In this study, we have measured the thermodiffusion coefficients of six hydrocarbon liquid ternary mixtures at 25 degrees C using the thermogravitational technique. Mixtures of 1,2,3,4-tetrahydronaphthalene-isobutylbenzene-n-dodecane at four different concentrations and 1,2,3,4-tetrahydronaphthalene-isobutylbenzene-n-decane at two concentrations have been considered. We have used a plane-thermogravitational column with a small gap dimension to improve the accuracy of the recently reported data. The obtained results have been confirmed by measurements in a cylindrical column. We have also measured the thermodiffusion coefficients of 13 binary mixtures between the different components of ternaries in order to analyze the validity of the additive rule proposed in the literature to determine thermodiffusion coefficients of ternary mixtures from binary thermodiffusion data. A new correlation based on column separation, which reproduces the data within the experimental error, is proposed.

In this article we determined the thermal diffusion coefficient (D(T)) in equimolar mixtures of n-alkanes nC(i)-nC(12) (i=5,6,7,8,9,17,18), nC(i)-nC(10) (i=5,6,7,15,16,17,18), and nC(i)-nC(6) (i=10,12,14,16,18) at 25 degrees C and at atmospheric pressure using the thermogravitational technique. The results obtained from this study together with the previously published ones in the series of nC(i)-nC(18) (i=5,6,7,8,9,10,11,12,13) show that the main parameter that determines D(T) in each series is in association with the molecular weights of the mixture's components. However, an empirical quantitative correlation has been obtained between D(T), the molecular weights of the components, the viscosity, and the thermal expansion coefficient of the mixtures. This is the first report of a closely accurate correlation for D(T) in liquid mixtures.

We investigated the thermal diffusion behavior of aqueous solutions of monosaccharides with the infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS) setup. As monosaccharides, we studied the three aldohexoses glucose, galactose, and mannose and the two ketohexoses sorbose and fructose. All sugars have the same molecular weight, but their structures differ as well as some physical properties such as viscosity, density, thermal expansion coefficient, and optical rotation. Additionally, we measured the viscosity and the optical rotation of the monosaccharide solutions in the investigated temperature and concentration range. While there is a clear correlation between the structure and the thermal diffusion behavior for alkanes, the situation is much more complicated for the monosaccharides. Nevertheless, as in the case of the alkanes, we find a correlation between the thermal diffusion coefficient with the ratio of the thermal expansion coefficient and the kinematic viscosity. We discuss the physical principles, which connect the thermal diffusion behavior with other thermophysical properties and the structure of the different sugars.

We investigated the thermal diffusion phenomena of a rod-like mutant filamentous fd-Y21M virus in the isotropic phase, by means of an improved infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS) set-up crucial for measurements of slowly diffusing systems.Since this is the first thermal diffusion study of a stiff anisotropic solute, we investigate the influence of the shape anisotropy on the thermal diffusion behavior. The influence of temperature, fd-Y21M concentration and ionic strength in relation with the thermodiffusion properties is discussed. We characterize and eliminate the effect of these parameters on the absolute diffusion of the rods and show that diffusion determines the behavior of the Soret coefficient because the thermal diffusion coefficient is constant in the investigate regime. Our results indicate that for the thermal diffusion behavior structural changes of the surrounding water are more important than structural changes between the charged macroions. In the investigated temperature and concentration range, the fd-Y21M virus is thermophobic for the low salt content, while the solutions with the high salt content change from thermophobic to thermophilic behavior with decreasing the temperature. A comparison with recent measurements of other charged soft and biological matter systems shows that the shape anisotropy of the fd-virus becomes not visible in the results.

In the present work we studied the thermal diffusion behavior of n-decane in various alkanes by thermogravitational column (TC) technique and the thermal diffusion forced Rayleigh scattering (TDFRS) method. The investigated lighter alkanes compared to n-decane are n-pentane, n-hexane, n-heptane, n-octane, and the heavier ones are n-tetradecane, n-pentadecane, n-hexadecane, n-heptadecane, n-octadecane, and n-eicosane. The binary mixture n-decane/ n-pentane we investigated at several different concentrations; all other mixtures were only investigated at a mass fraction of 50%. Even for the volatile n-pentane/ n-decane mixture the deviations between the thermal diffusion coefficients determined by the different methods agreed within the error bars. Typically the agreement between the two methods was in the order of 5%. In comparison to recently published TC and TDFRS data we found deviations in the order of 30% up to 40%. We analyze and discuss the possible reasons for the discrepancies for the present and the past publications.