Lanthanum peroxide

An oxide of lanthanum higher than La₂O₃ cannot be prepared in the dry way, but indications of the existence of such an oxide have been obtained.

When a mixture of ammonia and hydrogen peroxide is added to a solution of a lanthanum salt, a gelatinous, hydrated peroxide, La₉O₅.xH₂O, is obtained, to which the constitution (OH)₂La(O.OH) has been ascribed. Dilute sulphuric acid and carbonic acid set free hydrogen peroxide from the precipitate, and concentrated sulphuric acid decomposes it with the liberation of ozonised oxygen.