The term "cobalt" is met with in the writings of Paracelsus, Agricola and Basil Valentine, being used to denote substances which, although resembling metallic ores, gave no metal on smelting.
For the technical preparation of cobalt, and its separation from nickel, see Nickel.
Metallic cobalt may be obtained by reduction of the oxide or chloride in a current of hydrogen at a red heat, or by heating the oxalate, under a layer of powdered glass.
Cobalt burns in nitric oxide at 150° C. giving the monoxide.
Three characteristic oxides of cobalt are known, the monoxide, CoO, the sesquioxide, C0203, and tricobalt tetroxide, C0304; besides these there are probably oxides of composition Co02, Co 8 0 9, C0607 and C0405.
Cobalt monoxide, CoO, is prepared by heating the hydroxide or carbonate in a current of air, or by heating the oxide C0304 in a current of carbon dioxide.
Cobalt sesquioxide, Co 2 0 3, remains as a dark-brown powder when cobalt nitrate is gently heated.
Heated at 190-300° in a current of hydrogen it gives the oxide C0304, while at higher temperatures the monoxide is formed, and ultimately cobalt is obtained.
Cobalt dioxide, Co02, has not yet been isolated in the pure state; it is probably formed when iodine and caustic soda are added to a solution of a cobaltous salt.
The barium and magnesium salts of this acid are formed when baryta and magnesia are fused with cobalt sesquioxide.
By heating a mixture of cobalt oxalate and sal-ammoniac in air, it is obtained in the form of minute hard octahedra, which are not magnetic, and are only soluble in concentrated sulphuric acid.
They are precipitated from their alkaline solutions as cobalt sulphide by sulphuretted hydrogen, but this precipitation is prevented by the presence of citric and tartaric acids; similarly the presence of ammonium salts hinders their precipitation by caustic alkalis.
Cobalt chloride, CoC1 2, in the anhydrous state, is formed by burning the metal in chlorine or by heating the sulphide in a current of the same gas.
By the addition of excess of ammonia to a cobalt chloride solution in absence of air, a greenishblue precipitate is obtained which, on heating, dissolves in the solution, giving a rose-red liquid.
The iodide, Co12, is produced by heating cobalt and iodine together, and forms a greyish-green mass which dissolves readily in water forming a red solution.
Cobalt fluoride, CoF 2.2H 2 0, is formed when cobalt carbonate is evaporated with an excess of aqueous hydrofluoric acid, separating in rose-red crystalline crusts.
Sulphides of cobalt of composition C04S3, CoS, C03S4, C02S3 and CoS 2 are known.
The most common of these sulphides is cobaltous sulphide, CoS, which occurs naturally as syepoorite, and can be artificially prepared by heating cobaltous oxide with sulphur, or by fusing anhydrous cobalt sulphate with barium sulphide and common salt.
Cobaltous sulphate, CoSO 4.7H 2 O, is found naturally as the mineral bieberite, and is formed when cobalt, cobaltous oxide or carbonate are dissolved in dilute sulphuric acid.
In a similar way potassium and ammonium cobalt alums have been obtained.
It may be prepared by the addition of potassium nitrite to an acetic acid solution of cobalt chloride.
This salt may be used for the separation of cobalt and nickel, since the latter metal does not form a similar double nitrite, but it is necessary that the alkaline earth metals should be absent, for in their presence nickel forms complex nitrites containing the alkaline earth metal and the alkali metal.
Cobalt ammonium phosphate, CoNH4PO 4.12H 2 0, is formed when a soluble cobalt salt is digested for some time with excess of a warm solution of ammonium phosphate.
The double cyanides of cobalt are analogous to those of iron.
A large number of cobalt compounds are known, of which the empirical composition represents them as salts of cobalt to which one or more molecules of ammonia have been added.
The pentammine purpureo-salts are formed from the luteo-salts by loss of ammonia, or from an air slowly oxidized ammoniacal cobalt salt solution, the precipitated luteosalt being filtered off and the filtrate boiled with concentrated acids.
Cobalt salts may be readily detected by the formation of the black sulphide, in alkaline solution, and by the blue colour they produce when fused with borax.
For the quantitative determination of cobalt, it is either weighed as the oxide, C0304, obtained by ignition of the precipitated monoxide, or it is reduced in a current of hydrogen and weighed as metal.
For the quantitative separation of cobalt and nickel, see E.
Cobalt occurs in New South Wales, Victoria and South Australia, and efforts have been made in the former state to treat the ore, the metal having a high commercial value; but the market is small, and no attempt has been made up to 1907 to produce it on any large scale.
The manganese ores of the Bathurst district of New South Wales often contain a small percentage of cobalt - sufficient, indeed, to warrant further attempts to work them.
Iron, coal and slate are the chief products, and copper and cobalt may be added.
Ore of cobalt is obtained in no other locality in India, and although zinc blende has been found elsewhere it is known to have been extracted only in this province.
The mining industry, for which the town was formerly also famous and which embraced tin, silver and cobalt, has now ceased.
He found, however, that chromic acid, which he had represented as Cr06, neutralized a base containing 3 the 3 The following symbols were also used by Bergman: W, V, " + ", which represented zinc, manganese, cobalt, bismuth, nickel, arsenic, platinum, water, alcohol, phlogiston.
Towards the middle of the 18th century two new elements were isolated: cobalt by G.
The condensation of acetylene to benzene is also possible at ordinary temperatures by leading the gas over pyrophoric iron, nickel, cobalt, or spongy platinum (P. Sabatier and J.
If the bead is coloured we may have present: cobalt, blue to violet; copper, green, blue on cooling; in the reducing flame, red when cold; chromium, green, unaltered in the reducing flame; iron, brownish-red, light-yellow or colourless on cooling; in the reducing flame, red while hot, yellow on cooling, greenish when cold; nickel, reddish to brownish-red, yellow to reddish-yellow or colourless on cooling, unaltered in the reducing flame; bismuth, yellowish-brown, light-yellow or colourless on cooling; in the reducing flame, almost colourless, blackish-grey when cold; silver, light yellowish to opal, somewhat opaque when cold; whitish-grey in the reducing flame; manganese, amethyst red, colourless in the reducing flame.
To the filtrate from the aluminium, iron and chromium precipitate, ammonia and ammonium sulphide are added; the precipitate may contain nickel, cobalt, zinc and manganese sulphides.
The next group may contain black nickel and cobalt sulphides, flesh-coloured manganese sulphide, and white zinc sulphide.
Trans., 1900, p. 233) investigated nickel and cobalt over a wide range of temperature (from -182.5° to loo°); his results are: It is evident that the atomic heats of these intimately associated elements approach nearer and nearer as we descend in temperature, approximating to the value 4.
Small amounts of nickel and cobalt are often present.
Cobalt is deposited by a method analogous to that used for its sistermetal nickel.
Nickel and cobalt are also strongly magnetic, and in 1903 the interesting discovery was made by F.
Practically the metals iron, nickel and cobalt, and some of their alloys and compounds constitute a class by themselves and are called ferromagnetic substances.
The applicability of the law to cobalt has been investigated by Fleming (Phil.
Mag., 1899, 48, 271), who used a ring of cast cobalt containing about 96% of the pure metal.