Ionic Mobilities in Hydrogen. 



341 



range of voltage. From this it is to be inferred that the 

 carriers in the gas are all electrons, moving so freely that 

 very few become permanently attached to hydrogen mole- 

 cules. This state of things does not last long. During 

 the first few hours the electrons diminish in number and 



Fur. 3. 



Volts. 



freedom, while the appearance of heavier ions of definite 

 mobility is marked by changes in slope of the curve occur- 

 ring at definite voltages. Fig. 1 shows a typical case at a 

 pressure of 68 cm. The initial curve has a slight upward 

 curvature, showing that some material ions are already 

 formed, the smoothness of the curve indicating that the 

 electrons forming these ions traverse part of the journey 

 between the plates free, and the remainder attached to a 

 molecule. For an abrupt change of slope in the curve it is 

 requisite that the ions be in definite allignment at one plate 

 when beginning their journey, and that they preserve their 

 character throughout the journey. The second curve was 

 taken after an interval of three hours. It shows a diminished 

 electronic freedom (D), while the two ions C and B appear 

 at about 100 and 230 volts respectively. The readings have 

 not been extended far enough in this case to indicate the 

 normal ion A, but, judging from other curves, it is likely 

 that there would only be a small proportion present at this 

 stage. After one day the ion A is shown largely pre- 

 dominant, B and C being indicated in smaller proportions, 

 while D is wholly absent. If at this stage the collected 

 impurities from the charcoal bulb are admitted to the 



