On the Method of extracting Iodine from Kelp. 207 



from what has been already said, and may be thus summed up 

 in few words : viz. To encourage and promote their peculiar science 

 by every means in their power, but especially — by collecting, re- 

 ducing, and publishing useful observations and taUles — bytetting 

 on foot a minute and systematic examination of the heavens — by 

 encouraging a general spirit of inquiry in practical astronomy— 

 by establishing communications with foreign observers — by cir- 

 culating notices of all remarkable phaenomena about to happen, 

 and of discoveries as they arise — by compciring the merits of dif- 

 ferent artists eminent in the construction of astronomical instru- 

 ments — by proposing prizes for the improvement of particular 

 departments, and bestowing medals or rewards on successful re- 

 search in all — and finally, by acting as far as possible, in concert 

 with every institution, both in England and abroad, whose ob- 

 jects have any thing in common with their own; but avoiding all 

 interference with the objects and interests of established scientific 

 bodies. 



XXX. On the Method of extracting Iodine from Kelp, By 

 M. Van Mons*. 



X HOSE chemists who have directed their attention to a method 

 for obtaining iodine by the decomposition of the iodate of potash 

 existing in kelp, have proposed several methods for the purpose. 

 Some recommend to sejjarate from the lye of the kelp all the 

 crystailizable salts, and to treat the mother-water with sulphu- 

 ric acid ; — others advise that the sub-carbonate of soda alone 

 should be separated, and the liquid or the remaining salts treated 

 with sulphuric acid ; — a third class suggest methods more or less 

 complicated, among which they cite as advantageous the additiou 

 of the superoxide of manganese, or the hypo-superoxide of lead; 

 — and lastly, it has been prescribed to separate the iodate from 

 the other salts, by taking advantage of its solubihty in alcohol. 



Each of these processes has its inconveniences. In adopting 

 the first, there is a risk of making the sulphuric acid act on the 

 mother water, which often contains no more than one atom of 

 salt to furnish the iodine. We have experienced this, and have re- 

 marked, that from the moment that the greater part of the saits 

 became separated by crystallization, and that the lye began to 

 thicken, when it was desired to carry the separation further, the 

 salt containing the iodic acid was at the same time carried away j 

 already even more or less of it had passed with the first crystals ; 

 80 that, when the mother-water contained no more crystailizable 

 salts, there ordinarily remained no more iodats. 



• From Annalcs Centrales da S'^lsincva Phij^'qucj. 



The 



