FASIH A. SIDDIQI, M. NASIM BEG, M. IBADUR RAHMAN KHAN, ABDUL HAQ, S. K . SAKSENA, and BADRUL ISLAM. Can. J. Chem. 56,2205Chem. 56, (1978.The various ionic processes in the membrane system, notably (a) ionic transport, (6) membrane potential, (c) electrical conductivity, (d) ionic distribution equilibria, and (e) spatial distribution of ions and the potential within the membrane have been thoroughly studied with parchment-supported membranes. By applying the theory of absolute reaction rate, various thermodynamic parameters, namely, enthalpy of activation A H * , energy of activation AF*, and entropy of activation AS* were evaluated. The AS* values were found to be negative, indicating that diffusion takes place with partial immobilization in the membrane phase. A formal relation between AHhydralion, AFhydrPlion, and AS,,,,,,,,, of cations with corresponding values of A H * , AF*, and AS* for diffusion was also worked out. Thermodynamically fixed charge density was evaluated using methods based on thermodynamics of irreversible processes. Potentiometric selectivity and recent theory of bi-ionic potential based on nonequilibrium thermodynamics was tested and found applicable to parchment membranes. On a trouve que les valeurs de AS* sont negatives; ceci indique que la diffusion a lieu par une immobilisation partielle dans la phase de la membrane. On a aussi pu etablir une relation formelle entre les AH,IYdIPldllOn, AFhydr.lil,ion et des cations avec les valeurs correspondantes de A H * , AF* et AS* pour la diffusion. On a evalue la densite de charge fixe thermodynamique en faisant appel a des methodes basCes sur la therrnodynamique de processus irreversibles. On a Cvalue la selectivitk potentiometrique et la thtorie ricente du potentiel bi-ionique, basee sur la thermodynamique des phenomenes irreversibles, et on a trouvC qu'on peut I'appliquer aux membranes de parchemin.