Sodium Azide
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
NaN3 65.01 CAS RN®: 26628-22-8.—White powder.
Assay
[Caution—Sodium azide is a potent poison. Its conjugate acid HN is more toxic than hydrogen cyanide and is readily liberated from neutral aqueous solutions. Contact of NaH or hydrazoic acid (HN ) with certain metals may produce explosive salts. Work in a well-ventilated hood, and handle the sample with care.]
Dissolve about 100 mg, accurately weighed, in 50 mL of water, and add 3 drops of phenolphthalein. Adjust the pH, if necessary, to 7.0, and add 35.0 mL of 0.1 N perchloric acid. Pipet, while stirring, 2.5 mL of 1.0 M sodium nitrite into the solution, and stir for 15 seconds. Titrate rapidly to the phenolphthalein endpoint with 0.1 N sodium hydroxide. The endpoint should be reached in less than 4 minutes after addition of perchloric acid because HN is readily volatile. Calculate the percentage of azide by the formula:
[(Np )(Vp ) − (NS )(VS )](65.01)(100)/2C
where Np is the normality of perchloric acid solution; Vp is the volume of perchloric acid, in mL, taken; NS is the normality of sodium hydroxide solution; VS is the volume, in mL, of sodium hydroxide taken; 65.01 is the molecular weight of sodium azide; and C is the weight, in mg, of sodium azide. Not less than 98.5% of NaN3 is found.
