Hypersonic velocities in aqueous alkali chloride solutions

Measurements of Brillouin scattering in aqueous solutions of LiCl, NaCl, KCl, RbCl, and CsCl are presented, and the values of the hypersonic velocity as a function of molal concentration are determined. The velocity change with concentration depends markedly on the type of solute ion, it increases monotonically above the value for pure water for the light ions, while in the case of the heavy ions, the velocity first dips below the value of pure water, and then increases with larger concentration of solute. In all cases, the measured hypersonic velocity thus obtained was found to be lower than the corresponding ultrasonic one.