Sulphate of copper has been so fully treated of among the tonics (i. 406), and emetics (ii. 481), that we have here to consider it only as an external remedy. Locally applied, it is stimulant, astringent, and escharotic. It acts mildly as a caustic; its influence, like that of nitrate of silver, being generally confined to the surface of the tissue. Like that medicine, moreover, it produces its escharotic effect by combining with the albumen or other organic constituent of the tissue, and thus causing decomposition. Applied to an ulcer, it forms a bluish-white compound upon the surface.

With reference to its escharotic property, it is used to destroy warts, fungous granulations, and the surface of indolent or callous ulcers, the healing of which it thus greatly promotes. For these purposes, it is often applied in the solid state, and may be conveniently shaped into the form of a small cylindrical stick, which may be attached to a handle.

In solution it is used as a stimulant, alterative, and styptic. It is not unfrequently applied as a wash to chancres and other specific ulcers, indolent ulcers of all kinds, and those ulcerous affections of the mouth and fauces denominated cancrum and gangraena oris, in which it is often extremely useful. For these purposes, a solution may be employed containing from ten to twenty grains to one fluidounce; and, in applying it, care must be taken not to bring it unnecessarily into contact with the sound tissue.

Of a similar strength, it may be used as a wash for bleeding surfaces; and, when the source of the hemorrhage is not extensive, it may even be applied in the solid state.

It has also been used in weaker solutions as a stimulant and astringent wash for chronically inflamed mucous membranes, as in ophthalmia, gleets, and leucorrhoea. In these cases, the strength of the solution should not at first exceed one or two grains to the fluidounce.

A solution containing a grain to the fluidounce may be inhaled in the form of spray, in chronic inflammation and ulceration of the fauces and larynx.