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Ammonia is a compound of
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about t ...
and
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. With a standard atomic weight of , hydrogen is the lightest element in the periodic table. Hydrogen is the most abundant chemical substance in the universe, constitut ...

hydrogen
with the
formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a chemical formula. The informal use of the term ''formula'' in science refers to the general construct of a relationship between given ...
NH3. A stable binary hydride, and the simplest
pnictogen hydridePnictogen hydrides or hydrogen pnictides are binary compounds of hydrogen with pnictogen atoms (elements of group 15: nitrogen, phosphorus, arsenic, antimony, and bismuth) covalently bonded to hydrogen. Pnictogen trihydrides The simplest series has ...
, ammonia is a colourless
gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compo ...
with a distinct characteristic of a pungent smell. It is a common
nitrogenous waste Metabolic wastes or excrements are substances left over from metabolic processes (such as cellular respiration) which cannot be used by the organism (they are surplus or toxic), and must therefore be excreted. This includes nitrogen compounds, wate ...
, particularly among aquatic organisms, and it contributes significantly to the
nutrition Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It includes ingestion, absorption, assimilation, biosynthesis, catabolism and excretion. The science that studies the physiological proces ...
al needs of terrestrial organisms by serving as a precursor to
food Food is any substance consumed to provide nutritional support for an organism. Food is usually of plant, animal or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is i ...
and
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from li ...
s. Ammonia, either directly or indirectly, is also a building block for the synthesis of many
pharmaceutical products A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and relies on ...
and is used in many commercial cleaning products. It is mainly collected by downward displacement of both air and water. Although common in natureboth terrestrially and in the
outer planets The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
of the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

Solar System
and in wide use, ammonia is both
caustic Caustic most commonly refers to: * Causticity, a property of various corrosive substances ** Sodium hydroxide, sometimes called ''caustic soda'' ** Potassium hydroxide, sometimes called ''caustic potash'' ** Calcium oxide, sometimes called ''caustic ...
and
hazard A hazard is a potential source of harm. Substances, events, or circumstances can constitute hazards when their nature would allow them, even just theoretically, to cause damage to health, life, property, or any other interest of value. The probabil ...

hazard
ous in its concentrated form. It is classified as an extremely hazardous substance in the United States, and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities. The global industrial production of ammonia in 2018 was 175 million tonnes, with no significant change relative to the 2013 global industrial production of 175 million tonnes. 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. NH3 boils at at a pressure of one
atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in pla ...
, so the liquid must be stored under pressure or at low temperature. Household ammonia or
ammonium hydroxide Ammonia solution, also known as ammonia water, ammonium hydroxide, ammoniacal liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or (inaccurately) ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH3(aq). Although ...
is a solution of NH3 in water. The concentration of such solutions is measured in units of the
Baumé scale The Baumé scale is a pair of hydrometer scales developed by French pharmacist Antoine Baumé in 1768 to measure density of various liquids. The unit of the Baumé scale has been notated variously as ''degrees Baumé'', ''B°'', ''Bé°'' and simply ...
(
density The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter '' ...
), with 26 degrees Baumé (about 30% (by weight) ammonia at ) being the typical high-concentration commercial product.


Etymology

Pliny, in Book XXXI of his
Natural History Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is calle ...
, refers to a salt produced in the Roman province of
Cyrenaica Cyrenaica ( ; ar, برقة, Barqah; grc-koi, Κυρηναϊκή παρχίαKurēnaïkḗ parkhíā}, after the city of Cyrene) is the eastern coastal region of Libya. Also known as ''Pentapolis'' ("Five Cities") in antiquity, it formed part o ...
named ''hammoniacum'', so called because of its proximity to the nearby Temple of
Jupiter Amun
Jupiter Amun
(
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of ...
Ἄμμων ''Ammon''). However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride. According to
Herbert Hoover's
Herbert Hoover's
commentary in his English translation of
Georgius Agricola's
Georgius Agricola's
''
De re metallica#REDIRECT De re metallica#REDIRECT De re metallica {{R from other capitalisation ...
{{R from other capitalisation ...
'', it is likely to have been common sea salt. In any case, that salt ultimately gave ammonia and
ammonium The ammonium cation is a positively charged polyatomic ion with the chemical formula . It is formed by the protonation of ammonia (NH3). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ammoni ...
compounds their name.


Natural occurrence

Ammonia is a chemical found in trace quantities in nature, being produced from nitrogenous animal and vegetable matter. Ammonia and ammonium salts are also found in small quantities in rainwater, whereas
ammonium chloride Ammonium chloride is an inorganic compound with the formula NH4Cl and a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of the natural, mineralogical form of ammoniu ...

ammonium chloride
(
sal ammoniac Salammoniac, also sal ammoniac or salmiac, is a rare naturally occurring mineral composed of ammonium chloride, NH4Cl. It forms colorless, white, or yellow-brown crystals in the isometric-hexoctahedral class. It has very poor cleavage and is britt ...
), and
ammonium sulfate Ammonium sulfate (American English and international scientific usage; ammonium sulphate in British English); (NH4)2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen an ...
are found in volcanic districts; crystals of
ammonium bicarbonate Ammonium bicarbonate is an inorganic compound with formula (NH4)HCO3, simplified to NH5CO3. The compound has many names, reflecting its long history. Chemically speaking, it is the bicarbonate salt of the ammonium ion. It is a colourless solid that ...
have been found in
Patagonia Patagonia () is a sparsely populated region at the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains, lakes, fjords, and glaciers in the west and deserts, tablelands a ...
guano Guano (Spanish from qu, wanu) is the accumulated excrement of seabirds and bats. As a manure, guano is a highly effective fertilizer due to its exceptionally high content of nitrogen, phosphate, and potassium: key nutrients essential for plant ...

guano
. The
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ex ...
s secrete ammonia to neutralize excess acid. Ammonium salts are found distributed through fertile soil and in seawater. Ammonia is also found throughout the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

Solar System
on
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury. In English, Mars carries the name of the Roman god of war and is often referred to as the "Red Planet". The latter refe ...

Mars
,
Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined. Jupiter is the th ...

Jupiter
,
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It only has one-eighth the average density of Earth; how ...

Saturn
,
Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus, who, according to Greek mythology, was the grandfather of Zeus (Jupiter) and father of Cronus (Saturn). It has the third-largest planetar ...

Uranus
,
Neptune Neptune is the eighth and farthest-known Solar planet from the Sun. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, slightly mor ...

Neptune
, and
Pluto Pluto (minor planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It was the first and the largest Kuiper belt object to be discovered. After Pluto was discovered in 1930, it w ...
, among other places: on smaller, icy
bodies Bodies may refer to: * The plural of body * ''Bodies'' (TV series), BBC television program * "Bodies" (''Law & Order''), 2003 episode of ''Law & Order'' * Bodies: The Exhibition, exhibit showcasing dissected human bodies in cities across the globe ...
such as Pluto, ammonia can act as a geologically important antifreeze, as a mixture of water and ammonia can have a melting point as low as if the ammonia concentration is high enough and thus allow such bodies to retain internal oceans and active geology at a far lower temperature than would be possible with water alone. Substances containing ammonia, or those that are similar to it, are called ''ammoniacal''.


