D31 Pr. w I PF 1 * ', i <\ *^-Vr - 4 UNIVERSmfgrCALIFORNIA 1 COLLEGE of MINING DEPARTMENTAL LIBRARY BEQUEST OF SAMUELBENEDlCrCHRISTY PROFESSOR OF MINING AND METALLURGY 1885-1914 A SYSTEM OF IlSrSTEUCTIOX IN QUALITATIVE CHEMICAL ANALYSIS. In tJie Press, BY THE SAME AUTHOR. QUANTITATIVE CHEMICAL ANALYSIS. Third Edition. Svo. cloth. SYSTEM OF INSTRUCTION QUALITATIVE CHEMICAL . ANALYSIS. BY DR C. KEMIGIUS FRESENIUS, PRtVY ATTLIC COUNSELLOR OF THE DUKE OF NASSAU; DIRECTOR OF THK CHEMICAL LABORATORY AT "WIESBADEN ; PROFESSOR OF CHEMISTRY, NATURAL PHILOSOPHY, AND TECHNOLOGY AT Till WIESBADEN AGRICULTURAL INSTITUTE. Jtftfj CEfoition. EDITED BY J. LLOYD BULLOCK, F.C.S. LONDON: JOHN CHURCHILL, NEW BUKLINGTON STREET. MDCCCLIX. f 8 EDITOR'S PREFACE TO THE FIFTH EDITION. THIS Edition of Dr. Fresenius's Qualitative Chemical Analysis, though simply professing to be a translation from the NIKTH GERMAN Edition, is really very much in advance of that work ; it contains a large amount of important original matter communicated by the Author during the time it was passing through the press. Some of the sections have also been remodelled, to adapt them to the more advanced state of scientific instruction. It is very gratifying to the Editor to find that, notwithstanding the numerous and important English works on chemical analysis published within the last few years, the valuable system of Dr. tYesenius still enjoys the undirninished confidence of British chemists. In conclusion, the Editor expresses a hope that the present edition will receive the same amount of favor as the former works of the dis- tinguished Author. J. LLOYD BULLOCK. 3, HANOVER STREET, W. October, 1859. EDITOK'S PREFACE. THIS work of Dr. Fresenius has already gone through two editions in Germany. The abundant opportunities enjoyed by its Author of dis- covering the wants felfc by students in entering upon the practice of che- mical analysis, and his position in the School of Giessen, have enabled him to devise a method of study of the highest value. That it has re- ceived the approbation of the illustrious HEAD of that school, and the benefit of three years' practical experience under his immediate observa- tion, must powerfully recommend 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 anything of Giessen, will bear testimony to the rigid economy of time, and the reso- lute adoption of every improvement in method which characterize that school, and serve to accomplish the many chemists annually 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's, and others, although admirable in themselves, present great difficulties to beginners, which difficulties maybe summed -up under three heads ; 1st, Too great copiousness and detail; 2nd, The absence of explanations of the causes of phenomena, i. e. the theory of the opera- tions and reactions ; and 3rd, The omission altogether of many substances viii EDITOR'S PREFACE. of very frequent occurrence, especially in the operations of the pharma- ceutist, such as the organic 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 concise or elementary. The student may, perhaps, at first be disappointed in taking up this work to find that there are no tables constructed 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 disadvantage 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 consecutively, 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 compound 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 necessity. In the Preface to the Second Edition, Dr. Fresenius tells us that his work has met with much success, having been adopted in the Pharma- ceutical Institution of Bonn, &c., as well as in the laboratory of Giessen ; and that he has improved it by many corrections and additions. IX 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 intrusted 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, October 1, 1843. CONTENTS. PART I. INTRODUCTORY PART. PRELIMINARY REMARKS. Definition, objects, general principles, utility, and importance of qualitative chemical analysis, the conditions and requirements for a successful study of that science SECTION I. OPERATION, 1 .... "' ' 1. Solution, 2 2. Crystallization, 3 3. Precipitation, 4 4. Filtration, 5 . , ' . . 3 . 3 5 . 5 6 5. Decantation, 6 6. Evaporation, 7 7. Distillation, 8 . 8. Ignition, 9 9. Sublimation, 10 10. Fusion and Fluxing, 11. Deflagration, 12 12. The use of the blowprj . 8 . 9 9 .',' ...,'." . 10 . 11 11 . .11 . 12 >e, 13 .12 Appendix to the First Section. Apparatus and utensils, 14 . .16 SECTION II. Reagents, 15 . . . .20 A. EEAGENTS IN THE HUMID WAT. I. SIMPLE SOLVENTS . . .22 1. Water, 16 . . .22 2. Alcohol, 17 . '" *.". . , . 23 3. Ether, 18 23 II. ACIDS AND HALOGENS, 19 . .23 a. Oxygen acids. 1. Sulphuric acid, 20 . . .24 2. Nitric Acid, 21 . . .25 3. Acetic acid, 22 . . .26 4. Tartaric acid, 23 . . .27 6. Hydrogen acids and halogens. 1. Hydrochloric acid, 24 . .27 2. Chlorine, 25 . . . .28 3. Nitrohydrochloric acid, 26 .29 4. Hydrofluosilicic acid, 27 . .29 35 37 PAGE c. Sulphur acids. 5. Hydrosulphuric acid, 28 . .30 III. BASES AND METALS, 29 .34 a. Oxygen l)ases. a. Alkalies. 1. Potassa and soda, 30 2. Ammonia, 31 . . /3. Alkaline earths. 1. Baryta, 32 . . .38 2. Lime, 33 . . . .39- 7. Heavy metals and their oxides. 1. Zinc, 34 . . . .40 2. Iron, 35 . . . .40 3. Copper, 36 . . .40 4. -Hydrate of teroxide of bismuth, 37 ..... 40 6. Sulphur bases. 1. Sulphide of ammonium, 38 2. Sulphide of sodium, IV. SALTS. 39 10. 11. 12. 13. 14. 15. 16. a. Salts of the alkalies. Sulphate of potassa, 40 Phosphate of soda, 41 Oxalate of ammonia, 42 . Acetate of soda, 43 . Carbonate of soda, 44 Carbonate of ammonia, 45 Bisulphate of soda, 46 Nitrate of potassa, 47 Bichromate of potassa, 48 Antimouate of potassa, 49 Molybdate of ammonia, 50 Chloride of ammonium, 51 Cyanide of potassium, 52 . Ferrocyanide of potassium, 53 Ferricyanide of potassium, 54 Sulphocyanide of potassium, 55 6. Salts of the alkaline earths. Chloride of barium, 56 Nitrate of baryta, 57 Carbonate of baryta, 58 . 41 42 43 43 43 44 44 45 45 46 46 46 47 47 48 4& 49- 50 50 51 51 Xll CONTKNTS. 4. Sulphate oflimo, . r -0 5. Hiloridi' of calcium. $ tiO u*. Sulphato of magnesia, 55 61 PAGE . 61 . 52 .52 r. ttifo o/ f/5 . . 5. Nitrate of suboxide of mercury 52 53 53 54 54 55 55 65 56 6. Chloride of mercury, 67 . 7. Sulphate of copper, 68 . 8. rrotoehloruie of tin, >5 09 . 9. Bichloride of platinum, 70 10. Sodio-protochloride of palladium in..,. 56 11. Tercklorideofgold, 72 . 56 V. COLOURING MATTERS AND INDIF- FERENT VKOKTABLK SCBSTASOKS, 73 57 1. Test papers. a. Blue litmus paper . 57 p. Reddened litmus paper 57 7. Georgiua paper . 57 5. Turmeric paper . 58 2. Indigo solution, 74 . 58 B. REAGENTS IN TITE DRY WAY. I. Fluxes and decomposing agents. 1. Mixture of carbonate of soda and earb.n'.at o of pofcussa, 75 .58 . Hydrate of baryta, TO . . 60 3. Fluoride of calcium, 77 . .60 4. Nitrate of soda, 78 . . .60 II. Elotcpipe reagents. 1. Carbonate of soda, 79 . . 61 J. Cyanide of potassium, 80 . . 61 3. Biborate of soda, 81 . .62 4. Phosphate of soda and ammonia, $$2 ..... 63 5. Nitrate of protoxide of cobalt, S3 63 6. Chloride of silver, 84 . .64 SECTION III. ON THE DEPORTMENT OP BODIES WITH RKAGEXTS, 85 . . . .64 A. DEPORTMENT AND PROPERTIES OF THR METALLIC OXIDES AXD THEIR RADICALS, 86 . . . .65 FIRST GROUP. Potassa, soday and ammonia, 87 .66 Special inactions. . V. :>>:-..*>>. . , 66 b. Soda, 89 ..... 67 c. Ammonia, 90 . . . .68 Recapitulation and remarks, 91 . 69 Supplement to the first group. Lithia, 92 ..... 70 SECOND GROUP. Baryta, ttrontia, lime, magnesia, \ Special reactions. a. Ivirvta, 94 l>. StrJntia, 95 . <-. Lime, 90 . . d. Magnesia, 97 . l\(capitnlation and remarks, 98 PAGE 93 71 71 72 73 74 70 THIRD GROUP. Alumina, scsqirio.ridcofdtromium, 99 77 Special reactions, a. Alumina, 100 . . . .78 6. Sesquioxide of chromium, 101 . 79 Recapitulation and remarks, 102 . 80 Supplement to tftc third group. Titanic acid, 103 . . SO FOURTH GROUP. Oxide of zinc, protoxide of inanyancttc, protoxide of nickel, protoxide of cobalt, protoxide of trow, scsqui- oxide of iron, 104 '. . .81 Special reactions. a. Oxide of zinc, 105 . . 82 b. Protoxide of inamranoso, 100 S3 e. Protoxide of nickel, 107 . 84 d. Protoxide of cobalt, 108 . 86 e. Protoxide of iron, 109 . 87 f. Sesquioxide of iron, 110 . 89 Recajiitttlation- and remarks, 111 i)0 Supplement to the fourth group. Sesquioxide of uranium, 112 . . 92 FIFTH GROUP. Oxide of silver, si&oxide of mercury, oxide of mercury, oxide of lead t teroxide of bismuth, oxide of cop- per, oxide of cadmium, 113 . 93 First dirifionof thcjifth group : oxides which are precipitated b;/ hydro- chloric acid. Special reactions. a. Oxide of silver, 114 . * . 93 6. Suboxide of mercury, 115 . 94 c. Oxide of lead, 116 . . 95 Recapitulation and remarks, 117 . 97 Second division of thefifth group: oxides which arc not precipitated by hy- drochloric acid. Special reactions. a. Oxide of mercury, 118 . .97 b. Oxide of copper, * 119 , .98 c. Teroxide of bismuth, 120 . . 100 d. Oxide of cadmium, 121 . . 101 Recapitulation and remarks, 122 . 102 CONTKNT-i. XU1 Supplement to thefiff,!> Protoxide of palladium, 1 123 103 SIXTH 0BOVF. '/<: o/yo/'/, t/inoxide of platinum, ts.r'txifa (ff antimony, bmftxide of tin. f,r',toxide of tin, arscnious />>/, ou//./ artf.ti.ic acid, 124 . 104 ivision of the sixth group. Special reaction*. a. Teroxideofgold,|125 . . 104 &. Binoxide of platinum, 1 126 . 105 Recapitulation and remark*, 127 . 106 Second division of the sixth group. Special reaction*. .. Protoxide of tin, 1 128 . ', Kinoxideoftin, 129 . c. Teroxide of antimony, 130 d. Araeniotu acid, 131 . . Arsenic acid, $132 . . Recapitulation and remark*, 133 .piemen* to the tixth group. Molybdic acid, 134 . . .125 B. DBPORTME5T OF THE ACIDS AWD THEIR RADICALS WITH RKACtEYTS, f 135 126 Classification of acida in gronpa, 136 126 I. IKOROAJTIC ACIDS. FIRST GROUP. 106 108 109 112 121 122 Acid* vJi.if.J'. art wt& tralsolutionsby chloride of barium: arsenious acid, arsenic acid, chro- mic acid, sulphuric add, phot- jtkoric acid, boradc acid, oxalic o.c/W, hydrofluoric add, carbonic acid, iiicic acid, 137 . . 127 Pint division of the first group of the inorganic add*, 138 . . 128 a. Ar*OTioiw acid and arsenic acid . 128 6. Chromic acid .... 128 Remark*, $139 . . . .129 Supplement to the first division of the 129 129 130 130 a. Selenions acid . b. Snlphuricacid c. Hypoeulpliiiric acid d. lodicacid . Second diritionof the first group of the inorganic acids. Sulphoric acid, 141 . . .131 Remarks . ..... 131 Supplement to the second division of the first group. HydrofluoBiiicic acid, 142 . . 132 Tfiird division of the first group of the inorganic add*. a. Phosphoric acid, 143 Supplement, 144 . a. Bibasic phosphoric acid 8. Monobasic phosphoric acid o. Boracic acid, 145 . wltdk notpredpitated by salt* of baryta nor by salts of tUver: nitric add, cldoric add. a. Nitric acid, 159 . . .155 6. Chloric acid, 1 160 ... 156 Recapitulation and remark*, 161 . 157 IL OROAJTIC ACTDS. FIRST OROCP. ^4 .: * . 300 V. Table of weights and measures . 303 INDEX , 305 PART I. INTRODUCTORY, PRELIMINARY REMARKS. DEFINITION, GENERAL PRINCIPLES, OBJECTS, UTILITY, AND IMPORTANCE OF QUALITATIVE CHEMICAL ANALYSIS, THE CONDITIONS AND REQUIRE- MENTS FOR A SUCCESSFUL STUDY OF THAT SCIENCE. CHEMISTRY is the science which treats of the various materials entering into the structure of the earth, their composition and decomposition, their mutual relations and deportment in general. A special branch of this science is designated Analytical Chemistry, inasmuch as it pursues a distinct and definite object viz., the analysis of compound bodies, and the examination of their component elements. Analy- tical chemistry, again, is subdivided into two branches viz., qualitative analysis, which simply studies the nature and properties of the com- ponent parts of bodies ; and quantitative analysis, which ascertains the quantity of every individual element present. The office of quali- tative analysis, therefore, is to exhibit the constituent parts of a substance of unknown composition in forms of known composition, from which the constitution of the body examined, and the presence of its several component elements may be positively inferred. The efficiency of its method depends upon two conditions viz., it must attain the object in view with unerring certainty, and in the most expeditious manner. The object of quantitative analysis, on the other hand, is to exhibit the elements revealed by the qualitative investigation in forms which will permit the most accurate estimate of their weight, or to effect by other means the determination of their quantity. These different ends are, of course, attained respectively by very different ways and means. The study of qualitative analysis must, therefore, be pursued separately from that of quantitative analysis, and must naturally precede it, Having thus generally denned the meaning and scope of qualitative analysis, we have now still to consider, in the first place, the preliminary information required to qualify students for a successful cultivation of this branch of science, the rank which it holds in the domain of chemistry, the bodies that fall within the sphere of its operations, and its utility and importance ; and, in the second place, the principal parts into which its study is divided. 2 PRELIMINARY REMARKS. It is, above all, absolutely indispensable for a successful pursuit of qua- litative investigations, that the student should possess some knowledge of the chemical elements, and of their most important combinations, as well as of the principles of chemistry in general ; and that he should combine with this knowledge some readiness in the apprehension of chemical processes. The practical part of this science demands, more- over, strict order, great neatness, and a certain skill in manipulation. If the student joins to these qualifications the habit of invariably ascribing the failures with which he may happen to meet, to some error or defect in his operations, or, in other words, to the absence of some condition or other indispensable to the success of the experiment and a firm reliance on the immutability of the laws of nature cannot fail to create this habit he possesses every requisite to render his study of analytical che- mistry successful. Now, although chemical analysis is based on general chemistry, and cannot be cultivated without some previous knowledge of the latter, yet, on the other hand, we have to look upon it as one of the main pillars upon which the entire structure of the science rests ; since it is of almost equal importance for all branches of theoretical as well as of practical chemistry ; and I need not expatiate here on the advantages which the physician, the pharmaceutist, the mineralogist, the rational farmer, the manufacturer, the artisan, and many others derive from it. This consideration would surely in itself be sufficient reason to re- commend a thorough and diligent study of this branch of science, even it its cultivation lacked those attractions which yet it unquestionably pos- sesses for every one who devotes himself zealously and ardently to it. The human mind is constantly striving for the attainment of truth ; it delights in the solution of problems ; and where do we meet with a greater variety of them, more or less difficult of solution, than in the province of chemistry ? but as a problem to which, after long pondering, we fail to discover the key, wearies and discourages the mind : so. in like manner, do chemical investigations, if the object in view is not attained if the results do not bear the stamp of truth, of unerring certainty. A half-knowledge is therefore, as indeed in every department of science, but more especially here, to be considered worse than no know- ledge at all ; and a mere superficial cultivation of chemical analysis is consequently to be particularly guarded against. A qualitative investigation may be made with a twofold view viz., either, 1st, to prove that a certain body is or is not contained in a sub- stance, e.g. lead in wine ; or, 2ud, to ascertain all the constituents of a chemical compound or mixture. Any substance whatever may of course become the object of a chemical analysis. In the present work, however, we purpose to confine ourselves to those elements and compounds which are more generally employed in pharmacy, in the arts and manufactures, and in agriculture. The study of qualitative analysis is most properly divided into four principal parts viz., 1. CHEMICAL OPERATIONS. 2. REAGENTS AND THEIR USES. 3. DEPORTMENT OP THE VARIOUS BODIES WITH REAGENTS. 4. SYSTEMATIC COURSE OF QUALITATIVE ANALYSIS. It will now be readily understood that the pursuit of chemical 1, 2.] OPERATIONS. 3 analysis requires practical skill and ability, as well as theoretical know- ledge ; and that, consequently, a mere speculative study of that science can be as little expected to lead to success as purely empirical expe- riments. To attain the desired end, theory and practice must be com- bined. SECTION I. OPERATIONS. I- THE operations of analytical chemistry are essentially the same as those of synthetical chemistry, though modified to a certain extent to adapt them to the different object in view, and to the small quantities operated upon in analytical investigations. The following are the principal operations in qualitative analysis. 2. 1. SOLUTION. The term " solution" in its widest sense, denotes the perfect union of a body, no matter whether gaseous, liquid, or solid, with a fluid, resulting in a homogeneous liquid. However, when the substance dissolved is gaseous, the term " absorption" is more properly made use of; and the solution of one fluid in another is more generally called a mixture. The application of the term solution, in its usual and more restricted sense, is confined to the perfect union of a solid body with a fluid. A solution is the more readily effected the more minutely the body to be dissolved is divided. The fluid by means of which the solution is effected, is called the solvent. We call the solution chemical, where the solvent enters into chemical combination with the substance dissolved ; simj)le, where no definite combination takes place. In a simple solution the dissolved body exists in the free state, and retains all its original properties, except those dependent on its form and cohesion ; it separates unaltered when the solvent is withdrawn. Com- mon salt dissolved in water is a familiar instance of a simple solution. The salt in this case imparts its peculiar taste to the fluid. On evapo- rating the water, the salt is left behind in its original form. A simple solution is called saturated when the solvent has received as much as it can hold of the dissolved substance. But as fluids dissolve generally larger quantities of a substance, the higher their temperature, the term saturated, as applied to simple solutions, is only relative, and refers invariably to a certain temperature. It may be laid down as a general rule, that elevation of temperature facilitates and accelerates simple solution. A chemical solution contains the dissolved substance not in the same state nor possessed of the same properties as before ; the dissolved body is no longer free, but intimately combined with the solvent, which latter also has lost its original properties ; a new substance has thus been pro- duced, and the solution manifests therefore now the properties of this new substance. A chemical solution also may be accelerated by elevation of temperature ; and this is indeed usually the case, since heat generally B 2 SOLUTION. [2- 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 the combining proportions of substances being invariable, and altogether independent of the gradations of temperature. The reason of this is, that in a chemical solution the solvent and the body upon which it acts have invariably opposite properties, which they strive mutually to neutralize. Further solution ceases as soon as this tendency of mutual neutralization is satisfied. The solution is in this case also said to be saturated or, more properly, neutralized, and the point which denotes it to be so is termed the point of saturation or neu- tralization. The substances which produce chemical solutions are, m most cases, either acids or alkalies. With few exceptions, they have first to be converted to the fluid state by means of a simple solvent. When the opposite properties of acid and base are mutually neutralized, and the new compound is formed, the actual transition to the fluid state will ensue only if the new compound possesses the property of forming a simple solution with the liquid present; e.g. when solution of acetic acid in water is brought into contact with oxide of lead, there ensues, first, a chemical combination of the acid with the oxide, and then a simple solution of the new-formed acetate of lead in the water of the menstruum. In pharmacy, solutions are often made in a mortar having a lip, by triturating the body to be dissolved with the solvent added gradually in small quantities at a time ; in chemical laboratories solutions are rarely made in this manner, but generally by digesting or heating the substance to be dissolved with the fluid in beaker-glasses, flasks, test-tubes, or dishes. In the preparation of chemical solutions, the best way generally is to mix the body to be dissolved in the first place with water (or with whatever other indifferent fluid may happen to be used), and then gradually add the chemical agent. By this course of proceeding a large excess of the latter is avoided, an over-energetic action guarded against, the process greatly facilitated, and complete solution ensured, which is a matter of some importance, as it will not seldom happen in chemical combinations that the product formed refuses to dissolve if an excess of the chemical solvent is present ; in which case the molecules first formed of the new salt, being insoluble in the menstruum present, gather round and enclose the portion still unacted on, weakening thereby or preventing altogether further chemical action upon them. Thus, for instance, Witherite (carbonate of baryta) dissolves readily when, after being reduced to powder, water is poured upon it, and hydrochloric acid gradually added ; but it dissolves with difficulty and imperfectly when projected into a concentrated solution of hydrochloric acid in water, for chloride of barium will indeed dissolve in water, but not in hydro- chloric acid. CRYSTALLIZATION and PRECIPITATION are the reverse of solution, since they have for their object the conversion of a fluid or dissolved substance to the solid state. As both generally depend on the same cause, viz., on the absence of a solvent, it is impossible to assign exact limits to either ; in many cases they merge into one another. We must, however, con- sider them separately here, as they differ essentially in their extreme forms, and as the special objects which we purpose to attain by their application are generally very different. 3, 4.] CRYSTALLIZATION. 5 3. 2. CRYSTALLIZATION. We understand by the term crystallization, in a more general sense, every operation, or process, whereby bodies are made to pass from the fluid to the solid state, and to assume certain fixed, mathematically definable, regular forms. But as these forms, which we call crystals, are the more regular, and consequently the more perfect, the more slowly the operation is carried on, we always connect with the term " crystal- lization" the accessory idea of a slow separation of a gradual conversion to the solid state. The formation of crystals depends on the regular arrangement of the ultimate constituent particles of bodies (molecules or atoms) ; it can only take place, therefore, if these atoms possess perfect freedom of motion, and thus in general only when a substance passes from the fluid or gaseous to the solid state. Those instances in which the mere ignition, or the softening or moistening of a solid body, suffices to make the tendency of the molecules to a regular arrangement (crystal- lization) prevail over the diminished force of cohesion such as, for instance, the turning white and opaque of moistened barley-sugar are to be regarded as exceptional cases. To induce crystallization, the causes of the fluid or gaseous form of a substance must be removed. These causes are either heat alone, e.g., in the case of fused metals ; or solvents alone, as in the case of an aqueous solution of common salt ; or both combined, as in the case of a hot satu- rated solution of nitrate of potassa in water. In the first case we obtain crystals by cooling the fused mass ; in the second, by evaporating the menstruum ; and in the third by either of these means. The most frequently occurring case is that of crystallization by cooling hot saturated solutions. The liquors which remain after the separation of the crystals are called mother-waters, or mother-liquors. The term amorphous is applied to such solid bodies as have no crystalline form. We have recourse to crystallization generally either to obtain the crystallized substance in a solid form, or to separate it from other sub- stances dissolved in the same menstruum. In many cases also the form of the crystals or their deportment in the air, viz., whether they remain unaltered or effloresce, or deliquesce, upon exposure to the air, will afford an excellent means of distinguishing between bodies otherwise resembling each other ; for instance, between sulphate of soda and sulphate of potassa. The process of crystallization is usually effected in dishes, or, in the case of very small quantities, in watch-glasses. In cases where the quantity of fluid to be operated upon is only small, the surest way of getting well-formed crystals is to let the fluid evaporate in the air, or, better still, under a bell-glass, with an open vessel half-filled with concentrated sulphuric acid. Minute crystals are examined best with a lens, or under the microscope. 4. 3. PRECIPITATION. This operation differs from the preceding one in this much, that the dissolved body is converted to the solid state, not slowly and gradually, 6 FILTRATION. [ 5. but suddenly, no matter whether the substance separating is crystalline or amorphous, whether it sinks to the bottom of the vessel, or ascends, or remains suspended in the liquid. Precipitation is either caused by a modification of the solvent thus sulphate of lime (gypsum) separates immediately from its solution in water upon the addition of alcohol ; or it ensues in consequence of the separation of an educt insoluble in the menstruum thus when ammonia is added to a solution of sulphate of alumina, the latter salt is decomposed, and the alumina, not being soluble in water, precipitates. Precipitation takes place also when, by the action of simple or double chemical affinity, new compounds are formed which are insoluble in the menstruum ; thus oxalate of lime precipitates upon adding oxalic acid to a solution of acetate of lime \ chromate of lead upon mixing chromate of potassa with nitrate of lead. In decompositions of this kind, induced by simple or double affinity, one of the new compounds remains generally in solution, and the same is sometimes the case also with the educt ; thus in the instances just men- tioned the sulphate of ammonia, the acetic acid, and the nitrate of potassa, remain in solution. It may, however, happen also that both the product and the educt, or two products, precipitate, and that nothing remains in solution ; this is the case, for instance, when a solution of sulphate of magnesia is mixed with water of baryta, or when a solution of sulphate of silver is precipitated with chloride of barium. Precipitation is resorted to for the same purposes as crystallization, viz., either to obtain a substance in the solid form, or to separate it from other substances dissolved in the same menstruum. But in qualitative analysis we have recourse to this operation more particularly for the purpose of detecting and distinguishing substances by the color, pro- perties, and general deportment which they exhibit when precipitated either in an isolated state or in combination with other substances. The solid body separated by this process is called the precipitate, and the sub- stance which acts as the immediate cause of the separation is termed the precipitant. Various terms are applied to precipitates by way of par- ticularizing them according to their different nature ; thus we distin- guish crystalline, pulverulent, flocculent, curdy, gelatinous precipitates, &c. The terms turbid, turbidity, are made use of to designate the state of a fluid which contains a precipitate so finely divided and so inconsiderable in amount, that the suspended particles, although impairing the trans- parency of the fluid, yet cannot be clearly distinguished. The separation of flocculent precipitates may generally be promoted by a vigorous shake of the vessel ; that of crystalline precipitates, by stirring the fluid and rubbing the sides of the vessel with a glass rod ; elevation of tempera- ture is also an effective means of promoting the separation of most pre- cipitates. The process is therefore conducted, according to circumstances, either in test-tubes, flasks, or beakers. The two operations described respectively in 5 and 6, viz., filtration and decantation, serve to effect the mechanical separation of fluids from matter suspended therein. 5. 4. FILTRATION. This operation consists simply in passing the fluid from which we wish to remove the solid particles mechanically suspended therein through a 5.] FILTRATION. filtering apparatus, formed usually by a properly arranged piece of unsized paper placed in a funnel ; an apparatus of this description allows the fluid to trickle through with ease, whilst it completely retains the solid particles. We employ smooth filters and plaited filters ; the former in cases where the separated solid substance is to be made use of, the latter in cases where it is simply intended to clear the solution. Smooth filters are prepared by double-folding a circular piece of paper, with the folds at right angles ; they must in every part fit close to the funnel. The preparation of plaited filters is more properly a matter for ocular demonstration than for description. In cases where the contents of the filter require washing, the paper must not project over the rim of the funnel. It is in most cases advisable to moisten the filter previously to passing the fluid through it ; since this not only tends to accelerate the process, but also renders the solid particles less liable to be carried through the pores of the filter. The paper selected for filters must be as free as possible from inorganic substances, especially such as are dissolved by acids, e.g., sesquioxide of iron and lime. The common filtering paper of commerce seldom comes up to our wants in this respect, and I would therefore always recommend to wash it carefully with dilute hydrochloric acid whenever it is intended for use in accurate analyses. With the stronger sorts of paper this may be done by placing the paper cut in circular discs, in a layer of moderate thickness, in a shallow porcelain, dish, pouring over it a mixture of one part of hydrochloric acid or nitric acid with about nine parts of water, and letting it digest for several hours at a moderate heat. The fluid is then poured off, and the paper repeatedly washed with water (finally with distilled water), until litmus paper is no longer reddened by the washings : the water is then drained off, and the entire layer is carefully transferred to a quire of blotting- paper, and left there until they can be taken off singly without injury; they are then hung up to dry on lines in a place free from dust. With the finer sorts of paper (Swedish paper) I prefer washing the filters in the funnel. To this end they are first sprinkled with a little moderately diluted hydrochloric or nitric acid, and then thoroughly washed with Avater, finally with distilled water. Fil- tering paper, to be considered good, must, besides being pure, also let fluids pass readily through, whilst yet completely re- taining even the finest pulverulent preci- pitates, such as sulphate of baryta, oxalate of lime, &c. If a paper satisfying these requirements cannot be readily procured, it is advisable to keep two sorts, one of greater density for the separation of very finely divided precipitates, and one of greater porosity for the speedy separation of grosser particles. The funnels must be of glass or por- celain ( 14, 10); they are usually placed on an appropriate stand, to keep them in a fixed position. The stand shown in Fig. 1 is particularly well adapted for the reception of the small-sized funnels used in quali- tative analyses. Fig. 1. 8 DECANTATION. [ 6. 6. 5. DECANTATION. This operation is frequently resorted to instead of nitration, in cases where the solid particles to be removed are of considerably greater specific gravity than the liquid in which they are suspended ; as they will in such cases speedily subside to the bottom, thereby rendering it easy either to decant the supernatant fluid by simply inclining the vessel, or to draw it off by means of a syphon or pipette. In cases where nitration or decantation are resorted to for the purpose of obtaining the solid substance, the latter has to be freed afterAvards by repeated washing from the liquid still adhering to it. This operation is termed washing or edulcoration. The washing of precipitates collected on a filter is usually effected by means of a washing bottle, such as is shown in Fig. 2. Fig. 2. This washing bottle consists of a flask closed with a perforated cork, into which a small glass tube is fitted, with the outer end drawn out to a fine point. By blowing air into the flask through this tube and, when the air is sufficiently compressed, reversing the flask, so as to place the inner aperture of the tube under water, a tine jet of that fluid is ex- pelled with a certain degree of force ; this contrivance is well adapted for washing precipitates. Fig. 3 represents a washing bottle of a dif- ferent construction, which is used more especially to wash precipitates with boiling water, and affords also the advantage that it enables the operator to produce an uninterrupted jet of water. The drawing needs no explanation ; the outer end of the tube a is drawn out to a fine point. An India-rubber cap fitted with two tubes may be used instead of the double-perforated cork. There are four operations which serve to separate volatile substances from less volatile or from fixed bodies, viz., evaporation, distillation, ignition, and sublimation. The two former of these operations are ap- plied exclusively to fluids, the two latter exclusively to solids. 7, 8.] EVAPORATION. 9 7. 6. EVAPORATION. This operation is of very frequent occurrence. It serves to separate volatile fluids from less volatile or from fixed bodies (no matter whether solid or fluid), in cases where the residuary substance alone is of im- portance, whilst the evaporating matter is entirely disregarded ; thus, for instance, we have recourse to evaporation for the purpose of removing from a saline solution part of the water, in order to bring about crystal- lization of the salt ; we resort to this process also for the purpose of re- moving the whole of the water of the menstruum from the solution of a non-crystallizable substance, so as to obtain the latter in a solid form, &c. The evaporated water is entirely disregarded in either of these cases, the only object in view being to obtain, in the former case a more concentrated fluid, and in the latter a dry substance. These objects are invariably attained by converting the fluid which is to be removed to the gaseous state. This is generally done by the application of heat ; sometimes also by leaving the fluid for a certain time in contact with the atmosphere, or with an enclosed volume of air constantly kept dry by hygroscopic substances, such as concentrated sulphuric acid, chloride of calcium, crystallized Hg 2 0,N0 6 + 2 Preparation. Pour 1 part of pure nitric acid on 1 part of mercury, in a porcelain dish, and let the vessel stand twenty-four hours in a cool place ; separate the crystals formed from the undissolved mercury and the mother-liquor, and dissolve them in water mixed with one-sixteenth part of nitric acid, by trituration, in a mortar. Filter the solution, and keep the filtrate in a bottle, with metallic mercury covering the bottom of the vessel. Uses. Nitrate of suboxide of mercury acts in an analogous manner to the corresponding salt of silver. In the first place, it precipitates many acids, especially the hydracids ; and, in the second place, it serves for the detection of several readily oxidizable bodies, e. g., of formic acid, as the oxidation of such bodies, at the expense of the oxygen of the sub- oxide of mercury, is attended with the highly characteristic separation of metallic mercury. 67 69.] CHLORIDE OF MERCURY. 55 67. 6. CHLOKIDE OF MERCURY (Hg Cl). The chloride of mercury of commerce is sufficiently pure for the pur- pose of chemical analysis. For use, dissolve 1 part of the salt in 16 parts of water. Uses. Chloride of mercury gives with several acids, e. g., with hydri- odic acid, peculiarly colored precipitates, and may accordingly be used for the detection of these acids. It is an important agent for the detec- tion of tin, when that metal is in solution in the state of protochlo- ride ; if only the smallest quantity of that compound is present, the addition of chloride of mercury in excess to the solution is followed by separation of subchloride of mercury insoluble in water. In a similar manner chloride of mercury serves also for the detection of formic acid. 68. 7. SULPHATE OF COPPER (Cu 0, S 8 , crystallized Cu 0, S 8 , H + 4 aq.). Preparation. This reagent may be obtained in a state of great purity from the residue remaining in the retort in the process of preparing bisulphite of soda ( 46), by treating that residue with water, apply- ing heat, filtering, crystallizing, and purifying the salt by recrystal- lization. For use, dissolve 1 part of the pure crystals in 10 parts of water. Tests. Pure sulphate of copper must be completely precipitated from its solutions by hydrosulphuric acid ; ammonia and sulphide of ammo- nium must accordingly leave the nitrate unaltered. Uses. Sulphate of copper is employed in qualitative analysis to effect the precipitation of hydriodic acid in the form of subioclide of copper. For this purpose it is necessary to mix the solution of 1 part of sulphate of copper with 2^ parts of sulphate of protoxide of iron, otherwise half of the iodine will separate in the free state. The protoxide of iron changes, in this process, to sesquioxide, at the expense of the oxygen of the oxide of copper, which latter is thus reduced to the state of suboxide. Sulphate of copper is used also for the detection of arsenious and arsenic acid ; it serves, likewise, as a test for the soluble ferrocyanides. 69. 8. PROTOCHLORIDE OF TIN (Sn 01, crystallized Sn Cl + 2 aq.). Preparation. Reduce English tin to powder by means of a file, or fuse it in a small porcelain dish, remove from the fire, and triturate the fused liquid mass with a pestle until it has passed again to the solid state ; boil the powder for some time with concentrated hydrochloric acid in a flask (taking care always to have an excess of tin) until no more hydrogen gas is evolved ; dilute the solution with 4 times the quantity of water slightly acidulated with hydrochloric acid, and filter. Keep the filtrate for use in a well-stoppered bottle containing small pieces of metallic tin, or some pure tin-foil. If these precautions are neglected, the protochloride will soon change to bichloride, which will, of course, render the reagent totally unfit for the purpose for which it is intended. Tests. Solution of protochloride of tin, when added to a solution of 56 BICHLORIDE OF PLATINUM. [ 70 72. chloride of mercury, must immediately produce a white precipitate of sub- chloride of mercury ; when treated with hydrosulphuric acid, it must give a dark brown precipitate ; it must not be precipitated nor rendered turbid by sulphuric acid. Uses. The great tendency of protochloride of tin to absorb oxygen, and thus to form binoxide, or rather bichloride as the binoxide, in the moment of its formation, decomposes with the free hydrochloric acid pre- sent makes this substance one of our most powerful reducing agents. We employ it in the course of analysis as a test for mercury, and also to effect the detection of gold, for which latter purpose it is previously mixed with some nitric acid, without heat. ^7 f\ 70. 9. BICHLORIDE OF PLATINUM (Pt C1 2 , crystallized Pt Cl a + 10 aq.). Preparation. Treat platinum filings purified by boiling with nitric acid, with concentrated hydrochloric acid and some nitric acid, in a narrow-necked flask, and apply a very gentle heat, adding occasionally fresh portions of nitric acid, until the platinum is completely dissolved. Evaporate the solution to dryness on the water-bath, with addition of hydrochloric acid, and dissolve the residue in 1 parts of water for use. Tests. Bichloride of platinum must, upon evaporation to dryness in the water-bath, leave a residue which dissolves completely in spirit of wine. Uses. Bichloride of platinum forms very sparingly soluble double salts with chloride of potassium and chloride of ammonium, but not so with chloride of sodium ; it serves, therefore, to detect ammonia and potassa, and is, indeed, almost our most delicate reagent for the latter substance. 71. 10. SODIO-PROTOCHLORIDE OF PALLADIUM (NaCl, PdCl). Dissolve 5 parts of palladium in nitrohydrochloric acid (comp. 70), add 6 parts of pure chloride of sodium, evaporate in the water-bath to dryness, and dissolve 1 part of the residuary double salt in 12 parts of water for use. The brownish solution forms an excellent means of detecting and separating iodine. 72. 11. TERCHLORIDE OF GOLD (AuCl 2 ). Preparation. Take fine shreds of gold, which may be alloyed with silver or copper, treat them in a flask with nitrohydrochloric acid in excess, and apply a gentle heat until no more of the metal dissolves. If the gold was alloyed with copper, which is known by the brownish-red precipitate produced by ferrocyanide of potassium in a portion of the solution diluted with water, mix it with solution of sulphate of pro- toxide of iron in excess ; this will reduce the terchloride to metallic gold, which will separate in the form of a fine brownish-black powder ; wash the powder in a small flask, and redissolve it in nitrohydrochloric acid ; evaporate the solution to dryuess on the water-bath, and dissolve the residue in 30 parts of water. If the gold was alloyed with silver, the latter metal remains as chloride upon treating the alloy with nitro- hydrochloric acid. In that case evaporate the solution at once to dryness, and dissolve in water for use. 73.] TEST PAPERS. 57 Uses. Terchloride of gold has a great tendency to yield up its chlorine ; it therefore readily converts protochlorides into higher chlorides, protoxides, with the co-operation of water, into higher oxides. These peroxidations are usually indicated by the precipitation of pure metallic gold in the form of a brownish-black powder. In the course of analysis this reagent is used only for the detection of protoxide of tin, in the solu-tions of which it produces a purple color or a purple pre- cipitate. Y. COLORING MATTERS AND INDIFFERENT VEGETABLE SUBSTANCES. 73. 1. TEST PAPERS. a. BLUE LITMUS PAPER. Preparation. Digest 1 part of litmus of commerce with 6 parts of water, and filter the solution ; divide the intensely blue filtrate into 2 equal parts ; saturate the free alkali in the 1 part, by re- peatedly stirring with a glass rod dipped in very dilute sulphuric acid, until the colour of the fluid just appears red ; add now the other part of the blue filtrate, pour the whole fluid into a dish, and draw strips of fine unsized paper through it ; suspend these slips over threads and leave them to dry. The color of litmus paper must be perfectly uniform, and neither too light nor too dark. Uses. Litmus paper serves to detect the presence of free acid in fluids, as acids change its blue color to red. It must be borne in mind, however, that the soluble neutral salts of most of the heavy metallic oxides produce the same effect. j3. REDDENED LITMUS PAPER. Preparation. Stir blue solution of litmus with a glass rod dipped in dilute sulphuric acid, and repeat this process until the fluid has just turned distinctly red. Steep slips of paper in the solution, and dry them as in a. The dried slips must look distinctly red. Uses. Pure alkalies and alkaline earths, and also the sulphides of their metals, restore the blue color of reddened litmus paper ; alkaline carbonates and the soluble salts of several other weak acids, especially of boracic acid, possess the same property. This reagent serves therefore for the detection of these bodies in general.