ABSTRACT
Usuallythecurrentatoneelectrodeismonitored,whichiscalledthe workingorindicatorelectrode.Theotherelectrodeisknownasthereferenceelectrode.Insomeelectrochemicalmeasuringsystems,especially thoseusinglargerelectrodes,itisconvenienttohaveathirdcounterorauxiliaryelectrode,asshowninFigure2.1.Thisisespeciallyimportantwhen theelectricalresistanceofthesurroundingsolution(R.)ishigh.Microelectrodesaremuchlessaffectedbythesolutionresistance,andcanbeoperated insimpler,two-electrodesystemsusingonlytheworkingandreference electrodes.Thereferencecanbeeitherahydrogen,calomel,orAg/AgCl electrode,usuallyplacedveryclosetotheworkingelectrode.Whenan auxiliaryelectrodeisused,itcanbeplacedfurtherawayinthemeasurementsolutiontocompletetheelectricalcircuit.Thisarrangementallows therespectivecathodeandanodepotentialsattheworkingandreference electrodestobemeasured.Thesimplestmethodofoperationistoapplya constantvoltageattheredoxpotentialofthetargetanalyteandmeasurethe resultingcurrent.Thisapproachmaynotalwaysbepossible,andanumber ofothertechniqueshavebeentried.
