An electrical resistivity determination was first made at room temperature with the samples resting on knife edges at a fixed distance apart and serving as potential contacts. The experimental methods used have been similar to those described previously ( 1, 12). They at the same time make a plea for accurate determinations of the thermal conductivity at 300° or 400°K to be made. These workers note that extrapolation of their thermal data suggest a thermal conductivity at room temperature of about 0.9☐.1 W cm -1deg -1 for osmium and about 1.1☐.1 W cm -1deg -1 for ruthenium. The thermal conductivities of osmium and ruthenium have been measured by White and Woods ( 11), but only below 150°K. Of the four metals of the platinum group yet to be considered, no thermal conductivity values appear to have been measured at normal temperatures or higher for osmium and ruthenium, those for palladium in the range 0° to 100☌ ( 2, 3, 4) show differences of up to 27 per cent, and, whereas most available values for platinum show closer agreement in this temperature range ( 2, 4, 5, 6, 7), differences of about 30 per cent occur between the fewer measurements made at 1000☌ ( 8, 9, 10). The new values found for iridium and rhodium have already been reported ( 1) and it may be noted that at room temperature the value of thermal conductivity for iridium is greater than the value previously quoted by a factor of about 2.5 and that for rhodium by about 1.7. When the previously reported data were examined it was found that the values of the Lorenz number (thermal conductivity multiplied by electrical resistivity divided by the absolute temperature) gave unusually low values for these metals, and investigations were put in hand to make new determinations of thermal conductivity and electrical resistivity. It became apparent during a recent revision by one of the authors of the thermal conductivity section of Kaye – Laby’s well-known book of tables of physical constants that the values hitherto quoted for the thermal conductivity of some metals, and in particular of rhodium and iridium, were clearly in error.
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