Ceroceric hydroxide

Ceroceric hydroxide, Ce(OH)₃.Ce(OH)₄ or 4Ce(OH)₃.3Ce(OH)₄. - When white cerous hydroxide is exposed to air or oxygen, it absorbs oxygen and is eventually converted into yellow ceric hydroxide, but the initial product of oxidation has a violet or purple tint. A precipitate of the same violet colour is obtained by adding an alkali hydroxide to a solution of a mixture of a cerous and a ceric salt, and the colour attains a maximum intensity when the ratio Ce^III Ce^IV has a certain definite value, which, however, can only be approximately estimated. Wyrouboff and Verneuil consider that this intermediate hydroxide is obtained in a pure state by precipitating ceroceric hydrosulphate with alkali, and, if this is the case, its composition is probably expressed by one or other of the alternative formulae given above. The violet hydroxide becomes bluish-black in colour when dried in vacuo, but a slight oxidation to ceria is always observed.