20 Wellisch — Motion of Ions and Electrons through Gases. 



the Tallies of the mobilities obtained bj Zelenj"^ are given 

 below : 





Ki 



K, 



K^/Ki 



Air 



1-36 



1-87 



1^375 



CO, 



•76 



•81 



1-07 



H, 



6-70 



7-95 



1-19 



Zelenj's values for air and CO^ are in fair agreement with 

 those obtained by the writer in former experiments and by 

 several other observers. The cause of the discrepancy is not 

 apparent ; it is scarcely probable that any defect either in the 

 method employed in the present experiments or in the deter- 

 mination of any of the constants involved would cause the 

 ascertained values of K, and K, to vary in different directions. 

 It should be mentioned that the present values for CO2 and Hg. 

 are in fair agreement with those obtained by Blancf who used 

 Franck and Fohl's method with X-rays as the ionizing agent, 

 Blanc's values are : 





Ki 



K2 



K2/K1 



CO, 



•83 

 5-33 



1-027 

 10-00 



1-24 



1-88 



Haines:}: has recently obtained the value 5*4 for the mobility 

 of the positiv^e ion in pure hydrogen ; the negative ions did 

 not appear till a trace of impurity was present and under these 

 conditions their mobility was about 8. 



Effect of Water Vcq^or. 



A few experiments were performed to ascertain the effect on 

 the ionic mobilities of saturating with water vapor the ga& 

 under consideration. In these experiments the water vapor 

 was introduced by ebullition when the gas in the vessel was at 

 a low pressure ; after this operation the gas was admitted till 

 the desired pressure was attained. As a result of condensation 



*Zeleny, Phil. Trans., A, cxcv, p. 193, 1900. 



f Blanc, Jour. de. Phys., vol. vii, p. 825, 1908. 



X Haines, loc. cit., also Phil. Mag. xxxi, p. 339, 1916. 



