Eugene W.Hilgard 
 

 t>~-*---i 
 
ELEMENTARY INSTRUCTION 
 
 CHEMICAL ANALYSIS. 
 
 BY 
 
 DR. C. REIIGIUS FRESENIUS, 
 
 CHEMICAL ASSISTANT IN THE LABORATORY OF THE 
 UNIVERSITY OF GIESSEN. 
 
 WITH 
 
 A PREFACE BY PROFESSOR LIEBIG. 
 
 EDITED BY 
 
 J. LLOYD BULLOCK, 
 
 MEMBER OF THE CHEMICAL SOCIETY, LATE OF THE GIESSEN 
 AND PARIS LABORATORIES. 
 
 NE W-YORK: 
 D. APPLETON & CO., 200 BROADWAY. 
 
 PHILADELPHIA : GEORGE S. APPLETON. 
 
 M.DCCC.XLIV. / 
 
1 I 
 
 
 iS/H 
 
 NEW- YORK: 
 
 PRINTED SY HBNRY LUDWIG, 72 VBSKY-BTRBET. 
 

 PREFACE 
 
 BY PROFESSOR IIEBIG. 
 
 DR. FRESENIUS conducts the course of elementary in- 
 struction, in mineral analysis, in the laboratory of the 
 University of Giessen. During the two last sessions he 
 has followed the method described in his work, entitled* 
 " Elementary Instruction in Qualitative Chemical Analy- 
 sis." This method I can confidently recommend from my 
 own personal experience to all who are desirous of obtain- 
 ing instruction in inorganic analysis, for its simplicity, 
 usefulness, and the facility with which it may be appre- 
 hended. 
 
 I consider Dr. Fresenius' work extremely useful as an 
 introduction to Professor H. Rose's excellent manual, and 
 for adoption in institutions where practical chemistry is 
 taught, but it is especially adapted to the use of Pharma- 
 ceutical Chemists. 
 
 Further, a number of experiments and discoveries have 
 been recently made in our laboratory, which have enabled 
 Dr. Fresenius to give many new and simplified methods of 
 separating substances, which will render his work equally 
 welcome to those who already are familiar with the larger 
 works on inorganic analysis. 
 
 JUSTUS LIEBIG. 
 
 415394 
 
EDITOR'S PREFACE. 
 
 THIS work of Dr. Fresenius has already gone through 
 two editions in Germany. The abundant opportunities 
 enjoyed by its author of discovering the wants felt by stu- 
 dents in entering upon the practice of chemical analysis^ 
 and his position in the school at Giessen, has enabled him 
 to devise a method of study of the highest value. That it 
 has received the approbation of the illustrious HEAD of that 
 school, and the benefit of three years' practical experience 
 under his immediate observation, must powerfully recom- 
 mend it to the English student of chemistry. Whoever 
 is desirous of obtaining the knowledge necessary to become 
 a practical chemist, will be in no small degree indebted to 
 Dr. Fresenius for the facilities thus afforded him. Every 
 one who knows any thing of Giessen, will bear testimony 
 to the rigid economy of time, and the resolute adoption of 
 every improvement in method which characterise that 
 school, and serve to accomplish the many chemists annu- 
 ally flocking- there for the completion of their studies. The 
 author, in his preface to the first edition, tells us that he 
 was led to compose this volume upon perceiving that the 
 larger works on chemical analysis, such as H. Rose's, 
 Duflos', and others, although admirable in themselves, 
 present great difficulties to beginners, which difficulties 
 may be summed up under three heads J 1st, Too great 
 
 * 
 
VI. 
 
 copiousness and detail ; 2d, The absence of explanations 
 of the causes of phenomena, i. e. the theory of the opera- 
 tions and reactions ; and 3d, The omission altogether of 
 many substances of very frequent occurrence, especially 
 in the operations, of the pharmaceutist, such as the or- 
 ganic acids, &c. 
 
 In avoiding these objections to former works on chemical 
 analysis, Dr. Fresenius, I think, is not chargeable with 
 having fallen into the opposite extreme of being too con- 
 cise or elementary. 
 
 The student may, perhaps, at first be disappointed in 
 taking up this work, to find that there are no tables con- 
 structed to furnish him at a glance with all he is desirous 
 to know of tests and reactions, and to save him, as he 
 may think, trouble and time. But this has not arisen 
 from oversight; the question of the advantage or disad- 
 vantage of tables to the student has been fully considered, 
 and the author has decided- and the decision is borne out 
 by the highest authorities that such tables serve no really 
 good purpose ; they rather, on the contrary, supply but 
 very superficial information, and satisfy the student before 
 they have really informed him. The information contained 
 in this work, like every other professing to teach a practical 
 science, requires application and perseverance to attain ; 
 but if begun at the beginning, if the student will carefully 
 go over the necessary preliminary facts, the examination 
 of his tests, and the reaction of the simple bodies consecu- 
 tively, and make himself master of this very simple and 
 elementary part of the course, he will find few or no 
 difficulties when entering upon the more elaborate, and 
 what might appear, without this preparation complex and 
 intricate processes of the second part, the analysis of corn- 
 
Vll. 
 
 pound bodies. It is altogether another question whether 
 the student should or should not exercise himself and his 
 memory by tabulating the results of his experiments as he 
 proceeds ; and to this question we reply in the affirmative : 
 but it must be left to individuals to act in this, according 
 to their own judgment, and their own feeling of its ne.ces- 
 sity. 
 
 In the preface to the Second Edition, Dr. Fresenius tells 
 us that his work has met with much success, having been 
 adopted in the Pharmaceutical Institution of Bonn, &c., 
 as well as in the laboratory of Giessen ; and that he^ has 
 improved it by many corrections and additions. 
 
 For my own part, I may be allowed to observe that the 
 English edition was undertaken by the express desire of 
 Professor Liebig, who kindly recommended its being en- 
 trusted to my care. The author has supplied me with 
 many corrections, and some additions, and the hope is 
 shared by us in common that it will facilitate the study of 
 analytical chemistry to the English student, and in every 
 way serve to promote the interests of the science. 
 
 J. LLOYD BULLOCK. 
 22, Conduit Street, Oct. 1, 1843. 
 

 *- ^ 
 
INDEX, 
 
 PART I. 
 
 INTRODUCTORY COURSE OF QUALITATIVE CHEMICAL 
 ANALYSIS. 
 
 Page 
 PRELIMINARY REMARKS. 
 
 Definition, design, and utility of qua- 
 litative chemical analysis, and con- 
 ditions whereon a successful study 
 of this science depends . 13 
 
 CHAPTER I. 
 
 Operations, $ 1 . 16 
 
 1. Solution, $ 2 ... 17 
 
 2. Crystallization, $ 3 . 19 
 
 3. Precipitation, 4 . . . 20 
 
 4. Filtration, 5 ... 21 
 
 5. Decantation, $ 6 ... 22 
 
 6. Evaporation, $ 7 . 23 
 
 7. Distillation, $8 ... 24 
 
 8. Roasting, $9 ... 24 
 
 9. Sublimation, $ 10 ... 25 
 
 10. Smelting and fluxing, $ 11 . 25 
 
 11. The use of the blow-pipe, 12 26 
 
 Appendix to Chapter I. 
 Apparatus and utensils, $ 13 .29 
 
 CHAPTER n. 
 
 REAGENTS, $ 14 ... 31 
 
 A. Reagents in the humid way. 
 
 I. General Reagents, 
 a. Reagents principally used as sim- 
 ple solvents. 
 
 1. Water, 15 ... 34 
 
 2. Alcohol, 16 ... 35 
 
 3. Ether, $ 17 .... 35 
 If. Reagents which are principally 
 
 used as chemical solvents. 
 
 1. Hydrochloric acid $18 .35 
 
 2. Nitric acid, 19 . . 37 
 
 3. Nitro-muriatic acid, 20 .37 
 
 4. Acetic acid, $ 21 . 38 
 
 5. Muriate of ammonia, $ 22 . 39 
 e. Reagents which serve especially to 
 
 separate or otherwise to charac- 
 terize groups of substances. 
 
 Pa 
 
 1. Reagent papers, $ 23 
 
 2. Sulphuric acid, 24 . 
 
 3. Sulphuretted hydrogen, $ 25 
 
 4. Hydrosulphuret of ammonia, 
 $26 
 
 5. Sulphuret of potassium, $ 27 
 
 6. Potash, 28 ... 
 
 7. Carbonate of potash, $ 29 
 
 8. Ammonia, $30 . 
 
 9. Carbonate of ammonia, $ 31 
 
 10. Chloride of barium, 32 
 
 11. Nitrate of barytes, 33 
 
 12. Chloride of calcium, $ 34 
 
 13. Nitrate of silver, $35 
 
 14. Perchloride of iron, $ 36 
 
 II. Special reagents in the humid way 
 a. Reagents which serve especially 
 for the detection or separation of 
 individual bases. 
 
 1. Sulphate of potash, $ 37 
 
 2. Phosphate of soda, $ 38 
 
 3. Neutral chromate of potash, $ 39 
 
 4. Cyanide of potassium, 40 . 
 
 5. Ferrocyanide of potassium, 41 
 
 6. Ferricyanide of potassium, $ 42 
 
 7. Hydrofluosilicic acid, $ 43 
 
 8. Oxalic acid, $44 . . 
 
 9. Oxalate of ammonia, 45 
 
 10. Tartaric acid, 46 . . 
 
 11. Bitartrate of potash, 47 
 
 12. Acetate of barytes, $ 48 
 
 13. Caustic barytes, $ 49 
 
 14. Protochloride of tin, 50 . 
 
 15. Chloride of gold, $ 51 . 
 
 16. Chloride of platinum, $ 52 
 
 17. Zinc, $ 53 . ... 
 
 18. Iron, $ 54 ... 
 
 19. Copper, $ 55 ... 
 b. Special reagents which are parti- 
 cularly employed for the detec- 
 tion and separation of acids. 
 
 1. Acetate of potash, $ 56 
 
 2. Caustic liine, $ 57 
 
 54 
 
 54 
 55 
 50 
 57 
 
 57 
 58 
 59 
 GO 
 
INDEX. 
 
 3. Sulphate of lime, $58 . 66 
 
 4. Chloride of magnesium, $59 66 
 
 5. Protosulphateofiron, $60 . 67 
 
 6. Solution of magnetic oxide of 
 
 iron, $ 61 ... 67 
 
 7. Oxide of lead, 62 ' . . 68 
 
 8. Neutral acetate of lead, $ 63 68 
 
 9. Basic acetate of lead, $ 64 . 68 
 
 10. Hydrated oxide of bismuth, $ 65 69 
 
 11. Sulphate of copper, $66 . 70 
 
 12. Protonitrate of mercury, $ 67 70 
 
 13. Peroxide of mercury, $ 68 . 71 
 
 14. Perchloride of mercury, $69 71 
 
 15. Ammonia-nitrate of silver, $70 71 
 
 16. Sulphurous acid, $ 71 .72 
 
 17. Chlorine, $ 72 . 72 
 
 18. Solution of indigo, 73 .73 
 
 19. Starch paste, $ 74 . . 73 
 
 B. Reagents in the dry way. 
 I. Fluxes and means of decomposition. 
 
 1. Mixture of carbonate of soda 
 
 and carbonate of potash, $ 75 74 
 
 2. Carbonate of barytes, 76 . 75 
 
 3. Nitrate of potash, $ 77 . 75 
 
 n. Slow pipe reagents. 
 *. Charcoal, $ 78 ... 
 
 2. Carbonate of soda, $ 79 
 
 3. Cyanide of potassium, $ 80 
 
 4. Biborate of soda, $ 81 
 
 5. Phosphate of soda and ammo- 
 
 nia, $ 82 .... 
 
 6. Protonitrate of cobalt, 83 . 
 
 CHAPTER ra. 
 
 On the relation of the various sub- 
 stances to reagents, 84 . ' \ 
 
 A. Relation of the metallic oxides. 
 First group, 85 
 
 a. Potash .... 
 
 ft. Soda 
 
 e. Ammonia 
 Second group, 86 . . . 
 
 a. Barytes .... 
 
 b. Strontian .... 
 
 c. Lime .... 
 
 d. Magnesia .... 
 Third group, 87 ... 
 
 a. Alumina . . *. 
 
 b. Oxide of chromium 
 
 Fourth group, $ 88 . . i 
 
 a Oxide of zinc . ; . 
 
 b. Protoxide of manganese 
 
 e. Oxide of nickel 
 
 d. Protoxide of cobalt 
 
 e. Protoxide of iron 
 /. Peroxide of iron 
 
 Fifth group, $ 89 ... 
 
 87 
 
 First section, $ 90 ... 107 
 
 fl. Oxide of silver ... 107 
 
 b. Protoxide of mercury . 108 
 
 c. Oxide of lead ... 109 
 Second section, $ 91 . . Ill 
 
 a. Peroxide of mercury . . Ill 
 
 ft. Oxide of copper . . 112 
 
 c. Oxide of bismuth . . 114 
 
 d. Oxide of cadmium . . 115 
 Sixth group, $ 92 ... 117 
 First class, $ 93 ... 117 
 
 a. Peroxide of gold . . 117 
 
 ft. Peroxide of platinum . 118 
 
 Second class, $ 94 119 
 
 a. Oxide of antimony . . 119 
 
 A. Protoxide of tin ... 122 
 
 c. Peroxide of tin ... 124 
 
 d. Arsenious acid ... 126 
 
 e. Arsenic acid ... 134 
 B. Relations of the acids to reagents, 
 
 95 137 
 
 I. Inorganic acids First group. 
 
 First section, 96 ... 139 
 
 a. Arsenious and arsenic acid 139 
 
 ft. Chromic acid , . . 139 
 
 Second section, 97 . . 141 
 
 Sulphuric acid ... 141 
 
 Third section, $ 98 ... 142 
 
 a. Phosphoric acid ... 142 
 
 b. Boracic acid ... 144 
 
 c. Oxalic acid ... 145 
 
 d. Hydrofluoric acid . . 146 
 Fourth section, $ 99 . . . 149 
 
 a. Carbonic acid . . 149 
 
 ft. Silicic acid ... 150 
 
 Second group of inorganic acids, 100 151 
 
 a. Hydrochloric acid . . 152 
 
 b. Hydrobromic acid . . 152 
 
 c. Hydriodic acid . . 154 
 
 d. Hydrocianic acid . . 155 
 . Hydrosulphuric acid . 157 
 
 Third group of the inorganic acids, 
 
 $ 101 159 
 
 a. Nitric acid ... 159 
 
 ft. Chloric acid ... 160 
 
 II. Organic Acids. 
 
 First group, $ 102 . . . 162 
 
 a. Oxalic acid ... 162 
 
 b. Tartaric acid *,. . . 162 
 
 c. Paratartaric acid . . 163 
 
 d. Citric acid . ... 164 
 
 e. Malic acid . . . . 166 
 Second group, $ 103 . . . 168 
 
 a. Succinic acid ... J68 
 
 ft. Benzoic acid . . . 168 
 
 Third group, 104 . . . 170 
 
 a. Acetic acid .... 170 
 
 b. Formic acid ... 171 
 
 ! 
 
INDEX. 
 
 XI. 
 
 PART II. 
 
 SYSTEMATIC COURSE OF QUALITATIVE ANALYSIS. 
 
 Preliminary remarks on the Course of 
 qualitative analysis in general, and 
 on the plan of this second part 
 in particular . . i%.;* 
 
 First Section. 
 
 PRACTICAL PROCESS. 
 
 I. Preliminary Examination, $105 
 j9. The body under examination is 
 
 solid . " . 
 
 1. It is neither a pure metal nor an 
 
 alloy . . . V- 
 
 2. It is a metal or an alloy 
 
 B. The substance under examination 
 is a fluid .... 
 
 II. Solution of bodies, or classifica- 
 
 tion of substances according to 
 their relations to certain sot- 
 vents, 106 
 
 A. The substance under examination 
 
 is neither a metal nor an alloy 
 
 B. The substance under examination 
 
 is a metal or an alloy 
 
 III. Real Examination. 
 
 Compounds supposed to consist sim- 
 ply of one base and one acid, or 
 one metal and one metalloid. 
 
 A. Substances soluble in water. 
 Detection of the base, $ 107 
 Detection of the acid. 
 
 I. Detection of inorganic acids, $ 1 08 
 
 II. Detection of organic acids, 109 
 
 B. Substances insoluble, or sparing- 
 
 ly soluble in water, but soluble 
 in hydrochloric acid, nitric 
 acid, or aqua regia. 
 
 Detection of the base, I) 110 . 
 
 Detection of the acid. 
 
 Detection of inorganic acids, $ 111 
 
 Detection of organic acids, <) 112 
 
 C. Substances insoluble, or sparing- 
 
 ly soluble both in water and 
 acids. 
 
 Detection of the base and the acid. 
 113 . 
 
 Page 
 
 177 
 
 181 
 185 
 
 180 
 
 190 
 
 192 
 
 199 
 201 
 
 206 
 208 
 
 Compounds in which all the more 
 frequently occurring bases, acids, 
 metals and metalloids, are suppos- 
 ed to be present. 
 
 A. Substances both soluble and inso- 
 luble in water, and soluble in 
 hydrochloric acid, or nitric 
 acid. 
 
 Detection of the bases, $ 114 
 I. The solution is aqueous 
 Detection of silver and protoxide 
 of mercury 
 
 208 
 
 210 
 211 
 
 212 
 
 [I. The solution is hydrochloric . 214 
 [II. The solution is nitric . . . 214 
 Detection of silver ... 214 
 Precipitation with sulphuretted hy- 
 drogen, $ 115 . . . .214 
 Treating the precipitated metallic 
 sulphurefs with hydrosulphuret 
 of ammonia . . . .216 
 Detection of the oxides of the sixth 
 group, arsenic, tin, antimony, 
 gold, platinum, $116 . . 217 
 Treating the metallic sulphurets 
 insoluble in hydrosulphuret of 
 ammonia, with nitric acid, $ 117 221 
 Detection of the oxides of the fifth 
 group; lead, bismuth, copper, 
 cadmium, peroxide of mercury 221 
 Precipitation with hydrosulphuret 
 
 of ammonia, $118 . . 223 
 
 Detection of the oxides of the third 
 and fourth group, &c. ; alumina, 
 oxide of chromium, iron, manga- 
 nese, zinc, cobalt, nickel, phos- 
 phates, and oxalates of the alka- 
 line earths, 118 . . .224 
 Precipitations with carbonate of 
 
 ammonia, $ 119 . . . 230 
 Detection of the oxides of the se- 
 cond group; barytes, strontian, 
 lime, $119 . . . . 231 
 
 Magnesia, $ 120 ... 232 
 
 Detection of the oxides of the fifth 
 
 group, $ 121 .... 232 
 
 Potash, soda .... 233 
 
 Ammonia, $ 122 . . . .234 
 
 Detection of acids and metalloids 234 
 
 A. 1. Substances soluble in water. 
 
 I. Absence of organic acids, $ 123 . 234 
 
 II. Presence of organic acids, $ 124 238 
 
 A. 2. Substances insoluble in water 
 
 but soluble in hydrochloric acid 
 
 and in nitric acid . . . 242 
 
 I. Absence of organic acids, $ 125 242 
 
 II. Presence of organic acids, $ 126 243 
 
 B. Substances insoluble, or sparingly 
 
 soluble both in water and in hy- 
 drochloric acid . . . 244 
 
 Detection of the bases, acids, and 
 metalloids, $ 127 . . .244 
 
 Special method for the decomposi- 
 tion of insoluble cyanides, ferro- 
 cyanides, &c., 128 . . 251 
 
 General rules for the detection of 
 inorganic substances, in cases 
 where organic substances are 
 present, which by their colour, 
 consistence, or other properties, 
 impede the application of the 
 reagents, or render the phenom- 
 ena obscure, $ 129 . . .252 
 IV. Confirmatory experiments, $ 130 254 
 
Xll. 
 
 CHAPTER IT. 
 
 Explanatory notes and additions to 
 the practical course 
 I. Remarks on the preliminary exa- 
 mination 
 II. Additional remarks upon solu- 
 tion, &c 
 in. Additional remarks upon the 
 real examination, t) 107 to 
 <S 129 .... 
 
 IN] 
 Page 
 
 254 
 254 
 255 
 
 257 
 
 257 
 257 
 201 
 
 264 
 264 
 2G6 
 267 
 
 DEX. 
 
 To $117 . . * . 
 To HIS 
 To 127 . 
 To $128 
 
 Appendix to Part II. 
 
 I. General scheme for a judicious ar- 
 rangement of the succession in 
 which substances ought to be 
 analyzed 
 II. Table of the more frequently oc- 
 curring forms and combinations 
 of the substances considered in 
 the present work, with especial 
 regard to the classes to which 
 they belong, according to their 
 various degrees of solubility in 
 water, &c. 
 
 Page 
 268 
 270 
 272 
 273 
 
 277 
 280 
 
 ^. General survey and explanation 
 of the analytical course 
 a. Detection of the bases 
 b. Detection of the acids 
 B. Special and additional remarks 
 upon the systematic course of 
 analysis 
 To 4 114 
 To HIS . 
 To $116 
 
ELEMENTARY INSTRUCTION 
 
 IN 
 
 QUALITATIVE CHEMICAL ANALYSIS. 
 
 PRELIMINARY REMARKS, 
 
 DEFINITION, DESIGN, AND UTILITY OF QUALITATIVE! 
 
 CHEMICAL ANALYSTS, AND CONDITIONS WHEREON A 
 
 SUCCESSFUL STUDY OF THIS SCIENCE DEPENDS. 
 
 CHEMISTRY is that science which leaches us the know- 
 ledge of the elements of which our earth consists, their 
 composition and decomposition, and, in general, their re- 
 lation to each other. A special branch of this science is 
 designated by the name of analytical chemistry, inasmuch 
 as it has a definite object in view, viz., the analysis of com- 
 pound bodies, and the determination of their constituent 
 parts. If this determination of the constituent parts merely 
 refers to their nature, the analysis is called qualitative; 
 but if the quantity of every single element is to be ascer- 
 tained, the analysis is called quantitative. The object of 
 the first, therefore, is to exhibit the constituent parts of an 
 unknown substance in forms already known, so that these 
 new forms admit of safe inferences as to the presence of 
 the single elements. The value of its method depends on 
 two circumstances, viz. it must attain the object in view 
 infallibly, and in the quickest possible manner. Whereas, 
 it is the object of quantitative analysis, to exhibit those 
 elements rendered manifest by qualitative investigation, in 
 such forms as admit of an exact determination of their 
 amount. 
 1 
 
 
14 PRELIMINAR REMARKS. 
 
 ways 'tod ' rriearis by" which these various objects 
 are attained, differ, of course, materially from each other, 
 The study of qualitative analysis must, therefore, be 
 separated from that of quantitative analysis, and, as a mat- 
 ter of course, must precede it. 
 
 After having thus generally defined the meaning and 
 objects of qualitative analysis, we must now shortly con- 
 sider, in the first place, the preliminary information which 
 qualifies students to cultivate this- science successfully, the 
 rank which it occupies in the department of chemistry, the 
 objects to which it extends, the advantages derived from 
 it ; and, in the second place, the main points whereon its 
 study is based, and the principal branches into which it is 
 distributed. 
 
 In order to enter with any prospect of success upon 
 qualitative experiments, the student mast previously have 
 acquired some knowledge of the chemical elements, and of 
 their most important combinations, as well as of the princi- 
 ples of chemistry generally, together with a certain readi- 
 ness in the apprehension of chemical processes. This 
 practical art demands, moreover, strict order, great neat- 
 ness, and a certain degree of skill in manipulations. If 
 the pupil combines with these qualifications a habit, in all 
 cases in which phenomena contrary to experience appear, 
 of imputing, first the fault to himself, or rather to the ab- 
 sence of some condition or other indispensable to the suc- 
 cess of the experiment, and a firm reliance on the immu- 
 tability of the laws of nature cannot fail to create this habit, 
 he possesses every requisite to render his study of 
 analytical chemistry successful. 
 
 Now, although chemical analysis is based on general 
 chemistry, and cannot be cultivated without some know- 
 ledge of the latter, yet/ on the other hand, we must con- 
 sider it also as a kind of corner stone, upon which the en- 
 tire structure of this science rests ; for it is almost of equal 
 importance for all branches of theoretical, as well as of 
 practical chemistry ; and we need not expatiate here on 
 the utility and advantages which the physician, the apo- 
 thecary, the mineralogist, the rational farmer, the artisan* 
 and many others, derive from it. 
 
PRELIMINARY REMARKS. 15 
 
 This alone would be a sufficient reason to recommend 
 a thorough and diligent study of this science, if even its 
 cultivation possessed none of those attractions which, I 
 may safely assert, without fear of contradiction, it must of 
 necessity possess for every one who devotes himself zeal- 
 ously and ardently to its acquisition. For the human 
 mind is constantly striving for the attainment of truth ; it 
 delights in the solution of enigmas, and where do we meet 
 with a greater variety of problems, of more or less diffi- 
 cult solution, than in the province of chemistry ? But as 
 a problem, an enigma, for which, after long pondering, we 
 can find no solution, wearies and discourages th^mind j 
 so, in like manner, do all chemical investigations, if the 
 object in view be not attained, if our results do not bear 
 the stamp of truth, of unquestionable certainty. A half- 
 knowledge is therefore, in every 'province of science, but 
 principally here, to be considered worse than no knowledge 
 at all, and the student must, therefore, be especially warn- 
 ed against a mere superficial cultivation of chemical 
 analysis* 
 
 A qualitative experiment may be made with a twofold 
 view, viz. either, 1st, to prove that some definite body or 
 other is or is not contained in a substance, e. g. lead in 
 wine ; or, 2d, to ascertain all the constituents of a chemi- 
 cal combination or mixture. Any substance whatever 
 may, of course, become the object of chemical analysis. 
 
 In the present work, however, we purpose to confine our- 
 selves to those elements and combinations which are 
 employed in pharmacy, arts, and trades, and understand 
 thereby the following : 
 
 I. BASES'. 
 
 Potash, Soda, Ammonia, Barylgs, Strontian, Lime, 
 Magnesia, Alumina, Oxide of Chromium, Oxide of Zinc, 
 Protoxide of Manganese, Protoxide of Cobalt, Oxide of 
 Nickel, Protoxide of Iron, Peroxide of Iron, Oxide of 
 Cadmium, Oxide of Lead, Oxide of Bismuth, Oxide 
 of Copper, Oxide of Silver, Protoxide of Mercury, Pe- 
 roxide of Mercury, Oxide of Platinum, Oxide of Gold, 
 Protoxide of Tin, Peroxide of Tin, Oxide of Anti- 
 mony. 
 
16 OPERATIONS. 
 
 II. ACIDS. 
 
 Sulphuric Acid, Nitric Acid, Phosphoric Acid, Ar- 
 senious Acid, Arsenic Acid, Boracic Acid, Carbonic Acid, 
 Chromic Acid, Chloric Acid, Silicic Acid, Oxalic Acid, 
 Tartaric Acid, Paratartaric Acid, Citric Acid, Malic 
 Acid, Benzoic Acid, Succinic Acid, Acetic Acid, Formic 
 Acid. 
 
 III. SALT-RADICALS, AND NON-METALLIC SUBSTANCES. 
 
 Chl&ine, Iodine, Bromine, Cyanogen, Fluorine, Sul- 
 phur, Carbon. 
 
 The study of qualitative analysis depends principally 
 on four points, viz. 1st, "on the knowledge of operations ; 
 2d, on that of reagents and of their application; 3d, 
 on that of the relation of bodies to reagents ; and 4th, on 
 that of the systematic course to be pursued in every ex- 
 periment. 
 
 Chemical analysis, therefore, requires not only theoreti- 
 cal knowledge, but also practical skill ; and it is obvious 
 that a mere speculative study of it can no more lead to 
 success, than experimenting at random ; but in order to 
 obtain satisfactory results, theory and practice must be 
 combined. 
 
 CHAPTER I. 
 
 OPERATIONS. 
 
 THE operations of analytical and synthetical chemistry 
 are essentially the same, modified however to a certain ex- 
 tent, according to the object we have in view, and the 
 quantities upon which we operate. 
 
SOLUTION. 17 
 
 The following are the principal operations employed in 
 qualitative investigations. 
 
 2. 
 
 1. SOLUTION. 
 
 The general meaning of " solution" is " the combina- 
 tion" of a gaseous, liquid, or solid substance, with a fluid, 
 forming a homogeneous liquid. But we call the solution 
 more properly absorption when the dissolved substance is 
 gaseous ; and when liquid, the term mixture or intermix- 
 ture is more frequently made use of. The term solution, 
 in its usual and more restricted sense, is confined to the 
 perfect union of a solid substance with a fluid. The 
 more minutely we divide the substance to be dissolved, 
 the more we facilitate its solution. The liquid, by means 
 of which the solution is effected, is called the solvent. We 
 call the solution chemical, if this solvent forms a chemical 
 combination with the substance dissolved ; simple, if no 
 definite combination takes place. 
 
 A simple solution contains the dissolved body in a free 
 and unconnected state, and with all its original properties, 
 except those dependent on its form and cohesion ; and 
 when it separates from the solvent in the same unaltered 
 state, as soon as the latter is withdrawn. Common salt 
 dissolved in water is a familiar instance of a simple solu- 
 tion. The salt here imparts its peculiar taste to the water, 
 and on evaporating the latter, we re-obtain common salt in 
 its original form. A simple solution is called saturated 
 when the solvent has received as much as it can hold of 
 the substance to be dissolved. But as fluids, on an aver- 
 age, dissolve larger quantities of a substance, the higher 
 their temperature, the term saturated can only refer to a 
 certain temperature ; and it must be considered a rule, that 
 elevation of temperature facilitates and accelerates simple 
 solution. 
 
 A chemical solution contains the substance dissolved, 
 not in the same state nor with the same properties as be- 
 fore ; the dissolved body is no longer free, but intimately 
 combined with the solvent, which latter has likewise lost 
 its original properties ; the result of this combination has 
 
18 SOLUTION. 
 
 been the formation of a new body, the solution, therefore, 
 now manifests the properties of this newly-formed sub- 
 stance. A chemical solution, too, may certainly be ac- 
 celerated by elevation of temperature, and this is indeed 
 usually the case, as 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 of 
 temperature ; their combining proportions are invariable, 
 and independent of the gradations of temperature. 
 
 In chemical solution, the solvent and the body, on which 
 it acts, have always opposite properties, and their tendency 
 is mutually to neutralize these opposite properties. Fur- 
 ther, solution ceases as soon as this tendency is satisfied ; 
 if we add more of the solid body it remains unaltered. 
 The solution in this case also is called saturated, or more 
 properly neutralized^ and the point which denotes it to be 
 completely so, is called the point of saturation or neutrali- 
 zation. The substances by means of which chemical so- 
 lutions are effected, are, in most cases, either acids or 
 alkalies. They all require, first, a simple solvent to be 
 converted to the fluid state. When the opposite properties 
 of acid and base have mutually neutralized each other, 
 and the new combination has been formed, the real con- 
 version into fluid form takes place, only, if the product of 
 this new combination possesses the property of forming a 
 simple solution with the liquid present: e. g. when an 
 aqueous solution of acetic acid is brought into contact 
 with oxide of lead, there ensues, first, a chemical combina- 
 tion of the acid with the oxide, and then a simple solution 
 of the thereby produced acetate of lead, in the water of the 
 menstruum. 
 
 Crystallization and precipitation are the reverse of so- 
 lution, as they have for their object the conversion of a 
 fluid or dissolved substance into the solid state. As both 
 depend on the same cause, viz. on the absence of a sol- 
 vent, it is impossible to assign exact limits to either, and 
 in many cases they merge into each other. We must, 
 however, consider them separately, since they essentially 
 differ, as well in their extreme forms, as, in most cases, 
 
CRYSTALLIZATION. 19 
 
 in the special objects we purpose to attain by their appli- 
 cation. 
 
 5 3. 
 
 %. CRYSTALLIZATION. 
 
 We understand by the term crystallization, in a more 
 general sense, every operation, every process in which 
 bodies pass from a fluid to a solid state, assuming certain 
 regular, determinate, geometrical figures. But, as these 
 figures, which we call c^stals, are the more regular, and 
 consequently the more perfect, the more slowly the opera- 
 tion is carried on, we always connect with the term " crys- 
 tallization," the accessary idea of a slow separation, of a 
 gradual conversion to the solid state. The formation of 
 crystals depends on the regular arrangement of atoms ; it 
 can only take place if these atoms possess perfect free- 
 dom of motion, and thus, generally, only when a substance, 
 from the fluid or gaseous, changes to the solid state. 
 Those cases, in which it is sufficient merely to heat or to 
 soften a solid body, to induce crystallization, must be con- 
 sidered as exceptions, as, e. g. barley-sugar becoming 
 white and opaque, or crystallizing, when moistened. 
 
 To induce crystallization we must remove the causes of 
 the fluid or gaseous form of a substance. These causes, 
 .are either heat alone, e. g. in metals in fusion, or sol- 
 vents alone, as in an aqueous solution of common salt ; 
 or both combined, as in a hot and saturated aqueous solu- 
 tion of nitre. In the first instance, we can obtain crys- 
 tals only by cooling the substance we wish to crystallize; 
 in the second, only by evaporating the menstruum ; and in 
 the third, by either of these means. The most frequently 
 occurring cases of crystallization are those by means of 
 cooling hot ard saturated solutions. The liquors which re- 
 main after the separation of the crystals, are called mother 
 waters. The term, amorphous bodies, is applied to such 
 soli'l substances as have no crystalline form. 
 
 We cause crystallization to take place, generally, either 
 to obtain the substance crystallized in a solid form, or to 
 separate it from other substances dissolved in the same 
 menstruum. 
 
20 
 
 4. 
 
 3. PRECIPITATION. 
 
 This operation differs from crystallization inasmuch as 
 in precipitation the substance dissolved is converted to the 
 solid state, not in a slow and gradual manner, but sud- 
 denly ; it is a matter of perfect indifference, as regards the 
 application of the term precipitation to the process, whether 
 this substance is crystalline or amorphous j whether it 
 gravitates to the bottom of the vessel, or whether it as- 
 cends or remains suspended in the liquid. We may cause 
 precipitation to take place, either, 1st, by modifying the 
 solvent ; thus sulphate of lime (gypsum) separates im- 
 mediately from its solution in water, if this water y by the 
 addition of alcohol, is converted into diluted alcohol ; or 
 2d, By separating some substance insoluble in the men- 
 *g|ruumVj thus, if ammonia be added to a solution .of sul- 
 pf&te of alumina, the composition of this latter salt takes 
 placfe and alumina, not being soluble in water, is precipi- 
 tated.^ Precipitation takes place also when, by the action 
 of single or compound chemical affinity, new combina- 
 tions ejisue which are insoluble in the menstruum ; thus 
 ox1ftate y Qlime precipitates on adding oxalic acid to a solu- 
 tion pf acetate of lime ; chromate of lead on mixing, chro- 
 maje of potash with nitrate of lead. In decompositions of 
 /this kind, induced by simple or compound affinity, one of 
 the new combinations generally remains in solution, and 
 the same is sometimes the case with the substance separ- 
 ated, thus in the instances just mentioned, the sulphate 
 of ammonia, the acetic acid, and the nitrate of potash, re- 
 main in solution. Cases may, however, happen, where 
 both products precipitate, so that nothing remains in solu- 
 tion, e. g. when a solution of sulphate of magnesia is mix- 
 ed with water of barytes ; or a solution of sulphate of 
 silver with chloride of barium. 
 
 Precipitation is applied to the same purposes as crys- 
 tallization: either, 1st, to obtain a substance in a solid 
 form ; or 2d, to separate it from other substances dis- 
 solved in the same menstruum. But in qualitative analysis 
 we employ this operation especially, in order to detect 
 
FILTRATION. 21 
 
 substances by the colour, and the properties and relations 
 in general, which they exhibit when precipitated, either 
 alone or in combination with other substances. The solid 
 body separated by this process, is called precipitate, and 
 the substance, which is the immediate cause ot this sepa- 
 ration, is termed the precipitant. For the sake of a more 
 particular designation, we apply various terms to precipi- 
 tates, according to their different nature ; thus we distin- 
 guish crystalline, pulverulent, flocculent, curdy, gelatinous 
 precipitates, &c. &c. 
 
 The term turbid is made use of, when a precipitate is 
 in a state of such minute division, and so small in quan- 
 tity, that its particles cannot be clearly distinguished, and 
 that the fluid in which it is suspended merely appears 
 troubled. We may generally promote the separation of a 
 precipitate by strongly agitating the menstruum, as well 
 as elevating its temperature. The vessels used for the 
 purpose of precipitation, must, therefore, admit of either 
 of these operations. In qualitative analysis we principally 
 make use of tubes of thin glass, closed at the bottom, such 
 as are usually called test-tubes, or test-cylinders. Beside 
 the advantages just mentioned, they permit the experi- 
 mentalist closely to inspect the whole process, as well as 
 the colour of the liquids and precipitates, and to experi- 
 mentalize with very small quantities. 
 
 Two different operations, according to circumstances, 
 are employed in analysis, in order mechanically to sepa- 
 rate a fluid from matter suspended therein, namely, "Jil- 
 tration" and " decantation" 
 
 5. 
 
 4. FILTRATION. 
 
 We purify liquids, by means of this operation, in pour- 
 ing the fluid from which we wish to remove the mechani- 
 cally-suspended solid particles, on a filter, for which 
 purpose we usually employ unsized paper, supported by 
 a funnel ; for an apparatus of this description allows the 
 liquid to trickle through with ease ; and, on the other hand, 
 completely retains the solid particles. We use smooth 
 
22 DECANTATION. 
 
 filters and plaited filters : the former, in such cases where 
 the defiltrated solid substance is to be made use of ; the 
 latter, when we merely wish to clear the solution. Smooth 
 filteis are produced by folding a circular paper doubly to- 
 gether, so that the folds form right angles. The prepara- 
 tion of plaited filters is more properly a matter for ocular 
 demonstration than for description, In minute operations, 
 care should be taken that the filters do not reach over the 
 brim of the funnel. It is in most cases advisable to moisten 
 the filter previous to use, because then, not only the filtra- 
 tion proceeds more rapidly, but the solid particles of the 
 substances to be filtered are less liable to pass through the 
 pores of the filter. The paper selected for the purpose of 
 filtration, must be as free as possible from inorganic sub- 
 stances, especially iron and lime. It is advisable to have 
 always two sorts on hand, one of greater density for the 
 separation of very minute precipitates, and one of greater 
 porosity for the speedy separation of grosser particles. 
 The funnels must be either of glass or of porcelain. 
 
 6. 
 
 5. DECANTATION. 
 
 This operation is frequently made use of instead of fil- 
 tration, if the solid particles to be removed are of consider- 
 ably greater specific gravity than the liquid in which they 
 are suspended. They in such cases speedily gravitate to 
 the bottom, and are deposited there, so that it becomes 
 easy, either to decant the supernatant liquid by sim- 
 ply inclining the vessel, or to remove it by means of a 
 syphon. 
 
 In such cases where we employ these operations (filtra- 
 tion or decantation) in order to obtain the solid substance 
 out of the liquid in which it is suspended, we must after- 
 wards free this substance by repeated washing or rinsing 
 from the liquid still adhering to it. This operation is 
 termed edulcoration or rinsing. In order to edulcorate a 
 precipitate collected on a filter, we most frequently make 
 use of the syringe bottle, a glass vessel, stopped with a 
 perforated cork, into which a small glass tube is adapted, 
 
EVAPORATION, 23 
 
 drawn out at the top into a fine point. If air be blown 
 through this tube, into the flask, and, when the air is suffi- 
 ciently compressed^ the flask be reversed, so that the inner 
 aperture of the tube comes under water, a minute stream 
 of water is expelled, peculiarly adapted to the rinsing of 
 precipitates. 
 
 There are four operations by means of which we sepa- 
 rate volatile substances from less volatile or from fixed 
 bodies, viz, EVAPORATION, DISTILLATION, ROASTING, and 
 SUBLIMATION. The two former of these operations always 
 refer to fluids, the two latter only to solid*. 
 
 7. 
 
 6. EVAPORATION, 
 
 This is one of the most frequently-employed operations. 
 We have recourse to it when a volatile fluid is to be sepa- 
 rated from another less volatile, or from a fixed substance, 
 (either fluid or solid,) if by this separation we only intend 
 to obtain this residuary substance, without heeding the 
 evaporating substance. Thus, evaporation serves, for in- 
 stance, to remove from a saline solution part of its water, 
 in order to induce the salt to crystallize, or, also, to re- 
 move all the water from the solution of an uncrystallizable 
 substance, so as to obtain this latter in a solid form, &c. &c. 
 The evaporating water is entirely disregarded, in either of 
 these cases, and the only object in view is to obtain in the 
 former case a more concentrated fluid, and, in the latter, 
 a dry substance. These objects ' are always attained by 
 converting the fluid to be removed, into the gaseous state j 
 in ordinary cases, therefore, by exposing it to heat ; some- 
 times, also, by leaving the fluid for a certain time, in con- 
 tact with the atmosphere, or in confined air, constantly kept 
 dry by hygroscopic substances ; or, in many cases, by 
 placing the fluid in a rarified air, with the simultaneous 
 application of hygroscopic substances. The heating pro- 
 cess is conducted either over a free fire, (coal-fire or flame 
 of spirits of wine,) or in the sand-bath, or by means of 
 steam, (in the water-bath,) &c. &c. Concentrated sul- 
 phuric acid and slaked lime, and also chloride of calcium, 
 
24 DISTILLATION. ROASTING. 
 
 are used as the cheapest and most efficient hygroscopic 
 substances. The vessels used in evaporation are of por- 
 celain, glass, platinum, or silver, and have usually the 
 shape of a shallow basin. 
 
 8. 
 
 7. DISTILLATION* 
 
 This operation has for its object the separation of a vol- 
 atile liquid from a less volatile or fixed substance, either 
 solid or fluid, and the recovery of the evaporating fluid, 
 In order to attain this object, it is necessary to reconvert 
 the liquid from the gaseous form in which it evaporated, 
 into the fluid state. A distilling apparatus r therefore, con- 
 sists of three parts, whether separated from each other or 
 not, is quite indifferent. These three parts are, 1st, a 
 vessel in which the liquid to be distilled is heated, and 
 thus converted into vapour ,' 2d, an apparatus in which 
 this vapour is cooled again or condensed, and thus recon- 
 verted to the fluid state ; and 3d, a vessel which receives 
 the distilled fluid. In distillation on a small scale, we 
 generally employ small glass retorts and receivers, but in 
 the distillation of large quantities, either a metallic appa- 
 ratus, a copper still with helmet, and condensing tube of 
 pewter, or large glass retorts. 
 
 9. 
 
 8. ROASTING* 
 
 Roasting is, in a certain measure, for solid bodies, what 
 evaporation is for fluids ; for the object to which we ap- 
 ply it is, (at least generally,) the separation of a volatile 
 substance from a less volatile, or from a fixed body, mere- 
 ly for the purpose of purifying this latter residuary sub- 
 stance. Roasting always presupposes the application of 
 a high temperature, and in this it differs from exsicca- 
 tion. The form or state which the volatilized substance as- 
 sumes on cooling, is a matter of perfect indifference as to 
 the name of the operation* 
 
 This is the usual design in the application of roasting. 
 Jn some instances, however, substances are heated merely 
 
SUBLIMATION. SMELTING AND FLUXING* 25 
 
 for the purpose of modifying their state, without any vola- 
 tilization taking place ; e. g. in the conversion of oxide of 
 chromium into its insoluble modification, &c, &c. Cruci- 
 bles are the vessels made use of in roasting. In analytical 
 experiments we select, according to the substances to be 
 heated, either porcelain, or platinum, or silver crucibles. 
 In operations on a large scale, wa employ either hessian 
 or black-lead crucibles. The necessary heat we obtain 
 either from a coal-fire, or in experiments on a small scale, 
 most usually by means of a Berzelius spirit-lamp. 
 
 10. 
 
 * . 
 
 9. SUBLIMATION 
 
 Is that operation, whereby solid bodies are converted in- 
 to vapours by the application of heat, and condensed again 
 by cooling, to a solid state ; the substance thus volatilized 
 and recondensed is called a sublimate. Sublimation is 
 consequently a distillation of solid bodies. We generally 
 employ this process for the separation of substances of 
 different degrees of volatility. Its application is of the 
 highest importance in analysis, for the detection of divers 
 substances, e. g, of arsenic. The vessels used in sublima- 
 tion are of various shapes, according to the different de- 
 grees of volatility of the substance we have to operate upon. 
 In sublimation for analytical purposes we generally em- 
 ploy glass tubes closed at both ends. 
 
 11. 
 
 10. SMELTING AND FLUXING. 
 
 We designate by the term " smelting," the conversion 
 of a solid substance into a fluid form, by the application of 
 heat, and apply this operation generally to the purpose 
 either of combination or of decomposition of bodies. The 
 term " fluxing" is applied to this process in such cases 
 where a substance, either insoluble or difficult of solution 
 in water and acids, is, by being fused with some other body, 
 modified or decomposed in such a manner, that the former 
 or its new-formed combinations, afterwards admit of solu- 
 tion in water or acids. We employ in analysis, according 
 
26 USE OF THE BLOW-PIPE. 
 
 to circumstances, either porcelain, silver, or platina cruci- 
 bles, for the purposes of these operations. It we are una- 
 ble to produce the necessary degree of heat by means of a 
 Berzelius spirit-lamp, the crucible containing the substance 
 or substances to be fused, may be placed in a larger, hes- 
 sian crucible, and this latter exposed to a charcoal or coke 
 fire. 
 
 The application of fluxing is especially required in the 
 analysis of the sulphates of alkaline earths, and of many 
 silicates. The flux most commonly used is carbonate of 
 soda, or carbonate of potash, or, better still, a mixture of 
 both, in equal atomic proportions, (vide 75.) In cer- 
 tain cases, carbonate of barytes is used instead of carbon- 
 ate of soda or potash, (vide 76.) But in either case 
 the operation is conducted in platina crucibles. 
 
 We will here briefly lay down a few precautionary rules 
 for the prevention of damage to the platinum vessels used 
 in these operations. No substance, evolving chlorine, 
 ought to be treated in platinum vessels ; no nitrate of pot- 
 ash, caustic potash, metals, sulphur or sulphurets, should 
 be fused in such vessels, nor ought easily deoxidizable 
 metallic oxides, organic metallic salts, and phosphoric salts, 
 to be heated therein when organic compounds are present. 
 It is also detrimental to platinum crucibles ; and especially 
 to their covers, to expose them directly to a strong coal- 
 fire, (i e. without shielding them in larger, hessian cruci- 
 bles,) because siHcide of platinum is easily formed, in such 
 cases, by the influence of the ashes, and this renders the 
 vessels brittle* 
 
 12. 
 
 11. THE USE OF THE BLOW-PIPE. 
 
 The application of the blow-pipe is of the utmost im- 
 portance in analytical chemistry* We have here to con- 
 sider, first, the necessary apparatus ; then, the manner of 
 its application; and, lastly, the results of the operation. 
 
 A blow-pipe is a small instrument, usually made of brass. 
 It was originally used by metallurgists for the purpose of 
 soldering, whence it derived the name of soldering-pipe. 
 It consists of three distinct parts : viz. 1st, a tube through 
 which air is blown from the mouth ; 2d, a small vessel 
 
USE OF THE BLOW-PIPE. 27 
 
 into which this tube is ground air-tight ; this vessel serves 
 to collect and retain the moisture of the air blown into the 
 tube ; and 3d, a smaller tube, also closely fitted into this 
 vessel, forming a right angle with the large tube, and hav- 
 ing a very fine aperture at its anterior extremity. The 
 blow-pipe serves to conduct a fine and continuous stream 
 of air into the flame of a candle or lamp. Such a flame, 
 under ordinary circumstances, presents to the eye three 
 distinct parts ; viz. 1 st, a dark nucleus in the centre ; 2d, 
 a luminous part surrounding this nucleus ; and 3d, a kind 
 of mantle encircling the whole flame, and but feebly lu- 
 minous. The dark nucleus is formed by the gases which 
 the heat evolves from the fuel ; these gases cannot burn, 
 from want of oxygen. In the luminoussphere they come 
 into contact with a certain quantity of oxygen, although in- 
 sufficient for their complete combustion. The hydrogen 
 of the carburetted hydrogen gases evolved, therefore, burns 
 principally here, whilst the carbon separates in a state of 
 intense white heat, and is thus the cause of the luminous- 
 ness of this part. In the outer coat, the access of air is 
 no longer limited, and all the gases not yet consumed, are 
 consumed there. This part of the flame is the hottest. 
 Oxidizable bodies, therefore, oxidize with the greatest pos- 
 sible rapidity when placed in it, as the conditions of oxi- 
 dizement are here combined, viz. high temperature, 
 and an unlimited supply of oxygen. This part of the 
 flame is therefore called the oxydizing flame. But the 
 contrary ensues when we place oxydized bodies having a 
 tendency to yield up their oxygen, within the luminous 
 part of the flame, i. e. these substances lose their oxygen, 
 the carbon and the still unconsumed carburetted hydro- 
 gen withdraw it from them, and thus reduce them. The 
 luminous part of the flame is therefore called the reducing 
 flame. Now, if we conduct a fine stream of air into a 
 flame, we have oxygen, not merely around the outward 
 flame, but also in its interior part. Combustion takes 
 place, therefore, in either part. But this air rushes with a 
 certain vehemence into the flame, and carries forward the 
 gases evolved, mixes intimately with them, and effects 
 their combustion at a certain distance from the point of the 
 blow-pipe. This spot is marked by a bluish light. It is 
 
28 USE OF THE BLOW-PIPE. 
 
 the hottest of the whole flame, since the combustion is 
 most complete there, owing to the intimate intermixture 
 of the air with the gases. The luminous part of the flame 
 being thus surrounded on all sides by very hot flames, its 
 temperature also becomes exceedingly elevated, and this 
 elevation of temperature is the principal object in the ap- 
 plication of the blow-pipe ; the hottest point is then, of 
 course, somewhat before the aperture of the blow-pipe. In 
 this reducing flame many bodies fuse with ease, which re- 
 main unaltered in a common flame. The heat of the oxi- 
 dizing flame also is considerably increased by the blow- 
 pipe, since it becomes more concentrated upon one point. 
 
 As fuel we use either an oil-lamp, or a wax candle, or 
 a lamp fed with a solution of oil of turpentine in spirits of 
 wine. A common spirit-lamp does not yield, in all cases, 
 the requisite degree of heat. 
 
 The blowing is effected by the cheek-muscles alone, 
 and not by the lungs. This way of blowing may easily 
 be acquired by practising for some time to breathe gently, 
 with puffed up cheeks. If by this means the student has 
 succeeded so far as to be able to continue calmly breath- 
 ing in this manner, even when holding the blow-pipe be- 
 tween his lips, nothing except a little practice will be re- 
 quired to enable him to produce a continuous, correct and 
 steady flame. 
 
 The supports on which the substances to be examined 
 are exposed to the flame of the blow-pipe, are usually 
 either charcoal, platinum wire, or platinum plate. In the 
 choice of charcoal for the purpose of blow-pipe experi- 
 ments, we must especially look to its being thoroughly 
 charred, because, if not so, it will split and throw off the 
 substances placed on it. The substances to be examined 
 are put into small conical cavities carved into the piece of 
 charcoal by means of a pen-knife. We generally employ 
 charcoal as a support, when we want to reduce a metallic 
 oxide, or to test its substance as to its fusibility. If metals 
 are volatile in the heat of the reducing flame, they evapo- 
 rate partly or entirely during their reduction. But these 
 metallic vapours reoxidize in their transit through the ex- 
 ternal flame. 
 
 Many of them have a peculiar colour, by means of 
 which the metals maybe detected. The platinum wire, 
 
APPARATUS AND UTENSILS. 29 
 
 as weU as the platinum plate, should be selected rather 
 thin. vVe generally make use of platinum wire when fus- 
 ing bodies together, by means of fluxes, in order to ascer- 
 tain their nature, by the colour and other properties of the 
 button produced. 
 
 The blow-pipe flame is of especial importance in chem- 
 ical experiments, because its effects yield immediate re^ 
 suits. These are of two different kinds ; either, 1st, we ob- 
 tain merely a knowledge of the general properties of the 
 body, and are consequently only enabled to determine the 
 class to which it belongs, i. e. we ascertain whether it is a 
 fixed, volatile, or fusible substance, &c. &c. ; or, 2d, the 
 phenomena we observe at once point out what special body 
 we have before us. The phenomena in question, we shall 
 have occasion to examine when we treat of the relation of 
 various substances to reagents. 
 
 APPENDIX TO THE FIRST CHAPTER, 
 13. 
 
 APPARATUS AND UTENSILS. 
 
 As the student cannot be supposed to know the appa- 
 ratus, &c., necessary for chemical analysis, it may be well 
 here to furnish him with a list of indispensable articles, 
 and to point out the qualities they should possess, in order 
 to guide him in their purchase. 
 
 1. A BERZELIUS SPIRIT-LAMP. The vessel containing 
 the spirit of wine should be connected with the wick by 
 means of a narrow tube, to avoid explosions j the chimney 
 should not be too narrow. The aperture through which 
 the spirit of wine is poured should not be air-light. 
 
 2. A LAMP-STAND with moveable rings and brackets. 
 
 3. A GLASS SPIRIT-LAMP with ground cover and brass 
 wick-tube. 
 
30 APPARATUS AND UTENSILS. 
 
 4. A BRASS BLOW-PIPE with a mouth-piece made f horn 
 or bone, (vide 12.) The longer tube may be about 
 seven inches, slightly varying, of course, according to the 
 visual distance of the individual ; the length of the smaller 
 tube ought to be about two inches. Both must be ground 
 air-tight into the small vessel, which, as we have stated, 
 ( 12,) collects and retains the moisture of the air blown 
 through the pipe. It is advisable to keep two small tubes 
 at hand, one with a wider, and the other with a narrower 
 opening. 
 
 5. A. PLATINUM CRUCIBLE with ground cover ; this 
 should not be too deep, in proportion to its breadth. 
 
 6. A PLATINUM SPATULA ; this ought not to be selected 
 too thin, and must be as clean and. even as possible, and 
 about two inches long and one inch in breadth. 
 
 7. A FEW PIECES OF PLATINUM WIRE, of the S1Z6 of hlte- 
 
 strings, varying in length from three to four inches, and 
 twisted at both ends into a small loop. It is advisable to 
 keep these wires in a small glass containing water. 
 
 8. A STAND WITH FROM TWELVE TO TWENTY TEST TUBES. 
 
 The latter may vary from four to six or eight inches in 
 length, and must be of different width. They should be 
 made of thin white glass, and so well annealed, that they 
 do not crack even if boiling water be poured into them. 
 Their brim must be quite round, and slightly turned down ; 
 it ought to have no lip whatever, as the latter is not of the 
 slightest use, and prevents the tube from being closely 
 stopped with* the ringer. 
 
 9. SEVERAL BEAKER GLASSES AND SMALL RETORTS of 
 thin, well-annealed glass. 
 
 10. SEVERAL PORCELAIN EVAPORATING DISHES, AND A 
 
 VARIETY OF SMALL PORCELAIN CRUCIBLES. ThoSC of the 
 
 royal manufacture of Berlin are quite unexceptionable in 
 shape as well as durability. 
 
 11. SEVERAL GLASS FUNNELS of various sizes. They 
 must be inclined at an angle of sixty degrees, and ought to 
 merge into their tube at a definite angle. 
 
 12- A SYRINGE BOTTLE, capable of holding from twelve 
 to sixteen ounces of water, (vide 5.) 
 
 13. SEVERAL GLASS RODS AND VARIOUS GLASS TUBES. 
 
REAGENTS. 31 
 
 The latter may be bent, drawn out, &c., over a Berzelius 
 spirit-lamp. 
 
 14. A selection of WATCH-GLASSES. 
 
 15. A small AGATE MORTAR. 
 
 16. Several small IRON SPOONS. 
 
 17. A pair of small PINCERS, with scissor-handles, the 
 blades close together, and bent at their extremity at an 
 obtuse angle. 
 
 These should be varnished. 
 
 CHAPTER II 
 
 REAGENTS. 
 
 VARIOUS phenomena may manifest themselves during 
 the decomposition or combination of bodies. In some 
 cases liquids change their colour, in others precipitates 
 are formed, sometimes effervescence takes place, and 
 sometimes deflagration, &c. Now, if these phenomena 
 are very striking, and if they accompany only the com- 
 bination or decomposition of two definite bodies, it be- 
 comes evident that by means of one of these bodies the 
 presence of the other may be detected and proved : e. g. 
 if we know that a white precipitate, of determinate pro- 
 perties, is formed on mixing barytes with sulphuric acid, 
 there can be no difficulty in understanding that, if by 
 adding barytes to any liquid we obtain a precipitate of 
 these determinate properties, the conclusion must follow, 
 that this liquid contains sulphuric acid. 
 
 Those substances which indicate the presence of other 
 bodies, by somewhat striking phenomena, are called 
 reagents^ on account of their mutual action upon each 
 other. 
 
 Reagents are divided into general and special, accord- 
 ing to the object obtained by their application. By general 
 reagents, we understand those by means of which we deter- 
 
32 REAGENTS. 
 
 mine the class or group to which the substance under in- 
 vestigation belongs ; and by special reagents those, by 
 means of which we detect a single definite substance. It 
 c'annot be considered an objection to this classification, 
 that the limits between these two divisions cannot be 
 drawn with any degree of exactness. I suggest it only 
 to induce the student to keep distinctly in view his pre- 
 cise object, i. e. whether a group is to be determined or a 
 single substance. 
 
 The value of reagents depends on two circumstances : 
 1st, whether they are characteristic ; and 2d, whether 
 they are sensible. We call a reagent characteristic, if 
 the alteration it produces by the detection of the sub- 
 stance, the presence of which (in -mixture or combination) 
 we wish to ascertain, is of so distinct a character as to 
 admit of no erroneous conclusion. Thus, iron is a charac- 
 t&ristic reagent for copper, protochloride of tin for, mer- 
 cury, because the phenomena thereby produced, such* as 
 the separation of metallic copper and of globular mercury, 
 admit of no mistake. We call a reagent sensible, if its 
 action is still clearly perceptible, although but a very small 
 qtfantity of the substance to be detected may be present, 
 &* g. the action of starch upon iodine. We need scarcely 
 mention that reagents "must in general be chemically pure ; 
 they must contain no foreign substance, but simply consist 
 of their essential constituents, for their evidence cannot 
 be relied upon if this be not the case. We must there- 
 fore make it a rule carefully to test reagents as to their 
 purity, before we use them in experiments, no matter whe- 
 ther they be articles of our own production or of purchase. 
 As a matter of course, in the instruction we shall give 
 when treating of each reagent in particular, and of the 
 mode of testing its purity, we cannot take cognizance of 
 all those substances with which the reagent may, acci- 
 dentally, have become mixed, but only of those, the pre- 
 sence of which is probable from the manner of its prepa- 
 ration. 
 
 One of the most common sources of mistakes in quali- 
 tative analysis, proceeds from missing the proper measure 
 the right quantity in the addition of a reagent to a sub- 
 stance under examination. Such terms as " addition in 
 
&EAGENTS, 83 
 
 excess," l< supersaturation," &c., often induce novices er- 
 roneously to suppose that they cannot add too much of the 
 reagent^ and, to avoid using too small quantities, many fill 
 a test cylinder with acid for the supersaturation of a few 
 drops of an alkaline fluid, whilst yet every drop of acid 
 added, after the neutralization point has once been reached, 
 must be considered an excess of acid. But, on the other 
 hand, an insufficient addition is just as much to be avoided 
 as a too copious one, since a reagent in insufficient quan- 
 tity often produces phenomena quite different from those 
 manifested when added in excess : e. g. chloride of mer- 
 cury, wheji treated with a small quantity of sulphuretted 
 hydrogen, gives a white precipitate ; but when treated with 
 sulphuretted hydrogen in excess, the precipitate is black. 
 Experience has, however, proved that the most common 
 mistake beginners are liable to, and which renders their 
 operations difficult and uncertain, is to add the reagents in 
 too copious quantities. The reason why the experiment 
 loses thereby in certainty, is clear, if we recollect that all 
 the changes effected by reagents are perceptible only 
 within certain limits, and that consequently they become 
 less and less evident, and may the easier be overlooked 
 the more we approach this point by diluting the fluid. 
 
 No definite rules can be given for avoiding this source 
 of errors ; a general rule may, however, be laid down, 
 and this even is sufficient to point out the proper measure 
 in all, or at least in most cases. It is simply this : let the 
 student always, before the application of a reagent, well 
 consider to what purpose he applies it, and what are the 
 phenomena he intends to produce. 
 
 We divide reagents into two classes, according as the 
 fluid state of substances, indispensable to the action of 
 the reagents, is caused either by the application of heat, 
 or by means of liquid solvents; viz. 1, Reagents in the 
 humid way ; and 2, Reagents in the dry way. For the 
 sake of facility and simplicity, we subdivide these two 
 classes as follows : 
 
 A. REAGENTS IN THE HUMID WAY. 
 
 I. GENERAL REAGENTS. 
 
 a. Reagents principally used as SIMPLE SOLVENTS. 
 
34 WATER. 
 
 b. Reagents principally used as CHEMICAL SOLVENTS. 
 
 c. Reagents which serve especially to separate, or 
 otherwise to characterise groups of substances. 
 
 II. SPECIAL REAGENTS. 
 
 a. Reagents which serve especially for the detection of 
 the various BASES. 
 
 6* Reagents which are particularly applied to the de- 
 tection of the various ACIDS. 
 
 B. REAGENTS IN THE DRY WAY. 
 
 I. FLUXES. 
 
 II. BLOW-PIPE REAGENTS. 
 
 A. REAGENTS IN THE HUMID WAY. 
 
 I. GENERAL REAGENTS. 
 a. Reagents principally used as simple solvents. 
 
 15. 
 1. WATER. (H O.) 
 
 Preparation. Pure water is obtained by distilling 
 spring-water from a copper still, or from a glass retort. 
 This distillation should not be carried beyond three-fourths 
 of its quantity. Rain-water received in the open air may 
 in most cases be substituted for distilled water. 
 
 Testing. Distilled water must leave no residue on 
 evaporation, and must not alter the colour of Georgina 
 paper. Nitrate of silver, chloride of barium, oxalate of 
 ammonia, and lime-water, should not disturb its transpa- 
 rency. 
 
 Uses. We use water* chiefly as a simple solvent for 
 a great variety of substances. It has, moreover, a special 
 application for the decomposition of several neutral metaj- 
 lic salts, giving rise to the formation of soluble acid, and 
 insoluble basic compounds ; this is particularly the case 
 with the salts of bismuth and the chloride of antimony. 
 
 * In chemical experiments we never make use of any other but 
 distilled water ; whenever therefore the term " water" occurs in the 
 present work, distilled water is meant. 
 
ALCOHOL. ETHER. HYDROCHLORIC ACID. 35 
 
 2. ALCOHOL. (C 4 H 6 O 2 = E, O + Aq.) 
 
 Preparation. Two sorts of alcohol are used in chemi- 
 cal analysis ; 1st. spirit of wine of 0'83 or 0*84, (spiritus 
 vini rectificatissimus of the shops ;) and 2d,. absolute 
 alcohol. The latter may.be obtained by distilling the 
 former, with the addition of fused chloride of calcium. 
 
 Testing. Pure alcohol must completely volatilize, 
 and ought not to cause any enipyreumatic smell when 
 rubbed between the hands, nor should it redden litmus 
 paper. 
 
 Uses. Many substances are soluble in alcohol, others 
 remain insoluble. It may, therefore, frequently be em- 
 ployed for the separation of the former from the latter, e. 
 g. of chloride of strontium from chloride of barium. We 
 use alcohol also to precipitate from their aqueous solutions 
 such substances as are insoluble in alcohol, e. g. to pre- 
 cipitate malate of lime. We employ alcohol, moreover, 
 in the production of various kinds of ether, especially of 
 ascetic ether, (which is so particularly characterised by 
 its agreeable odour.) Alcohol serves also for the detection 
 of various substances which impart a characteristic tint to 
 its flame, especially boracic acid, strontian, soda, and potash. 
 
 17. 
 
 3. ETHER. (C 4 H 5 O = E O.) 
 
 Ether has but a very limited application in the analysis 
 of inorganic bodies. We use it in fact only to detect and 
 isolate bromine, ( 100, 6.) and for this purpose commer- 
 cial officinal ether is sufficiently pure and strong. 
 
 b. Reagents which are principally used as chemical 
 solvents. 
 
 7 
 
 18. 
 
 1. HYDROCHLORIC ACID. ' (Cl H.) 
 
 Preparation. A mixture of thirteen and a half parts 
 of oil of vitriol and four parts of water, when cold, is 
 
ACID. 
 
 poured upon eight parts of common salt contained in a 
 retort ] the neck of the retort is then somewhat raised, and 
 the heat of the sand-bath applied to the latter, as long as 
 gas passes over. The gas evolved is by means of a bent 
 tube, transmitted through twelve parts of water, in a glass 
 flask, which must be constantly kept cool. In order to 
 prevent the gas from receding, the tube is only permitted 
 to dip about one line into the water of the receiver. If 
 the sulphuric acid contains nitric acid, the gas which 
 passes over first, (and which in that case contains chlorine,) 
 must be received separately. The hydrochloric acid thus 
 produced is tested as to its specific gravity, and diluted 
 with water until its specific gravity is I'll or 1*12. 
 
 Testing. Hydrochloric acid, used for the purposes of 
 chemical analysis, must be colourless and leave no residue 
 upon evaporation, nor ought it to discolour indigo-solution, 
 even when heated with it to boiling. Chloride of barium 
 ought not to produce any precipitate of barytes, neither in 
 the highly diluted acid, (sulphuric acid,) nor even after 
 having been boiled with nitric acid, (sulphurous acid.) 
 Sulphuretted hydrogen must leave it unaltered. Ferro- 
 cyanide of potassium must not cause any precipitate in it, 
 nor even impart the slightest blue tinge to it, after neu- 
 tralization with ammonia and subsequent addition of some 
 acetic acid in excess. 
 
 Uses. We employ hydrochloric acid as a chemical sol- 
 vent for a very great variety of bodies, especially for oxides 
 and peroxides (on the solution of which, chlorine is libera- 
 ted,) and salts with weaker acids. A solution of this kind, 
 always depends on the formation of a chloride soluble in 
 water. Muriatic acid serves also as a simple solvent for 
 many salts, e. g. the phosphates, borates, and oxalates of 
 the alkaline earths. We use it, moreover, to expel weaker 
 acids from their salts ; e. g. carbonic acid, hydro'sulphuric 
 acid. It has also a special application in the detection 
 and precipitation of oxyde of silver, protoxyde of mercury, 
 and oxyde of lead, (vide infra,) as well as in the detection 
 of free ammonia, by producing dense white fumes with it, 
 dependent on the formation of sal ammoniac, in the air. 
 
NITRO-MURIATIC ACID. AQUA REGIA. 37 
 
 . f 
 
 2. NITRIC ACID, (NO 5 .) 
 
 Preparation. The nitric acid of commerce almost in- 
 variably contains sulphuric acid and hydrochloric acid. In 
 order to purify it for the purpose of chemical analysis, a 
 solution of nitrate of silver is added to it, as long as any 
 precipitate of chloride of silver is formed ; this precipitate 
 is allowed to settle, and the supernatant acid decanted into 
 a retort, and distilled to within a small fraction of its whole 
 amount. The distillate is then, if necessary, diluted with 
 water till the acid has a specific gravity of 1'2. 
 
 Testing. Pure nitric acid must be colourless, and, 
 when evaporated on a platinum plate, leave no residue 
 behind. Nitrate of barytes, or nitrate of silver, must not 
 render it turbid. It is advisable to dilute the acid highly 
 with water before the application of these reagents, since 
 nitrates will be precipitated if this precaution be neglected. 
 
 U ses , Nitric acid serves, in the first place, as a chemi- 
 cal solvent for metals, oxides, sulphurets, oxygen salts, 
 &c. Its action on metals and sulphurets depends on the 
 oxidation of these bodies, at the expense of part of its 
 oxygen, and on the subsequent chemical solution of the 
 thereby formed oxides, giving rise to the formation of ni- 
 trates. Most oxides dissolve in nitric acid, directly as 
 nitrates, and the same is the case with most insoluble 
 (i. e. in water) salts with weaker acids, the nitric acids 
 expelling the latter. For many salts with stronger acids 
 it is (like hydrochloric acid) used as a simple solvent, e. g. 
 the phosphates of the alkaline earths. Nitric acid serves, 
 moreover, as the most common means of oxidation ; thus 
 we use it, for instance, to convert protoxide of iron into 
 peroxide, to decompose hydriodic acid and the iodides, &c. 
 
 20. 
 
 NITRO-MURIATIC ACID. AQUA REGIA. (NO 4 +C1.) 
 
 Preparation. One measure of pure nitric acid is mixed 
 with from three to four measures of pure hydrochloric acid. 
 Uses. Nitric acid and hydrochloric acid decompose 
 2 
 
00 ACETIC ACID. 
 
 each other in such a manner as to give rise to the forma- 
 tion of chlorine, hyponitric acid, and water* This decom- 
 position ceases as soon as the liquid is saturated with 
 chlorine, but it is resumed immediately, if this state of 
 saturation is disturbed, by the application of heat, or by 
 the chlorine combining with some other substance. Thus 
 we have, in aqua regia, 1st, a continuous source of chlo- 
 rine ; and 2d, hyponitric acid, and consequently a com- 
 bination which has the property of readily yielding oxygen. 
 The mixture of those two substances renders aqua regia 
 the most powerful solvent we possess for metals, (those 
 excepted which form insoluble compounds, with chlorine.) 
 We use aqua regia chiefly for the solution of gold and 
 platinum, (both of which are insoluble in hydrochloric "acid 
 alone, as well as in nitric acid alone,) and for the decom- 
 position of various sulphurets, e. g. cinnabar, &e. 
 
 21. 
 
 4, ACETIC ACID. (C 4 H 3 O 3 =A.) 
 
 Preparation. Pure acetic acid is best obtained by 
 rubbing ten parts of crystallized neutral acetate of lead 
 together, with three parts of anhydrous sulphate of soda, 
 pouring the mixture into a retort, adding a cooled mixture 
 of two and a half parts of sulphuric acid, with an equal 
 weight of water, and distilling to dryness, in a sand-bath. 
 The receiver is best connected with the retort by means of 
 a Liebig's condensing apparatus. 
 
 Testing. Pure acetic acid must leave no residue upon 
 evaporation. Sulphuretted hydrogen, and solution of sil- 
 ver and of barytes, must not precipitate it when diluted, 
 solution of barytes not even when the acetic acid has been 
 previously boiled with nitric acid. Indigo solution must 
 not be discoloured on being heated with the acid, (vide 
 101, a.) 
 
 Uses. The application of acetic acid in qualitative 
 analysis is chiefly based upon its possessing an unequal 
 power of solution for different substances, so it serves, for 
 instance, to distinguish oxalate of lime from phosphate of 
 lime. We apply acetic acid also for the acidulation of 
 liquids, -when we wish to avoid the use of mineral acids. 
 
CHLORIDE OF AMMONIUM. 39 
 
 , 22. *l 
 
 5. CHLORIDE OF AMMONIUM. (N H 4 Cl.) 
 
 Muriate of Ammonia. 
 
 Preparation. The sal ammoniac of commerce may 
 generally be purified for the purposes of chemical analysis 
 by simple recrystallization. If it contains iron, a small 
 quantity of hydros ulphuret of ammonia must be added to 
 the solution ; the precipitate formed is allowed to settle, 
 the solution filtered, and hydrochloric acid added to it until 
 a feeble acid re-action manifests itself ; the mixture then 
 is boiled, filtered, saturated with ammonia, and crystal- 
 lized. For use as a reagent, one part of the salt is dis- 
 solved in eight parts of water. 
 
 Testing. Solution of sal ammoniac, when evaporated 
 on a platinum plate, must leave a residue which com- 
 pletely volatilizes upon a higher degree of heat being ap- 
 plied. Hydrosulphuret of ammonia ought not to change 
 it. Its reaction ought to be completely neutral. 
 
 Uses. We employ sal ammoniac chiefly to keep in so- 
 lution certain oxides, e- g. protoxide of manganese, mag- 
 nesia, or certain salts, e. g. tartrate of lime, when other 
 oxides or salts are precipitated by ammonia or by some 
 other reagents. This application of sal ammoniac is based 
 on the tendency of the ammoniacal salts to form double 
 combinations with other salts. Sal ammoniac also serves 
 to distinguish between precipitates possessed of similar 
 properties, e. g. to distinguish the basic phosphate of mag- 
 nesia and ammonia which is insoluble in sal ammoniac, 
 from other precipitates of magnesia. We employ sal am- 
 moniac besides to precipitate from their solutions, various 
 substances soluble in potash, and insoluble in ammonia, 
 e. g. alumina, oxide of chromium ; for in this process the 
 sal ammonia decomposes with the potash, and chloride of 
 potassium, water, and ammonia are formed. Sal ammo- 
 niac is moreover specially used to precipitate platinum as 
 ammonio chloride of platinum. 
 
