Interpreting freezing point depression of stearic acid and methyl stearate

The empirical Margules, NRTL, and Wilson activity coefficient models fit data for the solvent activity coefficients well, while the UNIQUAC model combined with the predictive abilities of UNIFAC could not accurately predict activity coefficients. Despite questions on the fundamental interpretation of the data, modeling the activity coefficients for the solvent is sufficient to approximate the effect the solvent will have on the melting point depression. Relatively simple experiments following the total pressure of mixtures as a function of composition and temperature can be used to obtain activity coefficient model parameters for the Margules, NRTL, UNIQUAC, and Wilson.