Pnl Adapted Printed -, GIFT OF PROF. w.B. RISING s, and stack. y H. R. r ol. IS. s., A.M., ..A.S., ond.,) Poly tiools, H. ilfour, 20. N AV IUH. I iuis . J5y iienry rweib, L,L,.U., iiyuiuum. 21. NAUTICAL ASTRONOMY. By Henry Evers, LL.D. 22A STEAM AND THE STEAM ENGINE LAND AND MARINE. By Henry Evers, LL.D., Plymouth. 22B STEAM AND STEAM ENGINE LOCOMOTIVE. By Henry Evers, LL.D., Plymouth. 83. PHYSICAL GEOGRAPHY. By John Macturk, F.R.GS. 24. PRACTICAL CHEMISTRY. By John Howard, Loacon. 25. ASTRONOMY. By J. J. Plummer, Observatory, Durham. IN COURSE OP PUBLICATION. ADVANCED SCIENCE SERIES. Adapted tu the requirements of Students in Science and Art Classes, ana Higher and Middle Class Schools. Printed uniformly in I2mo, averaging 350 //., fully Illustrated, cloth extra, price, $1.50 each. I. PRACTICAL PLANE AND SOLID GEOMETRY. ByJ fesaor F. A. Brodley, London. . MACHINE CONSTRUCTION AND DRAWING. ^ 7 E. Tomkins, Queen's College, Liverpool. 2 vols. : Vol. I, Text; Vol. II, Plates. 3. BUILDING CONSTRUCTION. By R. Scott Burn, C. E 2 vola Vol. I, Text; Vol. H, Plates. 4. NAVAL ARCHITECTURE SHIPBUILDING AND LAYING OFF. By S. J. P. Thearle, F.R.S.N.A., London. 2 vols.: Vol. I, Text; Vol. n, Plates, $2.50. 5. PURE MATHEMATICS, By Edward Atkins, B.Sc., (Lond.,) Leices- ter. 2 vols. 6. THEORETICAL MECHANICS. By P. Guthrie Tait, Professor of Natural Philosophy, Edinburgh. 7. APPLIED MECHANICS. By Professor O. Reynolds, Owens College, Manchester. 8. ACOUSTICS, LIGHT AND HEAT. By W. S. Davis, LL.D., Derby. 9. MAGNETISM AND ELECTRICITY. By F. Guthrie, B.A., Ph.D., Royal School of Mines, London. 10. INORGANIC CHEMISTRY. By T. E.Thorpe, Ph.D., F.R.S.E. Professor of Chemistry, Andersonian University, Glasgow 2 Vols. 11. ORGANIC CHEMISTRY. By James Dewar, F.R.S.E., F.C.S., Lecturer on Chemistry, Edinburgh. 12. GEOLOGY. By John Young, M.D., Professor of Natural History, Glasgow University. 14. ANIMAL PHYSIOLOGY. By J. Cleland, M.D:, F.R.S., Professor of Anatomy and Physiology, Galway. 15. ZOOLOGY. By E. Ray Lankester, M.A., (Oxon.,) London. 16. VEGETABLE ANATOMY AND PHYSIOLOGY. By J. II. Balfour, M.D., Edinburgh University. 17. SYSTEMATIC AND ECONOMIC BOTANY. By J. H. Balfour, M.D., Edinburgh University. 19. METALLURGY. By W. H. Greenwood, A.R.S.M. 2 VcCs. 20. NAVIGATION. By Henry Evers, LL.D., Professor of Applied Mechanics, Plymouth. 21. NAUTICAL ASTRONOMY. By Henry Evers, LL.D., Plymouth. 22. STEAM AND THE STEAM ENGINE LAND, MARINE, AND LOCOMOTIVE. By Henry Evers, LL.D., Plymouth. 23. PHYSICAL GEOGRAPHY. By John Young, M.D., Professor of Natural History, Glasgow University. ^ LECTURE NOTES QUALITATIVE ANALYSIS. HENRY B. HILL, A.M., Assistant Professor of Chemistry in Harvard University. NEW YORK : G. P. PUTNAM'S SONS. 1874. PREFACE. ALTHOUGH the advantages to be gained by teaching qualitative analysis by lecture are sufficiently obvious, it is a serious disadvantage to the student that the necessity of taking proper notes often pre- vents him from seeing what takes place upon the lecture table. This little book was intended to give concisely the most important facts essential to intelligent work in the laboratory, and thus give the stu- dent more leisure for observation in the lecture room. A comparative description of those compounds of bases and acids which are commonly found or used in analysis is first given, and after- wards a method of separation which experience has proved to be suf- ficiently simple and accurate, is briefly explained. This method of procedure from the properties of compounds to the methods of sepa- ration will also serve to show the way in which the more difficult problems of analysis must be solved. No tables for analysis have been given, since their use is of ques- tionable advisability, and, if used, are much better drawn up by the student himself. Symbols have been used throughout for reagents for the sake of brevity, those used in solution being distinguished by the addition of "Aq." For the sake of simplicity, water has often been omitted from the formulae of compounds, inasmuch as the number of molecules of water 237570 iv PREFACE. is largely dependent upon circumstances, and its presence is of minor importance. Of a compilation of this sort, it is hardly necessary to add that its facts are taken mainly from the text-books of Fresenius and Rose, and the Dictionary of Solubilities of Storer. CAMBRIDGE, Sept i, 1874. INTRODUCTION. QUALITATIVE ANALYSIS is that branch of chemistry which treats of the recognition of elements or their compounds. It demands a thor- ough study and comparison of the several elements and their com- pounds, of the phenomena exhibited by them under various conditions, and the determination of the particular conditions essential to the manifestation of each. It is advisable, at first, to take into consider- ation only the more common compounds, and to leave for subsequent study all rare elements and all but a few of the compounds of carbon (organic substances). The phenomena exhibited by a substance under various conditions are termed its reactions. The conditions under which reactions are studied may be divided into two classes : those dependent upon solu- tion, and those independent of it ; the two modes of examination are known as the wet and the dry way. In either case any known sub- stance which is used in effecting a reaction is called a reagent. Reactions in the dry way are dependent upon volatilization, or chemical change effected by heat. The nature of these changes will be sufficiently clear after a study of the reactions described in the pre- liminary examination. In the wet way a reagent is used to effect solution or to determine a metathesis. Experience has shown that when the solutions of two substances are mixed, and a compound insoluble under the existing conditions can be formed by metathesis, that this insoluble compound is formed ; or when a substance volatile under the existing conditions can be formed, that it is formed and escapes. An insoluble substance VI INTRODUCTION. separating from solution is called a precipitate. If the precipitate settles readily, the liquid may be decanted, or, in any case, it may be separated by filtration, when the liquid is called the filtrate. Inas- much as the completeness of the separation of those subst an ces which are precipitated by a reagent from those which are left in solution depends upon the insolubility of the precipitate, all the conditions which may affect its solubility must be known and considered. A general reagent is used to precipitate a number of substances, a special reagent as a test for a single substance. Some special re- agents give no precipitate, but cause a change of color. The precip- itate thrown down by a general reagent always requires further ex- amination, and it is better to submit to a confirmatory test the pre- cipitate caused by a special reagent. A precipitate or reaction is said to be characteristic when no further test is needed. There are two things essential to success in -qualitative analysis, the accurate observation of phenomena and a correct interpretation of their significance, neither of which can be attained without con- scientious work in the laboratory. By studying the reactions of known substances, taking care to observe everything which takes place, however small it may seem, the power of observation will be educated, and it will soon be possible to determine what is acci- dental and what essential, and experience will show what is the meaning of each reaction observed. In this book it is supposed that the student already has a good knowledge of general chemistry. Such knowledge is essential, and may be gained by the aid of any good text-book on chemistry. Experience in laboratory work and manipulation, though not abso- lutely necessary, is on all accounts desirable.* It is best to begin with the study of the bases, and, taking each group by itself, to compare the properties of the different members. The description of the properties of bases is intended as a guide * The student may be referred to the following text-books : PRINCIPLES OF CHEMICAL PHILOSOPHY. By Josiah P. Cooke, Jr. Boston, 1874. A MANUAL OF INORGANIC CHEMISTRY : Arranged to facilitate the Experimental Demonstration of the Facts and Principles of the Science. By C. W. Eliot and F. H. Storer. New Yqrk, 1868. INORGANIC CHEMISTRY. By T. E. Thorpe. New York, 1874. INTRODUCTION. Vll in this work. The truth of each important fact given there should be experimentally proved, and reactions seen in the lecture-room should be repeated, if possible. After a thorough study of the properties of a group of bases, a method of separation should be devised and compared with that given in course of analysis. The members of the group must then be separated from each other, taking care that the facts upon which the method of separation is based are well understood, and the sources of error distinctly recognized. The separation of the group as a whole from the other groups must then be considered, and the conditions necessary for complete separation clearly made out. After the basic groups have been studied in order, and each of the bases can be detected with certainty, a similar method should be followed with acids, taking as a guide the description of the properties of acids, and the methods given for their detection. The student will then be prepared to make complete analyses. He should begin with simple salts, and proceed gradually to com- plex mixtures and insoluble substances, in every case proving the presence or absence of each base and acid which he has studied. In the analysis of such compounds the reactions in the dry way should first be observed. Here the significance of each reaction may be learned, as before, by practice upon known substances, or the reactions of a substance may be carefully observed,, and its com- position afterward determined by analysis in the wet way. The correct interpretation of reactions in the preliminary examination requires long practice. Great care must be taken to distinguish between those reactions which are so decisive that they may be taken as tests for the presence or v absence of certain substances, and those which are proofs or indications of presence, if observed, but from whose non-appearance no negative conclusions can be drawn. As far as