Selective measurements of the self-diffusion coefficients in acetic acid-water and methanol-water systems by pulsed-gradient fourier-transform NMR

Abstract Measurement of the self-diffusion coefficients was performed for the binary liquid mixtures acetic acid—water and methanol—water by the pulsed-field-gradient method over the whole concentration range at 32°C. The self-diffusion coefficient of each component was determined from the Fourier-transformed spectra of proton echo signals by means of a conventional Fourier-transform NMR system. In the methanol—water system a minimum of the self-diffusion coefficient of water appeared at mole fraction 0.4, and that of methanol appeared at mole fraction 0.25. In the acetic acid—water system the self-diffusion coefficient of water did not show a minimum, and the values were nearly constant above mole fraction 0.5. The self-diffusion coefficients of water in both mixtures were larger than those of solutes over the whole concentration range. The long-lived hydrated complexes do not exist in the acetic acid—water system.