Magnesium chloride
Names | |
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Other names
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Identifiers | |
3D model (
JSmol ) |
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ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard
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100.029.176 |
EC Number |
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E number | E511 (acidity regulators, ...) |
9305 | |
PubChem CID
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RTECS number
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UNII |
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CompTox Dashboard (EPA)
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Properties | |
MgCl2 | |
Molar mass | 95.211 g/mol (anhydrous) 203.31 g/mol (hexahydrate) |
Appearance | white or colourless crystalline solid |
Density | 2.32 g/cm3 (anhydrous) 1.569 g/cm3 (hexahydrate) |
Melting point | 714 °C (1,317 °F; 987 K) anhydrous 117 °C (243 °F; 390 K) hexahydrate on rapid heating; slow heating leads to decomposition from 300 °C (572 °F; 573 K) |
Boiling point | 1,412 °C (2,574 °F; 1,685 K) |
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Solubility | slightly soluble in acetone, pyridine |
Solubility in ethanol | 7.4 g/(100 mL) (30 °C) |
−47.4·10−6 cm3/mol | |
Refractive index (nD)
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1.675 (anhydrous) 1.569 (hexahydrate) |
Structure | |
CdCl2 | |
(octahedral, 6-coordinate) | |
Thermochemistry | |
Heat capacity (C)
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71.09 J/(mol·K) |
Std molar
entropy (S⦵298) |
89.88 J/(mol·K) |
Std enthalpy of (ΔfH⦵298)formation |
−641.1 kJ/mol |
Gibbs free energy (ΔfG⦵)
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−591.6 kJ/mol |
Pharmacology | |
A12CC01 (WHO) B05XA11 (WHO) | |
Hazards[1] | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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Irritant |
GHS labelling: | |
Warning | |
H319, H335 | |
NFPA 704 (fire diamond) | |
Flash point | Non-flammable |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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2800 mg/kg (oral, rat) |
Safety data sheet (SDS) | ICSC 0764 |
Related compounds | |
Other anions
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Other cations
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Magnesium chloride is an
Production
Magnesium chloride can be extracted from
In the
- )
It can also be prepared from magnesium carbonate by a similar reaction.
Structure, preparation, and general properties
MgCl2 crystallizes in the cadmium chloride CdCl2 motif, which features octahedral Mg centers. Several hydrates are known with the formula MgCl2·nH2O, and each loses water upon heating: n = 12 (−16.4 °C), 8 (−3.4 °C), 6 (116.7 °C), 4 (181 °C), 2 (about 300 °C).[4] In the hexahydrate, the Mg2+ is also octahedral, but is coordinated to six water ligands.[5] The thermal dehydration of the hydrates MgCl2·nH2O (n = 6, 12) does not occur straightforwardly.[6] Anhydrous MgCl2 is produced industrially by heating the complex salt named hexamminemagnesium dichloride [Mg(NH3)6]2+(Cl−)2.[2]
As suggested by the existence of hydrates, anhydrous MgCl2 is a
Applications
Precursor to Mg metal
Anhydrous MgCl2 is the main precursor to metallic magnesium. The reduction of Mg2+ into metallic Mg is performed by electrolysis in molten salt.[2][9] As it is also the case for aluminium, an electrolysis in aqueous solution is not possible as the produced metallic magnesium would immediately react with water, or in other words that the water H+ would be reduced into gaseous H2 before Mg reduction could occur. So, the direct electrolysis of molten MgCl2 in the absence of water is required because the reduction potential to obtain Mg is lower than the stability domain of water on an Eh–pH diagram (Pourbaix diagram).
- MgCl2 → Mg + Cl2
The production of metallic magnesium at the cathode (reduction reaction) is accompanied by the oxidation of the chloride anions at the anode with release of gaseous chlorine. This process is developed at a large industrial scale.
Dust and erosion control
Magnesium chloride is one of many substances used for dust control, soil stabilization, and wind erosion mitigation.[10] When magnesium chloride is applied to roads and bare soil areas, both positive and negative performance issues occur which are related to many application factors.[11]
Catalysis
Magnesium chloride is also a
Ice control
Magnesium chloride is used for low-temperature de-icing of highways, sidewalks, and parking lots. When highways are treacherous due to icy conditions, magnesium chloride is applied to help prevent ice from bonding to the pavement, allowing snow plows to clear treated roads more efficiently.
For the purpose of preventing ice from forming on pavement, magnesium chloride is applied in three ways: anti-icing, which involves spreading it on roads to prevent snow from sticking and forming; prewetting, which means a liquid formulation of magnesium chloride is sprayed directly onto salt as it is being spread onto roadway pavement, wetting the salt so that it sticks to the road; and pretreating, when magnesium chloride and salt are mixed together before they are loaded onto trucks and spread onto paved roads. Calcium chloride damages concrete twice as fast as magnesium chloride.[15] The amount of magnesium chloride is supposed to be controlled when it is used for de-icing as it may cause pollution to the environment.[16]
Nutrition and medicine
Magnesium chloride is used in
Cuisine
Magnesium chloride (E511[17]) is an important coagulant used in the preparation of tofu from soy milk.
