Disappearance of Gas in the Electric Discharge. G09 



The only objection to this view that can lie suggested is 

 that if ionization is all that is necessary to cause these 

 actions to proceed, the gas should disappear before the glow 

 discharge starts ; for, as has been insisted already, there is 

 ionization before the glow. But the difference may be 

 merely one of degree * ; the actions may proceed before the 

 glow, but so slowly that they are inappreciable. For, in 

 order that the compounds may be formed, the charged 

 atoms, which are a small fraction of the ionized molecules, 

 have to meet. If n of them have to meet to form the com- 

 pound, the rate of the reaction will vary as the nth power of 

 the concentration of the ions. The greater concentration of 

 the ions in the glow discharge would account for the far 

 greater rate of chemical combination. Indeed, in order that 

 the view offered should explain the facts, it is necessary 

 to suppose that the actions do proceed to some extent even 

 when there is no glow ; for the conversion into carbon 

 dioxide of the gas originally disappearing, when the tube A 

 was warm, is effected by the continuance of the discharge 

 at a pressure too low for the applied voltage to cause the 

 glow. We must suppose that this discharge, in which the 

 thermionic current is very much greater than the ionization 

 current, is capable of causing the reaction to proceed, and of 

 maintaining the change whereby the solid products are 

 converted reversibly into C0 2 , which is condensed in the 

 liquid air. The reaction proceeds at an appreciable rate 

 because a high potential can be applied ; at higher pressures 

 it is not possible to apply so high a potential without causing 

 the glow. 



Two further observations may be quoted in support of the 

 view that the chemical actions involved are essentially 

 reversible : — First, if, after the gas has been rest red to the 

 lam]) in the form of C0 2 by warming the previously cooled 

 tube A, the discharge is passed (of course, with A warm), 

 its first effect is to increase and not decrease the pressure ; 

 it is only after the discharge has lasted some time that the 

 pressure begins to decrease again. The increase of pressure 

 doubtless represents the conversion of the C0 2 back into 

 (JO and the tendency towards the equilibrium concentration. 

 Second, the rate at which the gas disappears in the presence 



* If (the hypothesis is not thought probable) the glow represents 

 the incoming 1 of some new form of ionization, it is just possible that it is 

 only this form of ionization which is effective in inducing chemical 

 changes. But the idea is not plausible, for many lines <>t argument — 

 especially that based on work on " delta rays " — show that the ionization 

 of a molecule is of the same nature by whatever agent it is effected. 



