Cobalt, Chlo′′ride of. CoCl2. Syn. Hydrochlo′′rate of c., Mu′′riate of c. Prep. By dissolving the carbonate or protoxide in hydrochloric acid; the solution deposits deep rose-red crystals on standing, which contain water. By evaporating the solution by heat, anhydrous blue crystals of the chloride are obtained. Both of them yield a deep rose-red solution with water, which is turned green by a little acid. This solution forms a well-known sympathetic ink, the traces of which become blue when heated. If the solution contains either chloride of iron or chloride of nickel, the traces become green. (Klaproth.) The addition of a little nitrate of copper to the above solution forms a sympathetic ink, which by heat gives a very rich greenish-yellow colour. (Ure.) The addition of a very little common salt makes the traces disappear with greater rapidity, on the withdrawal of the heat. In each case, when the paper is laid aside, moisture is absorbed, and the writing once more disappears. If, however, much heat has been used the traces become permanent.
Cobalt, Ni′trate of. Co(NO3)2. Prep. As the last, substituting nitric for hydrochloric acid; it forms deliquescent crystals.
Cobalt, Ox′alate of. CoC2O4. Prep. As the acetate, from oxalic acid and the carbonate or protoxide; or by double decomposition.
Cobalt, Ox′ides of. Of these there are two, the protoxide and the sesquioxide; besides an acid compound of cobalt and oxygen, to which the name cobaltic acid has been given.
1. Cobalt, Protox′ide of. CoO. Syn. Oxide of cobalt, Grey o. of c., Black o. of c., Cobalt black. Prep. 1. By precipitating a solution of sulphate of chloride of cobalt with carbonate of sodium, and washing, drying, and igniting the powder which subsides.
2. By boiling powdered bright-white cobalt ore (from Cornwall) in dilute nitric acid, and adding a solution of carbonate of potassium, very gradually, until the clear liquor, after the impurities have settled, becomes of a rose colour; and then as long as a precipitate falls; wash and dry it as before.
Prop., &c. A grey powder, turning black on exposure to the air; strongly basic; and forming salts with the acids, having a fine red tint. It is remarkable for the magnificent blue colour it communicates to glass, and by this character its presence may be readily detected before the blowpipe; the substance to be examined being fused with borax on a loop of platinum wire. Used to make blue colours for painters, stains and glazes for enamellers, glass-melters, potters, &c. In medicine it has occasionally been given as a remedy for rheumatism.
2. Cobalt, Sesquiox′ide of. Co2O3. Syn. Perox′ide of Cobalt. A black, insoluble, neutral powder, obtained by mixing solutions of cobalt and of chloride of lime; or, by heating the protoxide to redness in an open vessel.
Cobalt, Phos′phate of. Co3(PO4)2. Prep. As the acetate, substituting phosphoric for acetic acid. An insoluble purple powder, which, when heated along with eight times its weight of gelatinous alumina, produces a blue pigment (COBALT BLUE, COBALT ULTRAMARINE), almost equal in beauty to ultramarine. (See below.)
Cobalt, Sul′phate of. CoSO4. By boiling sulphuric acid on the metal, or by dissolving the oxide in the acid. It forms reddish crystals, soluble in 24 parts of water.