SOURCES AND USE OF POTASH SALTS 



143 



An inorganic source of potash that seems to offer some 

 possibilities is the mineral alunite, which exists in large 

 deposits in some of our western States. This material 

 contains aluminium sulphate and potassium sulphate, and, 

 when burned, the aluminium sulphate is decomposed, 

 leaving alumina, which is insoluble in hot water, while 



FIG. 55. Sweet potatoes grown without fertilizer. 



potassium sulphate is quite soluble and can be removed 

 by lixiviation. 



At the prices that have formerly prevailed, the Stass- 

 furt salts have crowded the other sources out of the gen- 

 eral market. 



103. Commercial Salts of Potash. Two of these salts, 

 kainit and sylvinit, already mentioned in Sec. 99, are 

 exported and sold in the crude state. Kainit is a crys- 

 talline gray material with some red and yellow particles. 



