Distribution Potentials for Binary Electrolytes

In the case of an electrolyte of the type in the state of distribution equilibrium, 

When the distribution equilibrium refers to the 1 1 valent electrolyte, e.g. MX, where Zx - = 1, i.e. for the system 

The above dependence, which has been known for a long time, can be directly derived from Eq. (3) and the electroneutrality condition of Eq. (9) which for that case are in the form  

The formal Galvani potential, described by Eq. (14), does not depend on the concentration of ions of the electrolyte MX. Since the term containing the activity coefficients of ions in both solutions is, as experimentally shown, equal to zero [48,69, 75, 76, 65] (Sect. 3.4) it may be neglected. This results predominantly from the crosssymmetry of this term and is even more evident when the ion activity coefficients are replaced by their mean values. A decrease of the difference in the activity coefficients in both phases is, in addition, favored by partial hydration of the ions in the organic phase. Thus, a liquid interface is practically characterized by the standard Galvani potential, usually known as the distribution potential [1, 2, 48]. It can be expressed in three 

It is obvious from Eq. (13) that Eqs. (14, 18, 19, and 20) apply to aU symmetrical electrolytes, i.e. to electrolytes dissociating into the same number of cations and anions. 

---