MANUFACTURED COMMERCIAL FERTILIZERS 531 



There are three principal potassium fertilizers brought to 

 America from Germany: potassium chlorid, kainit, and potassium 

 sulfate. The commerical kainit usually consists of two thirds of 

 the mineral and one third sodium chlorid, and contains about 

 10 per cent of potassium. It is ground and used very generally 

 for direct application. 



Potassium chlorid is obtained from carnallite, and potassium 

 sulfate from kainit, by dissolving the minerals and allowing these 

 salts to crystallize out at suitable temperatures. Commercial 

 potassium chlorid is usually at least 80 per cent pure, while the 

 sulfate has a purity of nearly 95 per cent. Each contains about 

 42 to 43 percent of potassium. Potassium sulfate is also produced 

 from potassium chlorid and sulfuric acid in the manufacture of 

 hydrochloric acid, for which sodium chlorid was formerly used. 



Sylvanite and hartsalz (hard salt) are sometimes ground and 

 applied in the crude state, but the concentrated salts may also 

 be derived from them by solution and recrystallization. 



Potassium-magnesium sulfate, or " double manure salt," is 

 another Stassfurt preparation which is used to some extent. It 

 contains, as found in the market, about 20 per cent of potassium. 

 Its special value, like that of potassium sulfate, is for use in fer- 

 tilizing those crops whose " quality " is injured by salts containing 

 chlorin, particularly the tobacco crop. 



Wood ashes. Unleached wood ashes commonly contain 5 per 

 cent of the element potassium (as carbonate), 50 per cent of cal- 

 cium carbonate, and .5 per cent of phosphorus. On most soils 

 they are likely to be more valuable for the lime than for their 

 potassium content; and, when applied at the rate of a ton or 

 more per acre, even the phosphorus added is more than that con- 

 tained in 200 or 300 pounds of the common " complete " commer- 

 cial fertilizer. 



Potassium from sea water. Where common salt is obtained 

 from the evaporation of sea water, as has been done to some extent 

 on the southern coast of France, potassium is secured as a by- 

 product from the concentration of the " mother liquor," and one 

 may conceive of unlimited supplies being produced in this manner 

 where the climatic conditions and other natural advantages can 

 be utilized, as on an arid coast and under a tropical sun, especially 



