| 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.
AUTHORITIES CITED IN
PART FIRST.
[1] Day, Mineral Resources of the United States 193, pp. 703, et seq.
[2] Massachusetts Agricultural Experiment Station, Bulletin 51, March, 1894.
[3] Brown, Manual of Assaying, p. 24.
[4] Bulletin de l’Association des Chimistes de Sucrèrie, No. 2, pp. 7, et seq.