﻿Ultra-violet Light on Chlorine. 767 



0*15 per cent, chlorine 30 volts are necessary. The drop in 

 the number of negative ions on the first addition of chlorine 

 is again very clearly brought out. 



Curve IV. 



4 lu ou Condenser Potential 



Influence of various proportions of chlorine on the number and 

 mobility of ions. 



Curve V represents the effect observed with increased 

 percentage of chlorine. The number o£ ions in 3 per cent, 

 chlorine is pretty much the same as was found in air con- 

 taining only 1 per cent., but when the chlorine is increased 

 to 20 per cent, the ionization drops to about one third the 

 value. This result might have been attributed merely to the 

 increase in the rate of recombination due to the absence of 

 sufficient diluting gas, but another possibility suggested itself, 

 namely, that the stream of cool air drawn past the apparatus 

 by the fan had so lowered the temperature of the carbon 

 bisulphide tube as to reduce its vapour pressure below the 

 minimum necessary to provide a sufficient number of nuclei 

 to efficiently conserve the ions, now that the proportion of 

 chlorine was very considerable. Consequently, the experi- 

 ment was repeated with the carbon bisulphide tube immersed 

 in water at 27° k C, whereupon the number of ions was almost 

 trebled *. This result opened the question as to whether the 



*VPofCsl 10 ° 20 ° 27 ° 



V .1 . 01 UD 2 j 2Q cm> 3 Q cm> 4 Q cm ap p r0X i mate ly t 



