Zinc Group. [Lead (Pb)] Silver, .... (Ag) Mercurosuin, . (Hg') Mercuricum, (Hg") Lead, . . (Pb) Bismuth, . (Bi) Copper, . (Cu) Cadmium,. (Cd) Tin, . . . (Sn) Arsenic, . (As) Antimony, (Sb) Aluminium, (Al) Iron,. . . (Fe) Chromium, (Cr) Zinc,. . . (Zn) Manganese,(Mn) Nickel, . . (Nt) Cobalt, . . (Co) Barium,. . . (Ba) Strontium,. . (Sr) Calcium, . . (Ca) Ammonium,. . (NH,) Potassium, . . (K) Sodium, . . . (Na) Magnesium, . . (Mg) 1. 2. 3. 4. 5. 6. 7. Table showing the Analytical Classification of the Metals. 330.] ANALYSIS OF SIMPLE SALTS, ETC. 187 After discovering to which analytical group 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 solu- tion.” * The examination for the acid radicle, if it has not been already detected during the examination for the metal, is carried out 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 exam- ined 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 de- tected with certainty, and the examination for the acid radicle 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 an- alysis are liable to contain impurities which will yield only slight corresponding precipitates; if in the course of analysis, therefore, only a slight precipitate is obtained, proceed until some substance is detected in larger quantity, entering against the small precipitate “ Trace of .” The separation and washing of a precipitate by “de- cantation” (23 6, 24 6) is recommended wherever it is possible, 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. * By the “original solution” is meant the solution of the substance, or the substance itself if a liquid is under analysis, to which no reagent has been added. 188 ANALYSIS OF A SOLID SUBSTANCE. [331. For examples of substances to be given for analysis by Section V, see par. 537. *** Note.—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. Caution.—In every analysis each result must be fully entered in the note-book as soon the experiment has been performed. The form of entry being the same as that adopted for the directions in the text. The substance given for analysis may be either a solid or a liquid. If it is a solid examine by A (331 et seq.), if a liquid by B (334 et seq.). A.—THE SUBSTANCE GIVEN FOR ANALYSIS IS A SOLID. 331. Make a careful examination of the properties of the substance, noting down its color, its smell if it pos- sesses any ; also its form, whether it is in powder, crystals, or non-crystalline pieces. Note carefully also any ap- pearance or property which may strike you on examin- ing the substance with the naked eye or with the assist- ance of a lens. 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 par. 332, and, according to the result thus obtained, conduct the further analysis of the substance by par. 333 or by par. 367. 332.] SOLUBILITY OF THE SUBSTANCE. 189 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 sub- stance in a broad test-tube or a boiling-tube, fill the tube about one-third with water, and heat to boiling: 1 The substance The substance does not dissolve: heat a fresh portion with strong dissolves. HC1 to boiling, if it does not dissolve, add water and boil: After examin- 2. The. substance The substance does not dissolve: put aside the test- dissolves. tube containing the substance with HC1, and boil a fresh portion of the substance with strong substance by (See note below.) lINOa; if it is not dissolved, add water and boil: the prelimina- ry tests (333) Absence of Group 3. The substance The substance does not dissolve: dissolves. mix together the contents of After examin- the two tubesin which thesub- After examin- stance was In ated with 11C1 tion of the liquid to lit- mus by (334. I, II), and refer of the solid substance by ing a portion of the solid substance by the prelimina- and with HNOa, and heat the mixture. the prelim- inary tests (333) proceed to examinethe HC1 solution (after noting its color, see 4. The substance 5. The substance to (335) for di- rections for analysis. The examina- tion for the ry tests (333) examine the UNO* solution Rafter noting its color, see (334, I) for the dissolves. After examin- ing a portion of the solid does not dis- solve. Examineafresh portion of the arid radicle substance i>y substance by will be found iiit.'till bj (Jo6 et seq.) taking care after test- ing for Group I by HC1 to boil down consid- erably in a porcelain dish the prelimi- (367). in paragraphs (346-358 6). 345) Examine afresh portion for the acid radicle by (343 et seq.). [Note.—The re- nary tests (333 jrg.)examine the solution in HNO,aud HC1 mixed, as di- rected in the preceding col- suits mention- ed in (346)may be here obtain- ed, if any one of them occurs it should be no- ted down ; ob- serve especial- little strong HCl,*and then add dilute HC1 before testing for Group II by HjS. for the metal, and a fresh portion of the substance for acid radicles by (346 et seq.). ly whether any portion of the elfervescence substance for occurs with HC1.] acids by (346 el seq.). * This method of proceeding removes HNOa, which would cause with H2S a deposit of S. 190 preliminary examination [333. THE SUBSTANCE IS SOLUBLE IN WATER OR ACIDS. 333. Preliminary Examination. 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 ob- served ; and in the third the inferences to be drawn from the results. Confirmatory or supplementary ex- periments are occasionally entered. A more complete preliminary examination will be found in (387-408). Experiment. Observation. Inference. I. Heat a portion of the substance in an ignition-tube, or in a small dry test-tube. 1. The substance does not change, 2. The substance changes color: Absence of volatile, fusible and organ- ic substances, and of water. ye low, hot. Yellow-brown, “ Dark red or ) « brown. | White, cold. Yellow, “ Red brown, “ ZnO. PbO,SnOa or BiaOs. FeaO„ Confirmatory.—If a sublimate forms, boil another por- tion of the sub- stance with KHO solution. 3. The substance fuses easily, 4. The substance sublimes, . . . A smell of Nil, is evolved, and white fumes appear when a rod moistened with strong HC1 is held to the mouth of the tube. 5. The substance blackens, and gives ofF COa, which makes a drop of lime-water on a glass rod milky. If the cool residue in the tube effervesces with HCI, whereas the original sub- stance did not. Probable presence of a salt of Na or K, possibly also of Ba, Sr, Ca, Mg. Presence of a salt of NII41 As, or Hg; possibly also of Har,0«. S (yel- low,),and of I (pur- ple vapor). N1I4 is found by the fol- lowing confirma- tory test,—As is detected in Exp.V, Hg may be found by (147), or its de- tection may be omitted here. Presence of NH4. If N1I4 is found here, the examination for the metal need not be further con- tin ued. Presence of an or- ganic acid radicle, probably A or T or O; the last is known by a smell of burnt sugar. The organic acid radicle is united with K, Na, Ba, Sr, Ca, or Mg. 333.] OF A SIMPLE SOLID. 191 Preliminary Examination—Continued. Experiment. Observation. Inference. 6. Gas or vapor is given off: smell the vapor: Red nitrous fumes, recognized by their ) smell, / S05, known by its smell and by turning K,Cr,0, solution green. Cl, Br, I, known hy smell and color: Br and I by action on starch-paste, and Cl by bleaching moist litmus. A slip of wood with a spark at its end, glows brightly or bursts into flame. From nitrate of a heavy metal. From' combustion of free S or a sul- phide ; possibly also from a sul- phate or sulphite. From certain chlo- rides, bromides, or iodides, also free I. 0 from chlorate or nitrate, or NaO from decomposi- tion of NII.NO,. II. Dip into the powdered sub- stance a moist- ened loop of pla- tinum-wire, and hold the loop in the Bunsen flame; moisten with strong HC1, and again hold in the flame. 1. The flame is not colored, .... 2. The flame is colored: Intense yellow, Pale-violet, appearing violet-red, through \ the indigo-prism, j ' Appearing green through the 1 Rd indigo-prism, . j ’ Appearinginten.se redthrough 1 the indigo-prism, . . j Yellmv ish-g reen, . Bright-green, with blue centre t tr een, after moistening with HCl,j Green, < Pale-blue (livid), . Blue, •< Vivid-blue, The gas burns at the mouth of the tube; note the color of the flame: Pale grayish-green Bright, white, Purple Probable absence of the substances enumerated below. Presence of Na. “ K. “ Ca. “ Sr. “ Ba. “ Cu. “ IW “ As,Sb, Pb. “ CuCl,. Presence of NH„ probably from strongly heated NII.NO,. Presence of PII,. probably from a hypophosphite; the unburnt gas smells of garlic. Presence of Cy from a cyanogen com- pound, probably HgCy,. III. Heat a por- tion of the sub- stance in a cavity scooped in char- coal, in the blow- pipe flame. 1. The charcoal “deflagrates,” or burns rapidly. 2. A white mass is left in the charcoal, which does not fuse, and shines brightly when strongly heated. Presence of a ni- trate or chlorate. Presence of Ba, Sr, Ca, Mg, Al, or Zn. 192 PRELIMINARY EXAMINATION [333. Preliminary Examination—Continued. Experiment. Observation. Inference. Confirmatory. — De- tach a small portion of the un fused white mass, place it on red litmus-paper and moisten it with a drop of water. Confirmatory.—If the moist residue is not alkaline to test- paper, moisten the remainder on the charcoal with Co (NO,)a solution and heat again strongly in the blowpipe flame. The red paper becomes blue in a short time where the substance rests. A hive residue, ...... A pink residue, A green residue, 3. The residue is not white, and does not con- sist of globules of metal; neither is there any incrustration formed upon the char- coal ; proceed to Exp. IV. 4. The residue contains metallic globules or an incrustation forms on the charcoal; pro- ceed to Exp. Y, omitting Exp. IV. Presence of Ba, Sr, Ca, or pos- sibly of Mg. Presence of Al, or possibly of a phosphate, sil- icate, or bo- rate. Presence of Mg. “ Zn. IY. Fuse a small quantity* of the substance into a clear borax bead first in the inner then in the outer flame, noting in both cases the color of the bead whilst hot and when cold. The bead is colorless when heated in both flames. The bead is colored: Absence of the metals below. In outer flame. Blue, hot; green, cold. Blue, hot and cold. Brown or dingy4 purple, hot; light- > brown, cold. J Brown, hot; yellow, 1 cold. J Green,f- hot and cold. Purple, hot and cold. In inner flame. Red or colorless. Blue, hot and cold. Gray or black, hot 1 and cold, . . j Bottle-green, hot and) cold, . . . J Green, hot and cold, . Colorless, hot and) cold, . j Presence of Cu. “ Co. “ Ni. “ Fe.f “ Cr. “ Mn. Confirmatory. — The presence of Cr or Mn may be con- firmed by fusing a portion of the sub- stance on platinum foil or wire with NaaCOj and KNOs. A yellow mass on cooling, A bluish-green mass on cooling, “ Cr. “ Mn. * 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, adding more if no color, or but a faint color, is produced. t Cr if present as a chromate gives a bead brown whilst hot, after having been fused in the outer blowpipe flame; but this brown color is not reproduced in the case of Cr when the bead, after becominggreen by being heated in the inner flame, is again heated in the outer flame. 333.] OF A SIMPLE SOLID. 193 Preliminary Examination—Continued. Experiment. Observation. Inference. Y. Mix the substance Metallic scales or globules are obtained, or in a small cavity an incrustation on the charcoal: on wood-charcoal with Naa('Oj and Globules. Incrustation. White, . Presence of Sh. White and brittle. ner blowpipe flame White and brittle. Red and malleable. Yellow,. None, . “ Bi. w Cu. White and malleable Confirmatory.—If me- marking paper Yellow,. “ Pb. tallic globules are easily. obtained, detach White and malleable one and strike it not marking pa- None, . “ Sn. sharply on the bottom of an in- per, and readily fusible. verted mortar with White and malleable the pestle,and note not marking pa- “ Ag. whether it is crushed to powder (brittle) or merely flattened out into per, fusible only with difficulty. Yellow whilst hot, ' white when cold; a cake (malleable). becomes green If the globules are None, . when moistened “ Zn. white and malle- with (Jo(N03)2 able,take one upon solution and re- the point of a pen- lieat-d in the knile and see >f it outer flame. “ Cd. will mark paper as a black lead-pen- None, . Brown,. None, . White; on smelling cil does. the charcoal, a smell of onions is “ As. perceived. After the completion of the preliminary tests for the metal, a solution of the substance is made according to the direc- tions in par. (332), and this solution is examined as there di- rected. 194 PRELIMINARY EXAMINATION. [334. B.—THE SUBSTANCE FOR ANALYSIS IS A LIQUID. 334. Preliminary Examination. Note.—The experiments or observations which are to be made on the liquid are stated in succession in the first column : opposite to these there are drawn out in the second column the results, any one of which may be obtained ; and corresponding to these in the third column are given the inferences to be drawn from each of these results. Observation or experiment to be made. Result of observation or experiment. Inference to be drawn from the result. 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 obtain- ed by burning a piece of magnesi- um ribbon. Deli- cate tints are best seen by looking through some thickness of the liquid at a sheet of perfectly white pa- per. (Very delicate, .... Pink •< [intense f Very delicate, . . . . Green j [intense f Reddish-yellow Yellow -< [Light yellow, .... Blue, Violet (or purple) The liquid is colorless Presence of Mn or diluteCo solution. Presence of Co. “ Fe" or dilute Ni or Cr so- lution. “ Ni, Cr, or Cu solution. “ Fe'" or a bi- chromate. “ Neutralchro- inate. “ Cu. “ Cr or a Per- manganate. Absence of Co, Ni, Cr, Cu, etc. II. Dip pieces of red and blue lit- mus-paper into the liquid. It is neutral, (Not affecting the color of either paper.) Absenceof 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.) Note.—If, on adding Na,COs to a part of the solution 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 reac- tion. It is alkaline, (Turning red paper blue.) Note.—If the color of the paper becomes only slightly changed, it indicates, proba- bly, the presence of an alkaline salt. Presence of a hy- drate of K, Na, Am, Ca, Sr, or Ba, or of a salt with alkaline re- action. 334] EXAMINATION OF A LIQUID. 195 Preliminary Examination—Continued. Observation Inference or experiment to Result of observation or experiment. to be drawn from be made. the result. III. Evaporate (21) A residue is left Presence of some some of tbe liquid dissolved solid. upon a thin On being strongly heated tbe residue black- ens, and emits a smell of burning, . Pres, of A, O, or T. heated very gen- tly by supporting The smell resembles that of burning sugar, Presence of T. it some inches Note.—If the cold residue after ignition above a small effervesces with a drop of HC1, whereas the flame upon a unignited residue did not, the organic acid gauze, or by radicle is united with Ba, Sr, Ca, Mg, Na, or K. means of a sand or water bath. If a residue re- [The results in Exp. 1,1,2,3,5, par. 333, may be here observed, and should be noted.] mains on the glass bring this gradually into No residue is left, Absence of any dis- the flame and solved solid. heat it more strongly. Note.—If the liquid is also colorless, taste- less, and without action on litmus-paper, it must consist only of distilled water, and no furtherexamination of it need be made. If the liquid is alkaline NH3 must be looked for; if it is acid, H/'03 HaS03, HOI, HN03, HjSOj, and other volatile acids only need be tested for. IV. Add excess of Smell of NH3; moist red litmus is turned Presence of Am. strong NaflO or blue, and a rod moistened with strong No further test KHO solution HOI produces white fumes when held in need be tried for a and boil (51). the mouth of the test-tube. metal if Am is de- tected here. V. Pip a loop of The flame is colored: platinum wire in- to the liquid, and hold it in the Intense yellow, Pale violet,\ violet red when seen! through the indigo-prism, . . j Presence of Na. “ K. f Appearing green through the 1 “ Ca. or of the flame, Red J indigo-prism, f > j Appearing intense red through | “ Sr. loop with a drop of strong HOI, and hold again in the flame. i the indigo-prism, . . j dreen J Yellowish-green, dreen, j Bright-green, .... “ Ba. “ BjOa,Cu (usu- ally blue in centre). Blue \ Pale (livid) mue< l Vivid “ As, Sb, Pb. “ CuCl3. * A piece of thin glass from the side of a broken flask is a cheap and useful substi- tute for a watch-glass. f This color is often rendered somewhat indefinite by the presence of a trace of Na. K is then found by the indigo-prism (49) or spectroscope. 196 EXAMINATION OF A SIMPLE SUBSTANCE. [335. Preliminary Examination—Continued. Observation Inference or experiment to Eesult of observation or experiment. to be drawn from be made. the result. VI. Make a clear The bead is colorless both hot and cold,) Absence of the borax bead in a after having been heated in both flames,/ metals below. platinum wire loop (ill); dip it into a small quan- tity of the liquid The bead is colored : contained in a In outer flame. In inner flame. watch-glass,* Blue, hot; green, cold. Red or colorless, . Presence of Cu. then fuseit in the Blue, hot and cold. Blue, hot and cold, . “ Co. outer and inner Braun or dingy) blowpipe flames; purple, hot; light > Gray or black, “ Ni. observe the color brown, coif1, . J of the bead care- Broun, hot; yellow, ) i BolHe-green, hot 1 “ Fe.f fully both whilst cold, . \ | and cold, . ( hot and when Green,f hot and cold. Green, hot and cold, . “ Cr. > See cold. Purple, hot and cold. Colorless, “ Mn. s Via. Via. Confirmatory. A yellow mass on cooling (105), Presence of Cr. —The presence of Cr and Mn may be confirmed, if A bluish-green mass on cooling (119), . “ Mn. detected by the borax bead, by moistening a mixture of a little solid Na2f03, and KN03 on platinum foil, with a few drops of the original solution, drying by gently heating it at a short distance above the flame, and then fusing by directing the blowpipe flame on the lower sur- face of the foil. EXAMINATION FOR THE METAL. 335. If the original liquid leaves a residue on evap- oration (334, III), and is neutral or acid to litmus-paper (334, II), examine as directed under I (336 etseq.)-, if it is alkaline work by II (359). The method of analysis given below will be best un- derstood by a reference to the Table of Analytical Classification of the metals (p. 186): the list of metals possibly present, which is entered here at the head of * If the solution is very dilute, a portion of it should be evap- orated nearly to dryness in a small porcelain dish before the bead is dipped into it; if after dipping the bead once and fusing, no color is seen, it should he wetted once more with the solution and dried in the flame, and this process should be several times repeated before again fusing the bead. f Cr, if present as a chromate, gives a bead brown while hot after having been fused in the outer blowpipe flame, but becoming permanently green in both flames after having been heated in the inner flame. 336.] EXAMINATION FOR THE METAL GROUP 1. 197 each Group Table, will be seen to correspond with the groups in that table. I. The Liquid is Neutral or Acid to Litmus, 336. Examination for Group I (Pb, Ag, Hgr).—To a portion of the liquid add HC1 in excess (35 a), and note any change which occurs (see Note 1). If a white precipitate forms,* add more HC1 and heat for a moment to boiling, then cool at once; if any precipitate remains, work as directed under the left-hand column; if no precip- itate remains, refer to the right-hand column (note 2). A white precipitate forms 'see note 3), and is either not dissolved when boiled with HCl.or dissolves and reappears on cooling the liquid (showing the Presence of Pb). The precipitate may consist of AgCl, PbCla, HgsCla. Let the precipitate settle and decant the liquid (see note 4); boil the precipitate in the test-tube with ArnHO (see note 5): No precipitate forms, or a precipitate forms in the cold, but disappears on boiling after addi- tion of more HC1, and does not reap- pear on cooling the 1. The precipitate 2. The precipitate does not dissolve : liquid: dissolves, at least Absence of Ag, and in part >see note probably of Pb and below l: The color of the precip- The precipitate be- Hg'. Presence of Ag. Hate is unchanged: comes black: Confirm by add- Presence, of Pb. Presence of ITg' ing excess of Confirm by decant- (Mercnrosnm). HNOa to the ing the liquid, dis- Confirm by immers- AmHOsolution, solving the precipi- ing a bright slip of HgCli" very readily a milkiness ap- tate in HA. and add- copper in a portion when warmed with pears: of the original solu- 1IC1 and HNG3, and Presence of Ag. solution; a yellow tion, made acid with slowly when boiled precipitate: a few drops of HNO, with Hi 1 alone. a gray deposit forms Hence it is most safe on the Cu, which be- to examine some of Note.—The presence comes white and the original precipi- of Pb is also confirm- tate (before it has Note.—Ooagula- ed by the precipitate Pi esence oj Hg' been boiled with ted AgCl often with HC1 dissolving HC1) by the first dissolves only on boiling and reap- column. slowly in ArnHO. pearing on cooling. Pass on to (337). Note 1.—Effervescence may be noticed on the addition of HC1, owing to certain gases being evolved, a list of which will be found in (349); some of them are readily detected by their smell or color, but special tests need not be tried, as they will be afterwards used in the Preliminary Examination for acid radicles (348 et seq.); the fact that a gas is evolved should however always be noted down, even if the nature of the gas is not ascertained. A yellow liquid whose color is due to the presence of a neutral chromate turns reddish-yellow on addition of HC1 ; this confirms the presence of a chromate. Note 2.—A white precipitate which disappears on boiling after * Yellow S may separate from a theiosulphate (see 349, 2); tills precipitate requires no further examination. 198 EXAMINATION OF A SIMPLE SUBSTANCE. [337. addition of more HC1, and does not reappear on cooling, may con- sist of BiOCl or SbOCl A little of the milky liquid produced by the first addition of HC1 should be mixed with H2T solution, if the precipitate consists of SbOCl it will disappear, BiOCl is not thus dissolved. Note 3.—A colorless, gelatinous precipitate of hydrated Si02 may form here; confirm the presence of Si02 by evaporating a portion of the original solution to dryness with HC1, and warming the residue with HC1; a residue insoluble in HC1 proves the pres- ence of Si0.z; filter or decant from the residue of Si02, and employ the HC1 solution to detect the metal present bv (337 et seq.). Note 4.—In this and all subsequent places where decantation of the liquid is recommended, it should be understood that a precipi- tate will usually settle if the liquid is well shaken or heated and allowed to stand for several minutes. (See 23 b.) Note 5.—In case the liquid cannot be completely decanted, add the AmHO in excess to the liquid in which the precipitate is suspended. 337. Examination for Group II (Hg, Pb, Bi, Cu, Cd, Sn, As, Sb).—To the above portion of the solution, made acid with HC1 and boiled until free from Cl or SO,2 if these gases are evolved on heating, add water; a milkiness due to precipitation of BiOCl or SbOCl may result, SbOCl being distinguished from BiOCl by a few drops of the liquid becoming clear on addition of H,T solution. Whether a milkiness has been produced or not by water, add strong H2S-water or pass H2S until the liquid after having been well shaken smells strongly of the gas, and heat gently (see Note 1 below); if no precipitate forms, heat to boiling, since Sn (as stanni- cum) and As (as arsenieum) are only precipitated by H2S on boiling; if a precipitate has formed examine it by the following table; if none has appeared, or only a white milkiness due to precipitation of sulphur (see Note 2 below), the absence of Hg, Pb, Bi, Cu, Cd, Sn, As, and Sb is proved ; pass on to (338). Note 1.—Certain changes in the color of the precipitate may be noticed if the H2S is slowly added ; thus Hg// gives a precipitate which is at first white, then yellow, brown, and ultimately black ; Pb, in strongly-acid solutions, gives a red precipitate, becoming black on addition of water and more H2S. Note 2.—Characteristic changes of color of the solution often accompany the separation of sulphur; thus A reddish-yellow solution changing to pale green indicates a ferric salt. A reddish-yellow solution changing to green indicates a chromate. A green solution changing to colorless indicates a manganate. A purple solution changing to colorless indicates a permanganate. The precipitated S need not be examined. 337.] EXAMINATION FOR GROUP II. 199 Note the color of the precipitate yielded by H3S, and examine it according to 1, 2, or 3, below: 1. The precipitate is dark-brown or black; it may consist of SnS, CuS, HgS, Bi.jS3, PbS. Add pure NaHO in excess to the liquid and precipitate, or to the precipitate alone after decanting the liquid if possible (see note 4, p. 198), and boil: The precipitate dis- solves : to a por- tion of the NaHO solution add HCl in ex- cess, brown SnS is reprecipita- ted. Boil another por- tion after add- ing a little yel- low AnijS, then add HCl in ex- cess, a yellow precipitate of SnSjt Presence of Sn" (Stannosum). [The presence of Sn" may also be confirmed by adding HgCl3to a part of the ori- ginal solution, a white precipi- tate shows Pres- ence of Sn".] The precipitate does not dissolve: it may consist of CuS, HgS, Bia?*, PbS. a. The original solution is blpe or green, and becomes intensely blue on addition of excess of AmHO: Presence of Cu. Confirm by adding a few drops of HaS04 to the original solution, and dip- ping into it a bright knife-blade or piece of steel, a red film of Cu deposits: Presence of Cu. Note.—To detect small quantities of Cu the K4Cfy test (in 163) should be used. (J- The original solution is colorless. Test in separate portions for Hg, Bi, Pb, by the following special tests: After acidifying with HCl (if not already acid), im- merse in the so- lution for a few minutes a bright strip of Cu; a gray film is de- posited, which be- comes white and brilliant when rubbed : Presence of Hg" (Mercuricum). [The SnCla test (145) may also be used as confirma- tory.] Pour another portion of the original solution into much cold distilled water; a white precipitate or milkiness: Presence of Bi. 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 HCl upon the precipitate and let them drop through into large excess of water; a milkiness, on stirring, shows Presence of Bi. To a portion add H3S04, a white precipitate: Presence of Pb. [The presence of Pb may be con- firmed by add- ing to a part of the original so- lution AmHO in excess, then HA in excess, then K3Cr04. A yellow precipi- tate shows Pres- ence of Pb.] 2. Theprecipitaleis yellow: it may consist of CdS, As'jS3. SnS,,: Boil the precipitate with NaHO in excess, after decanting the liquid if possible: The precipitate does not dissolve: it is bright yellow and pulverulent: Presence of Cd. [The presence of Cd may be con- firmed by show- ing that the pre- cipitate produced by H3S dissolves on being boiled with dilute H^04.] The precipitate dissolves: it may consist of As3S3 or SnS3; examine portions of the original solution as directed below : Acidify a portion with HCl and place in it a piece of Zn resting on a piece of platinum foil: Sn is deposited on the Zn : Presence of Sniv. (Stannieum.) [The deposit of Sn may be detach- ed from the Zn, and dissolved by boiling it in a test-tube with a little strong HCl, then HgCl3 added; a white precipitate confirms Presence of -SYiiv.] Acidify a portion with strong HCl, immerse in it some pieces of bright Cu and boil, a black film is deposited on the Cu: Presence of As. Note.—If the yellow precip- itate formed by 11aS appear- ed at once in the cold, the As is present as Arsenosum; if it formed only on boiling, Arsenicum is present. 3. The precipitate is orange-red: it may consist of SbaS3. Confirm by acidifying a portion of the original solution with HCl, and immersing in it a piece of Zn resting on a slip of platinum foil, a black stain on the platinum (193): Presence of Sb. Note.—It occasionally happens, if the solution has not been sufficiently diluted, that HaS gives a reddish precipitate with Pb solution; such a precipitate, however, becomes black on adding more MaS-water. 200 EXAMINATION OF A SIMPLE SUBSTANCE. [338. 338.—Examination for Group III. (Al, Fe, Cr; Zn, Mn, Ni, Co; Ba, Sr, Ca, Mg as phosphate, fluoride, or oxalate; BaCrO*). Caution.—It is of the greatest importance to remem- ber that if an organic salt—more especially a tartrate— has been detected in the preliminary examination, and it has not been proved to be a salt of Ba, Sr, Ca, Mg, K, or Na, and must therefore be a salt of one of the metals of Group III, the detection of the metal by the direc- tions given below may be hindered or prevented. It is therefore necessary to destroy the organic acid radicle by evaporating some of the substance to dryness after add- ing a little strong HNOs, and then gently igniting the residue. The residue, when cool, is dissolved by warm- ing with a few drops of HC1, the solution diluted, and this solution is to be substituted for the original solution in the examination for Group III. To another portion of the original solution add first AmCl solution, then AmHO in excess; note carefully the color and appearance of any precipitate (which is probably due to Al, Fe or Cr, but if white or nearly so may be a phosphate, oxalate, etc.), or the color of the liquid if no precipitate forms (Ni yields a violet-colored liquid); then whether a precipitate has been produced or not, add Am2S or better II2S, and boil. (See note below.) Note.—If no precipitate forms on addition of AmCl and AmHO, or of Am,S, until the liquid is boiled, when a pale-green precipi- tate is produced, this precipitate is due, to the presence of a chromate, which will have been already detected by the liquid turning from yellow to green on addition of H2S. The pale-green precipitate need not be further examined, but its formation should be noted as confirmatory of the presence of a chromate. Proceed to exam- ine for the metal present by (342). If a precipitate forms examine it by the table below.* * White S, separated from the Am2S by the action of a ferri- cyanide or other oxidizer, may here render the liquid milky : it is recognized bv disappearing again when a small quantity of the milky liquid is warmed with more Am,S. Its appearance should be noted, but it is not to be considered as a third group precipitate. 338.] EXAMINATION FOR GROUP III. 201 If no precipitate forms, the absence of Al, Fe, Cr, Zn, Mn, Ni, Co, and of Ba, Sr, Ca, Mg as phosphate, oxalate, and probably as fluoride, also of BaCr04, is proved ; pass on to (342). Note the color of the precipitate, and examine it accord- ingly by 1 or 2 below. 1. The precipitate after addition of Am.,S 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). a. The color of the original solution was yellow or red- dish brown:—Pres- ence of Fe'". b. The color of the original solution was pink, or possi- bly blue, be- coming pink c. The color of the original solution was green:—Presence of M or Fe". Note the effect which was produced by the addition of AmCl and AmHO: on dilution: —Presence of A blue solution was A dingy-green pre- Co• produced: — Pres- cipitate, which, ence of A i. when shaken This is confirmed The presence round in a por- by the precipi- of Co may be The presence of Ni celain dish and tate produced by confirmed by may be confirmed left for several AmCl and AmHO adding ex- by adding excess minutes exposed in the original so- cess of KHO of KHO to a part to the air, be- lution having to the origi- of the original comes brown:— been reddish- nal solution, solution; a light- Presence of Fe". brown, and be- a blue pre- green precipitate coming black on cipitate turn- shows the pres- Confirm by adding addition of Am«S. ing red on ence of A'i. KjCtVj to some boilingshows of the original As a confirmatory the presence of Ni will also have solution (acidi- test add to a por- Co. been detected by tied with IIC1, tion of the origi- its borax bead if necessary); a nal solution Co will also (334, VI). dark-blue pre- (acidified with have been de- cipitate: — Pres- HC1 if necessary), teeted by its ence of Fe" (Fer- a few drops of borax bead rositm). KCyS solution, a (334, VI). blood-red colora- tion, destroyed by HgCla shows: Presence of Fe'" (Ferricum). 2. The precipitate, after addition of Am.,S, is white or light- colored.—It may consist of Cr2Ho6, Al2Ho6, ZnS, MnS; [or of BaCrO,,, or Ba, Sr, Ca, Mg, as phosphate, oxalate, fluoride, silicate, or possibly borate]. The substances 202 [338. EXAMINATION OF A SIMPLE SUBSTANCE. in brackets can however only be present if the liquid given for analysis was acid in reaction, 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 appearance of this precipitate, then add a larger quantity of KHO and stir or shake well; one of the following results (4. heat to burning with note), hold in the vapor the Prob.presence of a tartrate. boiling, and a blue flame when kin- end of a glass rod covered with moist starch powder: kindle the al- cohol,it burns died :— Presence of an the starch becomes brown:— Presence of a bromide. Confirm by (358). with a green edged flame:— oxalate. The starch becomes blue:— Presence of a borate. Presence of an iodide. Note.—The vapor is much Confirm by (357). more easily obtained by mix- ing the substance with MnOa powder before adding H3S04 and heating. 351. After heating the tube containing the strong and substance, let it stand for some time, then rinse it out, dry the inside thoroughly; if it is seen to be corroded and dimmed :—Presence of a fluoride is shown. The presence of a fluoride, if decisively indicated here, requires no con- firmation. * Obtained by boiling the substance if a solid with water, and filter- ing or decanting the liquid, if the substance does not completely dis- solve. 