Silver orthothioarsenate

Silver Thioarsenates.—Silver Ortkothioarsenate, Ag3AsS4, is formed as a dark brown precipitate when an aqueous solution of silver nitrate is treated with sodium orthothioarsenate.1 If, however, silver nitrate is added to a solution of sodium orthothioarsenate, silver orthothioarsenate is not formed but silver sulphide is precipitated and arsenious acid, nitric acid and sodium nitrate are formed in solution.8 The reactions involved probably take the following course 3... 

Silver orthothioarsenate readily decomposes on heating, yidding sulphides of silver and arsenic and free sulphur. It is found in Nature as a yellow or orange-red mineral, generally in the form of powder, known as xanthoconite (see p. 13), and sometimes associated with selenium as rittingerite. 

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