“…In recent years, PFP theory (which is applied to both nonpolar and polar molecules present in the mixtures) has been successfully used for theoretical analysis of the excess thermodynamic functions of binary liquid mixtures [16,19,20,27]. In this paper, we have applied PFP theory for prediction of the V E values of four binary (ionic liquid + MeCN or MeOH) systems at T = (298.15 to 318.15) K. According to PFP theory, V E is presented as the sum of three contributions: an interactional contribution V E ðint.Þ , a free volume one V E ðfv.Þ and that of internal pressure contribution V E ðP ÃÞ .…”