Properties

Ammonia is a colourless
gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compo ...
with a characteristically pungent smell. It is
lighter than air A lifting gas or lighter than air gas is a gas that has a lower density than normal atmospheric gases and rises above them as a result. It is required for aerostats to create buoyancy, particularly in lighter-than-air aircraft, which include free b ...
, its density being 0.589 times that of
air
air
. It is easily liquefied due to the strong
hydrogen bond#REDIRECT Hydrogen bond#REDIRECT Hydrogen bond {{R from other capitalisation ...
{{R from other capitalisation ...
ing between molecules; the
liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, and ...
boils A boil, also called a furuncle, is a deep folliculitis, infection of the hair follicle. It is most commonly caused by infection by the bacterium ''Staphylococcus aureus'', resulting in a painful swollen area on the skin caused by an accumulation o ...
at , and freezes to white crystals at . Ammonia may be conveniently deodorized by reacting it with either
sodium bicarbonate Sodium bicarbonate (IUPAC name: sodium hydrogen carbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation (Na+) and a bicarbonate anion (HCO3−). ...

sodium bicarbonate
or
acetic acid Acetic acid , systematically named ethanoic acid , is a colourless liquid organic compound with the chemical formula CH3COOH (also written as CH3CO2H, C2H4O2, or HC2H3O2). Vinegar is no less than 4% acetic acid by volume, making acetic acid ...

acetic acid
. Both of these reactions form an odourless ammonium salt. ;Solid: The crystal symmetry is cubic,
Pearson symbolPearson may refer to: Organizations Education *Lester B. Pearson College, Victoria, British Columbia, Canada *Pearson College (UK), London, owned by Pearson PLC *Lester B. Pearson High School (disambiguation) Companies *Pearson PLC, a UK-based inte ...
cP16,
space group In mathematics, physics and chemistry, a space group is the symmetry group of a configuration in space, usually in three dimensions. In three dimensions, there are 219 distinct types, or 230 if chiral copies are considered distinct. Space groups a ...
P213 No.198, lattice constant 0.5125  nm. ;Liquid:
Liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, and ...
ammonia possesses strong
ion An ion () is a particle, atom or molecule with a net electrical charge. The charge of the electron is considered negative by convention. The negative charge of an ion is equal and opposite to charged proton(s) considered positive by convent ...
ising powers reflecting its high ε of 22. Liquid ammonia has a very high
standard enthalpy change of vaporization The enthalpy of vaporization (symbol ), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas. Th ...
(23.35  kJ/mol, ''cf.''
water Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent). It is vita ...
40.65 kJ/mol, methane 8.19 kJ/mol,
phosphine Phosphine (IUPAC name: phosphane) is a colourless, flammable, very toxic gas compound with the chemical formula PH3, classed as a pnictogen hydride. Pure phosphine is odourless, but technical grade samples have a highly unpleasant odour like rott ...

phosphine
14.6 kJ/mol) and can therefore be used in laboratories in uninsulated vessels without additional refrigeration. See liquid ammonia as a solvent. ;Solvent properties: Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The
aqueous An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be repr ...
solution of ammonia is
basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use. The original version was designed by John G. Kemeny and Thomas E. Kurtz and ...
. The maximum concentration of ammonia in water (a
saturated solution Solubility is the property of a solid, liquid or gaseous chemical substance called ''solute'' to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depends on the physical and chemical properties of the ...
) has a
density The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter '' ...
of 0.880 g/cm3 and is often known as '.880 ammonia'. ;Combustion: Ammonia does not burn readily or sustain
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
, except under narrow fuel-to-air mixtures of 15–25% air. When mixed with
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well a ...
, it burns with a pale yellowish-green flame. Ignition occurs when
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a y ...
is passed into ammonia, forming nitrogen and
hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride gas ...
; if chlorine is present in excess, then the highly explosive
nitrogen trichloride Nitrogen trichloride, also known as trichloramine, is the chemical compound with the formula NCl3. This yellow, oily, pungent-smelling and explosive liquid is most commonly encountered as a byproduct of chemical reactions between ammonia-derivatives ...

nitrogen trichloride
(NCl3) is also formed. ;Decomposition: At high temperature and in the presence of a suitable catalyst, ammonia is decomposed into its constituent elements. Decomposition of ammonia is slightly endothermic process requiring 23 kJ/mol (5.5 kcal/mol) of ammonia, and yields
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. With a standard atomic weight of , hydrogen is the lightest element in the periodic table. Hydrogen is the most abundant chemical substance in the universe, constitut ...

hydrogen
and
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about t ...
gas. Ammonia can also be used as a source of hydrogen for acid
fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requir ...
s if the unreacted ammonia can be removed.
Ruthenium Ruthenium is a chemical element with the symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemicals ...
and
platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name is derived from the Spanish term ''platino'', meaning "little si ...
catalysts that utilizes a low-temperature oxidation catalyst to convert carbon monoxide to less toxic carbon dioxide at room temperature. It can also remove formaldehyde from the air. Catalysis () is the process of increasing the reaction rate, rate of a ...
were found to be the most active, whereas supported Ni catalysts were the less active.


Structure

The ammonia molecule has a
trigonal pyramidal In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base, resembling a tetrahedron (not to be confused with the tetrahedral geometry). When all three atoms at the corners a ...
shape as predicted by the
valence shell electron pair repulsion theory#REDIRECT VSEPR theory {{R from other capitalisation ...
(VSEPR theory) with an experimentally determined bond angle of 106.7°. The central nitrogen atom has five outer electrons with an additional electron from each hydrogen atom. This gives a total of eight electrons, or four electron pairs that are arranged
tetrahedrally
tetrahedrally
. Three of these
electron pair In chemistry, an electron pair or Lewis pair consists of two electrons that occupy the same molecular orbital but have opposite spins. Gilbert N. Lewis introduced the concepts of both the electron pair and the covalent bond in a landmark paper he pu ...
s are used as bond pairs, which leaves one
lone pair In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone pa ...
of electrons. The lone pair repels more strongly than bond pairs, therefore the bond angle is not 109.5°, as expected for a regular tetrahedral arrangement, but 106.7°. This shape gives the molecule a
dipole In electromagnetism, there are two kinds of dipoles: *An electric dipole deals with the separation of the positive and negative charges found in any electromagnetic system. A simple example of this system is a pair of electric charges of equal ma ...

dipole
moment and makes it
polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates *Polar climate, the clima ...
. The molecule's polarity, and especially, its ability to form
hydrogen bond#REDIRECT Hydrogen bond#REDIRECT Hydrogen bond {{R from other capitalisation ...
{{R from other capitalisation ...
s, makes ammonia highly miscible with water. The lone pair makes ammonia a
base Base or BASE may refer to: Brands and enterprises *Base (mobile telephony provider), a Belgian mobile telecommunications operator *Base CRM, an enterprise software company founded in 2009 with offices in Mountain View and Kraków, Poland *Base De ...
, a proton acceptor. Ammonia is moderately basic; a 1.0 M
aqueous solution An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be repr ...
has a pH of 11.6, and if a strong acid is added to such a solution until the solution is neutral (pH = 7), 99.4% of the ammonia molecules are
protonated In chemistry, protonation (or hydronation) is the addition of a proton (or hydron, or hydrogen cation), (H+) to an atom, molecule, or ion, forming the conjugate acid. (The complementary process, when a proton is removed from a Brønsted–Lowry acid ...
. Temperature and
salinity upInternational Association for the Physical Sciences of the Oceans (IAPSO) standard seawater. Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). This is usually measured in \ ...

salinity
also affect the proportion of NH4+. The latter has the shape of a regular
tetrahedron In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the ord ...

tetrahedron
and is
isoelectronic Isoelectronicity is an effect observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electron configurations, but differ by what specific elements are at certain locations in the struct ...
with
methane Methane ( or ) is a chemical compound with the chemical formula (one atom of carbon and four atoms of hydrogen). It is a group-14 hydride and the simplest alkane, and is the main constituent of natural gas. The relative abundance of methane on ...
. The ammonia molecule readily undergoes
nitrogen inversion In chemistry, nitrogen inversion (also umbrella inversion) is a fluxional process in nitrogen and amines, whereby the molecule "turns inside out". It is a rapid oscillation of the nitrogen atom and substituents, the nitrogen "moving" through the p ...
at room temperature; a useful analogy is an
umbrella An umbrella or parasol is a folding canopy supported by wooden or metal ribs that is usually mounted on a wooden, metal, or plastic pole. It is designed to protect a person against rain or sunlight. The term ''umbrella'' is traditionally used w ...
turning itself inside out in a strong wind. The energy barrier to this inversion is 24.7 kJ/mol, and the
resonance frequency Resonance describes the phenomenon of increased amplitude that occurs when the frequency of a periodically applied force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillati ...
is 23.79
GHz The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second. It is named after Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of ...
, corresponding to
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges ...
radiation of a
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...
of 1.260 cm. The absorption at this frequency was the first microwave spectrum to be observed.


