Benzoic 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)
Benzoic Acid
C₇H₆O₂ 122.12
Benzoic acid
CAS RN®: 65-85-0.
1 DEFINITION
Benzoic Acid contains NLT 99.5% and NMT 100.5% of benzoic acid (C₇H₆O₂), calculated on the anhydrous basis.
2 IDENTIFICATION
A.
Sample solution: Prepare a saturated solution of Benzoic Acid in water, and filter twice.
Analysis 1: To one portion of the filtrate add ferric chloride TS.
Acceptance criteria 1: A salmon-colored precipitate is formed.
Analysis 2: To a separate 10-mL portion of the filtrate add 1 mL of 7 N sulfuric acid, and cool the mixture.
Acceptance criteria 2: A white precipitate forms in 10 min. This precipitate is soluble in ether.
3 ASSAY
Procedure
Sample: 500 mg of Benzoic Acid
Analysis: Dissolve the Sample in 25 mL of diluted alcohol that previously has been neutralized with 0.1 N sodium hydroxide. Add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS to a pink color. Each mL of 0.1 N sodium hydroxide is equivalent to 12.21 mg of benzoic acid (C₇H₆O₂).
Acceptance criteria: 99.5%–100.5% on the anhydrous basis
4 IMPURITIES
Residue on Ignition 〈281〉: NMT 0.05%
5 SPECIFIC TESTS
Congealing Temperature 〈651〉: 121°–123°
Water Determination, Method I〈921〉
Sample solution: A 1-in-2 solution of methanol in pyridine is used as the solvent.
Acceptance criteria: NMT 0.7%
Readily Carbonizable Substances Test 〈271〉
Sample solution: 500 mg in 5 mL of sulfuric acid
Acceptance criteria: The solution has no more color than Matching Fluid Q.
Readily Oxidizable Substances
Sample solution: Add 1.5 mL of sulfuric acid to 100 mL of water. Heat to boiling, and add 0.1 N potassium permanganate, dropwise, until the pink color persists for 30 s. Dissolve 1.00 g of Benzoic Acid in the hot solution.
Analysis: Titrate with 0.1 N potassium permanganate VS to a pink color that persists for 15 s.
Acceptance criteria: NMT 0.50 mL of 0.10 N potassium permanganate is consumed.
6 ADDITIONAL REQUIREMENTS
Packaging and Storage: Preserve in well-closed containers.
