Description of the mutual solubilities of fatty acids and water with the CPA EoS

Data for the mutual solubilities of fatty acid + water mixtures are scarce and so measurements for seven fatty acid (C 5 ‐C 10 , C 12 ) + water systems were carried out. This new experimental data was successfully modelled with the cubic plus association EoS. Using data from C 6 to C 10 and the Elliot's cross‐associating combining rule a correlation for the k ij binary interaction parameter, as a function of the acid chain length, is proposed. The mutual solubilities of water and fatty acids can be adequately described with average deviations inferior to 6% for the water rich phase and 30% for the acid rich phase. Furthermore, satisfactory predictions of solid‐liquid equilibria of seven fatty acids (C 12 ‐C 18 ) + water systems were achieved based only on the k ij correlation obtained from liquid–liquid equilibria data. © 2009 American Institute of Chemical Engineers AIChE J, 2009