Section III., 1905 [ 65 ] Trans. R. S C. 



VII. — Researches in Physical Chemistry carried out in the U^iiversity of 

 Toronto during the past year. 



Communicated by Prof. W. Lash Miller. 

 (Read May 25, 1905.) 



1. Mr. W. C. Clark: The rate of oxidation of potassium iodide hy 

 hromic acid. — The rate of this reaction, which has already been the 

 subject of papers by Ostwald, Magnanini, and JSToyes, was studied by 

 the method adopted in this laboratory, and found to be proportional to 

 the concentration of the bromate and of the iodide, and to the square of 

 that of the acid. 



The potassium bromide produced during the reaction is also 

 oxidized by the bromic acid, but without affecting the rate of oxidation 

 of the iodide. 



2. Mr. W. C. Clarh: The catalytic action of chromic acid on the 

 oxidation of potassium bromide and iodide hy chloric, bromic, and iodic 

 acids. — Of the six reactions, one only, viz., that between potassium iodide 

 and bromic acid, is accelerated by the addition of potassium bichromate. 



In dilute solutions of these reagents, iodine is liberated by two inde- 

 pendent reactions, the rate of the first being proportional to the concen- 

 trations of the bromate, iodide, bichromate and acid; and the second 

 to the concentrations of the bromate and the iodide, and to the square 

 of that of the acid. The bichromate is not reduced. 



3. Mr. R. E. DeLury: The rate of oxidation of arsenious acid hy 

 chromic acid, is proportional to the concentration of the arsenite and of 

 the chromate, and to the 1.6th power of that of the acid. 



Mr. DeLury has employed the results of these measurements, 

 together vnth. those of his former research on the oxidation of potassium 

 iodide by chromic acid (these transactions, VIII., 57) to interpret 



4. The reactions in solutions containing arsenious acid, potassium 

 iodide, potassium bichromate, and sulphuric acid. — This furnishes the 

 first case in which the assumption of primary formation of a peroxide 

 in solution and its subsequent reduction by an " acceptor " is borne out 

 by a study of the kinetics of the system. 



The results of the experiments are in quantitative agreement with 

 the hj-pothesis that the arsenious acid is first oxidized to AsoOg (or 

 HAsOg ion) which is then reduced to arsenic acid by potassium iodide or 

 by arsenious acid, the rates of these subsequent reactions being propor- 

 tional to the concentration of the iodide or arsenite respectively. 



Sec. III., 190.5. 5 



