magnesium chloride

Magnesium chloride can be extracted from brine or sea water. In North America and South America, it is obtained primarily from Great Salt Lake brine. In the Jordan Valley, it is obtained from the Dead Sea. The mineral bischofite ({{chem2|MgCl2*6H2O}}) is extracted (by solution mining) out of ancient seabeds, for example, the Zechstein seabed in northwest Europe. Some deposits result from high content of magnesium chloride in the primordial ocean.{{cite journal |author=Hisahiro Ueda and Takazo Shibuya|title=Composition of the Primordial Ocean Just after Its Formation: Constraints from the Reactions between the Primitive Crust and a Strongly Acidic, CO2-Rich Fluid at Elevated Temperatures and Pressures |journal=Minerals |year=2021 |volume=11 |issue=4 |page=389 |publisher=Minerals 2021, 11(4), p. 389|doi=10.3390/min11040389 |bibcode=2021Mine...11..389U |doi-access=free }} Some magnesium chloride is made from evaporation of seawater.

In the Dow process, magnesium chloride is regenerated from magnesium hydroxide using hydrochloric acid:

:{{chem2|Mg(OH)2(s) + 2 HCl(aq) → MgCl2(aq) + 2 H2O(l)}}

It can also be prepared from magnesium carbonate by a similar reaction.

{{chem2|MgCl2}} crystallizes in the cadmium chloride {{chem2|CdCl2}} motif, therefore it loses water upon heating: n = 12 (−16.4 °C), 8 (−3.4 °C), 6 (116.7 °C), 4 (181 °C), 2 (about 300 °C).Holleman, A. F.; Wiberg, E. Inorganic Chemistry Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}. In the hexahydrate, the {{chem2|Mg(2+)}} is also octahedral, being coordinated to six water ligands.Wells, A. F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. {{ISBN|0-19-855370-6}}. The octahydrate and the dodecahydrate can be crystallized from water below 298K. As verified by X-ray crystallography, these "higher" hydrates also feature [Mg(H₂O)₆]²⁺ ions.{{cite journal |doi=10.1107/S0108270113028138 |title=Crystal Structures of Hydrates of Simple Inorganic Salts. I. Water-Rich Magnesium Halide Hydrates MgCl₂·8H₂O, MgCl₂·12H₂O, MgBr₂·6H₂O, MgBr₂·9H₂O, MgI₂·8H₂O and MgI₂·9H₂O |date=2013 |last1=Hennings |first1=Erik |last2=Schmidt |first2=Horst |last3=Voigt |first3=Wolfgang |journal=Acta Crystallographica Section C Crystal Structure Communications |volume=69 |issue=11 |pages=1292–1300 |pmid=24192174 }} A decahydrate has also been crystallized.{{cite journal |doi=10.1107/S205252061500027X |title=Crystal structure of magnesium dichloride decahydrate determined by X-ray and neutron diffraction under high pressure |date=2015 |last1=Komatsu |first1=Kazuki |last2=Shinozaki |first2=Ayako |last3=Machida |first3=Shinichi |last4=Matsubayashi |first4=Takuto |last5=Watanabe |first5=Mao |last6=Kagi |first6=Hiroyuki |last7=Sano-Furukawa |first7=Asami |last8=Hattori |first8=Takanori |journal=Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials |volume=71 |issue=Pt 1 |pages=74–80 |pmid=25643718 }}

Anhydrous {{chem2|MgCl2}} is produced industrially by heating the complex salt named hexamminemagnesium dichloride {{chem2|[Mg(NH3)6](2+)(Cl−)2}}. The thermal dehydration of the hydrates {{chem2|MgCl2*nH2O}} (n = 6, 12) does not occur straightforwardly.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). {{cite web |url=http://www.orgsyn.org/orgsyn/pdfs/CV6P0845.pdf |title=Archived copy |access-date=2007-05-10 |url-status=dead |archive-url=https://web.archive.org/web/20070930212159/http://www.orgsyn.org/orgsyn/pdfs/CV6P0845.pdf |archive-date=2007-09-30 }}

As suggested by the existence of hydrates, anhydrous {{chem2|MgCl2}} is a Lewis acid, although a weak one. One derivative is tetraethylammonium tetrachloromagnesate {{chem2|[N(CH2CH3)4]2[MgCl4]}}. The adduct {{chem2|MgCl2(TMEDA)}} is another.N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984. In the coordination polymer with the formula {{chem2|MgCl2(dioxane)2}}, Mg adopts an octahedral geometry.{{cite journal |doi=10.1002/chem.201903120|title=Structure–Solubility Relationship of 1,4-Dioxane Complexes of Di(hydrocarbyl)magnesium |year=2019 |last1=Fischer |first1=Reinald |last2=Görls |first2=Helmar |last3=Meisinger |first3=Philippe R. |last4=Suxdorf |first4=Regina |last5=Westerhausen |first5=Matthias |journal=Chemistry – A European Journal |volume=25 |issue=55 |pages=12830–12841 |pmid=31328293 |pmc=7027550 }} The Lewis acidity of magnesium chloride is reflected in its deliquescence, meaning that it attracts moisture from the air to the extent that the solid turns into a liquid.

