Potentiometric titration of naphthyl esters of carboxylic acids in non-aqueous solvent

Abstract

A simple and rapid potentiometric method for the non-aqueous titration of naphthyl esters of carboxylic acids is described. This method enables free acid and ester in a sample to be distinguished in a single titration. The titration is performed with sodium methoxide in pyridine solution, the equivalence point being indicated by means of antimony and calomel electrodes with a potentiometer. In the first stage of the titration, the free acid present in an ester sample is neutralised, while in the second the ester is saponified by the titrant. If an ester contains only traces of free acid, determination of the latter on a separate, larger amount of sample is preferred.