Oxidizahle Variety of Nitrogen. 



415 



that an insufficient time had been allowed for nitric oxide to 

 be oxidized to nitrogen peroxide by atmospheric oxygen 

 before the gas escaped from the trunk, unless the oxidation 

 were accelerated by ozonizing the air. That such an effect 

 may exist is shown by the fact that, whilst the proportion of 

 nitrogen peroxide present in the gas obtained from a series 

 •of 17 spark-gaps amounted to about y Vo wnen the g as was 

 passed rapidly through the trunk (Plate X.e), it was in- 

 creased to about 3 o^o (Plate XI. d) when the velocity was 

 reduced to \ c.f.m., by blowing off most of the gas, in order 

 to allow ample time for the gas in the trunk to mature. 

 But this explanation is not sufficient to account for the whole 

 •of the observations, since even under the very favourable 

 conditions of the low-velocity experiments 17 spark-gaps 

 were required to produce a yield of nitrogen peroxide only 

 one-third greater than that obtained from '6 spark-gaps with 

 the help of ozone. 



Fie. 1. 



Apparatus for preparing Standard Mixtures of Nitric Oxide and Air. 



The efficiency of the ozonizer must evidently be attributed 

 to its ability to oxidize to nitrogen peroxide some substance 

 which cannot be so oxidized by air. This oxidizable sub- 

 stance can scarcely be other than a variety of nitrogen itself, 

 produced by the spark-discharge in much the same way that 

 ozone is produced by the silent discharge. The most efficient 

 way of oxidizing it is to produce it in an atmosphere already 

 charged with ozone (Plate XI. c). A rather less efficient 

 method is to pass the air in which it is produced directly 



