222 PHOSPHATE FERTILIZERS 



together with the ossein protecting the phosphate from being 

 acted upon by soil solvents. 



170. Steamed Bone, Bone-Meal. — The fat in bone is 

 valuable for various commercial purposes and the ossein 

 can be converted into gelatine and glue. There are two 

 ways of removing fat: By extraction with a solvent like 

 benzine; or by treatment with boiling water or steam under 

 pressure. Subsequent cooling allows the fat to solidify on top 

 of the water, and to be removed. Steaming under pressure 

 also converts ossein to gelatine, soluble in water. The bone 

 that is left can be dried and easily ground fine. This material 

 is sold as steamed bone-meal or bone-meal. The best 

 grades contain 25 to 30 per cent, of phosphoric acid, but 

 frequently less than 1 per cent, nitrogen. The removal of 

 fat and ossein leaves the tricalcium phosphate in much 

 better physical condition both for grinding and subsequent 

 solution in the soil. Steamed bone-meal is a very excellent 

 phosphate fertilizer and fairly available. 



Bone products have had a value as a fertilizer for centuries 

 and even now are considered by many to be superior to other 

 forms of phosphate, consequently the temptation to adulter- 

 ate bone-meal with worthless substances has been very 

 great. This fact together with differences in method of 

 treatment and quality of original bones makes the product 

 one of great variation in phosphoric acid content. The 

 figures given are average for a good product. 



171. Bone-Black. — When bones are subjected to destruc- 

 tive distillation, the organic matter is largely driven off and 

 there remains the inorganic matter and about 10 per cent, 

 of carbon. This material is known as bone-black, or animal 

 charcoal, and on account of its porosity and absorptive power 

 is used after grinding for clarifying sugar solutions in sugar 

 refineries, and for other similar purposes. But little of it is 

 used as fertilizer in the freshly made form, most of it being 

 first employed as above stated. 



After a time it loses its absorptive or clarifying power and 

 then is sold as a fertilizer, although the presence of the 

 carbon prevents ready solution of the tricalcium phosphate. 

 It contains about 30 per cent, phosphoric acid. 



