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Cobalt(II) carbonate

Names
IUPAC name Cobalt(II) carbonate
Other names Cobaltous carbonate; cobalt(II) salt
Identifiers
CAS Number	513-79-1 12602-23-2 (cobalt carbonate hydroxide)
3D model (JSmol)	Interactive image
ChemSpider	10123
ECHA InfoCard	100.007.428
PubChem CID	10565
UNII	7H73A68FUV W58TNI7T29 (cobalt carbonate hydroxide)
CompTox Dashboard (EPA)	DTXSID7052151
InChI InChI=1S/CH2O3.Co/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2Key: ZOTKGJBKKKVBJZ-UHFFFAOYSA-L InChI=1/CH2O3.Co/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2Key: ZOTKGJBKKKVBJZ-NUQVWONBAB
SMILES C(=O)().
Properties
Chemical formula	CoCO3
Molar mass	118.941 g/mol
Appearance	pink solid
Density	4.13 g/cm
Melting point	427 °C (801 °F; 700 K) decomposes before melting to cobalt(II) oxide (anhydrous) 140 °C (284 °F; 413 K) decomposes (hexahydrate)
Solubility in water	0.000142 g/100 mL (20 °C)
Solubility product (Ksp)	1.0·10
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 (S298)	79.9 J/mol·K
Std enthalpy of formation (ΔfH298)	−722.6 kJ/mol
Gibbs free energy (ΔfG)	-651 kJ/mol
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H315, H317, H319, H335, H351
Precautionary statements	P261, P280, P305+P351+P338
NFPA 704 (fire diamond)	2 0 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 , 100 kPa). N verify (what is  ?) Infobox references

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

Preparation and structure

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

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

This reaction is used in the precipitation of cobalt from an extract of its roasted ores.

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

Reactions

Like most transition metal carbonates, cobalt carbonate is insoluble in water, but is readily attacked by mineral acids:

CoCO₃ + 2 HCl + 5 H₂O → 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).

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

6 CoCO₃ + O₂ → 2 Co₃O₄ + 6 CO₂

The resulting Co₃O₄ converts reversibly to CoO at high temperatures.

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.

Related compounds

At least two cobalt(II) carbonate-hydroxides are known: Co₂(CO₃)(OH)₂ and Co₆(CO₃)₂(OH)₈·H₂O.

The moderately rare spherocobaltite is a 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.

Safety

Toxicity has rarely been observed. Animals, including humans, require trace amounts of cobalt, a component of vitamin B12.

References

1. Haynes, W.M., ed. (2017). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press, Taylor & Francis Group. pp. 4–58. ISBN 978-1-4987-5429-3.
2. "Solubility product constants". Archived from the original on 2012-06-15. Retrieved 2012-05-17.
3. ^ "Cobalt(II) carbonate".
4. ^ Sigma-Aldrich Co., Cobalt(II) carbonate. Retrieved on 2014-05-06.
5. ^ Donaldson, John Dallas; Beyersmann, Detmar (2005). "Cobalt and Cobalt Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_281.pub2. ISBN 3527306730.
6. ^ "Spherocobaltite: Spherocobaltite mineral information and data". www.mindat.org. Retrieved 7 August 2018.
7. 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.
8. Bryant, Burl E.; Fernelius, W. Conard (1957). "Cobalt(III) Acetylacetonate". Inorganic Syntheses. pp. 188–189. doi:10.1002/9780470132364.ch53. ISBN 9780470132364.
9. 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
10. Bhojane, Prateek; Le Bail, Armel; Shirage, Parasharam M. (2019). "A Quarter of a Century After its Synthesis and with >200 Papers Based on its Use, 'Co(CO₃)_0.5(OH)_0.11H₂O′ Proves to be Co₆(CO₃)₂(OH)₈·H₂O from Synchrotron Powder Diffraction Data". Acta Crystallographica Section C: Structural Chemistry. 75 (Pt 1): 61–64. doi:10.1107/S2053229618017734. PMID 30601132. S2CID 58657483.

External links

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

• Cobalt(II) compounds
• Carbonates