476 Dr. Megh Nad Saha on Ionization 



Eggert *-— " On the State of Dissociation in the Inside of 

 fixed Stars." In this problem, Eggert has shown that by 

 applying Nernst's formula of " Reaction-isobar/' 



an v mrp v n < 



T7- ' M -*N 



to the problems of gaseous equilibrium in the inside of stars, 

 it is possible to substantiate many of the assumptions made 

 by Eddington f in his beautiful theory of the constitution of 

 stars. These assumptions are that in the inside of stars the 

 temperature is of the range of 10 5 to 10 6 degrees and the 

 pressure is about 10 7 Atm #J and the atoms are so highly 

 ionized that the mean atomic weight is not much greater 

 than 2. This method is directly applicable to the study of 

 the problems sketched above. The equation of the Reaction- 

 isobar is 



p v ™p v x... tt y n 



logK=log |#^ = ~™ + ^ +2 "°' (1> 



where K = the Reaction-isobar, 

 U = heat of dissociation, 

 C p = specific heat at constant pressure, 

 C = Nernst's Chemical constant, 



and the summation is extended over all the reacting sub- 

 stances. The present case is treated as a sort of chemical 

 reaction, in which we have to substitute ionization for 

 chemical decomposition. The next section shows how U is 

 to be calculated. The equation will be resumed in §3. 



§2. 



We may regard the ionization of a calcium atom as 

 taking place according to the following scheme, familiar in 

 physical chemistry, 



Ca —^ Ca, +e-U. (2) 



Where Ca is the normal atom of calcium (in the state of 

 vapour) Ca + is an atom which has lost one electron, U is the 



* Eggert, Phys. Zeitschrift. Dec. 1919. 



t Eddington, M. N. R. A. S. vol. lxxvii. pp. 16 and 596. 