352-355.] 211 examination of simple substance. Actual Examination for the Acid Radicle. 352. The examination for the metal, or the prelimin- ary examination for the acid radicle, will have detected any one of the commonly occurring acid radicles, except those whose detection is provided for below (353-358). For the tests given below, use separate portions of the original substance. 353. Acidify a portion of the liquid (or if a solid, boil it) with HC1 and add BaCl2, or if Pb, Hg', or Ag has been found, acidify with HNOs and add Ba(NOs)2, since HC1 and chlorides would precipitate the above metals as chlorides. Either no precipitate forms—pass on to (354),—or a white precipitate forms which does not disappear on boiling: Presence of a sulphate. 354 Acidify a portion of the liquid, or if a solid is being examined heat the solid, with HN03; filter off any precipitate or residue which may form, and add AgNOs solution : either no precipitate forms (see note on p. 212), showing the absence of 'Cl, 'Br, 'I, 'Cy ""(FeCy6), Ti(Fe2Cy12), and (CyS)', pass on to (356); or a precipitate forms, which does not disappear on warm- ing, see (355): 355. A precipitate forms. Note its color; and ac- cording as it is white, yellow, or orange, examine it by 1, 2, or 3 : 212 [356. EXAMINATION FOR THE ACID RADICLE. 1. The precipitate is white, and may consist of AgCl, AgCy (Ag4FeCvs, or AgCyS). To a portion of the original solution add HC1 in excess, and then FesCl,: A deep blue precipitate: Presence of a ferrocyanide. A blood-red coloration. Presence of a sulphocyanide. If Fe4ng has yielded neither a precipitate nor coloration (indicating absence of a ferro-, ferri-, and sulphocyanide), decant the liquid from the precipitate caused by AgNO,, pour upon the precipitate some strong HNO, 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 heating it with FeS04.Fe1CJ6, and KHO, and acidifying with HC1. A blue precip- itate:—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 solu- tion and KNOa solution, and then acidifying (if not acid) with HC1: a deep blue coloration: Presence of an iodide. If an iodide is not thus de- tected, add to another portion of the original solution several drops of Cl water; if the liquid becomes yellow, and on being shaken with CS, colors that liquid red- dish-brown, it shows: Presence of a bromide. 3. Orange-red precipi- tate. To a portion of the original solution add HCl in excess, then FeS04 solu- tion ; a deep blue precipitate shows: Presence of a ferri- cyanide. Note.—If Hg has been found, HgCv2 may be present, notwith- standing the formation of no precipitate with AgNU3. It is de- tected by (306, note 2, p. 178). If HgCy2 is not present pass on to (356). 356. Acidify some of the original solution if it is not already acid, with dilute HNO:j; filter if necessary, add a small quantity of this acid solution to some AmHMo04 solution, stir well and warm gently: A yellow precipitate shows If no precipitate forms, heat to presence of a phosphate. boiling; the formation of a yel- low precipitate shows presence of an arsenate. If no precipitate forms even on boiling the liquid, pass on to (357). Note.—The presence of a phosphate or arsenate may be confirmed by dissolving the yellow precipitate, separated by filtration or de- cantation, by pouring upon it a little AmHO; then adding to this 357,358a.] examination for acid radicle. 213 solution AraCl and MgS04, a crystalline precipitate will form which is to be filtered off and washed with a little cold water; on pouring upon this precipitate on the filter several drops of AgN03 solution, the precipitate becomes yellow if phosphate is present, and brown if arsenate is present. The presence of arsenate is further con- firmed by a yellow precipitate (As2S3) appearing with H2S (337) when the liquid is boiled. 357. Acidify a portion of the original solution with HC1, dip into it 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 AmHO, the presence of a bo- rate is shown. If no reaction is obtained pass on to (358). 358. The acid radicles, one of which may still be pres- ent, are "T, "C204 and 'F. If the metal found belongs to Groups I, II, III, or IV, the examination must be begun at (358 6); if the metal present is K, Na, or NH4, examine by (358 a). 358 a. Make the solution just alkaline with AmHO, then add CaCl2 [or Ca (N03)2] solution in some quan- tity, shake well and let it stand if no precipitate forms at once; the preliminary examination will usually have indicated which of these acid radicles is present, and thus show according to which of the three columns below, the precipitate is to be further tested : I. A crystalline precipitate, ap- II. A while pulverulent pre- III. A gelatinous pearing after some time shows cipitate shows probable flocculent precipi- tate shows proba- probabl v presence of a tartrate. presence of an oxalate. Confirm either by 1 or 2 The presence of an oxalate, ble presence of a below: already indicated by the fluoride. 1. Decant the liquid from the test in 350,4, must be con- Confirm by filter- precipitate, add a little water firmed either bjv warm- ing and warming and a single drop of Am HO, ing some of the original some of the pre- drop in a small crystal of substance with Midland cipitate (or of AgNOs and warm very care- I [QS04, and testing for the substance, if fully ; a mirror is formed C<>a gas (319); or by the solid) in a small below the crystal, presence of a tartrate. This test may be more tedious method of cup of lead or filtering off and drying platinum, with tried also with the original some of the above precip- strong H,S04; solution by (322). itate of CaCa04 and test- fumes will be 2. On acidifying some of the ing for a carbonate with evolved which neutral original solution HC1 (318 a). etch a properly with HA, and adding alcohol and KA (unless K or NH( has been detected in the sub- stance), and stirring or shak- ing well, the formation of a crystalline precipitate shows presence of a tartrate. prepared watch- glass (296). 214 examination for acid radicle. [3586, 359. 358 b. An oxalate or fluoride of Ba, Sr, Ca, or Mg will have been already detected in par. 339. A tartrate of any one of these metals is found by gently heating the finely powdered substance (if it is a solid, or neutralizing the solution, if a liquid) with very dilute AmHO and a crystal of AgNOs; 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 origi- nal solution just acid with HC1, and add II2S solution or pass H2S (500 a) into the liquid for about five min- utes ; filter off the precipitate and add more II2S to the filtrate; if no more precipitate forms* boil in a porce- lain dish until the liquid ceases to smell of H2S, and examine by (358 a). If the metal belongs to Group III add AmCl, AmHO till alkaline and Am2S; boil and filter, add to the filtrate Am2S; if no more precipitate forms* add HA in excess, boil, filter oft' S if necessary, and examine by (358 a). The Liquid for Analysis is Alkaline (334, II). 359. The following special course of examination should be pursued if the liquid under analysis is alka- line in reaction, since it is possible in such a case that two metals may be present, one of them as a constituent of the acid radicle. In the preceding course the detec- tion of one metal only is provided for. An alkaline solution may contain the oxide of any one of the metals Pb, Zn, As, Sn, Sb, Al, or Cr, together with the oxide of one of the metals K or Na; it may also contain K or Na as silicate. The detection of such sub- stances is provided for in paragraph 360. Certain other salts of K, Na, and NH4, which also have an alkaline re- action, may however be analyzed by the usual plan (336 et seq.), as will be seen below (360 et seq.). * 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. 360, 360a.] analysis of liquid, etc. 215 360. To a small portion of the alkaline solution add several drops of dilute HNOs; either no precipitate will form (see column 2, p. 216), or a precipitate forms; in the latter case note the color and appearance of the pre- cipitate, and proceed to test further as directed in 1 of table, p. 216. 360 a. The presence of Na, K or NH4 will probably have been already detected in the preliminary examina- tion ; NH4 or Na, if thus found, require no further con- firmation. The presence of K will usually not require confirma- tion, but if any doubt is felt concerning its presence, confirm by adding to a part of the original solution ex- cess of HC1, evaporating to dryness, stirring and warm- ing the residue with a few drops of water and several drops of HC1, decanting or filtering if necessary from any undissolved residue, and stirring several drops of the cold, clear liquid on a watch-glass with PtCl4 solu- tion for some time; a yellow precipitate forming on the lines rubbed by the rod confirms the presence of K. 216 ANALYSIS OF A LIQUID, ETC. [S60. 1. A precipitate forms on addition of the first, few drops of HNOa. To another portion of the solution add HaS-water drop by drop, and note if any precipitate forms, then add HCl in excess: if a precipitate is formed (see 3 below), if no precipitate appears (see 4 below): 2. No precipitate is produced by addition or HNOa except possibly a slight milkiness due to the separation of S. Acidity another portion with HC1 and employ it as the original solution for the examination for the metal by pars. 336 et seq. It must be remembered that in this case a silicate may be present. 3. A precipitate is formed by addition of and excess of HCl: note its color and appearance : A black precipitate: Presence of Pb. Confirm by adding to another portion of the solution HA in excess, then KaCr04la yellow pre- cipitate : Presence of Pb. Proceed to (360 a). A white precipitate forms on addition of HaS, but is dis- solved by the HCl: Presence of Zn. Proceed to (360 a). A bright yellow very floccuient precipitate: Presence of As as arse- nite. Confirm by shaking well,and letting the precipitate settle; on decanting the liquid and boiling the precipitate with strong HCl, it is not dissolved: Presence of As as ar- senite.* Proceed to (360 a). A yellow precipitate, not separating in large flocks; Presence of Sn asst an- nate. Confirm by warming, allowing the preci- pitate to settle, de- cantina the liquid if possible, or filter- ing,and boiling the precipitate with strong HCl; it dis- solves readily: Presence of Sn as stannatefi Proceed to (360 a). An orange-red precipitate: Presence of 8b. Confirm by adding HCl in excess to a portion of the original solution, and boiling; poursome of this solution, when cool, upon a piece of platinum foil on which a piece ol Zn is resting; a black stain on the Pt appears after a few minutes: Presence of Sb as anti- monale. Proceed to (360 a). A semitransparent gelati- nous precipitate. Presence of a silicate. Confirm by evaporating some of the original so- lution to dryness after acidifying it with HCl: warm the residue in the dish with HCl; an in- soluble powder is left: Presence of a silicate. Proceed to (360 a). 4. No precipitate is formed by addition of HtS and excess of HCl: The original solution was green: Presence of Or. The presence of Cr is confirmed by the formation of a pale green precipitate on addi- tion of the first few drops of HN03. It will probably also have been found in the preliminary examination by the borax bead and by fusion with KN<)3and NajC03 Its presence may be further confirmed by adding to some of the original solution excess of KHO, then PbOaand boiling, on acidifying with HA yellow PbAa is precipitated. Proceed to (360 a). The original solution was colorless:—acidify a portion with HCl and evaporate to dryness, then warm the residue with HCl: The residue dissolves completely:— Add to the solution AmliO in excess, a white gelatinous pre- cipitate shows: Presence of Al. Proceed to (360 a). The residue is not com- pletely dissolved : Presence of a silicate. Proceed to (360 a). * Tests (180,189)may also be used here with a portion of the original solution. t Confirmed also by AmllO giving a precipitate in the solution formed by adding excess of HCl and boiling, whereas it gives no precipitate with AsqOj solution similarly prepared. 366.] ANALYSIS OF A METALLIC SUBSTANCE. 217 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 metallic in appearance.* The presence of the metals Ni, Co, Fe 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 disappears if wetted with dilute HNOs. The preliminary examination may be advantageously modified and curtailed as shown below. Experiment. Observation. Inference. I. Heat a portion of the substance in a small ignition-tube (10). 1. A black lustrous mirror forms, . 2. A yellow sublimate forms, melt- ing, 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 en- tirely 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 appearance of the incrusta- tion 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 portion of the substance in a piece of hard glass tube, open at both ends, and he it it strongly in the Bun- sen flame, and after- wards in the blow- pipe flame, if neces- sary (Fig. 35, p. 132). 1. A gas is evolved from the upper end which smells of burning sul- phur, and turns a piece of filter- paper moistened with K2CraO, so- lution green, 2. The substance burns completely but slowly away, glowing when strongly heated. This etfect is best seen by heating it strongly on Pt foil by directingthe blowpipe flame on the under surface of the foil, . Presence of S. Presence of C. * The most common sulphides which possess metallic lustre are “copper pyrites,” and “iron pyrites,” which resemble brass in appearance; and “galena,” resembling lead. 218 ANALYSIS OF INSOLUBLE SUBSTANCES. [367,368. After completing the preliminary examination proceed as directed under (332), using however strong HC1 and strong HN03 instead of the dilute acids. No acid radicle need be tested for unless S has been found in the preliminary examination, when in a portion of the HNO3 solution H2S04 is tested for by BaCI2; 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, (CaS04), PbS04, (PbCl)2, AgCl,* SiOa (A1203 ignited), Sn02, Sb2Os, Sb204, CaF2. 2. Dark-colored: ignited Fe203 (dark-brown or black), ignited Cr2Os (dark-green), Fe0r2O4 and ignited Pb0rO4 (dark-brown), C (black). 3. Yellow: S, AgBr,* Agl,* (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 ; 1, 2, or 3). 368. The preliminary tests given below will indicate or confirm the composition of the substance very rapidly, and may be substituted for those described in (333). 1. The substance is white (see 367, 1): Pour upon a small portion of it a drop of Am2S; if 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. * Darkens quickly in sunlight, and slowly in ordinary daylight. 368.] ANALYSIS OF A SIMPLE SUBSTANCE. 219 Experiment. Eesult. Inference. I. Moisten a clean loop of platinum-wire, immerse it in the powdered sub- stance, and heat the ad- hering powder for a short time strongly in the inner blowpipe flame; moisten the loop with a drop of strong HC1, and hold it in the Bunsen flame. A yellowish-green flame. A crimson flame, appear- ing deep red through the indigo-prism. A reddish flame, appear- ing dusky green through the indigo-prism. Presence of Ba. [Test an- other portion for SO« by (III), and see note below ] Presence of Sr [ “ “ ] Presence of Ca [ “ “ ] If S04 is not found, test for F by (351 and 296). Note.—The above result may be confirmed by ;369). II. Mix some of the finely powdered substance with powdered Na,CO, and KCy, in a small cav- ity made in a piece of wood-charcoal, and heat the mixture in the inner blowpipe flame. White metallic malleable globules, which if taken upon the point of a pen- knife are found to mark paper as black lead docs, and if dissolved in HN03 give a white precipitate with HjSO«; a yellow in- crustation 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 HgCli Slight incrustation or none. White metallic brittle globules, which, if dis- solved in boiling HC1, give an orange-red pre- cipitate with H3S; white incrustation. White scales, no incrusta- tion ; the metal is insol- uble in HC1, and if dis- solved in HNOj gives no precipitate with HaS04l but a white precipitate with HC1; the original substance is instantly blackened by a drop of Am9S, and is dissolved on being warmed with AmHO (212-216). Presence of Pb as chloride, sulphate or chromate. Test for chloride by boil- ing some of the substance with much water, adding HNO*and AgN03; white precipitate: Presence of Pb C/Q. Test for sulphate by till). (See also 369.) Test for chromate by fus- ing in a porcelain cru- cible, with fusion mix- ture; yellow mass on cooling : Presence of PbCrOt. Presence of SnOa. Presence of SbtOt or Sb^Ot. Presence of AgCl. [See also (369 a) ]. III. Fuse a portion of the substance mixed with Na3C03 in fine powder, in a cavity scooped upon a piece of wood-charcoal, in the inner blowpipe flame, produced from a ' spirit-lamp flame. The cooled mass, if de- tached from the char- coal, placed upon a bright silver coin, and moistened with water, gives, when crushed with the blade of a knife, a black stain. Presence of a sulphate. 220 ANALYSIS OF INSOLUBLE SUBSTANCES. [368. Note.—The presence of PbS04 may be confirmed by pouring upon the original substance HA, then excess of Am HO, and boil- ing; the substance will dissolve: acidify a portion of the solution with HA, and add K20r04, a yellow precipitate: Presence of Pb. Acidify another portion with HC1, and add BaCl2 a white precipi- tate insoluble on boiling : Presence of S04 If none of the substances mentioned in the above table have been detected, test for A1203 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 Al203. If A12Os is not found fuse some of the substance in a clear bead of NaAmHP04, it floats undissolved: Pres- ence of Si 02. Proceed to (369 6). 2. The substance is dark-colored. (See 367, 2.) Place the substance on a piece of platinum foil and heat the foil strongly on its under surface by the blow- pipe flame : The substance burns away slowly but completely: Presence of C. The substance does not burn away; place upon it three or four times as much powdered NaaCO, and KNOj, and fuse for some time. 1. The substance dissolves, forming a yellow mass when cold :—Presence of Crf\. 2. The substance remains undissolved as a dark- brown powder, and the mass on cooling is white: — Presence of FtOt* Confirm by boiling the mass with water, filtering and fusing the brown residue into a borax bead (100). 3. 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 by (368 when heated: II), and another portion for Presence of S. Br and I by (369 a). Note.—If the substance sublimes en- tirely it consists only of sulphur. * FeCr204 shows both reactions 1 and 2, since it contains both Fe and Cr. 369.] ANALYSIS OF INSOLUBLE SUBSTANCES. 221 369. Fuse a portion of the substance, mixed with two or three times as much fusion mixture, for several min- utes on a piece of platinum foil (or if Pb is present, in a porcelain crucible) in the blowpipe flame; boil the cool mass with water until only a white powder remains undis- solved, filter or decant: Filtrate: acidify with HC1 and Residue: after washing several add BaCl2, a white precipi- times with boiling water dis- tate which does not disappear solve it in a little hot HC1 and on boilin'?: examine the solution for the Presence of 04, a yellow precipitate : Presence of Pb. Since a nitrate was found in the preliminary examina- tion, its presence was confirmed by adding strong H.jS04 to the aqueous solution of the substance, and pouring solution of FeS04 carefully upon the cooled liquid in a test-tube; a brown ring formed on the surface of the acid : Presence of NOv Also some of the solution when heated with Cu and strong evolved reddish-brown fumes: Presence of NOy Found: Pb,NOv 226 EXAMPLES OF ENTRY D. A white powder emitting no smell, given for An- alysis. Boiled some of the powdered substance with water, it did not dissolve : added a few drops of strong HCl 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 crys- tallization, etc. 2 Dipped a moistened loop of pla- tinum-wire into the powdered substance, moistened the powder with strong HC1, and held it in the Bunsen flame. No flame coloration, . Probable absence of K, Na, Ba, Sr, Ca, Cu, etc. 3. Heated a portion of the powder st rongly on charcoal in the inner blowpipe flame. The substance did not fuse. A white luminous resi- due, which, when moistened on red lit- mus-paper, showed an alkaline reaction, Absence of alkali salt. Presence of Ba, Sr, Oa, Mg. Examination of the Solution To a portion of the HC1 solution added H2S water; no precipitate:—Absence of Group II. To another portion of the HCl solution added AmCl and AmHO in excess, a white flocculent precipitate; then added Am2S, the color of the precipitate was un- changed. To a few drops of the HCl solution added KHO 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, Ca, Mg as phosphate, oxalate, etc. Added a few drops of the original HCl solution to some AmHMo04 solution in a test-tube, and warmed gently, a yellow precipitate:—Presence of POv To another portion of the cold HCl solution added AmHO, drop by drop, until a precipitate formed which did not dissolve when shaken, then added HA until this OF RESULTS OF ANALYSIS. 227 precipitate dissolved when the liquid was well shaken. Some small crystals of NaA were then dissolved in the cold liquid by shaking it, and Fe2ClB added until the liquid appeared red ; it was then boiled and immediately filtered. To the filtrate Am HO was added in excess (no precipitate), then AinaC03, a white precipitate formed:— Presence of Ba, Sr, or Ca. Filtered and dissolved the precipitate by pouring upon it a few drops of boiling HC1; dipped a loop of plati- num-wire into the solution, and held it in the Bunsen flame, a reddish 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 15a 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, P0V E. A white odorless powder given for Analysis. Boiled a portion of the substance with water, it did not dissolve: added HC1 and heated again, it dissolved completely (absence of Group I) without effervescence. Preliminary Examination. Experiment. Observation. Inference. 1. Heated a portion in a small dry test-tube. The substance blackened slightly; it evolved C09 which turned a drop of lime-water milky. The residue in the test-tube effervesced 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 the Bunsen flame; then moistened witli 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 when moistened on red lit- mus-paper, turned it blue. Presence of Ba, Sr, Ca, or Mg. 228 EXAMPLES OF ENTRY Examination for the Metal. Added to a portion of the HC1 solution strong H2S- water. No precipitate: To another portion of the HC1 solution added Absence of AinCl then ArnHO in excess, a white precipi- Group II. tate formed; added Am2S, the color of the precipitate remained unaltered. To another portion of the solution added KHO, drop by drop, until a precipitate formed, then more KHO and boiled ; a white precipitate insoluble 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 preliminary examination, a portion of the orig- inal substance was heated on platinum foil, then dissolved in HC1, and to the solution ex- cess of Am HO and of Am2C03 was added. The liquid was warmed and put aside till the precipitate subsided, then the liquid was de- canted and the precipitate dissolved in a few drops of HOI. A platinum wire dipped into this HC1 solution gave a red flame coloration, appearing dusky green through the indigo-prism:—Presence of Ca. [Confirmed by another portion of the HC1 solution giving a white precipitate with excess of Am HO and Am2C204 ] The presence of C204 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 flame, showing presence of C02 and CO :—Presence of C2Ot. Found Ca, C204. OF RESULTS OF ANALYSIS. 229 F. A yellow metallic-looking substance given for An- alysis. Preliminary Examination: Experiment. Observation. Inference. 1. Heated a portion of the substance strongly in a small tube closed at one end. A yellow sublimate form- ed, which melted into brown drops; a smell of burning 8 was evolved, and a piece of paper dipped into KaOra<), so- lution, 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. Strong smell of burning S. The residue fused into a dark-colored globule, which, when cold, was strongly at- tracted by the magnet, Presence of S. Probable presence ef Fe. 3. Heated a fragment strongly in a glass tube, open at both ends, and held oblique- ly in the flame. A gas was evolved with a suffocating smell, and which turned KQCr,0, paper green SO, from combustion of S. Solution of substance. Warmed the powdered substance with a mixture of strong HNOs and HCl, it dissolved completely; boiled down in an evaporating-dish, adding strong HCl 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: The solution be- To another part of the solution added AmCl, came colorless, then excess of AmHO; a brown flocculent and white S was precipitate formed, probable presence of precipitated : Probable presence of a ferric salt. Fe'"; then added Am2S, and heated; the precipitate became black, and on settling left a yellow solution :—Absence of Ni. Confirmed the presence of Fe by adding to a fresh part of the original solution K4FeCv6 solution, a dark-blue precipitate:—Presence of Fe'". 11 230 EXAMPLES OF ENTRY 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 SO 4 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 HNOa 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 consist of one of the following substances: BaS04, SrS04 (CaS04), PbS04 (PbCl2), AgCl, Si02, A12Os, Sn02, Sb204, CaF2. Preliminary Examination: Experiment. Observation. Inference. 1. Took some of the pow- der up with a loop of moist platinum-wire, ig- nited it strongly in the inner blowpipe flame, moistened it with HC1, and held in the Bunsen flame. A yellowish-green color- ation. Presence of Ba. 2. Fused a portion with NaaCOs on charcoal in the in tier blowpipe flame, placed the cooled mass on a bright shiling, and moistened it with a drop of water. A black stain on the coin. Presence of S. Examination of the Solution. Fused some of the powder with fusion mixture on platinum foil: boiled the cold mass with water, filtered. OF RESULTS OF ANALYSIS. 231 Filtrate, made acid with HC1 and added BaCl2, a white precipitate, which did not disappear on boiling the liquid : Presence of SOv The residue on the filter was well washed with boiling water, and boiling dilute HC1 poured upon it, it dis- solved completely: Absence of Group I. To a portion added strong HaS-water and heated: No precipi- tate. Absence of Group II. To another portion added AmCl, then AmHO 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 AM,( :0, 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, S0V 232 ANALYTICAL COURSE AND TABLES. [370. SECTION VI FULL ANALYTICAL COURSE AND TABLES. After having tried the reactions for the members of the analytical groups, and learnt for each group how to detect its members occurring singly or two or more to- gether, solutions containing a single metal 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 p. 186. HC1, which is the first reagent added, precipitates only Group I, leaving Groups II, III, IV, and V in solution; hence, if a precipitate is obtained on adding excess of HC1, after filtering it off any member or mem- bers 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,* mem- bers of Group II alone will be precipitated and may be filtered off; the filtrate,* after removal of H2S and oxi- dation of any Fe present by boiling with HNOs, may be mixed with AmCl and excess of ArnllO ; the Am HO will precipitate any members of Group III a, Group III B, and Mg remaining dissolved by the AmCl; the addition of AmsS to the filtrate* will separate Group III b as sulphides. Group IV is precipitated from * Or solution, supposing no precipitate to have been obtained, and filtration therefore to have been unnecessary. 371, 372.] ADDITION OF REAGENTS IN EXCESS. 233 the filtrate* by the last group-reagent Am2C03, and the filtrate* is examined 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 precipitate 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 process 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 ex- ample with HjS and AmHO. In other cases the excess is seen by the color of the filtrate, as with yellow Am2S for example. 372, Since certain organic substances hinder or pre- vent the precipitation of the members of Group III a by AmHO, it is necessary, if the preliminary examina- tion has shown the presence of organic matter, to de- stroy it by evaporation and ignition before proceeding to precipitate Groups III and IV; evaporation to dry- ness and gentle ignition are also necessary to separate Si()2, which if remaining in solution might be mistaken for Al2IIo6. But if it is known that neither organic substances nor Si02 are present, a considerable saving of * Or solution, supposing no precipitate to have been obtained, and filtration therefore to have been unnecessary. 234 preliminary examination [373-375. time may be effected by boiling the H2S filtrate until it no longer smells of H2S, then continuing to boil for several minutes after adding a few drops of strong HN03; this process may replace the evaporation to dryness and ignition. 373. The ordinary method of analysis drawn out in the general table and in the tables for examination of the group precipitates will present little difficulty if the directions therein given are strictly complied with. Table III c will perhaps be found a little 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 con- siderable proficiency has been attained. 374. It will be seen that the full course of the 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 solu- tion ; 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 student will do well to examine a few solid substances for metals and acid radicles by the tables given in para- graphs 387-418.* 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. * For examples of substances to be analyzed by the Preliminary Examinations, see paragraph 538. 376-379.] OF SOLID SUBSTANCES. 235 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 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 experiments; 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 indicated by large type letters, the subsidiary divisions are marked by small numbers, and the individual results are simply placed in succession in a vertical column. Occasionally an observation is made which it is advisa- ble to confirm by an additional experiment: this “ con- firmatory” test is then entered in the first column, just below the observation to be confirmed, and is marked “ confirm3'*” 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 exam- ination 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 explana- tion 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. Simple Substances, detection of Acid Radicles and Metals by Preliminary Tests and by Examination of the Solution. 379. After having become familiar with the prelimi- nary examination of solid substances the student may 236 ANALYSIS OF COMPLEX SUBSTANCES. [379. analyze some simple 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 pres- ence of any particular metals or acid radicles, but also the absence of all other commonly occurring metals and acid radicles. 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 Group III A and III B should not be present together in the same solution, also substances containing organic matter and Si02 should be avoided ; the examination of the filtrate after passing HjS 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. 380-381. ANALYSIS OF COMPLEX SOLIDS. 237 GENERAL COURSE OF ANALYSIS FOR SOLID AND LIQUID SUBSTANCES. The substance given for analysis* will be either a liquid or a solid, since the analysis of gases forms a department 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 tests (304 or 306); 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. Solid substances require to be dissolved before they can be fully analyzed ; H20, HC1, HNOa and aqua regia are the solvents usually employed. A. THE SUBSTANCE IS A LIQUID. 380. 1.—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). (turningblue litmus red). (turning red litmus blue). Absence of acids and alka- lies and of salts with acid or alkaline reaction. The salts of Ag and Mg and certain salts of Am, Na, K, Ba, Sr, and Pa are the only neu tral solu- ble salts. Presence of an acid, or salt with acid reac- tion. Presence of a hydrate of Am, Na, K, Ba, Sr, or Ca, or of a salt with alkaline reaction. 381. 2.—Evaporate a few drops of the liquid upon a piece of platinum foil or a piece of thin glass,f smelling it occasionally: * For examples of substances to be analyzed, see par. 539. f A piece of the side of a broken flask will serve well. 11* 238 ANALYSIS OF COMPLEX SOLIDS. [382, 383. No residue is lejt. A residue is left:—Examine the liquid by The liquid must consist of some vola- the further preliminary tests in (334; or evaporate a portion of the solution tile substance, probably of water, to dryness in a porcelain dish, avoid- either pure or containing certain ing heating the substance after it is gases or volatile substances dis- dry; and examine it by the prelimi- solved in it (e. g , Nil,, IIC1, Br, etc.), nary tallies for metals and acid radi- which are detected by their smell, cles (387-418). by the action of the liquid on litmus- paper, or by special tests. If the Examine the larger portion of the re- liquid has no action on litmus, no maining solution for metals by the smell, and leaves no residue on evap- general table which follows (419), and oration, and is tasteless, it is pure the remainderof the solution for acid water. radicles by (440 el seq ). B. THE SUBSTANCE IS A SOLID. 