WILEY-VCH Verlag GmbH, Weinheim (1998)Ĭhen, X., Mao, S.S.: Titanium dioxide nanomaterials: synthesis, properties, modifications, and applications. Vincentz Verlag, Hannover (2000)īauxbaum, G. Oyarzún, J.M.: Pigment Processing Physico-Chemical Principles. Woodhead Publishing Ltd., Cambridge (1999) (eds.): Paint and Surface Coatings Theory and Practice, 2nd edn. Golgschmidt, A., Streitberger, H.J.: BASF-Handbuch Lackiertechnik. 1, 10–13 (2012)Įndriβ, H.: Inorganic Coloured Pigments Today. The refractory industry has found chromite useful for forming bricks and shapes, as it has a high melting point, moderate thermal expansion, and stability of crystalline structure.Garo, D.: Pigments – a growth market. Chromium gives glass an emerald green color and is widely used as a catalyst. Much is used in plating to produce a hard, beautiful surface and to prevent corrosion. Chrome green is a mixture of chrome yellow and Prussian blue.Ĭhromium is used to harden steel, to manufacture stainless steel, and to form many useful alloys. The chromates are generally yellow, the best known being lead chromate (PbCrO 4), an insoluble solid widely used as a pigment called chrome yellow. Potassium dichromate (K 2Cr 2O 7) is a red, water-soluble solid that, mixed with gelatin, gives a light-sensitive surface useful in photographic processes. In chromates and dichromates, chromium has a valence of +6. Chromic oxide (Cr 2O 3) is a green solid. Most of these compounds are green, but some are red or blue. In chromites and chromic salts, chromium has a valence of +3. The extensive use of chromite as a refractory is based on its high melting point, its moderate thermal expansion, and the stability of its crystalline structure. For this reason it is widely used as body trim on automobiles and other vehicles. When deposited electrolytically, chromium provides a hard, corrosion-resistant, lustrous finish. Because of its hardness, an alloy of chromium, cobalt, and tungsten is used for high-speed metal-cutting tools. In the stainless steels, chromium makes up 10 percent or more of the final composition. The addition of chromium imparts hardness, strength, and corrosion resistance to the alloy. The chief use of chromium is to form alloys with iron, nickel, or cobalt. It is an ingredient in several important catalysts. More than half the production of chromium goes into metallic products, and about another third is used in refractories. The Cr-Cr bond distance in a range of these quadruply bonded species has been found to vary between 195-255 pm. Each Cr(II) ion has 4 d electrons but the complex is found to be diamagnetic which is explained by the formation of a quadruple bond between the two metal ions. 2H 2O is an example of a Cr(II) complex which is reasonably stable in air once isolated. See the laboratory manual for this course for a range of other Cr(III) complexes for which you should know the structure. This allows a small amount of the Cr(II) ion to be formed, which is very labile but unstable with respect to oxidation back to Cr(III).
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