782 



Prof. A. LI. Hughes on Dissociation of 

 Table II. 



Electron current 650 microamperes. 

 Initial pressures approximately constant. 

 Unit of pressure 10~ 5 mm. 

 Pressure taken at intervals of 4 minutes. 



Pressure. 



E 



F 



G 



a 



I 



J 



K 



291 



141 



71 



43 



28-3 



237 



17 9 



volts. 



volts. 

 970 



volts. 



volts. 



volts. 



volts. 



volts. 



918 



942 



970 



900 



892 



884 



656 



636 



642 



730 



724 



738 



796 



532 



480 



482 



586 



612 



662 



744 



462 



398 



398 



512 



552 



592 



708 



398 



344 



338 



450 



508 



572 



692 



376 



294 



292 



404 



456 



506 



676 



344 



264 



252 



364 



414 



480 



662 



328 



248 



230 



328 



392 



450 



656 



298 



224 



204 



304 



360 



416 



648 



288 



216 



184 



278 



338 



398 



642 



j 270 



I 



200 



164 



252 



318 



380 





clean up obtained was no bigger than the effect (a small 

 thermal clean up) obtained during the next 90 minutes 

 without an electron current. 



Proportionality between electron currents and clean up. — 

 Run G was repeated with the electron current reduced 

 fivefold. The interval between the pressure readings was 

 increased five fold. The readings obtained were practically 

 identical with those of run Gr, showing that the clean up, 

 over this range of five-fold decrease in the electron current, 

 is proportional to the electron current. 



Number of Hydrogen Molecules cleaned up 



Number of Collisions between Electrons and Molecules ' 



The Ratio 



Let 



V = total volume of apparatus ( = 302 c.c.), 



Vi=part of volume at room temp. ( =267 c.c. approx.), 



V 2 = „ „ liquid air temp. ( = 35 c.c. approx.), 



n! = no. of molecules per c.c. in V 1? 



^2 = 5 5 1) 5) ^25 



n — total number of molecules ; 

 then n' = n l Y 1 + n 2 V 2 = n 1 (y i -h- 2 V, 



\ Uy ~ 



N = number of electrons emitted per unit time, 

 \ =mean free path of electron (in V 2 ) ; 



then 1$ (l — e~*)dt = number of electrons which collide with 

 ^ ' molecules between the filament and 



gauze in time dt. (# = 1 cm.) 