40 REAGENT PAPERS. GEORGINA PAPERS. 
 
 c. Reagents which serve especially to separate or other- 
 wise to characterize groups of substances. 
 
 23. 
 
 1. REAGENT PAPERS : <*>. BLUE LITMUS PAPER. 
 
 Preparation. One part of commercial litmus is digested 
 with six parts of water ; the intensely blue liquid obtained 
 is divided into two parts, and the free alkali contained in 
 the one half saturated by stirring it repeatedly with a glass 
 rod dipped into very dilute sulphuric acid, until the colour 
 exhibits a shade of red ; then the other blue half is added, 
 the whole poured into a cup, and slips of fine unsized pa- 
 per are dipped into this tincture. These slips are then 
 suspended on threads for the purpose of drying. The 
 colour of litmus paper must be uniform, and neither too 
 light nor too dark. 
 
 Uses. Litmus paper serves for the detection of free 
 acids in liquids, since its blue colour becomes thereby 
 changed into red. It must, however, be borne in mind, 
 that it undergoes the same alteration by the neutral salts 
 of most metallic oxides. 
 
 ft. REDDENED LITMUS PAPER. 
 
 Preparation. Blue litmus tincture is repeatedly stirred 
 wilh a glass rod dipped into dilute sulphuric acid, until its 
 colour has assumed a distinct shade of red. Slips of pa- 
 per are then dipped into this tincture. They must be 
 distinctly red when dry. 4 
 
 Uses. The blue colour of reddened litmus paper is 
 restored by pure alkalies and alkaline earths, as well as 
 by their sulphur combinations, by alkaline carbonates, and 
 also by the soluble salts of several other weak acids, 
 especially of boracic acid. It serves, therefore, for the de- 
 tection of these substances in general. 
 
 V. GEORGINA PAPER. 
 
 Preparation- The violet coloured petals of Georgina 
 purpurea are boiled in water or digested with spirits of 
 
TURMERIC PAPER. SULPHURIC ACID. 41 
 
 wine, and slips of paper dipped into the tincture. Care 
 should be taken to concentrate the liquor only to such a 
 degree as to impart to the paper when dry, a fine violet- 
 blue colour, which must not be too dark (deep.) A small 
 quantity of ammonia is added to the tincture, if the colour 
 is too red. 
 
 Uses. Georgina paper is reddened by acids ; alkalies 
 impart a beautiful green tinge to it. It is, therefore, of very 
 convenient application, as a substitute for the blue as well 
 as the red litmus paper. It is of extreme susceptibility, if 
 properly prepared, for acids as well as for alkalies. Con- 
 centrated solutions of caustic alkalies, colour it yellow by 
 destroying its colouring matter. 
 
 . TURMERIC PAPER. 
 
 * 
 
 Preparation. One part of bruised turmeric-root is di- 
 gested and heated with six parts of dilute spirit of wine ; 
 the tincture obtained is filtered, and slips of fine paper are 
 dipped into it. Turmeric paper, when dry, must have a 
 fine yellow colour. 
 
 Uses. It serves in the same manner as reddened litmus 
 paper and Georgina paper, for the detection of free alka- 
 lies, &c. ; as they change its yellow colour into brown. 
 It is not so susceptible as the other reagent papers, but the 
 change of colour it produces is highly characteristic, and 
 can be especially well perceived in several coloured li- 
 quids ; we consequently cannot well dispense with tur- 
 meric paper. It must be borne in mind, when using it as 
 a test, that, besides the substances mentioned above, (vide 
 reddened litmus paper,) several other bodies, e. g. boracic 
 acid, change its yellow colour into brown. 
 
 All reagent papers should be cut into slips, and kept in 
 well-closed glass jars or small boxes. 
 
 24. ty' 
 
 2. SULPHURIC ACID. (S O 3 .) 
 
 English sulphuric acid may always be used in qualita- 
 
42 SULPHURETTED HYDROGEN. 
 
 live analysis, provided it contains no arsenic, and has pre- 
 viously been freed from nitric acid, by boiling.* 
 
 Testing. Pure sulphuric acid, when boiled with a 
 small quantity of indigo solution, must not destroy its blue 
 colour. When mixed with pure zinc and water, it must 
 yield hydrogen, which, on being passed through a tube 
 heated to redness, does not deposit the slightest crust of 
 arsenic. (Compare 93, d.) 
 
 Uses. Sulphuric acid having to most bases a greater 
 affinity than almost any other acid, is principally employed 
 for the liberation and expulsion of other acids, especially 
 of phosphoric, boracic, muriatic, nitric, and acetic acids. 
 Sulphuric acid serves also for the liberation of iodine from 
 the iodides. It oxidizes, in this process,*the metals at 
 the expense of its own oxygen, and is converted into sul- 
 phurous acid. Several substances which cannot exist in 
 an anhydrous state (e. g. oxalic acid) are decomposed 
 when brought into contact with concentrated sulphuric 
 acid ; this decomposition is caused by the great affinity 
 which sulphuric acid has for water. The nature of the 
 decomposed body may in such cases be determined by 
 the liberated products of its decomposition. Sulphuric 
 acid is, moreover, frequently used for the evolution of sev- 
 eral gases, especially of hydrogen and sulphuretted hy- 
 drogen. It is, besides, especially employed for the detec- 
 tion and precipitation of barytes, strontian, and lead. The 
 acid used for this purpose is diluted with four parts of 
 water. 
 
 25. 
 
 3. SULPHURETTED HYDROGE^. (HS.) 
 
 DROGEN. 
 
 Preparation. Mix intimately thirty-two parts of iron 
 filings with twenty-one parts of sublimed sulphur, divide 
 into small portions, and gradually project them into a cru- 
 cible heated to redness, and before adding new portions, 
 wait until the last are red-hot. Aftkr the entire mixture 
 has thus been fused, the crucible is well covered, and al- 
 
 * The sulphuric acid of commerce often contains lead, which ren- 
 ders it turbid when diluted ; this may be removed by allowing the 
 lead to subside, or by distillation. ED. 
 
SULPHURETTED HYDROGEN. 43 
 
 lowed to remain a short time longer exposed to the fire. 
 The sulphuret of iron thus obtained is broken into lumps, 
 when cool, covered with water, in an evolution bottle 
 (a,) and concentrated sulphuric acid 'added by means of 
 (through) a funnel tube (b.) The gas evolved is transmit- 
 ted through some water (c.) for the purpose of purifying 
 it. 
 
 Sulphuretted hydrogen water is prepared by conduct- 
 ing the gas obtained in the preceding process into water of 
 the lowest possible temperature (d,) until it is saturated, 
 consequently until the whole volume of the gas added in 
 excess begins to escape completely unabsorbed. Sul- 
 phuretted hydrogen water must be kept in well-closed ves- 
 sels, as it soon undergoes complete decomposition, if this 
 precaution is neglected. It keeps very long if it is im- 
 mediately after preparation put into little flasks, and these 
 latter, being well corked, are placed in an inverted position 
 into small vessels filled with water. Sulphuretted hydro- 
 gen water must be clear, possess the odour of the gas to a 
 high degree, and yield a strong precipitate of sulphur," 
 when treated with chloride of iron. It must not assume a 
 blackish tinge upon the addition of ammonia. 
 
 Uses. Sulphuretted hydrogen has a strong tendency to 
 decompose with metallic oxides, forming water and sul- 
 phurets. As these latter are mostly insoluble in water, a 
 decomposition of this kind is usually attended with pre- 
 cipitation of the metallic oxides from their solutions. The 
 
44 HYDROSULPHURET OP AMMONIA. 
 
 conditions under which these precipitations take place, 
 differ in such a manner, that by altering them we are en- 
 abled to divide all precipitable metals into groups, (as we 
 shall afterwards explain, vide 26, uses.) Sulphuretted 
 hydrogen is, therefore, an invaluable means for the division 
 of metals into groups. Some of these sulphuret precipi- 
 tates have so distinct a colour, that we are enabled there- 
 by to determine the particular metals they contain. Sul- 
 phuretted hydrogen serves for the special detection of the 
 following metals : tin, antimony, arsenic, cadmium, man- 
 ganese, and zinc. For more ample information we refer 
 the reader to the third chapter. From it's property of 
 being readily decomposed, sulphuretted hydrogen serves 
 also as means of reduction for many substances ; thus, 
 for instance, salts of peroxide of iron are converted by it 
 into salts of protoxide of iron, chromic acid is changed into 
 chromic oxide, &c. Sulphur separates in these reduc- 
 tions, in the form of a white powder. 
 
 26. 
 
 2. HYDROSULPHTJRET OF AMMONIA. (NH 4 SHS.) 
 
 Preparation. This liquid is formed by transmitting 
 sulphuretted hydrogen through liquor of ammonia, to com- 
 plete saturation, consequently till it no longer causes pre- 
 cipitation in a solution of sulphate of magnesia. The so- 
 lution obtained must be kept in well-closed bottles, since 
 contact with the atmosphere decomposes it. 
 
 Testing. Hpdrosulphuret of ammonia is transparent at 
 first, and yields no sulphur on being mixed with acids ; in 
 contact with the atmosphere . it assumes a yellow tint 
 caused by the formation of sulphuret of ammonium, in ex- 
 cess. This yellow tinge, however, does not render the 
 reagent useless. But it now yields sulphur when mixed 
 with acids, and this ought to be overlooked in experiments. 
 Hydrosulphuret of ammonia must be transparent, and 
 when heated evaporate without residue : and, as already 
 mentioned above, ought not to precipitate solution of mag- 
 nesia. 
 
 Uses* The arrangement into groups of the metallic ox- 
 ides, precipitable by sulphuretted hydrogen, depends upon 
 

 SULPHURET OF POTASSIUM. POTASH. 45 
 
 certain conditions indispensable to their precipitation. The 
 presence of an alkali is one of these conditions its ab- 
 sence is another ; i. e. certain sulphurets precipitate only 
 if the liquid is alkaline, because they are soluble in acids ; 
 others precipitate only if the liquid is acid, as they are 
 soluble in alkaline sulphurets. Now, hydrosulphuret of 
 ammonia may be considered as a reagent in which sul- 
 phuretted hydrogen acts in conjunction with ammonia. 
 Here, we have, therefore, as well as those conditions which 
 are necessary for the precipitation of the first-mentioned 
 group, as also those conditions which prevent the precipi- 
 tation of the other group of sulphurets, or cause their re- 
 solution, when those precipitated from acid solutions are 
 digested with the reagent. For the purposes of this latter 
 application, the hydrosulphuret of ammonia must, in cer- 
 tain cases, contain sulphur in excess. Besides the sul- 
 phurets the precipitation of which is effected by the joint 
 action of sulphuretted hydrogen and of ammonia, the hy- 
 drosulphuret of ammonia by the sole action of its ammo- 
 nia, precipitates oxide of chromium and alumina as hy- 
 drated oxides, and also such substances as are only dis- 
 solved by free acids, e. g. phosphate of lime, dissolved in 
 hydrochloric acid, and this property of hydrosulphuret of 
 ammonia must not be lost sight of in experiments. 
 
 27. 
 
 SULPHURET OF POTASSIUM. (KS 5 ) 
 
 Preparation. This"reagent must not be kept in store, 
 but prepared immediately previous to its application. 
 It maybe produced by boiling sulphur, in proper propor- 
 tions, with solution of caustic potash. 
 
 Uses. Sulphuret of potassium must be substituted for 
 hydrosulphuret of ammonia, when sulphuret of copper is 
 to be separated from sulphur combinations soluble in al- 4 
 kaline sulphurets, e. g. from sulphuret of tin, because the 
 sulphuret of copper is not quite insoluble in hydrosulphuret 
 of ammonia. 
 
 28. i 
 
 6. POTASH. (KOJ I 
 
 Preparation. One ounce of pure carbonate of potash 
 2* 
 
46 POTASH. 
 
 ( 29) is dissolved in twelve ounces of water, the solution 
 boiled in a clean iron pan, and whilst the liquid is kept 
 constantly at a boiling point, hydrate of lime added in small 
 portions until a portion of the fluid thus obtained, causes 
 no longer any effervesence when filtered into hydrochloric 
 acid. (The proportions used are, the hydrate of about one 
 part of the caustic lime in two parts of carbonate of pot- 
 ash.) The pan is then taken off the fire. If the process 
 has been conducted exactly according to the direction here 
 given, the carbonate of lime which has been formed will 
 quickly subside. When all the carbonate of lime has set- 
 tled at the bottom of the vessel, the supernatant solution of 
 potash may be filtered through bleached linen, and the fil- 
 trate obtained rapidly evaporated in a clean iron pan, or 
 more properly in a silver basin, until four ounces only re- 
 main, which, consequently, will give a specific gravity of 
 T33. Solution of potash is kept best in small bottles, shut 
 in the manner of glass spirit-lamps by a .ground-glass 
 cover, in default of which a small slip of paper ought to be 
 rolled around the glass stopper of a common bottle. If 
 this precaution be neglected, it will be found impossible, 
 after a short time, to take the stopper off. 
 
 Testing. Pure solution of potash ought to be colour- 
 less. It must form no precipitate with chloride of barium 
 nor with nitrate of silver, when supersaturated with nitric 
 acid, during which latter operation a slight effervesence 
 only ought to take place. It must leave no silicic acid be- 
 hind, when after evaporation to dryness the residue is 
 washed off with water. It ought not to be rendered tur- 
 bid on being heated with an equal measure of solution of 
 sal ammoniac. 
 
 Uses. By means of its great affinity for acids, potash 
 decomposes the salts of most bases, and precipitates there- 
 fore from their solutions all those salts which are insoluble 
 in water. Many of these oxides are dissolved by potash 
 in excess, e g. alumina, oxide of chromium, oxide of lead ; 
 others are not, e. g. oxide of iron, oxide of bismuth, &c. 
 Potash thus furnishes us with a means of separating the 
 former oxides from the latter. Potash, besides, dissolves 
 many salts, (e. g. chromate of lead,) sulphurets a. s. 
 o., and thus enables us as well to separate as to dis- 
 
 
CARBONATE OF POTASH. 47 
 
 tinguish them from other substances. Many of the pre- 
 cipitates produced by potash exhibit particular colour or 
 other characteristic properties, as, e. g. suboxide of man- 
 ganese, suboxide of iron, suboxide of mercury, and by 
 means of these colours or properties we may detect the na- 
 ture of the metals they contain. Potash expels ammonia 
 from its salts, and thus enables us to detect the latter sub- 
 stance by its odour, its reaction on vegetable colours, &c. 
 
 4- 129. 
 
 7. CARBONATE OF POTASH. (KO C0 2 .) 
 
 Preparation. Puie carbonate of potash, for chemical 
 purposes, is prepared by calcining purified bitartrate of 
 potash in an iron pan, to complete carbonization ; the resi- 
 due is then boiled with water ; the solution thus obtained 
 is purified by filtration and evaporated to dryness, in a 
 clean iron pan ; towards the latter end of this process the 
 mass must be constantly stirred. The residuary dry salt 
 is kept in a well-closed bottle. For use, one part of it is 
 dissolved in five parts of water. 
 
 Testing. Pure carbonate of potash must be perfectly 
 white. Its solution, when supersaturated with nitric acid, 
 must not be rendered turbid by chloride of barium nor by 
 nitrate of silver ; and, when supersaturated with hydro- 
 chloric acid and evaporated to dryness, must leave no resi- 
 due (silica) when redissolved in water. 
 
 Uses. Carbonate of potash precipitates all bases, with 
 the exception of the alkalies, most of them as carbonates, 
 but also a few as oxides. Those bases which are soluble 
 in water, as bicarbonates, are only on boiling completely 
 precipitated from their acid solutions. Many of the pre- 
 cipitates produced by carbonate of potash exhibit par- 
 ticular colours, and may therefore serve for the detection 
 of the various metals. The solution of carbonate of pot- 
 ash is moreover employed for the decomposition of many 
 insoluble salts with metallic bases, or bases of the alkaline 
 earths, especially of those with organic acids: For these 
 salts, on being boiled with carbonate of potash, are con- 
 verted into carbonates, whilst the acids combine with the 
 potash, forming soluble salts. Carbonate of potash is also 
 
48 AMMONIA. 
 
 used to saturate free acids, in order to obtain them in com- 
 bination with potash as salts, and is, moreover, especially 
 used to precipitate platinum from solutions containing 
 hydrochloric acid. 
 
 7 ^ ; - ; /:" '.'.so. Z * ' ! 
 
 8. AMMONIA. (NH 4 0.) 
 
 Preparation. Pure liquor of ammonia is prepared by 
 slaking four parts of quick lime with one and one-third 
 part of water, mixing this hydrate of lime, in a glass re- 
 tort,- with five parts of sal ammoniac reduced to powder, 
 and cautiously adding as much water as will cause the 
 powder to form into lumps when agitated. Tfre retort is 
 then placed in a sand-bath, and brought into connexion 
 with two gas conducting tubes, joined to each other in the 
 middle by means of a rinsing apparatus, containing only a 
 small quantity of water, such as has been described in the 
 preparation of sulphuretted hydrogen, (vide $ 25 r and en- 
 graving.) The absorbing receiver should contain ten 
 parts of water. This receiver is placed in a vessel filled 
 with cold water j heat is then applied to. the retort. The 
 evolution of gas immediately ensues. The heat is con- 
 tinued until no more bubbles appear, and the stopper of 
 the retort is then quickly taken off, to prevent the fluid 
 from receding. The liquor of ammonia contained in the 
 washing apparatus is impure, but that in the receiver is 
 pure ; it contains about sixteen per cent, of ammonia, and 
 thus has a specific gravity of 0.93. It is kept in phials 
 closed with glass stoppers. 
 
 Testing. Pure liquor of ammonia must be colourless, 
 and upon evaporation on a watch-glass not leave the slight- 
 est residue. It ought not to render lime-water turbid, 
 (carbonic acid,) and after supersaturation with nitric acid, 
 must not be rendered turbid by solution of barytes nor by 
 solution of nitrate of silver, nor be coloured by sulphu- 
 retted hydrogen. 
 
 Uses. Ammonia is one of the most frequently used rea- 
 gents. It is especially applied for the saturation of acid 
 liquids, for the precipitation of a great many metallic ox- 
 ides and earths, as well as for their separation from each 
 
CARBONATE OF AMMONIA* 49 
 
 other, as many of them are dissolved as ammoniacal dou- 
 ble salts, by ammonia in excess ; such as the oxides of 
 zinc, cadmium, silver, copper, nickel, and cobalt, whilst 
 others remain insoluble in free ammonia. The precipi- 
 tates, as well as their ammoniacal solutions, sometimes 
 exhibit a very distinct and peculiar colour, by means of 
 which we may at once detect the metals which they con- 
 tain. 
 
 Many oxides which are precipitated by ammonia from 
 neutral solutions, are not precipitated from acid solutions, 
 their precipitation being here prevented by the formation 
 of an ammoniacal salt. (Compare Chloride of Ammonium, 
 
 31. ) 
 
 9. CARBONATE OF AMMONIA. (NH 4 O, CO 2 .) 
 
 Preparation. We use, for the purposes of chemical 
 analysis, sesquicarbonate of ammonia, which must be en- 
 tirely free from any smell of animal oil, (such as is pre- 
 pared on a large scale, by the sublimation of sal ammoniac 
 and chalk.) The outer and inner surface of the mass 
 must be carefully scraped off ; and then one part of the 
 salt dissolved in a mixture of four parts of water, and one 
 part of caustic liquor of ammonia. 
 
 Testing. Pure carbonate of ammonia must completely 
 evaporate, and after supersaturation with nitric acid, nei- 
 ther be coloured nor precipitated by solution of barytes, 
 nor by solution of silver, nor by sulphuretted hydrogen. 
 
 Uses. Carbonate of ammonia precipitates most metal- 
 lic oxides and earths, like carbonate of potash. The com- 
 plete precipitation of many of them takes place only on 
 boiling. Several of the precipitated combinations redis- 
 solve again when this reagent is added in excess. Car- 
 bonate of ammonia dissolves many hydrates of oxides in a 
 like manner, and thus enables us to separate them from 
 others which are insoluble. This power of solution depends 
 upon the tendency of ammoniacal salts, to form soluble 
 double salts, indecomposible by free ammonia as well as 
 by carbonate of ammonia. 
 
 Like caustic ammonia, and for the same reason, carbon- 
 
50 CHLORIDE OF BARIUM. 
 
 ate of ammonia does not precipitate from acid solutions, 
 many oxides which it precipitates from neutral solutions. 
 ( 30.) We apply carbonate of ammonia, in chemical an- 
 alysis, especially for the precipitation of barytes, of stron- 
 tian and of lime, and for the separation of these substan- 
 ces from magnesia, as the latter is not precipitated in the 
 presence of ammoniacal salts. 
 
 $ 32. 
 
 10. CHLORIDE OF BARIUM. (Ba, Cl.) 
 
 Preparation. Six parts of heavy spar reduced to a fine 
 powder are mixed with one part of powdered charcoal 
 and one and a half part of flour ; this mixture is put into 
 ahessian crucible and exposed to the strongest possible 
 red heat. The fused mass is rubbed to powder when cool ; 
 about nine-tenths of the powder are boiled with four times 
 their weight of water, and hydrochloric acid is added; un- 
 til no more effervescence of sulphuretted hydrogen takes 
 place, and the liquid manifests an acid reaction. Then 
 the last tenth of the fused mixture is added, and the boil- 
 ing still continued for some time. The alkaline liquid is 
 then filtered and chrystallized* The crystals when dry 
 are digested and washed with alcohol, redissolved in wa- 
 ter, and again crystallized. For use, one part of the crys- 
 tals is dissolved in ten parts of water. 
 
 Testing. Pure chloride of barium must not affect veg- 
 etable colours, nor ought its solution to be altered by sul- 
 phuretted hydrogen, nor by hydrosulphuret of ammonia. 
 Pure sulphuric acid must precipitate every fixed particle 
 from it, so that the filtered liquid leaves not the slightest 
 residue when evaporated on a platinum plate. 
 ^ Uses. Barytes forms, with many acids, soluble salts ; 
 with others, insoluble combinations. This property of 
 barytes affords us a means of distinguishing the former 
 acids, which are not precipitated by chloride of barium, 
 from the latter in saline solutions which are precipitated by 
 chloride of barium. These barytes precipitates manifest 
 to other substances (acids) relations differing from each 
 other. Consequently, by subjecting them to the action of 
 such bodies, we may subdivide again the group of precipi- 
 
NITRATE OF BARYTES. CHLORIDE OF CALCIUM. 51 
 
 table acids, and even directly detect certain acids. Chlo- 
 ride of barium is one of our most important reagents, on 
 account of its application distinguishing one group of acids 
 from another, and especially as a means of detecting sulphu- 
 ric acid. 
 
 33. 
 
 11. NITRATE OF BARYTES. (Ba O, NO ... .) 
 
 Preparation. A dilute solution of chloride of barium 
 is boiled, and carbonate of ammonia added, as long as it 
 causes any precipitate, and further until the liquid mani- 
 fests an alkaline reaction. The carbonate of barytes 
 obtained by this process is carefully washed, and then dis- 
 solved in hot and dilute nitric acid, until the liquid no 
 longer manifests any acid reaction. The solution is then 
 filtered, and afterwards crystallized by evaporation. One 
 part of the crystallized salt is dissolved in ten parts of 
 water, for use. The tests as to its purity are the same as 
 in chloride of barium. Nitrate of silver must not render 
 its solution turbid. 
 
 Uses. Nitrate of barytes is analogous in its action to 
 chloride of barium, and may be substituted for this latter 
 substance, when we wish to avoid the formation of a 
 chloride in a liquid. 
 
 34. "* 
 
 CHLORIDE OF CALCIUM. (Ca Cl.) 
 
 Preparations. Chalk is added to hot and dilute hy- 
 drochloric acid, until all acid reaction ceases ; the solution 
 is then filtered, and, with the addition of some ammonia, 
 allowed to stand a few hours, at a moderate heat. It is 
 then filtered again; the filtrate is heated to boiling, and 
 carbonate of ammonia added until all the lime is precipi- 
 tated; the thus obtained carbonate of lime is carefully 
 washed. A mixture of one part of pure hydrochloric acid, 
 with five parts of water, is then heated and the washed 
 carbonate of lime added to complete neutralization; the 
 solution is then boiled up several times, filtered, and pre- 
 served for use. 
 
 Testing. Solution of chloride of calcium must be per- 
 fectly neutral, and neither be tinged nor precipitated by 
 
52 NITRATE OF SILVER. 
 
 hydrosulphuret of ammonia ; nor ought it to evolve am- 
 monia when mixed with potash or with hydrate of lime. 
 
 Use. Chloride of calcium is, in its action and applica- 
 tion, analogous to chloride of barium. For, as the latter is 
 applied to divide the inorganic acids into groups, so the 
 former serves for the same purpose with the organic acids, 
 since it precipitates some of them, whilst it forms soluble 
 combinations with others. And, as is the case with the 
 barytes precipitates, the different conditions under which 
 the various insoluble lime salts are precipitated, furnish us 
 with means for a more special classification of these acids. 
 
 35. 
 
 13. NITRATE OF SILVER. (Ag 0, N0 5 .) 
 
 Preparation. To obtain nitrate of silver in a state of 
 purity, silver alloyed with copper, as e. g. a piece of 
 standard coin, is dissolved in nitric acid. The solution is 
 evaporated to dryness, and the residue fused in a small 
 porcelain crucible, at a moderate heat, by means of a 
 spirit-lamp, till all the nitrate of copper is decomposed, 
 i. e. till the green colour of the salt has completely vanish- 
 ed, even in the portions adhering to the upper sides of the 
 crucible, and a portion dissolved in water becomes no 
 longer blue when ammonia in excess is added. The mass, 
 when cooled, is boiled with water, filtered, and crystallized. 
 One part of the crystals is dissolved in twenty parts of 
 water, for use. The oxide of copper remaining after the 
 solution of the fused mass, always contains some silver, 
 to remove which the residue is dissolved in nitric acid, 
 and the silver precipitated from the solution, as chloride 
 of silver. 
 
 Testing. Nitrate of silver may be considered pure, if 
 the fixed part of its solution is completely precipitated by 
 dilute hydrochloric acid, so that the fluid filtered from the 
 chloride of silver leaves no residue upon evaporation on a 
 watch-glass, and is neither precipitated nor tinged by sul- 
 phuretted hydrogen. 
 
 Use. Oxide of silver forms, with many acids, soluble, 
 with others, insoluble combinations ; nitrate of silver may 
 
PERCHLORIDE OF IRON. 53 
 
 therefore be used, like chloride of barium, for the classifica- 
 tion of acids into groups. 
 
 Most of the insoluble silver combinations are soluble in 
 dilute nitric acid, chloride, iodide, bromide, and cyanide 
 of silver excepted. Nitrate of silver is, therefore, an excel- 
 lent means for distinguishing and separating the hydracids 
 corresponding to the last-named silver combinations from 
 all other acids. Nitrate of silver is also of great impor- 
 tance for the detection of individual acids, as many of the 
 silver precipitates exhibit a particular colour, (chromate, 
 and arseniate of silver, for example,) or a particular relation 
 to other reagents, or peculiar properties, on being heated, 
 e. g. formiate of silver. 
 
 36. 
 
 14. PERCHLORIDE OF IRON. (Fe 2 C1 3 .) 
 
 Preparation. To obtain pure perchloride of iron, two 
 parts of hydrochloric acid, diluted with from six to eight 
 parts of water, are heated with an excess of small iron 
 nails free from rust, until the evolution of hydrogen ceases ; 
 the solution is then decanted, mixed with one part of hydro- 
 chloric acid, boiled in a very capacious vessel, and, whilst 
 boiling, nitric acid in small portions cautiously and gradually 
 added, till a further addition produces no longer any effer- 
 vescence ; i. e. till no more red vapours of nitrous acid 
 appear, and solution of ferricyanide of potassium ( 42) no 
 longer tinges the mixture blue. A small excess of nitric 
 acid does no harm whatever. The solution obtained is 
 then diluted with water, boiled, ammonia added to alkaline 
 reaction, and the produced precipitate of hydrated peroxide 
 of iron well washed with hot water, and when still moist, 
 added to a heated mixture of 272 parts of hydrochloric 
 acid, and ten parts of water, till the last portions are not 
 dissolved, even on continued heating. The solution is 
 then filtered, and kept for use. 
 
 Testing. Solution of perchloride of iron, for the pur- 
 poses of chemical analysis, must not contain acid in excess; 
 a portion of it must, therefore, when stirred with a small 
 rod dipped in ammonia, yield a precipitate, which is not 
 re-dissolved on shaking the vessel. Ferricyanide of potas- 
 sium must not impart a blue tinge to it. 
 
54 PHOSPHATE OF SODA. 
 
 Use. Chloride of iron serves for a further classification 
 of those organic acids which are not precipitated by chloride 
 of calcium, as it produces precipitates with benzoic and 
 succinic salts, whilst it leaves acetic and formic salts in 
 solution. The neutral salts which these latter acids form 
 with peroxide of iron, dissolve in water, imparting an 
 intensely red colour to the latter ; chloride of iron affords, 
 therefore, a useful means for their detection. (Vide 98, 
 a 7, for its application for the decomposition of phosphates 
 of the alkaline earths, to which purpose it is exceedingly 
 well adapted.) Chloride of iron serves also for the detec- 
 tion of ferrocyanide of hydrogen, producing Prussian blue 
 with this substance. 
 
 II. - SPECIAL REAGENTS IN THE HUMID WAY. 
 
 a. Reagents which serve especially for the detection or 
 separation of individual bases. 
 
 1. SULPHATE OF POTASH. (KO, S0 3 .) 
 
 Preparation. The sulphate of potash of commerce is 
 purified by re-crystallization, and one part of the pure salt 
 is dissolved in twelve parts of water, for use. 
 
 Uses. Sulphate of potash precipitates from solutions 
 of barytes and strontian the sulphates of the oxides, which 
 are insoluble in water. It serves, therefore, for their de- 
 tection and separation. It also produces a precipitate in 
 very highly concentrated solutions of lime, but, in most 
 cases, only after the lapse of some time. It does not pre- 
 cipitate dilute solution of lime. The action of sulphate of 
 potash being analogous to that of dilute sulphuric acid, it 
 is in many cases preferable to the latter reagent, since it 
 does not disturb the neutrality of the solution. 
 
 38. A, 
 
 2. PHOSPHATE OF SODA. (2 N<Z O, PO 5 -) 
 
 Preparation. To obtain this reagent pure, dilute com- 
 
 mercial phosphoric acid is heated, and solution of carbonate 
 
NEUTRAL CHROMATE OF POTASH. 55 
 
 of soda added, till all effervescence ceases, and the liquid 
 manifests a feeble alkaline reaction. The liquid is then 
 filtered, evaporated, and crystallized. The crystals are 
 dried, triturated with a portion of charcoal and flour, and 
 the entire mass strongly heated in a hessian crucible. The 
 heated mass is then boiled with water, filtered, and crys- 
 tallized. One part of the salt obtained is dissolved in ten 
 parts of water, for use. This solution must not become 
 turbid on being heated with ammonia. The precipitates 
 produced by the addition of solution of barytes. and of 
 silver, must completely redissolve on the addition of dilute 
 nitric acid. 
 
 Uses. Phosphate of soda precipitates the alkaline 
 earths, and all metallic oxides, by double affinity. It serves 
 in the course of analysis, after the separation of the heavy 
 metallic oxides, as a test for alkaline earths in general; 
 and, after the separation of barytes, strontian, and lime, 
 with simultaneous addition of ammonia, as a test for the 
 detection of magnesia, which precipitates under these cir- 
 cumstances as basic phosphate of ammonia and magnesia. 
 
 39. T~ 
 
 3. NEUTRAL CHROMATE OF POTASH. (KO, Cr O 3 .) 
 
 Preparation. To obtain this reagent pure, the com- 
 mercial bichromate of potash is dissolved in water, and 
 carbonate of potash added, till the solution manifests a 
 feeble alkaline reaction. The liquid, which is now of a 
 yellow colour, is then crystallized. The crystals are well 
 washed and re-dissolved in water, in the proportion of one 
 part of the crystals to ten parts of water. The solution 
 must be neutral. 
 
 Uses. Chromate of potash decomposes, by double af- 
 finity, most of the soluble metallic salts. The precipitated 
 metallic chromates are, for the most part, very difficult of 
 solution, and often manifest such peculiar colourings, that 
 the metals they contain may be easily detected. We use 
 chromate of potash principally as a test for lead. 
 
56 CYANIDE OP POTASH. 
 
 40. 
 4. CYANIDE OF POTASSIUM. (KCy.) 
 
 Preparation. To obtain this reagent pure, commercial 
 ferrocyanate of potash is gently heated and stirred, till its 
 water of crystallization is completely expelled ; it is then 
 pounded, and eight parts of the dry powder are mixed 
 with three parts of perfectly dry carbonate of potash. 
 This mixture is put into a crucible heated to redness, and 
 the latter well closed and kept at a bright red heat, till the 
 mass is in a state of clear and calnj, fusion. The fused 
 cyanide of potassium is then poured into a heated porcelain 
 basin ; this must be done cautiously, in order to prevent 
 the passing over of any particles of the iron which, in a 
 highly-divided state, has separated from the mass, and sub- 
 sided to the bottom of the crucible. The thus obtained 
 cyanide of potassium is exceedingly well adapted for 
 application in analysis, although it contains cyanate of 
 potash. It must be perfectly white. One part is dissolved 
 in four parts of cold water. 
 
 Uses. Cyanide of potassium (containing cyanate of pot- 
 ash) produces in the solutions of most metallic salts in wa- 
 ter, insoluble precipitates of cyanides, oxides, or carbon- 
 ates. The former of these precipitates are soluble in cy- 
 anide of potassium ; they may, therefore, by a further ad- 
 dition of the reagent, be separated from the oxides, &c. 
 which are insoluble in cyanide of potassium. Some of 
 the cyanides of metals always dissolve as cyanides com- 
 bined with cyanides of potassium, even if free prussic acid 
 be present; others combine with cyanogen, forming 
 new radicals, and as such, combined with potassium, re- 
 main in solution. Cobalti-cyanide of potassium, ferro and 
 ferri-cyanide of potassium, are ihe most common combi- 
 nations of the latter kind. They differ from the double 
 cyanogen compounds of the former description, especially 
 inasmuch as dilute acids do not separate from them the 
 cyanides of metals. Those metals forming such com- 
 binations may, therefore, by syanide of potassium, be 
 separated from all those metals, the cyanides of which 
 are precipitated by acids, from their Solutions in cy- 
 anide of potassium. This reagent has a highly impor- 
 
FERRICYANIDE OF POTASSIUM. 57 
 
 tant special application, in analysis, for the separation of 
 nickel from cobalt. 
 
 5. FERROCYANIDE OF POTASSIUM. 
 
 (C 6 N 3 Fe+2K=Cfy+2K.) 
 
 Preparation. Commercial ferrocyanide of potassium 
 is sufficiently pure for the purposes of chemical analysis. 
 One part is dissolved in twelve parts of water, for use. 
 
 Uses. Ferrocyanide forms with most metals combina- 
 tions insoluble in water, and often very peculiarly coloured. 
 These combinations occur when ferrocyanide of potassium 
 is brought into contact with soluble salts of metallic ox- 
 ides, with chlorides, &c. the potassium changing .places 
 with the metals. Ferrocyanide of copper, and ferrocyan- 
 ide of iron, show the most characteristic colourings of all ; 
 and ferrocyanide of potassium is, therefore, especially ap- 
 plied as a reagent for the detection of oxide of copper 
 and peroxide of iron* 
 
 42. 
 
 6. FERRICYANIDE OF POTASSIUM. 
 
 (C 12 N 6 Fe +3K=2Cfy+3K.) 
 
 Preparation. This reagent is obtained by transmitting 
 chlorine gas through a solution of one part of ferrocyanide 
 of potassium in ten parts of water, till a portion of the 
 fluid, when added to a solution of perchloride of iron, no 
 longer produces a blue precipitate, or even a blue tinge. 
 The solution is then concentrated by evaporation, and 
 some carbonate of potash added, until a feeble alkaline re- 
 action becomes manifest. The liquid is then filtered, and 
 allowed to cool. The crystals obtained are of a magnifi- 
 cent red colour. One part is dissolved in ten parts of wa- 
 ter, for use. The solution, as already remarked, must 
 neither produce a blue precipitate nor a blue tinge, when 
 added to solution of perchloride of iron. 
 
 Uses. Ferricyanide of potassium decomposes with so- 
 lutions of metallic oxides, in the same manner as ferrocy- 
 anide of potassium. Of all ferricyariides of metals, ferri- 
 
58 HYDROFLUO SILICIC ACID. 
 
 cyanide of iron is peculiarly characterized by its colour, 
 and we apply, therefore, ferricyanide of potassium espe- 
 cially as a reagent for protoxide of iron. And for this pur- 
 pose it may very well be prepared extempore, by gradual- 
 ly adding nitric acid to a solution of ferrocyanide of potas- 
 sium, till a portion of the mixture no longer imparts a blue 
 colour to a solution of chloride of iron. All elevation of 
 temperature must be avoided in this process, and the ves- 
 sel ought to be agitated whilst the nitric acid is added. 
 
 43. 
 
 7. HYDROFLUO SILICIC ACID. (3.HF + 2 Si F 3 .) 
 
 Preparation. This reagent is obtained in the following 
 manner : equal parts of fluor spar and sand, in powder, 
 are mixed in a glass retort, with six parts of English sul- 
 phuric acid ; the opening of the retort is closed with a 
 perforated cork, into which one end of a double-limbed 
 tube is fitted air tight. The exit limb must reach to the 
 bottom of a flat-bottomed glass jar, and its extremity be 
 covered with a column of mercury, to the extent of a few 
 lines; this glass-jar receiver contains four parts of water. 
 A disengagement of the fluo-silicic gas immediately takes 
 place, even without the application of heat ; a gentle heat 
 by the sand-bath is, however, required to aid the opera- 
 tion. Every bubble of gas, as it ascends through the mer- 
 cury, produces a precipitate of hydrate of silicic acid. One 
 equivalent of every threue equivalents of* the fluoride of sili- 
 con is decomposed in this process, and combines with 
 three equivalents of water, forming silicic acid which pre- 
 cipitates, and hydrofluoric acid, which combines with the 
 two remaining equivalents of the fluoride of silicon, form- 
 ing hydrofluo silicic acid . The precipitated hydrate of si- 
 licic acid renders the liquid gelatinous, and it is on this 
 account that the aperture of the exit tube must be placed 
 under mercury, for it would speedily be choked if this 
 precaution were neglected. It sometimes happens in the 
 course, and especially towards the end, of the operation, 
 that the gas forms complete tubes or channels of silica in 
 the gelatinous liquid, through which it gains the surface 
 without decomposition, if they are not broken from time to 
 
OXALIC ACID.. 59 
 
 time by stirring. When the disengagement of gas has 
 ceased, the gelatinous mass is poured on a piece of linen, 
 and the fluid squeezed through. The liquid obtained is 
 then filtered, and kept^pr use. The hydrofluo-silicic acid, 
 mixed with two parts OT water, produces no precipitate in 
 the solution of salts of strontian. 
 
 Uses. Bases decompose with hydrofluo-silicic acid, 
 forming water, and metallic fluo-silicates. Many of these 
 combinations are soluble, others insoluble ; the latter may, 
 therefore, by means of this reagent, be distinguished from 
 the former. In the course of analysis it is only applied 
 for the detection of barytes. 
 
 44. 
 
 8. OXALIC ACID. (2 CO+Or=C 2 O 3 = O.) 
 
 Preparation. This acid is prepared by pouring upon 
 one part of starch, contained in a porcelain basin, five 
 parts of nitric acid, of 1.42, diluted with two parts of 
 water, and applying a gentle heat, till no more nitrous gas 
 is evolved. The liquid is then filtered and crystallized ; 
 the crystals obtained are drained and purified by a second 
 crystallization. Oxalic acid must be preserved in the 
 form of a powder, as it soon decomposes in solution. 
 Pure oxalic acid, when boiled with a small quantity of 
 solution of indigo, does not discolour the latter. 
 
 Uses. Oxalic acid combines with many bases, forming 
 salts insoluble in water ; it may, therefore, be used to 
 precipitate these bases. Many of the oxalates insoluble 
 in water, are easily dissolved by an excess of oxalic acid, 
 whilst others dissolve with difficulty in the same men- 
 struum. This relation affords us, therefore, a means of 
 distinguishing the precipitated bases from each other. 
 As all oxalates insoluble in water are soluble in stronger 
 acids, (hydrochloric acid, nitric acid,) a complete precipi- 
 tation by oxalic acid ensues, in most cases, only when the 
 liberated acid is saturated by an alkali. In analysis, 
 oxalic acid is of great importance for the detection and 
 precipitation of lime. 
 
60 BITARTRATE OF POTASH. 
 
 45. 
 9. OXALATE OF AMMONIA. (NH 4 -fO, 6.) 
 
 Preparation. This reagent il^repared by dissolving 
 oxalic acid in water, adding ammonia till a feeble alkaline 
 reaction takes place, and crystallising. One part of the 
 salt is dissolved in twenty -four parts of water, for use. 
 
 Uses. Oxalate of ammonia is conveniently employed 
 instead of oxalic acid and ammonia. It possesses this 
 advantage over the free acid, that its solution does not 
 decompose on keeping. 
 
 46. 
 
 10. TARTARIC ACID. (C 3 H 4 O 10 =T.) 
 
 The tartaric acid of commerce is sufficiently pure for 
 the purposes of analysis.* It is best preserved in powder, 
 since it decomposes with the formation of a white film 
 when kept in solution for some time. 
 
 Uses. The addition of tartaric acid to solutions of iron, 
 manganese, chromium, alumina, cobalt, and many other 
 metals, prevents their precipitation by alkalies, by the 
 formation of double tartrates indecbmposible by alkalies. 
 Tartaric acid may, therefore be employed to separate these 
 metals from others, the precipitation of which it does not 
 prevent. Tartaric acid forms with potash, but not with 
 soda, a bi-salt difficult of solution ; it is, therefore, one of 
 the best means of distinguishing potash from soda. 
 
 47. 
 
 11. BITARTRATE OF POTASH. (KO, HO, T.) 
 
 The cream of tartar of commerce is sufficiently pure 
 for the purposes of qualitative analysis. It should be pre- 
 served in powder. 
 
 Uses. Many metals dissolve in hot solution of tartar, 
 forming double tartrates ; others do not. The former may, 
 therefore, by means of this reagent, be separated from the 
 
 * In cases where commercial salts are mentioned, well-defined 
 crystals should be selected. ED. 
 
CAUSTIC BARYTES. 61 
 
 latter. In analysis, tartar is employed in certain cases to 
 separate oxide of antimony from oxide of tin. 
 
 48. 
 
 12. ACETATE OF BARYTES. (Ba O, A.) 
 
 Preparation. This reagent is obtained in the same 
 manner as nitrate of barytes, (vide 33,) substituting, of 
 course, acetic acid for the nitric acid. It may conveniently 
 be preserved in a dry state, as it is but of rare application. 
 
 Uses. The acetate of barytes is employed to convert 
 sulphates into acetates, (especially sulphate of magnesia, 
 and the alkaline sulphates). As these acetates are con- 
 verted by heat into carbonates, and as carbonate of mag- 
 nesia is insoluble, whilst the alkaline carbonates are 
 soluble in water, acetate of barytes indirectly serves to 
 separate magnesia from the alkalies. 
 
 49 
 
 13. CAUSTIC BARYTES. (Ba 0.) 
 
 Preparation. To prepare this reagent, one part of 
 sulphuret of barium is boiled with twenty parts of water ; 
 copper scales are then added in excess to the solution, 
 whilst boiling, till a filtered portion of the liquid ceases to 
 blacken a solution of acetate of lead. The solution is then 
 filtered, while still hot, and as much water added as will 
 prevent any considerable portion of the hydrate of barytes 
 in solution from crystallizing on cooling. The saturated 
 water of barytes obtained is kept in well-closed bottles. 
 Should it contain a small quantity of copper, some sul- 
 phuretted hydrogen must be cautiously added, and the 
 liquid filtered from the precipitated sulphuret of copper. 
 
 Uses. Caustic barytes is analogous in its action to 
 potash, i. e. it precipitates, as a strong base, from saline 
 solutions, those metallic oxides and earths which are in- 
 soluble in water. In analysis, we apply this reagent only 
 for the precipitation of magnesia. For this purpose a 
 solution of sulphuret of barium may equally well be em- 
 ployed, inasmuch as (as is generally the case) it contains 
 caustic barytes. Water of barytes may also, like the 
 3 
 
62 CHLORIDE OF 
 
 various salts of barytes, of which we have already treated 5 , 
 be used to precipitate those acids which form insoluble 
 combinations with barytes ; we generally employ it thus 
 only for the detection of carbonic acid. 
 
 50, 
 
 14, PROTOCHLORIDE OF TIN. (S?l CI.) 
 
 Preparation. To obtain this reagent, English tin is 
 reduced to powder, by being fused in an iron spoon, then 
 taken from the fire and rubbed in a mortar till it has re- 
 assumed the solid state. This powder is then, for some 
 length of time, boiled with concentrated hydrochloric acid 
 in a glass vessel * (care must always be taken that the 
 mixture contains tin in excess ;) the solution is diluted with 
 four times its quantity of water, slightly acidulated with 
 hydrochloric acid, and filtered. The clear solution is kept 
 in a small closed bottle, containing small pieces of metallic 
 tin. If this latter precaution be neglected^ the reagent 
 soon becomes useless, the protochloride being converted 
 into perchloride of tin. 
 
 Testing. Pure protochloride of tin, when mixed with 
 perchloride of mercury, immediately produces a white 
 precipitate of protochloride of mercury \ it yields a dark 
 brown precipitate with sulphuretted hydrogen, and is 
 neither precipitated nor disturbed by sulphuric acid. 
 
 Uses. The great tendency which protochloride of tin 
 has to absorb oxygen, and thus to form peroxide of tin, or 
 rather perchloride of tin, as the oxide at the moment of its 
 formation, unites with the free hydrochloric acid present, 
 renders it one of the most powerful means of reduction. 
 We employ it, in analysis, for the detection of gold, for 
 which purpose it must first be mixed with some nitric acid, 
 without the application of heat j we also use it to detect 
 the presence of mercury. 
 
 51. 
 
 15. CHLORIDE OF GOLD* (Au Cl .) 
 
 Preparation. To obtain this reagent, fine shreds of 
 gold, which may be alloyed either with silver or with cop- 
 
CHLORIDE OF PLATINUM. 63 
 
 per, are drenched, in a small retort, with aqua regia in 
 excess, and a gentle heat is applied till no more gold is 
 dissolved. If the gold was alloyed with copper, which is 
 detected by the brown red precipitate produced by fer- 
 rocyanide of potassium, in a portion of the solution diluted 
 with water, the gold solution containing copper is mixed 
 with sulphate of iron in excess. The gold becomes re- 
 duced, and separates as a fine brownish black powder ; it 
 is then washed in a small retort, re-dissolved in aqua re- 
 gia, the solution evaporated to dryness in the water-bath, 
 and the residue dissolved in thirty parts of water. If the 
 gold is alloyed with silver, the latter metal remains undis- 
 s<?lved as chloride of silver when treated with aqua regia. 
 In this case, the first solution is evaporated to dryness, and 
 the residue dissolved for use. 
 
 Uses. Chloride of gold has a great tendency to yield 
 its chlorine to other substances ; it, therefore, easily converts 
 protochlorides into perchlorides, protoxides into peroxides 
 and perchlorides, &c. These oxidations usually manifest 
 themselves by the precipitation of pure metallic gold, in the 
 shape of a blackish brown powder. In analysis, chloride 
 of gold serves only for the detection of protoxide of tin, as 
 it produces a purple colour or precipitate in solutions con- 
 taining this substance. (Vide infra.) 
 
 552. 
 
 16, CHLORIDE OF PLATINUM> (Pt C1 2 .) 
 
 Preparation. To obtain this reagent, platinum in pow- 
 der is boiled with nitric acid, for the purpose of purifica- 
 tion, and then, in a retort with narrow neck, drenched with 
 concentrated hydrochloric acid, and some nitric acid ; a 
 gentle heat is applied, and, from time to time, some nitric 
 acid added, until all the platinum is dissolved. The solu- 
 tion is, with the addition of hydrochloric acid, evaporated 
 to dryness by a water-bath, and the residue dissolved in 
 ten parts of water. 
 
 Uses. Chloride of platinum forms very sparingly solu- 
 ble double salts, with chloride of potassium and hydro- 
 chlorate of ammonia, whilst it enters into no such combina- 
 tions with chloride of sodium. It serves, therefore, to 
 
64 ZINC* more. 
 
 detect ammonia and potash, and is, indeed, for the latter 
 substance, nearly the most susceptible reagent we possess. 
 
 17. ZINC. (Zn.) 
 
 
 
 Pure, sublimed zinc, is selected for the purposes of che- 
 mical analysis ; it must especially be free from arsenic. 
 The method described in 24 may be employed as a test 
 to detect the presence of any trace of this latter substance. 
 The pure zinc should be fused, and a portion of it gradu- 
 ally dropped into a large vessel, containing water; the 
 remainder should be poured into wooden moulds, coated 
 with chalk, for the purpose of casting it into little cylin- 
 ders. 
 
 Uses. Zinc precipitates many metals in their metallic 
 state, by depriving them of their oxygen and acid, owing 
 to the great affinity it possesses for oxygen, and its oxide 
 for acids. As the precipitated metals vary in colour, form, 
 &c., zinc may serve as well for their detection and dis- 
 tinction from each other, as for their precipitation. We 
 employ it especially for the precipitation of antimony and 
 of tin. Zinc is also frequently used for the production of 
 hydrogen. 
 
 54. ^ 
 
 18. IRON. (Fe.) 
 
 Iron, like zinc, reduces many metals, and precipitates 
 them in a pure state. We employ it especially for the de- 
 tection of copper, which is precipitated on it with its cha- 
 racteristic colour. All clean surfaces of iron, such as 
 knife-blades, needles, pieces of wire, &c., are well adapted 
 to this purpose. 
 
 55. 
 19. COPPER. (Cu.) 
 
 We employ copper exclusively for the reduction of mer- 
 cury, which precipitates thereon as a white coating, which 
 
ACETATE OP POTASH. CAUSTIC LIME. 65 
 
 shines with silvery lustre when rubbed. Any copper coin 
 scoured with fine sand, in fact, any clean copper surface, 
 may be employed for this purpose. 
 
 b. Special reagents which are particularly employed for 
 the detection and separation of acids. 
 
 56. 
 
 1. ACETATE OF POTASH. (KO, A.) 
 
 Preparation. This reagent is obtained by dissolving 
 one part of pure carbonate of potash in two parts of water, 
 heating the solution and exactly saturating with acetic acid. 
 
 Uses. Every salt of potash may serve to produce a 
 precipitate of tartar, and, therefore, to detect tartaric acid. 
 But the acetate of potash is peculiarly adapted for this 
 purpose, as the precipitated tartar is insoluble in the lib- 
 erated acetic acid. As this test is rarely employed, it is 
 best to prepare it when needed. 
 
 57. 
 
 2. CAUSTIC LIME. (Ca. 0.) 
 
 Newly prepared hydrate of lime is agitated and digested 
 for some time in cold distilled water, allowed to settle, 
 and the clear fluid decanted and kept in well-closed bot- 
 tles. Lime-water must impart a bright green tinge to 
 Georgina paper, and yield with carbonate of potash no in- 
 considerable precipitate. It becomes useless as soon as 
 it no longer manifests these properties, which soon takes 
 place when it is exposed to the access of air. Besides 
 lime-water, hydrate of lime also ought to be kept at hand. 
 
 Uses. Lime forms with some acids insoluble, with 
 others, soluble salts. Lime-water may, therefore, be em- 
 ployed to distinguish these acids from each other, as it pre- 
 cipitates the former whilst it yields no precipitate with the 
 latter. Many of the precipitable acids are precipitated 
 only under certain conditions, as e. g. on boiling, (citric 
 acid ; ) and it is therefore easy to distinguish them from 
 each other by altering these conditions. We employ lime- 
 water especially for the detection of carbonic acid, and to 
 
66 CHLORIDE OF MAGNESIUM. 
 
 distinguish from each other paratartaric acid, tartaric acid, 
 and citric acid. Hydrate of lime serves, like caustic potash, 
 to liberate ammonia, and is in many cases preferable to 
 the latter reagent. 
 
 58. 
 
 3. SULPHATE OF LIME. (CaO, S0 3 .) 
 
 Preparation. To obtain this reagent, a concentrated so- 
 lution of chloride of calcium is mixed with dilute sulphuric 
 acid ; the precipitate produced is well washed, digested, 
 and for some time agitated with water, then allowed to 
 settle, and the clear fluid decanted and kept for use. 
 
 Uses. Sulphate of lime serves for the further subdi- 
 vision of those acids which are precipitable by chloride of 
 calcium, as, owing to its difficult solubility, a few acids 
 only of that group (oxalic acid, paratartaric acid,) cause 
 precipitates in its solution. The solution of sulphate of 
 lime serves, moreover, as a reagent for bases, viz., to distin- 
 guish barytes, strontian, and lime from each other. For, 
 of course, it cannot precipitate the latter, whilst it behaves 
 with solutions of barytes and of strontian, in the same 
 manner as highly dilute sulphuric acid, i. e. it precipitates 
 barytes immediately, and strontian only after the lapse of 
 some time. 
 
 59. 
 
 4. CHLORIDE OF MAGNESIUM. (Mg. Cl.) 
 
 Preparation. Chloride of magnesium is prepared by 
 heating a mixture of one part of hydrochloric acid and two 
 and a half parts of water, and adding basic carbonate of 
 magnesia, (magnesias carbonas of the shops,) till the liquid 
 ceases to manifest any acid reaction. The solution is once 
 more boiled up, filtered, and kept for use. Sulphate of 
 magnesia may, in most cases, be substituted for chloride of 
 magnesium. 
 
 Uses. Chloride of magnesium almost exclusively serves 
 for the detection of phosphoric acid, as it precipitates from 
 the aqueous solutions of phosphates, with presence of am- 
 monia, a double salt, (basic phosphate of magnesia and 
 
NEUTRAL ASCETATE OF LEAD. 67 
 
 ammonia,) which is almost insoluble and highly character- 
 istic in its properties. Chloride of magnesium is, more- 
 over, employed as a test of the purity of hydros ulphuret of 
 ammonia. (Vide 26.) 
 
 6(X 
 
 5. PROTO-SULPHATE OF IRON. (Fe O, SQ 3 .) 
 
 Preparation. To obtain this reagent, a quantity of 
 iron nails, (free from rust,) in excess, is heated with dilute 
 sulphuric acid till no more hydrogen is evolved ; the so- 
 lution is then filtered, and after the addition of a few drops 
 f dilute sulphuric acid, left to cool. Crystals are imme- 
 diately obtained, if the solution was sufficiently concentra- 
 ted, but if more dilute, evaporation must be had recourse to. 
 The crystals are washed with water slightly acidulated 
 with sulphuric acid, dried and preserved. 
 
 Uses. Proto-sulphate of iron has a great, disposition to 
 change to persulphate of iron, i. e. to absorb oxygen. It 
 acts, therefore, as a powerful means of reduction. We 
 employ it especially for the reduction of nitric acid, from 
 which it separates nitric oxide, by depriving it of three 
 -atoms of oxygen. As this decomposition is attended with 
 the formation of a characteristic, intensely brownish-black 
 coloured combination of nitric oxide with undecomposed 
 protosulphate of iron, this reaction is particularly charac- 
 teristic and susceptible for the detection of nitric acid. 
 Protosulphate of iron serves, moreover, for the detection of 
 ferricyanide of hydrogen, with which it produces a kind of 
 Prussian blue, and for the detection of gold, which it preci- 
 pitates from its solutions in its metallic state, 
 
 NEUTRAL ACETATE OF LEAD. 
 
 $ 61. 
 
 6. SOLUTION OF MAGNETIC OXIDE OF IRON (FERROSO-FERRIC 
 
 OXIDE.) (FeO, Fe 2 O 3 .) 
 
 This reagent is not kept on hand, but prepared, when 
 needed, by mixing solution of protosulphate of iron with 
 some perchloride of iron, (Fe 0, SO +Fe 2 Cl .) It 
 
6S BASIC ACETATE OF LEAD. 
 
 serves for the detection of hydrocyanic acid, which, when 
 previously combined with alkalies, yields with it a precipi- 
 tate of sesquiferrocyanide of iron (Prussian blue.) 
 
 62. 
 
 7. OXIDE OF LEAD. (Pb O.) 
 
 Oxide of lead is employed for the detection of free acetic 
 acid, as it forms with no other acid than this, a soluble 
 combination with an alkaline reaction. Finely- washed 
 litharge answers this purpose sufficiently well. (Compare 
 104, a.) 
 
 V, v 63. \ 
 
 8. NEUTRAL ACETATE OF LEAD. (Pb O, A.) 
 
 The better sorts of commercial acetate of lead are suffi- 
 ciently pure for the purposes of chemical analysis. One 
 part is dissolved in ten parts of water for use. 
 
 Uses. Oxide of lead forms, with a great many acids, 
 combinations which are insoluble in water, and are distin- 
 guished by their colour, or by some characteristic property. 
 The acetate of lead produces, therefore, precipitates in 
 solutions of these acids or their salts, and essentially con- 
 tributes to ascertain and characterize several of them. 
 Thus, in particular, chromate of lead is distinguished by 
 its yellow colour, phosphate of lead by its peculiar relation 
 before the blow-pipe, and malate of lead by its easy 
 fusibility* 
 
 64. 
 
 BASIC ACETATE OF LEAD. (3PbO, A.) 
 
 Preparation. This reagent is obtained by drenching in 
 a well-stopped bottle, seven parts of finely-washed litharge, 
 and six parts of neutral acetate of lead, with thirty parts of 
 water, and allowing them to stand at a moderate heat, shak- 
 ing it from time to time, till the sediment in it has become 
 perfectly white. The clear fluid is then decanted and pre- 
 served in a well-stopped bottle. This acetate of lead is un- 
 fit for use, if it contains copper, which is detected by the 
 
HYDRATED OXIDE OF BISMUTH. 69 
 
 blue colour it exhibits on the addition of ammonia. It must, 
 in this case, be purified by digesting it with metallic lead, 
 till all the copper is precipitated. 
 
 Uses. The basic acetate of lead, like the neutral ace- 
 tate, precipitates those acids which form insoluble combi- 
 nations with oxide of lead, and, indeed, all those soluble in 
 acetic acid, more completely than the former reagent. We 
 employ it in analysis especially for the detection of sulphu- 
 retted hydrogen, for which substance at is nearly the most 
 susceptible reagent. It serves, moreover, to neutralize free 
 acids, in cases where it is desirable to avoid the application 
 of an alkali, e. g. to render solutions of highly* acid nitrate 
 of bismuth precipitable by water. 
 
 65. 
 
 HYDRATED OXIDE OF BISMUTH. (Bi O + HO.) 
 
 Preparation. Bismuth reduced to a gross powder is 
 projected into pure nitric acid, 1, 2 as long as solution 
 takes place ; this prpcess may be promoted by the appli- 
 cation of a gentle heat. The solution obtained is diluted 
 with about an equal quantity of warm water, (slightly acidi- 
 fied w r ith nitric acid,) and then filtered ; the filtrate is mixed 
 with from ten to twenty parts of water, and ammonia added 
 to the milky fluid, till the reaction becomes perceptibly alka- 
 line; the solution is then heated, and the precipitate obtained 
 washed, first, by decanting the supernatant liquid, and then 
 rinsing the precipitate upon a filter, and afterwards drying 
 it between some sheets of blotting-paper, at a moderate 
 heat. 
 
 Uses. The oxide of bismuth, when boiled with alkaline 
 solutions of sulphurets, decomposes with the latter, giving 
 rise to the formation of metallic oxides, (corresponding 
 with the various degrees of sulphuration of the sulphurets,) 
 and of sulphuret of bismuth. It affords us, therefore, 
 especially, a very proper and efficient means, to convert 
 the sulphuret or bisulphuret of arsenic into arsenious or 
 arsenic acid. 
 
70 PROTONITRATE OF MERCURY. 
 
 66. 
 SULPHATE OF COPPER. (Cll O, SO 3 .) 
 
 Preparation. The blue vitriol of commerce may be 
 purified by repeated recrystallization. 
 
 Uses. Sulphate of copper is employed in qualitative 
 analysis, for the precipitation of hydriodic acid, as protio- 
 dide of copper. For this purpose a solution of one part 
 of the blue vitriol must be mixed with two and a quarter 
 parts of protosulphate of iron, or else half of the iodine will 
 separate in # free state. The protoxide of iron, in this 
 process, changes to peroxide, by reducing the peroxide of 
 copper to protoxide. Sulphate of copper is besides used 
 as a test for the detection of arsenious and arsenic acid, 
 and it is, indeed, as such very susceptible, but by no means 
 characteristic. For this purpose it is best to prepare am- 
 monio- sulphate of copper by adding ammonia to a solution 
 of sulphate of copper till the precipitate which appears at 
 first, is redissolved. We refer to 94, d. 6, for the man- 
 ner in which sulphate of copper is employed, in junction 
 with caustic potash, to detect arsenious acid, and especially 
 to distinguish it from arsenic acid. Sulphate of copper 
 may, moreover, be employed for the detection of ferrocy- 
 anide of hydrogen. 
 
 67. 
 
 12. PROTONITRATE OF MERCURY. (Hg 2 O, N0 5 .) 
 
 Preparation. To prepare this reagent, nine parts of 
 nitric acid, of 1.23, are gently heated in a small retort, 
 with ten parts of mercury, till no more red vapour of ni- 
 trous acid appear ; the solution is then boiled for some 
 time with the undissolved metallic mercury, taking care to 
 replace the water lost by evaporation, till a solution of com- 
 mon salt in excess precipitates from a portion of the liquid, 
 all the mercury it contains, as a protochloride, so that pro- 
 tochloride of zinc produces no precipitate in the filtered 
 liquid. The original solution is then shaken until cold ; 
 the crystals obtained are pounded, and agitated with 
 twenty parts of cold water, to which a very small quantity 
 
AMMONIO-NITRATE OF SILVER. 71 
 
 of nitric acid is added. The solution is then filtered, if 
 necessary, and kept in a glass bottle, the bottom of which 
 is covered with mercury. 
 
 Uses, The protonitrate of mercury acts in a manner 
 analogous to the corresponding salt of silver. In the first 
 place, it precipitates many acids, especially the hydracids ; 
 and 2, it serves for the detection of several substances of 
 easy oxidation, e. g. of formic acid, since their oxidation at 
 the expense of the oxygen of the black oxide of mercury, 
 is attended by the highly characteristic precipitation of me- 
 tallic mercury. 
 
 68. 
 
 13. PEROXIDE OF MERCURY. {Hg O.) ^ 
 
 The peroxide of mercury of commerce is reduced to a 
 fine powder, after having been moistened with some alco- 
 hol, in order to prevent its minute particles from rising into 
 the air. This powder is then kept for use. As a reagent 
 it affords us a certain means of detecting hydrocyanic acid, 
 since it dissolves in an alkaline fluid only when this acid 
 is present (Compare 100, d.) 
 
 69, 
 
 14- PERCHLORIDE OF MERCURY, (Hg Cl.) 
 
 The commercial perchloride of mercury is sufficiently 
 pure for the purposes of chemical analysis. For use, one 
 part is dissolved in sixteen parts of water. 
 
 Uses. Perchloride of mercury yields with various 
 acids, e. g. with hydriodic acid, precipitates of the charac- 
 teristic colour, but it is, nevertheless, one of the less essen- 
 tial reagents for the determination of acids. It acts, more- 
 over, as a means of oxidation, and allows us to detect the 
 presence of easily oxidizable bodies, e. g. of protoxide of 
 tin, by the precipitation of protochloride of mercury, 
 
 70. 
 
 AMMONIO-NITRATE OF SILVER. (Ag O, NO 5 + SNHs.) 
 
 This reagent is not kept on hand, but prepared, when 
 
72 SUPHUROTJS ACID. CHLORINE. 
 
 needed for use, by cautiously dropping caustic ammonia 
 into a solution of nitrate of silver, till the precipitate which 
 at first appears is re-dissolved. It serves for the detection 
 of arsenious and arsenic acid in solutions which contain a 
 free acid. 
 
 71. 
 
 SULPHUROUS ACID. (S0 2 .) 
 
 Preparation. To obtain this acid, small pieces of char- 
 coal are heated in a retort with six or eight times their 
 weight of English sulphuric acid, and the evolved gas is 
 transmitted through water (which must be kept cool) till 
 no more sulphurous acid is absorbed. The solution obtained 
 nius4 be kept in well-closed bottles. 
 
 Uses. Sulphurous acid has a great disposition to be 
 converted into sulphuric acid, by the absorption of oxygen. 
 It is, therefore, one of our most powerful means of reduc- 
 tion; it precipitates metallic mercury from its solutions, 
 and converts chromic acid into oxide of chromium, in the 
 same manner as protochloride of tin. We employ sul- 
 phurous acid principally for the conversion of arsenic acid 
 into arsenious acid, in order to be enabled to precipitate 
 arsenic more rapidly and more completely, by means of 
 sulphuretted hydrogen. (Vide 93, e.) Before applying 
 this reagent, it is always necessary to ascertain byjts 
 odour whether it has undergone decomposition. 
 
 72. 
 
 17. CHLORINE. (Cl.) 
 
 Preparation. One part of pounded peroxide of manga- 
 nese is drenched in a retort, with from four to five parts 
 of commercial hydrochloric acid ; a gentle heat is then 
 applied to the retort, and the evolved gas is conducted into 
 a jar containing about from thirty to forty parts of water at 
 the lowest possible temperature* The chlorine water ob- 
 tained must be kept in a well closed bottle, and cautiously 
 protected from the influence of light, for if this precaution 
 be neglected, it will soon become completely decomposed, 
 i. e. converted into dilute hydrochloric acid, with evolution 
 of oxygen, (owing to the decomposition of the water.) 
 
SOLUTION OF INDIGO. STARCH-PASTE. 73 
 
 Uses. Chlorine has a greater affinity for metals and 
 for hydrogen than iodine and bromine. Chlorine water is, 
 therefore, an efficient means of expelling iodine and bromine 
 from their combinations. Free chlorine forms with bromine 
 chloride of bromine, and with iodine, chloride of iodine, 
 and these combinations present a different relation to that 
 of the uncombined metalloids ; we must, therefore, in cer- 
 tain cases, e. g. when testing for iodine by means of 
 starch, ( 100,) carefully avoid adding chlorine water in ex- 
 cess. Chlorine serves, moreover, for the destruction of 
 organic substances, by depriving water, which contains 
 these substances, of its hydrogen, so that the liberated 
 oxygen is enabled to combine with the vegetable elements, 
 and thus to effect their decomposition. For this latter 
 purpose it is most advisable to evolve chlorine in the fluid 
 which contains the organic substances, by adding hydro- 
 chloric acid to it, heating it to boiling, and then adding 
 chlorate of potash. In this process chloride of potassium 
 and water are formed, and chlorous acid and chlorine 
 liberated. 
 
 73. 
 
 18* SOLUTION OF INDIGO. 
 
 Preparation. One part of pounded indigo is heated 
 with seven parts of fuming sulphuric acid. The solution 
 obtained is diluted for use, with so much water that the 
 fluid just appears still distinctly blue, 
 
 Uses. Indigo becomes decomposed when boiled with 
 nitric acid, giving rise to the formation of oxidation-pro- 
 ducts of a yellow colour. It is, therefore, employed for 
 the detection of nitric acid, either in its free and uncom- 
 bined state or in its salts ; in which latter case, however, 
 the nitric acid must first be liberated by means of sul- 
 phuric acid. 
 
 74. 
 
 19. STARCH-PASTE. 
 
 Common starch is rubbed with cold water, and the mix- 
 ture then heated to the boiling point, being at the same 
 time constantly stirred. The paste must be uniform, and 
 so thin as almost to run. 
 
74 MIXTURE OF SODA, &C. 
 
 Uses. Starch, when brought into contact with free 
 iodine, forms, with this latter substance, a peculiar dark- 
 blue combination, the colour of which is so intense that it 
 is distinctly perceptible, even when the two substances 
 are brought together, in a highly dilute state. Starch- 
 paste is, therefore, a most excellent and delicate test for 
 free iodine. It is by far less susceptible with regard to 
 bromine, as the fiery yellow colour of bromide of starch is 
 far less characteristic and intense than that of iodide of 
 starch. 
 
 B. REAGENTS IN THE DRY WAY. 
 
 1. Fluxes and means of decomposition. 
 
 75. 
 
 1. MIXTURE OF CARBONATE OF SODA AND CARBONATE OF 
 POTASH. 
 
 (NaO, CO 2 +KO, C0 2 .) 
 
 Preparation. Ten parts of dried carbonate of soda are 
 rubbed together with thirteen parts of dry carbonate of 
 potash ; the mixture is kept in a closed vessel. 
 
 Uses.-* When silicic acid or silicates are fused with 
 about four parts, (and consequently with an excess,) of 
 carbonate of potash or soda, a basic alkaline silicate is 
 formed, (carbonic acid escaping with effervescence,) which, 
 being a combination soluble in water, may be separated 
 from such metallic oxides as it may peradventure contain, 
 and from which hydrochloric acid always separates silicic 
 acid in its soluble modification. When a fixed alkaline 
 carbonate is fused together with sulphate of barytes, of 
 strontia, or of lime, carbonates of the alkaline earths and 
 sulphate of the alkali present are formed, in which com- 
 binations the base, as well as the acid of the previously 
 insoluble salts, may now be ascertained with facility. In 
 order to enable us to render soluble the insoluble silicates 
 and sulphates, we use neither carbonate of potash nor 
 carbonate of soda, separately, but the above mixture of 
 both, because this mixture requires a far lower degree of 
 heat for fusion than either of its components, and thus 
 
CARBONATE OF BARYTES. NITRATE OF POTASH. 75 
 
 renders it possible to conduct the operation over a Ber- 
 zelius lamp. This should always be done in a platinum 
 crucible, when no easily reducible metallic oxides are 
 present. 
 
 76. 
 
 2. CARBONATE OF BARYTES. (Ba O, CO 2 .) 
 
 For the preparation of this reagent we refer the reader 
 to 33. 
 
 Uses. When silicates are heated with about six times 
 their weight of carbonate of barytes till they begin to fuse 
 together, the silicates decompose with the salt of barytes, 
 in the same manner as with alkaline carbonates, i. e. su- 
 perbasic silicate of barytes is formed, which is easily de- 
 composed by hydrochloric acid, the carbonic acid escapes 
 and the oxides separate. It is, however, by far more dif- 
 ficult to render silicates completely soluble by this method, 
 than by means of alkaline carbonates ; and we use car- 
 bonate of barytes, therefore, only, when we intend to test 
 silicates as to the presence of alkalies. The operation 
 with carbonate of barytes is conducted in a platinum 
 crucible. 
 
 77. 
 
 3. NITRATE OF POTASH. (KO, No fi .) 
 
 Preparation. Commercial saltpetre is dissolved to 
 saturation in boiling water. The solution is then diluted 
 with a small quantity of water, filtered hot into a glass 
 beaker ; this latter put into cold water, and the solution 
 stirred till cold. The crystalline powder obtained is 
 thrown on a filter and washed with cold water till the 
 filtrate is no longer disturbed by nitrate of silver. It is 
 then well dried and kept for use. 
 
 Testing. A solution of pure nitrate of potash must 
 neither be disturbed by solution of silver, nor by solution 
 of barytes, nor precipitated by carbonate of potash. 
 
 Uses. Saltpetre serves as a very powerful means of 
 oxidation, by yielding oxygen to combustible substances 
 
76 CHARCOAL. 
 
 when heated with them. We use it principally to convert 
 several metallic sulphurets, especially the sulphurets of 
 tin, of antimony, and of arsenic, into oxides and acids ; and 
 also for the rapid and complete combustion of organic 
 bodies. For this latter purpose, however, nitrate of am - 
 monia is, in most cases, preferable : we obtain this by sa- 
 turating nitric acid with carbonate of ammonia. 
 
 II. BLOW-PIPE REAGENTS. 
 
 78. 
 
 1. CHARCOAL. (C.) 
 
 Any kind of completely calcined -wood charcoal may be 
 used for blow-pipe experiments. The charcoal of pine or 
 linden-wood is, however, preferable to any other sort. 
 Smooth pieces ought to be selected, as knotty pieces split 
 and throw off fragments of the test specimen when heated. 
 
