BULLETIN OF THE UNIVERSITF OF WISCONSIN 



Preliminary Experiments. — It is well known that when po- 

 tassium iodide, potassium chlorate, and hydrochloric acid 

 are mixed in solution, iodine is liberated according to this 

 reaction, — 



K CI O3 + 6 H CI + 6 K I = 7 K CI + 3 H, O + lo. 



In order to ascertain the conditions favorable for study- 

 ing the speed of the liberation of iodine in such mixtures, 

 several preliminary experiments on the effects of tempera- 

 ture and concentration became necessary. 



It was found that in mixtures containing equivalents^ of 

 the salts according to the foregoing reaction as deci-nor- 

 mal solutions at 0° C, iodine is liberated very slowly, a 

 sample of twenty cubic centimeters of the mixture after 

 twenty-four hours requiring only one-tenth cubic centime- 

 ter of a deci-normal solution of sodium thiosulphate to 

 destroy the blue color produced by the addition of starch 

 paste. 



The same mixture at 100" C. proved well adajDted for 

 investigation, as the following table shows: — 



Preparation of Solutions. — The solutions used were pre- 

 pared as follows: A normal solution of potassium iodide 

 free from iodate served throughout the investigation. It 



1 Whenever this term is used it is understood to mean equivalents according to the reac- 

 tion already given. 



