Ammonia: Difference between revisions

Ammonia

Names
IUPAC name Ammonia [1]
Systematic IUPAC name Azane
Other names Hydrogen nitride R-717 (refrigerant) R717 (refrigerant alternative spelling)
Identifiers
CAS Number	7664-41-7 Y
3D model ( JSmol )	Interactive image
3DMet	B00004
Beilstein Reference	3587154
ChEBI	CHEBI:16134 Y
ChEMBL	ChEMBL1160819 Y
ChemSpider	217 Y
ECHA InfoCard	100.028.760
EC Number	231-635-3
Gmelin Reference	79
KEGG	D02916 Y
MeSH	Ammonia
PubChem CID	222
RTECS number	BO0875000
UNII	5138Q19F1X Y
UN number	1005
CompTox Dashboard (EPA)	DTXSID0023872
InChI InChI=1S/H3N/h1H3 Y Key: QGZKDVFQNNGYKY-UHFFFAOYSA-N Y InChI=1/H3N/h1H3 Key: QGZKDVFQNNGYKY-UHFFFAOYAF
SMILES N
Properties
Chemical formula	NH3
Molar mass	17.031 g/mol
Appearance	Colourless gas
Odor	strong pungent odour
Density	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) 681.9 kg/m3 at −33.3 °C (liquid)[3] See also Ammonia (data page) 817 kg/m3 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)
Solubility in water	47% w/w (0 °C) 31% w/w (25 °C) 18% w/w (50 °C)[5]
Solubility	soluble in chloroform, ether, ethanol, methanol
Vapor pressure	857.3 kPa
Acidity (pKa)	32.5 (−33 °C),[6] 10.5 (DMSO)
Basicity (pKb)	4.75
Conjugate acid	Ammonium
Conjugate base	Amide
Magnetic susceptibility (χ)	−18.0·10−6 cm3/mol
Refractive index (nD)	1.3327
Viscosity	10.07 µPa·s (25 °C)[7] 0.276 mPa·s (−40 °C)
Structure
Point group	C3v
Molecular shape	Trigonal pyramid
Dipole moment	1.42 D
Thermochemistry
Std molar entropy (S⦵298)	193 J·mol−1·K−1[8]
Std enthalpy of formation (ΔfH⦵298)	−46 kJ·mol−1[8]
Hazards
GHS labelling:
Pictograms	[9]
Signal word	Danger
Hazard statements	H290, H301, H311, H314, H330, H334, H336, H360, H362, H373, H400
Precautionary statements	P202, P221, P233, P261, P263, P271, P273, P280, P305+P351+P338, P310[9]
NFPA 704 (fire diamond)	3 1 0 COR
Flash point	132
Autoignition temperature	651 °C (1,204 °F; 924 K)
Explosive limits	15–28%
Lethal dose or concentration (LD, LC):
LD50 (median dose)	0.015 mL/kg (human, oral)
LC50 (median concentration)	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]
LCLo (lowest published)	5000 ppm (mammal, 5 min) 5000 ppm (human, 5 min)[10]
NIOSH (US health exposure limits):[11]
PEL (Permissible)	50 ppm (25 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
Other cations	Phosphine Arsine Stibine Bismuthine
Related nitrogen hydrides	Hydrazine Hydrazoic acid
Related compounds	Ammonium hydroxide
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). Y verify (what is YN ?) Infobox references

Ammonia is a

Although common in nature—both terrestrially and in the

Pliny, in Book XXXI of his Natural History, refers to a salt produced in the Roman province of Cyrenaica named hammoniacum, so called because of its proximity to the nearby Temple of Jupiter Amun (Greek Ἄμμων Ammon).^[17] However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride. According to Herbert Hoover's commentary in his English translation of Georgius Agricola's De re metallica, it is likely to have been common sea salt.^[18] In any case, that salt ultimately gave ammonia and ammonium 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

Ammonia is also found throughout the Solar System on Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, among other places: on smaller, icy bodies 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 173 K (−100 °C; −148 °F) 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.^[21][22] Substances containing ammonia, or those that are similar to it, are called ammoniacal.

Properties

Ammonia is a colourless

Ammonia may be conveniently deodorized by reacting it with either sodium bicarbonate or acetic acid. Both of these reactions form an odourless ammonium salt.

Solid

The crystal symmetry is cubic, Pearson symbol cP16, space group P2₁3 No.198, lattice constant 0.5125 nm.^[23]

Liquid

ε of 22. Liquid ammonia has a very high standard enthalpy change of vaporization (23.35 kJ/mol, cf. water 40.65 kJ/mol, methane 8.19 kJ/mol, 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

saturated solution) has a density

of 0.880 g/cm³ and is often known as '.880 ammonia'.

