Nitric Acid
(nye' trik as' id).
HNO3 63.01

Nitric acid.
Nitric acid [7697-37-2].
» Nitric Acid contains not less than 69.0 percent and not more than 71.0 percent, by weight, of HNO3.
[Caution—Avoid contact, because Nitric Acid rapidly destroys tissues. ]
Packaging and storage— Preserve in tight containers.
Clarity and color— Mix it in its original container, and transfer 10 mL to a 20- × 150-mm test tube. Compare with water in a similar test tube: the liquids are equally clear and free from suspended matter, and, when viewed transversely by transmitted light, exhibit no apparent difference in color.
Identification— It responds to the tests for Nitrate 191.
Residue on ignition 281 To 70 mL (100 g) in a tared crucible add 2 drops of sulfuric acid, and evaporate to dryness. Ignite for 15 minutes: the weight of the residue does not exceed 0.5 mg (5 ppm).
Chloride 221 A 35-mL (50-g) portion shows no more chloride than corresponds to 35 µL of 0.020 N hydrochloric acid (0.5 ppm).
Sulfate 221 Add about 10 mg of sodium carbonate to 28 mL of Nitric Acid. Evaporate to dryness, dissolve in a mixture of 4 mL of water and 1 mL of dilute hydrochloric acid (1 in 20), and filter if necessary. Wash with two 2-mL portions of water, dilute with water to 10 mL, and add 1 mL of barium chloride TS. Observe 10 minutes after adding the barium chloride: any turbidity produced is not greater than that produced by 40 µL of 0.020 N sulfuric acid in an equal volume of solution containing the quantities of reagents used in the test (1 ppm).
Iron 241 Evaporate 35 mL (50 g) to dryness, dissolve the residue in 2 mL of hydrochloric acid, and dilute with water to 47 mL: the limit is 0.2 ppm.
Heavy metals, Method I 231 To 70 mL (100 g) in a 250-mL beaker add about 10 mg of sodium carbonate, and evaporate on a steam bath to dryness. Add 25 mL of water: the limit is 0.2 ppm.
Assay— Weigh accurately about 2 mL of Nitric Acid in a tared, glass-stoppered conical flask, and add 25 mL of water. Add methyl red TS, and titrate with 1 N sodium hydroxide VS. Each mL of 1 N sodium hydroxide is equivalent to 63.01 mg of HNO3.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, M.S.
Scientific Liaison
(EXC2010) Monographs - Excipients
USP35–NF30 Page 1875