Ionization Potentials of Argon, Nitrogen, Carbon Monoxide, Helium, Hydrogen and Mercury and Iodine Vapors

Measurement of the Ionization potential of Gases was accomplished by means of a two electrode tube, by determining the point on the current-voltage curve at which the current increases at a rate faster than that given by Langmuir's equation i=A (V+{V₀) }^3{2}. The effect of a voltage drop along the cathode was eliminated by a commutator arrangement which broke the filament heating circuit while the electron current was being measured. The initial velocity of the electrons, V₀, was determined directly from the currentvoltage curve. Ionization potentials were obtained by measurement as follows: Argon 15. 6, nitrogen 15. 8, carbon monoxide 15. 0, hydrogen 15. 1, helium 20. 5, mercury vapor 10. 1, iodine vapor 8. 5. The ionization potential of argon was found to be constant for pressures between 1 and 200 bars.