Iodine
I2 253.81

Iodine.
Iodine [7553-56-2].
»Iodine contains not less than 99.8percent and not more than 100.5percent of I.
Packaging and storage— Preserve in tight containers.
Identification—
A: Solutions (1in 1000)in chloroform and in carbon disulfide have a violet color.
B: To a saturated solution add starch-potassium iodide TS: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.
Limit of nonvolatile residue— Place 5.0g in a tared porcelain dish,heat on a steam bath until the iodine has been driven off,and dry at 105for 1hour:not more than 0.05%of residue remains.
Chloride or bromide— Triturate 250mg of finely powdered Iodine with 10mLof water,and filter the solution.Add,dropwise,sulfurous acid (free from chloride),previously diluted with several volumes of water,until the iodine color just disappears.Add 5mLof 6Nammonium hydroxide,followed by 5mLof silver nitrate TSin small portions.Filter,and acidify the filtrate with nitric acid:the resulting liquid is not more turbid than a control made with the same quantities of the same reagents to which 0.10mLof 0.020Nhydrochloric acid has been added,the sulfurous acid being omitted (0.028%as chloride).
Assay— Place about 500mg of powdered Iodine in a tared,glass-stoppered flask,insert the stopper,weigh accurately,and add 1g of potassium iodide dissolved in 5mLof water.Dilute with water to about 50mL,add 1mLof 3Nhydrochloric acid,and titrate with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Each mLof 0.1Nsodium thiosulfate is equivalent to 12.69mg of I.
Auxiliary Information— Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 1029
Phone Number:1-301-816-8394