Department of Chemistry, Urmia University, Urmia, I.R. IRAN
A modification of Peng-Robinson equation is described wherein in the parameter b is expressed as a linear function of temperature. The modified equation is then applied to a series of light hydrocarbons and refrigerants, and predicted values for vapor pressure, saturated vapor volume, saturated liquid volume and the heat of evaporation are compared with the corresponding experimental data. Considerable improvement is clearly observed.