Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 15: POSTERS Dynamics and Diffusion

CPP 15.3: Poster

Tuesday, March 24, 2009, 14:00–16:30, P3

Precise determination of the mutual diffusion and Soret coefficient by a laser beam deflection technique — •Andreas Königer, Börn Meier, and Werner Köhler — Physikalisches Institut, Universität Bayreuth

We have built a diffusion cell with optical beam deflection readout to measure the mutual diffusion and Soret coefficients in binary liquid mixtures, following a design suggested by Piazza [1]. Utilizing a fiber coupled laser with a very short coherence length, a particularly precise determination of the transport coefficients is possible by comparing the measured beam deflection signal to a numerical solution of the coupled heat and mass transport equations. The onset of convection can be suppressed both for heating from above and from below at least up to temperature differences of 2^∘C for ethanol-water mixtures.

We performed numerous tests to validate the measurement method and the procedure for data analysis. Measurements of three organic benchmark systems [2] consisting of tetralin, dodecane and isobutylbenzene and the system water-ethanol demonstrate compliance with existing literature values. In the case of ethanol-water, the concentration and temperature range could be expanded in comparison with data available in literature [3].

[1] Piazza R., Phil. Mag. 83, (2003) 2067

[2] Platten J., Bou-Ali M., Costesèque P., Dutrieux J. Köhler W., Leppla C., Wiegand S., Wittko G., Phil. Mag. 83, (2003) 1965

[3] Kolodner P., Williams H., Moe C., J. Chem. Phys. 88, (1988) 6512