On the derivation and application of a new vapor pressure equation

Starting from the Clapeyron equation and making use of the equivalent expression for the reference state for latent heat of vaporization of pure liquids, namely at 0°K., a new vapor pressure equation is derived as follows: _χ(T_r) has been tabulated for T_r values in the range 0.50 < T_r <0.99 after programming on an IBM 1620 computer. The new vapor pressure equation has been tested with a variety of liquids both polar and non-polar, and found to predict vapor pressure data in the orthobaric range with an average error of ± 1.90% and maximum error of ± 3.20%. A significant outcome of this investigation is the identification of Riedel's factor α_o and Pitzer's acentric factor ω These have been shown to be functions of critical properties and reduced boiling point.