Nickel (sym. Ni; atom. wt. 58.6; sp. gr. 8.3 to 8.7). This metal was discovered by Cronstedt in 1751; but long before he isolated the metal, alloys of it obtained from ore were used by the Chinese. Within living memory it was considered a feat to fuse a piece of nickel as large as a hazel-nut, so that it may be said to be a comparatively recent addition to the useful metals. It was shown by Richter in 1804, and again by Deville in 1856, that the pure metal is malleable and ductile and of higher tenacity than wrought-iron. Nevertheless the only application of nickel previous to 1879 was as a constituent of certain alloys—German Silver (q.v.), for example—usually for the purpose of giving them a white colour. In that year Fleitmann of Iserlohn, having previously ascertained that the brittle nature of all commercial nickel was due to occluded carbonic oxide, discovered that the addition of one-eighth per cent. of magnesium (which requires to be made with due precaution in an atmosphere of carbonic acid) conferred upon it the malleability of the pure metal. He was likewise successful in welding nickel thus refined to wrought-iron so thoroughly that two pieces of these metals—i.e. one of each—joined in this way could be rolled out into a very thin sheet without any break in the continuity of either surface. Fleitmann's firm have turned this to useful account by manufacturing cooking-pots and other articles iron-plated with nickel on both sides. The action of organic acids on nickel is so slight that these cooking utensils may be safely used. Nickel can also be made malleable by the addition of metallic manganese in the proportion of 5 parts of the latter to 100 parts of the former. This process was patented by Messrs Wiggins of Birmingham on 11th March 1880, specification No. 1058. Wharton in 1873 or earlier made vessels in America of pure nickel rendered malleable by forging it in a spongy state with a steam-hammer.
Nickel is of a white colour, its peculiar hue being between that of silver and bright steel. It is not altered by exposure even to moist air, and it is not tarnished by sulphuretted hydrogen. Dilute sulphuric and hydrochloric acid attack it only slowly, but it dissolves readily in nitric acid. Caustic alkali lyes have no action upon the metal. Owing to these properties and to its having the strength and malleability of wrought-iron, nickel is a valuable metal for many purposes. Besides its use in forming highly serviceable alloys with copper and zinc, of which German silver and some of the white compounds used for coinage on the continent of Europe are the most important, it is employed alone for nickel-plating, for chemical vessels, and, as has been stated, for coating iron cooking-pots in thin layers. An electro-deposit of nickel on steel instruments, such as those used in surgery, is specially useful in preventing rust. Magnets are sometimes made of nickel; and now that it can readily be made pure enough to be welded, rolled into sheets, drawn into wire, stamped, or raised by beating, it is likely to receive new applications. In 1890 it was reported that the Americans had proved by trials at Annapolis that armour-plates of steel alloyed with nickel are superior to such plates made of steel itself; and preparations were made in other countries to try this nickel-steel on a large scale. In 1873 the price of nickel rose from 4s. to 16s. per lb. on Germany adopting a nickel alloy for coinage. Owing to the now abundant supply, it has fallen to 2s. per lb. In 1889 it was announced by the German chemist Kruss that he had succeeded in splitting up nickel and cobalt each into two parts, and that both these metals have one component in common; but this has not been confirmed by subsequent research. See the Chemical News (1889).