 Uses. Charcoal is principally used as a support for 
 the matter under examination in blow-pipe experi- 
 ments, (vide 12.) The following are the properties 
 which render it so valuable in this respect. First, its infu- 
 sibility ; 2d, its low conducting power for heat, which 
 admits of a substance being heated more strongly upon a 
 charcoal than on any other support ; 3d, its porosity, by 
 means of which it imbibes easily fusible substances, such 
 as borax, soda, &c., whilst infusible bodies remain on its 
 surface ; 4th, its property of reducing oxidized bodies, by 
 means of which it co-operates in the reduction of oxides by 
 the inner flame of the blow-pipe. Charcoal serves, more- 
 over, for the -reduction of arsenious acid and of arsenic 
 acid, by depriving them of their oxygen, at a red heat. 
 Charcoal, for this purpose, is employed either in the shape 
 of small splinters, or reduced to powder. Sometimes the 
 simultaneous application of an alkaline carbonate is neces- 
 sary for the separation of arsenic ; in such cases it is best 
 to use a mixture of soda in powder and lamp-black ; this 
 mixture is heated in a covered crucible, and kept in a- well- 
 stopped bottle. 
 
CARBONATE OF SODA. 77 
 
 79. 
 
 2. CARBONATE OF SODA. (Na 0, CO 2 .) 
 
 Preparation. One part of chrystallized and three parts 
 of dried carbonate of soda are intimately mixed together 
 and then put into the broken-off neck of a retort, or into a 
 wide glass tube, or some vessel of that description ; one 
 aperture is closed by means of a perforated cork, the other 
 remains open. To the perforated cork a tube is fitted, 
 which is connected with a gas evolution flask, in which, 
 when the entire apparatus is ready, carbonic acid is 
 evolved from limestone and hydrochloric acid. We ob- 
 tain in this manner bicarbonate of soda. The complete 
 saturation of the carbonate of soda with carbonic acid is 
 known by the falling of the temperature of the mixture 
 which had become elevated in the course of the operation, 
 and by the immediate extinction of an ignited wood-splint, 
 when held before the open aperture of the tube. The salt 
 is then thrown on a filter-funnel and washed with cold 
 water, till the liquid which runs off, after supersaturation 
 with nitric acid, is no longer disturbed by chloride of 
 barium, or by nitrate of silver; the salt is then dried, and 
 heated in a crucible of silver, platinum, or porcelain. Car- 
 bonate of soda is thus obtained, one atom of carbonate 
 acid being expelled. The purity of carbonate of soda is 
 tested like that of carbonate of potash. Hydro- sulphuret 
 of ammonia must not alter its solution. 
 
 Uses. We employ carbonate of soda, on account of its 
 fusibility, to promote the reduction of oxidized substances 
 by the inner flame of the blow-pipe. In fusing it brings 
 the oxides into most intimate contact with the charcoal sup- 
 port, and allows the flame -of the blow-pipe to embrace 
 every part of the specimen. But it does not co-operate in 
 this process by its matter, or by decomposition. If the 
 quantity operated upon is very minute, the reduced metal 
 will often be found in the pores of the coal. In such cases, 
 the parts surrounding the little hole which contained the 
 sample, are taken off with a knife, triturated in a mortar, 
 and the coal washed off from the metallic particles, which 
 then become visible, either as powder or as small and flat 
 spangles, according to their various nature. 
 
78 CYANIDE OP POTASSIUM. 
 
 In many cases, e. g. in the reduction of peroxide of tin, 
 it is advantageous to add some borax to the carbonate of 
 soda, in order to render the mass more easily fusible. In 
 the second place, carbonate of soda serves as solvent. It 
 is best to use platinum wire as the support, when testing 
 whether bodies are soluble in carbonate of soda. For this 
 purpose the substance is made into a paste with some car- 
 bonate of soda and water ; this paste is placed on the loop 
 of a platinum wire, and heated. A few only of the bases 
 dissolve in* melting carbonate of soda, but acids dissolve 
 with facility therein. Silicic acid differs from all other 
 acids, inasmuch as the glass which it forms with carbon- 
 ate of soda, remains clear on cooling, if, of course, the two 
 constituents are present in the right proportion to each 
 other. Carbonate of soda is, moreover, applied as a means 
 of decomposing, and rendering other bodies soluble, espe- 
 cially the insoluble sulphates, with which it exchanges 
 acids, whilst, at the same time, a reduction of the new- 
 formed sulphate of soda to sulphuret of sodium takes place ; 
 when fused together with sulphuret of arsenic, both are 
 decomposed, giving rise to the formation of sulphuret of 
 arsenic and sodium, and of arsenite, or asseniate of soda, 
 and thus converting it into such a form as to admit of its being 
 reduced by means of hydrogen. Finally, carbonate of soda 
 is the most susceptible reagent in the dry way, for the de- 
 tection of manganese, since, when fused together in the 
 outer flame of the blow-pipe, with a substance containing 
 manganese, it produces a green, turbid button, owing to the 
 formation of manganate of soda. 
 
 80. 
 
 3. CYANIDE OF POTASSIUM. (KCy.) 
 
 For the preparation of this reagent, vide 40. 
 
 Uses. Cyanide of potassium is so powerful as a re- 
 ducing agent in the dry way, that it excels in its action al- 
 most all other reagents, and, indeed, it separates the radi- 
 cals not only from oxygen combinations, but also from sul- 
 phur combinations, giving rise, in the first case, to the for- 
 mation of cyanate of potash, by absorbing oxygen, and, in 
 the latter case, to the formation of sulphocyanide of potas- 
 sium. We may, by means of this reagent, in the easiest 
 
CYANIDE OF POTASSIUM. 79 
 
 manner (commonly merely in a porcelain crucible over a 
 spirit-lamp) obtain pure metals from their combinations, as 
 e. g. antimony from antimonious acid or from sulphuret of 
 antimony, iron from peroxide of iron, &c. &c. The separ- 
 ation of these metals is much promoted by the easy fusi- 
 bility of cyanide of potassium. Jn analysis, this reagent is 
 of the highest importance, for the reduction of arsenites 
 and arseniates, especially of some of those salts which 
 have the heavy metals for bases, and the reduction of which 
 by the usual means of deoxidizing succeeds only with 
 difficulty. As cyanide of potassium is not yet universally 
 known as a reagent in this respect, I invite particular at- 
 tention to its superior usefulness in the reduction of arsenic. 
 For experiments on a larger scale, glass tubes are selected, 
 rounded at their closed end. The salt which it is intended 
 to reduce, e. g. arseniate of silver, is thrown into a tube of 
 this description, and covered by a small piece of cyanide 
 of potassium ; all moisture is first removed from the tube 
 by gently heating it from below upwards ; the cyanide of 
 potassium is then heated to fusion and allowed to act on 
 the test specimen. The deoxidation begins in a brisk man- 
 ner, and with ignition ; it is, therefore, unnecessary to ap- 
 ply much external heat, at this point of the operation. Up 
 to this time, generally, no incrustation of arsenic appears, 
 but if the melting mass be now somewhat more strongly 
 heated, the arsenic will, after some time, completely sub- 
 lime ; and as the fused mass does notspout, if the interior 
 of the tube is perfectly dry and clean, exceedingly beauti- 
 ful mirror-incrustations will be obtained. For the reduc- 
 tion of very small quantities of compounds of arsenic, we 
 use a perfectly dry mixture of equal portions of carbonate 
 of soda and of cyanide of potassium, and cover the test 
 specimen with about six times its quantity of this mixture ; 
 conducting the operation in a small glass tube expanded at 
 one end into a small bulb. From sulphuret of arsenic also 
 we may completely sublime the arsenic, by fusing the 
 sulphuret together with cyanide of potassium. Several 
 arsenious and arsenic metallic-salts, when fused together 
 with cyanide of potassium, are reduced in such a manner 
 as .to give rise to the formation of fixed arseniuret, (e. g. 
 arseniate of iron.) In such cases no mirror incrustations 
 
80 BIBORATE OF SODA. 
 
 of arsenic are obtained, which must be borne in mind. 
 As a blow-pipe reagent, cyanide of potassium is also 
 highly useful ; its action is indeed extraordinary ; sub- 
 stances like peroxide of tin, sulphuret of tin, &c. &c., 
 which for their reduction with carbonate of soda, require 
 rather a strong flame, are reduced with the greatest facility 
 when cyanide of potassium is used. In blow-pipe experi- 
 ments we always use a mixture of equal parts of carbon- 
 ate of soda and of cyanide of potassium, since the cyanide 
 of potassium alone fuses too easily. This mixture, be- 
 sides its more powerful action, has another advantage over 
 carbonate of soda : it is with extreme facility imbibed by 
 the porous charcoal, so that the purest metallic globules 
 are obtained. 
 
 81. 
 
 BIBORATE OF SODA. (BORAX.) (Na O, '2 B, C 3 .) 
 
 The purity of commercial borax may be tested, by add- 
 ing to its solution, either carbonate of potash, or, after a 
 previous addition of nitric acid, solution of nitrate of ba- 
 rytes or solution of nitrate of silver. The borax may be 
 considered pure if these reagents cause no alteration ; but 
 if they either disturb or precipitate its solution, it must be 
 purified by recrystallization. The pure crystallized borax 
 is exposed to a gentle heat, in a platinum crucible, till it no 
 longer swells up ; it is then triturated and kept for use. 
 
 Uses. Boracic acid shows a grea affinity for oxides, 
 when brought into contact with them whilst fusing. It 
 combines, therefore, in the first place, directly with oxides. 
 2. It expels weaker acids from their salts ; and 3, with the 
 co-operation of the outer flame of the blow-pipe, it disposes 
 metals, sulphur combinations, and haloid combinations to 
 oxidize, in order to combine with the oxides. The borates 
 produced, generally fuse readily by themselves, but by far 
 more easily when fused together with borate of soda ; the 
 latter salt acts in this operation either as a mere flux, or 
 by giving rise to the formation of double salts. In the 
 biborate of soda, we have 1, free boracic acid; and 2, 
 borate of soda ; and thus, both conditions united, by which, 
 as before stated, oxides, sulphurets, metals, &c. are dis- 
 
PHOSPHATE OP SODA AND AMMONIA. 81 
 
 posed for solution and fusion ; borax is, therefore, as a 
 blow-pipe reagent, of the greatest importance in analytical 
 chemistry. We generally select platinum wire as support 
 in this operation, heating the loop of it to redness, dipping 
 it into the borax powder, and holding it in the outer flame, 
 whereby a colourless pearl is obtained. This pearl is 
 brought into contact with the test specimen, either when 
 still hot, or after being moistened, and thus a small quan- 
 tity of the latter attached to it ; it is then again exposed, 
 first, to the flame of a spirit-lamp, then to that of the blow- 
 pipe, observing the phenomena which appear. The fol- 
 lowing points ought to be examined with especial care : 
 1 . Whether the specimen dissolves transparent or not, and 
 whether it retains this transparency on cooling or not. 2. 
 Whether this specimen shows a distinct and definite colour, 
 which in many cases, e. g. with cobalt, leads to an in- 
 stantaneous and certain detection ; and 3. Whether the 
 pearls show the same or a different relation in the outer 
 and inner flame. Phenomena of the latter kind depend on 
 the mutation from higher degrees of oxidation to lower, or 
 even to the metallic state, and are for some substances par- 
 ticularly significant. 
 
 82. 
 
 5. PHOSPHATE OF SODA AND AMMONIA. (MICROCOSMIC SALT.) 
 
 (NaO, NH 4 O, P0 5 .) 
 
 Preparation. This salt is obtained by dissolving six 
 parts of phosphate of soda and one part of pure sal-ammo- 
 niac in two parts of hot water, and allowing the mixture 
 to cool, The crystals of the double salt thus obtained are 
 purified by recrystallization from the chloride of sodium 
 which still adheres to them. They are then dried, pow- 
 dered, and kept for use. 
 
 Uses. When phosphate of soda and ammonia is heat- 
 ed, the ammonia escapes together with the water of crys- 
 tallization. There remains, consequently, a compound, 
 which, with regard to composition, (free acid and fusible 
 salt,) very nearly approaches borax. The action of mi- 
 crocosmic salt is, therefore, quite analogous to that of 
 biborate of soda. We prefer it, however, to borax in many 
 cases as a solvent or flux, knowing, by experience, that the 
 
82 PROTO-NITRATE OF COBALT. 
 
 glasses which it forms with many substances, are more 
 beautifully and distinctly coloured than those of borax. 
 Platinum wire is equally used as a support when employ- 
 ing microcosmic salt as a flux ; it ought, however, here to 
 be remarked, that the loop of the wire must be small and 
 narrow, or else the pearl will not stick to it. The opera- 
 tion is conducted as stated 81 in the preceding paragraph. 
 
 83. 
 
 PROTO-NITRATE OF COBALT. (CoO, NO 5 .) 
 
 Preparation. To obtain this reagent, an intimate mix- 
 ture of two parts of very finely pounded cobalt, four parts 
 of saltpetre, one part of effloresced carbonate of soda, and 
 one part of dry carbonate of ipotash, is projected in small 
 portions in^o a crucible heated to redness ; the latter is 
 then left exposed to the strongest possible heat, till the 
 mass, although perhaps not in perfect fusion, yet is melt- 
 ing. The mass is then allowed to cool, and afterwards 
 reduced to powder and boiled with water ; the impure 
 peroxide of cobalt obtained is completely washed, digested 
 and heated with hydrochloric acid until dissolved. This 
 solution is of a dark green colour, and generally ge- 
 latinous, owing to the separation of silicic acid. It is 
 evaporated to dryness, the residue boilefl with water, fil- 
 tered, and carbonate of ammonia added to the filtrate, 
 whilst kept at the boiling point, till all acid reaction ceases. 
 The filtered solution is precipitated by means of carbonate 
 of potash, the precipitate obtained washed, and then dis- 
 solved in nitric acid. The solution is evaporated to dry- 
 ness, at a gentle heat, and one part of the residue dissolved 
 in ten parts of water, for use. 
 
 Uses. The protoxide of cobalt, when heated with cer- 
 tain infusible substances, forms with them combinations of 
 divers various characteristic colours, and may, therefore, 
 serve for the detection of those substances. Experiments 
 of this kind are conducted in the following manner. The 
 substance under examination, reduced to powder, is heated 
 to redness, on a charcoal support, the smallest possible drop 
 of solution of proto-nitrate of cobalt is then dropped upon 
 it, and it is again heated to redness. In this process, 
 

 RELATION OF SUBSTANCES TO REAGENTS. 83 
 
 oxide of zinc assumes an intensely green colour, alumina 
 a blue, and magnesia a feeble rose tint. The rose tint of 
 magnesia is of so little intensity that beginners may easily 
 overlook this reaction. Silica also, when moistened with 
 solution of nitrate of cobalt and heated to redness, assumes 
 a feeble blue tint, which ought to be borne in mind when 
 testing for alumina. The blue compound of the latter is, 
 however, by far more beautifully and intensely coloured, 
 than that of silica. 
 
 CHAPTER III. 
 
 ON THE RELATION OF THE VARIOUS SUBSTANCES TO 
 REAGENTS. 
 
 84. 
 
 As we have stated in our introductory remarks, qualita- 
 tive analysis is based on experiments by means of which 
 we endeavour to convert the unknown constituents of a 
 substance into forms with the relations and properties of 
 which we are familiar, so as to enable us to determine the 
 nature of constituents. It is the same with such experi- 
 ments as with inquiries and investigations in general. They 
 are the better the more certainly they lead to a definite re- 
 sult, no matter whether of a positive or negative charac- 
 ter. But as a question does not render us a whit the wiser, 
 if we do not understand the language in which the answer 
 is returned, so an experiment cannot avail us if we do 
 not know the manner of expression in which the infor- 
 mation is conveyed to us, i. e*, if we do not know what 
 conclusion we are to draw from a reagent leaving a body 
 unaltered, or producing some phenomenon or other, 
 owing to a mutation of form, or state, in the substance 
 operated upon. 
 
 Before we can, therefore, proceed to the practice of 
 analysis, we must, as an indispensable condition, first really 
 and completely know those forms and combinations of sub- 
 stances, which are supposed to be known. But this perfect 
 knowledge depends first, on a comprehensive conception of 
 
84 POTASH, SODA, AMMONIA. 
 
 the conditions which are necessary for the formation of the 
 new combinations, and thus, in short, for the mani- 
 festation of the various reactions ; and 2dly, on a dis- 
 tinct impression of the colour, form, and physical pro- 
 perties in general which characterize the new combina- 
 tions. 
 
 It is, therefore, of paramount importance to the student, 
 not merely theoretically to study this branch of qualitative 
 analysis, but also, by actual experiments, to verify every 
 part of it. To teach the relation of the various bodies to 
 reagents, it is usual, in works like the present, to treat of 
 the substances individually and separately, and to point 
 out their characteristic reactions. I have, however, in the 
 present work, deemed it more judicious and better adapted 
 to its elementary character, to collect into groups those 
 substances which are in many respects analogous, and 
 thus, by confronting their analogies with their differences, 
 to 'place the latter in the clearest possible light. 
 
 A. RELATION OF THE METALLIC OXIDES. 
 
 85. 
 First Group. 
 
 POTASH, SODA, AMMONIA. 
 
 Properties of the Group. The alkalies are easily solu- 
 ble in water, as whether in their pure or caustic state 
 or as sulphurets and carbonates. They, therefore, do not 
 precipitate each other, neither in their pure state nor as 
 carbonates, nor are they precipitated by sulphuretted hy- 
 drogen under any condition whatever. The solutions of 
 the purer alkalies, as well as of their sulphurets and car- 
 bonates, tinge reddened litmus paper blue, and impart an 
 intensely brown tint to turmeric paper* 
 
 Special reactions characteristic of the individual sub- 
 stances, 
 
 a. POTASH. (K O.) 
 1. The salts of potash are not volatile in the heat of a 
 
POTASH, SODA, AMMONIA. 85 
 
 spirit-lamp. They almost all dissolve in water with facility. 
 Their solutions are colourless provided the constituent acid 
 be so. The neutral salts of potash with strong acids, do 
 not affect vegetable colours. Carbonate of potash is of 
 difficult crystallization. The dry salt as well as the crys- 
 tals, (KO, CO a , 2aq.) which are formed in concentrated 
 aqueous solutions of carbonate of potash, when allowed to 
 stand for some time, deliquesce with rapidity when exposed 
 to humid air. 
 
 2. Chloride of platinum produces in the neutral and acid 
 solutions of the salts of potash, a yellow crystalline heavy 
 precipitate. (CHLORIDE OF PLATINUM AND POTASSIUM. K 
 C1+ P-f- C1 2 .) In concentrated solutions, the formations 
 of this precipitate is immediate, in dilute solutions it takes 
 place after a short time, and frequently even after 
 the lapse of some time. The presence of free hydrochloric 
 acid promotes its formation. It is difficultly soluble in 
 water, and wholly insoluble in alcohol. Chloride of plati- 
 num is, therefore, a particularly delicate test for salts of 
 potash when the latter is in alcoholic solution. Care should 
 be taken to avoid confounding chloride of platinum and 
 potassium with chloride of platinum and ammonium. 
 
 3. Tartaricacid produces, in neutral or alkaline solutions 
 of salts of potash, (to alkaline solutions the reagent must 
 be added till a strongly acid reaction becomes manifest,) a 
 white, quickly subsiding, granular crystalline precipitate 
 of BI-TARTRATE OF POTASH. (KO, HO, T.) In concen- 
 trated solutions this precipitate is formed immediately, in 
 dilute solutions frequently only after the lapse of some time. 
 Violent agitation of the liquid considerably promotes the for- 
 mation of the precipitate. Free alkalies and free mineral 
 acids dissolve the precipitate ; it is difficultly soluble in 
 cold, but more easily so in hot water. 
 
 4. When salts of potash, by means of a platinum wire, 
 are held in the summit of the inner blow-pipe flame, the 
 outer flame assumes a VIOLET tint, owing to a reduction of 
 potash, and a reoxidation of the potassium thus formed. This 
 reaction is hardly perceptible in phosphates and borates of 
 potash. The presence of soda renders it completely im- 
 perceptible. 
 
 5. When a salt of potash is heated with a small quantity 
 
 4 
 
86 
 
 of water, alcohol added, and the latter ignited, the flame 
 appears VIOLET. The presence of soda renders this reac- 
 tion also imperceptible. 
 
 b. SOI>A. (Na O.) 
 
 1 . The salts of soda present the same general relations 
 as those of potash. Carbonate of soda crystallizes readily ; 
 the crystals (Na O, CO 2 + 10 aq.) effloresce rapidly when 
 exposed to dry air. 
 
 2. If a neutral or alkaline solution of a soda salt be mix- 
 ed with a solution of neutral antimoniate of potash* a 
 white granular crystalline precipitate,, ANTIMONIATE OP 
 SODA (Na O, Sb O 6 ) is formed, (in concentrated solutions, 
 almost immediately, in dilute solutions after the lapse of 
 some time.) Violent agitation of the mixture promotes the 
 separation of the precipitate very much ; rubbing the inner 
 sides of the vessel with a glass rod is even more effective. 
 Even in solutions of soda, diluted to the extent of 1000 to 
 1, we observe, after the lapse of some time, a certain milk- 
 iness, and, finally, the formation of a crystalline precipitate. 
 This reaction is not interfered with by the presence of salts 
 of potash ; the presence of carbonate of potash, in excess, 
 alone has a preventive influence on the formation of the 
 precipitate, since antimoniate of soda dissolves more readily 
 in solution of carbonate of potash, than in water. The 
 presence of free acids must always be avoided, since they 
 separate from the reagent, bi-antimoniate of potash, or hy- 
 drate of antimonic acid, in the form of a white precipitate. 
 
 3. Salts of soda exposed on a platinum wire to the inner 
 blow-pipe flame, colour the outer flame INTENSELY YEL- 
 LOW, owing to a reduction of soda, and a re-oxidation of 
 the sodium formed. This reaction is visible even if a 
 large quantity of potash is mixed with the soda. 
 
 * This reagent is prepared by exposing fifty parts of antimoniuro 
 diaphoreticum ablutum, mixed with twenty and four tenth parts of pure 
 carbonate of potash, to a red heat for half an hour. The crumbling 
 mass is kept in a well-stopped glass vessel. The solution is prepared 
 by drenching four parts of the powder with one hundred parts of 
 warm water, allowing it to digest, and to cool completely, and then 
 filtering the solution and preserving the clear filtrate, protected from 
 the access of air. 
 
AMMONIA. 87 
 
 4. When a salt of soda is heated with a small quantity 
 of water, alcohol added, and the latter ignited, the flame 
 appears strongly YELLOW. The presence of a salt of 
 potash has no preventive influence on this reaction* 
 
 5. Chloride of platinum produces no precipitate, in so- 
 lutions of soda : tartaric acid only when they are highly 
 concentrated. The BITARTATE OF SODA, (Na O, HO, T + 
 2 aq.) which crystallizes out in such cases, appears always 
 in the shape of small needles and columns, and not, like 
 the corresponding salt of potash, in the form of a granular 
 crystalline precipitate. . 
 
 C. AMMONIA. (NH 4 O.) /] 
 
 \ . All salts of ammonia are volatile at a high lempera- 
 ture, either with decomposition, or remainingin combina- 
 tion. Most of them are easily soluble in water. Their 
 solutions are colourless. The neutraF ammoniacal com- 
 pounds with strong acids do not alter vegetable colours. 
 
 2. When salts of ammonia are triturated with hydrate 
 of lime, with the addition of a few drops of water, or when 
 they are heated, either in a solid forrri or in solution, with 
 solution of potash, ammonia becomes liberated in its 
 gaseous state, and manifests itself, 1 , by its characteristic 
 odour ; 2, by its reaction on moistened test-papers ; and 
 3, by giving rise to the formation of white fumes, when 
 any object (e. g. a glass rod) moistened with hydrochloric 
 acid, nitric acid, acetic acid, any volatile acids, is brought 
 in contact with it. These fumes are caused by the forma- 
 tion of fixed salts, produced by the contact of the gases in 
 the air. Hydrochloric acid is the most delicate test in this 
 experiment; acetic acid, however, less easily admits of 
 any mistake. 
 
 3. Chloride of platinum shows the same relation to salts 
 of ammonia as to salts of potash ; the yellow precipitate 
 
 of CHLORIDE OF PLATINUM AND AMMONIUM (NH 4 C14-P + 
 
 C1 2 ) has, however, a somewhat lighter colour than chloride 
 of platinum and potassium. 
 
 c- Tartaric acid produces in solutions of salts of ammo- 
 nia a precipitate of BITARTRATE OF AMMONIA, (NH 4 O, 
 HO, T,) which is formed in the same manner, and under 
 the same circumstances as the corresponding salt of potash, 
 but is somewhat more soluble than the latter. 
 
88 BARYTES, STRONTIAN, LIME, MAGNESIA. 
 
 Recapitulation and remarks. Salts of potash and of 
 soda are not volatile at a conjmon red heat ', salts of 
 ammonia volatilize easily. The latter may, therefore, be 
 easily separated from the former by the application of a 
 red heat. The surest test of ammonia is its expulsion by 
 lime or potash. Salts of potash can only be detected 
 when salts of ammonia are removed, since both show the 
 same or similar relations to chloride of platinum and tar- 
 taric acid. Potash is characterized with certainty by 
 either of these two reagents, when ammonia is removed. 
 Soda can only be positively detected by the figure of crys- 
 tallization, and the properties of some of its salts by its be- 
 haviour with antimoniate of potash, and by the colour which 
 its salts impart to the flame of the blow-pipe, and to that of 
 alcohol. When testing for soda with antimoniate of pot- 
 ash, ammoniacal salts must not be present, as they also 
 yield precipitates with the same reagent. If the soda is 
 combined with potash in alkaline solution, and we intend 
 to test for it with antimoniate of potash, acetic acid, or 
 hydrochloric acid, must first be added, until the alkaline 
 reaction has nearly but yet not completely disappeared. 
 If the fluid under examination contains a free acid, pure 
 carbonate of potash is added, until the solution has acquired 
 an incipient alkaline reaction. 
 
 86. . A 
 
 Second Group. 
 
 BARYTES, STRONTIAN, LIME, MAGNESIA. 
 
 Properties of the group. The alkaline earths are solu- 
 ble in water, in their caustic state and as sulphurets. 
 Magnesia, however, is very difficult of solution. These 
 solutions manifest alkaline reactions. The neutral carbo- 
 nates and phosphates of the alkaline earths are insoluble 
 in water. The solutions of the salts of the alkaline earths 
 are, therefore, not precipitated by sulphuretted hydrogen, 
 under any condition, but alkaline carbonates and phos- 
 phates do precipitate them. This relation distinguishes 
 the oxides of the second group from those of the first. 
 The salts of the alkaline earths are colourless, partly 
 soluble, partly insoluble, and not volatile. 
 

 BARYTES. 89 
 
 Special Reactions-. ") 
 
 a. BARYTES. (Ba O.) 
 
 1. Ammonia causes no precipitate in the solutions of 
 salts of barytes ; POTASH only when they are concentrated. 
 Water re-dissolves the precipitate of HYDRATE OF BARYTES 
 (Ba O-f-aq.) which is formed. 
 
 2. Alkaline carbonates throw down from solutions of 
 barytes CARBONATE OF BARYTES, (Ba O, CO 2 .) in the 
 form of a white precipitate. In acid solutions, however, 
 complete precipitation takes place only on boiling ; the 
 same is the case when carbonate of ammonia is employed 
 as the precipitant. The presence of salts of ammonia 
 does not prevent this precipitation. 
 
 3. Sulphuric acid, and all the soluble sulphates, pro- 
 duce, even in the most highly diluted solutions of barytes, 
 immediately, a fine white precipitate, SULPHATE OF 
 BARYTES, (Ba O, SO 3J ) which is insoluble in acids and 
 alkalies. 
 
 4. Hydrofluo-silicic acid precipitates from solution of 
 barytes SILICOFLUORIDE OF BARIUM, (3 Ba Fl-J-2 Si F1 3 ,) 
 in the form of a colourless, crystalline, quickly-subduing 
 precipitate. In dilute solutions this precipitate is formed 
 only after the lapse of some time ; hydrochloric acid and 
 nitric acid dissolve it, but only to a hardly perceptible 
 extent. 
 
 5. Phosphate of soda causes in neutral or alkaline solu- 
 tion, a white precipitate of PHOSPHATES OF BARYTES, 
 (Ba O, PO 5 ) which is soluble in free acids. Addition of 
 ammonia neither increases the quantity of this precipitate, 
 nor promotes its formation. 
 
 6. Oxalic acid causes only in concentrated solutions a 
 white precipitate of OXA.LATE OF BARYTES, (Ba O, O-Htq.) 
 which is soluble in acids. But if ammonia be added, the 
 reaction is by far more susceptible, anS the solution must 
 be highly dilute indeed if no precipitate is formed. 
 
 7. Salts of barytes, when heated with diluted spirit 
 of wine, impart to the flame of the latter a but little cha- 
 racteristic YELLOWISH Colour. 
 
90 STRONTIAN. LIME. 
 
 b. STRONTIAN. (Sr O.) 
 
 1. Salts of strontian show completely the same rela- 
 tions as salts of barytes, to ammonia and potash, as well 
 as to the alkaline carbonates and to phosphate of soda. 
 
 2. Sulphuric acid and sulphates precipitate from solu- 
 tions of strontian, SULPHATE OF STRONTIAN, (Si O, SO 3 ,) 
 in form of a while powder, which is insoluble in acids and 
 alkalies. Sulphate of strontian is by far more soluble in 
 water than sulphate of barytes, owing to whith the preci- 
 pitate in rather dilute solutions is generally only formed 
 after the lapse of some time ; and this is always the case 
 (even in concentrated solutions) if solution of gypsum is 
 employed as the precipitant. 
 
 3. Hydrofluo-silicic acid does not cause any precipi- 
 tate, even in concentrated solutions of strontian. 
 
 4. Oxalic acid precipitates even from rather highly 
 dilute solutions, after^the lapse of some time, OXALATE OF 
 STRONTIAN, (Sr O, O-faq.) as a white powder. Addition 
 of ammonia promotes the formation of the precipitate, and 
 considerably increases its quantity. 
 
 5. If such salts of strontian as are soluble in water or 
 alcohol, be heated with diluted alcohol, and the latter 
 ignited, they impart to its flame, especially on stirring, an 
 intense CARMINE RED colour. This colour must not be 
 confounded with that which salts of lime communicate to 
 the flame of alcohol. 
 
 c. LIME. (Ca O.) 
 
 1. Ammonia, potash, alkaline^arbonates, and phosphate 
 of soda, show the same relations to salts of lime as to sails 
 of barytes. 
 
 2. Sulphuric acid and sulphate of soda produce in high- 
 ly-concentrated solutions of lime immediately, white pre- 
 cipitates of SULP^TE OF LIME, (Ca O, SO 3 , HO-f-aq.) 
 
 I which are completely dissolved by a large proportion of 
 ! water, but are far more soluble in acids than in water. In 
 less concentrated solutions the precipitates are only formed 
 after the lapse of some time ; and no precipitation what- 
 ever takes place in highly dilute solutions. Solution of 
 gypsum, of course, cannot produce any precipitate ; but 
 
MAGNESIA. 91 
 
 even a cold saturated solution of sulphate of potash, mixed 
 with an equal quantity of water, produces no precipitate 
 in solutions of lime, at least never immediately. If solu- 
 tions of lime are so highly dilute, that sulphuric acid causes 
 mo precipitation in them, a precipitate is immediately 
 formed on the addition of alcohol. 
 
 3. Hydrofluo-silicic acid does not precipitate salts of 
 lime. 
 
 4. Oxalic acid produces a white precipitate of ox A LATE 
 OP LIME, (Ca O, O + 2 aq.) even in highly dilute neutral 
 solutions of lime. Addition of ammonia promotes the for- 
 mation of this precipitate, and increases its quantity. Oxa- 
 late of lime is easily soluble in hydrochloric acid and nitric 
 acid, but not in acetic acid, nor in oxalic acid. 
 
 Soluble salts of lime, when heated with dilute alcohol, 
 impart to the flarne of the latter a YELLOWISH RED colour, 
 which is often confounded with that caused by strontian. 
 
 d. MAGNESIA. (Mg O.) 
 
 1 . Ammonia throws down from the solutions of neutral 
 salts of magnesia, a portion of the magnesia as HYDRATE 
 OF MAGNE-SIA, (Mg O, HO,) in the form of a white bulky 
 precipitate. The other portion of magnesia remains in so- 
 lution, combined with the salt of ammonia to which the 
 decomposition has given rise, and forming with it a double 
 salt, not decoinposible by ammonia. This disposition of 
 the salts of magnesia to form such double salts with salts 
 of ammonia, is the cause that salts of magnesia are not pre- 
 cipitated when salts of ammonia are present, or, what is in 
 fact the same, that ammonia does not produce any preci- 
 pitate in acid solutions of magnesia, and that a precipitate 
 caused by ammonia, in neutral solutions, is re-dissolved on 
 the addition of a salt of ammonia. 
 
 2. Potash and caustic barytes precipitate from solutions 
 of magnesia, HYDRATE OF MAGNESIA. The formation of 
 this precipitate is much promoted by boiling. Salts of am- 
 monia redissolve the precipitated hydrate ; and no precipi- 
 tate is formed at all, if they are mixed in sufficient quantity 
 with the magnesia solution, before the addition of the pre- 
 cipitant. But it will, of course, make its appearance if the 
 
92 MAGNESIA. 
 
 solution be then boiled with an excess of potash, for in 
 that case the condition of its remaining in solution, i. e. the 
 salt of ammonia, becomes decomposed and is thus re- 
 moved. 
 
 3. Carbonate of potash causes in neutral solutions of 
 magnesia a white precipitate, A COMPOUND OF ONE EQUIV- 
 ALENT OF HYDRATE OF MAGNESIA, AND THREE EQUIVA- 
 LENTS OF CARBONATE OF MAGNESIA. (Mg O, HO + 3 
 
 Mg O, CO 2 .) The fourth part of the carbonic acid con- 
 tained in the carbonate of potash becomes liberated on the 
 decomposition of this salt, and combining with a portion of 
 the new-formed carbonate of magnesia, keeps this part in 
 solution as a bicarbonate of magnesia. This carbonic 
 acid may be expelled by boiling ; the application of heat to 
 the solution, therefore, promotes the formation and in- 
 creases the quantity of the precipitate. Salts of ammonia 
 prevent this precipitation also, and re-dissolve a precipitate 
 already formed. 
 
 4. Carbonate of ammonia does not precipitate solutions 
 of magnesia when cold, and but imperfectly when boiling. 
 The addition of salts of ammonia completely prevents the 
 formation of a precipitate. 
 
 Phosphate of soda precipitates PHOSPHATE OF MAGNE- 
 SIA (2 Mg O, PO 5 ) as a white powder, from solutions of 
 magnesia, provided they be not too highly dilute. The 
 precipitation is much promoted by boiling the solution. 
 But if ammonia be added to even a highly diluted solution 
 of magnesia, no matter whether before or after the addi- 
 tion of the phosphate of soda, a white crystalline precipi- 
 tate Of BASIC PHOSPHATE OF MAGNESIA AND AMMONIA 
 
 (2 Mg 0, NH 4 O,) (PO S + 2 HO + 10 aq.) is formed. 
 Its separation from dilute solutions is much promoted by 
 violent stirring (with a glass rod,) if even the solution is too 
 highly diluted as to admit of the formation of a precipitate ; 
 yet, white lines appear after some time in those places of 
 the sides of the vessel which have been touched by the 
 glass rod whilst stirring the fluid. Muriate of ammonia 
 and salts of ammonia, in general, do not dissolve the basic 
 phosphate of magnesia and ammonia, but it is soluble in 
 free acids, (even in acetic acid.) 
 
 6. Oxalate of ammonia (but not free oxalic acid) pro- 
 
MAGNESIA. 93 
 
 duces a white precipitate of OXALATE OF MAGNESIA. (Mg 
 O, -f- 2 aq.) Salts of ammonia prevent its formation. 
 
 7. Sulphuric acid and hydrofluo-silicic acid do not pre- 
 cipitate salts of magnesia. 
 
 8. If magnesia, or a salt of magnesia, be moistened with 
 solution of protonitrate of cobalt, and for some time ex- 
 posed on a coal to a strong blow-pipe flame, a FEEBLY 
 FLESH-COLOURED mass is obtained, the tint of which only 
 becomes distinct on cooling, but is never very intense. 
 
 Recapitulation and remarks. The difficult solubility 
 of the hydrate of magnesia, the easy solubility of the 
 sulphate of magnesia, and the disposition of salts of mag- 
 nesia to form double salts with salts of ammonia, are 
 the three main points in which magnesia differs from the 
 other alkaline earths. To detect magnesia, we remove 
 always first barytes, strontian, and lime, if they are present; 
 and we effect this purpose, either by boiling with carbon- 
 ate of ammonia with addition of sal ammoniac, or by 
 means of sulphate of potash and of oxalate of ammonia, 
 with addition" of sal ammoniac, and then select for the de- 
 tection of magnesia, the reaction with phosphate of soda, 
 with addition of ammonia. The detection of barytes is al- 
 ways easy, for the immediately forming precipitate which 
 it yields with solution of gypsum, and its reaction with 
 hydrofluo silicic acid, leave no doubt as to its presence. 
 Strontian may also easily be detected by its relation to so- 
 lution of gypsum, except in cases where barytes is present. 
 It must, therefore, in such cases first be separated from 
 barytes. This separation may best be effected by con- 
 verting both earths into dry chlorides, and digesting the 
 latter with absolute alcohol. The chloride of strontian dis- 
 solves whilst the chloride of barium remains undissolved. 
 When testing for strontian by means of the alcohol flame, 
 we must avoid confounding the colour it imparts to it, with 
 that communicated by salts of lime. For the detection of 
 lime, oxalic acid is always selected. Barytes and strontian 
 must, however, first have been removed by means of sul- 
 phate of potash, since they manifest with oxalic acid an 
 analogous reaction, only varying in intensity. On the 
 separation of barytes and strontian, by means of sulphate 
 4* 
 
94 ALUMINA, OXIDE OF CHROMIUM. 
 
 ot potash, it may possibly happen that also a portion of the 
 lime precipitates. This is, however, a matter of indiffer- 
 ence, since, at any rate, sufficient remains dissolved in the 
 fluid to admit of its presence being ascertained with in- 
 dubitable certainty, by means of oxalic acid. 
 
 87. 
 Third Group. 
 
 ALLUMINA, OXIDE OF CHROMIUM. 
 
 Properties of the group. Alumina and oxide of chro- 
 mium are both in their pure state, and, as hydrates, inso- 
 luble in water. They form no neutral salts with carbonic 
 acid. Their sulphur combinations cannot be formed in 
 the humid way. Sulphuretted hydrogen, therefore, does 
 not precipitate solutions of alumina or oxide of chromium ; 
 hydrosulphuret of ammonia precipitates the hydrated 
 oxides from these solutions. This relation to hydrosul- 
 phuret of ammonia distinguishes the oxides "of the third 
 from those of the two preceding groups. 
 
 Special Reactions, 
 a. ALUMINA. A1 2 O 3 .) 
 
 1. The salts of alluminaare colourless, for the most part 
 not volatile ; some of them are soluble, others insoluble. 
 The soluble salts redden litmus paper and lose their acids 
 when heated to redness. 
 
 2. Potash throws down from the solutions of alumina a 
 bulky precipitate of HYDRATE OF ALUMINA, (Ala O 3 +HO,) 
 containing potash, which easily and completely dissolves 
 in an excess of the precipitant, but may again be preci- 
 pitated from this solution by the addition of hydrochlorate 
 of ammonia, even when the solution is cold, but more com- 
 
 . pletely on heating it. The presence of salts of ammonia 
 does not prevent this precipitation by potash. 
 
 3. Ammonia also produces a precipitate of HYDRATE 
 OF ALUMINA ; and this precipitate also is redissolved by a 
 very considerable excess of the precipitate, but only in 
 such cases where the solution of alumina contains no salts 
 of potash or soda. But if a certain quantity of these salts 
 is present, ammonia is not able to redissolve the precipi- 
 
 \ tate first formed. 
 
OXIDE OF CHROMIUM. 35 
 
 Upon this relation, the complete precipitation of the 
 hydrate of alumina from a potash solution, by means of 
 hydrochlorate of ammonia, depends. For in this process, 
 potash and hydrochlorate of ammonia mutually decompose, 
 giving rise to the formation of chloride of potassium and 
 of ammonia ; and ammonia not being able to maintain the 
 hydrate of alumina in solution, when a salt of potash is 
 present, this hydrate of course precipitates, 
 
 4. If alumina, or a compound of alumina, be heated to 
 redness, on charcoal, before the blow-pipe, and then mois- 
 tened with a few drops of solution of protonitrate of cobalt, 
 and again strongly heated, an unfused mass of a deep SKY- 
 BLUE colour is obtained, a compound of the s 
 The colour becomes distinct only on cooling* 
 light it appears violet. 
 
 &, OXIDE OF CHROMIUM. (Cl 2 O 3 .) 
 
 1. The solutions of the compounds of oxide of chro- 
 mium, have always, even when highly diluted, either an 
 emerald-green or a nigrescent violet colour. The soluble 
 neutral salts of oxide of chromium redden litmus paper, 
 and are decomposed by heat. 
 
 2. Potash produces in solutions of oxide of chromium, 
 a bluish green precipitate of HYDRATED OXIDE OF CHROMIUM 
 (Cr 2O 3 + HO) which easily and completely redissolves 
 in an excess of the precipitant, imparting an emerald-green 
 colour to the fluid. If this solution is kept constantly 
 boiling for a certain time, the precipitate completely sepa- 
 rates again, so that the supernatant liquor appears perfectly 
 colourless. The dissolved hydrated oxide of chromium is 
 also precipitated, if the potash solution is mixed with hy- 
 drochlorate of ammonia and heated. 
 
 3. Ammonia produces the same precipitate of HYDRATED 
 OXIDE OF CHROMIUM. An excess of the precipitant redis- 
 solves it to a small extent, at a low temperature, but the 
 precipitation is complete, if the solution is boiled after the 
 addition of ammonia in excess. 
 
 4. If oxide of chromium, or a compound of this sub- 
 stance, are fused together with nitre, CHROMATE OF POT- 
 ASH, (KO, Cr O ,) is obtained in all cases ; in this process 
 a portion of the oxygen of the nitric acid leaves its com- 
 
96 OXIDE OF 2INC, &C. 
 
 bination, and forms with the oxide of chromium, chromic 
 acid, which then combines with the potash of the decom- 
 posed saltpetre. For the Reaction of Chromic Acid, vide 
 infra, 95, b. 
 
 5. Phosphate of soda and ammonia dissolves oxide of 
 chromium and its salts, as well in the oxidizing as in the 
 reducing flame of the blow -pipe, giving rise to the forma- 
 tion of clear, FEEBLY YELLOWISH-GREEN GLASS, the Colour 
 of which changes to emerald-green, on cooling. Borax 
 manifests a similar relation. 
 
 Recapitulation and remarks. The solubility of the 
 'chromium and alumina, in potash and their 
 pre from potash solutions, by means of hydro- 
 
 ammonia, allows us, in the first place, to sepa- 
 rate them from the oxides of other groups, and affords us, 
 in the second place, a certain means of detection for 
 alumina, when no oxide of chromium is present. If the 
 latter, therefore, is present which we may ascertain either 
 by the colour of the solution, or, at any rate, by the re- 
 action with phosphate of soda and ammonia, it must be 
 separated before we can proceed to test for alumina. This 
 separation may be effected most completely by fusing the 
 mixed oxides together with nitre. The precipitation of 
 oxide of chromium, by means of boiling its potash solu- 
 tion, is also a sufficiently exact indication j it gives, how- 
 ever, frequently rise to mistakes. 
 
 88. 
 Fourth Group. 
 
 OXIDE OF ZINC, PROTOXIDE OF MANGANESE, OXIDE OF 
 NICKEL, PROTOXIDE OF COBALT, PROTOXIDE OF IRON, 
 PEROXIDE OF IRON. 
 
 Properties of the group. The sulphurets correspond- 
 ing with these oxides, are more or less soluble in dilute 
 acids, but insoluble in water, alkalies, and alkaline sul- 
 phurets. The solutions of the salts of these oxides, are, 
 therefore, not at all precipitated by sulphuretted hydrogen, 
 when they contain free acid, and either not at all, or at 
 . least but incompletely, when they are neutral, but com- 
 
OXIDE OF ZINC. 97 
 
 pletely, when they are alkaline, or when an alkaline sul- 
 phuret is employed instead of sulphuretted hydrogen. 
 
 Special Reactions, 
 a. OXIDE OF ZINC. (Zn 0.) 
 
 1. The compounds of oxide of zinc are colourless. Its 
 soluble neutral salts* redden litmus paper, and are easily 
 decomposed by heat, with the exception of sulphate of 
 zinc, which can bear a slight degree of red heat, 
 
 2. Sulphuretted hydrogen precipitates from neutral 
 zinc solutions, a portion of the zinc as white IURET 
 OF ZINC (Zn S.) In acid solutions no ; 
 
 formed, if the free acid present be one i mger 
 
 acids. 
 
 3. Hydrosulphuret of ammonia throws down from 
 neutral as sulphuretted hydrogen does from alkalirie solu- 
 tions, all the zinc they contain, as SULPHURET OF ZINC, in 
 the form of a white precipitate. This precipitate is not 
 redissolved by hydrosulphuret of ammonia in excess, nor 
 by potash or ammonia ; it is sparingly soluble in hydro- 
 chloric acid, but easy of solution in aqua regia. 
 
 4. Potash and ammonia throw down from solutions of 
 zinc, HYDRATED OXIDE OF ZINC (Zn Q, HO) in the form 
 of a white gelatinous precipitate, whicHls easily and com- 
 pletely redissolved by an excess of the precipitant. 
 
 5. Carbonate of potash produces a precipitate of BASIC 
 CARBONATE OF ZINC 3 (Zn O, HO) + 2 (Zn O, CO 2 ) 
 which is insoluble in an excess of the precipitant. The 
 presence of salts of ammonia prevents its formation, or 
 they redissolve it when already formed, giving rise to the 
 formation of double salts of oxide of zinc and ammonia. 
 
 6. Carbonate of ammonia produces the same precipi- 
 tate as carbonate of potash ; addition of carbonate of < 
 ammonia in excess redissolves it. 
 
 7. Oxide of zinc, or a salt of oxide of zinc mixed with 
 carbonate of soda, and exposed to the reducing flame of 
 the blow-pipe, covers the coal support with an incrustation 
 of OXIDE OF ZINC, presenting a yellow colour, as long as it 
 is hot, and changing to white, on cooling. This is caused 
 by the reduced metallic zinc volatilizing at the moment of 
 
98 PROTOXIDE OF MANGANESE. 
 
 its reduction, and reoxidizing in passing through the outer 
 flame. 
 
 8. If oxide of zinc, or a salt of zinc, be moistened with 
 solution of protonitrate of cobalt, and heated before the 
 blow-pipe, an unfused beautifully GREEN coloured mass is 
 obtained, consisting of a combination of oxide of zinc with 
 protoxide of cobalt. 
 
 b. PROTOXIDE OF MANGANESE. (Mn 0.) 
 
 1. The protosalts of manganese are colourless or of a 
 
 pale red ; some of them ' are soluble, others insoluble. 
 
 i salts are decomposed by a red heat, with the 
 
 f protosulphate of manganese. The solutions 
 
 yanese salts do not alter vegetable colours. 
 
 retted hydrogen does not precipitate acid nor 
 neutral solutions of prototoxide of manganese. 
 
 3. Hydrosulphuret of ammonia throws down from neu- 
 tral solutions, as sulphuretted hydrogen does from alkaline, 
 all the manganese they contain, as SULPHURET OF MANGA- 
 NESE (Mn S) in the form of a bright flesh-coloured preci- 
 pitate, which changes to a dark-brown when exposed to 
 the air ; this precipitate is insoluble in hydrosulphuret of 
 ammonia and in alkalies, but easily soluble in hydrochloric 
 acid and nitric acid. 
 
 4. Potash aiid^mmonia produce whitish precipitates of 
 
 HYDRATED PROTOXIDE OF MANGANESE, (Mn O, HO,) 
 
 which, when exposed to the air, soon change to a brownish, 
 and at last, to a dark blackish brown colour, owing to the 
 hydrated protoxide being converted into hydrated peroxide, 
 by the absorption of oxygen from the air. Ammonia and 
 carbonate of ammonia do not redissolve this precipitate ; 
 but sal ammoniac prevents the precipitation by ammonia 
 completely, and that by potash partly. Solution of sal 
 ammoniac redissolves only those parts of the already- 
 formed precipitates which have not yet undergone a higher 
 degree of oxidation. The solution of the hydrated protox- 
 ide in sal ammoniac depends on the disposition of the pro- 
 tosalts of manganese to form double salts with salts of 
 ammonia. The pellucid solutions of these double salts 
 become brown, when exposed to the air, and depose dark- 
 brown peroxide of manganese. 
 
'. OXIDE OF NICKEL. 99 
 
 5. If any compound of manganese be fused with car- 
 bonate of soda, on a platinum wire, in the outer flame, 
 MANGANATE OF SODA is formed, which makes the test 
 specimen appear GREEN, as long as it is hot. but, after 
 cooling, of a bluish green and opaque. This reaction 
 enables us to detect the smallest quantities of manganese. 
 The delicacy of the test is still further increased if a minute 
 quantity of nitre is added to the carbonate of soda. 
 
 6. Borax and phosphate of soda and ammonia dis- 
 solve manganese compounds, in the outer flame of the 
 blow-pipe, giving rise to the formation of clear and VIOLET- 
 RED glasses, which, on cooling, appear of an amethyst 
 red, and lose their colour when exposed to the inner flame, 
 owing to the peroxide becoming reduced to proton 
 
 glass which borax forms with manganese, appears black 
 when containing a considerable proportion of peroxide of 
 manganese, but the glass formed by phosphate of soda 
 and ammonia never loses its transparency. The latter, 
 when exposed to the inner flame, becomes colourless far 
 more easily than the former. 
 
 C. OXIDE OF NICKEL. (Ni O.) 
 
 1. The salts of nickel are yellow or green ; their 
 solutions are of a bright green colour. The soluble 
 neutral salts redden litmus paper and are decomposed at a 
 red heat. 
 
 2. Sulphuretted hydrogen precipitates neither acid nor" 
 neutral solutions of nickel ; or the latter at least but very 
 incompletely. 
 
 3. Hydrosulphuret of ammonia produces in neutral, as 
 sulphuretted hydrogen does in alkaline solutions, a black 
 precipitate of SULPHURET OF NICKEL, (Ni S,) which is not 
 altogether insoluble in hydrosulphuret of ammonia, owing to 
 which property the fluid from which it has been precipita- 
 ted, presents always a brownish colour. Sulphuret of 
 nickel is dissolved with difficulty by hydrochloric acid, but 
 easily by aqua regia. 
 
 4. Potash produces a bright green precipitate of 
 HYDRATED OXIDE OF NICKEL, (Ni O, HO,) which is insolu- 
 ble in potash, and does not alter when exposed to the air. 
 Carbonate of ammonia re-dissolves this precipitate to a 
 
100 PROTOXIDE OF COBALT. 
 
 greenish-blue fluid, from which potash again precipitates 
 the nickel it contains, as a_ yellow-green hydrated oxide of 
 nickel. 
 
 5. Ammonia precipitates also HYDRATED OXIDE OF 
 NICKEL, but an excess of the precipitant easily re-dissolves 
 it to a blue fluid, as a double salt of oxide of nickel and 
 ammonia. Potash precipitates hydrated oxide of nickel 
 from this solution. 
 
 6. Cyanide of potassium produces a yellowish-green 
 precipitate of CYANIDE OF NICKEL, (Ni Cy,) which by an 
 excess of the precipitant is easily redissolved to a brownish- 
 yellow fluid, containing cyanide of nickel and cyanide of 
 potassium combined. Sulphuric acid and hydrochloric acid 
 again precipitate from this solution cyanide of nickel, 
 which is very difficultly soluble in an excess of these acids, 
 at a low temperature, 
 
 7. Borax and phosphate of soda and ammonia dissolve 
 compounds of oxide of nickel, in the outer flame of the 
 blow-pipe, giving rise to the formation of clear glasses of a 
 dark yellow colour? with a tinge of red-brown, which become 
 clearer and almost colourless on cooling. Addition of nitre 
 or carbonate of potash changes the colour to blue or to dark 
 purple. The glass which phosphate of soda and ammonia 
 forms with nickel remains unaltered when exposed to the 
 inner flame, but that of borax bepomes grey and troubled 
 owing to the reduction of nickel. 
 
 d. PROTOXIDE Or COBALT. (Co O,) 
 
 1. The protosalts of cobalt are blue in their anhydrous, 
 and of a characteristic bright red tint in their hydrated state. 
 Their solutions show their colour even when considerably 
 diluted. The soluble neutral salts redden litmus paper, 
 and are decomposed by a red heat. 
 
 2. Sulphuretted hydrogen does not precipitate acid so- 
 lutions of cobalt, and neutral solutions at the most, very 
 incompletely, when they contain weak acids ; these latter 
 precipitates are of a black colour. 
 
 3. Hydrosulphuret of ammonia precipitates from neutral, 
 as sulphuretted hydrogen do esfrom alkaline solutions, all 
 the cobalt they contain, as black SULPIIURET OF COBALT. 
 
PEROTOXIB& OT JjROtf- _ , ^ , , ^ 101 
 
 (Co S.) This substance is insoluble in alkalies" and hydro- 
 sulphuret of ammonia, difficultly soluble in hydrochloric 
 acid, easily soluble in aqua regia. 
 
 4. Potash produces in solutions of cobalt BLUE precipi- 
 tates of basic salts of cobalt, which become GREEN when 
 exposed to the air, owing to the absorption of oxygen, and 
 are converted into hydrates of a jjale red colour when 
 boiled. They are insoluble in potash. But neutral car- 
 bonate of ammonia dissolves them completely to intensely 
 violet-red fluids, in which potash does not cause any, or, at 
 least, but a very scanty precipitate. 
 
 5. Ammonia produces the same precipitate as potash, 
 but an excess of the precipitant redissolves it to a reddish- 
 brown fluid, in which potash does not cause any, or aUeast 
 but a very scanty, precipitate. 
 
 6. If to a solution of cobalt acidified with some hydro- 
 chloric acid, cyanide of potassium be added, a brownish- 
 white precipitate of PROTOCYANIDE OF COBALT is formed, 
 which by an excess of the precipitant, with presence of 
 free hydrocyanic acid, is easily dissolved to COBALTOCYA- 
 NIDE OF POTASSIUM. (Cy 6 Co 2 +3K.) Acids cause no 
 precipitation in the solutions of this salt. 
 
 7. Borax dissolves compounds of cobalt in the inner as 
 well as in the outer flame of the blow-pipe, TO CLEAR 
 SPLENDIDLY BLUE COLOURED GLASSES which appear almost 
 black, when cobalt is present in any considerable propor- 
 tion. This test is as delicate as it is characteristic. Phos- 
 phate of soda and ammonia manifest the same reaction, 
 but in a lesser degree. 
 
 . PROTOXIDE OF IRON. (Fe O.) 
 
 1. The protosalts of iron have a greenish colour ; their 
 solutions appear coloured only when quite concentrated. 
 The soluble neutral salts redden litmus paper and are de- 
 composed by a red heat. 
 
 2. Acid solutions are not precipitated by sulphuretted 
 hydrogen, and neutral solutions, with weak acids, at the 
 most but incompletely. These precipitates are of a black 
 colour. 
 
 3. Hydrosulphuret of ammonia precipitates from neu- 
 tral, as sulphuretted hydrogen does from alkaline solutions, 
 
102 ERpX!DE OP IRON. 
 
 all the iron they contain, as black SULPHURET OP IRON, 
 (Fe S,) which is insoluble in alkalies and alkaline sul- 
 phurets, but easy of solution in hydrochloric acid and nitric 
 acid. 
 
 4. Potash and ammonia produce a precipitate of HY- 
 DRATED PROTOXIDE OF IRON, (Fe O, HO,) which, in the 
 first moment, appears^lmost white, but, after a very short 
 time, becomes of a dirty green, by absorption of oxygen from 
 the air, and at last assumes a red-brown colour. The 
 presence of salts of ammonia prevents the precipitation by 
 potash partly, and that by ammonia totally. 
 
 Verrpcyanide of potassiun produces in solutions of 
 protoxide of iron a bluish-white precipitate of FERROCYA- 
 NIDB OF POTASSIUM AND IRON, (2 Cfy+K+3 Fe,) which, by 
 absorption of oxygen from the air, soon becomes blue. In 
 this change, all the potassium of three equivalents of the 
 compound, and one equivalent of iron, become oxidized, 
 and Prussian blue (3 Cfy+2 Fe 2 ) remains. Nitric acid 
 or chlorine causes this oxidation immediately. 
 
 6. Ferricyanide of potassium produces a splendidly 
 blue precipitate of FERRICYANIDE OF IRON, (2 Cfy-f-3 Fe.) 
 This precipitate does not differ in colour from Prussian 
 blue. It is insoluble in hydrochloric acid, but easily de- 
 composed by potash. When the solution of protosalt of 
 iron is highly dilute, the reagent imparts to it only a dark 
 bluish green colour. 
 
 7. Borax dissolves protosalts of iron in the oxidising 
 flame, forming DEEP RED GLASSES, the colour of which 
 changes to bottle 'green when exposed to the inner flame, 
 owing to the reduction of the first formed peroxide to 
 magnetic-oxide. Both tints disappear totally, or in a great 
 measure, when the glasses become cool. Phosphate of 
 soda and ammonia shows a similar relation to the proto- 
 salts of iron, but the colour of its glass vanishes even more 
 decidedly than is the case with borax. 
 
 /. PEROXIDE OF IRON. (Fe a O 3 .) 
 
 1. The persalts of iron are of a more or less red yel- 
 low colour. Their solutions present this colour even 
 when pretty highly diluted. The soluble neutral salts 
 redden litmus paper and are decomposed by heat. 
 
PEROXIDE OF IRON. 103 
 
 / 2. Sulphuretted hydrogen produces in neutral and acid 
 solutions a slight precipitate of SULPHUR, which renders the 
 solution turbid and imparts a milky white tint to it. Pe- 
 roxide of iron and sulphuretted hydrogen decompose each 
 other ; in this process the hydrogen withdraws from the 
 peroxide of iron, one-third of its oxygen combining with it 
 to form water ; the persalt of iron is thus converted into a 
 protosalt, and the sulphur of the decomposed sulphuretted 
 hydrogen separates. 
 
 3. Hydrosulphuret of ammonia precipitates from neu- 
 tral, as sulphuretted hydrogen does from alkaline solutions, 
 all the peroxide of iron they contain, as black SULPHURET 
 OF IRON ; this precipitation is preceded by the conversion 
 of the persalt into a protosalt. The reagent produces only 
 a blackish-green tint in the fluid, if the solution is very 
 dilute. The minutely divided sulphuret of iron subsides 
 in such cases only after the lapse of some time. For the 
 several degrees of solubility of sulphuret of iron in vari- 
 ous substances, vide e. (Protoxide of iron.) 3. 
 
 4. Potash and ammonia produce bulky red brown pre- 
 cipitates of HYDRATED PEROXIDE OF IRON, which are inso- 
 luble in an excess of the precipitant, as well as in salts of 
 ammonia. 
 
 / 5. Ferocyanide of potassium produces even in highly 
 - / dilute solutions a splendidly blue precipitate of SESQUIFER- 
 / ROCYANIDE OF IRON, (3 Cfy~h4 Fe,) (Prussian blue) which . 
 is insoluble in hydrochloric acid, but easily decomposed 
 ^ by potash, with precipitation of peroxide of iron. 
 
 6. Ferricyanide of potassium imparts a reddish-brown 
 tint to solutions of peroxide of iron, but it causes no pre- 
 cipitate. 
 
 7. The per salts of iron present the same appearances as 
 the protosalts, when exposed to the action of the blow-pipe 
 flame, vide e. (Protoxide of iron) 7. 
 
 Recapitulation and remarks. Of the metallic oxides 
 belonging to the fourth group, oxide of zinc alone is soluble 
 in potash. It is this property which distinguishes it from 
 the other oxides of this group, and connects it with those 
 of the third group. But it differs from oxide of chromium 
 and from alumina, inasmuch as sulphuretted hydrogen 
 precipitates it from its solutions in potash. This charac- 
 teristic property is the surest test of oxide of zinc. Pro- 
 
104 PEROXIDE OF IROIf. 
 
 toxide of manganese, oxide of nickel, protoxide of cobalt, 
 and protoxide of iron form with salts of ammonia double 
 salts, from which the metallic oxides are not precipitated 
 by free ammonia ; but peroxide of iron, just like the oxides 
 of the third group, is completely precipitated by ammonia, 
 even when salts of ammonia are present. Hence it follows, 
 in the first place, that by means of this property, manganese, 
 nickel and cobalt may be separated, as well from peroxide 
 of iron as from oxide of chromium and from alumina ; and, 
 in the second place, that, in order to separate these metals 
 from protoxide of iron, the latter substance must first be 
 peroxidized, which operation is best performed by boiling 
 its solution with nitric acid. The peroxide of iron differs 
 from oxide of chromium, and from alumina, inasmuch as it 
 is insoluble in potash ; and peroxide of iron may be distin- 
 guished from protoxide, by means of ferrocyanide of potas- 
 sium. Hydrated oxide of nickel and hydrated protoxide of 
 cobalt dissolve in carbonate of ammonia, whilst hydrated 
 protoxide of manganese is insoluble in this substance. We 
 may, therefore, by means of this solvent, separate the pro- 
 toxide of manganese from the two other oxides. The 
 brown tint assumed by the white hydrated protoxide when 
 exposed to the air, and the blow-pipe reactions, especially 
 that with soda, are the surest test of protoxide of manga- 
 nese. Cyanide of nickel, and cyanide of cobalt are soluble 
 in cyanide of potassium. But cyanide of nickel may be 
 precipitated from this solution by acids, which is not the 
 case with cyanide of cobalt. This property, i. e. the for- 
 mation of a precipitate in a solution of these two cyanides 
 in cyanide of potassium, by the addition of hydrochloric 
 acid, is, under all circumstances, a perfectly sure test of 
 the presence of nickel. Whether this precipitate be cyanide 
 of nickel or cobalticyanide of nickel, is quite immaterial 
 as far as the detection of nickel is concerned ; we have 
 only to bear in mind that no precipitate forms if cobalt 
 alone be contained in the solution, since cobalticyanide of 
 potassium is not decomposed by hydrochloric acid. To 
 explain the composition of the precipitates formed, and the 
 process in general, we will now proceed to consider and 
 examine three special cases, the difference of which de- 
 pends on the unequal relative proportion of the nickel and 
 the cobalt. 
 
PEROXIDE or IRON. 105 
 
 X Ni : Co = 3 eq. : 2 eq. 
 
 2, Ni : Co = 3 eq. : 2 eq.+x 
 
 3, Ni : Co = 3 eq. + x : 2 eq. 
 
 Consequently, we get in solution in the first case, one eq. : 
 of cobalticyanide of potassium, (Cy 6 , Co 2 + 3 K,) and 
 3 eq. : of cyanide of nickel and cyanide of potassium com- 
 bined, (Cy 3 Ni, + Cy 3 K,) and if we add hydrochloric acid 
 in excess to this solution, we obtain a dirty green precipi- 
 tate of cobalticyanide of nickel, (Cy 6 Co 2 +3 Ni,) which 
 contains all the nickel and cobalt of the solution ; in this 
 process the combination of cyanide of nickel and cyanide 
 of potassium is decomposed, and the potassium in the co- 
 balticyanide of potassium changes places with the nickel 
 in the cyanide of nickel. Besides the cobalticyanide of 
 nickel, chloride of potassium and hydrocyanic acid are 
 formed. In the second case we obtain also a precipitate of 
 cobalticyanide of nickel, but this precipitate, though con- 
 taining all the nickel, does not contain all the cobalt of the 
 solution, for the excess of cobalticyanide of potassium is 
 not decomposed. In the third case, at last, we obtain a pre- 
 cipitate of cobalticyanide of nickel, which contains all the 
 cobalt and a portion of the nickel, mixed with insoluble 
 cyanide of nickel, which contains the remaining part of 
 the nickel. The precipitate of cobaltcyanide of nickel has 
 been formed, as in the first case, whilst the cyanide of 
 nickel is formed by the decomposition of the double cy- 
 anide of nickel and potassium in excess. Hence it is evi- 
 dent, that nickel is, in all cases, a necessary condition to 
 the formation of a precipitate, and consequently that this 
 precipitate can leave no doubt as to its presence. As co- 
 balt may, under all circumstances, be safely and easily 
 detected by its characteristic properties before the blow- 
 pipe, any further indications for the mere detection of 
 either metal, would almost seem superfluous ; but since 
 we are now already far advanced towards the complete 
 separation of these two substances from each other, we 
 may as well briefly state how to effect it. In the first and 
 second of the above-mentioned cases, we have, after the ad- 
 dition of the hydrochloric acid, only to heat the fluid to- 
 gether with the therein suspended precipitate of cobalti- 
 cyanide of nickel, till the free hydrocyanic acid is expelled, 
 
106 OXIDE OF SILVER, &C. 
 
 (the cobalticyanide of nickel as well as the cobalticyanide 
 of potassium present in the second case, remain unaltered 
 during this operation ; ) and then we may, by addition of 
 caustic potash, easily decompose the cobalticyanide of 
 nickel, into cobalticyanide of potassium, which remains in 
 solution, and oxide of nickel which precipitates as hy- 
 drated oxide. But in the third case we must add a larger 
 quantity of hydrochloric acid, and boil the solution there- 
 with, till the cyanide of nickel contained in the precipitate 
 (which would only be incompletely decomposed by pot- 
 ash) is converted into chloride of nickel, and till the hy- 
 drocyanic acid, formed during this operation, is completely 
 expelled ; and then, after this preparatory process, we 
 may, by boiling with caustic potash, obtain all the nickel 
 as an insoluble hydrated oxide, and all the cobalt as soluble 
 cobalticyanide of potassium. Lastly, we must still men- 
 tion, that the oxides of the fourth group are not precipi- 
 tated by alkalies, if non-volatile organic substances, (such 
 as sugar, tartaric acid, &c.) are contained in their solu- 
 tions. The same is the case with alumina and oxide of 
 chromium. 
 
 89. 
 Fifth Group. 
 
 OXIDE OF SILVER, PROTOXIDE OF MERCURY, PEROXIDE OF 
 MERCURY, OXIDE OF LEAD, OXIDE OF BISMUTH, OXIDE OF 
 COPPER, OXIDE OF CADMIUM. 
 
 Properties of the group. The sulphurets correspond- 
 ing with the oxides of this group, are insoluble both in 
 dilute acids and in alkaline sulphurets. The solutions of 
 these oxides are, therefore, completely precipitated by 
 sulphuretted hydrogen, no matter whether their reaction be 
 neutral, alkaline, or acid. 
 
 We divide the oxides of this group into two sections, 
 and distinguish 
 
 1. OXIDES PRECIPITABLE BY HYDROCHLORIC ACID, viz. I 
 
 oxide of silver, protoxide of mercury, and oxide of lead, 
 from 
 
 2. OXIDES, NOT PRECIPITABLE BY HYDROCHLORIC ACID, 
 ivz. : peroxide of mercury, oxide of copper, oxide of bis- 
 
OXIDE OP SILVER. 107 
 
 muth, oxide of cadmium. Lead must be considered in 
 both sections, as the difficult solubility of its chloride 
 renders it possible to confound it with protoxide of mer- 
 cury and oxide of silver, without affording us .any means of 
 separating it completely from the oxides of the second 
 section. 
 
 90. 
 
 FIRST SECTION. OXIDES PRECIPITABLE BY HYDROCHLORIC 
 
 ACID. 
 
 Special Reactions. 
 
 a. OXIDE OF SILVER. (Ag 0.) 
 
 1. The salts of oxide of silver are fixed and colourless ; 
 most of them blacken when exposed to light. The soluble 
 neutral salts do not alter vegetable colours, and are decom- 
 posed at a red heat. 
 
 2. Sulphuretted hydrogen and hydrosulphuret of am- 
 monia precipitate black SULPHURET OF SILVER, (Ag S,) 
 which is insoluble in dilute acids, alkalies, alkaline sul- 
 phurets, and cyanide of potassium. Boiling concentrated 
 sulphuric acid easily decomposes and dissolves this pre- 
 cipitate, with separation of sulphur. 
 
 3. Potash and ammonia precipitate OXIDE OF SILVER, in 
 the form of a BRIGHT BROWN powder, which is insoluble 
 in potash, but easy of solution in ammonia. The presence 
 of salts of ammonia prevents this reaction either totally or 
 partly. 
 
 4. Hydrochloric acid and soluble chlorides produce a 
 white curdy precipitate of CHLORIDE OF SILVER. (Ag Cl.) 
 In very dilute solutions, this precipitate merely imparts to 
 the fluid a bluish white opalescent appearance. The white 
 chloride of silver, when exposed to light, acquires first a 
 violet tint, and at last a black colour, but without any alter- 
 ation in its composition ; it is insoluble in nitric acid, but 
 dissolves easily in ammonia, giving rise to the formation of 
 chloride of silver and ammonia. Acids precipitate it again 
 from this combination. Chloride of silver, when heated, 
 fuses without decomposition, forming a transparent horny 
 mass. 
 
108 PROTOXIDE OP MERCURY. 
 
 5. When silver compounds, mixed with carbonate of 
 soda, are on a charcoal support, exposed to the inner 
 flame of the blow-pipe, WHITE, SHINING, AND DUCTILE 
 METALLIC GLOBULES are obtained, whilst no incrustation 
 takes place. 
 
 b. PROTOXIDE OF MERCURY. (Hg 2 0.) 
 
 1. The salts of protoxide of mercury, when exposed to 
 a red heat, either volatilize without decomposition, or de- 
 compose ; in the latter case the mercury separated volatili- 
 zes in a metallic state. They are colourless. The soluble 
 salts, when neutral, redden litmus paper ; when mixed 
 with much water, they separate into insoluble basic and 
 soluble acid salts- 
 
 2. Sulphuretted hydrogen and hydrosulphuret of am- 
 monia produce black precipitates of SULPHURET OF MER- 
 CURY, (Hg 2 S,) which are insoluble, as well in dilute acids 
 as in alkaline sulphurets, and in cyanide of potassium. 
 Potash resolves this sulphuret into bisulphuret and glo- 
 bules of metallic mercury. Sulphuret of mercury is easily 
 decomposed and dissolved by aqua regia, but not by boil- 
 ing concentrated nitric acid. 
 
 3. Potash and ammonia produce black precipitates, 
 which are insoluble in an excess of the precipitants. The 
 potash precipitates consist of PROTOXIDE OF MERCURY ; 
 those of ammonia, of BASIC SALT OF PROTOXIDE OF MER- 
 CURY AND AMMONIA. 
 
 4. Hydrochloric acid and soluble chlorides precipitate 
 PROTOCHLORIDE OF MERCURY (Hg 2 Cl) as a shining white, 
 fine powder. Cold hydrochloric acid, and cold nitric 
 acid, do not dissolve this precipitate ; but it dissolves, al- 
 though very difficultly and slowly, when long boiled with 
 these acids, being converted by hydrochloric acid into 
 chloride of mercury, by nitric acid into chloride of mercury 
 and per-nitrate of mercury. Ammonia and potash decom- 
 pose protochloridc of mercury, giving rise to the forma- 
 tion of black protoxide of mercury. 
 
 5. If a drop of a neutral or feebly acid solution of prot- 
 oxide of mercury be poured on a clean and smooth surface 
 of copper, washed off after some time, and the spot rubbed 
 with cloth or paper, &c. &c., it will appear of a* SILVERY 
 
OXIDE OP LEAD. 109 
 
 WHITE COLOUR, with metallic lustre. This apparent sil- 
 vering vanishes when the copper is heated, owing to the 
 volatilization of the metallic mercury precipitated on its 
 surface. 
 
 6. Protochloride of tin produces in solutions of prot- 
 oxide of mercury, a gray precipitate of METALLIC MER- 
 CURY, which may be united into globules by heating and 
 agitating it, but most easily by boiling it with hydrochloric 
 acid. 
 
 7. If mercury compounds, intimately mixed with efflor- 
 esced carbonate of soda, and covered with a layer of 
 carbonate of soda in a distended glass-tube, are heated 
 before the blow-pipe, a decomposition always takes place 
 to the effect of liberating metallic mercury, which sublimes 
 as a gray crust above the heated part of the tube. The 
 fine particles of mercury unite into globules on this crust 
 being rubbed with a glass rod. 
 
 C. OXIDE OF LEAD. (Pb O.) 
 
 1. The salts of oxide of lead are colourless and not 
 volatile ; the soluble salts, when neutral, redden litmus 
 paper, and are decomposed at a red heat. 
 
 2. Sulphuretted hydrogen and hydrosulphuret of am- 
 monia produce black precipitates of SULPHURET OF LEAD, 
 (Pb.S,) which are insoluble in dilute acids, alkalies, alka- 
 line sulphurets, and cyanide of potassium. This sulphuret 
 of lead is decomposed by boiling concentrated nitric acid ; 
 all the lead is first converted into nitrate of lead, the 
 greater portion of the sulphur separates, another portion is 
 converted into sulphuric acid, and this again decomposes 
 a part of the nitrate of lead^ and thus, besides the precipi- 
 tated sulphur, sulphate of lead is formed, and remains 
 undissolved as a white powder. 
 
