Based on Pitzer's thresparameter corresponding states principle (1 955), we have developed a correlation of the latent heat of vaporization of aromatic coal liquid model compounds. Temperature ranges from the freezing point to the critical point. An expansion of the form L = L *(o) + o ' L is used for dimensionless latent heat of vaporization. This model utilizes a nonanalytic functional form based on results derived from renormalization group the0 of the critical point. A simple expression for the latent heat of vaporization, L = coal liquid compounds. Benzene, the basic constituent of the functional groups of the multi-ring coal liquid compounds, is used as the reference compound in the present correlation. This model works very well at both low and high reduced temperatures approaching the critical point (0.02 < E = (T, -T ) / T , < 0.69). About 16 compounds, including single, two, and threering compounds, have been tested and the percent root-mean-square deviations in latent heat of vaporization reported and estimated through our model are 0.42 to 5.27 % . Tables of the coefficients of L *(o) and L *(1) are presented. The contributing terms of the latent heat of vaporization function are also presented in a table for small increments of E. of fluids in the vicin ~~~0 7 3 3 3 + D E0.8333 + D 2 2083 + El€ + i -E3t3 is cast in a corresponding states principle correlation for 2

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A hlgh-temperature static apparatus Is used to Investigate vapor pressures In the range 1-2780 ironHg over the temperature range 425-840 K for three aromatic compounds similar to those which are often found In coal liquide: fluorene, dlbenzofuran, and dibenzothlophene. The experimental vapor pressure data of fluorene and Its homomorphs cited above have been fitted to Chebyshev polynomials. The values of dp/dT calculated from the Chebyshev polynomials, the compressibility factors of saturated vapor and liquid estimated from three-parameter corresponding states correlation, and the acentric factors determined from their experimental vapor pressure data presented In this paper were used to evaluate the heats of vaporization of the aromatic compounds mentioned above from the Clapeyron equation.

Phase equilibria have been studied in ternary mixtures of methane with 2,2- and 2,3-dimethylbutane near the tricritical point. The quasi-binary approximation allows the path to the tricritical point to be defined experimentally, making it possible to study the details of the phase behavior as the tricritical point is approached. The decrease in the differences in temperature and pressure between the upper and lower critical end points is consistent with the asymptotic classical theory of tricritical phenomena; an extended classical theory is necessary to account for the shape of the coexistence curves.

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