Evaporation of Tungsten Under Various Pressures of Argon

Theory of the mechanism of the evaporation of a tungsten filament in the presence of an inert gas.—A theory of the evaporation of a heated tungsten filament immersed in an inert gas is developed in which it is assumed that the evaporating atoms diffuse through a film of stationary gas surrounding the filament. The diameter of the film is calculated from Langmuir's equation for the heat loss from a filament. The theory leads to the relation $\mathrm{maP}log\frac{b}{a}=\mathrm{constant}$, where $m$ is the rate of evaporation, $P$ is the pressure, and $a$ and $b$ are the diameters of the filaments and gas film respectively.