| The Fluctuation Solution Theory relates derivatives of thermodynamic properties to spatial integrals of direct correlation function. This formalism has been used as the basis for a model of activities and densities of aqueous strong electrolyte solutions. The advantages of this method are: it gives both properties from the same expression; it uses integrals rather than derivatives of the model to obtain the desired properties; it also has fewer parameters most of which may be ionically additive.;In this work, a model for direct correlation function integrals (DCFI) of solutes and solvents in aqueous solutions has been evaluated. The model contains long range ionic interactions which are based on the Debye-Huckel theory and short range interactions which are expressed as a virial expansion. The connections among Kirkwood-Buff, Lewis-Randall, and McMillan-Mayer systems have been carefully examined. It is found that the common Debye-Huckel equation does not accurately estimate the extended long range term of the model. An adequate expression for the long range ionic interaction terms that is analytically integrable has been determined to obtain the thermodynamic properties.;The model has been integrated to obtain activity coefficients and densities. Parameters have been determined for fifteen salts of various charge types by using experimental activity coefficient and density data at a pressure of 0.1Mpa and temperature 25... |