 3. Potash and ammonia throw down BASIC SALT OF 
 LEAD in the form of white precipitates, which are insolu- 
 ble in ammonia, and of difficult solution in potash. 
 
 4. Hydrochloric acid and soluble chlorides produce in 
 concentrated solutions heavy white precipitates of CHLO- 
 RIDE OF LEAD, (Pb Cl,) which are soluble in much water, 
 especially if the water be heated. This chloride of lead 
 
 5 
 
110 OXIDE OF LEAD. 
 
 is not altered by ammonia, and is more difficult of solution 
 in hydrochloric acid and in nitric acid than in water. 
 
 5. Sulphuric acid and sulphates produce white preci- 
 pitates of SULPHATE OF LEAD, (Pb O, SO 3 ,) which are 
 almost insoluble in water and dilute acids, but to a small 
 extent soluble in concentrated nitric acid, difficult of solu- 
 tion in boiling concentrated hydrochloric acid, and more 
 easily soluble in solution of potash. Salts of ammonia? 
 and especially sulphate of ammonia, prevent the precipita- 
 tion partly or altogether. 
 
 6. Chromate of potash produces a yellow precipitate of 
 CHROMATE OF LEAD, (Pb O, Cr O 3 ) which is easilysolu- 
 ble in potash, but insoluble in dilute nitric acid. 
 
 7. Lead compounds, mixed with carbonate of soda, and 
 on a charcoal support, exposed to the reducing blow-pipe 
 
 flame, very easily yield soft and ductile METALLIC GLO- 
 BULES ; whilst the coal is, at the same time, covered with 
 a YELLOW incrustation of OXIDE OF LEAD. 
 
 Recapitulation and remarks. The metallic oxides of 
 the first section of the fifth group are the most easily cha- 
 racterized in their corresponding chlorides, since the 
 divers relations of these different chlorides to ammonia 
 afford us means as well of detecting as of separating them 
 from each other. For chloride of silver, as we have stated, 
 is dissolved by ammonia, whilst protochloride of mercury 
 and chloride of lead remain undissolved. By adding nitric 
 acid to a solution of chloride of silver and ammonia, we 
 may again precipitate the chloride of silver ; and as this 
 reaction admits of no mistake, we want in fact no further 
 means for the detection of silver. Of the two remaining 
 chlorides, the protochloride of mercury is converted by 
 ammonia into black protoxide of mercury, whilst the chlo- 
 ride of lead remains unaltered. The new-formed protoxide 
 of mercury may be separated from the chloride of lead by 
 treating with nitric acid, whereby the protoxide of mercury 
 is dissolved ; or by boiling with water, when solution of 
 the chloride of lead takes place. These relations suffi- 
 ciently characterize the protoxide of mercury ; as further 
 tests for lead, its reaction with sulphuric acid or with 
 chromate of potash may be employed. 
 
PEROXIDE OF MERCURY. Ill 
 
 91. 
 
 SECOND SECTION OF THE FIFTH GROUP. OXIDES WHICH 
 ARE NOT PRECIPITATED BY HYDROCHLORIC ACID. 
 
 Special Reactions. 
 
 a. PEROXIDE OF MERCURY. (Hg O.) 
 
 1. The salts of peroxide of mercury volatilize when 
 heated to redness, some with, some without decomposi- 
 tion. Most of them are colourless. The neutral soluble 
 salts redden litmus paper. The nitrate and sulphate of 
 peroxide of mercury are decomposed by much water 
 into soluble acid and insoluble basic salts. 
 
 2. If sulphuretted hydrogen^ or hydrosulphuret of am- 
 monia, be added in very small proportions to solutions 
 of peroxide of mercury, and these solutions be then agi- 
 tated, a perfectly white precipitate is obtained. The 
 addition of somewhat large quantities of these reagents 
 causes the precipitate to acquire a yellow, orange, or 
 brown-red colour, as more or less of them is added ; an 
 excess of the precipitate produces a black precipitate of 
 
 BISULPHURET OF MERCURY, CINNABAR. (Hg S.) This 
 
 variation of colour depends on the different proportions 
 added of sulphuretted hydrogen, distinguishing the perox- 
 ide of mercury from all other substances. It is caused 
 by the formation, at first, of a white-coloured double com- 
 pound of bisulphuret of mercury, with still undecompos- 
 ed salt of peroxide of mercury, which then, becoming 
 more and more mixed with black bisulphuret, causes the 
 precipitate successively to assume the various tints de- 
 scribed above. Bisulphuret of mercury is not dissolved 
 by hydrosulphuret of ammonia, nor by cyanide of potas- 
 sium ; it is quite insoluble in hydrochloric acid and nitric 
 acid, even on being boiled with these acids. Potash 
 ley dissolves it completely, and aqua regia decomposes 
 and dissolves it with facility. 
 
 3. Potash, when added in insufficient quantity to neutral 
 or feebly acid solutions of peroxide of mercury, yields with 
 them a RED-BROWN precipitate, which acquires a TELLOW 
 tint when the reagent is added in excess. The red-brown 
 precipitate is a BASIC SALT ; the yellow, on the contrary, 
 consists of pure HYDRATED PEROXIDE OF MERCURY. (Hg. 
 
112 OXIDE OF COPPER. 
 
 O, HO.) An excess of the precipitant does not re-dis- 
 solve these precipitates. In very acid solutions this reac- 
 tion either does not take place at all, or is at least incom- 
 plete. If salts of ammonia be present, the precipitates 
 formed are neither red, brown, nor yellow, but white ; 
 consisting of basic compounds of peroxide of mercury and 
 ammonia. 
 
 4. Ammonia causes the same WHITE PRECIPITATE, 
 which potash produces when salts of ammonia are pre- 
 sent. 
 
 5. Protochloride of tin, when added in small propor- 
 tions to salts of peroxide of mercury, causes a reduc- 
 tiori of this peroxide to protoxide, in consequence of which 
 a white precipitate of PROTOCHLORIDE OF MERCURY forms ; 
 but when added in excess, it completely withdraws the 
 oxygen and acid or the salt-radical from the mercury and 
 causes the latter to separate in a metallic form, just as is 
 the case with protoxide of mercury, (vide 90, b 6.) 
 The pfecipitate, therefore, which in the first place was 
 white, acquires now a gray tint, and may be united into 
 globules of metallic mercury, by being boiled with hydro- 
 chloric acid. 
 
 5. The salts of peroxide of mercury present the same 
 relation to metallic copper as those of the protoxide ; 
 and the same is the case with regard to their behaviour 
 before the blow-pipe, when mixed with carbonate of soda. 
 
 b. OXIDE OF COPPER. (Cu O.) 
 
 1. The salts of oxide of copper undergo decomposition, 
 even at a gentle red heat, with the exception of blue 
 vitriol, which can bear a somewhat higher temperature. 
 They present in their anhydrous state a white, but as 
 hydrates, a blue or green colour, which their solutions 
 still retain, though rather highly diluted. Most of the 
 neutral salts of oxide of copper are soluble in water ; those 
 which are soluble redden litmus paper. 
 
 2. Sulphuretted hydrogen and liydrosulphuret of am- 
 monia produce, under any circumstances, brown-black 
 precipitates of BISULPHTJRET OF COPPER (Cu S.) This 
 substance is insoluble in dilute acids and caustic alkalies, 
 as well as in hot solutions of sulphuret of potassium and 
 
OXIDE OP COPPER. 113 
 
 of sulphuret of sodium ; but it is not quite insoluble in 
 hydrosulphuret of ammonia, on account of which this 
 reagent is not applicable for the separation of bisulphuret 
 of copper from other metallic sulphurets. Boiling concen- 
 trated nitric acid readily decomposes and dissolves bi- 
 sulphuret of copper. Solution of cyanide of potassium 
 dissolves it completely. 
 
 3. Potash produces a bright blue, bulky precipitate of 
 HYDRATED OXIDE OF COPPER, (Cu O, HO.) In highly 
 concentrated solutions this precipitate becomes, on addition 
 of potash in excess, black, and loses its bulkiness, even at 
 a low temperature, after some time, but at any rate on being 
 boiled with the fluid wherein it is suspended. In this 
 process the hydrated oxide is converted into oxide. 
 
 4. Ammonia, when added in a small proportion, produces 
 a GREENISH BLUE precipitate, consisting of a BASIC SALT OF 
 COPPER. This precipitate is easily redissolved when the 
 addition of ammonia is continued and a PERFECTLY TRANS- 
 PARENT MAGNIFICENTLY AZURE BLUE SOLUTION obtained, 
 
 which owes its colour to the new-formed BASIC AMMONIACAL 
 SALT OF OXIDE OF COPPER. This tint vanishes only when 
 the solution is highly diluted. Potash causes in this blue 
 solution (at a low temperature only after having been 
 allowed to stand at rest for some time) a precipitate of 
 BLUE HYDRATED OXIDE, but at the boiling point, it precipi- 
 tates the entire copper as BLACK OXIDE. Carbonate of 
 ammonia presents the same relation to salts of copper, as 
 pure ammonia. 
 
 5. Ferrocyanide of potassium produces even in highly- 
 dilute solutions, a reddish-brown precipitate of FERROCY- 
 ANIDE OF COPPER (Cfy + 2 Cu) which is insoluble in dilute 
 acids, but decomposed by potash. 
 
 6. Metallic iron, when in contact with concentrated 
 solutions of copper, is almost immediately covered with a 
 
 COPPERY RED CRUST OF METALLIC COPPER J but when 
 
 the copper solution is highly dilute, this coating only takes 
 place after the lapse of some time. This test is very deli- 
 cate, but especially so, when the solution contains a free 
 acid, (e. g. hydrochloric acid.) 
 
 7. If copper compounds, mixed with carbonate of soda, 
 be exposed on a charcoal support to the reducing flame of 
 
114 OXIDE OF BISMUTH. 
 
 the blow-pipe, METALLIC COPPER is obtained without simul- 
 taneous incrustation of the coal. The best method of 
 examining this copper, so as to leave no doubt of its 
 presence, is to triturate the fused mass together with the 
 surrounding particles of the charcoal support, in a mortar 
 with some water, and then to wash off the charcoal powder. 
 The coppery-red metallic spangles will remain. 
 
 C. OXIDE OF BISMUTH. (Bi O.) 
 
 1. The salts of bismuth are not volatile, with the excep- 
 tion of a few, (chloride of bismuth.) Most of them de- 
 compose at a red heat. They are colourless ; some are 
 soluble in water, whilst others are insoluble. The soluble 
 salts, when neutral redden litmus paper, and are d-ecompos- 
 ed by much water into soluble acid and insoluble basic salts. 
 
 2. Sulphuretted hydrogen and hydrosulphuret of 
 ammonia produce, under all circumstances, black precipi- 
 tates of SULPEIURET OF BISMUTH (Bi S) which are insoluble 
 in dilute acids, alkalies, alkaline sulphurets, and cyanide of 
 potassium. Boiling concentrated nitric acid readily de- 
 composes and dissolves it. 
 
 3. Potash and ammonia throw down from solutions of 
 salts of bismuth, HYDRATED OXIDE OF BISMUTH (BiO, HO) 
 as a white precipitate, which is, insoluble in an excess of 
 he precipitants. 
 
 4. Chromate of potash precipitates CHROMATE OF BIS- 
 MUTH (Bi O, Cr O 3 ) as a yellow powder. This substance 
 differs from chromate of lead, inasmuch as it is soluble in 
 dilute nitric acid, and insoluble in potash. 
 
 5. The reaction which particularly characterizes the 
 oxide of bismuth, is the decomposition of its neutral salts 
 by water into acid soluble and basic insoluble salts. For 
 when a solution of bismuth is diluted w T ith much water, a 
 shining white precipitate immediately forms, provided free 
 acid be not present in a too large proportion. This re- 
 action is the most susceptible with chloride of bismuth, the 
 basic chloride of bismuth being almost absolutely insoluble 
 in water. If water causes no precipitate in nitric solu- 
 tions of. bismuth, owing to the presence of a too large 
 quantity of free acid, precipitation may immediately be 
 induced by the addition of basic acetate of lead in excess. 
 
OXIDE OF CADMIUM. 115 
 
 Before recurring to this means, we must, of course, be 
 convinced of the absence of sulphuric acid, &c. &c. The 
 precipitates of bismuth are easily to be distinguished by 
 means of their insolubility in tartaric acid, from the basic 
 salts of antimony which are formed under analogous cir- 
 cumstances. 
 
 6. If bismuth compounds, mixed with carbonate of soda, 
 be exposed on a charcoal support, to the reducing flame, 
 BRITTLE GRAINS OF BISMUTH are obtained, which fly into 
 pieces under the stroke of the hammer. The charcoal at 
 the same time becomes covered with a slight yellow in- 
 crustation of OXID3 OF BISMUTH- 
 
 d. OXIDE OF CADMIUM. (Cd 0.) 
 
 1. The salts of oxide of cadmium are either colourless 
 or white ; most of them are soluble in water. The soluble 
 salts, when neutral, redden litmus paper and decompose 
 at a red heat. 
 
 2. Sulphuretted hydrogen and hydrosulphuret of am- 
 monia produce, under all circumstances, precipitates of a 
 rich yellow colour, consisting of sulphuret of- cadmium 
 (Cd, S.) This substance is insoluble in dilute acids, in 
 alkalies, alkaline sulphurets, and cyanide of potassium. 
 Boiling concentrated nitric acid readily decomposes and 
 dissolves it. 
 
 3. Potash produces a white precipitate of HYDRATED 
 OXIDE OF CADMIUM (Cd O, HO) which is insoluble in an 
 excess of the precipitant. 
 
 4. Ammonia also precipitates white HYDRATED OXIDE OF 
 CADMIUM, but readily redissolves into a colourless fluid, 
 when added in excess. 
 
 5. Carbonate of potash and carbonate of ammonia pro- 
 duce white precipitates of CARBONATE OF CADMIUM (Cd O, 
 CO 2 ) which are insoluble in an excess of the precipitants. 
 The presence of salts of ammonia does not prevent the 
 formation of these precipitates. 
 
 6. If cadmium compounds mixed with carbonate of 
 soda be exposed on a charcoal support, to the reducing 
 
 jlame, the charcoal becomes covered with a REDDISH YEL- 
 LOW incrustation of OXIDE OF CADMIUM, owing to the re- 
 
 
116 OXIDE OP CADMIUM. 
 
 duced metal immediately volatilizing, and then becoming 
 reoxidized in passing through the oxidizing flame. 
 
 Recapitulation and remarks. The metallic oxides of 
 the second section of the fifthgroup may, as we have 
 stated, be completely separated, by means of hydrochloric 
 acid, from protoxide of mercury and oxide of silver, but 
 only incompletely from oxide of lead. The peroxide of 
 Tnercury is distinguished from the other oxides of this 
 section, by the insolubility of its bisulphuret in boiling 
 nitric acid. This property affords a convenient means for 
 its separation. Moreover, the reactions with protoxide of 
 tin, or with metallic copper, as well as those in the dry 
 way, readily admit of its detection when the protoxide has 
 been previously removed. 
 
 Of the still remaining oxides, those of copper and cad- 
 mium are distinguished, inasmuch as the precipitates 
 which ammonia causes in their solutions, are soluble in an 
 excess .of ammonia, whilst the precipitates which this re- 
 agent produces in solutions of lead and bismuth, are not 
 redissolved by an excess of the precipitant. The oxide of 
 bismuth may be separated from the oxide of lead by means 
 of sulphuric acid, but is most safely detected by the de- 
 composibility of its salts by water. The other tests of 
 lead have already been stated in the first section of this 
 group. The oxide of copper may be separated from the 
 oxide of cadmium, by means of carbonate of ammonia ; 
 the former is especially characterized by the reactions with 
 ferrocyanide of potassium and with iron, as well as by its 
 relations before the blow-pipe ; and oxide of cadmium may 
 always be detected by its yellow sulphuret, which is in- 
 soluble in hydrosulphuret of ammonia, and by the charac- 
 teristic incrustation with which it covers charcoal when 
 exposed to the reducing flame. For a separation of the 
 oxides of the fifth group from each other, by means of 
 cyanide of potassium, we refer to the second section of 
 Part II. 
 
PEROXIDE OF GOLD. 1 17 
 
 92. 
 Sixth Group. 
 
 PEROXiDE OF GOLD, PEROXIDE OF PLATINUM, OXIDE OF 
 ANTIMONY, PEROXIDE OF TIN, PROTOXIDE OF TIN, 
 ARSENIOU3 AND ARSENIC ACID.* 
 
 Properties of the group. The sulphurets correspond- 
 ing with the oxides of the sixth group are insoluble in dilute 
 acids. They combine with alkaline sulphurets, forming 
 soluble sulphur salts, in which compounds they perform 
 the part of an acid. Sulphuretted hydrogen, therefore, 
 precipitates them completely from acidified, but not from 
 alkaline solutions. The precipitated sulphurets dissolve 
 in hydrosulphuret of ammonia, sulphuret of potassium, &c 
 &c., and are again precipitated from these solutions by the 
 addition of acids. 
 
 We divicfe the oxides of this group into two classes, and 
 distinguish, 
 
 1. OXIDES THE CORRESPONDING SULPHURETS OP'WHICH 
 ARE INSOLUBLE IN HYDROCHLORIC ACID AND IN NITRIC 
 
 ACID, viz. peroxide of gold and peroxide of platinum, from 
 
 2. THOSE THE CORRESPONDING SULPHURETS OF WHICH 
 ARE SOLUBLE IN HYDROCHLORIC ACID OR NITRIC ACID, 
 viz- oxide of antimony, protoxide and peroxide of tin| 
 arsenious and arsenic acid. 
 
 93. 
 
 1 First Class. 
 Special Reactions. 
 
 a. PEROXIDE OF GOLD. (Au 3 .) 
 
 1. Salts of gold with oxygen acids are, at present, almost 
 unknown. The haloid salts of gold are yellow, and their 
 
 * The two acids of arsenic will be again referred to, when we 
 treat of the relations between acids and reagents. We join them 
 here to the metallic oxides, since the relation of sulphuret of arsenic 
 easily admits of their being confounded with several oxides of the 
 sixth group, and because in analysis we always obtain the sulphuret 
 of arsenic as a precipitate, together with sulphuret of antimony, sul- 
 phuret oftin, &c. &c. 
 5* 
 
118 PEROXIDE OF PLATINUM. 
 
 solutions present this tint up to a high degree of dilution. 
 They all readily decompose at a red heat ; the soluble salts, 
 when neutral, redden litmus paper. 
 
 2. Sulphuretted hydrogen precipitates from neutral and 
 acid solutions all the gold they contain, as black SULPHURET 
 OP GOLD (Au S 3 ) which is insoluble in potash and in any 
 single acid, but soluble in alkaline sulphurets and in aqua 
 regia. 
 
 3. Hydrosulphuret of amm,onia produces the same pre- 
 cipitate. A considerable" excess of the precipitant redis- 
 solves it. 
 
 4. Potash in excess causes no precipitation, but a small 
 proportion of potash produces in concentrated solutions, 
 especially when heated, a reddish yellow precipitate of 
 PEROXIDE OF GOLD, which is always mixed with an auric 
 salt of cihloride of gold, as well as with potash. 
 
 5. Ammonia produces also only in concentrated solu- 
 tions, reddish yellow precipitates of AURATE OF AMMONIA 
 (fulminating gold.) 
 
 6. Protocldoride of tin, containing perchloride of tin, 
 produces even in highly dilute solutions of gold, a purple- 
 red precipitate or tint at least, which sometimes inclines 
 more to violet or to brown-red. This precipitate has re- 
 ceived the name of PURPLE OF CASSIUS ; it is a mixture 
 of peroxide of tin and metallic gold, and is insoluble in 
 hydrochloric acid. 
 
 7. Protosalts of iron reduce the peroxide of gold when 
 added to its solutions, and precipitate metallic gold as a 
 very fine brown powder, which shows a metallic lustre, 
 when pressed upon with the blade of a knife, or when 
 rubbed. The fluid in which the precipitate is suspended, 
 appears of a blackish-blue colour, by transmitted light. 
 
 b. PEROXIDE OF PLATINUM. (Pt Oz.) 
 
 1 . The persalts of platinum decompose at a red heat. 
 They are of a red-brown colour, which their solutions still 
 show, though considerably diluted. The soluble salts when 
 neutral redden litmus paper. 
 
 2. Sulphuretted hydrogen precipitates from acid and 
 neutral solutions (but not from alkaline solutions) after 
 
OXIDE OP ANTIMONY. 119 
 
 the lapse of some time blackish-brown SULPHURET OP PLA- 
 TINUM (Pt 82.) Potash and alkaline sulphurets dissolve 
 It when added greatly in excess. Sulphuret of platinum 
 is insoluble in hydrochloric acid as well as in nitric acid, 
 but dissolves readily in aqua regia. 
 
 3. Hydrosulphuret of ammonia produces the same pre- 
 cipitate, which completely redissolves in a large excess of 
 the precipitant. Acids precipitate it again unaltered from 
 this solution. 
 
 4. Potash and ammonia produce in solutions of platinum 
 when not too highly dilute, yellow crystalline precipitates 
 
 of CHLORIDE OF PLATINUM AND POTASSIUM and of CHLO- 
 RIDE OF PLATINUM AND AMMONIA, which are insoluble in 
 acids, but soluble in an excess of the precipitants, upon 
 the application of heat. The presence of free hydrochloric 
 acid promotes the precipitation in a high degree, by effect- 
 ing the conversion of the free alkalies into chlorides. 
 
 5. Protochloride of tin imparts an INTENSE DARK BROWN- 
 ISH RED COLOUR to solutions of persalts of platinum, but 
 without yielding a precipitate ; this reaction is owing to a 
 reduction of the peroxide or the perchloride to protoxide 
 or protochloride. 
 
 Recapitulation and remarks. The reactions of gold 
 and platinum afford, at least partly, the means of detecting 
 these metals as well|when many other oxides are present, 
 as also and especially, when platinum and gold are con- 
 tained in one and the same solution. Protochloride of tin 
 and protoxide of iron must be mentioned here as particu- 
 larly characteristic tests of gold, and with regard to pla- 
 tinum the same may be said of potash and ammonia with 
 the presence of free hydrochloric acid, or what, in fact, is 
 the same, of chloride of potassium and muriate of am- 
 monia. 
 
 94. 
 
 Second Class of the Sixth Group. 
 Special Reactions. 
 
 a. OXIDE OF ANTIMONY. (Sb Os.) 
 
 1 . The salts of oxide of antimony partly decompose at 
 a red heat ; the haloid salts volatilize readily, and without 
 
120 OXIDE OF ANTIMONY. 
 
 undergoing decomposition. The soluble neural salts of 
 antimony redden litmus paper. The solution of oxide of 
 antimony in hydrochloric acid is characterized by the na- 
 ture of the decomposition it undergoes when diluted with 
 water ; in this decomposition, an acid salt remains in solu- 
 tion whilst a basic salt is thrown down as a white, bulky 
 precipitate, which, however, after some time, becomes 
 dense and crystalline. Tartaric acid readily dissolves 
 this precipitate, and, consequently, prevents its precipita- 
 tion when added to the solution before the dilution with 
 water. It is by this property that the basic protochloride 
 of antimony is distinguished from the basic salts of bis- 
 muth formed under analogous circumstances. The oxide 
 of antimony, in whatever manner it may have been pre- 
 pared, is completely soluble in a hot solution of bitartrate 
 of potash.- 
 
 2. Sulphuretted Hydrogen precipitates the oxide of an- 
 timony from neutral solutions very incompletely, from al- 
 kaline solutions not at all, but from acid solutions com- 
 pletely, as orange-red SULPHURET OF ANTIMONY (Sb S 3 .) 
 This precipitate is readily dissolved by potash and by al- 
 kaline sulphurets, especially if the latter contain sulphur 
 in excess, whilst it is almost insoluble in ammonia, and 
 totally so in bicarbonate of ammonia, when free from any 
 admixture of sulphur, as well as from sulphantimonious and 
 sulphantimonic acid. It is insoluble in dilute acids. Con- 
 centrated boiling hydrochloric acid dissolves it, with evo- 
 lution of sulphuretted hydrogen gas. When heated, with 
 free access of air, it is converted into a mixture of anti- 
 monious acid with sulphuret of antimony. When defla- 
 grated with saltpetre, it yields sulphate of potash and an- 
 timoniate of potash. If a potash solution of sulphuret of 
 antimony be boiled together with oxide of copper, sul- 
 phuret of copper is formed, and oxide of antimony dis- 
 solved in potash remains in solution. 
 
 3. Hydrosulphuret* of ammonia produces an orange- 
 red precipitate of SULPHURET OF ANTIMONY, which readily 
 redissolves in an excess of the precipitant. Acids pre- 
 cipitate from this solution the sulphuret of antimony unal- 
 tered. But the colour of this second precipitate usually 
 appears somewhat lighter, owing to an admixture of sul- 
 phuf. " ', ' 
 
OXIDE OF ANTIMONY. 121 
 
 4. Potash, ammonia^ carbonate of potash, and carbonate 
 of ammonia, throw down from the solutions of simple 
 salts of oxide of antimony, but not, at least not immedi- 
 ately, from those of tartar emetic or analogous compounds, 
 a white and bulky precipitate of HYDRATED OXIDE OF 
 ANTIMONY Sb O 3 , HO) which readily redissolves in an 
 excess of potash, but is very difficult of solution in an ex- 
 cess of the other three precipitants. 
 
 5. Metallic zinc precipitates from all solutions of oxide 
 of antimony, unless containing free nitric acid, METALLIC 
 ANTIMONY as a BLACK POWDER. But if they contain free 
 nitric acid, a precipitate of oxide of antimony forms simul- 
 taneuiisly with the metallic precipitate. 
 
 6. If a solution of oxide of antimony is mixed with zinc 
 and sulphuric acid, the zinc oxidizes not only at the ex- 
 pense of the oxygen of the water, but also at the expens e 
 of that of the oxide of antimony. Antimony, therefore, 
 separates in its METALLIC STATE, but a portion of the 
 metal in the moment of its separation combines with the 
 liberated hydrogen of the water, forming ANTIMONIURETTED 
 HYDROGEN (Sb H. { .) Ifthis operation be conducted in a 
 gas-evolution flask, connected by means of a perforated cork 
 with one limb of a bent tube, the other limb of which ends 
 in a finely drawn-out point, pinched off at the top,*) and 
 the hydrogen passing through this fine aperture, be kindled, 
 after all atmospheric air has been previously expelled, the 
 flame appears of a bluish-green, owing to the antimony 
 separating in a state of intense heat, during the combustion 
 of the antimoniuretted hydrogen ; white fumes of oxide of 
 antimony rise from the flame, which readily condense upon 
 cold substances, and are not dissolved by water. If a cold 
 substance (such as a porcelain plate) be depressed upon the 
 flame, a deep black and almost lustreless spot of metallic 
 antimony in a state of minute division is formed upon the 
 surface of the plate. If the tube through which the gas is 
 passing be heated to redness in the middle, the bluish- 
 
 * In very minute and exact experiments, it is necessary further to 
 transmit the gas through another connecting tube, loosely filled with 
 cotton, in order to prevent it from carrying with it any moisture with 
 which it may be charged, into the emission part of the tube. Vide 
 engraving of Marsh's apparatus for the reduction of arsenic, 94 d 7. 
 
122 PROTOXIDE OF TIN. 
 
 green tint of the flame disappears, and a metallic mirror 
 of antimony of silvery lustre is formed within the tube on 
 both sides of the heated spot. If a stream of dry sulphu- 
 retted hydrogen be now very slowly transmitted through 
 this tube, and the mirror be heated by a spirit-lamp, from 
 its outer towards its inner extremity, i. e. in a direction 
 opposite to that of the gas stream, the mirror of antimony 
 changes into sulphuret of antimony, which appears of a 
 more or less red-yellow colour, and almost black when in 
 thick layers. If a weak stream of dry hydrochloric acid 
 gas be then transmitted through the same glass tube, the 
 sulphuret of antimony disappears, immediately, when only 
 present in thin layers, and, after a few seconds, when the 
 incrustation is somewhat thicker. For sulphuret of anti- 
 mony readily decomposes with hydrochloric acid gas, and 
 the nascent chloride of antimony is very volatile in the 
 stream of hydrochloric acid gas. If this gas stream be 
 transmitted through water, the presence of antimony in the 
 latter may easily be proved by means of sulphuretted hy- 
 drogen. By this combination of reactions, antimony may 
 be distinguished with certainty from all other metals. 
 
 7. If compounds of antimony mixed with carbonate of 
 soda, on a charcoal support, be exposed to the reducing 
 blow-pipe flame, BRITTLE GLOBULES OF METALLIC ANTI- 
 MONY are obtained. At the same time, volatilization of 
 the reduced and reoxidized metal takes place, which, even 
 after the removal of the test specimen from the flame, con- 
 tinues for some time, and becomes especially evident when 
 a stream of air is directed by means of the blow-pipe 
 upon the surface of the cooling mass. The oxide formed 
 is partly deposed on the charcoal as a white crust, and 
 partly surrounds the metallic globule in the form of fine 
 crystalline needles. 
 
 b. PROTOXIDE OF TIN. (Sn O.) 
 
 1. The protosalts of tin are colourless, and decompose 
 when heated. The soluble salts when neutral, redden 
 litmus paper. When solutions of neutral stannous salts 
 are diluted with water, they become turbid and of a milky- 
 white colour, owing to their decomposition into soluble 
 acid and insoluble basic salts. The addition of hydro- 
 chloric acid causes the milkiness to disappear. 
 
PROTOXIDE OF TIN. 123 
 
 2. Sulphuretted hydrogen precipitates from neutral and 
 acid, but not from alkaline solutions, dark brown SUL- 
 PHURET OF TIN, (Sn S,) which is soluble as well in potash 
 and in alkaline sulphurets, especially in such as contain 
 larger proportions of sulphur, as also in concentrated boil- 
 ing hydrochloric acid. Boiling nitric acid converts it into 
 insoluble peroxide of tin. - 
 
 3. Hydrosulphuret of ammonia occasions the same pre- 
 cipitate of SULPHURET OF TIN, which very sparingly dis- 
 solves in an excess of the precipitant. If the hydrosul- 
 phuret of ammonia has already turned yellow, i. e, if it 
 contains an excess of sulphur, or if finely powdered sulphur 
 be added, the solution is much facilitated. From this 
 solution, in hydrosulphuret of ammonia, with excess of 
 sulphur, acids precipitate yellow bisulphuret of tin mixed 
 with sulphur. 
 
 4. Potash, ammonia, carbonate of potash, and carbonate 
 of ammonia, produce a white and bulky precipitate of 
 HYDRATED PROTOXIDE OF TIN, (Sn O, HO,) which readily 
 dissolves in an excess of potash, but is insoluble in an 
 excess of the other three precipitants. 
 
 5. Per chloride of gold produces in solutions of pro- 
 tochloride or protoxide of tin, a precipitate or tinge of 
 PURPLE OF CASSIUS, on the addition of some nitric acid, 
 (without the application of heat,) vide 93, a. 6. 
 
 6. If to a solution of protochloride or protoxide of tin, 
 solution of perchloride of mercury be added in excess, a 
 white precipitate of PROTOCHLORIDE OF MERCURY will be 
 formed owing to the salt of tin depriving the perchloride of 
 mercury of half its chlorine. 
 
 7. If proto-compounds of tin be mixed with carbonate 
 of soda and some borax, or better still, with equal parts of 
 carbonate of soda and cyanide of potassium, and then, on 
 a charcoal support, be exposed to the inner blow-pipe 
 
 flame, ductile grains of METALLIC TIN will be obtained, 
 without simultaneous incrustation. They may be most 
 easily detected by scraping off the specimen and the par- 
 ti cles surrounding, that part of the charcoal which con- 
 tained the specimen, strongly triturating them in a mortar* 
 and washing the coal off from the metallic particles. 
 
124 PEROXIDE OF TIN. 
 
 C. PEROXIDE OF TIN. (Sn 2 .) 
 
 1. Peroxide of tin exists in two modifications which ex- 
 hibit a different relation to solvents. When precipitated 
 from its salts, by alkalies, it is easily soluble both in pot- 
 ash and acids, but when produced by oxidation of metallic 
 tin by means of nitric acid, it is insoluble in these solvents, 
 (the precipitated oxide of tin also becomes insoluble on 
 being heated to redness.) The insoluble modification is 
 converted into the soluble, by fusion with carbonate of 
 soda. - 
 
 2. The persalts of tin are colourless and decompose at a 
 red heat. The soluble neutral persalts of tin redden litmus 
 paper. 
 
 3. Sulphuretted hydrogen throws down, from acid and 
 neutral solutions, a yellow precipitate of BISULPHURET OF 
 TIN, (Sn 82.) Alkaline solutions are not precipitated. 
 The bisulphuret of tin is soluble in pure alkalies, in alka- 
 line carbonates and bicarbonates, in alkaline sulphurets, 
 and in concentrated and boiling hydrochloric acid. Nitric 
 acid converts it into insoluble peroxide of tin. On defla- 
 grating bisulphuret of tin with nitre, sulphate of potash, and 
 stannate of potash are formed. If a solution of bisulphuret 
 of tin in potash be boiled with oxide of copper, sulphuret 
 of copper and peroxide of tin will be formed, which latter 
 substance remains in solution in the potash. 
 
 4. Hydrosulphuret of ammonia produces the same pre- 
 cipitate of BISULPHURET OF TIN, which readily redissolves in 
 an excess of the precipitant. Acids reprecipitate from their 
 solution, the bisulphuret of tin in its unaltered state. 
 
 5. Potash and ammonia, carbonate of potash and car- 
 bonate of ammonia, precipitate a white HYDRATED PE- 
 ROXIDE OF TIN, which readily redissolves in potash and car- 
 bonate of potash (in excess,) but is sparingly soluble in 
 ammonia, and quite insoluble in carbonate of ammonia. 
 
 6. Metallic zinc precipitates, from solutions of perchlo- 
 ride or persalts of tin, when containing no free nitric acid, ME- 
 TALLIC TIN, in the shapeof small gray leaves or as a spongy 
 mass. If, on the contrary, nitric acid be present, white 
 peroxide or a mixture of metallic tin and of peroxide of tin 
 will precipitate. 
 
ARSENIOUS ACID. 125 
 
 7. The per-compounds of tin exhibit the same proper- 
 ties before the blow-pipe as the proto-compounds. 
 
 d. ARSENIOUS ACID. (AsOs.) 
 
 1 . Arsenious acid on being heated volatilizes in white 
 inodorous vapours. Its salts, on being heated to redness, 
 generally are decomposed into fixed arseniates and arsenic, 
 which volatilizes. Of the arsenites, only those with an 
 alkaline base are soluble. 
 
 2. Sulphuretted hydrogen precipitates the solutions of 
 arsenious acid and of neutral arsenites, slowly and incom- 
 pletely, but when a free acid is present, totally and imme- 
 diately ; these precipitates have a lively yellow colour. 
 Alkaline solutions are not precipitated. The yellow pre- 
 cipitate of SULPHO-ARSENIOUS ACID, (As S 3 ,) is readily 
 and completely redissolved in pure alkalies, in alkaline 
 carbonates and bicarbonates, and in alkaline sulphurets, 
 but is almost insoluble in hydrochloric acid. Boiling nitric 
 acid readily decomposes and dissolves it. On deflagrating 
 it with carbonate of soda and nitrate of potash, arseniated 
 alkali and sulphated alkali are obtained. When a solution 
 of sulpharsenious acid in potash is boiled with oxide of 
 copper, sulphuret of copper and arseniate of potash are 
 formed ; and when the same solution is boiled with pure 
 oxide of bismuth, or with a carbonate of basic' nitrate of 
 the same substance, sulphuret of bismuth and arsenious 
 acid are formed. If sulpharsenious acid be mixed with 
 from three to four parts of carbonate of soda, with the ad- 
 dition of some water, and the magma be then spread over 
 some small glass splinters, and the latter, after having been 
 well dried, be rapidly heated to redness, in a glass tube, 
 (c. vide sketch,) through which dry hydrogen gas is trans- 
 mitted, half of the arsenic contained in the mixture forms 
 a metallic mirror within the tube. For when fusing two 
 eq. of sulpharsenious acid, together with four eq. of soda 
 sulpharsenico sulphuret of sodium and arsenite of soda are 
 formed ; heating these products in hydrogen gas, all the 
 arsenic is expelled, if the heat is strong and continuous. 
 This method, although a great portion of the reduced 
 arsenic is carried off, suspended in the hydrogen gas, 
 yields, nevertheless, very good results. If the hydrogen 
 
126 ARSENIOUS ACID 
 
 gas be kindled at the exit aperture of the tube c, and a 
 cold porcelain plate depressed on the flame, this arsenic 
 (carried away with the hydrogen gas) will condense upon 
 the plate. If a red heat be applied to another part of the 
 tube Cj more towards its anterior aperture, (the part first 
 heated being at the same time maintained at a red heat,) 
 another sublimate will be formed beyond the heated spot, 
 the particles of arsenic carried away with the stream of the 
 hydrogen gas, being reconverted, at the red hot spot, into ar- 
 senic vapours in a state of expansion, and thus condensing 
 again as a sublimate, on coming into contact with the cold part 
 of the glass tube. If the heat thus simultaneously applied 
 to two parts of the tube be strong, whilst the stream of 
 the hydrogen gas is feeble, scarcely any arsenic will be 
 carried away with the gas. No arseniuretted hydrogen is 
 formed in this operation and those who explain the pheno- 
 mena just described, by the formation of arseniuretted hy- 
 drogen, are in error. (Fresenius and Babo.) The appa- 
 ratus may be constructed as in the annexed sketch. 
 
 a is the evolution flask, b a tube containing chloride of cal- 
 cium, c the tube in which, at the point d, the glass splin- 
 ter with the specimen is placed. This part is then (the 
 apparatus being completely filled with pure hydrogen gas) 
 exposed to a slight heat, at first, in order to expel all 
 moisture, and then suddenly to a very strong heat, (this is 
 best done with a blow-pipe,) to prevent the sublimation 
 of undecomposed sulphuret of arsenic. The metallic mfrror 
 is formed near the point e. 
 
ARSENIOUS ACID. 127 
 
 3. Hydrosulphuret of ammonia causes also the forma- 
 tion of SULPHARSENIOUS ACID. In neutral or alkaline so- 
 lutions, however, this substance is not precipitated, but 
 remains in solution as sulpharsenico sulphuret of ammo- 
 nia. On the addition of free acid it precipitates imme- 
 diately from this solution. 
 
 4. Nitrate of silver produces in neutral solutions of the 
 arsenites, a yellow precipitate of ARSENITE OF SILVER, 
 (2 Ag O, As O.) which is soluble both in dilute nitric 
 acid and in ammonia. AMMONIO-NJTRATE OF SILVER 
 yields the same precipitate with solutions of arsenious acid 
 or arsenites when containing free acid. 
 
 5. Sulphate of copper and ammonio sulphate of copper 
 produce, under the same circumstances as the salts of 
 silver, yellow reen precipitates of ARSENITE OF COPPER, 
 (2 Cu O, As O 3 .) 
 
 6. If arsenious acid be dissolved in solution of caustic 
 potash in excess, or if the solution of an alkaline arsenite 
 be mixed with caustic potash, and a few drops of a dilute 
 solution of sulphate of copper be added and the mixture 
 boiled, a red precipitate of protoxide of copper is formed, 
 and arseniate of potash remains in solution. This reac- 
 tion is highly sensible, provided only a minute quantity of 
 solution of blue vitriol be used* If the red precipitate of 
 protoxide of copper is no longer distinctly visible on the 
 light falling through the tube in which the solution is con- 
 tained, it will yet be distinctly seen on looking in at the 
 top of the tube. That this reaction, though really im- 
 portant in individual cases as a confirmatory test of arse- 
 nious acid, and especially as a means of distinguishing 
 arsenious acid from arsenic acid, yet cannot be employed 
 as a means of directly detecting the presence of arsenic, 
 is a matter of course, since grape sugar and other organic 
 substances in the same manner separate protoxide of cop- 
 per from salts of copper. 
 
 7. If an acid or neutral solution of arsenious acid, or of 
 an arsenite, be mixed with zinc, water, and sulphuric acid, 
 ARSENIURETTED HYDROGEN (As Ha) will be formed ; for 
 the mode of its formation we refer to 94, a 6. This pro- 
 perty of arsenic affords us a most delicate test for its de- 
 tection, and a highly important means for its isolation. The 
 
128 
 
 ARSENIOUS ACID. 
 
 operation is, under all circumstances, conducted in the ap- 
 paratus alluded to, 94, a 6, of which we annex a sketch. 
 
 a is the evolution flask, containing fragments of metal- 
 lic zinc, and water; 6 a funnel tube, through which the 
 sulphuric acid, and afterwards the liquor to be tested for 
 arsenic, are poured into the flask ; c is a glass tube, loosely 
 filled with smooth cotton, % to which a bent tube, d, is fitted 
 by means of a perforated cork ; this tube is drawn out into 
 a point, at its emission extremity, e, and pinched off at the 
 top. When'the evolution of hydrogen has proceeded for 
 some considerable time, so that it may safely be inferred 
 that all atmospheric air has been expelled from the appar- 
 atus, the gas is kindled at the emission aperture of the 
 tube, d, e. (It is advisable to envelop the flask with a 
 piece of cloth before kindling the gas, as an eifectua means 
 of preventing any accident, should an explosion take place. ) 
 It is absolutely necessary to ascertain, first, whether the 
 zinc and the sulphuric acid are quite free from arsenic. 
 For this purpose, 1st, a porcelain plate is depressed upon 
 the flame, and,. 2d, the tube d e is heated to redness in the 
 middle, the limb e being turned into a horizontal position 
 for this purpose. If no incrustation be formed, neither on 
 the plate nor in the tube, the zinc and sulphuric acid con- 
 tain no arsenic. The liquor to be tested is then introduced 
 into the flask through the funnel tube. If it contain arsenic, 
 
ARSENIOUS ACID. 129 
 
 arseinuretted hydrogen will be evolved together with the 
 hydrogen, imparting a bluish tint to the flame, owing to the 
 arsenic separating at a red heat. At the same time white 
 fumes of arsenious acid are observed, which condense upon 
 cold objects. If a porcelain plate be now depressed upon 
 the flame, black spots are formed on its surface, owing to 
 the reduced and not yet reoxidized arsenic condensing on 
 the plate. (Tide antimony, 94, a 6.) Arsenic spots are 
 of a rather blackish brown colour, and bright metallic lus- 
 tre ; whilst those of antimony are of a deep black colour, 
 and but very feebly lustrous. If the tube d e be heated to 
 redness in the middle of its limb d, the arsenic will con- 
 dense in the cold part of the tube, forming. a particularly 
 beautiful and distinct metallic crust, which is of a darker 
 appearance and less silvery than that formed by antimony 
 under similar circumstances ; it may, moreover, be clearly 
 detected by the characteristic odour of garlic which is per- 
 ceived, if the tube is cut off near the incrustation, and the 
 latter then volatilized by heat. The characteristic odour 
 of alcarsin (vide 10 seq.) is even a safer indication than 
 that of garlic. If the metallic spots of crust formed on the 
 porcelain plate seem to indicate the presence of arsenic, it 
 is still necessary to make quite sure that it is really a^nic 
 and not antimony we have before us, for even the charac- 
 teristic odour of garlic or alcarsin is not sufficient to set 
 all doubts at rest as to this point. The following are the 
 best methods of ascertaining the presence of arsenic be- 
 yond doubt : 
 
 #, fine and distinct metallic mirror is formed within the 
 tube through which the arseniuretted hydrog^i passes, on 
 heating its middle part to redness. A very feeble stream 
 of dry sulphuretted hydrogen is then transmitted through 
 this tube, with simultaneous application of the heat of a 
 spirit-lamp to the metallic crust, from its outer towards its 
 inner extremity. If-arsenic alone be present, a yellow sul- 
 plmret of arsenic will be formed within the tube ; and if 
 antimony alone be present, an orange or black sulphuret of 
 antimony : but if both metals be present, both sulphurets 
 will be formed side by side, the sulphuret of arsenic, as the 
 more volatile, always preceding the sulphuret of anti- 
 mony. Not long ago, this conversion of antimony and 
 
130 ARSENIOUS ACID. 
 
 arsenic into sulphurets was suggested as the surest means 
 of distinguishing these two metals from each other. Ex- 
 perience has, however, taught us that these differences in 
 colour and volatility are not striking enough to prevent the 
 possibility of mistakes. But if dry hydrochloric acid gas 
 be transmitted through the tube containing the deposit 
 under examination, without application of heat, no altera- 
 tion whatever will take place if sulphuret of arsenic alone is 
 present, even if the gas be transmitted through the tube 
 for a considerable time. If sulphuret of antimony alone be 
 present, it will entirely vanish, and if both sulphurets be 
 present, the sulphuret of antimony will vanish immediately, 
 whilst the yellow sulphuret of arsenic remains. If a small 
 quantity of ammonia be then introduced into the tube, the 
 sulphuret of arsenic will dissolve, and may thus easily be 
 distinguished from the sulphur, which, peradventure, may 
 have separated. My personal experience has convinced 
 me of the infallibility of these tests for the detection of 
 arsenic. 
 
 b. The limb e (vide sketch of the apparatus) is turned 
 into an horizontal position, and the gas kindled and made 
 to burn in a small glass receiver, having a capacity of about 
 twe^e ounces. This receiver is placed in a beaker glass 
 filled with cold water, and constantly turned and moved, 
 so as to prevent its becoming hot. After some time, 
 when the oxygen in the receiver becomes exhausted, and 
 the flame grows feeble, another is substituted for the first, 
 and several are filled in this manner. They contain, 1st, 
 arsenious acid alone, or, 2d, oxide of antimony alone, or, 
 3d, both together. If the first be the case, the white sub- 
 limate obtained will completely dissolve in hot water, ami 
 the solution may then be further tested for arsenic. In the 
 second case, nothing will dissolve, nor in the third, if the 
 oxide of antimony is present in sufficient quantity, as this 
 gives rise to the formation of arsenite of antimony. The 
 arsenic in this last case may be detected by dissolving the 
 sublimate in slightly dilute solution of potash, and adding 
 sulphuretted hydrogen first, and then bicarbonate of am- 
 monia in excess* All the antimony will precipitate as. 
 sulphuret of antimony, whilst the sulphuret of arsenic 
 remains dissolved in the excess of bicarbonate of ammonia. 
 
ARSENIOUS ACID. 131 
 
 The sulphuret of arsenic precipitates on the addition of 
 hydrochloric acid to the solution, till an acid reaction 
 becomes manifest. Marsh was the first who suggested 
 the method of detecting arsenic by the production of arse- 
 niuretted hydrogen. 
 
 8. If arsenious acid or an arsenite be mixed with car- 
 bonate of soda and charcoal, and the mixture (which 
 must be perfectly dry) be then heated over a spirit-lamp 
 to redness, in a well-dried glass tube, closed at one end, 
 and drawn out into a point at the other, the charcoal will 
 oxidize at the expense of the oxygen of the arsenious acid, 
 and arsenic will become liberated, which volatilizes and 
 condenses above the heated part of the tube, forming a 
 more or less dark brown metallic mirror of great lustre. 
 This crust may be further driven on in the tube by gra- 
 dually heating the latter to redness towards its emission 
 aperture, and may thus finally be expelled, when the cha- 
 racteristic odour of arsenic (on volatilizing in the air) will 
 afford a further proof of its presence. For the reduction 
 of the free arsenious acid, a mere fragment of charcoal is 
 used, instead of carbonate of soda and charcoal ; the arse- 
 nious acid is introduced into the drawn-out point of the 
 tube, the fragment of charcoal is placed over it and heated 
 to redness ; heat is then applied to the point of the tube. 
 This process has the advantage over the former of not 
 soiling the tube, which is done when operating with car- 
 bonate of soda and charcoal. The non-appearance of the 
 metallic crust is not always a sure sign that no arsenic is 
 present, when testing a supposed arsenite by means of 
 carbonate of soda and charcoal, as there are several com- 
 pounds of arsenious acid, especially of those with heavy 
 metallic oxides, as e. g. oxide of iron, which do not yield 
 metallic mirrors. 
 
 9. If arsenites, or arsenious acid, or a sulphuret of arse- 
 nic, be fused together with a mixture of dry carbonate of 1 
 soda and cyanide of potassium, all the arsenic contained 
 in the test specimen will become reduced, under all cir- 
 cumstances, and sometimes the bases also, if their proper- 
 ties admit of this reduction ; in this process the oxygen 
 which these substances lose, converts a portion of the 
 cyanide of potassium into cyanate of potash. The opera- 
 
132 ARSENIOUS ACID. 
 
 tion is conducted in the following manner : the arsenic 
 compound, which must be perfectly dry, is put into a 
 small glass tube, expanded into a bulb at one end, and 
 covered with six fimes its quantity of the mixture of per- 
 fectly dry carbonate of soda and cyanide of potassium. 
 The quantity of the whole mass must not fill more than 
 half of the bulb, or else the cyanide of potassium, when 
 in fusion, will get into the tube. The heat of a spirit- 
 lamp is then applied to the bulb, and continued, as the 
 arsenic often requires some time for its complete sublima- 
 tion. The mirrors which are obtained in this process are 
 of exceeding purity. These crusts are produced from all 
 arsenites, the bases of which remain either altogether un- 
 reduced, or are converted into such arseniurets as partly 
 >r totally lose their arsenic on the simple application of 
 heat. This method may be especially recommended on 
 account of its simplicity, neatness, and cleanness, as well 
 as for the certainty of its results, even though but minute 
 quantities of arsenic be present. It is especially adapted 
 for the direct production of arsenic from sulphuret of arse- 
 nic, and is, in this respect, superior to all other methods 
 suggested. The most exact results are obtained by 
 placing the sulphuret of arsenic, rubbed together with 
 twelve times its amount of a mixture consisting of three 
 parts of dry carbonate of potash, and one part of cya- 
 nide of potassium, into a glass tube, open at its anterior 
 extremity. 
 
 The mixture is best introduced into the tube by means of 
 a slip of paper, folded into the shape of a gutter. This 
 paper containing the mixture is inserted into the tube, and 
 the latter then being turned half way round its axis, the 
 powder falls into it (at the spot a c) without soiling any 
 other part. The tube is then gently heated in its entire 
 length, transmitting at the same time a very slow stream 
 of dry carbonic acid gas (dried by means of sulphuric acid) 
 through it, till all water is expelled. The spot b is then 
 heated to a feeble degree of redness, when, as this point is 
 
ARSENFOUS ACID. 133 
 
 attained, the mixture is heated from a towards c, by means 
 of a second lamp. The arsenic condenses at d, forming 
 a crust of admirable purity. In this manner the most 
 distinct metallic mirrors may be obtained, from one 260th 
 part of a grain of sulphuret of arsenic, and even less. 
 Fresenius and Babo. 
 
 10. If to arsenious acid (either in solid form or in solu- 
 tion) some acetic acid, and then some potash in excess, 
 be added, the mixture evaporated to dryness, and the resi- 
 due heated to redness in a tube, alcarsin (Oxide of cacodyl. 
 C 4 H 6 As + O) will be formed, which is immediately 
 detected by its characteristic and insupportable odour. 
 This odour immediately changes into that not less charac- 
 teristic of chloride of cacodyl, when the contents of the 
 tube are again exposed to heat, with the addition of a few 
 drops of protochloride of tin. This property affords us 
 also a means of further testing the metallic crusts obtained 
 by Marsh's apparatus. They are for this purpose boiled 
 with water containing atmospheric air, till completely 
 dissolved; acetic acid, and potash in excess, are then 
 addexl to the solution, which is evaporated to dryness, the 
 residue heated to redness in a small tube, and the further 
 operation conducted as just now stated. BUNSEN has 
 recently suggested this method of testing crusts of arse- 
 nic ; these are, however, but slowly dissolved in boiling 
 water containing air. 
 
 11. If arsenious acid or an arsenite be exposed on a 
 charcoal support to the reducing flame of a blow-pipe^ a 
 highly characteristic odour of garlic will be perceived, 
 especially if some carbonate of soda be added to the test 
 specimen. This odour is owing to the reduction and reox- 
 idation of the arsenic, and enables us to detect even minute 
 quantities of this substance. This test, however, cannot 
 be implicitly relied upon. The garlic odour belongs nei- 
 ther to the vapour of arsenious acid, nor to those of arsenic, 
 but probably to a lower degree of oxidation of the latter 
 substance. It is always perceived on exposing arsenic to 
 heat, with the free access of air, 
 
 6 
 
134 ARSEJSIC ACID, 
 
 . ARSENIC ACID. (As 5 J 
 
 1. Arsenic acid and the arseniates are volatile only at a 
 very high degree of heat. Nearly all the arseniates are 
 colourless, and insoluble in water, with the exception of the 
 alkaline arseniates. 
 
 2. Sulphuretted hydrogen does not precipitate alkaline 
 and neutral solutions ; in acid solutions it produces a yel- 
 low precipitate of SULPHARSENIC ACID, (As S s .) In dilute 
 solutions this precipitate is often formed after the lapse of 
 a considerable time (twenty -four hours.) Heat promotes 
 its separation. The sulpharsenic acid shows the same 
 relations as the sulpharsenious acid to these solvents and 
 means of decomposition which we have mentioned when 
 treating of the latter substance. If to a solution of free 
 arsenic acid or of an arseniate, sulphurous acid is added, 
 this latter substance decomposes with the arsenic acid, 
 giving rise to the formation of arsenious acid and sulphuric 
 acid. If sulphuretted hydrogen, and if needed, an acid be 
 then added, all the arsenic will immediately precipitate as 
 sulpharsenious acid. 
 
 3. Hydrosulphuret of ammonia in neutral and alkaline 
 solutions, converts arsenic acid into sulpharsenic acid, 
 which remains in solution, as sulpharsenico-sulphuret of 
 ammonium. This compound is decomposed on the addition 
 of an acid, and sulpharsenic acid precipitates. This pre- 
 cipitation is more rapid than that from acid solutions 
 by means of sulphuretted hydrogen. It is promoted by 
 heat. 
 
 4. Nitrate of silver produces in neutral solutions of the 
 arseniates highly characteristic reddish-brown precipitates 
 of ARSENIATE OF SILVER, (3 Ag O, As O 5 ) which is solu- 
 ble both in dilute nitric acid and in ammonia. Ammonio- 
 nitrate of silver yields the same precipitate with solutions 
 of arsenic acid or arseniates. 
 
 5. Ammonia-sulphate of copper produces under the same 
 circumstances as the salts of silver, greenish blue pre- 
 cipitates Of ARSENIATE OF COPPER. (2 Cu O, As O 5 .) 
 
 6. The arseniates present the same relations as ihe 
 arsenites to hydrogen, to carbonate of soda t and char- 
 coal, to cyanide of potassium and before the blow-pipe. 
 
ARSENIC ACID. 135 
 
 Recapitulation and remarks. The separation and safe 
 detection of the oxides belonging to the second section of 
 the sixth group, and especially of oxide of tin, presents 
 difficulties under certain circumstances. The protoxide 
 of tin may be easily and safely detected by its reaction 
 with perchloride of gold, even in the presence of other 
 oxides. The separation of peroxide of tin from oxide of 
 antimony succeeds pretty well in the humid way by means 
 of a hot solution of bitartrate of potash, or of a solution of 
 free tartaric acid ; but it succeeds only when the peroxide 
 of tin is present in the form of the modification obtained by 
 the action of nitric acid on metallic tin. To obtain this 
 modification, it is necessary to reduce the substance under 
 examination by means of zinc, if this substance is not an 
 alloy ; in this reduction the presence of nitric acid must be 
 carefully avoided. The method of separating the sulphu- 
 rets by means of ammonia gives rise to errors, as the higher 
 degrees of sulphuration of the antimony are soluble in 
 ammonia ; and even the simple sulphuret of antimony is not 
 absolutely insoluble in it, when mixed with a trace of free 
 sulphur, which cannot easily be avoided. The presence 
 of peroxide of tin is certain only when a ductile metallic 
 grain of tin is obtained in the reducing flame ; its ductility 
 in this case enables us to distinguish it from antimony. This 
 reduction is very easily effected before the blow-pipe by 
 means of a mixture of equal parts of cyanide of potassium 
 and carbonate of soda ; but care should be taken that the 
 peroxide of tin be not mixed with nitre, which causes it to 
 deflagrate, &c. Peroxide of tin and oxide of antimony 
 may be detected before the blow-pipe, even if combined, 
 the antimony being distinguished by its characteristic oxi- 
 dation crust, and the tin by its ductility after the volatili- 
 zation of the antimony* Inexperienced students, however, 
 generally fail in this method. Antimony may, moreover, be 
 detected by the decomposition of chloride of antimony by 
 means of water, and by the colour of its sulphuret. If the 
 sulphuret of antimony is mixed with a large proportion of 
 any of the sulphur-compounds of arsenic, this latter mark 
 of "detection is unsafe. In this case the mixed sulphurets 
 may be heated to redness, which causes the sulphuret of 
 arsenic to volatilize ; and the residue may be dissolved in 
 
136 ARSENIC ACID. 
 
 hydrochloric acid, and this solution again tested by means 
 of sulphuretted hydrogen. 
 
 The detection of arsenic upon the whole can by no 
 means be said to be difficult ; but, nevertheless, frequent 
 errors take place, especially if we content ourselves with 
 drawing definite conclusions from individual reactions, 
 such as the characteristic odour when heated on charcoal. 
 We must, therefore, lay it down as a rule that the presence 
 of arsenic can only be proved by a concurrence of the 
 various reactions, and especially by the formation of me- 
 tallic arsenic. It may be pretty completely separated from 
 tin by deflagrating the sulphurets with carbonate of soda 
 and nitre. The presence of tin does not, however, prevent 
 the detection of arsenic. But the case is different with 
 antimony, especially in testing by Marsh's method, which 
 is now so generally followed. A metallic mirror obtained 
 by Marsh's apparatus ought, therefore, never to be consi- 
 dered as a proof of the presence of arsenic, if further tests 
 do not give the most certain conviction that the metallic 
 crust is indeed produced by arsenic. And this conviction 
 is sometimes very difficult to be obtained, when we operate 
 upon very minute quantities, so that the formerly used 
 methods of reduction are by far superior to Marsh's me- 
 thod, as far as certainty is concerned, although it cannot 
 be denied that they do not equal it in delicacy, nor in 
 rapidity and convenience. The complete separation of 
 arsenic from antimony may be effected by means of bicar- 
 bonate of ammonia, the simple sulphuret of antimony being 
 insoluble in this substance, whilst sulphuret of arsenic 
 readily dissolves in it. But this method of distinction 
 yields a positive and certain result only in a few cases, 
 viz. in those where we are quite sure that the simple sul- 
 phuret of antimony cannot be mixed with a higher sul- 
 phuret of antimony, nor with free sulphur, whilst in all 
 other cases it easily gives rise to mistakes. It is, there- 
 fore, exceedingly well adapted for the testing of the 
 products of combustion obtained by means of Marsh's 
 apparatus, (vide 94, d 7, &,) but it cannot be used for the 
 separation of the sulphurets obtained in the usual way. 
 And even less complete are those separations of antimony 
 from arsenic which are founded on the relations of their 
 
RELATIONS OF THE ACIDS TO REAGENTS. 137 
 
 sulphurets to concentrated hydrochloric acid or to caustic 
 ammonia. The separation of both metals from each other 
 does not succeed even by dissolving the sulphuret in 
 potash, and boiling the solution with oxide of copper. A 
 far more certain result may be obtained by deflagrating 
 the sulphurets with carbonate of soda and nitre, treating 
 the mass obtained with water, filtering, and decomposing 
 with nitric acid the basic alkaline antimoniates, which the 
 filtrate contains in solution to a small extent. By means 
 of this process almost all the antimony is obtained as an 
 insoluble, and all the arsenic as a soluble compound. 
 
 The presence of antimony cannot easily give rise to any 
 errors in the reduction of arsenites or arseniates, by means 
 of carbonate of soda and charcoal, or cyanide of potassium 
 and carbonate of soda. The reduction of sulphuret of 
 arsenic by means of cyanide of potassium and carbonate 
 of soda, in a stream of carbonic acid gas, does not admit 
 even of the possibility of confounding arsenic with anti- 
 mony, and is of all methods best adapted to yield a most 
 conclusive proof of the presence of arsenic. Nitrate of 
 silver is the safest test for distinguishing arsenious acid 
 from arsenic acid, in their aqueous solutions. If extra- 
 neous substances be contained in the solution, they prevent 
 its being directly tested for arsenious or arsenic acid ; in 
 that case the solution must be completely precipitated by 
 means of sulphuretted hydrogen, and the sulphurets 
 obtained dissolved in liquor of potash ; this solution must 
 then be boiled with pure oxide of bismuth, or with the 
 carbonate or basic nitrate of bismuth ; the liquid is then 
 filtered off from the sulphuret of bismuth formed ; one 
 part of the filtered liquid is tested for arsenious acid by 
 means of sulphate of copper, according to the method 
 described 94, d 6, and the other part for arsenic acid, by 
 means of nitrate of silver, after neutralization with nitric 
 acid. 
 
 B. RELATIONS OF THE ACIDS TO REAGENTS. 
 
 95. 
 
 We divide the reagents which serve for the determina- 
 tion of acids, in like manner as those used for the deter- 
 
138 INORGANIC ACIDS. 
 
 mination of the bases into GENERAL REAGENTS, i. e. such 
 as indicate the GROUP to which the acid under examina- 
 tion belongs ; and SPECIAL REAGENTS, i. e. such as en- 
 able us to detect the INDIVIDUAL ACIDS. The determina- 
 tion and limitation of the groups can hardly be made with 
 the same degree of exactness with the acids as with the 
 bases. 
 
 The two principal groups into which acids are divided 
 are that of INORGANIC and that of ORGANIC ACIDS. No 
 characteristic distinction can, however, be selected which 
 is applicable through the entire series ; for we can neither 
 select the ternary composition as a distinguishing mark of 
 organic acids, nor can we define organic acids to be such 
 as require for their formation the co-operation of the vital 
 power, for this definition not only leaves us in doubt as to 
 a great many acids, for instance, formic acid, uric acid, 
 &c., but it is in itself altogether unscientific, since all the 
 vital processes in the animal and vegetable body are, in 
 fact, merely modified chemical processes. We shall, 
 therefore, select, as the characteristic mark by which we 
 divide organic from inorganic acids, the properties they 
 exhibit at a high temperature, calling those organic acids, 
 the salts of which (especially those with alkaline bases 
 or bases of the alkaline earths) are decomposed at a red 
 heat, with separation of carbon. This mark of distinction 
 has the advantage of being easily perceived, and of en- 
 abling us by a very simple preliminary experiment imme- 
 diately to decide upon the principal group to which an 
 acid belongs. 
 
 1. INORGANIC ACIDS. 
 First Group. 
 
 ACIDS WHICH ARE PRECIPITATED FROM THEIR NEUTRAL 
 SOLUTIONS BY CHLORIDE OF BARIUM '. ArSCUlC Add, 
 
 Arsenious Acid, Chromic Acid, Sulphuric Acid, Phos- 
 phoric Acid, Boracic Acid, Oxalic Acid, Hydrofluoric 
 Acid, Carbonic Acid, Silicic Acid. 
 
 We subdivide this group into four classes, as follow : 
 1. Acids which are decomposed, in their acid solutions, 
 by sulphuretted hydrogen, and which we have, there- 
 
CHROMIC ACID, 139 
 
 fore, already remarked upon, when treating of the 
 bases, viz. ARSENIOUS ACID, ARSENIC ACID, and CHRO- 
 MIC ACLD. 
 
 S. Acids which are not decomposed, in their acid solu- 
 tions, by sulphuretted hydrogen, and the barytes com- 
 pounds of which are insoluble in hydrochloric acid. 
 SULPHURIC ACID alone belongs to this class. 
 
 3. Acids which are not decomposed, in their acid solu- 
 
 tions, by sulphuretted hydrogen, and the barytes com- 
 pounds of which are dissolved by hydrochloric acid, 
 WITHOUT DECOMPOSITION: these are PHOSPHORIC 
 
 ACID, BGRACIC ACID, OXALIC ACID, and HYDROFLUORIC. 
 
 (Although we intend to treat of oxalic acid also in the 
 organic group, yet we must consider this acid, in the 
 inorganic group too, since its salts have the property 
 of being decomposed at a red heat, without real car- 
 bonization, and it might, therefore, easily foe over- 
 looked as an organic acid.) 
 
 4. Acids which are not decomposed, in their acid solu- 
 
 tions, by sulphuretted hydrogen, and the barytes salts 
 of which are soluble in hydrochloric acid, WITH DE- 
 COMPOSITION: CARBONIC ACID, SILICIC ACID. 
 
 First Section of the First Group ef the Inorganic 
 
 Acids. 
 
 96. 
 
 a. The ARSENIOUS ACID and ARSENIC ACID, are, as we 
 have stated, decomposed by sulphuretted hydrogen, so as 
 to separate their corresponding sulphurets. On account 
 of this property, we have considered them together 
 with the bases, as it leads to confounding them with the 
 metallic oxides rather than with other acids* (Vide 93.) 
 
 6. CHROMIC ACID. (Cr O 3 .) 
 
 1. The chromates are all red or yellow ; most of them 
 are insoluble in water. Some of them are decomposed at 
 a red heat ; those with an alkaline base are fixed, and solu- 
 ble in water ; the solutions of the neutral chromates are 
 yellow, those of the acid chromates are red. These tints 
 
140 CHROMIC ACID. 
 
 are still visible in highly dilute solutions. The yellow 
 colour of a neutral solution changes into red on the addi- 
 tion of a mineral acid, owing to the formation of an acid 
 salt. 
 
 2. Sulphuretted hydrogen reduces the chromic acid, as 
 Well when free as combined in solution, so as to give rise 
 to the formation of oxide of chromium, water, and sulphuric 
 acid, with precipitation of sulphur. Heat promotes this 
 decomposition. If no free acid is present, only a portion 
 of the oxide of chromium formed is kept in solution by the 
 sulphuric acid formed at the same time, and a greenish- 
 gray precipitate is obtained, consisting of a mixture of 
 hydrated oxide of chromium and sulphur. But if free 
 acid is present, a far less considerable precipitate of pure 
 sulphur is obtained. The salt of oxide of chromium formed 
 imparts a green tint to the fluid, in either case. 
 
 3. Chromic acid may be reduced to chromic oxide by 
 means of many other substances, especially by sulphurous 
 acid, or by being heated with hydrochloric acid, particu- 
 larly on the addition of alcohol, (whereupon hydrochloric 
 ether and aldehyde escape,) or by metallic zinc, or by 
 heating with tartaric acid, oxalic acid, &c. All these re- 
 actions are clearly characterized by the red or yellow colour 
 of the solution changing into the green tint of the salt of 
 oxide of chromium. 
 
 4. Chloride of barium produces a yellowish white 
 precipitate of CHROMATE OF BARYTES (Ba 0, Cr 3 ) 
 which is soluble in hydrochloric and in nitric acid. 
 
 5. Nitrate of silver produces a dark purple precipitate 
 of CHROMATE OF SILVER (Ag O, Cr O 8 .) which is soluble 
 in nitric acid and in ammonia. 
 
 6. Acetate of lead produces a yellow precipitate of 
 CHROMATE OF LEAD (Pb O, Cr O 3 ) which is soluble in 
 potash, and sparingly soluble in dilute nitric acid. The 
 yellow colour of this precipitate changes to red, on the ad- 
 dition of ammonia. 
 
 7. If insoluble chromates be fused with carbonate of 
 soda and nitre, and the fused mass dissolved in water, .a 
 YELLOW coloured fluid will be obtained, the colour of which 
 is owing to the dissolved alkaline chromate ; on the addi- 
 
SULPHURIC ACID. 141 
 
 tion of an acid, this colour changes to red. The oxides 
 remain either in their pure state or as carbonates* 
 
 Remarks. When testing for bases we always find the 
 chromic acid as chromic oxide, since sulphuretted hydrogen 
 converts the acid into the oxide. The colour of the solution 
 is so characteristic, that a further testing for it is almost 
 unnecessary. If we have any reason to suppose that chro- 
 mic acid is present in a substance under examination, and 
 if metallic oxides are at the same time in the solution, we 
 prefer reducing the chromic acid by means of hydrochloric 
 acid and alcohol, to effecting this reduction by sulphuretted 
 hydrogen. The reactions with salts of silver and of lead 
 afford a safe test in aqueous solutions. 
 
 Second Section of the First Group of the Inorganic Acids. 
 
 97. 
 
 SULPHURIC ACID. (S O 3 .) 
 
 1. The sulphates are, for the most part, soluble in 
 water ; the insoluble sulphates are generally white, the 
 soluble sulphates are for the most part colourless in their 
 crystalline state. The sulphates of alkalies and of alka- 
 line earths are not decomposed by a red heat. 
 
 2. Chloride of barium produces in solutions of sul- 
 phuric acid and sulphates, even when extremely dilute, a 
 heavy white precipitate of SULPHATE OF BARYTES (Ba O, 
 SOa) in the form of a fine powder ; this precipitate is inso- 
 luble in hydrochloric acid and in nitric acid. 
 
 3. Acetate of lead produces a heavy, white precipitate 
 of SULPHATE OF LEAD (Pb O, SO a) which is sparingly 
 soluble in dilute nitric acid, but completely so in hot and 
 concentrated hydrochloric acid. 
 
 4. Those sulphates which are insoluble in water and 
 acids, are converted into CARBONATES on being fused with 
 alkaline carbonates, giving at the same time rise to the 
 formation of an alkaline sulphate. 
 
 5. The sulphates of alkalies and alkaline earths, may 
 be reduced to sulphurets by being exposed on charcoal to 
 the reducing flame of the blow-pipe either by themselves 
 
 6* 
 
142 PHOSPHORIC ACID. 
 
 or (and with greater facility) mixed with carbonate of 
 soda and charcoal. These sulphurets may be detected by 
 the odour of sulphuretted hydrogen which they emit upon 
 being moistened with a few drops of an acid. If this is 
 done on a paper which has been previously dipped into a 
 solution of lead, or on a clean silver plate, (such as a po- 
 lished coin,) a black stain of sulphuret of lead or sulphuret 
 of silver is immediately formed. 
 
 Remarks. Of all acids, sulphuric acid is almost the 
 easiest to be detected, by its characteristic and excessively 
 sensible reaction with salts of barytes. It is only neces- 
 sary to take care not to mistake for sulphate of barytes, 
 precipitates of chloride of barium, and especially of nitrate 
 of barytes, which are formed when aqueous solutions of 
 these salts are mixed with fluids containing a large pro- 
 portion of free hydrochloric acid or free nitric acid. It is 
 very easy to distinguish these precipitates from sulphate 
 of barytes, as they immediately disappear again, on the acid 
 fluid being diluted with water. It is, however, possible 
 to be misled by this relation to barytes, so as to confound 
 sulphuric acid with hydrofluosilicic acid. Although we 
 have not treated of this acid, yet we may here as well 
 point out, that should any doubt exist as to the nature of a 
 precipitate of barytes, this may be easily set at rest by 
 treating the precipitate before the blow-pipe, with carbo- 
 nate of soda and charcoal. (Compare 97, 5.) 
 
 Third Section of the First Group of the Inorganic Acids . 
 
 98. 
 
 a. PHOSPHORIC ACID. (PO 5 .) 
 
 We consider here only the tribasic phosphoric acid, 
 since this and its salts alone are most frequently employed 
 in pharmacy, &c. ; we disregard altogether the mono- 
 basic and bibasic phosphoric acid. 
 
 1. The phosphates with a fixed base are not completely 
 decomposed by heat, but they may thereby be converted, 
 according to the higher or lower degree applied, into pyro- 
 phosphates or metaphosphates. Of the phosphates, only 
 
PHOSPHORIC ACID, 143 
 
 those with an alkaline base are soluble in water, in their 
 neutral state. The solutions have an alkaline reaction. 
 
 2. Chloride of barium produces in aqueous solutions of 
 neutral or basic phosphates, a white precipitate of PHOS- 
 PHATE OF BARYTES (2 Ba O, PO 5 ) which is soluble in 
 hydrochloric acid and in nitric acid, and sparingly solu- 
 ble in muriate of ammonia. 
 
 3. Solution of gypsum produces in neutral or alkaline 
 solutions, a white precipitate of PHOSPHATE OP LIME 
 (2 Ca O, PO 6 ) which is easily soluble in acids, even in 
 acetic acid. 
 
