Magnesium chloride is mainly used to make metal magnesium, used as disinfectant, fire extinguishing agent, ice salt refrigerant, and also used in ceramics, textiles, papermaking and other industries. Magnesium chloride solution is mixed with magnesium oxide in a certain proportion, commonly known as magnesia cement, which is hard and wear-resistant. Mixing magnesium chloride with magnesia can be used as a lining for steelmaking furnaces. Both seawater and brine contain magnesium chloride. It can be obtained by the reaction of magnesium oxide or magnesite with hydrochloric acid.