4 Taylor, Reaction of Iodine ivith Mercuric Oxide. 



N/io arsenite, and allowance was of course made for the 

 fact that only one-half of the filtrate was used, and that 

 the iodine liberated was twice that which existed as 

 liypoioditc. The whole of the above operations — shaking 

 with mercuric oxide, filtering from 50 to 75 cc. of the 

 liquid, adding alkali, potassium iodide, and soda-water — 

 usually occupied not more than a minute and a quarter. 



Using iodine in the proportions of 2, 3, 4 to 5 parts 

 per 1,000 of water, I found that, as was to be expected, 

 the best results were obtained with the first. In that case 

 the iodine existing in the filtrate as hypoiodite amounted 

 to from 44 to 52 per cent, of the total possible amount. 

 (Compare with the 80 to 90 per cent, of the possible 

 amount obtained with aqueous iodine.) With the larger 

 proportions of iodine, while the filtered liquid contained, 

 as a rule, a greater amount of iodine as hypoiodite, the 

 percentage of the {possible amount was less, — generally 

 from 30 to 40 per cent. 



After titration of the iodine liberated by soda-water, 

 the addition of a little dilute hydrochloric or sulphuric 

 acid to the liquid usually liberates more iodine. This is 

 due to the iodic acid or iodate in the solution, and is pro- 

 duced by the interaction of iodic and hydriodic acids : — 

 HIO^, + 5HI = 6I + 3Hp. 



From the amount of iodine liberated in this way the 

 quantity present in the liquid as iodate or iodic acid is 

 easily found. This second amount of iodine was deter- 

 mined in the same way as the first, after neutralising the 

 added acid with sodium hydrogen carbonate. /\s the 

 result of a number of experiments I have found that, of 

 the total iodine in the filtered liquid, the amount existing 

 as hypoiodite (or hypoiodous acid) varied from 90 to 95 

 per cent., while that existing as iodic acid was never more 

 than 10 per cent. 



