20 INFLUENCE OF RADIUM ON HYDRIODIC ACID. 



in vacuum at the end of several days. It was found that the 

 radium also produced no effect. The experiment was tried at 

 room temperature only. 



Summary. 



1. When prepared with very pure water a hydriodic acid 

 solution decomposes in the dark, reaching an equilibrium value. 

 (Experiments made up to 36C.) 



2. Ordinary distilled water contains impurities producing 

 some catalytic action which accelerates the decomposition of 

 hydriodic acid solution in the dark, at the same time intro- 

 ducing another reaction, which causes the amount of free iodine 

 to reach a maximum value and then fall off indefinitely. 

 (Experiments made at 15C. only.) 



3. At any temperature up to 24C, more iodine is liberated 

 in a given time from a solution of hydriodic acid in the dark, 

 under the influence of radium, than from one that is not so 

 influenced. 



4. When the experiment is tried at 36C. this last statement 

 is only true up to 24 hours ; for whereas the amount of free 

 iodine with no radium reaches an equilibrium value, with 

 radium it reaches a maximum and then falls off indefinitely. 



5. At 36C. radium seems to cause the formation of the 

 same third product which impurity in water produces at low 

 temperature. 



6. In general, increase of temperature tends to increase the 

 amount of free iodine at any time, whether radium is used 

 or not. 



7. The 7 rays alone cause more iodine to be free than do 

 the @ and 7 rays together. (Experiments made at 24C. only.) 



8. Neither sunlight nor radium causes decomposition of 

 hydriodic acid solution in absence of oxygen. (Experiment 

 made at room temperature only.) 



I wish, in conclusion, to thank Professors Mackay and 

 Mackenzie, for their kind suggestions and criticisms during the 

 progress of this work. 



Dalhousie University, June 1st, 1907. 



