Measurements and Estimate of Heat Capacity for Some Pure Fatty Acids and Their Binary and Ternary Mixtures

The heat capacities in the liquid phase of the fatty acids hexadecanoic acid, octadecanoic acid, and cis -9-octadecenoic acid were measured, as well as those of their binary and ternary mixtures from temperatures close to solidification to 528 K. The measurements were correlated and contrasted with equations, methods, and values for the pure fatty acids, Ruzicka and Domalski's method providing better results for most of the temperature range studied. For binary and ternary mixtures, molar fraction average and corresponding states methods were used. The convenience of the former with respect to the latter was demonstrated; it is easier to apply and provides suitable results. Furthermore, in the case of the mixtures, only slight variations in heat capacity with composition were experienced. All the measurements were carried out using a DSC differential scanning calorimeter.