Determination of Weak Acid and Its Salt or Strong Acid in their Mixture by pH Titration

Abstract

A pH titration method for the analysis of binary mixtures of the weak and strong acids is presented. A sample solution of volume V is titrated with a strong base of concentration CB and subsequently with a solution containing a known amount (c_A) of the weak acid to be determined. The volumes, which correspond to the identical pH value on the titration curves, are read off and denoted by υ_B and υ_A, respectively, and concentrations of the weak and strong acids, c_W and c_S, are determined from the slope and intercept, respectively, of a linear plot of y vs. x:
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where x is a function of υ_B, υ_A and pH, and y is a function of υ_B and pH.
The present method has such advantage that dissociation constants of the weak acid are not required for the' calculation of concentrations, and is also utilized for the determination of weak acid and its salt in their mixture.