Positive ions emitted from heated iron filaments consist mainly of the alkali‐metal atoms, such as lithium, sodium, and potassium, which are present in iron as trace impurities. Changes in the work function with different applied partial pressures of oxygen and hydrogen have been recorded. From the results of measurement it is concluded that the effect of oxygen on the work function of iron is much stronger than that of hydrogen. Kinetic data representing the emission of Na and K ions from Fe were obtained in the temperature range of 1050°–1350°K. Diffusion and ion desorption are discussed as possible rate‐controlling processes. Activation energies, believed to represent the diffusion of Na and K atoms in Fe, are found to be approximately 38 kcal/mole (1.7 eV) and 53 kcal/mole (2.3 eV), respectively. The Richardson work function of iron varies from &phgr;≃4.0 eV atP02≃10−9Torr to &phgr;≃5.6 eV atP02≃10−5Torr. When a diffusion‐controlled process is assumed, the difference between the activation energies, for the above two oxygen pressure conditions, is found to be the same as the difference (I‐ &phgr;); that is, the difference between the first ionization potential of the atom and the work function of the metal surface. The experimentally determined values of (I‐ &phgr;)exDfor K and Na agree within experimental error with the calculated values.