A single-pass method for the ion-exchange separations of binary mixtures of metals is described, and experimental applications are presented. The method consists of complexing each of the components in the mixture with a separate complexing agent at a pH sufficient to ensure maximum coordination of the metals. The complexing agents are chosen such that the metal complexes formed are of opposite charge. The mixture is then passed through an ion-exchange resin which absorbs one species completely, allowing the other to be collected in the effluent. An anion-or cation-exchange resin is used.