382. B. a. It is not a Metal. Finely powder it in a mortar, using an agate mortar if the substance is very hard. A part of this powder is examined by the preliminary tables for metals and acid radicles (387-418). 383. A large part of the remainder* is boiled in a flask or boiling-tube with distilled water, if it dissolves, see (384): if the powder does not dissolve, allow the liquid to stand still until the undissolved portion has settled, then decant through a filter: Filtrate:—It is usu- ally possible to tell whether anything has been dissolved Residue in flask:—Boil with dilute HC1 (385), allow any residue to settle, decant through the filter used above, and boil the residue with strong HC1, let settle, decant through the filter: serving whether it Filtrate. Residue:—Heat with dilute.then with strong UNO,, as was directed above for HC1; de- upon litmus-paper. cant: If there is any doubt, try whether Filtrate. The residue may be warmed for a residue remains when a few drops of strong UNO. with three are evaporated: also. times as much HC1; if this whether Na,COa does not dissolve it, decant causes any preeipi- the acid mixture. tate. It none of these tests proves the presence of dis- Residue: Washwell solved matter, the with water, dry, water solution may and examine as be neglected. directed (475 et If anything is in so- seq.) for sub- *lution, it is kept stances insolu- and marked. ble in water and Solution I. Solution II. Solutionlll. Solution IV. acids. * If the whole of the substance left after completing the Pre- liminary Examination has to be employed in making the solution, 384, 385.] SOLUTION OF A SOLID. 239 384. If at any of the preceding stages the substance dissolves entirely, proceed at once to examine the solu- tion by the General Table (419). The Solutions I, II, III, IV, need rarely be examined separately; a general method is to add to I some IIN03 (see 420), and then some HC1 to the clear liquid; add also to the HN03 solution (III) some HC1; any precipitate thus caused by HOI is examined by Table I, and any precipitate caused then on mixing the solutions I, II, III, IV, is examined by (475) as an insoluble 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 HN03 as much as possible, then dilute with dilute HC1; any precipitate caused bv HC1 being examined by Table I. On cooling the hot IIC1 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 of the crystals a yel- low precipitate forms, it shows the presence of Pb. 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 at once boiled with aqua regia for a few minutes, then filtered: the residue is examined as a substance insoluble in water and acids (475 et seq.). and the filtrate is evaporated nearly to dryness: dilute BCI is added, and the solution examined by the General Table (419). IIX03 seldom requires to be used in dissolving a sub- stance, and when necessary should be employed only in small quantity, since it is liable to cause a precipitate of S from H2S (423). 385. Any changes which occur whilst preparing the solution should be noted down ; notice more particularly whether any gases are given off on heating with HC1; 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 the method given below must be employed; if, however, plenty of the substance is in hand, the method given under (332) may be used, the process of solution will thus be much more rapidly executed. 240 PRELIMINARY EXAMINATION FOR [386,387. radicles (411). If the gases come off from the aqueous solution on adding HC1, or on mixing the HC1 and aqueous solutions, they must have been present combined with metals as soluble salts, probably salts of alkalies; if they are evolved on treating the residue insoluble in water with HC1, they were present as insoluble salts. 386. B. b. The Substance is judged from its Metallic lustre to be a Metal or Alloy. Examine it according to the directions (467). 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 substance: whether it is crystalline or amorphous ;* its hardness,f color, smell, and anything which strikes you on a careful examination aided by a pocket lens. The following three experiments, together with some confirma- tory ones (marked “ Confr.”) when necessary, are then to be tried on small quantities of the finely powdered substance, and the results obtained noted down. For a further explanation of the form of the table, see paragraph 376. * 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. f 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). 388, 389. METALS IN COMPLEX SUBSTANCES. 241 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 and 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. H changes color: Yellow, hot while, cold. Yellow, brown, “ yellow, “ Yellow-brown, “ yellow, “ “ The substance blackens— a. Emitting a smell of burning. The black carbon may be burnt off by strongly heat- ing on platinum foil with the blowpipe flame. ZnO. PbO Sn02 or Bi203. FeaO*. 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, crystalline (sparkling) sub- limate. White, non-crystalline sublimate. Black sublimate, becomes red when rubbed. Yellow sublimate. Salts of alkalies or certain salts of the alkaline earths. Compounds of Am, As, Hg; or free S or I. HgCla, As903. Probably Am salt. HgS. f AsjSj. -< Hgla becomes scar- ( let when rubbed. 389. Confirmatory. — If a sublimate has been ob- tained, but not other- wise, heat another por- tion of the substance, mixed with about three times as much NajCO, in tine dry powder and a little KCy, in a tube closed at one end, in the manner described under par. 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. 242 PRELIMINARY EXAMINATION FOR [390-395. Experiment. Observation. Inference. 390. Confirmatory.—Mix also some of the sub- stance with soda-lime in a mortar and moisten ; or pour a little strong KHO solution upon it, and heat to boiling. NH3 is given off, known by its smell, and by turning moist red litmus-paper blue or turmeric- paper brown. Note.—The change in color is only a trustworthy indication if it occurs very soon, as the NH, in laboratory air often causes it to occur after a time. Sublimate of reddish drops, \ which are yellow when cold. / Violet vapor, cooling to blackish crystals. 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. Presence of NH,. S, free or from certain polysulphides. Presence of I. Presence of water, ab- sorbed or combined. Water of crystalliza- tion. Borax and certain bo- rates, alums, and phosphates. 391. Confirmatory. — Ex- amine the drops of water on the sides of the tube with blue and The water is alkaline. Probably NH, com- pounds. red litmus-papers. The water is acid. 5. Gas or vapor is given off.* a. It is without smell. Presence of volatile acids, e. g., UNO,, HC1, HsS04. 392 Confirmatory. — In- It burns more brightlv, and if in- 0, from chlorates, ni- troducea burningsplin- trodueed with a spark at the trates, peroxides, etc. ter of wood into the end is inflamed. tube. The flame is extinguished. CO, or N. 393. Confirmatory. — In- troduce a glass rod, The lime-water turns milky. CO, from carbonates or oxalates. drawn out if necessary, The lime-water does not turn N (from AmNO, prob- and moistened with lime-water, into the tube. milky. b. The gas or vapor has a smell. ably). 394. Confirmatory. — In- Smell of burning S. SO, from combustion troduce a glass rod or The K2CraO, turns green ; moist of free S, or from acid slip of paper moistened blue litmus is also reddened by sulphites, hyposul- with K,CraO,. the gas. Red nitrous fumes are given off, known by their peculiar smell, and by not coloring starch paste orange red. Smell resembling Cl: phites, reduction of sulphates or oxida- tion of sulphides. Nit rates of heavy met- als (e. g., of Pb, Bi, Hg, etc.). 395. Confirmatory. — In- Yellowish gas, which bleaches Cl from certain chlo- troduce a glass rod car- rying a piece of moist litmus. moist litmus. rides. * This will usually be shown by effervescence of the substance, or the gas or vapor is detected by the color or smell; but the gas or vapor is often only found on testing for it specially by (392) and (393), 396-399.] METALS IN COMPLEX SUBSTANCES 243 Experiment. Observation. Inference. 396. Confirmatory. — In- Brown vapor, which colors the Br from certain bro- troduee a glass rod with moist starch powder orange red. mides. moist starch powder on Violet vapor, which colors starch I, free or from cer- its end, obtained bv powderfor better, starch solution) tain iodides. wetting a glass rod and blue. dipping it into starch c. The gas burns at the mouth of the powder. tube with, a:— Pale grayish-green flame. NH, probably from strongly heated NII.NO,. Bright white flame. PH,, probably from a hypophosphite; the unburnt gas smells of garlic. Purple flame. Cy, from a cyanide, probably HgCy2. 397. Exp. II. — Dip a. 1. The substance colors the flame: moistened loop of plati- Intense yellow. Na. If a violet or red nmn-wire, which gives color is seen on ex- no color to the Bunsen amining the flame flame, into the sub- through cobalt stance, and hold the glass or the indigo- loop with the adhering prism, either K or powder near the top of Sr, or both, are also the Bunsen flame or in present. the inner blowpipe flame. Then moisten Pale violet, reddish-violet through 1 K. with a drop of strong cobalt glass or indigo-prism. J IIC1 and heat again. Continue the heating for some time. Yellowish-green. Ba. Certain other substances also give Note.—If silicic acid is green colorations. present, the colorations Crimson, deep-red through cobalt 1 Sr. forKand Nausuallyshow glass or indigo-prism. J onlv after ignition of the Oranae-red. dingy green through I Ca. powdered substance with indigo-prism. j powdered CaSO,. Green. Cu,B./)s Cu show's green outside and blue in the centre, after being moist- ened with HC1. Blue. As, Sb, Pb, CuCl2, Cu Br, 2. The substance does not color Probable absence of the flame. the above sub- stances. 398. Exp. III.—Heat the a. The substance decrepitates NaCl and certain other substance in a small (crackles). crystalline salts. cavity scooped in a b. The substance deflagrates Chlorates, nitrates, piece of wood-charcoal, (causes charcoal to burn rapidly). etc. in the blowpipe flame. c. The substance fuses easily, and Salts of alkalies and is absorbed bv the charcoal, or certain salts of the forms a liquid bead. d. An infusible residue is left on the charcoal. alkaline earths. 1. The residue is while and very lumi- Probably BaO, SrO, nous. CaO, MgO, Al,0,, ’ ZnO (or SiO,). 399. Confirmatory. — Do- The paper turns blue, showing the taeh a portion of the residue to be alkaline. BaO, SrO, CaO(MgO). cool residue from the charcoal, place it upon a piece of red litmus- paper,and moisten with a drop of water. 244 PRELIMINARY EXAMINATION FOR [400-404. Experiment. Observation. Inference. 400. Confirmatory.—Mois- A blue residue, the color of which AlaO,(and some phos- ten the residue on the does not disappear with intense phates, silicates, charcoal when cool, heat. and borates). with several drops of A pink residue. MgO. Co(NOj)a solution, and heat again strongly in the outer blowpipe A green residue. ZnO. flame. 2. The residue is colored. 401. Confirmatory.—Heat a small quantity of the Color of bead. In outer flame. In inner flame. substance in a clear col- Green, hot. ( Bed or col-lld orless, j Cu. orless borax bead, first Jilue, cold. J in the outer, then in the Blue, hot and ) Blue, hot and 1 Co. inner blowpipe flame. cold. cold. / Violet, hot, 1 Yellow, cold. j Gray or opaque. Ni. Brown-red, hot i Yellow or color- V less, cold. j Green, hot ami 1 cold. J Fe. Green, hot and Green, hot and 1 Cr. 1 ) See (402). Mn. cold. Beddish-purple, cold. / Colorless, hot | 402. Confirmatory.—The hot and cold. and cold. J Light-yellow mass presence ot Mil andCr, on cooling. Or. if suspected, may be Blue-green mass on cooling. Mn. (See 406.) confirmed by tusingthe substance with some powdered Na*CO* and KNOton 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, Cu, Pb, Sn, also some of the sub- metallic state. (See 407.) Sb, Hi; [Co, Ni, Ke, stance, mixed or cov- Mn form oulv gray ered with powdered powders]. KCy and Na3<'<>, (or a. Without incrustation. Au, Ag, Cu, Co, Ni, K3< VV, on charcoal Fe, Mu. in the inner blowpipe [Brilliant white metal. Ag.] flame. [ Yeilow metal. Au.] Bed scales or globules. Gray powder, attracted by a magnetized knife-blade. Cu. Fe, Co, Ni, Mn. (See 407.) b. With incrustation: Globules. Incrustation. 404. Confirmatory. — He- While, malleable. None, or very Sn : differs from Pb tach several of the glo- slight. in beingdifficultto bules with the point of a knife,and strike them on the bottom of an in- verted mortar with the “ brittle. Orange, hot; 1 fuse into globules, and in not mark- ing paper. Bi. pestle: if they flatten to ye/low, cold, f a cake they are matte- “ malleable. Y-lloiu, hot and Pb. Tlie globules of able, if crushed to a powder they are brittle. cold. Pb differ from those of Sn by marking paper as Note.—The appearance black lead does, if and malleability of one taken on the point reduced metal is fre- of a knife. quently much altered by “ brittle; White, close to Sb. the presence of another giving white substance. metal. fumes. 405-409.] METALS IN COMPLEX SUBSTANCES. 245 Experiment. Observation. Inference. Globules. White or none. None. Incrustation. Yellow, hot; white, cold. Red-brown, easily volati- lized when heated in the flame. IFAiVe.and white fumes; smell of garlic. ] Zn. 1 j-Cd. | As. 405. Exp. IV. — Fuse On rinsing off the substance, the Presence of S, free some of the substance, coin is found to be stained black or combined. mixed with NaaC03. on (408). Also, if a drop of HC1 be charcoal in the inner placed upon the mass, a smell of H3s is perceived, and lead-paper is blackened. blowpipe flame pro- duced from a spirit- lamp; remove the fused mass when cold, place it on a bright silver coin, moisten with a drop of water, crush the mass, and let stand for several minutes. Note.—Since this reaction serves to detect S and sulphur acid radicles, it more properly belongs to the Preliminary Ex- amination for acid radicles. Notes to the preceding Preliminary Table. 406. The green color produced by Mn conceals the light yellow of Cr, but on boiling the residue with water it dissolves, giving a pink or purple solution, the color of which is best seen on filtering ; this color is due to the presence of KMn04, and shows Mn to be present. On acidifying this solution with HA and boiling again for several minutes, the purple color is destroyed ; and on filtering, the yellow color due to the Cr is seen : the presence of Cr may be further confirmed by the formation of a yellow precipitate in the acid solution on addition of PbA2. 407. The metal is best separated and examined by detaching the mass when cold from the charcoal, and powdering it by crushing in an agate 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 metal- lic particles alone are left in the mortar or watch-glass. 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 hot and blue when 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 examina- 246 PRELIMINARY EXAMINATION [410,411. tion, 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. 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 reactions may be more or less perfectly concealed or altered, hence failure in obtaining a certain reaction does not necessarily prove the absence of an acid radicle. Experiment. Observation. Inference. 411. Exp. I.—Treat some of the sub- stance with dilute HC1 and note the result, then heat (416;. One or more of the following gases may be evolved: A colorless gas without smell, which turns milky a drop of lime-water on the end of a glass rod. CO* from a carbonate. . A gas of suffocating smell, which turns a drop of K,Cr,0, solution green. Yellow S is precipitated at the same time. SO* from a sulphite. SO* and S from a theio- sulphate.* A gas with fetid odor which blackens a drop of PbAj solution, or a piece of lead-paper. (See 417.) H*S from a sulphide; or possibly from a sulphite or hyposulphite, if Zn or other reducing agent be present. Reddish fumes. N*Os from a nitrite. A yellowish green gas, of suffocating smell, which bleaches moist litmus- paper, is evolved: a. In the cold; and also evolved on adding HA. Cl from hypochlorites. 6. Only when heated. A colorless gas, smelling of bitter almonds. Cl from action of HC1 on oxidizing substances, e.g., MnO*, chromates, ni- trates, chlorates, Ac. HCy from a cyanide. * Formerly called a “ hyposulphite.” 412-414.] FOR ACID RADICLES 247 Experiment. Observation. Inference. 412. Exp. II.—Heat Any gas or gases evolved another portion in Exp. I will probably gently with strong HaSO«. be evolved also by strong H2S()4; no further atten- tion need be paid to them; but in addition to these one or more acid gases may be given off. A gas is evolved with pun- gentsmell,which fumesin the air, and renders milky HC1, HBr, HI, (HF)*from a drop of AgNO* solution chloride, bromide, iodide made acid with HNOa (fluoride). 1 The liquid does not be- Probably HClfrom achlor- come brown or violet or ide, confirmed by heating give off colored vapor with Mn03 and H3S04 when heated. when Cl is given off (418). 2. Brown vapors are given off on heating, which color a little moist starch powder, orange-red. Br from a bromide.f 3. Violet vapors are given off, when the mixture is heated, which color a drop of starch-paste blue. I from an iodide.f 4 A heavy fuming suffo- HF from a fluoride. eating gas is evolved, and Note.—The HF acting the liquid behaves as if the glass were greasy; on rinsing out the tube, and upon the silica of the glass evolves SiF4, which is de- tected by holding a moist- drying it thoroughly, the ened glass rod in the gas, inside is seen to be cor- SiOj is deposited as a ge- rodtd and dimmed. latinous film upon it. 413. Confirmatory — Drop into the hot liquid a few small pieces of copper. 5. The acid fumes are red- Presence of a nitrate. dish, usually seen only on Note.—If iodine is present heating after adding a few it must be separated by fragments of Cu. CujS04 (266) before a ni- trate can be detected. 414. Confirmatory.— A dark brown ringorlayer forms upon the surface of acid, best obtained on cooling the liquid by im- mersing the test-tube in water (or take some Presence of a nitrate. liquid), add about twice as much strong H2S04, cool, cold water. and pour solution of FeSO, carefully in upon the top of the acid liquid. 6. Greenish - yellow gas, smelling like Cl, and ex- Presence of a chlorate. ploding when warmed. Confirm by adding indigo solution and H3SOa to the colorless aqueous solution of the substance (252). For detection of a nitrate and chlorate when mixed, see (256). * HK would also render the drop milky by depositing SiOa from the SiF4, formed by its action on the glass, but it is distinguished by corroding the glass. (See 412, 4, note.) f Br and I may be more perfectly liberated by mixing the substance with a little MuOj before adding HjSOi and heating. 248 EXAMINATION FOR ACID RADICLES. [415-418. Experiment. Observation. Inference. 7. The substance changes from yellow to green, O being evolved, as is shown by a glowing taper. Presence of a chromate. 8. Yellowish - green gas, with suffocating smell, which bleaches moist litmus. Cl from a hypochlorite (detected already in 411), or from a chloride in presence of MnOa, etc. 9. The same gas as in 8, hut colored reddish - brown by nitrous fumes: A chloride in presence of a nitrate or nitrite. 9a. Or colored by CrOClj. 10. Substance does not blacken, but evolves CO (burning with a blue flame) and COa (turning a drop of lime-water milky). A chloride in presence of a chromate. Presence of an oxalate. 11. Substance blackens, and SOa is smelt. Presence of a tartrate. 415. Confirmatory.— Add a little alcohol to the substance and heat with HiSO,. 12. A smell of acetic acid (vinegar) is noticed. Strong fragrant odor. Ha from an acetate. Ethyl-acetate from an acetate. Notes on the preceding Table. 416. If HC1 hns 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 by fusing the powdered substance with two or three times as much fusion mixture in a covered crucible, boil- ing with a little water, and placing a drop upon a piece of bright silver (e. g., a silver coin), when a dark stain will be produced ; or by adding excess of an acid to the solution, when H2S will be evolved. Smaller quantities of S may be detected by tne forma- tion of a black color or precipitate 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 MnC2 evolve Cl when warmed alone with II2S04. 419.] ACTUAL EXAMINATION. 249 ACTUAL EXAMINATION FOR METALS. After the preceding Preliminary Examinations have been made, the substance is further examined in a more systematic manner in solution. This is often called “The Examination in the Wet Way.” 419. GENERAL TABLE FOR SEPARATION OF METALS INTO GROUPS BY GROUP-REAGENTS. Note.—If the substance for analysis be a liquid with alkaline re- action, it requires special treatment (see 420); if its reaction be neutral or acid, it may be at once examined as directed below. In this table (p. 250), and also in the group tables which follow, it has been supposed that all metals are present: if a metal or group of metals is absent, no precipitate will be produced when the reagent is added for its detection ; and hence no filtration is necessary, the solution being then treated as the filtrate. 250 TABLE FOR SEPARATION INTO GROUPS. [419. Add to the greater part of the “ original solution ”* (421), warm and filter : IICl; if any precipitate is produced, continue to add HC1 as long as it causes any further precipitate The precipitate may contain— The filtrate or solution, which must give no further precipitate on addition of several drops ot HU (423), is diluted w ith water (425), unless it is already dilute; then saturated with H,S by passing the gas through the solution)-(500 a), and warmed gently (42b and 426 a) and filtered. . _ _ Pbr]3—white. AgCl—white. HgjClrj—ivhite. (See 422.) Examine the precipi- tate by Table I (433). The precipitate may con- tain— 1 Insoluble Pbb-6/acfc 1 in KH0 [ and in CuS—black, \ » c CdS—yellow, J * ' SnS—brown, 1 SnS,—yellow, Soluble Sbj^j—orange, in KHO AssSj—yellow, [and in [Aia«,—black], Am,S. [PtS,—black], Examine the precipitate Boil the solution or the filtrate (which hasbeen diluted and had HaS passed again into it, to make suie that Group II is completely precipitated) in a porcelain dish until it ceases to smell of HaS (42/), then add a little strong HNO* and boil for several minutes, concentrating if necessary : J (If the presence of Si()a be suspected, or if organic substances are likely to be present (the presence of organic substances will usually have been indicated by the body blackening in Exp. 388) the solution must here be evaporated to complete dryness, and the residue gently ignited in the dish, then dis- solved (after cooling) by warming with a little strong HC1 and adding water; SiOa, if present, will remain undissolved (428)J. A If the presence of a phosphate is suspected, add a few drops of the acid solution to some solution in a test-tube, and warm gently ; a yellow precipitate shows the presence of a phosphate, and the rest of the solution must be examined by Table III d (466); if no precipitate is formed with AmHMo04, phosphates are absent. A , , . . , Add to the rest of the IICl solution (which has been freed from HaS as directed above) AmCl, heat it to boiling, then add Am HO in excess, boil again and filter off at once any precipitate which may form as quickly as possible, keeping the funnel closely covered with a glass plate (429): [Refer to par. 463, et seq.] t.y Table II (435). The precipitate may con- tain— Add to the filtrate or solution, which may be colored (430), Am,S in excess, boil and filter: Note.—1. This precipitate should not be examined at once,as possibly a precipi- tate maybe formed on boil- ing the filtrate, and this precipitate would have to be added to the above. Note 2.—Unless the liquid hasbeen sufficientlydiluted some of the above metals may be afterwards precipi- tated by Am,S in Group III, and cause much confusion. AljHos—almost colorless. C r, if 1 light-green. The precipitate may con- tain— ZnS—white. Add to the filtrate or solution, which must be distinctly yellow or brown (431), AmaCO,, warm gently and filter : Note.—The absence of Pb is not proved, if it is not precipitated in this group,as Pbf'lj is some- what soluble, and Pb maytherefore be found only in Group 11. tVj Hos-—redd ish-brown. Examine the precipitate by Table III a (436). M nS—light-pink. CoS—black. NiS—black. Examine this precipitate at once, by Table III b (437). Note.—If the filtrate is brown, Ni is often easily detected in it. (See 431.) The precipitate (432) may contain— BaCO,—white. SrCOj—white. CaCOj—white. Examine the precipi- tate by TableIV(438). The filtrate may con- tain Mg, K, Na. Examine by Table V (439). * Bv 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. t Instead of diluting and passing the gas, HaS solution may be added. . , , , .,,, % II silicates, phosphates, and organic substances are known to be absent, the following portion, inclosed in square brackets, may be omitted. 420-423 NOTES TO THE GENERAL TABLE. 251 420. If the liquid under examination is alkaline in reaction, before commencing to examine it by the General Table HN03 must be added in excess; if no precipitate forms, proceed at once to examine the liquid by the general table ; if a precipitate is pro- duced, more HNOs is to be added, and the liquid heated; should a precipitate still remain, it is filtered off and the filtrate examined by the general table, commencing with the addition of HC1. The precipitate caused and not dissolved by HNO, may be finely divided sulphur, separated as a white powder from a sulphide, or yellow from a theiosulphate ;* 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 H4S104 (gelatinous, .almost colorless), Sn02 (or metastannic acid, see 420 a), Sl>205, AgCl (all three white), SnS2, As2S3 (both yellow), Sb283 (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 insolu- ble in water and acids (475), and the aqua regia solution is added to the filtrate from the precipitate caused by HN03, any precipi- tate 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 precipitate, which becomes yolden-yellow when moistened with SnCl2 solution ; it is further recognized by its dissolving whilst being washed in the washing-water, but being reprecipitated when the washings run into the acid filtrate. 421. Even if I1C1 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 IIC1 precipitates (in addition to AgCl, PbCl2, Hg2Cl2) strong Ba solutions ; this precipitate how- ever disappears on diluting with water and heating, thus differing from the three chlorides mentioned above. 423. If HN03 or aqua regia has been used in dissolving the substance, or if the solution smells of Cl or SO?, it should be boiled down considerably until after adding HC1 and boiling, neither of the above gases is smelt; it is then diluted, and HaS passed 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 alter 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 reduces arsenic or stannic compounds to the arsenious 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 (un- like SnS) readily runs through the filter, and being yellow in color may be passed over as S. It will of course be necessary to Notes to the General Table. * Often called a “ hyposulphite.*’ 252 NOTES TO THE GENERAL TABLE. [424-428. 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 produced by boiling with H2S03 other than white sulphur, refer to (424). 424. Whilst boiling with H2S03 some H2S04 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 precipitate thus formed by H2S03 by Table G (434). 425. On addition of water, Bi, Sb, Sn may give white precipi- tates of their oxychlorides; these precipitates may be disregarded, since H2S readily converts them into sulphides. 426. H2S often causes a fine white precipitate of S, owing to the presence of certain oxidizing sub-tances, such as Cl, HN03, HC103, H2Cr04, H2Mn04, HMn04, H2S03, Fe2Cl6. etc.; this precipitate is known by its perfect whiteness, and by not being separable by standing or filtration, it may be neglected ; great care must, how- ever, be taken not to pass over SnS2 as S; it resembles S in run- ning 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 H2S, show characteristic colors (149, 144); a so- lution colored reddish-yellow by H2Cr04 becomes green; and a solution colored green by H2Mn04 or purple by HMnG4 becomes colorless. 427. If on boiling the filtrate or solution after passing H2S a yellow precipitate forms, this shows the presence of an arsenic or a stannic compound ; in this case pass H2S into the boiling-hot liquid as long as it causes any further precipitate, filter off and add this precipitate to any precipitate already obtained by 1I2S to be examined by Table II. 428. Other substances may be present in this residue besides Si02, but Si02 is distinguished from them all by readily dissolving in hot KHO solution. The other substances which may remain undissolved by HC1 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 de- tected 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, appear- ing red through the indigo-prism, prove the presence of Sr ; a yel- lowish-green flame coloration shows Ba. A less ready method of detecting Ba and Sr is to dry the insol- uble 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 examine it by Table IV (438) for Ba and Sr only. 429-432.] notes to the general table. 253 429. Mn and Zn are very liable to be precipitated with Fe2Ho6, Al2Ho6, Cr.2Ho6 The precipitation of Mn is partly prevented by keeping the liquid from exposure to the air after adding AmHO : but the further precaution should he taken of dissolving the pre- cipitate produced by AmHO in HC1 and reprecipitating it by AmHO, then filtering and adding the filtrate to the original fil- trate from the Group III a precipitate: this treatment of the pre- cipitate should be repeated several times, if small quantities of Zn or Mn have to he 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 examined by Table III c (464, 465). 430. The filtrate or solution, after adding AmCl and AmHO, may be colored blue by Ni, or reddish-violet by Cr2Ho6, which is dissolved in the excess of AmHO. The Cr2Ho6 must be removed before proceeding to examine for the three remaining groups ; it is readily separated as a pale-green flocculent precipitate by boiling the liquid for a short time in a porcelain dish, adding a little more AmHO if the liquid does not smell of Nllj after 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 V, 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 brown or dark-colored tiitrate shows that Ni is present,* some of the NiS precipitated by Am2S 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, the colorless filtrate examined by the General Table for Groups IV and V, and the black precipitate tested for Ni by fusing a por- tion 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 be- comes gray and opaque in the inner flame, Ni is certainly present, and need not be further tested for in Table III b. 432. Pa rt 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. * If Groups III a and III B have been precipitated together bv ArnCl, AmIIO, and Anr2S added in succession (459) the brown coloration of the filtrate may also be due to Cr2Ho6: on boiling the filtrate colored by Cr2Ho6 in a porcelain dish for several min- utes, pale-green Cr2Ho6 is precipitated, which cannot be mistaken for black. N iS. 12 254 TABLE I. — SILVER GROUP. 433, 434. The precipitate produced by HC1 may consist of PbCl2, AgCl, and Hg'2Cl2; the precipitate on the filter is washed live or six times with boiling water, the first portions of the washings being kept apart : 433. TABLE I.—SILATER GROUP. The first portions of the washings may con- tain PbCls in solution, which if present in any quantity will be Residue: pour upon the precipitate on the filter some hot AtnHO; when this has run through, heat it again, and pour it once more upon the filter : Filtrate: add HN03 Residue on the filter is black; crystals on cooling. until the liquid is dry at a gentle heat (best In acid: white precip- a steam bath), scrape the pre- itate, uniting into cipitate off the filter, mix curdy particles with some dry NaQCO,, and ings KjCrO,; a yellow precipitate, readily when shaken or heat in a small tube closed at boiled: one end, observing the precau- soluble in KIIO: Presence, of Pb. Presence of Ag. tions in the note to par. 147. Small globules of llg form on the sides of the tube, often appearing only when the in- side of the tube is rubbed or examined with a lens: Presence of llg' (Mercurosuin). 434. Table G.—Examination of Precipitate formed on Boiling the HOI Solution with H2S03. (See par. 424. p. 252.) The precipitate produced by H2SO<3 may contain Au, PbS04, BaS04, andSrS04; the last three substances are perfectly white, and Au, if present, is therefore usually seen by coloring the pre- cipitate brown or black; the Au is also usually visible during precipitation by H.2S03, nr alter the white sulphates have subsided, since it colors the liquid blue by transmitted, and reddish by re- flected light. Ba and Sr can often be at once detected (if present) by taking a little of the moist precipitate on a loop ot platinum wire, heating in the inner blowpipe flame for some time, moistening with HC1, and examining the flame coloration ; but a more reliable method of proceeding is the following: liinse the precipitate into a small porcelain dish, using as little water as possible ; dissolve in the liquid a small crystal of H2L', or add a few drops of strong HA; then add AmHO, until it is just in excess, and boil for a short time; let stand and decant through a filter : Solution may con- tain PbS04; add HA in excess, then KaCr04; a yellow precipitate soluble in KHO: Presence of Pb. Residue: pour upon the residue in the dish a little HC1 and a few drops of HNOj heat to boiling, let stand, de- cant into a porcelain dish : Solution: boil until the smell Residue: dry by gently heat- of Cl is removed, add sev- ing the dish, fuse with fu- eral drops of fresh FeSO, sion mixture on platinum solution; blue coloration foil, and examine the mass and reddish precipitate: for 15a and Sr as directed _ , in the last par. of (428). Presence of Au. 435.] 