Origin. - Prepared by adding potassium carbonate to acid potassium sulphate.

Description and Properties. - Hard, colorless, transparent, six-sided, rhombic prisms terminated by pyramids, or in white powder; odorless, and having a somewhat bitter, saline taste. Permanent in the air. Soluble in about 9 parts of water, insoluble in alcohol.

Dose. - 1/2-4 drams (2.0-16.0 Gm.) [30 grains (2 Gm.), U. S. P.].