THE measurement of the transport properties of thorium at low temperatures has until fairly lately been largely overlooked, although judging by the electrical resistivity measurements of Meissner and Voigt t metal of good purity was available for research purposes as long ago as 1930. In fact, it is only since 1958 that properties other than the electrical resistivity, namely the Hall effect 2 and the thermoelectric power, a have been studied at low temperatures.
Published work on the thermal conductivity is limited solely to that of Marsh and Keeler 4 for the high temperature region between 300 and 923 ° K. Whereas in most metals the thermal conductivity is approximately temperature independent above room temperatUre, thorium shows uncommon behaviour in having a conductivity that rises monotonically with increasing temperature. At 373°K the conductivity of Marsh and Keeler's specimen was 0-38 W cm -1 deg.K -1 and at 923°K it was 0-454 watt units. From these figures it would appear that their specimen was much less pure than ours.
The thermoelectric power has been determined above room temperature by Thompson, s Bender,6 and