Sodium Iodide

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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NaI 149.89

Sodium iodide CAS RN®: 7681-82-5; UNII: F5WR8N145C.

1 DEFINITION

Sodium Iodide contains NLT 99.0% and NMT 101.5% of NaI, calculated on the anhydrous basis.

2 IDENTIFICATION

A. Identification Tests—General, Sodium〈191〉

Sample solution: 50 mg/mL

Acceptance criteria: Meets the requirements

B. Identification Tests—General, Iodide〈191〉

Sample solution: 50 mg/mL

Acceptance criteria: Meets the requirements

3 ASSAY

Procedure

Sample: 500 mg

Analysis: Dissolve the Sample in 10 mL of water. Add 35 mL of hydrochloric acid, and titrate with 0.05 M potassium iodate VS until the dark brown solution that is produced becomes pale brown. Add 1 mL of amaranth TS, and continue the titration slowly until the red color just changes to yellow. Each mL of 0.05 M potassium iodate is equivalent to 14.99 mg of NaI.

Acceptance criteria: 99.0%–101.5% on the anhydrous basis

4 IMPURITIES

4.1 Iodate

Iodate solution: Dilute 1 mL of potassium iodate solution (1 in 2500) with water to 100 mL.

Standard solution: Dissolve 100 mg of Sodium Iodide in ammonia- and carbon dioxide-free water and add 1 mL of Iodate solution to obtain 10 mL of solution. Transfer to a color-comparison tube.

Sample solution: Dissolve 1.1 g in sufficient ammonia- and carbon dioxide-free water to obtain 10 mL of solution. Transfer to a color- comparison tube.

Analysis: To each color comparison tube add 1 mL of starch TS and 0.25 mL of 1.0 N sulfuric acid, and mix.

Acceptance criteria: Any color produced in the Sample solution does not exceed that in the Standard solution (NMT 4 ppm).

4.2 Thiosulfate and Barium

Sample solution: Dissolve 0.5 g in 10 mL of ammonia- and carbon dioxide-free water.

Analysis: Add 2 drops of 2 N sulfuric acid to the Sample solution.

Acceptance criteria: No turbidity develops within 1 min.

4.3 Potassium

Sample solution: Dissolve 1.0 g in 2 mL of water.

Acceptance criteria: The Sample solution yields no precipitate with 1.0 mL of sodium bitartrate TS.

Limit of Nitrate, Nitrite, and Ammonia

Sample solution: Dissolve 1.0 g in 5 mL of water.

Analysis: To the Sample solution contained in a test tube of 40-mL capacity add 5 mL of 1 N sodium hydroxide and about 200 mg of aluminum wire. Insert a pledget of purified cotton in the upper portion of the test tube, and place a piece of moistened red litmus paper over the mouth of the tube. Heat the test tube and its contents on a steam bath for 15 min.

Acceptance criteria: No blue coloration of the paper is discernible.

5 SPECIFIC TESTS

Alkalinity

Sample solution: Dissolve 1.0 g in 10 mL of water.

Analysis: Add 0.15 mL of 0.10 N sulfuric acid and 1 drop of phenolphthalein TS to the Sample solution.

Acceptance criteria: No red color is produced.

Water Determination, Method I〈921〉: NMT 2.0%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.