Aqueous solutions. Part 2.—The compressibility and acoustic relaxations of water

Abstract

The anomalous relaxational compressibility, β_y, obtained previously from aqueous-solution studies has been found to be proportional to T(∂ ln δH/∂T), where δH is the ‘dispersion’ hydrogen-bond energy derived in Part 1. The relaxation associated with β_u can be ascribed to the equilibrium between the single- and zero-hydrogen-bonded OH groups. The volume viscosity of water, η_v, contains contributions from both structural and thermal relaxations. This was indicated from a comparison of the entropies of fusion for water and for a series of alcohols and the temperature variation of η_v/η_sh, where η_sh is the shear viscosity. The anomalous component is associated with the thermal relaxation.