Title: Nitric Acid

CAS Registry Number: 7697-37-2

Additional Names: Aqua fortis; azotic acid; Salpetersäure (German)

Molecular Formula: HNO3

Molecular Weight: 63.01

Percent Composition: H 1.60%, N 22.23%, O 76.18%

Literature References: Strong monobasic acid and oxidizing agent. Usually produced by the catalytic oxidation of ammonia. Reviews of industrial processes: F. D. Miles, Nitric Acid, Manufacture and Uses (Oxford Univ. Press, 1961, 1963); W. Sommer in Ullmanns Encyklopädie der technischen Chemie vol. 15, pp 3-67 (3rd ed., 1964). Pure acid prepd by distillation of concd nitric acid with concd sulfuric acid; by treating sodium or potassium nitrate with 100% H2SO4 and removing HNO3 by distillation; by fractional crystallization of concd HNO3. Review of preparation and properties of pure HNO3: S. A. Stern et al., Chem. Rev. 60, 185-207 (1960); S. S. Pannu, J. Chem. Educ. 61, 174-176 (1984). Reviews: Mellor's Vol. VIII, supplement II, Nitrogen (part 2), 278-352 (1967); Jones in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 375-388; D. J. Newman in Kirk-Othmer Encyclopedia of Chemical Technology vol. 15 (Wiley-Interscience, New York, 1981) pp 853-871. Review of photochemistry: J. R. Huber, Chem. Phys. Chem. 5, 1663-1669 (2004).

Properties: Colorless liquid. Fumes in moist air. Characteristic choking odor. d425 1.51. mp -41.59°. bp760 82.6°. Forms white, monoclinic crystals; d-41.6 (solid) 1.895. Heat of fusion: 2.503 kcal/mole. Heat of infinite dilution (298.1 K): -7971 cal/mole. Forms an azeotrope with water, so-called constant boiling acid at 68% HNO3, bp 120.5°, d420 1.41. Develops yellow color in the presence of light due to nitrogen oxide formation. Stains woolen fabrics and animal tissue a bright yellow. Reacts violently with combustible or readily oxidizable materials such as alcohols, turpentine, charcoal, organic refuse. Reacts with most metals to release hydrogen gas.

Melting point: mp -41.59°

Boiling point: bp760 82.6°; bp 120.5°

Density: d425 1.51; d-41.6 (solid) 1.895; d420 1.41

Derivative Type: Nitric acid, concentrated

Literature References: Defined as an aqueous solution containing approx 70% HNO3.

Properties: Density of aq solns: d420 1.0036 (1% HNO3 w/w); 1.0543 (10%); 1.1150 (20%); 1.1800 (30%); 1.2463 (40%); 1.3100 (50%); 1.3667 (60%); 1.4134 (70%); 1.4521 (80%); 1.4826 (90%); 1.5129 (100%): International Critical Tables III, 58 (1928).

Density: d420 1.0036 (1% HNO3 w/w); 1.0543 (10%); 1.1150 (20%); 1.1800 (30%); 1.2463 (40%); 1.3100 (50%); 1.3667 (60%); 1.4134 (70%); 1.4521 (80%); 1.4826 (90%); 1.5129 (100%)

Derivative Type: Nitric acid, fuming

Literature References: Concentrated nitric acid containing dissolved nitrogen dioxide. May be prepared from concd nitric acid by passing nitrogen dioxide into it or by adding a small amount of organic reducing agent, such as formaldehyde.

Properties: Yellow to brownish-red, clear, strongly fuming, very corrosive liq; evolves suffocating, poisonous, yellowish-red fumes of nitrogen dioxide and nitrogen tetroxide. The density increases as the free NO2 content increases: concd HNO3 with 7.5% NO2 added d420 = 1.526; with 12.7% NO2 d420 = 1.544. Miscible with water. Handle with extreme care.

Density: d420 = 1.526; d420 = 1.544

CAUTION: Potential symptoms of overexposure are irritation of eyes, mucous membranes and skin; delayed pulmonary edema, pneumonitis and bronchitis; dental erosion. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 224. See also Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984) Section III, pp 8-11.

Use: Manufacture of inorganic and organic nitrates and nitro compounds for fertilizers, dye intermediates, explosives, rocket fuels. As laboratory reagent, in photoengraving, metal etching. Pharmaceutic aid (acidifier).