Sound Propagation in Chemically Active Media

A fluid containing chemically active ingredients in equilibrium may exhibit unique physical properties: the compressibility may depend on the rate of compression; similarly the specific heat may depend on the rate of temperature change. This rate dependence arises from the finite reaction rate of the chemical components. One phenomenon resulting from this behavior is the anomalous absorption and dispersion of sound. Expressions are given relating the chemical reaction rate, the equilibrium constant, and other chemical parameters, to the acoustical properties of the fluid. As an illustration of these relationships the unusual sound absorption in aqueous MgS${\mathrm{O}}_4$ solution is discussed. Calculation shows that the partial compressibility associated with the ionization process is of the correct magnitude to explain the observed absorption.