» Iodine contains not less than 99.8 percent and not more than 100.5 percent of I.
Packaging and storage Preserve in tight containers.
A: Solutions (1 in 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 5.0 g in a tared porcelain dish, heat on a steam bath until the iodine has been driven off, and dry at 105 for 1 hour: not more than 0.05% of residue remains.
Chloride or bromide Triturate 250 mg of finely powdered Iodine with 10 mL of 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 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: 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).
Assay Place about 500 mg of powdered Iodine in a tared, glass-stoppered flask, insert the stopper, weigh accurately, and add 1 g of potassium iodide dissolved in 5 mL of water. Dilute with water to about 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 I.