Thermogravitational measurement of the Soret coefficient of liquid mixtures

We have designed and constructed a thermogravitational column for determining the Sorer coefficient of liquid mixtures. The excellent agreement of the results obtained for toluene and n-hexane mixtures with recent accurate measurements performed by optical methods shows the validity of the thermogravitational method when a column with the correct geometry is used. We have applied this technique to determine the Soret coefficient of the binary systems benzene-n-heptane and carbon tetrachloride with cyclohexane, methanol and ethanol. Comparison with the literature data allows us to determine the reliability of the existing measurements of thermal diffusion for these mixtures.