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André-Marie Ampère | Table of Content | Short description, Biography, Early life, French Revolution, Teaching career, Work in electromagnetism, Honours, Legacy, Writings, References, Further reading, External links |
Ammonia | Short description | Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula . A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. Biologically, it is a common nitrogenous waste, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers. Around 70% of ammonia produced industrially is used to make fertilisers in various forms and composition, such as urea and diammonium phosphate. Ammonia in pure form is also applied directly into the soil.
Ammonia, either directly or indirectly, is also a building block for the synthesis of many chemicals.
Ammonia occurs in nature and has been detected in the interstellar medium. In many countries, it is classified as an extremely hazardous substance.
Ammonia is toxic, causing damage to cells and tissues. For this reason it is excreted by most animals in the urine, in the form of dissolved urea.
Ammonia is produced biologically in a process called nitrogen fixation, but even more is generated industrially by the Haber process. The process helped revolutionize agriculture by providing cheap fertilizers. The global industrial production of ammonia in 2021 was 235 million tonnes. Industrial ammonia is transported by road in tankers, by rail in tank wagons, by sea in gas carriers, or in cylinders.
Ammonia boils at at a pressure of one atmosphere, but the liquid can often be handled in the laboratory without external cooling. Household ammonia or ammonium hydroxide is a solution of ammonia in water. |
Ammonia | Etymology | Etymology
Pliny, in Book XXXI of his Natural History, refers to a salt named hammoniacum, so called because of the proximity of its source to the Temple of Jupiter Amun (Greek Ἄμμων Ammon) in the Roman province of Cyrenaica. 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. In any case, that salt ultimately gave ammonia and ammonium compounds their name. |
Ammonia | Natural occurrence (abiological) | Natural occurrence (abiological)
Traces of ammonia/ammonium are found in rainwater. Ammonium chloride (sal ammoniac), and ammonium sulfate are found in volcanic districts. Crystals of ammonium bicarbonate have been found in Patagonia guano.
Ammonia is 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 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.Shannon, Francis Patrick (1938) Tables of the properties of aqua–ammonia solutions. Part 1 of The Thermodynamics of Absorption Refrigeration. Lehigh University studies. Science and technology seriesAn ammonia–water slurry may swirl below Pluto's icy surface. Purdue University (9 November 2015) Substances containing ammonia, or those that are similar to it, are called ammoniacal. |
Ammonia | Properties | Properties
Ammonia is a colourless gas with a characteristically pungent smell. It is lighter than air, its density being 0.589 times that of air. It is easily liquefied due to the strong hydrogen bonding between molecules. Gaseous ammonia turns to a colourless liquid, which boils at , and freezes to colourless crystals at . Little data is available at very high temperatures and pressures, but the liquid-vapor critical point occurs at 405 K and 11.35 MPa. |
Ammonia | Solid | Solid
The crystal symmetry is cubic, Pearson symbol cP16, space group P213 No.198, lattice constant 0.5125 nm. |
Ammonia | Liquid | Liquid
Liquid ammonia possesses strong ionising powers reflecting its high ε of 22 at . Liquid ammonia has a very high standard enthalpy change of vapourization (23.5 kJ/mol; for comparison, water's is 40.65 kJ/mol, methane 8.19 kJ/mol and phosphine 14.6 kJ/mol) and can be transported in pressurized or refrigerated vessels; however, at standard temperature and pressure liquid anhydrous ammonia will vaporize. |
Ammonia | Solvent properties | Solvent properties
Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic, and may be described as aqueous ammonia or ammonium hydroxide. The maximum concentration of ammonia in water (a saturated solution) has a specific gravity of 0.880 and is often known as '.880 ammonia'.
+Thermal and physical properties of saturated liquid ammoniaTemperature(°C)Density(kg/m3)Specific heat(kJ/(kg·K))Kinematicviscosity(m2/s)Thermalconductivity(W/(m·K))Thermaldiffusivity(m2/s)PrandtlNumberBulk modulus(K−1) −50703.694.4634.35×10−70.5471.74×10−72.6 −40691.684.4674.06×10−70.5471.78×10−72.28 −30679.344.4763.87×10−70.5491.80×10−72.15 −20666.694.5093.81×10−70.5471.82×10−72.09 −10653.554.5643.78×10−70.5431.83×10−72.070640.14.6353.73×10−70.5401.82×10−72.0510626.164.7143.68×10−70.5311.80×10−72.0420611.754.7983.59×10−70.5211.78×10−72.022.45×10−330596.374.893.49×10−70.5071.74×10−72.0140580.994.9993.40×10−70.4931.70×10−7250564.335.1163.30×10−70.4761.65×10−71.99
+Thermal and physical properties of ammonia () at atmospheric pressureTemperature(K)Temperature (°C)Density(kg/m3)Specific heat(kJ/(kg·K))Dynamicviscosity(kg/(m·s))Kinematicviscosity(m2/s)Thermalconductivity(W/(m·K))Thermaldiffusivity(m2/s)PrandtlNumber273 −0.150.79292.1779.35×10−61.18×10−50.02201.31×10−50.9032349.850.64872.1771.10×10−51.70×10−50.02701.92×10−50.8837399.850.5592.2361.29×10−51.30×10−50.03272.62×10−50.87423149.850.49342.3151.47×10−52.97×10−50.03913.43×10−50.87473199.850.44052.3951.65×10−53.74×10−50.04674.42×10−50.84480206.850.42732.431.67×10−53.90×10−50.04924.74×10−50.822500226.850.41012.4671.73×10−54.22×10−50.05255.19×10−50.813520246.850.39422.5041.80×10−54.57×10−50.05455.52×10−50.827540266.850.37952.541.87×10−54.91×10−50.05755.97×10−50.824560286.850.37082.5771.93×10−55.20×10−50.06066.34×10−50.827580306.850.35332.6132.00×10−55.65×10−50.06386.91×10−50.817
Liquid ammonia is a 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 with those of water shows has the lower melting point, boiling point, density, viscosity, dielectric constant and electrical conductivity. These differences are attributed at least in part to the weaker hydrogen bonding in . The ionic self-dissociation constant of liquid at −50 °C is about 10−33.
thumb|A train carrying anhydrous ammonia
Solubility (g of salt per 100 g liquid ) Ammonium acetate 253.2 Ammonium nitrate 389.6 Lithium nitrate 243.7 Sodium nitrate 97.6 Potassium nitrate 10.4 Sodium fluoride 0.35 Sodium chloride 157.0 Sodium bromide 138.0 Sodium iodide 161.9 Sodium thiocyanate 205.5
Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many nitrates, nitrites, cyanides, thiocyanates, 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 . However, few oxyanion salts with other cations dissolve.
