Thermodynamic confirmation of unresponding of ion-selective electrodes to oxidation-reduction potentials

Abstract EN

The potentials with iodimetric reaction of sulphur reducing agents using sulphide and Cyanide ion_Selective electrodes were all negative resulting from ion_exchange of produced iodide ions on the membrane surfaces of the electrodes .The calculated free energy changes values were positive with negative entropy change values which are an inverse to corresponding values obtained with Platinum electrode .ΔH values were mostly low and positive while equilibrium constants were extremely low as it seems to be no occurrence of iodimetric reactions that have been trustly confirmed by platinum electrode .

This discrepancy was attributed to high input impedance of ISEs membranes which prevent the flow of electrons across their membranes, and the conductivity is ionic .

Therefore , this research confirmed experimentally that these ISEs are unresponsive to oxidation _ reduction potentials and the results obtained might well be considered for other ISEs.