practical work is concerned, it will be necessary to give here only a few general directions, and point out a few common errors. Neatness and cleanliness are absolutely neces- sary. The reagents must be carefully preserved from contamina- tion. The stoppers of the bottles must not be misplaced, nor laid down while the reagent is used. The reagent bottles should Vlll INTRODUCTION. be kept clean and plainly labelled, they should be conveniently arranged, and the order of arrangement never changed. The quantity of a substance taken for analysis should be small. This facilitates the manipulation, and unless carried to extreme, affords better practice. Each reagent must be added cautiously, in quantity just sufficient. Too little fails to effect complete precipitation, and separation ; too much is often quite as objectionable. If the first few drops of a reagent cause a precipitate, more must be added until a drop allowed to run into the solution gives no further precipitate. The filtrate should also be tested with a few drops of the reagent in confirmation. In using an acid or an alkaline solution the reaction on test-paper will show when an excess has been added. In the use of a few reagents the necessary quantity can be learned by ex- perience alone. In any case, the reagent must be thoroughly mixed with the solution by shaking or stirring. If a solution is moderately concentrated, the precipitation is usually immediate ; but in dilute solutions it often takes place only after some time. If separation is to be effected, time should be allowed for com- plete precipitation. Occasionally half an hour, or even several hours, are necessary ; but more frequently five or ten minutes will be found sufficient. Heat almost always facilitates precipitation ; in a few cases, however, which are mentioned in the course of analysis, a re- agent must be used in the cold. In filtering, the filter must be evenly folded and carefully fitted to the funnel. For rapid filtration a creased or star filter is better, and in any case a hot solution filters more rapidly. Precipitates must be thoroughly washed, though only the first part of the wash water should be saved with the filtrate. If the precipitate is granular and settles readily, it may be advantageously washed by decantation before it is collected on a filter. A precipitate may be removed from the filter with a small spatula, or by washing it off with a stream of water, and removing by decantation most of the water. A precipi- tate may be readily dried by supporting the filter over a hot sand-bath, either in the funnel or on a triangle. In fusions the well-dried substances should be intimately mixed in a mortar ; the crucible containing the mixture should be supported just INTRODUCTION. IX above the point of the blue cone of the lamp flame. The removal of the fused mass from a platinum crucible is much facilitated by setting it, while cooling, upon a thick, cold bit of metal. In blowpipe work full time must be allowed for reduction on char- coal. With borax but little substance must be used, and care must be taken to get a good oxidizing or reducing flame, as the case may be. It is essential that concise and accurate notes should be kept of all laboratory work. They should record the reactions, the condi- tions under which they take place, and the conclusions drawn from them. In other words, they should give in order what is done, what is observed, and what is inferred. These notes should be taken as the work is done, and are of value only as they are a truthful record of fact. CONTENTS. PAGE Introduction v Table showing Division of Bases into Groups I Properties of Bases 2 Group 1 2 Group II 3 Group III... 5 Group IV 6 Group V 9 Group VI 13 Table showing Division of Acids into Groups 15 Properties of Acids 16 Group I 16 Group II 22 Group III 24 Preliminary Examination 25 Reactions in closed Tube. 25 " on Charcoal 27 " with Borax 28 Flame Colors 29 Examination with H 2 SO4 29 Treatment with Water 30 " " Acids 31 Xll CONTENTS. PAGB Treatment of Insolubles 32 Detection of Bases 34 Group 1 44 Group II 42 Group III 38 Group IV 38 Group V 35 Group VI 35 Detection of Acids 45 Group 1 46 Group II 50 Group III 52 QUALITATIVE ANALYSIS. BASES. GROUP I Sulphides and carbonates soluble : NaJC, L^JJ^N, Cs, Rb. GROUP H. Sulphides soluble, carbonates insoluble : Ba, Sr, fe Mg. GROUP III. Sulphides not formed in wet way. (H 4 N) 2 S + Aq pre- cipitates hydrates : Al a , Cr 2 , Tli, Zr, G, Y, E, Ce, La, D, Cb, Ta. GROUP IV. Sulphides not formed in acid solutions, but precipi- tated in alkaline : Fe, Fe,*, Ni, Co, Mn,^ U, V, Te, In. GROUP V. Sulphides formed in acid solutions, insoluble in al- kaline : Ag, Hg, Hg jf Pb, Cu, Cd ? Bi, Rh, Os, Ru, Pd. GROUP VI. Sulphides formed in acid solutions, soluble in alkaline : As, Sb, Sn, Sn IV , Au, Pt, Ir, W, Mo, Te, Se. * Is precipitated as Fe S. LECTURE 'NOTES ON PROPERTIES OF BASES. GROUP I. Ha, K, Li, ILN. Metals. Na, K, Li. Soft, very fusible, and lighter than water. Oxidize rapidly in air, or in water setting free H 2 . H 4 N. Known only in combination, as it is decomposed, when set free, into 2NH ;{ and H.,. Oxides. Na 2 O and K 2 O absorb water eagerly from the air, Li./) unites with water rca lily, (I I,N"),.O unknown. Hydrates. NaOH and KOH are deliquescent, LiOH sparingly soluble, and H 4 NOH known only in solu- tion. Sulphides. All soluble. Chlorides. LiCl is deliquescent, the rest readily soluble. K 4 PtCl 6 and (H 4 N) 2 PtCl 6 are quite insoluble in water, or HCl-f-Aq, more insoluble in alcohol. The other double chlorides with Pt are soluble. Carbonates. Li 2 CO 3 sparingly soluble, the other neutral carbonates readily soluble, K. 2 CO 3 deliquescent. KHCO 3 and NaHCO 3 are less soluble than the neu- tral salts, LiHCO 3 more soluble. Sulphates. Na.,SO 4 , (H 4 N),SO 4 and Li,SO 4 very sol- uble, K. 2 SO 4 less so. The acid salts of the form MHSO 4 are all more soluble than the neutral. Chromates. All soluble. The salts of the form M 2 CrO 4 give "a yellow solution, of the form M 2 Cr,,O 7 a red. Phosphates. All Na, K and H 4 N salts soluble. Na 2 HPO 4 + Aq precipitates Li 3 PO 4 insoluble in water, quite soluble in H 4 NCl+Aq, and soluble in acids. Oxalates. All soluble, KHC 2 O 4 not readily. QUALITATIVE ANALYSIS. 3 Tartrates. Salts of the form M 2 C 4 H 4 O 6 all sol- uble. KHC 4 H 4 O 6 and H 4 NHC 4 H 4 O 6 are sparingly sol- uble in cold water. HC 2 H 3 O 2 does not increase the sol- ubility, though they are soluble in mineral acids, or in an alkaline solution. The other acid salts readily soluble. Cyanides. Soluble in water, the salts readily de- composed in solution. Ferrocyanides. All soluble. GROUP II. Ba,Sr, Ca, Mg. Metals. Harder than metals of Gr. I. Ba, Sr, and Ca oxidize rapidly in air or water, Mg slowly in moist air, or water at 100. Oxides. Combine with water to form hydrates. Hydrates. BaO 2 H 2 is soluble, SrO 2 H 2 less so ; CaO 2 H 2 sparingly soluble, and the solubility decreased by heat. MgO 2 H 2 is insoluble in water, though soluble in solutions of H 4 N salts. All are readily soluble in acids. NaOH -f Aq precipitates the hydrates of the' group ; Ba, Sr and Ca hydrates only from concentrated solutions. H 4 NOH + Aq precipitates only MgO 2 H 2 , that partially, or not at all, in presence of H 4 NC1. Sulphides. BaS, SrS and CaS are soluble; MgS de- composes water, and therefore is not formed in the wet way. Chlorides. BaCl 2 and SrCl. 2 readily soluble, CaCl 2 and MgCl 2 deliquescent. MgCl 2 in solution is partially decomposed by evaporation to dryness. Carbonates. Carbonates of the form M"CO 3 insol- uble in water, soluble in acids. CaCO 3 and SrCO 3 are 4 LECTURE NOTES ON slightly soluble in H 4 NC1 + Aq, BaCO 3 more markedly, MgCO 3 readily. Na 2 CO 3 4- Aq precipitates Ba, Sr and Ca as carbonates, Mg as basic carbonate. (H 4 N). 2 CO 3 -f Aq precipitates Ba, Sr and Ca completely, Mg partially in con- centrated solutions, or not at all in presence of H 4 NC1. The salts of the form M"H 8 (CO 3 ) 2 are soluble ; on boiling their solutions the neutral carbonates are precipitated. Sulphates. BaSO 4 and SrSO 4 are insoluble, CaSO 4 sparingly soluble in cold water, less in hot, MgSO 4 readily soluble. Mineral acids increase the solubility of BaSO 4 but slightly, of SrSO 4 and CaSO 4 very decidedly. In strong H 2 SO 4 all these are soluble, forming acid salts M"H(SO4)fli decomposed by water with formation of M"SO 4 . Chromate's. BaCrO 4 insoluble in water or HC. 2 U S O^ soluble in HC1 -f Aq or HNO 3 . SrCrO 4 quite soluble in water, readily in HC 2 H 3 O 2 , CaCrO 4 and MgCrO 4 soluble in water. Phosphates. Of the three classes of phosphaTes^ those of the form M" 3 (PO 4 ). 2 are insoluble ; those of the form M" 2 H 2 (PO 4 ) 2 are practically insoluble in water, though the Ba and Sr salts are markedly soluble and the Ca salt somewhat soluble in H 4 NC1 -f Aq. The salts of the form M"H 4 (PO 4 )j are soluble in water. The insoluble salts are soluble in acids. In neutral solution Na. 2 HPO 4 -f- Aq precipitates phosphates of the form M" S H 2 (PO 4 ) 2 , in an H 4 NOH solution Ba, Sr and Ca precipitated in the form M" 3 (PO 4 ) 2 . Mg is precipitated by Na 8 HPO 4 -f Aq in presence of H 4 NC1 and H 4 NOH as Mg,(H 4 N). 2 (PO 4 ),, insoluble in water, though soluble in acids. Oxalates. Neutral oxalates of the form M"C 2 O 4 in- QUALITATIVE ANALYSIS. 5 soluble in water, soluble in mineral acids ; MgC 2 O 4 is soluble in H 4 NC1 + Aq. Tartrates. Neutral salts of Ba. Sr and Ca insoluble in water, soluble in mineral acids, or NaOH-f Aq; more or less soluble in H 4 NCl + Aq. MgC 4 H 4 O 6 sparingly soluble in water, readily soluble in H 4 NC1 + Aq. Cyanides. Soluble in water, the solutions decom- posed by heat. Ferrocyanides. Ba 2 Fe(CN) 6 sparingly soluble, the rest soluble. GROUP HI AL, Cr 2 . Metals. Al white, ductile, fusible, and does not readily oxidize. It is soluble in HCl + Aq, in dilute H 2 SO 4 , or in NaOH, + Aq with difficulty in HNO 3 . Cr very hard and infusible. Oxides. Insoluble in water; before ignition they are soluble in acids, after ignition insoluble. Fusion with Na 2 CO 3 and KNO 3 converts A1 2 O 3 into soluble Na 6 O 6 Al,, and Cr 2 O 3 into Na 2 CrO 4 . Hydrates. Insoluble in water, soluble in acids, or NaOH-j-Aq. Cr 3 precipitated from NaOH solution by boiling as Cr 8 O 6 H 6 , A1 2 is not. Both slightly soluble in H 4 NOH + Aq, the solubility of AloO 6 H 6 diminished by presence of H 4 NCL On heating the solution the dis- solved hydrates are precipitated. Sulphides. Not formed in the wet way A1. 