Prep. By dissolving half an ounce of crystallized sulphate of copper in eight fluid ounces of distilled water, and adding solution of ammonia to the solution until the precipitate formed at first is nearly dissolved, filtering and adding sufficient distilled water to the clear solution to make it measure ten fluid ounces.

The ammonio-sulphate of copper is represented by the formula (CuO, So3 + 2Nh3,HO).

Use. Ammonio-sulphate of copper may be employed in lieu of ammonio-nitrate of silver as a test for the presence of arsenious acid. It gives a green precipitate (Scheele's green) which is soluble in excess of ammonia.