Anhydrous {{chem2|MgCl2}} is the main precursor to metallic magnesium. The reduction of {{chem2|Mg(2+)}} into metallic Mg is performed by electrolysis in molten salt.{{Ullmann | title = Magnesium Compounds | author1 = Margarete Seeger | author2 = Walter Otto | author3 = Wilhelm Flick | author4 = Friedrich Bickelhaupt | author5 = Otto S. Akkerman | doi = 10.1002/14356007.a15_595.pub2}}Hill, Petrucci, McCreary, Perry, General Chemistry, 4th ed., Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA. 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 {{chem2|H+}} would be reduced into gaseous {{chem2|H2}} before Mg reduction could occur. So, the direct electrolysis of molten {{chem2|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 E_h–pH diagram (Pourbaix diagram).

:{{chem2|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.

Magnesium chloride is one of many substances used for dust control, soil stabilization, and wind erosion mitigation.{{cite web |url=http://www.fs.fed.us/eng/pubs/html/99771207/99771207.html#EI |title=Dust Palliative Selection and Application Guide |publisher=Fs.fed.us |access-date=2017-10-18}} 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.{{Cite web |title=FSE Documents |url=https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1043546.pdf |url-status=dead |archive-url=https://web.archive.org/web/20221016220324/https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1043546.pdf |archive-date=2022-10-16 |website=www.nrcs.usda.gov}}

Ziegler-Natta catalysts, used commercially to produce polyolefins, often contain {{chem2|MgCl2}} as a catalyst support.{{cite book|chapter=Commercially Available Metal Alkyls and Their Use in Polyolefin Catalysts|editor=Ray Hoff |editor2=Robert T. Mathers|author=Dennis B. Malpass|doi=10.1002/9780470504437.ch1|year=2010|publisher= John Wiley & Sons, Inc.|title= Handbook of Transition Metal Polymerization Catalysts|pages=1–28|isbn=9780470504437}} The introduction of {{chem2|MgCl2}} supports increases the activity of traditional catalysts and allowed the development of highly stereospecific catalysts for the production of polypropylene.{{cite journal |title=The Discovery and Progress of MgCl₂-Supported TiCl₄ Catalysts |author=Norio Kashiwa |doi=10.1002/pola.10962 |journal=Journal of Polymer Science A |volume=42 |issue=1 |year=2004 |pages=1–8|bibcode=2004JPoSA..42....1K }}

Magnesium chloride is also a Lewis acid catalyst in aldol reactions.{{cite journal |doi=10.1021/ja0119548|title=Diastereoselective Magnesium Halide-Catalyzed anti-Aldol Reactions of Chiral N-Acyloxazolidinones |year=2002 |last1=Evans |first1=David A. |last2=Tedrow |first2=Jason S. |last3=Shaw |first3=Jared T. |last4=Downey |first4=C. Wade |journal=Journal of the American Chemical Society |volume=124 |issue=3 |pages=392–393 |pmid=11792206 }}

{{Main article|Road salt}}

File:Snow-removal-cleveland-1.jpg

Magnesium chloride is used for low-temperature de-icing of highways, sidewalks, and parking lots. When highways have dangerous ice buildup, road maintainers apply magnesium chloride to deter 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.Jain, J., Olek, J., Janusz, A., and Jozwiak-Niedzwiedzka, D., "Effects of Deicing Salt Solutions on Physical Properties of Pavement Concretes", Transportation Research Record: Journal of the Transportation Research Board, No. 2290, Transportation Research Board of the National Academies, Washington, D.C., 2012, pp. 69-75. {{doi|10.3141/2290-09}}. 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.{{Cite journal|last1=Dai|first1=H.L.|last2=Zhang|first2=K.L.|last3=Xu|first3=X.L.|last4=Yu|first4=H.Y.|date=2012|title=Evaluation on the Effects of Deicing Chemicals on Soil and Water Environment|journal=Procedia Environmental Sciences|language=en|volume=13|pages=2122–2130|doi=10.1016/j.proenv.2012.01.201|doi-access=free|bibcode=2012PrEnS..13.2122D }}

Magnesium chloride is used in nutraceutical and pharmaceutical preparations. The hexahydrate is sometimes advertised as "magnesium oil". Magnesium Chloride is also an electrolyte.

Magnesium chloride (E511{{cite web

| last = Food Standard Agency

| author-link = Food Standard Agency

| title = Current EU approved additives and their E Numbers

| url = http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist

| access-date = 22 March 2010

}}) is an important coagulant used in the preparation of tofu from soy milk.