2 S 3 decom- poses water, liberating H.,S and forming Al^H^. (H 4 N),S + Aq precipitates A1 2 O 6 H 6 and Cr a O 6 H with evolution of HaS. 1 1 (AlaCle + 3(H 4 N 2 )S + 6H 2 + Aq) = + (6H 4 NC1+ Aq). LECTURE NOTES ON Chlorides. Soluble, Al.Cle deliquescent. Carbonates. Normal salts unknown. Na. 2 CO 3 or (H 4 N) 2 CO 3 -}-Aq precipitate essentially A1,,O 6 H 6 and Cr,O 6 H 6 with escape of CO 2 .' Sulphates. Soluble. Most commonly found with K 2 SO 4 as alums. Phosphates. Salts of the form (M,) VI H 1 ,(PO 4 ) ti are soluble, the other phosphates insoluble in water, soluble in acids or NaOH + Aq; the Cr 2 salts precipitated on boiling the NaOH solution. Oxalates. The normal A1 2 salt insoluble, the Cr 2 salt soluble. Tartr at es. Readily soluble in water. From their solutions A1 2 O 6 H 6 and Cr^OgHe cannot be precipitated. Cyanides. Cr,(CNj 6 insoluble in water, slowly solu- ble in KCN + Aq. GROUP IV. Fe, Ni, Co, Mn, Zn. Metals. Fe, Ni, Co, Mn, hard, fuse only at high temperatures, Zn soft, readily fusible, boils at red heat. Mn and Fe oxidize readily in moist air, Co and Ni do not. All soluble in acids. Oxides. All insoluble in water, soluble in acids, though FeO and Fe s O 8 dissolve very slowly after igni- tion. MnO 2 dissolves in HCl-f-Agwith evolution of a 2 2' Hydrates. Insoluble in water, soluble in acids. FeO 2 H. 2 , white, rapidly turning green or black, and MnO 4 H 2 , 1 (Al 2 Cl 6 + 3Na 2 CO 3 + 3H. 2 O + Aq) = Al.O 6 H 6 + 3CO 2 + (6NaCl + Aq). 2 (MnO a + 4HCl + Aq) = (MnCl 4 + 2H 2 O + Aq). The solution then gently heated ; (MnCl 4 -f Aq) (MnCl a + Aq) + Cl 2 . QUALITATIVE ANALYSIS. 7 flesh colored, turning brown, are soluble in H 4 NCl + Aq; NiO 2 H s , pale green, and CoO 2 H 2 , pink, are soluble in H 4 NOH-f Aq or H 4 NC1 + Aq ; ZnO. 2 H 2 , white, is soluble in H 4 NOH + Aq, NaOH + Aq or H 4 NC1 + Aq. H 4 NOH + Aq and NaOH + Aq precipitate the hydrates, with Co a blue basic salt in the cold, but the hydrate on boiling. Mn 8 O 4 H s , brown, Ni 2 O 6 H 6 , black, CoO 6 H 6 , black, and Fe 2 O 6 H 6 , red brown, are insoluble in water or H 4 NCl+Aq, but soluble in acids. Sulphides. Insoluble in water or in solutions of the hydrates or sulphides of Gr. I. When moist they are oxi- dized upon exposure to the air, some of them, at least, turning into soluble sulphates. FeS, black, MnS, flesh col- ored, soluble in dilute acids ; ZnS,. white, soluble_in dilute mineral acids, insoluble in HC 2 H 3 O 2 ; NiS, black, CoS, black, insoluble in cold dilute acid, soluble in strong hot HCl+Aq or HNO 3 . The sulphides are not precipitated by H 3 S from acid, or, at best, partially from neutral solu- tions, except ZnS, which is precipitated from solution in HC 2 H 3 O 2 . Fe 2 S 3 cannot be formed in the wet way. From solutions of Fe 2 salts (H 4 N) 2 S-|-Aq precipitates FeS with separation of S. 1 In acid solutions H 2 S converts Fe 2 salts into Fe. 2 (H 4 N) 2 S-f Aq precipitates the other members as hydrated sulphides. Chlorides. All readily soluble, ZnCl 2 very deliques- cent. Carbonates. Neutral salts M"CO 3 insoluble in water, soluble in acids. FeCO 3 soluble, MnCO 3 slightly solu- ble in H 4 NC1+ Aq; NiCO 3 and CoCO 3 are soluble in (Fe 2 Cl 8 + 3 (H 4 = S + (2FeCl a +2HCl+Aq). 8 LECTURE NOTES ON H 4 NCl+Aq or H 4 NOH + Aq; ZnCO 3 soluble in NaOH-f-Aq, H 4 NCl + Aq or H 4 NOH-fAq. From solutions of Fe 2 salts soluble carbonates precipitate essentially Fe s O 6 H 6 with evolution of CO 2 . From solu- tions containing other members of the group Na^COg + Aq precipitates basic carbonates; (H 4 N) 2 CO 3 + Aq precipi- tates similar basic salts, those of Ni, CO and Zn being soluble in an excess. Sulphates. All readily soluble. Phosphates. Salts of the form M"H 4 (PO 4 ) 3 solu- ble, of the forms M" 2 H 2 (PO 4 ) 2 and M" 3 (PO 4 ) 3 insoluble in water, soluble in acids, more or less soluble in solu- tions of the soluble salts of the same member of the group. The Mn salts are soluble in H 4 NCl + Aq; the Ni and Co salts in H 4 NC1 + Aq or H 4 NOH + Aq ; the Zn salts in H 4 NCl + Aq, H 4 NOH + Aq or NaOH-f Aq. Na. 2 HPO 4 + Aq added in excess precipitates members of the group in the form M 3 (PO 4 ). : . Oxalates. The neutral salts insoluble in water, soluble in acids. The Ni and Co salts readily soluble in H 4 NOH + Aq; ZnC,O 4 soluble in H 4 NOH + Aq, H 4 NCl + Aq and NaOH+Aq. Tartrates. ZnC 4 H 4 O 6 and NiC 4 H 4 O 6 insoluble in water, soluble in acids or NaOH + Aq ; MnC 4 H 4 O 6 and FeC 4 H 4 O 6 sparingly soluble in water, readily soluble in NaOH + Aq; CoC 4 H 4 O 6 and Fe 2 (C 4 H 4 O 6 ) 3 soluble in water, the solutions not precipitated by NaOH + Aq, or Na 2 CO 3 + Aq. Cyanides. With the exception of the Fe 2 salt, which is unknown, the cyanides are all insoluble in water and soluble in KCN-f Aq. Ni(CN) 2 and Co(CN) 9 are also QUALITATIVE ANALYSIS. 9 soluble in H 4 NOH + Aq, Zn(CN) 2 in H 4 NOH -f Aq or NaOH + Aq. From the solutions in KCN + Aq Ni(CN) 2 and Zn(CN) 2 are reprecipitated by neutralizing the KCN with acids. The solutions of the other cyan- ides in KCN + Aq contain (in the case of Mn- and Co only after heating or exposure to air) K 4 Fe(CN) 6 , K 6 Mn 2 (CN) 12 and K e Co 2 (CN)i 2 from which acids do not separate the simple cyanides, and from which Fe, Mn and Co cannot be precipitated by ordinary reagents. Ferrocyanides. Insoluble in water, decomposed by NaOH + Aq into hydrate of the metal, and Na 4 Fe(CN) 6 . Zn 2 Fe(CN) 6 , white, Ni 2 Fe(CN) 6 , greenish white, Co,Fe(CN) 6 , green, FeK 2 Fe(CN) 6 , white, rapidly turning blue, and (Fe 2 ) 2 (Fe(CN) 6 ) 3 , blue, insoluble in HCl + Aq; Mn 2 Fe(CN) 6 , reddish white, soluble in HC1 + Aq. All are decomposed by heating with H 2 SO 4 diluted with ^ its volume of water ; HCN evolved, and sulphates left. GROUP V. Ag, Hg, Pb, Cu, Cd, Bi. Metals. Bi brittle, Ag and Pb soft, Cu and Cd hard- er, Hg liquid at ordinary temperatures. Exposed to the air Ag, Bi and Hg do not oxidize, Pb, Cu and Cd not readily. All but Ag oxidize rapidly at high temperatures. HNO 3 is the best solvent for all, though Cd dissolves in any acid. HCl + Aq does not act upon Ag, Hg, Pb, or Bi, and acts upon Cu only in presence of O. Hot concentrated H.SO 4 dissolves all but Pb, which it affects but little. Oxides. AgjO, brown, slightly soluble in water, readi- ly soluble in H 4 NOH-h.Aq, and in solutions of chlorules, cyanides or hyposulphites or in HNO 3 . HgO, yellow 10 LECTURE NOTES ON or red, and Hg.^0, black, insoluble in water, soluble in HNO 3 . PbO, reddish yellow, CuO, black, Cu,O, red, CdO, brown, and Bi-jOg, yellow, in solubility are like the hy- drates. Hydrates. Ag and Hg form no hydrates. PbO.jH 2 is practically insoluble in water, though alkaline to test paper, readily soluble in NaOH-j-Aq. CuOgH,, blue, and Cu a O a H 8 , orange yellow, insoluble in water, slightly solu- ble in cold NaOH + Aq, soluble in H 4 NCl + Aq, or in H 4 NOH+Aq. On boiling CuO.H, with NaOH-f Aq it is converted into CuO, the small amount dissolved in the cold being precipitated ; CdO-^Hj, white, insoluble in water, soluble in H 4 NOH-f Aq; BiO 3 H 3 , white, insoluble in water or H 4 NOH+Aq. All these hydrates readily soluble*in acids. From solutions containing members of the group NaOH + Aq precipitates Ag, Hg and Hg 2 as oxides, the rest as hydrates, PbO^H.., soluble in an excess ; H 4 NOH + Aq precipitates Ag as oxide, Hg and Hg 2 as insoluble amine compounds, the rest as basic salts, or hydrates, the Ag, Cu, and Cd precipitates being soluble in an excess. Sulphides. Insoluble in water, cold dilute acids or solutions of the hydrates or sulphides of Gr. I. ; allexcept HgS and Hg,S soluble in hot dilute HNO, ; . ifgS, black, Ag.,S, black, CuS, black, and Bi.,8;., black, may be complete- ly precipitated from solutions containing HC1 -f Aq, unless present in very great excess. PbS, black, and CdS, yellow, are not completely precipitated, if much HC1 -f Aq is present. Hg solutions are precipitated by H 2 S first white, then yellow, the color changing to brown red, and QUALITATIVE ANALYSIS. II becoming black only with excess of H 2 S. The change of color is due to the formation of various insoluble com- pounds of HgS with undecomposed Hg salt. Chlorides. AgCl insoluble in water or acids, soluble in H 4 NOH-{-Aq and in solutions of chlorides, -cyanides or hyposulphites. Hg 2 Cl 2 insoluble in water but gradually decomposed by boiling with water, HC1 + Aq or solutions of chlorides ; H 4 NOH + Aq converts it into (Hg a ) 8 H 4 N 2 C1 2 , black, insoluble in water or H 4 NOH + Aq. PbCl 2 crystalline, sparingly soluble in cold water, still less soluble in dilute HCl-j-Aq, soluble in hot water, in concentrated HC1 + Aq, or in NaOH 4- Aq. BiCl 3 is soluble in a small quantity of water, more water separates BiOCl, white, insoluble in water, soluble in acids. HgCl 2 and CuCL 2 soluble in water, CdCl 2 deliquescent. Carbonates. Neutral salts insoluble in water, solu- ble in acids. Ag 2 CO 3 and CuCO 3 are readily soluble in H 4 NOH + Aq, PbCO 3 soluble in NaOH -f Aq. From solutions containing members of the group Na 2 CO 3 -f Aq precipitates carbonates, generally basic, insoluble in an excess ; (H 4 N). 2 CO 3 + Aq precipitates Hg and Hg 2 as in- soluble amine compounds, the rest as carbonates or basic salts, the Ag and Cu salts being readily soluble in an excess. Sulphates. CuSO 4 and CdSO 4 readily soluble; HgSO 4 and Bi,(SO 4 ) 3 decomposed by water, giving insolu- ble Hg.SO,; yellow, and Bi. 2 H 4 SO 8 white ; Ag.jSO 4 sparingly soluble ; PbSO 4 insoluble in water, much more soluble in strong acids, readily soluble in NaOH+Aq, or in solu- tions of some H 4 N salts, especially H 4 NC 2 H 3 O 2 and (H 4 N).C 4 H 4 6 . 