255 TABLE II. — COPPER AND ARSENIC GROUPS. 435. TABLE II.—COPPER AND ARSENIC GROUPS. The precipitate produced by H2S in the HC1 solution, after having been well washed with hot water until the last few drops of the washing water, collected in a test- tube, give no precipitate or only a very slight milkiness on addition of AgN03, is removed from the filter and boiled with KHO or a small quantity of Am2S,* and filtered: 435 a. Group II a.—Copper Group. The Residue may contain HgS, PbS. KijSV CuS, CdS. After having vi ashed the precipi- tate and allowed it to drain. remove it from the into a porcelain dish (26 d), pour upon it strong UNO, sufficient to cover it completely, and heat gently as long as anv red fumes come off, adding more strong HN()3 if necessary to prevent evapo- ration to drvness. Boil off nearly all the acid, add a little water and dilute lUSO,, let stand for some time, stirring occasionally, and filter: Residue may contain HgS Filtrate may contain Bl, Cu, Cd. (black), Yh'SOt'whiJe), (note 1). Add AmHO in excess, boil and filter: R< move the precipitate into a [Note.—A blue coloration shows presence of Cu.] porcelain dish, using as little water as possible; add a little Preci)dtale (not Filtrate: Add HCI until the liquid is HA, then AmIIO in excess, easily seen in acid, then pass HaS to saturation, uoii ana niter: dark-blue solu- filter and wash quickly, keeping tions): wash the filter covered with a glass plate; with hot water, dissolve off the remove the precipitate into a small porcelain dish, pour upon it some gentle heat [best in the steam oven]. Scrape the dried resi- due off the filter (note 2), and heat it, mixed with dry Naa' 0,, in a small igni- tion tube; glob- ules of Hg lorm Add HA in excess, then filter by pouring upon it a few dilute HjS04, boil and filter through a covered filter (note 3): Kat,r04, a drops of boiling dilute HCI: pour this solution in- to a large quan- tity of cold dis- tilled water, a milkiness ap- pearing at once or after stirring, and letting yellow pre- cipitate : Presence of Pb. Residue: Dissolve by pouring a lit- tle boiling HNO, upon the filter; add to the solu- tion AmHO in excess, then HA in excess, and a few drops of Filtrate: Add much water and pass H,S for some time (or add much Has- water), a yel- low precipitate shows: stand for some Presence of Cd. time, shows K4FeCye; a choc- olate-red precip- itate shows: when rubbed or Presence of Bi. [Note.—If this precipitate is by a lens: [Note,—A precip- Presence of Cu. dark-colored, CuS is present (see Presence of Hg" note 3); filter it (as Mercurieum). off, boil it ■ once more with HaS04; filter and test the possibly appear here as’ white pre- filtrate by H,S, as above, for Cd.J cipitates, and be mistaken for Bi.] * If traces of Cu have to be tested for, Na2S should be substituted for Ani2S, since CuS is somewat soluble in Am2S. 256 TABLE II.—COPPER AND ARSENIC GROUPS. [435 b. Group II b.—Arsenic Group. The filtrate may contain Asaa3 SbjSj, SnH, (SnS) [Au.,ss, PtSj], Add to it HC1 until it is acid; the above sulphides if present will be reprecipitated ; filter. [Nate.—A mere milkiness due to precipitation of S may be disregarded. If KHO or NaHO have been used above to dissolve th se sulphides, must he passed into the acid filtrate, and any further precipitate thus obtained must be added to «lie precipi- tate obtained on acidifying; this precaution is unnecessary if Aid9S or NasS has been employed.] The following method of examining the precipitate may then be employed (see note 4, below): 435 6- Remove the precipitate from the filter, using as little water as possible, into a porcelain dish ; add a little strong HC1 and heat, occasionally dropping in a crystal of KClOj until the precipitate dissolves entirely, or leaves only a slight residue of sulphur. Heat this solution just short of boiling (note 5i 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 Utile strong HC1, and cause the gas, after passing t hrough some PbA, solution (see caution 181), to bubble through some AgN<'* solution contained in a broad test-tube. As soon as the evolution of gas slackens, drop in more Zn, unless some remains undis- solved in the flask; and as soon as the gas ceases to come off (some Zn still remaining undissolved), the test-tube containing the AgNOs solution is removed; if any black precipitate has formed in this solution, it must be tested as below; if the liquid has remained clear and colorless, it may be rejected, since As and Sb are absent. Residue in the flask may con- sist of Sn (Pt,Au), and ex- cess of Zn; remove any de- posit of Sn 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; boil the residue with a little strong HC1 in a test-tube, then quickly dilute, decant (note 7), and add HgCls to the solution ; a white pre- cipitate (becoming black with AmllO) shows: Presence of Sn (note 8). To the liquid in the test-tube add several drops of AgNO* solution ; filter : Precipitate: Wash well with Filtrate: Dilute several boiling water until HC1 drops of Am HO large- gives no milkiness with the ly in a test-tube, and last few drops of the wash- add this liquid drop by ing-water, then pour upon drop to the filtrate; a the filter a little boiling di- light-yellow precipi- lute HjT solution; boil it tate which settles into and pour it again through nocks on shaking the the filter; repeat this several liquid, shows: times, then add to the solu- Presence of As (note 8). tion HC1 and pass H,S; an orange-red precipitate shows: Presence of Sb. Note.—This precipitate is often only seen on settling from the yellow liquid. Note 1.—A v)hite residue does not necessarily show the absence of Hg. 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 Na2C03 For the precautions requisite in performing this test see par. (147). Note 3.—Unless this precipitate is filtered in a covered funnel, washed quickly, and examined at once, CuS is liable to be oxi- dized and to pass into the filtrate as CuS04; it then discolors the CdS precipitate, or may be entirely overlooked if present in small quantity. Note 4.—The detection of As, Sb, Sn by the method given in 436.] TABLE III A.— IKON GROUP. 257 (435b) is very trustworthy and delicate (208); it is excelled in these respects by the 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 SnCI4 might be volatilized if present. Note 6.—In this solution As and Sn will be present as stannicwm and arsenicum, 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 quan- tity. After warming until the liquid ceases to smell of Cl, add HjS03 drop by drop, until the liquid after being warmed for a short time smells of S02; then heat it short of boiling until the .-mell of S02 is removed, and pour (through a filter, if necessary,) into the H apparatus. Great care must be taken to remove the S02 entirely, else Sb and As may remain as sulphides in the H apparatus. Note 7.—A residue here will contain Au or Pt if they are pres- ent ; if they are to be tested for refer to (473 and 474). Note 8.—The precipitation by H2S in the General Table will often show in what condition As or Sn were present (427); further distinctive 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, Cr2Ho6, Fe2Ho6; the color of the precipitate will usually show whether it contains any quantity of Fe2Ho6 (red- dish-brown), or Cr2Ho6 (pale-green), since Al2Ho6 is colorless. Dissolve the precipitate by pouring upon the filter a little boiling dilute HC1, add to the solution pureNaHO in excess, boil for some time and filter: 258 [436. TABLE III A.—IRON GROUP. 1. Filtrate may contain AlaHo6 dissolved in excess of NaHO. Add HC1 gradually to the liquid, shaking meanwhile with a small piece of blue litmus-paper; just as the liquid becomes neutral, a colorless gelatinous precipitate • will form, should A1 be present. If acid is added in excess, this precipitate dis- solves, hut reappears on adding ArnHO in excess. The appear- ance of this precipi- 2. Precipitate may contain Cr,Ho, and Fe„HoG. Dry upon the iilter, carefully avoiding charring the paper; when sufficiently dried the substance will have shrunk considerably into small, hard, dark-col- ored pieces; detach these from the filter and fuse them with a little solid NaaOO, and KNO, upon a piece of platinum foil with turned-up edges, and either supported upon a pipeclay triangle or held in the Bunsen flame by crucible-tongs. Continue the fusion by heating the undersurface of the foil in the blowpipe flame as long as any frothing occurs; then allow to cool; a yellow mass indicates the presence of Cr (note 1). Boil the platinum foil in a small por- celain dish with water until the substance is entirely dissolved or only a dark-brown powder (FegO,) re- mains undissolved; takeout the foil, allow the powder to settle, and decant the liquid through a filter: 3. Residue in porcelain 4. Filtrate will be yellow if Presence of At. disli ; dissolve by pour- Cr is present (note 1 a). ing in a little HC1 and Add HA gradually until Note. — Caustic soda boiling, add some water. it is in excess (shown by and potash is verv lia- then a few drops of the color becoming red- ble to contain A1„II()S; K( yS solution ; a blood- the analyst must ascer- red coloration shows: tain that the A1 does not come from this Presence of Fe (note 2). tion; a yellow precipitate source. Presence of Cr (note 3). Note 1.—If Mn was present in the original substance, it is often precipitated more or less completely with the Fe, and will be de- tected by imparting to the fused mass a bluish-green color ; this should be noted, as the Mn may possibly he 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 Cr ; but on dissolving the cool mass in water and boiling with HA, the manganese coloration is de- stroyed ; and, on filtering from any dark-colored precipitate, the yellow color due to the Cr becomes evident. Note 2.—Fe is always detected here in the ferric condition, since even if originally present as ferrosum, it will have been oxidized by boiling with HISTO,, as directed in the General Table. To as- certain in which condition the Fe was present, boil some of the original substance with HC1, and divide the HC1 solution (filtered if necessary) into two parts: to one portion add K6Fe2Cy12, a dark-blue precipitate shows presence of Fe" (Ferrosum) to another portion add KCyS, a blood-red color shows presence of Fe'" (Ferricum). Note 3.—Cr may have been present as a chromic salt (Cr re- placing H in an acid) or 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 PbA2, shows that Cr was present as a 437.] 259 TABLE III B. — ZINC GROUP. chromate ; Cr previously combined with an acid as a chromic salt, remains undissolved as green Cr2U<>6, and does not color the fil- trate : It is found by 2 (in the above Table). 437. TABLE III b.—ZINC GROUP. The precipitate produced by Arn2S 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). Note.—The presence of Ni, indicated by the filtrate, after boil- ing with AmHO in the General Table, being blue in color, and also by a dark-brown filtrate being obtained after boiling with Am2S, will usually have been proved to a certainty by the exami- nation in the borax bead of the black NiS, precipitated by boiling the dark-brown filtrate from Am,S (431) ; if Ni has been thus de- tected its further detection in the Am2S precipitate, as directed below, will be unnecessary. Remove the precipitate from the filter with cold dilute HC1 in the way described in par. 26 c; take out the paper and allow the liquid to stand, occasionally stirring it well. The precipitate will either dissolve leaving only white sulphur, in which case the milky liquid may be at once examined by 2 (below), or a black residue will be left which must be filtered off and examined by 1 (below), the filtrate being examined by 2: 260 TABLE III B. — ZINC GROUP. [437. 1. Residue (black) may contain NiS, CoS. Examination by the borax bead. Fuse a small quantity in a clear borax beat! in the extreme tip of the outer blow- i pipe flame, note its color; then fuse the bead for some time in.the inner blow- pipe flame, and again observe its color. Any one of the following observations 2. Solution or filtrate may contain Zn, Mn. Boil it in a porcelain dish until it ceases to smell of HaS, then drop in a small crystal of KC10Sl and boil for several minutes. After cooling the liquid add pure NaHO until after stirring the liquid it turns red litmus-paper blue, stir well and filter: Blue, bead in both | flames shows: ; Presence of Co. Co need not be fur- ther tested tor, but [ if any doubt exists j as to the presence j of Ni the rest of ! the residue must j be examined as | below. Brown or yellow bead, when cold after fusing in the outer flame, which be- comes 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 examination need be made. A bead which is neither brown nor blue, but of some inter- mediate hue on cooling from the outer flame, indi- cates the probable presence of both Co and Ni. Examine the remainder of the black residue as direct- ed below for Ni and Co, or for Co alone if Ni basbeen already detected by (431). 5. Precipitate is while, at first, but rapidly darkens in the air. Fuse a por- tion of it with solid Na2<03 and KNO, on platinum; a bluish- green mass is obtained on cooling, showing: Presence of Mn. Note.— Mn may have been originally present, either replacing H in an 6. Filtrate; pass HoS a white precipitate forms, often somewhat discolored, showing: Presence of Zn. Note—From a dilute solution of ZnHo, in NaHO the ZnHoa is precipitated on boiling; hence after adding NaHO, as directed above, the liquid must not be hoi'ed, else Zn might be precipitated with the MnIIoa and escape detection. Rut by diluting and boiling the above filtrate it is usually possible to cause any | Further examination of the residue.—Rinse the residue from the filter into a poree- | lain dish, using as little water as possible: pour in a little strong HC1 and boil for some time, adding occasionally a small crystal of KCIO, 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 Co), dilute with a little water, filter (it necessary) into a boiling-tube and pour in KCy solu- tion slowly until the precipitate formed at first is just redissolved, boil briskly for several minutes, and add much strong (or make decidedly alkaline with NaHO and add Br-water); heat nearly to boiling, and allow the liquid to stand at least ten minutes, filter. (Note 1, below): acid, or combined with 0 as an acid radicle. Its presence in an acid radi- cle is indicated by the color of the original so- lution, since in the form of manganate it is green, and as permanganate it is purple; these colors disappear on boiling the HC1 solution for some ZnHoa it holds in solution to precipitate (especially if the alkalinity of the liquid be somewhat reduced by cautious addi- tion of HC1 in quantity insufficient to make the liquid acid). If this precipi- tate be separated tty pouring the liquid through a double filter and then be dis- solved off the filter and the sides of the boiling-tube by a little boiling HA, ZnS may be jtrecipitati d perfectly white from this solution, bv HaS showing: Presence of Zn. 1 3. Precipitate (black): wash and confirm the presence of 4. Filtrate must be warmed with more Na./1aO (or Br-water), and filtered from any additional pre- cipitate which may form, then evaporated to dry- ness, and strong HNOspoured upon the residue as long as any frothing is caused; this is then evapo- rated just to dryness, the residue dissolved in water, excess of K HO added to it, and any precipi- tate filtered off and fused into a borax bead (taking the paper stained by the precipitate if the precipi- tate is not easily removed): a blue bead shows: Presence of Co. time, or on passing HaS. Ni by fusing some of the pre- ! eipit'ate(orthe paperstained with the precipitate) in a borax bead in the outer and inner blowpipe flames: a bead yellow when cold, be- i coming black in the inner ; flame shows: Presence of Ni. JSole 1 —If this precipitate adheres to the sides of the boiling- tube, it is dissolved off (after the liquid has been emptied out) by pouring in a little boiling HC1; from this solution the Ni is pre- cipitated by addition of KHO, and the precipitate filtered and tested by the borax bead from Ni. 438.] TABLE IV. — BARIUM GROUP. 261 The precipitate produced by Am2C03 may contain BaC03, SrC03, CaC03; it is to be well washed with boiling water. Before dissolving the precipitate off the filter much may usually be learnt by an examination of the flame coloration (see 1 below) yielded by the HC1 solution. The results thus obtained are afterwards con- firmed in the wet way (see 2 below). 1. Examination by Flame Coloration.—Take a small quantity of the precipitate out of 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 pro- cess 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 colora- tions yielded bv Ca and Sr are distinguished by viewing the flame through the indigo-prism; the Ca coloration then appears dingy-green, whilst the Sr coloration still appears crimson; Ba is usually found by its coloration remaining after the others have disappeared. When all three metals are present together their colorations are apt to interfere with one another; but if at any time a red color is visible through the indigo-prism, Sr is cer- tainly present; if a green coloration is visible without using the prism, the presence of Ba is proved. 2. Examination in the Wet Way.—The rest of the precipitate is dissolved off the filter by pouring upon it a little boiling HA, again boiling the liquid, and pour- ing it once more through the filter if the precipitate is not entirely dissolved. Test whether the solution is acid, and if it is not add HA whilst stirring until the liquid is acid, then pour off' a small portion (A) of the acid solution into a test-tube, and put by the larger por- tion (B). To the portion (A), after it has been cooled by immersing the lower part of the tube in cold water or holding it in a stream from the tap, add several drops 438. TABLE IV.—BARIUM GROUP. 262 TABLE IV. — BARIUM GROUP. [438 of CaS04 solution; if an immediate precipitate forms refer to I (below); if no immediate precipitate forms heat the liquid to boiling, and if a precipitate then forms refer to II, if no precipitate forms even after several minutes refer to III. I. An immediate precipitate is produced by CaS04 in the cold, showing: Presence of Ba. Portion (B) must then be tested for Sr and Ca which may also be present: examine it as directed below : Add K3Cr04 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, AmHO until the color changes to pale yellow, then add AmsC03 solution : No precipitate forms, show- ing: 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, reserving the larger portion (B'). To (A') add CaS04 solution and boil: No precipitate forms : A bsence of Sr. Examine portion (7?/) for Ca as directed at (C) in III. A precipitate forms : Presence of Sr. Examine portion (B') for Ca as directed at (CM, ii. II. A ‘precipitate is not formed at once on the addition of CaSOi. but appears on boiling the liquid, showing: Absence of Ba and Presence of Sr. C. Portion (B) is then examined for Ca as directed below: Add dilute II2S04 in excess, boil and filter, reject the precipi- tate; add to the filtrate several drops more H2S04 and boil; if this causes any precipitate boil and filter, and again test the filtrate by addition of H2SU4 and boiling: repeat this process if necessary. To the clear filtrate, which gives no further precipitate on addition of II2S04 and boiling, add gradually AmHO until after mixing the liquid by thorough stirring or shaking it turns red litmus-paper blue, then add Am2C204 solution and warm gently; a white precipitate, often appearing only after a time, shows: Presence of Ca. (See note below.) 439.] TABLE V. — POTASSIUM GROUP. 263 III. No precipitate is produced by CaSOv even on boiling, show- ing: Absence of Ba and Sr and. Presence of Ca. C. Confirm the presence of Ca by adding to portion (B) excess of AmHO (.35 a), then Am3C264 solution ; a white precipitate forms, showing: Presence of Ca. (See note below ) Note.—If mere traces of Ca have to be tested for, the filter- paper used in the analysis must first he freed from any traces of Ca it may contain by wetting it with dilute HC1, and then thoroughly washing it with distilled water, as described in the note to par. 23 a (p. 59). 439. TABLE V.—POTASSIUM GROUP. The filtrate, after addition to the original solution of all the group-reagents in succession, may still contain Mg, K, Na, and NH4. Since, however, NH4 salts have been added as group reagents, it is useless to test for NH4 in this filtrate; NH4 must be detected by boiling a portion of the original substance with KHO solution, and ascertaining whether any XH3 gas is evolved, which would be recognized by its smell or its action on moist- ened red litmus-paper. It is, however, usually un- necessary to test specially here for NII4, since it will have been already tested for in the preliminary exami- nation (390). Proceed to examine for Group V as directed below. Evaporate the filtrate from Group IV to dryness in a porcelain dish, scrape out the solid residue 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 1). All Am compounds are thus entirely re- moved. If any residue remains (Note 2) it is to be dissolved by boiling the foil in a test-tube with a small quantity of water to which several drops of dilute HC1 have been added. Divide this solution into two equal parts: TABLE V.—POTASSIUM GROUP. [439. Examination for Mg. Examination for K and Na. Before testing for Mg in one In the other portion proceed to test for K portion of this solution it is and Na as directed below. The presence necessary to remove from it of Mg in no way interferes with the de- anv traces of Ba, Sr, or Ca tection of K and Na, and hence if it has which it may possibly ontain, been detected its removal is unnecessary. and which might else be mis- Flame coloration.— Dip into the solution a taken for Mg. loop of platinum-wire which has bee” Add, therefore, several drops of proved when held in a Bunsen flame not to the liquid, boil for to impart any color to it. Hold the loop a short time and let stand; in the Bunsen flame; oneof the following then, whether a precipitate lias formed or not, add a little AmCl and Am HO in excess, results will be observed: then several drops of Ama''/)t, A bright yellow flame col ora- A pale violet and warm gently; it any pre- cipitate has tormed proceed to ence of Aa (note 3). pearing red filter at once as quickly as pos- Examine this coloration sible and test ttie filtrate once more by adding H,S04, then AmCl, Am HO in excess, and through the indigo- prism ; it appears red, indicating presence of K: through the indigo-prism, shows; Am,'and warming as di- if no red color is visible reeled above; and it any fur- K is probably absent or Presence of K. ther precipitate forms, filter and again test the filtrate. To the liquid in which the addi- tion of HsS(>4, AmCl, AmHO present only in very mi- nute quantity. absence of Aa. in excess, and Am,' yi4 causes no precipitate, add NaaiP<)4, It is usual to confirm tlie results of the ex- amination of the flame coloration by pour- mg the remainder of the solution upon a stir the liquid violently and watch-glass, adding to it several drops of rt(J4 (note 4) and stirring well tor some white, crystalline precipitate time; the formation of a yellow precipi- tate shows: Presence of Mg. Presence of K (note 5). Note 1—If the residue is small in amount it may he 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 N Ht salts by heating only in porcelain. Note 2.—It is not safe to place much reliance upon an examina- tion 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 few drops of HOI, and the solution examined for Mg, K, and IN a, as directed above. Note 3.—A yellow coloration, more or less intense, will almost always be obtained here, since nearly all substances anti reagents contain small quantities of Na; hence the student must note the intensity of the coloration, and judge from it whether the quantity of Na is small or large; he must then enter accordingly, either “ Presence of Naor “ 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 add- 440.] EXAMINATION FOR ACID RADICLES. 265 ing PtCl4 the above solution should be evaporated to dryness with a little strong HNOs. the residue dissolved in a few drops of dilute HCI and tested with PtCl4 for K. This is of course unnecessary if, before precipitating Group III in the General Table, the solu- tion has been evaporated to dryness with HN03. In case of uncer- tainty, 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 PtCI4, 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 filter- ing off the yellow residue and washing it with absolute alcohol, it will yield the pure K flame coloration. EXAMINATION FOE ACID EADICLES. 440. Several acid radicles will probably have been already detected for certain, if present, by the prelimi- nary examination. Such are COs, SOs,S, N02, CIO, NOs, ClOj, 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 H2S into the HC1 solution: A reddish-yellow solution, becoming green and depositing white sul- phur, shows: Presence of OrOi A green solution, becoming colorless, Presence of (MnOi)" A purple solution, “ Presence of [MnOf)' A yellow precipitate of As2S3, ap- pearing only when the liquid is boiled, shows : Presence of As Oi An insoluble residue of SiOa, after evaporating to dryness the filtrate from the H2S group, shows: Presence of Si 0.^ 266 examination for acid radicles. [441-442. And a yellow precipitate obtained with AmHMo04 before precipi- tating Group III, shows : Presence o/POv The presence of any of these acid radicles thus de- tected 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 lim- ited this number considerably, and it may be further reduced 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 Am, 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 Na2COa 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, HX03, and HA respectively: examine these portions as directed below, using a separate part for each test: 443, 444.] EXAMINATION FOR ACID RADICLES. 267 443. I. Portion acidified with HC1. Present. On addition of BaCla solution, a white precipitate insol-1 (S04)". uble on boiling (444,1), I On addition of BaCla solution, a semi-transparent precip-\ (SiF,)". itate insoluble on boiling (444, 2), J On addition of AmOl and AmaCo3, a semi-transparent 1 (Si03," precipitate, . On addition of FeS04 solution, a dark-blue precipitate, . (FeaCyla'vi. On addition of FeaCls solution, a dark-blue precipitate:) (FeOyt)iv. FeSO« yielding a light-blue precipitate,. . . . J On addition of FeaCl0 solution, a red coloration destroyed ) by Hg(Jla, / (CyS)'. II. Portion acidified Present. Present. with UNO,. Refer to (444, 3). with IIA. On addition of AgNO*. 4 On addition of PbA2'l a pure white precipi- [ tate, easily soluble [ in AmHO (444,1), . J CF solution a yellow > precipitate, . . .) (Cr()4)" On addition of OaCla) On addition of AgNOa 4 solution a white gel- > F'* (probably). alight-yellow precipi- [ tate, with difficulty f Br' atinous precipitate, j soluble in AmHO, . J On addition of CaCl.j'l a white pulverulent > (Pv°4)"* (proba- bly). On addition of AgN03, \ precipitate ) a yellmv precipitate, [ almost insoluble in [ I' On addition of FeaCls) AmHO, J a yellowish-white > precipitate (449),. . j (P04)"',or(As04)"' Refer to (445). Notes on the preceding Table. 444. 1. Unless the Na2C03 solution used in preparing the solu- tion for these tests was pure (S04)// and (Cl)/, if detected, may have been present only as impurities in the Na2C03; portions of the original substance should then be tested by (44b) and (447). 2. The presence of (SiFJ" should be confirmed by other tests, such as adding KC1 (300) and evolving HF by strong H2S04 (301) ; the HF is most readily evolved from the BaSiFfl precipitate (301 a). 3. Should AgN03 yield a black precipitate, this proves the pres- ence of a sulphide, or possibly a theiosulphate; add HN03, and boil; the black Ag2S will thus be decomposed, leaving a milky liquid * F will bo readily detected in this precipitate, or better in the original substance by (452); (C204)// by (453). 268 SPECIAL TESTS FOR ACID RADICLES. f445-449. in which any other precipitate is readily seen after being coagu- lated by heating or shaking. 445. It must he remembered that (Cy)', (FeCy6)lr, (Fe2Cy12')vl, and (CyS) are also precipitated by AsiNG3, and therefore if these acid radicles have been already found, a precipitate produced by AgN03 does not prove the presence of (Cl)', (Br)', or (T)', which acid radicles must be especially examined for, as directed below. If chloride, bromide, and iodide have all to be tested for, a por- tion of the Na2C03 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 IIC1, the liquid decanted (or filtered if not clear),and BaCl2 added to it: a white precipitate shows presence of SO4. 447. Chloride.—A portion of the original substance is warmed with HN03, the solution decanted (or filtered if necessary), and AgN03 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 fora short time, acidify with HC1 and add Fe2Clfi; a red coloration, not destroyed by heat, but removed by addition of HgCl2, shows presence of Cy [possibly as (FeCy„)iv, (Fe2Cy„)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)"' 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 450-458.1 SPECIAL TESTS FOR ACID RADICLES. 269 (442) HC1 until it is acid, then AmCl, AmHO in ex- cess 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 (AsOf'". 450. Phosphate.—Boil some of the original sub- stance with dilute HNOs, add a little of this clear solu- tion (filtered if necessary) to some AmHMo04 solution, shake and stir the liquid well, and if no precipitate forms warm very gently, a yellow precipitate shows pres- ence of (POf'". Note.—If (As04)/// has been detected (449) this test for (P04)/// is only reliable when the yellow precipitate has been obtained either in the cold or by employing a very gentle heat. If any doubt is felt concerning the presence of (P()4)///, boil some of the substance with strong HC1, and examine for (P04)// after having entirely separated the (As04)/// by passing U2S into the boiling HC1 solution. A doubtful precipitate with AmHMoO, may be proved to contain phosphate by dissolving it in AmHO, adding AmCl and MgS04, filtering and dropping AgNOg upon the pre- cipitate, if phosphate 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 tur- meric-paper and dry it in a steam-oven (or at a gentle heat), if the slip is reddish-brown and becomes blue-black when moistened with AmHO, the presence of (BOs)"' is shown. 452. Fluoride.—Pour upon a portion of the powdered substance strong II2S04; 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. If Si02 is known to be present, the test must be made by conducting the gas, evolved on heating the substance with strong H2S04 into dilute AmHO, when a deposit of gelatinous H4Si04 proves the presence of F. 453. Oxalate.—The precipitate produced by CaCl2 in III (443), or the original substance if it contains no car- 270 TESTS FOR ACID RADICLES. 453 a, 454. bonate, is mixed on a watch-glass with MnO,2 free from carbonate and strong H2S04, and gently warmed; CO,2 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 containing 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 H2S or Am2S (see last two pars, of 358 6), 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 letting stand for some time. A precipitate may consist of CaT, Ca3(P04)2, or CaO. By shaking this precipitate with cold KHO solu- tion, CaT is dissolved and may be reprecipitated from the solution (or filtrate) by diluting and boiling for some time; the precipitate is then gently warmed, after de- canting the liquid, with a little very dilute AmHO and a crvstal 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 KHO for some time, and adding to the clear solution alkaline PbA2 so- lution, when a black precipitate or coloration will ap- pear. The above directions must only be considered as affording examples of how the principal acid radicles are detected. By reference to the individual reactions in Section IV, and to the directions there given for the detection of similar acid radicles when occurring to- gether, this method will serve for the detection of all the commonly occurring acid radicles. 455.] SOLUBILITY IN WATER AND ACIDS. 271 K. Na. Am. Mg. Ba. Sr. Ca. Fe" Fe'" Al. Cr. Zn Mn. Ni. Co. Hg" Pb. Bi. Cu. Cd. Sb. Sn". Sn"". As'". Ag. Hg.' 1. Oxide w. w. w. a. w. w. w-a. a. a. a.i. a.i. a. a. a. a. a. an. a. a. a. am. a. a.i. w-am. an. an. 0. 2. Sulphide.... w. w. w. w-a. w w. w-a. am. a. - — a. a. amn amn. amn an. an. an. a. am. am. am. an. an. an. s. 3. Chloride w. w. w. w. w. w. w. w. w. w. a.i. w. w. w. w. w. w.i. w.b. w. w. w.b. w.b. w. w. i. a.i. Cl. 4. Iodide w. w. w. w. w. w. w. w. w. — — w. w. — — a. w.am. — — w. — w. w. — i. an. I. 5. Sulphate w. w. w. w. i. i. w-am.-i. w. w. w. w.a. w. w. w. w. w.b. a.i. w.b. w. w. a. V, w.b. — w.an. wb.an so4. 6. Nitrate w. w. w. w. w. w. w. w. w. W. w. w. w. w. w. w.b. w. w.b. w. w. — — w. — w. w.b. NO,. 7. Phosphate.. w. w. w. a. a. a. a. a. a. a. a. a. a. a. a. a. an. - a. a. — a. - — an. an. P04. 8. Carbonate.. w. w. w. a. a. a. a. a. - - — a. a. a. a. a. an. a. a. a. — — — - an. an. CO,. 9. Borate w. w. w. a. a. a. a. a. a. a. a. a. a. a. a. — an. a. a. w.a. — a. — — — w. BO,. 10. Arsenite w. w. w. a. a. a. a. a. a. a. a. a. a. a. a. a. an. a. a. — a. — — — an. an. AsOj. 11. Arsenate.... w. w. w. a. a. a. a. a. a. — — — - a. a. a. an. — a. — a. — — — an. a“. As04. 