US EPA

8372234 

Journal Article 

Vapor pressures and latent heats of vaporization of hydrocarbons 

Maxwell, JB 

1932 

0 

Industrial & Engineering Chemistry
ISSN: 0019-7866 

24 

5 

502-505 

English 

10.1021/ie50269a007 

Data on paraffin hydrocarbons above propane and benzene have been correlated by plotting the reciprocals of the absolute temperatures against those of hexane at the same vapor pressures. As in the case of the Cox chart, these reciprocal temperature lines are all straight lines and intersect at one point. The average deviation of reliable data on paraffins from isobutane through nonadecane and benzene is less than 1.0° F. A relation between the latent heats of hexane and those of other hydrocarbons is developed from the exact Clapeyron equation, the vapor pressure equation, and the deviations of the saturated vapors and liquids from the ideal gas law. It is found that the ratios of the latent heats of any hydrocarbon to those of hexane are constant at the same reduced pressures. This constant can be determined from either the critical pressure and the slope of the reciprocal temperature line or the latent heat at any vapor pressure. The average deviation of data on isobutane through octane, benzene, toluene, and m-xylene is about 1 per cent. Although the theoretical development is restricted to hydrocarbons above propane, it is found that other substances obey the rule mentioned above. That is, if the latent heat at any vapor pressure and the critical pressure of a substance are known, latent heats at other vapor pressures can be determined from a standard substance, such as hexane or water. © 1932, American Chemical Society. All rights reserved.