The Evaporation of Thorium From Tungsten

Abstract

The rate of evaporation of thorium from pure tungsten and from carbonizedtungsten was measured between 2000\ifmmode^\circ\else\textdegree\fi{} and 2500\ifmmode^\circ\else\textdegree\fi{}K. The thorium was deposited on these surfaces by evaporation either from thoriated filaments or from metallic thorium. Evaporation from both surfaces was found to vary directly with the fraction covered, being more rapid from pure tungsten than from carbonized tungsten. Heat of evaporation from tungsten was calculated to be 177000 cal/gr-atom and from carbide 202000 cal.