Chromium(III) oxide

• Chromium oxide
• Chromsesquioxid
• Dichromium

Green, odorless powder

Fixed

5.22 g · cm -3

2435 ° C

~ 3000 ° C.

Practically insoluble in water

> 15,000 mg · kg -1 ( LD50, rat, oral)

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Chromium (III ) oxide, Cr2O3, is a chemical compound of chromium and oxygen. It is often just called chromium oxide, although this name to avoid confusion with the other three chromium oxides of chromium (II ) oxide, chromium ( IV) oxide and chromium ( VI) oxide may cause. As a synthetically produced pigment chrome oxide green, it was brought in 1929 by Bayer AG to market.

Properties

Chromium ( III ) oxide, depending on the preparation method before as a green powder or iridescent, metallic -like glossy, very hard, hexagonal, rhombohedral crystals. Chromium ( III) oxide (as opposed to the hazardous chromium ( VI) oxide ), non-toxic.

Use

Chromium ( III) oxide is used, due to its hardness abrasives. In many organic reactions, it is used as a catalyst.

Under the name Chrome Oxide is available in Olive pigment. It also serves as enamel paint and glass staining. The coaches of the Deutsche Reichsbahn of the GDR were with paints containing chromium oxide green, painted (see also the Cologne bridge green). The pigment chrome oxide should not be confused with the toxic chrome green, a mixture of chrome yellow and Prussian blue.

Proof

Chromium oxide can be demonstrated by oxidation of yellow chromate. For this purpose, the sample is, for example, fused together with potassium nitrate and sodium hydroxide ( oxidation melt):