[819] Zeitschr. f. rationelle Med., vol. xxix. p. 1, 1867.
§ 771. Separation and Detection of Cadmium.—If cadmium be in solution, and the solution is not too acid, on the addition of SH2 there is precipitated a yellow sulphide, which is distinguished from antimony and arsenical sulphides by its insolubility in ammonia and alkaline sulphides. Should all three sulphides be on the filter (an occurrence which will seldom, perhaps never, happen), the sulphide of arsenic can be dissolved out by ammonia, the antimony by sulphide of sodium, leaving the sulphide of cadmium as the residue.[820]
[820] It is unnecessary to state that absence of sulphur is presupposed.
The further tests of the sulphide are:—
(1) It dissolves in dilute nitric acid to a colourless fluid, with separation of sulphur.
(2) The solution, filtered and freed from excess of nitric acid by evaporation, gives with a solution of ammonic carbonate a white precipitate of carbonate of cadmium insoluble in excess. This distinguishes it from zinc, which gives a similar white precipitate, but is soluble in the excess of the precipitant.