Liquid ammonia will dissolve all of the alkali metals and other electropositive metals such as Ca, Sr, Ba, Eu and Yb (also 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 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. |
Ammonia | Redox properties of liquid ammonia | Redox properties of liquid ammonia
thumb|upright|Liquid ammonia bottle
E° (V, ammonia) E° (V, water) −2.24 −3.04 −1.98 −2.93 −1.85 −2.71 −0.53 −0.76 0.00 — +0.43 +0.34 +0.83 +0.80
The range of thermodynamic stability of liquid ammonia solutions is very narrow, as the potential for oxidation to dinitrogen, E° (), 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 | Structure | Structure
thumb|Molecular structure of ammonia and its three-dimensional shape. It has a net dipole moment of 1.484 D.
class=skin-invert-image|thumb|Dot and cross structure of ammonia
The ammonia molecule has a trigonal pyramidal shape, as predicted by the valence shell electron pair repulsion theory (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. Three of these electron pairs are used as bond pairs, which leaves one lone pair 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 moment and makes it polar. The molecule's polarity, and especially its ability to form hydrogen bonds, makes ammonia highly miscible with water. The lone pair makes ammonia a base, a proton acceptor. Ammonia is moderately basic; a 1.0 M aqueous solution has a pH of 11.6, and if a strong acid is added to such a solution until the solution is neutral (), 99.4% of the ammonia molecules are protonated. Temperature and salinity also affect the proportion of ammonium . The latter has the shape of a regular tetrahedron and is isoelectronic with methane.
The ammonia molecule readily undergoes nitrogen inversion at room temperature; a useful analogy is an umbrella turning itself inside out in a strong wind. The energy barrier to this inversion is 24.7 kJ/mol, and the resonance frequency is 23.79 GHz, corresponding to microwave radiation of a wavelength of 1.260 cm. The absorption at this frequency was the first microwave spectrum to be observed and was used in the first maser. |
Ammonia | Amphotericity | Amphotericity
One of the most characteristic properties of ammonia is its basicity. Ammonia is considered to be a weak base. It combines with acids to form ammonium salts; thus, with hydrochloric acid it forms ammonium chloride (sal ammoniac); with nitric acid, ammonium nitrate, etc. Perfectly dry ammonia gas will not combine with perfectly dry hydrogen chloride 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 solutions produce a cloud of ammonium chloride, which seems to appear 'out of nothing' as the salt aerosol forms where the two diffusing clouds of reagents meet between the two bottles.
The salts produced by the action of ammonia on acids are known as the ammonium salts and all contain the ammonium ion ().
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 ion). For example, lithium dissolves in liquid ammonia to give a blue solution (solvated electron) of lithium amide: |
Ammonia | Self-dissociation | Self-dissociation
Like water, liquid ammonia undergoes molecular autoionisation to form its acid and base conjugates:
Ammonia often functions as a weak base, so it has some buffering ability. Shifts in pH will cause more or fewer ammonium cations () and amide anions () to be present in solution. At standard pressure and temperature, |
Ammonia | Combustion | Combustion
thumb|right|Heated Cr2O3 catalyzes the combustion of a flask of ammonia.
Ammonia does not burn readily or sustain combustion, except under narrow fuel-to-air mixtures of 15–28% ammonia by volume in 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 () is also formed.
The combustion of ammonia to form nitrogen and water is exothermic:
The standard enthalpy change of combustion, ΔH°c, expressed per mole of ammonia and with condensation of the water formed, is −382.81 kJ/mol. Dinitrogen is the thermodynamic product of combustion: all nitrogen oxides are unstable with respect to and , which is the principle behind the catalytic converter. Nitrogen oxides can be formed as kinetic products in the presence of appropriate catalysts, a reaction of great industrial importance in the production of nitric acid:
A subsequent reaction leads to :
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 vapourization, 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. 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 kinetics of ammonia combustion, knowledge of a detailed reliable reaction mechanism is required, but this has been challenging to obtain. |
Ammonia | Precursor to organonitrogen compounds | Precursor to organonitrogen compounds
Ammonia is a direct or indirect precursor to most manufactured nitrogen-containing compounds. It is the precursor to nitric acid, which is the source for most N-substituted aromatic compounds.
Amines can be formed by the reaction of ammonia with alkyl halides or, more commonly, with alcohols:
Its ring-opening reaction with ethylene oxide give ethanolamine, diethanolamine, and triethanolamine.
Amides can be prepared by the reaction of ammonia with carboxylic acid and their derivatives. For example, ammonia reacts with formic acid (HCOOH) to yield formamide () when heated. Acyl chlorides are the most reactive, but the ammonia must be present in at least a twofold excess to neutralise the hydrogen chloride formed. Esters and anhydrides also react with ammonia to form amides. Ammonium salts of carboxylic acids can be dehydrated to amides by heating to 150–200 °C as long as no thermally sensitive groups are present.
Amino acids, using Strecker amino-acid synthesis
Acrylonitrile, in the Sohio process
Other organonitrogen compounds include alprazolam, ethanolamine, ethyl carbamate and hexamethylenetetramine. |
Ammonia | Precursor to inorganic nitrogenous compounds | Precursor to inorganic nitrogenous compounds
Nitric acid is generated via the Ostwald process by oxidation of ammonia with air over a platinum catalyst at , ≈9 atm. Nitric oxide and nitrogen dioxide are intermediate in this conversion:
Nitric acid is used for the production of fertilisers, explosives, and many organonitrogen compounds.
The hydrogen in ammonia is susceptible to replacement by a myriad substituents.
Ammonia gas reacts with metallic sodium to give sodamide, .
With chlorine, monochloramine is formed.
Pentavalent ammonia is known as λ5-amine, nitrogen pentahydride decomposes spontaneously into trivalent ammonia (λ3-amine) and hydrogen gas at normal conditions. This substance was once investigated as a possible solid rocket fuel in 1966.
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
Urea, in the Bosch–Meiser urea process and in Wöhler synthesis
ammonium perchlorate, ammonium nitrate, and ammonium bicarbonate
class=skin-invert-image|thumb|Cisplatin () is a widely used anticancer drug.|upright=0.6
Ammonia is a ligand forming metal ammine complexes. For historical reasons, ammonia is named ammine in the nomenclature of coordination compounds. One notable ammine complex is cisplatin (, a widely used anticancer drug. Ammine complexes of chromium(III) 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 could be formed, and concluded the ligands must be arranged around the metal ion at the vertices of an octahedron.
Ammonia forms 1:1 adducts with a variety of Lewis acids such as , phenol, and . Ammonia is a hard base (HSAB theory) and its E & C parameters are EB = 2.31 and CB = 2.04. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots. |
Ammonia | Detection and determination | Detection and determination |
Ammonia | Ammonia in solution | 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 (NaOH) or potassium hydroxide (KOH), the ammonia evolved being absorbed in a known volume of standard sulfuric acid and the excess of acid then determined volumetrically; or the ammonia may be absorbed in hydrochloric acid and the ammonium chloride so formed precipitated as ammonium hexachloroplatinate, . |
Ammonia | Gaseous ammonia | 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 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 by volume.(OSHA) Source: Sax, N. Irving (1984) Dangerous Properties of Industrial Materials. 6th Ed. Van Nostrand Reinhold. . 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.
