Strong Iodine Solution
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Strong Iodine Solution contains, in each 100 mL, NLT 4.5 g and NMT 5.5 g of iodine (I), and NLT 9.5 g and NMT 10.5 g of potassium iodide (KI).
Strong Iodine Solution may be prepared by dissolving 50 g of Iodine and 100 g of Potassium Iodide in 100 mL of Purified Water, then adding
Purified Water to make the product measure 1000 mL.
2 IDENTIFICATION
A. Analysis: Dilute 1 drop with 10 mL of water, and add 1 mL of starch TS.
Acceptance criteria: A deep blue color is produced.
B. Identification Tests—General, Potassium〈191〉andIodide〈191〉
Analysis: Evaporate a few mL on a steam bath to dryness, and ignite gently to volatilize any free iodine.
Acceptance criteria: Meets the requirements
3 ASSAY
3.1 Iodine
Sample solution: Transfer 10.0 mL of Solution into a glass-stoppered 500-mL flask, and add 10 mL of water.
Titrimetric system
Mode: Direct titration
Titrant: 0.1 N sodium thiosulfate VS
Endpoint detection: Visual
Analysis: Titrate the Sample solution with Titrant, adding 3 mL of starch TS as the endpoint is approached. Each mL of 0.1 N sodium thiosulfate is equivalent to 12.69 mg of iodine (I).
Acceptance criteria: 4.5–5.5 g of iodine (I) in each 100 mL
3.2 Potassium Iodide
Sample solution: Transfer 10.0 mL of Solution to a glass-stoppered 500-mL. flask, add 30 mL of water and 50 mL of hydrochloric acid, and cool to room temperature.
Titrimetric system
Mode: Direct titration
Titrant: 0.05 M potassium iodate VS
Endpoint detection: Visual
Analysis: Titrate the Sample solution with Titrant 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. The difference between the number of mL of 0.05 M potassium iodate used and half the number of mL of Titrant used in the Assay for Iodine, multiplied by 16.60, represents the number of mg of KI in the volume of the Solution taken.
Acceptance criteria: 9.5–10.5 g of potassium iodide (KI) in each 100 mL
4 ADDITIONAL REQUIREMENTS
Packaging and Storage: Preserve in tight containers, preferably at a temperature not exceeding 35°.
