Application to Other Thermodynamic Properties

The same methods used to describe activity coefficients here can also be applied to other thermodynamic properties such as excess volumes, enthalpies, entropies, heat capacities, and so on by manipulating the defining equation (17.38) appropriately (see Pitzer, 1987). Experimental data useful in deriving the ion-interaction parameters of 

For example, excess volumes can be derived from the derivative 

This approach has been used quite successfully, for example, by Christophe Mon-nin (1989) to model densities of concentrated, multi-component natural brines based on volumetric data from one- and two-salt systems. Monnin s predictions agree very well with observations made on natural brines in settings such as the Red Sea and Persian Gulf sabkha regions. 

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