Manchester Memoirs, Vol. xli. (1897), No. 8. 19 



solutions, complicated a little, in some cases, by the silver 

 which is present. It bleaches indigo slowly, but much 

 more rapidly than the acid prepared with mercuric oxide ; 

 it also bleaches cochineal and logwood, and oxidises cobalt 

 and manganese salts in presence of an alkali. The action 

 of the iodine upon the silver carbonate may probably be 

 represented by the following equation : — 



Ag 2 C O0+2 I 2 +H 2 0 = 2 Ag 1+2 H O I+C 0 2 . 



If a drop of silver nitrate is added to the solution and 

 the liquid boiled, a yellow precipitate is produced, con- 

 taining iodide and iodate of silver. 



I made many attempts to ascertain, by various 

 methods, the proportion of the iodine used which was 

 converted into hypoiodous acid. I filtered the liquid into 

 an acidified solution of potassium iodide, whereby iodine 

 is liberated, the amount of which I estimated. Another 

 method tried was to allow the liquid to run into a standard 

 solution of sulphurous acid, and then to find the amount 

 of this which was oxidised. The results were not satisfac- 

 tory, as I seldom found that more than 50 °/ Q of the iodine 

 was converted into bleaching iodine. I have reason to 

 believe that this result was due to some insoluble hypo- 

 iodite of silver being left in the precipitate. Finally I 

 tried the standard indigo solution, and found that it was 

 possible to estimate the bleaching power even in the 

 muddy liquid containing the excess of silver carbonate 

 and the silver iodide which was produced in the reaction. 

 Shaking up a known volume of the iodine solution with 

 silver carbonate and immediately running in the indigo 

 solution, the bleaching action indicated about 50 to 6o°/ Q 

 of the theoretical amount ; but the addition of a few drops 

 of dilute sulphuric acid carried the bleaching power still 

 further, owing no doubt to the decomposition of some 

 insoluble silver hypoiodite by the acid. By adding the 



