In this work, vapor pressure, water activity and liquid-liquid equilibrium of aqueous PVP + Na3cit solutions have been determined at different temperatures. The effect of temperature on the vapor-liquid equilibrium and liquid-liquid equilibrium of aqueous PVP + Na3cit system has been studied. It was found that, an incresing in temperature caused the expansion of two-phase region. Increasing temperature also increases the concentration of PVP in the PVP-rich phase, while the salt-rich phase will be somewhat mole diluted. Furthermore, it was found that, as temperature is increased, this aqueous two-phase system exhibits a phase inversion. Specifically, the PVP-rich phase − which at low temperatures is the less dense top phase− becomes the lower phase at elevated temperatures. It was also observed that, the slope of constant water activity lines increased with increasing the temperature. The results have been discussed on the basis of the effect of temperature on the hydrophobicity of the polymer.
