Ultrasonic Absorption and Velocity near the Critical Region of Nitrobenzene-n-Hexane Mixtures

Ultrasonic absorption and velocity measurements have been performed in nitrobenzene‐n‐hexane mixtures over wide ranges of temperatures and frequencies, and over the full range of compositions. The general behavior of the absorption coefficient is found to be similar to the one shown by other binary critical mixtures. The results are discussed in connection with Fixman's theory. An attempt is also made to explain the composition dependence of the absorption coefficient by using the Flory‐Huggins approximation for the long‐range correlation function ${\mathrm{(\kappa }}^{\text{−1}})$ in the Fixman theory.