Extension of Chen's (1982) theory to correlate densities of aqueous electrolytes



The model proposed by Chen et al. for treating nonideality in concentrated electrolyte solutions has been extended to the correlation of the densities of solutions of single electrolytes (1:1, 2:1, 1:2, and 2:2) in terms of Chen's energy interaction parameters τca,m and τm,ca. At any single temperature, only three adjustable parameters, Vmath image (the partial molar volume of the solute at infinite dilution), and the pressure derivatives (δτca,mp)T and (δτm,cap)T are required for correlating the density as effectively as the conventional treatment employing a power series in (molality)1/2. For some electrolytes, only the latter two parameters are required, as tabulated Vmath image values also lead to satisfactory correlations. The treatment can be extended to cover the temperature range 0–100°C, using either τca,m and τm,ca values derived from activity or osmotic coefficients, or constant τm,ca and τca,m values, but the irregular variation with temperature of the pressure derivatives precludes their representation by simple analytical functions, and individual values of the pressure derivatives at each temperature are necessary.