 4. Chloride of magnesium or sulphate of magnesia 
 produce in neutral or alkaline solutions white precipitates 
 of PHOSPHATE OF MAGNESIA (2 Mg O, POs) which are, 
 however, perceptible only in rather concentrated solutions, 
 especially on the application of heat. But if free am- 
 monia or carbonate of ammonia be added to a even 
 highly dilute solution, a white crystalline and quickly sub- 
 siding precipitate of BASIC PHOSPHATE OF MAGNESIA AND 
 AMMONIA (2 Mg 0, NH4 O) (PO 5 +2 HO+10 aq.) is 
 formed, which is insoluble both in ammonia and in mu- 
 riate of ammonia, but is of easy solution in acids, even in 
 acetic acid. This precipitate often becomes visible only 
 after the lapse of some time ; agitation promotes its sepa- 
 ration. (Vide 86, d 5 ) 
 
 5. Nitrate of silver throws down from the solution of 
 the neutral and basic alkaline phosphates, a bright yellow 
 precipitate of PHOSPHATE OF SILVER. (3 Ag O P, O 5 .) If 
 the solution contained a basic phosphate, the fluid in which 
 the precipitate is suspended, manifest a neutral reaction, 
 whilst it has an acid reaction if the solution contained a 
 neutral phosphate. This is owing to the nitric acid re- 
 ceiving for 3 eq. of oxide of silver which it yields to the 
 phosphoric acid, only 2 eq. of alkali and 1 eq. of water, 
 (for the water does not neutralize the characteristic pro- 
 perties of the acid.) 
 
 6. Acetate of lead produces in neutral and alkaline so- 
 lutions a white precipitate of PHOSPHATE OF LEAD, (2 Pb 
 O, P O 5J ) which is easily soluble in nitric acid, and al- 
 most insoluble in acetic acid. By its behaviour before the 
 blow-pipe this precipitate affords us an excellent means of 
 
J44 BORACIC ACID. 
 
 detecting the presence of phosphoric acid. For, in the 
 first place, it is not reduced, or at least, only with the great- 
 est difficulty, on being exposed on charcoal, even to the 
 reducing flame ; and it is, in the second place, distinguish- 
 ed inasmuch as the transparent and colourless pearl which 
 it presents in the oxidizing flame, crystallizes on cooling, 
 becomes opaque, and generally shows quite distinct dode- 
 cahedrons. 
 
 7. If to a hydrochloric solution of a phosphated alkaline 
 earth perchloride of iron be added in excess, and then 
 ammonia till the solution manifest an alkaline reaction, a 
 bulky, more or less dark, reddish-brown precipitate is ob- 
 tained, consisting of a mixture of hydrated peroxide of 
 iron and BASIC PERPHOSPHATE OF IRON. Ammonia with- 
 draws from it but very little of its phosphoric acid, whilst 
 hydrosulphuret of ammonia completely decomposes it into 
 sulphuret of iron and phosphate of ammonia. If an in- 
 sufficient quantity of perchloride of iron, is used, a 
 white precipitate of neutral perphosphate of iron is- 
 formed, which redissolves on the addition of ammonia in 
 excess. 
 
 b. BORACIC ACII>. (B O 3 .) 
 
 1. The aqueous solution of boracic acid reddens litmus 
 paper, but it tinges tumeric paper brown. The borates are 
 not decomposed by a red heat ; only those with alkaline 
 bases are easily soluble in water. The solutions are co- 
 lourless, and all of them, even those of the acid salts mani- 
 fest an alkaline reaction. 
 
 2. Chloride of barium produces in solutions of borates, 
 when not too highly dilute, a white precipitate of BORATE 
 OF BARYTES, (Ba O. B O 3 ,) which is soluble in acids and 
 ammoniacal salts. 
 
 3. Nitrate of silver produces in rather concentrated 
 solutions of borates, a white precipitate of BORATE OF 
 SILVER, (Ag O, B O 3J ) which is soluble in nitric acid and 
 in ammonia. 
 
 4. If Sulphuric acid or hydrochloric acid be added to 
 highly concentrated, hot solutions of borates, the BORACIC 
 ACID will separate on cooling, in the form of shining 
 crystalline scales. 
 
OXALIC ADID. 145 
 
 5. If free boracic acid or a borate (in which latter case 
 the boracic acid must be liberated by the addition of 
 sulphuric acid) be ignited with alcohol, the flame will ap- 
 pear of a very distinct YELLOWISH-GREEN colour, especially 
 on stirring the mixture, owing to the boracic acid evapor- 
 ating together with the alcohol, and becoming incandes- 
 cent in the flame. This reaction becomes most sensible, 
 if the cup containing the mixture is first heated, the alco- 
 hol then ignited, allowed to burn for a short time, then ex- 
 tinguished and rekindled. At the first flickering of the 
 flame its borders appear green in that case, even though 
 the quantity of the boracic acid be so minute as to produce 
 no perceptible colouring of the flame,^ when treated in the 
 usual manner. 
 
 c. OXALIC ACID. (O = C 2 O 3 .) 
 
 1 . All the oxalates are decomposed at a red heat, owing 
 to the oxalic acid decomposing into carbonic acid and car- 
 bonic oxide. Those which have an alkali or an alkaline 
 earth for their base, are in this process converted into car- 
 bonates (without separation of carbon, when pure ;) those 
 with a metallic base leave the metal behind either in its 
 metallic state or as an oxide, according to the degree of 
 reducibility of the metallic oxide. The alkaline oxalates 
 are soluble in water, and so are some oxalates with metal- 
 lic base. 
 
 2. Chloride of barium produces in the neutral solutions 
 of oxalates, a white precipitate of OXALATE OF BARYTES, 
 (Ba O,O + aq.,) which is soluble in nitric acid and in hy- 
 drochloric acid, but is more sparingly soluble in ammoniacal 
 salts than bSrate of barytes. 
 
 3. Nitrate of silver produces in neutral solutions of 
 oxalates, a white precipitate of OXALATE OF SILVER, (Ag 
 O 6,) which is soluble in nitric acid and in ammonia. 
 
 4. Lime-water, and all the soluble salts of lime, and thus 
 also solution of gypsum, produce in even highly dilute 
 solutions of free oxalic acid or of oxalates, precipitates of 
 OXALATE OF LIME, (Ca O, 6 + 2 aq.) in the form of a fine 
 white powder, which readily dissolve in hydrochloric acid 
 and in nitric acid, but are almost insoluble in oxalic acid, 
 and in acetic acid. The presence of ammoniacal salts does 
 
146 HYDROFLUORIC ACID. 
 
 not at all prevent the formation of these precipitates. The 
 addition of ammonia considerably promotes the precipitation 
 of the free oxalic acid, by salts of lime. 
 
 5. If oxalic acid or an oxalate in a dry state be heated 
 with concentrated sulphuric acid in excess, the latter with- 
 draws from the oxalic acid its necessary constitutional 
 water, the oxalic acid is decomposed into CARBONIC ACID 
 and CARBONIC OXIDE, and both these gases escape with 
 effervescence. If the quantity operated upon is not too 
 minute, the escaping carbonic oxide gas may be kindled ; 
 it burns with a blue flame. If in this reaction the sulphuric 
 acid assumes a dark tinge, it is a sign that the oxalic acid 
 contained an admixture of some organic substance. 
 
 d. HYDROFLUORIC ACID. (H Fl.) 
 
 1 . Hydrofluoric acid is distinguished from all other acids 
 by its property of dissolving the insoluble modification of 
 silicic acid, as well as the silicates insoluble in hydrochloric 
 acid, giving rise to the formation of fluoride of silicon, and 
 of water. The hydrofluoric acid decomposes in the same 
 manner with metallic oxides, giving rise to the formation 
 of fluorides and of water. The fluorides of the alkaline 
 metals are soluble in water ; those corresponding with the 
 alkaline earths are either not at all or but very sparingly 
 soluble in water; floride of aluminum is easily soluble. 
 Most of the fluorides corresponding with the oxides of the 
 heavy metals are very sparingly soluble in water, such as, 
 for instance, fluoride of copper, fluoride of lead, fluoride of 
 zinc ; many other fluorides are of easy solution in water, as, 
 for instance, perfluoride of iron, fluoride of tin, perfluoride 
 of mercury, &c. Of those compounds which are either 
 insoluble or but sparingly soluble in water, many dissolve 
 in free hydrofluoric acid, whilst others remain undissolved. 
 Most of the fluorides do not undergo decomposition, when 
 heated to redness in a crucible. 
 
 2. If to the aqueous solution of hydrofluoric acid or of a 
 fluoride, chloride of calcium be added, FLUORIDE OF CAL- 
 CIUM, (Ca Fl,) is obtained in the form of a gelatinous pre- 
 cipitate, which is so transparent, as at first to induce the 
 belief, that the fluid has remained clear and unaltered. The 
 addition of ammonia promotes the complete separation of 
 
HYDROFLUORIC ACID. 147 
 
 this precipitate, which is insoluble in hydrochloric acid and 
 nitric acid, as well as in alkaline fluids when cold ; a minute 
 quantity is, however, dissolved on boiling with hydrochloric 
 acid. It is scarcely more soluble in free hydrofluoric acid 
 than in water. 
 
 3. If any fluoride, reduced to a fine powder, be mixed 
 with pounded glass or sand, and the mixture be drenched 
 in a test tube, with concentrated sulphuric acid and heat 
 applied, FLUOSILICIC GAS (Si F1 3 ) is evolved, giving rise to 
 dense white fumes in the air when the latter contains moisture. 
 If the gas be transmitted through water (by means of a bent 
 tube fitted to the test tube) silicic acid separates in a gel- 
 atinous form, whilst the fluid becomes strongly acid, owing 
 to the formation of hydrofluosilicic acid. (Compare 43.) 
 
 4. If a plate of glass be covered with bees-wax, which 
 can readily be done by heating it and allowing the wax to 
 spread equally over the surface, and lines be traced on it 
 with a point, (which should not be too hard, a point of 
 wood answers best,) and the plate be then covered with 
 the solution of a fluoride mixed with sulphuric acid, and 
 allowed to dry, the lines exposed will be found, on remov- 
 ing the wax, to be etched upon the glass. If we have 
 but very minute quantities to test, the acid solution of a 
 fluoride mixed with sulphuric acid is, at a gentle heat, 
 evaporated to dryness, in a watch glass ; after washing off 
 the salt mass remaining, the internal surface of the glass 
 appears dimmed. 
 
 5. If a fluoride, reduced to a fine powder, no matter 
 whether soluble or insoluble, is drenched, in a platinum 
 crucible, with concentrated sulphuric acid and the cruci- 
 ble, being covered with a glass plate, prepared as stated 
 above, is exposed fifteen minutes or half-an-hour to a gentle 
 heat, taking always care not to melt the wax, the exposed 
 lines are found engraved after the removal of the wax. If 
 the quantity of hydrofluoric acid evolved by means of the 
 sulphuric acid was very minute, the etching frequently is 
 not perceived, after the removal of the wax ; but if the 
 glass be breathed upon, the exposed lines become visible 
 again, owing to the unequal capacity of condensing water, 
 which the etched and untouched parts of the plate 
 possess. 
 
148 HYDROFLUORIC ACID. 
 
 Remarks. The third section contains, as we have 
 stated, phosphoric acid, boracic acid, oxalic acid and hydro- 
 fluoric acid. The barytes compounds of these acids, as we 
 have seen, are dissolved by hydrochloric acid, without de- 
 composition ; alkalies, therefore, precipitate them unaltered, 
 by neutralizing the hydrochloric acid. The barytes com- 
 pounds of arsenious acid, arsenic acid, and chromic acid, 
 present the same property, and must, therefore, if present, be 
 removed before any conclusion, as to the presence of phos- 
 phoric acid, boracic acid, oxalic acid, or hydrofluoric acid, 
 can be drawn from this precipitation of a salt of barytes. 
 But even without regard to this point, no great value can be 
 placed on their reaction, not even for the detection of these 
 acids, and far less for their separation from other acids, 
 since the salts of barytes in question, and especially the 
 borate of barytes, are not precipitated from their hydro- 
 chloric solutions, by ammonia, if the quantity of free acids 
 present is to any extent, or if any ammoniacal salt in a cer- 
 tain quantity is present. Boracic acid may always be 
 delected by the tint which it communicates to the flame of 
 alcohol, if care is taken that the solution be sufficiently con- 
 centrated before the addition of the alcohol, and when the 
 substance under examination is a borate, that it be mixed 
 with a sufficient quantity of sulphuric acid (best concen- 
 trated). If the boracic acid is free, it should first be 
 combined with an alkali when evaporating its solution, 
 or else a large portion of it will volatilize with the vapours 
 of the water. The phosphoric acid is sufficiently charac- 
 terized by the yellow silver precipitate, by the character- 
 istic properties of the basic phosphate of magnesia and 
 ammonia, (especially the insolubility of this compound in 
 sal ammoniac,) and finally, by the behaviour of phosphate 
 of lead before the blow-pipe. Perchloride of iron is un- 
 doubtedly the best means of decomposing those phosphates 
 which have an alkaline earth for their base, after they have 
 been dissolved in hydrochloric acid. Oxalic acid may 
 always easily be detected by solution of gypsum, if we 
 only keep in view, that the precipitate thereby formed 
 must not disappear on the addition of acetic acid, (herein 
 it is distinguished from phosphoric acid,) and must readily 
 dissolve in dilute hydrochloric acid, and.be converted into 
 
CARBONIC ACID. 149 
 
 carbonate of lime on the application of a red heat, (herein 
 it differs from hydrochloric acid). The oxalates of the 
 alkaline earths are completely decomposed by boiling 
 with carbonate of soda. Lastly, the hydrofluoric acid 
 cannot easily be confounded with other acids ; since, 
 under all circumstances, it is certainly detected by its 
 property of etching glass. The most sensitive results are 
 always obtained by treating solid fluorides with sulphuric 
 acid. 
 
 Fourth Section of the First Group of Inorganic Acids. 
 
 99. 
 
 6% CARBONIC ACID. (CO2.) 
 
 1. The carbonates lose a part of their carbonic acid, at a 
 red heat. All carbonates or colourless oxides appear 
 white or colourless. Only those with an alkaline base 
 are soluble in water, in their neutral stale. Their solu- 
 tions have a very strong alkaline reaction. Further, the 
 bi-carbonates with alkaline bases, those also which have 
 an alkaline earth for their base, and some with metallic 
 bases, are soluble in water. 
 
 2. The carbonates are decomposed by all free acids so- 
 luble in water, with the exception of hydrocyanic acid and 
 hydrosulphuric acid. In this process, the carbonic acid 
 escapes with effervescence, as a colourless and almost in- 
 odorous gas, which imparts a transient reddish tint to 
 litmus paper. It is necessary to use the decomposing acid 
 in excess, especially when operating upon a salt with an 
 alkaline base, since frequently no effervescence takes 
 place, when adding the acid in too small a quantity, owing 
 to the formation of acid carbonates. 
 
 3. Lime-water and water of barytes produce, when 
 brought into contact with carbonic acid or soluble car- 
 bonates, white precipitates of NEUTRAL CARBONATE OP 
 LIME or BARYTES. When testing for free carbonic acid, 
 the reagent ought always to be employed in excess, as the 
 acid carbonates of the alkaline earths are soluble in water. 
 The precipitates formed dissolve in acids, with efferves- 
 
150 SILICIC ACID. 
 
 cencej and are not precipitated again by ammonia, after 
 the complete expulsion of the carbonic acid, by boiling. 
 
 4. Chloride of calcium and chloride of barium yield 
 with neutral alkaline carbonates immediately, and with bi- 
 carbonates only on boiling, precipitates of CARBONATE OF 
 LIME or of BARYTES. These reagents yield no precipi- 
 tate with free carbonic acid. 
 
 b. SILICIC ACID. (Si 3 .) 
 
 1. Silicic acid occurs in two modifications, the one is 
 soluble in acids and water, the other is affected only by 
 hydrofluoric acid. The soluble modification is converted 
 by heat into the insoluble. If the insoluble modification is 
 fused with pure alkalies or alkaline carbonates, a basic 
 alkaline silicate is produced, which is soluble in water and 
 from which acids separate the silicic acid in its soluble 
 modification. The soluble modification readily dissolves 
 when boiled with solution of potash, the insoluble modi- 
 fication dissolves only very slowly in the same menstruum. 
 The silicates of the alkalies alone are soluble in water. 
 
 2. The solutions of the alkaline silicates are decomposed 
 by all acids ; when the solutions are highly concentrated 
 the SILICIC ACID precipitates in the form of gelatinous 
 flakes, whilst it remains dissolved in more dilute solutions. 
 If a solution of this kind, mixed with an acid, (hydrochloric 
 acid or nitric acid,) is evaporated to dryness, the silicic 
 acid is converted from its soluble into its insoluble modi- 
 fication, and remains, therefore, as a white gritty powder, 
 on the residue being treated with water. 
 
 3. In the silicates which have an earth or a metal for 
 their base, the silicic acid is also present either in its solu- 
 ble or in its insoluble modification. The silicates with 
 the soluble modification are decomposed by boiling hydro- 
 chloric or nitric acid, the silicic acid separating as a gela- 
 tinous hydrate, and the decomposing acid combining with 
 the base. But on silicates with the insoluble modification, 
 these acids have no action ; in order to separate the silicic 
 acid from its base, such silicates must be either treated in 
 the humid way, with hydrofluoric acid, or fused with al- 
 kaline carbonates. 
 
INORGANIC ACIDS. 151 
 
 4. Carbonate of soda dissolves a large proportion of 
 silicic acid in the flame of the blow-pipe, forming SILICATE 
 OF SODA as a colourless glass, which remains transparent 
 on cooling; the carbonic acid escapes with effervescence. 
 Inexperienced students often fail in obtaining a clear glass, 
 because they use too much carbonate of soda in propor- 
 tion to the quantity of the test specimen. 
 
 5. Phosphate of soda and ammonia leave silicic acid 
 almost entirely undissolved. The silicic acid floats about 
 as an opaque mass in the transparent glass, and may, there- 
 fore, be perceived with greater facility in the glass when 
 red hot than after cooling. The silicates present the same 
 property ; the phosphate of soda and ammonia withdraws 
 their base from them, and separate silicic acid. The bases 
 are dissolved, whilst the silicic acid remains undissolved. 
 
 Recapitulation and Remarks. Carbonic acid is generally 
 very easily detected by its salts evolving an almost inodorous 
 gas when treated with acids. We transmit the gas through 
 lime-water or water of barytes, when operating upon com- 
 pounds which evolve other gases at the same time. Silicic 
 acid in its soluble modification, (into which it must always 
 be converted first,) is detected, under all circumstances, by 
 supersaturating its compounds with hydrochloric acid, 
 evaporating to dryness. treating the residue with water, and 
 testing the undissolved part before the blow-pipe. 
 
 Second Group of Inorganic Acids. 
 
 ACIDS WHICH ARE PRECIPITATED BY NITRATE OF SILVER, 
 
 BUT NOT BY CHLORIDE OF BARIUM i Hydrochloric Acid, 
 Hydrobromic Acid, Hydriodic Acid, Hydrocyanic Acid t 
 Hydrosulphuric Acid. 
 
 100. 
 
 All the silver compounds of the oxides belonging to 
 this gronp are insoluble in dilute nitric acid. The acids of 
 this group decompose with metallic oxides, so as to give 
 rise to the combination of the metals with the metalloids, 
 whilst the oxygen of the oxide at the same time combines 
 with the hydrogen of the acid forming water. 
 
152 HYDROBROMIC ACID. 
 
 a. HYDROCHLORIC ACID. (Cl H.) 
 
 1. The chlorides are easily soluble in water, with the 
 exception of chloride of lead, chloride of silver, and pro- 
 tochloride of mercury ; most of the chlorides are white or 
 colourless. Many of them volatilize at a high temperature, 
 without decomposition ; many chlorides are decomposed 
 at a red heat, and but few of them are fixed. 
 
 2. Hydrochloric acid, and solutions of chlorides, yield 
 with nitrate of silver, even when highly dilute, white pre- 
 cipitates of CHLORIDE OF SILVER, (Ag Cl,) which, when 
 exposed to light, change first into a violet colour and then 
 into a black ; these are readily soluble in ammonia, insolu- 
 ble in nitric acid, and fuse without decomposition when 
 heated. (Vide 90, a 4.) 
 
 3. Protonitrate of mercury and acetate of lead pro- 
 duce in solution, containing free hydrochloric acid or 
 chloride, precipitates of CHLORURET OF MERCURY (Hg 2 
 Cl) and CHLORIDE OF LEAD (Pb Cl.) For the properties 
 of these precipitates, vide 90, b 4, and 90, c 4. 
 
 4. When chlorides are heated with manganese and sul- 
 phuric acid, chlorine is evolved, which is easily detected 
 by its YELLOWISH-GREEN colour, and its odour. 
 
 5. If a chloride be rubbed together with chromate of 
 potash, and the mixture be drenched with concentrated 
 sulphuric acid, in a tubular retort, and gentle heat applied, 
 a deep brownish-red gas will be copiously evolved ; (CHRO- 
 MATE OF PERCHLORIDE OF CHROMIUM, Cr Cl + 2 Cr 
 
 O 3 ;) this gas condenses into a fluid of the same colour, 
 and passes over into the receiver. If this chromate of 
 perchloride of chromium is mixed with ammonia in excess, 
 a yellow -coloured liquid is obtained, owing to the forma- 
 tion of chromate of ammonia ; this yellow colour changes 
 into a reddish yellow, on the addition of an acid, owing 
 to the formation of acid chromate of ammonia. 
 
 6. HYDROBROMIC ACID. (Br H.) 
 
 1. The bromides have, in general, a great analogy with 
 the chlorides, in insolubility and in their relations when 
 exposed to heat. 
 
HYDROBROMIC ACID. 153 
 
 2. Nitrate of silver produces in aqueous solution of 
 hydrobromic acid and bromides a yellowish-white precipi- 
 tate of BROMIDE OF SILVER, (Ag Br,) which is insoluble 
 in dilute nitric acid, and somewhat sparingly soluble in 
 ammonia. 
 
 3. Nitric acid decomposes hydrobromic acid and the 
 bromides, with the application of heat, liberating bromine, 
 by oxidizing the hydrogen or the metal. The liberated 
 bromine colours the solution yellowish-red ; but if we 
 operate upon a bromide in a solid form, yellowish red 
 vapours of bromine gas escape, with the odour of chlo- 
 rine ; these vapours, when present in sufficient quantity, 
 condense in the cold part of the test-tube into small drops. 
 
 4. Chlorine, or solution of chlorine, also liberates bro- 
 mine in solutions of its compounds ; the fluid assuming a 
 yellowish-red tint, if the quantity of the bromine present 
 is not too minute. If a yellow-coloured solution of this 
 kind be agitated with ether, it becomes colourless ; all the 
 bromine dissolves in the ether, which appears distinctly 
 yellow, even though but a very minute quantity of bromine 
 be present. If the etherial solution of bromine be agitated 
 with some solution of potash, the yellow tint vanishes, and 
 we have bromide of potassium and bromate of potash in 
 solution. If the solution be then evaporated, and the resi- 
 due heated to redness, the bromate of potash is converted 
 into bromide of potassium. This substance may be fur- 
 ther tested as follows : 
 
 5. If bromides are heated with manganese and sulphuric 
 acid, YELLOWISH-RED VAPOURS OF BROMINE are evolved, 
 If the bromine is present only in very minute quantity, the 
 colour of their vapours may not be visible. The experi- 
 ment, in that case, must be conducted in a small retort, 
 and the vapours passing over transmitted through a long 
 condensing glass tube into small test-tubes, containing 
 some starch, for if 
 
 6. Moist starch is brought into contact with free bro- 
 mine, no matter whether in solution or in gaseous form, 
 YELLOW BROMIDE OF STARCH is formed. The colouring 
 does not always take place immediately. The reaction is 
 rendered most delicate by closing the test-tube which con- 
 tains the starch drenched with the fluid under examina- 
 tion, before a spirit-lamp, and then inverting it, so that 
 
154 HYDRIODIC ACID. 
 
 the moist starch becomes placed above the liquid. The 
 slightest trace of bromine will then, after twelve to twenty- 
 four hours, impart a yellow tinge to the starch. This 
 colour vanishes again on the tube being allowed to stand 
 for a longer time. 
 
 7. If a mixture of a bromide and of chromate of potash 
 be drenched with sulphuric acid, and heat applied, a 
 brownish-red gas is evolved, just as is the case with the 
 chlorides. But this gas consists of pure BROMINE, and the 
 fluid passing on, therefore, becomes not yellow, but colour- 
 less, when supersaturated with ammonia. 
 
 C. HYDRIODIC ACID. (I H.) 
 
 1. The iodides also correspond, in many respects, with 
 the chlorides.. Of those, however, which contain heavy 
 metals, by far more are insoluble in water than is the case 
 with the chlorides. Many iodides present characteristic 
 tints. 
 
 2. Nitrate of silver produces in aqueous solutions of 
 hydriodic acid and of iodides, yellowish white precipitates 
 of IODIDE OF SILVER, (Ag I,) which blacken when exposed 
 to light, are insoluble in dilute nitric acid, and very spar- 
 ingly soluble in ammonia. 
 
 3. A solution of one part of sulphate of copper, and 
 two and a quarter parts of sulphate of iron, precipitates 
 from aqueous neutral solutions of the iodides, PROTIODIDE 
 OF COPPER, (Cu ? I,) in the form of a dirty-white precipi- 
 tate. The addition of some ammonia promotes the com- 
 plete precipitation of the iodine. Chlorides and bromides 
 are not precipitated by this reagent. 
 
 4. Nitric acid decomposes the hydriodic acid and the 
 iodides in the same manner as the bromides. Colourless 
 solutions of hydriodic acid or of the iodides are, therefore, 
 immediately coloured BROWNISH-YELLOW by nitric acid, 
 even at a low temperature ; and from concentrated solu- 
 tions the IODINE separates as a BLACK PRECIPITATE, whilst 
 nitric oxide gas escapes with effervescence. Solid iodides, 
 when heated with nitric acid, evolve, besides the nitric acid 
 gas VIOLET vapours of iodine, which condense on the colder 
 parts of the vessel into a blackish sublimate. 
 
 5. Chlorine and solution of chlorine, liberate iodine from 
 
HYDROCYANIC ACID. 155 
 
 its combinations, but the liberated iodine combines with 
 these reagents when they are added in excess, forming a 
 colourless CHLORIDE OF IODINE. 
 
 6. If iodides are heated with concentrated sulphuric 
 acid, or with sulphuric acid and manganese, IODINE be- 
 comes liberated, and may be easily detected by the violet 
 colour of its gas. If concentrated sulphuric acid alone has 
 been used, sulphurous acid is evolved at the same time. If 
 the quantity of the iodine present is very minute, it can no 
 longer be detected by the colour of its gas, and we have 
 recourse to the test with starch, as follows : 
 
 7. If to a solution of iodine or of hydriodic acid, or of an 
 iodide, (the iodine in the latter must first be liberated by 
 means of nitric acid,) thin starch paste be added, a more or 
 less blackish-blue tint or precipitate of IODIDE OF STARCH 
 is formed, even though but the most minute traces of iodine 
 be present. When solution of chlorine is employed for 
 the liberation of the iodine, it ought to be added very cau- 
 tiously, as, owing to the formation of chloride of iodine, the 
 blue tint does not appear, or at least manifests itself only 
 after the addition of sulphuretted hydrogen, protochloride of 
 tin, or some other means of reduction. Even the most 
 minute traces of iodine in dry compounds of any description, 
 may be detected most safely by means of starch, in the 
 following manner. The substance under examination is 
 drenched in a retort, with concentrated nitric acid, and the 
 retort loosely closed with a stopper, to which a moistened 
 slip of paper, or, better still, a moistened strip of white cot- 
 ton cloth, imbued with starch, is attached ; after a few hours 
 this will appear blue, even though but the most minute 
 trace of iodine be present. 
 
 8. The iodides present the same relation to chromate of 
 potash and sulphuric acid combined, as to sulphuric acid 
 alone. (Compare 100, a 5.) 
 
 d- HYDROCYANIC ACID. (Cy H.) 
 
 1 . Those cyanides which have an alkali or alkaline earth 
 for their base, are soluble in water, as hydrocyanates. They 
 are easily decomposed by acids, even by carbonic acid, but 
 are not decomposed by heat when the access of air is pre- 
 vented. When fused with the oxide of lead, of copper, of 
 
156 HYDROCYANIC ACID. 
 
 antimony, of tin, and many other oxides, they reduce these 
 oxides, and are converted into cyanates. Only a few of 
 those cyanides which contain heavy metals are soluble in 
 water ; all of them are decomposed at a red heat, giving 
 rise either to the formation of cyanogen and metals, as the 
 cyanides of the noble metals, or of nitrogen gas and carbo- 
 nates, as the cyanides of the other heavy metals. Many 
 combinations of cyanogen with heavy metals are not de- 
 composed by dilute oxygen acids, and with difficulty by 
 concentrated nitric acid. Hydrochloric acid and sulphur- 
 etted hydiogen decompose most of them easily and com- 
 pletely. Cyanogen combines with several metals, (iron, 
 manganese, cobalt, chromium,) forming compound radicals, 
 in which these metals cannot be detected by many of the 
 usual methods. 
 
 2. Nitrate of silver produces, in solutions of free hydro- 
 cyanic acid and of alkaline hydrocyanates, white precipitates 
 of CYANIDE OF SILVER, (Ag Cy,) which are easily soluble 
 in cyanide of potassium, somewhat difficult of solution in 
 ammonia, and insoluble in dilute nitric acid ; these precipi- 
 tates are decomposed at a red heat, leaving the pure 
 metallic silver behind; 
 
 3. If to the solution of an alkaline hydrocyanate, solution 
 of sulphate of iron, which has been for some time in contact 
 with the air, (magnetic oxide of iron ,) is added, a precipi- 
 tate or tint of PRUSSIAN BLUE is formed. (Compare 88, 
 f 5.) Free hydrocyanic acid, to be detected in this manner, 
 must, therefore, first be combined with an alkali. If the 
 alkali is present in excess, hydrated magnetic oxide of iron 
 is precipitated beside the Prussian blue ; in that case this 
 latter precipitate must first be redissolved by hydrochloric 
 acid, before the blue colour of the precipitate can appear 
 clearly and distinctly. 
 
 3. If to a solution of hydrocyanic acid, potash be added 
 in excess, and then finely pounded peroxide of mercury ^ 
 the latter substance readily dissolves just as well as in free 
 hydrocyanic acid. As peroxide of mercury is soluble in 
 an alkaline fluid only in presence of hydrocyanic acid, it 
 follows that by means of this reaction we can safely detect 
 the presence of hydrocyanic acid. 
 
 4. The cyanogen cannot be detected in cyanide of mer^ 
 
HYDROSULPHURIC ACID. 157 
 
 cury by any of these methods. To detect it in this combi- 
 nation, we add hydrochloric acid and metallic iron to a 
 solution of cyanide of mercury. Metallic mercury is sepa- 
 rated in this process, and hydrocyanic acid and protochloride 
 of iron formed, (which latter substance is partly converted 
 into perchloride of iron, on exposure to the air,) If an 
 alkali is then added to the fluid, Prussian blue is formed, 
 the colour of which, however, becomes distinct only after 
 having removed, by the addition of hydrochloric acid, the 
 excess of the hydrated magnetic oxide of iron present 
 Cyanide of mercury may also be easily decomposed by 
 sulphuretted hydrogen, giving rise to the formation of 
 sulphuret of mercury and hydrocyanic acid. When heated, 
 the cyanide of mercury decomposes, as we have already 
 stated, (I,) into metallic mercury and cyanogen, which 
 latter substance may be detected by its characteristic effect 
 on the olfactory organs. 
 
 5. In the ferrocyanides and ferricyanides with alkaline 
 bases, the presence of these compound radicals may be 
 easily detected, in the former by solutions of protoxide of 
 iron, or solution of copper, and in the latter by solution of 
 peroxide of iron. Free hydrocyanic acid may be obtained 
 from these cyanides by distilling them with sulphuric acid. 
 The insoluble ferrocyanides and ferricyanides are decom- 
 posed by being heated with caustic potash or carbonate of 
 potash, giving rise to the formation of ferrocyanide of 
 potassium, and the separation of the metals either as car- 
 bonates or as pure oxides. 
 
 6. HYDROSULPHURIC ACID. (H S.) 
 
 Sulphuretted Hydrogen Gas. 
 
 1 . Only those sulphurets are soluble in water which have 
 an alkali or an alkaline earth for their base. These as well 
 as those which contain metals of the fourth group, (such 
 as iron, manganese, &c.,) are decomposed by dilute min- 
 eral acids, with evolution of sulphuretted hydrogen gas, 
 which may easily be detected by its odour, and by its 
 action on solution of lead. (Vide infra 2.) If the sulphu- 
 ret is of a higher degree of sulphuration, a white precipi- 
 tate of minutely divided sulphur is formed at the same 
 time, which can easily be distinguished from similar pre* 
 
15& HYDROSULPHURIC ACIF. 
 
 cipitates by its inflammability* Part of the sulphurets of 
 the fifth and sixth group are decomposed by concentrated 
 and boiling hydrochloric acid, with evolution of sulphuret- 
 ted hydrogen gas, whilst others are not dissolved by hy- 
 drochloric acid, but by concentrated and boiling nitric acid- 
 The combinations of sulphur with mercury resist both 
 these acids, but dissolve readily in aqua regia. On the so- 
 lution of sulphurets in nitric acid, and in aqua regia,- sul- 
 phuric acid is formed ; amj in most cases, moreover, sul- 
 phur separates, which is easily detected by its colour and 
 behaviour when heated. 
 
 2. If sulphuretted hydrogen in solution, or in a gaseous 
 form, is brought into contact with nitrate of silver or ace- 
 tate of lead, black precipitates of SULPHURET OF SILVER 
 and SULPHURET OF LEAD are formed. (Vide supra, 89, a, 
 and 89 c.) If the odour of sulphuretted hydrogen is r 
 therefore, not sufficient for its detection, these reagents 
 will afford the surest proof of its presence. When the 
 sulphuretted hydrogen is in a gaseous form, a small slip of 
 paper, moistened with solution of lead, is placed in the air 
 to be tested ; if sulphuretted hydrogen is present, this 
 paper will become covered with a thin, brownish-black and 
 lustrous film of sulphuret of lead. 
 
 3. If sulphurets are exposed to the oxidizing flame of 
 the blow-pipe, their sulphur burns with a blue flame, emitting 
 at the same time the well-known odour of sulphurous acid.. 
 
 Recapitulation and remarks. Most of the acids of the 
 first group are precipitated by nitrate of silver ; but these 
 precipitates will not be confounded with the silver com- 
 pounds of the acids of the second group, as the former are 
 soluble in dilute nitric acid, whilst the latter are insoluble 
 in that fluid. The presence of hydrosulphuric acid pre- 
 vents us more or less from testing for the other acids of the 
 second group ; this acid must, therefore, if present, first be 
 removed previous to testing for the other acids. This re- 
 moval may be effected by mere boiling, if the hydrosul- 
 phuric acid is free, but, if combined with an alkali, by the 
 addition of a metallic salt, which does not precipitate the 
 other acids, or at least not from acid solutions. Hydriodic 
 and hydrocyanic acid may be detected even in the presence 
 
NITRIC ACID. 159 
 
 of hydrochloric or hydrobromic acid, by the reactions with 
 starch and magnetic oxide of iron, which are as charac- 
 teristic as they are delicate. But the detection of chlorine 
 and bromine is more or less difficult in presence of iodine 
 and cyanogen. These latter substances, if present, must, 
 therefore, be removed first, before we can test for chlorine 
 and bromine. The separation of cyanogen is easily effected 
 by heating to redness the silver compounds of the group. 
 Cyanide of silver decomposes at a red heat, whilst chloride, 
 bromide, and iodide of silver undergo no decomposition. 
 Iodine may' be separated from bromine and chlorine, by 
 treating the silver compounds with ammonia, as the iodide 
 of silver is almost insoluble in this substance. But the 
 separation is more perfect by precipitating the iodine as 
 protiodide of copper, whilst chlorine and bromine remain 
 in solution. Bromine may be detected and distinguished 
 from chlorine, by mixing the compound containing both 
 substances with hydrochloric acid and chloride of lime, or 
 with solution of chlorine, and absorbing the liberated 
 bromine by ether. Chlorine may be detected when pre- 
 sent with bromine, by the reaction with carbonate of 
 potash and sulphuric acid. 
 
 Third Group of the inorganic Acids. 
 
 ACIDS WHICH ARE PRECIPITATED NEITHER BY SALTS OP 
 BARYTES NOR SALTS OF SILVER '. Nitric Add, CkloriC 
 
 Acid. 
 
 101. 
 
 a. NITRIC ACID. (N0 5 .) 
 
 1. All the neutral salts of nitric acid are soluble in 
 water ; only a few basic nitrates are insoluble in water. 
 All nitrates are decomposed at a strong red heat. Those 
 with alkaline bases yield oxygen and nitrogen : the other 
 salts, oxygen and nitrous acid. 
 
 2. If a nitrate is thrown upon red-hot charcoal, or if 
 charcoal or some organic substance, paper, for instance, is 
 brought into contract with a nitrate in fusion, DEFLAGRA- 
 TION takes place, i. e. the charcoal burns at the expense of 
 the oxygen of the nitric acid, with vivid scintillations, 
 
160 CHLORIC ACID. 
 
 3. If a nitrate is mixed with cyanide of potassium in 
 powder and the mixture heated on a platinum plate, a 
 vivid DEFLAGRATION takes place combined with distinct 
 ignition and feeble detonation. Even very minute quan- 
 tities of nitrates may be detected by this reaction. 
 
 4. If the solution of a nitrate be mixed with one-fourth 
 part of its quantity of concentrated sulphuric acid, and a 
 chrystal of protosulphate of iron be thrown into the mix- 
 ture, the fluid immediately surrounding this crystal will 
 assume a DEEP BROWN TINT. This tint generally vanishes 
 by merely agitating the fluid, and always after the applica- 
 tion of heat for some time. In this process, the nitric acid 
 is decomposed by the protoxide of iron, three-fifths of its 
 oxygen combine with the protoxide, and convert a portion 
 of it into peroxide, and the remaining nitric oxide combines 
 with the remaining protoxide of iron, forming a charac- 
 teristic compound, which dissolves in water producing a 
 brownish-black colour. 
 
 5. If to the solution of a nitrate some sulphuric acid be 
 added, and as much solution of sulphate of indigo as to 
 make the fluid appear of a feeble light-blue colour, and the 
 mixture be then heated to boiling, this blue tint will disap- 
 pear, owing to the indigo becoming oxidized at the expense 
 of the oxygen of the nitric acid liberated by the sulphuric 
 acid ; the fluid becomes colourless, or assumes a feeble 
 yellowish tint. Several other substances, especially free 
 chlorine, cause the same discoloration, which ought to be 
 especially borne in mind. 
 
 6. If a nitrate is mixed with copper filings, and the 
 mixture drenched with concentrated sulphuric acid, in a 
 text tube, the air in the tube assumes a yellowish red tint, 
 owing to the nitric oxide gas which becomes free on the 
 oxidation of the copper by the nitric acid, combining with" 
 the oxygen of the air, and forming nitrous acid. 
 
 b. CHLORIC ACID. (Cl Os.) 
 
 1. All chlorates are soluble in water. When heated 
 to redness, their oxygen escapes completely, leaving chlo- 
 rides behind, 
 
 2. When heated with charcoal or some organic sub- 
 
CHLORIC ACID. 161 
 
 stance) the chlorates DEFLAGRATE, and this with by far 
 greater violence than the nitrates. 
 
 3. If the chlorate is mixed with CYANIDE OF POTASSIUM, 
 and the mixture heated on a platinum plate, DEFLAGRATION 
 takes place, with strong detonation and the appearance of 
 flame, even though the chlorate be present only in a very 
 minute quantity. 
 
 4. Free chloric acid oxidizes and discolours indigo in 
 the same manner as nitric acid ; if. therefore, the solution 
 of a chlorate is mixeckwith sulphuric acid and solution 
 of indigo, the phenomena manifest themselves, which we 
 have described when treating of nitric acid, (vide su- 
 pra, a 5.) 
 
 5. If chlorates be heated with hydrochloric acid, the 
 constituents of both acids are mutually decomposed, giving 
 rise to the formation of water, chlorous acid and chlorine, 
 which latter substances may easily be detected by their 
 odour and their greenish colour. (Cl H+C1 O 3 = Cl 
 O4 + C1+HO.) 
 
 6. If a chlorate be drenched with concentrated sulphuric 
 acid, two-thirds of the metallic oxide are converted into a 
 sulphate, and the other third into a hyperchlorate, whilst 
 chlorous acid escapes, which is characterized by its odour 
 and greenish colour. [3 (KO, Cl O J +2 S0 3 = 2 (KO, 
 2 SO 3 )+KO, Cl O 7 + 2 (Cl 4 .) ]' The application of 
 heat must be avoided in this experiment, and small quanti- 
 ties only operated upon, or else the decomposition might 
 take place with great violence, so as to occasion an ex- 
 plosion. 
 
 Recapitulation and remarks. Of the reactions which 
 have been suggested for the detection of nitric acid, those 
 with sulphate of iron and sulphuric acid, and with copper 
 filings and sulphuric acid, give the safest results, for de- 
 flagration with charcoal, detonation with cyanide of potas- 
 sium, and discolouration of solution of indigo take place, 
 as we have stated also when chlorates are present instead 
 of nitrates. These latter reactions, therefore, are decisive 
 only when no chloric acid is present. The best test to 
 ascertain whether chloric acid be present or not, is to heat 
 
 
162 TARTARIC ACID. 
 
 the test specimen to redness, dissolving it and then testing 
 its solution with nitrate of silver. 
 
 If a chlorate be present, it is converted into a chloride, 
 on being heated to redness, and a precipitate of chloride of 
 silver is obtained, on testing the solution with nitrate of 
 silver. But this test is thus simple only when no chloride 
 is present at the same time. But if the latter is the case, 
 nitrate of silver must be added as long as any precipitate is 
 formed ; the supernatant liquid is then filtered from this 
 precipitate, evaporated to dryness, and the residue heated 
 to redness. The results obtained by the fusion of chlorates 
 with cyanide of potassium are less certain. The violence 
 and detonation, with which the deflagration takes place, 
 render it, however, scarcely possible to confound the chlo- 
 rates with nitrates. 
 
 II. ORGANIC ACIDS. 
 
 First Group. 
 
 ACIDS WHICH ARE PRECIPITATED BY CHLORIDE OF CAL- 
 CIUM : Oxalic Acid) Tartaric Acid, Par alar tar ic Acid, 
 Citric Acid, Malic Acid. 
 
 102. 
 None of these 'acids volatilize without decomposition. 
 
 a. OXALIC ACID. 
 . For the reactions of oxalic acid we refer to 98 c. 
 
 b. TARTARIC ACID. (T = (C 8 H 4 O 10 .) 
 
 1. The combinations of tartaric acid with alkalies, as 
 well as with those metallic oxides which are weak bases, 
 are soluble in water* All tartrates insoluble in water are 
 dissolved by hydrochloric acid. 
 
 2. The tartaric acid and the tartrates carbonise when 
 heated to redness, emitting a perfectly characteristic odour. 
 The salts which have an alkali or alkaline earth for their 
 base, are in this process converted into carbonates. 
 
 3. If to a solution of tartaric acid, or to that of a tartrate, 
 solution of peroxide of iron, protoxide of manganese, or 
 
PARATARTARIC ACID, 163 
 
 and then ammonia or potash be added, no preci- 
 pitation takes place of peroxide of iron, protoxide of man- 
 ganese or alumina, since the new-formed double tartrates 
 are not decomposed by alkalies. Tartaric acid prevents 
 also the precipitation of several other oxides by alkalies. 
 
 4. Free tartaric acid yields, with a salt of potash, and 
 best with acetate of potash, a sparingly soluble precipitate 
 of BITARTRATE OF POTASH (KO, HO, t). The same pre- 
 cipitate is formed, if acetate of potash and free acetic acid, 
 or bisulphate of potash, be added to a neutral tartrate. 
 When using bisulphate of potash, we must be careful not 
 to add it in excess. The acid tartrate of potash readily 
 dissolves in alkalies and mineral acids ; tartaric acid and 
 ^acetic acid do not increase its solubility in water. Violent 
 agitation greatly promotes the precipitation of tartar. 
 
 5. Chloride of calcium throws down from the solutions 
 of neutral tartrates, TARTRATE OF LIME as a white preci- 
 pitate. The presence of amrnoniacal salts prevents the 
 formation of this precipitate more or less* The precipi- 
 tate of tartrate of lime dissolves to a clear fluid, in cold and 
 dilute solution of caustic potash. If this solution is boiled, 
 the dissolved tartrate of lime separates in the form of a 
 gelatinous precipitate. On cooling, the solution becomes 
 clear again. 
 
 6. Lime-water produces in solutions of neutral tartrates, 
 or even in solutions of free tartaric acid, when added till 
 an alkaline reaction manifests itself, white precipitates of 
 TARTRATE OF LIME (f , 2 Ca O 8 aq.) which readily dis- 
 solve in tartaric acid. This precipitate of tartrate of lime 
 dissolves with the greatest facility in solution of sal am- 
 moniac, and separates from this solution only after the 
 lapse of several hours, in the form of small crystals, depo- 
 sited on the sides of the vessel. 
 
 7. Solution of gypsum does not produce any precipi- 
 tate in a solution of tartaric acid, and causes only a minute 
 precipitate after the lapse of some time in the solution of 
 a neutral tartrate. 
 
 C. PARATARTARTC ACID. (RACEMIC ACID.) R = (C 4 H 2 O 5 .) 
 
 1 . The relations which paratartrates present to solvents, 
 and their behaviour when heated, are very analogous to 
 
164 CITRIC ACID. 
 
 those of the tartrates, prevent, like the latter, the precipi- 
 tation by alkalies of protoxide of manganese, peroxide of 
 iron, alumina, &c. 
 
 2. Paratartaric acid has the same relations to salts of 
 potash, as tartaric acid. The precipitate of acid paratar^ 
 trate of potash is as difficult of solution as tartar. 
 
 3. Chloride of calcium precipitates from the solutions 5 
 of free as well as of combined paratartaric acid, PARATAR- 
 TRATE OF LIME, as a shining white powder. This preci- 
 pitate is not soluble in sal ammoniac. Cold and concen- 
 trated solution of potash dissolves it completely, dilute 
 solution of potash only partly \ this solution becomes turbid 
 and gelatinous, on boiling, and clear again on cooling. 
 
 4. Lime-water produces in the solutions of neutral 
 paratartrates, instantaneously, white precipitates of PARA- 
 TARTRATE OF LIME. (R, Ca O + 4 aq.) It yields the 
 same precipitate with a solution of paratartarie acid, when 
 added, till an alkaline reaction becomes manifest. "When 
 added in a smaller proportion, so that the solution still re- 
 mains acid, this precipitate is formed only after the lapse 
 of a few moments. Paratartrate of lime is insoluble in pa- 
 ratartaric acid as well as in tartaric acid ; when it is dis- 
 solved in hydrochloric acid, and ammonia added in excess, 
 it precipitates again instantaneously, or at least after the 
 lapse of a few moments. 
 
 6. Solution of gypsum does not instantaneously produce 
 a precipitate in a solution of "paratartaric acid ; after ten or 
 fifteen minutes, however, paratartrate of lime precipitates ; 
 in solutions of neutral paratartrates the precipitation is in-- 
 stantaneous. 
 
 7. If crystallized paratartaric acrd, or a paratartrate is 
 heated with concentrated sulphuric acid, the latter assumes 
 a black tinge, owing to the evolution of sulphurous acid and 
 carbonic oxide gas. Tartarie acid has the same property. 
 
 d. CITRIC ACID. (Ci = (C 12 H On.) 
 
 1. The citrates with alkaline bases are ea&ly soluble in 
 water, as well in their neutral as in their acid stale; the 
 same is the case w r ith the combinations of citric acid with 
 such of the metallic oxides as are weak bases. Citric acid 
 prevents the precipitation of peroxide of iron, protoxide of 
 
CITRIC ACID. 165 
 
 manganese, alumina, &c., in the same manner as tartaric 
 acid. 
 
 2. Citric acid and the citrates carbonize when heated to 
 redness, emitting pungent acid vapour, which maybe easily 
 distinguished by their odour from those caused by the com- 
 bustion of tartaric acid. 
 
 3. Chloride of calcium produces no precipitate in a solu- 
 tion of citric acid, not even on boiling. But if the free acid 
 be saturated with potash or soda, a precipitate of NEUTRAL 
 CITRATE OF LIME (ci, 3 Ca O, 4 aq,) is formed instanta- 
 neously. This precipitate is insoluble in potash, but readily 
 dissolves in solution of sal ammoniac. If this solution in 
 sal ammoniac is boiled, a white and heavy precipitate of 
 BASIC CITRATE OF LIME (ci, 3 Ca O + Ca O + aq.) separates 
 immediately. If a solution of citric acid, mixed with chlor- 
 ide of calcium, be saturated with ammonia, no precipitate 
 will be formed at a low temperature, (if the solution was 
 not highly concentrated.) But if the clear fluid be then 
 boiled, a white, heavy precipitate of basic, citrate of lime 
 separates suddenly. 
 
 4. Lime-water produces no precipitate in a cold solution 
 of citric acid or of a citrate. But on heating the solution 
 to boiling with excess of lime-water, a white precipitate of 
 BASIC CITRATE OF LIME is formed, which disappears again 
 on cooling. 
 
 5. If to a solution of citric acid, acetate of lead be added 
 in excess, a white precipitate of CITRATE OF LEAD (ci, 3 
 Pb O, aq.) is formed, which is very sparingly soluble in 
 ammonia, but easy of solution in citrate of ammonia. A 
 precipitate of citrate of lead is equally formed, on adding 
 citric acid in excess to a solution of neutral acetate of lead. 
 This precipitate readily redissolves on the addition of am- 
 monia. We have just now seen that the citrate of lead is 
 very sparingly soluble in ammonia ; this solution therefore 
 is not caused by the ammonia, but by the new citrate of 
 ammonia. 
 
 6. If citric acid or a citrate is heated with concentrated 
 sulphuric acid, carbonic oxide gas and carbonic acid escape 
 first, without simultaneous blackening of the sulphuric acid ; 
 but after boiling for some time, the solution becomes dark 
 coloured, and sulphurous acid escapes. 
 
 7* 
 
166 MALIC ACID. 
 
 . MALIC ACID. (M = (C 8 H 4 O 8 .) 
 
 1. Malic acid forms with most bases, salts soluble in 
 water. The acid malate of potash is not of difficult solution 
 in water. Malic acid prevents the precipitation of the pe- 
 roxide of iron, &c. by alkalies, in the same manner as tar- 
 taric acid. 
 
 2. When heated to 200 Reaumur, malic acid is de- 
 composed into MALEIC ACID and HUMARIC ACID. This 
 property is highly characteristic. If the experiment is 
 made in a spoon, pungent acid vapours of maleic acid are 
 evolved with froth, but if conducted in a tube, these 
 vapours condense in the cold part of the tube, forming 
 crystals. The fumaric acid remains behind. 
 
 3. Chloride of calcium produces no precipitates, neither 
 in solutions of free malic acid, nor in those of the malates. 
 But if after the addition uf chloride of calcium, alcohol is 
 added to the solution of a malate, MALATE OF LIME, (M, 
 2Ca O) immediately precipitates as a white powder. 
 
 4. Lime-water pre c ipitates neither the free nor the 
 combined malic acid. 
 
 5. Acetate of lead throws down from solutions of malic 
 acid and of malates, a white precipitate of MALATE OF LEAD 
 (M, 2Pb O, 6 aq.) This precipitate is distinguished, 1st, 
 by losing its curdiness, and changing into concentrically- 
 grouped^needles, with the lustre of mother-o'-pearl, when 
 the fluid is allowed to 'stand for some time; and, 2d, by 
 its meltingpoint being lower than the boiling point of water. 
 On heating, therefore, the fluid wherein this precipitate is 
 suspended to the boiling point, the precipitate fuses and 
 resembles resin which has been melted under water. 
 
 6. On heating malic acid with concentrated sulphuric 
 acid, the latter substances become black with evolution of 
 sulphurous acid. 
 
 Recapitulation and remarks. Of the organic acids of 
 this group, the tartaric acid and paratartaric acid are suffi- 
 ciently characterized by the sparing solubility of their acid 
 salts of potash, by the relation of their lime salts to solution 
 of potash, and by the characteristic odour which they emit 
 during their combustion. Tartaric acid may be distin- 
 
' MALIC ACID. 167 
 
 guished from paratartaric acid best by means of its combina- 
 tion with lime, since tartrate of lime is soluble in free tartaric 
 acid, and also in solution of sal ammoniac, and thus pre- 
 sents two properties, which are wanting in paratartrate of 
 lime. The paratartaric acid, moreover, differs from tar- 
 taric acid in its relation to solution of gypsum. This 
 relation to a certain extent assimilates paratartaric acid to 
 oxalic acid ; it does not, however, give rise to any mistake 
 when operating upon the free acids, since the precipitate 
 which solution of gypsum produces in solutions of para- 
 tartaric acid, is never formed instantaneously. The oxa- 
 lates, moreover, are easily to be distinguished from the 
 paratartrates by the properties they exhibit when heated 
 either by themselves or with sulphuric acid- Citric acid 
 is best detected by its relations to lime-water, or to chloride 
 of calcium and ammonia. 
 
 The sparing solubility of the washed citrate of lead in 
 ammonia, distinguishes citric acid from tartaric and para- 
 tartaric acid. The other re-agents which produce preci- 
 pitates or other alterations in its solutions, such as chloride 
 of gold, and salts of silver and mercury, &c., show the 
 same or similar relations to tartaric and paratartaric acid, 
 and, therefore, do not afford us safe means of distinguishing 
 citric acid from the two latter substances. Malic acid 
 would be sufficiently characterized by the properties which 
 malate of lead presents when heated under water, if this 
 re-action were of greater sensibility, and if it were not 
 prevented so easily by the presence of other acids. The 
 precipitation of malate of lime by alcohol can only be of 
 value for the detection of malic acid, when we have previ- 
 ously convinced ourselves of the absence of all other acids, 
 the lime salts of which are sparingly soluble in water, and 
 quite insoluble in alcohol, such, for instance, as sulphuric 
 acid or boracic acid. It is, however, always necessary 
 further to test the precipitate produced by alcohol. The 
 heating of malic acid in a glass tube leads to the most 
 certain result ; this test is, however, not applicable under 
 all circumstances. 
 
168 BENZOIC ACID. 
 
 Second Group of the Organic Acids. 
 
 ACIDS, WHICH ARE UNDER NO CONDITION WHATEVER PRE- 
 CIPITATED BY CHLORIDE OF CALCIUM, BUT ARE PRECI- 
 PITATED FROM THEIR NEUTRAL SOLUTIONS BY PERCHLOt- 
 
 RIDE OF IRON i Succimc aoid, Benzoic acid. 
 
 103, 
 a. SUCCINJC ACID, s = (C 4 H 2 O 3 .) 
 
 1. Pure succinic acid is inodorous, dissolves readily ire 
 water, and volatilizes completely when heated. The offi- 
 cinal acid, which has an empyreumatic odour, leaves a 
 small carbonaceous residue. The succinates are decom- 
 posed at a red heat, with the exception of succinate of 
 ammonia ; those which have an alkali or alkaline earth for 
 their base, are converted inta carbonates in this process. 
 Most of the succinates are soluble in water ; succinic acid 
 enters into insoluble or sparingly soluble combinations only 
 with the metallic oxides which are weak bases. 
 
 2. Perchloride of iron produces, in a solution of succinic 
 acid brownish pale red, bulky precipitate of PERSUCCINATE 
 OF IRON (Fe 2 O 3 ,. 3s). To render this precipitation com- 
 plete, the free acid must first be neutralized with ammonia. 
 Persuccinate of iron readily dissolves in acids, and is 
 decomposed by ammonia; the hydrated peroxide of iron 
 separates, in this process of decomposition, and succinic 
 acid dissolves as succinate of ammonia. 
 
 3. Acetate of lead yields with succinic acid a white pre- 
 cipitate of SUCCINATE OF LEAD (Pb O, s) which is soluble 
 in succinic acid in excess, in solution of acetate of lead, and 
 in acetic acid. 
 
 4. Protonitrate of mercury and nitrate of silver aTso 
 precipitate the succinates ; these precipitates, however, are 
 by no means characteristic. 
 
 5. The alkaline succinates are insoluble in alcohol. 
 
 b. BENZOIC ACID. (e=Bz O =C 14 H 5 (X.) 
 
 1 . Pure benzoic acid appears in the form of white scales 
 or needles, or merely as a crystalline powder. It volatili- 
 zes completely when heated. Its vapours cause a peculiar 
 
BENZOIC ACID. 169 
 
 irritating sensation in tne throat, and provoke coughing. 
 The common officinal benzoic acid has the odour of benzoin, 
 and on being heated, leaves a small carbonaceous residue. 
 The benzoates of the alkalies and alkaline earths, are con- 
 verted into carbonates by heat. Benzoic acid is very 
 sparingly soluble in cold water, but of pretty easy solution 
 in hot water and in alcohol. It forms with most oxides 
 salts soluble in water, and enters into insoluble or sparingly 
 soluble combinations only with those oxides which are weak 
 bases. 
 
 2. Benzoic acid shows the same relation to chloride of 
 iron as succinic acid. The PERBENZOATE OF IRON, (Fe 2 , 
 O 3 , See,) is however by far brighter and more yellow than 
 the succinate. Ammonia decomposes it in like manner as 
 the succinate. When treated with stronger acids, the latter 
 combine with the peroxide of iron, and the benzoic acid, on 
 account of its sparing solubility, separates as a white 
 precipitate. 
 
 2- If to the solution of a benzoate a strong acid be added, 
 the benzoic acid is expelled, and separates in the form of a 
 shining white, sparingly soluble powder. The benzoic 
 acid separates in the same manner from its soluble salts, 
 as already stated, 2,) if some stronger acid is added to these 
 salts which forms soluble salts with the bases with which 
 the benzoic acid was combined. 
 
 Acetate of lead does not, or at least not immediately, 
 precipitate the free benzoic acid nor the benzoate of ammo- 
 nia, but it precipitates benzoates with fixed alkaline bases, 
 in the form of white flakes. 
 
 5. The alkaline benzoates are soluble in alcohol. 
 
 Recapitulation and R emarks. Succinic and benzoic 
 acid are distinguished from all other acids by their ready 
 volatility and their relation to perchloride of iron. They 
 differ from each other in the colour of their persalts of iron, 
 but especially in their solubility, succinic acid being readily 
 soluble, whilst benzoic acid is very difficult of solution. 
 Benzoic acid may, moreover, be detected by its irritating 
 and cough-provoking vapours. Succinic acid is generally 
 not quite pure, and may, therefore, also be detected by its 
 odour of oil of amber. 
 
170 ACETIC ACID. 
 
 A separation of these acids rrom each other may be 
 effected by decomposing their persalts of iron by ammonia, 
 and treating the new-formed compounds with alcohol, 
 after previous evaporation to dryness. The separation of 
 these acids is, of course, even more simple, if we can 
 combine them with alkalies in a more direct way. The 
 benzoate in that case dissolves, whilst the succinate remains. 
 
 Third Group of the Organic Acids. 
 
 ACIDS WHICH ARE NOT PRECIPITATED, UNDER ANY CONDI- 
 TION, BY CHLORIDE OF CALCIUM OR PERCHLORIDE OF 
 
 IRON : Acetic Acid, Formic Acid* 
 
 104. 
 a. ACETIC ACID. (A=C 4 H 3 3 .) 
 
 1. Acetic acid is completely volatilized by heat, forming 
 vapours of a pungent odour, which in their concentrated 
 slate are inflammable and burn with a blue flame. The 
 acetates are decomposed at a red heat. Among the pro- 
 ducts of their decomposition we usually find acetic acid, 
 and invariably acetone. The acetates which have an alkali 
 or alkaline earth for their base are converted into carbon- 
 ates, in this process. Many of those with a metallic base 
 leave the metal behind in its metallic state, others as oxide. 
 All the residues are carbonaceous. Almost all acetates 
 are soluble in water and alcohol ; most of them readily 
 dissolve in water, but a few are difficult of solution. 
 
 2. If perchloride of iron is added to acetic acid, no 
 alteration takes place, but if the acid is previously satu- 
 rated with ammonia, or if a neutral acetate is mixed with 
 perchloride of iron, the solution assumes a deep and dark 
 red tint, owing to the formation of PERACETATE OF IRON. 
 Ammonia precipitates all the peroxide of iron from" such 
 a solution. 
 
 3. Neutral acetates (but not free acetic acid) yield with 
 nitrate of silver, white crystalline precipitates of ACETATE 
 OF SILVER, (Ag O, A) which are very sparingly soluble in 
 cold water. They dissolve more readily in hot water, but 
 they separate again from the solution, on cooling, in the 
 
FORMIC ACID. 171 
 
 form of very fine crystals. Ammonia dissolves them 
 readily ; free acetic acid does not increase their solubility 
 in water. 
 
 4. Protonitrate of mercury produces in solutions of 
 acetic acid, and even with greater facility in solutions of 
 acetates, white scaly crystalline precipitates of PROTACE- 
 TATE OF MERCURY, (Hg 3 O, A,) which are sparingly 
 soluble in water and acetic acid, at a low temperature, but 
 easily soluble in an excess of the precipitant. Protacetate 
 of mercury dissolves in water on the application of heat, 
 but separates again, on cooling, in the form of small crys- 
 tals ; it becomes partly decomposed in this process, me- 
 tallic mercury separates and imparts a gray colour to the 
 precipitate. If protonitrate of mercury is boiled with 
 dilute acetic acid instead of water, the quantity of the 
 metallic mercury separating is exceedingly minute. 
 
 5. If acetates are heated with dilute sulphuric acidj 
 ACETIC ACID is evolved, which may be detected by its pun- 
 gent odour. And if the acetates are heated with about 
 equal weights of concentrated sulphuric acid and alcohol, 
 ACETIC ETHER is evolved ; the odour of this ether is highly 
 characteristic and agreeable ; it becomes particularly per- 
 ceptible on agitating the mixture when somewhat cooled 
 down, and scarcely admits of any mistake, and certainly 
 far less than the pungent odour of free acetic acid. 
 
 6. If acetates are distilled with dilute sulphuric acid, 
 and the distillate digested with oxide of lead in excess, 
 part of this oxide will be dissolved as a basic acetate of 
 lead, which may easily be detected by its alkaline reaction. 
 
 b. FORMIC ACID. (Fo O 3 = C 2 HO 3 .) 
 
 1. Formic acid has a characteristic pungent odour; it 
 volatilizes completely on heating ; the vapours of the con- 
 centrated acid are inflammable and burn with a blue flame. 
 The formiat.es, like the corresponding acetates, when 
 heated to redness, leave either carbonates or oxides, or 
 metals behind ; with simultaneous separation of carbon, 
 carburetted hydrogen, and escape of carbonic acid and of 
 water. All combinations of formic acid with bases are 
 soluble in water ; alcohol does not dissolve all of them. 
 
172 FORMIC ACID- 
 
 2. Formic acid presents the same relation to perchloride 
 of iron as acetic acid. 
 
 3. Nitrate of silver does not precipitate free formic acid, 
 and precipitates alkaline formiates only from concentrated 
 solution. The white, sparingly soluble, crystalline pre- 
 cipitate of FORMIATE OP SILVER (Fo O- { AgO) soon assumes 
 a deeper tint owing to the separation of metallic silver. 
 This reduction to metallic silver takes place, even at a low 
 temperature, after the solution containing the formiate of 
 silver has been allowed to stand for some time, but it fol- 
 lows instantaneously upon the fluid being heated with the 
 precipitate. The same reduction of the oxide of silver 
 ensues even if the solution of the formate was so dilute, 
 that no precipitate had been formed, or if we have to ope- 
 rate upon free formic acid. In this process, the formic 
 acid, which may be considered a compound of carbonic 
 oxide and water, deprives the oxide of silver of its oxygen, 
 giving rise to the formation of carbonic acid, which escapes, 
 and of water ; the metal is precipitated in its metallic state. 
 
 4. Protonitrate of mercury does not produce precipita- 
 tion in free formic acid ; but in concentrated solutions of 
 alkaline formiates it causes a white, sparingly soluble 
 precipitate of PROTOFORMIATE OF MERCURY, '(Fo O 3 Hg 3 
 O,) which after a very short time turns gray, owing to the 
 separation of metallic mercury ; complete reduction takes 
 place, sometimes even at a low temperature, but instanta- 
 neously on heating. In this process, also, carbonic acid 
 and water are formed. This reduction, in the same 
 manner, as is the case with the nitrate of silver, takes 
 place, even if the fluid is so dilute, that the protoformiate 
 of mercury remains in solution, or if we have free formic 
 acid to operate upon. 
 
 5. If formic acid or an alkaline formiate be heated with 
 perchloride of mercury to 60-70 Reaumur,*a precipitate 
 of PROTOCHLORIDE OF MERCURY is obtained. When heated 
 to the boiling point of water, metallic mercury separates 
 besides the protochloride. 
 
 6. If formic acid or a formiate is heated with concen- 
 trated sulphuric acid, it becomes decomposed without 
 blackening the fluid, giving rise to the formation of water 
 and carbonic oxide gas, which escapes with effervesence, 
 
FORMIC ACID. 173 
 
 and when ignited, burns with a blue flame, The sulphuric 
 acid withdraws from the formic acid, the water or oxide 
 necessary to the existence of this substance, and thus 
 causes a transposition of m its atoms to take place (C 2 
 H O 3 = 2 CO-I-HO.) If a formiate is heated with dilute 
 nitric acid, formic acid escapes, which may easily be 
 detected by its odour. If a formiate is drenched with a 
 mixture of sulphuric acid and alcohol, formic fither is- 
 evolved, which is characterized by its peculiar arraek 
 smell. 
 
 Recapitulation andremarks. As the reactions of acetic 
 acid and formic acid are not so characteristic as those of 
 many other acids, their safe detection can only be based 
 on the concurrence of all the reactions we have stated. 
 Acetic acid is most easily detected by its odour or by that 
 of acetic ether, but most safely by its behaviour with oxide 
 of lead. Formic acid may best be- detected by its beha- 
 viour with sulphuric acid and with the salts of the noble 
 metals. The separation of acetic acid from formic acid is 
 effected by heating both acids with peroxide of mercury in 
 excess, or with oxide of silver. The formic acid reduces 
 the oxides, and becomes decomposed at the same time ; 
 the acetic acid combines with them and remains in solution. 
 
 ' 
 
PART II. 
 
 SYSTEMATIC COURSE 
 
 OF 
 
 QUALITATIVE CHEMICAL ANALYSIS. 
 
PART II, 
 PRELIMINARY REMARKS 
 
 ON THE 
 
 COURSE OF QUALITATIVE ANALYSIS IN GENERAL, 
 
 AND ON THE 
 
 PLAN OF THIS SECOND PART OF THE PRESENT WORK 
 
 IN PARTICULAR. 
 
 WHEN we are once acquainted with the reagents and 
 the relation of other bodies to them, we are immediately 
 able to determine, whether some simple compound or 
 other, the physical qualities of which admit of drawing an 
 inference as to its nature, is in reality what we take it to 
 be. Thus, for instance, a few simple reactions convince 
 us that a body which we suppose to be calcareous spar, is 
 really carbonate of lime ; and another substance, which we 
 deem gypsum, is really sulphate of lime. This know- 
 ledge is usually equally sufficient to ascertain, whether a 
 certain body be present or not in some compound sub- 
 stance or other ; for instance, whether a white powder 
 contains protochloride of mercury or not. But if our de- 
 sign is to ascertain the chemical nature of a substance en- 
 tirely unknown to us if we wish to discover all the con- 
 stituents of a mixture or a chemical combination if we 
 intend to prove that) besides certain bodies we have de- 
 tected in a mixture or compound, no other substance can 
 be present with it, and, consequently, if a COMPLETE quali- 
 tative analyses our object, the mere knowledge of rea- 
 gents and reactions is no longer sufficient ; we must of ne^ 
 cessity know besides how to proceed systematically in our 
 analysis ; i. e. we must know in what order we have to 
 
178 PRELIMINARY REMARKS. 
 
 apply solvents, and general and especial reagents, so as to 
 be enabled with celerity and certainty to determine that 
 all those substances which a compound or mixture does 
 NOT contain, ARE REALLY NOT contained in it ; and on the 
 other hand, quickly and safely to detect those bodies which 
 ARE PRESENT in the substance under examination. If we 
 do not possess the knowledge of this systematic course, 
 or if, in the hope of more rapidly attaining our object, we 
 adhere to no method whatever in our investigations and 
 experiments, analysis becomes (at least in the hand of a 
 novice) mere guessing, and the results obtained are 110 
 longer the fruits of scientific calculation, but mere matters 
 of accident, which sometimes may prove lucky hits, and at 
 others total failures. 
 
 A definite method, therefore, must form the basis of 
 every analytical investigation. But it is not by any means 
 necessary that this method should be in all cases one and 
 the same. Practice, reflection, and a due attention to cir- 
 cumstances, will, on the contrary, in most cases direct us 
 to various and different methods. But all analytical me- 
 thods agree in this, that the substances existing, or sup- 
 posed to exist, must first be divided info certain groups, 
 and the bodies belonging to these groups be further dis- 
 tinguished from each other, so as at last to admit of their 
 individual detection. The diversity of analytical methods 
 depends partly on the order in which reagents are applied, 
 and partly on their selection. 
 
 Before we can venture upon inventing methods of our 
 own for individual cases, we must first make ourselves 
 thoroughly conversant with a certain definite course or 
 system of chemical analysis in general. This system 
 must have passed through the ordeal of experience, and 
 must be adapted to every case imaginable, so as to enable 
 us afterwards, when we have acquired some practice in 
 analysis, to determine which modification of ttie general 
 method will, in certain given cases, most easily and rapidly 
 lead to the attainment of the object in view. 
 
 The exposition of such a systematic couise, adapted to 
 all cases, tested by experience, and combining the greatest 
 possible simplicity with the greatest possible security, is 
 the object of the second part of this work. 
 
PRELIMINARY REMARKS. 179 
 
 The elements and combinations comprised in it are the 
 same which we have enumerated in our preliminary 
 remarks. 
 
 Since it is necessary in the formation of such a system- 
 atic course to provide for every possible circumstance which 
 may occur, it follows, as a matter of course, that we are 
 obliged to suppose those substances which we treat of 
 (however mixed and intermixed with each other we may 
 admit them to be) free from extraneous organic matters, 
 since the presence of such matters prevents the manifesta- 
 tion of many reactions, and causes various modifications in 
 others. We by no means intend to assert here that the 
 proposed systematic course may not be exactly followed 
 even in presence of many organic substances, especially of 
 those which dissolve in water, forming colourless transpa- 
 rent fluids. Experience and reflection in every individual 
 case will best instruct us how to act in cases where dark 
 colouring slimy matters are present. For the most impor- 
 tant rules, and the method in general, we refer to 129. 
 
 This second part is divided into two sections ; the first 
 contains PRACTICAL INSTRUCTIONS IN ANALYSIS, wherein 
 we have pointed out a way which must lead to the end in 
 view, if systematically followed. At first sight, many parts 
 of it may, perhaps, be deemed rather prolix ; I think, howe- 
 ver, that it would have scarcely been possible to abbreviate 
 it, except at the expense of clearness and perspicuity for 
 beginners. I hope, moreover, that my readers will soon 
 become convinced by experience that this prolixity, after all, 
 does not prove any bar to the celerity with which the sys- 
 tematic course may be gone through, as I have always 
 divided the phenomena which may occur, into clearly cha- 
 racterized instances; and thus a given object being the only 
 one to be considered, and one number always referring to 
 the other, the student may save himself the trouble of read- 
 ing through those parts which are not adapted for the 
 especial case engaging his attention. 
 
 The subdivisions of this practical course are, 1 , Preli- 
 minary examination ; 2, Solution ; 3, Real examination ; 
 4, Confirmatory experiments. The third subdivision (the 
 real examination) is again subdivided into, 1, Examination 
 of compounds in which we suppose but one basis and but 
 
180 PRELIMINARY REMARKS. 
 
 one acid present; and, 2, Examination of mixtures or com- 
 pounds in which we suppose that all those substances 
 which we have taken into consideration may be present. 
 With respect to the latter, it must be observed that where 
 the preliminary examination has not afforded us the most 
 certain conviction of the absence of certain groups of sub- 
 stances, we cannot safely disregard any paragraph to which 
 we refer, in consequence of the phenomena that manifest 
 themselves. In cases where we merely intend to test a 
 combination or mixture for certain substances, and not for 
 all its constituents, it will be easy to find those numbers 
 which we have to take into consideration. 
 
 The second section contains an EXPLANATION OF THE 
 PRACTICAL PROCESS, an exposition and explanation of the 
 grounds whereon the separation, and the causes, whereon 
 the detection of substances depend ; and, moreover, various 
 additions to the first section. Students would do well to 
 make themselves early acquainted with this section, which 
 may be advantageously studied, concurrently with the 
 practical process. 
 
