The conductances, transference numbers, and activity coefficients of aqueous solutions of the chlorides of lanthanum, cerium, praseodymium, and neodymium have been determined for concentrations up to 0.1 normal . The transference numbers were determined by the moving-boundary method as developed by Longsworth and MacInnes; the activity coefficients were measured by using concentration cells with transference; and the conductances were obtained with a conventional apparatus of the type recommended by Jones and Josephs. The accuracy of all measurements was within 0.1 per cent.</p
