Thermal-Diffusion Measurements near a Consolute Critical Point

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 $T-T_c$ with a critical exponent close to that of the long-range correlation length $\xi$, while $D_T$ is practically constant at 4.5×${10}^{-6\mathrm{}}$ ${\mathrm{cm}}^2$/sec.