Concerning the Thermodynamic Temperatures of the Silver and Gold Points

This is a short note presenting some results that follow from an analysis of several well-known experiments performed employing radiation pyrometry. This is done in the light of a recently published experiment which indicates that, at least up to the aluminium point, temperatures measured on the IPTS-68 are systematically higher than the corresponding thermodynamic values. The present evaluation of those experiments shows that the same is also true for the silver and gold points, leading to 1234.88 ± 0.13 K for silver and 1337.22 ± 0.16 K for gold, i.e. 0.20 K and 0.36 K below the stated IPTS-68 values. An approximation to the exact integral equation arising in optical pyrometry was used. The error introduced by this approximation is evaluated in terms of the half-transmittance bandwidth of a pyrometer and its maximum-transmittance wavelength.