12 THE ROYAL SOCIETY OF CANADA 



ozonizing agent and that light of wave-length between X = 2300 Â.U. 

 and X = 2900 Â.U. has an equally effective decomposing effect. It 

 was thought that some weak radiation of wave-length approaching 

 that necessary to produce ozone might be emitted by the spark 

 between the aluminium terminals under water, which would be 

 sufficient to produce a small percentage of ozone in the oxygen whose 

 absorption was being tested. 



The apparatus for the experiment described in Section II was 

 again set up, but in this case a glycerine screen, 1 cm. in thickness, 

 was placed in the path of the light from the Henri spark between 

 the lens and the brass absorption tube. This glycerine screen was 

 found to cut off all radiation below the wave-length X = 2300 A.U. 

 so that there was no possibility of any radiation entering the oxygen 

 absorption tube which would transform ozone into oxygen. The 

 tube was filled with oxygen at 140 atmospheres pressure and a photo- 

 graph of the absorption spectrum taken, a reproduction of which is 

 shown in Fig. 4(a). The screen was then removed and the experiment 

 repeated, and the absorption bands shown in Fig. 4(e) were obtained. 

 From these photographs it will be seen that the ultraviolet bands 

 were present in both cases, but when the glycerine screen was inserted 

 the intensity of the light was somewhat reduced so that the bands 

 were shown to better advantage than with the screen removed. 

 However, this experiment showed that these absorption bands were 

 not due to the presence of ozone which may have been formed by 

 ultraviolet light falling on the oxygen gas in the absorption tube. 



(c) To make a more definite test as to whether the ultraviolet 

 bands were due to ozone or not, the absorption spectrum of a mixture 

 consisting of a small percentage of ozone in oxygen was obtained in 

 the following way. 



The absorption tube in this case consisted of a glass tube 25 cms. 

 long and 1 cm. in diameter with a small side tube sealed in near each 

 end. The ends of the tube were closed by plane parallel plates of 

 clear quartz securely waxed on so that when mounted in position the 

 radiation from the source, which as before, was the Henri spark, 

 passed along the absorption tube through the quartz windows into 

 the slit of the spectrograph. The absorbing gas was obtained by 

 slowly passing oxygen gas through a Heumann ozonizer and the 

 resulting mixture of ozone and oxygen was led in at one end of the 

 absorption tube through the side tube, passing out through the 

 second side tube at the other end. The gas coming from the tube 

 was allowed to escape into the atmosphere, so that the pressure of the 



