Thermionic Properties of the Iron Group

As a preliminary to the main problem, the temperature scales for Fe, Ni, and Co have been determined for vacuum heat treated specimens of the metals. The thermionic work functions found differ from those reported by other investigators and are as follows: $\beta -\mathrm{Fe}4.48$ ev, $\gamma -\mathrm{Fe}4.23$ ev, Ni 4.61 ev, and Co 4.40 ev. The probable cause for the difference between these results and those of others is discussed and the effect of minute quantities of certain impurities is described.