 As an appendix, we give A GENERAL SCHEME OF THE 
 
 ORDER IN WHICH THOSE SUBSTANCES WHICH ARE TO BE 
 ANALYZED FOR THE SAKE OF PRACTICE MAY MOST JUDI- 
 CIOUSLY BE SUCCESSIVELY TAKEN; and ALSO A TABULAR 
 ARRANGEMENT OF THE MORE FREQUENTLY OCCURRING 
 FORMS AND COMBINATIONS OF THE SUBSTANCES ENUME- 
 RATED IN OUR PRELIMINARY REMARKS, ACCORDING TO 
 THEIR VARIOUS DEGREES OF SOLUBILITY IN WATER AND 
 
 ACIDS. The first is intended to serve the pupil as a guide 
 to the rapid and certain attainment of his object ; i. e. a 
 sound and complete acquisition of qualitative analysis; and 
 the second will, undoubtedly, prove useful to many who are 
 not yet quite conversant with the various degrees of solu- 
 bility of compound bodies, especially in cases where they 
 have to draw conclusions as to how the detected acids, 
 bases, &c., have been combined, or what particular acids 
 cannot possibly be present in aqueous or acid solutions, 
 when the latter contain certain bases. 
 
' 
 
 PRELIMINARY EXAMINATION. 181 
 
 FIRST SECTION. 
 PRACTICAL PROCESS. 
 
 I. PRELIMINARY EXAMINATION. 
 
 105. 
 
 In the first place, the external and sensible properties 
 of the substance under examination should be considered, 
 such as its colour, shape, hardness, gravity, odour, &c., as 
 many conclusions may often be drawn therefrom. Before 
 proceeding any further, we ought to consider well how 
 much of the substance to be examined we have at com- 
 mand, since it is necessary at this early period of the exa- 
 mination to determine the quantity which we may use in 
 the preliminary investigation. A reasonable economy is 
 in all cases advisable, though we may possess the sub- 
 stance in large quantities ; and it must be laid down as a 
 fixed rule, never to use at once all we possess of a sub- 
 stance, but always to keep at least a small portion of it 
 for unforeseen accidents, and for confirmatory experi- 
 ments. 
 
 A. THE BODY UNDER EXAMINATION IS SOLID. 
 
 I. IT IS NEITHER A PURE METAL NOR AN ALLOY. 
 
 1. The substance is fit for examination when in powder 
 or in small crystals ; but when in larger crystals or in 
 solid pieces, a -portion of it, if possible, must first be re- 
 duced to powder. 
 
 2. The powder is heated over the spirit-lamp, in a small 
 iron spoon. The phenomena resulting admit of many 
 safe inferences as to the nature of the substance, and allow 
 us to draw many probable conclusions. 
 
 a. THE SUBSTANCE REMAINS UNALTERED : no or- 
 ganic substances, no salts containing water of crys- 
 tallization, no easily fusible matter, no volatile bodies. 
 
 b. IT FUSES EASILY, AND BECOMES SOLID AGAIN 
 WITH THE EXPULSION OF AQUEOUS VAPOUR J Salts 
 
 which contain water of crystallization. If the solidi- 
 
 8 
 
182 PRELIMINARY EXAMINATION. 
 
 fied residue fuses again upon the application of an 
 increased heat, c must be referred to. 
 
 ; \ C. IT FUSES WITHOUT EXPULSION OF AQUEOUS VA- 
 POUR. A small piece of paper is added to the melt- 
 in,/ mass ; if deflagration lakes place, it indicates 
 NITRATES, or more rarely, CHLORATES. 
 
 d. IT VOLATILIZES COMPLETELY OR PARTLY. In 
 
 the first case, no fixed bases are present ; in the latter, 
 the substance contains a volatile body in admixture. 
 
 a. No odour is emitted. In this case we must 
 especially have regard to compounds of AMMONIA, 
 MERCURY, and ARSENIC. 
 
 j8. An odour is emitted at the same time. If it 
 is that of sulphurous acid, SULPHUR is present ; if 
 that of iodine, and if the vapours arc violet, the 
 presence of free IODINE is certain. With equal cer- 
 tainty free BENZOIC ACID, and many other substances, 
 may be detected by the odourfof their vapours. 
 e. THE SUBSTANCE is A WH|TE POWDER TURNING 
 TO .YELLOW ON HEATING ] this indicates OXIDE OF 
 ZINC or OXIDE OF LEAD } the latter substance remains 
 yellow on cooling, whilst the oxide of zinc resumes 
 its white colour. 
 
 /. CARBONIZATION TAKES PLACE : organic sub- 
 stances. If the residue effervesces when drenched 
 with acids, whilst the original substance does not 
 present that property, it indicates the presence of 
 ORGANIC ACIDS, comb.iiicd with alkalies or alkaline 
 matter. If the odour of cyanogen is perceptible, it 
 indicates the presence of a CYANIDE. . 
 
 Many substances, moreover, swell up considerably, 
 as for instance, borax, sulphate of alumina ; others 
 decrepitate, e. g. chloride of sodium, and chloride of 
 potassium, &c. ; these phenomena, however, less 
 admit of general and certain conclusions than those 
 stated above. 
 
 |VK 3. A small portion of the substance is put on a charcoal 
 support, and exposed to the reducing flame of the blow- 
 pipe. Since most of the phenomena just now described 
 (2) are equally obtained by this process, we will here 
 mention only those which particularly belong to the latter. 
 
BY HEAT. THE BLOW PIPE. 183 
 
 a. THE SUBSTANCE VOLATILIZES PARTLY OR COM- 
 PLETELY. This indicates besides the substances 
 mentioned in 105, 2, d, also OXIDE OF ANTIMONY, 
 and several other oxides. (Compare 105, 6, d, /3.) 
 Oxide of antimony fuses previous to its volatilization, 
 in the form of a white vapour. It must, moreover, be 
 remarked, that when ARSENIOUS or ARSENIC ACID are 
 present, a characteristic odour of garlic is perceptible, 
 which is stronger if soda has previously been added 
 to the test specimen. 
 
 b. TlIE BODY FUSES, AND IS IMBIBED BY THE 
 
 CHARCOAL ; this indicates the presence of. ALKALIES. 
 This process is conducted by putting a portion of the 
 substance reduced to powder on the moistened loop 
 of a platinum wire, and applying the heat of the re- 
 ducing blow-pipe flame to it. If the oxidizing flame 
 assumes a violet tint, it indicates the presence of POT- 
 ASH alone ; if a yellow tint, the presence of SODA, 
 which may, however, be mixed with potash, even in 
 a considerable proportion, since the flame always ap- 
 pears yellow when both these alkalies are present. 
 
 C. AN INFUSIBLE WHITE RESIDUE REMAINS ON THE 
 CHARCOAL, EITHER IMMEDIATELY, OR AFTER .PREVIOUS 
 MELTING IN THE WATER OF CRYSTALLIZATION ] this 
 
 indicates especially the presence of barytes/strontian, 
 lime, magnesia, alumina, zinc, and silicic acid. Of 
 these substances STRONTIAN, LIME, MAGNESIA, and 
 ZINC, are distinguished by being very luminous in the 
 blow pipe flame. A drop of solution of nitrate of 
 cobalt is added to the white residue, and the latter 
 then again strongly heated. ALUMINA presents a fine 
 blue tint, MAGNESIA a reddish, and ZINC a green 
 colour. When SILICIC ACID is present, the flame as- 
 sumes also a feeble bluish tint, which should not be 
 confounded with that produced by alumina. Silicic 
 acid is moreover distinguished by forming a clear 
 glass, with effervescence, when mixed with carbonate 
 of soda, and exposed to a strong blow-pipe flame. 
 ( 99, b.) 
 
 d. AN INFUSIBLE RESIDUE OF A DIFFERENT CO- 
 LOUR REMAINS, OR A METALLIC REDUCTION TAKES 
 
184 PRELIMINARY EXAMINATION. 1 
 
 PLACE, WITH OR WITHOUT INCRUSTATION OF THE 
 
 CHARCOAL SUPPORT. A portion of the powder is 
 mixed with carbonate of soda, and heated in the re- 
 ducing flame on charcoal. 
 
 . A metallic grain is obtained, without simulta- 
 neous incrustation of the charcoal ; this indicates 
 the presence of GOLD, SILVER, TIN, OR COPPER. 
 Platinum, iron, cobalt, and nickel, equally become 
 reduced, but yield no metallic grains. 
 
 /3. The charcoal support is coated over with an 
 incrustation, either with or without simultaneous 
 formation of a metallic grain : this indicates the 
 presence of bismuth, lead, cadmium, antimony, or 
 zinc. 
 
 aa. If the incrustation is white, ANTIMONY 
 or ZINC may be supposed present. The in- 
 crustation produced by zinc appears yellow as 
 long as it remains hot. The pure metallic 
 grain of antimony evolves white vapour, even for 
 a long time after all application of heat has been 
 withdrawn ; and at last, on cooling, becomes 
 generally surrounded with crystals of oxide of 
 antimony. It is brittle under the stroke of a 
 hammer. 
 
 bb. The incrustation is more or less yellow 
 or brown ; this indicates the presence of BISMUTH, 
 LEAD, or CADMIUM. The yellow incrustation of 
 oxide of cadmium has a shade of orange colour 
 in." it; the brownish-yellow incrustations of oxide 
 of lead and oxides of bismuth change into a light 
 yellow on cooling. Cadmium immediately volati- 
 lizes on becoming reduced. The grains of lead 
 are very ductile, whilst the grains of bismuth 
 are brittle under the stroke of the hammer. 
 
 The student must be prepared, of course, to meet with 
 combinations of bodies giving rise to mixed phenomena, 
 and must deduce his conclusions accordingly, since we 
 cannot give strictly denned cases in these general rules. 
 
OF METALS AND ALLOYS. 185 
 
 II. THE SUBSTANCE IS A METAL OR AN ALLOY. 
 
 1 . The test-specimen is drenched and heated with water, 
 mixed with some acetic acid. 
 
 a. HYDROGEN is EVOLVED ; this indicates the pre- 
 sence of a light metal. The presence of alkalies and 
 of alkaline earths must be had regard to in the real 
 examination. 
 
 6. No HYDROGEN is EVOLVED ; this indicates the 
 absence of light metals. Alkalies and alkaline earths 
 need not be considered in the course of the special 
 investigation. 
 
 2. The test-specimen is heated on charcoal, in the redu- 
 cing blow-pipe flame, and the phenomena observed, such 
 as, for instance, whether the substance fuses, whether 
 an incrustation is formed, whether any odour is emit- 
 ted, &c. 
 
 a. THE SUBSTANCE REMAINS UNALTERED ; this is 
 pretty conclusive of the absence of antimony, zinc, 
 lead, bismuth, cadmium, tin, mercury, and arsenic ; 
 the absence of gold, silver, and copper, is also proba- 
 ble ; it indicates the presence of PLATINUM, IRON, 
 
 MANGANESE, NIKEL, Or COBALT. 
 
 b. THE SUBSTANCE FUSES WITHOUT SIMULTANEOUS 
 INCRUSTATION, AND WITHOUT EMISSION OF ODOUR J 
 
 this indicates the absence of antimony, zinc, lead, bis- 
 muth, cadmium, and arsenic, and the presence of GOLD, 
 
 SILVER, COPPER, Or TIN. 
 
 C. THE SUBSTANCE FUSES WITH THE FORMATION OF 
 A CRUST, BUT WITHOUT EMITTING ANY ODOUR ', this 
 
 indicates the absence of arsenic, and the presence of 
 
 ANTIMONY, ZINC, BISMUTH, LEAD, Or CADMIUM. (Com- 
 
 pare 105 A. I., 3 d, ft.) 
 
 d. THE SUBSTANCE EMITS A GARLIC ODOUR } this Ul- 
 
 dicates the presence of ARSENIC. For the other phe- 
 nomena which may manifest themselves, we refer to 
 a. 6, or c. 
 
 3. The substance is heated before the blow-pipe in a 
 glass tube, closed at one end. 
 
 a. No SUBLIMATE IS FORMED IN THE COLDER PART 
 
 OF THE TUBE ; this indicates the absence of mercury. 
 
 b. A SUBLIMATE is FORMED ; this indicates the pr e- 
 
186 PRELIMINARY EXAMINATION. 
 
 sence of MERCURY, CADMIUM, or ARSENIC. The sub- 
 limate of mercury, which consists of small globules, 
 cannot be confounded with the sublimate of cadmium 
 or arsenic. 
 
 B. THE SUBSTANCE UNDER EXAMINATION IS A FLUID. 
 
 1 . A small portion of the fluid is evaporated in a plati- 
 num spoon, or in a small porcelain crucible, to enable us 
 to determine whether the fluid contains any substance in 
 solution, and what is the nature of the residue. ( 105 
 A.) 
 
 2. The fluid is tested by litmus papers. 
 
 a. BLUE LITMUS PAPER BECOMES RED. This reac- 
 tion may be caused either by a free acid, or an acid 
 salt, or by a soluble metallic salt. In order to distin- 
 guish these two cases from each other, a small quanti- 
 ty of -the liquid is. poured into a watch-glass, and a lit- 
 tle rod placed into it, the extreme point of which has 
 previously been dipped into dilute solution of carbo- 
 nate of potash; if the fluid remains clear, or if the 
 precipitate which may form is redissolved on stirring 
 the liquid, it indicates the presence of a free acid or 
 an acid salt ; but if the fluid becomes turbid, it proves 
 the presence of a soluble metallic salt, at least gene- 
 rally. As a matter of course, with the presence of a 
 free acid or acid salt, the solution cannot be considered 
 as a mere aqueous one, and consequently we must look 
 carefully to all those phenomena which may indicate 
 the presence of bodies insoluble in water, and soluble 
 
 . only in acids. 
 
 b. REDDENED LITMUS PAPER BECOMES BLUE ; this 
 indicates the presence of free alkalies, or alkaline 
 carbonates, free alkaline earths, or alkaline sulphu- 
 rets, and also of a series of other salts of which this 
 reaction is characteristic. With the presence of a 
 free alkali, a body dissolved in the fluid may as well 
 belong to those soluble as to those insoluble in water. 
 We refer to 114 I., 2, for further information on 
 this subject. 
 
 3. We test by smelling and tasting, or should this n^t 
 yield any safe results, by distillation, whether the simple 
 
CLASSIFICATION OF SUBSTANCES. 187 
 
 solvent present is water, alcohol, ether, &c. If it is found 
 not to be water, the solution is evaporated to dryness, and 
 the residue treated according to 106 A. 
 
 4. If the solution is aqueous, and manifests an acid 
 reaction, a portion of it is highly diluted: with water. If 
 it becomes milky, the presence of ANTIMONY, BISMUTH, or 
 TIN, may be supposed. If the precipitate disappears on 
 the addition of tartaric acid, we may conclude that anti- 
 mony is present, whilst its disappearance on the addition 
 of acetic acid, but not of tartaric acid, indicates the pre- 
 sence of bismuth. The original fluid is then treated either 
 as 107 directs, or 114, according to whether we have 
 reason to suppose it to be the solution of a simple or of a 
 compound or mixed substance. 
 
 II. SOLUTION OF BODIES OR CLASSIFICATION OF SUB- 
 STANCES ACCORDING TO THEIR RELATIONS TO CERTAIN 
 SOLVENTS. 
 
 106. 
 
 Water and hydrochloric acid, or in certain cases acetic 
 acid, are the solvents used to classify simple or compound 
 substances, and to isolate the component parts of mixtures. 
 We divide . substances into three classes, according to 
 their relations to these solvents. 
 
 First class, SUBSTANCES SOLUBLE IN WATER. 
 Second class. SUBSTANCES INSOLUBLE OR SPAR- 
 INGLY SOLUBLE IN WATER, BUT SOLUBLE IN HYDRO- 
 CHLORIC OR NITRIC ACID. 
 
 Third class. SUBSTANCES INSOLUBLE OR SPAR- 
 INGLY SOLUBLE, BOTH IN WATER, AND ALSO IN HYDRO- 
 CHLORIC OR IN NITRIC ACID. 
 
 A special method for the solution of alloys is given in 
 106 B, as it is advisable to dissolve them in a manner 
 somewhat different from that employed by other bodies. 
 
 The process of solution or separation is conducted in 
 the following manner. 
 
 A. THE SUBSTANCE UNDER EXAMINATION IS NEITHER A METAL 
 NOR AN ALLOY. 
 
 1. About fifteen or twenty grains of the substance to 
 
188 SOLUTION AND SEPARATION. 
 
 be examined, reduced to powder, are covered in a test- 
 tube with ten or twelve times as much water, and heated 
 to the boiling point over a spirit-lamp. 
 
 a. THE SUBSTANCE is COMPLETELY DISSOLVED. In 
 this case it belongs to the first class ; regard must be 
 had to what we have stated in 105 B, 2, concerning 
 reactions. The solution is treated either as stated 
 at 107, and at 114, according as to whether one 
 or several acids and bases are supposed to be present. 
 
 b. A RESIDUE REMAINS, EVEN AFTER BOILING THE 
 
 SOLUTION FOR A LONG TIME. The solution is allowed 
 to settle, and filtered, so that the residue remains in 
 the test-tube if possible ; a few drops of the clear 
 filtrate are then evaporated on a clean platinum plate ; 
 if no residue remains, the substance is completely 
 insoluble in water, and is then further tested, as stated 
 in 106, 2. But if a residue remains, the substance 
 is at least partly soluble. It is then again boiled with 
 water, filtered, and the filtrate added to the original 
 solution. This fluid is treated, according to circum- 
 stances, either as 107 directs, or as stated 114. 
 The residue is washed, and treated according to 
 106, 2. 
 
 2. This residue is drenched with dilute hydrochloric 
 acid. If it does not dissolve, it is heated to the boiling 
 point, and if even then no complete solution lakes place, 
 the fluid is decanted, and the residue boiled with concen- 
 trated hydrochloric acid. 
 
 The phenomena which may manifest themselves 
 in this operation, and which ought to be carefully 
 observed, are, *, Effervescence, which indicates the 
 presence of carbonic acid, or sulphuretted hydrogen, 
 vide 108, 2. P>. Evolution of chlorine, which indi- 
 cates the presence of hyperoxides. chromates, &c. 
 y. Emission of the odour of hydrocyanic acid, which 
 indicates the presence of insoluble cyanides. Since 
 it is advisable to decompose the latter in a different 
 manner, a special paragraph will be devoted to them. 
 (Vide 128.) 
 
 a. The RESIDUE is COMPLETELY DTSSOLVED BY THE 
 HYDROCHLORIC ACID ; the solution is treated accord- 
 
SOLUTION AND SEPARATION. 189 
 
 ing to circumstances, either as directed 110, or as 
 stated 114. The substance belongs to the second 
 class* 
 
 The separation of undissolved sulphur, which is 
 easily detected by its colour and specific gravity, 
 belong also to this category. 
 
 b. A RESIDUE REMAINS. In this case the test-tube 
 containing the specimen boiled with hydrochloric 
 acid, is put aside pro tempore, and another specimen 
 of the substance under examination is boiled with 
 nitric acid, with the subsequent addition of water. 
 
 <*, The specimen is completely dissolved, or 
 undissolved sulphur alone remains ; the body in 
 these cases also belongs to the second class ; 
 the solution is further tested for bases, according 
 to circumstances, either as directed $ 110, or as 
 stated 114, iii. 
 
 /3. A residue remains. 
 
 aa. WE HAVE REASON TO SUPPOSE THAT THE 
 
 SUBSTANCE UNDER EXAMINATION CONTAINS BUT 
 
 ONE BASE AND ONE ACID. The substance is 
 drenched with aqua regia, and then heated. 
 
 *. The substance dissolves. The solu- 
 tion is treated according to 1 10. 
 
 . The substance does not dissolve. In 
 that case we proceed according to 113. 
 
 bb. WE HAVE REASON TO SUPPOSE THAT THE 
 SUBSTANCE UNDER EXAMINATION IS A COMBINA- 
 TION OR MIXTURE OF SEVERAL COMPOUNDS. Inthis 
 
 case the reserved hydrochloric solution ( 106 A. 
 2, &,) is used to test for the bases. It is for this 
 purpose heated to boiling with the insoluble 
 residue (which latter must then be treated as 
 stated, 106, 3) and filtered hot into a tube 
 containing some water, the residue is then 
 boiled with some water, filtered hot, and the 
 filtrate added to the hydrochloric solution. 
 
 <*. The filtrate becomes turbid and milky ; 
 this indicates ANTIMONY OR BISMUTH ; or it 
 deposits fine crystals ; this indicates the pre- 
 sence of LEAD. The filtrate is heated again 
 8* 
 
190 ' DIVISION OF METALS. 
 
 (if needed, wilh the addition of some hydro- 
 chloric acid) till it appears clear, and then 
 treated, according to 114. II. 
 
 ,fl/3. The Jiltrate remains clear. A few 
 drops of it are evaporated to satisfy ourselves 
 whether the hydrochloric acid has dissolved 
 anything. If any residue remains, the filtrate 
 is treated according to 114, II. 
 3. If boiling concentrated- hydrochloric acid has left a 
 
 residue, it is washed with water, and treated as directed, 
 
 127. 
 
 B. THE SUBSTANCE UNDER EXAMINATION IS A METAL OR 
 AN ALLOY. 
 
 The metals are best divided according to their beha- 
 viour with nitric acid. 
 
 I. METALS WHICH ARE NOT AFFECTED BY NITRIC ACID : 
 gold, platinum. 
 
 II. METALS WHICH ARE OXIDIZED BY NITRIC ACID, 
 
 BUT THE OXIDES OF WHICH DO NOT DISSOLVE IN AN 
 
 EXCESS OF THE ACID: antimony tin. 
 
 III. METALS WHICH ARE OXIDIZED BY NITRIC ACID, 
 
 iAND THE OXIDES OF WHICH DISSOLVE IN AN EXCESS OF 
 
 THE ACID, FORMING NITRATES: all other metals. 
 
 A specimen of the substance is drenched with nitric 
 acid of 1*25 sp. gr., and heated. 
 
 1. COMPLETE SOLUTION TAKES PLACE, OR is EFFECT- 
 ED BY THE ADDITION OF WATER; this indicates the 
 absence of platinum, gold, antimony, and tin ; a small spe- 
 cimen of the solution is diluted with much water. 
 
 a. The solution remains clear ; some hydrochloric acid 
 is added ; if this produces a white precipitate, which 
 does not dissolve? on heating the fluid, but is dissolved 
 by ammonia, after having been rinsed previously, 
 SILVER is present. The original solution is treated 
 as directed 115. 
 
 b. The solution becomes turbid and milky ; this 
 indicates the presence of BISMUTH. The solution is 
 
SOLUTION. 191 
 
 filtered, and the filtrate tested for silver, as stated, 
 106, B, 1, a. The original solution is treated accord- 
 ing to 115. 
 
 2. A RESIDUE REMAINS. 
 
 a. A metallic residue remains. The solution is 
 filtered, and the filtrate treated as directed 106, B, 1 , 
 after having examined whether anything has been dis- 
 solved. The residue is by rinsing freed from all dis- 
 solved metallic particles, dissolved in aqua regia, and 
 divided into two portions ; chloride of potassium is 
 added to one portion : if a yellow precipitate is formed, 
 it indicates the presence of PLATINUM. Protosulphate 
 of iron is added to the other portion : if a black pre- 
 cipitate is formed, it indicates the presence of GOLD. 
 
 6. A white pulverulent residue remains ; this indi- 
 cates the presence of ANTIMONY OR TIN. The solution 
 is filtered, and the filtrate treated as directed 106, 
 B, 1, after having examined whether ^jything has 
 been dissolved. The residue is carefully rinsed, and 
 heated with a hot saturated solution of bitartrate of 
 potash or a solution of tartaric acid. 
 
 <*. Complete solution takes place : this indicates 
 the presence of oxide of ANTIMONY alone; the 
 solution is tested with solution of sulphuretted 
 hydrogen, 
 
 /3. A white precipitate remains, even after boiling 
 with a fresh portion of solution of bitartrate of potash 
 or of tartaric acid", this indicates the probable pres- 
 ence of tin. The solution is filtered and mixed with 
 solution of sulphuretted hydrogen. If an orange-red 
 precipitate is formed, oxide of antimony is present. 
 The presence of oxide of tin is ascertained by mixing 
 the residue with cyanide of potassium and carbonate 
 of soda, and reducing it before the blow-pipe. 
 (Compare 94, c, 7.) 
 
192 SUBSTANCES SOLUBLE IN WATER. 
 
 III. REAL EXAMINATION. 
 
 Compounds supposed to consist simply of one base and one 
 acid ; or one metal and one metalloid. 
 
 A. SUBSTANCES SOLUBLE IN WATER. 
 
 Detection of the base.* 
 
 107. 
 
 1. Some Hydrochloric acid is added to a portion of the 
 aqueous solution. 
 
 a. No PRECIPITATE is FORMED; this indicates the 
 absence of silver and protoxide of mercury with cer- 
 tainty, and is also a probable indication of the absence 
 of lead. For further examination, vide 107, 2. 
 
 b. A PRECIPITATE is FORMED. Divide the fluid, 
 in which the precipitate is suspended, into two por- 
 tions, and add ammonia in excess to the one. 
 
 ef The precipitate vanishes, and the fluid be- 
 comes clear ; the precipitate in this case consists 
 of chloride of silver, and is, therefore, indicative of 
 the presence of SILVER. To obtain a conviction 
 on this point the original solution must be tested 
 , with chromate of potash, and with sulphuretted 
 
 hydrogen. (Vide 90, 0, 2, and 96, b, 5-) 
 K :. f ^/3. The precipitate becomes black; it consists 
 '-ul. -this case of protochloride of mercury, whicb 
 has been converted by the ammonia into protoxide 
 of mercury, and is, consequently, indicative of the 
 presence of PROTOXIDE OF MERCURY. To set all 
 doubt at rest as to this point, test the original solu- 
 tion with protochloride of tin and with metallic 
 copper. (Vide 90, 5.) 
 
 y. The precipitate remains unaltered / it con- 
 sists in this case of chloride of lead, which is nei- 
 4her decomposed nor dissolved by ammonia ; this 
 reaction is, therefore, indicative of the presence of 
 LEAD. We assure ourselves of the presence of 
 this substance ; 1st, by diluting the second portion 
 of the fluid in which the precipitate produced by 
 
 *We include here arsenious and arsenic acid. 
 
SUBSTANCES SOLUBLE IN WATER. 193 
 
 hydrochloric is suspended, with much water and 
 applying heat. The precipitate must dissolve if it 
 really is chloride of lead ; 2d, by adding dilute sul- 
 phuric acid to the original solution, ( 90, c.) 
 2. Solution of sulphuretted hydrogen is added to the 
 fluid acidified with hydrochloric acid, till it has imparted 
 its characteristic odour to this fluid, which the latter must 
 still retain even after stirring and shaking ; the liquid is 
 then heated. 
 
 a. THE FLUID REMAINS CLEAR. Pass over to 3, 
 for lead, bismuth, copper, cadmium, peroxide of mer- 
 cury, gold, platinum, tin, antimony, arsenic, and pe- 
 roxide of iron, are not present. 
 
 b. A. PRECIPITATE IS FORMED. 
 
 a. THIS PRECIPITATE is WHITE ; it is in this 
 case produced by the separation of sulphur, and is 
 indicative of the presence of PEROXIDE OF IRON. 
 ( 88, /.) The original solution is then further 
 tested with ammonia and with ferrocyanide of po- 
 tassium, in order to ascertain whether the sub- 
 stance present is really peroxide of iron. 
 
 p. THE PRECIPITATE is YELLOW; in this case 
 it may consist either of sulphuret of cadmium, or 
 a sulphuret of arsenic, or bisulphuret of tin, and in- 
 dicates therefore the presence either of cadmium, 
 or of arsenic, or of peroxide of tin. To distinguish 
 them, ammonia in excess is added to the fluid, 
 wherein the precipitate is suspended. 
 
 aa. The precipitate does not disappear ; CAD- 
 MIUM is present, sulphuret of cadmium being so- 
 luble in ammonia. The blow-pipe is resorted 
 to for further proof. (91, d.) 
 
 bb. The precipitate disappears. It consists 
 either of peroxide of tin or of arsenic. Ammo- 
 nia is added to a portion of the original solu- 
 tion. 
 
 a*. A white precipitate is formed- PE- 
 ROXIDE OF TIN is the substance present. As 
 a conclusive proof, the precipitate is then 
 mixed with cyanide of potassium and carbo- 
 nate of soda, and reduced before the blow- 
 pipe. ( 94, 6.) 
 
1 94 DETECTION OF THE BASES. 
 
 AS. No precipitate is formed. This indi" 
 cates the presence of ARSENIC. The real 
 presence of the arsenic may then be ascer- 
 tained by the production of a metallic crust, 
 either from the original substance, or from the 
 precipitated sulphuret of arsenic, mixed with 
 cyanide of potassium and carbonate of soda, 
 or in some other way, and also by mixing the 
 original substance with carbonate of soda, and 
 exposing it to the reducing flame of the blow- 
 pipe. ( 94, d.) 
 
 V. THE PRECIPITATE IS ORANGE COLOURED J in 
 
 this case it consists of sulphuret of antimony, and 
 indicates the presence of OXIDE OF ANTIMONY. The 
 blow-pipe is resorted to for further proof. ( 94, a.) 
 
 &. THE PRECIPITATE IS BROWN. It Consists of 
 
 sulphuret of tin, and indicates the presence of 
 PROTOXIDE OF TIN. For conclusive proof, one 
 portion of the original solution is tested with so- 
 lution of perchloride of mercury, and another with 
 solution of gold. ( 94, b.) 
 
 e. THE PRECIPITATE is BLACK. It may in this 
 case consist of sulphuret of lead) or sulphuret of 
 copper, or sulphuret of bismuth, or sulphuret of gold, 
 or sulphuret of platinum, or bisulphuret of mercury. 
 To distinguish these from each other, the following 
 experiments are made with the original solution. 
 
 aa. Dilute sulphuric acid is added to a portion 
 of it ; a white precipitate is formed ; this indicates 
 the presence of LEAD. Chromate of potash is em- 
 ployed as a conclusive test. ( 90, c.) 
 
 bb. Ammonia in excess is added to a portion of 
 it. A blue precipitate is formed which redissolves 
 in the excess of the precipitant, imparting an azure 
 colour to the solution ; this indicates COPPER. Fer- 
 rocyanide of potassium is resorted to as a conclu- 
 sive test. (91, b.) 
 
 cc. Potash is added to a portion of it. A yellow 
 precipitate is formed ; this indicates the presence 
 of PEROXIDE OF MERCURY. Protochloride of tin 
 and metallic copper are employed as conclusive 
 
SUBSTANCES SOLUBLE IN WATER. 195 
 
 tests. (91, a.) The presence of peroxide of mer- 
 cury may generally also 'be detected by the preci- 
 pitate which it yields with sulphuretted hydrogen, 
 not appearing black from the beginning, but on the 
 addition of an excess of the precipitant, passing 
 through white, yellow, and orange, and then at last 
 changing its colour into black. (91, , 2.) 
 
 dd. A portion of the original solution is evapo- 
 rated nearly to dryness, in a porcelain crucible, and 
 the residue put into a test tube, half filled with 
 water. If the solution becomes milky, a basic 
 salt of bismuth is present ; this reaction, therefore, 
 indicates BISMUTH. The blow-pipe is resorted to, 
 as a conclusive test. (91, c.) 
 
 ee. Solution of sulphate of iron is added to a 
 portion of the original solution. A fine black pre- 
 cipitate is indicative of the presence of GOLD. The 
 blow-pipe is resorted to as a conclusive test ; or 
 the original solution is tested with protochloride of 
 tin.- (93, a.) 
 
 ff. Chloride of potassium is added to a portion 
 of the original solution ; the formation of a yellow 
 crystalline precipitate is indicative of the presence 
 of PLATINUM. For further proof this precipitate is 
 heated to redness. ( 93, 6.) 
 
 3. To the fluid in which sulphuretted hydrogen has not 
 produced any precipitate, or should this have become too 
 dilute to a portion of the original solution, ammonia is 
 added, till the solution has an alkaline reaction ; hydrosul- 
 phuret of ammonia is then added. (If the solution was 
 not acid, and thus no ammoniacal salt has been formed on 
 the addition of ammonia, the addition of the hydrosulphu- 
 ret of ammonia is preceded by that of sal ammoniac.) 
 
 a. No PRECIPITATE is FORMED ; pass over to 
 107, 4 ; for iron, cobalt, nickel, manganese, zinc, 
 chromium, and alumina are not present. 
 
 b. A PRECIPITATE IS FORMED. 
 
 *. The precipitate is black ; protoxide of iron, 
 nickel, or cobalt. A portion of the original solution 
 is treated with caustic potash. 
 
 aa. A dirty greenish white precipitate is ob- 
 
196 DETECTION OF THE BASES. 
 
 tained, which soon changes into a reddish-brown, 
 when exposed to the air : PROTOXIDE OF IRON. 
 Ferricyanide of potassium is resorted to as a 
 conclusive test. ( 88, e.) 
 
 bb. A precipitate of a light greenish tint is 
 producedj which does not change its colour : 
 NICKEL. Ammonia and addition of potash are 
 resorted to as conclusive tests. ( 88, c.) 
 
 cc. A sky-blue precipitate is formed, which 
 changes its tint into red, on boiling : COBALT. 
 The blow-pipe is resorted to as a conclusive test. 
 88, d.) 
 /s. The precipitate is not black. 
 
 aa. If the precipitate is of a clear flesh colour, 
 it consists of sulphuret of manganese, and is, 
 therefore, indicative of the presence of PROTOX- 
 IDE OF MANGANESE. The addition of potash to 
 the original solution, or the blow-pipe, are 
 resorted to as conclusive tests. ( 88, b.) 
 bb. If the precipitate is bluish-green, it consists of 
 hydrated OXIDE OF CHROMIUM. The addition of pot- 
 ash to the original solution, and the blow-pipe are re- 
 sorted to as conclusive tests. ( 87, b.) 
 
 cc. If the precipitate is white, it may consist eith- 
 er of hydrate of alumina, or of sulphuret of zinc, and 
 thus be indicative of the presence either of alumina or 
 of oxide of zinc. To distinguish these, solution of 
 potash is gradually dropped into a portion of the ori- 
 ginal solution, till the precipitate is redissolved, and 
 then 
 
 *&. Solution of sulphuretted hydrogen is added to 
 a portion of it ; the formation of a white precipi- 
 tate is indicative of the presence of zinc. For fur- 
 ther proof, the reaction with solution of cobalt be- 
 fore the blow-pipe is selected. ( 88. a.) 
 
 /3j8. Muriate of ammonia is added to another por- 
 tion of the alkaline solution. The formation of a 
 white precipitate is indicative of the presence of AL- 
 UMINA. The test with solution of cobalt before 
 the blow-pipe is selected as' a conclusive proof. ( 
 87. a.) 
 
SUBSTANCES SOLUBLE IN WATER. 197 
 
 Note to 107. 3. /3. 
 
 As very slight contaminations may impair the distinct- 
 ness of the tints which the precipitates considered under 
 107. 3. 6. /3 present, it is advisable where such are sus- 
 pected to adopt the following method for the detection of 
 manganese, chromium, zinc, and alumina. 
 
 Potash in excess is added to a portion of the original 
 solution. 
 
 aa. A whitish precipitate is formed, which is not 
 redissolved in an excess of the precipitant, and soon 
 changes its colour to a blackish brown when exposed 
 to the air : MANGANESE. The blow-pipe is resorted 
 to as a conclusive test. ( 88, 6.) 
 
 bb. A precipitate is formed which redissolves in 
 an excess of the precipitant : oxide of chromium, alu- 
 mina, zinc. 
 
 <*. Sulphuretted hydrogen is added to a portion 
 of the solution with potass. The formation of a 
 white precipitate indicates the presence of ZINC. 
 
 /3/3. If the original or solution with potass appear 
 green, and the precipitate, first produced by potash 
 and then redissolved in the excess of the precipi- 
 tant, was bluish, OXIDE OF CHROMIUM is present. 
 For further proof, the solution with potass may be 
 boiled, or the blow-pipe resorted to. ( 87, b.) 
 
 yy. Muriate of ammonia is added to the solution 
 with potass. The formation of a white precipitate 
 indicates the presence of ALUMINA. The test with 
 solution of cobalt before the blow-pipe is selected 
 as a further proof, ( 87, a.} 
 
 4. Muriate of ammonia and carbonate of ammonia, mix- 
 ed with a small quantity of caustic ammonia, are added to 
 a portion of the original solution, which is then BOILED. 
 
 a. No PRECIPITATE is FORMED : absence of bary- 
 tes, strontian, or lime. Pass over to 107, 5. 
 
 b. A PRECIPITATE is FORMED Presence of bary- 
 tes, strontian, or lime. Solution of gypsum is added 
 to a portion of the original solution, and heat applied. 
 
 . The solution does not become turbid even af- 
 ter the lapse of Jive to ten minutes : LIME. The 
 
198 DETECTION OF THE BASES. 
 
 test with oxalic acid is selected for further proof. 
 (86,c.) 
 
 /3. The solution does not become turbid at first, 
 but after the lapse of some time : STRONTIAN. The 
 alcohol flame is resorted to as a conclusive test. 
 ( 86,^.). 
 
 y. A precipitate is immediately formed : BARY- 
 TES. For further proof, test with hydrofluosilicic 
 acid. ( 86, a.) 
 
 5. Phosphate of soda is added to the solution of (4) in 
 which carbonate of ammonia, after the addition of muriate 
 of ammonia has produced no precipitate. 
 
 a. No PRECIPITATE is FORMED, not even after agi- 
 tating the solution : absence of magnesia. Pass over 
 to 107, 6. 
 
 b. A FINE CRYSTALLINE PRECIPITATE IS FORMED I 
 MAGNESIA. 
 
 6. A drop of the original solution is evaporated on a 
 platinum plate and the residue heated to redness. 
 
 a. No FIXED RESIDUE REMAINS. The original so- 
 lution is tested for AMMONIA, by adding potash to it, 
 and examining the odour, the vapours formed with 
 acetic acid, and the reaction of the escaping gas. 
 ($ 85, c.) 
 
 b. A FIXED RESIDUE REMAINS. Potash OF Soda. 
 
 Tartaric acid is added to a portion of the original 
 
 solution, and the latter well shaken. 
 
 <*. 'No precipitate is formed, not even after the 
 lapse of ten to fifteen minutes : SODA. The blow- 
 pipe flame and alcohol flame, and especially the 
 reaction with > antimoniate of potash, are selected 
 as conclusive tests. ( 85, b.) 
 
 , . . ] /3. A crystalline granular precipitate is formed : 
 POTASH. Chloride of platinum, 1 the 'blow-pipe 
 flame, "and alcohol flame, are selected as conclusive 
 tests. ( 85, a.). 
 
 Compounds which are supposed to contain but one 
 acid and one base, fyc. 
 
DETECTION OF INORGANIC ACIDS. 199 
 
 A. SUBSTANCES SOLUBLE IN WATER. DETECTION OF THE 
 ACID. 
 
 I. Detection of inorganic acids. 
 $ 108. 
 
 We must in the first place consider what acids form 
 combinations soluble in water, with the base detected, and 
 bear it in mind in the subsequent examination. 
 
 1. We have already spoken of the detection of the 
 ARSENIOUS and ARSENIC ACID in treating of the detection 
 of the bases. They are distinguished from each other by 
 their behaviour with nitrate of silver, or with potash and 
 sulphate of copper. ( 94, d and e.) 
 
 2. The detection of CARBONIC ACID, HYDROSULPHURIC 
 ACID and CHROMIC ACID, has also already been pointed out, 
 when treating of the detection of the bases. The two 
 former betray their presence by effervescing on the addi- 
 tion of hydrochloric acid ; they may be distinguished from 
 each other by their odour, and if needed, the presence of 
 carbonic acid may be proved by its reaction with lime- 
 water, ( 99, a,) and that of sulphuretted hydrogen by the 
 reaction with solution of lead. ( 100, e.) Chromic acid 
 may, in most cases, be detected by the yellow or red tint 
 of its solution, and also by its solution changing colour 
 and yielding a precipitate of sulphur, on the addition of 
 sulphuretted hydrogen. We may assure ourselves of the 
 presence of chromic acid by the reaction with solution of 
 lead, and solution of silver. ( 96, b.) 
 
 3. Chloride of barium is. added to a portion of the solu- 
 tion ; should the latter have an acid reaction, it must first 
 be neutralized or rendered feebly alkaline, by the addition 
 of ammonia. 
 
 a. THE FLUID REMAINS CLEAR. (Pass over to 
 1Q8, 4.) The absence of sulphuric acid, phospho- 
 ric acid, and silicic acid is certain, that of oxalic acid 
 and boracic acid, probable. For the barytes com- 
 pounds of these two latter acids are kept in solution 
 by ammoniacal salts, and borate of barytes does not 
 at all precipitate from dilute solutions. 
 
200 DETECTION OP INORGANIC ACIDS. 
 
 b. A PRECIPITATE is FORMED. Hydrochloric acid 
 is added in excess. 
 
 <*. The precipitate redissolves. Absence of sul- 
 phuric acid. Pass over to 4. 
 
 /3. The precipitate remains and does not dissolve 
 even in a large proportion of water : SULPHURIC 
 ACID. 
 
 4. Solution of gypsum is added to a portion of the ori- 
 ginal solution, which, should it have an acid reaction, 
 must first be rendered neutral or feebly alkaline, by the 
 addition of ammonia. 
 
 a. No PRECIPITATE is FORMED i absence of oxalic 
 acid and phosphoric acid. Pass over to 108, 5. 
 
 6. A PRECIPITATE is FORMED. Acetic acid is 
 added in excess. 
 
 *. The precipitate is redissolved : PHOSPHORIC 
 ACID. The reactions with sulphate of magnesia 
 and ammonia, with solution of silver, and before 
 the blow-pipe, are selected as conclusive tests. 
 ( 98, a.} 
 
 p. .The precipitate remains undissolved, but 
 dissolves readily in hydrochloric acid : OXALIC ACID. 
 The reaction with concentrated sulphuric acid is 
 selected as a conclusive test. ( 98, c.) 
 
 5. A fresh portion of the original solution is acidified 
 with nitric acid, and solution of nitrate of silver is then 
 added. 
 
 a. THE FLUID REMAINS CLEAR. This is a certain 
 indication of the absence of chlorine and iodine. The 
 absence of cyanogen is also probable. For cyanide 
 of mercury is not precipitated by nitrate of silver ; 
 and from the detected base we may conclude whether 
 we have to look for the presence of this substance or 
 not ; for the manner in which the presence of the 
 cyanogen in it is proved, we refer to 100, d. Pass 
 over to 108, 6. 
 
 b. A PRECIPITATE is FORMED. Ammonia is added 
 in excess. 
 
 . The precipitate does not dissolve IODINE. 
 As a conclusive test, we select the reaction with 
 starch. ( 100, c.) 
 
DETECTION OF ORGANIC ACIDS. 201 
 
 /3. The precipitate is redissolved. If it redis- 
 solves readily, we have reason to suppose 
 that CHLORINE is present; if it dissolves with 
 difficulty and only on the addition of much ammo- 
 nia, we may suppose that CYANOGEN is present. 
 We assure ourselves of the presence of chlorine, 
 by testing the original solution with protonitrate of 
 mercury, and by the behaviour of the silver preci- 
 pitate formed when exposed to a high temperature. 
 ( 100, a.) The presence of cyanogen may be 
 further proved by adding potash, solution of mag- 
 netic oxide of iron and hydrochloric acid to the 
 original solution. ( 100, d.) 
 
 6. A portion of the solid substance (or if we have a 
 fluid to operate upon, the residue obtained by evaporation) 
 is drenched with some sulphuric acid, alcohol added, and 
 then kindled. BORACIC ACID is present if the flame ap- 
 pears green on stirring. 
 
 7. The preliminary examination generally enables us 
 to detect nitric acid. ($ 105, A, I, 2, c.) The reactions with 
 sulphate of iron and sulphuric acid, or solution of indigo, 
 are selected as conclusive proofs. ( 101, a.) 
 
 8. We refer to 123 for the detection of chloric acid, 
 hydrofluoric acid, cilicic acid, and bromine. 
 
 Compounds which we suppose to contain only one acid 
 and one base, $*c. 
 
 A. SUBSTANCES SOLUBLE IN WATER. DETECTION OP 
 
 THE ACID. 
 
 II. DETECTION OF ORGANIC ACIDS. 
 109. 
 
 1. To a portion of the aqueous solution, ammonia is 
 added till a feeble alkaline reaction becomes manifest, and 
 then chloride of calcium. If we have to operate upon a 
 neutral solution, some muriate of ammonia is added to it, 
 previous to the addition of the chloride of calcium. 
 
 a. No PRECIPITATE IS FORMED, NOT EVEN AFTER JLGI- 
 
202 DETECTION OF ORGANIC ACIDS. 
 
 TATING THE SOLUTION, NOR AFTER; THE LAPSE OF A FEW 
 
 MINUTES : absence of oxalic acid and tartaric acid. 
 
 Pass over to 1 09, 2. 
 
 b. A PRECIPITATE is FORMED. Lime-water is 
 
 added in excess to a portion of the original solution, 
 
 and the precipitate formed treated with solution of 
 
 sal ammoniac. 
 
 et. The precipitate vanishes: TARTARIC ACID. 
 The reaction, with acetate of potash may be re- 
 sorted to for further proof;' but the safest test is 
 the behaviour of the precipitate produced by chlo- 
 ride of calcium, with caustic potash. ( 102, 6.) 
 /3. The precipitate does not vanish : OXALIC 
 
 ACID. 
 
 2. The fluid of 1, a, is heated to boiling, kept at the 
 boiling point for some time, and some ammonia added 
 
 whilst boiling.) 
 
 a.' IT REMAINS TRANSPARENT; no citric acid. Pass 
 over to 109, 3. 
 
 6. IT BECOMES TURBID, AND DEPOSITS A PRECIPI- 
 TATE I CITRIC ACID. 
 
 3. The fluid of 2, a, is mixed with alcohol. 
 
 a. IT REMAINS TRANSPARENT i no malic acid. 
 Pass over to 109, 4. 
 
 b. A PRECIPITATE IS FORMED: MALIC ACID. The 
 
 re-action with acetate of lead is selected as a conclu- 
 sive test. ( 102, e.) 
 
 4. A portion of the original solution is rendered perfectly 
 neutral (if it is not already so) by ammonia or hydro- 
 chloric acid, and solution of perchloride of iron added. 
 
 a. A CINNAMON-COLOURED OR DIRTY YELLOW BUL- 
 KY PRECIPITATE is FORMED.. This precipitate is 
 treated with dilute hydrochloric acid. 
 
 . It dissolves transparent ; SUCCINIC ACID. 
 
 /3. It dissolves, with the separation of a white 
 precipitate: BENZOIC ACID. We assure ourselves 
 of the real presence of this substance, by heating 
 the precipitate. It must manifest the properties of 
 free benzoic acid. (Vide 103, b.) 
 
 b. THE LIQUID ASSUMES AN INTENSE RED TINT, 
 AND UPON BOILING FOR SOME TIME, A LIGHT RED- 
 DISH-BROWN PRECIPITATE SEPARATES: acetic acid or 
 
SUBSTANCES INSOLUBLE IN WATER. 203 
 
 formic acid. A portion of the solid salt under exami- 
 nation, or the residue obtained by evaporating the 
 liquid (if the liquid is acid, it must be neutralized 
 with potash, previous to the evaporation) is heated 
 with sulphuric acid and alcohol, ( 104, a.) The cha- 
 racteristic odour of acetic ether, indicates the presence 
 
 of ACETIC ACID. 
 
 If we do not detect acetic acid in the fluid, we 
 must conclude that the substance under examination 
 contains FORMIC ACID: the certain presence of this 
 latter substance may be proved by its behaviour with 
 nitrate of silver and protoxide of mercury. ( 104, 6.) 
 
 Compounds which are supposed to consist of but one acid 
 and one base. 
 
 B. SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE IN 
 
 WATER, BUT SOLUBLE IN HYDROCHLORIC ACID, NITRIC 
 ACID, OR AQUA REG1A. 
 
 Detection of the base.* 
 110. 
 
 A portion of the solution in hydrochloric acid, nitric acid, 
 or aqua regia, is diluted with water,! and the further 
 operations conducted exactly as directed 107, beginning 
 at 1, when the substance is dissolved in nitric acid, and at 
 2, when it contains already hydrochloric acid. The follow- 
 ing circumstances must be well attended to '. we have seen 
 that if in cases where we have A SUBSTANCE SOLUBLE IN 
 WATER before us, we obtain in the course of the examina- 
 tion, a white precipitate on testing with hydrosulphuret of 
 ammonia (after having neutralized with ammonia the free 
 acid either originally contained in or previously added to 
 the solution under examination) this precipitate can consist 
 only either of sulphuret of zinc, or of alumina. But the 
 case is different, when the substance is INSOLUBLE IN 
 
 * Regard has here been had also to several salts, since this course 
 of examination directly leads to their detection. 
 
 flf, on the addition of the water, the liquid becomes turbid or is 
 precipitated, it indicates the presence of antimony, bismuth, or tin. 
 (Compare $ 105, B 4.) 
 
204 SUBSTANCES SOLUBLE IN WATER. 
 
 '_ 
 
 WATER, but dissolved by hydrochloric acid ; for in that case 
 the white precipitate produced by hydrosulphuret of ammo- 
 nia, with the presence of sal ammoniac, may also consist 
 of a phosphate of the alkaline earths as well as of oxalate of 
 lime, (barytes and strontian.) If, therefore, we obtain a 
 white precipitate when testing an acid solution, under the 
 circumstances stated, and as directed 107, at 3 /3. cc, the 
 following method must be employed. Caustic potash in 
 excess is added to a small portion of the original hydrochlo- 
 ric solution. 
 
 1. THE PRECIPITATE AT FIRST FORMED, REDISSOLVES IN 
 
 EXCESS OF THE PRECIPITANT } absence of the salts of the al- 
 kaline earths ; presence of zinc or of alumina : to distinguish 
 these from each other, the solution with potass is tested 
 with sulphuretted hydrogen and muriate of ammonia. (Vide 
 supra 107, 3 b. /3 cc.) Alumina may have- been present 
 and precipitated as phosphate of alumina. This is ascer- 
 tained by dissolving the precipitate in hydrochloric acid, 
 adding tartaric acid, supersaturating with ammonia and 
 mixing with sulphate of magnesia. If phosphoric acid is 
 present, a precipitate of basic phosphate of ammonia and 
 magnesia is formed. 
 
 2. THE PRECIPITATE FORMED DOES NOT REDISSOLVE IN 
 
 AN EXCESS OF THE PRECIPITANT. Presence of a phosphate 
 or oxalate with an alkaline earth for its base. In this case 
 a portion of the original substance is heated to redness, in 
 order to ascertain whether we have an oxalate or a phos- 
 phate before us. If the substance is converted by this pro- 
 cess into a carbonate (slightly blackening or not at all) 
 which is easily detected by the heated mass effervescing 
 when treated with acids, whilst previous to the heating it 
 did not present this property, we may conclude that the 
 salt is an OXALATE ; if, on the contrary, no alteration takes 
 place, on the application ol a red heat, we have a PHOS- 
 PHATE before us. 
 
 a. THIS PRELIMINARY EXAMINATION DENOTED THE 
 PRESENCE OF A PHOSPHATE. 
 
 A certain, not too inconsiderable quantity, of perchlo- 
 ride of iron is added to a portion of the hydrochloric 
 solution, which is then brought to alkaline reaction by 
 the addition of ammonia, and the liquid filtered off 
 
SUBSTANCES INSOLUBLE IN WATER. 205 
 
 from the bulky precipitate formed, which should pre- 
 sent a reddish-brown tint. In this operation the phos- 
 phoric acid is separated from its base, and, combined 
 with peroxide of iron, precipitated together with free 
 hydrate peroxide of iron, whilst the alkaline earth base 
 is contained in the filtered liquid as a chloride. The 
 further process of the detection of this base is conduct- 
 ed as directed 107, 4. 
 
 In order to determine the presence of the phospho- 
 ric acid also, the iron precipitate is rinsed, and di- 
 gested with hydrosulphuret of ammonia. We obtain 
 in this process sulphuret of iron and phosphate of am- 
 monia. These are separated from each other by fil- 
 tration, and sal ammoniac and sulphate of magnesia is 
 then added to the filtered liquid ; the precipitate 
 which forms, of basic phosphate of ammonia and 
 magnesia, is a safe indication of the presence of phos- 
 phoric acid. In more minute examinations, the ex- 
 cess present of hydrosulphuret of ammonia is first de- 
 composed by the addition of hydrochloric acid, the so- 
 lution heated to boiling, and the precipitated sulphur fil- 
 tered off; the filtered solutions, if needed, concentrated 
 by evaporation, supersaturated with ammonia, and 
 sulphate of magnesia then added. 
 
 b. THE PRELIMINARY EXAMINATION INDICATED THE 
 PRESENCE OF AN OXALATE. 
 
 Two methods may be pursued, with certainty, to 
 determine the base and the acid. 
 
 1. A portion of the compound is heated to red- 
 ness, the residue dissolved in hydrochloric acid, 
 and the alkaline earth which forms the base, de- 
 tected in the usual manner in this solution. Of the 
 presence of the oxalic acid, we assure ourselves by 
 testing another portion of the substance with con- 
 centrated sulphuric acid. ( 98, c.) 
 
 2. A portion of the compound is boiled for some 
 time in a concentrated solution of carbonate of pot- 
 ash, and the fluid filtered from the residue. In 
 this manner we obtain in the residue the alkaline 
 earth which forms the base of the substance under 
 examination, combined with carbonic acid, whilst 
 
 9 
 
206 DETECTION OP INORGANIC ACIFS. 
 
 we have the oxalic acid combined with potash in 
 the filtered solution; to assure ourselves of the 
 real presence of this acid, the solution is first acid- 
 ified with acetic acid, and then treated with solution 
 of gypsum. ( 98, c.). The residue is rinsed and 
 dissolved in hydrochloric acid, and the solution 
 treated as directed 107, 4. 
 
 Compounds which are supposed to consist of but one acid 
 and one base, fyc. 
 
 B. ' SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE IN 
 
 WATER, BUT SOLUBLE IN HYDROCHLORIC ACID, NITRIC ACID* 
 OR AQUA REGIA. 
 
 DETECTION OF THE ACID. 
 
 1. Detection of inorganic acids,, 
 111. 
 
 1. CHLORIC ACID cannot be present, for all chlorates are 
 soluble in water ; the nitrates also, with the exception of a 
 few, beiag soluble in water, we may generally disregard 
 the presence of NITRIC ACID. The basic nitrate of bismuth 
 forms the most frequently occurring exception to the gene- 
 ral rule of solubility of the nitrates in water. The presence 
 of nitric acid in such insoluble compounds may be imme- 
 diately detected by deflagration taking place when the 
 substance under examination is thrown upon red-hot char- 
 coal. The deflagration which ensues on fusing a nitrate 
 together with cyanide of potassium, is a safer test of the 
 presence of nitric acid. (Vide 101, a.) For the 
 CYANIDES insoluble in water, we refer to 1 28. 
 
 2. The detection of ARSENIOUS and ARSENIC ACID, CAR- 
 BONIC ACID, HYDROSULPHURIC ACID, and CHROMIC ACID, has 
 
 already been pointed out, when treating of the detection of 
 bases ; as the best tests and indications of the presence 
 of chromic acid, we have pointed out the yellow or red 
 colour of the compound, the evolution of chlorine, upon a 
 chromate being boiled with hydrochloric acid, and the 
 subsequent detection of chromic oxide in the solution. But 
 the safest method, and that which was applicable in all 
 
SUBSTANCES INSOLUBLE IN WATER. 207 
 
 cases, is to fuse the substance supposed to contain chromic 
 acid, together with some carbonate of soda and nitre. 
 ( 96, 6.) 
 
 3. A portion of the substance under examination is 
 boiled with nitric acid. 
 
 a. If nitric oxide gas is evolved, which is easily 
 detected by the red fumes of nitrous acid, formed on 
 coming in contact with the air, it indicates the pre- 
 sence of a SULPHURET } if carbonic acid is evolved, 
 that of a CARBONATE. Of the presence of a sulphuret 
 we may easily assure ourselves, by testing the nitric 
 solution with chloride of barium ; it should yield with 
 this reagent a precipitate of sulphate of barytes, which 
 must remain undissolved even in a large quantity of 
 water. Sulphurets may as safely be detected by their 
 behaviour before the blow-pipe. (Vide 100, c.) 
 
 b. If violet vapours escape, the compound may be 
 supposed to be an IODIDE. A slip of paper, covered 
 with starch, forms the best conclusive test of the 
 presence of iodine. ( 100, c.) 
 
 4. Nitrate of silver is added to a portion of the nitric 
 solution, (this solution must previously be filtered, if upon 
 treating the substance with nitric acid any insoluble residue 
 has remained.) If a white precipitate is formed soluble in 
 ammonia, and fusing without decomposition when heated, 
 it indicates the presence of CHLORINE. 
 
 5. A portion of the substance is boiled with hydrochloric 
 acid, filtered, if needed, and nitrate of barytes added. The 
 formation of a white precipitate, which does not disappear, 
 even on the addition of a large proportion of water, indi- 
 cates the presence of sulphuric acid. 
 
 6. ForBORAcic ACID, test as stated supra, 108. 
 
 7. If none of all these acids is present, we have reason 
 to suppose the presence of either PHOSPHORIC ACID or 
 OXALIC ACID, or the absence of all acids. If the phosphoric 
 acid had been combined with an alkaline earth, and the 
 oxalic acid with lime, (barytes, or strontian,) either of them 
 would have already been detected when testing for these 
 bases. (110.) We may therefore disregard the presence 
 of these two acids, except when other bases than those 
 enumerated are present. In the latter case the fluid is 
 prepared for further examination by precipitating and sepa- 
 
208 DETECTION OF ORGANIC ACIDS. 
 
 rating the heavy metals from it (this is effected in acid 
 solutions by means of sulphuretted hydrogen, and in alka- 
 line solutions by hydrpsulphuret of ammonia) and is then 
 tested for phosphoric acid or oxalic acid, as directed 108, 4. 
 8. For the detection of SILICIC ACID, BROMINE, AND 
 FLUORINE, vide 123, at the end. 
 
 Compounds which are supposed to consist of but one base 
 and one acid, $*c. 
 
 B. SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE IN WATER, 
 
 BUT SOLUBLE IN HYDROCHLORIC ACID, NITRIC ACID, OR 
 AQUA REGIA. 
 
 DETECTION OF THE ACID. 
 
 II. Detection of organic acids. 
 112. 
 
 1. A portion of the substance under examination is dis- 
 solved in the smallest possible quantity of hydrochloric 
 acid. If a residue remains, this must be tested for BEN- 
 ZOIC ACID by heating. Carbonate of potash in excess is 
 then added to the hydrochloric solution, and the latter 
 boiled for some time and filtered. The alkaline nitrate 
 contains the organic acid, under all circumstances. This 
 filtered solution is therefore exactly saturated with hydro- 
 chloric acid, and the fluid tested, as directed 109. No 
 regard need be had to formic acid, all the formiates being 
 soluble in water. 
 
 2. ACETIC ACID is most readily detected in such com- 
 pounds by means of sulphuric acid and alcohol. ( 104, a.) 
 
 Compounds which are supposed to consist of but one acid 
 and one base, $*c- 
 
 C. SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE IN WATER, 
 
 HYDROCHLORIC ACID, NITRIC ACID, AND AQUA REGIA. 
 
 DETECTION OF THE BASE AND THE ACID. 
 
 113, 
 
 Under this head we propose to consider SULPHATE OP 
 
 BARYTES, SULPHATE OF STRONTUN, SULPHATE OF LIME, 
 
DETECTION Otf THE BASE AND ACID. 209 
 
 SILICA, SULPHATE OF LEAD, CHLORIDE OF LEAD, and CHLO- 
 RIDE OF SILVER, as the most frequently occurring com- 
 pounds belonging to this class. For the less frequently 
 occurring compounds of this kind, we refer to 127. 
 
 Sulphate of lime and chloride of lead are not altogether 
 insoluble in water, and sulphate of lead may be dissolved 
 in hydrochloric acid. As these compounds are, however, 
 so sparingly soluble that we seldom can effect their com- 
 plete solution, we mention them here once more, in order 
 that they may be detected by the method laid down in 
 this section, should they have escaped detection in the 
 examination of their aqueous or acid solutions. 
 
 1. A very minute quantity of the substance under exam- 
 ination is treated with hydrosulphuret of ammonia. 
 
 a. IT BECOMES BLACK ; this indicates the presence 
 
 of a SALT OF LEAD Or CHLORIDE OF SILVER. A SOmC- 
 
 what larger portion of the substance is then digested 
 for some time with hydrosulphuret of ammonia. In 
 this process the metallic salt becomes decomposed, 
 and a sulphuret is formed, which remains undissolved> 
 whilst we have in solution the acid of the metallic 
 salt combined with the ammonia of the hydrosul- 
 phuret of ammonia. The solution is then filtered, the 
 undissolved sulphuret washed and dissolved in nitric 
 acid, and this nitric solution tested, with sulphuric 
 acid, for lead ; and with hydrochloric acid, and sub- 
 sequent addition of ammonia, for SILVER. One portion 
 of the filtered liquid is tested for SULPHURIC ACID, with 
 chloride of barium, after having previously decom- 
 posed the excess of the hydrosulphuret of ammonia, 
 by the addition of hydrochloric acid and boiling up ; 
 another portion is tested for HYDROCHLORIC ACID, with 
 solution of silver ; after having previously acidified 
 the liquid with nitric acid, and then boiled it. 
 
 b. IT BECOMES WHITE. Absence of a heavy me- 
 tallic oxide. A small portion of the substance under 
 examination is reduced to a very fine powder, and 
 then mixed with four times its quantity of carbonate 
 of soda and potash, put into a small platinum crucible, 
 and fused over a Berzelius spirit-lamp. The fused 
 mass is boiled with water. 
 
210 DETECTION OF THE BASES. 
 
 *>. Complete solution takes place : SILICA. We 
 assure ourselves of the presence of this substance 
 by supersaturating the solution with hydrochloric 
 acid, and evaporating to dryness. In this operation, 
 silicic acid is converted from its soluble into its 
 insoluble modification. It remains, therefore, un- 
 dissolved on treating the residue with water. When 
 mixed with carbonate of soda, and exposed to a 
 strong blow-pipe flame, a transparent glass is pro- 
 duced. ( 99, b ) 
 
 /3. A white residue remains ; this indicates one 
 
 of the SULPHATES OF THE ALKALINJE EARTHS. The 
 
 solution is filtered, and the filtered liquid acidified 
 with hydrochloric acid, and then tested for SULPHU- 
 RIC ACID, with chloride of barium. The white 
 residue (which contains the alkaline earth as a 
 carbonate) is carefully washed, dissolved in a small 
 quantity of dilute sulphuric acid, and the solution 
 tested for BARYTES, STRONTIAN, or LIME, as directed 
 107, 4. 
 
 Compounds in which all the more frequently occurring 
 Bases, Acids, Metals, and Metalloids, are supposed to 
 be present. 
 
 A. SUBSTANCES BOTH SOLUBLE AND INSOLUBLE IN WATER, 
 
 AND SOLUBLE IN HYDROCHLORIC ACID OR NITRIC ACID. 
 
 Detection of the bases* 
 114. 
 
 In this scheme for the testing of the bases we have 
 united the compounds belonging to classes I. and II., 
 (vide 106,) since the method of detection is in most cases 
 the same for both classes. Those parts which refer only 
 to substances insoluble in water, and soluble in hydrochlo- 
 ric acid and nitric acid, are enclosed between inverted 
 
 * The arsenious and arsenic acid, and several salts, have here been 
 had regard to, since we are, in this course of examination, led to their 
 detection. 
 
SUBSTANCES SOLUBLE IN ACIDS. 211 
 
 trommas, (" "), and may, therefore, be passed over 
 
 unnoticed, when examining substances soluble in water. 
 
 I. THE SOLUTION is AQUEOUS, 
 
 A small quantity of hydrochloric acid is added. 
 1. THE SOLUTION HAD AN ACID OR NEUTRAL REACTION 
 PREVIOUS TO THE ADDITION OF THE HYDROCHLORIC ACID. 
 
 a. No PRECIPITATE is FORMED : this indicates the 
 absence of silver and protoxide of mercury. Pass 
 over to 115. 
 
 b. A PRECIPITATE is FORMED; hydrochloric acid 
 is added to the solution drop by drop, as long as the 
 quantity of the precipitate increases. This precipi- 
 tate may consist of chloride of silver, protochloride of 
 mercury, chloride of lead, or a basic salt of antimony, 
 or, possibly, also of benzoic acid. The fluid is agi- 
 tated, and a portion of it, together with the therein 
 suspended particles of the precipitate, mixed with a 
 large quantity of water, and heated to boiling. If 
 compounds of antimony, bismuth, or tin are present, 
 the dilution with water may render the liquid turbid, 
 which phenomenon is usually distinctly perceived, 
 notwithstanding the precipitate which the fluid already 
 contained previous to the addition of the water. In 
 order to judge with certainty, whether the precipitate 
 produced by hydrochloric acid redissolves in the wa- 
 ter on boiling or not, and, therefore, whether the 
 further operation is to be conducted according to *> or 
 , hydrochloric acid is added to the dilute solution 
 {previous to heating) till the milkiness has com- 
 pletely vanished. 
 
 The precipitate vanishes ; this indicates the ab- 
 sence of silver and protoxide of mercury. The ori- 
 ginal solution, together with the precipitate produced 
 in it by hydrochloric acid is heated to boiling and 
 filtered hot. Should the precipitate not completely 
 redissolve, the residue is once more boiled with water, 
 and the solution filtered hot into the first filtrate. 
 The filtered solution is treated as directed 115. 
 Should it have deposited a precipitate, or small crys- 
 tals .{chloride of lead) have formed on cooling, it must 
 
212 DETECTION OF THE BASES. 
 
 be previously heated, till it appears transparent again. 
 
 /3. The precipitate does not vanish, at least not 
 
 completely ; this indicates the presence of SILVER or 
 
 PROTOXIDE OF MERCURY. 
 
 The original solution (with the hydrochloric acid) is 
 treated as directed 114, I. 1, b, * The residuary inso- 
 luble precipitate is washed and tested as follows : it is, if 
 possible, removed from the filter and treated with ammo- 
 nia, in a small tube. If it dissolves in this substance, it 
 consists exclusively of SILVER ; if it becomes black, PROT- 
 OXIDE OF MERCURY is present. In this case, or whenever 
 a residue insoluble in ammonia remains, this must be fil- 
 tered off, and nitric acid in excess added to the filtered 
 liquid ; the formation of a white, curdy precipitate indi- 
 cates SILVER. 
 
 2. THE AQUEOUS SOLUTION HAI> AN ALKALINE REACTION. 
 
 fl. No EVOLUTION OF GAS TAKES PLACE AND NO PRE- 
 CIPITATE IS FORMED, ON THE ADDITION OF HYDROCHLO- 
 RIC ACID, OR, A PRECIPITATE IS AT FIRST FORMED, BUT 
 REDISSOLVES ON THE FURTHER ADDITION OF HYDRO- 
 CHLORIC ACID; pass over to 115. For all that 
 relates to substances belonging to the second class 
 (i. e. those insoluble in water, and soluble in hydro- 
 chloric acid or nitric acid) enclosed between in- 
 verted commas, look to the passages upon phosphate 
 of alumina, but, if an ammoniacal salt is present, 
 also to those upon the oxalates of the alkaline earlhs ? 
 since the solution of these compounds in a fluid with 
 alkaline reaction is not impossible. 
 
 b. A PRECIPITATE IS FORMED, ON THE ADDITION OF 
 HYDROCHLORIC ACID, WHICH DOES NOT REDISSOLVE IN 
 AN EXCESS OF THE PRECIPITANT. 
 
 <*. The precipitate is formed without simulta- 
 neous evolution of sulphuretted hydrogen gas. A 
 portion of the fluid with the precipitate suspended 
 therein, is diluted with a large proportion of water, 
 and heated. The solution of the precipitate is 
 indicative of LEAD, or possibly also of benzoic acid. 
 The original solution is then heated to boiling, toge- 
 ther with the precipitate produced by hydrochloric 
 acid, filtered hot, and the residue (if any remain) 
 boiled with water and filtered hot into the hydro- 
 
DETECTION OF THE BASES. 213 
 
 chloric solution. The filtrate is treated according 
 to 115; should it become turbid on cooling, it 
 must be heated again previous to being further 
 tested. If the precipitate does not redissolve on 
 heating the fluid diluted with water, but is dis- 
 solved by ammonia, SILVER is present. The ori- 
 ginal solution is treated in the same manner as if 
 the precipitate had been redissolved. 
 
 /3. The precipitate is formed with simultaneous 
 evolutions of sulphuretted hydrogen gas. 
 
 aa. The precipitate is of a pure white colour, 
 and consists of sulphur. In this case an alka- 
 line bisulphuret is present. Filter the solution 
 and pass over to 118, bearing in mind that of 
 the substances considered 118, oxide of chro- 
 mium and alumina alone can be present. 
 
 bb. The precipitate is coloured. In this case 
 we must suppose that a metallic sulphur salt is 
 present, i. e. a combination of an alkaline sul- 
 phur base with an electro-negative sulphuret. 
 The solution is heated to boiling and filtered ; 
 the nitrate is further tested as stated under aa. 
 The precipitate is treated as 116 directs; it 
 may consist of SULPHURET OF GOLD, SULPHURET 
 
 OF PLATINUM, SULPHURET OF TIN, SULPHURET OF 
 ARSENIC, OR SULPHURET OF ANTIMONY. 
 C. No LASTING PRECIPITATE IS FORMED, ON THE 
 
 ADDITION OF HYDROCHLORIC ACID, BUT EVOLUTION OF 
 
 GAS TAKES PLACE. 
 
 *. The escaping gas has the odour of sulphuret- 
 ted hydrogen; this indicates a simple alkaline 
 sulphur compound. The further operations are 
 conducted as directed aa. 
 
 /3. The escaping gas emits no odour ; in this 
 case it is carbonic acid which was combined with 
 an alkali. Pass over to 115, bearing in mind, 
 that mercury, bismuth, insoluble salts of magnesia, 
 and (if the reaction is strongly alkaline) barytes, 
 strontian, and lime cannot be present, or at least 
 only under very peculiar circumstances, (e. g. 
 mercury as a cyanide.) 
 9* 
 
214 DETECTION OF THE BASES. 
 
 II. THE SOLUTION is HYDROCHLORIC. 
 It is treated as 115 directs. 
 
 III. THE SOLUTION is NITRIC. 
 
 A small portion of it is diluted with much water. 
 
 1. IT REMAINS TRANSPARENT ; add hydrochloric acid. 
 
 a. No precipitate is formed. Absence of silver. 
 The original solution is treated according to 115. 
 
 b. A precipitate is formed. If it does not redis- 
 solve on heating the fluid, but is dissolved by ammo- 
 nia, after washing, SILVER iV present. The original 
 solution is treated as staled 1 15. 
 
 2. THE SOLUTION BECOMES TURBID AND MILKY: BISMUTH 
 or ANTIMONY. The fluid is filtered, and the filtrate tested 
 for silver according to 114, III. 1 ; the original solution 
 is tested as 115 directs. 
 
 H5. 
 
 Solution of sulphuretted hydrogen is added to a SMALL 
 PORTION of the transparent acid solution, till the fluid, after 
 agitation, and application of heat, emits a clearly percep- 
 tible odour of sulphuretted hydrogen. 
 
 a. No PRECIPITATE is FORMED, not even after the 
 lapse of some time. Pass over to 118, for neither 
 lead, bismuth, cadmium, copper, mercury, gold, pla- 
 tinum, antimony, tin, nor arsenic,* are present ; the 
 absence of peroxide of iron and^ of chromic acid is 
 also indicated by this negative reaction. 
 
 b. A PRECIPITATE IS FORMED. 
 
 aa. It is of a pure white colour, thin, in the form 
 of a fine powder, and does not vanish on the addi- 
 tion of hydrochloric acid. It consists of sulphur, 
 and indicates PEROXIDE OF IRON.! None of the 
 
 * To assure ourselves of the certain absence of arsenic acid, we must 
 allow the test solution to stand for some time, or add sulphurous acid, 
 previous to the addition of the sulphuretted hydrogen. (Compare 93, g.) 
 
 t Sulphur is also precipitated in presence of sulphurous acid, iodic acid, 
 bromic acid, which substances we do not treat of in the present work, 
 and also when chromic acid, chloric acid, or free chlorine are present. 
 
DETECTION OF THE BASES. 215 
 
 other metals, enumerated at 115, a, can be pre- 
 sent. The original solution is treated as 118 
 directs. 
 
 bb. The precipitate is coloured. 
 