Combustion

Ammonia does not burn readily or sustain combustion, except under narrow fuel-to-air mixtures of 15–25% air. When mixed with oxygen, it burns with a pale yellowish-green flame. Ignition occurs when chlorine is passed into ammonia, forming nitrogen and hydrogen chloride; if chlorine is present in excess, then the highly explosive 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 5.5 kcal/mol of ammonia, and yields hydrogen and nitrogen gas. Ammonia can also be used as a source of hydrogen for acid fuel cells if the unreacted ammonia can be removed. Ruthenium and Platinum catalysts were found to be the most active, whereas supported Ni catalysts were the less active.

Structure

The ammonia molecule has a

The salts produced by the action of ammonia on acids are known as the ammonium salts and all contain the ammonium ion (NH₄⁺).^[26]

Although ammonia is well known as a weak base, it can also act as an extremely weak acid. It is a protic substance and is capable of formation of amides (which contain the NH₂⁻ ion). For example, lithium dissolves in liquid ammonia to give a solution of lithium amide:

Self-dissociation

Like water, liquid ammonia undergoes

Ammonia often functions as a weak base, so it has some buffering ability. Shifts in pH will cause more or fewer ammonium cations (NH⁺
₄) and amide anions (NH⁻
₂) to be present in solution. At standard pressure and temperature, K=[NH⁺
₄][NH⁻
₂] = 10⁻³⁰

Combustion

The combustion of ammonia to nitrogen and water is

The

The combustion of ammonia in air is very difficult in the absence of a catalyst (such as platinum 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 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.^[28] The flammable range of ammonia in dry air is 15.15%-27.35% and in 100% relative humidity air is 15.95%-26.55%.^[29] For studying the kinetics of ammonia combustion a detailed reliable reaction mechanism is required, however knowledge about ammonia chemical kinetics during combustion process has been challenging.^[30]

Formation of other compounds

In

The hydrogen in ammonia is susceptible to replacement by myriad substituents. When heated with sodium it converts to sodamide, NaNH₂.^[26] 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.^[31]

Ammonia as a ligand

Ammonia can act as a

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 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 is still rare. One example is the Calomel reaction, where the resulting amidomercury(II) compound is highly insoluble.

Ammonia forms 1:1 adducts with a variety of Lewis acids such as I₂, phenol, and Al(CH₃)₃. Ammonia is a hard base and its E & C parameters are E_B = 2.31 and C _B = 2.04. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by 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

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 quicklime, when the characteristic smell of ammonia will be at once apparent.^[34] Ammonia is an irritant and irritation increases with concentration; the permissible exposure limit is 25 ppm, and lethal above 500 ppm.^[35] 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.^[36]

Ammoniacal nitrogen (NH₃-N)

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.^[13] When applied to soil, it helps provide increased yields of crops such as maize and wheat.^[56] 30% of agricultural nitrogen applied in the US is in the form of anhydrous ammonia and worldwide 110 million tonnes are applied each year.^[57]

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 is used for the production of fertilizers, 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 process
• Phenol, in the Raschig–Hooker process
• Bosch–Meiser urea process and in Wöhler synthesis
• Strecker amino-acid synthesis
• 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.

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.

Solutions of ammonia ranging from 16% to 25% are used in the 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

Because of ammonia's vaporization properties, it is a useful refrigerant.^[54] 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 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.^[68][69]

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.^[70]

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 (NO_x) pollutants emitted by diesel engines. This technology, called SCR (

Ammonia may be used to mitigate gaseous spills of phosgene.^[72]

As a fuel

Even though ammonia production currently creates 1.8% of global CO2 emissions, a 2020 Royal Society report[84] 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 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 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.^[85][86] 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.^[87]

Compared to

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.^[95] 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.^[96]

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.^[97]

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.^[98]

Safety precautions

The U.S. 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.^[100] 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.^[101] 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.^[100] 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).^[102]

Liquid ammonia is dangerous because it is

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.^[103] 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 classified as dangerous for the environment.

