Latent heat of crystallization and fusion melting

The latent heat of fusion (crystallization) or the enthalpy difference 

Application of this method to the heat content of homologous series of organic compounds in the liquid state would result in a non-linear course of the heat content as a function of the number of methylene groups. This is exactly what is found experimentally for the heat of fusion as a function of the number of methylene groups. A second order additivity rule, however, is too complicated for practical application if a large number of structural groups is involved. It would require the compilation of innumerable group pair contributions. 

As was stated by Bondi (1968) the entropy of fusion, ASm shows a more regular relation with structure than the enthalpy of fusion. At the melting point Tm the entropy of fusion may be calculated as  

The available experimental values of AHm for a number of polymers, mentioned in Table 5.6, permit the calculation of ASm for these polymers group contributions can be derived according to the equation  

The (partly still tentative) values of ASm i are given in Table 5.7. This table also shows tentative values for AHm. 

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