calcium chloride, CaCl2, chemical compound that is crystalline, lumpy, or flaky, is usually white, and is very soluble in water. The anhydrous compound is hygroscopic; it rapidly absorbs water and is used to dry gases by passing them through it. Calcium chloride is commercially available usually as the dihydrate, CaCl2·2H2O; it is used to melt ice on roads, to control dust, in brines for refrigeration, and as a preservative in foods. It is also used in the monohydrate and hexahydrate forms. Calcium chloride is a byproduct of the Solvay process (a major source of the compound) and is present in natural brines.