260 
PHYSICS: G. R. HARRISON 
Proc. N. a. S. 
The investigation will be continued with the idea of extending the 
observations to other elements and, also, of getting more accurate measure- 
ments of various factors involved. 
1 Hughes, Bulletin, Nat. Res. Council, Washington, 2, 1921 (86). 
2 Steubing, Physik. Zs., 10, 1909 (787). 
3 Anderson, Physic. Rev., 1, 1913 (233). 
4 Gilbreath, Ibid., 10, 1917 (166). 
5 Kunz and Williams, Ihid., 15, 1920 (550). 
6 Tate & Foote, Phil. Mag., 36, 1918 (64). 
^ Hughes, /oc. (168). 
8 Wood, Phil. Mag., 18, 1909 (531). 
THE ABSORPTION OF LIGHT BY SODIUM 
AND POTASSIUM VAPORS 
By Gkorgk R. Harrison 
Department of Physics, Stanford University 
Communicated June 13, 1922 
The continuous absorption found at the limit of the principal series in 
sodium and potassium is of great importance on the Bohr theory of atomic 
structure, corresponding as it does to the ejection of an electron from the 
atom. It was first noticed by Wood^ in sodium, who mentioned that it 
began in his pictures at the last resolved line, and extended to the extreme 
ultraviolet. Holtsmark^ studied it in sodium and found it also in potassium 
though to a less marked degree. 
The present work was undertaken to study the relation of the band, 
line, and continuous absorption in sodium and potassium vapors, to 
temperature, hydrogen pressure, and vapor saturation. It was thought 
that some change in absorption might be obtained if the vapor was super- 
heated. 
Experimental Arrangements. — The metal was enclosed in iron tubes of 
4 cm. diameter and length from 15 to 200 cm., depending upon the type 
of absorption to be studied. A side arm was welded to the center of the 
absorption tube, and so arranged that it could be heated separately. 
Clean sodium was then placed directly in the side arm, and after the main 
tube had been pumped out and raised to the desired temperature a small 
quantity of sodium could be distilled into it from the side tube at will. 
In this way a rough degree of control could be exercised on the saturation 
of the vapor. 
Blast flames were used as a source of heat. The main tube was closed 
by quartz lenses kept cool with water jackets. To prevent too rapid 
