Peter Debye and Erich Hückel had developed a theory for the ionic activity coefficients in dilute solutions of strong electrolytes some 95 years ago . Their limiting law still stands and is confirmed as close to reality in many experiments. In a previous article , it is shown that these limiting activity coefficients arise because the electrical contribution in the electrochemical potential of ionic species is overestimated traditionally with a factor 2. The smaller value removes inconsistencies in the models and complies better with the basic electrostatic principles. In this article further evidence is given in support of this alternative description. As consequence the dilute activity coefficients become unity, e.g. are removed, which means that the electrochemical potential of ions in dilute solutions is expressed directly in concentration, instead of activity, which simplifies modelling in such dilute solutions.
van der Weg, P.B. (2009) The Electrochemical Potential and Ionic Activity Coefficients. A Possible Correction for Debye-Hückel and Maxwell-Boltzmann Equations for Dilute Electrolyte Equilibria. Journal of Colloid and Interface Science, 339, 542-544.
van der Weg, P.B. (1985) Surface Tension and Differential Capacitance of the Ideally Polarised Electrical Double Layer of Aqueous Potassium Bromide on Mercury. Ph.D. Dissertation, Free University, Amsterdam.