12. Chromate... w. w. w. w. a. a. a. — w. a. a. w. i. a. — w-a. a».i. a. w. — a. — — — an. an. Cr04. 13. Fluoride w. w. w. a. a. i. — — — - — - — — — w. a. — — — — — — — w. — F. 14. Oxalate w. w. w. a. a. a. a. a a. a. w-a. a. w-a. a. a. a. a. a. a. a. a. a. w. — a. a. cao4. Only the most commonly occurring compounds are contained in this table, the solubility of other substances may be obtained by reference to a treatise on chemistry, or to Storer’s Dictionary of Solubilities. 455. Table showing Solubility of Substances in Water and Acids. A blank signifies that the solubility is unknown or unimportant. 272 USE OF THE TABLE OF SOLUBILITY. [456-458. 456. The table is thus arranged: in a horizontal line at the head 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 portion of the names of the compounds thus formed, which corresponds to the acid radicle; the same are also placed in chem- ical symbols in a vertical column on the right. The solubility of a compound is denoted by letters : w. Signifies soluble in water. a. Soluble in acids; the term standing for HC1, HN03, and aqua regia. ani. Soluble in muriatic (hydrochloric) acid. an. Soluble in nitric acid. amn. Soluble in a mixture of muriatic and nitric, 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 differ- ent solubilities. 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 not soluble 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” (!504) stands the letter w, showing that 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 ivaier, the metals found were K, Ha, 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 S04, P04, C03, Bt)3, AsOa, As04, Cr04, 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 N03 need be tested for. This example shows how much we may often simplify the exam- ination 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. 273 REMARKS ON THE PRECIPITATION OE GROUP III. 459. In the General Table (419) it is assumed that in the absence of (P04)"' the two Sub-groups III a and III b can be separated from one another by adding first AmCl and then excess of AinHO to the solution ; Group III a alone being thus precipitated, and Group III b being afterwards precipitated by adding Am2S to the filtrate. Now although AmCl entirely prevents the precipitation 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 solu- tion they are precipitated by AmHO, and the presence of AmCl will not prevent Mn and Zn from being pre- cipitated with them in smaller or larger quantity, Mn particularly showing a tendency to be precipitated with Fe, and Zn with Cr. Hence if either Mn or Zn, espe- cially the former, be present in small quantity only, it may be entirely precipitated in Group IIT 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 Na2C03 and KNO,; but Zn may thus be entirely passed over, since if precipitated with Cr2Ho6 its presence would certainly not be detected in Table III A. The method of dissolving the precipitate several times in HC1 and reprecipitating 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 adding 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 Table III b, since in the absence 274 REMARKS ON TIIE [460-461. of Group III A the members of Group III b are not precipitated by Am HO in the presence of AmCl. 460. The presence of (POi)r" in the HCl solution which is to be examined for Groups III, IV, and V involves no special procedure if AmHO added after AmCl produces no precipitate, since the phosphates of Groups III and IV and of Mg must be absent. If, however, on adding AmCl and AmHO 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 AmHO, the phosphates of Ni, Co, Mn, Zn, and Fe, are only partially precipitated by AmHO; they are, however, entirely precipitated by AnijjS. The filtrate from Am2S is then examined as directed in the General Table for Groups IV and V. The principles 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 HA in the presence of alkaline acetates, the other portions of the precipitate being soluble. 2. The separation of all the (P04)"' which is in the HA solution combined with Ba, Sr, Ca, or Mg, by Fe2 Cl6 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) and (291). 461. The reason why, in obtaining the precipitate for Table III d, the precipitates produced by AmHO and Am2S are filtered and washed separately, is that phos- phates of Fe, Zn, Mn, Ni, and Co are converted by Am2S into sulphides, forming at the same time ammonium phosphate which remains in solution, and this would precipitate Ba, Sr, Ca, Mg as phosphates from the solu- 462-463.] PRECIPITATION OF GROUP III. 275 tion, even if they were not originally present in that condition. Now this besides complicating the process 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 are first pre- cipitated by AmCl and AmHO, then any members of Group III b are precipitated from the filtrate by Am,S. The two precipitates are mixed and treated with Am2S, which will dissolve away the (P04)"' from Fe, Zn. Mn, Ni, Co phosphates if present, leaving the other phos- phates undecomposed ; hence, if on filtering and testing the filtrate with AmCl, AmHO, and MgS04 a white crystalline precipitate is obtained, this indicates the presence of (POJ'" and indirectly establishes the pres- ence 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 IICl solution after passing H2S, H3BOs, and HF are usually volatilized, and H2Si03 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 par. 463. 463. RULES FOR THE PRECIPITATION AND EXAMINATION OF GROUPS III a AND III b. Note.—Refer to pars. 459- 462 for explanation of these rules. Hence the following rules may be laid down for pre- cipitating and detecting members of Group 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 AmHO after AmCl causes no precipitate, Am.2S is at once added, the liquid boiled, and the precipitate, if any, examined for members of Group 276 TABLE III Cx FOR GROUP III [464. III b by Table III b (437); this course is pursued whether (PO,)"' is present or absent. II. If the addition of AmllO after AmCl causes a precipitate and (POf)'" is not present, the plan of pre- cipitation depends upon the object of the analysis. If small quantities of Zn need not be examined for, the method given in the General Table (419) may be followed. If traces of Zn have to be tested for in the solution, add AmCl, then AraHO and Am2S in excess, boil, filter, and examine the precipitate by Table III c (464), or III c2 (465). Note.—The method described in Table III c, gives reliable 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 (POf)"' is present, the method of precip- itation to be adopted will be found in par. 466, together with the table for the examination of the group pre- cipitate. 464. TABLE III c,. —FOR THE SEPARATION OF GROUPS III a AND III b BY BaCOr 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 KC10;j, until all is dissolved but a small quantity of yellow sulphur. Evaporate 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 BaCOa suspended in water, cork the flask tightly and shake well; repeat the addition of BaCOs and agitate until the precipitate is distinctly whitened bv 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 464.] TABLE III c2 FOR DETECTION, ETC. 277 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 by pour- ing a little boiling HC1 upon the filter, returning the boiling acid to the filter if necessary to dis- solve any undissolved precipi- tate; remove Ba from the boiling solution by adding dilute Hss04 gradually, until after allowing the precipitate to settle, a few additional drops of acid cause no further precipitate (Note 1): filter, add pure NaHO in excess to the filtrate, boil and filter: 2. Filtrate may contain Zn, Mn, Ni, Co, and BaClj. Remove Ba by adding to the boiling liquid dilute HjS1 >4 gradu- ally, 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 HCi and boil; evaporate nearly to d ry n ess, add a 1 ittle water and dissolve some solid NaA in the liquid, pass H3S to saturation, filter; Filtrate.: pass HaS, a white pre- cipitate in- dicates : Presence of Zn. Precijntate: 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 pre- cipitate being at once boiled with NaH<): in this case much white BaCO, will remain with the Fe,(), after fusion to separate Cr; it will however dissolve with the Fe and cause no complication. Precipitate: examine for Ni and Co accord- ing to Ta- ble III B, column 1 (437). Filtrate: add Am HO in excess; a flesh-color- ed precipi- tate shows: Presence of Mn. 13 278 GROUPS III A AND III B. [465 465. Table III c2.—For Examination of Groups III a and III b when Mixed. Remove the precipitate produced by AmCl, AmHO and Am2S from the filter by opening the filter out inside a porcelain dish, pouring in dilute HC1, and gently stirring and shaking the liquid : take out the filter-paper, stir well, and if any black residue is left, filter (see Note 1): Residue if black may con- tain NiS and CoS: examine it as di- rected in Table III b, col- umn 1 (437). Filtrate may contain Al, Fe, Cr, Zn, Mn. Carefully note its color, which is best seen by pouring it into a white porcelain dish, and according to the result of this observation, examine the liquid by column I and II. 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 then add a small crystal K01O3 and boil down to a small bulk: allow to cool, add NallO in excess, stir well and filter: II. The liquid has a violet or bright green color: Presence of Cr. Boil the liquid in the dish until II2S is no longer smelt, drop in a small crystal of KC103and boil down nearly to dryness; dilute with a little water, pour into a small flask and add BaC03fsus- pended in water) gradually whilst constantly shaking the liquid until the excess of BaCOj whitens the precipitate, cork the flask and allow it to stand for not less than fifteen minutes, occasion- ally shaking it well; filter, wash first with cold water, letting the washings run into the filtrate, then with boiling water, re- jecting the washings : Precipitate may contain Fe, Mn. Dry and use it on platinum foil with Na„Co3 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 Idood-red coloration shows: Presence of Fe [see Note 2, after Table III a (436)]. Filtrate may contain Zn,Al. Divide into two equal parts (Note 2). Into one portion pass a white precipitate forms at once: Presence of Zn.' To the other portion add dilute HC1 gradually whilst stirring; if no precipitate forms, add HC1 in excess, then AmtlO in excess, and heat. A colorless floc- culent precipitate: Presence of Al. Precipitate. may con- tain Fe, Al, Cr: examine it by col- umn 1, Table III C, (464). Filtrate may contain Zn, Mn : boil, and whilst boiling add dilute HaS04 gradually until the last few drops no further precipitate, filter from BaSD4; cool, add pure NaHO in excess, stir well and filter: Precipitate: dry and fuse with Na3C03’and KNC3 on platinum foil; blue- green mass: Presence of Mn. Filtrate: pass li3S; white precipitate: Presence of Zn. 466.] 279 PHOSPHATES IN GROUP III. Note 1.—A mere milkiness, due to the separation of sulphur, shows the absence of Ni and Co, and does not render filtration necessary. Note 2.—A1 and Zn may also be detected without dividing the filtrate by adding to it HC1 gradually, until it becomes acid ; then AmHO until alkaline, a colorless flocculent precipitate shows Pres- ence of Al: this is filtered off and H2S passed into the filtrate, a white precipitate shows Presence of Zn. TABLE III d FOR EXAMINATION OF PHOS- PHATES IN GROUP III. 466. If (P04)/r/ is found in the HC1 solution in the General Table (419) after precipitating Groups I and II, and a precipitate forms on addition of AmCl and AmHO, these reagents are added, the latter in slight excess, to the HC1 solution; it is then gently heated, filtered quickly, and washed well with hot water. To the filtrate Am2S is added in excess and the solution boiled, then filtered, and the filtrate examined for Groups IV and V (419) and (431). Transfer the twro precipitates yielded by AmHO and Am2S to a porcelain dish, and stir well with a little Am2S, filter off and wash well. Examine the precipitate by the following table : Filtrate: Add FpaC]s ''note 2) drop by drop as long as a precipitate forms (large excess must be carefully avoided), and until the liquid, after being well stir- red or shaken, remains reddish. Warm gently for some time, filter whilst hot, and wash with hot water: Filtrate: add AmCl, ArnHO (note 3), and AmaS: filter: Precipitate contain- Filtrate: add AmaC03: filter: Precipitate: exam- ine by Table III ing bePQ, may be neglected. Precipitate maycontain BaCOt, SrC<’3 CaC<>3 Examine this pre- cipitate by itself by Table IV (438). Ba, Sr or Ca, if found in this precipitate, were present in the solu- tion as phosphates. Filtrate may contai n M g; add Naall P04, warm and shake well. White crys- talline precipi- tate: Presence of Mg (as phosphate). c (464, 465) for Zn, Mu, Ni, Co, also for A1 and Cr. Test a portion of the original solu- tion (or solution of the substance in HC1) for Fe" and Fe"' by note 2 (436). Note—The filtrate should be examined for (P04)/// by adding MgS04; if this is present Fe, Zn, Mn, Ni, Co, one or more were present as phosphates. 280 PHOSPHATES IN GROUP III. [466. * The precipitate produced by AmCl, AmHO, and Am2S may contain Ba, Sr, Ca, Mg as phosphates; Fe, Zn, Mn, Ni, Co as sulphides; and Al, Cr as hydrates. Remove it from the filter, and heat it with dilute HC1 in a porcelain dish. If this does not dissolve it, drop in several small crystals of KC103, and evaporate very nearly to dryness. Filter off S, if necessary (note 1); then add a solution of HA and NaA (No. 84) (526), as long as any precipitate is produced. Heat gently, and filter while hot: Precipitate may consist of FeP04, A1P04, CrPO, ("note 4). Dry the precipitate on the filter, and fuse it for a short time with finely powdered !SiO„ and fusion-mixture, adding a little KNO*, in a platinum crucible or on platinum foil. When cold, dissolve by boiling with a little distilled water, add Ama('03, allow to stand for a short time, stirring occasionally; let the precipitate subside, filter: Filtrate: add HA until the solu- tion is acid, boil for a short time, then add PbAa: Precipitate: may contain H4Si04, Fe and A1 as silicates, and Fi,Ho,. 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: yellow precipi- tate of Pbf’rO,. Presence, of Cr, (as phosphate). Filtrate: add pure NaHO in excess, boil and filter: Residue is SiOj and may be Note. — A white precipitate on additionof PbA„ may be disre- garded. Filtrate: acidify with HC1, and add AmHO in excess, boil: white, gelatinous precipitate: Presence of Al, (as phosphate). Precipitate is brown Feallo6: dissolve by boiling with HC1, and add KCyS: blood-red colora- tion : Presence of Fe, (as phosph ate). neglected. Note. 1.—Add several drops of this HC1 solution to some AmllMoO, solution in a test-tube and warm gently ; if no yellow precipitate forms, even after standing for a time (P04)/// is ab- sent ; this proves that only Ni, Co, Mn, Zn, and Fe can be present in the solution, which may therefore be at once examined by Table 111 c (464, 465), or as directed in Note 3 below. Note 2.—A few drops of Fp2C16 should be added to a small part only of the filtrate and heated ; if it causes no precipitate (PU4)///, and therefore Ba, Sr, Ca, and Mg, are absent, and to the other portion AmCl, AmllO, and Am2S may be at once added, and the precipitate examined by Table III o (464, 465), or the solution may be examined as directed in Note 3. Note 3.—Since this filtrate has to be tested for Groups III a and ill n, it may be examined either by adding AmCl, Am HO, and Am2S together, and analyzing the precipitate by Table 467.] EXAMINATION OF A METAL OR ALLOY. 281 III c, or by precipitating Groups III a and III b, separately by AmCl and Am HO, and then Arn2S, and examining the precipi- tates by Tables III a and III b (436, 437). Note 4 —Since CrP04 is rarely present, this precipitate may generally be tested by boiling with exeessof NaHO, and filtering; A1P04 will be in solution, and is detected by acidifying with HC1 and adding AmHO in excess, which gives a gelatinous precipitate ; Fe2Ho6 remains as a precipitate, and is detected by dissolving in HCl and adding KCyS. B b. THE SUBSTANCE POSSESSES METALLIC LUS- TRE, AND IS PROBABLY A METAL OR ALLOY. After making the Preliminary Examination in (467— 469), either of the two methods given below (470, 471) may be adopted. The first method is by far the most ready and certain for the examination of a metal or alloy of unknown 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 recom- mended 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 solu- tion; 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 exam- ined for other metals, which are thus 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. Preliminary Examination. 467. Note its color, and smell, if any, when rubbed with the hand; also whether it is crystalline or not. 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 282 [468-470. EXAMINATION OF A METAL. (brittle), or flattens out (malleable). Then try the fol- lowing experiments: Experiment. Observation. Inference. 468. I.—Heat a small por- The results obtained by (403) The inference will tion on charcoal in the and (404) in the Preliminary he found stated inner blowpipe flame. Table may be here obt ained. in (403) and (404). 469. II.—Heat a portion A metallic sublimate forms. Presence of Hg, in a small tube closed at It consists of small liquid Cd, As, two lat- one end. globules. ter detected by (468). Note.—As and S can fre- quently only be detected as arsenate and sulphate by fusion in the outer A yellow sublimate melting to reddish-yellow drops, and the substance heated slowly in a tube open at both ends Presence of Hg. flame with KKOa. evolves SOa. [See (368), III. (417).] Presence of S from a sulphide. 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 dis- solves readily, continue heating until the metal is com- pletely dissolved, and examine the HC1 solution accord- ing 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 HNOa and HC1 added occasionally when the action ceases, or when red fumes are no longer given off. When the metal has entirely disappeared, 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: 471.] 283 EXAMINATION OF A METAL. Residue, if crystalline, is prob- Filtrate (note 1): dilute largely ablv PbCl2, and will be found with H20 (see note 2), and to dissolve entirely if washed whether this causes a precipi- with sufficient boiling water. tate or not, pass IPS to satu- In this solution the presence ration into the solution ; ex- of Pb is confirmed by adding amine any precipitate thus K2Cr04, which gives a yellow produced by Table II (435), precipitate soluble in excess and proceed to examine the of KHO: filtrate for Groups III, IV, and V, as directed in the Presence of Pb. If any residue is left after wash- ing with boiling water, it is General Table (419). probably AgCl; confirm the Note 1.—If Au and Pt maybe presence of Ag by pouring present, they must be tested for upon the residue hot AmHO, it dissolves completely, but in the H2S precipitate, according to the directions in (472-474). is reprecipitated on adding Note 2.—A white precipitate HN03 in excess: appearing on dilution, is due to the presence of Bi, Sb, or Presence of Ag. Sri. 471. Method II.— Pour upon the finely divided metal some strong HN03,* and heat in a small flask covered with a watch-glass as long as any red fumes appear. One of two results will occur: I. II. The substance dissolves completely with or with- out addition of water. Absence of Pt, Au, Sb, Sn (note 1). Examine the solution, after boiling nearly to dryness, and dilut- ing with water (note 2), by the General Table (419;. A Residue is left: add some hot water and boil, thpn 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 com- pletely dissolved add more HC1, and boil down in an evaporating basin nearly to dryness, examine the solution for Au and Pt by (474) commencing with the addi- tion of KC1, and using only the left-hand side of the table, since Sn will be absent. 2. While powder may contain Sn,Sb, As, pos- sibly also Pt and Au con- cealed in it (note 3). * If Hg is found in the preliminary examination and small quantities of Ag have to be tested for, the Hg should be expelled bv heating the substanee 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. 284 NON-METALLIC RESIDUE. [471. 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.—BiOCl will often precipitate on dilution, but the pre- cipitate will disappear on adding HC1 and boiling, being thus easily distinguished from the Group I precipitate. Note 3—If much residue is obtained a small quantity of it may be heated in a test-tube with HC1 adding KC10g, if it dissolves entirely dissolve the whole of the residue, then examine the solu- tion by Table II, commencing at (4356) : if it refuses to dissolve, proceed with the rest of the residue as directed helow. If the residue is small in quantity, examine it at once as directed below. Examination of the Non-metallic Residue insoluble in HNOy—Dry the residue on the filter at a gentle heat, mix it thoroughly with about an equal quantity of powdered Na2C03 and NaN03, and fuse the mixture in a porcelain crucible for some time; then pour the melted substance out into a porcelain dish; allow it to cool, and pour upon it cold water; 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: Residue may contain Sn, Sb, Pt, Au. Filtrate may contain Place it in a small porcelain dish, pour ( As04 Y": add in a little HC1 and heat, then add water ; HNOj until the whether the residue has dissolved or not solution is acid and place in the liquid a slip of Pt foil and •boil, evaporating drop upon it a piece of pure Zn ; H gas the liquid in a is given off; wait until this ceases, dish if very bulky. taking care that there is some Zn left Pour in AgN03 as undissolved, and adding more Zn if the long as it gives any first piece has entirely dissolved. Now precipitate,and add remove the platinum strip; if it is gradually AmHO stained black Sb is present. diluted with 10 or The residue in the dish may consist of Sn, 12 times its bulk of Au,and Pt; remove the Zn, rinsing off water, a brown pre- any substance adhering to it into the cipitate shows : dish, stir the liquid in the dish well, then Presence of As. pour off the liquid, carefully leaving the residue; pour in water, stir well and again pour off carefully. Boil the resi- due for some time with strong HC1 in a test-tube, dilute, decant, add HgCl2, a white precipitate forms :—Presence of $7Z Residue: dissolve by warming with HC1 and HNOs, and examine the solution for Au and Pt by (474), using only the left-hand portion. 472-474.] DETECTION OP GOLD AND PLATINUM. 285 SEPARATION AND DETECTION OF Au AND Pt. 472. An and Pt will, in the ordinary course of analy- sis, be entirely precipitated as sulphides in the Second Group, if H2S is passed for some time into the hot HC1 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 modification of the process described in Table II is re- quired for the detection of these two metals until the examination of the residue in the hydrogen flask is com- menced. The Au and Pt will be present in this residue, associated with Sn if it be present, and usually also with at least a part of the Sb (if present), since Zn and Pt if 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 below (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. Residues:* Pour upon the residue in the dish a little HOI, and several drops of HN()3, and boil gently very nearly t<> dryness; add some KOI solution, and evaporate once more very nearly to dryness. Pour some absolute alcohol into the cool dish and stir well for a time, allow the precipitate to settle and decant the liquid, wash the pre- cipitate by stirring it with a little more alcohol, and decant the liquid when the precipitate has settled: Solution: Add HgCl, a white precipitate, which does not appear at once if only traces of Sn are pres- ent : Presence of Sn. Precipitate will consist of yellow K3Pt016 and excess of K.C1, dissolve it in a little boiling water, pour it into a white dish, add severaldrops of HC'l, then SnCl3: an orange-red col- oration confirms the Presence of Pt. Solution will he yellow if An is present; evaporate carefully on a water-bath just to dry- ness, dissolve in a little water and add a few drops of freshly prepared FeSO« solution. Au will be precipitated in a fine powder, causing the liquid to appear reddish by reflected and blue by transmitted light: Presence of Au. * IfSb has not been detected already in the precipitate produced by the gases in AgNOa solution (435 ft), this residue should be examined for Sb. Boil it once more for some time with strong HC1 to remove all Sn, wash the residue well by decantation and boil it in the dish with H3T adding a few drops of HN0S, decant and test the liquid for Sb by adding HC1 and passing IIaS: the residue is then examined as above (474). 13* 286 INSOLUBLE substances. [475, 476. EXAMINATION OF SUBSTANCES INSOLUBLE IN WATER AND ACIDS. 475. An insoluble substance may consist of one or more of the following substances, all of which are white ex- cept Fe203, Cr203, FeCr204, Pb0rO4, S, C, and AgCl which has been exposed to light. Note.—Substances embraced in brackets ( ) may possibly be present, those in square brackets [ ] improbably, because they are soluble in water. 1. BaSOv Insoluble in water and acids. 2. SrSOv Insoluble “ “ 3. [CaS04], \ 4. (P6S0J, / f Not perfectly insoluble in water, soluble in ■j hot HC1 : hence it should pass into the acid ( solution. 5. PbCr 04, Insoluble after being strongly heated, f Soluble in boiling water, and should there- 6. [P6Cy, fore have been removed if the residue was ( well washed with boiling water. f This may have been originally present as such, or may have been derived from the 7. J use of HCl in making the solution, or by ] the action of aqua regia on the insoluble | substances AgBr, Agl, AgCy, Ag6Fe2Cy12, l Ag4FeCy6. 8. Si02, Either uncombined, or as a silicate. 9. (Al203), I Insoluble after being strongly ignited, but 10. (Fe203), j. these are usually dissolved by long boiling 11. (Cr203), J 12. FeCr2Ov 13. (S»0,), 14. Sbi05,Sb.10i with strong HCl. Chrome iron ore, native. Native or ignited. 15. CaF2, f Also a few other fluorides, and some meta- \ phosphates and arsenates. 16. S, f Yellow, slowly soluble in strong HN03, giv- 17. C, \ ing red fumes, and yielding H2S04. Black, and quite insoluble. Note.—If sufficient of the substance is at disposal, the prelimi- nary examination (476) may be made on a portion of it. In case the quantity of substance is small, however, the whole of the sub- stance must be employed for the examination by fusion (477). Note.—The substance must be in the state of dry powder. Make 476. Preliminary Examination. 476.] INSOLUBLE SUBSTANCES. 287 a careful examination of it with a pocket lens. Expts. I and II need only be made if the substance is light in color. Experiment. Observation. Inference. I. Observe whether th ■ The color changes to violet Presence of AgCl. substance darkens when allowed to stand in the light for some time. or black. II. Pour a little Am,S The substance blackens; Presence of Pb or Ag. upon a portion of the pass on to III. substance on a watch- The substance does not glass. blacken; pass on to V, omitting III and IV, since Pb and Ag must be absent. III. Heat some of the sub- Brownish precipitate. Presence of AgCl. stance with a little water and a small piece of Confirmatory. By warm- ing the substance with KCy , filter off (keeping AmHO, filtering, and the residue), to the fil- trate add AnijS. adding excess ol HN03 to the filtrate, a white precipitate will form, IV. Wash the residue which,on being shaken from Exp. Ill well upon well or heated, coagu- the filter: lates into flocks. a. It is while; drop AmaS The residue blackens. Presence of PbS04 (or upon it. b. It is dark-colored; pour PbCla). in a little HA, and boil after adding AmHO in excess ; filter, to the fil- * trate add IIA in excess Yellow precipitate, soluble Presence of PbS04 (or and K.jCrO,. in KIIO. PbClj). V. Take up some of the A rediHsh-yellow coloration, substance upon a tnois- dusky-green when seen tened loop of platinum through the indigo-prism. Presence of Ca ) wire; heat it for a short A crimson-red coloration ap- time in the inner blow- pipe flame, then mois- pearing deep-red through the indigo-prism. Presence of Sr 1 P^ia*'u ten with a drop of A yellowish-green coloration. Presence of Ba J strong HC1, and hold in [Note.—If all these are the outer part of a Bun- present the colorations may sen flame. often be seen in succession, Ca first, then Sr, and Ba last and very permanent.] VI. Heat in a small test- Yellow sublimate forms on tube or ignition-tube, the sides of tube. Presence of S. ~then on a piece of por- When stronglv heated the celain or broken glass, substance smoulders, and Presence of C. or platinum foil. VII. Heat with strong ultimately burns away. HaS04 in a platinum crucible or leaden cup covered with a watch- glass (296). The glass is etched. Presence of F. Presence of F. Or if a silicate is pres- Gelatinous precipitate ob- ent examine by passing the gas into AmIIO(297) tained in the Ain HO. Particles are seen floating VIII. Fuse some of the substance in a bead of undissolved in the melted Presence of SiOa. NaAmHP04 first in the bead. outer then in the inner blowpipe flame. Green-colored bead. Reddish-brown bead color- Presence of Cr. less when cold, and be- coming greenish in the inner flame. Presence of Fe. 288 INSOLUBLE SUBSTANCES. [477, 478. Actual Examination of Insoluble Substances. 477. Mix the finely powdered substance* with three or four times its weight of fusion-mixture, and heat the mixture in a small covered porcelain crucible,f 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 distilled 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 the residue through into a test-tube by pouring upon it a little boiling dilute HNOs (see Note 1, foot of table), and boil; the residue dissolves entirely if the fusion has been continued sufficiently long (see Note 2). Filter if necessary, and add to this filtrate or solution HC1., filter: * Which, if it is found by Exp. VI, to contain free S or C, must first be heated strongly for some time in a porcelain crucible. f If Pb and Ag have been proved to be absent by the prelimin- ary tests, or if they have been first removed by boiling the sub- stance with KCy solution, then with HA and excess of Am HO 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 A1203 and SiO,2 will always be found, being derived from the action of the Na2C03 on the porcelain. 479.] INSOLUBLE SUBSTANCES. 289 Precipitate may con- tain AgCl, PbCla Filtrate, which must give no more precipitate with HC1, is boiled in a porcelain di-h as long as any Cl is given off, diluted with cold water, saturated with HaS, and filtered : Examine by Table I (433). Precipitate may con- tain PI'S, SriS2 Sba«3. Examine by Table II (435). Filtrate, which must give no further precipitate when IIaS is again passed through it, is boiled in a porcelain dish until it no longer smells of HaS; a little strong HNOa is then added, and the liquid boiled again for several minutes (note 3); AmCl is then added and the liquid boiled; then ArnHO is added in excess : Precipitate may con- tain EeaHos, AlaHos, CraHOg Examine by Table III a (436). To filtrate, add AnqS: [this will rarely cause any precipitate, but a precipi- tate here is to be examined by Table III b (437)]; then to the solution or filtrate add AmaCOa; filter: Precipitate may contain BaCOa, SrCOa, CaCOa. Examine by Taljle IV (438). Filtrate may be ex- amined for Mg ac- cording to Table V (439), but this is only necessary if SiOa is present. Note 1.—Tf Ac and Pb are known to be absent by the prelimin- ary experiments, HC1 may be used for dissolving the residue and is preferable; if effervescence is produced by these acids the pres- ence of an alkaline earth is proved. Note 2.—A residue here may consist of chrome iron ore ; this may be dissolved by heating with HN03and KC103. and the solu- tion tested by the General Table, when Or and Fe will be found. Note 3.—It is best to evaporate this solution quite to dryness, using a water-bath towards the end if the substance spirts. This is always necessary if SiO,2 is present in the substance, 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 pres- ence of Si02. Filter, and examine the filtrate by the General Table (419) more particularly for Al, but other bases should 290 ANALYSIS OF SILICATES. [480. also be tested for, which being; soluble in alkalies pass into this solution, such as Cr, Mn, Zn, Sn. B. Test separate portions for the following acid radicles as described below: 1. {Cl)': Acidify with HNOa and add AgN03, white precipitate easily soluble in AraHO. 2. ($04)'": Acidify with HC1 and add BaCl2, white precipitate insoluble on boiling. Note.—U nl <*ss the fusion mixture employed was free from NaCl and Na2SU4, tests 1 or 2 are worthless. 3. (Cr04)": 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. {POi)'": Acidify with HN03, add a few drops to AmHMo04 solution, and warm gently. A yel- low precipitate forms, often only after a time, or on gently heating. If As has been found on passing H2S into the hot HC1 solution (P04)'" 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. (F)'. Add HC1 in excess to a part of the solution, 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 platinum crucible covered with a watch glass (296). 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. ANALYSIS OF SILICATES. 481,482.] ANALYSIS OF CYANOGEN COMPOUNDS. 291 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 when filtered off is completely dissolved by heating it with Na2C03 solution. 