Hypophosphorous Acid, 50 Percent
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
(Hypophosphorous Acid), HPH2O2 66.00 CAS RN: 6303-21-5.—A colorless to faintly yellow liquid. Miscible with water and with alcohol.
ASSAY: Accurately weigh about 4 mL, dilute with 25 mL of water, add methyl red TS, and titrate with 1 N sodium hydroxide VS: each mL of 1 N sodium hydroxide is equivalent to 66.00 mg of HPH2O2. Not less than 48% is found.
CHLORIDE: Add 0.2 mL to a mixture of 10 mL of silver nitrate TS and 5 mL of nitric acid, and heat until brown fumes are no longer evolved: any white, insoluble residue remaining is negligible.
PHOSPHATE: Dilute 1 mL with water to 50 mL, render alkaline with ammonia TS, filter if a precipitate is formed, and add to the filtrate 5 mL of magnesia mixture TS: not more than a slight precipitate is formed within 5 minutes.
SULFATE (Reagent test, Method I): Dilute 1 mL with water to 50 mL: 20 mL of the solution shows not more than 0.2 mg of SO4