Amphotericity

One of the most characteristic properties of ammonia is its
basicity In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases and Lewis bases. All definitions agree that bases are substances which react with acids as originally proposed by G.-F. Rouelle ...
. Ammonia is considered to be a weak base. It combines with
acid An acid is a molecule or ion capable of donating a proton (hydrogen ion H+) (a Brønsted–Lowry acid), or, alternatively, capable of forming a covalent bond with an electron pair (a Lewis acid). The first category of acids are the proton do ...
s to form
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in its natural form as a crystalline mineral is known as rock salt or halite. Salt is present in vast quantities ...
s; thus with
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestive ...
it forms
ammonium chloride Ammonium chloride is an inorganic compound with the formula NH4Cl and a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of the natural, mineralogical form of ammoniu ...

ammonium chloride
(sal ammoniac); with
nitric acid Nitric acid (), also known as ''aqua fortis'' (Latin for "strong water") 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 ...
, ammonium nitrate, etc. Perfectly dry ammonia gas will not combine with perfectly dry
hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride gas ...
gas; moisture is necessary to bring about the reaction. As a demonstration experiment under air with ambient moisture, opened bottles of concentrated ammonia and
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestive ...
solutions produce a cloud of
ammonium chloride Ammonium chloride is an inorganic compound with the formula NH4Cl and a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of the natural, mineralogical form of ammoniu ...

ammonium chloride
, which seems to appear "out of nothing" as the salt aerosol forms where the two diffusion, diffusing clouds of reagents meet between the two bottles. The salts produced by the action of ammonia on acids are known as the :Ammonium compounds, ammonium salts and all contain the ammonium, ammonium ion (NH4+). Although ammonia is well known as a weak base, it can also act as an extremely weak acid. It is a protic, protic substance and is capable of formation of amides (which contain the NH2 ion). For example, lithium dissolves in liquid ammonia to give a blue solution (solvated electron) of lithium amide:


Self-dissociation

Like water, liquid ammonia undergoes molecular autoionisation to form its conjugate acid, acid and base conjugates: Ammonia often functions as a weak base, so it has some buffer solution, buffering ability. Shifts in pH will cause more or fewer
ammonium The ammonium cation is a positively charged polyatomic ion with the chemical formula . It is formed by the protonation of ammonia (NH3). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ammoni ...
cations () and Azanide, amide anions () to be present in solution. At standard pressure and temperature, K = [] × [] = 10.


Combustion

The
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
of ammonia to decompose in nitrogen and water is exothermic: The standard enthalpy change of combustion, Δ''H''°c, expressed per mole (unit), mole of ammonia and with condensation of the water formed, is −382.81 kJ/mol. Dinitrogen is the thermodynamic product of
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
: all nitrogen oxides are unstable with respect to N2 and O2, which is the principle behind the catalytic converter. Nitrogen oxides can be formed as chemical kinetics, kinetic products in the presence of appropriate catalysis, catalysts, a reaction of great industrial importance in the production of
nitric acid Nitric acid (), also known as ''aqua fortis'' (Latin for "strong water") 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 ...
: A subsequent reaction leads to NO2: The combustion of ammonia in air is very difficult in the absence of a catalysis, catalyst (such as
platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name is derived from the Spanish term ''platino'', meaning "little si ...
gauze or warm chromium(III) oxide), due to the relatively low heat of combustion, a lower laminar burning velocity, high auto-ignition temperature, high heat of vaporization, and a narrow Flammability limit, flammability range. However, recent studies have shown that efficient and stable combustion of ammonia can be achieved using swirl combustors, thereby rekindling research interest in ammonia as a fuel for thermal power production. The flammable range of ammonia in dry air is 15.15% – 27.35% and in 100% relative humidity air is 15.95% – 26.55%. For studying the chemical kinetics, kinetics of ammonia combustion a detailed reliable reaction mechanism is required, however knowledge about ammonia chemical kinetics during combustion process has been challenging.


Formation of other compounds

In organic chemistry, ammonia can act as a nucleophile in Nucleophilic substitution, substitution reactions. Amines can be formed by the reaction of ammonia with alkyl halides, although the resulting -NH2 group is also nucleophilic and secondary and tertiary amines are often formed as byproducts. An excess of ammonia helps minimise multiple substitution and neutralises the hydrogen halide formed. Methylamine is prepared commercially by the reaction of ammonia with chloromethane, and the reaction of ammonia with 2-bromopropanoic acid has been used to prepare racemic alanine in 70% yield. Ethanolamine is prepared by a ring-opening reaction with ethylene oxide: the reaction is sometimes allowed to go further to produce diethanolamine and triethanolamine. Amides can be prepared by the reaction of ammonia with carboxylic acid derivatives. Acyl chlorides are the most reactive, but the ammonia must be present in at least a twofold excess to neutralise the
hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride gas ...
formed. Esters and anhydrides also react with ammonia to form amides. Ammonium salts of carboxylic acids can be Dehydration reaction, dehydrated to amides so long as there are no thermally sensitive groups present: temperatures of 150 – 200 °C are required. The hydrogen in ammonia is susceptible to replacement by a myriad of substituents. When dry ammonia gas is heated with metallic sodium it converts to sodamide, NaNH2. With chlorine, monochloramine is formed. Pentavalent ammonia is known as λ5-amine or, more commonly, ammonium hydride. This crystalline solid is only stable under high pressure and decomposes back into trivalent ammonia and hydrogen gas at normal conditions. This substance was once investigated as a possible solid rocket fuel in 1966.


Ammonia as a ligand

Ammonia can act as a ligand in transition metal complex (chemistry), complexes. It is a pure σ-donor, in the middle of the spectrochemical series, and shows intermediate HSAB concept, hard-soft behaviour (see also ECW model). Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by ECW model, C-B plots. For historical reasons, ammonia is named ammine in the nomenclature of coordination compounds. Some notable ammine complexes include tetraamminediaquacopper(II) ([Cu(NH3)4(H2O)2]2+), a dark blue complex formed by adding ammonia to a solution of copper(II) salts. Tetraamminediaquacopper(II) hydroxide is known as Schweizer's reagent, and has the remarkable ability to dissolve cellulose. Diamminesilver(I) ([Ag(NH3)2]+) is the active species in Tollens' reagent. Formation of this complex can also help to distinguish between precipitates of the different silver halides: silver chloride (AgCl) is soluble in dilute (2 M) ammonia solution, silver bromide (AgBr) is only soluble in concentrated ammonia solution, whereas silver iodide (AgI) is insoluble in aqueous ammonia. Ammine complexes of chromium(III) were known in the late 19th century, and formed the basis of Alfred Werner's revolutionary theory on the structure of coordination compounds. Werner noted only two isomers (''fac''- and ''mer''-) of the complex [CrCl3(NH3)3] could be formed, and concluded the ligands must be arranged around the metal ion at the wikt:vertex, vertices of an octahedron. This proposal has since been confirmed by X-ray crystallography. An ammine ligand bound to a metal ion is markedly more acidic than a free ammonia molecule, although deprotonation in
aqueous solution An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be repr ...
is still rare. One example is the Mercury(I) chloride, Calomel reaction, where the resulting amidomercury(II) compound is highly insoluble. Ammonia forms 1:1 adducts with a variety of Lewis acids such as Iodine, I2, phenol, and Trimethyl aluminium, Al(CH3)3. Ammonia is a HSAB theory, hard base (HSAB theory) and its ECW model, E & C parameters are EB = 2.31 and C B = 2.04. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by ECW model, C-B plots.


