Theory of a “two-dimensional electrolyte solution”

Abstract

Let us assume that on a flat interface of two semi-infinite nonmetallic media, which we designate by indices 0 and 1, there occurs nonlocalized adsorption of ions of both signs from medium 0. Since the adsorbed ions are fairly strongly bonded to the interface, they are simultaneously capable of freely moving over the surface. Such a possibility leads to a correlation of the mutual arrangement of ions and, hence, to the appearance of an electric twodimensional (negative) pressure in addition to an ordinary osmotic pressure and the surface tension of a pure solvent. Further, we limit ourselves to considering such a system at an isoelectric point, in which both the bulk of the electrolyte and the interface are electrically neutral. Moreover, let us assume that the bulk concentration of ions is very small. To calculate the thermodynamic values of such a two-dimensional electrolyte solution, let us apply a method which is analogous to the three-dimensional theory of strong electrolyte solutions, i.e., the DebyeHiickel theory (see, for example, (1)). First, it will be necessary to calculate the Coulomb part of the internal energy of twodimensional solution :