The elastic coefficients of benzene are determined from sound velocities measured with the use of an ultrasonic pulse technique over a temperature range of 170° to 250 0 K. At 250 0 K the results are (in units of 10 10 dyn/cn;2): cu=? 14; C22=6.56; .c33=5.83; c«=1.97; C55=3.78; C66=1.53; cI2=3.52; cI3=4.01; C23=3.90. The~e elastic coe~Clents generally mcrease as the temperature is lowered. The observed absorption coeffiCIents are relatively large, thus confirming data reported by L. N. Liebermann. However. it was found that .the .absorption is not isotropic a~d that the absorption for shear waves is comparable with that for longltudmal waves. Some of the expenmental techniques used are described.

The elastic coefficients of benzene have been determined from sound velocities measured with the use of an ultrasonic-pulse technique over a temperature range of 170° to 250°K. At 250°K, the results are (in units of 1010 dyn/cm2): C11=6.14; C22=6.56; C33=5.83; C44=1.97; C55=3.78; C66=1.53; C12=3.52; C13=4.01; C23=3.90. These elastic coefficients generally increase as the temperature is lowered. The observed absorption coefficients are relatively large, thus confirming data reported by L. N. Liebermann. However, it was found that the absorption is not isotropic and that the absorption for shear waves is comparable with that for longitudinal waves. Some of the experimental techniques used are described. [Supported by the U. S. Office of Naval Research.]