Masumeh Foruotan - Department of Physical Chemistry, Faculty of Chemistry, University Collage of Science, University of Tehran, Tehran, Iran.
Marmar Haghighi Khomami - Department of Physical Chemistry, Faculty of Chemistry, University Collage of Science, University of Tehran, Tehran, Iran.
Mona Zarrbi - Department of Physical Chemistry, Faculty of Chemistry, University Collage of Science, University of Tehran, Tehran, Iran.

Liquid-liquid equilibrium (LLE) data of the aqueous polyvinylpyrrolidone (PVP) + K2HPO4 / KH2PO4 buffer system at various temperatures ( 298.15, 308.15 and 318.15 ) K and pH 5 and pH 7 were studied. It was found that, an increasing in temperature and pH caused the expansion of two-phase area. Furthermore the osmotic virial equation and Flory-Huggins- Debye-Huckel theory were used to correlate the phase behavior data of this system. Good agreement was obtained with the experimental data using these models.

Liquid-liquid equilibrium; K2HPO4 / KH2PO4 buffer; Poly vinylpyrrolidone; Osmotic virial equation; Flory-Huggins- Debye-Huckel theory