Vol. 8, 1922 CHEMISTRY: NO YES AND WILSON 
303 
statistician who wishes to make analytical studies of medical and hygienic 
data by modern statistical methods. 
^ Papers from the Department of Biometry and Vital Statistics, School of Hygiene and 
Public Health, Johns Hopkins University, No. 69. 
2 Pearl, R. Proc. Nat. Acad. Sci., 6, pp. 427-^31, 1920. 
3 Glover, J. W. United States Life Tables, igio. Bureau of the Census, 1916. 
* Census of Iowa, iQij). Published by the Executive Council. 
THE THERMAL lONIZA TION OF GASEO US ELEMENTS A T HIGH 
TEMPERATURES 
A CONFIRMATION OF THE SAHA THEORY 
By Arthur A. Noyes and H. A. W11.SON 
Gates Chemicai. Laboratory, California Institute of Technology, and Physics 
Laboratory oe the Rice Institute 
Read before the Academy, April 25, 1922 
In a recent article Eggert^ has shown that the ordinary thermodynamic 
expression for the effect of temperature on the equilibrium of chemical re- 
actions, when supplemented by assumptions as to the values of the special 
constants occurring in it, can be applied to the calculation of the extent 
to which under different conditions neutral atoms of the gaseous elements 
are converted into positive ions and free electrons. Saha^ has shown 
that the most uncertain factor in Eggert's formulation can be eliminated 
by introducing the ionization-potential of the element. He has then 
calculated the dissociation of the first electron from the atoms of many 
important elements, thus, the extent to which such reactions as Na = Na+ 
+ E~ take place, where E~ represents electron gas. He has tabulated the 
values of this percentage ionization at various temperatures and pressures ; 
and he has especially pointed out the great significance which these con- 
siderations may have for the interpretation of the spectra of elements 
under solar and stellar conditions. 
These principles are of great interest to astroph3^sicists, as may be 
illustrated by the following applications. It has long been known that 
the solar prominences show strongly the hydrogen and helium lines and 
the enhanced (H and K) lines of calcium, but not the blue line of calcium 
nor the familiar lines of sodium or of other alkali elements. The re- 
markable absence of these lines had not been explained; but the thermo- 
dynamic relations now show that the extremely small pressure combined 
with the high temperature of the prominences must greatly promote the 
