Abstract
The Stefan-Boltzmann constant σ has been evaluated by using an absolute radiometer of the electrical substitution type to measure the radiance of a cavity radiator at the freezing-point of gold, TAu. The value obtained for σ, based on the IPTS-68 value of 1337.58 ± 0.20 K for TAu, is (5.6644 ± 0.0075) × 10-8 W m-2 K-4. Unlike most earlier experimental values, this result is not inconsistent with the theoretical value of (5.6696 ± 0.0025) × 10-8 W m-2 K-4 calculated from the present best values of c, h, and k. Alternatively, the experiment may be regarded as a radiometric determination of the gold-point based on the theoretical value for σ, the result then being TAu = 1337.27 ± 0.40 K. This value is 0.31 K below the IPTS-68 value, derived by gas thermometry.