Dept. of Chem., Rutgers Univ., New Brunswick, NJ 08903
The major accomplishments in molecular acoustics of liquid systems are summarized. The most promising direction in this field is acoustical thermodynamics. The possibility of acoustical evaluation of thermodynamic parameters of liquids comes from the fact that compressibility of the fluid is the second derivative of Gibbs free energy on pressure. Changes of enthalpy, entropy, free energy, and their pressure and temperature derivatives (heat capacity, volume, expansibility, compressibility, etc.) can be calculated from the pressure and temperature dependencies of sound velocity in the fluid by using additionally the data on the temperature dependencies of density and heat capacity of the fluid at 1 atm. Another new area is related to the studies of the acoustic nonlinearity parameter B/A which is a simple function of the pressure derivative of the bulk modulus and provides unique information on the character of intermolecular forces in the liquid. In aqueous solutions B/A is significantly determined by the structure of water in the hydration shell of the solute. The state of the art in the instrumentation for molecular acoustic studies is presented. New types of acoustical resonators based on the use of cylindrical standing waves enabling one to make measurements in microliter volume samples will be described. [sup a)]Permanent address: Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences.