18 THE INFLUENCE OF RADIUM ON THE 



From this work on the effect of temperature we are again 

 led to conclude that the radium intensifies the action that is 



already going on. 



Effect of 7 Rays A lone. 



Hardy and Wilcocks 1 have shown that the 7 rays from 

 radium accelerate slightly the decomposition of iodoform, but 

 that the acceleration is small as compared with that due to the 

 ft rays. In order to determine whether the 7 rays behave in 

 the same way upon the hydriodic acid reaction, the rays from 

 the radium were made to pass through 6 millimetres of lead 

 before entering the solution. This thickness of lead is sufficient 

 to absorb all but the fastest ft rays, and does not appreciably 

 absorb the 7 rays. The reaction was first allowed to go on for 

 ten hours at 24C, when the amount of free iodine was found to 

 be equivalent to 2.10 cc. sodium thiosulphate solution. 



For the sake of comparison the results for ten hours are here 

 grouped : 



No radium for 10 hrs. at 24C 1.23 cc. ~ Na 2 S 2 3 solution 



ft and 7 rays " " 1.73 " " 



7 rays " " 2.10 " 



At first this result seems to disagree with that obtained by 

 Hardy and Wilcocks. Indeed it does not seem reasonable that 

 the 7 rays, whose energy is much less than that of the ft rays, 

 should accelerate the decomposition more than the latter. Closer 

 consideration, however shows that the disagreement is only 

 apparent and that the result is in accordance with the above 

 theory of the break down of hydriodic acid. 



For if, as we have supposed, there are two successive 

 reactions taking place, both of which are accelerated by the 

 influence of radium, then since it has been shown that the 

 second one of these is the more influenced, it is quite probable 

 that when the energetic ft rays are absorbed and not allowed to 

 enter the solution, the second reaction is relatively retarded, and 

 so we have the amount of free iodine in the solution increased. 

 If this is what is happening, then for a few hours after the 



1. Loc. cit. 



