Copper appearance

For a given amplitude of the quasi-elastic release wave, the more the release wave approaches the ideal elastic-plastic response the greater the strength at pressure of the material. The lack of an ideally elastic-plastic release wave in copper appears to suggest a limited reversal component, however, this is much less than in the silicon bronze. Collectively, the differences in wave profiles between these two materials are consistent with a micro-structurally controlled Bauschinger component as supported by the shock-recovery results. Further study is required to quantify these findings and... 

In practice vapours of the hydrocarbon halide, e.g. methyl chloride, are passed through a heated mixture of the silicon and copper in a reaction tube at a temperature favourable for obtaining the optimum yield of the dichlorosilane, usually 250-280°C. The catalyst not only improves the reactivity and yield but also makes the reaction more reproducible. Presintering of the copper and silicon or alternatively deposition of copper on to the silicon grains by reduction of copper (I) chloride is more effective than using a simple mixture of the two elements. The copper appears to function by forming unstable copper methyl, CUCH3, on reaction with the methyl chloride. The copper methyl then decomposes into free methyl radicals which react with the silicon. 

There appears to be concentration of rhodium in the surface of the iridium-rhodium clusters, on the basis that the total number of nearest neighbor atoms about rhodium atoms was found to be smaller than the nunber about iridium atoms in both catalysts investigated. This conclusion agrees with that of other workers (35) based on different types of measurements. The results on the average compositions of the first coordination shells of atoms about iridium and rhodium atoms in either catalyst Indicate that rhodium atoms are also incorporated extensively in the interiors of the clusters. In this respect the iridium-rhodium system differs markedly from a system such as ruthenium-copper (8), in which the copper appears to be present exclusively at the surface. 

Copper appears as the a2-globulin ceruloplasmin in the human body (Sarkar 1994). Deficiency of this protein in serum is characteristic of both Menkes and Wilson s diseases. Wilson s disease is an abnormal storage of Cu(II) in body tissues. Cu(II) in biological material can be determined by spectrophotometry or by FAAS, ceruloplasmin in serum by a spectrophotometric method. 

Few studies have been made of benzene chemisorption by the volumetric method. Zettlemoyer et al. (8) have examined the adsorption of benzene vapor at 0°C on powders of nickel and of copper. First, the monolayer coverage of argon (vm) A, was measured. The argon was then removed by pumping and the amount of benzene required to form a monolayer, (vmi) Bz, was measured. Weakly adsorbed benzene was then removed by pumping, after which further benzene adsorption provided the value (vm2) Bz. Some results are reproduced in Table I. On the assumption that the same extent of surface is accessible both for argon and for benzene adsorption, it is clear that complete monolayers of benzene were not achieved, that some (Ni) or all (Cu) of the benzene was adsorbed reversibly. It was considered that only the irreversibly adsorbed benzene was chemisorbed, the remainder being physically adsorbed. Thus chemisorption of benzene on copper appeared not to occur. The heat of adsorption of benzene on nickel at zero... 

More advanced semiempirical molecular orbital methods have also been used in this respect in modeling, e.g., the structure of a diphosphonium extractant in the gas phase, and then the percentage extraction of zinc ion-pair complexes was correlated with the calculated energy of association of the ion pairs [29]. Semiempirical SCF calculations, used to study structure, conformational changes and hydration of hydroxyoximes as extractants of copper, appeared helpful in interpreting their interfacial activity and the rate of extraction [30]. Similar (PM3, ZINDO) methods were also used to model the structure of some commercial extractants (pyridine dicarboxylates, pyridyloctanoates, jS-diketones, hydroxyoximes), as well as the effects of their hydration and association with modifiers (alcohols, )S-diketones) on their thermodynamic and interfacial activity [31 33]. In addition, the structure of copper complexes with these extractants was calculated [32]. 

The word copper appears in the Old Testament only in the passage where Ezra describes the treasure which he weighed out and committed to the twelve priests. Besides the silver and gold were two vessels of fine copper, precious as gold (11). Leroy Waterman, however, interprets this word as fine burnished bronze (37) The modem Spanish and Brazilian Portuguese translations also render it as bronze (88, 91). 

Figure 4.42. The turnover frequencies for the low-temperature WGS reaction as a function of adsorption energies of oxygen and carbon monoxide. The positions of the step sites on noble and late transition metals are shown. As observed experimentally only copper appears to be a suitable pure metal catalyst for the process. Adapted from [139].

In the United Stales, (he term copper signifies copper that contains less than 0.5% impurities or alloying elements. Copper-base alloys arc those that contain no less than 40% copper. Additionally, copper appears as a minor, hut important ingredient of several alloys. There are six major types of commercial, unalloyed copper. These are described briefly in Table I. 

Although the nodules vary widely in their composition over the world oceans, metals are concentrated in three distinct types. One type comprises the nickel-copper-iich nodules of the Clarion-Clipperton variety, which is mainly formed in the equatorial regions. Another type, high in cobalt (1% or more) and low in nickel and copper, appears to be most commonly formed on sea mounts. The third type is high in manganese (35% or more), but low in other metals it is known mainly on the eastern side of the Pacific Basin. As of the early 1980s. the most economically attractive were the cobalt-rich nodules. 

It is evident that copper appears to be the major component in most of the coins of all emperors and titles. What becomes interesting is that lead is almost always the major component in the percent fraction of elements other than copper, even more so than tin. In Figures 1 - 3, for instance, it appears most prominently that even with the outliers removed, lead is present in greater amounts than tin. 

Copper appears to function only as a surface heat transfer agent. Broken pieces of porous plate, for example, may also be used. 

