# 1911 Encyclopædia Britannica/Nickel

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​NICKEL (symbol Ni, atomic weight 58·68 (O＝16)), a metallic element. It has been known from the earliest times, being employed by the Chinese in the form of an alloy called pakfong. It was first isolated in an impure condition in 1751 by A. F. Cronstedt from niccolite, and his results were afterwards confirmed by T. O. Bergman in 1775 (De niccolo, opusc. 2, p. 231; 3, p. 459; 4, p. 374). It occurs in the uncombined condition and alloyed with iron in meteorites; as sulphide in millerite and nickel blende, as arsenide in niccolite and cloanthite, and frequently in combination with arsenic and antimony in the form of complex sulphides. In recent years it has been found in considerable quantities in New Caledonia in the form of a hydrated silicate of nickel and magnesia approximating to the constitution (NiO, MgO)SiO$_2$·nH$_2$O (J. Garnier, 1865), and in Canada in the form of nickeliferous pyrrhotines, which consist of sulphides of iron associated with sulphides of nickel and copper, embedded in a matrix of gneiss. At the present time nickel is obtained practically entirely from garnierite and the nickeliferous pyrrhotines. When the former is used it is roasted with calcium sulphate or alkali waste to form a~ matte which is then blown in a Bessemer converter or heated in a reverberatory furnace with a siliceous flux with the object of forming a rich nickel sulphide. This sulphide is then by further heating converted into the oxide and finally reduced to the state of metal by ignition with carbon in clay crucibles. The process adopted for the Canadian ores, which are poor in copper and nickel, consists in a preliminary roasting in heaps and smelting in a blast furnace in order to obtain a matte, which is then further smelted with a siliceous flux for a rich matte. This rich matte is then mixed with coke and salt-cake and melted down in an open hearth furnace. The nickel sulphide so obtained is then roasted to oxide and reduced to metal. For a wet method of extraction ​ of the matte see Christofle and Bouilhet, French Patent 111591 (1876). L. Mond (Jour. Soc. Chem. Ind. 1895, p. 945) has obtained metallic nickel from the Canadian mattes by first roasting them and then eliminating copper by the action of sulphuric acid, the product so obtained being then exposed to the reducing action of producer gas at about 350° C. The reduced metal is then passed into a “volatilizer” and exposed to the action of carbon monoxide at about 80° C., the nickel carbonyl so formed being received in a chamber heated to 180–200° C., where it decomposes, the nickel being deposited and the carbon monoxide returned to the volatilizer. For an electrolytic method of treating mattes, see T. Ulke, Moniteur scient., 1897, 49, p. 450. The metal as obtained by industrial methods rarely contains more than about 99–99·5% of nickel, the chief impurities being copper, iron, cobalt, silicon and carbon.
The following tables show the output of nickel from Canada and the shipments of nickel ore from New Caledonia in recent years:—
(see Rothwell’s Mineral Industry (1908), pp. 666,670).
The metal may also be obtained on the small scale by the reduction of the oxide by hydrogen or by carbon, by ignition of the oxalate or of nickel ammonium oxalate (J. J. Berzelius), by reduction of the chloride in a current of hydrogen (E. Péligot), by electrolysis of nickel ammonium sulphate (Winkler, Zeit. anorg. Chem. 1894, 8, p. 1), and by reduction of the chloride with calcium carbide.
