Cobalt(II) oxide is an inorganic compound that has been described as an olive-green or gray 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.
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||74.9326 g/mol|
|Appearance||olive or gray powder|
|Density||6.45 g/cm3 |
|Melting point||1,933 °C (3,511 °F; 2,206 K)|
|insoluble in water|
|Fm3m, No. 225|
|H302, H317, H410|
|P260, P280, P284, P301+P310+P330, P304+P340+P310, P342+P311, P403+P233|
|NFPA 704 (fire diamond)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|Safety data sheet (SDS)||ICSC 1551|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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It may also be prepared by precipitating the hydroxide, followed by thermal dehydration:
As can be expected, cobalt(II) oxide reacts with mineral acids to form the corresponding cobalt salts:
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. It also is used in cobalt blue glass.