Science in China Series B: Chemistry

, Volume 44, Issue 3, pp 315-319

First online:

A principle to correlate extreme values of excess thermodynamic functions with partial molar quantities

  • Zhiwu YuAffiliated withDepartment of Chemistry, Tsinghua University Email author 
  • , Yun LiuAffiliated withDepartment of Chemistry, Tsinghua University
  • , Rui ZhouAffiliated withDepartment of Chemistry, Tsinghua University
  • , Fangyu XueAffiliated withDepartment of Chemistry, Tsinghua University

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Excess thermodynamic properties are widely used quantitatively for fluids. It was found that at constant temperature and pressure a molar excess quantity of a mutually miscible binary mixture at the extreme points equals the excess partial molar quantities of the two components, i.e.F E 1=F E 2=F E m, forming a triple cross point. The relationship is hold for properties such as enthalpy, entropy, Gibbs free energy, and volume, and is applicable for excess functions with multi extreme points. Solutions at extreme points can be referred to as special mixtures. Particularly for a special mixture of Gibbs free energy, activity coefficients of the two components are identical.


excess properties Gibbs energy activity coefficient enthalpy triple cross point