Sodium Iodide
(soe' dee um eye' oh dide).

NaI 149.89
Sodium iodide     [7681-82-5].
DEFINITION
Sodium Iodide contains NLT 99.0% and NMT 101.5% of NaI, calculated on the anhydrous basis.
IDENTIFICATION
•  A. Identification Tests—General, Sodium 191
Sample solution:  50 mg/mL
Acceptance criteria:  Meets the requirements
•  B. Identification Tests—General, Iodide 191
Sample solution:  50 mg/mL
Acceptance criteria:  Meets the requirements
ASSAY
•  Procedure
Sample:  500 mg
Analysis:  Dissolve the Sample in 10 mL of water. Add 35 mL of hydrochloric acid, and titrate with 0.05 M potassium iodate VS 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. Each mL of 0.05 M potassium iodate is equivalent to 14.99 mg of NaI.
Acceptance criteria:  99.0%–101.5% on the anhydrous basis
IMPURITIES
•  Iodate
Iodate solution:  Dilute 1 mL of potassium iodate solution (1 in 2500) with water to 100 mL.
Standard solution:  Dissolve 100 mg of Sodium Iodide in ammonia- and carbon dioxide-free water and add 1 mL of Iodate solution to obtain 10 mL of solution. Transfer to a color-comparison tube.
Sample solution:  Dissolve 1.1 g in sufficient ammonia- and carbon dioxide-free water to obtain 10 mL of solution. Transfer to a color-comparison tube.
Analysis:  To each color comparison tube add 1 mL of starch TS and 0.25 mL of 1.0 N sulfuric acid, and mix.
Acceptance criteria:  Any color produced in the Sample solution does not exceed that in the Standard solution (NMT 4 ppm).
•  Thiosulfate and Barium
Sample solution:  Dissolve 0.5 g in 10 mL of ammonia- and carbon dioxide-free water.
Analysis:  Add 2 drops of 2 N sulfuric acid to the Sample solution.
Acceptance criteria:  No turbidity develops within 1 min.
•  Potassium
Sample solution:  Dissolve 1.0 g in 2 mL of water.
Acceptance criteria:  The Sample solution yields no precipitate with 1.0 mL of sodium bitartrate TS.
•  Limit of Nitrate, Nitrite, and Ammonia
Sample solution:  Dissolve 1.0 g in 5 mL of water.
Analysis:  To the Sample solution contained in a test tube of 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 on a steam bath for 15 min.
Acceptance criteria:  No blue coloration of the paper is discernible.
•  Heavy Metals 231
Sample solution:  Dissolve 2.0 g in 25 mL of water.
Acceptance criteria:  NMT 10 ppm
SPECIFIC TESTS
•  Alkalinity
Sample solution:  Dissolve 1.0 g in 10 mL of water.
Analysis:  Add 0.15 mL of 0.10 N sulfuric acid and 1 drop of phenolphthalein TS to the Sample solution.
Acceptance criteria:  No red color is produced.
ADDITIONAL REQUIREMENTS
•  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 Mary S. Waddell
Scientific Liaison
1-301-816-8124
(SM42010) Monographs - Small Molecules 4
USP35–NF30 Page 4663