Thermodynamic models of molten salts

In order to compare the theoretical models with the experimental results, we need to know the form of the functional dependence ai = f(Xi). This dependence can be obtained either on the basis of a certain structural model or empirically. The dependence of such a kind must, however, fulfill certain limiting conditions. 

According to the character of the functional dependence a, = /(x ) it is convenient to distinguish molten salt systems of type I and II. The systems of type I must fulfill two conditions  

Concept of activity and activity coefficients in molten salts 

Definition of single ion activity coefficient. For simplicity, only solutions of symmetrical binary univalent electrolytes will be considered here. 

The measurable thermodynamic quantity of interest in this connection is the change in chemical potential, A/u-ma, of the component MA in the mixture. The activity of MA, 

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