Magnesium carbonate

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Magnesium carbonate
Magnesium carbonate.png
Uhličitan hořečnatý.PNG
Identifiers
CAS number 546-93-0 (anhydrous) YesY
13717-00-5 (monohydrate),
5145-48-2 (dihydrate),
14457-83-1 (trihydrate),
61042-72-6 (pentahydrate)
PubChem 11029
ChemSpider 10563 YesY
ChEBI CHEBI:31793 YesY
ChEMBL CHEMBL1200736 N
RTECS number OM2470000
ATC code A02AA01,A06AD01
Jmol-3D images Image 1
Properties
Molecular formula CMgO3
Molar mass 84.31 g mol−1
Appearance white solid
hygroscopic
Odor odorless
Density 2.958 g/cm3 (anhydrous)
2.825 g/cm3 (dihydrate)
1.837 g/cm3 (trihydrate)
1.73 g/cm3 (pentahydrate)
Melting point 540 °C (1,004 °F; 813 K)
decomposes (anydrous)
165 °C (329 °F; 438 K)
(trihydrate)
Solubility in water anhydrous:
0.0106 g/100ml (25 °C)
0.0063 g/100ml (100 °C)[1]
pentahydrate:
0.375 g/100ml (20 °C)
Solubility product, Ksp 10−7.8[2]
Solubility soluble in acid, aqueous CO2
insoluble in acetone, ammonia
Refractive index (nD) 1.717 (anhydrous)
1.458 (dihydrate)
1.412 (trihydrate)
Structure
Crystal structure Trigonal
Thermochemistry
Specific
heat capacity
C
75.6 J/mol·K[1]
Std molar
entropy
So298
65.7 J/mol·K[1][3]
Std enthalpy of
formation
ΔfHo298
-1113 kJ/mol[3]
Gibbs free energy ΔG -1029.3 kJ/mol[1]
Hazards
MSDS ICSC 0969
EU Index Not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions Magnesium bicarbonate
Other cations Beryllium carbonate
Calcium carbonate
Strontium carbonate
Barium carbonate
Related compounds Artinite
Hydromagnesite
Dypingite
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Magnesium carbonate, MgCO3, is an inorganic salt that is a white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals.

Forms[edit]

The most common magnesium carbonate forms are the anhydrous salt called magnesite (MgCO3) and the di, tri, and pentahydrates known as barringtonite (MgCO3·2 H2O), nesquehonite (MgCO3·3 H2O), and lansfordite (MgCO3·5 H2O), respectively.[4] Some basic forms such as artinite (MgCO3·Mg(OH)2·3 H2O), hydromagnesite (4 MgCO3·Mg(OH)2·4 H2O), and dypingite (4 MgCO3· Mg(OH)2·5 H2O) 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 Mg2+ 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).[5]

Preparation[edit]

  • Magnesium carbonate is ordinarily obtained by mining the mineral magnesite.
  • Laboratory synthesis is simple: a metathesis reaction combining any soluble magnesium salt with sodium carbonate in solution, precipitating magnesium carbonate.
MgSO4(aq) + Na2CO3(aq) → MgCO3(s) + Na2SO4(aq)
Mg(OH)2 + 2 CO2 → Mg(HCO3)2
Mg(HCO3)2 → MgCO3 + CO2 + H2O

Reactions[edit]

With acids[edit]

Like many common carbonates, magnesium carbonate reacts with acids to release carbon dioxide and water:

MgCO3 + 2 HCl → MgCl2 + CO2 + H2O
MgCO3 + H2SO4 → MgSO4 + CO2 + H2O

Decomposition[edit]

At high temperatures MgCO3 decomposes to magnesium oxide and carbon dioxide. This process is important in the production of magnesium oxide.[4] This process is called calcining:

MgCO3 → MgO + CO2 (ΔH = +118 kJ/mol)

There is a lot of conflicting information about the decomposition temperature.

  • Iowa State has an MSDS which shows 350 °C[6]
  • The original text here had 400 °C[7]
  • The original chembox here had 540 °C[8]
  • CMU offers a Gibbs free energy model[9] which gives 575K (302 °C)
  • Science Lab has an MSDS which shows 662 °C[10]

Uses[edit]

The primary use of magnesium carbonate is the production of magnesium oxide by calcining (see #Reactions). Magnesite and dolomite minerals are used to produce refractory bricks.[4] MgCO3 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, hygroscopic properties MgCO3 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 MgCO3-containing salt would not stick together in humid weather.[11] Magnesium carbonate, most often referred to as 'chalk', is used as a drying agent for hands in rock climbing, gymnastics, and weight lifting.

As a food additive magnesium carbonate is known as E504, for which the only known side effect is that it may work as a laxative in high concentrations.[12]

Magnesium carbonate is also used in taxidermy for whitening skulls. It can be mixed with hydrogen peroxide to create a paste, which is then spread on the skull to give it a white finish.

Safety[edit]

Magnesium carbonate itself is not toxic. It is slightly hazardous in case of skin and eye contact[citation needed] and may cause respiratory and digestive tract irritation in case of ingestion or inhalation.

Compendial status[edit]

Notes and references[edit]

  1. ^ a b c d http://chemister.ru/Database/properties-en.php?dbid=1&id=634
  2. ^ Bénézeth, Pascale, et al. "Experimental determination of the solubility product of magnesite at 50 to 200 C." Chemical Geology 286.1 (2011): 21-31.
  3. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X. 
  4. ^ a b c d Margarete Seeger; Walter Otto; Wilhelm Flick; Friedrich Bickelhaupt; Otto S. Akkerman (2005), "Magnesium Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a15_595.pub2 
  5. ^ Botha, A.; Strydom, C.A. (2001). "Preparation of a magnesium hydroxy carbonate from magnesium hydroxide". Hydrometallurgy 62 (3): 175. doi:10.1016/S0304-386X(01)00197-9. 
  6. ^ "IAState MSDS". 
  7. ^ "prior Wikipedia "reactions" text". 
  8. ^ "prior Wikipedia "chembox" value". 
  9. ^ "CMU Gibbs model". 
  10. ^ "Science Lab MSDS". 
  11. ^ "Morton Salt FAQ". Retrieved 2007-05-14. 
  12. ^ "Food-Info.net : E-numbers : E504: Magnesium carbonates".  080419 food-info.net
  13. ^ British Pharmacopoeia Commission Secretariat (2009). "Index, BP 2009". Retrieved 31 January 2010. 
  14. ^ "Japanese Pharmacopoeia, Fifteenth Edition". 2006. Retrieved 31 January 2010. 

See also[edit]

External links[edit]

H2CO3 He
LiCO3 BeCO3 B C (NH4)2CO3,
NH4HCO3
O F Ne
Na2CO3,
NaHCO3,
Na3H(CO3)2
MgCO3,
Mg(HCO3)2
Al2(CO3)3 Si P S Cl Ar
K2CO3,
KHCO3
CaCO3,
Ca(HCO3)2
Sc Ti V Cr MnCO3 FeCO3 CoCO3 NiCO3 CuCO3 ZnCO3 Ga Ge As Se Br Kr
Rb2CO3 SrCO3 Y Zr Nb Mo Tc Ru Rh Pd Ag2CO3 CdCO3 In Sn Sb Te I Xe
Cs2CO3,
CsHCO3
BaCO3   Hf Ta W Re Os Ir Pt Au Hg Tl2CO3 PbCO3 (BiO)2CO3 Po At Rn
Fr Ra   Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo
La2(CO3)3 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Ac Th Pa UO2CO3 Np Pu Am Cm Bk Cf Es Fm Md No Lr