Chrome iron ore

Chrom-echtschwarz, n. fast chrome black, -eisen, -eisenerz, n., -eisenstein, m. chrome iron ore, chromite. 

Fourcroy predicted that this mineral would give chemists the opportunity to make a more thorough study of the properties of chromium and perhaps to discover compounds of it which, because of their rich and varied colors, would be useful in painting and in the manufacture of glass and enamel (90). He also encouraged study of the chromium alloys. The chrome-iron ore is now known as chromite. It is not a chromate, but has the spinel composition, Fe(Cr02)2-... 

Calcium Chromate, CaCr04, CaCr04.2H20, mw 192.12 yel, monocl crysts mp - loses 2HzO at 200° sol in w(22.2% at 0° 18.2% at 43°) sol in acids si sol in alcohol. Can be prepd from chrome-iron ores as described under CHROMATES. Its toxicity is discussed in Ref 7. It exists also as monohydrate and as... 

Chromite or Chrome Iron Ore, (Chrome Iron Stone) (Chromerz, Chromeisenstein, Chromit or Ferrochrom in Ger), Q O. FeO or Fe2(Cr02)2- This ore, which is the most important commercial source of chromium and and its compds, is not found in nature in pure form but mixed with oxides of A1 and/or Mg. Its color varies from iron-blk to brn-blk or streak dr brn. There are several grades metallurgical, refractory, or chemical av d 4.6 and hardness 5.5. Several methods for production of chromium from chromite are known, such as silicothermic, alumino-thermic electrolytical... 

Chromite, chromo-ferrite, sidero-chrome, or chrome iron ore,... 

W. H. Patterson gives the melting-point of various chrome iron ores as ranging from 1545° to 1730° C. (J. Iron Steel Inst., Carnegie Schol. Memoirs, 1914, 6, 238). 

Acids do not attack chromite, but fusion with alkali hydrogen sulphates effects its decomposition. The Grecian ore, which occurs mainly in the Eastern Provinces and in the island of Skyros, is particularly refractory on account of the impurities it contains. Chrome iron ores containing some Fe203 may be regarded as mixtures of chromite and chromitite (p. 17). Platmiferous chromites are found in the Urals.1... 

Preparation.—Metallic chromium is usually obtained by reduction of the sesquioxide, CtjOj, the chief source of which is chrome iron ore (p. 7). The latter, after separation from gangue, is powdered, washed, mixed with lime and potassium carbonate, dried, and then roasted, the mass being continually stirred. The potassium chromate produced is extracted with water and converted into the dichromate by treatment with sulphuric acid. After recrystallisation the potassium dichromate is reduced by heating wth sulphur, starch, or other suitable material, and finally washed with water the chromium sesquioxide remains undissolved. 

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. 

Potassium Dichromate, KjCcjO, may be prepared from the sodium salt and potassium chloride, or by a direct method. In the latter ease, chrome iron ore (p. 7) is calcined in the air with calcium carbonate, and the mass extracted with water containing a little sulphuric acid. Potassium carbonate is then added, and, after filtration and addition of sulphuric acid, the potassium dichromate is separated by fractional crystallisation. An alternative method consists in heating chromite with calcium carbonate and potassium sulphate, and lixiviating the mass with water. Oxidation of chromite by means of fused potassium nitrate is sometimes convenient, especially upon a small scale. Potassium dichromate is formed by the addition of any acid to a solution of potassium chromate (see p. 4.4 ). ... 

The raw material for all chromium chemicals is chrome iron ore, so-called chromite, which is a spinel. It contains magnesium and aluminum as minor constituents and has the approximate composition (Fe, Mg)[Cr,Al,Fe(III)]204. Calcium, silicon dioxide and, in some cases, vanadium are also present in small quantities. 

Derivation Chrome iron ore is melted in a reverberatory furnace with lime and soda, in presence of air. The melt is dissolved in water, a small amount of sodium carbonate added, the solution decanted, acidified with acetic acid, concentrated, and crystallized. 

Fourcroy and Hatiy suggested chromium as a suitable name for the element in recognition of the various colours shown by its derivatives, Greek khroma colour. The same year Vauquelin detected chromium in the spinel ruby while Taessert showed it to be an essential constituent of chrome iron ore or chromite, FeO.Cr2Os — now the main source of chromium compounds. The colour of the ruby is now usually attributed to its chromium content and artificial rubies are manufactured by fusing pure alumina with a little oxide of chromium, to colour it, in an... 

Occurs in nature, in union with oxygen, as chromic acid in chromate of lead, and as oxide of chromium in chrome iron ore, from which latter all the compounds of chromium are obtained. The metal is very infusible, and has probably never been completely melted. It is obtained with difliculty in hard coherent masses of an iron grey colour, by heating the oxide to the highest temperature of a wind furnace for some hours in a crucible lined with charcoal. In this state it is hardly at all acted on by the strongest acids, but is oxidised by fusion with nitre, yielding chromic acid. 

Bichromate of potash, KO, 2 Cr O3, is much used in calicor g, and is obtained by fusing chrome iron ore with nitre. 

The principal mineral for the supply of chromium is chromite. It has a variety of names -. chrome ore, chrome-ironstone, or chrome iron ore, Fe0.Cr203, in which the iron and chromium are more or less replaced by magnesium and aluminium. Iron ore with up to about 3 per cent, of chromium is called chromiferous iron ore. The origin of the chromite deposits has been discussed by M. E. Glasser, L. W. Fisher, E. 8ampson, F. Ryba, C. 8. Hitchin, J. 8. DiUer, P. A. Wagner,... 

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