The velocity of the propagation of sound («) in Na, Pb, and Pb-Bi(e) was mainly measured at normal atmospheric pressure and at temperatures below 1773 K for Na, <1423 K for Pb, and <1073 K for Pb-Bi(e).7,33,34,60-64 It decreases with temperature due to decreasing interatomic interactions. In the temperature range limited by the normal melting and boiling temperatures, the temperature depen­dence of the sound velocity in Na, Pb, and LBE is almost linear and can be presented as follows:

u(T; P0) = »M,0 — A*,0 (T — TM,0) [7]

The recommended values of the sound velocity at the normal melting temperature «M0 and the coefficients Au,0 of eqn [7] for liquid Na, Pb, and Pb-Bi(e) are given in Table 8 and their sound velo­cities as a function of temperature are presented in Figure 6.

Experimental results at higher temperatures were found only in a few publications. For Na, the mea­surements of the sound velocity were performed in the temperature range from Tm,0 up to 1773 K, and a parabolic function was proposed in Fink and Leibowitz7 to take into account its deviation from the linear temperature dependence. In Mustafin and Shaikhiev,63 it was shown that the sound velocity in the liquid Pb can also deviate from the linear tem­perature dependence at high temperatures.

Temperature (K)

The adiabatic (isentropic) compressibility bs can be deduced from the results of the measurements of the sound velocity and density:

= 4@r) = — L2 M

P dp S — L2

The adiabatic compressibility of the liquid Na, Pb, and Pb-Bi(e), at normal atmospheric pressure, calcu­lated with formula [8] and correlations [4] and [7], and using the parameters given in Tables 7 and 8, are presented in Figure 7 as a function of temperature.

The isothermal compressibility can be expressed through the adiabatic compressibility (bs), the iso­baric molar heat capacity (Cp, see Section 2.14.4.4), the density (-), and the isobaric volumetric CTE (ap, see Section 2.14.4.1): мат

-Cp where Ma is the molar mass.