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 arV19346 
 
 A manual of qualitative analysis / 
 
 3 1924 031 245 669 
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 http://www.archive.org/details/cu31924031245669 
 
A MANUAL 
 
 QUALITATIVE ANALYSIS. 
 
 BY 
 
 ROBERT GALLOWAY, F.C.S., 
 
 PROFESSOR OP APPLIED CHEMISTRY IN THE ROYAL COLLEGE OF SCIENCE FOR 
 
 IRELAND, AUTHOR OF "THE SECOND STEP IN CHEMISTRY," "THE 
 
 FIRST STEP IN CHEMISTRY," ETC. 
 
 FKOM THE 
 
 FIFTH REWRITTEN AND ENLARGED LONDON EDITION. 
 
 WITH ILLUSTRATIONS. 
 
 PHILADELPHIA: 
 
 HENRY O . LEA. 
 
 1872. 
 
o_l 
 
 fV^Wf 
 
 ^v</ 
 
 COLLINS, P1UNTER, 705 J.VYNK STRKET. 
 
PREFACE TO THE FIFTH EDITION. 
 
 This Edition contains numerous and important addi- 
 tions, and some alterations have been made in the arrange- 
 ment of the different divisions of the book ; but the plan 
 or scheme of analysis which formed the foundation of the 
 First Edition, and which is explained in the Preface to 
 the Second and in the Introduction to the present one, 
 remains unchanged, and is the foundation of the present 
 as it was of all the previous Editions. I have continued 
 it, not simply because other teachers, as well as myself, 
 prefer it to the system of Fresenius or that of the Giessen 
 outlines, having found it more successful, especially with 
 students who can only devote a portion of their time to 
 the study of analytical chemistry, but because I believe it 
 to be in accordance with the laws of thought. (1) It 
 exhibits a like progression to the mind ; it begins with a 
 few subjects and successively adds to them until the entire 
 system is reached; it proceeds, in short, from the simple 
 to the complex. (2) The Tables are not constructed on 
 the bad system of the Giessen outlines and some other 
 analytical works, or on the system of Fresenius, which is 
 quite as faulty, and still more unpractical for the learner 
 — of telling this and showing that, making the learner a 
 mere recipient — but on the better system of making the 
 
IV PREFACE TO THE FIFTII EDITION. 
 
 student compare, distinguish, judge ; so that thus, instead 
 of being a recipient, he may become an intelligent and 
 active discoverer. In addition to the methods developed 
 in the Tables for separating the members of the different 
 groups, others are given to this Edition which the student 
 ought to practise as soon as he can examine substances 
 correctly by the methods given in the Tables. 
 
 The old system of teaching Practical Chemistry had 
 some advantages over the method now generally in use. 
 I have endeavored in the present Edition to remove the 
 defects of the present system by describing very fully the 
 properties of the metals, their oxides and chief salts, in 
 order that the student may carry on with the study of 
 analysis other experimental inquiries, either by preparing 
 substances or by studying other than the analytical pro- 
 perties of bodies. 
 
 I have given at the end of each group and important 
 division of the book a series of examination questions in 
 Practical Chemistry; many of them, so far as I am aware, 
 are of an entirely new character, and these have been 
 framed, not for testing the memory, which is the only 
 faculty of the mind exercised by the questions usually 
 given at chemical examinations, but for ascertaining 
 whether the student has so studied the science that he is 
 capable of reasoning upon it. Owing to memory-questions 
 forming the bulk of the questions usually given at chemical 
 examinations, it has become no uncommon practice with 
 those who are going in for examination, to commit to 
 memory some one of the smaller text-books on the science, 
 or the pet subjects of the examiner. As the new class of 
 questions I have given cannot be answered by the cram- 
 
PREFACE TO THE FIFTH EDITION. V 
 
 ming process, I believe they will ultimately be as generally 
 adopted as what are termed the "arithmetical questions," 
 which I was the first to introduce in my " First Step in 
 Chemistry." 
 
 In the portion of the work more immediately devoted 
 to analysis, the following are some of the additions which 
 have been made: 1st. Bunsen's flame reactions have been 
 given, with figures of the apparatus. 2d. The detection of 
 the poisonous metals and acid-radicals in the presence of 
 organic matter. 3d. Additional tests for the detection of 
 the individual alkaloids, and more complete systematic 
 methods for the detection of these bodies. 
 
 The new notation has been adopted ; and the division of 
 the book into three chief parts, and the arrangement of 
 these parts, will, I hope, be found an improvement. 
 
 In conclusion, allow me to direct the student's attention 
 to the following extract from Thomas Carlyle's '' Address 
 to the Students of the University of Edinburgh :" " By 
 diligence I mean among other things — and very chiefly — 
 honesty in all your inquiries. Pursue your studies in the 
 way your conscience calls honest. More and more en- 
 deavor to do that. Keep, I mean to say, an accurate sepa- 
 ration of what you have really come to know in your 
 own minds, and what is still unknown. Be careful not to 
 stamp a thing as known when you do not yet know it. 
 Count a thing known only when it is stamped on your 
 mind, so that you may survey it on all sides with intelli- 
 gence. There is such a thing as a man endeavoring to 
 persuade himself, and endeavoring to persuade others, that 
 he knows about things when he does not know more than 
 the outside skin of them, and he goes flourishing about 
 
 1* 
 
VI PREFACE TO THE FIFTH EDITION. 
 
 with them. There is also a process called cramming in 
 some universities — that is, getting up such points of things 
 as the examiner is likely to put questions about. Avoid 
 all that; it is entirely unworthy of an honorable habit. 
 Gradually see what kind of work you can do ; for it is the 
 first of all problems for a man to find out what kind of 
 work he is to do in this universe. In fact, morality as 
 regards study is, as in all other things, the primary con- 
 sideration, and overrides all others. A dishonest man can- 
 not do anything real He does nothing but darken 
 
 counsel by the words he utters." 
 
 ROBERT GALLOWAY. 
 
 December, 1869. 
 
PREFACE TO THE SECOND EDITION. 
 
 In issuing a New Edition of this Manual, I will here 
 briefly describe the scheme or plan of analysis developed 
 in the work, and the way in which the book ought to be 
 used. 
 
 In all other works on Qualitative Analysis with which I 
 am acquainted, the properties of the bases and acids, and 
 the application of these properties to the analysis of sub- 
 stances, are treated separately. As a consequence, the 
 student, when he goes through the experiments on each 
 base and acid, performs these illustrations of the properties 
 without perceiving their use or application. In the part 
 of the Work devoted to the analytical course, he is told 
 what to do either by tables (as in the "Giessen Outlines," 
 and some other works), or, as in Presenilis, by a more 
 tedious, and, in my opinion, as defective a method. The 
 principles upon which these instructions are based are not 
 given with the instructions, but in a separate chapter of 
 the Work; and unless the student is able himself to unite 
 the two — the principles with the practical instruction — he 
 
Vlii PREFACE TO THE SECOND EDITION. 
 
 becomes a mere analytical machine. Students who can 
 give their whole time and attention to the study of the 
 science can, if they will, accomplish this ; but I have found 
 by experience that those who can only devote some five 
 or six hours in the week to the acquirement of the science 
 fail to become intelligent analysts by this system. 
 
 The system is very difficult, as well as defective ; it is so 
 difficult that those who employ it generally teach one 
 thing, useless in itself, in order that they may teach 
 another ; they teach the student first to look for one acid 
 and one base — a limitation which is not adopted in actual 
 practice — solely for the purpose of rendering the course 
 in which they have to look for all the bases and acids 
 less difficult. 
 
 In the plan I have adopted the properties of the differeut 
 members of each "group are contrasted by placing them in 
 parallel columns; the advantage of this is, that the stu- 
 dent, after he has performed the experiments, is able him- 
 self to devise methods for the detection and separation 
 of the different members; it places him, in fact, in the 
 position of a judge who has to decide some cause after 
 having heard all the pleadings. It enables him also to 
 judge for himself how many different methods might be 
 adopted in the separation of substances; it therefore en- 
 larges his views, and enables him to reason on the methods 
 he adopts. 
 
PREFACE TO THE SECOND EDITION. ix 
 
 This Manual is intended to be used in the following 
 way: The student commences with the first group; and 
 after he has performed all the experiments given in the 
 table of that group, several analyses are given him, each 
 of which he examines for the members of this group. 
 When he can perform these practical exercises correctly, 
 he commences the second group — first performing the 
 experiments in the group, and then analyzing several 
 solutions for the members of this group. When he can 
 perform these correctly, he examines several solutions for 
 the members of the first and second groups. In this pro- 
 gressive way he passes through the groups ; so that by 
 the time he has completed them he will have become an 
 accurate analyst. 
 
 In the former Edition I proposed, and partially carried 
 out, the division of the third group of bases, by employing 
 ammonia as a group reagent; this alteration not only sim- 
 plifies the subject, but it makes the plan of analysis taught 
 in the laboratory more consonant with the methods 
 adopted in actual practice. This alteration is fully car- 
 ried out in this Edition, and a more complete description 
 of the properties of the basic groups is given. I have also 
 given in this Edition an outline of the special tests to be 
 adopted in the detection of the acids, and considerable 
 additions have been made in the chapter on the Prelimi- 
 nary Examination of Solids. I have also introduced a 
 
X PREFACE TO THE SECOND EDITION. 
 
 new feature at the very commencement of the book ; a 
 series of experimental exercises are given, illustrating the 
 principles upon which analytical operations are based, 
 which it is intended the student should perform before he 
 commences the groups. My aim in writing the book has 
 been to furnish a suitable guide to the beginner; and I 
 confidently hope that this Edition will be found superior 
 to the former in this respect, and that it is what I wish it 
 to be — a Student's Book. 
 
 R. G. 
 
 Dublin, Nov. 1857. 
 
CONTENTS. 
 
 PART I. 
 
 j PA<iE 
 
 Preliminary remarks 25 
 
 how the book ought to be studied .... 27 
 
 Sources of error 29 
 
 Arrangements of the results of an analysis ... 30 
 First basic group. — Potassic, sodic, amnionic, and lithic oxides 33 
 Table I. — Behavior of the members of the group with the spe- 
 cial reagents 34 
 
 Precautions to be attended to in the analysis of this group . 3G 
 Properties of the metals, the oxides, the sulphides, the chlorides, 
 
 the nitrates, the sulphates, of this group .... 37 
 General characters of the salts of this group .... 41 
 Eemarks on the individual members of the group, with addi- 
 tional special tests 41 
 
 Exercises on this group .... ... 46 
 
 Second basic group. — Baric, strontie, calcic, and magnesic 
 
 oxides 47 
 
 Table II. — Behavior of the members of the first division of 
 
 the second group with the special reagents .... 49 
 Precautions to be attended to in the analysis of this group . 51 
 Properties of the metals, the oxides, the sulphides, the chlo- 
 rides, the nitrates, the sulphates, of this group ... 51 
 General characters of the salts of this group .... 54 
 Eemarks on the individual members of the group, with addi- 
 tional special tests 55 
 
 Exercises on this group 59 
 
Xll CONTENTS. 
 
 PAGE 
 
 Third basic group. — Zincic, manganous, niekelous, and cobal- 
 tous oxides 61 
 
 Table III. — Behavior of the third group with the special re- 
 agents 62 
 
 Precautions to be attended to in the analysis of this group . 64 
 
 Properties of the metals, the oxides, the sulphides, the chlo- 
 rides, the nitrates, the sulphates, of this group ... 65 
 
 General characters of the salts of this group .... 68 
 
 Remarks on the individual members of the group, with addi- 
 tional special tests 69 
 
 Exercises on this group 74 
 
 Fourth basic group. — Ahiminic, chromic, ferric, ferrous ox- 
 ides; aluminic, chromic, and iron phosphates ; the phosphates 
 of the alkaline earths, barie, strontic and calcic oxalates; 
 uranic and titanic oxides .... 76 
 
 Table IV. — Behavior of the fourth group with the special 
 reagents 78 
 
 Properties of the metals, the oxides, the sulphides, the chlo- 
 rides, the nitrates, the sulphates, of this group, ... 79 
 
 General character of the salts of this group .... 83 
 
 Remarks on the individual members of the group, with addi- 
 tional special tests 84 
 
 Exercises on this group .... . . . 8S 
 
 Properties of the phosphates and oxalates of the croup . 90 
 
 Table V. — Method for separating these phosphates and ox- 
 alates .""" 93 
 
 Precautions to be attended to in their analysis . . 92 
 
 Other methods for the separation of these phosphates and 
 
 oxalates, and other members of the group . 
 Exercises on the phosphates and oxalates 
 
 Properties of uranic oxide 
 
 " of titanic oxide 
 
 Fifth basic group.— -Auric, platinic, stannous, stannic, anti- 
 monious oxides ; arsenious and arsenic anhydrides . 99 
 
 Methods for the examination of TnE group .... 100 
 
 Properties of the metals, the oxides, the sulphides, the chlo- 
 rides, and the hydrides, of As and Sli 102 
 
 General characters of the salts of this group . . . .112 
 
 94 
 96 
 
 07 
 97 
 
CONTENTS. Xlii 
 
 PAUE 
 
 Remarks on the individual members, with their special tests . 115 
 
 Exercises on this group 134 
 
 Sixth basic group. — Argentic, mercurous, mercuric, plumbic, 
 
 bismuthous, cupric, and cadmic oxides . . . . 136 
 Table VI. — Behavior of the sixth group with the special re- 
 agents 138 
 
 Precautions to be attended to in the analysis of the group . 140 
 Properties of the metals, the oxides, the sulphides, the chlo- 
 rides, the nitrates, the sulphates, of the group . . . 142 
 Remarks on the individual members of the group, with addi- 
 tional special tests 147 
 
 Exercises on this group 160 
 
 General peopebties of the different basic groups . . 163 
 Table VII. — Behavior of the basic groups with the general 
 
 reagents 166 
 
 Precautions to be observed in examining for the basic groups . 171 
 
 Exercises on the basic groups 174 
 
 Classification of the acids 175 
 
 Inorganic acids 176 
 
 Behavior of the inorganic acids and their radicals with reagents 176 
 
 Chromic acid 176 
 
 Sulphuric acid 178 
 
 Sulphurous acid 179 
 
 Hyposulphurous acid 180 
 
 Boracic acid 180 
 
 Orthophosphoric acid 182 
 
 Pyrophosphoric acid 185 
 
 Metaphosphoric acid 185 
 
 Carbonic acid 185 
 
 Oxalic acid 187 
 
 Silicic acid 188 
 
 Hydrofluoric acid 191 
 
 Hydrosulphuric acid 193 
 
 Hydrochloric acid 194 
 
 Hydriodic acid 195 
 
 Iodic acid 197 
 
 Hydrobromic acid 198 
 
 Hydrocyanic acid 200 
 
 Nitric acid 203 
 
 Nitrous acid 206 
 
 2 
 
XIV CONTENTS. 
 
 PAGE 
 
 Chloric acid 206 
 
 Classification of the inorganic acids, including oxalic 
 
 acid 208 
 
 General properties of the inorganic acids . . . 208 
 Characteristic tests for the inorganic acids . . . 211 
 Preparation of the substances for the examination of 
 the acids, and the methods to be followed in the ex- 
 amination 212 
 
 Preliminary examination for the inorganic acids . . 214 
 
 Exercises on the inorganic acids 215 
 
 Organic acids 216 
 
 Behavior of the organic acids and their radicals with 
 
 reagents 217 
 
 Tartaric acid 217 
 
 Citric acid 219 
 
 Malic acid 221 
 
 Benzoic acid 222 
 
 Succinic acid 222 
 
 Tannic acid . . 223 
 
 Gallic acid . 224 
 
 Acetic acid 224 
 
 Formic acid 226 
 
 Uric acid 227 
 
 Classification of the organic acids 22S 
 
 General properties of the organic acids .... 228 
 
 Characteristic tests for the organic acids . . 229 
 Preparation of the substances for the examination of 
 the acids, and the methods to be followed in the f.x- 
 
 amination 230 
 
 Preliminary examination for organic acids . . . 231 
 
 Exercises on the organic acids 232 
 
 Examination of liquids and solids 233 
 
 Preliminary examination of a liquid 233 
 
 Exercises 236 
 
 Preliminary examination of solids 236 
 
 Classification oe solids 236 
 
 Coloration of the gas flame uy solids .... 237 
 
CONTENTS. XV 
 
 PAGE 
 
 Table VIII. — Examination of a solid in a glass tube closed at 
 
 one end ' 242 
 
 Examination of a solid in an open tube 247 
 
 Table IX. — Examination of a solid on charcoal . . . 250 
 Table X. — Examination of a solid with cobaltic nitrate, with 
 
 sodic carbonate, and with borax 251 
 
 Fusibility of minerals 255 
 
 Table of volatile elements which can be reduced as 
 
 films 258 
 
 Solution of a solid which is neither a pure metal nor 
 
 an allot, and is destitute of organic matter . . 261 
 Treatment and solution of a solid which is neither a 
 
 pure metal nor an alloy, and which contains organic 
 
 MATTER 264 
 
 Solution of a pure metal or an alloy .... 267 
 
 Exercises 268 
 
 PART II. 
 
 ANALYSIS OF ORGANIC SUBSTANCES. 
 
 Preliminary remarks 269 
 
 Elementary analysis 270 
 
 Test of an organic compound 270 
 
 Tests for nitrogen 270 
 
 " sulphur 271 
 
 " phosphorus 272 
 
 " inorganic substances 272 
 
 Proximate analysis of organic substances ... 272 
 
 Analysis of the inorganic portion of organic substances . 273 
 
 Animal chemistry ......... 277 
 
 Albuminoid group, its properties 278 
 
 Properties and reactions of albumen 282 
 
 fibrin 286 
 
 casein 288 
 
 " " globulin 289 
 
 Recapitulation and remarks on the group .... 290 
 
 Gelatigenous group, its properties 291 
 
 Properties and reactions of gelatine 292 
 
 " " chondrin 293 
 
XVI 
 
 CONTENTS. 
 
 Saccharine group 
 
 Properties and reactions of milk sugar 
 " " glucose 
 
 " " inosite . 
 
 Organic bases .... 
 Properties and reactions of urea 
 
 " " creatinine 
 
 " " creatin 
 
 Organic acids .... 
 Properties and reactions of lactic and sarcolactic acids 
 " " hippuric acid 
 
 " " glycocholic acid . 
 
 " '■ glyco-hyocholic acid 
 
 " " taurocholalic acid 
 
 " " cystine 
 
 " " xanthine 
 
 " " cholestrin 
 
 Coloring matter 
 
 " " of the urine . 
 
 " bile . 
 " blood 
 Tests for blood 
 bile. 
 
 Methods for analyzing qualitatively animal secretions 
 Qualitative analysis of urine 
 
 " " urinary calculi 
 
 Properties of vegetable albumen 
 fibrine 
 " " caseine 
 
 The saccharine group . 
 Properties of celuloso 
 " starch 
 
 " gum . 
 
 " cane-sugar 
 
 Exercises .... 
 
 Organic bases and mecoxic acih 
 Properties and mictions of nicotine 
 " " morphine 
 
 " " nnivotine 
 
CONTENTS. 
 
 
 PAflE 
 
 Properties and reactions of quinine 
 
 334 
 
 cinchonine 
 
 336 
 
 strychnine 
 
 336 
 
 bruoine 
 
 339 
 
 meconic acid .... 
 
 340 
 
 Detection of opium in organic mixtures .... 
 
 341 
 
 Methods for the detection of the poisonous alkaloids in 
 
 
 
 341 
 
 
 345 
 
 PART III. 
 
 Operations 346 
 
 Solution 346 
 
 Precipitation 347 
 
 Filtration 348 
 
 Decantation 349 
 
 Evaporation 349 
 
 Distillation 350 
 
 Ignition 350 
 
 Sublimation 350 
 
 Fusion 350 
 
 Deflagration 351 
 
 The blowpipe 351 
 
 Blowpipe lamps 352 
 
 " supports 353 
 
 " apparatus . 354 
 
 Bunsen's gas lamp and the chief divisions of its flame . . 358 
 
 The six points in Bunsen's gas lamp flame .... 360 
 
 Method of examination in these different points of the flame . 361 
 
 Emission of light by substances 363 
 
 The melting-point of the flame 364 
 
 Flame-coloration 364 
 
 Oxidation and reduction of substances in the gas-flame . . 365 
 
 Reduction in glass tubes 365 
 
 Eeduction on splinters of charcoal 366 
 
 Films upon porcelain 367 
 
 Examination of the films 368 
 
 Reactions of the elements in the gas-flame .... 370 
 
 Apparatus required in photo-chemical experiments . . . 370 
 
XV111 CONTENTS. 
 
 PAGE 
 
 Reagents 373 
 
 Hydrochloric acid 373 
 
 Nitric acid 373 
 
 Aqua regia .......... 373 
 
 Sulphuric acid 374 
 
 Tartaric acid 375 
 
 Sodic hydric tartrate 375 
 
 Acetic acid 375 
 
 Hydrosulphuric acid 375 
 
 Sulphurous acid and anhydride 376 
 
 Chlorine-water 376 
 
 Hydrofluosilicic acid 376 
 
 Oxalic acid 376 
 
 Amnionic oxalate 376 
 
 Ammonia 376 
 
 Amnionic chloride ......... 377 
 
 Amnionic sulphide 377 
 
 Amnionic carbonate ........ 377 
 
 Amnionic nitrate .... .... 377 
 
 Amnionic arseniate 377 
 
 Arsenic acid 377 
 
 Ammonic molybdate ... .... 377 
 
 Potassic sulphate 378 
 
 Potassic nitrite 37S 
 
 Potassic ferrocyanide 378 
 
 Potassic ferricyanide 378 
 
 Ammonic sulphocyanide 379 
 
 Potassic sulphocyanide 379 
 
 Potassic chromate 379 
 
 Potassic cyanide 379 
 
 Sodic hydrate 380 
 
 Sodic carbonate 380 
 
 Disodic hydric phosphate 380 
 
 Sodic acetate 380 
 
 Sodic hydric sulphite 380 
 
 Borax 3S1 
 
 Sodic potassic carbonate 381 
 
 Sodic ammonic hydric phosphate 381 
 
 Dihydric dipotassic metautimoniate 381 
 
 Baric-chlorido 381 
 
 Baric-nitrate 382 
 
CONTENTS. XIX 
 
 PAGE 
 
 Lime-water 3g2 
 
 Calcic chloride 382 
 
 Calcic sulphate 382 
 
 Magnesic sulphate 382 
 
 Baric carbonate 382 
 
 Ferrous sulphate 382 
 
 Ferric chloride ... 382 
 
 Plumbic acetate 382 
 
 Mercurous nitrate 382 
 
 Mercuric chloride 383 
 
 Oupric sulphate 383 
 
 Ammonio-sulphate of copper 383 
 
 Argentic nitrate 383 
 
 Ammonio-nitrate of silver 383 
 
 Cobaltic nitrate 383 
 
 Platinic chloride 383 
 
 Auric chloride 383 
 
 Stannous chloride 384 
 
 Plumbic peroxide 384 
 
 Copper turnings 384 
 
 Zinc 384 
 
 Nessler's test 384 
 
 Solution of indigo 385 
 
 Distilled water 385 
 
 Reagent papers 385 
 
 Preparation of blue litmus paper 385 
 
 " reddened litmus paper 385 
 
 " turmeric paper 386 
 
 Schonbein's test-papers for hydrocyanic acid .... 386 
 
 Preparation of Brazil-wood paper 386 
 
 List of apparatus required for qualitative analysis . 386 
 
 Appendices 387 
 
 Appendix A. — Treatment of silver residues .... 387 
 
 Appendix B. — Treatment of platinum residues . . . 388 
 
 Appendix C. — Treatment of gold residues .... 389 
 
 Index 391 
 
QUALITATIVE ANALYSIS. 
 
 PAET I. 
 
 Preliminary remarks, 1. How the book ought to be 
 studied, 6. Sources of error, 11. Arrangement op 
 the results of an analysis, 12. 
 
 1. Preliminary remarks The object of qualitative 
 
 analysis is to ascertain what elements are present, and 
 how they are combined in substances of unknown compo- 
 sition. The object of quantitative analysis is to determine 
 the quantity of each element present in substances. Hence, 
 qualitative must always precede quantitative analysis, and 
 in numerous cases it is not necessary to make a quantita- 
 tive investigation, the quality of the substance affording 
 all the information that is required. Qualitative and quan- 
 titative analysis, forming, therefore, two distinct branches 
 of chemical analysis, are studied separately and independ- 
 ently of each other, and the study of the former, by which 
 the component parts of substances are revealed, naturally 
 precedes that of the latter. 
 
 2. The complete aim of qualitative analysis is to discover 
 unknown as well as known bodies in substances, but it will 
 be manifest that a course of qualitative analysis designed 
 to teach students this branch of analytical chemistry must 
 be more restricted ; not only must the unknown form no 
 part of the scheme, but those elements and compounds 
 must also be excluded which, from their rarity, or from 
 their having no useful application, are comparatively un- 
 important. Organic bodies, with the exception of a few of 
 the more commonly occurring organic acids, are also ex- 
 cluded and a student's course is confined, with the ex- 
 ception named, to the inorganic or mineral substances 
 
 3 
 
26 PRELIM1NAIIY REMARKS. 
 
 ■which are commonly met with in nature, or which have 
 some useful application. A course of this kind is given in 
 Part I. of this book. 
 
 3. The methods of qualitative analysis consist in bring- 
 ing the substance under examination in contact with other 
 bodies of known properties, and observing the phenomena 
 which ensue. These phenomena consist in alterations of 
 form or color, depending upon some chemical change; 
 the change of form most frequent is the formation of a 
 precipitate which, in many cases, possesses a characteristic 
 color, but sometimes effervescence takes place, and some- 
 times deflagration. The bodies with 'which the substance 
 under examination is brought into contact are called tests 
 or reagents, and the phenomena produced by their contact 
 with the substance are called reactions. Acids, bases, salts, 
 and elements are alike used as reagents, and the methods 
 for preparing them in a state of purity, and the prepara- 
 tion of their solutions, are described in Part III. of the 
 book, along with a description of the principal operations 
 employed in analysis, and a list of the apparatus required. 
 Reagents emploj'ed for the detection of individual bodies 
 are called special reagents ; reagents which are employed 
 to detect groups of substances are called general or group 
 reagents. A special reagent is said to be characteristic 
 when it produces a reaction so decisive that it admits of no 
 mistake. 
 
 4. It has not only to be proved, in complete and accurate 
 analytical investigations, that certain substances are pre- 
 sent, but it lias also to be proved, which is generally more 
 difficult, that all other bodies but those discovered are ab- 
 sent. This cannot be accomplished by testing indiscrimi- 
 nately and separate^ for each base and acid radical; it 
 requires, not only that the reagents be added in a certain 
 order, but that the bodies which have to be sought for be 
 separated first into groups or families, and afterwards each 
 group divided and subdivided until the presence or absence 
 of each of its members is indubitably established. The 
 separation of bodies into groups is effected by observing 
 some chemical property common to several substances, and 
 peculiar to them, by which means they can be classified 
 into a group, and all other bodies excluded. 
 
 5. The analyst, by means of reagents, interrogates the 
 substance to be analyzed as to what arc its component 
 parts; the reactions are the language in which the answer 
 is returned. The student has, therefore, to learn the mode 
 
PRELIMINARY REMARKS. 27 
 
 of questioning the substance, and the language in which 
 the answer will be conve3'ed; in other words, he has to 
 learn, not only what general and special reagents are to be 
 employed, but the order in which they are to be applied, 
 and also, the reactions they produce with the bases and 
 acid radicals, before he can attempt to search for these 
 bodies in substances. No amount of reading or lecture- 
 hearing will furnish the student with this knowledge ; he 
 can only obtain it by making the experiments himself of 
 the different bases and acid radicals with the reagents, and 
 " he must always reflect, before the addition of the reagent, 
 for what purpose he applies it, and what are the pheno- 
 mena he intends to produce," and the conditions indis- 
 pensable for the production of correct and decisive re- 
 actions must be carefully observed, for a half knowledge 
 in all departments of science is of little worth, but in 
 chemical analysis it is worse than useless. The phrase 
 " the behavior or deportment of bodies with reagents" is 
 frequently substituted for the term reactions. 
 
 6. How the book ought to be studied. — In the group tables, 
 the behavior of the different members of the group with 
 the special reagents are contrasted by placing them in 
 parallel columns ; the student has to perform these experi- 
 ments, and to note the analogies and differences the mem- 
 bers display with the same reagents. The order in which 
 the experiments are to be made will be best explained by 
 the aid of Table I.; the experiments in the paragraphs 
 marked A 1, B 1, and C 1, are first made, and in the order 
 given ; then those in A 2, B 2, and 2 ; then those in A 3, 
 B 3, and C 3 ; and, finally, those in A 4, B 4, and C 4. In 
 making the experiments, the conditions which favor or 
 prevent precipitation, together with the appearances of 
 the precipitates, must be carefully noted and remembered, 
 and in all the experiments the chemical change must be 
 described, when possible, in the form of a diagram or 
 equation in the student's note-book. The student, after 
 he has made the experiments, will be able of himself to de- 
 vise methods for the separation and detection of the differ- 
 ent members; the knowledge he has acquired of the pro- 
 perties of the bodies places him, in fact, in the position of 
 a judge who has to decide some cause, after having heard 
 all the pleadings. He will also be able to decide whether 
 more methods than one could be adopted for the separa- 
 tion of the members by the aid of the reagents given in 
 the table. After he has devised a method for the separa- 
 
28 PRELIMINARY REMARKS. 
 
 tion of the members of a group, he compares it with the 
 one given in the text. He may then proceed to perform 
 the experiments on the different members given under the 
 head of " Remarks on the Individual Members." 
 
 1. The student commences with the first group, and 
 after he has performed all the experiments as previously 
 described, several solutions are given him, each of which 
 he examines for the members of the group. When he can 
 perform these practical exercises correctly, he proceeds to 
 the second group, first performing the experiments and 
 then analyzing several solutions for the members. When 
 he can perform these exercises correctly, he learns by ex- 
 periment how to separate the two groups by means of 
 Table VII. He then analyzes several solutions for the 
 members of the first and second groups. When he has 
 completed all the basic groups in the manner described, 
 he should analyze about twenty different solutions, and 
 look for all the bases given, after which, the experiments 
 given under the different acids must be performed. The 
 student is then capable of undertaking a complete course of 
 qualitative analysis, commencing with substances already 
 in a state of solution, and concluding with the examina- 
 tion of solids. 
 
 8. In this edition, the behavior of the bases and acid 
 radicals with a larger number of reagents has been given, 
 and also more methods for the separation of substances. 
 The student ought, after he can analyze solutions for the 
 members of a group by one method correct^', to analyze 
 other solutions of the same group by another method, and 
 so learn all the different methods given for the separation 
 and detection of the different members of any group. He 
 ought, whilst studying each group, to learn to prepare 
 the solutions of the reagents in that group, and also the 
 reagents themselves when methods for their preparation 
 are given in Part III. He ought also to study carefully 
 
 THE PROPERTIES OP THE METALS AND THE SALTS, and ft 
 
 would be well if he were to make some of the experiments 
 there described ; answers to the questions given on each 
 group must also be written out. 
 
 9. The bases are divided into the following groups: 
 
BASIC GROUPS. 
 
 29 
 
 Group I. 
 
 Potassic Oxide. 
 Sodic Oxide. 
 Ammonic Oxide. 
 
 Group II. 
 1st Division. 
 Baric Oxide. 
 Strontic Oxide. 
 Calcic Oxide. 
 
 2d Division. 
 Magnesic Oxide. 
 
 Group III. 
 Zincic Oxide. 
 Manganous Oxide. 
 Nickelous Oxide. 
 Cobaltous Oxide. 
 
 Group IV. 
 Aluminic Oxide. 
 Chromic Oxide. 
 Ferrous Oxide. 
 Ferric Oxide. 
 
 Group V. 
 
 Arsenious Acid. 
 Arsenic Acid. 
 Antimonous Oxide. 
 Stannous Oxide. 
 Stannic Oxide. 
 Auric Oxide. 
 Platanic Oxide. 
 
 Group VI. 
 1st Division. 
 
 Argentic Oxide. 
 Mercurous Oxide. 
 Plumbic Oxide. 
 
 2d Division. 
 
 Plumbic Oxide. 
 Mercuric Oxide. 
 Bismuthous Oxide. 
 Cadmic Oxide. 
 Cupric Oxide. 
 
 10. We may here point out another advantage arising 
 from the separation of substances into groups. It is as 
 easy, for instance, to discover the absence or presence of a 
 group as that of an individual substance; and the absence 
 of a group being proved, it is unnecessary to examine fur- 
 ther for any member contained iii it. 
 
 11. Sources of error. — One frequent source of error with 
 the young analyst is the imperfect mixture of the reagents 
 with the solutions to which they are added. Another pro- 
 lific source of error is the too liberal or the too sparing 
 addition of the reagent, both being objectionable. To show 
 the objectionable nature of a too sparing addition of the 
 reagent, we will suppose the student to be examining a so- 
 lution for barium and calcium ; we will further suppose he 
 has added potassic chromate and obtained a precipitate,* 
 
 * Whenever a precipitate is obtained, it must be separated from the 
 fluid by filtration, if either the fluid or the precipitate has to be examined 
 
 3* 
 
30 RECORDING ANALYSES. 
 
 which proves the presence of Ba. He filters, and to the fil- 
 trate he adds amnionic oxalate, to test for Ca ; he obtains 
 a precipitate with amnionic oxalate, although Ca is absent, 
 because he has not added a sufficient quantity of the potas- 
 sic chromate to precipitate all the Ba : thus, by the imper- 
 fect addition of a reagent, he arrives at awrong conclusion. 
 This fruitful source of error, viz., imperfect precipitation, 
 may be avoided by adding to the filtrate a little more of 
 the reagent with which the precipitation was effected. If 
 this produces no further precipitate, the substance- has 
 been fully precipitated. Should a further precipitate be 
 produced, it must be removed Ivy filtration before attempt- 
 ing to throw down any other substance. The student must 
 also carefully distinguish between the terms precipitate 
 and filtrate, and be very particular in thoroughly washing 
 the precipitates which require further examination. The 
 wash-water must not be collected with the filtrate, if this last 
 should be required for further examination. But all these 
 precautions will have been attended to in Tain should the 
 experiments be performed in dirty apparatus, this being 
 sufficient of itself to render the results unsatisfactory, if 
 not erroneous. 
 
 12. Arrangement of the results of the analysis. — The 
 student, during the course of his analytical studies, ought 
 invariably to record the results of each analysis in his note- 
 book, in a systematic and tabular form. An illustration 
 is given to show the method to be pursued. 
 
 13. Preliminary examination of a solid substance. — 1st. 
 It is a colorless, crystallized substance, probabty a salt. 
 2d. Heated alone on charcoal, it deflagrates; a white, in- 
 fusible substance remaining behind, which becomes lumi- 
 nous, and imparts a crimson color to the flame, probably 
 strontia. 3d. Soluble in water ; the solution is neutral to 
 test-paper. As it is soluble in water, a large number of 
 substances, all the insoluble salts, must be absent ; as it is 
 neutral to test-paper, all the salts of the alkalies and alka- 
 line earths having an alkaline reaction must be absent; 
 and the soluble salts of the other metals, with the excep- 
 tion of manganese and silver, must be absent, because their 
 soluble neutral salts redden blue litmus paper. 
 
 14. The preliminary experiments indicate the presence 
 of strontic nitrate. 
 
 further; the fluid for other substnnoes, the precipitate for the detection 
 of the several substances wliieli niny have been precipitated, or for the 
 confirmation of any one substance. 
 
RECORDING ANALYSES. 31 
 
 15. Examination of acids and acid radicals. — The fol- 
 lowing acids, viz. C0 2 , H 2 S, As 2 3 , As 2 5 , and Cr0 3 , were 
 proved to be absent on the examination for the bases. 
 
 16. The remainder of the acids, which give precipitates 
 with a baric salt, could not be present ; as they likewise 
 form, with strontic salts, insoluble salts. 
 
 17. Added to a portion of the original solution AgN0 3 , 
 no precipitate ; absent, CI, Cy, Br, and I. 
 
 18. Added to another portion H 2 SO, and copper turn- 
 ings, nitrous fumes were evolved, showing the presence of 
 nitric acid. 
 
 19. The examination for chloric acid yielded a negative 
 result. 
 
32 
 
 RECORDING ANALYSES. 
 
 O 
 
 M 
 EH 
 
 ■< 
 
 l-H 
 
 g 
 ■< 
 
 X 
 
 fd 
 iJ 
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 EH 
 
 CO 
 
 w" 
 
 13 
 
 n 
 
 W 
 
 o 
 o 
 
 o 
 
 S3 
 
 ■a 
 
 o 
 o 
 
 s 
 
 O 
 
 l 5 !^ 
 
 
 
 
 
 nia 
 
 sence 
 
 aoal 
 
 ~ e x a 
 
 
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 = '§£•3 
 
 9 
 
 ■o 
 
 o> 
 
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 O 
 25 
 
 CM 
 
 
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 No ammo 
 
 evolved; ab 
 
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 Baits. 
 
 Evapor 
 other po 
 dryness, 
 ammoniac 
 
 1°" 
 
 
 Boiled 
 tion of t 
 nal solut 
 NaHO. 
 
 a 
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 Q 
 
 
 
 
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 por 
 ded 
 HPO 
 
 
 
 
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 c eg e5 
 
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 rr t~ •- - <u 
 
 e. 3 -a Fj £ 
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 M "" c . - 
 
 "3 a „"" E 
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 •a 
 
 GO O 
 
 .5 6 
 
 too a) ' © » 
 c ^= "5 fl ua 
 
 £ .- o "3 ■" 
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 3 J» J= 'g m ■£ 
 
 J" 3 n ■ *• M 
 
 cH-5.2 » * « 
 
 T3 
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 ca 
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 3 
 
 
FIRST BASIC GROUP. 33 
 
 20. A few of the rarer elements and compounds have 
 been given, but as they do not form a part of the course, 
 they are not included in the tables ; they are distinguished 
 from the more commonly occurring ones by being printed 
 in smaller type. 
 
 21. Part II. is intended for advanced students. 
 
 PROPERTIES OF THE BASIC GROUPS. 
 
 First Group. 
 
 Potassic Oxide (K 2 0). Sodio Oxide (Na 2 0). Ammonio 
 Oxide (NH t ) 2 0). Lithio Oxide (Li 2 0). 
 
 Solutions for the reactions.*— KC1, NaCl, NH 4 C1, LiCl, 
 in water. 
 
 22. There are certain names in frequent use for these 
 oxides, their hydrates, and salts, which it is necessary for the 
 student to be familiar with at the very outset. 1st. Potash, 
 soda, ammonia, lithia, are names veiy frequently and indis- 
 criminately employed for these oxides and their hydrates; 
 but the terms caustic potash, caustic soda, etc., are strictly 
 limited to the hydrates ; thus the term caustic potash in- 
 variably signifies KHO. 2d. These oxides, and no others,f 
 are termed '•'•the alkalies;" this term is also indiscriminately 
 employed for the oxides and hydrates ; but the term u the 
 caustic alkalies" invariably signifies the hydrates. 3d. 
 Potash, soda, lithia, and their salts, are not volatile at a 
 moderate heat, whilst ammonia and its salts are volatile; 
 the first three are therefore frequently called the fixed alka- 
 lies, whilst the fourth is called the volatile alkali. 4th. 
 Their salts are termed "salts of the alkalies," or "alkaline 
 salts;" and" nitrates of the alkalies," " alkaline chlorides," 
 and similar terms are in constant use. 
 
 * At the head of eaoh group will be given the solution of salts which 
 may be employed for the reactions. 
 
 f With the exception of two rare ones, viz., caesic and rubidic oxides. 
 
34 
 
 THE SPECIAL PROPERTIES 
 
 TABLE I. 
 
 Behavior of the FIRST GROUP with the Special Reagents. 
 
 (NH 4 ) 2 0. 
 A 1. Ammonia and its 
 salts are volatile. 
 
 A 2. All amnionic salts 
 are decomposed with the 
 liberation of free ammo- 
 nia, when any stronger 
 base, such as CaH 2 0„.* 
 KHO or NaHO, is added 
 to their solutions. If the 
 liquid be gently heated 
 the ammonia is volatilized, 
 and its presence may then 
 be recognized in three dis 
 tinct ways. a. By its 
 pungent odor. g. By turn- 
 ing red litmus paper blue. 
 y. By forming whUefum.es, 
 when any volatile acid, as 
 HOI, is brought into con- 
 tact with it.f 
 
 K 2 0. 
 B 1. Potash and its 
 salts are not volatile. 
 
 C 1. Soda and its 
 salts are not volatile. 
 
 _ A 3. H 2 C 1 H 4 6 =H,'l', 
 in solution, produces in 
 neutral or alkaline solu 
 tions of NH 4 a white crys- 
 talline precipitate of NH 4 
 HC 4 H 4 6 =NH 4 HT, which 
 is rather more soluble in 
 water than the corre- 
 sponding potassic salt 
 Vigorous shaking pro- 
 motes the formation of 
 this and the correspond 
 ing potassic salt. 
 
 A 4. Ammonio com- 
 pounds impart to a lamp 
 flame no characteristic 
 color. 
 
 B 2. When potassic C 2. When sodic salts 
 saltsare decomposed by^re decomposed by a 
 a stronger base, KHOjstronger base, NaHO is 
 is liberated, but, noijliberated, but, mo* being 
 being volatile like am- \volalile like ammonia, 
 monia, cannot be de-:cannot be detected in a 
 tected in a similar way. similar manner. 
 
 B3 H 2 T, in solution, 
 throws down from neu- 
 tral or alkaline solu- 
 tions of K a white 
 crystalline precipitate 
 of KH'F. This salt, arid 
 the corresponding am- 
 nionic one, are soluble 
 in free alkalies and free 
 mineral acids. Slightly 
 soluble in cold, much 
 more so in hot water. 
 (Consult par. 44.) 
 
 B 4. Potassio com- 
 pounds tinge the outer 
 lamp flame violet 
 (Consult par. 46.) 
 
 C 3. H 2 T. in solution, 
 produces no precipitate 
 solutions of No, 
 except in extremely 
 concentrated solutions, 
 NallT being soluble. 
 
 C 4. Sodic compounds 
 impart to the outer 
 lamp flame an intense 
 yellow color. !<niall 
 quantities of N'ii can by 
 this means be detected 
 in the presence of much 
 K, the yellow flame 
 overpowering the vio- 
 let. (Swpar 61.) 
 
 * If ('alf 2 Oj is employed, it must be in the solid state, not in solution, 
 f This experiment is best performed by inserting a glass rod moistened 
 
OF THE EIE6T GROUP. 35 
 
 23. HOW TO ASCERTAIN THE PRESENCE OR ABSENCE OF 
 EACH OP THE THREE MEMBERS OP THIS GROUP IN A SOLUTION 
 ■WHICH CAN ONLY CONTAIN THESE THREE BASES. — The Only 
 
 test for a potassic compound which can be relied upon in 
 the presence of an amnionic one is the flame reaction (B 4), 
 as the reagents which precipitate K from its solutions form 
 precipitates similar in appearance with NH t ; it is ne- 
 cessary, therefore, to get rid of the amnionic compound, if 
 one is present, before H a T or PtCl 4 can be employed as a 
 characteristic test for K ; consequently, ammonia has to be 
 sought for first, and as the reagent employed for its de- 
 tection would be an impediment (A 2) when searching for 
 the other two members, we, on this account, test for 
 ammonia in a portion only of the solution under examina- 
 tion ; we divide, therefore, the solution into two parts, 
 which we shall call A and B. 
 
 24. In A we examine for ammonia accordingto the method 
 described in A 2 and par. 40, or by the one described in 
 par. 42; these are characteristic tests for ammonia, dis- 
 tinguishing it from other substances. When ammonia is 
 absent examine the B portion according to par. 25, and 
 when it is present according to par. 26. 
 
 25. Examine for sodic and potassic compounds in the 
 following way : A clean {see Precautions, par. 28) platinum 
 wire is dipped into the solution, and then introduced into 
 the flame of a Bunsen's gas lamp. If the flame is colored 
 yellow, Ka is present; if it is colored violet, it proves the 
 absence of Na (C 4) and the presence of K (B 4). If1$& 
 is present, examine for K by the photo-chemical method 
 (par. 46). The presence of K may be confirmed by adding 
 to the solution under examination, which must be cold 
 (B 3), a solution of H 2 T or NaHT (see par. 44) in excess, 
 and shaking the mixed liquid very violently, and then 
 allowing it to rest for some time; if a crystalline precipi- 
 tate appears after this, K is present (B 3). The time 
 required for the appearance of the precipitate depends 
 upon the amount of K in the solution; if the quantity of 
 K is small, the precipitate may not appear until several 
 hours after the addition of the reagent. 
 
 26. The solution must be evaporated to dryness and 
 
 with HC1 into the mouth of the test-tube in which the decomposition of 
 the amnionic salt is being effected, and immediately withdrawing it. The 
 HC1 employed should not be concentrated, but should be diluted with an 
 equal volume of water. (Consult par. 40.) 
 
36 THE SPECIAL PROPERTIES 
 
 ignited, in order to volatilize the amnionic substance (A 1) ; 
 the ignition must be continued as long as any white fumes 
 or smoke are evolved. If a residue remains after the ex- 
 pulsion of the amnionic body, one or both of the other two 
 members of the group are present; this residue must be 
 dissolved in the smallest possible quantity of water, and 
 examined for K and Na, in the way described in the pre- 
 ceding paragraph. 
 
 27. When the examination is not confined to the 
 alkalies, but all, or, at least, some of the other bases 
 have to be sought for in the solution, the solution, after 
 being freed from all the other bases but MgO and those of 
 the first group, must be evaporated to dryness, and ignited, 
 to expel the ammonic salts, which have been added for 
 their discovery. If a residue remain,* after the vapor of 
 the ammonic salts has ceased to be evolved, it must be 
 examined for K and Na, in the way described in par. 25. 
 In this case — that is, when other bases besides those of the 
 first group have to be sought for — NH^ is to be tested for 
 in a part of the original solution. 
 
 28. The following precautions are to be attended to in the 
 
 analysis of this group Moist turmeric paper will turn 
 
 brown by the mere exposure for a short time to the atmos- 
 phere of the laboratory, owing to the ammonia present in 
 the air; this must be remembered in testing for ammonia 
 in the manner described in par. 40. If the test-paper does 
 not brown in the course of a few seconds or a minute, no 
 ammonic compound is present, and the browning which 
 may occur by longer exposure must be regarded as due to 
 the ammonia in the air. In testing for potassic or sodic 
 compounds by the lamp-flame, it is necessary that the 
 platinum wire should be perfectly clean; this is secured by 
 keeping it in the lamp-flame until it imparts no color to it. 
 Care should then be taken not to touch with the fingers 
 that end of it on which the substance to be examined is to 
 be placed. The ilame reaction is not a reliable test for 
 K in the presence of organic matter, as organic substances 
 which burn with the separation of carbon color the flame 
 violet; organic matter, if present, must be got rid of by 
 igniting the substance if it is a solid, or if a solution by 
 evaporating it to dryness, and then igniting the residue ; in* 
 
 * A fixed residue is not a certain proof of the presence of potash or 
 soda, us it may arise from the presence of one of the uon-\olatile acids, 
 viz. phosphoric, boracic, or silicic aoid. 
 
OP THE FIRST GROUP. 37 
 
 either case the solid after ignition ought to be dissolved in 
 a small quantity of water and filtered, if, after the water is 
 added, any brownish-black particles appear. Young stu- 
 dents seldom continue the ignition for the expulsion of the 
 amnionic salts sufficiently long, and, if these solids are 
 not completely expelled, precipitates will be obtained with 
 H 2 T, NaHT, PtCl 4 , which will be regarded as indicative 
 of the presence of the potassic compound. The solution 
 must be as concentrated as possible for the detection of K 
 by H 2 T, or NaHT, and the student is directed to par. 44 
 as regards the neutrality, acidity, and alkalinity of the 
 liquids. 
 
 Properties op the metals, the oxides, the sulphides, 
 the chlorides, the nitrates, the sulphates, op this 
 
 GROUP. 
 
 29. The metals. — K, Na, and Li are lighter than H 2 0. 
 Li is the lightest of all known solids ; the sp. gr. of Na is 
 0.985, that of K is 0.865, and that of Li 0.589. K melts 
 at 62.5° C, Na at 95.5° C, and Li at 180° C. At a red 
 heat, K and Na may be distilled ; the vapor of K is a 
 beautiful green color, that of Na is colorless; Li is vola- 
 tile at high temperatures. These three metals oxidize on 
 exposure to air; K is the most and Li the least oxidiz- 
 able of the three; they decompose water at all tempera- 
 tures, uniting with the oxygen and liberating the hydro- 
 gen ; K decomposes it most rapidly, the hydrogen taking 
 fire from the heat evolved by the combination of the metal 
 with O. They combine directly with CI, I, Br, S, etc. 
 
 30. The oxides.— Kfi, Na,0, Li 2 may be obtained 
 either by introducing the metals into an atmosphere of 
 oxygen, or by heating the metals and their bydric oxides 
 together in equivalent proportions. K 2 and Na 2 melt 
 at a red heat, and volatilize without decomposition at very 
 high temperatures; these two oxides attract H 2 very 
 rapidly from the air, and after they have become hydrated 
 they cannot be dehydrated by heat alone. These anhy- 
 drous oxides are instantly converted into the hydrates on 
 being brought into contact with H 2 0, and it is in the 
 form of hydrates they are employed in the laboratory and 
 in the arts ; the anhydrous oxides are, therefore, unimpor- 
 tant. 
 
 The hydrates— KHO and NaHO are usually prepared 
 
 4 
 
38 THE SPECIAL PROPERTIES 
 
 from K 2 CO„ and NaXIO,,, by adding to boiling solutions 
 of these salts CaH 2 O a until the clear solution no longer 
 effervesces on the addition of HC1 in excess. They may 
 also be obtained, and it is in this way that LiHO is gene- 
 rally prepared, by adding to a solution of their sulphates 
 a solution of BaH 2 2 . These hydrates are white solids ; 
 they melt below redness, and KHO and NaHO volatilize 
 at a pale red heat ; LiHO does not appear to volatilize at 
 a white heat. KHO and NaHO absorb H 2 and C0 2 
 from the air; by the absorption of the H 2 they are con- 
 verted into syrupy liquids ; as they become transformed 
 into carbonates, the syrupy solution of the potash con- 
 tinues, whereas the soda becomes converted into an efflo- 
 rescent paste, because K,C0 3 is deliquescent, and Na„CO, 
 is not ; LiHO absorbs CO a from the air, but not H„0. 
 They are soluble in water and alcohol ; LiHO is the least 
 soluble of the three. Their aqueous solutions are very 
 alkaline and absorb C0 2 from the air. These alkalies are 
 not reducible by H ; KHO and NaHO are reducible by C, 
 the K and Na passing off in vapor ; but Li, and the metals 
 of the next group, although they have less affinity for O 
 than K and Na, cannot be obtained in this manner, their 
 oxides not being reducible by C because the metals are 
 not sufficiently volatile to pass off in vapor. Heated in a 
 current of CI, they are converted into chlorides with dis- 
 engagement of O. A current of CI passed into their solu- 
 tions converts them into a mixture of alkaline chlorides, 
 and, according to the strength of the solution and the 
 temperature, alkaline hypochlorites or chlorates; if the 
 solutions are weak and not heated, hypochlorites are pro- 
 duced, when these conditions are reversed, the chlorates 
 are formed. When fused with S at a temperature not 
 above 200° C, or if the S is boiled in their solutions, an 
 alkaline hyposulphite and an alkaline polysulphide are 
 formed ; but if the reaction takes place at a red heat, 
 an alkaline sulphate and an alkaline pentasulphide are 
 produced. By the action of F on the alkalies, a mixture 
 of alkaline hypophosphites and phosphides is formed. 
 The alkalies dissolve alumina and silica, and attack glass 
 and porcelain; the student will study the behavior of the 
 insoluble basic oxides with the alkalies in the next groups. 
 31. NH 4 . — This radical has never been obtained uncom- 
 bined ; when set free from its combinations it decomposes 
 at the same moment, if it exists at all, into NII S and II. 
 Although it has never been isolated, the theory of its ex- 
 
OP THE FIRST GEOUP. 39 
 
 istence is considered to derive great support from the fact 
 that Hg forms with NH„ as it does with the true metals, 
 an amalgam. This compound of Hg and NH 4 is easily 
 obtained by introducing sodium amalgam into a strong 
 solution of NH,CI; the Na rapidly dissolves by combin- 
 ing with the CI, the liberated SH, combining with the 
 Hg ; a soft, butteiy mass is thus obtained, occupying an 
 enormous volume compared with that of the Hg by itself. 
 
 32. NH S and NH 4 HO. — The name ammonia has been 
 given to these two different compounds ; the first is a gas, 
 and the other is obtained by dissolving the gas in water; 
 the same name was given to the gas and its solution, 
 because it was considered the gas suffered no chemical 
 change by its solution in water, inasmuch as it (NH.,) is 
 not only expelled from the solution by heat, but it even 
 escapes from it at the ordinary temperature of the air; 
 and the solution likewise retains the smell and other pro- 
 perties of the gas; hence the gas and its solution was re- 
 garded as the same chemical compound. They are now 
 viewed as two distinct compounds. It is supposed that 
 when NH, is dissolved in H 2 0, they enter into combina- 
 tion in equivalent proportions, NH 4 HO (amnionic hy- 
 drate) being formed, corresponding to KHO and NaHO, 
 the compound radical NH, having functions similar to the 
 simple bodies K and Na. The radical XH, is supposed to 
 exist in all amnionic salts, whether the salts be formed by 
 the action of the acids on NH 4 HO, or on NH 3 ; thus — 
 
 (l)2NH 4 HO + H,SO,= (NH J ),S0 1 + 2H > 0. 
 
 (2)2NH 3 +H 2 S0 4 =(NH 4 ) 3 S0 4 . 
 
 NH. is remarkable for its pungent and peculiar smell, 
 which is shared by the hydrate; the gas and the liquid 
 have a strong alkaline reaction, and they both neutralize 
 the strongest acids. 
 
 33. The sulphides, including the ammonic, may be ob- 
 tained by dividing a solution of them into equal portions, 
 and passing through one portion H 2 S to saturation ; an 
 alkaline sulph-hydrate (MHS) is formed ; on adding to 
 this the other portion, the sulphide is produced; thus, 
 MHS + MHO = M 2 S + H a O; K,S and NajS may be ob- 
 tained by deoxidizing their sulphates with H or C at a 
 red heat. Their solutions have an alkaline reaction, and 
 are colorless at first, but after a time they become colored 
 from absorbing O from the air, and becoming transformed 
 
40 THE SPECIAL PROPERTIES 
 
 into a mixture of free alkali and a polysulphide. If heated 
 in contact with the air or O, they become converted into 
 sulphates. They readily dissolve S, and are converted in- 
 to polysulphides. Acids decompose them with liberation 
 of H a S. 
 
 34. The chlorides may be formed by dissolving the alka- 
 lies or their carbonates in HC1 ; these salts are soluble in 
 water, and are sparingly soluble in spirit of wine ; their 
 solutions are neutral to test-paper. NH 4 C1 does not vola- 
 tilize at 100° C, but at higher temperatures it volatilizes 
 readily without decomposition ; heated in open vessels, 
 KC1, NaCl, and LiCl volatilize at a red heat. The double 
 salts they form with PtCl 4 are noticed in pars. 41, 45, 55, 
 5f. KC1 and NaCl, when evaporated with excess of H 2 
 and HN0 3 , are converted into oxalates and nitrates, and 
 on igniting these two chlorides with (NH,) 2 0, alkaline 
 carbonates are formed in considerable quantities. 
 
 35. The nitrates may be formed by adding HN0 3 to the 
 alkalies or their carbonates. They are readily soluble in 
 H 2 0, only slightly soluble in spirit of wine; their solutions 
 are neutral to test-paper. They liquefy on application of 
 heat ; at a red heat NaN0 3 and KN0 8 are converted by the 
 expulsion of one-third of their O into nitrites, and at a 
 still stronger heat a further quantity of O, along with all 
 the N, is expelled, and a mixture of the pro- and per-oxides 
 of the metals remains ; at 108° C, NH^NO^ liquefies, and 
 at 249° 0. it undergoes complete decomposition into N 2 
 and Tlfi. The fixed alkaline nitrates heated with C and 
 with S are converted into carbonates and sulphates, the X 
 being expelled ; when thej' are ignited with NH 4 C1, or in a 
 current of dry HC1 gas, they are converted into ehlorides; 
 and if repeatedly evaporated with excess of liquid HC1, 
 they are completely converted into chlorides. If they are 
 also repeatedly evaporated with H 2 in excess, they are 
 converted into oxalates. 
 
 36. The sulphates may be formed by adding H a S0 4 to the 
 alkalies or their carbonates, or by evaporating the nitrates 
 or chlorides with H 2 S0 4 . They are soluble in water ; the 
 solution of those the general formula for which is M.SO, 
 is neutral to test-paper; the solution of those whose general 
 formula is MHSO i is acid to test-paper. K,.SO, and Na a SO„ 
 at a white heat, are slightly decomposed; (NlI t ) a S0 4 melts 
 at 140° C, and between 260° C. and 315° C. it volatilizes 
 and undergoes decomposition, (NH t ) a SO a being among the 
 
OP THE FIBS1 GROUP. 41 
 
 products. Fe decomposes K 2 S0 4 and Na 2 S0 4 at a red heat, 
 the alkalies are liberated, and a mixture of sulphide and 
 oxide- of iron formed ; they are converted into chlorides 
 by ignition with NH.C1, and we have already noticed (38) 
 they are deoxidized by ignition with C. One of the two 
 atoms of radical in these sulphates can be replaced by one 
 of the other radicals, or by H ; thus, NH 4 NaS0 4 , KHS0 4 , 
 etc. 
 
 3t. General characters of the salts of this group. — The 
 metals of this group, compared with those of the other 
 groups, furnish the largest number of salts soluble in 
 water; the sodic salts are almost all soluble in H 2 0, hence 
 there are no very good direct tests for sodic compounds, 
 and owing to the greater number of the salts of these 
 metals being soluble, we have no group or general reagents 
 for this group as we have for the other groups. Not only are 
 the oxides soluble inH 2 0,but also their sulphides, sulphates, 
 oxalates, carbonates, phosphates, nitrates, and other salts. 
 The sparing solubility of lithic phosphate and carbonate 
 in H 2 distinguishes it from the other members of the 
 group, and renders it more nearly allied in this respect to 
 the next group. The solutions of the sulphides and car- 
 bonates, as well as the solution of the alkalies themselves, 
 restore the blue color to reddened litmus, and impart an 
 intensely brown tint to turmeric paper. The salts of these 
 bases are colorless, provided the constituent acid be so. 
 
 REMARKS ON THE INDIVIDUAL MEMBERS OP THE GROUP, WITH 
 ADDITIONAL SPECIAL TESTS. 
 
 38. NH, and its compounds. — NH 3 , we have already 
 stated, is remarkable for its pungent smell, and it exerts 
 a powerfully corrosive action on moist animal tissues, 
 hence serious consequences might arise from inhaling a 
 considerable quantitj-. The white fumes produced when 
 NH, is brought into contact with a volatile acid are due 
 to the formation of a solid amnionic salt. All ammonic 
 salts containing volatile acids, on being heated, volatilize 
 either with or without decomposition; but the ammonic 
 salts of the non-volatile acids, viz., phosphoric, boracic, and 
 silicic, are decomposed by heat ; the ammonia escapes, but 
 the non-volatile acid remains behind. 
 
 39. When organic substances containing N decay and 
 putrefy, ammonic carbonate is constantly produced ; the 
 
 4* 
 
42 THE SPECIAL PEOPEETIES 
 
 same salt is likewise formed when nitrogenized organic 
 substances are submitted to destructive distillation. 
 
 40. The following modification of the test (A 2) for am- 
 monia is to be preferred: If the substance is in solution, 
 mix it in a small beaker, with sufficient CaH 2 0., to render 
 the mixture solid ; but if it is a solid, moisten it slightly 
 with H 2 before mixing it in the beaker with excess of 
 CaH 2 Oj. The beaker is covered, after the mixing, with a 
 glass plate, on the lower side of which adheres a small 
 piece of moist turmeric or moist reddened litmus paper. 
 
 41. PtCl 4 produces in neutral and acid amnionic, as in 
 potassic, solutions, a yellow crystalline precipitate 2NH 4 C1, 
 PtCl 4 , very sparingly soluble in alcohol. 
 
 42. If a solution of HgK„I t in KHO be added in excess 
 to a liquid containing a trace of NH 4 HO or its salts, it 
 assumes a brownish tinge or furnishes a brown precipitate, 
 according as the proportion of the ammonic compound is 
 less or more, tetramercuric diammonic diniodide being 
 formed, thus: — 
 
 4HgKJ 4 + 6KHO + 2NH 4 HO=Hg 4 N 2 I 3 , 2H a O + 14KI 
 + 6H a O. 
 
 This test is called Nessler's test. 
 
 Characteristic — The reactions with CaH a 2 (40), and 
 with Nessler's test. 
 
 43. K and its compounds. — K is of a bluish-white color ; 
 it is brittle at 0° C. ; a little above this temperature it is 
 malleable; at 16° it is soft; at 62.5° it is liquid, and at a 
 red heat it may be distilled; when freshly cut, it possesses 
 considerable lustre, but instantly oxidizes on exposure to 
 the air ; it can only be preserved in the metallic state by 
 keeping it in some liquid, like coal naphtha, which contains 
 no oxygen, or in exhausted hermetically sealed glass tubes. 
 It- occurs in felspar, mica, etc., as silicate, in combination 
 with aluminic and other silicates. It is also found as 
 sulphate, nitrate (saltpetre), and in a mineral called car- 
 nallite, which is a double Lydrated potassic and magnesic 
 chloride (KC1, MgCl 2 , 6H 2 0), which occurs above the bed 
 of rock salt at Stassfurth,"near Magdeburg. 
 
 44. NaHT* is ;a much more delicate test for K than 
 1I 8 T, because KIIT in neutral solutions is soluble in acids, 
 
 * My friend, Mr. W. Plunkett, suggested the employment of NaHT. 
 See " Chemical Gazette," vol. xvi. p. 217. 
 
OF THE FIRST GROUP. 43 
 
 and an acid must be set free whenever H 2 T is added to a 
 solution containing a potassic salt. If the solution is 
 acid, the free acid must be expelled, if practicable, by 
 evaporation or ignition ; or if not expelled, it must be 
 neutralized with NaHO or Na 2 C0 3 before testing for K 
 either with NaHT or H a T. NaHT cannot, of course, re- 
 place H 3 T as a test for K when the solution to be tested 
 contains a free alkali, because KHT is soluble in free alka- 
 lies ; but when the bases of the other groups are sought 
 for, the solution cannot be alkaline when we arrive at the 
 examination for K, and it is not often that we have to deal 
 with an alkaline solution, even when the alkalies are the 
 only bases that have to be examined for. 
 
 45. PtCl 4 produces, in neutral and acid solutions of K, 
 a yellow crystalline precipitate* of 2KC1, PtCl 4 . The 
 presence of HC1 promotes the formation of this precipi- 
 tate. It is slightly soluble in water, but wholly insoluble 
 in alcohol. This is a very delicate test for any potassic 
 compound ; the best method of applying it is to mix the 
 solution with PtCl j5 evaporate to dryness upon a water- 
 bath, and treat the residue with alcohol ; the excess of 
 PtCl, dissolves in the alcohol, coloring the solution yellow ; 
 2KC1, PtCl 4 is left undissolved as a yellow crystalline pre- 
 cipitate. The addition of PtCl, should always be preceded 
 by that of HC1, to convert the potassic compound into the 
 chloride, if it should not exist already in that form. 
 
 46. If a small particle of a potassic compound be intro- 
 duced on the loop of a platinum wire into the flame of a 
 Bunsen's gas-lamp, it will, if volatile at the temperature of 
 the flame, color the part of the flame above the sample 
 blue-violet; if the substance examined contains a sodic as 
 well as a potassic compound, the yellow color imparted to 
 the flame by the sodic compound overpowers and obscures 
 the violet tint produced by the potassic one. But K can 
 be detected in the presence of Na (or Li) if we look at the 
 flame through deep blue cobalt glass ;f through this colored 
 
 * PtCl 4 gives with iodine a dark red color ; and as this color prevents 
 the yellow precipitate of 2KC1, PtCl 4 from being distinctly seen, iodine 
 should be expelled, if present, before testing for K by this reagent. To 
 expel it, evaporate to dryness ■with concentrated HN0 3 ; dissolve the 
 residue in water, and add HC1 and PtCl 4 , and then proceed in the usual 
 way. 
 
 f The cobalt blue glass can be obtained at the operative chemists. 
 Befoue using the glass, it must first, of course, be ascertained how small 
 a quantity of potash mixed with soda (or lithia) it will clearly indicate. 
 
44 THE SPEOIAT, PROPERTIES 
 
 glass no colored rays from Na (or Li) can pass, but it 
 transmits those peculiar to K. The flame, when viewed 
 through this colored glass, is of an intense violet color, 
 and is even visible when one part of potash is present with 
 two hundred parts of soda. As all substances which make 
 flame luminous, especially all organic substances which 
 burn with separation of carbon, give the same violet color, 
 these substances must first be removed by heat before the 
 color of the flame can be used as a test for K. 
 
 41. The potassic flame may be viewed through the in- 
 digo prism instead of the blue glass ; the flame appears 
 through the prism of sky blue, then violet, and at last of an 
 intense crimson red, even when seen through the thickest 
 layers of solution ; admixtures of Na or Ca do not hinder 
 the reaction. 
 
 48. The potassic flame viewed through the violet-colored 
 glass appears violet, and through the green colored glass 
 blue-green. 
 
 49. The more volatile the salt, the more intense is the 
 coloration it imparts to the flame ; potassic chloride and 
 potassic nitrate volatilize rapidly, the carbonate and sul- 
 phate less rapidly, and the phosphate still more slowly, 
 but they all of them distinctly show the reaction, though 
 decreasing in degree. The sensibility of the test may, in 
 many cases, be increased by moistening the substance 
 under examination with H 2 S0 4 , drying the substance at 
 the border of the flame, and then introducing it into the 
 melting space. With silicates and other difficultly vola- 
 tile potassic compounds the reaction is best secured by 
 fluxing it with pure gypsum in the melting space; there is 
 formed a calcic silicate and volatile potassic sulphate which 
 color the flame. It is advisable to ignite decrepitating 
 salts in a platinum spoon before attaching them to the 
 loop of the platinum wire. 
 
 Characteristic The flame test, the reaction with PtCl 4 
 
 and NaHT. 
 
 50. Na and its compounds. — The color of this metal is 
 bluish-white; in properties it much resembles K. The 
 salts of this base, with a few exceptions, are very soluble ; 
 the means we have of detecting it are therefore limited. It 
 exists in the mineral kingdom as cnLORiPE (kitchen salt), 
 sulphate (Glauber's salt), iiorate (bora.r or lineal), ni- 
 trate and carbonate. It likewise forms a constituent of 
 many siuceoik minerals. 
 
OF THE FIRST GROUP. 45 
 
 51. If a small particle of a sodic compound be introduced, 
 on the loop of a platinum wire, into the melting space of 
 the flame of a Bunsen's gas-lamp, it will, if volatile at the 
 temperature of the flame, color the part of the flame above 
 the sample intense yellow ; this is the most characteristic 
 test for sodic compounds. If the sodic flame is made to 
 illuminate a crystal of potassic bichromate, this salt appears 
 perfectly colorless and transparent, and with an adaman- 
 tine lustre. The following reaction is even more delicate. 
 A piece of paper about a centimetre square is coated with 
 red mercuric iodide, and placed upon a small holder, which 
 is movable on an arm, also movable, attached to the chim- 
 ney of the lamp. When the least quantity of NaHO, 
 Na 2 S0 4 , or NaCl, is introduced into the melting space of 
 the flame, the red iodide becomes white, with a faint tinge 
 of fawn color. The glaring contrast of these colors is 
 apparent when the paper is lit up by being placed close to 
 the red-hot wire and bead, and the wire then placed in the 
 flame, so that the bead only reaches the melting space. 
 Potassic, lithic, and calcic compounds do not interfere 
 with this reaction. 
 
 52. The sodic flame appears orange-yellow, through the 
 green glass, even with the smallest quantities. This glass 
 is particularly adapted to the recognition of all sodic com- 
 pounds (Merz). 
 
 53. Although the sodic salts are a little less volatile 
 than the potassic salts, they display, with regard to their 
 relative volatility, and the influence of H 2 SO t and pure 
 gypsum in increasing their sensibility, the same behavior 
 as the potassic ones. 
 
 54. Di-hj'dric di-potassic metantimoniate (K^H^Sb./X) 
 produces, in neutral or alkaline solutions of sodic salts, a 
 white crystalline precipitate of Na 2 H 1J Sb ;i 7 . In concen- 
 trated solutions the precipitate is formed immediately ; but 
 from dilute solutions it separates only after the lapse of 
 some time. Violent agitation of the fluid promotes the 
 separation of the precipitate. Acid solutions decompose 
 the potassic salt, antimonic acid being precipitated; free 
 acids must therefore be first neutralized with potash before 
 this test can be applied. Na.^H^Sb^O, is soluble in K 2 C0 3 ; 
 if this substance be present in the solution it must be 
 nearlv saturated with acetic acid. 
 
 55." The double chloride of 2NaCl, PtCl 4 is soluble in al- 
 cohol, and very soluble in water; therefore PtCl, produces 
 
46 EXERCISES. 
 
 no insoluble salt with sodic compounds, either in an aque- 
 ous or alcoholic solution. 
 
 Characteristic. — The flame reaction. 
 
 56. Li and its compounds. — Lithia occurs in certain minerals, particu- 
 larly in spodumene, petalite, and lepidolite. 
 
 67. Na 2 HP0 4 produces in not over dilute solutions of tithic salts, upon 
 boiling, a heavy white crystalline precipitate of Li 3 P0 4 ; if the solution 
 is then evaporated to dryness, and the residue treated with cold water, 
 the lithic phosphate remains undissolved. We can, therefore, in this 
 way distinguish Li from, and in the presence of, K and Na. LiCl forms 
 with PtCl 4 a double salt, 2LiCl, PtCl 4 , which is even more soluble in 
 water than the corresponding sodic salt. 2N T aCl, PtCl 4 . 
 
 58. "If a lithic salt, particularly LiCl, is exposed on a platinum wire 
 in the melting space of the flame of a Bunsen's gas-lamp, the outer flame 
 shows a strong cakhinb tint. Presence of sodic salts, but not potassic 
 salts, conceals this reaction." 
 
 59. If the lithic flame be viewed through the indigo prism, it appears 
 through the thinnest layer of the indigo solution of a carmine-red, which, 
 with increasing thickness of the solution, becomes gradually feebler, and 
 disappears before the thickest layers pass before the eye; whereas the 
 potassic flame appears through the thinnest layer of the indigo solution 
 of a sky-blue, then violet, and at last of an intense crimson-red, even 
 when seen through the thickest layers of the solution. Admixtures of 
 sodic or calcic compounds do not hinder the reaction of either the Li or K. 
 
 60. As of all lithic compounds the carbonate and chloride give the 
 most intensely colored flame, it is only necessary to mark on the prism 
 the place at which the lithic rays from these salts disappear, to obtain a 
 space above this mark which transmits only red potassic rays. As this 
 part of the prism acts in the same way as a thick cobalt glass in detect- 
 ing potassic compounds in the presence of sodic ones, the cobalt glass 
 can be dispensed with for detecting K. 
 
 61. Lithia with an admixture of potash is detected by bringing a sam- 
 ple into the melting space, and comparing its flame with that of a sam- 
 ple of pure potash placed side by side with it in the melting space. 
 With thin layers of the solution the lithic flame appears redder than the 
 pure potassic flame ; with somewhat thicker layers the flames are equally 
 red, if the proportion of lithia to potash be very small: if the lithia be 
 in excess, the intensity of the red lithic flame sensibly diminishes with 
 thicker layers, while the red flame of potash is scarcely weakened. In 
 this manner a few thousandths of lithia maybe detected hi the presence 
 of potash. Soda has almost no influence on the reaction. 
 
 62. Characteristic. — The flame test and the reaction with Na a IIP0 4 . 
 
 63. Answers to the following exercises must be written 
 out. 
 
 EXERCISES. 
 
 1. In what arc K and Na found in nature? 
 
 2. Describe the different parts of a flame, and explain 
 the action of those in blow-pipe experiments. 
 
 3. Describe a method for the preparation of sodic hydrio 
 tartrate. 
 
SECOND BASIC GROUP. il 
 
 4. Knowing that N 2 is produced by subjecting dry NH ( 
 N0 3 to heat, what gas would you infer would be produced 
 by subjecting NH^NO,, to heat? 
 
 5. Under what circumstances would you employ tartaric 
 acid in preference to sodic hydric tartrate as a test for K? 
 
 6. Describe some of the physical and chemical properties 
 of K and Na. 
 
 7. Account for the formation of ammonic sulphide and 
 carbonate in the manufacture of gas from coal. 
 
 8. State how you would prepare PtCl 4 . 
 
 9. Describe the preparation and application of the test 
 called " Nessler's test.'' 
 
 10. Do solid KHO and NaHO undergo any change on 
 exposure to air ; and if so, name the changes and any 
 differences which they may exhibit. 
 
 11. What are the characteristic tests for K, Xa, and 
 NH 4 ? 
 
 12. How are the alkaline hydrates prepared ? 
 
 13. Describe as many methods as you are able for dis- 
 tinguishing K from Na. 
 
 14. Describe a method for the preparation of K a H a 
 Sb,0 7 . 
 
 15. Show by means of an equation the chemical changes 
 which take place in the preparation of KC10 3 from the 
 action of CI on KHO. 
 
 16. Show by means of equations the action of sulphur 
 on the fixed alkalies at different temperatures, and the 
 action of phosphorus on the fixed alkalies. 
 
 17. To what are the terms " precipitation," and " evapo- 
 ration," and "distillation" applied ? 
 
 18. What is the difference between a simple and a chemi- 
 cal solution? 
 
 SECOND GROUP. 
 
 Baric Oxide (BaO), Strontic Oxide (SrO), Calcic Oxide 
 (CaO), Magnesic Oxide (MgO). 
 
 Solutions J 'or the reactions.— BaCl 2 , SrCl 2 , CaCl 2 , MgS0 4 , 
 in water. 
 
 64. " Baryta," " Strontia," " Lime," " Magnesia," are 
 names very frequently given to these oxides, they are also 
 employed occasionally to signify the hydrates of the ox- 
 ides; but if the term caustic be employed along with them, 
 
48 SPECIAL PROPERTIES OP SECOND GROUP. 
 
 they refer then exclusively to the anhydrous oxides. These 
 oxides and their hydrates are called " the alkaline earths," 
 and their salts are called " the salts of the alkaline earths." 
 
 65. (NH 4 ) B C0„ precipitates Ba, Sr, and Ca completely 
 from their solutions as carbonates, but it precipitates Mg 
 only partially, and this partial precipitation is prevented, 
 at least for a time, if NH 4 C1 is present in the solution (see 
 par. 108). Owing to this difference in their behavior 
 ■with (NH 4 ) g C0 3 , the group is subdivided ; the members of 
 the first division are BaO, SrO, and CaO ; MgO forms 
 the second. The group reagent for the first division is 
 (NH 4 ) a CO„ its addition is preceded by that of NH 4 C1 and 
 NH 4 HO. The reagent for MgO is Na 2 HP0 4 , but as it also 
 precipitates the members of the first division, it can only 
 be employed for MgO after the removal, or in the absence, 
 of BaO, SrO, and CaO. 
 
 66. Examination for the members of the first division. — 
 When a solution is examined for the members of this divi- 
 sion only, the group reagent must be added, and as directed 
 at par. 369. 
 
 61. The precipitate produced by the group reagent, after 
 being well washed, must be dissolved in acetic acid, and 
 the solution divided into two parts, which we shall call A 
 and B. 
 
 68. Add a solution of (not too little) CaS0 4 , to the A por- 
 tion As CaS0 4 precipitates Ba immediately, Sr after the 
 
 lapse of some time, and Ca not at all {see D 1 , E 1, and F 1), 
 one of three cases will occur on the addition of CaSO, to 
 the A portion ; either there will be no precipitate, or there 
 will be one after the lapse of some time, or there will be an 
 immediate one. If there is no precipitate, examine accord- 
 ing to par. 69 ; if there is one after the lapse of some time, 
 examine according to par 70 ; if there is one immediately, 
 examine according to par. 71. 
 
 69. As Ba and Sr are absent, add to the B portion XII, 
 HO and a solution of (KHJ^C^O,; if a precipitate is pro- 
 duced, Ca is present. 
 
SPECIAL PItOl'EttTIES OF SECOND GROUP. 49 
 
 TABLE II. 
 
 Behavior of the Members of the First Division of the 
 SECOND GROUP with the Special Reagents. 
 
 BaO. 
 
 D 1 . CaS0 4 , in solution, 
 precipitates Ba immedi 
 ately, from its solutions, 
 as BaS0 4 , which is insol- 
 uble in acids and alkalies, 
 
 D 2. K 2 Cr0 4 , in solu- 
 tion, produces, in neutral 
 and alkaline solutions of 
 Ba-, a pale yellow preci- 
 pitate of BaCr0 4 , insolu- 
 ble in the alkalies and 
 acetic acid, soluble 
 HC1 and HN0 3 . 
 
 D 3. H 2 S0 4 and the 
 soluble sulphates behave 
 in the same manner in 
 solutions of Ba as CaS0 4 . 
 
 D 4. H 2 C 2 4 , in solu 
 tion, produces only in 
 concentrated solutions of 
 Ba a white precipitate of 
 BaC 2 4 , soluble in acids. 
 The addition of NH 4 HO 
 renders this reaction 
 therefore more suscepti- 
 ble. 
 
 SrO. 
 
 E 1. CaSO„, in solu 
 tion, precipitates Sr 
 after the lapse of some 
 time,*£rom its solutions, 
 as SrS0 4 , which is al- 
 most absolutely insolu- 
 ble in acids and alka- 
 lies. 
 
 E 2. K,O0 4 , in solu- 
 tion, produces in con- 
 centrated, but not 
 dilute, solutions of Sr, 
 or such as contain free 
 acetic acid, a bright 
 yellow precipitate of 
 SrCr0 4 . 
 
 E 3. H 2 S0 4 and the 
 soluble sulphates pre- 
 cipitate Sr from its so- 
 lutions, as SrS0 4 . The 
 precipitate will not ap- 
 pear immediately, un- 
 less the solution be very 
 concentrated. 
 
 E 4. H 2 C 2 4 , in solu- 
 tion, precipitates, even 
 from dilute solutions of 
 Sr, a white precipitate 
 of* SrC 2 a 4 . The addi- 
 tion of NH 4 HO pro- 
 motes the formation of 
 the precipitate. 
 
 CaO. 
 
 F 1 CaS0 4 produces 
 no precipitate in solu- 
 tions of Ca. 
 
 F 2. K 2 Cr0 4 , in solu- 
 tion, produces no pre- 
 cipitate in solutions of 
 Ca, CaCr0 4 being solu- 
 ble. 
 
 F 3. H 2 S0 4 and the 
 alkaline sulphates cause 
 only in concentrated 
 solutions of Ca a partial 
 precipitate of 0aS0 4 , 
 which redissolves com- 
 pletely in a large amount 
 of water. 
 
 F 4. n 2 C 2 4 , in so- 
 lution, throws down 
 from neutral solutions 
 of Ca, even if highly 
 diluted, a precipitate of 
 CaC 2 4 . The addition of 
 NH 4 HO renders this 
 reaction more delicate. 
 
 70. Ba is absent; Sr is, and Ca may be, present. The 
 presence or absence of Ca cannot be determined, as long 
 as any Sr remains in solution; because the reagents, which 
 precipitate Ca, precipitate Sr also (E 3, F 3, E 4, F 4). 
 
 «• The formation of the precipitate is much promoted by agitation. 
 5 
 
50 THE SPECIAL PROPERTIES 
 
 We add, therefore, to the B portion dilute H 2 S0 4 , which 
 precipitates all the Sr (B 3), and only a small portion of 
 Ca in a concentrated and none at all from a dilute solution 
 (F 3) ; in any case, sufficient Ca remains in solution for 
 detection. Filter off from the precipitate produced by the 
 H a S0 4 , after sufficient time (one or two hours) has been 
 allowed for the precipitation of the SrS0 4 , and add to the 
 filtrate NH 4 HO in excess, and then (NH 4 ) 2 C 2 4 , which 
 will cause a precipitate if Ca is present. 
 
 71. Ba is, and Sr and Ca may be, present. As CaS0 4 
 cannot be employed to detect Sr in the presence of Ba, 
 and as Ba causes a precipitate with all the reagents which 
 precipitate Sr and Ca, the former must be got rid of before 
 we can ascertain the absence or presence of the two latter 
 substances. For this purpose, K„Cr0 4 must be added to 
 the B portion, which precipitates Ba only (D 2, E 2, F 2); 
 filter, and to the filtrate* (which will be of a yellow color; 
 from the excess of K a Cr0 4 , if the Ba has been completely 
 precipitated) add NH 4 HO in excess and (NH 4 ) ? CO s , and 
 warm the solution ; if a precipitate is produced, it may be 
 due to the presence both of Sr and Ca ; if no precipitate is 
 produced, Sr and Ca are absent. If a precipitate is pro- 
 duced, wash it until all excess of K 2 Cr0 4 has been re- 
 moved, then dissolve it in acetic acid, filter, if necessarj-, 
 through a very small filter, and add to the clear solution 
 not too small a quantity of the dilute solution of K 2 S0 4 ,f 
 after which addition the solution must be well agitated ; if 
 the K a S0 4 produces a precipitate, after the lapse of some 
 time, Sr is present. If the K 2 S0 4 solution has produced a 
 precipitate, add some dilute H 2 S0 4 to complete the preci- 
 pitation, and allow sufficient time (one or two hours) for 
 the complete separation of the SrSO, before filtering ; add 
 to the filtrate, or to the solution, without filtering, if 
 K 2 S0 4 has produced no precipitate, XH 4 HO in excess and 
 (NH 4 ) 2 C 2 0. ; if this last reagent produces a precipitate, Ca 
 is preserit.f 
 
 * It is absolutely necessary to have the filtrate from the BaCr0 4 per- 
 fectly bright and transparent, -which sometimes is troublesome to ob- 
 tain. See filtration in Fart III. 
 
 \ Care must be taken to make the solution of K a S0 4 of the strength 
 direoted in the list of rengcnts. Of that strength, it contains the same 
 quantity of S0 4 as a saturated solution of CaS0 4 contains in a like 
 quantity of liquid ; it is, therefore, sufficiently strong to precipitate SrO, 
 but not to precipitate CaO. 
 
 I For another method for the separation and detection of these three 
 substances, and for the pholo-chemical method, the student is referred 
 to pars. 99 and 101. 
 
OP THE SECOND GROUP. 51 
 
 72. The filtrate from the (NH 4 ) 2 C0 8 or the solution with 
 winch (NH^CO, has failed to give a precipitate, mast be 
 examined for Mg as directed at par. 312. 
 
 73. The following precautions are to be attended to in the 
 analysis of this group .- The solution of CaS0 4 must be 
 added in not too small a quantity, and it must always be 
 added in the cold, as this reagent is less soluble in hot than 
 cold water. Time must be allowed for the formation of 
 the precipitate produced by this reagent in solutions of Sr, 
 the formation of which is much promoted by agitation. In 
 separating Sr from a solution by K 2 S0 4 , the liquid ought 
 not to be Altered immediately, but a due time allowed for 
 the complete separation of the precipitate from the solu- 
 tion; and the solution ought not to be warmed, owino- to 
 the less solubility of CaS0 4 in hot than cold water. 
 
 PROPERTIES OF THE METALS, THE OXIDES, THE SULPHIDES, 
 THE CHLORIDES, THE NITRATES, THE SULPHATES, OF THIS 
 GROUP. 
 
 74. The metals are heavier than water, and decompose it, 
 at common temperatures, although Mg does so only slowly, 
 with the formation of the oxides and evolution of H. Mg 
 is nearly as volatile as Zn ; the other three are not sensibly 
 volatile. Ba, Sr, and Ca, oxidize on exposure to dry as 
 well as moist air, but Mg oxidizes only in moist air. They 
 dissolve easily in dilute HN0 3 , H 2 S0 4 and HC1, with dis- 
 engagement of H; concentrated HNO s is almost without 
 action on Sr, even when boiled upon it. They combine 
 with CI, I, Br, O, S, P, etc., at ordinary or more elevated 
 temperatures. Mg unites directly with N ; and when ig- 
 nited in air or O it takes fire, burning with a dazzling light, 
 which is remarkably rich in chemical rays ; it is on this ac- 
 count employed for photographic purposes. 
 
 75. The oxides may be formed either by the ignition of 
 their carbonates, nitrates, or any of their salts containing 
 volatile acids, or by expelling the H 2 from their hydrates 
 by heat. BaO, SrO, and MgO, fuse only at the very highest 
 temperatures, as in the oxhydrogen blowpipe flame, but 
 even in this intense heat CaO exhibits no signs of fusing. 
 These oxides are not reduced by H or by C. BaO, SrO, 
 and CaO, when heated with S, are converted into a mixture 
 of sulphate and sulphide, but MgO is not altered by it. 
 
52 THE SPECIAL PROPERTIES 
 
 Dry CI converts them, with the exception of MgO,* at a 
 full red heat into chlorides, with disengagement of O. 
 BaO, SrO, and CaO, combine readily with H 2 0, forming 
 hydrates ; the combination is attended with disengagement 
 of heat. MgO combines only slowly with H 2 0, and no 
 sensible disengagement of heat attends the combination. 
 These hydrates can also be prepared by dissolving one of 
 their soluble salts in a boiling solution of NaHO; BaH a O a 
 is very frequently prepared by heating a solution of BaS 
 with CuO. BaH 2 2 is soluble in twenty times its weight of 
 cold, and three times its weight of boiling, water; SrH 2 0, 
 is soluble in fifty times its weight of cold, and 2.4 times 
 its weight of boiling, water; CaH 2 2 dissolves in about 
 "TOO pts. of cold, and is less soluble in boiling, water; 
 MgH 2 O a is almost insoluble in water; the aqueous solu- 
 tions of these hydrates have an alkaline reaction. In their 
 dry state and in solution they attract C0 2 from the air, and 
 become converted into carbonates. When CI is passed over 
 them in their dry state, or into solutions of them, without 
 the aid of heat, bleaching compounds (hypochlorites) are 
 formed, thus : — 
 
 2CaH 3 0. 2 + 2CI 2 = CaCl 3 + Ca2C10 + 2H s O. 
 
 They, like the alkalies, are converted by the CI at higher 
 temperatures into chlorates and chlorides. By the action 
 of S upon the hydrates, a sulphide and a hyposulphite are 
 formed, thus: — 
 
 3BaH s O, + 2S 2 = 2BaS + BaS 2 3 + 3H a O. 
 
 76. The metals of this group furnish no other basic ox- 
 ides but these. 
 
 11. The sulphides may be prepared by mixing their 
 sulphates with C or carbonaceous matter, as starch, and 
 subjecting the mixture to a strong heat, or by passing the 
 vapor of CS„ over the oxides in a state of ignition ; MaS, 
 on account of its sparing solubility, may be prepared ^3' 
 adding a solution of K 2 S to a solution of its sulphate. 
 They are soluble, MgS only sparingly, in water, and arc 
 
 * MgO, Al 2 3 , and the other oxides termed earths, are not acted on 
 by CI; butif they are mixed with C theynre then converted in an atmos- 
 phere of dry CI into chlorides; the affinity of the C for the 0, and the 
 affinity of CI for tho metal effecting the transformation of those metallic 
 oxides into chlorides. 
 
OF THE SECOND GROUP. 53 
 
 decomposed by it into sulph-hydrates and hydrates of the 
 oxides ; the solutions possess an alkaline reaction. Ex- 
 posed to the air, they absorb H 2 and CO,, and are con- 
 verted into carbonates with evolution of H..S ; they are 
 also decomposed with evolution of H 2 S by HC1, H> T 3 , 
 C0 2 , etc. Heated in a current of air they are converted 
 into sulphates ; in a current of CI the chloride of the metal 
 and chloride of sulphur are formed, in the moist state the 
 chloride of the metal is also formed, but S is set free. If 
 H 2 S is passed into their solutions, they combine, forming 
 hydric sulphides (M"S,H 2 S) which are soluble; these 
 hydric sulphides are also obtained by passing H 2 S into 
 solutions of the oxides. CaS, H 2 S, and MgS, H 2 S, are de- 
 composed by boiling H 2 into their hydric oxides and 
 H 2 S. A greater number of the sulphides than of the ox- 
 ides of these metals have been formed. 
 
 78. The chlorides may be prepared by dissolving the 
 oxides, their hydrates, the carbonates, or the sulphides, in 
 dilute HC1 ; BaCl 2 may be obtained by fusing together 1 
 part of CaCl and 2 pts. of powdered native BaS0 4 ; CaS0 4 
 and BaCl 2 are formed, and may be separated \>y treating 
 the fused mass rapidly with boiling water. They are 
 soluble in H 2 ; BaCl 2 does not deliquesce in moist air, and 
 is insoluble in absolute alcohol ; the other three deliquesce 
 in moist air, and are soluble in absolute alcohol; their 
 aqueous solutions are neutral to test-paper; CaCl 2 , from 
 its extreme deliquescence, is frequently employed for desic- 
 cating substances. They all melt when heated; Ca Cl 2 
 and Mg Cl 2 melt at a low red heat. Mg Cl 2 is partially de- 
 composed during the evaporation of its solution, HC1 and 
 MgO being formed; by adding XH 4 C1 to the solution 
 before commencing the evaporation, this decomposition is 
 prevented, as a double chloride (MgCl 2 , XH t Cl) is formed, 
 which does not lose acid on evaporation ; MgCl 3 forms, as 
 we see in this case, double chlorides with the alkaline 
 chlorides. The chlorides of this group are not decomposed 
 on being heated in a current of H. 
 
 79. The nitrates may be formed by dissolving the ox- 
 ides, their hydrates, or the carbonates, in dilute HNO„. 
 They are soluble in water ; Ca(X0 3 ) 2 and Mg(N0 3 ) 2 deli- 
 quesce in moist air, and are soluble in alcohol; the other 
 two do not deliquesce, and are insoluble in alcohol. These 
 nitrates are decomposed, as we have seen, by heat (75). 
 
 80. The sulphates BaSQ 4 is insoluble in H Q and in 
 
 acids but it is rendered notably soluble in H 2 by the 
 
 ' 5* 
 
54 THE SPECIAL PROPERTIES 
 
 presence of several salts, especially MgCl a and NH 4 N0 3 . 
 SrS0 4 is sparingly soluble in H 2 0, 1 pt. dissolving in 6895 
 pts. of H 2 0; its solubility is increased by the presence of 
 NaCl, and decreased by the presence of alkaline sulphates ; 
 or, if the water is acidulated with H a S0 4 , it is rather more 
 soluble in dilute HC1 and in dilute HN0 3 than in pure 
 water. Ba and Sr are not completely precipitated from 
 solutions containing metaphosphoric acid by H 2 S0 4 , and 
 alkaline citrates impede their precipitation by H 2 S0 4 in a 
 high degree, but the precipitation appears on the addition 
 of HC1. CaS0 4 is soluble in from 250 to 300 pts. of cold 
 water ; its solubility is increased if the water is acidulated 
 with H 2 S0 4 , HC1, or HN0 3 ; its solubility is also increased 
 in the presence of NH 4 C1, NaCl, and other substances; it 
 is less soluble in hot than cold water. MgS0 4 is readily 
 soluble in water, is insoluble in absolute alcohol, and only 
 slightly soluble in dilute spirit. The aqueous solutions of 
 these salts do not alter vegetable colors. These sulphates, 
 we have noticed, if mixed with C and strongly heated, are 
 deoxidized. Heated to intense redness, MgS0 4 loses part 
 of its acid, the other three are not altered at that heat. 
 Solutions of the alkaline carbonates in the cold decompose 
 SrS0 4 , CaS0 4 , and MgS0 4 , but they have only a slight de- 
 composing action in the cold on BaS0 4 ; but when boiling, 
 and upon repeated application, they decompose completely 
 this baric salt. These sulphates are also readily decom- 
 posed on being fused with alkaline carbonates. 
 
 81. General characters of the salts of this group. — The 
 salts of these metals are colorless unless the acid is colored. 
 The soluble neutral salts are neutral or alkaline, not acid, 
 to test-paper. The soluble baric, strontic, and calcic salts, 
 with the exception of the chlorides, are decomposed upon 
 ignition ; all the soluble magnesic salts are decomposed, 
 the sulphate partiallj 7 , upon ignition, some of them even 
 on the simple evaporation of their solutions. Most of the 
 insoluble salts of this group are dissolved by dilute HCL 
 MgO differs from the other members, not only by its non- 
 precipitation by (NH 4 ) 2 CO s and by (XH 4 ) a C a 4 in the pre- 
 sence of amnionic salts, but by the difficult solubility of its 
 hydrate, and the ready solubility of its sulphate. A larger 
 number of the salts of this group are insoluble than those 
 of the first ; the insolubility of the carbonates, phosphates, 
 and oxalates, especially distinguish this group from the 
 first; they aro distinguished from the following groups by 
 
OF THE SECOND GROUP. 55 
 
 the solubility of their sulphides ; they are therefore neither 
 precipitated by (NH 4 ) 2 S nor by H 2 S. 
 
 REMARKS ON THE INDIVIDUAL MEMBERS OF THE GROUP, WITH 
 ADDITIONAL SPECIAL TESTS. 
 
 82. Barium and its compounds Ba, according to Davy, 
 
 is a silver-white metal, with less lustre than cast-iron. 
 According to Matthiesen, it is a powder of a yellow color. 
 BaO is a grayish-white friable mass. BaH 2 O a is a white 
 powder ; it crystallizes from its solutions in colorless 
 crystals, containing 8 at. of water of crystallization. 
 
 83. The principal minerals of Ba are the sulphate {heavy 
 spar), and the carbonate (witherite). 
 
 84. H 2 SiF„ throws down, both from neutral and alkaline 
 solutions of Ba, a white precipitate of BaSiF„, which 
 appears only after much agitation and the lapse of some 
 time in dilute solutions ; it is perceptibly soluble in HC1 
 and in ffiSr0 3 . Addition of an equal volume of alcohol 
 l'enders the precipitation rapid, and so complete that the 
 filtrate remains clear upon addition of H 2 S0 4 . 
 
 85. If baric salts are held on the loop of a platinum wire 
 in the hottest part of Bun sen's gas flame, the part of the 
 flame above the sample is colored yellowish-green. "With 
 the soluble baric salts, and also with baric carbonate and 
 sulphate, the reaction is immediate, or very soon ; but the 
 phosphate, and also the silicates decomposable by acids, 
 demand previous moistening of the sample with H 2 S0 4 or 
 HC1, by which means the Ba may be detected by the flame 
 coloration. The silicates which HC1 fails to decompose 
 must be fluxed with Na 3 C0 3 , when the BaC0 3 produced 
 will show the reaction. It is characteristic of the yellowish- 
 green baric coloration of the flame that it appears bluisu- 
 o-reen when viewed through the green glass. If the sulphates 
 are selected, presence of calcic and strontic sulphates will 
 not interfere with the reaction. — Fresenius. 
 
 Characteristic. — The reactions with CaS0 4 , K 2 Cr0 4 , and 
 H 2 SiF 6 . 
 
 86. When is passed over BaO at a dull red heat, they 
 combine, forming Ba0 2 (baric peroxide), which is an indif- 
 ferent body, and is decomposed at a bright red heat into 
 BaO and O. Dissolved in H 2 acidulated with HC1, it is 
 converted into BaCl a and H 2 2 hydric peroxide. 
 
 87. Strontium and its compounds. — The color of Sr is 
 yellow, darker in shade than that of Ca. SrO is a grayish- 
 
56 THE SPECIAL PROPERTIES 
 
 white powder or porous mass ; SrH s O a is also a grayish- 
 white powder ; it crystallizes from its solutions in trans- 
 parent crystals containing 8 at. of water of crystallization. 
 
 88. The principal minerals of Sr are the sulphate (celes- 
 tine) and the carbonate {xtrontianite). 
 
 89. H 2 SiF„ causes no precipitate in solutions of Sr; even 
 upon addition of an equal volume of alcohol no precipita- 
 tion takes place, except in very highly concentrated solu- 
 tions. 
 
 90. SrCL, is soluble in alcohol ; the solution burns with 
 a beautiful crimson flame, which becomes more apparent 
 on stirring the solution. 
 
 91. If a small particle of a strontic compound be intro- 
 duced on the loop of a platinum wire into the flame of a 
 Bunsen's gas-lamp, it will impart an intensely red color to 
 the flame. As SrCl, gives the most intense coloration of 
 all the strontic compounds, it is advisable, with all the 
 other compounds, first to ignite them in the flame, then 
 moisten with HC1, and again to introduce them into the 
 flame. " Viewed through the blue glass, the strontic flame 
 appears purple or rose (difference between Sr and Ca, 
 which latter body shows a faint greenish-gray color when 
 treated in this manner) ; this reaction is the most clearly 
 apparent if the sample moistened with HC1 is let spirt up 
 into the flame. In presence of Ba the strontic reaction 
 shows only upon the first introduction into the flame of 
 sample moistened with HC1." 
 
 Characteristic. — The precipitation %y CaS0 4 after the 
 lapse of some time, and the color of the alcohol flame. 
 
 92. Calcium and its compounds. — The color of Ca is 
 light yellow. CaO and CaH a 2 are white powders. 
 
 93. The principal minerals of Ca are the sulphate 
 gypsum, selenite, CaS0 4 , 2H a O, anhydrite CaSO,) the car- 
 bonate (chalk, limestone, marble, arragonite, Iceland or 
 calcareous spar), the double carbonate of lime and mag- 
 nesia (dolomite, CaC0 8 , MgCO s ), and the fluoride (Jluor 
 spar, CaF 2 ). 
 
 94. H 2 SiF„ does not precipitate Ca from its solutions. 
 
 95. The alcoholic solution of CaCl, or Ca(NO a )„ when 
 ignited, burns with a yellowish-red colored flame. 
 
 96. Ammonic arsenite produces, in aqueous solutions of 
 CaCl a , an immediate precipitate of calcic arsenite. In 
 solutions of BaCl, or SrCl, a precipitate is produced by 
 this reagent only after the lapse of some time. Should 
 this test be resorted to for confirming the presence of Ca, 
 
OP THE SECOND GROUP. 57 
 
 amnionic salts (if present) must first of all be removed 
 from the solution, because the arsenites which are insoluble 
 in water dissolve in it if amnionic salts are present. 
 
 9*1. If a small particle of a calcic compound be introduced 
 on the loop of a platinum wire into the melting space of 
 the flame of a Bunsen's gas-lamp, it will impart an orange- 
 red color to the outer flame. As CaCl 2 gives, of all the 
 calcic compounds, the most intense coloration, it is advi- 
 sable with all the other compounds to moisten them with 
 HC1 before introducing them into the flame. The colora- 
 tion appears of a finch-green color when viewed through 
 the green glass, whilst the strontic flame, when viewed 
 through the green glass, appears only of a weak yellow. 
 In the presence of Ba the calcic coloration shows only 
 upon the first introduction of the substance into the flame. 
 
 Chacteristic — The non-formation of a precipitate on the 
 addition of CaS0 4 , and the formation of a precipitate on 
 the addition of (NH 4 ) 2 C 2 4 , and the coloration of the flame 
 seen through the green glass. 
 
 98. Before describing the special properties of MgO we 
 will give Fresenius's method for the separation and detec- 
 tion of BaO, SrO, and CaO (par. 99), and also the photo- 
 chemical method (par. 101). 
 
 99. Dissolve the precipitate produced by the group re- 
 agent (NH 4 ) 3 C0 3 , after it has been well washed in the least 
 possible quantity of HC1, and add to a small portion of the 
 fluid some solution of CaS0 4 (not too little) ; a precipitate 
 is formed immediately;* Ba is, and Sr and Ca maybe, 
 present. 
 
 100. Evaporate the remainder of the HC1 solution to 
 dryness, digest the residue with absolute alcohol, which 
 dissolves SrCl 2 and CaCl 2 , but leaves the greater part of 
 the BaCl a undissolved, filter after having moistened the 
 filter with alcohol, dilute the filtrate with an equal volume 
 of H 3 0, mix with a few drops of H 2 SiFl 6 , let the mixture 
 stand several hours to allow time for the trace of BaSiF 6 
 to precipitate, then filter and add dilute H 2 S0 4 to the alco- 
 holic filtrate ; the Sr and Ca will be precipitated as sul- 
 phates ; filter and wash the precipitate with weak alcohol, 
 then boil the precipitated sulphates in a solution of Na 2 C0 3 ; 
 
 * If a precipitate is not formed immediately, but only after the lapse 
 of some time, examine the other portion of the solution according to 70 ; 
 if no precipitate is formed, examine the other portion of the solution 
 according to 69. 
 
58 SPECIAL PROPERTIES OF SECOND GROUP. 
 
 SrC0 8 and CaCO a •will be formed. Filter, wash the preci- 
 pitated carbonates with distilled water, then dissolve them 
 in HC1, evaporate the solution to dryness, and dissolve 
 the residue in a small quantity of water and examine for 
 Sr and Ca as directed in par. 71 after the Ba has been re- 
 moved. 
 
 101. " The three alkaline earths may be detected in mix- 
 tures containing all three of them by the different colora- 
 tion which they severally impart to the flame. To this 
 end the sample under examination is repeatedly moistened 
 with H a S0 4 , then cautiously dried, and introduced into the 
 fusion zone of the gas flame. After the evaporation of the 
 alkalies that may chance to be present, the baric coloration 
 will make its appearance alone. After this coloration has 
 completely disappeared, and the sample moistened with 
 HC1 gives on spirting no longer a flame coloration of a 
 bluish-green tint when viewed through the green glass, the 
 sample is moistened again with HC1 and tested for Ca by 
 viewing it through the green glass when spirting, for Sr 
 by viewing it under the same circumstances through the 
 blue glass." — Fresenius. 
 
 102. Magnesium and its compounds. — Mg is the color of 
 silver ; MgO and MgH a O a are white powders. 
 
 103. Mg is found in nature principally in the state of 
 sulphate {Epsom salts, MgS0 4 , 7H,0) of carbonate chlo- 
 ride (see par. 43,) and in combination with silicic acid in 
 various proportions, forming the meerschaum, serpentine, 
 etc. 
 
 104. NH 4 HO precipitates from aqueous solutions of 
 magnesic salts a portion as MgH a O„, the rest of the Mg re- 
 mains in solution as a double salt with the amnionic one 
 produced. 
 
 105. The fixed alkalies and the other alkaline earths 
 precipitate Mg from its solutions as MgH 2 8 , which is 
 soluble in ammonic salts ; their addition, therefore, either 
 before or after the precipitation, prevents or redissolves 
 the precipitate of MgH a O a . 
 
 106. (NH 4 ) 3 As0 4 produces in neutral or alkaline solu- 
 tions of Mg a precipitate of MgXH 4 AsO„, which is soluble 
 in acetic and other weak acids. 
 
 107. Na a IIP0 4 produces in concentrated neutral solu- 
 tions of Mg a precipitate of MgHP0 4 . A magnesic phos- 
 phate more soluble in H.,0 may be produced jjy adding, 
 before the Na a lIP0 4 , MI 4 C1 and NH 4 HO; in this case the 
 
EXERCISES 59 
 
 precipitate is MgNH 4 P0 4 . Both these magnesic phosphates 
 are soluble in acids. 
 
 108. According to the experiments of Dr. Divers, (NH 4 ) 2 
 CO s , other amnionic salts being absent, precipitates Mg 
 completely from its solutions after the lapse of gome time, 
 the precipitation commencing to form a few minutes after 
 the addition of the reagent. The precipitate is MgCO s , 
 unless 4 eq. of (NH 4 ) 2 C0 3 is added to every one of the 
 magnesian salt ; in that case the precipitate is MgCO,, 
 (NH 4 ) 2 CO a . When NH 4 C1 is present, the simple carbonate 
 (MgC0 3 ) never precipitates, it is always the double car- 
 bonate ; and when the NH 4 C1 is added in the proportion 
 of 2 eq. to every one of the magnesic salt, the precipitate 
 does not begin to form until about a quarter of an hour 
 after the addition of the (NH 4 ) a C0 3 , and even after the 
 lapse of twenty-four hours the precipitation of the Mg is 
 not complete. The ammonic magnesic carbonate is more 
 soluble in H 2 than in solutions of NH 4 C1 or (NH,), S0 4 , 
 and it is almost totally insoluble in solutions of (NH 4 ) a CO a . 
 
 109. If magnesic compounds, after being ignited strongly 
 by the blowpipe flame upon a charcoal support, be moist- 
 ened with a solution of Co(j\ T 3 ) a , and again ignited, the 
 mass assumes, on cooling, a pale flesh color. 
 
 110. Magnesic salts impart no color to the flame. 
 Characteristic. — The reactions with the soluble phos- 
 phates and arseniates, and with Co(N0 3 ) 2 . 
 
 111. Answers to the following exercises must be written 
 out. 
 
 EXERCISES. 
 
 19. In what state is Ba, Sr, Ca, and Mg met with in 
 nature ? 
 
 20. Do you know any baric salt which is insoluble in 
 acids ? 
 
 21. Mention the similarity and dissimilarity in proper- 
 ties of the metals of this group ? 
 
 22. Why are you directed to dissolve the precipitated 
 carbonates of the 1st division in acetic acid ? Why not 
 dissolve them in HC1 ? 
 
 23. I have some baric sulphate, and I wish to prepare 
 some baric hydrate in solution: how am I to proceed ? 
 
 24. By what single reagent and in one operation can the 
 absence of Ba and Sr be discovered ? 
 
 25. Describe the action of CI upon CaH„O a at the com- 
 
60 EXERCISES. 
 
 mon temperature, at the temperature of boiling water, and 
 at a red heat. 
 
 26. How can Ca be detected in the absence of Ba and Sr? 
 
 21. Are the oxides of the metals of the alkalies and 
 alkaline earths reducible by H or C ? 
 
 28. How can Sr be detected in the absence of Ba? 
 
 29. Can the presence or absence of Ca be determined as 
 long as Sr remains in solution ? 
 
 30. If a solution of baric, strontic, or calcic hydrate is 
 exposed to the air it becomes covered with a film : explain 
 the cause of this. 
 
 31. Can the presence or absence of Ca and Sr be deter- 
 mined as long as Ba is present in a solution ? 
 
 32. How is fluoride of silicon prepared ? Illustrate by 
 symbols the changes which take place in passing it into 
 water. 
 
 33. What occurs when BaO, SrO, CaO, or MgO, is 
 treated with S ? 
 
 34. Why does the addition of NH 4 HO to a solution ofa 
 baric, strontic, or calcic salt, to which a solution of H 2 
 has been previously added, promote the formation of the 
 precipitate ? 
 
 35. Describe as many methods as you are able for dis- 
 tinguishing Ba, Sr, Ca, when they occur in the same solu- 
 tion. 
 
 36. What is the action of reagents on solutions of Mg? 
 
 37. If you had a solution to examine for the members of 
 the 1st and 2d groups, and from its nature you were cer- 
 tain that baric and strontic compounds were absent, what 
 reagent would you employ to detect and separate the Ca, 
 if present, from Mg and the alkalies? 
 
 38. How would you prepare baric carbonate from the 
 sulphate ? 
 
 39. Supposing you had a solution containing an alkaline 
 carbonate, how could you ascertain qualitatively whether 
 it contained any free alkali ? 
 
 40. From your knowledge of Berthollet's laws, what 
 would you infer would be the result of adding a solution 
 of BaH 2 O a to an aqueous solution of a magnesic salt ? 
 
 41. If an oxalate of Ba, Sr, or Ca, was dissolved in an 
 acid, and NH^O were added in excess to the acid solu- 
 tion, what would be the effect? 
 
 42. Among the impurities contained in coal gas are, as 
 already noticed (NH^CO,, (XH 4 ),S, CO a , and H a S. The 
 
THIRD-BASIC GROUP. 61 
 
 gas is frequently made to pass through calcic hydrate: 
 does the lij-drate effect any change in these impurities? 
 Illustrate j-our answer by equations. 
 43. How is hydric peroxide prepared ? 
 
 THIRD GROUP. 
 
 Zincic Oxide (ZnO), Manganous Oxide (MuO), Xickelotjs 
 Oxide (NiO), Cobaltous Oxide (CoO). 
 
 Solutions for the reactions : ZnSO t , MnCl 2 , NiS0 4 , 
 CoS0 4 , in water. 
 
 112. Examination for the members of the group. — When 
 a solution is examined for this group only, the group re- 
 agent (NH 4 ) a S must be added as directed at par. 366, and 
 the precipitate, after being well washed with water con- 
 taining a little (NH,) 2 S, must be examined, if it is of a 
 light color, according to par. 113; if it is of a black color, 
 according to par. 114. 
 
 113. As the precipitate is of a light color, Ni and Co 
 must be absent (J 1, K 1). Examine it for Mn by the 
 blowpipe test; if Mn is absent, examine it for Zn by the 
 blowpipe test. When Mn is present, dissolve it in as small 
 a quantity of boiling dilute HC1 as possible ;* boil to expel 
 H a S,f then add (NH,) 3 C0 3 in excess and boil for some 
 time; the Mn will be precipitated as MnC0 3 (G 3), whilst 
 Zn, if present, will remain in solution. Filter, and to the 
 filtrate add (NH 4 ) S S, when Zn, if present, will be precipi- 
 tated as sulphide ; confirm its presence by dissolving the 
 precipitate, after it has been well washed, in hot dilute 
 JTN 3 , adding toit a small quantity of a solution of Co(N0 3 ) 2 
 (not even enough to impart a pink color), then a solution 
 of Na 3 C0 3 in slight excess ; the solution must then be boiled 
 for a minute or two and the precipitate afterwards collected 
 on a filter and washed ; the filter with the precipitate is 
 then incinerated on platinum foil. The green color is very 
 
 * In order to use as little acid as possible, pour the boiling acid in 
 small quantities at a time upon the precipitate collected upon the filter. 
 If the precipitate be very large, remove it from the filter into an evapo- 
 rating dish before adding the acid. 
 
 f To ascertain when all the H 2 S is expelled, hold a piece of bibulous 
 paper, moistened with a solution of some soluble lead salt, over the boil- 
 ing liquid; when the lead paper does not alter in color, all the H 2 S is 
 expelled. 
 6 
 
62 
 
 THE SPECIAL PROPERTIES 
 
 TABLE III. 
 
 Behavior op the THIRD GEOUP with the Special Reagents. 
 
 MnO. 
 
 G 1. MnS is 
 flesh-colored, but 
 becomes brown on 
 exposure to the 
 air ; soluble 
 the weak acids, 
 as acetic, as well 
 as in the dilute 
 mineral acids. 
 
 2. The fixed 
 alkalies precipi 
 tate from solu- 
 tions of Mn 
 MnH 2 2 , which is 
 of a whitish color 
 at first, but speed- 
 ily becomes black 
 ish-brown on ex- 
 posure to the air; 
 it is insoluble 
 an excess of either 
 of the fixed alka- 
 lies. The pre- 
 sence of amnionic 
 salts prevents in 
 a great measure 
 the precipitation 
 
 ZnO. 
 
 H 1. ZnS, like 
 the oxide, is 
 white; insoluble 
 in acetic acid, but 
 dissolves in the 
 dilute mineral 
 acids. 
 
 G3. (NH 4 ) 2 CO ; 
 produces in so- 
 lutions of Mn 
 a precipitate of 
 MnCO s , which is 
 white, and insol- 
 uble in an excess of 
 the reagent, espe- 
 cially on boiling. 
 
 H 2. The fixed 
 alkalies precipi- 
 tate from solu 
 tions of Zn, 
 ^0,, which ii 
 white ; it is com- 
 pletely soluble in 
 an excess of either 
 of the fixed alka- 
 lies, if the alkali 
 perfectly free 
 from carbonate. 
 
 CoO. 
 
 J. 1. CoS is 
 black; insoluble 
 in the dilute mine- 
 ral acids, as well 
 as in the weaker 
 acids. Soluble in 
 nitro-hydrochloric 
 acid. 
 
 H 3. (NH 4 ) 2 C(\ 
 produces in solu- 
 tions of Zn a pre 
 cipitate of white 
 basic carbonate 
 op zinc, which is 
 easily soluble in 
 an excess of the 
 reagent. 
 
 J. 2. The fixed 
 alkalies precipi- 
 tate, from solu- 
 tions of Co, blue 
 basic sails, which 
 turn green on ex- 
 posure to the air; 
 and are converted, 
 upon boiling, into 
 
 the PALE BED HY- 
 DRATE, which ii 
 generally disco 
 lored, owing to 
 ,le Co 2 3 be- 
 ing formed. Each 
 of these precipi- 
 tates is insoluble 
 in an excess of 
 either of the fixed 
 alkalies. 
 
 mo. 
 
 K 1. NiS is 
 black ; insoluble 
 in the dilute mine- 
 ral acids, as well 
 as in the weaker 
 acids. Soluble in 
 ni tro-hydrochloric 
 acid. 
 
 J. 3. (NH 4 ) 2 CO, 
 produces in solu- 
 tions of Co a 
 red precipitate of| 
 
 CARBONATE OF 
 
 cobalt, which is 
 readily soluble in 
 an excess of the 
 reagent, the solu 
 tion having a red 
 oolor. 
 
 K 2. The fixed 
 alkalies precipi- 
 tate from so- 
 lutions of Ni, 
 NiH 2 2 , in the 
 form of a light 
 green precipitate, 
 which is unalter- 
 able in the air, 
 and insoluble in an 
 excess of either of 
 the fixed alkalies. 
 
 
 K 3. (NH 4 )„CO s 
 produces in solu- 
 tions of Ni an 
 apple-green preci- 
 pitate of carbo- 
 nate of nickel, 
 which is readily 
 soluble in an ex- 
 cess of the reagent, 
 the solution hav- 
 ing u greenish- 
 blue color. 
 
 The alkalies fail to prooipitate the members of this group in the pre- 
 sence of non volatile organio matter, suoh as starch, sugar, tartario 
 acul, etc 
 
OF THE THIRD GROUP. 63 
 
 bright if an excess of cobalt be avoided, and is best seen 
 after the gritty residue has been powdered under a glass 
 rod Bloxam. 
 
 114. The precipitate is black ; all the members of the 
 group must therefore be sought for. Examine a portion 
 of the precipitate for Mn by the blowpipe test. Treat the 
 rest of the precipitate, whether Mn is present or not, with 
 cold dilute HC1 ; NiS and CoS will remain undissolved, 
 whilst MnS and ZnS will dissolve; examine the acid solu- 
 tion according to par. 115, and the undissolved portion 
 according to par. 116. 
 
 115. Boil the filtered HOI solution, which may contain 
 Mn and Zn, until all H.,S is expelled (see second note, page 
 41), then add a solution of one of the fixed alkalies in 
 excess ; Mn* will be precipitated, whilst Zn will remain in 
 solution ; filter if the alkali has produced any precipitate, 
 and add to the filtrate or to the solution (when it does not 
 require filtering) H 2 S, when Zn, if present, will be precipi- 
 tated; confirm its presence as directed at par. 113. 
 
 116. After having washed the black residue, examine it 
 for Ni and Co in the following way : Expose a small por- 
 tion of it on a bead of borax to the outer blowpipe flame, 
 in the way directed in par. 152. A blue bead denotes the 
 presence of Co ; this is a safe and certain test for Co ; con- 
 sequently, if a blue bead is not produced, Co is absent. If 
 
 * It is almost impossible to prevent a minute quantity of CoS and NiS 
 oxidizing, even if the precipitate is washed most carefully with water 
 containing (NH 4 ) 2 S ; the oxidized portion of these two bodies will, there- 
 fore, be present in the HC1 solution, and consequently be precipitated 
 by the fixed alkali ; a precipitate may, therefore, be produced by the 
 alkali, when no Mn is present. It will not be necessary te examine this 
 precipitate for Ni and Co, as sufficient will remain undissolved, unless 
 the student has allowed the (NH 4 ) 2 S precipitate to remain on the filter 
 for a great length of time. 
 
 KHO and NaHO solutions very frequently blacken slightly on the 
 addition of H 2 S from their containing small traces of oxides of iron and 
 copper; it is therefore necessary before employing the alkali solution to 
 examine it for these oxides ; if one or both of them are present the pre- 
 cipitate produced by H 2 S must be redissolved in a few drops of dilute 
 HN0 3 , and if Cu as well as Fe is present H 2 S must be passed through 
 the solution until it is in excess, the liquid must then be filtered, and 
 the filtrate boiled in an evaporating dish with a few drops of HN0 3 until 
 all the H 2 S is expelled and the Fe has become peroxidized, NH 4 HO is 
 then added in excess, the liquid filtered, and to the filtrate must be 
 added (NH 4 ) 2 S, which will produce a white precipitate if Zn is present. 
 If the alkali solution does not contain Cu, but only Fe, after the solution 
 of the precipitate in HN0 3 , NH 4 HO is at once to be added in excess, and 
 the filtrate from the NH 4 HO precipitate tested for Zn with (NH 4 ) 2 S. 
 
64 THE SPECIAL PROPERTIES 
 
 a yellow, and not a blue bead has been formed, which be- 
 comes gray and dull in the inner flame, Ni is present. When 
 Co is present, Ni is sought in the following way : The re- 
 mainder of the precipitate is dissolved in aqua regia, and 
 the acid solution evaporated almost to dryness; a concen- 
 trated solution of KCy is then added in excess, and the 
 whole solution must then be boiled for some time, adding 
 a little water from time to time, to replace that which 
 evaporates. To the solution, which must not be filtered 
 even if a precipitate has been formed, is added, when it is 
 cold, H 2 S0 4 slightly in excess ; if in some hours after the 
 acid has been added a precipitate appears, Ni is present ; 
 if no precipitate appear, or at least only a crystalline one, 
 which redissolves in water, Ni is absent. 
 
 lit. Ni may also be detected in the presence of Co by 
 the two following methods. 1st method : The acid solu- 
 tion which contains Co, and which may contain Ni, must 
 be evaporated nearly to drj'ness, KNO a must then be added 
 in not too small a proportion, and acetic acid to strongly 
 acid reaction, let the mixture stand for at least several 
 hours in a moderately warm place, when Co will separate 
 as nitrate of sesquioxide of cobalt and potash ; the Ni may 
 then be readily precipitated from the filtrate by NaHO or 
 (NH 4 ) a S. 2d method: Saturate with CI the very dilute 
 solution of the two metals in HC1, having the acid slightly 
 in excess ; add BaC0 3 in excess, and let the fluid stand 
 twentj'-four hours. The Co is entirely precipitated in this 
 process as black sesquioxide, whilst the Ni remains in 
 solution, and may, after the removal of the Ba by H a S0 4 , 
 be precipitated by solution of NaHO. 
 
