Electrolytic process
Dehydration of aqueous magnesium chloride solutions:

Chlorination of magnesia and magnesite:

Most difficult after eliminating impurities as sulfate, is separating the magnesium chloride from the six molecules of water that are chemically bound to it. The first 4,5 molecules can be removed by heating but the last 1,5 molecule will hydrolyze and form undesirable products upon further heating. Each method deals with this problem in a different way.  About half of all the energy required to produce electrolytic magnesium is consumed in the cell feed preparation.

Several types of electrolytic cells are in use today. Two with the longest history are the Dow cell which is an externally heated rectangular steel pot, and the I.G. Farben type cell which is lined with insulating refractory brick contained in a steel tank without provision for external heating. There are advantages and disadvantages to both types.
Other cell-types are:

  • ALCAN CELL, developed by Alcan from Canada and running since 1961 in the United States and Japan
  • VAMI CELL, developed by VAMI from Russia and based on the Norsk Hydro principles
  • ISHIZUKA CELL, developed by the Ishizuka Research Institute from Japan and running since 1983 in Japan