Mgcl2, either as a solid hydrate or in solution as a brine, in the presence of a slight excess of an amine hydrochloride is heated to evaporate water and produce successively a hydrated equimolar addition compound, the anhydrous addition compound, and anhydrous mgcl2 suitable for electrolysis to mg metal. The volatilized amine hydrochloride is condensed and recycled. Suitable amines include diethylamine, triethylamine, and ethylenediamine; aniline; pyridine; toluidine; and picoline. In an example, 105 parts of mgcl2.Nh2o is mixed with 130 parts of aniline hydrochloride and heated to 100 deg c to evaporate free h2o. On further heating, hydrate h2o is evaporated at 180 deg c, mg oxides are converted to mgcl2 at 198 deg c, and the complex is decomposed to mgcl2 and aniline hydrochloride at 250 deg-320 deg c.
U.S. Pat. 3,962,408; June 8, 1976; Chem. Abstr. 84:P166,871a