Calculations of thermodynamic derivative properties from the NRTL and UNIQUAC models

Y. Demirel, H. O. Paksoy

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The local composition models NRTL and UNIQUAC with temperature-dependent parameters have been employed to calculate the surfaces of excess heat capacity, CEp, excess enthalpy, hE and thermodynamic factor, Γ for binary liquid mixtures. These thermodynamic properties represent the derivatives of the models with respect to temperature, CEp, hE and composition, Γ. The parameters used in evaluating CEp and hE are directly obtained from separate CEp and hE data at different isotherms. Experimental gE and hE data at more than one different isotherm are used simultaneously to estimate the parameters in the evaluation of Γ. The following mixtures are considered: methanol(1)-methyl acetate(2); 2-propanol(2)-n-heptane(2); methanol(1)-water(2); benzene(1)-n-heptane(2) and ethanol(1)-water(2). These mixtures show close deviations between experimental and calculated values obtained from both models and also include associating mixtures. Performances of the models based on different types of experimental data have been compared. The models show considerable regional discrepancies of the same thermodynamic property over the entire composition and temperature ranges for the mixtures that show small overall deviations between the calculated and experimental data.

Original languageEnglish (US)
Pages (from-to)129-136
Number of pages8
JournalThermochimica Acta
Issue number2
StatePublished - Oct 30 1997


  • Binary liquid mixtures
  • NRTL and UNIQUAC models
  • Surfaces of derivative properties

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry


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