Spectral emissivity, spectral reflectivity, resistivity, radiation intensity, and thermal expansion measurements as a function of temperature have been made for well seasoned molybdenum and tantalum. From the data thus obtained values for many other physical quantities as functions of temperature have been computed. As such physical quantities, average visible emissivity, color emissivity, total emissivity, brightness temperature, color temperature, radiation temperature, normal brightness, luminous efficiency, and certain temperature variation coefficients have been included. Comparison measurements on moderatly pure and very pure molybdenum showed no appreciable variation in radiation properties, though appreciable variations appeared in their resistivities. The results for very pure molybdenum and moderately pure tantalum are incorporated in tables giving values where known for every 200 degrees between room temperature and the melting points.

• Received 1 September 1925

DOI:https://doi.org/10.1103/PhysRev.28.190