Heats of sublimation and vaporization at 25° of long-chain fatty acids and methyl esters

The vapour pressures of nonanoic (20–30°), decanoic (20–30°), undecanoic (20–35°), and dodecanoic (20–35°) acids have been measured using a modified Knudsen effusion method. The vapour pressure of methyl tridecanoate (22.3°, 26°) and methyl pentadecanoate (22–30°) have also been measured using the classical Knudsen method. Heats of sublimation and vaporization at 25° are calculated and compared to literature values for other fatty acids and methyl esters. Empirical equations are derived to predict the heats of sublimation and vaporization at 25° of fatty acids and methyl esters.