Chromium appearance

Since the depletion of the matrix with respect to chromium appears to be the basic factor involved, it would be expected that additions of elements having greater affinity than chromium for carbon would increase resistance to attack and such effects have been demonstrated by several investigations where the beneficial effects of additions of titanium. 

Methyl benzoate, anisole, and diphenyl ether each give sandwich compounds with chromium vapor, although in rather low yield (32, 55, 110). Chromium appears to attack alkyl ethers and this deoxygenation probably competes with complexation with the aromatic oxygen compounds. No simple product has been isolated from chromium atoms and aniline, but bis(7V,7V-dimethylaniline)chromium has been prepared (32). The behavior of molybdenum and tungsten vapors closely resembles that of chromium in reactions with oxygen- and nitrogen-substituted arenes (113). 

Vanadium and chromium appear to be essential elements, while this claim has also been made recently for tin (N. F. Cardarelli, Tin as a Vital Nutrient Implications in Cancer Prophylaxis and other Physiological Processes , CRC Press, Fort Lauderdale, 1985). For a recent account of the biochemistry of the trace elements see Biochemistry of the Essential Ultratrace Elements , ed. E. Frieden, Plenum, New York, 1984... 

The influences of vanadium compounds on cardiovascular function, a major complication of diabetes, has been reviewed [144], One of the first papers on the antidiabetic effects of oral administration of vanadium compounds (vanadyl sulfate) to rats with STZ-induced diabetes showed improvement of diabetes-impaired cardiac function [122], Recent work has focused on the correction of metabolic defects of diabetes by vanadium and learning more about the immediate mechanism of the antidiabetic effect. The assumption is made that amelioration of the basic metabolic problems of diabetes by vanadium or any other drug will alleviate the long-term complication arising from disease. Diet supplementation with minerals, such as chromium, appears to complement traditional treatments of diabetes to slow the development of complications. Mineral supplementation is believed to be most effective when dietary supplementation is used to correct a deficiency of a mineral [145],... 

Chromium appeared to be better absorbed from the soil than from chromate salts, but less than 50% of the administered chromium could be accounted for in these studies, partly because not all tissues were examined for chromium content and excretion was not followed to completion (Witmer et al. 1989,... 

Chromium appeared randomly at 0-4 /xg/cm2. The Amies yellow paper had 54 /xg/cm2 together with a 325-/xg/cm2 lead level, which is within 40% of the stoichiometric ratio of lead chromate, the same pigment used in U.S. currency. 

Chromium appeared in highest concentration on the green side as barium or lead chromate (yellow). 

It is thought by some that the metal acts as a tetravalent element in chromium dioxide, CrOa, but this compound may also be considered as a basic chromic chromate, CrgOg-CrOg. Chromium appears to function as a pentavalent element in the oxychloride, CrOClg, and its derivatives. The perchromic adds and perchromates have Jong been thought to contain heptavalent chromium, but it would appear that... 

Chromium is a trivalent cption that occurs as A typical daily intake isO-5 3-8 jimoJ (25-200 ig/day). After absorption from the diet, chromium occurs bound to transferrin. A safe and adequate intake of 50 to 200 ffg Cr/day has been established. Chromium appears to participate in glucose metabolism. The ion may play a part in mediating the hormonal effects of insulin. Chromium deficiency results in abnormally high glucose tolerance curves and impaired clearance of plasma glucose. Chromium deficiency can be induced in animals. There is evidence that... 

G. KirohhofE, J. N. Lockyer, and F. MoClean, reported that the spectral lines of chromium appear in the solar or in stellar spectra. H. Deslandies also found chromium lines in the ultra-violet spectrum of the corona. 

The initial reaction results in the formation of a continuous film of oxide that is firmly attached to the metal surface. The rate of growth of the film is controlled by the slow diffusion of the Cu ions. However, no corrosion could occur without the transport of electrons, as the mechanism depends on electron transport. The electronic conductivity of the film is therefore of major importance. The reason why both aluminium and chromium appear to be corrosion-resistant lies in the fact that, although oxide films form very rapidly in air, the films are insulators and prevent reaction from continuing. As the thin films are also transparent, the metals do not lose their shiny appearance. 

Change in the oxidation state of an element can have a profound effect on bioavailability and toxicity. Fe(II) is biologically the main usable form of iron, Fe(III) in excess can cause stomach lesions.When chromium appears as a pollutant in a sample of river water or in a Cr complex dye, its valency is of relevance in ascertaining the relative toxicity of the sample. Trivalent chromium is an essential element in mammalian systems, hexavalent chromium is considered to be a moderate to severe industrial hazard. 

When added in combination with copper, chromium and nickel further increase the corrosion resistance of weathering steels. Chromium is usually added in a content of 0.4-1%, whereas nickel is usually added up to 0.65%. Chromium appears to be more effective than nickel. The mechanical properties of the steel are improved by both elements. 

Chromium appears to have a role in the intermediary metabolism of carbohydrates. Deficiency of chromium may be associated with some cases of diabetes mellitus or impaired glucose tolerance. 

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