Prep. By exposing copper-plates to the action of the fermenting marc of grapes, or pyroligneous acid, when this salt forms on the surface.

Prop. & Comp. In powder or masses consisting of very minute crystals, of a bluish-green colour, with a peculiar sour metallic odour, and styptic metallic taste; resolved by water into a soluble acetate and insoluble tris-acetate; when treated with sulphuric acid, it gives off acetic acid fumes; it dissolves in this acid when dilute, and from the solution ammonia precipitates the oxide, but re-dissolves it when in excess. Composition (2 Cu O, a + 6 HO).

A solution of acetate of copper is used for detecting the presence of butyric acid in valerianate of zinc. For this purpose the valerianate of zinc is distilled with sulphuric acid, and to the distillate the solution of copper is added; if any butyric acid be present a bluish-white precipitate of butyrate of copper is produced, but pure valerianic acid gives rise to no precipitate.

Therapeutics. Verdigris is used externally as an escharotic, in powder, or mixed with honey and vinegar, under the name of Linimentum AEruginis; it should be applied with a camel's-hair brush.

Adulteration. It sometimes contains chalk and sulphate of copper, detected by its effervescing with an acid, and by the solution precipitating with ammonia and chloride of barium. Other impurities can be detected by the tests given above.