LAUSR

Osmotic coefficient measurements have been reported for binary aqueous solutions of urea (0.11400 to 1.03192 mol·kg–1) and ternary aqueous solutions containing a fixed concentration (0.10065 mol·kg–1) of polyethylene glycol 4000 (PEG-4000) and various concentrations of urea (0.03882 to 0.70509 mol·kg–1) at 298.15 K using vapor pressure osmometry. For the binary (urea + water) system, using experimental osmotic coefficient data, the activity and activity coefficient of urea and water are calculated, and further activity data are processed to obtain the Gibbs free energy change of mixing and excess Gibbs free energy change of mixing. The water activities for the studied ternary system (water + 0.10065 mol·kg–1 PEG-4000 + urea) were calculated and used to obtain the activity coefficient of PEG-4000 and urea. The transfer free energy changes of PEG-4000 from water to aqueous urea solutions (ΔGtr1) and that of urea from water to aqueous PEG-4000 solutions (ΔGtr2) have been calculated using the activity data. T...