Origin. - Prepared by mixing aqueous solutions of calcium chloride and sodium carbonate, the resulting precipitate of calcium carbonate being purified.

Description and Properties. - A fine white powder, without odor or taste, permanent in the air. Nearly insoluble in water, its solubility being increased by the presence of ammonium salts, and especially by carbonic acid, and diminished by alkali hydrates. Insoluble in alcohol, but in diluted acetic, hydrochloric, or nitric acid completely soluble, with effervescence.

Dose. - 15-30 grains (1.0-2.0 Gm.) [15 grains (1 Gm.), U. S. P.].