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Hermann Weingärtner, Ulrich Klask, Gerhard M. Schneider
Solute Diffusion in Supercritical Solvents – Diffusion Coefficients D12∞ and Diffusion–Viscosity Relationship for the Aromatic Model Solute Biphenyl in Carbon Dioxide
The temperature and density dependence of the mutual diffusion coefficient D12∞ of biphenyl at infinite dilution in supercritical carbon dioxide has been measured by the Taylor dispersion method at several temperatures from 309 K to 331 K and at pressures between about 8 MPa and 20 MPa, corresponding to densities from about 500 kg m−3 to 850 kg m−3. The observed diffusion coefficients are of the order of 10−8 m2 s−1. They decrease about linearly with increasing density and increase slightly with increasing temperature. The experimental data show a density and temperature dependence of the quantity D12∞η/T, indicating a breakdown of the Stokes–Einstein relation. The use of empirical fractional power laws for describing the self-diffusion–viscosity relationship is discussed.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 219, 09/2005
Pages: 1261 - 1271