Quinary Mutual Diffusion Coefficients of Aqueous Mannitol plus Glycine plus Urea plus KCl and Aqueous Tetrabutylammonium Chloride plus LiCl plus KCl plus HCl Solutions Measured by Taylor Dispersion

摘要

Taylor dispersion is widely used to measure binary mutual diffusion. Studies of three- and four-component solutions show that the dispersion method is also well suited for multicomponent diffusion measurements, including cross-coefficients for coupled diffusion. Numerical procedures are reported here to calculate mutual diffusion coefficients from dispersion profiles measured for solutions of any number of components. The proposed analysis is used to measure the sixteen quinary mutual diffusion coefficients of five-component aqueous mannitol + glycine + urea + KCl solutions and aqueous NBu4Cl + LiCl + KCl + HCl solutions. Mannitol, glycine, urea and KCl interact weakly at the low solute concentrations used (0.010 mol center dot dm(-3)). The diffusion coefficients of this system are compared with pseudo-binary predictions. Strong coupling of the NBu4Cl, LiCl, KCl and HCl fluxes is interpreted by using ionic conductivities and Nernst equations to calculate limiting quinary diffusion coefficients for mixed electrolytes that interact by the electric field generated by ion concentration gradients.