14 Wellisoh — Motion of Ions and Electrons through Gases. 



trials with a few vapors justified this conchision. With the 

 high frequency commutator there was not the slightest indica- 

 tion of the presence of free electrons either in dry SO2 at a 

 pressure of 7™"" or in CH3I at a pressure of 28™™. It was how- 

 ever quite possible that lower pressures would bring the elec- 

 trons into evidence, but as the apparatus did not readily lend 

 itself to securing low vapor pressures the investigation was 

 resumed in a slightly different manner. A small quantity of 

 the vapor under consideration was mixed with a permanent gas 

 and experiments were made to ascertain whether free electrons 

 could continue to exist in this mixture ; if the vapor molecules 

 behaved as electron sinks and were present in appreciable 



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amount then the number of collisions and subsequent attach- 

 ments between electrons and vapor molecules would be suf- 

 ficiently great to prevent the existence of free electrons. This 

 information was of importance in view of the experimental 

 results with regard to the effect of impurities on the number of 

 free electrons in a gas. Three vapors were tried in this con- 

 nection, viz.: ether, alcohol and water; these were chosen 

 because they were deemed to be the most probable absorbers 

 of electrons. In each of these instances hydrogen at a reduced 

 pressure was chosen as the gas with which the vapor was mixed 

 because of the copious supply of free electrons which it affords. 

 An EI curve was first obtained for dry hydrogen at a pres- 

 sure of 36™™ (fig. 7) ; ether vapor was then admitted until the 

 pressure of the mixture was 38™™, and the readings were again 

 taken. It was found that even in the presence of 2™™ of ether 



