Partition coefficients of some cations between cation exchange membrane and solution were measured. The reciprocals of the partition coefficients were plotted against the corresponding: dimensionless concentrations of ions in solution. The relations obtained experimentally for monovalent-monovalent and monovalent-bivalent ions systems were in agreement with the respective theoretical equations. For the monovalent-monovalent exchange the relation was linear. While in the monovalent-bivalent case it was non linear. We proposed an empirically obtained linear relation for the monovalent-bivalent system. Therefore, the dependence of the reciprocal of partition coefficients on the dimensionless concentration of solution can be represented by a linear relation for both systems.