12 LECTURE NOTES ON Phosphates. The salts of the forms M" 2 H 2 (PO 4 ) $ and M" 3 (PO 4 ) 2 are insoluble in water, soluble in HNO 3 , many of them in H 4 NCl-J-Aq. Ag 3 PO 4 and the Cu salts are soluble in H 4 NOH + Aq, the Pb salts in NaOH-f Aq. From solutions of the members of the group Na a HPO 4 -|-Aq precipitates Ag as Ag 3 PO 4 , and, if added in excess, the rest in the form M" 8 (PO 4 )j. Oxalates. Insoluble in water, soluble in HNO S . Ag 2 C 8 O 4 and CuC 8 O 4 soluble in H 4 NOH + Aq; PbC 2 O 4 soluble in NaOH + Aq. Chromates. Ag 2 CrO 4 , brick red, insoluble in water, soluble iaH 4 NOH -f Aq, or HNO 3 ; Hg 2 CrO 4 , red, and Bi 2 (CrO 4 ) 3 , yellow, insoluble in water, soluble in HNO 3 ; PbCrO 4 bright yellow, insoluble in water or HC 2 H 3 O 2 , soluble in NaOH + Aq, with difficulty in HNO 3 . CuCrO 4 , brown, soluble, and HgCrO 4 sparingly soluble in water. Tartrates. The Cu, Cd and Hg s salts sparingly solu- ble in water, the rest insoluble. CuC 4 H 4 O 6 is readily sol- uble inNaOH+Aq; PbC 4 H 4 O 6 soluble in H,C 4 H 4 O 6 + Aq or in NaOH + Aq. Cyanides. Hg(CN), soluble in water, the rest insol- uble in water, soluble in HNO 3 , except AgCN. In KCN -f Aq AgCN, Cu(CN),, Cd(CN) 2 are soluble, Pb(CN), and Bi(CN) 3 insoluble. KCN + Aq added to solutions of Hg 2 salts precipitates Hg, forming Hg(CN) 2 in so- lution. Ferrocyanides. Pb,Fe(CN) 6 and Cd s Fe(CN) 6 in- soluble in water, soluble in HNO 3 ; Ag 4 Fe(CN) 6 , white, Cu,Fe(CN) 6 , red brown, Bi 4 (Fe(CN) 6 ) 3 , white, insoluble in acids, or H 4 NOH + Aq. QUALITATIVE ANALYSIS. 13 GROUP VI, As, Sb, Sn. Metals. As and Sb brittle, Sn soft and malleable. As volatilizes without fusion ; Sb and Sn fuse readily. As oxi- dizes at ordinary temperatures, all oxidize readily when heated. As and Sb are hardly attacked by HCl+Aq, Sn is easily dissolved. HNO 3 oxidizes all three, Sn and Sb without solution. HCl + Aq with HNO 3 dissolve all. Oxides. As 2 O 3 sparingly soluble, Sb 2 O 3 and Sb 2 O 5 slightly soluble - in water ; the rest insoluble in water. All soluble in HCl + Aq or HCl + Aq with HNO 3 . As 2 O 3 readily soluble in NaOH + Aq. SnO 2 is often insoluble in HCl+Aq, but rendered soluble by fusion with NaOH. SnO and Sb 2 O 3 heated in air give SnO 2 and Sb 2 O 4 . As 2 O 5 and Sb 2 O 5 when heated become As 2 O 3 and Sb 2 O 4 . Hydrates. H 3 AsO 3 known only in solution or in its salts, H 3 AsO 4 soluble. HSbO 3 slightly soluble in water. The other hydrates are insoluble in water, solu- ble in HC1 + Aq or NaOH + Aq. The Sn IV hydrates more readily soluble in KOH + Aq than in NaOH + Aq ; one modification of it insoluble in acids, and with great difficulty soluble in KOH + Aq. Sulphides. Insoluble in water or dilute acids, readily soluble in solutions of the hydrates or sulphides of Gr. I. If dissolved in soluble sulphides they form sul- phur salts, 1 or if in solutions of the hydrates, a mixture of sulphur salt with oxygen salt. 2 On adding acid to either of the solutions the original sulphide is reprecipi- 1 As 2 S 3 + ( 3 (H,N) 2 S + Aq) = ( 2 (H 4 N) 3 AsS 3 + Aq). 2 As a S 3 + (6NaOH + Aq) = (Na 3 AsO 3 + NasAsS. + 3H 2 O-f- Aq). 14 LECTURE NOTES ON tated. 1 SnS dissolved in yellow (H 4 N) 8 S + Aq precipi- tated as SnS a . As 2 S 3 , yellow, insoluble in strong HCl + Aq, soluble in (H 4 N) S CO, +Aq; Sb. 2 S 3 and Sb.(S 5 , orange, SnS, brown, SuS^, yellow, are soluble in strong HC1 + Aq, insoluble in (H 4 N) i CO 3 + Aq. As v in acid solution is slowly reduced by H 2 S and precipitated as As.jS 3 . Chlorides. AsCl 3 , SbCl 5 , SnCl 4 volatile liquids; SbCl 3 , SnCl 2 solids. All decomposed by water ; SnCl s and SnCl 4 slowly or when treated with a large amount. SbCl 3 gives at once SbOCl insoluble in water, soluble in acids ; AsCl 3 gives As 2 O 3 as the chief product. Hydrides. AsH 8 and SbH 3 , gaseous, are formed when a soluble As or Sb compound is treated with Zn and dilute H 2 SO 4 . .They are decomposed below red heat into Sb or As and H 2 . Passed into AgNO 3 -f Aq, AsH 3 precipitates Ag and leaves H 3 AsO 3 in solution ; a SbH 3 precipitates SbAg 3 . 3 Tartrates. (SbO)KC 4 H 4 O 6 soluble in water. The presence of H 2 C 4 H 4 O 6 in sufficient quantity prevents the precipitation of basic Sb salts by water. 1 (2(H4N) 3 AsS 3 + 6HC1 + Aq) = As 2 S 3 + 3H 2 S + (6H 4 NC1 + Aq). (Na 3 AsO s -f Na 3 AsS 3 + 6HC1 + Aq) = As 2 S 3 + (6NaCl + aH 2 O + Aq). * AsH, + (6AgN0 3 -+ 3 H a O 4- Aq) = 3Ag 2 + (6HN0 3 + H 3 AsO 3 + Aq). 8 SbH 3 + (3AgN0 3 + Ag) = SbAg, + (3HNO 3 + Aq). QUALITATIVE ANALYSIS. 1 5 ACIDS. GROUP I. Ba Salts insoluble in water. i. Acids decomposed in acid solution by H 2 S. M 2 CrO 4 H 3 AsO 4 M 2 SO 3 M 3 AsO 3 M 2 S 2 O 3 2. Acids not decomposed in acid solution by H 2 S. a. Ba Salts soluble in HC1 -f Aq. H 3 PO 4 HF H 2 C 4 H 4 O 6 H 3 BO 3 M 2 CO 3 H 2 C 2 4 H 4 Si0 4 . b. Ba Salts insoluble in HC1 + Aq. H 2 SO 4 H,SiF, GROUP H. Ba Salts soluble, Ag Salts insoluble in water. HC1 H 4 Fe(CN) 6 HNO* HBr H 6 Fe 2 (CN) 12 HCIO HI H 2 S HCIO, HCN GROUP III. Ba and Ag Salts soluble in water. HNO 3 HC1O 3 HC 2 H 3 O S ECHO* I 6 LECTURE NOTES ON PROPERTIES OF ACIDS. GROUP I 1. M 2 CrO<, M 3 AsO>, ILAsO*, M.SOs, M.S.Os. Chromates. Salts generally insoluble in water, the most important soluble salts being those of Gr. I., Sr, Ca, Mg, and the normal salts of Mn and Zn. The acid is unknown, since it breaks upon liberation from its salts in- to H 2 O and CrO 3 ; it also gives no salts of the form MHCrO 4 . If acid be added to a solution of M 2 CrO 4 it turns from yellow to red with the formation of a salt of the form MjCrjO,, 1 further addition of acid sets CrO 3 free. 8 If HjSO 4 is used the CrO 3 separates as a red mass, or in red needles. CrO 3 heated with H 2 SO 4 loses oxygen and becomes Cr 2 (SO 4 ) 3 , 3 with HCl + Aq it gives Cr 2 Cl 6 water and C1 9 . 4 Organic matter or reducing agents, like H^ or SO.^ effect a similar change, 2CrO 3 becoming Cr. 2 O 3 . 6 In any case the change of CrO 3 to Cr 2 O 3 is accompanied by a corresponding change of color from red to green. BaCrO 4 and PbCrO 4 , yellow, insolu- ble in water or in HC 2 H 3 O 2 . Ag 2 CrO 4 , brick red, soluble in HNO 3 or H 4 NOH-f Aq, Arsenites. The salts of Gr. I. are soluble, the neu- tral salts of the other groups insoluble in water, though many are soluble in H 4 NC1 + Aq. The acid is unknown, 1 (2K 2 CrO 4 4- H 2 SO 4 + Aq) = (K 2 Cr 2 O 7 + K a SO 4 + H 2 O + Aq). 5 (K 2 Cr 2 O 7 + H 2 SO 4 + Aq) = (2CrO 3 + K 2 SO 4 + H 2 O + Aq). 8 4CrO s + 6H 2 S0 4 - 2Cr 2 (SO 4 ) 3 + 6H 2 O + 3O 2 . 4 (2CrO 3 + I2HCI + Aq) = (Cr 2 Cl 3 + 6H 2 O -t- Aq,+ 3Cl a . * (2CrO 3 + 6HC1 + 3H 2 S 4- Aq) = (Cr a Cl 8 + 6H 2 O + Aq) + 38. QUALITATIVE ANALYSIS. I/ although acid salts of the forms MH 2 AsO 3 and M 2 H AsO 3 are known. From acid solutions of all salts H 2 S readily precipitates As 2 S 3 yellow. Oxidizing agents convert the salts into arseniates. Cu 2 H 2 (AsO 3 ) 2 is green, insoluble in water, soluble in acids, and soluble in NaOH + Aq. On warming the NaOH solution Cu 2 O 2 H 2 , orange yellow, is precipitated, Na 3 AsO 4 being left in solution. Mg 3 (AsO 3 ) 2 and Ba 3 (AsO 3 ) 2 insoluble in water, soluble in acids, or H 4 NC1 -f Aq ; Ag 3 AsO 3 , pale yellow, insoluble in water, soluble in H 4 NOH + Aq or HNO 3 . Arseniates. The salts resemble the phosphates closely. Of the neutral salts only those of Gr. I. are soluble. The acid is solid, soluble in water. From acid solutions of its salts H 2 S at first precipitates nothing, but on long standing, or more quickly on warming, it is re- duced and As.,S 3 is precipitated. SO 2 reduces it quite rapidly to arsenious acid with formation of H 2 SO 4 ; H 2 S then at once, precipitates As 2 S 3 . Ba 3 (AsO 4 ) 2 and Mg 3 (AsO 4 ). 2 are insoluble in water, soluble in acids. Ag 3 AsO 4 , red brown, insoluble in water, soluble in H 4 NOH 4- Aq or HNO 3 . Mg 2 (H 4 N) 2 (AsO 4 ),, insoluble in water or H 4 NC1 + Aq, soluble in acid, is formed when H 4 NOH + Aq, H 4 NC1 + Aq and MgSO 4 + Aq are added to aqueous solutions of arseniates. A solution of (H 4 N) 2 MO 4 in HNO 3 gives no precipitate in acid solu- tions of arseniates in the cold, but gives a yellow precipi- tate on boiling. Sulphites. The neutral salts are all insoluble or sparingly soluble in water; of the acid salts many are soluble, though many are decomposed by boiling their solutions, neutral salts being formed. The acid is un- 1 8 LECTURE NOTES ON known. From its salts stronger acids liberate SO 2 ' soluble in water; in this solution H 2 S forms H.,S 5 O,; with separation of S. SO 2 is a powerful reducing agent but is itself reduced by nascent H with formation of H 2 S. 2 BaSO 3 is insoluble in water, soluble in HC1 -f Aq ; from this solution C1 8 or Br 2 precipitate BaSO 4 . Hyposulphites. Most of the salts are soluble in water. The acid is unknown. Stronger acids liberate from its salts SO 2 and S. The same decomposition 3 takes place when HCl-fAq is added to solutions of its salts, though slowly in dilute solutions. With H 2 S in acid solutions, or with nascent hydrogen the reactions are the same as with the sulphites. BaS,O 3 insoluble in water soluble in HCl-fAq. Ag^Os, white, insoluble in water, soluble in solutions of hyposulphites ; blackens on heat- ing, Ag 2 S being formed. PbS 2 O 3 , insoluble in water, solu- ble in solutions of hyposulphites, forms PbS on heating." GROUP I 2. (a) H 3 P04, HnBO,, H,C 2 04, HF, M,C0 3 , H.SiO*, H.C JLOn ; (b) H 2 SO. Phosphates. Salts of the forms M 3 PO 4 and M 2 HPO 4 insoluble except those of Gr. I., salts of the form MH 2 PO 4 soluble. All the insoluble salts are soluble in acids, and these solutions are precipitated by H 4 NOH +Aq; the precipitate is usually a phosphate of the form M 3 PO 4 . Ba 3 (PO 4 ) 2 and Ca 3 (PO 4 ) 2 , insoluble in water, are soluble in HCl + Aq and in HC. 2 H 3 O 2 . Ag,PO 4 , pale yellow, insoluble in water, is soluble in H 4 NOH-f Aq or 1 (NaSO 3 + 2 3 SO a + 3H 2 = H 3 S + 2H 2 O. 3 (Na 2 S 2 O 3 + 2HC1 + Aq) (2NaCl + H 2 O + SO a + Aq) + S. 4 rbS a 3 + H a O = QUALITATIVE ANALYSIS. 19 HNO 3 . From aqueous solutions of the phosphates MgSO 4 + Aq, after adding H 4 NC1 -f Aq and H 4 NOH -f Aq, precipitates Mg. 2 (H 4 N) 2 (PO4). 2 insoluble in water or H 4 NCl-fAq, soluble in acids. In acid solutions of the phosphates (H 4 N) 2 MO 4 dissolved in HNO 3 gives a yellow precipitate in the cold, insoluble in water or in dilute acids, if (H 4 N). 