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CHLORIDES > Magnesium Chloride

Magnesium chloride is the name for the chemical compounds with the formulas MgCl2 and its various hydrates MgCl2x. These salts are typical ionic halides, being highly soluble in water.

Formula: MgCl2, Molar mass: 95.211 g/mol, Melting point: 714 °C, IUPAC ID: Magnesium chloride, Density: 2.32 g/cm³, Boiling point: 1,412 °C, Soluble in: Water

Niche uses
Diagram showing concentrations of various salt ions in seawater: Note that the diagram is only correct in units of wt/wt, not wt/vol or vol/vol.

Magnesium in natural seawater values are between 1250 mg/L and 1350 mg/L. (approximately 3.7% of the total seawater mineral content. See thumbnail chart.) Dead Sea minerals contain a significantly higher magnesium chloride ratio (50.8%). Carbonates and calcium are essential for all growth of corals, coralline algae, clams, and invertebrates. Magnesium can be depleted by mangrove plants and the use of excessive Kalkwasser or by going beyond natural calcium, alkalinity, and pH values.

Culinary use

Magnesium chloride is an important coagulant used in the preparation of tofu from soy milk. In Japan it is sold as nigari, derived from the Japanese word for "bitter"), a white powder produced from seawater after the sodium chloride has been removed, and the water evaporated. In China, it is called lushui . Nigari or lushui consists mostly of magnesium chloride, with some magnesium sulfate and other trace elements. It is also an ingredient in baby formula milk.

Gardening and Horticulture

Because magnesium is a mobile nutrient, magnesium chloride can be effectively used as a substitute for magnesium sulfate (Epsom salt) to help correct magnesium deficiency in plants via foliar feeding. It is advisable to use a smaller dose when using magnesium chloride compared to the recommended dose of magnesium sulfate (20 g/L).This is due primarily to the chlorine present in magnesium chloride, which can easily reach toxic levels if over-applied and/or applied too often.

It has been found that higher concentrations of magnesium in tomato and some pepper plants can make them more susceptible to disease caused by infection of the bacteria Xanthomonas campestris, since Mg is essential for bacterial growth.