It is a greyish white metal, and is very malleable and ductile. Its specific gravity varies according to the method employed for its preparation, the extreme values being 8·279 and 9·25. It melts between 1400–1600° C. Its specific heat increases with rise of temperature, the mean value from 15° to 100° C. being 0·1084 (A. Naccari, Gazz., 1888, 18, p. 13). It is magnetic, but loses its magnetism when heated, the loss being complete at about 340–350° C. On the physical constants see H. Copaux, Comptes rendus, 1905, 140, p. 651. Nickel occludes hydrogen readily, is attacked by the halogen elements, and oxidizes easily when heated in air. In the massive state it is unacted upon by dry air, but if moistened with acidified water, oxidation takes place slowly. When obtained by reduction processes at as low a temperature as possible the finely divided metal so formed is pyrophoric, and according to P. Schutzenberger (Comptes rendus, 1891, 113, p. 177) dry hydrochloric acid gas converts this form into nickel chloride and a volatile compound of composition NiHCl. It decomposes water at a red heat. According to E. St Edme (Comptes rendus, 1886, 106, p. 1079) sheet nickel is passive to nitric acid, and the metal remains passive even when heated to redness in a current of hydrogen. On the reduction of organic compounds by hydrogen in the presence of metallic nickel see P. Sabatier and J. B. Senderens, Ann. Chim. Phys., 1905 [8], 4, pp. 319, 433.
It rapidly oxidizes when fused with caustic soda, but is scarcely acted upon by caustic potash (W. Dittmar, Jour. Soc. Chem. Ind., 1884, 3, p. 103). Hydrochloric and sulphuric acids are almost without action on the metal, but it dissolves readily in dilute nitric acid. Nickel salts are antiseptic; they arrest fermentation and stop the growth of plants. Nickel carbonyl, however, is extremely poisonous. On the toxic properties of nickel salts see A. Riche and Laborde, Jour. Pharm. Chem., 1888, [5], 17, pp. 1, 59, 97.
Nickel is used for the manufacture of domestic utensils, for crucibles, coinage, plating, and for the preparation of various alloys, such as German silver, nickel steels such as invar (nickel, 35·7%; steel, 64·3%), which has a negligible coefficient of thermal expansion, and constantan (nickel, 45%; copper, 55%), which has a negligible thermal coefficient of its electrical resistance.
Compounds.
Nickel Oxides.—Several oxides of nickel are known. A suboxide, Ni$_2$O (?), described by W. Muller (Pogg. Ann., 1869, 212, p. 59), is not certainly known. The monoxide, NiO, occurs naturally as bunsenite, and is obtained artificially when nickel hydroxide, carbonate, nitrate or sulphate is heated. It may also be prepared by the action of nickel on water. by the reduction of the oxide Ni$_2$O$_3$, with hydrogen at about 200° C. (H. Moissan, Ann. Chim. Phys., [5], 21, p. 199), or by heating nickel chloride with sodium carbonate and extracting the fused mass with water. It is a green powder which becomes yellow when heated. It dissociates at a red heat, and is readily reduced to the metal when heated with carbon or in a current of hydrogen. It is readily soluble in acids, forming salts, the rate of solution being rapid if the oxide is in the amorphous condition, but slow if the oxide is crystalline. The hydroxide, Ni(OH)$_2$, is obtained in the form of a greenish amorphous powder when nickel salts are precipitated by the caustic alkalis. It is readily soluble in acids and in an aqueous solution of ammonia. Nickel sesquioxide, Ni$_2$O$_3$, is formed when the nitrate is decomposed by heat at the lowest possible temperature, by a similar decomposition of the chlorate, or by fusing the chloride with potassium chlorate. It is a black powder, the composition of which is never quite definite, but approximates to the formula given above. When heated with oxy-acids it dissolves, with evolution of oxygen, and with hydrochloric acid it evolves chlorine. Numerous hydrated forms of the oxide have been described (see W. Wernicke, Pogg. Ann., 1870, 217, p. 122). A peroxide, NiO$_2$, has been obtained in the form of dinickelite of barium, BaO·2NiO$_2$, by heating the monoxide with anhydrous baryta in the electric furnace (E. Dufau, Comptes rendus, 1896, 123, p. 495). G. Pellini and D. Meneghini (Zeit. anorg. Chem., 1908, 60, p. 178) obtained a greyish green powder of composition NiO$_2$·xH$_2$O, by adding an alcoholic solution of potassium hydrate to nickel-chloride and hydrogen peroxide at −50°. It has all the reactions of hydrogen peroxide, and S. Tanatar (Ber., 1909, 42, p. 1516) regards it as NiO·H$_2$O$_2$. An oxide, Ni$_3$O$_4$, has been obtained by heating nickel chloride in a current of moist oxygen at about 400° C. (H. Baubigny, Comptes rendus, 1878, 87, p. 1082), or by heating the sesquioxide in hydrogen at 190° C. (H. Moissan, Ann. Chim. Phys., 1890 [5], 21, p. 199). The former method yields greyish, metallic-looking, microscopic crystals, the latter a grey amorphous powder. A hydrated form, Ni$_3$O$_4$·2H$_2$O, is obtained when the monoxide is fused with sodium peroxide at a red heat and the fused mass extracted with water.
