| When potassium chromate, or dichromate, is added to a solution of a bismuth salt, the yellow precipitate formed, if allowed to remain in contact with the solution, gradually darkens in colour, yielding the double salt, K2O.Bi2O3.4CrO3. Boiling with water removes all the alkali and leaves the basic salt, Bi2O3.2CrO3. On warming the double salt with a concentrated solution of chromic acid, dark red crystals of the compound, K2O.Bi2O3.6CrO3.H2O, are formed, which likewise decompose on boiling with water. |