336 THE PRINCIPLES OF SOIL MANAGEMENT 



form of tricalcium phosphate, but the materials asso- 

 ciated with it vary greatly. 



Apatite is found in large quantities in the provinces 

 of Ontario and Quebec, Canada. It occurs chiefly in 

 crystalline form. 



The tricalcium phosphate of which it is composed 

 is in one form associated with calcium fluoride, and 

 in the other with calcium chloride. The Canadian 

 apatite contains about 40 per cent phosphoric acid, 

 being richer than that found elsewhere. Phosphorite 

 is another name for apatite, but is chiefly applied to 

 the impure amorphous form. 



Caprolites are concretionary nodules found in the 

 chalk or other deposits in the south of England, and in 

 France. They contain 25 to 30 per cent of phosphoric 

 acid, the other constituents being calcium carbonate and 

 silica. 



South Carolina phosphate contains from 26 to 28 per 

 cent of phosphoric acid, and but a very small amount 

 of iron and alumina. As these substances interfere with 

 the manufacture of superphosphate from rock, their 

 presence is very undesirable, rock containing more than 

 from 3 to 6 per cent being unsuitable for that purpose. 



Florida phosphates occur in the form of soft phos- 

 phate, pebble phosphate, and boulder phosphate. 

 Soft phosphate contains from 18 to 30 per cent of phos- 

 phoric acid, and, on account of its being more easily 

 ground than most of these rocks, is often applied to 

 the land without being first converted into a superphos- 

 phate. The other two, pebble phosphate and boulder 

 phosphate, are highly variable in composition, ranging 



