TIME-DEPENDENT EFFECTS IN PVC MEMBRANES

A number of situations which give rise to time dependent impedances have been explored experimentally for plasticized PVC membranes in contact with aqueous solutions. Most of the measurements can be explained by assuming that there is loss (or in some cases gain) of ions from the membranes to the contacting aqueous solutions, in such a way that electroneutrality is maintained within the membranes. It is shown that a membrane containing KBPh//4 would readily lose both K** plus and BPh//4** minus ions to a contacting solution of KCl, if an excess of valinomycin is also present in the membrane the rate of loss of both ions is much less since K** plus is effectively 'locked' into the membrane by the valinomycin and the BPh//4** minus ion is in turn 'locked' into the membrane by the electroneutrality condition.