Ammonia is a constituent of tobacco smoke.^[104]

Coking wastewater

Ammonia is present in coking wastewater streams, as a liquid by-product of the production of

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.[107] 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.^[108] Exposed to excess ammonia, fish may suffer loss of equilibrium, hyper-excitability, increased respiratory activity and oxygen uptake and increased heart rate.^[107] At concentrations exceeding 2.0 mg/L, ammonia causes gill and tissue damage, extreme lethargy, convulsions, coma, and death.^[107][109] Experiments have shown that the lethal concentration for a variety of fish species ranges from 0.2 to 2.0 mg/l.^[109]

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^[109] 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 250 psi (1.7 MPa) is suitable to contain the liquid.^[110] 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.^[111] Ammonium compounds should never be allowed to come in contact with bases (unless in an intended and contained reaction), as dangerous quantities of ammonia gas could be released.

Household use

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-containing products or strong oxidants, such as household bleach, can generate chloramines.^[112]

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 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 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 (

Ammonia reacts violently with the halogens.

Ammonia is one of the most produced inorganic chemicals, with global production reported at 175 million tonnes in 2018.^[13] China accounted for 28.5% of that, followed by Russia at 10.3%, the United States at 9.1%, and India at 6.7%.^[13]

Before the start of

For small scale laboratory synthesis, one can heat urea and calcium hydroxide:

Haber-Bosch process

Mass production of ammonia mostly uses the

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

Solubility of salts

Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many

Solutions of metals

Liquid ammonia will dissolve all of the alkali metals and other electropositive metals such as Ca,^[127] Sr, Ba, Eu, and Yb (also Mg using an electrolytic process^[128]). 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 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, 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 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 symbiotic relationships with rhizobia that create ammonia from atmospheric nitrogen.^[130]

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.^[131]

Ammonia is also a metabolic product of amino acid deamination catalyzed by enzymes such as 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 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

Ammonium ions are a 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.^[134]

Reference ranges for blood tests, comparing blood content of ammonia (shown in yellow near middle) with other constituents

In astronomy

Ammonia has been detected in the atmospheres of the giant planets, including Jupiter, along with other gases like methane, hydrogen, and helium. The interior of Saturn may include frozen crystals of ammonia.^[135] It is naturally found on Deimos and Phobos – the two moons of Mars.

Interstellar space

Ammonia was first detected in interstellar space in 1968, based on

The following isotopic species of ammonia have been detected:

The detection of triply 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.^[138]

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

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.[142] The rate constant was calculated from the formula ${\displaystyle k=a(T/300)^{B}}$. For the primary formation reaction, a = 1.05×10⁻⁶ and B = −0.47. 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 1.6×10⁻⁹ cm⁻³s⁻¹ in a molecular cloud of total density 10⁵ cm⁻³.^[143]

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.^[144] As an example of the minor contribution other formation reactions play, the reaction:

has a rate constant of 2.2×10⁻¹⁵. Assuming H₂ densities of 10⁵ and [NH₂]/[H₂] ratio of 10⁻⁷, this reaction proceeds at a rate of 2.2×10⁻¹², 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.^[145] A review of interstellar ammonia cites the following reactions as the principal dissociation mechanisms:^[137]

with rate constants of 4.39×10^−9[146] and 2.2×10⁻⁹,^[147] respectively. The above equations (1, 2) 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.^[148] Clearly, between these two primary reactions, equation (1) is the dominant destruction reaction, with a rate ≈10,000 times faster than equation (2). 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.^[149] 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.^[150]

Microwave radiation from ammonia was observed in several galactic objects including W3(OH), 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.^[151]

Interferometric studies

VLA observations of NH₃ in seven regions with high-velocity gaseous outflows revealed condensations of less than 0.1 pc in L1551, S140, and 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.^[152]

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.^[153] 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.^[154]

Infrared detections

Absorption at 2.97 micrometres due to solid ammonia was recorded from interstellar grains in the

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.^[156]

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.^[157]

Ammonia has been detected in the 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.^[158]

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 lines—indicative 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 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,^[159][160] 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 galaxy—hot 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

• Ammonia (data page) – Chemical data page
• Ammonia fountain – Type of chemical demonstration
• Ammonia production – Overview of history and methods to produce NH₃
• Ammonia solution – Chemical compound
• Cost of electricity by source – Comparison of costs of different electricity generation sources
• Forming gas – Mixture of hydrogen and nitrogen
• Haber process – Industrial process for ammonia production
• Hydrazine – Colorless flammable liquid with an ammonia-like odor
• Water purification – Process of removing impurities from water

