Determination of equivalence volumes in potentiometric titrations of weak acid mixtures of nearly equal acid strengths

Abstract

Potentiometric titration method for quantitative analysis of binary mixtures of weak acids of nearly equal acid strengths (∆pka <2) are studied. The multiple linear equations derived are corrected by using the activity dissociation constant (Ka˚) instead of the concentration dissociation constant (Ka) since the ionic strength of the solution titrated would be changed during the course of titration. Titration data obtained are analysed by multiple linear regression regression analysis, using SPSS/PC⁺ computer program. Factors affecting the accuracy and precision of equivalence volumes determination such as ∆pka, changes of the ionic strength of solution titrated and especially, the titration data ranges applied to analysis to find the appropriate ranges are discussed.