Manchester Memoirs, Vol. xlvii. (1902), No. 1. 3 



was used for the quantitative experiments was dried by 

 long standing over strong sulphuric acid. The quantities 

 used varied from 2 to 5 parts of iodine to 1,000 of water. 



The method I employed was to shake up from 100 cc. 

 to 150 cc. of water, containing a weighed quantity 

 of iodine, with precipitated mercuric oxide (no definite 

 amount). The shaking did not occupy, as a rule, more 

 than a {^.w seconds, and then the whole, or nearly the 

 whole, of the liquid was thrown on to a large folded filter, 

 so as to filter it as rapidly as possible. 



The solution of hypoiodous acid obtained by using 

 these comparatively large quantities of iodine rapidly 

 decomposes and turns brown owing to the liberation 

 of iodine. Indeed, it is impossible to filter the whole, or 

 nearly the whole, of the liquid before decomposition 

 begins. I found, however, that even with the largest 

 amounts of iodine employed, it was possible to filter one- 

 half of the total quantity before there was any sign of 

 decomposition, and it was with this first half of the 

 filtrate that all my determinations vvere made. 



As quickly as possible, the first half of the filtrate was 

 poured into a beaker containing a little alkali (sometimes 

 the filtrate was allowed to run into a measured quantity 

 of alkali, as a hypoiodite is more stable than hypoiodous 

 acid) ; a little solution of potassium iodide was next 

 added, and then a considerable amount of soda-water was 

 run in from a syphon. (Free carbonic acid liberates iodine 

 from a mixture of iodide and hypoiodite, but has no 

 effect upon a mixture of iodide and iodate. The action 

 may be represented as follows : — 



KOI + KI + 2 H.^CO, = 2KHCO, + L + H„0. 



The quantity of iodine liberated is manifestly twice 

 the amount which existed in the solution as hypoiodite.) 



The liberated iodine was determined by titrating with 