 118. The following precautions are to be attended to in 
 the analysis of this group : When Mn is present, care must 
 be taken to expel all the H 8 S from the HC1 solution, before 
 (NH 4 ) 2 CO s is added to separate the Mn from the Zn. 
 Before adding H s S0 4 to the KCj' solution, it will be better 
 to add a little water, in order to prevent any K 2 S0 4 from 
 crystallizing out, which might mislead the student as re- 
 gards Ni. On adding NaHO to the HC1 solution, which 
 may contain the Zn and Mn and small traces of Ni and 
 Co, from the partial oxidation of their sulphides, a small 
 precipitate will frequently be formed, if only Zn be present. 
 This is occasioned by the caustic alkali having absorbed 
 some CO„ from the air, and become partially converted 
 into carbonate, which causes a partial precipitation of 
 the Zn. 
 
OP THE THIRD GROUP. 65 
 
 PROPERTIES OP THE METALS, THE OXIDES, THE SULPHIDES, THE 
 CHLORIDES, THE NITRATES, THE SULPHATES, OF THIS GROUP. 
 
 119. The metals. — Zn melts at 412° C, and at a bright 
 red heat volatilizes ; the other three metals are almost as 
 infusible as Fe. In damp air Mn gradually crumbles 
 down to a brown oxide, Zn is tarnished, the other two are 
 less affected by it than Fe ; they all combine with O on 
 exposure to air or O, at a red heat, the combination with 
 Zn being attended with flame. Mu decomposes water 
 slowly at common temperatures ; the other three decom- 
 pose it at a red heat, with disengagement of H. They 
 dissolve in dilute H 2 S0 4 and in HC1, H being evolved, and 
 salts of the metals formed. HXO s oxidizes and dissolves 
 them, a nitrate of the metal being formed. The gaseous 
 compound formed in the case of Co and Ni is N0 2 ; N 2 
 is one of the gaseous products when Zn is acted upon by 
 dilute acid. The gaseous body formed depends in this, as 
 in other cases, on the strength of the acid and the tem- 
 perature, for if Zn be acted upon by undilute HNO a , NH 3 
 is one of the products. These two reactions are repre- 
 sented in the following equations : — 
 
 (1) 4Zn -f 10HNO 3 = N 2 + 4(Zn2NO s ) + 5H,0 
 
 (2) 4Zn + 9HNO s = XH 3 + 4(Zn2N0 3 ) + 3H a O 
 
 If an excess of acid be employed, it, or a portion of it, 
 combines, of course, with the NH S formed in the second 
 reaction. Zn decomposes CO a at a red heat ; it dissolves 
 in boiling KHO, H being evolved ; thus, Zn + 2KHO = 
 K 2 0, ZnO + H 2 . 
 
 Co and Ni are magnetic; the Ni loses this property 
 almost entirely if heated to a point exceeding 332° C, but 
 recovers its magnetic power on cooling. 
 
 1 20. The oxides may be obtained by igniting the hydrates 
 or carbonates out of contact of the air ; they are non-vola- 
 tile, and are not decomposed by heat alone ; they may be 
 reduced to the metallic state by ignition with C, or, with 
 the exception of Mn, on being heated in a current of H or 
 CO. On being heated with NH 4 C1, CoO and MO are 
 reduced to the metallic state, but ZnO and MnO are left 
 by it in the state of chlorides. On being heated in contact 
 with air, ZnO and NiO suffer no change, but MnO and CoO 
 are converted into Mn 3 4 and Co a 4 . ZnO, CoO, and NiO, 
 on being heated with S, are converted into sulphides, S0 2 
 being evolved ; in the case of MnO an oxysulphide is 
 formed. Heated in a current of CI, they are converted 
 
 6* 
 
66 THE SPECIAL PROPERTIES 
 
 into chlorides, being evolved. The hydrates are obtained 
 by adding to solutions of their salts one of the fixed alka- 
 lies, as shown in Table III. ZnO and ZnH 2 3 are white ; 
 ZnO, when heated, turns lemonsyellow, and on cooling 
 turns white again ; MnO is grayisJis-green, MnH 2 O g is white; 
 both absorb from the air, and become converted into 
 brown Mn a 8 HO. NiO is grayish-green ; NiH s 2 is green; 
 CoO is an olive-green ; CoH.,0,, is pale red. These oxides 
 and hydrates are in the form of powders, and are insoluble 
 in H 2 0, but dissolve readily in HN0 3 , HC1, and H 2 S0 4 . 
 ZnO and its hydrate are soluble in the alkalies, CoO and 
 NiO and their hydrates in the volatile alkali, and MnO and 
 its hydrate in NH 4 C1. If CI is passed through H 2 in 
 which MnO, NiO, or CoO, or their hydrates, are suspended, 
 a part of the metal is precipitated in the state of M 2 H O 6 , 
 and the remainder remains in solution as MC1 2 , if the 
 liquid, in which the oxides or the hydrates are suspended, 
 is strongly alkaline the whole of the Co and Ni are con- 
 verted into the hydrates of the sesquioxides Co 2 H 6 0„ and 
 Ni 2 H 8 8 , and the Mn is converted into the hydrated 
 MnH 4 4 . 
 
 121. The sulphides are obtained in the hydrated state 
 by adding to a solution of their salts an alkaline sulphide, 
 or by passing into their alkaline solutions H 2 S ; their color 
 and their solubility in acids are noticed in Table III. 
 They are insoluble in H 3 in the alkalies and alkaline sul- 
 phides, with the exception of NiS, which, under certain 
 circumstances, dissolves to a slight extent in the alkaline 
 sulphides, imparting thereby to the solution a brownish 
 color. H a S causes no precipitate in solutions of these 
 metals containing free mineral acids, but it precipitates 
 completely Zn from the solution of the acetate, even if free 
 _ acetic acid is present. In neutral solutions H B S does not 
 completely precipitate the metals as hj'drated sulphides, 
 the solutions of zincic, cobaltous, and nickelous acetates 
 excepted. They all oxidize more or less on exposure to 
 air. S0 2 converts MnS and ZnS into hyposulphites, but it 
 dissolves only sparingly the other two. Ileated out of 
 contact with air, they are converted into anhydrous sul- 
 phides, 1I U being expelled. In the anhydrous state ZnS 
 is of a yellowish color, MnS is green, NiS bronze yellow 
 with metallic lustre, CoS is gray with metallic lustre. In 
 the anhydrous as well as in the hydrated state the}' are 
 decomposed more or less readily when heated in a current 
 of CI, metallic chlorides being formed, and chloride of sul- 
 
Or TEE THIRD GRODP. 67 
 
 phur* evolved. Roasted in air, they are converted into 
 oxides with evolution of S0 2 . The hydrated sulphide of 
 Mn precipitates Co as CoS from solutions of its salts, and 
 the hydrated sulphides of Mn and Co precipitate Ni from 
 the solutions of its salts, and Fe from Fe a Cl 6 , Pb from 
 Pb(A) 2 , Cu from CuS0 4 , and Ag from AgN0 3 , as sulphides. 
 
 122. The chlorides may be obtained by dissolving the 
 metals, the anhydrous or hydrated oxides or carbonates 
 in HC1, or by dissolving in this acid by the aid of heat any 
 of the higher oxides of Mn, Co, or Ni ; in these latter cases 
 CI is evolved. On evaporating the solutions obtained by 
 any of these modes, the salts are obtained crystallized and 
 hydrated, thus: ZnCl. 2 H 2 0,f MnCl 2 4H 2 0, CoCl 2 6H 2 0, 
 NiCl 2 9H 2 0. They may be obtained in the anhydrous 
 state by igniting the hydrates, or by heating the metals in 
 a current of CI ; in the anhydrous state they all attract 
 moisture from the air, but the first two deliquesce in the 
 hydrated state. MnCl 2 and ZnCl 2 melt at a dull red heat ; 
 at higher temperatures they sublime, and the latter can 
 be distilled ; the other two may sublime without first 
 fusing; if ignited in the air above the fusing point MnCl,, 
 if the ignition is protracted, becomes converted into oxide, 
 and the others lose more or less CI, a corresponding quan- 
 tity of oxide being formed. Heated in PHj, they are con- 
 verted into phosphides, HC1 being evolved ; and with the 
 exception of MnCl 2 they are reduced to the metallic state 
 when heated to redness in a current of H. If CI is passed 
 through solutions of MnCl 2 and CoCl 2 , they are converted 
 into Mn 2 Cl B an d Co^Cl^, and on the subsequent addition of 
 BaC0 3 , Mn 2 3 and Co 2 3 are precipitated. 
 
 123. The nitrates may be obtained by dissolving the 
 metals in HN0 3 , or the anhydrous or hydrated oxides or 
 the carbonates in the acid diluted; they are soluble in 
 H 2 0, and on evaporating their aqueous solutions crystal- 
 lized hydrated salts are obtained; they are decomposed on 
 ignition, a higher oxide of Mn, Ni, and Co, than the mon- 
 oxide being left. 
 
 124. The sulphates may be obtained by dissolving the 
 metals, the anhydrous or hydrated oxides, or the carbon- 
 
 * There are two chlorides of sulphur, S 2 Clj and SCI 2 ; they are de- 
 composed by water into S0 2 , HC1, and S. 
 
 f ZnClj in solution, under the name of Burnett's Disinfecting Fluid, 
 has been extensively used as an antiseptic and as a preservative of wood 
 and vegetable fibre. 
 
68 THE SPECIAL PROPERTIES 
 
 ates in dilute H 2 SO„ ; or by heating the higher oxides of 
 Mn, Ni, Co, in undilute acid, and ZnS0 4 may be prepared 
 by gently roasting in the air zinc blende. They are soluble 
 in H 2 0, and crystallize from their aqueous solutions on 
 evaporation, MnS0 4 with 5 atoms,* and the other three 
 with 7, atoms, of H 2 0. On being heated the water is ex- 
 pelled, and they are left in the anhydrous state ; they bear 
 a moderately strong red heat without decomposing, but at 
 a bright red heat they are decomposed, the metals being 
 left in the state of oxides, higher oxides than the monoxides 
 in the case of Mn, Ni, and Co. 
 
 125. The general characters of the salts of this group. — 
 The zincic salts, in the ahhydrous and hydrated states, 
 are white ; the manganous salts are white or red ; most of 
 the nickelous salts are yellow in the anhydrous, and green 
 in the hydrated state, their solutions are of a light green 
 color ; the cobaltous salts are red in their hydrated, and 
 mostly blue in their anhydrous state, their solutions, even 
 when much diluted, have a delicate rose tint; the red solu- 
 tion of CoCl 2 on evaporation turns blue, or on the addition 
 of strong mineral acids to its solutions. The neutral salts 
 of these metals, soluble in water, are decomposed by heat, 
 the sulphates being the least decomposable ; the manganous 
 soluble neutral salts are neutral, and the soluble neutral 
 salts of the other three metals are acid, to litmus paper. 
 Zincic and manganous compounds, which are insoluble in 
 H 2 0, dissolve in HC1; and most of the nickelous and 
 cobaltous compounds, which are insoluble in H.,0, are 
 soluble in HC1. BaCO s , or CaCO s does not precipitate 
 the oxides from aqueous solutions of the salts upon diges- 
 tion in the cold, with the exception of the sulphates ,- but 
 if the solution has been treated with CI or Br, Mn and Co 
 are precipitated from their salts by these carbonates, as 
 Mn 2 O a and Co 2 8 . A solution of Nn. ; C0 3 precipitates from 
 solutions of the normal salts of Co, Ni, and Zn, as it does 
 
 * MnSO < crystallizes below 42° with 7 ats. of 11,0, and between 45° 
 and 68° with 5 atoms, and between 68° and 80° with 4 atoms. The 
 sulphates of Mg, Zn, Mn, Co, Ni, and Fe are isomorphous ; they usually 
 orystallize with 7 ats. 11,0, but under certain conditions with 5, and 
 cuprio sulphate, which belongs to the group, never contains more than 
 6 ; they sometimes crystallize with 4, and sometimes even with 2. 
 These sulphates, which are frequently termed magnesian sulphates, re- 
 tain 1 at. 1-1,0 with considerable force, and it can bo replaced by an 
 anhydrous sulphate, as K,S0 4 ; theso double sulphates, even the double 
 ouprio Bulphate, always orystallizo with ats. 11,0. This atom of water 
 was called by Graham constitutional water. 
 
OP THE THIRD GROUP. 69 
 
 also from similar salts of Mg and Cu, not a normal, but a 
 basic, carbonate. The members of this group are distin- 
 guished from those of the preceding by the insolubility of 
 their oxides and sulphides in H 2 0, and from those of the 
 next group by their behavior with NH 4 HO.* 
 
 REMARKS ON THE INDIVIDUAL MEMBERS OF THE GROUP, WITH 
 ADDITIONAL SPECIAL TESTS. 
 
 126. Mn and its compounds. — Mn is grayish-white, very 
 brittle, and melts only at the strongest heat of a blast 
 furnace. 
 
 12T. The most important and most valuable ore of Mn 
 is the peroxide (Mn0 2 ) ; it is employed for obtaining CI 
 from HC1. 
 
 128. NH 4 H0 precipitates from solutions of manganous 
 salts part of the Mn as MnH 2 2 , which an excess of the 
 reagent does not redissolve ; but NH 4 H0 produces no 
 precipitate in the presence of NH 4 C1, or any amnionic salt 
 the acid of which forms no insoluble salt with Mn. An 
 ammonic solution of Mn rapidly attracts O from the air, 
 one of the higher oxides of Mn being formed, which is in- 
 soluble in NH 4 HO, and therefore precipitates as quickly as 
 it is formed, and in brownish flocks. 
 
 129. If a few drops of a fluid containing a manganous 
 compound, and free from CI, are sprinkled on Pb0 2 or 
 Pb 3 4 , and HN0 3 free from CI is then added, and the mix- 
 ture boiled and allowed to settle, the Mn(N0 3 ) 3 formed 
 imparts a purple-red color to the fluid. 
 
 130. The smallest quantity of Mn can be detected in any 
 of its compounds, by fusing them, in conjunction with 
 Na 2 C0 3 and a small quantity of KN0 3 , upon platinum foil 
 or wire, in the outer blowpipe flame ; sodic manganate 
 (Na 2 MnOj, which is of a bluish-green color, being pro- 
 duced^ which, on being dissolved in H 2 0, yields a green 
 solution, turning red on the addition of acetic acid, and 
 
 * Cobaltous and nickelous oxalates are nearly insoluble in water and 
 in a solution of oxalic acid, but they are soluble in NHHO ; on exposing 
 to the air an ammonic solution of the two oxalates for several days, the 
 nickelous oxalate is deposited, whilst the cobaltous oxalate remains in 
 solution. 
 
 f The manganates and permanganates, especially the latter, are em- 
 ployed as oxidizing and disinfecting agents ; under the name of Oondt/'s 
 fluid, they are largely used for these purposes. 
 
 Before making the blowpipe experiments, consult the pars, under the 
 head "Blowpipe" in Part III. 
 
70 THE SPECIAL PROPERTIES 
 
 often afterwards becoming colorless, with separation of 
 brown flocculi. " This method fails to detect manganese 
 in limestone rocks, on account of the insolubility of the 
 lime salt in Na 2 CO s and KN0 3 ; but if, along with the two 
 reagents just mentioned, a little borax be added, so as to 
 attack and dissolve a portion of the mass, the well-known 
 greenish-blue enamel is quickly produced." — Chapman. 
 
 Characteristic. — The reactions with (NH 4 ) 2 S, Pb0 2 and 
 the blowpipe test. 
 
 131. Five other oxides of Mn are known : Mn 2 3 , feebly 
 basic, is found in nature in the anhydrous and hydrated 
 states; it may be formed by exposing MnO or MnH 2 2 
 to air, or by passing CI, not to saturation, through H 2 
 in which MnH 2 2 or MnC0 3 is suspended. Mn 3 4 is found 
 
 •in nature; the other oxides of Mn are converted into this 
 one by igniting them in the air. Mn0 2 is found in nature 
 in the anhydrous and the hydrated state ; this and the 
 previous oxide are indifferent bodies ; Mn0 2 is left in the 
 hydrated state when Mn 3 4 is treated with HN0 3 . The 
 two next are acid bodies ; they cannot exist except in 
 combination, with H, or a metal ; the general formula of 
 their salts is M 2 Mn0 4 , M 2 Mn 2 8 . The first are termed 
 manganates and the latter permanganates ; they are formed 
 by fusing MnO s with KHO. Each of these oxides is con- 
 verted into MnCl 2 , with evolution of CI on being heated 
 with HC1. 
 
 132. Zn and its compounds — Zn is a hard, bluish-white 
 metal ; it is rather brittle at ordinary temperatures, but 
 between 94° and 149° C, it possesses considerable ductility 
 and malleability ; at a little higher temperature it again 
 becomes so brittle that it may be powdered in a mortar. 
 Zn is a constituent of several alloys ; brass, pinchbeck, 
 nmntz or yellow metal, and hard solder for brass are alloys 
 of Cu and Zn; other alloys we shall notice under the other 
 metals. 
 
 133. The principal minerals of Zn are the anhydrous 
 Carbonate (calamine, ZnC0 3 ) and the Sulphide (Zinc 
 blende ZnS). 
 
 134. When compounds of Zn mixed with Xa,CO s are 
 subjected upon a charcoal support to the inner blowpipe 
 flame, Zn is produced, which volatilizes, and, on passing 
 through the oxidizing flame, becomes again converted into 
 oxide. The charcoal support becomes incrusted with this 
 oxide, which is of a, yellow color while hot, and turns 
 whito on cooling. 
 
OP THE THIRD GROUP. 71 
 
 135. If a compound of Zn be moistened with Co(NOJ 2 
 and exposed on charcoal to the outer blowpipe flame, a 
 mass of a beautiful green color will be produced ; the color 
 is best seen when the mass has become cold. 
 
 136. (a) " Reduction-film black, in the thin parts brown. 
 (6) " Oxide-film white, and therefore invisible. To test 
 
 it, a square centimetre of filter-paper moistened with HX0 3 
 is rubbed over the surface and then rolled up on two rings 
 on fine platinum wire, three millimetres in diameter, and 
 burnt. If the paper is burnt in the upper oxidizing flame 
 at as low a temperature as possible, the ash forms a small 
 solid mass about a square millimetre in area, which can 
 be ignited without fusion, and becomes yellow on gently- 
 heating, and appearing white on cooling. If this be moist- 
 ened with a few milligrammes of very dilute Co(KO a ) 2 
 solution and ignited, it appears of a beautiful green color 
 on cooling; the same reaction can be effected with the 
 metallic-film." — Bunsen. 
 
 Characteristic. — The reactions with KHO, (NH 4 ) 2 S and 
 the blowpipe test. 
 
 137. Zn forms only one oxide, so far at least as is at 
 present known. 
 
 138. Ni and its compounds. — Ni is a brilliant, silver- 
 white, hard but ductile metal ; it surpasses Fe in tenacity. 
 It may be obtained pure by heating the oxalate intensely 
 in a crucible with a luted cover. The principal ore of Ni 
 is copper-nickel (NiAs). NiO yields insoluble compounds 
 with K,0, Na^O, BaO, SrO, and several other bases ; some 
 of them are decomposed by frequent washings with boiling 
 water. German silver, packfong, and tutenag (a Chinese 
 alloy), are alloys of Ni, Zn, and Cu. 
 
 139. NH 4 HO, added in small quantity to solutions of 
 Ni, produces in them a trifling greenish turbidity ; upon 
 further addition of the reagent, this redissolves readily to 
 a blue fluid, containing a compound of oxide of nickel and 
 ammonia. 
 
 140. KCy throws down from solutions of Ni a yellowish- 
 green precipitate of NiCy 2 , which redissolves in an excess 
 of the precipitant as NiCy 2 , 2KCy ; the solution is browish- 
 yellow, on the addition of HC1 or H 2 S0 4 to this solution 
 NiCy 2 is reprecipitated, whilst the KCy is decomposed, 
 HCy being evolved ; the NiCy 2 is very difficultly soluble 
 in an excess of either of the acids in the cold, but more 
 readily upon boiling. 
 
72 THE SPECIAL PROPERTIES 
 
 141. KN0 2 , used in conjunction with acetic acid, fails to 
 precipitate Ni even in concentrated solutions. 
 
 142. In the exterior flame of the blowpipe, nickel com- 
 pounds impart to beads of borax a reddish-yellow tint ; 
 the color fades upon cooling, and finally disappears almost 
 entirely. If exposed with borax to the inner flame, the 
 bead becomes gray ; if a minute fragment of KNO a be 
 added to the bead after exposure to the inner flame, and it 
 is then fused in the outer flame, it acquires a rich purple 
 color. 
 
 143. '•'■Reduction on charcoal splinter On pulverizing 
 
 the charcoal white, lustrous, ductile, metallic particles are 
 obtained, forming a brush on the magnetized blade. The 
 metal dissolved in HNO a on paper gives a green solution, 
 which on moistening with soda, exposure to bromine 
 vapor, and subsequent addition of soda, gives a brownish- 
 black spot of Ni 2 3 . The ash of the paper, from which the 
 excess of soda has been washed out, can be used for the 
 borax-bead test." — Bunsen. 
 
 144. Borax-bead — " Oxidizing flame grayish-brown, or 
 dirty violet. Upper reducing flame gray, from reduced 
 Ni, which often collects to a spongy mass of metal, ren- 
 dering the bead colorless." — Bunsen. 
 
 Characteristic. — The reactions with NH,HO, KCy, and 
 the blowpipe test. 
 
 145. There is one other oxide of Ni known, viz. Ni,O s ; 
 it forms no salts, and is converted on being heated with 
 acids into nickelous salts ; it may be obtained by digesting 
 NiH 2 2 with CI, or with an alkaline hypochlorate. 
 
 146. Go and its compounds Co is hard and of a reddish- 
 gray color. The principal minerals of this metal are the 
 Tin-white cobalt, or Smaltine (CoAs.,), and the bright 
 white cobalt, or cobalt glance (CoS a , CoAs.,). 
 
 147. " CoO combines with bases as well as with acids. 
 If fused with KHO it forms a blue compound, which is 
 decomposed by the free addition of H,0 ; when heated 
 with Mg(NO a ) 2 a pale pink residue is obtained, a combina- 
 tion of MgO and CoO ; with Al 3 O s , it forms the blue pig- 
 ment known as Thenard's blue, and with ZnO the compound 
 known as llimner's green." This, and other oxides of Co, 
 on being treated with ammonia, unite with it forming 
 ammonio-cobalt bases of complex constitution. Characters 
 traced on paper with a dilute solution of CoCl.,, are invisible 
 in the cold, but become blue by heat, and again fade in the 
 cold as the hygroscopic moisture of the paper is restored. 
 
OP THE THIRD GROUP. 73 
 
 The chief use of cobalt in the arts is in the production of 
 smalts (powdered blue glass), Thenard's blue, Rimner's 
 green, and other pigments. 
 
 148. NH 4 HO produces in solutions of cobaltous salts 
 the same precipitate as the fixed alkalies do ; but the pre- 
 cipitate is soluble in an excess of NH 4 HO, the ammonic 
 solution having a reddish-brown color : the fixed alkalies 
 produce no precipitate, or at least a very slight one, in 
 the ammonic solution. NH 4 HO causes no precipitate, if 
 NH 4 C1 is present.- 
 
 149. KCy precipitates from acid solutions of cobalt 
 salts a brownish-white cobaltous cyanide CoCy 5 , dissolving 
 easily in an excess of the precipitant, from which solution 
 the 0oCy 3 cannot be again precipitated by acids, as it ex- 
 ists now in the form of potassic cobalti-cyanide,K B Co / " a Cy 12 . 
 
 20oCy 2 -f 6KCy + 2HCy = K 6 Co'" 2 Cy 13 + H 2 . 
 
 150. "If the solution contains Ni, as well as Co, the 
 addition of HC1 to the solution of the cyanides produces 
 a greenish precipitate, which always contains the whole of 
 the Ni, and under particular circumstances all the Co — 
 that is, when these two metals are in the proportion of 3 
 eq. of Ni to 2 eq. of Co. The precipitate consists then of 
 nickelous cobalti-cyanide, Ni 3 Co 2 Cy 12 . In case of a larger 
 proportion of Ni, the precipitate is a mixture of NiCy 2 and 
 the former compound ; but if the proportion of Ni is smaller, 
 a part of the Co remains in solution as K 3 Co 2 Cy la ." — Will. 
 
 151. Co may be completely precipitated from its neutral 
 solutions by KNO a as an orange-yellow body (Co 2 3 , 
 2N 3 0„ 6(KN0 2 )2H a O). Before adding the KN0 2 the 
 solution must be evaporated to a small bulk, and neutral- 
 ized by KHO if it contains excess of acid ; acetic acid 
 must be added after the KN0 3 to strongly acid reaction, 
 and the mixture is left to stand for some time. This re- 
 action separates Co from Ni, Mn, Zn, and many other metals. 
 
 152. The compounds of Co fused with borax in the loop 
 of a platinum wire, in either flame of the blowpipe, produce 
 a beautiful blue glass, which is a very delicate and charac- 
 teristic test for Co. The cobalt compound must be used 
 in very small proportion. 
 
 153. Reduction on charcoal splinter. — " By pulverizing 
 the charcoal, white, ductile, lustrous, metallic particles are 
 obtained, which form a brush on the magnetic blade. The 
 metal, rubbed off on to paper, gives a red solution when 
 moistened with HNO s ; this yields a green color on addi- 
 
 7 
 
14 EXERCISES. 
 
 tion of HC1 and drying, which disappears again on moist- 
 ening. The paper moistened with soda, brought into 
 bromine-vapor and again moistened with soda, yields a 
 brownish-black spot of C0(,0 8 . This reaction is plainly 
 seen with a few tenths of a milligramme of metal. The 
 paper can also be 'used, after washing out the soda and 
 burning, for the coloration of the borax bead." — Bunsen. 
 
 Gharacteric Reactions with KHO, NH 4 HO, KCy, 
 
 KN0 2 , and the blowpipe tests. 
 
 154. Co unites with O in several other proportions, the 
 oxide Co 2 O a is formed as hydrate by suspending CoH 2 2 
 in H 2 0, and passing into it CI, Co 2 H„0 6 is precipitated as 
 a black powder, whilst CoCl 2 remains in solution ; thus : — 
 
 3(CoH 2 2 ) + Cl 2 = Co 2 H 6 8 + CoCl 2 . 
 
 If the oxide is suspended in solution of KHO it is all 
 converted into Co 2 H„0 8 . The other oxides of Co are 
 formed by a combination of these two in different propor- 
 tions. Co s 4 is formed by heating CoO to dull redness in 
 the air, or \>y igniting Co a 3 . Co 2 3 is converted into co- 
 baltous salts on being heated with acids. 
 
 155. Answers to the following exercises must be written 
 out: — 
 
 EXERCISES. 
 
 44. In what state do Co, Ni, Mn, and Zn, occur in 
 nature ? 
 
 45. If I desired to precipitate manganese completely 
 from a solution by ammonia, in what state must I take 
 care to have it in the solution ? 
 
 46. A mixture of MnO, MO, and CoO, is placed in a 
 tube, a current of dry HC1 gas is passed over it, and it is 
 at the same time exposed to a moderate red heat; the 
 transmission of the gas and the ignition are continued until 
 the formation of H„0 ceases ; what change has the HC1 
 effected ? Dry H is then passed over iCand a stronger 
 heat applied until a slight cloud only is perceptible upon 
 approaching a glass rod, moistened with ammonia, to the 
 mouth of the tube — what changes has the H effected ? 
 
 47. If you had to manufacture zinc sulphate, what sub- 
 stance or substances would you employ ; give the compo- 
 sition of crystallized salt. 
 
 48. A mixture of ZnO, NiO, and CoO is mixed with 
 sugar, and the mixture is then placed in a covered crucible, 
 which is then heated gradually, until it attains the very 
 
EXERCISES. 75 
 
 highest degree obtainable in a wind furnace, at which 
 temperature it is kept for some time. State what changes 
 the oxides have undergone, and what remains in the cru- 
 cible ? 
 
 49. When any of the oxides of manganese are ignited 
 in contact with the air, in what state are they left ? 
 
 50. A mixture of MnO, NiO, ZnO, and CoO, is placed on 
 a piece of porcelain and inserted in a tube ; a stream of 
 H 3 S is passed through the tube, and the tube is then 
 heated to dull redness ; after allowing the substance to 
 cool in the tube in an atmosphere of the H a S, it is digested 
 for some time in cold dilute HC1 — what occurs? To the 
 filtered HC1 solution is added sodic acetate in excess, and 
 H 2 S is then passed through the solution. What changes 
 take place, and why is the sodic acetate added ? 
 
 51. Name the principal ore of manganese, and state for 
 what it is chiefly employed ; illustrate your answer by au 
 equation. 
 
 52. Illustrate by means of equations the changes which 
 take place in a solution containing a salt of nickel and one 
 of cobalt (say NiS0 4 and CoCl 2 ), when a solution of KCy 
 is added in excess, aud the solution afterwards slightly 
 acidulated with H 2 S0 4 : (!) When the metals are in the 
 proportion of 3 atoms of Ni to 2 of Co ; (2) When they 
 are in the proportion of 6 of Ni to 2 of Co ; (3) When they 
 are in the proportion of 3 of Ni to 6 of Co. 
 
 53. I treat a mixed precipitate of the sulphides of Mn, 
 Ni, Zn, and Co, with acetic acid. What change (if any) 
 takes place? 
 
 54. A colorless solution is given you to examine for the 
 members of the first, second, and third groups. State 
 what members of these groups are probably absent. 
 
 55. Describe the chief properties and the applications of 
 Ni and Co. 
 
 56. Describe the changes which would take place on 
 roasting ZnS at a gentle heat in contact with the air, and 
 exposing the roasted mass to a red heat. 
 
 57. Describe as many methods as possible for separating 
 the members of this group by the aid of Table III. and 
 the text. 
 
 58. How is NH 4 HS and (NH 4 ) a S prepared, and describe 
 by means of equations the changes which take place on 
 treating neutral solutions of MnCl 2 with these sulphides ? 
 
 59. I mix ZnO, obtained by roasting blende or calamine, 
 with one-half its weight of charcoal, coke, or anthracite in 
 
76 THE SPECIAL PROPERTIES 
 
 powder. The mixture is introduced into a crucible, in the 
 bottom of which is an opening into which an iron pipe has 
 been accurately fitted ; the upper end of the tube reaches 
 nearly to the top of the crucible, the lower end projects 
 some distance out of it. After the introduction of the 
 mixture the crucible is covered with a lid, made air-tight 
 by means of fire-clay ; the crucible is then placed in a fur- 
 nace, in the sole of which there is a hole for the lower end 
 of the iron tube to pass through ; the crucible is exposed 
 in the furnace to a strong heat — what occurs ? 
 
 60. How is potassic nitrite prepared ? 
 
 61. How is chlorine prepared? 
 
 62. Describe the method for the preparation of micro- 
 cosmic salt, and give its formula. 
 
 63. Describe by means of equations the two methods 
 given in Part III. for the preparation of potassic cyanide. 
 
 FOURTH GROUP. 
 
 Aluminic Oxide (A1 3 3 ), Chromic Oxide (Cr_O a ), Ferric 
 Oxide (Fe 2 3 ), Ferrous Oxide (FeO). 
 
 Aluminic, chromic, and iron phosphates; the phosphates 
 of the alkaline earths. Baric, strontic, and calcic 
 oxalates.* 
 
 Dranic Oxide (D a O a ). Titanic Oxide (Ti0 2 ). 
 
 Solutions for reactions.— Al 2 3SO t , Cr 2 Cl 6 , Fe.Cl 6 , FeSO, 
 in H 2 0. 
 
 156. Examination for the members of the group. When 
 
 a solution is examined for the members of this group onlv. 
 the group reagent, NH 4 HO, must be added, as directed at 
 par. 363, and the precipitate, after being thorough- washed 
 
 * The phosphates and oxalates do not engage the attention of the 
 student as he passes through the basic groups ; he has therefore only 
 to deal with the substances given in Table IV. It is not until he has 
 had some practice in examining both for acids and bases that the insoluble 
 salts whioh are precipitated along with the oxides of this group are in- 
 cluded in the course; the precipitate is then examined according to 
 Table V. Manganous phosphate is also precipitated by NH,HO, although 
 it has not been inoluded in the list of phosphates precipitated by that 
 reagent. 
 
 Uranio and titanio oxides are olassed amongst the rare substances ; 
 they do not therefore form a part of the group, and are therefore not 
 inoluded in Tables IV. or V. 
 
OF THE FOURTH GROUP. 77 
 
 with boiling water, must be examined for the members of 
 this group and also for Mn, as it is precipitated in greater 
 or less quantity by NH 4 HO ; the cause of its precipitation 
 is explained in par. 128. We shall describe three methods 
 for the examination of this group; the first or second is 
 probably the best when Fe or Mn is present. Separate 
 portions of the original solution must be tested for Pe both 
 in the ferrous and ferric states ; for Fe" according to par. 
 177, for Pe'" according to par. 176 or 179, the latter if Cu 
 is in the solution. A small portion of the precipitate must 
 be examined for Mn by the blowpipe test (par. 130). 
 
 157. 1st Method. — Fuse* the precipitate with equal parts 
 of Na 2 C0 3 and NaN0 3 f or KN0 3 in a platinum crucible; 
 after the fusion, allow the mass to cool, and then boil it 
 with water and filter. If much Cr is present the filtrate 
 will have a yelloiv color ; add to the filtrate acetic acid in 
 excess, then Pb(A) 2 ; if a yellow precipitate (PbCrOJ is 
 produced,! a chromic compound is present in the substance 
 under examination. Dissolve the residue in HNO„ add 
 NaHO in excess, warm the solution and filter, to the filtrate 
 add HN0 3 in excess, then NH 4 HO in excess, and again 
 warm the solution ; if no precipitate should appear, even 
 after some time (half an hour), no aluminio compound is 
 present. 
 
 158. 2d Method. — The group precipitate after being 
 carefully washed and dried is dissolved in strong HNO, 
 and boiled, fragments of KC10 3 being added from time to 
 time till the oxidation is complete, which generally happens 
 in four or five minutes if no water is present, as H 2 retards 
 the oxidation ; KHO is then added in excess, Fe 2 H a O„ and 
 Mn 2 H 6 O will be precipitated if present ; filter if necessary 
 and add to the filtrate NH,C1 and NH 4 HO, which will pre- 
 cipitate Al 2 H fi O„ if present ; filter if necessary and add to 
 the filtrate BaCl 2 or Ba (N0 3 X, a yellow precipitate of 
 BaCr0 4 will be produced if chromic oxide were present. — 
 (Earth.) 
 
 * See Fusion, in Part III. 
 
 f About one part of the precipitate to two of Na 2 C0 3 and two of KN0 3 . 
 
 J The sodio carbonate and nitrate employed in the fusion must be en- 
 tirely free from sulphate, otherwise, on the addition of Pb(A) 2 , a white 
 precipitate of PbS0 4 will be formed, which the student might mistake 
 for PbCrO,. 
 
 7* 
 
78 
 
 THE SPECIAL PROPERTIES 
 
 TABLE IV. 
 
 Behavior of the FOURTH GROUP with the Special Reagents. 
 
 Al/V 
 
 L 1. A1 2 0, 
 and A1 2 H,,0 6 art 
 white. 
 
 L 2. NH 4 HO, 
 even in the pre- 
 sence of its salts, 
 precipitates from 
 aluminic solutions 
 A1 S H 6 6 , which 
 an excess of the 
 reagent does not 
 redissolve. 
 
 L 3. The fixed 
 Alkalies precipi 
 tate from alu 
 minic solutions 
 A1 2 H 6 6 , which 
 is soluble in an 
 excess of reagent, 
 from which solu- 
 tion it may be 
 again precipitat- 
 ed on the addition 
 of NH 4 C1. 
 
 L4.(NH 4 ) 2 C0 3 
 precipitates from 
 aluminic solutions 
 A1 2 H 6 6 . This 
 precipitation is 
 attended with an 
 evolution of CO.. 
 
 Cr 2 3 . 
 
 M 1. Cr 2 3 is 
 green, and Cr,H 6 
 8 a bluish-green 
 powder. 
 
 M 2. NH 4 HO, 
 even in the pre- 
 sence of its salts, 
 precipitates from 
 chromic solutionsl/i 
 Cr 8 H 6 O e , which an 
 excess of the re- 
 agent does not 
 redissolve. 
 
 M 3. The fixed 
 Alkalies precipi 
 tate from chro- 
 mic solutions Cr, 
 H 6 6 , which is 
 soluble in an ex- 
 cess of the reagent 
 in the cold; but 
 on boiling the so 
 lution it is again 
 precipitated. 
 
 M4.(NH 4 ) 2 C0 3 
 precipitates from 
 chromic solutions 
 Cr 2 H a 6 , C0 2 be- 
 ing given off. 
 
 N 1. F 2 3 and 
 Fe 2 H 6 O e are of 
 a reddish-brown 
 color. 
 
 N 2. NH 4 H0, 
 even in the pre- 
 sence of its salts, 
 precipitates from 
 "erne solutions Fe 2 
 which an 
 excess of the re 
 agent does not 
 redissolve. 
 
 FeO. 
 
 1. FeO 
 black; FeH 2 2 
 while.* 
 
 2. NH 4 H0, 
 but not in the pre- 
 sence of its salts, 
 precipitates from 
 ferrous solutions 
 FeBjOy which an 
 excess of the re- 
 agent does not re- 
 dissolve. 
 
 3. The fixed 
 Alkalies precipi- 
 
 N 8. The fixed 
 Alkalies precipi- 
 tate from ferric tate from ferrous 
 solutions Fe 2 EI 6 6 , solutions FeH 2 Oj, 
 insoluble in aD insoluble in au 
 
 excess of the re- 
 agent. 
 
 N 4. (NH 4 ),CO, 
 precipitates from 
 ferric solutions Fe, 
 H 6 6 , CO, 
 given off. 
 
 excess of the re- 
 agent. 
 
 4. (NIT 4 ) 2 C0 3 
 
 precipitates iiom 
 
 {ferrous solutions 
 
 being FeC0 3 , soluble in 
 
 * The student will most probably not obtain the precipitate of the 
 colors here stated, as ferrous salts are rarelv ever free from ferric salt* 
 and the colors of the precipitate by this mixture are altered. 
 
 The fixed alkalino carbonates throw down from their solutions all the 
 members of this group, some as oxides, the rest as carbonates. An ex- 
 cess of the reagent does not redissolve the preoipitate. 
 
 The alkalies fail to precipitate the members of this "group in the ore- 
 aoiTet'c n ° n " Volatil ° or S<w\° matter, such as starch, sugar, tartaric 
 
OP THE FOURTH GROUP. 79 
 
 159. 3d Method. — Dissolve the precipitate in as small a 
 quantity of boiling dilute HC1 as possible; add to this 
 acid solution when cold, a cold solution of NaHO or KHO, 
 •which will precipitate Fe 2 H 6 B (N3) if Fe is present;* 
 filter when a precipitate is produced and boil the filtrate, 
 or the solution in which there was no precipitate, in a dish 
 for a considerable time ; if a precipitate is produced by the 
 boiling, it is due to Cr 2 3 ; filter, and add to the filtrate, or 
 to the solution which has failed to give a precipitate, HC1, 
 until the solution is acid, then add one grain of KC10 4 , 
 and warm the solution so as to destroy all organic matter; 
 add, lastly, NH 4 H0 in excess, and again warm the solu- 
 tion ; if no precipitate should appear, allow it to stand for 
 a short time (half an hour) ; if no precipitate should even 
 then appear, A1 2 3 is absent. 
 
 Properties of the metals, the oxides, the sulphides, 
 the chlorides, the nitrates, and the sulphates of 
 the group. 
 
 160. T7ie Metals — Cr and Al are not oxidized when 
 heated even to redness in the open air. Fe oxidizes at 
 the common temperatures in moist air. Al and Fe oxidize, 
 Al only slowly, in an atmosphere of steam at a red heat, 
 Al 2 O s and Fe 3 4 being formed. Fe decomposes also at a 
 red heat CO., and CO. Cr is not acted upon by any acid 
 except HF.f Al is not acted upon in the cold by strong 
 or dilute HN0 3 , and very slowly at the boiling heat ; dilute 
 H 2 S0 4 dissolves it with difficult}', but HC1, either dilute 
 or concentrated, dissolves it readily even at low tempera- 
 tures, Al 2 Clg being formed. Pure Fe is scarcely acted 
 upon by acids at the ordinary temperature, but dissolves 
 
 * Manganese, if present, will also be precipitated by the sodic or po- 
 tassie solution, so that a precipitate may be produced by the alkali when 
 ferric oxide is absent. 
 
 f The properties of Cr differ considerably according to the manner 
 in which it is prepared, the difference depending doubtless on the state 
 of aggregation. Cr made by Peligot's process oxidizes with great 
 facility, taking fire in the air even at a heat below redness ; it also dis- 
 solves in dilute H 2 S0 4 and HC1, and is oxidized by HN0 3 . The pro- 
 perties of most metals vary very much with the state of aggregation ; 
 thus, even lead and several other metals, which will only combine with 
 the oxygen of the air with vivid combustion at very high temperatures 
 when in masses, will when in a state of fine powder combine with the 
 oxygen of the air with vivid combustion at the ordinary temperature of 
 the atmosphere. 
 
80 THE SPECIAL PROPERTIES 
 
 with the aid of heat, H being evolved ; but Fe as usually 
 obtained dissolves readily in dilute mineral acids, but 
 strong HNO, covers it with a film of Fe 2 O a , which prevents 
 the further action of the acid, whether dilute or undilute ; 
 but reducing agents remove the film, the passive iron is 
 thereby again rendered active and capable of dissolving in. 
 dilute HNO„. Al is not acted on by H 2 S or by (NH 4 ) 2 S ; 
 KHO or NaHO in a state of fusion do not act upon it, but 
 their solutions dissolve it readily, forming Al 2 Na a O„ or 
 A1 2 K„0 6 and H being evolved. Cr and Fe are oxidized 
 by fusion with KN0 3 , K 2 Cr0 4 and K 2 Fe0 4 being formed. Al 
 may be obtained by passing A1 2 C1 6 in vapor over Na, and 
 Cr may be obtained by passing the vapor of Cr 2 Cl„ over Zn. 
 161. The Oxides Al 2 O s , Cr 2 3 , and Fe 2 3 may be ob- 
 tained by igniting their Irydrates ; FeO by precipitating 
 FeH 2 2 from a ferrous salt by an alkali, and boiling it in a 
 vessel from which is excluded, the hydrate being ren- 
 dered anhydrous below the boiling point. They are not 
 altered by heat except Fe 2 O s , which at a white heat is 
 converted into Fe 3 4 , and FeO is converted, on exposure 
 to air without the aid of heat, into Fe 2 3 . A1 2 3 and Cr 2 O s 
 are not reduced by H, A1 2 3 is not reduced by C, and 
 Cr 2 O s is reduced by C at a white heat, but only at the 
 points of contact ; the oxides of Fe are reduced by H and 
 C with the aid of heat. A1 2 3 and Cr,0 3 are unaltered on 
 being heated with S, but FeO and Fe,O s are converted by 
 it into FeS with evolution of S0 2 . Al^O, and Cr a 3 are 
 not converted into chlorides by CI unless they are mixed with 
 C (see note, page 52); CI displaces the O in the iron oxides. 
 FeO and Cr 2 3 are, with one other oxide (the molybdic), 
 the only oxides which melt at a temperature below that of 
 the metal from which they are produced. The hydrates may 
 be obtained by adding to a solution of their saits XH .HO, 
 or one of the fixed alkalies, or in the case of Al 2 H e 6 , Cr,H, 
 0„, and Fe 2 H„O by adding (NH 4 ) _.CO„ as shown in Table 
 IV. Al 2 H„O and Cr 2 H,,O e may also be obtained by 
 adding (NH 4 ) 2 S to a solution of their salts with evolution 
 of H,S, thus: — 
 
 Al 2 (S0 4 ) a + ((NH 4 ) 2 S) 3 +6H.0 = A1.H.O, + ((NIIJ.SOJ, 
 + 3H„S. 
 
 FeO is the only member which is acted upon by CI when 
 suspended in pure II a O, or in a solution moderately alka- 
 line. The following is the change in H 2 : — 
 
 3FcO + Cl 2 = Fe 2 O a + FeCI, 
 
OF THE FOURTH GROUP. 81 
 
 If it be suspended in an alkaline liquid the following is the 
 reaction : — 
 
 2FeO + 2KHO + CI, = Fe 2 3 + 2KC1 + H 2 0. 
 
 Fe 2 3 may be converted into a higher oxide (ferric acid) 
 by CI if the solution contains a large quantity of KHO, 
 thus : 
 
 Fe 2 3 + 10KHO + 3C1 2 = 2(K 2 Fe0 4 ) + 6KC1 + 5H 2 0. 
 
 These oxides and their hydrates are insoluble in H 2 0, 
 but they dissolve in the dilute mineral acids ; after ignition, 
 however, they dissolve with great difficulty, even in the 
 concentrated mineral acids ; but even after ignition, if 
 fused with KHS0 4 , they dissolve readily along with the 
 other fused particles in H.O. Although it has just been 
 stated that these oxides and their hydrates are insoluble 
 in H 2 0, a modification of aluminic hydrate, which will be 
 noticed under the remarks on Aluminic Compounds (par. 
 161), is soluble in H 2 0, and it appears probable there is 
 also a soluble ferric hydrate. 
 
 162. The Sulphides — It has already been stated that 
 aluminic and chromic sulphides are not formed in the 
 humid wa3^, but they may be obtained by passing the 
 vapors of CS 2 over the Al 2 O a and Cr 2 3 intensely heated. 
 These sulphides are black, they are decomposed by H 2 
 into hydric oxides, H 2 S being evolved. Fe 2 S 3 and FeS 
 may be obtained in the anhydrous state by the direct 
 combination of Fe and S ; the color of the first is yellowish- 
 gray and the other yellow. Fe 2 S 3 may be obtained in the 
 hydrated state by dropping a solution of a ferric salt into 
 a solution of an alkaline sulphide which is in excess, or by 
 passing H 2 S over the dry hydrate ; this sulphide is speedily 
 altered by exposure to air, Fe 2 3 being formed and S set 
 free ;* if the alkaline sulphide is added to the solution of 
 the ferric salt, ferrous sulphide is formed and S set free ; 
 thus : — 
 
 (Fe 2 3S0 4 ) 2 + ((NH 4 ) 2 S) a = 4FeS + S 2 + ((NH 4 ) 2 S0 4 ) 6 . 
 
 * Ferric hydrate is employed to some extent in removing H 2 S from 
 coal-gas ; for this purpose it is mixed with sawdust and placed in layers 
 about twelve inches deep on perforated shelves ; when the mixture 
 ceases to remove the H 2 S, ferric oxide is reproduced and S set free by 
 exposing the Fe 2 S 3 to a current of air ; the revivified oxide is again em- 
 ployed, and this continues until the accumulation of S in the mixture 
 impairs its absorbing power ; the S is then utilized by the sulphuric 
 acid manufacturer, and the Fe a 3 which remains may be again employed 
 for purifying the gas. 
 
82 THE SPECIAL PROPERTTEB 
 
 Alkaline sulphides precipitate from solutions of ferrous 
 salts FeS in the hydrated state ; its color is black ; it is 
 insoluble in alkalies and alkaline sulphides, but dissolves 
 readily in HC1 and HN0 3 ; it oxidizes quickly on exposure 
 to air, turning reddish-brown, Fe 2 O a being formed and S 
 set free. 
 
 163. The Chlorides.— Al a Cl s , Cr 2 01 6 , and Fe 2 Cl„ may be 
 obtained in the hydrated state by dissolving the anhydrous 
 chlorides in water or the sesquioxides of these metals in 
 HC1 ; these hydrous chlorides cannot be rendered anhy- 
 drous by heating them in the air, as they are decomposed 
 into the corresponding metallic oxides, HOI being evolved. 
 A1 2 C1 6 , Cr a Ci c , and Fe 2 Cl 6 may be obtained in the anhydrous 
 state ; the first two by heating a mixture of Al. 2 O s or Cr 2 3 
 with C and igniting in a current of dry CI ; the following 
 is the reaction : — 
 
 A1 2 3 + 30 + 3C1 2 = A1 2 C1„ + 3CO. 
 
 Fe 2 Cl„ may be obtained by passing dry 01 over Fe heated 
 to redness ; these anhydrous chlorides are volatile, deli- 
 quescent, and dissolve readily in H,0 with considerable evo- 
 lution of heat ; Fe 2 Cl 8 is reduced by H 2 S and other reducing 
 agents to the state of ferrous chloride. Anhydrous FeClj 
 may be prepared by passing dry HC1 gas over ignited Fe ; 
 it may be obtained in the hydrated state by dissolving Fe 
 in HC1 ; it is very soluble in H a 0, and if heated in the open 
 air 01 escapes and Fe 2 3 remains ; it is converted into Fe a Cl„ 
 on passing 01 into its solution. Al a Cl 8 is not decomposed 
 at any temperature by H ; if H be passed over perfectly 
 anhydrous Cr a Cl„, very gently heated, CrCl 2 is formed ; if 
 the heat be strong, Or is separated ; the iron chlorides are 
 decomposed by H with the aid of heat, HC1 being formed 
 and Fe remaining. 
 
 164. The nitrates may be obtained by dissolving the 
 oxides in HN0 3 ; they are soluble in H 2 0, and readily de- 
 composed by heat. 
 
 165. The sulphates, Al 2 (S0 4 ) a , Cr a (S0 4 ) 3 , and Fe/SO,), 
 may be obtained by dissolving the hydrates of these metals 
 in H a SO, ; the first is also formed by adding to clay which 
 has been gently heated H 2 S0 4 and then heating the mixture 
 for a considerable time; the latter may be prepared by add- 
 ing to every 1 cq. of FeS0 4 in solution -i eq. of H,S0 4 , and 
 then adding to the heated liquid HN0 3 in small quantities 
 as long as any red fumes are given off. These sulphates 
 are soluble in H a ; they arc decomposed by heat, the 
 
OF THE FOUKTH GROUP. 83 
 
 metallic oxides being left; they and Mn'" 2 (S0 4 ), form 
 with the alkaline sulphates double salts, which are termed 
 alums. The general formula for this class of salts is M'" 2 
 (S0 4 ) 3 , M 2 S0 4 + 24H 2 0. A solution of Fe 2 (S0 4 ) 3 , especi- 
 ally if it contains a little free acid, dissolves many metals, 
 even Ag, and the Fe 2 (S0 4 ) 3 is reduced to FeS0 4 . FeS0 4 
 may be obtained by dissolving Fe in H 2 S0 4 ; it is also form- 
 ed by the conversion of iron pyrites (FeS 2 ) into FeS, and 
 this by oxidation into FeS0 4 . It crystallizes with seven 
 atoms of H 2 ; the crystals, when pure, are bluish-green, 
 but if they contain ferric sulphate they are grass green ; at 
 a red heat FeS0 4 is decomposed into Fe 2 3 , S0 2 , and S0 3 ; 
 the little water which distils over forms with the S0 3 the 
 Nordhausen sulphuric acid.* 
 
 166. The general characters of the salts of this group. — 
 Aluminic salts, with the exception of the chloride, are 
 colorless, both in the hydrous and anhydrous states. 
 Chromic oxide forms at least two varieties of salts ; there 
 is a variety which is uncrystallizable and of a green color, 
 another variety is crystallizable and of a violet color ; the 
 solutions of the violet salts change to green on heating, 
 and the green solutions generally transmit a red light. 
 Ferric salts are nearly white in the anhydrous, and yellow 
 or yellowish-red in the hydrous, state ; the color of the 
 solutions is brownish-yellow. Ferrous salts are white in 
 the anhydrous and bluish-green in the hydrous state ; their 
 solutions, if concentrated, have a greenish color. Ferric 
 salts are converted into ferrous ones by reducing agents, 
 as nascent H, H 2 S, S0 2 , Fe, Zn, SnCl,, etc. Ferrous salts 
 are converted into ferric ones by oxidizing agents, as O, 
 CI, HNO„ etc. Solutions of the ferrous salts rapidly ab- 
 sorb O from the air, and if the solution is neutral a yellow 
 basic ferric salt is deposited. The soluble neutral salts of 
 the metals of this group redden litmus paper, and are decom- 
 posed by heat. The members of this group are precipi- 
 tated by (NH 4 ) 2 S, Al and Cr, as hydric oxides ; consequently 
 H 2 S is always envolved when (NH 4 ) 2 S is added to a solu- 
 tion containing either or both these metals. FeS is always 
 formed when (NH 4 ) 2 S is added either to a solution of ferrous 
 or ferric salts. Fe 2 3 , and also A1 2 3 , are frequently sepa- 
 
 * This acid has a composition corresponding to H 2 S0 4 , S0 3 ; it is prin- 
 cipally prepared at the town of Nordhausen, in Saxony, by dryiDg crys- 
 tallized ferrous sulphate at a moderate heat to expel the water of crystal- 
 lization, and then distilling the dried sulphate in earthen retorts. 
 
84 THE SPECIAL PROPERTIES 
 
 rated from their solutions, and from other bases, by adding 
 an alkaline acetate or formiate, previously adding to the 
 solution one of Na 2 CO s or (NH 4 ) 2 CO s until the precipitate 
 which is formed only. just redissolves on stirring ; the formi- 
 ate or acetate is then added, and the solution boiled ; ferric 
 and aluminic acetates or formiates are formed in the first 
 instance, and are decomposed by boiling into insoluble 
 basic acetates or formiates. Fe 2 3 and A1 2 3 are completely 
 precipitated from solutions of their salts in the cold by di- 
 gesting in the solutions finely powdered BaC0 3 or CaC0 3 ; 
 they are precipitated principally in the state of hydrates 
 and partly as basic salts. Other insoluble carbonates also , 
 precipitate them ; thus, if it is desired to purify MnCl 2 or 
 ZnS0 4 from a ferric salt, it may be accomplished by boiling 
 the solution of the MnCl, with MnC0 3 , and the solution of 
 the ZnS0 4 with ZnCO s . Cr 2 3 is also precipitated from 
 its solutions by digesting with BaC0 3 , but the precipitation 
 takes place in the cold only after long-continued digesting. 
 BaC0 3 does not precipitate FeO from solutions of fer- 
 rous salts, with the_exception of the sulphatej"when it is 
 digested in the solutions in the cold. The members of this 
 group, with the exception of FeO, differ from the preceding 
 group by being insoluble in NH 4 HO, and they and the third 
 group differ from those of the fifth and sixth by not being 
 precipitated by H 2 S in the presence of free mineral acids. 
 
 REMARKS ON INDIVIDUAL MEMBERS OF THIS GROUP, WITH 
 ADDITIONAL SPECIAL TESTS. 
 
 16?. Al and its compounds Al is a bluish-white metal, 
 
 very malleable, ductile and sonorous ; it is very light, its sp. 
 gr. being about 2.5 ; its sp. heat is very great, its melting- 
 point is intermediate between the melting-points of Zn and 
 Ag, but nearer to the former ; it is a better conductor of 
 heat than Ag, and about equal to it as a conductor of elec- 
 tricity. The now well-known alloy of aluminum and copper, 
 viz. aluminum bronze, contains 10 per cent, of Al. In com- 
 bination it is very abundant in nature ; it forms not only 
 the basis of common clay, but is likewise a principal in- 
 gredient in many of the precious stones. As A1 2 0„ with 
 slight traces of Si0 2 and Fe.,0 3 , it forms the corundum, 
 sapphire, ruby, diamant spar, etc. As hydrate, it is 
 known under the names diaspore and oibbsite. Combined 
 with silica and glucina, it forms the emerald, beryl, 
 euuxase, and ciirysoberyu Al 2 O s has the property of 
 
OP THE FOURTH GROUP. 85 
 
 combining very intimately with certain kinds of organic 
 matter, especially coloring matters ; it attaches itself to 
 the fibres of cloth, and retains in the cloth the power of 
 attracting and retaining coloring matters; its salts are 
 therefore extensively employed as mordants. It is ob- 
 tained in a form soluble in H 2 by exposing a dilute solu- 
 tion of an aluminic acetate to a temperature of 100° C. 
 in a close vessel for several days ; this solution is coagu- 
 lated by mineral and most vegetable acids, by alkalies and 
 decoctions of dye woods, but the alumina in this form does 
 not act as a mordant. A1 2 3 is the only oxide known of 
 Al ; it is regarded as a sesquioxide on account of its iso- 
 morphism with, and general resemblance in properties to, 
 Fe 2 2 . 
 
 168. If aluminic compounds be ignited upon charcoal by 
 the blowpipe flame, afterwards moistened with a few drops 
 of Co(N0 3 ) 2 , and again strongly heated, the mass assumes 
 a blue color on cooling. This can only be used as a 
 confirmatory test, as other substances, phosphates and 
 readily fusible salts, exhibit the same reaction. 
 
 Characteristic. — The reactions with NH 4 HO, KHO, and 
 the blowpipe test. 
 
 169. Cr and its compounds. — The principal mineral of 
 Cr, and from which the oxide is obtained, is the chrome 
 iron (FeO, Cr 2 A 3 ), which is found principally in Sweden, 
 in the Uralian Mountains, and in America ; it is scarcely 
 attacked by any of the acids. 
 
 l^O. On fusing an}' chromic compound with KN0 3 or 
 NaX0 8 , yellow chromate of the alkali (M 2 Cr0 4 ) is formed, 
 which is soluble in water, and by adding to the solution 
 acetic acid in excess, and then PbA 2 , j-ellow PbCr0 4 pre- 
 cipitates ; this test distinguishes it from all other sub- 
 stances. In the fixed alkalies, a small quantity of Cr 2 3 
 in the presence of a large quantity of Fe 2 3 is totally 
 insoluble; but a small quantity of the latter dissolves 
 readily when a large quantity of the former is present. 
 Under these circumstances the two oxides are best sepa- 
 rated from each other by fusing the mixed substances with 
 KX0 3 and Na,C0 3 . On treating the fused mass with 
 water, the K 2 Cr0 4 dissolves, but the Fe 2 3 does not. The 
 solution may be tested with PbA .,. 
 
 111. If a solution of Cr 2 3 in "XaHO or KHO is boiled 
 with Pb0 2 in excess for a short time, the Cr a 3 reduces 
 some of the PbO , PbCr0 4 being formed, which dissolves 
 8 
 
86 THE SPECIAL PROPERTIES 
 
 in the alkaline solution ; if to the filtered liquid acetic 
 acid be added in excess, the PbCrO, precipitates. 
 
 172. Borax dissolves chromic compounds, both in the 
 inner and outer blowpipe flame ; the bead, on cooling, 
 assumes an emerald green color. Microcosmic salt has 
 the same effect. 
 
 Chai-acterisiic. — The color of its salts, its conversion by 
 oxidizing agents into chromic acid, and the blowpipe test. 
 
 173. Three other oxides of Cr are known, viz., CrO, a 
 base; CrO, Cr 2 3 , corresponding to magnetic oxide of 
 iron; and Cr0 3 , an anhydride, which forms salts with 
 bases, and is noticed amongst the acids. CrO is known 
 only in the bydrated state ; it is obtained by adding KHO 
 to a solution of CrCl 2 ; it absorbs O with great rapidity ; 
 it decomposes even H 2 0, H being evolved, and the other 
 oxide (CrO, Cr 2 3 , H 2 0) in the hydrated state being 
 formed. Chromic oxide and many of the chromates are 
 employed as coloring materials in painting on porcelain 
 and in calico printing. 
 
 174. Fe and its compounds. — Very little is known about 
 perfectly pure Fe ; it is met with in the arts in three differ- 
 ent forms, cast iron, malleable iron, and steel; each of these 
 varieties contains carbon and other foreign matters, but 
 the differences of character in these varieties appear to be 
 chiefly due to the different proportions of C which are 
 disseminated through, or combined with, the metal. The 
 ores of iron are numerous, the most valuable are specular 
 iron ore, red haematite, varieties of Fe.,0 3 , brown haematite 
 (2Fe 2 3 , 3H 2 0), spathic iron or carbonate of iron (FeC0 3 ), 
 clay ironstone and the black band are an impure ferrous 
 carbonate, and the magnetic iron ore, or loadstone (FeO, 
 Fe 2 3 ). 
 
 115. Potassic ferrocyanide (K 4 FeCy„) produces in fer- 
 rous solutions a white precipitate of FeK 2 FeCy„, which 
 speedily becomes blue by absorbing oxygen from the air. 
 Free alkalies prevent its formation, and they readily de- 
 compose it. It is insoluble in the dilute acids. 
 
 176. KjFeCy,. produces, even in highly dilute ferric so- 
 lutions, a beautiful blue precipitate of Prussian blue, Fe 4 
 (FeCy 6 ) 3 , which is insoluble in acids, but is decomposed 
 by the alkalies ; in highly dilute solutions only a blue 
 tinge is produced at first; after long standing a scanty 
 precipitate is formed. The same precautions are required 
 in this case as in par. 177. 
 
 177. J'ulaxxic ferrieyanide (K^Fe.^Cy,,) produces iu fer- 
 
OP THE FOURTH GROUP. 87 
 
 rous solutions a beautiful blue-colored precipitate of turn- 
 bull's blue (Fe 3 Fe 2 Cy l2 ), which is insoluble in HC1, but 
 is decomposed by the alkalies. In highly dilute solutions 
 only a bluish-green coloration is produced. If the solution 
 is alkaline, it must be acidified -with acetic acid ; if it is 
 acid, and the acidity is caused by one of the mineral acids, 
 as they decompose both the potassic ferri- and ferro-cyan- 
 ides, rendering their solutions green, an alkaline acetate 
 must be added in sufficient quantity so that the base of the 
 acetate may neutralize the free mineral acid. 
 
 1*78. K 6 F 3 Cy 12 deepens the color of the solution of ferric 
 salts to a ruddy brown, but causes no precipitate; if the 
 ferricyanide contains a trace of ferrocj'anide,* it will im- 
 part to the ferric solution a greenish tinge. 
 
 179. Potassic sulphocyanide (KCyS) produces in neu- 
 tral and even in moderately acid ferric solutions a very 
 intense blood red, arising from the formation of Fe 2 (CyS) 3 , 
 which is soluble. The color disappears on the addition 
 of an alkaline acetate, but is restored by adding to the so- 
 lution dilute HC1; it also disappears on the addition of 
 alkalies, or of a large quantity of strong acid. This is by 
 far the most delicate test for ferric compounds. 
 
 180. Flame reactions. — Seduction on charcoal splinter 
 gives no metallic bead or ductile lustrous particles ; the 
 finely divided metal forms a black brush on the end of the 
 magnetized knife-blade; this, when rubbed off on paper 
 and dissolved in a drop of aqua regia, yields a yellow spot 
 when warmed over the flame, which, when moistened with 
 K 4 FeCy 6 , gives a deep coloration of Prussian blue. The 
 yellow spot moistened with NaHO, and then held for a few 
 moments in a vessel with bromine vapor, gives, on a second 
 addition of soda, no coloration of a higher oxide. 
 
 181. Borax bead "In the oxidizing flame, when hot, 
 
 yellow to brownish-red ; when cold, yellow to brownish- 
 yellow ; reducing flame, bottle-green." — Bunsen. 
 
 Characteristic For ferrous compounds, the reactions 
 
 with KgFe^y,,, ; for ferric compounds, the reactions with 
 K 4 FeCy B and KCyS. 
 
 182. Two other iron oxides are known, viz., the black or 
 magnetic oxide, Fe 3 4 , which may be viewed as a compound 
 of FeO and Fe^Oa, and ferric acid. The magnetic oxide 
 
 * The solution of potassio ferricyanide ought to be made as it is 
 wanted, as it decomposes when in a state of solution, a trace of ferro- 
 cyanide being formed. 
 
88 EXERCISES. 
 
 occurs in nature ; it may be formed, as we have already 
 noticed, by passing steam over Fe, and it may be obtained 
 in the hydrated state by dissolving a ferrous and ferric 
 salt in equal atomic proportions, and adding to the so- 
 lution KHO or NaHO. Ferric acid, H 2 Fe0 4 , may be ob- 
 tained, we have seen, by fusing Fe with KN0 3 (160), or by 
 passing CI into an alkaline solution of Fe 2 O a (161). 
 
 Answers to the following exercises must be written out. 
 
 EXEECISES. 
 
 64. Name the substances which will be precipitated when 
 (NH,) 2 S is added to an aqueous solution containing Alj 
 3S0 4 , Cr 3 Cl 6 , Fe 2 Cl B , FeSO„ ZnS0 4 , Co(N0 3 ) 2 , and K,S0 4 , 
 and the form in which they will be precipitated. 
 
 65. A solution which has to be examined for the mem- 
 bers of this and the preceding groups is alkaline to test- 
 paper ; the alkalinity is found to be due to the presence 
 of Na 2 C0 3 ; what members must be absent ? 
 
 66. I have a quantity of zincic sulphate which contains 
 some ferrous sulphate ; how must I get rid of the iron so 
 that after its removal no other salt but the zinc sulphate 
 will remain in solution ? 
 
 67. How are ferrous and ferric oxides distinguished from 
 each other ? Illustrate your answer by equations. 
 
 68. The members of the third and fourth groups have 
 been precipitated together by (XH 4 ) 2 S ; how must the pre- 
 cipitate be treated so as to isolate and detect each of the 
 members (the phosphates and oxalates not being present)? 
 
 69. How are potassic ferrocyanide and ferricyanide pre- 
 pared? 
 
 70. I require some ferric chloride, and I have only some 
 ferrous sulphate ; how must I proceed so as to obtain from 
 the latter salt the Fe 2 Cl ? ? 
 
 71. How can the precipitation of Fe 2 H 6 6 , Al a H 6 0,., and 
 of Cr,H e O c , from solutions of their salts by the alkalies, be 
 prevented ? 
 
 72. Ferric oxide is employed to purify coal gas; on 
 ceasing to purify it, it is exposed to the air ; the exposure 
 restores its purifying powers. State what impurities it 
 removes, and how the air revivifies it; state what impurity 
 calcic hydrate removes which the iron oxide does not re- 
 move. 
 
 7:5. You are given a solution which is neutral to test- 
 paper, and which can contain only the members of this 
 
EXERCISES. 89 
 
 and the preceding groups : what members must be absent, 
 and what salts of those members which may be present 
 must be absent either from their insolubility or from their 
 being alkaline or acid to test-paper ? (The student is only- 
 expected to answer it to the extent of the salts with which 
 he has been made acquainted in the first four groups.) 
 
 74. I fuse in a furnace 2 parts of chrome iron mixed 
 with 1 part of potassic nitrate ; I treat the fused mass 
 with water, and add H 2 S0 4 or HN0 3 until the solution is 
 acid to test-paper ; I then evaporate the solution to the 
 crystallizing point, and allow time for the crystallization. 
 State what substances are formed in the fusion, what sub- 
 stances are dissolved and what are not dissolved by the 
 water, what alteration the added acid effects, and what 
 substance crj'stallizes out. 
 
 75. There is present in a solution Fe 2 Cl c , Al 2 Cl r , CoCl 2 , 
 MnCl 2 and MC1 2 ; the solution is placed in a flask, BaCO, 
 is added a little in excess, the flask is corked and allowed 
 to stand some time in the cold, with occasional shaking. 
 What occurs? The mixture is filtered into a flask, the 
 filtrate is slightly acidulated with HC1, CI is then trans- 
 mitted through it to saturation, BaC0 3 or CaC0 3 is then 
 added slightly in excess, the mixture is allowed to stand 
 some hours in the cold and shaking it repeatedly. State 
 the changes which ensue. 
 
 76. How is amnionic sulpho-cyanide prepared ? 
 
 Tt. I wish to prepare some pure MnCl 2 from the waste 
 product obtained in the manufacture of CI by acting on 
 Mn0 2 with HC1 ; it contains, in addition to the MnCl 2 , 
 Fe 2 Cl 3 and HC1. How shall I proceed ? I have another 
 quantity of the waste product, containing in addition to 
 the impurities already named some CuCl 2 , CoCI,,, and 
 NiCl 2 : how shall I proceed in this case to obtain pure 
 MnCl 2 ? Describe a different method in each case. 
 
 78. A colorless solution is given you to examine for the 
 members of this and the preceding groups ; what members 
 are probably absent ? 
 
 79. Enumerate the chief ores of iron, and give their 
 composition. 
 
 80. There is present in an acetic acid solution Al'", Fe'", 
 Co", Zn", M", and Mn"; H 2 S is passed through it; what 
 changes, if any, take place ? 
 
 81. You have to examine a mixture which can only con- 
 tain ferrous, ferric, calcic, magnesic, potassic, and amnionic 
 
 8* 
 
90 TIIE SPECIAL PROPERTIES 
 
 salts : describe the methods you would adopt in the ex- 
 amination. 
 
 82. Describe the manufacture of aluminum. 
 
 83. Give the composition of Nordhausen sulphuric acid, 
 and state how it is prepared. 
 
 84. How would you prepare anhydrous Fe 2 Cl 6 and an- 
 hydrous A1 2 C1„ ? 
 
 85. How would you prepare Fe 2 S 3 ? 
 
 86. Describe a method for the preparation of PbO^. 
 
 The 'following Salts, being insoluble in Neutral and Alka- 
 line Solutions, are precipitated along with the members 
 of the Fourth Group* 
 
 ALUMINIC, CHKOMIC, AND FERRIC PHOSPHATES; THE PHOS- 
 PHATES OF THE ALKALINE EARTHS ; BARIC, STRONTIC, AND 
 ■ CALCIC OXALATES. 
 
 183. Aluminic phosphate varies considerably in compo- 
 sition, according to the proportions of the acting solutions 
 and the temperature at which they are mixed ; it behaves 
 in the same way with reagents as A1 2 3 , with this excep- 
 tion, that it is insoluble in acetic acid, whilst A1 2 8 is 
 soluble. The presence of PO„ when combined with Al,O s , 
 may be detected by the following method : After having 
 dissolved the aluminic compound in a small quantity of 
 HC1, H 2 T must be added and then NH 4 HO in excess. If 
 on the addition of MgSO, to this solution a precipitate be 
 formed, P0 4 is present. When the quantity of acid pre- 
 sent is small, the precipitate will not appear until after the 
 lapse of some time ; in all cases the formation of the pre- 
 cipitate is much promoted by agitation. 
 
 184. P0 4 in combination with A1 2 3 may also be detected 
 in the following way: "Add Ka u C0 3 to the HC1 solution 
 until the free acid is nearty neutralized; mix with BaC0 3 
 in excess, add solution of SaHO or KHO, and boil. This 
 process gives the A1 2 3 in solution, the TO, in a precipi- 
 tate of baric phosphate. Dissolve this precipitate in HC1, 
 decompose by H a S0 4 , filter, and test the filtrate with 
 MgS0 4 , with addition of NH 4 C1 and NIIJIO."— Frcsenius. 
 
 1 85. P0 4 may be detected in almost all salts and most 
 
 * The student will do well to omit this section of the group until he 
 has had some praoticoin detecting the more simple coinbinntions of acid 
 and baso. 
 
OP THE FOURTH GROUP. 91 
 
 minerals containing it by the amnionic molybdate test (see 
 par. 428). 
 
 186. Chromic Phosphate behaves in the same way with 
 reagents as Cr 2 3 , with this exception, that it is insoluble 
 in acetic acid, in which reagent the latter is soluble. The 
 presence of P0 4 when combined with Cr 2 3 may be detected 
 in the same way as when combined with alumina. To as- 
 certain whether Cr 2 3 and the chromic phosphate are both 
 present in the precipitate produced by boiling the fixed 
 alkaline solution, dissolve the precipitate produced on 
 boiling in HC1, add an alkaline acetate in excess ; if a pre- 
 cipitate is produced, the phosphate is present, filter off, 
 and to the filtrate add XH^HO in excess; if a precipitate 
 is produced, the oxide is present. 
 
 187. Ferric phosphate, like aluminic phosphate, varies 
 considerabl3 r in composition, and from the same causes; it 
 behaves in the same way with reagents as Fe 2 3 , with this 
 exception, that it is insoluble in acetic acid, in which re- 
 agent the latter is soluble. (XHJ^S decomposes iron 
 phosphate,* precipitating the metal in the state of sulphide 
 whilst the acid remains in solution in combination with 
 the ammonia. The acid is therefore sought for in the fil- 
 trate, and not in the precipitate, when (NH,) 2 S has been 
 employed as the precipitating reagent. The same method 
 maj' be employed for the detection of P0 4 , when combined 
 with Fe, as is employed when this acid is in combination 
 •with Al. ■<• 
 
 188. The different calcic ortho-phosphates are soluble in 
 acetic acid. They may be decomposed in several ways. 
 The following are those which are most applicable in quali- 
 tative analysis : 1. Dissolve the phosphate in a small 
 quantity of HC1 ; add to the solution an alkaline acetate, 
 and after that a few drops of Fe 2 Cl 3 (consult par. 427). 
 Ferric phosphate will be precipitated, whilst the Ca will 
 remain in solution along with the excess of the Fe 2 Cl 3 . 
 To detect the Ca, precipitate Fe by (XHJ^S, and add to 
 the filtrate H 2 0. If a precipitate be produced, Ca is pre- 
 sent. 2. Dissolve the phosphate in a small quantity of 
 HX0 3 ; add to this solution HgN0 3 , and then NH 4 HO 
 slightly in excess ; mercurous phosphate along with the 
 excess of Hg a O will be precipitated, whilst the Ca will re- 
 main in solution, from which solution it will be thrown 
 
 * Aluminic and chromic phosphates are not decomposed by (NET 4 ) 2 S ; 
 they are precipitated unchanged by that reagent. 
 
92 THE SPECIAL PROPERTIES 
 
 down on the addition of H 2 0. Boil the mixed precipitate 
 of mercurous phosphate and oxide in (NH 4 ) 2 S ; filter, and 
 to the filtrate add NH 4 C1 and MgS0 4 ; if a precipitate be 
 produced, it proves the presence of P0 4 . The above 
 remarks upon calcic phosphates apply to the correspond- 
 ing baric, strontic, and magnesic salts. 
 
 189. Calcic oxalate is insoluble in acetic acid. By 
 ignition, this salt, like all the other oxalates, is decomposed, 
 a carbonate being left. To separate the O from the Ca, to 
 its solution in HN0 3 add HgN0 3 ; Hg 2 will be precipitated, 
 whilst Ca(NO ) 2 will remain in solution along with the 
 excess of HgNO s . To detect Ca, remove the Hg from the 
 solution by NH 4 HO, and add to the filtrate H 2 6. Hg 2 <5 
 is decomposed by boiling it in (NHJJ3, Hg 2 S being pre- 
 cipitated, whilst the acid remains in combination with 
 ammonia, in which solution it may be detected on the addi- 
 tion of any soluble calcic salt. The above remarks apply 
 to the corresponding baric and strontic salts. 
 
 190. The following precautions are to be attended to in 
 the analysis of this section : Before dissolving the precipi- 
 tate produced by XH 4 HO, it must be completely freed by 
 washing from all trace of that reagent. Frequently a small 
 precipitate will appear after boiling the NaHO solution, 
 when Cr is absent; the presence of this member must 
 therefore in all crises be confirmed by other tests. Alj0 3 
 and its phosphafiSGpre sometimes overlooked by the opera- 
 tor, from his neglecting to add acetic acid in excess. The 
 precipitate produced by 2saHO, after being well washed, 
 should be dissolved in as small a quantity of UNO, as 
 possible, to which solution a moderate quantity of H 2 T 
 should be afterwards added, and finally NH 4 HO in excess ; 
 the solution ought, after the additibn of these reagents, to 
 be well agitated, and time allowed for the separation of the 
 precipitate. In testing for P0 4 in the amnionic solution, 
 a precipitate will frequently be formed on the addition of 
 MgS0 4 when P0 4 is absent. To distinguish the phosphate 
 precipitate from this, the precipitate produced ought to be 
 dissolved in II a T, and XII 4 IIO added in excess. If a pre- 
 cipitate again appears, after agitating the liquid and allow- 
 ing it to stand, it must be due to the presence *>f P0 4 . 
 The precipitate produced by NHJIO in the H 2 T solution 
 must be well washed before dissolving it in dilute UNO,. 
 A slight turbiilness will generally be formed on the addi- 
 
OP THE FOURTH GROUP. 
 
 93 
 
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 ft 3 
 
94 THE SPECIAL PEOPEETIES 
 
 tion of HgNO a to the HNO„ solution, even in the absence 
 of oxalates, owing to the HNO s containing a slight trace 
 ofHCl. 
 
 191. The following is another method for the separation 
 of the members of the fourth group and the phosphates 
 and oxalates which are precipitated along with them by 
 the group reagent ; the precipitate produced by NH 4 HO, 
 after being well washed, is ignited upon a piece of platinum 
 foil, or in a small crucible ; if one or more of the three 
 oxalates (baric, strontic, and calcic) are present, they will 
 be converted by the ignition into carbonates ; dissolve the 
 ignited precipitate in as small a quantity of boiling dilute 
 HC1 as possible ; if it dissolves with effervescence, one or 
 more of the three oxalates are present ; examine the solu- 
 tion in this case according to par. 192. If the solution is 
 unattended with effervescence, the three oxalates are ab- 
 sent; examine the solution in this case according to 
 par. 193. 
 
 192. When the solution is attended with effervescence, 
 add NH 4 HO in excess to the solution, warm, and filter ; the 
 filtrate will contain the base or bases originally existing 
 as oxalates ; examine for these bases in the way directed 
 in the second group, par. 68 ; wash the precipitate very 
 well, then dissolve it in as small a quantity of boiling di- 
 lute HC1 as poasiUe ; examine the solution according to 
 
 193. Add=M| Hfthe fixed alkalies in excess in the cold 
 to the HC1 sorhUOT ; if ferric phosphate or oxide, or any 
 of the phosphates op the alkaline earths are present, 
 they will be precipitated, whilst aluminic and chromic 
 oxides and their phosphates will be retained in solution; 
 examine the precipitate according to par. 195, and the so- 
 lution according tcr'par. 194. 
 
 194. Boil the fixed alkaline solution for some time; if a 
 precipitate is produced, it is due to the presence of chromic 
 phosphate or oxide, or both ; filter when a precipitate is 
 produced, add to the filtrate, or to the solution, without 
 filtering, when no precipitate has been produced,* acetic 
 acid in excess ; aluminic phosphate, if present, will be 
 precipitated ; add to the filtrate NII,HO in excess, when 
 Al 2 O s , if present, will be precipitated. Dissolve the chro- 
 
 • 
 * If no precipitate is produoed on boiling tho fixed alkaline solution, 
 a portion of tho prooipitate produoed by the group rengent ought to be 
 examined for chromium, in the way direoted at par. 157. 
 
OF THE FOURTH GROUP. 95 
 
 mic precipitate in as small a quantity of boiling dilute 
 IIC1 as possible, add an alkaline acetate in excess ; chromic 
 phosphate, if present, will be precipitated ; to the nitrate 
 add NH 4 HO in excess ; if chromic oxide be present, it will 
 be precipitated. 
 
 195. After the precipitate produced by the fixed alkali 
 has been well washed, it must be dissolved in as small a 
 quantity of boiling dilute HC1 as possible, then add one 
 of the alkaline acetates in excess, and boil for some 
 minutes ; the ferric phosphate and oxide (the latter as 
 basic acetate), will be precipitated, if present, whilst the 
 phosphates of the alkaline earths will remain in solu- 
 tion ; examine the solution according to par. 196, and ex- 
 amine the precipitate for P0 4 in the following way : Digest 
 the precipitate in (NH ( ) S S for a few minutes, then filter 
 and examine the filtrate for P0 4 , according to par. 424. 
 To ascertain whether there was any Fe uncombined with 
 P0 4 , add to the original solution an alkaline acetate ; filter 
 and to the nitrate add potassic ferrocyanide. If a blue 
 precipitate is formed, it proves that all the Fe did not ex- 
 ist as phosphate. 
 
 196. To the solution add Fe 3 Cl 8 , drop by drop; if no 
 precipitate is produced on the addition of the first two 
 drops, the phosphates of the alkaline earths are absent; 
 if a precipitate is produced, continue^tffijaddition of the 
 Fe a Cl B until the solution is of a sliglaHHpddish cojor, 
 then boil until the excess of Fe is remo^KpFrOm the solu- 
 tion by boiling, then filter, and examine the filtrate for Ba, 
 Sr, Ca, Mg, in the usual waj r . 
 
 1 97. When substances are examined, the nature of which 
 is a sufficient proof that the chromic oxide and phosphate, 
 and the baric and strontic phosphates, and the baric, 
 strontic, and calcic oxalates must be absent, as in the case 
 of soils, natural and artificial manures, etc.,* the last 
 method may be much simplified; — the precipitate pro- 
 duced by the group reagent need not be ignited, the free 
 alkali need not be added in the cold, and after its addition 
 the mixture may be boiled, in order to hasten the filtration ; 
 and lastly, Ca and Mg have only to be sought for. 
 
 198. When substances are examined, the nature of 
 which is a sufficient proof that calcic oxalate is the only 
 oxalate, and that calcic and magnesic phosphates are the 
 
 * Guano generally contains oxalate of lime ; examine the ammonia 
 precipitate of this manure according to par. 198. 
 
96 THE SPECIAL PROPERTIES 
 
 only phosphates of the alkaline earths which can be present, 
 as in the case of guano, urine, urinary deposits, etc.,* a 
 simpler method may be employed for detecting and sepa- 
 rating these salts than the one given in Table V. : after 
 having separated them from all the other substances in the 
 way directed in Table V., dissolve the precipitate produced 
 by NH 4 HO in the H 2 T solution in a small quantity of HC1, 
 and to the solution add acetate of soda in excess. CaO, 
 if present, will be precipitated, whilst the calcic and mag- 
 nesic phosphates will remain in solution. Filter, and to 
 the filtrate add H a O, which will precipitate the Ca existing 
 originally as phosphate in the state of oxalate. Mag- 
 nesio phosphate will be precipitated from this filtrate on 
 the addition of NH 4 HO in excess. 
 
 199 The borates and fluorides of baryta, strontia, 
 and lime are also precipitated by NH 4 HO ; but they are 
 not completely precipitated by NH 4 HO in the presence of 
 NH 4 C1 ; therefore, a portion at least of the bases of these 
 salts will be found as a member of the second group, and 
 the acids in these salts will be discovered in the ordinary- 
 examination of the acids ; for these reasons we have not in- 
 cluded these salts in the group ; but it is necessary for the 
 student to know that, when present in considerable quan- 
 tities, they are^upart precipitated by NH 4 HO, as other- 
 wise their prjflj B|ion along with the members of the 4th 
 group mightlH Hn him much perplexity. 
 
 Answers tcFTne following exercises must be written 
 out: — 
 
 EXERCISES. 
 
 8 1 ?. What change does calcic oxalate undergo on being 
 heated ? 
 
 88. How would you examine a substance for baric and 
 calcic phosphate ? 
 
 89. If there were present in an acid solution CaO, 
 BaHPO, Fe"'P0 4 , and Al'"PO, and NH 4 HO, and (XH 4 )„S 
 were added to it, which of the substances would be pre- 
 cipitated, and in what state would they be precipitated ? 
 
 90. If there were present in an HO solution CaO, 
 Fe"'P0 4 , A1'"P0 4 , CaHP0 4 , and sodic acetate in excess 
 
 * Of oourso in suoh substnnoes as guuno, urine, and urinary deposits, 
 chromic oxide and its phosphate oannot be present. 
 
OF THE FOURTH GROUP. 97 
 
 were added, which of the substances would be precipitated, 
 and in what state would they be precipitated? 
 
 91. If you had a solution which could only contain calcic 
 oxalate, calcic phosphate, and magnesia phosphate, devise 
 a speedy method for the examination of these substances. 
 
 200. Uranio Oxide (U»0 3 ) Solution of uranic nitrate in water may be 
 employed for the reactions. This oxide is of a brick-red color, its hydrate 
 is yellow; by ignition it loses part of its oxygen, being converted into 
 U 3 4 , the color of which is a very dark green, approaching black. U 2 3 
 dissolves iu acids, forming salts, the solutions of which have a fine yellow 
 color, and redden blue litmus paper. H 2 S converts U 2 3 into UO, which 
 attracts from the air, becoming converted into U 2 3 again : oxidizing 
 agents have the same effect. 
 
 201 . (NH 4 ) 2 S precipitates, from alkaline solution of this oxide, a brown- 
 ish-colored precipitate, which subsides slowly, and is readily soluble in 
 acids, even in HA ; NH 4 C1 promotes the formation of the precipitate. 
 
 202. The volatile nai fixed alkalies precipitate this oxide from its solu- 
 tions completely, in the form of a yellow precipitate, which is insoluble 
 in an excess of the reagent. 
 
 203. (NH 4 ),CO s produces a yellow precipitate, which is soluble in an 
 excess of the reagent, but is deposited again from this solution on boil- 
 ing. In its behavior with this reagent, U 2 3 differs from Fe 2 3 , which 
 it so closely resembles in its other reactions. KHC0 3 or NaHC0 3 pro- 
 duces a yellow precipitate which dissolves readily in an excess of the 
 reagent. 
 
 204. K,FeCy 6 produces in solution of this oxide a fine brown-red pre- 
 cipitate ; this is a very delicate test for uranium. 
 
 205. " Uranium compounds give a yellow bead in the oxidizing flame, 
 which becomes green in the reducing flame, especially on addition of 
 SnCI 2 These colors closely resemble those of the iron compounds, but 
 may easily be distinguished, at least if no other coloring metallic oxide 
 is present, by the fact that the uranium bead, when incandescent, emits 
 ■a, bluish-green light, analogous to that which the uranium compounds 
 exhibit when fluorescing. Beads of lead-oxide, stannic acid, and a few 
 other substances, exhibit a similar phenomenon when incandescent, but 
 they do not yield, like uranium compounds, a colored bead on cooling. 
 
 200. " Heated gently on the platinum spiral with KHS0 4 the insoluble 
 uranium compounds can be decomposed. The melted mass is powdered 
 with a few particles of crystallized sodic carbonate, and the moistened 
 mass is absorbed by filtering paper. A brown spot is formed by the 
 addition of a drop of K 4 FeCy s to the moistened paper." — Bunsen. 
 
 Characteristic. — The reactions with the caustic and carbonated alkalies 
 and with K 4 FeCy 6 
 
 207. Titanic oxide or Anhtdkide (Ti0 2 ). — This compound, although 
 comparatively a rare substance, occurs in some iron ores, and as it is 
 considered by some to improve the quality of the iron, we have given, 
 on this account, a short description of its properties, and the mode of 
 detecting it. 
 
 208. It varies in color according to the mode of preparation ; it some- 
 times appears as a white powder, which, when heated, acquires, during 
 the time it is heated, a yellow tint, and sometimes it appears in the form 
 of small lumps of a reddish brown color. The acid H 2 TiO a is white. 
 
 9 
 
98 THE SPECIAL PROPERTIES 
 
 The anhydride is insoluble in water and acids, with the exception of con- 
 centrated H 2 S0 4 , which dissolves it with the aid of heat ; when fused 
 with NaHS0 4 , the fused mass dissolves completely in a large quantity of 
 cold water; when fused with Na 2 C0 3 , Nn 2 Ti0 3 is formed, whichls de- 
 composed by H 2 into an acid salt, insoluble in H 2 but soluble in HC1 
 and NaHO. 
 
 209. The acid in the moist state, and also when dried at a tempera- 
 ture not exceeding 100° C, is soluble in dilute acids, especially HC1 and 
 H 2 S0 4 . When the acid solutions of it are greatly dilluted with water, 
 and boiled for a long time, it, H 2 Ti0 3 , is completely precipitated as a 
 white powder, insoluble in dilute acids ; this precipitate possesses the 
 marked property of passing through the filter when washed, unless an 
 acid or NH 4 C1 is added along with it. It is precipitated from its acid 
 solutions* in the form of a milky-white precipitate by the volatile and 
 fixed alkalies and their carbonates, by BaC0 3 and by (NH 4 ) 2 S; the pre- 
 cipitate is insoluble in an excess of the precipitant; but if it has been 
 precipitated by any of these reagents in the cold, and washed with cold 
 water it is soluble in dilute HC1 or H 2 SO.. 
 
 210. When the solution of titanic acid in HC1 does not contain too 
 much free HC1 — when, for example, it has been prepared in such a way 
 that part of the titanate treated by the HC1 has remained undissolved, 
 and has been filtered from the solution diluted with water — the solution 
 of the acid behaves with the reagents named a, b, and c, in the way de- 
 scribed in these paragraphs. 
 
 (a) Infusion of galls produces in the solution a reddish orange-yellow 
 precipitate of tannate of titanic oxide. 
 
 (6) K 4 FeCy 6 gives a dense orange-brown precipitate ; the precipitate 
 is soluble in an excess of the precipitant. 
 
 (c) White precipitates are produced by adding to the solution dilute 
 sulphuric, arsenic, phosphoric, or tartaric acid but more especially oxalic 
 acid; these precipitates are completely redissolved in an excess of the 
 precipitating acid; jnd likewise by HC1; the precipitate produced by 
 H 2 is the most insoluble. 
 
 211. If a strip of zinc, ikon, or tin be introduced into a solution of 
 titanic acid in U CI, the solution will become blue ; and from this a red- 
 dish or violet precipitate will separate, which gradually oxidizes into the 
 white oxide. 
 
 212. " Titanic compounds give a colorless bead with microcosmic salt 
 in the oxidizing flame, which turns of a pale amethystine color in the re- 
 ducing flame. On addition of FeS0 4 the bead assumes in the reducing 
 flame the peculiar red color of venous blood, whilst in the oxidizing flame 
 the light brown color of Fe 2 3 can be obtained at pleasure. The titanic 
 compounds form with soda a bead, which at first effervesces, and when 
 hot is colorless and transparent, but on cooling becomes opaque. If to 
 the hot bead SnCl 2 be added, and if it then be heated in the lower reduc- 
 ing flame, a gray mass is formed, which dissolves on heating in HO, 
 yielding a pale amethystine-colored solution." — Jiunstn. 
 
 * Not in tho presence of tartario acid, or other non-volatile organic 
 matter. 
 
OF THE FIFTH GROUP. 99 
 
 FIFTH GROUP. 
 
 Stannous Oxide (SnO), Stannic Oxide (Sn0 2 ), Antimo- 
 nious Oxide (Sl) !i 3 ), Arsenious Anhydride (As/),), 
 Arsenic Anhydride (As a 5 ), Auric Oxide (Au a 8 ), 
 Platinic Oxide (Pt0 2 ). 
 
 Solutions for the reactions. — SnCl. 2 , SnCl„ As 2 0., PtCl 4 , 
 AuCl s , in water; SbCl 3 , As 2 3 in dilute HCl.* 
 
 213. Examination for the members of the group. — Auric 
 and platinic compounds produce reactions so decisive — 
 the former with the tin chlorides (284), and the latter with 
 NH 4 C1 (287) — that they may invariably be detected in the 
 presence of all the other metals ; they may, therefore, in 
 all cases be sought for in the original solution. The ex- 
 amination of the precipitate produced by the group re- 
 agent, which must be added as directed at 357, is, therefore, 
 confined to the other members of the group. Six differ- 
 ent methods for the analysis of the group precipitate are 
 given. 
 
 214. First method. — The group precipitate must be well 
 washed, and then treated with a dilute solution of NH 4 H 
 HCO,.f As. 2 S 3 is soluble, and Sb 2 S 3 , SnS, SnS a are in- 
 soluble in NH 4 HC0 3 ; filter if necessary, and add to the 
 filtrate HCl in excess. If a yellow precipitate, or a slight 
 yellow color, is produced, As^Sj is present ; the original 
 solution must be examined to ascertain which of the two 
 oxides of As is, or whether both are, present. The sub- 
 stance insoluble in NH 4 HC0 3 , after having been dried, 
 must be mixed with three parts of fused NH 4 NO a ,J and 
 the mixture projected in small portions at a time into a 
 porcelain crucible, containing two parts of NH 4 N0 3 in a 
 state of liquefaction. The ignition should be continued 
 
 * As no table is given with this group the student ought to perform 
 the experiments given under the individual members before attempting 
 the analysis of the group. 
 
 f The solution is prepared. by dissolving one ounce of NH 4 HC0 3 in 
 twelve ounces by measure of water; the precipitate must be agitated 
 for a few seconds only with the solution, and then quickly filtered. 
 
 J When the amount of precipitate is so small that little or nothing 
 can be detached from the filter, the precipitate as well as the filter, after 
 having been cut into small pieces, must be mixed up with the amnionic 
 nitrate, and subsequently projected into the crucible. 
 
100 THE SPECIAL PROPERTIES 
 
 for a short time after all fuming has ceased, and the residue, 
 when cold, must be treated with a saturated solution of 
 H 2 T ; if complete solution takes place, SB 2 3 only can be 
 present ; but if a portion remains undissolved, one or both 
 of the tin oxides are probably present. Filter the H 2 T 
 solution when necessary, and add to the filtrate HC1 and 
 H 2 S in excess ; if an orange-red precipitate is formed, 
 Sb 2 3 is present. The substance insoluble in H 2 T must be 
 examined for Sn by fusing it with Na 2 C0 3 and KCy, as 
 directed at par. 236. 
 
 215. Second method. — Dry the precipitate, then treat it 
 with boiling concentrated HC1; Sb,S„ SnS, and SnS 2 will 
 dissolve with decomposition, whilst As 2 S 3 will remain un- 
 dissolved. Add a little water to the HC1 solution, and 
 pour it into a platinum crucible or lid, and introduce into 
 it a piece of pure zinc, the Sn and Sb are reduced to the 
 metallic state, and the latter blackens the platinum ; when 
 H ceases to be evolved remove the zinc, washing into the 
 crucible or lid any reduced metal adhering to it, then free the 
 reduced metal from the ZnCl 2 by washing, boil it in strong 
 HC1, Sn will dissolve, whilst Sb will remain undissolved. 
 Dilute the HC1 solution a little, and then test it for Sn by 
 adding to it HgCl a (235), or a mixture of Fe,Cl a and K 6 Fe, 
 Cy„ (234) ; dissolve the portion of the metal insoluble in 
 HC1 in aqua regia, and test it for Sb by passing H,S 
 through the solution. Dissolve the portion of the sulphide 
 insoluble in HC1 in boiling HNO., evaporate nearly to dry- 
 ness, add cold water, and test for H 3 As0 4 by adding NH 
 CI, NH 4 HO, and MgS0 4 (211), or by adding AgX0 3 (275>. 
 
 216. Third method. — Mix the dried sulphides with an 
 equal quantity of Na 2 C0 3 and a like quantity of NaX0 3 ; 
 transfer the mixture graduallj- into a porcelain crucible 
 containing twice the quantity of NaX0 3 in a state of fusion; 
 when the deflagration is over* allow the crucible to cool ; 
 treat the fused mass with cold water and filter ; wash the 
 insoluble portion with equal parts of alcohol and water ; 
 filter the washings and mix them with the filtrate; add 
 HN0 3 to the solution until it is distinctly acid ; heat to 
 expel CO a and N a 3 and test for H 3 As0 4 as directed in the 
 
 * The heat must not bo too high nor continued too long, otherwise 
 the NaNOj will be decomposed and oaustio soda formed; and this latter 
 will form with SnO, sodio stnnnate which will dissolve in the water. 
 
OF THE FIFTH GROUP. 101 
 
 second method; heat the insoluble residue with HC1; 
 transfer to a platinum vessel, and test for Sn and Sb as 
 directed in preceding par. 
 
 217. Fourth method. — Dissolve the sulphides in K 2 S ; add 
 a concentrated solution of S0 2 in large excess, and digest 
 the mixture in the water-bath for some time, then boil un- 
 til all S0 3 is expelled, and afterwards filter; the filtrate 
 will contain the As. 2 3 , if present ; test for it by passing 
 H 2 S into the solution ; dissolve the insoluble portion in 
 HC1 and test it for Sb and Sn as in the second method. 
 
 218. Fifth method. — Dissolve the precipitated sulphides 
 in as small a quantity of hot aqua regia as possible ; intro- 
 duce the solution into a hydrogen apparatus, along with 
 some Zn and diluted H 2 S0 4 . The gas bottle must be con- 
 nected with a second one containing a dilute solution of 
 Pb2A,* through which the gas in passing is freed from any 
 HC1 and H 2 S. The exit tube from the wash bottle dips 
 into a precipitating glass or test tube containing a solution 
 of AgN0 3 . If a precipitate is produced continue the trans- 
 mission through the solution as long as it continues to be 
 produced ; then filter, carefully neutralize the HN0 3 in the 
 filtrate with NH 4 HO ; the characteristic j'ellow AG 3 AsO , is 
 precipitated. If the gas has passed through the solution 
 for a long time, the solution may contain no Ag. If, there- 
 fore, after neutralizing it no yellow precipitate is formed, 
 add a drop or two of AgNO, to it. Wash the silver pre- 
 cipitate thoroughly with boiling water, and then boil it with 
 a solution of H 2 T. Filter and acidify the filtrate with HCI, 
 and pass H 3 S through it ; if Sb be present orange-colored 
 Sb. 2 S s will be produced. In order to detect Sn the metallic 
 precipitate is washed off the Zn in the gas bottle and boiled 
 in HCI ; then diluted with a little H 2 0, and tested for Sn 
 by adding a solution of HgCl a (235). 
 
 219. Sixth method. — "If in a mixture of these three sul- 
 phides, containing only traces of Sb and Sn, they are 
 separated according to the ordinary rules of qualitative 
 analysis by dissolving in alkaline sulphides and reprecipi- 
 tation with acids, the detection of these two metals by the 
 regular tests is extremely uncertain and troublesome. 
 According to the following method the detection of these 
 metals is rendered easy and certain when the proportion 
 
 * A tube containing glass- splinters, moistened with a solujJQa of Pb 
 ( A),, may be employed in plaoe of the wash-bottle. 
 
 9* 
 
102 THE SPECIAL PROPERTIES 
 
 of Sn is only a few thousandths, and that of the Sb only 
 a few hundredths, of the total weight of the mixture. 
 
 220. "Three decigrammes of the sulphides are roasted 
 on a curved piece of glass small enough to be altogether 
 surrounded by the flame, and the residue, weighing only a 
 few milligrammes, is scraped together with the knife. The 
 moistened mass is then collected on the end of a thread of 
 asbestos and a strong metallic film obtained on the test 
 tube. In order to prevent the deposition of any carbon 
 with the metals, which would act injuriously in the subse- 
 quent operations, the upper reducing flame is made so 
 small that the luminous point is only just visible. The 
 film is next dissolved in a drop or two of HN0 3 in the 
 curved rim (fig. 3) of the Plate, and the solution evapo- 
 rated below its boiling-point by gently warming and blow- 
 ing, so as to obtain the solid residue in as small a space 
 as possible. A drop of neutral silver solution is now 
 brought on. to the residue at the moment when it becomes 
 solid; and on blowing withammoniacal air a characteristic 
 black stain is formed, whilst the reaction of As is also 
 generally noticed. 
 
 221. "In order to detect Sn, a few scarcely visible parti- 
 cles of the roasted sulphides are fused on to a borax bead 
 which has been very slightly tinted with cupric oxide. If 
 the bead is now brought into the lower reducing flame, it 
 becomes a ruby-red color from reduced cuprous oxide. If 
 the oxide be present in too large a quantity, the bead can 
 be obtained transparent by the process described under 
 the reactions of the copper compounds. This reaction can 
 only be obtained in the lower reducing flame of the non- 
 luminous gas-lamp, as in the ordinary blowpipe flame, the 
 cupric oxide is reduced to cuprous oxide without the pres- 
 ence of tin-salt," — Bunsen, 
 
 PROPERTIES OF THE METALS, THE OXIDES, THE SULPHIDES, 
 THE CHL0RIPES, AND THE HY.BR1DES OF As AND Sb. 
 
 222. TJie metals — As volatilizes at a dull red heat with- 
 out previous fusion^ its vapor is colorless and has a garlic 
 odor. Sb melts at 432° (_'., and at a bright red heat vola- 
 tilizes slowly, which is facilitated by transmitting a current 
 of H over it. Sn melts at US C, and boils at a white 
 heat; Au melts at above 1040° C; Au and Sn arc but 
 slightly volatile in the heat of a furnace. Pt does not njelt 
 j.n the strongest forgo fire, but it is fused and volatilized by 
 
OF THE FIFTH GROUP. 103 
 
 tlie voltaic current, and in the oxyhydrogen blowpipe flame. 
 Au and Pt suffer no change by exposure to air and mois- 
 ture at any temperature. The other three metals undergo 
 no change at ordinary temperatures in dry air, neither in 
 moist air does Sb suffer any change, but Sn tarnishes, and 
 As slowly oxidizes ; they all three unite with if heated in 
 the air, and at high temperatures burn with a brilliant light, 
 As 2 8 , Sb 2 3 , and Sn0 2 being formed. Sb and Sn decom- 
 pose steam at a red heat. As decomposes it only slightty. 
 Pt is not acted upon by any single acid, and selenic acid is 
 the only one that acts on Au. HC1 does not attack Sb, 
 and has little action on As, but if heated it dissolves Sn, 
 SnCl 2 being formed and H evolved. Dilute H 3 S0 4 is 
 without action on them, but boiling concentrated H 2 S0 4 
 acts on them, S0 2 being evolved and As 2 3 , Sb 2 (S0 4 ) d , 
 Sn(S0 4 ) 2 being formed ; in the last case there is also a 
 separation of S. Dilute HN0 3 converts As and Sb with 
 the aid of heat into As a 3 and Sb.,0,,. The concentrated 
 and boiling acid converts them into As 2 O s and Sb 2 O s . 
 HNO s , if its sp. gr. is 1.5, does not act on Sn, but if it be 
 diluted to 1.3 it acts violently upon it, converting it into me- 
 tastannic acid (H 2 Sn.O n ,4H 2 0), nitrous fumes are evolved, 
 ammonia is also formed owing to the decomposition of 
 H 2 0. Aqua regia attacks all the five metals, converting 
 them into PtCl 4 , AuCl,, SnCl 4 , SbCl s , and As 2 5 . Sb, As, 
 and Sn, combine readily with CI, Br, I, P, and S; with 
 some at ordinary, with others of them at higher tempera- 
 tures. Au combines directly with 01, Br, and F, without 
 the aid of heat, and with P when heated ; dry CI is without 
 action on Pt; P and As combine with it when heated, form- 
 ing phosphides and arsenides, which are very fusible ; S also 
 combines with spongy Pt, with the aid of heat. Chlorine 
 water acts slowly upon Pt, and it converts Au into AuCl 3 . 
 The caustic alkalies do not affect Au, but the hydrates of 
 the alkalies and alkaline earths, especially LiHO and 
 BaH 2 2 , act on Pt if heated to redness with it in the air. 
 It is even attacked at high temperatures by KHS0 4 . As 
 and Sn are also attacked by these hydrates at high tempera- 
 tures ;* in the case of Sn a metastannate is formed and H 
 evolved; and in the case of As an arsenite and an arsenide 
 are formed and H evolved. As and Sb, if in the form of 
 an alloy, may be completely separated by heating the com- 
 
 * When As ia boiled in a strong solution of KHO, arsenite of potash 
 is formed and H evolved. 
 
104 THE SPECIAL PROPERTIES 
 
 pound to low redness in a stream of C0 2 , the As volatilizes 
 whilst the Sb remains. Sb is the only metal which can be 
 separated completely from As in this way, with all other 
 metals a part of the As always remains combined. In their 
 chemical relations these metals exhibit rather a chlorous 
 than a basylous character, so that their oxides tend to 
 unite with bases rather than with acids. 
 
 223. The oxides.— SnO, Sn0 2 , PtO a , As 2 O s may be ob- 
 tained by igniting with care their hj'drates; As 2 3 may be 
 obtained by burning As in air or 0, or by roasting arsen- 
 ical ores ; Sb 2 0, by burning Sb in air; Au 2 3 by adding to 
 a solution of AuCl 3 MgO, and then dissolving out theMgO 
 with HN0 3 .* Au 3 3 and Pt0 2 are completely decomposed 
 below a red heat, and As 2 6 is resolved somewhat above its 
 melting point into As 2 3 and O. On being heated in air, 
 SnO and Sb 2 3 are converted into Sn0 2 and Sb 2 4 ; Pt0 2 
 and Au 2 3 are decomposed; As 2 O s is converted into As 2 3 ; 
 Sn0 2 and As 2 3 are unchanged. As 2 3 , As 2 5 , SnO, Sn0 2 
 and Sb 2 3 are reduced to the metallic state on being heated 
 in a current of H or CO, or if mixed with C or KCy ; in 
 the latter case potassic cyanate is formed. SnO, SnO,, 
 and Sb 2 3 , on being heated with S, are converted into the 
 corresponding sulphides, S0 2 being evolved; As a S 3 is 
 formed on heating As 3 3 with S, but a varying amount of 
 As a O s always escapes unconverted. If the oxides of Sn, 
 Sb, and As are heated with NH 4 C1, chlorides of the metals 
 are formed which volatilize ; they are likewise converted 
 into chlorides when heated in an atmosphere of CI. PtO a 
 and Au 2 3 are reduced to the metallic state on being heated 
 in an atmosphere of CI. If As and Sb, or their sulphides, 
 are diffused through a solution of KHO, and CI conducted 
 into the fluid, they are converted into arsenic and antimo- 
 nic acids, which combine with some of the potash; SnO is 
 converted into Sn0 2 by adding to its solution CI. SnO, on 
 being boiled in a small quantity of solution of KHO, is de- 
 composed into Sn and Sn0 2 . The hydrates of these oxides 
 may be obtained as follows: Sb 2 3 H 2 and 2SnO, HO by 
 adding solutions of their chlorides to a solution of Na 2 COJ; 
 H 2 Sn0 3 by adding to a solution of SnCl 4 an insoluble car- 
 bonate, as CaC0 3 , in quantity insufficient for the entire 
 
 * Mngncsio aurate is precipitated, and on the addition of IIN0 3 to tbe 
 precipitate the MgO is dissolved, and tlie auric oxide is left in the anhy- 
 drous state if strong acid be employed, but in the hydrous slate if the 
 acid employed be weak. 
 
OF THE FIFTH GROUP. 105 
 
 decomposition of the chloride; Pt0 2 , 2H 2 by adding to a 
 solution of platanic nitrate a solution of Na 2 CO, in quan- 
 tity insufficient for its complete decomposition ; H 3 As0 3 by 
 evaporating the arsenic solution obtained by oxidizing As 2 3 
 ■with HN0 3 ; H 3 As0 3 is supposed to exist in solution, but it 
 has never yet been isolated. Auric hydrate is obtained as 
 directed in the note, page 104. As 2 3 , As 2 5 , and H 3 As0 4 
 are white ; they are soluble in H 2 0. SnO is black, 2SnO, 
 H 2 is white; they are insoluble in H 2 0. The hydrate is 
 dissolved readily by acids, the anhydride is more slowly 
 acted upon by them, the hydrate is soluble in the fixed al- 
 kalies, but if boiled with them is decomposed, Sn0 2 remain- 
 ing in solution, and Sn separating. Sn0 2 is of a light 
 straw color, the hydrate is white ; they are insoluble in 
 H 2 0; the anhydride is insoluble in acids, but forms soluble 
 compounds with the alkalies; the hydrate is soluble in 
 acids and the fixed alkalies. Sb 2 3 and its hydrate are 
 white; they are insoluble in H 2 0, but soluble in HC1 and 
 H 2 T ; their solution in this latter acid distinguishes them 
 from the other anhydrous and hydrous oxides of the group ; 
 they are also readily soluble in solution of the fixed alka- 
 lies. HNO„ or fusion with nitrates, converts Sb 2 3 into 
 a higher oxide. Au 2 O s is of a deep brown color ; its hy- 
 drate is somewhat lighter in color. Pt0 2 and its hydrate 
 are reddish-brown. The auric and platinic oxides and 
 their hydrates are readily soluble in HC1, but dissolve 
 with difficulty in the oxygen acids. 
 
 224. The sulphides are formed, and in the amorphous 
 state, on passing H 2 S into a solution of their salts contain- 
 ing some free mineral acid,* with the exception of As„S„ 
 as As a S 3 , with separation of sulphur, and not As^S 5 , is 
 formed on passing H. 2 S into acid solutions of As 2 5 . The 
 amorphous Sb 2 S 3 , SnS, and SnS 2 , obtained in this manner, 
 are hydrated. As 2 S 5 may be formed by adding HC1 or 
 other acid to a dilute aqueous solution of Na 3 AsS 4 , or any 
 soluble sulph-arsenic salt. The following is the reaction : — 
 
 2Xa 3 AsS 4 + 6HC1 = As 2 S 5 + 6NaCl + 3H 3 S 
 
 precipitated 
 
 Sb a S 3 may be obtained in crystals by melting together at 
 a red heat a mixture of S and Sb 2 3 . SnS may be obtained 
 crystalline by heating Sn, in a finely-divided state, with S. 
 
 * AUjS 3 is precipitated by H^ from cold solutions of AuClj, but if the 
 solution of AuCl 3 is boiling Au a S is precipitated. » 
 
106 THE SPECIAL PROPERTIES 
 
 SnS 2 may be obtained crystalline by heating a mixture of 
 tin-filings, S, and NH,C1, or Hg ; slowly to redness in a 
 glass retort or loosely-covered flask. SnS 2 cannot be ob- 
 tained by simply heating Sn and S, because the union is 
 attended with such a development of heat that SnS 2 is re- 
 solved into SnS and S. A volatile substance, as NH 4 C1 or 
 Hg, is added to lower the temperature by rendering latent 
 some of the heat evolved. The sulphides of this group 
 are insoluble in H 2 0, but soluble in the alkalies and alka- 
 line sulphides. These sulphides possess acid characters ; 
 they, therefore, combine with the alkaline sulphides, which 
 are basic, and form sulphur salts. When dissolved in the 
 alkalies an oxygen, as well as a sulphur salt, is formed, 
 thus : — 
 
 As 2 S s + 6KHO = K 3 AsS„ + K 3 AsO s -f 3H 2 0. 
 
 The solutions of these sulphides in the alkalies and alka- 
 line sulphides are decomposed by the stronger acids, the 
 sulphides reprecipitating, an alkaline salt of the acid added 
 being formed, and when alkaline sulphides are employed 
 H 2 S being evolved. The members of this group are not 
 precipitated by H S S from alkaline solutions. Heated out 
 of contact of the air, Au 2 S 3 is decomposed into its elements, 
 PtS„and SnS 2 are converted into the protosulphides, S being 
 given off, Sb 2 S 3 , As 2 S 6 , and Asj3 3 melt below a red heat, 
 and volatilize unchanged at a higher temperature. Heated 
 in air, Au 2 S a and PtS 2 yield Au, Pt, and S0 2 , SnS and 
 SnS 2 yield Sn0 2 and S0 2 , As 2 S 5 and As a S 3 yield As/),, and 
 SO a , Sb a S 3 , is converted into a fusible mixture of Sb a O, 
 and Sb a S 3 , which is of a red color, and constitutes the 
 commercial glass of antimony. Heated in a current of CI, 
 1'tS, and Au a S 3 are decomposed, Pt and Au remaining, 
 As a S 3 , Sb 2 S a , SnS, and SnS 2 , are converted into AsCl s , 
 SbCl 3 , and SnCl., chloride of sulphur being also formed. 
 Au 2 S 3 , PtS 2 , Sb 2 S 3 , and SnS, arc reduced, the latter only 
 slowlj', when heated in a current of H ; As a S 3 is only partly 
 reduced by H. The sulphides of As, Sn, and Sb are con- 
 verted into their highest oxides on being fused with XaXO, 
 and Na,C0 3 ; the fused mass contains, if all these sulphides 
 were present, SnO u , sodic arseniate and antimoniate, with 
 sodic, sulphate, carbonate, nitrate, and nitrite. Sl\,S, 
 and As 2 S.„ when heated in a current of steam, are partially 
 oxidized, a sublimate composed of the oxide and sulphide 
 in each case being formed, and 1I,S evolved ; if recently 
 precipitated Sb a S 3 and As^ are boiled in H a O for some 
 
OP THE FIFTH GROTJP. 10? 
 
 time, a small portion becomes decomposed, Sb„0 3 and 
 As 2 3 being formed, and dissolved in the water, whilst H 2 S 
 is evolved. Dry HC1 gas decomposes Sb 3 S 3 , but not 
 As 2 S a ; the SbCl 3 which is formed is very volatile in a cur- 
 rent of the HC1 gas. Recently precipitated A 2 S 3 dissolves 
 in KHSO3 (the sulphides of Sn and Sb do not) ; if the so- 
 lution is heated, S0 2 and S are set free, and there remain 
 in solution K 2 S 2 3 and KH 2 As0 3 ; the following is the 
 reaction : — 
 
 2As 2 S 3 + I6KHSO3 = 6K 2 S.O, + 4KH 2 As0 3 + 4H 2 + 
 
 * so, + s 3 . 
 
 Sb 2 S 3 is decomposed by C with heat, Sb and CS a being 
 formed, but As 2 S 3 is not. If vapor of As 2 S 3 or As 2 S 5 be 
 passed over heated Fe or Ag, or other metals, they are de- 
 composed, the S combines with the heated metal, and the 
 As is set free, which also combines with the reducing 
 metal if it be in excess. Sn, Fe, Cu, and other metals, de- 
 compose Sb 2 S 3 at a red heat by combining with the S, the 
 liberated Sb combines with the redueing metal if it be in 
 excess. If the sulphides of As, Sn, and Sb, are fused with 
 KCy, the metals are obtained, and potassic sulphocyanide 
 is formed. The arsenic sulphides are soluble in NH 4 HO 
 and in solutions of NH 4 HCO„ whilst the antimony and tin 
 sulphides are almost insoluble in these reagents. The 
 color of the sulphides and their solubility in acids : Cry- 
 stallized Sb 2 S 3 is bluish-black, the hydrated amorphous 
 Sb 2 S 3 is orange-red, whether in the crystallized or amor- 
 phous state it is insoluble in dilute acids, but concentrated 
 HC1 dissolves it, SbCl 3 and H U S being formed; concen- 
 trated H 2 S0 4 decomposes it, yielding S0 2 , S and a sulphate 
 of Sb 2 3 ; concentrated HN0 3 also decomposes it. Cry- 
 stallized and amorphous As 2 S 3 , also called orpiment,* is 
 lernon-j'ellow, concentrated and boiling HC1 decomposes it 
 only very slightly ; HN0 3 decomposes it, H 3 As0 4 and 
 H B S0 4 being formed ; it is also decomposed by aqua regia. 
 SnS in the crystalline form is bluish-gray, the hydrated 
 amorphous SnS is chocolate-brown ; it is insoluble in dilute 
 acids ; it dissolves in boiling HC1 ; boiling HN0 3 converts 
 it into insoluble hydrate of metastannic acid. SnS 2 ob- 
 tained in the dry way is a beautiful flaky compound, which 
 is known under the name of mosaic gold ; hydrated amor- 
 phous SnS a is faintly yellow ; aqua regia is the only acid 
 
 * Realgar is a sulphide of arsenic, its formula is As 2 S s . 
 
108 THE SPECIAL PROPERTIES 
 
 which decomposes mosaic gold, but the hydrated sulphide 
 is not only decomposed by that acid, but also by boiling 
 HC1, and also by concentrated HN0 3 , which converts it 
 into insoluble hydrate of metastannic acid. PtS 5 is black- 
 ish-brown, and Au 2 S 3 is black ; they are not attacked by 
 HN0 3 or by HC1, but they are dissolved by aqua regia. 
 
 225. The chlorides.— AsCl 3 ,* SbCl 3 , SnCl 2 , and SnCl 4 
 may be obtained in the anhydrous state by distilling a 
 mixture of the metals and HgCl 3 . The following are the 
 
 I'Piirtiriim * 
 
 (1) 2As + 3HgCl 2 = 2AsCl 3 + 3Hg. 
 
 The AsCl 3 passes over into the receiver as an oily color- 
 less liquid. 
 
 (2) 2Sb + 2HgCl 2 = SbCl 3 4- SbHg + HgCl. 
 
 (3) Sn + HgCl ? = SnCl a + Hg. 
 
 The SnCl 2 remains behind as a gray brilliant mass, with 
 a vitreous fracture ; at a dull red heat it may be distilled. 
 
 (4) Sn + 2HgCl 2 = SnCl 4 Hg 2 . 
 
 On the application of heat, SnCl 4 distils over as colorless 
 liquid. AsCl a , SbCl 3 ,f and SnCl 4 , may also be prepared 
 by passing a current of CI over the metals or the sulphides, 
 or by heating stannic or antimonious sulphate with NaCI, 
 and by heating As a 3 with HS0 4 and NaCl. AsCl 3 is a 
 dense, transparent, oily, and volatile liquid, which does not 
 solidify at 18° C, and boils about 132° C. It evaporates 
 in the air at ordinary temperatures. SbC^ is a colorless, 
 fusible, volatile solid, which is crystallizable and deliques- 
 cent ; from its ready fusibility it was formerly known 
 under the name of butter of antimony. SnCl, is a white, 
 frequently gray, solid, fusible, and volatile at a high heat. 
 SnCl 4 is a transparent, colorless fluid, which does not con- 
 geal at — 29° C, and boils at 121° C; it emits dense white 
 fumes when exposed to the air, it absorbs water rapidly 
 from the air, forming a terhydrate SnCl 4 , 3H 2 0. These 
 four chlorides are decomposed by H 2 0, AsCl s , if much 
 water is added, is decomposed into ASjO, and HC1, but if 
 only a small quantity is added, into (AsCl„ As a 3 ) and 
 HC1; SbCl 3 is soluble in a small quantity of H a O, but in a 
 large quantity it is decomposed into (SbCl s Sb 2 0,J) and 
 HC1 ; if tartaric is added to the solution this decomposi- 
 
 * There is no other compound of As nnd CI known. 
 