* y. GEORGIKA. PAPER (Dahlia Paper). Preparation. Boil the violet-colored petals of Georgina purpurea (purple dahlia) in water, or digest them with spirit of wine, and steep slips of paper in the tincture obtained. The latter should be neither more nor less concentrated than is necessary to make the paper, after drying, appear of a fine and light violet blue color. Should the color too much incline to red, this may be remedied by adding a very little ammonia to the tincture. * Mr. A. S. Taylor has suggested that a very delicate test paper for detecting alkalies may be prepared by steeping slips of paper in an acid infusion of rose petals. 53 TURMERIC PAPEE. [ 74, 75. Uses. Georgina paper is reddened by acids, whilst alkalies impart a beautiful green tint to it. It is therefore an extremely convenient sub- stitute both for the blue and the reddened litmus paper. This reagent, if properly prepared, is a most delicate test both for acids and alkalies. Concentrated solutions of caustic alkalies turn Georgina paper yellow, by destroying the coloring matter. 8. TURMERIC PAPER, Preparation. Digest and heat 1 part of bruised turmeric root with 6 parts of weak spirit of wine, filter the tincture obtained, and steep slips of fine paper in the filtrate. The dried slips must exhibit a fine yellow tint. Uses. Turmeric paper serves, like reddened litmus paper and dahlia paper, for the detection of free alkalies, &c., as they change its yellow color to brown. It is not quite so delicate a test as the other reagent papers ; but the change of color which it produces is highly characteristic, and is very distinctly perceptible in many colored fluids ; we cannot well dispense, therefore, with this paper. When testing with turmeric paper, it is to be borne in mind that, besides the substances enumerated in /3, several other bodies (boracic acid, for instance) possess the property of turning its yellow color to brown -red. It affords an excellent means for the detection of the latter substance. All test papers are cut into slips, which are kept in small well- closed boxes, or in bottles covered with black paper, as continued action of light destroys the color. 74. 2. SOLUTION OF INDIGO. Preparation. Take from 4 to 6 parts of fuming sulphuric acid, add slowly, and in small portions at a time, 1 part of finely pulverized indigo, taking care to keep the mixture well stirred. The acid has at first imparted to it a brownish tint by the matter which the indigo con- tains in admixture, but it subsequently turns deep blue. Elevation of temperature to any considerable extent must be avoided, as part of the indigo is thereby destroyed ; it is therefore advisable, when dissolving larger quantities of the substance, to place the vessel in cold water. When the whole of the indigo has been added to the acid, cover the vessel, let it stand forty-eight hours, then pour its contents into 20 times the quantity of water, mix, filter, and keep the filtrate for use. Uses. Indigo is decomposed by boiling with nitric acid, yellow- colored oxidation products being formed. It serves, therefore, for the detection of nitric acid. Solution of indigo is also well adapted to effect the detection of chloric acid and of free chlorine. B. REAGENTS IN THE DRY WAY. I. FLUXES AND DECOMPOSING AGENTS. 75. 1. MIXTURE OF CARBONATE OF SODA AND CARBONATE OF POTASSA (NaO,C0 2 + KO,C0 2 ). Preparation. Digest 10 parts of purified bitartrate of potassa in powder with 10 parts of water and 1 part of hydrochloric acid for 75.] CARBONATE OF SODA AND POTASSA. 59 several hours on the water-bath, with frequent stirring ; put the mass into a funnel with a small filter inserted into the pointed end ; let it drain ; cover with a disc of rather difficultly permeable filtering paper with upturned edges, and wash by repeatedly pouring upon this small quantities of cold water ; continue this washing process until the fiuid running off is no longer rendered turbid by solution of nitrate of silver, after addition of nitric acid. Dry the bitartrate of potassa freed in this manner from lime (and phosphoric acid). It is now necessary to prepare pure nitrate of potassa. To effect this, dissolve nitrate of potassa of commerce in half its weight of boiling water, filter the solution into a porcelain or stoneware dish, using a hot funnel, and stir it well with a wooden or porcelain spatula until cold. Transfer the crystalline powder to a funnel loosely stopped with cotton, let it drain, press down tight, make it even at the top, and cover with a double disc of difficultly permeable filtering paper with upturned edges, and pour upon this at proper intervals small portions of water, until the washings are no longer made turbid by solution of nitrate of silver. Empty now the contents of the funnel into a porcelain dish, dry in this vessel, and reduce the mass to a fine powder by trituration. Mix now 2 parts of the pure bitartrate of potassa with 1 part of the pure nitrate of potassa ; put the perfectly dry mixture in small portions at a time into a clean- scoured cast-iron pot heated to gentle redness ; when the mixture has deflagrated, heat strongly, until a sample taken from the edges gives with water a per- fectly colorless solution. Triturate the charred mass with water, filter, wash slightly, and evaporate the filtrate in a porcelain or, better still, in a silver dish, until the fluid is covered with a persistent pellicle. Let the mixture now cool, with constant stirring ; put the crystals of car- bonate of potassa on a funnel, let them well drain, wash slightly, dry thoroughly in a silver or porcelain dish, and keep the crystals in a well- stoppered bottle. The mother-liquor leaves, upon evaporation, a salt which, though containing traces of alumina and silicic acid, may still be turned to account for many purposes. Mix 13 parts of the pure carbonate of potassa prepared in the manner just now described, with 10 parts of pure anhydrous carbonate of soda, and keep the mixture in a well-stoppered bottle. The mixture of carbonate of potassa and carbonate of soda may also be prepared by deflagrating 20 parts of pure bitartrate of potassa with 9 parts of pure nitrate of soda, treating with water, and evaporating the solution to dryness. Tests. The purity of the mixed salt is tested as directed 44 (car- bonate of soda). Uses. If silicic acid or silicates are fused with about 4 parts (con- sequently with an excess) of carbonate of potassa or soda, carbonic acid escapes with effervescence, and a basic alkaline silicate is formed, which, being soluble in water, may be readily separated from such metallic oxides as it may contain in admixture ; from this basic alkaline silicate, hydrochloric acid separates the silicic acid as hydrate. If a fixed alkaline carbonate is fused together with sulphate of baryta, strontia, or lime, there are formed carbonates of the alkaline earths and sulphate of the alkali, in which new compounds both the base and the acid of the originally insoluble salt may now be readily detected. However, we do not employ carbonate of potassa separately, nor carbonate of soda, to effect the decomposition of the insoluble silicates and sulphates ; but we 60 HYDRATE OP BARYTA. [ 76 78. apply for this purpose the above-described mixture of both, because this mixture requires a far lower degree of heat for fusion than either of its two components, and thus enables us to conduct the operation over a Berzelius lamp, or over a simple gas lamp. The fusion with alkaline carbonates is invariably effected in a platinum crucible, provided no reducible metallic oxides be present. 76. 2. HYDEATE OF BARYTA (Ba 0, H 0). Preparation. The crystals of baryta prepared in the manner directed 32, are heated gently in a silver or platinum dish, until the water of crystallization is completely expelled. The residuary white mass is pulverized, and kept for use in a well-closed bottle. Uses. Hydrate of baryta fuses at a gentle red heat without losing its water. Upon fusing silicates together with about 4 parts of hy- drate of baryta, a basic silicate of baryta is formed, and the oxides are liberated. If the fused mass is treated with hydrochloric acid, the solu- tion evaporated to dryness, and the residue digested with hydrochloric acid, the silicic acid is left behind, and the oxides are obtained in solu- tion in the form of chlorides. We use hydrate of baryta as a flux when we wish to test silicates for alkalies. This reagent is preferable as a flux to the carbonate or nitrate of baryta, since it does not require a very high temperature for its fusion, as is the case with the carbonate, nor does it cause any spirting in the fusing mass, arising from disengage- ment of gas, as is the case with the nitrate. The operation is conducted in silver or platinum crucibles. 77. 3. FLUORIDE OF CALCIUM (Ca Fl). Take fluor-spar as pure as can be procured, and more particularly free from alkalies, reduce to fine powder, and keep this for use. Uses. Fluoride of calcium applied in conjunction with sulphuric acid, serves to effect the decomposition of silicates insoluble in acids, and more especially to detect the alkalies which they contain. Compare Section III. Silicic acid, 150. 78. 4. NITRATE OF SODA (Na 0, N0 6 ). Preparation. Neutralize pure nitric acid with pure carbonate of soda exactly, and evaporate to crystallization. Dry the crystals thoroughly, triturate, and keep the powder for use. Tests. A solution of nitrate of soda must not be made turbid by solution of nitrate of silver or nitrate of baryta, nor precipitated by carbonate of soda. Uses. Nitrate of soda serves as a very powerful oxidizing agent, by yielding oxygen to combustible substances when heated with them. We use this reagent principally to convert several metallic sulphides, and more particularly the sulphides of tin, antimony, and arsenic, into oxides and acids; and also to effect the rapid and complete combustion of organic substances ; for the latter purpose, however, nitrate of ammonia 79j 80.] CARBONATE OF SODA. 61 is in many cases preferable ; this latter reagent is prepared by saturating nitric acid with carbonate of ammonia. II. BLOWPIPE REAGENTS. 79. 1. CARBONATE OF SODA (Na 0, C 2 ). Preparation. See 44. Uses. Carbonate of soda serves, in the first place, to promote the reduction of oxidized substances in the inner flame of the blowpipe. In fusing it brings the oxides into the most intimate contact with the char- coal support, and enables the flame to embrace every part of the substance under examination. It co-operates in this process also chemically by the transposition of its constituents (according to R. Wagner, in consequence of the formation of cyanide of sodium). If the quantity operated upon was very minute, the reduced metal is often found in the pores of the charcoal. In such cases, the parts surrounding the little cavity which contained the sample are dug out with a knife, and triturated in a small mortar ; the charcoal is then washed off from the metallic particles, which now become visible either in the form of powder or as small flat spangles, according to the nature of the particular metal or metals present. Carbonate of soda serves, in the second place, as a solvent. Platinum wire is the most convenient support for testing the solubility of substances in fusing carbonate of soda. A few only of the bases dissolve in fusing carbonate of soda, but acids dissolve in it with facility. Carbonate of soda is, moreover, applied as a decomposing agent and flux, and more par- ticularly to effect the decomposition of the insoluble sulphates, with which it exchanges acids, the newly formed sulphate of soda being reduced at the same time to sulphide of sodium ; and to effect the decomposition of sulphide of arsenic, with which it forms a double sulphide of arsenic and sodium, and arsenite or arsenate of soda, thus converting it to a state which permits its subsequent reduction by hydrogen. Finally, carbonate of soda is the most sensitive reagent in the dry way for the detection of manganese, since when fused in the outer flame of the blowpipe together with a substance containing manganese, it produces a green opaque bead, owing to the formation of manganate of soda. 80. 2. CYANIDE OF POTASSIUM (K Cy). Preparation. See 52. Uses. Cyanide of potassium is an exceedingly powerful reducing agent in the dry way ; indeed it excels in its action almost all other reagents of the same class, and separates the metals not only from most oxygen com- pounds, but also from sulphur compounds : this reduction is attended in the former case with formation of cyanate of potassa, by the absorption of oxygen, and in the latter case with formation of sulphocyanide of potassium. By means of this reagent we may effect the reduction of metals from their compounds with the greatest possible facility ; thus we may, for instance, produce metallic antimony from antimonious acid or from sulphide of antimony, metallic iron from sesquioxide of iron, &c. 62 BIBORATE OF SODA. [ 81. The readiness with which cyanide of potassium enters into fusion facili- tates the reduction of the metals greatly ; the process may usually be conducted even in a porcelain crucible over a spirit lamp. Cyanide of potassium is a most valuable and important agent to effect the reduction of arsenites and arsenates, and more particularly of tersulphide of arsenic (see 131). Cyanide of potassium is equally important as a blowpipe reagent. Its action is exceedingly energetic ; substances like binoxide of tin, bisulphide of tin, &c., the reduction of which by means of car- bonate of soda requires a tolerably strong flame, are reduced by cyanide of potassium with the greatest facility. In blowpipe experiments we in- variably use a mixture of equal parts of carbonate of soda and cyanide of potassium ; the admixture of carbonate of soda is intended here to check in some measure the excessive fusibility of the cyanide of potas- sium. This mixture of cyanide of potassium with carbonate of soda, besides being a far more powerful reducing agent than the simple car- bonate of soda, has, moreover, this great advantage over the latter, that it is absorbed by the pores of the charcoal with extreme facility, and thus permits the production of the metallic globules in a state of the greatest purity. si. 3. BIBOKATE OF SODA (Sorax) (Na 0, 2 B O 3 , crystallized +10 aq.). The purity of commercial borax may be tested by adding to its solu- tion carbonate of soda, or after previous addition of nitric acid, solu- tion of nitrate of baryta or of nitrate of silver. The borax may be considered pure if these reagents fail to produce any alteration in the solution ; but if either of them causes the formation of a precipitate, or renders the fluid turbid, recrystallization is necessary. The pure crys- tallized borax is exposed to a gentle heat, in a platinum crucible, until it ceases to swell ; when cool, it is pulverized and kept for use. Uses. Boracic acid manifests a great affinity for oxides when brought into contact with them in a state of fusion. This affinity enables it, in. the first place, to combine directly with oxides ; secondly, to expel weaker acids from their salts ; and, thirdly, to predispose metals, sul- phides, and haloid compounds to oxidize in the outer flame of the blow- pipe, that it may combine with the oxides. Most of the thus produced borates fuse readily, even without the aid of a flux, but far more so in conjunction with borate of soda ; the latter salt acts in this operation either as a mere flux, or by the formation of double salts. Now, in the biborate of soda we have both free boracic acid and borate of soda ; the union of these two substances renders it one of our most important blow- pipe reagents. In the process of fluxing with borax, we usually select platinum wire for a support ; the loop of the wire is moistened or heated to redness, then dipped into the powder, and exposed to the outer flame ; a colourless bead of fused borax is thus produced. A small portion of the substance under examination is then attached to the bead, by bring- ing the latter into contact with it, either whilst still hot or having previously moistened it. The bead with the sample of the substance intended for analysis adhering to it, is now exposed to the blowpipe flame, and the phenomena to the manifestation of which this process gives rise are carefully observed and examined. The following points ought to be more particularly watched: (1) Whether or not the sample under examination dissolves to a transparent bead, and whether or not the bead retains its transparency on cooling ; (2) whether the bead exhibits a dis- 82, S3.] PHOSPHATE OF SODA AND AMMONIA. 63 tinct color, which in many cases at once clearly indicates the individual metal which the analysed compound contains, as is the case, for instance, with cobalt ; and (3) whether the bead manifests the same or a different deportment in the outer and in the inner flame. Phenomena of the latter kind arise from the ensuing reduction of higher to lower oxides, or even to the metallic state, and are for some substances particularly characteristic. 82. 4. PHOSPHATE OF SODA AND AMMONIA (Microcosmic Salt) (Na O, N H 4 O, H O, P 5 , crystallized + 8 aq.). Preparation. Heat to boiling 6 parts of phosphate of soda and 1 part of pure chloride of ammonium with 2 parts of water, and let the solution cool. Free the crystals produced of the double phosphate of soda and ammonia by recrystallization from the chloride of sodium which adheres to them. Dry the purified crystals, and pulverize them for use. Uses. When phosphate of soda and ammonia is subjected to the action of heat, the ammonia escapes with the water of crystallization, and readily fusible metaphosphate of soda is left behind. The action of microcosmic salt is quite analogous to that of biborate of soda. We prefer it, however, in some cases, to borax as a solvent or flux, the beads which it forms with many substances being more beautifully and dis- tinctly colored than those of borax. Platinum wire is also used for a support in the process of fluxing with microcosmic salt ; the loop of the wire must be made small and narrow, otherwise the bead will not adhere to it. The operation is conducted as directed in the preceding para- graph. 83. 5. NITRATE OP PROTOXIDE OF COBALT (Co 0, N 5 , crystallized + 5 aq.). Preparation. Fuse in a Hessian crucible 3 parts of bisulphate of potassa, and add to the fused mass, in small portions at a time, 1 part of well roasted cobalt ore (the purest zaffre you can procure) reduced to fine powder. The mass thickens, and acquires a pasty consistence. Heat now more strongly, until it has become more fluid again, and continue to apply heat until the excess of sulphuric acid is completely expelled, and the mass accordingly no longer emits white fumes. Remove the fused mass now from the crucible with an iron spoon or spatula, let it cool, and reduce it to powder ; boil this with water until the undissolved portion presents a soft mass ; then filter the rose-red solution, which is free from arsenic and nickel, and mostly also from iron, and remove the copper, &c., from the filtrate by means of hydrosulphuric acid. Filter again, and evaporate the filtrate, with addition of some chlorine water, until it is much concentrated. Mix the concentrated filtrate now with a hot saturated solution of binoxalate of potassa, and let the mixture stand at a gentle heat until the fluid appears colorless. Wash the precipitated oxalate of protoxide of cobalt thoroughly, dry, and heat to redness in a covered platinum or porcelain crucible. This decomposes the oxalate into water and carbonic acid, which escapes, and metallic cobalt, which is left behind. Dissolve a portion of the latter in nitric acid, taking care to avoid a large excess of the solvent ; evaporate the solution in the water-bath to dryness, and dis- solve 1 part of the residue in 10 parts of water for use. 64 CHLORIDE OP SILVER. [ 84, 85. Tests. Solution of nitrate of protoxide of cobalt must be free from other metals, and especially also from salts of the alkalies ; when pre- cipitated with sulphide of ammonium and filtered, the filtrate must, upon evaporation on platinum, leave no fixed residue. jj ses , Protoxide of cobalt forms, upon ignition with certain infusible bodies, peculiarly colored compounds, and may accordingly serve for the detection of these bodies (oxide of zinc, alumina, and magnesia ; see Section III.). 84. 6. CHLOEIDE OF SILVER (Ag Cl). Preparation. Precipitate solution of nitrate of silver with hydro- chloric acid ; wash the precipitate, mix it with water to a thick pulp, and keep in a small bottle for use. Uses. Chloride of silver has lately been recommended by Gericke as a means of making the colorations more distinct and lasting which certain bodies, upon exposure to the inner blowpipe flame, impart to the outer flame. I can from my own experience confirm the results arrived at by Gericke. The action of the chloride of silver is owing to the cir- cumstance that this compound loses its chlorine only gradually upon exposure to heat, and gives rise accordingly for a certain time to the formation of metallic chlorides, which it is well known impart more distinct colorations to flame than any other class of salts. As platinum wire would speedily be rendered unfit for use by the reduced silver, thin iron wire is employed ; every operation requires a new loop. SECTION III. ON THE DEPORTMENT OF BODIES WITH REAGENTS. 85. I STATED in my introductory remarks that the operations and experi- ments of qualitative analysis have for their object the conversion of the unknown constituents of any given compound into forms of which we know the deportment, relations, and properties, and which will accord- ingly permit us to draw correct inferences regarding the several con- stituents of which the analysed compound consists. The greater or less value of such analytical experiments, like that of all other inquiries and investigations, depends upon the greater or less degree of certainty with which they lead to definite results, no matter whether of a positive or negative nature. But as a question does not render us any the wiser if we do not know the language in which the answer is returned, so, in like manner, will analytical investigations prove unavailing if we do not understand the mode of expression in which the desired information is conveyed to us ; in other words, if we do not know how to interpret the phenomena produced by the action of our reagents upon the substance examined. Before we can therefore proceed to enter upon the practical investiga- 86.] METALLIC OXIDES AND THEIR RADICALS. 65 tions of analytical chemistry, it is indispensable that we should really possess the most perfect knowledge of the deportment, relations, and properties of the new forms into which we intend to convert the sub- stances we wish to analyse. Now, this perfect knowledge consists, in the first place, in a clear conception and comprehension of the condi- tions necessary for the formation of the new compounds and the manifestation of the various reactions; and, in the second place, in a distinct impression of the color, form, and physical properties which characterize the new compound. This section of the work demands therefore not only the most careful and attentive study, but requires moreover that the student should examine and verify by actual experiment every fact asserted in it. The method usually adopted in elementary works on chemistry is to treat of the various substances and their deportment with reagents in- dividually 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 arrange those substances which are in many respects analogous into groups, and thus, by com- paring their analogies with their differences, to place the latter in the clearest possible light. A. DEPORTMENT AND PROPERTIES OF THE METALLIC OXIDES AND OF THEIR RADICALS. 86. Before proceeding to the special study of the several metallic oxides, I give here a general view of the whole of them, classified in groups showing which oxides belong to each group. The grounds upon which the classification has been arranged will appear from the special con- sideration of the several groups. First group Potassa, soda, ammonia (lithia). Second group Baryta, strontia, lime, magnesia. Third group Alumina, sesquioxide of chromium (glucina, thorina, noria, yttria, terbia, erbia, zirconia earths ; oxides of cerium, lanthanium, didymium ; oxide of titanium and titanic acid ; tantalic acid, niobic acid). Fourth group s * ; Oxides of zinc, manganese, nickel, cobalt, iron (uranium). Fifth group Oxides of silver, mercury, lead, bismuth, copper, cadmium (palladium, rhodium, osmium, ruthenium). Sixth group Oxides and acids of antimony, tin, arsenic, gold, platinum (iridium, molybdenum, tellurium, tungsten, vanadium). Of these metallic oxides only those printed in italics are found exten- sively and in large quantities in that portion of the earth's crust which is accessible to our investigations ; these, therefore, are most important to chemistry, arts and manufactures, agriculture, pharmacy, &c. &c. ; and these therefore we shall dwell upon at greater length. The more important among the remainder are more briefly considered in sup- plementary paragraphs; and the less important ones are altogether i. F 66 POTASSA, SODA, AMMONIA. [ 87, 88. omitted. The deportment of the metals I have given only in the case of tiiose that are more frequently met with in analytical operations in the metallic state. 87. FIRST GROUP. POTASSA, SODA, AMMONIA. Properties of the group. The alkalies are readily soluble in water, as well in the pure or caustic state as in the form of sulphides, carbonates, and phosphates. Accordingly they do not precipitate one another in the pure state, nor as carbonates or phosphates, nor are they precipitated by hydrosulphuric acid under any condition whatever. Tbe solutions of the pure alkalies, as well as of their sulphides and carbonates, restore the blue color of reddened litmus-paper, and impart an intensely brown tint to turmeric paper. Special Reactions. 88. a. POTASSA (K 0). 1. Potassa and its hydrate and salts are not volatile at a faint red- heat. Potassa and its hydrate deliquesce in the air ; the oily liquids formed do not solidify by absorption of carbonic acid. 2. Nearly the whole of the salts of potassa are readily soluble in water. They are colorless, if the constituent acid is so. The neutral salts of potassa with strong acids do not alter vegetable colors. Carbonate of potassa crystallizes with difficulty, and deliquesces in the air. Sulphate of potassa is anhydrous, and suffers no alteration in the air. 3. Bichloride of platinum produces in the neutral and acid solutions of the salts of potassa a yellow, crystalline, heavy precipitate of BICHLO- RIDE OP PLATINUM AND CHLORIDE OF POTASSIUM (potassio-Uchloride of platinum) (K 01, Pt C1 2 ). In concentrated solutions this precipitate separates immediately upon the addition of the reagent : in dilute solu- tions it forms only after some time, often after a considerable time. Yery dilute solutions are not precipitated by the reagent. The preci- pitate consists of octahedrons discernible under the microscope. Alka- line solutions must be acidified with hydrochloric acid before the bi- chloride of platinum is added. The precipitate is difficultly soluble in water ; the presence of free acids does not greatly increase its solubility ; it is insoluble in alcohol. Bichloride of platinum is therefore a par- ticularly delicate test for salts of potassa dissolved in spirit of wine. The best method of applying this reagent is to evaporate the aqueous solution of the potassa salt with bichloride of platinum nearly to dryness on the water-bath, and to pour a little water on the residue, or, better still, some spirit of wine, provided no substances insoluble in that menstruum be present : the potassio-bichloride of platinum is left un- dissolved. Care must be taken not to confound this double salt with ammonio-bichloride of platinum, which greatly resembles it (see 90, 4). 4. Tartaric acid produces in neutral or alkaline* solutions of salts of potassa a white, quickly subsiding, granular crystalline precipitate of * In the case of alkaline solutions, the reagent must be added until the fluid shows a strongly acid reaction. 89.] SODA. 67 BITABTRATE OF POTASSA (K 0, H 0, C H 4 OJ. In concentrated solu- tions this precipitate separates immediately ; in dilute solutions often only after the lapse of some time. Yigorous shaking or stirring of the fluid promotes its formation considerably. Very dilute solutions are not precipitated by this reagent. Free alkalies and free mineral acids dis- solve the precipitate ; it is difficultly soluble in cold, but pretty readily soluble in hot water. In the case of acid solutions, the free acid must, if practicable, first be expelled by evaporation and ignition, or the solution must be neutralized with soda or carbonate of soda, before we can pro- ceed to test for potassa with tartaric acid. 5. If a salt of potassa, more particularly chloride of potassium, is held on a platinum wire in the apex of the inner blowpipe flame, the outer flame acquires a VIOLET color. The tint which phosphate and borate of potassa impart to the outer blowpipe flame is scarcely perceptible. Presence of a salt of soda completely obscures the reaction. Decre- pitating salts are pulverized and made to adhere to the wire with water. Addition of chloride of silver promotes the reaction in the case of nitrate, carbonate, &c., of potassa ( 84). 6. If a salt of potassa (more particularly chloride of potassium) is heated with a small quantity of water, alcohol (burning with colorless flame) added, heated, and then kindled, the flame appears VIOLET. The presence of soda obscures this reaction, 89. 6. SODA (NaO). 1. Soda and its hydrate and salts present in general the same deport- ment and properties as potassa and its corresponding compounds. The oily fluid which soda forms by deliquescing in the air, resolidifies speedily by absorption of carbonic acid. Carbonate of soda crystallizes readily ; the tabular crystals (Na 0, C O 2 + 10 aq.) effloresce rapidly when ex- posed to the air. The same applies to the prismatic crystals of sulphate of soda (Na 0, S O 3 + 10 aq.). 2. Antimonate of potassa produces in neutral or feebly alkaline solu- tions of salts of soda a white, crystalline precipitate of METANTIMONATE OF SODA (Na O, Sb O 6 + 7 aq.). Yigorous shaking of the mixture pro- motes its formation. If the fluid, after the addition of the reagent, be stirred with a glass rod, moving the latter along the sides of the vessel, the lines described will, even in very dilute solutions, speedily become visible, since the precipitate forms first on the parts rubbed by the rod. If the precipitate separates slowly, it consists of well- formed microscopic quadrilateral octahedrons. The presence of neutral salts of potassa interferes only slightly with the formation of the preci- pitate ; but carbonate of potassa, when present in larger proportion, wholly prevents its separation from more dilute solutions. In cases, therefore, where the solution under examination contains this salt, it is necessary to precede the application of the antimonate of potassa by addition of hydrochloric or acetic acid until the reaction of the solution remains only feebly alkaline. Acid solutions must first be neutralized with potassa, since otherwise the reagent would suffer decomposition, and hydrated antimonic acid or acid antimonate of potassa be precipi- tated from it. 3. Salts of soda (more particularly chloride of sodium), when exposed F 2 68 AMMONIA. [ 90. on a platinum wire to the inner blowpipe flame, color the outer flame INTENSELY YELLOW. This reaction remains clearly perceptible, even if the soda contains a considerable admixture of potassa. Chloride of silver promotes the reaction in the case of some, but not of all salts of soda. 4. If a salt of soda (more particularly chloride of sodium) is heated with a small quantity of water, alcohol added, and the latter heated and then kindled, the flame appears strongly YELLOW. The presence of a salt of potassa does not impair the distinctness of this reaction. 5. Bichloride of platinum produces no precipitate in solutions of salts of soda ; tartaric acid only when a highly concentrated solution of soda or carbonate of soda is mixed with a saturated solution of tartaric acid in excess. The bulky precipitate of BITARTRATE OF SODA which in that case separates, consists of small needles and columns, and requires only 12 parts of cold water for its solution ; it is not likely, therefore, to be confounded with the granular crystalline precipitate of bitartrate of potassa. 90. c. AMMONIA (NH 4 0). 1. Anhydrous ammonia (N H~ 3 ) is gaseous at the common temperature ; but we have most frequently to deal with it in its aqueous solution, in which it betrays its presence at once by its penetrating odor. It is expelled from this solution by the application of heat. It may be assumed that the solution contains it as oxide of ammonium (N H 4 0) (see 31). 2. All the salts of ammonia are volatile at a high temperature, either with or without decomposition. Most of them are readily soluble in water. The solutions are colorless. The neutral compounds of ammonia with strong acids do not alter vegetable colors. 3. If salts of ammonia are triturated together with hydrate of lime, best with the addition of a few drops of water, or are, either in a solid form or in solution, heated with solution of potassa or of soda, the ammonia is liberated in the gaseous state, and betrays itself ( 1 ) by its characteristic odor ; (2) by its reaction on moistened test-papers ; and (3) by giving rise to the formation of white fames, when any object (e.g., a glass rod) moistened with hydrochloric acid, nitric acid, acetic acid, or any of the volatile acids, is brought in contact with it. These fumes arise from the formation of solid ammoniacal salts produced by the con- tact of the gases in the air. Hydrochloric acid is the most delicate test in this respect ; acetic acid, however, admits less readily of a mistake. In cases where the quantity of ammonia present is only very small, the best way of testing the alkaline reaction of the fumes is to cover a small beaker containing the mixture with a watch-glass, having a slip of moistened turmeric or reddened litmus-paper attached to the convex side, to place it on a hot slab, and observe, after a few minutes, whether the test-paper has changed color. 4. Bichloride of platinum shows the same deportment with salts of ammonia as with salts of potassa ; the yellow precipitate of BICHLORIDE OF PLATINUM AND CHLORIDE OF AMMONIUM (N H 4 Cl, Pt C1 2 ) is. however, of a somewhat lighter color than potassio-bichloride of platinum. It consists, like the corresponding potassium compound, of octahedrons, dis- cernible under the microscope. 5. Tartaric acid added in excess to a solution of ammonia or carbonate 91.] RECAPITULATION. 69 of ammonia, produces a white crystalline precipitate of BITARTRATE OF AMMONIA (N H 4 H O, C 8 H 4 10 ). In concentrated solutions this preci- pitate forms immediately ; in dilute solutions only after some time. The solutions of other ammoniacal salts (chloride of ammonium, nitrate of ammonia, &c.) are not precipitated by this reagent, even when highly concentrated ; or a trifling precipitate only separates after long stand- ing. Bitartrate of ammonia comports itself with solvents like the corre- sponding salt of potassa; however, it is some what "more readily soluble in water and acids than the latter. 6. If a solution of potassio-iodide of mercury* containing much caustic potassa, is mixed with a fluid containing ammonia or an ammo- niacal salt, a reddish-brown precipitate of hydrated TETRAHYDRARGYRO- IODIDE OF AMMONIUM (N HgJ + 2 H 0) : 4 (Hg I, K I) + 3 K O + N H 3 = (N Hg 4 1+ 2HO) + 7K1 + HO, separates immediately or upon ap- plication of a gentle heat. This precipitate redissolves in presence of an excess of ammoniacal salts ; but reprecipitates upon further addition of potassa ; it is soluble also in solution of iodide of potassium, but the less so the more free potassa happens to be present. When a considerable excess of potassa exists, therefore, the precipitate is insoluble in iodide of potassium. Presence of chlorides of the alkali metals, or of salts of potassa and soda, does not interfere with the reaction ; but cyanides and sulphides of the alkali metals prevent it. This reaction was first pointed out by Nessler; it is not required for ordinary analyses, but is ex- tremely valuable in cases where the presence of minute traces of ammoniacal salts are to be detected. I have found it to give distinct indications of the presence of ammonia in solutions of '00001 gramme of chloride of ammonium in 1 cubic centimetre of water. 91. Recapitulation and remarks. The salts of potassa and soda are not volatile at a moderate red heat, whilst the salts of ammonia volatilize readily ; the latter may therefore be easily separated from the former by ignition. The expulsion of ammonia from its compounds, by hydrate of lime, affords the surest means of ascertaining the presence of this sub- stance. Salts of potassa can be detected positively only after the removal of the ammoniacal salts which may be present, since both classes of salts manifest the same or a similar deportment with bichloride of platinum and tartaric acid. After the removal of the ammonia, the potassa is clearly and positively characterized by either of these two reagents. The most simple way of detecting the potassa in the two difficulty-soluble compounds that have come under our consideration here viz., the potassio-bichloride of platinum and bitartrate of potassa is to decompose these salts by ignition ; the former, thereupon, yields the potassa in the form of chloride of potassium, the latter in the form of carbonate of potassa. With respect to soda, the yellow tint which its salts impart to the blowpipe flame and to the flame of alcohol, is a safe and mostly in itself sufficient proof of its presence, provided always no other bodies be present besides salts of fixed alkalies. In form of chlorides, T ^th part of soda may by this means be detected in presence of potassa. Anti- * To prepare this reagent, digest at a gentle heat 2 grammes of iodide of potassium, and 3 grammes of iodide of mercury, in 5 cub. cent, of water ; add 20 cub. cent, of water, let the mixture stand for some time, then filter ; add to the filtrate 30 cub. cent, of pure concentrated solution of potassa (1 : 4) ; and, should a precipitate form, let this settle ; decant, and use the clear decanted fluid. 70 LITHIA. [ 92. monateof potassa also gives decisive results when no other bases besides soda or potassa are present, and especially if these latter are present as chlorides or nitrates. Even from very dilute solutions of salts of soda, antimonate of potassa added in excess will, after twelve hours' standing, throw down antimonate of soda, the crystals of which may always be readily and distinctly recognised under the microscope by their form quadrilateral octahedrons. 92. SUPPLEMENT TO THE FIRST GROUP. LITHIA (Li 0). Lithia dissolves with difficulty in water ; it does not attract moisture from the air. Most of its salts are soluble in water ; some of them are deliquescent (chloride of lithium). Carbonate of lithia is difficultly soluble, particularly in cold water. Phosphate of soda produces, in not over dilute solutions of salts of lithia, upon boiling, a heavy white crystalline precipitate of basic phosphate of lithia (3 Li O, P 5 4 aq.). From very dilute solutions of lithia the same basic phosphate is obtained by adding phosphate of soda and one or two drops of solution of soda to the solu- tion, evaporating the mixed fluid to clryness, and treating the residue with water. The basic phosphate of lithia obtained is sparingly soluble in water, and still less so in ammoniated water ; it dissolves much more readily in water containing salts of ammonium. It is immediately dis- solved by acids ; addition of ammonia produces no precipitate in some- what dilute acid solutions in the cold, but upon boiling, a precipitate separates. The basic phosphate of lithia fuses before the blowpipe, and gives upon fusion with carbonate of soda on the platinum wire a clear bead ; when fused upon charcoal, it is absorbed by the pores of the latter body (another difference between it and the phosphate of the alkaline earths). Tartaric acid and bichloride of platinum fail to precipitate even concentrated solutions of salts of lithia ; but in a solution of chloride of potassium containing chloride of lithium, bichloride of platinum readily produces a precipitate containing lithia (Jenzsch). If a salt of lithia (more particularly chloride of lithium) is exposed on a platinum wire to the inner blowpipe flame, the outer flame shows a strong CARMINE tint. Presence of salts of soda (but not of salts of potassa) conceals this reaction. Addition of chloride of silver promotes it in the case of some, but not of all salts of lithia. If spirit of wine is poured over a salt of lithia (more particularly chloride of lithium), and then kindled, the flame appears of a CARMINE colour ; presence of salts of soda conceals this reaction. To detect lithia in presence of potassa and soda, convert the bases into dry chlorides ; treat them, after addition of a drop of hydrochloric acid, with a mixture of absolute alcohol and anhydrous ether ; filter, distil, and treat the residue remaining after distillation again with the said mixture, after previous addition of a drop of hydrochloric acid ; filter, concentrate the filtrate by evaporation, and then set fire to the concentrated fluid. A carmine-coloured flame indicates the presence of lithia. The residue remaining after evaporation of the alcohol must dissolve in water to a clear fluid ; the solution must not be precipitated by carbonate of am- monia (lime, strontia), and must give the above-mentioned reaction with phosphate of soda. This method is based upon the insolubility of chloride 93, 94.] BARYTA. 71 of potassium, and chloride of sodium in absolute alcohol and ether, in which chloride of lithium readily dissolves. 93. SECOND GROUP. BARYTA, STRONTIA, LIME, MAGNESIA. Properties of the group. The alkaline earths are soluble in water in the pure (caustic) state and as sulphides. Magnesia, however, dissolves but very sparingly in water. The solutions manifest alkaline reaction ; the alkaline reaction of magnesia is most clearly apparent when that earth is laid upon moistened test-paper. The neutral carbonates and phosphates of the alkaline earths are insoluble in water. The solutions of the salts of the alkaline earths are therefore precipitated by alkaline carbonates and phosphates, whilst hydrosulphuric acid fails to precipi- tate them under any condition. This deportment distinguishes the oxides of the second group from those of the first. The alkaline earths and their salts are non-volatile and colorless ; their solutions are not precipitated by sulphide of ammonium, nor by carbonate of baryta. Special Reactions. 94. a. BARYTA (Ba 0). 1. Caustic baryta is pretty readily soluble in hot water, but rather difficultly so in cold water ; it dissolves easily in dilute hydrochloric or nitric acid. Hydrate of baryta does not lose its water upon ignition. 2. Most of the salts of baryta are insoluble in water. The soluble salts do not affect vegetable colors, and are decomposed upon ignition, with the exception of chloride of barium. The insoluble salts dissolve in dilute hydrochloric acid, except the sulphate of baryta. Nitrate of baryta and chloride of barium are insoluble in alcohol, and do not deli- quesce in the air. Concentrated solutions of baryta are precipitated by hydrochloric or nitric acid added in large proportions, as chloride of barium and nitrate of baryta are not soluble in the aqueous solutions of the said acids. 3. Ammonia (free from carbonic acid) produces no precipitate in the aqueous solutions of salts of baryta ; potassa or soda (free from carbonic acid) only in highly concentrated solutions. Water redissolves the bulky precipitate of CRYSTALS OF BARYTA (Ba 0, H + 8 aq.) produced by potassa or soda. 4. Alkaline carbonates throw down from solutions of baryta CARBONATE OF BARYTA (Ba O, C 2 ) in the form of a white precipitate. When car- bonate of ammonia is used as the precipitant, or if the solution was previously acid, complete precipitation takes place only upon heating the fluid. In chloride of ammonium the precipitate is soluble to a trifling yet clearly perceptible extent ; in very dilute solutions of baryta, therefore, which contain much chloride of ammonium, carbonate of ammonia pro- duces no precipitate. 