212 On the Method of extracling Iodine from Kelp. 



oil a large scale dissipated in air the muriatic gas by decom- 

 posing with a slow fire the salt mixed with the sulphuric acid. 



In following our process, no more need at first be incorporated 

 than the sulphuric acid indispensable for the decomposition of 

 muriates; and after that decomposition, the remainder of the acid 

 may be added by spreading it uniformly over the whole mass of 

 salt ; but this precaution is not necessary when the process is 

 followed throughout in the way which we have pointed out. 



The separation of the salts may be also attempted by subject- 

 ing their mixture in a dry state to a heat capable only of liqui- 

 fying the iodate of potash, and the sulphate of soda ; the super- 

 natant liquid will cover two muriates, and the sulphate of potash 

 not melted. 



We expected to have found the means of separating the io- 

 date with the muriatic acid, when we had poured the ammonia- 

 cal liquid »n the acid, which passed red at the distillation. There 

 was not at first any mixture between the two liquids; but on 

 coming in contact they were observed to separate, and cry- 

 stallize in irregularly faced pyramids with their base turned 

 upwards. The crystals were very numerous. We expected 

 that by agitation they would have fallen to the bottom bf the li- 

 ^ quid, but it made them disappear; some new alkali reproduced, 

 them, and that until the ammonia was in excess ; — the colour of 

 the acid, far from disappearing, became livelier. We repeated 

 this experiment several times, and always with the same result. 

 We made the experiment each time with three or four ounces of 

 liquid. Thus, in that operation which without contradiction had 

 been the simplest and the easiest, our attempt was unfortunately 

 abortive. 



We made an experiment on the volatility of iodine in air : five 

 grains of crystal of that substance were placed in the morning 

 on the reverse of a cup ; — towards evening a great part had been 

 already dissipated ; and next morning the whole had disappeared. 

 The temperature of the apartment varied from 8° to 10" R., and 

 the odour of chlorine continued for several days. 



Two grains of iodine placed in the palm of the hand, dissi- 

 pated in less than twelve minutes ; the spot remained muck 

 longer. It was when at another time making the same experi- 

 ment, with the view of ascertaining the identity of the odour of 

 iodine with that of chlorine, that we discovered the property which 

 the former substance has of colouring starch blue. A napkin 

 passed through starch, with which we wiped our hands, was co- 

 vered with large blue spots, which by little and little became 

 violet, and ultimately disappeared. Since then we have em- 

 ployed as a reagent for iodine small strips of cloth steeped in 

 starch water. 



When 