In a laboratorial setting, gaseous ammonia can be detected by using concentrated hydrochloric acid or gaseous hydrogen chloride. A dense white fume (which is ammonium chloride vapor) arises from the reaction between ammonia and HCl(g). |
Ammonia | Ammoniacal nitrogen (NH<sub>3</sub>–N) | Ammoniacal nitrogen (NH3–N)
Ammoniacal nitrogen (NH3–N) is a measure commonly used for testing the quantity of ammonium 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). |
Ammonia | History | History
thumb|upright|Jabir ibn Hayyan wrote about ammonia in the 9th century
thumb|upright|This high-pressure ammonia reactor was built in 1921 by BASF in Ludwigshafen and was re-erected on the premises of the University of Karlsruhe in Germany.
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).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.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. The Greek geographer Strabo also mentioned the salt from this region. However, the ancient authors 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 rock salt.Kopp, Hermann, Geschichte der Chemie [History of Chemistry] (Braunschweig, (Germany): Friedrich Vieweg und Sohn, 1845), Part 3, p. 237. [in German] Hammoniacus sal appears in the writings of Pliny, 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. although it is not known whether the term is equivalent to the more modern sal ammoniac (ammonium chloride).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.
The fermentation of urine by bacteria produces a 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 dyeing cloth, and to remove rust from iron.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 vapours. It was also used by ancient dentists to wash teeth.
In the form of sal ammoniac (نشادر, nushadir), ammonia was important to the Muslim alchemists. It was mentioned in the Book of Stones, likely written in the 9th century and attributed to Jābir ibn Hayyān. It was also important to the European alchemists of 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.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 vapours, 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] 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, 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'.See:
Priestley, Joseph (1773) "Extrait d'une lettre de M. Priestley, en date du 14 Octobre 1773" (Extract of a letter from Mr. Priestley, dated 14 October 1773), Observations sur la Physique ..., 2 : 389.
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. Eleven years later in 1785, Claude Louis Berthollet ascertained its composition.Berthollet (1785) "Analyse de l'alkali volatil" (Analysis of volatile alkali), Mémoires de l'Académie Royale des Sciences, 316–326.
The production of ammonia from nitrogen in the air (and hydrogen) was invented by Fritz Haber and Robert LeRossignol. The patent was sent in 1909 (USPTO Nr 1,202,995) and awarded in 1916. Later, Carl Bosch developed the industrial method for ammonia production (Haber–Bosch process). 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. The Nobel Prize in Chemistry 1918 was awarded to Fritz Haber "for the synthesis of ammonia from its elements".
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. |
Ammonia | Applications | Applications |
Ammonia | Fertiliser | Fertiliser
In the US , approximately 88% of ammonia was used as fertilisers 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.
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. |
Ammonia | Refrigeration–R717 | Refrigeration–R717
Because of ammonia's vapourization 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 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 vapour-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 radiators aboard the International Space Station in loops that are used to regulate the internal temperature and enable temperature-dependent experiments. The ammonia is under sufficient pressure to remain liquid throughout the process. Single-phase ammonia cooling systems also serve the power electronics in each pair of solar arrays.
The potential importance of ammonia as a refrigerant has increased with the discovery that vented CFCs and HFCs are potent and stable greenhouse gases. |
Ammonia | Antimicrobial agent for food products | 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 (broth).' In one study, anhydrous ammonia destroyed 99.999% of zoonotic bacteria in three types of animal feed, but not silage. Anhydrous ammonia is currently used commercially to reduce or eliminate microbial contamination of beef."Evaluation of Treatment Methods for Reducing Bacteria in Textured Beef", Jensen, Jean L et al., American Society of Agricultural and Biological Engineers Annual Meeting 2009Reference Document: Antimicrobial Interventions for Beef, Dawna Winkler and Kerri B. Harris, Center for Food Safety, Department of Animal Science, Texas A&M University, May 2009, page 12
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 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. |
Ammonia | Fuel | Fuel
thumb|Ammoniacal Gas Engine Streetcar in New Orleans drawn by Alfred Waud in 1871
Ammonia has been used as fuel, and is a proposed alternative to fossil fuels and hydrogen. Being liquid at ambient temperature under its own vapour pressure and having high volumetric and gravimetric energy density, ammonia is considered a suitable carrier for hydrogen, and may be cheaper than direct transport of liquid hydrogen.
Compared to hydrogen, ammonia is easier to store. 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. The raw energy density of liquid ammonia is 11.5 MJ/L, which is about a third that of diesel.
Ammonia can be converted back to hydrogen to be used to power hydrogen fuel cells, or it may be used directly within high-temperature solid oxide direct ammonia fuel cells to provide efficient power sources that do not emit greenhouse gases. Ammonia to hydrogen conversion can be achieved through the sodium amide process or the catalytic decomposition of ammonia using solid catalysts.
thumb|The X-15 aircraft used ammonia as one component fuel of its rocket engine
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 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. However, ammonia cannot be easily used in existing Otto cycle engines because of its very narrow flammability range. Despite this, several tests have been run. Its high octane rating of 120 and low flame temperature allows the use of high compression ratios without a penalty of high production. Since ammonia contains no carbon, its combustion cannot produce carbon dioxide, carbon monoxide, hydrocarbons, or soot.
Ammonia production currently creates 1.8% of global emissions. 'Green ammonia' is ammonia produced by using green hydrogen (hydrogen produced by electrolysis with electricity from renewable energy), whereas 'blue ammonia' is ammonia produced using blue hydrogen (hydrogen produced by steam methane reforming) where the carbon dioxide has been captured and stored.
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 oxidiser, liquid oxygen, which simplified the aircraft's design.
In 2020, Saudi Arabia shipped 40 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 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. The use of ammonia as a potential alternative fuel for aircraft jet engines is also being explored.
Japan intends to implement a plan to develop ammonia co-firing technology that can increase the use of ammonia in power generation, as part of efforts to assist domestic and other Asian utilities to accelerate their transition to carbon neutrality.
In October 2021, the first International Conference on Fuel Ammonia (ICFA2021) was held.
In June 2022, IHI Corporation succeeded in reducing greenhouse gases by over 99% during combustion of liquid ammonia in a 2,000-kilowatt-class gas turbine achieving truly -free power generation.
In July 2022, Quad nations of Japan, the U.S., Australia and India agreed to promote technological development for clean-burning hydrogen and ammonia as fuels at the security grouping's first energy meeting. , however, significant amounts of are produced. Nitrous oxide may also be a problem as it is a "greenhouse gas that is known to possess up to 300 times the Global Warming Potential (GWP) of carbon dioxide".
