The Thermal Conductivities of Mercury, Sodium, and Sodium Amalgams in the Liquid State

A guard ring method for the measurement of the thermal conductivities of liquid metals in which the furnace automatically attains equilibrium is described. The design of the furnace permits frequent and easy replacement of specimens; a layer of paraffin over the liquid metal prevents oxidation by the air. The thermal conductivities of mercury, of sodium, and of sodium amalgams ranging in concentration from 70 to 94 atoms percent sodium are measured over these temperature ranges: mercury, 40°C-220°C; sodium 85°C-210°C; sodium amalgams, 100°C-150°C. Sodium behaves as a normal metal, but mercury and the sodium amalgams are abnormal. Some evidence for the existence of the intermetallic compounds ${\mathrm{Na}}_5$ ${\mathrm{Hg}}_2$ and ${\mathrm{Na}}_3$Hg in the liquid amalgams at 100°C is presented by breaks in the thermal conductivity-concentration curve. An eutectic at 86.5 atoms percent sodium is evident from the same curve. Calculations of Lorentz' number for sodium and for mercury are given.