The distribution coefficients (K-d) of some metal ions have been determined at various pH values on stannic(IV) antimonate cation exchanger. Based on this study, the separations of some important pairs of metal ions have been achieved. The separation of Mg(II) from AI(III) has been achieved quantitatively in some synthetic mixtures and in commercially available 32 antacid formulations using stannic (IV) antimonate columns. The method is simple, rapid and highly selective with good accuracy and precision within the experimental error range (+/-2%).