Cobalt(II) oxide
Cobalt(II) oxide
IUPAC name
Cobalt(II) oxide
Other names
Cobaltous oxide
Cobalt monoxide
3D model (JSmol)
ECHA InfoCard 100.013.777 Edit this at Wikidata
EC Number
  • 215-154-6
RTECS number
  • GG2800000
UN number 3288
  • InChI=1S/Co.O/q+2;-2 checkY
  • InChI=1/Co.O/rCoO/c1-2
  • InChI=1/Co.O/q+2;-2
  • [Co]=O
  • [Co+2].[O-2]
Molar mass 74.9326 g/mol
Appearance olive or gray powder
Odor odorless
Density 6.45 g/cm3 [1]
Melting point 1,933 °C (3,511 °F; 2,206 K)
insoluble in water[2]
+4900.0·10−6 cm3/mol
cubic, cF8
Fm3m, No. 225
GHS labelling:
GHS07: Exclamation markGHS09: Environmental hazard
H302, H317, H410
P260, P280, P284, P301+P310+P330, P304+P340+P310, P342+P311, P403+P233
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
202 mg/kg
Safety data sheet (SDS) ICSC 1551
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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Cobalt(II) oxide is an inorganic compound that has been described as an olive-green[3] or gray[4] solid. 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. A related material is cobalt(II,III) oxide, a black solid with the formula Co3O4.

Structure and properties

CoO crystals adopt the periclase (rock salt) structure with a lattice constant of 4.2615 Å.[5]

It is antiferromagnetic below 289 K.[6]


Cobalt(II) oxide is prepared by oxidation of cobalt powder with air or by thermal decomposition of cobalt(II) nitrate or the carbonate.[3][4]

Cobalt(II,III) oxide decomposes to cobalt(II) oxide at 950 °C:[7]

2 Co3O4 → 6 CoO + O2

It may also be prepared by precipitating the hydroxide, followed by thermal dehydration:[citation needed]

CoX2 + 2 KOH → Co(OH)2 + 2 KX
Co(OH)2 → CoO + H2O


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

CoO + 2 HX → CoX2 + H2O


Cobalt(II) oxide has for centuries been 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.[citation needed] It also is used in cobalt blue glass.

See also


  1. ^ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3.
  2. ^ Advanced Search – Alfa Aesar – A Johnson Matthey Company Archived 2011-07-19 at the Wayback Machine. Retrieved on 2011-11-19.
  3. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. ^ a b 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 978-3527306732.
  5. ^ 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. Bibcode:1987PhRvB..35.6847K. doi:10.1103/PhysRevB.35.6847. PMID 9940938.
  6. ^ Silinsky, P. S.; Seehra, Mohindar S. (1981). "Principal magnetic susceptibilities and uniaxial stress experiments in CoO". Physical Review B. 24 (1): 419–423. Bibcode:1981PhRvB..24..419S. doi:10.1103/PhysRevB.24.419.
  7. ^ US 4389339, James, Leonard E.; Crescentini, Lamberto & Fisher, William B., "Process for making a cobalt oxide catalyst", published 1983-06-21