(eye' oh dine).

I2 253.81
Iodine     [7553-56-2].
Iodine contains NLT 99.8% and NMT 100.5% of I.
•  A. Solutions (1 in 1000) in chloroform and in carbon disulfide have a violet color.
•  B.
Analysis:  To a saturated solution add starch–potassium iodide TS.
Acceptance criteria:  A blue color is produced. When the mixture is boiled, the color vanishes but reappears as the mixture cools, unless it has been subjected to prolonged boiling.
•  Procedure
Sample:  500 mg of powdered Iodine
Analysis:  Place the Sample in a tared, glass-stoppered flask, insert the stopper, and add 1 g of potassium iodide dissolved in 5 mL of water. Dilute with water to 50 mL, add 1 mL of 3 N hydrochloric acid, and titrate with 0.1 N sodium thiosulfate VS, 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:  99.8%–100.5%
•  Limit of Chloride or Bromide
Sample solution:  Triturate 250 mg of finely powdered Iodine with 10 mL of water, and filter the solution.
Analysis:  To the Sample solution add, dropwise, sulfurous acid (free from chloride), previously diluted with several volumes of water, until the iodine color just disappears. Add 5 mL of 6 N ammonium hydroxide, followed by 5 mL of silver nitrate TS in small portions. Filter, and acidify the filtrate with nitric acid.
Acceptance criteria:  The resulting liquid is not more turbid than a control made with the same quantities of the same reagents to which 0.10 mL of 0.020 N hydrochloric acid has been added, the sulfurous acid being omitted (0.028% as chloride).
•  Limit of Nonvolatile Residue
Analysis:  Place 5.0 g in a tared porcelain dish, heat on a steam bath until the iodine has been driven off, and dry at 105 for 1 h.
Acceptance criteria:  NMT 0.05% of the residue remains.
•  Packaging and Storage: Preserve in tight containers.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Behnam Davani, Ph.D., M.B.A.
Senior Scientific Liaison
(SM12010) Monographs - Small Molecules 1
USP35–NF30 Page 3515