Using PVT measurements available in the literature for argon, the following equation of state involving the excess properties r and r was developed:where a, /?, and $ are densitydependent functions. The results of this relationship for argon have been compared with those obtained using the BWR and the Stewart et al. (198l)equations of state. The present expression was applied in a generalized manner to nitrogen, methane, carbon dioxide, and ammonia. In addition, comparisons have been made using these four substances with three generalized relationships: a truncated virial, a modified Redlich-Kwong, and the HirschfelderBuehler-McCee-Sutton equations of state.
R. A. WILSAK and GEORGE THODOS
CONCLUSIONS AND SIGNIFICANCEA comprehensive literature search for PVT measurements of fluid argon yielded 100 sources of information that provided a total in excess of 4,400 unscreened values. These values were compiled and were used to define the entire fluid region ranging from the dilute gaseous state up to the freezing curve. This compilation accommodates the saturated vapor, liquid, and Although the development of the equation of state presented in this study has been based only on data for argon, its application has been extended to include the PVT behavior of nitrogen (2, = 0.291), methane (2, = 0.289), carbon dioxide (2, = 0.275), and ammonia (2, = 0.242). This extension required information relating to the saturated vapor and liquid states for these four substances. This information was extracted from generalized correlations available in the literature. The average density deviations were found to be 1.17% (233 points) for nitrogen, 0.50% (792 points) for methane, 2.86% (495 points) for carbon dioxide, and 3.90% (517 points) for ammonia. For comparison, three generalized equations of state were applied to these four substances with the Hirschfelder-Buehler-McGee-
