Transport processes in compressed liquid methanol

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Abstract
The self‐diffusion coefficient of liquid methanol–OD has been measured as a function of temperature and pressure over the density range ∼0.8–1.0 g cm−3 and the temperature range 223 – 323°K using the NMR spin‐echo technique. The shear viscosities and densities have also been determined under the same experimental conditions. The diffusion data are interpreted in terms of a model based on the modified smooth hard sphere theory corrected for the effects of hydrogen bonding. The reduction of the smooth hard sphere self‐diffusion coefficient D SHS as a result of hydrogen bonding is expressed in terms of the parameter αHB. The strongly temperature dependent parameter αHB correlates well with the extent of hydrogen bonding as estimated from the proton NMRchemical shift studies. The Stokes–Einstein relation is found to be valid at the molecular level for liquid CH3OD. Increases in both the density and temperature cause the value of Dησ/k T to a shift from the sticking boundary condition towards the slipping boundary condition.