Related Experiment Video
Updated: Aug 14, 2026

Thermal Measurement Techniques in Analytical Microfluidic Devices
Published on: June 3, 2015
Molecular thermodiffusion (thermophoresis) in liquid mixtures
Semen N Semenov1, Martin E Schimpf
1Institute of Biochemical Physics RAS, 117977 Moscow, Kosygin Street 4, Russia.
Abstract:
Thermodiffusion (thermophoresis) in liquid mixtures is theoretically examined using a hydrodynamic approach. Thermodiffusion is related to the local temperature-induced pressure gradient in the liquid layer surrounding the selected molecule and to the secondary macroscopic pressure gradient established in the system. The local pressure gradient is produced by excess pressure due to the asymmetry of interactions with surrounding molecules in a nonuniform temperature field. The secondary pressure gradient is considered an independent parameter related to the concentration gradient formed by volume forces, calculated from the generalized equations for mass transfer. Values of Soret coefficients for mixtures of toluene and -hexane are calculated using parameters in the literature. When the molecules are assumed to be similar in shape, the calculated Soret coefficients are lower than the empirical values found in the literature. However, by introducing an asymmetry parameter, which is calculated from independent measurements of component diffusion in the literature, very good agreement is obtained.
Related Concept Videos
Distillation: Vapor–Liquid Equilibria
Phase Transitions: Melting and Freezing
Temperature and Thermal Equilibrium
The concept of temperature has evolved from the common concepts of hot and cold. The scientific definition of temperature explains more than just our sense of hot and cold. Temperature is operationally defined as the quantity measured with a thermometer. Furthermore, temperature is...
Thermodynamic Properties of Ideal Solutions
Solid–Solid Solutions
Phase Transitions: Vaporization and Condensation

