Novel data and a group contribution method for the prediction of the speed of sound and isentropic compressibility of pure fatty acids methyl and ethyl esters

Speed of sound of fatty acid esters are relevant for the formulation of biodiesel fuels but data on this property are scarce on literature. In this work speeds of sound of three saturated fatty acid methyl esters (caprate, myristate, palmitate) two unsaturated (oleate, linoleate) as well as two fatty acid ethyl esters (caprate, myristate) were measured using a pulse echo technique operating at 3 MHz. The measurements were carried out at atmospheric pressure in the temperature range 283.15–373.15 K. Additional density measurements were performed in order to estimate the isentropic compressibility and the molecular compressibility. From these data, a group contribution method was developed to predict the molecular compressibility and speed of sound of both methyl and ethyl esters with an uncertainty of circa 0.1%.