ULTRASONIC VELOСITY, HEAT CAPACITY AND INTERNAL PRESSURE OF THE LaCl₃+LiCl AND LaCl₃+RbCl MELTS

V.I. Minchenko, V.A. Khokhlov, S.O. Vinogradov-Zhabrov, I.V. Korzun

Institute of High-Temperature Electrochemistry, Ekaterinburg, RUSSIA

Enthalpy and ultrasonic veloсity on the frequency 5 MHz have been measured as a function of the temperature and composition in the LaCl₃+LiCl and LaCl₃+RbCl melts. Using the experimental data on the enthalpy and ultrasonic veloсity and literature values of the density of the melts we have calculated isobaric and isohoric heat capacities.

 

Temperature dependence of both quantities were istablished.

 

Internal pressure of the melts under investigation was found using well-known equation:

p_i = u²·ρ·α·T/γ,

here: p_i, u, ρ, α and γ are the internal pressure, ultrasonic veloсity, density, temperature coefficient of the molar volume, γ = c_p/c_v respectively.

 

Internal pressure is 10⁴ times as large as atmospheric one, p₀, and determines the work which carries out under heating of the melts:

A = c_p – c_v = (p_i+ p₀)·dv/dT

here: A is the work, v is volume.

 

Internal pressure decreases in going from LiCl to LaCl₃ and RbCl.