H3PO4 98.00

Phosphoric acid.
Phosphoric acid [7664-38-2].

Packaging and storage— Preserve in tight containers.

Identification— When carefully neutralized with 1 N sodium hydroxide, phenolphthalein TS being used as the indicator, it responds to the tests for Phosphate 191.

Sulfate 221— Dilute 6 mL of Phosphoric Acid with 90 mL of water, and add 1 mL of barium chloride TS: no precipitate is formed immediately.

Heavy metals, Method I 231: 0.001%.

Alkali phosphates— Transfer 1 mL of it to a graduated cylinder, and add 6 mL of ether and 2 mL of alcohol: no turbidity is produced.

Limit of nitrate— Dilute 6 mL of Phosphoric Acid with 14 mL of water, mix 5 mL of the dilution with about 0.1 mL of indigo carmine TS, then add 5 mL of sulfuric acid: the blue color is not discharged within 1 minute.

Phosphorous or hypophosphorous acid— Dilute 6 mL of Phosphoric Acid with 14 mL of water. Gently warm 5 mL of the dilution, and add 2 mL of silver nitrate TS: the mixture does not become brownish.

Residual solvents 467: meets the requirements.

Assay— Weigh accurately about 1 g of Phosphoric Acid in a tared, glass-stoppered flask, and dilute it with water to about 120 mL. Add 0.5 mL of thymolphthalein TS, and titrate with 1 N sodium hydroxide VS to the first appearance of a blue color. Perform a blank determination, and make any necessary correction. Each mL of 1 N sodium hydroxide is equivalent to 49.00 mg of H3PO4.

Expert Committee : (EM105) Excipient Monographs 1

USP29–NF24 Page 3391

Phone Number : 1-301-816-8262