80 ROYAL SOCIETY OF CANADA 



Influence of Dissolved Salt. 



From experiments such as described it was found that the pre- 

 sence of a dissolved salt in water slightly lessens the absorption. 

 For example, when calcium chloride, phosphorus pentoxide, or sugar 

 were dissolved, the values of the ionization current for a given speed of 

 air flow were a little above those in the case of distilled water for 

 the same speed. The differences, although distinct, were small, and 

 it was seen that the method could not very well be utilized to examine 

 the effect of varying the concentration of the salt. 



That the absorbing power does fall off under these circumstances 

 is in accordance with the work of Koffler on the absorption of radium 

 emanation in solutions. Koffler found that there was a decrease of 

 the absorption coefficient with increasing concentration of solution 

 and an increase of absorption coefficient with increase of molecular 

 weight of the dissolved salt. He summarized his work in the state- 

 ment — " the absorption coefficient decreases, for one and the same 

 salt as well as for different salts, with increasing number of dissolved 

 molecules." No doubt, if we had a suitable method of experiment 

 the statement would be found to hold for thorium emanation also. 



