Characters. - In colourless transparent prismatic crystals with a strong metallic styptic taste.

Reactions. - Its solution in water gives the reactions of zinc and of a sulphate (p. 595).

Dose. - 1 to 3 grains as a tonic; 10 to 30 grains as an emetic.

Uses. - Sulphate of zinc is used as an astringent to lessen discharges from mucous membranes; it is employed as a lotion in gonorrhoea and leucorrhoea; as a wash to the eye in ophthalmia; and, mixed with honey, in gangrene of the mouth in children. It is used as a gargle to the throat in relaxed sore-throat, pendent uvula, and enlarged tonsils.

As an emetic it is chiefly employed in narcotic poisoning, where the rapidity of its action, unaccompanied by any depressing influence on the circulation, is very serviceable. It is sometimes used, also, to cause vomiting in croup. It is employed as an astringent in chronic diarrhoea and dysentery. It has also been used as a tonic in flatulence and flatulent distension of the colon. After absorption into the blood it has a tonic action on some parts of the nervous system, and is used in the treatment of convulsive diseases, such as chorea, epilepsy, hysteria, as well as in spasmodic affections of involuntary muscular fibre, such as angina pectoris and spasmodic asthma.