Nesquehonite

Magnesium carbonate

Names
Other names Magnesite Barringtonite (dihydrate) Nesequehonite (trihydrate) Lansfordite (pentahydrate)
Identifiers
CAS Number	546-93-0 (anhydrous) Y 13717-00-5 (monohydrate) N 5145-48-2 (dihydrate) N 14457-83-1 (trihydrate) N 61042-72-6 (pentahydrate) N
3D model (JSmol)	Interactive image
ChEBI	CHEBI:31793 Y
ChemSpider	10563 Y
ECHA InfoCard	100.008.106
E number	E504 (acidity regulators, ...)
PubChem CID	11029
RTECS number	OM2470000
InChI InChI=1S/CH2O3.Mg/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2 Y Key: ZLNQQNXFFQJAID-UHFFFAOYSA-L Y InChI=1/CH2O3.Mg/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2 Key: ZLNQQNXFFQJAID-NUQVWONBAU
SMILES [Mg+2].[O-]C([O-])=O
Properties
Chemical formula	MgCO3
Molar mass	84.3139 g/mol (anhydrous)
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	350 °C (662 °F; 623 K) decomposes (anydrous) 165 °C (329 °F; 438 K) (trihydrate)
Solubility in water	anhydrous: 0.0139 g/100ml (25 °C) 0.00603 g/100ml (100 °C)
Solubility product (Ksp)	10−7.8
Solubility	soluble in acid, aqueous CO2 insoluble in acetone, ammonia
Magnetic susceptibility (χ)	−32.4·10−6 cm3/mol
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
Std molar entropy (So298)	65.7 J/mol·K
Std enthalpy of formation (ΔfHo298)	-1113 kJ/mol
Gibbs free energy (ΔfG˚)	-1029.3 kJ/mol
Pharmacology
ATC code	A02AA01 (WHO) A06AD01 (WHO)
Hazards
Safety data sheet	ICSC 0969
NFPA 704	0 1 0
Flash point	Non-flammable
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)
Related compounds
Other anions	Magnesium bicarbonate
Other cations	Beryllium carbonate Calcium carbonate Strontium carbonate Barium carbonate
Related compounds	Artinite Hydromagnesite Dypingite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

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

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. 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).