 \ If the Sb is kept in excess, SbCl, is formed ; but if the CI is in ex- 
 cess, SbCl 6 is produced. 
 
 J By continued washing with water the chloride in these two com- 
 pounds becomes removed uud Sb,t> s only remains. 
 
OF THE FIFTH GROUP. 109 
 
 tion is prevented. If hot water be added to a hot solution 
 of SbCl 3 in HC1, it is decomposed into (2SbCl 3 , 5Sb a O,*), 
 formerly called powder of Algarolh, and IIC1. SnCl 2 is 
 decomposed, if mixed with a large quantity of water, into 
 (SnCl 2 , SnO, 2H 2 0) and HC1. SnCl 4 is readily soluble in 
 a small quantity of water, but it is decomposed if much 
 water be added into H a SnO„ and HC1; the precipitate of 
 the antimony, stannous and stannic compounds is pre- 
 vented if HC1 be added along with the water. In the hy- 
 dra ted state SnCl 2 is obtained by dissolving Sn in HC1, 
 the solution is usually effected in copper vessels on a large 
 scale, since the voltaic opposition of the two metals favors 
 the solution of the Sn; it crystallizes on evaporating the 
 liquid in prismatic needles, the formula being SnCl 2 , 2H 2 0. 
 A solution of SnCl 4 may be prepared by dissolving stannic 
 hydrate in HC1, or 03' treating a solution of SnCl 3 with 
 CI or by mixing SnCL, with HC1 and treating it with 
 HN0 3 ; when its aqueous solution is mixed with one of the 
 alkaline sulphates, hydrated stannic oxide is precipitated 
 thus : — 
 
 SnCl, + 4Na 2 S0 4 + 4H 2 = SnO s , 2H 2 + 4NaCl + 
 4NaHS0 4 . Hydrated SbCl, is obtained in solution by dis- 
 solving Sb 2 O s or SbCl 3 in HC1, the addition of tartaric 
 acid to the solution prevents its decomposition by water; 
 by evaporating the solution of Sb in HC1 anhydrous SbCl 3 
 is obtained. As 2 3 dissolves copiously in HC1; and if 
 As 2 3 or one of its salts is distilled with HC1 of at least 
 1.1 density, AsCL, passes over with the aqueous acid, As 
 may by this means be separated from most other metals 
 and from organic matter; and the reaction explains the 
 presence of As in hydrochloric acid made with oil of 
 vitriol containing As; dilute solutions of As 2 3 in HC1 
 may be evaporated below 100° C. without any AsCl 3 vola- 
 tilizing; but if the mixture be distilled to dryness in a 
 retort, the AsCl, passes over with the last portions of the 
 acid liquid. SbCl 3 combines with HC1 and other chlorides, 
 especially the alkaline chlorides, the general formula for 
 which is (M'C1) 3 SbCl b . SbCL, is employed for bronzing 
 gun-barrels to prevent them rusting, the iron decomposes 
 SbCl 3 and there is formed on the iron a covering of Sb. 
 SnCl 2 , 2HO in crystals or in solution absorbs oxygen on 
 exposure to the air, and forms a mixture of SnCl 4 and an 
 
 * By continued washing with water the chloride in these two com- 
 pounds becomes removed and Sb 2 (> 3 only remains. 
 10 
 
110 THE SPECIAL PROPERTIES 
 
 oxychloride ;* SnCl 3 Las a strong attraction for CI and for 
 0, and is therefore a powerful reducing agent; it reduces 
 gold, silver, and mercury salts to the metallic state; it con- 
 verts ferric and cupric salts into ferrous and cuprous ones ; 
 it reduces chromic, manganic, arsenic, antimonic acids, etc., 
 and the higher oxides of Pb and Bi, etc., into lower oxides; 
 it reduces nitric acid to nitric or nitrous oxide, hypochlo- 
 rous acid to chlorine; it deprives sulphurous acid of its 
 oxygen; it converts indigo-blue into indigo-white; it is 
 extensively employed as a mordant by the dyer and calico- 
 printer under the name of salts of tin, and they also employ 
 it for deoxidizing indigo and ferric and manganic oxides. 
 It forms double chlorides with many of the chlorides of 
 the alkalies and alkaline earths. SnCl 4 forms double salts 
 with the soluble chlorides; the double salt 2NH 4 Cl,SnCl 4 
 is the pink salt of the dj'er; an impure SnCl 4 is used by 
 dyers under the name nitro-muriate of tin, composition, 
 physic, or tin solution, it is used for brightening and fixing 
 red colors. PtCl 4 and AuCl 3 are obtained by dissolving 
 the metals in aqua regia, and evaporating the solution to 
 dryness, the former by steam heat, and the latter at a 
 temperature not exceeding 250° C; in each case a red de- 
 liquescent mass is obtained, which is soluble in water, in 
 alcohol and ether; these chlorides combine with other 
 chlorides, forming double salts ; they combine with most 
 of the chlorides of the organic bases, they are therefore 
 employed to determine the combining number of organic 
 alkalies. They both give off CI when heated, but Pt re- 
 tains CI much more tenaciously than Au. SO s and alka- 
 line sulphites reduce PtCl 4 to PtClj, but those reagents 
 precipitate Au from AuCl.,; this latter chloride is easily 
 reduced by many substances, for instance by P, by most 
 metals, by ferrous salts, by oxalates, by As a O, and Sb 2 0„ 
 by many vegetable and animal substances. When Sn is 
 digested in a neutral solution of AuCl., or a mixture of 
 SnCl„, and SnCl 4 , very much diluted, is added by degrees 
 to a neutral solution of AuCl 3 , a flocculent purple deposit 
 called purple of Cassius is obtained. " The nature of this 
 compound has been the subject of much discussion ; Ber- 
 zelius considered that it consists of a hydrated double 
 stannate of gold and tin (Sn"Au,Sn ll O, 1 4H0 1 ) ; it is decom- 
 
 * The decomposition may be prevented and the solution kept clear, by 
 the addition of HCI, HT\ or Nil/ 1 !, with which SnCl, forms a double 
 salt not decomposable by ll„0 or by exposure to air. 
 
OF THE FIFTH GROUP. Ill 
 
 posed by acids, Au being left; it is unaffected by light; it 
 is insoluble in the fixed alkalies, but soluble in NH 4 HO, 
 forming a deep purple solution from which it is deposited 
 unchanged if the ammonia be expelled by heat or neutral- 
 ized by an acid. The ammonic solution is bleached by the 
 action of light and Au is deposited. Purple of Cassius, 
 when mixed with a little borax or some fusible glass, and" 
 applied to the surface of china, imparts to it a beautiful 
 rose or a rich purple color. It is this compound which is 
 added as the coloring material in the red glass of Bohemia." 
 
 226. Hydrides of As and Sb As and Sb form with H 
 
 gaseous compounds, viz., arsenuretted hydrogen AsH 3 , and 
 antimonuretted hydrogen SbH 3 ; these compounds may be 
 prepared — 1. By acting upon metallic arsenides and anti- 
 monides with acids : — * 
 
 (1) As 2 Zn 3 + 3H 2 S0 4 = 2AsH 3 + 3ZnS0 4 . 
 
 (2) Sb 2 Zn 3 + CHC1 = 2SbH 3 + 3ZnCl 2 . 
 
 2. By the action of nascent hydrogen, evolved, for instance, 
 from Zn and H 2 S0 4 , upon soluble arsenic and antimony 
 compounds : — 
 
 (1) As 2 3 + 6Zn -f 6H 2 S0 4 = 2AsH 3 + 6ZnS0 4 + 3H 2 0. 
 
 (2) SbCl 3 + 3Zn + 3HC1 = SbH 3 + 3ZnCl 2 . 
 
 Fe and Sn act much less efficiently than Zn in producing 
 these compounds. The SbH 3 is always mixed with free 
 H. The H evolved from the negative pole of a battery of 
 several cells converts As 2 3 into AsH 3 , but a weak current 
 produces only a deposit of As; electrolytic H converts a 
 portion only of the Sb of soluble antimony compounds into 
 SbH 3 , the remainder of the Sb being deposited in the me- 
 tallic state on the negative plate. 
 
 227. The nascent H evolved by the action of KHO on 
 Zn or Al, combines with As in arsenites forming AsH 3 , but 
 it does not act upon antimony compounds and form SbH 3 ; 
 hence Fleitman generates hydrogen in this manner to dis- 
 tinguish between As and Sb (par. 229). 
 
 228. AsH 3 and SbH 3 are colorless gases, the former has 
 a most unpleasant odor, the latter is odorless; if passed 
 through a heated tube they are decomposed into their ele- 
 ments, as they decompose below a red heat. When burnt 
 
 * Water decomposes the compounds of the alkaline metals with As 
 nnd Sb, AsH 3 and SbH 3 being formed along with the hydrate of the al- 
 kali. 
 
112 THE SPECIAL PEOPEETIES 
 
 in the air they yield H 2 and As 2 3 , and Sb 2 3 , respect- 
 ively. If the supply of air is limited by depressing the 
 Jlame, with a piece of porcelain for instance, the H only is 
 oxidized, the metal, being set free, is deposited on the por- 
 celain, if cold. They are decomposed by CI and by S0 2 , 
 HN0 3 , aqua regia, and by all oxygenated acids, including 
 strong H 2 S0 4 ; they are also decomposed by solutions of 
 mercury, and most other heavy metallic salts. They are 
 decomposed when passed through concentrated HN0 3 , 
 H 3 AsO s , and H 3 As0 4 , and Sb 2 O s being formed. When 
 passed through a solution of AgN0 3 the following changes 
 ensue : 
 
 (1) AsH 3 + 6AgN0 3 + 3H 2 = H 3 As0 3 + 3 Ag 2 + 6HNOy 
 
 (2) SbH 3 + 3AgN0 3 = Ag 3 Sb + 3HN0 3 . 
 
 229. If a solution containing H 3 AsO a , or an arsenite, be 
 mixed with a large excess of a concentrated solution of 
 KHO, and boiled with fragments of granulated Zn, H 3 As 
 is evolved, and may be readily recognized by allowing it to 
 pass on to a piece of filter-paper moistened with a solution 
 of AgN0 3 ; the paper assumes a purplish-black color, even 
 when a small quantity of arsenic is present. This test 
 serves to distinguish As from Sb (Fleitmann). 
 
 230. As forms one other compound with H; it is a brown 
 powder, and is obtained by passing an electric current 
 through water, the negative pole being formed of metallic 
 arsenic. Its formula appears to be AsH r 
 
 GENERAL CHARACTERS OF THE SALTS OP THIS GROUP. 
 
 231. Stannous salts are either colorless or possess a yel- 
 lowish tinge, they have a disagreeable metallic taste, and 
 rapidly abstract oxygen from the air and from oxygen com- 
 pounds, and become converted into stannic salts. When 
 largely diluted with water their solutions become milky ; 
 on the addition of a small quantity of HCl they are again 
 rendered clear. Stannic oxide forms two hydrates distin- 
 guished as stannic (H.,Sn0 3 ) and metastannic hydrates 
 (H 2 Sn s O n ,4H 2 0), the H 2 Sn0 3 is obtained by adding N H,HO 
 to a solution of SnCl 4 ; it is an amorphous gummy sub- 
 stance, soluble in HCl, HN0 3 , H,S0 4 ,II/r, and in KHO and 
 NaHO, but not in NII 4 1I0. ll a Sn 5 O u , 4H a O is obtained 
 by heating Sn or SnO with HN0 3 , it is insoluble in H S T, 
 and in HNO,; when heated with concentrated H 2 S0 4 , it 
 readily dissolves, forming a compound soluble in water, 
 
OF THE FIFTH GROUP. 113 
 
 but on boiling the solution the compound is decomposed, 
 the two acids separating. It is also insoluble in HC1, but 
 it forms with it a compound insoluble in acids, but soluble 
 in water ; it is readily soluble in solutions of the fixed al- 
 kalies and their carbonates, but it is not dissolved by 
 NH 4 HO unless recently precipitated from a cold solution 
 of its salts by the addition of an acid. By a heat of 284° 
 C. stannic is converted into a metastannic acid, and the 
 latter is converted into the former by fusion with an excess 
 of caustic alkali. Both these acids unite with bases and 
 form salts; the metastannates can exist only in the hy- 
 drated state, and those of potash and soda are the only 
 ones soluble in water; the soluble stannates have a strong 
 alkaline reaction, and their solutions absorb C0 2 from the 
 air. Stannic hydrate dissolves in the stronger acids, form- 
 ing stannic salts ; these salts can also be prepared by add- 
 ing to solutions of stannous ones an excess of acid, and 
 then adding CI or a small quantity of HN0 3 . The stannic 
 salts of the oxygen acids are very unstable. The acid 
 properties of stannic hydrate are more powerful than the 
 basic ones. Na 2 S0 4 , NH 4 N0 3 , and most of the neutral 
 salts of the alkalies, if added in excess, and the solution be 
 not too acid, precipitate from both the stannates and me- 
 tastannates their hydrates. Some of the antimonious salts 
 are decomposed by ignition, the haloid salts volatilize read- 
 ily and unaltered; the antitnon}' salts are decomposed 
 when treated with a large quantity of water into soluble 
 acid and insoluble basic salts ; the basic salts are distin- 
 guished from the basic bismuth salts formed under like cir- 
 cumstances by being dissolved by a solution of H/P, in 
 which the latter are insoluble. The hydrate HSb0 2 * pos- 
 sesses more of the characters of a base than of an acid, 
 nevertheless it can combine with bases. Potassic antimo- 
 nious tartrate (tartar emetic) KSbG 4 H 4 7 is employed in 
 medicine ; it is prepared by boiling three parts of Sb,0 3 with 
 four parts ofKHGJIfie for about half an hour, renewing 
 the water as it evaporates and filtering whilst hot ; it is 
 viewed by many chemists as containing the monatomic 
 radical antimonyl (SbO); its formula according to this 
 view is K(SbO)'C 4 H 4 6 , and it is named potassic antimo- 
 nylic tartrate. Arsenious acid unites with bases in several 
 proportions; the arsenites are not very stable; the alkaline 
 are the only arsenites soluble in H a O, their concentrated 
 
 * The normal hydrate H 3 Sb0 3 is not known. 
 10* 
 
114 TEE SPECIAL PROPERTIES 
 
 solutions are decomposed by the C0 2 in the air; the insolu- 
 ble arsenites are dissolved with decomposition by HC1. 
 The arsenites of the metals of the alkalies and alkaline 
 earths are decomposed by heat into arseniates, As being 
 given off; plumbic arsenite is not decomposed by heat; 
 the other arsenites are decomposed by heat, As 2 8 being 
 given off, and the metal left as oxide unless it is reducible 
 by heat. Potassic arsenite is used in medicine under the 
 name of Fowler's solution, and CuHAs0 3 , and thedouble salt 
 of arsenite and acetate of copper (3CuAs a O s , Cu2C 2 H 3 2 ) 
 are employed as pigments, the first under the name of 
 Scheele's green and the latter under the name of Schwein- 
 furt or emerald green. Arsenic acid is a powerful acid, it 
 takes away the bases from volatile acids; its salts have 
 the general formula M' 3 As0 4 ; one or two atoms of M' can 
 be replaced by an equal number of atoms of H ; the alkaline 
 arseniates are soluble in water, but the other arseniates 
 are insoluble ; most of the arseniates can bear a strong red 
 heat without suffering decomposition. The salts of gold 
 and platinum are decomposed on ignition. KHO, NaHO, 
 NH 4 HO, and their carbonates produce in solutions of 
 stannous salts a precipitate of SnH 2 2 , and in solutions 
 of stannic salts a precipitate of stannic or metastannic 
 hydrate, according to the nature of the solution; these 
 different precipitates are soluble in an excess of KHO or 
 NaHO, but are insoluble in an excess of the other precipi- 
 tants ; these reagents precipitate also Sb,0 3 from solutions 
 of SbCl 3 , and also from other salts of Sb 2 3 but from solu- 
 tions of tartar emetic less completely, and only after the 
 lapse of some time; the precipitate redissolves pretty 
 readily in KHO or NaHO, but requires the application of 
 heat for its solution in K 2 C0 3 , and is altogether insoluble 
 in NHJHO. Zinc precipitates from stannous, stannic, and 
 antimonious solutions in the presence of free HC1, the 
 metal; if the reduction takes place in a platinum vessel 
 the part of the platinum covered by the liquid is stained 
 brown or black by Sb but not by Sn; HC1 does not re- 
 move the stain, hot HN0 3 removes it immediately. The 
 members of this group are distinguished from those of the 
 other groups by the solubility of their sulphides in the 
 alkalies and alkaline sulphides ; unlike the members of 
 the previous groups, but like those of the sixth, they are 
 precipitated from their acid solutions by IIS. 
 
OP THE FIFTH GROUP. 115 
 
 REMARKS ON THE INDIVIDUAL MEMBERS OF THE GROUP, WITH 
 ADDITIONAL SPECIAL TESTS. 
 
 232. Sn and 'its compounds. — Sn has very little tenacity; 
 it can easily be obtained in crystals ; it is expanded by 
 combined hammering and heating into sheets or leaves 
 called tinfoil. Sn0 2 occurs native as tinstone or cassiterite ; 
 this is the only ore of tin that is worked. Tin is a con- 
 stituent of several important alloys. Speculum metal for 
 the mirrors of reflecting telescopes, bell metal, and gun 
 metal, are alloys of Sn and Cu ; and the bronze used for 
 coin consists of 95 pts. Cu, 4 of Sn, and 1 of Zn ; solder is 
 an alloy of Sn and Pb, and the amalgam of Sn and Hg is 
 employed for the silvering of mirrors. 
 
 233. AuCl 3 produces, in solutions of stannous salts con- 
 taining a small quantity of free HN0 3 , a precipitate (.purple 
 of Cassius). 
 
 234. If a solution of a stannous salt is added to a mix- 
 ture of K 8 Fe 2 Cy, 2 and Fe 2 Cl B , Prussian blue precipitates 
 immediately. This delicate test for a stannous salt can 
 only be conclusive in cases where there are no other re- 
 ducing agents present. 
 
 235. Solution of HgCl 2 produces in solutions of stannous 
 salts a white precipitate of HgCl, owing to the tin salt 
 withdrawing half the CI from the HgCl 3 . If sufficient 
 quantity of the tin salt be present, it removes, after a time, 
 all the CI from the Hg ; the color of the precipitate then 
 becomes gray. Since this reaction takes place even in 
 highly dilute solutions, and in the presence of much free 
 HC1, it is very valuable for the detection of stannous 
 compounds. 
 
 236. If Na^COg be mixed with equal parts of KCy and 
 stannous or stannic compounds, and the mixed mass be 
 subjected, upon a charcoal support, to the inner blowpipe 
 flame, ductile metallic grains of tin will be obtained, unac- 
 companied by any incrustation upon the charcoal.* 
 
 23"7. On the charcoal splinter the Sn compounds are 
 easily reduced to white, lustrous, ductile, metallic beads. 
 
 * Bloxam has pointed out that if the ECy contains any K^SO,,, the 
 whole of the Sn is not obtained in the metallic state; if the quantity of 
 K 2 S0 4 is small, a portion of the Sn is converted into SnS, which sepa- 
 rates as a black powder on treating the fused mass with H 2 ; if there 
 be much K 2 S0 4 , a portion of the Sn is converted into SnS 2 , which is found 
 in the aqueous solution of the fused mass, and from which it may be 
 precipitated by HC1. 
 
116 THE SPECIAL PROPERTIES 
 
 The flattened particles, transferred to the curved glass, 
 slowly dissolve in HC1 ; and the solution, when absorbed 
 by paper, gives a red precipitate with selenious, and a 
 black precipitate with tellurous acid dissolved in HC1. If 
 to the solution a trace of bismuth-nitrate be added, an ex- 
 cess of soda gives a black precipitate of Bi 2 3 . The metal, 
 acted on by HN0 3 , yields a white powder of insoluble 
 Sn0 3 . 
 
 238. A borax bead, containing enough CuO to render it 
 faintly blue, serves as a delicate test to ascertain with cer- 
 tainty the presence of a trace of a Sn compound, as the 
 bead, placed in the lower reducing^ flame, turns reddish- 
 brown, or forms a clear ruby-red glass. — Bunsen. 
 
 239. Whether the Sn exists as a stannous or a stannic 
 compound may be ascertained by adding to one portion of 
 the solution HgCl 2 , AuCl 3 , or a mixtnre of K 6 Fe,Cy 12 and 
 Fe a Cf B , and by adding another portion to a hot concen- 
 trated solution of Na 2 S0 4 . These, along with the blowpipe 
 tests, are characteristic of Sn. 
 
 240. Another oxide, Sn 2 O s , is known. It is obtained as 
 a slimy gray hydrate by boiling Fe 2 H O 6 in a solution of 
 SnCl 2 :— 
 
 2SnCl 2 + Fe 2 3 = Sn 2 3 + 2FeCl 2 . 
 
 It dissolves in NH 4 HO, which distinguishes it from SnO; 
 and it is distinguished from Sn0 2 by forming with AuCl 3 a 
 purple precipitate. It does not appear to form definite 
 salts. 
 
 241. Sb and its compounds. — Sb is a brilliant bluish- 
 white metal. It is hard, and so brittle that it can be easily 
 reduced to powder. It is inferior to most of the metals as 
 a conductor of heat and electricity. In the state of fine 
 powder it is easily dissolved by digesting it in a solution 
 of a potassic polysulphide. If one part of tartar emetic 
 is dissolved in four parts of a solution of SbCl„ and the 
 solution is subjected to the action of two or three cells of 
 Smee's battery, using a plate of Sb for the positive, and a 
 copper wire for the negative electrode, a metallic deposit of 
 Sb, having the color and lustre of highly-polished steel, 
 and a bright metallie amorphous fracture, is deposited, the 
 deposit retains 5 or 6 per cent, of SbCl 3 . This amorphous 
 Sb, when heated or struck, undergoes a rapid and intense 
 molecular change throughout its mass, attended with great 
 evolution of heat, increasing, at the same time, in density ; 
 it retains its cohesion and metallic aspect, but becomes 
 
OP THE FIFTH GROUP. 117 
 
 gray, and acquires a granular fracture, and an increased 
 density. The change is attended with an abundant disen- 
 gagement of fumes of SbCl 3 (Gore). Sb is a constituent 
 of several important alloys. It confers on these compounds 
 hardness and the property of expansion in the act of solidi- 
 fication. Ordinary type metal is composed of 3 or 4 parts 
 of Pb and 1 of Sb ; the best is composed of 2 parts of Pb, 
 1 of Sn, and 1 of Sb. The principal mineral of Sb is the 
 sulphide Sb 3 S 3 . 
 
 242. Introduce an antimonial solution into the apparatus 
 (fig. 2), and add some Zn and dilute H 2 S0 4 , the presence 
 of Sb in the evolved gas may be recognized by the following 
 reactions: — 
 
 1st. The gas will burn with a bluish-green flame, emit- 
 ting white fumes of teroxide of antimony, which may be 
 condensed in a cold beaker, dissolved in hydrochloric acid 
 and tested with hydrosulphuric acid. 
 
 2d. If the inner surface of a porcelain capsule be de- 
 pressed upon the ilame, a black spot of metallic antimony 
 will be deposited upon it, which is lustrous, only when in 
 thin layers. This deposit is distinguished from the similar 
 arsenical stain by its solubility in solution of chloride of 
 soda (NaClQ), and by its ready solubility in (NHJ 2 S. 
 Another method of testing the deposit is to moisten it 
 with HN0 3 of sp. gr. 1.42, then heat the vessel over a 
 lamp, and blow over the surface to cause the acid to evapo- 
 rate ; the white deposit which remains will turn deep black 
 with ammonio-nitrate of silver. 
 
 3d. The glass tube from which the gas issues should be 
 heated with a spirit lamp, in the centre ; a lustrous mirror 
 of antimony will be deposited on the inside of the tube, 
 immediately around the flame of the lamp, whilst the 
 bluish-green tint of the hydrogen flame in great measure 
 disappears. The means for distinguishing this mirror 
 from the arsenical one are given at pars. 262 — 2d, and 263. 
 
 243. These reactions should be compared with those of 
 terhydride of arsenic under similar circumstances. 
 
 244. If a solution of Sb 2 3 in one of the fixed alkalies is 
 mixed with a solution of AgNO,, a deep black precipitate 
 of Ag 4 forms with the grayish-brown precipitate of Ag. 2 0. 
 Upon now adding NH 4 HO in excess, the Ag 2 is redis- 
 solved, whilst the Ag 4 is not (H. Rose). This very deli- 
 cate test enables one to detect readily the presence of 
 Sb 2 3 in the presence of Sb 2 5 . 
 
 245. Detection of Sb in organic mixtures. — If it be in 
 
118 THE SPECIAL PEOPEETIES 
 
 the solid state it should be cut up into small pieces ; if it 
 is a liquid, and in large quantity, it should by evaporation 
 be reduced to a convenient bulk. It is then mixed with 
 IIC1 and KCIO3, as directed at par. 133 ; from the filtered 
 liquid the Sb may be precipitated by H 2 S, or it may be in- 
 troduced into the apparatus (fig. 2) and the gas tested for 
 Sb, as directed in par. 242— 1st, 2d,' and 3d. 
 
 246. If compounds of Sb, mixed with Na 2 C0 3 and KCy, 
 be exposed, upon a charcoal support, to the reducing flame 
 of the blowpipe, brittle grains of Sb will be formed, accom- 
 panied with a white incrustation on the charcoal. 
 
 247. Flame coloration, by treatment in the upper re- 
 ducing flame, pale green, unaccompanied by any smell. 
 
 248. Reduction film, black, sometimes dead, sometimes 
 bright. 
 
 249. Oxide film, white ; moistened with a perfectly neu- 
 tral solution of AgN0 3 , and then blown on by ammoniacal 
 air, it gives a black spot which does not disappear in 
 NH 4 HO. If the film be first placed over bromine vapor 
 the reaction cannot be obtained, owing to the oxidation of 
 Sb 2 3 into Sb 2 6 . It is unaltered by SnCl 2 , either with or 
 without NaHO. 
 
 250. Iodide film, orange red, disappearing by breathing, 
 and reappearing by blowing or warming ; blown on with 
 ammoniacal air it disappears, but does not return. Gen- 
 erally it gives the same reactions as the oxide. 
 
 251. Sulphide film, orange red. The film is difficult to 
 blow away with NH 4 S 2 ; returns on blowing with air ; in- 
 soluble in water. 
 
 252. With soda on charcoal splinter gives no black stain 
 on silver, but 3'ields a white, brittle, metallic bead. 
 
 Characteristic reactions. — The orange-colored precipi- 
 tate with H 2 S, the film reactions, and the decomposition of 
 the neutral salts by water, and the solubility of the pre- 
 cipitate in H 2 T. 
 
 253. Two other oxides of Sb are known, viz. Sb ,0 4 , which 
 is generally regarded as composed of equal equivalents of 
 Sb 2 3 and Sb 2 6 , and is therefore named antimoniate of 
 antimony. This oxido is obtained by heating strongly 
 Sb 2 6 , which loses by the ignition one-fifth of its O and be- 
 comes converted into Sb a 4 , or it may be obtained by roast- 
 ing Sb 2 O a in the air. It is white, infusible, and unalterable 
 by heat; slightly soluble in H,0, more soluble in 1IC1; it 
 is resolved into Sb 2 3 and Sb,0 5 on boiling it in a solution 
 of KHT. The other oxide is Sb a 6 , it is called antimonic 
 
Or THE FIFTH GROUP. 119 
 
 oxide, or anhydride, and is obtained by heating below red- 
 ness one of its hydrates. It is a yellowish powder insolu- 
 ble in water and acids, but soluble in a solution of KHO ; 
 and when fused with K 2 C0 3 the C0 2 is expelled, and potas- 
 sic antimoniate is left. It appears to form three hydrates, 
 forming three distinct acids, thus: H 3 Sb0 4 , the normal 
 hydrate ; HSb0 3 , antimonic acid ; H 4 Sb 2 7 , metantimonic 
 acid. 
 
 254. As and its compounds. — As has a brilliant dark 
 steel-gray lustre. It is very brittle, and is easily reduced 
 to powder. As 2 3 is the arsenic, or white arsenic, of the 
 shops. There are two varieties of this oxide, one, from its 
 appearance, is termed the vitreous, and the other the milky 
 variety ; when heated, they volatilize in white inodorous 
 fumes. Both kinds are more easily soluble in hot than in 
 cold water. As 3 2 is exceedingly poisonous; and being 
 altogether inodorous, almost destitute of taste, and readily 
 obtainable, is frequently employed as a poison. The best 
 antidote is the moist and well-washed ferric hydrate. 
 Arsenic anhydride (As 2 6 ) is a white solid ; it has no 
 action on litmus paper; is nearly insoluble in H 2 and in 
 NH 4 HO ; it fuses at a low red heat without undergoing de- 
 composition, but at a higher temperature it is resolved into 
 O and As 2 3 , which volatilizes. Arsenic acid (H 3 As0 4 )is 
 readily soluble in water, and it maybe obtained in large 
 transparent crystals by exposing a concentrated solution 
 to a very low temperature. Its aqueous solution dissolves 
 Zn and Fe with evolution of H ; but if H 2 S0 4 , or HC1, is 
 present it is reduced and converted into H 3 As. S0 2 passed 
 through a solution of it reduces it to As 2 O s , H 2 S0 4 being 
 formed. The greater part of AS 2 3 of commerce is pre- 
 pared from mispickel (FeAsS), an arsenical sulphide of 
 iron furnished abundantly by the Silesian mines ; and from 
 the arsenides of Ni and Co, which yield As 2 3 , as a se- 
 condary product in the ordinary process of working these 
 ores. In the manufacture of shot a small quantity of As 
 is added to the Pb to facilitate its assuming the globular 
 form. 
 
 BEHAVIOE OF As 2 3 AND THE AESENITES WITH REAGENTS. 
 
 255. AgN0 3 produces in neutral solutions of the arse- 
 nites a yellow precipitate of Ag 2 HAs0 2 , soluble in HN0 3 
 and NH 4 HO ; AgNO s , therefore, produces no precipitate, 
 or only a slight turbidity in solutions of As 2 3 , but on 
 
120 THE SPECIAL PROPERTIES 
 
 neutralizing the acid with NH 4 HO the precipitate appears. 
 Ammonio-nitrate of silver is, therefore, a more appropriate 
 reagent than AgNO s if the acid be free. 
 
 256. CuSO, produces in neutral solutions of the arse- 
 nites a yellowish-green precipitate of CuHAsO, soluble in 
 NH 4 HO, and in acids ; CuS0 4 produces, therefore, no pre- 
 cipitate in solutions of As 2 3 but on neutralizing the acid 
 with NH 4 HO the precipitate appears ; ammonio-sulphate 
 of copper is, therefore, a more suitable reagent than CuS0 4 
 in testing an acid solution. 
 
 257. If to a solution of As 2 3 , or an arsenite, solution of 
 KHO be added in excess, and a few drops only of a dilute 
 solution of CuSO,, and the liquid subsequently boiled, a 
 red precipitate of Cu 2 will fall down, whilst the solution 
 will contain potassic arseniate. This test is particularly 
 applicable in distinguishing As 2 3 from As 2 5 It cannot 
 be employed with safety as a direct means for detecting 
 As 2 0„ as many organic substances possess the property of 
 reducing CnO to the state of Cu 2 0. 
 
 258. " If to As 2 O s , no matter whether in the solid form 
 or in solution, some HC 2 H 3 2 is added, and then KHO in 
 slight excess, the mixture evaporated to dryness, and the 
 residue heated to redness in a small tube — or if a trace of 
 As 2 3 is introduced into a narrow test-tube, and there 
 covered with a somewhat larger quantity of NaCjH 3 0„, 
 and heat applied — part of the As 2 3 is reduced, but there 
 forms at the same time alkarsin (oxide of cacodyl) 2(As 
 (CH 3 ) 2 )0, which makes its presence immediately known by 
 its equally characteristic and formidable odor, which 
 somewhat resembles that of sharp onions. This changes 
 speedily to the not less characteristic odor of chloride of 
 cacodyl (As(CH 3 ) 2 Cl), if the ignited contents of the tube 
 are heated with a few drops of SnCV — Bunsen. 
 
 259. If arsenites, or As 9 O a , or As 2 S„ are fused together 
 with a mixture of equal parts of dry > T a 2 CO, and KCy, the 
 whole of the As, and also the base, if an easily reducible 
 one, is reduced to the metallic state, the converts part 
 of the KCy into KCyO. In the reduction of As,S 3 , KCyS 
 is formed. The operation is conducted as follows : Intro- 
 duce the perfectly dry arsenic compound into the bulb of 
 a small bulb-tube, and cover it with six times the quantity 
 of a perfectly dry mixture of Na 2 C0 3 and KCy. The 
 whole quantity must not more than half fill the bulb, other- 
 wise the fusing KCy is likely to ascend into the tube. 
 Apply the heat of a lamp to the bulb, and continue this 
 
OP THE FIFTH GROUP. 
 
 121 
 
 for a while, as the As frequently requires some time for 
 its complete sublimation. The metallic mirror is deposited 
 on the cold part of the tube of exceeding purity; and is 
 obtained from all arsenites whose bases remain either al- 
 together untouched, or are reduced to arsenides which lose 
 their As partly or totally upon the application of heat. 
 By this method minute quantities of As can be detected, 
 and it is especially adapted for obtaining As from As 2 S 3 . 
 The delicacy is increased by heating the mixture in a 
 stream of dry C0 2 , as described in the next par. 
 
 260. The apparatus (fig. 1) consists of a flask A capable 
 of holding about eight or twelve fluidounces; it is fitted 
 with a funnel-tube, and a bent tube which dips into a 
 smaller flask, B. In A C0 2 is slowly generated from 
 
 Fig. 1. 
 
 pretty large fragments of marble (no powder) and dilute 
 HC1; it is conveyed into B, which is partly filled with 
 concentrated H 2 S0 4 , in order to dry the gas. The exit- 
 tube from B is bent at right angles, and connected, by 
 means of a cork, with the reduction-tube ; this latter tube 
 is made out of a piece of hard glass tube (combustion- 
 tube) somewhat more than three-eighths of an inch in 
 diameter, and drawn out at one extremity to a long point ; 
 the length of the body of the tube should be about four 
 inches, that of the point at least two and a half inches. 
 
 261. A mixture of 3 parts of anhydrous Na 2 C0 3 and 1 
 part of KCy is dried in the water bath ; about 12 parts of 
 this dried mixture is mixed with 1 part of As 2 S 3 , or the 
 arsenite, which has been also dried in the water-bath ; the 
 mixture, before it has time to get damp, is put upon a 
 narrow slip of card-paper bent into the shape of a gutter ; 
 11 
 
122 THE SPECIAL PROPERTIES 
 
 it is then introduced into the tube, and the latter is turned 
 half round upon its axis ; the mixture falls upon the glass, 
 and the gutter is withdrawn. The mixture should be in 
 the middle of the tube, and it ought not to occupy more 
 than an inch. The reduction-tube must now be fixed, by 
 means of the cork, to the exit-tube of B, and a moderate 
 stream of C0 2 ought to be evolved, by pouring some HC1 
 into A, by means of the funnel-tube. Heat the reduction- 
 tube, in its whole length, very gently with a lamp, until 
 the mixture is perfectly dry ; when all the water is ex- 
 pelled, moderate the gas stream so that only one bubble 
 shall pass through the H 2 S0 4 in B in a second ; the gas 
 stream may be moderated by pouring water into A. When 
 the gas stream is moderated, apply the flame of a lamp to 
 the shoulder of the tube ; and when this part of the tube 
 is red hot, apply the flame of a second lamp, commencing 
 at the end of the reduction-tube nearest B, and heating 
 along up to the mixture ; continue to apply the flame at 
 the part where the mixture is, until all the As is expelled. 
 The far greater portion of the volatilized As recondenses 
 in the narrow part of the tube, whilst an extremely minute 
 portion only escapes through the fine point, imparting to 
 the surrounding air the peculiar odor of garlic. Advance 
 the flame of the second lamp slowly and gradually up to 
 the first, by which means the whole of the As which may 
 have condensed in the wide part of the tube is driven into 
 the narrow part. When this end has been attained, close 
 the fine point of the tube by fusion, and apply heat, pro- 
 ceeding from the closed point towards the part where the 
 greater part of it is condensed, by which means the extent 
 of the mirror is narrowed, whilst its beauty and lustre are 
 correspondingly increased. In this manner, perfectly dis- 
 tinct mirrors of As may be produced from as little as the 
 one-hundredth part of a grain of As,S s . Xo mirrors are 
 obtained by this process from Sb 2 S 3 , nor from any other 
 compound of Sb. 
 
 262. MarsJi's test for Arsenic The apparatus (fig. 2) is 
 
 a convenient one, as the AsH 3 can be both tested by rea- 
 gents, decomposed in the tube by heating the tube, and the 
 AsH 3 may also be burnt as it escapes from the opening of 
 the tube, and the As deposited in the tube and the As.,0, 
 produced by burning the gas can each be tested. A is a 
 flask for the acid, the Zn, and the solution to be tested. 
 It is provided with a funnel-tube for conveying the liquids. 
 b is a tube filled with fragments of fused calcic chloride for 
 
OP THE FIFTH GROUP. 
 
 123 
 
 drying the gas. c d is a tube of hard-glass (free from 
 lead) about one-quarter of an inch in diameter, and having, 
 as shown in the figure, two or three capillary contractions, 
 and bent at a right angle, so that it may form a jet, or that 
 it may dip into a solution of AgN0 3 . 
 
 Fig. 2. 
 
 The first thing to be ascertained is whether the Zn and 
 dilute H. 2 S0 4 to be employed are free from As ; for this 
 purpose they must first be introduced into A, loithout the 
 solution to be tested, and after the evolution of the H has 
 continued long enough to expel all the air, the tube is to 
 be heated at a for about five or ten minutes, and the 
 escaping gas conducted into a solution of AgN0 3 . If no 
 deposit is produced in the tube or a precipitate in the Ag 
 solution, the Zn and H 2 S0 4 are free from As, and the solu- 
 tion to be examined for As may be introduced into A,* and 
 the evolved gas then examined in the following manner: — 
 
 1st. Hold a piece of filter-paper, moistened with a solu- 
 tion of AgNO.,, over the open end of c d; if H 3 As is present 
 the paper will assume a purplish-black color. Inflame 
 the gas, if H 3 As is present it will burn with a livid blue 
 ■flame, producing a white smoke of As,0 8 ; condense the 
 As. 2 3 by holding a wide, cold test-tube over the flame ; 
 dissolve the condensed matter in hot water, and test it for 
 HAsO s , especially with ammonio-nitrate of silver, and 
 with H 2 S, after acidifying with HOI. 
 
 * If there. is much frothing when organic matter is present, a little 
 alcohol must be added to prevent it. 
 
124 THE SPECIAL PROPERTIES 
 
 2d. Heat the tube at a by means of a lamp, As will be 
 deposited a little beyond the flame as a steel-gray ring ; 
 after a sufficient deposit has been obtained at that point, 
 remove the lamp to the next division and obtain a second 
 deposit ; if necessary, a third maybe obtained in the third 
 division. Let the escaping gas during the heating of the 
 tube pass into a solution of AgN0 3 ; when the operation is 
 over the portions of the reduction-tnbe containing the de- 
 posits may be cutoff with a file and the deposits examined. 
 The As deposit is soluble in a solution of chloride of soda 
 (NaCIO), and it is perceptibly dissolved if a drop of (NHJ 2 S 
 be added to it. If the crust be dissolved in concentrated 
 HN0 3 , and evaporated just to dryness upon a sandrbath, 
 a little water added, and afterwards ammonio-nitrate of 
 silver, a brick-red precipitate of Ag 3 As0 4 will be obtained ; 
 an antimony spot, when treated in this way, generally 
 gives a slight dirty white precipitate with the Ag solution. 
 The AgNO„ solution, through which the gas has been passed, 
 ought to be examined for As as in the fifth method (par. 
 218). 
 
 263. Another method for distinguishing which of the 
 two metals, As or Sb, has produced the mirror, and also 
 for distinguishing and detecting the two metals when they 
 occur together, is the following: Having obtained the 
 mirror in the tube c d in the manner already described 
 (par. 262— 2d), a feeble stream of dry H,S must be trans- 
 mitted through the tube, the metallic mirrors being gently 
 heated from their outward to their inward border. If only 
 As be present, the yellow sulphide As a S a will be formed. 
 If Sb only be present, the orange or black Sb s S a will be 
 produced ; but if both metals be present, the two sulphides 
 will be formed ; and the As s S 3 , being the more volatile of 
 the two, will be the further removed from the flame. A 
 stream of dry HC1 gas must be passed through the tube 
 without the application of heat ; by this means the Sb.,S 3 
 will be converted into volatile SbCl 3 , which will entirely 
 disappear, whilst the As 2 S 3 will remain unaltered, and may 
 be distinguished from any sulphur which may have sepa- 
 rated, by dissolving readily in NIL.HO. 
 
 264. In employing Marsh's test for the detection of As 
 it is necessary, as has already been stated, to have the 
 solution free from CI, HN0 3 , HC10 S , SO.,, aqua regia, mer- 
 cury salts, etc. SO a may be present if the organic matter 
 has been carbonized by H.,S0 4 and the presence of S0 2 
 may give rise to the production of II S by the action of 
 
OF THE FIFTH GROUP. 125 
 
 the nascent H upon it ; H 2 S may also be formed if the 
 H 3 S0 4 is not sufficiently diluted to prevent its acting too 
 violently upon the Zn. H 2 S must not be present, because 
 it would form with the arsenic As 2 S 3 which is not con- 
 verted by the H into AsH 3 . In conclusion, it may be 
 remarked that the presence of organic matter sometimes 
 completely prevents the detection of minute quantities of 
 As by Marsh's method. 
 
 265. If clean metallic copper is boiled in a solution con- 
 taining As 2 3 , acidified with HC1, the copper becomes 
 coated with a steel-gray film of As ; if the quantity of 
 As 2 3 is considerable, the reduced As will separate from 
 the Cu, when the liquid is boiled for some time, in large 
 black scales. As many other metallic oxides are reduced 
 to their metallic state under the same circumstances, it is 
 necessary to submit the crust to further examination. 
 This test, which is called " Reinsch's test," is particularly 
 useful for the detection of As in organic liquids or solids. 
 " The suspected liquid is simply to be acidulated with 
 about one-sixth of its bulk of HC1, and boiled. The solid 
 tissue must be cut up into very small pieces, and boiled 
 for some time in a mixture of about one part of HC1 with 
 six of water, until the whole is disintegrated ; then strained 
 through muslin, or filtered through a previously wetted 
 filtering paper. 
 
 266. "Into either of the above boiling liquids dip the 
 end of a piece of clean polished copper wire ; examine the 
 wire from time to time, and as soon as its surface acquires 
 a gray metallic discoloration remove it, and add in its 
 stead fragments of fine copper gauze, continuing the sup- 
 ply as long as the last added piece assumes any definite 
 alteration in color. 
 
 26?. " Remove the pieces of copper gauze, wash them in 
 water, and dry them between folds of filtering paper ; the 
 deposit will not rub off unless the amount of As be very 
 large. If the As exist in but very small quantity, the 
 color of the precipitated metal is bluish ; otherwise of a 
 dark iron-gray tint. Holding the piece of gauze in the 
 fingers, warm it over a flame, coil it up into a small com- 
 pass, and introduce it into a reduction-tube : now apply 
 heat cautiously ; the As will volatilize, oxidize, and con- 
 dense in the cold part, in the form of a white crystalline 
 sublimate. Several pieces of coated gauze may be thus 
 treated successively, until a sufficiently obvious sublimate 
 of As 3 is procured ; by examination with a lens, or with 
 
 11* 
 
126 THE SPECIAL PROPERTIES 
 
 the low power of a mici - oscope, the crystals will be seen 
 to consist of highly iridescent octo- and tetra-hedra." File 
 off the piece of tube containing the sublimate, boil it for a 
 minute or two in a little water; test the water after the 
 boiling for As 2 8 , one portion with HC1 and H 2 S, and 
 another portion with ammonio-nitrate of silver. 
 
 268. As is not deposited on the Cu in the presence of 
 oxidizing bodies, and the HC1 in their presence dissolves 
 the Cu. When present they must be got rid of by reduc- 
 tion or other means before introducing the copper foil or 
 gauze. As a small quantity of Cu is always dissolved, 
 the foil or gauze employed should be at least so far free 
 from As that a solution of four or five grains of it should 
 not yield a perceptible trace of it. The HC1 to be em- 
 ployed should also be free from As ; its purity may be 
 conveniently ascertained by diluting it with three or four 
 times its own volume of water and boiling in it, for some 
 time, a piece of the copper foil to be employed ; if pure, 
 the Cu will not be stained. We may observe, in conclusion, 
 that the arsenical film which peels off from the Cu is not 
 pure As, but an arsenide of copper (Cu 5 As 2 ). On heating 
 the copper foil in the tube only a portion of the As, and 
 relatively only a small portion, volatilizes, the rest of it 
 remains behind united with the Cu. 
 
 269. Detection of As in organic mixtures. — Before ex- 
 amining for arsenic in articles of food and dead bodies, 
 it is necessary in the generality of cases to destroy the 
 organic matter before attempting to search for the arsenic 
 compound, as, from its consistence, etc., it impedes the 
 application of the reagents or masks their reactions ; the 
 destruction involves the use of chemical reagents, which 
 as far as possible ought to be avoided, on account of the 
 difficulty of obtaining many of them perfectly free from 
 arsenic; as by the dialytic method no chemical reagent of 
 any kind is introduced into the organic mixture, it is de- 
 sirable first to dialyse the suspected organic matter; for 
 this purpose the solid portion is cut into small pieces, the 
 mixed solid and liquid portion is then placed in the 
 dialyser* to the depth of not more than half an inch, the 
 dialyser is then floated in a basin containing a volume of 
 water about four times greater than the organic fluid. 
 After twenty-four hours about three-fourths of the As,0 3 
 
 * The dialyser ought to be about ten inches in diameter, nnd perfectly 
 sound. See the Author's "Second Step in Chemistry," p. 681. 
 
OF THE FIFTH GROUP. 127 
 
 (or other crystalloid poison) will be found in the water of 
 the basin, which is generally colorless. To this liquid, 
 after concentration on the water-bath, all the ordinary 
 tests of arsenic may be applied. 
 
 270. Destruction of the organic matter. — Sulphuric acid, 
 hydrochloric acid and potassic chlorate, chlorine, aqua 
 regia, nitric acid and potassic nitric, sulphuric acid and 
 sodic chloride, have been respectively proposed and re- 
 commended by different chemists for the destruction of the 
 organic matter in the examination for arsenic in medico- 
 legal cases ; we shall describe a few of these methods. 
 
 1st. The organic matter, after it has been minutely 
 divided, is mixed with about a fifth of its weight of pure 
 concentrated H 2 S0 4 , and heated for some time, continually 
 stirring with a glass rod ; the mass becomes brown and 
 finally black, and white fumes of H„S0 4 are evolved along 
 with S0 2 ; the heat must be continued, but not so high as 
 to volatilize any arsenic, until the residue is reduced to a 
 dry friable carbonaceous mass; it is then pulverized, and 
 afterwards treated with a small quantity of concentrated 
 HN0 3 for oxidizing As 2 S 3 , which may have been contained 
 in the suspected matter, or which may have been formed 
 by the simultaneous reduction of H 2 S0 4 and the As s O s 
 during the carbonization ; the mixture is again evaporated 
 to dryness to expel completely the HN0 3 ; it is then boiled 
 in water and filtered, and the filtrate examined for arsenic 
 by Marsh's test. The employment of H 2 S0 4 was proposed 
 by MM. Flandin and Danger. The process is open to 
 some objections ; some NaCl will always be present in the 
 organic matter, and under certain conditions AsCi, will be 
 formed by the reciprocal reaction of the H 2 S0 4 , the NaCl 
 and the As 2 3 ; the AsCl 3 , if formed, will volatilize, and 
 consequently escape detection ;* it is also very difficult to 
 obtain H 2 S0 4 perfectly free from arsenic. 
 
 2d. The employment of HC1 and KC10 3 for the destruc- 
 tion of the organic matter possesses many advantages ; it 
 is certain, and in the examination other metallic poisons 
 as well as arsenic can be sought for and detected, and it 
 allows of a quantitative determination of the poison ; the 
 process is described in par. 733. 
 
 3d. M. Schneider has proposed to separate the arsenic 
 
 * To avoid this loss it has been proposed to conduct the operation in 
 a retort, and collect any matter that distils over in water, but this 
 modification renders the method less simple and convenient. 
 
128 
 
 THE SPECIAL PROPERTIES 
 
 from the organic matter with which it is mixed by con- 
 verting it into the volatile AsCl ? ; for this purpose the 
 organic mixture under examination is inti - oduced into a 
 retort (fig. 3) and a quantity of NaCl added, and then 
 
 Fig. 3. 
 
 through the safety tube a little at a time some pure con- 
 centrated H 2 S0 4 ; the mixture is then distilled, the receiver 
 being kept cool ; the three-bulb tube connected with it con- 
 tains distilled water. It is necessary to keep the NaCl in 
 the retort in excess, to prevent the formation of SO,, when 
 the liquid becomes concentrated in the retort. As AsCl 3 
 is decomposed by H 2 0, it cannot be formed when there is 
 much of that liquid present ; if the oi'ganic mixture contains 
 much water it ought, therefore, to be concentrated by dis- 
 tilling it by the aid of the water-bath before adding the 
 NaCl and H 2 SO\. The distillate is diluted with water and 
 treated with HJ3, and the As,S 3 is reduced by KCy(259), 
 or it is converted into As,O t by means of HNO a ; the excess 
 of the latter being expelled, the As is detected by means of 
 Marsh's method. 
 
 271. Bloxam has proposed to employ the electric current 
 for the conversion of As into H 3 As. This, the electrolytic 
 method of eliminating arsenic, possesses certain advantages 
 over that of Marsh: 1. It avoids the use of Zn, and there- 
 by obviates a frequent source of error arising from the 
 presence of As'in that metal. 2. It introduces no sub- 
 
OP THE FIFTH GROUP. 
 
 129 
 
 stances into the liquid that can interfere with its subsequent 
 examination for other metals. If any other metals are 
 present it precipitates them on the surface of the negative 
 plate. When the AsH 3 is obtained by means of Zn, Sb, if 
 also present, is evolved together with the As, and the sub- 
 sequent separation of these two metals is troublesome ; but 
 with the electrolytic method only a very small quantity 
 of Sb is evolved as SbH s , and even this quantity may be 
 complete^ arrested by adding to the liquid a solution of 
 H 2 S. Both Sb and As are then converted into sulphides, 
 but the As 2 S 3 is converted by the electrolytic hydrogen as 
 easily as As 2 3 into AsH 3 , whereas the Sb 2 S 3 completely 
 resists the action of it, and consequently remains in the 
 liquid. 
 
 272. The apparatus consists of a two-ounce narrow- 
 mouthed bottle, the bottom of which has been cut off and 
 replaced by a piece of vegetable parchment, tightly stretched 
 over it and secured by a ligature of thin platinum wire 
 (a ligature of organic matter is quickly destroyed). The 
 bottle is furnished with a cork, in which is fitted air-tight 
 
 a quill tube bent at right angles ; also a platinum wire, to 
 which is attached a plate of the same metal, which forms 
 the negative pole of the voltaic circuit ; it is also convenient 
 to have fitted in the cork, although it is not shown in fig. 
 4, a funnel tube for introducing the liquid to be tested. 
 
130 THE SPECIAL PROPERTIES 
 
 The bottle is placed within a glass of such a size as to 
 leave a small interval between the two, and this glass is 
 allowed to stand in a vessel of cold water. About an ounce 
 of dilute H 2 S0 4 is introduced into the apparatus, so as to 
 fill the bottle and the outer vessel to about the same level, 
 the positive plate being immersed in the acid in the outer 
 vessel. The current of a voltaic battery (six Grove's cells 
 of ordinary size) is then passed through the arrangement, 
 and when the bottle has become filled with hydrogen the 
 tube is heated to redness during fifteen minutes, to ascertain 
 the purity of the H 2 S0 4 ; the liquid to be tested is then 
 introduced into the bottle by means of the funnel tube, or 
 by a pipette, the cork being removed for an instant ; a 
 drachm of alcohol is also added to prevent frothing ; the 
 heating of the reduction-tube is then continued for thirty 
 minutes before the absence of arsenic is inferred. 
 
 2T3. The following method has been recommended by 
 Bloxam for the detection of poisonous metals by electro- 
 lysis, viz : The mixture, which maj', of course, have been 
 previously examined for organic poisons by the usual 
 methods, is digested on a water-bath, with so much water, 
 HC1, and KC10 3 as may be required to disintegrate the 
 solid organic portions, and to render the liquid capable of 
 filtration; the filtrate is evaporated on the water-bath to 
 a small bulk; it is then treated with an excess of H 2 S 
 water, and introduced into the decomposing cell along 
 with some alcohol, to prevent frothing ; and the passage 
 of the current is continued for about an hour. In the 
 heated tube the As, if present, will be found, and on the 
 negative plate and in the liquid the other poisonous metals 
 will have to be sought for. 1st. As regards the tube, the 
 As, if H 2 S or S0 2 has been introduced into the decom- 
 posing cells, is deposited either in part or entirely as 
 As 2 S 3 in the tube a little beyond the heated portion ; 
 there is generally a deposit also of As, and if an excess of 
 H. 2 S has been employed a deposit of S, which is nearer the 
 orifice than the deposit of As 2 S„ and from which it may 
 easily be distinguished by its much lighter color, and by 
 its insolubility in a warm solution of NHJICO., which 
 readily dissolves As,S,. It is probable that the deposit of 
 As. 2 S 3 is occasioned by the Asll, and H 3 S reacting upon 
 each other under the influence of heat. If H 2 S is added, 
 and no As is present, a thin white film of S will generally 
 be deposited in the tube. 2d. If no H S S has been em- 
 
OF THE FIFTH GROUP. 131 
 
 ployed, the metals to be sought for on the negative plate 
 are Sb, Hg, Cu, and Bi; the plate having been washed, is 
 boiled in somewhat dilute yellow (NH,) 2 S for a minute-or 
 two. This solution is then evaporated on a watch-glass 
 placed in the water-bath, and the orange residue of Sb 2 S 3 
 identified by the usual tests. The platinum plate having 
 been again washed is boiled in a few drops of concentrated 
 HN0 3 , to which a drop of dilute HC1 should be added to 
 dissolve the HgS. The acid solution is boiled down to a 
 small bulk and mixed with an excess of NH^HO, by which 
 the presence of Cu will be rendered evident, and the Bi. 2 O a 
 will be precipitated, together with a little 2NH 4 C1, PtCl t . 
 To examine for Bi the precipitate is dissolved in HC1 
 evaporated and largely diluted with H 2 0. The filtered 
 ammoniacal liquid, acidulated with HC1, and boiled with 
 clean copper, will prove the presence or absence of Hg. If 
 H 2 S has been added, this plan will have to be modified, 
 as the Sb 2 S 3 and other sulphides which have been formed 
 will be found suspended in the liquid of the decomposing 
 cell, and not deposited in the metalline state on the nega- 
 tive plate. 
 
 274. Flame reactions 1. Flame-coloration in upper re- 
 ducing flame pale blue, giving the well-known arsenical 
 smell. 
 
 2. Reduction-film black, dead or brilliant, thin film 
 brown. 
 
 3. Oxide-film white ; touched with a perfectly neutral 
 solution of AgN0 3 , and then blown with ammoniacal air, 
 it gives a canary-yellow precipitate, soluble in NH 4 HO. 
 Together with this yellow precipitate, a brick-red one of 
 silver-arseniate occurs when the film has previously been 
 treated with bromine vapor. SnCl 2 , with aud without soda, 
 produces no change. 
 
 4. Iodide-film is deep yellow, disappears on breathing, 
 but returns on drying; disappears in ammoniacal air, and 
 does not return ; reappears unaltered after the action of 
 HC1. 
 
 5. Sulphide-film lemon yellow, disappears easily on 
 blowing with (NH 4 ),S, and reappears on warming or blow- 
 ing ; insoluble in H,0, and does not disappear by breathing. 
 
 6. Reduction on charcoal splinter yields no metallic bead. 
 
132 THE SPECIAL PROPERTIES 
 
 BEHAVIOR OF ARSENIC ACID AND THE ARSENIATES 
 WITH REAGENTS. 
 
 275. AgNO a produces, in neutral solutions of the arse- 
 mates, a characteristic reddish-brown precipitate of 
 Ag 3 As0 4 , soluble in dilute HN0 3 and in NH.HO ; AgNO a 
 produces, therefore, no precipitate, or only a slight tur- 
 bidity in solutions of H 3 As0 4 , but on neutralizing the 
 acid with NH 4 HO the precipitate appears ; ammonio-nitrate 
 of silver is, therefore, a more appropriate reagent than 
 AgN0 3 if the acid be free. 
 
 276. CuS0 4 produces, in neutral solutions of the arse- 
 mates, a greenish-blue precipitate of CuHAs0 4 . 
 
 277. MgS0 4 , in the presence of NH 4 C1 and of NH 4 HO, 
 produces, in solutions of the arseniates, a white precipitate 
 of MgNH 4 As0 4 , soluble in acids. 
 
 278. H 3 As0 4 produces, not only with magnesian salts, 
 but also with ferric salts and with amnionic molybdate, 
 precipitates similar in appearance and in constitution to 
 those produced by these reagents with H s P0 4 , but it is 
 distinguished from this latter acid by the color of its 
 silver salts, and by its conversion into As 2 S s on being 
 treated with H 2 S. 
 
 279. Nascent H, evolved by the action of Zn on dilute 
 H 2 S0 4 or HC1, converts H 3 AsO„ as it does ASj0 3 , into 
 H 3 As, but the conversion is much slower, and in those re- 
 actions which depend upon the reduction to the metallic 
 state H a As0 4 resembles As 2 O a . 
 
 280. Whether As exists as As 2 3 or as H 3 As0 4 may be 
 ascertained by testing a portion of the original solution 
 with the copper test (257), and another portion of the 
 original solution with the silver (275) or magnesian test 
 (277). 
 
 281. Au and its compounds. — An is the only metal of a 
 yellow color. It unites with nearly all the metals, but its 
 most important alloys are those which it forms with Ag 
 and Cu. The standard gold for coin in England contains 
 8.33 per cent, of Cu. In France and the United States it 
 contains 10 per cent, of Cu. Jewellers frequently alloy 
 their gold with Ag as well as Cu ; the Ag gives it a lighter 
 color. The solder used for gold trinkets is composed of 
 5 parts of Au and 1 part of Cu, or of 4 parts of Au, 1 
 part of Cu, and 1 part of Ag. Gold is always found in 
 the metallic state generally more or less alloyed with Ag. 
 
OF THE FIFTH GROUP. 133 
 
 232. Ferrous salts precipitate Au from its solutions as 
 a bluish-black precipitate, which acquires a metallic lustre 
 when rubbed. 
 
 283. A solution of SnCl a and some SnCl 4 produces, even 
 in very dilute solutions of Au, a purple precipitate (purple 
 of Cassius), the tint of which varies according to the 
 quantity of Au present. The precipitate is insoluble in 
 dilute acids ; the Au solution should be first mixed with 
 the SnClj, and the SnCl 2 then added drop by drop. When 
 the quantity of Au is extremely minute, a pink tinge per- 
 vades the solution. 
 
 284. A very delicate method of applying this test is a3 
 follows : Fe 2 Cl 6 is added to SnCl 2 until a permanent yellow 
 color is produced ; the solution is then considerably di- 
 luted ; the Au solution, having likewise been much diluted, 
 is poured into a beaker, which is placed on a sheet of white 
 paper; a glass rod is dipped into the Fe solution, and 
 afterwards into the Au solution, when, if even a trace of 
 Au be present, a blue or purple streak will be observed in 
 the track of the glass rod. This test has the advantage 
 of being applicable even in very acid solutions. 
 
 285. One other oxide of gold is known, viz. the aurous 
 oxide Au 2 0. It is a green powder, and is obtained by de- 
 composing Au C 3 with a cold solution of KHO. 
 
 286. Pt and its compounds. — Pt in compact masses is 
 white, but in a finely divided state, obtained by precipita- 
 tion, it is as black as soot, and is termed platinum black. 
 It is obtained as a gray, porous, slightly coherent mass, 
 called spongy platinum, by igniting the double chloride 
 of 2NH 4 C1, PtCl 4 . Pt possesses the valuable property of 
 uniting when two masses of it are pressed or hammered 
 together at a high temperature. This operation of uniting 
 masses of metal into one is termed "welding." Wollaston, 
 who first devised a process of working Pt, made use of 
 this property. He purified 'he Pt from other metals by 
 boiling it in HXO,,. He then dissolved it in aqua regia, 
 and converted it into 2NH 4 Cl,PtCl 4 . From this salt he 
 obtained " spongy platinum."' This was heated, com- 
 pressed, and hammered, until it became homogeneous and 
 ductile, and had a sp. gr. of about 21.5. Deville and 
 Debray have lately proposed a new plan. They dissolve 
 out the Pt from its ore by liquid Pb, which does not dis- 
 solve the impurities. The Pb is subsequently separated 
 from the Pt by cupellation, and the Pt is finally melted in 
 a crucible of lime by means of the oxyhydrogen blowpipe. 
 
 12 
 
134 EXERCISES. 
 
 "The most important applications of Pt are confined to the 
 laboratory of the manufacturing and experimental chemist; 
 they depend upon its great infusibility and its power of 
 resisting chemical reagents. Pt always occurs in the me- 
 tallic state, usually in small flattened grains, in which it 
 is mixed with palladium, rhodium, osmium, ruthenium, 
 and iridium — metals which are rarely found except when 
 associated with Pt." 
 
 287. KC1 or NH 4 C1 produces, in solutions of Pt, a 
 yellow crystalline precipitate of 2KC1, PtCl 4 , or 2NH 4 C1, 
 PtCl 4 . The presence of HC1 promotes the formation of 
 this precipitate. Dilute solutions should be evaporated 
 along with the KC1 or NH 4 C1 and the HC1 on the water- 
 bath to dryness, and the residue digested in weak spirits 
 of wine until the excess of the alkaline chloride employed 
 is dissolved. 
 
 288. Solutions of platinic salts produce, in solutions of 
 SnCl 2 , which contain much HC1, a dark brownish-red color ; 
 in exceedingly dilute solutions the color is yellow, and be- 
 comes darker on standing. This test is a very delicate 
 one for Pt. The dark brown color is owing to the reduc- 
 tion of the platinic to a platinous salt. 
 
 289. Platinum forms with oxygen another oxide, viz. 
 platinous oxide (PtO). 
 
 290. Answers to the following exercises must be written 
 out: — 
 
 EXERCISES. 
 
 92. Give the results of the action of Fe"S0 4 and of H.,0 
 on AuCl,. 
 
 93. Give the theory of the method of Marsh for the de- 
 tection of As. 
 
 94. How would you distinguish the product of the action 
 of H a O on SbClj from the similar one produced on BiCl, 
 byH s O? 
 
 95. Describe by equations, the reactions which take place 
 when H 2 S is passed into a solution of arsenious acid, 
 through one of arsenic acid, and through one of tartar 
 emetic. 
 
 96. Describe b3' equations the reactions which take place 
 when a stannous salt is added to a mixture of K 6 Fe 6 Cy„ 
 and Fc.,01,,, and to a solution of HgCl a . 
 
 97. For what purposes is Pt employed in the metallic 
 state, and how is it obtained in mass? 
 
EXERCISES. 135 
 
 98. Describe the method proposed by Schneider for 
 separating As from organic matters. 
 
 99. For what purposes is Sb employed in the arts in the 
 metallic state? 
 
 100. Describe by an equation the reaction which takes 
 place when a mixture of As 2 3 , KHO, and acetate acid is 
 evaporated to dryness, and the residue heated, and what 
 is the name of the arsenic compound which is produced. 
 
 101. Describe the dialytic method of separating crystal- 
 loid poisons from the contents of the stomach. 
 
 102. I have got some copper nickel, NiAs, containing 
 some CoAs 2 , and I wish to prepare some pure nickel : how 
 shall I proceed ? 
 
 103. Give an account of the method of employing elec- 
 trolysis for the separation of As and Sb from liquids con- 
 taining organic matter. 
 
 104. Give the composition of tartar emetic, a method 
 for preparing it, its properties, and the action of chemical 
 reagents upon it. 
 
 105. How would you convert arsenious acid into arsenic 
 acid, and reconvert the latter acid into the former one ; 
 and how would you distinguish solutions of these acids 
 from each other ? 
 
 106. Describe the changes which take place when As 3 S 3 
 is digested with H 3 S0 3 and KHSO :i . 
 
 107. Describe by an equation the changes which take 
 place when H 3 As and H 3 Sb are passed through a solution 
 ofAgNO,. 
 
 108. What is the action of reagents upon argentic and 
 cupric arsenite, and how would you detect the metals in- 
 cluding As in these compounds? 
 
 109. Describe by an equation the changes which take 
 place when a solution of an arsenious compound, KHO, and 
 fragments of Zn are boiled together. 
 
 110. How do you account for the presence of As in HC1 ? 
 
 111. How are gun-barrels bronzed? 
 
 112. How would you detect and how remove the oxides 
 of nitrogen and As 2 3 , so often present as impurities in 
 sulphuric acid ? 
 
 113. To what acid is the term aqua regia applied? and 
 describe its chemical properties. 
 
136 THE SPECIAL PROPERTIES 
 
 SIXTH GROUP. 
 
 Argentic Oxide ( Ag 2 0), Merctjrous Oxide (Hg 3 0), Mer- 
 curic Oxide (HgO), Bismuthoub Oxide (Bi 2 0„), 
 Plumbic Oxide (PbO), Cupric Oxide (CuO), Cadmic 
 Oxide (CdO). 
 
 For the reactions.— AgN0 3 , HgNO„ HgCl 2 , Pb(NO„)„ 
 CuS0 4 , CdCI 2 or CdSO,— dissolved™ H 2 ; BiCl, dissolved 
 in dilute HC1. 
 
 291. The insolubility of AgCl, HgCl, the slight solubility 
 of PbCl 2 , and the ready solubility of the other chlorides, 
 enables one to divide this group into two sections. 
 
 First section The oxides which form with HC1 insoluble 
 
 chlorides are the members of this section. They are Ag 2 0, 
 Hg 2 0, and PbO. 
 
 Second section. — The oxides which do not form with HC1 
 jnsoluble chlorides are the members of this section. They 
 are HgO, Bi 2 3 , CuO, CdO, and PbO, as the slight solu- 
 bility of PbCl 2 in water renders it impossible to confine this 
 member exclusively to the first section — a portion of the 
 PbCl 2 , varying according to the amount of liquid present, 
 always remaining dissolved ; the Pb it contains is precipi- 
 tated along with the members of the second section on the 
 addition of H 2 S. If attention be paid to the following 
 facts, they will frequently remove a source of much con- 
 fusion : 1. If Pb has been discovered in the first section, 
 a precipitate must always be obtained on passing H^ 
 through the filtrate, even if no other member of the group 
 be present. 2. If only a small quanty of Pb be present, 
 HC1 may cause no precipitate, as a sufficient quantity of 
 water may be present to dissolve the chloride formed. Iu 
 this case all the Pb will be found in testing for the mem- 
 bers of the second section. 
 
 292. Examination for the members of the first section. — 
 When a solution is examined for the members of this group 
 only, the general reagent for this section must be added, as 
 directed at par. 355 ; and when a precipitate is produced, 
 it must be washed as there directed, and then examined 
 according to the method described in next par. 
 
 293. Add boiling-water to the precipitate; PbCL, will be 
 dissolved, if present, which is ascertained by H 2 SO, pro- 
 ducing in the filtrate a precipitate of PbS0 4 . If a residue 
 remain after removing the PbCl., by adding snecesively to 
 the mixed chlorides fresh quantities of boiling water, until 
 
OF TIIE SIXTH GROUP. 137 
 
 the last washings give on the addition of H s S0 4 no further 
 precipitate, it proves that either AgCl or HgCl, or both, 
 must be present. NH 4 HO being added to the residue, 
 dissolves the AgCl, whilst it converts HgCl into the black 
 mercurous amnionic compound. To detect the AgCl in 
 the amnionic solution, HN0 3 must be added in excess, 
 which, by neutralizing the solvent, causes the AgCl, if 
 present, to be re-precipitated. 
 
 294. Examination for the members of the second sec- 
 tion. — When a solution is examined for the members of 
 this group onlj>-, the general reagent must be added as di- 
 rected at pars. 357 and 358, and when a precipitate is pro- 
 duced it must be washed until the last washings contain 
 no trace of CI;* it must then be examined according to 
 the next par. 
 
 295. The washed precipitate must be boiled in dilute 
 HN0 3 . If it all dissolves, with tHe exception of a light 
 3'ellow mass of sulphur, HgO is absent ; but if, after boil- 
 ing for some time, the undissolved mass presents a black 
 appearance, it points out the probable presence of that 
 member. Examine the black mass for HgO, as directed 
 in par. 296. To the acid solution, after it has been filtered 
 from the yellow or black mass, and subsequently evapo- 
 rated nearly to dryness, so as to remove! ;the greater part 
 of the free acid, must be added a little -tyater, and then a 
 few drops of dilute H 2 S0 4 , which will precipitate the Pb as 
 PbS0 4 after the lapse of a longer or shorter time ; the so- 
 lution must therefore be allowed to stand some time before 
 NH 4 HO is added. NH 4 HO being added in excess to the 
 filtrate, throws down the Bi (confirm its presence according 
 to par 324). The filtrate from the ammonic precipitate, or 
 the solution with which that reagent has failed to give a 
 precipitate, is divided into two parts, which we shall call 
 A and B. 
 
 A. The A portion is acidulated with acetic acid and tested 
 for Cu, if the presence of that metal has not been already 
 manifested by the blue color of the ammonic solution, by 
 adding to it K 4 FeCy 6 ; if Cu is present, a brownish-red 
 colored precipitate will be produced ; if Cu is absent, the 
 color of the solution will not be altered by the reagent 
 (346). 
 
 * The removal of the CI is ascertained by the wash-water giving no 
 precipitate on the addition of a few drops of a solution of AgN0 3 ; the 
 wash-water to be tested must not be collected with the previous wash- 
 ings, but by itself, and in a clean test-tube. 
 
 12* 
 
1338 
 
 THE SPECIAL PROPERTIES 
 
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OF THE SIXTH GROUP. 
 
 139 
 
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140 THE SPECIAL PROPERTIES 
 
 B. The B portion, when Cu is absent, is examined for Cd 
 in the following manner : (NH 4 ), ; S is added to the am- 
 nionic fluid, and if it produces a yellow precipitate Cd is 
 present. 
 
 When Cu is present, the B portion is examined for Cd 
 in the following manner : Add a small quantity of dilute 
 H 3 S0 4 to the solution and evaporate it to dryness and ig- 
 nite, continuing the ignition until the ammonic salt is 
 expelled ; then add a concentrated solution of NH 4 HCO K , 
 and boil for a short time ; if no precipitate is produced, 
 Cd is absent. If a precipitate is produced, wash it with 
 the NH 4 HCO s solution until all the Cu is removed ; then 
 dissolve the residue in a little dilute HC1, and afterwards 
 add NH 4 HO in excess, and finally one drop of (NH 4 ) 2 S ; 
 if a yellowish precipitate* is produced on the addition of 
 the (NH 4 ) 2 S, Cd is present.f 
 
 If Pb has not been discovered in either section, the 
 black or light-colored precipitate insoluble in HN0 3 ought 
 to be digested in NH 4 A and filtered, to the filtrate add 
 HA in excess, and then a solution of K,Cr0 4 ; if Pb is 
 present, a yellow precipitate, PbCr0 4 ,will be formed. 
 
 296. If a black residue remain after boiling the mixed 
 sulphides in HN0 3 , it must be collected upon a filter, to 
 separate it from the other members, and specially examined 
 for HgO by one of the two following methods: 1st. After 
 having dried the black mass thoroughly in a water-bath, 
 mix it with dry Na a C0 3 , and proceed with the examination 
 for Hg in the way described in par. 319. 2d. Dissolve 
 the black mass in as small a quantity of aqua regia as 
 possible, or dissolve it by heating it with HC1 and a few 
 crystals of KC10 a , then add NH 4 HO in slight excess, and 
 then a slight excess of HC1 ; examine the solution, 
 thus prepared, for Hg by means of copper wire, in the way 
 described at par. 314 or 315. 
 
 297. The following precautions must be attended to in 
 
 * The reason for recommending the addition of only one drop of 
 (NH 4 ),S is this — a small quantity of Cu frequently remains undissolved 
 by the NH 4 IIC0 3 ; in such case, if only a drop of (NH,),S be added, the 
 Cd, if present, will be first precipitated; whereas, if more (NH 4 ) 2 S were 
 added, the Cu would also be preoipitatcd, and consequently obscure tbe 
 Cd. When the color of the preoipitate produced by (NH 4 ),S is black or 
 of a doubtful color, it must, after being washed, be dissolved in UNO., 
 the solution must be evaporated to dryness, and the residue treated us 
 before with the concentrated solution of NH 4 HC0 3 , etc 
 
 f For other methods for the separation of Cd and Cu, see par. 862. 
 
op the sixth cJnour. 141 
 
 analyzing this group: The means, both for separating and 
 detecting the members of the first section are so simple 
 and positive, that no difficulty will be experienced by the 
 student. It may, nevertheless, be as well to observe," that 
 PbCl 2 ought to be completely removed before NH 4 HO is 
 added, for if it is not, a white residue, which is nothing 
 more than PbCl 2 , may remain after the addition of NH^HO, 
 when Hg is absent, which may perplex the student. And 
 if the PbCl 2 be not completely removed before the addition 
 of NH 4 HO, the ammonic solution will appear turbid, owing 
 to the separation of an insoluble basic salt of lead ; this 
 will not, however, interfere with the test for Ag, since it 
 (the basic salt of lead) redissolves upon the addition of 
 HN0 3 . The difficulties which occur in examining the se- 
 cond section will be easily overcome by a little attention. 
 Many erroneous conclusions will be formed if the simple 
 yet necessary precaution of washing the H 2 S precipitate be 
 neglected, because a small quantity of the HC1 employed 
 to precipitate the first section, being left behind, will form 
 with the HN0 3 aqua regia, which, by dissolving the HgS, 
 may cause that member to be overlooked ; and should the 
 mercury thus pass into solution, a compound of that me- 
 tal will be precipitated on the addition of NH 4 HO, which 
 may be mistaken for Bi. The precipitate must, therefore, 
 before it is treated with HN0 3 , be washed with water 
 until the wash-water, acidulated with HN0 3 , gives no pre- 
 cipitate with AgNO.,. It is difficult to free the mass of 
 sulphur, which separates on the addition of HN0 3 , entirely 
 from some of the undecomposed sulphides, which, by com- 
 municating to it a black appearance, might lead to the 
 belief that HgO was present, even in the absence of that 
 member. An experienced eye can generally distinguish 
 between this mixture of undecomposed sulphide and sul- 
 phur, and HgS, the former being light and flocculent, 
 whilst the latter is dense and heavy ; but a safe and legi- 
 timate conclusion can only be arrived at by examining it 
 specially for Hg. A varying amount of H,S0 4 is always 
 formed by dissolving the sulphides in HNO,: a portion of 
 the Pb will therefore be precipitated as sulphate, and 
 remain behind mixed with the substance insoluble in HNO, ; 
 it is necessary, on this account, to examine the insoluble 
 mass for this member, if it should not be met with in its 
 proper place. As PbSO i precipitates from dilute solutions, 
 and especially from those which contain much free acid, 
 only after the lapse of some considerable time, the solution 
 
142 THE SPECIAL PROPERTIES 
 
 ought, after the addition of H 2 S0 4 , to be allowed to stand 
 for a considerable time (an hour) before adding the NH 4 HO. 
 A precipitate will be formed on the addition of NH 4 HO to 
 the solution in HNO s , if either of these reagents contains 
 a trace of Fe, but this precipitate cannot be mistaken for 
 Bi if the confirmatory test be applied. 
 
 PROPERTIES OP THE METALS, THE OXIDES, THE SULPHIDES, 
 THE CHLORIDES, THE NITRATES, THE SULPHATES OP THIS 
 GROUP. 
 
 298. The metals. — None of the metals of this group, 
 when perfectly pure, oxidize in dry air or oxygen at ordi- 
 nary temperatures ; in moist air or oxygen Pb, Bi, Cu, and 
 Cd* undergo a slight superficial oxidation ; these four 
 metals oxidize rapidly on exposure to air or oxygen at a 
 red heat, PbO,f Bi 2 3 , CuO, and CdO being formed. Ag 
 does not oxidize in air or at any temperature ; Hg oxi- 
 dizes at 371° C, HgO being formed ; at 427° C. the oxide 
 is decomposed into its elements. Ag, Hg, Pb do not de- 
 compose H 2 0, even at a very elevated temperature; Bi 
 and Cu decompose it at slightly elevated temperatures, and 
 Cd decomposes it at a red heat. Cd is the only metal in this 
 group which can displace the hydrogen in H 2 SO t ; the 
 action takes place even when the acid is dilute, CdS0 4 and 
 H 2 being formed ; the dilute acid, and even the undiluted 
 acid in the cold, has no action on the other metals,^ but 
 if they are boiled in the undiluted acid they become.-.oxi- 
 dized, sulphates of the metals, H 2 and S0 2 , beingfeirtned.§ 
 HC1 in solution has no action on Hg, and it onj$ acts ou 
 Ag, Pb, Bi, and Cu when they are boiled iu it. and even 
 then very slowly ;|| it acts readily on Cd, CdCl 2 and H s 
 being formed. HCl in the gaseous state acts on Ag and 
 Cu, when they are heated to redness in it, a chloride of the 
 metal and H 2 being formed. HNO, oxidizes and dissolves 
 
 * Pb, Bi, and Cd oxidize if exposed to the combined action of air and 
 water. 
 
 + At a low red heat red lead (2PbO, Pb0 2 ) is formed. 
 
 % If oopper-foil be moistened with dilute U 2 S0 4 and then exposed to 
 the air, CuS0 4 will be formed. 
 
 g A portion of H.80 4 , in its action on Ou, suffers more complete de- 
 composition, for sulphur is deposited. 
 
 || HCl with excess of air dissolves Cu at ordinary temperatures ; the 
 weaker acids, suoh as the acetio, have no effect upon Cu unless assisted 
 by the oxygen of the air ; the oopper under such circumstances rapidly 
 combines with 0, and a salt of the aoid is formed. 
 
OP THE SIXTH GROUP. 143 
 
 all the metals of this group, a nitrate of the metal being 
 formed, and generally NO (nitric oxide) is the other ni- 
 trogen compound produced ; but the degree of reducing 
 action which these and other metals exercise on HN0 3 
 varies with the strength of the acid and the temperature; 
 for example, when Ag is acted upon by dilute HN0 2 in ex- 
 cess at ordinary temperatures, AgN0 3 and HN0 2 (nitrous 
 acid) and the anhydride -are formed, but at higher tem- 
 peratures the oxide of nitrogen formed is NO. When Cu 
 and Hg are acted upon by HN0 3 of moderate concentration, 
 NO is disengaged, but with a stronger acid N 2 4 (nitric 
 peroxide) is evolved, and if the action takes place at a 
 higher temperature N is generally one of the gaseous sub- 
 stances set free. 
 
 299. The oxides.— PbO, Bi 2 3 , CuO, and CdO, may be 
 formed either by exposing the metals to a red heat, in air 
 or oxygen, or by igniting their hydrates, carbonates, or 
 nitrates. HgO may be formed either by heating Hg(N0 3 ) 2 
 or by heating Hg in air at a temperature of 371° C. Ag 2 
 and Hg 2 may be obtained by adding to a solution of any 
 ' of their soluble salts a solution of KHO or NaHO, and 
 drying the precipitate with care. Ag 2 0, Hg a O, and PbO 
 are perceptibly soluble in H 2 0, the other oxides are not. 
 Ag 2 0, Hg 2 0, and HgO are decomposed by heat alone, the 
 other oxides are not, they are, however, reduced to the 
 ■metallic state on being heated in a current of H, or by 
 being ignited in contact with C, and PbO and Bi a 3 are 
 reduced on being heated in an atmosphere of CO. The 
 metals are obtained on fusing their oxides with KCy, po- 
 tassic cyanate being formed. On being heated with an 
 excess of S these oxides are converted into sulphides, S0 2 
 being evolved. Dry CI converts them into chlorides, the 
 conversion in the case of Ag 2 0, Hg 2 0, and HgO takes 
 place without the aid of heat ; PbO, suspended in H 2 0, is 
 converted by CI into Pb0 2 and PbCl 2 , a similar reaction 
 takes place with Br. Some of the other oxides are con- 
 verted by CI in the presence of a solution of KHO into 
 higher oxides. They all form hydrates with the exception 
 of Hg 2 0. The hydrate of argentine oxide, when dried at a 
 temperature above 60° O, is decomposed into Ag 2 and 
 H 2 0. The hydrates are formed by adding to the solution 
 of these salts one of the alkalies in excess. The behavior 
 of these oxides with the volatile and fixed alkalies is given 
 in Table VI. Ag 2 0, Hg 2 0, and CuO are black; HgO is 
 black when hot, light red when cold ; Bi a 3 is yellow, PbO 
 
144 THE SPECIAL PROPERTIES 
 
 is also yellow or reddish-yellow; CdO is brown or yellow- 
 ish-brown ; AgHO is brown, HgH 2 0„ is yellow, CuH 2 2 is 
 light blue, and PbH 2 2 , CdH,0 2 , and Bi 2 H 6 6 are white. 
 
 300. The sulphides The sulphides of this group are 
 
 insoluble in water, and dilute acids in the cold. Ag 2 S, 
 PbS, Bi 2 S 8 , CdS are also insoluble in the alkalies, alkaline 
 sulphides, and KCy ; Hg 2 S and HgS are insoluble in solu- 
 tions of the alkalies, amnionic- sulphide, and KC3', but 
 these sulphides dissolve in K 2 S or Naj3 in the presence 
 of NaHO or KHO, the solution in the case of Hg 2 S being 
 attended with a separation of Hg. CuS is insoluble in the 
 caustic alkalies, and in the fixed alkaline sulphides it dis- 
 solves only to a very trifling extent, but it is a little more 
 soluble in amnionic sulphide ; it is soluble in a solution of 
 KCy. They are all decomposed and dissolved with sepa- 
 ration of sulphur in boiling HN0 3 , with the exception of 
 Hg 2 S and HgS ; these latter, and also the other sulphides, 
 are decomposed and dissolved by aqua regia. Out of con- 
 tact with the air Hg 2 S is decomposed at a gentle heat into 
 Hg and HgS, which sublimes without fusing or decom- 
 posing ; Bi 2 S 3 volatilizes at a red heat ; PbS fuses at a red 
 heat and volatilizes at a stronger heat without decom- 
 posing ; CuS loses one-half its S on being heated, and be- 
 comes converted in Cu 2 S, which is not decomposed by 
 heat alone. If heated in a current of air or O they are 
 decomposed, Hg and Ag being left in the metallic state, 
 the other metals are left as oxides ; CuS in the moist state 
 oxidizes on exposure to the air at ordinary temperatures. 
 HgS, Ag 2 S, PbS, Bi 2 S 3 are reduced to the metallic state on 
 being heated strongly in a current of H; Cu 2 S is not re- 
 duced. Some of these sulphides, and probably all, undergo 
 partial decomposition on being heated in a current of 
 steam. On fusion with many metals, as Fe, Zn, Cu, Pb, 
 Sn, Sb, etc., HgS and Ag 2 S are decomposed, the added 
 metal taking the S; PbS is deprived of its S by Fe, Zn, 
 Cu, Sn, etc.; Cu 2 S is not completely decomposed on fusing 
 it with Fe, Sn, or Sb. If Cu^.S* or Ag 2 S is roasted with 
 NaCl, CuCl or AgCl and Na,S0 4 are formed. If a solu- 
 tion of CuCl 2 and NaCl is added to -Ag.S, AgCl and CuS 
 are formed. PbO and CuO, mixed with their sulphides in 
 equivalent proportions and heated, yield the metals and 
 SO„; and a mixture of their sulphates and sulphides in 
 
 * FoSj on being roasted with NaCl becomes oonvcrted into FejCl 6 , 
 Nn 8 S0 4 being formed. 
 
OF THE SIXTH GROUP. 145 
 
 equivalent proportions, on being heated, likewise yields 
 the metal and S0 2 , thus: — 
 
 PbS + PbSO t = 2Pb + 2S0 2 . 
 
 The colors of the sulphides, when obtained by precipita- 
 tion, are given in the table, with the exception of those of 
 Hg 2 S and Ag 2 S, which are black. They can be obtained 
 in the dry way by heating together the metal and S, with 
 the exception of Hg 3 S and CuS ; their color, when so ob- 
 tained, is the same as that of the native sulphides; the 
 artificial or native Ag 2 S is blackish gray, PbS and Bi a S 3 are 
 lead gray, the color of CdS is the same as that of the precipi- 
 tated sulphide ; HgS exists both amorphous and crystalline, 
 the crystalline sulphide in mass is of a cochineal color and 
 is called cinnabar, its powder is scarlet and is called ver- 
 milion; the amorphous sulphide is black, it is converted 
 into the red both by sublimation and by the action of 
 aqueous alkaline persulphides ; the red is converted into the 
 black by heating it moderately out of contact of the air. 
 
 301. The chlorides.— CuCl 2 , CdCl a , and BiCl, may be 
 obtained by dissolving their oxides or carbonates in HC1 ; 
 HgCl (calomel), AgCl, and PbCl 2 are best formed by add- 
 ing to any of their soluble salts in solution HC1 or an 
 alkaline chloride in solution ; HgCl 2 (corrosive sublimate) 
 may be formed by dissolving HgO in boiling dilute HCI. 
 In the dry way HgCl is formed by triturating equivalent 
 proportions of Hg and HgCl 3 until the metallic globules 
 disappear, and then subliming the mixture. HgCl 2 is 
 formed by mixing intimately 2£ parts of HgS0 2 and 1 part 
 of NaCl, and then subliming the mixture, and BiCl 3 may 
 be formed by heating Bi in CI, or by mixing Bi in fine 
 powder with twice its weight of HgCl 2 and then distilling. 
 HgCl and AgCl are insoluble, but the latter is soluble in 
 strong solutions of NaCl. PbCl 2 is difficultly soluble, the 
 other chlorides are soluble in water ; BiCl 3 is decomposed 
 by H 2 0, BiOCl being formed, which is insoluble in H 2 0, 
 but soluble in diluted HCI. The chlorides of this group 
 are not decomposed by heat alone ; on being heated HgCl 
 volatilizes below a red heat and without first melting ; 
 HgCl.,, BiCl 3 , and CdCl 2 fuse before volatilizing; the first 
 of these boils at 295°, the other two volatilize at a mode- 
 rate heat; AgCl volatilizes partially at a red heat; PbCl 2 
 not in contact with the air volatilizes at high temperatures, 
 but in contact with air a portion volatilizes with excess of 
 CI, whilst a residue of PbO, PbCl 2 remains; CuCl 2 at a 
 13 
 
146 THE SPECIAL PROPERTIES 
 
 red heat loses half its CI, CuCl remaining. They are all 
 decomposed on being heated in a brisk current of hy- 
 drogen. They are all, with the exception of the mercury 
 chlorides, decomposed when heated in a. current of steam, 
 the metal being left in the state of oxide, excepting in the 
 case of bismuth and silver, the former of these being left 
 as an oxychloride, the latter in the metallic state. With 
 the exception of AgCl, HgCI, and HgCl 2 , they are all con- 
 verted into oxides on being heated in a current of O or of 
 atmospheric air. 
 
 302. The nitrates The oxides and their hydrates are 
 
 readily soluble in HN0 3 , most of them form basic as well 
 as neutral nitrates ; the neutral nitrates are all soluble in 
 water; Pb(NO„) 2 and Bi(N0 3 ) 3 are, however, only sparingly 
 soluble in H 2 6; HgN0 3 , Hg(N0 3 ) 2 , Bi(NO,), are decom- 
 posed by H 2 0, an insoluble, or sparingly soluble, salt being 
 one of the substances formed. Freshly precipitated Ag 2 
 decomposes Cu(N0 3 ) 2 by boiling the oxide in a solution of 
 that salt, CuO being precipitated, and AgX0 3 (lunar 
 caustic) being formed. 
 
 303. The sulphates. — Bi a 3 , CuO, CdO, and their hy- 
 drates dissolve readily in diluted H 2 S0 4 . HgS0 4 is decom- 
 posed by H 2 into a sparingly soluble basic salt. PbS0 4 
 is insoluble in water, the sulphates of the other metals are 
 soluble ; Hg 2 S0 4 is decomposed by H 3 0, especially if hot, 
 into a soluble acid and insoluble basic salt"; under certain 
 circumstances Bi 2 (S0 4 ) 3 is decomposed by H 2 into an in- 
 soluble salt. PbS0 4 is not decomposed by heat alone, the 
 other sulphates are ; but Agj30 4 is very difficultly reduced 
 by heat, it is not decomposed by a red heat, bearing a 
 much higher temperature than CuS0 4 , FeS0 4 , and Fe 2 3S0 4 . 
 
 304. The general characters of the salts of this group. — 
 The salts of Pb, Cd, and Bi are colorless if the acid be 
 colorless ; the soluble silver salts are colorless, so are 
 many of the mercury salts, but some of the basic mercuric 
 salts are yellow; many of the silver salts acquire a violet 
 tint, and ultimate^ turn black on exposure to light ; the 
 cupric salts in the anhydrous state are white, but in the 
 hydrous state they are blue or greenish-blue, which color 
 their solutions exhibit even when much diluted. The solu- 
 ble neutral silver salts are neutral, but the soluble neutral 
 salts of the other metals of the group are acid, to test- 
 paper. The mercurous and mercuric salts volatilize when 
 heated either with or without decomposition ; the soluble 
 neutral salts of Ag, Bi, Cd, and Cu are decomposed at a 
 
OF THE SIXTH GROUP. 147 
 
 red heat; the plumbic salts sustain a red heat without 
 alteration, unless the acid is very volatile or decomposable. 
 The basic salts of Pb are alkaline to test-paper. Nearly 
 all the silver salts are anhydrous. Ag and Hg are pre- 
 cipitated from the solutions of their soluble salts by many 
 reducing agents, as S0 2 , FeSO,, and by the following 
 metals: Fe, Zn, As, Sb, Sn, Bi, Cu, Cd, Pb; and Hg 
 also precipitates Ag. Fe, Zn, and other metals separate 
 Ag from AgCl in the presence of H 3 0. Hg, on being 
 separated, frequently forms an amalgam with the metal; 
 Bi is precipitated from its solutions by Zn, Fe, Sn, Cd, 
 Pb, and Cu; Pb is thrown down by Zn, Cd, Sn, and 
 slowly by Fe ; Cu is precipitated by Zn, Fe, Cd, Sn, Pb ; 
 and Cd is precipitated from its solutions by Zn. BaC0 3 or 
 CaCO.,precipitates CuO, Hg 2 0, HgO, Bi 2 3 , as hydrates from 
 solutions of their salts by digesting them in the solution. 
 
 REMARKS ON THE INDIVIDUAL MEMBERS OF THIS GROUP, 
 WITH ADDITIONAL SPECIAL TESTS. 
 
 305. Ag and its compounds Ag is the whitest of all 
 
 metals; in the finely divided state, as obtained by the 
 precipitation of metals, it is a dull dark gray powder. It 
 is harder than Au, and softer than Cu. It melts at a 
 white heat. Its conductivity for electricity and heat is 
 greater than that of any other metal; its conductivity de- 
 creases with the temperature. It combines with CI, Br, I, 
 at ordinary temperatures, and readily with S, P, and As. 
 It undergoes no change when heated in contact with 
 melted alkaline nitrates or with the hydrates of the alka- 
 lies ; crucibles of silver are, therefore, very useful when 
 these substances have to be fused, as Pt is acted upon by 
 them in their fused state. The affinity of Ag 2 for acids 
 is greater than that of CuO and ZnO. Ag 2 Q is insoluble 
 in the fixed alkalies, but readily soluble in NH 4 HO, with 
 which it combines, giving rise to a dangerous compound 
 (fulminating silver), the composition of which has not 
 been ascertained with certainty ; by some it is supposed 
 to be a compound of Ag 2 and NH 3 , by others an amide 
 or nitride of silver. AgCl, when strongy heated, melts, 
 and on cooling has the appearance of horn, from which 
 circumstance it has been named horn silver. If recently 
 precipitated and still moist AgCl is boiled with excess of 
 KHO, it is converted into Ag 2 0. By the action of light 
 argentic salts turn black, and are readily decomposed, Ag 
 
148 THE SPECIAL PROPERTIES 
 
 being separated; if any oxidizable matter is present, and 
 even when no organic- matter is present, many of them 
 acquire a violet tint, and ultimately turn black. Silver 
 forms the best surface for reflectors by reason of its supe- 
 rior power for reflecting light. Pure silver is unfitted for 
 the manufacture of coins or other articles intended for 
 useful purposes, owing to its softness ; it is, therefore, 
 alloyed with a small quantity of Cu, which increases its 
 hardness without affecting its color much ; the proportion 
 of Cu in the "standard" silver employed for coinage varies 
 in different countries ; in England it amounts to 7.5 per 
 cent., and in Trance to 10 per cent. Silver solder is an 
 alloy of Ag, Cu, and Zn, containing about 66 per cent, of 
 
 -Ag- 
 
 306. The principal minerals of this metal are the sul- 
 phide (silver glance, Ag 2 S), the chloride (horn silver, 
 AgCl), sulphide or silver and arsenic (3Ag 2 S -f As 2 S 3 ), 
 and sulphide of silver and antimony (3Ag„S -)- Sb 2 S s ) ; 
 silver is also met with in the metallic state. It is likewise 
 found in small quantities in most lead and copper ores. 
 
 30 7. When silver compounds, mixed with carbonate of 
 soda, are subjected on charcoal to the inner blowpipe flame, 
 brilliant metallic globules are produced, which are not 
 attended with any incrustation. 
 
 308. " If silver occurs only in traces in slags or complex 
 ores, it can only be detected by the well-known method of 
 cupellation. If, however, the silver compound is not mixed 
 with a very large amount of foreign matter, it can be de- 
 tected in very minute quantities by reduction with soda on 
 the charcoal splinter. The white ductile beads dissolve 
 easily on warming in dilute KN T 3 , and yield AgCl with 
 HC1, which can then readily be recognized by its behavior 
 with UNO, and NH 4 HO. Less than one-tenth of a milli- 
 gramme of silver can thus be easily detected with cer- 
 tainty." — Bunsen. 
 
 Characteristic reactions.— That with HC1 and the solu- 
 bility of the AgCl in NH 4 HO. 
 
 309. Ag forms at least one other oxide, the neutral 
 peroxide, Ag 2 0,, which is formed by decomposing by the 
 voltaic current a weak solution of AgXO, ; there is' also 
 some reason to believe in the existence of a suboxide 
 Ag/). Both these oxides, if the latter exists, are decom- 
 posed by acids, argentic salts being formed. 
 
 310. Hg and its compounds — Hg is the only metal that 
 is fluid at common temperatures. It freezes at 39°, and 
 
OF THE SIXTH GROUP. 149 
 
 boils at 350° C. It enters into combination with CI and 
 Br at ordinary temperatures. It combines with I and S in 
 the cold, if triturated with them. HI and H 2 S are slowly 
 decomposed by it, H being evolved. It combines with 
 most of the metals at ordinary temperatures, forming alloys 
 which are termed amalgams. Hg 2 is so unstable that it 
 is decomposed even when dry on exposure to diffuse day- 
 light into HgO and Hg. HgO is obtained in the form of 
 red scales by the ignition of Hg(N0 3 )„ and in the form of 
 a bright yellow powder by adding KHO to solutions of 
 mercuric salts. When the scales are heated they become 
 nearly black, but on cooling the red color returns. HgO 
 forms a soluble compound with BaO. H 2 C 2 4 combines 
 with the yellow oxide in the cold, but does not act on the 
 red oxide; an alcoholic solution of HgCl 2 converts the 
 yellow oxide into the black oxychloride, but it does 
 not act on the red oxide. When NH 4 HO is added to the 
 yellow oxide, a yellowish-white amorphous powder is pro- 
 duced, which is the hydrate of a powerful base, mercuramine 
 (Hg 4 H 4 N 2 3 , 3H 2 0). The precipitate produced by K 2 CO, 
 in solutions of HgCl 2 is the yellow oxide ; that by KHCO s 
 is the red oxychloride. 
 
 311. The fixed alkalies, like NH..HO, change HgCl into 
 a black compound ; but the compound produced by the 
 action of the fixed alkalies on HgCl is Hg 2 0, whilst the 
 compound produced by XH 4 HO is, as is shown in the 
 table, diniercurous-ammonic chloride. The following is 
 the reaction : 2HgCl + 2NH 4 HO = Hg 2 H 2 NCl + NH 4 C1 
 + 2H 2 0. NH 3 is absorbed by HgCl, mercurous-ammonic 
 chloride being formed, thus : HgCl -f NH, = HgH s NCl. 
 
 312. NH 4 HO, added in excess to a solution of HgCl ? , 
 produces a white precipitate of dimercuric diammonic di- 
 chloride (Hg 2 H„N 2 Cl 2 ). This substance is used in medicine 
 under the name "white precipitate." The action of NH 4 H0 
 on the two mercury chlorides is very analogous. The 
 following is the reaction on HgCl 2 : — 
 
 2HgCl 2 + 4NH 4 HO = Hg 2 H 4 N 2 Cl 2 + 2NH 4 C1 + 4H 2 0. 
 
 If on the addition of NH 4 HO to the HgCl 2 solution the 
 latter is maintained in considerable excess, the precipitate 
 has a different composition to what it has in the preceding 
 case. The empirical formula of the precipitate in this 
 latter case is Hg 4 H 4 N.,Cl„; its rational formula may be 
 Ho- H N CI + 2Ho-Cl„ a double salt, composed of one 
 °- •> - - ' 13* 
 
150 THE SPECIAL PROPERTIES 
 
 equivalent of diraercuric diammonic dichloride and two 
 equivalents of mercuric chloride. 
 
 313. For the action of soluble iodides on mercurous and 
 mercuric salts see pars. 478 and 479. 
 
 314. The presence of Hg may be detected in solution by 
 placing in it a small strip of Zn, round which a thin strip 
 of gold foil is twisted. The Hg will be deposited on the 
 Au by voltaic action in the form of a white stain, which 
 disappears on heating the Au to redness. 
 
 315. Cu, introduced into a solution of a mercurous or a 
 mercuric salt, especially after adding HC1, becomes covered 
 with a white lustrous coating; when moderately heated, 
 the Cu regains it original color, vapors of Hg being evolved : 
 this test is exceedingly delicate. Slips of copper wire, 
 about an inch in length, may be used ; they should be 
 cleaned by shaking for a few moments with concentrated 
 HN0 3 , and thoroughly washed. Half a dozen such slips 
 should be boiled for three or four minutes in the solution, 
 previously acidulated with HC1 ; they are then well rinsed, 
 dried by pressure between blotting-paper, and heated in a 
 glass tube of one-quarter of an inch diameter, constructed 
 so as to allow the passage of a feeble current of air. A 
 coating of minute globules of Hg is formed upon the cool 
 part of the tube ; these may be united into larger globules 
 by rubbing with a glass rod. The copper wire being 
 removed, a- very minute particle of I may be introduced 
 into the tube, and a gentle heat applied to vaporize it. 
 The sublimate of Hg will thus be converted into Hgl„ 
 which is yellow at first, and becomes scarlet when rubbed 
 with a glass rod. 
 
 316. If SnCl 2 be added in small quantity to mercuric 
 salts, it reduces them to mercurous salts, and, as a conse- 
 quence, HgCl precipitates ; but if it be added in excess, 
 the mercury salt (mercurous as well as mercuric) is com- 
 pletely decomposed, Hg being thrown down as a gray 
 precipitate, which maj' be united into globules by heat and 
 agitation — but most readily by boiling the metallic deposit, 
 after decantation of the supernatant fluid, with HC1. 
 
 317. Detection of Hg in organic liquids Acidify with 
 
 a few drops of HC1 ; add a few strips of copper wire or foil, 
 and boil for about half an hour; then remove the Cu from 
 the liquid and wash it with a little dilute solution of 
 NH 4 HO, so as to remove any copper oxide ; then dry it by 
 gentle pressure between folds of bibulous paper, and ex- 
 amine it according to par. 315. 
 
OF THE SIXTH GEOUP. 151 
 
 318. Detection of 'Hg in organic solids. — The solid cut into 
 small pieces is heated with HC1 and KC10 3 , as directed in 
 par. 733 ; after being boiled for a few minutes, it must, 
 after cooling, be filtered, and the filtrate evaporated to a 
 small bulk ; if any solid separates during the evaporation, 
 it is again filtered, washed H 2 S is passed through the con- 
 centrated fluid ; if a black precipitate is formed, it must be 
 collected upon a filter, and washed with H 2 until all CI is 
 removed, and then purified by boiling it in dilute HN0 3 ; 
 it is afterwards dissolved in as small a quantity of aqua 
 regia as possible, and examined for Hg according to par. 
 296— 2d. 
 
 319. Solid compounds of Hg, mixed with a large excess 
 (at least twelve parts) of dry Na 2 CO.„ and heated in a 
 perfectly dry tube of hard glass, having a diameter of 
 about one-quarter of an inch, and expanded into a bulb at 
 one end, furnish minute globules, Hg, which are deposited 
 on the cool part of the tube and may be united into larger 
 globules by rubbing with a glass rod. This test is exceed- 
 ingly delicate ; in order that it may be perfectly successful, 
 the Hg compound should be thoroughly dried (in a water 
 bath) , and the Na 2 C0 3 should be ignited immediately 
 previous to use. In order to prevent the sublimation of 
 undecomposed Hg compounds, it is well to cover the mix- 
 ture in the bulb-tube with a layer of pure Na 2 C0 3 . 
 
 320. The chief mineral of this metal is the mercuric sul- 
 phide {cinnabar) ; it is likewise met with in the metallic 
 state. 
 
 321. Flame reactions (a) Metallic film is mouse-gray, 
 
 noncoherent, and spreads over the whole basin. To obtain 
 small traces of Hg in the reduced state, the sample is mixed 
 with soda and KN0 3 and filled into a thin test-tube five 
 to six millims. wide and ten to twenty millims. long This 
 is held by a Pt wire in the flame, whilst the bottom of the 
 basin, filled with cold water, is placed close above the open 
 end of the tube. If the quantity of Hg is considerable, it 
 collects in the form of globules, which can be seen with a 
 lens, and which can be collected into larger drops by wiping 
 the basin with a piece of moistened filter-paper. 
 
 (c) Iodide-film is obtained by breathing on the metallic 
 film, and then placing it over the vessel (fig. 8 of the Plate) 
 containing moist Br. It first becomes 'black, and then 
 disappears, but not until after some time ; HgBr 2 is formed. 
 If the basin be now placed above the vessel of fuming HI, 
 a very characteristic carmine-colored film of Hgl 2 is pro- 
 
152 THE SPECIAL PROPERTIES 
 
 duced ; this is often accompained by Hgl, but neither of 
 these disappears on breathing, nor when blown with 
 amnionic air. 
 
 (d) Sulphide-film black, not altered by breathing or by 
 blowing with (NH 4 ),S — Bunsen. 
 
 Characteristic reactions For mercurous compounds 
 
 those with HC1 and NH 4 HO. For mercuric compounds 
 those with KI, NH 4 HO, and KHO 
 
 322. No other oxides of Hg are known. 
 
 323. Bi and its compounds. — The color of Bi is reddish- 
 white ; it is hard and brittle, and wiien pure crystallizes 
 more readily than any other metal. It melts at 264° C, 
 and it volatilizes at high temperatures. If projected into 
 an atmosphere of CI it takes fire; it also unites readily 
 with I, Br, and S. Bi 2 8 melts at a red heat ; it and the 
 hydrate are both readily soluble in dilute mineral acids. 
 The hydrate is dehydrated on boiling it in solutions of 
 KHO. Many of the bismuthic salts crystallize well, but 
 they cannot exist in solution unless an excess of acid is 
 present, as they are decomposed by water (and this is one 
 of their distinguishing characters) into insoluble basic and 
 soluble acid salts ; this property is exhibited in the most 
 decided manner by the chloride. Bi is found principally 
 in the metallic state. Pewter and Britannia metal are 
 alloys of Cu, Sn, Sb, and Bi. Newton's fusible metal and 
 the metal for calico-printing blocks are alloys of Sn, Pb, 
 and Bi. 
 
 324. The decomposition of the chloride by H,0 is em- 
 ployed as a confirmatory test for Bi. The precipitate pro- 
 duced by NH,HO is dissolved in a small quantity of HC1, 
 evaporated to all but dryness, and is then poured into a 
 large quantity of water ; when Bi is present, a milky 
 turbidness will be produced. 
 
 325. K. 2 Cr0 4 throws down from solution of Bi the tellow 
 chromate. Bi a (Cr0 4 ), differs from PbCr0 4 by its solubility 
 in dilute HNO,, and its insolubility in KHO. 
 
 326. For detecting Bi in the presence of Pb, see par 337. 
 
 327. When bismuth compounds mixed with Na.,C0 3 are 
 exposed on charcoal to the inner blowpipe flame, brittle 
 metallic globules are obtained, attended with a yellow 
 incrustation of Bi 2 O a . 
 
 328. Flame reactions (b) Reduction-film black, dead 
 
 or brilliant; thin portion of film brownish-black. 
 
 (<■) Oxide-film light yellow ; unaltered by AgNO, with 
 
OF THE SIXTH GROUP. 153 
 
 or without ammonia ; gives no reaction with SnCl 2 , but 
 yields black precipitate of Bi 2 2 on addition of NaHO. 
 
 (d) Iodide-film is very characteristic, and remarkable 
 for the number of tints which it assumes. The thick part 
 is of a brown or blackish-brown color, with a shade of 
 lavender blue ; the thin film vai'ies from flesh color to light 
 pink ; it easily disappears on breathing, and appears again 
 on blowing. In a stream of amnionic air it passes from 
 pink to orange, and on blowing or warming it again attains 
 a chestnut-brown color ; it resembles the oxide-film in its 
 behavior with SnCl 2 and NaHO. 
 
 (e) Sulphide-film is of a burnt umber color ; the thin 
 parts are of a lighter coffee-brown color, does not disappear 
 on blowing, and is not soluble in (NH 4 ) 2 S. 
 
 {/) On charcoal splinter with soda the bismuth com- 
 pounds are reduced to a metallic bead, yielding, when 
 rubbed in the mortar, bright, shining, yellowish splinters of 
 metal soluble in HX0 3 . The solution gives, with SnCl 2 
 and NaHO, black Bi. 2 2 . 
 
 Characteristic. — The decomposition of the chloride by 
 water, the reaction with K 2 Cr0 4 , and the flame reactions. 
 
 329. Three other oxides of Bi are known, viz. bismuthie 
 anhydride (Bi a 5 ), also Bi 2 4 , which may be regarded as a 
 compound of Bi 2 s and Bi 2 5 , and a dioxide, Bi 2 2 . The 
 first of these oxides is obtained by passing CI into a strong 
 solution of KHO, in which is suspended bismuthous 
 hydrate ; a blood-red solution of potassic bismuthate and 
 a red precipitate is formed. The red precipitate is digested 
 in HN0 3 to remove the bismuthous oxide, with which it 
 is always mixed ; a red powder is left, which is bismuthie 
 acid, HBi0 3 . By a heat of 210° it is rendered anhydrous, 
 and assumes a brown color. At a somewhat higher tem- 
 perature it loses oxygen, and becomes converted into the 
 second oxide, Bi 2 4 . Bi^O, is obtained by treating equiva- 
 lent quantities of BiCl, and SnCl 2 with an excess of KHO, 
 filtering and drying in an atmosphere of CO ; it is black 
 in color, and takes fire when heated in the air, being con- 
 verted into Bi 2 3 . 
 
 230. Cd and its compounds. — This metal is of a white 
 color ; it is soft, it melts below a red heat ; it is more 
 volatile than Zn, and it volatilizes somewhat below the 
 boiling-point of Hg. CdO is quite fixed in the fire, and 
 does not melt at the strongest white heat. CdO and its 
 hydrate are both easily soluble in dilute mineral acids ; most 
 of the salts of Cd are soluble in water. Cd occurs only in 
 
154 THE SPECIAL PROPERTIES 
 
 zinc ores. It is found as sulphide in zinc blende, and as 
 oxide or carbonate in calamine. 
 
 331. When compounds of Cd, mixed with Na 2 C0 3 or 
 other reducing agents, are exposed on charcoal to the 
 inner blowpipe flame, the charcoal becomes covered with 
 a yellow or reddish-yellow incrustation of CdO. 
 
 332. Flame reactions. — (a) Metallic-film black ; the thin 
 parts brown. 
 
 (b) Oxide-film brownish-black, shading off through brown 
 to a white invisible film of suboxide, which is not altered 
 by stannous chloride, either alone or with soda ; AgNO, 
 produces a blackish-blue coloration of reduced metal, which 
 is very characteristic and does not disappear on addition 
 of Nil, HO. 
 
 (c) Iodide-film white, no change produced by NH 4 HO. 
 
 (d) Sulphide-film lernon-3-ellow, insoluble in ammonia. 
 
 (e) Reduction on charcoal splinter with soda. — The metal, 
 owing to its volatility, can only with difficulty be obtained 
 as a silver-white ductile bead. 
 
 Characteristic reactions The color of the sulphide and 
 
 the flame reactions. 
 
 333. Cd forms another oxide, Cd 2 ; it is obtained by 
 heating CdC a 4 ; it is a green powder, and is decomposed 
 by heat or acids into Cd and CdO. 
 
 334. Pb and its compounds Pb is of a bluish-white 
 
 color; when cut, the fresh surfaces have considerable 
 lustre ; it is very soft, malleable, and ductile ; it leaves a 
 streak upon paper ; it fuses completely at 335° C, and at 
 a red heat gives off vapors. It combines directly with S, 
 P, and As, and alloys with most of the metals. The chief 
 of the useful alloys of which this metal is a constituent 
 have already been noticed. It is readily oxidized by CuO, 
 which is reduced to the state of Cu a O. PbO in commerce 
 frequently goes under the name of massicot, and when 
 partially fused is called litharge. PbO melts readily at a 
 low red heat, and dissolves glass and earthenware, forming 
 readily fusible silicates. It has a considerable affinity for 
 acids ; the best solvent both for it and the hydrate is HK0 3 
 or acetic acid ; the hydrate speedily absorbs CO., from the 
 air. Oxide of lead dissolves in 7000 parts of pure water ; 
 its solubility is greatly diminished in the presence of 
 certain salts, sulphates, phosphates,* and carbonates for 
 
 * Dr. Frankland has recently observed that water which dissolves 
 lead ceases to do so after it has boon passed through animal charcoal, by 
 
OF THE SIXTH GROUP. 155 
 
 example, and increased by NH 4 HO and its salts. Metallic 
 lead undergoes no change when sealed up in pure water, 
 from which the air has been expelled by boiling. It is 
 oxidized, however, when exposed to the influence both of 
 air and water ; the oxide thus formed dissolves in the 
 water, and this solution absorbs CO a from the air ; a film 
 of li3 7 drated carbonate of lead, PbH a 2 PbC0 3 , is thus 
 formed which is deposited in silky scales. Another por- 
 tion of oxide becomes formed on the surface of the metal, 
 which is also dissolved by the water, and thus a rapid 
 solution of the metal ensues. This action is materially 
 modified when certain salts exist in the water, even when 
 they do not exceed three or four grains in the gallon. The 
 solvent action is increased by the presence of chlorides 
 and nitrates, but is diminished when sulphates, phosphates, 
 or carbonates are present, the PbO being scarcely soluble 
 in water containing these latter salts. Acid carbonate of 
 lime is remarkable for its preservative influence, and in 
 consequence of the presence of this salt in most spring 
 water these waters do not act on lead to any serious 
 extent, a film of carbonate of lead being deposited on the 
 surface of the metal and protecting it from further action. 
 The presence of nitrogenous organic matter in water is 
 dangerous, as nitric acid may be formed bj T its oxidation. 
 As lead is so constantly employed in making cisterns, pipes, 
 etc., for domestic purposes, the action of water on this 
 metal is very important in a sanitary point of view. 
 
 335. The principal minerals of this metal are the sul- 
 phide (galena or lead glance, PbS) and the carbonate 
 (PbCO,). 
 
 336. K u Cr0 4 produces, in solutions of Pb, a yellow 
 precipitate of PbCr0 4 , insoluble in HX0 3 , but soluble in 
 the fixed alkalies, from which solutions PbCr0 4 is precipi- 
 tated on adding acetic acid in excess. 
 
 337. When Ki is added to a solution of a salt of Pb, 
 yellow Pbl 2 is precipitated, which dissolves on heating the 
 liquid, and is re-precipitated on cooling in brilliant golden- 
 colored scales.* The solution of the amorphous iodide 
 may be greatly facilitated by the addition of a small quan- 
 
 reason of its having dissolved some of the phosphate of lime in the char- 
 coal. 
 
 * Pbl 2 is very soluble in solutions of the acetates of soda, potnsh, 
 and ammonia, even in the cold, forming colorless solutions, from which 
 KI, added in excess, precipitates Pbl 2 in the crystalline state, although 
 no heat has been applied. 
 
156 THE SPECIAL PROPERTIES 
 
 tity of IIC1. If the least trace of Bi is present in the lead 
 salt, the re-reprecipitated scales are no longer yellow, but 
 assume a dark orange or crimson tint, varying in intensitj^ 
 of color according to the amount of Bi present. This test 
 for Bi is of extraordinary delicacy. 
 
 338. Detection of Pb in waters. — Place two beakers on 
 white paper, side by side ; pour into each a pint of the 
 water to be examined ; add a little pure HC1 to the water 
 in one of the beakers, and subsequently some H 2 S ; if, 
 after the addition of the H 2 S, the water becomes browner 
 in color than the water to which no H 2 S has been added, 
 lead is indicated ; by this method a quarter grain of lead 
 in a gallon of water can be detected. As organic matter 
 interferes with the reaction, it is necessary to evaporate 
 the water, if it contains much organic matter, to dryness 
 with a few drops of HNO a , and ignite the residue; to the 
 residue afterwards should be added some HC 2 H 3 0, and 
 water, and the mixture heated, and, if necessary, filtered, and 
 to the filtered or unfiltered liquid H 2 S should be applied. 
 
 339. Detection of Pb in organic mixtures. — If the mix- 
 ture is in the liquid state, a little HN0 3 is added, and the 
 mixture must be then filtered, and washed H 2 S passed 
 through the filtered liquid to excess ; a dark-colored 
 precipitate will be formed if lead is present. When a dark- 
 colored precipitate is formed, it is allowed to subside, it is 
 then collected on a filter, and after being thoroughly washed 
 with water, it is dissolved in HN0 3 , and the solution tested 
 for lead according to 336. 
 
 340. If the mixture is in the solid form, it may either 
 be heated with HC1 and KC10 3 , as described at par. 733, 
 or it may be dried, and the dried mass heated to dull red- 
 ness until the ash is of a gray color ; it is then dissolved 
 in dilute HNO„ and treated with H 2 S, etc., as in the 
 preceding case. 
 
 341. When lead compounds, mixed with Na^CO.,, are 
 exposed upon charcoal to the inner blowpipe flame, ductile 
 metallic globules are formed, accompanied with an incrus- 
 tation which is yellow whilst hot, but becomes paler on 
 cooling. 
 
 342. Flame reactions of plumbic compounds (o) Tliey 
 
 color the flame pale blue. 
 
 (b) Reduction film black, dead or brilliant. 
 
 (c) Oxidc-Jilm bright yellow-ochre-colored ; stannous 
 chloride gives no reaction even on addition of NaHO ; 
 
OP THE SIXTH GROUP. 15T 
 
 AgN T O a does not produce any reaction, either alone or on 
 addition ofXH 4 HO. 
 
 (d) Iodide-film orange- to lemon-yellow, insoluble on 
 breathing or on moistening ; disappears on blowing with 
 ammoniacal air, and again appears on warming. 
 
 (e) Sulphide-film brownish-red to black : by blowing or 
 moistening with (NH 4 ) a S it remains unaltered. 
 
 (f) On charcoal splinter with soda gives a gray, very 
 soft, ductile metallic bead, which is slowly but completely 
 soluble in HN0 3 , yielding a white easily crystallizable salt, 
 soluble in H,0, and precipitated as a white powder on 
 addition of H 2 S0 4 from a capillary tube. 
 
 Characteristic reactions Those with H a S0 4 , HC1, 
 
 K a Cr0 4 , and H. 2 S. 
 
 343. Although PbO is the only lead oxide which forms 
 salts with acids, three other oxides are known, viz. Pb 2 
 (black suboxide), Pb0 2 (binoxide), and red lead, which is 
 a compound of the two oxides, PbO a and PbO ; its com- 
 position varies, but 2PbO, Pb0 2 represents an average 
 composition. Pb 2 is obtained by heating PbC. 2 4 cau- 
 tiously in a retort, from which air is excluded ; it is con- 
 verted with acids into plumbic salts. Red lead is obtained 
 by keeping PbO, at a dull-red heat, in contact with the air 
 for a considerable time ; it is decomposed at a red heat 
 into PbO and O ; HNO, decomposes it, dissolving out 
 PbO, and leaving PbO,. Pb0 2 , sometimes called puce 
 oxide, is a brownish-black substance ; it may be obtained, 
 as we have noticed, by treating red lead with HN0 3 ; it 
 may be prepared in many other ways it may be obtained, 
 for instance, by adding to PbO or PbA, in the presence of 
 water, CI or CaOCl ; it is decomposed by heat into PbO 
 and ; S0 2 converts it into PbS0 4 ; it is often employed 
 in the laboratory to absorb S0 2 ; H 2 S0 3 converts it into 
 PbS0 4 , thus :— 
 
 Pb0 2 + H 2 S0 3 = PbS0 4 -f H 2 ; 
 
 treated with concentrated HC1 in the cold, or heated with 
 dilute HC1, it is converted into PbCl 2 , thus : — 
 
 Pb0 2 + 4HC1 = PbCl 2 + 2H 2 + Cl 2 . 
 
