Phenol

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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Phenol CAS RN^®: 108-95-2.

1 DEFINITION

Phenol contains NLT 99.0% and NMT 100.5% of phenol (C₆H₆O), calculated on the anhydrous basis. It may contain a suitable stabilizer.

2 IDENTIFICATION

[CAUTION-Avoid contact with skin because serious burns may result.]

A.

Analysis: To a solution add bromine TS.

Acceptance criteria: A white precipitate is formed, and it dissolves at first but becomes permanent as more of the reagent is added.

B.

Sample solution: 1 in 100

Analysis: To 10 mL of the Sample solution add 1 drop of ferric chloride TS.

Acceptance criteria: A violet color is produced.

3 ASSAY

PROCEDURE

Sample: 2 g

Titrimetric system

(See Titrimetry (541).)

Mode: Residual titration

Titrant: 0.1 N bromine VS

Back-titrant: 0.1 N sodium thiosulfate VS

Endpoint detection: Visual

Analysis: Place the Sample in a 1000-mL volumetric flask, and dilute with water to volume. Pipet 20 mL of the solution into an iodine flask, add 30.0 mL of Titrant, then add 5 mL of hydrochloric acid, and immediately insert the stopper. Shake the flask repeatedly during 30 min, allow it to stand for 15 min, quickly add 5 mL of potassium iodide solution (1 in 5), taking precautions against the escape of bromine vapor, and at once insert the stopper. Shake thoroughly, remove the stopper, and rinse it and the neck of the flask with a small quantity of water so that the washing flows into the flask. Add 1 mL of chloroform, and shake the mixture. Titrate the liberated iodine with Back-titrant, adding 3 mL of starch TS as the endpoint is approached. Perform a blank determination. Each mL of 0.1 N bromine is equivalent to 1.569 mg of phenol (C₆H₆O).

Acceptance criteria: 99.0%-100.5% on the anhydrous basis

4 IMPURITIES

LIMIT OF NONVOLATILE RESIDUE

Sample: 5 g

Analysis: Heat the Sample in a tared porcelain dish on a steam bath until it has evaporated, and dry the residue at 105° for 1 h.

Acceptance criteria: NMT 0.05%

5 SPECIFIC TESTS

5.1 CLARITY OF SOLUTION AND REACTION

Sample solution: 1 in 15

Acceptance criteria: The Sample solution is clear, and it is neutral or acid to litmus paper.

5.2 CONGEALING TEMPERATURE (651)

NLT 39°

5.3 WATER DETERMINATION, Method I (921)

NMT 0.5%

6 ADDITIONAL REQUIREMENTS

6.1 PACKAGING AND STORAGE

Preserve in tight, light-resistant containers.

6.2 LABELING

Label it to indicate the name and amount of any substance added as a stabilizer.