B. Or the original substance may be placed in the flask, treated at once with the zinc and dilute acid, and the As H3 and Sb H3 passed together into silver nitrate solution, and separated by filtration as directed under arsenic. See p. 389, also as to the distinctions between the stains of Sb and As. To these add, that metallic spots of both As and Sb are soluble in yellow ammonium sulphide: the solutions on evaporation to dryness on the water-bath give:
(a). With arsenic a yellow stain, soluble in ammonia, insoluble in hydrochloric acid;
(b). With antimony an orange stain, insoluble in ammonia, soluble in hydrochloric acid.
Metallic antimony can be precipitated as a black powder from its solutions by acidulating with hydrochloric acid and treating with a slip of pure tin, which does not precipitate arsenic. Zinc or electrolysis also precipitate Sb, along with copper and many other metals. Hence this method is not available in mixtures.
Sulphuretted hydrogen gives with antimonial solutions slightly acidulated an orange-red precipitate of sulphide, insoluble in ammonia or ammonium carbonate, soluble in ammonium sulphide, soluble in hot strong hydrochloric acid by conversion into antimonious chloride, and sulphuretted hydrogen: the former then gives a white precipitate with water, the latter gives the characteristic odour and blackens lead paper.
The reactions with sodium hydrate and sodium carbonate, are not so clear or decisive. Potass. ferrocyanide gives no precipitate. Tannin and tincture of galls give a yellowish white precipitate. Before the blowpipe with sodium carbonate on charcoal, solid Sb compounds give a grey brittle globule of the metal and a white incrustation. But there is rarely sufficient for such a test to be of use in toxicological work, there is also a risk of loss, and other metals give a similar reaction.
N.B.—Among other substances, sulphide of antimony is frequently added to caoutchouc in the process of vulcanising india-rubber: in all toxicological experiments involving tests for antimony (and arsenic), great danger of a mistake is thus attendant on the use of ordinary vulcanised india-rubber tubing. Black unvulcanised tubing should alone be employed.
II. Preparation Used.
The insoluble compounds would act very slowly as poisons and would require very large doses, hence would be found in the solid form in the stomach, and could be identified by appearance, by the microscope, and by the tests, after washing and settling down.