Magnesium carbonate
383220
223887897
2008-07-06T10:16:00Z
222.166.160.141
/* Forms */
{{Chembox new
| Name = Magnesium carbonate
| ImageFile=Magnesium carbonate.png
| ImageSize=120px
| OtherNames = [[Magnesite]]<br />dihydrate: [[Barringtonite]]<br />trihydrate: [[Nesequehonite]]<br />pentahydrate: [[Lansfordite]]<Br/>White gold:
| Name = Safety data
| Section1 = {{Chembox Identifiers
| CASNo = 546-93-0
| RTECS = OM2470000
}}
| Section2 = {{Chembox Properties
| Formula = MgCO<sub>3</sub>
| MolarMass = 84.32 g/mol
| Appearance = white solid
| Density = 2.958 g/cm<sup>3</sup>, solid
| Solubility = 10.6 mg/100 ml
| MeltingPt = 350 °C ''decomp.''
}}
| Section3 = {{Chembox Structure
| Coordination =
| CrystalStruct = [[Trigonal]]
}}
| Section4 = {{Chembox Thermochemistry
| DeltaHf = -1111.69 kJ/mol
| Entropy = 65.84 J.K<sup>−1</sup>.mol<sup>−1</sup>
}}
| Section8 = {{Chembox Related
| OtherCations = [[Calcium carbonate]]<br />[[Strontium carbonate]]<br />[[Barium carbonate]]
| OtherCpds = [[Artinite]]<br />[[Hydromagnesite]]<br />[[Dypingite]]}}
}}
'''Magnesium carbonate''', MgCO<sub>3</sub>, is a white [[solid]] that occurs in nature as a [[mineral]]. Several [[hydrated]] and [[Base (chemistry)|basic]] forms of magnesium carbonate also exist as [[mineral]]s. In addition, MgCO<sub>3</sub> has a variety of applications.
==Forms==
The most common magnesium carbonate forms are the [[anhydrous]] salt called ''[[magnesite]]'' (MgCO<sub>3</sub>) and the di, tri, and pentahydrates known as ''barringtonite'' (MgCO<sub>3</sub>·2H<sub>2</sub>O), ''nesquehonite'' (MgCO<sub>3</sub>·3H<sub>2</sub>O), and ''lansfordite'' (MgCO<sub>3</sub>·5H<sub>2</sub>O), respectively. Some basic forms such as ''artinite'' (MgCO<sub>3</sub>·Mg(OH)<sub>2</sub>·3H<sub>2</sub>O), ''hydromagnestite'' (4MgCO<sub>3</sub>·Mg(OH)<sub>2</sub>·4H<sub>2</sub>O), and ''dypingite'' (4MgCO<sub>3</sub>· Mg(OH)<sub>2</sub>·5H<sub>2</sub>O) also occur as [[minerals]]. Magnesite consists of white [[trigonal]] [[crystals]]. The [[anhydrous]] salt is practically [[insoluble]] in [[water]], [[acetone]], and [[ammonia]]. All forms of magnesium carbonate react in [[acids]]. Magnesium carbonate crystallizes in the [[calcite]] structure where in [[magnesium|Mg<sup>2+</sup>]] is surrounded by six [[oxygen]] atoms. The dihydrate one has a [[triclinic]] structure, while the trihydrate has a [[monoclinic]] structure.
References to 'light' and 'heavy' magnesium carbonates actually refer to the magnesium hydroxy carbonates [[hydromagnesite]] and [[dypingite]] (respectively)<ref>A. BOTHA and C. A. STRYDOM; “Preparation of a magnesium hydroxy carbonate from magnesium hydroxide;” Hydrometallurgy; Elsevier Science; December 2001; 62 (3): pp. 175–183.</ref>.
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==Properties==
Magnesium carbonate has properties as given in this article.
