NICK′EL. Ni. Syn. Nickelium, L. A metal obtained from kupfernickel, a native arsenide of nickel found in Westphalia; also from nickel speiss, an impure arsenio-sulphide of nickel left after the manufacture of cobalt blue from its ores.
Prep. The powdered ore is roasted first by itself, and next with charcoal powder, until all the arsenic is expelled, and a garlic odour ceases to be evolved; the residuum is mixed with sulphur 3 parts, and potassium hydrate, 1 part, and the compound is melted in a crucible with a gentle heat; the fused mass when cold, is reduced to powder, edulcorated with water, dissolved in sulphuric acid mixed with a little nitric acid, and precipitated with potassium carbonate; the precipitate (nickelous carbonate) is washed, dried, mixed with powdered charcoal, and, lastly, reduced by the heat of a powerful furnace.
When nickel predominates in the ore, after the arsenic, iron, and copper have been separated, ammonia is digested in the mixed nickelous and cobaltous oxides, and the resulting blue solution, after dilution with boiled pure water, is treated with potassium hydrate until the colour disappears, when the whole is put into an air-tight vessel, and set it aside for some time. The powder (nickelous hydrate) which subsides, after edulcoration, is mixed with charcoal, and reduced by fusion in a crucible containing some crown glass.
On the small scale, for chemical purposes, pure nickel is best obtained by moderately heating nickelous oxalate in a covered crucible lined with charcoal.
Prop. White; hard; malleable; magnetic; capable of receiving the lustre of silver; sp. gr., when hammered, about 8·82; fusibility between that of manganese and iron; it is not oxidised in the air; and is little attacked by dilute acids unless when nitric acid is present;
this last acid dissolves it freely. With the acids, &c., it forms numerous compounds, most of which may be prepared by the direct solution of the carbonate. A specimen of the metal reduced from the pure oxide in a current of hydrogen was beautifully white and silvery; its sp. gr. was 8·575, and it was almost as soft as copper.
Tests. The salts of nickel in the anhydrous state are for the most part yellow; when hydrated, green,—and furnish solutions possessing a pale green colour. Solutions of its salts exhibit the following reactions:—Alkaline hydrates give a pale apple-green precipitate, insoluble in excess, but soluble in a solution of carbonate of ammonium, yielding a greenish-blue liquid. Ammonia gives a similar precipitate, soluble in excess, yielding a deep purplish-blue solution. The presence of ammonium salts or free acids interferes with this reaction. Cyanide of potassium produces a green precipitate, soluble in excess, forming an amber-coloured liquid, which is reprecipitated by hydrochloric acid. This last precipitate is scarcely soluble in excess of the acid in the cold, but readily so upon boiling the liquid. Ferrocyanide of potassium gives a greenish-white precipitate. Sulphuretted hydrogen occasions no change in solutions of nickel containing free mineral acid; but in alkaline solutions gives a black precipitate. Sulphide of ammonium in neutral solutions gives a black precipitate, soluble with difficulty in hydrochloric acid; but freely soluble in aqua regia.
Estim. Nickel may be thrown down from its ore in the form of either carbonate or hydrate, and after ignition may be weighed as oxide, each grain of which is equal to 7⁄8 gr. of pure nickel; or, more accurately, ·7871 gr.
According to Rose, nickel may be separated from cobalt as follows:—The mixed metals are dissolved in considerable excess of hydrochloric acids, and the solution is diluted with a very large quantity of water; a current of chlorine is then passed through the liquor for several hours, and the upper part of the flask is left filled with the gas after the current has ceased; barium carbonate is next added, in excess, the whole digested together, with frequent agitation for 15 or 18 hours, and then thrown on a filter. The filtrate yields pure nickelous oxide by precipitation with hydrate of potassium; whilst the residuum on the filter, after being washed in water, dissolved in hot hydrochloric acid, and the barium precipitated with sulphuric acid, furnishes, with hydrate of potassium, a precipitate of cobaltous hydrate, free from nickel, which, when washed and dried, is reduced in a platinum or porcelain crucible by hydrogen gas.
Uses. Nickel is chiefly employed in the manufacture of German silver. Some of its salts have been recently introduced into medical practice, and appear likely to prove most valuable additions to the materia medica. It has also been recently used for deposition by