Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Nitric Acid, 90% Part 4, Monographs for Reagent Chemicals: General Descriptions, Specifications, and Tests eISBN: 9780841230460 Tom Tyner Chair, ACS Committee on Analytical Reagents James Francis Secretary, ACS Committee on Analytical Reagents
ABSTRACT This monograph for Nitric Acid, 90% provides, in addition to common physical constants, a general description including typical appearance, applications, aqueous solubility, density, and pKa. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Dilution Test, Residue after Ignition, Dissolved Oxides, Chloride, Sulfate, Arsenic, Heavy Metals, and Iron.
HNO3
Formula Wt 63.01
CAS No. 7697-37-2
GENERAL DESCRIPTION Typical appearance Applications . . . . . Aqueous solubility . Density . . . . . . . . pKa . . . . . . . . . .
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clear, yellow, fuming liquid oxidizing solvent miscible 1.52 –2.3
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥90.0% HNO3 Dilution test. . . . . . . . . . . . . . . . . . . . . . . . Passes test Maximum Allowable Residue after ignition. . . . . . . . . . . . . . . . . . 0.002% Dissolved oxides . . . . . . . . . . . . . . . . . . . . . 0.1% as N2O3 Chloride (Cl) . . . . . . . . . . . . . . . . . . . . . . . 0.7 ppm Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Arsenic (As) . . . . . . . . . . . . . . . . . . . . . . . . 0.3 ppm Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 2 ppm
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4243 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By acid–base titrimetry). Tare a small glass-stoppered flask containing about 15 mL of water. Quickly pipette about 2 mL of the sample under the surface, stopper, cool, and weigh accurately. Dilute with about 40 mL of water, add 0.15 mL of methyl orange indicator solution, and titrate with 1 N sodium hydroxide volumetric solution. One milliliter of 1 N sodium hydroxide corresponds to 0.06301 g of HNO3.
Dilution Test Dilute 1 volume of acid with 3 volumes of water. Mix, and allow to stand for 1 h. No turbidity or precipitate should be observed.
Residue after Ignition To 50 g (33 mL) in a tared, preconditioned dish add 0.10 mL of sulfuric acid, evaporate as far as possible on low heat (~100 °C), and heat gently to volatilize the excess sulfuric acid. Finally, ignite at 800 ± 25 °C for 15 min.
Dissolved Oxides Dilute 10 g (6.6 mL) to 150 mL with cold water in a casserole. Add 20 mL of dilute sulfuric acid (1:4), and titrate with 0.1 N potassium permanganate volumetric solution, rapidly at first, then slowly until the pink color lasts 3 min. Not more than 5.0 mL of the potassium permanganate solution should be required. One milliliter of 0.1 N potassium permanganate solution corresponds to 0.0019 g of N2O3.
Chloride Dilute 15 g (10 mL) with 10 mL of water, and add 1 mL of silver nitrate reagent solution. Prepare a standard of 0.01 mg of chloride ion (Cl) in 20 mL of water and add 1 mL of silver nitrate reagent solution. Evaporate the solutions to dryness on a hot plate (~100 °C). Dissolve the residues in 0.5 mL of ammonium hydroxide, dilute with water to 20 mL, and add 1.5 mL of nitric acid. Any turbidity in the solution of the sample should not exceed that in the standard.
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 3]. Use 10.0 g (6.6 mL) of sample.
Arsenic [Part 2: Colorimetry and Turbidimetry; Arsenic]. To 10 g (6.6 mL) in a 150 mL beaker, add 5 mL of sulfuric acid, and evaporate on a hot plate (~100 °C) to a volume of about 5 mL. Transfer the beaker to a hot plate in a hood, and heat to dense fumes of sulfur trioxide. Cool, cautiously wash down the sides of the beaker with about 10 mL of water, evaporate again to dense fumes of sulfur trioxide, and continue the fuming for 15 min. Cool, cautiously wash down the sides of the beaker with about 10 mL of water, and repeat the fuming. Cool, cautiously wash the solution into an arsine generator flask
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4243 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
with 35 mL of water, add 0.5 g of hydrazine sulfate, and proceed as described. For the standard, use 0.003 mg of arsenic ion (As).
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. To 4 g (2.7 mL), add 1 mL of 1% sodium carbonate reagent solution, evaporate to dryness on a hot plate (~100 °C), dissolve the residue in about 20 mL of water, and dilute with water to 25 mL.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Evaporate 5 g (3.3 mL) to dryness, dissolve the residue in 2 mL of hydrochloric acid, dilute with water to 50 mL, and use the solution without further acidification.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4243 ACS Reagent Chemicals, Part 4
