Volume 78, Number 4, May 2007
|Number of page(s)||6|
|Section||Condensed Matter: Structural, Mechanical and Thermal Properties|
|Published online||11 May 2007|
On the temperature dependence of thermal diffusion of liquid mixtures
Physikalisches Institut, Universität Bayreuth - D-95440 Bayreuth, Germany
Accepted: 12 April 2007
Concentration- and temperature-dependent measurements of the Soret coefficient ST have been performed for binary mixtures containing benzene and cyclohexane, both of different degrees of deuteration, and dibromohexane. They are discussed together with data on ethanol/water, toluene/n-hexane, and benzene in heptane, tridecane, and 2,2,4-trimethylpentane taken from the literature. ST can be negative or positive and change its sign both as a function of concentration and temperature. For all systems the Soret coefficient can be expressed by the empirical function , and for all but one (dibromohexane/cyclohexane) systems there exists a concentration where ST becomes temperature invariant, corresponding to a zero of . is of similar magnitude for all mixtures investigated. neither depends on temperature nor on concentration, and isotopic substitution changes only , but not or . For benzene/cyclohexane is related to differences of molecular mass and moment of inertia, and is identified with the chemical contribution to the Soret coefficient.
PACS: 66.10.Cb – Diffusion and thermal diffusion
© Europhysics Letters Association, 2007
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