Lydersen method

The Lydersen method is a group contribution method for the estimation of critical properties temperature (T c ), pressure (P c ) and volume (V c ). The method is named after Aksel Lydersen who published it in 1955¹. The Lydersen method is the prototype for and ancestor of many new models like Joback, Klincewicz, Ambrose, Gani-Constantinou and others. The Lydersen method is based in case of the critical temperature on the Guldberg rule which establishes a relation between the normal boiling point and the critical temperature.

The Lydersen method is a group contribution method for the estimation of critical properties temperature (T c ), pressure (P c ) and volume (V c ). The method is named after Aksel Lydersen who published it in 1955. The Lydersen method is the prototype for and ancestor of many new models like Joback, Klincewicz, Ambrose, Gani-Constantinou and others. The Lydersen method is based in case of the critical temperature on the Guldberg rule which establishes a relation between the normal boiling point and the critical temperature. T_c=\frac{T_b}{0.567+\sum G_i-\left(\sum G_i\right)^2} Guldberg has found that a rough estimate of the normal boiling point T b , when expressed in kelvins (i.e., as an absolute temperature), is approximately two-thirds of the critical temperature T c . Lydersen uses this basic idea but calculates more accurate values. P_c=\frac{M}{\left(0.34+\sum G_i\right)^2} V_c\,=\,40+\sum G_i M is the molar mass and G i are the group contributions (different for all three properties) for functional groups of a molecule. V c = 40 + 60.0 + 2 * 55.0 = 210 cm 3 In the literature (such as in the Dortmund Data Bank) the values 215.90 cm 3 , 230.5 cm 3 and 209.0 cm 3 are published.

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