Chromite (compound)

This article is about oxyanions of chromium(III). For the mineral chromite, see chromite. For oxyanions of chromium(VI), see Chromate.

Crystal structure of spinel

In chemistry the term chromite has been used in two contexts. Under IUPAC naming conventions, chromate(III) is preferred to chromite.^{[ citation needed ]}

1. For compounds containing an oxyanion of chromium in oxidation state of +3
2. For other compounds of chromium(III) as a means of distinguishing a chemical species such as hexacyanochromite(III). [Cr(CN)₆]³⁻ from an analogous compound in which chromium is a different oxidation state.

The mineral chromite is an iron chromium oxide with empirical formula FeCr₂O₄. Structurally, it belongs to the spinel group. Magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite (MgCr₂O₄);. ^[1] Zincochromite is another example. The crystal structure of the acid, HCrO₂ has been determined by neutron diffraction. ^[2]

Chromites may be formed by reaction of chromium(III) oxide with a metal oxide: ^[3]

Cr₂O₃ + MgO → MgCr₂O₄

References

1. http://www.mindat.org/min-8675.html Mindat
2. Hamilton, W. C.; Ibers, J. A. (1963). "Structures of HCrO
   _² and DCrO
   _²". Acta Crystallographica . 16 (12): 1209–1212. doi: 10.1107/S0365110X63003182 .
3. Kunnmann, W.; Bellavance, D. (1973). "Magnesium Chromite". Inorganic Syntheses. Vol. 14. p. 134. doi:10.1002/9780470132456.ch26. ISBN   978-0-470-13174-9.