Polarographic determination of hydrogen ion activities in strongly acidic media: a new acidity function

Abstract

An electrochemical method of determination of the activity of hydrogen ions in strongly acidic media has been developed. The novelty of the method rests in the way in which the potential of a glass electrode is measured. The glass electrode is connected to the reference electrode input of a three-electrode polarograph and the oxidation wave of ferrocene at a dropping mercury electrode is recorded for media of various hydrogen ion activities. The apparent shift of the ferrocene half-wave potential is then a measure of the change of the glass electrode potential. This arrangement has no liquid junction, and so is free of the error due to liquid junction potential.

The new acidity function, H_GF, is identical with the pH scale in dilute aqueous solutions. The H_GF function in aqueous sulphuric and perchloric acid and in several mixed solvents has been determined and referred to the aqueous standard state.