5. Sulphuric acid and all the soluble sulphates, also solution of sul- phate of lime, produce even in very dilute solutions of baryta, a 72 STRONTIA. [95. heavy, finely pulverulent, white precipitate of SULPHATE OF BARYTA (Ba O, S 3 ), which is insoluble or very difficultly soluble in dilute acids, alkalies, and salts of ammonia. As a rule, this precipitate is formed immediately upon the addition of the reagent ; from highly dilute solutions, however, especially when strongly acid, it separates only after some time. Sulphate of baryta is completely decomposed by fusion with carbonates of the alkalies less readily and less com- pletely by boiling with solution of carbonate of soda and carbonate of potassa. The decomposition leads to the formation of sulphates of the alkalies, which are soluble in water, and carbonate of baryta, which is insoluble in that fluid. Digestion with solution of carbonate of ammonia in the cold fails to effect the decomposition of sulphate of baryta, as also boiling with a solution of 1 part of carbonate and 3 parts of sulphate of potassa (H. Rose). 6. Hydrofluosilicic acid throws down from solutions of baryta SILICO- FLUORIDE OF BARIUM (Ba Fl + Si F1J, in form of a colorless, crystalline, quickly subsiding precipitate. In dilute solutions this precipitate is formed only after the lapse of some time ; it is perceptibly soluble in hydrochloric and nitric acids. Addition of an equal volume of alcohol hastens the precipitation and makes it so complete that the filtrate remains clear upon addition of sulphuric acid. 7. Phosphate of soda produces in neutral or alkaline solutions of baryta a white precipitate of PHOSPHATE OF BARYTA (2 Ba 0, H O, P 6 ), which is soluble in free acids. Addition of ammonia only slightly increases the quantity of this precipitate ; chloride of ammonium dissolves it to a clearly perceptible extent. 8. Oxalate of ammonia produces in moderately dilute solutions of baryta a white, pulverulent precipitate of OXALATE OF BARYTA (Ba O, O + aq.), which is soluble in hydrochloric and nitric acids. When recently thrown down, this precipitate dissolves also in oxalic and acetic acicte; but the solutions speedily deposit binoxalate of baryta (Ba O, O + H O,0 + 2 aq.) in the form of a crystalline powder. 9. Salts of baryta in powder, when heated with dilute spirit of wine, impart to the flame a YELLOWISH colour, which, however, is not very characteristic. 10. Salts of baryta, particularly chloride of barium, when exposed on a platinum wire to the inner blowpipe flame, color the outer flame YEL- LOWISH-GREEN. With chloride of barium and nitrate and acetate of baryta this reaction is the most distinct, but it is also shown by carbonate and sulphate of baryta. The presence of salts of lime and strontia does not prevent the reaction ; addition of chloride of silver considerably heightens its intensity. 95. 6. STRONTIA (Sr 0). 1. Strontia and its hydrate and salts manifest nearly the same general deportment and properties as baryta and its corresponding compounds. Hydrate of strontia is more difficulty soluble in water than hydrate of baryta. Chloride of strontium dissolves in absolute alcohol, and deli- quesces m moist air. Nitrate of strontia is insoluble in absolute alcohol, and does not deliquesce in the air. 2. The salts of strontia manifest with ammonia and potassa, and also 96.] LIME. 73 with the alkaline carbonates and with phosphate of soda, nearly the same deportment as the salts of baryta. Carbonate of strontia dissolves some- what more difficultly in chloride of ammonium than is the case with car- bonate of baryta. 3. Sulphuric acid and sulphates precipitate from solutions of strontia SULPHATE OF STRONTIA (Sr 0, S OJ, in form of a white powder, which is insoluble in dilute acids and alkalies. Application of heat greatly promotes the precipitation. Sulphate of strontia is far more soluble in water than sulphate of baryta ; owing to this readier solubility, the pre- cipitated sulphate of strontia separates from rather dilute solutions in general only after the lapse of some time ; and this is invariably the case (even in concentrated solutions) if solution of sulphate of lime is used as precipitant. In boiling hydrochloric acid sulphate of strontia dissolves perceptibly, a solution of the kind showing, after dilution with water, a distinct turbidity upon the addition of a drop of solution of chloride of barium. Sulphate of strontia is readily and completely decomposed by fusion with carbonates of the alkalies, and by boiling with their solutions ; it is decomposed also when long digested in the cold with solution of carbonate of ammonia, or boiled with a solution of 1 part of carbonate of potassa and 3 parts of sulphate of potassa (difference from sulphate of baryta). 4. Hydrojluosilicic acid fails to produce a precipitate even in concen- trated solutions of strontia ; even upon addition of an equal volume of alcohol no precipitation takes place, except in very highly concentrated solutions. 5. Oxalate of ammonia precipitates even from rather dilute solutions, OXALATE OF STRONTIA (2 S 2 O, O +5 aq.), in form of a white powder, which dissolves readily in hydrochloric and nitric acid, and percep- tibly in salts of ammonia, but is only sparingly soluble in oxalic and acetic acid. 6. If salts of strontia soluble in water or alcohol are heated with dilute spirit of wine, and then kindled, the flame appears of an in- tense CARMINE color, more particularly upon stirring the alcoholic mixture. 7. Chloride of strontium when exposed on platinum wire to the inner blowpipe Jlame, imparts an intense RED color to the outer flame. With carbonate and sulphate of strontia the coloration is less intense ; addition of chloride of silver, however, makes the reaction with these two salts also lasting and distinct. Presence of baryta prevents this reaction of strontia. 96. c. LIME (Ca 0). 1. Lime and its hydrate and salts present, in their general deportment and properties, a great similarity to baryta and strontia and their cor- responding compounds. Hydrate of lime is far more difficultly soluble in water than the hydrates of baryta and strontia ; it dissolves, besides, more sparingly in hot than in cold water. Hydrate of lime loses its water upon ignition. Chloride of calcium and nitrate of lime are soluble in absolute alcohol, and deliquesce in the air. 2. Ammonia, potassa, alkaline carbonates, and phosphate of soda, pre- sent nearly the same deportment with salts of lime as with salts of 74 MAGNESIA. [97. baryta. Recently precipitated carbonate of lime (Ca 0, C 2 ) is bulky and amorphous after a time, and immediately upon application of heat, it falls down and assumes a crystalline form. When recently precipitated, it dissolves pretty readily in solution of chloride of ammonium ; but the solution speedily becomes turbid, and deposits the greater part of the dissolved salt in form of crystals. 3. Sulphuric acid and sulphate of soda produce immediately in very concentrated solutions of lime white precipitates of SULPHATE OF LIME (Ca 0, S O 3 , H O 4- aq.), which redissolve completely in a large propor- tion of water, and are still far more soluble in acids. In less concen- trated solutions the precipitates are formed only after the lapse of some time ; and no precipitation whatever takes place in dilute solutions. Solution of sulphate of lime of course cannot produce a precipitate in salts of lime ; but even a cold saturated solution of sulphate of potassa, mixed with 3 parts of water, produces a precipitate only after standing from twelve to twenty -four hours. In solutions of lime which are so very dilute that sulphuric acid has no apparent action on them, a preci- pitate will immediately form upon addition of alcohol. When fused with carbonates of the alkalies, or boiled or digested with their solu- tions, sulphate of lime comports itself the same as sulphate of strontia. 4. Hydrofluosilicic acid does not precipitate salts of lime. 5. Oxalate of ammonia produces even in very dilute solutions of lime a white pulverulent precipitate of OXALATE OF LIME. The composition of this precipitate, when thrown down hot or from concentrated solu- tions, is Ca O, C 2 O 3 + aq. ; whilst when thrown down cold from dilute solutions, it consists of a mixture of Ca O, C 3 4- aq. with Ca O, C 2 O 3 + 3 aq. In very dilute solutions the precipitate forms only after some time. It is readily soluble in hydrochloric and nitric acids, but dis- solves to a trifling extent only in acetic and oxalic acids. 6. Soluble salts of lime, when heated with dilute spirit of wine, im- part to the flame of the latter a YELLOWISH-KED color, which is often con- founded with that communicated to the flame of alcohol by salts of strontia. 7. Chloride of calcium, when exposed on a platinum wire to the inner blowpipe flame, imparts a RED colour to the outer flame. With the other salts of lime this reaction is less intense ; with phosphate and borate of lime it fails altogether. Chloride of silver, as a rule, heightens the in- tensity of the color. Presence of baryta prevents this reaction of lime. 97. d. MAGNESIA (Mg 0). 1. Magnesia and its hydrate are white powders of far greater bulk than. the other alkaline earths and their hydrates. Magnesia and hydrate of magnesia are nearly insoluble both in cold and hot water. Hydrate of magnesia loses its water upon ignition. 2. Some of the salts of magnesia are soluble in water, others are in- soluble in that fluid. The soluble salts of magnesia have a nauseous bitter taste ; in the neutral state they do not alter vegetable colors ; with the exception of sulphate of magnesia, they undergo decomposition when ignited, and the greater part of them even upon simple evapora- tion of their solutions. Nearly all the salts of magnesia which are in- soluble in water dissolve in hydrochloric acid. 97.] MAGNESIA. 75 3. Ammonia throws down from the solutions of neutral salts of mag- nesia part of the magnesia as hydrate (Mg O, H O), in form of a white, bulky precipitate. The rest of the magnesia remains in solution as a double salt, viz., in combination with the ammoniacal salt which forms upon the decomposition of the salt of magnesia; these double salts are not decomposed by ammonia. It is owing to this tendency of salts of magnesia to form such double salts with ammoniacal compounds, that ammonia fails to precipitate them in presence of ammoniacal salts in sufficient proportion, or, what is the same, that ammonia produces no precipitate in solutions of magnesia containing a sufficient quantity of free acid ; and that precipitates produced by am- monia in neutral solutions of magnesia are redissolved upon the addition of chloride of ammonium. 4. Potassa, soda, and caustic baryta throws down from solution of magnesia HYDRATE OF MAGNESIA. The separation of this precipitate is greatly promoted by boiling the mixture. Chloride of ammonium and other similar salts of ammonia redissolve the precipitated hydrate of mag- nesia if the precipitant has not been added greatly in excess. If the salts of ammonia are added in sufficient quantity to the solution of mag- nesia before the addition of the precipitant, small quantities of the latter fail altogether to produce a precipitate. However, upon boiling the solution afterwards with an excess of potassa, the precipitate will of course make its appearance, since this process causes the decomposition of the ammoniacal salt, removing thus the agent which retains the hydrate of magnesia in solution. 5. Carbonate of potassa and carbonate of soda produce in neutral solu- tions of magnesia a white precipitate of BASIC CARBONATE OF MAGNESIA 3 (Mg O, C 2 , + aq.) + Mg O, H O. One fourth of the carbonic acid of the decomposed alkaline carbonate is liberated in the process, and combines with a portion of the carbonate of magnesia to bicarbonate, which remains in solution. This carbonic acid escapes upon ebullition ; application of heat therefore promotes the separation and increases the quantity of the precipitate, Chloride of ammonium and other similar salts of ammonia prevent this precipitation also, and redissolve the pre- cipitates already formed. 6. Carbonate of ammonia does not precipitate solutions of magnesia in the cold (at least never immediately, nor even after a short time) ; upon boiling, it precipitates them only incompletely. Addition of chloride of ammonium and other similar salts of ammonia, in sufficient quantity, entirely prevents the formation of a precipitate. 7. Phosphate of soda precipitates from solutions of magnesia, if they are not too dilute, PHOSPHATE OF MAGNESIA (2 Mg O, H 0, P 5 ) as a white powder. The separation of the precipitate is greatly promoted by ebullition. But if the addition of the precipitant is preceded by that of chloride of ammonium and ammonia, a white crystalline precipitate of BASIC PHOSPHATE OF MAGNESIA AND AMMONIA (2 Mg O, N H 4 O, P O g + 12aq.) will separate, even from very dilute solutions of magnesia; its separation may be greatly promoted and accelerated by vigorous stirring with a glass rod : even should the solution be so extremely dilute as to forbid the formation of a precipitate, yet the lines of direction in which the glass rod has moved along the side of the vessel will after the lapse of some time appear distinctly as white streaks. Water and solutions of salts of ammonia dissolve the precipitate but very slightly ; but it is 76 RECAPITULATION. [ 98. readily soluble in acids, even in acetic acid. In water containing ammo- nia it may be considered insoluble. 8. Oxalate of ammonia produces no precipitate in highly dilute solu- tions of magnesia ; in less dilute solutions no precipitate is formed at first, but after some time crystalline crusts of various oxalates of ammonia and magnesia make their appearance. In highly concentrated solutions oxalate of ammonia very speedily produces precipitates of oxalate of magnesia (Mg 0, O + 2 aq.), which contain small quantities of the above-named double salts. Chloride of ammonium, especially in presence of free ammonia, interferes with the formation of these preci- pitates ; but, as a rule, it does not absolutely prevent it. 9. Sulphuric acid and hydrofluosilicic acid do not precipitate salts of magnesia. 1 0. If magnesia, or a salt of magnesia, is moistened with water, heated to redness on a charcoal support, then moistened with 1 drop of solution of nitrate of protoxide of cobalt, and again heated at first to gentle red- ness, ultimately to intense redness, in the oxidation flame, a pinkish mass is obtained, the color of which becomes distinctly apparent only upon cooling, but is never very intense. Alkalies, alkaline earths, and heavy metallic oxides prevent the reaction. 98- Recapitulation and remarks. The difficult solubility of the hydrate of magnesia, the ready solubility of the sulphate, and the disposition of salts of magnesia to form double salts with ammoniacal compounds, are the three principal points in which magnesia differs from the other alkaline earths. To detect magnesia we always first remove the baryta, strontia, and lime, if these bodies happen to be present. In cases re- quiring no very high degree of accuracy, and where the quantity of salts of ammonia present in the solution is inconsiderable, this removal may be effected by means of carbonate of ammonia and ammonia ; but the separation is never perfect, owing to the solvent action which salts of ammonia exercise more especially upon carbonate of baryta and lime j indeed, minute traces of baryta and lime can rarely be precipitated in this manner. Baryta is separated the most completely by sulphuric acid or a sulphate ; lime, by oxalate of ammonia in presence of ammonia and some chloride of ammonium j strontia, in the same manner as lime, or by ammonia and carbonate of ammonia in presence of chloride of ammo- nium. After the removal of the other alkaline earths, the magnesia may be readily detected in the filtrate by phosphate of soda in conjunction with ammonia. The detection of baryta is an easy task under any circum- stances ; since the precipitate of sulphate of baryta which separates from baryta solutions immediately upon the addition of sulphate of lime, and the reaction of baryta with hydrofluosilicic are indubitable proofs of the presence of this earth. Strontia may likewise be readily detected by its deportment with solution of sulphate of lime, provided of course no baryta be present. If baryta is present, the detection of the strontia may be effected by converting the two earths into dry chlorides, and digesting the latter with absolute alcohol ; the greater part of the chloride of barium is left undissolved, whilst the chloride of strontium, dissolves ; if the alcohol is now heated, and then ignited, the carmine tint of the flame will indicate the presence of strontia. However, the results obtained in this way can only be considered satisfactory if the 99.] ALUMINA, SESQUIOXIDE OF CHROMIUM. 77 quantity of the strontia is not too minute, and if there is not much lime present ; since in the latter case the yellowish-red flame of the lime will mask the carmine flame of the strontia. In cases of this kind strontia is detected best by the following process. Mix the solution containing baryta, strontia, and lime with hydrofluosilicic acid and a volume of alcohol equal to that of the fluid present ; let the mixture stand several hours ; filter off the silicofluori.de of barium, and mix the filtrate with sulphuric acid ; filter the precipitate formed, wash, arid convert the sulphates into carbonates by boiling with solution of carbonate of soda ; wash the car- bonates, dissolve them in a small quantity of hydrochloric acid, and test the solution for strontia with solution of sulphate of lime. The preci- pitate of sulphate of strontia thus obtained may then be tested before the blowpipe, with addition of chloride of silver. For the detection of lime we invariably select oxalate of ammonia. Before applying this test, however, baryta and strontia must be removed, as they are equally pre- cipitated by it. This removal is effected best by adding to the solution sulphate of potassa in excess, and boiling the mixture for some time. If there is much lime present, a portion of the latter earth precipi- tates with the baryta and strontia; this is, however, a matter of indifference, since there remains always a sufficient amount of lime in solution to permit the positive and indubitable detection of this substance in the filtrate by oxalate of ammonia ; to prevent precipitation of traces of oxalate of strontia, the filtrate must be diluted with J volume of water. The best way of effecting the detection of the alkaline earths, when in the form of phosphates, is to decompose these latter by means of sesqui- chloride of iron with the addition of acetate of soda ( 143). The oxalates of the alkaline earths are converted into carbonates by ignition, preparatory to the detection of the individual earths which they contain. Sulphate of baryta and sulphate of strontia are fused with alkaline car- bonates, to effect the detection of the baryta and strontia (compare 141). To separate sulphate of baryta from sulphate of strontia and sulphate of lime, digest the finely triturated substance with solution of carbonate of ammonia for twelve hours in the cold, or boil it ten minutes with a solution of 3 parts of sulphate and 1 part of carbonate of potassa ; sulphate of strontia and sulphate of lime are decomposed in both cases, whilst sulphate of baryta remains unaltered. Filter, wash thoroughly with hot water, and test the washed residue with dilute hydrochloric acid, which will dissolve the carbonate of strontia and carbonate of lime formed, leaving the sulphate of baryta undissolved (H. Rose). 99. THIRD GROUP. ALUMINA, SESQUIOXIDE OF CHROMIUM. Properties of the group. Alumina and sesquioxide of chromium are insoluble in water, both in the pure state arid as hydrates. They form no neutral salts with carbonic acid. Their sulphides cannot be produced in the humid way. Hydrosulphuric acid therefore fails to precipitate solutions of alumina and sesquioxide of chromium ; sulphide of ammonium precipitates the hydrated oxides from these solutions. This deportment with sulphide of ammonium distinguishes the oxides of the third from those of the two preceding groups. 78 ALUMINA. [ 100. Special Reactions. 100. a. ALUMINA (A1 2 3 ). 1. Alumina is non-volatile and colorless ; the hydrate is also colorless. Alumina dissolves in acids (particularly when dilute) slowly and with very great dimculty ; in fusing bisulphate of potassa it dissolves readily to a mass soluble in water. The hydrate in an amorphous state, and recently precipitated, is readily soluble in acids ; but after being left some time in the fluid from which it was precipitated, its solubility decreases, and in the crystallized state it dissolves with very great dimculty in acids. After pre- vious ignition with alkalies, which leads to the formation of aluminates of the alkalies, alumina is readily dissolved by acids. 2. The salts of alumina are colorless, and most of them are non- volatile : some of them are soluble, others insoluble. The soluble salts have a sweetish, astringent taste, redden litmus-paper, and lose their acids upon ignition. The insoluble salts are dissolved by hydro- chloric acid, with the exception of certain native compounds of alumina ; the compounds of alumina which are insoluble in hydrochloric acid are decomposed and made soluble by ignition with carbonate of soda and potassa, or bisulphate of potassa. 3. Potassa and soda throw down from solutions of alumina a bulky precipitate of HYDRATE OF ALUMINA (A1 2 3 , 3 H 0), which contains alkali, and generally also an admixture of basic salt ; this precipitate re- disfcolves readily and completely in an excess of the precipitant, but from this solution it is reprecipitated by addition of chloride of ammonium, even in the cold, but more completely upon application of heat (com- pare 51). The presence of salts of ammonia does not prevent the precipitation by potassa or soda. 4. Ammonia also produces in solutions of alumina a precipitate of HYDRATE OF ALUMINA, containing ammonia and an admixture of basic salt ; this precipitate also redissolves in a very considerable excess of the precipitant, but with difficulty only, which is the greater the larger the quantity of salts of ammonia contained in the solution. It is this deport- ment which accounts for the complete precipitation of hydrate of alumina from solution in potassa, by an excess of chloride of ammonium. 5. If the solution of a salt of alumina is digested with finely pulverized carbonate of baryta, the greater part of the acid of the alumina salt combines with the baryta, the liberated carbonic acid escapes, and the alumina precipitates completely as HYDRATE mixed with BASIC SALT OF ALUMINA ; even digestion in the cold suffices to produce this reaction. 6. If alumina or one of its compounds is ignited upon charcoal before the blowpipe, and afterwards moistened with a solution of nitrate of protoxide of cobalt, and then again strongly ignited, an unfused mass of a deep SKY-BLUE color is produced, which consists of a compound of the two oxides. The blue color becomes distinct only upon cooling. By candlelight it appears violet. This reaction is decisive only in the case of infusible or difficultly fusible compounds of alumina pretty free from other oxides, as solution of cobalt imparts a blue tint to readily fusible salts, even though no alumina be present. 101.] SESQUIOXIDE OF CHROMIUM. 79 101. b. SESQUIOXIDE OF CHROMIUM (Cr 2 3 ). 1. Sesquioxide of chromium is a green, its hydrate a bluish gray- green powder. The hydrate dissolves readily in acids } the non-ignited sesqui- oxide dissolves more difficultly, and the ignited sesquioxide is almost altogether insoluble. 2. The salts of sesquioxide of chromium have a green or violet color. Many of them are soluble in water. Most of them dissolve in hydro- chloric acid. The solutions usually exhibit a fine green color. Many double salts of sesquioxide of chromium, e.g., sulphate of sesqui- oxide of chromium and potassa (chrome alum), have a deep violet color, and give with cold water bluish-violet solutions which, however, acquire a green tint when even moderately heated. The salts of sesqui- oxide of chromium with volatile acids are decomposed upon ignition, the acids being expelled. The salts of sesquioxide of chromium which are soluble in water redden litmus. 3. Potassa and soda produce in solutions of salts of sesquioxide of chromium a bluish-green precipitate of HYDRATE OF SESQUIOXIDE OF CHROMIUM, which dissolves readily and completely in an excess of the precipitant, imparting to the fluid generally an emerald-green tint, but in cases where the solution originally precipitated was bluish-violet, a violet color. Upon long -continued ebullition of this solution, the whole of the hydrated sesquioxide separates again, and the supernatant fluid appears perfectly colorless. The same reprecipitation takes place if chloride of ammonium is added to the alkaline solution, and the mixture heated. If the alkaline solution of sesquioxide of chromium is gently heated with binoxide of lead, the sesquioxide of chromium is con- verted into chromic acid, and the alkaline fluid now holds chromate of lead in solution ; upon supersaturation with acetic acid, chromate of lead separates in form of a yellow precipitate. 4. Ammonia also produces in solutions of salts of sesquioxide of chro- mium a precipitate of HYDRATE OF SESQUIOXIDE OF CHROMIUM : this precipi- tate contains more or less water, according as the ammonia has been added gradually or suddenly, and appears, therefore, sometimes grayish-green, sometimes grayish-blue. A small portion of it redissolves in an excess of the precipitant in the cold, imparting to the fluid a peach-blossom red tint j but if, after the addition of ammonia in excess, heat is applied to the mixture, the precipitation is complete. 5. Carbonate of baryta precipitates from solutions of sesquioxide of chromium the whole of the sesquioxide as a GREENISH HYDRATE mixed with BASIC SALT. The precipitation takes place in the cold, but is com- plete only after long-continued digestion. 6. The fusion of sesquioxide of chromium or of any of its compounds with nitrate of soda and some carbonate of soda gives rise to the formation of yellow CHROMATE OF SODA, part of the oxygen of the nitric acid sepa- rating from the nitrate of soda, and converting the sesquioxide of chro- mium into chromic acid, which then combines with the soda. For the reactions of chromic acid, see 138. 7. Phosphate of soda and ammonia dissolves sesquioxide of chromium and its salts, both in the oxidizing and reducing flame of the blowpipe, to clear beads of a faint YELLOWISH- GREEN tint, which upon cooling 80 TITANIC ACID. [ 102, 103. changes to EMERALD-GREEN. The sesquioxide of chromium and its salts show a similar deportment with biborate of soda. 102. Recapitulation and remarks. The solubility of hydrate of alumina in solutions of potassa and soda, and its reprecipitation from the alkaline solutions by chloride of ammonium, afford a safe means of detecting alumina only in the absence of sesquioxide of chromium. If the latter is present therefore, which is seen either from the color of the solution, or by the reaction with phosphate of soda and ammonia, it must be removed before we can proceed to test for alumina. The separation of sesquioxide of chromium from alumina is effected the most completely by fusing 1 part of the mixed oxides together with 2 parts of carbonate and 2 parts of nitrate of soda, which may be done in a platinum crucible. The yellow mass obtained is boiled with water; by this process the whole of the chromium is dissolved as chromate of soda, and part of the alumina as aluminate of soda, the rest of the alumina remaining undis- solved. If the solution is acidified with nitric acid, it acquires a reddish tint ; if ammonia is then added to feebly alkaline reaction, the dissolved portion of the alumina separates. The precipitation of sesquioxide of chromium, effected by boiling its solu- tion in solution of potassa or soda, is also sufficiently reliable if the ebullition is continued a sufficient length of time ; still it is often liable to mislead in cases where only little sesquioxide of chromium is present, or where the solution contains organic matter, even though in small proportion only. The deportment of a solution of sesquioxide of chromium with solution of potassa or soda is completely changed by the presence of certain other metallic oxides, especially oxide of zinc, oxide of lead, sesquioxide of iron ; in presence of these oxides, and according to the greater or less relative proportion in which they happen to be present, sesquioxide of chromium does not dissolve, or dissolves only incompletely in an excess of solution of potassa. This circumstance should never be lost sight of in the analysis of compounds containing sesquioxide of chromium. Lastly, it must be borne in mind, also, that alkalies produce no precipi- tates in the solutions of alumina if non-volatile organic substances are present, such as sugar, tartaric acid, &c. ; whilst the precipitation of sesqui- oxide of chromium is less seriously interfered with by the presence of such bodies. 103. SUPPLEMENT TO THE THIRD GROUP. TITANIC ACID (Ti0 2 ). From among the other oxides enumerated in 86 as belonging to the third group, we have selected titanic acid as deserving of special notice, since this substance is met with more frequently than the others in analytical investigations, more especially also in the analysis of the slag adhering to the bottom of blast furnaces in which iron ore is reduced, which slag is often found to contain small copper-coloured cubes, consisting of a combination of cyanide of titanium with nitride of titanium ( Wohler). Titanium burns in the air with considerable brilliancy to titanic acid 104.] ZINC, MANGANESE, NICKEL, COBALT, IRON. 81 (TiO 2 ). Besides the acid, another oxide of titanium is known, the sesquioxide (Ti 2 O 3 ). According to the different mode of its prepa- ration, titanic acid appears sometimes as a white powder, which, when heated, transiently acquires a yellow tint, sometimes in the form of small lumps of a reddish-brown color. It is infusible, and insoluble in water and acid, with the exception of concentrated sulphuric acid. With bisulphate of potassa it fuses into a mass, which dissolves in a large proportion of cold water to a clear fluid. Fusion of titanic acid with carbonate of soda gives rise to the formation of titanate of soda, which is by addition of water converted into soda and bititanate of soda ; the latter salt is insoluble in water, but soluble in hydrochloric acid. The hydrate of titanic acid is white ; it dissolves, both in the moist state and when dried without the aid of heat, in dilute acids, especially hydrochloric and sulphuric acids. Solutions of titanic acid in hydrochloric or sulphuric acid, but more especially the latter, when subjected in a highly dilute state to long-continued ebulli- tion, deposit titanic acid as a white powder, insoluble in dilute acids. The precipitate thus formed in hydrochloric acid cannot be separated by nitration, unless an acid or chloride of ammonium is added, as it will pass through the filter with the washing water. Solution of potassa throws down from solutions of titanic acid in hydrochloric or sulphuric acid, hydrate of titanic acid in form of a bulky , white precipitate, which is insoluble in an excess of the precipitant ; am- monia, sulphide of ammonium, carbonates of the alkalies, and car- bonate of baryta act in the same way. The precipitate, if thrown down without application of heat, and washed with cold water, is soluble in hydrochloric acid and dilute sulphuric acid ; presence of tartaric acid prevents its formation. Ferrocyanide of potassium pro- duces in acid solutions of titanic acid a dark brown precipitate ; infusion of galls a brownish precipitate, which speedily turns orange- red. Metallic zinc produces, in consequence of the ensuing reduction of titanic acid to sesquioxide of titanium, at first a blue coloration of the solution, afterwards a blue precipitate of hydrate of sesquioxide of titanium. Phosphate of soda and ammonia readily dissolves titanic acid in the outer flame of the blowpipe to a clear bead of a yellowish color whilst hot, but colorless when cold. If this bead is exposed to the reducing flame, it acquires a yellow tint, which turns to red when the bead is half cold, and to violet when quite cold. 104. FOURTH GROUP. OXIDE OF ZINC, PROTOXIDE OF MANGANESE, PROTOXIDE OF NICKEL, PROTOXIDE OF COBALT, PROTOXIDE OF IRON, SESQUIOXIDE OF IRON. Properties of the group. The solutions of the oxides of the fourth group, when containing a stronger free acid, are not precipitated by hydrosulphuric acid ; neutral solutions also are not, or only very incom- pletely, precipitated by that reagent ', but alkaline solutions are com- pletely precipitated by hydrosulphuric acid ; and other solutions also if a sulphide of an alkali metal is used as the precipitant, instead of hydrosulphuric acid. The precipitated metallic sulphides corresponding 82 OXIDE OF ZINC. [ 105. to the respective oxides are insoluble in water; some of them are readily soluble in dilute acids ; others (sulphide of nickel and sulphide of cobalt) dissolve only with very great difficulty in these menstrua. Some of them are insoluble in sulphides of the alkali metals ; others are sparingly soluble in them, under certain circumstances. Special Reactions. .^' 105. a. OXIDE or ZINC (Zn 0). 1. Metallic zinc is bluish- white and very bright ; when exposed to the air, a thin coating of basic carbonate of zinc forms on its surface. It is of medium hardness, ductile at a temperature of between 212 and 302 Fah., and under ordinary circumstances more or less brittle ; it fuses readily on charcoal before the blowpipe, boils afterwards, and burns with a bluish-green flame, giving off white fumes, and coating the charcoal support with oxide. Zinc dissolves in hydrochloric and sulphuric acids, with evolution of hydrogen gas ; in dilute nitric acid, with evolution of nitrous oxide ; in more concentrated nitric acid, with evolution of nitric oxide. 2. The oxide of zinc and its hydrate are white powders, which dis- solve readily in hydrochloric, nitric, and sulphuric acids. The oxide of zinc acquires a lemon-yellow tint when heated, but it reassumes its original white color upon cooling. When ignited before the blow- pipe, it shines with considerable brilliancy. 3. The compounds of oxide of zinc are colorless ; part of them are soluble in water, the rest in acids. The neutral salts of zinc which are soluble in water redden litmus-paper, and are readily decomposed by heat, with the exception of sulphate of zinc, which can bear a dull red heat, without undergoing decomposition. Chloride of zinc is volatile at a red heat. 4. Hydrosulphuric acid precipitates from neutral solutions of salts of zinc a portion of the metal as white hydrated SULPHIDE of ZINC (Zn S). In acid solutions this reagent fails altogether to produce a precipitate if the free acid present is one of the stronger acids ; but from a solution of oxide of zinc in acetic acid, it throws down the whole of the zinc, even if the acid is present in excess. 5. Sulphide of ammonium throws down from neutral, and hydrosid- phuric acid from alkaline solutions of salts of zinc, the whole of the metal as hydrated SULPHIDE OF ZINC, in form of a white precipitate. This precipitate is not reclissolved by an excess of sulphide of ammonium, iior by potassa or ammonia ; but it dissolves readily in hydrochloric acid, nitric acid, and dilute sulphuric acid. 6. Potassa and soda throw down from solutions of salts of zinc HYDRATED OXIDE OF ZINC (Zn O, H O), in form of a white, gelatinous precipitate, which is readily and completely redissolved by an excess of the precipitant. Upon boiling these alkaline solutions they remain, if concentrated, unaltered ; but from dilute solutions nearly the whole of the oxide of zinc separates as a white precipitate. Chloride of ammonium does not precipitate alkaline solutions of oxide of zinc. If a solution of oxide of zinc in solution of potassa or soda is mixed with a solution of sesquioxide of chromium also in solution of potassa or soda, 106.] PROTOXIDE OF MANGANESE. 83 a green precipitate is formed, consisting of a compound of sesquioxide of chromium with oxide of zinc (Zu 0, Cr 2 3 ). A solution of caustic soda or potassa therefore can never contain both oxides together in solution (Chancel}. 7. Ammonia also produces in solutions of oxide of zinc, if they do not contain a large excess of free acid, a precipitate of , HYDRATED OXIDE OF ZINC, which readily dissolves in an excess of the precipitant. The con- centrated solution turns turbid when mixed with water. On boiling the concentrated solution, part of the oxide of zinc separates imme- diately ; on boiling the dilute solution, all the oxide of zinc precipitates. 8. Carbonate of soda produces in solutions of salts of zinc a precipitate of BASIC CARBONATE OF ZINC (3 [Zn O, H 0] 4 2 [Zn O, C 2 + 4 aq.), which is insoluble in an excess of the precipitant. Presence of salts of ammonia in great excess prevents the formation of this precipitate. 9. Carbonate of ammonia also produces in solutions of salts of zinc the same precipitate of BASIC CARBONATE OF ZINC as carbonate of soda ; but this precipitate redissolves upon further addition of the precipitant. On boiling the dilute solution, oxide of zinc precipitates. 10. Carbonate of baryta fails to precipitate solutions of oxide of zinc in the cold. 11. If a mixture of oxide of zinc, or one of its salts, with carbonate of soda is exposed to the reducing flame of the blowpipe, the charcoal support becomes covered with a slight coating of OXIDE OF ZINC, which presents a yellow color whilst hot, and turns white upon cooling. This coating is produced by the reduced metallic zinc volatilizing at the moment of its reduction, and being reoxidized in passing through the outer flame. 12. If oxide of zinc or one of the salts of zinc is moistened with solution of nitrate of protoxide of cobalt, and then heated before the blowpipe, an unfused mass is obtained, of a beautiful GREEN color : this mass is a compound of oxide of zinc with protoxide of cobalt. If there- fore in the experiment described in 1 1 the charcoal is moistened, around the little cavity, with solution of nitrate of protoxide of cobalt, the coating appears green when cold. 106. b. PROTOXIDE OF MANGANESE (Mn 0). 1. Metallic manganese has a whitish-gray color and but little lustre ; it is brittle, and fuses with very great difficulty ; it oxidizes slowly in cold water, rapidly in boiling water, and dissolves readily in acids. The solutions contain protoxide, 2. Protoxide of manganese is grayish-green ; the hydrated protoxide is white. Both the protoxide and its hydrate absorb oxygen from the air, and are converted into the brown sesquioxide. They are readily soluble in hydrochloric, nitric, and sulphuric acids. 3. The salts of protoxide of manganese are colorless or pale red ; part of them are soluble in water, the rest in acids. The salts soluble in water are readily decomposed by a red heat, with the exception of the sulphate. The solutions do not alter vegetable colors. 4. Hydrosulphuric acid does not precipitate acid solutions of salts of protoxide of manganese ; neutral solutions also it fails to precipitate, or precipitates them only very imperfectly. G 2 84 PEOTOXIDE OF NICKEL. [ 107. 5. Sulphide of ammonium throws down from neutral, and hydrosul- phuric acid from alkaline solutions of salts of protoxide of manganese, the whole of the metal as hydrated SULPHIDE OF MANGANESE (Mn S), in form of a light flesh-colored* precipitate, which acquires a dark-brown color in the air; this precipitate is insoluble in yellow sulphide of ammonium and in alkalies, soluble to a very trifling extent in color- less sulphide of ammonium, but readily soluble in hydrochloric and nitric acids. From very dilute solutions the precipitate separates only after standing some time in a warm place. ~v ' 6. Potassa, soda, and ammonia produce whitish precipitates of HY- DRATE OF PROTOXIDE OF MANGANESE (Mn O, H O), which upon exposure to the air speedily acquire a brownish and finally a deep blackish-brown color, owing to the conversion of the hydrated protoxide into hydrated sesquioxide, by the absorption of oxygen from the air. Ammonia and carbonate of ammonia do not redissolve this precipitate ; but presence of chloride of ammonium prevents the precipitation by ammonia alto- gether, and that by potassa partly. Of already formed precipitates solution of chloride of ammonium redissolves only those parts which have not yet undergone peroxidation. The solution of the hydrated protoxide of manganese in chloride of ammonium is owing to the dis- position of the salts of protoxide of manganese to form double salts with salts of ammonia. The ammoniacal solutions of the double salts turn brown in the air, and deposit dark-brown hydrate of sesquioxide of manganese (Otto). 7. If a few drops of a fluid containing protoxide of manganese, and free from chlorine, are sprinkled on binoxide of lead, or red-lead, nitric acid free from chlorine added, the mixture boiled and allowed to settle, the fluid is of a purple red color from the formation of perman- ganic acid. 8. Carbonate of baryta does not precipitate protoxide of manganese from its solutions, upon digestion in the cold. 9. If any compound of manganese, in a state of minute division, is fused with carbonate of soda on a platinum wire in the outer flame of the blowpipe, MANGANATE OF SODA (Na O, Mn O 3 ) is formed, which makes the fused mass appear GREEN while hot, and of a BLUISH-GREEN tint after cooling, the bead at the same time becoming turbid. This reaction enables us to detect the smallest quantities of manganese. The delicacy of the test may be still further increased by the addition of a minute quantity of nitrate of potassa to the carbonate of soda. 10. Borax and phosphate of soda and ammonia dissolve manganese compounds in the outer flame of the blowpipe to clear VIOLET-RED beads, which upon cooling acquire an AMETHYST-RED tint : they lose their color in the inner flame, owing to a reduction of the sesquioxide to protoxide. The bead which borax forms with manganese compounds appears black when containing a considerable portion of sesquioxide of manganese, but that formed by phosphate of soda and ammonia never loses its transparency. But the latter loses its color in the inner flame of the blowpipe far more readily than the former. 107. c. PROTOXIDE OF NICKEL (Ni O). 1. Metallic nickel in the fused state is silvery white, inclining to gray ; * If the quantity of the precipitate is only trifling, the color appears yellowish-white. 107.] PROTOXIDE OF NICKEL. 85 it is bright, hard, malleable, ductile, difficultly fusible ; it does not oxidize in the air at common temperatures, but it oxidizes slowly upon ignition ; it is attracted by the magnet, and may itself become magnetic. It slowly dissolves in hydrochloric acid and dilute sulphuric acid upon the applica- tion of heat, the solution being attended with evolution of hydrogen gas. It dissolves readily in nitric acid. 2. Protoxide of nickel is a gray, its hydrate a green powder. Both the protoxide and its hydrate are unalterable in the air, and readily soluble in hydrochloric, nitric, and sulphuric acids. 3. Most of the salts of protoxide of nickel are yellow in the anhydrous, green in the hydrated state ; their solutions are of a light green color. The soluble neutral salts slightly redden litmus paper, and are decom- posed at a red heat. 4. Hydrosulphuric acid does not precipitate acid solutions of salts of nickel ; it fails also to precipitate neutral solutions of salts of nickel with the stronger acids, or it precipitates them only very imperfectly. 5. Sulphide of ammonium produces in neutral, and hydrosulphuric acid in alkaline solutions of salts of protoxide of nickel, a black precipitate of hydrated SULPHIDE OF NICKEL (Ni S), which is not altogether insoluble in sulphide of ammonium, especially if containing free ammonia ; the fluid from which the precipitate has been thrown down exhibits therefore usually a brownish color. Sulphide of nickel dissolves with great difficulty in hydrochloric acid, but readily in nitrohydrochloric acid upon application of heat. 6. Potassa and soda produce a light green precipitate of HYDRATE OF PROTOXIDE OF NICKEL (Ni O, H 0), which is insoluble in an excess of the precipitants, and unalterable in the air. Carbonate of ammonia dis- solves this precipitate, when filtered and washed, to a greenish-blue fluid, from which potassa or soda reprecipitates the nickel as an apple-green hydrate of protoxide of nickel. 7. Ammonia added in small quantity to solutions of protoxide of nickel produces in them a trifling greenish turbidity ; upon further addition of the reagent this redissolves readily to a blue fluid containing a compound of protoxide of nickel and ammonia. Potassa and soda precipitate from this solution hydrate of protoxide of nickel. Solutions containing salts of ammonia or free acid are not rendered turbid by ammonia. 8. Cyanide of potassium produces a yellowish-green precipitate of CYANIDE OF NICKEL (Ni Cy), which redissolves readily in an excess of the precipitant as a double cyanide of nickel arid potassium (Ni Cy + K Cy) ; the solution is brownish-yellow. If sulphuric acid or hydro- chloric acid is added to this solution, the cyanide of potassium is decom- posed, and the cyanide of nickel reprecipitated ; the latter substance is very difficultly soluble in an excess of these acids in the cold, but more readily upon boiling. 