The Self-Diffusion Coefficient of Each Component in the Propionic Acid-Water and t-Butyl Alcohol-Water Systems

Abstract

The self-diffusion coefficient of each component in the binary systems was measured by the Fourier transform of the spin echo using the spin echo pulsed gradient method over the whole concentration range at 25 and 32°C. The self-diffusion coefficient of CH₃CD₂COOD in D₂O was measured by the steady gradient method at 25°C.
The values of the self-diffusion coefficient of CH₃CD₂COOD in D₂O corrected for the visco sity of water (η_D2o/η_H2o=1.23) was in good agreement with that of CH₃CD₂COOD in D₂O. The self-diffusion coefficients of water in both systems were larger than those of solute over the whole concentration range. This means that the long-lived hydrated complexes do not exist in both systems. The self-diffusion coefficients of propionic acid and t-butyl alcohol in water show minimum at x_s=0.35 and 0.3, respectively. The self-diffusion coefficients of the solutes in both systems closely correlate with the fluidities of the corresponding solutions.
The self-diffusion coefficient of water in t-butyl alcohol solution is constant a bove; x_s=0.5, while in propionic acid it shows a minimum at x_s=0.6. In both systems, the structural rein forcement appears in water-rich region, and the water molecule behaves as a normal polar molecule in water-poor region.