Nickel Salts.—Only one series of salts is known, namely those corresponding to the monoxide. In the anhydrous state they are usually of a yellow colour, whilst in the hydrated condition they are green. They may be recognized by the brownish violet colour they impart to a borax bead when heated in an oxidizing flame. The caustic alkalis added to solutions of nickel salts give a pale green precipitate of the hydroxide, insoluble in excess of the precipitant. This latter reaction is hindered by the presence of many organic acids (tartaric acid, citric acid, &c.). Potassium cyanide gives a greenish yellow precipitate of nickel cyanide, Ni(CN)$_2$, soluble in excess of potassium cyanide, forming a double salt, Ni(CN)$_2$·2KCN, which remains unaltered when boiled with excess of potassium cyanide in presence of air (cf. Cobalt). Ammonium sulphide precipitates black nickel sulphide, which is somewhat soluble in excess of the precipitate (especially if yellow ammonium sulphide be used), forming a dark-coloured solution. Ammonium hydroxide gives a green precipitate of the hydroxide, soluble in excess of ammonia, forming a blue solution. Numerous methods have been devised for the separation of nickel and cobalt, the more important of which are:—the cobaltinitrite method by which the cobalt is precipitated in the presence of acetic acid by means of potassium nitrite (the alkaline earth metals must not be present); the cyanide method (J. v. Liebig, Ann., 1848, ,65, p. 244; 1853, 87, p. 128), in which the two metals are precipitated by excess of potassium cyanide in alkaline solution, bromine being afterwards added and the solution warmed, when the nickel is precipitated. The latter method has been modified by adding potassium cyanide in slight excess to the solution of the mixed salts, heating for some time and then adding mercuric oxide and water, the whole being then warmed on the water bath, when a precipitate of mercuric oxide and nickel hydroxide is obtained ​(Liebig). M. Ilinski and G. v. Knorre (Ber., 1885, 18, p. 169) separate the metals by adding nitroso-β-naphthol in the presence of 50% acetic acid, a precipitate of cobalti nitroso-β-naphthol, [C$_{10}$H$_6$O(NO)]$_3$Co, insoluble in hydrochloric acid, being formed, whilst the corresponding nickel compound dissolves in hydrochloric acid. E. Pinerua separates the metals by taking advantage of the fact that cobalt chloride is soluble in ether which has been saturated with hydrochloric acid gas at low temperature. For an examination of the above and other methods see E. Hintz, Zeit. anal. Chem., 1891, 30, p. 227.
Nickel fluoride, NiF$_2$, obtained by the action of hydrofluoric acid on nickel chloride, crystallizes in yellowish green prisms which volatilise above 1000° C. It is difficultly soluble in water, and combines with the alkaline fluorides to form double salts. Nickel chloride, NiCl$_2$, is obtained in the anhydrous condition by heating the hydrated salt to 140° C., or by gently heating the finely divided metal in a current of chlorine. It readily sublimes 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 latter being the form usually obtained by the solution of the oxide or carbonate in hydrochloric acid. Nickel chloride ammonia, NiCl$_2$·6NH$_3$, is obtained as a white powder when anhydrous nickel chloride is exposed to the action of ammonia gas (H. Rose, Pogg. Ann., 1830, 96, p. 155), or in the form of blue octahedra by evaporating a solution of nickel chloride in aqueous ammonia. When heated to 100° C. it loses four molecules of ammonia. Two hydrated forms have been described, one containing three molecules of water and the other half a molecule. Numerous double chlorides of nickel and other metals are known. The bromide and iodide of nickel resemble the chloride and are prepared in a similar fashion.
