462 SCIENCE PROGRESS 



ultra-violet light is obtained with dry air or oxygen than in the 

 case of the moist gases. This influence of water has been 

 noticed by earlier investigators, and is possibly due to the 

 formation of traces of hydrogen peroxide which is known to 

 react with ozone according to the equation : 



H 2 0, + O, = H,0 + 20, 



Effect of Pressure on the Formation of Ozone. — In this series of 

 experiments, air after drying was circulated through the reaction 

 vessel at different pressures by means of the Topler pump. After 

 issuing from the radiation vessel the air was immediately led 

 through the reagent. Measurements were conducted at 

 pressures of 760, 70, and 30 mm. in the different cases. The 

 same total amount of air was passed in each experiment and 

 exposed to the radiation for the same intervals of time (10 mins.). 

 The results showed a great decrease in the formation of ozone 

 with decrease in pressure. Thus at 760 mm. pressure, the 

 yield amount to 0*01 per cent., and at 30 mm. to 00014 per cent. 



Formation oj Hydrogen Peroxide by Ultra-violet Light. — Experi- 

 ments which have been made on the exposure of water to ultra- 

 violet light have indicated that a slight decomposition takes 

 place in accordance with the reaction : 



2H a = H 3 2 + H 2 



It has also been stated that when moist air is submitted to the 

 action of ultra-violet light, traces of hydrogen peroxide are 

 formed. Thus, in one case, by circulating air at the rate ot 

 35 litres per hour through a reaction space where it was exposed 

 to a powerful source of ultra-violet rays, and then passing the 

 air through a solution of titanic acid, a slight yellow colour 

 developed in the reagent, thus indicating the presence of traces 

 of hydrogen peroxide. 



Experiments were made by the writer to detect the formation 

 of hydrogen peroxide by passing 60 litres of moist air through 

 the apparatus during two hours, and leading through a solution 

 of titanic acid in sulphuric acid contained in a small glass spiral 

 washer. No change in colour was observed. A comparative 

 test made by taking hydrogen peroxide solution showed that it 

 is possible to detect with certainty the presence of 1 x io _f ' gram 

 of this compound with the above reagent. In 60 litres of air, this 

 would correspond to a volume of r8 x io -6 per cent. The 



