New York Agricultural Experiment Station. 67 



CHEancAL Differences of the Three Phosphates of Lime. 



We notice the following points of difference in composition : 



First. The insohihle pliosphate of calcium contains the largest 

 amonut of calcinm, the smallest amount of phosphorus, the smallest 

 amount of oxygen and no hydrogen. 



Second. The soluble phospliate of calcium contains the smallest 

 amount of calcium and the largest amount of phosphorus, oxygen 

 and hydrogen. 



Third. The reverted calcium phospliate contains amounts of cal- 

 cium, phosphorus, oxygen and hydrogen which are intermediate 

 between the other two forms. 



With regard to phosphorus, which is the most valuable element 

 in these phosphates of lime, the soluble phosphate of lime contains 

 most of this element ; the insoluble phosphate of lime the least ; 

 and the 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 phosphoric is found, we are now prepared to consider more 

 intelligently the different materials in which the phosphoric acid 

 compounds of commerce are supplied for fertilizers. The materials 

 which furnish the greatest proportion of phosphoric acid used in 

 making fertilizers are the following : Bones, hone-ash, hone-hlack, 

 hone-meal, phosphatic guano, rock-phosphate, superphosphates,^ 

 Thomas slag, etc. 