 344. Cu and its compounds. — This metal is of a red color. 
 In the finely divided state it is a soft, dark red, dull-looking 
 powder. If exposed to a very intense heat it volatilizes, 
 but it is usually considered fixed in the fire. It is an 
 excellent conductor of heat and electricity, standing in 
 
 14 
 
158 THE SPECIAL PROPERTIES 
 
 this respect next to Ag. In the state of foil or filings it 
 takes fire in an atmosphere of CI. At ordinary tempera- 
 tures, and at a red heat, it unites directly with Br, I, S, 
 Si, etc. Concentrated HI dissolves it readily, H 2 being 
 evolved. ' The fixed alkalies have little or no action on it, 
 but NH 4 HO gradually dissolves it if exposed to the air ; 
 the compound in solution, which is of a deep blue color, 
 has the formula CuO(NH 3 ) 2 ; a nitrate is formed at the 
 same time. Cu, introduced into a gas or alcoholic flame, 
 communicates to it a green color. CuO and its hydrates 
 dissolve with facility in the mineral acids, even in their 
 diluted state. If CuO is gently ignited with Cu, there is 
 formed Cu 2 0. When CuO is boiled with SnCl,, Sn0 2 is 
 precipitated, and CuCl dissolved. With P at a red heat, 
 CuO yields phosphide and phosphate of copper. CuO 
 appears to unite with ammonia in more than one propor- 
 tion. When NH 4 HO is not added in excess to cupric 
 salts, a basic cupric salt, free from ammonia, is usually 
 precipitated. NH 4 HO added to CuS0 4 produces at first a 
 basic cupric sulphate, which dissolves on the addition of 
 more NH 4 HO, forming a deep blue solution, which may be 
 considered as containing amnionic sulphate in combination 
 with ammonic cuprate, having the following formula : 
 (NHj) ( Cu. Cu is a constituent of many useful alloys, the 
 chief of which have been already noticed under the heads 
 of the other metals. If bright metallic iron be introduced 
 into copper solutions, it becomes coated with a red deposit 
 of that metal, provided the solution be neutral or only 
 very slightly acid. 
 
 345. This metal is sometimes found in the native state, 
 but it chiefly occurs in combination with iron sulphide, con- 
 stituting the copper pyrites (Cu 2 S + Fe 2 S„), and in blue 
 copper ore, or malachite (CuC0 3 , CuO, H 2 0). 
 
 346. K 4 Fe"Cy B throws down, even from dilute solutions 
 of copper, a reddish-brown precipitate of Cu. J Fe"Cy, . which 
 is insoluble in dilute acids, is decomposed by the fixed al- 
 kalies, is soluble in NH 4 H0, which solution has a deep blue 
 color. 
 
 347. Detection of copper in organic liquids. — Acidulate 
 with HC1, introduce a piece of polished iron (344), and 
 allow it to remain in the liquid several hours if no percepti- 
 ble deposition takes place in a shorter time. If any doubt 
 exists about the deposit, examine either a portion of the 
 solution which has not had the iron test applied to it, or In- 
 dissolving some of the precipitate, which has been scraped 
 
OF THE SIXTH GROUP. 159 
 
 off the iron, in HNO„ and examining that or the original 
 solution with ?vH 4 H0 or K 4 Fe"Cy 6 . 
 
 348. Detection in organic solids. — The substance to be 
 examined is cut into small pieces, and treated with HC1 
 and KC10 3 , as directed at par. "733. The acid solution, 
 after filtering it, is evaporated nearly to dryness, and then 
 examined by one or other or by all the following tests : 
 Fe (par. 344), NHJEO (Table VI. W 3), K 4 Fe"Cy B (par. 
 346). 
 
 349. When any copper compounds, mixed with Na 2 C0 3 , 
 are exposed on a charcoal support to the inner blowpipe 
 flame, Cu is obtained, unaccompanied with any incrusta- 
 tion on the charcoal. 
 
 350. Flame reactions. — (a) On the charcoal splinter with 
 sodathe copper compounds yield a ductile lustrous metallic 
 bead, easily recognizable by its red copper color. By rub- 
 bing in the mortar, flat metallic particles are obtained, 
 which can be readily washed, and are easily soluble in 
 HN0 3 . The blue. solution, absorbed on filter-paper, yields 
 a brown stain on addition of K 4 Fe"Cy 6 . Instead of acting 
 upon a metal in a curved glass, it may be dissolved by 
 moistening paper upon which it is placed with HN0 3 . 
 
 (b) With borax on platinum wire. — Bine bead, not al- 
 tered to cuprous oxide when heated in the lower reducing 
 flame alone, but on addition of very little tin-salt forms a 
 reddish-brown bead. If this bead be frequently oxidized 
 and reduced in the flame, a ruby-red transparent bead is 
 obtained; this occurs most readily when the bead is al- 
 lowed to oxidize very slowly. — Bunsen. 
 
 Characteristic reactions. — Those with NH 4 HO and 
 K.FeCy,.,. 
 
 351. Three other oxides of copper are known, viz. Cu 2 0, 
 Cu 4 0, and Cu 2 3 ; there is very little known about the last 
 two. We have already noticed the formation of the first 
 oxide, Cu 2 (par. 257), and we shall learn hereafter some 
 other methods for its formation ; it is of a red color, and 
 its solution in HC1 absorbs O rapidly, and becomes con- 
 verted into a cupric salt. One of the most remarkable 
 properties of the solutions of this oxide in HC1 is that of 
 absorbing CO, and forming with it a crystalline compound. 
 
 352. The following methods have also been proposed for 
 the separation of Cd and Cu : — 
 
 1st Method. — Acidify the solution, if it is not acid, with 
 HC1 ; then pass H 2 S through the solution. The two metals, 
 if present, will be precipitated as sulphides ; the precipitate 
 
160 EXERCISES 
 
 must be well washed, and then boiled with dilute H 2 S0 4 . 
 The CdS is decomposed by the H 2 S0 4 , CdS0 4 being formed, 
 which dissolves, whilst the CuS is undecomposed and un- 
 dissolved. Separate the two by filtration, test the Gltrate 
 for Cd by H,S ; dissolve the CuS in HN0 3 ; neutralize with 
 NH,HO, acidify with acetic acid, then add K 4 Fe"Cy 6 . 
 This is a good method ; the only precaution to be attended 
 to is, that the mixed sulphides must be washed rapidly, so 
 that the CuS may not become oxidized by exposure to the 
 air. — Dr. A. W. Hoffman. 
 
 2d Method. — To one portion of the acetic solution add 
 H 2 S in excess. The formation of a yellow precipitate 
 denotes Cd. If, on account of the presence of Cu, the CdS 
 cannot be distinctly recognized, allow the precipitate pro- 
 duced by the H a S to subside, decant the supernatant fluid, 
 and add to the precipitate a solution of KCy until the 
 CuS is dissolved. If a yellow residue is left undissolved, 
 Cd is present; in the contrary case, not Fresenius. 
 
 353. Answers to the following exercises must be written 
 out: — 
 
 EXERCISES. 
 
 114. If after dissolving the precipitated sulphides of the 
 second division of the sixth group in HN0 8 , you were to 
 add NH 4 HO without first adding H a S0 4 , how would you 
 examine the precipitate for Bi and Pb ? Describe as many 
 methods as possible. 
 
 115. I have some ferrous sulphate which contains some 
 cupric sulphate ; how must I precipitate the Cu, so that 
 after the precipitation the ferrous sulphate remains perfectly 
 pure ? 
 
 116. How would you prepare pure argentic nitrate from 
 an alloy of copper and silver? 
 
 117. What substances increase, and what substances 
 decrease, the solvent action of water on lead ? 
 
 118. What is the action of KHO on cupric salts, and 
 how is this action modified in the presence of As a O s ? 
 
 119. How would you proceed to detect and separate all 
 the members of the sixth group, if you were to precipitate 
 the members of the first as well as those of the second 
 division with II..S? 
 
 120. A mixture of PbS and PbSO,, in the proportion of 
 one equivalent of PbS to three of PbS0 4 , is heated to near 
 the fusing point ; what changes take place ? 
 
ON THE SIXTH GROUP. lfil 
 
 121. Describe the processes for the detection of copper 
 in mixtures containing organic matter. 
 
 122. Give the formula of the different lead oxides, and 
 state how they are prepared. 
 
 123. A colorless solution is given you which you have to 
 examine for the members of the six groups. What members 
 must be absent? 
 
 124. Give the composition of the oxides and chlorides of 
 mercury, and describe by equations the action of the vola- 
 tile and fixed alkalies upon them ; and state how mercurous 
 and mercuric compounds are distinguished from each other. 
 
 125. The salts of another metal form, like the cupric 
 salts, a blue solution with NH,HO ; name the metal, and 
 state how you would distinguish the Cu and this metal 
 from each other in a solution. 
 
 12G. How would you detect corrosive sublimate in or- 
 ganic mixtures ? 
 
 12*7. Give several methods of reducing AgCl. 
 
 128. The water in copper mines contains Cu and Fe in 
 solution as sulphates, owing to the oxidation of some of the 
 copper ore, Cu 2 S, Fe 2 S 3 ; the water is pumped into wood 
 spouts, the bottoms of which are covered with pieces of 
 scrap iron. What is the object of passing the mine water 
 over the iron ? 
 
 129. Some red silver ore, 3Ag 2 S, Sb S 3 , is placed in the 
 bulb of a glass tube ; a stream of dry H is passed over it, 
 and it is heated to fusion by means of a lamp; when pure 
 H only escapes from the glass-tube the lamp is removed. 
 What change has the H effected? Dry CI is afterwards 
 passed through the tube, and a gentle heat applied to the 
 bulb; what change does the CI effect, and what substance 
 finally remains in the tube ? 
 
 130. I have in solution arsenious and arsenic acids, and 
 Cu, Ni, Co, and Fe in the ferric state. I diffuse CaC0 3 
 through the solution without heating it, and allow it to 
 stand for some time. I then filter off and pass CI through 
 the filtrate, and again add CaCO r I again filter, and to 
 the filtrate add lime-water. What change does the CaCO s 
 effect, for what purpose is the CI added, and of what does 
 the precipitate consist which is produced by lime-water, 
 and why is lime-water added in preference to KHO or 
 NaHO ? 
 
 131. An ore containing CuS, FeS 2 , and Ag 2 S, is roasted 
 in contact with the air, the heat being gradually raised 
 during the space of three or four hours to a dull red, and 
 
 14* 
 
162 EXERCISES. 
 
 finally to a bright red; the roasted mass is finally heated 
 with water, and metallic copper is introduced into the solu- 
 tion. What changes do the sulphides undergo in the first 
 stages of the roasting, in what state are the metals finally 
 left, and what substances remain undissolved, and what are 
 dissolved by the water and for what purpose is the Cu in- 
 troduced into the aqueous solution? 
 
 132. Different processes have been proposed, and are 
 carried out in the smelting of the sulphur ores of silver; 
 sometimes the Ag 2 S is fused with Pb ; sometimes it is fused 
 with PbS0 4 , in equivalent proportions; sometimes it is 
 fused with PbO in the proportion of an equivalent of the 
 Ag 2 S to two equivalents of PbO. Show by diagrams the 
 reactions which take place in each case. 
 
 133. There is present in solution in HC1, Fe 2 Cl 6 , CuCL, 
 CoCl a , NiCl 2 , and H 3 As0 4 . I nearly neutralize the solution 
 with Na 2 C0 3 . I then add sodic acetate in excess, and boil 
 for some time, and afterwards filter. The filtrate I acidu- 
 late with HC1, and then pass H 2 S through it to excess, and 
 again filter. I boil the filtrate to expel the excess of H 2 S, 
 and then pass CI through it to excess, and then diffuse 
 CaC0 3 through the liquid and allow it to stand for several 
 hours. I afterwards add to the filtrate lime-water. What 
 changes take place on boiling the solution after the addition 
 of the alkaline acetate ? What is precipitated by the HJS, 
 by the CaC0 3 , and by the lime-water? 
 
 134. A silver ore containing Ag 2 S, CuS, Fe s S 3 , XiAs, and 
 CoAs 2 , after being reduced to powder, is mixed with a tenth 
 of its weight of NaCl ; the mixture is afterwards roasted 
 for several hours ; when the roasting is complete the ore is 
 raked out and allowed to cool ; it is then sifted to separate 
 the fully roasted portion, which is in fine powder, from the 
 imperfectly roasted portion, which is in lumps ; the fine 
 powder, along with about a tenth of its weight of scrap- 
 iron, is introduced into casks about half filled with water; 
 the casks are then made to revolve for about two hours ; 
 about half its weight of mercury is then introduced into 
 the casks, which are then revolved for about twenty hours. 
 The amalgam and mercury in excess are then separated 
 from the spent material by washing, and the amalgam is 
 afterwards separated from the mercury by filtration ; the 
 amalgam is finally placed on trays supported on a tripod, 
 over which is placed a large bell-shaped iron vessel, the 
 bottom of which rests in a vessel into which water is con- 
 stantly flowing ; round the upper part of the bell a fire is 
 
GENERAL PROPERTIES OP BASIC GROUPS. 163 
 
 lighted, which brings that part of the bell and its contents 
 to a red heat. What change do the metals undergo in 
 roasting ? What change do the iron and mercury effect ? 
 And what is the object of placing the amalgam under the 
 iron vessel ? 
 
 THE GENERAL PROPERTIES OF THE DIFFERENT BASK! GROUPS. 
 
 354. It will be seen by consulting Table VII., that some 
 of the group-reagents precipitate more than one of the 
 groups; the analysis must therefore be commenced by re- 
 moving the group whose reagent does not precipitate the 
 members of any of the other groups under the same 
 circumstances. Such a course will be adopted, if the 
 reagents are employed in the order observed in the table. 
 
 355. First Division of the Sixth Group. — The analysis 
 must be commenced by adding to the solution HC1, which 
 precipitates the 1st section of the 6th group if present. 
 When a precipitate is produced, collect it upon a filter, 
 wash it twice with cold water, and then examine it, accord- 
 ing to the 1st section of Table VI. and par. 293. The wash- 
 water must be collected with the filtrate. Before adding 
 the HC1, consult pars. 316, 317, and 378. 
 
 356. The filtrate from the precipitate produced by HC1, 
 or the solution with which that acid has failed to give a 
 precipitate, must be examined for the 2d division of the 6th 
 and the whole of the bth group, in the manner described in 
 the next paragraph. 
 
 357. Second Division of the Sixth and the whole of 
 the Fifth Group.* — H^Sf must be passed through the 
 
 * Au and Pt are easily detected in the presence of all the metals 
 (paragraph 331) ; Northcote and Church, in their " Manual of Analysis," 
 recommend their separation from the solution, before precipitating the 
 other members of the fifth and the members of the sixth group by H 2 S ; 
 the following is their plan : The filtrate from the HC1 precipitate, or the 
 solution which has failed to give a precipitate, is freed from IIN0 3 (if 
 present) by one or two evaporations on the water-bath with HO ; to the 
 HC1 solution, which ought to be concentrated, a reasonable quantity of 
 NH 4 C1 solution is added, the liquid is then well agitated and allowed to 
 rest for some hours ; if Pt is present, a yellow crystalline precipitate of 
 2NH 4 C1, PtCl 4 is formed. The filtrate is mixed with a reasonable 
 quantity of a concentrated solution of H 2 C 2 4 , and moderately heated for 
 some hours. A precipitate consisting of yellow spangles or of a brown- 
 yellow sponge indicates Au. The filtrate is then treated with H 2 S. 
 
 f If the Ag 2 0, PbO, and Hg 2 0, had not to be sought for, we must 
 nevertheless add HC1 to the solution to render it acid, before adding 
 H 2 S, in order to prevent the members of the 3d and 4th groups from 
 being precipitated by that reagent, and to insure the complete precipi- 
 tation of the fifth group. 
 
164 THE GENERAL PROPERTIES 
 
 solution until it smells strongly of H 2 S after it has been 
 shaken and gently warmed for some time ; the 2d section 
 of the 6th, and the 5th group, when present, will be pre- 
 cipitated. When a precipitate is produced, collect it upon 
 a filter and wash it with hot water, until the wash-water is 
 no longer acid to test-paper ; the wash water need not be 
 collected with the filtrate, but may be thrown away. 
 
 358. If the PiFTn Group has not to be examined /or, the 
 washed precipitate is at once examined according to Table 
 VI. and par. 294. 
 
 359. When the Fifth'Group has to be examined for, the 
 washed precipitate must be treated with boiling solution 
 of NaHO ; the members of the Sixth Group are insoluble, 
 but the members of the fifth are soluble in NaHO ; if any 
 of the precipitate is insoluble in it, filter, and treat the in- 
 soluble portion according to par. 360. Examine the NaHO 
 solution for the 5th group according to par. 361. 
 
 360. The portion of the precipitate insoluble in NaHO 
 must be examined, after it has been well washed, according 
 to Table VI. and par. 294. 
 
 361. To the NaHO solution must be added HC1 in ex- 
 cess. If a precipitate is produced, on the addition of HC1, 
 the color of which is white, this arises merely from the 
 separation of S, none of the members of the group being 
 present ; if the precipitate is of a yellow or orange color, 
 Sb 2 S s , SnS a , and As a S 3 ,* can only be present. If the color 
 of the precipitate is black, then all the members of the 
 group must be sought for. The precipitate, after being 
 well washed with hot water, must be examined according 
 to the directions given under the 5th group (par. 213). 
 Before passing the H,S through the solution consult pars. 
 379, 380, and 381. 
 
 362. The filtrate from the H a S precipitate, or the solution 
 with which it has failed to give a precipitate, must be boiled 
 until a piece of bibulous paper moistened with a solution 
 of a lead salt does not alter in color when held over it, a 
 proof that all the H„S is expelled. If boiling the liquid 
 causes a separation of S, the solution, after the H 2 S is 
 expelled, must be filtered, and then examined for the 4lh 
 group as directed in the next par. 
 
 363. The Fourth Group — Before addingto the solution 
 the general reagent for this group, a small portion of the 
 solution must be tested for FeO, by adding to it a few 
 
 * For the color of tho sulphides of this group see par. 224. 
 
OP THE DIFFERENT BASIC GROUPS. 165 
 
 drops of a solution of K c Fe.,Cy u „* observing the precau- 
 tions mentioned in par. 117. When FeO is present the 
 remainder of the solution must be boiled in an evaporating 
 dish with a few drops of HN0 3 , until all the FeO is con- 
 verted into Fe 2 3 , which is accomplished when a drop of 
 the solution does not give a blue color with K G F 2 Cy 12 . 
 When FeO is not present, the solution does not require to 
 be boiled with HN0 3 , but it may at once be examined for 
 the 4th group as directed in the next par. 
 
 364. NH 4 C1 andNH 4 HO must then be added to the solu- 
 tion ; the NH 4 HO must be added until the solution smells 
 of it after it has been shaken. Warm the solution after 
 the addition of the NH 4 HO, and when a precipitate is pro- 
 duced collect it upon a filter, wash it with hot water until 
 the wash-water does not turn red test-paper blue ; examine 
 it then according to Table IV. and par. 156. Before add- 
 ing the NH 4 C1 and NHJ30 consult pars. 382, 383,and 384. 
 
 365. The filtrate from the precipitate produced by 
 NH 4 HO, or the solution with which it has failed to give a 
 precipitate, must be examined for the third group accord- 
 ing to the method described in the next par. 
 
 366. Third GROUP.f— (NH,)S % must be added to the 
 solution, the liquid must afterwards be shaken and gently 
 heated for some time. When a precipitate is produced,, 
 collect it upon a filter, and examine it according to Table 
 III. and par. 112. Before filtering the whole of the solu- 
 tion, add to that portion of the liquid which has been fil- 
 tered, a little more (NH 4 ) 2 S ; if the reagent produces a fur- 
 ther precipitate, add some to the nnfiltered as well as to 
 the filtered portion, refilter, and again test the filtrate with 
 it. If the (NH 4 ) 2 S causes no precipitate in the filtered 
 liquid, proceed with the filtration, as the group has been 
 
 * K 6 Fe 2 Cy, 2 precipitates other oxides besides the FeO, but with no 
 other oxide but FeO does it give a blue precipitate. 
 
 f Although FeO belongs, on account of its general properties, to this 
 group, we have placed it in the special table of the 4th ; because, in sepa- 
 rating the groups, it is converted by HN0 3 into Fe 2 3 —a member of the 
 4th : we have thought it advisable, therefore, to contrast its special pro- 
 perties with the members of that group. 
 
 J When the student does not look for the members of the three pre r 
 vious groups, viz. the 6th, 5th, and 4th. he must, before adding 
 (NH 4 ) 2 S to the solution, add NH 4 C1 and NH 4 HO ; in other words, he 
 must add them to the solution which he has to examine for the members 
 of the 3d group, if they have not been added in the previous course of 
 the analysis. The NH 4 C1 is added, to prevent the precipitation of 
 MgO by NH 4 HO. 
 
166 THE GENERAL PROPERTIES 
 
 TABLE VII— Behavior op the Basic Groups 
 
 FIRST GROUP. 
 
 K 3 0, Na a O, (NH 4 ),0. 
 
 1. HCl does not pre- 
 cipitate the members of 
 this group from their 
 eol u tlons,becauBe their 
 chlorides are soluble. 
 
 2. H,S does not pre- 
 cipitate the members of 
 this group, either from 
 their neutral, acid, or 
 
 ALKALINE solutions, 
 
 because their sul- 
 phides are soluble. 
 
 3. NHHO does not 
 precipitate either of 
 the other two members 
 of the group. 
 
 1. HCl does not precipitate the members of 
 this group from their solutions, because their 
 chlorides are soluble. 
 
 2. H a S does not precipitate the members of 
 this group either from their neutral, acid, or 
 alkaline solutions, because their sulphides 
 are soluble. 
 
 4. (NH 4 V,9 does not 
 precipitate the other 
 two members of this 
 group from their solu- 
 tions, because their 
 sulphides are soluble. 
 
 6. nXHJrfiOndoes not 
 precipitate either of the 
 other two members of 
 this group from their 
 eulutious. 
 
 SECOND GROUP. 
 
 First Division. 
 BaO, SrO, CaO. 
 
 Second Division. 
 MgO. 
 
 3. NH 4 HO does not* 
 precipitate the mem- 
 bers of this division 
 from their solutions. 
 
 THIRD GROUP. 
 
 MnO, ZnO, CoO, 
 NiO, FeO. 
 
 1 . HCl does not preci- 
 pitate the members of 
 this group from their 
 solutions, because their 
 chlorides are soluble. 
 
 2. H a S does not pre- 
 cipitate the members 
 of this group from 
 their acid solutions. 
 
 3, NH 4 HO precipt- 3. NH 4 H0 precipi- 
 tates Mg partly from tales the members of 
 its solutions as MgHythis group as ht- 
 O, ; the presence of drates. In an excess 
 
 ammonic salts pre- 
 vents the precipitation. 
 
 of the reagent ZuH 3 0„ 
 CoH 2 O a , and NiH,O a , 
 are readily soluble, 
 but MnH a 3 and FeH 9 
 O a are insoluble ; but 
 the presence of ammo- 
 nic salts prevents 
 their precipitation. 
 
 4. (NH 4 )«,S does not precipitate the members 4. (NH 4 ) 3 S precipi- 
 of this group from their solutions, because tales the members of 
 
 their sulphides are soluble. 
 
 this group from neu- 
 tral and alkaline so- 
 lutions, as sulphides. 
 
 5. (NHJ t COaprecipi- 
 tates the members of 
 this division from solu- 
 tions RE CARBONATES J 
 
 the presence of ammo- 
 nic balts does not in- 
 terfere with their pre- 
 cipitation. 
 
 6. Na a HP0 4 dofiff»oi 6. Na a HP0 4 precipt 
 precipitate the othertatee the members of 
 two members of this this division from >eu 
 eroup from their solu- tral and alkaline 
 
 tlons. 
 
 solutions, 
 
 PHATE9. 
 
 as phos 
 
 6. (HH 4 ) a C0 3 prec£»i- 5. (NH 4 ) a C0 3 preci- 
 tates Mg only partly, pit ales the members of 
 and the presence of am-| this group; but they 
 monio salts prevents are all, with the ex- 
 
 the precipitation. 
 
 ception of the Mn and 
 Fe precipitates, readily 
 soluble in an excess of 
 the reagent. 
 
 6. Na,HP0 4 precipi- 6. Na,HPO« precipi- 
 tates Mg from its sen- .tales the members of 
 teal and alkaline this group from their 
 
 NEUTRAL 80lutl0ns &8 
 PHOSPHATES. 
 
 t 
 
 solutions, 
 prate; violent 
 tation promotes 
 formation of the preci- 
 pitate. The precipi- 
 tate is more soluble in 
 hot than in cold water, 
 
 * The barto, strontlo, and calcic phosphates and oxalates, and magnesic phosphate, are 
 soluble fh dilute mineral acidw, but insoluble iu water and the alkalies ; consequently, when 
 their acid solutions are roudored neutral or alkaltue by ammonia, these salts are precipi- 
 tated ; therefore, when baryta, strontla, and lime are in combination with phosphoric and 
 oxalic aoidn, and when magnesia 1b In combination with phosphoric acid, they are precipitated 
 
of the different basic groups. 167 
 with the General or Group Reagents. 
 
 FOORTH GROUP. 
 Al a 3 , Cr a O a , Fe 2 O r 
 
 1. HC1 does not pre- 
 cipitate the members 
 of this group from 
 their solutions, be- 
 cause their cJdorides 
 are soluble. 
 
 FIFTH GROUP. 
 
 SnO, SnO* Sb x Os, 
 Aa 3 O a , ASjO,, 
 Au a 3 , PtO fl . 
 
 1- HC1 does not pre- 
 cipitate the members 
 of this group from 
 their solutions, be- 
 cause their chlorides 
 are soluble. 
 
 2. H Q S precipitates 
 all the members of this 
 group from their acid 
 solutions, as s 
 phides. 
 
 3. NH 4 H0 precipi- 
 tates some of the mem- 
 bers of this group. 
 
 2. H„S does not preci- 
 
 Eitate any of the mem- 
 erg of this group from 
 their acid solutions, 
 for FeS is readily solu- 
 ble in acids, and Al a S a 
 and Cr a S 3 are cot form- 
 ed in the humid way, 
 
 3. NH 4 HO, even in the 
 presence of Us salts, 
 precipitates the mem- 
 bers of this group as 
 hydrates, t which an 
 excess of the reagent 
 does not redissolve. 
 
 4. (NH 4 ) 2 S precipi- 4. (NH 4 ) a S, if added 
 totes the members of in excess, does not pre 
 this group from NEU-lcipitate the members 
 tral and alkaline so- of this group from 
 lutions; Fe w as FeS, their solutions, be- 
 Al and Cr as Al a H 6 G cause their sulphides 
 and Cr a H 6 e . are soluble in the al- 
 
 kaline sulphides. 
 
 5 (NK^CO^precfpi- 
 tales the members of 
 this group from their 
 solutions as oxides 
 an excess of the reage nt 
 does not redissolve 
 them. 
 
 6. Na a HP0 4 precipi- 
 tates the members of 
 this group from their 
 neutral solutions as 
 
 PHOSPHATES. 
 
 5. (NH.) a C0 3 preci- 
 pitates some of the 
 members of this group, 
 
 as OXIDES. 
 
 6. Na 2 HP0 4 preeipi- 
 tates kome of themem- 
 bersof this group from 
 their neutral solu- 
 tions, as PHOSPHATES. 
 
 SIXTH GROUP. 
 
 Second Division. 
 
 HgO.PbO, BLO,, 
 CdO, CuO. 
 
 First Division. 
 PbO, Ag a O, Hg a O. 
 
 1. HC1 does not pre- 1. HC1 precipitates 
 cipitate the members the members of this di- 
 of this division of lhe:vision, because their 
 group, because their chlorides are insolu- 
 
 chlorides are soluble. 
 
 ble. PbCl is slightly 
 soluble in water ; it U 
 more soluble in hot 
 than cold water. 
 
 2. H a S precipitates all the members of this 
 group from their neutral, alkaline, and acid 
 solutions, as sulphides. 
 
 3. NH 4 H0 precipitates the members of this 
 group ; but in an excess of the reagent the 
 Ag, Cd, and Cn precipitates redissolve 
 readily ; hut the Hg, Pb, and Bi precipitates 
 are insoluble in an excess of the reagent. 
 
 ■4. (NH t ) 3 S precipitates the members of this 
 group from their neutral and alkaline so- 
 lutions, as sulphides. 
 
 5. (NH 4 ) a C0 3 precipitates the members of 
 this group from their solutions; and an ex- 
 cess of the reagent does not redissolve them, 
 with the exception of the cupric precipitate. 
 
 . Na<,HP0 4 precipitates the members of 
 this group from their neutral solutions, as 
 
 PHOSPHATES. 
 
 in combination with these acids by ammonia, from their acid solutions, along with the 
 members of the fourth group. 
 
 f When the iron, chromic, and aluminic phosphates are present in a solution, they are 
 precipitated as phosphates, and not as hydrates, by ammonia. 
 
168 THE GENERAL PROPERTIES 
 
 completely precipitated. Before adding (NH^S to the so- 
 lution consult pars. 385, 386, 38V. 
 
 367. If the filtrate from the (NH 4 ) 2 S precipitate, or the 
 solution with which it has failed to give a precipitate, has 
 become, from its addition, of a dark brown color, the fil- 
 trate or solution must be evaporated aDd then acidified 
 
 witlrHCl, and filtered as directed in par. 387. N^HO 
 in excess must be added to the filtrate, which must then be 
 examined for the second group according to par. 369. 
 
 368. If the filtrate from the (NH 4 ) 2 S precipitate, or the 
 solution with which it has failed to give a precipitate, has not 
 altered in color, it can at once be examined for the second 
 group as directed in the next par. 
 
 369. First division of the second group. — (NH 4 ) 2 CO a * 
 must be added to the solution ; the solution must then be 
 gently warmed for some time, but not boiled. If one or all 
 of the members of this division are present, a precipitate 
 will be produced by the (NH 4 ) 2 CO a , especially after warm- 
 ing the solution. When a precipitate is produced, collect 
 it upon a filter and wash it with hot water, and afterwards 
 examine it according to Table II. and par. 66. Before fil- 
 tering the whole of the solution, add to that portion of the 
 liquid which has been filtered a little more (NH 4 ) 2 C0 3 ; if 
 the reagent produces a further precipitate, add some to the 
 unfiltered as well as to the filtered portion, re-filter, and 
 again test the filtrate with it. If the (2sH 4 \C0 3 causes no 
 precipitate in the filtered liquid, proceed with the filtration, 
 as the group has been completely precipitated. Before 
 adding the (NH 4 ) 2 CO s consult pars. 388 and 389. 
 
 370. The filtrate from the precipitate produced by 
 (NH 4 ) 2 C0 3 , or the solution with which it has failed to give 
 a precipitate, must be examined for Mg, K, and Na, as 
 directed in the next par. 
 
 371. The solution which has to be examined for Mg, K, 
 
 * When the student does not look for the members of the four previous 
 groups, viz. the 6th, 6th. 4th, and 8d, he must, before adding the 
 (NH 4 ) 2 C0 3 to the solution, add NH„C1 nnd NH 4 1I0 ; in other words, he 
 must add them to the solution which be has to examine for the members 
 of the second group, if they have not been added in the previous course 
 of the analysis. The NH 4 Cl is added to prevent the precipitation of the 
 MgO by the carbonate of ammonia ; any amnionic salt may be employed, 
 the acid of which forms no insoluble compound with MgO or the other 
 members of the group. If the amnionic carbonate employed is an acid 
 carbonate, a portion of the alkaline earths is apt to be dissolved by it. 
 The NH.IIO is added to prevent this ; it does so by converting it into 
 a neutral carbonate. 
 
OF THE BASIC GROUPS. 169 
 
 and Na must be divided into two parts, which we shall 
 call A and B. 
 
 372. The A portion may be employed for the examina- 
 tion for Mg; for this purpose we must add to the solution, 
 which must be quite cold, Na 2 HP0 4 and also NH 4 HO, if 
 this latter reagent is not already present in the solution, 
 the liquid after the addition of the reagent ought to be 
 shaken very violently ; and if, after time (one or two 
 hours) has been allowed for the formation of the precipi- 
 tate, there is no precipitate, Mg is absent. If there is a 
 precipitate, Mg is present. Before adding Na 2 HP0 1 , con- 
 sult pars. 390 and 391. 
 
 373. Examine B for K and Na according to par. 27. 
 
 374. When a precipitate has been produced by (NH 4 ) 2 CO a , 
 one drop of dilute H 2 S0 4 ought to be added to the B 
 solution before it is evaporated and ignited. The acid is 
 added to remove the minute quantity of Sr, if present, 
 which remains unprecipitated by (NHj a CO s , as Sr imparts 
 to the flame a color very similar to that produced by K. 
 
 375. Ammonia. A portion of the original solution must 
 be examined for ammonia according to par. 24. 
 
 PARTICULAR OBSERVATIONS REGARDING THE PRECIPITATES 
 PRODUCED BY THE GROUP REAGENTS, AND THE PRECAU- 
 TIONS TO BE OBSERVED IN EXAMINING FOR THE DIFFERENT 
 GROUPS. 
 
 376. Precautions to be attended to in examining for the 
 first section of the Sixth Group. — Before adding HC1 to 
 the solution under examination, it is necessary to ascer- 
 tain, by test papers, whether the solution is acid, neutral, 
 or alkaline. When it is one of the two former, a few 
 drops of the acid will generally be sufficient ; if alkaline, 
 the acid must be added until it is decidedly in excess. 
 When a precipitate is produced, add the acid, drop by 
 drop, until it ceases to increase; then add a few drops 
 more, shake the mixture, and filter. When no precipitate 
 is produced, a few drops of the acid will in most cases be 
 sufficient, since our only object in adding it then is to 
 acidify the solution, in order to prevent the precipitation 
 of the 3d and 4th groups by H 2 S. When evolution of gas 
 takes place on the addition of HC1, examine it for C0 2 , 
 H 2 S, and HCy, as directed under those heads. 
 
 377. As Ag is not precipitated, under certain circum- 
 stances, by HC1 — and as a precipitate may be produced 
 
 15 
 
170 PRECAUTIONS TO BE OBSERVED 
 
 on the addition of HC1, in the absence of Ag 2 0, PbO, and 
 Hg 2 — it is requisite to notice, 1st, the substances which 
 interfere with the precipitation of Ag; 2d, the substances 
 which may be precipitated, and under what condition the 
 precipitation takes place. 1st. When Hg(N0 3 ) 2 is present 
 in the solution, Ag, if present, will not be precipitated by 
 HC1, because AgCl is soluble in a solution of Hg(N0 3 ) s , 
 especially if the solution is hot and concentrated ; on the 
 addition of water and cooling, the solution may deposit 
 shining yellowish-white crystals, which are pure AgCl. 
 When Hg(N0 8 ) 2 is suspected to be present, amnionic 
 acetate ought to added to the solution after the addition 
 of the HC1, as this insures the complete precipitation of 
 the AgCl. 2d. The precipitate* may be occasioned by 
 the presence of some salt of Sb or Bi, as SbCl, and BiCl 3 
 are decomposed by much water into soluble acid and in- 
 soluble basic salts. The precipitatef may also arise from 
 the presence of some substance insoluble in water, but 
 soluble in the caustic, carbonated, or sulphurated alkalies, 
 or in an alkaline cyanide — for example, phosphate of 
 alumina, or alumina dissolved in NaHO, As 2 S 3 dissolved 
 in NH^HCO.,, Sb 2 S 3 dissolved in an alkaline sulphide 
 NiCy., dissolved in an alkaline cyanide, AgCl dissolved in 
 NH 4 HO; or the precipitate may be due to silicic acid, 
 some alkaline silicate being present. If the precipitate is 
 clue either to Sb or Bi, it will redissolve on the addition of 
 a few drops more of HC1. When silicic acid is the sub- 
 stance thrown down, the precipitate will appear very gela- 
 tinous, and will remain undissolved on the further addition 
 of acid ; a fresh portion of the original solution must, 
 therefore, be acidulated with HN0 3 , and evaporated to 
 dryness to render the silicic acid insoluble; the ignited 
 mas s may then be digested with dilute HN0 3 , and filtered.J 
 The analysis of the nitrate must then be conducted in the 
 regular way, by adding to it HC1, etc. If the precipitate 
 should be due to the presence of any of the other sub- 
 
 * If the HC1 employed contain a trace of H,S0 4 and Ba be present 
 in the fluid under examination, a slight trace of insoluble BaS0 4 will be 
 formed, which may be distinguished by the difficulty experienced in 
 separating it from the fluid by filtration. 
 
 t II CI precipitates, of the inorganio acids, boracic acid; and of the 
 orgnnio aoids, bonzoio and uric adds, if the solution is very concen- 
 trated. The two former are dissolved by hot water, and the uric acid 
 by heating with UNO,. 
 
 % The precipitate left upon the filter must be examined for silicic 
 acid according to the method desoribed under the head of that acid. 
 
IN EXAMINING FOR THE BASIC GROUPS. 171 
 
 stances, a fresh portion of the original solution ought to 
 be taken, and HNO a added to it until it is decidedly acid. 
 If the precipitate does not disappear on,the addition of 
 the acid, the solution ought to be warmed ; if this should 
 fail to dissolve the precipitate, it must be collected upon a 
 filter, and examined as a substance insoluble in water and 
 acids (see 112). 
 
 318. As the PbCl 3 , AgCl, and HgCl are very heavy, they 
 easily separate from the solution ; there is, therefore, no 
 need to warm the fluid to effect this object. Indeed, it 
 would be disadvantageous to do so, as a portion of the 
 HgCl would be converted into HgCl 2 , and the greater por- 
 tion, if not all, the PbCl 2 would be dissolved. 
 
 319. Precautions to be observed in examining for the 
 second section of the Sixth and the whole of the Fifth 
 Group. — Before passing H„S through the solution it will 
 be necessary to dilute it with water, if it be very acid, as 
 the members of the two groups are not readily precipitated 
 as sulphides from very acid solutions. Especially is it 
 very difficult to precipitate Od by H 2 S in the presence of 
 much HC1. If, therefore, the solution has not been diluted, 
 and Cd is present, a yellow precipitate may be obtained on 
 adding (NH 4 ) 2 S to precipitate the 3d group. It must also 
 be observed that if the solution has not been rendered 
 sufficiently acid, some of the Zn, if it be present, may be 
 precipitated by H 2 S. If on diluting the liquid it becomes 
 turbid, this arises from the presence of some salt of Sb or 
 Bi ; a few drops of acid will redissolve this precipitate. 
 Arsenic acid is reduced very slowly by H 2 S, but S0 2 * re- 
 duces it rapidly, if assisted by a gentle heat; if, therefore, 
 arsenic acid is present or its presence suspected, S0 2 ought 
 to be added in excess, the solution then gently warmed for 
 some time, and finally boiled until the excess of S0 2 is ex- 
 pelled. If Zn is present, and the arsenic acid has not been 
 reduced, a precipitate would be produced having this com- 
 position, ZnAs 2 S 6 . 
 
 380. If, on the addition of H 2 S, no precipitate be pro- 
 duced, it proves the absence of the 2d section of the 6th and 
 the whole of the 5th group. If a precipitate be produced, 
 the color of which is white, f this likewise proves the ab- 
 
 * If Ba, Sr, or Pb be present, the S0 2 will give rise to a precipitation 
 of their sulphates ; the precipitate should be collected upon a filter, 
 washed, dried, and then examined as a substance insoluble in water and 
 acids, according to 729. 
 
 | If HN0 3 be present in the solution, a thick, tenacious, yellow mass of 
 
172 PRECAUTIONS TO BE OBSERVED 
 
 sence of these groups, as the white precipitate is merely 
 due to a separation of S, occasioned by some of the H 2 S 
 being decomposed by its reducing some higher oxide to a 
 lower degree of oxidation. If the color of the solution, 
 originally orange or yellow, change to a green, after the gas 
 is passed through it, the separation of sulphur is due to 
 the reduction of Cr0 3 to Cr a 3 ; the white S suspended in 
 the green solution frequently perplexes the student, as it 
 appears at first like a green precipitate. If the separation 
 of S be not attended with any change in color, it is (proba- 
 bly) attributable to the reduction of Fe 2 3 to FeO, Cr0 3 
 and Fe 2 3 being both found in their lower degree of oxida- 
 tion after H 2 S or any reducing agent has been added to 
 their solutions. 
 
 381. If on the first transmission of H 2 S through the 
 solution a white precipitate be formed, which, on a further 
 addition of the reagent, acquires an orange color, and 
 becomes finally black, it points out that some mercuric 
 salt is present. If the precipitate, on its first formation, 
 assumes a red or brownish-red color, and becomes finally 
 black, it indicates the probable presence of some lead salt. 
 
 382. Precautions to be observed in examining for the 
 Fourth Group If the H S were not expelled before boil- 
 ing the solution with HNO s , the latter would give rise, by 
 oxidation of the S, to H 2 S0 4 , which would precipitate Ba 
 and Sr, and possibly Ca, as sulphates, if they were present. 
 Even when HN0 3 has not to be added to the solution, no 
 FeO being present, it is necessary to expel the H 3 S before 
 adding NH 4 HO, otherwise (NHJ 2 S would be formed, and 
 consequently the third as well as the fourth group would 
 be precipitated. When the solution is very acid, no XH 4 C1 
 need be added, as a sufficient amount of ammonic salt will 
 be formed on the addition of the NII 4 HO. 
 
 383. When much Cr B 3 is present, a small quantity will 
 frequently dissolve in the NH,HO, and will impart to the 
 fluid a puce-red tint. When this occurs, it is difficult to 
 remove the last traces of Or from the solution. If warming 
 the solution fail, it is better to disregard it ; for if the 
 solution were evaporated to effect the object, a greater or 
 
 sulphur will separate, occasioned by the decomposition of the H„S by 
 the acid. When such is the case, the gas has to be passed through the 
 solution for Bome time before its characteristic odor will be imparted to 
 the liquid, showing that a sufficient quantity has been added. HC10 S 
 and free CI deoomposo H a S in tho samo way as HN0 3 . 
 
IN EXAMINING FOR THE BASIC GROUPS. 113 
 
 less quantity of the oxides of Mn, Ni, and Co, if they were 
 present, would be precipitated. 
 
 384. The precipitate produced by NH 4 HO may consist, 
 in addition to the members of the fourth group, of the 
 following salts : Al, Cr"', Fe, Mn, Ba, Sr, Ca, and Mg, in 
 combination with P0 4 ; and Ba, Sr, and Ca, in combination 
 with C 2 O t . When the student looks for acids as well as 
 bases, he must examine the precipitate produced by 
 NH 4 HO, according to Table V., or pars. 191, 197, or 198. 
 Ba, Sr, and Ca, in combination with F and B0 3 , may also 
 be precipitated by NH 4 HO in minute quantities ; but as a 
 sufficient quantity of the bases will always remain in solu- 
 tion, and be precipitated as members of the 2d group, and 
 as the acids will be found in the examination for acids, we 
 have not included these salts in the table. 
 
 385. Precautions to be observed in examining for the 
 Third Group. — If CrO, and Ba are both present in solu- 
 tion, a substance insoluble in acids is sometimes formed on 
 dissolving the precipitate produced by NH 4 HO, or that 
 produced by (NH 4 ) 2 S ; the insoluble substance is BaS0 4 . 
 A sulphur acid appears to be formed when Cr0 3 is reduced 
 by H 2 S, which becomes converted into S0 4 after some time. 
 
 386. The precipitate produced by (NH,) a S is very difficult 
 to filter; the filtrate will frequently come through the 
 filter turbid for some time; there is no remedy for this but 
 to pass it through the filter until it is perfectly clear. The 
 student must not mistake between a turbid filtrate and one 
 which is perfectly clear but colored. A filter can only re- 
 move what is held in suspension by a liquid, as in the first 
 case; it cannot remove what is dissolved, as in the second 
 case ; when the filtrate is colored, consult the next par. 
 The precipitate must be carefully washed with water con- 
 taining a little (NH 4 ) 2 S, in order to prevent the precipitated 
 sulphides from oxidizing. If the wash-water comes through 
 of a deep-brown color, it must be treated as directed in 
 the next par. 
 
 387. If the filtrate from the (NH 4 ) 2 S precipitate be of a 
 very dark brown color, it is occasioned by the presence of 
 Ni, the sulphide of that metal being slightly soluble in 
 (NH 4 ) a S. When a considerable portion of this substance 
 has passed into solution, the filtrate, and likewise the wash- 
 water if it is dark colored, must be evaporated until the 
 excess of (NH 4 ) 8 S is expelled; the solution is then acidified 
 with dilute HC1, and the black precipitate which separates 
 on the, addition of the acid collected upon a filter, and 
 
 15* 
 
174 EXEEOISES. 
 
 examined with that previously obtained. If Cd has not 
 been completely precipitated by H 2 S, the precipitate by 
 (NH 4 ) 2 S may be yellow in color from the presence of CdS. 
 
 388. Precautions to be observed in examining for the first 
 division of the Second Group. — After the addition of the 
 (NH 4 ) 2 C0 3 , the solution should be heated gently, but not 
 boiled, since the NH 4 C1 might then decompose and dissolve 
 some of the precipitated carbonates. 
 
 389. Although (NH 4 ) 2 C0 3 does not precipitate com- 
 pletely Ba, Sr, and Ca from their solutions, especially when 
 the quantity of amnionic salts present is considerable, it 
 is sufficiently exact for all ordinary qualitative purposes. 
 "The separation is never perfect, owing to the solvent 
 action which amnionic salts exercise, more especially upon 
 BaC0 3 and CaCO a ; indeed, minute traces of Ba and Ca 
 can rarely be precipitated in this manner. Ba is sepa- 
 rated the most completely by H 2 S0 4 or a sulphate ; Ca by 
 (NH 4 ) 2 C 2 4 in presence of NH 4 HO and some NH 4 C1 ; Sr 
 same manner as Ca, or by NH 4 HO and (NH 4 ) 2 C0 3 in pre- 
 sence of NH 4 C1." 
 
 390. Precautions to be observed in examining for the 
 second division of the Second Group. — If the solution has 
 become very dilute during the course of the analysis, it 
 will render the detection of the Mg more certain, if, before 
 adding the Na 2 HP0 4 , the solution is concentrated. In any 
 case, time must be allowed for the formation of the precipi- 
 tate, the solution must be quite cold when the reagent is 
 added, and after the addition of the reagent the solution 
 must be frequently shaken ; as MgNH 4 P0 4 is more insolu- 
 ble in water containing NH 4 HO than in pure water, it is 
 necessary to have NH 4 HO in excess. 
 
 391. Frequently a flocculent precipitate is obtained on 
 the addition of Na 3 HP0 4 , which is not due to the presence 
 of Mg ; Bloxam states that it is aluminic phosphate, but I 
 have found that it is sometimes due to calcic phosphate 
 arising from the lime in the filter-paper. 
 
 392. Answers to the following exercises must be written 
 out. 
 
 EXERCISES. 
 
 135. What are the characters of the solutions of salts of 
 Mn, Cu, Pb, Fe", and Fe'"? 
 
 136. What are the characteristic reactions by which you 
 would distinguish, by the blowpipe, ores of load, bismuth, 
 zinc, and antimony? 
 
ACIDS. 115 
 
 13 1. Express by means of equations the action of HNO, 
 of different strengths on Zn, Fe, Cu, Ag, Sn, and Hg re- 
 spectively; also the action of H 2 S0 4 and HC1 on these 
 metals. 
 
 138. Separate, 1st, into groups, and 2dly, from each other, 
 the following substances: Cu, Mn, Ba, Al, Cd, NH 4 , Zn, K, 
 and Ca ; confirm the presence of each by means of a charac- 
 teristic reagent. 
 
 139. Classify the following metals into those which (a) 
 decompose water in cold, (6) at the boiling temperature, 
 (c) at a red heat, and (d) not at all : — 
 
 Pt, K, Zn, Mg, Cu, Mn, Al, Ag, Fe. 
 
 140. A solution acid to test-paper gives an orange pre- 
 cipitate by the action of H 2 S : what substances must be 
 absent, what may the precipitate contain, and how would 
 you examine it ? 
 
 141. Classify the following oxides into those which (a) 
 are reduced to the metallic state by heat alone, (6) are not 
 reduced by heat alone, (c) are not reduced by charcoal 
 alone, (d) are reduced by charcoal, (e) are reduced by H, 
 (/) are not reduced by H, (g) are reduced by CO : — 
 
 Bi a 3 , PbO„ Fe. a 3 , K a O, Al 2 O s , As 2 5 , MNO, MgO, 
 Au 2 3 , FeO, Sn0 2 , BaO, CoO. 
 
 142. Do the sulphides of the 5th group experience any 
 change when dissolved in a solution of KHO or NaHO? 
 
 ACIDS. 
 
 393. The acids may be divided into two classes, the 
 inorganic and the organic. All the organic acids contain 
 carbon as a constituent, and they and their salts are de- 
 composed by heat, the metals of the salts being left, when 
 they are the alkaline or alkaline earth metals, in the state 
 of carbonates ; the decomposition of the organic acids or 
 their salts by heat is also attended in the majority of cases 
 with the separation of carbon. 
 
 394. Acids, both organic and inorganic, do not admit 
 of that accurate classification into groups which is the case 
 with bases, many of them being members of more than one 
 group. 
 
116 THE SPECIAL PROPERTIES 
 
 INORGANIC ACIDS.* 
 
 395. The special properties of each acid are first de- 
 scribed ; then their division into groups, with a description 
 of the properties of each group of acids ; and finally the 
 processes to be followed in preparing the solutions for the 
 examination of the inorganic acids, and the methods to be 
 pursued in the examination. 
 
 396. The student must make the experiments given under 
 the head of each acid, and then test the behavior of the 
 acids with the group reagents ; after he has made these 
 experiments he passes over the organic acids and proceeds 
 to the examination of liquids. 
 
 BEHAVIOR OP THE ACIDS AND THEIR RADICALS WITH 
 REAGENTS. 
 
 Chromic Acid, H a Cr0 4 . 
 
 Solution for the reactions, K 2 Cr0 4 in water. 
 
 397. This acid has not been obtained in the solid state ; 
 it is supposed to exist in solution. Chromic anhydride 
 (CrO s ) is a crystalline scarlet-colored solid, which deli- 
 quesces rapidly when exposed to the air ; its solution 
 possesses a deep reddish-brown tint. Cr0 3 may be ob- 
 tained by adding undiluted H 2 S0 4 to a concentrated so- 
 lution of K 2 Cr 2 0y Cr0 3 melts at 190° C; at higher 
 temperatures it is decomposed into Cr 2 3 and O. 
 
 398. There are normal, acid, and basic chromates. The 
 normal salts of the alkalies, of Ca, Sr, Mg, Ni, Zn, and Cu, 
 are soluble in water; the normal salts of the other metals 
 are insoluble in H 2 0, but they are nearty all soluble in 
 HN0 3 ; all the acid chromates are soluble in water. There 
 are two acid chromates of potash, viz. the bichromate 
 K 2 CrO,, CrO, or K a Cr 2 0„ and the terchroniate K,Cr0 4 , 
 2Cr0 3 or K 2 Cr s 1D . The normal chromates of the alkalies 
 and alkaline earths are yellow, the bichromates are red. 
 The chromates of the heavy metals are bright yellow, red, 
 or brown; the aqueous solutions of the soluble salts are 
 the same color as the salts themselves ; the yellow of the 
 solution of a normal chromate changes, on the addition of 
 an acid, to red, owing to the formation of an acid chromate. 
 
 * Oxalic acid, although an organio ncid, has, on account of its frequent 
 occurrence, been treated along with the inorganic acids. 
 
OF THE INOROANIC ACIDS. Ill 
 
 The solution of the normal chromates of the alkalies are 
 alkaline, and the bichromates are acid, to test-paper. 
 Alkaline chromates may be prepared from insoluble chro- 
 mates by fusing the latter in conjunction with alkaline 
 carbonates or nitrates. 
 
 399. The normal alkaline chromates are not decomposed 
 even at a full red heat. The normal chromates of the 
 weaker bases are decomposed by heat, the Cr0 3 being de- 
 composed into Cr 2 3 and O ; the acid chromates of the 
 alkalies are decomposed by heat, a mixture of normal 
 chromate and Cr 2 3 being left, and given off. All the 
 chromates are decomposed on being heated with undiluted 
 H. 2 S0 4 ; chromic sulphate and another sulphate being 
 formed and O given off, thus : — 
 
 2K 2 Cr0 4 + 5H 2 S0 4 = Cr 2 3S0 4 + 2K 2 S0 4 + 5H 2 + 3 . 
 
 They are also decomposed on being heated with HC1, chro- 
 mic chloride and another chloride being formed and CI 
 evolved, thus : — 
 
 2K 2 Cr0 4 + 16HC1 = Cr 2 Cl 6 + 4KC1 + 8H 2 + 3C1 2 . 
 
 CrO, and thechromates are also decomposed by H 2 S, Cr 2 0„ 
 and H a O being formed and S set free ; they are reduced 
 by SO a , and also on being heated with H 2 T, H 2 0, and by 
 many other substances ; on account of the facility with 
 which Cr0 3 is reduced to 0r 2 O 3 , it possesses considerable 
 oxidizing power. All these reactions are characterized by 
 the change of color, of the solution from a red or yellow 
 to green. As H 2 S converts CrO, into Cr 2 O s , we always 
 obtain the Cr0 3 in the form of Cr,0 3 in testing for the bases. 
 
 400. If a very dilute acid solution of bydvic peroxide 
 (H.,0 2 )* is covered with a layer of ether, and a fluid con- 
 taining chromic acid is added, the solution of H 2 2 acquires 
 a fine blue color. By inverting the test-tube, closed with 
 the thumb, repeatedly, without much shaking, the solution 
 becomes colorless, whilst the ether acquires a blue color. 
 The latter reaction is particularly characteristic. One part 
 of potassic chromate in 40,000 parts of water suffices to 
 produce it distinctly ; the presence of vanadic acid mate- 
 
 * Solution of H 2 2 may be easily prepared by triturating a fragment 
 of baric peroxide (13a0 2 ), about the size of a pea, with some water, and 
 then adding a little dilute HC1. The solution keeps a long time without 
 suffering decomposition. In default of Ba0 2 , impure Na 2 2 may be used 
 instead, which is obtained by heating a fragment of Na in a small porce- 
 lain dish until it takes ffte, and letting it burn. 
 
118 THE SPECIAL PROPERTIES 
 
 rially impairs the delicacy of the test. After some time 
 reduction of the Cr0 3 to Cr 2 3 takes place, and at the same 
 time decoloration of the ether — Fresenius. 
 
 Sulphuric Acid, H 2 S0 4 . 
 
 Solution for the reactions, Na 2 S0 4 in water. 
 
 401. H 2 S0 4 is a heavy, colorless fluid, of an oily appear- 
 ance, which possesses a strong affinity for H 2 0, producing 
 when mixed with it a great degree of heat. Its affinity for 
 H 2 is so great, that it decomposes organic substances 
 when placed in contact with them, removing their H and 
 O, whilst the C is left behind as a black, coaly mass, a por- 
 tion of which dissolves in the acid and communicates to it 
 a brown tint. If heat is applied, the C is oxidized at the 
 expense of the acid, C0 2 and S0 2 being formed ; these facts 
 may be illustrated by pouring some strong acid upon white 
 sugar. H 2 S0 4 , at temperatures below its boiling-point 
 (327°C), displaces all other acids from their combinations 
 with bases, but above that temperature it is itself displaced 
 by the non-volatile acids. Sulphuric Anhydride (SO,) 
 is a white solid, similar in appearance to asbestos. It 
 evaporates and emits dense fumes on exposure to air. Its 
 affinity for H.,0 is so great, that it hisses like red-hot iron 
 when brought in contact with it. 
 
 402. As H 2 S0 4 is bibasic, it forms with monatomic metals 
 two classes of salts, viz. neutral salts, M 2 S0 4 ,and acid salts, 
 MHS0 4 . The solutions of the neutral sulphates of the al- 
 kalies, of Ca, Mg, Mn, and Ag are neutral to test-paper; 
 the neutral sulphates of the other bases and the acid sul- 
 phates of the alkalies are acid to test-paper. BaS0 4 , PbS0 4 
 are insoluble, SrS0 4 , CaS0 4 are nearly insoluble, all the 
 other sulphates are insoluble, in water. Neither PbS0 4 nor 
 the sulphates of the metals of the alkalies and alkaline earths 
 are decomposed when heated to redness, except MgS0 4 , 
 which loses its acid partially. The sulphates of Zn, Cd, Ni, 
 Co, Cu, and Ag require an intense heat to decompose them ; 
 but the other sulphates part with their acid without diffi- 
 culty when strongly ignited. All the sulphates, on being 
 mixed with charcoal and heated, are decomposed ; the sul- 
 phates of the metals of the alkalies and alkaline earths, and 
 lead are reduced to sulphides. The other sulphates evolve 
 SO,, which maybe detected by the smell, and by its bleach- 
 ing moist Brazil-wood paper. 
 
 403. Sulphates in dilute solutions* containing organic 
 
OP THE INORGANIC ACIDS. 179 
 
 matter are gradually converted into sulphides. Water 
 containing a sulphate may therefore, after it has been kept 
 a long time in a bottle or any closed vessel, be found 
 to contain H a S, although originally it was perfectly free 
 from it. 
 
 404. BaS0 4 is distinguished from all other baric salts, 
 but baric selenate and baric fluosilicate, by its insolubility 
 in dilute acids. Any soluble baric salt is therefore the best 
 and most delicate test for H 2 S0 4 , whether free or com- 
 bined, the solution being acidified with dilute HC1 or 
 dilute HN0 3 before adding the baric salt. 
 
 405. Insoluble sulphates are completely decomposed by 
 fusion with alkaline carbonates, an alkaline sulphate 
 being produced along with a carbonate or an oxide of 
 the other metal. 
 
 406. When a sulphate, mixed with C and Na 2 C0 3 is fused 
 upon a charcoal support by the inner blowpipe flame, 
 Na 2 S is produced. If the fused mass, moistened with 
 water, be placed upon a piece of silver, a brown stain of 
 Ag 2 S will be formed. 
 
 407. " To detect free H 2 S0 4 in presence of a sulphate, 
 the fluid under examination is mixed with a very little 
 cane-sugar, and the mixture evaporated to dryness in a 
 porcelain dish at 100° C. If free H 2 S0 4 was present a 
 black residue remains, or, in the case of most minute 
 quantities, a blackish-green residue. Other acids do not 
 decompose cane-sugar in this vr&y." 
 
 Sulphurous Acid, H a S0 3 . 
 
 408. This acid is formed when S0 2 is passed into water ; it attracts 
 oxygen from the air, and becomes converted into H 2 S0 4 . Sulphurous 
 anhydride (SO,) is a colorless gas. The acid and the anhydride have 
 the odor of burning sulphur; they act as powerful reducing agents; 
 they redden litmus paper and blanch Brazil-wood paper. The sulphites 
 are decomposed by nearly all acids, save carbonic and boracic acids, 
 with the liberation of sulphurous acid. 
 
 409. BaCJ 2 and CaCl 2 produce white precipitates in solutions of the 
 sulphides soluble in HC1. 
 
 410. AgNO s produces a white precipitate in solutions of sulphides of 
 Ag 2 S0 3 , -which decomposes on the application of heat, becoming black: 
 Ag 2 S0 3 -f- H 2 = H 2 S0 4 + Ag 2 . 
 
 411. The smallest trace of S0 2 in a gaseous mixture or of free H 2 S0 3 
 may be detected by means of strips of paper steeped in starch-paste, to 
 which a small quantity of iodic acid or potassic iodate has been added. 
 The iodic acid is reduced, and the iodine set free, which forms with the 
 
 . starch the well-known blue compound. 
 
180 THE SPECIAL PROPERTIES 
 
 412. Sulphites when mixed with HC1 and SnCl 2 produce a yellowish 
 precipitate, SnS 2 ; sulphites treated with Zn and HC1 evolve H 2 S. 
 
 413. H 2 S produces in solutions of H 2 S0 3 a white precipitate of S, 
 whilBt in solution there remains pentathionic acid (H 2 S 6 8 ). 
 
 Hyposulphurous or Triosulphuric Acid, H 2 S 2 3 . 
 
 414. This acid is scarcely known in its free state; it is generally con- 
 sidered to be almost immediately resolved into H 2 SO, and S ; but, 
 according to Rose, it is comparatively stable in dilute solutions. 
 
 415. Solutions of hyposulphites give with mercuric, plumbic, and 
 argentic salts white precipitates, which speedily become yellow, brown, 
 and black. 
 
 416. Hyposulphites treated with HC1 give off S0 2 and S, which in this 
 case is yellow, not white. When the hyposulphites are treated with 
 iodine an iodide and a tetrathionate are formed : 2BaS 2 3 + I 2 = Bal s -+- 
 BaS 4 6 . These two reactions distinguish H 2 S 2 3 from ft 2 S0 3 . 
 
 Boracic Acid or Orthoboracic Acid, H 3 BO a . 
 
 Solution of Borax, 2NaB0 2 , B 2 3 , in water. 
 
 41T. This acid is best obtained on the small scale by- 
 adding to a boiling concentrated solution of borax con- 
 centrated H a S0 4 or HC1 until the liquid strongly reddens 
 litmus ; on cooling, the greater part of the acid separates 
 from the solution in pearly looking scales, and on evapo- 
 rating the mother-liquor another crop is obtained. The 
 crystals retain a portion of the HC1 or H 3 S0 4 ; from the 
 former they are freed by gentle heating and recrystalliza- 
 tion, but to free them from the latter acid they must be 
 fused in a platinum crucible, and the fused mass crystal- 
 lized. H3BO3 is sparingly soluble in cold water, but is 
 dissolved by three times its weight of boiling water ; its 
 aqueous solution turns blue litmus-paper, not bright red, 
 like other acids, but of a claret color, and if the solution 
 is allowed to evaporate on turmeric paper it turns the 
 paper brown like the alkalies. It is soluble in alcohol, 
 and the solution burns with a beautiful green-edged flame ; 
 this green color is not produced if the acid is in combina- 
 tion with a base. On evaporating an alcoholic or aqueous 
 solution of the acid, a portion of it volatilizes with the 
 vapor of the liquid, although it is not itself volatilized by 
 heat. It decomposes solutions of the carbonates in the 
 cold, but a brisk current of CO a or H.,S passed through a 
 concentrated solution will cause a separation of boracic 
 acid in crystals. At a temperature of 100° C. it is converted 
 into meta- or monobasic boracic acid, HBO a , thus : — 
 
 H 3 B0 3 = HBO, + H„0. 
 
OF THE INORGANIC ACIDS. 181 
 
 At a verl heat it is converted into horacic anhydrate, B 2 3 , 
 which is a brittle glassy solid; it volatilizes very slowly, 
 even on intense ignition ; at high temperatures it expels 
 from salts all anhydrides more volatile than itself. It dis- 
 solves rearlilj' in water, forming Ii 3 BO a . 
 
 418. H3BO3 is met with in its free state in many volcanic 
 districts, especially in Tuscany, where it issues from the 
 earth with the vapor of water. It is obtained in the form 
 of crude borax, or tincal, from the salt lakes of India, 
 Thibet, etc. "The borates arc chiefly of two classes, 
 namely, orthoborates (such as the normal trisodic borate, 
 Na 3 B0 3 , and the penta-hydro-potassio diborate, KH.2BO,,, 
 and metaborates (such as the potassic metaborate, EL130 2 )." 
 The borates are not decomposed on ignition, they are 
 colorless, and they all, even the salts that contain an excess 
 of acid, manifest alkaline reaction with test-paper. They 
 are all, with the exception of the alkali salts, almost totally 
 insoluble in water, but they dissolve readily in acids and in 
 water containing .amnionic salts. 
 
 419. To detect a borate, add to the powdered substance 
 under examination strong H 2 S0 4 and alcohol or wood 
 naphtha j ignite the mixture subsequently. If a borate be 
 present the borders of the flame will appear green, which 
 becomes more distinct upon stirring, and the delicacy is 
 further increased by repeatedly extinguishing and rekin- 
 dling the flame. Copper salts impart the same color to the 
 flame ; Cu, if present, ought to bo precipitated by H 2 S, 
 before testing for H 3 B0 3 . Chlorides interfere also with 
 the test. 
 
 420. If a solution of an alkaline borate is mixed with 
 HC1 to slight but distinct acid reaction, and a slip of 
 turmeric paper is half dipped into it, and then dried at 100° 
 C, the dipped half shows a peculiar red tint ; this reaction 
 is very delicate. Care must be taken not to confound this 
 coloration with the blackish-brown which turmeric paper 
 acquires when moistened with strong HC1 and dried, nor 
 with the brownish-red which Fe 2 Cl B imparts to turmeric 
 paper. By moistening turmeric paper reddened by H 3 B0 3 
 with a solution of an alkali, the color is changed to bluish- 
 black or greenish-black ; the addition of a little HC1 restores 
 the brownish-red color Fresenius. 
 
 421. To detect the boracic oxide, reduce the substance 
 to be examined for it to a very fine powder, and then mix 
 thoroughly with it five parts of KHS0 4 and one part of CaF,, 
 and fuse the mass by the blowpipe flame in the loop of the 
 
 16 
 
182 THE SPECIAL PROPERTIES 
 
 platinum wire; boric fluoride, BF 8 , escapes and tinges the 
 flame green for a few seconds. 
 
 Phosphoric Acid or Orthophosphoric Acid, H 3 P0 4 . 
 
 Solution of common sodic phosphate, Na 2 HP0 4 , in water. 
 
 422. H 8 P0 4 may be obtained in the form of colorless 
 crystals ; they deliquesce rapidly in the air. The aqueous 
 solution of H 8 P0 4 has a strong acid reaction, and at a 
 boiling heat expels most volatile acids from their combi- 
 nations with bases. The aqueous solution may be heated 
 to 160° C. without altering the character of the acid, but 
 at 215° it is converted into the pyro-phosphoric acid, 
 H 4 P,0„ while above this temperature metaphosphoric acid, 
 HP0 8 , begins to be formed, and, after the application of a 
 full red heat, constitutes the entire residue. Phosphoric 
 anhydride, P a 6 , is obtained by burning P in dry or 
 dry air ; it appears under the form of white flakes, which 
 rapidly absorb moisture from the air. It is a powerful dehy- 
 drating agent. It forms, by contact with water, HPO s , 
 but if boiled with the water H 3 P0 4 . After the P a 5 has 
 once been dissolved it cannot be converted back into the 
 anhydride by heat. 
 
 423. The following are the general formulae for the phos- 
 phates: M'H 2 P0 4 ; this class is frequently designated 
 acid phosphates. M' a HP0 4 M"HPO„ ; these are frequently 
 termed neutral phosphates. M»P0 4 , M"MP0 4 , M'"PO' 4 , 
 M",(PO ( ),, these are termed tribasic phosphates, there are 
 in addition basic phosphate. Na,jP0 4 and K s P0 4 are solu- 
 ble in water, their solutions are alkaline, and they are 
 decomposed by C0 2 , thus: Na 8 P0 4 + CO s + H 3 = 
 Na 2 HP0 4 + NaHCO„. Na 2 HP0 4 and E^HPO, are soluble 
 in water; their solutions have a feebly alkaline reaction. 
 NaH a P0 4 , KH a P0 4 are soluble in water ; their solutions 
 are strongly acid. The phosphates, with the exception of 
 the alkaline ones, are nearly all insoluble in water. 
 
 424. MgS0 4 or any soluble magnesic salt, produces in 
 aqueous solutions of the phosphates, if concentrated, a 
 white precipitate of MgHP0 4 . A salt much more insoluble 
 in water is produced by adding NII 4 C1, NH 4 HO, and then 
 MgS0 4 ; the precipitate produced in this case is Mg^H 4 P0 4 , 
 which is slightly soluble in pure water, but almost insolu- 
 ble in water containing NH.HO. In dilute solutions it 
 only appears after much agitation and the lapse of some, 
 time ; agitation promotes its formation in all cases. This 
 
OP THE INORGANIC ACIDS. 183 
 
 test can only be applied when the phosphates are soluble 
 in amnionic solutions. 
 
 425. Plumbic acetate produces a white precipitate of 
 Pb 3 (P0 4 ) 2 soluble in HN0 3 . If this precipitate after being 
 dried is heated in the outer flame of the blowpipe, it be- 
 comes distinctly crystalline on cooling. This test is very 
 characteristic, not only on account of the crystalline 
 structure of the bead, but also from the circumstance that 
 the Pb 3 (P0 4 ) 2 is the only lead salt which is not reduced to 
 the metallic state when heated in the inner blowpipe flame. 
 It is evident that, to render this test of any value, the 
 Pb 3 (P0 4 ) 2 must be freed thoroughly, by washing, from all 
 lead acetate. 
 
 426. AgNO„ throws down from solutions of phosphates 
 containing one, two, or three atoms of fixed base, a light 
 yellow precipitate of Ag 3 P0 4 , readily soluble in HN0 3 and 
 in NH 4 HO. If the solution contained a phosphate con- 
 taining three atoms of fixed base, after the precipitation 
 the solution will be neutral to test-paper, but acid if the 
 phosphate contains one or two atoms of fixed base, on 
 account of the HN0 3 that will be set free. 
 
 427. If to an acid solution of a phosphate containing 
 the least possible excess of HC1 or HN0 3 a tolerably large 
 amount of sodic acetate is added, and then a drop of 
 Fe 2 Cl B , a yellowish-white gelatinous precipitate of Fe"'P0 4 
 will be formed. An excess of Fe,Cl (i must be avoided, as 
 ferric acetate w r ould thereby be formed, in which Fe'"P0 4 
 is not insoluble. By this reaction the acid can be detected 
 when combined with the alkaline earths, but it can only be 
 held to be decisive in the absence of H 3 As0 4 , as this acid 
 forms a similar precipitate. To effect the complete separa- 
 tion of the acid from the alkaline earths, Fe 2 Cl 6 is added 
 until the solution begins to be of a reddish color ; it is 
 then boiled, when the whole of the Fe is precipitated, 
 partly as phosphate, partly as basic acetate. It must be 
 filtered whilst hot ; the filtrate contains the alkaline earths 
 as chlorides. To detect by means of this reaction the 
 acid in the presence of much Fe 2 3 , the HC1 solution must 
 be boiled with NaHS0 3 until the Fe 2 Cl 6 is reduced to FeCl,, 
 which is indicated by the decoloration of the solution; add 
 then Na a C0 3 until the fluid is nearly neutral, afterwards 
 sodic acetate, and finally one drop of Fe 2 Cl 6 . The reason 
 for this proceeding is that Fe" 2A does not dissolve 
 Fe"'P0 4 . 
 
 428. The solution of amnionic molybdate in HNO^ pro- 
 
184 THE SPECIAL PEOPERTIES 
 
 duces, immediately, in neutral or acid solutions of phos- 
 phates in the cold, a finely divided yellow precipitate, unless 
 the quantity of phosphate is very minute ; in that case the 
 precipitate appears only after some hours, and the solution 
 ought to be gently warmed. The precipitate is soluble in 
 H 3 P0 4 and other acids, but it is rendered insoluble in them 
 by an excess of the reagent ; an excess of the fluid con- 
 taining the phosphates must, therefore, be avoided. By 
 this method P0 4 can be separated from the metals of the 
 alkaline earths, from Fe, Al, and other metals whose phos- 
 phates are insoluble in water. Presence of H 2 T and other 
 organic substances, and of large quantities of HC1, inter- 
 feres with the precipitation. The precipitate is soluble in 
 NH 4 HO, and may, after it has been washed with the 
 molybdic solution, be dissolved in it, and the P0 4 precipi- 
 tated from the solution by adding NH 4 C1 and MgS0 4 . 
 H 8 As0 4 gives no precipitate in the cold with the molybdic 
 solution, but a yellow precipitate is formed if the solution 
 be heated. H 4 Si0 4 gives no reaction in the cold with 
 molybdic reagents, and only a yellow coloration, but no 
 precipitate, after heating the solution. The production of 
 a mere yellow coloration is, by the motybdic reagent, 
 therefore, no indication of phosphoric acid. 
 
 429. The properties of the phosphates of Fe, Cr, Al, and 
 of metals of the alkaline earths, and other methods for 
 detecting PO t , are given in pars. 183, 184, 185, 186, 1ST, 
 and 188. 
 
 430. As arsenic acid gives precipitates with MgS0 4 ,with 
 ferric salts and with molybdic acid similar to those given 
 by phosphoric acid, the arsenic acid, when present, must be 
 removed, either by reducing it by SO, or by H,S. 
 
 431. P may easily be detected in its compounds, even 
 when they are mixed with large quantities of other sub- 
 stances, as follows : — 
 
 (a) The sample, having been ignited, is rubbed fine on 
 the porcelain plate (see fig 3 iu Plate), and is then introduced 
 into a small glass tube of the thickness of a straw ; into 
 this tube, which is closed at the bottom, a piece of magne- 
 sium wire, about one-fourth of an inch in length, is placed 
 so that it is covered by the powder. On heating the tube, 
 magnesic phosphide is formed with incandescence. The 
 black contents of the tube powdered on the plate give, on 
 moistening with 11,0, the highly characteristic smell of 
 II, P. A piece of Na can bo equally well used if the Mg 
 wire cannot be procured. 
 
OF THE IN0ROANI0 ACIDS. 185 
 
 (6) If it lias been ascertained that the sample does not 
 .yield any film on porcelain in the upper oxidizing flame, 
 the phosphates may be recognized by heating on platinum 
 with borax and a thin piece of iron wire in the hottest part 
 of the reducing flame, when a bright molten bead of iron 
 phosphide is obtained, which can be extracted with the 
 magnetized knife on crushing the bead under paper. — 
 Bunsen. 
 
 Pyrophosphoric Acid, H 4 P 2 0,. 
 
 432. This acid may be obtained by exposing orthophosphorio acid to 
 a temperature of 215° C. ; it appears under the form of a soft glass ; it is 
 converted into orthophosphorio acid by boiling it in water, and it is con- 
 verted into metaphosphoric acid when heated to redness. The acid is 
 also converted into orthophosphorio acid on boiling solutions of its salts 
 with strong acids. 
 
 433. The free acid does not give precipitates with Bad, and AgN0 3 , 
 but its salts give white precipitates with them. 
 
 434. White of egg is not precipitated by a solution of the acid, nor by 
 solutions of its salts mixed with acetic acid. Amnionic molybdate, with 
 addition of NH 4 HO, fails to produce a precipitate. 
 
 Metaphosphoric Acid, HP0 3 . 
 
 435. This acid is obtained by acting on P 2 6 with cold water, or by 
 heating H 4 P 2 7 or H 3 P0 4 to redness ; it forms a transparent, colorless, 
 glassy, uncrystallizable mass. 
 
 436. The solution of the acid gives precipitates with white of egg, 
 with AgN0 3 and BaCl 2 . It gives no precii itate or coloration with am- 
 nionic molybdate. 
 
 437. The metaphosphates do not coagulntc the albumen of white of 
 egg unless acetic acid be added, which liberates HP0 3 . This is its most 
 characteristic test. 
 
 438. This acid is converted slowly at ordinary temperatures, quickly 
 at the boiling heat, into H 3 P0 4 . 
 
 Carbonic Acid, H 2 C0 3 . 
 
 Solution for the reactions, Na 2 C0 3 in water. 
 
 439. H 2 C0 3 is supposed to be formed when CO a is passed 
 into H 2 0, but it has never been obtained; if it exists it 
 decomposes when its solution is evaporated. Carbonic 
 anhydride, C0 2 , exists at the common temperature and 
 pressure as a colorless, inodorous, and non-inflammable 
 gas. Being heavier than the atmosphere in the proportion 
 of 1.5 to 1, it can be decanted from one vessel to another 
 like a liquid. It reddens blue litmus paper previously 
 
 16* 
 
186 THE SPECIAL PROPERTIES 
 
 moistened with water, which after a time returns to its 
 original color, owing to the CO„ having volatilized. It is 
 soluble in cold water, but when the solution is heated it 
 escapes. 
 
 440. As H 2 CO„ is bibasic, it forms with the monatomic 
 metals two classes of salts, viz., neutral or normal salts, 
 M' 2 CO a , and acid salts, M'HCO,; the neutral and acid 
 salts of the metals of the alkalies are alkaline to test- 
 paper. The neutral alkaline carbonates are the only 
 neutral salts of this acid which are soluble in water. The 
 carbonates are decomposed by all free acids soluble in 
 water (HCy and H 2 S excepted), with evolution of CO s . 
 
 441. To delect C0 2 , add to the solution or solid sub- 
 stance under examination HC1, and warm the solution, 
 if sufficient gas for detection cannot be procured without. 
 Should any gas be evolved, allow it to accumulate by 
 placing the thumb on the mouth of the test-tube, and 
 afterwards decant it (taking care not to allow any of the 
 liquid to pass over along with it) into another test-tube 
 half filled with lime-water. A white precipitate of CaC0 3 
 will be produced if C0 2 is present. 
 
 442. WHen the solution under examination contains 
 only a minute quantity of a carbonate, it is sometimes a 
 matter of difficulty, especially to young students, to decant 
 the C0 2 into the test-tube containing the lime-water; this 
 is especially the case if the solution contains Na a HP0 4 , as 
 CO a is very soluble in a solution of that salt. In such 
 cases it would be better first to precipitate the CO, in 
 conjunction with CaO or BaO, by adding to the solution 
 under examination a solution of CaCl a or BaCL, collecting 
 the precipitate produced upon a filter, and after all the 
 fluid has filtered off to transfer the precipitate again to the 
 test-tube, moisten with water, then add IIC1, and if any 
 effervescence takes place to collect the gas in lime-water in 
 the manner just described (441). 
 
 443. CaCl„ and 15aCl 2 produce in solutions of the neutral 
 alkaline carbonates an immediate precipitate of CaCO, or 
 of BaC0 3 ; but these chlorides in dilute solutions of the 
 acid carbonates (M'IlCO a ) form precipitates only after 
 ebullition; in solutions of the free acid these reagents 
 produce no precipitates. 
 
 444. Many of the insoluble' carbonates dissolve in water 
 containing CO„, from which solutions they are precipitated 
 on boiling, because the CO, is expelled. It is in this 
 state that most of the Ca and Mg in spring and river 
 
OP THE INORGANIC ACIDS. 187 
 
 water exists. The incrustations which are formed in the 
 vessels in which such waters are boiled are due to the pre- 
 cipitation of these carbonates occasioned by the expulsion 
 of the CO,. The C0 2 in waters is best detected by adding 
 to them lime-water ; by this means not only is the CaC0 3 
 whieh is formed precipitated, but also that which pre- 
 existed in the solution. This process is employed on the 
 large scale for softening hard waters (waters containing 
 in solution calcic and magnesic salts.) It is called, after 
 the inventor, Clark's process. 
 
 445. All the carbonates, with the exception of those of 
 the alkalies, lose their acid upon ignition, the metal being 
 left either in an oxidized or uncombined state, according 
 to its greater or less affinity for oxygen. 
 
 446. The following precautions must be attended to in 
 testing for this acid: When the substance is in the solid 
 state it should be reduced to fine powder, and a little 
 water should be added prior to the acid, to displace the 
 air in its pores, otherwise an apparent effervescence will 
 ensue from the expulsion of air. In the case of alkaline 
 carbonates the decomposing acid must be added until the 
 solution reddens blue litmus paper — that is, until the acid 
 is in excess; otherwise the carbonic acid set free may 
 combine with some of the undeconiposed carbonate, forming 
 with it an acid carbonate, no effervescence consequently 
 taking place. No decomposition takes place on the addi- 
 tion of strong HNO, to BaCO s , especially the native car- 
 bonate, because Ba(N0 3 ) 2 is insoluble in the strong acid. 
 Water must therefore be added, as well as the acid, for the 
 decomposition to be effected in this and many other cases. 
 
 Oxalic Acid, H ? C a 4 = H 2 0. 
 
 Solution for the reactions, (NHJ 2 in water. 
 
 447. H 2 crystallizes from its aqueous solutions in four- 
 sided prisms, which contain 2 ats. of water. The acid is 
 very soluble in water and alcohol ; its solution is very acid 
 and poisonous. The crystallized acid melts at about 98° 
 C. in its water of crystallization. The dry acid sublimes 
 at 165° in slender white needles ; part of it is, however, 
 decomposed, and larger portions of it at an increased tem- 
 perature, into C0 2 and formic acid, HCH0 2 , the latter 
 being resolved into carbonic oxide, CO, and H 2 0. Heated 
 with an excess of alkali, a carbonate is formed and H 
 evolved. CI does not act on dry H 2 C 3 4 , but in the presence 
 
188 THE SPECIAL PROPERTIES 
 
 of moisture it quickly decomposes it, thus : H 2 C 2 4 -f Cl 2 
 = 2CO + 2HC1. H 2 may be crystallized from hot HN0 8 , 
 but by long-continued boiling in HN0 3 it is slowly oxidized, 
 CO a and H 2 being formed. Oxalic anhydride, C 2 0.., has 
 not been obtained. When H 2 C 2 4 .is dehydrated by con- 
 centrated HjSO,, H a P0 4 , or other dehydrating substances, 
 the C 2 0, splits up at the same time into C0 2 and CO. 
 
 448. H 2 C 2 4 , like other bibasic acids, forms, with the 
 monatomic metals, two classes of salts, viz. neutral salts, 
 M' a C 2 4 , and acid salts, M'HC 2 4 ; but it also forms a third 
 group of super-acid salts, KH 3 2C 2 O r The oxalates of the 
 alkaline metals are soluble in water; the rest are almost all 
 insoluble in water, but soluble in dilute acids. All the 
 oxalates are decomposed by heat. The oxalates of the 
 more easily reducible metals, as Ag, Hg, Cu, give off C0 2 , 
 the metal being left in the metallic state ; the oxalates of 
 the less reducible metals, whose carbonates are decomposed 
 by heat, as Zn, Mg, etc., give off C0 2 and CO, the metal 
 being left as oxide. The oxalates of the metals whose 
 carbonates are not decomposed by heat, as K and Xa, or 
 not easily decomposed, as Ba, Sr, and Ca, give off CO, the 
 metal being left as carbonate. 
 
 449. The acid or oxalates, heated with concentrated 
 H 2 S0 4 , give off, with effervescence," C0 2 and CO, and if a 
 light be applied to these gases as they issue from the mouth 
 of the test-tube the CO will burn with a blue flame. 
 
 450. The acid or oxalates, on being mixed with some 
 finely powdered Mn0 2 (which must be free from carbonates), 
 a little H 2 added, and a few drops of concentrated H.SO,, 
 considerable effervescence ensues, owing to the CO., which 
 is formed thus: Mn0 2 + K 2 C 2 4 + 2H,S0 4 = Mn"S0 4 
 + K 2 S0 4 + 2H 2 + 2C0 2 . This reaction is employed for 
 estimating the amount of Mn0 3 in manganese ore (par. 127). 
 
 451. The soluble calcic salts and lime-water produce, 
 even in highly dilute solutions of oxalates, a white precipi- 
 tate of CaO, which is insoluble in acetic acid. 
 
 Silicic Acid or Orthosiucic Acid, H 4 Si0 4 . 
 
 452. II 4 Si0 4 may be obtained by passing silicic fluoride 
 into water : — 
 
 3SiF 4 + 4H 2 = H 4 Si0 4 + 2IT,SiP,,; 
 
 it may also be obtained by passing CO, into a solution of 
 a soluble silicate : — 
 
OP THE INORGANIC A0ID8. 189 
 
 Na 4 Si0 4 + 4H a O + 4C0 2 = H 4 Si0 4 + 4NaHC0 3 ; 
 
 or by treating a solution of a soluble silicate with HC1. 
 The H 4 Si0 4 , obtained in decomposing solutions of the 
 alkaline silicates with acids, separates from the solutions 
 in the form of a gelatinous mass, which is nearly insoluble 
 in water and acids ; but if a dilute solution of the silicate 
 be poured into a considerable excess of HC1 the H,Si0 4 
 remains in solution, but is precipitated on neutralizing the 
 solution with an alkali. If the solution of the H 4 Si0 4 is 
 placed in one of Graham's dialysers, and the water in the 
 outer vessel is changed every twenty-four hours, in four or 
 five days the alkaline chloride and the excess of HC1 have 
 diffusedso completely that the liquid in the dialyser contains 
 not even a trace of them, but is a pure solution of H 4 Si0 4 , 
 containing about 5 per cent, of the acid ; the solution may 
 be concentrated in a flask until it contains 14 per cent, of 
 the acid ; this solution is tasteless, limpid, colorless, and 
 feebly acid ; in a few days it becomes converted into a solid, 
 transparent, jelly-like mass, which shrinks and gives up 
 water even in closed vessels ; the coagulation is retarded 
 by HC1 and by small quantities of KHO or NaHO. By 
 evaporating this pure solution of H 4 Si0 4 at 15.5° C, in a 
 vacuum, a transparent, glassy, very lustrous mass is left, 
 which, after drying over H a S(5 4 , yields dibasic silicic acid, 
 H,SiO a ; in addition to these two there is evidence of other 
 silicic acids. Silicic anhydride, Si0 2 , is obtained on 
 igniting H 4 Si0 4 or H 2 Si0 3 as a gritty white powder ; it 
 occurs in nature in two forms, the cystalline and amor- 
 phous ; rock crystal, quartz, amethyst (colored purple by 
 ferric oxide) are pure, or nearly pure, crystallized Si0 2 ; 
 agate and chalcedony consist of a mixture of crystallized 
 and amorphous Si0 2 ; opal consists of the amorphous form 
 with a varying quantity of water. Silica is the principal 
 constituent of sandstones ; it is also one of the constituents 
 of felspar and of numerous other minerals. All the arti- 
 ficial forms of Si0 2 are amorphous. Si0 2 , whether natural 
 or artificial, is insoluble in water and all acids except HF, 
 and it requires for its fusion a heat as intense as that of 
 the oxyhydrogen blowpipe ; at that temperature it melts 
 to a transparent glass and is amorphous. H 4 Si0 4 and 
 amorphous Si0 3 dissolve in hot aqueous solutions of the 
 fixed and carbonated alkalies ; but the crystalline Si0 2 is 
 dissolved by these reagents with far greater difficulty and 
 in much less quantity, and it is also much more slowly 
 
190 THE SPECIAL PROPBKTIES 
 
 attacked by HF. The amorphous and crystallized SiO a , 
 on being fused with alkaline carbonates, are converted into 
 alkaline silicates, which are decomposed by acids, H,Si0 4 
 separating. At common temperatures the silicic acids are 
 weak acids, but at a red heat they expel H 2 S0 4 and the 
 more volatile acids from their salts. 
 
 453. "The composition of the silicates presents many 
 varieties ; some correspond to H 4 Si0 4 , for example 
 Mg" 2 Si0 4 ; others, such as Na 2 SiO„ correspond to the 
 bibasic acid H 2 SiO„ and there are also the following among 
 other silicates, K. 2 S'i a 5 , Na^O,, Na a Si 4 0„." The alkaline 
 silicates are the only silicates soluble in water ; their solu- 
 tions are alkaline to test-paper, and* they are decomposed 
 in solution by all acids ; on evaporating their solutions to 
 dryness along with a slight excess of HC1 or HXO s , and 
 igniting the residue for some little time and then treating 
 it with dilute HC1 or HNO„ the other substances dissolve, 
 whilst the whole of the Si0 2 remains undissolved as a 
 whitish gritty powder. On adding NH 4 C1 to a concentrated 
 solution of an alkaline silicate, a gelatinous precipitate 
 separates. - 
 
 454. Some of the silicates insoluble in H 2 are dissolved 
 with decomposition by HC1 or HN0 3 ; some that are not 
 decomposed by these acids are decomposed by concentrated 
 H 2 S0 4 . The silicates which are not acted upon by ant- 
 acids but HF are decomposed by fusion with the alkaline 
 carbonates, and also with BaH 2 O s . 
 
 455. The silicates decomposable by HC1 or HX0 3 ought 
 to be reduced to the finest powder, and be digested in the 
 acid for some time at a gentle heat, with constant stirring, 
 when the decomposition is effected ; the mixture must be 
 evaporated to dryness on the water-bath and the residue 
 heated until acid fumes cease to be evolved ; the dry mass 
 is then moistened with IIC1 and heated with water, and 
 then filtered ; the filtrate must be examined for the bases 
 and other acids, and the insoluble portion for SiO,. 
 
 456. HF and Si0 2 mutually decompose each other, gaseous 
 SiF 4 and H B being formed ; silicates are converted by HF 
 into silico-fluorides ; M"SiF 6 and these salts, on being 
 heated with H a S0 4 , are converted into sulphates, HF and 
 SiF, being evolved. The silicates undecouiposable by other 
 acids are decomposed by HF, but the fusion process is 
 better suited for qualitative purposes. 
 
 457. Silicates not decomposed by acids must be reduced 
 to the finest powder, and then intimately mixed with a 
 
(IF THE INORGANIC ACIDS. 191 
 
 mixture of Na 2 CO, and K.,C0 3 , and the mixed mass fused 
 in a platinum crucible until the evolution of C0 2 ceases. 
 The crucible, when cold, is put into an evaporating dish 
 containing dilute HC1. When the fused mass is detached 
 from the crucible, remove the crucible and evaporate the 
 mixture to dryness, and ignite just in the same way as the 
 solution in 455 is directed to be treated. The fixed alkalies 
 cannot, of course, be sought for in that portion which has 
 been fused with the alkaline carbonate ; to ascertain whether 
 they are present, another portion of the silicate must be 
 fused with BaH 2 2 . For this purpose " mix one part of 
 the very finely pulverized substance with four parts of 
 BaH 2 2 ; expose the mixture for half an hour, in a platinum 
 crucible, to strong heat, and then treat the fused or agglu- 
 tinated mass with HC1 and water until it is dissolved. 
 Precipitate the Ba and all the bases in the silicate, with 
 the exception of Mg and the alkalies, with N0 4 HO and 
 (NH 4 ) 2 C0 3 ; filter, evaporate to dryness, ignite, dissolve 
 the residue in water, precipitate again with NH 4 HO and 
 (NH 4 ) 2 C0 3 , filter, evaporate, ignite;" then test for K and 
 Na in the usual way. 
 
 458. When Si0 2 or H 4 Si0 4 is fused with Na 2 CO s before 
 the blowpipe, a transparent colorless bead is formed, the 
 CO, being expelled. A small quantity of Na 2 C0 3 ought 
 only to be employed, as an opaque bead is produced when 
 it is added in excess. 
 
 Hydrofluoric Acid, HF. 
 
 459. This acid is best obtained by the action of concen- 
 trated H,S0 4 on CaF 2 , fluor spar. The powdered mineral 
 is gently heated with the acid in a retort of lead, and the 
 HF condensed in a receiver of the same metal. It is ob- 
 tained in the form of a very volatile liquid, strongly acid 
 and corrosive, fuming in the air. It burns the skin like 
 red-hot iron, causing a sore which is not easily healed. It 
 is distinguished from all other acids by dissolving Si0 2 
 and the silicates which are insoluble in the other acids; on 
 this account it cannot be prepared or kept in glass vessels. 
 
 460. " If a finely pulverized fluoride, no matter whether 
 soluble or insoluble, is heated in a platinum crucible with 
 concentrated H 2 S0 4 , the crucible covered with the convex 
 face of a watch-glass, coated on that side with beeswax, 
 which has been removed again in some places by tracing 
 
192 THE SPECIAL PROPERTIES 
 
 lines in it with some pointed instrument,* the hollow of 
 the glass filled with water, and the crucible gently heated 
 for the space of half an hour or an hour, the exposed 
 lines will, upon the removal of the wax, he found etched 
 into the glass. If the quantity of HF disengaged by the 
 H 2 S0 4 is very minute, the etching is often invisible upon 
 the removal uf the wax; it will, however, in such cases re- 
 appear when the plate is breathed upon. This appearance 
 of the etched lines is owing to the unequal capacity of con- 
 densing water which the etched and the untouched parts 
 of the plate respectively possess." This method cannot 
 be adopted if the substance containing the F is not decom- 
 posed by H 2 S0 4 , or if silicic acid is present ; the silicic 
 acid must be got rid of, in the way to te described, before 
 we can discover F. 
 
 461. If nascent HF meet with Si0 2 , we have sceD they 
 are mutually decomposed (par. 456). Should the substance 
 examined contain, therefore, Si0 2 as well as F, SiF 4 , and 
 not HF, will be disengaged by the H 2 S0 4 . SiF, in the pure 
 state is a colorless gas, which has a suffocating acid smell, 
 and which emits fumes in contact with the air ; it reacts 
 with water, and forms H,Si0 4 , which is deposited in the 
 gelatinous state, and II 2 SiF e , hydrofluosilicic acid, which 
 remains in solution. SiF 4 dees not attack glass ; but the 
 glass becomes covered, when damp, with a very adhesive 
 coating of K 4 Si0 o which impairs its transparency, owing 
 to the decomposition of the H 2 and SiF 4 . H^iF, com- 
 bines with the metallic oxides, and forms with them a class 
 of salts called eilicofluorides, which are decomposed by 
 excess of alkali, Si0 2 being precipitated, and an alkaline 
 fluoride remaining in solution. 
 
 462. To detect F in silicated fluorides which are decom- 
 posable by H 2 S0 4 , boil the substance with concentrated 
 HJBOj in a flask, retort, or test-tube, to which is at- 
 tached a bent tube ; conduct the evolved SiF 4 into a 
 solution of NH 4 HO ; NH.F and Si0 2 will be formed; heat, 
 filter, evaporate in a platinum crucible to dryness, and 
 examine the residue by the method described in 460. If 
 the substance under examination contains only a slight 
 
 * The ocating with the wax mny be readily effected by heating the 
 glass cautiously, putting a bit of wax upon the convex face, and spread- 
 ing the fused mass equally over it. The instrument used for tracing the 
 exposed lines should not be too hard ; a pointed piece of wood answers 
 best. The removal of the wax ooating is effected by heating the glass 
 gently and wiping the wax off with a oloth. 
 
Or THE INORGANIC ACIDS. 193 
 
 trace of F and no other volatile acid, it is better to add a 
 very little marble to the substance, so as to insure a con- 
 tinuous slight evolution of gas. When the H 2 S0 4 boils, 
 all the SiF 4 is given off. 
 
 463. " Compounds not decomposable by H 2 S0 4 must 
 first be fused with four parts of Na 2 CO ;j and K,C0 3 . The 
 fused mass is treated with water, the solution filtered, the 
 filtrate concentrated by evaporation, allowed to cool, trans- 
 ferred to a platinum or silver vessel, HC1 added to feebly 
 acid reaction, and the fluid let stand until the C0 2 has 
 escaped. It is then supersaturated with NH 4 HO, heated, 
 filtered into a bottle, CaCl 2 added to the still hot fluid, the 
 bottle closed, and allowed to stand at rest. If a precipi- 
 tate (CaF 2 ) separates after some time, it is collected on a 
 filter, dried, and examined by the method described in 
 460."— H. Rose. 
 
 464. If a fluoride mixed with KHS0 4 is heated in a 
 test-tube, HF is disengaged, which is easily detected by 
 the etching of the glass. Consult also pars. 679 and 
 671, Wi b. 
 
 Hydrosulphuric Acid {Sulphuretted Hydrogen, H 2 S). 
 
 465. This acid exists at the common temperature and 
 pressure as a colorless inflammable gas, possessing a 
 highly offensive odor, resembling that of rotten eggs. It 
 burns with a blue flame, the products of combustion being 
 S0 2 and H 2 0. It is soluble in water, three volumes of 
 which dissolve one volume of the gas; this solution red- 
 dens litmus paper. On exposing the gas in a state of solu- 
 tion to the air, it is decomposed, H 2 being formed, and S 
 being separated. 
 
 466. The sulphides of the metals of the alkalies and 
 alkaline earths are the only metallic sulphides which are 
 soluble in water; we have seen that these metals of the 
 alkalies and alkaline earths form also sulph-hydrates and 
 polysulphides, and these, as well as the monosulphides, are 
 soluble in water, and their solutions are also alkaline to 
 test-paper. The sulph-hydrates .are distinguished from 
 the sulphides by evolving H..S on being decomposed by a 
 metallic salt: 2KHS+MnS0 4 =K 2 S0 4 +MnS + H 3 S ; and 
 the polysulphides are distinguished from the sulphides 
 and sulph-hydrates in that a separation of sulphur, as well 
 as an evolution of H 2 S, attends their decomposition by 
 acids. 
 
 17 
 
194 THE SPECIAL PROPERTIES 
 
 467. The color of the insoluble metallic sulphides and 
 their behavior with acids and other reagents have been 
 noticed in the basic groups. 
 
 468. The sulphides soluble in water and the sulphides 
 which are decomposed by HC1 evolve H 2 S on being treated 
 with J1C1, which, from its characteristic smell, is easily 
 recognized. When the quantity is so minute that the 
 smell fails to afford a sufficient proof, it may be detected 
 by holding a piece of paper moistened with a solution of 
 any soluble lead salt over the mouth of the test-tube, as 
 a brown or black coating of PbS will be formed upon the 
 paper. To detect a trace of an alkaline sulphide in the 
 presence of a free alkali or alkaline carbonate, add to the 
 solution a solution of PbO in NaHO, which may be pre- 
 pared by adding to a solution of PbA 2 one of NaHO until 
 the solution which first forms is redissolved. 
 
 469. Sulphides which are not readily acted on by dilute 
 HC1 alone are readily acted on and evolve abundance of 
 H 2 S on the addition of a piece of Zn. 
 
 470. When sulphides are dissolved in HX0 3 or aqua 
 regia, H 2 S0 4 is formed along with a separation of S. In 
 the case of sulphides, therefore, which, from their insolu- 
 bility in HC1, must be dissolved in HX0 3 or aqua regia, 
 the sulphur is converted into H 2 S0 4 , and not given off as 
 H 2 S. 
 
 471. To ascertain whether the S existed in an unoxidized 
 state, when HN0 8 or aqua regia has been employed as the 
 solvent of the substance under examination, a small portion 
 of the original substance, in fine powder, must be fused 
 with a little solid KHO or NaHO, in a platinum spoon, by 
 means of the blowpipe flame. The fused mass must then 
 be dissolved in a little water and filtered; a bright strip of 
 silver (or polished coin) is put into the solution, and the 
 fluid warmed. If a sulphide were present, a brownish-black 
 film of -Ag 2 S will form upon the metal. This film may be 
 removed afterwards by rubbing the metal with leather and 
 CaO. For other methods of detecting sulphides, see pars. 
 671, 1th; 673, d; 675 and 678. 
 
 Hydrochloric Acid, HC1. 
 
 Solutions for the reactions, NaCl in water. 
 
 472. This ncid is a transparent and colorless gas, of a 
 pungent, acrid, suffocating smell, and fuming strongly in 
 moist air. It is absorbed in large proportion by water, 
 
OE THE INORGANIC ACIDS. 195 
 
 forming the common liquid HC1, which is a mere solution 
 of the gas in water. "With the exception of AgCl and HgCl, 
 all the neutral metallic chlorides are soluble in water; the 
 solutions of the chlorides of the metals, of the alkalies, and 
 alkaline earths of Mil are neutral to test-paper. 
 
 473. When a chloride is heated with MnO, and H a S0 4 , 
 CI is evolved, which may be recognized by its odor and 
 
 GREENISH-YELLOW COLOR. 
 
 474. When a chloride in the solid state and dry is heated 
 with K 2 Cr0 4 in the solid state and concentrated H.,S0 4 , a 
 brown gas is disengaged, which condenses into a blood-red 
 liquid, chlorochromio acid, CrOjClj. On the addition of 
 NH 4 HO in excess the color changes to a yellow, owing to 
 the formation of (NH 4 ) a CrO, ; upon the addition of an acid, 
 the yellow changes to a reddish-yellow color, owing to the 
 formation of (NH 4 ) 2 Cr 2 7 . 
 
 475. If in a bead of NaNH 4 HP0 4 on a platinum wire, 
 CuO be dissolved in the outer blowpipe flame in sufficient 
 quantity to make the mass nearly opaque, a trace of sub- 
 stance containing CI added to it while still in fusion, and 
 the bead then exposed to the reducing flame, a fine blue- 
 colored flame, inclining to purple, will be seen encircling 
 it so long as CI is present. — Berzelius. 
 
 476. Free CI may be readily detected in a solution by 
 adding some of the fluid to a solution containing a ferrous 
 salt and a sulphoc3 - anide ; the solution turns red by reason 
 of the CI converting the ferrous into a ferric salt ; it may 
 also be detected in the absence of nitrous acid, by adding 
 the solution to one of KI and starch paste, when a blue 
 color will be instantly produced. 
 
 Hydriodic Acid, HI. 
 
 Solution for the reactions, KI in water. 
 
 477. HI and the iodides resemble in their properties the 
 corresponding compounds of CI and Br. Hi is gaseous ; 
 it is extremely soluble in water, and the solution, which is 
 colorless, resembles in properties that of HC1 and HBr; 
 but it is more easily decomposed than the two latter com- 
 pounds by substances which have an affinitj' for H, and 
 also by those substances which have an affinity for the 
 other constituent. The colorless solution turns speedily 
 to a reddish-brown when in contact with the air, owing to 
 the formation of H a O and the liberation of I, which is dis- 
 solved by the undecomposed HI. HI and the iodides are 
 
196 THE SPECIAL PROPERTIES 
 
 decomposed by CI and Br, owing to these two elements 
 having a greater affinity for H and the metals. HI, in the 
 gaseous state, may be obtained by placing in a small retort 
 10 parts of K I with 5 of H a O and 20 of I, then drop in cau- 
 tiously 1 part of Pin small pieces, a nd apply a gentle heat; the 
 following equation explains the reaction: 4KI + 5I 2 +P 2 + 
 8H 2 = 2K,HP0 4 + 14HI. HI in solution is easily prepared 
 by suspending I in water and passing H 2 S through the 
 mixture ; HI is formed and S is set free. " The iodides, as 
 a rule, are less volatile, more insoluble and more easily de- 
 composed, than the chlorides and bromides. The iodides 
 of Sn, Sb, and As, like the chlorides and bromides, are de- 
 composed by H 2 0. The hydrated iodides of Mg, Zn, and 
 Al are, like the chlorides and bromides, decomposed by 
 heat into metallic oxide and HI. In addition to the iodides 
 of Pd, Pt, and An, Agl, unlike the chloride and bromide 
 of Ag, is decomposed at a red heat. All iodides, except 
 those of the alkali- and alkaline-earth group, are decora- 
 posed at a red heat by a current of H. The iodides, with 
 the exception of those last mentioned, and those of Pb and 
 Bi, are also decomposed by O at a red heat." 
 
 478. HgNO s throws down from solutions of the iodides 
 a yellowish-green precipitate of Hgl. 
 
 479. HgCl 2 throws down a red precipitate of Hgl, which 
 is soluble in an excess of the HgCl 2 or of KI. 
 
 480. Soluble lead salts precipitate an orange-yellow of 
 Pbl 2 . 
 
 481. Pree I forms with starch, even in highly dilute so- 
 lutions, a compound of a deep blue color. If the I is in a 
 state of combination with H or any metal, it is necessary 
 to liberate it before applying the starch test ; the blue 
 compound is decolorized at a temperature of 70° or 80° 
 C, but recovers its color as the liquid cools ; it is decom- 
 posed by CI, Br, and the alkalies. 
 
 482. CI liberates I from its combinations ; if added in 
 excess, they combine, forming colorless IC1 3 . 
 
 ,483. If iodides are heated with H 9 S0 4 and MnO..„ the I 
 sublimes in the form of violet-colored vapors, which are 
 easily recognized ; this process is the one followed in the 
 manufactory for obtaining the iodine from the kelp liquors. 
 
 484. Palladions chloride, PdCl,, produces even in very 
 dilute solutions of HI and of metallic iodides a brownish- 
 black precipitate of Pdl.„ which is insoluble or nearly so 
 in cold dilute IIC1 and HNO a . PdCl s does not precipitate 
 Br from its solutions. 
 
OF THE INORGANIC ACIDS. 197 
 
 485. Pure HN0 3 , free from nitrous acid, decomposes HI 
 or iodides only when acting upon them in its concentrated 
 form, particularly when aided by the application of heat. 
 But HN0 2 and peroxide of nitrogen, N„0 4 , decompose HI 
 and iodides with the greatest facility even in the most 
 dilute solutions. Colorless solutions of iodides, therefore, 
 acquire immediately a brownish-red color upon the addi- 
 tion of some red fuming HNO a , or of a mixture of this 
 with concentrated H 2 SO„ or, better still, upon addition of 
 a solution of N.,0, in H 2 SO ( , or of nitrite of potash and 
 some H 2 S0 4 or HC1. From more concentrated solutions 
 the I separates under these circumstances in the form of 
 small black plates or scales, whilst nitric oxide gas, NO, 
 and iodine vapor escape. 
 
 486. The best method of detecting I in a solution is to 
 mix with the liquid a little starch ^paste, and acidify it with 
 HC1. A solution of KN0 3 * is then to be added, when, if 
 much I be present, a dark blue color will be instantly pro- 
 duced ; if a very small quantity only — as, for instance, the 
 two or three millionth part — then a few seconds elapse be- 
 fore the blue color makes its appearance. 
 
 487. When a solution containing 1 part of CuS0 4 and 
 1\ parts of FeSO t is added to a neutral or slightly alka- 
 line solution of an iodide, a white precipitate of cuprous 
 iodide, Cul, is formed. The FeS0 4 is added, to convert 
 the Cu"S0 4 into Cu'.SO,. The addition of a small quan- 
 tity of a solution of Na.^CO,, so as to render the solution 
 slightly alkaline, promotes the complete precipitation of 
 the I. Chlorides and bromides are not precipitated by this 
 reagent. 
 
 4~88. A bead of NaNH^PO, saturated with CuO, if 
 mixed with a substance containing I, and ignited in the 
 inner blowpipe flame 3 imparts an intense green color to 
 the flame. 
 
 Iodic Acid, HI0 3 . 
 
 489. This acid is a white crystalline solid; it is decomposed at a 
 moderate heat into and I ; it is readily soluble in water. Its salts are 
 decomposed by heat, a metallio iodide and free oxygen being formed, or 
 into iodine, oxygen, and a metallic oxide; the alkaline iodates are the 
 only salts of this acid which dissolve readily in water. AgN0 3 and 
 BaCl 2 precipitate it from its solutions. 
 
 * A solution of N 2 4 in H 4 S0 4 may be employed in plaoe of the KN0 2 
 and HCL. Fresenius states that a single drop on a glass rod of the N 2 4 
 solution suffices to produce the reaction most distinctly. 
 
 17* 
 
198 THE SPECIAL PROPERTIES 
 
 490. SO, and H 2 S each throw down I from foIutioDS of HI0 3 ; if an 
 excess of either reagent is added, the I becomes converted into HI. 
 
 491. An iodate can be detected in the presence of an iodide by the 
 simple addition of a BtroDg acid ; the HI and HI0 3 act upon each other 
 in the following manner: 6HI4-H10 3 =3I i! +3H 2 0. 
 
 Htdrobromio Acid, HBr. 
 
 Solution for the reactions, KBr in water. 
 
 492. Br at the ordinary temperature is a liquid of a deep 
 red color; it is soluble in water, but it is much more solu- 
 ble in alcohol, ether, chloroform, and bisulphide of carbon; 
 the solutions are reddish-j'ellow. Br, especially in its 
 vaporous state, turns moistened starch yellow ; the yellow 
 color does not always appear instantaneously. HBr is a 
 gas which closely resembles in its properties HC1 gas. It 
 emits in the air white fumes, which are denser than those 
 produced by HC1; it is decomposed by CI, Br being set 
 free, and HC1 formed; the liberated Br appears under the 
 form of reddish vapors, or condenses into reddish drops. 
 HBr is extremely soluble in H.,0 ; the solution is colorless, 
 unless it contains free Br, which it dissolves in large quan- 
 tities ; it has then a dark reddish color. HBr, in the 
 gaseous state, may be obtained by heating KBr with 
 H^PO^, or by acting on PBr s with water, HBr and phos- 
 phorous acid, H 3 PO a , being formed. It may be obtained 
 in solution b\ r passing H 2 S through water which contains 
 Br. The bromides are solid at ordinary temperatures; 
 most of them are fused by a moderate heat, and are par- 
 tially volatilized ; the bromides of An and Pt are decom- 
 posed bj' heat ; most of the bromides are readily soluble 
 in water. 
 
 493. HBr and the bromides, with the exception of AgBr 
 and HgBr, are decomposed by HNO„, on the application 
 of heat, the H or the metal being oxidized and the Br 
 liberated ; if the bromide operated upon is in the solid 
 state or as a concentrated solution, the Br vaporizes ; but 
 if the bromide is in a state of solution and not very con- 
 centrated, the Br dissolves in the liquid, coloring it yellow 
 or yellowish-red. In the cold, HNO.,, even the fuming red 
 acid, does not liberate Br from moderately dilute solutions 
 of the bromides, nor is it liberated by a solution of N,0, 
 in HC1, or by II a S0 4 and KNO„. 
 
 494. 01, in the gaseous state or in solution, immediately 
 liberates Br in the solutions of its compounds; the fluid 
 assuming a yellowish-red tint if the quantity of Br present 
 
OP THE INORGANIC ACIDS. 199 
 
 is not too minute. A large excess of CI must be avoided, 
 since this will cause the formation of chloride of bromine, 
 which will destroy the color wholly or nearly so. This 
 reaction is made much more delicate by addition of a fluid 
 which dissolves Brand does not mix with water, as sul- 
 phide of carbon or chloroform. Mix the neutral or feebly 
 acid solution in a test-tube with a little of one of these 
 fluids, sufficient to form a large drop at the bottom, then 
 add dilute chlorine water drop by drop, and shake the tube. 
 With appreciable quantities of Br, for example 1 part in 
 1000 parts of water, the drop at the bottom acquires a 
 reddish-yellow tint. A large excess of chlorine-water must 
 be avoided, and it must always be first ascertained whether, 
 when mixed with a large quantity of water and some sul- 
 phide of carbon or chloroform, and shaken, it leaves these 
 reagents quite uncolored ; if it does not, it ought not to 
 be employed. If the solution of Br in sulphide of carbon 
 or chloroform is mixed with a solution of KHO, the mix- 
 ture shaken, and heat applied, the 3-ellow color will disap- 
 pear, KBr and potassic bromate, KBr0 3 , being formed. 
 By evaporating this solution to dryness and igniting the 
 residue, the KBrO„ will be converted into KBr. On heat- 
 ing the bromide with Mn0 2 and H, 2 SO\ in a small retort, 
 yellowish-red vapors will be evolved unless the quantity 
 be very minute. These vapors, when brought in con- 
 tact with starch paste, will communicate to it an orange- 
 yellow color, which disappears on exposure to the air.* 
 
 495. Br in presence of I and CI may be identified by the 
 following simple operation : Mix the fluid with a few drops 
 of dilute H.,S0 4 , then with some starch paste, and add a 
 little red fuming HNO s , or, better still, a solution of N 2 4 
 in H. 2 S0 4 , whereupon the iodine reaction will show itself 
 immediatelv. Add now chlorine-water drop by drop until 
 that reaction has disappeared, then add some more chlorine- 
 water to set the Br also free, which may then be separated 
 and identified by means of chloroform or bisulphide of 
 carbon, or the liberated I may also be taken up with chlo- 
 roform or bisulphide of carbon, and chlorine-water cau- 
 tiously added, when the violet-red coloration imparted by 
 
 * Fresenius recommends that the fluid containing the free Br, or the 
 mixture of bromide, Mn0 2 , and H 2 S0 4 , be gently heated in a very snvill 
 beaker, covered with a watch-glass with a slip of paper attached to the 
 lower side, moistened with starch paste, and strewed over with starch 
 powder; in the course of a short time, if bromine is presnnt, a yellow 
 tint will be imparted to the starch. 
 
200 THE SPECIAL PROPERTIES 
 
 the iodine gradually fades away, and after its disappearance 
 the brownish-yellow color given by the Br is distinctly 
 visible. — Fresenius. 
 
 49.6. Solid bromides, when distilled with K 2 Cr 2 7 and 
 concentrated H 2 S0 4 , yield pure Br, which becomes color- 
 less, or nearly so, when treated with excess of NH 4 HO ; 
 by this means it is distinguished from chlorochromic acid, 
 which it resembles in color. (See par. i14.J 
 
 497. If a NaNH 4 HP0 4 bead saturated with CnO is mixed 
 with a substance containing Br, and then ignited in the 
 inner blowpipe flame, the flame is colored blue, inclining 
 to green, more particularly at the edges. — Berzelius. 
 
 Hydrocyanic Acid (Prussic Acid), HCX or HCy. 
 
 Solution for the reactions, KCy in water. 
 
 498. In its anhydrous state HCy is a colorless, volatile, 
 inflammable liquid, possessing a strong odor resembling 
 oil of bitter almonds'^itboils about 27° C, and evaporates 
 in large quantities far Bbk>w its boiling-point; a small 
 quantity of the vapor is sufficftl^tto produce instantaneous 
 death. Water dissolves it in allpmportions ; the solution 
 
 ■-is liable to undergo decomposition if exposed to the light, 
 the decomposition taking place more quickly as the acid 
 is stronger ; alkalies accelerate the decomposition, but the 
 presence of a small quantit} 7 of HC1 impedes decom- 
 position ; concentrated HC1, on the other hand, decomposes 
 HCy immediately into NH 4 C1 and HCH0 2 (formic acid) ; 
 concentrated H 2 S0 4 produces the same decomposition, but 
 further converts the HCIIO., into CO and H 2 0. Although 
 HCH0 2 is one of the products of decomposition of HCy, 
 NH 4 CHO a (ammonic formate) is converted by heat into 
 II Cy and H 2 ; on boiling HCy with an excess of KHO, 
 NH, is evolved and KCH0 2 remains in solution. " To 
 prepare a solution of HCy the usual plan is to decompose 
 in solution K 4 FeCy 6 by dilute H 2 S0 4 , and distil; the best 
 proportions are 10 parts of crystallized K 4 FeCy„ dissolved 
 in 50 parts of H,0 ; 3.5 parts of common H 2 S0 4 are then 
 mixed with 25 parts of H 2 0, and the mixture, when cold, 
 is poured into the solution of the salt, and then distilled ; 
 the equation explains the reaction: 2K 4 FeCy„ + 3H 2 S0 4 
 + Aq = 6 HCy + K„Fe 2 Cy 6 + 3K 2 S0 4 + Aq." The solu- 
 tion of HCy is feebly acid to test-paper; it does not de- 
 compose the alkaline carbonates ; it readily dissolves HgO, 
 forming HgCy„, and, when mixed with a solution of the 
 
OP THE INORGANIC ACIDS. 201 
 
 alkalies, alkaline cyanides are formed, which are soluble in 
 water; their solutions are alkaline to test-paper, and they 
 are decomposed with the liberation of HCy by the weakest 
 acid. HgCy, is soluble in water ; most of the cyanides of 
 the other heavy metals are insoluble. Some of the cyanides 
 give off HCy when treated with dilute solutions of the 
 stronger mineral acids ; others, as ferrous and aurous cya- 
 nides, may be boiled with moderately strong acids without 
 decomposition. Most of the insoluble c3-anides dissolve 
 in solutions of the alkaline cyanides, forming double cya- 
 nides. KCy and NaCy sustain a red heat without decom- 
 position, if air and moisture be excluded ; heated in contact 
 with the air, they are converted into cyanates, M'CyO, 
 and when further heated into carbonates. AgCy and 
 IlgCy, on being heated give off Cy as gas ; other cyanides 
 give off N, a mixture or compound of C and the metal 
 being left. All the cyanides, when heated in the presence 
 of water, are destroyed; the alkaline cyanides are con- 
 verted by continued boiling with water into SH, and alka- 
 line formates. 
 
 499. If to a solution of HCy or an alkaline cyanide 
 KHO and a mixed solution of a ferrous and ferric salt be 
 added, a greenish-blue precipitate will be produced ; on the 
 addition of HC1 insoluble Prussian blue separates. If 
 only a very minute quantity of HCy is present, the fluid 
 simply appears green after the addition of the HC1, and it 
 is only after long standing that a trifling blue precipitate 
 separates from it.* 
 
 500. " If to a solution of HCy KHO is added in excess, 
 and then finely pulverized HgO, the latter dissolves as 
 readily as it would in free HCy. Since HgO is soluble in 
 solutions of the alkalies only in presence of HCy, this 
 reaction may be looked upon as a positive test for that 
 acid." — Fresenius. 
 
 501. When HCy is added to (NHJS containing an ex- 
 cess of S, amnionic sulphocyanide, NH ( CyS 2 , is formed, 
 which gives a deep blood-red color with ferric salts (179). 
 This test may be applied in qualitative analysis in the fol- 
 lowing way: Add a few drops of yellow (NH 4 ) 2 S to the 
 
 * This test may be modified by heating gently the suspected mixture 
 with H 2 S0 4 , and suspending in the flask or retort, for a few minutes, a 
 piece of paper moistened with a solution of KHO ; on dropping a weak 
 solution of the mixed iron salts upon the paper, and immersing it in 
 diluted H 2 S0 4 , HCy may be recognized by the formation of Prussian 
 blue when very minute traces only are present. — Miller. 
 
202 THE SPECIAL PROPERTIES 
 
 liquid supposed to contain the HCy ; evaporate at a gentle 
 heat (not .above 100° C), until the excess of (XH,)_S has 
 completely volatilized, which is ascertained by the smell ; 
 then test the solution with a drop or two of Fe 2 Cl 6 . This 
 test is exceedingly delicate. " If an acetate is present, 
 the reaction takes place only upon addition of fiCl." — 
 Presenilis. 
 
 502. By neither of the above methods will Cy be dis- 
 covered in HgCy 2 ; the solution of HgCy 2 must be treated 
 with H a S, HgS will be precipitated, and HCy remain in 
 solution ; examine then for HCy according to pars. 499, or 
 501, or 503. 
 
 503. Schonbein has recently proposed a new and exceed- 
 ingly delicate test for this acid ; it consists of paper imbued 
 with resin of guaiacum, and moistened with a solution of 
 CuS0 4 , in contact with this acid the prepared paper imme- 
 diately assumes a blue color. To employ this test a slip of 
 the paper Imbued with guaiacum is moistened with the 
 solution of CuS0 4 , and brought in contact with HCy, 
 either dissolved in water or diffused in the ai", when it 
 immediately becomes blue; the color developed on the 
 paper remains for a long time, but diminishes as the paper 
 dries. After several days it passes to a greenish-gray, but 
 revives slightly on moistening the paper. 
 