Notes

References

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34. ^ ^{a b} Chisholm 1911, p. 863.
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37. ^ Herodotus with George Rawlinson, trans., The History of Herodotus (New York, New York: Tandy-Thomas Co., 1909), vol.2, Book 4, § 181, pp. 304–305.
38. ^ The land of the Ammonians is mentioned elsewhere in Herodotus' History and in Pausanias' Description of Greece:
    • Herodotus with George Rawlinson, trans., The History of Herodotus (New York, New York: Tandy-Thomas Co., 1909), vol. 1, Book 2, § 42, p. 245, vol. 2, Book 3, § 25, p. 73, and vol. 2, Book 3, § 26, p. 74.
    • Pausanias with W.H.S. Jones, trans., Description of Greece (London, England: William Heinemann Ltd., 1979), vol. 2, Book 3, Ch. 18, § 3, pp. 109 and 111 and vol. 4, Book 9, Ch. 16, § 1, p. 239.
39. ^ Kopp, Hermann, Geschichte der Chemie [History of Chemistry] (Braunschweig, (Germany): Friedrich Vieweg und Sohn, 1845), Part 3, p. 237. [in German]
40. ^ Chisholm 1911 cites Pliny Nat. Hist. xxxi. 39. See: Pliny the Elder with John Bostock and H. T. Riley, ed.s, The Natural History (London, England: H. G. Bohn, 1857), vol. 5, Book 31, § 39, p. 502.
41. ^ "Sal-ammoniac". Webmineral. Retrieved 7 July 2009.
42. ^ Pliny also mentioned that when some samples of what was purported to be natron (Latin: nitrum, impure sodium carbonate) were treated with lime (calcium carbonate) and water, the natron would emit a pungent smell, which some authors have interpreted as signifying that the natron either was ammonium chloride or was contaminated with it. See:
    • Pliny with W.H.S. Jones, trans., Natural History (London, England: William Heinemann Ltd., 1963), vol. 8, Book 31, § 46, pp. 448–449. From pp. 448–449: "Adulteratur in Aegypto calce, deprehenditur gusto. Sincerum enim statim resolvitur, adulteratum calce pungit et asperum [or aspersum] reddit odorem vehementer." (In Egypt it [i.e., natron] is adulterated with lime, which is detected by taste; for pure natron melts at once, but adulterated natron stings because of the lime, and emits a strong, bitter odour [or: when sprinkled [(aspersum) with water] emits a vehement odour])
    • Kidd, John, Outlines of Mineralogy (Oxford, England: N. Bliss, 1809), vol. 2, p. 6.
    • Moore, Nathaniel Fish, Ancient Mineralogy: Or, An Inquiry Respecting Mineral Substances Mentioned by the Ancients: ... (New York, New York: G. & C. Carvill & Co., 1834), pp. 96–97.
43. ^ See:
    • Forbes, R.J., Studies in Ancient Technology, vol. 5, 2nd ed. (Leiden, Netherlands: E.J. Brill, 1966), pp. 19, 48, and 65.
    • Moeller, Walter O., The Wool Trade of Ancient Pompeii (Leiden, Netherlands: E.J. Brill, 1976), p. 20.
    • Faber, G.A. (pseudonym of: Goldschmidt, Günther) (May 1938) "Dyeing and tanning in classical antiquity," Ciba Review, 9 : 277–312. Available at: Elizabethan Costume
    • Smith, William, A Dictionary of Greek and Roman Antiquities (London, England: John Murray, 1875), article: "Fullo" (i.e., fullers or launderers), pp. 551–553.
    • Rousset, Henri (31 March 1917) "The laundries of the Ancients," Scientific American Supplement, 83 (2152) : 197.
    • Bond, Sarah E., Trade and Taboo: Disreputable Professions in the Roman Mediterranean (Ann Arbor, Michigan: University of Michigan Press, 2016), p. 112.
    • Binz, Arthur (1936) "Altes und Neues über die technische Verwendung des Harnes" (Ancient and modern [information] about the technological use of urine), Zeitschrift für Angewandte Chemie, 49 (23) : 355–360. [in German]
    • Witty, Michael (December 2016) "Ancient Roman urine chemistry," Acta Archaeologica, 87 (1) : 179–191. Witty speculates that the Romans obtained ammonia in concentrated form by adding wood ash (impure potassium carbonate) to urine that had been fermented for several hours. Struvite (magnesium ammonium phosphate) is thereby precipitated, and the yield of struvite can be increased by then treating the solution with bittern, a magnesium-rich solution that is a byproduct of making salt from sea water. Roasting struvite releases ammonia vapors.
44. ISBN 978-0-7923-3254-1
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45. ^ Spiritus salis urinæ (spirit of the salt of urine, i.e., ammonium carbonate) had apparently been produced before Valentinus, although he presented a new, simpler method for preparing it in his book: Valentinus, Basilius, Vier Tractätlein Fr. Basilii Valentini ... [Four essays of Brother Basil Valentine ... ] (Frankfurt am Main, (Germany): Luca Jennis, 1625), "Supplementum oder Zugabe" (Supplement or appendix), pp. 80–81: "Der Weg zum Universal, damit die drei Stein zusammen kommen." (The path to the Universal, so that the three stones come together.). From p. 81: "Der Spiritus salis Urinæ nimbt langes wesen zubereiten / dieser proceß aber ist waß leichter unnd näher auß dem Salz von Armenia, ... Nun nimb sauberen schönen Armenischen Salz armoniac ohn alles sublimiren / thue ihn in ein Kolben / giesse ein Oleum Tartari drauff / daß es wie ein Muß oder Brey werde / vermachs baldt / dafür thu auch ein grosen vorlag / so lege sich als baldt der Spiritus Salis Urinæ im Helm an Crystallisch ... " (Spirit of the salt of urine [i.e., ammonium carbonate] requires a long method [i.e., procedure] to prepare; this [i.e., Valentine's] process [starting] from the salt from Armenia [i.e., ammonium chloride], however, is somewhat easier and shorter ... Now take clean nice Armenian salt, without sublimating all [of it]; put it in a [distillation] flask; pour oil of tartar [i.e., potassium carbonate that has dissolved only in the water that it has absorbed from the air] on it, [so] that it [i.e., the mixture] becomes like a mush or paste; assemble it [i.e., the distilling apparatus (alembic)] quickly; for that [purpose] connect a large receiving flask; then soon spirit of the salt of urine deposits as crystals in the "helmet" [i.e., the outlet for the vapors, which is atop the distillation flask] ...)
    See also: Kopp, Hermann, Geschichte der Chemie [History of Chemistry] (Braunschweig, (Germany): Friedrich Vieweg und Sohn, 1845), Part 3, p. 243. [in German]
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    • Priestley, Joseph, Experiments and Observations on Different Kinds of Air, vol. 1, 2nd ed. (London, England: 1775), Part 2, § 1: Observations on Alkaline Air, pp. 163–177.
    • Schofield, Robert E., The Enlightened Joseph Priestley: A Study of His Life and Work from 1773 to 1804 (University Park, Pennsylvania: Pennsylvania State University Press, 2004), pp. 93–94.
    • By 1775, Priestley had observed that electricity could decompose ammonia ("alkaline air"), yielding a flammable gas (hydrogen). See: Priestley, Joseph, Experiments and Observations on Different Kinds of Air, vol. 2 (London, England: J. Johnson, 1775), pp. 239–240.
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118. ^ See (Clark 2013): "Notice that there are 4 molecules on the left-hand side of the equation, but only 2 on the right. According to Le Chatelier's Principle, if you increase the pressure the system will respond by favouring the reaction which produces fewer molecules. That will cause the pressure to fall again. In order to get as much ammonia as possible in the equilibrium mixture, you need as high a pressure as possible. 200 atmospheres is a high pressure, but not amazingly high".
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Works Cited

