| Description | Catalyst for the hydrogenation of food fats and oils
Exposure to nickel metal and soluble compounds should not exceed 0.05 mg/cm³ in nickel equivalents per 40-hour work week. Nickel sulfide fume and dust is believed to be carcinogenic, and various other nickel compounds may be as well. Nickel carbonyl, [Ni(CO)4], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of a metal as well as the carbonyl's ability to give off highly toxic carbon monoxide gas, and this one is no exception. It is explosive in air.; Four halides are known to form nickel compounds, these are nickel(II) fluoride, chloride, bromide, and iodide. Nickel(II) chloride is produced analogously by dissolving nickel residues in hydrochloric acid. Tetracarbonylnickel (Ni(CO)4), discovered by Ludwig Mond, is a homoleptic complex of nickel with carbon monoxide. Having no net dipole moment, intermolecular forces are relatively weak, allowing this compound to be liquid at room temperature. Carbon monoxide reacts with nickel metal readily to give this compound; on heating, the complex decomposes back to nickel and carbon monoxide. This behavior is exploited in the Mond process for generating high-purity nickel.; Nickel (pronounced /?n?k?l/) is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium. Its use has been traced as far back as 3500 BC, but it was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. Its most important ore minerals are laterites, including limonite and garnierite, and pentlandite. Major production sites include Sudbury region in Canada, New Caledonia and Russia. The metal is corrosion-resistant, finding many uses in alloys, as a plating, in the manufacture of coins, magnets and common household utensils, as a catalyst for hydrogenation, and in a variety of other applications. Enzymes of certain life-forms contain nickel as an active center making the metal essential for them.; Nickel is a silvery-white metal with a slight golden tinge that takes a high polish. It is one of only four elements that are magnetic at or near room temperature. It belongs to the transition metals and is hard and ductile. It occurs most often in combination with sulfur and iron in pentlandite, with sulfur in millerite, with arsenic in the mineral nickeline, and with arsenic and sulfur in nickel galena. Nickel is commonly found in iron meteorites as the alloys kamacite and taenite. Similar to the elements chromium, aluminium and titanium, nickel is a very reactive element, but is slow to react in air at normal temperatures and pressures due to the formation of a protective oxide surface. Due to its permanence in air and its slow rate of oxidation, it is used in coins, for plating metals such as iron and brass, for chemical apparatus, and in certain alloys such as German silver.; Nickel is a solid, silver-white, hard, malleable transition metal with an atomic number of 28. It resists corrosion even at high temperatures. It is present in many alloys in widespread use, including stainless steels. It may also be present as an impurity in any alloy. Nickel is used in the production of coins, jewellery, and nickel-cadmium batteries, and as a catalyst for the hydrogenation of liquid oils to solid fats such as oleomargarine and vegetable shortening. Nickel-containing dental alloys continue to be used successfully in the provision of various forms of dental care. Many of these alloys have applications in the construction of restorations designed to remain in clinical service for many years, including crowns, fixed bridgework, and removable partial dentures. Furthermore, nickel containing alloys find extensive application in orthodontics, including metallic brackets, arch wires, bands, springs and ligature wires. Many instruments and devises, for example, endodontic instruments also contain nickel.; Allergic responses are mediated through the immune system. In a sensitized individual, allergic responses can be initiated by relatively small amounts of the allergen; Nickel plays numerous roles in the biology of microorganisms and plants, though they were not recognized until the 1970s. In fact urease (an enzyme which assists in the hydrolysis of urea) contains nickel. The NiFe-hydrogenases contain nickel in addition to iron-sulfur clusters. Such [NiFe]-hydrogenases characteristically oxidise H2. A nickel-tetrapyrrole coenzyme, F430, is present in the methyl coenzyme M reductase which powers methanogenic archaea. One of the carbon monoxide dehydrogenase enzymes consists of an Fe-Ni-S cluster. Other nickel-containing enzymes include a class of superoxide dismutase and a glyoxalase.; Nickel-56 is produced in large quantities in type Ia supernovae and the shape of the light curve of these supernovae corresponds to the decay via beta radiation of nickel-56 to cobalt-56 and then to iron-56. Nickel-59 is a long-lived cosmogenic radionuclide with a half-life of 76,000 years. 59Ni has found many applications in isotope geology. 59Ni has been used to date the terrestrial age of meteorites and to determine abundances of extraterrestrial dust in ice and sediment. Nickel-60 is the daughter product of the extinct radionuclide 60Fe (half-life = 1.5 Myr). Because the extinct radionuclide 60Fe had such a long half-life, its persistence in materials in the solar system at high enough concentrations may have generated observable variations in the isotopic composition of 60Ni. Therefore, the abundance of 60Ni present in extraterrestrial material may provide insight into the origin of the solar system and its early history. Nickel-62 has the highest binding energy per nucleon of any isotope for any element (8.7946 Mev/nucleon). Isotopes heavier than 62Ni cannot be formed by nuclear fusion without losing energy. Nickel-48, discovered in 1999, is the most proton-rich heavy element isotope known. With 28 protons and 20 neutrons 48Ni is "double magic" (like 208Pb) and therefore unusually stable.; Sensitized individuals may show an allergy to nickel affecting their skin, also known as dermatitis. Sensitivity to nickel may also be present in patients with pompholyx. Nickel is an important cause of contact allergy, partly due to its use in jewellery intended for pierced ears. Nickel allergies affecting pierced ears are often marked by itchy, red skin. Many earrings are now made nickel-free due to this problem. The amount of nickel which is allowed in products which come into contact with human skin is regulated by the European Union. In 2002 researchers found amounts of nickel being emitted by 1 and 2 Euro coins far in excess of those standards. This is believed to be due to a galvanic reaction.; Tetracoordinate nickel(II) takes both tetrahedral and square planar geometries. This is in contrast with the other group 10 elements, which tend to exist as square planar complexes. Bis(cyclooctadiene)nickel(0) is a useful intermediate in organometallic chemistry due to the easily displaced cod ligands. Nickel(III) oxide is used as the cathode in many rechargeable batteries, including nickel-cadmium, nickel-iron, nickel hydrogen, and nickel-metal hydride, and used by certain manufacturers in Li-ion batteries.; The most common oxidation state of nickel is +2 with several Ni complexes known. It is also thought that a +6 oxidation state may exist, however, this has not been demonstrated conclusively. The unit cell of nickel is a face centered cube with a lattice parameter of 0.352 nm giving a radius of the atom of 0.125 nm.; for example, if nickel ions are released from a nickel plated material following direct and prolonged contact with the skin. Individuals are first sensitized to the allergen. Subsequent exposures, if sufficiently high, may then result in an allergic reaction. A number of allergens are used in the clinical practice of dentistry, notably eugenol, mercury, nickel, chromium, cobalt, components of resin-based materials and a host of other chemical agents. The majority of dental allergies, including allergic responses to nickel-containing dental alloys, comprise Type IV hypersensitivity reactions, cell-mediated by T-lymphocytes. Physiologically, it exists as an ion in the body.(PMID: 17243350, 16405986) |
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