Nitric Acid

Nitric Acid HNO₃ = 63.0 (7697-37-2)

Content, 63.0% m/m to 70.0% m/m.

Clear, colourless or almost colourless liquid, miscible with water.

, 1.384 to 1.416.

A 10 g/L solution is strongly acid and gives the reaction of nitrates (2.3.1).

Appearance Nitric acid is clear (2.2.1) and not more intensely coloured than reference solution Y₆ (2.2.2, Method II).

Chlorides (2.4.4) Maximum 0.5 ppm.

To 5 g add 10 mL of water and 0.3 mL of silver nitrate solution R2 and allow to stand for 2 minutes protected from light. Any opalescence is not more intense than that of a standard prepared in the same manner using 13 mL of water, 0.5 mL of nitric acid, 0.5 mL of chloride standard solution (5 ppm Cl) and 0.3 mL of silver nitrate solution R2.

Sulfates (2.4.13) Maximum 2 ppm.

Evaporate 10 g to dryness with 0.2 g of sodium carbonate. Dissolve the residue in 15 mL of distilled water. Prepare the standard using a mixture of 2 mL of sulfate standard solution (10 ppm SO₄) and 13 mL of distilled water.

Arsenic (2.4.2, Method A) Maximum 0.02 ppm.

Gently heat 50 g with 0.5 mL of sulfuric acid until white fumes begin to evolve. To the residue add 1 mL of a 100 g/L solution of hydroxylamine hydrochloride and dilute to 2 mL with water. Prepare the standard using 1.0 mL of arsenic standard solution (1 ppm As).

Iron (2.4.9) Maximum 1 ppm.

Dissolve the residue from the determination of sulfated ash in 1 mL of dilute hydrochloric acid and dilute to 50 mL with water. Dilute 5 mL of this solution to 10 mL with water.

Heavy metals (2.4.8) Maximum 2 ppm.

Dilute 10 mL of the solution prepared for the limit test for iron to 20 mL with water. 12 mL of the solution complies with test A. Prepare the reference solution using lead standard solution (2 ppm Pb).

Sulfated ash Maximum 0.001%.

Carefully evaporate 100 g to dryness. Moisten the residue with a few drops of sulfuric acid and heat to dull red.

Assay To 1.50 g add about 50 mL of water and titrate with 1 M sodium hydroxide, using 0.1 mL of methyl red solution as indicator.

1mL of 1 M sodium hydroxide is equivalent to 63.0 mg of HNO₃.

Store protected from light.

When no molarity is indicated use analytical reagent grade of commerce containing about 70% w/w of HNO₃.

When solutions of molarity xm are required, they should be prepared by diluting 63x mL of nitric acid to 1000 mL with water.