The Absorption Spectra of the Vapors of Aluminum, Gallium, Indium and Thallium in the Ultraviolet

(1) Absorption in heated vapors. The metals were vaporized in a graphite tube 15 cm long heated with an oxyacetylene torch to temperatures up to 2000°C. A tungsten under-water condensed spark provided a continuous spectrum. Aluminum. At about 1200°C the first 7 pairs of the first subordinate series were absorbed. The relative intensities differ from what might be expected from the Bohr theory standpoint. No absorption was observed for the second subordinate series. Gallium. At a temperature of about 1500°C, 17 prominent lines appeared, including the first 4 pairs of the first and second subordinate series and the 5th term of the $2p_1-ms$ series. Indium. At a temperature of about 1200°C, 18 lines appeared, including the first 3 pairs of the first subordinate series, the first 5 pairs of the second subordinate series and the 4th term of the $2p_1-md$ series. Thallium. At 400°C, 4 lines of the $2p_2-ms$ and 4 of the $2p_2-md$ series appeared, widening into bands with increasing temperature. At 800°C, lines from the $2p_1$ level appeared as fine absorption lines. These results verify those of Grotrian. (2) Absorption in the arc. A bead of the metal was placed in a crater. Aluminum. In a 15 amp. arc the lines of the $2p_2-md$ and $2p_1-md$ ($m=5\mathrm{} \mathrm{to} 11$) were completely absorbed. Indium. Besides the resonance lines $2p_2-2s$ and $2p_2-3d$, the lines $2p_1-2s$ and $2p_2-3d$ were completely absorbed. (3) Relative behavior of lines from $2p_1$ and $2p_2$ levels. The lines for the $2p_1$ level for gallium and indium are as readily absorbed as those for the $2p_2$ level and therefore may also be resonance lines.