2 MO 4 be in excess, readily soluble in excess of phosphate. Borates. Only the salts of Gr. I. are readily soluble in water, though many salts insoluble in water are soluble in H 4 NC1 + Aq. The acid is separated from its salts by stronger acids ; soluble in water, the solution turning turmeric paper red, best seen when the paper is dried at 1 00. This red color is changed to greenish black when moistened with Na 2 CO 3 -f- Aq. H 3 BO 3 partially volatil- ized by evaporation of its solution. Its alcoholic solu- tion burns with a green flame.. The Ba and Ca salts are insoluble in water, soluble in HC1 + Aq, HC 2 H 3 O 2 or H 4 NC1 -f Aq. The Mg salt readily soluble in H 4 NC1 + Aq. Oxalates. Almost all the neutral salts, except those of Gr. I. are insoluble in water, soluble in acids. H 4 NOH precipitates the acid solutions of many of the salts insolu- ble in water, those of Ba, Sr and Ca completely. All the salts are decomposed by ignition ; the residue consists of carbonate, oxide or metal. The acid, readily soluble in water, is decomposed when heated by itself or with strong H,SO 4 into CO,, CO and H.O. 1 With the dry salts H 2 SO 4 gives the same reaction, first setting the acid free, then decomposing it. The acid or its salts warmed with ] H a C a 4 = H 3 + CO, -f CO. 20 LECTURE NOTES ON dilute H 2 SO 4 and MnO, give off CO.,, MnSO 4 and water being formed. 1 BaC,,O 4 is insoluble in water, soluble in HC1 4- Aq. CaC s O 4 is insoluble in water or HC,H :f O 2 , soluble in HCi -\- Aq. Ag a C s O 4 insoluble in water, soluble in H 4 NOH 4 Aq or HNO 3 , is decomposed with explosion on ignition, Ag being left. The salts of Gr. II. are decomposed on boiling with a concentrated solution of Na 2 CO 3 with formation of the corresponding carbonates and Na 2 C 2 O 4 in solution. Fluorides. Salts of Gr. I. readily soluble, as also A1 2 F 6 , Cr 2 F 6 , Fe s F 6 , AgF, HgF 9 . The rest are sparingly soluble or insoluble in water. HF is liberated from its salts by strong H 2 SO 4 as a gas readily soluble in water, the solution characterized by its power of dissolving SiO 4 or its compounds (glass). A fluoride mixed with silicates or SiO... gives, on heating with strong H S SO 4 , SiF 4 fuming in the air, and giving with water H 4 SiO 4 , gelatin- ous. 2 Fluorides not decomposed by H.^SO., must be fused with mixed Na 2 CO 3 and K 2 CO 3 . BaF 8 and CaF 2 , as precipitated, are gelatinous and transparent, soluble in hot HCI 4- Aq, though with difficulty, soluble in H 4 NC1 4 Aq. Tartrates. The neutral salts of Grs. I. and III. as well as of Fe 2 and Co readily soluble in water. The acid is very soluble in water, and its presence prevents partially or wholly precipitation with NaOH 4 Aq, H 4 NOH 4 Aq, Na,CO, 4Aq, or (H 4 N) 8 CO 8 4- Aq. The acid and its salts char on heating, giving off an odor like 1 (H 2 C 2 O 4 + H a SO 4 + Aq) + MnO a = (MnSO 4 + 2H 2 O + Aq) + 2CO 2 . 8 (3SiF 4 + 4H 2 O +Aq) = H.SiO, + (2H 2 SiF 6 + Aq). QUALITATIVE ANALYSIS. 21 burnt sugar. BaC 4 H 4 O 6 insoluble in water, soluble in HC1 + Aq or H 4 NC1 + Aq. CaC 4 H 4 O 6 insoluble in water, soluble in HC1 or HC 2 H 3 O 2 , quite soluble in H 4 NC1 + Aq, readily soluble in cold NaOH + Aq, re- precipitated gelatinous on boiling ; Ag;>C 4 H 4 O 6 , white, in- soluble in water, soluble in H 4 NOH + Aq or HNO 3 ; blackens immediately on boiling from separated Ag. KHC 4 H 4 O 6 is sparingly soluble in cold water, HC 2 H 3 O 2 or H 2 C 4 H 4 O 6 + Aq readily soluble in mineral acids or solu- tions of hydrates of Gr. I. Carbonates. The neutral salts are all insoluble in water, except those of Gr. I. ; the acid salts are generally soluble, though, if their solutions are boiled, all but those of Gr. I. are decomposed, and neutral salts precipitated. The acid is unknown, since it breaks up upon liberation from its salts into water and CO 2 , a gas heavier than air, quite soluble in water. CO 2 gives with CaO 2 H 2 CaCO 3 , white. BaCO 3 insoluble in water, soluble in acids. Ag 2 CO 3 , white, insoluble in water, soluble in H 4 NOH + Aq or HNO 3 . Silicates. The silicates of Gr. I. are alone soluble in water ; many of the insoluble salts are decomposed by strong acids with the separation of H 4 SiO 4 . When the 'acid is liberated from its salts by acids, the greater part generally separates in a gelatinous form, though more or less remains in solution. If such an acid solution is evaporated to dry ness, all its Si is left as a hydrate, insol- uble in water or acids (except HF1 + Aq). H 4 SiO 4 when once formed is insoluble in water or acids (except HF +Aq), though soluble in NaOH+Aq, and reprecipitated from this solution by H 4 NC1 + Aq. It loses water readily, 22 LECTURE NOTES ON and on ignition SiO 2 is left insoluble in a bead of microcos- mic salt (NaH 4 NHPO 4 ). All silicates are decomposed by fusion with mixed Na 2 CO 3 , and K 2 CO 3 . The Ba, Ca and Ag salts are insoluble, decomposed by HC1 + Aq. Sulphates. The normal salts are all soluble, except BaSO 4 , SrSO 4 and PbSO 4 , insoluble, and CaSO 4 sparing- ly soluble. The acid has great affinity for water, and dissolves with evolution of heat. When strong it black- ens organic water. Sulphates, when heated on charcoal with Na 2 CO 3 in the inner blowpipe flame, give Na 2 S. BaSO 4 , white, insoluble in water or acids. GROUP H HC1, HBr, HI, HCN, HFe a (CT)e, H.Fe a (CT)n, H.S. Chlorides. All soluble except AgCl, Hg 2 Cl 2 insolu- ble, and PbCl 2 sparingly soluble in water. From its salts H 2 SO 4 liberates HC1 (with effervescence, if little or no water is present), a gas very soluble in water ; H S SO 4 and MnO 8 evolve Clj, 1 a greenish gas, somewhat soluble in water, which bleaches. AgCl insoluble in water, or HNO 3 , soluble in H 4 NOH + Aq. Bromides. Salts soluble except AgBr and Hg 2 Br 2 . From its salts H 2 SO 4 liberates HBr, a gas very soluble in water, but mixed with more or less Br 2 ; H 2 SO 4 and MnO 2 liberate Br 2 , a red volatile liquid soluble in water, its vapors red. In solutions of the bromides C1 2 -f- Aq liberates Br 2 , which colors the liquid red. The Br 2 , thus liberated, can all be collected in a little CS 2 , in which it is much more soluble than in water. An excess of C1 2 bleaches the color. 1 2NaCl + 3H.SO 4 + MnO a = 2NaHSO 4 + MnSO 4 + 2 QUALITATIVE ANALYSIS. 23 Iodides. Soluble except Agl, yellowish white, Hg 2 I a , greenish, Hgl. 2 , red, PbI 2 , yellow, and Bijg, insoluble in water. From its salts H^SC^ liberates HI, but it is at once oxidized and I 2 set free. I 2 is almost insoluble in water, readily soluble in CS.,, which it colors violet ; solu- ble, also, in solutions of iodides with a deep brown color. It sublimes with gentle heat, its vapor being violet. C1 3 liberates I 2 from its salts, an excess of C1 2 then converts it into colorless IC1 8 . I 2 gives with dilute starch paste in a slightly acid solution a deep blue compound of starch and I, bleached by heat or C1 2 . Agl insoluble in water or HNO 3 , scarcely soluble in H 4 NOH + Aq, soluble in solutions of iodides. Cyanides. Salts of Grs.I. and II. and Hg(CN) 2 solu- ble, the rest insoluble in water though many are soluble in solutions of cyanides. HCN is a volatile liquid soluble in water. From the soluble salts even dilute acids liber- ate the acid ; strong H 2 SO 4 decomposes it, giving CO. The insoluble salts are all decomposed by ignition. Many of the insoluble salts are decomposed by HC1 + Aq, all by strong H,SO 4 . AgCN, white, insoluble in water or dilute HNO 3 , soluble in H 4 NOH + Aq, or in solutions of cyanides of Grs. I. and II. Ferrocyanides. All insoluble in water except the salts of Grs. I. and II. Many of the salts are colored, and all the insoluble salts decomposed by NaOH + Aq or H,SO 4 . H 4 Fe(CN) 6 is a white solid readily soluble in water. C1 2 converts K 4 Fe(CN) 6 in solution into K 6 Fe 2 (CN) la . Ag 4 Fe(CN) 6 , white, insoluble in water, H 4 NOH+ Aq or HNO 3 . (Fe 2 ) 2 (Fe(CN) 6 ) 3 , blue, and Cu 2 Fe(CN) 6 , red brown, insoluble in water, or HC1 + Aq. 24 LECTURE NOTES ON Ferricyanides. Salts of Grs. I. and II. and Fe 2 solu- ble in water. Many of the salts are colored, and all insolu- ble salts decomposed by NaOH + Aq or H 5 SO 4 . The acid, H 6 Fe 2 (CN) 12 , is readily soluble in water and convert- ed by reducing agents into H 4 Fe(CN) 6 . Ag 6 Fe.,(CN), 2 , or- ange, insoluble in water, or HNO 3 , soluble in H 4 NOH + Aq. Fe 3 Fe s (CN),j blue, insoluble in water, or HCl + Aq. FesFe^CN)^ soluble in water, the solution brown. Sulphides. The salts of Grs. I. and II. soluble, the rest insoluble in water. The salts of Gr. VI. soluble in NaOH 4- Aq. Most salts attacked by hot HCl + Aq, and all by HCl + Aq with HNO 3 . Solution is effected by HCl +Aq with liberation of the acid H 8 S, a gas somewhat sol- uble in water ; by HNO 3 , or HCl + Aq with HNO ;{ , with separation of S, which by boiling is slowly oxidized to H 2 SO 4 . Ag s S, black, insoluble in H 4 NOH + Aq, solu- ble in hot HNO 3 . GROUP m. HN0 3 , HClOa, HCa HaO*. Nitrates. Normal salts all soluble in water. From its salts H 2 SO 4 liberates HNO 3 , a fuming liquid, perfectly soluble in water. By the action of HNO 3 upon Cu, NO is formed ! , a colorless gas, which with the O of the air forms NOj, orange red. NO is also soluble in a concen- trated solution of FeSO 4 , forming a solution colored black, brown, or reddish, according to its concentration. On heating the solution NO is set free. All the salts deflagrate when heated on charcoal, and all are decom- posed by ignition. Chlorates. Normal salts all soluble in water. H 2 SO 4 1 3Cu + (8HNO 3 + Aq) = (3Cu(NO,) a + 4 H 2 + Aq) + 2 NO. QUALITATIVE ANALYSIS. 2$ added to the chlorates liberates C1.,O 4 , a yellow green gas, smelling like C1 2 and bleaching, the H^SOj becoming yel- low. Heat must be avoided or the decomposition is ac- companied by explosion. HC1 -f- Aq liberates a gas of similar color and odor, C1 6 O 13 . HC1O 3 is liquid, easily de- composed, and readily soluble in water. All' the salts deflagrate when heated on charcoal, and are decomposed on ignition into chloride and O 2 . Acetates. The normal salts are all soluble in water, although many are decomposed by boiling their solutions into insoluble basic salts. The salts are all decomposed by ignition ; aceton, C 3 H 6 O, is almost always one of the products of decomposition, and generally HCaHaOjj. Salts of Grs. I. and II. give a residue of carbonate, the rest either metal or oxide, generally mixed with C. Feo(C a H s Oj) 8 gives a deep red solution, which on boiling deposits all the Fe 2 as a brown basic salt insoluble in water. COURSE OF ANALYSIS. PRELIMINARY EXAMINATION. The physical properties of the substance under exam- ination must first be carefully noted. A solid must, if possible, be reduced to fine powder ; a portion of a liquid should be evaporated to dryness, and the residue, if any is left, powdered. A small quantity only is needed for each test. Heat in a Bulb Tube. Water is given ofE Crystal water usually given off with fusion, water of constitution without ; water mechanically enclosed often with decrepitation. If the 2 26 LECTURE NOTES ON water has an alkaline reaction, H 4 N is present ; if an acid reaction, some volatile acid as H 2 SO 4 , HC1, HNO,, etc. Gas escapes. 