BLOOD AND BONE-MEAL. 361 



Fresh blood contains on an average 3.7 per cent of nitro- 

 gen, whilst dried blood contains 16.8 per cent, of nitrogen. 

 Bones differ mainly in regard to the relative proportion of 

 cartilage (a nitrogenous substance) and of neutral phosphate 

 of lime. The harder bones are usually collected for the manu- 

 facture of buttons and bone-black, and the smaller and softer 

 bones are left for the manufacture of fertilizers. After havins: 

 passed through a boiling process, they count in the fertilizer 

 merely as the main source of phosphoric acid ; for the nitrogen 

 of the organic portion of the bones is almost entirely lost in 

 the soup. 



The main task for all manufacturers of fertilizers from 

 butcher's refuse, as previously described, is the production of 

 a uniform article, as far as its chemical composition is con- 

 cerned. Meat scraps, blood and bones ought to be mixed 

 within certain definite proportions, and the drying carried out 

 by a moderate heat to a state of moisture, not exceeding ten 

 per cent. The first-named rule secures a uniform agricult- 

 ural and commercial value, and the latter tends to keep the 

 animal matter in an unimpaired state of composition. 



Ground Bones (Bone-meal). 



The composition of the raw and dried bones of our markets 

 depends to a greater extent on the part of the animal whence 

 they are taken, than on the kind and the age of the latter. 

 Their main constituents consist : first, of neutral phosphate of 

 lime, commonly called bone phosphate ; secondly, of a nitrog- 

 enous substance, which is soluble in boiling- water, and con- 

 tains about 13 per cent, of nitrogen ; and, thirdly, of the fat. 

 The latter, and the nitrogenous substances, are quite fre- 

 quently removed before the bones are turned into fertil- 

 izers. 



A good bone-meal ought to contain still its original amount 

 of organic matter. The composition of fresh-ground bones, 

 containing but from 8 to 10 per cent, of moisture, is known 

 to vary from 22 to 24 per cent, of phosphoric acid, or from 

 48 to 54 per cent, of bone phosphate, and from 2.5 to 4.5 

 per cent, of nitrogen. Articles sold by the same name may, 

 for this reason, differ in value from $8 to $10 per ton. 

 Coarsely ground bone-meal has been offered of late at $30 per 



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