When animal bone is boiled or steamed under pressure for
removal of the fat and the cartilage, the content of nitrogen is
reduced, and the percentage of phosphoric acid is increased by this
removal of fat and nitrogenous substance. The nitrogen in steamed bone
may run as low as 1 per cent, and the phosphoric acid may go up to 30
per cent. The composition of steamed bone is so widely variable that
the name means little, and purchase should be made only on guaranteed
analysis. Some grades run very low both in nitrogen and phosphoric
acid, due probably to adulteration.
The boiling or steaming of bone makes fine grinding possible, and the
fineness and absence of fat permit quick decay in the soil. Steamed
bone is an excellent source of phosphoric acid. The availability is
less immediate than that of acid phosphate, but much greater than that
of raw bone.
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