OZONE IN THE UPPER ATMOSPHERE 461 



prevailing in the upper atmosphere could not be reproduced in 

 these experiments. This increase of temperature would be 

 expected to have no effect on the formation of oxides of nitrogen, 

 which are stable at moderately high temperatures, but would 

 lower the yield of ozone. 



Equilibrium Value of Ozone. — Air which had been stored over 

 water was passed directly through the vessel and then through 

 the wash bottle containing a concentrated solution of potassium 

 iodide. In measuring the equilibrium value of ozone produced 

 by circulating the air at very low speeds, it was found that the 

 temperature of the lamp quickly imposed a limit to the concen- 

 tration of ozone. The highest yield of this gas was obtained 

 when the arc was formed intermittently for a very short interval 

 every half minute, thus minimising the rise of temperature. A 

 confined volume of air in the annular space of the lamp was 

 exposed to the radiation. The arc was formed for 1 second 

 every 30 seconds, and the ozone estimated after different intervals. 

 It was found that the quantity of gas formed increased rapidly at 

 first and then slowly until after about 40 seconds' total exposure 

 a maximum was practically reached containing 0*15 per cent, 

 ozone. A similar result was obtained when the experiment was 

 conducted with pure dry oxygen. In this case, the maximum 

 amount of ozone formed was 0*2 per cent. 



These values are not definite constants, since by using other 

 types of apparatus it has been found possible to obtain a concen- 

 tration of 3'4 per cent, at 20 , and 27 per cent, at 54 . It follows 

 from the fact mentioned above of the formation and decomposi- 

 tion of ozone being effected by light of different wave-lengths, 

 that in the present experiments the equilibrium values obtained 

 will vary with the nature of the light, and this will be determined 

 by the relative transparency of the quartz to the waves of 

 different lengths. The nature of the light in the ultra-violet 

 region of the spectrum radiated from the sun on to the upper 

 layers of the atmosphere is not at all known, so that the con- 

 ditions prevailing in this region could not be reproduced in the 

 laboratory. The scope of the present experiments was con- 

 sequently limited to the determination of the relative formation 

 of the different products given under varying conditions by an 

 arbitrary source of light. 



Influence of Water Vapour on the Formation of Ozone. — It was 

 found that a more valuable yield in the formation of ozone by 



