A study of simultaneous heat and mass transfer in partially saturated capillaries has been performed in order to develop a method that determines the matrix of multicomponent diffusion coefficients in liquid phase. The literature provides a semi-empirical formula developed by Bandrowski and Kubaczka [4] to calculate the matrix of multicomponent diffusion coefficients. The method separates the kinetic and thermodynamic contributions to mass transfer, and it contains an empirical exponent to improve the calculations. The present work attempts an estimation of the empirical exponent by studying the redistribution of compositions in an unsaturated nonisothermal capillary, taking into consideration the nonideality described by the matrix of thermodynamic factors. Two different ternary mixtures were tested at different temperature gradients and saturation degrees. The results reveal that the method is effective since specific values of the empirical exponent that modifies the matrix of thermodynamic factors were obtained for each system. In addition, the exponent seems to be dependent on temperature.