![]() Nickel monoxides are available commercially in different forms as laboratory reagents and as industrial products. The temperature of formation may also affect the crystalline structure and the incidence of defects within it ( Sunderman et al., 1987 Benson et al., 1988a). The temperature of formation of nickel oxide (up to 1045 ☌) determines the colour of the crystal (jet-black to apple green), the crystalline surface area and the nickel content (< 0.03–0.81% by weight). Typical compositions are given in Table 4. Austenitic steels are the major group of nickel-containing steels. Nickel alloys can be categorized as nickel-chromium, nickel-chromium-cobalt, iron-nickel-chromium and copper-nickel alloys. Nickel-aluminium alloy (for the production of Raney nickel) is available as European Pharmacopoeia grade with the following typical analysis: nickel, 48–52% aluminium, 48–52% and chloride, 0.001% ( Riedel-de Haën, 1986). Metallic nickel undergoes surface oxidation in air oxidation of finely divided nickel powder can result in the conversion of a large fraction of the metal to oxide upon prolonged storage ( Cotton & Wilkinson, 1988). Other components include carbon (1.5–1.8%), sulfur ( 99% nickel, with carbon, copper, iron, sulfur and oxygen as impurities ( Sibley, 1985). ![]() For example, anhydrous nickel sulfate and the hexahydrate are similarly soluble in unbuffered water ( Grandjean, 1986), but the hexahydrate dissolves several orders of magnitude faster than the anhydrate.įerronickel contains 20–50% nickel ( Sibley, 1985). ![]() Different forms of nominally the same nickel compound can have very different solubilities in a given solvent, and particle size, hydration and crystallinity can markedly affect the rate of dissolution. Compounds with solubilities towards the middle of this range are not easily classified in this way. Water-soluble nickel compounds include nickel chloride (642 g/l at 20☌) and nickel sulfate (293 g/l at 20☌), while nickel monosulfide (3.6 mg/l at 18☌) and nickel carbonate (93 mg/l at 25☌) are classed as insoluble ( Weast, 1986). Nickel compounds are sometimes classed as soluble or insoluble in water such a classification can be useful in technical applications of the various compounds but may not be relevant to determining their biological activity. Data on solubility refer to saturated solutions of the compound in water or other specified solvents. Known physical properties of some of the nickel compounds considered in this monograph are given in Table 2. Chemical and physical properties of the pure substance
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