Positive and Negative Thermionic Emission from Columbium

The positive ion and electron work functions have been determined for well outgassed columbium and found to be for the electrons 3.96 volts with A equal to 57 amp./ ${\mathrm{cm}}^2$/${\mathrm{degree}}^2$ and for positive ions 5.52 volts. It has been found that by bombarding the ionization gauge at a high temperature the specimen could be contaminated so as to change the electron work function by about 16 percent. The effect of impurities on the positive ion work function has been studied and it is shown that these will in general cause an increase in this quantity.