A white solid compound, MgCl2. The anhydrous salt (hexagonal; r.d. 2.32; m.p. 714°C; b.p. 1412°C) can be prepared by the direct combination of dry chlorine with magnesium:Mg(s)+Cl2(g) → MgCl2(s) The compound also occurs naturally as a constituent of carnallite (KCl.MgCl2). It is a deliquescent compound that commonly forms the hexahydrate, MgCl2.6H2O (monoclinic; r.d. 1.57). When heated, this hydrolyses to give magnesium oxide and hydrogen chloride gas. The fused chloride is electrolysed to produce magnesium and it is also used for fireproofing wood, in magnesia cements and artificial leather, and as a laxative.
Mg(s)+Cl2(g) → MgCl2(s)