54 THE IJEIIAVIOUU OF SOLLTIOXS OF HVDRIODIC ACID 



The potassium hydroxide sohition from the U-tuhes was 

 diluted to 200 cc. 45 co. of this i^ohitiou were acidified aud 

 titrated with ^-^ sodium thiosulphate sohition, of which 1.58 cc. 

 were required to remove the l)hie colour due to the iodiiH'. From 

 this data it may he sho^\^l that the 200 cc. of hydroxide, there- 

 fore, contain 0.08(>4 gram of iodine. Only one-sixth of this 

 iodine was present as iodate in the ])otassium hydrt)xide solu- 

 tion, that is 0.0144 gram. The quantity of iodine as iodide 

 was estimated hy oxidising it to iodate hy means of potassium 

 pemianganate solution; 1 cc. of this solution = 0.0056 gram of 

 permanganat-e. 25 cc. of the solution of potassium hydroxide 

 which had heeu diluted to 200 cc. was acidified slightly witli 

 sulphuric acid and then made alkaline with ])otassium carbon- 

 ate. The ])ermanganate solution was then added until the 

 li(iuid hccaiiic slightly pink. In this titration 4.40 cc. of the 

 potassium ])ermang'anate solution, corresponding to 0. 0240 gram 

 of potassium permanganate, were required to oxidise the iodine. 

 It will readily Im? seen that this amount of potassium perman- 

 ganate has been used in oxidizing 0.0098 gram of iodine. 

 Therefore, the amount of iodine in the potassium hydroxide 

 solution as iodide was eight times this amount, or 0.07S4 gram. 

 Hience, tlic total amount of iodine lost by eva])oratiou from the 

 iodine solution and absorbed bv the potassium hydroxide solu- 

 tion was, 



0.0144 gram iodine as io(lat(^ 

 0.0784 ' iodid,. 



0.0028 " " absiirbed. 



In this experiment ."{OO ec. of iodide -solution (cone. 1 gram 

 per litre) which contained 0.2208 gram of iodine, were used. 

 From these numbers it will lie seen that the loss by evaporation 

 was 40.47 ])er cent., which leaves still sixty per cent, to be 

 accounted for. 



T'efore leaving this ex])eriment it would be well to mention 

 here that after all the iodine had di~ap])eared from the solution 