The IEA forecasts that ammonia will meet approximately 45% of shipping fuel demands by 2050.
At high temperature and in the presence of a suitable catalyst ammonia decomposes into its constituent elements. Decomposition of ammonia is a slightly endothermic process requiring 23 kJ/mol (5.5 kcal/mol) of ammonia, and yields hydrogen and nitrogen gas. |
Ammonia | Other | Other |
Ammonia | Remediation of gaseous emissions | Remediation of gaseous emissions
Ammonia is used to scrub from the burning of fossil fuels, and the resulting product is converted to ammonium sulfate for use as fertiliser. Ammonia neutralises the nitrogen oxide () 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. |
Ammonia | Stimulant | Stimulant
thumb|Anti-meth sign on tank of anhydrous ammonia, Otley, Iowa. Anhydrous ammonia is a common farm fertiliser that is also a critical ingredient in making methamphetamine. In 2005, Iowa used grant money to provide thousands of locks to prevent criminals from gaining access to the tanks.
Ammonia, as the vapour 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. |
Ammonia | Textile | 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. |
Ammonia | Lifting gas | 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 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). |
Ammonia | Fuming | Fuming
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 colour.Fuming white oak. woodweb.com |
Ammonia | Safety | Safety
thumb|upright|The world's longest ammonia pipeline (roughly 2400 km long),minerals year book, vol. 3 running from the TogliattiAzot plant in Russia to Odesa in Ukraine
The US 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 or Health, the level to which a healthy worker can be exposed for 30 minutes without suffering irreversible health effects) from 500 to 300 ppm based on recent more conservative interpretations of original research in 1943. Other organisations have varying exposure levels. US Navy Standards [U.S. Bureau of Ships 1962] maximum allowable concentrations (MACs): for continuous exposure (60 days) is 25 ppm; for exposure of 1 hour is 400 ppm.Ammonia, IDLH Documentation
Ammonia vapour has a sharp, irritating, pungent odor that acts as a warning of potentially dangerous exposure. The average odor 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 US 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 .Is Anhydrous Ammonia covered under the Hazardous Materials Safety Permit Program? from the website of the United States Department of Transportation (DOT)
Liquid ammonia is dangerous because it is hygroscopic and because it can cause caustic burns. See for more information. |
Ammonia | Toxicity | 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 classified as "dangerous for the environment". Atmospheric ammonia plays a key role in the formation of fine particulate matter.
Ammonia is a constituent of tobacco smoke. |
Ammonia | Coking wastewater | Coking wastewater
Ammonia is present in coking wastewater streams, as a liquid by-product of the production of 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 that discharges ammonia into marine waters. |
Ammonia | Aquaculture | 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. |
Ammonia | Storage information | 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.Electronic Code of Federal Regulations: . Ecfr.gpoaccess.gov. Retrieved on 22 December 2011. Ammonia is used in numerous different industrial applications requiring carbon or stainless steel storage vessels. Ammonia with at least 0.2% by weight water content is not corrosive to carbon steel. carbon steel construction storage tanks with 0.2% by weight or more of water could last more than 50 years in service. Experts warn that ammonium compounds not be allowed to come in contact with bases (unless in an intended and contained reaction), as dangerous quantities of ammonia gas could be released. |
Ammonia | Laboratory | Laboratory
thumb|155px|A standard laboratory solution of 28% ammonia
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.
Concentrationby weight (w/w) Molarity Concentrationmass/volume (w/v) GHS pictograms H-phrases 5–10% 2.87–5.62 mol/L 48.9–95.7 g/L 10–25% 5.62–13.29 mol/L 95.7–226.3 g/L >25% >13.29 mol/L >226.3 g/L
The ammonia vapour from concentrated ammonia solutions is severely irritating to the eyes and the respiratory tract, and experts warn that these solutions only be handled in a fume hood. Saturated ('0.880'–see ) solutions can develop a significant pressure inside a closed bottle in warm weather, and experts also warn that the bottle be opened with care. This is not usually a problem for 25% ('0.900') solutions.
Experts warn that ammonia solutions not be mixed with halogens, as toxic and/or explosive products are formed. Experts also warn that 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 that it needs to be lightly acidified but not concentrated (<6% w/v) before disposal once the test is completed. |
Ammonia | Laboratory use of anhydrous ammonia (gas or liquid) | 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 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, which makes brass fittings not appropriate for handling the gas. Liquid ammonia can also attack rubber and certain plastics.
Ammonia reacts violently with the halogens. Nitrogen triiodide, a 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, germanium or tellurium, and with stibine. Violent reactions have also been reported with acetaldehyde, hypochlorite solutions, potassium ferricyanide and peroxides. |
Ammonia | Production | Production
Ammonia has one of the highest rates of production of any inorganic chemical. Production is sometimes expressed in terms of 'fixed nitrogen'. Global production was estimated as being 160 million tonnes in 2020 (147 tons of fixed nitrogen). China accounted for 26.5% of that, followed by Russia at 11.0%, the United States at 9.5%, and India at 8.3%.
Before the start of World War I, most ammonia was obtained by the dry distillation of nitrogenous vegetable and animal waste products, including camel dung, where it was 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 quicklime:
For small scale laboratory synthesis, one can heat urea and calcium hydroxide or sodium hydroxide: |
Ammonia | Haber–Bosch | Haber–Bosch |
Ammonia | Electrochemical | Electrochemical
The electrochemical synthesis of ammonia involves the reductive formation of lithium nitride, which can be protonated to ammonia, given a proton source. The first use of this chemistry was reported in 1930, where lithium solutions in ethanol were used to produce ammonia at pressures of up to 1000 bar, with ethanol acting as the proton source. Beyond simply mediating proton transfer to the nitrogen reduction reaction, ethanol has been found to play a multifaceted role, influencing electrolyte transformations and contributing to the formation of the solid electrolyte interphase, which enhances overall reaction efficiency.
In 1994, Tsuneto et al. used lithium electrodeposition in tetrahydrofuran to synthesize ammonia at more moderate pressures with reasonable Faradaic efficiency. Subsequent studies have further explored the ethanol–tetrahydrofuran system for electrochemical ammonia synthesis.
In 2020, a solvent-agnostic gas diffusion electrode was shown to improve nitrogen transport to the reactive lithium. production rates of up to and Faradaic efficiencies of up to 47.5 ± 4% at ambient temperature and 1 bar pressure were achieved.
In 2021, it was demonstrated that ethanol could be replaced with a tetraalkyl phosphonium salt. The study observed production rates of at 69 ± 1% Faradaic efficiency experiments under 0.5 bar hydrogen and 19.5 bar nitrogen partial pressure at ambient temperature. Technology based on this electrochemistry is being developed for commercial fertiliser and fuel production.
