COMPLICATIONS IN THE USE OF THE TAYLOR-DISPERSION-METHOD FOR TERNARY DIFFUSION MEASUREMENTS - METHANOL-PLUS-ACETONE-PLUS-WATER MIXTURES

The Taylor dispersion technique is used to measure the ternary mutual diffusion coefficients of aqueous nonelectrolyte solutions at 25 degre es C. The dispersion of the injected solutes is recorded by a differen tial refractometer and an ultraviolet-visible detector. The diffusion coefficients are calculated directly by fitting the theoretical disper sion equations to about six experimental curves simultaneously. If the ternary diffusion effects in the measured dispersion profiles are not confused by the inaccuracy of the experimental method or an unfavorab le relative detector sensitivity, the diffusion coefficients are preci se. For the system methanol + acetone + water, it is shown that the Ta ylor dispersion method is unsuitable for the determination of all the diffusion coefficients if the methanol mole fraction is less than 0.45 or the acetone mole fraction if more than 0.001.