CHAPTER V 

 SUPERPHOSPHA TES POTASH 



THE different phosphates mentioned in the previous 

 chapter constitute the sources of supply for the manufac- 

 ture of commercial fertilizers. That is, with the exception 

 of animal bone, Thomas phosphate powder and natural 

 guanos, they are used more extensively for this purpose 

 than directly on the land in their raw state. They are the 

 raw materials from which the manufactured phosphatic 

 fertilizers are derived. The purpose of the manufacture 

 is to convert them into a form in which the phosphoric 

 acid is immediately available, and thus directly useful 

 to the plant. The term "available" in this case is used 

 in the same sense as in the discussion of the forms 

 of nitrogen (Chapter III), and it means that when 

 the phosphoric acid is in this form, the plants may 

 acquire it immediately. 



INSOLUBLE PHOSPHORIC ACID 



Phosphate of lime is, chemically speaking, a salt capable 

 of existing in various forms, the form measuring in large 

 degree the rate of availability. The phosphate of lime, 

 as it exists in the animal bone and mineral phosphates, 

 for example, consists of three parts of lime and one of 

 phosphoric acid. This is the insoluble form. It is not 

 immediately available, and because of the three parts of 

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