6> 2 shows presence of nitrates, chlo- rates, or dioxides ; a glowing match kindles. CO} shows presence of carbonates, or certain oxa- lates ; a drop of CaO s H 2 + Aq rendered turbid. CO shows presence of H 2 C 2 O 4 or some of its salts ; burns with a blue flame. JFf^S shows presence of hydrous sulphide ; recognized by its odor. CN formed from cyanides decomposed by heat; recognized by odor, or burning with crimson flame. NO} shows presence of nitrates ; recognized by orange red color, and odor. C/ 2 , Br* or / 2 liberated from chlorides, bromides or iodides which are decomposed by heat. H*N usually shows the decomposition of an H 4 N salt ; recognized by test paper, and odor. SO* often formed by decomposition of sulphates. Sublimate formed. 6* sublimes from many sulphides in red brown drops ; solidifies yellow on cooling. 7 2 from many iodine compounds ; vapor violet, the sublimate black. HN. Most salts give white crystalline sublimates. Hg and some of its compounds. Hg white metallic globules ; HgS black, turns red when rubbed ; HgCl 2 melts and sublimes white, Hg,Cl 2 sublimes without melt- ing. HgI 2 , red, sublimes yellow, turns red when rubbed. As and some of its compounds. As gives a metallic QUALITATIVE ANALYSIS. 2/ mirror, As 2 O 3 a crystalline sublimate ; As.;S 3 sublimes reddish yellow when hot, yellow when cold. Sb^Os melts and sublimes in needles. HjC^Oi sublimes in part, white and crystalline. Residue left -with change of color. A black residue may be due to the formation of a black oxide, or to carbonization showing the presence of an organic acid or other organic matter. In the latter case a characteris- tic odor is usually evolved. If the residue effervesces with acids, while the original substance did not, it shows the presence of acetates, tartrates, oroxalates of Grs. I. and II. The following changes of color are common. The residue Yellow while hot White when cold ZnO Red brown " " Yellow " " PbO Red brown " " Pale yellow " " Bi. 2 O 3 Black " " Red " " Fe 2 O 3 Heat on charcoal in inner blowpipe flame. Many of the reactions of the closed tube are repeated. If the odor of SO S is perceived sulphides are probably present. A garlic odor shows presence of As. Deflagration. Shows presence of nitrates or chlo- rates. Substance melts and runs into the charcoal. Salts of Gr. I. Residue white ; infusible, but luminous when heat- ed, Gr. II., Zn, A1 2 or SiO 2 . The residue must then be moistened with Co(NO 3 ) 2 + Aq and again heated in the outer flame. If the residue becomes colored, blue shows A1 2 ; green Zn ; flesh colored, Mg ; blue green, Sn. Phosphates and silicates also give a blue color. 28 LECTURE NOTES ON Residue colored or metallic, with or without a coat- ing upon the charcoal. In this case some of the sub- stance must be mixed with Na 2 CO 3 and heated in the inner blowpipe flame on charcoal. The color of the coating around the assay, and the nature of the metallic globule must be noted. If no one large globule can be obtained, the charcoal under the assay must be cut out and ground up with water in a mortar. The charcoal can readily be washed away and the metal left, in span- gles, if malleable. The presence of As shown by garlic odor. The character of the metallic globules of the re- ducible metals and the colors of the coating on the char- coal are as follows : ON CHARCOAL WITH Na a CO 3 . GLOBULE. COATING. Hot. Cold. Bi Brittle Dark orange Lemon yellow Sb " White White Ag Malleable (Dark red) Sn " Pale yellow White Pb " Orange yellow Yellow Cu " Zn Yellow White Ccf Red brown Red brown As White Reduced but not fused. Examination with Borax. A small quantity of the substance is melted into a QUALITATIVE ANALYSIS. 29 borax bead upon platinum wire. It should first be heated in the outer blowpipe flame, afterwards in the inner flame, the colors of the bead, both hot and cold, being carefully noted. An excess of substance must be avoided. The colors of the various beads, both hot and cold, in the inner and outer flames, are as follows : BORAX BEADS. OUTER FLAME. INNER FLAME. Hot. Cold. Hot. Cold. Cu Green Blue Colorless Red opaque Co Blue Blue 'Blue Blue Ni Violet Red brown Gray Gray Fe Red Yellow Bottle green Bottle green Mn Violet Amethyst Colorless Colorless Cr Green Green Green Green Flame Colorations. The coloration given by the substance to the flame of the lamp often gives more or less positive indications. The substance is introduced into the edge of the flame on platinum wire. Red flames. K, violet ; Li, carmine ; Sr, crimson ; Ca, orange red. Yellow flames. Na. Green flames. Cu (most salts) bright green ; Ba, yel- low green ; H 3 BO 3 pale green. Blue flames. CuCl 2 , bright blue ; Pb, As pale blue. Examination with ILS04. On heating the substance with strong H 2 SO 4 the 30 LECTURE NOTES ON presence or absence of certain acids may be established. If, on adding H-jsO,, HC1O 3 is found present, heat must not be applied? HNO 3 , HCl, HF, H 2 S, CO 2 are liberated from their compounds. SO 8 shows presence of sulphites or hypo- sulphites ; CO of oxalates or cyanides. HC 2 H 3 O 3 set free and recognized by odor. Br 2 and I 2 liberated from bromides and iodides, C1 2 O 4 from chlorates. Tartrates blacken. SOLUTION. Treatment with Water. The substance in fine powder must be treated with water, first cold then hot. Most salts are more readily soluble in hot water than in cold ; in a few cases the re- verse is true, and some salts, though soluble in cold water, are decomposed by boiling water into insoluble basic salts. Salts of Bi, and some salts of Sb, Hg and Hg 2 are thus decomposed even by cold water. After boiling for some time, if a portion remains undis- solved, it must be collected upon a filter, washed and treated with acids. If there be any doubt whether even a part of the substance is soluble, a few drops of the fil- trate must be evaporated on platinum foil. The reaction of the aqueous solution should be tested, or, if the substance under examination is liquid, the re- action of the original solution. An alkaline reaction shows the presence of Gr. I. or II. An acid reaction may be due to the presence of a free acid or acid salt, or due to the presence of a neutral QUALITATIVE ANALYSIS. 31 salt with acid reaction. In the first case a drop of Na 2 CO 3 -f- Aq gives no precipitate, or the precipitate which is formed redissolves ; in the second the turbidity is usually permanent. Treatment with Acids. For the solution of a substance insoluble in water HC1 + Aq, HNO 3 or a mixture of the two (aqua regia) is used. A solution in HC1 + Aq is much the best for subsequent work. Many substances are soluble in dilute acids, though in- soluble in strong, many soluble only in strong, and again many, that are not attacked by dilute acids, are decom- posed, though not dissolved, by stronger acids, so that solution can only be effected by treatment with strong acids and subsequent dilution. The substance should therefore be boiled successively with HC1 + Aq, HNO 3 and HC1 +Aq with HNO 3 , using first dilute, then strong, and finally adding water to that which has been boiled with strong acid. Effervescence may show CO 2 present, or if HC1 -f Aq is used H. 2 S or SO 2 . With HC1 + Aq HCN is often set free from insoluble cyanides, or C1 2 is evolved if dioxides or chromates are present. S or gelatinous H 4 SiO 4 are also often separated. Unless As or Sb may be present, the solution should be freed from any great excess of acid by evaporation. It is much better, in any case, to avoid an excess from the first, taking care also that the solution be properly diluted before beginning the analysis. HCl + Aq and HNO 3 together dissolve by converting into chlorides. 32 LECTURE NOTES ON If the substance is a metal or alloy, as will appear in the preliminary examination, it should be treated at once with hot HNO 3 , i part strong acid to 3 of water. Sb and Sn are oxidized to SnO a and Sb. 2 O 3 (Sb 2 O 4 ) insol- uble in water, or dilute HNO 3 , the other metals are found in solution. As many nitrates are insoluble in strong HNO 3 , though readily soluble in water, care must be taken not to mistake the crystalline nitrates for oxides of Sn or Sb. The insoluble residue may contain a part of any As present. Treatment of Substances Insoluble in Water or Acids. The most common substances insoluble in water or acids are : BaSO 4 , SrSo 4 , (CaSO 4 ), PbSO 4 ; the Ag salts of acids of Or. II., except Ag. 2 S ; ignited A1 2 O 3 , Cr. 2 O 3 or SnO 2 ; SiO 2 and many silicates ; CaF 2 , S- and C. S is recognized in the preliminary examination. C is present if the substance is black, and part of it burns before the blowpipe. If Pb and Ag have not been found in the preliminary examination, special tests must be made for their presence. Ag may be found, if present, by warming the substance with KCN 4- Aq, which dis- solves all the Ag salts insoluble in acids, and testing the filtrate with (H 4 N). 2 S + Aq. To test for Pb, warm the substance with H 4 NC s H a O 2 -f Aq, which dissolves PbSO 4 , and add to the filtered solution (H 2 N),S + Aq. If Ag or Pb are present they must be removed by suc- cessive treatment with H 4 NC 2 H 3 O. 2 + Aq, and KCN + Aq. If S is also present, it must be volatilized in a porcelain crucible after the removal of Pb and Ag. If QUALITATIVE ANALYSIS. 