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 10 to 40° C. 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.