Platinum Metals Rev., 1964, 8, (1), 13
Determination of Thermal Conductivity
Platinum as A Reference Standard
The growing demand for materials to operate at high temperatures has brought a need for accurate knowledge of the manner in which they conduct heat. Reliable figures for thermal conductivity are, however, notoriously difficult to determine, and standard reference materials would be invaluable for checking the reliability of testing equipment and as standards in comparative methods.
Platinum has many advantages as a standard for use at high temperatures, but the values previously determined by various authorities for thermal conductivity up to about 1000°C have shown significant differences. A careful redetermination at the National Physical
Laboratory over the range 0° to 950°C has now been reported by R. W. Powell and R. P. Tye (Brit. J. Appl. Phys., 1963, 14, 662), who have for the first time used substantial bars of platinum for the measurements. Two sets of observations were made on bars having diameters of 1/4 and 1/2 inch respectively; with both samples the conductivity was found to remain constant within 0.5 per cent of 0.73 w cm-1 deg C-1 over the whole range. This result is as much as 20 per cent lower than four out of the five previous deter- minations, but yields values of Lorenz function in much closer agreement with the theoretical