At 48° At 50° At 52° At 54° At 55°
B. B. B. B. B.
Tricalcium phosphate 1.590 1.517 1.446 1.382 1.352
Iron phosphate 1.630 1.558 1.485 1.420 1.390
Aluminum phosphate 2.025 1.930 1.839 1.756 1.721
Calcium carbonate 1.640 1.565 1.495 1.428 1.411
Calcium fluorid 2.006 2.010 1.916 1.830 1.794
Magnesium carbonate 1.940 1.860 1.775 1.690 1.660
_Example._—Suppose for example a phosphate of the following
composition is to be treated with sulfuric acid; _viz._,[124]
Moisture and organic 4.00 per cent.
Calcium phosphate 55.00 “
Calcium carbonate 3.00 “
Iron and aluminum phosphate
nearly all alumina 6.50 “
Magnesium carbonate 0.75 “
Calcium fluorid 2.25 “
Insoluble 28.00 “
Using sulfuric acid of 50° B., the following quantities will be
required for each 100 kilograms.
Kilos of
acid required.
Calcium phosphate, fifty-five kilos 83.44
“ carbonate three and a half kilos 5.48
“ fluorid, two and a quarter “ 4.52
Aluminum and iron phosphate, six and a half kilos 12.55
Magnesium carbonate, three-quarters of a kilo 1.40
-----
Total 107.39
=142. Phosphoric Acid Superphosphates.=—If a mineral phosphate be
decomposed by free phosphoric in place of sulfuric acid the resulting
compound will contain about three times as much available phosphoric
acid as is found in the ordinary acid phosphate. The reaction takes
place according to the following formulas:
(1) Ca₃(PO₄)₂ + 4H₃PO₄ + 3H₂O = 3[CAH₄(PO₄)₂·H₂O].
(2) Ca₃(PO₄)₃ + 2H₃PO₄ + 12H₂O = 3[Ca₂H₂(PO₄)₂·4H₂O].
In each case the water in the final product is probably united as
crystal water with the calcium salts produced. The monocalcium salt
formed in the first reaction is soluble in water and the dicalcium salt
in the second reaction in ammonium citrate. Where fertilizers are to
be transported to great distances there is a considerable saving of
freight by the use of such a high-grade phosphate, which may, at times,
contain over forty per cent of available acid. The phosphoric acid used
is made directly from the mineral phosphate by treating it with an
excess of sulfuric acid.