Nickel occurrence

Continued exposure of the nickel-chromium alloy to more severely sulphurising and reducing atmospheres results in local depletion of chromium to such an extent that nickel sulphide and the eutectic are formed internally. The latter constituents are not often observed in service failures, but the relative instability of nickel sulphide in the presence of chromium sulphide can result in its reduction to nickel during slow cooling on shut down. That nickel sulphide is formed is suggested by the frequent occurrence of blisters, associated with the formation of molten eutectic on the surface of sulphur-attacked specimens . 

Ni3(2,2,2-tet)3(/u-N3)3](PF6)3 and its perchlorate analogue have been suggested as trinuclear complexes with an irregular triangle structure.2117 While a crystal structure is lacking, EXAFS and XANES spectra support the occurrence of azido-bridged trinuclear nickel(II) compounds with Ni- -Ni separations of 5.16 A and 5.12 A, respectively. Two J parameters had to be... 

Occurrence. Iron is highly abundant (about 5.5% of the earth s crust) it is believed that the core of earth is mostly molten iron together with nickel. The most common ore is haematite (Fe203). Iron is found in other minerals such as magnetite, limonite, siderite, pyrite. Iron is found native in meteorites known as siderites. 

Occurrence. Arsenic is associated with sulphide minerals (As4S4 realgar, As2S3 orpiment, FeAsS arsenopyrite, Cu3AsS4, enargite, etc.). Occasionally arsenic is found as free element, usually in ore containing cobalt, antimony, nickel. 

Nickel porphyrins are of interest because of their occurrance in coal, shale, and petroleum deposits (1) and because of their key role in biological conversion of COg to methane (2--5). The enzyme methylreductase is the nickel-tetrapyrrole-containing enzyme that catalyses the final step, and possibly other steps, in the 6-electron reduction of CO2 to methane (6). The active site of the methylreductase enzyme contains a nickel-sirochlorin derivative called F 3q (6-8). Understanding the involvement of in methane... 

Figure 2.9 Redox-driven translocation of the anion X (e.g., chloride), based on the Nin/Nim change. The nickel center acts both as an engine and as areceptor for the X anion (when in the Ni111 state). Occurrence of the reversible X translocation is afforded by the following sequence of anion affinity Nim > Cu11 > Ni11.

The SSM sample was spiked with seven different heavy metals. The concentrations of each spike were followed arsenic - 500 mg/kg, cadmium-1000 mg/kg, chromium - 1500 mg/kg, copper - 9500 mg/kg, lead - 14,000 mg/kg, nickel - 1000 mg/kg, and zinc - 22,500 mg/kg. The concentrations used were based on the occurrence, frequency and concentration of contaminants commonly found in Superfund soils. 

Jhe distribution of beryllium, boron, titanium, vanadium, chromium, cobalt, nickel, copper, zinc, gallium, germanium, tin, molybdenum, yttrium, and lanthanum in the principal coal-producing beds of the Interior Province has been studied by the U. S. Geological Survey. Data, methods of sampling, and analyses are discussed by Zubovic and others (II, 12). This chapter discusses the occurrence of 13 of these elements with respect to geological and geochemical environments of coal deposition and chemical properties of the elements. Zinc and tin are not included in this study because they were detected in only a few samples. 

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