Hoffmann-Florin equation

Although estimation methods for the acentric factor are available (e.g., group contribution method of Constantinou and Gani [11]), this concept is not recommended, as an estimation of co would only be a redundancy of the normal boiling point estimation. To avoid inconsistencies, it is recommended that co is always calculated by its defining equation 2.157. If the vapor pressure curve is unknown, the normal boiling point and the critical point can be estimated, and the Hoffmann-Florin equation or the Rarey/Moller method (Section 3.2.1) can be used to calculate the vapor pressure curve. 

Therefore, the average deviations are less important for a vapor pressure estimation method than the number of substances where the method fails completely. In this area, a simple estimation procedure based on the vapor pressure equation of Hoffmann and Florin [34] has proved to be more appropriate than various methods from the literature [35-37] that are based on corresponding states or group contributions. The equation of Hoffmann-Florin is based on the charts developed by Cox [38]. Cox charts are constructed in a way that for some reference fluids the scale of the abscissa is adjusted to make the vapor pressure curve in a log P -T-diagram a straight line. The Hoffmann-Florin equation has two adjustable parameters o and P ... 

The Hoffmann-Florin equation can be transformed to the extended Antoine equation (3.36) by setting... 

Estimate the enthalpy of vaporization at = 5 C using the Clausius-Clapeyron equation and interpolate the vapor pressure at = 5 C with the Hoffmann-Florin equation. 

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See also in sourсe #XX -- [ ]

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