Ceric hydroxide, Ce(OH)₄

Ceric hydroxide, Ce(OH)₄. - The normal hydroxide is not known. When ammonia or an alkali hydroxide is added to a solution of a ceric salt, a yellow, gelatinous precipitate of ceric hydroxide is obtained, insoluble in excess of precipitant; it is usually contaminated with basic salt and adsorbed alkali hydroxide. A pure hydroxide may be prepared from ceric ammonium nitrate by precipitation with ammonia from a cold solution, the precipitate being washed, allowed to become nearly dry at a low temperature, and again washed with cold water to remoye ammonium nitrate. When dried over potassium hydroxide, its composition corresponds with the formula Ce₂O(OH)₆ or 2CeO₂.3H₂O.

Ceric hydroxide may be conveniently prepared by the oxidation of cerous hydroxide. For this purpose excess of alkali hypochlorite or hypobromite may be added to a cerous salt, or, what amounts to the same thing, precipitation may be effected by alkali hydroxide and the oxidation then accomplished by the use of chlorine or bromine. Ceric hydroxide may also be prepared by heating hydrated perceric hydroxide to 120° or boiling its aqueous suspension until decomposition of the peroxide has been completed.

Ceric hydroxide dissolves in nitric or sulphuric acid with the production of a ceric salt, but reduction to the cerous state usually occurs to a slight extent. According to Brauner, the reduction is complete if the hydroxide has been prepared from perceric hydroxide and its solution in sulphuric acid is effected in a platinum dish, but this is denied by Barbieri. Ceric hydroxide reacts with hydrochloric acid to produce cerous chloride, chlorine, and water.

Colloidal ceric hydroxide may be prepared by dialysing a 10 per cent, aqueous solution of ceric ammonium nitrate for four or five days. The hydrosol thus obtained is very readily coagulated; when evaporated, it leaves a gummy residue, soluble in hot water. The hydroxide is positively charged.