Thermodynamic Confirmation of Unresponding of Ion- Selective Electrodes to Oxidation-Reduction Potentials.

الملخص

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.