A new instrument is presented to measure the thermal conductivity of p
olar and electrically conducting liquids based on the transient coated
hot-wire method. The performance of the apparatus has been assessed w
ith toluene and water, which are recognized as standard reference mate
rials for nonpolar and polar fluids, respectively. New results are rep
orted fort the thermal conductivity of these liquids between 298 and 3
70 K and at pressures slightly above the saturation. The results show
that the instrument is capable of an accuracy better than +/-0.5%, whi
le the precision and reproducibility are better than +/-0.3%.