Copper, Ba′sic Acetates of

Syn. Ba′sic cu′pric acetates , Sub-ac′etates of copper . Common verdigris is a mixture of several basic acetates which have a green or blue colour. One of these ( SESQUIBASIC ACETATE ) is obtained by digesting powdered verdigris in tepid water, filtering, and leaving the soluble part to spontaneous evaporation. It may also be obtained in a state of purity by adding liquor of ammonia in small portions to a boiling concentrated solution of the neutral acetate till the precipitate is just redi olved, and leaving the solution to cool. It forms a blue, crystalline ma , but little soluble in cold water. The green, insoluble residue of the verdigris, after treatment with tepid water, contains another acetate ( TRIBASIC ACETATE ); this may be formed by digesting neutral acetate of copper with the hydrated oxide. A third salt ( DIBASIC ACETATE , BLUE VERDIGRIS ) is prepared on a large scale in France by exposing copper to the air in contact with fermenting wine-lees.