Magnesium chloride
E 511
- 7786-30-3 (anhydrous)
- 7791-18-6 (hexahydrate )
Colorless, bitter-tasting, deliquescent hexagonal crystals
- 95.21 g · mol -1 ( anhydrous)
- 203.3 g · mol -1 ( hexahydrate)
Fixed
2.32 g · cm -3 ( 20 ° C, anhydrous)
708 ° C
1412 ° C
Well in water (542 g · l-1 at 20 ° C)
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Magnesium chloride, MgCl 2, is the magnesium salt of hydrochloric acid. It forms several hydrates.
Occurrence
Magnesium chloride occurs naturally in the mineral bishofite (MgCl2 • 6H2O ) as well as a double salt carnallite ( KMgCl3 · 6 H2O ) before. Another natural source is the sea water. In some salt lakes, the concentration of magnesium ions is even higher than that of sodium ions.
Production and representation
The technical production of magnesium chloride is carried out by evaporation of the Endlaugen from the production of potassium chloride. In this case, first, the magnesium chloride hexahydrate (MgCl2 · 6H2O ) is obtained. More evaporation provides a water -leaner product. Anhydrous magnesium chloride is obtained by reacting magnesium oxide with coke and chlorine:
In the laboratory, can magnesium chloride from magnesium hydroxide and hydrochloric acid
Or by reaction of magnesium with a hydrochloric acid
Be obtained.
Properties
Magnesium chloride is highly hygroscopic. His tendency to hydrolyze is less pronounced than in the aluminum chloride ( AlCl3 ). Anhydrous magnesium chloride crystallizes in the CdCl2 - lattice type.
Magnesium chloride hexahydrate has a molar mass of 203.3 g · mol -1, a density of 1.57 g · cm -3, and a melting point of about 117 ° C ( decomposition). The solubility of the hexahydrate is 1700 g / l ( at 20 ° C).
The standard enthalpy of formation of magnesium chloride is -642 kJ · mol -1.
Use
Magnesium chloride is used for the recovery of elemental magnesium by fused-salt electrolysis:
It is used together with magnesium oxide in screed cements.
In the food industry, magnesium chloride is used as acidity regulator, firming agents, flavor enhancers, carrier or release agent. It is in the EU as a food additive under the E number 511 without a maximum limit ( quantum satis ) permitted for all approved additives for food, as well as for organic food. It is the main component of the coagulant nigari and serves as the manufacture of tofu. It continues to be used as road salt supplement.
Furthermore, magnesium chloride to increase the magnesium concentration used in reef aquariums.
It is used in coal mines and for dust suppression ( explosion protection).
For binding of road dust, it was tentatively used in a Antistaubit called leaching.
As the magnesium oil, a saturated magnesium chloride -water solution with an oily consistency, it is used in concentrated form for transdermal magnesium substitution ( dermal ).