An amorphous sample of inorganic cation-exchanger Zr(IV) tungstomolybdate was prepared by mixing varying ratios of 0. 1 M aqueous solution of sodium tungstate and 0. 1 M aqueous solution of sodium molybdate into 0. 1 M aqueous solution of zirconium oxychloride at pH 1. This cation-exchanger was found to have a good ion-exchange capacity (2.40 mequiv. g(-1) for Na+), high thermal and chemical stability. A tentative structural formula was proposed on the basis of chemical composition, FTIR and thermogravimetric analysis. Distribution coefficients (K-d) values of metal ions in various solvent systems were determined. Some important and analytically difficult quantitative binary separations viz. Ni(II)-Pb(II), Ni(II)-Zn(II), Ni(II)-Cd(II), Mg(II)-Al(III), etc. were achieved. The practical applicability of the cation-exchanger was demonstrated in the separation of Cu(II)-Zn(II) from a synthetic mixture as well as from real samples of pharmaceutical formulation and brass alloy. (c) 2006 Published by Elsevier B.V.