Because of the very high melting point of chromium, chromium thermite casting is impractical. Unlike the classic thermite reaction involving iron oxides, the chromium oxide thermite creates few or no sparks, smoke or sound, but glows brightly. When heated with finely divided carbon or aluminium, it is reduced to chromium metal: It is also attacked by concentrated alkali to yield salts of [Cr(OH) Although insoluble in water, it reacts with acid to produce salts of hydrated chromium ions such as [Cr(H Reactions Ĭhromium(III) oxide is amphoteric. However, its use in animal science research has been diminishing with the increased use of Titanium dioxide due to the latter being consider more food safe, allowing for the public sale of animals used in research trials that use an inert digestion marker. It is used as a component of refractories due to its high melting point.įrom 1962, it has been used as an inert marker in livestock intake research. It is available in powder or wax form, and in this context it is known as "green compound". on a piece of leather, balsa, cloth or other material. It is the colorant in "chrome green" and "institutional green." Chromium(III) oxide is a precursor to the magnetic pigment chromium dioxide, by the following reaction: CrĪlong with many other oxides, it is used as a compound when polishing (also called stropping) the edges of knives, razors, surfaces of optical devices etc. Applications īecause of its considerable stability, chromia is a commonly used pigment. The reaction has a low ignition temperature of less than 200 ☌ and is frequently used in “volcano” demonstrations. The oxide is also formed by the decomposition of chromium salts such as chromium nitrate, or by the exothermic decomposition of ammonium dichromate. The conversion of chromite to chromia proceeds via Naħ, which is reduced with sulfur at high temperatures: Na It is derived from the mineral chromite, (Fe,Mg)CrĤ. The Parisians Pannetier and Binet first prepared the transparent hydrated form of Crģ in 1838 via a secret process, sold as a pigment. The mineral is named after Finnish geologist Pentti Eskola. Eskolaite is also a rare component of chondrite meteorites. It is not readily attacked by acids.ģ occurs naturally as the mineral eskolaite, which is found in chromium-rich tremolite skarns, metaquartzites, and chlorite veins. It is antiferromagnetic up to 307 K, the Néel temperature. Similar to corundum, Crģ is a hard, brittle material ( Mohs hardness 8 to 8.5). In nature, it occurs as the rare mineral eskolaite.ģ has the corundum structure, consisting of a hexagonal close packed array of oxide anions with 2⁄ 3 of the octahedral holes occupied by chromium. It is one of the principal oxides of chromium and is used as a pigment. Chromium(III) oxide (or chromia) is an inorganic compound with the formula Crģ.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |