Chromium(III) oxide 2492567 222661252 2008-06-30T14:13:16Z 24.17.60.11 Grammar {{Chembox new | Name = Chromium(III) oxide | ImageFile = Chromium(III)-oxide-sample.jpg <!-- | ImageSize = 250px --> | ImageName = A sample of chromium(III) oxide | OtherNames = Chromium sesquioxide<br />Chromia<br />Chrome green | Section1 = {{Chembox Identifiers | CASNo = 1308-38-9 }} | Section2 = {{Chembox Properties | Formula = Cr<sub>2</sub>O<sub>3</sub> | MolarMass = 151.99 g/mol<br /> | MolarMass_notes = ''Cr=68.43%, O=31.57%'' | Solvent = other solvents | SolubleOther = Insoluble | MeltingPt = 2435 °C (4415 °F) | BoilingPt = ''approx.'' 4000 °C (7250 °F)}} }} '''Chromium(III) oxide''' is the [[inorganic compound]] of the [[Chemical formula|formula]] Cr<sub>2</sub>O<sub>3</sub>. It is one of principal oxides of [[chromium]]. it is a widely used precursor to other chromium compounds. ==Structure and properties== Cr<sub>2</sub>O<sub>3</sub> adopts the [[corundum]] structure, consisting of cubic close packed oxides with 2/3 of the octahedral holes occupied by chromium. It is [[antiferromagnetism|antiferromagnetic]] up to 307 K, the Neel temperature.<ref>J.E Greedon, (1994), ''Magnetic oxides'' in Encyclopedia of Inorganic chemistry Ed. R. Bruce King, John Wiley & Sons ISBN 0471936200</ref> It is an [[amphoteric oxide]], dissolving in acids to give chromium(III) [[salt]]s and in molten alkali to give [[Chromite (ion)|chromite]]s. ==Production== The Parisians Pannetier and Binet first prepared Cr<sub>2</sub>O<sub>3</sub> in 1838 via a secret process. It is manufactured from the mineral [[chromite]], Fe(CrO<sub>2</sub>)<sub>2</sub>, which is mined in southern Africa, Asia, Turkey, and Cuba. The conversion of chromite to chromia entails air oxidation to Na<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub>, 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 Fe<sub>2</sub>O<sub>3</sub> and Fe<sub>3</sub>O<sub>4</sub>. 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. ==Pigment== 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. ==References== {{Citationstyle|date=September 2007}} <references/> * A. F. Holleman and E. Wiberg "Inorganic Chemistry" Academic Press, 2001, New York. ==See also== * [[Chromium(II) oxide]] * [[Chromium(IV) oxide]] * [[Chromic acid]] ==External links== * [http://www.npi.gov.au/database/substance-info/profiles/24.html National Pollutant Inventory: Chromium (III) compounds fact sheet] [[Category:Chromium compounds]] [[Category:Oxides]] [[Category:Inorganic pigments]] [[Category:Alchemical substances]] [[ar:أكسيد كروم ثلاثي]] [[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)]] [[zh:三氧化二铬]]