In Japan it is sold as nigari (にがり, 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 (卤水).

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.

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).{{cite journal |title=Comparison of Magnesium Sulfate and THIS Mg Chelate Foliar Sprays |journal=Canadian Journal of Plant Science |date=January 1985 |doi=10.4141/cjps85-018 }} This is due primarily to the chlorine present in magnesium chloride, which can easily reach toxic levels if over-applied or applied too often.{{cite web |url=http://www.ext.colostate.edu/pubs/garden/07425.html |title=Magnesium Chloride Toxicity in Trees |publisher=Ext.colostate.edu |access-date=2017-10-18 |archive-date=2009-01-15 |archive-url=https://web.archive.org/web/20090115223000/http://www.ext.colostate.edu/pubs/garden/07425.html |url-status=dead }}

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.{{cite web |url=http://www.apsnet.org/publications/plantdisease/backissues/Documents/1983Articles/PlantDisease67n06_623.pdf |title=Effect of Foliar and Soil Magnesium Application on Bacterial Leaf Spot of Peppers |access-date=2017-10-18}}

It is used to supply the magnesium necessary to precipitate phosphorus in the form of struvite from agricultural waste{{cite journal |last1=BURNS |first1=R.T. |title=Laboratory and In-Situ Reductions of Soluble Phosphorus in Swine Waste Slurries |journal=Environmental Technology |date=15 January 2001 |volume=22 |issue=11 |pages=1273–1278 |doi=10.1080/09593332208618190 |pmid=11804348 |bibcode=2001EnvTe..22.1273B |url=http://www.stormwater.ucf.edu/chemicaltreatment/documents/Burns%20et%20al.,%202001.pdf |archive-url=https://web.archive.org/web/20120327181220/http://www.stormwater.ucf.edu/chemicaltreatment/documents/Burns%20et%20al.,%202001.pdf |access-date=30 December 2023|archive-date=2012-03-27 }} as well as human urine.

File:Sea salt-e-dp hg.svg

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|reason=which carbonates and calcium in what form?|date=June 2022}} 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.{{cite web |url=http://www.advancedaquarist.com/issues/oct2003/chem.htm |title=Aquarium Chemistry: Magnesium In Reef Aquaria — Advanced Aquarist | Aquarist Magazine and Blog |publisher=Advancedaquarist.com |date=2003-10-15 |access-date=2013-01-17}} The most common mineral form of magnesium chloride is its hexahydrate, bischofite.{{Cite web |title=Bischofite: Mineral information, data and localities |url=https://www.mindat.org/min-681.html |website=mindat.org}}{{Cite web |date=21 March 2011 |title=List of Minerals |url=https://www.ima-mineralogy.org/Minlist.htm |website=International Mineralogical Association}} Anhydrous compound occurs very rarely, as chloromagnesite. Magnesium chloride-hydroxides, korshunovskite and nepskoeite, are also very rare.{{Cite web |title=Korshunovskite: Mineral information, data and localities |url=https://www.mindat.org/min-2256.html |website=mindat.org}}{{Cite web |title=Nepskoeite: Mineral information, data and localities |url=https://www.mindat.org/min-7189.html |website=mindat.org}}

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 urine by the kidneys. A few cases of oral magnesium toxicity have been described in persons with normal renal function ingesting large amounts of magnesium salts, but it is rare. If a large amount of magnesium chloride is eaten, it will have effects similar to magnesium sulfate, causing diarrhea, although the sulfate also contributes to the laxative effect in magnesium sulfate, so the effect from the chloride is not as severe.

Chloride ({{chem2|Cl−}}) and magnesium ({{chem2|Mg(2+)}}) 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 {{chem2|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.{{cite web |url=http://www.ext.colostate.edu/pubs/garden/07425.html |title=Publications – ExtensionExtension |publisher=Ext.colostate.edu |access-date=2017-10-18 |archive-url=https://web.archive.org/web/20150924005210/http://www.ext.colostate.edu/pubs/garden/07425.html |archive-date=2015-09-24 |url-status=dead }}

• Acceptable daily intake
• Sorel cement

;Notes

{{Reflist|30em}}

;References

• Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.

• [https://web.archive.org/web/20040314010235/http://www.usda.gov/rus/electric/engineering/2001/magnesium_chloride.htm Magnesium Chloride as a De-Icing Agent]
• [http://www.mistralni.co.uk/msds/mmgc200.gdsbusapb.pdf MSDS file for Magnesium Chloride Hexahydrate]

{{Magnesium compounds}}

{{Chlorides}}

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Category:Chlorides

Category:Magnesium compounds

Category:Alkaline earth metal halides

Category:Deliquescent materials

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Category:E-number additives