Detection and determination


Ammonia in solution

Ammonia and ammonium salts can be readily detected, in very minute traces, by the addition of Nessler's solution, which gives a distinct yellow colouration in the presence of the slightest trace of ammonia or ammonium salts. The amount of ammonia in ammonium salts can be estimated quantitatively by distillation of the salts with sodium hydroxide, sodium or potassium hydroxide, the ammonia evolved being absorbed in a known volume of standard sulfuric acid and the excess of acid then determined volumetric analysis, volumetrically; or the ammonia may be absorbed in
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestive ...
and the ammonium chloride so formed precipitated as ammonium hexachloroplatinate, (NH4)2PtCl6.


Gaseous ammonia

Sulfur sticks are burnt to detect small leaks in industrial ammonia refrigeration systems. Larger quantities can be detected by warming the salts with a caustic alkali or with calcium oxide, quicklime, when the characteristic smell of ammonia will be at once apparent. Ammonia is an irritant and irritation increases with concentration; the permissible exposure limit is 25 ppm, and lethal above 500 ppm. Higher concentrations are hardly detected by conventional detectors, the type of detector is chosen according to the sensitivity required (e.g. semiconductor, catalytic, electrochemical). Holographic sensors have been proposed for detecting concentrations up to 12.5% in volume.


Ammoniacal nitrogen (NH3-N)

Ammoniacal nitrogen (NH3-N) is a measure commonly used for testing the quantity of
ammonium The ammonium cation is a positively charged polyatomic ion with the chemical formula . It is formed by the protonation of ammonia (NH3). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ammoni ...
ions, derived naturally from ammonia, and returned to ammonia via organic processes, in water or waste liquids. It is a measure used mainly for quantifying values in waste treatment and water purification systems, as well as a measure of the health of natural and man-made water reserves. It is measured in units of mg/L (milligram per litre).


History

The ancient Greek historian Herodotus mentioned that there were outcrops of salt in an area of Libya that was inhabited by a people called the "Ammonians" (now: the Siwa oasis in northwestern Egypt, where salt lakes still exist). The Greek geographer Strabo also mentioned the salt from this region. However, the ancient authors Pedanius Dioscorides, Dioscorides, Apicius, Arrian, Synesius, and Aëtius of Amida described this salt as forming clear crystals that could be used for cooking and that were essentially Halite (mineral), rock salt. ''Hammoniacus sal'' appears in the writings of Pliny the Elder, Pliny, although it is not known whether the term is identical with the more modern sal ammoniac (ammonium chloride). The fermentation of urine by bacteria produces a Ammonia solution, solution of ammonia; hence fermented urine was used in Classical Antiquity to wash cloth and clothing, to remove hair from hides in preparation for tanning, to serve as a mordant in dying cloth, and to remove rust from iron. In the form of sal ammoniac ''(نشادر, nushadir)'', ammonia was important to the Alchemy and chemistry in medieval Islam, Muslim alchemists as early as the 8th century, first mentioned by the Persian-Arab chemist Jābir ibn Hayyān, and to the European Alchemy, alchemists since the 13th century, being mentioned by Albertus Magnus. It was also used by dyers in the Middle Ages in the form of fermented urine to alter the colour of vegetable dyes. In the 15th century, Basilius Valentinus showed that ammonia could be obtained by the action of alkalis on sal ammoniac. At a later period, when sal ammoniac was obtained by distilling the hooves and horns of oxen and neutralizing the resulting carbonate with
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestive ...
, the name "spirit of hartshorn" was applied to ammonia. Gaseous ammonia was first isolated by Joseph Black in 1756 by reacting ''sal ammoniac'' (Ammonium Chloride) with ''calcined magnesia'' (Magnesium Oxide). It was isolated again by Peter Woulfe in 1767, by Carl Wilhelm Scheele in 1770 and by Joseph Priestley in 1773 and was termed by him "alkaline air". Eleven years later in 1785, Claude Louis Berthollet ascertained its composition. The Haber–Bosch process to produce ammonia from the nitrogen in the air was developed by Fritz Haber and Carl Bosch in 1909 and patented in 1910. It was first used on an industrial scale in Germany during World War I, following the allied blockade that cut off the supply of nitrates from Chile. The ammonia was used to produce explosives to sustain war efforts. Before the availability of natural gas, hydrogen as a precursor to ammonia production was produced via the electrolysis of water or using the chloralkali process. With the advent of the steel industry in the 20th century, ammonia became a byproduct of the production of coking coal.


Uses


Fertilizer

In the US as of 2019, approximately 88% of ammonia was used as fertilizers either as its salts, solutions or anhydrously. When applied to soil, it helps provide increased yields of crops such as maize and wheat. 30% of agricultural nitrogen applied in the US is in the form of anhydrous ammonia and worldwide 110 million tonnes are applied each year.


Precursor to nitrogenous compounds

Ammonia is directly or indirectly the precursor to most nitrogen-containing compounds. Virtually all synthetic nitrogen compounds are derived from ammonia. An important derivative is
nitric acid Nitric acid (), also known as ''aqua fortis'' (Latin for "strong water") 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 ...
. This key material is generated via the Ostwald process by oxidation of ammonia with air over a
platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name is derived from the Spanish term ''platino'', meaning "little si ...
catalyst at , ≈9 atm. Nitric oxide is an intermediate in this conversion: Nitric acid is used for the production of
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from li ...
s, explosives, and many organonitrogen compounds. Ammonia is also used to make the following compounds: * Hydrazine, in the Olin Raschig process and the peroxide process * Hydrogen cyanide, in the BMA process and the Andrussow process * Hydroxylamine and ammonium carbonate, in the Raschig hydroxylamine process, Raschig process * Phenol, in the Raschig–Hooker process * Urea, in the Bosch–Meiser urea process and in Wöhler synthesis * Amino acids, using Strecker amino-acid synthesis * Acrylonitrile, in the Sohio process Ammonia can also be used to make compounds in reactions which are not specifically named. Examples of such compounds include: ammonium perchlorate, ammonium nitrate, formamide, dinitrogen tetroxide, alprazolam, ethanolamine, ethyl carbamate, hexamethylenetetramine, and
ammonium bicarbonate Ammonium bicarbonate is an inorganic compound with formula (NH4)HCO3, simplified to NH5CO3. The compound has many names, reflecting its long history. Chemically speaking, it is the bicarbonate salt of the ammonium ion. It is a colourless solid that ...
.


