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
Cobalt(II) carbonate powder
Names
IUPAC name
Cobalt(II) carbonate
Other names
Cobaltous carbonate; cobalt(II) salt
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.007.428
UNII
  • 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
  • C(=O)([O-])[O-].[Co+2]
Properties
CoCO3
Molar mass 118.941 g/mol
Appearance red-pink solid
Density 4.13 g/cm3
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)
Cobalt (II) Carbonate is insoluble in distilled water.
1.0·10−10[2]
Solubility soluble in acid
negligible in alcohol, methyl acetate
insoluble in ethanol
1.855
Structure
Rhombohedral (anhydrous)
Trigonal (hexahydrate)
Thermochemistry
79.9 J/mol·K[1]
−722.6 kJ/mol[1]
-651 kJ/mol[1]
Hazards
GHS labelling:
GHS07: Exclamation markGHS08: Health hazard[3]
Warning
H302, H315, H317, H319, H335, H351[3]
P261, P280, P305+P351+P338[3]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
2
0
0
Lethal dose or concentration (LD, LC):
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 checkY☒N ?)
Infobox references

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.[4]

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

Reactions

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).[7]

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.[8]

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.

At least two cobalt(II) carbonate-hydroxides are known: Co2(CO3)(OH)2 and Co6(CO3)2(OH)8·H2O.[9]

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.[5]

Safety

Toxicity has rarely been observed. Animals, including humans, require trace amounts of cobalt, a component of vitamin B12.[4]

References
  1. "Cobalt(II) carbonate".
  2. "Solubility product constants". Archived from the original on 2012-06-15. Retrieved 2012-05-17.
  3. Sigma-Aldrich Co., Cobalt(II) carbonate. Retrieved on 2014-05-06.
  4. 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.
  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. Bryant, Burl E.; Fernelius, W. Conard (1957). "Cobalt(III) Acetylacetonate". Inorganic Syntheses. pp. 188–189. doi:10.1002/9780470132364.ch53. ISBN 9780470132364.
  8. 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
  9. 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.
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