Packaging and storage—
Preserve in tight, light-resistant containers.
Labeling—
Label the container to indicate that the contents are not intended for parenteral use.
Identification—
A:
Dilute a volume of Solution, if necessary, with a 0.8 in 1000 solution of sodium hydroxide in methanol to obtain a test solution having a concentration of 1 mg per mL. The test solution responds to the
Thin-layer Chromatographic Identification Test 
201
, the Standard solution being prepared at a concentration of 1 mg of
USP Diatrizoic Acid RS per mL in a 0.8 in 1000 solution of sodium hydroxide in methanol, the solvent mixture being a mixture of chloroform, methanol, and ammonium hydroxide (20:10:2), and short-wavelength UV light being used to locate the spots.
B:
Evaporate a volume of Solution, equivalent to about 500 mg of diatrizoate sodium, to dryness, and heat the residue so obtained in a suitable crucible: violet vapors are evolved.
Iodine and iodide—
Using as the
Test preparation a volume of Solution equivalent to 2.0 g of diatrizoate sodium and diluting it with water to 24 mL in a 50-mL centrifuge tube provided with a stopper, proceed as directed for
Procedure in the test for
Iodine and iodide under
Diatrizoate Meglumine.
Assay—
Pipet a volume of Solution, equivalent to about 400 mg of diatrizoate sodium, into a 125-mL conical flask. Add 30 mL of 1.25 N sodium hydroxide and 500 mg of powdered zinc, connect the flask to a reflux condenser, and reflux the mixture for 1 hour. Cool the flask to room temperature, rinse the condenser with 20 mL of water, disconnect the flask from the condenser, and filter the mixture. Rinse the flask and filter thoroughly, adding the rinsings to the filtrate. Add 5 mL of glacial acetic acid and 1 mL of
tetrabromophenolphthalein ethyl ester TS, and titrate with 0.05 N silver nitrate VS until the yellow precipitate just turns green. Each mL of 0.05 N silver nitrate is equivalent to 10.60 mg of C
11H
8I
3N
2NaO
4.
