Phosphates Their Sources ' 63 



differ in composition from the softer and more porous 

 bones of other parts of the body. 



The phosphate of lime of the harder bones is dense 

 and compact; that from the softer bone is more open 

 and porous. The chief cause of variation in the com- 

 position of bones used as manure, however, is due to 

 the treatment they receive. This is recognized by 

 manufacturers and dealers, and different names of brands 

 are used to indicate the method of manufacture or treat- 

 ment. As applied, however, they do not always corre- 

 spond to the methods of treatment. 



Raw bone. 



The term "raw bone" is properly applied to bone 

 that has not suffered any loss of its original constituents 

 in the processes of its manufacture, and is for this reason 

 highly regarded by farmers, who believe that it is purer 

 than any other form. This is true in a large measure, 

 though the fact that it is raw bone is not altogether an 

 advantage from the standpoint of usefulness. Raw bone 

 too often contains considerable fatty matter, which 

 makes it a difficult process to grind it fine, and which 

 also has a tendency to retard the decay of the bone in 

 the soil. A considerable amount of fat also reduces 

 proportionately the percentage of the valuable constitu- 

 ents, phosphoric acid and nitrogen. Good raw bone, 

 free from meat and excess of fat, should contain on the 

 average 22 per cent of phosphoric acid and 4 per cent of 

 nitrogen. 



Fine bone. 



The trade terms "bone meal,'* "bone dust" and 

 "fine bone" are used to indicate mechanical condition, 