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 JNa 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 H.2S04, or with five times its weight of calcium fluoride mixed into a paste with strong H2S04, in either case heating finally until no more white fumes are evolved. Boil the cool residue with water, add BaCl, solution as long as it causes any precipitate, then add AmHO in excess and Am2C03 as long as it causes any precipitate, filter and examine the filtrate for K and Na as directed under Table V (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 as under Table V (439). 482. ANALYSIS OF SUBSTANCES CONTAINING CYANOGEN. If a small quantity of the substance to be analyzed, when examined by (304) or (306), is found to contain 292 ANALYSIS of cyanogen compounds. [483. cyanogen, the usual course of analysis must be some- what modified, since the presence of cyanogen would produce confusing results. The cyanogen may be pres- ent as a cyanide, sulphocyanide, ferrocyanide, ferri- cyanide, or cobalticyanide, rarely as a manganocyanide or chromicyanide. 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 men- tioned, it is advisable first to ascertain in what form the cyanogen occurs, by the following preliminary experi- ments made on a small portion of the substance; ac- cording to the results yielded by these experiments the further examination of the substance 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 Na2CG3 solu- tion as long as it causes any precipitate, and boil again for several minutes; filter, make the cold filtrate just acid with HC1, filter if necessary, and to separate por- tions add: Reagent added. Result. Inference. 1. FeSO, solution j Blue precipitate { White precipitate. Presence of (FeCyB'>r (FeOv.V'i. Probable presence of 2. Fe,Cls solution J Blue precipitate (CoCyu 3vi. Presence of (FeCvs'iv. 3. ZnSO, solution as long as 1 Blood-red coloration Light-brown preci- pitate . .White precipitate . Presence of (CyS)'. V Presence of (FeCy6V‘- it causes any precipitate. ) Presence of (FeCy6)h Confy—Filter off the pre- (CoCy.y. cipitate, add ZnSO, solu- tion to the filtrate, and if it causes any precipitate, pour again through the fil- A blue bead is pro-1 Presence of (CoCy6Y<- ter, repeating this process until no further precipitate is produced by ZnSO,. Fuse some of the precipitate in a clear borax bead duced j 484,485.] ANALYSIS OF CYANOGEN COMPOUNDS. 293 If these preliminary tests show the presence of (FeCy6)iT, (FeCy6)2Ti, (CoCy6)2vi, one or more, examine the remainder of the substance by Method II (485). If the absence of these acid radicles is indicated by not obtaining the results in the 2d column which indicate their presence proceed according to Method I (484). If none of the above acid radicles are found in the preliminary experiments, the only modification requisite in the ordinary analytical course is to expel HCy by boiling after adding HC1 in preparing the solution (383), or in testing for Group I (419). 484. Method I.—If (CyS)' is present, boil the por- tion of the substance which is to be examined for metals with strong HlsOg for some time, dilute a little and boil again. If any residue remains decant the solution and proceed to endeavor to dissolve the residue as directed at the end of (420), any undissolved residue being then examined according to (475 et seq.). The HNOs solu- tion is evaporated nearly to dryness and examined by (419). Another portion of the substance is examined for acid radicles in the usual way. 485. Method II.—(Fresenius.) Boil the substance with water, filter, and wash the residue with boiling water, adding the washings to the filtrate: 294 ANALYSIS OF CYANOGEN COMPOUNDS. [485. Filtrate: Examine this for metals (more especially the alkalies) and for acid radicles according to the di- rections given for analyzing a liquid (380). The acid radicle should be first tested for in a por- tion of the solution and if (FeCy„)iv, (BeaCyia;vi, (Co.,('y n)vi, (one or more) be found, the solu- tion must be evap- orated to dryness with HNOs, and the residue strongly heated (see General Table) after filter- ing from the H/> precipitate, in or- der to destroy these cyanogen radicles. Residue: Boil with KHO solution for several minutes, then add some NaaC03 solution as long as it causes any precipitate in the solution or the filtrate, and boil again; filter and wash the residue: Filtrate: Pass HaS, and if it causes any precipitate continue to pass the gas until the liquid is saturated, then add more KHO,* heat and filter: Residue: Dis- solve and ex- amine for met- als in the usual manner (383). A'ole.—Fe, Co, Mn,Cr, if found in this residue, were not pres- ent as (FeCyi)vi) (FeaCyla)vi, (Coa<_y»a)*i. Precipitate: Wash well with boiling water, and boil the precipitate with strong HN03, a black residue of HgS may remain, filter this otf after diluting the acid, and confirm the presence of Hg in the precipitate by heating it with NaaC03in a bulb-tube (147). The filtrate (or solution if HgS is absent) is evaporated to dry- ness, the residue is then dis- solved iu a little hot strong HCl, the solution is much di- luted, saturated with and filtered: Filtrate: Add dilute HNOsgradually until the liquid is just acid, pass HaS to saturation and filter: Precipitate: Boil wiLh KHO, filter otf any black pre- cipitate, and ex- amine it for Hg by heating it with BaaC<>3 iu a bulb- tube (147). Add to the filtrate or solution 11C1 until it is acid, pass HaS to satu- ration, and ex- amine for As, Sb, tin (Pt, Au), by Table II (435), commencing at (435 b). Filtrate: Divide into two parts, a, jj\ a. Examine for acid radicles in the usual way, testing for (Coa Cyla)vi by adding excess of ZuS04, filtering and try- ing whether the precipitate gives a blue bead with borax. 0. Evaporate to dryness and fuse the residue. When cold boil it with water and filter:— Residue: Dis- solve in HC1, and test for Al, Fe, Mu, Co (465); the last three if found were present as cy- anogen acid radicles. Filtrate: Acidify a portion if yel- low with 11A and add PbAa, a yellow pre- cipitate shows (CrO«)", the Cr having been present as cy- anogen acid radicle. Test another part for Ai by adding HCl in excess, then AmHO in ex- cess. Precipitate,: Ex- amine for Pb andCuby Ta- ble li (435 a). Filtrate: Add ArnCl, AmllO in excess, and AuijS, and ex- amine for Zn, Mn, Ni, Co, etc., by Table III C„ (465). * If HjS causes a precipitate to form, NaHS (or KHS) may be added drop by drop until it no longer gives any precipitate in the liquid or in the filtrate ; this may be done instead of passing HaS to saturation and then adding KHO. 486, 487.] CYANOGEN COMPOUNDS. 295 486. The advantage of employing this somewhat com- plicated and tedious method of Fresenius is that it usu- ally enables the analyst to ascertain whether Fe, Co, (Mn, Cr), when present, form a part of a complex cyano- gen acid radicle or simply act as metals combined with acid radicles. For if Fe, Co, Mn, Cr, are found in the residue left after boiling with KHO and Na2COs, 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 aque- ous solution they were entirely present in that solution in that form, although they will also be detected in the examination for metallic acid radicles; if they were de- tected only as metallic 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 etseq.); 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 H2S04 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 AmN03.” The residue left in the crucible is dissolved and ex- amined for metals in the usual way. 296 [488. EXAMPLE OF ENTRY. EXAMPLE SHOWING HOW TO ENTER THE RE- SULTS OF ANALYSIS OF A COMPLEX SUB- STANCE. The substance given for analysis consisted of a pow- der containing pink, blue, white, and black particles. It smelt faintly of ammonia. 488. Preliminary Examination for Metals. Experiment. Observation. Inference. Experiment I.—Heated in a small dry test-tube. Confy—Held in the upper Water given off which turned red litmus- paper blue. St rong smell of NHa gas. Substance blackened, no smell of burning. Slight white sublimate. The lime-water became Pres, of NH4. Pres, of NH4. Prob. pres, of Co, Cu, and abs. of T and A. Pres, of As, NH4, or Hg. part of the tube a glass rod, with a drop of lime- water hanging on its end. Confy.—Boiled a portion of the substance with KHO solution. milky. Brown' nitrous fumes evolved, recognized by their smell. Cl gas evolved; found by smell and bleaching litmus. NHj gas was evolved; recognized by its smell, and by giving white fumes with strong HC1. Coa evolved. Pres, of nitrate. Pres, of Cl. Pres, of Nil,. Confy—Heated strongly another portion of the dried substance with NaaCOa in a bulb-tube. No mirror formed. Abs. of Hg. and As. Experiment II.—Heated a portion of the substance on a loop of platinum Bright-yellow flame. The flame appeared pur- ple through the indigo- Pres, of Na. wire in the Bunsen flame, moistened with HC1, and heated again in the flame. Heated for some time in the tip of the inner blow- prism. Crimson coin, appearing intense red through the Pres, of K. pipe flame, moistened with HC1, and again held indigo-prism. Bright green coin, with Pres, of Sr. in the Bunsen flame. blue core. i Pres, of Cu. 489.] EXAMPLE of entry. 297 Experiment. Observation. Inference. Experiment III.—Heated a portion of the sub- stance on charcoal in the inner blowpipe flame. The greater part of the substance fused read- ily, aud was absorbed by the charcoal. Pres, of alkali salt. Confv—Fused in a clear borax bead in the outer Deflagration occurred. A red metallic residue re- mained. Pres, of chlorate, ni- trate. Pres, of Cu. and inner blowpipe flames. Confv—Fused on platinum foil with NaaC03 and In the outer flame al bead green whilst hot; blue when cold. In the inner flame red and nearly opaque. J No bluish-green or yellow mass on cooling. Pres, of Cu. Abs. of Mn and Cr. KNOa. Confy—Fused on charcoal Red metallic residue. Pres, of Cu. in the inner blowpipe flame with Na3C03. A portion, placed on a sil- ver coin and moisten- ed, gave no black stain. Abs. of S. 489. Preliminary Examination for Acid Radicles. Experiment. Observation. Inference. Experiment I.—Added di- lute HC1 without heat- ing. Heated to boiling. A colorless gas was evolved, which was free from smell, 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. Ah-, of sulphite, hypo- chlorite, etc. Pres, of nitrate, chlo- rate, or some other oxidizing substance. Experiment II. — Added strong HjS04. Heated strongly, cooled, and rinsed out. A bright yellow chlorous gas evolved, which crackled when wanned. The tube when dry was seen not to be etched. Pres, of chlorate. Abs. of fluoride. Confy—Dropped in copper turnings and heated. Reddish-brown fumes evolved. Pres, of nitrate. Confy—Boiled a portion of the substance with water, added strong HjSO,, cool- ed, and poured in FeS04 solutiou carefully. A brown ring formed on the surface of the acid. Pres, of nitrate. 298 [490. example of entry. 490. Examination for Metals in the Wet Way. Boiled a portion of the substance with Fe2Cl6, FeS04, and KHO, added HC1 in excess, no blue pp.—Absence °f Q/- Proceeded to dissolve the substance and examine the solution by the General Table. (See pp. 230, 250.) Boiled a portion of the substance with water; as it did not completely dissolve, the soln was decanted, and a little dilute HC1 poured upon the undissolved residue: effervescence occurred, and on boiling Cl was smelt. Added a little strong HC1, boiled as long as any smell of Cl was perceived; the substance was completely dis- solved. Cooled this soln- and mixed it with the water soln- which had been proved previously to give no pp. on addition of a little dilute HNO,: No pp. was formed. Abs. of Group I. Hg', Ag, and prob. Pb. Diluted with water and passed H„S until the liquid smelt strongly of the gas, Altered: A black pp. Examd. by Table II. Filtrate which gave no further pp. with IIaS was pink (prob. pres, of Co.). Boiled until it no longer smelt of H*S, added some strong HNOj and boiled to dryness (the color of the sol”, changed to light-brown on addition of HNO, prob.pres, of Fe), warmed the residue with HC1, it dis- solved completely (Ah.s\ of HjSiOt) To a small por- tion of the IK 1 sol” added AmHMo04and warmed: no pp.: Absence of (/IOt)'". To the rent”, added AmCl then excess of AmllO, and boiled ; Altered: A brown pp. Examd. by Table III a. Filtrate was again pink (presence of Co): added much AnijS and boiled, Altered: A black pp. Examd. bv Table III B. Filtrate was yellow (Absence of M): added Arn/O,, Al- tered : A trhite, pp. Examd by Table IV. Filtrate. Examd by Table V. 491.] 299 EXAMPLE OF ENTRY. 491. Exam"’ of pp. in Group II.—Removed from the filter into a porcelain dish and boiled with KHO, filtered : Filtrate: Acidified with HC1, a white milky Pp. removed from filter by a knife-blade into a porcelain dish and boiled with strong HN03 as long as any red fumes came otf, added dilute HjSQ, and stirred well: liquid only: Abs. of Group 11b. No pp: Abs. of fig Added to soln- excess of AmHO : and Pb. No. pp.: Abs. of Bi. Acidified the soln. with HC1 and satu- rated with HjS; filtered otf the black pp. rapidly and boiled it with dilute H^SO,: Pp.: dissolved in a little boiling di- lute HNO, added AmHO in excess, then excess of H A, then K4FeCy8, chocolate-red pp.: Pres, of Cu. Filtrate: diluted much and passed HjS, no pp.: Abs. of Cd. Exam” of pp. in Group III a. Dissolved in a little boiling dilute HC1, added pure NaHO in excess, boiled and filtered: Filtrate: added HC1 gradually till the liquid became acid Pp.: dried and fused on platinum foil with and KNOj, boiled the colorless (abs. of Cr) mass when cold with water: decanted from the undissolved residue: (no pp.), then AmHO in ex- cess : no pp : Abs. of Al. Residue, in the dish dissolved by boiling with a little HC1, added several drops of KCyS: a blood-red coloration: Pres, of Fe. Sofa ■ being colorless proved abs. of t r. Acidified with HA, boiled, and added PbAa, no yel- low pp.: Abs. of Or. Exam" 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 noNi: fused a portion into a clear bo- rax bead: bead blue in both flames: Filtrate: boiled until it no longer smelt of H3S, added a crystal of KC10S, boiled until the smell of Cl ceased, added pure NallO in excess: No pp. Passed HaS into the sola, no pp.: Pres, of Co. Abs. of Mn. Abs. of Zn. 300 EXAMPLE OF ENTRY. [491. 1. Examn by Flame coln.—Dissolved a small quantity of the pp. in a few drops of HC1 upon a watch-glass, dipped a loop of platinum wire into the sol“' 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 fol- lowed by a yellowish-green, very persistent, colnq Pres- ence of Ba. 2. Exam11• in the Wet Way.—Dissolved the rest of the pp. in as little boiling HA as possible; to a small part of the solution, perfectly cool, added CaS04 sol“‘; an immediate pp. formed: Pres, of Ba. To the remainder of the HA soln- (proved to be acid to litmus) added K20rO4 until the liquid appeared yel- low, warmed and poured through a double filter: Exam” of pp. in Group IV. Pp., which contained all the Ba present, To the clear filtrate (which was orange red in color) added AniHO until the color changed to light yellow, then added AmaCOa in excess and filtered: was re- jected. Filtrate, was Pp.: dissolved in as little boiling HA as possible; rejected. added to a small portion of the soln- CaS04 soln. and boiled, a pp. formed, showing pres, of Sr. To the remainder of the HA solution added HaSO«, boiled, filtered, and to the filtrate (which gave no pp. after being boiled with more HaSOt) added AmHO in ex- cess and AmaCa04, no pp.: Aiw. of Ca. Exam” of Filtrate from General Table for Group V. Evaporated the filtrate to dryness in a porcelain dish, scraped out the residue upon platinum foil, and ignited strongly until white fumes ceased to appear: dissolved the residue off the foil by boiling with water to which several drops of HC1 had been added, divided the sol11, into two unequal parts : 492.] EXAMPLE OF ENTRY. To the larger portion added several Into the smaller portion dipped a loop of drops of HaS04, then AmllO in ex- cess and several drops of Ama0aO4, on heating a slight pp. formed ; fil- platinum-wire, and held it in the Bun- sen flame, an intense yellow coln-: tered, and added to the clear flit rate Pres, of Na, NaaHP04, a white crystalline pp.: Pres, of Mg. appearing violet through the indigo- prism : Pres, of K. Confirmed the pres, of K by stirring a fresh portion of the soln. with PtCl4 on a watch-glass, a yellow pp.: Pres, of K. Metals found: Cu, Fe, Co, Ba, Sr, Mg, Na, K, NH4. 492. Examn- for Acid Radicles. The following acid radicles have already been de- tected : (CO,)", (NOs)', (C103)'. 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 ($04) is absent. The following acid radicles have also been proved to be absent in the general examination for metals: (Cr04)", by the HC1 solution not becoming green on passing H2S. (AsOj)"' and (As04)'", by no pp. forming in Group II B. (Si03)" and (SiF6)", by no residue insol. in HC1 re- maining on evaporating to dryness with HC1 for Group III A. (P04)"', by testing with AmHMo04 in the HC1 sol" 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 (BO3)'" ; and of these Br and I are probably absent, 302 EXAMPLE OF ENTRY. [493. since no violet fumes of I or brown fumes of Br were evolved with strong H2S04. Boiled a portion of the substance with pure Na2COs sol11., and filtered ; acidified portions of the filtrate with— HNOg. HA. Added AgN03, a perfectly white pp., easily sol. in AmHO : Pres, of Cl. Added CaSOv no pp.: Abs. of (CM". Moistened a piece of turmeric- stance, and dried at 100° ; no paper with HC1 sol. of the sub- brown stain produced: Aba. of(B03)'". 493. Found Metallic radicles: Cu, Fe, Co, Ba, Sr, Mg, Na, K, NH4. Acid radicles: C03, NOs, C103, Cl. 494.] 303 LIST OF APPARATUS. 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 ex- periments in Section I will require the apparatus in Di- visions 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. Division I. (See also the note at the end of this list.) 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, 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. 1 small retort, best tubulated with stopper, about 4 to 6 oz. capacity. 304 LIST of apparatus. [494. Division II. 6 test-tubes, 5 or 6 inches long and from \ to f inch in diameter. 1 test-tube cleaner. 2 lengths of hard glass tubing, rather more than inch internal diameter. 1 thistle funnel. [1 clock-glass, about 4 inches across.] 2 round ground-glass plates, 3 inches across. 2 porcelain dishes, one 2J inches across, one 3 inches across. 3 watch-glasses, about 2 inches across. 2 small flasks, about 4 oz. capacity. lied or black india-rubber tubing;* 1 piece 18 inches long and j5gth inch internal diameter, 1 piece 6 inches long and T38th inch internal diameter. 1 Bunsen burner* 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 2J inches across at the top. 2 tobacco-pipe cleaners, for cleaning glass tubes. 2 boiling tubes, 6 or 7 inches long, from to 1J inches across. 1 test-tube stand with at least 12 holes. 1 nest of 3 or 4 small-sized beakers. 1 length of glass rod. * The Bunsen burner and gas-tubing may be fixtures on each working bench, and will not then be required for each student. 494.] 305 LIST OF APPARATUS. 1 small porcelain crucible about \\ inch across, and lid. 1 strip of platinum foil, 2 inches by 1 inch. 2 pieces of platinum wire,* each If to 2 inches long. 1 Black’s blowpipe. 1 pipeclay 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 If 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. 20). 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. * Platinum wire containing Ba is not uncommon in commerce; it is known by giving a persistent green color to the Bunsen flame, and is useless for flame colorations. 306 LIST OE 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 readi- ness for general use: 496. An Indigo-prism.—A hollow glass-prism hav- ing an extremely small angle at its extremity, with ground-glass stopper fitting water-tight into the neck, is purchased ; this is to be very nearly filled with solu- tion of indigo, and the stopper then tied in securely with fine copper wire. The indigo solution is made by di- luting a solution of indigo in strong sulphuric acid with water, in a thin glass beaker or a porcelain dish, until it has the required intensity of color;* the liquid is then allowed to stand for several days to give time for a sediment to form and 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 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 ex- amination for Sr. 498. Set of Cork-borers.—These are used for perfo- rating a cork into which a piece of glass tubing has to be inserted. Nests of borers, containing three or four small sizes, will be sufficient. 499. Sulphuretted-hydrogen Apparatus.—It is highly advisable to employ a large apparatus which will supply the 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 sup- ply the gas in a constant stream; probably the follow- * The addition of the indigo solution to 10 times its measure of water will usually give the required shade. 500.1 SULPHURETTED HYDROGEN APPARATUS. 307 ing, the simplicity, efficiency, and cheapness of which render it very satisfactory, will be found the most gen- erally useful: Fig. 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 Figure 39.* India-rubber stop- pers should be used instead of corks, as the latter soon become sodden with acid and rotten, and also lose their elasticity and permit leakage. Into B (after laying it upon its side to prevent breaking the bottom) is placed a quantity of small pebbles or broken glass, sufficient to form a layer about half an inch deep; upon this is dropped the ferrous sulphide in lumps; the cork is then inserted the clamp at E being closed. The glass tube fixed in the lower tubulure of B should be bent downwards, so that its end nearly touches the bottom of the vessel. This * This apparatus may be purchased completely fitted from Messrs. Mottershead of Manchester and from most apparatus sellers. 308 SULPHURETTED HYDROGEN APPARATUS. [500. drains the acid out of B to the lowest possible level when A is lowered. Strong commercial hydrochloric acid* is poured into A, then an equal bulk of water is added, and the liquids are well 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 this 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 a small 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 regu- lated 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 some bricks, 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 re- quired through the neck of B. The removal of the spent acid and the cleansing of the apparatus should be performed in the open air, or at a sink in a cupboard provided with a good draught. The neck of A should be kept stopped with a cork carrying a bent funnel whose bend is tilled with oil or glycerin; this lessens the escape of gas dissolved in the acid, and tends to prevent the apparatus from causing a * H2S04 does not answer for this purpose as well as HC1, since FeS04 is apt to crystallize in the apparatus, impeding or prevent- ing the action of the acid and its flow through the connecting- tube. 500a.] PASSING SULPHURETTED HYDROGEN. 309 smell. If several students require to use the gas at the same time, the broad stopper of B is perforated and 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 ferrous sulphide upon which HC1, diluted with an equal measure of water, is poured through the thistle- funnel : the gas bubbles through a little water in the smaller bottle, and thence into the solution required to be satu- rated. The sulphuretted hydrogen ap- paratus should stand in a cup- board with a glass front and small doors : the cupboard must be fur- nished with a flue in which a strong draught is created by an argand or ring gas-burner, made of fireclay 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 avoid allowing its un- necessary 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 must keep a bent glass tube (D, 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 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 regulated 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. Fig. 40. 310 STEAM -OVEN. [501-50 h The tube D must be thoroughly cleansed after use, em- ploying a tobacco-pipe cleaner if necessary for its inside. 501. A small Agate Pestle and Mortar (Fig. 32, p. 72). —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/’* 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.” Caution—On no account must a substance 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 Cups or a Platinum Crucible should be kept in readiness for testing F by paragraph (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 covered 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 * Kubbing round and round under the pestle, 504.] WATER -BATH. 311 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, which serves as a water-bath (504). The level of water in the jacket is maintained constant by a little contri- vance shown in section at c: a small reservoir com- municating by a lateral tube with the space between the oven and its jacket is constantly replenished by water which drops into it from the supply-tube (d), the over- flow 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 bv the condensation of the steam drops into the reservoir (c\ or it may be made to com- municate with the worm of the still (506), the escape steam being thus condensed into distilled water. Dis- tilled water should always be supplied to the steam oven, as this prevents the formation of a troublesome incrusta- tion in the interior; and since the above arrangement, which is all that can be desired when tap-water is sup- plied, would occasion much waste of distilled water, a better plan of supplying the oven is to place a vessel of distilled water beside the oven, and connect them with a siphon, having a bulb or vertical closed tube at its bend, to prevent the air boiled out from the water from stop- ping the action of the siphon. 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 consists 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 and 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 boiling quietly. A 312 WATER-BATH. [504 a, 505. small-sized saucepan is a homely substitute for the cop- per water-bath. Any liquid requiring to be evaporated at a gentle heat is placed in an evaporating basin upon this bath, its temperature during evaporation cannot then exceed the temperature 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 be 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,* 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 filled 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 of the still-worm. 505. Several Small Tubulated Flasks.—The small flask shown in Fig. 38 (p. 149) is very convenient for the re- actions described in pars. 260, 264, and 273. It is per- haps 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 * Any working tinman will make them to order. 506.] DISTILLATION OF WATER. 313 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. DISTILLATION OF WATER. As has been already shown (Exp. 31, p. 37), water ordinarily contains certain solid substances dissolved in it which render it in a chemical sense impure; such water is therefore unlit to be employed for the processes of solution and washing, since any impurity thus intro- duced into a substance during analysis would be consid- ered when detected to have been present in the original substance. 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 pre- vious to its collection. The water supplied in some districts will be found when subjected to the test given in [(526) Remark 41] to be almost perfectly pure; care- fully collected rain-water will invariably yield no indi- cation 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 314 DISTILLATION OF WATER. [506. 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 the supply-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 a ring gas-burner, the steam passing off from the top Fig. 42. of the still through a tin tube bent into a spiral form in the condensing-tub (B) which is made of galvanized iron ; from this condenser the distilled water flows into a large stoneware vessel (C), with a tap below from 506.] 315 DISTILLATION OF WATER. which the water is drawn when required. A long siphon-tube (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 and B; this level is marked by the single-dotted line, and is kept constant by the overflow-tube e, which is connected with a pipe leading to a sink or drain. Just below 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 condenser 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 cir- culation of water between the still and condenser. This still is supported on an iron ring, projecting as a bracket from the condenser. By having two taps in the inlet-tube (d), 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 regulated 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 re- moving the deposit which collects within, and into this lid should be fastened a brass tube carrying a screw- union by which the tin condensing-pipe may be fastened steam-tight to the still. The wooden stand for the still and storing jar is conveniently fitted with shelves and doors to serve as a cupboard. For tests of purity see Remark 41 (-526). 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 litres of distilled water per hour. 316 SILVER RESIDUES. [507. RECOVERY OF THE METALS FROM SILVER AND PLATINUM RESIDUES. When AgNOs or PtCl4 has been added to a solution the liquid is not to be thrown into the sink. 507. Silver Residues.—If AgNOa has been added to a liquid it must be emptied into a vessel* labelled “Silver Residue,” containing strong HC1 which pre- cipitates 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 Na2CO, and K2COs; 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. This AgNOs is then dissolved in the right proportion of water to furnish reagent No. 48 (par. 525). 2. A readier method for decomposing the AgCl con- sists in placing it in a dish with a little water acidified * Most conveniently a large bottle, with a funnel in its neck. 508.] PLATINUM RESIDUES. 317 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 HN03 as di- rected in the first process, the solution evaporated to dryness, and the AgN03 used for preparing the reagent. Any residue insoluble in HNOa will be unreduced AgCl; this may be filtered otf and added to the silver residues for subsequent reduction. 508. Platinum Residues.— Liquids to which PtCl4 has been added are poured into a vessel* labelled “ Pla- tinum 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 resi- due some solution of oxalic acid is poured ; this is evapo- rated to dryness 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 HC1 to which one-third its measure of HNOs has been added ; the solution is evaporated to dryness, the last part of the process being performed over a water-bath. HCl 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 No. 28 (525). * Conveniently a large glass bottle, with a funnel in its neck. 318 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 there- fore processes of preparation, which formerly of necessity occupied a large portion of Manuals of Practical Chemistry, are here omit- ted. It will be 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 arbitrarily; indeed, the strength of a solution may be varied with advantage, according to the different pur- poses for which the reagent is to be employed. It is found, however, that practically a solution of one strength may usually be made to serve all analytical purposes. The proportions 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 practically useful. 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 fol- lowing methods of filling these have been found simple and easy of execution. The process of preparing solutions divides itself natu- rally into the “dilution of liquids” (511), and the “so- lution 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 mixed; these preparations are roughly, but sufficiently 512, 513.] SOLUTION OF SOLIDS. 319 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 file. 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 “ Win- chester” 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 distilled 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 preparation of No. 1, see column of remarks in the same paragraph. 512. Solution of Solids. For dissolving solids two methods are here described ; the former (514) is useful when the solution has to he rapidly prepared, the latter (515) requires less attention and may be used when the solution is not required at once. 513. Note.—Against each reagent prepared from a solid there is placed, in paragraph (524) a number, signifying the number of grammes (see Weights and Measures, 560 et seq.) to be dissolved in 1 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 con- sidering that an average-sized “ Winchester,” tilled an inch above the ridge round its shoulder, holds about 2400 c.c., and since each c c. (see Weights and Measures, 560 et seq.) of water weighs ap- proximately one gramme, we have at once the weight of water (2400 grammes) contained in the bottle, from knowing its capacity ;* and * This method may also be employed when smaller quantities of the reagent are to be prepared. Measure the number of c c. required, count the number as grammes, and calculate the propor-. tion of solid required as above. 320 PREPARATION OF REAGENTS. [514,515. the weight of water being known, the weight of solid to be dis- solved in it is readily calculated 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 weight of water must have dissolved in it £th its weight of AmCl; since a “ Winchester” holds 2400 grammes of water, we must then dissolve 2~— = 300 grammes of AmCl in it, to obtain a solution of proper strength. 514. Weigh out the required quantity of the solid substance, dissolve by heating it with distilled 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 “Win- chester.” 