What Is Magnesium Chloride?
Magnesium chloride, with the formula MgCl2・6H2O, is an inorganic compound derived from the reaction of magnesium hydroxide and hydrochloric acid. Commonly referred to as “salt mag,” it is a major component of bittern—a solution left after sodium chloride is extracted from seawater.
This compound is produced both as a byproduct of salt production and in the manufacture of titanium tetrachloride from titanium metal, resulting in both hexahydrate (MgCl2・6H2O) and anhydrous (MgCl2) forms.
Uses of Magnesium Chloride
Magnesium chloride is versatile, used as a coagulant in tofu production and civil engineering as an anti-icing agent, wood preservative, fire-resistant material, and as a base for magnesia cement. In healthcare, it serves as a laxative, dialysis fluid, and infusion solution. The anhydrous form is crucial for producing magnesium metal, acting as a desiccant and exothermic agent, and as a catalyst precursor.
Properties of Magnesium Chloride
Magnesium chloride exists primarily in hexahydrate and anhydrous forms, with the hexahydrate being a highly soluble white crystal and the anhydrous form being known for its exothermic dissolution in water.
1. MgCl2・6H2O
This hexahydrate form is a white crystal with a solubility of 160 g/100ml in water and can hydrolyze at high temperatures to form magnesium hydroxide chloride and magnesia.
2. MgCl2
The anhydrous form is also a white crystal, with a solubility of 54 g/100 ml in water, and exhibits significant exothermicity upon dissolution.
Other Information on Magnesium Chloride
How Magnesium Chloride Is Produced
Magnesium chloride is primarily extracted from bittern. The production process involves removing bromide and sulfate from bittern, then concentrating the solution to precipitate and separate potassium chloride and magnesium chloride crystals.
Anhydrous magnesium chloride can be produced by dehydrating the hexahydrate form, using methods like heating in hydrochloric acid gas or adding ammonium chloride. Additionally, magnesium chloride is a byproduct of titanium smelting in the Kroll process, where titanium tetrachloride is reduced with magnesium, yielding magnesium chloride as a byproduct.