9. Carbonate of baryta does not precipitate protoxide of nickel from its solutions, upon digestion in the cold. 10. Nitrite of potassa, used in conjunction with acetic acid, fails to precipitate even concentrated solutions of nickel. 11. Borax &nd phosfihate of soda and ammonia dissolve compounds of protoxide of nickel in the outer flame of the blowpipe to clear beads ; the bead produced with borax is violet whilst hot, reddish-brown when cold ; the bead produced with the phosphate of soda and ammonia is reddish, inclining to brown whilst hot, but turns yellow or reddish-yellow upon cool- 86 PROTOXIDE OF COBALT. [ 108. ing. The bead which phosphate of soda and ammonia forms with salts of protoxide of nickel remains unaltered in the inner flame of the blow- pipe, but that formed with borax turns gray and turbid from reduced metallic nickel. Upon continued exposure to the blowpipe flame the particles of nickel unite, but without fusing to a grain, and the bead becomes colorless. 108. d. PROTOXIDE OF COBALT (Co 0). 1. Metallic cobalt is reddish-gray, slightly lustrous, pretty hard, slightly malleable, ductile, and difficultly fusible ; it does not oxidize in the air at the common temperature, and oxidizes only slowly at a red heat ; with acids it comports itself like nickel. 2. Protoxide of cobalt is an olive-green, its hydrate a pale red powder. Both dissolve readily in hydrochloric, nitric, and sulphuric acids. 3. The salts of protoxide of cobalt, containing water of crystallization, are red, the anhydrous salts mostly blue. The moderately concentrated solutions appear of a light red color, which they retain even though considerably diluted. The soluble neutral salts redden litmus paper slightly, and are decomposed at a red heat ; sulphate of protoxide of cobalt alone can bear a moderate red heat without suffering decomposi- tion. When a solution of chloride of cobalt is evaporated, the light red color changes towards the end of the operation to blue; addition of water restores the red color. 4. Hydrosulphuric acid does not precipitate acid solutions of cobalt ; it also fails to precipitate neutral solutions of salts of protoxide of cobalt with the stronger acids, or it precipitates them only very imperfectly. 5. Sulphide of ammonium precipitates from neutral, and hydrosulphuric acid from alkaline solutions of salts of protoxide of cobalt, the whole of the metal as black hydrated SULPHIDE OF COBALT (Co S). This substance is insoluble in alkalies and sulphide of ammonium, very difficultly soluble in hydrochloric acid, but readily so in nitrohydrochloric acid upon appli- cation of heat. 6. Potassa and soda produce in solutions of cobalt BLUE precipitates of basic salts of cobalt, which turn GREEN upon exposure to the air, owing to the absorption of oxygen ; upon boiling, they are converted into pale red hydrate of protoxide of cobalt, which contains alkali, and generally appears rather discolored from an admixture of sesquioxide formed in the process. These precipitates are insoluble in solutions of potassa and soda ; but neutral carbonate of ammonia dissolves them completely to intensely violet-red fluids, in which a somewhat larger proportion of potassa or soda produces a blue precipitate, the fluid still retaining its violet color. 7. Ammonia produces the same precipitate as potassa, but this redis- solves in an excess of the ammonia to a reddish-brown fluid, from which solution of potassa or soda throws down part of the cobalt as a blue basic salt. Ammonia fails to precipitate solutions of protoxide of cobalt containing salts of ammonia or free acid. 8. Addition of cyanide of potassium to a solution of cobalt gives rise to the formation of a brownish-white precipitate of PROTOCYANIDE OF COBALT (Co Cy), which dissolves readily as a double cyanide of cobalt and potassium in an. excess of solution of cyanide of potassium. Acids precipitate from this solution cyanide of cobalt. But if the solution is 109.] PROTOXIDE OF IRON. 87 boiled with cyanide of potassium in excess, in presence of free hydrocyanic acid (liberated by addition of one or two drops of hydrochloric acid), a double compound of sesquicyanide of cobalt and cyanide of potassium (K 3 , Co 2 Cy 6 = K 3 Ckdy) is formed, in the solution of which acids pro- duce no precipitate. 9. Carbonate of baryta does not precipitate solution of protoxide of cobalt in the cold. 10. If nitrite of potassa is added in not too small proportion to a solution of protoxide of cobalt, then acetic acid to strongly acid reaction, and the mixture put in a moderately warm place, all the cobalt separates, from concentrated solutions immediately or very soon, from dilute solu- tions after some time, as NITRITE OF SESQUIOXIDE OF COBALT AND POTASSA (Co 2 O 3 , 3 K O, 5 K 3 , 2 H O), in form of a crystalline precipitate of a beautiful yellow color. The mode in which this precipitate forms may be seen from the following equation : 2 (Co O, S 3 ) + 6 (K O, N O 3 ) + A = K 0, A + 2 K 0, S O 3 + Co, O 3 , 3 K O, 5 N O 3 + N 2 . The pre- cipitate is only sparingly soluble in pure water, and altogether insoluble in saline solutions and in alcohol. When boiled with water, it dissolves, though not copiously, to a red fluid, which remains clear upon cooling, and from which alkalies throw down hydrate of protoxide of cobalt (Fischer, Aug. Stromeyer). This excellent reaction enables us to dis- tinguish nickel from cobalt. It is always necessary to concentrate the solution of protoxide of cobalt to a considerable extent before adding the nitrite of potassa. 11. Borax dissolves compounds of cobalt both in the inner and outer flame of the blowpipe, giving clear beads of a magnificent BLUE color, which appear violet by candle-light, and almost black if the cobalt is present in considerable proportion. This test is as delicate as it is cha- racteristic. Phosphate of soda and ammonia manifests with salts of cobalt before the blowpipe an analogous but less delicate reaction. 109. e. PROTOXIDE OF IRON (FeO). 1. Metallic iron in the pure state has a light whitish gray color (iron containing carbon is more or less gray) ; the metal is hard, lustrous, malleable, ductile, exceedingly difficult to fuse, and is attracted by the magnet. In contact with air and moisture a coating of rust (hydrate of sesquioxide of iron) forms on its surface ; upon ignition in the air, a coating of black protosesquioxide. Hydrochloric acid and dilute sulphuric acid dissolve iron, with evolution of hydrogen gas ; if the iron contains carbon, the hydrogen is mixed with carbide of hydrogen. The solu- tions contain protoxide. Dilute nitric acid dissolves iron in the cold to nitrate of protoxide, with evolution of nitrous oxide ; at a high tem- perature, to nitrate of sesquioxide, with evolution of nitric oxide ; if the iron contains carbon, some carbonic acid is also evolved, and there is left undissolved a brown substance resembling humus, which is soluble in alkalies. 2. Protoxide of iron is a black powder ; its hydrate is a white powder, which in the moist state absorbs oxygen and speedily acquires a grayish-green, and ultimately a brownish-red color. Both the protoxide and its hydrate are readily dissolved by hydrochloric, sulphuric, and nitric acids. 88 PROTOXIDE OF IRON. [ 109. 3. The salts of protoxide of iron have in the anhydrous state a white, in the hydrated state a greenish color ; their solutions appear colored only when concentrated. Exposed to the air, they absorb oxygen and are converted into salts of the protosesquioxide. The soluble neutral salts redden litmus paper, and are decomposed at a red heat. 4. Acid solutions of salts of protoxide of iron are not precipitated by hydrosulphuric add; neutral solutions of salts of protoxide of iron with weak acids are precipitated by this reagent at the most but very in- completely ; the precipitates are of a black color. 5. Sulphide of ammonium precipitates from neutral, and hydrosul- phuric acid from alkaline solutions of salts of protoxide of iron, the whole of the metal as black hydrated PROTOSULPHIDE OF IRON (Fe S), which is insoluble in alkalies and sulphides of the alkali metals, but dissolves readily in hydrochloric and nitric acids : this black precipi- tate turns reddish-brown in the air by oxidation. To highly dilute solutions of protoxide of iron, addition of sulphide of ammonium imparts a green color, and it is only after some time that the protosulphide of iron separates as a black precipitate. 6. Potassa and ammonia produce a precipitate of HYDRATE OF PROT- OXIDE OF IRON (FeO, HO), which in the first moment looks almost white, but acquires after a very short time a dirty green, and ultimately a reddish-brown color, owing to absorption of oxygen from the air. Pre- sence of salts of ammonia prevents the precipitation by potassa partly, and that by ammonia altogether. If alkaline solutions of protoxide of iron thus obtained by the agency of salts of ammonia are exposed to the air, hydrate of sesquioxide of iron precipitates. 7. Ferrocyanide of potassium produces in solutions of protoxide of iron a bluish-white precipitate of FERROCYANIDE OF POTASSIUM AND IRON (K, Fe 3 , Cfy 2 ), which, by absorption of oxygen from the air, speedily acquires a blue color. Nitric acid or chlorine converts it immediately into Prussian blue, 3 (K, Fe 3 , Cfy 2 ) + 4 01 = 3 K 01 + Fe Cl + 2 (Fe 4 Cfyj. 8. ferricyanide of potassium produces a magnificently blue precipitate of FERRICYANIDE OF IRON (Fe g Cfdy). This precipitate does not differ in color from Prussian blue. It is insoluble in hydrochloric acid, but is readily decomposed by potassa. In highly dilute solutions of salts of protoxide of iron the reagent produces simply a deep blue-green coloration. 9. Sulphocyanide of potassium does not alter solutions of protoxide of iron free from sesquioxide. 10. Carbonate of baryta does not precipitate solutions of protoxide of iron in the cold. 11. Borax dissolves salts of protoxide of iron in the oxidizing flame, giving beads varying in color from YELLOW to DARK RED ; when cold, the beads vary from colorless to dark yellow. In the inner flame the beads change to bottle-green, owing to the reduction of the newly-formed sesquioxide to protosesquioxide. Phosphate of soda and ammonia mani- fests a similar deportment with the salts of protoxide of iron ; the beads produced with this reagent lose their color upon cooling still more com- pletely than is the case with those produced with borax ; the signs of the ensuing reduction in the reducing flame are also less marked. 110.] SEsquioxiDE or IKON. 89 HO. / SESQUIOXIDE OF IRON (Fe a 3 ). 1. The native crystallized sesquioxide of iron is steel-gray ; the native as well as the artificially prepared sesquioxide of iron gives upon trituration a brownish-red powder ; the color of hydrate of sesquioxide of iron is more inclined to reddish-brown. Both the sesquioxide and its hydrate dissolve in hydrochloric, nitric, and sulphuric acids; the hydrate dissolves readily in these acids, but the anhydrous sesquioxide dissolves with greater difficulty, and completely only after long exposure to heat. 2. The neutral anhydrous salts of sesquioxide of iron are nearly white ; the basic salts are yellow or reddish-brown. The color of the solution is brownish-yellow, and becomes reddish-yellow upon the application of heat. The soluble neutral salts redden litmus paper, and are decomposed by heat. 3. Hydrosulphuric acid produces in neutral and acid solutions of salts of sesquioxide of iron a milky white turbidity, proceeding from separated SULPHUR. This reaction is caused by a mutual decomposition of the sesquioxide of iron and the hydrosulphuric acid, in which the former is deprived of one-third of its oxygen, and thus reduced to the state of protoxide ; the oxygen forms water with the hydrogen of the hydro- sulphuric acid, and the liberated sulphur separates. Solution of hydro- sulphuric acid, rapidly added to neutral solutions, imparts to the fluid a transitory blackening. In solution of neutral acetate of sesquioxide of iron it produces a permanent precipitate of sulphide of iron. 4. Sulphide of ammonium precipitates from neutral, and hydrosulphuric acid from alkaline solutions of salts of sesquioxide of iron, the whole of the metal as black hydrated PROTOSULPHIDE OF IRON (FeS).. This pre- cipitation is preceded by the reduction of the sesquioxide to protoxide. In very dilute solutions the reagent produces only a blackish-green colora- tion. The minutely divided protosulphide of iron subsides in such cases only after long standing. Protosulphide of iron, as already stated ( 109, 5), is insoluble in alkalies and alkaline sulphides, but dissolves readily in hydrochloric and nitric acids. 5. Potassa and ammonia produce bulky reddish-brown precipitates of HYDRATE OF SESQUIOXIDE OF IRON (F 2 O 3 , H 0), which are insoluble in an excess of the precipitant as well as in salts of ammonia. In presence of sesquioxide of chromium, an excess of solution of potassa or ammonia will dissolve, part of the sesquioxide of iron along with the sesquioxide of chromium. Generally, however, a portion of both oxides remains undis- solved ; and, moreover, the dissolved oxides speedily separate again from the solution. 6. Ferrocyanide of potassium produces even in highly dilute solutions a magnificently blue precipitate of FERROCYANIDE OF IRON, or Prussian blue (Fe 4 Cfy 3 ), which is insoluble in hydrochloric acid, but is decom- posed by potassa, with separation of hydrate of sesquioxide of iron. 7. Ferricyanide of potassium deepens the color of solutions of salts of sesquioxide of iron to reddish-brown ; but it fails to produce a precipitate. 8. Sulphocyanide of potassium imparts to neutral or slightly acid solu- tions of salts of sesquioxide of iron a most intense blood-red color, arising from the formation of a soluble SULPHOCYANIDE OF IRON. Addi- tion of acetate of soda destroys this color, hydrochloric acid restores it 90 RECAPITULATION AND REMARKS. [ 111. again. This test is the most delicate of all ; it will indicate the presence of sesquioxide of iron even in fluids which are so highly dilute that every other reagent fails to produce the slightest visible alteration. The red coloration may in such cases be detected most distinctly by resting the test-tube upon a sheet of white paper, and looking through it from the top. 9. Carbonate of baryta precipitates even in the cold all the iron as a basic salt mixed with hydrate of sesquioxide. 10. The reactions before the Uovjpipe are the same as with the prot- oxide. 111. Recapitulation and remarks. On observing the behavior of the oxides of the fourth group with solution of potassa, it would appear that the separation of the oxide of zinc, which is soluble in an excess of this reagent, might be readily effected by its means ; however, in the actual experiment, we find that in the presence of sesquioxide of iron, protoxide of cobalt, &c., some of the oxide of zinc precipitates with these oxides ; and if only a small quantity of oxide of zinc is present, it frequently occurs that no trace of this metal can be detected in the alkaline filtrate. Again, from the behavior of the different oxides with chloride of ammonium and an excess of ammonia, one would conclude that the sepa- ration of sesquioxide of iron from the protoxides of cobalt, nickel, and manganese, and from oxide of zinc, might be readily effected by these agents. But this method also applied to the mixed oxides, is inaccurate, since greater or smaller portions of the other oxides will always preci- pitate with the sesquioxide of iron ; and it may therefore happen that, in this process, small quantities of cobalt, manganese, ) of bodies with moisture externally adhering to them. 174.] PRELIMINARY EXAMINATION. 175 Test the reaction of the condensed fluid in the tube: if it is alkaline, ammonia may be assumed to be present; if acid, a volatile acid (sulphuric acid, sulphurous acid, hydro- fluoric acid, hydrochloric, hydrobromic, or hydriodic acids, nitric acid, &c.). e. GASES OR FUMES ESCAPE. Observe whether they have a 8 color, smell, acid or alkaline reaction, whether they are inflam- mable, &c. aa. OXYGEN. The disengagement of this gas indicates the presence of peroxides, chlorates, nitrates, i n cases where the substance is dissolved innitricacid, and at 2 (50)>if the solution already contains hydrochloric acid. Particular regard must be had in this to the following observa- tions : we have seen 180, 3, b, (3, cc (59)> tna ^ if? i n cases where we * Regard is also had here to certain salts of the alkaline earths, as this course of examination leads directly to their detection. f If upon the addition of water the liquid becomes white and turhid or deposits a white precipitate, this indicates the presence of antimony or bismuth. Compare 176, 4 (29)- Heat with hydrochloric acid until the fluid has become clear again, and then pass on to 180, 2 (50). 183.] DETECTION OF BASES. 193 have A SUBSTANCE SOLUBLE IN WATER, we obtain, in the course of the examination, a white precipitate upon adding chloride of ammonium, ammonia, and sulphide of ammonium, this precipitate can consist only of sulphide of zinc, or alumina, or hydrate of silicic acid. But the case is different if the body is INSOLUBLE IN WATER, but dissolves in hydrochlo- ric acid ; for in that case a white precipitate produced by sulphide of ammonium, in presence of chloride of ammonium, may consist also of phosphates, borates, oxalates, silicates of the alkaline earths, or of fluorides of their metals, or all their bodies are insoluble in water, but dissolve in hydrochloric acid, and (being only very sparingly soluble also in solution of chloride of ammonium) accordingly separate again upon neutralization of that acid. If, therefore, a white preci- pitate is produced upon testing an acid solution, under the circum- stances stated, and according to the directions of 180, 3, b, (3, cc (59) proceed as follows : 1. If the results of the preliminary examination have given you reason 85 to suspect the presence of SILICIC ACID ( 174, 4, b, a [20]), evaporate a portion of the hydrochloric acid solution to dryness, moisten the residue with hydrochloric acid and add water. If silicic acid is present, it will remain undissolved. Determine the base in the solu- tion as directed 180, 3 (56), or 4 (62). 2. Add to a portion of the original hydrochloric acid solution some tartaric acid, and after this ammonia in excess. a. No PERMANENT PRECIPITATE is FORMED : absence of the 86 above enumerated salts of the alkaline earths. Mix another por- tion of the original solution with solution of soda in excess, and add to the one half of the clear fluid chloride of ammonium, to the other half hydrosulphuric acid. The formation of a preci- pitate in the former indicates the presence of ALUMINA ; in the latter, the presence of ZINC. Whether the alumina was com- bined with PHOSPHORIC ACID, may be ascertained by testing a portion of the original hydrochloric acid solution with molybdate of ammonia (143). b. A PERMANENT PRECIPITATE is FORMED : presence of a salt of an alkaline earth. a. If by ignition of the substance in a glass tube (in the 87 course of the preliminary examination see 174, 2) carbonic oxide and carbonic acid have been evolved, the body turning slightly black in the process, you may assume the presence of an OXALATE. Heat a sample of the original substance to slight redness, dissolve the residue with hydrochloric acid, when ensuing effervescence will confirm the presence of oxalic acid ; and ascertain the nature of the alkaline earth in the solution as directed 180, 4 (62). )3. Add to a portion of the hydrochloric acid solution ammo- 88 nia until a precipitate forms ; then acetic acid until this is re- dissolved ; lastly, acetate of soda and a drop of solution of ses- quichloride of iron : the formation of a white flocculent preci- pitant indicates the presence of PHOSPHORIC ACID. Add now some more sesquichloride of iron until the fluid has acquired a distinct red color, boil, filter boiling, and test the filtrate, which is now free from phosphoric acid, for the alkaline earth with which the phosphoric acid was combined, as directed 180, 4 194? DETECTION OF INORGANIC ACIDS. [ 184. (62)> after having previously removed, by precipitation with ammonia, the iron which may have been dissolved. y. Test a portion of the original substance, or of the preci- 89 pitate produced in the hydrochloric acid solution by ammonia, with sulphuric acid for FLUORINE ( 147). After removal of the fluorine, ascertain the nature of the alkaline earth now in the residue, combined with sulphuric acid. & BORACIC ACID is detected in the hydrochloric acid solution by means of turmeric paper ( 145), and the base combined with it, by means of solution of sulphate of lime (baryta, strontia), sulphuric acid, and alcohol (lime), or a large proportion of chloride of ammonium, ammonia, and phosphate of soda (magnesia). Simple Compounds. B. SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE IN WATER, BUT SOLUBLE IN HYDROCHLORIC ACID, NITRIC ACID, OR NITRO-HYDRO- CHLORIC ACID. DETECTION OF THE ACID. I. Detection of Inorganic Acids. 184. 1. CHLORIC ACID cannot be present, since all chlorates without QO 1 exception are soluble in water ; NITRIC ACID, which may be present in form of a basic salt, must have been revealed already by ignition of the body in a glass tube ( 174), and so must CYANOGEN ( 174, 2, e [8]). For the analysis of the insoluble metallic CYANIDES insoluble in water see 202. The results of the test with phosphate of soda and ammonia will have directed attention to the presence of SILICIC ACID ( 174, 4, b, a [20])- Evaporation of the hydrochloric acid solution to dryness, and treatment of the residue with hydrochloric acid and water will set all doubt at rest on the point. 2. The course of examination laid down here for the detection of 91 the bases leads likewise to that of ARSENIOUS and ARSENIC ACIDS, CAR- BONIC ACID, HYDROSULPHURIC ACID, and CHROMIC ACID. With regard to the latter acid, I repeat that its presence is indicated by the yellow or red color of the compound, the evolution of chlorine which ensues upon boiling with hydrochloric acid, and the subsequent presence of sesquioxide of chromium in the solution. Fusion of the compound tinder examination with carbonate of soda is, however, the most con- clusive test for chromic acid ( 138). 3. Boil a portion of the substance with nitric acid. 92 a. If nitric oxide gas is evolved, and sulphur separates, this is confirmative of the presence of a metallic sulphide. b. If violet vapors escape, the compound is a metallic IODIDE. c. If reddish-brown fumes of a chlorine-like smell are evolved, the compound is a metallic BROMIDE, in which case the fumes will color starch yellow ( 153). 4. Dilute a portion of the solution obtained by boiling with nitric 93 acid (3 [921) or of the nitrate of this solution, should the nitric acid have left an undissolved residue with water, and add solution of nitrate of silver to the fluid. The formation of a white precipitate 185.] DETECTION OF ORGANIC ACIDS. 195 which, after washing, is soluble in ammonia, and fuses without de- composition when heated, indicates the presence of CHLORINE. 5. Boil a portion of the substance with hydrochloric acid, filter, i necessary, dilute with water, and add chloride of barium. The for- mation of a white precipitate, which does not redissolve even upon addition of a large quantity of water, indicates the presence of SUL- PHURIC ACID. 6. Test for BORACIC ACID as directed 181, 6 (76)- 7. If none of the acids enumerated from 1 to 6 are present, there 95 is reason to suspect the presence of PHOSPHORIC ACID, OXALIC ACID, or FLUORINE, or the total absence of acids. To the presence of oxalic acid your attention will have been called already in the course of the preliminary examination, 174, 2, e (8). If the acids named had been combined with an alkaline earth, or, as regards phosphoric acid, with alumina, they would already have been detected in the course of the examination for these bases ( 183) ; they need therefore here be tested for, only in case the examination has revealed the presence of some other base. To that end, precipitate the base, according to circumstances, either with hydrosulphuric acid or with sulphide of ammonium, and filter. If you have precipitated with sulphide of ammonium, add to the filtrate hydrochloric acid to acid reaction, expel in either case the hydrosulphuric acid by boiling, and filter if necessary. Test a portion of this solution for phosphoric acid, oxalic acid, and fluorine, as directed 181, 4 (71). Simple Compounds. B. SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE IN WATER, BUT SOLUBLE IN ACIDS. DETECTION OF THE ACID. II. Detection of Organic Acids. I 185. 1. FORMIC ACID cannot be present, as all the formates are soluble 96 in water. 2. ACETIC ACID has been revealed already in the course of the preliminary examination, by the disengagement of acetone. The re- action with sulphuric acid and alcohol ( 170) will afford conclusive proof. _ 3. Boil a portion of the substance for some time with solution ol 97 carbonate of soda in excess, and filter hot. You have now the organic acid in solution in combination with soda. Acidulate the solution slightly with hydrochloric acid, expel the carbonic acid by heat, and test as directed 182. o 2 196 DETECTION OF THE BASE AND THE ACID. [ 186. Simple Compounds. C. SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE IN WATER, HYDRO- CHLORIC ACID, NITRIC ACID, AND NITROHYDROCHLORIC ACID. ' DETECTION OF THE BASE AND THE ACID. Under this head we have to consider here, SULPHATE OF BARYTA, 98 SULPHATE OF STRONTIA, SULPHATE OF LIME, FLUORIDE OF CALCIUM, SILICA, SULPHATE OF LEAD, Compounds of LEAD with CHLORINE and BROMINE, compounds of SILVER with CHLORINE, BROMINE, IODINE, and CYANOGEN, and lastly, SULPHUR and CHARCOAL, as the only bodies belonging to this class which are more frequently met with. For the simple silicates I refer to 203, for the ferro- and ferricyanides, to 202. The preliminary examination will have informed you whether you need pay any regard to the possible presence of their compounds. Sulphate of lime and chloride of lead are not altogether insoluble in water, and sulphate of lead may be dissolved in hydrochloric acid. However, as these compounds are so difficultly soluble that complete solution of them is seldom effected, they are included here also among the class of insoluble substances, to insure their detection, should they have been overlooked in the course of the examination of the aqueous or acid solution of the body to be analyzed. 1. Free SULPHUR must have been detected already in the course of the preliminary examination. 2. CHARCOAL is black; it is insoluble in aqua regia ; put on platinum foil, with the blowpipe flame playing upon the under side of the foil, it is always consumed ; by deflagration with nitrate of potassa it yields carbonate of potassa. 3. Pour sulphide of ammonium over a very small quantity of the 99 substance under examination. a. It TURNS BLACK ; this indicates the presence of lead or a salt of silver. a. The body fused in the glass tube without decomposition ( 174, 2 [3]) : chloride of lead, bromide of lead, chloride of silver, bromide of silver, iodide of silver. Fuse 1 part of the com- pound with 4 parts of carbonate of soda and potassa in a small porcelain crucible, let cool, boil the residue with water, and test the filtrate for CHLORINE, BROMINE, and IODINE, as directed, 181, 5 (73)- Dissolve the residue, which consists either of metallic SILVER or OXIDE OF LEAD, in nitric acid, and test the solution as directed, 180, 1 (46)- /3. The body evolved cyanogen, and left metallic silver behind : CYANIDE OF SILVER. y. The body remained unaltered : SULPHATE OF LEAD. Boil a sample of it with solution of carbonate of soda, filter, acidu- late the filtrate with hydrochloric acid, and test with chloride of barium for SULPHURIC ACID ; dissolve the washed residue in nitric acid, and test the solution with hydros ulphuric acid and with sulphuric acid for LEAD. I. IT REMAINS WHITE : absence of an oxide of a heavy metal. 100 187.] COMPLEX COMPOUNDS - DETECTION OF BASES. 197 a. The body fused before the blowpipe; this indicates the . presence of FLUORIDE OF CALCIUM. Keduce a portion of the substance to a fine powder, decompose this in a platinum crucible with sulphuric acid, and try the reaction on glass ( 147), to prove the presence of FLUORINE ; boil the residue with hydrochloric acid, filter, neutralize the filtrate with ammonia, and test for LIME with oxalate of ammonia, /3. The body did not fuse before the blowpipe. Mix a small ., - portion of the very finely pulverized substance with 4 times the quantity of pure carbonate of soda and potassa, and fuse the mixture in a platinum crucible, or else on platinum foil. Boil the fused mass with water, filter, should a residue be left, and wash the latter. Acidulate a portion of the filtrate with hydrochloric acid, and then test with chloride of barium for SULPHURIC ACID ; and in case you do not find that acid, test another portion of the filtrate for SILICIC ACID, by eva- porating the fluid acidified with hydrochloric acid. If the SILICIC ACID was present in the pure state, the mass resulting from the fusion of the substance with carbonate of soda and potassa must have dissolved in water to a clear fluid; but if silicates also happened to be present, the bases of them are left behind undissolved, and may be further examined. If, on the other hand, sulphuric acid has been found, the alkaline earth which was combined with it is found on the filter as a carbonate. Wash this, then dissolve it in dilute hydrochloric acid, and test the solution for BARYTA, STRONTIA, -j-v and LIME, as directed 180, 4 (62). Complex Compounds* A. SUBSTANCES SOLUBLE IN WATER, AND ALSO SUCH AS ARE INSOLUBLE IN WATER, BUT DISSOLVE IN HYDROCHLORIC ACID, NITRIC ACID, OR NlTROHYDROCHLORIC ACID. Detection of the Basest 187.J (Treatment with Hydrochloric Acid : Detection of Silver, Suboxide of Mercury [Lead].) The systematic course for the detection of the bases is essentially 101 the same for bodies soluble in water, as for those which are soluble only in acids. Where, in consequence of the different nature of the original solution, deviations are rendered necessary, the fact will be distinctly stated. * I use this term here, and hereafter in the present work, to designate compounds in which all the more frequently occurring bases, acids, metals, and metalloids are supposed the explanations in the Third Section. Kegard is here had also to the pre- sence of the acids of arsenic, and of those salts of the alkaline earths whjch dissolve m hydrochloric acid, and separate again from that solution unaltered, upon neutralization of the acid by ammonia. Consult the remarks in the Third Section. 198 COMPLEX COMPOUNDS DETECTION OF BASES. [ 187. I. SOLUTION IN WATER. MlX THE PORTION INTENDED FOR THE DETECTION OF THE BASES WITH SOME HYDROCHLORIC ACID. 1. THE SOLUTION HAD AN ACID OR NEUTRAL REACTION PREVIOUSLY 102 TO THE ADDITION OF THE HYDROCHLORIC ACID. a. No PRECIPITATE is FORMED j this indicates the absence of silver and suboxide of mercury. Pass on to 188. b. A PRECIPITATE is FORMED. Add more hydrochloric acid drop by drop until the precipitate ceases to increase ; then add about six or eight drops more of hydrochloric acid, shake the mixture, and filter. The precipitate produced by hydrochloric acid may consist of chloride of silver, subchloride of mercury, chloride of lead, a basic salt of antimony, possibly also of benzoic acid. The basic salt of antimony, however, redissolves in the excess of hydrochloric acid ; consequently, if the instructions given have been strictly followed, the precipitate collected upon the filter can consist only of chloride of silver, subchloride of mercury, or chloride of lead (possibly also of benzoic acid, which, how- ever, is altogether disregarded here). Wash the precipitate collected upon the filter twice with cold water, add the washings to the filtrate, and examine the solution as directed 188, even though the addition of the washings to the acid nitrate should produce turbidity in the fluid (which indicates the presence of compounds of antimony or bismuth). Treat the washed precipitate on the filter as follows : 103 a. Pour hot water over it upon the filter, and test the fluid running off with sulphuric acid for LEAD. The non-forma- tion of a precipitate upon the addition of the sulphuric acid simply proves that the precipitate produced by hydrochloric acid contains no lead, and does not by any means establish the total absence of this metal, as hydrochloric acid fails to precipitate lead from dilute solutions. /3. Pour over the now thrice-washed precipitate upon the filter solution of ammonia. If this changes its color to black or gray, it is a proof of the presence of SUBOXIDE OF MER- CURY. y. Add to the ammoniacal fluid running off in (3 nitric acid to strongly acid reaction. The formation of a white, curdy precipitate indicates the presence of SILVER.* (If the precipitate did contain lead, the ammoniacal solution gene- rally appears turbid, owing to the separation of a basic salt of lead. This, however, does not interfere with the testing for silver, since the basic salt of lead redissolves upon the addition of nitric acid.) 2. THE ORIGINAL AQUEOUS SOLUTION HAD AN ALKALINE RE- ACTION. 104 a. THE ADDITION OF HYDROCHLORIC ACID TO STRONGLY ACID * If the quantity of silver is only very small, the presence is indicated by opalescence of the fluid. 187.] DETECTION OF BASES. 199 REACTION FAILS TO PRODUCE EVOLUTION OF GAS OR A PRE- CIPITATE, OR THE PRECIPITATE WHICH FORMS AT FIRST REDIS- SOLVES UPON FURTHER ADDITION OF HYDROCHLORIC ACID : pass on to 188. b. THE ADDITION OF HYDROCHLORIC ACID TO THE ORIGINAL SOLUTION PRODUCES A PRECIPITATE WHICH DOES NOT RED1S- SOLVE IN AN EXCESS OF THE PRECIPITANT, EVEN UPON BOILING. a. The formation of the precipitate is attended neither with 1Q5 evolution of hydrosulphuric acid nor of hydrocyanic acid. Filter, and treat the nitrate as directed 188. aa. THE PRECIPITATE is WHITE. It may, in that case, consist of a salt of lead or silver, insoluble in water and hydrochloric acid (CHLORIDE OF LEAD, SULPHATE OF LEAD, CHLORIDE OF SILVER, &c.). Test for the bases and acids of these compounds as directed 201, bearing in mind that the chloride of lead or chloride of silver which may- be present may possibly have been formed in the pro- cess. bb. THE PRECIPITATE is YELLOW OR ORANGE. In that case it may consist of SULPHIDE OF ARSENIC (and if the fluid from which it has separated was not boiled for a long time, or only with very dilute hydrochloric acid, also of sulphide of antimony or bisulphide of tin), which substances were originally dissolved in solution of ammonia, borax, phos- phate of soda, or some other alkaline fluid, with the ex- ception of solutions of alkaline sulphides and cyanides. Examine the precipitate as directed 190. /3. The formation of the precipitate is attended with evolu- 106 tion of hydro sulphuric acid gas, but not of hydrocyanic acid.* aa. THE PRECIPITATE is OF A PURE WHITE COLOR, AND CONSISTS OF SEPARATED SULPHUR. In that Case a SUL- PHURETTED ALKALINE SULPHIDE is present. Boil, filter, and pass onto 192, bearing in mind that of the substances considered in that paragraph the heavy metals cannot be present if the original solution was colorless. bb. THE PRECIPITATE is COLORED. In that case you may conclude that a METALLIC SULPHUR SALT is present, i. e., a combination of an alkaline sulphur base with a metallic sulphur acid. The precipitate may accordingly Consist of TERSULPHIDE OF GOLD, BISULPHIDE OF PLA- TINUM, BISULPHIDE OF TIN, TERSULPHIDE OF ARSENIC, Or TERSULPHIDE OF ANTIMONY. It might, however, consist also of SULPHIDE OF MERCURY Or of SULPHIDE OF COPPER, or contain these substances, as the former is readily soluble in sulphide of potassium, and the latter slightly soluble in sulphide of ammonium. Filter, and treat the filtrate as in aa, the preciptate as directed 189. y. The formation of the precipitate is attended with evolu- 107 tion of hydrocyanic acid, with or without simultaneous dis- engagement of hydrosulphuric acid. This indicates the pre- * Should the odor of the evolved gas leave any doubt regarding the presence or absence of hydrocyanic acid, add some chromate of potassa to a portion of the fluid, previously to the addition of the hydrochloric acid. 200 ACTUAL EXAMINATION COMPLEX COMPOUNDS. [ 188. sence of an ALKALINE CYANIDE, and, if the evolution of the hydrocyanic acid is attended with that of hydrosulphuric acid, also of an alkaline SULPHIDE. In that case the precipi- tate may, besides the compounds enumerated in a (105) an( l /3 (106)) contain many other substances (e. g. } sulphide of nickel, cyanide of nickel, cyanide of silver, &c.). Boil, with further addition of hydrochloric acid, or of nitric acid, until the whole of the hydrocyanic acid is expelled, and treat the solution, or, if an undissolved residue has been left, the ni- trate, as directed 188; and the residue (if any) according to 201. C. THE ADDITION OF HYDROCHLORIC ACID FAILS TO PRO- 108 DUCE A PERMANENT PRECIPITATE, BUT CAUSES EVOLUTION OF GAS. a. The escaping gas smells of hydrosulphuric acid ; this indicates the presence of a SIMPLE ALKALINE SULPHIDE. Proceed as in b, /3, aa (106)- (3. The escaping gas is inodorous; in that case it is CAR- BONIC ACID which was combined with an alkali. Pass on to 188. y. The escaping gas smells of hydrocyanic acid (no matter whether hydrosulphuric acid or carbonic acid is evolved at the same time or not). This indicates the presence of an ALKALINE CYANIDE. Boil until the whole of the hydrocyanic acid is expelled, and then pass on to 1 88. II. SOLUTION IN HYDROCHLORIC ACID OR IN NITROHYDROCHLORIC ACID. Proceed as directed 188. III. SOLUTION IN NITRIC ACID. Dilute a small sample of it with water ; should this produce tur- 109 bidity or a precipitate (indicative of the presence of bismuth) add nitric acid until the fluid is clear again, then hydrochloric acid. 1. No PRECIPITATE is FORMED. Absence of silver and sub- oxide of mercury. Treat the principal solution as directed 188. 2. A PRECIPITATE is FORMED. Treat a larger portion of the nitric acid solution the same way as the sample, filter, and examine the precipitate as directed 187, I. 1, b (103), the filtrate as directed 188. 188.* (Treatment with Hydrosulphuric Acid, Precipitation of the Metallic Oxides of Group V. 2nd Section, and of Group VI.) ADD TO A small PORTION OF THE CLEAR ACID SOLUTION HYDRO- SULPHURIC ACID WATER, UNTIL THE ODOR OF HYDROSULPHURIC ACID IS DISTINCTLY PERCEPTIBLE AFTER SHAKING THE MIXTURE, AND WARM GENTLY, 1. No PRECIPITATE is FORMED, even after the lapse of some HO * Consult the remarks in the Third Section. 188.] DETECTION OF BASES. 201 time. Pass on to 192, for lead, bismuth, cadmium, copper, mercury, gold, platinum, antimony, tin, and arsenic,* are not present ;t the absence of sesquioxide of iron and of chromic acid is also indicated by this negative reaction. 2. A PRECIPITATE IS FORMED. a. The precipitate is of a pure white color, light and finely HI pulverulent, and does not redissolve on addition of hydro- chloric acid. It consists of separated sulphur, and indicates the presence of SESQUIOXIDE OF IRON.* None of the other metals enumerated in 188, 1 (HO), can be present. Treat the principal solution as directed 192. b. The precipitate is colored. ^ Add to the larger proportion of the acid or acidified solu- H2 tion, best in a small flask, hydrosulphuric acid water in excess, i. e., until the fluid smells distinctly of it, and the precipitate ceases to increase upon continued addition of the reagent; apply a gentle heat, shake vigorously for some time, filter, keep the filtrate (which contains the oxides pre- sent of Groups I. IV.) for further examination, according to the instructions of 192, and thoroughly wash the pre- cipitate which contains the sulphides of the metals present of Groups V. and VI. In many cases, and more particularly when there is any reason to suspect the presence of arsenic, it will be found more convenient to transmit hydrosulphuric acid gas through the solution DILUTED WITH WATER, instead of adding hydrosulphuric acid water. If the precipitate is yellow, it consists principally of tersul- H3 phide of arsenic, bisulphide of tin, or sulphide of cadmium ; if orange-colored, this indicates tersulphide of antimony ; if brown or black, one at least of the following oxides is pre- sent : oxide of lead, teroxide of bismuth, oxide of copper, oxide of mercury, teroxide of gold, binoxide of platinum, protoxide of tin. However, as a yellow precipitate may contain small admixtures of an orange-colored, a brown, or even a black precipitate, and yet its color not be very per- ceptibly altered thereby, it will always prove the safest way to assume the presence of all the metals named in 188, 1 (110)> in any precipitate produced by hydrosulphuric acid, and to proceed accordingly as the next paragraph ( 189) directs. * Should the preliminary examination have led you to suspect the presence of arsenic acid, you must endeavor to obtain the most conclusive evidence of the absence of this acid ; this may be done by allowing the fluid to stand for some time, or by heating it with sul- phurous acid previous to the addition of the hydrosulphuric acid. (Compare 132.) t In solutions containing much free acid, the precipitates are frequently formed only after dilution with water. J Sulphur will precipitate also if sulphurous acid, iodic acid, or bromic acid are pre- sent (which substances are not included in our analytical course), and also if chromic acid, chloric acid, or free chlorine are present. In presence of chromic acid, the separation of the sulphur is attended with reduction of the acid to sesquioxide of chromium, in con- sequence of which the reddish-yellow color of the solution changes to green. (Compare 138.) The white sulphur suspended in the green solution looks at first like a green pre- cipitate, which frequently tends to mislead beginners. 202 ACTUAL EXAMINATION COMPLEX COMPOUNDS. [ 189. 189. (Treatment of the Precipitate produced ~by Hydro sulphuric Acid with Sul- phide of Ammonium; Separation of the 2nd Section of Group V. from Group VI.) INTRODUCE A SMALL PORTION OF THE PRECIPITATE PRODUCED BY 114 HYDROSULPHURIC ACID IN THE ACIDIFIED SOLUTION INTO A TEST- TUBE,* ADD A LITTLE WATER, AND THREE OR FOUR DROPS OF YELLOW- ISH SULPHIDE OF AMMONIUM, AND EXPOSE THE MIXTURE FOR A SHORT TIME TO A GENTLE HEAT, t 1. THE PRECIPITATE DISSOLVES COMPLETELY IN SULPHIDE OF H5 AMMONIUM (or SULPHIDE OF SODIUM, as the case may be) : absence of the metals of Group V. cadmium, lead, bismuth, copper, mercury. Treat the remainder of the precipitate (of which you have digested a portion with sulphide of ammonium) as directed 190. If the precipitate produced by hydrosulphuric acid was so trifling that vou have used the whole of it in treating with sulphide of ammo- nium, precipitate the solution obtained in that process by addition of hydrochloric acid, filter, wash the precipitate, and treat the latter as directed 190. 2. THE PRECIPITATE IS NOT REDISSOLVED, OR AT LEAST NOT H6 COMPLETELY : presence of the metals of Group V. Dilute with 4 or 5 parts of water, filter, and mix the filtrate with hydrochloric acid in slight excess. a. The fluid simply turns- milky, owing to the separation cf sulphur. Absence of the metals of Group VI. gold, platinum, tin, antimony, and arsenic. J Treat the rest of the precipitate of which you have digested a portion with sul- phide of ammonium, according to the directions of 191. b. A colored precipitate is formed : presence of metals of H7 Group VI. by the side of those of Group V. Treat the entire precipitate produced by hydrosulphuric acid the same as you have treated a portion of it, i. e. } digest it with yellow * * If there is a somewhat large precipitate, this may be readily effected by means of a small spatula of platinum or horn ; but if you have only a very trifling precipitate, make a hole in the bottom of the filter, insert the perforated point into the mouth of the test- tube, rinse the precipitate into the latter by means of the washing-bottle, wait until the precipitate has subsided, and then decant the water. t If the solution contains copper, which is generally revealed by the color of the fluid, and may be ascertained positively by testing with a clean iron rod (see 119, 10), use solution of sulphide of sodium instead of sulphide of ammonium (in which sulphide of copper is not absolutely insoluble, see 119, 5), and boil the mixture. But if the fluid, besides copper, also contains oxide of mercury (the presence of which is generally suffi- ciently indicated by the several changes of color exhibited by the precipitate forming upon the addition of the hydrosulphuric acid [ 118, 3], and which, in doubtful cases, may be detected with positive certainty by testing a portion of the original solution acidified with hydrochloric acid, with protochloride of tin), sulphide of ammonium must be used, although the separation of the sulphides of the antimony group from the sulphide of copper is not fully effected in such cases ; since, were sulphide of sodium used, the sulphide of mercury would dissolve in this reagent, and this would impede the ulterior examination of the sulphides of the antimony group. That this inference becomes uncertain if the precipitate produced by hydrosulphuric acid, instead of being digested with a small quantity of sulphide of ammonium, has been treated with a larger quantity of that reagent, is self-evident ; for the large quantity of sulphur which separates in that case will, of course, completely conceal any slight traces of sulphide of arsenic or bisulphide of tin which may have been thrown down. 190.] DETECTION OF BASES. 