68 Fertilizers 



bone charcoal, consisting chiefly of carbon and phosphate 

 of lime, though also containing small amounts of magnesia 

 and carbonate of lime. 



Bone-black, as received from the refineries, contains 

 the impurities gathered there, consisting chiefly of vege- 

 table matter and moisture. It is somewhat variable in 

 composition, containing from 32 to 36 per cent of phos- 

 phoric acid and a small amount of nitrogen. It decays 

 slowly in the soil, and is not now used to any extent 

 directly as a manure. 



Bone-ash. 



Bone-ash is an excellent, though not large, source 

 of phosphoric acid. It is exported in considerable quan- 

 tities from South America, where the bones are burned 

 and the bulk reduced, in order to facilitate transporta- 

 tion. It does not contain nitrogen, and is more variable 

 in composition than bone-black, though usually somewhat 

 richer in phosphate of lime. Good samples contain 

 from 27 to 36 per cent of phosphoric acid. 



Bones themselves, and the phosphates derived from 

 bones, constitute a class differing from other phosphates 

 used in making manures, in that they are derived directly 

 from organic materials and, as a class, they possess char- 

 acteristics, due to this fact, which render them more 

 useful than those derived from purely mineral sources. 



MINERAL PHOSPHATES 



These constitute a class of products differing from those 

 of immediate or recent animal origin mainly in the fact 

 that they are not combined with organic matter, and are 

 more dense and compact in their structure. They occur 



