CHAPTER IV 



Iodine and Otlier Chemicals from Seaweed 



RECENTLY, since science has discovered that 

 iodine is one of the essential elements for the 

 growth and health of man and animals, the 

 public has become interested in it. A lack of iodine 

 in food and drinking-water causes disorders of the 

 thyroid gland commonly known as goiter and cre- 

 tinism. The soil, rocks, and the plants grown on the 

 earth contain, in general, but extremely minute 

 amounts of this valuable element. The only impor- 

 tant deposits containing iodine found on the earth 

 are the Chile nitrate beds, and those are doubtless of 

 marine origin. 



Despite the fact that the ocean contains sixty bil- 

 lion tons of iodine, which is practically all of the 

 iodine of the earth's surface, no iodine is obtained 

 directly from the sea. Although sea-water contains 

 only two parts of iodine per million, certain sea- 

 weeds have the remarkable ability to extract iodine 

 from the ocean. A seaweed called tangle possesses 

 this power to a marked degree ; its ash contains more 

 than twenty thousand parts of iodine per million. 



Ever since its discovery in 1812, iodine has been 

 manufactured from the ashes of seaweed. Until that 



time seaweed was burned to produce lye. The sea- 



59 



