A simple perturbation method for electrolyte solutions

The first order perturbation expansion of the Helmholtz free energy was used to calculate the thermodynamic properties of aqueous electrolytes. The restricted primitive model was used as the reference system. Its properties were determined using semiempirical formulae consistent with simulated Monte Carlo data. A simple expression with two adjustable parameters was chosen for the perturbation potential. Integral heats of dilution and osmotic coefficients of alkaline halides and tetraalkylamonium bromides were calculated. An excellent agreement with the tabulated data was found up to the concentrations of 2-3mol/dm3.