Thermodynamic study of the ternary system NaCl–H2O–Et3N at 25 °C. Part 3.—Solubilities

Abstract

Solubilities of triethylamine in water and in aqueous NaCl solutions at concentrations ranging from 0 to 0.3 mol kg^–1 have been evaluated at 25 °C from density measurements. Density data for about 65 binary and ternary mixtures have been least-squares fitted to an 11 constant double polynomial equation, within the accuracy of the measurements, Et₃N molalities of the saturated aqueous phases were estimated by extrapolation from the equation of state obtained. Solubility ratios of Et₃N in pure water, in relation to aqueous NaCl solutions, were calculated from experimental values and using the approaches of McDevit and Long, scaled particle theory and electrostatic theories. By comparing the results, it can be concluded that the main positive contribution to the resulting salting-out effect in less concentrated NaCl solutions comes from geometrical features, whereas in more concentrated NaCl solutions a non-electrolyte ion electrostatic interaction accounts for the significant negative effect observed. These results are in good agreement with predictions based on assumptions concerning intermolecular interactions and packing efficiencies taken from volumetric and ultrasonic velocity data.