 Solution of sulphuretted hydrogen is added to 
 the larger portion of the acid or acidified solution, 
 till the latter has acquired the distinct odour of 
 sulphuretted hydrogen, and the precipitate no longer 
 increases on the continued addition of the reagent ; 
 the solution is then heated to boiling, and strongly 
 agitated for some time* 
 
 In many cases, and especially when there is any 
 reason to suppose arsenic to be present, it isdbetter 
 to transmit sulphuretted hydrogen gas through the 
 solution, 
 
 1. THE PRECIPITATE IS OF A PURE YELLOW COLOUR. 
 
 In this case it can consist only of ARSENIOUS or ARSENIC 
 
 ACID, Of PEROXIDE OF TIN, Or of OXIDE OF CADMIUM. The 
 
 fluid (which is then further to be tested according to 
 1 1 8) is separated from the precipitate,* and the latter 
 washed and drenched with ammonia. 
 
 a. The precipitate is completely redissolved : ab- 
 sence of cadmium. Acetic acid is added slightly in 
 excess to the solution, and the precipitate formed is 
 tested for TIN and ARSENIC, as 116, 1, directs. 
 
 b. A yellow residue remains, even after a further 
 addition of ammonia and the application of a mo- 
 derate heat : CADMIUM. The solution is filtered, 
 and acetic acid, slightly in excess, added to the filtrate. 
 If no precipitate is formed, the first precipitate con- 
 sisted exclusively of sulphuret of cadmium ; but if a 
 precipitate is formed, it denotes the presence of PE- 
 ROXIDE OF TIN, or ARSENIC; this precipitate is tested 
 as directed 116, 1. 
 
 2. THE PRECIPITATE IS ORANGE-RED, OR YELLOW, 
 WITH A SHADE OF ORANGE-COLOUR. It indicates ANTI- 
 MONY, but may, morover, contain TIN (should it have 
 
 * The best method of separating a precipitate from a fluid, is to 
 allow the precipitate to settle (this is facilitated by heating and 
 agitating) the fluid may then be decanted and the precipitate 
 washed, 
 
 
216 DETECTION OF THE BASES. 
 
 been present as a peroxide) ARSENIC or CADMIUM ; the 
 precipitate is separated from the fluid (which is tested 
 as 118 directs) washed, and a small portion of it di- 
 gested with hydrosulphuret of ammonia, which contains 
 sulphur in excess. 
 
 a. It redissolves completely : absence of cadmium. 
 The rest of the precipitate is treated as directed $ 
 116,2. 
 
 b. A yellow residue remains, even after a more 
 protracted digestion, with a larger quantity of hydro- 
 sulphuret of ammonia : CADMIUM. The entire pre- 
 cipitate is then treated in the same manner as the 
 ^>ecimen, the fluid filtered off from the sufphuret of 
 cadmium, and acetic acid in a slight excess added to 
 the filtrate ; the precipitate formed is treated as 1 16, 
 2, directs. 
 
 3. THE PRECIPITATE is or A DARK BROWN OR BLACK 
 COLOUR. The precipitate is separated from the fluid 
 (which is then tested as 118 directs) washed with 
 water, drenched and digested for some time, with hydro- 
 sulphuret of ammonia, containing sulphur in excess.* 
 
 a. The precipitate is completely redissolved in 
 hydrosulphuret of ammonia, or in sulphur et of po- 
 tassium ; absence of cadmium, lead, bismuth, copper, 
 and mercury: 117 may, therefore, be passed over 
 unnoticed. The solution is diluted, and acetic acid 
 added, till an acid reaction becomes manifest ; it is 
 then heated to boiling, and the precipitate formed, 
 treated as 116 directs. 
 
 b. It does not dissolve, or at least not completely. 
 The fluid is filtered off from the precipitate, and the 
 latter is washed, (in case 115, 3 b ,) or (in case ft) 
 once more digested with hydrosulphuret of ammonia, 
 filtered into the first solution, and then washed. The 
 residue is reserved for further examination, as di- 
 rected 117. A small portion of the filtrate contain- 
 
 * If the solution contains copper, which may generally be detected by 
 its colour, but with certainty by testing with a clean iron rod, (vide 91, 
 i, 6,) solution of sulphuret of potassium must be substituted for hydrosul- 
 phuret of ammonia, and the sulphur precipitate be boiled in it, (i. e. in tho 
 sulphuret of potassium,) vide 91, , 2. 
 
DETECTION OF THE BASES. 217 
 
 ing hydrosulphuret of ammonia is diluted with from 
 three to four parts of water, acetic acid added, till an 
 acid reaction becomes manifest, and the liquid heated 
 to boiling. 
 
 *. The fluid simply becomes milky, owing to the 
 separation of sulphur. Absence of gold, platinum, 
 tin, antimony, and arsenic. Pass over to 117. 
 
 . A coloured precipitate is formed. The colour 
 of the precipitate is minutely inspected ; the entire 
 solution containing the hydrosulphuret of ammonia is 
 then slightly diluted, acetic acid added, till an acid 
 reaction becomes manifest, and the fluid heated to 
 boiling. 
 
 116. 
 
 The precipitate which acetic acid has produced in the 
 solution containing hydrosulphuret of ammonia or sul- 
 phuret of potassium, is 
 
 1. OF A PURE YELLOW COLOUR, WITHOUT THE SLIGHT- 
 EST SHADE OF ORANGE : ARSENIC or TIN. The solution is 
 filtered off from the precipitate, the latter well washed, and 
 together with the filter placed between some sheets of 
 blotting-paper ; when the paper has imbibed the greater 
 part of the water, the still moist precipitate is removed 
 from the filter, and mixed in a small porcelain crucible 
 with about half its amount of pure anhydrous carbonate of 
 soda, and one and a-half its amount of pure nitre ; the 
 mass is then gently heated, and stirred, till it has be- 
 come completely dry, when a stronger heat is applied 
 (beginning at the edge of the crucible) till the entire mass 
 fuses, and every particle of the sulphuret is decomposed. 
 (If after drying the mass a very high degree of heat is 
 suddenly applied and allowed to act upon the whole cruci- 
 ble at once, slight explosions take place, whereby more or 
 less of the mass is thrown out of the crucible.) 
 
 a. The melting mass is transparent. Absence of 
 tin. The mass, after cooling, is boiled with water, 
 the solution divided into two portions, and very dilute 
 nitric acid very cautiously added to the one, till a 
 feebly acid reaction becomes manifest ; heat is then 
 
218 DETECTION OF THE BASES. 
 
 applied. (If there is really no tin present, no white 
 pulverulent residue must remain, on boiling the de- 
 flagrated mass with water, neither must any precipi- 
 tate be formed, on acidulating the solution with nitric 
 acid, not even after standing at rest for some time.) 
 Nitrate of silver is added to the acidified solution, after 
 cooling, and the fluid filtered ; if any traces of chloride 
 of silver should still separate, which is frequently the 
 case if the reagents are not absolutely pure, or the pre- 
 cipitate not completely washed. The filtrate is then 
 slowly and cautiously covered in a test-tube with very 
 dilute ammonia (one part of ammonia to twenty parts 
 of water and allowed to stand for some time, without 
 agitating. The formation of a reddish brown precipi- 
 tate, which appears like a cloud between the two 
 layers (of the test .specimen and the dilute ammonia,) 
 indicates ARSENIC ; (this precipitate is more clearly 
 seen, on the light falling upon than through it.) As 
 a further proof, the second portion of the solution of 
 the deflagrated mass is precipitated by solution of 
 neutral acetate of lead, the precipitate filtered off, 
 dried between some sheets of blotting-paper, and 
 then, on charcoal, exposed to the reducing flame of 
 the blow-pipe. If arsenic is really present, a grain 
 of metallic lead containing arsenic will be obtained, 
 which emits the garlic odour of arsenic very long and 
 continuously ; as often as it is exposed to the reducing 
 blow-pipe flame. For further confirmation, the arsenic 
 must be obtained in its metallic state. (Compare 94, 
 d and (&.) Whether the arsenic was present in the 
 compound under examination as arsenic acid, or as 
 arsenious acid, may be ascertained according to the 
 method described at the end of 94. 
 
 b. The melting mass is milky and turbid. This 
 is a probable indication of the presence of tin. The 
 mass is digested with cold water, and rubbed with it 
 in a mortar j the solution is then filtered, and the pre- 
 cipitate which remains, if tin is really present, very 
 carefully washed, and then tested for tin, by reducing 
 it before the blow-pipe mixed with cyanide of potas- 
 sium and carbonate of soda, and strongly rubbing the 
 
DETECTION OF THE BASES. 219 
 
 specimen in a mortar, with the addition of water; vide 
 94, b. The liquid filtered off from this precipitate 
 is divided into two portions and tested for arsenic as 
 116, 1, a, directs. A slight precipitate generally 
 separates on acidifying the solution with nitric acid. 
 This may be filtered off and tested for tin in the same 
 manner as the undissolved residue, (vide supra.) But 
 if the tin has already been detected, this precipitate 
 may be left in the solution, nitrate of silver added, 
 filtered, and the fluid tested for arsenic acid, as directed 
 above. Whether the tin was present as protoxide, is 
 ascertained, by mixing a portion of the original solu- 
 tion in water or hydrochloric acid, with a drop of nitric 
 acid and some chloride of gold. ( 94, b, 5.) 
 2. ORANGE-RED, OR YELLOW, WITH A SHADE OF OR- 
 ANGE; ANTIMONY; and besides TIN and ARSENIC may be 
 present. The precipitate is washed and fused with nitre 
 and carbonate of soda, in short, tested for arsenic and prot- 
 oxide of tin, exactly as 116, 1, 6, directs. The residue 
 remaining on treating the deflagrated mass with cold 
 water, as well as the precipitate which may perchance be 
 formed un acidifying the solution with nitric acid, may be 
 tested in three different ways. 
 
 a. The residue (or precipitate) is most carefully 
 washed, mixed with cyanide of potassium and carbon- 
 ate of soda, and exposed on charcoal, to the reducing 
 flame of the blow-pipe. 
 
 . Metallic globules appear, which at last com- 
 pletely volatilize, with the emission of white fumes 
 and the formation of a white crust. This is con- 
 firmatory of the presence of ANTIMONY, and of the 
 absence of tin. 
 
 /3. White metallic globules remain, after long 
 blowing : TIN. Their presence and nature may 
 best be ascertained by rubbing the particles of the 
 charcoal surrounding the test-specimen, together 
 with the latter, in a mortar with some water. 
 ( 94, 6.) 
 
 b. The residue (or precipitate) is very carefully 
 washed with water, dried, and fused for some time in 
 a small porcelain crucible, together with from four to 
 
220 DETECTION OF THE BASES. 
 
 five times its amount of cyanide of potassium. The 
 mass, after cooling, is drenched with water heated to 
 boiling, and thus the dross is separated from the metal- 
 lic globules. These are treated with nitric acid, and 
 the operation for the detection of tin and antimony 
 conducted exactly as 106 B, 2, 6, directs. 
 
 c. The residue (or precipitate) is well washed, dis- 
 solved in hydrochloric acid, the solution diluted, and a 
 small zinc rod placed into it. When the action of the 
 latter has ceased, and the reduction is complete, the 
 reduced metals (which can be easily separated from 
 the compact piece of zinc,) are boiled with nitric acid, 
 and the operation is carried on exactly as 106 B, 2, 
 bj directs. 
 
 The two latter methods of distinguishing tin and 
 antimony from each other, when together in the same 
 substance, are for beginners at least, far safer than 
 the first. 
 
 3. BROWNISH-BLACK; GOLD or PLATINUM ; besides, per- 
 haps, also ANTIMONY, ARSENIC, TIN. Add to the original 
 solution of the substance. 
 
 a. Protochloride of tin ; the formation of a reddish- 
 brown or purple red precipitate denotes GOLD. We 
 assure ourselves of the presence of this metal by test- 
 ing the original solution wilh protosulphate of iron, 
 whereby metallic gold is precipitated as a black pow- 
 der. 
 
 b. Muriate of ammonia ; the formation of a yellow 
 precipitate is indicative of the presence of PLATINUM. 
 The solution, if highly dilute, should be concentrated 
 by evaporation, previous to adding this reagent. 
 
 A portion of the precipitate is tested for ARSENIC, as 
 directed 116, 1. The rest is boiled with hydrochlo- 
 ric acid and filtered off; the filtrate is tested for ANTI- 
 MONY by dropping one drop of it into water; (after 
 having previously removed, as much as possible, the 
 excess of acid by evaporation ; if the water becomes 
 turbid and milky, antimony is present. Or a small 
 portion of the filtrate is mixed with solution of sulphu- 
 retted hydrogen ; the formation of an orange-coloured 
 precipitate indicates antimony. The rest of the hy- 
 drochloric solution is evaporated to dryness, mixed 
 
DETECTION OF THE BASES. 221 
 
 with carbonate of soda and cyanide of potassium, and 
 tested for peroxide of tin, as 1 16, 2, directs. Anti- 
 mony and tin may, however, more safely be detected 
 by precipitating them from the hydrochloric filtrate, 
 by means of zinc ; in fact, by treating exactly as 1 1 6, 
 2, c, directs. 
 
 117. 
 
 The precipitate which has not been dissolved by hydro- 
 sulphuret of ammonia, is washed, and then boiled with 
 nitric acid. This may best be done in a small porcelain 
 basin, constantly stirring with a glass rod. 
 
 1. THE PRECIPITATE DISSOLVES, AND NOTHING REMAINS 
 FLOATING IN THE FLUID EXCEPT THE SEPARATED LIGHT, 
 
 FLOCCULENT YELLOW SULPHUR ] this indicates the absence 
 of mercury. CADMIUM, COPPER, LEAD, and BISMUTH, may 
 be present. If the precipitate was of a pure yellow colour, 
 it consisted of CADMIUM alone ; if it was brown or black, 
 it must be filtered off from the separated sulphur, and the 
 filtrate tested as follows. 
 
 a. Ammonia in excess is added to one portion of 
 the filtrate. 
 
 , No precipitate is formed, or the precipitate 
 formed at first, redissolves completely in an excess 
 of the precipitant. Absence of lead and bismuth* 
 The solution is treated as 117, 1, 6, directs, bear- 
 ing in mind 117, 1, a, y. 
 
 /3. A lasting precipitate is formed : LEAD or 
 BISMUTH. The liquid is filtered off, and the filtrate 
 treated according to 1 1 7, 1 , 6, bearing in mind 
 117, l,c, y. 
 
 y. The fluid is blue-coloured; no matter whether 
 a precipitate is formed or not ; COPPER. 
 
 b. Hydrochloric acid is added to the ammoniacal 
 solution till a slightly acid reaction becomes manifest ; 
 carbonate of ammonia is then added in excess. 
 
 . The fluid remains clear : absence of cad- 
 mium- 
 
 /3. A white precipitate is formed immediately, 
 or after applying heat to the solution : CADMIUM. 
 We assure ourselves of the presence of this sub- 
 
222 DETECTION OP THE BASES. 
 
 stance by filtering the fluid off from the precipitate, 
 washing the latter, dissolving it in hydrochloric 
 acid, and adding solution of sulphuretted hydro- 
 gen. A yellow precipitate must appear, if cad- 
 mium is present. 
 
 Should copper not yet have been indicated by a 
 blue colouring of the ammoniacal solution, the fluid 
 in which carbonate of ammonia has produced no pre- 
 cipitate, (117, 1, b, *,) or the filtrate of 1 17, 1, 6, /a, 
 must be further and more minutely examined, by 
 slightly acidifying the one or the other with acetic 
 
 acid, and adding ferrocyanide of potassium. If cop- 
 per is present 
 be produced. 
 
 er is present, a brownish-red precipitate or tint will 
 
 c. In the case of 117, 1, a, /3, a not too incon- 
 siderable quantity of sulphuric acid is added to a 
 second portion of the solution of the sulphurets in 
 nitric acid : the" formation of a precipitate is indica- 
 tive of the presence of LEAD. This reaction may 
 be rendered more obvious and distinct by expelling 
 the greater part of the free nitric acid by evaporation. 
 
 d. The rest of the solution (in the case of 117, 
 1, a, ,) is evaporated to dryness, a few drops of 
 water added, and, in proportion to the quantity, one 
 or two drops of hydrochloric acid, and the fluid 
 heated. The solution is then poured into a test-tube 
 containing water ; if the water becomes turbid and 
 milky, BISMUTH is present.* 
 
 2. THE PRECIPITATE OF THE SULPHURETS DOES NOT 
 COMPLETELY REDISSOLVE IN THE BOILING NITRIC ACID, 
 AND A PRECIPITATE REMAINS, BESIDES THE LIGHT FLOC- 
 
 CULENT SULPHUR. This indicates PEROXIDE OF MER- 
 CURY, with a certain degree of probability, (and almost 
 with certainty, if the precipitate is heavy and black.) The 
 precipitate is allowed to settle, and the fluid filtered off 
 from it ; this filtrate must be tested for CADMIUM, COPPER, 
 LEAD, and BISMUTH, by mixing a small portion of it with a 
 large volume of solution of sulphuretted hydrogen, and if a 
 
 We refer to chapter TL (additions and remarks to 117) for another 
 method of distinguishing cadmium, copper, lead, and bismuth, from each 
 other 
 
DETECTION OF THE BASES. 223 
 
 precipitate is formed, treating the rest of the filtrate as 
 117, 1, directs. The residuary precipitate is washed, 
 dissolved by the addition of a few drops of aqua regia, 
 ammonia added, till the solution retains only a feeble acid 
 reaction, and a drop of it placed upon a clean copper plate. 
 If MERCURY is really present, a white stain will appear 
 after some time upon the copper surface, which presents 
 a metallic lustre when rubbed, and disappears on heating. 
 Or the solution in aqua regia is, with addition of hydro- 
 chloric acid, evaporated till nearly dry, diluted with some 
 water, and protochloride of tin added. The formation of 
 a precipitate, white at first, but changing into gray on the 
 protochloride of tin being added in excess, is a safe indica- 
 tion of the presence of mercury. 
 
 118. 
 
 A portion of the fluid in which solution of sulphuretted 
 hydrogen has produced no precipitate, ( 115, a,) or of the 
 fluid which has been filtered off from the precipitate form- 
 ed, is mixed with ammonia, till an alkaline reaction be- 
 comes manifest, and hydrosulphuret of ammonia is then 
 added. 
 
 In cases where but a minute quantity of hydrochloric 
 acid is present, and where, therefore, but little muriate of 
 ammonia has been formed, a not too inconsiderable meas- 
 ure of a solution of this latter salt must be added, previous 
 to the addition of the hydrosulphuret of ammonia. 
 
 a. No PRECIPITATE is FORMED. Pass over to 
 119, for neither iron, manganese, cobalt, zinc, nickel, 
 oxide of chromium, nor alumina, are present ; neither 
 are the phosphates of the alkaline earths, nor oxalate 
 of lime (barytes, strontian). 
 
 b. A PRECIPITATE is FORMED. The whole fluid is 
 treated in the same manner as the first portion. 
 
 1. The precipitate is white. Absence of iron, cobalt, nick- 
 el. We must look for the presence of all the other metals 
 and compounds enumerated at 118, a, since the faint 
 tints of sulphuret of manganese and oxide of chromium 
 vanish altogether if the quantity of white precipitate is con- 
 siderable. The precipitate is filtered off (the filtrate is- 
 
224 DETECTION OF THE BASES. 
 
 treated according to 119) washed, dissolved in hydro- 
 chloric acid,* boiled up, the solution filtered, and potash in 
 excess added. 
 
 a. THE PRECIPITATE FORMED AT FIRST ON THE AD- 
 DITION OF POTASH, REDISSOLVES COMPLETELY IN THE 
 EXCESS OF THE PRECIPITANT. Absence of the pllOS- 
 
 phates and oxalates of the alkaline earths, and manga- 
 nese. The solution with potash is divided into two 
 portions ; one portion is slightly acidified with hydro- 
 chloric acid, ammonia in excess added, and the fluid 
 boiled for a short time. 
 
 . No lasting precipitate is formed. Absence of 
 .alumina and of oxide of chromium. Solution of 
 sulphuretted hydrogen is added to the other portion 
 of the solution with potash. The formation of a 
 white precipitate indicates ZINC. 
 
 /3. A lasting precipitate is formed. It is filtered 
 off, and, (should a green tint of the solution with 
 potash, or a green, yellow, or red tint of the origi- 
 nal solution make us conclude that OXIDE OF CHRO- 
 MIUM is present,) a small portion of it tested for 
 this substance, with phosphate of soda and ammo- 
 nia, ( 87, b, 5,)t solution of sulphuretted hydrogen 
 is added to the filtrate. The formation of a white 
 precipitate indicates ZINC. For alumina we test as 
 follows. 
 
 aa. No oxide of chromium has been detected. 
 This is sufficient to prove the presence of ALUMI- 
 NA. To assure ourselves of it we lest the precipi- 
 tate produced by ammonia, before the blow-pipe. 
 (Vide 87, , 4.) 
 
 bb. Oxide of chromium has been detected. 
 
 * If the precipitate is inconsiderable, this may best be done by forcing 
 it to the lower part of the filter, by means of a syringe bottle, allowing the 
 water to run off, and adding hydrochloric acid drop by drop. If sulphu. 
 ret of zinc is present, the solution effected by hydrochloric acid is but in. 
 complete ; some nitric acid is added in that case, and heat applied. 
 
 t For even if chromic acid is present, a precipitate of oxide of chromi. 
 -.m is produced by hydrosulphuret of ammonia, the chromic acid being re- 
 duced by sulphuretted hydrogen. In such cases, the yellow or red colour 
 'f the solution changes into a green tint, on the addition of the sulphuret. 
 )d hydrogen J and sulphur separates at the same time. 
 
DETECTION OF THE BASES. 225 
 
 In this case, the second portion of the solution 
 with potash is boiled, until the oxide of chro- 
 mium has completely precipitated ; the fluid is 
 then slightly diluted, filtered off from the oxide 
 of chromium, slightly acidified with hydrochloric 
 acid, arid ammonia in excess added. The forma- 
 tion of a precipitate indicates ALUMINA. The 
 blow-pipe, as in aa, is resorted to as a conclusive 
 test. Should the separation of the oxide of 
 chromium from the solution with potash not 
 succeed by boiling, as may be the case under 
 certain circumstances, the precipitate produced 
 by ammonia must be fused with nitre and car- 
 bonate of soda, to remove the chromium. 
 (Vide 87, 6, 4.) *' Alumina may have been 
 present as a PHOSPHATE, and may have precipi- 
 tated as such. For the way in which this may 
 be ascertained, we refer to 110, 1." 
 
 b. A. PRECIPITATE INSOLUBLE IN POTASH HAS RE- 
 MAINED. The solution is filtered off and the filtrate 
 treated as 118, 1, , directs. The residuary preci- 
 pitate may consist of MANGANESE, " of the phosphates 
 and oxalates of the alkaline earths." The presence 
 of MANGANESE is indicated by the precipitate assum- 
 ing a brown colour when exposed to the air. The 
 test with carbonate of soda before the blow-pipe is 
 resorted to as a conclusive proof. ( 88, 6, 5.) If 
 manganese is present, the precipitate is dissolved in 
 hydrochloric acid, some tartaric acid mixed with it, 
 and then ammonia in excess added. If no precipi- 
 tate is formed, neither phosphates nor oxalates of the 
 alkaline earths are present ; the formation of a preci~ 
 pitate indicates the presence of these compounds. 
 This precipitate, (or, if no manganese was present, 
 the residuary precipitate undissolved by potash), is 
 washed and subjected to the following preliminary 
 examination, in order to ascertain, whether it consists 
 of phosphates of the alkaline earths alone or of oxa- 
 lates of the alkaline earths alone, or whether it is a 
 mixture of both. A small portion of the precipitate 
 is gently heated upon a platinum plate, and the resi- 
 due treated with hydrochloric acid. 
 
226 DETECTION OF THE BASES. 
 
 *. It dissolves without effervescence : absence 
 of oxalates. The rest of the precipitate is then 
 dissolved in hydrochloric acid, perchloride of iron 
 added in excess, and then ammonia, and the fur- 
 ther operations, for the detection of the bases and 
 of the phosphoric acid, conducted as directed 
 110, 2, a. 
 
 /3. It dissolves with effervescence : presence of 
 an oxalate. In this case a preliminary examina- 
 tion for phosphates becomes necessary. For this 
 purpose the hydrochloric solution is boiled, to 
 expel the carbonic acid, and ammonia added. 
 
 aa. No precipitate is formed. Absence of 
 phosphates : oxalates alone can be present. 
 For the detection of the bases, and the confirma- 
 tory examination for oxalic acid, vide 110, 
 2, b. 
 
 bb. A precipitate is formed: presence of a 
 phosphate and an oxalate. The rest of the pre- 
 cipitate is then heated to redness and dissolved 
 in very slightly diluted hydrochloric acid ; the 
 solution is boiled to expel the carbonic acid ; 
 ammonia in excess is added, and the solution fil- 
 tered. The earths which were combined with 
 the oxalic acid, are detected in the filtrate, as 
 119 directs. The precipitate is treated as 
 stated 118, 1, b. 
 
 2. THE PRECIPITATE PRODUCED BY HYDROSULPHURET OF 
 
 AMMONIA is NOT WHITE ; this indicates chromium, manga- 
 nese, iron, cobalt, or nickel. If the precipitate is black 
 or has a shade of black, one of the three latter metals is 
 certainly present. But, under all circumstances, we must 
 look for all the metals and compounds enumerated 1 18, a. 
 The precipitate is filtered off from the solution (the fil- 
 trate is treated as 119 directs) carefully washed and 
 treated with dilute hydrochloric acid. 
 
 a. No SOLUTION TAKES PLACE, OR THE SOLUTION IS IN- 
 COMPLETE INASMUCH AS THE BLACK COLOUR OF THE PRECI- 
 PITATE DOES NOT 'DISAPPEAR J COBALT, NICKEL- Some 
 
 nitric acid is then added to the hydrochloric acid, and the 
 solution boiled and treated as follows. The fluid is filtered 
 
DETECTION OF THE BASES. 227 
 
 off from the separated sulphur, and a small portion of it 
 mixed with solution of sal ammoniac, ammonia in excess 
 added, and heat applied. 
 
 a. No LASTING PRECIPITATE IS FORMED BY 
 
 AMMONIA : absence of peroxide of iron, oxide of 
 chromium, alumina, phosphates and oxalates of the 
 alkaline earths. The rest of the acid solution of 
 the sulphurets is mixed with caustic potash in 
 excess, heated, and the fluid filtered off from the 
 precipitate formed. The filtrate is tested for zinc 
 with solution of sulphuretted hydrogen. (Compare 
 118, 1, a, *.) The precipitate is washed and 
 drenched, heated and agitated for some time with 
 a somewhat considerable quantity of solution of 
 carbonate of ammonia, mixed with half its measure 
 of caustic ammonia. 
 
 aa. The precipitate is completely redissolved. 
 Absence of manganese. The ammoniacal solu- 
 tion is evaporated to dryness, the residue dis- 
 solved in a few drops of hydrochloric acid, once 
 more slightly evaporated, and a portion of a resi- 
 due (which should still be moist) tested for 
 COBALT, with borax, ( 88, d, 7.) The rest of 
 the moist residue is then dissolved in some 
 . water, and solution of cyanide of potassium 
 added, till the precipitate formed at first, is re- 
 dissolved in an excess of cyanide of potassium ; 
 dilute sulphuric acid is then added and heat 
 applied ; the solution is allowed to stand for 
 some time. The formation of a greenish white 
 precipitate, immediately or after the lapse of 
 some time, indicates NICKEL. ( 88, c. 6, and 
 Recapitulation and Remarks, 88.) 
 
 bb. An insoluble residue remains, on treating 
 the precipitate produced by caustic potash t with 
 carbonate of ammonia and caustic ammonia. 
 This is tested for MANGANESE, with carbonate of 
 soda. ( 88, bj 5.) If the precipitate really 
 consists of protoxide of manganese, it may almost 
 always safely be detected by its assuming a 
 brown tint, when exposed to the air. The am- 
 
228 DETECTION OF THE BASES. 
 
 moniacal solution is tested for cobalt and nickel, 
 
 as directed 1 18, 2, a, <*, aa. 
 
 ft. AMMONIA PRODUCES A LASTING PRECIPITATE. 
 The entire solution of the sulphurets in aqua regia 
 is then treated in the same manner as the first por- 
 tion, the precipitate produced by ammonia, in pre- 
 sence of sal ammoniac, is filtered off from the 
 solution and washed ; the further operations for 
 testing both the filtrate and precipitate are con- 
 ducted as follow. 
 
 1. Hydrosulphuret of ammonia is added to the FILTRATE, 
 till it causes no longer any precipitation ; the precipitate 
 obtained is filtered off from thesolution, carefully was hed, 
 dissolved in aqua regia, mixed with caustic potash in 
 excess and tested for cobalt, nickel, manganese, and zinc, 
 exactly as $ 118, 2, a, *, directs. 
 
 2. The PRECIPITATE is digested with dilute solution of 
 potash. (If we have obtained only a very minute precipi- 
 tate, this should be dissolved, on the filter, by means of 
 hydrochloric acid, and caustic potash in excess added to 
 tne solution.) 
 
 aa. The precipitate redissolves completely in. 
 the caustic potash : absence of peroxide of iron, 
 and of the phosphates, and oxalates of the alka- 
 line earths. The solution with potash is tested 
 for alumina and oxide of chromium, exactly as 
 118, 1,0, directs. 
 
 bb. The precipitate does not redissolve, or at 
 least not completely. The solution is filtered 
 and the filtrate tested for oxide of chromium and 
 alumina, as stated at aa. The residue is dis- 
 solved in dilute hydrochloric acid, and a small 
 portion of the solution mixed with ferrocyanide 
 of potassium. The immediate formation of a 
 blue precipitate or even a blue tint in the solu- 
 tion indicates IRON. If iron is present, the rest 
 of the hydrochloric solution is mixed with some 
 tartaric acid, and ammonia in excess added. 
 Should no iron be present, the solution is simply 
 supersaturated with ammonia. If no precipitate 
 is formed, neither phosphates nor oxalates of the 
 
DETECTION OF THE BASES. 229 
 
 alkaline earths are present ; if a precipitate is 
 formed, this is treated as 118, 1, 6, directs. 
 To ascertain whether the iron was present as 
 peroxide or protoxide, the original solution in 
 water or in hydrochloric acid (but not in nitric 
 acid) is tested with ferrocyanide of potassium 
 and with ferricyanide of potassium. The forma- 
 tion of a dark blue precipitate with the former 
 reagent, indicates PEROXIDE j with the latter, 
 PROTOXIDE, 
 b. THE PRECIPITATE PRODUCED BY HYDROSULPHURET 
 
 OF AMMONIA REDISSOLVES READILY AND COMPLETELY 
 UPON BEING TREATED WITH HYDROCHLORIC ACID, OR, 
 AT LEAST, ITS BLACK COLOUR DISAPPEARS IMMEDIATELY : 
 
 absence of cobalt and nickel. The solution is boiled 
 with some nitric acid, filtered off from the sulphur 
 which precipitates in this operation, and a small por- 
 tion of the filtrate mixed with sal ammoniac J ammonia 
 in excess is then added and heat applied. 
 
 a.. No lasting precipitate is formed upon the ad- 
 dition of ammonia: absence of iron, oxide of chro- 
 mium, alumina phosphates, and oxalates of the alka- 
 line earths. The rest of the hydrochloric solution is 
 mixed with potash in excess, and the precipitate 
 formed tested for MANGANESE, with carbonate of 
 soda ; the alkaline filtrate is tested for ZINC, with 
 sulphuretted hydrogen. 
 
 . A lasting precipitate is formed upon the ad- 
 dition of ammonia* The entire solution of the 
 sulphurets is treated in the same manner as the 
 first portion. The precipitate is tested exactly as 
 118, 2, a, /3, 2 directs. The solution which has 
 been filtered off from the precipitate, is mixed 
 with hydrosulphuret of ammonia in excess. 
 
 aa. No precipitate is formed : absence of 
 manganese and zinc, 
 
 bb. A precipitate is formed. This is well 
 washed and dissolved in aqua regia, and potash 
 in excess added to the solution. 
 
 <*. No lasting precipitate is formed: ab- 
 sence of manganese and consequently prej 
 10 
 
 
230 DETECTION OF THE BASES. 
 
 gence of ZINC, For further proof sulphuretted 
 hydrogen is added to the solution with potash, 
 p/3. A precipitate is formed : MANGANESE* 
 The blow-pipe is resorted to as a conclusive 
 te&t. The fluid which has been filtered off 
 from this precipitate is treated with sulphu- 
 retted hydrogen. The formation of a white 
 precipitate indicates ZINC. 
 
 119. 
 
 A portion of the fluid in which hydrosulphuret of am- 
 monia has produced no precipitate, or which has been fil- 
 tered off from the precipitate formed, is mixed with phos- 
 phate of soda and with ammonia (if it does not already 
 contain free ammonia) and strongly agitated. 
 
 a. No PRECIPITATE is FORMED j this indicates the 
 absence of all the alkaline earths. A fresh portion of 
 the fluid is evaporated to dryness and the residue 
 heated to redness. If no residue remains, (on heating 
 to redness,) neither potash nor soda are present : pass 
 over to 122. If a residue remains, the entire fluid 
 is treated in the same manner as the first portion, 
 and the further operations are conducted as 121 
 directs. 
 
 b. A PRECIPITATE* is FORMED. The remainder of 
 the fluid, if containing sulphuretted hydrogen or hy- 
 drosulphuret of ammonia (in which latter case it 
 must first be acidified with hydrochloric acid) is 
 heated, till it has lost all odour of sulphuretted hydro- 
 gen, and then filtered off from the sulphur, if any has 
 been precipitated. To this filtrate a mixture of car- 
 bonate of ammonia and some caustic ammonia is 
 added in excess after having previously added mu- 
 riate of ammonia, should this substance not already 
 have been formed in the fluid in sufficient quantity 
 during the course of examination. The solution is 
 boiled for some time. 
 
 1. No PRECIPITATE IS FORMED. PaSS OVCr tO 120, 
 
 neither lime, nor barytes, nor strontian being present. 
 
 2. A PRECIPITATE IS FORMED! presence of LIME, BA- 
 
 w. 
 
DETECTION OF THE BASES. 231 
 
 RYTES, or STRONTIAN. The precipitate is filtered off 
 
 (the filtrate is tested as 120 directs) and dissolved in 
 
 the least possible quantity of very dilute hydrochloric acid. 
 
 a. Solution of gypsum is added to a portion of the 
 
 solution. 
 
 *. No precipitate is formed, NOT EVEN AFTER 
 
 THE LAPSE OF SOME TIME. PaSS OVCr tO 119, 2, 
 
 b } for barytes and strontian are not present- 
 /3. A precipitate is formed. 
 
 aa. It is formed Immediately upon the addition 
 of the soluution of gypsum : this indicates BARY- 
 TES. Strontian may be present besides. 
 
 A portion of the hydrochloric solution (vide 
 119, 2) is evaporated to dry ness, and the residue 
 digested with absolute alcohol (at least, with 
 very strong alcohol) and the solution filtered. 
 A few drops of the filtrate are evaporated upon 
 a platinum plate. 
 
 *. No residue remains. Passover to 120: 
 for neither strontian nor lime are present. 
 
 /3/3. A residue remains. The alcoholic so- 
 lution is divided into two portions : one portion 
 is heated in a small crucible and ignited ; a 
 carmine red tint of the flame indicates STRON- 
 TIAN. If the flame does not appear red, or if 
 any doubt exists as to its exact tint, the second 
 portion of the alcoholic solution is evaporated 
 to dryness, the residue dissolved in a small 
 proportion of water, and the solution tested 
 with solution of gypsum. The formation of a 
 precipitate after the lapse of some time, indi- 
 cates STRONTIAN. 
 
 We can best assure ourselves of the pre- 
 sence of barytes by adding hydrofluosilicic 
 acid to the solution in hydrochloric acid, and 
 applying heat. The formation of a precipitate 
 after the lapse of some time denotes the pre- 
 sence of BARYTES. 
 
 bb. The precipitate is formed, only after the 
 lapse of some time : absence of barytes ; pre- 
 sence of STRONTIAN. 
 
232 DETECTION OF THE BASES. 
 
 b. Oxalic acid is added to a fresh portion of the 
 hydrochloric solution, (vide 119, 2,) after having 
 previously made it alkaline by the addition of ammonia. 
 Should (after 1 19, 2, a, /3,) barytes or strontian have 
 been detected, these must be first precipitated with 
 sulphate of potash, the solution filtered off, and the 
 oxalic acid added to the filtrate, after the previous ad- 
 dition of ammonia. If a precipitate is formed, lime 
 is present. 
 
 120. 
 
 Two small portions are taken of the fluid, in which car- 
 bonate of ammonia has produced no precipitate, (119, 1.) 
 or of that which has been filtered off from the precipitate 
 formed, and sulphate of potash is added to the one, oxalate 
 of ammonia to the other. 
 
 1. BOTH THESE REAGENTS PRODUCE NO LONGER ANY 
 
 PRECIPITATE. This is a certain proof that all barytes, 
 strontian, and lime, have been completely precipitated by 
 carbonate of ammonia. Phosphate of soda is added to a 
 third portion of the fluid with carbonate of ammonia, and 
 the mixture stirred with a glass rod. The formation of a 
 crystalline precipitate, (vide 86, d, 5,) indicates MAGNE- 
 SIA. The rest of the fluid, a portion of which has been 
 tested for magnesia, is evaporated to dryness, and heated 
 till all the ammoniacal salts have been expelled. If no re- 
 sidue remains, pass over to 122; if a residue remains, 
 pass over 121. 
 
 2. BOTH THE REAGENTS, OR AT LEAST ONE OF THEM, 
 
 PRODUCE STILL A PRECIPITATE. In that case, barytes, 
 strontian, and lime, have not yet been completely precipi- 
 tated by carbonate of ammonia. This reagent, mixed 
 with caustic ammonia, is, therefore, once more added to 
 the rest of the fluid, and the mixture again boiled for some 
 time. The precipitate formed is filtered off from the fluid, 
 and again treated as 120 directs. 
 
 121. 
 
 We have now still to treat of the examination for fixed 
 alkalies and for ammonia. 
 
DETECTION OP THE BASES. 233 
 
 The combinations of the former are, with very few ex- 
 ceptions, soluble in water. It is, therefore, not necessary 
 to look for them when testing compounds insoluble in 
 water. 
 
 When we have to operate upon a substance insoluble 
 in water, but soluble in hydrochloric acid, or in nitric acid, 
 a portion of the fluid, in the specimen of which phosphate 
 of soda did produce no precipitate, ( 119, a,) or of that 
 in which carbonate of ammonia has occasioned none, 
 ( 119, 1,) or of that which has been filtered off from the 
 precipitate formed, ( 119, 2 3 ) is preserved and tested for 
 phosphoric acid and oxalic acid, as 1 25, 8, directs. 
 
 1. MAGNESIA is NOT PRESENT. The roasted residue 
 of 119, , is dissolved in a small proportion of water, 
 and alcohol added to the solution ; this is then heated to 
 the boiling point and ignited. 
 
 a. THE FLAME HAS A VIOLET TINT. Absence of 
 soda ; probable presence of POTASH. 
 
 b. THE FLAME is YELLOW : presence of SODA. The 
 solution is evaporated to dryness, and the test with 
 antimoniate of potash, and the blow-pipe flame, are 
 resorted to as conclusive proofs of the presence of 
 soda. (Vide $ 85, 6, 3.) We assure ourselves of the 
 presence of potash, by dissolving this residue in wa- 
 ter, or, better still, in alcohol, if possible, and heating 
 one half of the solution with tartaric acid, and the 
 other half with chloride of platinum. If potash be 
 present, the tartaric acid will produce a colourless, 
 granular, crystalline precipitate, after the lapse of 
 some time, whilst the chloride of platinum will pro- 
 duce a yellow precipitate. 
 
 2. MAGNESIA is PRESENT. The residue is dissolved in 
 water, and water of barytes, or solution of sulphuret of 
 barium (containing caustic barytes) added, as long as any 
 precipitate is formed ; the solution is then boiled, filtered, 
 and dilute sulphuric acid dropped into the filtrate till the 
 reaction has become acid. The fluid is then filtered off 
 from the precipitated sulphate of barytes, the filtrate eva- 
 porated to dryness, and the residue which, perchance, may 
 remain, tested for potash and soda, as directed 121, 1. 
 Or the residue containing magnesia (and perhaps alkalies 
 
234 ABSENCE OF ORGANIC ACIDS. 
 
 besides) is treated with sulphuric acid, the solution evapo- 
 rated to dryness, and the residue heated to redness as long 
 as any vapour escapes ; the residuary mass is then dis- 
 solved in water, and the solution precipitated by acetate of 
 barytes in excess, filtered off from the precipitate, and the 
 filtrate again evaporated to dryness ; the residue is exposed 
 to a strong red heat, and then treated with a small propor- 
 tion of water ; the solution is filtered and further tested for 
 potash and soda, as 121, 1, directs. Should the filtrate 
 manifest an alkaline reaction, it must first be neutralized 
 with hydrochloric acid. 
 
 122. 
 
 We have now still to consider the examination for am- 
 monia. A portion of the substance under examination is 
 treated with concentrated solution of potash, and heat 
 applied. AMMONIA is present, if the escaping gas emits 
 its characteristic odour, if it restores the blue colour of 
 moist reddened litmus-paper, and if white fumes arise upon 
 a small glass rod, moistened with hydrochloric acid, being 
 dipped into the tube. 
 
 Compounds in which all the more frequently occurring 
 acids and bases, metals and metalloids, are supposed to 
 be present. 
 
 A. 1. SUBSTANCES SOLFBLE IN WATER. DETECTION OF ACIDS 
 
 AND METALLOIDS. 
 
 I. Absence of Organic Acids. 
 123. 
 
 1. Concerning the detection of ARSENIOUS and ARSENIC 
 
 ACID, CARBONIC ACID, HYDROSULPHURIC ACID, and CHROMIC 
 
 ACID, compare 108, 1 and 2. 
 
 2. Nitrate of barytes is added to a portion of the solu- 
 tion ; if the solution is acid, it must first be neutralized 
 with ammonia. 
 
 a. No PRECIPITATE is FORMED. Absence of sul- 
 phuric acid, phosphoric acid, boracic acid, chromic 
 
 
ABSENCE OF ORGANIC ACIDS. 235 
 
 acid, silicic acid, oxalic acid, arsenious and arsenic 
 acid.* (Pass over to &) 
 
 b. A. PRECIPITATE is FORMED. The fluid is di- 
 luted, and hydrochloric acid added ; if the precipitate 
 does not redissolve, or, at least, not completely, SUL- 
 PHURIC ACID is present. 
 
 S. Nitrate of silver is added to a portion of the solution ; 
 Shis is previously EXACTLY neutralized, if acid, by means 
 f ammonia ; if alkaline, by means of nitric ac^d, 
 
 a. No PRECIPITATE is FORMED. Pass over to 4 ; 
 neither chlorine, nor iodine, cyanogen, phosphoric 
 acid, silicic acid, oxalic acid, nor chromic acid are 
 present, nor boracic acid, if the solution was not too 
 dilute- 
 
 b. A PRECIPITATE is FORMED. The colour of the 
 precipitate is inspected, and the nitric acid then 
 added. 
 
 . The precipitate redissolves completely. Pass 
 
 over to 1 23, 4 ; for neither chlorine, iodine, nor 
 
 cyanogen are present. 
 
 /s. A residue remains: CHLORINE, IODINE, or 
 
 CYANOGEN. The residue is washed and digested 
 
 with ammonia. 
 
 aa. A yellowish residue remains. This is 
 caused by the presence of IODINE. We assure 
 ourselves of the presence f this substance as 
 100, c, directs. The solution is filtered off 
 from the residue, and nitric acid in excess added 
 to the filtrate ; if a precipitate is formed, it indi- 
 cates chlorine or cyanogen. For the further 
 operation, vide bb* 
 
 bb. No residue remains^ CHLORINE or CYANO- 
 GEN ; absence of iodine. For further examina- 
 tion, the solution is again precipitated with nitric 
 acid. Previous to beginning the operation of 
 distinguishing chloride of silver from cyanide of 
 
 * If muriate of ammonia is present in the fluid under examination, the 
 non-formation of a precipitate is not a conclusive proof of the absence of 
 oxalic acid, arsenious and arsenic acid, and especially not of that 'of bo- 
 racic acid, the barytes salts of these acids not being insoluble in water, in 
 presence cf anamoni&cal salts. 
 
236 ABSENCE OF ORGANIC ACIDS. 
 
 silver, the fluid is tested for cyanogen, in order 
 to see whether this operation is at all necessary. 
 For this purpose solution of magnetic oxide of 
 iron is added to a portion of the original solu- 
 tion, followed by the addition of hydrochloric 
 acid. The formation of a blue precipitate indi- 
 cates CYANOGEN.* If no precipitate is formed, 
 and the fluid assumes no blue tint, the precipitate 
 redissolved by ammonia consists of chloride of 
 silver alone. If cyanogen has been detected, the 
 precipitate to be examined is washed, taken from 
 the filter when still mcist, dried in a porcelain 
 crucible, and heated to redness. Chloride of 
 silver merely fuses, whilst cyanide of silver be- 
 comes reduced. The metallic silver may be 
 separated from the chloride of silver by means 
 of nitric acid. 
 
 4. The aqueous solution is tested for nitric acid, by 
 mixing solution of indigo with it, till it has acquired a light 
 blue tint, and then adding some sulphuric acid, and apply- 
 ing heat ; and, moreover, by throwing a crystal of proto- 
 sulphate of iron into the solution, previously mixed with 
 the third part of its amount of concentrated sulphuric acid. 
 If nitric acid is present, the blue solution loses its colour, 
 and a brown-coloured halo forms round the crystal. 
 
 We have now still to speak of the examinations for phos- 
 phoric acid, boracic acid, silicic acid, oxalic acid, and chro- 
 mic acid. It is necessary to make these examinations only 
 in such cases where chloride of barium, as well as nitrate of 
 silver, have caused the formation of precipitates, in neutral 
 solutions. Compare note to 123, 2, a. 
 
 5. If the precipitate produced by nitrate of silver was of 
 a yellowish colour, we must especially look for phosphoric 
 acid. For this purpose, ammonia in excess is added to a 
 portion of the fluid ; if a precipitate is formed, the fluid is 
 filtered, and muriate of ammonia added to the filtrate, and 
 
 * Should the cyanogen be present as free hydrocyanic acid, which may 
 easily be detected by its characteristic odour, this ought to be saturated 
 with potash, previous to the addition of the solution of iron. We have 
 already stated at 100, d, that the cyanogen is not detected by nitrate of 
 silver, in certain combinations, e. g. cyanide of mercury. 
 
ABSENCE OF ORGANIC ACIDS. 237 
 
 then sulphate of magnesia. The formation of a crystalline 
 precipitate denotes PHOSPHORIC ACID- 
 
 6. A small portion of the substance under examination is 
 drenched with alcohol, sulphuric acid added, and the mixture 
 heated to boiling in a small crucible, and then ignited. If 
 the flame has a green tint, BORACIC ACID is present. If 
 copper is present, this must first be removed, either by 
 means of sulphuretted hydrogen, or by boiling the fluid with 
 potash in excess. 
 
 7. If the fluid was red, or yellow changing to red, on the 
 addition of hydrochloric acid, and if the precipitate produ- 
 ced by nitrate of silver in the neutral solution had a purple 
 red colour, the presence of CHROMIC ACID is confirmed. 
 
 8. For silicic acid, test as 99, b, 2, directs. 
 
 9. For the detection of OXALIC ACID, solution of gypsum 
 is added to a portion of the fluid under examination, which 
 must first be neutralized with ammonia, if it manifests an 
 acid reaction. The formation of a white precipitate, which 
 does not vanish upon the addition of acetic acid, indicates 
 the presence of oxalic acid. 
 
 CHLORATES, BROMIDES, and FLUORIDES, are of less fre- 
 quent occurrence. Chlorates may be detected by their 
 violent deflagration with charcoal, when in a state of fusion, 
 (vide 105, A. I. 2, c.) Chloric acid is best detected by 
 heating a portion of the solid salt in a glass tube, closed at 
 the lower end, and placing a wood-splinter which has been 
 kindled and the flame extinguished, near the open end. If 
 CHLORIC ACID be present, the flame of the wood-splinter 
 will be rekindled. The residue dissolved in water yields 
 in that case with nitrate of silver a copious precipitate of 
 chloride of silver. Other tests are, to throw a few grains 
 of the salt into fuming sulphuric acid, ( 101, b. 6,) or fus- 
 ing a portion of the salt with cyanide of potassium. ( 101, 
 b, 3.) The detection of BROMIDES is simple, if iodides 
 are not present, at the same time. Vide 100, for the 
 safe detection of bromine in both cases. For the detec- 
 tion of the FLUORIDES, the methods described 98, d, 4 
 and 5, are the safest under all circumstances. 
 10* 
 
238 PRESENCE OF ORGANIC ACIDS. 
 
 Compounds in which all the more frequently occurring 
 acids and bases, metals and metalloids, are supposed to 
 be present. 
 
 A. 1. SUBSTANCES SOLUBLE IN WATER. DETECTION OF 
 
 ACIDS AND METALLOIDS. 
 
 II. Presence of Organic Acids. 
 124. 
 
 1. CHROMIC ACID, ARSENIOUS, and ARSENIC ACID, have 
 already been detected when testing for the bases ; concern- 
 ing the distinction of arsenious from arsenic acid, compare 
 93, additions and remarks. 
 
 2. Hydrochloric acid is added to a portion of the solu- 
 tion. The formation of a precipitate, which, upon being 
 heated on a platinum plate volatilizes partly or totally, 
 emitting the characteristic odour of BENZOIC ACID, indicates 
 the presence of this acid. Effervescence, upon the addition 
 of the hydrochloric acid, may be caused by the presence 
 of CARBONIC ACID, or by that of SULPHURETTED HYDROGEN. 
 (Vide 108, 2.) 
 
 3. Ammonia is added, to a portion of the solution, till 
 the latter manifests a feebly alkaline reaction ; the solu- 
 tion is then filtered, if necessary, and chloride of barium 
 added. 
 
 Should hydrochloric acid have produced a precipi- 
 pitate in the original solution, the nitrate of this ought 
 to be used for this experiment. 
 
 a. No PRECIPITATE is FORMED. Absence of sul- 
 phuric acid, phosphoric acid, chromic acid, boracic 
 acid, arsenic acid, arsenious acid, silicic acid, oxalic 
 acid, tartaric acid, citric acid ; these may, therefore, 
 be disregarded in the further course of examination. 
 What we have stated at 123, 2, a, (note,) applies 
 also to the last six of these acids. 
 
 b. A PRECIPITATE is FORMED. Hydrochloric acid 
 is added. 
 
 <*. The precipitate redissolves : Absence of 
 sufphuric acid. 
 0. A residue remains : SULPHURIC ACID. 
 
PRESENCE OF ORGANIC ACIDS. 239 
 
 4. Nitrate of silver is added to a portion of the solution, 
 which must first be EXACTLY neutralized with nitric acid, 
 if alkaline, and with ammonia, if acid. 
 
 a. No precipitate is formed absence of phospho- 
 ric acid, boracic acid, chromic acid, silicic acid, oxalic 
 acid, tartaric acid, citric acid ; these may, therefore, 
 be disregarded in the further course of examination. 
 
 b. A PRECIPITATE IS FORMED. 
 
 <*. It is whitish or yellow. A portion of the fluid, 
 together with the precipitate suspended therein, is 
 boiled. Complete and rapid reduction indicates 
 FORMIC ACID. Protonitrate of mercury is used as 
 a conclusive test, 104, 6, bearing in mind the 
 remarks which will be found at the end of this 
 number, (4.) The rest of the precipitate is treated 
 with nitric acid. If it is redissolved, neither CHLO- 
 RINE, nor IODINE, nor CYANOGEN, are present ; but 
 if the precipitate does not completely redissolve in 
 nitric acid, the residue is tested for these salt radi- 
 cals, as 123, 3, 6, /3, directs. 
 
 /3. The precipitate produced by nitrate of silver 
 is purple : CHROMIC ACID. Should arsenic acid be 
 present, acetate of lead is added, or (as a conclu- 
 sive test, to a fresh portion of the solution) the 
 formation of a yellow precipitate proves the pre- 
 sence of CHROMIC ACID, CHLORINE, IODINE, and 
 
 CYANOGEN, may also be present in the silver pre- 
 " cipitate: test for these salt radicals as 123, 3, 6, 
 directs. 
 
 In the presence of chromic acid, formic acid 
 cannot be detected with certainty, by the reduction 
 of silver and mercury. In this case there remains 
 no other means of its certain detection, except dis- 
 tilling the compound under examination, with the 
 addition of some sulphuric acid. The distillate is 
 saturated with soda, and then tested with perchlo- 
 ride of iron, (which chromic acid tinges blood-red,) 
 and with nitrate of silver. (Compare 104, b,) 
 5. If chloride of barium and nitrate of silver have given 
 rise to the formation of precipitates, test for PHOSPHORIC 
 ACID, as directed 123, 5, and for SILICIC ACID as directed 
 99, 6, 2. 
 
240 PRESENCE OF ORGANIC ACIDS. 
 
 6. A portion of the solid substance under examination 
 (or, if in solution (should the latter be acid, it must first 
 be saturated with potash) the residue obtained by eva- 
 porating the solution to dryness) is drenched with alcohol 
 in a small tube, concentrated sulphuric acid to the extent 
 of about one-third of the volume of the alcohol, and the 
 mixture heated to the boiling point. If any odour of acetic 
 ether is emitted which, in many instances, may be clearly 
 detected upon agitating the mixture, whilst cooling or 
 when cold ACETIC ACID is present. The contents of the 
 tube are poured into a small crucible, heated, and ignited. 
 If the flame is green, BORACIC acid is present. 
 
 7. A portion of the fluid is rendered feebly alkaline by 
 the addition of ammonia, filtered, if necessary, and chlo- 
 ride of calcium added. If the solution was neutral, some 
 sal ammoniac must be added before the addition of chlo- 
 ride of calcium. 
 
 a. No PRECIPITATE IS FORMED, NOT EVEN AFTER 
 
 THE LAPSE OF SOME TIME. Absence of oxalic acid 
 and tartaric acid ; pass over to 8. 
 
 b. A PRECIPITATE IS FORMED IMMEDIATELY, OR 
 AFTER THE LAPSE OF A FEW MINUTES. The Solution 
 
 is filtered off from this precipitate, and the filtrate 
 further tested as 8 directs. 
 
 The precipitate is washed, digested, and agitated 
 with somewhat dilute solution of potash in excess, 
 without the aid of heat, filtered, and the filtrate boiled 
 for some time. If a precipitate is formed which 
 disappears again, on cooling, tartaric acid is present. 
 Solution of gypsum is added to a portion of the 
 original solution, which, if acid, must first be made 
 neutral by the addition of ammonia. The formation 
 of a precipitate, which does not disappear upon the 
 addition of acetic acid, but is dissolved by hydrochlo- 
 ric acid, indicates OXALIC ACID. 
 
 8. The fluid in which chloride of calcium has produced 
 no precipitate, or that which has been filtered off from 
 the precipitate formed (in which latter case some more 
 chloride of calcium is added) is mixed with alcohol. 
 
 a. No PRECIPITATE is FORMED. Absence of citric 
 acid and of malic acid. Pass over to 9. 
 
PRESENCE OF ORGANIC ACIDS. 241 
 
 b. A PRECIPITATE is FORMED. The solution is 
 filtered off and the filtrate treated as 9 directs. The 
 precipitate is washed with alcohol, and (being left on 
 the filter) dissolved in the least possible quantity of 
 dilute hydrochloric acid. Ammonia is then added to 
 this latter filtrate, till it manifests a feebly alkaline 
 reaction, and heat applied to the boiling point, at 
 which it must be kept for some. time. 
 
 *. THE FILTRATE REMAINS CLEAR. Absence of 
 
 citric acid. Presence of MALIC ACID ; alcohol is 
 again added to the fluid, and the lime precipitate 
 which is formed, heated to redness, as a conclu- 
 sive test for malic acid ; the reaction with acetate of 
 lead is moreover resorted to as a confirmatory proof, 
 102, e, 5. 
 
 /3. A HEAVY, WHITE PRECIPITATE IS FORMED. 
 
 Presence of CITRIC ACID. The solution is filtered 
 whilst boiling, and the filtrate tested for malic acid, 
 as described at *. 
 
 9. Perchloride of iron is added to the filtrate of 8, 6, or 
 to the fluid, in which no precipitate has been formed, on 
 mixing with alcohol, ( 128, 8, a,) after having previously 
 expelled the alcohol by heat, and after having exactly neu- 
 tralized with hydrochloric acid. If no light brown floccu- 
 lent precipitate is formed, neither succinic acid nor benzoic 
 acid are present ; if a precipitate of this kind is formed, 
 and no benzoic acid has been detected during the previous 
 examination, ( 124, 2,) this consists of SUCCINIC ACID. 
 But if benzoic acid was present, the solution is filtered off, 
 and the precipitate washed and then digested with ammo- 
 nia in excess, filtered, the filtrate evaporated to dryness, 
 and the benzoate of ammonia dissolved out of it by alco- 
 hol ; the succinate of ammonia remains undissolved. This 
 succinate is dissolved in water, and both solutions are 
 tested with perchloride of iron. 
 
 10. Test for NITRIC ACID as directed 123. 
 
 Compounds in which all the more frequently occurring 
 bases, acids, metals, and metalloids, are supposed to be 
 present. 
 
242 ABSENCE OP ORGANIC ACIDS. 
 
 A. 2. SUBSTANCES INSOLUBLE IN WATER, BUT SOLUBLE IN 
 
 HYDROCHLORIC ACID AND IN NITRIC ACID. DETECTION 
 OF THE ACIDS AND METALLOIDS. 
 
 I. Absence of Organic Acids. 
 125. 
 
 In examining these compounds we must look for all the 
 acids occurring at 123, with the exception of chloric 
 acid. Cyanogen compounds are not examined after this 
 method: compare 128. 
 
 1 . What we have stated at 111, 2, with regard to AR- 
 SENIOUS and ARSENIC ACID, HYDROSULPHURIC ACID and 
 CHROMIC ACID, applies also to this paragraph. 
 
 2. A portion of the substance is boiled with nitric acid, 
 and the solution filtered, should any residue remain. 
 
 a. Effervescence takes place ; this may be caused 
 by the presence of CARBONIC ACID, or by that of NI- 
 TRIC OXIDE GAS ; the former may be detected as 99, 
 , directs, the latter usually indicates the presence of 
 a sulphur compound. 
 
 b. Violet vapours escape, which impart a blue tint 
 to starch: IODINE. 
 
 3- Nitrate of silver is added to a portion of the nitric 
 solution. 
 
 <z. No PRECIPITATE is FORMED : pass over to 4, for 
 no chlorine is present. 
 
 b. A PRECIPITATE is FORMED. The solution is fil- 
 tered off, and the precipitate washed, and digested 
 with ammonia ; if it redissolves completely or partly, 
 CHLORINE is present. 
 
 4. A portion of the substance under examination is boiled 
 with hydrochloric acid, and the solution filtered, if necessary. 
 A portion of the solution or filtrate is mixed with chloride 
 of barium. The formation of a precipitate indicates SUL- 
 PHURIC ACID. 
 
 5. Another portion of the hydrochloric solution is test- 
 ed for NITRIC ACID, with indigo and protosulphate of iron. 
 (Vide 1 23, 4.) In many cases it will already have been de- 
 tected by the deflagration on charcoal before the blow- 
 pipe. 
 
 6. If the experiment, 125, 2, 6, has not yet indicated 
 the presence of iodine, a portion of the substance under ex- 
 
PRESENCE OF ORGANIC ACIDS. 243 
 
 animation is heated with concentrated sulphuric acid. If 
 any IODINE compound be present, violet vapours will be 
 evolved, which impart a blue tint to starch. (Compare 
 100, c, 6.) 
 
 7. Test for BORACIC ACID by treating a portion of the 
 substance to be examined with sulphuric acid and alco- 
 hol. (Vide 98, b, 5.) 
 
 8. The fluid of 119, , (in which phosphate of soda 
 produces no precipitate,) or that of 119, 1, (in which car- 
 bonate of ammonia produces no precipitate,) or (should 
 carbonate of ammonia have produced a precipitate in it) 
 the nitrate of the same ( 119, 2,) (vide 121,) are tested 
 for PHOSPHORIC ACID and OXALIC ACID, as directed 123, 
 
 5, and 9. (Oxalic acid, when combined with barytes, 
 strontian, or lime, will have been detected already, in test- 
 ing for the bases ; the same applies to phosphoric acid 
 when combined with magnesia.) 
 
 9. Test for SILICIC ACID as 99, b, 3, directs. With 
 regard to the more rarely occurring BROMINE and FLUORINE 
 compounds, we refer to the remarks made at the end of 
 123. 
 
 Compounds in which all the more frequently occurring 
 bases, acids, metahj and metalloids, are supposed to 
 be present. 
 
 A. 2. SUBSTANCES INSOLUBLE IN WATER, BUT SOLUBLE IN 
 
 HYDROCHLORIC ACID, AND IN NITRIC ACID. DETEC- 
 TION OF THE ACIDS AND METALLOIDS. 
 
 II. Presence of Organic Acids. 
 126. 
 
 1. Test for CARBONIC ACID, ARSENIC ACID, ARSENIOUS 
 
 ACID, SULPHURIC ACID, NITRIC ACID, BORACIC ACID, CHRO- 
 MIC ACIDj SILICIC ACID, CHLORINE, IODINE, and SULPHUR, 
 
 as directed at 125 ; for ACETIC ACID as stated at 124, 
 
 6. CYANOGEN compounds are not examined after this 
 method: compare 128. 
 
 2. A portion of the compound under examination is dis- 
 
244 INSOLUBLE SUBSTANCES. 
 
 solved in hydrochloric acid, and the solution filtered, should 
 any residue remain, (which latter is tested for BENZOIC 
 ACID, as directed at 124, 2.) The filtrate is mixed with 
 solution of carbonate of potash, and the mixture boiled for 
 some time. The fluid is filtered off from the precipitate 
 formed, and the filtrate saturated with dilute hydrochloric 
 acid, and tested for PHOSPHORIC ACID and OXALIC ACID, as 
 directed at 123, 5, and 9 ; and for TARTARIC ACID, CITRIC 
 
 ACID, MALIC ACID, SUCCINIC ACID and BENZOIC ACID, CXaCt- 
 
 ly as directed at 124, 7, 8, and 9. 
 
 Compounds in which all the more frequently occurring 
 bases, acids, metals, and metalloids, are supposed to 
 be present. 
 
 B. SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE BOTH 
 
 IN WATER AND IN HYDROCHLORIC ACID. DETECTION 
 OF THE BASES, ACIDS, AND METALLOIDS. 
 
 127. 
 
 The following substances and combinations belong to 
 this class : 
 
 SULPHATE OF BARYTES, SULPHATE OF STRONTIAN, SUL- 
 PHATE OF LIME, CHLORIDE OF SILVER, CHLORIDE OF LEAD, 
 SULPHATE OF LEAD, SULPHURET OF MERCURY, BISUL- 
 PHURET OF MERCURY, PROTOCHLORIDE OF MERCURY, 
 SOME OF THE FERROCYANIDES, SEVERAL SULPHURETS, 
 SILICIC ACID, SULPHUR and CARBON. 
 
 Besides these, a few acid arseniates belong to this class ; 
 they are, however, as rarely occurring in the analyses of 
 those mixtures and compounds important in pharmacy, 
 manufacture, arts, and trades, as the insoluble modification 
 of oxide of chromium, or as roasted peroxide of tin, or as 
 fluoride of calcium. Of these latter less frequently oc- 
 curring substances^ we purpose to treat separately. 
 
 For the insoluble cyanides, vide 128. 
 
 A. THE RESIDUE is WHITE. It may in that case con- 
 tain SULPHATE OF BARYTES, SULPHATE OF STRONTIAN, 
 SULPHATE OF LIME, SULPHATE OF LEAD, CHLORIDE OF 
 LEAD, CHLORIDE OF SILVER, PROTOCHLORIDE OF MERCURY, 
 SILICIC ACID, SULPHUR. 
 
PRESENCE OF ORGANIC ACIDS. 245 
 
 No attention need be paid to the presence of sulphate of 
 lime, if this substance lias already been detected in the 
 aqueous solution. The same remark applies to the lead 
 compounds : we may disregard these, if the previous ex- 
 amination has not already proved their presence. 
 
 1. A small portion of the substance under examination 
 is heated upon a platinum plate, and flame allowed to play 
 on it. If any odour of sulphurous acid is emitted, SUL- 
 PHUR is present. If no residue remains, sulphur alone is 
 present. If the heat applied was very intense, protochlo- 
 ride of mercury may have volatilized. The sensible pro- 
 perties of the residue will show whether this is to be ap- 
 prehended. 
 
 2. Hydrosulphuret of ammonia is added to a very small 
 portion of the substance under examination. 
 
 a. It remains white. Pass over to 127, 3, for no 
 metallic compounds are present. 
 
 b. It becomes black. This proves with certainty 
 the presence of a metallic salt, either protochloride 
 of mercury, chloride of silver, chloride of lead, or 
 sulphate of lead. Moreover, all the other com- 
 pounds enumerated under A, may be present. The 
 method of the further operation varies according to 
 whether lead is present or not. 
 
 The following preliminary experiment is made in 
 order to ascertain which method ought to be adopted. 
 
 A small portion of the substance is mixed with 
 carbonate of soda, and exposed to the reducing flame 
 of the blow-pipe. The production of a metallic 
 grain, (which oxidizes in the oxidizing flame,) at- 
 tended with a yellow incrustation of the charcoal, in- 
 dicates lead. 
 
 *. THIS PRELIMINARY EXAMINATION INDICATES 
 THE PRESENCE OF LEAD IN THE WHITE PRECIPI- 
 TATE. 
 
 aa. The largest half of the residue (which, if 
 moist, must first be dried) is fused with three 
 parts of dry carbonate of soda and three parts of 
 cyanide of potassium, in a small crucible, over a 
 spirit-lamp. The mass fuses easily ; it is main- 
 tained in a state of fusion for some time. After 
 
246 PRESENCE OP ORGANIC ACIDS. 
 
 cooling, it is boiled with water, filtered, and the 
 residue very carefully washed. The greater 
 portion of the filtrate is supersaturated with 
 hydrochloric acid, and a portion of this solution 
 tested with chloride of barium. The formation 
 of a precipitate indicates the presence of a SUL- 
 PHATE. (Should a precipitate (silicic acid) be 
 formed, upon supersaturating the filtrate with 
 hydrochloric acid, the fluid must be diluted and 
 filtered, and then tested for sulphuric acid.) The 
 rest of the solution (supersaturated with hydro- 
 chloric acid) is evaporated to dryness and the 
 residue treated with water. If a residue remains, 
 this consists of SILICIC ACID. The formation 
 of a clear glass, when fused with carbonate of 
 soda in the blow-pipe flame, is a conclusive 
 proof of the presence of silicic acid. The rest 
 of the filtrate, which has not been mixed with 
 hydrochloric acid, is acidified with nitric acid, 
 boiled until it emits no longer any odour of 
 hydrochloric acid, and nitrate of silver added ; 
 the formation of a precipitate of chloride of silver 
 denotes that the residue, insoluble in water and 
 hydrochloric acid, contains a CHLORIDE, (pro- 
 vided always, the reagents be free from chlorine, 
 and the residue completely washed.) The resi- 
 due obtained upon treating the fused ma'ss with 
 water, and which has been very carefully washed, 
 (vide supra,) is treated with acetic acid ; if it 
 partly dissolves in this acid with effervescence, 
 the presence of sulphates of the alkaline earths 
 is certain. If no effervescence takes place, it 
 proves the absence of the sulphates of the alka- 
 line earths ; the residue is therefore treated with 
 nitric acid, and the solution treated as follows. 
 If effervescence has taken place, a portion of the 
 acetic solution is tested with sulphuretted hydro- 
 gen. If a black precipitate is formed, (sulphuret 
 of lead,) the lead is removed in the same man- 
 ner from the entire acetic solution, and the fil- 
 trate (which, if necessary, is concentrated by 
 
 
PRESENCE OP ORGANIC ACIDS. 247 
 
 evaporation) treated as 119 directs, beginning 
 at 2, #. If the test portion of the acetic solution 
 remains unaltered upon being treated with sul- 
 phuretted hydrogen, the rest of the solution is 
 directly tested as directed, 119, 2, a. The re- 
 sidue, which has remained on treating with the 
 acetic acid, is treated with nitric acid, and a 
 small portion of the solution is then tested with 
 sulphuric acid for lead, (after having removed 
 the excess of acid by evaporation;) the rest 
 strongly diluted with water, and then tested for 
 SILVER, with hydrochloric acid. If nitric acid 
 leaves a residue, this consists of undissolved si- 
 licic acid, or incompletely decomposed sulphate 
 of the alkaline earths, 
 
 bb. Half of the remainder of the residue is 
 boiled with carbonate of potash. If its white 
 colour change into gray or black, PROTOCHLO- 
 RIDE OF MERCURY is present. As a confirmatory 
 test the other half is heated in a small glass tube, 
 together with dry carbonate of soda. (Vide 90, 
 6,7.) 
 
 /3. THE PRELIMINARY EXAMINATION PROVES THE 
 ABSSNCE OF LEAD, IN THE WHITE PRECIPITATE. 
 
 The entire entire residue is drenched and digested 
 for some time, with hydrosulphuret of ammonia, 
 the solution filtered, and the filtrate tested for chlo- 
 rine, as aa directs. The precipitate is washed and 
 boiled with nitric acid. 
 
 aa. The precipitate dissolves with the excep- 
 tion of the separated sulphur. CHLORIDE OF 
 SILVER alone is present. To assure ourselves, 
 we test the nitric solution for silver, with hydro- 
 chloric acid. To prove the presence of chlorine, 
 the filtrate of 127, A, 2, , is supersaturated 
 with nitric acid, and boiled, in order to expel the 
 sulphuretted hydrogen. The fluid is then filtered 
 from the sulphur which has separated, and tested 
 with nitrate of silver. 
 
 bb. A residue remains besides the separated 
 sulphur. 
 
248 INSOLUBLE SUBSTANCES. 
 
 -*. This residue is black: MERCURY. The 
 fluid is filtered from the residue, and the fil- 
 trate tested for silver, with hydrochloric acid : 
 the residue is heated with aqua regia. If it is 
 completely redissolved, with the exception of 
 the separated sulphur, the investigation may 
 be considered at an end, the absence of the 
 sulphates of the alkaline earths and that of sili- 
 cic acid being proved; if a white residue 
 remains, this is washed and treated as 127, 
 A, 3, directs. The solution in aqua regia 
 is tested with polished copper or with pro- 
 tochloride of tin to assure ourselves of the 
 presence of mercury, (vide 117, 2.) The 
 chlorine, which must be present, is detected in 
 the filtrate of /3, as aa directs. 
 
 /3/3. THE RESIDUE is NOT BLACK : absence 
 of mercury. For the further operation vide 3. 
 
 3. This residue, or, in the case of 127, A, 2, a, the ori- 
 ginal residue is fused in a platinum crucible,* over a' spirit 
 lamp with a double draught of air, together with four parts 
 of carbonate of potash and soda ; the fused mass is soaked 
 in water, boiled, filtered, and the residue (if any remain) 
 washed until chloride of barium no longer produces any 
 precipitate in the water, which runs off. (This water must 
 not be added to the filtrate. The residue is treated as 4 
 directs. The filtrate is supersaturated with hydrochloric 
 acid, and a portion of it tested with chloride of barium ; 
 the formation of a precipitate indicates the presence of 
 
 SULPHATES OF THE ALKALINE EARTHS. The TCSt of the 
 
 filtrate is evaporated to dryness and then treated with water; 
 if any residue remains, this consists of SILICIC ACID. 
 
 4. The residue remaining upon boiling the fused 
 mass with water, (vide 3,) indicates SULPHATES OF 
 THE ALKALINE EARTHS. It is carefully washed and then 
 treated with hydrochloric acid. It is a certain proof 
 of the presence of sulphates of the alkaline earths, if 
 it dissolves partly or totally, and with effervescence in 
 
 * A porcelain crucible may be substituted for a platinum crucible, in 
 which case, six parts of a mixture of equal parts of dry carbonate of soda 
 and cyanide of potassium must be employed, instead of the carbonate of 
 potash and soda ; the method in the text is however the best. 
 
PRESENCE OP ORGANIC ACIDS. 249 
 
 this menstruum. The hydrochloric solution is tested 
 as 119 directs, beginning at 2, a. If a residue remains 
 upon treating with hydrochloric acid, this consists of 
 silicic acid or of a sulphate of the alkaline earths which 
 is not yet completely decomposed. 
 
 B. THE RESIDUE is NOT WHITE. Even its colour will 
 in that case enable us to draw some conclusions (cinnibar, 
 sulphuret of arsenic.) 
 
