Effective dielectric constant of electrolytes

We show that in the framework of the Poisson-Nernst-Planck model, where the ions are assumed point-like particles, the dielectric constant of the electrolyte coincides with that of the solvent in which the ions are dispersed. Only in the case where the ions are considered polarizable particles, their presence can contribute to the effective dielectric constant of the electrolyte and can play a role in the non-linear version of the Poisson-Nernst-Planck model. From this observation, it follows that generalizations of the linear Poisson-Nernst-Planck model in which the dielectric constant of the solution is considered depending on the ionic distributions are questionable. (C) 2014 AIP Publishing LLC.