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==Reactions==
Although magnesium carbonate is ordinarily obtained by mining the mineral magnesite, the trihydrate salt, MgCO<sub>3</sub>·3H<sub>2</sub>O, can be prepared by mixing [[solutions]] of [[magnesium]] and [[carbonate]] [[ions]] under an atmosphere of [[carbon dioxide]]. Magnesium carbonate can also be synthesized by exposing a [[magnesium hydroxide]] slurry to [[carbon dioxide]] under [[pressure]] (3.5 to 5 atm) below 50 °C, which gives soluble magnesium bicarbonate:
::Mg(OH)<sub>2</sub> + 2 CO<sub>2</sub> → Mg(HCO<sub>3</sub>)<sub>2</sub><br />
Following the filtration of the solution, the filtrate is dried under vacuum to produce magnesium carbonate as a hydrated salt:
::Mg<sup>2+</sup> + 2 HCO<sub>3</sub><sup>-</sup> → MgCO<sub>3</sub> + CO<sub>2</sub> + H<sub>2</sub>O<br />
When dissolved with [[acid]], magnesium carbonate decomposes with release of [[carbon dioxide]]:
::MgCO<sub>3</sub> + 2 HCl → MgCl<sub>2</sub> + CO<sub>2</sub> + H<sub>2</sub>O<br />
::MgCO<sub>3</sub> + H<sub>2</sub>SO<sub>4</sub> → MgSO<sub>4</sub> + CO<sub>2</sub> + H<sub>2</sub>O<br />
At high temperatures (800C-1000C), MgCO<sub>3</sub> decomposes to [[magnesium oxide]] and [[carbon dioxide]] with reaction [[enthalpy]] 118 kJ / mole, this process is called [[calcining]]:
::MgCO<sub>3</sub> → MgO + CO<sub>2</sub><br />
==Uses==
Magnesite and [[dolomite]] [[minerals]] are used to produce [[magnesium]] metal and basic refractory bricks. MgCO<sub>3</sub> is also used in flooring, fireproofing, fire extinguishing compositions, cosmetics, dusting powder, and toothpaste. Other applications are as filler material, smoke suppressant in plastics, a reinforcing agent in neoprene rubber, a drying agent, a laxative to loosen the bowels, and color retention in foods. In addition, high purity magnesium carbonate is used as [[antacid]] and as an additive in table salt to keep it free flowing.
Because of its water-insoluble, [[hygroscopy|hygroscopic]] properties MgCO<sub>3</sub> was first added to salt in [[1911]] to make the salt flow more freely. The [[Morton Salt]] company adopted the slogan "When it rains it pours" in reference to the fact that its MgCO<sub>3</sub>-containing salt would not stick together in wet weather.<ref>{{cite web |title=Morton Salt FAQ |url=http://www.mortonsalt.com/faqs/index.html#q3 |access-date = 2007-05-14 }}</ref>
Magnesium carbonate, most often referred to as 'chalk', is used as a drying agent for hands in [[rock climbing]], [[gymnastics]], and [[weight lifting]].
== Food additive ==
As a food additive it's known as E504. And the only known side effect is that it may work as a [[laxative]] in high concentrations. <ref>{{cite web|title=Food-Info.net : E-numbers : E504: Magnesium carbonates|url=http://www.food-info.net/uk/e/e504.htm}} 080419 food-info.net</ref>
== References ==
<references/>
*{{cite web
| title = Magnesium Carbonate Light
| work = Safety Data Sheet
| publisher = Vet Way Limited
| format = pdf
| url = http://www.vet-way.com/liq-pow-pdfs-eng/Magnesium%20Carbonate%20Light.pdf
| accessdate = 2008-01-06
}}<br />
*{{cite book
| first = Pradyot
| last = Patnaik
| year = 2003
| title = Handbook of Inorganic Chemicals
| publisher = McGraw Hill
| location = New York
}}<br />
*{{cite book
| first = A.F "(ed.)"
| last = Trotman-Dickenson
| year = 1973
| title = Comprehensive Inorganic Chemistry
| publisher = Pergamon Press
| location = Oxford
}}<br />
==External links==
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc09/icsc0969.htm International Chemical Safety Card 0969]
*[http://webbook.nist.gov/chemistry/ NIST Standard Reference Database]
[[Category:Magnesium compounds]]
[[Category:Carbonates]]
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