NICKEL is a silver-like metal, sp. gr. 8.9. It is magnetic, and is greedy of oxygen, forming gray protoxide and black peroxide. Heat will not oxidate it be cause it drives off oxygen as fast as it fixes ; but the oxides are formed by solu tion in nitric acid, precipitating by pot ash, and then heating to redness. It is usually associated with cobalt : it is al ways present in meteoric stones : in the Harz Mountains it is associated with copper, as kupfernickel ore; with arsenic and iron, as arsenic-nickel. It also exists as an oxide, a sulphuret, and an arsenate, in gneiss, mica slate, and sienite.
The chief of these ores, and that from which most of the nickel of Conemera is obtained, is the copper-colored ore above described as kupfermickel—nickel being a term of detraction used by the German miners, who expected from the color of the ore to find that it contained copper. The salifiable oxide of nickel consists of 30 nickel-1-8 oxygen. Its salts are most of a grass-green color, and the ammo macal solution of its oxide is deep blue, like that of copper. Ferrocyanate of pot assa precipitates it of a white or very pale green color.
Since the manufacture of German sil ver, or argentine, became an object of commercial importance, the extraction of nickel has been undertaken upon a con siderable scale. The cobalt ores are its most fruitful sources, and they are now treated by the method of Wohler to effect the separation of the two metals. The arsenic is expelled by roasting the powdered speiss first by itself, next with the addition of charcoal powder, till the garlic smell be no longer perceived. The residuum is to be mixed with three parts of sulphur and one of potash, melted in a crucible with a gentle heat, and the pro duct being edulcorated with water, leaves a powder of metallic lustre, which is a sidatiret of nickel free from arsenic; while, the arsenic associated with the sul phur, and combined with the resulting sulphuret of potassium, remains dis solved. Should any arsenic still be found
in the sulphuret, as may happen if the first roasting heat was too great, the above process must be repeated. The sulphuret must be finally washed, dis solved in concentrated sulphuric acid, with the addition of a little nitric ; the metal must be precipitated by a carbon ated alkali, and the carbonate reduced with charcoal.
In operating upon kupfernickel, or speiss, in which nickel predominates, after the arsenic, iron, and copper have been separated, ammonia is to be digest ed upon the mixed oxides of cobalt and nickel, which will dissolve them into a blue liquor. This being diluted with distilled water deprived of its air by boil ing, is to be decomposed by caustic pot ash till the blue color disappears, when the whole is to be put into a bottle tightly stoppered, and set aside to settle. The green precipitate of oxide of nickel, which slowly forms, being freed by de cantation from the supernatant red solu tion of oxide of cobalt, is to be eduleo rated and reduced to the metallic state in a crucible containing crown glass. Pure nickel, in the form of a metallic powder, is readily obtained by exposing its oxal ate to moderate ignition.
Since the application of Liebig's cyan ide of potassium to the separation of me tals in a mixed solution, the foregoing mode is generally given up for the use of the cyanide. A solution of cyanide of potassium is added to the mixed oxide, and heat applied. The cyanide must be quite free from cyanate. The solution is boiled to drive off excess of acid. Per oxide of mercury is then added to the solution, when the nickel is precipitated, partly as oxide, partly as pure metal : it is then collected, dried, and calcined, at a red heat, leaves the oxide perfectly free from cobalt.