Based on the Frost - Kalkwarf Equation

Methods Based on the Frost-Kalkwarf Equation The Frost-Kalkwarf equation relies on four compound-specific coefficients to correlate vapor pressure-temperature data  

The four coefficients A, B, C, and D have been derived, for example, with selected hydrocarbons [25, 26], Equation 7.4.3 accurately represents the vapor pressure function over the entire temperature range between the triple point and the critical point. If the coefficients are not available for a given compound, they can be calculated. D is calculated from the pressure van der Waals constant, a, which can be estimated from group contributions. B is calculated directly from group contributions. Then the coefficients A and C can be estimated from two pv/T points (e.g., normal boiling point and critical point). This approach has been evaluated for various classes of hydrocarbons commonly encountered in petroleum technology [25, 26]. 

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