In 2022, ammonia was produced via the lithium mediated process in a continuous-flow electrolyzer also demonstrating the hydrogen gas as proton source. The study synthesized ammonia at 61 ± 1% Faradaic efficiency at a current density of −6 mA/cm2 at 1 bar and room temperature. |
Ammonia | Biochemistry and medicine | Biochemistry and medicine
thumb|upright=1.15|Main symptoms of hyperammonemia (ammonia reaching toxic concentrations).
Ammonia is essential for life. For example, it is required for the formation of amino acids and nucleic acids, fundamental building blocks of life. Ammonia is however quite toxic. Nature thus uses carriers for ammonia. Within a cell, glutamate serves this role. In the bloodstream, glutamine is a source of ammonia.
Ethanolamine, required for cell membranes, is the substrate for ethanolamine ammonia-lyase, which produces ammonia:
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 atmospheric nitrogen in its diatomic form, 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 bacteria that create ammonia from atmospheric nitrogen.
In humans, inhaling ammonia in high concentrations can be fatal. Exposure to ammonia can cause headaches, edema, impaired memory, seizures and coma as it is neurotoxic in nature.Identifying the direct effects of ammonia on the brain – PubMed |
Ammonia | Biosynthesis | 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 ensemble.
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 (by liver), 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. |
Ammonia | Physiology | Physiology
Ammonia 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 neurological 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. |
Ammonia | Excretion | Excretion
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, which 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. |
Ammonia | Extraterrestrial occurrence | Extraterrestrial occurrence
thumb|Ammonia occurs in the atmospheres of the outer giant planets such as Jupiter (0.026% ammonia), Saturn (0.012% ammonia), and in the atmospheres and ices of Uranus and Neptune.
Ammonia has been detected in the atmospheres of the giant planets Jupiter, Saturn, Uranus and Neptune, along with other gases such as methane, hydrogen, and helium. The interior of Saturn may include frozen ammonia crystals.Edited by Kirk Munsell. Image page credit Lunar and Planetary Institute. NASA. "NASA's Solar Exploration: Multimedia: Gallery: Gas Giant Interiors ". Retrieved 26 April 2006. It is found on Deimos and Phobos–the two moons of Mars. |
Ammonia | Interstellar space | Interstellar space
Ammonia was first detected in interstellar space in 1968, based on microwave emissions from the direction of the 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: ,, , , and . 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.
Since its interstellar discovery, 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, 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. |
Ammonia | Interstellar formation mechanisms | Interstellar formation mechanisms
The interstellar abundance for ammonia has been measured for a variety of environments. The []/[] 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 is the reaction:
The rate constant, k, of this reaction depends on the temperature of the environment, with a value of at 10 K. The rate constant was calculated from the formula . For the primary formation reaction, and . Assuming an abundance of 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 two 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 densities of 105 and []/[] ratio of 10−7, this reaction proceeds at a rate of 2.2, more than three orders of magnitude slower than the primary reaction above.
Some of the other possible formation reactions are: |
Ammonia | Interstellar destruction mechanisms | Interstellar destruction mechanisms
There are 113 total proposed reactions leading to the destruction of . 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 []/[] = 10−5, []/[] = 2×10−5, []/[] = 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 . |
Ammonia | Single antenna detections | Single antenna detections
Radio observations of 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 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. |
Ammonia | Interferometric studies | Interferometric studies
VLA observations of 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.
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. 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. |
Ammonia | Infrared detections | 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 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. |
Ammonia | Observations of nearby dark clouds | 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 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. |
Ammonia | UC HII regions | 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. |
Ammonia | Extragalactic detection | 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 parsecs. 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 parsecs (giant molecular clouds; GMCs). |
Ammonia | See also | See also
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Ammonia | References | References |
Ammonia | Works cited | Works cited
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Ammonia | Further reading | Further reading
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Ammonia | External links | External links
International Chemical Safety Card 0414 (anhydrous ammonia), ilo.org.
International Chemical Safety Card 0215 (aqueous solutions), ilo.org.
Emergency Response to Ammonia Fertiliser 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
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Ammonia | Table of Content | Short description, Etymology, Natural occurrence (abiological), Properties, Solid, Liquid, Solvent properties, Redox properties of liquid ammonia, Structure, Amphotericity, Self-dissociation, Combustion, Precursor to organonitrogen compounds, Precursor to inorganic nitrogenous compounds, Detection and determination, Ammonia in solution, Gaseous ammonia, Ammoniacal nitrogen (NH<sub>3</sub>–N), History, Applications, Fertiliser, Refrigeration–R717, Antimicrobial agent for food products, Fuel, Other, Remediation of gaseous emissions, Stimulant, Textile, Lifting gas, Fuming, Safety, Toxicity, Coking wastewater, Aquaculture, Storage information, Laboratory, Laboratory use of anhydrous ammonia (gas or liquid), Production, Haber–Bosch, Electrochemical, Biochemistry and medicine, Biosynthesis, Physiology, Excretion, Extraterrestrial occurrence, Interstellar space, Interstellar formation mechanisms, Interstellar destruction mechanisms, Single antenna detections, Interferometric studies, Infrared detections, Observations of nearby dark clouds, UC HII regions, Extragalactic detection, See also, References, Works cited, Further reading, External links |
Amethyst | Short description | Amethyst is a violet variety of quartz. The name comes from the Koine Greek from - , "not" and (Ancient Greek) / (Modern Greek), "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. Ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxication.
Amethyst, a semiprecious stone, is often used in jewelry. |
Amethyst | Structure | Structure
Amethyst is a violet variety of quartz () and owes its violet color to irradiation, impurities of iron () and in some cases other transition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions.
The irradiation causes the iron ions that replace Si in the lattice to lose an electron and form a color center.
Amethyst is a three-dimensional network of tetrahedra where the silicon atoms are in the center and are surrounded by four oxygen atoms located at the vertices of a tetrahedron. This structure is quite rigid and results in quartz's hardness and resistance to weathering. The hardness of the mineral is the same as quartz, thus making it suitable for use in jewelry. |
Amethyst | Hue and tone | Hue and tone
Amethyst occurs in primary hues from a light lavender or pale violet to a deep purple. Amethyst may exhibit one or both secondary hues, red and blue.
High-quality amethyst can be found in Siberia, Sri Lanka, Brazil, Uruguay, and the Far East. The ideal grade, called "Deep Siberian", has a primary purple hue of around 75–80%, with 15–20% blue and (depending on the light source) red secondary hues.
"Rose de France" is defined by its markedly light shade of the purple, reminiscent of a lavender / lilac shade. These pale colors were once considered undesirable, but have recently become popular due to intensive marketing.
Green quartz is sometimes called green amethyst; the scientific name is prasiolite.
