TOBACCO CULTURE. 69 



35 per cent, phosphoric acid, all of which is insoluble and 

 not available for plant food. The mineral has to be treated 

 with sulphuric acid, before the phosphoric acid can be liber- 

 ated. 



Acid Phosphates are known under several different 

 names, such as superphosphates, dissolved bone, dissolved 

 rock, dissolved bone-black, etc. Acid phosphates are formed 

 by treating some form of insoluble phosphate of lime, as 

 rock-phosphate, bone, bone-ash, etc., with sulphuric acid. 

 By this treatment there are formed soluble phosphates of 

 lime and gypsum (sulphate of lime) in nearly equal pro- 

 portions. 



Cotton Seed Hull Ashes were produced in the South 

 at the cotton seed oil factories, where the hulls, after being 

 removed from the cotton seed, were used as fuel. This ma- 

 terial is not commonly found now. 



Kainit is the most common product of the German 

 potash mines. It is a mixture of several different com- 

 pounds, containing 12 to 13 per cent, of actual potash, to- 

 gether with about 35 per cent, of common salt, also mag- 

 nesia salts. 



Muriate of Potash also a product of the Stassfurt 

 mines, is the main source of supply for potash for com- 

 mercial fertilizers in our market, and contains from 50 to 

 53 per cent, of actual potash. 



Sulphate of Potash is a product of the German miri^s. 

 The product found in the market contains from 48 to 51 

 per cent . of actual potash. 



