Chromium (II) oxide of red color is not pyrophoric, and this same substance of black color is pyrophoric. Oxide of bivalent chromium is a solid of black or red color with a melting point of 1550 ° C. Wiberg "Inorganic Chemistry" Academic Press, 2001, New York. In nature it occurs in the form of FeO Cr2O3 chromium iron ore. As a general rule, all stainless weldments require postweld cleaning to ensure that a surface’s chrome-oxide film is intact. Chromium oxide forms immediately when the chromium atoms in stainless steel are exposed to oxygen in the atmosphere.
The references in this article would be clearer with a different or consistent style of citation, footnoting, or external linking. A microscopic layer of chromium oxide provides stainless steel with its stainless characteristic. 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. Because of the very high melting point of chromium, chromium thermite casting is impractical. Unlike iron oxide thermites, chromium oxide thermite creates little or no sparks, smoke or sound, but it glows with a blinding light. The conversion of chromite to chromia entails air oxidation to Na 2Cr 2O 7, which is subsequently reduced with carbon or sulfur.Ĭhromium oxide can be converted into elemental chromium metal through the thermite reaction, although this metal oxide is much less commonly used than Fe 2O 3 and Fe 3O 4. It is manufactured from the mineral chromite, Fe(CrO 2) 2, which is mined in southern Africa, Asia, Turkey, and Cuba. Cr 3+ ions are rarely present at pH values over 5, because hydrated chromium oxide (Cr(OH) 3) is hardly water soluble. The Parisians Pannetier and Binet first prepared Cr 2O 3 in 1838 via a secret process. Chromium (III) oxides are only slightly water soluble, therefore concentrations in natural waters are limited. It is an amphoteric oxide, dissolving in acids to give chromium(III) salts and in molten alkali to give chromites. Retrieved 15 November 2010.Cr 2O 3 adopts the corundum structure, consisting of cubic close packed oxides with 2/3 of the octahedral holes occupied by chromium.
Archived from the original on 3 December 2007. It is a dangerous hazard to the environment.
It can be destroyed by reacting it with a reducing agent like ferrous sulfate. It is a carcinogen and can cause mutations. It reacts with metals to make a metal chromate which stops the metal from corroding.Ĭhromium(VI) oxide is very toxic and irritating. SDS CoA Synonyms: Chromic anhydride, Chromium trioxide CAS : EC Number: 215-607-8 Molar Mass: 99.99 g/mol Hill Formula: CrO. It is also used to plate chromate on things. Chromium(VI) oxide MSDS (material safety data sheet) or SDS, CoA and CoQ, dossiers, brochures and other available documents.
It can also be made by drying chromic acid. Chromic Oxide is not listed in Appendix A and B, 40 CFR 355, as an extremely hazardous substance. It is normally made by reacting sodium chromate or potassium chromate with sulfuric acid. Chromic Oxide is subject to the reporting requirements of sections 311, 312, and 313. It gives off oxygen when heated and turns into chromium(III) oxide. It reacts with strong bases to make chromates. It dissolves in water to make chromic acid, which is acidic. It is a stronger oxidizing agent than chromate. Combining good dispersibility and heat stability, with excellent hiding power, weather fastness and batch-to-batch. It can ignite alcohol when it is mixed with it. Widely used in the formulation of paints, coatings, enamels and plastic products, our chromium oxide pigments are also extensively employed in the mass coloration of construction materials such as decorative concrete and mortar.