Ions and Electrons through Gases. 



49 



atoms of carbon and hydrogen. A number of determinations 

 of ionic mobilities were also made for this vapour ; reference 

 is, however, made to these only as far as they concern the 

 motion of electrons, the actual values obtained for the mobi- 

 lities of the ions being deferred to a later section (4 D). 



The first experiments with this vapour, which was in- 

 troduced at a pressure of 95 mm., gave a normal value 

 (K = *41) for the mobility of the positive ion; the current- 

 potential curve for the negative carriers (fig. 8) was distinctly 

 abnormal, as it afforded evidence of two types of carriers : 



Fig. 8. 



20 



16 



I 12 

 8 





























































f&Troleum ETher 















3 























* 







/s* 



>?y 





















$ 







f 1 

















c I 





<$ 























,*&. 









# 

















< 



'y 



^ 











$/ 









h 



w 



W*'* 



fx> 



' £ 







A° 



Y 



y 

























v^ 













of 









Jo< 



£L@! 



















a^. 



























20 



40 



60 



80 



100 



120 YAQ 



Vo/ts. 



in addition to the normal negative ion (K = *44) there 

 appeared a carrier (a, fig. 8) for which K had the value 

 1*692, which is about four times as great as one might have 

 reasonably expected for the negative ion, and, on the other 

 hand, considerably less than the value corresponding to a 

 free electron. On attempting to repeat the experiment after 

 the vapour had been allowed to remain for about two hours 

 in the vessel, only the normal value was obtained for the 

 mobility of the negative ion. 



In the next experiment, after a preliminary evacuation of 

 the vessel, streams of vapour were swept through repeatedly 

 in the hope of removing traces of impurities ; the vapour 

 was finally admitted at a pressure of 76 mm. and the 

 readings quickly taken. The curve obtained is given in 

 fig. 8; the direction of the arrow signifies that the current 

 measurements were made in descending order of potential. 

 It will be seen that this curve shows the presence both of 



Phil. Mag. S. 6. Vol. 34. No. 199. July 1917. E 



