Nickel Fluoride, obtained by the action of hydro fluoric acid on nickel chloride, crystallizes in yellowish green prisms which volatilise above i,000° C. It is difficultly soluble in water, and combines with the alkaline fluorides to form double salts. Nickel chloride, is obtained in the anhydrous condi tion by heating the hydrated salt to 14o° C., or by gently heating the finely divided metal in a current of chlorine. It readily sub limes when heated in a current of chlorine, forming golden yellow scales. It is easily reduced when heated in hydrogen. It forms crystalline compounds with ammonia and the organic bases. It is soluble in alcohol and in water. Three hydrated forms are known, viz., a mono-, di- and hexa-hydrate, the last being the form usually obtained by the solution of the oxide or carbonate in hydrochloric acid. Nickel chloride ammonia, is obtained as a white powder when anhydrous nickel chloride is exposed to the action of ammonia gas, or in the form of blue octahedra by evaporating a solution of nickel chloride in aqueous ammonia. When heated to 1 oo° C. it loses four molecules of am monia (see AMMINES). Numerous double chlorides of nickel and other metals are known. The bromide and iodide of nickel resem ble the chloride and are prepared in a similar fashion.
Several sulphides of the element have been obtained. The monosulphide, NiS, is obtained by heating nickel with sulphur, by heating the monoxide with sulphuretted hydrogen to a red heat, and by heating potassium sulphide with nickel chloride to 160 18o° C. When prepared by dry methods it is an exceedingly stable, yellowish, somewhat crystalline mass. When prepared by the precipitation of nickel salts with alkaline sulphide in neutral solu tion it is a greyish black amorphous compound which readily oxi dizes in moist air, forming a basic nickel sulphate. The freshly precipitated sulphide is somewhat soluble in hydrochloric acid and yellow ammonium sulphide. Nickel sulphate, is obtained anhydrous as a yellow powder when any of its hydrates are heated. When heated with carbon it is reduced to the metal. It forms hydrates containing one, two, five, six and seven molecules of water. The heptahydrate is obtained by dissolving the metal or its oxide, hydroxide or carbonate in dilute sulphuric acid (pref erably in the presence of a small quantity of nitric acid), and allowing the solution to crystallize between 15° and 2o° C. It crystallizes in emerald green rhombic prisms and is moderately soluble in water. It effloresces gradually on exposure to air and passes into the hexahydrate. It loses four molecules of water of crystallization when heated to ioo° C. and becomes anhydrous at about 300° C. Nickel sulphate combines with many metallic sul phates to form double salts, and also forms additional compounds with ammonia, aniline and hydroxylamine. The nitrate, Ni is obtained by dissolving the metal in dilute nitric acid and concentrating the solution between 40° and 50° C. It crystallizes in green prisms which deliquesce rapidly on exposure to moist air.
Nickel Carbonyl, is obtained as a colourless mobile liquid by passing a carbon monoxide over reduced nickel, at a temperature of about 8o° C. (see above). It boils at 43° C. (751 mm.), and sets at — 25° C. to a mass of crystalline needles. It is readily soluble in hydrocarbon solvents, in chloroform and in alcohol. Its critical pressure is 3o atmospheres and its critical temperature is in the neighbourhood of 195° C. It decomposes
with explosive violence when heated rapidly, and is decomposed by the halogens (dissolved in carbon tetrachloride) with libera tion of carbon monoxide and formation of a nickel halide. With aromatic hydrocarbons in the presence of anhydrous aluminium chloride, in the cold, there is a large evolution of hydrochloric acid gas, and an aldehyde is formed; at 100° C., on the other hand, anthracene derivatives are produced. Thus by using benzene, benz aldehyde and anthracene are obtained. Nickel carbonate, NiCO3, is obtained in the anhydrous state by heating nickel chloride with calcium carbonate in a sealed tube to 15o° C. It crystallizes in microscopic rhombohedra insoluble in cold acids. By precipitation of nickel salts with solutions of the alkaline carbonates, basic carbonates of variable composition are obtained. (X.) The world's chief source of nickel is Canada : in 1913 she con tributed 69% of the world's production. The heavy World War demand caused the Canadian output to increase, and by 1918 it had risen from 20,000 tons in 1914 to 41,000 tons in 1918, which latter figure represented 87% of the world's production for that year. The highest percentage was reached in 192o, when Canada produced 88% of the world's supply. As a result of the market being congested with large stocks and accumulated scraps at the end of the war, Canadian production declined, reaching its lowest ebb in 1922, when less than 8,000 tons of Canadian nickel were mined. When the congested supplies had been absorbed, the industry quickly revived; demand soon ex ceeded production, and a steadily increasing output has since been maintained. The world's output in 1923 was estimated at about 30,00o tons, of which approximately 27,000 tons were produced from the nickel mines in Canada, including a relatively small quantity of nickel recovered as a by-product from the cobalt-silver ores in that Dominion.
With regard to foreign producers of nickel, the most important is the island of New Caledonia, a French possession about 1,25o m. north-east of Australia. This island's output, in spite of the increased demand for the metal between 1914 and 1918, has since then gradually fallen, being in 1921 only about 14% of the world's output. Norway, which in the earliest days of the industry held a monopoly of the world's supply, closed down her mines in 1921 for economic reasons. In the United States the nickel deposits are nowhere being worked for the metal, though a small quantity is incidentally recovered there each year in the process of electrolytic refining of blister copper. Under the exigencies of war Germany produced from her own low-grade mines a small tonnage of nickel ore, but since the close of hos tilities she has reverted to the practice of importing refined metal. Besides the above, there have been obtained from time to time small supplies of ore from Greece, Tasmania, Sweden, etc.
Practically the whole of the Canadian output is obtained from the Sudbury district in the Province of Ontario, relatively small quantities being obtained from the deposits 15o m. due north of Sudbury in the Temiscaming district, and from the cobalt-silver area in the same province. Other occurrences are known in the townships of MaCart, Munro, Strathy and near Lake Sheben dowan in the district of Thunder Bay, Ontario, and nickeliferous pyrrhotite associated with copper occurs in the Gabbro copper mines, Vancouver Island, British Columbia.
For nickel plating see ELECTROPLATING.