The absolute values of $W$, the energy required to produce one ion pair, for electrons have been determined for several gases. A parallel plate extrapolation ionization chamber in conjunction with a ferrous sulfate dosimeter was used. The gases investigated were air, nitrogen, oxygen, carbon dioxide, argon, methane, and ethylene; and the absolute values of $W$ were 33.9, 34.8, 30.9, 32.6, 25.5, 26.8, and 26.3 ev, respectively.

• Received 25 February 1955

DOI:https://doi.org/10.1103/PhysRev.98.1828