Oxidation of chrome

Various tints of green are produced from the oxide of chrome, with the addition of yellow as given. 

Corrosion and oxidation of chrome structures in DUV iithographic masks... 

The synthesis of ADP and ATP by the aerial oxidation of ferro-haemo-chrome solutions is knownand the participation of an imidazole... 

Technogenic phases, such as various Fe-alloys ((Cr,Ni)-ferroalloy, (Cu,Ni)-alloy, and (Fe, Si)-alloy), Fe-oxides ((Cr,V,Fe)-oxide, (Mo,W,V,Cr,Fe)-oxide, (Monoxide, (W,Cr,Fe)-oxide), and spherical particles ((Cr,Ni)-oxide or chrome-nickel-spinel (Fig. 3), (Cr.Fe)-oxide or chrome-spinel), were recognized in the area of the Ravne ironworks. 

Technically important dyes are salicylic acid derivatives that function as chrome mordant dyes for wool. Thus Cl Mordant Blue 1 (6.187) is made by the aldehyde synthesis from 2,6-dichlorobenzaldehyde and 2-hydroxy-3-methylbenzoic (o-cresotinic) acid in concentrated sulphuric acid. Oxidation of the leuco base is achieved by the addition of sodium nitrite. On wool the product, which is isolated as the sodium salt, is a dull maroon colour, changing to a bright blue on treatment with a chromium salt. Some dyes of this type, such as Cl Mordant Violet 1 (6.188), also contain a basic group. This compound is also prepared by the aldehyde route. 

The yellow color of urine is due to uro-chromes, which are related to the bile pigments produced by hemoglobin degradation (see p. 194). If urine is left to stand long enough, oxidation of the urochromes may lead to a darkening in color. 

Refractory bricks composed of oxides of magnesium, chromium, aluminum and iron and trace amounts of silica and calcium oxide are used in roofs of open hearths, sidewalls of electric furnaces and vacuum apparatus and copper converters. Such refractories are made in an arc furnace by fusing mixtures of magnesite and chrome ore. 

Relatively little is known concerning the oxidation of azolium salts. Most of the publications deal with thiazolium salts due to the significant biochemical role of thiamin as a coenzyme in a variety of enzyme-catalyzed decarboxylations and aldol-type condensations. The chemistry of thiamin has been extensively reviewed (83MI1). Depending on the reaction conditions, thio-chrome (197) and the disulfide 198 are formed by oxidation of thiamin (57JA4386). 

The oxidation of adrenaline with excess potassium iodate in unbuffered aqueous solution gives a violet-brown solid this solid was first obtained by Richter and Blaschko in 1937 and considered to be 2-iodoadrenochrome (11).69 The iodine atom in the iodoamino-chromes (or the bromine atom in bromoadrenochrome) has recently been shown to occupy the 7-position in the aminochrome molecule,70 rather than the 2-position as originally believed. Consequently, the iodoadrenochrome referred to above should be formulated as a 7-iodo derivative (i.e., as 12). The iodoaminochromes presumably arise by iodination of the initially formed aminochromes (cf. ref. 3). 

In summary, it would appear that the oxidation of a catecholamine probably first involves the formation of a semi-quinone radical (this can be brought about by an one-electron transfer, e.g. from Cu++ ions,14 or by photoactivation 1) which rapidly undergoes further oxidation (e.g. with atmospheric oxygen) to an intermediate open-chain quinone (such as adrenaline-quinone) and then cyclizes by an oxidative nucleophilic intramolecular substitution to the amino-chrome molecule. Whilst the initial formation of a leucoaminochrome by non-oxidative cyclization of the intermediate open-chain quinone in some cases cannot be entirely excluded at the moment (cf. Raper s original scheme for aminochrome formation72), the... 

It has not yet been possible to isolate noradrenolutin from the products of the direct rearrangement of noradrenochrome in solution. [Noradrenolutin should probably be formulated in the keto form (38) however, it is often represented in the trihydroxy form (39).] However, pure samples of this valuable compound have recently been obtained by the cautious hydrolysis of 3,5,6-triacetoxyindole (40),70,71 obtained by deiodination of 3,5,6-triacetoxy-7-iodoindole (41),70,71 which can readily be obtained by the action of acetic anhydride and pyridine on 7-iodonoradrenochrome (42).70,71,74 7-Iodonoradreno-chrome (42) has been prepared in pure crystalline form by the oxidation of noradrenaline (43) with potassium iodate.70,71... 

No simple oxidation products of adrenochrome have been obtained in crystalline form. The evidence for and against the existence of oxoadrenochrome was summarized in an earlier review.3 Although the preparation of a substance described as 2-iodooxoadrenochrome (70) by the oxidation of adrenaline with iodic acid was reported,87,187 it was subsequently shown by an exhaustive consideration of its physical and chemical properties to be identical with 7-iodoadreno-chrome (12)109 (cf. ref. 70). 

Simple carboxylates of chromium(III) find industrial application as catalysts for the polymerization of to-alkenes854,855 and in the preparation of chrome-tanning solutions.856,857 There seems to be no simple carbonate of chromium(III). Compounds formed on the surface of Cr203, sometimes formulated Cr2(C03)3- H20, are best viewed as carbon dioxide adsorbed on the oxide.858 Carboxylate complexes of chromium(III) will now be considered in terms of the various ligand types. 

Sesquioxide of Chromium—chrome green—Cr, 0 — is generally prepared for potters use by calcining a mixture of equal parte of chromate of potessa and sulphur in a close earthenware crucible at a Ted heat, the green moss which is produced being well washed to dissolve out the sulphate and sulphide of potassium. The oxide of chromium which remains ia further purified by repeated elutriation. 

Bichromate of Lead—2 PbO, CrOj— chrome red— may bo obtained by boiling oxide of lead, or its car-bonato, with on aqueous solution of monochromate of potassa, or by digesting the neutral chromate of lead in a dilute solution of caustic potassa. Liebig prepared it by adding a neutral ebromate to fased nitre, and washing the residuum it is an insoluble, scarlet colored powder. 

Calcium Chromate. [CAS 13765-19-0]. CaCrOj. yellow solid, formed by lhe reaction of chrome ores and calcium oxide heated to a high temperature in a current of atr. pKip = 3.15. 

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... 

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