CHAPTER IX. 



POTASH FERTILIZERS. 



Before the discovery of the potash mines in Stassfurt, Ger- 

 many, the main source of supply of potash was wood ashes. 



History. — The following description tells how the deposits 

 of potash salts were formed. 



The Stassfurt salt and potash deposits had their origin, thous- 

 ands of years ago, in a sea or ocean, the waters of which gradual- 

 ly receded, leaving near the coast, lakes which still retained com- 

 munication with the great ocean by means of small channels. In 

 that part of Europe the climate was then tropical, and the waters 

 of these lakes rapidly evaporated, but were constantly replenished 

 through these small channels connecting them with the main 

 body. Decade after decade this continued, until by evaporation 

 and crystallization the various salts present in the sea water were 

 deposited in solid form. Overlying the deposits is a layer of 

 impervious clay which acts as a water-tight roof to protect and 

 preserve the very soluble salts.* 



Potash Salts Used for Fertilizing Purposes. — The principal pot- 

 ash salts obtained from these mines that are used as fertilizers in 

 the United States are : 



1. Kainit 



2. Sylvinit 



3. Muriate of potash 



4. Sulphate of potash 



5. Double sulphate of potash and magnesia 



6. Potassium — magnesium carbonate. 



These products may be classified as crude and manufactured as 

 follows : 



Crude salts | Kainit 



Natural products ( Sylvinit 



( Muriate of potash 



Manufactured salts ! Sulphate of potash 



Concentrated salts j Double sulphate of potash and magnesia 



1^ Potassium-magnesium carbonate. 



There are many other salts as carnallit, polyhalit, krugit, 



