Lanthanum Hydroxide is a highly water insoluble crystalline Lanthanum source, which can be obtained by adding an alkali such as ammonia to aqueous solutions of lanthanum salts such as lanthanum nitrate. This produces a gel-like precipitate that can then be dried in air. Lanthanum hydroxide does not react much with alkaline substances, however is slightly soluble in acidic solution. It is used compatibly with higher (basic) pH environments.