ELECTROCHEMICAL PROPERTIES OF CELLULOSIC ION-EXCHANGE MEMBRANES .2. TRANSPORT NUMBERS OF IONS AND ELECTROOSMOTIC FLOW

Transport numbers of counter-ions in cellulosic cation- and anion-exch ange membranes have been determined by both emf and Hittorf's methods for various (1:1)-electrolytes at different concentrations. The transp ort number derived from the emf data, in general, is lower than the va lue obtained by the Hittorf method, for any given external electrolyte concentration. This difference is attributed to transport of water oc curring across the membrane. Electro-osmotic water transport across th e membranes in equilibrium with several electrolytes has been determin ed at different concentrations. The data obtained have been interprete d in terms of the hydrated ion size of the counter-ions. Volume flow a nd electrical conductance across the membranes in the presence of vari ous electrolytes have been measured at several electrical potential di fferences. The experimental results have been interpreted in terms of linear phenomenological equations. These relationships have been used to estimate the magnitudes of the phenomenological coefficients for vo lume flow and conductance across the cationic and anionic membranes. T he validity of the phenomenological equation in volume flow across the membranes has been tested by comparison with the data obtained by dir ect measurements.