Electrical resistivity of liquid sodium + lithium mixtures. Evidence for incipient immiscibility?

Abstract

The electrical resistivity of liquid sodium + lithium solutions has been accurately determined by a capillary method from 100 to 450°C. The resistivity obeys a parabolic relationship over almost the full concentration range, but slight deviation occurs near the sodium axis. The excess resistivity of the solutions over that of the linear interpolation between the pure metals is relatively small. A comparison with the other alkali metals shows that the excess resistivity increases in the order Na + Li < Na + K < Na + Rb < Na + Cs. The temperature coefficient of resistivity, dρ/dT, shows a peak near 63 mole % Li but only at temperatures just above 305°C. This is attributed to incipient immiscibility. At higher temperatures the coefficient changes smoothly from Na to Li.