Investigations of the interactions in aqueous poly (vinyl pyrrolidone)Â +Â di-sodium hydrogen citrate solutions using vapor-liquid equilibria studies at different temperatures

Vapor-liquid equilibrium data of binary aqueous di-sodium hydrogen citrate (Na2HCit) aqueous poly (vinyl pyrrolidone), and ternary aqueous (Na2HCit) + poly (vinyl pyrrolidone) solutions were measured using the isopiestic method at T = (298.15, 308.15, 318.15) K. The obtained vapor-liquid equilibria data for binary aqueous di-sodium citrate system were successfully fitted with the Pitzer equation. From these data, the corresponding activity coefficients have been calculated. Using the general Pitzer formalism an equation was employed to correlate the obtained osmotic coefficient values for the ternary system. The thermodynamic behavior of aqueous (Na2HCit) + poly (vinyl pyrrolidone) solutions was discussed on basis of water, polymer and salt interactions.