Heat Capacities and Derived Thermodynamic Functions of <i>n</i>-Nonadecane and <i>n</i>-Eicosane between 10 K and 390 K

Abstract

Heat capacity measurements were made on n -nonadecane and n -eicosane from 10 K to 390 K with an adiabatic calorimeter. These measurements were used to calculate the entropy and the enthalpy relative to 0 K. The sum of the enthalpy of the solid−solid transition and of melting of n -nonadecane is 62659 ± 20 J·mol - 1 at the triple point, 305.00 K. The enthalpy of melting of n -eicosane was calculated to be 69922 ± 100 J·mol - 1 at the triple point, 309.65 K. The entropies were extrapolated from the liquid phase just above the melting point to 298.15 K and found to be respectively 715.8 and 748.1 J·K - 1 ·mol - 1 . The crystallization behavior of both compounds is discussed.