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Cobalt(II) oxide is an
inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...
that has been described as an olive-green or gray
solid Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...
. It is used extensively in the
ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...
s 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 In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...
Co3O4.


Structure and properties

CoO crystals adopt the periclase ( rock salt) structure with a lattice constant of 4.2615 Å. It is antiferromagnetic below 289 K.


Preparation

Cobalt(II) oxide is prepared by oxidation of cobalt powder with air or by thermal decomposition of cobalt(II) nitrate or the carbonate. Cobalt(II,III) oxide decomposes to cobalt(II) oxide at 950 °C: :2 Co3O4 → 6 CoO + O2 It may also be prepared by precipitating the hydroxide, followed by thermal dehydration: : CoX2 + 2 KOH → Co(OH)2 + 2 KX : Co(OH)2 → CoO + H2O


Reactions

As can be expected, cobalt(II) oxide reacts with mineral acids to form the corresponding cobalt salts: : CoO + 2 HX → CoX2 + H2O


Applications

Cobalt(II) oxide has for centuries been used as a coloring agent on
kiln A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or Chemical Changes, chemical changes. Kilns have been used for millennia to turn objects m ...
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

* Cobalt oxide nanoparticles *
Cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...
* Cobalt(II,III) oxide


References

{{Oxides Cobalt(II) compounds Transition metal oxides Rock salt crystal structure