The Rates of Evaporation and the Vapor Pressures of Tungsten, Molybdenum, Platinum, Nickel, Iron, Copper and Silver

Abstract

Langmuir and Mackay's data on the rates of evaporation of tungsten, molybdenum and platinum have been corrected to the tungsten temperature scale of Forsythe and Worthing. Similar data on nickel, iron, copper and silver are published for the first time on the same temperature scale. The third law of thermodynamics has been assumed in all calculations and the vapor pressures are calculated from the rates of evaporation. The experimental data check the third law as shown by the constancy of the calculated values of ${\lambda }_{\mathrm{o}}$, the latent heat of evaporation at the absolute zero. Tables are given of the rates of evaporation and the vapor pressures up to the boiling points. The data are compared with those of other investigators. The evaporation of metals heated in an atomic hydrogen flame was very rapid and gave results which confirmed the data on evaporation in vacuum. The values of ${\lambda }_{\mathrm{o}}$ expressed in cal. gm. ${\mathrm{}\left(\mathrm{atom}\right)\mathrm{}}^{-1\mathrm{}}$ and the boiling points in degrees Kelvin are