Osmotic coefficients of aqueous solutions of potassium acesulfame, sodium saccharin, and ammonium and tetramethylammonium cyclohexylsulfamates at the freezing point of solutions

Abstract

The osmotic coefficients of aqueous solutions of potassium acesulfame (0.67 mol kg⁻¹), sodium saccharin (0.75 mol kg⁻¹), and tetramethylammonium (0.55 mol kg⁻¹) and ammonium (0.35 mol kg⁻¹) cyclohexylsulfamates were determined up to the molality indicated in parentheses. The osmotic coefficients were fitted to the Pitzer equation, and the ion interaction parameters α ₁, β ⁽⁰⁾, and β ⁽¹⁾ were evaluated. The mean ionic activity coefficients of the solutes were calculated, and the non-ideal behaviour of the systems investigated were characterized by calculation of the excess Gibbs energy of the solution and the respective partial molar functions of solute and solvent. The partial molar excess Gibbs energies of the solutes are negative, as also are the corresponding excess Gibbs energies of their solutions, and the partial molar excess Gibbs energies of the solvent are positive and increase slightly with increasing concentrations of the solutes. The solvation ability of water was calculated from differences between the Gibbs energy of solution of water in the aqueous solutions and that of pure water, and are positive and small for all the solutes investigated, throughout the concentration ranges studied.

Graphical abstract