OZONE IN THE UPPER ATMOSPHERE 463 



amount formed under the conditions of the above experiment 

 must therefore be below this value, which is very small com- 

 pared with the amount of ozone formed. As hydrogen peroxide 

 is decomposed by this last gas, it is doubtful whether any 

 appreciable quantity would be permanently stable in presence 

 of ozone. 



Formation of Oxides of Nitrogen. — By employing as a reagent 

 meta-phenylene-diamine, which undergoes a change of colour in 

 presence of nitrogen peroxide, an indication has been obtained 

 that very small quantities of this gas are obtained by the action 

 of ultra-violet light on air. This method of testing is extremely 

 sensitive and probably not free from objection. The formation 

 of this oxide has not been demonstrated by any corroborative 

 test. 



The only method, apart from colorimetric tests with organic 

 reagents, which appears to have been applied hitherto for 

 distinguishing ozone from oxides of nitrogen when at high 

 dilutions is one which consists in passing the gas into liquid air, 

 when ozone dissolves and nitrogen peroxide separates as a solid. 

 This method was applied in experiments made by the writer. 

 A total volume of 66 litres of air, after passing through a con- 

 centrated solution of potassium hydroxide and then through 

 sulphuric acid, was led through the reaction vessel, where the 

 arc was formed continuously, and was then passed into liquid 

 air. A period of six hours was taken for the passage of the total 

 volume. After this time, a small quantity of white solid, which 

 appeared to be mainly ice, had collected in the liquid air. On 

 separating by filtration through fine cloth, and then collecting 

 the gas evolved on evaporation in a gasometer over mercury, 

 about a litre of gas was obtained. This did not give any 

 coloration with tetra-methyl base paper, nor, on passing the 

 whole through acidified potassium iodide solution, was any 

 iodine liberated. 



Though it cannot finally be stated from these experiments 

 that no formation of oxides of nitrogen or hydrogen peroxide 

 occurs through the influence of ultra-violet light, yet it is shown 

 that the quantity obtained is negligibly small when compared 

 with the ozone. Further researches on these points will have 

 to take into account the refrangibility of the light applied. 



The experiments show clearly that in the higher atmosphere 

 the conditions are present for the formation of a considerable 