203 sulphide of ammonium, or, as the case may be, sulphide of sodium, let it subside, pour the supernatant liquid on a filter, digest the residue in the tube once more with yellow sulphide of ammonium (or sulphide of sodium), and filter. Wash the residue* (containing the sulphides of Group V.), and treat it afterwards as directed 191. Dilute the filtrate which contains the metals of Group VI. in the form of sulphur salts with water, add hydrochloric acid to slightly acid reaction, heat gently, filter the precipitate formed which contains the sulphides of the metals of Group VI. mixed with sulphur wash thoroughly, and proceed as directed next paragraph ( 190). 190. (Detection of the Metals of Group VI. : Arsenic, Antimony, Tin t Gold, Platinum.) If the precipitate consisting of the sulphides of Group VI. has a 118 PURE YELLOW COLOR, this indicates principally arsenic and tin; if it is distinctly ORANGE- YELLOW, antimony is present ; if it is BROWN or BLACK, this denotes the presence of platinum or gold. Beyond these general indications, the color of the precipitate affords no safe guidance. It is therefore always advisable to test yellow precipitate also for antimony, gold, and platinum, since minute quantities of the sulphides of these metals are completely hid by a large quantity of bisulphide of tin or tersulphide of arsenic. Proceed accordingly as follows : Heat a little of the precipitate on the lid of a porcelain crucible, or on a fragment of porcelain or glass, t 1. Complete vocalization ensues : probable presence of ARSENIC, 119 absence of the other metals of Group VI. Reduction of a portion of the precipitate with cyanide of potassium and car- bonate of soda ( 131, 12) will afford positive proof of the presence or absence of arsenic. Whether that metal was pre- sent in the form of arsenious acid or in that of arsenic acid, may be ascertained by the method described 1 33. 2. A fixed residue is left. In that case all the metals of 120 Group VI. must be sought for. Dry the remainder of the precipitate thoroughly upon the filter, triturate it together with about 1 part of anhydrous carbonate of soda and 1 part of nitrate of soda, and transfer the mixture in small portions at a time to a little porcelain crucible, in which you have previously * If the residue suspended in the fluid containing sulphide of ammonium, and inso- luble therein, subsides readily, it is not transferred to the filter, but washed in the tube by decantation. But if its subsidence proceeds slowly and with difficulty, it is transferred to the filter, and washed there ; a hole is then made in the bottom of the filter, and the residue rinsed into a small porcelain basin by means of a washing-bottle ; the application, of a gentle heat will now materially aid the subsidence of. the residue, and the super- natant water may then be decanted. t That this preliminary examination may be omitted if the precipitate is not yellow, and that it can give a decisive result only if the sulphur precipitate submitted to the test has been thoroughly washed, is self-evident. 204) DETECTION OF BASES. [ 190. heated 2 parts of nitrate of soda to fusion.* As soon as com- plete oxidation is effected, pour the mass out on a piece of por- celain. After cooling, soak the fused mass (the portion still sticking to the inside of the crucible as well as the portion poured out on the porcelain) in cold water, filter the insoluble residue which will remain if the mass contained antimony, tin, gold, or platinum and well wash with a mixture of about equal parts of water and alcohol. (The alcohol is added to prevent the solution of the antimonate of soda. The washings are not added to the nitrate.) The filtrate and the residue are now examined as follows : a. EXAMINATION OF THE FILTRATE FOR ARSENIC (which 121 must be present in it in the form of arsenate of soda). Divide the filtrate into two portions, add highly dilute nitric acid cautiously to the one portion to slightly acid reaction, and apply heat.t Add to the acidified solution some nitrate of silver (not too little), filter (in case some chloride of silver J or nitrite of silver should have separated), pour upon the filtrate, along the side of the tube held slanting, a layer of dilute solu- tion of ammonia, 5 parts of water to 1 part of solution of ammonia and let the mixture stand for some time with- out shaking. The formation of a reddish-brown precipitate, which appears hovering cloud-like between the two layers (and may be seen far more readily and distinctly by re- flected than by transmitted light), denotes the presence of ARSENIC. If the arsenic is present in some quantity, and the free nitric acid of the solution is exactly saturated with ammonia, the fluid being stirred during this process, the precipitate of arse- nate of silver which forms imparts a brownish-red tint to the entire fluid. To gain more positive information respecting the presence of 122 arsenic, precipitate the second portion of the filtrate with solu- tion of neutral acetate of lead, filter the precipitate (which con- sists of sulphate, carbonate, and if arsenic is really present arsenate of lead), dry between blotting paper, and then expose on charcoal to the inner flame of the blowpipe. If arsenic is present, a globule of metallic lead containing arsenic will be produced, which will long continue to exhale the odor of * Should the amount of the precipitate be so minute that this operation cannot be con- veniently performed, cut the filter, with the dried precipitate adhering to it, into small pieces, triturate these together with some carbonate of soda and nitrate of soda, and pro- ject both the powder and the paper into the fusing nitrate of soda. It is preferable, however, in such cases, to procure at once, if practicable, a sufficiently large amount of the precipitate, as otherwise there will be but little hope of effecting the positive detec- tion of all the metals of Group VI. Supposing all the metallic sulphides of the sixth group to have been present, the fused mass would consist of antimonate and arsenate of soda, binoxide of tin, metallic gold and platinum, sulphate, carbonate, nitrate, and some nitrite of soda. Compare also 133, 1. *f In some cases where a somewhat larger proportion of carbonate of soda had been used, or a very strong heat applied, a trifling precipitate (hydrated binoxide of tin) may separate upon the acidification of the filtrate with nitric acid. This may be filtered off, and then treated in the same manner as the undissolved residue. J Chloride of silver will separate if the reagents were not perfectly pure, and the pre- cipitate has not been thoroughly washed. 190-] DETECTION OF BASES. -205 garlic whenever the inner flame of the blowpipe is made to act upon it. For further confirmation of the presence of arsenic this substance may be exhibited in the metallic state. (Compare 131 and 132.) Whether the arsenic was present in the form of arsenious acid or in that of arsenic acid, may be ascer- tained by the method described, 133, at the end. b. EXAMINATION OF THE RESIDUE FOR ANTIMONY, TIN, GOLD, 123 PLATINUM. (As the antimony, if present in the residue, must exist as white, pulverulent antimonate of soda, the tin as white, flocculent binoxide, the gold and platinum in the metallic state* the appearance of the residue is in itself indicative of its nature.) Dry the residue on the filter. If there is much of it, separate it from the filter, and fuse it together with about 4 parts of cyanide of potassium, either in a small porcelain crucible or in a somewhat wide glass tube sealed at one end. If the quantity is small, insert the filter together with the precipitate in a platinum wire twisted into a spiral coil, and incinerate in the outer mantle of a small spirit-lamp or gas-flame ; transfer the residue together with the filter-ash to a narrow glass tube sealed at one end, and fuse it in this together with 4 parts of cyanide of potassium insert the ignited part of the tube, whilst still red-hot, into a test-tube filled with cold water, which will cause the part containing the fused mass to crack off" in splinters. In either case remove the soluble salts com- pletely by repeated warming with water and decantation, pour hydrochloric acid over the metallic residue, heat to boiling, and test the solution, which in case of the presence of TIN must contain protochloride of tin, with chloride of mercury ( 128, 8). Boil the residue once more with hydrochloric acid, decant the fluid, then dissolve the residue still remaining in hydro- chloric acid with addition of the least possible amount of nitric acid to effect solution, mix this with solution of hydrosulphuric acid, and heat to incipient boiling. If a precipitate of a distinct orange color forms, ANTIMONY is 124 present. In presence of much tin, the color is usually more or less concealed by an admixture of bisulphide of tin (for it is not easy to effect a complete separation of the two metals by boil- ing with hydrochloric acid) ; the precipitate may also contain bisulphide of platinum and metallic gold (resulting from the reduction by heat of precipitated tersulphide of gold). Let the precipitate, therefore, subside, wash it several times by decantation, and finally heat it with hydrochloric acid, to dissolve the sulphide of antimony present. If the precipitate did contain gold or bisulphide of platinum, a black pulverulent residue will remain. Test now in the first place the hydro- chloric acid solution for ANTIMONY, by means of zinc and pla- tinum ( 130, 8), then dissolve the residue, if any, in some nitrohydrochloric acid, and test a portion of the solution for GOLD, with protochloride of tin, another portion for the same metal with sulphate of protoxide of iron ( 125). Evaporate the remainder of the solution with addition of some chloride of potassium, and add to the residue a mixture of equal parts of alcohol and water. The formation of a yellow precipitate indicates the presence of PLATINUM. 206 ACTUAL EXAMINATION COMPLEX COMPOUNDS. [ 191. 191. (Defection of the Metallic Oxides of Group V. 2nd Section : Oxide of Lead. Teroxide of Bismuth. Oxide of Copper. Oxide of Cadmium. Oxide of Mercury.) WASH THE PRECIPITATE WHICH HAS NOT BEEN DISSOLVED BY SUL- 125 PHIDE OF AMMONIUM, AND BOIL WITH NITRIC ACID. This operation is performed best in a small porcelain dish ; the boiling mass must be constantly stirred with a glass rod during the process. A great excess of acid must be avoided. 1. THE PRECIPITATE DISSOLVES, AND THERE REMAINS FLOATING IN 126 THE FLUID ONLY THE SEPARATED, LIGHT, FLOCCULENT, YELLOW SUL- PHUR j this indicates the absence of mercury. CADMIUM, COPPER, LEAD, and BISMUTH may be present. Filter the fluid from the separated- sulphur, and treat the nitrate as follows (should there be too much nitric acid present, the greater part of this must first be driven off by evaporation) : add to a portion of the filtrate dilute sulphuric acid in moderate quantity, heat gently, and let the fluid stand some time. a. No PRECIPITATE FORMS j absence of lead. Mix the re- 127 mainder of the filtrate with ammonia in excess, and gently heat. a. No precipitate is formed; absence of BISMUTH. If the 128 liquid is blue, COPPER is present; very minute traces of copper, however, might be overlooked, if the color of the ammoniated fluid alone were consulted. To be quite safe, and also to test for cadmium, evaporate the ammoniated solu- tion nearly to dryness, add a little acetic acid, and, if neces- sary, some water, and aa. Test a small portion of the fluid for copper with 129 ferrocyanide of potassium. The formation of a reddish- brown precipitate, or a light brownish-red turbidity, indi- cates the presence of COPPER (in the latter case only to a very trifling amount). lb. Mix the remainder of the fluid with solution of 130 hydrosulphuric acid in excess. The formation of a yellow precipitate denotes CADMIUM. If, on account of the pre- sence of copper, the sulphide of cadmium cannot be dis- tinctly recognised, allow the precipitate produced by the hydrosulphuric acid to subside, decant the supernatant fluid, and add to the precipitate solution of cyanide of potassium until the sulphide of copper is dissolved. If a yellow residue is left undissolved, CADMIUM is present in the contrary case, not. /3. A precipitate is formed. BISMUTH is present. Filter 131 the fluid, and test the filtrate for copper and cadmium, as directed in a (128)- To test the washed precipitate more fully for bismuth, slightly dry the filter containing it between blotting-paper, remove the still moist precipitate with a platinum spatula, dissolve in a watch-glass in the least possible quantity of hydrochloric acid, and then add a 192.] DETECTION OP BASES. 207 sufficient quantity of water. The appearance of a milky bidity confirms the presence of bismuth. b. A PRECIPITATE is FORMED. Presence of LEAD. Treat the 132 entire fluid the same as you have treated the sample, filter off the precipitate of sulphate of lead, and test the filtrate for bismuth, copper, and cadmium, as directed in a (127)-* Test the precipitate, after washing, by pouring solution of hydro- sulphuric acid over it. 2. THE PRECIPITATE OF THE METALLIC SULPHIDES DOES NOT COM- 133 PLETELY DISSOLVE IN THE BOILING NITRIC ACID, BUT LEAVES A RESIDUE, BESIDES THE LIGHT FLAKES OF SULPHUR THAT FLOAT IN THE FLUID. Probable presence of OXIDE OF MERCURY (which may be pronounced almost certain, if the precipitate is heavy and black). Allow the precipitate to subside, filter off the fluid, which must still be tested for CADMIUM, COPPER, LEAD, and BISMUTH ; mix a small portion of the filtrate with a large amount of solution of hydro- sulphuric acid, and should a precipitate form or a coloration become visible, treat the remainder according to the directions of 191, 1 (126). Wash the residue (which, besides sulphide of mercury, may alsa contain sulphate of lead, formed by the action of nitric acid upon sulphide of lead, and also binoxide of tin, as the complete separa- tion of bisulphide of tin from many of the sulphides of the metals of Group Y. is rather difficult), and examine one half of it for mercury,t by dissolving it in some hydrochloric acid, with addition of a very small proportion of nitric acid, and testing the solution with copper, or protochloride of tin ( 118); fuse the other half with cyanide of potassium and carbonate of soda. If you obtain metallic grains, wash, heat with nitric acid, and test the solution obtained with sulphuric acid for lead, the residue, which may be left, for tin, according to the directions of 190, 2, b (123). 192. (Precipitation with Sulphide of Ammonium, Separation and Detection of the Oxides of Groups III. andlV. : Alumina, Sesquioxide of Chromium ; Oxide of Zinc, Protoxide of Manganese, Protoxide of Nickel, Protoxide of Cobalt, Proto- and Sesquioxide of Iron ; and also of those Salts of the Alkaline Earths which are precipitated by Ammonia from their Solution in Hydrochloric Acid; Phosphates, B orates, Oxalates, Silicates, and Fluorides.) PUT A small portion OF THE FLUID IN WHICH SOLUTION OF HYDRO- 134 SULPHURIC ACID HAS FAILED TO PRODUCE A PRECIPITATE ( 188, 1, [110]), OR OF THE FLUID WHICH HAS BEEN FILTERED FROM THE PRECI- * For another method of distinguishing cadmium, copper, lead, and bismuth from each other, I refer to the Third Section (additions and remarks to 191) page 274. _ f If you have an aqueous solution, or a solution in very dilute hydrochloric acid, the oxide of mercury formed was present in the original substance in that form ; but if the solution has been prepared by boiling with concentrated hydrochloric acid, or by heating with nitric acid, the mercury may most likely have been originally present in the form of suboxide, and may have been converted into oxide in the process. 08 ACTUAL EXAMINATION COMPLEX COMPOUNDS. [ 192. PITATE FORMED, in a test-tube, observe whether it is colored or not,* boil to expel the hydrosulphuric acid which may be present, add a few drops of nitric acid, boil, and observe again the color of the fluid ; then cautiously add ammonia to alkaline reaction, observe whether this produces a precipitate, and then add some sulphide of ammo- nium, no matter whether ammonia has produced a precipitate or not. a. NEITHER AMMONIA NOR SULPHIDE OF AMMONIUM PRO- 135 DUCES A PRECIPITATE. Pass on to 193, for iron, nickel, cobalt, zinc, manganese, sesquioxide of chromium, alumina, are not present, nor are phosphates, borates,t silicates, and oxalates of the alkaline earths ; nor fluorides of the metals of the alkaline earths. b. SULPHIDE OF AMMONIUM PRODUCES A PRECIPITATE, AMMO- 136 NIA HAVING FAILED TO DO so ; absence of phosphates, borates,t Silicates, and oxalates of the alkaline earths ; of the fluorides of the metals of the alkaline earths ; and also, if no organic matters are present, of iron, sesquioxide of chromium, and alumina. Pass on to 192, 1 (138). c. AMMONIA PRODUCES A PRECIPITATE before the addition of 137 sulphide of ammonium. The course of proceeding to be pur- sued now, depends upon whether, (a) the original solution is simply aqueous, and has a neutral reaction, or (/3) the original solution is acid. In the former case, pass on to 192, 1 (138)> f r phosphates, borates, oxalates, and silicates of the alkaline earths cannot be present ; nor can fluorides of the metals of the alkaline earths. In the latter case, regard must be had to the possible presence of all the bodies enumerated in ' 192, a (135) ; pass on to 192, 2 (150). 1. DETECTION OF THE BASES OF GROUPS III. AND IY. IF PHOS- 138 PHATES, &C., IF THE ALKALINE EARTHS ARE NOT PRESENT. Mix the fluid mentioned at the beginning of the paragraph (134) ; a portion of which you have submitted to a preliminary examina- tion with some chloride of ammonium, then with ammonia, just to alkaline reaction ; lastly, with sulphide of ammonium, until the fluid, after being shaken, smells distinctly of that reagent ; shake the mixture until the precipitate begins to separate in flakes, and filter. Keep the FILTRATED which contains, or may contain, the basis of Groups II. and I., for subsequent examination according to the directions of 193. Wash the PRECIPITATE with water, to which a very little sulphide of ammonia has been added, and then proceed with it as follows : * If the fluid is colorless, it contains no chromium. If colored, the tint will to some extent act as a guide to the nature of the substance present ; thus a green tint, or a violet tint turning green upon boiling, points to the presence of chromium ; a light green tint to that of nickel ; a reddish color to that of cobalt ; the turning yellow of the fluid upon boiling with nitric acid, to that of iron. It must, however, be always borne in mind that these tints are perceptible only if the metallic oxides are present in larger quantity, and also that complementary colors, such as, for instance, the green of the nickel solution and the red of the cobalt solution will destroy each other, and that, accordingly, a solu- tion may contain both metals and yet appear colorless. f* Presence of much chloride of ammonium has a great tendency to prevent the precipi- tation of borates of the alkaline earths. If the filtrate has a brownish color, this points to the presence of nickel, sulphide of nickel, as is well known, being "slightly soluble in sulphide of ammonium ; this, however, involves no modification of the analytical course. 1-92.] DETECTION OF BASES. 209 a. IT is PERFECTLY WHITE ; absence of iron, cobalt, 139 nickel. You must test for all the other bases of Groups III! and IV., as the faint tints of sesquioxide of chromium and sul- phide of manganese are imperceptible in a large quantity of a white precipitate. Dissolve the precipitate by heat- ing it in a small dish with the least possible amount of hydro- chloric acid ; boil should hydrosulphuric acid be evolved until this gas is completely expelled, concentrate by evaporation, neutralize with carbonate of soda, then add solution of soda in excess, heat to boiling, and keep the mixture for some time in a state of ebullition. a. The precipitate formed at first dissolves completely in the 140 excess of solution of soda. Absence of manganese and chro- mium, presence of alumina or oxide of zinc. Test a portion of the alkaline solution with solution of hydrosulphuric acid for ZINC ; acidify the remainder with hydrochloric acid, add ammonia slightly in excess, and apply heat. The formation of a white, flocculent precipitate shows the presence of ALUMINA. /3. The precipitate formed does not dissolve, or dissolves only 141 partially, in the excess of solution of soda. Filter and test the FILTRATE, as in a (140), for ZINC and ALUMINA. With the undissolved PRECIPITATE proceed as follows : aa. If the color of the solution indicates the presence of chromium, fuse the precipitate in the cover of a platinum crucible, together with carbonate and nitrate of soda; treat the fused mass with water, and filter. If the nitrate is yellow, and, after being acidified with acetic acid, gives with acetate of lead a yellow precipitate, CHROMIUM is present. bb. Test a portion of the precipitate for MANGANESE, by means of the reaction with carbonate of soda in the outer blowpipe flame. If chromium has been found in aa, the residue left upon treating the fused mass with water, is used for this purpose. b. IT is NOT WHITE ; this points to the presence of chromium, 142 manganese, iron, cobalt, or nickel. If it is black, or inclines to black, one of the three metals last-mentioned is present. Under all circumstances, all the oxides of Groups III. and IY. must be looked for. Remove the washed precipitate from the filter with a spatula, or by rinsing it, with the aid of a washing-bottle, into a test- tube, through a hole made in the bottom of the filter, and pour over it rather dilute cold hydrochloric acid in moderate excess. a. It dissolves completely (except perhaps a little sulphur, 143 which may separate) ; absence of cobalt and nickel, at least of notable quantities of these two metals. Boil until the hydrosulphuric acid is completely expelled, filter if particles of sulphur are suspended in the fluid, con- centrate by evaporation, neutralize with carbonate of soda, then add solution of potassa or soda in excess, boil, filter the fluid from the insoluble precipitate which is sure to remain, I. P 210 ACTUAL EXAMINATION COMPLEX COMPOUNDS. [ 192. wash the latter, and proceed first to examine the filtrate, then the precipitate. aa. Test a portion of the filtrate with hydrosulphuric 144 acid for zinc; acidify the remainder with hydrochloric acid, and then test it with ammonia for ALUMINA. Com- pare 192, 1, a, a (140). 66. Dissolve a portion of the precipitate in hydrochloric acid, and test the solution with sulphocyanide of potas- sium for IRON. Test other portions for chromium and manganese, according to the directions of 192, 1, a, ft (141). N. B. If it is intented to make a very accurate 146 analysis, you have still to subject the remainder of the precipitate mentioned in bb (145) to further exa- mination, since it may contain magnesia (thrown down with the alumina) ; or some other alkaline earths, which may have been carried down along with the sesqui- oxide of chromium, owing to presence of carbonate of ammonium in the ammonia or sulphide of ammo- nium ; and lastly, also traces of cobalt, nickel, and zinc. Dissolve it, accordingly, in hydrochloric acid, and test the solution for the bodies enumerated, according to the directions of 192, 2, 6, a and /3 (155 and 156), omit- ting, however, the addition of sesquioxide of iron, recom- mended in 156- (3. The precipitate is not completely dissolved, a black re- sidue being left; this indicates the presence of cobalt and nickel. Filter, wash the undissolved precipitate, and test the filtrate as directed 192, 1, b, a (143) ', proceed with the residuary precipitate as follows: aa. Test a portion of it with borax, first in the outer, 148 then in the inner blowpipe-flame. If the bead in the oxidizing flame is violet whilst hot, and of a pale reddish-brown when cold, and turns in the reducing flame gray and turbid, nickel is present ; but if the color of the bead is and re- mains blue, in both flames, and whether hot or cold, COBALT is present. As in the latter case the presence of nickel cannot be distinctly recognised ; examine 66. The remainder of the precipitate by incinerating it 149 together with the filter in a coil of platinum wire, heating the ash with some hydrochloric acid, filtering the solution, then evaporating nearly to dryness, and adding nitrite of potassa, and then acetic acid ( 108, 10). The formation of a yellow precipitate confirms the presence of COBALT. Let the fluid, with the precipitate in it, stand for some time at a gentle heat, then filter, and test the filtrate with solu- tion of soda for nickel. 2, DETECTION OF THE BASES OF GROUPS III. AND IY. IN CASES 150 WHERE PHOSPHATES, BORATES, OXALATES, OR SILICATES OF THE AL- KALINE EARTHS, OR FLUORIDES OF THE METALS OF THE ALKALINE EARTHS, MAY POSSIBLY HAVE BEEN THROWN DOWN ALONG WITH THESE BASES, ?'.&, in cases where the original solution was acid, and 192.] DETECTION OF BASES. 211 a precipitate was produced by ammonia in the preliminary exami- nation. See (134). Mix the fluid mentioned in the beginning of this paragraph (134) with some chloride of ammonium, then with ammonia just to alkaline reaction, lastly with sulphide of ammonium, until the fluid, after being shaken, smells distinctly of this reagent ; shake the mixture until the precipitate begins to separate in flakes, and filter. Keep the FIL- TRATE, which contains, or may contain, the bases of Groups II. and I., for subsequent examination according to the directions of 193. Wash the precipitate with water to which a very little sulphide of ammonium has been added, and then proceed with it as follows. To give a clear notion of the obstacle to be overcome in this analytical process I must remind you that it is necessary to ex- amine the precipitate for the following bodies : Iron, nickel, cobalt (these show their presence to a certain extent by the black or blackish coloration of the precipitate), manganese, zinc, sesquioxide of chro- mium (the latter generally reveals its presence by the color of the solution), alumina ; baryta, strontia, lime, magnesia, which latter substances may have fallen down in combination with phosphoric acid, boracic acid, oxalic acid, silicic acid, or in form of fluorides. Besides these bodies, free silicic acid may also be contained in the precipitate as hydrate. As the original substance must, under all circumstances, be 151 afterwards examined for all acids that might possibly be present, it is not indispensable to test for the above enumerated acids at this stage of the analytical process ; still, as it is often interesting to know the presence of these acids at once, more especially in cases where a somewhat large proportion of some alkaline earth has been found in the precipitate produced by sulphide of ammonium, a method for the detection of the acids in question will be found appended by way of supplement to the method for the detection of the bases. Remove the precipitate from the filter with a small spatula, or 152 by rinsing it off with the washing-bottle, and pour over it cold dilute hydrochloric acid in moderate excess. a. A RESIDUE REMAINS. Filter, and treat the filtrate as 153 directed in 6 (154). The residue, if it is black, may contain sulphide of nickel, and sulphide of cobalt, and besides these, sulphur and silicic acid. Wash, and examine a sample of it in conjunction with phosphate of soda and ammonia before the blowpipe, in the outer flame. If a silica skeleton remains un- dissolved, ( 150, 8), this proves the presence of silicic acid. If the color of the bead is blue, COBALT is present ; if reddish, turning yellow on cooling, NICKEL. Should the color leave you in doubt, incinerate the filter containing the remainder of the residue, and test for cobalt and nickel by means of nitrite of potassa, as directed 192, 1, b, (3, bb (149). b. No RESIDUE is LEFT (except perhaps a little sulphur, 154 which may separate) : absence of nickel and cobalt, at least in any notable proportion. Boil the solution until the sulphuretted hydrogen is expelled, and then proceed as follows : p2 212 ACTUAL EXAMINATION COMPLEX COMPOUNDS. [ ]92. a. Mix a small portion of tlie solution with dilute sul- 155 phuric acid. If a precipitate forms, this may consist of sulphates of BARYTA and STRONTIA, possibly also of sulphate of lime. Filter, wash the precipitate, decompose it by boiling or fusion with carbonated alkali, wash the carbonates pro- duced, dissolve them in hydrochloric acid, and test the solu- tion as directed 193. Mix the fluid which has not been precipitated by dilute sulphuric acid, or the fluid filtered from the precipitate produced, with 3 volumes of spirit of wine. If a precipitate forms, this consists of sulphate of LIME. Filter, dissolve in water, and add oxalate of ammonia to the solution, as a confirmatory proof of the presence of lime. /3. Heat a somewhat larger sample with some nitric acid, 156 and test a small portion of the fluid with sulphocyanide of potassium for IRON;* mix the remainder with sesqui- chloride of iron in sufficient quantity to make a drop of the fluid give a yellowish precipitatet when mixed, on a watch- glass, with a drop of ammonia ; concentrate the fluid now until there is only a small quantity left ; add to this some water, then a few drops of solution of carbonate of soda, just sufficient to nearly neutralize the free acid, and lastly carbonate of baryta in slight excess; stir the mixture, and let it stand in the cold until the fluid above the precipitate has become colorless. Filter now the precipitate (aa) from the solu- tion (bb), and wash. aa. Boil the precipitate for some time with solution of 157 soda, filter, and test the filtrate for ALUMINA,:}: by heating with chloride of ammonium in excess. The part of the precipitate insoluble in solution of soda is examined for CHROMIUM, as directed in 192, 1, a, j3, aa (141). bb. Mix the solution with some ammonia and sulphide of ammonium. aa. No precipitate forms : absence of manganese and 158 zinc. Mix the solution containing chloride of barium with dilute sulphuric acid in slight excess, boil, filter, supersaturate with ammonia, and mix with oxalate of ammonia. If a precipitate of oxalate of LIME forms, filter, and test the filtrate with phosphate of soda for MAGNESIA. /3/3. A precipitate forms. Filter, and proceed with 159 the filtrate according to the directions of aa (158) * Whether the iron was present as sesquioxide or as protoxide, must be ascertained by testing the original solution in hydrochloric acid with ferricyanide of potassium and sul- phocyanide of potassium. t The addition of sesquichloride of iron is necessary, to effect the separation of phos- phoric acid and silicic acid which may be present. If the solution contains silicic aeid, the precipitate taken for alumina may contain also silicic acid. A simple trial with phosphate of soda and ammonia, on a platinum wire, in the blowpipe flame, will show whether the precipitate really contains silicic acid. Should this be the case, ignite the remainder of the supposed alumina precipitate on the cover of a platinum crucible, add some acid sulphate of potassa, fuse the mixture, and treat the fused mass with water, which will dissolve the alumina, leaving the silicic acid undissolved ; precipitate the alumina from the solution by ammonia. 193.] DETECTION OF OXIDES. 213 The precipitate may consist of sulphide of manganese and sulphide of zinc, and may contain traces also of sulphide of cobalt and sulphide of nickel. Wash it with water containing some sulphide of ammonium, and then treat it with acetic acid, which will dissolve the sulphide of MANGANESE, if any is present, leaving the other sulphides undissolved. Filter, boil the filtrate with solution of soda, and test the precipitate, which may form, with carbonate of soda in the outer blow- pipe flame for MANGANESE. Free the residuary part of the precipitate, which acetic acid has failed to dissolve, by washing, from the acetic acid solution still adhering to it, and then treat it with dilute hydrochloric acid, which will dissolve the zinc, if any is present. Filter, add some nitric acid to the filtrate, and concentrate the mixture considerably by boiling then add to it solution of soda in excess, boil, filter, if necessary, and test the filtrate with sulphide of ammonium for ZINC. Should a precipitate insoluble in solution of soda remain in the last operation, or should the dilute hydrochloric acid have left a black residue, test this precipitate and residue for COBALT and NICKEL, if you have not already previously detected the presence of these bodies ; compare 192, 1, b, fl (148 and 149). y. If you have found alkaline earths in a and /3, and 160 wish to know the acids in combination with which they have passed into the precipitate produced by sulphide of ammo- nium, this may be ascertained by making the following expe- riments with the remainder of the hydrochloric acid solu- tion : aa. Test a small portion of it for PHOSPHORIC ACID, by 161 means of molybdic acid ( 143, 11). bb. Mix another portion with carbonate of soda in excess, boil for some time, filter, and test one-half of the filtrate for OXALIC ACID, by acidifying it with acetic acid, and adding solution of sulphate of lime ; the other half for BORACIC ACID, by slightly acidifying it with hydro- chloric acid, and testing with turmeric paper ( 145 and 146). cc. Evaporate a third portion in a small dish or in a 162 watch-glass, dry the residue thoroughly, and then treat with hydrochloric acid. If there was any SILICIC ACID in the solution, this will be left undissolved. dd. Precipitate the remainder with ammonia, filter, wash and dry the precipitate, and examine it for FLUORINE according to 147, 5. 193. (Separation and Detection of the Oxides of Group II., which are pre- cipitated by Carbonate of Ammonia in Presence of Chloride of Ammonium, viz., Baryta, Strontia, Lime). To A SMALL PORTION OF THE FLUID IN WHICH AMMONIA AND 214 ACTUAL EXAMINATION COMPLEX COMPOUNDS. [ 193. SULPHIDE OF AMMONIUM HAVE FAILED TO PRODUCE A PRECIPITATE, OR OF THE FLUID FILTERED FROM THE PRECIPITATE FORMED, ADD CHLORIDE OF AMMONIUM, IF THE SOLUTION CONTAINS NO AMMO- NIACAL SALT, THEN CARBONATE OF AMMONIA AND SOME CAUSTIC AMMONIA, AND HEAT FOR SOME TIME VERY GENTLY (not to boiling). 1. No PRECIPITATE FORMS: absence of any notable quantity of 163 baryta, strontia, and lime. Traces of these alkaline earths may, however, be present ; to detect them, add to another portion of the fluid some sulphate of ammonia (prepared by supersaturating dilute sulphuric acid with ammonia) : if the fluid becomes turbid, it contains traces of BARYTA ; add to a third portion some oxalate of ammonia ; if the fluid turns turbid which reaction may perhaps require some time to manifest itself traces of lime are present. Treat the remainder of the fluid as directed 194, after having previously removed the traces of lime and baryta which may have been found, by means of the reagents that have served to effect their detection. 2. A PRECIPITATE is FORMED. Presence of LIME, BARYTA, or 164 STRONTIA. Fitter, test portions of the filtrate with sulphate and oxalate of ammonia, for traces of lime and baryta, which it may pos- sibly still contain, remove such traces, should they be found, by means of the said reagents, and examine the fluid, thus perfectly freed from baryta, strontia, and lime, for magnesia according to the directions of 194. Wash the precipitate produced by car- bonate of ammonia, dissolve it in the least 'possible amount of dilute hydrochloric acid, and add to a small portion of the fluid some solution of sulphate of lime (not too little). a. No precipitate is formed, NOT EVEN AFTER THE LAPSE OF SOME TIME. Absence of baryta and strontia; presence of LIME. To remove all doubt, mix another sample with oxalate of ammonia. b. A precipitate is formed ~by solution of sulphate of lime. a. It is formed immediately ; this indicates BARYTA. Be- 165 sides this, strontia and lime may also be present. Evaporate the remainder of the hydrochloric acid solu- tion of the precipitate produced by carbonate of ammonia to dryness, digest the residue with strong alcohol, decant the fluid from the undissolved chloride of barium, dilute with an equal volume of water, mix with a few drops of hydrofluo- silicic acid which throws down the small portion of baryta that had dissolved in form of chloride of barium allow the mixture to stand for some time ; filter, evaporate the alcoholic solution to dryness, dissolve the residue in water, and test a portion of the fluid with a dilute solution of sulphate of potassa ( 96, 3). If a precipitate forms imme- diately, or in the course of half an hour, the presence of STRONTIA is demonstrated. In that case, let the fluid with the precipitate in it stand at rest for some time, then filter, and add ammonia and oxalate of ammonia to the filtrate. The formation of a white precipitate indicates LIME. If sulphate of potassa has failed to produce a precipitate, the remainder of the solution of the residue left upon evapora- 194, 195.] EXAMINATION FOR MAGNESIA. 215 tion of the alcoholic fluid is tested at once with ammonia and oxalate of ammonia for lime. ft. It is formed only after some time. Absence of baryta, 166 presence of STRONTIA. Mix the remainder of the hydro- chloric acid solution with sulphate of potassa, let the mix- ture stand for some time, then filter, and test the filtrate with ammonia and oxalate of ammonia for LIME. (Examination for Magnesia.) To A PORTION OF THE FLUID IN WHICH CARBONATE, SULPHATE, AND OXALATE OF AMMONIA HAVE FAILED TO PRODUCE A PRECIPITATE ( 193, 1 [163] ), OR OF THE FLUID FILTERED FROM THE PRECIPITATES FORMED ( 193, 2 [164]), ADD AMMONIA, THEN SOME PHOSPHATE OF SODA, AND, SHOULD A PRECIPITATE NOT AT ONCE FORM, RUB THE INNER SIDES OF THE VESSEL WITH A GLASS ROD, AND THEN LET THE MIXTURE STAND FOR SOME TIME. 1. No PRECIPITATE is FORMED : absence of magnesia. Evapo- 167 rate another portion of the fluid to dryness,* and ignite gently. If a residue remains, treat the remainder of the fluid the same as the sample, and examine the residue, which by the moderate ignition to which it has been subjected has been freed from ammonia, for potassa and soda, according to the directions of 195. If no residue is left, this is a proof of the absence of the fixed alkalies ; pass on to 196. 2. A PRECIPITATE is FORMED : presence of MAGNESIA. As testing 168 for alkalies can proceed with certainty only after the removal of magnesia, evaporate the remainder of the fluid to dryness, and ignite until all ammoniacal salts are removed. Warm the residue with water, add baryta-water, prepared from the crystals, as long as a precipitate continues to form, boil, filter, add to the fil- trate a mixture of carbonate of ammonia with some caustic ammonia in slight excess, heat for some time gently, filter, evapo- rate the filtrate to dryness, adding some chloride of ammonium dur- ing the process (to convert into chlorides the caustic alkalies that may have formed), ignite the residue gently, then dissolve it in a little water, precipitate, if necessary, once more, with ammonia and carbonate of ammonia, evaporate again, and if a residue remains, ignite this gently, and finally examine it according to the directions of 195. 195. (Examination for Potassa, and Soda.) YOU HAVE NOW TO EXAMINE FOR POTASSA AND SODA THE GENTLY IGNITED RESIDUE, FREE FROM SALTS OF AMMONIA AND ALKALINE EARTHS, WHICH HAS BEEN OBTAINED IN 194, 1 (167), OR m 194, 2 (168). ,., Dissolve it in a little water, filter, if necessary, evaporate until * The most convenient way is to conduct the evaporation in the cover of a platinum crucible. 216 EXAMINATION FOR AMMONIA. [ 196, 197. there is only a small quantity of fluid left, and transfer one half of this to a watch-glass, leaving the other half in the porcelain dish. 1. To the one-half in the porcelain dish add, after cooling, a few 169 drops of solution of bichloride of platinum. If a yellow, crystal- line precipitate forms immediately, or after some time, POTASSA is present. Should no precipitate form, evaporate to dryness at a gentle heat, and treat the residue with a very small quantity of water or, if chlorides alone are present, with a mixture of water and alcohol, when the presence of minute traces of potassa will be revealed by a small quantity of a heavy yellow powder being left undissolved. 2. To the other half of the fluid (in the watch-glass) add some 170 antimonate of potassa. If this produces at once or after some time a crystalline precipitate, SODA is present. If the quantity of soda present is only very trifling, it often takes twelve hours before minute crystals of autimouate of soda will separate ; you must therefore always wait full that time for the possible manifestation of the reaction, before deciding, from its non-appear- ance, that no soda is present. As regards the form of the crystals, consult 91. 196. (Examination for Ammonia.) There remains still the examination for ammonia. Triturate 171 some of the body under examination, or, if a fluid, a portion of the latter, together with an excess of hydrate of lime, and, if necessary, a little water. If the escaping gas smells of ammonia, if it restores the blue color of reddened litmus paper, and forms white fumes with hydrochloric acid vapors, brought into contact with it by means of a glass rod, AMMONIA is present. The reaction is the most sensitive, if the trituration is made in a small beaker, and the latter covered with a glass plate with a slip of moistened turmeric or moist reddened litmus paper adhering to the under side. Complex Compounds. A, 1. SUBSTANCES SOLUBLE IN WATER. DETECTION OF ACIDS.* I. In the Absence of Organic Acids. 197. Consider, in the first place, which are the acids that form with the bases found compounds soluble in water, and let this guide you in the examination. To students the table given in Ap- pendix IV. will prove of considerable assistance. 1. The ACIDS of ARSENIC, as well as CARBONIC ACID, HYDROSUL- 172 PHURIC ACID, CHROMIC ACID, and SILICIC ACID, have generally been detected already in the course of testing for the bases j compare also 181, 1 and 2. * Consult also Section III. 197.] DETECTION OF ACIDS. 217 2. Add to a portion of the solution chloride of barium or, if lead, silver, or suboxide of mercury are present, nitrate of baryta, and, should the reaction of the fluid be acid, add ammonia to neutral or slightly alkaline reaction. a. No PRECIPITATE is FORMED : absence of sulphuric acid, 173 phosphoric acid, chromic acid, silicic acid, oxalic acid, arsenious and arsenic acids, as well as of notable quantities of boracic acid and hydrofluoric acid.* Pass on to 3 (175). b. A PRECIPITATE is FORMED. Dilute the fluid, and add 174 hydrochloric acid ; if the precipitate does not redissolve, or at least not completely, SULPHURIC ACID is present. 