33 S is present, cold KCN -f- Aq must be used for the re- moval of Ag. The substance free from Agj Pb and S, may then be mixed with 2 parts Na,CO 3 , 2 parts K 2 CO 3 , and i part KNO 3 , and heated to quiet fusion in a platinum cru- cible. From the cooled mass water then dissolves alka- line salts of the acids present, and the bases are left as carbonates, soluble in HCl + Aq, after thorough washing. A1 2 is found in solution, and Cr 2 as chromate. To find the acids of the insoluble Ag salts, NaOH + Aq, dilute, will decompose the ferro- and ferricyanide, sodic salts of those acids going into solution by boiling ; AgCl, AgBr, Agl and AgCN are reduced by Zn and dilute H 2 SO 4 ; in the solution HC1, HBr, HI and HCN may be found. If the members of Gr. I. must be looked for in silicates, fuse with 4 parts of BaO 2 H 2 . Some substances insoluble, or slowly, soluble, in acids, may be decomposed with advantage by NaOH + Aq. The insoluble ferrocyanides and ferricyanides are de- composed by hot NaOH + Aq, into sodic salts of the acids and insoluble or soluble hydrates. The solution may therefore be examined for Pb, Zn and A1 2 , and, after their removal, for the acids, although it must be remem- bered that H 6 Fe 2 (CN) 12 in the alkaline solution is readily converted into H 4 Fe(CN) 6 by H 2 S. The portion insolu- ble in NaOH -j- Aq may be dissolved in acids and tested as usual. The three portions of any substance, that soluble in water, that soluble only in acids, and that insoluble in water and acids, must be separately examined. The. larger portion should first be analyzed, inasmuch as a 34 LECTURE NOTES ON knowledge of its constitution may greatly facilitate the analysis of the smaller portions. DETECTION OF BASES. The bases may be divided according to their behavior with reagents into six groups, and, for convenience in analysis, these groups are separated from each other by general reagents before proceeding to test for the individ- ual members of each group. 1 In an acid solution H 2 S precipitates only members of Grs. V. and VI. The pre- cipitation is complete, unless the solution is very strongly acid, in which case more or less Pb and Cd remain in so- lution. The sulphides of the two groups are separated by an alkaline solution, the sulphides of Gr. V. being in- soluble, those of Gr. VI. soluble, but precipitated by the addition of acid. As the HC1 + Aq, best used to acidify the solution, precipitates AgCl, Kg^C^ andPbClj (partial- ly), it is more convenient to separate these by nitration, and test for them apart. The members of Grs. III. and IV. are not precipitated by H 2 S in a solution acidified with HC1 -f- Aq, but are precipitated by (H 4 N) tf S + Aq in an alkaline solution Gr. III. as hydrates, Gr. IV. as sul- phides. Grs. V. and VI. are also precipitated by (H 4 N) 8 S + Aq, though the precipitate of Gr. VI. redis- solves in an excess. Grs. V. and VI. must therefore be removed before precipitating Grs. III. and IV. It is more convenient not to separate Gr. III. as a whole from Gr. IV., but to test the general precipitate for members of both groups. The members of Gr. II. are not precipita- ted by H. 2 S or (H 4 N) 2 S + Aq, and are distinguished from Gr. 1 Compare table of bases on page i. QUALITATIVE ANALYSIS. 35 I. by the insolubility of their carbonates. (H 4 N) 2 CO 3 + Aq precipitates Ba, Sr and Ca as carbonates, but as Mg is not precipitated as carbonate in presence of H 4 N salts, it is more convenient to make a special test for its presence, and remove it after the H 4 N salts have been expelled by ignition. (H 4 N). 2 CO 3 -|-Aq precipitates most of the mem- bers of Grs. VI. -III., and these groups must therefore be removed before the precipitation of Gr. II. Members of Gr. I. are precipitated by no general reagent, but are left in solution after the removal of the higher groups. Since H 4 N salts are used as reagents, tests for H 4 N must be made in the original solution. GROUPS V. and VI. Ag, Hg 2 , Pb, Hg, Cu, Bi, Cu; As, Sb. Sn, Sn iv . To the solution add HC1 + Aq. If a white precipitate * falls, it may contain AgCl, Hg 2 Cl2 and PbCl 2 . Filter, wash the precipitate with a little cold water, and set aside the filtrate. The precipitate must then be washed with hot water ; AgCl and Hg 2 CI 2 are insoluble, PbCl 2 is dissolved, if present, and by adding dilute H 2 SO 4 to the solution PbSO 4 is precipitated. The residue, which may consist of AgCl and Hg 2 Cl 2 , is next treated on the filter with H 4 NOH + Aq. Hg 2 Cl 2 , if present, is converted into black insoluble [Hg,]. 2 H 4 N 2 Cl 2 , and AgCl is dissolved. To the 1 If the solution is alkaline, on the addition of HC1 + Aq As 2 S 3 , Sb 2 S 3 or SnSj may be precipitated ; cyanides dissolved in KCN + Aq may be thrown down ; gelatinous H iSiO 4 separated, or S from alkaline sulphides. CO,, II, S, SO, and HCN may be set free AgCl is soluble in Hg(NO 3 ) 3 + Aq, but is precipitated by the addi- tion of HjNCaHaOj + Aq. 36 LECTURE NOTES ON HjNOH l + Aq which has run through the filter is then added HNO 3 in excess ; if Ag is present, AgCl is precipi- tated, white and curdy, or, if in small quantity, opalescent. To the filtrate from the precipitate caused by HC1 4- Aq, add H 2 S + Aq, or better, pass into it H 2 S ; warm for some time, adding H 2 S + Aq until the solution smells strongly of it after shaking, and filter. The filtrate, which may contain Grs. I. IV. is set aside ; the precipitate may contain PbS, HgS, CuS, Bi,S 3 , CdS, As,S 3 , Sb,S 3 , SnS and SnS.;. It must be washed with hot water until AgNO 3 gives no precipitate of AgCl in the wash water, and then gently warmed with very little yellow (H 4 N). 2 S + Aq. The sul- phides of Gr. VI. are thus dissolved: Filter and set the filtrate aside to be examined for members of Group VI. The precipitate, which may contain PbS, HgS, CuS, BLS 3 and CdS, after being well washed, is boiled with dilute HNO 3 . HgS alone is insoluble, although the S which separates is often colored with a little of one of the other sulphides, and a black residue must therefore be tested for Hg. The residue is filtered" off, dissolved in HC1 -f Aq with the addition of a very little KC1O 3 , and bright bits of Cu wire put into the solution. Hg, if present, is deposited on the Cu, and when dried may be sublimed in a bulb tube. The HNO 3 solution filtered from HgS or separated S may contain the nitrates of Pb, Cu, Bi and Cd. If Pb has already been found, it must be removed, and if not found, it may yet be present in quantity too small to be precipitated by HC1 + Aq. The solution must be 1 If PbCL is not completely washed out, the IL.NOH + Aq is often turbid from the presence of a basic Pb salt. This does not interfere with the detection of Ag, as it dissolves readily in HNO 3 . QUALITATIVE ANALYSIS. 37 concentrated by evaporation until the greater part of the HNO 3 has been driven off, dilute H 2 SO 4 added, the solu- tion gently warmed and allowed to stand for some time. A white precipitate is PbSO 4 and shows Pb present. If Pb is present, the solution must be evaporated with dilute H 2 SO 4 until the HNO 3 is all expelled, water slightly acid with H 2 SO 4 added, and the insoluble PbSO 4 filtered off. The solution now may contain Cu, Bi and Cd. Add H 4 NOH + Aq in excess, which precipitates BiO 3 H 3 white and flocculent, if Bi is present ; if the solution is blue, Cu is present. Filter from the precipitated BiO 3 H 3 . If the filtrate is not blue, a very small quantity of Cu may be de- tected by acidifying a portion with HC 2 H 3 O 2 and adding K 4 Fe(CN) 6 -f Aq which precipitates red brown Cu 2 Fe (CN) 6 . If Cu is absent, (H 4 N) 2 S + Aq added will precipitate yellow CdS. If Cu is present, precipitate CuS and CdS with H 2 S + Aq, and boil the mixed sulphides with dilute H 2 SO 4 , avoiding exposure to the air. CdS, if pres- ent, is alone dissolved, and, after filtering off the undis- solved CuS, maybe precipitated by H 2 S, or H 4 NOH -f Aq and (H 4 N) 2 S + Aq, as yellow CdS. The (H 4 N) a S + Aq solution which may contain Gr. VI. is acidified with dilute HC1 + Aq. The sulphides are thus precipitated mixed with S. If too much (H 4 N) 2 S + Aq was not used for solution, the presence of the sulphides is readily recognized. The precipitate, which may contain As 2 S 3 , Sb 2 S 3 and SnSa, 1 is collected on a filter and washed, then treated in the cold with (H 4 N).,CO 3 + Aq. As. 2 S 3 dissolves and may be precipi- 1 Brown SnS dissolved in yellow (H 4 N) 2 S + Aq is precipitated by HC1 + Aq as yellow SnS 2 . 38 LECTURE NOTES ON tated from the filtered solution by acidifying with HC1 + Aq as yellow As 2 S 3 , if As is present. In order to confirm the presence of As, the precipitate must be thoroughly dried, "mixed with dry KCN and Na 2 CO 3 , and the mixture heated in CrO 4 . In a part of the solution A1 2 may be precipitated by adding H 4 NC1 + Aq as A1 2 O 6 IV or, after acidifying with HNO 3 , H 4 NOH + Aq causes the same precipitate; another portion of the solution is acidified with HC 8 H 8 O 8 and BaCl 2 + Aq added, which precipitates BaCrO 4 , if Cr 2 is present. If NaOH -f Aq precipitates Fe 2 O 6 H 6 , the original solution must be tested by adding to a small portion K 6 Fe 2 (C]Sr), ? -f Aq, which gives blue Fe 3 Fe 2 (CN), 2 , if Fe is present ; 1 NaOH often contains silicate, and gelatinous H 4 SiO 4 is then precipitated here. It may be distinguished from ALO 8 H 6 by its in- solubility in H 4 NNaHPO 4 bead, and readily separated from it by fu- sion with KHSO 4 , treatment with HCl + Aq and precipitation of Al a O 8 H e from the solution, if present, by H 4 NOH + Aq. QUALITATIVE ANALYSIS. 