 504. Detection of the acid in organic mixtures. — Place 
 the suspected mixture in a wide-mouthed bottle. (1) In- 
 troduce into the atmosphere of the bottle Schonbein's 
 paper. (2) Smear a glass plate with a drop of yellow 
 amnionic sulphide, and place it over the month of the 
 bottle; subsequently evaporate the excess of (XH 4 )„S at a 
 low temperature, and proceed as directed at par. 501. (3) 
 Smear a glass plate with a mixture of KHO and FeSO,, 
 and place it over the mouth of the bottle for a few minutes, 
 then acidify with HC1 (par. 499). u In order to obtain the 
 acid from the coats of the stomach or its contents, the 
 substance, cut into small pieces, should be mixed with cold 
 distilled water, and distilled by a water-bath at a low tem- 
 perature (77° C), the distillate being collected in a cold 
 receiver; if the suspected liquid is alkaline, a small quan- 
 tity of tartaric acid may be added to neutralize it; the 
 distillate may then be examined by the three preceding 
 tests."- 
 
OP THE INORGANIC AOIDS. 203 
 
 Nitric Acid, HN0 3 . 
 
 Solution for reactions, KXO, in water. 
 
 505. HNO., when pure, is a colorless liquid, boiling at 
 86° C. with partial decomposition, a weaker acid being left 
 behind ; it fumes strongly in the air, and absorbs water 
 from it, but with less avidity than H 2 S0 4 . It is frequently 
 of a yellowish or red color, owing to the presence of some 
 of the lower oxides of nitrogen. Owing to the facility 
 with which it gives up oxygen, it is, especially when 
 heated, a most powerful oxidizing agent; its action upon 
 the metals has been already noticed, it acts more or less 
 powerfully on all the solid non-metallic elements. It acts 
 with great energy on most organic bodies, the kind of 
 action varying with the strength of the acid and the 
 temperature; organic substances containing nitrogen are 
 stained yellow by the acid. Nitric anhydride (N 2 O s ) is a 
 very unstable body. 
 
 506. All the neutral nitrates are soluble in water; a few 
 of the basic salts are insoluble in that liquid, the solutions 
 of the nitrates of the metals of the alkalies and alkaline 
 earths, and of silver and manganese are neutral to test- 
 paper. Most of the nitrates fuse readily when heated ; 
 they are all decomposed at an elevated temperature; "the 
 nitrates of the highly basylous metals at first give off 
 nearly pure 0, and are converted into nitrites, afterwards 
 a mixture of O and N, together with some nitric peroxide 
 (N 2 4 ). Other nitrates, which decompose at a lower tem- 
 perature, those of Hg, Pb, and Ag, for instance, evolve a 
 mixture of N 2 4 and 0. A few still more easily decom- 
 posable hydrated salts, alutninic and bismuthic trinitrates,^ 
 for instance, give off HN0 3 . Ignited AgN0 3 leaves a 
 residue of Ag, but most normal nitrates, when strongly 
 heated, leave residues of oxides analogous in composition 
 to the original salt, but ferrous and manganous nitrates 
 leave oxides richer in oxygen than those which correspond 
 to the original salts, viz. Fe 2 3 and Mn 3 4 . Nitrates heated 
 with combustible bodies produce a more or less violent 
 deflagration or explosion. The acid-forming bodies, metallic 
 or non-metallic, when deflagrated with nitre, leave potassic 
 or sodic salts of the respective acids." 
 
 507. To detect HNO, in a solution, add to it one-fourth 
 of its volume of undiluted II 2 SO,, and gently warm the 
 solution ; a solution of a ferrous salt must then be added, 
 
204 THE STBOIAL PROPERTIES 
 
 along with a few drops more of the H 2 S0 4 , when the liquid 
 will become of a deep brown color, attended, most likely, 
 with an energetic disengagement of gas ; the color, in this 
 case, will soon disappear, for a reason presently to be named, 
 but can readily be reinstated by afresh addition of the fer- 
 rous solution. Or the solution of the ferrous salt may be 
 added first to the solution of the nitrate, and then the 
 undiluted H 2 S0 4 poured in, in such a way that it forms a 
 layer at the bottom of the test-tube ; in this case the deep- 
 brown color will be produced at the contact-surface of the 
 two liquids. The dark brown color is owing to the forma- 
 tion of a compound of nitric oxide (NO) and the ferrous 
 salt, the formula of the compound being 2Fe"S0 4 ,NO; 
 this compound is destroyed by heat with the disengage- 
 ment of the NO, hence the fading of the color when the 
 solution is heated. 
 
 508 When nitrates are heated with undiluted H 2 S0 4 , in 
 the presence of copper turnings, NO is evolved, which, in 
 contact with the air, forms red fumes, owing to its absorp- 
 tion of oxj'geu and its conversion into nitrous anhydride 
 (N 2 3 ) and nitric peroxide (N 2 4 ). This experiment ought 
 to be conducted in a narrow test-tube. The color is best 
 observed by looking into the test-tube lengthways. 
 
 509. The following is an exceedingly delicate test for 
 detecting HN0 3 , it is therefore specialty adapted for de- 
 tecting the acid in water. Dissolve brucin in 1000" times 
 its weight of water, pour about 15 grains of this solution 
 into a test-tube, then add a little of the water to be tested, 
 and lastly, some H 2 S0 4 ; the acid is made to flow down the 
 side of the tube so as to gather beneath the water. At 
 the place of contact of the two liquids a rose-red zone 
 immediately form s, - if H NO, be present in detectable quan- 
 tity. The reagents must be specially purified before they 
 can be employed. The water employed to dissolve and 
 wash the brucin must be repeatedly rectified over KHO. 
 The brucin is washed with the pure water several times to 
 remove nitrates. The H^O, is mixed with 5 per cent, of 
 NH 4 HCO a , and three-fourths distilled off in a glass vessel. 
 — Kersten. 
 
 510. The following has recently been proposed as a deli- 
 cate test for nitrates, and, therefore, specialty applicable 
 for their detection in water. Into a test-glass about 1 cub. 
 cent, of pure concentrated H..SO, is placed (sp. gr. 1.84), 
 to this is added drop by drop ^ cub. cent, of a solution of 
 sulphate of aniline prepared by adding 10 drops of aniline 
 
Or THE INORGANIC ACIDS. 205 
 
 of commerce to 50 cub. cent, of dilute H 2 S0 4 diluted in the 
 proportion of 1 of acid to 6 of water. A glass rod is dipped 
 into the liquid to be tested and then into the test-glass ; 
 on moving the stirrer about gently, when the slightest 
 trace of NHO, is present, red streaks mark the course of 
 the glass rod ; when there is slightly more than the merest 
 trace, the liquid becomes carmine tinted ; and with a still 
 further quantity a deep red tint, which turns reddish-brown. 
 Hyponitric acid produces the same reaction. 
 
 511. Dissolve 1 part of carbolic acid (phenol) in 4 parts 
 of concentrated H 2 S0 4 , and dilute the solution with 2 
 parts of water. If the substance to be examined for H.N0 3 
 is in solution, evaporate it in a porcelain crucible or its 
 cover, and let fall one or two drops of the phenyl-sulphuric 
 acid solution upon the residue at a temperature of about 
 100° C. By the excess of the H SO, any nitrates, if present, 
 will be decomposed, and the HNO, derived from them will 
 directly form nitro-compounds with the phenol, which are 
 indicated by the production of a reddish-brown color. 
 When neither organic matters, nor compounds of CI, I, 
 and Br, from which H,S0 4 easily separates carbon or the 
 haloids, are present, this coloration is in itself convincing. 
 But fpr fear of their presence, it is better, in all cases, to 
 add a^drop or two of strong NH.HO to the colored pro- 
 duct, when the haloids will be dissolved in the form of 
 coloraes salts, and the carbon remain suspended in the 
 small particles, not interfering with the recognition of the 
 characteristic yellow solution of the nitro-phenylate of 
 ammonia. Frequently, after the addition of IN H 4 HO, there 
 appears'fhstead of a yellow an unstable emerald-green color, 
 which changes into a rose color after the addition of an acid 
 and occasionally becomes greenish-yellow. — Sprengel. 
 
 512. When a minute quantity of gold-\ea.f is boiled in 
 HC1, no action is produced ; but on the addition of a little 
 HNO = , or a nitrate, the gold quickly disappears and may 
 be detected in solution by the method described in par. 284. 
 
 513. When a moderately concentrated solution of KHO 
 is poured upon a mixture of Zn and Fe, H is freelj- dis- 
 engaged, even without the application of heat ; if a nitrate 
 is added to this mixture evolving the H, it is followed by 
 an immediate development of ammonia. This reaction 
 furnishes a good qualitative test of the presence of nitric 
 or nitrous acid. The fluid to be examined is reduced to a 
 small bulk, and poured into a test-tube containing two or 
 three grammes of a mixture of granulated zinc and clean 
 
 18 
 
206 THE SPECIAL PROPERTIES 
 
 iron filings. A small quantity of strong KHO solution is 
 added, and the whole heated to boiling. The usual tests 
 for ammonia may be applied at the mouth of the tube — 
 Har court. 
 
 514. Very minute quantities of HX0 3 may be detected 
 by reducing it first to nitrous acid which may be effected 
 both in the moist and the dry way ; in the former by 
 treating the solution of the HNO„ or of the nitrate for some 
 time with finely divided zinc, best with zinc amalgam, and 
 then filtering (Schonbeiv); in the dry way by fusing the 
 substance under examination witli Na 2 CO, and K,CO ;1 at a 
 moderate heat, exhausting the mass, after cooling, with 
 water, and filtering. Upon adding either of the filtrates 
 to a solution of KI, mixed with starch and dilute H^SO,, 
 the fluid acquires a blue color from iodide of starch; see 
 pars. 485 and 486 Fresevius. 
 
 515. If a mixture of nitrate with KCN" in powder is 
 heated upon platinum foil, a violent deflagration will ensue, 
 owing to the sudden evolution of C0 2 and N, produced by 
 the oxidation of the CN. Tery minute quantities of 
 nitrates may be detected in this way. 
 
 Nitrous Acid, HXO a . 
 
 516. Nitrites give a brown color with ferrous salts without the addition 
 of an acid. Acidulated solutions of nitrites produce at once a purple 
 color with starch and KI. The nitrates do not color ferrous salts brown 
 or decompose KI until the nitric acid has been liberated and reduced to 
 nitrous acid by warming with sulphuric acid. 
 
 617. Nitrites are, like nitrates, oxidizing agents, but they act more 
 readily than the latter. Nitrites act also as reducing agents, acidulated 
 solutions decolorize potassic permanganate, and gradually change 
 potassic bichromate to a greenish hue: they also reduce AuCl 3 and mer- 
 curous salts; these reducing actions distinguish them from nitrates. 
 
 Chloric Acid, HC10 3 . 
 
 518. This acid, in its concentrated state, appears in the 
 from of a yellow syrupy liquid, the odor of which resembles 
 that of UNO,; the dilute acid is colorless and inodorous. 
 HC10 3 is an unstable acid, it gradually undergoes decom- 
 position on exposure to light; at a temperature of 40° C. 
 it undergoes decomposition, and at 100° C, or a little 
 above, it is rapidly converted into perchloric acid (HCIO,), 
 oxygen, chlorine, and water: 3liclOj = HCIO + CI 
 + 20, + 11,0. 
 
 It is decomposed by contact with organic matter ; it is 
 
Or THE INORGANIC ACIDS. 207 
 
 a very powerful oxidizing and bleaching agent; it reddens 
 litmus first and afterwards bleaches it. Chloric anhydride 
 has not been obtained. 
 
 519. All the chlorates are soluble in water; they are 
 decomposed upon ignition, oxygen being given off, and 
 generally the metal is left as a chloride ; but in the case of 
 mngnesic and some other chlorates the metal is left as an 
 oxide, CI and being given off: 2MgC10 3 = 2MgO + Cl 2 
 + 20 2 . 
 
 Fused chlorates are powerful oxidizing agents ; when 
 heated with organic substances, they deflagrate with far 
 greater violence than the nitrates. The solutions of the 
 chlorates of the metals of the alkalies and alkaline earths 
 are neutral to test-paper. 
 
 520. To detect this acid, add to a small quantity of the 
 solid substance under examination a few drops of undiluted 
 H. ; SO, in the cold. The chlorate will be decomposed, 
 KHS0 4 and potassio perchlorate (KCIOJ being formed, 
 along with a greenish-yellow colored explosive gas, 
 perchloric oxide (CljO,), which escapes : 3KC10 3 -f 2H 2 S0 4 
 = KC10 4 + Cl.O, + 2KHS0 4 + H a O, the application of 
 heat must be avoided, and the quantities operated upon 
 should be small, to prevent any loud and violent explosion 
 taking place. 
 
 521. If the solution of a chlorate is colored light blue, 
 with some solution of indigo in sulphuric acid, a litle dilute 
 H 2 SO ( added, and a solution of sulphite of soda dropped 
 cautiously into the blue fluid, the color of the indigo dis- 
 appears immediately. The cause of this equally charac- 
 teristic and delicate reaction is, that the sulphurous acid 
 deprives the chloric acid of its oxygen, and the liberated 
 chlorine decolorizes the indigo. {Fresenius.) This test 
 readily distinguishes chlorates from nitrates. 
 
 522. Upon heating chlorates with HC1 the constituents 
 of the two acids decompose, forming water, chlorine, and 
 an oxide of chlorine. The test-tube in which the experi- 
 ment is made becomes filled in this process with a greenish- 
 j'cllow gas, of a very disagreeable odor, resembling that of 
 chlorine ; the HC1 acquires a greenish-yellow color. 
 
 523. If a mixture of chlorate and KCy is gently heated 
 upon platinum foil, a very violent deflagration ensues, even 
 with a minute quantity of chlorate. The experiment must 
 only be made with very minute quantities of chlorate. 
 
208 the general properties 
 
 Classification of the Inorganic Acids, including 
 Oxalic Acid, with a Description of the Processes 
 to be followed in the examination of Substances 
 for these Acids. 
 
 524. Classification of the acids. — The inorganic acids 
 described in this book may be conveniently divided into 
 four groups, as follows: — 
 
 First Group. 
 
 1st Division. — Acids which are precipitated by HS from 
 acid solutions, as Sulphides — arsenious and arsenic acids. 
 M Division. — Acid which is converted by H 2 S into a 
 base — chromic acid. The acids contained in this group 
 are detected in testing for the bases. Arsenious and 
 arsenic acids, being precipitated by H,S, are classed 
 amongst the bases ; whilst chromic acid is converted into 
 Cr 2 0.,, a member of the fourth group of bases ; the change 
 of color attending this conversion is so characteristic, 
 that it cannot be overlooked by the most inexperienced 
 student. The onlj r thing which can cause the least diffi- 
 culty or perplexity is the mistaking a green solution, with 
 a light-colored precipitate suspended in it, for a green 
 precipitate. 
 
 Second Group. 
 
 525. 1st Division. — Acids which are precipitated by 
 BaCl, or any soluble baric salt from neutral, but not from 
 acid, solutions, their baric salts being soluble in acids. The 
 members of the 1st group, and likewise phosphoric, oxa- 
 lic, hydrofluoric, boracic, silicic, and carbonic acids.* 
 2d Division. — Acid which is precipitated b}' BaCl,, or 
 any soluble baric salt from acid, as well as neutral solu- 
 tions — sulphuric acid. 
 
 (a) All these baric salts are colorless, with the excep- 
 tion of baric chromate, which is of a pale-yellow color. 
 If arsenious, arsenic, or chromic acid has been detected in 
 
 * Baric borate, nlso baric oxalate and fluoride, nre soluble in solutions 
 containing nmmonio salts; the lust two nre soluble in a loss degree 
 than the bario borate. A borate, oxalate or fluoride may be present in 
 a solution which gives no precipitate on the addition of a soluble bario 
 salt, if aramouic salts are prcseut. 
 
OP THE INORGANIC ACIDS. 209 
 
 examining for the bases, it should be got rid of from the 
 portion of the solution to which the baric and silver salts 
 are to be added bj 7 slightly acidifying the solution with 
 HXO„ if it is not acid to test-paper, and treating it with 
 an excess of H V S, filtering if necessary, gently boiling the 
 solution until the excess of II a S is removed, and neutral- 
 izing it with NII 4 HO. If C0. 2 has been detected in testing 
 for the bases, it is better to get rid of it also before add- 
 ing the baric salt, by adding, as before, HN0 3 until it is 
 slight^' in excess, and then boiling for a short time ; and, 
 as before, neutralizing the solution with NH 4 HO. To 
 the neutral solution thus prepared, if one or all of these 
 four acids were present, or to the neutral solution if they 
 are not present, a solution of BaCl 2 is added, or if an 
 argentic or mercurous compound is present, a solution of 
 Ba(jS'0 3 ) 2 ; if no precipitate is formed the acids of this 
 group, with the exception of those got rid of, are absent;* 
 if a precipitate is produced add dilute HC1, or dilutellHO^ 
 if Ba(NOJ 2 f nas been employed; if the whole of the preci- 
 pitate, or a portion of it, is dissolved, one or more of the 
 acids whose baric salts are soluble in acids are present; if 
 the whole or a portion of it is insoluble in acids, H 2 S0 4 or 
 a sulphate is present. 
 
 Third Group. 
 
 526. 1st Division Acids which are pi*ecipitated from 
 
 neutral, but not from acid, solutions by AgNO . The 
 members of the 1st and 2d groups, with the exception of 
 sulphuric acid. 2d Division. — Acids which are precipi- 
 tated from acid as well as neutral solutions — hydrosul- 
 phuric, hydrochloric, hydrobromic, and hydriodic acids. 
 
 The following silver salts are colored : Argentic sul- 
 phide, black; the chromate, red; the arseniate, reddish- 
 brown; the arsenite, phosphate, and iodide, yellow; the 
 silicate, yellow or white; the bromide, yellowish-white. 
 The silver salts of the rest of the acids of the group are 
 colorless. Besides removing the acids of the 1st group 
 
 * The absence of the acids whose baric salts am soluble in amnionic 
 Baits, if these are present, is not established by this experiment (see 
 note, page 208). 
 
 f Concentrated HC1 or HN0 3 must not be employed, because BaCI, 
 and Ba(N0 3 ) s are insoluble iu them, and would therefore separate from 
 the solution. 
 
 18* 
 
210 THE GENERAL PROPERTIES 
 
 and CO,, it is necessary also to get rid of a sulphide before 
 adding the silver salt, and as ferrous sulphate reduces the 
 silver salt, Ag being precipitated, it is necessary to convert 
 it, if it is present, into the ferric slate ; the solution must, 
 therefore, be rendered slightly acid, if it is not so already, 
 with HNO s ; it must then be treated with an excess of H 2 S, 
 if any of the members of the 1st group of acids are present, 
 and filtered if necessary ; the solution must be gently boiled 
 to expel the H 2 S and C0 2 , and to convert the ferrous salt 
 into the ferric state; NH 4 HO must then be added to the 
 solution slightly in excess, and the solution again boiled 
 until it is neutral to test-paper ; if a precipitate has been 
 formed, filter and add a solution of AgNO, to the clear 
 liquid. If the solution becomes acid after the addition of 
 the silver solution, it ought to be very carefully neutralized 
 with NH 4 HO; if no precipitate is produced by AgNO , all 
 the acids of the group, with the exception of those got rid 
 of, are absent. If a precipitate is produced, its color ought 
 to be observed; HiNO s , entirely free from HC1, must be 
 added, and the mixture shaken ; if the whole of the pre- 
 cipitate or a portion of it is dissolved, one or more of the 
 acids whose silver salts are soluble in HNO, are present; 
 if the whole or a portion of the silver precipitate is insolu- 
 ble in HNO b , HC1, HBr, HI, HCN, or their radicals, may 
 be present. As AgNO, causes no precipitate in solutions 
 of mercuric cyanide, if Hg in the mercuric state is present, 
 cyanogen may be present, although AgX0 3 produces no 
 precipitate ; cyanogen must, therefore, be examined for ac- 
 cording to par. 502, when mercury is present. 
 
 When the silver precipitate does not entirely redissolve 
 in HN0 3 , examine the original solution for Cy, I, Br, and 
 CI. 
 
 Fourth Group. 
 
 527. Acids which are not precipitated by any reagent — 
 nitric and chloric acids. A special examination must 
 always he made for the acids contained in this group. 
 
 528. We will now give directions for testing for each acid 
 individually by means of characteristic tests, and after- 
 wards the methods to be pursued in preparing solutions for 
 the examination of the acids. 
 
OF THE INORGANIC A0ID8. 211 
 
 Characteristic Tests for the Inorganic Acids. 
 
 529. The characteristic tests must be applied to the ori- 
 ginal solution ; a separate portion must be taken for each 
 acid. 
 
 530. Arsenious Acid, Arsenic Acid, Chromic Acid. — 
 As these acids are discovered in testing for the bases, no 
 experiments require to be made for their detection when 
 testing for the acids. 
 
 531. Sulphuric Acid. — The presence or absence of this 
 acid is ascertained on testing a part of the solution with 
 the general reagent, BaCl,, and if a precipitate is produced 
 digesting it in dilute HC1 or HN(\, if it dissolves the acid 
 is absent, if it does not dissolve it is present (404). 
 
 532. Boracic Acid. — This acid can be detected in most 
 cases, by the method described in par. 419 ; but the most 
 certain test is the one described in par. 420. 
 
 533. Phosphoric Acid. — When the phosphates are solu- 
 ble in amnionic solutions (and the student can decide this 
 when he knows what bases are present), this acid can be 
 detected by the method described in par. 424, but the most 
 certain tests are 427 and 428, especially the last. The 
 student must, however, remember that arsenic acid gives 
 precipitates with these reagents, similar to those given by 
 phosphoric acid; when present, it must, on this account, 
 be removed from the solution by H 2 S, or be reduced to the 
 state of arsenious acid, before testing for phosphoric acid. 
 P0 4 may also be detected by the method given in par. 431. 
 
 534. Carbonic Acid. — This acid is distinguished from 
 the other gaseous- acids by giving a precipitate with lime- 
 water; the way for evolving the gas, when combined, and 
 testing it when liberated, with lime-water, is described in 
 pars. 441 and 442. 
 
 535. Oxalic Acid. — This acid is detected by the method 
 described at 449 ; but very minute quantities of it are 
 more securely detected by boiling the substance with a 
 solution of Na.CO ,, for some time ; subsequently Altering, 
 and acidifying the filtrate witli acetic acid, and then add- 
 ing to it a solution of CaSO, (451). 
 
 536. Silicic Acid. — To test for this acid, evaporate the 
 solution to dryness with an acid, and proceed as directed 
 at 453" or 455. 
 
 537. Hydrofluoric Acid. — Test for this acid, when 
 silicic acid is absent, by the method described at 460 ; 
 
212 PREPARATION OP THE SOLUTIONS 
 
 when silicic acid is present, by the one described at 462 
 or 463. 
 
 538. Sulphide of Hydrogen. — This acid is distinguished 
 from the other gaseous acids by giving, with soluble salts 
 of silver and lead, black precipitates ; the way for applying 
 the test is described in par. 468. The sulphur in sulphides 
 which are not decomposed by HC1, but require for their 
 decomposition HN0 3 , or aqua regia, cannot be detected in 
 this way: recourse must be had in these cases to the pro- 
 cess described in par. 471- 
 
 539. Hydrochloric Acid. — When HBr and HCy are 
 absent the presence of this acid is proved by the insoluv 
 bility of the silver precipitate in HN0 3 , and by its solu- 
 bility in NH 4 HO ; when HCj 7 is present, and HBr absent, 
 its presence is proved, if, after igniting the silver precipi- 
 tate, which was insoluble in HNO, but soluble in XHJIO, 
 a whitish residue remains, which is insoluble in HN0 3 . 
 When HBr is present, no matter whether HCy is present 
 or absent, the presence of HC1 can only be ascertained by 
 the test described at 474. 
 
 540. Hydriodic Acid. — Iodine is best discovered by the 
 test described at 486. 
 
 541. Hydrobromic Acid. — Examine for Br, according to 
 the method given in par. 494 ; in the presence of I or CI, 
 according to par. 495. 
 
 542. Hydrocyanic Acid This acid can be distinguished 
 
 from all other acids by the tests described in pars. 499, 
 501, and 503; if, however mercuric compounds are present 
 which will have been discovered in testing for the bases, 
 the process described in par. 502 must be employed. 
 
 543. Nitric Acid The tests described at 507. 508, 512, 
 
 513, or 514, may be employed, but for the detection of the 
 acid in waters the tests described at pars. 509 and 510 are 
 the best. 
 
 544. Chloric Acid. — The presence or absence of this 
 acid is proved by the tests described at 521 and 522. 
 
 545. Preparation of the solutions and examination for 
 the acids. 
 
 The examination for the metallic or basic constituents 
 must always precede the examination for the acids, for 
 in the search for acids, the student will be greatly assisted 
 by knowing what basic substances are present, which of 
 their salts are soluble in water, and the reaction of the 
 aqueous solutions of those salts on vegetable colors, also 
 which of the salts of the metals found are insoluble in 
 
FOR THE EXAMINATION OP THE AOIDS. 213 
 
 water, but soluble in acids, and which of them are insolu- 
 ble both in water and acids. He will, from a knowledge 
 of the metals present, the solubility or insolubility of the 
 substance under examination in water or acids, be able to 
 form a tolerably correct conclusion as to the acid or acids 
 which must be absent; thus, for instance, if the substance 
 is a solid soluble in water, or it is a solution, water being 
 the solvent, and the solution in either case is neutral to 
 test-paper and the basic constituents present are K, Na 
 and NH, all the acid radicals whose salts of K, Na and 
 NH„ are alkaline to test-paper must be absent, and if any 
 polybasic acid i - adical is present which class of salts of 
 this radical it is that is present will also be known. To 
 take another example: if Ba, K, and Na were the metals 
 present, and the solution was neutral to test-paper, all the 
 acid radicals whose baric salts are insoluble in water, and 
 all the soluble salts of Ba, K, and Na that are alkaline or 
 acid to test-paper, must be absent. Again, S0 4 or CI need 
 not be sought for in soluble compounds containing Ba or 
 Ag respectively. 
 
 54fi If the substance is a solid soluble in water, or it is 
 a solution, water being the solvent, and if any of the mem- 
 bers of the 1st group of acids or C0 2 , or H„S, have been 
 detected, they must be got rid of and the solution neu- 
 tralized as described at par. 525-a, the solution must then 
 be examined for the other acids, as there directed. If 
 none of the acids of the 1st group, nor C0 2 , or H 2 S, have 
 been detected, proceed at once with the examination for 
 the other acids according to par. 525-a, if the solution is 
 neutral ; if it is alkaline, first render it exactly neutral 
 with HSOj, and then proceed with the examination; if it 
 is acid, neutralize it with NII,HO ; filter, if necessary, and 
 then proceed with the examination according to 525-a. 
 
 547. If the substance is insoluble in water but soluble 
 in acids, or if it is a solution, an acid being the solvent, it 
 is better in the majority of cases to get rid of all the metals 
 but the alkaline ones, as the presence of some of the other 
 metals interferes with the detection of some of the acids ; 
 they may be got rid of by one or other of the three fol- 
 lowing methods: 1. Precipitate the members of the 5th 
 and 6th groups of bases, when they are present, from the 
 acid solution with H 2 S ; filter, boil the filtrate gently until 
 the excess of H 2 S is expelled, then add a solution of Na 2 C0 3 
 (entirely free from sulphate and chloride) in excess, and 
 then a little Na 2 C0 3 in the solid state, and boil for some 
 
214 PRELIMINARY EXAMINATION 
 
 time ; 2d. Boil the dry solid with an excess of a concen- 
 trated solution of Na 2 CO„ for some time ; 3d. Mix the solid 
 with four parts of NaKCO.,, and fuse the mixture ; boil the 
 fused mass in water; whichever of these plans has been 
 adopted the bases remain in the residue, and the acid radi- 
 cals in combination with the Na ; filter and add to tie fil- 
 trate HN0 3 , slightly in excess, heat the solution gently, 
 taking care that it remains permanently acid, until all the 
 C0 2 is expelled, then add NH^HO, slightly in excess, again 
 warm the solution until it is neutral to test-paper ; if a pre- 
 cipitate has been formed, filter and examine the clear solu- 
 tion according to par. 550. 
 
 548. It is not necessary to remove the bases in order to 
 test for I^SO,, HC1, and HN0 3 . All the chlorates are 
 soluble in water, and so are all the nitrates, with the excep- 
 tion of a few basic ones ; if a substance is, therefore, en- 
 tirely insoluble in water, chlorates must be, and nitrates 
 probably are, absent; if a portion only of a substance is 
 soluble in water, treat a portion of the substance with 
 water, and examine the aqueous solution specially for the 
 acids of the 4th group. 
 
 549. In testing for the acids the general reagents are used 
 in most cases only to prove the presence or absence of an 
 entire group of acids. The detection of each of the acids 
 in the groups requires the further application of the charac- 
 teristic tests, par. 529. 
 
 550. Test a portion of the solution with one of BaCl 4 or 
 Ba(N0 3 ) 2 , as directed at par. 525 ; test another portion with 
 one of AgN0 3 , as directed at par. 526, then test specially 
 for the acids indicated by these reagents, and also for those 
 of the 4th group. 
 
 551. Preliminary examination for acids By heating 
 
 the substance with concentrated H ; S0 4 the presence or ab- 
 sence of volatile inorganic acids is at once ascertained, these 
 acids either volatilizing undecomposed, or yielding volatile 
 products of decomposition. For this purpose a small por- 
 tion of the dry substance is heated in a test-tube (not to 
 boiling), with three or four times its volume of concentrated 
 H a S0 4 ; when, in the case of all acids which are either vola- 
 tile without decomposition, or are decomposed by H v S0 4 at 
 a high temperature, gases or vapors are evolved, the proper- 
 ties of which, in most cases, indicate the nature of the acids 
 present. The following table exhibits the behavior of the 
 salts of the volatile acids with concentrated ILSO, : — 
 
FOR THE INORGANIC ACIDS. 
 
 215 
 
 Without Decomposition. 
 
 CO a . Inodorous ; causes a precipi- 
 tate in lime water. 
 
 S0 2 . Odor of burning S ; turns a 
 solution of K 2 Cr0 3 green. 
 
 H 2 S. Odor of rotten eggs; turns 
 paper moistened with a lead 
 solution brown. 
 
 HC1. Irritating gas, which gives 
 white fumes in contact with 
 NH 3 
 
 HF. Fuming gas, which corrodes 
 glass. 
 
 HN0 3 . Colorless acid gns, some- 
 times having brownish tiut 
 from a portion of it being 
 decomposed; on the addition 
 of copper filings red fumes, 
 which color starch paste and 
 KI blue. 
 
 With Decomposition. 
 
 HI. Violet vapors of I, which color 
 starch-paste blve. 
 
 HBr. Red vapors of Br, which color 
 starch-paste orange. 
 
 HCN. Disengages CO, which burns 
 with a blue flame. 
 
 Cr0 3 . Evolves 0, the solution be- 
 coming brown or green. 
 
 HC10 3 . Greenish- yellow explosive 
 
 gas. 
 H 2 C 2 4 . Evolves C0 2 and CO. 
 
 552. It must be observed that the behavior of a mixture 
 of salts when heated with H 2 S0 4 is often different to the 
 behavior of the salts when heated separately with H 2 S0 4 ; 
 thus, for instance, a mixture of a nitrate and chloride, when 
 heated with H a S0 4 , evolves CI, and red nitrous fumes. 
 Mercury and tin chlorides are decomposed with difficulty, 
 if at all, by H 2 SO> 
 
 553. Answers to the following exercises must be written 
 out. 
 
 EXERCISES. 
 
 143. Describe the chemical reactions involved in the etch- 
 ing of glass. 
 
 144. How can small quantities of HC10 3 be recognized 
 in the presence of HC1? 
 
 145. What is meant by stating that a water is hard? 
 and describe Clarke's process for softening hard water. 
 
 146. What is the action of HJ3 and S0 2 on highly oxi- 
 dized bodies? Illustrate your answer by diagrams show- 
 ing the action of H 2 S on Fe,3S0 4 and SO a on K 2 Cr 2 7 . 
 
 147. What changes do NiC 2 4 and CoC 2 4 undergo when 
 heated in close vessels? 
 
 148. What is the action of HC1 and H 2 S0 4 on chromates? 
 Illustrate your answer by diagrams. 
 
216 ORGANIC ACIDS. 
 
 149. How is iodine prepared on the manufacturing scale? 
 
 150. How is fluorine detected in the presence of silicates? 
 
 151. Describe the properties and some of the transforma- 
 tions of HgCjO,. 
 
 152. How is HCy prepared ? what transformations does 
 it undergo in the presence of acids and alkalies ? and give 
 the different methods for ascertaining its presence. 
 
 153. What change do the neutral and acid chromates of 
 the alkaline metals undergo on being heated? 
 
 154. What is the action of HF upon Si0 2 in the presence 
 of water ? 
 
 155. Chrome iron ore in fine powder is mixed with chalk, 
 and the mixture is heated to bright redness in a current 
 of air in a reverberatory furnace for nine or ten hours, the 
 mixture being frequently stirred ; it is afterwards treated 
 with water, the clear solution drawn off from the insoluble 
 matter, and H 2 SO t is then added to the solution until it 
 is slightly acid ; K 2 CO a is then added, the mixture is after- 
 wards filtered, and the solution is evaporated until crystals 
 begin to form. What change does the chrome iron uudergo 
 in roasting? what is dissolved out of the roasted mass by 
 the water ? why is the H 2 S0 4 addetl ? what change does 
 the K,C0 3 effect? and, finally, what substance is it that 
 crystallizes out ? 
 
 156. What takes place when a mixture of NaCl, K,CrO„ 
 H a SO t is submitted to distillation ? 
 
 157. Acids which form insoluble lead salts are frequently 
 separated from other acids and substances which are not 
 precipitated by lead salts, bj' means of lead acetate or 
 nitrate, and washing the precipitate to free it from the other 
 impurities and the excess of the soluble lead salt added, 
 afterwards suspending the insoluble lead salt in water, and 
 passing H 2 S through the mixture to excess; the lead is 
 converted into insoluble PbS, whilst the acid remains in 
 solution ; could chromic acid be purified in this manner? 
 Give reasons for the opinion expressed. 
 
 158. Describe the effect of heat on the following phos- 
 phates, Na 3 PO„ Na,Hl'0 # , and >*aH„P0 4 . 
 
 159. Is there any method of disintegrating a silicate 
 insoluble in acids without fusing it? 
 
 Organic Acids. 
 
 554. Organic ncids cannot be detected with the same cer- 
 tainty and precision as the inorganic acids. To detect with 
 
ORGANIC ACIDS. 21T 
 
 certainty even some of those which we have given requires 
 on the part of the analyst great skill and judgment. The 
 special properties of each of the acids are first described, 
 their division into groups, with a description of the pro- 
 perties of each group of acids, and afterwards the processes 
 to be followed in preparing solutions for their examination. 
 
 BEIIAVIOE OF THE ACIDS AND THEIR RADICALS 
 WITH REAGENTS. 
 
 Tartaric Acid, H H 2 C 4 H 2 6 = H 2 T. 
 
 Solution for the reactions, NaHH a C 4 H 2 O fi in water. 
 
 555. This acid is tetratomic, but only two of its four re- 
 placeable atoms of H can be replaced by metals, the other 
 two are replaceable by alcoholic and acid radicals. This 
 acid forms with monatomic metals both acid and neutral 
 salts, for example, hydric potassic tartrate KHH,C 4 H 2 6 , 
 potassic tartrate K 2 H 2 C 4 H a O , potassic sodic tartrate (Ro- 
 chelle salt) KNaH^HjO,,; with diatomic metal's it forms 
 neutral salts, having the general formula M"H 2 C 4 H 2 6 ; 
 one of the commonest tartrates is the so-called tartar 
 emetic KSbOH 2 C 4 H 2 O , which may be considered as con- 
 taining the monatomic radical SbO in place of an atom of 
 H, or a monatomic metal. 
 
 556. This acid exists in grapes, tamarinds, and many 
 other fruits; it is deposited during the fermentation of the 
 grape juice as the acid potassic salt KHH 3 C 4 H,O h , this 
 deposit is called in commerce crude tartar, or argol, and 
 when purified by recrystallization, cream of tartar. The 
 acid is obtained by precipitating from the tartar solution 
 the calcic salt, and decomposing this salt with dilute 
 HjSOj, and then evaporating the solution to the crystal- 
 lizing point. It occurs in the form of colorless, transparent 
 crystals : it dissolves in cold, as well as in hot water, and 
 is soluble also in alcohol, the solution is acid to test-paper, 
 and if kept for a short time, becomes mouldy and decom- 
 poses. It can be produced artificially by acting upon milk 
 sugar with HN0 3 ; it is also obtained by treating dibromo- 
 succinic acid, C^Bi^O,, with Ag 2 0, in the presence of 
 water, thus : C 4 H 4 Br 2 4 + Ag 2 + H 2 = C 4 H 6 6 + 2AgBr. 
 
 By the action of HI or iodide of phosphorus, it is reduced 
 to malic, or to succinic acid : — 
 
 (1) C 4 H 6 6 + 2HI = C 4 H 6 5 + I 2 + H 2 0, 
 Malic acid. 
 
218 THE SPECIAL PROPERTIES 
 
 (2) C 4 H„0 6 + 4HI = C 4 H„0 4 + 21, + 2H 2 0, 
 Succinic acid. 
 
 In the presence of oxidizing agents it is converted (gene- 
 rally) into carbonic, formic, and oxalic acids. When fused 
 with KHO the acid and tartrates break up into an acetate 
 and an oxalate : C 4 H 6 0„ + 3KHO = KC 2 H 3 2 + K a C 2 4 
 + 3H 2 0. 
 
 557. The acid and its salts, when heated, char, and emit 
 a peculiar and very characteristic odor, resembling that of 
 burnt sugar, which is best perceived when the substance 
 is heated in a tube open at both ends. If the acid, or a 
 tartrate in the solid state, be heated with concentrated 
 H 2 S0 4 , the mixture acquires a black or a brownish-black 
 color, owing to the separation of carbon, which takes place 
 simultaneously with the evolution of CO. If a solution of 
 potassic permanganate be rendered strongly alkaline, and 
 a tartrate be added and the solution boiled, the solution 
 becomes decolorized, the permanganate being reduced to 
 Mn0 2 . 
 
 558. The tartrates of the alkaline metals and of those 
 of the 3d and 4th groups are soluble in water. The tar- 
 trates that are insoluble in water are soluble in HC1 or 
 HNO> 
 
 559. As tartaric acid is a test for K, so in like manner 
 potassic salts, especially the acetate, can be employed as a 
 test for tartaric acid, free and combined ; for this purpose 
 a concentrated solution of potassic acetate is added to the 
 solution, and the mixture is then shaken very violently, as 
 the precipitate is greatlj' promoted by shaking, and the 
 addition of an equal volume of alcohol heightens the deli- 
 cacy of the reaction. 
 
 560. BaCl 2 produces in solutions of the tartrates a white 
 precipitate of BaH 2 C 4 H 2 O e , which is soluble in solutions 
 containing ammonic salts and in HC1. 
 
 561. CaCl 2 precipitates from solutions of the tartrates a 
 white precipitate of CaH ,O 4 II.,O , 4H 2 0, which is soluble in 
 acetic and the mineral acids; ammonic salts retard the 
 formation of the precipitate. It is distinguished from 
 calcic phosphate, calcic borate, and calcic oxalate, by dis- 
 solving in a cold not over-dilute solution of KHO, from 
 which solution it is precipitated on boiling, and again 
 redissolved as the liquid cools. 
 
 562. Lime-water produces in solutions of the tartrates 
 and also in solutions of the acid, if added until the solution 
 
OP THE ORGANIC ACIDS. 219 
 
 is alkaline, a white flocculent precipitate of calcic tartrate, 
 which becomes crystalline after some time ; this precipitate 
 is soluble in tartaric acid and in solution of NH.C1, from 
 which solutions the calcic tartrate separates after some 
 time in the crystalline form. 
 
 563. Plumbic acetate produces in solutions of tartaric 
 acid and the tartrates a white precipitate of PbH,C 4 H 2 0, i , 
 which dissolves readily in HN0 3 , in jN t H 4 HO, in tartaric 
 acid, and in amnionic tartrate, 
 
 564. AgN0 3 produces, in solutions of the neutral tar- 
 trates, a white precipitate of Ag^H^H^O,,, which is soluble 
 in NH 4 HO ; if the amnionic solution be gentty heated a 
 bright metallic deposit of silver is formed. 
 
 Citric Acid, H 3 HC (i H 4 7 . 
 
 Solution for the reactions Na 3 HC 6 H 4 0, in water. 
 
 565.' This acid is tetratomic, but only three of its four 
 replaceable atoms of H can be replaced by metals ; the fourth 
 is called alcoholic hydrogen. It forms with the alkali 
 metals, one neutral and two acid salts, ex. tripotassic citrate 
 K 3 HC 6 H 4 0„ hydric dipotassic citrate K^HHCgH^O;, and 
 dihydric potassic citrate KH 2 HC e H 4 T ; it forms with dj-ad 
 metals two classes of salts having the following general 
 formulae: M"HHC 6 H 4 7 and M" 3 (HC 6 H 4 7 ) 2 . 
 
 566. This acid exists in lemons, oranges, citrons, goose- 
 berries and many other fruits ; it is prepared from lemon 
 juice by neutralizing it with chalk 2 after it has fermented a 
 little to separate the mucilage and other impurities; the 
 lime salt thus obtained is decomposed with dilute H 2 S0 4 , 
 and the solution evaporated to the crystallizing point. 
 It forms large transparent ciystals, it is very soluble in 
 hot and cold water, and also in alcohol ; its solution is 
 acid to test-paper 3 and decomposes on keeping. Fused 
 with KHO it gives potassic acetate and oxalate — C 6 H B 7 
 + 4KHO = 2KC 2 H 3 2 + K. 2 C 2 4 + 3H 2 0. 
 
 567. Citric acid chars when heated ; the charring is 
 attended with an evolution of pungent fumes which cannot 
 be mistaken for those evolved by tartaric acid. If the acid 
 or a citrate in the solid state be heated with concentrated 
 H a S0 4 , CO, and C0 2 are evolved without any change of 
 color in the liquid ; the mixture blackens only after long 
 boiling. If a solution of potassic permanganate be ren- 
 dered strongly alkaline, and a salt of citric acid be added 
 
220 THE SPECIAL PROPERTIES 
 
 and the mixture boiled, the solution gradually becomes 
 green, and so remains on continued boiling. 
 
 568. Both the neutral and acid salts of the alkaline 
 citrates are readily soluble in water ; citric acid is not, 
 therefore, precipitated from its solutions on the addition of 
 potassic acetate. Citric acid, like tartaric acid, prevents 
 the precipitation of alumina, ferric oxide, and other bases, 
 by the alkalies. 
 
 569. A solution of BaCl 2 produces in solutions of the 
 citrates a white precipitate of baric citrate, which is soluble 
 in much water, in free acids, and in solutions of ammonic 
 salts. 
 
 570. A solution of CaCl 2 produces in solutions of citrates, 
 but not in citric acid, a precipitate of calcic citrate, which 
 is more insoluble in hot water than cold, insoluble in 
 KHO, soluble in a cold solution of XH 4 C1, from which it 
 is precipitated on boiling the solution. Free citric acid 
 must be neutralized by KHO or NaHO before adding CaCl a 
 to its solution. 
 
 471. Lime-water produces no precipitate in cold solu- 
 tions of citric acids or the citrates; but on boiling the 
 solution a precipitate is produced, which redissolves almost 
 entirely when the liquid becomes cold. 
 
 572. If a solution of ferric tartrate is evaporated on the 
 water-bath to a syrupy consistence, a solid basic salt is 
 deposited, but ferric citrate under the same circumstances 
 deposits no solid salt. Upon this difference of deport- 
 ment of the ferric salts of the two acids has been based a 
 method for the detection of tartaric acid in citric acid ; 
 by this method even minute quantities of tartaric acid 
 admit of being detected in citric acid ; the following is the 
 method: the citric acid to be examined is dissolved in 
 water, hydrate of ferric oxide is added to the solution in 
 excess and the mixture is heated to about 90° C. When 
 the acid has become saturated with oxide, the iron is filtered 
 off from the undissolved portion ; the solution is then eva- 
 porated on the water-bath to a syrupy consistence ; if the 
 citric acid contained tartaric acid, there would be formed 
 a deposit of an insoluble basic ferric tartrate ; if, on the 
 contrary, the citric acid is pure, there is no deposit from 
 the syrupy liquid, it remains perfectly clear. 
 
 573. A solution of plumbic acetate, when added in ex- 
 cess, produces in solution of citric acid a white precipitate 
 of PblinCJIjOjjHgO, which, when washed, dissolves readily 
 in ammonia. 
 
OP THE ORGANIC ACIDS. 221 
 
 574. Tartaric and citric acids are largely used by calico 
 printers as discharges in the production of white spots on 
 a colored ground. 
 
 Malic Acid, H 2 C 4 H 4 5 . 
 
 Solution for the reactions, Na 2 C 4 H 4 5 . 
 
 575. This acid contains only two atoms of H replaceable 
 by metals, although it is, probably, a triatotnie acid. It 
 forms with the alkaline metals a neutral and an acid salt; 
 it forms, also, with calcium and other diatomic metals, an 
 acid as well as a neutral salt. Nearly all the malates are 
 soluble in water. It is the acid of apples, pears, and 
 various other fruits. It crystallizes with great difficulty, it 
 is deliquescent, and is soluble in alcohol as well as water ; 
 its solution is acid to test-paper, and becomes mouldy 
 and decomposes by keeping. It can be produced artifi- 
 cially by the action of moist Ag 2 on monobromosuccinic 
 acid. 
 
 2C 4 H 5 Br0 4 + Ag 2 + H 2 = 20 4 H 6 O 5 + 2AgBr. 
 
 It is also produced by the action of nitrous acid on aspa- 
 ragin, and on aspartic acid. 
 
 (1) C 4 H 8 N a 3 + 2HN0 3 = C 4 H„0, + 2H 2 + 2N a . 
 Asparagin. 
 
 (2) C 4 H r N0 4 + HN0 2 = C 4 H a 5 + H 2 + N, 
 Aspartic acid. 
 
 By the action of HI it is converted into succinic acid — 
 C 4 H„.0 5 +2HI = C 4 H,.0 4 -(-H 2 0-l-I 2 . If kept at a temperature 
 of 150° C, it is slowly resolved into water and fumaric 
 acid (C 4 H 4 4 ) ; if kept for some hours between 115° and 
 180°, it is resolved into water, fumaric acid, and maleic 
 acid, an acid isomeric with fumaric acid. Fused with 
 KHO it splits up like tartaric and citric acids into oxalic 
 and acetic acids. Concentrated H 2 S0 4 decomposes the 
 acid and the malates in the solid state with evolution of 
 CO ; the mixture blackens only after long boiling. 
 
 5T6. A solution of CaCl 2 does not produce a precipitate 
 in solutions of the free acid or its salts until alcohol is 
 added. 
 
 577- "Lime-water produces no precipitate in solutions 
 of free malic acid, nor in solutions of malates. The fluid 
 
 19* 
 
222 THE SPECIAL PROPERTIES 
 
 remains perfectly clear even upon boiling, provided the 
 lime-water is prepared with boiling-water." 
 
 578. A solution of lead acetate throws down, from a 
 solution of the acid or its salts, a white precipitate of 
 PbC 4 H 4 6 ,3H s O. If the fluid in which the precipitate is 
 suspended is boiled, the precipitate fuses to a mass resem- 
 bling resin melted under water. But this reaction is only 
 distinctly marked when the plumbic malate is tolerably 
 pure ; if mixed with other lead salts, it does not present 
 this appearance, or at least imperfectly. 
 
 Benzoic Acid, HC 7 H 6 0. 
 
 Solution for the reactions, NH 4 C,H 5 0, in water. 
 
 579. This acid is monatomic. It is contained in gum 
 benzoin. The pure acid appears under the form of white 
 scales or needles, or simply as a crystalline powder. It 
 is readily dissolved by alcohol and ether; it is only 
 slightly soluble in cold water; on the addition of HC1 to 
 an aqueous solution of any of its salts, it separates from 
 the solution as a white crystalline powder. It volatilizes 
 completely when heated, with partial decomposition, the 
 fumes cause a peculiar irritating sensation, and provoke 
 coughing. When heated in a tube open at both ends, a 
 portion of the acid condenses upon the cool part of the 
 tube. When heated with concentrated H 2 S0 4 it volatilizes 
 without carbonizing. 
 
 580. It can be produced artificially by oxidizing bitter 
 almond oil, or by boiling hippuric acid with HC1, or by 
 oxidizing benzilic alcohol. 
 
 581. Ba01 2 and CaCl 2 do not precipitate this acid under 
 any circumstances. 
 
 582. Fe 2 Cl„ produces in neutral solutions of this acid a 
 precipitate of ferric bonzoatc, the color of which is pale 
 buff; NH 4 HO in excess withdraws the acid from this pre- 
 cipitate, Fe 2 H 6 O remaining. Ferric benzoate differs from 
 ferric succinate in this — that it dissolves in a little HC1 
 ■with separation of the greater portion of the benzoic acid. 
 
 Succinic Acid, n.,C 4 II 4 4 . 
 
 Solution for the reactions, (NH^CJI.O.,, in toater. 
 
 583. This acid is bibasic, it therefore forms an acid and 
 a neutral salt with the alkaline metals. It occurs ready 
 formed in amber and in certain lignites. It is crystalline 
 
OP THE ORGANIC ACIDS. 223 
 
 and melts at 180°, but begins to emit suffocating vapors 
 below its melting point; it does not carbonize when heated. 
 It is more soluble in hot than cold water ; it is less soluble 
 in alcohol, and nearly insoluble in ether. Fused with 
 KHO it yields a carbonate and an oxalate, together with a 
 gaseous hydrocarbon. It offers great resistance to the 
 action of oxidizing agents ; in fact it is a frequent product 
 of the oxidation of organic substances, especially fats. It 
 is also formed in many processes of fermentation, and we 
 have already noticed that it is produced from malic and 
 tartaric acids, by acting on them with HI. It is not 
 attacked by concentrated H 2 SO„ even when heated. 
 
 584. The succinates of the alkali metals and of mag- 
 nesium are easily soluble in water ; those of the alka- 
 line earth metals, and most other diatomic metals, are 
 sparingly soluble; those of the sesqui-atomic metals are 
 insoluble. 
 
 585. BaCl 2 after the addition of NH 4 HO and alcohol, 
 precipitates this acid from its solutions in the form of 
 BaC 4 H 4 4 , benzoic acid does not exhibit this reaction ; 
 succinic acid is further distinguished from benzoic acid 
 by not being precipitated from its soluble salts by the 
 mineral acids. 
 
 586. Fe 2 Cl 6 produces, in neutral solutions of the succi- 
 nates, a precipitate of the ferric succinate, the color of 
 which is reddish-brown. It is decomposed in the same 
 manner as ferric bonzoate by NH 4 HO. 
 
 Tannic Acid (Tannin) H 3 C 27 H IS 17 . 
 
 Solution for the reactions, the acid in water. 
 
 587. This acid is a solid body, of alight straw color, and 
 not crystalline. It is very soluble in water ; the solution 
 absorbs oxygen from the air, which converts the acid into 
 two others, gallic and ellagic. It is precipitated from con- 
 centrated solutions by dilute H 2 S0 4 and HC1, in the form 
 of a paste. It is also precipitated by dilute starch-paste, 
 by gelatine, and albumen. It is completely removed from 
 its solutions by placing in the liquid a piece of animal 
 membrane. 
 
 588. Fe a Cl 6 produces, in solutions of tannic acid or tan- 
 nates, a dark blackish-blue precipitate. 
 
 589. Tartar emetic gives in solutions of this acid a white 
 gelatinous precipitate. 
 
 590. Concentrated H a S0 4 , treated with the acid or the 
 
224 THE SPECIAL PROPERTIES 
 
 tannates in the solid stale, produces a dark purplish-black 
 liquid immediately, but does not evolve CO. 
 
 Gallic Acid, H a C,H 3 5 . 
 
 Solution for the reactions, the acid in ivater. 
 
 591. This acid is tribasic, it therefore forms with the 
 monatomic metals three series of salts. It is contained in 
 green and black tea, and in many other plants. It can be 
 produced artificially by the action of acids or alkalies on 
 tannic acid. It crystallizes in prisms of a silky lustre, of 
 a very pale yellow color. It is not very soluble in cold 
 water, but dissolves in three parts of boiling water. Its 
 alkaline solutions, when exposed to the air, become first 
 yellow, then green, red, brown, and finally nearly black, 
 owing to the absorption of oxygen. It is not precipitated 
 by gelatine or animal membrane. By this behavior it may 
 be distinguished and separated from tannic acid. 
 
 592. Fe 2 Cl 6 produces, in solutions of this acid and its 
 salts, a bluish-black color. 
 
 593. Concentrated H a S0 4 behaves with gallic acid much 
 in the same waj' as with tannic acid. 
 
 Acetic Acid, HC 2 H a 2 . 
 
 Solution for the reactions, NaC s H s O a , in water. 
 
 594. This acid, so well known under the name of vinegar, 
 is monobasic ; the normal salts are all soluble in water ; 
 the normal acetates of the alkali metals can combine with 
 a molecule of acid as they do with water. These salts are 
 called diacetates. Some normal salts in the same way 
 can combine with a molecule of a metallic oxide or its hy- 
 drate, and form basic salts. Solutions of ferric and alumi- 
 nic acetates are decomposed by boiling into basic salts and 
 free acid which is expelled; these salts experience the same 
 decomposition, if a cotton cloth is immersed in their solu- 
 tions and hung up in a moist and warm atmosphere ; this 
 process is called ageing by the cotton-printers, and the de- 
 posit of the basic salts in the cloth is called a mordant, the 
 commercial names of ferric and aluminic acetate solutions 
 are iron liquor and red liquor. 
 
 595. Acetic acid exists in the juices of many plants, espe- 
 cially of trees. It is formed in the destructive distillation 
 of organic substances, especially of wood. The greater part 
 of the acid used in the arts is obtained from this source, 
 
OP THE ORGANIC ACIDS. 225 
 
 and goes under the name of ivood vinegar, or pyroligneons 
 acid. Alcohol is converted into acetic acid by various pro- 
 cesses of oxidation ; in the ordinary processes for making 
 vinegar, either from wine or malt, an alcoholic solution is 
 exposed to the joint influence of air and a ferment. Ace- 
 tates are formed by heating cyanide of methyl (CH 3 CN) 
 with the caustic alkalies, and by acting on sodium-methyl 
 (CH„NA) with C0 2 , and by other processes. 
 
 596. It is a colorless crystalline solid below 16° C, above 
 that temperature it is a thin colorless liquid of an exceed- 
 ingly pungent and well-known odor of vinegar. It is 
 miscible in all proportions with water, alcohol, and ether, 
 and dissolves camphor and several resins. In the liquid 
 state it has a density of 1.063, and boils at 120° C. ; its 
 vapor is inflammable. On account of its solidifying below 
 16°, it has received the name of glacial acetic acid, in con- 
 tra-distinction to the mixtures of water and the acid which 
 do not crystallize ; it is to these mixtures that the name 
 acetic acid is commonly applied. 
 
 597. If Fe.^Cl,, is added to acetic acid, and the acid is then 
 nearly saturated with NH 4 HO, or if a neutral acetate is 
 mixed with Fe 2 Cl 6 , the fluid acquires a deep dark-red color, 
 owing to the formation of ferric acetate. By boiling, the 
 fluid becomes colorless if it contains an excess of acetate, 
 the whole of the Fe precipitating as a basic acetate, in the 
 form of brown-yellow flakes. NH 4 HO precipitates from it 
 the whole of the Fe as Fe 2 H 6 6 . By addition of HC1 a 
 fluid which is red from the presence of ferric acetate turns 
 yellow (difference from ferric sulphocyanide). 
 
 598. Acetic acid or acetates when heated with HgCl, 2 
 produce no precipitate of HgCl. 
 
 599. When H 5 S0 4 is added to acetates, the acetic acid is 
 liberated, and is recognized by its odor of vinegar. If the 
 acetate is distilled with the H 2 S0 4 , the acetic acid is 
 obtained in the distillate. 
 
 600. When acetates are heated with about equal vol- 
 umes of concentrated H 2 SOj and alcohol, acetic ether 
 (C 2 H 5 ,C 2 H 3 O a ) is formed, which is readily distinguished by 
 its characteristic odor. 
 
 601. Concentrated H 2 SO t occasions no blackening when 
 heated with acetic acid or its salts. 
 
 602. If an excess of PbO be digested in acetic acid, there 
 is formed a soluble basic lead acetate, which has an alka- 
 line reaction. 
 
226 THE SPECIAL PROPERTIES 
 
 Formic Acid, HCH0 2 . 
 
 Solution for the reactions, NaCHO, in water. 
 
 603. This acid is monobasic ; all its salts are soluble in 
 water ; it occurs in ants, in caterpillars, and in several 
 secretions of the human body ; it is present in the juice of 
 the stinging-nettle and other vegetables ; it has been found 
 in some mineral waters. It may be prepared by passing 
 CO over moist KHO, and by passing C0 2 and aqueous 
 vapor over K at a moderate heat, KHC0 3 being formed at 
 the same time ; it is also formed by acting on HCN with 
 an alcoholic solution of KHO ; and by distilling dry oxalic 
 acid mixed with glycerin, which takes no part in the de- 
 composition, but appears to act by preventing the tempe- 
 rature rising too high; it is formed by the partial oxida- 
 tion of a great variety of organic bodies, as starch, gum, 
 tartaric acid, etc. 
 
 604. This acid is a clear colorless liquid which fumes 
 slightly in the air ; it has an exceedingly penetrating odor ; 
 it boils at 101.1° C, and crystallizes in large brilliant 
 plates when cooled below — 1° C. Its sp. gr. is 1.235, and 
 it mixes with water and alcohol in all proportions. When 
 exposed to the action of heat, it volatilizes completely; 
 the vapor is inflammable and burns with a blue flame. 
 
 605. The formates are all decomposed by heat ; the for- 
 mates of the alkalies and alkaline earth metals ignited out 
 of contact with air leave carbonates slightly blackened by 
 charcoal, CO and H being evolved ;* the formates of other 
 metals (copper and lead for example) when heated give off 
 CO, CO,, and H 2 0, the metal being left in the metallic 
 state. NH 4 CH0 2 when exposed to a high temperature is 
 decomposed into HCN and H 2 0. 
 
 606. If Fe 2 Cl 6 is added to a neutral formate, the fluid 
 acquires a blood-red color; the liquid becomes colorless on 
 boiling if an excess of the formate be present, all the iron 
 being precipitated in the form of a basic salt. The for- 
 mates, in fact, exactly resemble the acetates in their beha- 
 vior with ferric salts. 
 
 607. This acid is a powerful reducing agent; it reduces 
 the oxides of the noble metals, yielding 11,0 and CO,; by 
 heating it with a solution of AgNO, the Ag is deposited 
 sometimes in the pulverulent state and sometimes as a 
 
 ' * Bario formate yields the products above mentioned, together with 
 gaseous hydrocarbons, viz. marsh-gns, ethylene, and tritylene. 
 
OP THE ORGANIC ACIDS. 227 
 
 specular coating on the glass tube ; this reaction distin- 
 guishes it from acetic acid, -which does not reduce the silver 
 nitrate. » 
 
 608. If the acid or an alkaline formate is heated to from 
 60° to 70° C. with HgCl.,, HgCl precipitates. If the 
 mixture is heated to 100° C, Hg separates along with 
 HgCl. 
 
 609. When dilute H,S0 4 is added to formates the acid is 
 liberated and is recognizable by its odor; if the formiate 
 is distilled with the H a S0 4 , the formic acid is obtained in 
 the distillate. 
 
 610. Upon heating a formate with a mixture of H. 2 S0 4 
 and alcohol, formic ether (C 2 H.CHO,,) is produced, which 
 has an agreeable odor resembling peach kernels. 
 
 611. Concentrated H^SC,,, when heated with formic acid 
 or a formate, decomposes the acid into CO and H 2 ; there 
 is therefore no blackening, however long the heat may be 
 continued. 
 
 Uric Aoid, H 2 C 5 N 4 H 2 3 . 
 
 Solution for the reactions, the acid. 
 
 612. This acid is bibasic ; it therefore forms two series 
 of salts with the monatomic metals, viz., neutral salts and 
 acid salts. " It is a product of the incomplete oxidation 
 of animal tissues In combination chiefly with ammonia 
 it forms the principal urinary constituent voided by insects, 
 land-reptiles, and birds (whence it is found in guano). 
 Normally it occurs but in small proportion in the urine of 
 man, and is found in yet smaller proportions in that of car- 
 nivorous quadrupeds, and can scarcely be said to exist in 
 that of herbivorous and omnivorous quadrupeds." The 
 solid white excrement of serpents consists almost entirely 
 of uric acid and ammonic urate. This acid has never yet 
 been formed by artificial means. 
 
 613. This acid occurs in delicate white needles; it is 
 scarcely soluble in cold water, dilute HC1 or HC 2 H 3 2 ; it 
 is soluble in alcohol and ether. It dissolves in concentrated 
 H z S0 4 without apparent decomposition, and is precipitated 
 by dilution with water. It is soluble in the alkalies and 
 alkaline salts, from which solutions it is precipitated on the 
 addition of acids. 
 
 614. Urates, with the exception of the potassic and sodic 
 ones, are almost all insoluble in water; the ammonic salt is 
 
228 ORGANIC ACIDS. 
 
 extremely insoluble in water; it is however dissolved by 
 NaCl or Na 2 HP0 4 , sodic urate being formed. 
 
 615. The calcic salt is white ; the ferric salt brown ; 
 the copper salt green ; the silver salt white, rapidly be- 
 coming black if the liquid be heated ; the mercury and 
 lead salts are white. 
 
 616. Uric acid yields by destructive distillation cyanic, 
 hydrocyanic, and carbonic acids, amnionic carbonate, and a 
 black coaly residue rich in nitrogen. By fusion with KHO 
 it furnishes carbonate cyanate and cyanide of the alkaline 
 metal. 
 
 617. It dissolves with the aid of heat in dilute HN0 3 ; 
 the solution is attended with effervescence and evolution of 
 red fumes, the uric acid being oxidized at the expense of 
 the HNO s . If the HNO s solution be evaporated in a por- 
 celain dish on the water-bath just to drjness, and a glass 
 stopper moistened with strong ammonia-water be then held 
 over the residue in the dish, a magnificent purple color is 
 produced, owing to the formation of Murexide (C 8 N 6 H 8 6 ). 
 
 618. If uric acid be dissolved in sodic carbonate, and a 
 drop of the solution be laid on paper moistened with silver 
 solution, a brown spot is formed, argentic carbonate being 
 reduced by uric acid at ordinary temperatures. 
 
 619. Concentrated H 2 S0 4 dissolves uric acid, with the 
 aid of heat, without change; if the heat be long continued, 
 the liquid becomes dark. 
 
 classification of toe organic acids, with a descrip- 
 tion OF THE PROCESSES TO BE FOLLOWED IN THE EXAMI- 
 NATION OF SUBSTANCES FOR THESE ACIDS. 
 
 Classification of the acids. — The organic acids described 
 in this part (Part I.) of this book may be conveniently 
 divided into four groups, as follows : — 
 
 First Group. 
 
 620. 1st Division. — Acid which is precipitated from neu- 
 tral solutions in the cold by CaCl 2 , tartaric acid ; the 
 properties of calcic tartrate are given in par. 561. -2d 
 Division. — Acid which is precipitated by CaOl, from boil- 
 ing solutions rendered alkaline bj- lime-water, citric acid. 
 3d Division — Acid which is not precipitated from hot or 
 cold solutions by OaCH., but its calcic salt is precipitated 
 on adding alcohol to the solution, malic acid. 
 
ORGANIC ACIDS. 229 
 
 Oxalic, boracic, phosphoric, hydrofluoric, carbonic, arse- 
 nions, and arsenic acids are also precipitated from neutral 
 solutions by CaCl 2 . 
 
 Second Group. 
 
 621. 1st Division Acids which give precipitates in neu- 
 tral solutions with Fe a Cl,., tannic, benzoic, and succinic 
 acids. Tannic acid gives a precipitate with Fe 2 Cl 8 in acid, 
 as well as neutral solutions. The iron salt does not pre- 
 cipitate benzoic and succinic acids in the presence of a 
 citrate. 
 
 2d. — Acids which give a coloration in neutral solutions 
 with Fe. 2 Cl 6 , acetic, formic, and gallic acids; the two 
 former give a reddish and the latter a black coloration. 
 
 Phosphoric, arsenic, and boracic acids give precipitates 
 in neutral solutions witli Fe 2 Cl o , the first two in acid as well 
 as neutral solutions. 
 
 Third Group. 
 
 622. Acids which are precipitated from neutral solutions 
 by AgXO.,. Tartaric, citric, malic, benzoic, succinic, 
 and formic acids. Argentic tartarate, and argentic for- 
 mate are reduced on being heated, Ag separating. 
 
 Fourth Group. 
 
 Acetic acid, uric acid. 
 
 623. These acids are not precipitated by the group rea- 
 gents, nor do they give any peculiar coloration with them. 
 
 Detection of the Organic Acids. 
 
 624. Tartaric Acid. — The peculiar and highly character- 
 istic odor which this acid evolves on ignition (557), prevents 
 it from being overlooked if present in any quantity. But 
 the test with acetate of potash (559) ought to be made in 
 all cases; the solution to be examined for tartaric acid must 
 be neutral, or if acid the free acid must only be acetic acid 
 or tartaric acid. For detecting minute quantities of tar- 
 taric acid in the presence of citric acid, employ the method 
 described in par. 5 '12. 
 
 625. Citric Acid. — Oxalic and tartaric acids, if present, 
 require to be removed before examining for this acid, add, 
 therefore, to the solution ill the cold CaCl 2 and lime-water 
 
 20 
 
230 METHODS FOE THE DETECTION 
 
 to alkaline reaction ; calcic tartrate and oxalate will be 
 precipitated,* filter and heat the filtrate to boiling. Calcic 
 citrate will precipitate ; filter and examine the filtrate for 
 malic acid as directed in next par. 
 
 626. Malic Acid To the filtrate from the calcic citrate 
 
 precipitate, is added alcohol, calcic malate will precipitate 
 if that acid be'present. Malic acid is further distinguished 
 from tartaric and citric acids, by not being blackened when 
 heated with concentrated H 2 S0 4 . 
 
 627. Benzoic Acid. — This acid, in the presence of suc- 
 cinic acid, is best detected by treating the iron precipitate 
 of the two acids, after it has been washed, with NH 4 HO, 
 and then filtering, and after concentrating the filtrate 
 dividing it into two parts, mixing one part with HC1, when 
 benzoic acid, if present, will be precipitated ; in the other 
 part, succinic acid is examined for by adding BaCl 2 and 
 alcohol (585). 
 
 628. Succinic Acid. — This acid is best detected in the 
 presenee of benzoic acid, by the method described in the 
 previous paragraph. The student must remember what 
 has been stated in the 2d group of acids that Fe 2 Cl,. does 
 not precipitate these two acids in the presence of alkaline 
 citrates. 
 
 629. Tannic Acid — This acid is best detected in the 
 presence of gallic acid, by the method described at 587. 
 
 630. Gallic Acid. — This acid is best detected in the 
 presence of tannic acid, by the method described at 591. 
 
 631. Acetic Acid. — This acid is best detected by the 
 methods described at 597 and 600. 
 
 632. Formic Acid. — This acid is best detected by the 
 methods described at 607, 608, and 611. 
 
 633. TJric Acid This acid is best detected by the 
 
 method described at 617 and 618. 
 
 634. Preparation of the Solution. — When the sub- 
 stance under examination is soluble in water, or if it is in 
 solution and the fluid is water, it requires a little prepara- 
 tion before it can be examined with advantage for the oi - - 
 ganic acids, as it conduces much to the success of the ex- 
 amination if no other metals but the alkaline ones are pre- 
 sent. In order to remove the other metals, the solution 
 has sometimes to be treated with 11,8, and (X1I 4 ),S ; but 
 
 * The sepnrntion of caloio tnrtrnto is promoted by ngitntion. Calcic 
 tnrtrnto is sepnnited from oaloio oxnlnto by treating the precipitate with 
 solution of KUO(5bl). 
 
OF THE ORGANIC ACIDS. 231 
 
 generally it jp'only necessary to boil the solution with a 
 slight excess of Na 2 CO, ; by this reagent the majority of 
 the metals, especially if citric acid is absent, except the 
 alkaline ones, are removed. After the solution has been 
 boiled for some time it is filtered, and to the filtrate is 
 added HNO s , very slightly in excess ; the solution is then 
 gently heated in order to expel the C0 2 . After this, NH 4 HO 
 is added in very slight excess ; and when it is required to 
 have the solution perfectly neutral, as in testing with 
 AgN0 3 , and Fe,Cl c ; the solution, which has been rendered 
 slightly alkaline with NH 4 HO, is boiled in an evaporating 
 dish until it is neutral to test-paper. When ammonic salts 
 are present in the substance under examination, the solu- 
 tion must, even if no other metals but the alkaline ones are 
 present, be boiled with ]STa 2 C0 3 until all the NH 4 HO is ex- 
 pelled, and the solution is then rendered neutral in the way 
 just stated. 
 
 635. When Na 2 CO„ fails to precipitate the metals, as it 
 will frequently when the organic acid is non-volatile, espe- 
 cially if it be citric acid, add to the solution neutral lead 
 acetate in excess, collect the precipitate and wash it 
 thoroughly, then suspend it in water and pass H 2 S through 
 the mixture to excess, filter off from the PbS, and after 
 expelling the excess of H a S from the filtrate by heating it, 
 neutralize exactly with Na 2 C0 3 , and then examine for the 
 acids. 
 
 636. It is frequently advisable to separate the volatile 
 acids, for this purpose the solution must be treated, if not 
 acid already, with dilute H 3 S0 4 , and then distilled in a 
 small retort, the liquid in the retort must be heated gently, 
 not to boiling, and the distillate must be collected ; the 
 distillate may contain the following acids : HCy, HC1, 
 HBr, HI, HNO s , HCH0 2 , HC 2 H s O a , H,C ,H 4 4 , and HC,H.O. 
 
 631. Preliminary examination for organic acids. — Heat 
 a portion of the dry solid in a test-tube, with 3 or 4 times 
 its volume of concentrated H^O^ the organic acids treated 
 of in this part of the book show the following behavior : 
 Tartaric, tannic, and gallic acids are immediately black- 
 ened ; CO g is evolved at the same time from tartaric, but 
 not from the other two acids. Citric, malic, and uric acids 
 are not blackened unless boiled with the H 2 S0 4 , for some 
 time, citric acid evolves CO, and C0 2 , and malic acid, CO, 
 on being acted on by H 2 S0 4 . Benzoic, succinic, and acetic 
 acids are not blackened under any circumstances by H 2 S0 4 , 
 but the}' volatilize in an unchanged state. Formic acid is 
 
232 EXEEOISES ON THE ORGANIC AOIDS. 
 
 decomposed on being heated with H 2 S0 4 intdflPO and H 2 
 without any blackening. 
 
 638. Answers- to the following exercises must be written 
 out. 
 
 Exercises. 
 
 160. What is the source of tartaric acid, and how is the 
 acid obtained in the free state ? 
 
 161. How is succinic acid distinguished from benzoic 
 acid? 
 
 162. How can formic acid be obtained from inorganic 
 sources, and what is the action of concentrated H 2 S0 4 
 upon it ? 
 
 163. Give the formula for tartar, Rochelle salt, argol, 
 tartar emetic, and cream of tartar. 
 
 164. A crystalline powder, representing a sample of or- 
 ganic acid, is given to you, and you are asked to say whether 
 it is tartaric, citric, or oxalic acid. What tests would you 
 apply for the solution of this problem ? 
 
 165. How is succinic acid converted into malic and tar- 
 taric acids, and how is tartaric acid reconverted into malic 
 and succinic acid ? 
 
 166. How would you distinguish a tartrate from an oxa- 
 late and a citrate respectively ? 
 
 161. Describe some methods for the manufacture of citric 
 acid, and state some of its applications. 
 
 168. Malic acid is extracted from the juice of the moun- 
 tain-ash berries; there are present along with it small 
 quantities of tartaric and citric acids. The following 
 method is followed for its extraction. Explain the differ- 
 ent parts of the process. The juice, after being filtered, is 
 partly neutralized with K a CO,, but the solution must still 
 redden litmus pretty strongly, solution of Pb (XO ;i ).„ or 
 Pb(C 2 H,0 2 ).,, is then added in excess, a curdy precipitate 
 is formed, the mixture is then set aside for some days ; 
 with the exception of the mucous flocculent compound of 
 lead and coloring matter, the precipitate by standing be- 
 comes converted into small needles ; these are carefully 
 freed from the coloring precipitate and other impurities 
 by washing, thoy are then boiled in a quantity of dilute 
 li.,S0 4 not sufllcient to decompose the \\\\o\s> of them, as 
 long as any granular deposit continues to subside: to the 
 mixture is then added an aqueous solution of BaS, until a 
 filtered sample is found to contain l!:i; the liquid is then 
 
PRELIMINARY EXAMINATION OF LIQUIDS. 233 
 
 filtered and the filtrate is boiled with an excess of BaCO, ; 
 the mixture is again filtered, and the Ba is precipitated 
 from the filtrate by the careful addition of dilute H 2 S0 4 ; 
 the liquid is again filtered and the filtrate evaporated to 
 the ciystallizing point. 
 
 169. From the properties and reactions which have been 
 given of oxalic, tartaric, citric, and malic acid, devise an- 
 other method which, from its cheapness and simplicity, 
 would be suitable as a manufacturing process for the ex- 
 traction of malic acid from vegetable juice, containing small 
 quantities of oxalic, tartaric, and citric acids. 
 
 Examination op Liquids and Solids, 
 examination of a liquid. 
 
 639. The student, after he has passed through the differ- 
 ent groups of bases and acids, in the manner previously 
 described, commences the analysis of liquids, in which he 
 has to look for all these bases and acids, with the exception 
 of the organic acids.* 
 
 640. Before commencing the actual analysis, it is neces- 
 sary to ascertain by preliminary experiments — 1. Whether 
 there is any solid substance in solution. 2. Whether the 
 solution is neutral, acid, or alkaline. 
 
 641. 1st. To ascertain whether there is any solid substance 
 in solution. — Evaporate, by a gentle heat, a portion of the 
 liquid to dryness, on platinum-foil. If no residue remain, 
 it is probably pure water, which will be further confirmed 
 if it has no action upon test-paper. If a residue remain, 
 which is completely volatilized when the temperature is 
 increased, the only basic substances which can be present 
 are NH,, Hg, As, and Sb. If the residue is not volatile, 
 or at least not completely so, other substances besides these 
 
 * The student will find it conducive to his success in many respects, if 
 he does not engage in the detection of organic acids until he enters upon 
 the examination of solid substances. He will, of course, in practice, 
 have always first to ascertain whether organic substances are really 
 present or absent in a solution, before he commences the actual analysis, 
 as the presence of fixed organic matter prevents the detection of many 
 inorganic substances ; he will, likewise, in practice, have frequently to 
 separate, by distillation, the liquid from the solid portion of a solution, 
 in order to be perfectly certain that the fluid is water, and not any other 
 liquid. This he will ascertain by examining the distilled fluid by the 
 smell, taste, boiling point, specific gravity, etc. 
 
 20* 
 
234 EXAMINATION OP LIQUIDS. 
 
 must be present. In both cases it is requisite to perform 
 the next experiment. 
 
 642. 2d. The solution is examined by well-prepared 
 test-papers, as to its neutrality, etc. Each of the three 
 cases which may occur, and the conclusions to which they 
 lead, are considered in pars. 643, 645, 646. 
 
 643. The solution is neutral. A large number of sub- 
 stances must therefore be absent, because the soluble neu- 
 tral salts of the greater proportion of the metals possess an 
 acid reaction. The only salts which are neutral to test- 
 papers are the soluble salts of silver and manganese, and 
 some of the soluble salts of the alkalies and alkaline earth 
 
 »metals ; some of the salts of these metals are therefore the 
 only ones which can be present; but to distinguish still 
 further, add to a portion of the solution (XH,),S, if no 
 precipitate is formed, Ag and Mn are absent, add then to 
 the solution Na 2 C0 3 and boil, if this produces no precipi- 
 tate the metals of the alkaline earths are absent; the only 
 metals therefore which can be present are the alkaline 
 metals. If (NH 4 ) 2 S produces no precipitate, but a precipi- 
 tate is produced by tne Na 2 C0 3 , the alkaline earths and the 
 alkaline metals have to be sought for, and if both reagents 
 produce a precipitate, the one by (XHJ.S being black, 
 then all the metals whose salts are neutral to test-paper 
 must be sought for. Add HC1 in the first instance, filter 
 off from the insoluble AgCl, and add to the filtrate NH 4 C1, 
 NI[ 4 HO, and (NH,) 2 S; if a precipitate is produced filter 
 and examine the filtrate for the members of the 2d and 
 1st groups in the usual manner. 
 
 644. Examination for the acids. — Very few acid radicals 
 can be present if Ba, Mn, or Ag are present, as so many 
 of their ssdts are insoluble in water, and some of the baric 
 salts which are soluble in water are alkaline to test-paper; 
 and if K, Xa, and NH ( are the only basic radicals that are 
 present, a large number of acid radicals must be absent, 
 as so many of the alkaline salts are alkaline to test-paper; 
 add to separate portions of solution BaCl 2 and AgX0 3 , 
 according to par 550. 
 
 645. The solution is aeiil. The acidity may proceed 
 from the presence of a free acid, an acid salt, or* a neutral 
 salt having an acid reaction. To ascertain to which of 
 these causes the acidity is due, place the end of a glass 
 rod moistened with a solution of Xa^CO,, into a portion of 
 the fluid in a watch-glass. If the solution becomes turbid 
 and remains so, it is due to the presence of a neutral salt; 
 
EXAMINATION OF LIQUIDS. 235 
 
 if it becomes clear again, the reaction is due either to an 
 acid salt or a free acid. Carbonates and sulphides cannot 
 be present in an acid solution. Examine for the basic 
 constituents in the usual manner. Examine for the acids 
 according to par. 546 if it is a neutral salt having an acid 
 reaction ; if an acid salt or a free acid is present, examine 
 according to par. 547. 
 
 646. The solution is alkaline. The alkalinity may pro- 
 ceed from an alkaline carbonate, silicate, borate, or phos- 
 phate; or it may arise from the presence of a free alkali or 
 alkaline earth, or from the cyanogen and sulphur com- 
 pounds of these metals. If the alkalinity proceeds from 
 ammonia or its carbonate, a large number of substances 
 (those which are insoluble in these reagents) must be ab- 
 sent. If it is due to the presence of the fixed alkalies or 
 their carbonates, a still larger number of substances are 
 excluded. If it is occasioned by the sulphides of the alka- 
 line, or alkaline earth metals, all the metals whose sulphides 
 are insoluble in water and alkaline sulphides must be ab- 
 sent. Examine for the basic constituents in the usual 
 manner, paying strict attention to the* precautions given in 
 pars. 376 and 377. Commence the examination of the acids 
 by rendering the solution exactly neutral with HN0 3 . If 
 no precipitate is produced on neutralizing the solution, 
 proceed with the examination according to par. 550 ; if a 
 precipitate is produced on neutralizing the solution, filter, 
 examine the filtrate according to par. 550 ; and treat the 
 precipitate according to par. 547. 
 
 647. The student should never employ the whole of the 
 solution at his disposal, but should always reserve a por- 
 tion, in the event of any unforeseen accident occurring, and 
 for confirmatory experiments. 
 
 648. If the liquid under examination contains inorganic 
 matter in suspension,* the latter, after being separated by 
 filtration, must be brought into solution according to the 
 methods described under the head of " Solid Substances." 
 The solid and liquid portions ought in most cases to be 
 examined separate!)'. 
 
 649. Answers to the following exercises must be written 
 out. 
 
 * Tbe method of preparing for analysis a solution which is thick or 
 turbid from the presence of organic matter, is described under the head 
 of " Solid Substances containing Organic Matter" (par 731). 
 
236 EXAMINATION OP SOLIDS. 
 
 Exercises. 
 
 1*70. A solid inorganic substance volatilizes completely 
 at a heat below redness. How does this observation sim- 
 plify its subsequent examination ? 
 
 171. A solution is neutral to test-paper, and the only 
 metals present are K, Na, and Ca, what acids must be ab- 
 sent ? 
 
 172. A solution is alkaline to test-paper, the alkalinity is 
 due to the presence of ammonic carbonate ; what substances 
 must be absent 1 
 
 173. A solution acid to test-paper is colorless, what sub- 
 stances must be absent ? 
 
 174. A solution acid to test-paper contains Ba and Ag, 
 what acids must be absent ? 
 
 Examination of Solids. 
 
 650. The substance is first examined as to its lustre, co- 
 lor, odor, and whether it is crystalline or amorphous, since 
 these will frequency afford a means of classifying the 
 substance. Thus, a metallic lustre will indicate probably 
 a pure metal or any alloy. A blue color will indicate the 
 probable presence of some salt of copper; a crystalline 
 structure the probable presence of salt. 
 
 651. The Substance will either be a Pdbe Metal or 
 an Alloy, or it will not. 
 
 652. If it is a pure metal or an alloy, treat it according 
 to par. 737, after it has been examined in a glass tube 
 closed at one eud and exposed on charcoal to the reducing 
 flame of the blowpipe* (see pars. 656, 2d and 4th). 
 
 653. If it is neither a pure metal nor an alloy, it toill be 
 free from or contain organic matter which will be ascer- 
 tained in making the preliminary experiment (par. 656, 
 2d). When it is destitute of organic matter, treat it ao- 
 cording to par. 717. When it contains organic matter, 
 according to par. 731. 
 
 654. It has already been stated that the substance is 
 submitted to different blowpipe operations before ascer- 
 taining in what liquid it will dissolve; the blowpipe opera- 
 tions and the order in which they are to be performed are 
 described in the next paragraph. In these blowpipe experi- 
 ments, only small quantities of the substance ought to be 
 
 * Those are the only blowpipe experiments which require to be made 
 with a pure motal or no alloy. 
 
EXAMINATION OF SOLIDS. 237 
 
 employed; for if too much is operateJ upon, uncertain 
 results are the consequence. A particle the size of a mus- 
 tard seed is sufficient, and that of the flux added about the 
 size of a hemp-seed. In reductions, a larger quantity niay 
 be employed, because, in that case, the more metal is pro- 
 duced, the more easily can its nature be ascertained. In 
 all cases the substance operated upon must be reduced to 
 the finest powder. 
 
 655. We give — 1st, the blowpipe operations; and 2d, 
 Bunsen's flame reactions.* We recommend the student to 
 make himself acquainted with both modes of examination. 
 
 656. The following are the principal blowpipe operations 
 and the order in which they are to be performed : — 
 
 1st. Examine whether the substance imparts a color to 
 the flame, see Table page 238, and par. 660. 
 
 2d. Examine the substance in a glass tube closed at one 
 end, see Table VIII. and par. 670. 
 
 3d. Examine the substance in a glass tube open at both 
 ends, see par. 676. 
 
 4th. Expose the substance to the inner blowpipe flame 
 on charcoal, see Table IX. and par. 682. 
 
 5th. Treat the substance with protonitrate of cobalt on 
 charcoal, see Table X. and par. 684. 
 
 6th. Examine the substance with carbonate of soda on 
 charcoal, see Table X. and par. 685. 
 
 7th. Fuse a portion of the substance with borax on pla- 
 tinum wire, see Table X. and par. 700. 
 
 8th. Examine the substance as to its fusibility, see par. 
 702. 
 
 657. Coloration of the Flame. — As many substances 
 tinge the lamp flame with various characteristic colors, the 
 substance under examination ought to be submitted to the 
 flame in order to ascertain the presence or absence of these 
 substances. To obtain the color the substance ought to 
 be exposed to the flame on a platinum wire, and the ex- 
 periment ought to be conducted in a dark room. 
 
 658. Merz,who has made a complete investigation of this 
 subject, employs Bunsen's burner, and also a flame of pure 
 hydrogen, and in addition makes use of blue, violet, red, 
 and green glasses. The substances which he describes as 
 giving characteristic colors to the flame of Bunsen's burner, 
 in addition to those previously known, are nitric and chro- 
 mic acids, while phosphoric and sulphuric acids give a 
 
 * The student must study carefully the paragraphs under the head 
 " Blowpipe," iu Part III., when he makes these experiments. 
 
238 PRELIMINARY EXAMINATION 
 
 peculiar coloration to the dark core of the flame of 
 hydrogen. 
 
 659. The flame of Bunsen's burner gives three sorts of 
 color : a. Border colors. These are of course peculiar only 
 to the most volatile substances. To produce them, the 
 loop of platinum wire is to be held outside of the flame 
 about one or two millimetres from the lower portion of the 
 outer limit, b. Mantle colors — those, namely, which are 
 seen when the substance is held in the bright blue-colored 
 mantle which forms the outer portion of the flame, c. 
 Flame colors. To produce these, the loop is to beld hori- 
 zontally and in the hottest part of the mantle. The hydro- 
 gen flame yields another species of color, viz., the core 
 colors. These are produced only by sulphuric and phos- 
 phoric acids, which communicate respectively a blue and 
 green tinge to the cold core of the hydrogen flame. 
 
 660. The following is a list of the substances* which 
 color the Same, with the color they impart : — 
 
 blue flames. 
 (Consult pars. 661 and 662.) 
 Intense blue .... Cupric chloride. 
 Pale clear blue . 
 Light blue . 
 Greenish blue 
 Blue mixed with green 
 Blue core color . 
 
 Lead 
 Arsenic. 
 Antimony. 
 Cupric bromide. 
 Sulphuric acid. 
 
 GREEN FLAMES. 
 
 (Consult pars. 663, 664, and 665.) 
 
 Bronze-green border color . . Nitric and Nitrous acids. 
 
 " " " " . . Ammonic compounds. 
 
 " " " " . Cyanogen " 
 
 Greenish-blue border color . . Hj'drochloric acid. 
 
 Green mantle color . . . Boracic acid. 
 
 Gray yellow-green border color - Thosphoric acid. 
 
 Yellowish-green flame color . Baric compounds. 
 
 Dark green .... Iron wire. 
 
 Full green Copper. 
 
 Intense emerald green . . Cuprous iodide. 
 
 Emerald green, mixed with blue . Cupric bromide. 
 
 Pale green Phosphoric acid. 
 
 Intense whitish-green . . Zinc. 
 
 * Iu this list only the more oommonly occurring substances are given. 
 
OF SOLID SUBSTANCES. 239 
 
 RED FLAMES. 
 
 {Consult pars. 666, 667, and 668.) 
 
 Intense crimson .... Strontic compounds. 
 Reddish purple .... Calcic compounds. 
 
 Violet Potassic compounds. 
 
 Dark brownish-red border color) 
 and a rose-red mantle color | 
 
 Chromic acid. 
 
 YELLOW FLAMES. 
 
 {Consult par. 669.) 
 
 Yellow Sodic compounds. 
 
 Feeble brownish-3'ellow . . Water. 
 
 •661. Blue Flames. — CuCl 2 gives an azure-blue zone, and 
 Cu(NO s ) 2 a pure green flame color. By the combiaed ob- 
 servation of both colors, Cu may be distinguished from all 
 other metals which give similar colors. The other flame 
 coloring metals, such as As, Sb, Sn, Pb, Hg, and Zn ex- 
 hibit, especially in the form of chlorides, more or less intense 
 bluish or greenish mantle colors, which, however, cannot 
 be advantageously used as reactions for the metals them- 
 selves. 
 
 662. Sulphuric acid produces a beautiful blue core color, 
 being reduced to S0 2 . The free acid gives the color when 
 the platinum loop is held in the border of the flame, but a 
 sulphate must be held in the middle of the flame. In the 
 latter case, it is well to dip the test into strong HC1 or 
 fluosilicic acid. 
 
 663. Green Flames.— Nitric and nitrous acids give a 
 bronze-green border color, usually with an orange-colored 
 border. The test is to be previously dried in the flame, 
 and dipped into a solution of KHS0 4 , or into dilute HC1, 
 according as we wish to test for nitric or nitrous acid. 
 Amnionic and cyanogen compound give the same bronze- 
 green border, but more faintly. HC1 gives a very weak 
 greenish-blue border color, which lasts for a very short 
 time, and therefore does not deserve attention. The acid 
 is however decomposed, and the CI may easily be recog- 
 nized. 
 
 664. Boracic acid gives a beautiful green mantle color, 
 which is so intense that the acid may be recognized in the 
 presence of large quantities of phosphoric acid. Borates 
 are to be decomposed with H s S0 4 . Phosphoric acid gives 
 
240 PRELIMINARY EXAMINATION 
 
 a gray yellow-green border color as well as a beautiful green 
 core color. The dry test is to be dipped into H 2 S0 4 and 
 held in the flame in the manner already pointed out', in 
 order to show the border color. The green core color is 
 less sensitive, but indispensable in recognizing phosphoric 
 acid in the presence of large quantities of boracic acid, and 
 is produced by alternately moistening the test with a solu- 
 tion of fluosilicic acid, and igniting it in the hydrogen flame, 
 until the color distinctly appears. 
 
 665. Ba may be recognized by the yellowish-green flame 
 color which appears blue green through the green glass. 
 If the green disappears, and a red flame color makes its 
 appearance, the test is to be repeatedly moistened with 
 HC1, and immediately introduced while wet into the hottest 
 part of the flame. When the blue-green color is no longer 
 seen, proceed to examine for Ca. 
 
 666. Red Flames. — Ca is present when the red flame 
 color, on evaporating the last portion of HC1, appears 
 siskin green through the green glass. Sr gives in this ease 
 a weak yellow. Sr may be recognized by the purple or 
 rose color which is seen through the blue glass, when the 
 test, after moistening with HC1, is evaporated to dryness 
 in the flame. 
 
 667- K gives a gray-blue mantle color, and a rose-violet 
 flame color. These colors appear reddish-violet through 
 the blue glass, violet through a violet glass, and blue-green 
 through a green glass. The test is to be moistened with 
 HjSOj, and repeatedly exposed to the flame for a short 
 time. 
 
 668. Chromic acid gives a dark brownish-red border 
 color, and a rose-red mantle color. The dry test is to be 
 moistened with concentrated H,SO ( , and held in the border. 
 Chromic oxide gives no color, and is to be first oxidized 
 to chromic acid by moistening with a solution of sodic 
 hypochlorite and drying. 
 
 669. Yellow Flames. — Na gives an orange-yellow flame 
 color, which in very large quantities appears blue, but 
 in small quantities is invisible through the blue glass. 
 Through the green glass the flame appears orange-yellow, 
 even with the smallest quantities ; this glass is particularly 
 adapted to the recognition of Na in all its compounds. 
 The test is to be moistened with H a S0 4 , dried and held in 
 the hottest point of the flame.* 
 
 * For this description of flame coloration I am indebted to Men's 
 paper on the subject. 
 
op solid substances. 241 
 
 670. Examination of the substance in the glass tube 
 closed at one end. — The tube* having been thoroughly 
 cleaned and dried, a small portion, in the state of powder, 
 of the substance to be examined is introduced into it, and 
 heated over a spirit or gas lamp, at first gently in order to 
 ascertain whether any volatile substances or organic 
 matter form part of it ; the tube is subsequently heated 
 more strongly with the blowpipe until the glass begins to 
 soften; for the changes consult Table X., and pars. 671, 
 675. 
 
 671. Gases oe fumes escape. — " Observe whether they 
 have a color, a smell, an acid or alkaline reaction, whether 
 they are inflammable, etc. 
 
 1st. "Oxygen. — The disengagement of this gas indicates 
 the presence of peroxides, chlorates, nitrates, etc. A glim- 
 mering slip of wood is relighted in the gaseous current. 
 
 2d. "Sulphurous acid. — This is often produced by the 
 decomposition of sulphates, it may be known bj T its peculiar 
 odor and by its acid reaction. 
 
 3d. " Hyponilric acid, resulting from the decomposition 
 of nitrates, especially with oxides of the heavy metals ; it 
 may be known by the brownish-red color of the fumes. 
 
 4th. "Carbonic acid. — The evolution of C0 2 indicates 
 the presence of carbonates decomposable by heat. The gas 
 evolved is colorless and tasteless, non-inflammable ; a drop 
 of lime-water on a watch-glass becomes turbid on exposure 
 to the gaseous current. 
 
 5th. " Carbonic oxide. — The escape of this gas indicates 
 the presence of oxalates and also of formates. The gas 
 burns with a blue flame. In the case of oxalates the CO 
 evolved is generally mixed with CO,, and is therefore more 
 difficult to kindle ; in the case of formates the evolution of 
 the gas is attended with marked carbonization. Oxalates 
 evolve C0 2 when brought into contact with Mn0 2 , a little 
 water, and some concentrated H 2 S0 4 , on a watch-glass ; 
 formates evolve no C0 2 under similar circumstances. 
 
 6th. " Cyanogen. — The evolution of CN denotes the pre- 
 sence of cyanides decomposable by heat. The gas may be 
 known by its odor, and by the crimson flame with which it 
 burns. 
 
 7th. "Hydrosulphuric acid. — The escape of H 2 S indicates 
 the presence of sulphides containing water ; the gas may be 
 readily known by its odor. 
 
 * For the size of the tubes see " Blowpipe," Part III. 
 21 
 
242 
 
 PRELIMINARY EXAMINATION 
 
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OP SOLID SUBSTANCES. 
 
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244 PRELIMINARY EXAMINATION 
 
 8th. " Ammonia resulting from the decomposition of 
 amnionic salts, or also of cyanides or nitrogenous organic 
 matters, in which latter case browning or carbonization of 
 the substance takes place, and either cyanogen or offensive 
 empyreumatic oils escape with the NH 3 ." — Fresenius's 
 " Chemical Analysis." 
 
 9th. Nitric acid, fluorine, chlorine, bromine and iodine 
 
 The detection of these in the preliminary examination is 
 best effected by mixing the substance under examination 
 with rather more than its own weight of fused KHS0 4 , and 
 then heating the mixture in a glass tube closed at one end ; 
 before making the examination the student ought to con- 
 sult pars, a, b, c. 
 
 a. Nitric acid. — If a nitrate is present, nitrous fumes are 
 disengaged, the color of which may be best perceived by 
 looking directly down the neck of the tube, inasmuch as a 
 thicker stratum of the gas is in this way seen. 
 
 b. Fluorine. — According to Berzelius the substance 
 ought, for the examination of F, to be mixed with four 
 times its weight of fused KHS0 4 , and the tube, after the 
 introduction of the mixture, strongly heated with the blow- 
 pipe flame until H 2 S0 4 begins to be evolved, and in order 
 to avoid too great frothing up, the mass should be heated 
 from the top downwards. If F is present, the tube will be 
 encrusted more or less with silica deposited from the fluo- 
 silicic acid gas which passes off. The lower extremity of 
 the tube containing the fused mass is then cut off, and the 
 upper part rinsed out with water and dried with blotting- 
 paper. If much F is present in the substance operated 
 upon, the glass tube will be dull all over its inner surface, 
 but if a small quantity only is present, the corrosion will 
 be only partial. 
 
 c. Iodine, bromine, and chlorine Violent fumes of I are 
 
 evolved, along with SO u , on heating a substance containing 
 an iodine compound with KHSO, in the tube ; some of the 
 I is generally deposited as a black sublimate on the upper 
 part of the tube. Br and 01 are in like manner evolved 
 from their compounds. 
 
 672. Aqueous Vapors are given off The water may 
 
 have existed either mechanically, or as water of ci^-stalli- 
 zation, or as constitutional water. If the body decrepi- 
 tates on ignition, the decrepitation is due probably to the 
 presence of an anhydrous salt which contains water me- 
 chanically between its crystalline plates, and the expulsion 
 of which gives rise to the decrepitation. If the water is 
 
OP SOLID SUBSTANCES. 245 
 
 present as water of crystallization, the crystalline body 
 will generally fuse during the expulsion, and resolidify 
 after it ; some substances swell considerably during the 
 expulsion — borax and alum for example. If the water 
 comes from some decomposable hydrate, the substance will 
 not fuse during its explosion. 
 
 6T3. A Sublimate is formed. — The sublimate may be 
 due to some volatile metal, metallic oxide, volatile salt, or 
 npn-metallic body. 
 
 a. The volatile metals are principally As, Hg, and Cd ; 
 these metals form a black or gray sublimate having more 
 or less of a metallic lustre. As is sublimed not only when 
 it exists in its free state, but also from some metallic ar- 
 senides, which are decomposed by heat into As and an 
 arsenide containing a less quantity of arsenic ; a few arse- 
 nites also yield As, when heated out of contact with the 
 air. Hg may be sublimed from most of its compounds ; if 
 the quantity is inconsiderable, it may only yield a gray 
 sublimate ; the globules can sometimes be rendered appa- 
 rent by touching the sublimate with a glass rod, or on 
 examining the sublimate with a lens. Cd may be sublimed 
 from some of its alloys ; it may be recognized by heating 
 it in contact with the air, when it becomes converted into 
 the brownish-yellow oxide. 
 
 b. Volatile Metallic Oxides. — Sb 2 3 first fuses into a 
 yellow liquid, and then sublimes under the form of shining 
 crystalline needles. The sublimate As 2 3 may either be in 
 the form of shining crystals or in the form of a white 
 powder, which the magnify ing-glass reveals, however, to be 
 crystalline. 
 
 c. Volatile salts. — Amnionic salts form white subli- 
 mates ; heated with jSJaHO and a drop of water on plati- 
 num foil, they evolve NH 3 . HgCl, begins to melt at a 
 very gentle heat, and then sublimes ; HgCl sublimes with- 
 out previous fusion ; the sublimate has a yellowish tinge 
 whilst hot, but is perfectly white when cold. Hgl a , which 
 is red, yields a yellow sublimate which becomes red by 
 trituration. HgS gives a black sublimate which acquires 
 a red tint when rubbed. When mercury compounds are 
 mixed with XaHO, and then heated in the tube, a subli- 
 mate of mercurial globules will be obtained. PbCl, first 
 fuses and then sublimes. The sublimate of arsenic sul- 
 phide ma}' be easilj' mistaken for pure sulphur. 
 
 d. Non-metallic Bodies, — S sublimes in reddish-brown 
 drops, which solidify on cooling, and turn yellow or yel- 
 
 21* 
 
246 PRELIMINARY EXAMINATION 
 
 lowish-brown. The S may be present merely in the state 
 of mixture, or it may be combined with some metal which 
 abandons a portion of it when heated out of contact of the 
 air. Oxalic acid j'ields a white crystalline sublimate, at- 
 tended with thick fumes ; the sublimate, when heated on 
 platinum foil with a drop of concentrated H 2 S0 4 , gives rise 
 to a copious evolution of gas. 
 
 674. The Non-volatile Matter. — The non-volatile por- 
 tion of the substance may liquefy, carbonize, or merely 
 change color : — 
 
 a. If it liquefies without expulsion of aqueous vapor, 
 and resolidifies when the heat is removed, the liquefaction 
 may be due to various substances, as argentic chloride, the 
 alkaline nitrates and chlorates, etc. If, by intense heat, O 
 is evolved, and if a small piece of charcoal on being thrown 
 into the fused mass is readily consumed, nitrates and chlo- 
 rates are indicated. 
 
 b. If it carbonizes, organic matter is present. " Car- 
 bonization is always attended with evolution of gases (ace- 
 tates evolve acetone) and water, which latter has an alka- 
 line or acid reaction. If the residue effervesces with acids, 
 whilst the original substance did not show this reaction, 
 organic acids may be assumed to be present in combination 
 with the alkalies or alkaline earths." 
 
 c. It changes color. "From white to yellow, turning 
 white again on cooling, indicates ZnO ; from white to yel- 
 lowish-brown, turning to a dirty light yellow on cooling, 
 indicates SnO„ ; if the color changes from white to brownish- 
 red, turning to yellow on cooling, and the body is fusible 
 at a red heat, this indicates the presence of PbO ; if the 
 color changes from white, or pale yellow, to orange-yellow, 
 or to a deeper and more reddish tint np to reddish-brown, 
 becoming pale yellow on cooling, and the body fuses at 
 an intense heat, this indicates the presence of Bi 2 3 ; if 
 the color changes from red to black, turning reddish- 
 brown again on cooling, this indicates the presence of 
 Fe 2 3 ; if the color changes from yellow to dark orange, 
 and the body fuses at an intense heat, this indicates 
 K^CrO,, etc." 
 
 6t5. In case of the non-appearance of any of these re- 
 actions, it must not be always concluded that the above- 
 mentioned bodies are entirely absent ; for S and As may 
 be present in such forms that the simple application of 
 heat will either not sublime them, or will expel them in 
 combinations which afford none of the distinctive charac- 
 
Of SOLID SUBSTANCES. 247 
 
 ters of the simple bodies ; moreover, two or more of these 
 may be present together in a substance, and afford sub- 
 limates having mixed characters, so that the individual 
 elements are difficult to distinguish. Such is frequently 
 the case with As and S, which, together, form a coating 
 on the tube having a metallic lustre at its lower extre- 
 mtty, and passing upwards successively into black, brown, 
 red, and finally yellow — these colors being due to combi- 
 nations of S and As, which are more volatile than As; 
 therefore, the examination of a substance in the glass 
 tube affords frequently no positive indication of the pre- 
 sence of a body, but merely intimates its probable exist- 
 ence, to establish which further investigations are necessary. 
 Such intimations are, however, of importance, as they serve 
 as guides in after-processes. 
 
 676. Examination in the open Tube. — A small par- 
 ticle of the substance, in powder, is introduced into the 
 tube at about half an inch from its extremity, and gradu- 
 ally heated, the tube being held in a slightly inclined 
 position, so that a current of air may pass fully through 
 it. By this means the substance is roasted, or oxidized, 
 and various matters contained in it are volatilized and pass 
 off up the tube. 
 
 677. The roasting must be performed slowly, with a 
 gradually increasing temperature, and with a good current 
 of air* passing through the tube, otherwise unoxidized 
 matter may be volatilized, and the mineral substance 
 clotted and fused together. If a perfect roasting be re- 
 quired, the substance, after being heated for some minutes 
 in the tube, is shaken out into an agate mortar, remixed, 
 and roasted, and this process is repeated until fumes are 
 no longer evolved. (Consult pars. 678 to 681.) 
 
 678. Almost all metallic sulphides disengage on roasting 
 S0 2 ; some sulphides yield besides a sublimate of S. S0 2 
 may be recognized by its odor, or by its decolorizing 
 moistened Brazil-wood paper, f a strip of which ought to 
 be introduced in the interior of the raised end of the tube. 
 
 679. Fluorine. — Very minute quantities of F can be 
 detected by the following method : " Mierocosmic salt, 
 
 * By inclining the tube more or less, we have the means of regulating 
 the current of air; very little passes through the tube when it is held 
 in a horizontal position, but it becomes more and more active as the 
 tube is held more and more vertically. 
 
 f Prepared by moistening slips of fine printing-paper with decoction 
 of Brazil wood. 
 
248 PRELIMINARY EXAMINATION 
 
 which has been previously fused upon charcoal or platinum, 
 is finely powdered and mixed with some of the substance 
 to be examined, also finely pulverized. A portion of the 
 mixture is introduced into an open glass tube, and the 
 blowpipe flame so directed upon it that a part of the flame 
 passes up the tube. By this means HF is formed (if the 
 substance be free from silica), which passes up the tube, 
 and may be recognized both by its peculiar pungent smell 
 and by the mode in which it corrodes the sides of the glass 
 tube, rendering them dull and opaque wherever any moisture 
 condenses. If Brazil-wood paper, moistened, be exposed 
 to the action of the gases passing up the tube, it will be 
 colored yellow, affording another indication of the presence 
 of F. If the substance also contains silica, fluoride of 
 silicon will be formed, which also colors yellow moist 
 Brazil-wood paper, and is decomposed by water,* silica 
 being formed, which, as the water evaporates, is deposited 
 on the sides of the tube, and is clearly perceptible either 
 with or without the aid of a lens. If now the tube be 
 washed out with water and dried, it will be generally found 
 corroded by the F, which leaves a dull spot wherever it 
 attacks the glass. As this experiment requires the appli- 
 cation of a strong heat, so that the glass tube is frequently 
 softened and bent, thus interfering materially with the suc- 
 cess of the experiment, Smithson lias recommended a piece 
 of platinum foil to be bent into the form of a gutter, and 
 inserted to about half its length into the glass tube ; the 
 mixture of the fused microcosmic salt and the substance 
 under examination is laid upon the projecting part of the 
 platinum, and the flame so directed upon it that the pro- 
 ducts of combustion pass up the tube. This arrangement 
 has the advantage that the fused substance does not come 
 in contact with the glass tube, and the inconveniences at- 
 tending the fusing and softening of the glass are altogether 
 avoided." 
 
 680. A sublimate may be formed in the second operation 
 when none has been formed in the first, as Bi 0, will be 
 formed when the Bi 2 S 3 or a bismuth alloy (scarcely any 
 sublimate is produced on roasting Bi itself) is present in 
 the substance under examination, and PbSO, will be formed 
 if VbS is present; in like manner, As.O, and Sb 2 3 will be 
 formed if an arsenide or an antimonide is present. If the 
 
 * Water will be preBcnt, owing to the products of the combustion of 
 the lamp passing up the tube. 
 
OP SOLID SUBSTANCES. 249 
 
 fumes formed have an odor of garlic it shows the presence 
 of As. 
 
 681. All the sublimates which are formed by oxidizing 
 substances in the open tube are white, but the colored 
 subs' ances which are volatilized in the closed tube are still 
 more easily volatilized in the open tube ; for it need scarcely 
 be observed that most of the reactions produced in the 
 closed tube are also produced in the open one. 
 
 682. Examination on Charcoal. — Most of the reactions 
 described in pars. 670 to 679 are also produced on the 
 charcoal ; but only those reactions which are special to this 
 operation are noticed in Table IX. and text. 
 
 683. In addition to the points which require to be at- 
 tended to, as pointed out in the table, it should be particu- 
 larly noticed whether the substance disengages a peculiar" 
 odor, as As and S might be detected by the odors the}' 
 produce ;* and it should also be noticed whether the sub- 
 stance fuses ; the oxides and acids which fuse are the oxides 
 of Sb, Bi, Pb, and Cu. " Most metallic sulphides fuse when 
 heated before the blowpipe upon charcoal, and this effect 
 often takes place with sulphides of those metals whose 
 oxides are infusible ; but many of these sulphides become 
 rapidly oxidized during the operation, and exhale an odor 
 of S0 2 in the same way as when heated in the open tube, 
 and are thus converted into metallic oxides. Most metals 
 fuse before the flame of the blowpipe; and all of them, 
 except those called noble, are subsequently oxidized by the 
 exterior flame." After this examination is complete, the 
 substance must still be retained on the charcoal for the 
 examination with Co(N0 3 ). 2 . 
 
 684. Treatment with Cobaltic Nitrate No explana- 
 tion beyond that given in Table X. is required. 
 
 685. Examination with Sodic Carbonate on Char- 
 coal. — The substance (in powder) under examination is 
 mixed with an equal quantity of Na 2 C0 3 , and the mixture 
 is made into a paste with a drop of water. After it has 
 been dried at a moderate heat, it is exposed on the char- 
 coal to the reducing flame of the blowpipe, the oxidizing 
 flame spreading over the charcoal. (See Table X., and 
 pars. 686 to 699.) Should no reduced metal make its 
 appearance, after exposure for two or three minutes to the 
 flame, a little KCN may be added, and the experiment 
 
 * It must be remembered that charcoal becomes, on exposure to the 
 blowpipe flame, covered with a bluish-white ash. 
 
250 
 
 PRELIMINARY EXAMINATION 
 
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252 PRELIMINARY EXAMINATION 
 
 continued for two or three minutes longer. Many of the 
 metallic arsenides and sulphides require to be carefully 
 roasted, and thus deprived of their As and S and the metals 
 themselves oxidized, before they can be reduced by Na 2 C0 3 ; 
 in this case, the residue which remains from the open-tube 
 experiment can be employed. It must be remembered, 
 however, that Cd as well as S and As may have been 
 expelled by the roasting. 
 
 686. The metals which can be reduced by this means, 
 besides Au, Pt, and Ag, are Pb, Sb, Sn, Cu, Zn, Bi, Ni, Co, 
 Fe, Cd, As, and Hg. "Au, Ag, Cu, and Sn compounds 
 yield metallic beads, but no incrustations ; Fe, Xi, Co, and 
 Pt compounds give neither beads nor incrustations ; Bi, Pb, 
 and Cd compounds produce a j'ellow or brown deposit 
 on the charcoal ; Sb and Zn give a white incrustation ;* As 
 may easily be recognized by its odor." 
 
 687. If a globule has been obtained, it is necessary to 
 ascertain whether it is malleable or brittle: "for this 
 purpose, it is allowed to cool perfectly, and carefully 
 removed with a pair of tweezers. Having been placed upon 
 a little anvil,")- and struck with a small hammer — or, if these 
 two blowpipe instruments are not at hand, upon the bottom 
 of a strong mortar, and struck sharply with the pestle — if 
 brittle, it of course falls to powder (as in the case of Sb) ; if 
 semi-malleable, it flatten^ out, at the same time breaking 
 into several pieces (as with Bi); and if fully malleable, 
 flattens out without breaking (like Pb).J 
 
 688. " The globule obtained is malleable. — Pb (makes a 
 black streak upon paper) ; a yellow incrustation is formed 
 upon the charcoal. Sn ; a slight white incrustation. Cu 
 (known by its color). Ag. 
 
 689. " The globule is semi-malleable Bi; a yellow in- 
 crustation. 
 
 690. " The globule is brittle Sb; abundant white in- 
 crustation. 
 
 * The ash of the charcoal may sometimes be mistaken by beginners 
 for a sublimate, but it may be distinguished from such by remaining 
 unaltered before the inner flame. 
 
 •j- The nnvil is a small block of hardened steel about two inches square 
 and three-quarters of an inch thick, polished upon one or more of its 
 faces. The hammer is made of hardened steel, one face must be square 
 with sharp edges, for trying the malleability of substances, and the 
 opposite end should bo bevelled off like » chisel to detach email frag- 
 ments of minerals oto. 
 
 % To prevent tho fragmonts from dispersing from the striking they 
 may bo folded in a piece of thin paper, the corner of which may be held 
 during the operation. 
 
OP SOLID SUBSTANCES. 253 
 
 * 
 
 691. " If no metallic globule is obtained, but shining 
 metallic spangles are observed after levigation ; probably 
 Sn, Sb, or Cu." 
 
 692. Magnetism. — To ascertain whether the reduced 
 metal is magnetic, an ordinary steel magnet must be pre- 
 sented to it ; if any of the metallic particles are magnetic 
 they will adhere to it. The trial may be made with far 
 more delicacy by bringing the metallic particles near a 
 magnetic needle which is supported on a centre, on which 
 it turns. 
 
 693. Only one mineral, magnetic oxide of iron, possesses 
 magnetic polarity and attraction, all other minerals, which 
 are attracted by the magnet, possess attraction only. The 
 magnetic character serves to distinguish a few of the mine- 
 ral species, which otherwise have very close resemblances ; 
 especially, magnetic iron ore from specular iron, and mag- 
 netic pyrites from common pyrites. 
 
 694. Many minerals become attractable by the magnet, 
 only after undergoing the high heat of the blowpipe; this 
 is the result of a partial decomposition. 
 
 695. Cupellation. — This is the process of separating 
 gold and silver from other substances by heat, and obtain- 
 ing them in a state of purity. The following is Berzelius' 
 method : — 
 
 696. "A small quantity of bone-ashes (in powder) is to 
 be taken on the point of a knife, moistened with the tongue, 
 and kneaded in the palm of the left hand, with a very little 
 soda, into a thick paste. A hole is then made in a piece of 
 charcoal, and filled with the paste, and its surface smoothed 
 by pressure with the agate pestle. It is then to be gently 
 heated by the blowpipe till perfectly dry (the soda only 
 assists the cohesion, and may be omitted). The assay,* 
 previously fused with pure lead, is placed in the middle of 
 this little cupel, and the whole heated by the exterior flame. 
 When the operation is finished, the precious metals are left 
 on the surface of the cupel. This experiment is so delicate 
 that grains of Ag, visible to the naked eye 2 and, indeed, 
 such as may be collected by the forceps and extended under 
 the hammer, may in this way be extracted from the lead 
 met with in commerce. 
 
 697. "If the button obtained by cupellation does not 
 possess the color of Au, but appears white, the quantity 
 
 * It would be better to roast the substance under examination with 
 Nfi 2 C0 3 on charcoal before assaying it with the pure lead. 
 22 
 
254 PRELIMINARY EXAMINATION 
 
 of Au is less than that of Ag, in which case, the button 
 should be placed in a porcelain capsule, a few drops of 
 HN0 3 poured on it, and the capsule heated over the lamp. 
 
 698. "If the button does not contain more than a fourth 
 part of its weight in Aw, it becomes completely black, and 
 then decomposes, the Ag being dissolved, while the Au 
 remains in black flakes. When the silver button contains 
 more than a fourth of its weight of Au, it is blackened, but 
 the Ag is not dissolved. It is neither blackened nor dis- 
 
 <*<* solved, if the proportion of Au to Ag is nearly equal ; in 
 this case the button must be melted with twice its bulk of 
 pure Ag, on charcoal, and again heated with HN0 3 , by 
 which the mass becomes black, and dissolves; the pure Au 
 being left behind." 
 
 699. If the substance fuses into a transparent glass with 
 the Na 2 CO„, it shows the presence of silica, par. 458. 
 
 TOO. Treatment with Borax To obtain a bead of 
 
 borax, one end of the platinum wire is bent into a small 
 hook. This is heated in the blowpipe flame, aud then dipped 
 into the borax ; a small portion of the borax will adhere to 
 it, and this being fused in the flame, and while hot dipped 
 again into the powdered borax, a fresh quantity will ad- 
 here, which is fused as before, and this continued until a 
 bead of the requisite size is obtained. A great many 
 metallic oxides dissolve in borax, forming colored glasses. 
 If any metallic arsenides or sulphides are present, it is 
 necessary to roast the substance in the way previously 
 described (6T6) before making the examination with borax ; 
 and it is frequently advantageous, before roasting the 
 powdered substance, to mix it with a little powdered char- 
 coal, so as to prevent the formation of sulphates and 
 arseniates. 
 
 701. While the bead of borax is still hot, it is touched 
 with a small quantity of the powder of the substance under 
 examination, and that which adheres is fused into it. The 
 operator must then observe — 1st, whether the substance is 
 soluble or insoluble in borax ; and 2d, the color of the 
 borax bead in (1) the oxidizing flame, and (2) in the re- 
 ducing flame, both in the hot and in the cold state. In 
 performing this experiment, care must be taken not to dis- 
 solve up, in the first instance, too large an amount of the 
 oxide or other subtance under examination. If a small 
 quantity ntford no distinct reaction, more may be easily 
 added. If, however, the color of the bead is too intense to 
 be clearly distinguished, the bead may be jerked off the 
 
OP SOLID SUBSTANCES. 255 
 
 wire, and that which still adheres fused up with a fresh 
 quantity of borax, by which a paler and more transparent 
 glass will be obtained. 
 
 702. Examination in the Platinum Forceps " If the 
 
 operator has convinced himself by a preliminary experi- 
 ment that the substance under examination does not, when 
 heated, attack platinum,* a small splinter of it is to be 
 taken between the platinum forceps, and subjected to the 
 oxidizing flame ; but if the substance is very fusible, a 
 piece of platinum wire, hooked at one end, may be used 
 instead of the forceps. If, however, the substance be one 
 which exerts a chemical action on platinum, and would 
 therefore injure the forceps or wire, charcoal must be em- 
 ployed as the support. 
 
 "703. " In order to test the fusibility of a mineral, a small 
 splinter, having a sharp edge or point, should be broken 
 orf and held in the forceps at a short distance beyond the 
 point of the inner blue flame, so that the sharp edge is 
 strongly heated. If a gas flame be employed, the mineral 
 must be held somewhat further from the point of the blue 
 flame than is necessary in the case of an oil-lamp, in order 
 to prevent any reduction taking place, which would mate- 
 rially interfere with the results. If a powdered substance 
 is to be tested, or one which decrepitates when heated, and 
 which must therefore be previously pulverized, the follow- 
 ing process may be resorted to: A small quantity of the 
 powder is made into a paste with water, and spread upon 
 a piece of charcoal ; it is then dried, and strongly heated 
 with an oxidizing flame, it will then (generally) cohere suf- 
 ficiently to allow of its being taken up between the forceps 
 and tested in the usual manner. Care must be taken that 
 the substance, if a fusible one, and one which acts upon 
 platinum, does not fuse upon the platinum points of the 
 forceps. 
 
 704. " Of the metallic oxides, the following only are 
 fusible in the oxidizing flame, viz., the oxides of Cu, Pb, 
 Sb, and Bi. Metallic sulphides are, with few exceptions, 
 readily fusible under the blowpipe flame ; these exceptions 
 are ZnS and MnS." 
 
 705. " Of the simple silicates, i. e. silicates with a single 
 base, those of the alkalies are most fusible. The silicates 
 
 * Platinum cannot be employed when compounds of the easily reduci- 
 ble metals, as Ag and Pb, are present. 
 
256 PRELIMINARY EXAMINATION 
 
 of Ca and Mg are with a few exceptions practically infusi- 
 ble. Alnminic silicates are infusible. 
 
 706. "Of the iron silicates those of ferrous and mag- 
 netic oxide are very fusible, but the ferric silicates are 
 practically infusible. Consequently, under the blowpipe 
 flame, the fusibility of an iron silicate much depends upon 
 whether it be submitted to the oxidizing or the reducing 
 flame ; for the ferric silicates infusible in the former become 
 fusible and magnetic in the latter. If, therefore, a sub- 
 stance be infusible, or only very slighly fusible in the 
 oxidizing flame, it may afterwards be submitted to the 
 extremity of the reducing flame, since many substances 
 infusible in the former become fusible on undergoing a 
 partial reduction. 
 
 "707. " The fusibility of a compound silicate, i. e. a sili- 
 cate containing two or more bases, depends upon that of the 
 simple silicates of which it is composed, but is generally 
 greater than the mean of these latter. Thus many calcic 
 and magnesic silicates, and calcic and aluminic silicates, are 
 more fusible than any of the simple silicates which enter 
 into their composition. 
 