Ores of Nickel.—Till about 1875 the most important ore was kupfer-nickel (false copper). This mineral is arsenide of nickel, and contains from 35 to 45 per cent. of the metal. It is found in Norway, Germany, Hungary, France, and the United States. It is abundant in some districts of South America, and sometimes is found in Cornwall. Magnetic pyrites or pyrrhotite, a compound of iron and sulphur, often contains from 3 to 5 per cent. of nickel. When it does so it is used as an ore of that metal. It has been largely smelted for nickel at New Jersey, and a nickelferous ore of this kind is now found plentifully in Norway. Nickel glance is a compound of nickel with arsenic and sulphur, in which the percentage of nickel varies from 25 to 35 per cent. It is found in Sweden, in the Harz, in Thuringia, and one or two other places. Pentlandite is a sulphide of iron and nickel, found in Norway and in Argylshire. It has from 14 to 20 per cent. of nickel. Millerite, a sulphide of nickel, rich in the metal, is found in Lancaster county, Pennsylvania. Ullmanite is a compound of sulphur, antimony, and nickel; and Annabergite is an arseniate of nickel. Garnierite is an ore of nickel, which was first discovered about 1874 in New Caledonia, and is now the most important source of the metal. It is a hydrosilicate of magnesia and nickel, and contains on an average from 7 to 10 per cent. of the latter. Its value as an ore is increased by the fact that it is without either arsenic or sulphur. Large quantities of it have been shipped to England and France, and in some years the total production of the island amounted to 12,000 tons, representing 850 tons of nickel. An ore similar to that from New Caledonia has been discovered in Oregon and in North Carolina, apparently in rich deposits in the former state. Discoveries of nickel ore have also been made in Texas and Nevada. Extensive deposits of mixed nickelferous pyrrhotite and copper pyrites have within the last four years been found in Canada (Sudbury district), and some are now being vigorously worked. Kupfer-nickel or nickeline and a rich amorphous nickel ore are known to occur on Michipicoton Island. The nickel ore raised in Canada in 1888 amounted to 1,220,000 lb.
Nickel is not found separately in the native state, but it is always present in meteoric iron. Cobalt is very frequently associated with nickel in ores. In the smelting of arsenical ores the product obtained in the first instance is called speiss, but in one smelting operation regulus, metal, and slag may be obtained as well as speiss. Nickel speiss is a mixture chiefly of the arsenides and sulphides of nickel, iron, and copper, left as a residue in the pot used in the preparation of Smalt (q.v.), from complex arseniferous nickel and cobalt ores previously roasted. In this process the cobalt practically all passes into the blue glass of which smalt consists.
Smelting.—At the older nickel-works in different parts of Europe much of the nickel produced is extracted from speiss or from regulus, in either of which the metal has become concentrated, and may amount to from 30 to 60 per cent. A good deal of secrecy has been observed regarding the smelting of nickel, but accounts of some of the processes in use have been published. Briefly stated, one of these consists in removing by suitable methods the metals other than nickel in the speiss, in getting rid of the arsenic by forming an alkaline arsenite which is soluble in water, and in obtaining a sulphide of nickel which is usually mixed with a small quantity of cobalt. This sulphide when boiled with sulphuric acid yields sulphate of nickel, from which potash precipitates the hydrated oxide mixed with a little cobalt. The separation of the oxides of nickel and cobalt is effected by dissolving the mixture of them in an acid, neutralising, and adding a slight excess of nitrite of potassium and acetic acid. After a few hours the double nitrite of cobalt and potassium is deposited, while the filtered liquid contains only the nickel. Its hydrate is precipitated by caustic potash and redissolved in oxalic acid. When the oxalate of nickel is heated in a wind-furnace fused metallic nickel is obtained.
The New Caledonia ore (garnierite) is smelted by one process in this way. It is placed along with limestone and coke or charcoal in a furnace about 16 feet high with tuyères. Here a regulus is produced with 60 or 70 per cent. of nickel, and containing also some iron, some carbon, and sometimes a little sulphur. This is manipulated in a Siemens' furnace to remove the iron, and also sulphur if present, and the nickel is then refined with oxide of manganese and alkaline flux in a plumbago crucible.
Oxides of Nickel.—These are nickel monoxide, NiO, the hydrate of this oxide, Ni(OH)2,—both of which are green—and nickel sesquioxide, Ni2O3, which is a black powder. The monoxide of nickel is used to give a soft brown colour to pottery.
Salts of Nickel.—Of these Roscoe and Schorlemmer, in their Treatise on Chemistry, say they are derived from the monoxide. In the anhydrous condition they are usually yellow-coloured, whilst in the hydrated state and combined with colourless acids they possess an apple-green to an emerald-green colour. The soluble normal salts have a slightly acid reaction and a sweetish, astringent, metallic taste, and act as emetics.