Magnesium chloride is the name for the chemical compound with the formula MgCl2 and its various hydrates MgCl2(H2O)x. Anhydrous MgCl2 contains 25.5% elemental magnesium by mass. These salts are typical ionic halides, being highly soluble in water. The hydrated magnesium chloride can be extracted from brine or sea water. In North America