As a cleaner

Household ammonia is a solution of NH3 in water, and is used as a general purpose cleaner for many surfaces. Because ammonia results in a relatively streak-free shine, one of its most common uses is to clean glass, porcelain and stainless steel. It is also frequently used for cleaning ovens and soaking items to loosen baked-on grime. Household ammonia ranges in concentration by weight from 5 to 10% ammonia. United States manufacturers of cleaning products are required to provide the product's material safety data sheet which lists the concentration used. Solutions of ammonia (5–10% by weight) are used as household cleaners, particularly for glass. These solutions are irritating to the eyes and mucous membranes (respiratory and digestive tracts), and to a lesser extent the skin. Caution should be used that the chemical is never mixed into any liquid containing bleach, as a toxic gas may result. Mixing with
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a y ...
-containing products or strong oxidants, such as household bleach, can generate chloramines.


Fermentation

Solutions of ammonia ranging from 16% to 25% are used in the Industrial fermentation, fermentation industry as a source of nitrogen for microorganisms and to adjust pH during fermentation.


Antimicrobial agent for food products

As early as in 1895, it was known that ammonia was "strongly antiseptic ... it requires 1.4 grams per litre to preserve beef tea." In one study, anhydrous ammonia destroyed 99.999% of zoonotic bacteria in 3 types of compound feed, animal feed, but not silage. Anhydrous ammonia is currently used commercially to reduce or eliminate microbial contamination of beef. Lean finely textured beef (popularly known as "pink slime") in the beef industry is made from fatty beef trimmings (c. 50–70% fat) by removing the fat using heat and centrifugation, then treating it with ammonia to kill ''Escherichia coli, E. coli''. The process was deemed effective and safe by the US Department of Agriculture based on a study that found that the treatment reduces ''E. coli'' to undetectable levels. There have been safety concerns about the process as well as consumer complaints about the taste and smell of ammonia-treated beef.


Minor and emerging uses


Refrigeration – R717

Because of ammonia's vaporization properties, it is a useful refrigerant. It was commonly used before the popularisation of chlorofluorocarbons (Freons). Anhydrous ammonia is widely used in industrial refrigeration applications and hockey rinks because of its high Energy conversion efficiency, energy efficiency and low cost. It suffers from the disadvantage of toxicity, and requiring corrosion resistant components, which restricts its domestic and small-scale use. Along with its use in modern vapor-compression refrigeration it is used in a mixture along with hydrogen and water in absorption refrigerators. The Kalina cycle, which is of growing importance to geothermal power plants, depends on the wide boiling range of the ammonia–water mixture. Ammonia coolant is also used in the S1 radiator aboard the International Space Station in two loops which are used to regulate the internal temperature and enable temperature dependent experiments. The potential importance of ammonia as a refrigerant has increased with the discovery that vented CFCs and HFCs are extremely potent and stable greenhouse gases.


For remediation of gaseous emissions

Ammonia is used to scrub SO2 from the burning of fossil fuels, and the resulting product is converted to ammonium sulfate for use as fertilizer. Ammonia neutralizes the nitrogen oxide (NOx) pollutants emitted by diesel engines. This technology, called SCR (selective catalytic reduction), relies on a vanadia-based catalyst. Ammonia may be used to mitigate gaseous spills of phosgene.


As a fuel

The raw energy density of liquid ammonia is 11.5 MJ/L, which is about a third that of diesel fuel, diesel. There is the opportunity to convert ammonia back to hydrogen, where it can be used to power hydrogen fuel cells or it may be used directly within high-temperature solid oxide fuel cell, solid oxide direct ammonia fuel cells to provide efficient power sources that do not emit greenhouse gases. The conversion of ammonia to hydrogen via the sodium amide process, either for combustion or as fuel for a proton exchange membrane fuel cell, is possible. Conversion to hydrogen would allow the storage of hydrogen at nearly 18 Mass fraction (chemistry), wt% compared to ≈5% for gaseous hydrogen under pressure. Ammonia engines or ammonia motors, using ammonia as a working fluid, have been proposed and occasionally used. The principle is similar to that used in a fireless locomotive, but with ammonia as the working fluid, instead of steam or compressed air. Ammonia engines were used experimentally in the 19th century by Goldsworthy Gurney in the UK and the St. Charles Avenue Streetcar line in New Orleans in the 1870s and 1880s, and during World War II ammonia was used to power buses in Belgium. Ammonia is sometimes proposed as a practical alternative to fossil fuel for internal combustion engines. Its high octane rating of 120 and low flame temperature allows the use of high compression ratios without a penalty of high NOx production. Since ammonia contains no carbon, its combustion cannot produce carbon dioxide, carbon monoxide, hydrocarbons, or soot. Even though ammonia production currently creates 1.8% of global CO2 emissions, a 2020 Royal Society report claims that "green" ammonia can be produced by using low-carbon hydrogen (blue hydrogen and green hydrogen). Total decarbonization of ammonia production and the accomplishment of net-zero targets are possible by 2050. However ammonia cannot be easily used in existing Otto cycle engines because of its very narrow #Combustion, flammability range, and there are also other barriers to widespread automobile usage. In terms of raw ammonia supplies, plants would have to be built to increase production levels, requiring significant capital and energy sources. Although it is the second most produced chemical (after sulfuric acid), the scale of ammonia production is a small fraction of world petroleum usage. It could be manufactured from renewable energy sources, as well as coal or nuclear power. The 60 MW Norsk Hydro Rjukan, Rjukan dam in Telemark, Norway produced ammonia for many years from 1913, providing fertilizer for much of Europe. Despite this, several tests have been done. In 1981, a Canadian company converted a 1981 Chevrolet Impala to operate using ammonia as fuel. In 2007, a University of Michigan pickup powered by ammonia drove from Detroit to San Francisco as part of a demonstration, requiring only one fill-up in Wyoming. Compared to hydrogen as a fuel, ammonia is much more energy efficient, and could be produced, stored, and delivered at a much lower cost than hydrogen which must be kept compressed or as a cryogenic liquid. Rocket engines have also been fueled by ammonia. The Reaction Motors XLR99 rocket engine that powered the hypersonic research aircraft used liquid ammonia. Although not as powerful as other fuels, it left no soot in the reusable rocket engine, and its density approximately matches the density of the oxidizer, liquid oxygen, which simplified the aircraft's design. In early August 2018, scientists from Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) announced the success of developing a process to release hydrogen from ammonia and harvest that at ultra-high purity as a fuel for cars. This uses a special membrane. Two demonstration fuel cell vehicles have the technology, a Hyundai Nexo and Toyota Mirai.'Carbon-free fuel': Australian hydrogen car breakthrough could go global
Lexy Hamilton-Smith, ABC News Online, 2018-08-08
In 2020, Saudi Arabia shipped forty metric tons of liquid "blue ammonia" to Japan for use as a fuel. It was produced as a by-product by petrochemical industries, and can be burned without giving off greenhouse gases. Its energy density by volume is nearly double that of liquid hydrogen. If the process of creating it can be scaled up via purely renewable resources, producing green ammonia, it could make a major difference in Climate change mitigation, avoiding climate change. The company ACWA Power and the city of Neom have announced the construction of a green hydrogen and ammonia plant in 2020. Green ammonia is considered as a potential fuel for future container ships. In 2020 the companies DSME and MAN Energy Solutions announced the construction of an ammonia-based ship, DSME plans to commercialize it by 2025.


As a stimulant

Ammonia, as the vapor released by smelling salts, has found significant use as a respiratory stimulant. Ammonia is commonly used in the illegal manufacture of methamphetamine through a Birch reduction. The Birch method of making methamphetamine is dangerous because the alkali metal and liquid ammonia are both extremely reactive, and the temperature of liquid ammonia makes it susceptible to explosive boiling when reactants are added.


