Filament Sources of Positive Ions

Efficient filament sources of ions of the alkali metals have been produced by heating synthetic alkali aluminum silicates. Studies of emission of the lithium sources as a function of composition reveal that the silicate 1 ${\mathrm{Li}}_2$O: 1 ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$: 2 Si${\mathrm{O}}_2$ is the most satisfactory ion emitter. Similar sources of the other alkalies prove stable and copious. Ions of Mg, Ca, Sr, Ba, Al, Ga, In, Ti, V, Mn, Y, and Ce, are emitted when the oxide of the metal in question is heated to a white heat on a tungsten filament. The $\mathrm{O}_2^{}{}_{}{}^{-}$ peak observed by Barton has been checked. In the case of aluminum, negative ions of mass 27—presumably ${\mathrm{Al}}^{-}$—were observed.