Determination of autoprotolysis (autoionization) constant according to gran’s procedure on potentiometric titrations

Abstract

Gran’s plot is an ingenious tool to find endpoints in potentiometric neutralization titrations. It can also be utilized for determining the formal potential of the electrodes, which is required in the case of obtaining the hydrogen ion concentration with pH sensor electrodes involving glass electrodes. Furthermore, autoprotolysis constants can be determined through Gran’s plots with high accuracy, even those containing impurities. Gran’s plot is thus a fundamental technique for investigating the properties of novel solvents such as protic ionic liquids as acid-base media. However, there are limitations in the autoprotolysis constants of the solvents and the ionization constants of the impurities, and so on, where Gran’s plots work well. Hence, we have clarified the reliable range of these constants to be determined through Gran’s plot by calculating the titration curves under various conditions and simulating these determination processes.