3. Add nitrate of silver to a portion of the solution. If this fails 175 to produce a precipitate, test the reaction, and add to the fluid, if it is acid, some dilute ammonia, taking care to add the reagent so gently and cautiously that the two fluids do not intermix ; if the reaction is alkaline, on the other hand, add with the same care some dilute nitric acid, instead of ammonia, and watch attentively, whether a precipitate or a cloud forms in the layer between the two fluids. a. NO PRECIPITATE IS FORMED IN THE LAYER BETWEEN THE 176 TWO FLUIDS, NEITHER IMMEDIATELY NOR AFTER SOME TIME. Pass on to 4 (181) '> there is neither chlorine, bromine, iodine, cyanogen,t ferro- and ferricyanogen present, nor sulphur ; nor phosphoric acid, arsenic acid, arsenious acid, chromic acid, silicic acid, oxalic acid \ nor boracic acid, if the solution was not too dilute. b. A PRECIPITATE is FORMED. Observe the color J of it, 177 then add nitric acid, and shake the mixture. a. The precipitate redissolves completely : absence of chlorine, bromine, iodine, cyanogen, ferro- and ferricyanogen, and also of sulphur. Pass on to 4 (181)' ft. A residue is left : chlorine, bromine, iodine, cyanogen, 178 ferro- or ferricyanogen may be present ; and if the residue is black or blackish, HYDROSULPHURIC ACID or a soluble METALLIC SULPHIDE. The presence of sulphur may, if necessary, be readily established beyond doubt, by mixing another portion of the solution with some solution of sul- phate of copper. aa. Test another portion of the fluid for IODINE, and subsequently for BROMINE, by the methods described in 157. bb. Test a small portion of the fluid with sesqui- 179 chloride of iron for FERROCYANOGEN ; and, if the color of the silver precipitate leads you to suspect the presence of * If the solution contains an ammoniacal salt in somewhat considerable proportion, the non-formation of a precipitate cannot be considered a conclusive proof of the absence ot these acids, since the baryta salts of most of them (not the sulphate), are, m prei ammoniacal salts, more or less soluble in water. t That the cyanogen in cyanide of mercury is not indicated by nitrate of i been mentioned 181, 5 (73). . r , j J Chloride, bromide, cyanide, and ferrocyanide of silver, and oxalate, silicate, an borate of silver are white ; iodide of silver, tribasic phosphate, and arsemte vei are yellow ; arsenate of silver and ferricyanide of silver are brownish-red ; chromate o silver is purple-red j sulphide of silver black. 218 DETECTION OF ACIDS. [ 197. FERRICYANOGEN, test another portion for this latter substance with sulphate of iron. If the original solu- tion has an alkaline reaction, some hydrochloric acid must be added before the addition of the sesquichloride of iron, or the sulphate of iron. cc. CYANOGEN, if present in form of a simple metallic cyanide soluble in water, may usually be readily re- cognised by the smell of hydrocyanic acid which the body under examination emits, and which is rendered more strongly perceptible by addition of a little dilute sulphuric acid. If no ferrocyanogen is present, the presence of cyanogen may be ascertained by the method given in 155, 6. dd. Should bromine, iodine, cyanogen, ferrocyanogen, 180 ferricyanogen, and sulphur not be present, the preci- pitate which nitric acid has failed to dissolve, consists of CHLOKIDE of silver. However, should the analytical process have revealed the presence of any of the other bodies, a special examination for chlorine may become necessary, viz., in cases where the quantity of the precipitate will not enable the operator to pronounce with positive certainty on the presence or absence of the latter element.* In such cases, which are of rare occurrence, however, the method given in 157 is resorted to. 4. Test another portion for NITRIC ACID, by means of sulphate of 181 iron and sulphuric acid ( 159). 5. To ascertain whether CHLORIC ACID is present, pour a little con- centrated sulphuric acid over a small sample of the solid body under examination : ensuing yellow coloration of the acid resolves the question in the affirmative ( 160). You have still to test for phosphoric acid, boracic acid, silicic acid, oxalic acid, and chromic acid, as well as for hydrofluoric acid. For the first five acids test only in cases where both chloride of barium and nitrate of silver have produced precipitates in neutral solutions. Compare also foot note to 197, 2, a. 6. Test for PHOSPHORIC ACID, by adding to a portion of the fluid 182 ammonia in excess, then chloride of ammonium and sulphate of magnesia ( 143, 7). Very minute quantities of phosphoric acid are detected most readily by means of rnolybdic acid ( 143, 7. To effect the detection of OXALIC ACID and HYDROFLUORIC ACID, add chloride of calcium to a portion of the solution. If this produces a precipitate which is not redissolved by addition of acetic acid, one or both bodies are present. Examine therefore now a sample of the original substance for fluorine, according to the directions of 147, 5, another sample for oxalic acid, by the method given in 146, 7. 8. Acidulate a portion of the fluid slightly with hydrochloric 183 * Supposing, for instance, the solution of nitrate of silver to have produced a copious precipitate insoluble in nitric acid, and the subsequent examination to have shown mere traces of iodine and bromine, the presence of chlorine may be held to be demonstrated without requiring additional proof. 198.] DETECTION OF ACIDS. 219 acid, and then test for BORACIC ACID, by means of turmeric paper 9. Should SILICIC ACID not yet have been found in the course of testing for the bases, acidulate a portion of the fluid with hydro- chloric acid, evaporate todryness, and treat the residue with hydro- chloric acid ( 150, 3). 10. CHROMIC ACID is readily recognised by the yellow or red color of the solution, and by the purple-red color of the precipi- tate produced by nitrate of silver. If there remains the least doubt on the point, test for chromic acid with acetate of lead and acetic acid ( 138). Complex Compounds. A, 1. SUBSTANCES SOLUBLE IN WATER. DETECTION OF ACIDS. II. In Presence of Organic Acids. 198. 1 . The examination for inorganic acids, inclusive of oxalic acid, 184 is made in the manner described in 197. As the tartrates and citrates of baryta and oxide of silver are insoluble in water, tartaric acid and citric acid can be present only in cases where both chloride of barium and nitrate of silver have produced precipitates in the neutral fluid j still, in drawing a conclusion, you must bear in mind that the said salts are slightly soluble in solutions of salts of ammonia. The examination for the organic acids is conducted as follows : 2. Make a portion of the fluid feebly alkaline by addition of am- 185 monia, filter, if necessary, add some chloride of ammonium, then chloride of calcium, shake vigorously, and let the mixture stand at rest from ten to twenty minutes. a. No PRECIPITATE IS FORMED, NOT EVEN AFTER THE LAPSE OF SOME TIME. Absence of tartaric acid ; pass on to 3. b. A PRECIPITATE IS FORMED IMMEDIATELY, OR AFTER SOME 186 TIME. Filter, wash, and keep the filtrate for further examina- tion according to the directions of 3. Digest and shake the precipitate with solution of soda, without applying heat, then dilute with a little water, filter, and boil the filtrate some time. If a precipitate separates, TARTARIC ACID may be assumed to be present. Filter hot, and subject the precipitate to the ammonia and nitrate of silver test described in 162, 8. 3. Mix the fluid in which chloride of calcium has failed to pro- duce a precipitate, or that which has been filtered from the precipi- tate in which latter case some more chloride of calcium is to be added with alcohol. a. No PRECIPITATE is FORMED. Absence of citric acid and 187 malic acid. Pass on to 4. b. A PRECIPITATE is FORMED. Filter and treat the filtrate 188 as directed in 4. As regards the precipitate, treat this as follows : 220 DETECTION OF ACIDS. [ 198. After -washing with some alcohol, dissolve on the filter in a little dilute hydrochloric acid, add ammonia to the filtrate to feebly alkaline reaction, and then boil for some time. a. THE FILTRATE REMAINS CLEAR. Absence of citric acid. Probable presence of MALIC ACID. Add alcohol again to the fluid, and test the lime precipitate in the manner directed 165, to make sure whether malic acid is really present or not. ft. A HEAVY, WHITE PRECIPITATE IS FORMED. Presence 189 of CITRIC ACID. Filter boiling, and test the filtrate for malic acid in the same manner as in a. To remove all doubt as to whether the precipitate is citrate of lime or not, it is advisable to dissolve once more in some hy- drochloric acid, to supersaturate again with ammonia, . and to boil ; if the precipitate really consisted of citrate of lime, it will now be thrown down again. (Compare 164, 3.) 4. Heat the filtrate of 3, b (188) (or the fluid in which addition 190 of alcohol has failed to produce a precipitate, 3, a [187])? to expel the alcohol, neutralize exactly with hydrochloric acid, and add ses- quichloride of iron. If this fails to produce a light brown, floccu- lent precipitate, neither succinic nor benzoic acid is present. If a precipitate of the kind is formed, filter, digest, and heat the washed precipitate with ammonia in excess ; filter, evaporate the filtrate nearly to dryness, and test a portion for SUCCINIC ACID with chloride of barium and alcohol ; the remainder for BENZOIC ACID with hydro- chloric acid ( 169). Benzoic acid may generally be readily detected also in the original substance, by pouring some dilute hydrochloric acid over a small portion of the latter, which will leave the benzoic acid undissolved ; it is then filtered and heated on platinum foil ( 168, 1). 5. Evaporate a portion of the solution to dryness if acid, after 191 previous saturation with soda introduce the residue, or a portion of the original dry substance into a small tube, pour some alcohol over it, add about an equal volume of concentrated sulphuric acid, and heat to boiling. Evolution of the odor of acetic ether de- monstrates the presence of ACETIC ACID. This odor is rendered more distinctly perceptible by shaking the cooling or cold mixture. 6. To effect the detection of FORMIC ACID, add to a portion of 192 the solution nitrate of silver in not too small a proportion, then soda until the fluid is exactly neutralized, and boil . If formic acid is present, reduction of the silver to the metallic state ensues ( 171, 4). The reaction with nitrate of suboxide of mercury may be had recourse to as a conclusive test ( 171, 4).* * In presence of chromic acid the reduction of oxide of silver and of suboxide of mercury is not a positive proof of the presence of formic acid. In cases where the two acids are present, the following method must be resorted to : Mix the original solution with some nitric acid, add oxide of lead in excess, shake the mixture, filter, add to the filtrate dilute sulphuric acid in excess, and distil. Test the distillate as directed 172. In presence of tartaric acid also it is the safest way to distil the formic acid first, with addition of dilute sulphuric acid. 199.] .DETECTION OF ACIDS. 221 Complex Compounds. A, 2. SUBSTANCES INSOLUBLE IN WATER, BUT SOLUBLE IN HYDRO- CHLORIC ACID, NITRIC ACID, OR NITROHYDROCHLORIC ACID. DETECTION OF THE ACIDS. I. In the Absence of Organic Acids. 199. In the examination of these compounds attention must be directed, to all acids, with the exception of chloric acid. Cyanogen com- pounds and silicates are not examined by this method. (Com- pare 202 and 203.) 1. CARBONIC ACID, SULPHUR (in form of metallic sulphides), ARSE- 193 NIOUS ACID, ARSENIC ACID, and CHROMIC ACID, if present, have been found already in the course of the examination for bases j NITRIC ACID, if present, has been detected in the course of the preliminary examination, by the ignition of the powdered substance in a glass tube( 174). 2. Mix a sample of the substance with 4 parts of pure carbonate 194 of soda and potassa, and, should it contain a metallic sulphide, add some nitrate of soda \ fuse the mixture in a platinum crucible if there are no reducible metals present, in a porcelain crucible if re- ducible metals are present ; boil the fused mass with water, and add a little nitric acid, leaving the reaction of the fluid, however, still alkaline ; heat again, filter, and proceed with the filtrate accord- ing to the directions of 197, to effect the detection of all the acids which were combined with the bases.* 3. As the phosphates of the alkaline earths are only incompletely 195 decomposed by fusion in conjunction with carbonate of soda and potassa, it is always advisable in cases where alkaline earths are present, and phosphoric acid has not yet been detected, to dissolve a fresh sample of the body under examination in hydrochloric acid or nitric acid, and test the solution for PHOSPHORIC ACID with molybdic acid. 4. If in the course of the examination for bases, alkaline earths have been found, it is also advisable to test a separate portion of the body under examination for FLUORINE, by the method described in 147, 5. 5. That portion of the substance under examination which is 196 treated of in 199, 2 (194), can be tested for SILICIC ACID only in cases where the fusion has been effected in a platinum crucible ; in cases where a porcelain crucible has been used, it is necessary to examine a separate portion of the body for silicic acid, by evaporat- ing the hydrochloric or nitric acid solution. 6. Examine a separate sample of the body for OXALIC ACID as directed in 200, 3. * If the body examined has been found to contain a metallic sulphide, a separate por- tion of it must be examined for sulphuric acid, by heating it with hydrochloric acid, filtering, adding water to the filtrate, and then testing the fluid with chloride of barium. 222 DETECTION OP ACIDS. [ 200, 201. Complex Compounds. A, 2. SUBSTANCES INSOLUBLE IN WATER, BUT SOLUBLE IN HYDRO- CHLORIC ACID, NITRIC ACID, OR NITROHYDROCHLORIC ACID. DETECTION OP THE ACIDS. II. In Presence of Organic Acids. 200. 1. Conduct the examination for inorganic acids according to the 197 direction of 199. 2. Test for ACETIC ACID as directed 198, 5 (191). 3. Dissolve a portion of the compound under examination in the 198 least possible amount of hydrochloric acid, filter, if necessary, and test the undissolved residue which may be left, for BENZOIC ACID by application of heat ; add to the filtrate solution of carbonate of soda in considerable excess, and, besides this, also a little solid carbonate of soda, boil the mixture for a few minutes, and then filter the fluid from the precipitate. In the filtrate you have now all the organic acids in solution, combined with soda. Acidify the filtrate with hydrochloric acid, heat, and proceed according to the direction of 198. Complex Compounds. B. SUBSTANCES INSOLUBLE OR SPARINGLY SOLUBLE BOTH IN WATER AND IN HYDROCHLORIC ACID, NITRIC ACID, OR NITROHYDRO- CHLORIC ACID. DETECTION OF THE BASES, ACIDS, AND NON-METALLIC ELEMENTS. 201. To this class belong the following bodies and compounds. 199 SULPHATE OP BARYTA, SULPHATE OF STRONTIA, and SULPHATE OF LIME.* SULPHATE OF LEADt and chloride of lead.{ CHLORIDE OF SILVER, bromide of silver, iodide of silver, cyanide of silver, 1 1 ferro- and ferricyanide of silver.^]" SILICIC ACID and many SILICATES. Native alumina, or alumina which has passed through a process of intense ignition, and many aluminates. Ignited sesquioxide of chromium and chrome-ironstone (a com- pound of sesquioxide of chromium and protoxide of iron). * Sulphate of lime passes partially into the solution effected by water, and often com- pletely into that effected by acids. *f Sulphate of lead may pass completely into the solution effected by acids. Chloride of lead can here only be found if the precipitate insoluble in acids has not been thoroughly washed with hot water. || Bromide, iodide, and cyanide of silver are decomposed by boiling with nitrohydro- chloric acid, and converted into chloride of silver; they can accordingly be found here only in cases where the operator has to deal with a substance which as nitrohydrochloric acid has failed to effect its solution is examined directly by the method described in this paragraph { 201). U With regard to the examination of these compounds, compare also 202. 201.] DETECTION OP BASES, ACIDS, ETC. 223 Ignited, and native binoxide of tin (tin-stone). Some metaphosphates and some arsenates. FLUORIDE OF CALCIUM and a few other compounds of fluorine. SULPHUR. CARBOX. Of these compounds those printed in small capitals are more frequently met with. As the silicates perform a highly important part in mineral analysis, a special chapter ( 203 206) is devoted to them. The substance Bunder examination which is insoluble in water and in acids is in the first place subjected to the preliminary experiments here described in a e, if the quantity at your disposal is not absolutely too small to admit of this proceeding ; in cases where the quantity is insufficient for the purpose, the operator must omit this preliminary examination, and at once pass on to 1, bearing in mind, however, that the body may contain all the afore- said substances and compounds. a. Examine closely and attentively the physical state and con- 200 dition of the substance, to ascertain whether you have to deal with a homogeneous mass or with a mass composed of dis- similar particles ; whether the body is sandy or pulverulent, whether it has the same color throughout, or is made up of variously-colored particles, &c. The microscope, or even a simple magnifying glass, will be found very useful at this stage of the examination. b. Heat a small sample in a glass tube sealed at one end. If 201 brown fumes arise, and SULPHUR sublimes, this is of course a proof of the presence of that substance. c. If the substance is black, this indicates, in most cases, the pre- 202 sence of carbon (wood-charcoal, pit-coal, bone-black, lamp-black, graphite, &c). Heat a small sample on platinum foil over the blow- pipe flame ; if the substance which blackens the fingers is con- sumed, this may be held to be a positive proof of the presence of CARBON in some shape or other. Graphite, which may be readily recognised by its property of communicating its blackish-gray color to the fingers, to paper, &c., requires the application of oxygen for its easy combustion. d. Warm a small sample, together with a small lump of cyanide 203 of potassium and some water, for some time, filter, and test the filtrate with sulphide of ammonium. The formation of a brownish- black precipitate shows that the substance under examination con- tains a compound of SILVER. e. If an undissolved residue has been left in d, wash this tho- 204: roughly with water, and, if white, sprinkle a few drops of sul- phide of ammonium over it j if it turns black, salts of LEAD are present. If, however, the residue left in d is black, heat it with some acetate of ammonia, adding a few drops of acetic acid, filter, and test the filtrate for LEAD, by means of sulphuric acid and hydrosulphuric acid.* The results obtained by these preliminary experiments serve to guide the operator now in his further course of proceeding. * The presence of lead in silicates, e. g. in glass containing lead, cannot be detected by this method. 224 DETECTION OF BASES, ACIDS, ETC. [ 201. 1, a. SALTS OF LEAD ARE NOT PRESENT. Pass on to 2 (206)- 205 b. SALTS OF LEAD ARE PRESENT. Heat the substance re- peatedly with a concentrated solution of acetate of ammonia, until the salt of lead is completely dissolved out. Test a por- tion of the nitrate for CHLORINE, another for SULPHURIC ACID, and the remainder for LEAD, by addition of sulphuric acid in excess, and by hydrosulphuric acid. If acetate of ammonia has left a residue, wash this, and treat it as directed in 2. 2, a. SALTS OF SILVER ARE NOT PRESENT. Pass on to 3. 206 b. SALTS OF SILVER ARE PRESENT. Digest the substance free from lead, or which has been freed from that metal by acetate of ammonia, repeatedly with cyanide of potassium and water, at a gentle heat (in presence of sulphur, in the cold), until all the salt of silver is removed. If an undis- solved residue is left, wash this, and then proceed with it according to the directions of 3 (207)- Of the filtrate, which contains cyi nide of potassium, mix the larger portion with sulphide of ammonium, to precipitate the silver. Wash the precipitated sulphide of silver, then dissolve it in nitric acid, dilute the solution, and add hydrochloric acid, to ascertain whether the precipitate really consisted of sulphide of silver. Test another small portion of the nitrate for SULPHURIC ACID.* * 3, a. SULPHUR is NOT PRESENT. Pass on to 4. 207 b. SULPHUR is PRESENT. Heat the substance free from silver and lead in a covered porcelain crucible until all the sulphur is expelled, and, if a residue is left, treat this according to the directions of 4 (208). 4, Mix the substance free from silver, lead, and sulphur with 208 2 parts of carbonate of soda, 2 parts of carbonate of potassa, and 1 part of nitrate of potassa, f heat the mixture in a platinum crucible until the mass is in a state of calm fusion, place the red hot crucible on a thick, cold iron plate, and let it cool. By this means you will generally succeed in removing the fused mass from the crucible in an unbroken lump. Soak the mass now in water, boil, filter, and wash the residue until chloride of barium no longer produces a precipitate in the washings. (Add only the first washings to the filtrate.) a. The solution obtained contains the acids which were 209 present in the substance decomposed by fluxing (208)- But it may, besides these acids, contain also such bases as are soluble in caustic alkalies. Proceed as follows : a. Test a small portion of the solution for SULPHURIC ACID. /3. Test another portion with molybdic acid for PHOS- PHORIC ACID and ARSENIC ACID. If a yellow precipitate * As the carbonate of potassa contained in the cyanide of potassium may have pro- duced a total or partial decomposition of any sulphates of the alkaline earths which happened to be present. f* Addition of nitrate of potassa is useful even in the case of white powders, as it counteracts the injurious action of silicate of lead, should any be present, upon the platinum crucible. In the case of black powders, the proportion of nitrate of potassa must be correspondingly increased, in order that carbon, if present, may be consumed as completely as possible, and that any chrome-ironstone existing iu the compound, may be more thoroughly decomposed. 201.] DETECTION OP BASES, ACIDS, ETC. 225 forms, remove the arsenic acid which may be present with hydrosulphuric acid, and then test once more for phosphoric acid. y. Test another portion for FLUORINE ( 147, 7). & If the solution is yellow, CHROMIC ACID is present. To remove all doubt on the point, acidify a portion of the solution with acetic acid, and test with acetate of lead. e. Acidify the remainder of the solution with hydrochloric 210 acid, evaporate to dryness, and treat the residue with hydro- chloric acid and water. If a residue is left which refuses to dissolve even in boiling water, this consists of SILICIC ACID. Test the hydrochloric acid solution now in the usual way for those bases which, being soluble in caustic alkalies, may be present. b. Dissolve the residue left in 4 (208) in hydrochloric acid 211 (effervescence indicates the presence of alkaline earths), and test the solution for the bases as directed in 188. (If much silicic acid has been found in e (210), it is advisable to evapo- rate the solution of the residue to dryness, and to treat the residuary mass with hydrochloric acid and water, in order that the silicic acid remaining may also be removed as completely as possible.) 5. If you have found in 4 that the residue insoluble in acids 212 contains a silicate, treat a separate portion of it according to the directions of 205, 2 (228), to ascertain whether or not this sili- cate contains alkalies. 6. If a residue is still left undissolved upon treating the 213 residue left in 4 with hydrochloric acid (211)? this may consist either of silicic acid, which has separated, or of an undecomposed portion of sulphate of baryta ; it may, however, also be fluoride of calcium, and if it is dark- colored, chrome-ironstone, as the last- named two compounds are only with difficulty decomposed by the method given in 4. I would therefore remind the student that fluoride of calcium may be readily decomposed by means of sul- phuric acid ; and, as regards the decomposition of chrome-ironstone, I can recommend the following method, first proposed by Hart : Project the fine powder into 8 times the quantity of fused borax, stir the mixture frequently, and keep the crucible for half- an-hour at a bright red heat. Add now to the fusing mass car- bonate of soda so long as effervescence continues, and then finally add 3 times the weight of the chrome-ironstone of a mix- ture of equal parts of carbonate of soda and nitrate of potassa, whilst actively stirring the mixture with a platinum wire. Let the ma >s cool, and, when cold, boil it with water. 7. If the residue insoluble in acids contained silver, you have 214 still to ascertain whether that metal was present in the original substance as chloride, bromide, iodide, &c., of silver, or whether it has been converted into the form of chloride of silver by the treatment employed to effect the solution of the original substance. For that purpose, treat a portion of the original substance with boiling water until the soluble part is completely removed ; then treat the residuary portion in the same way with dilute nitric acid, wash the undissolved residue with water, and test a small i. Q 226 ANALYSIS OF INSOLUBLE CYANIDES, FE11ROCYANIDES, ETC. [ 202, sample of it for silver according to the directions of 201, d (203)- If silver is present, proceed to ascertain the salt-radical with which the metal is combined ; this may easily be effected by boiling the remainder of the residue in the first place with rather dilute solution of soda, filtering, and testing the filtrate, after acidifying it, for ferro- and ferricyanogen. Digest the washed residue now with finely granulated zinc and water, with addition of some sulphuric acid, and filter after the lapse of ten minutes. You may now at once test the filtrate for chlorine, bromine, iodine, and cyanogen ; or you may first throw down the zinc with carbonate of soda, in order to obtain the salt-radicals in combination with sodium. SECTION II. PRACTICAL COURSE IN PARTICULAR CASES. I. SPECIAL METHOD OP EFFECTING THE ANALYSIS OF CYANIDES, FERROCYANIDES, ETC., INSOLUBLE IN WATER, AND ALSO OF INSO- LUBLE MIXED SUBSTANCES CONTAINING SUCH COMPOUNDS.* 202. THE analysis of ferrocyanides, ferricyanides, r ? if necessary, fuse a separate portion of the finely pulverized substance with 4 parts of pure carbonate of soda and potassa until the mass flows calmly ; boil the fused mass with water, filter the solution, which contains all the fluorine as fluoride of sodium, all the chlorine as chloride of sodium, all the boracic acid 206, 207.] ANALYSIS or SILICATES. 231 as borate, all the sulphuric acid as sulphate, all the arsenic acid as arsenate, and at least part of the phosphoric acid as phosphate of soda, and treat the nitrate as follows : a. Acidify a small portion of it with nitric acid, and test for chlorine with nitrate of silver. b. Test another portion for boracic acid as directed $ 205 2 a (224). c. Test a third portion, after addition of hydrochloric acid, with molybdate of ammonia for phosphoric acid and arsenic acid. d. To effect the detection of the fluorine, treat the remainder of the filtrate as directed 147, 7. C. SILICATES WHICH ARE PARTIALLY DECOMPOSED BY ACIDS. 206. Most of the native rocks and minerals are mixtures of several 231 silicates, of which the one is often decomposed by acids, the other not. If such minerals were analyzed by the same method as the absolutely insoluble silicates, the analyst would indeed detect all the elements present, but the analysis would afford no satisfactory in- sight into the actual composition of the mineral. It is, therefore, advisable to examine separately those parts of the mineral which show a different deportment with aoids. For this purpose digest the very finely pulverized mineral for some time with hydrochloric acid at a very gentle heat, then evaporate to dry ness, and expose to a temperature somewhat exceeding 212F., with stirring, until no more, or very few, hydrochloric acid vapors are evolved ; let the residue cool, moisten it when cold with hydro- chloric acid, heat gently with water, and filter. The filtrate contains the bases of the decomposed part of the mixed mineral ; examine this as directed 204. The residue con- tains, besides the silicic acid separated from these bases by the action of the hydrochloric acid, that part of the mixed mineral which has resisted the action of the acid. Boil this residue with an excess of solution of carbonate of soda, filter hot, and wash, first with hot solution of carbonate of soda, finally with boiling water. Treat the residuary undecomposed part of the mineral, from which the admixed free silicic acid has thus been removed, according to the instructions given in 205. In cases where it is of no conse- quence or interest to effect the separation of the silicic acid of the part decomposed by acids, you may omit the laborious treatment with carbonate of soda, and may proceed at once to the decomposi- tion of the residue. III. ANALYSIS OF NATURAL WATERS. 207. In the examination of natural waters the analytical process is 232 simplified by the circumstance that we know from experience the elements and compounds which are usually found in them. Now, although a quantitative analysis alone can properly inform us as to the true nature and character of a water, since the differences be- 232 ANALYSIS OF FEESH WATERS. [ 08. tween the various waters are principally caused by the different pro- portions in which the several constituents are respectively present, a qualitative analysis may yet render very good service, especially if the analyst notes with proper care, whether a reagent produces a faint or a distinctly marked turbidity, a slight or a copious precipi- tate, since these circumstances will enable him to make an approxi- mate estimation of the relative proportions in which the several constituents are present. I separate here the analysis of the common fresh waters (spring- water, well-water, brook-water, river-water, &c.) from that of the mineral waters, in which we may also include sea- water ; for, although no well-defined limit can be drawn between the two classes, still the analytical examination of the former is necessarily far more simple than that of the latter, as the number of substances to be looked for is much more limited than in the case of mineral waters. A. ANALYSIS OF FRESH WATERS (SPRING- WATER, WELL-WATER, BROOK WATER, RIVER- WATER, &c.). 208. We know from experience that the substances to be had regard 233 to in the analysis of such waters are the following : a. BASES : Potassa, soda, ammonia, lime, magnesia, protoxide of iron. 6. ACIDS, &c. : Sulphuric acid, phosphoric acid, silicic acid, car- bonic acid, nitric acid, chlorine. c. ORGANIC MATTERS. d. MECHANICALLY SUSPENDED SUBSTANCES : Clay, &c. The fresh waters contain indeed also other constituents besides those enumerated here, as may be inferred from the origin and for- mation of springs, &c., and as has, moreover, been fully established by the results of analytical investigations ;* but the quantity of such constituents is so trifling that they escape detection, unless hundreds of pounds of the water are subjected to the analytical pro- cess. I omit, therefore, here the mode of their detection, and refer to 209. 1. Boil the carefully collected water in a glass flask or retort 234 to one half. This generally produces a precipitate. Pass the fluid through a perfectly clean filter (free from iron and lime), wash the precipitate well, after having removed the filtrate, and then examine both as follows : a. Examination of the precipitate. The precipitate contains those constituents of the water 235 which were only kept in solution through the agency of free * Chatin (" Journ. de Pharm. etde Chim.," 3 Ser. t. xxvii. p. 418) found iodine in all fresh-water plants, but not in land plants, a proof that the water of rivers, brooks, ponds, &c., contains traces, even though extremely minute, of metallic iodides. According to Marchand ("Compt. Rend.," t. xxxi. p. 495), all natural waters contain iodine, bromine, and lithia. Van Ankum has demonstrated the presence of iodine in almost all the potable waters of Holland. And it may be affirmed with the same cer- tainty that all, or at all events most, natural waters contain compounds of strontia, fluorine, &c. 208.] ANALYSIS OF FRESH WATERS. 233 carbonic acid, or, as the case may be, in the form of bicar- bonates, viz., carbonate of lime, carbonate of magnesia, hydrated sesquioxide of iron (which was in solution as bicarbonate of protoxide of iron, and precipitates upon boiling as sesquioxide, and if phosphoric acid is present, also in combination with that acid), phosphate of lime ; and besides, silicic acid, and some- times also sulphate of lime, if that substance is present in large proportion ; and clay which was mechanically suspended in the water. Dissolve the precipitate on the filter in the least possible quantity of dilute hydrochloric acid (effervescence indicates the presence of CARBONIC ACID), and mix separate portions of the solution : a. With sulphocyanide of potassium : red coloration indi- cates the presence of IRON ; /3. With ammonia ; warm, filter, if necessary, mix the 236 filtrate with oxalate of ammonia, and let the mixture stand for some time in a warm place. The formation of a white precipitate indicates the presence of LIME in the form of carbonate, or also in that of sulphate if sulphuric acid is de- tected in y. Filter, mix the filtrate again with ammonia, add some phosphate of soda, stir with a glass rod, and let the mixture stand for twelve hours. The formation of a white, crystalline precipitate, which is often visible only on the sides of the vessel when the fluid is poured out, indicates the presence of MAGNESIA (carbonate of) ; y. With chloride of barium, and let the mixture stand for twelve hours in a warm place. The formation of a pre- cipitate which, when very inconsiderable, is best seen if the supernatant clear fluid is cautiously decanted, and the small quantity remaining shaken about in the glass indicates the presence of SULPHURIC ACID. <). Add some of the fluid to a solution of molybdate of 237 ammonia, acidified with hydrochloric acid, and boil. The appearance of a yellow color, or the formation of a yellow precipitate, indicates the presence of PHOSPHORIC ACID.* b. Examination of the filtrate. a. Mix a portion of the filtrate with a little hydrochloric 238 acid and chloride of barium. The formation of a white pre- cipitate, which makes its appearance at once or perhaps only after standing some time, indicates SULPHURIC ACID. /3. Mix another portion with nitric acid, and add nitrate of silver. A white precipitate or a white turbidity, indi- cates the presence of CHLORINE. y. Test a portion of the filtrate for PHOSPHORIC ACID as in a, S (237). <). Evaporate another and larger portion of the filtrate until 239 * In default of molybdate of ammonia, evaporate the remainder of the hydrochloric acid solution of the precipitate to dryness, redissolve the residue in a little hydrochloric acid and water, filter the solution, and mix the filtrate with carbonate of soda until it is nearly neutralized, then with acetate of soda and a very small quantity of sesquicbloride of iron. The formation of a white precipitate, which generally becomes visible only after long standing, indicates the presence of PHOSPHORIC ACID. 234 ANALYSIS OF FRESH WATERS. [ 208. highly concentrated, and test the reaction of the fluid. If it is alkaline, and a drop of the concentrated clear solu- tion effervesces when mixed on a watch-glass with a drop of acid, a CARBONATE of an alkali is present. Should this be the case, evaporate the fluid to perfect dryness, boil the residue with spirit of wine, filter, evaporate the alcoholic solution to dryness, dissolve the residue in a little water, and test the solution for NITRIC ACID as directed 159, 5, or by the method given in 159, 8, which is still more delicate. e. Mix the remainder of the filtrate with some chlo- ride of ammonium, add ammonia and oxalate of ammonia, and let the mixture stand for a considerable time. The formation of a precipitate indicates the presence of LIME. Filter, and test, aa. A small portion with ammonia and phosphate of soda for MAGNESIA. bb. Evaporate the remainder to dryness, heat the resi- due to redness, remove the magnesia, which may be pre- sent ( 194), and test for POTASSA and SODA, according to the directions of 195. 2. Acidify a tolerably large portion of the filtered water with 240 pure hydrochloric acid, and evaporate nearly to dryness ; divide the residue into 2 parts, and, a. Test the one part with hydrate of lime for AMMONIA (com- pare 196). b. Evaporate the other part to dryness, moisten with hydrochloric acid, add water, warm, and filter, if a residue remains. The residue may consist of SILICIC ACID, and of CLAY which has been mechanically suspended in the water ; these two substances may be separated from each other by boiling with solution of carbonate of soda. The precipitate is often dark-colored from the presence of organic substances ; but it becomes perfectly white upon ignition. 3. Mix another portion of the water, fresh taken from the well, 241 &c., with lime-water. If a precipitate is thereby produced, FREE CARBONIC ACID or BiCARBONATES are present. If the former is pre- sent (free carbonic acid), no permanent precipitate is obtained when a larger portion of the water is mixed with only a small amount of lime-water, since in that case soluble bicarbonate of lime is formed. 4. To detect the presence of ORGANIC MATTERS, evaporate a portion 242 of the water to dryness, and gently ignite the residue : blackening of the mass denotes the presence of organic substances. If this ex- periment is to give conclusive results, the evaporation of the water, as well as the ignition of the residue, must be conducted in a glass flask or a retort. 5. If you wish to examine the MATTERS MECHANICALLY SUSPENDED 243 in a water (in muddy brook or river-water, for instance), fill a large glass bottle with the water, cork securely, and let it stand at rest for several days, until the suspended matter has subsided ; remove now the clear supernatant fluid with the aid of a syphon, filter the remainder, and examine the sediment remaining on the filter. As this sediment may consist of the finest dust of various minerals, treat it first with hydrochloric acid, and examine the part insoluble 209, 210.] ANALYSIS OF MINERAL WATERS. 035 in that menstruum in the manner directed 203 (Analysis of Silicates). B. ANALYSIS OF MINERAL WATERS. 209. The analysis of mineral waters embraces a larger number of con- 244 stituents than that of fresh water. The following are the principal of the additional elements to be looked for : LlTHIA, BARYTA, STRONTIA, ALUMINA, PROTOXIDE OF MANGANESE, BORACIC ACID, BROMINE, IODINE, FLUORINE, HYDROSULPHURIC ACID, CRENIC ACID and APOCRENIC ACID. The^ analyst has, moreover, to examine the muddy ochreous or hard sinter-deposits of the spring for ARSENIOUS ACID, ARSENIC ACID, OXIDE OF COPPER, OXIDE OF LEAD, and the oxides of other heavy metals. The greatest care is required in this examination, to ascer- tain whether these oxides come really from the water, and do not proceed from metal pipes, stopcocks, &c.* The absolute purity of the reagents employed in these delicate investigations must also be ascertained with the greatest care. 1. EXAMINATION OF THE WATER. a. OPERATIONS AT THE SPRING. 210. 1. Filter the water at the spring, if not perfectly clear, through 245 Swedish filter paper, and collect the filtrate in large bottles with glass stoppers. The sediment remaining on the filter, which con- tains, besides the nocculent matter suspended in the water, also those constituents which separate at once upon coming in contact with the air (hydrate of sesquioxide of iron, and compounds of ses- quioxide of iron with phosphoric acid, silicic acid, arsenic acid), is taken to the laboratory, to be examined afterwards according to the directions of 212. 2. The presence of FREE CARBONIC ACID is usually sufficiently 246 visible to the eye. However, to convince yourself by positive re- actions, test the water with fresh-prepared solution of litmus, and with lime-water. If carbonic acid is present, the former acquires a wine-red color ; the latter produces turbidity, which must disappear again upon addition of the mineral water in excess. 3. Free HYDROSULPHURIC ACID is most readily detected by the 247 smell. For this purpose half fill a bottle with the mineral water, cover with the hand, shake, take off the hand, and smell the bottle. In this way distinct traces of hydrosulphuric acid are often found, which would escape detection by reagents. However, if you wish to have some visible reactions, fill a large white bottle with the water, add a few drops of solution of acetate of lead in solution of soda, place the bottle on a white surface, and look in at the top, to * Compare " Chemische Untersuchung der wichtigsten Mineral wasser des Herzogthums Nassau," von Professor Dr. Fresenius ; I. Der Kochhrunnen zu Wiesbaden; II. Die Mineralquellen zu Ems ; III. die Quellen zu Schlangenbad ; IV. die Quellen zu Langen- schwalbacb. ; published at Wiesbaden, by Kriedel und Niedner. 1850-1855. 236 ANALYSIS OF MINERAL WATERS. [ 211. see whether the water acquires a brownish color or deposits a blackish precipitate ; or half fill a large bottle with the water, and close with a cork to which is attached a small slip of paper, pre- viously steeped in ' solution of acetate of lead and then moistened with a little solution of carbonate of ammonia; shake the bottle gently from time to time, and observe whether the paper slip acquires a brownish tint in the course of a few hours. If the addition of the solution of acetate of lead to the water has im- parted a brown color to the fluid or produced a precipitate in it, whilst the reaction with the paper slip gives no result, this indi- cates that the water contains an alkaline sulphide, but no free hydrosulphuric acid. 4. Mix a wineglass-full of the water with some tannic acid, 248 another wineglass-full with some gallic acid. If the former imparts a blue violet, the latter a red violet color to the water, PROTOXIDE OF IRON is present. Instead of the two acids, you may employ in- fusion of galls, which contains them both. b. OPERATIONS IN THE LABORATORY. 211. As it is always desirable to obtain even in the qualitative exami- nation some information as to the quantitative composition of a mineral water, i. e. as to the proportions in which the several consti- tuents are contained in it, it is advisable to analyze a comparatively small portion for the principal constituents, and to ascertain, as far as may be practicable, the relative proportions in which these constituents exist, and thus to determine the character of the water ; and then to examine a very large amount of the water for those elements which are present only in minute quantities. For this purpose proceed as follows : 1. EXAMINATION FOR THOSE CONSTITUENTS OF THE WATER WHICH 249 ARE PRESENT IN LARGER QUANTITIES. Boil about 31bs. of the clear water, or of the nitrate, brought from the spring, in a glass flask for 1 hour, taking care, however, to add from time to time some distilled water, that the quantity of liquid may remain un- diminished, and thus the separation of any but those salts be pre- vented which owe their solution to the presence and agency of carbonic acid. Filter after an hour's ebullition, and examine the precipitate and the filtrate as directed 208. 2. EXAMINATION FOR THOSE FIXED CONSTITUENTS OF THE WATER 250 WHICH ARE PRESENT IN MINUTE QUANTITIES ONLY. Evaporate a large quantity (at least 20 Ibs.) of the water in a silver or porce- lain dish to dry ness ; conduct this operation with the most scrupulous cleanliness in a place as free as possible from dust. If the water contains no carbonate of an alkali, add pure carbonate of potassa to slight predominance. The process of evaporation may be conducted in the first place over a gas-lamp, but ultimately the sand-bath must be employed. Heat the dry mass to very faint redness ; if in a silver dish, you may at once proceed to ignite it ; but if you have it in a porcelain dish, first transfer it to a silver or platinum vessel before proceeding to ignition. If the mass 211-] ANALYSIS OF MINERAL WATEUS. 237 turns black in this process, ORGANIC MATTERS may be assumed to be present.