The impossibility of measuring individual ion activity coefficients using ion selective electrodes

The pressing aim of this work is to prevent an error from proliferating. In a recent paper, a new procedure for calculating the junction potentials has been presented, whose purported goal is to allow individual ion activities and activity coefficients to be identified using the appropriate ISEs. As convincing and useful as this procedure may seem, it is, however; fallacious. The present analysis considers the results obtained when applying the procedure to typical friendly cases liable to precise thermodynamic-mathematical treatments. It is shown that the individual ion activities found are a mere artifact of the initial settings and, therefore, Change accordingly. The implications raised from the values of such individual ion activities and, in particular, those concerned with the modified Hydration Theory, are, in turn, devoid of any real experimental validation.