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Nitric Acid

Nitric acid
Resonance description of the bonding in the nitric acid molecule
Ball-and-stick model of nitric acid
Resonance space-filling model of nitric acid
Names
IUPAC name
Nitric acid
Other names
Aqua fortis, Spirit of niter, Eau forte, Hydrogen nitrate, Acidum nitricum
Identifiers
7697-37-2 YesY
3D model (Jmol) Interactive image
Interactive image
3DMet B00068
ChEBI CHEBI:48107 YesY
ChEMBL ChEMBL1352 YesY
ChemSpider 919 YesY
ECHA InfoCard 100.028.832
EC Number 231-714-2
1576
KEGG D02313 YesY
MeSH Nitric+acid
PubChem 944
RTECS number QU5775000
UNII 411VRN1TV4 YesY
UN number 2031
Properties
HNO3
Molar mass 63.01 g·mol−1
Appearance Colorless, yellow or red fuming liquid
Odor acrid, suffocating
Density 1.5129 g cm−3
Melting point −42 °C (−44 °F; 231 K)
Boiling point 83 °C (181 °F; 356 K) 68% solution boils at 121 °C (250 °F; 394 K)
Completely miscible
Vapor pressure 48 mmHg (20 °C)
Acidity (pKa) -1.4
−19.9·10−6 cm3/mol
1.397 (16.5 °C)
2.17 ± 0.02 D
Thermochemistry
146 J·mol−1·K−1
−207 kJ·mol−1
Hazards
Safety data sheet ICSC 0183
PCTL Safety Website
Corrosive C Oxidizing Agent O Very Toxic T+
R-phrases R8 R35
S-phrases (S1/2) S23 S26 S36 S45
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
138 ppm (rat, 30 min)
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 2 ppm (5 mg/m3)
REL (Recommended)
TWA 2 ppm (5 mg/m3) ST 4 ppm (10 mg/m3)
IDLH (Immediate danger)
25 ppm
Related compounds
Other anions
Nitrous acid
Other cations
Sodium nitrate
Potassium nitrate
Ammonium nitrate
Related compounds
Dinitrogen pentoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
Infobox references

Nitric acid (HNO3), also known as aqua fortis and spirit of niter, is a highly corrosive mineral acid.

The pure compound is colorless, but older samples tend to acquire a yellow cast due to decomposition into oxides of nitrogen and water. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% HNO3, it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as white fuming nitric acid or red fuming nitric acid, at concentrations above 95%.

Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is also commonly used as a strong oxidizing agent.

Commercially available nitric acid is an azeotrope with water at a concentration of 68% HNO3, which is the ordinary concentrated nitric acid of commerce. This solution has a boiling temperature of 120.5 °C at 1 atm. Two solid hydrates are known; the monohydrate (HNO3·H2O) and the trihydrate (HNO3·3H2O).

Nitric acid of commercial interest usually consists of the maximum boiling azeotrope of nitric acid and water, which is approximately 68% HNO3, (approx. 15 molar). This is considered concentrated or technical grade, while reagent grades are specified at 70% HNO3. The density of concentrated nitric acid is 1.42 g/cm3. An older density scale is occasionally seen, with concentrated nitric acid specified as 42° Baumé.


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