Cobalt(II) carbonate

Cobalt(II) carbonate is the inorganic compound with the formula CoCO₃. This reddish paramagnetic solid is an intermediate in the hydrometallurgical purification of cobalt from its ores. It is an inorganic pigment, and a precursor to catalysts.[4] Cobalt(II) carbonate also occurs as the rare red/pink mineral spherocobaltite.[5]

Cobalt(II) carbonate

Names
IUPAC name Cobalt(II) carbonate
Other names Cobaltous carbonate; cobalt(II) salt
Identifiers
CAS Number	513-79-1^Y 12602-23-2 (cobalt carbonate hydroxide)^Y
3D model (JSmol)	Interactive image
ChemSpider	10123^N
ECHA InfoCard	100.007.428
PubChem CID	10565
UNII	7H73A68FUV^Y W58TNI7T29 (cobalt carbonate hydroxide)^Y
CompTox Dashboard (EPA)	DTXSID7052151
InChI InChI=1S/CH2O3.Co/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2^N Key: ZOTKGJBKKKVBJZ-UHFFFAOYSA-L^N InChI=1/CH2O3.Co/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2 Key: ZOTKGJBKKKVBJZ-NUQVWONBAB
SMILES C(=O)([O-])[O-].[Co+2]
Properties
Chemical formula	CoCO3
Molar mass	118.941 g/mol
Appearance	red/ pink crystals (anhydrous) pink, violet, red crystalline powder (hexahydrate)
Density	4.13 g/cm^3
Melting point	427 °C (801 °F; 700 K) [1] decomposes before melting to cobalt(II) oxide (anhydrous) 140 °C (284 °F; 413 K) decomposes (hexahydrate)
Solubility in water	Cobalt (II) Carbonate is insoluble in distilled water.
Solubility product (Ksp)	1.0·10^−10[2]
Solubility	soluble in acid negligible in alcohol, methyl acetate insoluble in ethanol
Refractive index (nD)	1.855
Structure
Crystal structure	Rhombohedral (anhydrous) Trigonal (hexahydrate)
Thermochemistry
Std molar entropy (S^o298)	79.9 J/mol·K[1]
Std enthalpy of formation (ΔfH^⦵298)	−722.6 kJ/mol[1]
Gibbs free energy (ΔfG˚)	-651 kJ/mol[1]
Hazards
GHS pictograms	[3]
GHS Signal word	Warning
GHS hazard statements	H302, H315, H317, H319, H335, H351[3]
GHS precautionary statements	P261, P280, P305+351+338[3]
NFPA 704 (fire diamond)	0 2 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	640 mg/kg (oral, rats)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is ^YN ?)
Infobox references

Preparation and structure

It is prepared by combining solutions cobaltous sulfate and sodium bicarbonate:

CoSO₄ + 2 NaHCO₃ → CoCO₃ + Na₂SO₄ + H₂O + CO₂

CoCO₃ adopts a structure like calcite, consisting of cobalt in an octahedral coordination geometry.[6]

Reactions

Heating the carbonate, proceeds in a typical way for calcining, except that the material is partially oxidized:

6 CoCO₃ + O₂ → 2Co₃O₄ + 6 CO₂

The resulting Co₃O₄ converts reversibly to CoO at high temperatures.[7] Like most transition metal carbonates, cobalt carbonate is insoluble in water, but is readily attacked by mineral acids:

CoCO₃ + 2 HCl + 5 H₂O → [Co(H₂O)₆]Cl₂ + CO₂

It is used to prepare many coordination complexes. The reaction of cobalt(II) carbonate and acetylacetone in the presence of hydrogen peroxide gives tris(acetylacetonato)cobalt(III).[8] These complexes are chiral and often can be resolved into the individual enantiomers.

Uses

Cobalt carbonate is a precursor to cobalt carbonyl and various cobalt salts. It is a component of dietary supplements since cobalt is an essential element. It is a precursor to blue pottery glazes, famously in the case of Delftware.

Natural occurrence

The moderately rare spherocobaltite is the natural form of cobalt carbonate, with good specimens coming especially from the Republic of Congo. Cobaltocalcite is a cobaltiferous calcite variety that is quite similar in habit to spherocobaltite.[5]

Safety

The compound is harmful if swallowed, and irritating to eyes and skin.

References

1. http://chemister.ru/Database/properties-en.php?dbid=1&id=573
2. "Archived copy". Archived from the original on 2012-06-15. Retrieved 2012-05-17.CS1 maint: archived copy as title (link)
3. Sigma-Aldrich Co., Cobalt(II) carbonate. Retrieved on 2014-05-06.
4. John Dallas Donaldson, Detmar Beyersmann, "Cobalt and Cobalt Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a07_281.pub2
5. "Spherocobaltite: Spherocobaltite mineral information and data". www.mindat.org. Retrieved 7 August 2018.
6. Pertlik, F. (1986). "Structures of hydrothermally synthesized cobalt(II) carbonate and nickel(II) carbonate". Acta Crystallographica Section C. 42: 4–5. doi:10.1107/S0108270186097524.
7. G.A. El-Shobaky, A.S. Ahmad, A.N. Al-Noaimi and H.G. El-Shobaky Journal of Thermal Analysis and Calorimetry 1996, Volume 46, Number 6 , pp.1801-1808. online abstract
8. Bryant, Burl E.; Fernelius, W. Conard (1957). "Cobalt(III) Acetylacetonate". Inorganic Syntheses. pp. 188–189. doi:10.1002/9780470132364.ch53. ISBN 9780470132364.

External links

• Media related to Cobalt(II) carbonate at Wikimedia Commons