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 precautions 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 fidl 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. II.—The following liquid is advantageous, be- cause the process of solution once started proceeds con- tinuously without further attention. It depends on the fact that the specific gravity of water becomes 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 515.] SOLUTION OF SOLIDS. 321 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. This circula- tion of water over the solid, gradually dissolves it with- out the use of heat, and without requiring any attention 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 cylinder stands at such a height that the muslin bottom is about two inches below the mark made on the beaker to show the Winchester 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 re- quire 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 the least. Perhaps the most advantageous way of using this pro- cess, especially for dissolving large quantities of sub- stance, is to start it overnight ; 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 Fig. 43. 322 PREPARATION OF REAGENTS. [516,517. 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 solution has been ef- fected. As a convenient substitute for the glass cylinder, A, with muslin bottom, an earthenware colander may be em- ployed (Fig. 43 a), filtration being ef- fected 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 stoppered bottle of suitable size may be immersed in it to raise the water-level sufficiently to reach the substance. Preparation of Solutions required for trying the Reactions 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 readiness, since if the student has to dissolve some of the solid substance himself, he is liable not to obtain satis- factory results, either because his solution is made in- conveniently strong, or because it is in a too diluted state. The plan of keeping these solutions in stock is also rec- ommended 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 number, the second the name, and the third the formula of each substance; in the fourth is stated the number of 518-520.] LIST OF THE REAGENTS. 323 grammes 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 column 4 was derived ; and in the sixth column will be found special remarks relating to the preparation of particular solutions. The general methods of preparing 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 purified 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 there should be at least one complete set for the use of two students. The sec- ond 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 strongly recommended to keep his bottles arranged in the order indicated by these 324 LABELLING. [520, 522. numbers. The full name and chemical formula accom- pany 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 each list are placed remarks as to the preparation and the condition of the reagent. 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 measure (m.), in the case of solids the proportion by weight (w.). A number is also placed in the fourth column opposite each reagent prepared by dissolving a solid substance, which denotes the weight in grammes 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 dissolving solid AmCl in 8 times its weight of water, or by dis- solving 300 grammes 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, paragraphs (524) in 4 or 6 oz. wide-mouthed stoppered bottles, which are filled when necessary from the store-jars (stoneware jars with ground clasp-covers),* the liquids (Nos. 1-17, par. 524) in narrow-necked 4 or 6 oz. bottles supplied from the Winchester quart bottles in which the store solutions are kept. The general re- agents (525, 526) should be kept in bottles of not less than 12 oz. capacity. 522. Labelling.—Bottles intended to contain strong * Powdered solids are conveniently removed from large stone jars by means of wooden spoons. 523.] REAGENT-BOTTLES. 325 acids or alkalies should have labels etched upon the glass: such bottles are easily purchased. An ordinary paper label, however, protected by paraffin varnish, which is applied according to the directions given below (5'23), will last for a considerable length of time. The paper labels required for reagents and store-bottles 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, as was mentioned in (519), 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.* Great care should be bestowed on making the moist- ened label adhere over its whole surface by gentle pres- sure with a clean cloth. 523. Varnishing Labels.—It is advisable to varnish each 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 solution 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 ; a little practice will soon enable one to apply a uniform film which does not soak into the paper, hardens immediately, and resists the action of water, acids, and alkalies. 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. * A hook of labels (“ A Series of Chemical Labels for Use in Laboratories ”) 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 specially for use with this book, containing all the numbers, names, and formulas in the lists in pars. 524, 525, 526, 529, 530, 531, and 532. 15 826 REAGENTS REQUIRED [524. 524.—Reagents required Reference number. Name. [The numbers in brackets refer to re- marks correspondingly numbered in the sixth column.] Formula. Weight of solid in grammes to be dissolved in 1 “ Winches- ter ” ol water. Liquids. 1. Sulphuric acid (*) h,so. — 2. Hydrochloric acid (3) IK 1 — 3. Nitric acid (a) HNO, — 4. Acetic acid (*) HA. or HC3H,0,.. — 5. Ammonium chloride(*) Ammonia, or Ammonium hydrate(8), NH.C] 300 6. NH.IIO — 7. Ammonium sulphide (’) (NH.)*S — 8. Ammonium carbonate (8) (Nil, ,CO, 500 9. Ammonium oxalate (NII.jC.jO.2HjO.. 100 10. Potash, or potassium hydrate Potassium chromate KHO 200 11. KjCrO. 200 12. Potassium ferrocvanide K.FcCy8,3HjO 200 13. Potassium ferricyanidef9) f*Sodium phosphate (I0), or "| K.Fe,Cy„ 200 14. •< Hydric disodic phosphate, or v... (Hydrogen disodium phosphate, j Na4HP04.12Ha0... 200 15. Sodium carbonate (“) NiijCOj 1011,0 600 16. Calcium sulphate (13) CaSO. ( (Saturated 1 (solution.) j 17. Solids. 18. 19. 20. 21. Barium chloride Sodium carbonate (1S) Borax (14) Potassium chlorate (,5) Test-papers (16) BaCla.2HjO Na,C0,. Na.B.O,. KC10,. 200 * Hydrogen sodium ammonium phosphate (NaAmllPO). solution serves better for given the above for NaHPO.. 524.] FOR EACH BENCH. 327 for each Bench Proportion of solid by weight (w.) and liquid by measure (in.) to water. Remarks. [The small numbers refer to corresponding numbers in the second column.] 1 : 5 m. 1. The strong pure HaS04 must be poured in the proper proportion into the water contained in a large thin 1 : 3 “ beaker or an earthen jar, constantly stirring the w ater 1:3“ all the time: the right proportions are obtained by mea-urement of the height of the vessel (511). The hot 1 * 8 w liquid is cooled by immersing the vessel in cold water, 1 : 3 m. 1 • 3 “ and is then poured into thestore-bottle. If the acid is pure, no white precipitate (PbS04l forms on dilution. 1 : 5 w. 1 : 24 “ 1 : 12 “ 1 • 12 “ 2. Must be colorless, and give alter dilution no precipi- tate with either Ba€Ia or HaS. 3. Must give no precipitate, after dilution with BaClaor AgNOa added to separate portions. 4. Must give no precipitate with Ba01a. 1 : 12 “ 5. Must give no precipitate or coloration with AmaS. 6. Must give only a very slight precipitate with lime- 1 : 12 “ water, no coloration with AmaS, and separate portions acidified with HNOj must give no precipitates with Bat'ljand AgNOj. The “ Liquor ammonite fortissima” is purchased of 880° specific gravity. — 7. Must be yellow, and give with acids HjS and a white precipitate of S: it must give no precipitate with solu- 1 : 12 “ tions of Ca or Mg salts. 8. The solid AmaCOa is dissolved by being heated with water in a porcelain dish (514): in'diluting, one-fourth of the “ Winchester” must be filled with strong AmHO. 9. Must give no blue precipitate with FeaCl6 solution. 10. Must yield no precipitate with AmHO. 11. The crystallized salt. 12. See (527). 13. Dry, finely-powdered solid. It must, after having been dissolved in excess of HNOa, give no precipitate with Bat la or AgNOa, or AmIiMo04 (277), and if evap- orated with excess of HC1 must leave no residue in- soluble in dilute HC1 (290 a). 14. The borax is best dried by heating in a platinum or porcelain dish until after melting it has again become solid; this solid mass is then finely powdered in a mor- tar and kept in a stoppered bottle. 15. In small crystals. 16. Red and blue litmus-papers and turmeric paper in small strips. precipitation of Mg than does NaaHP04 solution: it is prepared of the strength 328 [525. GENERAL REAGENTS 525.—Reagents for General Use, Note.—Except in lar£je laboratories it will be unnecessary to keep which they are contained in the laboratory, may be made up to the the proportion stated below in column 4. Name. Reference number. [The small numbers in brackets refer to re- Formula. marks correspondingly numbered in the fifth column.] 25. HjSO, 26. HC1 27. HNOs 28. Pt< V 29. C,HbO 30. 5 H,T l ( Ha( 4H406 > 31. Acid sodium tartrate, Hydric sodic tartrate(*°) /NaHT.H.O ) (NaHC.ll.Oj.IIjO / 32. ('a(lIO)g 33. J 1IA \ 34. 0o(N03 a.6HaO 35. 36. /Sulphuretted hydrogen solution, | Hydrogen sulphide, / ' 37. ) HaO,2HaO \ f oOi.-HijO 38. KCvS 39. KNOj 40. Lead acetate (35) 1 PbAa3HaO ) \ Pb(( cHj()a)a.3H50 i 41. Sodium acetate / NaA.3HaO i t NaCaHaOa.3HaO \ - 42. J KCy t 1 K( N | 43. /NaaClaO \ / NaClO.NaCl j ' 44. SuCla.2HaO Cu 45. Conner i3’) Zu 46. 47. 48. 49. 50. Zinc (30) Fe AgNO, HaSOs". CuS04.5HjO MgSO. 7HaO 51. 52. 53. AuCla * See last column on the preceding page. f Must be used in very small quantity only, being an expensive reagent. 525.] FOR DETECTION OF METALS. 329 for the Detection of Metals. these reagents in store in quantity. The 12 oz. or 14 oz. bottles in right strength as soon as they are empty, by calculation (513) from Proportion by weight of solid to water. Kemarks. [The numbers in this column refer to those in brackets in the second column.] Strong pure. 17. Must be colorless, and form no brown ring when poured below some FeSO* solution '247). “ “ 18. Strong rectified spirit (methylated), which must leave no 1 : 30. residue on evaporation. Strong. 19. The solution should be mixed immediately after prepara- tion with several drops of carbolic acid to prevent a vege- 1 : 10. table growth forming in it. 20. Dissolve 10 grammes of HaT in 100 c.c.Jof water, divide this solution into equal parts, exactly neutralize (35) one part Solid. by heating it nearly to boiling, and stirring in solid Na3C0* in powder; add to this the other part, cool and dilute to Strong. 150 c.c. A few drops of carbolic acid should be added to the solution. 1 : 12. 21. Pieces of freshly-burnt lime are placed on a plate, and water is poured upon them until they begin to appear moist on their surface; the superfluous water is then drained otf, and as soon as the lime has crumbled to powder, the pow- 1 : 12. der is placed in a broad-mouthed stoppered bottle. 1 : 100. Solid. 22. The bottle should be closed with a loosely-fitting india- rubber stopper, perforated, and with a glass tube passed through it and dipping into the solution ; when a drop of the solution is required, the upper end of the glass tube is closed by the finger, and a drop is delivered from the Solid. opposite end by slightly relaxing the pressure of the finger. 23. The solution must give no precipitate with Sr(N03 3 solu- Solid. tion. For the preparation of it see (528, 4). 24. For preparation of this solution see (528, 1). It must not darken on adding AmHO. 25. A little HA must be added to this solution to make it clear. 1 : 12. 26. Solution of Kt'y is made (1:12); it decomposes so readily by beiug kept in water,that it isbest made immediately before use by heating a small piece of solid KCy with distilled water. 1 : 20. 27. The strongest “Liquor Sod* Chlorinat*” of commerce. (See 528,2). 28. Crystals of ftnt l,should be dissolved by heating them with 1 : 12. water containing some HC1; the solution should be kept 1 : 12. in a well-stoppered bottle containing pieces of granulated 1 : 20. or sheet tin. 1 : 30. 29. In strips cut from copper-sheet. 30. In strips or rods, or granulated; it must be proved to be free from As by (181, 182, or 183). 31. Common knittiug-kneedles broken into short lengths, and kept in a bottle containing pieces of quicklime to prevent rusting. J c.c. is the contraction for cubic centimetre. See weights and measures (par. 560). 330 GENERAL reagents [526. 526.—Reagents for General Use, Refer to note under Reference number. Name. [The small numbers in brackets refer to cor- responding numbers in the fifth column.] Formula. 57. 58. Ca(HO), PbAj+KHO 59. 60. KjOijOt 61. 62. Fe,CI„ FeSO«.7HaO 63. KI...' .'. 64. ба. бб. 67. MnO, 68. (i'Hj',0 69. c si..* r. 70. KNOa 71. 72. (NH4)HMo04 78. CaF, 74. K1IS04 75. (Microcosmie salt, or 1 . NaAmllPO, 4HjO... 76. S Hydrie a in mo me sodic phosphate f v 77. CaCla 6H,0 78. K.C1 * .' 79. 80.* H.0 81. NaHO 82. N a jOf), KaCOj 83. Ba"btT......"....r 84. Solution ofsodium acetate in dilute acetic acidv4S) NaA + HA 85. NaNOs 86. Silica, or finely powdered white saud. (See 548,4), 87. hf' 88. Ba(H0)j8H40 89. ZnS04.7Hab. * Nos. 80-89 are certain special 526.] FOR DETECTION of acid radicles. 331 for the Detection of Acid Radicles the heading of (525). Proportion by weight of solid to water. Remarks. [The numbers in this column refer to corresponding numbers in the second column.] See (527). 32. To some of the PbAa solution (No. 40) KHO solu- tion is added until, on warming, the precipitate at first formed is just redissolved: paper dipped into this liquid is a very delicate test for HaS(230). 33. The solution should not contain any free acid : its absence is shown by a single drop of AmHO giving a reddish-brown precipitate Of FeaHoe in the so- lution. 34. FeS04 solution rapidly oxidizes in the air, hence the FeS04 should be kept in the solid state as small green crystals, which should not show a yellow coating in any part; these are dissolved when required, by heating them with water. 35. Starch solution rapidly changes, it is best therefore to keep the starch as a powder. Starch solution is made by stirring 2 grms. of this powder, which has been made into a paste with 10 c c. of cold water, into 100 c.c. of boiling water and cooling. 36. Made by diluting the ordinary solution of indigo in strong HaS04 with about ten times its volume of water, and cooling the mixture; a precipitate will separate after a time, from which the solu- tion is separated by decantation or filtration. 37. Should be kept in fine powder: it must not evolve Cl or 0()a when warmed with strong IIaS04. 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 II>S04. 40. Make the solution with the following proportions: 1 gramme of AmaMo04 is dissolved in 12.5 c.c. 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 12.5 c.c. of strong HNOa mixed with an equal volume of water ; the liquid will become hot, and should be allowed to stand until it is cool before being used. 1 : 24. See (528 1 : 24. Solid. 1 : GO. Solid. 3). Solid. Solid. 1 : 24. See (528, 5). In powder. In small pieces. In small crystals. Solid, in pieces. 1 : 12. Crystals. 1 : 12. In pieces as large as a pea. 40 a. The solution of this salt must yield no precipitate with AgN03 in- soluble in HN03. 41. Must leave no residue on evaporation ; in separate portions no pre- cipitates must be caused by BaCIa, AgN03l or AmaCa04) neither must any precipitate or even dark coloration be produced by addition of AnijS. 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 HaS, nor give a gelatinous precipitate (AlaHoe when mixed with excess of AmCl solution. 43. Dry finely powdered Naa003 and KaC03 are intimately mixed in the proportion of 53: 69 by weight, and kept in a stoppered bottle. 44. Pure powdered BaC03 is either purchased, or is made by precipitat- ing BaCljsolution completely with AmaC03 (or NaaC03) solution, and washing the precipitate well by decantation. This powder is then mixed with distilled water to the consistency of thin cream. 45. Dissolve 20 grammes of NaA in 60 c.c. of distilled water, and add to the solution 40 c.c. of strong HA. 46. By neutralizing strong hot NaaC03 solution with HNOa and evapo- rating to dryness. Sold also as Chili saltpetre. 47. Purchased and kept in gutta-percha bottles. reagents entered apart. 332 PREPARATION of [527,528. PREPARATION OF SATURATED SOLUTIONS.* Preparation of Saturated 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 filtration. The most ready method of preparing a satu- rated 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 repeated at intervals during half an hour or more ; the bottle is then allowed to stand until the excess of pow- der has 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 con- stant 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 per- fectly clear before it is required for use. 1. Lime-water is 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. Prep a ration 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 bottom of the liquid (Fig. 44); the liquid must be kept cold, and be contained in a bottle which is fitted with an accurately ground stopper. In order to ascertain whether * By a “saturated solution ” is meant a solution containing the maximum quantity of the substance which the solvent can dissolve. 528.] SATURATED SOLUTIONS. 333 the solution is saturated, the bubbles of the gas are oc- casionally watched to see whether they diminish in size as they rise through the liquid; if they do not, the bot- tle, after being closed tightly by the thumb or by insert- ing 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 in- haled. 1. Sulphuretted Hydrogen Solution is made by fitting the bent tube a b (Fig. 44) by means of the india-rubber joint e, upon either of the apparatus de- scribed in (500) for the preparation of II2S gas; the gas is thus made to bubble through the distilled water (best recently boiled to expel air, and cooled) until it is saturated. The solution should not be made in large quantities at a time, as it gradually decomposes, depositing sul- phur and losing its smell; it is then un- fit for use. 2. Sulphurous Acid Solution is prepared by passing sulphur dioxide gas into distilled water until it is saturated. The gas is made by heating scraps of copper with strong H.2S04 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 dis- tilled water (Fig. 44) through the tube a b, which is connected with the outlet tube of the washing bottle by means of the india-rubber joint e. The solution must be kept in a well-stoppered bottle. 3. Chlorine-water.—Chlorine gas is made in the appa- ratus shown in Fig. 45, by gently heating manganic oxide Fig. 44. 334 PREPARATION OF [528. (in lumps or in the flask A with some strong commercial hydrochloric acid, previously mixed with a third its volume of wrater. The gas bubbles through a little in the washing-bottle B, and thence through the bent tube a b into the distilled water (Fig. 44). Fig. 45. Fig. 46. 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. Hydrofluosilicic Acid is made by passing silicium 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 mixture of 50 grammes of dry, pure, finely-pow'dered fluor-spar; 300 grammes of strong H2S04 are then poured into 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 the tube, a b, is made to dip into mercury contained in a small beaker d (Fig. 46), which stands in a large beaker containing 400 c.c. of water. As soon as the silicium fluoride gas comes into the vrater, after escaping from the mercury, it is 528.] SATURATED SOLUTIONS. 335 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 im- mersed 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 ar- rested, 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 de- livery-tube (Fig. 47), and the red fumes which escape are pass- ed into dilute H2S04. Care must be taken to maintain the heat uniformly after the fumes commence to be evolved, else the liquid may be sucked back into the hot tube by the contraction of the gas on cooling; also the delivery-tube must be removed from the liquid as soon as the heating is stopped. Fig. 47. 336 SOLUTIONS FOR THE REACTIONS [529. 529.—Solutions for the Note.—Each bottle should boar on its label the number, name, and ties should be kept near the solutions containing the powdered solid these bottles should also carry on their label the name, number, and Name. Reference [The numbers in brackets refer to simi- Formula. larly numbered remarks in the last column.] 100. s KOI 101.s 102. s NaOI MgSO, 7H20 104 Ba0122H20 105 Sr(N()sV4H«0 106 107. s f Alum, or < ( Aluminium potassium sulphate ( A1K(S04V12H20 108 s Fe,0!s 109. s FeS()j.7 HoO 110. s (Chrome alum, or ( CrK'SO,W12HoO ( chromium potassium sulphate | 111. 8 ZnSO«.7H«0 112. s MnOljj 113. s NiSO, 7H«0 114. s Oo(N< >jV.6H»6 HirCl2 116. s PbAo3HoO 117. s Bi' NOj j.5H.)0 118.s CuS04 6rf20." 119. s CdS( )«.4H20 120. s f Arsenious oxide («)' (4l) ) J Solution in dilute HOI f " 120 1 Arsenious oxide («)(") ( ' [ Solution in water f 121.s NaoTIAsO, 12H20 122. s 123. s SnCI°.2H.,0 124 125 126 Hgo(NOjkH»0 * a signifies that, the solid substance is not f Solid Sb2Oj or K(SbO)T (Tartar emetic) 529.] OF THE METALS. 337 Reactions of the Metals. formula of the substance. Small (4 or 6 ounce) wide-mouthed bot- of each of those substances whose number has a small (s) affixed to it; formula of the substance. Weight of solid in grammes to be dissolved in one “Winches- ter.” Proportion by weight of solid to water. Remarks. [These numbers correspond to the small reference numbers in brackets in the second column.] 100 1: 25 1 : 12 1 : 50 1 : 50 1 : 100 1 : 50 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 48. The solution must be made acid with a little H2SO4, and some clean iron nails kept in it. 49. A little HA must be added to this solution to make it clear. 50. 25 grammes of Bi(Nf>3'3 must he dissolved by heat- ing with 25 c.c. 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-twentieth of its volume of strong HC1. 51. Dissolve 10 grammes of Ak203 by heating it with 50 c.c. of strong HCI mixed with 50 c.c. of water, and dilute to the quart.]: 52. Boil excess of As2f>j for several minutes with 200 c.c. of water, filter, and dilute to the quart.]: 53. 25 grains of crystallized SbCls are dissolved in 25 c.c. of strong HC1 mixed with 25 c.c. of water, and diluted to the quart] with HC1 mixed with four times its measure of water. 54. Boil 25 grammes of SnClo with 50 c.c. of strong HC1 mixed with 50 c.c. 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 grammes of SnCl2 with 25 c.c. of strong Ht'l and 100 c c. of water; whilst constantly stirring, add KC'IO, 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 grammes of Hg/N03)2 with 6 c.c. of strong HN< »3 diluted with 114 c.c. of water, then pour water into this solution until it isdiluted to a quart.] Keep Hg in the bottom of the bottle. 200 50 50 25 50 200 (in crystals) 200 25 25 50 25 5) 50 50 50 25 50 25 10 50 1 ; 50 1 : 100 1 : 100 25 25 25 1 : 100 1 :100 25 in the crystalline condition. may be used for the blowpipe reaction. ] Winchester quart. SOLUTIONS FOR THE 530. 530.—Solutions for the Reactions of the Acid Radicles. [Note.—Refer to note at the head of the preceding Table (529), which is also applicable to this. Many of the solutions in this list are already prepared amongst the reagents (524, 525, 526), and the solutions for reactions for metals (529).] Reference number. Name. [The small numbers in brackets refer to corresponding num- bers in the sixth column.] Formula. Weight of solid in grammes to be dissolved in one Winchester quart. Proportion by weight of solid to water. Remarks. [The numbers correspond to the small reference numbers in biackets in the second column.] 130 131. s 132. s 133. s 134 135 136. s 137. s 138.3 139. s 140. s 141. s 142 143 144.s 145 146. s 147. s 148 149. s 150 151 152 153.s 154 .s 155.8 Sodium sulphate J Sodium carbonate (”) 1 Marble (calcium carbonate)(51) ( Ferrous sulphide i48) ■I Ammonium sulphide (") f Acid sodium sulphite Sodium hyposulphite Sodium hypochlorite (“) Potassium nitrite (a) Potassium nitrate Potassium chlorate Sodium chloride (eo) Sodium bromide Potassium iodide Sodium phosphate Sodium arsenate (B1) Borax (*•) .Potassium bichromate J Sodium silicate (ra) fSilica (white sand) Fluor-spar ('-alcium fluoride).. Hydrofluosilicic acid (M) Potassium cyanide (ssj Potassium ferrocyanide Potassium ferricyanide Potassium sulphocyanide Ammonium oxalate (m) 1 Tartaric acid (CT) (Sodium tartrate (68) Sodium acetate (m) Na2SO4.10H2O N a2C< >3 Cato, FeS NatlSOg N a2S2f I3 5 H 20 Na2CI20 KNOo KNO» KCIO, Nad NaBr N HF04.i2il2().... Na2HA.'04.12H20. Na*B4(), ioll20 K2( r2(), NaaSiOj Si02 Kty K4FeCv,.3H20 Am2C204 2H20 H2T Na2T.2H20 NaA.3H20 25 100 100 100 100 50 50 50 12 60 50 25 In fine powder. 50 25 25 25 100 1 : 100 1 : 25 1 : 25 1 : 25 1 : 25 1 : 50 1 : 50 1 : 50 1 : 200 1 : 50 1 : 50 1 : 100 1 : 50 1 : 100 1 : 100 1 : 100 1 : 25 1 : 10 57. The Na2COg 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 (526). 58. The FeS is kept as a solid in small pieces as large as a pea. The Am2S can betaken from reagent bottle No. 7, on the working bench. 59. Strong “Liquor Sodse Chlorinatse,” diluted with an equal measure of water. 60. No. 102, paragraph 529. 61. No. 121, paragraph 529. 62. No 19, paragraph 524. 63. The solution is made by dissolving 100 grammes of the thick syrup, sold as “soluble glass,” in water, and diluting to a quart.* The solid sub- stance to be used is sand finely ground. 64. No. 35, paragraph 525. 65. No. 42, paragraph 525. 66. No. 9, paragraph 524. 67. No. 30, paragraph 525. 68. 120 grms. of H2T are dissolved by heat in 500 c.c. 0! water, the hot solution is exactly neutralized with solid Na2OOt, and then diluted to a quart.* 69. A little of the soliu substance (see No. 41, 525) is dissolved, when required, in water. * Winchester quart. 531.] REACTIONS OF THE ACID RADICLES. 339 531. 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 ar- ranged apart in alphabetical order. Against others a number is placed ; this indicates that the substance is used for analytical purposes, and will therefore be found, together with any necessary descriptive remarks, in one of the foregoing lists (524, 525, 526, 529, 530). [See note at head of Table (532).] Letter or No. of refer- ence. Name. Formula. Remarks. A. HgO KC103 Mn02 C The orange-colored precipitated, ox- ide is best. 20. B. C. Manganese dioxide In powder. No. 66 would serve the purpose, but it is unnecessary that the substance should be pure. In pieces as large as a hazelnut. 57. Ca(HO)2 S I). Roll sulphur broken into pieces as large as a pea. 21. 59. E. / Litmus and turmeric1 \ papers j Potassium dichromate... K20r207 P In small pieces as large as half a pea, kept in a stoppered bottle under water. No. 46 would serve the purpose, but it is not necessary that this zinc should be free from As. Strong, commercial. In pieces not larger than a hazelnut In any form—e. g., turnings, clip- pings, filings, etc. Strong, commercial. (Solid, commercial. The solid (No. < 101) will also serve; but for this ( purpose it need not be pure. F. G. Zn HC1 H. CaCO, I. Cu J. K. 32. UNO, /Ammonium chloride,/ ( or Sal-ammoniac j NII.Cl Oa(HO>> H2C2O4.2H20 HaSO. NaHO L. Solid, iii crystals. Strong, commercial, j Strong solution of the commercial ) solid. In strips. (In pieces as large as a hazelnut •< broken from a lump of rock salt ( or of fused table salt. M. N. O. /Sodium hydrate, or > ( caustic soda j P. 3. (Sodium chloride, or J J common salt J NaCl HNO, 48. AgNO, NH.HO (NH4l2r204 Bat 12 6. 9. 17. Ammonium oxalate 7. 39. Ammonium sulphide.... Potassium nitrate AmaS KNdj 340 CHEMICALS for section hi. [532. 532. Chemicals required for the Experiments on Analytical Operations (Section III). All the substances, with those exceptions* 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 reference indicates that the substance is re- quired in the solid condition (see note at heading of 529). 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. Number or letter of reference. Name. Formula. 39. Potassium nitrate KNO,. 118. s. Copper sulphate (solid) CuS04.6H20. 79. Marble CaCO,. 2. Hydrochloric acid HC1. 45. Copper Cu. 3. Nitric acid II NO,. 17. Barium chloride BaC1.2H20. 8. Ammonium carbonate AnioCO,. 161. * Filter-paper In sheet. 1. Sulphuric acid H.,SO«. A. Mercuric oxide HgO. K. Ammonium chloride NH»C1. ion. s. Potassium chloride KC1. 18. Sodium carbonate Nil .,00,. 112. s. Manganese chloride M nCl2. 19. Borax NaoB40,. 62. s. Ferrous sulphate FeS04.7H20. 102. Sodium chloride NaCl. 160. * Wood-charcoal C. 116. S. Lead acetate (solid) PbA2.3H20. — Red cabbage leaves — 2. Hydrochloric acid HC1. 6. Ammonia NH4HO. 5. -Ammonium chloride nh4ci. 21. J Litmus-paper — j Turmeric-paper * The exceptions are Nos. 160 and 161, which numbers refer to paragraph 533; tain able. also the red cabbage leaves, which are readily ob- 533-535.] substances for analysis. 341 533. Sundry other Requisites not included in the Preceding Lists. 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. 58). Keady 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£ inch and | 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 al- most imperishable, and retain their elasticity very much longer than corks do. SUBSTANCES TO BE G1YEN FOR ANALYSIS BY THE PRECEDING TABLES AND DIRECTIONS. 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 or ex- tending the list. 535. Substances for Analysis whilst trying THROUGH THE REACTIONS FOR METALS AND ACID Radicles. If the student, after trying 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 give him first a few substances containing only one member and to 342 SUBSTANCES FOR ANALYSIS. 536, 537. gradually increase the number present in those subse- quently given. It is well to give these substances in the dissolved state* 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 de- tected by blowpipe 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 following selected for Groups V, IV, and III b will serve: Group V. Group IV. Group III b. Solution of NaCl Solution of BaCl2-2HoO Solution of ZnS04.7H20 “ NIl.Cl “ Sr(N(),V4H20 “ Mn< 12 “ KC1 “ CaCl».6lloO “ NiSO4.7H20 “ NaCl + KOI “ Sr(N0aV4H20 + “ Co(N H,,0 “ Na01 + NH4C1 + CaCI2.6H20 “ MnCl„ + ZnSb.7H.,0 KOI il BaC] o.2 II .>0 -h “ CoNOj2.6H20 + “ NaCl -t-NH401 Sr(N< “f* NiS(>4 7H..O + “ MgS04.7Ho0 + CaCl2 GHoO ZnS04.7H20 NaCl+KCl “ BaCI2.2H20 + etc., etc., etc. Solids: — NaCl, NH.Cl, KC1, AmOi+NCl, etc. Sr(N0,)..4H20 Solids.—MnCl*, NiS04.7H20 Co(NO3'i2.6H20, ZnS04.71120, etc. 536. Substances are given to be tested for the members of an acid-radicle group in the same order (535),* the first substances containing one member only, those sub- sequently 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 * The solutions already made for the reactions, paragraphs 529 and 530, will serve very well for this purpose, being given either singly or mixed. 538.] SUBSTANCES FOR ANALYSIS. 343 in reaction. The following more difficult solutions with acid or alkaline reaction mav also be added to the list: Acid. Alkaline. Ca3'P04 dissolved in dilute HOI. uble glass”). Mg(B» >2 2* “ “ HOI. Na2Sn03 “ “ (“preparing salt” BaCr04 “ “ I1C1. 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 (Knpfernickel). Pb, Graphite (Black lead). FeSj (Iron Pyrites). Iron filings. As insoluble substances which require to be exam- ined by (367 et seq.), the following may be given for analysis: BaS04. CaF2. PbS04. FeCr204 (Chrome Iron Ore). AgCl. S (as pieces of roll sulphur). Sn02 (Tinstone). C (as powdered wood-charcoal or plumbago). 538. Solid Substances to be analyzed by the Preliminary Examinations. For the Preliminary Examinations for Metals (387): Simple. Complex. NH«C1 Hg» 1, As3( )3 KNO, Cr203 Pb(NO,)2 NaCI BaCl2.2If.,0 Sr(N032.4H20 CuS04.6H4.7H20 SnU2 AmCl + NaCl HgCI2 + BaCl2.2H20 MnCUfKCl NiSO4.7FI,0-t- ZnSU4.7H,0 A1K(S04)2.12H0 Sn02+Sr(N,.7H20 KNO, KKr Cat Uo+Cal'., Cat 120 KClOj Na2tOs-f KI. MaCl KI A few of the above-mentioned solids may then be examined by both Preliminary Examinations for both Metals and Acid Radicles. 539. Substances to be analyzed by the Gen- eral Course (380 et seq.). The following lists are so arranged that the analysis of the substances contained in them is more difficult in each column proceeding from left to right, and usually also in proceeding in one and the same column from top to bottom. For examples of Alkaline Solutions, see (537): Substances for Analysis by the General Course 1. Simple soluble substances. 2. Complex soluble substances. 3. Complex soluble substances. BaCl2.2H20 MnClo HgCl2 MgS047H»0 KC1 NiS04.7IIo0 *Caro3 Pb(N03)2 *As2<)3 Fe2Cl6 NH.Cl NaCl etc., etc. CaCl2.fiH20+BaCl«.2H20+Sr(N03'2.4KU0 AlK(S04'2.12HoO+CrK(S04'2 MnCl2 + ZnS04JH20+CuSO4.6H20 Pb(N03'2+HgCl2+NaCl *As203 f"CaC03-f B:i003 *ZnO + MgCOa + KC10, *MgC0„+BaCOs+PbCO, etc., etc. fFe2Cl. j MnCl2 1 ZiiS04.7H20 1 KC1 f As203 ■{ CrK(S04)2 12H20 ICo(N02)2.6H„0 f Hg2fNOoi.jlfoO I Sr(N02)2.4H20 1 kno2 [Bi(N02)2.5H20 etc., etc. * To be given in the solid state. 539.] SUBSTANCES FOR ANALYSIS. 