Normal spectral emissivity of platinum in the red and in the green in vacuum and helium

The spectral emissivity of platinum for λ=0.645 μm and λ=0.546 μm has been measured by using a De Vos blackbody in ultrahigh vacuum and in helium. Changes in enissivity brought about by heat treatment and changing ambiences, are illustrated and discussed and the results are compared with previously published data. The emissivities determined turned out to be appreciably lower than the measurements of previous investigators. The determined values for 1100<T(K)<1800 are for 0.645 μ between 0.237 and 0.249 in vacuum, and between 0.185 and 0.290 in helium; and for 0.546 μm between 0.250 and 0.312 for vacuum and between 0.219 and 0.321 in helium.