522 Mr. A. W. Ashton on the 



applied in a darkened room, and a faint odour of ozone could 

 generally be noticed. An experiment was therefore made to 

 ascertain the amount of decomposition taking place when 

 each kind of indiarubber was exposed to the action of ozone. 

 This was effected by placing the samples in a glass tube 

 leading from an ozone generator through which air was 

 forced, each sample being thus subjected to the action of 

 ozone for five minutes. It will be seen from Table XI. that 

 though No. 1 was apparently not attacked, the pure Para 

 No. 2 was left in shreds. 



16. The above experiments having directed attention to the 

 probability of the rubber being attacked by ozone or other 

 gases at the edges of the tinfoil, a condenser was made in 

 which the rubber samples were inclosed between glass plates 

 and were not in contact with the tinfoil. This condenser 

 consisted of two plates of glass kept apart by glass distance- 

 pieces of the same thickness, and having sheets of tinfoil 

 6 in. x 8 in. fixed to the outer surfaces. This formed a 

 condenser with plates 0*25 in. apart, two thirds of this 

 distance being glass, and the remaining third air-space in 

 which the samples of rubber were placed. The air-space 

 was not sealed up, a limited circulation of air being permitted 

 through the spaces between the glass distance-pieces. After 

 this condenser had been kept continuously on the transformer 

 for a fortnight, a slight discoloration, due to the formation of 

 a buff-coloured powder, was noticed round the edges and on 

 the surface of the samples of No. 2 rubber. This discoloration 

 was also noticed on some samples of pure Para strip such as 

 is used for jointing. This condenser was kept continuously 

 on the transformer for six months, and although the surfaces 

 of samples from No. 2 were almost covered with the buff- 

 coloured powder, no change could be detected in Nos. L 

 and '6. Different forms of condenser have been tried for the 

 above test, in which each sheet of tinfoil was inclosed 

 between two sheets of mica *002 in. in thickness. Two sheets- 

 which have been made thus were fixed one on each side of 

 a rectangular framework, cut out of sheet ebonite. In this 

 way the gases evolved at the edges of the tinfoil were 

 prevented from attacking the rubber, and it was also possible 

 to seal up the samples in the air-space. Experiments were 

 made with condensers of this kind having ebonite 5 milli- 

 metres in thickness, (1) with the air-space sealed up; (2) the 

 condenser placed in a sealed bell-jar, the condenser itself not 

 being sealed, but having a space left for the air in the bell-jar to 

 circulate into the air-space of the condenser ; (3) with air 

 having free access to the condenser which was not sealed. 

 Each experiment was continued for two weeks, and no action 



