82 Fertilizers 



lime to one of phosphoric acid, which it contains, it is also 

 called tricalcic, tribasic or bone phosphate, and is graph- 

 ically expressed in this formula : 



Lime 



Lime Phosphoric Aoid 



Lime 



That is, in each molecule, however small, there are three 

 parts of lime and one part of phosphoric acid. 



SOLUBLE PHOSPHORIC ACID 



In another form, the phosphate consists of one part of 

 lime and one of phosphoric acid, two parts of the lime in 

 the tricalcic form being replaced with water. This form 

 is called monobasic, or monocalcic. It is a saturated 

 phosphate. There could be no less than one part of lime 

 to one of phosphoric acid, and such phosphates are called 

 acid phosphates, or superphosphates. The combination 

 of the lime and phosphoric acid may be shown as follows : 



Lime 



Water Phosphoric Aoid 



Water 



This form is completely soluble in water and immedi- 

 ately available, and when applied to the soil readily distrib- 

 utes itself everywhere, thus making it more useful than 

 any other form. 



REVERTED PHOSPHORIC ACID 



Another form of phosphate consists of two parts of lime 

 and one part of phosphoric acid, and is called dicalcic, 



