White nickel

F. B. Howard-White, Nickel, An HistoricalRepieii>, Methuen Company, London, 1963, pp. 69—71. 

White nickel. Wolfachite (See Chloanthite) Ni(SbAs)S Silver-white 6-4 4-5-5 Rhombic... 

Today nickel is the fourth most-used metal after iron, chromium and lead. During the 19th century, white-nickel-containing alloys were produced in Europe as substitutes for silver and, around 1870, nickel began to be used in steels and platings. Nickel production has increased considerably since 1940, and today half the nickel produced is used in stainless steels. Nickel is used in numerous alloys and coatings, and in chemical compounds. It is also found in products for occupational and private use, many of which may come into contact with the skin (Grandjean et al. 1989 Sunderman 1989). 

Chloanthite (syn., white nickel) [Named from Greek, chloantos, greenish) (ICSD 2518 and PDF 35-752) (Ni,Co)As, Cubic 432 Isotropic 5.5 6400- 6600 Habit massive, granular, euhedral crystals. Color tin white or dark gray. Luster metallic. Diaphaneity opaque. Streak grayish black. Fracture uneven. 

Nickel is silvery white and takes on a high polish. It is hard, malleable, ductile, somewhat ferromagnetic, and a fair conductor of heat and electricity. It belongs to the iron-cobalt group of metals and is chiefly valuable for the alloys it forms. 

Copper and nickel can be alloyed with zinc to form nickel silvers. Nickel silvers are ductile, easily formed and machined, have good corrosion resistance, can be worked to provide a range of mechanical properties, and have an attractive white color. These alloys are used for ornamental purposes, as sHverplated and uncoated tableware and flatware in the electrical iadustry as contacts, connections, and springs and as many formed and machined parts (see Electrical connectors). 

Substituted Nickel Carbonyl Complexes. The reaction of trimethyl phosphite and nickel carbonyl yields the monosubstituted colorless oil, (CO)2NiP(OCH )2 [17099-58-0] the disubstituted colorless oil, (CO)2Ni[P(OCH )2]2 [16787-28-3] and the trisubstituted white crystalline soHd,... 

Nickel Oxalate. This salt, NiC204, mol wt 146.7, is produced as a greenish white crystalline dihydrate [6018-94-6]. It decomposes by heating at 320°C under vacuum into Ni metal and carbon dioxide. Nickel oxalate is used for the production of nickel catalysts and magnetic materials. 

Fig. 5. A 90° polished cross section of a production white titania enamel, with the microstructure showing the interface between steel and direct-on enamel as observed by reflected light micrography at 3500 x magnification using Nomarski Interface Contrast (oil immersion). A is a steel substrate B, complex interface phases including an iron—nickel alloy C, iron titanate crystals D, glassy matrix E, anatase, Ti02, crystals and F, quart2 particle.

Alloyed white cast irons fall into the second categoiy. This group includes the nickel-chromium grades known as Ni-nards (Durman,... 

The electrolytes used were acetate buffer at pEI values 2, 4 and 6 and the same electrolyte is used in the presence of EDTA at pEI values of 2 and 6. Iron and copper contents could be most easily determined in EDTA medium at pH 6. The best medium for nickel was found to be as ammonia buffer pH 9.5 qg/L, it could be separated from zinc in this medium. The elements determined in white and red wine were Cu, Pb, Zn, Cd, Fe and Ni. The quantities found were for iron about 9000 qg/L, for copper 290 qg/L, Ni 80 qg/L, lead 150 qg/L and zinc 460 qg/L. The validation was made by determining each element under different conditions. 

Fig. 20.3(a) A piece of a nickel-based super-alloy cut open to show the structure there are two sizes of precipitates in the alloy - the large white precipitates, and the much smaller black precipitates in between. 

Xep4 is best prepared by heating a 1 5 volume mixture of Xe and Fi to 400°C under 6 atm pressure in a nickel vessel. It also is a white, crystalline, easily sublimed solid the molecular shape is square planar (Xe-F 195.2pm) and is essentially the same in both the solid and gaseous phases. Its properties are similar to those of XeFi except that it is a rather stronger fluorinating agent, as shown by the reactions ... 

The product is hydrogenated in 4,000 cc of ethanol at room temperature and under normal atmospheric pressure with a catalyst prepared In the usual manner from 400 g of Raney nickel alloy. The calculated amount of hydrogen is taken up in approximately 75 hours. After filtration and evaporation to a small volume, the residue Is distributed between 1,000 cc of chloroform and water each. The chloroform solution is then dried over sodium sulfate and evaporated to a small volume. Precipitation of the hydrogenation product with petroleum ether yields an amorphous white powder which Is filtered by suction, washed with petroleum ether and dried at 50°C In a high vacuum. 1. athyl-2-podophyllinic acid hydrazide is obtained in a practically quantitative yield. 

Steam forms a protective white film at temperatures up to about 250°C, but above this temperature steam can, under some conditions, react with aluminium progressively to form aluminium oxide and hydrogen. Sintered aluminium powder (S. A.P.) has relatively good resistance to steam at 500°C, but at about 300°C an addition of 1% nickel to the S.A.P. is needed to prevent rapid disintegration. 

White brass deposits containing 85% zinc and 15% copper have also been plated to a limited extent , mainly as an undercoating for chromium during the nickel shortage, but they did not prove fully satisfactory. 

The first major use of titanium dioxide was as a replacement for toxic lead compounds in paint It combines a brilliant white color with very high covering power. Addition of certain compounds of nickel changes the white color to yellow cobalt compounds give a green paint. 

Kinetics. Extensive studies of the kinetics of methane synthesis were reported by White and co-workers (10,11, 12, 13, 14, 15). They studied the reaction between CO and hydrogen over a reduced nickel catalyst on kieselguhr at 1 atm and 300°-350°C (10). They correlated the rate of methane formation by the equation ... 

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