Textile

Liquid ammonia is used for treatment of cotton materials, giving properties like mercerisation, using alkalis. In particular, it is used for prewashing of wool.


Lifting gas

At standard temperature and pressure, ammonia is less dense than atmosphere and has approximately 45-48% of the lifting power of hydrogen or helium. Ammonia has sometimes been used to fill weather balloons as a lifting gas. Because of its relatively high boiling point (compared to helium and hydrogen), ammonia could potentially be refrigerated and liquefied aboard an airship to reduce lift and add ballast (and returned to a gas to add lift and reduce ballast).


Woodworking

Ammonia has been used to darken quartersawn white oak in Arts & Crafts and Mission-style furniture. Ammonia fumes react with the natural tannins in the wood and cause it to change colours.


Safety precautions

The U.S. Occupational Safety and Health Administration, Occupational Safety and Health Administration (OSHA) has set a 15-minute exposure limit for gaseous ammonia of 35 ppm by volume in the environmental air and an 8-hour exposure limit of 25 ppm by volume. The National Institute for Occupational Safety and Health (NIOSH) recently reduced the IDLH (Immediately Dangerous to Life and Health, the level to which a healthy worker can be exposed for 30 minutes without suffering irreversible health effects) from 500 to 300 based on recent more conservative interpretations of original research in 1943. Other organizations have varying exposure levels. U.S. Navy Standards [U.S. Bureau of Ships 1962] maximum allowable concentrations (MACs): continuous exposure (60 days): 25 ppm / 1 hour: 400 ppm. Ammonia vapour has a sharp, irritating, pungent odour that acts as a warning of potentially dangerous exposure. The average odour threshold is 5 ppm, well below any danger or damage. Exposure to very high concentrations of gaseous ammonia can result in lung damage and death. Ammonia is regulated in the United States as a non-flammable gas, but it meets the definition of a material that is toxic by inhalation and requires a hazardous safety permit when transported in quantities greater than 13,248 L (3,500 gallons). Liquid ammonia is dangerous because it is hygroscopic and because it can cause caustic burns. See for more information.


Toxicity

The toxicity of ammonia solutions does not usually cause problems for humans and other mammals, as a specific mechanism exists to prevent its build-up in the bloodstream. Ammonia is converted to carbamoyl phosphate by the enzyme carbamoyl phosphate synthetase, and then enters the urea cycle to be either incorporated into amino acids or excreted in the urine. Fish and amphibians lack this mechanism, as they can usually eliminate ammonia from their bodies by direct excretion. Ammonia even at dilute concentrations is highly toxic to aquatic animals, and for this reason it is Directive 67/548/EEC, classified as ''dangerous for the environment''. Ammonia is a constituent of tobacco smoke.


Coking wastewater

Ammonia is present in coking wastewater streams, as a liquid by-product of the production of Coke (fuel), coke from coal. In some cases, the ammonia is discharged to the marine environment where it acts as a pollutant. The Whyalla steelworks in South Australia is one example of a coke-producing facility which discharges ammonia into marine waters.


Aquaculture

Ammonia toxicity is believed to be a cause of otherwise unexplained losses in fish hatcheries. Excess ammonia may accumulate and cause alteration of metabolism or increases in the body pH of the exposed organism. Tolerance varies among fish species. At lower concentrations, around 0.05 mg/L, un-ionised ammonia is harmful to fish species and can result in poor growth and feed conversion rates, reduced fecundity and fertility and increase stress and susceptibility to bacterial infections and diseases. Exposed to excess ammonia, fish may suffer loss of equilibrium, hyper-excitability, increased respiratory activity and oxygen uptake and increased heart rate. At concentrations exceeding 2.0 mg/L, ammonia causes gill and tissue damage, extreme lethargy, convulsions, coma, and death. Experiments have shown that the lethal concentration for a variety of fish species ranges from 0.2 to 2.0 mg/l. During winter, when reduced feeds are administered to aquaculture stock, ammonia levels can be higher. Lower ambient temperatures reduce the rate of algal photosynthesis so less ammonia is removed by any algae present. Within an aquaculture environment, especially at large scale, there is no fast-acting remedy to elevated ammonia levels. Prevention rather than correction is recommended to reduce harm to farmed fish and in open water systems, the surrounding environment.


Storage information

Similar to propane, anhydrous ammonia boils below room temperature when at atmospheric pressure. A storage vessel capable of is suitable to contain the liquid. Ammonia is used in numerous different industrial application requiring carbon or stainless steel storage vessels. Ammonia with at least 0.2 percent by weight water content is not corrosive to carbon steel. NH3 carbon steel construction storage tanks with 0.2 percent by weight or more of water could last more than 50 years in service. Ammonium compounds should never be allowed to come in contact with base (chemistry), bases (unless in an intended and contained reaction), as dangerous quantities of ammonia gas could be released.


Laboratory use of ammonia solutions

The hazards of ammonia solutions depend on the concentration: "dilute" ammonia solutions are usually 5–10% by weight (<5.62 mol/L); "concentrated" solutions are usually prepared at >25% by weight. A 25% (by weight) solution has a density of 0.907 g/cm3, and a solution that has a lower density will be more concentrated. The Directive 67/548/EEC, European Union classification of ammonia solutions is given in the table. The ammonia vapour from concentrated ammonia solutions is severely irritating to the eyes and the respiratory tract, and these solutions should only be handled in a fume hood. Saturated ("0.880" – see #Properties) solutions can develop a significant pressure inside a closed bottle in warm weather, and the bottle should be opened with care; this is not usually a problem for 25% ("0.900") solutions. Ammonia solutions should not be mixed with halogens, as toxic and/or explosive products are formed. Prolonged contact of ammonia solutions with silver, mercury (element), mercury or iodide salts can also lead to explosive products: such mixtures are often formed in qualitative inorganic analysis, and should be lightly acidified but not concentrated (<6% w/v) before disposal once the test is completed.


Laboratory use of anhydrous ammonia (gas or liquid)

Anhydrous ammonia is classified as toxic (T) and dangerous for the environment (N). The gas is flammable (autoignition temperature: 651 °C) and can form explosive mixtures with air (16–25%). The permissible exposure limit (PEL) in the United States is 50 Parts per million, ppm (35 mg/m3), while the IDLH concentration is estimated at 300 ppm. Repeated exposure to ammonia lowers the sensitivity to the smell of the gas: normally the odour is detectable at concentrations of less than 50 ppm, but desensitised individuals may not detect it even at concentrations of 100 ppm. Anhydrous ammonia corrodes copper- and zinc-containing alloys, and so brass fittings should not be used for handling the gas. Liquid ammonia can also attack rubber and certain plastics. Ammonia reacts violently with the halogens. Nitrogen triiodide, a primary explosive, primary high explosive, is formed when ammonia comes in contact with iodine. Ammonia causes the explosive polymerisation of ethylene oxide. It also forms explosive fulminating compounds with compounds of gold, silver, Mercury (element), mercury, germanium or tellurium, and with stibine. Violent reactions have also been reported with acetaldehyde, hypochlorite solutions, potassium ferricyanide and peroxides.