In Japan it is sold as
Nigari or Iushui is, in fact, natural magnesium chloride, meaning that it is not completely refined (it contains up to 5% magnesium sulfate and various minerals). The crystals originate from lakes in the Chinese province of Qinghai, to be then reworked in Japan.
It is an inexpensive dietary supplement providing magnesium, hence its interest in view of a general deficit in our current consumption (to be in full health, the human body must in particular benefit from a balance between calcium and magnesium). It is also an ingredient in baby formula milk.[18]
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. The recommended dose of magnesium chloride is smaller than the recommended dose of magnesium sulfate (20 g/L).[19] This is due primarily to the chlorine present in magnesium chloride, which can easily reach toxic levels if over-applied or applied too often.[20]
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 bacterium Xanthomonas campestris, since magnesium is essential for bacterial growth.[21]
Wastewater Treatment
It is used to supply the magnesium necessary to precipitate phosphorus in the form of struvite from agricultural waste[22] as well as human urine
Occurrence
Magnesium concentrations in natural seawater are between 1250 and 1350 mg/L, around 3.7% of the total seawater mineral content. Dead Sea minerals contain a significantly higher magnesium chloride ratio, 50.8%. Carbonates and calcium[clarification needed] are essential for all growth of corals, coralline algae, clams, and invertebrates. Magnesium can be depleted by mangrove plants and the use of excessive limewater or by going beyond natural calcium, alkalinity, and pH values.[23] The most common mineral form of magnesium chloride is its hexahydrate, bischofite.[24][25] Anhydrous compound occurs very rarely, as chloromagnesite.[25] Magnesium chloride-hydroxides, korshunovskite and nepskoeite, are also very rare.[26][27][25]
Toxicology
Magnesium ions are bitter-tasting, and magnesium chloride solutions are bitter in varying degrees, depending on the concentration.
Magnesium toxicity from magnesium salts is rare in healthy individuals with a normal diet, because excess magnesium is readily excreted in
Plant toxicity
Chloride (Cl−) and magnesium (Mg2+) are both essential nutrients important for normal plant growth. Too much of either nutrient may harm a plant, although foliar chloride concentrations are more strongly related with foliar damage than magnesium. High concentrations of MgCl2 ions in the soil may be toxic or change water relationships such that the plant cannot easily accumulate water and nutrients. Once inside the plant, chloride moves through the water-conducting system and accumulates at the margins of leaves or needles, where dieback occurs first. Leaves are weakened or killed, which can lead to the death of the tree.[28]
See also
Notes and references
- Notes
- ^ "Summary of Classification and Labelling". echa.europa.eu.
- ^ ISBN 978-3527306732.
- .
- ISBN 0-12-352651-5.
- ISBN 0-19-855370-6.
- ^ See notes in Rieke, R. D.; Bales, S. E.; Hudnall, P. M.; Burns, T. P.; Poindexter, G. S. "Highly Reactive Magnesium for the Preparation of Grignard Reagents: 1-Norbornane Acid", Organic Syntheses, Collected Volume 6, p. 845 (1988). "Archived copy" (PDF). Archived from the original (PDF) on 2007-09-30. Retrieved 2007-05-10.
{{cite web}}
: CS1 maint: archived copy as title (link) - ^ N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984.
- PMID 31328293.
- ^ Hill, Petrucci, McCreary, Perry, General Chemistry, 4th ed., Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA.
- ^ "Dust Palliative Selection and Application Guide". Fs.fed.us. Retrieved 2017-10-18.
- ^ "FSE Documents" (PDF). www.nrcs.usda.gov. Archived from the original (PDF) on 2022-10-16.
- ISBN 9780470504437.
- .
- PMID 11792206.
- doi:10.3141/2290-09.
- .
- Food Standard Agency. "Current EU approved additives and their E Numbers". Retrieved 22 March 2010.
- ^ "Listed under ingredients for Similac Hypoallergenic Infant Formula with Iron (Abbott Nutrition)". abbottnutrition.com. Retrieved 2013-07-22.
- .
- ^ "Magnesium Chloride Toxicity in Trees". Ext.colostate.edu. Archived from the original on 2009-01-15. Retrieved 2017-10-18.
- ^ "Effect of Foliar and Soil Magnesium Application on Bacterial Leaf Spot of Peppers" (PDF). Retrieved 2017-10-18.
- ^ BURNS, R.T. (15 January 2001). "LABORATORY AND IN-SITU REDUCTIONS OF SOLUBLE PHOSPHORUS IN SWINE WASTE SLURRIES" (PDF). Environmental Technology. 22: 1273–1278. Retrieved 30 December 2023.
- ^ "Aquarium Chemistry: Magnesium In Reef Aquaria — Advanced Aquarist | Aquarist Magazine and Blog". Advancedaquarist.com. 2003-10-15. Retrieved 2013-01-17.
- ^ "Bischofite: Mineral information, data and localities". mindat.org.
- ^ a b c "List of Minerals". International Mineralogical Association. 21 March 2011.
- ^ "Korshunovskite: Mineral information, data and localities". mindat.org.
- ^ "Nepskoeite: Mineral information, data and localities". mindat.org.
- ^ "Publications – ExtensionExtension". Ext.colostate.edu. Archived from the original on 2015-09-24. Retrieved 2017-10-18.
- References
- Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.