Cobalt Chromate, CoCrO4, results as a greyish-black crystalline powder when a mixture containing cobalt carbonate (12.4 grams), chromium trioxide (20 grams), and water (20 grams) is heated for four hours in a sealed tube at 185° C. It is much more soluble than the corresponding nickel salt. The dihydrate CoCrO4.2H2O yields bronze-coloured acicular prisms.
Basic salts are produced when cobalt salts are precipitated with sodium chromate, or when the alkali-containing double salts first produced by precipitation with ammonium or potassium chromates are subjected to continued treatment with hot water. The following double salts have been described:
(NH4)2Co(CrO4)2.6H2O; (NH4)2CrO4.3CoCrO4.2NH3.3H2O; K2O.4CoO.4CrO3.3H2O and K2Co(CrO4)2.2H2O; Cs2Co(CrO4)2.6H2O. |