On the interaction of spherical double layers

The mean spherical approximation of the primitive model of electrolyte solutions is analyzed for the case of two large, charged spherical ions separated by a distance r in a supporting medium of small ions of arbitrary size and concentration. It turns out that the case in which the radii of the small ions is zero (Debye–Hückel approximation) yields a simple analytic solution in agreement with the Verwey–Overbeek asymptotic results for this system. Simple analytic results are employed to illustrate the more general case.