The structure of the reduced protein903 involves displacement of the Cu atom by about 0.4 A in a direction such that the Cu—S(Met) bond decreases to 2.74 A, while the imidazole of His-87 is displaced about 0.4 A away from the copper. The copper appears to move within the ligand cage. 

The greater affinity of humic acids for copper or lead ions is clearly reflected in the extraction values reported in Fig. 2.1. In particular, far less of the adsorbed material was displaced by the salt solutions. The amount of lead retrieved by these extractants, and also with the mineral acids and buffer solutions, exceeded the copper recoveries, so copper appears to be more firmly bound than lead on the humic acid samples studied. 

The other two redox-active metals are two copper ions designated CuA and CuB also bound in different ways to the protein. The CuA is located in subunit II, and CuB appears to be in subunit I, together with the two cytochromes (Holm et al., 1987). There is evidence that in some oxidase preparations there are three rather than two coppers, but the third copper appears to be non-functional. 

In the case of the purely aliphatic ligand 2,2,6,6-tetrakis(amino-methyl)-4-azaheptane (12), complex formation with copper appears to proceed in two steps, as elucidated by titration experiments with the fully protonated ligand (12 5 HC1). Three and two protons from (Hr,12) + are sequentially abstracted, and the predominant species after full deprotonation appears to be a dinuclear complex in which two copper(II) ions are coordinated, each in square planar fashion, by the l,3-diaminoprop-2-yl units of two molecules of pentaamine ligand, thus forming a macrocyclic complex of composition [Cu2(12)2]4+ (23). The UV/vis spectral data show an interesting solvent dependence, suggesting an equilibrium between [Cu2(12)2]4 + and two equivalents of mononuclear complex [Cu(12)]2+ under suitable conditions. ESR spectroscopic data are also compatible with the formulation of a dinuclear species. Further addition of base to an aqueous solution of [Cu2(12)2]4+ gives the mononuclear hydroxo complex [(12)Cu(OH)]+, as inferred from the UV/vis spectroscopic data. 

A quantitative X-ray diffraction study of the Cu/ZnO catalysts (41) has revealed that varying amounts of copper appear in an X-ray amorphous... 

Copper appeared generally distributed at about 2 /xg/cm2, probably from the processing water or equipment. Copper was the blue colorant in the French papers, perhaps Blue Verditer, 2CuC03 Cu(OH)2 (8). Copper was present at the 10-/xg/cm2 level in Amies pink, blue, cream, and white papers, but was absent in his yellow paper. 

Degradation of PEEK in the presence of copper appears to be catalyzed by Cu(II) or the reduction of Cu(II) to Cu(I). Metallic copper does not catalyze the decomposition of PEEK. On metallic copper, the PEEK remains intact to at least 350°C. Cu(I) does not show a strong interaction with PEEK. PEEK loss from the Cu(I) surface, possibly due to desorption, is apparent below 300 C. Up to 250°C, Cu(II) retains the PEEK in a manner similar to the metallic copper. However, there is a marked loss of PEEK on Cu(II) near 250 C and a reduction in the copper oxidation state. These two observations suggest that chemical reaction is occurring. 

After aqueous impregnation, copper(II) chloride is present as a highly dispersed phase on the surface of zeolites. After a thermal treatment in nitrogen and subsequently in ammonia, the copper appears to be present as isolated ions in the zeolite. Therefore, impregnation is a suitable method to prepare non-acidic copper-zeolites. As copper vaporization is limited with a catalyst not having a cation excess, a zeolite pre-exchanged with ammonium ions and consecutively impregnated with copper seems especially suitable. 

The absorption of ozone by cyanide solutions in stirred reactors is complicated by mass transfer considerations. The presence of ozone gas in the exhaust from such a reactor does not indicate that equilibrium has been obtained between ozone gas bubbles and ozone in solution, but rather that the mass transfer through the individual bubbles is not complete, because of the resistance on the gas side. In other words, mass transfer controls the reaction, as the ozone will react almost instantaneously with the cyanide ion in solution. The presence of some metals, particularly copper, appears to speed up the absorption by acting as oxygen carriers. A solution of ozone in dilute acid decomposes somewhat more quickly when a trace of cupric ion is added. The presence of these metal catalysts, if this be their function, does not appear to be a necessary condition to ozone oxidation. What is important is that adequate mass transfer time and surface be available, as would be found in a countercurrent packed tower. 

Ceruloplasmin is synthesized primarily by the hepatic parenchymal cells, with small amounts synthesized by macrophages and lymphocytes. The peptide chain is formed first, then copper is added from an intracellular ATPase (absent in Wilson s disease see later in this chapter) Cu "-glutathione complexes may be involved in the transfer. The CHO side chains are subsequently added in the endoplasmic reticulum. Copper appears to be essential for the normal folding of the polypeptide chain and possibly for normal CHO side chain attachment. However, apoCp is synthesized even in the absence of copper or the ATPase most is degraded intraceHularly, but moderate amounts are released into the circulation, where apoCp has a very short half-life. 

Differences between copper and silver have been seen for the heterogeneously catalysed liquid-phase oxidation of cumene. Copper appears to initiate the reaction by decomposition of the hydroperoxide. The subsequent free-radical reaction occurs in the liquid phase. There is some evidence that silver initiates, this process via an adsorbed molecular oxygen species. If this is correct, this species is reacting in a different manner when compared to its reaction with gas-phase alkenes. In the latter, O—O bond cleavage occurs while the cumene oxidation mechanism would necessarily involve Ag—O bond cleavage. 

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