Ion transport in free and supported nitrobenzene aliquat nitrate liquid membrane ion-selective electrodes : I. Bulk electrical properties including ion association and dielectric constant

A controlled-thickness thin layer cell and wide-band cross correlator bridge have been used to characterize ion transport in free liquid and supported ion exchange membranes. The base system of Aliquat nitrate in nitrobenzene was measured, and transport parameters were used to establish properties of supports: cellulose triacetate, PVC-acrylonitrile, polypropylene and Teflon. From DC to 0.5 MHz impedance measurements, geometrical capacitance, electrical relaxation time constants and dielectric constants were determined over a range of temperatures and membrane loadings. Depression of dielectric constant with loading and temperature coefficients are reported. Conductivities were analyzed classically to yield equivalent conductances of ions, transference numbers and ion pairing constants. Temperature coefficients gave transport enthalpy and thermodynamic quantities. Data from supported membranes gave direct measures of void volumes of inert membrane supports, and clear evidence for cases of membrane solubilization by entrapped solvents.