CHAPTER VII 

 ARTIFICIAL MANURE MANUFACTURE 



Phosphatic Manures Mineral Phosphates Superphosphates 

 Precipitated Phosphates Mixed Manures. 



THE only abundant form in which phosphorus is 

 found, is as the various forms of calcium phos- 

 phate, and, to a smaller extent, as aluminium and 

 iron phosphates. Of these, the calcium phos- 

 phates can better supply phosphorus to the plant 

 than can iron and aluminium phosphates, prob- 

 ably because of the greater ease with which this 

 compound is dissolved by feeble acids, e.g., car- 

 bonic acid, and by saline solutions. Deposits of 

 calcium phosphate are widely distributed. The 

 most definite mineral containing calcium phos- 

 phate is apatite. 



Phosphates, even when very finely ground, are 

 but slowly assimilated by plants, and are, there- 

 fore, almost exclusively used for making super- 

 phosphate, the process consisting in treating them 

 with sulphuric acid in order to realize the follow- 

 ing equation 



Ca 3 (P0 4 ) 2 +2H 2 SO 4 = 2CaS0 4 +CaH 4 (P0 4 ) 2 



Superphosphate 



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