THE A L UMNI JO URN A I. . 



i>7 



ciation and takes an active interest in their pro- 

 ductions, which are always favorably received 

 by Brooklyn society. 



Krueder and Wurthmann have for some 

 time been busy preparing for their examinations, 

 which resulted quite satisfactorily to both par- 

 ties. The ex-Secretary will relieve the most of 

 the summer, except the time he will devote to 

 his vacation. 



Nelson S. Kirk, Ph. G. 



9 E. 59^ St. 



THIACETIC ACID AS A SUBSTITUTE 



FOR HYDROGEN SULPHIDE IN 



QUALITATIVE ANALYSIS. 



Many have been the attempts to eliminate 

 from analytical analysis the exceedingly annoy- 

 ing reagent hydrogen sulphide, but without 

 success. Now, however, this difficulty appears 

 to have been overcome by Robert Schiff and N. 

 Tarugie who not long ago reported (Berichte d. 

 Deut. , Chem. Ges. ) that thiacetic acid, in form 

 of ammonium salt, not only forms a complete 

 substitute, but that its employment serves to 

 simplify even the course of qualitative analysis. 

 The new method has been successfully intro- 

 duced by them in the university laboratory, 

 fully displacing the hydrogen sulphide appara- 

 tus. The rapidity and completeness of metallic 

 precipitation is claimed to be astounding, while 

 in the hands of tyros even it gives good results. 



The reagent, ammonium thiacetate [CH ; . 

 C:0(S. NH 4 )] is prepared as follows : Dissolve 

 thiacetic acid in a slight excess of dilute am- 

 monia, and then dilute to three times the vol- 

 ume of the acid employed. The solution has a 

 faint odor of ammonium sulphide. Not more 

 than about ten days' supply should be prepared, 

 since the solution gradually becomes turbid. 

 Thiacetic acid may easily be prepared by the 

 action of glacial acetic acid on phosphorus pen- 

 tasulphide; but it may be expected to be soon 

 placed on the market by the manufacturers, 

 Thiacetic acid is but slightly soluble in water 

 and has a disagreeable odor. 



The directions for use are to add to the cold 

 solution ofo 5 to 1.0 gm. of the metals, the lat- 

 ter in the form of chlorides, from 15 to 2.0 

 cubic centimeters of the test solution and then 

 to heat to nearly 1 not quite) the boiling point. 

 When perfectly cooled the precipitate is separat- 

 ed by filtration and the filtrate tested with a 

 few additional drops of the reagent During 

 the reaction a very faint odor of hydrogen sul- 

 phide is noticeable. 



In this manner all the metals of group II may 



be completely precipitated as sulphides, not a 

 trace of metals remaining in solution, even 

 when the difficultly separable arsenates were at 

 first present. 



Hot hydrochloric acid liberates from ammon- 

 ium thiacetate intensively active nascent hydro- 

 gen sulphide, without, however, causing a pre- 

 cipation of sulphur. No objectionable chemi- 

 cals are introduced by this method into the 

 liquid to be analyzed, the resulting ammonium 

 chloride being rather desirable, while the little 

 free acetic acid does no harm. 



METALS IN HYDROCHLORIC ACID SOLUTION 

 AND AMMONIUM THIACETATE. 



Arsenites and Arsenates. — In cold solution 

 whitish turbidity ; in warm solution instant- 

 aneous and complete precipitatation asarsenium 

 trisulphide. 



Bismuth, Copper, Stannic and Stannous 

 Salts. — In cold solution partial precipitation ; 

 in warm solution complete precipitation. 



Lead Salts. — In cold solution a dark red 

 precipitate (possibly a sulphoprotochloride), 

 which on warming is completely converted into 

 lead sulphide. 



Silver Salts.— Silver chloride, dissolved in hot 

 concentrated hydrochloric acid, is completely 

 precipitated as silver sulphide. The chloride, 

 bromide, and iodide of silver, when heated with 

 the test solution, are converted into silver sul- 

 phide, f 



Cadmium Salts. — Cadmium sulphide being 

 quite soluble in warm hydrochloric acid, the 

 precipitate formed by ammonium thiacetate 

 will disappear on heating ; however, it appears 

 again when the solution has completely cooled. 



Platinum Salts. — In cold solution a red 

 precipitate which on warming is converted into 

 platinum sulphide. 



Gold Salts act precisely as those of platinum. 



Ferric Salts are instantaneously reduced to 

 ferrous salts. 



Chromic Acid Salts are immediately reduced 

 to chrome salts. 



Nickel, Cobalt, Manganese, Zinc, Alumi- 

 nium, etc., Salts, as was to be expected, are not 

 affected by the test solution. However, the 

 sulphur compounds of nickel, cobalt, man- 

 ganese, and nickel in ammonical solutions are 

 i istantly precipitated by it ; but since there are 

 no objections to ammonium sulphide solution, 

 as well as for some other cogent reasons, the 

 latter is retained for precipitatiug the metals of 

 group IV. — Western Druggist. 



