444 SCIENCE PROGRESS 



was that relating to the influence of water vapour on the change. 

 It has been stated already that Shenstone found that ozone 

 prepared from very carefully dried oxygen was extremely 

 unstable and that Shenstone's result was accounted for by Arm- 

 strong by the assumption that oxides of nitrogen had been 

 produced, in small quantity, in the dried gas by the action of the 

 silent discharge on the oxygen and the small quantity of 

 nitrogen with which it was contaminated. That Armstrong's 

 explanation of Shenstone's result is correct has been recently 

 established by a series of experiments by Jones and the writer. 

 Accordingly the question as to whether or not moisture is 

 essential for the destruction of ozone again becomes an open one. 

 To settle the point, ozone which had been kept for some time in 

 the presence of sulphuric acid (which is known to remove the 

 oxides of nitrogen) was heated at ioo° C. in the presence of vary- 

 ing amounts of water vapour. The rate of decomposition was 

 found to be a constant for the same concentration of ozone and 

 independent of the partial pressure of the water vapour. More- 

 over the constant of decomposition was the same when the gas 

 had been thoroughly dried by long exposure to phosphorus 

 pentoxide. So that we were forced to conclude not only that 

 moisture is unessential for the decomposition of ozone but that 

 it does not accelerate the rate of decomposition even to an 

 appreciable extent. It would appear therefore that ozone can 

 undergo decomposition without the assistance of a catalytic 

 agent and that only those gases which can combine with 

 ozone accelerate the rate of decomposition of this latter. 



Experiments performed with the object of determining the 

 order of the change showed that it was a little less than 

 though almost bimolecular — a result which is in agreement with 

 those of Jahn and Warburg. 



We are therefore, I think, justified in assuming that the 

 decomposition of ozone is in ordinary circumstances a chemical 

 process of exceptional simplicity. It is the result of the forma- 

 tion of three molecules of oxygen from two molecules of ozone 

 during a fruitful collision of the latter. It is, in fact, a change 

 which can be correctly expressed by the simple equation : 



2O3 -» 3O2. 



If the above conclusions are justifiable, they have an im- 

 portant bearing on the much disputed problem of gaseous 



