Experimental Confirmation of the Kawasaki-Einstein-Stokes Formula; Measurement of Small Correlation Lengths

The Kawasaki formula $D=\frac{\mathrm{kT}}{6\pi \eta \xi }$ is experimentally verified using the measured values in a cyclohexane-aniline critical mixture near $T_c$. Its application in a wide range of temperatures above $T_c$, where the viscosity is known, is completely verified by the measurements of the diffusion coefficient $D$ and allows a direct determination of the correlation length $\xi$ in a domain where no other optical method is suitable. We show that the power law $\xi =\xi {\left(\epsilon \right)}^{\nu }$ is followed up to 40° from $T_c$.