Glacial Acetic Acid

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₂H₄O₂ 60.05

Acetic acid CAS RN®: 64-19-7.

1 DEFINITION

Glacial Acetic Acid contains NLT 99.5% and NMT 100.5%, by weight, of C₂H₄O₂.

2 IDENTIFICATION

Identification Tests - General 〈191〉, Acetate: Meets the requirements

Sample solution (for test A): Glacial Acetic Acid and water (1:100)

3 ASSAY

Procedure

Sample solution: Measure 2 mL of Glacial Acetic Acid into a glass-stoppered flask, previously tared while containing about 20 mL of water, and weigh again to obtain the weight of the substance under assay.

Analysis: Add 20 mL of water, then add phenolphthalein TS. Titrate with 1 N sodium hydroxide VS. Each mL of 1 N sodium hydroxide is equivalent to 60.05 mg of C₂H₄O₂.

Acceptance criteria: 99.5%–100.5%

4 IMPURITIES

4.1 Inorganic Impurities

Limit of Nonvolatile Residue: Evaporate 20 mL in a tared dish, and dry at 105° for 1 h: the weight of the residue does not exceed 1.0 mg.

4.1.1 Chloride and Sulfate, Chloride

Sample solution: Dilute 1.0 mL with 20 mL of water.

Analysis: Add 5 drops of silver nitrate TS.

Acceptance criteria: No opalescence is produced.

4.1.2 Chloride and Sulfate, Sulfate

Sample solution: Dilute 1.0 mL with 10 mL of water.

Analysis: Add 1 mL of barium chloride TS.

Acceptance criteria: No turbidity is produced.

4.2 Organic Impurities

Procedure: Readily Oxidizable Substances

Sample solution: Dilute 2.0 mL in a glass-stoppered vessel with 10 mL of water.

Analysis: Add 0.10 mL of 0.10 N potassium permanganate.

Acceptance criteria: The pink color is not changed to brown within 2 h.

5 SPECIFIC TESTS

Congealing Temperature 〈651〉: NLT 15.6°

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers, and store at room temperature.