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An Equation of State for the Thermodynamic Properties of Cyclohexane



Yong Zhou, Jun Liu, Steven Penoncello, Eric Lemmon


In this work, an equation of state for cyclohexane has been developed using the Helmholtz energy as the fundamental property with independent variables of density and temperature. Multi-property fitting technology was used to fit the equation of state that includes pρT, heat capacity, sound speed, virial coefficient, vapor pressure and saturated density data. The equation of state has been developed to conform to the Maxwell criterion for two-phase vapor-liquid equilibrium states, and is valid from the triple point temperature to 700 K, with pressures up to 250 MPa and densities up to 10.3 mol dm-3. Overall, the uncertainties in density for the equation of state are 0.1% (liquid and vapor) up to 500 K, and 0.2% above 500 K, with higher uncertainties within the critical region. Between 283 K and 473 K with pressures less than 30 MPa, the uncertainty may be as low as 0.03% in density in the liquid phase. The uncertainties in the speed of sound are 0.2% between 283 K and 323 K in the liquid, and 1% elsewhere. Other uncertainties are 0.05% in vapor pressure and 1% in heat capacities. The behavior of the equation of state is reasonable within the region of validity and at higher and lower temperatures and pressures. A detailed analysis has been performed in the article.
J. Phys. & Chem. Ref. Data (JPCRD) -


cyclohexane, equation of state, thermodynamic properties


Zhou, Y. , Liu, J. , Penoncello, S. and Lemmon, E. (2014), An Equation of State for the Thermodynamic Properties of Cyclohexane, J. Phys. & Chem. Ref. Data (JPCRD), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed June 24, 2024)


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Created December 4, 2014, Updated October 12, 2021