Velocity and Absorption of Sound in Suspensions and Emulsions

Measurements have been made of the velocity and absorption of sound in kaolin‐water suspensions and in a number of emulsions. The size of the suspended particles was small compared to the wave‐length of sound used. The data obtained do not substantiate a theory proposed by K. F. Herzfeld, which considers the effect on sound velocity of multiple scattering by spherical particles. Instead, the behavior of suspensions and emulsions with respect to sound velocity is as though they were homogeneous mixtures of the substances in suspension. Thus, the compressibility of a suspension is an additive function of the product of the compressibility and the concentration of the constituent materials, similar to its behavior in ideal solutions. These considerations have possible application to the determination of the compressibility of finely divided substances by means of sound velocity measurements.