Application of an Interstitial Lattice Model

We extend here the application of the interstitial model for water (section 7.9) to aqueous solutions of simple solutes. The merits of this model are essentially the same as those discussed in section 7.9. As before, we only outline the derivation of the various thermodynamic quantities and leave the details to the reader. 

The basic assumptions of the model have been introduced in section 7.9. To adapt the model for aqueous solutions, we further assume that solute molecules occupy the interstitial positions in the framework built up by the L molecules. Only one new molecular parameter is introduced in the new model, i.e., the interaction energy between the solute s and its surroundings, which we denote by.  

The combinatorial factor in (7.12.23) is the number of ways in which one can place Nh H molecules and A(, solute molecules into NJ l holes. The summation is carried over all 

As in the case of the one-component system, we take the maximal term in the sum (7.12.23), from which we obtain the equilibrium condition 

The mole fractions of empty holes, holes occupied by H-molecules, and holes occupied by s are 

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