• "Aqua Ammonia". airgasspecialtyproducts.com. Archived from the original on 19 November 2010. Retrieved 28 November 2010.
•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Ammonia". Encyclopædia Britannica. Vol. 1 (11th ed.). Cambridge University Press. pp. 861–863.
• Clark, Jim (April 2013) [2002]. "THE HABER PROCESS". Retrieved 15 December 2018.{{cite web}}: CS1 maint: ref duplicates default (link)

Further reading

• Bretherick, L., ed. (1986). Hazards in the Chemical Laboratory (4th ed.). London: Royal Society of Chemistry.
  OCLC 16985764
  .
• ISBN 978-0-08-037941-8
  .
• Housecroft, C. E.; Sharpe, A. G. (2000). Inorganic Chemistry (1st ed.). New York: Prentice Hall.
  ISBN 978-0-582-31080-3
  .
• Weast, R. C., ed. (1972). Handbook of Chemistry and Physics (53rd ed.). Cleveland, OH: Chemical Rubber Co.

External links

Wikimedia Commons has media related to Ammonia.

• International Chemical Safety Card 0414 (anhydrous ammonia), ilo.org.
• International Chemical Safety Card 0215 (aqueous solutions), ilo.org.
• CID 222 from PubChem
• "Ammoniac et solutions aqueuses" (in French). Institut National de Recherche et de Sécurité. Archived from the original on 11 December 2010.
• 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
• NIOSH Pocket Guide to Chemical Hazards – Ammonia, cdc.gov
• Ammonia, video