Other names for green quartz are vermarine and lime citrine.
Amethyst frequently shows color zoning, with the most intense color typically found at the crystal terminations. One of gem cutters' tasks is to make a finished product with even color. Sometimes, only a thin layer of a natural, uncut amethyst is violet colored, or the color is very uneven. The uncut gem may have only a small portion that is suitable for faceting.
The color of amethyst has been demonstrated to result from substitution by irradiation of trivalent iron (Fe3+) for silicon in the structure, in the presence of trace elements of large ionic radius, and to a certain extent, the amethyst color can naturally result from displacement of transition elements even if the iron concentration is low. Natural amethyst is dichroic in reddish violet and bluish violet, but when heated, turns yellow-orange, yellow-brown, or dark brownish and may resemble citrine, but loses its dichroism, unlike genuine citrine. When partially heated, amethyst can result in ametrine.
Amethyst can fade in tone if overexposed to light sources, and can be artificially darkened with adequate irradiation. It does not fluoresce under either short-wave or long-wave UV light. |
Amethyst | Geographic distribution | Geographic distribution
Amethyst is found in many locations around the world. Between 2000 and 2010, the greatest production was from Marabá and Pau d'Arco, Pará, and the Paraná Basin, Rio Grande do Sul, Brazil; Sandoval, Santa Cruz, Bolivia; Artigas, Uruguay; Kalomo, Zambia; and Thunder Bay, Ontario. Lesser amounts are found in many other locations in Africa, Brazil, Spain, Argentina, Russia, Afghanistan, South Korea, Mexico, and the United States.
thumb|Main amethyst-producing countries
thumb|A 3.7 meters tall, 4 ton amethyst geode on display at the American Museum of Natural History collected from Artigas, Uruguay.
Amethyst is produced in abundance in the state of Rio Grande do Sul in Brazil where it occurs in large geodes within volcanic rocks.
Many of the hollow agates of southwestern Brazil and Uruguay contain a crop of amethyst crystals in the interior. Artigas, Uruguay and neighboring Brazilian state Rio Grande do Sul are large world producers, with lesser quantities mined in Minas Gerais and Bahia states.
thumb|left|An amethyst geode that formed when large crystals grew in open spaces inside the rock
Amethyst is also found and mined in South Korea. The large opencast amethyst vein at Maissau, Lower Austria, was historically important, but is no longer included among significant producers. Much fine amethyst comes from Russia, especially near Mursinka in the Ekaterinburg district, where it occurs in drusy cavities in granitic rocks. Amethyst was historically mined in many localities in south India, though these are no longer significant producers. One of the largest global amethyst producers is Zambia in southern Africa, with an annual production around 1000 tons.
Amethyst occurs at many localities in the United States. The most important production is at Four Peaks, Gila and Maricopa Counties, Arizona, and Jackson's Crossroads, Wilkes County, Georgia.
Smaller occurrences have been reported in the Red Feather Lakes, near Fort Collins, Colorado; Amethyst Mountain, Texas; Yellowstone National Park; Delaware County, Pennsylvania; Haywood County, North Carolina; Deer Hill and Stow, Maine, and in the Lake Superior region of Minnesota, Wisconsin, and Michigan.
Amethyst is relatively common in the Canadian provinces of Ontario and Nova Scotia. The largest amethyst mine in North America is located in Thunder Bay, Ontario.
Amethyst is the official state gemstone of South Carolina. Several South Carolina amethysts are on display at the Smithsonian Museum of Natural History. |
Amethyst | History | History
Amethyst was used as a gemstone by the ancient Egyptians and was largely employed in antiquity for intaglio engraved gems. — Castellani was a 19th century Italian jeweler, now famous
The ancient Greeks believed amethyst gems could prevent intoxication,
while medieval European soldiers wore amethyst amulets as protection in battle in the belief that amethysts heal people and keep them cool-headed.
Beads of amethyst were found in Anglo-Saxon graves in England.
Anglican bishops wear an episcopal ring often set with an amethyst, an allusion to the description of the Apostles as "not drunk" at Pentecost in Acts 2:15. name=google
A large geode, or "amethyst-grotto", from near Santa Cruz in southern Brazil was presented at a 1902 exhibition in Düsseldorf, Germany. |
Amethyst | Synthetic amethyst | Synthetic amethyst
Synthetic (laboratory-grown) amethyst is produced by a synthesis method called hydrothermal growth, which grows the crystals inside a high-pressure autoclave.
Synthetic amethyst is made to imitate the best quality amethyst. Its chemical and physical properties are the same as those of natural amethyst, and it cannot be differentiated with absolute certainty without advanced gemmological testing (which is often cost-prohibitive). One test based on "Brazil law twinning" (a form of quartz twinning where right- and left-hand quartz structures are combined in a single crystal) can be used to identify most synthetic amethyst rather easily. Synthesizing twinned amethyst is possible, but this type is not available in large quantities in the market.
Treated amethyst is produced by gamma ray, X-ray, or electron-beam irradiation of clear quartz (rock crystal), which has been first doped with ferric impurities. Exposure to heat partially cancels the irradiation effects and amethyst generally becomes yellow or even green. Much of the citrine, cairngorm, or yellow quartz of jewelry is said to be merely "burnt amethyst". |
Amethyst | Cultural history | Cultural history |
Amethyst | Ancient Greece | Ancient Greece
thumb|Emerald cut amethyst
The Greek word may be translated as "not drunken", from Greek , "not" + , "intoxicated". Amethyst was considered to be a strong antidote against drunkenness.
In his poem "L'Amethyste, ou les Amours de Bacchus et d'Amethyste" (Amethyst or the loves of Bacchus and Amethyste), the French poet Rémy Belleau (1528–1577) invented a myth in which Bacchus, the god of intoxication, of wine, and grapes was pursuing a maiden named Amethyste, who refused his affections. Amethyste prayed to the gods to remain chaste, a prayer which the chaste goddess Diana answered, transforming her into a white stone. Humbled by Amethyste's desire to remain chaste, Bacchus poured wine over the stone as an offering, dyeing the crystals purple.
Variations of the story include that Dionysus had been insulted by a mortal and swore to slay the next mortal who crossed his path, creating fierce tigers to carry out his wrath. The mortal turned out to be a beautiful young woman, Amethystos, who was on her way to pay tribute to Artemis. Her life was spared by Artemis, who transformed the maiden into a statue of pure crystalline quartz to protect her from the brutal claws. Dionysus wept tears of wine in remorse for his action at the sight of the beautiful statue. The god's tears then stained the quartz purple.
This myth and its variations are not found in classical sources. However, the goddess Rhea does present Dionysus with an amethyst stone to preserve the wine-drinker's sanity in historical text.Nonnus, Dionysiaca, 12. 380 |
Amethyst | Other cultural associations | Other cultural associations
Tibetans consider amethyst sacred to the Buddha and make prayer beads from it. Amethyst is considered the birthstone of February.