Synthesis and production

Ammonia is one of the most produced inorganic chemicals, with global production reported at 175 million tonnes in 2018. China accounted for 28.5% of that, followed by Russia at 10.3%, the United States at 9.1%, and India at 6.7%. Before the start of World War I, most ammonia was obtained by the dry distillation of nitrogenous vegetable and animal waste products, including camel manure, dung, where it was distillation, distilled by the reduction of nitrous acid and nitrites with hydrogen; in addition, it was produced by the distillation of coal, and also by the decomposition of ammonium salts by alkaline hydroxides such as calcium oxide, quicklime: For small scale laboratory synthesis, one can heat urea and calcium hydroxide:


Haber-Bosch process

Mass production of ammonia mostly uses the Haber process, Haber–Bosch process, a gas phase reaction between hydrogen (H2) and nitrogen (N2) at a moderately-elevated temperature (450 °C) and high pressure (): : \ce \quad \Delta H^\circ = -91.8~\text This reaction is both exothermic and results in decreased entropy, meaning that the Gibbs free energy, reaction is favoured at lower temperatures and higher pressures. This makes it difficult and expensive to achieve, as lower temperatures result in slower reaction kinetics (hence a slower reaction rate) and high pressure requires high-strength pressure vessels that aren't weakened by hydrogen embrittlement. In addition, diatomic nitrogen is bound together by an exceptionally strong triple bond, which makes it rather inert. Both the yield and efficiency of the Haber-Bosch Process are low, meaning that ammonia produced must be continuously separated and extracted for the reaction to proceed at an appreciable pace. Combined with the energy needed to Hydrogen production, produce hydrogen and purified atmospheric nitrogen, ammonia production is a very energy-intensive process, consuming 1 to 2% of global energy, 3% of global carbon emissions, and 3 to 5% of natural gas consumption.


Liquid ammonia as a solvent

Liquid ammonia is the best-known and most widely studied nonaqueous ionising solvent. Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conductive solutions containing solvated electrons. Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions. Comparison of the physical properties of NH3 with those of water shows NH3 has the lower melting point, boiling point, density, viscosity, dielectric constant and electrical conductivity; this is due at least in part to the weaker hydrogen bonding in NH3 and because such bonding cannot form cross-linked networks, since each NH3 molecule has only one lone pair of electrons compared with two for each H2O molecule. The ionic self-dissociation constant of liquid NH3 at −50 °C is about 10−33.


Solubility of salts

Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many nitrates, nitrites, cyanides, thiocyanates, Cyclopentadienyl complex, metal cyclopentadienyl complexes and metal bis(trimethylsilyl)amides. Most ammonium salts are soluble and act as acids in liquid ammonia solutions. The solubility of halide salts increases from fluoride to iodide. A saturated solution of ammonium nitrate (Divers' solution, named after Edward Divers) contains 0.83 mol solute per mole of ammonia and has a vapour pressure of less than 1 bar even at .


Solutions of metals

Liquid ammonia will dissolve all of the alkali metals and other electronegativity, electropositive metals such as calcium, Ca, strontium, Sr, barium, Ba, europium, Eu, and ytterbium, Yb (also magnesium, Mg using an electrolytic process). At low concentrations (<0.06 mol/L), deep blue solutions are formed: these contain metal cations and solvated electrons, free electrons that are surrounded by a cage of ammonia molecules. These solutions are very useful as strong reducing agents. At higher concentrations, the solutions are metallic in appearance and in electrical conductivity. At low temperatures, the two types of solution can coexist as Wiktionary:immiscible, immiscible phases.


Redox properties of liquid ammonia

The range of thermodynamic stability of liquid ammonia solutions is very narrow, as the potential for oxidation to dinitrogen, Standard electrode potential, ''E''° (N2 + 6NH4+ + 6e ⇌ 8NH3), is only +0.04 V. In practice, both oxidation to dinitrogen and reduction to dihydrogen are slow. This is particularly true of reducing solutions: the solutions of the alkali metals mentioned above are stable for several days, slowly decomposing to the Amide, metal amide and dihydrogen. Most studies involving liquid ammonia solutions are done in reducing conditions; although oxidation of liquid ammonia is usually slow, there is still a risk of explosion, particularly if transition metal ions are present as possible catalysts.


Ammonia's role in biological systems and human disease

Ammonia is both a metabolic waste and a metabolic input throughout the biosphere. It is an important source of nitrogen for living systems. Although atmospheric nitrogen abounds (more than 75%), few living creatures are capable of using this atmospheric nitrogen in its diatomic form, N2 gas. Therefore, nitrogen fixation is required for the synthesis of amino acids, which are the building blocks of protein. Some plants rely on ammonia and other nitrogenous wastes incorporated into the soil by decaying matter. Others, such as nitrogen-fixing legumes, benefit from symbiosis, symbiotic relationships with rhizobia that create ammonia from atmospheric nitrogen.


Biosynthesis

In certain organisms, ammonia is produced from atmospheric nitrogen by enzymes called nitrogenases. The overall process is called nitrogen fixation. Intense effort has been directed toward understanding the mechanism of biological nitrogen fixation; the scientific interest in this problem is motivated by the unusual structure of the active site of the enzyme, which consists of an Fe7MoS9 ensemble. Ammonia is also a metabolic product of amino acid deamination catalyzed by enzymes such as Glutamate dehydrogenase 1#Function, glutamate dehydrogenase 1. Ammonia excretion is common in aquatic animals. In humans, it is quickly converted to urea, which is much less toxic, particularly less #Basicity, basic. This urea is a major component of the dry weight of urine. Most reptiles, birds, insects, and snails excrete uric acid solely as nitrogenous waste.


In physiology

Ammonia also plays a role in both normal and abnormal animal physiology. It is biosynthesised through normal amino acid metabolism and is toxic in high concentrations. The liver converts ammonia to urea through a series of reactions known as the urea cycle. Liver dysfunction, such as that seen in cirrhosis, may lead to elevated amounts of ammonia in the blood (hyperammonemia). Likewise, defects in the enzymes responsible for the urea cycle, such as ornithine transcarbamylase, lead to hyperammonemia. Hyperammonemia contributes to the confusion and coma of hepatic encephalopathy, as well as the neurologic disease common in people with urea cycle defects and organic acidurias. Ammonia is important for normal animal acid/base balance. After formation of ammonium from glutamine, α-ketoglutarate may be degraded to produce two bicarbonate ions, which are then available as buffers for dietary acids. Ammonium is excreted in the urine, resulting in net acid loss. Ammonia may itself diffuse across the renal tubules, combine with a hydrogen ion, and thus allow for further acid excretion.


Excretion

Ammonium ions are a Toxicity, toxic waste product of metabolism in animals. In fish and aquatic invertebrates, it is excreted directly into the water. In mammals, sharks, and amphibians, it is converted in the urea cycle to urea, because it is less toxic and can be stored more efficiently. In birds, reptiles, and terrestrial snails, metabolic ammonium is converted into uric acid, which is solid, and can therefore be excreted with minimal water loss.


In astronomy

Ammonia has been detected in the atmospheres of the giant planets, including
Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined. Jupiter is the th ...

Jupiter
, along with other gases like methane, hydrogen, and helium. The interior of Saturn may include frozen crystals of ammonia. It is naturally found on Deimos (moon), Deimos and Phobos (moon), Phobos – the two moons of Mars.


Interstellar space

Ammonia was first detected in interstellar space in 1968, based on
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges ...
emissions from the direction of the Milky Way, galactic core. This was the first polyatomic molecule to be so detected. The sensitivity of the molecule to a broad range of excitations and the ease with which it can be observed in a number of regions has made ammonia one of the most important molecules for studies of molecular clouds. The relative intensity of the ammonia lines can be used to measure the temperature of the emitting medium. The following isotopic species of ammonia have been detected: The detection of triply deuterium, deuterated ammonia was considered a surprise as deuterium is relatively scarce. It is thought that the low-temperature conditions allow this molecule to survive and accumulate. Since its interstellar discovery, NH3 has proved to be an invaluable spectroscopic tool in the study of the interstellar medium. With a large number of transitions sensitive to a wide range of excitation conditions, NH3 has been widely astronomically detected – its detection has been reported in hundreds of journal articles. Listed below is a sample of journal articles that highlights the range of detectors that have been used to identify ammonia. The study of interstellar ammonia has been important to a number of areas of research in the last few decades. Some of these are delineated below and primarily involve using ammonia as an interstellar thermometer.


