Nitric Acid → Calcium nitrate

Participants

Reaction Steps

In Austrian Patent No. 176,219, Joham, Sept. 25, 1953 there is described the reaction of nitric acid with phosphate rock to produce a liquid reaction mixture which is subsequently evaporated and dried at 200° C. to provide a solid material which was dispersed in water and filtered to produce a concentrated calcium nitrate solution and a solid product containing 34.3 percent P2O5, of which 88 percent was citrate soluble. A variation of the procedure involved the addition of lime to the initially produced acidulate to bring the pH to 1.4 and to precipitate CaF2, which was then filtered along with the gangue. Subsequent treatment of the filtrate, as described above, resulted in a solid product containing 44.8 percent P2O5, of which 89 percent was citrate soluble. It should be noted, however, that this procedure probably also results in partial reversion of phosphate to fluorapatite as indicated by the phase equilibria of Farr, et al., supra. Furthermore, neither variation of the procedure provides for a completely citrate soluble phosphate product, or for the recovery of the excess nitric acid liberated during the evaporation process.

Provenance & Evidence