Vapor pressure prediction and correlation from the triple point to the critical point

Abstract

Vapor pressure constants for Wagner-type vapor pressure equations are reported for 11 compounds. The constants in these equations have been determined from heat capacity data at low temperatures and vapor pressure data at higher temperatures. Thus, a single equation is able to give accurate vapor pressures from the triple point to the critical point. The commonly used 3–6 form of the Wagner vapor pressure equation successfully correlated the behavior over the entire temperature range for 9 of the 11 compounds examined. For the two alcohols examined, ethanol and isopropanol, an additional term was required to reproduce the behavior over the entire temperature range. Of the various forms that were examined, the form with exponents 2.5, 5 and 6 performed best for ethanol and isopropanol.