Lanthanum hydroxide, La(OH)₃

Lanthanum hydroxide, La(OH)₃, is produced by the direct union of lanthana and water, and may be obtained as a white, gelatinous precipitate by the addition of an excess of ammonia or alkali hydroxide to a solution of a lanthanum salt. The precipitate is sufficiently soluble in water to turn red litmus blue; it easily absorbs carbon dioxide from the air and sets free ammonia from ammonium salts. Lanthanum hydroxide is, in fact, the strongest base of all the rare earth hydroxides, being comparable with calcium hydroxide in its strength, and on this account the claim of Baskerville and Catlett to have prepared metallic lanthanates, in which lanthana acts as an acid, cannot be accepted until independent confirmation of their results is forthcoming.