Browsing by Author "Migiro, Cleophas L. C"

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    The determination of the film thickness of a stationary liquid film (Nernst film) on the surface of a cation exchange membrane
    (University of Dar es Salaam, 1975) Migiro, Cleophas L. C
    Ag(s) /AgC1(s)| NaC1 (aq. C)|Cation exchange membrane|NaC1 (aq. 0.1M)|AgC1(s) /Ag(s) The two cells together gave us a set up which enabled us to measure the limiting current values as a function of concentration in the anode chamber and the stirring rate in that compartment. The limiting current was the only unknown parameter in the equation which could be used to determine the thickness of a liquid film adhering on the surface of the cation exchange membrane. The equation was a mathematical derivation by theoretical consideration of what is happening in the liquid layer. Fick’s 1. Law and the depletion of the 〖Na〗^+ in the layer were considered. Two methods were tried out: first the measurement of the potential drop across the cation membrane with the variation of current in the system (42) and the secord one was based on the hypothesis that water molecules in the layer dissociate at a certain limiting current value into protons and hydroxyl ions. With an appropriate experimental set up the amount of produced protons could be determined as a function of current. The plot of the rate of change of the produced protons against current density could enable one determine the limiting current value by extrapolation. Permaplex C-20 and Permaplex A-20 from Permutit Co. Lts., were used as the cation and anion exchange membrane respectively. AG/aGc1 electrodes were used both for emf measurements and as current transporting electrodes. Sodium chloride was the electrolyte used.