Wellisch — Motion of Ions and Electrons through Gases. 7 



same paper there were given the curves corresponding to the 

 negative carriers in air at relatively low pressures ; the charac- 

 teristic feature of these curves is their compound nature result- 

 ing from the independent passage through the gas of electrons 

 and ions. It is convenient to designate as 1 curves the former 

 type which is due solely to ions, while the latter type may be 

 referred to as EI curves ; moreover, those curves or parts of 

 curves which arise solely from the motion of electrons will be 

 called E curves. 



On resuming the experiment an investigation was made of 

 the gases CO^ and H^. The CO2 was prepared in a Kipp's 

 apparatus by means of the action of dilute HCl on marble and 

 was passed through JN'aHCOg Aq. in order to remove acid 

 fumes ; the H^ was obtained by the action of dilute HCl on 

 zinc and was passed through KOH Aq. In each case the gas 

 was passed through a series of tubes of CaCl^ and Tfi^ in order 

 to remove traces of moisture. A series of I and EI curves was 

 obtained for these gases under various conditions, a few 

 examples of the latter type being given in iig. 4. The free 

 electrons were more numerous in each of these gases than in air 

 at the corresponding pressure ; this point is brought out by 

 the fact that with the same frequency of commutation the 

 electrons appeared at much higher pressures than in air, e. g. 

 it was just possible to detect electrons in air at S"""" pressure 

 whereas in CO, they appeared in large numbers at a pressure 

 of li^'" and in H^ they were readily observable at atmospheric 

 pressure (v. Curve A Hg. 4 which was obtained with a fre- 

 quency of only 42*6 ; also curve in fig. 5). This result was 

 to be expected from the conchisions of previous experimenters 

 who had found that the abnormal increase in the ionic mobility 

 set in for these gases at higher pressures than for air. It 

 should be remembered that we cannot form any definite infer- 

 ence as to the relative number of electrons by comparing the 

 ionization currents in the E curves for different gases at the same 

 pressure because these currents are due to the electrons which 

 have passed through the meshes of the gauze electrode and the 

 fraction of electrons which accomplish this depends upon the 

 gas concerned. 



When the pressure of the CO^ or H^ was relatively high the 

 free electrons appeared to be extremely sensitive to the pres- 

 ence of impurities in the gas under consideration ; the number 

 of free electrons was greatly decreased if the gas were allowed 

 to stand undisturbed for a few hours in the measuring vessel 

 which was presumably air-tight. This effect is illustrated in the 

 curves of fig. 5 ; curve A refers to CO, at 79""" pressure, the 

 readings being taken quickly after the introduction of the gas ; 

 curve B exhibits the values after the gas had been allowed to 

 remain 2^ hours in the closed vessel. 



