The enhancement of acidity in non-aqueous solvents. Part I. An improved procedure for the determination of short-chain carboxylic acids in the presence of their anhydrides

Abstract

Weak short-chain carboxylic acids can be determined potentiometrically in the presence of their acid anhydrides after enhancement of their acidity by reaction with alkaline earth perchlorates. The method is particularly suitable for the determination of acid contents in the range 0·5 to 5 per cent. Of five electrode systems examined, glass-modified calomel and platinum-in-stream platinum combinations gave responses exceeding 500 mV per millilitre of titrant at the end-point. Both acetonitrile and acrylonitrile are satisfactory solvents, but the latter is generally preferable for non-aqueous titration because, while it leads to equally sharp end-points, it is more readily available in a pure, acid-free form.