UTILIZATION OF SOME ION-SELECTIVE ELECTRODES IN THE DETERMINATION OF SOME SULPHUR REDUCING AGENTS BY IODINE TECHNIQUE

Abstract

:Cyanide and Sulphide ion – selective electrodes were successfully exploited in thedetermination of the : Thiosulphate , Sulphite , Sulphide , Dithionite and Disulphite individually and intheir mixtures by direct titration with iodine prepared in glacial acetic acid .The potentials respondedby these two electrodes were compared to those recorded by platinum electrode versus Calomelreference electrode at different temperatures . Optimistic and encouraging results were obtained withan accuracy of ±3.5% attributed to experimental errors . The three electrodes were successfullyapplied to the monitoring of sulphur in three sulphur springs in Heet City . High concentrations ofsulphide were obtained which were matching the results obtained by other studies and assisting thehigh efficiency of the iodimetric technique using iodine in glacial acetic acid .The positive potentialmeasurements of platinum electrode of the sulphur compounds and their negative free energy haveclarified that the iodimetric reactions are irreversible and completely displaced to the products whichwere insured by positive entropy results .The negative potentials of cyanide and sulphide electrodeshave rendered the free energy values to be positive and negative values of entropy which indicated thatthere is no passage of electrons through the cells and these two ion – selective electrodes do notrespond to oxidation – reduction potentials because of the high impedence of their membranes .