76 GARDENING FOR THE SOUTH. 



half to three-fifths of the weight of the bone. The remain- 

 ing portion consists largely of a soft, flesh-like substance 

 called ossein, or, more coniinonly, gelatin. It is dis- 

 tributed throughout the entire mass of bone, and is rich 

 in nitrogen. When bones are burned, the nitrogenous 

 matter is driven off and only the mineral portion, or phos- 

 phate of lime, remains. Bones, such as are used in 

 making commercial fertilizers, contain four to five per 

 cent, nitrogen and from twenty to twenty-five per cent, 

 of phosphoric acid, equivalent to forty-five to fifty-five 

 per cent, of phosphate of lime. 



"Bone-Ash. — As the name implies, bone-ash is made by 

 simply burning bones in the open air. The nitrogen, of 

 course, is driven off and lost in burning, and the chief 

 constituent is insoluble calcium phosphate, equivalent 

 to thirty to thirty-five or more per cent, of phosphoric 

 acid. 



"Bone-Black, known also as bone-charcoal, is exten- 

 sively used in refining sugar. After it has been used sev- 

 eral times, portions become useless for refining purposes, 

 and are then sold for fertilizers. Bone-black is made by 

 heating bones in closed vessels, the air being excluded. 

 By heating bones in this manner the fat, water, and 

 nitrogen are removed from the bones, and the bone-black 

 remaining consists mainly of insoluble calcium phosphate 

 and carbon or charcoal. The presence of carbon hinders 

 the decomposition of the phosphate, so that in this form, 

 it is not readily available as food, for plants. Good 

 bone-black may contain thirty or more per cent, of phos- 

 phoric acid. 



"Bone-Meal goes under various names, such as ground- 

 bone, bone-flour, bone-dust, etc. We find in the market 

 raic bone-meal and steamed bone-meal. Raw bone-meal 

 contains the fat naturally present in bones. The presence 

 of the fat is objectionable, because it makes the grinding 