 708. "According to their relative fusibility, minerals 
 may be classified as follows : — 
 
 I. Readily fusible to a bead. 
 II. With difficulty fusible to a bead. 
 
 III. Readily fusible on the edges. 
 
 IV. With difficult}' fusible on the edges. 
 V. Infusible. 
 
 709. "In testing the fusibility of a mineral substance, it 
 should be noticed whether, if fusible, a clear or opaque 
 bead is obtained ; also, whether the substance changes 
 color, becomes magnetic, or exhibits any phenomena of 
 intumescence, ebullition, etc., all of which arc useful charac- 
 ters in indicating the nature of the mineral." 
 
 710. " The degree of fusibility is a very important point 
 to ascertain, when the examination in question refers to 
 the native combinations of silica and certain other 
 minerals, for this characteristic feature displaj'ed by the 
 blowpipe is often the only one by which we ma)* distin- 
 guish those which consist of earths, and which contain no 
 notable quantities of metallic oxides, properly so called. 
 Amongst the minerals most frequently met with, the fol- 
 lowing are infusible : — 
 
OF SOLID SUBSTANCES. 
 
 257 
 
 Quartz, 
 
 Corundum, 
 
 Tourmaline (both that -which 
 
 contains alumina and even 
 
 that which contains soda), 
 Zircon, 
 Cyanite, 
 Phenakite, 
 Leucite, 
 Talc, 
 
 Pyrcphyllite, 
 Apatite, 
 Gehlenite, 
 Apophyllite, 
 Staurotide, 
 Refractory clays, 
 Aluminic hydrate, 
 Magnesic hydrate, 
 Aluminic sulphate, 
 Calcic carbonate, 
 Magnesic carbonate, 
 Zincic carbonate, 
 Allophane, 
 
 711. "Amongst those which are almost infusible and 
 only become rounded at the edges, the following may be 
 named : — 
 
 Spinel, 
 
 Pleonaste, 
 
 Gahnite, 
 
 Olivine, 
 
 Cerite, 
 
 Cymophane, 
 
 Gadolinite (which, being 
 heated, becomes suddenly 
 luminous, as if it caught 
 fire), 
 
 Vitreous tin, 
 
 P utile, 
 
 Titanic iron, 
 
 Tantalite, 
 
 Turquoise, 
 
 Titaniferous oxide of iron, 
 
 Chrome iron, 
 
 Native oxides of iron, 
 
 Yttrotantalite, 
 
 Dioptase, 
 
 Chondrocyte, 
 
 Topaz. 
 
 Felspar, 
 
 Albite, 
 
 Petalite, 
 
 Labradorite, 
 
 Anorthite, 
 
 Nepheline, 
 
 Tubular spar, 
 
 Pyroxene (which contains 
 
 much magnesia), 
 Epidote (which intumesces 
 
 by the first impression of 
 
 the heat), 
 Euclase (which intumesces by 
 
 the first impression of the 
 
 heat), 
 
 Emerald, 
 
 Titanite, 
 
 Sorlalite, 
 
 Calcareous Scheelin, 
 
 Meerschaum, 
 
 Soapstone, 
 
 Serpentine, 
 
 Mica (some species,especially 
 
 those found in granite), 
 Dichroite, 
 Heavy spar, 
 Celestine, 
 Gypsum, 
 A patite, 
 Fluor spar. 
 
 22* 
 
358 PRELIMINARY EXAMINATION 
 
 Table of Volatile Elements which 
 
 Te 
 
 Metallic-film. 
 
 Black ; thin 
 part brown. 
 
 Oxide-film. 
 
 White. 
 
 Oxide-film 
 
 with stannous 
 
 chloride. 
 
 Black. 
 
 Oxide-film 
 
 with stannous 
 
 chloride and 
 
 soda. 
 
 Black. 
 
 Oxide-film with 
 
 silver-nitrate and 
 
 ammonia. 
 
 Yellowish- 
 white. 
 
 Se 
 
 Cherry-red ; 
 thin part 
 brick-red. 
 
 White. 
 
 Brick-red. 
 
 Black. 
 
 White. 
 
 Sb 
 
 Black ; thin 
 part brown. 
 
 White. 
 
 White. 
 
 White. 
 
 Black ; 
 
 insoluble in 
 
 ammonia. 
 
 As 
 
 Black ; thin 
 part brown. 
 
 White. 
 
 White. 
 
 White. 
 
 Lemon-yellow 
 
 or reddish- 
 brown ; soluble 
 in ammonia. 
 
 Bi 
 
 Black ; thin 
 part brown. 
 
 Yellowish- 
 white. 
 
 White. 
 
 Black. 
 
 White. 
 
 Hg 
 
 Gray non-co- 
 herent thin 
 film. 
 
 Tl 
 
 Black ; thin 
 part brown. 
 
 White. 
 
 White. 
 
 White. 
 
 White. 
 
 Pb 
 
 Black ; thin 
 part brown. 
 
 Yellow-ochre 
 color. 
 
 White. 
 
 White. 
 
 White. 
 
 Cd 
 
 Black ; thin 
 part brown. 
 
 Blaokish- 
 brown ; thiu 
 part white. 
 
 White. 
 
 White. 
 
 White ; in the 
 
 thin parts turns 
 
 bluish-black. 
 
 Zn 
 
 Sn 
 
 Black ; thin 
 part brown. 
 
 White. 
 
 White. 
 
 White. 
 
 White. 
 
 Blaok ; thiu 
 part brown. 
 
 Yellowish- 
 white. 
 
 White. 
 
 White. 
 
 White. 
 
OP SOLID SUBSTANCES. 
 
 can be reduced as Films. 
 
 259 
 
 Iodide-film. 
 
 Iodide-film 
 with ammonia. 
 
 Sulphide-film. 
 
 Sulphide-film 
 with ammo- 
 nium-sul- 
 phide. 
 
 Brown ; 
 
 disappears for a 
 
 time on breathing. 
 
 Disappears 
 
 altogether on 
 
 blowing. 
 
 Black to 
 blackish- 
 brown. 
 
 Disappears 
 for a time. 
 
 Brown ; does not 
 
 wholly disappear 
 
 on breathing. 
 
 Does not dis- 
 appear on 
 blowing. 
 
 Yellow to 
 orange. 
 
 Orange, and 
 then disap- 
 pears for a 
 time. 
 
 Orange-red to yel- 
 low ; disappears 
 on breathing. 
 
 Disappears 
 
 altogether on 
 
 blowing. 
 
 Orange. 
 
 Disappears 
 for a time. 
 
 Orange-yellow ; 
 disappears for a 
 time on breath- 
 ing. 
 
 Disappears | 
 
 altogether onj 
 
 blowing. 
 
 Lemon- 
 colored. 
 
 Does not dis- 
 appear. 
 
 Elements whose 
 reduction-films 
 are soarcely dis- 
 solved in dilute 
 nitric acid. 
 
 Bluish brown ; 
 thin parts pink; 
 disappear for a 
 
 Pink to Burnt-um- 
 
 orange; ehest-j ber-color to 
 nut colored coffee- 
 
 time on breathing, when blowing colored. 
 
 Does not dis- 
 appear. 
 
 Carmine-colored 
 and lemon-yel- 
 low ; does not 
 disappear on 
 breathing. 
 
 Lemon-yellow ; 
 does not disap- 
 pear on breath- 
 ing. 
 
 Disappears 
 
 for a time on 
 
 blowing. 
 
 Does not dis- 
 appear on 
 blowing. 
 
 Black. 
 
 Does not dis- 
 appear. 
 
 Black ; thin 
 
 parts bluish 
 
 gray. 
 
 Does not dis 
 appear. 
 
 Elements whose 
 reduction-films 
 are with diffi- 
 culty dissolved 
 in dilute nitric 
 acid. 
 
 Orange-yellow to 
 lemon-color ; 
 does not disap- 
 pear on breath- 
 ing. 
 
 Disappears 
 
 for a time on 
 
 blowing. 
 
 Brownish-red 
 to black. 
 
 Does not dis 
 appear. 
 
 White. 
 
 White. 
 
 White. 
 
 Lemon- 
 colored. 
 
 Does not dis 
 appear. 
 
 White. 
 
 White. 
 
 Does not dis- 
 appear. 
 
 Yellowish-white. 
 
 Yellowish- 
 white. 
 
 White. 
 
 Does not dis- 
 appear. 
 
 Elements whose 
 reduction-films 
 are instantly 
 dissolved in di- 
 lute nitric acid. 
 
260 
 
 FLAME REACTIONS. 
 
 108. " The following are fusible :— 
 
 Hydroboracite, 
 
 Datholite, 
 
 Botryolite, 
 
 Cryolite, 
 
 Mica (several species, espe- 
 cially those which contain 
 lithia), 
 
 Tourmaline (those which con- 
 tain potash), 
 
 Axinite (intumesces whilst 
 fusing), 
 
 Amblygonite, 
 
 Lazulite, 
 
 Haiiyne, 
 
 Nosin, 
 
 Eudialyte, 
 
 Pyrosmalite." — Eose's Man- 
 uel of Analysis. 
 
 Zeolites (most of them intu- 
 mesce), 
 
 Spodumene (which intumes- 
 ces), 
 
 Mejonite (which froths up be- 
 fore fusing), 
 
 Elaeolite, 
 
 Amphibole (most of which 
 boil up whilst in fusion), 
 
 Pyroxene (those which con- 
 tain no excess of mag- 
 nesia), 
 
 Idocrase (intumesces in 
 fusing), 
 
 Garnet, 
 
 Ceiine, 
 
 Orthite (boils in fusing), 
 
 Ferruginous Scheelin, 
 
 Boracite, 
 
 712. Bunsen's flame reactions Almost all the reac- 
 tions which can be performed by means of the blowpipe 
 may be accomplished with far greater ease and precision 
 in the flame of the non-luminous gas-lamp.* This flame, 
 moreover, possesses several peculiarities which render it 
 available for reactions, by which the smallest traces of many 
 substances occurring mixed together can be detected with 
 certainty when the blowpipe, and even still more delicate 
 methods fail. The method of examination of the various 
 parts of the flame for these flame reactions is described in 
 pars. 1167 to 1113, and the special behavior of the bodies 
 themselves has been described under the head of their spe- 
 cial properties ; we shall, therefore, onby here give a table 
 (given by Bunsen in his paper on flame reactions) of the 
 volatile elements which can be reduced as films. This table 
 contains some of the rarer elements which are not given in 
 the book. 
 
 713. When the student has completed the preceding pre- 
 liminary experiments, he will be able to arrange the sub- 
 stance under examination under one of the three fol- 
 lowing divisions : — 
 
 * See description of Bunscu's lamp in Tart III. 
 
solution of solids. 261 
 
 714. The solid is neither a pure metal nor an alloy, 
 and is destitute of organic matter. See par. 117. 
 
 715. The solid is neither a pure metal nor an alloy, 
 
 BUT CONTAINS ORGANIC MATTER. See par. 731. 
 
 716. The solid is either a pure metal or an alloy. 
 See par. 737- 
 
 717. THE SOLID IS NEITHER A PURE METAL 
 NOR AN ALLOY, AND IS DESTITUTE OF OR- 
 GANIC MATTER. 
 
 718. Before, a solid can be acted upon by reagents, it 
 must be brought into a state of solution. For this purpose 
 it is submitted to the action of different fluids, and the one 
 in which, it dissolves is termed its solvent. The solvents 
 employed in qualitative analysis are water, HC1, HX0 3 , 
 and aqua regia. Water, when it can be employed, is always 
 to be preferred. 
 
 719. The student must particularly guard against adding 
 too much of the solvent, especially if it be an acid. To 
 avoid this, he must add it in small quantities at a time, and 
 apply heat after each addition. The substance should, be- 
 fore being submitted to the action of solvents, be reduced 
 to the state of a very fine powder, and fifteen or twenty 
 grains employed for the analysis. The whole of the sub- 
 stance must, however, never be employed, but always a 
 portion kept in case of any unforeseen accident, or for con- 
 firmatory experiments. In ascertaining in what liquid the 
 substance is- soluble, the student ought only to employ about 
 three or four grains of the substance ; after he has ascer- 
 tained the solvent he can then dissolve up the fifteen or 
 twenty grains for the analysis. 
 
 720. The powdered substance is boiled in ten times its 
 amount of water. It all dissolves. — Examine it according 
 to par. 640. A portion remains undissolved. — Filter a few 
 drops of the liquid, and evaporate them to dryness on pla- 
 tinum foil. If a large residue remains on evaporation, the 
 whole of the solution must be filtered, and examined accord- 
 ing to par. 640. The insoluble residue, after being well 
 washed with boiling water, must be examined according to 
 721. If no residue remains on evaporating the aqueous 
 solution, or at all events a very slight one, pour the remain- 
 
262 THE SOLUTION OP SOLID BODIES. 
 
 dcr of the water off, and treat the insoluble substance ac- 
 cording to 721. 
 
 721. The substance which was partly or entirely insoluble 
 in water, is boiled in dilute HC1, and if not soluble in dilute, 
 then in concentrated HCl.* It all dissolves. — Treat the 
 fifteen or twenty grains in the same way and proceed with 
 the examination for the bases in the usual way, and for the 
 acids according to 547.f A portion remains undissolved. — 
 Ascertain if anything has dissolved, by evaporating a por- 
 tion of the fluid to dryness on platinum foil. Should this 
 be the case, place the tube, with its contents, on one side, 
 and proceed with the next experiment. 
 
 722. A fresh portion of the original substance is boiled 
 in HN0 3 . The substance dixxolves.% — Remove as much of 
 the free acid as possible by evaporation ; dilute the concen- 
 trated solution with water, and then proceed with the exa- 
 mination for the bases in the usual waj 7 , and for the acids 
 according to 547. It does not dissolve. — Allow it to settle; 
 pour off one-half the acid, add a like quantity of concen- 
 trated HC1, and again boil. If a portion still remains un- 
 dissolved, return to the strong HCl mixture (721); filter, 
 and analyze the filtrate in the usual way. The residue 
 insoluble in acids, after being well washed, must be treated 
 according to 723. 
 
 723. The usually occurring substances, which are insolu- 
 ble in water and acids, are the baric, strontic, calcic, and 
 plumbic sulphates, alumina, FERRic oxide, and vtheir 
 phosphates, the argentic and plumbic chlorides, calcic 
 fluoride, silicates, silica, and SULPHUR. 
 
 724. A small portion of the residue, insoluble in water 
 and acids, is heated on a slip of platinum foil. If S0 2 is 
 evolved along with the volatilization of the whole of the 
 substance, sulphur only can be present. When other sub- 
 stances are present, add to another small portion a drop of 
 (NH,),S. If the color remains white, Ag, Pb, and probably 
 Fe, are absent. 
 
 * If HCl causes any effervescence, the evolved gas must be examined 
 for C0 2 , H 2 S, mid HCN, ns directed under tliese acids. 
 
 f 11 tlie substance is Bilicatc decomposable by HCl, treat it according 
 to pnr 465. 
 
 % If the substance dissolves with the separation of n light yellow 
 colored mass of sulphur, it points out the presence of n sulphide. When 
 HNO is employed as the solvent, as niuou of the free acid as possible 
 ought to be removed by evaporation, before passing H,S through the 
 solution, as they deoomposo each other, the decomposition being attended 
 with the separation of a large amount of sulphur. 
 
THE SOLUTION OF SOLID BODIES. 263 
 
 125. A small quantity of the dry residue, in the state of 
 a very fine powder, is mixed with four times its weight of 
 a mixture of equal parts Na,CO s and K 2 CO :) . The mixed 
 mass is placed in a platinum crucible,* and heated over a 
 gas lamp for about half an hour; or, what is still better, 
 the platinum vessel is placed within a Hessian crucible 
 containing a little MgC0 3 , and exposed to a full red heat, 
 for the same length of time, in a furnace. The magnesic 
 carbonate is employed to prevent the platinum from coming 
 in contact with the Hessian crucible. 
 
 726. On cooling, the fused mass is boiled with water, and 
 filtered. The filtrate is to be examined for the acids and 
 alumina, the residue for the bases. 
 
 721. Examination of the filtrate. — To one portion of the 
 filtrateadd HC1 until the solution is distinctly acid ; evapo- 
 rate to dnness, and ignite until acid fumes are no longer 
 evolved. To the dried mass add dilute HC1 and boil ; if 
 a residue remains, silicic acid is present. To the filtrate 
 from the silica add NH 4 HO in excess, and then warm the 
 solution ; if a precipitate is formed, it must be due either 
 to alumina or its phosphate. After having filtered and 
 washed the precipitate, examine it for alumina and aluminie 
 phosphate according to Table V. In the filtrate from the 
 alumina precipitate, or in the solution which has failed to 
 give a precipitate, test for phosphoric acid by adding 
 NH t Cl, and then MgSO + . Acidulate another portion of 
 the original filtrate with HC1, and examine for sulphuric 
 acid by adding BaCl 2 . Another portion must be acidulated 
 with HNO.., and tested for chlorine by AgN0 3 . To detect 
 fluorine, an examination must be made according to 462 
 or 463. 
 
 728. Examination of the residue. — After having removed 
 all the substances soluble in water, by repeated washings, 
 dissolve the residue, if Pb and Ag are absent, in HC1, and 
 proceed with the anabysis in the usual way. If the residue 
 does not completely dissolve in the acid, and the two metals 
 just named are absent, it shows that a portion of the sub- 
 stance has not been decomposed. When this is the case, 
 filter off, and examine the filtrate. 
 
 729. When the fixed alkalies are to be looked for in the 
 
 * The compounds of the easily reduced metnls, such as Ag, Pb, etc., 
 must not be fused in platinum vessels, as they form alloys with that 
 metal, which greatly injures or altogether destroys the platinum vessel : 
 porcelain crucibles must therefore be employed in such cases. 
 
264 THE SOLUTION OF SOLID BODIES. 
 
 insoluble residue, another portion, in fine powder, must be 
 mixed with about four times its weight of BaC0 3 , and fused 
 in a platinum crucible, in the manner already described. 
 On cooling, the fused mass is digested with dilute HC1, and 
 filtered. The filtrate is evaporated to dryness, and ignited ; 
 the dry residue must be treated with water, and again 
 filtered. The filtrate, after being freed from iron oxide, 
 alumina, baryta, lime, and magnesia (if present) must be 
 evaporated to dryness, to expel the amnionic salts which 
 have been employed in their precipitation ; if a residue 
 remains, it must be examined for K and Na. 
 
 730. Bloxam has proposed to fuse insoluble substances 
 by mixing them with a deflagrating mixture. A great saving 
 of time and labor is thus effected by causing the heat to be 
 applied inside the mass to be fused. The following is the 
 process: 5 grains of the substance are intimately mixed 
 with 10 grains of dried Na 2 C0 3 and 70 grains of the defla- 
 grating flux, composed of charcoal* and nitre in the pro- 
 portion of one part by weight of the former to six of the 
 latter. The mixture is placed in a thin porcelain dish, or 
 clean iron tray, and a lighted match applied to the centre 
 of the heap. The deflagration is completed in two or three 
 seconds, and a well-fused mass remains. This is easily 
 detached from the cooled dish (in which a little unburnt 
 charcoal may be left), and boiled with water, being occa- 
 sionally stirred with a glass rod. Two or three minutes 
 always suffice for the extraction of the soluble portion, 
 which is then filtered off, and examined for acids and for such 
 bases as are compatible in solution with the alkaline carbon- 
 ates (par. 121). The residue left by water, after having 
 been washed, is treated with acids, and examined in the usual 
 way (par. 728). A little charcoal is generally left undis- 
 solved by acids, and with it any of the substances which 
 may have escaped decomposition. If it be thought neces- 
 sary, the dried residue may be ignited until the charcoal is 
 consumed, and the incombustible portion examined. 
 
 731. The solid substance under examination is 
 neither a pure metal nor an alloy, but contains 
 organic matter. 
 
 * The charcoal should, of oourse, bo chosen so as to yield a very small 
 proportion of ash, and must be reduced to a fiue powder; the charcoal 
 from tho powder-mills is most suitable for the purpose. The nitre must 
 bo chemically pure. 
 
THE SOLUTION OP SOLID BODIES. 265 
 
 732. The presence of fixed organic matter* interferes with 
 the detection of many substances. Thus, in the presence 
 of tartaric acid, which is a fixed organic acid, aluminic, 
 chromic, iron, and many other metallic oxides, are not pre- 
 cipitated by the alkalies ; alkaline citrates prevent the pre- 
 cipitation of acids by bases, with which the acids form in- 
 soluble salts under ordinary circumstances ; a soluble baric 
 salt will not produce a precipitate, even in a solution of a 
 sulphate, if an alkaline citrate be present, unless the sul- 
 phate is present in the proportion of three or more equiva- 
 lents for every one of the citrate. Soluble plumbic and 
 strontic salts produce, likewise, no precipitate in solutions 
 of sulphates in the presence of citrates, the citrates inter- 
 fere with the precipitation of a large number of substances, 
 Mn, for instance, is not precipitated from its solutions by 
 amnionic sulphide."}" It is therefore necessary, after pre- 
 cipitating the fifth and sixth groups by HC1 and H 2 S, to 
 destroy the fixed organic matter, when it is present, which 
 will have been ascertained in the preliminary examination. 
 For this purpose, the filtrate from the H 2 S precipitate, or 
 the solution which has failed to give a precipitate with this 
 reagent, is evaporated to dryness and ignitedj until all the 
 organic matter has been destroyed, the residue must then 
 be dissolved in water or acids as directed at par. 118 and 
 then examined for the 4th, 3d, 2d, and 1st groups of basic 
 substances in the usual way. The examination of the acids 
 must be conducted as directed at par. 720, and following 
 pars. 
 
 733. Sometimes we are obliged to have recourse to the 
 following method for destroying the organic matter, espe- 
 cially in the case of liquids and solids which have to be ex- 
 amined for poisons. The solid or liquid is placed in a por- 
 celain dish, and to it is added pure concentrated HC1, about 
 equal in weight to the dry solid present, and then, if re- 
 
 * Organic substances are termed fixed when they cannot be distilled 
 or volatilized without decomposition. The organic matter ought to be 
 tested for nitrogen ; for this purpose it is mixed with caustic potash in 
 powder or with soda-lime, and the mixture heated in a test-tube, when, 
 if it contains nitrogen, NH 3 will be evolved. 
 
 f Spiller on the Influence of Citric Acid on Chemical reactions. Quar- 
 terly Journal of the Chemical Society of London, vol. x. 
 
 X Many substances, especially aluminic and the iron oxides, after igni- 
 tion dissolve with very great difficulty even in the concentrated mineral 
 acids. The residue may therefore require protracted boiling in acids, 
 although the original substance dissolved in water or dilute acid very 
 readily. 
 
 23 
 
266 THE SOLUTION OF SOLID BODIES. 
 
 quired, water to make the mass of a thin pasty consistence, 
 the dish is placed on the water-bath, and small portions of 
 pure potassic chlorate are added every five minutes or so, 
 stirring constantly at the same time the contents of the dish ; 
 the addition of the potassic chlorate is continued until the 
 mixture is perfectly fluid and of a light-yellow color ; when 
 this is attained we add 20 or 30 grains more of the KC10 3 , 
 and continue the heat until the liquid ceases to smell of chlo- 
 rine ; the mixture is then filtered through paper or linen, the 
 residue thoroughly washed, and the wash-water concentrated 
 over the water-bath, and then added to the filtrate ; the 
 filtrate is examined as directed in the next par. The resi- 
 due must be examined for AgCl, PbS0 4 , and SnO s , as 
 directed at par. '723. 
 
 134. The filtered liquid is placed in a flask and kept at a 
 temperature between 60° and 70° C, and washed H 2 S trans- 
 mitted through it for about twelve hours, it is then allowed 
 to cool, and during the cooling the transmission of the gas 
 through it is continued ; it is then covered over with paper 
 and placed in a moderately warm place, and allowed to 
 stand for twenty-four hours; if at the end of that time it 
 has only a faint odor of H 2 S, the gas is again passed through 
 it to excess, and it is again allowed to stand until the odor 
 of H 2 S has again nearly disappeared ; the precipitate is then 
 collected upon a filter and washed until the washings are 
 quite free from CI ; the filtrate is examined for the members 
 of the 4th and 3d groups. 
 
 735. The precipitate contains, besides any metals that 
 may be present, organic matter and sulphur ; if the analysis 
 has been instituted, not for the examination of the poison- 
 ous metals, the precipitate can be examined in the usual 
 manner ; but if the examination is made to ascertain whether 
 any of the poisonous metals are present, it may be conducted 
 in the following manner: Digest the precipitate for some 
 time in NH 4 HO ; the As,S 3 dissolves, and the other sul- 
 phides remain undissolved ; filter off and evaporate the 
 filtrate along with the wash-water to dryness on the water- 
 bath, the As a S 3 will remain ; it is generally of a brown color, 
 from the presence of organic matter which has been dissolved 
 by the NH 4 IIO. Examine the precipitate according to the 
 electrolytic method (273), or according to the method de- 
 scribed in par. 260. 
 
 736. The precipitate insoluble NH 4 HO, after it has been 
 thoroughly washed, is digested in yellow (NH 4 ) a S ; it is 
 then filtered, and the filtrate, along with the wash-water, is 
 
THE SOLUTION OF SOLID BODIES. 26| 
 
 evaporated to dryness over a water-bath ; the residue is ex- 
 amined for Sb. 2 S., by the usual tests. Treat the sulphides 
 insoluble in (NH 4 ) 2 S according to par. 294. 
 
 13?. The substance under examination is a pure 
 metal or an alloy. 
 
 138. Nitric acid behaves with metals in the following 
 manner : Au and Pt are neither dissolved nor altered in the 
 least degree by it. Sn and Sb are converted by it into 
 oxides, which do not dissolve in or combine with an excess 
 of the acid. The other metals are oxidized and converted 
 by it into soluble nitrates. On account of the different 
 behavior, therefore, which UNO, exhibits with the metals, 
 it is usual to employ it as the solvent of alloys, etc. 
 
 "139. To the metal or alloy under examination, which is 
 placed in a small flask, is added BUSTO,, of sp. gr. 1.20, and 
 heat applied. One of the three following cases will then 
 occur : 1. Complete solution takes place. 2. A white in- 
 soluble substance separates. 3. A metallic residue remains. 
 Each of the three cases is considered separately in detail. 
 
 '740. 1. If complete solution ensues, Au, Pt,* Sn, and Sbf 
 must be absent. After removing the greater part of the 
 free acid by evaporation, dilute the solution with water,J 
 and proceed with the analysis in the regular wa} r . Hg, if 
 present, will be found in the mercuric state. 
 
 141. 2. If a white insoluble substance separates, Sn or Sb 
 is indicated. After removing the greater part of the free 
 acid by evaporation, dilute the solution with water, filter, 
 and proceed with the filtrate in the ordinary way. The 
 precipitate, after being well washed with water, is treated 
 with a hot concentrated solution of tartaric acid. If it all 
 dissolves, Sn is absent. The presence of Sb is confirmed by 
 H 2 S producing in the tartaric acid solution, to which HC1 
 has been added, an orange-red precipitate. If the whole of 
 the insoluble substance does not dissolve in tartaric acid, 
 the solution is filtered. The filtrate is examined for Sb by 
 the method just stated. The residue, after being well washed, 
 is mixed with Na 2 C0 3 and KCN, and exposed on a charcoal 
 
 * Alloys of Ag and Pt, with the latter metal present in small propor- 
 tion only, dissolve in HN0 3 . 
 
 f Very minute traces of Sb are often completely dissolved by HN0 3 . 
 
 J If the solution becomes turbid on the addition of water, it indicatea 
 the presence of Bi. 
 
268 EXERCISES. 
 
 support to the inner blowpipe flame. If Sn is present, duc- 
 tile metallic grains will be obtained. 
 
 742. 3. If a metallic residue remains, Au or Pt is indi- 
 cated. After removing the greater part of the free acid by 
 evaporation, dilute the solution with water, filter, and ex- 
 amine the filtrate in the usual way. The metallic residue 
 is dissolved in aqua regia. One portion of the solution is 
 tested for Au according to 284. The other portion is tested 
 for Pt according to 287. 
 
 743. Answers to the following exercises must be writ- 
 ten out. 
 
 EXERCISES. 
 
 175. If you had such a mixture as the following, whether 
 would it be more advantageous to treat it, first with water 
 until all the soluble matter was removed, and then with 
 HC1, or to treat it at once with HC1 : what difference would 
 there be between the two modes of treatment : Na 2 S0 4 , 
 KN0 3 , NH 4 C1, BaCO,? 
 
 176. Whether would it be better to treat such a mixture 
 as the following, first with water, and second with HC1, 
 or to treat it at once with HC1 : Fe„0 8 , Ba(N0 3 ) 2 , MnCl a , 
 As 2 O s , CuS0 4 ? 
 
 177. Name the more frequently occurring mineral com- 
 pounds which are insoluble both in water and acids, and 
 describe the processes for rendering them soluble. 
 
 178. How would you perform the qualitative analysis 
 of an alloy containing arsenic, copper, silver, lead, and 
 iron 'I 
 
 179. Name the chief blowpipe reactions employed in 
 qualitative analysis. 
 
PART II. 
 
 ANALYSIS OF ORGANIC SUBSTANCES. 
 
 744. All organic substances contain carbon ; a large 
 number are composed of carbon and hydrogen only ; a 
 still larger number contain oxygen in addition to the two 
 last-named elements ; and a large number are composed of 
 carbon, hydrogen, oxygen, and nitrogen. A smaller 
 number contain sulphur in addition to these four elements, 
 and a still smaller number contain phosphorus. Organic 
 substances, therefore, unlike inorganic ones, are all com- 
 posed of some two, three, four, or five elements, and these 
 elements are the same for all the different organic bodies. 
 But although the formation of organic substances is re- 
 stricted to some three, four, or five of the elementary 
 bodies, their atomic constitution is far more complex than 
 that of mineral substances, and this is one of the most 
 marked distinctions between organic and inorganic bodies. 
 For example, "a particle of common salt, or of cinnabar, 
 presents a group of not more than two atoms, whilst an 
 atom of sugar contains thirty-six elementary atoms, and 
 the smallest particle of olive oil consists of several hun- 
 dred simple atoms. 
 
 745. " It is upon the greater complexity of composition 
 of organic bodies, together with the lesser force with which, 
 consequently, their constituent atoms attract each other, 
 that their easier decomposability depends : heat, for exam- 
 ple, disturbs their composition with much greater facility 
 than it does that of inorganic bodies. The atoms of the 
 former, once put in motion, or by the action of heat being 
 separated to a greater distance from each other, arrange 
 themselves into less complex atoms, in which the force of 
 attraction acts in fewer directions and in which it is conse- 
 quently able to oppose a proportionably stronger resistance 
 to the further action of causes of disturbance — decompo- 
 sition." — Liebig. 
 
 23* 
 
270 ELEMENTARY ANALYSIS. 
 
 746. Organic compounds may be analyzed either with a 
 view simply to resolve them into their proximate con- 
 stituents, as, for instance, resolving wheat flour into its 
 proximate constituents, starch, sugar, gluten, ligneous fibre, 
 and oily matter; this kind of analysis is called the proxi- 
 mate analysis of organic substances ; or the analysis may 
 have for its object the mere testing the organic compound 
 for some one or two elements, as nitrogen and sulphur ; 
 this is called, elementary or ultimate analysis. 
 
 747. We will first describe the method of testing organic 
 substances for nitrogen, sulphur, phosphorus, and inorganic 
 substances,* and afterwards describe the proximate analysis 
 of organic substances. 
 
 ELEMENTARY ANALYSIS. 
 
 748. Test for an organic compound. — As all organic sub- 
 stances contain carbon, and as very few of them contain 
 oxygen in sufficient quantity to combine with the whole of 
 their carbon and hydrogen, it follows that if they are 
 heated in a closed vessel, as a small glass tube, so as to 
 exclude the air, a black or carbonized residue will remain. 
 No inorganic compound leaves a residue of carbon when 
 heated under similar circumstances. Volatile bodies re- 
 quire to be mixed with CuO or PbCrO,, and burned in a 
 glass tube for the detection of their carbon, which is con- 
 verted into C0 2 , and if passed into a solution of BaH„O s , 
 causes a white precipitate of BaCO s , the H in the organic 
 substance becomes converted into H 2 0, which may be col- 
 lected in drops in a cooled receiver, or passed through a 
 tube containing CuSO„ which has been dried at 205° C, 
 water changes the color of the dry cupric salt from white 
 to blue. 
 
 749. Tests for Nitrogen — Substances containing a toler- 
 ably large quantity of N, emit in burning the familiar smell 
 of singed hair or feathers ; if this smell is distinctly per- 
 ceptible, no further test is required to confirm the presence 
 of this element. When there is no distinct smell of burnt 
 feathers, one of the two following tests may be employed : — 
 
 1st. The substance to be examined, which must be in the 
 
 * Animal and vegetable substances are frequently composed of inor- 
 ganic as well as organio oompouuds, and it is as necessary to determino 
 the nature of the inorganio as of the orgauio matter. 
 
ANALYSIS OF ORGANIC SUBSTANCES. 271 
 
 solid state, is mixed with solid KHO or with soda-lime,* 
 the mixture is introduced into a dry test-tube, and then 
 ignited ; the C is converted into C0 2 'by the in the alka- 
 line hydrate, while all or the greater part of the H combines 
 with N when present, and forms NH„ which is evolved, and 
 may be detected in the usual way (Table I. A 2, page 34). 
 
 2d. "Lassaigne has proposed another method which is 
 based upon the property of potassium to form KCN when 
 ignited with a nitrogenous organic substance. The fol- 
 lowing is the best method of performing the experiment: 
 Heat the substance under examination, in a test-tube, with 
 a small lump of K, and after its complete combustion, 
 treat the residue with a little water (cautiously) ; filter the 
 solution, add two drops of solution- of FeS0 4 containing 
 some ferric salt, digest the mixture a short time, and add 
 HC1 in excess. The formation of a blue or bluish-green 
 precipitate or coloration proves the presence of nitrogen 
 (499). 
 
 "Both methods, 1st and 2d, are delicate; the 1st is the 
 one most generally employed ; it fully answers the purpose 
 in nearly all cases. 
 
 3d. " If, however, the nitrogen exists in the organic com- 
 pound in an oxidized state, it cannot be detected by either 
 of the methods just given, but it may readily be detected 
 •by heating the substance in a tube, when the evolution of 
 red acid fumes, imparting a blue tint to iodide of starch 
 paper, will incontestably prove it." 
 
 750. Tests for sulphur. — If the substance is in the solid 
 state, it may be mixed with about twelve times its weight of 
 pure solid KHO, and about stx times its weight of pure 
 KN0 3 ; or it may be intimately mixed with some pure 
 KN0 3 and Na 2 CO a ; the mixture is then heated to fusion in 
 a crucible. The fused mass is allowed to cool, then dis- 
 solved in water, the solution acidified with HC1 and tested 
 subsequently for H 2 S0 4 with BaCl 2 . 
 
 751. Fluids are treated with fuming HN0 3 , or with a 
 mixture of HC1 and KC10 3 , at first in the cold, finally with 
 heat ; the solution is then tested for H 2 S0 4 with BaCl a or 
 Ba(N0 3 ) a . 
 
 752. As the two methods just described serve simply to 
 indicate the presence of sulphur in a general way, but afford 
 no information regarding the state or form in which that 
 
 * Soda-lime is a mixture of CaO with NaHO. The lime ia simply em- 
 ployed to prevent the soda fusiDg. 
 
272 ANALYSIS OF ORGANIC SUBSTANCES. 
 
 element may be present, we give another method (753), 
 which serves to detect only the sulphur in the non-oxidized 
 state in organic compounds. 
 
 "753. Boil the substance with a strong solution of KHO, 
 and evaporate nearly to dryness. Dissolve the residue in 
 a little water, pour the solution into a flask,* and slowly 
 add dilute H 2 S0 4 through the funnel-tube, if sulphur is 
 present the lead test-paper will turn brown. 
 
 154. Tests for phosphorus. — The methods described in 
 pars. 750 and 751, will likewise serve for P. The solutions 
 obtained are tested for phosphoric acid either according to 
 par. 424, 427, or 428. If the method described in par. 751 
 has been employed, the greater part of the HN0 3 must be 
 removed before employing the test. The P may be detected 
 by slightly carbonizing the substance, then reducing it to 
 powder, and conducting the operation as at par. 431. 
 
 755. Test for inorganic substances "A portion of the 
 
 substance under examination is heated on platinum foil, to 
 see whether or not a residue remains. When acting upon 
 difficultly combustible substances, the process may be accel- 
 erated by heating the spot which the substance under ex- 
 amination occupies on the platinum foil, to the most intense 
 redness, directing the flame of the blowpipe upon the cor- 
 responding point of the lower surface of the foil." The 
 methods for examining the residue are described in pars. 
 760 to 771. 
 
 PROXIMATE ANALYSIS OP ORGANIC SUBSTANCES. 
 
 756. Organic substance^ like inorganic ones, are either 
 acids, bases, salts, or indifferent bodies, and the resolution 
 of organic compounds into their proximate constituents, is 
 effected by methods perfectly similar to those used in the 
 analysis of inorganic compounds; that is, the operator 
 endeavors to separate (by solvents, application of heat, etc. 
 etc.) the individual constituents from one another, either in 
 the direct way, or after having previously converted them 
 into appropriate forms. 
 
 757. Of the solvents employed in organic analysis ether 
 is particularly valuable as a solvent for fatty substances, 
 and for caoutchouc and camphor ; alcohol, for the solution 
 
 * The flask must be provided with a fur.nel-tube whioh is fitted into a 
 cork, on the under surface of the cork is nttaehed a slip of paper which 
 lias been thoroughly moistened with a solution of lead acetate, and then 
 touched with a few drops of a solution of (N H 4 ),CO,. 
 
ANALYSIS OP ORGANIC SUBSTANCES. 273 
 
 of many crystallizable organic principles, such as the vege- 
 table alkalies; whilst water dissolves sugar, gum, starch, 
 and other bodies, which are nearly insoluble in alcohol and 
 ether. In some cases benzole, in others chloroform, is a 
 valuable solvent, and may be substituted for ether, which 
 they most resemble in their solvent action. In particular 
 cases dilute acids, and in others dilute alkalies may be 
 employed, but they must be used with caution, as they 
 are liable to act not merely as solvents, but also to produce 
 important chemical changes upon the compounds submitted 
 to them. No general rule can be laid down for the extrac- 
 tion of the different proximate principles, each class of sub- 
 stances requiring special modifications, which experience 
 alone can indicate. 
 
 "158. In all cases of proximate analysis, the employment 
 of the microscope will be found invaluable as a means of 
 watching the progress of the separation of the various prin- 
 ciples, and of ascertaining whether the substances which 
 the chemist has isolated are mixed with other bodies which 
 may resemble them in chemical habitudes. When a sub- 
 stance or deposit assumes the crystalline state, such an ex- 
 amination, by revealing the similarity or difference in form 
 of its component particles, is often more valuable for ascer- 
 taining the purhVy of a substance than ordinary chemical 
 reagents. — Miller. 
 
 759. We shall now give the method for the examination 
 of the ash, whether derived from animal or vegetable sub- 
 stances, and we shall then give under Animal and Vegetable 
 Chemistry the properties and reactions of the chief organic 
 compounds of animal and vegetable origin, and along with 
 this the proximate analysis of mixed animal substances and 
 the analysis of urine. 
 
 EXAMINATION OF THE INORGANIC CONSTITUENTS OF ANIMAL 
 AND VEGETABLE SUBSTANCES. 
 
 760. Preparation of the ash. — The incineration of the 
 substance* is best effected by placing it in a platinum dish, 
 or other shallow vessel, and introducing the vessel into a 
 muffle, which should then be gradually heated; but not car- 
 ried beyond a very faint redness.f For merely qualitative 
 
 * Before incinerating the substance care must be taken to free it from 
 all adhering impurities, as these are frequently attached to plants. 
 
 f Substances to which this mode of incineration is unsuited, are 
 charred first at a gentle red heat in a large covered platinum or Hessian 
 crucible, and the charred mass is subsequently incinerated in the muffle 
 
274 ANALYSIS OP THE ASH. 
 
 analysis it will generally be found sufficient to char the sub- 
 stance in a porcelain or platinum dish, with the aid of a 
 wide glass tube or lamp-glass to increase the draught. 
 " The heat must always be moderate to guard against the 
 volatilization of certain constituents, more especially of 
 metallic chlorides. It is not always necessary to continue 
 the combustion until all the carbon is consumed. With 
 ashes containing a large proportion of fusible salts, as e. g. 
 the ash of beetroot molasses, it is even advisable at first, 
 simply to char the mass in a crucible at the lowest possible 
 temperature, then to treat with water until the principal 
 portion of the soluble salts is extracted, afterwards dry the 
 residue, and finally, incinerate it in the muffle" (Fresenius). 
 Alkaline sulphates are frequently converted by the reducing 
 action of carbon, into sulphides and hyposulphites. The 
 ashes of animal substances often contain cyanates, which 
 are best destroj'ed by moistening the ashes with water, and 
 then gradually heating to redness; one moistening is usually 
 sufficient to convert them completely into carbonates. 
 
 761. Analysis of the ash. — In the qualitative examina- 
 tion it is usual to examine the aqueous solution, the HC1 
 solution, and the portion insoluble in acids separately — 
 supposing the ash is not entirely soluble in water— as we 
 thereby obtain a better acquaintance with its general cha- 
 racter, and in the state or condition in which the constitu- 
 ents are present. In this examination we shall confine 
 ourselves to the natural constituents of the ashes of plants 
 and animals ; if accidental constituents require to be sought 
 for, a complete qualitative inorganic analysis, according 
 to the methods given in Part I. of this work, must be 
 undertaken. 
 
 762. The following are the natural constituents: — 
 
 Bases. Acids. 
 
 Iron oxide. Silica. 
 
 Manganese oxide. Phosphoric acid. 
 
 Lime. Sulphuric acid. 
 
 Magnesia. Carbonic acid. 
 
 Soda. Chlorine. 
 
 Potash. Fluorine. 
 
 Lithia.* Iodine."!" 
 
 * Lithia has lately been foaml in the ash of many plants; Rubidium 
 has also been found, but this can only be discovered by spectrum 
 analysis. 
 
 f lodino and bromine need only bo looked for in marine plants. 
 
ANALYSIS OP THE ASH. 275 
 
 763. Boil the ash with water, filter, and examine the fil- 
 trate according to next par., and the portion insoluble in 
 water after it has been well washed according to par. 767. 
 
 764. Examination of the aqueous solution. — Add to about 
 one-half the aqueous solution HC1, if effervescence ensues, 
 it may be due to CO„, H 2 S, or S0 2 , arising from the decom- 
 position of hyposulphites ; examine the evolved gas for 
 carbonic acid according to par. 441 ; the other two gaseous 
 acids need not be attended to, as they, if present, are only 
 due to the reduction of the alkaline svdphates (406). 
 
 765. Evaporate the solution, which has been acidulated 
 with HC1, to dryness, treat the residue with HC1 and water ; 
 if a portion remains undissolved it is due to "silicic acid, in 
 this case filter and add to the filtrate, or to the solution if 
 there is no silicic acid, NH 4 H0 slightly in excess, and then 
 acetic acid in excess, and then a drop of Fe 2 Cl 6 (427); if a 
 precipitate is produced, phosphoric acid is present, in that 
 case add more Fe. 2 Cl,, until the solution is of a slightly 
 reddish color. Boil the solution whether phosphoric acid 
 is present or not, in order to get rid of the iron which has 
 been added ; when all the iron has been precipitated, which 
 is known by the complete decoloration of the liquid, filter, 
 and to the filtrate add NH 4 HO and (NH 4 ) 2 C 2 4 , if, after 
 allowing the liquid to stand for some three or four hours, a 
 precipitate is formed, Ca is present ;* filter and divide the 
 filtrate into two parts, to one part add NH^HO and ]SFa 2 HP0 4 , 
 if a precipitate is formed after some time, Mg is present. 
 Evaporate the other portion of the filtrate to dryness, and 
 ignite to get rid of and burn off all carbonaceous matter ; 
 examine the residue for Na (51), for K (46), and for lithia 
 (61). 
 
 766. Add to a portion of the aqueous solution, which 
 has not been acidified, AgN0 3 as long as a precipitate con- 
 tinues to form ; warm gently, and then cautiously add 
 NH,HO ; if a black residue is left, this consists of Ag 2 S, 
 proceeding from a sulphide or a hyposulphite. Mix the 
 amnionic solution — after previous filtration if necessary — • 
 cautiously with pure HN0 3 in slight excess, to effect the 
 solution of the precipitate of silver phosphate formed, thus 
 leaving only AgCl, Agl, AgBr undissolved. Test sepa- 
 
 * If C0 2 is present, Ca and Mg must of course be absent, when this 
 is the case, divide the filtrate from the silicic acid precipitate into two 
 portions, test one for phosphoric acid by adding NH 4 C1, NH 4 HO, MgS0 4 
 (424), and test in the other portion for Na, K, and Li, in the manner 
 directed in pars. 51, 46, 61. 
 
216 ANALYSIS OF THE ASH. 
 
 rately for I according to 540, for Br 541, for CI 539. Neu- 
 tralize the filtrate from the portion of the Ag precipitate 
 insoluble in HN0 3 exactly with NH 4 HO ; if on the neutral- 
 ization, a bright yellow precipitate is produced, it is ortho- 
 phosphoric acid that is present, but if the precipitate is 
 while, the acid is either the pyrophosphate or the meta- 
 phosphate.* 
 
 76T. Warm then the portion of the ash insoluble in water, 
 with HC1, if effervescence ensues it indicates C0 2 combined 
 with Ca or Mg ; if CI is evolved it denotes one of the 
 higher manganese oxides. 
 
 768. Examination of the hydrochloric solution. — Add 
 NH 4 HO very slightly in excess, then add acetic acid in 
 excess ; if a white precipitate remains undissolved by the 
 
 * If a phosphate contains three atoms of fixed base, the fluid, after 
 the complete precipitation of the phosphoric acid by means of AgN0 3 , 
 will be neutral, but if it contained only two atoms or one atom of fixed 
 base, the fluid after the precipitation of the acid with the silver salt, 
 will be acid. Further, argentic ortho-phosphate (Ag 3 P0 3 ) is yellow, whilst 
 argentic pyro-phosphate (Ag 4 P 2 7 ), and meta-phosphate (AgPO s ), are 
 white. Again, an ortho-phosphate containing two atoms of fixed base 
 is converted by ignition into a pyrophosphate ; and an ortho-phosphate 
 containing one atom of fixed base is converted by ignition into a meta- 
 phosphate. We will now see how Liebig employed these facts in his 
 investigation into the constitution of the ash of the juice of the flesh 
 from different animals : — 
 
 Liebig found th it the ash of the juice of the flesh in the case of the 
 ox, horse, fox, and roe-deer, gave with water a strongly alkaline solu- 
 tion, and that it was precipitated, first white, then yellow, by neutral 
 AgN0 3 ; and the mixture, after complete precipitation, was perfectly 
 neutral. This proves that the ash contains an alkaline pyro-phosphate 
 and an alkaline ortho-pbosphate. When this ash was mixed with HNO,, 
 dried up, and again ignited (by which means the CI of the alkaline 
 chlorides was expelled), and the metals added to the phosphates in the 
 form of oxides, the proportion between the while and the yellow precipi- 
 tate with AgN0 3 was altered, the quantity of the yellow precipitate 
 being increased ; but the two colors of the precipitate were constantly 
 observed. 
 
 The ash of the juice of the flesh of fowl, Liebig discovered, gave a 
 different result. The aqueous solution gave with AgN0 3 a. precipitate 
 of pure white; the ash, therefore, contains an alkaline pyro-phosphate, 
 and when it was acted on by HN0 3 and again ignited, the soluble por- 
 tion still precipitated AgNO s only white, although an additional quantity 
 of alkali was thus added to the phosphate originally present. From 
 this it follows, that the juice of the flesh of fowl must contain a 
 certain, though small quantity of an alkaline meta-phosphate, since, 
 otherwise, after the action of HN0 9 on the ash, a certain quantity of an 
 alkaline ortho-phosphate must have been produced, and thereby a yel- 
 low precipitate must have been formed, to a corresponding extent, with 
 A K N0 3 . 
 
ANIMAL CHEMISTRY. 211 
 
 acetic acid it is due to the presence of ferric phosphate ; 
 filter a small portion of the liquid, and test for Fe"' with 
 K 4 FeCy B , if it is present in the filtrate it shows that all the 
 iron does not exist as phosphate ; if there is no iron present 
 in the filtrate add some Fe.,Cl 8 to the unfiltered portion 
 until the fluid looks reddish ; in either case, that is, whether 
 the iron is in excess or it is added in excess, boil the unfil- 
 tered portion until it is all removed ; when this is accom- 
 plished filter hot, and add to the filtrate NH 4 HO and 
 (XHJ 2 S, and allow it to stand in a corked flask for some 
 time ; if a precipitate should form, test it for Mn ; filter 
 and examine the filtrate for Ca and Mg in the usual way. 
 769. Examination of the residue insoluble in hydrochloric 
 acid. — The residue insoluble in HC1 contains — 
 
 1. The silicic acid which has separated on treating with 
 HC1. 
 
 2. Those ingredients of the ash which are insoluble in 
 HC1. These are, in most cases, ashes, sand, claj', carbon ; 
 substances, therefore, which are present in consequence of 
 defective cleaning or imperfect combustion of the plants, 
 or matter derived from the crucible. Only the ashes of 
 the stalk of cereals and others abounding in silicic acid 
 are not completely decomposed by HC1. 
 
 110. It is rarely necessary in an examination which is 
 not going to be extended beyond a qualitative analysis to 
 examine this residue further ; but in cases where it is desir- 
 able, the analysis for all the bases, with the exception of 
 the alkalies, must be conducted according to par. 725, and 
 for the alkalies according to par. "729. 
 
 ANIMAL CHEMISTRY. 
 
 111. We shall first give in groups, as far as it is possible, 
 the chief organic compounds met with in the animal organ- 
 ism, with their properties and reactions; and afterwards a 
 method for the proximate analysis of mixed animal sub- 
 stances (940), and lastly a method for the analysis of urine 
 (964). Before commencing the proximate analysis the stu- 
 dent is recommended to go through the chief groups, per- 
 forming all the experiments given. 
 
 24 
 
278 THE GENERAL PROPERTIES 
 
 THE ALBUMINOID OR PROTEIC GROUP. 
 
 ALBUMEN, FIBRIN, CASEIN, GLOBULIN, VITELLIN. 
 
 *7 72. Properties of the group.* — The members composing 
 this group are met with in the vegetable as well as the ani- 
 mal kingdom ; they are uncrystallizable, and in their pure 
 state they are tasteless and inodorous. They exist in the 
 living organism both in the soluble and insoluble state; 
 thej' are present in the soluble form in the fluids, and in the 
 insoluble form in the solid parts of plants and animals. 
 When freshly precipitated from their solutions, and whilst 
 still moist, they are usually whitish in color, and appear as 
 a flocculent precipitate or in small clots ; when dried and 
 unpowdered they are tough and gelatinous. 
 
 773. These substances when dried, and if not exposed to 
 moist air, will keep for any length of time unchanged. But 
 if moist, or exposed to moisture, they speedily decompose 
 and putrefy, and this is one of their most striking charac- 
 ters ; they are ferments in their decomposing or putrefy- 
 ing state ; yeast, wine-lees, diastase, synaptase, pepsin, for 
 instance, are albuminoids in a peculiar state of decompo- 
 sition. 
 
 774. If these bodies are heated in close vessels (subjected 
 to dry distillation), they first swell up and fuse, then 
 blacken, and emit a large quantity of fetid empyreumatic 
 products, among which NH 3 and H,S are always present ; 
 and they leave in the retort a porous, brilliant, carbonaceous 
 mass. When burned they leave a notable amount of ash ; 
 this varies in quantity in different cases, but it always con- 
 tains phosphate of lime. 
 
 775. They all yield the same products when treated with 
 oxidizing agents, such as MnO„, or K^C^O. and H..SO, ; 
 the volatile products are the only class which have been 
 fully examined ; the following are the volatile substances 
 which have been identified: — 
 
 Formic acid. Propionic aldehyd. 
 
 Acetic acid. Butyric aldehyd. 
 
 Propionic acid. Benzoic acid. 
 
 Butyric acid. Hydride of benzoyl. 
 
 Valeric acid. Hydrocyanic acid. 
 
 Caproic acid. Valeronitrile. 
 Acetic aldehyd. 
 
 * Globulin is not included in the remarks on the properties of the 
 group ; these observations only striotly apply to albumen, fibrin, and 
 oosein. 
 
OP THE ALBUMINOID GROUP. 279 
 
 776. The albuminoids are insoluble in alcohol and ether, 
 and are even precipitated from their aqueous solutions on 
 the addition of alcohol to the liquid ; the precipitate is 
 generally insoluble in water after its precipitation by 
 alcohol. 
 
 777. " These substances, either in their soluble or insolu- 
 ble state, are readily dissolved by the aid of a gentle heat 
 in a solution of KHO or NaHO, the addition of an acid to 
 their alkaline solution so obtained causes the separation of 
 a grayish flocculent precipitate, termed by Mulder protein, 
 ■while a slight odor of H 2 S is emitted, and a small quantity 
 of phosphoric acid is also found in the solution. This pre- 
 cipitation is best effected by means of acetic acid, since the 
 mineral acids are obstinately retained by the ilocculi." — 
 Miller. 
 
 778. In concentrated H 2 S0 4 these substances dissolve 
 •with a brownish-red color. 
 
 779. Concentrated HN0 3 produces in solutions of these 
 substances a precipitate of a bright orange color, which 
 gradually dissolves in the acid with effervescence ; HN0 3 
 added to the substances in the insoluble state colors them 
 yellow and finally dissolves them. Mulder considers the 
 yellow color to be due to the formation of a distinct com- 
 pound which he has called xanthoproteic acidi 
 
 780. When to a solution of these substances concentrated 
 HC1 is added, and the solution is gently warmed, a white 
 precipitate is first produced, which gradually dissolves, 
 forming, if in contact with atmospheric air, a blue or violet- 
 colored liquid. The reactions with HN0 3 and HC1 are 
 very characteristic of the albuminoids. 
 
 781. Most acids produce a precipitate in solutions of 
 these substances, but when they are added in excess redis- 
 solve the precipitate ; when these acid solutions are diluted 
 with a moderate quantity of water, a precipitate is formed 
 which disappears on the further addition of water. 
 
 782. Metaphosphoric acid produces a precipitate in so- 
 lutions of these substances, but an excess of the acid does 
 not redissolve the precipitate. 
 
 783. Tannic acid produces a precipitate in solutions of 
 these substances, and an excess of the acid does not redis- 
 solve the precipitate. 
 
 784. The acid solutions, but not the aqueous solutions, 
 of the albuminoids give a precipitate with potassic ferro- 
 cyanide and ferricyanide ; the next group of substances 
 gives no precipitate with these reagents. 
 
280 
 
 THE GENERAL PROPERTIES 
 
 785. If a solution of Hg, prepared by dissolving two 
 parts of it in four parts of HN0 3 , of sp. gr. 1.40, be added 
 to a solution of the albuminoids, or, if in the solid state, 
 they are moistened with the Hg solutions, and the moistened 
 solid or the fluid is then heated to a temperature from 60° 
 to 100° C, an intense red color is produced, which is not 
 destroyed by boiling water, nor by exposure to the air ; the 
 color is so intense that it may be perceived on adding the 
 mercurial solution to a liquid containing not more than 1 
 part of albumen in 100,000 parts of water. The Hg solu- 
 tion gives a similar coloration with the members of the 
 next group. 
 
 786. The aqueous solution of these bodies is precipitated 
 by copper, lead, and mercury salts, the precipitate generally 
 consists of the employed salt as well as the albuminoid. 
 
 787. If a solution of these substances be mixed with a 
 solution of CuS0 4 , and then . a large excess of KHO be 
 added, the greenish precipitate first formed is redissolved, 
 and the liquid acquires a purple tint of great intensity and 
 magnificence. The same reaction takes place with the next 
 group of substances, and probably with any of the more 
 complex nitrogenous substances. 
 
 788. In the living organism, fibrin, casein, and albumen 
 are converted into one another ; for example, the casein in 
 milk, when this substance is used as food, must be con- 
 verted in the animal economy into albumen and fibrin, and 
 the two latter albuminoids must be converted into casein 
 in the formation of milk. As the albuminoids have the 
 same or nearly the same constitution, as shown by the 
 following analyses, their conversion into one another can 
 be easily accounted for. In the subjoined analyses, the 
 ash has been deducted previous to calculating the compo- 
 sition in 100 parts: — 
 
 Carbon 
 
 Hydrogen 
 
 Oxygon 
 
 Nitrogen 
 
 Sulphur 
 
 68.3 
 7.2 
 
 22. 
 
 15 7 
 1.8 
 
 100.0 
 
 Fibrin. 
 
 53.0 
 
 6.9 
 
 23.5 
 
 15.4 
 
 1.2 
 
 100.0 
 
 Casein. 
 
 53.83 
 
 7.15 
 
 22.52 
 
 15.65 
 
 0.85 
 
 100.00 
 
 789. The determination of the rational formula of bodies 
 like the albuminoids is beset with difficulties ; the difficulties 
 
OF THE ALBUMINOID GROUP. 281 
 
 are so great with regard to these substances that they have 
 not yet been overcome, and consequently their rational for- 
 mula has not been determined. Different views have, how- 
 ever, been put forward to explain the relation between them, 
 for, from their great similarity in composition and proper- 
 ties, there can be no doubt but that they are very closely 
 related. The first view we shall notice is that of Mulder, 
 as, although now abandoned, it is constantly referred to in 
 works on the science ; this view when first promulgated by 
 the author was almost universally accepted by chemists, 
 but they have long regarded it as erroneous. 
 
 790. Mulder considered that the flocculent precipitate 
 obtained by adding an acid to an alkaline solution of the 
 albuminoids was free from sulphur and phosphorus, and 
 that this nitrogenized precipitate has identically the same 
 composition, whether obtained from fibrin, albumen, or 
 casein. This substance, which he called protein, he regarded 
 as the fundamental principle of each of the albuminoids, 
 and that albumen, fibrin, and casein were produced by the 
 combination of different quantities of sulphur and phos- 
 phorus with protein; admitting this view of the construc- 
 tion of these bodies, it was easy to account for their con- 
 version into one another, for the elimination or combination 
 of small quantities of sulphur and phosphorus was all that 
 was required to effect the change. 
 
 791. The so-called protein substance, Liebig has shown, 
 is never obtained free from sulphur, that it always contains 
 a small but variable quantity of this element ; he considers 
 that the precipitate is not a new and distinct substance, but 
 that it is the original body slightly modified by the action 
 of the potash. 
 
 702. " Gerhardt was of opinion that all the albuminoids 
 are identical, not only in composition, but in chemical con- 
 stitution, and that they differ from one another only in 
 molecular arrangement, and by the nature of the mineral 
 substances with which they are associated ; in fact, that 
 they contain a common proximate element, which, like 
 many other organic compounds, is capable of existing in a 
 soluble and an insoluble modification. Designating this 
 common element by the name albumin, he supposed that 
 white of egg and serum consist of acid albuminate of so- 
 dium, which is separated by heat into free albumin and 
 neutral albuminate of sodium, the latter remaining dis- 
 solved ; that casein, which is soluble and non-coagulated 
 by heat, consists of neutral albuminate of potassium, from 
 
 24* 
 
282 THE PROPERTIES OP ALBUMEN. 
 
 which the organic compound may be precipitated by neu- 
 tralizing the alkali with an acid ; and that fibrin is albumin 
 in the insoluble state, more or less mixed with earthy phos- 
 phates. This view is in accordance with the fact that fibrin 
 and casein may be dissolved in neutral potash salts (better 
 with addition of a little caustic alkali), forming a liquid 
 which coagulates by heat, and deflects the plane of polari- 
 zation of a luminous ray to the left, like albumin ; and that 
 fibrin and albumin, dissolved in a certain quantity of caustic 
 alkali, exhibit the characters of soluble casein. Neverthe- 
 less, it is possible to obtain the albuminoids in some cases 
 wholly, in others very nearly, free from mineral matters, 
 and nevertheless exhibiting their distinguishing character- 
 istics. 
 
 193. " Strecker supposes the albuminoids to be composed 
 of a great number of radicles (a supposition in accordance 
 with the variety of their products of decomposition), that 
 the greater number of these radicals are the same in all, 
 hence their great similarity ; but that each contains one or 
 more such radicles peculiar to itself. Thus, when casein is 
 converted in the animal body into albumen and fibrin, it 
 may take the radicles required for that transformation from 
 the other constituents of the milk, viz. the fat and the 
 sugar." — Watts' "Dictionary of Chemistry?' 
 
 ALBUMEN. 
 
 794. Properties of soluble Albumen An aqueous solu- 
 tion of albumen is a tasteless, odorless, and colorless, but 
 somewhat glairy liquid. It exerts a left-handed rotatory 
 action upon a ray of polarized light. It is adhesive, and 
 when spread on paper it forms when dried a varnished sur- 
 face. Soluble albumen in the solid state is translucent and 
 of a pale yellow color ; it is tasteless and odorless ; it swells 
 in water, assuming a gelatinous appearance ; it does not 
 dissolve freely in pure water, but very readily in water 
 containing any alkaline salt. 
 
 795. If its aqueous solutions are evaporated to dryness 
 at a temperature not exceeding 49° C, the solid albumen 
 thus obtained will dissolve, though slowly, in water ; its 
 solution is greatly promoted by the addition of NaCl or 
 any salt of the alkalies ; a varying quantity of the albumen 
 always becomes converted by the evaporation into the in- 
 soluble state. 
 
THE PROPERTIES OP ALBUMEN. 283 
 
 796. If an aqueous solution of albumen is heated to about 
 66° C. it becomes opalescent, and at 77° C. it becomes en- 
 tirely converted into the insoluble form. This conversion 
 of the soluble into the insoluble form by heat, is the most 
 characteristic property of albumen. The reason of the con- 
 version is not known. Dumas thinks that it is probably 
 a simple isomeric modification analogous to the conversion 
 of cyanic into cyanuric acid. 
 
 797. Action of alcohol, ether, etc., on soluble Albumen. 
 — Strong alcohol precipitates albumen from its solutions, 
 and after its precipitation by this liquid it will not i - edis- 
 solve in water. If the alcohol is rendered slightly alka- 
 line by KHO it causes no precipitate in solutions of albu- 
 men. Weak alcohol also precipitates albumen from its solu- 
 tion, but the precipitate redissolves completely in water. 
 
 798. Ether, if free from alcohol, only gelatinizes the albu- 
 men, it does not coagulate it. 
 
 799. Kreasote and aniline precipitate and coagulate it 
 im mediately. 
 
 800. Rennet does not precipitate it from its solutions. 
 The volatile and fixed oils have no action upon it. 
 
 801. Action of acids on soluble Albumen. — The action of 
 concentrated H 2 S0 4 , HC1, and HN0 3 on albumen and the 
 other albuminoids has already been noticed (778, 779, 780). 
 
 802. Dilute H,S0 4 produces no precipitate in solutions 
 of albumen until the liquid is boiled. 
 
 803. Dilute HC1 precipitates it at first, but afterwards 
 redissolves it ; this solution becomes milky on the addition 
 of a little water ; but if more water is added it becomes 
 perfectly clear again. 
 
 804. Dilute HNO s precipitates it readily and completely, 
 and does not redissolve it ; the precipitate is soluble in a 
 large quantity of water. Dilute HN0 3 is frequently em- 
 ployed as a test for the presence of albumen. 
 
 805. Metaphosphoric acid precipitates it immediately and 
 completely. The ortho- and pyrophosphoric acids do not 
 precipitate it. 
 
 806. The organic acids, tannic acid excepted (783), 
 cause no precipitate in moderately concentrated solutions 
 of albumen ; its solutions, in the presence of organic acids 
 do not coagulate by heat, but a pellicle gradually forms 
 over the surface during evaporation. 
 
 807. Serum or white of egg mixed with a certain quan- 
 tity of NaCl, or other salt of an alkali-metal, forms a liquid 
 precipitable by phosphoric, acetic, tartaric, oxalic, and 
 
284 THE PROPERTIES OP ALBUMEN. 
 
 lactic acids, etc.; conversely, a solution of albumen (or 
 other albuminoidal substance) in acetic acid is precipitated 
 by the salts of the alkali-metals. The precipitation is greatly 
 facilitated by heat, and likewise takes place with greater 
 facility as the proportion of salt added is greater. The 
 precipitate dissolves in pure water, with greater facility in 
 proportion as less heat has been applied in producing it; 
 the solution is not coagulated by heat'. It is soluble also 
 in acetic acid, phosphoric acid, and even in alcohol, pro- 
 vided it has not been altered by desiccation, or by contact 
 with the air. The aqueous solution is precipitated by cer- 
 tain salts, potassic ferrocyanide for example. 
 
 808. When a small quantity of acetic acid is added to 
 white of egg or serum, so as just to saturate the alkali, and 
 the liquid is then largely diluted with water ; flocks of albu- 
 men are deposited after a while. If the supernatant liquid 
 be then decanted, and the precipitate treated with a small 
 quantity of solution of KN0 3 or NaCl, it immediately dis- 
 solves, and the solution is coagulated on boiling. 
 
 809. Dried soluble albumen suspended in acetic, tartaric, 
 or citric acid, swells up and is converted into coagulated 
 albumen, which may -be completely freed from acid by 
 washing. 
 
 810. CI and Br precipitate albumen from its solutions. 
 
 811. Action of salts on soluble Albumen " The greater 
 
 number of the metallic salts, as iron, copper, lead, mercury, 
 silver, antimony, aluminum, precipitate albumen; the pre- 
 cipitate consisting either of a combination of a basic salt 
 with albumen, or a mixture of two compounds, one of 
 which consists of the acid of the salt and albumen, and 
 the other of the base of the salt and albumen. The albumen 
 generally passes into the insoluble state in these combina- 
 tions ; the precipitate is generally soluble in an excess of 
 serum or white of egg, and in some cases in the salt which 
 produces it. Albumen, owing to its forming precipitates 
 with them, is a valuable antidote in cases of poisoning by 
 metallic salts. 
 
 812. " HgCl 2 is a delicate test of the presence of albumen, 
 a liquid containing only a two-thousandth part of solid al- 
 bumen is precipitated by it. The white precipitate formed 
 is an insoluble compound of the salt with the organic 
 substance ; albumen, it is well known, is the antidote which 
 is employed in this form of poisoning." 
 
 813. The action of the alkalies and alkaline carbonates on 
 soluble Albumen — The presence of an alkali or an alkaline 
 
THE PROPERTIES OF ALBUMEN. 285 
 
 carbonate, in a liquid containing albumen, greatly modifies 
 the reactions of that substance ; if the alkali is present in 
 considerable quantities the solution does not coagulate by- 
 heat; but if it be evaporated, a pellicle forms over the 
 surface similar in appearance to that produced upon a 
 solution of casein by heat. Also, if to an alkaline solution 
 of albumen, acetic, tartaric, or ortho-phosphoric acid, 
 acids which in neutral or slightly alkaline solutions of 
 albumen cause no precipitate, is added, a precipitate is 
 produced which readily, dissolves in an excess of the 
 acid. These characters resemble those of casein, and some 
 chemists have supposed that casein is simply an albumi- 
 nate of potash. 
 
 814. If alcohol be added to an alkaline solution of albu- 
 men, it causes, as we have already noticed, no precipitate. 
 
 815. If a concentrated solution of KHO be added to a 
 concentrated solution of albumen, albuminate of potash in 
 the form of a gelatinous mass is produced ; by washing 
 the precipitate with cold water the greater part of the 
 alkali can be removed, 5.4 per cent, of the alkali only 
 remaining. If the gelatinous mass be washed with alcohol 
 and then with water, it is insoluble in boiling alcohol and 
 boiling water ; but if it be washed with cold water, it is 
 soluble in boiling water and boiling alcohol. 
 
 816. Properties of insoluble Albumen. — Insoluble albu- 
 men when moist appeai - s as a white opaque elastic solid, it 
 turns blue litmus red. "When dried it is of a pale yellow 
 color, and becomes brittle and translucent like horn. If 
 the dried substance be immersed in water, it absorbs about 
 four or five times its weight of water and regains the 
 consistence of the undried substance. When coagulated 
 albumen is boiled in water for about sixty hours in 
 open vessels, it undergoes gradual decomposition, and a 
 soluble compound is obtained which according to Mulder is 
 teroxide of protein and ammonia. If heated to 149° C. 
 with a small quantity of water in a sealed tube the albumen 
 is redissolved, and furnishes a liquid which does not coagu- 
 late by heat, but which, when acidulated with acetic acid, 
 gives a precipitate with potassic ferroc3 7 anide. 
 
 81 1. On the varieties of Albumen. — "The properties of 
 albumen vary in some degree with the source from which 
 it is derived. The differences may in some cases be at- 
 tributed to the presence of different mineral substances, 
 but in others they are of such a nature as rather to point 
 to the existence of different modifications of albumen. 
 
286 THE PROPERTIES OP FIBRIN. 
 
 Thus Fre"my and Valenciennes have found that the albumen 
 of the eggs of certain tribes of birds exhibits peculiar 
 modifications. That from the eggs of different species of 
 gallinaceous birds always exhibits the characters above 
 described; but the eggs of swimming and wading birds 
 yield an albumen which, when diluted with three measures 
 of water, is not coagulated by heat, but is precipitated by 
 HN0 3 ; and the albumen from the eggs of predacious birds 
 and some kinds of perching and climbing birds is neither 
 coagulated by heat nor precipitated by nitric acid. The 
 composition was, however, found to be the same in all 
 cases. 
 
 81 8. " Blood-albumen exhibits the same reactions as that 
 from white of egg, Excepting that the latter when boiled 
 gives up part of its sulphur in the form of sulphuretted 
 hydrogen, which blood-albumen does not ; nevertheless 
 coagulated white of egg appears to contain more sulphur 
 than blood-albumen. 
 
 819. " Scherer found in a liquid obtained from a case of 
 ovarian dropsy a substance resembling albumin, but differ- 
 ing from it in not being completely precipitated by ebulli- 
 tion even after addition of acetic acid, and in dissolving in 
 water after being precipitated by alcohol ; this modification 
 he named Paralbumin. 
 
 820. " Metalbumin is the name given by the same chemist 
 to another supposed modification of albumin, likewise ob- 
 tained from a pathological fluid, which exhibited similar 
 peculiarities to the preceding, and was further distinguished 
 by giving no precipitate with HC1, or with potassic ferro- 
 cyanide after acidulation with acetic acid.'' — Watts' Dic- 
 tionary of Chemistry. 
 
 FIBRIN. 
 
 821. Fibrin exists only in solution in the living plant or 
 animal, for as soon as the solution is removed from the 
 living organism it immediately begins to coagulate ; this 
 character distinguishes it from other analogous substances. 
 The coagulation of the fibrin is prevented if the blood or 
 other liquid containing the fibrin, at the moment it leaves 
 the living organism, is mixed with solutions of certain 
 salts, such as potassic carbonate or nitrate, sodic acetate, 
 sulphate or chloride. 
 
 822. Properties of Fibrin Undried coagulated fibrin 
 
THE PROPERTIES OP FIBRIN. 287 
 
 appears in the form of long, white, elastic filaments, but 
 when dried it forms a horny yellowish or gray solid. Both 
 in the dried and undried state it is tasteless and insoluble 
 both in hot and cold water, in alcohol, ether, etc. When 
 long boiled, however, with water, it is, like albumen, gradu- 
 ally dissolved ; by the exposure to heat and moisture it 
 has evidently undergone decomposition, for the solution 
 contains traces of ammonia. If undried fibrin is covered 
 with water, it becomes in a few days viscid and acquires 
 the odor of old cheese. 
 
 823. Actio)! of acida on Fibrin. — The action of concen- 
 trated HC1, H. 2 S0 4 , and HN0 3 , on fibrin and the other albu- 
 minoids has already been noticed (118, 779, 780). 
 
 824. When fibrin is immersed for about twelve hours in 
 water slightly acidulated with HC1, it becomes gelatinous, 
 and when this jelly is triturated with water, it yields a 
 solution which coagulates by heat, is precipitated by po- 
 tassic ferrocyanide, and affords a precipitate on the addi- 
 tion of HC1, not soluble except in an excess of this acid. 
 According to Dumas and Cahours, water containing a mil- 
 lionth part of HC1 or HBr gelatinizes fibrin, and if a few 
 drops of gastric juice (pepsine) be then added, it is entirely 
 dissolved in a couple of hours at a temperature of 35° to 
 38° C. Rennet produces the same effect. 
 
 825. Metaphosphoric acid does not dissolve fibrin. Ortho- 
 phosphoric acid converts it into a gelatinous mass which is 
 soluble in water, the fibrin is not precipitated from this 
 solution on the further addition of the acid. 
 
 826. Concentrated acetic acid converts it into a gelatin- 
 ous mass which is soluble in pure water. H a S0 4 and HP0 3 
 precipitate it from this solution, the precipitate consisting 
 of a compound of fibrin and the precipitating acid. Potas- 
 sic ferrocyanide precipitates fibrin from its acetic solution. 
 Alkalies also precipitate it, but it is redissolved by an ex- 
 cess of the alkali. According to Dumas the fibrin of young 
 animals is more easily acted on by acetic acid than that of 
 old ones, so that there is in this respect a material differ- 
 ence between the fibrin of veal and of beef. 
 
 827. Action of the alkalies on Fibrin. — Weak solutions 
 of KHO and NaHO dissolve fibrin, NH t HO exerts the 
 same influence, but less rapidly ; acetic and phosphoric 
 acids and also the metallic salts precipitate fibrin, as they 
 do albumen, from its alkaline solutions. Indeed an alka- 
 line solution of fibrin resembles an alkaline solution of 
 albumen in most of its characters. 
 
288 THE PROPERTIES OF CASEIN. 
 
 CASEIN. 
 
 828. Properties of soluble Casein. — Although this sub- 
 stance is met with in a state of solution in milk, it is doubt- 
 ful whether it has a soluble form ; it is considered that its 
 soluble state in milk is due to a small quantity of free 
 alkali ; casein in solution does not coagulate by heat, the 
 solution merely becomes covered with a film whicli is formed 
 as often as it is removed. The casein of milk when ob- 
 tained in the solid state does not redissolve completely in 
 water. 
 
 829. Action of alcohol, rennet, etc., on soluble Casein 
 
 Casein in solution is coagulated by alcohol, a portion at 
 the same time entering into solution ; a larger quantity is 
 dissolved by boiling alcohol. The coagulum produced 
 by absolute alcohol is insoluble in pure water ; but the 
 portion dissolved by alcohol is, after the removal of the 
 alcohol, found to be still soluble in water. 
 
 830. Eennet (the inner membrane of the fourth stomach 
 of the calf, salted and dried), or an infusion of it prepared 
 at a low temperature, coagulates casein completely ; this 
 is the most remarkable and important mode of coagulating 
 casein. 
 
 831. Action of acids on Casein The action of concen- 
 trated HC1, H 2 SO„ and HN0 3 , on fibrin and the other 
 albuminoids has already been noticed (778, 779, 780). 
 
 832. Casein is precipitated from its solutions by all acids 
 with the exception of carbonic acid, the precipitate redis- 
 solves in an excess of the acid ; from its solution in acetic 
 acid the mineral acids and potassic ferrocyanide precipi- 
 tate it. 
 
 833. The coagulation of milk is due to the lactic acid, 
 which is formed from lactine, neutralizing the alkali which 
 renders the casein soluble, and thus causing that substance 
 to pass into its insoluble state. 
 
 834. Action of bases and of salts " Coagulated casein 
 
 is readily dissolved by solutions of the alkalies aud of the 
 alkaline carbonates ; and if the solution be very feebly 
 alkaline, the alkaline reaction may be completely neutral- 
 ized by the casein. Solutions of NaCl, of KNO,, and of 
 NITjCl, likewise dissolve casein with facility, and these 
 solutions, when evaporated by the aid of heat, become 
 covered with an insoluble pellicle. Casein also unites with 
 the alkaline earths and forms compounds which are inso- 
 
THE PROPERTIES OF GLOBULIN. 289 
 
 luble in water. If a piece of poor cheese, which consists 
 principally of casein, be reduced to a paste with water and 
 mixed with CaH 2 2 , it produces a tenacious lute, which 
 sets very hard, and may be used for cementing pieces of 
 broken earthenware. In consequence of the tendency to 
 the formation of these insoluble compounds, a solution of 
 casein is precipitated by calcic salts or by MgS0 4 , upon 
 the application of heat to the mixture ; tuis reaction is 
 very characteristic of casein. Most of the metallic salts, 
 such for instance as acetate and basic acetate of lead, CuS0 4 , 
 HgN0 3 , and HgCl 2 , occasion precipitates in the cold with 
 solutions of casein." — Miller. 
 
 Globulin. 
 
 835. Globulin occurs in the cells of the crystalline lens 
 in a very concentrated solution ; it was also considered to 
 be present in red globules of Vertebrata, but later re- 
 searches regard the two substances as distinct, the sub- 
 stance extracted from the blood is called Hsematoglobulin 
 or Haematocrystallin ; it is decomposed by heat, by alcohol, 
 by acids, and by alkalies into hsematin and albumen. 
 
 836. Globulin is very similar to albumen in its proper- 
 ties, but it is distinguished from that substance by " its 
 solutions not becoming opalescent at a lower temperature 
 than 73°; at 83° it assumes a milky turbidity, and at 93° 
 C. separates as a milky coagulum which never becomes 
 clear on filtration, and from which neither small quantities 
 of acetic acid nor ammonia separate flakes capable of being 
 removed by filtration ; it is only when neutral alkaline salts 
 are added, and the solution is then boiled, that the fluid 
 becomes perfectly clear and flakes and small clots are de- 
 posited. The following reaction is very characteristic of 
 globulin ; its solution is not precipitated either by acetic 
 acid or by ammonia, but it becomes strongly turbid when 
 the fluid treated with acetic acid is neutralized with am- 
 monia, or conversely when after the addition of ammonia 
 it is neutralized with acetic acid. No other soluble albu- 
 minoid is precipitated both from its acid and its alkaline 
 solution by neutralization, although almost all the insolu- 
 ble albuminoids possess this property — a circumstance 
 which affords a proof that globulin is reduced to the coagu- 
 lated state both by an excess of alkali and by an excess of 
 acid." — Lehmann. 
 
 25 
 
290 THE PROPERTIES OF GLOBULIN. 
 
 83T. Vitellin. — This name was given to the albuminous 
 body of the yelk of egg ; it is now known to be merely a 
 mixture of albumin and casein. 
 
 838. Recapitulation and remarks. — This group of sub- 
 stances is distinguished from a large number of substances 
 by containing nitrogen; the method for testing organic 
 substances for this element is given at par. 749. 
 
 839. The substances forming this group are distinguished 
 from a large number of organic substances containing ni- 
 trogen, by containing sulphur ; the method for testing or- 
 ganic substances for this element is given at pars. t50 to 
 754. They are distinguished from the next group of sub- 
 stances by being precipitated from their acid solutions by 
 potassic ferrocyanide. 
 
 840. Albumen is usually distinguished and separated 
 from the other members of the group, by warming the fluid 
 and coagulating ; if the solution is alkaline it is necessary 
 to neutralize it with acetic acid, care being taken not to 
 add the acid in excess before warming the liquid ; if the 
 solution is very acid it ought to be neutralized, or the acid 
 or alkaline liquid, instead of being neutralized, is treated 
 with a strong saturated solution of NH 4 C1 ; when NH,C1 
 is employed, the solution requires a longer boiling in order 
 to completely precipitate the albumen from the fluid than 
 if it had been neutralized. 
 
 841. Fibrin is distinguished from the other albuminoids 
 by the property which it possesses of coagulating spon- 
 taneously ; it can exist only in the soluble form in the 
 living plant or animal. 
 
 842. Casein in the absence of, or after the removal of, 
 albumen, may be detected by adding to the solution MgSO„ 
 or CaCl a , and then warming the solution ; if casein is 
 present a precipitate will be formed. But the test which 
 distinguishes it from the other albuminoids is rennet ; to 
 render this test reliable, the rennet must be tolerably fresh, 
 or at least free from all putridity ; the mixture should be 
 digested for a period not exceeding two hours, and at the 
 temperature of 40° C. 
 
THE PROPERTIES OF GELATIN. 291 
 
 GELATIGENOUS GROUP. 
 
 Gelatin. Chondrin.* 
 
 843. Properties of the group Under the term gelatin 
 
 we include the organic tissue of bone, cartilage, sinew, 
 ligament, skin, cellular tissue, and serous membrane ; all 
 these substances dissolve by long-continued boiling in 
 water, and the solution on cooling becomes a consistent 
 gelatinous mass. It is represented in various degrees of 
 purity by glue, size, and isinglass. Gelatin does not exist 
 as gelatin in the animal tissues, but is formed from them 
 by the action of boiling water. Miiller has shown that 
 there are two (if not three) distinct forms of gelatin. To 
 that which is obtained from the permanent cartilages, the 
 cornea, fungous bones, etc., the term chondrin is given, 
 while glutin includes those forms of gelatin which are ob- 
 tained from skin, serous membrane, hoof, bone, tendon, 
 fibrous and spongy cartilage, cartilage of bone, etc. 
 
 844. The gelatigenous substances have hitherto been 
 found only in animals. They contain a smaller amount of 
 carbon and sulphur and a larger amount of nitrogen than 
 the members of the albuminoid group, as will be seen on 
 comparing the following table with the one given at par. 
 788. 
 
 
 Chondrin. 
 
 
 Gelatin. 
 
 Carbon 
 
 . 49.97 
 
 
 50.40 
 
 Hydrogen . 
 
 . 6.63 
 
 
 6.G4 
 
 Nitrogen 
 
 . 14.44 
 
 
 18 34 
 
 Sulphur 
 Oxygen 
 
 . 0.38 
 . 28.58 
 
 } 
 
 24.62 
 
 100.00 100.00 
 
 845. The members of this group yield the same products 
 as the members of the preceding group when treated with 
 oxidizing agents, such as Mn0 2 , or K 2 Cr 2 0., and H 2 S0 4 
 (175). 
 
 846. These substances also give the same reaction as the 
 members of the previous group with HgNO s , par. 785. 
 
 847. The members of this group are especially distin- 
 guished by the following properties : they swell and become 
 very translucent in cold water ; they dissolve in hot water ; 
 
 * There are two other bodies known— Fibroin and Chitin — which 
 belong to this group, but we have omitted them on account of their 
 unimportance. 
 
292 THE PROPERTIES OP GELATIN. 
 
 on cooling they separate as translucent masses, and are 
 precipitated from the most dilute solutions by chlorine, 
 tannic acid, and most of the salts of the earths and metals. 
 
 Gelatin (Glutin). 
 
 848. Gelatin in a state of purity is a colorless transparent 
 solid, which is hard, horny, and brittle ; it is devoid of taste 
 and smell, and has no action on vegetable colors. It is 
 insoluble in alcohol and ether ; it is insoluble in cold water, 
 but softens and swells up in it ; in warm water it dissolves, 
 but the liquid as it cools becomes converted into jelly, gela- 
 tinizes, hence the name gelatine; 1 part of pure gelatin 
 dissolved in about 80 parts of water, is sufficient to cause 
 the liquid to gelatinize when it cools. If a solution of gela- 
 tin is boiled for a length of time, it does not gelatinize on 
 cooling ; the gelatin appears to be converted by the boiling 
 into an isomeric modification which does not possess the 
 property of gelatinizing. 
 
 849. Lime and lime phosphate are much more soluble in 
 a solution of gelatin than in cold water. Common glue 
 always contains a large quantity of lime phosphate, and this 
 substance is considered by Mulder to be an essential con- 
 stituent of gelatin, and it may be observed that chemical 
 compounds of gelatin and lime phosphate can be prepared. 
 
 850. Moist gelatin exposed to the air rapidly putrefies ; 
 the liquid at first becomes highly acid, but afterwards gives 
 off a large quantity of ammonia. This property of first 
 becoming acid is characteristic of gelatin. 
 
 851. Action of acids on Gelatin. — Gelatin is soluble in 
 all the dilute acids with the exception of tannic acid, and it 
 is not precipitated from its solutious by any of the acids 
 except tannic acid. 
 
 852. It is dissolved by concentrated H 2 S0 4 in the cold 
 without change of color. The solution diluted with water 
 and boiled, yields leucine, gtycocine (sugar of gelatin), and 
 some other products. 
 
 853. When gelatin is boiled with concentrated HXO,, it 
 becomes gradually converted into oxalic acid, saccharic 
 acid and two substances resembling suet and tannic acid. 
 When a solution of gelatin in dilute HXO, is evaporated, 
 nitrous gas is evolved, and the residue deflagrates just 
 before dryness. 
 
 854. Tannic acid is a most delicate test of the presence 
 of gelatin ; when it is added to a solution of 1 part of gela- 
 
THE PROPERTIES OP OHONDRIN. 293 
 
 tin iii 5000 of water, a cloud is evident, and on adding the 
 acid to a strong solution, a dense light colored precipitate 
 is produced (tanno-gelatin), which is insoluble in water, 
 alcohol, and ether, but soluble in a warm solution of potash. 
 The composition of the precipitate does not appear to be 
 constant. Tanno-gelatin is identical with leather. 
 
 855. Action of chlorine. — If CI is passed through a solu- 
 tion of gelatin, a white pellicle forms round each bubble of 
 the gas, and finally the whole of the gelatin is precipitated 
 in the form of white elastic flakes or filaments. The pre- 
 cipitate is tasteless, slightly acid, imputrescible, insoluble 
 in water and alcohol, but soluble in acids ; its composition 
 is not known. No similar substance is obtained by sub- 
 stituting Br or I for CI. 
 
 856. Action of the alkalies. — A pure solution of gelatin 
 is not precipitated by dilute solutions of the alkalies. 
 When the gelatin solution is boiled with a concentrated 
 solution of KHO it is decomposed into leucine, glycocine, 
 and other products. The same change takes place when 
 gelatin is carefully fused with solid KHO. 
 
 857. The solubility of lime and its phosphate in solutions 
 of gelatin has already been noticed. 
 
 858. Action of salts. — " Lead, copper, aluminum, and 
 iron salts, do not produce any precipitates in solutions of 
 gelatin, but if a solution of KHO be added to the mixture 
 of gelatin with alum, or with ferric sulphate, the basic 
 aluminic or ferric sulphate which is formed carries down a 
 large proportion of gelatin." 
 
 859. HgCl 2 precipitates gelatin from its aqueous solution. 
 
 Chondrin. 
 
 860. Chondrin is transparent, horny, and glistening, it 
 softens to a jelly in cold water, and in warm water it dis- 
 solves, but the liquid as it cools gelatinizes. It is insolu- 
 ble in alcohol and ether. If a solution of chondrin be boiled 
 for a length of time, it does not gelatinize on cooling. 
 
 861. Action of acids "Nearly all acids even organic 
 
 acids, precipitate chondrin from its aqueous solution. The 
 precipitate formed by hydrochloric, sulphuric nitric, phos- 
 phoric, phosphorous, chloric, or iodic acid,redissolves easily 
 in excess of the acid ; that formed by sulphurous, pyro- 
 phosphoric, hydrofluoric, carbonic, arsenic, acetic, tartaric, 
 oxalic, citric, lactic, succinic or tannic acid does not redis- 
 solve in excess of the acid employed. 
 
 25* 
 
294 THE PROPERTIES OP THE SUGARS. 
 
 862. " Strong H 2 S0 4 dissolves chondrin, forming a syrupy 
 liquid, -which, when diluted with water and boiled, yields 
 leucine without glycocine. H 2 S0 3 slowly decomposes 
 chondrin. HNO s , by prolonged action, converts it into 
 xanthoproteic acid. 
 
 863. Action of chlorine " The aqueous solution of 
 
 chondrin treated with CI yields a precipitate.. 
 
 864. Action of salts "Alum, aluminic sulphate, plum- 
 bic acetate and basic acetate, cupric sulphate, ferrous and 
 ferric sulphates, ferric chloride, mercurous and mercuric 
 nitrates, produce copious precipitates in a solution of chon- 
 drin, soluble for the most part in excess of the reagent. 
 The precipitates formed by acetic acid, alum, and aluminic 
 sulphate, dissolve completely on adding a sufficient quan- 
 tity of potassic or sodic acetate, or of common salt. The 
 precipitate formed by Fe 2 3S0 4 , redissolves on heating the 
 liquid. 
 
 865. " HgCl 2 does not precipitate a solution of chondrin ; 
 sometimes a slight turbidity is produced, owing apparently 
 to the presence of a little gelatin." 
 
 866. Recapitulation and remarks. — This group of sub- 
 stances is distinguished from a large number of organic 
 substances by containing nitrogen. They are distinguished 
 from the members of the preceding group by potassic ferro- 
 cyanide producing no precipitate in their solutions. And 
 their peculiar behavior with water at once distinguishes 
 them from all other substances. 
 
 86*7. Gelatin is distinguished from chondrin by giving a 
 precipitate with HgCl.,. 
 
 868. Chondrin is distinguished from gelatin by being 
 coagulated by the vegetable acids such as acetic acid; as 
 well as by alum, and by the neutral and basic lead acetates. 
 
 SUGARS. 
 
 Milk-sugar, Grape-sugar (Glucose), Inosite. 
 
 869. As milk-sugar, glucose, and inosite, are the chief 
 varieties of sugar met with in the animal kingdom, they 
 are the only sugars wo shall notice in this part of the work. 
 
 870. The sugars are all soluble in both cold and warm 
 water, but they are more soluble in hot water than cold. 
 They all possess a sweet taste ; but there are great differ- 
 ences in the relative sweetness of the different varieties. 
 
THE PROPERTIES OP GLUCOSE. 295 
 
 Sugar of milk (Lactin, Lactose) C 12 R. a O u TI.fl. 
 
 811. This variet}' of sugar is an animal product, it is 
 found only in the milk of the mammalia, and is the sub- 
 stance which gives the sweet taste to fresh milk. It forms 
 white, translucent four-sided prisms, of great hardness. 
 It is soluble in about six parts of cold, and two parts of 
 boiling water ; it does not form a syrup, and has only a 
 feeble sweet taste. It is insoluble in alcohol and ether. 
 Its aqueous solution produces right-handed rotation of a 
 ray of polarized light. 
 
 8*72. It is converted into glucose when boiled with dilute 
 acids. HX0 3 converts it into mucic acid, with a little 
 oxalic acid ; it differs from the other sugars, and resembles 
 the gums in furnishing these acids by the action of H2s0 3 
 upon it. 
 
 813. It becomes gradually converted in milk, from the 
 influence of the caseous matter, into lactic acid, thus : — 
 C 12 H 22 O n H 5 = 4(H 2 C 3 H 4 :f ). 
 
 814. Milk-sugar reacts with. CuS0 4 and KHO, exactly in 
 the same manner as glucose (880). 
 
 Grape or Starch Sugar, Glucose, C 6 H ]2 6 H a O. 
 
 815. Grape-sugar abounds in grapes, figs, plums, and 
 other fruits ; it is also formed from starch, cane-sugar, and 
 wood}- fibre, by processes which will be described under 
 Vegetable Chemistry. It is also a morbid constituent of 
 the urine in the disease called diabetes, its appearance in 
 the urine is the most characteristic feature of the disease. 
 
 816. "Glucose crystallizes with difficult}' in warty concre- 
 tions, composed of hard transparent cubes. It forms with 
 NaCl a compound that crystallizes with facility, which is a 
 distinctive character of this variety of saccharine matter. 
 
 811. '' Glucose is distinguished from cane-sugar by several 
 characters ; it is considerably less soluble in water than 
 cane-sugar, though it is more readily taken up by alcohol, 
 and crystallizes from a hot solution of alcohol containing 
 not more than 5 per cent, of water in anhydrous prisms 
 (C 6 H 12 6 ). It requires nearly two and a half parts of glu- 
 cose to produce the same sweetening effect as is produced 
 by one part of cane-sugar. The action of H 2 S0 4 upon 
 grape-sugar is quite different from its action upon cane- 
 sugar, as, instead of charring and destroying it as it does 
 cane-sugar, it forms with it a definite compound acid, the 
 solution of which is pale yellow ; this acid has been termed 
 sulphosaccharic acid" (C 6 H 12 5 S0 3 ). 
 
296 THE PROPERTIES OF GLUCOSE. 
 
 818. Grape-sugar is resolved in contact with yeast or 
 other ferments into alcohol, carbonic acid and water : thus — 
 C.^.O.H.O = 2C 2 H 6 + 2C0 2 + H 2 0. 
 
 879. When a solution of grape-sugar is heated with a 
 solution of one of the fixed alkalies it is rapidly decomposed, 
 which is evidenced by the fact that the liquid darkens in 
 color and finally becomes nearly black. This action of the 
 fixed alkalies on grape-sugar has been proposed as a test 
 for sugar in urine ; it is called Moore's test, and is employed 
 as follows : To the suspected urine, an equal bulk of the 
 ordinary solution of KHO is to be added and the whole 
 boiled gently for about five minutes ; a deep orange-brown 
 or black color will be produced if sugar is present. This 
 ought only to be employed as a confirmatory test, as in 
 many cases it might prove very fallacious. 
 
 880. The dark brown substance (melassic acid), which is 
 produced when an alkaline solution of sugar is heated, has 
 a very powerful affinity for oxygen, it speedily reduces 
 CuO black oxide to Cn 2 the red oxide when a cupric salt 
 is added to the alkaline solution of sugar. On this pro- 
 perty is founded the most valuable chemical test for sugar 
 which we possess ; this is known as Trommer's test. The 
 simplest plan of employing this test is to add a solution 
 of KHO in tolerable excess,* if a precipitate is produced, 
 as is frequently the case in urine, filter and to the filtrate 
 (in a test-tube) add a few drops of a very dilute solution 
 of CuS0 4 .f If sugar is present, the precipitate which first 
 forms is redissolved on shaking, and the fluid becomes of a 
 clear blue color. This blue solution is then heated to boil- 
 ing, whereon a yellow cloud (hydrated Cu a O) forms, which 
 speedily changes to a red (the anhydrous Cu,0) precipitate. 
 
 881. f When testing urine for sugar by this method the 
 mixture of urine and KHO should not be warmed before 
 the addition of the copper solution, and it ought only to be 
 boiled gently for a minute or two, as several substances 
 besides sugar separate Cu^O from alkaline solutions of copper 
 if the boiling is prolonged. A counter experiment ought 
 
 * An excess of KHO is productive of no harm. 
 
 ■f The solution of the copper salt ought to be so dilute as only to have 
 a faintly blue tinge. Instead of cupric sulphate, Drs. Taylor and Brande 
 recommend cupric tartrate, whioh is certniuly to be preferred to the 
 sulphate ; they reoommend recently precipitated cuprio tartrate to be 
 dissolved in a solution of NaHO or Nii,CO s . Cuprio tartrate is more 
 easily decomposed than the sulphate, less boiling is therefore required, 
 whioh is a great advantage. 
 
THE PROPERTIES OF GLUCOSE. 297 
 
 therefore always to be made by leaving at rest one-half the 
 mixture of urine, potash, and copper solution, before it has 
 been warmed, for six to twenty-four hours without being 
 heated, if sugar is present in the urine a separation of Cu.,0 
 will also take place in this mixture. Sugar is the only sub- 
 stance which can be present in the urine which reduces the 
 copper salt without heat. 
 
 882. Fermentation test. — Fermentation is frequently em- 
 ployed as a test for the presence of sugar. " When used 
 merely as a qualitative test to indicate whether sugar is or 
 is not present in urine, the following is the simplest way of 
 applying it. Fill a test-tube with the suspected urine, 
 having previously mixed with it a few drops of fresh yeast, 
 or still better, a little of the dried German yeast; close the 
 open end with a small saucer or evaporating dish, and 
 ■while gentty pressing the latter upon the tube invert them. 
 A little more of the urine is then poured into the saucer 
 in order to prevent the escape of any of the liquid from 
 the tube, and if any bubbles of air have accidentally been 
 allowed to enter, the exact height of the upper surface of 
 the liquid in the tube must be marked with ink or with a 
 strip of gummed paper. The tube with its contents is then 
 set aside in a warm place having a temperature of about 
 21° or 27 °C, for 24 hours. If sugar is present it begins 
 almost immediately to undergo the vinous fermentation, 
 the CO, as it is formed rises in minute bubbles, causing 
 gradual and gentle effervescence, and collects in the upper 
 tube, displacing an equal volume of liquid which escapes 
 through the open end of the tube into the saucer. When 
 the quantity of sugar present is at all considerable, the 
 urine, after fermentation, will be found to possess a faint 
 vinous smell. As bubbles of gas are sometimes given off 
 by the yeast itself, it is a good precaution to put the same 
 quantity of yeast into a second tube of equal size, and fill 
 it up with pure water. The amount of gas, if any, derived 
 from the yeast will thus be rendered apparent, and may 
 afterwards be detected from the volume of gas in the tube 
 containing the urine." — Bowman. 
 
 Inosite or Phaseomannite C 6 H I2 5 , 2H 2 0. 
 
 883. " This sugar occurs in almost all parts of the animal 
 system and is identical with phaseomannite, which occurs 
 in unripe beans, and in many other plants. It forms pris- 
 matic crystals of the form of gypsum ; it is soluble in 
 water, but insoluble in alcohol and ether; it has a sweet 
 
298 ALKALOIDS. 
 
 taste ; and is not susceptible of the vinous fermentation, 
 but with chalk and cheese it yields lactic and butyric acids. 
 It does not reduce cupric salts. If it be evaporated with 
 UNO, nearly to dryness, and then mixed with a little 
 NH 4 HO and CaCl.,, and again evaporated, a beautiful rose 
 tint is produced, which is quite characteristic of it." 
 
 ALKALOIDS. 
 
 Urea, Creatinine, Creatin. 
 
 884. The only bodies we shall notice belonging to this 
 class are the three given in the list; creatin is neutral to 
 test-paper, but it has been combined with acids, and has 
 the characters of a weak base. It will be seen that it is 
 closely connected with creatinine. The three substances 
 possess no marked properties which are common to the 
 three. 
 
 Urea (CH 4 N. 2 0). 
 
 885. "This important compound is an essential con- 
 stituent of the urine of animals ; it is abundant in that of 
 the mammalia and particularly so in the urine of the carni- 
 vora ; but it has also been met with in the urine of birds 
 and of amphibia. Urea is the principal outlet for the 
 nitrogen of the system, after the materials which compose 
 the animal tissues have experienced oxidation under the 
 influence of the respired air, a healthy human adult ex- 
 creting about an ounce of urea daily. Urea is not formed 
 in the kidneys ; these glands appearing to act somewhat 
 in the manner of filters, by means of which the urea is 
 separated from the mass of the blood, in which it exists 
 already foi'med before reaching the kidneys." — Miller. 
 
 886. Urea can be formed artificially in a variety of ways; 
 one of the simplest methods for its formation is by evapo- 
 rating ammonic cyanate (NII,CNO), which is metameric 
 with uvea, at a gentle heat; by a mere alteration of the 
 elements of ammonic cyanate urea is formed as shown in 
 the following equation : NH,CNO = CH,N t O. 
 
 887. Urea is formed whenever cyanic acid or cyanates 
 come in contact with ammonia or amnionic salts. It is also 
 formed by the spontaneous decomposition of an aqueous 
 solution of cyanogen. Amnionic cyanate is first formed, 
 and this body becomes converted into urea as the liquid 
 
THE PROPERTIES OF UREA. 299 
 
 evaporates. It is also formed when ammonia is acted 
 upon by phogene gas (COCl 2 ). 
 
 888. Bechamp has recently succeeded in preparing urea 
 from albumen, by subjecting it to the oxidizing action of 
 potassic permanganate. 
 
 889. "A solution of urea, if pure, may be kept at ordi- 
 nary temperatures without alteration, and it may even be 
 boiled without undergoing decomposition; but if heated 
 in a sealed tube to about 100°, it combines with four 
 equivalents of water and is converted into amnionic car- 
 bonate— CH\ ; + 2H 2 = (XH ( ) 2 CO s . The same change 
 takes place slowly at ordinary temperatures in the presence 
 of the mucus of the bladder, the ammoniacal odor acquired 
 by urine after keeping it for a few days being due to this 
 alteration. A similar decomposition into carbonic acid 
 and ammonia occurs when urea is fused with KHO or 
 treated with concentrated H 2 S0 4 . 
 
 890. CI, when transmitted into an aqueous solution of 
 urea, resolves it into C0 3 and X and HC1 : thus, 2CHX 2 
 + 2H 2 + 3C1 2 = 2C0 2 + 2X 2 = 6HC1. 
 
 891. Nitrous acid decomposes urea immediately into CO.,, 
 N, and H 2 0: CH 4 N a O + 2HN0 2 + = C0 2 + 2X 2 + 3H 2 0. 
 
 892. Urea crystallizes in flattened four-sided prisms ; they 
 generally resemble KXO s in appearance, and have a similar 
 cooling, saline taste ; they are inodorous. They are soluble 
 in their own weight of cold water and in every proportion 
 in hot water ; they dissolve in 4.5 of cold and in two parts 
 of boiling alcohol ; but they are insoluble in ether, and in 
 an excess of strong nitric acid. Its solution is neutral to 
 test-paper. 
 
 893. Urea is basic in its characters, although neutral to 
 test-paper ; it combines with acids to form salts, some of 
 which are crystalline. " Of these, the two which are of 
 the most practical importance, are the oxalate (2CH,N 2 0, 
 H 2 C,0,), and the nitrate (CH 4 X 2 0, HX0 3 ), which, on ac- 
 count of their sparing solubility in water, supply a ready 
 means of separating urea from the other matters coexisting 
 in the urine. 
 
 894. " Oxalate of urea may be prepared by concentrating 
 urine on a water-bath to about one-eighth of its bulk, and 
 filtering through muslin, in order to separate the insoluble 
 sediment of phosphates and urates, which are gradually 
 deposited during the evaporation. The liquid thus clarified 
 is mixed with about an equal bulk of a strong solution of 
 oxalic acid in hot water, or the solid acid in powder may 
 
300 THE PROPERTIES OS CREATININE. 
 
 be added as long as the liquid, heated to about 88° or 94° 
 C, continues to dissolve it. The mixture, on cooling, de- 
 posits an abundant crop of crystals of oxalate of urea, 
 mixed with a little of the excess of oxalic acid, and 
 colored brown by the adhering impurities. The crystals 
 are then gently pressed between folds of filtering paper, 
 washed with a small quantity of ice-cold water, and puri- 
 fied by recivystallization ; the last traces of coloring matter 
 being removed, if necessary, by boiling the solution with 
 animal charcoal. The oxalate thus obtained is colorless, 
 and in the form of tabular or prismatic crystals, which are 
 readily soluble in hot water, but only sparingly so in cold, 
 25 parts of which dissolve not more than 1 part of the 
 salt. 
 
 895. " Nitrate of urea may be obtained by adding strong 
 colorless HN0 3 , free from HN0 2 (891), to urine previously 
 concentrated by evaporation to about one-third its bulk ; 
 the nitrate gradually separates in irregular rhomboidal 
 plates, more or less colored and modified in form by the 
 impurities present. The crystals are washed with a little 
 ice-cold water, then pressed between folds of filtering paper, 
 and redissolved in lukewarm water ; lastly, they are puri- 
 fied by recrystallization, and, if necessary, the last traces 
 of coloring matter may be removed by boiling the solution 
 with animal charcoal. It is soluble in about 8 times its 
 weight of cold water, and in a much smaller quantity of 
 hot. It is tolerably soluble also in alcohol, especially when 
 warm, but almost insoluble in ether. 
 
 896. " The formation of this crystalline compound on 
 the addition of HNQ 3 , is one of the most distinctive tests 
 for the presence of urea which we possess. The experiment 
 is made easily, and with great delicacy, under the micro- 
 scope, by concentrating a drop or two of urine on a glass 
 slide, and adding to it about an equal quantity of pure 
 IIN0 3 ; the nitrate will gradually crystallize in delicate 
 rhomboidal plates, the number and abundance of which 
 will furnish some indication of the quantity of urea present 
 in the secretion."* 
 
 Creatinine (C,H.N :i O). 
 
 897. This substance is a powerful organic base; its 
 aqueous solution restores the blue color to reddened litmus 
 
 * Bowniau'a Medical Chemistry. 
 
THE PROPERTIES OP CREATIN. 301 
 
 paper, and when heated with solutions of ammonio salts it 
 expels the ammonia like the fixed inorganic alkalies. It 
 forms colorless prismatic crystals, and its salts are also 
 crystalline. It dissolves in about 12 parts of cold water ; 
 it is much more soluble in hot water; it is very soluble in 
 boiling alcohol, but much less so in cold alcohol, it there- 
 fore crystallizes out as the boiling solution cools. 
 
 898. It has a strong tendency to form basic double salts ; 
 example: if a solution of AgNO.,, moderately concentrated, 
 be mixed with one of creatinine, it becomes converted into 
 a magma of white needles, which are very soluble in boiling 
 water, and it forms a similar compound with a solution of 
 HgCl 2 . On the addition of a concentrated solution of 
 ZnCl, to a solution of this base, a double compound 
 (C 4 H,N 3 0). 2 ZnCl 2 is precipitated in a crystalline form ; 
 when very slowly formed the crystals _ are distinctly 
 prismatic, but when quickly produced, and as seen under 
 the microscope, fine needles are observed concentrically 
 grouped together, forming either perfect rosettes, or tufts 
 which cross each other, or of which each two are connected 
 by thin short stalks, so as to resemble brushes passing one 
 into the other. As ZnCl 2 is the test usually employed to 
 detect this base, it is important to observe that the double 
 compound of zinc and creatinine is not precipitated on the 
 addition of the zinc chloride to the creatinine chloride ; 
 but that the separation at once takes place, if before the 
 addition of the ZnCl, solution, a sufficiency of sodic acetate 
 is mixed with the creatinine salt. 
 
 899. This base has been found in the juice of muscle, 
 in the blood as well as in the urine. Creatin is converted 
 into creatinine by the action of strong acids. 
 
 Creatin (C 4 H 9 N 3 2 2H a O). 
 
 900. In its pure state, this substance forms brilliant, 
 colorless, prismatic crystals, which become dull by loss of 
 water at 100° C. It has a bitter, pungent taste. It dis- 
 solves in 75 parts of cold water. Boiling water takes up 
 a much larger quantity of it, but, as it cools, the creatin 
 separates in the crystalline form. Alcohol takes up only 
 one part in 9410 parts ; and in ether it is completely inso- 
 luble. In an impure state the solution readily putrefies. 
 
 901. It dissolves without change in dilute mineral acids ; 
 but when boiled with concentrated acids, it gives off water, 
 
 26 
 
302 PROPERTIES OP THE AOIDS. 
 
 and is converted into creatinine: C 4 H 9 N 3 2 2H 2 — 3H a O = 
 C 4 H 7 N 3 0. 
 
 902. ZnCl 2 produces no precipitate with perfectly pure 
 creatin ; but, if creatinine is present, a triple compound 
 consisting of chloride of zinc, creatin, and creatinine, is 
 precipitated in the form of radiating crystals. 
 
 903. This substance is found in the juice of muscles ; 
 and it is also found in the urine. 
 
 ACIDS. 
 
 Lactic acid, Hippuric acid, Gltcocholic acid, Htocholio 
 acid, taurocholic acid. 
 
 904. These acids are grouped together simply on ac- 
 count of their acid character. 
 
 Lactic acid H,C,H 4 8 . 
 
 905. There are two modifications of this acid, the one 
 called ordinary lactic acid is formed by the fermentation 
 of milk, cane, and grape sugars ; it is also found in vege- 
 table matters which have turned sour. The other modi- 
 fication, called sarcolactic or paralactic acid, exists in 
 muscular flesh. 
 
 906. The ordinary lactic acid, in its most concentrated 
 state, is a colorless, inodorous, thick, syrupy fluid, which 
 cannot be solidified by the most intense cold ; its specific 
 gravity = 1.215, it dissolves readily in water, alcohol, and 
 ether, attracts water from the atmosphere, has a strongly 
 acid taste and reaction, decomposes when heated, and dis- 
 places not only volatile acids, but even many of the 
 stronger mineral acids from their salts. 
 
 90*7. With bases lactic acid generally forms neutral salts, 
 all of which are soluble in water, and many in alcohol, but 
 none in ether. Most of the lactates may be heated to 150° 
 or 110°, and some even to 210°, without undergoing de- 
 composition. 
 
 908. Sarcolactic acid is hai'dly distinguishable from or- 
 dinary lactic acid ; the difference between the two is mostly 
 distinctly marked in the calcic and zinc salts. If sarco- 
 lactic acid be heated for a long time to 130° or 140°, it is 
 converted into the anhydride, which, when boiled with 
 water, is converted into ordinary lactic acid. 
 
the properties of hippuric aoid. 303 
 
 Hippuric Acid or Benzamidacetio Acid, HC 9 H 8 XO s . 
 
 909. This acid occurs in combination with K or Na in 
 large quantity in the urine of herbivorous animals, and in 
 smaller quantity also in human urine. 
 
 910. This acid, when treated with nitrous acid, under- 
 goes the decomposition peculiar to amidogen compounds, 
 viz., the formation of a non-nitrogenous acid, water, and 
 the liberation of nitrogen. The acid formed on treating 
 hippuric acid with nitrous acid is benzo-glycolic acid 
 (C g H 8 4 ). Under the influence of boiling water, benzo- 
 glycolic splits up into benzoic and glycolic (oxyacetic) 
 acids. 
 
 911. When hippuric acid is boiled for some hours with 
 concentrated HC1, it assimilates the elements of water, 
 and is resolved into benzoic acid and amidacetic acid or 
 glycocine : — 
 
 HC 9 H 8 ]Sr0 3 + H 2 = HC 7 H 5 2 + HC 2 H 4 ISrO r 
 
 Hippuric acid. Benzoic acid. Glycocine. 
 
 912. Hippuric acid has been artificially made by acting 
 upon the zinc salt of glj'cocine with chloride of benzoyl: — • 
 
 Zn(C 2 H,N0 2 ) 2 + 2C,H 5 0C1 = ZnCl 2 + 2HC 9 H 8 NO a . 
 
 913. This acid crystalizes in rhomboidal prisms, or in 
 thin plates. It is sparingly soluble in cold water, one part 
 requiring 400 parts for its solution ; but it is very freely 
 soluble in hot water. It is readily soluble in alcohol; 
 but only sparingly soluble in ether, which distinguishes it 
 from benzoic acid (b'lQ). Exposed to a high temperature it 
 is decomposed into hydrocyanic acid, benzoic acid, amnio- 
 nic benzoate, and other products. Heated with a fragment 
 of KHO it disengages NH a . If placed in contact with fer- 
 ments, it undergoes a kind of fermentation, the products 
 of which are benzoic acid and ammonia. 
 
 914. Owing to this speedy conversion of it into benzoic 
 acid and ammonia bj r ferments, it is not surprising that if 
 the urine becomes in the slightest degree putrid, it is 
 speedily decomposed into benzoic acid and ammonia. On 
 the other hand, when benzoic acid is taken into the system, 
 it is converted into hippuric acid, and is found in the urine 
 in that state. 
 
304 PROPERTIES OF G L YC 0-H YOC HOLI AOID. 
 
 GliYCO-OHOLAMC acid or Glycocholic Acid ( Cholic acid 
 of Streoker) HC 26 H 12 N0 6 . 
 
 915. This acid, in combination with the fixed alkalies, 
 exists in the bile of man and other animals, but it is 
 present in the greatest quantity in ox-bile. The acid is a 
 white crystalline solid; it has a strong acid reaction, and 
 a bitterish-sweet taste. It is more soluble in hot water than 
 cold ; alcohol dissolves it freely, but leaves it as a resinous 
 mass on evaporation; it is very sparingly soluble in ether. 
 The salts which it forms with the alkalies and alkaline 
 earths may be crystallized ; they are soluble in alcohol. 
 
 916. When this acid is boiled with an alkaline solution, 
 as solution of KHO or BaH,0„ it is decomposed into gly- 
 cocine (amidacetic acid), and a non-nitrogenous acid, called 
 cholalic acid* (the cholic acid of Demarcay) : — 
 
 HC 26 H M N0 6 + H 2 = HC 24 H 39 5 + CftNO, 
 
 Glyco-cholalic acid. Cholalic acid. Glycocine. 
 
 917. When it is boiled with concentrated HJ30, or HC1, 
 it is split up into glycocine and choloidinic acid (C^H^O^ = 
 cholalic acid — 1 eq. of water) ; if the ebullition with the 
 acids be continued, the choloidinic acid is decomposed into 
 a resinous substance, called, from its insolubility in water, 
 dy sly sin (O M H 30 O 3 ), and water. 
 
 Glyco-hyocholic Acid, HC^H^NOj. 
 
 918. Pig's bile differs from the bile of other animals, inas- 
 much as it contains glyco-hyocholic acid instead of glyco- 
 cholalic acid; the former acid is decomposed like the latter 
 by alkaline solutions and acids and into substances of 
 analogous composition. 
 
 919. When it is boiled with an alkaline solution, it is 
 decomposed for instance into glycocine and hyocholic 
 acid : — 
 
 IIC 27 H J9 X0 5 + H 2 = HC,,H., O 4 + C\.II,XO, 
 
 Glyco-hyocholio acid. Ilyocholio aoid. Glycocine. 
 
 920. When it is boiled with acids it is decomposed into 
 glycocine and a substance homologous with dyslysin, which 
 is termed hyodyslysin (C^.11,,,0,). 
 
 * This aoid is soluble in HjSO,, and on the addition of a drop of this 
 acid and a solution of sugar (one part of sugar to four of water) a pur- 
 plo violet color is produced which constitutes Pettcnkofer's test for bile. 
 
CYSTINE, XANTHINE, AND CHOLESTRIN. 305 
 
 Tacrocholalic Acid or Taurochoi.ic Acid (Choleic 
 Acid of Strecker) HC M H 44 NS0 7 . 
 
 921. The bile of man and most animals, with theexception 
 of the ox and pig, consists mainly of taurocholalate of soda 
 or potash. The alkaline salts of this acid are verj- soluble 
 in water and alcohol. They give no precipitate with neutral 
 lead salts, but with the basic salts they deposit a plaster- 
 like compound, which is soluble in boiling water. They 
 yield with H 2 S0 4 and sugar a violet color similar to that 
 produced by the cholates. 
 
 922. When this acid is boiled with alkaline solutions it 
 is decomposed into cholalic acid and taurine : — 
 
 HC^NSO, + H a O = HCJH^Oj + C 2 H ; NS0 3 . 
 
 Taurooholalic acid. Cholalic acid. Taurine. 
 
 923. When it is boiled with acids it is decomposed into 
 taurine* and choloidinic acid or dyslysin, according to the 
 duration of the experiment (917). 
 
 CYSTINE, XANTHINE, AND CHOLESTRIN. 
 
 924. These three substances are met with in calculi. 
 
 925. Cystine or Cystic Oxide (C 8 H,NS0 2 ). This sub- 
 stance is met with nowhere but in the urine; it was 
 originally discovered by Wollaston in a urinary calculus ; 
 calculi of this nature, although very rare, have since been 
 found by many other chemists. L ' It occurs in colorless, 
 transparent, hexagonal plates or prisms ; it is devoid of 
 taste and smell, and is insoluble in water and alcohol. It 
 dissolves in oxalic and the mineral acids, forming with them 
 saline combinations, most of which are crystallizable, but 
 it does not unite with acetic, tartaric, or citric acid; it is 
 decomposed by nitric acid, leaving, on the evaporation of 
 the fluid, a reddish-brown mass ; it dissolves freely in the 
 caustic fixed alkalies and their carbonates. It dissolves in 
 NH 4 HO, but does not unite with it, so that on evaporation 
 it crystallizes unchanged. It is insoluble in (NHJ.,CO s ; 
 hence it is best precipitated from its acid solutions by 
 (NH i ) 2 CO s , and from its alkaline solutions by acetic acid. 
 
 * The student is referred to the author's " Second Step in Chemistry," 
 page 625, for an account of Kolbe's important experiments on the con- 
 stitution of taurine. 
 
 26* 
 
306 CYSTINE, XANTHINE, AND CHOLESTEIN. 
 
 926. " Cystine does not fuse on the application of heat, 
 but it burns with a bluish-green flame, developing at the 
 same time a very peculiar acid odor ; on dry distillation it 
 develops a stinking enapyreuma and ammonia, and leaves 
 a voluminous porous coal. On boiling it with alkalies, 
 ammonia is first developed, and subsequently an easily 
 inflammable gas, which burns with a blue flame. 
 
 921. " Cystine is characterized by the readiness with 
 which it crystallizes in well-formed hexagonal plates, which 
 may be distinguished with great ease under the microscope, 
 and by its solubility both in alkalies and mineral acids. 
 Further, it may be known by the peculiar odor which it 
 develops on dry distillation and on burning, which is unlike 
 that evolved by any other similar substance. Liebig has 
 given the following test for cystine. The potash-extract of 
 the substance in which we are searching for cystine must 
 be decomposed with a solution of PbO in KHO ; if, on the 
 application of heat, there be a precipitation of PbS, cystine 
 is probably present ; we must, however, previously satisfy 
 ourselves that no other organic substance containing 
 sulphur, as for instance, albumen, mucus, etc., be simulta- 
 neously present. 
 
 928. " If cystine be mixed with a small quantity of the 
 urates, the two substances may be separated by the aid of 
 boiling water, in which the former is insoluble. Uric acid 
 occasionally appears under the microscope in the form of 
 hexagonal tablets, but we should never trust in these cases 
 to microscope examinations." — Lehmann. 
 
