Packaging and storage—
Preserve in well-closed containers.
Identification—
A solution of it meets the requirements of the tests for
Potassium 
191
and for
Iodide 191.
Alkalinity—
Dissolve 1.0 g in 10 mL of water, and add 0.1 mL of 0.1 N sulfuric acid and 1 drop of
phenolphthalein TS: no color is produced.
Iodate—
Dissolve 1.1 g in sufficient ammonia- and carbon dioxide-free water to obtain 10 mL of solution, and transfer to a color-comparison tube. Add 1 mL of starch TS and 0.25 mL of 1.0 N sulfuric acid, mix, and compare the color with that of a control containing, in a similar volume, 100 mg of Potassium Iodide, 1 mL of standard iodate solution [prepare by diluting 1 mL of potassium iodate solution (1 in 2500) with water to 100 mL], 1 mL of
starch TS, and 0.25 mL of 1.0 N sulfuric acid. Any color produced in the solution of the test specimen does not exceed that in the control: not more than 4 µg per g is found.
Limit of nitrate, nitrite, and ammonia—
To a solution of 1 g in 5 mL of water contained in a test tube of about 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 in a steam bath for 15 minutes: no blue coloration of the paper is discernible.
Thiosulfate and barium—
Dissolve 0.5 g in 10 mL of ammonia- and carbon dioxide-free water, and add 2 drops of 2 N sulfuric acid: no turbidity develops within 1 minute.
Organic volatile impurities, Method I 467:
meets the requirements.
Assay—
Dissolve about 500 mg of Potassium Iodide, accurately weighed, in about 10 mL of water, and add 35 mL of hydrochloric acid. Titrate with 0.05 M potassium iodate VS until the dark brown solution which is produced becomes pale brown. Add 2 to 3 drops 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 16.60 mg of KI.
for 4 hours: it loses not more than 1.0% of its weight.