How does the IG Farben process produce anhydrous magnesium chloride?

The IG Farben process produces anhydrous magnesium chloride through the chlorination of magnesium oxide rather than by dehydrating brines.1

The process follows these steps:

• Preparation: Lightly burned dolomite is mixed with seawater to precipitate magnesium hydroxide, which is then filtered and calcined to produce magnesium oxide.1
• Forming: The magnesium oxide is mixed with charcoal and a magnesium chloride solution, then formed into globules and dried.1
• Chlorination: These globules are charged into a brick-lined shaft furnace (a chlorinator) and heated by carbon electrodes to approximately 1,000–1,200 °C (1,800–2,200 °F).1
• Reaction: Chlorine gas is introduced through furnace portholes, reacting with the magnesium oxide to produce molten magnesium chloride.1

Once produced, this molten, essentially water-free magnesium chloride is tapped from the furnace and sent to electrolytic cells for the production of magnesium metal.12