IODINE AND OTHER CHEMICALS 63 



amount of weed has been washed up, whole families 

 go to the beaches and pull the algae out of the surf. 



In the early days of the European potash indus- 

 try, the dried seaweed was burned in large heaps or 

 piles. From time to time more seaweed was added, 

 until all had been burned, and a hard cake of fused 

 ashes had been obtained. The product was called 

 kelp and usually contained much sand and foreign 

 matter. 



Now most of the seaweed is burned in long low 

 kilns. After a fire has been kindled with brush or 

 straw, the dried algae are slowly added until the fire 

 has been burning for six or eight hours, or until all 

 the dried seaweed has been added. The porous ash 

 in the bottom of the kiln is then worked with a rake 

 until all of the dried weed has been burned and the 

 resultant ash is all melted. A single burning of sea- 

 weed forms a cake of kelp from three to six inches 

 thick. When more weed has been dried, it is burned 

 on top of the ash from the first burning. This is 

 repeated until a cake of ash about two feet thick 

 has been built up. This cake is broken up while hot 

 by throwing cold water on it. The kelp is stored in 

 a dry place until it is shipped to a chemical plant, 

 where it is made into iodine, bromine, potassium 

 sulphate, and potassium chloride. 



The Manufacture of Iodine 



The process by which iodine, bromine, and po- 

 tassium salts are obtained from seaweed ashes is 

 rather simple. The seaweed ash is broken up and 



