Local composition and preferential solvation in electrolyte solutions

5 Local composition and preferential solvation in electrolyte solutions 

All the definitions of the local composition and preferential solvation are applicable for any mixture, including electrolyte solutions. Suppose for simplicity we have a solution of an electrolyte D in water W. Viewing this system as a mixture of a two-component system, we can apply all the equations of the previous section. 

However, we could also view this system as a three-component system of W, the anion A, and the cation C. If the system is open with respect to W and D, but not to the individual ions, then we must have the following conditions  

The total number of A s around W must be equal to the total number of C s around W, hence 

The upper limit of the integrals in (8.48) should be understood to be very large compared with the correlation distance. Likewise, the total number of C around A must be equal to the total number of C around C, hence 

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