64. THE WEALTH OF THE SEA 



dissolved in hot water. The saturated solution is then 

 evaporated, and the potassium salts are crystallized 

 out. The mother liquor is acidified with sulphuric 

 acid, mixed with manganese dioxide, and heated in 

 an iron retort; iodine and bromine are obtained in 

 the distillate. 



Iodine is purified by sublimation, which is accom- 

 plished by heating it and condensing the resulting 

 fumes. It is sold either as subHmed iodine or as a 

 salt, such as potassium iodide. Externally it is usu- 

 ally administered in the form of tineture of iodine, 

 which is a solution in alcohol with or without the 

 addition of potassium iodide. When iodine is taken 

 internally, potassium iodide is usually prescribed. 

 In addition to its use in medicine, iodine is utilized in 

 photography and in the manufacture of many dyes 

 and chemicals. 



The time-honored method of obtaining iodine and 

 potassium salts by burning seaweed and extracting 

 the ash is not economical, since nearly half of the 

 iodine and some of the potash contained in the algae 

 are lost by volatilization during the combustion of the 

 weed. Moreover the seaweed must be dried before it 

 is burned ; on this account the process can be carried 

 out only during the summer months. For this reason, 

 no weed is gathered in winter, when large amounts 

 usually are available because of the severe storms 

 which dislodge much seaweed and wash it ashore. 



On account of this waste a clever British chemist 

 named Stanford devoted the greater portion of his 

 life to an effort to invent a method of treating the 

 weed which would yield more iodine and potash. His 



