The new approach has been developed for the analysis of the data on the equilibria in the systems ionite-aqueous salt solution, based on the application of effective auxiliary functions. With the use of the procedure, that was worked out within the context of the mentioned approach, K + to Bu 4 N + cation-exchange equilibria have been studied between slightly cross-linked sulfonated poly(sterene) cationite Dowex 50Wx2 and three component aqueous solutions of the salts Bu 4 NBr, KBr. The formation of clathrate-like ion pairs, proposed earlier in the studied system (on the basis of general knowledge on clathrate hydrates), was not revealed in the solution. The suggested approach and procedure can be widely applied to the investigation of all specific cation-anion interactions in aqueous salt solutions.