Preparation

By dissolving copper in sulphuric acid, with the aid of heat,

Cu + 2H1SO4, = CuSO4, + 2H1O, + SO2, treating the product with hot water, filtering, and crystallizing.

Characters And Tests

Occurs in oblique prisms of deep blue color, and metallic styptic taste; soluble in 4 parts of cold, and 2 of boiling water, insoluble in alcohol, efflorescing slightly in dry air. The anhydrous salt is white, but turns blue when moistened with water, and hence serves as a test for the presence of water in absolute alcohol. The sulphate answers to the tests for copper already given, and like other sulphates, gives a white precipitate of sulphate of baryta with barium chloride.

Ammonio-Sulphate of Copper in solution is used as a test for the presence of sulphides in liq. ammoniae fort., and also as a test for arse-nious acid, with which it produces a light-green precipitate of arsenite of copper (Scheele's green).