* Mix the residue thoroughly, that it may have the same composi- tion throughout, and then divide it into 3 portions, one (c) amount- ing to about one-half, and each of the other two (a and b) to one- fourth. , a. EXAMINATION FOR IRON, PHOSPHORIC ACID (ARSENIC ACID). Warm the portion a with some water, add perfectly pure 251 hydrochloric acid in moderate excess, digest for some time at a temperature near the boiling point, filter through paper washed with hydrochloric acid and water, and test. a. A sample for IRON, by means of sulphocyanide of potassium. /3. Treat the remainder with hydrosulphuric acid, let the fluid saturated with that acid stand for twenty-four hours, filter from the separated sulphur, concentrate the filtrate by boiling, and test it with molybdate of ammonia for PHOS- PHORIC ACID. 7 . If the sulphur deposited in /3 is not perfectly white, treat it as directed 212, 1, a, a (263), in order to detect the arsenic, copper, &c., which may be present. b. EXAMINATION FOR FLUORINE. Heat the portion b with water, add chloride of calcium as 252 long as a precipitate continues to form, let deposit ; filter the fluid from the precipitate, which consists chiefly of carbonate of lime and carbonate of magnesia. After having washed and dried the precipitate, ignite, then pour water over it in a small dish, add acetic acid in slight excess, evaporate on the water-bath to dryness, heat until all smell of acetic acid has disappeared, add water, heat again, filter the solution of the acetates of the alkaline earths, wash, dry or ignite the residue, and test it for FLUORINE as directed 147, 5. c. EXAMINATION FOR THE REMAINING CONSTITUENTS PRESENT 253 IN MINUTE QUANTITIES. Boil the portion c repeatedly with water, filter, and wash the undissolved residue with boiling water. You have now a residue (a), and a solution (/?). a. The residue consists chiefly of carbonate of lime, car- 254 bouate of magnesia, and in the case of chalybeate springs hydrate of sesquioxide of iron. But it may contain also minute quantities of BARYTA ,STRONTIA, ALUMINA, and PROT- OXIDE OF MANGANESE, and must accordingly be examined for these substances. Put the residue in a platinum or porcelain dish, pour water over it, add hydrochloric acid to slightly acid reaction, then 4 or 5 drops of dilute sulphuric acid, evaporate to dryness, moisten with hydrochloric acid, then add water, * This inference is, however, correct only if the water has been effectually protected from dust during the process of evaporation ; if this has not been the case, and you yet wish to ascertain beyond doubt whether organic matters are present, evaporate a sepa- rate portion of the water in a retort. If you find organic matter, and wish to know whether it consists of crenic acid or of apocrenic acid, treat a portion of the residue as directed 212, 3. 238 ANALYSIS OF MINERAL WATERS. [ 211. warm gently, filter, and wash the residue which is left un- dissolved. cia, EXAMINATION OF THE RESIDUE INSOLUBLE IN HY- 255 DROCHLORIC ACID FOR BARYTA AND STRONTIA. This residue will generally consist of silicic acid ; but it may contain also sulphates of the alkaline earths and carbon. If there is much silicic acid present, remove this in the first place, as far as practicable, by boiling with dilute solution of soda ; filter, wash the residue, if any has been left, dry, incinerate the filter in a platinum crucible, add some carbonate of soda and potassa and, in presence of carbon, some nitrate of potassa, and ignite for some time. If the residue contains but little silicic acid, the treatment with solution of soda may be omitted, and the fusion with carbonate of potassa and soda, &c., at once proceeded with. Boil the fused mass with water, filter, wash thoroughly, dissolve the residue (which must have been left, if sulphates of the alkaline earths were present) on the filter in the least possible quantity of dilute hydrochloric acid, add an equal volume of spirit of wine, then some pure hydrofluosilicic acid, and let the mixture stand 12 hours. If in the course or at the end of the 12 hours a precipitate makes its ap- pearance, this denotes the presence of BARYTA. Filter, and warm the filtrate in a platinum dish, adding from time to time some water, until the spirit of wine is quite driven off. Mix the fluid now with saturated solu- tion of sulphate of lime. If this produces a precipitate, whether after some time or after several hours' standing, this precipitate consists of sulphate of STRONTIA. To make quite sure, examine it before the blowpipe (see 95, 7). bb. EXAMINATION OF THE HYDROCHLORIC ACID SOLU- 256 TION FOR PROTOXIDE OF MANGANESE AND ALUMINA. Mix the solution in a flask with some pure chloride of ammonium, add ammonia until the fluid is just turning alkaline, then some yellow sulphide of ammonium, close the flask, and let it stand for 12 hours in a moderately warm place. If a precipitate has formed at the end of that time, filter, dissolve the precipitate in hydrochloric acid, boil, add solution of potassa ( 30, c) in excess, boil again, filter, and test the filtrate for ALUMINA ;* the residue with carbonate of soda before the blowpipe for MANGANESE. /3. The alkaline solution contains the salts of the alkalies, 257 and usually also magnesia and traces of lime. You have to examine it now for NITRIC ACID,T BORACIC ACID, IODINE, * You are not justified in regarding this substance as an ingredient of the water, except in cases where the process of evaporation has been conducted in a platinum or silver dish, but not in a porcelain dish. + The nitric acid originally present may have been destroyed by the ignition of the residue in 211, 2 (250), u*fce latter contained organic matter. If you have reason to fear that such has been the case, and you have not already found nitric acid in 211, 1, examine a larger portion of non-ignited residue for that acid, according to the directions of 211, 2, c, p, aa (258)- 211.] ANALYSIS OF MINERAL WATERS. 239 BROMINE, and LITHIA. Evaporate the fluid until highly concentrated, let it cool, and place the dish in a slanting position, that the small quantity of liquid may separate from the saline mass ; pour a few drops of the concentrated solution in a watch-glass, acidify very slightly with hy- drochloric acid, and test with turmeric paper for BORACIG ACID. Pour back into the dish the remainder of the liquid, of which you have just tested a few drops, evaporate, with stirring, to perfect dryness, and divide the residuary powder into 2 portions, one (aa) of two-thirds, the other (66) of one-third. aa. EXAMINE THE LARGER PORTION FOR NITRIC ACID, 258 IODINE, AND BROMINE. Put the powder into a flask, pour pure spirit of wine of 90 per cent, over it, boil on the water bath, and filter hot ; repeat the same operation a second and a third time. Mix the alcoholic extract with a few drops of solution of potassa, distil the spirit of wine off to within a small quantity, and let cool. If minute crystals separate, these may con- sist of nitrate of potassa ; pour off the fluid, wash the crystals with some spirit of wine, dissolve them in a very little water, and test the solution for nitric acid, best by means of brucia ( 159, 8). Evaporate the alcoholic solution now to dryness. If you have not yet found nitric acid, dissolve a small portion of the residue in a very little water, and examine the solution for that acid. Treat the remainder of the residue or, if it has been unnecessary to search for nitric acid, the entire residue, three times with warm alcohol, filter, evaporate the filtrate to dryness, dissolve the residue in a very little water, add some starch-paste, acidify slightly with sul- phuric acid, and test for iodine by adding some nitrite of potassa in solution, or a drop of solution of hyponitric acid in sulphuric acid. After having carefully observed the reactions, test the same fluid for bromine with ether and chlorine water in the manner described in 1ST. bb. EXAMINE THE SMALLER PORTION FOR LITHIA. Warm the smaller portion of the residue, which. 259 if lithia is present, must contain that alkali as car- bonate or phosphate, with water, add hydrochloric acid to distinctly acid reaction, evaporate nearly to dryness, and then mix with pure spirit of wine of 90 per cent, which will separate the greater portion of the chloride of sodium, and give alt the lithia in the alcoholic solu- tion. Drive off the alcohol by evaporation, dissolve the residue in water mixed with a few drops of hydrochloric acid, add a little sesquichloride of iron, then ammonia in slight excess, and a small quantity of oxalate of ammonia, and let the mixture stand for sometime ; then filter off the fluid, which is now entirely free from phosphoric acid and lime'; evaporate the filtrate to dryness, and gently ignite the residue, until the salts of ammonia are expelled; 240 ANALYSIS OF MINERAL WATERS. [ 212. treat the residue with some chlorine water (to remove the iodine and bromine) and a few drops of hydrochloric acid, and evaporate to dryness ; add a little water and (to remove the magnesia) some finely divided oxide of mercury, eva- porate to dryness, and gently ignite the residue, until the chloride of mercury is completely driven off ; treat the residue now with a mixture of absolute alcohol and anhy- drous ether, filter the solution obtained, concentrate the filtrate by evaporation, and set fire to the alcohol. If it burns with a carmine flame, LITHIA is present. By way of confirmation, convert the lithia found into phosphate of LITHIA.* 3. If you have not yet clearly detected ammonia in 1 (249)> add 260 to a large quantity of the water hydrochloric acid to acid reaction, and concentrate the fluid considerably by boiling in a retort. Add now, through the tubular neck of the retort, an excess of milk of lime, made with recently calcined hydrate of lime, boil, and conduct the vapor into a flask containing very dilute hydrochloric acid, which is kept cool by surrounding it with ice or with very cold water ; evaporate the contents almost to dryness, and then test for ammonia with hydrate of lime or with bichloride of platinum. 2. EXAMINATION OF THE SINTER-DEPOSIT. 212. 1. Free the ochreous or sinter-deposit from impurities, by picking, 261 sifting, elutriation, &c., and from the soluble salts adhering to it, by washing with water; digest a large quantity (about 200 grammes) of the residue with water and hydrochloric acid (effervescence : CARBONIC ACID) until the soluble part is completely dissolved ; dilute, cool, filter, and wash the residue. a. Examination of tJie filtrate. a. Saturate the larger portion of the filtrate nearly with 262 carbonate of soda, add a few drops of dilute sulphuric acid, and let the mixture stand for 24 hours at a gentle heat. If a precipitate is found to have formed after this time, filter, wash the precipitate, pour hydrosulphuric acid over it, that you may not overlook the possible presence of sulphate of lead, and test for BARYTA and STRONTIA as directed 211, 2, c, a, aa (255). Boil the fluid filtered from this precipitate with sulphite of soda if necessary, with addi- tion of some hydrochloric acid, as the fluid must always remain acid to reduce the sesquioxide of iron to protoxide, and the arsenic acid, which may be present, to arsenious acid ; heat finally, until all sulphurous acid is expelled, and conduct for some hours a slow stream of washed hydrosul- phuric acid gas into the fluid ; let the latter now stand in a moderately warm place, until the smell of hydrosulphuric acid has become quite faint. If a precipitate has formed, 263 * The precipitate designated in 92 as phosphate of soda and lithia, is 3 Li 0, P O t (Mayer, "Annal. d. Chem. u. Pharm.," 98, 193). 21--] ANALYSTS OF MINERAL WATERS. 241 filter, wash, and digest with dilute solution of soda and some sulphide of sodium ; filter, and mix the filtrate with hydrochloric acid to acid reaction. If a precipitate is pro- duced, test, a. A portion of it for ARSENIC, with cyanide of potas- sium and carbonate of soda in a stream of carbonic acid. b. Treat the remainder as directed 190, that traces of ANTIMONY and TIN, which may be present, may not be overlooked. If a residue has been left upon treating the precipitate 264 produced by hydrosulphuric acid with solution of soda and sulphide of sodium, boil it, together with the filter, with a very little dilute nitric acid, filter, wash, and examine the contents of the filter, as directed in 212, a, a (262), for sulphate of lead, sulphate of baryta, and sulphate of strontia (the two latter salts are more soluble in solution of sesquichloride of iron than in solution of protochloride of iron. Mix the filtrate (the nitric acid solution) with some pure sulphuric acid, evaporate on the water-bath to dryness, and treat the residue with water. If this leaves an undissolved residue, the latter consists of sulphate of LEAD. To make quite sure, filter, wash the residue, treat it with hydrosulphuric acid water, and observe whether that reagent imparts a black color to it. Test the fluid fil- tered from the sulphate of lead which may have separated, a with ammonia, b with ferrocyanide of potassium, for COPPER. Of the fluid filtered from the precipitate produced by 265 hydrosulphuric acid, examine in the first place, after having expelled the hydrosulphuric acid by boiling, a portion with molybdate of ammonia for PHOSPHORIC ACID; mix the remainder in a flask with chloride of ammonium, ammonia, and yellowish sulphide of ammonium, close the flask, and let it stand in a moderately warm place until the fluid above the precipitate looks no longer greenish, but yellow; filter, and wash the precipitate with water to which some sulphide of ammonium has been added. Dissolve the washed precipitate in hydrochloric acid, separate the SILICIC ACID by evaporation, moisten the residue with hydrochloric acid, add water, warm, and test the solution for ALUMINA, IRON, MAN- GANESE, and ZINC, according to the directions of 192, 1. Examine now the fluid filtered from the precipitate pro- duced by sulphide of ammonium, for LIME and MAGNESIA in the usual way. /3. Mix a portion of the hydrochloric acid solution with chloride of barium, and let the mixture stand 12 hours in a warm place. The formation of a white precipitate indi- cates the presence of SULPHURIC ACID. b. Examination of the residue. This consists usually of silicic acid, clay, and organic mat- 268 ters, but it may also contain sulphate of baryta and sulphate of strontia. Boil in the first place with solution of soda or potassa, to dissolve the SILICIC ACID; then fuse the residue I. R 242 ANALYSIS OF SOILS. [ 213. with carbonate of soda and potassa, and a little nitrate of potassa. Boil the mass, wash the residue, and then dissolve it in some hydrochloric acid ; boil the solution, add ammonia, filter the fluid from the ALUMINA, &c., which may precipitate, evaporate the filtrate to dryness, gently ignite the residue, re- dissolve it in very little water, with addition of a drop of hydrochloric acid, and test for BARYTA and STRONTIA as directed 211, 2, c, a, aa (255> 2. As regards the examination for FLUORINE, the best way is to 267 take for this purpose a separate portion of the ochreous or sinter- deposit. Ignite (which operation will also reveal the presence of organic matters), stir with water, add acetic acid to acid reaction, evaporate until the acetic acid is completely expelled, and proceed as described in 211, 2, b (252). 3. Boil the ochreous or sinter-deposit for a considerable time with 268 concentrated solution of potassa or soda, and filter. a. Acidify a portion of the filtrate with acetic acid, add ammonia, let the mixture stand 12 hours, and then filter the fluid from the precipitate of alumina and hydrated silicic acid, which usually forms ; again add acetic acid to acid reaction, and then a solution of neutral acetate of copper. If a brownish precipitate is formed, this consists of APO- CRENATE of copper. Mix the fluid filtered from the precipitate with carbonate of ammonia, until the green color has changed to blue, and warm. If a bluish-green precipitate is produced, this consists of CRENATE of copper. b. If you have detected arsenic, use the remainder of the alkaline fluid to ascertain whether the arsenic existed in the sinter as arsenious acid or as arsenic acid. Compare 133, 6. IV. ANALYSIS OF SOILS. 213. Soils must necessarily contain all the constituents which are found in the plants growing upon them, with the exception of those sup- plied by the atmosphere and the rain. When we find, therefore, a plant the constituent elements of which are known, growing in a certain soil, the mere fact of its growing there gives us some insight into the composition of that soil, and may accord- ingly save us, to some extent, the trouble of a qualitative- analysis. Viewed in this light, it would appear quite superfluous to make a qualitative analysis of soils still capable of producing plants ; for it is well known that the ashes of plants contain almost invariably the same constituents, and the differences between them are caused principally by differences in the relative proportions in which the several constituents are present. But if, in the qualitative analysis of a soil, regard is had also in so far as may be done by a simple estimation to the quantities and proportions of the several con- stituent ingredients, and to the state and condition in which they are found to be present in the soil, an analysis of the kind, if com- bined with an examination of the physical properties of the soil, 14.] ANALYSIS OF SOILS. 243 and a mechanical separation of its component parts * may to guard even against overlooking the minutest traces of ar- senic, &c. 6. A precipitate is formed, of a pure yellow color like that 295 of tersulphide of arsenic. Take a small portion of the fluid, together with the precipitate suspended therein, add some ammonia, and shake the mixture for some time, without application of heat. If the precipitate dissolves readily and, with the exception of a trace of sulphur, completely, arid if, in the preliminary examination (293)? carbonate of ammonia has failed to produce a precipitate, arsenic alone is present, and no other metal (tin or antimony), at all events, no quantity worth mentioning. Mix the solution of the small sample in ammonia with hydrochloric acid to acid reaction, return the acidulated sample to the fluid from which it was taken, and which contains the yellow precipitate produced by the hydrosulphuric acid, and proceed as directed in 5 (297)- If, on tne other hand, the addition of ammonia to the sample completely or partially fails to redissolve the precipitate, or if, in the preliminary examination (293), carbonate of ammonia has produced a precipitate, there is reason to suppose that another metal is present, perhaps with arsenic. In this latter case also, add to the sample in the test- tube hydrochloric acid to acid reaction, return the acidulated sample to the fluid from which it was taken, which contains the yellow precipitate produced by the hydrosulphuric acid, and proceed as directed in 6 (298)- c. A precipitate is formed, which is not yellow. In that 296 case you have to assume that other metals are present, perhaps with arsenic. Proceed as directed in 6 (298)- 5. Treatment of the Yellow Precipitate produced by Hydrosulphuric Acid, in Gases where the Results of the Examination in 4 b (295) lead to the Assumption that Arsenic alone is present. Determina- tion of the Weight of the Arsenic. As soon as the fluid precipitated according to the directions of 297 4 (293) has nearly lost the smell of sulphuretted hydrogen transfer 254 DETECTION OF AESENIC. [ 223. the yellow precipitate to a small filter, wash thoroughly, pour upon the still moist precipitate solution of ammonia, and wash the filter on which, in this case, nothing must remain undis- solved, except sulphur thoroughly with dilute ammonia; eva- porate the ammoniacal fluid in a small, accurately tared porce- lain dish, on the water-bath, dry the residue at 212 F. until its weight suffers no further diminution, and weigh. If it is found, upon reduction, that the residue consisted of perfectly pure tersulphide of arsenic, calculate for every part of it 0*8049 of arsenious acid, or 0'6098 of arsenic. Treat the residue in the dish according to the instructions given in 7 (300)- G. Treatment of the Yellow Precipitate produced ~by Hydro sulphuric Acid, in Gases where the Results of the Examination in 4, b (295)> or in 4. c (296); lead to the Assumption that another Metal is present perhaps with Arsenic. Separation of the Metals from each other. Determination of the Weight of the Arsenic. If you have reason to suppose that the precipitate produced by 298 hydrosulphuric acid (293) contains other metals, perhaps with arsenic, proceed as follows : As soon . as the precipitation is thoroughly accomplished, and the smell of sulphuretted hydrogen nearly disappeared, pour the precipitate on a small filter, wash thoroughly, perforate the point of the filter, and rinse the contents with the washing-bottle into a little flask, using the least possible quantity of water for the purpose ; add to the fluid in which the precipitate is now suspended, first ammonia, then some yellowish sulphide of ammonium, and let the mixture digest for some time at a gentle heat. Should part of the precipitate remain undissolved, filter this off, wash, perforate the filter, rinse off the residuary precipitate, mark it III., and reserve for further examination according to the instructions given in 223, 8, c (305)- Evaporate the filtrate, together with the washings, in a small porcelain dish, to dryness. Treat the residue with some pure fuming nitric acid (free from chlorine), nearly expel the acid by evaporation, and then add, as C. Meyer was the first to recommend, gradually, and in small portions at a time, a solution of pure carbo- nate of soda until it predominates. Add now a mixture of 1 part of carbonate and 2 parts of nitrate of soda, in suffi- cient, yet not excessive quantity, evaporate to dryness, and heat the residue very gradually to fusion. Let the fused mass cool, and, when cold, extract it with cold water. If a residue remains undissolved, filter, wash with a mixture of equal parts of spirit 299 of wine and water, mark it IV., arid reserve for further exa- mination, according to the directions of 223, 8, d (306)- Mix the solution, which must contain all the arsenic as arsenate of soda, with the washings, previously freed from alcohol by evaporation, add gradually and cautiously pure dilute sulphuric acid to strongly acid reaction, evaporate in a small porcelain dish, and, when the fluid is tolerably concentrated, add again sulphuric acid, to see whether the quantity first added has been sufficient to expel all nitric and nitrous acids ; heat now very cautiously until heavy fumes of hy- drated sulphuric acid begin to escape; then let the liquid cool, 223.] DETECTION OP ARSENIC. 55 and, when cold, add a little of a concentrated ^solution of sulphurous acid in water; warm until the excess of the sulphurous acid is driven off, and then conduct hydrosulphuric acid into the fluid. If arsenic is present, a yellow precipitate will form. When the precipitate has completely subsided, and the fluid has nearly lost the smell of sulphuretted hydrogen, filter, wash the precipitate, dissolve it in ammonia, and proceed with the solution as directed in 5, (297), to determine the weight of the arsenic. 7. Deduction of the Sulphide of Arsenic. The production of metallic arsenic from the sulphide, which may 300 be regarded as the keystone of the whole process, demands the greatest care and attention. The method recommended in 131, 12, viz., to fuse the arsenical compound, mixed with cyanide of potassium and carbonate of soda, in a slow stream of carbonic acid gas, is the best and safest, affording, besides the advantage of great accuracy, also a positive guarantee against the chance of con- founding the arsenic with some other body, more particularly anti- mony ; on which account it is more especially adapted for medico- legal investigations. As regards the process of reduction, either proceed at once with the sulphide of arsenic, or previously convert the latter into arsenic acid (see 301). In the former case take care, if possible, not to use the whole of the residue in the dish, obtained by the evapo- ration of the ammoniacal solution, but only a portion of it, so that the process may be repeated several times, if necessary. Should the residue be too trifling to admit of being divided into several por- tions, dissolve it in a few drops of ammonia, add a little carbonate of soda, and evaporate on the water-bath to dryness, taking care to stir the mixture during the process ; divide the dry mass into several portions, and proceed to reduction. Otto* recommends to convert the sulphide first into arsenic acid, 301 and then to reduce the latter with cyanide of potassium. The fol- lowing is the process given by him to effect the conversion of the sul- phide into the acid ; pour concentrated nitric acid over the sulphide of arsenic in the dish, evaporate, and repeat the same operation several times, if necessary, and then remove every trace of nitric acid by repeatedly moistening the residue with water, and drying again ; when the nitric acid is completely expelled, treat the residue with a few drops of water, add carbonate of soda in powder, to form an alkaline mass, and thoroughly dry this in the dish, with frequeot stirring, taking care to collect the mass within the least possible space in the middle of the dish. The dry mass thus obtained is admirably adapted for reduction. I can, from the results of my own experience, fully confirm this statement of Otto; but I must once more repeat, that it is indispensable for the success of the operation that the residue should be perfectly free from every trace of nitric acid or nitrate ; otherwise deflagration is sure to take place during the process of fusion with cyanide of potassium, and, of course, the experiment will fail. * " Anleitung zur Ausmittelung Jer Gifte," von Dr. Fr. Jid. Otto, p. 33. 256 DETECTION OF ARSENIC. [ 223. When the operation is finished, cut off the reduction tube at c (see 302 Fig. 30), set aside the fore part, which contains the arsenical mirror, put the other part of the tube into a cylinder, pour water over it, and let it stand some time; then filter the solution obtained, add to the filtrate hydrochloric acid to acid reaction ; then again some hydro- sulphuric acid, and observe whether this produces a precipitate. In cases where the reduction of the sulphide of arsenic has been effected in the direct way, without previous conversion to arsenic acid, a trifling yellow precipitate will usually form ; had traces of antimony been present, the precipitate would be orange-colored and insoluble in carbonate of ammonia. When all the soluble salts of the fused mass have been dissolved out, examine the metallic residue, which may be left behind, according to the directions of 133, 1, for traces of tin and antimony; these being the only metals that can possibly be present if the instruc- tions here given have been strictly followed. Should appreciable traces of these metals, or of either of them, be found, proper de- duction and correction must be made in calculating the weight of the arsenic. 8. Examination of the reserved Residues, marked severally I., II., III., and IV., for other Metals of the Fifth and Sixth Groups. a. Residue I. Compare 223, 1 (290)- This may contain chloride of silver and sulphate of lead, 303 possibly also binoxide of tin. Incinerate the residue (I.) in a porcelain dish, burn the carbon with the aid of some nitrate of ammonia, extract the residue with water, dry the part left undissolved, and then fuse it with cyanide of potassium in a porcelain crucible. When the fused mass is cold, treat it with water until all that is soluble in it is completely removed ; warm the residue with nitric acid, and proceed as directed in 179. b. Residue II. Compare 223, 3 (292). The carbonaceous residue which is obtained by the purifica- 304 tion of the crude sulphide by means of nitric acid and sulphuric acid, may more particularly contain lead, mercury, and tin ; antimony and bismuth may also be present. Heat the residue for some time with nitrohydrochloric acid, and filter the solution ; wash the undissolved residue with water mixed with some hydrochloric acid, add the washings to the filtrate, and treat the dilute fluid thus obtained with hydrochloric acid ; should a precipitate form, examine this according to the instructions given in 189. Incinerate the residue insoluble in nitrohydrochloric acid, fuse the ash in con- junction with cyanide of potassium, and proceed with the fused mass as directed in 8, a (303)- 224.] DETECTION OF HYDROCYANIC ACID. 257 c. Residue III. Compare 223, 6 (298). Examine the precipitate insoluble in sulphide of ammonium 3Q5 for the metals of the fifth group according to the instructions given in 191. d. Residue IV. Compare 223, 6 (299). ong This may contain tin and antimony, perhaps also copper. Proceed as directed 190, 2, b (123). If the color of the re- siaue was black (oxide of copper), treat the reduced metals according to the instructions given in 179. 9. Examination of the Filtrate reserved 233, 2 (291), /or Metals of the Fourth and Third Groups, especially for Zinc and Chromium. a. As we have seen in 223, 2 (291), the fluid filtered from 3Q7 the precipitate produced by hydrosulphuric acid, and tempo- rarily reserved for further examination, has already been mixed with sulphide of ammonium. The addition of this reagent to the filtrate is usually attended with the formation of a precipitate, consisting of sulphide of iron and phosphate of lime, but which may possibly also contain sulphide of zinc. Filter the fluid from this precipitate, and treat the filtrate as directed in b (308) ; wash the precipitate with water mixed with some sulphide of ammonium, dissolve by warming with hydrochloric acid, and boil the solution with nitric acid, to convert the protoxide of iron into sesquioxide ; add, if neces- sary, sufficient sesquichloride of iron for carbonate of soda to produce a brownish-yellow precipitate in a sample of the fluid ; neutralize almost completely with carbonate of soda, precipitate with carbonate of baryta, and filter ; the precipi- tate contains all the sesquioxide of iron and all the phos- phoric acid. Concentrate the filtrate, precipitate the baryta with dilute, sulphuric acid, filter, add to the filtrate ammonia to alkaline reaction, and precipitate with sulphide of ammo- nium the zinc which may be present. For the further exami- nation of the precipitate, see 105. b. If the analyzed substance contained chromium, this will 308 be found in the fluid filtered from the precipitate produced by sulphide of ammonium, 223, 2 (291). Compare 223, 9, a (307). If you wish to ascertain whether chromium is really present, evaporate the filtrate to dryness, mix the residue with 3 parts of nitrate of potassa and 1 part of carbonate of soda, put the mixture into a Hessian crucible and heat to moderate redness. Allow the fused mass to cool, and, when cold, boil with water : yellow coloration of the fluid shows the presence of alkaline chromate, and accordingly of chromium. For con- firmatory tests, see 138. II. METHOD FOB THE DETECTION OF HYDROCYANIC ACID. 224. In cases of actual or suspected poisoning with hydrocyanic acid, 309 I. s 258 DETECTION OF HYD110CYANIC ACID. [ 224. where it is required to separate that acid from articles of food or from the contents of the stomach, and thus to prove its presence, it is highly necessary to act with the greatest expedition, as the hydrocyanic acid speedily undergoes decomposition. Still this de- composition is not quite so rapid as is generally supposed, and indeed it requires some time before the complete decomposition of the whole of the acid present is effected.* Although hydrocyanic acid betrays its presence, even in minute quantities, by its peculiar odor, still this sign must never be looked upon as conclusive. On the contrary, to adduce positive proof of the presence of the acid, it is always indispensable to separate it, and to convert it into certain known, compounds. The method of accomplishing this is based upon distillation of the acidified mass, and examination of the distillate for hydrocyanic acid. Now, as the non-poisonous salts, ferro- and ferricyanide of potassium, on distillation, likewise yield a distillate containing hydrocyanic acid, it is, of course, indispensable as Otto very pro- perly observes first to ascertain whether one of these salts may not be present. For this purpose, stir a small portion of the mass to be examined with water, filter, acidify the filtrate with hydrochloric acid, and test a sample of it with sesquichloride of iron, another with sulphate of protoxide of iron. If no blue pre- cipitate forms in either, soluble ferro- and ferricyanides are not pre- sent, and you may safely proceed as follows : Test, in the first place, the reaction of the mass under examina- 310 tion ; if necessary, after mixing and stirring it with water. If it is not already strongly acid, add solution of tartaric acid until the fluid strongly reddens litmus paper ; introduce the mixture into a retort, and place the body of the retort, with the neck pointing upwards, in an iron or copper vessel, but so that it does not touch the bottom, which should, moreover, by way of precaution, be covered with a cloth ; fill the vessel with a solution of chloride of calcium, and apply heat, so as to cause gentle ebullition of the con- tents of the retort. Conduct the vapors passing over, with the aid of a tight-fitting tube, bent at a very obtuse angle, through a Liebigs condensing apparatus, and receive the distillate in a small, weighed flask. When about half-an-ounce of distillate has passed over, re- move the receiver, and replace it by a somewhat larger flask, also previously tared. Weigh the contents of the first receiver, and proceed as follows : a. Mix one-fourth of the distillate with solution of potassa 311 or soda to strongly alkaline reaction, and then add a small quantity of solution of sulphate of protoxide of iron, mixed with a little sesquichloride of iron. b. Treat another fourth as directed 155, 7, to convert the 312 hydrocyanic acid into sulphocyanide of iron. As the distillate might, however, contain acetic acid, do not neglect to add some * Thus I succeeded in separating a notable quantity of hydrocyanic acid from the sto- mach, of a man who had poisoned himself with that acid in very hot weather, and whose intestines were handed to me full 36 hours after death. A dog was poisoned with, hydrocyanic acid, and the contents of the stomach, mixed with the blood, were left for 24 hours exposed to an intense summer-heat, and then examined : the acid was still detected. DETECTION OF PHOSPIIOEUS. 259 hydrochloric acid after the sesquicliloride of iron, in order to neutralize the adverse influence of the acetate of ammonia. Compare 155, 7. c. If the experiments a and 6 have demonstrated the pre- 313 sence of hydrocyanic acid, and you wish now also to approxi- mately determine its quantity, continue the distillation, until the fluid passing over contains no longer the least trace of hydrocyanic acid ; add one-half of the contents of the second receiver to the remaining half of the contents of the first, mix the fluid with nitrate of silver, then with ammonia until it predominates, and finally with nitric acid to strongly acid reac- tion. Allow the precipitate which forms to subside, filter on a tared filter, dried at 212F., wash the precipitate, dry it tho- roughly at 212 F., and weigh. Ignite the weighed precipitate in a small porcelain crucible, to destroy the cyanide of silver, fuse the residue with carbonate of soda and potassa to effect the decomposition of the chloride of silver which it may con- tain boil the mass with water, filter, acidify the filtrate with nitric acid, and precipitate with nitrate of silver ; determine the weight of the chloride of silver which may precipitate, and deduct the amount found from the total weight of the chloride and cyanide of silver : the difference gives the quantity of the latter ; by multiplying the quantity found of the cyanide of silver by O2017, you find the corresponding amount of an- hydrous hydrocyanic acid ; and by multiplying this again by 2 as only one-half of the distillate has been used you find the total quantity of hydrocyanic acid which was present in the examined mass. Instead of pursuing this indirect method, you may also deter- 314 mine the quantity of the hydrocyanic acid by the following direct method : Introduce half of the distillate into a retort, together with powdered borax ; distil to a small residue, and deter- mine the hydrocyanic acid in the distillate as cyanide of silver. Hydrochloric acid can no longer be present in this distillate, as the soda of the borax retains it in the retort ( Wackenroder). III. METHOD FOR THE DETECTION OF PHOSPHORUS. 225. Since phosphorus paste has been employed to poison mice, &c., 315 and the poisonous action of lucifer matches has become more ex- tensively known, phosphorus has not unfrequently been resorted to as an agent for committing murder. The chemist is therefore occasionally called upon to examine some article of food, or the contents of a stomach, for this substance. It is obvious that, in cases of the kind, his whole attention must be directed to the separation of the phosphorus in the free state, or to pro- ducing such reactions as will enable him to infer the presence of free phosphorus ; since the mere finding of phosphorus in form of phosphates would prove nothing, as phosphates invariably form constituents of animal and vegetable bodies. s 2 260 DETECTION OF PHOSPHORUS. [ 225. K Mitech&rlich, who has published the latest treatise on the 316 subject,* recommends the following method as the simplest and best:f Mix the substance under examination with water and some sul- phuric acid, and subject the mixture to distillation in a flask, A (see .Fig. si). This flask is connected with an evolution tube, b, and Fig. 31. the latter again with a glass cooling or condensing tube, c c c, which passes through a perforated cork a, in the bottom of a cylinder, B, into a glass vessel, C. Cold water runs from D, through a stop- cock, into a funnel, i, which extends to the bottom of B ; the warmed water flows off through g. Now, if the substance in A contains phosphorus, there will ap- pear, in the dark, in the upper part of the condensing tube at the point r, where the aqueous vapors distilling over enter that part of the tube, a strong luminosity, usually a luminous ring. If you take for distillation 5 oz. of a mixture containing only of a grain of phosphorus, and accordingly only 1 part of * "Journal fur prakt. Chemie," vol. 66, p. 238. I have tried this method, and found it to answer perfectly. 226.] ANALYSIS OF ASHES. 261 phosphorus in 100,000 parts of mixture, you may distil over 3 oz. of it which will take at least half-an-hour without the lumi- nosity ceasing ; Mitscherlich, in one of his experiments, stopped the distillation after half-an-hour, allowed the flask to stand uncorked a fortnight, and then recommenced the distillation : the luminosity was as strong as at first. If the fluid contains sub- stances which prevent the luminosity of phosphorus in general, such as ether, alcohol, or oil of turpentine, no luminosity is observed so long as these substances continue to distil over. In the case of ether and alcohol, however, this is soon effected, and the luminosity accordingly very speedily makes its appearance ; but it is different with oil ot turpentine, which exercises a lasting pre- ventive influence upon the manifestation of this reaction. After the termination of the process, globules of phosphorus 317 are found at the bottom of the receiver, C. MitscJierlich obtained from 5 oz. of a mixture containing ^ grain of phosphorus, so many globules of that body that the one-tenth part of them would have been amply sufficient to demonstrate its presence. In medico- legal investigations these globules should first be washed with alcohol, and then weighed. A portion may afterwards be sub- jected to a confirmatory examination, to make quite sure that they really consist of phosphorus : the remainder, together with a portion of the fluid which shows the luminosity upon distillation, should be sent in with the report. 3. Examination of the Inorganic Constituents of Plants, Animal*, or Parts of the same, of Manures, &c. (Analysis of Ashes.) 226. A. PREPARATION OF THE ASH. It is sufficient for the purposes of a qualitative analysis to in- 318 cinerate a comparatively small quantity of the substance which it is intended o examine for its inorganic constituents ; the substance must previously be most carefully cleaned. The incineration is effected best in a small clay muffle, but it may be conducted also in a Hessian crucible placed in a slanting position, or, under certain circumstances, even in a small porcelain or platinum dish. The heat must always be moderate, to guard against the volatilization of cer- tain constituents, more especially of metallic chlorides. It is not always necessary to continue the combustion until all the carbon is consumed. With ashes containing a large proportion of fusible salts, as, e. g. the ash of beetroot molasses, it is even advisable to effect, in the first place, complete carbonization, then to boil the charred mass with water, and finally to incinerate the washed and dried residue. For further particulars see Quantitative Analysis, 3rd Edition, 250. B. EXAMINATION OP THE ASH. As the qualitative analysis of the ash of a vegetable substance 319 is usually undertaken, either as a practical exercise, or for the purpose of determining its general character, and the state or condition in which any given constituent may happen to be pre- 262 ANALYSIS or ASHES. [ 226. sent, or also with a view to make, as far as practicable, an approxi- mate estimation of the respective quantities of the several constituents, it is usually the best way to examine separately ; (1) the part so- luble in water ; (2) the part soluble in hydrochloric acid ; and (3) the residue which is insoluble in either menstruum. This can be done the more readily, as the number of bodies to which regard must be had in the analysis is only small, and the several processes may accordingly be expeditiously performed. a. Examination of the Part soluble in Water. Boil the ash with water, filter, and whilst the residue is being washed, examine the solution as follows : 1. Add to a portion, after heating it, hydrochloric acid in excess, 320 warm, and let the fluid stand at rest. Effervescence indicates CAR- BONIC ACID, combined with alkalies ; odor of hydrosulphuric acid indicates the SULPHIDE of an ALKALI METAL, formed from an alkaline sulphate by the reducing action of the carbon. Turbidity from separation of sulphur, with odor of sulphurous acid, denotes a HYPO- SULPHITE (which occurs occasionally in the ash of coal). Filter, if necessary, and add to the filtrate or to the fluid if no filtration is required some chloride of barium ; the formation of a white precipitate indicates the presence of SULPHURIC ACID. 2. Evaporate another portion of the solution until it is reduced 321 to a small volume, add hydrochloric acid to acid reaction efferves- cence indicates the presence of CARBONIC ACID evaporate now to dryness, and treat the residue with hydrochloric acid and water. The portion left undissolved consists of SILICIC ACID. Filter, add ammonia, chloride of ammonium, and sulphate of magnesia j the formation of a white precipitate indicates the presence of PHOS- PHORIC ACID. Instead of this reaction, you may also mix the fluid filtered from the silicic acid with acetate of soda, and then cautiously add, drop by drop, sesquichloride of iron, or you may test with molybdate of ammonia ( ] 43). 3. Add to another portion of the solution nitrate of silver as 322 long as a precipitate continues to form ; warm gently, and then cautiously add ammonia : if a black residue is left, this consists of sulphide of silver, proceeding from the sulphide of an alkali metal, or from a hyposulphite. Mix the ammoniacal solution now after previous filtration if necessary cautiously with nitric acid until it is exactly neutralized. If this produces a bright yellow precipitate, the phosphoric acid found in 2 was present in the tribasic, if a white precipitate, it was present in the bibasic form. Add more nitric acid. This effects the solution of the phosphate of silver precipitate. But if CHLORINE (iodine,* bromine) is present, a portion of the precipitate remains undissolved, or the fluid appears turbid. 4. Acidify a portion of the solution with hydrochloric acid, and 323 then make it alkaline with ammonia ; mix the alkaline fluid with oxalate of ammonia, and let it stand at rest. The formation . of a * To detect the iodine in aquatic plants, dip the plant in a weak solution of potassa (Chatiri), dry, incinerate, treat with water, and examine the aqueous solution as directed 211, 2, c, ft aa (258). 22G.] ANALYSIS OF ASHES. 263 white precipitate indicates LIME. Filter, and mix the nitrate with ammonia and phosphate of soda ; the formation of a crystalline pre- cipitate, which often becomes visible only after long standing, indi- cates MAGNESIA. Magnesia is often found in distinctly appreciable, lime only in exceedingly minute, quantity, even when alkaline car- bonates and phosphates are present. 5. For POTASSA and SODA examine as directed S 195. b. Examination of the Part soluble in Hydrochloric Acid. Warm the residue left undissolved by water with hydrochloric 324 acid* effervescence indicates CARBONIC ACID, combined with alka- line earths ; evolution of chlorine denotes OXIDES OF MANGANESE evaporate to dryness, and heat a little more strongly, to effect the separation of the silicic acid ; moisten the residue with hydrochloric acid and some nitric acid, add water, warm, and filter. 1. Test with hydrosulphuric acid. If this produces any other than a perfectly white precipitate, you must examine it in the usual way. The ashes of plants occasionally contain COPPER ; if the plant has been manured with excrements deodorized by nitrate of lead, they may contain LEAD ; other metals are also occasionally found. 