184 ANNUAL OF SCIENTIFIC DISCOVERY. 



factory, the iodine being liberated by ordinary chemical operations 

 with the greatest ease. In repeating the process on a large scale, 

 the weeds were cut fine with a vegetable-cutter, and the slices left in 

 a heap for about twelve hours ; a species of fermentation then com- 

 mences, which reduces the whole mass to a pulp, which on the appli- 

 cation of an adequate pressure yields a liquor containing the principal 

 portion of the iodine. With reference to another species of sea-weed, 

 the Laminaria saccharina, which in the autumn is very rich in iodine, 

 the plan of extraction is still more simple. Having collected this 

 as drift- weed, it is only necessary to heap it up in vats with a tap at 

 the bottom to allow the draining liquid to escape. For some hours 

 nothing but sea-water runs off; but at a certain stage, dependent 

 mainly upon temperature and quantity, fermentation sets in, and iodino 

 makes its appearance in the liquid. When this is ascertained by 

 testing, the tap should be closed, and the mass suffered to remain for 

 twelve hours, being occasionally stirred. When the contents of the 

 vat have been reduced to a soft pultaceous magma, in which all the 

 remaining cellular tissue can be readily broken down by the hand, the 

 addition of quicklime, varying with the amount of substance operated 

 upon, and which may easily be determined by experience, completes 

 the process. The iodides in solution may then be removed by expres- 

 sion. 



The subsequent steps of the operation will be much influenced by 

 circumstances. If the object be merely to save the iodine, a variety 

 of methods may be adopted to effect this purpose, one of which will 

 be mentioned hereafter. If, on the other hand, it be a consideration to 

 obtain the potash salts, evaporation, and probably repeated crystalliza- 

 tions, must be resorted to ; and the facility of obtaining fuel at little 

 expense will of course become an important element for consideration. 

 It will, however, at once occur, that the cellular tissue which remains 

 after pressure will render important service in this case ; at all 

 events but little experience and ingenuity will be required for com- 

 bining all the favorable circumstances in such a manner as to insure 

 a profitable arrangement. Whilst the use of iodine remains a matter 

 of importance only in a pharmaceutical point of view, the demand must 

 necessarily be limited, and such a supply as could easily be obtained 

 by the above method would materially affect the market. Should any 

 means, however, be discovered of rendering it useful for the purposes 

 of dyeing, the application of sufficient capital would doubtless be at- 

 tended with very profitable results. The complete separation of 

 iodine from its solutions, Dr. Kemp has found to be best effected by 

 an insoluble compound of starch with oxide of lead, which is formed 

 by adding common starch to a solution of neutral acetate of lead and 

 ammonia. By means of this mixture, any quantity of iodine may be 

 precipitated from a solution, and by taking advantage of the weight 

 and denseness of the precipitate, we can decant the supernatant liquid, 

 and repeatedly wash the residue without loss. 



The course proper to be adopted by the agriculturalist, in making a 

 practical application of the facts above stated, is simply this. The 

 sea-weed, bsing collected in heaps, may be suffered to drain itself of 



