Cobalt(II) oxide

Cobalt(II) oxide
IUPAC name
Cobalt(II) oxide
Other names
Cobaltous oxide
Cobalt monoxide
1307-96-6 YesY
3D model (Jmol) Interactive image
Interactive image
ChemSpider 8117730 YesY
ECHA InfoCard 100.013.777
EC Number 215-154-6
PubChem 9942118
RTECS number GG2800000
UN number 3288
Molar mass 74.9326 g/mol
Appearance black powder
Odor odorless
Density 6.44 g/cm3 [1]
Melting point 1,933 °C (3,511 °F; 2,206 K)
insoluble in water[2]
cubic, cF8
Fm3m, No. 225
Safety data sheet ICSC 1551
Harmful (Xn)
Dangerous for the environment (N)
R-phrases R22, R43, R50/53
S-phrases (S2), S24, S37, S60, S61
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
202 mg/kg
Related compounds
Other anions
Cobalt(II) sulfide
Cobalt(II) hydroxide
Other cations
Iron(II) oxide
Nickel(II) oxide
Related compounds
Cobalt(II,III) oxide
Cobalt(III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Cobalt(II) oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder.[3] It is used extensively in the ceramics industry as an additive to create blue colored glazes and enamels as well as in the chemical industry for producing cobalt(II) salts.

Structure and properties

CoO crystals adopt the periclase (rock salt) structure with a lattice constant of 4.2615 Å.[4]

It is antiferromagnetic below 16 °C.[5]


Cobalt(II,III) oxide decomposes to cobalt(II) oxide at 950 °C:[6]

2 Co3O4 → 6 CoO + O2

Though commercially available, cobalt(II) oxide may be prepared in the laboratory by electrolyzing a solution of cobalt(II) chloride.[7]

CoCl2 + H2O → CoO + H2 + Cl2

It may also be prepared by precipitating the hydroxide, followed by thermal dehydration:

CoX + 2 KOH → Co(OH)2 + K2X
Co(OH)2 → CoO + H2O


As can be expected, cobalt(II) oxide reacts with mineral acids to form the corresponding cobalt salts:

CoO + 2 HX → CoX2 + H2O


Cobalt(II) oxide has for centuries used as a coloring agent on kiln fired pottery. The additive provides a deep shade of blue named cobalt blue. The band gap (CoO) is around 2.4 eV. It also is used in cobalt blue glass.

See also


  1. Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. ISBN 0-07-049439-8. Retrieved 2009-06-06.
  2. Advanced Search – Alfa Aesar – A Johnson Matthey Company. Retrieved on 2011-11-19.
  3. "Safety (MSDS) data for cobalt oxide". The Physical and Theoretical Chemistry Laboratory, Oxford University. Retrieved 2008-11-11.
  4. Kannan, R.; Seehra, Mohindar S. (1987). "Percolation effects and magnetic properties of the randomly diluted fcc system CopMg1-pO". Physical Review B. 35 (13): 6847–6853. doi:10.1103/PhysRevB.35.6847.
  5. Silinsky, P. S.; Seehra, Mohindar S. (1981). "Principal magnetic susceptibilities and uniaxial stress experiments in CoO". Physical Review B. 24: 419–423. doi:10.1103/PhysRevB.24.419.
  6. US 4389339, James, Leonard E.; Crescentini, Lamberto & Fisher, William B., "Process for making a cobalt oxide catalyst"
  7. Kern, S. (1876). "Inorganic chemistry". J. Chem. Soc. 29: 880. doi:10.1039/JS8762900876.
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