The Lee–Kesler method Lee B.I., Kesler M.G., "A Generalized Thermodynamic Correlation Based on Three-Parameter Corresponding States", AIChE J., 21(3), 510–527, 1975 allows the estimation of the saturated vapor pressure at a given temperature for all components for which the critical pressure Pc, the critical temperature Tc, and the acentric factor ω are known.
Equations
with
(reduced pressure) and (reduced temperature).
Typical errors The prediction error can be up to 10% for polar components and small pressures and the calculated pressure is typically too low. For pressures above 1 bar, that means, above the normal boiling point, the typical errors are below 2%. Reid R.C., Prausnitz J.M., Poling B.E., "The Properties of Gases & Liquids", 4. Auflage, McGraw-Hill, 1988
Example calculation For benzene with Tc = 562.12 KBrunner E., Thies M.C., Schneider G.M., J.Supercrit. Fluids, 39(2), 160–173, 2006 Pc = 4898 kPa Tboiling = 353.15 KSilva L.M.C., Mattedi S., Gonzalez-Olmos R., Iglesias M., J. Chem. Thermodyn., 38(12), 1725–1736, 2006 ω = 0.2120Dortmund Data Bank
the following calculation for T = Tb results:
Tr = 353.15 / 562.12 = 0.628247 f(0) = −3.167428 f(1) = −3.429560 Pr = exp( f(0) + ω f(1) ) = 0.020354 P = Pr · Pc = 99.69 kPa
The correct result would be P = 101.325 kPa, the normal (atmospheric) pressure. The deviation is −1.63 kPa or −1.61 %.
It is important to use the same absolute units for T and Tc as well as for P and Pc. The unit system used (K or R for T) is irrelevant because of the usage of the reduced values Tr and Pr.
See also Vapour pressure of water Antoine equation Tetens equation Arden Buck equation Goff–Gratch equation
References