Ferrous chromite

Chrome Ore. Chromia-beating spinel materials, although considered neutral, are generally used in combination with basic magnesite. Chrome ores consist essentially of a complex soHd-solution series of spinels including hercynite, FeO 202 ferrous chromite, FeO Cr20 magnesioferrite,... 

Ferrous castings industry, 21 414 Ferrous chromite, 5 602 Ferrous dititanate, 25 46 Ferrous foundries, types of, 21 412 Ferrous iron salts, in selenium recovery, 22 79-81... 

Chromium occurs chiefly as chromite (ferrous chromite). Fe(CrOy)-. in Zimbabwe, the Republic of South Africa, the former USS.R, New Caledonia. India. Philippine Islands. Japan, Turkey. Greece. Cuba, and California. (I I Healing chromite in the elcclric furnace with carbon yields ferrochrume for alloys, and (2) when chromite is heated with sodium earhonale and nilralc. sodium chromate is formed, which is then extracted with HyO. This is the substance from which chromium compounds are obtained. See also Chromite. 

Ferrous chromite, Fe0.Cr203, occurs in nature as chromite (see p. 13). It may be prepared in the laboratory by heating to a high temperature an intimate mixture of iron filings, ferrous carbonate, and potassium bichromate, covered with a thin layer of cryolite. The cooled product is extracted with water and concentrated acids in succession a residue is obtained containing chromite as small octahedra, cubo-octahedra, and cubes.7... 

Iron and Chromium—Ferrous Chromite and Chromate—Basic Double Chromates. 

Ferrous Chromite, FeO.CrgOg, occurs in nature as chrome iron ore (see p. 7). It has been obtained in the form of octahedra, of density 4-97 and specific heat 0-159. 

Similar phenomena have been observed in numerous other systems such as those of aluminum quartz (Ananthapadmanabhan and Somasundaran, 1985), nickel-quartz (Nagaraj and Somasundaran, 1981), cupric-chrysocolla (Latiner, 1952), manganous-rhodonite (Butler, 1967) and ferrous-chromite. 

The discovery of ferrous chromite, Fe(Cr02)2. or Fe0.Cr203, by L. N. Vauquelin 2 has been previously discussed. The occurrence and some analyses of the mineral have also been indicated. 

Chromite. Ferrous chromite. Fe0.Cr203 sp. gr. 4.88 thermal expansion (0-1200 °C) 8.3 X 10- Chromite is a major constituent of many chrome ores (q.v.). 

The advantage over most other kinds of reduction is that usually the product can be obtained simply by filtration from the catalyst, then distillation. The common catalysts are nickel, palladium, copper chromite, or platinum activated with ferrous iron. Hydrogenation of aldehyde and ketone carbonyl groups is much slower than of carbon-carbon double bonds so more strenuous conditions are required. This is not surprising, because hydrogenation of carbonyl groups is calculated to be less exothermic than that of carbon-carbon double bonds ... 

The chief ore1 is chromite (FeCr2C>4), which is a spinel with Crm on octahedral sites and Fe11 on the tetrahedral ones. If pure chromium is not required—as for use in ferrous alloys such as the chromium additive used to make stainless steel—the chromite is reduced with carbon in a furnace, affording the carbon-containing alloy ferrochromium ... 

The recently described metal-rich Tafassasset meteorite has an oxygen isotopic composition similar to CR chondrites and an equigranular texture (Bourot-Denise et al., 2002). It is, however, characterized by uniformly ferrous ohvine (Fa3o) and orthopyroxene (FS25), and the presence of albitic plagioclase (An24 4s), chromite, and merrilite it may be the first metamorphosed CR chondrite. 

The catalytic action of iron oxides (mainly ferrous oxide) was described by Bakhman and co-workers [20]. They also reviewed the literature on the catalytic action of Fe, FcjOj, Fej04, oigano-iron compounds, CojOj, NiO, Cu, CU2O, CuO, Cu chromite, Cu chlorides, Cr2 0j, salts of chromic acid, MnOj, KMn04, VjOs,Si02,TiOj,... 

Chromite, FeCr204, is the principal ore of chromium. Chromates and dichromates are obtained from it by fusion with sodium or potassium carbonate with access of air the iron is oxidized from the ferrous to the ferric condition and the chro-... 

K. Fischbeck and E. Einecke found that the cathodic polarization of ferrous, cuprous, calcium, and magnesium chromites produces chromic acid, whilst the other chromites are unaffected, and natural chrome ironstone behaves in a like manner, but other commercial chromites are reduced on cathodic polarization, and yield chromic acid on anodic polarization. Chromites behave as an intermediate electrode. 0. Unverdorben observed that chromyl fluoride, prepared by heating a mixture of fluorspar, lead chromate, and sulphuric acid, when passed into water, furnishes an aq. soln. of this oxide. The soln. was treated with silver nitrate, and the washed precipitate of silver chromate decomposed by hydrochloric acid. A. Mans said that anhydrous sulphuric acid or fuming sulphuric acid is not suited for the preparation because of its volatilization with the chromyl fluoride. 

Su C, Ludwig RD. (2005). Treatment of hexavalent chromium in chromite ore processing residue solid waste using a mixed reductant solution of ferrous sulphate and sodium dithionite. Environmental Science and Technology 39 6208-6216. 

Nay] Naylor, B.F., High-Temperature Heat Contents of Ferrous and Magnesium Chromites , Indust. Eng. Chem., 36(10), 933-934 (1944) (Experimental, Thermodyn., 2)... 

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