Radiance Temperature of Niobium at its Melting Point.

A subsecond duration pulse heating method is used to investigate variations in the radiance temperature (at 650 nm) of niobium near and at its melting point. Measurements were made on several specimens with different surface conditions. The results do not indicate any dependence of radiance temperature (at the melting point) on initial surface conditions. The average radiance temperature (at 650 nm) at the melting point for twelve different niobium specimens is 2425 K on the International Practical Temperature Scale of 1968, with an average absolute deviation of 0.6 K and a maximum deviation of 1.2 K.