ENTHALPY CHANGE FROM 260K TO 340K FOR ALL NORMAL PARATINS FROM OCTADECANE (N-C18) TO HEXACOSANE (N-C26)

The enthalpies of all normal paraffins from octadecane (n-C18) to hexacosane (n-C26) have been measured by differential calorimetry from 260 K to 340 K. The enthalpy differences between the high-temperature rotator phase and the liquid or between the low-temperature phases (beta-0 orthorhombic n-C2n+1 or beta-T triclinic n-C2n) and the liquid increases regularly with the number of carbon atoms. The alternation of the thermodynamic properties between the even-and odd-numbered paraffins appearf only in the case of the solid state transitions (beta-T --> alpha-RII and beta-0 --> RI respectively).