Phosphotungstic Acid
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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)
approximately 24WO3·P2O5·51H2O 6624.84-White or yellowish-green crystals or a crystalline powder. Soluble in water, in alcohol, and in ether.
INSOLUBLE MATTER (Reagent test): not more than 1 mg, from 5 g (0.02%).
CHLORIDE (Reagent test): One g shows not more than 0.3 mg of CI (0.03%).
NITRATE: Dissolve 500 mg in 10 mL of water, and add about 10 mg of sodium chloride, 0.1 mL of indigo carmine TS, and 10 mL of sulfuric acid: the blue color does not disappear within 1 minute (about 0.01%).
SULFATE (Reagent test, Method I): A 500-mg portion shows not more than 0.1 mg of SO4 (0.02%).
