Wellisch — Motion of Ions and Electrons through Gases. 9 



the experimental evidence indicates that the molecules of oxy- 

 gen do not belong to this class of impurities and that the larger 

 electron velocities attendant upon the act of ionization are 

 necessary for the formation of negative oxygen ions. 



It is oY course possible that the decay of the electrons in CO^ 

 and H2 does not arise from an air leak biit is due to an ageing 

 effect similar to that in petroleum ether. In this connection 

 several unsuccessful attempts were made to remove possible 

 nuclei from CO^ which had been allowed to remain for several 

 hours at a pressure of SI""" in the measuring vessel. In one 

 experiment the gauze electrode was maintained for several 

 hours at a potential of -160 volts in the hope that the electrons 

 which were being continually produced would ultimately 

 remove the nuclei from the gas ; however the current meas- 

 urements failed to indicate any tendency to restore the original 

 condition of the gas under which permanently free electrons 

 were in evidence. 



The same gas was subsequently passed several times through 

 P^O^ by means of a mercury reservoir attachment in order to 

 remove any trace of water vapor which might have arisen from 

 the metal walls : the free electrons, however, did not reappear 

 and the possibility of the existence of nuclei consisting of 

 molecules of water vapor was thus excluded. 



A few experiments were made to ascertain whether free 

 electrons are present in carbon monoxide. This gas was liber- 

 ated by the action of concentrated sulphuric acid on potassium 

 ferrocyanide and was passed through solid caustic potash, cal- 

 cium chloride and phosphorus pentoxide before admission into 

 the measuring vessel. A typical EI curve was obtained for 

 CO at a pressure of 13"""", demonstrating thus the existence of 

 free electrons ; these were, however, not nearly so numerous as 

 in air at the same pressure and, as the manipulation with this 

 gas presented difficulties, it was not considered expedient to 

 extend the investigation. 



It seems fitting to refer here to an apparent difficulty in 

 connection with the existence of free electrons in gases. The 

 electrons were shown to appear in measurable amount in dry 

 air at pressures as high as B'^"' and yet it has been mentioned in 

 this section that a trace of oxygen is sufficient to cause them to 

 disappear from CO^ or H^ at relatively high pressures. Kefer- 

 ence is made later (sec. 5) to this apparent discrepancy ; the dif- 

 ficulty is in large measure removed by a consideration of the 

 experimental fact that the sensitivity to oxygen decreases 

 rapidly as the pressure of the original gas is reduced. To take 

 actual figures, it was found that a trace of air would rob H^ at 

 1 atmosphere of its free electrons and yet in a mixture of H^ 

 at 82^""'" and air at SI-"'"" the electrons appeared in consider- 

 able numbers. 



