Lanthanum acetate, 2La(C₂H₃O₂)₃

Lanthanum acetate, 2La(C₂H₃O₂)₃.3H₂O, crystallises from its aqueous solution in thin prisms.

When a cold aqueous solution of lanthanum acetate is made ammoniacal, a colloidal basic acetate is precipitated; if a little solid iodine be added to the precipitate a blue adsorption compound is produced, similar in appearance to the familiar "starch-iodide" precipitate. The blue substance may conveniently be prepared by adding a solution of iodine in potassium iodide to a cold solution of lanthanum acetate (or nitrate acidified with acetic acid), adding ammonia cautiously until very little iodine is left unchanged, and then warming the mixture very gently.