Characters. - Orange-yellow crystalline masses, very deliquescent, odourless or having a faint odour of hydrochloric acid, a styptic taste, and an acid reaction.

Solubility. - Freely and wholly soluble in water, alcohol, or ether. Reactions. - The dilute aqueous solution gives a brown-red precipitate with water of ammonia, a blue one with test solution of ferrocyanide of potassium, and a white one, insoluble in nitric acid, with test solution of nitrate of silver.

Uses. - In the solid state it keeps indefinitely, whereas in solution it is apt to deposit ferric oxide leaving excess of acid in the solution which renders it irritating. When required it may be dissolved in water in the proportion of 1 1/2-6 drachms to the ounce of water. When semi-deliquesced it is an efficient styptic.