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Measurements of enthalpy increments from the temperature of the ordered phases of low temperatures at 293.4 K and 298.3 K up to the liquid phase above the melting point were carried out by differential scanning calorimetry using a discontinuous mode of temperature programming on the n-alkanes from C 18 to C 38 and C 41 , C 44 , C 46 , C 50 , C 54 , and C 60 . The temperatures and enthalpies of the solid-solid transitions and of the fusion were also determined and compared with the values of the literature.

Simple predictive relationships for the estimation of pure normal alkanes' thermodynamic properties, like transition temperatures, phase change enthalpies, and heat capacities in the solid or liquid state, are established as a function of carbon atom number n c , by combining our own calorimetric experimental results and a general review of literature data. This study underlines that total and melting enthalpies vary linearly with n c carbon atom number, whatever the parity of n c , while order-disorder transition enthalpies show a quadratic variation and an alternating effect between odd-and even-numbered n-alkanes. Heat capacity variations versus temperature and the carbon chain length were represented by a model of group contributions for the liquid phase and by an expression derived from Einstein's model for the solid state.

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