Precipitated Sulfur

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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S 32.07

Sulfur CAS RN^®: 7704-34-9; UNII: 70FD1KFU70.

1 DEFINITION

Precipitated Sulfur contains NLT 99.5% and NMT 100.5% of sulfur (S), calculated on the anhydrous basis.

2 IDENTIFICATION

A. It burns in the air to sulfur dioxide, which can be recognized by its characteristic odor.

3 ASSAY

3.1 Procedure

Sample: 60 mg of Precipitated Sulfur

Titrimetric system

Mode: Direct titration

Titrant: 0.1 N sodium hydroxide VS

Endpoint detection: Visual

Analysis: Proceed as directed in oxygen Flask Combustion 〈471〉, using a 1000-mL flask and using a mixture of 10 mL of water and 5.0 mL of Hydrogen peroxide TS as the absorbing liquid. When the combustion is complete, fill the lip of the flask with water; loosen the stopper; then rinse the stopper, the sample holder, and the sides of the flask with water; and remove the stopper assembly. Heat the contents of the flask to boiling, and boil for 2 min. Cool to room temperature, add phenolphthalein TS, and titrate with Titrant. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N sodium hydroxide is equivalent to 1.603 mg of sulfur (S).

Acceptance criteria: 99.5%–100.5% on the anhydrous basis

4 OTHER COMPONENTS

Other Forms of Sulfur

Sample: 1.0 g

Analysis: Shake the Sample with 5 mL of carbon disulfide.

Acceptance criteria: It dissolves quickly, with the exception of a small quantity of insoluble matter that is usually present.

5 IMPURITIES

Residue on Ignition 〈281〉: NMT 0.3%

6 SPECIFIC TESTS

Water Determination, Method I 〈921〉: NMT 0.5%

Reaction

Sample: 2.0 g

Analysis: Agitate the Sample with 10 mL of water, and filter.

Acceptance criteria: The filtrate is neutral to litmus.

7 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.