PHOSPHORUS 



115 



gelatine and glue. In this process, much of the nitrogenous 

 material is removed; but, as the phosphoric acid is not 

 removed to any extent, the decrease in weight of the 

 bones caused by the materials extracted brings about a 

 corresponding increase of the percentage of phosphoric 

 acid. The process of extraction also removes the greases 



FIG. 40. Corn grown without the use of special fertilizer. 



and fats which interfere with the decomposition of the raw 

 bone in the soil. Experiments show that steamed bone 

 acts more quickly and is more valuable as a source of 

 phosphorus than raw bone. Raw bone is especially prized 

 as a source of phosphorus and nitrogen for fruit trees, 

 where a slowly available supply of these elements is desired. 

 86. Mineral Phosphate. Deposits of mineral phosphates 

 which are not derived directly from organic sources are 



