Nitric Acid

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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HNO₃ 63.01

Nitric acid CAS RN^®: 7697-37-2.

1 DEFINITION

Nitric Acid contains NLT 69.0% and NMT 71.0%, by weight, of nitric acid (HNO₃). [CAUTION-Avoid contact, because Nitric Acid rapidly destroys tissues.]

2 IDENTIFICATION

A. IDENTIFICATION TESTS-GENERAL, Nitrate (191): Meets the requirements

3 ASSAY

3.1 PROCEDURE

Sample solution: Weigh 2 mL of Nitric Acid in a glass-stoppered conical flask, and add 25 mL of water. Add methyl red TS.

Analysis: Titrate the Sample solution with 1 N sodium hydroxide VS. Each mL of 1 N sodium hydroxide is equivalent to 63.01 mg of HNO₃ (see Titrimetry (541)).

Acceptance criteria: 69.0%-71.0%

4 IMPURITIES

4.1 RESIDUE ON IGNITION (281)

Sample: 70 mL (100 g)

Analysis: Place the Sample in a tared crucible, add 2 drops of sulfuric acid, and evaporate to dryness. Ignite for 15 min.

Acceptance criteria: NMT 0.5 mg (5 ppm)

4.2 CHLORIDE AND SULFATE, Chloride (221)

Sample: 35 mL (50 g)

Control: 35 µL of 0.020 N hydrochloric acid

Acceptance criteria: NMT 0.5 ppm; the Sample shows no more chloride than corresponds to the Control.

4.3 CHLORIDE AND SULFATE, Sulfate (221)

Sample: 28 mL

Control: 40 µL of 0.020 N sulfuric acid in an equal volume of solution containing the quantities of reagents used in the analysis

Analysis: Add 10 mg of sodium carbonate to the Sample. Evaporate to dryness, dissolve in a mixture of 4 mL of water and 1 mL of dilute hydrochloric acid (50 mg/mL), 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 min after adding the barium chloride.

Acceptance criteria: 1 ppm; any turbidity produced by the Sample is not greater than that produced by the Control.

Change to read:

4.4 IRON (241), Procedures, Procedure 1 (CN 1-JUN-2023)

Sample: 35 mL (50 g)

Analysis: Evaporate the Sample to dryness, dissolve the residue in 2 mL of hydrochloric acid, and dilute with water to 47 mL.

Acceptance criteria: NMT 0.2 µg/g

5 SPECIFIC TESTS

CLARITY AND COLOR OF SOLUTION

Analysis: Mix it in its original container, and transfer 10 mL to a 20-x 150-mm test tube. Compare with water in a similar test tube.

Acceptance criteria: The liquids are equally clear and free from suspended matter, and when viewed transversely by transmitted light, exhibit no apparent difference in color.

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers.