Valour pressures using a static method have been measured for (n-hexane+n-hexadecane), (n-hexane+n-octane), and (n-octane+n-hexadecane) at 29815 K. The results have been fitted using a polynomial and agreement wilhin experimental error was obtained. Excess molar Gibbs free energies calcuated from the results and plotted against carbon number have been shown to agree wen with the principle of congruent.