Chromite pigments

The first chromium compound was discovered in the Ural mountains of Russia, during the latter half of the eighteenth century. Crocoite [14654-05-8] a natural lead chromate, found immediate and popular use as a pigment because of its beautihil, permanent orange-red color. However, this mineral was very rare, and just before the end of the same century, chromite was identified as a chrome bearing mineral and became the primary source of chromium [7440 7-3] and its compounds (1) (see Chromiumand chromium alloys). 

Around 1800, the attack of chromite [53293-42-8] ore by lime and alkaU carbonate oxidation was developed as an economic process for the production of chromate compounds, which were primarily used for the manufacture of pigments (qv). Other commercially developed uses were the development of mordant dyeing using chromates in 1820, chrome tanning in 1828 (2), and chromium plating in 1926 (3) (see Dyes and dye intermediates Electroplating Leather). In 1824, the first chromyl compounds were synthesized followed by the discovery of chromous compounds 20 years later. Organochromium compounds were produced in 1919, and chromium carbonyl was made in 1927 (1,2). 

Pigments. Pigments employed include TiONA Ti02, SCM Chemicals, lot 25-JKSJ, Baltimore, MD 21202 lampblack, lot 97 Pfizer Minerals and Pigments Div., New York, NY 10017 manganese ferrite and copper chromite, Ferro Colors, Ferro Corp., Pittsburgh, PA 15204. 

Copper Chromate Black, pigment for plastics, 7 369t Copper chromite, molecular formula, properties, and uses, 6 563t Copper chromite black spinel, formula and DCMA number, 7 348t Copper citrate, molecular formula, 6V638t Copper compounds, 7 767-783 analytical methods, 7 773-776 economic aspects, 7 773 health and safety factors, 7 776 properties and manufacture, 7 768-773 uses, 7 776-780... 

Iron Chromite Brown, pigment for plastics, 7 369t... 

IRON COBALT CHROMITE BLACK, PIGMENT FOR PLASTICS... 

Zinc Chrome Cobalt Aluminate Blue pigment for plastics, 7 370t Zinc chromite... 

Zinc-iron alloy plating, 9 831 Zinc iron chromite brown spinel formula and DCMA number, 7 348t Zinc Iron Chromite Brown pigment for plastics, 7 369t Zincite... 

An industrial method is briefly described in Ref 2, p945 Chromic oxide has been used in metallurgy, in manuf of soluble Cr salts, as a green pigment in manuf of glasses and ceramics and as a catalyst. C O -CuO catalysts are widely used, such as in manuf of methanol and in cyclizations of hydrocarbons (Refs 2 5). Its use in smoke -producing pyrotechnic compns is discussed under Chromium Compounds for Smoke Production, Chromic oxide, as well as Cr hydroxide, are parent compds of Chromites Refs l)Mellor 1 1 (1931), 176-85 2)Kirk Othmer 3 (1949), 944-5 3)Ullmann 5... 

Chromium (IV) Production of chromium compounds, paint pigments, reduction of chromite ore Lung cancer... 

Chromium metal is commercially produced in the United States by the reduction of chromite ore with carbon, aluminum, or silicon, and subsequent purification. Sodium chromate and dichromate are produced by roasting chromite ore with soda ash. Most other chromium compounds are produced from sodium chromate and dichromate (Hartford 1979 Westbrook 1979). For example, basic chromic sulfate (Cr(0H)S04), commonly used in tanning, is commercially produced by the reduction of sodium dichromate with organic compounds (e.g., molasses) in the presence of sulfuric acid or by the reduction of dichromate with sulfur dioxide. Lead chromate, commonly used as a pigment, is produced by the reaction of sodium chromate with lead nitrate or by reaction of lead monoxide with chromic acid solution (IARC 1990). 

Cobalt chromite blue-green Pigment blue 36 Co(Al,Cr)204... 

Cobalt chromite green Pigment green 26 CoCr204... 

Copper chromite black Pigment black 28 CuCr204... 

Estimation of Chromium.—In the analysis of chromites or of other substances containing chromium, such as leather ashes, pigments, etc., it is first necessary to obtain a solution. This is done by finely powdering the substance and heating it with a suitable flux in a crucible, preferably of nickel. Many fluxes have been employed, usually caustic alkali or alkali carbonates, but the one in most common use at present is sodium peroxide, whereby the chromium compound is rapidly converted to a chromate. - Excess of alkali is removed by boiling with ammonium carbonate, which also precipitates any iron present. The filtrate is then acidified with dilute sulphuric acid and the chromium estimated either by gravimetric or volumetric methods. 

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