Cathode Rays and certain Chemical Effects. 233 



♦chamber P cannot be made with any accuracy. Recom- 

 bination and diffusion o£ ions are factors that enter into any 

 •calculation of this kind. At the low pressures at which the 

 work was necessarily carried out, these are factors that cannot 

 be neglected; and we have as yet no working data to allow 

 of any calculation of these factors. From a general con- 

 sideration of our results, however, it is evident that, in any 

 one experiment, the proportion of ions in the "active" 

 portion of nitrogen concerned is small ; and hence that the 

 ■observed combination between nitrogen and phosphorus is 

 not in the main a combination between ions and the 

 phosphorus. The combination is a well-defined function of 

 the equilibrium ionization of the nitrogen. But the function 

 of the ions in P need be no more than that of assisting a 

 combination which could not otherwise effect itself. 



On the other hand, the observed activity of the nitrogen 

 may be due to some effect of the cathode rays on the gas 

 quite apart from the ionizing effect. The corpuscles in the 

 g;is molecule are attracted or repelled by cathode rays as 

 they pass through or near the molecule and so acquire 

 kinetic energy. If this energy does not exceed a certain 

 value — the value necessarv for ionization — the effect on the 

 gas molecule may yet be such as to effect its stability. The 

 molecule may break up with the formation of two free atoms. 

 This monatomic nitrogen would constitute the active gas ; 

 and the results described above would show that this 

 atomizing of the gas by cathode rays is proportional to the 

 ionization by the rays. 



Summary. 



I. The action of cathode rays on white phosphorus has 

 been made a special study. The action is at least twofold : 



(1) There is a purely thermal effect of the rays, resulting 



in the formation of red phosphorus ; 



(2) There is a more directly chemical effect due to an 



effect of the corpuscles on the nitrogen in the 

 tube, followed by a reaction between the modified 

 gas and the phosphorus. 



The latter effect is proportional to the equilibrium ionization 

 of the nitrogen ; but the total number of active atoms or 

 molecules in the gas is of a much higher order than the 

 number of ions present in the gas at the instant of 

 combination. The function of the ions may be that of 

 assisting a combination which does not otherwise effect 

 itself. More probably, the activity of the gas is not directly 



Phil. Mag. S. 6. Vol. 25. No. 146. Feb. 1913. R 



