Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/530

Rh 488 NICKEL when refined and puddled, yields a very superior kind of wrought iron, harder and less liable to oxidation than the ordinary metal. Extraction of Metal from Mats and Speises. The first step as a rule is a roasting process, which, in the case of a speis, yields an arseni- ferous mixture of oxides ; a mat, in general, passes into a mixture of oxide, sulphate, and unchanged sulphide. Either roasted material is easily disintegrated by being treated with aqueous muriatic or sulphuric acid, with formation of a solution of nickel- salt, contaminated, in general, with arsenic, antimony, bismuth, copper, iron, cobalt, and zinc, which must be removed by suitable analytical methods. But, as we have no space to consider this problem in its general form, we will assume antimony, bismuth, and zinc to be absent. If, in this case, the iron predominates sufficiently over the arsenic, these two can both be removed at one stroke by evaporating the solution to dryness and calcining the residue at the lowest sufficient temperature ; the iron-salt only is reduced to an insoluble basic salt (of Fe 2 3 ), which includes all the arsenic, so that by redissolving in water and passing the liquor through a filter press we obtain a solution which, by theory, is free of iron and arsenic. Practically, however, a trace of iron remains, and must be removed by precipitation with carbonate of lime in the cold and filtration. A repetition of the same process at about 60 C. elimi nates the copper, so that only the cobalt is left, which, however, is no impurity metallurgically, and consequently may be suffered to remain, but, if present in sufficient quantity, must be recovered for its own sake. This is effected by addition of bleaching powder and gentle heating. If care be taken to let a little of the cobalt escape, the rest goes down as black peroxide, Co 2 3, sufficiently pure for its ordinary applications. From the filtered nickel solution the metal is precipitated, by addition of milk-of-lime, as a green hydrated oxide, which is collected and washed in a filter press. The precipitate, being inconveniently gelatinous and bulky, is next rendered compact by a gentle calcination, and, if it is, as usual, contaminated with sulphate of lime, is freed from this impurity by judicious washing with highly dilute muriatic acid or otherwise. The purified oxide then, either by mere pressure or with the help of starch or other plastifying material, is shaped into little cubes of about one centimetre s side, embedded in charcoal dust within graphite or fire-clay crucibles and heated in a fire. A dull red heat suffices for the mere reduction of the oxide to metal ; but a strong red heat is applied in order to cause the nickel cubes to sinter together and become fast and compact. No degree of red heat will fuse them unless they are contaminated with copper. There is no need to explain how, with cupriferous leys, the process has to be modified to lead ultimately to a fused regulus of copper- nickel available for the preparation of german silver. From a copper-free liquor, provided only it contains its iron all as ferric snlt, a pure nickel precipitate can be obtained at once by addi tion of oxalic acid. The (green) oxalate of nickel precipitate need only be washed, dried, and ignited to be converted into a pure (but partially oxidized) metal. This process has actually been applied, at least experimentally, in the working of the New Caledonian ore, with this modification, however, that the oxalic acid was recovered by boiling the oxalate of nickel with carbonate of potash, and precipitating the acid by milk-of-lime from the alkaline solution. Ordinary cube-nickel contains from 94 to 99 per cent, of real nickel. The purest commercial metal is that extracted from the New Caledonian ore ; it often contains only a fraction of a per cent, of impurities. The present writer has no information regarding the mechanical characters of such highly-refined New Caledonian metal. The best com mercial cube-nickel (although it may contain less than 1 per cent, of impurities) is always utterly devoid of plasticity ; it breaks under the hammer, although the pure metal, as was shown as early as 1804 by Bichter, and confirmed by Deville in 1856, is highly ductile and tenacious. To obtain the pure metal, the best laboratory method is to prepare pure oxalate and heat it intensely in a close crucible made of quicklime, when it is obtained as an almost silver-white regulus, which has all the ductility and malleability of the best wrought iron combined with one and a half times the breaking strain and greater hardness. It is attracted by the magnet. Its specific gravity is 8 279 for ingot, and 8 666 (Richter) for the forged metal. It can be welded at a red heat like wrought iron, which it exceeds in relative infusibility. It does not tarnish