In the Middle Ages, it was considered a symbol of royalty and used to decorate English regalia. In the Old World, amethyst was considered one of the cardinal gems, in that it was one of the five gemstones considered precious above all others, until large deposits were found in Brazil. |
Amethyst | Value | Value
Until the 18th century, amethyst was included in the cardinal, or most valuable, gemstones (along with diamond, sapphire, ruby, and emerald), but since the discovery of extensive deposits in locations such as Brazil, it has lost most of its value. It is now considered a semiprecious stone.
Collectors look for depth of color, possibly with red flashes if cut conventionally.
As amethyst is readily available in large structures, the value of the gem is not primarily defined by carat weight. This is different from most gemstones, since the carat weight typically exponentially increases the value of the stone. The biggest factor in the value of amethyst is the color displayed.
The highest-grade amethyst (called deep Russian) is exceptionally rare. When one is found, its value is dependent on the demand of collectors; however, the highest-grade sapphires or rubies are still orders of magnitude more expensive than amethyst. |
Amethyst | Handling and care | Handling and care
The most suitable setting for gem amethyst is a prong or a bezel setting. The channel method must be used with caution.
Amethyst has a good hardness, and handling it with proper care will prevent any damage to the stone. Amethyst is sensitive to strong heat and may lose or change its colour when exposed to prolonged heat or light. Polishing the stone or cleaning it by ultrasonic or steamer must be done with caution. |
Amethyst | Footnotes | Footnotes |
Amethyst | See also | See also
Ametrine
List of minerals
Specimen Ridge |
Amethyst | References | References
|
Amethyst | External links | External links
Category:Quartz gemstones
Category:Provincial symbols of Ontario
Category:Trigonal minerals
Category:Minerals in space group 152 or 154
Category:Symbols of Rio Grande do Sul |
Amethyst | Table of Content | Short description, Structure, Hue and tone, Geographic distribution, History, Synthetic amethyst, Cultural history, Ancient Greece, Other cultural associations, Value, Handling and care, Footnotes, See also, References, External links |
Albertosaurus | Short description | Albertosaurus (; meaning "Alberta lizard") is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which the genus is named, although an indeterminate species ("cf. Albertosaurus sp.") has been discovered in the Corral de Enmedio and Packard Formations of Mexico. Scientists disagree on the content of the genus and some recognize Gorgosaurus libratus as a second species.
As a tyrannosaurid, Albertosaurus was a bipedal predator with short arms, two-fingered hands, and a massive head with dozens of large, sharp teeth, a strong sense of smell, powerful binocular vision, and a bone crushing bite force. It may have even been the apex predator in its local ecosystem. While Albertosaurus was certainly large for a theropod, it was still much smaller than its larger and more famous relative Tyrannosaurus rex, growing up to in length and weighing .
Since the first discovery in 1884, fossils of more than 30 individuals have been recovered that provide scientists with a more detailed knowledge of Albertosaurus anatomy than what is available for most other tyrannosaurids. The discovery of 26 individuals in one particular site provides evidence of gregarious behavior and allows for studies of ontogeny and population biology. These are near impossible with lesser-known dinosaurs because their remains are rarer and more fragmentary when compared to those of Albertosaurus. |
Albertosaurus | History of discovery | History of discovery |
Albertosaurus | Naming | Naming
thumb|left|Holotype specimen CMN 5600
Albertosaurus was named by Henry Fairfield Osborn in a one-page note at the end of his 1905 description of Tyrannosaurus rex. Its namesake is Alberta, the Canadian province established the very same year where the first remains were found. The generic name also incorporates the Greek word /sauros, meaning "lizard", which is the most common suffix in dinosaur names. The type species is Albertosaurus sarcophagus and the specific name is derived from the Ancient Greek term σαρκοφάγος (), meaning "flesh-eating", and having the same etymology as the funeral container with which it shares its name, which is a combination of the Greek words σαρξ/ ("flesh") and / ("to eat"). More than 30 specimens of all ages are known to science. |
Albertosaurus | Early discoveries | Early discoveries
thumb|The Red Deer River near Drumheller, Alberta. Almost three-quarters of all Albertosaurus remains have been discovered alongside the river, in outcrops like the ones on either side of this picture.
The type specimen is a partial skull collected on June 9, 1884, from an outcrop of the Horseshoe Canyon Formation alongside the Red Deer River in Alberta. It was recovered by an expedition of the Geological Survey of Canada, led by the famous geologist Joseph Burr Tyrrell. Due to a lack of specialised equipment, the almost complete skull could only be partially secured. In 1889, Tyrrell's colleague Thomas Chesmer Weston found an incomplete smaller skull associated with some skeletal material at a location nearby. The two skulls were assigned to the preexisting species Laelaps incrassatus by Edward Drinker Cope in 1892. Although the name Laelaps was preoccupied by a genus of mite and had been changed to Dryptosaurus in 1877 by Othniel Charles Marsh, Cope stubbornly refused to recognize the new name created by his archrival. However, Lawrence Lambe used the name Dryptosaurus incrassatus instead of Laelaps incrassatus when he described the remains in detail in 1903 and 1904, which was a combination first coined by Oliver Perry Hay in 1902.Hay, Oliver Perry, 1902 Bibliography and Catalogue of the Fossil Vertebrata of North America. Bulletin of the United States Geological Survey, N° 117, Government Printing Office. pp 868
Shortly later, Osborn pointed out that D. incrassatus was based on generic tyrannosaurid teeth, so the two Horseshoe Canyon skulls could not be confidently referred to that species. The Horseshoe Canyon skulls also differed markedly from the remains of D. aquilunguis, type species of Dryptosaurus, so Osborn gave them the new name Albertosaurus sarcophagus in 1905. He did not describe the remains in any great detail, citing Lambe's complete description the year before. Both specimens, the holotype CMN 5600 and the paratype CMN 5601, are stored in the Canadian Museum of Nature in Ottawa. By the early twenty-first century, some concerns had arisen that, due to the damaged state of the holotype, Albertosaurus might be a nomen dubium that could only be used for the type specimen itself because other fossils could not reliably be assigned to it. However, in 2010, Thomas Carr established that the holotype, the paratype, and comparable later finds all shared a single common unique trait, or autapomorphy. The possession of an enlarged pneumatic opening in the back rim of the side of the palatine bone proves that Albertosaurus is a valid taxon. |
Albertosaurus | Dry Island bone bed | Dry Island bone bed
thumb|upright|Teeth from Dry Island and Drumheller, Royal Tyrrell Museum
On August 11, 1910, American paleontologist Barnum Brown discovered the remains of a large group of Albertosaurus at another quarry alongside the Red Deer River. Because of the large number of bones and the limited time available, Brown's party did not collect every specimen, but made sure to collect remains from all of the individuals that they could identify in the bone bed. Among the bones deposited in the American Museum of Natural History collections in New York City are seven sets of right metatarsals, along with two isolated toe bones that did not match any of the metatarsals in size. This indicated the presence of at least nine individuals in the quarry. Palaeontologist Philip J. Currie of the Royal Tyrrell Museum of Palaeontology rediscovered the bonebed in 1997 and resumed fieldwork at the site, which is now located inside Dry Island Buffalo Jump Provincial Park. (not printed until 2000) Further excavation from 1997 to 2005 turned up the remains of 13 more individuals of various ages, including a diminutive two-year-old and a very old individual estimated at over long. None of these individuals are known from complete skeletons and most are represented by remains in both museums. Excavations continued until 2008, when the minimum number of individuals present had been established at 12 (on the basis of preserved elements that occur only once in a skeleton) and at 26 if mirrored elements were counted when differing in size due to ontogeny. A total of 1,128 Albertosaurus bones had been secured, which is the largest concentration of large theropod fossils known from the Cretaceous. |
Albertosaurus | Other discoveries | Other discoveries
thumb|left|Skull TMP 1985 098 0001
In 1911, Barnum Brown, during the second year of the American Museum of Natural History's operations in Alberta, uncovered a fragmentary partial Albertosaurus skull at the Red Deer River near Tolman Bridge (specimen AMNH 5222).Carpenter, K., 1992, "Tyrannosaurids (Dinosauria) of Asia and North America", In: N. Mateer and P.-J. Chen (eds.) Aspects of nonmarine Cretaceous geology. China Ocean Press, Beijing, China, pp. 250–268
William Parks described a new species in 1928, Albertosaurus arctunguis, based on a partial skeleton lacking a skull that was excavated by Gus Lindblad and Ralph Hornell near the Red Deer River in 1923, but this species has been considered identical to A. sarcophagus since 1970. Parks' specimen (ROM 807) is housed in the Royal Ontario Museum in Toronto.
