230 



Bureau of Farmers' Institutes. 



The soluble and reverted forms of phosphoric acid, taken to- 

 gether, are called available phosphoric acid. 



Chemical Differences of the Four Phosphates of Lime. 



u 

 o 

 p. 



s 



el 



.5 w 



o 



f— I 



o 



O 4» 



ft ^ 

 to ® 

 o ft 



■a. 



h 



(1) 



ft 



>-> 



M 



o 



§ a 

 o® 



•C a) 

 ."•ft 



w 



Insoluble phosphate of lime 

 Insoluble calcium phosphate 

 Normal calcium phosphate . 



Tri-caleium phosphate 



Bono phosphate of lime, etc. 



Soluble phosphate" of lime 



Acid phosphate of lime 



Superphosphate of lime 



Mono-calcium phosphate 



Acid calcium phosphate, etc. . . 



Reverted calcium phosphate . . 

 Precipitated phosphate of limo 



Tetra-calcium phosphate 



33.7 20.0 41.3 



17.1 26.5 54.7 



| 29.4 22. SO 47.0 

 43.7 17.0 39.3 



1.7 



0.8 

 



We notice the following points of difference in composition: 



1. The insoluble phosphate of calcium contains the second 

 largest amount of calcium, the second smallest amount of phos- 

 phorus, the second smallest amount of oxygen and no hydrogen. 



2. The soluble phosphate of calcium contains the smallest 

 amount of calcium and the largest amount of phosphorus, oxygen 

 and hydrogen. 



3. The reverted calcium phosphate contains amounts of cal- 

 cium, phosphorus, oxygen and hydrogen which are intermediate 

 between the two forms preceding. 



4. The tetra-calcium phosphate contains the largest amount 

 of calcium, the smallest amounts of phosphorus and oxygen and 

 no hydrogen. 



With regard to phosphorus, which is the most valuable element 

 in these phosphates of lime, the soluble phosphate of lime con- 

 tains most of this element; the tetra-calcium phosphate of lime 

 the least, and reverted phosphate is second in regard to the amount 

 of phosphorus contained in it. 



Having called attention to the different kinds of compounds in 

 which phosphorus is found, we are now prepared to consider more 

 intelligently the different materials in which the phosphoric acid 