even on long exposure to the air. Sulphuretted hydrogen does not blacken it. Liquid water, even in the presence of air, has no action upon it. Aqueous non-oxidizing acids act upon it as they do on iron, but more slowly. Nitric acid and aqua regia dissolve it as nitrate Ni(NO 3 ) 2 and chloride NiCl 2 respectively. When heated strongly in air it is gradually oxidized ; it decomposes steam, slowly, at a red heat. In brief, it unites in itself all the virtues of iron with some of the characteristics of the noble metals, and yet its application in the mechanical arts was never thought of until Fleitmann in 1879 made a most remarkable observation. Finding that even the purest nickel which he could produce on a manufacturing scale was brittle, he attributed this defect not to the traces of metallic impurities still present in it but to occluded carbonic oxide, and tried to remove this by addition of magnesium to the molten metal. He suc ceeded beyond expectation : one-eighth of a per cent, of magnesium added to the metal (in an atmosphere of carbonic acid) before pouring imparted to it all the plasticity of the pure metal. 1 Fleitmann also found that the thus purified nickel could be permanently welded on wrought iron, and that a combination plate thus produced could be rolled out into the thinnest sheet without breach of continuity. Since that time his firm (Fleitmann & Witte of Iserlohn) have made a business of the manu facture of cooking utensils and other useful articles out of such nickel-plated iron. Physiological experiments on a dog, instituted at the instance of the firm, showed that the metal is innocuous. Cobalt, as Fleitmann found, behaves in every respect like nickel, and even exceeds it in whiteness and brilliancy. 2 The writer has for more than a year been in the habit of using a nickel basin (supplied by Messrs Johnson & Matthey of London) for operations with caustic-alkali lye, and finds it to work admirably better, in fact, than a silver one. Nickel Electroplating. This art, invented by Bottcher about 1848, has developed into an important industry, especially in the United States. The best kind of solution to use is one of the double sul phate of nickel and ammonia, which should be saturated at 25 and used in conjunction with a plate of nickel as positive electrode. Alloys. Nickel alloys were used practically long before Cronsted s discovery of the metal. GERMAN SILVER (q.v.), long known to the Chinese as &quot; Pack Tong,&quot; i.e., &quot; white copper,&quot; consists of nickel, copper, and zinc united in varying proportions, 3 of copper, 1 of zinc, and 1 of nickel is said to give the most silver-like alloy. An alloy of &quot; german &quot; with real silver has lately been introduced as &quot;tiers-argent&quot;; it consists of silver 27 6, copper 59 0, zinc 9 6, nickel 3 4 per cent. In the United States, in Belgium, and in Germany, an alloy of 1 of nickel with 3 of copper serves for the making of minor coins. All these alloys are non-magnetic. Salts. For nickel salts see CHEMISTRY and chemical hand books. Analysis. Nickel-salts, as a rule, and their solutions more gene rally, exhibit a green colour. Sulphuretted hydrogen does not precipitate the metal from solutions containing free mineral acid. Sulphide of ammonium, from neutral or alkaline solutions, precipi tates a black sulphide which, like sulphide of cobalt, when once produced is almost insoluble in dilute cold hydrochloric acid, and has the specific property of being very appreciably ^soluble in a mixture of yellow (i.e., ordinary) sulphide of ammonium and free ammonia, forming a dark coffee-brown solution. Unlike iron-salts, nickel-salts are not oxidized into sesquioxide (analogous to Fe 2 3 ) salts by nitric acid or chlorine. Carbonate of baryta, which readily precipitates oxide of iron (Fe 2 3 ) and alumina, does not precipitate nickel from its solutions in the cold. By means of these reactions nickel is easily distinguished and separated from all other metals except cobalt. To test a nickel solution for cobalt, add excess of nitrite of potassium and acidify with acetic acid. Cobalt, if present, comes down gradually as &quot;Fischer s salt,&quot; a double nitrite of Co 2 3 and K 2. The atomic weight of nickel, according to the latest determina. tions, is identical with that of cobalt : Ni( = Co) = 58 6, being 16. Karmarsch and Heeren s Technisches Wiirterbuch gives a very full account of the metallurgy of nickel, quite up to date (1883). (W. D.) 1 It is perhaps well to repeat a warning given by Fleitmann, that the introduction of the magnesium, if not very cautiously done in the absence of air, leads to violent explosions. 2 It is only fair to state that as early as the Universal Exhibition of Vienna in 1873 the American Wharton exhibited vessels of pure forged nickel, prepared from the spongy metal by strong compression under a steam hammer at a red heat.