Sbction III., 1904. [ 25 ] Trans. R.S C. 



111. — Researches in Physical Chemistry, carried out in the University of 

 Toronto during the Past Year. 



Communicated by Peof. W. Lash Miller. 



(Read June 23. 1904.) 



1. The Chromâtes of Bismuth: — Dr. F. B. Allan. A study of the 

 reactions between chromic acid and bismuth salts from the standpoint 

 of the phase rule has led not only to a correct enumeration and descrip- 

 tion of the various basic and acid chromâtes, but to the discovery of 

 cases of false equilibrium, which are of great interest from the theor- 

 etical point of view. 



2. The Rates of the Reactions in solutions containing Potassium 

 iodide, Arsenious acid, and Chromic acid: — Mr. Ralph E. DcLury. The 

 rate at which iodine is liberated in solutions containing potassium iodide 

 and chromic acid has already been studied by Mr. DeLury (Trans. Roy. 

 Soc. Canada, IX., 49). Addition of arsenious acid much increases the 

 rate/ and the present investigation has been undertaken in order to study 

 this case of catalysis in detail. 



The experiments show that the rate of oxidation of arsenious acid 

 by chromic acid is proportional to the concentration of the bichromate, 

 to that of the arsenite, and to the l-6th power of the concentration of 

 the acid, whether potassium iodide be present or not. Addition of 

 potassium iodide somewhat retards the rate at which arsenic acid is 

 formed, while in the presence of arsenious acid the liberation of iodine 

 is almost independent of the concentration of the iodide, if the latter 

 be greater than a certain low value. 



The results of the investigation lead to the hypothesis that the 

 primary product of oxidation of arsenious acid by chromic acid is a 

 peroxide, As^O^, which is then reduced to As^Og by the action of 

 arsenious acid or potassium iodide. Although it has long been custom- 

 ary to explain cases of catalytic action such as the above l)y the assump- 

 tion of peroxides, tliis is the first case in which the hypothesis has been 

 borne out by direct measurements of the rates of the reactions involved ; 

 the only other reaction studied from this point of view is that between 

 chromic acid, potassium iodide, and ferrous sulphate (Miss Benson, 

 these Transactions, IX., 49), in which the results of the measurements 

 are in direct opposition to the peroxide hypothesis. 



3. llie Rate of the Reaction between Hydrogen iodide and Iodic 

 acids: — Mr. Saul Dushman. In the present investigation Mr. Dush- 

 man adopted a modification of a method which was originally employed 