 929. Xanthine or Xanthic oxide (C 5 H 4 X t O s ). This 
 substance has also been named uric oxide and urous acid, 
 owing to its being regarded as ui-ic acid in a lower stage of 
 oxidation. It is the principal constituent of a very rare 
 variety of urinary calculus. It is one of the products in 
 the decomposition of guanine, a substance found in guano 
 and in the excrement of the garden spider. It is likewise 
 present in nearly every part of the animal organism, and, 
 although in very minute quantities, in urine. It is a white 
 amorphous powder, and it acquires a waxy lustre on friction 
 with a hard body. It is very slightly soluble in water; it 
 is insoluble in alcohol and ether. It dissolves easily in 
 ammonia. It also dissolves freely in the fixed alkalies ; 
 carbonic acid separates it from its alkaline solution. It 
 is all but insoluble in HC1 and H^C.O,; it is soluble in 
 11,S0 4 and IINO. t . It dissolves in UNO, without disen- 
 gagement of gas, and gives on evaporation a yellow residue, 
 
COLORING MATTERS. 307 
 
 ■which, on addition of NH,HO or KHO, turns yellowish- 
 ml. From the circumstances under which it occurs it can 
 only be confounded with cystine or uric acid ; it differs 
 from these by its amorphous condition. It is distinguished 
 from cystine by its insolublity in HC1 and H,C 2 Oj. It is 
 distinguished from uric acid by its solubility in NH^HO, and 
 by the residue obtained on evaporating its HX0 3 solution 
 not turning red on the addition of NH 4 HO (617). 
 
 930. Cholestrin C m H J4 " This substance is found in 
 
 small quantity in various parts of the animal system, as in 
 the bile, in the brain and nerves, and in the blood. It forms 
 the chief ingredient of biliary calculi, from which it is 
 easily extracted by boiling the powdered gall-stones in 
 strong alcohol, and filtering the solution while hot ; on 
 cooling the cholestrin crystallizes in brilliant colorless 
 plates. It has the physical characters of a fat, is insolu- 
 ble in water, tasteless and inodorous ; it is freely soluble in 
 boiling spirit and also in ether. It is not saponified by 
 potash ; thus differing from other fatty and oily substances 
 which it resembles in many respects. It melts at 137°, and 
 sublimes at 200° C." 
 
 COLORING MATTERS 
 
 931. We group together the coloring matter of the urine, 
 the bile, and the blood. 
 
 932. Coloring matter of the urine. — " The coloring mat- 
 ter of the urine is constantly undergoing change ; by means 
 of neutral and basic lead acetate it may be separated into 
 two substances which contain different amounts of carbon. 
 The substance which contains most carbon may be obtained 
 as a dark-blue powder ; when dry it has a copper color like 
 indigo and dissolves in alcohol, giving a purple-blue solu- 
 tion. It is said to occur most evidently in Bright's dis- 
 ease. Virchow states that he met with this blue pigment 
 in crystals in unhealthy urine." Thudicum believes there 
 is only one normal urinary pigment which he has named 
 tirochrome, an amorphous substance of a pure yellow color ; 
 Sclmnk believes there are two. 
 
 933. Coloring matter of the bile. — The principal coloring 
 matter of the bile has been called cholepyrrhin or biliru- 
 bine (C ]6 H 1S N 2 3 ). When dry it is reddish-brown and un- 
 crystallizable, insoluble in water, slightly soluble in alcohol 
 and ether, easily soluble in chloroform and in solutions of 
 
308 TESTS FOR BLOOD AND BILE. 
 
 the alkalies. The color of these solutions is yellow or 
 orange ; if to the alkaline solution is added an equal volume 
 of alcohol and then fuming nitric acid charged with nitrous 
 vapors, it passes through green, blue, violet, and red; after 
 some time it again turns yellow ; this reaction is very 
 delicate. 
 
 934. Another coloring matter has been called biliverdin. 
 It is dark green, amorphous, without taste or smell, inso- 
 luble in water, slightly soluble in alcohol, but soluble in 
 ether. 
 
 935. Coloring matter of the blood. — The red coloring 
 matter of the blood-corpuscles is called haematm or hsema- 
 tosin ; it leaves when burnt a residue of ferric oxide and 
 calcic phosphate. It is unaffected by dilute NHJEEO, but 
 is entirely destroyed by ebullition, with the formation of a 
 dirty-colored coagulum, which dissolves in KHO with an 
 indistinct greenish color. 
 
 936. Tests for blood " Blood-stains on articles of 
 
 clothing may be identified — 1. By their peculiar crimson- 
 red color. 2. By the shining and raised surface of the 
 stain or spot (dried albumen and fibrin). 3. By their ready 
 solubility in water to which they give a red color. The 
 water under these circumstances contains albumen as well 
 as hsematosin. Weak ammonia does not change the red 
 color to a blue, green, or crimson tint. When boiled, the 
 albumen and hsematosin are both coagulated, and the red 
 color is entirely destroyed ; a muddy brown coagulum sub- 
 sides which is quite insoluble in water and alcohol." 4. 
 Bloxam has proposed the following test, which is very deli- 
 cate. A mixture of tincture of guaiacum and oxonized 
 ether (that is a solution of hydric peroxide (H 2 OJ in ether.) ; 
 this mixture instantly produces with blood or blood-stains 
 a beautiful blue tint. For the examination of such stains 
 in a dry state, an inch power of the microscope will be 
 found convenient. 
 
 937. " By employing a small quantity of water on a glass 
 slide in order to dissolve the stain, the clot may be broken 
 up and the red corpuscles separated. These may be ex- 
 amined by a quarter-inch power under the microscope. 
 When detected, the evidence of the presence of blood is 
 placed beyond doubt. No other red coloring matter, vege- 
 table or animal, owes its color to corpuscles or cells. A 
 small quantity of glycerine added to the water which is 
 used as a solvent prevents it from drying too rapidly." — 
 Brande and Taylor. 
 
ANALYSIS OF ANIMAL SECRETIONS. 309 
 
 938. Test for bile. — Bile is essentially composed of soda 
 salts of the two acids, glycocholic and taurocholic, cho- 
 lestrin, mucus, and coloring matter. It is a ropjr, viscid, 
 and saponaceous liquid of a greenish-yellow color in rnanj 
 greenish-brown in the ox, and emerald or grass-green in 
 birds, reptiles, and fish. It has a bitter taste and an offen- 
 sive odor. Its reaction is general alkaline ; it is sometimes 
 neutral but never acid, excepting in peculiar states of dis- 
 ease. It mixes in all proportions with water ; it is not co- 
 agulated by heat. Alcohol renders it turbid by precipi- 
 tating the mucus. 
 
 939. We have noticed (par. 921 and note page 304) that 
 the two acids in the bile when treated with sulphuric 
 acid and sugar acquire a purple color. Upon this reaction 
 a test, called Pettenkofer's test, for bile has been founded. 
 The best mode of applying the test for the detection of small 
 quantities of bile in blood or other animal fluids is as fol- 
 lows : The alcoholic extract of the liquid to be tested for 
 biliary matter is dissolved in a little water and mixed with 
 a single drop of a solution of sugar (one part of sugar to 
 four parts of water), and pure strong H 2 S0 4 is then added 
 in small quantities till the turbidity at first produced dis- 
 appears, cooling after each addition ; it then for a few mo- 
 ments exhibits a yellowish color, which, however, soon 
 changes to a pale cherry-red, then to deep carmine, then to 
 purple, and finally to an intense violet tint. For the suc- 
 cess of the experiment, care must be taken not to add too 
 much sugar, otherwise a black mass will be formed which 
 will completely mask the reaction. The temperature of the 
 mixture must be allowed to rise to about 50° C, but not 
 higher. The reaction takes place with any kind of sugar 
 and likewise with acetic acid. 
 
 A METHOD FOR ANALYZING QUALITATIVELY ANIMAL 
 SECRETIONS.* 
 
 940. The physical characters, such as color, taste, odor, 
 consistence, etc., should first be carefully observed. The 
 specific gravity may also be ascertained, when it can con- 
 veniently be done, as a knowledge of the density of the fluid 
 will serve to furnish some indication of the amount of solid 
 matter held in solution. 
 
 * The method for analyzing the animal secretions, and for the analysis 
 of urine, has been taken mainly from Gerhardt and Chancel's Qualita- 
 tive Analysis. 
 
310 THE QUALITATIVE ANALYSIS 
 
 941. The liquid should be examined by test-papers 
 ■whether it is neutral, alkaline, or acid. 
 
 942. When the liquid holds in suspension any solid or 
 semi-solid matter the dissolved should be separated from 
 the undissolved portion either b3 r decantation or by filter- 
 ing it through paper or fine muslin. The microscopic ex- 
 amination of the residue generally furnishes some useful 
 indications. The spontaneous coagulation in a secretion, 
 at first limpid, is due almost always to fibrin. 
 
 943. The clear liquid is then submitted to the following 
 examinations : — 
 
 944. First examination We heat a portion of the liquid 
 
 in a test-tube ; when the liquid is neutral or alkaline, one 
 or two drops of acetic acid is first added to produce a. faint 
 acid reaction. If the liquid remains clear on warming it, 
 we can be certain of the absence of albumen ; in that case 
 we pass on to the second examination (948). 
 
 945. If, on the contrary, the liquid becomes troubled or 
 coagulated, it becomes necessary, after having agitated it, 
 to divide it into two portions. To one portion add a few 
 drops of dilute HC1 ; if the precipitate disappears it has 
 not been due to albumen but was probably due to calcic or 
 
 "magnesic phosphate, or both. The other portion of the 
 liquid must be examined by the microscope. 
 
 946. When the dilute HC1 does not redissolve the pre- 
 cipitate, we then add a larger quantity of it and finally boil 
 the mixture ; if the precipitate becomes slowly dissolved 
 and the liquid assumes a violet color (780), this reaction 
 indicates the presence of albumen. We control this result 
 by examining the action of nitric acid upon the primitive 
 secretion (7T9 and 804). 
 
 947. If the coagulum formed by boiling the liquid, or the 
 liquid itself, has a reddish tinge, hsemaline and also globulin 
 may be present. In this case, we dry the coagulum ; it 
 then assumes a brown or black tint. It is afterwards boiled 
 with alcohol to which a little H 2 S0 4 has been added; if 
 it contains hsematine, the liquid is colored red, and the 
 alcoholic extract after having been evaporated to dryness 
 furnishes a residue which gives, after calcination, the reac- 
 tions of iron (935). • 
 
 948. Second examination. — A liquid which does not con- 
 tain albumen, or from which it has been separated by 
 coagulation and filtration, may yet contain the following 
 albuminoidal substances, casein, globulin, glut in, chondrin, 
 pus, and mucus, and possibly paralbumin and metalbumin. 
 
Or ANIMAL SECRETIONS. 311 
 
 949. A sample of the liquid is mixed with potassic 
 ferrocyanide. If it remains clear, casein and globulin are 
 absent (784), pass on to the third examination (par 951). 
 
 950. If a precipitate is formed, test for casein with solu- 
 tion of CaCl 2 , and boil the mixture, which becomes turbid 
 if casein is present (842). When this effect is manifested 
 digest the liquid with rennet at a temperature of 40° C. in 
 order to render the coagulation of the casein complete. If 
 globulin is present the liquid will be rendered turbid by the 
 addition of a few drops of acetic acid, and give afterwards 
 a flaky precipitate when neutralized with NH,HO (836). 
 
 951. Third examination. — To a portion of the liquid add 
 acetic acid. If it remains clear, pus, mucus, and chondrin 
 are absent ; pass on to the fourth examination (par 953). 
 
 952. A precipitate is formed ; test the solution with 
 HgCl 2 , if no precipitate is formed pus is absent. If the 
 HgCl 2 produces merely a turbidity, mucus or chondrin is, 
 perhaps, present. Concentrate a portion of the liquid ; the 
 formation of a jelly indicates chondrin (860), the presence 
 of which may be confirmed by its behavior with alum and 
 metallic salts (864). 
 
 953. Fourth examination The liquid in which acetic 
 
 acid produced no precipitate may yet contain glutin. 
 Concentrate a portion strongly and leave it to cool ; the 
 formation of a jelly will indicate glutin, which may be 
 further tested with HgCl 2 (859). 
 
 954. Fifth examination The original liquid, or, if it 
 
 contained albumen, the liquid freed from that compound 
 by boiling, is concentrated by a gentle heat to a half or 
 one-third of its volume, and is then left to cool ; if no pre- 
 cipitate forms, the urates are probably absent. Pass on to 
 the sixth examination. 
 
 955. If a precipitate is formed add acetic acid. If the 
 deposit previously amorphous is seen (after the addition of 
 the acid), under the microscope, to assume the form of 
 rhombic tablets uric acid is indicated ; confirm its presence 
 by dissolving the deposit in HNO a and examining it for uric 
 acid as directed in par. 61Y. 
 
 956. If the deposit is crystalline and does not change its 
 form by acetic acid, it points to the presence of calcic sul- 
 phate or magnesic phosphate ; the presence of these salts 
 must be confirmed by their reactions. The precipitate, if 
 crystalline, may also contain benzoic acid, calcic hippurate, 
 tyrosine, and allantoin. 
 
 957. Sixth examination. — The concentrated liquid in 
 
312 THE QUALITATIVE ANALYSIS 
 
 •which no precipitate is formed by boiling and subsequent 
 cooling, or the liquid filtered from such a precipitate, is 
 evaporated to a syrup on the water-bath and left to itself 
 for a considerable time. If crystals gradually form, it is 
 left to stand as long as they continue to increase. They 
 may consist of creatine, creatinine, glycocine, leucine, 
 allantoin, taurine, sarcosine, inosite, alkaline hippurate, 
 sodic chloride, and other inorganic salts. 
 
 958. It must in the first place be determined whether 
 these crj'stals are organic or inorganic. In the former case 
 they must be tested especially for nitrogen, sulphur, and 
 phosphorus (149, 750, 754), their chemical naturedetermined 
 as nearly as possible, and the further examination regulated 
 accordingly. If inorganic they must be examined according 
 to the usual methods. If they blacken when strongly 
 heated, but also leave a fixed residue, they probably con- 
 sist of an organic acid, combined with an inorganic base ; 
 in that case the fixed residue will effervesce strongly with 
 acids. 
 
 959. The syrupy residue itself, or the liquid, separated 
 from the crystals which have formed in it, is evaporated 
 nearly to dryness on the water-bath, and the residue is 
 digested with alcohol of a sp. gr. of 0.83. The alcoholic 
 solution and the substance insoluble in alcohol are sepa- 
 rately examined. 
 
 960. The alcoholic solution is submitted to the following 
 examinations : — 
 
 1. To a small portion of the alcohol solution concentrated 
 and then diluted with water, is added, drop by drop, fuming 
 nitric acid (containing nitrous vapors) ; if there is formed, 
 after the addition, at the bottom of the liquid a zone at 
 first green, next blue, violet, red, and lastly of a dirty 
 3'ellow, it proves the presence of the coloring matter of the 
 bile (933). 
 
 2. Another portion also concentrated and then diluted 
 with water is mixed with sugar and H„S0 4 ; a beautiful 
 purple red color proves the presence of the acids in the 
 bile (939). 
 
 3. In a third portion we look for glucose. This substance 
 generally communicates to the liquid a sweet taste. This 
 portion of the alcoholic solution is evaporated to dryness 
 on the water-bath, the residue is redissolved in water and 
 examined for glucose by the copper test (880 and 881). 
 The result ought to bo controlled by the fermentation 
 test (882). 
 
OF URINK. 313 
 
 4. The greater part of the alcoholic solution is evapo- 
 rated to a very small volume, it is then mixed with ■pure 
 nitric acid, which must be free especially from nitrous acid, 
 and we place the vessel in a cooling mixture. If a crystal- 
 line deposit is formed, it is examined by the microscope to 
 ascertain whether it has the appearance of nitrate of urea* 
 (895 to 897) or of hippuric acid or benzoic acid. The 
 indications obtained by the microscope are confirmed by 
 the chemical reactions. 
 
 5. A portion of the concentrated alcoholic solution is 
 mixed with a syrupy solution of ZnCl 2 ; if a precipitate is 
 not formed even after a length of time, the liquid does not 
 contain creatinine (898). If a precipitate is produced, we 
 submit it to some special examinations, to ascertain the 
 presence of creatine as well as creatinine (902). 
 
 6. Lastly, if the alcoholic solution possessed a strong 
 acid reaction, it has still to be examined for lactic acid. 
 To effect this the extract is concentrated and heated along 
 with oxide or carbonate of zinc ; a drop of the boiling fil- 
 tered liquid is placed between two plates of glass, and we 
 examine it Ivv the microscope to see if the characteristic 
 crystals of lactate of zinc are formed (908). 
 
 961. Insoluble residue. — In addition to mucus and unde- 
 fined extractive matters, this residue can contain uric acid, 
 a little casein, etc. 
 
 962. Seventh Examination. — After having finished the 
 previous examinations, a portion of the original solution 
 is evaporated to dryness on the water bath and the residue 
 treated with ether. This dissolves the fatty matters, the 
 presence of which we ascertain by evaporating the ethereal 
 solution. 
 
 963. The portion insoluble in ether must be incinerated 
 in a platinum crucible, and the inorganic salts determined 
 by the ordinary methods. 
 
 QUALITATIVE ANALYSIS OF URINE. 
 
 964. The preceding method can, with some slight modi- 
 fications, be applied to the analysis of most of the animal 
 secretions. 
 
 965. Of the secretions, the urine presents a particular 
 interest for the medical practitioner, owing to the changes 
 
 * Care must be taken not to confound the alkaline nitrates for nitrate 
 of urea. 
 
 27 
 
314 
 
 THE QUALITATIVE ANALYSIS 
 
 which it undergoes in its composition by the effects of cer- 
 tain diseases, and which can be made use of as a means of 
 diagnosis. 
 
 966. The bodies which normal urine holds in solution in 
 .water are : 
 
 Organic Substances. 
 
 Urea. 
 
 Uric acid. 
 
 Hippuric acid. 
 
 Creatine. 
 
 Creatinine. 
 
 Coloring and extractive mat- 
 ters. 
 
 Mucus of the bladder (in sus- 
 pension). 
 
 Mineral Substances. 
 
 Potassic 
 
 Sodic 
 
 Calcic \- Salts. 
 
 Magnesic 
 
 Iron 
 
 Silicates. 
 
 Phosphates. 
 
 Sulphates. 
 
 Chlorides. 
 
 967. We find in addition, in normal urine, very small 
 quantities of ammonia and of carbonic acid gas. 
 
 968. Recently emitted, it always possesses an acid reac- 
 tion,* due very probably to the presence of hippuric or 
 uric acid. It behaves with reagents in the following man- 
 ner : — 
 
 1. It is not coagulated by boiling. 
 
 2. The caustic alkalies, on being added to it, produce a 
 turbidness, or a precipitate of the phosphates of the alka- 
 line earths. 
 
 3. BaCl 2 gives a precipitate of baric sulphate and phos- 
 phate. 
 
 4. AgN0 3 gives a precipitate of argentic chloride and 
 phosphate. 
 
 5. Lead acetate gives a precipitate of plumbic phosphate, 
 sulphate and chloride. 
 
 6. (NH 4 ) a C 3 0, gives a precipitate of calcic oxalate. 
 
 7. Alcohol determines a turbidness which disappears by 
 the addition of a sufficient quantity of water. 
 
 969. The following substances are only contained in the 
 urine in certain diseases : — 
 
 1. Ammonic carbonate. Lactic acid. Albumen (in many 
 diseases). Fibrine (found only in the sediments). Fatty 
 substance (very rarely). Coloring matter of the bile (in 
 
 * The experiments of Dr. Benoo Jones show that when passed shortly 
 after entiug, the urine is often neutral, or even alkaline, becoming again 
 gradually more and more acid up to the time when the nest meal is 
 taken. 
 
OF URINE. 315 
 
 liver complaints). Acids of the bile rarely. Glucose (dia- 
 betes). Sulphuretted hydrogen (very rarely). Calcic oxa- 
 late and cystine. 
 
 970. Before proceeding to the examination of the sub- 
 stances contained in the urine, it is necessary to observe 
 the color, the transparencj', the odor, the action upon test- 
 paper. When the urine possesses an alkaline reaction, it 
 is necessary to note if it is fresh, or if it is already com- 
 mencing to undergo putrefaction. 
 
 971. It is equally useful to determine its density; the 
 density of healthy human urine varies from 1.005 to 1.030. 
 
 972. After having obtained this preliminary information, 
 we allow a quantity of the urine to stand for some time in 
 order to allow time for the formation of a sediment. We 
 then filter and examine separately the filtrate and the sedi- 
 ment. 
 
 973. The filtrate A quantity of the urine is boiled in 
 
 order to coagulate the albumen* when it is present, after 
 that we examine the filtered liquid as described in par. 954. 
 We at first look for the normal constituents of the urine, 
 such as uric acid, the urates, hippuric acid, and urea ; lastly 
 those which are accidental, as amnionic carbonate, lactic 
 acid, the coloring matter of the bile and glucose. 
 
 974. Amnionic carbonate can only be present in urine 
 which has an alkaline reaction. The urine, which contains 
 this amnionic salt, effervesces on the addition of an acid ; 
 when the urine is boiled with KHO, XH 3 is disengaged, 
 and is recognized by its reactions (24). 
 
 975. Urine containing biliary matter is in general strongly 
 colored; its tint varies from saffron yellow, to yellowish- 
 brown ; if the urine has a sediment, this is also colored. 
 When we agitate a sample of this urine, there is formed on 
 the surface a yellow scum.f 
 
 976. Urine containing sugar is usualty characterized by 
 its high specific gravity, which is frequently from 1.030 to 
 1.045, and occasionally as high as 1.050 and 1.055. If, 
 
 * The precipitate produced by boiling is not a sure proof of albu- 
 men ; since a white precipitate is also produced by boiling, when the 
 urine (free from albumen) contains an excess of earthy phosphates; 
 see pars. 945 and 946 for distinguishing the two precipitates. 
 
 f The taste of urine containing biliary matter is remarkably bitter, 
 u peculiarity which furnishes a ready indication of its presence when 
 other tests are not to hand; though it must not be implicitly relied on, 
 since small traces may exist in the secretion without communicating to 
 it any very decided taste (Bowman). 
 
316 THE QUALITATIVE ANALYSIS 
 
 however, the sugar is present only in small quantity, the 
 specific gravity may not be higher than usual ; so that a 
 moderately low specific gravity is of itself no proof of the 
 absence of sugar. It is generally paler in color than nor- 
 mal urine ; and it is generally slightly turbid. 
 
 977. Urine containing fatty or chylous matter is usually 
 more or less turbid, and frequently has an almost milky 
 appearance. 
 
 978. Urine containing sulphuretted hydrogen has the 
 odor of rotten eggs ; test for it as directed in par. 468. 
 
 919. Sediments The sediments ought to be examined 
 
 microscopically as well as chemically. 
 
 980. The bodies contained in urinary sediments are — 
 Uric acid ; the urates of lime, magnesia, potash, soda, 
 
 and ammonia. Calcic oxalate. Calcic phosphate and mag- 
 nesic ammonic phosphate. Cystine. Different organic 
 materials, such as mucus, blood, pus, spermatozoa, etc. 
 
 981. Free uric acid is only found in the sediments fur- 
 nished by dark-colored urine, and it possesses a distinct 
 acid reaction. These sediments are also colored ; they can 
 have a pale tint, but it is generally yellow, orange yellow, 
 or brown ; they have a granular appearance, and frequently 
 even visibly crystalline to the naked eye. The uric acid 
 can be very well detected with the microscope, or by its 
 reaction with HN0 3 and XH,HO (617). It is distinguished 
 from the urates by its insolubility in water, and by the 
 fixed residue which these leave on incineration ; it is dis- 
 tinguished from urate of ammonia by the latter disengaging 
 ammonia in contact with KHO. 
 
 982. The urates also form a part of the sediments depo- 
 sited from acid urine. The color of these sediments, as 
 well as the urine, varies much. The urates contained in 
 the sediments present frequently, to the naked eye, the 
 appearance of mucus, of pus, and of blood, and can be 
 distinguished only from these matters by microscopic ob- 
 servation and chemical analysis. Sodic urate is the one 
 most frequently met with. 
 
 983. Calcic oxalate can make part of the sediment fur- 
 nished by urine, the reaction of which is acid, neutral or 
 alkaline, and it is not rare to find it associated with the 
 urates. The urine containing calcic oxalate possesses a 
 coloration, sometimes clearer, sometimes darker, than that 
 of normal urine; its color is frequently that of amber yel- 
 low. Calcic oxalate, obtained by double decomposition, is 
 an amorphous powder, whilst that found in the urinary 
 
OF URINARY OALOULI. 317 
 
 sediments is distinguished by its crystalline form. The 
 identity of calcic oxalate is easily determined by the aid 
 of its chemical reactions ; when it is heated upon platinum 
 foil, it is transformed into calcic carbonate without carbon- 
 ization. 
 
 984. The phosphates of the alkaline earths are easily 
 identified by the chemical reactions. (See par. 198.) 
 
 Analysis op Calculi and Concretions. 
 
 985. The number of substances which compose the cal- 
 culi and concretions of animals is not considerable ; the 
 most frequent are: — 
 
 Uric acid and the urates. Calcic oxalate. 
 
 Xanthine. Calcic carbonate. 
 
 Cystine. Magnesic carbonate. 
 
 Amnionic hippurate. Cholesterin (with other 
 
 Calcic phosphate. fatty matters). 
 
 Magnesic amnionic phos- Coloring matter of the bile, 
 
 phate. Fibrine. 
 
 986. The preceding substances are accompanied by the 
 following bodies : — 
 
 The acids of the bile. Extractive matters. 
 
 Albumen. Soluble salts. 
 
 Mucus. 
 
 987. The manner in which calculi comport themselves 
 when calcined upon platinum foil by the aid of heat, permits 
 of their division into many groups: — - 
 
 Calculi which do not leave a fixed residue. 
 
 988. Calculi entirely combustible. — They can be formed 
 of uric acid, of amnionic urate, amnionic hippurate, of 
 xanthine, of cystine, of cholesterin, of the coloring matter 
 of the bile, of fibrine, or of albumen. 
 
 Calculi which leave a fixed residue. 
 
 A. Calculi partially combustible. — They can contain 
 sodic urate, calcic urate, and all the organic matters quoted 
 in combination with mineral substances. 
 
 B. Calculi entirely fixed.— They cannot contain any 
 organic matter, 
 
 27* 
 
31$ 
 
 THE QUALITATIVE ANALYSIS 
 
 989. Calculi which do not leave a fixed residue. — 
 "We treat a portion of this material with concentrated HN0 4 , 
 we evaporate to dryness, and we moisten the residue with a 
 drop of ammonia. 
 
 990. It is colored purple-red (611) :— 
 
 We pour upon the calculus a solution of KHO, no 1 
 disengagement of ammonia. J 
 
 In contact with the KHO solution ammonia is 1 
 disengaged. / 
 
 991. It is not colored purple-red : — 
 
 The HN0 3 solution becomes yellow during the eva- \ 
 poration ; the residue is insoluble in K s C0 3 . / 
 
 The HN0 3 solution is colored dark brown by the "| 
 evaporation; the residue dissolves in NH 4 HO, and ' 
 
 Uric Acid. 
 
 Ammonic 
 Ubite. 
 
 Xanthine. 
 
 deposits from this solution under the form of micro- 
 scopic hexagonal tables. 
 
 Cystine. 
 
 J 
 
 Cholestebin. 
 
 Fl BRINK. 
 
 992. The calculus is heated upon platinum foil ; it takes 
 fire and burns with a very clear white flame ; it cannot 
 consist of cholesterin or of fibriue. 
 
 The calculus possesses evidently a crystalline tex- "| 
 ture, it dissolves in boiling alcohol, and is deposited [_ 
 as the solution cools under the form of shining | 
 spangles ; it is insoluble in KHO. 
 
 The calculus during the combustion develops the 1 
 odor of burnt horn and becomes swollen ; it dissolves j 
 in KHO, from which acetic acid precipitates it ; the ! 
 precipitate dissolves in an excess of acetic acid, j 
 gives a solution which yields a precipitate with po- j 
 tassic ferrocyanide. 
 
 993. The calculus possesses a brown color; it is friable, 
 ochreous, and disengages the odor of calcined animal 
 matter in burning. 
 
 It is little soluble in alcohol and water, it dissolves 1 
 in KHO which it colors dark brown; HN0 3 produces, I 
 in this solution, change of coloration characteristic j 
 of the coloring matter of the bile (933). j 
 
 It is soluble in alcohol ; the solution possesses a \ 
 bitter taste ; with U a S0 4 and sugar it takes a beau- I 
 
 Coloring 
 
 Matter ok the 
 
 Bile. 
 
 Acins of the 
 Bile. 
 
 tiful reddish-violet oolor (939). 
 
 994. Calculi which leave a fixed residue Two cases 
 
 can present themselves : — 
 
 A. The matter does not give, with IIXO a and XH HO, the 
 reaction of uric aojd. (See par. 617.) 
 
0E URINARY CALCULI. 
 
 319 
 
 a. The residue from the calcination melts easily by heat. 
 
 The calculus does not effervesce with acids either 
 before or after the calcination ; it dissolves in HCI, 
 NH 4 HO precipitates it from this solution; 
 (N1I 4 ) 2 C 2 4 also precipitates it; heated with the 
 blowpipe flame, moistened with a solution of cobaltic 
 nitrate and again heated, it furnishes a blackish- 
 brown enamel. (See par. 198.) 
 
 During the calcination the calculus disengages an 
 ammonic odor; it dissolves without effervescence in 
 acetic acid; NH 4 HO forms in this solution a crystal- 
 line precipitate. Heated with the blowpipe flame 
 along with a solution of cobaltic nitrate, it furnishes 
 a dark-red glass. (See par. 198.) 
 
 b. The residue from the calcination does not melt on being 
 heated. 
 
 Calcic 
 Phosphate.* 
 
 Magnesic 
 
 Ammonic 
 
 Phosphate. 
 
 Calcic 
 Phosphate. 
 
 Calcic 
 Oxalate. 
 
 Calcic 
 Cakbonate. 
 
 The residue is white and does not turn red litmus 
 blue ; it gives the reactions of calcic phosphate (par. 
 188). 
 
 The original matter is not attacked by acetic acid ; 
 the mineral acids dissolve it without effervescence, 
 and NH 4 HO precipitates it from this solution ; after 
 calcination the residue possesses an alkaline reaction, j" 
 and the acids then dissolve it with effervescence. (See \ 
 par. 189.) J 
 
 When heated by the blowpipe flame the calculus "| 
 becomes luminous ; before calcination the acids dis- j 
 6olve it with effervescence ; after the acid solution }- 
 has been neutralized with NH HO it gives a white j 
 precipitate with ammonic oxalate. 
 
 B. The matter gives with HN0 3 and NH,HO, the reaction 
 peculiar to uric acids. (See par. 617.) 
 
 a. It melts on being heated : — 
 
 It communicates an intense yellow coloration to 
 the flame. 
 
 It does not color the flame yellow, but violet. (See 
 par. 46.) 
 
 b. It does not melt on being heated : — 
 
 The residue after calcination comports itself as 
 calcic carbonate. 
 
 Sodic Ukate. 
 
 Potassic 
 Ukate. 
 
 Calcic Ukate. 
 
 * Calcic phosphate, although infusible itself, becomes fusible if mixed 
 with magnesic ammonic phosphate ; the calculus produced by the mixture 
 of these two phosphates is named, from its easy fusibility, the fusible 
 calculus. 
 
320 PROPERTIES OF ALBUMINOID GROUP. 
 
 The residue after calcination dissolves with a slight , 
 effervescence in dilute H 2 S0 4 ; the solution neu- ! Magnesic 
 tralized by NH 4 HO gives with sodichydric phosphate { Ueate. 
 
 a white precipitate. J 
 
 995. When the nature of the calculus has been deter- 
 mined, it is always necessary to control the results by special 
 reactions. 
 
 VEGETABLE CHEMISTRY. 
 
 996. We have given the properties and reactions of the 
 chief members in the three following groups : Albuminoid 
 group ; the saccharine or amylaceous group, and the group 
 of the vegetable bases. 
 
 The albuminoid group. 
 Albumen, Fibrin, Casein. 
 
 997. Vegetable Albumen This substance exists in the 
 
 juice of most vegetables, and in the solid form in certain 
 parts of the plant, especially in the seed. It exhibits the 
 reactions, and appears to have the same composition, as 
 animal albumen (794). " The mode of its occurrence dingers, 
 however, remarkably from that of animal albumen in this 
 respect, that it is always found iu plants in neutral or acid 
 liquids, whereas animal albumen exists only in alkaline 
 liquids." 
 
 998. Vegetable fibrine, gluten. — This substance is also 
 found in the juices of all nutritious vegetables. When the 
 newly expressed juice is allowed to stand for a few minutes, 
 the fibrine it contains separates in a coagulated state, more 
 or less impure. The juice of grasses is especially rich in 
 this constituent, but it is most abundant in the seeds of 
 wheat and other corn plants. It may be obtained from 
 wheat flour by a mechanical operation, and in a state of 
 tolerable purity ; it is then called gluten. It is a soft, 
 glutinous, and elastic substance, which can be drawn out 
 into long strings ; it has scarcely any color, taste, or smell. 
 
 999. It exhibits the same reactions, and has the same 
 composition, as animal fibrine (821). 
 
 1000. Vcgatable casein, legumine — This substance is 
 found chiefly in the seeds of peas, beans, and similar 
 leguminous seeds ; hence it is frequently called legumine. 
 Its composition has not been well determined, but Liebig 
 
THE PROPERTIES OP CELLULOSE. 321 
 
 considers it to be identical with the caseine of milk, which 
 it resembles it its reactions (828). 
 
 THE SACCHARINE OR AMYLACEOUS GROUP. 
 
 1001. The substances forming this group are numerous ; 
 they contain, with a few exceptions, oxygen and hydrogen, 
 in the proportion to form water. The sugars and gums are 
 the only members of the group which are soluble in cold 
 water ; starch and other similar bodies are insoluble in cold, 
 but soluble in hot water; whilst cellulose is quite insoluble 
 in water, whether hot or cold. 
 
 1002. We may here observe that there are three leading 
 varieties of sugar — cane-sugar (sucrose), grape-sugar 
 (glucose), milk-sugar (lactose), and some chemists add a 
 fourth, fruit-sugar or fructose; other chemists consider it 
 to be merely grape-sugar. 
 
 1003. AVe have restricted our notice of this group to the 
 following members : cellulose, starch, gum, dextrine 
 cane- and grape-sugars. 
 
 Cellulose (Lignin, woody fibre, C„H ]0 O 6 ). 
 
 1004. Cellulose forms the framework of all plants ; its 
 composition and reactions are always the same, but the 
 properties which depend upon its state of aggregation 
 present the greatest differences, as its texture varies with 
 the plant from which it is extracted. Cotton, linen, hemp, 
 and unsized white paper, consist of cellulose very nearly 
 pure. "The easiest method of obtaining pure cellulose, is 
 to wash white cotton, unsized paper, old linen, or elder- 
 pith with a hot solution of KHO or NaHO, then with cold 
 dilute HCI, then with NH 4 HO, washing thoroughly with 
 water after the application of each of these reagents, and 
 lastlj', with alcohol and ether ; it is often necessary to 
 repeat this series of operations two or three times. To 
 obtain pure cellulose from wood it is necessary, after boil- 
 ing the wood with KHO till the liquid is almost dry, to treat 
 it with chlorine water, or with a weak solution of chloride 
 of lime, repeating these successive operations several times, 
 in order to free the cellular tissue from the encrusting 
 matter which is so intimately united with it. 
 
 1005. " Cellulose thus purified is white, translucent, of 
 specific gravity about 1.5, insoluble in water, alcohol, ether, 
 
322 THE PROPERTIES OP E L L TJ L SE . 
 
 and oils, both fixed and volatile. When quite pure it is 
 unalterable in the air, but as it exists in wood, in contact 
 ■with azotized and other easily alterable matters, it gradually 
 decomposes in moist air, undergoing a slow combustion, 
 and being converted into a yellow or brown friable substance 
 called touchwood." 
 
 1006. Dilute acids do not act on cellulose. 
 
 1007. Gold concentrated H 2 SO t disintegrates it and con- 
 verts it into dextrine, a substance isomeric with cellulose, 
 without blackening; if water be then added, and the liquid 
 be subsequently boiled, the dextrine is converted into 
 glucose. 
 
 1008. By immersion iu strong HN0 3 , or in a mixture of 
 HN0 3 and H.SO,, or of KN0 3 and H 2 S0 4 , cellulose is con- 
 verted, without dissolving or undergoing any alteration of 
 form, into a mixture of several explosive nitrogenous com- 
 pounds, called gun-cotton, or pyroxylin. More dilute HXO a 
 converts it into substances allied to or identical with starch, 
 gum, lactic acid, and malic acid ; and if it is boiled with the 
 acid for a length of time it is dissolved with complete 
 decomposition. 
 
 1009. By immersion for a few seconds in HNO s of ordi- 
 nary strength hemp appears pale yellow, flax remains unal- 
 tered in color. New Zealand hemp (Phormium tenax) im- 
 mediately becomes blood-red; the latter coloration is pro- 
 duced, even after bleaching, or after the fibre has been 
 treated with a solution of KHO. This reaction may there- 
 fore serve for the detection of New Zealand hemp fibre in 
 fabrics. The fibres of several plants are colored pale-red 
 by the acid. The coloring is due to the incrusting sub- 
 stances. Cotton is scarcely or not at all colored by HNO a , 
 whereas animal fibres are colored permanently yellow. This 
 reaction may serve for the detection of cotton -in wollen 
 textures. 
 
 1010. Unsized paper, if immersed for half a minute in a 
 mixture of ^ to £ volume of water and 1 volume of H 2 S0 4 , 
 of ordinary strength, and immediately washed first with pure 
 water, and then with water slightly ammoniacal, is changed 
 into a substance called vegetable parchment. This sub- 
 stance can be formed from cotton as well as from flax fibres. 
 
 1011. The property of linen-fibre to acquire a deep yellow 
 color by boiling with a mixture of equal quantities of water 
 and KHO, whereas cotton is little or not at all colored by 
 it, is applied by Bottgerto the detection of linen in cotton. 
 
 1012. Alkaline liquids when dilute do not act upon cellu- 
 
THE PROPERTIES OF STAROH. 323 
 
 lose, but when concentrated they gradually destroy its 
 texture. 
 
 1013. " Cellulose, in its natural state, is not colored blue 
 by iodine; but after it has been digested for a short time 
 with H 2 SO„ it becomes of a flue blue when free iodine is 
 added. This reaction is sometimes serviceable in the mi- 
 croscopic examination of vegetable tissues ; cellulose being 
 thus easily distinguished from tissues into the composition 
 of which nitrogen enters. By the prolonged action of H 2 S0 4 , 
 the property of being colored blue by iodine disappears, the 
 dextrine and sugar which are formed not being susceptible 
 of the blue coloration." 
 
 1014. Cellulose dissolves completely in an ammonic solu- 
 tion of CuO,* forming a syrupy liquid, which may be filtered 
 after dilution with an equal bulk of water. It is precipi- 
 tated from this solution in flakes on the addition of HC1. 
 
 Starch (Amylum, Fecula, C 6 H I0 O 5 ). 
 
 1015. This substance is deposited in grains in the cellular 
 tissue of certain parts of plants. The form and dimension 
 of the starch grains are tolerably uniform in the same plant, 
 but are very variable in different species of plants. 
 
 1016. It is insoluble in alcohol, elher, and cold water, but 
 when a mixture of starch and water is heated to near the 
 boiling point, the granules burst and disappear, forming a 
 gelatinous mass. If this paste be largely diluted with 
 water, the swollen granules of the starch subside, whilst a 
 certain quantit}^ of amylaceous matter remains in solution. 
 
 1017. When dry starch is heated to about 205° C, it is 
 converted into a substance isomeric with starch, called dex- 
 trine or British gum. This substance is soluble in cold 
 water, forming a ropy solution much resembling gum in 
 properties; but it differs from gum in forming a deep blue 
 liquor in a solution of CuSO^, which deposits Cu 2 when 
 cold. It is rendered red and not blue with iodine. It has 
 been called dextrine from its turning the plane of polariza- 
 tion to the right, when acting on polarized light. 
 
 1018. Dilute alkalies and acids in the cold cause starch 
 to swell up and become partially disintegrated, but if the 
 solution is heated it is converted into dextrine. 
 
 1019. An aqueous solution of iodine forms with starch 
 a characteristic blue color ; this color disappears if the 
 
 * Prepared by dissolving CuO ia ammonia. 
 
324 THE PROPERTIES OF GUM. 
 
 iodine be added in excess, or if the solution be heated, but 
 in the latter case, the blue color returns as the liquid cools. 
 Decoloration of iodide of starch or its aqueous solution is 
 produced by all reagents which cause the iodine to enter 
 into combination, especially by chlorine, the color being 
 restored by Zn and H 2 S0 4 ; HN0 3 which converts iodine 
 into iodic acid and destroys the starch ; SO.^, H a S, As0 3 , 
 NH 4 HO, and KHO, the blue color when destroyed by the 
 alkalies being restored bj' acids. Iodide of starch is like- 
 wise decolorized by SbCl 3 , AsCl 3 , AuCl,, ferrous, manga- 
 nous, stannous, mercurous, mercuric and argentic salts. 
 Slightly blued starch is decolorized by fixed oils. Alcohol 
 and ether abstract part of the iodine from iodide of starch. 
 Infusion of galls decolorizes iodide of starch ; hence cer- 
 tain roots containing both starch and tannin are not ren- 
 dered blue by iodine till after the addition of HX0 3 . De- 
 coloration is also produced by pyrogallic acid, by wood 
 vinegar, by urine, and by tobacco vapor after the compound 
 has been moistened with HA. In presence of saliva, blood- 
 serum, and other substances it is not produced until the 
 liquid containing the starch has been mixed with 1-2 drops 
 of tincture of iodine, then with a few drops of a solution of 
 KHO, and lastly supersaturated with HNO s . 
 
 Gum (C lt H a O u ). 
 
 1020. This substance is found in the juices of almost all 
 plants, but is met with in its purest form in transparent 
 tears, which exude from various species of acacia. Gum- 
 arabic may be taken as its type. 
 
 1021. The gums proper are soluble in cold water or hot; 
 but mucilage or bassorin, a modification of gum, is insolu- 
 ble in water, but when moistened with it, swells up into a 
 gelatinous mass. Gum-arabic dried at 120° becomes in- 
 soluble in water. The gum of seeds and roots or mucilage, 
 which appears to be a universally diffused constituent of 
 plants, is soluble in cold water, but is insoluble in alcohol 
 and is precipitated from its aqueous solution by tincture of 
 galls. Neutral lead acetate does not precipitate it com- 
 pletely, but the basic acetate produces complete precipita- 
 tion. 
 
 1022. Alcohol and ether precipitate gum from its solution 
 in water, in the form of white flocculi, or if dilute, in the 
 form of a milky turbidity. 
 
THE PROPERTIES OF CANE-SUGAR. 325 
 
 1023. Solution of KHO coagulates a solution of gum; 
 but an excess of the reagent renders the liquid limpid. 
 
 1024. Concentrated HX0 3 converts gum into mucic and 
 oxalic acids. 
 
 1025. If it is boiled with dilute H,S0 4 it is transformed 
 first into dextrin and then into glucose. 
 
 1026. If a few drops of CuSO + be added to a solution of 
 gum mixed with KHO, a blue precipitate is produced, which 
 is insoluble in the liquid, but which is soluble in pure water, 
 this solution can be boiled without depositing Cu.,0. This 
 character distinguishes natural gum from dextrine (British 
 gum) (1017). 
 
 Cane-sugar or Sucrose (C 12 H. 22 O u ). 
 
 1021. This variety of sugar is widely spread in the vege- 
 table kingdom ; it has been called cane-sugar because it is 
 obtained chiefly from the sugar-cane. It has a specific 
 gravity of 1.6. It is soluble in about one-third of its weight 
 of cold, and is much more soluble in boiling water ; its 
 solution has, as is well known, a sweet taste. Absolute 
 alcohol dissolves about l-80th of this sugar at its boiling 
 point, nearly the whole of which separates in small crystals 
 on cooling. It is more soluble in ordinary alcohol. It 
 slowly separates from a strong watery solution in large, 
 transparent, colorless crystals, having the figure of a modi- 
 fied oblique rhombic prism ; if a solution of it is kept at a 
 temperature near the boiling point it gradually loses the 
 property of crystallizing. It melts, about 160° C, into a 
 viscous colorless mass, which, on cooling, forms the solid 
 known as barley sugar ; if long kept this amorphous form 
 cane-sugar gradually loses its transparency, and becomes 
 crystallized. If, after the sugar has melted, the applica- 
 tion of heat be continued, until the temperature reaches 204° 
 or 215° C. the sugar loses an equivalent of water, and a 
 brown, deliquescent, slightly bitter and unfermentiscible 
 substance called caramel remains, which is used as a color- 
 ing matter by cooks and confectioners. If the heat is con- 
 tinued beyond 215° C, complete decomposition ensues, in- 
 flammable gases are given off and a brilliant mass of porous 
 charcoal remains. 
 
 1028. Cane-sugar is not rendered brown as grape-sugar 
 is (879) on boiling it in a solution of KHO. 
 
 1029. " Concentrated H 2 S0 4 acts very energetically upon 
 cane-sugar, evolving water, carbonic and formic acids and 
 
 28 
 
326 EXERCISES. 
 
 charcoal. It is a striking experiment to mix about equal 
 bulks of H 2 S0 4 and strong syrup; the mixture, when 
 stirred, becomes brown and black, then suddenly heats, 
 boils up, and passes into the state of a bulky black 
 magma:* the acid appears suddenly to abstract the ele- 
 ments of water from the sugar, leaving charcoal." The 
 action of H 2 S0 4 upon grape-sugar is, as we have already 
 noticed (877), very different. 
 
 1030. Strong HN0 3 converts cane and grape-sugar into 
 oxalic acid. 
 
 1031. When cane-sugar is boiled with dilute HC1 or 
 H 2 S0 4 it assimilates water and becomes converted into 
 grape-sugar. Yeast effects the same change in its solu- 
 tions. The converse change, that of converting grape- 
 sugar into cane, has not yet been accomplished. 
 
 1032. A sugar solution has the property of dissolving 
 many basic oxides, baryta and lime are very soluble in 
 cold sugar solutions ; when the solution of the alkaline 
 earth is heated it becomes opaque, and when the solution 
 reaches the boiling point the compound of sugar and the 
 alkaline earth is deposited. 
 
 1033. If to a solution of cane-sugar a solution of caustic 
 potash is added, and then a drop or two of a dilute solu- 
 tion of sulphate of copper, a deep blue liquid is obtained, 
 which retains its blue lint, on being heated. This is a very 
 good test for distinguishing the two varieties of sugar, or 
 discovering an admixture of grape with cane-sugar. (See 
 par. 880.) 
 
 1034. The properties of grape-sugar have already been 
 described under animal chemistry, par. 876. 
 
 1035. Answers to the following exercises must be written 
 out : — 
 
 EXERCISES. 
 
 180. State the method of examining a blood stain on 
 linen, and the tests by which it is distinguished. 
 
 181. State the composition and principal properties of 
 cellulose, describing particularly the action of strong HX0 3 
 upon it. 
 
 182. How would you separate hippuricacid from human 
 urine and exhibit its characteristic properties ? 
 
 * (Vine su^nr lias been given ns n test for free sulphuric neid in the 
 presence of a sulphate, (Soe par. 407.) 
 
ORGANIC BASES. 327 
 
 183. Name the organic bodies usually present in urine, 
 and give the methods for detecting them. 
 
 184. How would you distinguish amnionic urate from 
 magnesic amnionic phosphate? 
 
 185. Give the composition of starch and the different 
 kinds of sugar, and name some of their characteristic 
 properties. 
 
 186. A deposit in urine is supposed to be uric acid. 
 How would you ascertain whether such is the case? 
 
 187. How may urea be extracted from urine? 
 
 188. What are the tests for gelatine? 
 
 189. A deposit from urine is given you for chemical 
 examination; what substances would you search for, and 
 how would you conduct the examination? 
 
 190. What is the action of KHO on cupric salts, and 
 how is this action modified in the presence of sugar ? 
 
 191. What are the distinctive properties of the uric acid, 
 xanthic acid, and cystic oxide calculi? 
 
 192. How would you analyze qualitatively a calculus 
 composed of calcic phosphate and magnesic amnionic phos- 
 phate ? 
 
 193. How is a solution of gelatine obtained, and how 
 does it differ from one of albumen ? 
 
 194. Enumerate the different varieties of urinary calculi, 
 and explain how they ma}- be distinguished ? 
 
 195. Why does urine become ammoniacal? 
 
 196. Describe the properties of albumen and fibrine. 
 
 197. Uric acid may exist as a urinary sediment in one 
 or other of three states. What are these, and how may 
 they be distinguished from each other ? 
 
 ORGANIC BASES AND MECONIC ACID. 
 
 1036. In this section the properties and reactions of the 
 most important of the medicinal alkaloids and meconic 
 acid, with reagents, are given, and the mode of extracting 
 them in a state of purity from complicated mixtures of 
 animal and vegetable substances ; together with the more 
 general methods of Stas and others, for the detection of 
 poisonous alkaloids in organic mixtures. 
 
328 the properties of nicotine. 
 
 Volatile Alkaloid. 
 Nicotina or Nicotine (C 10 H u N 2 ). 
 
 1037. This alkaloid is contained in tobacco, probably in 
 the state of malate and citrate ; in its pure state it is a 
 limpid, colorless, oily liquid ; it absorbs oxygen on ex- 
 posure to air, and turns brown and finally becomes solid. 
 It has a strong and irritating odor of tobacco ; is very 
 inflammable, and burns with a smoky flame. It is miscible 
 in all proportions with water, alcohol, and ether. It boils 
 at 250° C, suffering, however, partial decomposition in the 
 process ; but when heated in a stream of hydrogen gas, it 
 distils over unaltered, between 100° and 200° C. Its solu- 
 tions possess an alkaline reaction. It precipitates metallic 
 oxides from solutions of their salts, and unites with the 
 acids, forming salts. 
 
 1038. Salts of nicotine are in general very soluble in 
 water and alcohol, but insoluble in ether ; they are diffi- 
 cultly crystallizable and even deliquescent. 
 
 1039. If an aqueous solution of nicotine, or a solution of 
 a salt of nicotine mixed with a solution of NaHO or KHO, 
 is shaken with ether, the nicotine is dissolved by the ether; 
 if the latter is then allowed to evaporate on a watch-glass, 
 the nicotine remains behind in drops and streaks; on 
 warming the watch-glass, it volatilizes in white fumes of 
 strong odor. 
 
 . 1040. Chlorine-gas acts powerfnlly upon nicotine, pro- 
 ducing with it a blood-red liquid. 
 
 1041. Solution of I in KI and water, when added in 
 small qiiantit}^ to an aqueous solution of nicotine, produces 
 a yellow precipitate, which after a time disappears. Upon 
 a further addition of the iodine solution, a copious kermes- 
 colored precipitate separates ; but this also disappears again 
 after a time. 
 
 1042. When a glass rod moistened with HC1 is brought 
 into contact with vapor of nicotine, white fumes are pro- 
 duced, as with ammonia. Boiled with HC1, the nicotine 
 is colored violet. 
 
 1043. When IIN0 3 is heated with nicotine a red liquor 
 is produced. 
 
 1044. l'tCl 4 produces in aqueous solutions of the chloride 
 of nicotine a yellow crystalline precipitate of chloro-plati- 
 nate of nicotine, which is insoluble in alcohol and ether, 
 
THE PROPERTIES OP MORPHINE. 329 
 
 slightly soluble in cold water, readily soluble in an excess 
 of nicotine, and soluble in HC1 in the cold. 
 
 1045. AuClj produces a reddish-yellow flocculent precipi- 
 tate, sparingly soluble in HC1. 
 
 1046. "If an aqueous solution of nicotine is added to a 
 solution of HgCl 2 in excess, an abundant, flocculent, white 
 precipitate is formed. If solution of NH 4 C1 is now added 
 to the mixture in sufficient quantity, the entire precipitate, 
 or the greater part of it, redissolves. But the fluid very 
 soon turns turbid, and deposits a heavy white precipitate. 
 
 1047. " Solution of tannic acid, produces a copious white 
 precipitate, which redissolves upon addition of HC1." 
 
 1048. Nicotine is extremely poisonous, a single drop of 
 it being sufficient to kill a large dog. 
 
 1049. To extract nicotine from the animal tissues or the 
 contents of the stomach, the animal matter is treated with 
 a solution of KHO and then treated repeatedly with ether 
 or pure benzole. The benzole or ether solution is evapo- 
 rated at a gentle heat in a retort, the nicotine remains be- 
 hind in an impure state. It is then treated with H 2 SO„ 
 the solution, if necessary, filtered, and then treated with 
 solution of KHO and ether or benzole as in the first 
 instance. Nicotine may also be isolated from foreign or- 
 ganic matter by repeatedly exhausting the stomach, etc., 
 with dilute acid, the acid solution is filtered and evaporated 
 to dryness on the water bath ; it is then redissolved in 
 water and treated with KHO and ether in the manner 
 previously described. 
 
 1050. The volatility and odor of nicotine are its most 
 characteristic distinctions. 
 
 NON-VOLATILE ALKALOIDS. 
 
 1051. The non-volatile alkaloids are solid, and cannot 
 be distilled over with water. 
 
 Morphia or Morphine (C^H^NO,). 
 
 1052. This alkaloid is contained in opium associated 
 with narcotine and several other organic bases (see par. 
 1071). When crystallized from alcohol it forms small but 
 very brilliant prismatic crystals, which are transparent 
 and colorless; it crystallizes with an equivalent of water ; 
 at a gentle heat the water is expelled and the morphine 
 
 28* 
 
330 THE PROPERTIES OP MORPHINE. 
 
 melts and forms a tumid resinous mass which solidifies 
 into a radiated crystalline mass. When it is obtained by 
 precipitation it appears as a white crystalline mass. It is 
 soluble in about 1000 times its weight of cold and in 400 
 of boiling water; the solution has a bitter taste. It is 
 soluble in about 90 times its weight of cold, and from 20 
 to 30 parts of boiling alcohol. Its aqueous and alcoholic 
 solutions manifest distinctly alkaline reactions. It dis- 
 solves in amyl-alcohol in the cold but more freely with 
 the aid of heat ; it is soluble in acetic ether. It dissolves 
 according to Schlimpert in 60 parts and according to Pet- 
 tenkofer in 175 parts of chloroform. Its solubility in ether 
 varies according to its physical condition, recently pre- 
 cipitated morphia dissolves in ether about three times as 
 largely as the crystallized base ; therefore, if a solution of 
 a morphine salt has been neutralized with one of the fixed 
 alkaline carbonates or acid carbonates ether dissolves the 
 precipitated morphine if the ether is shaken up with the 
 liquid at once, but not after some time, or at least to a 
 very slight extent, as the precipitated base in time becomes 
 crystalline, and in that condition is nearly insoluble in 
 ether. Ether containing alcohol dissolves morphine. 
 
 1053. Acids dissolve morphine, forming with it salts 
 which are most of them crystallizable. They are readily 
 soluble in water and alcohol, but insoluble in ether. Its 
 salts are exceedingly bitter to the taste. 
 
 1054. The fixed alkalies and ammonia precipitate mor- 
 phine from the solution of its salts, an excess of the 
 precipitant redissolves the precipitate. The precipitated 
 morphine redissolves with great readiness in the fixed 
 alkalies, but much less readily in ammonia. Lime-water 
 behaves like the fixed alkalies. 
 
 1055. The fixed alkaline carbonates precipitate morphine 
 from the solution of its salts, and it does not redissolve in 
 an excess of the precipitant. The fixed alkaline acid car- 
 bonates also precipitate it, and an excess does not redis- 
 solve the precipitate; these reagents fail to precipitate 
 morphine from acid solutions in the cold. 
 
 1056. Precipitated morphine dissolves in NH,C1, and 
 with difficulty in (NH 4 ) s CO a . 
 
 1051- If a neutral and concentrated solution of a ferric 
 snlt bo added to neutral and concentrated solutions of 
 salts of morphine, a beautiful dark blue color is produced, 
 which is characteristic of morphine. The color is not per- 
 manent, and it is destroyed by an excess of acid, by the 
 
THE PROPERTIES OP MORPHINE. 33l 
 
 action of heat, and even by the addition of alcohol. If the 
 solution contains an admixture of animal or vegetable 
 extractive matters or of acetates, the color will appear 
 clouded or less distinct. 
 
 1058. Concentrated HN0 3 colors morphine or its salts in 
 the solid state, and also their concentrated solutions orange 
 red, which passes by degrees to yellow ; this coloration is 
 not peculiar to morphine. 
 
 1059. Iodic acid is reduced by morphine either free or 
 combined, the liquid turning brown and emitting an odor 
 of iodine. When solid morphine or a morphine salt is 
 moistened with a solution of 1 part of iodic acid in 15 
 parts of water, and a solution of 1 part of starch in 400 
 parts of water is added, a blue color is produced, by which 
 sxmth of a grain ma}' be detected : if a drop of the starch 
 solution be previously evaporated with the morphine, tho 
 reaction will suffice for the detection of i-^.^^th of a grain. 
 If a layer of very dilute ammonia be poured upon -a solu- 
 tion of morphine mixed with iodic acid and starch, then, 
 even if only jTr.Trinjth °f morphine is present, two colored 
 rings will be formed at the surface of contact, the upper 
 being blue, the lower brown ; in more dilute solutions only 
 the brown ring is produced. Other substances capable of 
 reducing iodic acid may likewise produce the blue ring, but 
 not the brown ring at the same time (A. Dupre). 
 
 1060. Dissolve morphine in strong H 2 S0 4 in the propor- 
 tion of 0.002 to 0.004 grain to 6 or 8 drops of the acid, 
 then add a^ drop of HN0 3 ; whereupon, if the morphine 
 solution has been recently prepared, a rose-color is pro- 
 duced, changing after a few seconds to yelloiv, then to 
 greenish, and finally to brown. If a small quantity of 
 water be added to the solution of morphine in H 2 S0 4 , so 
 that the mixture becomes hot, the coloring produced by 
 the subsequent addition of HNO s is of a much deeper 
 carmine red, and much more durable. If the sulphuric 
 solution is heated for a few minutes to 100°-150°, the 
 addition of a drop of nitric acid produces, after cooling, a 
 splendid deep violet color, which gradually disappears from 
 the centre outwards, passing through blood-red. If the 
 temperature is raised above 150° the liquid acquires of 
 itself, at a certain moment, a violet-rose color; at still 
 higher temperatures, a dirty green color is produced. On 
 adding a drop of HN0 3 , after cooling, the liquid imme- 
 diately turns red, without passing through violet. A 
 solution of morphine in H 2 S0 4 , left to itself for twelve to 
 
332 THE PROPERTIES OP NARCOTINE. 
 
 twenty-four hours at ordinary temperatures, behaves as if 
 it had been heated to 100°-150° ; as regards the sensibility 
 of these reactions J of a milligramme of morphine is suffi- 
 cient to produce a very bright carmine color; ^ of a 
 milligramme gives a very distinct reaction, and T ^ 5 milli- 
 gramme still gives a perceptible tint after half a minute — 
 Husemann. 
 
 1061. A solution of morphine in H 2 S0 4 , previously heated, 
 is colored deep red by ferric chloride, the color changing 
 after a time to dirty green. 
 
 1062. To detect morphine when mixed with animal matter, 
 the substance is mixed with alumina, dried between 100° 
 and 110°, then well pulverized and macerated in cold water 
 acidulated with acetic acid. The solution treated with 
 ammonia deposits morphine, which may then be recognized 
 by its reactions with iodic acid, ferric salts, H 3 SO., and 
 HN0 3 . 
 
 Narcotina or Narcotine (C^HjjNO,). 
 
 1063. Narcotine appears in the form of acidular groups, 
 or in colorless, brilliant, right rhombic prisms, or when 
 precipitated by the alkalies, as a white, loose, crystalline 
 powder. It fuses at 111 C, solidifies again at 130° C. in 
 the cr3 T stalline or amorphous state, according as the cooling 
 is slow or rapid. It is insoluble in cold water, but dis- 
 solves in boiling water to the extent of 1 part in 7000. 
 It dissolves sparingly in alcohol and ether in the cold, but 
 somewhat more readily upon heating. Solid narcotine is 
 tasteless, but the alcoholic and etherial solutions are in- 
 tensely bitter. It dissolves in 2.6 parts of chloroform, in 
 60 parts of acetic ether, also in oils, both fixed and volatile. 
 Its solutions do not possess an alkaline reaction. 
 
 1064. Narcotine dissolves readily in acids, forming with 
 them salts, but the basic powers of narcotine are so feeble 
 that its salts have invariabh' an acid reaction. "Those 
 with weak acids are decomposed by a large amount of 
 water, and, if the acid is volatile, even by simple evapora- 
 tion. Most of the naicotine salts are amorphous, and 
 soluble in water, alcohol, and ether; they have a bitter 
 taste." 
 
 1065. The alkalies, and the carbonates and acid carbon- 
 ates of the alkalies, precipitate narcotine immediate^' from 
 a solution of its salts, in the form of a white powder, which, 
 
THE PROPERTIES OP NARCOTINE. 333 
 
 seen through a lens magnifying 100 times, appears an aggre- 
 gate of small crystalline needles ; the precipitate is insoluble 
 in an excess of the precipitant. If a solution of narcotine 
 is mixed with ammonia, and ether added in sufficient 
 quantity, the narcotine which has separated upon the 
 addition of the ammonia redissolves in the ether, and the 
 clear fluid presents two distinct layers. If a drop of the 
 etherial solution is evaporated on a watch-glass, the residue 
 is seen, upon inspection through a lens magnifying a 
 hundred times, to consist of small, distinct, elongated, and 
 lance-shaped crystals. 
 
 1066. "Concentrated HN0 3 dissolves narcotine to a color- 
 less fluid, which acquires a pure yellow tint upon the appli- 
 cation of heat. 
 
 1067. "If the solution of a salt of narcotine is mixed 
 with chlorine-water, it acquires a yellow color, slightly 
 inclining to green ; if ammonia is then added, a much more 
 intensely colored yellowish-red fluid is obtained. 
 
 1068. "Narcotine added to cold H 2 S0 4 colors it bluish- 
 violet or yellow, which, if the liquid be gently heated, 
 changes to orange-red, then to violet-blue at the edge of 
 the dish, and lastly violet-red. This reaction is very dis- 
 tinct, if the H 2 S0 4 contains 1 part in 2000 of narcotine; 
 and even if it contains only 1 part in 40,000 a slight car- 
 mine color is still perceptible, passing into violet-red." — 
 Husemann. 
 
 1069. A solution of narcotine in cold H 2 SO t becomes 
 reddish-yellow on addition of HN0 3 ; with hypochlorite of 
 soda the same color is produced, but preceded by a carmine 
 tint. If the solution has been heated, both reagents imme- 
 diately produce a light yellow color, becoming slightly 
 reddish after a while. 
 
 1070. A solution of narcotine in H 2 S0 4 , previously heated, 
 acquires, on addition of ferric chloride, a dark red color, 
 changing into cherry-red, which lasts twenty-four hours. 
 
 1071. Opium contains, besides morphine and narcotine, 
 the following crystallizable alkaloids — codeine, thebaine, 
 narceine, and papaverine. The following table shows the 
 difference in the solubility of these alkalies in different 
 liquids : — 
 
334 
 
 THE PROPERTIES OP QUININE. 
 
 Water. 
 
 Alcohol. 
 
 Ether. 
 
 Potash. 
 
 Morphine 
 
 Narcotine . 
 Narceine 
 
 Codeine . , 
 
 Thebaine . 
 Papaverine 
 
 Slightly soluble 
 
 Almostinsoluble 
 Slightly soluble 
 
 Soluble 
 
 Insoluble 
 Insoluble 
 
 Easily soluble 
 
 Soluble 
 Soluble 
 
 Extremely solu- 
 ble 
 
 Soluble 
 
 Soluble 
 
 Almost insoluble 
 
 Soluble 
 Insoluble 
 
 Extremely solu- 
 ble 
 
 Soluble 
 
 Soluble 
 
 Soluble in an ex- 
 cess. 
 
 Insoluble. 
 
 Soluble in weak 
 potash. 
 
 Insoluble in con- 
 centrated pot- 
 ash. 
 
 Soluble in weak 
 potash. 
 
 Insoluble. 
 
 Quina or Quinine (C^HJ^Oj. 
 
 1072. This alkaloid exists in combination with kinic 
 acid in cinchona barks ; it forms two hydrates, containing 
 respectively 1 and 3 atoms of water ; the latter is the ordi- 
 nary hydrate. It appears either in the form of silky needles, 
 or as a loose white powder. It melts at 120° C, and gives 
 up its water of crystallization. It requires about 350 parts 
 of cold water and 200 of boiling water for its solution. It 
 is readily soluble in alcohol, both hot and cold ; it is less 
 soluble in ether ; it dissolves in 60 parts of the latter liquid. 
 It is also soluble in chloroform and the essential and fixed 
 oils. Its solutions have an alkaline reaction and are in- 
 tensely bitter. 
 
 lO^. Acids dissolve quinine, forming with it salts which 
 are crystallizable, and difficultly soluble in cold, but readily 
 soluble in hot water and in spirit of wine. The acid salts 
 dissolve very freely in water ; the solutions exhibit the 
 remarkable phenomenon of fluorescence or epipolic disper- 
 sion — a magnificent blue luminosity seen upon the surface 
 of the liquid when viewed in reflected light, and which is 
 owing to a change effected in the actinic rays by the dis- 
 solved quinine salt. The salts of this base are intensely 
 bitter. 
 
 1074. The fixed alkalies, ammonia, and the alkaline car- 
 bonates precipitate quinine as trihydrate from a solution 
 of its salts in an amorphous state, which after some time 
 becomes crystalline. The precipitate is only soluble in the 
 fixed alkalies to a barely perceptible extent"; but it is more 
 soluble in ammonia, in the solutions of the fixed alkaline 
 carbonates, it dissolves to about the same extent as in pure 
 water. 
 
 1075. " The addition of chlorine-water to the solution of 
 a salt of quinine fails to impart a color to the fluid, or at 
 
THE PROPERTIES OF QUININE. 335 
 
 least imparts to it only a very faint tint; but if ammonia 
 is now added, the fluid acquires an intense emerald-green 
 color ; by this reaction, especially by employing an etherial 
 solution, mere traces of quinine may be recognized; quini- 
 dine, however, exhibits the same reaction. If, after the 
 addition of the chlorine water, some solution of potassic 
 ferrocyanide is added, then a few drops of ammonia or 
 some other alkali, the fluid acquires a magnificent deep red 
 tint, which, however, speedily changes to a dirty brown. 
 This reaction is delicate and characteristic. Upon addi- 
 tion of an acid (acetic acid answers the purpose best) to 
 the red fluid, the color vanishes, but reappears afterwards 
 upon cautious addition of ammonia. 
 
 1076. As cinchonine and quinidine exist together with 
 quinine in cinchona-barks, their sulphates may occur as 
 impurities in sulphate of quinine ; they may be recognized 
 by the following quinine test of Liebig: 10 grains of the 
 sulphate to be tested are warmed with 10 drops of dilute 
 H 2 SOj, and 15 drops of water in a test tube, the solution 
 is allowed to cool, and then 60 drops of commercial ether 
 and 20 drops of ammonia-water are added, and the whole 
 is shaken and the tube stopped. If the quinine were free 
 from cinchonine, and did not contain more than 10 per 
 cent, of quinidine, the whole remains in solution ; but if 
 cinchonine were present, it is deposited as a white pul- 
 verulent layer between the ether and the water, as is also 
 the case with quinidine when present in large quantity. 
 Smaller portions of quinidine crystallize from the ether on 
 standing for a short time, and still smaller quantities when 
 ether saturated with quinidine is emplo3'ed in the first 
 instance. As it sometimes happens that the upper etherial 
 layer solidifies to a jelly, even with pure sulphate of qui- 
 nine, it is more convenient to employ ether containing 
 alcohol, or to take a somewhat larger proportion of ether 
 than is directed above. — Gmelin. 
 
 1077. Stoddart has proposed the following modification 
 of Liebig's process: Into a glass tube or bottle put 10 
 grains of the suspected salt, dissolve in 10 minims of dilute 
 HJSO, and 60 minims of distilled water; to this add 150 
 minims of pure ether, 3 minims of alcohol, and 40 minims 
 of a solution of soda (1 part of solid NaHO to 12 of water). 
 Agitate well and set aside for twelve hours, when, if the 
 slightest trace of quinidine or cinchonine be present, they 
 will be seen at the line of separation between the ether and 
 solution of Na 2 S0 4 . If only a small percentage of quini- 
 
336 THE PROPERTIES OP 
 
 dine be present, it will appear as an oily substratum appear- 
 ing under a lens as dust, from the minuteness of its parti- 
 cles. Cinchonine will appear more decidedly crystalline. 
 With a little practice the eye will easily distinguish which 
 of the alkaloids is deposited. 
 
 Cinchonine (C^B.^fi). 
 
 1078. This alkaloid exists together with quinine, in most 
 of the true cinchona barks ; it appears either in the form 
 of transparent brilliant, four-sided prisms, or fine, white, 
 crystalline needles, or, if precipitated from concentrated 
 solutions, as a loose white powder ; in its crystalline state 
 it is anhydrous. It is nearly insoluble in cold water, and 
 requires for solution 2500 parts of boiling water. It is less 
 soluble in alcohol than quinine and is more soluble in hot 
 than cold alcohol. The greater portion of the cinchonine 
 dissolved by hot alcohol, separates in a crystalline form 
 as the solution cools. It dissolves in 470 parts of boiling 
 ether and 23.2 parts of chloroform. Solutions of cinchonine 
 have an alkaline reaction and a bitter taste. It fuses at 
 165° C, to a colorless liquid which becomes a crystalline 
 mass on cooling. 
 
 1079. The acids dissolve cinchonine, forming with it 
 salts which are most of them crystallizable ; they are 
 soluble in water and alcohol, insoluble in ether. They are 
 exceedingly bitter to the taste. 
 
 1080. The fixed alkalies, ammonia, and the neutral alka- 
 line carbonates precipitate cinchonine from a solution of 
 its salts, in an amorphous state, an excess of the precipi- 
 tant does not redissolve the precipitate. 
 
 1081. "If the solution of a salt of cinchonine containing 
 only very little or no free acid, is mixed with potassic 
 ferrocyanide, a flocculent precipitate of ferrocyanide of 
 cinchonine is formed. If an excess of the precipitant is 
 added, and a gentle heat very slowly applied, the precipi- 
 tate dissolves, but separates again upon cooling, in brilliant 
 gold-yellow scales, or in long needles, often aggregated in 
 the shape of a fan. With the aid of the microscope, this 
 reaction is as delicate as it is characteristic." 
 
 Strychnine (C^H^N^O,). 
 
 1082. This alkaloid exists, together with brucine and 
 igasurine, in mix vomica, in St. Ignatius' beans, in the 
 strychnos colubrina, and several other varieties of strych- 
 
STRYCHNINE. 337 
 
 nos; it crystallizes from dilute alcohol, in 'white anhydrous 
 octohedra, or in square prisms, which do not fuse on the 
 application of heat ; when it is produced by precipitation 
 or rapid evaporation, it appears as a white powder. Cold 
 water does not dissolve more of it than y^^th of its weight, 
 and it is only slightly more soluble in hot water. It is 
 only sparingly soluble in dilute alcohol, and almost insolu- 
 ble in absolute alcohol and ether. It dissolves freely in 
 amyl-alcohol, and is soluble in chloroform and the essential 
 oils. It is very bitter to the taste ; even when its cold 
 aqueous solution is diluted with 100 times its weight of 
 water, it still possesses a distinctly bitter taste. 
 
 1083. Acids dissolve strychnine, forming with it salts, 
 most of which are ciystallizable ; they are soluble in water, 
 and are very bitter to the taste. 
 
 1084. The fixed alkalies and their carbonates precipitate 
 strychnine from solutions of its salts. The precipitate is 
 insoluble in an excess of these reagents ; and the strych- 
 nine is only precipitated after the lapse of some time from 
 dilute solutions. 
 
 1085. Ammonia precipitates strychnine from a solution 
 of its salts, but the precipitate is soluble in an excess of 
 the ammonia, from which solution the strychnine separates 
 after some time, in the form of needles ; the length of time 
 required for the separation depending upon the strength of 
 the solution. 
 
 1086. If strychnine is dissolved in a drop or two of pure 
 concentrated H 2 SO„ (the acid must be free from nitrous 
 acid), it forms a colorless solution, which yields colored 
 reactions with most oxidizing substances ; the oxidizing 
 substances are added in the solid form, and in small 
 quantities. The following reagents give the colorations 
 named, with the sulphuric solution of strychnine: a. Per- 
 oxide of lead gives a blue coloration, becoming violet, 
 then red, and finally, in a few hours, yellow, b. Acid 
 potassic chromate gives a fine violet coloration ; if the 
 quantity of strychnine present is large, the color is pale 
 blue. c. Potassic ferrocyanide yields a somewhat similar 
 reaction to b, but more permanent, d. Black oxide of man- 
 ganese affords a violet coloration, becoming dark red in 
 the course of an hour. The presence of santonin, or starch, 
 does not prevent the recognition of strychnine by acid 
 potassic chromate in the above solution ; sugar, quinine, 
 or morphine renders it indistinct, but does not affect the 
 reaction with peroxide of lead. The presence of thirty 
 
 29 
 
338 THE PROPERTIES OF STRYCHNINE. 
 
 parts of tartar emetic does not prevent the coloration with 
 acid potassic chromate, but sixty parts render it indistinct. 
 Very small quantities of animal or vegetable extractive 
 matters render the above reactions indistinct, where the 
 strychnine is present in minute traces only. It is, there- 
 fore, always advisable to free the strychnine first, as far as 
 practicable, from all foreign matters before proceeding to 
 try any of these color tests ; methods for freeing it from 
 organic matter are given in pars. 1089, 1090, and 1091. 
 These, and similar color experiments, ought to be per- 
 formed on a piece of white porcelain. 
 
 1087. Concentrated HNO, dissolves strychnine, forming 
 a solution colorless in the cold, but which becomes slightly 
 yellow on heating if the strychnine is pure.* If to this 
 solution a small quantity of peroxide of lead be added, the 
 same changes of color may be witnessed as in the preceding 
 experiment. 
 
 1088. " Strychnine is associated in nature with the next 
 base, brucine, which may be readily distinguished from it 
 by being soluble in absolute alcohol. The action, too, of 
 nitric acid upon the two bodies differs ; it dissolves brucine 
 and colors the solution intensely red ; when heated, this 
 color changes to yellow; and if SnCl, or (NH 4 ),S be then 
 added, the color again changes and becomes a most intense 
 violet." 
 
 1089. Detection of Strychnine in the presence of Animal 
 
 Matter The mixture to be examined, which, if solid, 
 
 should be cut into small pieces, must be digested in dilute 
 HC1 (one part of strong acid with ten parts of water) at a 
 temperature of 60° to 80° C. The liquid is strained and 
 the residue is again exhausted with hot water containing 
 HC1. The extracts are then mixed with a slight excess of 
 ammonia, and evaporated to dryness on the water-bath, 
 together with some clean sand. The dry residue is ex- 
 hausted three or four times with hot amyl-alcohol, and 
 these alcoholic solutions are filtered through paper mois- 
 tened with the alcohol. The filtrate contains, besides 
 strychnine, fat and coloring matter, which are got rid of 
 by shaking the filtrate with ten or twelve times its volume 
 of hot water containing IIC1 ; the strychnine is dissolved 
 in the acidulated water, whilst the greater part of the fat 
 
 * If brucine is present in the jtryohnine, which is the ense with most 
 commercial specimens, tlio oolor produoed by the HNO s is deep orange 
 or red. (See par. 1088 ) 
 
THE PROPERTIES OF'BRUCINE. 339 
 
 and coloring matter remains in the amylic alcohol. The 
 hot acid solution must be shaken with fresh portions of the 
 alcohol, so long as the alcohol continues to dissolve fat and 
 coloring matter; after this the acid solution, mixed with a 
 slight excess of ammonia, is evaporated on the water-bath, 
 and the residue again exhausted with hot aunylic alcohol, 
 which dissolves the free strychnine and leaves it behind on 
 evaporation. If the strychnine should not be sufficiently 
 pure, it is again dissolved in dilute HC1, shaken with amyl- 
 alcohol, and the process continued as before. When pure, 
 it may be recognized as directed at par. 1086. 
 
 1090. "The presence of strychnine maybe detected in 
 very minute quantities in complicated organic liquids, by 
 rendering them alkaline with a solution of KHO, and agi- 
 tating thoroughly with a few drachms of chloroform ; the 
 chloroform dissolves the strychnine, and leaves it in the 
 solid form on evaporation. From this residue it may be 
 extracted by dilute HC1, and may afterwards be submitted 
 to the usual tests." 
 
 1091. To detect strychnine in beer, shake the beer with 
 animal charcoal in the proportion of four ounces of char- 
 coal to a gallon ; let it stand over night, collect and wash 
 the charcoal once or twice with cold water, and boil it> for 
 half an hour with eight ounces of alcohol, which takes up 
 the str3'chnine. The residue which remains on evaporating 
 the alcohol is shaken with a few drops of KHO and ether, 
 the latter of which takes up the strychnine. The alkaloid 
 may be recognized after evaporating the etherial solution, 
 by means of H 2 S0 4 and acid chromate of potash. — Graham 
 and Hofmann. 
 
 Brucine (C^H^NjOJ. 
 
 1092. In addition to the sources of this alkaloid named 
 in par. 1082, it exists in large quantity, unaccompanied by 
 strychnine, in false angustura bark. It appears either in 
 the form of transparent oblique rhombic prisms, or in that 
 of crystalline needles. It melts readily on the application 
 of heat, and loses its water of crystallization. It is easily 
 distinguished from strychnine, which it resembles in many 
 respects, by its ready solubility, both in dilute and absolute 
 alcohol. It is difficultly soluble in cold, but somewhat 
 more soluble in hot water; one part dissolving in about 
 850 parts of cold and 500 parts of boiling water. It is 
 
340 THE PROPERTIES OF MECONIC ACID. 
 
 soluble in amyl-alcohol. It is insoluble in ether and fixed 
 oils. Its taste is intensely bitter. 
 
 1093. The acids dissolve brucine, forming salts, most of 
 ■which are crystallizable ; they are readily soluble in water 
 and are very bitter to the taste. 
 
 1094. The fixed alkalies and their carbonates precipitate 
 brucine from a solution of its salts ; the precipitate is not 
 soluble in an excess of these reagents. " Viewed under 
 the microscope immediately after precipitation it appears 
 to consist of very minute grains ; but upon further inspec- 
 tion these grains are seen — with absorption of water — to 
 suddenly form into needles, which latter subsequently 
 arrange themselves, without exception, into concentric 
 groups. These successive changes of the precipitate may 
 be traced distinctly even with the naked eye." 
 
 1095. Ammonia precipitates brucine from its solutions ; 
 the precipitate appears at first in the form of minute drops 
 of oil, but which finally change to white needles. The pre- 
 cipitate is very soluble in an excess of ammonia ; but it is 
 deposited after a time, the length of time depending upon 
 the strength of the solution, from the ammoniacal solution 
 in a crystalline state. 
 
 1096. The nitric acid reaction described in par. 1088 is 
 characteristic for brucine. • 
 
 Meconic Acid (C,H0 t H 3 ). 
 
 1097. This acid is one of the constituents of opium ; it 
 crystallizes in micaceous scales, or small rhombic prisms, 
 containing 3 atoms of water, which it gives off at 100° C, 
 leaving a white, opaque, effloresced mass. It has a sour 
 taste, and reddens litmus strongly. It dissolves readily in 
 water and alcohol, less easily in ether. 
 
 1098. It is easily oxidized by HNO s , and it is also decom- 
 posed on being boiled in a strong solution of KHO. 
 
 1099. Ferric chloride imparts to solutions of the acid 
 and its salts a blood-red color, which is distinguished from 
 ferric acetate by not altering in color by boiling, and from 
 ferric sulphocyanide by not being bleached by treatment 
 with corrosive sublimate. 
 
 1100. Plumbic acetate precipitates the acid from its solu- 
 tions as plumbic meconate; this lead salt is decomposed by 
 H. ; S, PbS being formed, and meconic acid set free. 
 
THE PROPERTIES OP MECONIO ACID. 341 
 
 Detection of opium in organic mixtures, tissues, etc. 
 
 1101. If the suspected substance is a solid it should be 
 cut into small pieces ; if it is not in the solid state it should 
 be evaporated nearly to dryness on the water-bath. The 
 original solid, or the solid obtained by evaporation, must 
 be digested in a small quantity of water containing a little 
 acetic acid either in a flask or dish on the water-bath for an 
 hour or so ; the mixture is then filtered, and to the filtrate, 
 which must still contain a slight excess of acetic acid, is to 
 be added plumbic acetate as long as any precipitate is pro- 
 duced ; the meconic acid, if present, will be precipitated 
 (par. 1100), whilst the morphia will remain in solution 
 in combination with acetic acid. The mixture must be 
 warmed, but not boiled, and afterwards allowed to cool. 
 When cold it is filtered, the filtrate is examined according 
 to 1103, and the precipitate according to 1102. 
 
 1102. The precipitate, having been thoroughly washed 
 with water, is removed into a beaker and mixed with water ; 
 a current of H 2 S is then passed through the mixture, which 
 is occasionally stirred during the passage of the gas ; when 
 the gas is in excess the mixture is filtered ; the filtrate con- 
 tains the meconic acid, the precipitate consisting of PbS. 
 The filtrate is warmed and, if necessary, concentrated at a 
 temperature not exceeding 71° C, to expel the H 2 S. It is 
 then tested for meconic acid as directed at par. 1099. 
 
 1103. To the filtrate from the acetate of lead precipitate, 
 and which will contain the morphia if present, is added H 2 S 
 in excess to precipitate the excess of Pb which was added ; 
 when the gas is in excess the mixture is filtered, and the 
 filtrate which contains the morphia as acetate is evaporated 
 to a small bulk on the water-bath. To the concentrated 
 solution is added potassic carbonate slightly in excess, 
 which precipitates the morphine : the mixture is then agi- 
 tated with an etherial solution of acetic ether. After sub- 
 sidence the etherial solution is poured off and allowed 
 to evaporate spontaneously, when there is left a residue of 
 morphia in more or less well-defined crystals, to which the 
 tests 1059, 1060, can be successfully applied. 
 
 Methods for the detection of poisonous alkaloids in organic 
 mixtures. 
 
 1104. When the organic bases have to be sought for 
 among the contents of the stomach or intestines, or in arti- 
 
 29* 
 
342 METHODS FOR THE DETECTION 
 
 cles of food, or in pappy matters, the substances to be 
 examined are treated with twice their weight of pure abso- 
 lute alcohol, to which from ten to thirty grains of tartaric 
 or oxalic acid, in preference tartaric acid, have been added, 
 and the mixture is heated in a flask or retort to between 
 •fO and *lb° C. When quite cold the mixture is filtered 
 and the insoluble portion is washed with strong alcohol, 
 the washings being collected with the filtrate. The filtered 
 liquid is evaporated in vacuo, or in a tubulated retort, 
 through which a strong current of air is passed at a tem- 
 perature of not more than 33° C. If, after the volatiliza- 
 tion of the alcohol, the liquid residue contains fatty or 
 other insoluble matters, it must be again filtered, the filter 
 being moistened with water, and the filtrate and the wash- 
 ings of the residue on the filter evaporated under an air- 
 pump or under a bell-jar over concentrated H 2 S0 4 until 
 nearly dry. The residue is then treated with cold absolute 
 alcohol, taking care to exhaust the substance thoroughly ; 
 this alcohol solution is left to evaporate in the open air at 
 the ordinary temperature, or still better in vacuo; this 
 residue we will name a. 
 
 1105. Solid matter, such as the lungs, liver, heart, etc., 
 must be cut into very small pieces, then moistened with 
 absolute alcohol acidified with tartaric or oxalic acid as in 
 the preceding par.; after pressing out the liquid this treat- 
 ment with alcohol must be repeated until all the soluble 
 matter is completely extracted. Collect the fluids obtained, 
 and filter and allow the filtrate to evaporate in the open 
 air at the ordinary temperature, or better still in vacuo; 
 this residue we will name b. 
 
 1106. The a or 6 residue must be dissolved in the 
 smallest possible quantity of water, and pure acid carbon- 
 ate of soda or potash in powder must be added gradually 
 to the solution until it is neutralized. The neutralized 
 solution must be immediately shaken with four or five 
 times its volume of pure ether to dissolve the alkaloid ; it 
 must be allowed to settle, and when the layer of ether has 
 become perfectly clear, a little of it is removed into a 
 watch-glass, and allowed to evaporate spontaneously. If 
 after the evaporation of the ether oily streaks remain 
 upon the glass and gradually collect together at the bottom 
 of it, a liquid and volatile alkaloid is probably present. If 
 this be the case, the warmth of the hand wili be sufficient 
 to cause the contents of the watch-glass to exhale a dis- 
 agreeable smell, which, according- to the nature of the alka- 
 
OF POISONOUS ALKALOIDS IN MIXTURES. 343 
 
 loid, is more or less sharp, choking, and irritating. Wlien 
 a volatile alkaloid is indicated., examine the ether solution 
 according to par. 1109. 
 
 HOT. If the residue left in the watch-glass on the evapo- 
 ration of the ether is a solid, or turbid fluid with solid 
 particles suspended in it, a solid non-volatile alkaloid is 
 indicated ; in this case the warmth of the hand may cause 
 the residue to emit a disagreable animal smell, but not a 
 pungent odor. When a non-volatile alkaloid is indicated 
 examine the ether solution according to par. 1111. 
 
 1 108. Stass's process is given for the purification when a 
 volatile alkaloid has been indicated, and Otto's modification 
 of Stass's method when a non-volatile alkaloid is suspected. 
 
 1109. A volatile alkaloid has been indicated in the trial 
 sample. To the solution from which the trial sample of 
 ether was taken, add one or two cubic centimetres of a 
 strong solution of KHO or NaHO; shake the mixture, 
 then let it rest until the ether solution has separated per- 
 fectly from the alkaline one; then remove the etherial 
 (supernatant) fluid into a flask, and treat the alkaline solu- 
 tion with a fresh portion of ether as before; draw off the 
 ether solution into the flask which contains the former ether 
 fluid, and repeat the treatment of the alkaline fluid with 
 ether two or three times more, the ether solutions so 
 obtained being all mixed together ; the mixture is then to 
 be shaken with 1 or 2 cubic centimetres of a mixture of 4 
 parts by weight of water and 1 part by weight of H 2 SO.,; 
 after being allowed to stand, the ether is drawn off, and the 
 acid liquid is washed with a second quantity of ether. As 
 the sulphates of the volatile alkaloids are soluble in water, 
 and as almost all of them are insoluble in ether, the alka- 
 loid sought is contained in the acid solution in the form of 
 pure sulphate.* The ether, on the other hand, retains all 
 the foreign organic matter which it has dissolved out from 
 the alkaline solution. The ether solution leaves, therefore, 
 upon spontaneous evaporation, a trifling faint yellow resi- 
 due, of a nauseous odor, and containing a small quantity 
 of conine sulphate, if that base were present. 
 
 1110. Mix the acid solution (which will contain one or 
 all of the following bases if they are present, as their sul- 
 phates are entirely insoluble in ether — sulphates of ammo- 
 
 * Sulphate of conine is not quite insoluble in ether, u. little of this 
 alkaloid will therefore remain in the ether solution; the greater part, 
 however, will remaiu in the aqueous acid solution. 
 
344 DETECTION OP POISONOUS ALKALOIDS. 
 
 nia, nicotine, aniline, picoline, and petinine; and the solu- 
 tion will also contain the greater part of theconine, if that 
 base is present) with a concentrated solution of NallO or 
 KHO in excess, then agitate and exhaust the mixture with 
 pure ether, which will dissolve the liberated bases, including 
 ammonia ; the ether solution is drawn off, and then allowed 
 to evaporate at as low a temperature as possible ;* almost 
 all the ammonia volatilizes with the ether, whilst the alka- 
 loid remains as residue. To eliminate -the last traces of 
 ammonia, the vessel containing the alkaloid is placed for a 
 few minutes in a vacuum over H 2 S0 4 ; the alkaloid then 
 remains in a state of purity, and the analyst must deter- 
 mine by appropriate tests what alkaloid it is. 
 
 1111. A non-volatile alkaloid has been indicated in the 
 trial sample. Let the etherial solution from which the trial 
 sample was taken evaporate spontaneously, dissolve the 
 residuary impure alkaloid in a little water containing some 
 H 2 S0 4 , and then shake the solution repeatedly with ether, 
 which will dissolve the foreign matters present, and will 
 not dissolve the sulphates of the alkaloids. Remove the 
 ether solution, and then add to the aqueous acid solution 
 Na 2 CO a in excess, and then add some ether immediately and 
 shake repeatedly (the ether dissolves the liberated alka- 
 loid) ; draw off the ether solution and let it evaporate, when 
 the alkaloids which were held in solution by the ether will 
 be left in a very pure state, and, to a great extent, in the 
 crystalline form ; the analyst must now determine by appro- 
 priate tests what alkaloid is present. 
 
 1112. Uslar and Erdmanu employ, instead of absolute 
 alcohol, an oxalic or tartaric acid, HC1 and amyl-alcohol in 
 the manner described at par. 1104. 
 
 1113. Dialytic method. — The dialy tic method devised by 
 Graham, and noticed at par. 269, may also be advanta- 
 geously employed to effect the separation of alkaloids from 
 the contents of the stomach, intestines, etc. Acidify with 
 HC1, and place the matter in the dialyzer. The alkaloids, 
 being crystalline bodies, dialyze into the outer fluid for the 
 greater part in about twenty-four hours; from this solution 
 they may then, according to circumstances, either be thrown 
 down at once, after concentration by evaporation, or they 
 may be purified according to the general method just given. 
 
 1114. Answers to the following exercises must be writ- 
 ten out. 
 
 * If oonino be present, some of it will evnporate with the ether. 
 
EXERCISES. 345 
 
 EXERCISES. 
 
 199. Specify the color-tests for morphia, strychnia, and 
 quinine. 
 
 200. Name the alkaloids in nux vomica, and describe 
 their characteristic reactions. 
 
 201. How is iodic acid emplo3'ed as a test for morphia? 
 
 202. How would you examine the contents of a stomach 
 for strychnine? What sort of evidence would you con- 
 sider necessary to place the presence of the alkaloid beyond 
 doubt ? 
 
 203. How is morphia detected in organic mixtures ? 
 
 204. Describe the processes required for the identification 
 of nicotine. 
 
 205. Give the tests by which quinine, cinchonine, and 
 quinidine, are distinguished from each other, particular- 
 izing the simplest and most certain. 
 
 206. Give an account of the preparation and leading 
 properties of meconic acid. 
 
 207. What are the distinguishing properties of meconic 
 acid and morphia ? 
 
PAET III. 
 
 OPERATIONS. 
 
 SOLUTION. 
 
 1115. Many solid bodies, when placed in contact with a 
 liquid, possess the property of becoming thoroughly incor- 
 porated with it, by passing into the fluid state. This change 
 is expressed by the term solution, and the liquid in which 
 the solid dissolves is called the solvent. 
 
 1116. Solutions are of two kinds, simple and chemical. 
 A simple or mechanical solution is the mere dissolving of 
 a solid in a liquid, no chemical change occurring in either; 
 on the removal, therefore, of the liquid by evaporation, the 
 solid is obtained in its original condition. Common salt 
 dissolved in water affords an illustration of a simple solu- 
 tion. 
 
 1117. In a chemical solution the solid and fluid combine 
 together, forming an entirely new substance, from which 
 the original solid and fluid can no longer be extracted by 
 mere mechanical operations. Chalk dissolved in HC1 affords 
 an example of a chemical solution. 
 
 1118. The solvent in a simple solution cannot dissolve 
 unlimited quantities of the substance to be dissolved ; it 
 can only dissolve certain fixed quantities of the solid, the 
 amount varying with the kind of solid, and the amount of 
 any particular solid varying with the solvent. When the 
 solution contains as great a quantity of the solid matter as 
 it is capable of dissolving, it is said to be saturated. A 
 solution is known to be saturated when fresh solid matter 
 of the same sort, on being put into it, remains undissolved. 
 But as fluids dissolve generally larger quantities of a sub- 
 stance the higher their temperature", the term saturated, as 
 applied to simple solutions, is only relative, and refers in- 
 variably to a certain temperature. From the tendency of 
 heat to diminish the force of cohesion, it naturally results 
 that the solubility of most bodies is increased 03- heat ; this, 
 
SOLUTION AND PRECIPITATION. 347 
 
 however, is not always the case; some bodies, as common 
 salt, are equally soluble in water at all temperatures, whilst, 
 in other cases, the solubility is greater at particular tem- 
 peratures than either above or below them. The liquids 
 employed as solvents in simple solutions are water, alcohol, 
 ether, oils, etc. The most important solvent is water ; the 
 others are only resorted to when the substance to be dis- 
 solved is insoluble in that liquid. 
 
 1119. "A chemical solution may be accelerated by eleva- 
 tion of temperature ; and this is, indeed, usually the case, 
 since heat generally promotes the action of bodies upon 
 each other. But the quantity of the dissolved body remains 
 always the same in proportion to a given quantity of the 
 solvent, whatever may be the difference in temperature — 
 the combining proportions of substances being invariable, 
 and altogether independent of the gradations of tempera- 
 ture." The liquids which produce chemical solutions are, 
 in most cases, either acids or alkalies. 
 
 1120. The process of solution is conducted either in 
 evaporating dishes or test-tubes. The latter are generally 
 employed when the quantity of the solid operated upon is 
 small. The more minutely any substance is powdered, 
 the more its solution is facilitated. Solid substances are 
 generally reduced to powder in mortars. 
 
 PRECIPITATION. 
 
 1121. It is frequently necessary to remove a constituent — 
 it may be either the metal or metalloid of some binary 
 compound, or the acid or base of some ternary one — from 
 the liquid in which the compound is dissolved. This is 
 effected by making it a constituent of some new compound, 
 which is insoluble in the liquid in which the original com- 
 pound was dissolved. This operation, which is called 
 precipitation, is owing, therefore, to the formation of a 
 new solid substance, which is insoluble in the liquid in 
 which its constituents were dissolved, and which falls, or 
 is precipitated to the bottom, owing to the solid being 
 specifically heavier than the liquid. Occasionally, how- 
 ever, it is lighter, and floats upon the surface. In both 
 cases, the insoluble substance is called the precipitate, and 
 the substance producing the precipitation is termed the 
 precipitant. 
 
 1122. Precipitation is an operation which is constantly 
 practised in the preparation of substances in the manufac- 
 
348 CHEMICAL OPERATIONS. 
 
 tory as well as in the laboratory. We also resort to it in 
 the laboratory for the purposes of detecting and separating 
 substances one from another. Thus, if we had a solution 
 which might contain some compound of Ba and Ca: to 
 ascertain whether Ba was present, and, if it was, to sepa- 
 rate it from the solution, before ascertaining whether Ca 
 was likewise present, we might add a soluble chromate ; 
 if Ba was present, BaCr0 4 would precipitate, being insolu- 
 ble in water, whilst CaCrO, being soluble, would remain in 
 solution. If we were now to add to the clear, filtered 
 solution, some soluble oxalate, CaC 2 4 , being insoluble in 
 water, would precipitate. If the chromate produced no 
 precipitate, there could be no Ba; if the oxalate produced 
 no precipitate, after having separated the Ba (if present), 
 Ca must be absent 
 
 1123. Precipitates are classified, according to their ap- 
 pearances, into crystalline, pulverulent, Jlocculent, curdy, 
 and gelatinous. The terms turbid and turbidity are applied 
 when the precipitate is so small that it cannot be distin- 
 guished, except by impairing the transparency of the fluid. 
 
 1124. The separation of precipitates from liquids is, with 
 some few exceptional cases, much assisted by the applica- 
 tion of heat and agitation. The operation, when performed 
 as an analytical operation, is conducted in test-tubes, which 
 from their transparency admit of an inspection of the 
 process. 
 
 FILTRATION AND DECANTATION. 
 
 1125. These terms are applied to a modification of the 
 same operation, viz., the mechanical separation of fluid 
 from solid matter mixed with them. 
 
 FILTRATION. 
 
 1126. In filtration, -the separation of the fluid from the 
 solid matter is accomplished by passing it through filtering 
 paper of a proper size and shape, supported in a funnel. 
 The pores of the paper permit the fluid to pass through ; 
 whilst the solid matter, being prevented, remains behind. 
 
 1127. To prepare a filter, take a small piece of filtering 
 paper (the best white blotting paper), and fold it twice, 
 from side to side ; then round off with scissors the project- 
 ing corners, so that the paper may fall wholly within' the 
 funnel; moisten the paper when placed within the funnel. 
 
DEOANTATION AND EVAPORATION. 349 
 
 and then carefully pour the liquid to be filtered upon it. 
 The funnel, when large quantities have to be filtered, is 
 supported in one of the rings of the retort stand ; but in 
 the ordinary filtrations required in qualitative analysis, it 
 may rest on the mouth of a test-tube. The filter should 
 not project over the edge of the funnel, especially if the 
 substance in the filter requires to be washed. Should the 
 first portions of the liquid which pass through the filter 
 not be perfectly bright, which is frequently the case, they 
 must be returned to the filter, and this must be repeated 
 until it is perfectly bright. The liquid which passes through 
 the filter is called the filtrate. 
 
 DEOANTATION. 
 
 1128. When the solid particles are very heavy, the super- 
 natant liquid can be perfectly separated, without passing 
 it through a filter, by simply inclining the vessel, so as to 
 allow the fluid to pass away unattended by the precipitate, 
 or by removing the fluid by a syphon. 
 
 1129. The separation in this way of a solid from a fluid 
 is called decantation. 
 
 1130. Too great attention cannot be paid to the washing 
 of precipitates when they are required for further examina- 
 tion. After the precipitate has been thrown upon the 
 filter, a stream of water must be projected from the wash- 
 bottle upon it from time to time, until it is perfectly freed 
 from soluble matter ; this is soon accomplished if hot water 
 be employed. Hot water may therefore be used in all cases 
 unless the contrary be expressly stated. 
 
 EVAPORATION. 
 
 1131. This process is used for the purpose of obtaining 
 matter in a solid state from solutions. By the aid of heat, 
 the volatile fluid passes off in the gaseous form, whilst the 
 non-volatile matter remains behind. 
 
 1132. If the evaporation be conducted slowly, the solid 
 matter will frequently, on being deposited, assume a crystal- 
 line form. The operation is then termed crystallization. 
 
 1133. This operation is frequently conducted for the 
 purpose of obtaining a liquid in a more concentrated form, 
 by volatilizing a portion only of the fluid. Vessels are 
 constructed expressly for the purpose called evaporating 
 dishes. 
 
 30 
 
350 CHEMICAL OPERATIONS. 
 
 DISTILLATION. 
 
 1134. This operation, like the former one, consists in the 
 separation of a volatile from a less volatile fluid, or in the 
 separation of a liquid from a solid. But in evaporation no 
 attention is paid to the volatilized fluid, whilst in distilla- 
 tion it is frequently the only substance required. A dis- 
 tilling appai'atus is therefore so constructed as to allow the 
 evaporated fluid to be collected, which is called the distil- 
 late. It consists of three parts : 1. A vessel in which the 
 liquid to be distilled is heated. 2. An apparatus in which 
 the vapor is cooled and condensed. 3. A vessel for receiv- 
 ing the distillate. 
 
 1135. On a small scale, glass retorts are employed; but 
 in the distillation of large quantities, the stills are usually 
 made of metal. 
 
 IGNITION. 
 
 1136. By this operation volatile is separated from non- 
 volatile solid matter ; it requires the application of a high 
 temperature, and must be conducted in crucibles. This 
 process is therefore an evaporation of solid bodies. 
 
 SUBLIMATION. 
 
 1 137. By sublimation we effect not only the separation 
 of volatile from less volatile solid matter, but by cooling 
 we bring the volatile matter back to the solid state, and in 
 this state it is called the sublimate. 
 
 1138. This process is therefore a distillation of solid 
 bodies. 
 
 FUSION. 
 
 1139. This term is applied to the liquefaction of a solid, 
 by the mere application of heat. It is also used for the 
 decomposition of solids in the "dry way." 
 
 1140. By this operation we are able to resolve insoluble 
 substances into forms which admit of solution. This is 
 accomplished by causing their proximate elements to unite 
 with bodies the compounds of which will be capable of 
 solution. Thus BaS0 4 , which, from its insolubility both 
 in wnter and acids, resists the action of reagents in the 
 fluid state, is decomposed in this way. It is mixed with 
 
THE BLOWPIPE. 351 
 
 three or four times its own weight of dry Xa.CO.,, and the 
 mixed mass exposed in a crucible for some time to a high 
 temperature. The two salts mutually suffer decomposition 
 when placed in these conditions, BaC0 3 and j\ T a 2 SO, being 
 formed. If the fused mass be treated with water, the 
 Na 2 S0 4 dissolves in that liquid, whilst the Ba 2 CO„ being in- 
 soluble, remains undissolved, and, after being well washed, 
 may be dissolved in HCl or HjS t 3 . The fusion takes place 
 at a lower temperature if a mixture of equal parts of 
 JSia^CO and K 2 C0 3 is employed, than if either of the 
 carbonates were used separately. 
 
 DEFLAGRATION. 
 
 1141. This term is applied to all decompositions attended 
 with noise. It also includes the oxidation of a substance 
 by a reagent, in the diy way, on account of the slight ex- 
 plosions which frequently attend this kind of oxidation. 
 
 THE BLOWPIPE. 
 
 1142. The mouth blowpipe is a small instrument which 
 is employed for directing a fine and continuous stream of 
 air into the flame of a candle or lamp. By the flame thus 
 produced two reverse chemical operations may be performed, 
 viz., oxidation and reduction. The flame is therefore dis- 
 tinguished by these properties into the outer or oxidizing 
 flame and the inner or reducing flame. 
 
 1143. In the oxidizing flame, the inflammable vapor is in 
 a state of complete combustion, being supplied and mixed 
 with an excess of atmospheric air. From the high tempera- 
 ture resulting from the perfect combustion of the inflamma- 
 ble vapor, and likewise from the excess of oxygen, all the 
 requisite -conditions are present for causing substances with 
 an affinity for that element to enter into union with it. 
 
 1144. In the reducingor deoxidizing flame the inflammable 
 vapor is in an incomplete state of combustion, due to a defl- 
 cienc}' of atmospheric air ; hence any metallic oxide placed 
 in this portion of the flame is robbed of its oxygen by the 
 inflammable vapor, which requires that element for its 
 combustion. 
 
 1 145. A reducing Jlame is obtained by keeping the nozzle 
 of the blowpipe in an inclined direction, parallel to the 
 surface of the wick, and just touching the exterior surface 
 of the flame. An oxidizing flame is obtained by keeping 
 
352 THE BLOWPIPE. 
 
 the nozzle of the blowpipe at the same inclination as in the 
 former ease, and introducing it into the flame to about one- 
 third the breadth of the wick, at such a distance only from 
 the surface of the latter as to obtain a clear, unbroken 
 flame. A weak blast of air is only required for the reducing 
 flame, but a strong blast is required for the oxidizing flame. 
 
 1146. The color of the reducing flame is bright yellow if 
 an oil lamp or candle is used ; but if gas is used, it should 
 be of the same blue color as the centre of the oxidizing 
 flame. The color of the oxidizing flame in all cases is a 
 pale-blue, almost invisible by daylight. 
 
 1147. "When any substance is submitted to the action 
 of the reducing flame, it should be so held as to be entirely 
 surrounded by the reducing flame, and protected from the 
 oxidizing action of the surrounding atmosphere ; but this 
 condition being fulfilled, it should be held as near as possible 
 to the point of the flame, in order to gain the greatest amount 
 of heat and prevent any deposition of soot, which would 
 shield the substance from the action of the flame, and would 
 be occasionally attended with other disadvantages." 
 
 1148. When a substance is submitted to the action of 
 the oxidizing flame, it should be held just beyond the point 
 of this flame if a candle or oil lamp is used ; but if gas is 
 used, it should be held at a considerable distance (viz., one- 
 half to three-quarters of an inch) beyond the point of the 
 visible flame. 
 
 1149. "As the current of air which is supplied ought to 
 be continuous, its production requires some attention and 
 address. The air is not blown directly from the lungs, but 
 is forced from the mouth by means of the cheeks. The 
 difficulty consists in inspiring and expiring through the 
 nose, while a continued stream escapes from the mouth. 
 This may be attained by attention to the following direc- 
 tions: Inflate the mouth fully, and then, with the lips 
 firmly closed, and the back of the mouth closed by the 
 tongue, breathe freely through the nostrils. While the 
 respiration proceeds, and the mouth is inflated, allow a 
 little air to escape through a very minute opening between 
 the lips, renewing the supply in the mouth by occasionally 
 admitting air from tho lungs without interfering with the 
 process of respiration through the nose." — Parnell. In 
 attempting this, the student will not, probably, be imme- 
 diately successful, but a few days' persevering practice 
 will enable him entirely to master this primary difficulty. 
 
 1150. The Jlame of (he blowpipe. — When coal-gas is 
 
BLOWPIPE SUPPORTS. 353 
 
 available, it is to be preferred, since it is perfectly free 
 from dirt and grease, and admits of being regulated with 
 the greatest nicety. The gasburner ought to be of an 
 oblong shape instead of round, the current of air being 
 blown lengthways. When gas cannot be procured, an oil 
 lamp or wax candle may be used. An oil lamp proper for 
 blowpipe operations can be obtained at any of the shops 
 where they sell chemical apparatus — it need not, therefore, 
 be described ; it will be sufficient to say that it must have 
 a broad and moderately thick wick, and that on each occa- 
 sion the wick must be trimmed* before employing the flame 
 for the blowpipe experiments. The best kind of oil for the 
 lamp is pure rape or olive oil. The flame of a wax candle 
 is far inferior in size and intensity to that of a lamp. Bun- 
 sen's lamp is described at par. HGT. 
 
 1151. Supports Various materials are used as supports 
 
 for substances during the time they are exposed to the blow- 
 pipe flame; the principal are charcoal, platinum wire and 
 foil, and glass tubes. The kind of support is regulated by 
 the change we wish to effect upon the substance under 
 examination. 
 
 1152. Charcoal. — The properties which make charcoal so 
 valuable as a material for supports in blowpipe experiments 
 are — 1st, its infusibility ; 2d, its low conducting power for 
 heat, which permits substances being heated more strongly 
 upon a charcoal than upon any other kind of support; 3d, 
 its porosity, which makes it imbibe readily fusible sub- 
 stances, such as borax, carbonate of soda, etc., whilst in- 
 fusible bodies remain on the surface ; 4th, its povver of 
 reducing oxides, which greatly contributes to effecting the 
 reduction of oxides in the inner blowpipe flame. 
 
 1153. Charcoal supports are used principally in the re- 
 duction of metallic oxides, etc., or in tiying the fusibility 
 of bodies. The substance to be subjected to the blowpipe 
 flame — which, if in powder, should be previously moistened 
 with a little water to make it cohere — is placed in a shallow 
 hole made in the charcoal either with a knife or with a 
 proper charcoal borer, and the charcoal is so held that the 
 flame may impinge upon it at an angle of about 20 degrees. 
 Metals that are volatile at the heat of the reducing flame 
 evaporate wholly or in part upon the reduction of their 
 oxides ; in passing through the outer flame the metallic 
 
 * The wick must be evenly out and perfectly free from all extraneous 
 fibres. 
 
 30* 
 
364 BLOWPIPE OPERATIONS, 
 
 fumes are reoxidized, and the oxide formed is deposited 
 around the portion of the matter upon the support. Such 
 deposits are called incrustations. Many of these exhibit 
 characteristic colors leading to the detection of the metals. 
 
 1154. Charcoal made from light woods — as the alder and 
 pine — is the best for blowpipe experiments. It must be 
 well-burned ; it must be compact and free from crevices; it 
 must not scintillate, smoke, or burn with flame ; and it 
 must, of course, be perfectly dry. It should be cut by a 
 small-toothed saw into pieces • about six inches in length 
 and from one to two inches in breadth, having a flat smooth 
 surface at right angles to the rings of growth. It is this 
 surface which is always to be used ; and a good piece of 
 charcoal may be made to serve for repeated experiments 
 by simply filing off the used surface, and exposing a new 
 one after each operation. As it is very difficult to get 
 charcoal sufficiently good for blowpipe experiments, Mr. 
 John J. Griffin has provided an excellent substitute, an 
 account of which is given in pars. 1160 to 1167. 
 
 1155. Platinum Platinum wire, and occasionally plati- 
 num foil, is used in all oxidizing processes before the blow- 
 pipe, and also when fusing substances with fluxes, with a 
 view to try their solubility in them and to watch the phe- 
 nomena attending the solution and mark the color of the 
 bead ; lastly, also to introduce substances into the flame, 
 to see whether they will color it. 
 
 1156. The ends of the wire are twisted into a small loop 
 (fig. 5), and when required for use, the loop is moistened with 
 a drop of water, then dipped into the powdered flux (when 
 a flux is used), the portion adhering to the wire is then 
 
 Fig- 5. 
 
 a — o 
 
 exposed to the flame of a gas or spirit-lamp, when fused, 
 and whilst still hot, it is dipped again into the powdered 
 flux, and this is continued until the loop is completely filled 
 with the flux after it has been fused. The bead when cold 
 is moistened again, and a small portion of the substance 
 to be examined put on and made to adhere to it by the 
 action of a gentle heat. The loop is then finally exposed, 
 according to circumstances, to the inner or to the outer 
 blowpipe Maine. 
 
 1157. A great many metallic oxides dissolve in borax, 
 
AND THE APPARATUS REQUIRED. 355 
 
 forming colored glasses. If any metallic arsenides or sul- 
 phides are present in the substance which has to ( be ex- 
 amined with borax, the substance must be roasted by the 
 method described in the next par. before making the exami- 
 nation with borax ; and it is frequently advantageous, before 
 roasting the powdered substance, to mix it with a little 
 powdered charcoal, so as to prevent the formation of sul- 
 phates and arseniates. 
 
 1158. Glass tubes. — Tubes of hard German glass of about 
 a quarter of an inch internal diameter, five or six inches long, 
 and open at both ends, are used in blowpipe experiments 
 principally for roasting substances containing sulphur, 
 arsenic, selenium, antimony, tellurium, etc., which, when 
 heated with access of air, evolve fumes which may be 
 recognized by color, odor, and chemical reaction. 
 
 1159. Small Glass Bulbs, or, what answer equally well, 
 glass tubes closed at one end, of about two and a half to 
 three inches long, and from one-eighth to one-fourth of an 
 inch internal diameter, are employed to test substances for 
 water, mercury, sulphur, or other bodies which are vola- 
 tilized by the application of heat without the access of air. 
 The volatile products collect in the neck of the bulb or 
 tube, and may be judged of by their color, odor, etc. 
 
 1160. Griffin's substitute for charcoal. — " The blowpipe 
 experiments that require the assistance of charcoal may be 
 divided into two classes. In the first class may be named 
 the formation of beads with microcosmic salt, the trial of 
 fusibility per se, and the roasting of the metallic com- 
 pounds that contain such volatile elements as sulphur and 
 arsenic. The second class of experiments is restricted to 
 the fusion of minerals or metallic compounds with carbonate 
 of soda, or with soda and borax, for the purpose of effect- 
 ing particular combinations, or of procuring their metals 
 in a state of regulus. For these two classes of experi- 
 ments I make use of two different composition supports, 
 the first of which I call Supports for Fusions, and the 
 second, Supports for Seductions. They are alike in appear- 
 ance. Each consists of two parts — an upper or combusti- 
 ble portion, and a base or incombustible portion. The 
 former is the proper substitute for the ordinary charcoal, 
 the under portion acting only as a crucible, in which the 
 combustible portion is contained. I shall first describe 
 the composition and formation of the supports, and after- 
 wards show the way to use them. 
 
 1161. "The incombustible portion of both supports is 
 
356 BLOWPIPE OPERATIONS, 
 
 made of fine pipeclay and charcoal powder, mixed in equal 
 parts by weight with as much water, slightly thickened 
 with rice paste, as is sufficient to form a stiff plastic mass. 
 
 1162. " The combustible portion of the Support for Fu- 
 sions consists of — 
 
 " Charcoal, in fine powder, - 12 parts. 
 Rice flour, .... i « 
 
 Water, about ... 8 " 
 
 The rice is boiled in the water to form a paste, with which 
 the charcoal is afterwards mixed into a mass of the con- 
 sistence of dough. 
 
 1163. "The upper part of the Support for Reductions 
 consists of the following mixture : — 
 
 "Charcoal, in fine powder, - 9 parts. 
 
 Carbonate of soda, crystallized 2 " 
 
 Borax, crystallized, - - 1 " 
 Rice flour, - 2 " 
 
 Water, about - - 8 " 
 
 The water is boiled, the soda and borax are dissolved in it, 
 and the rice is then added to form a paste, with which the 
 charcoal is finally incorporated, and the whole well kneaded 
 into a stiff mass. The mould in which these compositions 
 are pressed to form the supports is made of boxwood.* 
 
 1164. "The principal points which require attention to 
 insure success in this process are to have the materials in 
 the state of a very fine powder, and the moist compositions 
 of a proper degree of consistency. If they are too soft, 
 the support will not quit the mould without losing its form ; 
 if too dry, the particles of the support will not cohere. 
 The proper state is found after a few trials. It is most 
 convenient to begin by making the mixture too soft, and 
 then drying it slowly till it is found to be hard enough to 
 work easily. The composition is rolled into balls with the 
 fingers. The moulds should be kept clean, and the forming 
 parts of the pestle for the charcoal composition, and the 
 ring, should be oiled. The point of the pestle for the clay 
 composition must not be oiled, because grease prevents the 
 adhesion of the combustible portion of the clay base. A 
 pestle made on purpose for the operation, is used to remove 
 
 * Those moulds, nnd every other part of the apparatus, are sold by 
 Mr. Griffin, nnd, I have no doubt, can be procured through any of the 
 other dealers in ohemicnl apparatus. 
 
AND THE APPARATUS REQUIRED. 357 
 
 the finished support from the mould, by pressure on the 
 clay foundation. 
 
 1165. " When the support is taken from the mould, it is 
 placed on a hot plate or sand-bath to dry, after which the 
 rough edges are taken off by a rasp. It is then ready for 
 use. The bottoms of supports for reductions are painted 
 with red ochre mixed with rice paste, to distinguish these 
 from the other kind. The size I have fixed upon is as fol- 
 lows : height, half an inch ; diameter at top, half an inch ; 
 at bottom, two-fifths of an inch. The weight is about 16 
 grains, consisting of 10 grains of clay crucible, and 6 
 grains of combustible matter. I have tried several other 
 sizes, but this I find to be the most generally convenient. 
 Nevertheless, a higher temperature can be produced upon 
 a smaller support ; and I find that large masses of charcoal 
 are not essential, since many blowpipe experiments can be 
 finished during the combustion of only two grains of char- 
 coal. When in use, they are supported by a handle made 
 of wire, turned into the form of a ring ; a piece of tobacco 
 pipe can be used for the handle of the wire support. 
 
 1166. " The following is the method of using these sup- 
 ports. 
 
 " Firstly, the surface of one of the supports for fusion is 
 heated before the blowpipe flame. The support continues 
 to burn like an ordinary pastile, till it is consumed down 
 to the clay ; in this respect the support has a superiority 
 over common charcoal, which soon ceases to burn when 
 removed from the fire. The ignited support is then to be 
 rested upon a porcelain capsule, and a quantity of micro- 
 cosmic salt, sufficient to form a bead, is placed on its red- 
 hot surface. The salt instantly melts, and sinks into the 
 central cavity, so as to form a bead ; the heat, the form, and 
 the smoothness of the surface of the support, facilitating 
 this part of the process. The salt is then heated before the 
 blowpipe, till it is converted into a transparent, colorless 
 bead. The support is again placed on the porcelain cap- 
 sule, and the metallic substance intended to be incorporated 
 with the bead is added to it. The support continuing to 
 be red-hot, and the bead consequently continuing soft, the 
 substance so added is immediately absorbed, and its loss 
 by dispersion prevented ; whereas, upon common charcoal 
 the fused salt solidifies soon after it is removed from the 
 flame, and the substance added for examination, not ad- 
 hering to it, is often blown away by the first blast from the 
 blowpipe jet. The bead is now again fused, till the sub- 
 
358 
 
 BUNSEN'S GAS-LAMP. 
 
 stance added to it is decomposed, and the resulting glass is 
 observed to fuse quietly. It is then ready for examination ; 
 but it is sunk in the bottom of the hollow of the support, 
 and cannot be seen by transmitted light, unless the pro- 
 jecting sides of the support be removed. This is effected 
 as follows : the support is placed, as before, on the porce- 
 lain capsule, and the operator blows with his mouth, with- 
 out the blowpipe, strongly clown upon its surface. The 
 pastile then burns away rapidly, and the force of the blast 
 disperses the ashes, until the whole rim of the support is 
 consumed. The bead then appears situated on the summit 
 of a cone, and can be examined either by reflected or trans- 
 mitted light. It is also in a position adapted for exposure 
 to the different action of the oxidating and reducing flames, 
 so as to have the character of the included metal fully de- 
 veloped. If, finally, the charcoal is allowed to burn wholly 
 away, the colored bead can be lifted from the ashes and 
 preserved in a glass tube for subsequent examination and 
 comparison. 
 
 " Secondly, if the surface of one of the supports for re- 
 ductions be heated before the blowpipe, it becomes at first 
 like the simple charcoal support ; but in proportion as the 
 charcoal is consumed, the fluxes which were mixed with it, 
 and which are not volatile, concentrate and fuse upon the 
 surface of the residue. If, therefore, a reducible metallic 
 compound is heated upon such a support, it becomes at 
 once exposed to the reducing action of the high tempera- 
 ture, of the nascent oxide of carbon, and 
 of the carbonate of soda, whilst any 
 earthy matter that it may contain is vitri- 
 fied by the attendant borax." — Griffin. 
 
 1167. Bunsen's gas-lamp This gas- 
 lamp with non-luminous flame is repre- 
 sented in Fig. 6, and must be made ex- 
 actly to scale, 3^ times as large as the 
 drawiug. It must be furnished with a 
 cap at a for closing and opening the 
 draught-holes, so as to be able to regu- 
 late the supply of air for every dimen- 
 sion of the flame. The conical chimney, 
 d d d d, Fig. t, must also be made of 
 such a size that the flame burns perfectly 
 steady. Fig. 1 represents this flame of 
 its natural size. It is composed of the following three 
 chief divisions; — 
 
 Fig. 6. 
 
BUIMSJSN'S GAS-LAMP. 
 
