Measurement and correlation of vapor-liquid equilibria of the poly(vinylpyrrolidone)+NaH2PO4+H2O system at different temperatures

Vapor-liquid equilibrium data for the poly(vinylpyrrolidone) (PV P)+NaH2PO4+H2O system have been determined experimentally using the improved isopiestic method at 298.15, 308.15 and 318.15 K. The effect of temperature on the vapor-liquid equilibrium has been studied and compared with that on the liquid-liquid equilibrium of the aqueous PV P+NaH2PO4 two-phase system. It was found that the slope of constant water activity lines and tie-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. Furthermore, the segment-based local composition Wilson model has been used for the correlation of the experimental water activity data. The agreement between the correlation and the experimental data is good.