Interstellar formation mechanisms

The interstellar abundance for ammonia has been measured for a variety of environments. The [NH3]/[H2] ratio has been estimated to range from 10−7 in small dark clouds up to 10−5 in the dense core of the Orion Molecular Cloud Complex. Although a total of 18 total production routes have been proposed, the principal formation mechanism for interstellar NH3 is the reaction: The rate constant, ''k'', of this reaction depends on the temperature of the environment, with a value of 5.2×10−6 at 10 K. The rate constant was calculated from the formula . For the primary formation reaction, and . Assuming an NH4+ abundance of 3×10−7 and an electron abundance of 10−7 typical of molecular clouds, the formation will proceed at a rate of in a molecular cloud of total density . All other proposed formation reactions have rate constants of between 2 and 13 orders of magnitude smaller, making their contribution to the abundance of ammonia relatively insignificant. As an example of the minor contribution other formation reactions play, the reaction: has a rate constant of 2.2. Assuming H2 densities of 105 and [NH2]/[H2] ratio of 10−7, this reaction proceeds at a rate of 2.2, more than 3 orders of magnitude slower than the primary reaction above. Some of the other possible formation reactions are:


Interstellar destruction mechanisms

There are 113 total proposed reactions leading to the destruction of NH3. Of these, 39 were tabulated in extensive tables of the chemistry among C, N, and O compounds. A review of interstellar ammonia cites the following reactions as the principal dissociation mechanisms: with rate constants of 4.39×10−9 and 2.2×10−9, respectively. The above equations (, ) run at a rate of 8.8×10−9 and 4.4×10−13, respectively. These calculations assumed the given rate constants and abundances of [NH3]/[H2] = 10−5, [H3+]/[H2] = 2×10−5, [HCO+]/[H2] = 2×10−9, and total densities of ''n'' = 105, typical of cold, dense, molecular clouds. Clearly, between these two primary reactions, equation () is the dominant destruction reaction, with a rate ≈10,000 times faster than equation (). This is due to the relatively high abundance of H3+.


Single antenna detections

Radio observations of NH3 from the Effelsberg 100-m Radio Telescope reveal that the ammonia line is separated into two components – a background ridge and an unresolved core. The background corresponds well with the locations previously detected CO. The 25 m Chilbolton telescope in England detected radio signatures of ammonia in H II regions, HNH2O masers, H-H objects, and other objects associated with star formation. A comparison of emission line widths indicates that turbulent or systematic velocities do not increase in the central cores of molecular clouds. Microwave radiation from ammonia was observed in several galactic objects including W3(OH), Orion (constellation), Orion A, W43, W51, and five sources in the galactic centre. The high detection rate indicates that this is a common molecule in the interstellar medium and that high-density regions are common in the galaxy.


Interferometric studies

Very Large Array, VLA observations of NH3 in seven regions with high-velocity gaseous outflows revealed condensations of less than 0.1 Parsec, pc in L1551, S140, and Cepheus (constellation), Cepheus A. Three individual condensations were detected in Cepheus A, one of them with a highly elongated shape. They may play an important role in creating the bipolar outflow in the region. Extragalactic ammonia was imaged using the VLA in IC 342. The hot gas has temperatures above 70 K, which was inferred from ammonia line ratios and appears to be closely associated with the innermost portions of the nuclear bar seen in CO. NH3 was also monitored by VLA toward a sample of four galactic ultracompact HII regions: G9.62+0.19, G10.47+0.03, G29.96-0.02, and G31.41+0.31. Based upon temperature and density diagnostics, it is concluded that in general such clumps are probably the sites of massive star formation in an early evolutionary phase prior to the development of an ultracompact HII region.


Infrared detections

Absorption at 2.97 micrometres due to solid ammonia was recorded from interstellar grains in the Becklin-Neugebauer Object and probably in NGC 2264-IR as well. This detection helped explain the physical shape of previously poorly understood and related ice absorption lines. A spectrum of the disk of Jupiter was obtained from the Kuiper Airborne Observatory, covering the 100 to 300 cm−1 spectral range. Analysis of the spectrum provides information on global mean properties of ammonia gas and an ammonia ice haze. A total of 149 dark cloud positions were surveyed for evidence of 'dense cores' by using the (J,K) = (1,1) rotating inversion line of NH3. In general, the cores are not spherically shaped, with aspect ratios ranging from 1.1 to 4.4. It is also found that cores with stars have broader lines than cores without stars. Ammonia has been detected in the Draco (constellation), Draco Nebula and in one or possibly two molecular clouds, which are associated with the high-latitude galactic infrared cirrus. The finding is significant because they may represent the birthplaces for the Population I metallicity B-type stars in the galactic halo that could have been borne in the galactic disk.


Observations of nearby dark clouds

By balancing and stimulated emission with spontaneous emission, it is possible to construct a relation between excitation temperature and density. Moreover, since the transitional levels of ammonia can be approximated by a 2-level system at low temperatures, this calculation is fairly simple. This premise can be applied to dark clouds, regions suspected of having extremely low temperatures and possible sites for future star formation. Detections of ammonia in dark clouds show very narrow linesindicative not only of low temperatures, but also of a low level of inner-cloud turbulence. Line ratio calculations provide a measurement of cloud temperature that is independent of previous CO observations. The ammonia observations were consistent with CO measurements of rotation temperatures of ≈10 K. With this, densities can be determined, and have been calculated to range between 104 and 105 cm−3 in dark clouds. Mapping of NH3 gives typical clouds sizes of 0.1 Parsec, pc and masses near 1 solar mass. These cold, dense cores are the sites of future star formation.


UC HII regions

Ultra-compact HII regions are among the best tracers of high-mass star formation. The dense material surrounding UCHII regions is likely primarily molecular. Since a complete study of massive star formation necessarily involves the cloud from which the star formed, ammonia is an invaluable tool in understanding this surrounding molecular material. Since this molecular material can be spatially resolved, it is possible to constrain the heating/ionising sources, temperatures, masses, and sizes of the regions. Doppler-shifted velocity components allow for the separation of distinct regions of molecular gas that can trace outflows and hot cores originating from forming stars.


Extragalactic detection

Ammonia has been detected in external galaxies, and by simultaneously measuring several lines, it is possible to directly measure the gas temperature in these galaxies. Line ratios imply that gas temperatures are warm (≈50 K), originating from dense clouds with sizes of tens of pc. This picture is consistent with the picture within our Milky Way galaxyhot dense molecular cores form around newly forming stars embedded in larger clouds of molecular material on the scale of several hundred pc (giant molecular clouds; GMCs).


See also

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Notes


References


Works Cited

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Further reading

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External links


International Chemical Safety Card 0414
(anhydrous ammonia), ilo.org.

(aqueous solutions), ilo.org. * *
Emergency Response to Ammonia Fertilizer Releases (Spills)
for the Minnesota Department of Agriculture.ammoniaspills.org
National Institute for Occupational Safety and Health – Ammonia Page
cdc.gov

cdc.gov
Ammonia, video
{{Nitrides Ammonia, Inorganic amines, Bases (chemistry) Gaseous signaling molecules Household chemicals Industrial gases Inorganic solvents Nitrogen cycle Nitrogen hydrides Nitrogen(−III) compounds Refrigerants Toxicology Foul-smelling chemicals