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Chemical compound (NH₃) / From Wikipedia, the free encyclopedia

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Quick facts: Names, Identifiers, Properties, Structure, Th...
Stereo structural formula of the ammonia molecule
Ball-and-stick model of the ammonia molecule
Ball-and-stick model of the ammonia molecule
Space-filling model of the ammonia molecule
Space-filling model of the ammonia molecule
IUPAC name
Systematic IUPAC name
Other names
  • Hydrogen nitride
  • R-717
  • R717 (refrigerant)
  • Amidogen
  • Hydrogen amine
3D model (JSmol)
ECHA InfoCard 100.028.760 Edit this at Wikidata
EC Number
  • 231-635-3
MeSH Ammonia
RTECS number
  • BO0875000
UN number 1005
  • InChI=1S/H3N/h1H3 checkY
  • InChI=1/H3N/h1H3
  • N
Molar mass 17.031 g·mol−1
Appearance Colourless gas
Odor Strong pungent odour
  • 0.86 kg/m3 (1.013 bar at boiling point)
  • 0.769 kg/m3 (STP)[2]
  • 0.73 kg/m3 (1.013 bar at 15 °C)
  • 0.6819 g/cm3 at −33.3 °C (liquid)[3] See also Ammonia (data page)
  • 0.817 g/cm3 at −80 °C (transparent solid)[4]
Melting point −77.73 °C (−107.91 °F; 195.42 K) (Triple point at 6.060 kPa, 195.4 K)
Boiling point −33.34 °C (−28.01 °F; 239.81 K)
Critical point (T, P) 132.4 °C (405.5 K), 111.3 atm (11,280 kPa)
  • 47% w/w (0 °C)
  • 31% w/w (25 °C)
  • 18% w/w (50 °C)[5]
[clarification needed]
Solubility soluble in chloroform, ether, ethanol, methanol
Vapor pressure 857.3 kPa
Acidity (pKa) 32.5 (−33 °C),[6] 9.24 (of ammonium)
Basicity (pKb) 4.75
Conjugate acid Ammonium
Conjugate base Amide
−18.0·10−6 cm3/mol
  • 10.07 µPa·s (25 °C)[7]
  • 0.276 mPa·s (−40 °C)
Trigonal pyramid
1.42 D
193 J/(mol·K)[8]
−46 kJ/mol[8]
GHS labelling:[9]
GHS04: Compressed Gas GHS05: Corrosive GHS06: Toxic GHS09: Environmental hazard
H280, H314, H331, H410
P260, P273, P280, P303+P361+P353, P304+P340+P311, P305+P351+P338+P310
NFPA 704 (fire diamond)
Flash point 132 °C (270 °F; 405 K)
651 °C (1,204 °F; 924 K)
Explosive limits 15,0–33,6%
Lethal dose or concentration (LD, LC):
0.015 mL/kg (human, oral)
  • 40,300 ppm (rat, 10 min)
  • 28,595 ppm (rat, 20 min)
  • 20,300 ppm (rat, 40 min)
  • 11,590 ppm (rat, 1 hr)
  • 7338 ppm (rat, 1 hr)
  • 4837 ppm (mouse, 1 hr)
  • 9859 ppm (rabbit, 1 hr)
  • 9859 ppm (cat, 1 hr)
  • 2000 ppm (rat, 4 hr)
  • 4230 ppm (mouse, 1 hr)[10]
5000 ppm (mammal, 5 min)
5000 ppm (human, 5 min)[10]
NIOSH (US health exposure limits):[11]
PEL (Permissible)
50 ppm (25 ppm ACGIH- TLV; 35 ppm STEL)
REL (Recommended)
TWA 25 ppm (18 mg/m3) ST 35 ppm (27 mg/m3)
IDLH (Immediate danger)
300 ppm
Safety data sheet (SDS) ICSC 0414 (anhydrous)
Related compounds
Related nitrogen hydrides
Hydrazoic acid
Related compounds
Supplementary data page
Ammonia (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Ammonia is an inorganic compound of nitrogen and hydrogen with the formula NH3. A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to 45% of the world's food[12] and fertilizers. Around 70% of ammonia is used to make fertilisers[13] in various forms and composition, such as urea and diammonium phosphate. Ammonia in pure form is also applied directly into the soil.

Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceutical products and is used in many commercial cleaning products. It is mainly collected by downward displacement of both air and water.

Although common in nature—both terrestrially and in the outer planets of the Solar System—and in wide use, ammonia is both caustic and hazardous in its concentrated form. In many countries it is classified as an extremely hazardous substance, and is subject to strict reporting requirements by facilities that produce, store, or use it in significant quantities.[14]

The global industrial production of ammonia in 2021 was 235 million tonnes.[15][16] Industrial ammonia is sold either as ammonia liquor (usually 28% ammonia in water) or as pressurized or refrigerated anhydrous liquid ammonia transported in tank cars or cylinders.[17]

For fundamental reasons, the production of ammonia from the elements hydrogen and nitrogen is difficult, requiring high pressures and high temperatures. The Haber process that enabled industrial production was invented at the beginning of the 20th century, revolutionizing agriculture.

NH3 boils at −33.34 °C (−28.012 °F) at a pressure of one atmosphere, so the liquid must be stored under pressure or at low temperature. Household ammonia or ammonium hydroxide is a solution of NH3 in water. The concentration of such solutions is measured in units of the Baumé scale (density), with 26 degrees Baumé (about 30% of ammonia by weight at 15.5 °C or 59.9 °F) being the typical high-concentration commercial product.[18]