Activity Coefficients of Sodium Chloride in Water–Ethanol Mixtures: A Comparative Study of Pitzer and Pitzer–Simonson Models

Abstract

Activity coefficients of NaCl were determined in water–ethanol solvents, in the range 5–20% (w/w) ethanol, from emf data. The molalities varied from 0.1 mol-kg−1 to near saturation and measurements were taken in the temperature range 25–50°C. The Pitzer model was used to describe the nonideal behavior of the electrolyte and the corresponding coefficients were determined for each solvent. The Pitzer–Simonson equations were also applied and a detailed study, involving the short- and long-range forces, was done in order to better understand the different results obtained with both models.