Thermal-Diffusion Measurements near a Consolute Critical Point

Abstract

Using a classical Soret cell and the beam-deflection technique, we have, for the first time, accurately determined the nature of the divergence of the thermal-diffusion ratio ${k}_{T}$ near the consolute critical point of the aniline-cyclohexane mixture. Furthermore, having measured with the same technique the diffusion coefficient $D$, we have also determined the behavior of the thermal-diffusion coefficient ${D}_{T}={k}_{T}D$. The thermal-diffusion ratio diverges as a function of $T\ensuremath{-}{T}_{c}$ with a critical exponent close to that of the long-range correlation length $\ensuremath{\xi}$, while ${D}_{T}$ is practically constant at 4.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$ ${\mathrm{cm}}^{2}$/sec.