104 PRACTICAL FARM CHEMISTRY. 



phoric acid we are after, and this therefore makes 

 out twenty or more per cent of the fresh bone. 



Now, bones are treated in a variety of ways to fit 

 them for fertilizer. Often they are steamed, the gel- 

 atinous matter extracted for glue, the remainder 

 dried and ground. This process, of course, deprives 

 it of nitrogen, and leaves little besides the mineral 

 elements in it. Another way, and a good one, is to 

 crush and grind the fresh bones. This gives us the 

 "ground bone," "bone meal," "bone dust" and 

 "bone flour," which contain about twenty per cent 

 of phosphoric acid and two to three of nitrogen. 



Most of the phosphoric acid is insoluble; that is, 

 in its fixed combination of phosphate of lime, same 

 as it was in the whole bone. Its fine state of divi- 

 sion, especially as it appears in bone flour, exposes 

 it to contact with air, moisture, carbonic acid and 

 other influences in the soil, and offers to it many 

 chances of new chemical alliances, so that we need 

 not wonder that plants always know how to get 

 hold of some of this phosphoric acid almost from 

 the beginning, nor that the effect of this bone ap- 

 plication is usually quite lasting; of course, all the 

 slower and more lasting the coarser the bone was 

 ground. Its nitrogen also acts in a similar manner; 

 its effect is slow and lasting. Whenever the soil 

 needs phosphoric acid, and little else, and the crops 

 can be be given their own time to use it — as winter 

 grains, fruit trees, etc. — finely ground bone may be 

 used to good advantage. An average quality is 

 worth thirty dollars or more per ton. 



In bone meal, etc., we have the phosphoric acid 

 in the form of simple bone phosphate of lime. If 

 wanted in a more immediately available form, we 

 thus find it in dissolved bone, which is bone treated 



