Activity coefficients of sodium chloride in water-ethanol mixtures: A comparative study of Pitzer and Pitzer-Simonson models

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 degreesC. 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.