226 Mr. E. Jacot on a Relation between Ionization by 



the mean free path o£ the ions, the only loss is that due to 

 a direct impact o£ the ions on the Avails of the chamber ; and 

 this is proportional to N. 

 Hence, in the steady state, 



up = <yn, 



or N, the equilibrium ionization, becomes proportional to p r 

 the pressure. 



From a consideration of Townsend's work *, this mean free 

 path for pressures of the order of those involved here is 

 about 1 cm. The radius of the ionization-chamber I = 1*5 

 cm. ; a value of the same order as the mean free path of the 

 ions considered ; and Nj the equilibrium ionization, is there- 

 fore proportional to p, the pressure. 



The total mass of nitrogen which enters into combination 

 with phosphorus under circumstances treated of in Part I., 

 has been shown to be proportional to the pressure imme- 

 diately before the gas is admitted to the phosphorus in P. 

 It is therefore also proportional to the equilibrium ionization 

 in the gas. 



Glasson f has experimentally investigated the variation 

 of specific ionization with velocity of cathode rays for a 

 particular case, and has found that, in air, the ionization due 

 to cathode rays per unit length of path of the rays varies 

 nearly as the inverse square of the velocity of the rays and 

 directly as the pressure. 



If this applies to other gases, and more particularly for 

 present consideration to nitrogen, the specific ionization 

 due to cathode rays is proportional to the pressure, and hence 

 the equilibrium ionization is proportional to the specific 

 ionization. 



We therefore arrive at the result that the total mass of 

 nitrogen which enters into combination with phosphorus 

 under the circumstances treated of, is directly proportional 

 to the specific ionization of the nitrogen immediately before 

 combination occurs. 



The writer has extended Glasson's experiments, working 

 with pure nitrogen where Glasson worked with air. The 

 range of cathode-ray velocities examined was of course the 

 same as entered into the work described in Part I. above; 

 and this constituted a range of lower values than those 

 examined by Glasson. Glasson's work extended over the 

 range 4*08 x 10 9 to 6*12 x 10° cm. per sec. The work here 

 described covered the range 2'92 x 10° to 4-76 x 10 9 cm. 

 per sec. 



* Townsend, Phil. Mag. ser. 6, vol. i. p. 198. 

 t Glasson, Phil. Mag. Oct. 1911, p. 647. 



