Characters. - A yellowish-white powder, which becomes blue when moistened with water.

Action. - Sulphate of copper has little or no action on the skin covered by epidermis, but when applied to the denuded skin it combines with the albuminous constituents of the tissues, forming an albuminate of copper. It thus acts as a mild caustic, and is an astringent. It has a similar astringent action on mucous membranes, and when swallowed in large doses it acts as a powerful emetic, like the sulphate of zinc, and in smaller doses as an astringent. Like sulphate of zinc, it probably exerts its action partly on the stomach itself and partly on the vomiting centre. Small doses absorbed into the blood appear to have a tonic action on some parts of the nervous system, and to exert an astringent action on mucous membranes. The copper is excreted by the mucous membrane of the intestine, by the bile, sweat, and kidneys. It is probable that its effect as an emetic when injected into the blood is partially due to the action it produces upon the stomach or intestines in the process of elimination (p. 39). Its action as an astringent upon other mucous membranes is probably due to a similar cause.

Uses. - Sulphate of copper in substance is used as a mild caustic to the edges of sores, to repress exuberant granulations, both of ulcers and of trachoma, and as a styptic to arrest the blood from leech-bites. When mixed with honey it may be applied to the mouth in cancrum oris. In solution it may be applied to indolent ulcers, and to remove warts and parasitic skin-diseases, and as an injection into the nose to stop epistaxis. It is used as a wash to the eyes in ophthalmia, as an injection in gonorrhoea and leucorrhcea, and as a gargle in sore-throat. It is n efficient and rapid emetic in cases of narcotic poisoning, in phosphorus-poisoning, and in croup. It is a powerful astringent in chronic diarrhoea, dysentery, and colliquative diarrhoea of phthisical patients. It is employed, like zinc, in chorea, epilepsy, and hysteria, but seems less useful than zinc. The nitrate has a similar action to the sulphate, but is more powerful as a caustic and styptic. It is a useful application to syphilitic sores on the tongue.

1 Oleate of copper is a useful application in cases of ringworm, applied night and morning. It is first prepared by drying a mixture of sulphate of copper (3 in 8 of water) and a solution of Castile soap (8 in 32), and may be applied in the form of ointment, 1 in 4 of petroleum cerate. It has also been used for indolent ulcers, warts, and corns.

B.P. Test Solution of Ammonio-Sulphate of Copper. A test for arsenious acid, forming with it Scheele's green.

B.P. Subacetate of Copper of Commerce. Cu.CuO (C2H3O2)2. Verdigris, Aerugo. - Used in solution as a test.

B.P. Test Solution of Acetate of Copper.

Use. - In testing for butyric acid in valerianates.