Multicomponent diffusion in systems containing molecules of different size. 2. Mutual diffusion in the ternary system pentaethylene glycol-triethylene glycol-water

The diffusion coefficients of the ternary system pentaethylene glycol-triet hylene glycol-water have been measured at five compositions at constant tot al solute concentration. A theory that is an extension of the current hydro dynamic equations for calculation of D-ij has been tested on this ternary s ystem. These equations use values of what we will refer as the "effective" volumes of the solutes. These volumes were obtained by the analysis of the diffusion coefficients of the two corresponding binary systems. The agreeme nt between theory and the experimental values for the main-term diffusion c oefficients D-ii is quite good and the agreement between the predicted and measured cross-term diffusion coefficients D-ij (i not equal j) is very enc ouraging. The solute-solute nonbonding interactions seem not to have a sign ificant effect on the diffusion coefficients in our experimental conditions .