2. Mix a portion of the original solution with carbonate of soda, 325 as long as the precipitate formed redissolves upon stirring ; then add acetate of soda, and some acetic acid. This produces, in most cases, a white precipitate of PHOSPHATE OF SESQUIOXIDE OF IRON. If the fluid in which this precipitate is suspended is reddish, there is more sesquioxide of iron present than corresponds to the phosphoric acid ; if it is colorless, add sesquichloride of iron, drop by drop, until the fluid looks reddish. (From the quantity of the precipitate of phosphate of sesquioxide of iron formed you may estimate the PHOSPHORIC ACID present.) Heat to boiling,t filter hot, and mix the filtrate, after addition of ammonia, with yellowish sulphide of ammonium, in a stoppered flask ; should a precipitate form, after long standing, examine this before the blowpipe for MANGANESE, and the fluid filtered from it for LIME and MAGNESIA, in the usual way (226, B,a, 4 [323]). c. Examination of the Residue insoluble in Hydrochloric Acid. The residue insoluble in hydrochloric acid contains, 1. The silicic acid, which has separated on treating with hydro- 326 chloric acid. 2. Those ingredients of the ash which are insoluble in hydro- chloric acid. These are, in most ashes, sand, clay, carbon ; sub- stances, therefore, which are present in consequence of defective cleaning or imperfect combustion of the plants, or matter derived from the crucible. It is only the ashes of the stems of cereals and others abounding in silicic acid, that are not completely decomposed by hydrochloric acid. * If the residue still contains much carbon, after further incineration. f If this should fail to decolorize the fluid, add some more acetate ot soda. 26 i ADDITIONAL REMARKS. [To 173 176. Boil the washed residue with solution of carbonate of soda in 327 excess, filter hot, wash with boiling water, and test for silicic acid in the filtrate by evaporation with hydrochloric acid. If the ash was of a kind to be completely decomposed by hydrochloric acid, the analysis may be considered as finished for the accidental admix- ture of clay and sand will rarely interest the analyst sufficiently to warrant a more minute examination by fluxing. But, if the ash abounded in silicic acid, and it may therefore be supposed that the hydrochloric acid has failed to effect complete decomposition, evapo- rate half of the residue insoluble in solution of carbonate of soda, with pure solution of soda in excess, in a silver or platinum dish, to dryness. This decomposes the silicates of the ash, whilst but little affecting the sand. Acidify now with hydrochloric acid, evaporate to dryness, &c., and proceed as in b (324). For the de- tection of the alkalies use the other half of the residue. Compare 205, 2 (228). SECTION III. EXPLANATORY NOTES AND ADDITIONS TO THE SYSTEMATIC COURSE OF ANALYSIS. I. ADDITIONAL REMARKS TO THE PRELIMINARY EXAMINATION. To 173176. THE inspection of the physical properties of a body may, as already stated 173, in many cases enable the analyst to draw certain general inferences as to its nature. Thus, for instance, if the analyst has a white substance before him, he may at once conclude that it is not cinnabar, or if a light substance, that it is not a compound of lead, &c. Inferences of this kind are quite admissible to a certain extent ; but if carried too far, they are apt to mislead the operator, by blinding him to every reaction not exactly in accordance with his preconceived notions. As regards the examination of substances at a high temperature, platinum foil or small iron spoons may also be used in the process ; however, the experiment in the glass tube gives, in most cases, results more clearly evident, and affords, moreover, the advantage that volatile bodies are less likely to escape detection, and that a more correct and precise notion can be formed of the nature of the heated substance, than exposure on platinum foil or in an iron spoon will permit. In the case of minerals it is always advisable to extend the examination in the dry way, also to fluorine ( 147, 8). To ascertain the products of oxidation of a body, it is sometimes advisable also to heat it in a short glass-tube, open at both ends, and held in a slanting position ; small quantities of a metallic sulphide, for instance, may be readily detected by this means. (Compare 156, 6.) With respect to the preliminary examination by means of the blow- To 177 179.] ADDITIONAL REMARKS. 265 pipe, I have to remark that the student must avoid drawing positive conclusions from pyrochemical experiments, until he has acquired some practice in this branch of analytical chemistry. A slight incrustation of the charcoal support, which may seem to denote the presence of a cer- tain metal, is not always a conclusive proof of the presence of that metal ; nor would it be safe to assume the absence of a substance simply because the blowpipe flame fails to effect reduction, or solution of nitrate of protoxide of cobalt fails to impart a color to the ignited mass, &c. The blowpipe reactions are, indeed, in most cases, unerring, but it is not always easy to produce them, and they are moreover liable to suffer modification by accidental circumstances. The student should never omit the preliminary examination ; the notion that this omission will save time and trouble, is very erroneous. II. ADDITIONAL EEMARKS TO THE SOLUTION OF SUBSTANCES, ETC. To 177179. It is a task of some difficulty to fix the exact limit between substances which are soluble in water and those that are insoluble in that men- struum, since the number of bodies which are sparingly soluble in water is very considerable, and the transition from sparingly soluble to in- soluble is very gradual. Sulphate of lime, which is soluble in 430 parts of water, might perhaps serve as a limit between the two classes, since this salt may still be positively detected in aqueous solution, by the deli- cate reagents which we possess for lime and sulphuric acid. When examining an aqueous fluid by evaporating a few drops of it upon platinum foil, to see whether it holds a solid body in solution, a very minute residue sometimes remains, which leaves the analyst in doubt respecting the nature of the substance ; in cases of the kind test, in the first place, the reaction of the fluid with litmus papers ; in the second place, add to a portion of it a drop of solution of chloride of barium ; and lastly, to another portion some carbonate of soda. Should the fluid be neutral, and remain unaltered upon the addition of these reagents, the analyst need not examine it any further for bases or acids ; since if the fluid contained any of those bases or acids which principally form sparingly soluble compounds, the chloride of barium and the car- bonate of soda would have revealed their presence. The analyst may therefore feel assured that the detection of the substance of which the residue left upon evaporation consists, will be more readily effected in the class of bodies insoluble in water. If water has dissolved any part of the substance under examination, the student will always do well to examine the solution both for acids and bases, since this will lead more readily to a correct apprehension of the nature of the compound an advantage which will amply counter- balance the drawback of sometimes meeting with the same substance both in the aqueous and in the acid solution. The following substances (with few exceptions) are insoluble in water, but soluble in hydrochloric acid or in nitric acid : the phosphates, arse- nates, arsenites, borates, carbonates, and oxalates of the earths and metals ; and also several tartrates, citrates, malates, benzoates, and succinates ; the oxides and sulphides of the heavy metals; alumina, magnesia; many of the metallic iodides and cyanides, &c. Nearly the whole of these 266 EXPLANATION OF THE ANALYTICAL COURSE. [To 180 201. compounds are, indeed, decomposed, if not by dilute, by boiling concen- trated hydrochloric acid * but this decomposition gives rise to the for- mation of insoluble compounds when oxide of silver is present, and of sparingly soluble compounds in the presence of suboxide of mercury and lead. This is not the case with nitric acid, and accordingly the latter effects complete solution in many cases where hydrochloric acid has left a residue. But, on the other hand, nitric acid leaves, besides the bodies insoluble in any simple acid, teroxide of antimony, binoxide of tin, bin- oxide of lead, &c., undissolved, and fails also to effect the complete solution of many other substances. Substances not soluble in water are, therefore, treated as follows : try to dissolve them in dilute or concentrated hydrochloric acid, cold or boiling if this fails to effect complete solution, try to dissolve a fresh portion in nitric acid j if this also fails, treat the body with aqua regia, which is an excellent solvent, more particularly for metallic sulphides. To examine separately the solution in hydrochloric acid or in nitric acid, on the one hand, and that in nitrohydrochloric acid on the other, is, in most cases, unnecessary. With regard to the solution of metals and alloys, I have to remark that, upon boiling them with nitric acid, white precipitates will fre- quently form, although neither tin nor antimony be present. Inexpe- rienced students often confound such precipitates with the oxides of these two metals, although their appearance is quite different. These precipitates consist simply of nitrates sparingly soluble in the nitric acid present, but readily soluble in water. Consequently the analyst should ascertain whether these white precipitates will dissolve in water or not, before he concludes them to consist of tin or antimony. III. ADDITIONAL REMARKS TO THE ACTUAL EXAMINATION. To 180201. A. GENERAL REVIEW AND EXPLANATION OF THE ANALYTICAL COURSE. a. DETECTION OF THE BASES. The classification of the bases into groups, and the methods which serve to detect and isolate them individually, have been fully explained in Part I., Section III. The systematic course of analysis, from 180 to 196, is founded upon this classification of the bases j and as a correct apprehension of it is of primary importance, I will here subjoin a brief explanation of the grounds upon which this division rests. Respecting the detection of the several bases individually, I refer the student to the recapitulations and remarks in 91, 98, 102, 111, 117, 122, 127, and 133. The general reagents which serve to divide the bases into principal groups are HYDROCHLORIC ACID, HYDROSULPHURIC ACID, SULPHIDE OF AMMONIUM, and CARBONATE OF AMMONIA ; this is likewise the order of succession in which they are applied. Sulphide of ammonium performs a double part. Let us suppose we have in solution the whole of the bases, together * For tlie exceptions, see 5 201. To 180 201.] EXPLANATION OF THE ANALYTICAL COURSE. 267 with arsenious and arsenic acids, and also phosphate of lime which latter may serve as a type for the salts of the alkaline earths, soluble in acids, and reprecipitated unaltered by ammonia. Chlorine forms insoluble compounds only with silver and mercury ; chloride of lead is sparingly soluble in water. The insoluble subchloride of mercury corresponds to the suboxide of that metal. If, therefore, we add to our solution : 1. Hydrochloric Acid, we remove from it the metallic oxides of the first division of the fifth group, viz., the whole of the OXIDE OF SILVER and the whole of the SUB- OXIDE OF MERCURY. From concentrated solutions, a portion of the LEAD may likewise precipitate as chloride j this is, however, immaterial, as a sufficient quantity of the lead remains in the solution to permit the sub- sequent detection of this metal. Hydrosulphuric acid completely precipitates the oxides of the fifth and sixth group from solutions containing a free mineral acid, since the affinity of the metallic radicals of these oxides for sulphur, and that of the hydrogen for oxygen, are sufficiently powerful to overcome the affinity between the metal and the oxygen, and 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 these circumstances, since those of the first, second, and third group form no sulphur compounds insoluble in water j and the affinity which the metallic radicals of the oxides of the fourth group possess for sulphur, combined with that manifested by hydrogen for oxygen, is not sufficiently powerful to overcome the affinity of the metal for oxygen and of the oxide for a strong acid, IF THE LATTER IS PRESENT IN EXCESS. If, therefore, after the removal of the oxide of silver and suboxide of mercury, by means of hydrochloric acid, we add to the solution, which still contains free hydrochloric acid, 2. Hydrosulphuric Acid, we remove from it the remainder of the oxides of the fifth, together with those of the sixth group, viz., OXIDE OF LEAD, OXIDE OF MERCURY, OXIDE OF COPPER, TEROXIDE OF BISMUTH*, OXIDE OF CADMIUM, TEROXIDE OF GOLD, BINOXIDE OF PLATINUM, PROTOXIDE OF TIN, BINOXIDE OF TIN, TEROXIDE OF ANTIMONY, ARSENIOUS ACID, and ARSENIC ACID. All the other oxides remain in solution, either unaltered, or reduced to a lower degree of oxidation, e. g., sesquioxide of iron to protoxide ; chromic acid to sesquioxide of chromium, &c. The sulphides corresponding to the oxides of the sixth group com- bine with basic metallic sulphides (the sulphides of the alkali metals), and form with them sulphur salts soluble in water ; while the sulphides corresponding to the oxides of the fifth group do not possess this pro- perty, or possess it only to a limited extent.* If, therefore, we treat the whole of the sulphides precipitated by hydrosulphuric acid from an acid solution, with * Sulphide of mercury combines with sulphide of potassium and sulphide of sodium, but not with sulphide of ammonium ; sulphide of copper dissolves a little in sulphide of ammonium, but not in sulphide of potassium or sulphide of sodium. 268 EXPLANATION OF THE ANALYTICAL COURSE. [To 180201. 3. Sulphide of Ammonium (or, in certain cases, Sulphide of Sodium), the sulphides* of mercury, lead, copper, bismuth, and cadmium remain undissolved, whilst the other sulphides dissolve as double compounds of sulphide of GOLD, PLATINUM, ANTIMONY, TIN, ARSENIC, with SULPHIDE OF AMMONIUM (or, as the case may be, SULPHIDE OF SODIUM), and precipi- tate again from this solution upon the addition of an acid, either un- altered, or, as regards the protosulphide of tin, and the tersulphide of antimony, in a state of higher sulphtiration these two compounds taking up sulphur from the yellow sulphide of ammonium. The rationale of this precipitation is as follows : The acid decomposes the sulphur salt formed. The sulphur base (sulphide of ammonium or sul- phide of sodium) transposes with the constituents of the water, forming an oxygen base (oxide of ammonium or soda) and hydrosulphuric acid ; the former combines with the acid added, the latter escapes, and the liberated electro-negative sulphide (sulphur acid) precipitates. If the acid is an hydracid, its radical combines with the ammonium, its hydrogen with the sulphur. Sulphur precipitates at the same time, the sulphide of ammonium containing generally an excess of that element. The analyst must bear in mind that this eliminated sulphur makes the precipitated sulphides appear of a lighter color than they are naturally. The alkalies, the alkaline earths, alumina, and sesquioxide of chromium have remained in solution, because their sulphur compounds are soluble in water, or because their salts are not affected in the least by hydro- sulphuric acid ; the sulphides corresponding to the oxides of the fourth group are insoluble in water, and would have been precipitated accord- ingly by hydrosulphuric acid, but for the free acid present. If, there- fore, this free acid is removed, **. e., if the solution is made alkaline, and then treated with hydrosulphuric acid, or, what answers both purposes at once, if 4. Sulphide of Ammonium, is added to the solution,* the sulphides corresponding to the oxides of the fourth group will precipitate : viz., the SULPHIDES OF IRON, MANGA- NESE, COBALT, NICKEL, and ZINC. But in conjunction with them, ALUMINA, SESQUIOXIDE OF CHROMIUM, and PHOSPHATE OF LIME, are thrown down, because the affinity which the oxide of ammonium pos- sesses for the acid of the salt of alumina or of sesquioxide of chromium, or for that which keeps the phosphate of lime in solution, causes the elements of the sulphide of ammonium to transpose with those of the water, thus giving rise to the formation of oxide of ammonium and of hydrosulphuric acid. The former combines with the acid, the latter escapes, being incapable of entering into combination with the liberated oxides or with the phosphate of lime, the oxides and the lime-salt precipitate. There remain now in solution only the alkaline earths and the alkalies. The neutral carbonates of the former are insoluble in water, * After previous neutralization of the free acid by ammonia, to prevent unnecessary evolution of hydrosulphuric acid ; and the addition also, if necessary, of chloride of am- monium, to prevent the precipitation of magnesia by ammonia. TO 180201.] EXPLANATION OP THE ANALYTICAL COURSE. 269 whilst those of the latter are soluble in that menstruum. If therefore we now add 5. Carbonate of Ammonia, and apply a gentle heat, in order to decompose the bicarbonates which may have formed, the whole of the alkaline earths ought to precipitate. This is, however, the case only as regards BARYTA, STRONTIA, and LIME ; of magnesia we know that, owing to its disposition to form double com- pounds with salts of ammonia, it precipitates only in part ; and that the presence of an additional salt of ammonia will altogether prevent its precipitation. To guard against any uncertainty arising from this cause, chloride of ammonium is added previously to the addition of the carbonate of ammonia, and thus the precipitation of the magnesia is altogether prevented. We have now in solution magnesia and the alkalies. The detection of magnesia may be effected by means of phosphate of soda and ammonia ; but its separation requires a different method, since the presence of phosphoric acid would impede the further progress of the analysis. The process which serves to effect the removal of the magnesia is based upon the insolubility of that earth in the pure state. The substance under examination is accordingly ignited in order to expel the salt of ammonia, and the magnesia is then precipitated by means of baryta, the alkalies, together with the newly formed salt of baryta and the excess of the caustic baryta added, remaining in solution. By the addition of carbonate of ammonia, the compounds of baryta are removed from the solution, which now only contains the fixed alkalies, the salt of ammonia formed, and the excess of the salt of ammonia added. If the salts of ammonia are then removed by ignition, the residue consists of the fixed alkalies alone. This method of separating the baryta affords the advan- tage over that of effecting the removal of that earth by means of sul- phuric acid, that the alkalies are obtained in the most convenient form for their subsequent individual detection and isolation, viz., as chlorides. But as carbonate of baryta is slightly soluble in salts of ammonia, and gives, upon evaporation with chloride of ammonium, carbonate of baryta and chloride of barium, it is usually necessary, after the expulsion of the salts of ammonia by ignition, to precipitate it once more with car- bonate of ammonia, in order to obtain a solution perfectly free from baryta. Lastly, to effect the detection of the ammonia, a fresh portion of the substance must of course be taken. b. DETECTION OF THE ACIDS. Before passing on to the examination for acids and salt- radicals, the analyst should first ask himself which of these substances may be ex- pected to be present, from the nature of the detected bases and the class to which the substance under examination belongs with respect to its solubility in water or acids, since this will save him the trouble of unnecessary experiments. Upon this point I refer the student to the table in Appendix IV., in which the various compounds are arranged according to their several degrees of solubility in water and acids. The general reagents applied for the detection of the acids are, for the inorganic acids CHLORIDE OF BARIUM and NITRATE OF SILVER, for the 270 EXPLANATION OP THE ANALYTICAL COURSE. [To 180 201. organic acids CHLORIDE OF CALCIUM and SESQUICHLORIDE OP IRON. It is therefore indispensable that the analyst should first assure himself whether the substance under examination contains only inorganic acids, or whether the presence of organic acids must also be looked for. The latter is invariably the case, if the body, when ignited, turns black, owing to separation of carbon. In the examination for bases the different reagents serve to effect the actual separation of the several groups of bases from each other ; but in the examination for acids they serve simply to demonstrate the presence or absence of the acids belong- ing to the different groups. Let us suppose we have an aqueous solution containing the whole of the acids, in combination with soda, for instance. Baryta forms 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 ; fluoride of barium also is insoluble or, at least, difficultly soluble j all these com- pounds are soluble in hydrochloric acid, with the exception of sulphate of baryta. If, therefore, to a portion of our neutral or, if necessary, neutralized solution, we add, 1. Chloride of Barium, the formation of a precipitate will denote the presence of at least one of these acids. By treating the precipitate with hydrochloric acid, we learn at once whether sulphuric acid is present or not, as all the salts of baryta being soluble in this menstruum, with the exception of the sulphate, a residue left undissolved by the hydrochloric acid can consist only of the latter salt. When sulphate of baryta is present, the reaction with chloride of barium fails to lead to the positive detection of the whole of the other acids enumerated. For upon filtering the hydro- chloric solution of the precipitates and supersaturating the filtrate with ammonia, the borate, tartrate, citrate, &c., of baryta do not always fall down again, being kept in solution by the chloride of ammonium formed. For this reason, chloride of barium cannot serve to effect the actual separation of the whole of the acids named, and except as regards sul- phuric acid, we set no value upon this reagent as a means of effecting their individual detection. Still it is of great importance as a reagent, since the non-formation of a precipitate upon its application in neutral or alkaline solutions, proves at once the absence of so considerable a number of acids. The compounds of silver with sulphur, chlorine, iodine, bromine, cyanogen, ferro- and ferricyanogen, and of the oxide of silver with phos- phoric acid, arsenious acid, arsenic acid, boracic acid, chromic acid, silicic acid, oxalic acid, tartaric acid, and citric acid, are insoluble in water. The whole of these compounds are soluble in dilute nitric acid, with the exception of the chloride, iodide, bromide, cyanide, ferro- cyanide, ferricyanide, and sulphide of silver. If, therefore, we add to our solution, which, for the reason just now stated, must be perfectly neutral, 2. Nitrate of Silver, and precipitation ensues, this shows at once the presence of one or several of the acids enumerated ; chromic .acid, arsenic acid, and several TO 180201.] EXPLANATION OF THE ANALYTICAL COTJUSE. 271 others, which form colored salts with silver, may be individually re- cognised ^with tolerable certainty by the mere color of the precipitate. By treating the precipitate now with nitric acid, we see whether it con- tains any of the haloid compounds of silver, as these latter remain un- dissolved, whilst all the oxide salts dissolve. Nitrate of silver fails to effect the complete separation of those acids which form with oxide of silver compounds insoluble in water, from the same cause which renders the separation of acids by chloride of barium uncertain, viz. the ammo- niacal salt formed prevents the reprecipitation of several of the salts of silver by ammonia, from the acid solution. Nitrate of silver, besides effecting the separation of chlorine, iodine, bromine, cyanogen, &c., and indicating the presence of chromic acid, &c., serves, like the chloride of barium, to demonstrate at once the absence of a great many acids, where it produces no precipitate in neutral solutions. The deportment which the solution under examination exhibits with chloride of barium and with nitrate of silver, indicates therefore at once the further course of the investigation. Thus, for instance, where chloride of barium has produced a precipitate, whilst nitrate of silver has failed to do so, it is not necessary to test for phosphoric acid, chromic acid, boracic acid, silicic acid, arsenious acid, arsenic acid, oxalic acid, tartaric acid, and citric acid, provided always the solution did not already contain salts of ammonia. The same is the case if we obtain a precipitate by nitrate of silver, but none by chloride of barium. Returning now to the supposition which we have assumed here, viz., that the whole of the acids are present in the solution under examina- tion, the reactions with chloride of barium and nitrate of silver would accordingly have demonstrated already the presence of SULPHUKIC ACID, and led to the application of the special tests for CHLORINE, BROMINE, IODINE, CYANOGEN, FERROCYANOGEN, FERRICYANOGEN, and SULPHUR;* and there would be reason to test for all the other acids precipitable by these two reagents. The detection of these acids is based upon the results of a series of special experiments, which have already been fully described and explained in the course of the present work : the same remark applies to the rest of the inorganic acids, viz., nitric acid and chloric acid. Of the organic acids, oxalic acid, paratartaric acid, and tartaric acid, are precipitated by chloride of calcium in the cold, in presence of chloride of ammonium ; the two former immediately, the latter often only after some time ; but the precipitation of citrate of lime is pre- vented by the presence of salts of ammonia, and ensues only upon ebulli- tion or upon mixing the solution with alcohol ; the latter agent serves also to effect the separation of malate of lime from aqueous solutions. If, therefore, we add to our fluid, 3. Chloride of Calcium and Chloride of Ammonium, OXALIC ACID, PARATARTARIC ACID, and TARTARIC ACID are precipitated, but the lime-salts of several inorganic acids, which have not yet been separated, phosphate of lime for instance, precipitate along with them. We must therefore select for the individual detection of the precipitated organic acids such reactions only as preclude the possibility of con- * For the separation and special detection of these substances, I refer to 157. 272 SPECIAL REMARKS AND ADDITIONS. [To 187. founding the organic acids with the inorganic acids that have been thrown down along with them. For the detection of oxalic acid we select accordingly solution of sulphate of lime, with acetic acid ( 146) ; to effect the detection of the tartaric and paratartaric acids, we treat the precipitate produced by chloride of calcium with solution of soda, since the lime-salts of these two acids only are soluble in this menstruum in the cold, but insoluble upon ebullition. 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 precipitate upon addition of alcohol to the fluid filtered from the oxalate, tartrate, &c., of lime, and which still contains an excess of chloride of calcium. Sulphate and borate of lime invariably precipitate along with the malate and citrate of lime, if sulphuric acid and boracic acid happen to be present ; the analyst must therefore care- fully guard against confounding the lime precipitates of these acids with those of citric acid and malic acid. The alcohol is now removed by evaporation, and, 4. Sesquichloride of Iron added. This reagent precipitates SUCCINIC ACID and BENZOIC ACID, in combination with sesquioxide of iron, whilst FORMIC ACID and ACETIC ACID remain in solution. The methods which serve to effect the sepa- ration of the several groups from each other, and the individual detec- tion of the various acids, have been fully described and explained in the former part of this work. B. SPECIAL REMARKS AND ADDITIONS TO THE SYSTEMATIC COURSE OF ANALYSIS. To 187. At the commencement of 187, the analyst is directed to mix neutral or acid aqueous solutions with hydrochloric acid. This should be done drop by drop. If no precipitate forms, a few drops are sufficient, since the only object in that case is to acidify the fluid in order to prevent the subsequent precipitation of the metals of the iron group, by hydrosul- phuric acid. In the case of the formation of a precipitate, some chemists recommend that a fresh portion of the solution should be acidified with nitric acid. However, even leaving the fact out of consideration that nitric acid also produces precipitates in many cases in a solution of potassio-tartrate of antimony, for instance I prefer the use of hydro- chloric acid, i.e. the complete precipitation by that acid of all that is precipitable by it, for the following reasons : 1. Metals are more rea- dily precipitated by hydrosulphuric acid from solutions acidified with hydrochloric acid, than from those acidified with nitric acid ; 2. In cases where the solution contains silver, suboxide of mercury, or lead, the further analysis is materially facilitated by the total or partial pre- cipitation of these three metals in the form of chlorides ; and 3. This latter form is the best adapted for the individual detection of these three metals when present in the same solution. Besides, the application of hydrochloric acid saves the necessity of examining whether the mercury, which may be subsequently detected with the other metals of the fifth To 188.] SPECIAL REMARKS AND ADDITIONS. j>73 group, was originally present in the form of oxide or in that of suboxide 1 hat the lead, if present in large proportion, is obtained partly in the form of a chloride, and partly in the precipitate produced by hydro- sulphuric acid in the acid solution, can hardly be thought an objection to the application of this method, as the removal of the larger portion of the lead from the solution, effected at the commencement, will only serve to facilitate the examination for other metals of the fifth and sixth groups. As already remarked, a basic salt of teroxide of antimony may separate from potassio-tartrate of antimony, for instance, or from some other analogous compound, and precipitate along with the insoluble chloride of silver and subchloride of mercury, and the sparingly soluble chloride of lead. This precipitate, however, is readily soluble in the excess of hydrochloric acid which is subsequently added, and exercises therefore no influence whatever upon the further process. The application of heat to the fluid mixed with hydrochloric acid is neither necessary nor even advisable, since it might cause the conversion of a little of the preci- pitated subchloride of mercury into chloride. Should bismuth or chloride of antimony be present, the addition of the washings of the precipitate produced by hydrochloric acid to the first filtrate will cause turbidity, if the amount of free hydrochloric acid present is not sufficient to prevent the separation of the basic salt. This turbidity exercises, however, no influence upon the further process, since hydrosulphuric acid as readily converts these finely-divided precipitates into sulphides, as if the metals were in actual solution. In the case of alkaline solutions, the addition of hydrochloric acid must be continued until the fluid shows a strongly acid reaction. The substance which causes the alkaline reaction of the fluid combines with the hydrochloric acid, and the bodies originally dissolved in that acid separate. Thus, if the alkali was present in the free state, oxide of zinc, for instance, or alumina, &c., may precipitate. But these oxides re- dissolve in an excess of hydrochloric acid, whereas chloride of silver would not redissolve, and chloride of lead only with difficulty. If a metallic sulphur salt was the cause of the alkaline reaction, the sulphur acid, e. g., tersulphide of antimony, precipitates upon the addition of the hydrochloric acid, whilst the sulphur base, e. the presence or absence of a cyanide will generally not long remain a matter of doubfc. It must above all be borne in mind that the insoluble cyanogen com- pounds occurring in pharmacy, &c., belong to two distinct classes. Viz., they are either SIMPLE CYANIDES, or COMPOUNDS OF METALS WITH FERRO- CYANOGEN or some other analogous compound radical. To 202.] SPECIAL REMARKS AND ADDITIONS. 275 All the simple cyanides are decomposed by boiling with concentrated hydrochloric acid, into metallic chlorides and hydrocyanic acid Their analysis is therefore never difficult. But the ferrocyariides, &c., to which indeed the method described 202 more exclusively refers, suffer by acids such complicated decompositions that their analysis by means of acids is a task not so easily accomplished. Their decomposition by potassa (or soda) is far more simple. The alkali yields its oxygen to the metal combined with the ferrocyanogen, &c., the oxide thus formed pre- cipitates, and the reduced potassium or sodium forms with the liberated radical soluble ferrocyanide, &c., of potassium (or sodium, as the case may be). But several oxides are soluble in an excess of potassa, as, e. #., oxide of lead, oxide of zinc, &c. If, therefore, the double ferrocyanide of zinc -and potassium, for instance, is boiled with solution of caustic potassa, it dissolves completely in that menstruum, and we may assume that the solution contains ferrocyanide of potassium, and oxide of zinc dissolved in potassa. Were we to add an acid to this solution, we should of course simply re-obtain the original precipitate of the double ferrocyanide of zinc and potassium, and the experiment would consequently be of no avail. To prevent this failure, conduct hydrosulphuric acid into the solution in potassa. This serves to convert into sulphides all the heavy metals which the potassa holds in solution as oxides. Those sulphides which are insoluble in potassa, such as sulphide of lead, sul- phide of zinc, &c., precipitate, whilst those which are soluble in alkaline sulphides, such as bisulphide of tin, tersulphide of antimony, ..... . . 7, 19 Fusion ...... 11 G. Gas-lamp . .... 17 Geic acid, detection of, in soils . .246 Georgina paper . . . .57 Gold, properties of . . . .104 detection of, in alloys . .183 terchloride of (as reagent) . . 56 teroxide, deportment with re- agents . . .104 detection of, in simple compounds 186 in complex compounds 205 H. Humic acid, detection of, in soils . 246 Hydriodic acid, deportment with re- agents . .- t J - . . 148 Hydrobromic acid, deportment with re- agents . .146 Hydrochloric acid (as reagent) . . 27 deportment with re- agents . . 145 PAGE Hydrocyanic acid, deportment with re- agents . . 150 detection of, in simple compounds 190 in complex com- pounds 217, 218 in organic mat- ters . . 257 Hydroferricyanic acid, deportment with reagents 151 Hydroferrocyanic acid, deportment with reagents 151 Hydrofluoric acid, deportment with re- agents 138 Hydrofluosilicic acid (as reagent) . 29 deportment with reagents . .132 Hydrosulphuric acid (as reagent) . 30 deportment with reagents . 152 detection of, in sim- ple compounds 189 in complex com- pounds 216, 217, 221 in mineral waters 235 Hypochlorous acid, deportment with re- agents . . . . .154 Hyposulphurous acid, deportment with reagents . 130 Ignition . . . . . .10 Indigo solution (as reagent) . . 58 Inorganic bodies, detection of, in pre- sence of organic bodies . .247 Iodine, detection of, in simple com- pounds 190, 194 in complex com- pounds 217, 225 in mineral waters 239 properties of. . . .148 Iron (as reagent) . . . .40 properties of . .87 protoxide, deportment with reagents 87 detection of, in simple compounds . 186 in complex com- pounds 210, 212 in soils . . 244 in well and mi- neral waters 233, 237 sulphate of protoxide (as reagent) 52 sesquichloride (as reagent) . . 53 sesquioxide, deportment with re- agents . 89 detection of, in simple compounds . 184 in complex com- pounds 201, 210, 212 in soils . 244, 245 in well and mine- ral waters 233, 237 308 ALPHABETICAL INDEX. PAGE L. Lead, deportment with reagents . . 95 oxide, detection of, in soluble simple compounds 184, 185 in insoluble simple compounds . 196 in soluble complex compounds 198, 199, 201 in insoluble complex compounds 222, 223 in organic matters . 256 in sinter deposits . 241 acetate (as reagent) ... 54 Lime, deportment with reagents . . 73 detection of, in soluble simple compounds . 188 in soluble complex compounds 214, 215 in insoluble simple compounds . 196 in insoluble complex compounds . 222 in soils . . 244, 245 in well and mineral waters . . 233 sulphate (as reagent) . . 51 water (as reagent) ... 39 Lithia, deportment with reagents . 70 detection of, in mineral waters 239 Litmus-paper . . ^ , . 57 M. Magnesia, deportment with reagents . 74 detection of, in simple com- pounds . 188 in complex com- pounds . 215 in soils . 244, 245 in well and mi- neral waters . 233 sulphate of (as reagent) . 52 Malic acid, detection of, in simple compounds 192 in complex compounds 220 deportment with reagent . 160 Manganese, deportment of 83 protoxide, detection of, in simple compounds . 186 in complex compounds 209, 213 in soils . . . 244, 245 in well and mineral waters, 237, 238 protoxide, deportment with reagents . . . 83 Marsh's apparatus . . . .115 Mercury, detection of, in articles of food, &c. . . .256 properties of . . .94 chloride (as reagent) . . 55 oxide, deportment with re- agents . . .97 detection of, in soluble simple com- pounds . 185 Mercury, oxide, detection of, in soluble complex compounds . 207 suboxide, deportment with reagents . . .94 detection of, in sim- ple com- pounds 184 in complex compounds 198 nitrate of (as re- agent) . . 54 Metallic poisons, detection of, in ar- ticles of food, &c. . 248 Mineral waters, analysis of . . 235 Molybdic acid, deportment with re- agents 125 Morphia, deportment with reagents . 279 detection of, in simple com- pounds . 289 in complex com- pounds . 290 N. Narcotina, deportment with reagents . 280 detection of, in simple com- pounds . 289 in complex com- pounds . 290 Nickel, properties of . . . .84 protoxide, deportment with re- agents . . 84 detection of, in simple compounds 186 in complex compounds, 210, 211 Nicotia, deportment with reagents . 277 Nitric acid (as reagent) . . .25 deportment with reagents . 155 detection of, in simple com- pounds, 191, 194 in complex com- pounds, 218, 221 in soils . . 244 in well and mi- neral waters, 234, 239 Nitrohydrochloric acid (as reagent) . 29 Nitrous acid, deportment with reagents 154 0. Oxalic acid, properties of . . .137 deportment with reagents . 137 detection of, in simple com- pounds, 190, 191, 193 in complex com- pounds . 213, 218 Oxidizing flame . . . .14 Oxygen acids (as reagents) . 23, 24 bases (as reagents) . 34, 35 P. Palladium, protoxide of, deportment with reagents . .103 sodio-chloride as reagent . 56 ALPHABETICAL INDEX. 309 Paratartaric acid, deportment with re- agents 162 Phosphate of soda and ammonia (as reagent) 63 Phosphates of alkaline earths, detec- tion of, in simple compounds . 193 in complex compounds, 210, 221 Phosphate of alumina, detection of, in simple compounds . . .193 in complex compounds . 212, 213 Phosphoric acid, bibasic, deportment with reagents . 135 monobasic . .135 tribasic . . .132 detection of, in simple compounds, 190, 193 in complex compounds, 213, 218, 221, 224 in soils . 244 in mineral waters, 233, 237 in silicates, 229, 230, 231 132 259 19 179 105 56 Phosphorus, properties of in articles of food, &c. Pincers ..... Platinum, detection of, in alloys properties of bichloride of (as reagent) binoxideof, deportment wit] reagents detection in sim pie com- pounds in complex compounds crucibles and their use foil and wire Porcelain dishes and crucibles Potassa (as reagent) . antimonate (as reagent) bichromate (as reagent) nitrite (as reagent) sulphate (as reagent) deportment with reagents detection of, in simple com- pounds . in complex com- pounds 215, 216 in well and mi- neral waters . in silicates in soils Potassium, ferricyanide of (as reagent) ferrocyanide of (as reagent) sulphocyanide of (as reagent) Precipitation ..... Preliminary examination of solid bodies of fluids 105 186 205 11, 19 16, 19 19 35 4G 4G 4G 43 188 234 230 244 49 49 50 5 174 179 Q. Quina, detection of, in simple compounds 289 PAGE Quina, detection of, in complex com- pounds . . . .290 deportment with reagents . 281 R. Racemic acid, deportment with reagents 162 Reagents ...... 20 Reducing flame . . . ' . 14 Retorts ...... 19 S. 288 288 290 129 227 143 178 Salicine, deportment with reagents detection of, in simple com pounds. in complex com pounds Selenious acid, deportment with re agents . . . . Silicates, analysis of . . . Silicic acid, deportment with reagents detection of, by the blow- pipe . . in soluble com- pounds 187, 190 in insoluble simple compounds 193, 194 in soluble complex compounds 210, 219 in insoluble com- plex compounds 222 in soils . 244, 245 in well and mine- ral waters . 234 Silver, detection of, in articles of food, &c ..... 256, 257 properties of . . . .93 oxide of, deportment with re- agents . . 93 detection of, in simple compounds, 183, 196 in complex com- pounds 198, 222 nitrate (as reagent) . 53 Sinter deposits, analysis of . .240 Soda (as reagent) . . . .35 deportment with reagents . . 67 detection of, in simple compounds 188 in complex com- pounds . 215, 216 in well and mineral waters . .234 in silicates . . 230 in soils . . 244, 245 acetate of (as reagent) . . 44 biborate of (as reagent) . . 62 carbonate of (as reagent) . . 44 nitrate of (as reagent) . . 60 phosphate of (as reagent) . . 43 sulphite of (as reagent) . . 45 and ammonia, phosphate of (as reagent) . . . .63 and potassa, carbonate of (as re- agent) ..... 58 Sodio-protochloride of palladium (as reagent) ..... 56 310 ALPHABETICAL INDEX. PAGE Soils, analysis of .... 242 Solubility, table indicating degrees of . 300 Solution 3 of bodies for analysis . .180 Spirit- lamps . . . . 16, 17 Strontia, deportment with reagents . 72 detection of, in soluble simple compounds . 188 in insoluble simple compounds 196, 197 in soluble complex compounds . 214 in insoluble com- plex compounds 222 in mineral waters, 237, 238 in sinter deposits . 240 Strychnia, deportment with reagents . 284 detection of, in simple com- pounds . . 289 in complex com- pounds . . 291 Sublimation . . . . .11 Succinic acid, detection of, in simple com- pounds . 192 in complex compounds 220 deportment with reagents 162 Sulphate of lime (as reagent) . 51 Sulphide of ammonium (as reagent) 41 iron ... 30 sodium (as reagent) . 42 Sulphides, metallic, detection of, in sim pie compounds, 189, 194 detection of, in com- plex compounds, 217, 221 detection of, in sili- cates . . 229 Sulphocyanide of potassium (as reagent) 50 Sulphur acids (as reagents) . 24, 30 bases (as reagents) . 35, 41 detection of, in insoluble com- plex compounds . . 223 properties of . . .152 Sulphuretted hydrogen (see hydrosul- phuric acid) water (as reagent) 30 Sulphuric acid (as reagent) . . 24 deportment with re- agents . . .131 detection of, in soluble simple com- pounds . 189 in soluble com- plex compounds 217, 221 in insoluble sim- ple compounds 195, 196 in insoluble complex com- pounds . . 224 in soils . 244, 245 Sulphuric acid, detection of, in well and mineral waters 233 in silicates 229, 230 Sulphurous acid, deportment with re- agent 129 T. Tartaric acid (as reagent) ... 27 deportment with reagent 158 detection of, in simple corn- compounds . 191 in complex com- pounds . 219 Test tubes . ... 19 Tin, properties of . . .106 binoxide, deportment with reagents 108 detection of, in soluble sim- ple compounds 184 in soluble complex compounds . 205 in insoluble com- pounds 222, 223 in articles of food, &c. . 256, 257 protochloride (as reagent) . . 55 protoxide, deportment with re- agents . . .106 detection of, in simple compounds 185 in complex compounds 205 in articles of food, &c. 256, 257 Titanic acid, deportment with reagents 80 Turmeric paper . . . .58 TL Ulmic acid, detection of, in soils . 246 Uranium, sesquioxide of, deportment with reagents . . . . 92 V. Veratria, deportment with reagents . 286 detection of, in simple com- pounds . 289 in complex com- pounds . 291 W. Washing 8 bottles . . . 8, 19 Water (as reagent) .... 22 bath 9 Waters, analysis of natural . . 231 Well-water, analysis of ... 232 Z. Zinc (as reagent) . . . . 40 properties of . . .82 oxide of, deportment with reagents 82 detection of, in simple compounds 187, 193 in complex compounds 209, 210, 213 in sinter deposits . 241 THE END. LONDON SAVILL AND EDWARDS, PRINTERS, CHANDOS STREET, COVENT GARDEN. > 'A. * :K ' -r-vV-v 'A n - v^jex i3i' Ml; M^Jfc ^l^-.'^feK " X A t :^:i .' :- -*&3 m^^^^-^s^M- :\