ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
In previous applications of the Leung–Griffiths model as modified by Moldover and Rainwater, many near-critical vapor–liquid equilibrium surfaces have been described successfully in the space of pressure, temperature, density, and composition, but calorimetric properties such as entropy and enthalpy have not been examined. Such calculations are difficult in general because of the need to determine a parameter that is usually unknown in the definition of an independent field variable (the fugacity fraction). However, a generalization for mixtures of the Clapeyron equation is available which allows for the calculation of differences in entropy, enthalpy, and free energies between a pair of (noncoexisting) dew and bubble points at the same temperature and composition. A calculation of entropy differences from a correlation of carbon dioxide+propylene agrees well with results inferred indirectly from experimental data. As a more direct check, calculation of enthalpy differences from a correlation of n-pentane+benzene agrees with an interpolation of enthalpy data provided by calorimetric measurements of Lenoir and Hipkin. The generalized Clapeyron equation appears to be singular at the maxcondentherm point, but it is shown that the singular terms cancel one another and that the leading-order finite term is consistent with a thermodynamic Maxwell relation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.464211
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