Abstract. In order to anticipate radiation - chemical effects in solutions of active lanthanum, various solutions and suspensions containing lanthanum were irradiated with an electron beam. Separation of lanthanum from barium by the alcoholic HCl method is not rendered less efficient by radiation, although considerable gas evolution occurs. Suspensions of lanthanum as hydroxide and as ferrocyanide are not appreciably solubilized by radiation. Lanthanum oxalate is decomposed by radiation, is partially thrown into solution, and finally dissolves completely when all the excess oxalate ion in the solution has been destroyed.