Ultrasonic absorption has been measured in water, dioxane-water, and methanol-water solutions of MnS04 at 25°. The three-peak relaxation spectrum is interpreted by the three-step association between Mn+2(aq) and SOv-2(aq) proposed by Eigen. All six rate constants for the three-step process are calculated by a straightforward method.Step I is diffusion controlled with a forward rate constant of 4.2 X 10 ~1 sec.-1 in water while the step III forward rate (4.g X 107 sec.-1) seems controlled by the rate of exchange of solvent on the Mn+2 ion. The over-all equilibrium constant including the three ion-

Secondand third-order elastic-constant data have been used to determine the Griineisen mode y (y), average-square Griineisen constant (yt), and nonlinear constant D for Cu, Ag, and Au. The attenuation suffered by longitudinal ultrasonic waves propagating in the $00) and (t10) directions and transverse waves polarized along (100) and (110), owing to the phonon viscosity and thermoelastic phenomena, have been evaluated for the three metals at 293'K. The phonon viscosity and dislocation drag along the (100) and O10) directions are also discussed.

Ultrasonic attenuation was evaluated in metallic alloys, NixCu1-x( x= 1.00, 0.70, 0.60, 0.45 and 0) due to phonon-phonon (p-p) interaction and thermoelastic loss in a wide temperature region along (110) crystallographic direction for longitudinal and shear waves. Ultrasonic Grüneisen parameters, nonlinearity constants and ultrasonic attenuation due to p-p interaction and thermoelastic loss were determined from 50 K to 500 K using the Born-Mayer and electrostatic potentials. The results were compared with available experimental results.

No abstract

Hall's theory of structural relaxation is applied to explain the excess ultrasonic absorption in methyl alcohol in the pressure range 1-2000 kg/cm . Two states, one characterized by a higher volume (icelike structure) and the other by a lo~er volume (close-packed structure), are assumed to be available to each molecule of methanol, just as in water. It is found that Hall s theory for this case must be modified in order to be in agreement with the experimental results. The modification consists in assuming that the variation of the volume difference &V and the free-energy difference &F is nonlinear with pressure, in contrast with water. This leads to excellent agreement with theory, and also to the conclusion that t';ie variation of AF with pressure is similar to that of ultrasonic velocity in methanol. Assumed values of the relaxational compressibility P"and the structural relaxation time v(at P =1000 kg/cm ) are also justified because the other parameters calculated are as expected.