Observations on the theory of action of visual indicators

Abstract

Earlier treatments of visual indicator theory have made the tacit assumption that the molar absorptivities of the two forms of the indicator are equal, so equating the conditional indicator constant with the transition point and hence causing some confusion in certain instances. A more exact treatment of oxidation-reduction and ion-combination indicator parameters, conditional constant, transition point, transition range and transition interval, including the effects of molar absorptivities, indicator concentration and stoicheiometry, is outlined.