Prep. By dissolving zinc in dilute sulphuric acid, filtering and mixing with a solution of chlorine, and subsequently adding carbonate of zinc, as directed in the preparation of the chloride; evaporating, and crystallizing.

Prop. & Comp. Sulphate of zinc is in large or small crystals, of the same form as sulphate of magnesia; slightly efflorescent; soluble in water; precipitated and again re-dissolved by ammonia; precipitated by chloride of barium and hydrosulphuret of ammonia. Composition (Zn O, So3 +7 HO). Its watery solution is not tinged purple by tincture of galls, and when acidulated with hydrochloric or sulphuric acid is not precipitated by sulphuretted hydrogen. Boiled a few minutes with a little nitric acid, it yields with ammonia, a white precipitate, entirely soluble without colour in excess of the reagent, showing the absence of iron, etc.

Therapeutics. In small doses it acts as an astringent, and nervine tonic; in large doses as a quick, direct emetic; externally, as a powerful astringent. It is used as a tonic chiefly in diseases of the nervous system, as in chorea, epilepsy, hysteria, and allied spasmodic affections; and when gradually increased, tolerance soon becomes established: sometimes it is given as an astringent in chronic passive discharges, as in leucorrhcea, gleet, and bronchorrhoea. In large doses, as an emetic, it is used when the rapid emptying of the stomach is desired without the production of much depression, as in narcotic poisoning, phthisis, and dyspepsia. Externally, in solutions of different strengths, it is employed as a lotion or injection, as in ophthalmia, gleet, etc.

Dose. As a tonic, or astringent, 1 gr. to 10 gr., or more, in pills, or solution; as an emetic, 10 gr. to 30 gr. Externally, from 1 gr. to 30 gr. may be dissolved in an ounce of water.