Process for the preparation of anhydrous magnesium chloride having a high degree of purity

A process for the preparation of anhydrous magnesium chloride, which comprises the steps of:

• reacting magnesium chloride with ammonia in the presence of ammonium chloride in an aqueous medium at a temperature of from -30.degree. to 0.degree. C. while allowing the resultant magnesium chloride hexammoniate to precipitate from the reaction mixture;
• separating an aqueous solution containing unreacted magnesium chloride ammonia, and ammonium chloride from said precipitated magnesium chloride hexammoniate at a temperature of from -50.degree. to 0.degree. C;
• washing said magnesium chloride hexammoniate with liquid ammonia at a temperature of -30.degree. C. or lower;
• decomposing said washed magnesium chloride hexammoniate into anhydrous magnesium chloride and gaseous ammonia at a temperature of from 270.degree. to 400.degree. C.;
• isolating said anhydrous magnesium chloride from said decomposition mixture, and
• which is characterized in that a portion of said separated aqueous solution is subjected to evaporation at a temperature of from 80.degree. to 100.degree. C. under an ambient pressure whereby aqueous ammonia solution is removed to such an extent that the residual liquid of said evaporation contains 2.5% by weight or less of ammonia:
• mixing said residual liquid with fresh magnesium chloride and feeding said mixture into said reacting step, and
• directly recycling the remaining portion of said separated aqueous solution into said reacting step.