Ultrasonic Velocity of Molten ZnCl₂-MCl (M=Li, Na, K, Cs) Binary Systems

Abstract

Ultrasonic velocities of molten ZnCl₂-MCl (M=Li, Na, K, Cs) binary systems have been measured with a U.S. spectrometer by the double-transducer menthod over the frequency range of 5 to 55 MHz.
The results obtained are summarized as follows:
(1) Ultrasonic velocities of molten ZnCl₂-MCl binary systems decrease linearly with increasing temperature except the samples of pure ZnCl₂ and 6.6 mol%KCl. The dispersion of ultrasonic velocity is observed for the pure molten ZnCl₂ below about 730 K, and above this temperature ultrasonic velocity decreases linearly with increasing temperature.
(2) Thermodynamic quantities such as adiabatic and isothermal compressibilities, heat capacity at constant volume and internal pressure were calculated from the measured velocity data, and their composition dependences were obtained.
(3) Since the internal pressure indicates the magnitude of cohesive force in the liquid, it can be used as a measure in determing the types of liquid constituents. The fact that the internal pressure of pure molten ZnCl₂ is nearly equal to those of organic liquids obviously indicates the existence of polymer or complex ions in the melt.
(4) Composition dependence of the total structure factor at long wave length limit was determined over the entire composition range. On the basis of the present and previous results, the liquid structures of these binary systems are discussed.