798 Dissociation of Hydro (fen and Nitrogen. 



Summary. 



The disappearance of hydrogen and nitrogen at low pres- 

 sures when an electron stream is passed through them has 

 been investigated. For hydrogen, no disappearance was 

 obtained unless the electrons had energy nbove 13 volts. 

 The rate of disappearance rose rapidly as the energy of the 

 electron was increased to about 70 volts, after which no 

 rapid change was noted (the rate appeared to diminish 

 somewhat when the energy of the electrons was raised from 

 150 to 300 volts). For nitrogen, the rate of disappearance 

 was at first much less than for hydrogen, but when the 

 energy of the electrons was raised sufficiently (roughly 

 200 volts) the rate of disappearance of the nitrogen exceeded 

 that for hydrogen. 



Reasons are given for believing that this disappearance is 

 due to the splitting of the molecules into atoms when 

 electrons collide with the molecules, and that these atoms 

 condense on the adjacent surfaces particularly if they are 

 cold. The maximum rate of disappearance of hydrogen 

 occurred when electrons of ^energy corresponding to 140 

 volts were used. About one molecule disappeared for every 

 six collisions. Langmuir's work on the thermal dissociation 

 of hydrogen showed that the clean up, even under the most 

 favourable circumstances, accounted for only one-seventh of 

 the amount of dissociation. Hence it is possible that when 

 the electrons have the right amount of energy a dissociation 

 may occur almost at every collision. 



A peculiar clean up, apparently due to absorption of 

 nitrogen by a platinum filament covered with BaO and 

 SrO when cooled to the temperature of liquid air, was 

 noticed. 



The author wishes to express his thanks to Mr! A. E. 

 Harkness for his assistance in taking some of the obser- 

 vations. 



Physics Department, Queen's University, 

 Kingston, Ont. Canada. 



