Abstract: This paper proposes a new equation for the determination of the limiting slope of activity coefficient vs mole fraction (dlnγ_1/dx_1)_((x_1)→0) from gas chromatography measurements, the equation has been rigorously derived and is convenient to be applied. A method to predict the vapor liquid equilibrium of dilute solutions from the infinite dilute activity coefficient γ_1~∞ and (dlnγ_1/dx_1)_((x_1)→0) has also been presented by virtue of the activity coefficient models for dilute solutions proposed recently. The results of predictions for 7 systems are satisfactory in comparison with those from direct measurements by the GC method. Finally, our model for (dlnγ_1/dx_1)_((x_1)→0) is compared with that proposed by Valentin and Guiochon, and the results show that our model is a good improvement.

Key words: Vapor liquid equilibrim, Dilute solution, Gas ehromatographic measurement, Limiting value