In this paper, we report Soret coefficients obtained by two independent methods and for two different systems-(water-ethanol containing respectively 60.88 and 50 wt % of water). The Soret coefficient is defined by S T ) D T /D where D T is the thermal diffusion coefficient, and D is the isothermal diffusion coefficient. In the first method, D T is determined by a 5-point sampling process in a thermogravitational column and D by the well-known OEC technique (open-ended capillary). The ratio of the experimental values of D T and D gives the expected value of S T . A totally new method consists of velocity measurements of a transient natural convective state: indeed, the Soret effect induces modifications of density gradients and therefore of the buoyancy responsible for free or natural convection. The modifications of the convective amplitudes are thus an indirect way to have access to the Soret coefficient. The velocity measurements were obtained by LDV. The comparison between the two techniques shows a deviation of the order of 4%, which is quite satisfactory. The agreement with the literature is also excellent.

Articles you may be interested inAcceleration of the effect of solute on the entropy-volume cross fluctuation density in aqueous 2-butoxyethanol, 1-propanol, and glycerol: The fourth derivative of Gibbs energy Surface properties of diluted aqueous solutions of solutes containing isopropyl hydrophobic groupThe surface tension of aqueous solutions of normal alcohols ͑from methanol to n-butanol͒ was measured in the temperature range between 278 and 303 K using the Wilhelmy plate method. The surface entropies are calculated. The results are interpreted in terms of specific interactions of the hydrophobic parts of the molecules adsorbed at the interface. It is concluded that increasing surface concentration of alcohol molecules causes their rearrangement at the surface, similar to phase transition. This process depends on the symmetry of molecules.

When a liquid layer is heated from the side, a monocellular flow develops immediately, no matter how small the temperature difference is. If the temperature gradient between the side walls is increased, this flow becomes unstable. Laser Doppler velocimetry measurements are reported here in an attempt to describe the main features of both the basic flow and the instability modes. It is found that before the appearance of traveling waves ͑the most dangerous mode as predicted by the theory͒, stable rolls with their axes perpendicular to the temperature gradient, span over the whole liquid layer, starting from the hot side, even if the aspect ratio ͑the length of the layer divided by its thickness͒ is very high. This unexpected situation modifies the basic flow. A further increase of the temperature gradient leads to the appearance of a time periodic motion.

Computer experiments on aqueous solutions. VI. Potential energy function for tertbutyl alcohol dimer and molecular dynamics calculation of 3 mol% aqueous solution of tertbutyl alcohol J. Chem. Phys. 81, 4065 (1984); 10.1063/1.448150Ultrasonic absorption in binary solutions of pyridine with tertbutyl alcohol and phenol Surface tension of aqueous solutions of tert-butyl alcohol ͑2-methyl-2-propanol͒ was measured in the temperature range between 278 and 303 K using Wilhelmy plate method. The surface entropies and enthalpies are calculated. The results are interpreted in terms of changing structure of solution, especially formation of clathratelike hydrates.