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magnesium chloride[mag′nē·zē·əm ′klȯr‚īd]
MgCl2, a salt; colorless crystals. Density, 2.316 g/cm3; melting point, 713°C; boiling point, 1412°C. It is extremely hygroscopic; its solubility in water at 20°C is 35.3 percent (by weight). It forms crystalline hydrates with one, two, four, six, eight, and 12 water molecules. Hydrous magnesium chloride, MgCl2-6H2O, is stable at temperatures from —3.4° to 116.7°C. It occurs naturally as the mineral bischofite; it is extracted in large quantities during the concentration of ocean brines. Magnesium chloride forms double salts, an example of which is the highly valuable mineral carnallite, KCl.MgCl2-6H2O (a source of Mg and KC1). The production of magnesium chloride involves the dehydration of bischofite to MgCl2»2H2O, which is then dehydrated in a flow of HC1 at 100°-200°C. Magnesium chloride is primarily used in the manufacture of metallic magnesium; MgCl2 • 6H2O is used in the preparation of magnesia cements.