Definition. - A native aluminum silicate, consisting largely of the pure silicate, H1Al2Si2O8 + H10. It is a very pure clay.

Properties. - Soft, white or yellowish-white powder, odorless, and having an earthy or clay-like taste.

Insoluble in water.

Kaolin is contained in Cataplasma Kaolini (q. v.). It is used in dusting-powders; also in pills containing easily reduced bodies, such as silver nitrate or potassium permanganate, which cannot be mixed with ordinary excipients.

Official Preparation

Cataplasma Kaolini - Cataplasmatis Kaolini - Cataplasm of Kaolin (U. S. P.). - Introduced in response to a request for an external clay preparation; similar to a number of commercial articles. The constituents are kaolin (57.7 Per cent.), boric acid, methyl salicylate, glycerin, and small quantities of thymol and oil of peppermint.

Used as a poultice in mild local infections. Usually applied hot.