ABSTRACT
The Soret coefficients of a set of ternary systems of 1,2,3,4-tetrahydronaphthalene (THN), isobutylbenzene (IBB), and n-dodecane (nC12) at 298.15 K were measured under microgravity condition aboard the International Space Station in the frame of the DCMIX1 experiment. The present work includes a comprehensive study of possible data processing sequences for the interpretation of interferometric Soret experiments in ternary systems. Several data processing methodologies are discussed. A significant concentration dependence of the Soret coefficients is observed. In the present study, we have obtained large and positive values for THN and negative ones for IBB in all investigated systems. A linear relation between the Soret coefficients of two components is derived for each system and allows validating experimentally the coefficients measured in other experiments.
ABSTRACT
Dynamic analysis of the light scattered by non-equilibrium fluctuations in a thermodiffusion experiment has been performed on a sample of polystyrene-toluene-n -hexane, at 0.9-49.55-49.55% mass fraction. Time decays of the non-equilibrium fluctuations have been obtained revealing the accurate detectability of three modes. The slowest mode has been attributed to the mass diffusion of the polymer into the binary solvent; the intermediate one to mass diffusion of the two molecular components of the solvent; finally, the fastest one has been attributed to the thermal diffusivity of the overall mixture. The two eigenvalues of the mass diffusion matrix have been evaluated with accuracy in the order of 1%. Neglecting cross-diffusion effects we obtain a simplified expression for the relative amplitude of the two mass diffusion modes, allowing a parameterized determination of polystyrene and toluene Soret coefficients in the ternary mixture. We suggest that a two wavelength shadowgraph experiment is needed for a complete determination of all the coefficients.
