592 E. M. Wellisch — Mobilities of Ions in Air. 



carrier is regarded as the negative ion. It is easy to calculate 

 the mobility of this ion from the experimental curve ; the por- 

 tions of this curve corresponding to the ions and the electrons 

 are produced to meet and the abscissa of the point thus 

 obtained is obviously the critical potential corresponding to the 

 ionic current. In the case under consideration, we deduce 

 Y = 27*2 volts. The experimental data were : p — 12*22 mm ; 

 100,000 alternations in 203'8 sees; f='57. We obtain 



Fig. 6. 



D 









































//; 



3jjZ>- 









































25 



50 



75 



100 



125 



150 

 Volts 



175 



200 



& 2 = 125*6 cm/sec and K = 2*02. This is practically the same 

 as the value of K obtained for the negative ion in dry air at 

 the higher pressures; other determinations gave still closer 

 results. We are consequently led to the conclusion that the 

 negative ion corresponding to the conditions of the curve of 

 fig. 5 is exactly the same ion as is obtained at the higher 

 pressures. 



The current of negative electricity is thus due partly to 

 electrons and partly to ions ; the electrons traverse the whole 

 distance between the electrodes without attaching themselves 

 to neutral molecules ; the ions are of exactly the same nature 

 as those which are produced at the higher pressures. 



