Magnesium chloride is a chloride with the chemical formula MgCl2. It is colorless and hygroscopic crystalline substance. These salts are typical ionic halides, highly soluble in water. Hydrated magnesium chloride can be extracted from saltwater or seawater. It usually contains six molecules of crystalline water. However, it loses its crystalline water when heated to 95°C. Above 135°C, it releases (HCl) gas. It is an industrial raw material for magnesium production, found in seawater and salt brine. Hydrated magnesium chloride is the substance commonly used in oral magnesium supplements.