﻿7(36 Dr. E. B. Ludlam on the Action of 



Carve III. — The effect of gradually increasing the propor- 

 tion of chlorine is shown in a striking manner in Curve III. 

 With no chlorine at all, the negative ions are greatly in 



excess of the positive, but, directly so little as O'lo per cent, 

 is added, the number drops to one fifth its previous value, 

 and approximates to that of the positive ions. 



Curve III. 



0-3 0-4- 0-5 0-6 07 0-8 0-3 \% 



Proportion of Chlorine in air. 

 Influence of small per cent, of chlorine on the ionization of air. 

 (Potential =100 volts.) 



With further increase in the quantity of chlorine, both 

 positive and negative ions increase in number side by side, 

 the negative being always slightly in excess. 



In this series of experiments the potential was not varied, 

 being maintained at 100 volts, as previous results had indi- 

 cated that 100 volts was more than sufficient to catch all the 

 ions. However, to follow any changes which might have 

 taken place in the size and mobility of the ions due to the 

 addition of chlorine, a series of experiments was carried out 

 of which the results are represented in Curve IV. 



Curve IV. — The most striking fact indicated by this curve 

 is the small size of the ions produced in the presence of 

 1 per cent, of chlorine — the two highest curves may be said to 

 run horizontally from a potential of 4 volts, for 0*3 per cent, 

 chlorine, 30 volts were necessary to catch all the positive 

 ions — a value in agreement with Curve II. 



The curve also shows that the first effect of a small quantity 

 of chlorine (0*15 per cent.) is to increase the size of the ions, 

 tor with no chlorine present all are caught at 10 volts; with 



