Nitrous acid, sodium salt.
Sodium nitrite [7632-00-0].
» Sodium Nitrite contains not less than 97.0 percent and not more than 101.0 percent of NaNO2, calculated on the dried basis.
Packaging and storage Preserve in tight containers. Store at 25, excursions permitted between 15 and 30.
Loss on drying 731 Dry it over silica gel for 4 hours: it loses not more than 0.25% of its weight.
Heavy metals 231 Dissolve 1 g in 6 mL of 3 N hydrochloric acid, and evaporate on a steam bath to dryness. Reduce the residue to a coarse powder, and continue heating on the steam bath until the odor of hydrochloric acid no longer is perceptible. Dissolve the residue in 23 mL of water, and add 2 mL of 1 N acetic acid: the limit is 0.002%.
Assay Dissolve about 1 g of Sodium Nitrite, accurately weighed, in water to make 100.0 mL. Pipet 10 mL of this solution into a mixture of 50.0 mL of 0.1 N potassium permanganate VS, 100 mL of water, and 5 mL of sulfuric acid. When adding the Sodium Nitrite solution, immerse the tip of the pipet beneath the surface of the permanganate mixture. Warm the liquid to 40, allow it to stand for 5 minutes, and add 25.0 mL of 0.1 N oxalic acid VS. Heat the mixture to about 80, and titrate with 0.1 N potassium permanganate VS. Each mL of 0.1 N potassium permanganate is equivalent to 3.450 mg of NaNO2.
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USP32NF27 Page 3579Pharmacopeial Forum: Volume No. 29(5) Page 1577