345 4. Substances yielding a phosphate precipi- tate in Group III. 5. Substances partly or entirely insoluble. (CaC12.6II20 i Fe2CI8 (N HP04.12H20 f BaCl2.2H20 1 Mg«'l2 1 Fe2ri6 [Na2IIP04H20 BaS04 Si02+S BaS04 -|-CaF2-(-Sn02 f Ba01o.2H20 { A1K(S04)o.12II20 (AgNO, csio2 (C PI>SD4+BaS04 PbCrU4 (ignited) Metallic Substances (467 et seq.) Iron pyrites (FeS2) Iron filings (Fe) Zinc clippings (Zn) Brass filings (Cu+Zn) German silver (Cu+Zn+Ni) Bronze (Cu-fSn) Type-metal Sb+Sn+Pb) f Co(NOi2.6HoO CaCl2.6H20 <> Mn('T2 CrK SO4kl2II20 |_Na2HPO4~H20” etc., etc. Silicates (480)— Fire-clay (Al20,.2Si02) Brown-day ( “ +Fe) Window-glass (Na,Ca,Si02) Flint-glass (Pb, K, Si02) Cyanogen Compounds (482)— Any of the foregoing which has been mixed with KCy, KCyS, KtFVCys.3H20, Ks Fe2Cy12,KcCo2Cyt2 APPENDIX I. REACTIONS FOR THE RARER ELEMENTS. This Appendix contains some of the most important reactions for many of the rarer elements. The arrange- ment here used is that adopted in Section IV, those elements being placed together which are precipitated in the same analytical group: the groups are arranged in the order in which they occur in the General Table. A scheme for the detection of these elements follows (553), showing in which group they are precipitated in the General Table, and by which reactions they will be most readily found. GROUP I.—SILVER GROUP. In this group are included Tl and Wo: the former is par- tially precipitated as chloride by HCl, the latter com- pletely as tungstic acid. Thallium is only partially precipitated in Group I, since its chloride is not quite insoluble in water: it belongs also to Group III B, being entirely precipitated by Am2S. 540. Thallium (Tl).—Use T12S04 solution. T1 occurs in small quantity in many natural sulphides, often also in the ashes of plants and in mineral waters. Tl yields both thallic and thalliow.s' salts, but the former are very unstable, changing even when their solutions are heated into thalliows salts. HCl: a white precipitate, which rapidly settles, does not blacken in the light, and is soluble in aqua regia. It is soluble in a large quantity of water, and therefore does not form in dilute solutions. 541.] APPENDIX I. — TUNGSTATES. 347 KI: a yellow precipitate ; almost insoluble in water, more solu- ble in KI solution. In a solution containing Fe, any ferric salt must first be reduced by II2S03 before adding KI. PtCl4.* orange-red precipitate, slightly soluble in water. Am2S: black precipitate, which is easily coagulated by heat, is insoluble in AmHO, alkaline sulphides, and in KOy: it is readily oxidized by the air to T12S04, and is easily soluble in mineral acids. T1 is entirely precipitated by H2S from a solution in which HA is the only free acid present, but free mineral acids prevent the precipitation entirely. Flame coloration.—Thallium compounds impart to the Bunsen flame an intense green color, which, however, rapidly disappears. The spectrum (p. 360) is very characteristic, consisting of one bright emerald-green line. Thallium may usually be easily detected by the spectroscope in so- lution, or better in any of its precipitates mentioned above. 541. Tungstates.—Use Na2Wo04 solution. Wo usually occurs in the form of a tungstate. The insolu- ble tungstates yield soluble alkaline tungstates on being fused with alkaline carbonates. From a solution of alka- line tungstate HC1 precipitates the tungstic acid entirely. HCl (HNOj or HjS04), white precipitate (H2Wo04), becom- ing yellow on boiling: insoluble in excess of acid, but soluble in AmHO. A piece of Zn dropped into the acid liquid containing the precipitate yields a deep blue color. SnCI2 (a neutral solution made by dissolving SnCl2 crystals in water and filtering): yellow precipitate, becoming blue on addition of HCl and heating. Am2S yields no precipi- tate in a solution of alkaline tungstate ; but if, after add- ing Am2S, the liquid is made acid with HCl, brown WS3 is precipitated. Microcosmic bead:— In outer flame—Colorless or yellow. In inner flame—Blue: if a little FeS04 is fused into the head the color changes to blood-red. These colors are best seen when the head is perfectly cold. GEOUP II a.—COPPEE GEOUP. In this group are included Pd (Os, Eh, Eu): they are pre- cipitated as sulphides by H2S from acid solutions, and the sulphides are insoluble in Am,8, and in caustic alkali solution. 348 PALLADIUM, MOLYBDATES. [542, 543. 542. Palladium (Pd).—Use PdCl2 solution. Pd occurs as a metal in native platinum, also in gold and silver. Palladium solutions are reddish-brown, or yel- low if dilute : addition of water precipitates a basic salt, unless sufficient free acid is present to prevent it. H2S: a black pp., in neutral, alkaline, and acid solutions: this pp. is insoluble in Am2S, but soluble in boiling HCl or in aqua regia. AmHO: flesh-colored pp. (PdCl2.2NHs) ; soluble in excess of AmHO to a colorless liquid, from which HCl precipitates yellow crystalline paladammonium-chloride (N2H6Pd// ci,). IIgCyi: yellowish-white gelatinous pp. (PdCy2), slightly solu- ble in HCl, easily soluble in AmHO. Very characteristic reaction. KI: black pp. (Pdl2). Very characteristic. GROUP II b.—ARSENIC GROUP. In this group are included Mo, Se, Te (Ir). 543. Molybdates (Mo).—Use Am,Mo04 solution. Mo occurs as a molybdate; also as sulphide, which may be readily converted into MoOs by ignition in the air or heating with 1IN03. Unignited MoOs dissolves in acids; ignited MoOs is insoluble in acids, but easily soluble in alkalies. HCl (HN03 or H2S04), added in small quantity to an aqueous solution of a molybdate, yields a precipitate which is readily soluble in excess of the acid. H2S, added in very small quantity to the acidified solution gives a blue liquid, in larger quantities a brown pp. (MoSs); the precipitation becomes complete only when the solution is heated and H2S passed for some time: the pp. is soluble in solutionsof alkaline sulphides and hydrates, from which it is reprecipitated by acid added in excess. Zn or SnClv added to a solution of a molybdate in HCl, colors it brown, green, or blue, according to its state of concen- tration. KCyS, added to a solution acidified with HCl, gives no colora- tion ; but on dropping in a piece of Zn a beautiful crimson color is produced, which, when the liquid is shaken with ether, is taken up by the ether. NatHPOv added in very small quantity to an acidified solu- tion (best with HN03) of a molybdate, gives, on gently warming the liquid, a yellow precipitate readily soluble in excess of alkali-hydrate solution. Borax bead: outer flame, yellow; inner, dark-brown. Microcusmic bead: outer and inner flames, green. 544, 545. SELENIUM, TELLURIUM. 349 544. Selenium (Se).—Use a metallic selenide, an alkaline sele- nite and selenate. Se occurs as metallic selenides (e.g., of Fe, Cu, Ag). A selenide heated in an open tube evolves a smell of de- caying horse-radish, and produces a gray or red subli- mate of Se: the smell is very characteristic. a. Selenites: H2S gives in acid solutions, if cold a yellow, if hot a reddish-yellow pp.: soluble in Am2S. BaCl2 in neutral solutions a white pp : soluble in HC1 or HNOs. SnCl2 or //2.S03 gives in the presence of free HC1 a red, or in warm solutions a gray pp of Se. Cu in a hot HC1 solution becomes covered with a black film: the liquid on standing with the Cu for some time becomes colored red with Se. b. Selenates : HCl produces no change in the cold; but on boiling Cl is given off and the selenate reduced to selenite, to which the above tests under a. may be applied. BaCl2: a white pp. (BaSe04); insoluble in cold HCl; dissolved by boiling with HCl with evolution of Cl and reduction to BaSe03. c. Selenium in any form of combination is detected by the following reactions: Heated on charcoal in the inner blowpipe Dame a smell of rotten horse-radish is perceived. Fused on charcoal with Na2COs in the inner blowpipe flame a fused mass is obtained, which when moist- ened on Ag yields a black stain, and on addition of HCl evolves H,Se. 545. Tellurium (Te).—Use a metallic telluride, an alkaline tellurite and teliurate. Te occurs united with metals {e.g., Au, Ag, Bi, Cu, Pbj. A telluride heated in an open glass tube gives white fumes and a sublimate which differs from that given by Sb, by being fusible before the blowpipe. a. Tellurites: U20: on dilution with water tellurous acid is precipi- tated from the acid solution. H.2S: in acid solutions a brown pp. (TeS2); easily solu- ble in Am2S. H2SOv SnC/2, or Zn precipitates black Te. 16 350 APPENDIX I. — URANIUM. [546. b. Tellurates. HC1 produces no change in the cold, but on boiling Cl is evolved, and the tellurate is reduced tellurite; the solution then gives the above reactions under (a). c. Tellurium in any form of combination, if fused with Na2 C03 on charcoal in the inner blowpipe flame, gives so- dium telluride ; a solution of which gives a black stain on Ag, and on being acidified deposits black Te and evolves TeH2. GROUP III.—IRON AND ZINC GROUPS. In this group are included U, In, Ti, Be, T1 [V], (Zr, Ce, Ta, Nb, La, Di, Y, E, Th). Tl is often partially precipitated as chloride in Group I, and its reactions are given under that group. V is not pre- cipitated by Am2S unless acid is added in excess after Am2S. 546. Uranium (U).—Use (U02)//(N03)2. U occurs in nature principally as pitchblende (oxide), also as uranite (a hydrated uranium-calcium phosphate) and chalcolite (hydrated uranium-copper phosphate). AmHO (KHO, NaHO): yellow pp., insoluble in excess. Am2S gives in neutral solutions a dingy-yellow or brown pp. of uranium oxysulphide, which is soluble in Am2C03 (diff. from ZnS, MnS, FeS, etc.). The pp. settles slowly unless AmCl is added ; it is soluble in acids, even in HA : on heating with Am2S in excess it is changed into uranous oxide and sulphur. H2S produces no pp. in acid solutions. Am2C03 (KHC03, NaHC03): yellow pp., easily soluble in ex- cess; from this solution the uranium is reprecipitated by addition of NaHO or KHO, or by boiling. (Diff. from Fe.) KJ?eCy3 gives in acid solutions a reddish-brown pp. The pp. is distinguished from the similar one produced in a copper solution by dissolving in excess of AmHO to a yellow fluid. BaC03: complete precipitation even in the cold. Zn changes the yellow color of acid solutions to green. Borax and Microcosmic beads: Outer flame, yellow; inner flame, green. 547-549.] INDIUM,BERYLLIUM,TITANIUM. 351 547. Indium (In). Alkali-hydrates precipitate a hydrate resembling Al2Hog ; in- soluble in excess. Indium solutions are also precipitated by alkaline carbonates, by Nh2HP04, by boiling their neutral solutions with NaA, by BaCOa, and by alkaline oxalates. H2S gives no pp. in strong acid solutions, in dilute and feebly acid solutions a little sulphide separates, in a solution containing no free acid but HA the metal is entirely pre- cipitated as yellow sulphide: the pp. is insoluble in cold, soluble in boiling, Am2S ; from the boiling solution white sulphide separates on cooling. , Am2S, added after H2T and excess of AmHO, gives a white pp., becoming yellow on treatment with HA. Flame coloration: bluish-violet. The spectrum shows two very characteristic blue lines, which are brilliant, but very rapidly disappear when the chloride is employed: see p. 360. 548. Beryllium (Be).—Occurs as silicate in phenakite, and as silicate with Al-silicate in beryl and emerald. Am2S (AmHO, KHO, NaHO): flocculent hydrate is precipi- tated resembling Al2Ho6 in its appearance, and in being soluble in KHO. Differs from Al2Ho6 in being precipi- tated from its solution in KHO by dilution and long boil- ing, and by being soluble when freshly precipitated if it is long boiled with AmCl solution. Alkaline carbonates precipitate a carbonate'soluble in excess, especially in Am2C03; from these solutions the carbonate is reprecipitated, on diluting and boiling for some time, with especial ease from the Am2COs solution (diff. from Al). BaC03 precipitates Be solutions completely : 1/2C204 and alka- line oxalates produce no pp. Moistened with Co(NOs)2 solution and heated on charcoal in the outer blowpipe flame, a gray mass is obtained (diff. from Al). 549. Titanium (Ti.)—Occurs as Ti02 (with traces of Fe, Mn, Cr) in rutile, anastase, and brookite: also as Ti02 in com- bination with Ft; in titaniferous iron ore. Ignited Ti02 is insoluble in water and most acids: it is easily soluble in HF, less readily in boiling strong H2S04: it is also rendered soluble in cold water by fusion with KHSG4. Ti02 differs from Si02 in not being volatilized when heated in a platinum dish with HF and strong H2S04. By dilution and long boiling, hydrated Ti02 is precipitated as a white flocculent pp. from solutions in H2S04 (or HC1), and from the aqueous solution of the fusion with KH>504: 352 APPENDIX I. VANADIUM, LITHIUM. [550,551. the pp. is metatitanic acid. It cannot be filtered off un- less an acid or AmCl is added. AmldO (KUO, NaHO, Am2S, or BaC03)y white flocculent pp., insoluble in excess: if precipitated and washed in the cold the pp. dissolves in HC1 and in dilute H2S04. Zn or Sn gives in acid solutions a blue, or if dilute a rose- colored, liquid. Na2S203, on boiling, precipitates Ti solution entirely (diff. from Fe). Microcosmic bead: In the outer flame: yellow whilst hot; colorless, cold. In the inner flame: yellow, hot; violet, cold. The production of these colors is much aided by add- ing a fragment of Sn. Addition of a small quantity of FeS04 gives in the inner flame a blood-red bead. 550. Vanadium (V.) Occurs in vanadinite [3Pb3(P04)2.PbCl2], and in certain Fe and Cu ores. Vanadium is known in several stages of oxidation ; it will usually occur in analysis as vanadic acid or a vanadate, which in acid solution is of a yellow or reddish color. H.2S (H2S03 or if20204) reduces acid solutions of a vanadate, and causes the color of the solution to change to blue: with H2S a deposit of sulphur also forms. Am2S, if added in excess, gives a brown liquid, in which an excess of acid causes a brown pp. of V2S5 ; excess of Am2S dissolves this to a reddish-brown liquid. Zn gives in a very dilute solution acidified with H2S04, and gently warmed, a blue color, which changes into green and then lavender-blue. Solid AmCl, added until the solution is saturated, precipitates Am3V04, which is insoluble in saturated AmCl solution. Very characteristic reaction. H202 when shaken up with an acid solution imparts a red color, which is not removed by shaking with ether. This is a very delicate test. Borax bead : In outer flame; colorless or yellow if much V is present. In inner flame; green hot and cold; if much V is present, brown hot, and green cold. GROUP V.—POTASSIUM GROUP. In this group are included Li, Cs, Rb. 551. Lithium (Li). Li occurs frequently in mineral waters and in the ashes of plants, also in small quantities in the minerals 552.] APPENDIX I.—LITHIUM, RUBIDIUM. 353 lepidolite, triphane, and petallite. It is allied to the Barium Group by the difficult solubility of its car- bonate and phosphate ; and it differs from K and NH4 by not being precipitated by PtCl4 or by H2T: from Na it is readily distinguished by the flame coloration and spectroscope. LiCl is separated from KC1 and NaCI by its insolubility in a mixture of absolute alcohol and ether. Na.iHPOi added to the not too dilute solution, made decidedly alkaline with NaHO, gives, on boiling, a white crystal- line pp. (Li3P04) which quickly settles. Traces of Li may be precipitated by adding Na2HP04, then NaHO until the liquid remains alkaline, evaporating to dryness and washing the residue with dilute Am HO. This pp. differs from the phosphates of Ba, Sr, Ca, and Mg by fusing in the blowpipe flame and being absorbed by the charcoal support, also by its diluted solution in HC1 giving no pp. on addition of AmHO in excess in the cold, but a white crystalline pp. on boiling. Flame coloration: this is carmine-red; the spectrum (see p. 860) consists of two lines, an intense carmine-red line (*) and a feeble orange-yellow line ($). This coloration is concealed by that of Na, which, however, does not in- terfere with the lithium spectrum : the Na coloration is also removed if the flame is viewed through the indigo- prism, whereas that of Li can pass through the thinner parts of the prism ; it differs from the K coloration, how- ever, in being unable to penetrate the thiclc layers of indigo solution, or in being much weakened by its pas- sage. As silicate, Li only gives the flame coloration after fusion with CaS04; the phosphate requires to be first moistened with H(J1. 552. Rubidium (Rb), and Cesium (Cs). These metals occur in small quantities in some mineral waters and in a few minerals. Their compounds resemble those of K in being precipitated by PtCl4 and by H2T, and in giving a similar flame coloration. Characteristic differ- ences are, the much, greater insolubility in water of the platino-chlorides, which enables the K2PtCl6 to be dis- solved away from Rb2PtCl6 and Cs2PtCl6 by boiling the pp. with successive small quantities of water: the alums also show a similar difference in solubility in cold water. Cs and Rb are readily distinguished from one another and from other elements by their spectra (see p. 360). For Cs the blue lines (a, &) are especially distinct and charac- teristic: in the Rb spectrum the indigo-blue lines (a, @) are very distinct, but the red lines (■y, by KI (Pb is also thus ppd.): PtS2: the pp. is yellow, and gives the thallium spectrum. [/r-sulphide*] ] Mo- “ (brown) i Soluble in H-i WO,: a white pp., becoming Se- “ (red-yellow) f Ani2S. Te- “ (black) J yellow on boiling. Its pres- ence is confirmed by drop- ping a piece of Zn into a por- tion of the acid liquid and pp., when a deep blue color will be obtained. The yellow color of a solution containing V changes to blue. Also by fusion of the pp. in a microcosmic bead, which will be colorless or yellow in the outer flame, blue (or with Tl is readily found by the spectroscope in the FeSO*, blood-red) in the inner group pp. flame. Pd will remain in solution in excess of AniHO with Cd and Cu in Table II a ; from this solution it is ppd. by adding HC1: its presence may be further confirmed by the IIgCv2 or KI tests. The examination of the sulphides in Group II b, when the above elements may be present is best commenced by fusion with and NaNO*. From the fused mass, water dissolves sodium-arsenate, -molyb- date,-seienate, and -tellurate, leaving SnOg, sodium- antiinonate, An, Pt, and Ir undis- solved ; the elements may then be detected by special tests. For the separation and detection of the platinum metals a larger work must be consulted. * Only completely ppd. if the liquid has been 553.] PRECIPITATION OF RARER ELEMENTS. 355 Precipitation of Rarer Elements. Group III. Reagents Precipitated from the AmCl, AmHO, and filtrate from Group III by excess of HC1. Group V. AnisS. The group pp. may contain As sulphides: The filtrate after the sep- as sulphides, in addition aration of all the group to Fe, Zn, Mn, Ni, Co: V (black). precipitates, may con- W (trace, brown). tain besides Mg, K, and U (black-broum). /»( “ “ )• Tl ( “ “ ). Ni (trace, black). Na: This pp. is dried and then Li, Cs, Rb. fused with a mixture And as hydrates in addi- of Na2C03 and KNO,: These metals are readily lion to At, Or (and phos- on boiling the mass detected by their very phates, etc.): witli water, NiO re- characteristic spectra mains undissolved; it (p. 360). Ti (while, flocculent). is filtered off, and its LiCl may also be de- Be (colorless, gelatinous). presence confirmed by tected by its behavior 1Zr]( “ “ ) [To, Nb, Ce, La, Di, Y, E, fusion in a borax bead. with NajjHPO,. Th.} The aqueous solution Before proceeding to the may contain alkaline spectroscopic examina- vanadate and tung- tion, it is well to con- state. V is separated by vert them into chlo- Tl and In will usually be saturating the liquid rides if they are not readily detected by a with AmCl, and its already in that form. spectroscopic examina- tion of the pp. presence confirmed in the pp. by the borax If the chlorides are evap- bead, and by dissolving orated to dryness, and Tl may be first separated the pp. in HC1 and extracted with abso- and detected bv disolv- employing the reac- lute ether and alcohol, ing some of the group tions with H2Oo and to which a few drops pp. in boiling dilute with Zn. of HC1 have been add- HC1, and reducing any Fe present in the solu- The filtrate (after con- ed, LiCl, RbCl, CsCl dissolve, whilst the greater part of the tion by then centration, if neces- precipitating Tl by ad- sary) is acidified with KC1 and NaCl remain dition of KI, and test- HC1, and the pres- undissolved. ing the pp. by the spectroscope. enceof W confirmed by the Zn reaction and The solution is evapora- the microcosmic bead. ted to dryness, dissolv- ed in a little HC1 and Rb and Cs are pp. may con- sist of 77O2 (possibly also t races of Zr). Confirm the Filtrate: add a few drops of strong HNOt, concentrate by evaporation, and add AmHO in excess: filter, dissolve the pp. in HC1, and precipitate once more by adding excess of AmHO: * Pp. may contain Fe, In, U, Cr, Al, Be, etc. Dissolve it in HC1, and add excess of cold strong KHO solution: Filtrate may presence of Ti02 by the microcosmic Pp. may contain Fe. In. U, etc. Dissolve in HC1, boil off any large excess of HC1, add BaC03, and let stand: Filtrate may contain Al, Cr, Be: dilute and boil for some time, filter. Al re- mains in solution, and may be pp937 — .03937 Centimetre = 0.01 = .49371 — .39371 Decimetre = 0.1 = 3.93708 -= 3.9371 Metre = 1.0 — 39.37079 — 3 3.371 Decametre = 10.0 = 393.70790 = 10 2 9.7 Hectometre = loo.o = 3937.07900 — 109 1 1 Kilometre = lOOit.O = 39370.79000 = 4 213 4 10.2 Myriometre = 10000.0 = 393707.90000 = 6 1 156 0 6 1 inch = .0254 metre. 1 foot — .3048 44 * Frequently written “gram” in English, for the sake of brevity. f Usually written (m.m.). J Usually abbreviated (e.c.). 561.] FRENCH WEIGHTS AND MEASURES. 363 MEASURES OF CAPACITY. 1 Litre — 1 cubic decimetre. Litre. Cubic inches. Pints. Millilitre, or Cubic centimetre (c.c.) (- .001 = .06103 — 0.00176 Centilitre = .01 — .61027 = 0.10761 Decilitre = .1 = 6.1027 = 0.17608 Litre = 1.0 = 61.027 = 1.76077 Decalitre = 10.0 — 610.27 = 17.60773 Hectolitre 100.0 = 6102.7 = 176 07734 Kilolitre = 1000.0 = 61027.0 = 1760.77341 Myriolitre 10000.0 = 610270.0 = 17607.73414 1 cubic inch = 01639 litre. 1 cubic foot = 28.31531 litres. 1 gallon — 4.54336 “ 1 gramme = the weight of 1 cubic centimetre (c.c.) of water at 4° C. MEASURES OF WEIGHT. Gramme. Grains. Avoirdupois. Milligramme = .001 a— 0.01543 Centigramme — .01 0.15432 Decigramme = .1 = 1 54323 Ibs. drms. Gramme 1.0 — 15 43235 oz. Decagramme — 10.0 =-= 154.32349 «= 0 0 5.65 Hectogramme — 100.0 = 1543.23488 *= 0 3 8.5 Kilogramme — 1000.0 = 15432.34880 «= 2 3 5 Myriogramme — 10000.0 154323.48800 =” 22 1 2 1 grain — 0.0649 gramme. 1 oz. (Troy) *=> 31.1035 grammes. 1 lb. (Avoirdupois) = 453.593 “ ENGLISH WEIGHTS AND MEASURES. Apothecaries’ Weight. !b. oz. dims, scruples, grains. 1 _ 12 = 96 -= 288 — 5760 1 — 8 = 24 — 480 1 — 3 — 60 1 — 20 Avoirdupois Weight. Ib. oz. drms. grains. 1 — 16 = 256 — 7000 1 — 16 — 437.5 1 — 27.343 Imperial Measure. gallon. pints. fluid oz. fluid drms. 1 = 8 = 160 = 1280 1 =. 20 = 160 1 = 8 1 gallon =*= 70,000 grains of water at 16.7° C. 1 fluid ounce = pint = 437.6 “ 1 gallon — 277.280 cubic inches. 1 fluid ounce — 1.733 “ INDEX. Acid, test for an, 73 “ radicles, detection of in simple substances, . . . 207 “ “ detection of, in complex substances, . . 265 “ reactions of, ...... 146 Acids, removal from clothes, ...... 34 Acetates, reactions of 183 Acetic acid, 183 Alkaline reaction, .74 Aluminium, reactions of, 104 Ammonia gas, preparation of, . . . . . .31 “ “ properties of, 32 “ “ tests for, ....... 33 Ammonium, reactions of, ....... 92 Analysis, course of, 78 “ introduction to, ....... 80 “ of a simple liquid, 194 “ “ solid, 188 “ a complex liquid, 237 “ “ solid, 238 “ an alkaline liquid, ...... 214 “ cyanogen compounds, ..... 291 “ insoluble substances, . . . .218, 286 “ metallic substances, 217, 281 “ silicates, 290 “ substances for, ....... 341 Analytical classification, ....... 81 “ “ table of, 186 “ groups, ......... 82 “ reactions, 89, 146 Antimony, reactions of, ....... 135 Apparatus, list of students', ....... 303 “ list of general, 306 “ cleaning of, 49 Arsenic group, 127 “ “ separation and detection of, , . . .139 “ “ table of differences, ..... 139 “ “ table for analysis, 199, 256 “ “ reactions of, . . . . . . .128 Atomic weights, list of, , 361 PAGE 366 INDEX. Barium group, ......... 100 “ “ separation and detection of, . . . . 102 “ “ table of differences, ..... 102 “ “ table for analysis, ..... 206, 261 Barium, reactions of, 100 Bending glass tube, ........ 44 Beryllium, detection in analysis, ..... 355, 356 “ reactions of, ....... 351 Bismuth, reactions of, 122 Blowpipe, use of, . . . . . . . . 42, 66 Borates, reactions of, ....... 169 Borax bead, .......... 67 Boric acid, reactions of, 170 Boring corks, ......... 45 Bromides, reactions of, . 159 Bunsen burner, ......... 40 Cadmium, reactions of, 125 Csesium, detection in analysis, ...... 355 “ reactions of, ....... 353 Calcium, reactions of, . 101 “ sulphate, preparation of, ..... 332 Carbon dioxide, preparation of, . . . . .25 “ “ from combustion, 30 “ “ from respiration, ..... 29 “ “ properties of, .... 26-29 “ “ tests for, ....... 29 “ “ in the air, ....... 31 Carbon monoxide, preparation of, . . . . . .33 “ “ properties of, . . . . . .35 “ “ tests for, ....... 35 Carbonates, reactions of, 143 Carbonic acid, reactions of, . . . . . . .149 Centigrade scale, ......... 361 Charcoal, wood, ......... 341 “ combustion in oxygen, 20 “ ignition on, 70 Chemicals, list for Section I, 339 <« “ “ III, 340 Chlorates, reactions of, ........ 156 Chloric acid, reactions of, 157 Chloride group, separation and detection of, . . . . 164 Chlorides, reactions of, ....... 157 Chlorine, preparation and properties of, .... 36 “ tests for, 36 “ water, preparation of, 333 Chromium, reactions of,. . . . . . . . 106 Chromates, reactions of,. ....... 170 Classification of metals, 82 “ “ table of, ..... 186 PAGE 367 INDEX. Cleaning apparatus, 49 “ platinum, ........ 50 Cobalt glass, .......... 306 “ • reactions of, . . . . . . . .114 Combustion in oxygen, of charcoal, ..... 20 “ “ phosphorus, ..... 21 “ “ sulphur, ..... 21 Contractions, list of, ...... 82, 87 Copper group, separation and detection, .... 126 “ “ table of differences, ..... 125 “ “ “ for analysis, ..... 199, 255 “ reactions of, ....... 123 Corks, . 341 “ boring of, 45 Cutting glass tube, ......... 43 Cyanides, reactions of, . . . . . . . .176 Decantation, process of, . . . . . . . .60 Detection of gold and platinum, 285 Differences, table of: Group I, ...... 144 “ “ “ II A, 125 “ “ “ II b, 139 “ “ “ III a, 108 “ “ “ III b, 116 “ “ “ 1Y, 102 « « “ Y 96 Distillation of water, 37, 313 “ nitric acid, ....... 38 Distilled water, tests for, 38, 331 Drawing out glass tube, ........ 44 Drying precipitates, ........ 62 Elements, list of chemical, 361 Entry in note-book, rules for, ...... 84 “ of results, examples of, ..... 222, 296 Equation, chemical, ........ 85 Evaporation, process of, . . . . . , . .55 Fahrenheit scale, ......... 361 Ferricyanides, reactions of, . . . . . .179 Ferrocyanides, “ ....... 179 Filter-paper, .......... 341 Filtration, process of, ........ 58 Flame colorations, ......... 69 Flask, tubulated, 312 Fluorides, reactions of, . . . . . . . .173 Fluosilicates, “ “ . . . . . . . .175 Fusion, process of, . . . . . . . • .66 General table for groups, 249 “ “ detection of rarer elements, . . . 354 PAGE 368 INDEX Glass tube, bending, 44 “ “ cutting, ........ 43 “ “ drawing out, 44 Gold, reactions of, 145 “ detection of, 285 “ separation from platinum, 285 Gramme, 362 Group III, precipitation of, 273-276 “ tables for analysis of, 276-281 “ table for rarer elements, 356 Heating glass and porcelain, 51 Hydriodie acid, reactions of, 163 Hydrobromic acid, “ 161 Hydrochloric acid gas, preparation of, 36 “ “ tests for, ...... 36 “ acid, reactions of, ..... 159 Hydrocyanic acid, 178 Hydrofluoric acid, 175 Hydrofluosilicic acid, . . . . . . . .176 “ “ preparation of, .... 334 Hydrogen, collection of, 22 “ combustion of, 24 “ explosion of, ....... 25 “ preparation of, . 22 “ sulphide, reactions of, . . . . . . 150 “ test for,......... 25 Hydrosulphurie acid, reactions of, 150 Hypochlorites, reactions of, ....... 152 Hypochlorous acid, “ ...... 152 Hyposulphites, “ 152 Hyposulphurous acid, “ 151 Ignition, process of, 64 “ on charcoal, ........ 70 “ tubes, preparation of, 46 Indigo prism, 306 Indium, detection in analysis, 355, 356 “ reactions of, 351 Insoluble substances, analysis of, . . . . . 218, 286 Iodides, reactions of, 161 Iron group, 103 “ separation and detection of, ... 109 “ table of differences, ...... 108 “ table for analysis, ...... 257 Iron, reactions of, 105 Labelling bottles, ......... 324 Labels, varnishing of, 325 Lead, reactions of,. ........ 121 Lime-water, preparation of, 332 PAGE INDEX. Liquid reagents, dilution of, • 318 Lithium, detection in analysis, 355 “ reactions of, ....... 352 Litmus-paper, use of, 73 Litre, the, 362 Magnesium, reactions of, 94 Manganese, “ ....... Ill Mercuricum, “ ....... 118 Mercurosum, “ ....... 143 Metallic substances, analysis of, 217, 281 Metals, examination for, ...... 196, 249 Molybdates, detection in analysis, 354 “ reactions of, ...... 348 Mortar, agate, 310 Neutralizing, process of, ....... 74 Neutral reaction, ......... 73 Nickel, reactions of, 112 Nitrates, “ 154 Nitric acid, reactions of, ....... 155 Nitric oxide, preparation of, 30 Nitrites, reactions of, ....... 153 Nitrogen tetroxide solution, preparation of, . . . . 335 Nitrous acid, reactions of, 153 Notation, chemical, ........ 84 Note-book, rules for entry in, 84 “ examples of entry, 222, 296 Organic acid radicles, reactions of, 176 Oxalates, reactions of, ....... 180 Oxalic acid, “ 181 Oxygen gas, collection of, 18 “ “ experiments with, ..... 20, 21 “ “ preparation of, . . . . . . .17 “ “ test for, ........ 21 Palladium, detection in analysis of, 354 “ reactions of,. . 348 Phosphates, “ 166 “ table for analysis of, 279 Phosphoric acid, reactions of, 167 Phosphorus, combustion in oxygen, 21 Platinum, detection of, . . . . . . . . 286 “ reactions of, 145 “ separation from gold, ...... 286 Platinum wire, mounting, ....... 47 “ “ cleaning, ....... 50 Potassium group, 89 “ “ separation and detection, .... 97 PAGE 370 INDEX PAGE Potassium group, table of differences, 9b “ “ table of analysis, .... 99, 264 Potassium, reactions of,. . . . . . . .90 Precipitates, drying of, 62 “ “ removal from filter, . . . .62 “ “ washing, ...... 61 Precipitation, process of, 56 “ of Group III, remarks on, .... 273 “ “ “ rules for, ..... 275 Preliminary examination for metals, . . . 190, 194, 240 “ “ for acid radicles, „ . . 209, 246 “ “ of cyanogen compounds, . . 292 “ “ of insoluble substances, . 218, 287 “ “ of metallic substances, . . 217, 281 Prussic acid, reactions of, 178 Barer elements, reactions of, 346 “ “ tables for detection of, . . . . 354, 356 Reactions, entry of, 84 Reagents, addition of, in excess, . . . . . . 233 “ preparation of, . . . . . . .318 “ list of special, 326 “ “ general, for metals, ..... 328 “ “ “ “ acid radicles, .... 330 Residues, silver, ......... 316 “ platinum, 317 Rose burner, .......... 41 Rubidium, detection in analysis, 355 “ reactions of, ....... 353 Rules for working, ........ 87 Saturated solutions, preparation of, .... 332 Selenates, detection in analysis, ...... 354 “ reactions of, 349 Selenites, “ “ 349 Selenium, “ “ ....... 349 Silicates, analysis of, ....... 290 “ reactions of, . . . . . . .172 Silicic acid, “ “ 172 Silver group, 143 “ “ separation and detection of, ... 144 “ “ table of differences, ...... 144 “ “ table of analysis, ...... 254 “ reactions of, . . . . . . . .143 Simple substances, analysis of, ..... 185 Sodium, reactions of, . . . . . . .93 Solubility, table of, ........ 271 Solution, process of, ........ 53 Solution of solid reagents, ....... 319 Solutions for reactions of metals, ...... 336 “ “ “ “ acid radicles, .... 338 INDEX. 371 Spectroscope, its use in analysis, 357 Spectrum chart, ......... 360 Spirit-lamp, 42 Steam-oven, .......... 310 Stirring rods, preparation of, 46 Strontium, reactions of, ....... 101 Sublimation, process of, 65 Substances for analysis, ........ 341 Sulphates, reactions of, 147 Sulphides, 149 Sulphites, “ “ 151 Sulphoeyanides, reactions of, . . . . . .180 Sulphur, combustion in oxygen of, 20 Sulphuretted hydrogen tube, 45 “ “ apparatus, 306 “ “ reactions of, .... 150 “ “ passing, ...... 309 “ “ solution, ...... 333 Sulphurous acid, reactions of, 151 “ “ preparation of, . . . . . . 333 Sulphuric acid, reactions of, 147 Symbols, chemical, . . . . ... . .84 “ list of, 361 Table for analysis of Group I, ..... 254 “ “ II A, 255 “ “ III a, 257 “ “ III b, 259 “ « IIIa-b, . . 276,277,278,356 “ “ IV, 262 “ “ V, 99, 264 “ “ phosphates, 279 Tartaric acid, reactions of, 183 Tartrates, reactions of, ....... 181 Tellurates, detection in analysis, 354 “ reactions of, . . . . . . . . 350 Tellurites, “ 349 Tellurium, “ 350 Test papers, use of, ........ 72 Thallium, detection in analysis, .... 354, 355, 356 “ reactions of, . ....... 346 Theiosulphates, reactions of, . . . . . . . 151 Theiosulphuric acid, reactions of, 152 Thermometric scales, conversion of, .... 361 Tin, reactions of, ........ 137 Titanium, detection in analysis, ..... 355, 356 “ reactions of, ....... 351 Tungstates, detection in analysis, 354 “ reactions of, ....... 347 Turmeric-paper, use of, 75 PAGE 372 INDEX. PAGE Uranium, detection in analysis, 355 353 “ reactions of, ’ 359 Vanadium, detection in analysis, ...... 355 “ reactions of, Varnishing labels, ." .* ! 325 Wash-bottle, 47 Washing gases, ....... 33 “ precipitates, .61 Water-bath * . 311 Water, distillation of, 37 313 “ distilling apparatus, ’ 313 Weights and measures, French and English, . . 362, 363 Zinc group, “ “ separation and detection of, .... 117 “ “ table of differences, ...... 116 “ “ “ for analysis, 260 Zinc, reactions of, . . . Uq CATALOGUE OF BOOKS PUBLISHED BY HENRY O. LEA. (LATE LEA k BLANCHARD.) The books in the annexed list will be sent by mail, post-paid, to any P.ost Office in the United States, on receipt of the printed prices. No risks ofthemail, however, are assumed, either on money or books. Gen- tlemen will therefore, in most cases, find it mote convenient to deal with the nearest bookseller. Detailed catalogues furnished or sent free by mail on application. 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