a class of medicines which are used for binding or contracting the several parts, external or internal, of the human system, for restraining profuse discharges, coagulating the fluids, condensing and strengthening the solids. The principal astringents are the mineral acids, alum, lime-water, chalk, several preparations of copper, zinc, iron, &c., catchu, kino, oak-bark, galls, and all vegetable substances containing tannin.