ELECTROCHEMICAL-BEHAVIOR OF CELLULOSIC CATION MEMBRANES - BI-IONIC POTENTIALS IN ALKALI SYSTEMS

The behaviour of cationic ion-exchange membranes in bi-ionic cystems formed by pairs of alkali ions was studied. The membrane was prepared by grafting vinyl monomers on parchment paper, which gives it a marked hydrophilic character. The selectivity coefficients and bi-ionic potentials of the membrane in the presence of the ten possible pairs of alkali ions was measured in a wide range of electrolyte concentrations (10** minus **3-1 molal). The magnitude of these parameters is governed by the ions forming the bi-ionic system and their values are the higher the greater the difference in size of the ions. For those ion-pair systems formed from identical ions, both selectivity coefficients and bi-ionic potentials remain constant as the electrolyte concentration increases, whereas for those systems made up of dissimilar ions, the values are dependent on the concentration of electrolyte. The results are justified on the basis of the hydrophilic character of the membrane matrix.