Optical measurement of the Soret coefficient of ethanol/water solutions.

We have employed a laser-beam-deflection technique to measure the Soret coefficient of ethanol/water solutions with ethanol weight fractions ranging from 0.02 to 0.39, over the temperature range 10C to 40C. This technique also allows precise determination of the mass-diffusion coefficient and of the index of refraction. These results have permitted us to obtain a quantitative understanding of recent experiments on oscillatory traveling-wave convection in binary fluid mixtures.