Ammonium Phosphate
(NH4)2HPO4 132.06

Phosphoric acid, diammonium salt.
Diammonium phosphate [7783-28-0].
» Ammonium Phosphate contains not less than 96.0 percent and not more than 102.0 percent of (NH4)2HPO4.
Packaging and storage— Preserve in tight containers.
Identification— A solution (1 in 20) responds to the tests for Ammonium 191 and for Phosphate 191.
pH 791: between 7.6 and 8.2, in a solution (1 in 100).
Chloride 221 A 1.0-g portion shows no more chloride than corresponds to 0.40 mL of 0.020 N hydrochloric acid (0.03%).
Sulfate 221 A 0.20-g portion shows no more sulfate than corresponds to 0.30 mL of 0.020 N sulfuric acid (0.15%).
Heavy metals 231 Dissolve 2.0 g in 25 mL of water: the limit is 0.001%.
Assay— Dissolve about 600 mg of Ammonium Phosphate, accurately weighed, in 40 mL of water, and titrate with 0.1 N sulfuric acid VS to a pH of 4.6, determined potentiometrically. Each mL of 0.1 N sulfuric acid is equivalent to 13.21 mg of (NH4)2HPO4.
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Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, B.A.
(EM105) Excipient Monographs 1
USP32–NF27 Page 1165