4 Taylor, Hypoiodous Acid and Hypoiodites. 



Borrowing, with some modifications, a method 

 described by Lunge and Schoch in their paper, I 

 attempted, by means of a standard solution of indigo 

 carmine, to ascertain the strength of the bleaching 

 liquids, in order to find, if possible — assuming that the 

 reaction goes as Schonbein suggested, and as the corre- 

 sponding reaction with chlorine and bromine are well 

 known to go, — the amount of iodine converted into 

 what one may call " bleaching iodine." After many 

 attempts, I found that the best results were obtained 

 by standardising the solution of indigo carmine against 

 a dilute solution of chlorine, which had been titrated 

 against a standard iodine solution by means of potassium 

 iodide and sodium thiosulphate in the usual way. The 

 aqueous iodine solution was also standardised against 

 the same standard solution of iodine. The amount of 

 iodine present in the aqueous solution was usually from 

 0*17 to 0*22 grammes per litre. One of the difficulties 

 experienced in standardising the solutions was due to 

 the end-reaction with chlorine water and the indigo 

 solution being exceedingly slow. No such difficulty, 

 however, was anticipated with the iodine bleaching 

 solutions, the end-reaction with these being apparently 

 sharp and distinct. 



The method employed was to take a measured volume 

 (usually 20 c.c.) of the aqueous iodine solution, to add 

 one or two drops of potash or soda, and then immediately 

 run in the standard indigo carmine until there was a 

 distinct green colour. (The indigo solution is bleached 

 to a slightly yellow liquid, and this of course becomes 

 green as soon as an excess of indigo is added.) For a 

 long time the results were unsatisfactory. The bleaching 

 power of the solutions seemed to vary in an extraordinary 

 manner. Frequently the results obtained gave 90 % and 

 95% of the iodine converted into "bleaching iodine," and 



