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Chromium(III) oxide

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Chromium(III) oxide
A sample of chromium(III) oxide
Other names Chromium sesquioxide
Chromia
Chrome green
Identifiers
CAS number 1308-38-9
Properties
Molecular formula Cr2O3
Molar mass 151.99 g/mol
Cr=68.43%, O=31.57%
Melting point

2435 °C (4415 °F)

Boiling point

approx. 4000 °C (7250 °F)

Solubility in other solvents Insoluble
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox references

Chromium(III) oxide is the inorganic compound of the formula Cr2O3. It is one of principal oxides of chromium, it is widely used precursor to other chromium compounds.

Structure and propertiesEditar

Cr2O3 adopts the corundum structure, consisting of cubic close packed oxides with 2/3 of the octahedral holes occupied by chromium. It is antiferrmagnetic up to 307 K, the Neel temperature.[1] It is an amphoteric oxide, dissolving in acids to give chromium(III) salts and in molten alkali to give chromites.

ProductionEditar

The Parisians Pannetier and Binet first prepared Cr2O3 in 1838 via a secret process. It is manufactured from the mineral chromite, Fe(CrO2)2, which is mined in southern Africa, Asia, Turkey, and Cuba. The conversion of chromite to chromia entails air oxidation to Na2Cr2O7, which is subsequently reduced with carbon or sulfur.

Chromium oxide can be converted into elemental chromium metal through the thermite reaction, although this metal oxide is much less commonly used than Fe2O3 and Fe3O4. Unlike iron oxide thermites, chromium oxide thermite creates little or no sparks, smoke or sound, but it glows with a blinding light. Because of the very high melting point of chromium, chromium thermite casting is impractical.

PigmentEditar

It is commonly called chrome green or institutional green when used as a pigment; however it was referred to as viridian when it was first discovered.

ReferencesEditar

  1. J.E Greedon, (1994), Magnetic oxides in Encyclopedia of Inorganic chemistry Ed. R. Bruce King, John Wiley & Sons ISBN 0471936200
  • A. F. Holleman and E. Wiberg "Inorganic Chemistry" Academic Press, 2001, New York.

See alsoEditar

External linksEditar

cs:Oxid chromitý de:Chrom(III)-oxid ja:オキサイド・オブ・クロミウム pt:Óxido de cromo (III) ru:Оксид хрома(III)

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