Cobalt(II) oxide


Cobalt oxide or cobalt monoxide is an inorganic compound that appears as olive-green to red crystals, or as a greyish or black powder. 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 salts.

Structure and properties

CoO crystals adopt the periclase structure with a lattice constant of 4.2615 Å.
It is antiferromagnetic below 16 °C.

Preparation

decomposes to cobalt oxide at 950 °C:
Though commercially available, cobalt oxide may be prepared in the laboratory by electrolyzing a solution of cobalt chloride.
CoCl2 + H2O → CoO + H2 + Cl2
It may also be prepared by precipitating the hydroxide, followed by thermal dehydration:

Reactions

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

Applications

Cobalt 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 is around 2.4 eV.
It also is used in cobalt blue glass.