ISO SOILS AND FERTILIZERS 



introduction of the Stassfurt salts, wood ashes were 

 the main source of potash. Since the discovery and 

 development of the Stassfurt mines, the natural prod- 

 ucts as kainit, and muriate and sulphate of potash have 

 been extensively used for fertilizing purposes. A 

 small amount of potash is obtained also from waste 

 products as tobacco stems, cottonseed hulls, and the 

 refuse from beet-sugar factories. 



STASSFURT SALTS 



233. Occurrence. 6 * The Stassfurt mines were first 

 worked with the view of procuring rock salt. The 

 various compounds of potash, soda and magnesia, 

 associated with the layers of rock salt, were regarded 

 as troublesome impurities, and attempts were made by 

 sinking new shafts to avoid them, but with the result 

 of finding them in greater abundance. About 1864 

 their value as potash fertilizer was established. It is 

 supposed that at one time the region about the mines 

 was submerged and filled with sea-water. The tropi- 

 cal climate of that geological period caused rapid 

 evaporation, which resulted in forming mineral depos- 

 its, the less soluble material as lime sulphate being 

 first deposited, then a layer of rock salt, and finally 

 layers of potash and magnesium salts in the order of 

 their solubility. 



234. Kainit is a mineral composed of potassium 

 sulphate, magnesium sulphate, magnesium chloride 

 and water of crystallization. As it comes from the 

 mine it is mixed with gypsum, salt, potassium chlo- 

 ride, and other bodies. Kainit contains from 12 to 



