Theory of the Ultrasonic Absorption in Aqueous Solutions (I) Introduction and General Theory

The origin of the anomalous ultrasonic absorption in aqueous solutions has been attributed to the rearrangement process between the associated and the single molecules of water and the solute molecules accompanying the acoustic cycle. The excess pressure of sound wave changes the existence ratio between the associated and the single molecules of water and gives rise to the molecular rearrangement. This process accompanies a change in configurational entropy, the entropy increasing in the compressed volume element. This entropy increase is approximately reversible, becoming perfectly reversible in the quasi-stationary limit. This reversible increase Δ S in entropy, however, requires a heat quantity T Δ S ( T =absolute temperature), which must be supplied by the volume element itself. Thus the specific heat apparently increases by an amount C m , which corresponds to the specific heat of the internal degrees of freedom of the molecules by the molecular absorption of sound. The main part of Δ S is due to the...