442 Ionization and Dissociation of Hydrogen Molecules. 



different types of ionization. The results show also that H $ 

 cannot be regarded as a stable gas, but that it is a temporary 

 complex formed only when the hydrogen is in a dissociated 

 state. In his paper in Phil. Mag. xxiv. p. 241 (1912), 

 J. J. Thomson finds that H 3 " occurs under certain conditions 



Magnetic Field 



of pressure and current/' but later ('Rays of Positive 

 Electricity ') regards it as a stable gas which, among other 

 properties, combines with oxygen and mercury when under 

 the influence of the electric discharge. It is possible that 

 the disappearance of H 3 in the latter case is due to a higher 

 vacuum, for I find that the pressure is much reduced 

 when the discharge is passed through mercury-vapour and 

 hydrogen. 



Summary. 



Electrons of 800 volts speed ionize hydrogen by detaching 

 a single elementary charge from the molecule. They are 

 not able to dissociate the gas. 



