Determination of Ultrasonic Absorption and Velocity and the Derived Thermodynamic Properties of Pure and Binary Molten Salts

Abstract

The absorption and velocity of ultrasonic waves in molten salts are studied with an improved pulse method, which allows an exact and immediate measurement of the runtime of the impulses and of the amplitude of the recorded signals. The measurements are performed in the pure molten salts sodium nitrate, potassium nitrate, and silver nitrate as well as in the three binary mixtures of these salts in the temperature range between 430 K and 620 K at various compositions. All values are measured at 27.789 MHz, the resonance frequency of the quartz transducers being used. From the ultrasonic velocity, together with the expansion coefficient and the specific heat capacity, the adiabatic compressibility, the adiabactic constant, and the Rao's constant have been calculated. From the ultrasonic absorption and velocity results the volume viscosity, which can be referred to the structural relaxation of the molecules in the fused salts investigated here.