At pressures below 6 GPa, the melting temperatures of Na, Pb, and Pb-Bi(e) increase monotonically with decreasing rate with pressure. The melting tempera­ture of Na increases from 371 K at an atmospheric pressure up to 507-522 K when pressure increases up to 3 GPa37-39; the melting temperature of Pb increases from 600.6 to 795-815 K at the same pressure increase.38,40 For Pb, the rate of the melting tempera­ture increase of 0.0792 KMPa-1 in the pressure range of 15-200 MPa, 0.0671 K per 1 MPa in the range of 0.8-1.2 GPa, and an increase of 5.4 K for the pressure increase from 2 to 3 GPa, were cited in Hofmann.2

The eutectic point of Pb-Bi(e) is shifted to lower Pb contents and higher melting temperature with pres­sure. The eutectic temperature increases from 398 K at normal atmospheric pressure to ^422 K at pressure 0.75 GPa and to ~-481 K at 1.8 GPa41

In the pressure range of 0.1 MPa-3 GPa, the para­bolic function can be used for the description of the pressure dependence of the melting temperatures of Na, Pb, and Pb-Bi(e), (Table 3):

Tm(p) = tm, o + bTM (p — po) + cTm (p — po)2 I1]

The melting temperatures of Na and Pb as functions of pressure up to p = 6 GPa and up to 1.8 GPa for Pb-Bi(e), are presented in Figure 2. At higher pres­sures, a more complicated behavior of the melting temperatures of the considered metals in the function

of pressure is observed.39,42