Halazone

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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C₇H₅CI₂NO₄S 270.09

Benzoic acid, 4-[(dichloroamino)sulfonyl]-;

p-(Dichlorosulfamoyl)benzoic acid CAS RN^®: 80-13-7; UNII: G359OL82VB.

1 DEFINITION

Halazone contains NLT 91.5% and NMT 100.5% of C₇H₅CI₂NO₄S, calculated on the dried basis.

2 IDENTIFICATION

PROCEDURE

Sample: 100 mg

Analysis: Add the Sample to 5 mL of a sodium bromide solution (1 in 10).

Acceptance criteria: Bromine is liberated from the mixture.

3 ASSAY

PROCEDURE

Sample: 150 mg

Analysis: Add the Sample to 10 mL of 2.5 N sodium hydroxide in a 250-mL iodine flask, and stir well to dissolve. Add 75 mL of water, then promptly add 15 mL of potassium iodide solution (1 in 10), and mix. Acidify with 10 mL of 6 N acetic acid, and titrate immediately with 0.1 N sodium thiosulfate VS, adding 3 mL of starch TS as the endpoint is approached. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N sodium thiosulfate is equivalent to 6.752 mg of C₇H₅CI₂NO₄S.

Acceptance criteria: 91.5%-100.5% on the dried basis

4 IMPURITIES

ORGANIC IMPURITIES

PROCEDURE: READILY CARBONIZABLE SUBSTANCES TEST (271)

Sample: 100 mg

Analysis: Dissolve the Sample in 0.5 mL of sulfuric acid.

Acceptance criteria: No blackening occurs, although some effervescence may take place.

5 SPECIFIC TESTS

LOSS ON DRYING (731): Dry a sample over phosphorus pentoxide for 4 h: it loses NMT 0.5% of its weight.

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight, light-resistant containers.