8 MANUFACTURE OF FERTILIZING MATERIALS 



(C) Reverted phosphoric acid is formed from 

 soluble phosphoric acid under conditions to be 

 explained hereafter. 



(D) Precipitated phosphoric acid is simply an- 

 other name for reverted phosphoric acid. 



(E) Available phosphoric acid includes both 

 the soluble and reverted form of phosphoric 

 acid, because both forms are available for the 

 use of plants. 



(F) Soluble and available phosphoric acid is 

 an expression which means the same as avail- 

 able. 



(G) Insoluble phosphoric acid represents the 

 form of phosphoric acid in raw phosphate of 

 lime, and which is of least value for agricultural 

 purposes. 



(H) Total phosphoric acid represents the entire 

 phosphoric acid compounds without regard to the 

 forms in which they exist. The total phosphoric 

 acid is, therefore, the sum of the soluble, reverted 

 and insoluble forms; or, to state it in another 

 way, the sum of the available and insoluble 

 forms. 



(/) Phosphoric acid equal (or equivalent) to 

 bone phosphate of lime is an expression which 

 usually means nothing more nor less than insol- 

 uble phosphoric acid. 



(A) Potash, as used in connection with fer- 

 tilizers, always means a compound containing 

 potassium and oxygen, known chemically as 

 potassium oxide. Potash is never found as such 