Several sulphides of the element have been obtained. A subsulphide, Ni$_2$S(?), results when the sulphate is heated with sulphur or when the precipitated monosulphide is heated in a current of hydrogen. It forms a light yellow amorphous mass which is almost insoluble in acids. 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 160-180° 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 solution it is a greyish black amorphous compound which readily oxidizes in moist air, forming a basic nickel sulphate. The freshly precipitated sulphide is soluble in sulphurous acid and somewhat soluble in hydrochloric acid and yellow ammonium sulphide (see H. Baubigny, Comptes rendus, 1882, 94, pp. 961, 1183; 95, p. 34). Nickel sulphate, NiSO$_4$, 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 (preferably in the presence of a small quantity of nitric acid), and allowing the solution to crystallize between 15° and 20° 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 100° C. and becomes anhydrous at about 300° C. The hexahydrate is dimorphous, a tetragonal form being obtained by crystallization of a solution of the heptahydrate between 20° and 30° C., and a monoclinic form between 50° and 70° C. Nickel sulphate combines with many metallic sulphates to form double salts, and also forms addition compounds with ammonia aniline and hydroxylamine. The nitrate, Ni(NO$_3$)$_2$·6H$_2$O, 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, Ni(CO)$_4$, is obtained as a colourless mobile liquid by passing carbon monoxide over reduced nickel at a temperature of about 60° C. (L. Mond, Langer and Quincke, Jour. Chem. Soc., 1890, 57, p. 749). 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 30 atmospheres and its critical temperature is in the neighbourhood of 195° C. (J. Dewar, Proc. Roy. Soc., 1903, 71, p. 427). It decomposes with explosive violence when heated rapidly. Dewar and Jones (Journ. Chem. Soc., 1904, p. 203) have made an exhaustive study of its reactions, and find that it is decomposed by the halogens (dissolved in carbon tetrachloride) with liberation of carbon monoxide and formation of a nickel halide. Cyanogen iodide and iodine mono- and tri-chloride effect similar decompositions with simultaneous liberation of iodine; sulphuric acid reacts slowly, forming nickel sulphate and liberating hydrogen and carbon monoxide. Hydrochloric and hydrobromic acids are without action; hydriodic acid only reacts slowly. 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, benzaldehyde and anthracene are obtained. Dewar and Jones suggest that in the latter reaction it is the metallic nickel which is probably the reducing agent effecting the change, since it is only dissolved in any quantity when the anthracene hydrocarbon is produced. When mesitylene is used, the reaction does not proceed beyond the aldehyde stage since hydrocarbon formation is prevented by the presence of a methyl group in the ortho-position to the -CHO group. Acids and alkalis are in general without action on nickel carbonyl. The vapour of nickel carbonyl burns with a luminous flame, a cold surface depressed in the flame being covered with a black deposit of nickel. It is an extremely powerful poison. Mond and his assistants have discovered several other carbonyls. For example cobalt gives CO(CO)$_4$, as orange crystals which melt at 51°, decomposing at a higher temperature, giving CO(CO)$_3$ and CO at 60°; CO(CO)$_3$ forms jet black crystals. For iron carbonyls see Iron; also L. Mond, H. Hirtz and M. D. Cowap, Jour. Chem. Soc., 1910, 97, p. 798. Nickel carbonate, NiCO$_3$, is obtained in the anhydrous state by heating nickel chloride with calcium carbonate in a sealed tube to 150° C. (H. de Sénarmont, Ann. Chim. Phys., 1850 [3], 30, 138). 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.
Numerous determinations of the atomic weight of nickel have been published, the values obtained varying from 58·0 to approximately 59·5. The more recent work of T. W. Richards and Cushman (Chem. News, 1899, 79, 163, 174, 185) gives for the atomic weight of the metal the values 58·69 and 58·70.