Nitric acid

Nitric acid

Names
IUPAC name Nitric acid
Other names Aqua fortis, Spirit of niter, Eau forte, Hydrogen nitrate, Acidum nitricum
Identifiers
CAS Number	7697-37-2 Y
3D model (Jmol)	Interactive image Interactive image
3DMet	B00068
ChEBI	CHEBI:48107 Y
ChEMBL	ChEMBL1352 Y
ChemSpider	919 Y
ECHA InfoCard	100.028.832
EC Number	231-714-2
Gmelin Reference	1576
KEGG	D02313 Y
MeSH	Nitric+acid
PubChem	944
RTECS number	QU5775000
UNII	411VRN1TV4 Y
UN number	2031
InChI InChI=1S/HNO3/c2-1(3)4/h(H,2,3,4) Y Key: GRYLNZFGIOXLOG-UHFFFAOYSA-N Y InChI=1/HNO3/c2-1(3)4/h(H,2,3,4) Key: GRYLNZFGIOXLOG-UHFFFAOYAO
SMILES [N+](=O)(O)[O-] ON(=O)=O
Properties
Chemical formula	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)
Solubility in water	Completely miscible
Vapor pressure	48 mmHg (20 °C)
Acidity (pKa)	-1.4
Magnetic susceptibility (χ)	−19.9·10−6 cm3/mol
Refractive index (nD)	1.397 (16.5 °C)
Dipole moment	2.17 ± 0.02 D
Thermochemistry
Std molar entropy (So298)	146 J·mol−1·K−1
Std enthalpy of formation (ΔfHo298)	−207 kJ·mol−1
Hazards
Safety data sheet	ICSC 0183 PCTL Safety Website
EU classification (DSD)	C O T+
R-phrases	R8 R35
S-phrases	(S1/2) S23 S26 S36 S45
NFPA 704	0 3 0 OX
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LC50 (median concentration)	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).
Y  (what is YN ?)
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.