Chromite (compound)

This article is about the chromium(III) oxides. For the mineral, see chromite. For the chromium(VI) anion and its salts, see chromate.

In chemistry, a chromite refers to compounds formally containing the anion CrO−
2. The anion does not exist per se, unless combined with tightly bonded cations.[1] The most famous chromite is the mineral by the same name, FeCr2O4 but many other chromites are known.

Although the majority of chromites have the formula MCrO2 or MCr2O4, the term chromite refers also to other anionic compounds containing Cr(III). For example, hexacyanochromite and hexahydroxychromite refer to the anions [Cr(CN)
6]3−
 and [Cr(OH)
6]3−
, respectively.[2] Under IUPAC naming conventions, chromate(III) is preferred over chromite, although this nomenclature is rarely followed.

Chromite compounds such as FeCr2O4 may be regarded as being derived from the hypothetical "chromous acid", HCrO
2, but this species does not exist.[3] Chromites are formed by reaction of chromium(III) oxide with metal oxides:[4]

Cr2O3 + MgO → MgCr2O4

References

  1. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
  2. ↑ Mary Eagleson, ed. (1994). "Chromates". Concise encyclopedia chemistry. Walter de Gruyter. p. 220. ISBN 3-11-011451-8.
  3. ↑ Hamilton, W. C.; Ibers, J. A. (1963). "Structures of HCrO
    2     and DCrO
    2    ". Acta Crystallographica 16 (12): 1209–1212. doi:10.1107/S0365110X63003182.
  4. ↑ Kunnmann, W. (1973). "Magnesium Chromite: (Magnesium Chromium (III) Oxide)". Inorganic Syntheses 14: 134. doi:10.1002/9780470132456.ch26.
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