 359 
 
360 OHIEE DIVISIONS OP THE FLAME. 
 
 A. The dark cone, a a a a, containing the cold unburnt 
 gas mixed with about 62 per cent. 
 
 B. The flame mantle, ac ab, formed of the burning coal- 
 gas mixed with air. 
 
 C. The luminous point, aba, not seen when the lamp is 
 burning with the draught-holes open, but obtained of the 
 size required for the reactions by closing these holes up to 
 a certain point. 
 
 The following six points in the flame are used in the re- 
 actions : — 
 
 1. The base of the flame lies at a ; its temperature is com- 
 paratively very low, as here the burning gas is cooled by 
 the upward current of cold air, and much heat is absorbed 
 by the cold end of the metal tube. If mixtures of flame- 
 coloring substances are held in this part of the flame, it is 
 often possible to vaporize the most volatile constituent, 
 and thus in the first few moments to obtain tints which 
 cannot be observed at higher temperatures, because they 
 then become masked by colors produced by the volatiliza- 
 tion of the remaing substances. 
 
 2. The zone of fusion lies at |3, somewhat above the first 
 third of the flame in height, and midway between the inner 
 and outer limits of the mantle at the point where the flame 
 is thickest. This is the point in the flame which possesses 
 the highest temperature, and it is therefore used in testing 
 substances as regards their melting-point, their volatility, 
 emissive power, as well as for all processes of fusion at 
 high temperatures. 
 
 3. The lower oxidizing flame lies at y, in the outer mar- 
 gin of the zone of fusion, and is especially suitable for the 
 oxidation of substances dissolved in beads of fused salts. 
 
 4. The upper oxidizing flame at 8 is formed by the 
 highest point of the non-luminous flame, and acts most 
 powerfully when the draught-holes of the lamp are wide 
 open. This flame is suited for the oxidation of larger por- 
 tions of substance, for roasting off volatile-oxidation pro- 
 ducts, and generally for all those cases of oxidation in 
 which an excessively high temperature is not needed. 
 
 5. The lower reducing flame lies at 8, on the interior 
 edge of the mantle next to the dark central zone. As the 
 reducing gases at this point are mixed with unburnt 
 atmospheric oxygen, many substances remain here unal- 
 tered which become deoxidized on exposure to the upper 
 reducing flame. This point of the flame gives, therefore, 
 very valuable reactions which cannot be obtained with the 
 
METHOD OP EXAMINATION. 361 
 
 blowpipe. It is especially available for reductions on char- 
 coal, and in beads of fused salts. 
 
 fi. The upper reducing flame is formed by the luminous 
 point jj, produced over the dark zone when the admission 
 of air is lessened by the gradual closing of the draught- 
 holes (Fig. 6, a). If this luminous point is made too large, 
 it will be found that a test-tube filled with cold water 
 becomes covered with a film of lampblack: this never 
 ought to occur. This flame contains no free oxj'gen, is 
 rich in finely divided incandescent carbon, and hence it 
 possesses far more powerful reducing powers than the lower 
 reducing flame. It is especially available for reducing 
 metals when it is desired to collect them in the form of 
 films. 
 
 Method op Examination in the various parts of the 
 Flame. 
 
 A. Behavior of the Elements at High Temperatures.* 
 
 1168. This is one of the most important reactions which 
 can be employed for the detection and separation of sub- 
 stances. The possibility of producing, with the flame of 
 the lamp alone, a temperature as high as or higher than 
 that of the blowpipe depends upon the fact that the radi- 
 ating surface of the heated body be made as small as pos- 
 sible. The arrangement for bringing the substances into 
 the flame must therefore be on a very small scale. The 
 platinum wire upon which the substance is heated must 
 scarcely exceed the thickness of a horsehair, and one deci- 
 metre in length of the wire must not weigh more than 
 0.034 grin. It is impossible to obtain the results hereafter 
 detailed if a thicker wire than this is employed. Sub- 
 stances which act upon platinum, or which will not adhere 
 to the moistened surface of the metal, are held in the flame 
 upon a thin thread of asbestos, of which a hundred ma}' be 
 obtained from one splinter of the mineral. These threads 
 must not exceed in thickness one-fourth of that of an ordi- 
 nary lucifer-match. Decrepitating substances are ground 
 to the finest powder on the porcelain lamp-plate with the 
 elastic blade (a) of the knife (Fig. 8) and drawn up on to a 
 moistened strip of one square centimetre of filter paper. 
 
 * For further information with regard to the flame reactions the 
 student is referred to the translation of Bunsen's paper by Professor 
 Roscoe in the " Philosophical Magazine," for 1867. 
 31 
 
302 
 
 BEHAVIOR OB 1 THE ELEMENTS 
 
 If the paper is then burnt, being held with the platinum 
 forceps, or, better, between two rings of fine platinum wire, 
 the sample remains as a coherent crust, which now may 
 without difficulty be heated in the flame. 
 
 Fig. 9. 
 
 Fig. 10. 
 
 1169. If the substance requires to be heated in the flame 
 for a long period, the holder (Fig. 9) is used. The arm (a) 
 is fastened to the carrier (A), so fixed on the stand by a 
 spring (as seen at B) that it can be moved both horizon- 
 tally and vertically. The glass tube (Fig. 10) is held on 
 this arm (a), and the fine platinum wire fused on to the 
 
AT HIGH TEMPERATURES. 3G3 
 
 tube thus held in the flame. The splinters of asbestos are 
 stuck into the glass tube (6), which slips into the holder, 
 and may then be moved with the carrier (A). The carrier 
 (B) carries a spring-clamp for holding test-tubes which 
 have to be heated for a considerable time in a particular 
 part of the flame. The little turn-table (C) contains nine 
 upright supports to hold the wire tubes (Fig. 10) employed 
 in the experiments. By means of these arrangements a 
 particle of the substance under examination is brought 
 into the flame, and its behavior in the coldest and hottest 
 parts of the flame is ascertained, the substance being 
 examined with a lens after each change of temperature. 
 The following six different temperatures can be obtained in 
 the flame, and these points may be judged of by observing 
 the tints attained by the thin platinum wire : — 
 
 1. Below a red heat. 
 
 2. Commencing red heat. 
 
 3. Bed heat. 
 
 4. Commencing white heat. 
 
 5. White heat. 
 
 6. Strong white heat. 
 
 It is scarcely necessary to remark that these different 
 temperatures must not be ascertained by the glow of the 
 substances themselves, as the luminosity of different bodies 
 depends not only upon the temperature, but also mainly 
 upon their specific power of emission. 
 
 11 "70. The following phenomena are observed when a 
 sample of a substance is heated: — 
 
 1. Emission of Light The emissive power of substances 
 
 is ascertained bj' placing them on the platinum wire in the 
 hottest part of the flame. The sample is of weak emissive 
 power when it is less luminous than the platinum wire, of 
 a mean emissive power when both appear about equally 
 luminous, and of strong emissive power when the intensity 
 of the light which it emits is greater than that from the 
 platinum. Most solid bodies emit a white light, others (as, 
 for instance, erbia) colored light. 
 
 Some bodies, such as many osmium, carbon, and molybde- 
 num compounds, volatilize and separate out finely divided 
 solid matter, which renders the flame luminous. Gases and 
 vapors always exhibit a smaller power of emission than 
 fused substances, and these generally less than solid bodies. 
 The form of the substance under examination must always 
 
364 VOLATILITY OF SUBSTANCES. 
 
 be noted, as the emissive power depends upon the nature 
 of the surface: thus compact alumina, obtained by slowly 
 heating the hydrate, possesses only a moderate emissive 
 power, whereas the porous oxide prepared by quick igni- 
 tion of the sulphate possesses a high power of emission. 
 
 2. The melting point is determined by using the six 
 different temperatures already mentioned. At every in- 
 crease of temperature the bead is examined with the lens 
 to see whether the volume is decreased or increased, whether 
 bubbles are given off on melting, whether on cooling the 
 bead is transparent, and what changes of color it under- 
 goes during the action of the heat or on afterwards cooling. 
 
 3. TJie volatility is ascertained by allowing equallj' heavy 
 beads of the substance, placed on a platinum wire, to evapo- 
 rate in the zone of fusion, and observing the time, bv means 
 of a metronome, which the bead takes to volatilize. The 
 point at which the whole of the substance is converted into 
 
 vapor can be ascertained with great accuracy, 
 Fig. 11. often to a fraction of a second, by the sudden 
 disappearance of the coloration of the flame. 
 The platinum wire upon which the substance 
 is weighed is protected from the moisture of 
 the air by insertion in a tube (Fig. 11). If 
 we know the weight of the tube and wire, the 
 right weight of substance can easily be at- 
 tached, either by volatilizing a portion or by 
 fusing some more substance on to the bead, 
 aud thus making it lighter or heavier. The 
 experiments are best made with one centi- 
 gramme of substance. The position in the 
 flame where the highest constant temperature 
 exists can be found by moving a fine platinum 
 wire, fixed on a stand and bent at its point at 
 a right angle, slowly about the zone of fusion, 
 and noting the point where it glows most in- 
 tensely. The beads to be volatilized are then 
 most carefully brought into the flame at the 
 same distance from the point of this wire. 
 Care must also be taken that the dimensions of the flame 
 do not undergo change from alterations in the pressure of 
 the gas whilst the experiments are going on. 
 
 4. Flame-coloration. — Many substances which volatilize 
 in the flame may be detected by the peculiar kinds of light 
 which their glowing gases emit. These colorations appear 
 in the upper oxidizing flame when the substance causing 
 
REDUCTION OF SUBSTANCES. 
 
 365 
 
 them is placed in the upper reducing flame. Mixtures of 
 various flame-coloring substances are tested in the lowest 
 and coldest part of the flame; and here it is often possible 
 to obtain for a few moments the peculiar luminosity of the 
 most volatile of the substances unaccompanied by that of 
 the less volatile constituents. 
 
 B. Oxidation and Reduction of Substances. 
 
 1 I'll. In order to recognize substances by the phe- 
 nomena exhibited in their oxidation and reduction, and to 
 obtain them in a fit state for further examination, the fol- 
 lowing methods are emplo3 T ed: — 
 
 1. Beductionin glass tubes is especially employed for the 
 detection of Hg, or for the separation of S, Se, P, etc., when 
 in combination with Xa or Mg. A stock of very thin glass 
 tubes is prepared, each 2 to 4 millims. in width and 3 
 centims. in length ; forty of these are easily made out of 
 one ordinary-sized test-tube, by softening the glass before 
 the blowpipe, and then drawing it out until the requisite 
 size of tube is obtained. This long tube is then cut uj:> with 
 a diamond into pieces 6 to 8 centims. long, and each of these 
 again divided into two over the lamp, and the closed ends 
 neatly rounded. The sample, having been fiiiety powdered 
 with the knife-blade (Fig. 8, a) on the porcelain plate 
 (Fig. 12), is treated in a tube either by itself, or with a mix- 
 ture of carbon and soda, or 
 with Xa or Mg. A piece of Fig 12. 
 
 magnesium wire, a few mil- 
 lims. in length, is for this 
 purpose pushed down into 
 the .powdered sample con- 
 tained in the glass tube ; 
 the sodium is carefully freed 
 from rock oil, and rolled out 
 between the fingers to a 
 small cylinder, which is then 
 surrounded by the pow- 
 dered substance. The best 
 
 form of carbon is the soot from turpentine, which has been 
 deposited upon the outside of a basin filled with cold water. 
 As soon as the small tube containing the perfectly dry 
 sample has been heated to the point of fusion of the glass, 
 when generally an ignition inside the tube is noticed, it is 
 allowed to cool and then placed upon the porcelain plate 
 
 31* 
 
366 REDUCTION OF SUBSTANCES. 
 
 covered by a piece of paper and crushed to powder with 
 the knife, for the purpose of further examining the pro- 
 ducts of reduction. 
 
 2. Seduction on splinters of Charcoal. — In this way the 
 metal can be obtained in small globules, or as a porous 
 mass, from quantities often less than a milligramme of the 
 sample. 
 
 A transparent crystal of sodic carbonate is brought near 
 to the outside of the flame, and a common wooden lucifer- 
 match then rubbed over two-thirds of its length with the 
 drops of fused salt. If the match is then turned upon its 
 axis through the flame, the carbonized wood becomes sur- 
 rounded with a crust of solid sodic carbonate, which, on 
 heating in the zone of fusion, melts, and is absorbed by the 
 carbon. A splinter of charcoal is thus obtained, which is 
 prevented from burning by its glaze of soda. A mixture 
 of the substance is then made with the knife upon the hand 
 with one drop of the melted soda-crystal, and a portion of 
 this, of the size of a mustard seed, placed upon the point 
 of the splinter. As soon as this has been melted in the 
 lower oxidizing flame, it is passed through a part of the 
 dark interior zone to the hotter portion of the lower redu- 
 cing flame. The point at which the reduction occurs is 
 easily seen by the violent effervescence of the soda ; and 
 this is after a time stopped by bringing the splinter into 
 the dark zone. In order to isolate the reduced metal, the 
 end of the splinter is broken off and rubbed up with a few 
 drops of water in a small agate mortar, when the metallic 
 particles are generally visible without removal of the car- 
 bon. For further examination, the carbon and soda can 
 be easily removed by several careful washings, and the par- 
 ticles transferred to a small piece of curved glass cut out 
 from an old flask,* in which tliey are again washed by de- 
 cantation, the last drops of water removed bj- suction with 
 a piece of filter-paper, and the metallic particles dried at a 
 moderate heat. A few tenths of :i milligramme of the metal 
 is generally sufficient to yield a solution with which all the 
 characteristic precipitations can be accomplished, the re- 
 agents being contained in capillary glass threads, dropped 
 into the solution by the milligramme, and the effect thus 
 produced ascertained by examination with a lens. Iron, 
 cobalt, and nickel, which do not fuse to globules on the 
 
 * Wi\ toll -glasses crack much too readily to be used for such experi- 
 ments. 
 
METALLIC FILMS. 367 
 
 splinter, are withdrawn from the agate mortar by means of 
 the point of the magnetized blade (Fig. 8, 6), washed with 
 water, and dried high above the flame on the point of the 
 knife. If the blade be then tightly drawn between the upper 
 part of the thumb and the lower part of the first finger, and 
 if the point of the blade be then approached to the metallic 
 particles on the finger, they jump from the hand to the blade, 
 forming a brush-like bundle, which can be conveniently ex- 
 amined by the lens, and by touching with a melted borax 
 bead can be transferred in suitable quantities. The portion 
 of metal remaining on the knife is rubbed on to a small 
 piece of filter-paper, a drop of acid added, and the paper 
 warmed over the flame so as to allow the metal to dissolve ; 
 this solution can then be further examined with various 
 reagents. 
 
 3. Films upon Porcelain. — Those volatile elements which 
 are reduced by carbon and hydrogen can be deposited from 
 their compounds as films on porcelain either in the ele- 
 mentary state or as oxides. Such films can be extremely 
 easily converted into iodides, sulphides, and other com- 
 pounds, and thus ma}' be made to serve as most valuable 
 and characteristic tests. The films are composed in the 
 centre of a thick layer, which on all sides gradually becomes 
 thinner until the merest tinge is reached; it is therefore 
 necessary to distinguish between " thick" and "thin" parts 
 of the films. Both exhibit in their variation of thickness 
 all the tints of color characteristic of the substance under 
 different circumstances of division. One-tenth up to one 
 milligramme is in many cases sufficient for these reactions. 
 Many surpass Marsh's arsenic test in delicacy and certainty, 
 and approach in this respect the spectrum-analytical 
 methods. 
 
 The following films can be obtained: — 
 
 (a) Metallic films are prepared by holding in one hand a 
 particle of the substance on an asbestos-thread in the upper 
 reducing flame, which must not be too large, whilst with the 
 other hand a glazed porcelain basin, 1 to 2 decimetres in 
 diameter, filled with cold water, is held close above the 
 asbestos-thread in the upper reducing flame. The metals 
 separate out as dead-black or brilliantly-black films of 
 vaiying thickness. Even Pb, Sn, Cd, and Zn yield in this 
 way films of reduced metal, which by mere inspection can- 
 not be distinguished from the soot separated out on the 
 porcelain by a smoky flame. By means of a glass rod, these 
 films can be touched with a drop of dilute HN0 3 , contain- 
 
368 OXIDE AND IODINE-FILMS, 
 
 ing about 20 per cent, of real acid ; and the various degrees 
 of solubility of the films serves as a distinguishing charac- 
 teristic. 
 
 (6) Oxide-films are obtained by holding the porcelain 
 basin filled with water in the upper oxidizing flame, the 
 rest of the operation being the same as in the production 
 of the metallic films. If only a very small quantity of the 
 sample can be employed, care must be taken to lessen the 
 size of the flame, in order that the volatile products may 
 not be spread over too large a surface of porcelain. 
 
 The film of oxide is examined as follows : — 
 
 (a) The color of the thick and thin film is carefully 
 observed. 
 
 (18) The reducing action or otherwise of a drop of stan- 
 nous chloride is noted. 
 
 (y) If no reduction occurs, XaHO is added to the stan- 
 nous chloride until the precipitated hydrate redissolves, 
 and then it is to be observed whether a reduction occurs. 
 
 (6) A drop of perfectly neutral silver-nitrate is rubbed 
 over the film with a glass rod, and a current of ammoniacal 
 air is blown over the surface from a small wash-bottle 
 containing ammonia solution, and having the mouth tube 
 dipping under the liquid and the exit-tube cut off close 
 below the cork. If a precipitate is formed, the color is 
 observed, and the solubility or alteration, if any, noticed 
 which occurs when the current of alkaline air is continued, 
 or when a drop of ammonia-liquor is added. 
 
 (b) Iodide-films are simply obtained from the oxide-films 
 by breathing on the latter upon the cold basin, which is then 
 
 placed upon the wide-mouthed 
 Fig. 13. well-stoppered glass (Fig. 13) con- 
 
 taining fuming hydriodic acid 
 and phosphorous acid derived 
 from the gradual deliquescence 
 of phosphoric triiodide. When 
 the mixture no longer fumes, 
 owing to absorption of moisture, 
 it is easy to render it again 
 fuming by adding a little phos- 
 phoric anhydride. Other films, often containing both 
 iodides of a metal, and therefore frequently less regular in 
 color and appearance, may be easily obtained by smoking 
 the oxide-lilm with a tlainc of alcohol containing iodine in 
 solution placed upon a bundle of asbestos-threads and held 
 under the basin. If any iodine be condensed on the basin 
 
AND MODES OP TESTING THEM. 369 
 
 with the HI, it can easily be removed by gentle warming 
 and blowing. 
 
 The examination of the film is conducted as follows : — 
 
 (a) The solubility of the film is examined simply by 
 breathing upon it when the basin is cooled ; the color then 
 either changes or entirely disappears, the film being dis- 
 solved in the moisture of the breath. If the basin be gently 
 warmed, or if it be blown upon for some distance, the film 
 again becomes visible by the evaporation of the moisture 
 in the current of air. 
 
 (/3) The ammonia compound of the iodide is formed by 
 blowing ammoniacal air upon it, and noticing whether the 
 color of the thick and thin films alters quickly, slowly, or 
 not at all. The different colors reappear at once if the basin 
 be held for a few moments over an open bottle containing 
 fuming HC1. 
 
 (y) The iodide-films generally give the same reactions as 
 the oxide-films with silver-nitrate and ammonia, with stan- 
 nous chloride, and with caustic soda. 
 
 (b) The sulphide film is most easily obtained from the 
 iodide-film by blowing upon it a current of air saturated 
 with amnionic sulphide, and removing the excessof sulphide 
 by gently warming the porcelain. It is advisable to breathe 
 on the film from time to time whilst the current of sulphu- 
 retted air is being blown on the basin. The experiments 
 to be made with this film are : — 
 
 (a) The solubility or otherwise in water is ascertained 
 by breathing on to it, or by addition of a drop of water. 
 The sulphides often possess the same color as the iodide- 
 films ; they may, however, generally be distinguished by 
 their insolubility on breathing. 
 
 ((3) The solubility of the sulphide in amnionic sulphide 
 is ascertained by blowing or dropping. 
 
 (6) Films on Test-tubes Under certain circumstances it 
 
 is advisable not to collect the film on porcelain, but upon 
 the outside of a large test-tube (Fig. 9, D) ; this method is 
 especially used when it is needed to collect larger quantities 
 of the reduction film for the purposes of further examina- 
 tion. The fine asbestos-thread with the sample of substance 
 is held on the glass tube (6) before the lamp so that it is 
 placed at the height of the middle of the upper reducing 
 flame, and the test-tube fixed so that the lowest point is 
 just above the end of the asbestos-thread. If the lamp be 
 now pushed under the test-tube, the substance and the 
 asbestos-thread are in the reducing flame. By repeating 
 
370 APPARATUS REQUIRED 
 
 this operation the film can be obtained of any wished-for 
 thickness ; some pieces of marble are in this case placed in 
 the test-tube, to prevent the water from being thrown out 
 of the tube by percussive boiling. 
 
 III. The Reactions op the Elements. 
 
 1172. The elements, which can easily be recognized by 
 their flame reactions, are arranged in the following groups 
 and sub-groups according to their behavior in the reducing 
 and oxidizing flames: — 
 
 A. Elements which are reducible to metal and are de- 
 posited in films. 
 
 1. Films scarcely soluble in cold dilute nitric acid — 
 tellurium, selenium, antimony, arsenic. 
 
 2. Films slowly and difficultly soluble in cold dilute 
 nitric acid — bismuth, mercury, thallium. 
 
 3. Films instantly soluble in cold dilute nitric acid — 
 cadmium, zinc, indium. 
 
 B. Elements reducible to the metallic state, giving no 
 film. 
 
 1. Not fusible to a metallic bead. 
 
 a. Magnetic — iron, nickel, cobalt. 
 
 b. Non-magnetic — palladium, platinum, rhodium, 
 
 iridium. 
 
 2. Fusible to metallic beads — copper, tin, silver, gold. 
 
 C. Elements most easily separated and recognized as 
 compounds — tungsten, titanium, tantalum and niobium, 
 silicon, chromium, vanadium, manganese, uranium, sulphur, 
 phosphorus. 
 
 apparatus required in photo-chemical experimeots. 
 
 1173. A large number of substances are volatilized when 
 a small particle of the substance in the solid state is intro- 
 duced into the inner flame of a gas or spirit-lamp. Many 
 of these substances in volatilizing color the outer flame, 
 and as the color imparted to the flame is in most cases dif- 
 ferent and distinct for each substance, the coloration of the 
 flame has long been employed in chemical analysis as a test 
 for many substances. Thus — Soda and its salts impart to 
 the flame a yellow, potash and its salts a violet, stiontia 
 and its salts a crimson color. The intensity of the color 
 of the salts of the same base, varies with their volatility, 
 
IN PHOTO-CHEMICAL EXPERIMENTS. 371 
 
 the most volatile of the salts producing the most intense 
 coloration. Difficultly volatile salts produce only a slight, 
 and non-volatile salts no coloration ; thus, with silicates 
 and other non-volatile compounds, such as are met with in 
 nature, it is often difficult to detect 3 or 4 per cent, of the 
 alkalies. In such cases the coloration may frequently be 
 produced by adding some other substance which has the 
 power of decomposing the compound under examination, 
 and forming, with the substance we wish to detect, a com- 
 pound which will volatilize at the temperature of the flame. 
 If we add, for instance, to silicates containing only 3 or 4 
 per cent, of the alkalies, a little pure gypsum, this will 
 decompose the silicate, a volatile alkaline sulphate, which 
 will impart a color to the flame, being formed. 
 
 1174. As the color produced by one substance interferes 
 or entirely obscures that produced by another, we were 
 formerly unable to detect more than one body in a mixture 
 of substances by means of the color imparted to the flame. 
 This defect has latety been overcome by looking at the 
 colored flame through colored media, as colored glasses and 
 colored liquids, which intercept the color produced by one 
 substance, whilst they allow the color produced by another 
 substance to pass. Thus, the yellow color produced by 
 sodium compounds obscures the violet produced by potas- 
 sium ones ; Cartmell, who was the first to -employ colored 
 media, proposed, in order to detect potash in the presence 
 of soda by means of the colored flame, to view the flame 
 through a blue glass stained with cobalt : through this 
 colored glass no colored rays from soda (or lithia) can pass, 
 but it admits those peculiar to potash. 
 
 1175. A solution of indigo can also be employed for the 
 same purpose, Cartmell, for instance, detected lithia in the 
 presence of soda and potash, by comparing the mixed color 
 of the flames of those bases with that of the flame of pure 
 potash, when both are viewed through an indigo solution. 
 Bunsen has found that the discrimination of these bases in 
 presence of each other is more easily effected by observing 
 the succession of changes of color, which the mixed flame 
 produced by these substances experiences when the rays 
 reach the eye after passing through gradually thicker layers 
 of an indigo solution. For this purpose a hollow plate 
 glass prism (Fig. 14) is used, filled with indigo solution ; it 
 is 40 millimetres high, and its principal section is a tri- 
 angle, with two sides of 150 millimetres, and the other 
 of 35 millimetres. The indigo solution is made bj- dissolv- 
 
372 PHOTO-OHEMICAIi EXPERIMENTS. 
 
 ing 1 part of indigo in 8 parts of fuming sulphuric acid, 
 diluting with 1500 to 2000 parts of water, and filtering. 
 
 Fig. 14. 
 
 1176. In the following experiments the prism was moved 
 horizontally before the ej'e, so that the rays of the "flame 
 always passed through gradually thicker layers of the 
 medium. The alkaline substances, brought singly into the 
 melting-space, exhibited the following changes: — 
 
 1. Chemically pure CaCl 2 produces a yellow flame, which, 
 even with very thin layers of the indigo solution, passed 
 through a tinge of violet into the original blue lamp flame. 
 
 2. Chemically pure NaCl, the same. 
 
 3. Chemically pure K 2 CO, or KC1 appears of a sky blue, 
 then violet, and at last of an intense crimson red, even 
 when seen through the thickest layers of solution. Ad- 
 mixtures of soda or lime do not hinder the reaction. 
 
 4. Chemically pure L a C0 3 or LCI gives a carmine-red 
 flame, which, with increasing thickness of the medium, 
 becomes gradually feebler, and disappears before the thick- 
 est layers pass before the eye. Lime and soda are also 
 without influence on this reaction. 
 
 1177. Merz has proposed employing, in addition to the 
 cobalt blue glass, a violet, a red, and a green, glass; the 
 violet glass is tinted with manganesic oxide ; the red glass 
 (partly colored and partly uncolored) with cuprous oxide, 
 and the green glass with ferric and cupric oxides. The 
 common colored window glass will generally be found to 
 answer the purpose of the green glass. 
 
NITRIC AND NITR0-HYDR0CHL0RIC ACIDS. 373 
 
 REAGENTS. 
 
 1178. — LIST OF THE REAGENTS EMPLOYED IN THE FLUID 
 
 STATE. 
 
 1. HC1, Hydrochloric acid (muriatic acid), if pure, is 
 perfectly colorless, and leaves no residue when evaporated; 
 its sp. gr. should be 1.2. The substances with which it is 
 generally contaminated are Fe, As, and H 2 SO t . It may also 
 contain CI and S0 2 . 
 
 If it gives, after dilution with distilled water, a precipi- 
 tate with BaCl„, H 2 SO i is present. If it turns j r ellow on 
 evaporation, or if, after adding NH 4 HO in excess, then 
 acidifying with acetic acid, it gives a blue color after the 
 addition of a solution of potassic ferrocyanide, it contains 
 Fe'". If it imparts a blue tint to a solution of KI mixed 
 with starch paste, it contains CI, and if it discolors a fluid 
 made faintly blue with iodide of starch, it contains S0 2 . 
 Examine it for As by Marsh's test, described in the fifth 
 group of bases. 
 
 Dilute one part of the concentrated acid with two parts 
 of water. 
 
 2. HN0 3 , Nitric acid faqna fortis), when free from non- 
 volatile matter, leaves no residue on evaporation ; its sp. 
 gr. should be 1.517. The impurities often found in it are 
 HC1 and H 2 S0 4 . 
 
 If, after dilution with distilled water, it gives a precipi- 
 tate with BaCl a , H 2 S0 4 is present ; and if the diluted acid 
 gives a precipitate with AgN0 3 , HC1 is present. 
 
 Dilute one part of the concentrated acid with two of 
 water. 
 
 3. Nitro-hydrochloric acid (aqua regia) is prepared by 
 adding four parts of concentrated hydrochloric acid to one 
 of concentrated nitric acid. 
 
 " Nitric acid and hydrochloric acid decompose each other, 
 the decomposition mostly resulting, as Gay Lussac has 
 shown, in the. formation of two compounds which are gase- 
 ous at the ordinary temperature, N0C1 2 (chloronitric acid), 
 and NOC1 (chloronitrous gas), and of CI and water. If 
 one equivalent of HNO.. is used to three equivalents of 
 HC1, it may be assumed that only chloronitric acid (NOCl 2 ), 
 CI and H.,0 are formed (HNO, + 3HC1 = NOCl 2 + CI + 
 2H.,0). This decomposition ceases as soon as the fluid is 
 saturated with the gas ; but it recommences the instant 
 32 
 
374 SULPHURIC ACID. 
 
 this state of saturation is disturbed by the application of 
 heat or by decomposition of the acid. The presence of 
 the CI, and also, but in a very subordinate degree, that of 
 the acids named, makes aqua regia the most powerful sol- 
 vent for the metals, with the exception of those which 
 form insoluble chlorides." 
 
 This test is employed in an undiluted state. 
 
 4. H a S0 4 , Sulphuric acid (oil of vitriol), frequently con- 
 tains As, Pb, Fe"', Ca, and oxides of nitrogen. The Pb 
 is deposited to a great extent when the acid is diluted 
 PbSO, being less soluble in dilute than in concentrated 
 H 2 S0 4 . 
 
 This acid ought to leave no residue upon evaporation on 
 platinum; and if it does not remain perfectly clear upon 
 dilution with four or five parts of spirits of wine, PbSO.,, 
 Fr/" 3S0 4 , or CaS0 4 is present. " The presence of small 
 quantities of Pb is detected most easily by adding some 
 HC1 to the H 2 S0 4 in a test-tube ; if the point of contact is 
 marked by turbidity (PbCl 2 ), Pb is present." If a solu- 
 tion of FeSOj is poured upon some of the acid in a test- 
 tube, so that the iron solution floats upon the acid, a pur- 
 plish red ring will be formed at the junction of the two 
 solutions, if the acid contains nitric or hyponitric acid. If, 
 after dilution with 20 parts of water, it imparts a blue tint 
 to a solution of KI, mixed with starch paste, hyponitric 
 acid is present. Examine it for arsenic by Marsh's test, 
 described in the fifth group of bases. 
 
 Freseuius recommends the following process for the pre- 
 paration of pure sulphuric acid: Take of strong sulphuric 
 acid 1000 grm., amnionic sulphate 3 grm., manganic perox- 
 ide in powder 5 grm., put the acid in a porcelain dish, add 
 the ammonic sulphate, and heat till copious fumes of H,S0 4 
 escape ; this is done to destroy any oxides of nitrogen. 
 After cooling, add the manganic peroxide, and heat to boil- 
 ing, with stirring, in order to convert any arsenious into 
 arsenic acid. When cool, pour off the clear fluid into a 
 retort about a litre in capacity, and distil. The neck of 
 the retort must reach so far into the receiver that the dis- 
 tillate may drop directly into its bod}-. The receiver should 
 not be cooled with water. To prevent the neck of the 
 retort from touching the receiver, some long asbestos may 
 be used. When about 10 c. c. have been drawn over, change 
 the receiver, and distil off three-fourths of the contents of 
 the retort. This method depends upon the fact that sul- 
 
HYDRO SULPHURIC ACID. 375 
 
 phuric acid containing arsenic in the form of arsenic acid, 
 yields an arsenic-free distillate. 
 
 The dilute acid is prepared by adding four parts of water 
 to every one of the concentrated acid. 
 
 5. H, i C 4 H J O li H 2 T, Tartaric acid is generally sufficiently 
 pure for analytical purposes. As it undergoes decomposi- 
 tion in solution, a small quantity only should be prepared 
 at a time. 
 
 For use, dissolve one part, by weight, of acid, in two 
 parts, by measure, of water. 
 
 6. NaHC^HjOu, Soclic hydric tartrate is prepared by 
 dissolving a quantity of tartaric acid in water, dividing the 
 solution into two equal parts, and neutralizing one exactly 
 
 • with Na,CO.„ and then adding the other portion, and after- 
 wards evaporating the whole solution until the bitartrate 
 crystallizes. 
 
 For use, make a saturated solution. 
 
 7. HC 2 H 3 2 = HA, Acetic acid, when employed in analy- 
 sis, ought to leave no residue on evaporation, and after 
 saturation with Na 2 CO !( , emit no empyreumatic odor. It 
 ought to give no precipitate with BaCl 2 and AgN0 3 , and 
 it ought to give no color or turbidness with H,S, or with 
 (XHJJ3, after it has been neutralized with NH,HO. 
 
 The ordinary commercial acetic acid is sufficiently con- 
 centrated for analytical purposes. 
 
 8. H 2 S, Hydrosulphuric acid (sulphuretted hydrogen) is 
 prepared by adding to FeS, in an appropriate apparatus, 
 dilute H 2 S0 4 or HC1. The H 2 S is liberated in its gaseous 
 state, and may be passed through any solution under exami- 
 nation ; or a solution of the gas may be obtained by passing 
 it through pure water. As this solution very soon decom- 
 
 . poses by contact with the atmosphere, it ought to be pre- 
 pared very frequently, and kept in well-stoppered bottles. 
 
 FeS, from which H 2 S is obtained, is prepared b} T projecting 
 a mixture of thirty parts of iron filings with twenty-one of 
 flowers of sulphur, in small portions at a time, into a red- 
 hot crucible, replacing the cover after each addition. When 
 the whole has been added, the ignition must be continued 
 for a short time, until the excess of sulphur has been dis- 
 sipated. Bloxam has found that H 2 S, prepared from FeS, 
 contains arsenic, but if obtained from native sulphide of 
 antimony and HC1 it is free from it ; it ought, in examina- 
 tion for poisons at least, always to be prepared from the 
 antimony sulphide. 
 
316 IIYDROFLTJOSIIilOIO ACID. 
 
 9. SOv, Sulphurous anhydride, is prepared by acting upon 
 copper or charcoal with sulphuric acid. For this purpose 
 small pieces of charcoal are introduced into a flask, with 
 from six to eight times their weight of H 2 SO„ and a mode- 
 rate heat applied. The evolved gas must be conducted into 
 cold water until it is no longer absorbed. On account of 
 the great tendency which this reagent has to absorb more 
 oxygen, and become converted into H a S0 4 , it must be 
 preserved in well-stoppered bottles. 
 
 10. CI, Chlorine gas, is prepared by mixing 18 parts of 
 NaCl with 15 parts of finely powdered Mn0 2 ; the mixture 
 is placed in a flask and upon it is poured a. completely cooled 
 mixture of 45 parts of concentrated H 2 S0 4 , and 21 parts of 
 water, the flask is then shaken. A uniform and continuous . 
 evolution of CI will soon begin, which, when slackening, 
 may be easily increased again by the application of a gentle 
 heat. A solution of the gas may be prepared by passing it 
 into cold water. Chlorine water must be kept in well- 
 stoppered bottles, and excluded from the light; for if 
 exposed to light it is speedily converted into HC1, oxygen 
 being evolved ; when it has lost its odor it is unfit for use. 
 
 11. HJHiFg, Hydrojluosilicic acid. This acid is prepared 
 as follows : Take 1 part of sand, wash it and dry it tho- 
 roughly, mix it with 1 part of calcic fluoride, also -dry and 
 place the mixture in a flask'; 6 parts of concentrated H.SO, 
 are then added. The mixture must only fill the flask 
 one-third, as it swells up on being warmed ; heat the flask 
 by means of a sand-bath ; a gas delivery tube dips into a 
 vessel containing 4 parts of water and some mercury; the 
 tube dips beneath the surface of the mercury, to prevent 
 the tube from being stopped up by the silica which is 
 formed when the silicic fluoride (SiF < ) comes in contact 
 with water ; the following diagrams express the chemical 
 changes which ensue : — 
 
 (1) Si0 2 + 2CaF a + 2H 2 SO, = SiF 4 + 2CaSO, + 2H a O. 
 
 (2) 3SiF. ( -f 2H 2 = 2H J SiF + SiO... 
 
 12. H 2 (',0, = H,0, Oxalic acid. Dissolve one part, by 
 weight, of the acid, in twenty parts, by measure, of water. 
 
 13. (NHJjCjOj, Amnionic oxalate, ought to leave no 
 residue after ignition on platinum foil, and it ought not to 
 give a precipitate, nor be rendered turbid, by H.S nor by 
 (NH,) 2 S. 
 
 Dissolve one part, by weight, of the salt, in twenty-four 
 parts, by measure, of water. 
 
 14. NIIJIO, Avunonia, must be colorless, and leave no 
 
AMMONIO CHLORIDE. 811 
 
 residue upon evaporation to dryness. It ought not, after 
 being diluted with three volumes of distilled water, to give 
 a precipitate on the addition of lime-water. It ought not, 
 after being acidulated with pure HNO i5 to give a precipitate 
 with Ba(NO :i ), nor with AgXO.. H a S ought not to impart 
 to it the slightest color, and on the addition to it of a few 
 drops of a solution of ammonio-sulphate of copper, a black 
 precipitate ought not to be formed. 
 
 15. NH 4 C1, Amnionic chloride. — This salt ought to vola- 
 tilize completely when ignited on platinum foil ; the solution 
 ought to be neutral to test-paper, and it ought to give no 
 precipitate nor coloration on the addition of (NH,), 2 S. 
 
 Dissolve one part, by weight, of the salt, in eight parts, 
 by measure, of water. 
 
 16. (NH 4 )„S, Amnionic sulphide, is prepared b} r passing 
 hydrosulphuric acid through NH,HO, until it does not 
 produce a precipitate in a solution of MgS0 4 . It ought 
 not to produce a precipitate with a solution of lime, and it 
 ought to leave no residue on evaporation to dryness and 
 ignition. 
 
 17. Amnionic darbonate must completely volatilize. Its 
 solution ought to give no precipitate or coloration with 
 (NH ( ) 2 S nor with H 2 S after acidulation with HC1. Its 
 solution, after being acidulated with HNO :) , ought to pro- 
 duce no precipitate with Ba(XO,), nor with AgN0 3 . 
 
 Dissolve one part, by weight, of the salt, in four parts, 
 by measure, of water, and add one measure of ammonia. 
 
 18. NH 4 N0 3 , Ammonic nitrate, is made by neutralizing 
 HN0 3 with (NH 4 ) 2 C0 3 . The solution is evaporated until 
 crystals begin to be deposited, and is then allowed to cool ; 
 the crystals are afterwards fused. 
 
 19. Ammonic arseniate is prepared by neutralizing arsenic 
 acid with ammonic carbonate and evaporating to dryness. 
 
 Dissolve one part, by weight, of the salt, in ten parts, by 
 measure, of water. 
 
 Arsenic acid is prepared by dissolving arsenious acid in 
 HNO s , mixed with a little HC1, evaporating the solution to 
 dryness, and igniting somewhat below a low red heat until 
 all HN0 3 is expelled. 
 
 20. Ammonic molybdate in nitric acid. — Dissolve one part 
 of molybdic trioxide in eight parts of strong NH 4 HO, or one 
 part of acid ammonic molybdate in three parts of NH 4 HO, 
 with the aid of heat ; pour the solution into twenty parts of 
 HN0 3 , consisting of equal parts of strong HNO s and water. 
 
 32* 
 
378 POTASSIC FERRICYANIDE. 
 
 21. K 2 SO ( , Potassic sulphate — Recrystallize the K 2 S0 4 
 of commerce; dissolve one part, by weight, of the purified 
 salt in 200 parts, by measure, of water. 
 
 22. KN0 2 , Potassic nitrite, may be prepared "by heating 
 in a flask only half filled with the mixture two parts of 
 starch, in pieces, with eight parts of impure HX0 3 of 1.4 
 sp. gr. and eight parts of water, and conduct the nitrous 
 fumes* evolved first through a large empty flask, then into 
 a flask containing a solution of KHO until it is completely 
 saturated. If the potassic solution contains silicic acid or 
 alumina, as is mostly the case, the saturation point is 
 marked by the separation of these impurities. Five parts 
 of solution of KHO of l^Y sp. gr. is the quantity required 
 in the process. As soon as the action begins, the flame 
 under the evolution flask must be temporarily removed, or 
 otherwise the action might become too energetic. Evapo- 
 rate the filtered solution to dimness. Dissolve one part of 
 the dry salt to about two parts of water when the reagent 
 is required for use." 
 
 23. KjFeC.y,., Potassic ferrocyanide (yellow prussiate of 
 potash), is prepared on the manufacturing scale by adding 
 animal matter, such as horns, feathers, dried blood, leather- 
 clippings, etc., mixed with iron filings, to fused K 2 C0 3 , 
 lixiviating the fused mass with water, then filtering and 
 crystallizing by evaporation. The animal matter contains 
 nitrogen and carbon, the latter in larger proportion than is 
 required to form cj*anogen with the nitrogen; hence when 
 these substances are fused with K 2 C0 3 , the excess of carbon 
 reduces the K 2 C0 3 ; the K being set free, unites with the 
 cyanogen formed from the N and the remainder of the C 
 producing KCN, which is converted into the ferrocyanide 
 by the action of the KCN on the Fe when the fused mass 
 is heated with water. 
 
 The commercial K 4 FeCy c is sufficiently pure for analyti- 
 cal purposes; dissolve one part by weight, in twelve, by 
 measure, of water. 
 
 24. K 6 Fe 2 Cy 12 , Potassic ferricyanide (red prussiate of 
 potash), is prepared by the action of oxidizing agents on 
 the ferrocyanide. It is usually prepared by passing washed 
 chlorine gas (with constant agitation to insure uniformity 
 of action) through a cold solution of the ferrocyanide until 
 it no longep gjyes a blue but a brown color with a ferric 
 salt. 
 
 * Nitrous anhydride (N,0,) nearly in a state of purity. 
 
POTASSIO CHROMATE AND CYANIDE. 379 
 
 Dissolve one part, by weight, in twelve, by measure, of 
 water; the solution ought to be made as it is wanted, as 
 ferricyanide decomposes when in a state of solution, a 
 trace of ferrocyanide being formed. 
 
 25. NH 4 CyS, Ammonic sulphocyanide ; KCyS, Potassic 
 sulphocyanide. — NH 4 CyS may be prepared (1) by digesting 
 HCy with ammonic polysulphide, prepared by digesting 
 sulphur in (NH,).S, taking care to keep the latter slightly 
 in excess, which is indicated by the yellow color of the 
 solution, then boiling off' the excess of the latter, filter- 
 ing and evaporating to the crystallizing point: 2CNH + 
 (NH 4 ) 2 S,S 2 = 2NH 4 CyS + H 2 S. (2) A mixture of 750 
 parts of NH 4 HO and 100 parts of CS 2 (carbonic disul- 
 phide), and 750 parts of alcohol, 86 per cent., is distilled 
 down to one-half after standing for 24 hours, the residual 
 liquid is evaporated to the crystallizing point : 4NH,HO 
 + CS 2 = NH 4 CyS + (NH 4 ).,S + 4H a O. Potassic sulpho- 
 cyanide may be prepared by heating to low redness in a 
 covered vessel a mixture of 46 parts of dried K 4 FeCy„, 37 
 parts of S, and 17 parts of pure K 2 C0 3 ; the mass after 
 heating is exhausted with water; the watery solutionis 
 evaporated to dryness on the water-bath, and the residue 
 is exhausted with alcohol, which deposits crystals on cool- 
 ing or evaporation. 
 
 Dissolve 1 part, by weight, of either salt in 10 parts of 
 water. 
 
 26. K 2 Cr0 4 , Potassic chromate, in solution ought not, 
 after it has been acidulated with HC1, to give a precipitate 
 with BaCl 2 . 
 
 Dissolve 1 part, by weight, in 8 parts, by measure, of 
 water. 
 
 27. KCN = KCy, Potassic cyanide, is prepared by mix- 
 ing intimately 8 parts of anhydrous potassic ferrocyanide 
 and 3 parts of potassic carbonate, and introducing the 
 mixture by small portions into a cast-iron crucible previ- 
 ously heated to low redness ; after all the materials have 
 been added, the crucible is kept in the fire till a sample of 
 the fused mass taken out on a glass rod appears white, and 
 exhibits the aspect of porcelain on cooling; the crucible is 
 then removed from the fire and left at rest for a moment 
 to allow the iron liberated by the decomposition to settle 
 down; it is then poured out carefully, to prevent the run- 
 ning out of the minute particles of iron, into a clean iron 
 or silver vessel. Thus prepared, it always contains a little 
 
380 SODIO CARBONATE AND ACETATE. 
 
 potassic carbonate and cyanate. The potassic carbonate 
 employed must be free from sulphate, as this would be re- 
 duced to sulphide by the cyanide. It may also be prepared 
 by igniting the ferrocyanide alone ; but as one-third of the 
 cyanogen in this case is resolved into carbon and nitrogen, 
 only two-thirds is obtained in the form of the salt. 
 
 28. NaHO, Sodic hydrate (caustic soda), is prepared by 
 dissolving 1 part, by weight, of Na 8 CO.„ in 9 parts, by 
 measure, of water, and boiling the solution in a clean iron 
 pan ; milk of lime, prepared by adding 1 part of CaO (quick- 
 lime) to 3 parts of boiling water, is then added in small 
 portions to the boiling liquid, until HC1 causes no efferves- 
 cence in a portion of the clear liquid. When this point has 
 been attained, the pan must be removed from the fire, and 
 the precipitate allowed to subside. The supernatant liquid 
 must then be drawn off by means of a syphon, or passed 
 through a filter of bleached linen, and the filtrate evapo- 
 rated rapidly over a quick fire until it has been reduced to 
 half its original bulk. On supersaturating a portion of the 
 liquid with HC1, no, or only a slight, effervescence should 
 take place. H 2 S must not produce a precipitate or colora- 
 tion in its solution. The solution must be evaporated 
 until it has a sp. gr, of from 1.13 to 1.15 ; it must be kept 
 in well-stoppered bottles. 
 
 29. Na 2 C0 3 , Sodic carbonate, in solution ought not, after 
 it has been acidulated with H2\O s , to give a precipitate with. 
 BaCl 2 nor with AgNO.. 
 
 Dissolve 1 part, by weight, of the salt, in 10 parts, by 
 measure, of water. 
 
 30. Na 2 HPO„ Disodic hydric phosphate, must form no 
 precipitate with ammonia. 
 
 •Dissolve 1 part, by weight, of the salt, in 10 parts, by 
 measure, of water. 
 
 31. NaC 2 H 3 2 , Sodic acetate, is made by adding acetic 
 acid to a concentrated solution of Xa.CO, until all efferves- 
 cence ceases. This solution must be free from sulphates. 
 
 Dilute 1 part of the concentrated solution with 4 parts 
 of water. 
 
 32. NalISO :l , Sodic hydric sulphite. — Pass SO,, prepared 
 as directed at 9, page 376, through a bottle containing a 
 small quantity of water, then into a flask containing a 
 solution of Na,C0 3 (prepared by dissolving t parts of the 
 pure crystallized carbonate in from 'JO to 30 parts of water) 
 until CO a ceases to be evolved. The solution must bo 
 
BARIC CHLORIDE. 381 
 
 kept in a well-stoppered bottle, as it has a great tendency 
 to absorb oxygen, and pass from sulphite to sulphate. 
 
 33. Na 2 B 4 O.(H.,O), , Borax, is employed in blowpipe 
 analysis. It should be heated below the fusing point to 
 drive off its water of crystallization, and then powdered. 
 
 34. Sodic and Potassic carbonate Equal parts of these 
 
 two carbonates in the anhydrous state must be mixed 
 together. They must not contain any sulphate. 
 
 35. NaNHjHPO,, Sodic amnionic hydric phosphate (mi- 
 crocosmic salt). This salt, which is found in human urine 
 after putrefaction, and in guano from Ichaboe, may be 
 prepared artificially in several ways; the following is a 
 very convenient method: -6 or 7 parts of crystallized 
 disodic hydric phosphate (Na,HPO t ) and 1 part of NH,C1 
 are dissolved in 2 parts of boiling water, the NaNH,HPO, 
 crystallizes out as the solution cools, the NaCl remaining 
 in solution ; the phosphate may be freed from NaCl by 
 recrystallization from a small quantity of boiling water 
 containing a little NH 4 HO. 
 
 36. K a H.,Sb !) 0„ Dihydric dipotassic metantimoniate, may 
 be prepared by projecting a mixture of equal parts of pow- 
 dered tartar emetic and potassic nitrate in small portions 
 at a time into a red-hot crucible. After the mass is defla- 
 grated keep it at a moderate heat for a quarter of an hour 
 longer, then remove it from the fire, and when sufficiently 
 cold treat it with warm water ; transfer the mixture to a 
 suitable vessel, and decant the clear fluid from the heavy 
 powder and concentrate it. After one or two days a 
 doughy mass will separate from the liquid ; treat this 
 mass with three times its volume of cold water, working it 
 at the same time with a spatula. This operation will serve 
 to convert it into a fine granular powder, to which add the 
 powder from which the fluid was decanted, wash slightly, 
 and dry on blotting-paper. Prepare the solution only 
 immediately before it is required for use, by shaking the 
 salt with cold water, and filtering off the fluid from the 
 undissolved portion ; it must be clear, and of neutral reac- 
 tion ; it must give no precipitate with solution of KC1, or 
 with one of NH,C1, but must produce a crystalline precipi- 
 tate with one of NaCl. 
 
 37. BaCl 2 , Baric chloride. — A solution of this salt must 
 be neutral to test-paper; after precipitation by H 2 S0 4 the 
 filtrate ought not to leave the slightest residue when 
 evaporated on platinum foil. Its solution ought not to 
 
382 CALCIC CHLORIDE AND SULPHATE, ETC. 
 
 give a precipitate or be colored by the addition of H 2 S or 
 by (NH 4 ) 2 S. 
 
 Dissolve 1 part of the salt in 10 of water. 
 
 38. Ba(N0 3 ) 2 , Baric nitrate. — A solution of this salt 
 must not be rendered turbid by AgX0 3 ; for other impuri- 
 ties, test as directed in BaCl 2 . 
 
 Dissolve 1 part of the salt in 10 parts of water. 
 
 39. Lime-water is made by digesting recently prepared 
 CaH 2 2 for some time with cold distilled water, with fre- 
 quent agitation of the mixture ; allow the undissolved por- 
 tion of the lime to subside, decant subsequently, and keep 
 the clear fluid in well-stoppered bottles. 
 
 40. CaCl.j, Calcic chloride, is made by dissolving pure 
 CaC0 3 in dilute HC1; the solution thus obtained must be 
 neutral to test-paper, and it must not form a precipitate, 
 nor be colored by (NH 4 ) 2 S. 
 
 41. CaS0 4 , 2H 2 0, Calcic sulphate (gypsum). — Dissolve 
 as much of the salt as the water will take up. 
 
 42. MgS0 4 , 7H 2 0, Magnesic sulphate (Epsom salts). — 
 Dissolve 1 part in 8 of water. 
 
 43. BaCO,,, Baric carbonate, may be prepared by dis- 
 solving BaCi 2 in hot water, and precipitating by (NH 4 ),C0 3 
 and NH 4 HO ; the precipitate must be washed until the last 
 washing gives no turbidness with AgNO r Stir the pre- 
 cipitate with water to the consistence of cream, and keep 
 the mixture in a stoppered bottle ; shake the mixture before 
 using it. 
 
 44. FeS0 4 , TH 2 0, Ferrous sulphate. — The purified com- 
 mercial salt is sufficiently pure ; it is principally employed 
 for the detection of nitric acid. 
 
 Dilute 1 part of the concentrated solution with 3 parts 
 of water. 
 
 45. Fe^Cl,,, Ferric chloride, is prepared by dissolving re- 
 cently precipitated and well-washed Fe 2 H O,. in pure HC1 ; 
 the ferric hydrate must be kept during the solution slightly 
 in excess, as the ferric chloride must coutaiu no free acid; 
 it is afterwards diluted with an equal volume of water and 
 filtered. 
 
 46. Pb(C s H,0 _,).,, Plumbic acetate. — The best commercial 
 acetate is sufficiently pure to be used as a reagent ; dissolve 
 1 part, by weight, of the salt, in 10 parts, by measure, of 
 water. 
 
 47. llgNO,, Mereurous nitrate, is made by gently heat- 
 ing in a small flask 9 parts of UNO,, in conjunction with 
 10 parts of Ilg, until the disengagement of nitrous fumes 
 
MERCURIC CHLORIDE, ETC. 383 
 
 ceases ; the solution is then boiled for some time with the 
 undissolved portion oi' the Hg, care being taken to replace 
 the water lost by evaporation. The crystals, which sepa- 
 rate on the cooling of the liquid are dissolved in 20 parts 
 of cold water, slightly acidulated with HNO,. The fluid is 
 then filtered if necessary, and the filtrate kept in a glass 
 bottle, the bottom of which is covered with mercury. 
 
 48. HgCl 2 , Mercuric chloride. — Dissolve 1 part of the 
 salt in 16 parts of water. 
 
 49. CuS0 4 , 5H 2 0, Cupric sulphate. — The commercial salt 
 is purified by two or three crystallizations ; dissolve 1 part, 
 by weight, of the purified crystals, in 10 parts, by measure, 
 of water. 
 
 50. Ammonio-sulphate of copper is prepared by adding 
 NH t HO, drop by drop, to a not too concentrated solution 
 of CuS0 4 , until the precipitate at first produced is nearly 
 redissolved ; the clear solution to be employed. 
 
 51. AgNO a , Argentic nitrate, is prepared by dissolving 
 pure Ag in pure HISTOj diluted with an equal bulk of water, 
 evaporating the solution to dryness and gently fusing the 
 residue; if pure, its solution will, after addition of HC1 in 
 excess and. filtering, leave no fixed residue. Dissolve 1 
 part, by weight, of the salt, in 20 parts, by measure, of 
 water.* 
 
 52. Ammonio-nitrate of silver is prepared by adding 
 NH 4 HO, drop by drop, to a solution of AgN0 3 , until the 
 precipitate at first formed is nearly redissolved ; the clear 
 solution to be employed. 
 
 53. Co(N0 3 ) 2 , Cobaltic nitrate. — This salt can be pur- 
 chased fit for use ; dissolve 1 part, bj r weight, in 10 parts, 
 by measure, of water. 
 
 54. PtCl 4 , Platinic chloride. — Purify platinum scraps by 
 boiling them in HN0 3 ; when purified treat with concen- 
 trated HC1, and some HNO s , in a narrow-necked flask and 
 apply heat, add occasionally HN0 3 until the Pt is dissolved. 
 Evaporate the solution on the water-bath, to dryness, add- 
 ing during the evaporation HC1, dissolve the residue in 10 
 parts of water. Dry PtCl,, if pure, dissolves completely in 
 spirits of wine.f 
 
 55. AuCl s . Auric chloride. — If the gold is perfectly pure 
 it has simply to be dissolved in aqua regia, and evaporated 
 to dryness over the water-bath, and the residue redissolved 
 in water. If it contains silver, filter off from the insoluble 
 AgCl, which will remain on treating the residue with water. 
 
 * See Appendix A, page 887. f See Appendix B, page 388. 
 
384 STANNOUS CHLORIDE, ETC. 
 
 If it contains copper, which may be ascertained by diluting 
 a portion of the acid solution, and adding to it K ( Fe 2 Cy n , 
 mix it with a solution of FeSO, in excess ; collect the me- 
 tallic gold, wash it, and then redissolve in aqua regia, and 
 evaporate as before.* 
 
 56. SnCl 2 , Stannous chloride. — Boil granulated tin in 
 concentrated HC1 in a flask, keeping the tin always in ex- 
 cess until H ceases to be evolved, then dilute the solution 
 with four times its volume of water containing a little HC1, 
 and filter. Keep the filtrate in a well-stoppered bottle con- 
 taining some fragments of tin. 
 
 57. Pb0 2 , Plumbic peroxide, may be prepared by digest- 
 ing in boiling HN0 3 , diluted with four or five times its bulk 
 of water, red lead in fine powder ; the residue is washed 
 with a fresh quantity of the dilute HXO„ and then with 
 water until everything soluble is removed. 
 
 58. Copper turnings are emploj'ed for the detection of 
 nitric acid. 
 
 59. Zinc must be perfectly free from arsenic. Test for 
 this impurity as directed at par. 262. 
 
 60. Nessler's test " This reagent is an aqueous solution 
 
 of potassic iodide, saturated with mercuric iodide, and ren- 
 dered powerfully alkaline with soda or potash. It is pre- 
 pared by dissolving 50 grammes of KI in a small quantity 
 of hot distilled water. The vessel containing this solution 
 is placed on the water-bath, and to it is added a strong 
 solution of HgCl 2 , which will cause a red precipitate (Hglj, 
 that disappears on shaking the mixture. The HgOl, solu- 
 tion is carefully added, the liquid heing at the same time 
 shaken, so as to dissolve the precipitate as fast as it is 
 formed; the addition of the HgCl, solution is continued 
 until the precipitate ceases to be dissolved. When this 
 point is reached no more HgCl 2 must be added. The mix- 
 ture is then filtered, and to the filtrate is added 150 grammes 
 of solid NaHO in strong aqueous solution (or about 200 
 grammes of solid KIIO dissolved in water). After the 
 addition of the alkali solution, the liquid is diluted so as 
 to make its volume equal to one litre. Add to the diluted 
 liquid about 5 cub. cent, of a saturated aqueous solution of 
 HgCl 2 ; allow to subside, and decant the clear liquid. 
 
 "As exposure to the air is apt to render this reagent 
 somewhat turbid, it is advisable to keep the stock of the 
 reagent in a large bottle, which should only be opened to 
 supply a small bottle kept to hold that which is in imme- 
 
 * Sec Appendix O, pnge 380. 
 
REAGENT PAPERS. 385 
 
 rliate use. The addition of the 5 c. c. of solution HgCl 2 
 has two objects ; it causes the reagent to clear rapidly, and 
 imparts sensitiveness to the reagent when deficient in that 
 quality." (Wanklyn and Chapman on Water Analysis.) 
 
 61. Solution of indigo.- — ■" Take from 4 to 6 parts of 
 fuming H g S0 4 , add slowly and in small portions at a time 
 1 part of finely pulverized indigo, taking care to keep the 
 mixture well stirred. The acid has at first imparted to it 
 a brownish tint by the matter which the indigo contains in 
 admixture, but it subsequently turns blue. Elevation of 
 temperature to any considerable extent must be avoided, 
 as part of the indigo blue is thereby destroyed ; it is there- 
 fore advisable, when dissolving larger quantities of the sub- 
 stance, to place the vessel in cold water. When the whole 
 of the indigo has been added to the acid, cover the vessel, 
 let it stand forty-eight hours, then pour its contents into 
 twenty times the quantity of water, mix, filter, and keep the 
 filtrate for use." 
 
 62. Distilled water ought always to be employed in all the 
 above solutions and in all analytical operations. It should 
 leave no residue on evaporation, and should give no pre- 
 cipitate or even turbidity, with BaCl 2 , AgN0 3 , (NH 4 ) 2 C 2 4 , 
 or lime-water. 
 
 63. Reagent papers. — Blue litmus paper serves to detect 
 the presence of free acids or of acid salts in fluids, since 
 they change the blue color to red. Reddened litmus paper 
 serves to detect the presence of free alkalies, and of earths 
 and salts possessing an alkaline reaction, by changing the 
 
 . red color to blue. Turmeric paper aids, like reddened 
 litmus paper, in the detection of free alkalies, etc., by 
 changing its yellow color to brown. 
 
 Preparation of blue litmus paper. — "Digest 1 part of 
 litmus of commerce with 6 parts of water, and filter the 
 solution; divide the intensely blue filtrate into 2 equal 
 parts ; saturate the free alkali in the one part, by repeat- 
 edly stirring with a glass rod dipped in very dilute H 2 S0 4 , 
 until the color of the fluid just appears red; add now the 
 other part of the blue filtrate, pour the whole fluid into a 
 dish, and draw strips of fine, unsized paper through it; 
 suspend these strips over threads, and leave them to dry. 
 The color of litmus paper must be perfectly uniform, and 
 neither too light nor too dark." 
 
 Preparation of reddened litmus paper. — "Stir blue solu- 
 tion of litmus with a glass rod dipped in dilute H,SO,, and 
 repeat this process until the fluid has just turned distinctly 
 33 
 
386 APPARATUS. 
 
 red. Steep slips of paper in the solution, and dry them as 
 directed in the preceding paragraph. The dried slips must 
 look distinctly red." 
 
 Vacher prepares a paper of neutral tint thus: Digest 20 
 grm. litmus with 100 c. c. water for some days, shaking 
 occasionally, then filter. To the filtrate add slight excess 
 of HNO„ and boil; then neutralize exactly with KHO. 
 Now make a weak solution of gelatine by boiling 1 part of 
 isinglass with 50 parts of water ; draw white blotting-paper 
 through this, and hang it up to dry. When dry, paint one 
 side with the above solution. 
 
 Preparation of turmeric paper. — Digest and heat 1 part 
 of bruised turmeric root with 6 parts of weak spirit of 
 wine, filter the tincture obtained, and steep slips of fine 
 paper in the filtrate. The dried slips must exhibit a fine 
 yellow tint. 
 
 Schonbein's test-papers for hydrocyanic acid. — Three 
 parts of resin of guaiacum are dissolved in 100 parts of 
 rectified spirit ; white filtering paper is steeped in this solu- 
 tion and dried. The paper should remain white. The solu- 
 tion of cupric sulphate, with which these papers are to be 
 moistened just before being used, is prepared by dissolving 
 one part of cupric sulphate in 500 parts of water. 
 
 Brazil-wood paper is prepared by moistening slips of 
 fine writing paper with decoction of Brazil wood. 
 
 APPARATUS. 
 
 1119. The processes employed in qualitative analysis are 
 exceedingly simple, and do not require much apparatus for 
 their execution. The small amount actually requisite is 
 described in the following list, and may be procured in the 
 shops of operative chemists. 
 
 1^- dozen test-tubes. Small retort stand. 
 
 Test-tube stand. 3 small glass funnels. 
 
 2 small evaporating dishes. 2 porcelain crucibles. 
 
 Washing bottle. % lb. glass tubing. 
 
 Spirit lamp. \ lb. glass rod. 
 
 2 watch-glasses. Small mortar and pestle. 
 
 Rat-tail and triangular file. 1 quire filtering paper. 
 
 Platinum wire and foil. Crucible tongs. 
 
 Sulphuretted hydrogen ap- Black's blowpipe. 
 
 paratus. Tube cleaner. 
 
 A number of best corks. Small German beakers. 
 
 A few lengths of small vul- Litmus paper, blue and red. 
 
 canized tubing. Turmeric paper. 
 
APPENDICES. 
 
 Appendix A. Treatment op Silver Residues. — Waste 
 solutions containing silver must not be poured into the sink, 
 but into a bottle containing some commercial hydrochloric 
 acid ; when a quantity of the precipitated AgCl has collected 
 sufficient, in the opinion of the experimentalist, for reduc- 
 tion, it may be thrown upon a filter, washed thoroughly 
 with hot water and afterwards dried ; when dry it must be 
 detached from the filter, and the filter must then be burnt 
 until all the carbonaceous matter of the filter is destroyed ; 
 the filter ash along with the silver it may contain may be 
 added to the silver salt or placed in the silver residue 
 bottle. The silver may be obtained from the dried AgCl 
 by one or other of the following processes: (1) Mix it with 
 twice its weight of reagent 34 (page 381), and then intro- 
 duce the mixture into a Cornish clay crucible which it 
 ought only to half fill, and afterwards place the crucible in 
 a furnace and raise the heat gradually until the mixture 
 becomes fluid, keep it in that state for about five minutes, 
 and then remove the crucible from the furnace, tap it 
 slightly on the bottom two or three times so as to cause all 
 the particles of silver to collect together in a mass, and 
 then allow it to cool; when cold, the crucible is broken and 
 the silver, which has collected in the form of a button if 
 the operation has been well performed, is removed and 
 freed by washing from any adherent particles of the alkaline 
 salts. This process succeeds with experienced chemists, 
 but often fails with beginners, for the heat must be gradu- 
 ally applied and the crucible not more than half full, other- 
 wise the effervescence caused by the evolution of C0 2 and 
 may cause a loss of the substance ; and the heat finally 
 must be high enough, otherwise the silver remains dissemi- 
 nated through the mass of the alkaline salts; and yet it 
 must not be too high, otherwise the crucible is corroded 
 and the silver flows into the fire. In order to obviate these 
 
388 APPENDICES. 
 
 disadvantages, the late Professor Gregory recommended 
 the undried AgCl to be boiled with a verj' strong solution 
 of caustic potash, till it is entirely or in great part con- 
 verted into black oxide of silver ; this is then collected, 
 washed thoroughly, then dried, and, finally, fused with a 
 little potassic carbonate and borax, which yields a button 
 of silver without any risk. If all the AgCl was converged 
 into Ag 2 by boiling with KHO, simple ignition would be 
 sufficient to obtain the silver in the metallic state. (2) 
 Boil 6 parts of silver chloride for half an hour with 9 
 parts of a solution of caustic soda of 1.333 sp. gr., 1^ parts 
 of clarified honey, and 8 parts of water; when the heat is 
 withdrawn let the finely divided silver collect at the bottom 
 of the vessel, and then pour off the liquid and wash the 
 silver thoroughly by decantation. (3) The AgCl is placed 
 in contact with iron or zinc and water, to which, in order 
 to accelerate the action, a small quantity of HC1 or H^SO^ 
 may be added ; the reduced silver roust be quickly washed 
 first with acidulated and afterwards with hot pure water, 
 and then fused with borax and nitre. Convert the metallic 
 silver obtained by any of these different processes into 
 nitrate as directed at 51 (page 383). 
 
 Appendix B. Treatment of Platinum Residues 
 
 Platinum residues are collected in a bottle, and when a 
 sufficient quantity has collected the mixture, the liquid 
 and precipitate, is evaporated to dryness in a porcelain 
 dish, and ignited so as to decompose the platinic salts, and 
 the residue washed to remove the soluble matter ; a small 
 quantity of oxalic acid in solution is then added to it, and 
 the mixture is again evaporated and ignited so as to de- 
 compose any PtClj, 2KC1, which may have escaped decom- 
 position on the first ignition; the ignited mass is again 
 thoroughly washed with hot water, it must then be boiled 
 in dilute HC1 and the insoluble portion again washed 
 thoroughly with hot water ; it is then converted into PtCl 4 
 as directed at 54 (page 383). If the dry PtCl, does not 
 dissolve completely in spirits of wine it must be redis- 
 solved in water, and a saturated solution of N1I 4 C1 added 
 to it, the precipitated PtCl,, JNTI 4 C1 must be collected 
 upon a filter, washed first with a little water, and finally 
 with methylated spirit and ignited ; the spongy platinum 
 thus obtained must be converted into PtCl 4 as directed at 
 51 (page 383). 
 
APPENDICES. 389 
 
 "Appendix C. Treatment op Gold Residues — Gold 
 residues are collected in a bottle, and when a sufficient 
 quantity has collecled the mixture is evaporated to dryness 
 and ignited. The ignited mass is washed thoroughly with 
 hot water, and the insoluble matter is dissolved in aqua 
 regia; evaporate to dryness over the water-bath; redis- 
 solve the residue in water ; mix it with an excess of satu- 
 rated solution of oxalic acid and boil for some time; 
 finally, free by washing the spongy mass of gold from 
 foreign matter, and then convert it into AuCl 3 , as directed 
 at 55 (page 383). 
 
 33* 
 
INDEX. 
 
 ACETATES, properties of, 224 
 Acetic acid as reagent, 375 
 
 behavior of, with reagents, 22-1 
 detection of, 230 
 properties of, 224 
 Acids, classification of, 175 
 
 organic, classification of, 22S 
 of the bile in calculi, 318 
 volatile inorganic, behavior of salts 
 of, with sulphuric acid, 214 
 Action of water on lead, 15-1 
 Albumen, behavior of, with reagents, 283 
 composition of, 280 
 detection of, 2S9 
 examination for, 310 
 properties of, 27S, 320 
 varieties of, 2S5 
 Albuminoids, Gerhardt's views on the 
 constitution of, 2SI 
 Mulder's views on tho constitution 
 
 of, 281 
 Strecker's views on the constitution 
 of, 2S2 
 Albuminoid substances, 27S 
 Alcohol, conversion into acetic acid, 225 
 Alkaloids, poisonous, detectiou of, in or- 
 ganic mixtures, 311 
 Aluminic chloride, properties of, 82 
 compounds, blowpipe test for, 85 
 characteristic tests for, S3 
 properties of, SA 
 nitrate, properties of, 82 
 oxide, properties of, SO 
 phosphate, properties of, 90 
 sulphate, properties of, S2 
 sulphide, properties of, 81 
 Aluminum, properties of, 79, 81 
 Ammonia as reagent, 376 
 examination for, 35, 41 
 Nessler's test for, 42 
 properties of, 39 
 Ammouic arseuiate as reagent, 377 
 carbonate as reagent, 377 
 chloride as reagent, 377 
 
 properties of, 40 
 compounds, characteristic tests for, 
 42 
 properties of, 41 
 special tests for, 41 
 hydrate, properties of, 39 
 molybdate as reagent, 377 
 nitrate as reagent, 377 
 oxalate as reagent, 376 
 oxide, 33 
 sulphate, properties of, 40 
 
 Amnionic — 
 
 sulphide as reagent, 377 
 sulphocyanide as reagent, 379 
 urate in calculi, 317 
 Ammonio-nitrate of silver as reagent, 38 
 
 sulphate of copperas reagent, 383 
 Ammonium, compounds of, 39, 41 
 Analysis of animal secretions, 309 
 substances, 277 
 calculi, 317 
 
 ash of organic substances, 273 
 organic substances, 269 
 solids insoluble in acids, 2G2 
 soluble in acids, 262* 
 in water, 261 
 urine, 277, 313 
 first basic group, 35 
 
 precautions, 36 
 second basic group, 47 
 
 Fresenius's method, 57 
 photo-chemical method, AS 
 precautions, 51 
 third basic group, 61 
 
 precautions, 64 
 fourth basic group, first method, 77 
 second method, 77 
 third method, 79 
 containing phosphates and 
 oxalates, 94 
 fifth basic group, first method, 99 
 second method, 100 
 third method , 100 
 fourth method, 101 
 fifth method, 101 
 sixth method, 101 
 sixth basic group, 136 
 
 precautions, 140 
 first group inorganic acids, 20S 
 second group inorganic acids, 20S 
 third group inorganic acids, 209 
 fourth group inorganic acids, 210 
 first group organic acids, 22S 
 second group organic acids, 229 
 third group organic acids, 229 
 fourth group organic acids, 229 
 Animal secretions, analysis of, 309 
 
 substances, behavior of, with rea- 
 gents, 279 
 distillation of, 27S 
 oxidation of, 278 
 proximate analysis of, 277 
 Antimonious chloride, properties of, 103 
 hydrate, properties of, 113 
 oxide, properties of, 104 
 salts, properties of, 112 
 
392 
 
 INDEX. 
 
 Antimonious— 
 
 sulphide, properties of, 105 
 Antimonuretted hydrogen, properties of, 
 
 HI 
 Antimony compounds, blowpipe tests for, 
 118 
 characteristic tests for, 118 
 flame reactions, 118 
 properties of, 116 
 special tests for, 116 
 detection of, in organic mixtures, 117 
 hydride of, properties of, 111 
 properties of, 102, 116 
 Apparatus, list of, 386 
 Argentic chloride, properties of, 145 
 compounds, blowpipe tests for, 147 
 characteristic tests for, 148 
 properties of, 146 
 nitrate as reagent, 483 
 properties of, 146 
 oxide, properties of, 143 
 peroxide, 148 
 salts, properties of, 146 
 suboxide, 148 
 sulphate, properties of, 146 
 sulphide, properties of, 144 
 Arrangement of results, 30 
 ArseniateB, behavior of, with reagents, 
 132 
 properties of, 113 
 Arsenic acid as reagent, 377 
 
 behavior of, with reagents, 132 
 characteristic tests for, 211 
 properties of, 113 
 Arsenic anhydride, properties of, 104 
 compounds flame reactions, 131 
 properties of, 119 
 special tests for, 119 
 detection of, by electrolysis, 128 
 
 in organic mixtures, 126 
 dialytic method for detection of, 126 
 hydride of, properties of, 111 
 Marsh's test for, 122 
 
 precautions, 124 
 properties of, 102, 119 
 Keinsch's test for, 125 
 Bulphide, properties of, 105 
 Arsenious acid, characteristic tests for, 
 211 
 properties of, 113 
 Arsenious anhydride, properties of, 104 
 chloride, properties of, 108 
 oxide, behavior of, with reagents, 119 
 sulphide, properties of, 105 
 Arsenites, behavior of, with reagents, 120 
 
 properties of, 113 
 Arsenuretted hydrogen, properties of, 111 
 Ash of organic substances, analysis of, 273 
 
 constituents of, 274 
 Auric chloride as reagent, 383 
 properties of, 110 
 compounds, properties of, 132 
 
 special tests for, 133 
 oxide, properties of, 104 
 salts, properties of, 113 
 sulphide, properties of, 105 
 Aurous oxldb, proportles of, 133 
 
 BARIC carbonato as reagent, 382 
 ohlorldo as reagent, 381 
 properties of, 52 
 
 Baric- 
 compounds, special tests for, 55 
 characteristic tests for, 55 
 flame reactions, 55 
 properties of, 55 
 oxide, properties of, 51 
 nitrate as reagent, 382 
 
 properties of, 53 
 salts, general character of, 5i 
 sulphate, properties of, 53 
 sulphide, properties of, 52 
 
 Barium, properties of, 51, 55 
 
 Basic groups, behavior of, with reagents, 
 166 
 list of, 29 
 
 Bassorin, 324 
 
 Behavior of acetic acid with reagents, 224 
 albumen with reagents, 283 
 animal substances with reagents, 279 
 arseniates with reagents, 132 
 arsenic acid with reagents, 132 
 arsenious oxide with reagents, 119 
 arsenites with reagents, 120 
 basic groups with group reagents, 166 
 benzoic acid with reagents, 222 
 biliruhine with reagents, 307 
 boracic acid with reagents, ISO 
 brucine with reagents, 339 
 calculi on heating, 313 
 cane-sugar with reagents, 32-5 
 carbonic acid with reagents, 185 
 casein with reagents, 288 
 cellulose with reagents, 321 
 chloric acid with reagents, 206 
 cholepyrrhin with reagents, 307 
 cholestrin with reagents, 307 
 chondrin with reagents, 293 
 chromic acid with reagents, 176 
 cinchonine with reagents, 336 
 citric acid with reagents, 219 
 creatin with reagents, 301 
 creatinine with reagents, 300 
 cystine with reagents, 305 
 elements at high temperatures, 361 
 fibrin with reagents, 2S7 
 first basic group with special re- 
 agents, 34 
 formic acid with reagents, 226 
 fourth basic group with special re- 
 agents, 7S 
 gallic acid with reagents, 2-24 
 gelatin with reagents, 292 
 glucose with reagents, 294 
 glutin with reagents, 292 
 glyco-cholalio acid with reagents, 30* 
 grape sugar with reagents, '**j 
 gum with rengeuts 324 
 hlppuric acid with reagents, 303 
 bydriodic acid with reagents, 196 
 hydrobromic acid with reagents, 19S 
 hydrochloric acid with reagents, 194 
 hydrocyanic acid with reagents, 900 
 hydrofluoric acid with reagents, 191 
 hydrosulphuric acid with reageuts, 
 
 liyposulphurous acid with reagent* 
 
 ISO 
 innate with reagents, 2^7 
 iodic acid with rengouts, 107 
 lactic acid with reagents, 302 
 llguin with reagents, 321 
 malic acid with redouts, 221 
 
INDEX. 
 
 393 
 
 Behavior of — 
 
 meconic acid with reagents, 310 
 mctaphosphoric acid with reagents, 
 
 185 
 mik sugar with reagents, 295 
 morphine with reagents, 329 
 narcotine with reagents, 332 
 nicotine with reagents, 328 
 nitric acid with metals, 267 
 
 with reagents, 203 
 oxalic acid with reagents, 187 
 phaseomaunite with reagents, 297 
 phosphoric acid with reagents, 182 
 pyrophosphoric acid with reageDts, 
 
 185 
 quinine with reagents, 331 
 salts of volatile inorganic acids with 
 
 sulphuric acid, 214 
 second hasic group with special re- 
 agents, 49 
 silicic acids with reagents, 1SS 
 sixth basic group with special re- 
 agents, 138 
 starch with reagents, 323 
 strychnine with reagents, 336 
 succiuic acid with reagents, 222 
 sugar of milk with reagents, 295 
 sulphuric acid with reagonts, 178 
 sulphurous acid with reagents, 179 
 tannic acid with reagents, 223 
 tartaric acid with reagents, 217 
 taurocholalic acid with reagents, 305 
 taurocholic acid with reagents, 305 
 1 liiosulphuric acid with reagents, ISO 
 third basic group with special re- 
 
 iigenls, 62 
 titanic oxide with reagents, 97 
 uranic oxide with reagents, 97 
 urea with reagents, 29S 
 uric acid with reagents, 227 
 xanthine with reRgents, 306 
 Be nziL mid acetic acid, behavior of, with 
 reagents, 303 
 composition of, 303 
 properties of, 303 
 Benzoic acid, behavior of, with reagents, 
 222 
 detection of, 230 
 Bile acids, examination for, 312 
 
 coloring matter, examination for, 312 
 coloring matter of, 307 
 in urine, 315 
 
 Pettenkofer's test for, 304, 309 
 properties of, 308 
 tests for, 309 
 Bilirubine, behavior of, with reagents, 
 307 
 composition of, 307 
 detection of, 307 
 properties of, 307 
 Biliverdine, properties of, 308 
 Biuoxide of lead, 157 
 Bismuth compounds, blowpipe test for, 
 152 
 characteristic test**; 153 
 flame reactions, 152 
 properties of, 152 
 Bismuthic anhydride, 152 
 
 dioxide, 153 
 Bismuthous chloride, properties of, 145 
 nitrate, properties of, 146 
 oxide, properties of, 143 
 
 Bismuthous— 
 
 salts, properties of, 146 
 sulphide, properties of, 1-44 
 Bismuth, properties of, 142, 152 
 Blood, coloring matter of, 308 
 
 tests for, 308 
 Blowpipe, 351 
 
 operations, 237 
 
 supports for, 353 
 test for aluminic compounds, 85 
 antimony compounds, 118 
 argentic compounds, 148 
 bismuth compounds, 152 
 bromides, 200 
 chlorides, 195 
 chromic compounds, 85 
 cobalt compounds, 73 
 cupric compounds, 159 
 iodides, 197 
 load, 156 
 manganese, 69 
 nickel compounds, 72 
 silicic acid, 191 
 sulphates, 179 
 tin compounds, 115 
 zincic compounds, 70 
 Boracic acid, behavior of, with reagents, 
 180 
 characteristic tests for, 211 
 Borax as reagent, 381 
 Brazil-wood paper, 386 
 Bromides, blowpipe test for, 200 
 Bromine, detection of, in presence of 
 
 iodine and chlorine, 199 
 Brucine, behavior of, with reagents, 339 
 composition of, H39 
 properties of, 339 
 Bunsen's flame reactions, 260 
 gas lamp, 358 
 
 CADMIC chloride, properties of, 145 
 nitrate, properties of, 146 
 oxide, properties of, 143 
 salts, properties of, 146 
 sulphide, properties of, 144 
 Cadmium and copper, separation of, 159 
 compounds, blowpipe tests for, 154 
 flame reactions, 151 
 properties of, 154 
 properties of, 142, 154 
 Calcic carbonate in calculi, 319 
 chloride as reagent, 382 
 
 properties of, 53 
 compounds, characteristic tests for, 
 57 
 flame reactions, 5Q 
 properties of, 56 
 special tests for, 56 
 nitrate, properties of, 53 
 oxalate, detection of, 92 
 
 in calculi, 319 
 oxide, properties of, 53 
 phosphate, detection of, 91 
 
 in calculi, 319 
 salts, general character of, 54 
 sulphate as reagent, 3S2 
 
 properties of, 53 
 sulphite, properties of, 52 
 urate in calculi, 319 
 Calcium, properties of, 51, 56 
 Calculi, analysis of, 317 
 
394 
 
 INDEX. 
 
 Calculi— 
 
 behavior of, on heating, 317 
 classification of, 317 
 composition of, 317 
 containing amnionic urate, 318 
 
 cholesterlno, 318 
 
 cystine, 318 
 
 fibrin, 318 
 
 uric acid, 318 
 
 xanthine, 318 
 Cane-sngar, behavior of, with reagents, 
 325 
 composition of, 325 
 properties of, 325 
 Caramel, 325 
 
 Carbonates, properties of, 186 
 Carbonic acid, behavior of, with reagents, 
 185 
 
 characteristic tests for, 211 
 
 precautions In examiningfor, 187 
 Casein, behavior of, with reagents, 288 
 composition of, 280 
 detection of, 290 
 examination for, 310 
 properties of, 278, 288, 320 
 Cellulose, behavior of, with reagents, 321 
 composition of, 321 
 properties of, 321 
 Characteristic reagents, 26 
 
 tests for aluminic compounds, 85 
 
 amnionic compounds, 42 
 
 antimony compounds, 118 
 
 argentic compounds, 148 
 
 arsenic acid, 211 
 
 arsenious acid, 211 
 
 baric compounds, 55 
 
 bismuth compounds, 152 
 
 boracic acid, 211 
 
 calcic compounds, 57 
 
 carbonic acid, 211 
 
 chloric acid, 212 
 
 chromic acid, 211 
 compounds, 86 
 
 cobalt compounds, 74 
 
 cupric compounds, 159 
 
 ferric compounds, 87 
 
 ferrous compounds, S7 
 
 hydrlodic acid, 212 
 
 hydrochloric acid, 212 
 
 hydrocyanic acid, 212 
 
 hydrofluoric acid, 211 
 
 hydrosulphuric acid, 212 
 
 lead compounds, 157 
 
 lithic compounds, 46 
 
 magnesic compounds, 59 
 
 manganese compounds, 70 
 
 mercury compounds, 152 
 
 nickel compounds, 72 
 
 nitric acid, 212 
 
 oxalic acid, 211 
 
 phosphoric acid, 211 
 
 pottissic compounds, 44 
 
 silicic acid, 211 
 
 Bodic compounds, 46 
 
 strontic compounds, 56 
 
 sulphuric acid, 211 
 
 uranium compounds, 97 
 
 zinoio compounds, 70 
 Chloratos, properties of, 207 
 Chloric acid, behavior of, with roagouts, 
 20 U 
 
 characteristic tests for, 212 
 
 Chlorides, blowpipe test for, 195 
 Chlorine as reagent, 376 
 
 detection of, 195 
 Cholepyrrhin, behavior of, with re- 
 agents, 316 
 composition of, 307 
 detection of, 307 
 properties of, 307 
 Cholestrin, behavior of, with reagents, 
 307, 323 
 composition of, 307 
 in calculi, 318 
 properties of, 307 
 Chondrin, behavior of, with reagents, 293 
 composition of, 291 
 detection of, 291, 294 
 examination for, 311 
 oxidation of, 25*1 
 properties of, 291 
 Chromates, properties of, 176 
 Chromic acid, behavior of, with reagents, 
 176 
 characteristic tests for, 211 
 anhydride, properties of, 176 
 chloride, properties of, S2 
 compounds, blowpipe tests for, 85 
 characteristic tests for, 56 
 properties of, 84 
 special tests for, 86 
 oxide, properties of, 80 
 phosphate, properties of, 90 
 nitrate, properties of, S2 
 sulphate, properties of, S2 
 sulphide, properties of, 81 
 Chromium, properties, of, 79, S.J 
 Cinchooiue, behavior of, with reagents, 
 336 
 composition of, 336 
 properties of, 336 
 Citrates, properties of, 219 
 Citric acid, behavior of, with reagents, 
 219 
 detection of, 229 
 preparation of, 219 
 Classification of acids, 175 
 calculi, 317 
 inorganic acids, 20S 
 organic acids, 22S 
 Coagulation of milk, 2>S 
 Cabal t compounds, blowpipe tests for, 73 
 characteristic tests for, 74 
 flame reactions, 73 
 properties of, 72 
 special test;, for, 72 
 Cobaltic nitrate as reagent, 3S3 
 Cobaltous chloride, properties of, 67 
 nitrate, properties of. 67 
 oxide, properties of, 65 
 salts, properties of, 6S 
 sulphate, properties of, 67 
 sulphide, properties of, 66 
 Cobalt, 65, 72 
 Coloration of flame, 237 
 Coloring matter of the bile, 307 
 examination for, 212 
 in calculi, 319 
 blood, 308 
 urine, 307 
 Composition of albumen. 2S0 
 billrublue, 307 
 brucino, 339 
 calculi, 317 
 
INDEX. 
 
 395 
 
 Composition of — 
 cane-sugar, 323 
 casein, 280 
 cellulose, 321 
 cliolepyrrhin, 307 
 
 cholestrin, 307 
 
 chondrin, 2D1 
 
 cinchonine, 336 
 
 creatin, 301 
 
 creatinine, 300 
 
 cystine, 305 
 
 fibrin, 280 
 
 gelatin, 292 
 
 glucose, 295 
 
 glyco-cholalic acid, 304 
 
 grape-sugar, 295 
 
 gum, 324 
 
 hippuric acid, 303 
 
 inosite, 297 
 
 lactic acid, 302 
 
 lactin, 295 
 
 lactose, 293 
 
 lignin, 321 
 
 meconic acid, 340 
 
 milk-sugar, 295 
 
 morphine, 329 
 
 narcotine, 332 
 
 nicotine, 328 
 
 phaseomannite, 297 
 
 quinine, 334 
 
 silicates, 190 
 
 starch, 323 
 
 strychnine, 330 
 
 sugar of milk, 295 
 
 taurocholalic acid, 305 
 
 taurocholic acid, 305 
 
 urea, 298 
 
 urine, 314 
 
 xanthine, 306 
 Constituents of ash of organic substances, 
 
 274 
 Constitution of the albuminoids, Stac- 
 ker's views, 282 
 Gerhardt's views, 2S1 
 Mulder's views, 281 
 Conversion of alcohol into acetic acid, 225 
 Copper and cadmium, separation of, 159 
 
 detection of, in organic liquids, 153 
 solids, 159 
 
 properties of, 142, 157 
 
 turnings as reagents, 384 
 Creatine, behavior of, with reagents, 301 
 
 composition of, 301 
 
 examination for, 313 
 
 properties of, 301 
 Creatinine, behavior of, with reagents, 
 300 
 
 composition of, 300 
 
 detection of, 301 
 
 examination for, 313 
 
 properties of, 301 
 Cupellation, 253 
 Cupric chloride, properties of, 145 
 
 compounds, blowpipe test for, 159 
 characteristic tests for, 159 
 flame reactions, 159 
 properties of, 15S 
 
 nitrate, properties of, 146 
 
 oxide, properties of, 143 
 
 salts, properties of, 146 
 
 sulphate as reagent, 383 
 
 sulphide, properties of, 144 
 
 Cystine, behavior of, with reagents, 305 
 composition of, 305 
 detection of, 306 
 in calculi, 31S 
 properties of, 305 
 
 DECANTATION, 349 
 Deflagration, 26, 351 
 Detection of acetic acid, 230 
 albumen, 290 
 
 antimony in organic mixtures, 117 
 arsenic by dialytic method, 126 
 by electrolysis, 129 
 in organic mixtures, 126 
 benzoic acid, 230 
 bilirubine, 307 
 bromine in presence of iodine and 
 
 chlorine, 199 
 casein, 290 
 cholepyrrhin, 307 
 chondrin, 291, 294 
 citric acid, 229 
 copper in organic liquids, 158 
 
 solids, 159 
 creatinine, 301 
 cystine, 306 
 fibrin, 290 
 formic acid, 230 
 free sulphuric acid in presence of a 
 
 sulphate, 179 
 gallic acid, 230 
 gelatin, 292, 294 
 glucose, 295 
 grape-sugar, 296 
 
 hydrocyanic acid in mercuric cya- 
 nide, 202 
 organic mixtures, 202 
 iodates in presence of iodides, 197 
 lead in organic mixtures, 156 
 
 waters, 156 • 
 
 malic acid, 230 
 mercury in organic liquids, 150 
 
 solids, 131 
 opium in organic mixtures, 341, 
 poisonous alkaloids in organic mix- 
 tures, 341 
 metals by electrolysis, 130 
 strychnine in organic mixtures, 338 
 succinic acid, 230 . 
 sugar, 297 
 tannic acid, 230 
 tartaric acid, 229 
 
 in presence of citric acid, 220 
 urea, 300 
 uric acid, 230 
 xanthine, 306 
 Determination of fusibility of solids, 255 
 Dyalytic method for detection of arsenic, 
 
 126 
 Dibasic silicic acid, preparation of, 189 
 Dyhidric dipotassic metantimoniate as 
 
 reagent, 381 
 Disodic hydric phosphate, 380 
 Distillation, 350 
 
 of animal substances, 278 
 Distilled water, 385 
 
 EFFERVESCENCE, 26 
 Electrolytic detection of arsenic, 12S 
 of poisonous metals, 130 
 
396 
 
 INDEX. 
 
 Elements, behavior of, at high tempera- 
 tures, 361 
 
 flame reactions of, 370 
 Emerald green, 114 
 Evaporation, 319 
 Examination for albumen, 310 
 
 ammonia, 3d 
 
 bile acids, 312 
 
 casein, 311 
 
 chondrin, 311 
 
 coloring mattor of the bile, 312 
 
 creatine, 313 
 
 creatinine, 313 
 
 fatty matter, 313 
 
 globulin, 310 
 
 glucose, 312 
 
 hiematin, 310 
 
 inorganic acids, 212, 231 
 
 lactic acid, 313 
 
 morphine, 332 
 
 mucus, 311 
 
 nicotine, 328 
 
 nitrogen, 270 
 
 organic acids, 230 
 
 phosphorus in organic substances, 
 272 
 
 potassic compounds, 35 
 
 pus, 310 
 
 Kodic compounds, 35 
 
 sulphur in organic substances, 271 
 
 urea, 313 
 
 uric acid; 311 
 Examination of liquids, 233 
 
 solids, 236 
 
 with borax, 254 
 in closed tube, 241 
 in open tube, 247 
 on charcoal, 249 
 
 -with cobaltic nitrate, 249 
 with sodic carbonate, 219 
 Exercises on first basic group. 46 
 
 second basic group, 59 
 
 third basic group, 74 
 
 fourth basic group, SS, 96 
 
 fifth basic group, 134 
 
 sixth basic group, 160 
 
 all basic groups, 174 
 
 inorganic acids, 215 
 
 organic acids, 232 
 
 organic alkaloids, 345 
 
 examination of liquids, 235 
 solids, 26S 
 
 animal chemistry, 326 
 
 FATTY mattor, examloation for, 313 
 in urine, 316 
 Formontation of glucose, 295 
 of grape-sugar, 296 
 test for sugar, 207 
 Ferments, 278 
 
 Forrio chloride rb reagent, 3S2 
 properties of, s2 
 compounds, characteristic tests for, 87 
 nitrate, properties of, 82 
 oxide, properties of, 80 
 phosphate, properties of, 01 
 sulphate, properties of, 82 
 sulphide, properties of, SI 
 ForrouK oblorldo, prunm'tie* of, S3 
 
 compounds, eluiriicteiistie touts for, 
 87 
 
 Ferrous — 
 
 oxide, properties of, 80 
 sulphate as reagent, 382 
 
 properties of, 82 
 sulphide, 81 
 Fibrin, behavior of, with reagents, 287 
 composition of, 2S0 
 detection of, 290 
 in calculi, 318 
 properties of, 278, 2S6, 320 
 Fifth basic group, analysis of first method, 
 99 
 second method, 100 
 third method, 100 
 fourth method, 101 
 fifth method, 101 
 sixth method, 101 
 precautions in examining for, 171 
 precipitation of, 163 
 Films of volatile elements, 358,367 
 Filtration, 348 
 First basic group, analysis of, 35 
 
 behavior of, with special reagents, 
 
 34 
 examination for, 16S 
 precautions in analysis of, 36 
 properties of, 33 
 First group of inorganic acids, analysis 
 of, 208 
 organic acids, analysis of, 223 
 Flame coloration, 237, 364 
 reactions, 260 
 
 of antimony compounds, 118 
 arsenic compounds, 131 
 baric compounds, 55 
 bismuth compounds, 152 
 cadmium compounds, 153 
 calcic compounds, 56 
 cobalt compounds, 73 
 cnpric compounds, 159 
 iron compounds, S7 
 lend compounds, 150 
 litbic compounds, 46 
 mercury compounds, 151 
 nickel compounds, 72 
 pot a $>>ic compounds, 35, 43 
 sodic compounds. 45 
 strootic coinpouudf, 56 
 tin compounds. 115 
 titanic compounds, 9^ 
 nrauium compounds, 97 
 zincic compounds, 70 
 element;-. 370 
 Formates, proper lie-* of, 225 
 Formation of precipitates, _'i 
 Formic acid, behavior of, with reagents, 
 22ti 
 detection of, 230 
 preparation of, 226 
 Fourth basic group, analysis of first 
 method, 77 
 second method, 77 
 third method, 79 
 behavior of, with special re- 
 age uU, 7> 
 precautions in analysis of, 92 
 
 In examining for, 172 
 proclpttntion of, 164 
 Fourth i^ronp of inorgauic acids, analy- 
 sis of, 210 
 organic acids, analysis of, 229 
 Fowler's solution, 111 
 
INDEX. 
 
 397 
 
 Fresenius's method of analysis of second 
 
 basic group, 57 
 Fusibility of solids, determination of, 255 
 Fusible calculus, 319 
 Fusion, 350 
 
 of solids by deflagration, 264 
 
 GALLIC ACID, behavior of, with re- 
 agents, 224 
 detection of, 230 
 and tannic acids, separation of, 223 
 Gelaligenous substances, 291 
 Gelatine, behavior of, with reagents, 291 
 composition of, 291 
 detection of, 291, 291 
 oxidation of, 291 
 properties of, 291 
 General character of aluminic salts, 83 
 ammonic salts, 41 
 antimony salts, 112 
 argentic salts, 146 
 arsenic salts, 112 
 auric salts, 112 
 baric salts, 54 
 bismuthic salts, 146 
 cadmic salts, 146 
 calcic salts, 54 
 chromic salts, 83 
 cobaltous salts, 08 
 cupric salts, 146 
 ferric salts, S3 
 ferrous salts, S3 
 lithic salts, 41 
 magnesic salts, 54 
 mangauous salts, 68 
 mercuric salts, 146 
 mercurous salts, 146 
 nickelous salts, 6S 
 platinic salts, 112 
 plumbic salts, 146 
 potassic salts, 41 
 sodic salts, 41 
 stannic salts, 112 
 stannous salts, 112 
 slrontic salts, 54 
 zincic salts, 6S 
 Gerhardt's views on the constitution of 
 
 the albuminoids, 2S1 
 Globulin, examination for, 310 
 
 properties of, 289 
 Glucose, behavior of, with reagents, 294 
 composition of, 295 
 detection of, 296 
 examination for, 312 
 fermentation of, 296 
 properties of, 295 
 Gluten, properties of, 320 
 Glutin, behavior of, with reagents, 292 
 Glyco-cholalic acid, behavior of, with 
 reagents, 304 
 composition of, 304 
 properties of, 304 
 Glycocholic acid, behavior of, with re- 
 agents, 304 
 composition of, 304 
 properties of, 304 
 Glyco-hyocholic acid, behavior of, with 
 reagents, 301 
 composition of, 304 
 properties of, 304 
 Gold, properties of, 102, 132 
 
 residues, treatment of, 3S9 
 Grape-sugar, behavior of, with reagents, 295 
 
 34 
 
 Grape-sugar — 
 
 composition of, 295 
 
 detection of, 295 
 
 fermentation of, 296 
 
 properties of, 295 
 Group reagents, 26 
 
 behavior of basic groups with, 1 66 
 Gum, behavior of, with reagents, 324 
 
 composition of, 324 
 
 properties of, 324 
 
 HJSMATIN, examination for, 310 
 properties of, 308 
 Hippuric acid, behavior of, with reagents, 
 303 
 composition of, 303 
 properties of, 303 
 How the bouk ought to be studied, 27 
 Hydric peroxide, preparation of, 178 
 Hydride of antimony, properties of, 111 
 
 arsenic, properties of, 111 
 Hydriodic acid, behavior of, with re- 
 agents, 196 
 characteristic tests for, 212 
 Hydrobromic acid, behavior of, with re- 
 agents, 19S 
 Hydrochloric acid as reagent, 373 
 
 behavior of, with reagents, 194 
 characteristic tests for, 212 
 Hydrocyanic acid, behavior of, with re- 
 agents, 200 
 characteristic tests for, 212 
 detection of, in mercuric cyanide, 
 202 
 in organic mixtures, 202 
 test-papers for, 386 
 Hydrofluosilicic acid as reagent, 376 
 Hydrofluoric acid, behavior of, with re- 
 agents, 191 
 characteristic testa for, 211 
 Hpdrosulphuric acid as reagent, 37a 
 
 behavior of, with reagents, 193 
 characteristic tests for, 212 
 Hyposulphurous acid, behavior of, with 
 reagents, ISO 
 
 INDIGO, solution of, as reagent, 3S5 
 Ignition, 350 
 Imperfect precipitation, 29 
 Inorganic acids, classification of, 208 
 examination for, 212 
 first group of, analysis of, 208 
 second group of, analysis of, 208 
 third group of. analysis of, 209 
 fourth group of, analysis of, 210 
 Inosite, behavior of, with reagents, 297 
 composition of, 297 
 properties of, 297 
 Iodates, detection of, in presence of 
 
 iodides, 198 
 Iodic acid, behavior of, with reagents, 197^ 
 Iodides, blowpipe test for, 197 
 Iodine, detection of, 196, 197 
 Iron compounds, flame reactions, 87 
 properties of, 86 
 special tests for, S6 
 liquor, 224 . 
 properties of, 79, 84 
 
 T ACTIC ACID, behavior of, with re- 
 Li agents, 302 
 
 composition of, 302 
 
398, 
 
 INDEX. 
 
 Lactic acid — 
 
 examination for, 313 
 properties of, 302 
 Lactin, behavior of, with reagents, 295 
 composition of, 295 
 properties of, 295 
 Lactose, behavior of, with reagents, 295 
 composition of, 295 
 properties of, 295 
 Lead, action of water on, 154 
 binoxide, 154 
 
 compounds, blowpipe test for, 156 
 characteristic tests for, 157 
 flame reactions, 156 
 detection of, in organic mixtures, 156 
 
 waters, 156 
 properties of, 142, 154 
 suboxide, 157 
 Legumine, properties of, 320 
 Lignin, behavior of, with reagents, 321 
 composition of, 321 
 properties of, 321 
 Lime-water as reagent, 382 
 List of apparatus, 386 
 Litharge, 154 
 Lithic chloride, properties of, 40 
 
 compounds, characteristic tests for, 46 
 flame reactions, 46 
 properties of, 46 
 special tests for, 46 
 hydrate, preparation of, 37 
 oxide, properties of, 33, 37 
 Lithium, properties of, 37 
 Litmus papers, preparation of, 335 
 
 MAG XESIC amnionic phosphate in cal- 
 culi, 319 
 chloride, properties of, 53 
 compounds, characteristic tests for, 59 
 properties of, 58 
 special tests for, 5S 
 nitrate, properties of, 53 
 oxide, properties of, 51 
 salts, general character of, 54 
 sulphate as reagent, 382 
 
 properties of, 63 
 sulphide, properties of, 52 
 urate in caluli, 319 
 Magnesium, properties of, 51, 58 
 Malates, properties of, 221 
 Malic acid, behavior of, with reagents, 221 
 
 detection of, 230 
 Manganese, blowpipe test for, 69 
 
 compounds, characteristic tests for, 
 70 
 properties of, 69 
 special tests for, 69 
 properties of, 65, 69 
 Manganous chloride, properties of, 67 
 nitrate, properties of, 67 
 oxide, properties of, tf.5 
 salts, properties of, 63 
 sulphate, properties of, 67 
 Bulphlde, properties of, 66 
 Marsh's tost for arsenic, 122 
 precautions, 124 
 Massloot, 154 
 
 Meoonlo aold, hohavlor of, with rongents, 
 340 
 composition of, 340 
 properties of, 310 
 
 MelasBlc acid, 296 
 Melting point of substances, 364 
 Mercuric chloride as reagent, 383 
 properties of, 145 
 nitrate, properties of, 148 
 oxide, properties of, 143 
 salts, properties of, 146 
 sulphide, properties of, 144 
 Mercurous chloride, properties or, lla 
 nitrate as reagent, 382 
 properties of, 146 
 oxide, properties of, 143 
 salts, properties of, 146 
 sulphate, properties of, 146 
 sulphide, properties of, 144 
 Mercury compounds, characteristic tests 
 for, 152 
 flame reactions, 151 
 properties of, 14S 
 special tests for, 150 
 detection of, in organic liquids, 150 
 
 solids, 151 
 properties of, 142, 148 
 Metalbumin, 286 
 Metals of first basic group, 37 
 Metaphosphoric acid, behavior of, with 
 
 reagents, 185 
 Metastaunic hydrate, properties of, 113 
 Microcosmic salt as reagent, 3S1 
 Milk, coagulation of, 289 
 Milk-sngar, behavior of, with reagents, 
 295 
 composition of, 295 
 properties of, 295 
 Morphine, behavior of, with reagents, 329 
 composition of, 329 
 examination for, 332 
 properties of, 329 
 Mucus, examination for, 311 
 Mulder's views on the constitution of the 
 abuminoids, 2S1 
 
 YARCOTINE, behavior of, with, re- 
 !> agents, 332 
 
 composition of, 332 
 examination for, 325 
 properties of, 332 
 Nessler's test for ammonia, 42 
 preparation of, 3S4 
 Nickel compounds, blowpipe te«t for, 72 
 characteristic tests for, 72 
 flit me reactions, 73 
 properties of, 71 
 properties of, 63, 71 
 Nickelous chloride, properties of, 67 
 nitrate, properties of, 67 
 oxide, properties of, 65 
 salts, properties of, 6S 
 sulphate, properties of, 67 
 sulphide, properties of, 6(> 
 Nicotine, behavior of, with reagents, 323 
 composition of, "_S 
 properties of, S2S 
 Nitrate* of first basic group, 37 
 
 properties of, 203, 206 
 Nitric acid as reagout, 373 
 
 behavior of, with metal*, 267 
 
 reagents, 203 
 characteristic tests for, 212 
 Nitrogen, examination for, 270 
 Nitro-hydrochlorlc acid as reagent, 373 
 
INDEX. 
 
 399 
 
 OPIUM, detection of, in organic mix- 
 tures, 311 
 Organic acidH, 216 
 
 classification of, 228 
 preliminary examination for, 231 
 examination for, 230 
 analysis of first group of, 228 
 second group of, 229 
 third group of, 229 
 fourth group of, 229 
 Organic substances, analysis of ash of, 
 273 
 constituents of ash of, 274 
 analysis of, 269 
 proximate analysis of, 272 
 Oxalates, properties of, 92, 1S7 
 Oxalic acid as reagent, 376 
 
 behavior of, with reagents, 1S7 
 characteristic tests for, 211 
 Oxidation of animal substances, 278 
 chondrin, 291" 
 gelatin, 291 
 substances, 365 
 Oxides of first basic group, 37 
 
 PARALBUMIN, 286 
 Pettenkofer's test for bile, 304, 309 
 Phaseomannite, behavior of, with re- 
 agents, 297 
 composition of, 297 
 properties of, 297 
 Phenomena accompanying chemical 
 
 change, 26 
 Phosphates, properties of, 90, 182 
 Phosphoric acid, behavior of, with re- 
 agents, 1S2 
 characteristic tests for, 211 
 separation of, from alkaline 
 earths, 183 
 anhydride, preparation of, 182 
 Phosphorus, detection of, 184 
 
 examination for, in organic sub- 
 stances, 272 
 Photo-chemical method of analysis of 
 
 second basic group, 5S 
 Photo-chemistry, 370 
 Platinic chloride as reagent, 3S3 
 properties of, 110 
 compounds, properties of, 133 
 
 special tests for, 133 
 oxide, properties of, 104 
 salts, properties of, 114 ~ 
 sulphide, properties of, 105 
 Platinous oxide, 134 
 Platinum, properties of, 102, 133 
 
 residues, treatment of, 388 
 Plumbic acetate as reagent, 382 
 chloride, properties of, 145 
 compounds, properties of, 154 
 nitrate, properties of, 146 
 oxide, properties of, 143 
 peroxide as reagent, 384 
 salts, properties of, 146 
 sulphate, properties of, 146 
 sulphide, properties of, 144 
 Poisonous metals, detection of, by elec- 
 trolysis, 130 
 Polys ulphides, properties of, 40, 193 
 Potassic antimonious tartrate, pre ara- 
 tion of, 114 
 
 Potassic — 
 
 arscnito, 114 
 
 chloride, properties of, 40 
 chromate, as reagent, 379 
 compounds, characteristic tests for, 
 44 
 examination for, 35 
 flame reactions, 43 
 properties of, 42 
 special tests for, 42 
 cyanide as reagent, 379 
 ferricyanide as reagent, 378 
 ferrocyanide as reagent, 378 
 hydrate, preparation of, 37 
 nitrate, properties of, 40 
 nitrite as reagent, 378 
 oxide, properties of, 37 
 sulphate as reagent, 378 
 
 properties of, 40 
 sulphide, preparation of, 39 
 urate in calculi, 319 
 Potassium, properties of, 37, 42 
 Precautions in analysis of first basic 
 group, 36 
 second basic group, 51 
 third basic group, 64 
 fourth basic group, 92 
 fifth basic group, 171 
 sixth basic group, liO 
 in examining for carbonic acid, 187 
 first basic group, 36 
 second basic group, 174 
 third basic group, 173 
 fourth basic group, 172 
 fifth basic group, 171 
 sixth basic group, 169 
 Precipitation, 347 
 
 of second basic group, 168 
 third basic group, 165 
 fourth basic group, 164 
 fifth basic group, 163 
 sixth basic group, 163 
 Preliminary examination for organic 
 
 acids, 231 
 Preparation of blue litmus paper, 3So 
 reddened litmus paper, 385 
 Nessler's test for ammonia, 384 
 turmeric paper, 3S6 
 Proteic substances, 278 
 Protein, 281 
 
 Proximate analysis of animal substances, 
 277 
 organic substances, 272 
 Pus, examination for, 311 
 Pyroligneous acid, 225 
 Pyrophosphoric acid, behavior of, with 
 
 reagents, 185 
 Properties of albumen, 279, 282, 320 
 bile, 309 
 bilirubine, 307 
 biliverdine, 30S 
 brucine, 339 
 cane-sugar, 325 
 casein, 278, 288, 320 
 cellulose, 321 
 chollepyrrhin, 307 
 cholestrin, 307 
 chondrin, 291 
 cinchonine, 336 
 creatin, 301 
 creatinine, 300 
 cystine, 305 
 
400 
 
 INDEX. 
 
 Properties of— 
 
 fibrin, 278, 286, 320 
 gelatin, 291 
 globulin, 289 
 glucose, 295 
 gluten, 820 
 
 glycocholalic acid, 304 
 grape-sugar, 295 
 gum, 324 
 ha-matin, 30S 
 hippuric acid, 302 
 inoBite, 297 
 lactic acid, 302 
 legumine, 320 
 lignin, 321 
 meconic acid, 3W 
 milk-sugar, 294 
 morphine, 329 
 narcotine, 332 
 nicotine, 328 
 phaseomannite, 297 
 quinine, 334 
 starch, 323 
 strychnine, 336 
 Bugar of milk, 295 
 taurocholalic acid, 305 
 taurocholic acid, 305 
 urea, 298 
 vitellin, 290 
 xanthine, 306 
 
 QUININE, behavior of, with reagents, 334 
 composition of, 334 
 properties of, 334 
 test for, 335 
 
 REACTIONS, 26 
 Reagent papers, 385 
 Reagent*, 26 
 
 characteristic, 26 
 
 group, 26 
 
 special, 26 
 Red lead, 107 
 
 liquor, 224 
 Reduction of substances, 365 
 Reinsch's test for arsenic, 125 
 Residues, treatment of, 3S7 
 
 SARCOLACTIC ACID, properties of, 302 
 Scheele's green, 114 
 Schweinfurt green, 114 
 Second basic group, analysis of, 47 
 
 behavior of, with special reagents, 
 
 49 
 Fresetilus's method of analysis 
 
 of, 57 
 precautions in analysis of, 51 
 photo-chemical method of analy- 
 sis of, 07 
 precautions in examining for, 1 7 1 
 precipitation of, 168 
 group of inorganio acid a, analysis of, 
 208 
 organic acids, analysis of, 229 
 Sediments In urine, 316 
 Separation of ooppor and cadmium, 1 59 
 phosphoric nclds from the alkalino 
 oarthB. 183 
 
 oarthB, 183 
 tauuic nod gallic acids, 223 
 
 Silicates, composition of, 190 
 Silicic acid, behavior of, with reagents, 
 188 
 blowpipe test for, 191 
 characteristic tet-te for, 211 
 dibasic, preparation of, 189 
 anhydride, properties of, 189 
 Silver, properties of, 142, 147 
 residues, treatment of, 387 
 salts, colors of, 209 
 Sixth basic group, analysis of, 136 
 precautions, 140 
 precautions in examining for, 169 
 precipitation of, 163 
 exercises on, 160 
 Sodic ammonic hydric phosphate as re- 
 agent, 381 
 and potassic carbonate as reagent, 381 
 acetate, 380 
 carbonate, 380 
 chloride, properties of, 40 
 compounds, characteristic tests for, 
 46 
 examination for, 35 
 flame reactions, 44 
 properties of, 44 
 special tests far, 45 
 hydrate as reagent, 380 
 
 preparation of, 37 
 hydric sulphite as reagent, 3S0 
 
 tartrate as reagent, 375 
 nitrate, properties of, 40 
 oxide, properties of t 37 
 sulphate, properties of, 40 
 sulphide, preparation of, 39 
 urate in calculi, 319 
 Sodium, properties of, 37 
 Solids, determination of fusibility of, 255 
 insoluble in acids, analysis of, 262 
 soluble in acids, analysis of. 261 
 in water, analysis of, 261 
 Solution, 346 
 
 of indigo as reagent, 3S5 
 Sources of error, 29 
 Special reagents, 26 
 
 tests for ammonic compound*. 42 
 antimony compounds, 117 
 auric compounds, 132 
 baric compounds, 55 
 calcic compounds, 56 
 chromic compounds, S5 
 cobalt compounds, 72 
 iron compounds, 5tf 
 lithic compounds, 46 
 magnesic compounds, JiS 
 manganese compounds, tS9 
 potassic compounds. 42 
 sodic compounds, 45 
 stroutic compounds, 56 
 tin compounds, 115 
 lincic compounds, 70 
 Stannic chloride, properties of, 103 
 hydrate, properties of, 112 
 oxide, properties of, 104 
 salts, properties of, 114 
 sulphide, properties of, 105 
 Stanuons chloride as reagent, 3S4 
 properties of, 10S 
 oxide, properties of, 104 
 salts, properties of, 110, 114 
 sulphide, properties of, 105 
 Starcli, behavior of, with roagents, 3*23 
 
INDEX. 
 
 401 
 
 Starch — 
 
 composition of, 323 
 properties of, 323 
 Strecker's views on the constitution of 
 
 the albuminoids, 282 
 Strontic chloride, properties of, 53 
 
 compounds, characteristic tests for, 
 55 
 flame reactions, 56 
 properties of, 56 
 special tests for, 56 
 nitrate, properties of, 53 
 oxide, properties of, 51 
 salts, general characters of, 51 
 sulphate, properties of, 53 
 sulphide, properties of, 52 
 Strontium, properties of, 51, 55 
 Strychnine, behavior of, with reagents, 
 337 
 composition of, 337 
 detection of, 338 
 pi'operties of, 337 
 Sublimation, 350 
 Suboxide of lead, 157 
 Succinates, properties of, 223 
 Succinic acid, behavior of, with reagents, 
 222 
 detection of, 230 
 Sugar, detection of, 296 
 
 fermentation test for, 297 
 in urine, 315 
 
 of milk, behavior of, with reagents, 
 295 
 composition of, 295 
 properties of, 295 
 Trommor's test for, 296 
 Sulphates, blowpipe tost for, 179 
 of first basic group, 37 
 properties of, 178 
 Sulph-hydrates, properties of, 39, 52, 193 
 Sulphides of first basic group, 37 
 
 properties of, 193 
 Sulphur, detection of, 194 
 
 examination for, in organic Bub- 
 stances, 271 
 Sulphuric acid as reagent, 37-1 
 
 behavior of, with reagents, 178 
 characteristic tests for, 211 
 detection of, in presence of a sul- 
 phate, 179 
 anhydride, properties of, 178 
 Sulphurous acid, behavior of, with re- 
 agents, 179 
 properties of, 179 
 anhydride as reagent, 376 
 Sulphur salts, formation of, 106 
 Supports for blowpipe operations, 353 
 
 TANNIC ACID, behavior of, with re- 
 agents, 223 
 detectiou of, 230 
 and gallic acids, separation of, 224 
 Tartar emetic, preparation of, 113 
 Tartaric acid as reagent, 375 
 
 behavior of, with reagents, 217 
 detection of, 229 
 
 in presence of citric acid, 
 220 
 preparation of, 217 
 Tartrates, properties of, 217 
 
 Taurocholalic acid, behavior of, with re- 
 agents, 305 
 composition of, 30-5 
 properties of, 305 
 Taurocholic acid, behavior of, with re- 
 agents, 305 
 composition of, 305 
 properties of, 305 
 Tests, 26 
 
 for bile, 309 
 for blood, 308 
 for quinine, 335 
 Test-papers for hydrocyanic acid, 386 
 Third basic group, analysis of, 61 
 
 behavior of, with special re- 
 agents, 62 
 precautions in analysis of, 61 
 
 in examining for, 173 
 precipitation of, 165 
 group of inorganic acids, analysis of, 
 209 
 organic acids, analysis of, 229 
 Thiosulphuric acid, behavior of, with re- 
 agents, ISO 
 Tin compouuds, blowpipe test for, 115 
 flame reactions, 116 
 properties of, 115 
 special tests for, 115 
 properties of, 102, 115 
 Titanic compounds, flame reactions, 98 
 oxide, behavior of, with reagents, 97 
 properties of, 97 
 Treatment of gold residues, 389 
 platinum residues, 3S8 
 silver residues,' 387 
 Trommer's test for sugar, 297 
 Turmeric paper, pi-eparatioa of, 386 
 Type metal, composition of, 117 
 
 URANIC OXIDE, behavior of, with re- 
 agents, 97 
 properties of, 97 
 Uranium compounds, characteristic tests 
 for, 97 
 flame reactions, 97 
 Urates, properties of, 227 
 Urea, behavior of, with reagents, 298 
 composition of, 29S 
 detection of, 300 
 examination for, 313 
 properties of, 298 
 Uric acid, behavior of, with reagents, 227 
 detection of, 231 
 examination for, 311 
 Uric acid in calculi, 31S 
 Urinary sediments, 316 
 Urine, analysis of, 277, 313 
 coloring matter of, 307 
 composition of, :ii3 
 containing bile, 315 
 fatty matters, 316 
 sugar, 315 
 Urochrome, 307 
 
 VARIETIES of albumen, 285 
 Vitellin, properties of, 290 
 Volatile elements which can be reduced 
 
 as films, 35S 
 Volatility of substances, 864 
 
402 
 
 INDEX. 
 
 WATER, action of t on lead, 154 
 Waters, detection of lead in, 150 
 Water, distilled, 385 
 
 XANTHINE, behavior 
 agents, 306 
 composition of, 306 
 detection of, 306 
 in calculi, 318 
 properties of, 306 
 
 of with re- 
 
 ZINC as reagent, 384 
 properties of, 65, 70 
 Zincic chloride, properties of, 67 
 
 compounds, blowpipe tests for, 70 
 characteristic tests for, 71 
 flame reactions, 70 
 properties of, 71 
 special teBts for, 71 
 nitrate, properties of, 67 
 oxide, properties of, 65 
 salts, properties of, 68 
 sulphate, properties of, 67. 
 sulphite, properties of, 66 
 
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 ON THE SIGNS AND DISEASES OF PREGNANCY. First 
 
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 TUKE (DANIEL HACK). INFLUENCE OF THE MIND UPON THE 
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 TAYLOR (ALFRED S.) MEDICAL JURISPRUDENCE. Seventh 
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 — PRINCIPLES AND PRACTICE OF MEDICAL JURISPRU- 
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 ON POISONS IN RELATION TO MEDICINE AND MEDICAL 
 
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 THOMAS (T. GAILLARD). A PRACTICAL TREATISE ON THE 
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 TODD (ROBERT BENTLEY) . CLINICAL LECTURES ON CERTAIN 
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 THE PATHOLOGY AND TREATMENT OF STRICTURE OF 
 
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12 HENEY C. LEA'S PUBLICATIONS. 
 
 WOHLER'S OUTLINES OF ORGANIC CHEMISTRY. Translated 
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 WALES (PHILIP S.) MECHANICAL THERAPEUTICS. In one 
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 WELLS (J. S0ELBER6). A TREATISE ON THE DISEASES OF 
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 WHAT TO OBSERVE AT THE BEDSIDE AND AFTER DEATH 
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 WATSON (THOMAS). LECTURES ON THE PRINCIPLES AND 
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 WSST (CHARLES). LECTURES ON THE DISEASES PECULIAR 
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 LECTURES ON THE DISEASES OF INFANCY AND CUILD- 
 
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 ON SOME DISORDERS OF THE NERVOUS SYSTEM IN 
 
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 AN ENQUIRY INTO THE PATHOLOGICAL IMPORTANCE 
 
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 WILSON (ERASMUS). A SYSTEM OF HUMAN ANATOMY. A 
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 THE STUDENT'S BOOK OF CUTANEOUS MEDICINE. In 
 
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 WINSLOW (FORBES). ON OBSCURE DISEASES OF THE BRAIN 
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 WINCKEL ON DISEASES OF CHILDBED. Translated by Ch.id- 
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 ZEISSL ON VENEREAL DISEASES. Translated by Sturgis. 
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