41 to another portion add K 4 Fe(CN) 6 + Aq, which gives blue [FeJ 2 [Fe(CN) 6 ] 3 , or KCNS giving blood red solution of Fe 2 (CNS) 6 , if Fe 2 is present. Small quantities of Cr 2 may also be detected by fus- ing the dried precipitate with a mixture of equal % parts of Na 2 CO 3 and KNO 3 . If the cooled mass is boiled with water, the solution filtered and acidified with HC 2 H ;i O 2 , on the addition of Pb(C 2 H 3 O 2 ) 2 + Aq, PbCrO 4 is precipi- tated. The filtrate from the BaCO 3 precipitate, which may contain Zn and Mn, is heated to boiling and the Ba it contains completely precipitated with dilute H 2 SO 4 ; filter from the BaSO 4 , to the filtrate add NaOH + Aq in ex- cess and boil. MnO 2 H 2 is precipitated, if present, and the solution may contain Zn. The precipitate is collect- ed on a filter, and a portion of it fused on platinum wire with Na. 2 CO 3 and KNO 3 . Blue green K 2 MnO 4 is formed, if the precipitate was MnO 2 H 2 . The NaOH + Aq solu- tion, which may contain Zn, is acidified with HC 2 H 3 O S and ZnS, white, precipitated by H 2 S, if Zn is present. IfH 3 PO 4 and H 2 C 2 O 4 are present, the HC1 +Aq so- lution boiled with HNO 3 and treated as before must first be tested for Ba, Sr and Ca. To a small portion add dilute H 2 SO 4 . If a precipitate is formed filter, and ex- amine in the spectroscope. To the filtrate add 3 times its volume of alcohol ; CaSO 4 is precipitated,' if Ca is present, and its presence may be confirmed by dissolving the precipitate in water and throwing down CaC 2 O 4 with (H 4 N) 2 C 2 O 4 + Aq. To the rest of the solution add Fe 2 Cl 6 + Aq cautiously till a drop of the solution gives with H 4 NOH + Aq a yellowish precipitate. The solution must 42 LECTURE NOTES ON then be neutralized with NajCOg + Aq, as before, anc] BaCO 3 added. The precipitate with BaCO 3 is examined as above, except, of course, that Fe and Fe., must be proved present or absent by H 4 Fe(CN) 6 + Aq and K 6 Fe 2 (CN), + Aq, in the original solution. The nitrate from the BaCO 3 precipitate may contain Ca and Mg as well as Mn and Zn. After removing Ba with dilute H.SO 4 , H 4 NOH -f Aq must be added, ZnS and MnS precipitated, if present, by (H 4 N) 2 S + Aq, collected on a filter, and dissolved in HC1 -f Aq. They may then be separated and detected as before. The filtrate from the precipitate of ZnS and MnS may contain Ca and Mg. The Ca is precipitated as CaC 2 O 4 filtered off, and the filtrate tested for Mg by adding Na i HPO 4 + Aq. GROUP H Ba, Sr, Ca, Mg. To the filtrate from the general precipitate of Grs. III. and IV., or to the solution found not to contain Grs. III.-VI., add H 4 NCl-|-Aq, 1 if it be not already in solution, then H 4 NOH -f Aq in slight excess, unless the solution is already alkaline ; heat almost to boiling, add (H 4 N) 2 CO 3 -I- Aq to complete precipitation, and filter after allowing it to stand for a few minutes. The filtrate may contain Mg or members of Gr. I. To a small part of it add Na s HPO 4 + Aq. A white crystalline precipitate, forming only after the lapse of some time, if the solution be dilute, is Mg.XH.N^PO,).,. 2 The rest of the filtrate is then evaporated for Gr. I. 1 H 4 NC1 4- Aq prevents possible precipitation of Mg. a The nitrate may contain small quantities of Ba, Sr or Ca. A slight precipitate with Na 2 HPO 4 may therefore not be due to pres- ence of Mg. In a fresh portion Ba should be tested for and removed QUALITATIVE ANALYSIS. 43 The precipitate thrown down by (H 4 N) 2 CO 3 4- Aq may contain BaCO 3 , SrCO :! or CaCO 3 , and must be tested for all three. The carbonates are dissolved in HC 2 H 3 O 2 , and to a small part of the solution CaSO 4 + Aq is added. An immediate white precipitate is BaSO 4 , and shows that Ba is present, Ca and Sr may be; a tardy precipitate is SrSO 4 , and shows that Ba is absent and Sr present, Ca may be ; no precipitate even on long standing shows that Ba and Sr are absent, and the original precipitate was GaCO 3 alone. If Ba is present, it must be removed before testing for Sr or Ca. To the rest of the HC 2 H 3 O 2 solution is then added K 2 CrO 4 + Aq in slight excess, and the precipi- tated BaCrO 4 filtered off. To the filtrate add H 4 NOH +Aq in excess, warm and add (H 4 N) i CO 8 +Aq. The precipitate may contain SrCO 3 or CaCO 3 or both. It must be washed till all K 2 CrO 4 is removed and dissolved in HC.,H 3 O 2 . To a small portion of the solution add CaSO 4 -f-Aq. A white precipitate on standing is SrSO 4 and shows Sr present, Ca may be. If Sr is present, to the rest of the HC 2 H 3 O 2 solution, from which the Ba has been removed, or in which it was originally found absent, is added, dilute H 2 SO 4 in slight excess. After standing for some time SrSO 4 separates, mixed with CaSO 4 , if the solution is concentrated ; on fil- tering CaSO 4 will be found in solution, if present, by add- ing H 4 NOH+Aq in excess and (H 4 N) 2 C 2 O 4 + Aq ; Ca then falls as white CaC 2 O 4 . If Sr is absent, whether Ba was originally absent or was with dilute H 2 SO 4 , Ca with (H^N^CaO^ + Aq before accepting the precipitate with Na 2 HPO 4 + Aq as a proof of the presence of Mg. 44 LECTURE NOTES ON removed, H 4 NOH + Aq and (H 4 N) a C a O 4 added to the rest of the HC 2 H 3 O 2 solution precipitates CaC 2 O 4 if Ca is present. Ba, Sr and Ca may also be distinguished by the spectro- scope. Ba recognized by four green bands ; Sr by one orange, two red, and one blue band ; Ca best by a green and orange band. GROUP I. Na, K, Li, HN. The filtrate from the general precipitate of Gr. II. or the solution in which Grs. 1 1. -VI. have been found ab- sent, must be evaporated to dryness and ignited until H 4 N salts are expelled. If Mg was found to be absent, the residue contains only Na, K or Li, and should be tested with the spectro- scope. K gives a band in the extreme red, Na a yellow band, and Li a red band between the two. The presence of Na in notable quantity is shown by the intensity and duration of the yellow flame. NaHC 4 H 4 O 6 + Aq may also be used in a cold concentrated aqueous solution of the residue as a test for K, precipitating KHC 4 H 4 O 6 . NaC 2 O 3 +Aq precipitates from concentrated solutions LiCO 3 , or Na a HPO 4 + Aq, with the addition of a little NaOH -f-Aq, precipitates Li 3 PO 4 in a solution not too dilute. If Mg was found present, the residue from ignition l must be dissolved in a little water, and BaO 2 H 2 + Aq added in slight excess. The MgO.,H 2 thus precipitated is filtered out, the Ba completely precipitated from the boiling hot filtrate by dilute H 2 SO 4 , and the liquid freed 1 MgOoH 2 not precipitated from solutions containing H 4 N salts. QUALITATIVE ANALYSIS. 45 from BaSO 4 by filtration evaporated to dryness. The residue, after the excess of H 2 SO 4 has been driven off, is tested as before in the spectroscope. To test for H 4 N some of the original solution or sub- stance must be mixed with CaO 2 H 2 to a stiff ^aste, and gently warmed. H 3 N ! is then set free, which may be re- cognized by its action on moist test-paper, or by its form- ing white fumes of H 4 NC1 with HC1. 2 DETECTION OF ACIDS. The acids are divided into three groups, according to the solubility of the Ba and Ag salts. 3 BaCl 2 -f Aq precipi- tates all the members of Gr. I. in neutral or alkaline solu- tions, but does not precipitate Grs. II. and III. AgNO 3 + Aq precipitates in HNO 3 solution onry members of Gr. II., but in neutral solution almost all of Gr. I. Members of Gr. III. are precipitated by neither reagent. The acids are not separated after precipitation by the general reagents, as was the case with bases, the presence or absence of members of the groups alone being shown. In beginning the analysis for acids, those acids, which from the nature of the bases present and the solvent used are necessarily absent, must first be considered. In a substance soluble in water no acids can be present which form insoluble salts with any of the bases found in the solution. In a substance insoluble in water and 1 2H 4 NC1 + Ca0 3 H 3 = CaCl + 2H 2 O + 2H 3 N. 2 The HC1 + Aq used must not fume in the air. 3 See table of acids on page 19. 46 LECTURE NOTES ON soluble in acids, the number of acids which may thus be safely excluded, as forming soluble salts with the bases, is small, and it is better to look for all. In substances insoluble in water or acids, a knowledge of the bases will usually render the number of acids that must be tested for very small. If the substance is soluble in water, the bases will generally not interfere with the detection of those acids which can be present, although in testing for HC 2 H 3 O 2 and H 2 C 4 H 4 O 6 the solution cannot contain bases of Grs. III. -VI. If the substance is soluble in acids alone, the removal of the bases of Grs. III.-VI. always facilitates the detection of the acids, and is often essential. They should be removed with H V S, (H 4 N).,S + Aq, Na 8 CO 8 + Aq, NaOH + Aq, as the case may be, any excess of HoS removed, and the solution made neutral, carefully boiling out CO 2 , if Na 2 CO 3 was used. GROUP I. 1. M,Cr04, MnAsOn, H:,As04, MsSOs, M.S.On. These acids will have been discovered, if present, by the preliminary examination, or in the course of the anal- ysis for bases ; their presence must be confirmed by special tests. They are all decomposed by H^S in acid solution. Chromates. Pb(C 2 H 3 O 2 ) 2 + Aq gives yellow PbCrO 4 , insoluble in HC 2 H 3 O 2 . AgNO 3 + Aq in neutral solution precipitates brick red AgCrO 4 . Arsenites. H 2 S precipitates As 2 S 3 yellow immedi- ately from acid solutions ; AgNO 3 -fAq gives in neutral solutions pale yellow Ag 3 AsO 3 . Further recognized in presence of H 3 AsO 4 by adding a few drops of CuSO 4 QUALITATIVE ANALYSIS. 47 + Aq, then NaOH -f- Aq in excess ; on boiling Cu 2 O 2 H 2 precipitated, orange yellow. Arseniates. H 2 S precipitates As. 2 S 3 very slowly from acid solutions ; AgNO 3 + Aq gives in neutral solu- tions red brown precipitate of Ag 3 AsO 4 . Further distin- guished from arsenites by H 4 NOH + Aq, H 4 NC1 -f Ag, and MgSO 4 + Aq ; Mg. 2 (H 4 N). 2 (AsO 4 ), precipitated, easily mistaken for phosphate. Sulphites. Salts give off SO 2 when treated with H 2 SO 4 or HC1 + Aq. SO, recognized by smell and black- ening of paper moistened with Hg 2 (NO 8 ) 8 +-Aq by separa- tion of Hg. Zn and HCl + Aq liberate from solutions of sulphides H 2 mixed with H. 2 S. If sulphides also present, must they be removed by ZnSO 4 + Aq and the filtrate tested. Hyposulphites. From solutions H 2 SO 4 orHCl + Aq evolve SO 2 with separation of S. The reaction is delay- ed by dilution. Pb(C a H 8 O 2 ) 8 + Aq or AgNO 3 +Aq give white precipitates which blacken on boiling. 1 Sulphides, if present, must first be removed with ZnSO 4 +Aq. GROUP I. 2. (a) HsPO*, H 3 B0 3 , HCzCh, HF, M 2 C0 3 . H- <0 tO tO is tO tO 10 V - : l-*to: MtolM1*M H 2 CrO 4 . W : : : tO : tOtOtOlOtOtOto'- tOtO- tOtOtOtO>-'i-'>-i H 3 As0 3 . H 3 A 8 4 . k-itO^ "^ - H SO to to M H 3 P0 4 . : : ^Etoto: : tototo^totototototoSto^K, ^ H 3 B0 3 . h-l h-l H 2 C 2 0.. ^a t-i i-i^i-ii-i Jp>OtOtO HF1. : : to to to to to to to to to to to t* : : to to o to '-' i- *+ H 2 C0 3 . V ' toto- to- tototototototocototowto- MI-I H 4 SiO 4 . to: ^E^totoEtoto^toEtoE-^^E^^toMM^ H 2 C 4 H 4 . f T 1 coco- w- tocococotoioosco- t-i i-* -i to M i- i-. 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