The platinum-group metals (PGM) are technologically important metals which are becoming increasingly relevant in reducing harm to the environment. The separation and purification of the PGM is largely carried out by exploiting differences in the chemistry of their anionic chloro-complexes. These differences include ligand substitution kinetics, ammonium salt solubility, ion-exchange reactions and redox potentials. A general description of both classical and modem refining methods is presented together with a review of possible future technologies. (c) 2005 Elsevier B.V. All rights reserved.