 1. Test for SULPHUR as 127, A, 1, directs. 
 
 2. The greater part of the residue is treated with aqua 
 regia and boiled ; the solution is filtered whilst still hot, 
 and should any residue remain, besides the separated sul- 
 phur, this is once more boiled with water, filtered, and this 
 second filtrate added to the first. The filtrate is then eva- 
 porated nearly to dryness, redissolved in some water, and 
 one portion of the solution tested for LEAD, with sulphuric 
 acid, another portion for MERCURY by means of polished 
 copper. (If a hydrochloric solution has been employed in 
 testing for bases, ( 106,) the solution in aqua regia must 
 be tested for metals, in the usual way, as various other 
 sulphurets, insoluble or sparingly soluble in hydrochloric 
 acid, might be present.) 
 
 3. If aqua regia has left any residue undissolved besides 
 sulphur, which may have separated, this residue is careful- 
 ly washed. If a compound of lead has been present, this 
 rinsing process is conducted with hot water and continued 
 until the filtrate is no longer blackened by hydrosulphuret 
 of ammonia. 
 
 a. THE RESIDUE is WHITE : a portion of it is tested 
 with hydrosulphuret of ammonia. 
 
 . It becomes black. The entire residue is digest- 
 ed with hydrosulphuret of ammonia, and the further 
 operation conducted exactly as 127, A, 2, 6, /3, 
 directs. 
 
 $. It remains white. The residue is treated as 
 directed 127, A, 3. 
 
 6. THE RESIDUE INSOLUBLE IN AQUA REGIA, is 
 BLACK ; this indicates the presence of carbon in some 
 form. If it is totally consumed over a lamp, or in the blow- 
 pipe flame, nothing besides carbon is present ; but if a res- 
 idue remains, or if the combustion is not complete, (carbu- 
 
250 METHOD WITH INSOLUBLE CYANIDES. 
 
 ret of iron graphyte,) we must look moreover for CHLORIDE 
 
 OF SILVER, SULPHATES OF THE ALKALINE EARTHS and 
 
 SILICIC ACID ; the residue in that case, is treated as 127, 
 B, 3, a, *, directs. Of acids and electro-negative substan- 
 ces CHLORINE and SULPHURIC ACID alone can be present 
 besides those already mentioned. To assure ouselves 
 whether they are present or not, what remains of the resi- 
 due insoluble in hydrochloric acid is digested with hydro- 
 sulphuret of ammonia, super-saturated, filtered, and one-half 
 of the filtrate boiled with hydrochloric acid, the other half 
 with nitric acid ; both solutions are filtered and the hydro- 
 chloric fluid is tested with chloride of barium for sulphuric 
 acid, the nitric fluid with nitrate of silver for chlorine. 
 
 The insoluble PEROXIDE OF TIN and OXIDE OF 
 CHROMIUM may be detected before the blow-pipe. 
 Peroxide of tin, when mixed with carbonate of soda 
 and cyanide of potassium, and exposed on charcoal 
 to the reducing flame of the blow-pipe, yields a soft 
 metallic grain, without incrustation of the support. 
 Oxide of chromium, which is, moreover, distinguished 
 by its green colour, is treated with microcosmic salt, 
 as stated 87, 6, 5, or it is fused together with car- 
 bonate of soda and nitre, (vide 87, b, 4.) The 
 arsenic acid of the insoluble ARSENIATES is detected 
 before the blow-pipe or by means of reduction in a 
 glass tube. (Vide 94, d.} To enable us to test for 
 the bases, these insoluble arseniates must first be 
 decomposed by means of concentrated sulphuric acid. 
 FLUORIDE OF CALCIUM is decomposed by concentrated 
 sulphuric acid, in a platinum crucible : the fluorine is 
 detected by its property of etching glass ; the lime 
 remains as sulphate of lime. There are still several 
 other compounds which are rendered insoluble in 
 acids by being heated to redness ; but it would exceed 
 the limits of this work, to treat of them all. 
 
METHOD WITH INSOLUBLE CYANIDES. 251 
 
 128. 
 
 SPECIAL METHOD FOR THE DECOMPOSITION OF INSOLUBLE 
 CYANIDES, FERROCYANIDES, &C.* 
 
 Since in treating these compounds according to the 
 usual method, fallacious phenomena frequently occur, and 
 since moreover their solution in acids frequently succeeds 
 but imperfectly, it is advisable to pursue the following 
 method, in their analysis. The residue which has been 
 freed by water from, all soluble substances is boiled with 
 solution of carbonate of potash. 
 
 a. COMPLETE DECOMPOSITION TAKES PLACE, which 
 is easily detected by the change of colour and the 
 rapid deposition of the separated pure or carbonated 
 oxides ; the solution is filtered and the residue washed. 
 This residue may contain all the bases, which were 
 contained in the substance under examination as com- 
 pounds insoluble in water. For the determination of 
 these bases, the residue is treated exactly as 106, 
 A, 2, directs. A portion of the filtrate is tested for 
 CYANOGEN, by mixing it with hydrochloric acid, till 
 the reaction becomes strongly acid, and then adding 
 solution of the double proto- and per-chloride of iron ; 
 if cyanogen be present, Prussian blue precipitates. 
 For the detection of the other acids, the rest of the 
 filtrate is treated as 124 directs. This filtrate may, 
 moreover, possibly contain all the cobalt, all the iron 
 of the substance under examination, besides chromium 
 and manganese, since the combinations of their cya- 
 nides with other cyanogen compounds, on boiling 
 with alkalies, are decomposed in such a manner as 
 to cause the separation of insoluble oxides, whilst the 
 cobalticyanide of potassium, ferrocyanide of potas- 
 sium, &c., remain in solution. These metals must 
 not be disregarded. To detect them, a portion of the 
 fluid is mixed with nitric acid greatly in excess, the 
 mixture evaporated to dryness and the residue fused ; 
 
 * The student is advised to read the additional remarks to 128, con- 
 tained in the second chapter, previous to entering upon this method of 
 
252 PRESENCE OF ORGANIC MATTER. 
 
 should the quantity of the nitre formed not be suffi- 
 cient, some must be added whilst fusing the residue. 
 The metals, with the exception of chromium, remain 
 as oxides, and are separated and detected according 
 to the methods given above. The chromium is ob- 
 tained as soluble chromate of potash. 
 
 b* No COMPLETE DECOMPOSITION TAKES PLACE I Caustic 
 
 potash is added and the mixture boiled. Should any 
 residue remain, this is filtered, after the previous 
 addition of some water, and then dissolved and treated 
 as 106, A, 2, directs. The alkaline filtrate is satu- 
 rated with sulphuretted hydrogen. If any precipitate 
 be formed, this is again filtered, dissolved in nitric 
 acid, and the solution treated as 114,111. directs. 
 The filtrated liquor is slightly acidified .with hydro- 
 chloric acid and sulphuretted hydrogen added should 
 it appear necessary. If a precipitate be formed, this 
 is treated as 116 directs. The filtrate is tested for 
 cyanogen and the other electro-negative bodies, and 
 acids, and for cobalt, iron, manganese, and chromium, 
 as 128, a, directs. (When fusing the residue with 
 nitre, according to the method laid down in 128, , 
 (vide this section from the words, " These metals 
 must not be disregarded," to the end,) besides the 
 oxides, alumina is obtained, if any be present ; this 
 must be borne in mind.) 
 
 129. 
 
 GENERAL RULES FOR THE DETECTION OF INORGANIC SUB- 
 STANCES J IN CASES WHERE ORGANIC SUBSTANCES ARE 
 PRESENT, WHICH BY THEIR COLOUR, CONSISTENCE, OR 
 OTHER PROPERTIES, IMPEDE THE APPLICATION OF THE 
 REAGENTS, OR RENDER THE PHENOMENA OBSCURE. 
 
 We have already stated in our introductory remarks, 
 that cases of this kind are so manifold, that it is impossi- 
 ble to lay down a determinate method for every especial 
 case; we must, therefore, content ourselves with giving 
 only such methods as are applicable in most cases, and 
 leaving it to the judgment of the operator to adopt those 
 modifications which he may deem necessary. 
 
PRESENCE OF ORGANIC MATTER. 253 
 
 1. THE SUBSTANCE DISSOLVES IN WATER, BUT IS OF A DARK 
 COLOUR OR .HAS A SLIMY CONSISTENCE. 
 
 a. One part of the solution is boiled with hydro- 
 chloric acid, and chlorate of potash gradually added 
 till the fluid has become discoloured and limpid j the 
 solution is then heated until all odour of chlorine has 
 disappeared, diluted with water, and filtered. The 
 filtrate is treated after the usual method, beginning at 
 115. 
 
 b* Another portion of the solution is boiled for 
 some time with nitric acid,* filtered, and the filtrate 
 tested for silver, potash, and hydrochloric acid. This 
 kind of treatment is frequently preferable to all others 
 in such cases where the destruction of the colouring, 
 slimy matters, &c., succeeds well by means of nitric 
 acid. 
 
 2, The body does not dissolve in boiling water, or dis- 
 solves only in part. The solution is filtered, and the filtrate 
 treated either as 114 directs, or, if it be necessary to 
 destroy the colouring matters which it may contain in ad- 
 mixture, as directed 129, I. If it is impossible to filter 
 the solution, the further operation must be conducted as 
 stated 129, 2, c. The nature of the residue may be 
 various, 
 
 a. IT is GREASY. The fatty matters are removed 
 by means of ether, and should any residue remain, this 
 is treated as 106 directs. 
 
 b. IT is RESINOUS. Alcohol is employed instead 
 of ether, or a mixture of both liquids is used. 
 
 c. IT is OF ANOTHER NATURE, c. g. organic fibrine, 
 &c. The residue insoluble in water is dried, and the 
 greater part of it rubbed together with from three to 
 four parts of pure nitre ; the mixture is gradually- 
 deflagrated in a red hot crucible. The residue is 
 treated as 106, A, directs. Another part is boiled 
 with aqua regia, the solution filtered and the filtrate 
 tested for mercury. The rest is tested for ammonia, 
 as 122 directs. 
 
 11 
 
254: NOTES AND ADDITIONS, ETC. 
 
 130. 
 
 IV. k CONFIRMATORY EXPERIMENTS. 
 
 When the various bases, acids, and electro-negative 
 bodies, present in the substance under examination have 
 been detected, it is, in many cases, advisable, in others 
 absolutely necessary, to verify our conclusions. In many 
 cases this is easily accomplished, since certain substances 
 have such characteristic reactions that their presence or 
 absence may at once be determined, although many other 
 substances are present at the same time. But many sub- 
 stances have not such characteristic reactions, in which 
 cases we must satisfy ourselves by a strict and minute 
 examination, and by varying our processes, determine 
 whether the phenomena usually indicating the presence 
 of a substance, do not proceed from extraneous causes. 
 
 Thus ammonia may be erroneously supposed to be pre- 
 sent in a substance, whilst it is in fact derived from the 
 atmosphere of the laboratory, &c. 
 
 In the course of this work we have pointed out those 
 reactions which may be sought as confirmatory proofs, 
 and the precautions necessary to secure the purity of our 
 reagents. 
 
 CHAPTER II. 
 
 EXPLANATORY NOTES AND ADDITIONS TO THE 
 PRACTICAL COURSE. 
 
 I. REMARKS ON THE PRELIMINARY EXAMINATION. 
 105. 
 
 THE sensible qualities of bodies, as I before remarked, 
 may often enable us at once to deduce certain general con- 
 clusions, as to their nature, at least negatively. Thus, a 
 white powder cannot be cinnabar, a light flocculent body 
 
ADDITIONAL REMARKS. . 255 
 
 cannot be a compound of lead, &c. But the student must 
 beware of forming opinions prematurely, respecting the 
 nature of a body from its sensible properties only, lest it 
 give rise to such preconceptions as may lead him. to draw 
 fallacious conclusions from the reactions which manifest 
 themselves afterwards in the course of the real exam- 
 ination. 
 
 In the examination of bodies, at a high temperature, 
 small glass tubes may be often advantageously substituted 
 for a metallic spoon, since they enable us to observe any 
 substance which may volatilize in the process ; but as a 
 new tube is needed in every experiment, the metallic 
 spoons may serve in ordinary practice. 
 
 With respect to the blow-pipe examination, the student 
 must avoid drawing positive conclusions until he has ac- 
 quired a certain degree of experience, from practice ; a 
 slight incrustation may not imply the presence of a metal, 
 nor his inability to effect a reduction or to produce a colour 
 by solution of cobalt, the absence of a substance sought. 
 The blow-pipe phenomena are, indeed, in most cases 
 unerring, but they are easily modified by adventitious 
 circumstances. 
 
 The preliminary examination is in no case to be passed 
 over by the student. 
 
 II. ADDITIONAL REMARKS UPON SOLUTION, &c. 
 106. 
 
 There is some difficulty in determining the limits of the 
 two classes of bodies, soluble and insoluble, since these 
 terms are but relative, and we use the phrases easily, and 
 sparingly, or difficultly soluble ; and, indeed, these two 
 classes merge into each other. Sulphate of lime which 
 is soluble in four hundred and sixty-one parts of water 
 might perhaps serve as a limit between these two classes, 
 since it may still be distinctly detected in aqueous solu- 
 tions by means of the very susceptible reagents which we 
 possess for lime and sulphuric acid. 
 
 When examining an aqueous fluid by evaporating a 
 few drops of it upon a platinum plate, there remains some- 
 times a very minute residue, which leaves us in doubt as 
 
256 ADDITIONAL REMARKS. 
 
 to the nature of the substance ; in this case the fluid must, 
 1st, be tested with litmus papers ; 2d, one drop of solu- 
 tion of chloride of barium added to a portion of it ; and, 
 lastly, some carbonate of potash added to another portion. 
 If these tests produce no alteration, it is unnecessary to 
 examine it further for acids or bases. We may, in such 
 cases, feel certain, that the substance of which the residue 
 remaining upon evaporation consists, will be better de- 
 tected amongst the bodies insoluble in water, since both 
 the acids and bases, which principally form sparingly solu- 
 ble compounds, are sensibly indicated by the above-men- 
 tioned tests. 
 
 If water has dissolved any portion of the substance 
 under examination, the student will always do well to exa- 
 mine separately this solution for acids and bases, as this 
 will permit him to detect the nature of the compound under 
 examination with greater facility, and, moreover, will ren- 
 der his conclusions the safer, which advantages will coun- 
 terbalance the disadvantage of meeting sometimes with 
 the same substance in the aqueous and in the acid 
 solution. 
 
 The following substances are insoluble in water, but 
 soluble in hydrochloric acid or in nitric acid, (with some 
 exceptions,) the phosphates, arseniates, arsenites, borates, 
 carbonates, and oxalates of the earths and metals ; and 
 also several tartrates, citrates, malates, benzoates, and suc- 
 cinates, the oxides and sulphurets of the heavy metals, 
 alumina, magnesia, many metallic iodides and cyanides, 
 &c. Nearly all of these compounds are decomposed, if 
 not by dilute, yet by boiling concentrated hydrochloric 
 acid, (for the exceptions vide 127,) but this decomposi- 
 tion gives rise to the formation of insoluble compounds 
 when oxide of silver is present, and of sparingly soluble 
 compounds in the presence of protoxide of mercury and 
 lead. This is not the case with nitric acid, and thus we 
 often effect a complete solution by its means in cases 
 where hydrochloric acid has left a residue. But nitric 
 acid, besides the substances insoluble in simple acids, 
 leaves also oxide of antimony, peroxide of tin, peroxide of 
 lead, &c. undissolved, whilst it dissolves many other sub- 
 stances more or less completely. When, therefore, the 
 
DETECTION OP THE BASES. 257 
 
 compound under examination is not completely dissolved 
 by nitric acid, (with the exception of sulphur, which may 
 have separated,) we must in the course of analysis again 
 have recourse to the hydrochloric solution, in order to 
 assign exact limits in some measure to the third class of 
 substances, viz. those bodies which are insoluble in water 
 and simple acids. 
 
 With regard to the solution of pure metals or alloys, we 
 must remark, that white precipitates frequently are formed 
 upon boiling with nitric acid, though no tin or antimony be 
 present. Inexperienced students often confound these 
 precipitates with the oxides of these two metals, although 
 their external appearance is quite different. These preci 
 pitates consist of nitrates sparingly soluble in the nitric 
 acid present, but of easy solution in water. Consequently, 
 before we can pronounce these precipitates to consist of 
 tin or antimony, we must previously ascertain whether 
 they are soluble in water. 
 
 From 107 to 129. 
 
 A. GENERAL SURVEY AND EXPLANATION OF THE ANALYTICAL 
 COURSE. 
 
 a. DETECTION OF THE BASES. 
 
 We have divided the bases into six groups, (vide Chap- 
 ter III. Part I.) and explained the method of detecting and 
 isolating the individual bases. These objects we have kept 
 in view in the practical course, and as a correct apprehen- 
 sion of this is of primary importance, we subjoin a brief 
 explanation of the grounds of our division, a key, as it 
 were, to the analytical course of study, so far as those 
 bases are concerned. The general reagents which we 
 employ in the course of analysis to divide the bases into 
 principal groups, are HYDROCHLORIC ACID, SULPHURETTED 
 
 HYDROGEN, HYDROSULPHURET OF AMMONIA, and CARBONATE 
 
 OF AMMONIA ; this is also the order of succession in which 
 they are employed. Hydrosulphuret of ammonia performs 
 a double part. 
 
 Let us suppose we have in solution all the bases arse- 
 
258 DETECTION OP THE BASES. 
 
 nious acid, and phosphate of lime, (which latter may serve 
 as a type for the salts of the alkaline earths, soluble in 
 acids, and precipitated by ammonia, unaltered.) 
 
 Chlorine forms insoluble compounds with silver and 
 mercury alone , chloride of lead is sparingly soluble in 
 water. The insoluble protochloride of mercury corres- 
 ponds with the protoxide of mercury. If, therefore, we 
 L dd to our solution 
 
 1 . Hydrochloric acid, we remove from the solution the 
 metallic oxides of the first section of the fifth group, viz. 
 the OXIDE OP SILVER and the PROTOXIDE OF MERCURY. A 
 portion of the LEAD, also, may, perhaps, precipitate as chlo- 
 ride of lead, should the solution be concentrated ; this is, 
 however, immaterial, as a sufficient quantity of the lead 
 remains in solution as to admit of its detection afterwards. 
 
 Sulphuretted hydrogen precipitates the oxides of the 
 fifth and sixth group completely from solutions containing 
 a free mineral acid, as both the affinity which the metallic 
 radicals of these oxides have for sulphur, and that which 
 hydrogen possesses for oxygen, are so powerful as to 
 overcome the affinity between the metal and oxygen, 
 together with that between the oxide and a strong acid, 
 
 EVEN THOUGH THE ACID BE PRESENT IN EXCESS. But 
 
 none of the other bases are precipitated under those 
 circumstances, the bases of the first, second, and third 
 group forming no sulphur compounds insoluble in water ; 
 those of the fourth group are not precipitated, because the 
 affinity which their metallic radicals possess for sulphur, 
 together with that manifested by hydrogen for oxygen, are 
 not sufficiently powerful to overcome that of the metal 
 for oxygen, and of the oxide for a strong acid, IF THE 
 
 LATTER IS NOT PRESENT IN EXCESS. 
 
 If, therefore, after the removal of oxide of silver and of 
 p toxide of mercury, by means of hydrochloric acid, we 
 add to our solution, (which still contains free hydrochloric 
 ccid,) 
 
 2, Sulphuretted hydrogen : we remove from it the rest 
 of the oxides of the fifth, together with those of the sixth 
 
 group, Viz. OXIDE OF LEAD, PEROXIDE OF MERCURY, OXIDE 
 OF COPPER, OXIDE OF BISMUTH, OXIDE OF CADMIUM, PEROX- 
 IDE OF GOLD, PEROXIDE OF PLATINUM, PROTOXIDE OF TIN, 
 
DETECTION OF THE BASES. 259 
 
 PEROXIDE OF TIN, OXIDE OF ANTIMONY, ARSENIOUS ACID, 
 
 and ARSENIC ACID. All the other oxides remain in solu- 
 tion, either unaltered or reduced to a lower degree of oxi- 
 dation, e. g. peroxide of iron, chromic acid, &c. 
 
 The sulphurets corresponding with the oxides of the 
 sixth group have the property of combining with electro- 
 positive metallic sulphurets (the sulphurets of the alkali 
 metals) forming sulphur salts soluble in water, whilst the 
 sulphurets corresponding with the oxides of the fifth group 
 do not possess this property. If, therefore, we treat all 
 the sulphurets precipitated by sulphuretted hydrogen from 
 acid solution, with 
 
 3. Hydrosulphuret of ammonia, or sulphur et of potas 
 sium, the bisulphurets of mercury, lead, copper, bismuth, 
 and cadmium will remain undissolved, whilst the other 
 bisulphurets are dissolved as the double SULPHURETS OF 
 GOLD, PLATINUM, ANTIMONY, TIN, ARSENIC, ancl ammonium 
 or potassium, and from this solution they are precipitated 
 upon the addition of an acid, either unaltered, or having 
 acquired a higher degree of sulphuration, by receiving 
 sulphur from the hydrosulphuret of ammonia, (sulphuret 
 of tin.) In this process the acid decomposes the sulphur 
 salt formed. The sulphur base (hydrosulphuret of am- 
 monia or sulphuret of potassium) is decomposed at the ex- 
 pense of the constituents of decomposed water, into an 
 oxygen base (ammonia or potash) and sulphuretted hydro- 
 gen ; the former combines with the acid added, the latter 
 escapes, and the liberated electro-negative sulphur pre- 
 cipitates. (If the acid is an hydracid, its radical combines 
 with the ammonium and its hydrogen with the sulphur.) 
 Sulphur precipitates at the same time, the hydrosulphuret 
 of ammonia always containing sulphur in excess. This 
 sulphur renders the colour of the precipitated sulphurets 
 lighter, which must be always borne in mind, when deter- 
 mining their nature. 
 
 Of the oxides still in solution, the alkalies, the alkaline 
 earths, alumina and oxide of chromium have remained so ; 
 because their sulphur compounds are soluble in water, or 
 because their salts are not at all affected by sulphuretted 
 hydrogen ; the oxides of the fourth group would have been 
 precipitated by sulphuretted hydrogen, had not the free 
 
260 DETECTION OF THE BASES. 
 
 acid present prevented their precipitation, as their corre- 
 sponding sulphur compounds are insoluble in water. If, 
 therefore, this free acid be removed, i. e. if the solution be 
 made alkaline and sulphuretted hydrogen added, or if, what 
 answers both purposes at once, 
 
 4. Hydrosulphuret of ammonia be added to the solu- 
 tion, the sulphurets corresponding with the oxides of the 
 fourth group are precipitated, viz. : SULPHURET OF IRON > 
 
 SULPHUKET OF MANGANESE, StJLPHURET OF COBALT, STJL- 
 
 PHURET OF NICKEL, and si/LPHURET OF ZINC, and at the 
 same time, ALUMINA, OXIDE OF CHROMIUM, and PHOSPHATE 
 OF LIME, are precipitated, the affinity which the ammonia 
 possesses for the acid of the salt of oxide of chromium or 
 of alumina, or for the acid which keeps the phosphate of 
 lime in solution, causing decomposition of. the water and 
 subsequently formation of oxide of ammonium and of 
 sulphuretted hydrogen. The former combines with the 
 acid, the latter escapes, incapable of entering into com- 
 bination with the oxides deprived of their acids or with 
 the phosphate of lime, the oxides and the limesalt preci- 
 pitate. We have now remaining in solution only the 
 alkaline earths and the alkalies. The neutral carbonates 
 of the former are insoluble in water, whilst those of the 
 latter are soluble. If, therefore, we add 
 
 5. Carbonate of ammonia and apply heat, in order to 
 decompose acid carbonates which may, peradventure, have 
 been formed, all the alkaline earths ought to precipitate. 
 This is, however, the case only as regards BARYTES, 
 STRONTIAN, and LIME \ of magnesia we know that, owing 
 to its disposition of forming double compounds with 
 ammoniacal salts, it precipitates only in part, or, not at 
 all, in presence of another ammoniacal salt. To avoid 
 this uncertainty, sal ammoniac is added previous to the 
 addition of carbonate of ammonia, in order completely to 
 prevent the precipitation of magnesia. 
 
 We have now still in solution, magnesia and the alkalies ; 
 of the presence of magnesia we may assure ourselves by 
 means of phosphate of soda and ammonia ; but for its 
 separation we pursue a different way, since the presence 
 of phosphoric acid would impede the further progress of 
 the analysis. The process which we employ is based 
 
DETECTION OF THE ACIDS. 261 
 
 either upon magnesia being insoluble in its pure state or as a 
 carbonate. The substance under examination is heated to 
 redness in order to expel the ammoniacal salts, and the 
 magnesia is then either precipitated by means of barytes 
 whilst the alkalies remain in solution ; or the substance is 
 heated to redness, with the addition of sulphuric acid, and 
 the sulphates formed are by decomposition with acetate of 
 barytes, converted into acetates, and these, by the applica- 
 tion of a red heat, into carbonates ; upon treating these 
 latter with water, carbonate of magnesia remains, whilst 
 the alkaline carbonates are dissolved. A fresh specimen 
 must, of course, be employed for the detection of ammonia. 
 
 b. DETECTION OF THE ACIDS. 
 
 Previous to entering upon the examination for acids and 
 electro-negative substances, we must first consider which 
 of these bodies may and which of them cannot be present 
 according to the detected bases, and accordingly to the 
 solubility of the substances under examination ; thus we 
 shall avoid making unnecessary experiments. A table 
 useful for this purpose, will be found in the appendix. 
 The general reagents employed for the detection of acids 
 are, for the inorganic acids, CHLORIDE OF BARIUM and 
 NITRATE OF SILVER ; for the organic acids, CHLORIDE OF 
 CALCIUM and PERCHLORIDE of IRON. It is, therefore, in- 
 dispensable, first to assure ourselves whether we have 
 to operate upon a substance containing inorganic acids 
 alone, or organic acids alone, or both together. When 
 examining for bases, the general reagents serve for the 
 real separation of the various groups of bases from each 
 other ; in the examination for acids, we only use them to 
 assure ourselves of the presence or absence of the acids 
 belonging to the different groups. 
 
 Let us suppose we have in an aqueous solution all the 
 acids we have treated of in the present work, combined, 
 for instance, with soda. 
 
 Barytes form insoluble .compounds with sulphuric acid, 
 phosphoric acid, arsenious acid, arsenic acid, carbonic 
 acid, silicic acid, boracic acid, chromic acid, oxalic acid, 
 tartaric acid, and citric acid ; these compounds are soluble 
 in hydrochloric acid, with the exception of sulphate of 
 11* 
 
262 DETECTION OF THE ACIDS. 
 
 barytes. If, therefore, to a portion of our neutral or neu- 
 tralized solution, we add 
 
 1. Chloride of barium, the presence of at least one of 
 these acids will immediately become manifest. Upon 
 treating the precipitate formed with hydrochloric acid, the 
 presence of sulphuric acid will be detected, as all the salts 
 of barytes are soluble in this menstruum, with the excep- 
 tion of the sulphate. When sulphate of barytes is present, 
 the reaction with chloride of barium does not enable us to 
 detect all the other acids enumerated with safety. For 
 upon filtering the hydrochloric solution of the precipitates 
 and supersaturating with ammonia, the borate, tartrate, 
 citrate, &c. of barytes do not precipitate again, being kept 
 in solution by the sal ammoniac formed. Chloride of ba- 
 rium, therefore, cannot be employed to separate 'the indi- 
 vidual acids from each other, and thus is of no use for their 
 individual detection, except for that of sulphuric acid. It 
 is, however, of great importance as a reagent, since the 
 non-formation of a precipitate in neutral or alkaline solu- 
 tions, upon its application proves at once the absence of 
 a considerable number of acids. 
 
 Silver forms compounds insoluble in water, with chlo- 
 rine, iodine, bromine and cyanogen ; and oxide of silver, 
 with phosphoric acid, arsenious acid, arsenic acid, boracic 
 acid, chromic acid, silicic acid, oxalic acid, tartaric acid, 
 and citric acid. All these compounds are soluble in am- 
 monia, with the exception of iodide of silver, and in nitric 
 acid, with the exception of iodide, chloride, bromide, and 
 cyanide of silver. If, therefore, we add to our solution 
 (which must be completely neutral,) 
 
 2. Nitrate of silver, we detect immediately the pre- 
 sence of one or several of the acids enumerated ; chromic 
 acid, arsenic acid, and several other acids, the silver salts 
 of which are coloured, may even be individually detected 
 with a certain degree of safety, by the colour of their pre- 
 cipitates. If we add nitric acid to the precipitate, we 
 detect the presence of the haloid compounds, as these 
 remain undissolved, whilst the oxide salts are dissolved. 
 The complete separation and individual detection of those 
 acids which form insoluble compounds with oxides of 
 silver, are prevented by the same cause which renders the 
 
DETECTION OP THE ACIDS. 263 
 
 individual detection of acids by chloride of barium unsafe. 
 For the arnmoniacal salt formed prevents the reprecipita- 
 tion by ammonia, of several salts of silver, from the acid 
 solution ; nitrate of silver serves us, therefore, besides de- 
 tecting chlorine, iodine, bromine, and cyanogen, and indi- 
 cating chromic acid, &c., especially to prove at once the 
 absence of many acids, if it produces no precipitate in neu- 
 tral solutions. The behaviour of solutions under exami- 
 nation with chloride .of barium and with nitrate of silver, 
 therefore, points out at once what course we have further 
 to pursue in our investigation. Thus, for instance, if 
 chloride of barium has produced a precipitate, whilst we 
 have obtained none by nitrate of silver, it is not necessary 
 to test for phosphoric acid, chromic acid, boracic acid, 
 silicic acid, arsenious acid, arsenic acid, oxalic acid, tarta- 
 ric acid, and citric acid, provided always that the solution 
 does not already contain ammoniacal salts. The same is 
 the case if we obtain a precipitate by nitrate of silver, but 
 none by chloride of barium. Returning to our first sup- 
 position, viz., that all acids are present in the compound 
 under examination, we have thus detected CHLORINE, 
 BROMINE, IODINE, and CYANOGEN, (for their separation and 
 individual detection, vide 100,) as well as SULPHURIC " 
 ACID, and we have reason further to test for all the other 
 acids precipitated by these two reagents. Their detection 
 is based upon the results of special experiments, which 
 have already been explained in the course of the present 
 work : the same applies to the other inorganic acids, and 
 thus also to nitric acid and chloric acid. 
 
 Of the organic acids, oxalic acid, tartaric acid, and 
 paratartaric acid, are precipitated by chloride of calcium, 
 from aqueous solutions, at a low temperature, even in the 
 presence of sal ammoniac ; but the precipitation of citrate 
 of lime is prevented by the presence of ammoniacal salts, 
 and takes place only upon boiling or upon mixing the so- 
 lution with alcohol ; the latter means is also employed for 
 the separation of oxalic lime from aqueous solutions. If, 
 therefore, we add to our solution, 
 
 3. Chloride of calcium and sal ammoniac, OXALIC ACID, 
 TARTARIC ACID, and PARATARTARIC ACID are precipitated, 
 but the lime-salts of several inorganic acids, which have 
 not yet been separated, precipitate at the same time (phos- 
 
264 SPECIAL REMARKS. 
 
 phate of lime, for instance.) We must, therefore, select, 
 for the individual detection of the precipitated organic 
 acids, such reactions only as do not admit the possibility 
 of confounding the organic acids with the inorganic acids 
 precipitated at the same time. For the detection of oxalic 
 acid we thus select solution of gypsum, with the addition 
 of acetic acid, ( 98, c, 4,) for the detection of tartaric and 
 paratartaric acid ; we treat the precipitate produced by 
 chloride of calcium, with solution of potash, since the lime- 
 salts of these two acids alone dissolve in this menstruum, at 
 a low temperature, whilst all the other insoluble lime- salts 
 remain undissolved. 
 
 Of the organic acids we have now still in solution citric 
 acid and malic acid, succinic acid and benzoic acid, acetic 
 acid and formic acid. CITRIC ACID and MALIC ACID pre- 
 cipitate upon alcohol being added to the fluid filtered off 
 from the oxalate, tartrate, &c., of lime, and which contains 
 still chloride of calcium in excess. Sulphate and borate 
 of lime always precipitate together with the malate and 
 citrate of lime, if sulphuric acid and boracic acid are pre- 
 sent ; we must, therefore, carefully guard against con- 
 founding the lime precipitates of these acids with those of 
 citric acid and malic acid. The alcohol is then removed 
 by evaporation, and 
 
 4. Perchloride of iron added ; this precipitates SUC- 
 CINIC ACID and BENZOIC ACID in combination with pe- 
 roxide of iron, whilst FORMIC ACID and ACETIC ACID re- 
 main in solution. The methods for. the further separation 
 of the groups and the reactions whereupon the detection 
 of the individual acids depends, have already been de- 
 scribed. 
 
 B. SPECIAL AND ADDITIONAL REMARKS UPON THE 
 
 SYSTEMATIC COURSE OF ANALYSIS. 
 
 114. 
 
 We have at the beginning of 114, given the instruc- 
 tion to mix neutral or acid aqueous solutions with hydro- 
 chloric acid. This acid must be added drop by drop. If 
 no precipitate is formed, a few drops are sufficient ; if a 
 precipitate is formed, the acid must be added until the pre- 
 
ADDITIONAL REMARKS. 265 
 
 cipitate ceases to increase and the fluid has acquired a dis- 
 tinct acid reaction. The addition of a large proportion of 
 hydrochloric acid is not only unnecessary, but injurious. 
 The precipitate produced by hydrochloric acid in neutral 
 or acid solutions may consist of chloride of silver, proto- 
 chloride of mercury, chloride of lead, and a basic salt of 
 antimony. The two latter substances redissolve upon 
 diluting and heating the acid fluid, and thus the non-solu- 
 tion of the precipitate upon the application of these pro- 
 cesses, is an indication of the probable presence of chloride 
 of silver or protochloride of mercury. Should compounds 
 of antimony or bismuth be present, this dilution with water 
 will separate from them insoluble basic salts in a state of 
 most minute division ; these must be redissolved by the 
 addition of hydrochloric acid, before we can draw any cor- 
 rect conclusion from the remaining or disappearing of the 
 precipitate produced by hydrochloric acid. If we have to 
 operate upon an alkaline solution, the hydrochloric acid 
 must be added, until the fluid manifests a strong acid re- 
 action. A great excess of the acid must, however, be 
 avoided. The subsiance which causes the alkaline reac- 
 tion of the fluid, is neutralized by the hydrochloric acid, 
 and the bodies combined with it ? or dissolved in it, se- 
 parate. If the alkali present was in a free state, oxide of 
 zinc, for instance, alumina, &c., may be precipitated. But 
 these redissolve in an excess of the hydrochloric acid, 
 whilst chloride of silver, if present, will not redissolve, and 
 chloride of lead only sparingly. If a metallic sulphur salt 
 be the cause of the alkaline reaction, the electro-negative 
 sulphuret (e. g. sulphuret of antimony) will precipitate, on 
 the addition of the hydrochloric acid ; whilst the electro- 
 positive sulphuret, (e. g. sulphuret of sodium) will form 
 chloride of sodium, and sulphuretted hydrogen, with the 
 constituents of hydrochloric acid. If an alkaline carbonate, 
 or an alkaline sulphuret, be the cause of the alkaline reac- 
 tion, carbonic acid or sulphuretted hydrogen will escape. 
 All these phenomena ought to be carefully observed, for 
 they. not merely point out the presence of the relative sub- 
 stance, but also exclude entire series of substances from 
 the further examination. 
 
266 ADDITIONAL REMARKS. 
 
 115. 
 
 We have already had occasion to remark, that upon add- 
 ing a reagent (e. g. sulphuretted hydrogen) to a fluid un- 
 der examination, a precipitate may or may not ensue. If 
 a precipitate is formed, this may be, a, white, b, yellow, c, 
 orange, cZ, brown or black. Every one of these various 
 cases is a different answer given to the question put by 
 means of the reagent, and every answer has a different 
 meaning. An accurate distinction of the individual case is, 
 therefore, indispensable. Any error here must prevent the 
 student from obtaining correct results* 
 
 The colour of the precipitate is almost invariably point- 
 ed out as a criterion in the systematic course of analysis. 
 We may presume that a darker precipitate will sometimes 
 conceal one of a lighter colour, and thus, e. g. that yellow 
 sulphuret of arsenic may be present, invisible in a preci- 
 pitate of black sulphuret of mercury; and so we may al- 
 so conclude that no dark precipitate can be contained in 
 a light-coloured one, e. g. no black precipitate in a white* 
 These conclusions cannot, however, always be drawn with 
 the same degree of safety, all colours not contrasting so 
 pointedly with each other as black and white ; but many 
 of them rather merging into each other, e. g. yellow and 
 orange. Whenever the colour of the precipitate admits 
 of any doubt as to its nature, it is always advisable to pur- 
 sue that course which the darker of the colours in question 
 indicates, since in this regard has been had to all the me- 
 tals which can possibly have precipitated, whilst in the 
 other the metallic precipitates of darker colour are disre- 
 garded. The safer way is always to be preferred, although 
 it may be the more protracted. 
 
 A judicious distribution and economy of time is especial- 
 ly to be studied in the practice of analysis ; many of the 
 operations may be carried on simultaneously, which the 
 student will readily perceive and arrange for himself. 
 
 In such cases, where we have before us only metallic 
 oxides of the sixth group, (e. g. oxide of antimony,) and ox- 
 ides of the fourth group, (e- g. the oxides of iron,) it is not 
 necessary for their separation to precipitate them from 
 acidified solutions by means of sulphuretted hydrogen, but 
 we may at once add hydrosulphuret of ammonia in excess 
 
ADDITIONAL REMARKS. 26? 
 
 to the neutralized solution. The sulphuret of iron, &c., 
 will then- be obtained in a precipitate, whilst the antimony, 
 &c., will remain in solution, from which, upon the addi- 
 tion of an acid, it will immediately precipitate a sulphuret 
 of antimony. This method has the advantage of rendering 
 the fluid less dilute than when sulphuretted hydrogen is 
 employed, and moreover of facilitating and accelerating the 
 operation. 
 
 116. 
 
 When digesting the precipitates produced by sulphuret- 
 ted hydrogen from acid solutions, with hydrosulphuret of 
 ammonia, it is indispensable to apply this latter reagent 
 in a correct proportion. A small quantity is generally 
 sufficient, but if sulphuret of tin be present, a somewhat 
 larger amount must be employed. Inexperienced students, 
 however, use so much of it, that, upon the addition of an 
 acid, sulphur precipitates to such an amount that the colour 
 of the metallic sulphuret, which precipitates at the same 
 time, is quite obscured and concealed by it. The separa- 
 tion and individual detection of oxide of antimony, peroxide 
 of tin, and arsenic, is not very easy if all three oxides have 
 been precipitated as sulphurets. Inexperienced students 
 will find it difficult safely to detect and separate them be- 
 fore the blow-pipe. Of the many methods applicable for 
 the distinction of these three metals, that given at 116 
 has been proved the safest by experience. If sulphuret of 
 arsenic, sulphuret of antimony, and sulphuret of tin, are 
 deflagrated with nitre in excess, and carbonate of soda, the 
 metals and the sulphur oxidize at the expense of the oxygen 
 of the nitric acid : we have, therefore, in the fused mass 
 alkaline arseniate, antimoniate, sulphate, and stannate, be- 
 sides excess of nitre and carbonate of soda. On treating 
 with water, the alkaline sulphate and arseniate are dissolv- 
 ed; the alkaline antimoniate is decomposed ; an insoluble 
 acid salt remains, whilst a small amount of antimonic acid 
 is dissolved in the form of a basic salt. A portion of the 
 peroxide of tin also dissolves in the carbonated alkali pre- 
 sent. If boiling water is employed, the amount of the 
 dissolved antimonic acid and peroxide' of tin is not inconsi- 
 derable, whilst it is but minute in cold water ; the latter is, 
 therefore, preferable to boiling water in this operation. If 
 
268 ADDITIONAL REMARKS. 
 
 the alkaline solution obtained is then saturated with nitric 
 acid, and heat applied, the dissolved peroxide of tin and 
 antimonic acid precipitate ; but this precipitate is never 
 free from arsenic. This will show how caiefully we ought 
 to avoid getting much peroxide of tin or antimonic acid in 
 solution. In the fluid saturated with nitric acid, or slightly 
 acidified, filtered off from the precipitate formed, we have 
 now still arseniated and sulphated alkali. One portion of 
 this fluid is tested, as stated 116; with solution of silver and 
 ammonia, and another portion with solution of lead. Since 
 the fluid must be perfectly neutral to render the arseniate of 
 silver visible, and since it is not always easy to hit upon 
 the exact neutralization point, the fluid, after the addition of 
 the solution of silver, is covered with a layer of dilute am- 
 monia. This is the easiest method of producing a precip- 
 itate when but small quantities of arsenic are present. On 
 the precipitation with solution of acetate of lead, we obtain 
 a mixture of sulphate and arseniate of oxide of lead. The 
 presence of the sulphate of lead renders the quantity of the 
 precipitate greater, and thus its collection and testing before 
 the blow-pipe more easy *, it, moreover, increases the bulk 
 of the button obtained. Though by means of these reac- 
 tions the presence of arsenic may be proved beyond doubt, 
 yet the production of metallic crusts is the safest test. 
 
 If the residue remaining upon treating the deflagrated 
 mass with water, and which is to be examined for tin and 
 antimony, be not carefully washed, and thus freed from all 
 the nitre still adhering to it, previous to fusing with cyan- 
 ide of potassium, explosions will take place, ( 101, a, 3,) 
 whereby not only the test specimens are thrown off, but the 
 operator himself may meet with some injury. 
 
 117. 
 
 If the sulphurets of the second section of the fifth group 
 are heated to the boiling point with nitric acid, lead, bismuth, 
 copper, and cadmium, oxidize at the expense of a portion 
 of the nitric acid, which decomposes into nitric oxide and 
 oxygen, the sulphur separates, and the oxides formed com- 
 bine with another portion of the nitric acid, forming soluble 
 nitrates. Sulphuret of mercury is not decomposed by 
 
ADDITIONAL REMARKS. 269 
 
 nitric acid, provided no chloride be present at the same 
 time, owing to imperfect rinsing. Ammonia decomposes 
 all the metallic nitrate dissolved. But the oxides of lead 
 and bismuth are insoluble in an excess of ammonia, whilst 
 those of cadmium and copper are dissolved by this reagent. 
 Ammonia, therefore, affords us a means of testing the solu- 
 tion for the presence of the oxides of lead and bismuth, as 
 well as of precipitating and separating them from it. The 
 presence of oxide of copper is also detected by this rea- 
 gent ; the ammonia-nitrate of copper, which is formed upon 
 its addition to the fluid under examination, imparting a 
 blue colour to the fluid. The causes whereupon the fur- 
 ther separation and detection of the four metals in question 
 depends, have already been sufficiently explained at 91, 
 (recapitulation and remarks.) With regard to the detec- 
 tion of bismuth, it must be remarked, that it never suc- 
 ceeds if the excess of acid present is not as slight as 
 possible ; this is best attained in the manner described 
 117. But if the operator evaporates only nearly to dryness, 
 so much acid frequently remains present, that the separa- 
 tion of a basic salt cannot be accomplished. 
 
 Besides the method given at 91, (recapitulation and 
 remarks,) and at 117, for the distinction of cadmium, 
 copper, lead, and bismuth, the following method also 
 leads with great safety to the desired end. Carbonate of 
 potash is added to the nitric solution as long as any preci- 
 pitation takes place ; solution of cyanide of potassium in 
 excess is then added, and heat applied. Lead and bis- 
 muth are hereby completely separated as carbonates, whilst 
 copper and cadmium are obtained in solution as the double 
 cyanides of copper and potassium, and cadmium and pot- 
 assium. Lead and bismuth may then easily be separated 
 by means of sulphuric acid ; copper and cadmium, by 
 adding to the solution of their cyanides in cyanide of pot- 
 assium) sulphuretted hydrogen in excess, and applying 
 heat ; some more cyanide of potassium must then be 
 added to redissolve the sulphuret of copper, which, perad- 
 venture, may also have precipitated. A yellow precipitate 
 of sulphuret of cadmium, insoluble in cyanide of potas- 
 sium, indicates cadmium. The fluid is filtered off, and 
 hydrochloric acid added to the nitrate ; the formation of a 
 
 
270 ADDITIONAL REMARKS. 
 
 black precipitate of sulphuret of copper indicates copper. 
 The presence of mercury is indeed already proved by a 
 black residue remaining, upon heating the sulphurets with 
 nitric acid. A more minute examination of any residue 
 remaining upon boiling with nitric acid, is, however, neces- 
 sary, always provided this residue be not pure yellow 
 sulphur, which in most cases floats on the surface of the 
 fluid. The reasons for this further examination are the 
 following : separated sulphur frequently envelops small 
 particles of the other black sulphurets, and for this reason 
 appears black here and there. Sulphuret of mercury, 
 moreover, may, under certain circumstances, lose its black 
 colour, and the precipitate in that case be confounded with 
 sulphate of lead, (into which substance a portion of the 
 sulphuret of lead present is in most cases converted,) or 
 with pertoxide of tin, (which may have been formed by 
 the action of nitric acid upon sulphuret of tin present, and 
 not completely removed by hydrosulphuret of ammonia. 
 The test with polished copper is the most convenient, and 
 yields the quickest result. It must, however, be remarked, 
 that errors occur more frequently, when employing this 
 test, than when we select the reaction with protochloride 
 of tin. When employing the latter reagent, we must 
 especially assure ourselves of its being still undecomposed, 
 and of the solution of mercury containing no nitric acid. 
 If after the method described, the protoxide of mercury 
 has first been separated by hydrochloric acid, and a preci- 
 pitate of sulphuret of mercury is formed, upon the addition 
 of sulphuretted hydrogen, this corresponds always with 
 the peroxide and perchloride, &c. of mercury. If we have 
 to operate upon an aqueous solution, or a solution in very 
 dilute hydrochloric acid, it existed as such in the original 
 substance. But when we have a nitric solution before us, 
 it may have originally existed as protoxide, and subse- 
 quently acquired a higher degree of oxidation. 
 
 118. 
 
 The precipitate produced by hydrosulphuret of ammo- 
 nia, may (as we have already stated, page 259) consist of 
 sulphurets, of oxides, and of the phosphates of the alkaline 
 
ADDITIONAL REMARKS. 271 
 
 earths, phosphate of alumina, oxalate of lime (barytes and 
 strontian.) The borates of the alkaline earths and the 
 oxalate of magnesia would, moreover, be precipitated, but 
 they remain in solution, owing to the sal ammoniac formed 
 in the fluid or added to it. Upon dissolving the precipitate 
 in hydrochloric acid, or in aqua regia, the metallic sul- 
 phurets and the hydrated oxides are converted into soluble 
 chlorides, whilst the phosphates and oxalates dissolve 
 without decomposition. If to this acid solution, ammonia 
 is added, the phosphates and oxalates are re-precipitated, 
 and, together with them, alumina, oxide of chromium, and 
 peroxide of iron fall down, as these do not (like the oxides 
 of manganese, nickel, cobalt, and zinc) form soluble double 
 compounds with ammoniacal salts. This precipitation by 
 ammonia, in presence of sal ammoniac, is the base where- 
 on the further distinction and individual detection of the 
 substances enumerated depends. At this result we may 
 also arrive by merely adding sal ammoniac and ammonia in 
 excess to the fluid filtered from the precipitate produced 
 by sulphuretted hydrogen, after having expelled the excess 
 of sulphuretted hydrogen by boiling, and converted the 
 iron which, peradventure, may be present, into peroxide 
 of iron, by heating with nitric acid. We obtain thus, of 
 course, the peroxide of iron, the alumina, oxide of chro- 
 mium, and the phosphates, &c., of the alkaline earths 
 alone in the precipitate, whilst the manganese, cobalt, 
 nickel, and zinc, are contained in the fluid which runs off, 
 and may then be precipitated by means of hydrosulphuret 
 of ammonia. Under certain circumstances this method is 
 preferable to the first, and may then be employed with 
 advantage ; but in general it requires more time than the 
 other. With regard to the further detection of nickel, 
 cobalt, manganese, and zinc, we have nothing to add to 
 1 18, 2, except that ammoniacal salts must not be present, 
 if the separation of these four metals from each other is to 
 succeed after the method described at 118, 2. But as 
 the separation of manganese, nickel, &c., from iron, &c., 
 depends upon the presence of ammoniacal salts, these must 
 be removed either by evaporating the solution and heating 
 th residue to redness, or by precipitating these four me- 
 tals again by hydrosulphuret of ammonia, (which latter 
 
272 ADDITIONAL REMARKS. 
 
 method generally is preferable to the former.) The pre- 
 cipitate of the metallic sulphurets must, of course, be 
 carefully washed. The separation of the peroxide of iron, 
 and of the phosphates and oxalates of the alkaline earths 
 from alumina and oxide of chromium rests upon the solu- 
 bility of the latter and the insolubility of the former com- 
 pounds, in caustic potash ; and that of peroxide of iron 
 from the salts of the alkaline earths, upon the circumstance 
 that the precipitation of the former is prevented by adding 
 tartaric acid to the acid solution, previous to the addition 
 of ammonia, which is not the case with the latter. (Vide 
 recap, and rem. to 88.) 
 
 127. 
 
 The third class of substances also has no strictly defina- 
 ble limits, as the solubility or insolubility of several com- 
 pounds belonging to it, depends very much upon the 
 quantity and concentration of the acid and the time of 
 boiling. Besides the difficultly soluble substances enu- 
 merated, we must especially look for many metallic sul- 
 phurets and iodides, which also only dissolve after some 
 time in concentrated hydrochloric acid, at a high tempera- 
 ture. If a substance is dissolved in nitric acid after long 
 boiling, we must not conclude that protochloride of mercury 
 is absent, since this substance, as we have already stated, 
 is converted in this process into pernitrate of mercury and 
 perchloride of mercury, and is thus dissolved. 
 
 Chloride of silver, protochloride of mercury, and chlo- 
 ride of lead may have been present in the original com- 
 pound as such, or may have been formed upon treating 
 with hydrochloric acid. The" presence of chloride of lead 
 has in that case already been detected in the aqueous solu- 
 tion ; of the original presence of the two other substances 
 we may assure ourselves in the following manner. The 
 substance insoluble in water is treated with dilute nitric 
 acid. All the salts of protoxide of mercury and oxide of 
 silver present are thereby dissolved, whilst the chlorides 
 enumerated above remain undissolved together with iodide 
 of silver ; they are separated by means of ammonia, which 
 at the same time allows us to detect the protochloride of 
 mercury. 
 
ADDITIONAL REMARKS. 273 
 
 The decomposition of the sulphates of the alkaline earths 
 may be effected also in the humid way by boiling them 
 for some time with solution of carbonate of potash. But 
 the fusion with the carbonate of potash and soda, yields 
 far safer results, and leads quickly to the desired end, when 
 operating upon small quantities. This method has, more- 
 over, the advantage of leading to the safe detection of the 
 presence of silicic acid. 
 
 The sulphates of the alkaline earths are decomposed by 
 the alkaline carbonates in such a manner as to give rise to 
 the formation of carbonates of the alkaline earths and of 
 sulphates of the alkalies. If the precipitate of the former 
 be not carefully washed, previously to its solution in hy- 
 drochloric acid, sulphates of the alkaline earths will again 
 be formed by the action of the sulphated alkali still adher- 
 ing to the precipitate ; this would render the experiment 
 very unsafe at the least, since, for instance, all the barytes 
 dissolved might precipitate again. 
 
 Carbon has been connected with this third class, since 
 it occurs sometimes in the course of examinations, and thus 
 may become a great obstacle to the progress of the inex- 
 perienced student, if not prepared for its presence. Gra- 
 phites is distinguished from the other forms of carbon by 
 its difficult combustion before the blow-pipe, and its non- 
 combustion in a platinum spoon ; besides the iron, which 
 it generally contains in admixture, indicates its presence. 
 
 128. 
 
 The analysis of cyanogen compounds is not very easy 
 in certain cases, and sometimes it is indeed extremely diffi- 
 cult to ascertain whether we have a cyanide before us or 
 not* If, however, the phenomena which the substance un- 
 der examination manifests, when heated to redness ( 105, 
 A, I., 2, /,) be carefully observed, and also whether upon 
 boiling with hydrochloric acid any odour of hydrocyanic 
 acid manifests itself, ( 106, A, 2,) the presence or ab- 
 sence of a cyanide will generally not long be doubtful. 
 
 It must above all be borne in mind that the insoluble 
 cyanogen compounds occurring in pharmacy, &c., belong 
 to two quite different classes. They are either SIMPLE CY- 
 
274 ADDITIONAL REMARKS. 
 
 ANIDES, or compounds of metals with ferrocyanogen, or 
 with some other similar compound radical. 
 
 All the simple cyanides are decomposed by boiling with 
 concentrated hydrochloric acid, into metallic chlorides and 
 hydrocyanic acid. Their analysis, therefore, is never diffi- 
 cult. The ferrocyanides, &c., however, (to which the 
 method given 128 indeed exclusively refers,) undergo 
 by acids such complicated decompositions that their analy- 
 sis in this manner does not easily succeed. Their decom- 
 position by alkalies is far more simple ; these precipitate 
 the metal combined with the ferrocyanide, &c., as oxide, 
 by yielding their oxygen to it, and combining in their me- 
 tallic state with the compound radicals, forming soluble 
 ferrocyanide of potassium, &c. The method given at 
 128 endeavours first to effect a decomposition of this kind 
 by means of CARBONATE OF POTASH. If this succeeds, we 
 have the advantage of obtaining the oxides as a precipitate, 
 which circumstance renders their further analysis simple ; 
 if it does not succeed, we must "have recourse to CAUSTIC 
 POTASH. But in an excess of caustic potash, several ox- 
 ides are soluble, such as oxide of lead, oxide of zinc, &c. 
 If, therefore, e. g. the double ferrocyanide of zinc and po- 
 tassium, be boiled with caustic potash, it will completely 
 dissolve in that menstruum. Were we -to add an acid to 
 this solution, we should re-obtain our original precipitate 
 of the double ferrocyanide of zinc and potassium, and our 
 experiment thus would be of no avail. To prevent this, 
 we transmit sulphuretted hydrogen through the solution. 
 All the heavy metals dissolved as oxides in the potash so- 
 lution are thereby converted into sulphurets. Those of 
 them which are insoluble in potash, such as sulphuret of 
 lead, sulphuret of zinc, &c., precipitate, whilst those solu- 
 ble in alkaline sulphurets, such as sulphuret of tin, sulphu- 
 ret of antimony, &c., remain in solution, and precipitate 
 only upon the addition of an acid. 
 
 The cyanogen is always contained in the liquid filtered 
 from the precipitated oxides or sulphurets, as ferrocyanide, 
 &c., of potassium, (provided always the compound before 
 us has a double compound of cyanogen radicals.) From 
 most of them (ferrocyanide, ferricyanide, chromicyanide, 
 and manganocyanide of -potassium) the cyanogen partly 
 
ADDITIONAL REMARKS. 275 
 
 
 
 separates as hydrocyanic acid, upon boiling this solution 
 with sulphuric acid, and may thus be easily detected. But 
 the cobalticyanide of potassium is not decomposed by 
 sulphuric acid, and this renders it difficult DIRECTLY to 
 prove the presence of cyanogen in this double compound. 
 Upon fusion with nitre, all these double compounds are 
 decomposed, cobalticyanide of potassium not excepted. 
 They must previous to this operation be treated with an 
 excess of nitric acid, and then concentrated by evaporation, 
 or else explosions will ensue. Caution in this operation is 
 highly advisable. If we merely propose to detect the 
 bases present in simple or double cyanides, it is in most 
 cases sufficient either to heat the substance to redness for 
 some time by itself, or better still, to fuse it together with 
 the carbonates of potash and soda. By this process the 
 metals are obtained either in their metallic state, or com- 
 bined with carbon. If the compound has been fused 
 together with the carbonated alkalies, we obtain in the 
 dross, cyanate of potassium, if this substance has not been 
 converted into cyanate of potash, owing to the adventitious 
 presence of reducible oxides. (Vide 100, d, 1.) 
 
APPENDIX TO PART SECOND. 
 
 L 
 
 GENERAL SCHEME FOR A JUDICIOUS ARRANGEMENT OF THE 
 SUCCESSION IN WHICH SUBSTANCES OUGHT TO BE 
 ANALYZED. 
 
 IT is not a matter of indifference whether the student, 
 in analyzing for the sake of practice, follow no rule or 
 order whatever in the selection of substances to be ex- 
 amined, or whether, on the contrary, his investigations and 
 experiments follow a definite system. Many ways may 
 lead to the desired end, but one of them invariably will 
 prove the shortest. 1 will, therefore, here point out a sys- 
 tem 'which experience has shown will lead safely and 
 rapidly to the object in view. 
 
 Let the student take one hundred compounds, distributed 
 according to the following scheme, and the successful 
 examination of these will be amply sufficient to enable 
 him to attain the desired degree of skill in practical ana- 
 lysis. When analyzing for the sake of practice only, the 
 student must above all things possess the means of verify- 
 ing the results obtained by his experiments. The com- 
 pounds to be examined ought, therefore, to be mixed by a 
 friend who knows their exact composition. 
 
 A. From I to 20. 
 
 AQUEOUS SOLUTIONS OF SIMPLE SALTS : e. g. sulphate 
 of soda, sulphate of lime, chloride of copper, &c. ; for the 
 acquisition of the method to be pursued in the analysis of 
 substances soluble in water, and which contain but one 
 base. In these investigations it is only intended to ascer- 
 tain which base is present in the fluid under examination, 
 12 
 
278 APPENDIX TO PART SECOND. 
 
 without regard to the detection of the acid ; it is not neces- 
 sary to prove that no other base is present, besides the one 
 detected. 
 
 B. From 21 to 50. 
 
 SALTS, &c., (CONTAINING ONE BASE AND ONE ACID,) IN A 
 SOLID FORM, as powder : e. g. carbonate of barytes, borate 
 of soda, phosphate of lime, arsenious acid, chloride of 
 sodium, tartar, acetate of copper, sulphate of barytes, chlo- 
 ride of lead, &c J to learn how to convert a solid sub- 
 stance to a state which admits of its examination, (solution, 
 or fluxing,) how to detect ONE metallic oxide, even though 
 the substance under examination be NOT soluble in water, 
 and how to prove the presence of ONE acid. Base and 
 acid must be detected ; it is not necessary to prove that 
 no other constituents, &c. are present. 
 
 C. From 51 to 70. 
 
 AQUEOUS OR ACID SOLUTIONS OF SEVERAL BASES ; 
 to acquire the method of separating and distinguishing 
 several metallic oxides. It is necessary to prove that no 
 other bases are present besides those detected. No regard 
 is paid to the acids. 
 
 I. From No. 51 to 60. To acquire the method of se- 
 parating the metallic oxides into the principal groups. 
 The solutions contain, therefore, e. g. potash, lime, and 
 lead ; copper, iron, and arsenic ; barytes, antimony, bis- 
 muth, and potash, &c. 
 
 II. From No. 61 to 70. To acquire the method of 
 detecting side by side the individual bases belonging to the 
 same group. The solutions contain, e. g. potash, soda, 
 arid ammonia ; zinc, manganese, and nickel ; capper, 
 mercury, and lead ; antimony, tin, arsenic, &c. 
 
 D. From 71 to 80. 
 AQUEOUS SOLUTIONS CONTAINING SEVERAL ACIDS, EITHER 
 
 IN THEIR FREE OR IN THEIR COMBINED STATE, 6. g. Sul- 
 
 phuric acid, phosphoric acid, and boracic acid ; carbonic 
 acid, sulphuretted hydrogen, and hydrocyanic acid j tarta- 
 
APPENDIX TO PART SECOND. 279 
 
 ric acid, citric acid, and malic acid ; chlorine, iodine, and 
 bromine ; nitric acid, hydrochloric acid, and oxalic acid ; 
 to acquire the method of detecting several acids contained 
 in the same compound. It is necessary to prove that no 
 other acids are present besides those detected. The bases 
 are disregarded. 
 
 E. From 81 to 100. 
 
 ALLOYS, MINERALS, AND MIXED SUBSTANCES OF EVERY 
 DESCRIPTION ; for further practice, and to prove that the 
 student has attained the object he had in view when enter- 
 ing upon these experimental examinations. All the con- 
 stituents of a substance under examination must be 
 detected j the nature of the substance must be examined. 
 
II. 
 
 TABLE 
 
 OF THE 
 
 MORE FREQUENTLY OCCURRING FORMS AND 
 
 COMBINATIONS OF THE SUBSTANCES CONSIDERED IN 
 
 THE 'PRESENT WORK, 
 
 WITH ESPECIAL REGARD TO THE CLASSES TO WHICH THEY BELONG, 
 ACCORDING TO THEIR VARIOUS DEGREES OF SOLUBILITY 
 
 IN WATEE, IN HYDROCHLORIC ACID, OR IN NITRIC ACID. 
 
 PRELIMINARY REMARKS. 
 
 THE various classes to which compound substances be- 
 long according to the division specified at 106, are ex- 
 pressed by figures. Thus 1 or I means a substance solu- 
 ble in water ; 2 or II a substance insoluble in water, but 
 soluble in hydrochloric acid, or nitric acid ; 3 or III a sub- 
 stance insoluble both in water and acids. The Roman 
 figures denote officinal and more frequently occurring com- 
 pounds, whilst the Arabian figures indicate less frequently 
 occurring compounds. For those substances standing as it 
 were, on the limits between the various classes, the figures 
 of the classes in question are jointly expressed : thus 1 2 
 signifies a substance difficultly soluble in water, but soluble 
 in hydrochloric acid or nitric acid ; 1 3 a body difficultly 
 soluble in water and the solubility of which is not increased 
 by the addition of acids ; and 2 3 a substance insoluble 
 in water and difficultly soluble in hydrochloric acid and in 
 nitric acid ; wherever the relation of a substance to hydro- 
 
 
PRELIMINARY REMARKS. 
 
 281 
 
 chloric acid is different from that to nitric acid, this is 
 stated in the notes. 
 
 The haloid salts and sulphur compounds will be found 
 in the columns of the protoxide and peroxide- Most of 
 the salts given are neutral, the basic and acid and double 
 salts are mentioned in the notes j the small figures placed 
 near the corresponding neutral or simple salts, refer to 
 these. Cyanogen, chloric acid, citric acid, malic acid, 
 benzoic acid, succinic acid, and formic acid, are of more 
 frequent occurrence only in combination with a few bases, 
 and have, therefore, not been admitted into the table. The 
 most frequently occurring combinations of these substances 
 are : cyanide of potassium I, ferrocyanide of potassium I, 
 ferricyanide of potassium I, sesqui-ferrocyanide of potas- 
 sium (Prussian blue) III, ferrocyanide of zinc and potas- 
 sium II III, chlorate of potash I, the alkaline citrates I, 
 the alkaline malates I, perraalate of iron I, the alkaline ben- 
 zoates I, the alkaline succinates I, and the alkaline for- 
 miates L 
 
2S2 
 
 A TABLE OF THE VARIOUS FORMS 
 
 
 KO 
 
 NaONH4 O 
 
 BaO 
 
 SrO 
 
 CaO MgO 
 
 AlsOs 
 
 MnO 
 
 FeOFezOsCoONiO 
 
 ZnO 
 
 
 I 
 
 
 t 
 
 I 
 
 1 
 
 I-II 
 
 II 
 
 II 
 
 II 
 
 II 
 
 n 
 
 II 
 
 n 
 
 
 8 
 
 I 
 
 
 i 
 
 I 
 
 I 
 
 I-II 
 
 2 
 
 
 II 
 
 II 
 
 n 
 
 15 
 
 16 
 
 n 
 
 Cl 
 
 1 
 
 
 112 
 
 I 
 
 I 
 
 I 
 
 ] 
 
 1 
 
 I 
 
 I 
 
 Il2 
 
 1 
 
 I 
 
 1 
 
 J 
 
 I 
 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 
 1 
 
 1 
 
 1 
 
 
 
 1 
 
 80s 
 
 II 
 
 
 113 
 
 III 
 
 m 
 
 i-m 
 
 I 
 
 11-13 
 
 I 
 
 I 
 
 I 
 
 1 
 
 1 
 
 I 
 
 NOs 
 
 I 
 
 
 1 
 
 I 
 
 i 
 
 i 
 
 1 
 
 1 
 
 I 
 
 1 
 
 1 
 
 I 
 
 I 
 
 1 
 
 POs 
 
 1 
 
 Iio 
 
 110 
 
 2 
 
 2 
 
 IIU 
 
 2 
 
 2 
 
 2 
 
 2 
 
 n 
 
 2 
 
 2 
 
 2 
 
 C02 
 
 12 
 
 Iu 
 
 
 II 
 
 II 
 
 n 
 
 II 
 
 
 II 
 
 2 
 
 
 2 
 
 
 II 
 
 CaOs 
 
 13 
 
 1 
 
 
 2 
 
 2 
 
 ii 
 
 2 
 
 2 
 
 2 
 
 1-2 
 
 1-2 
 
 g 
 
 2 
 
 2 
 
 BOa 
 
 14 
 
 14 
 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 A 
 
 I 
 
 I 
 
 
 I 
 
 1 
 
 i 
 
 1 
 
 1 
 
 
 1 
 
 1 
 
 1 
 
 1 
 
 J 
 
 T 
 
 14-9 
 
 n 
 
 14 
 
 2 
 
 2 
 
 ii 
 
 1-2 
 
 1 
 
 1-2 
 
 1-2 
 
 18 
 
 1 
 
 
 2 
 
 As0 5 
 
 I 
 
 i 
 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 3 
 
 As Oa 
 
 I 
 
 i 
 
 
 2 
 
 1 
 
 2 
 
 
 
 
 2 
 
 
 2 
 
 2 
 
 
 Cr0 3 
 
 I 
 
 i 
 
 
 2 
 
 2 
 
 1 
 
 1 
 
 2 
 
 1 
 
 
 1 
 
 2 
 
 1 
 
 
 NOTES. 
 
 1. SULPHATE of potash and alumina I. 
 
 2. Bicarbonate of potash I. 
 
 3. Binoxalate of potash I. 
 
 4. Tartarized borax I. 
 
 5. Bitartrate of potash I. 
 
 6. Tartrate of potash and ammonia I. 
 
 7. Tartrate of potash and soda I. 
 
 8. Tartrate of potash and peroxide of iron I. 
 
 9. Tartrate of antimony and potash I. 
 
 10. Phosphate of soda^nd ammonia I. 
 
 11. Bicarbonate of soda I. 
 
 12. Chloride of iron and ammonium I. 
 
 13. Sulphate of ammonia and alumina I. 
 
 14. Basic phosphate of lime II. 
 
 15. Sulphuret of cobalt is easily decomposed by nitric 
 
 acid, but very difficultly by hydrochloric acid. 
 This substance is not officinal. 
 
283 
 
 AND COMBINATIONS OF BODIES. 
 
 
 CdO 
 
 PbO 
 
 SnO 
 
 SnO2 
 
 BiO 
 
 CuO 
 
 HGaO 
 
 HgO 
 
 AgO 
 
 PtO2 
 
 AuOa 
 
 SbOs 
 
 Cre 03 
 
 . 
 
 2 
 
 218 
 
 2 
 
 2&3 
 
 2 
 
 1122 
 
 II 
 
 n 
 
 2 
 
 2 
 
 
 35 
 
 n&in 
 
 s 
 
 2 
 
 2 
 
 20 
 
 20 
 
 2 
 
 23 
 
 III 
 
 in 
 
 30 
 
 3 
 
 
 1136 
 
 
 CI 
 
 1 
 
 I-IH 
 
 1 
 
 1 
 
 I 
 
 124 
 
 H-m 
 
 188 
 
 III 
 
 132-33 
 
 134 
 
 137 
 
 i 
 
 J 
 
 1 
 
 n 
 
 2 
 
 
 
 
 ii 
 
 II 
 
 3 
 
 
 
 
 
 S03 
 
 I 
 
 i 
 
 1 
 
 1 
 
 1 
 
 125 
 
 1-2 
 
 129 
 
 i-m 
 
 1 
 
 
 2 
 
 i 
 
 NOs 
 
 1 
 
 i 
 
 
 
 121 
 
 I 
 
 127 
 
 I 
 
 j 
 
 1 
 
 
 
 i 
 
 POs 
 
 2 
 
 2 
 
 
 
 
 2 
 
 2 
 
 2 
 
 2 
 
 
 
 
 2 
 
 CO? 
 
 2 
 
 II 
 
 
 
 2 
 
 II 
 
 2 
 
 2 
 
 2 
 
 
 
 
 
 C 2 03 
 
 2 
 
 II 
 
 2 
 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 
 
 1-2 
 
 1 
 
 B0 3 
 
 1-2 
 
 2 
 
 2 
 
 
 2 
 
 2 
 
 1 
 
 
 2 
 
 
 
 
 2 
 
 A 
 
 1 
 
 Il9 
 
 1 
 
 1 
 
 1 
 
 126 
 
 1-2 
 
 1 
 
 I 
 
 
 
 1 
 
 1 
 
 r 
 
 1-2 
 
 n 
 
 1-2 
 
 
 2 
 
 1 
 
 1-2 
 
 2 
 
 2 
 
 
 
 138 
 
 1 
 
 AsOs 
 
 
 2 
 
 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 
 
 2 
 
 1 
 
 As O3 
 
 
 2 
 
 
 
 
 n 
 
 2 
 
 2 
 
 2 
 
 
 
 2 
 
 
 CrOa 
 
 
 ii-in 
 
 2 
 
 
 2 
 
 2 
 
 2 
 
 1-2 
 
 2 
 
 
 
 2 
 
 2 
 
 16. The same applies to sulphuret of nickel. 
 
 17. The same applies to sulphuret of zinc. 
 
 18. Minium is converted by hydrochloric acid into chlo- 
 
 ride of lead, by nitric acid into an oxide soluble in 
 an excess of the acid and into brown peroxide of 
 lead, insoluble in nitric acid. 
 
 19. Basic acetate of lead I. 
 
 20. Sulphuret and bisulphuret of tin are decomposed and 
 
 dissolved by hydrochloric acid, whilst they are 
 converted into insoluble oxides by nitric acid in 
 excess. Sublimed bisulphuret of tin dissolves 
 only in aqua regia. 
 
 21. Basic nitrate of bismuth II. 
 
 22. Ammoniacal oxide of copper I. 
 
 23. Sulphuret of copper is difficultly decomposed by hy 
 
 drochloric acid, but with facility by nitric acid, 
 
 24. Chloride of copper and ammonium 1. 
 
 25. Sulphate of copper and ammonia 1. 
 
 26. Basic acetate of copper, soluble partially in water, and 
 
 completely in acids. 
 
284 NOTES. 
 
 27. Basic protonitrate of mercury and ammonia II. 
 
 28. Basic chloride of mercury and ammonium II. 
 
 29. Basic persulphate of mercury II. 
 
 30. Sulphuret of silver soluble only in nitric acid. 
 
 31. Sulphuret of platinum is not affected by hydrochloric 
 
 acid ; boiling nitric acid converts it into a soluble 
 sulphate of platinum. 
 
 32. Chloride of platinum and potassium 1 3. 
 
 33. Chloride of platinum and ammonium 1 3. 
 
 34. Chloride of gold and sodium I. 
 
 35. Oxide of antimony soluble in hydrochloric acid, but 
 
 not in nitric acid. 
 
 36. Sulphuret of antimony and calcium 1 2. 
 
 37. Basic chloride of antimony II. 
 
 38. Tartrate of antimony and potash I. 
 
 
D. APPLETON &, CO. 
 
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 plates more convenient, the engraved illustrations are published in a separate volume, in the folio 
 form. These plates are all drawn to certain scales, and the dimensions of every part may be taken, 
 and machines built from any of the designs. 
 
 " The most recent and approved engines of their respective classes appear to have been selected, 
 and, with four exceptions only, are all of American construction and arrangement. The volume of 
 plates, as a work of the art of drawing, forms one of the most splendid specimens that has ever fallen 
 under our observation. Mr. Hodge, the author of this truly practical and valuable work, is, it will be 
 recollected, the inventor of the steam fire-engine, the utility of which, in extinguishing fires, has been 
 fully tested." Courier <J- Enquirer. 
 
 LAFEVER'S MODERN ARCHITECTURE. 
 
 Beauties of Modern Architecture : consisting of forty-eight plates of Original Designs, with Plans, 
 Elevations and Sections, also a Dictionary of Technical Terms ; the whole forming a complete 
 Manual for the Practical Builder. By M. Lafever, Architect. 1 vol. large 8vo. half bound. $6 00 
 
 LAFEVER'S STAIR-CASE AND HAND-RAIL CONSTRUCTION. 
 
 The Modern Practice of Stair-case and Hand-rail Construction, practically explained, in a series f 
 Designs. By M. Lafever, Architect. With Plans and Elevations for Ornamental Villa*. Fifta 
 Plates. I vol. large 8vo. $300. 
 Tlu works of Lafever are pronounced by the practical man to be the most useful ever published. 
 

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