Chromium (IV) oxide
Crystal structure | |||||||||||||||||||
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__ Cr 4+ __ O 2− | |||||||||||||||||||
General | |||||||||||||||||||
Surname | Chromium (IV) oxide | ||||||||||||||||||
other names |
Chromium dioxide |
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Ratio formula | CrO 2 | ||||||||||||||||||
Brief description |
brown to black solid |
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External identifiers / databases | |||||||||||||||||||
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properties | |||||||||||||||||||
Molar mass | 83.99 g mol −1 | ||||||||||||||||||
Physical state |
firmly |
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density |
4.89 g cm −3 |
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Melting point |
Decomposes above 375 ° C |
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solubility |
almost insoluble in water |
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safety instructions | |||||||||||||||||||
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Chromium (IV) oxide (chemical formula CrO 2 ) is the oxide of tetravalent chromium .
Extraction and presentation
It was first synthesized by Norman L. Cox, a chemist at DuPont , by decomposing chromium (VI) oxide in the presence of water at temperatures around 500 ° C and a pressure of 200 MPa.
properties
Chromium (IV) oxide is a brown to black solid. It crystallizes in a tetragonal rutile structure.
use
The ferromagnetic and electrically conductive crystals are needle-shaped, which makes them suitable for use as magnetic pigments in magnetic tapes . Commercially, it was launched by DuPont as recording material under the brand name Crolyn in the late 1960s .
Individual evidence
- ↑ Entry on chromium oxides. In: Römpp Online . Georg Thieme Verlag, accessed on June 13, 2014.
- ↑ a b c d e Entry on chromium (IV) oxide in the GESTIS substance database of the IFA , accessed on May 27, 2015 (JavaScript required)