No Albertosaurus fossils were found from 1926 to 1972, but there has been an increase in findings since then. Apart from the Dry Island bonebed, six more skulls and skeletons have since been discovered in Alberta and are housed in various Canadian museums. Specimen RTMP 81.010.001 was found in 1978 by amateur paleontologist Maurice Stefanuk. RTMP 85.098.001 was found by Stefanuk on June 16, 1985. RTMP 86.64.001 was found in December 1985. RTMP 86.205.001 was found in 1986. RTMP 97.058.0001 was found in 1996 and then there is CMN 11315. Unfortunately, none of these skeletons were found with complete skulls. Fossils have also been reported from the American states of Montana, New Mexico, Wyoming, and Missouri, but they are doubted to be from A. sarcophagus and may not even belong to the genus Albertosaurus.
Two specimens from "cf Albertosaurus ".sp" have been found in Mexico (Packard Formation and Corral de Enmedio Formation).Listed as "cf. Albertosaurus sp." "Corral De Enmedio and Packard Formations, Cabollona Group, Sonora, Mexico," in Sullivan and Lucas (2006). Page 16. |
Albertosaurus | ''Gorgosaurus libratus'' | Gorgosaurus libratus
thumb|Gorgosaurus, which was described as a second species of Albertosaurus, A. libratus by Dale Russell.
In 1913, paleontologist Charles H. Sternberg recovered another tyrannosaurid skeleton from the slightly older Dinosaur Park Formation in Alberta. Lawrence Lambe named this dinosaur Gorgosaurus libratus in 1914. Other specimens were later found in Alberta and the US state of Montana. Finding no significant differences to separate the two taxa (due mostly to a lack of good Albertosaurus skull material), Dale Russell declared the name Gorgosaurus a junior synonym of Albertosaurus, which had been named first, and G. libratus was renamed Albertosaurus libratus in 1970. A species distinction was maintained because of the age difference. The addition extended the temporal range of the genus Albertosaurus earlier by several million years and its geographic range southwards by hundreds of kilometres.
In 2003, Philip J. Currie, benefiting from much more extensive finds and a general increase in anatomical knowledge of theropods, compared several tyrannosaurid skulls and came to the conclusion that the two species are more distinct than previously thought. As the two species are sister taxa, they are more closely related to each other than to any other species of tyrannosaurid. Recognizing this, Currie nevertheless recommended that Albertosaurus and Gorgosaurus be kept as separate genera, as he concluded that they were no more similar than Daspletosaurus and Tyrannosaurus, which are almost always separated. In addition to this, several albertosaurine specimens have been recovered from Alaska and New Mexico. Currie suggested that the Albertosaurus-Gorgosaurus situation may be clarified once these are fully described. Most authors have followed Currie's recommendation, but some have not. |
Albertosaurus | Other species | Other species
In 1930, Anatoly Nikolaevich Riabinin named Albertosaurus pericolosus based on a tooth from China that probably belonged to Tarbosaurus. In 1932, Friedrich von Huene renamed Dryptosaurus incrassatus, not considered a nomen dubium by him, to Albertosaurus incrassatus.Von Huene, F., 1932 Die fossile Reptil-Ordnung Saurischia: ihre Entwicklung und Geschichte. Monographie für Geologie und Palaeontologie, Parts I and II, ser. I, 4: 1–361 Because he had identified Gorgosaurus with Albertosaurus, in 1970, Russell also renamed Gorgosaurus sternbergi (Matthew & Brown 1922) into Albertosaurus sternbergi and Gorgosaurus lancensis (Gilmore 1946) into Albertosaurus lancensis. The former species is today seen as a juvenile form of Gorgosaurus libratus and the latter is seen as either identical to Tyrannosaurus or representing a separate genus, Nanotyrannus. In 1988, Gregory S. Paul based Albertosaurus megagracilis on a small tyrannosaurid skeleton, specimen LACM 28345, from the Hell Creek Formation of Montana. It was renamed Dinotyrannus in 1995, but is now thought to represent a juvenile Tyrannosaurus rex. Also in 1988, Paul renamed Alectrosaurus olseni (Gilmore 1933) into Albertosaurus olseni, but this has found no general acceptance. In 1989, Gorgosaurus novojilovi (Maleev 1955) was renamed by Bryn Mader and Robert Bradley as Albertosaurus novojilovi.
On two occasions, species based on valid Albertosaurus material were reassigned to a different genus, Deinodon. In 1922, William Diller Matthew renamed A. sarcophagus into Deinodon sarcophagus. In 1939, German paleontologist Oskar Kuhn renamed A. arctunguis into Deinodon arctunguis.Kuhn, O., 1939 Saurischia — Fossilium catalogus I, Animalia, Pars 87. 's-Gravenhage, W. Junk, 1939, 124 pp |
Albertosaurus | Description | Description
thumb|Size comparison
Albertosaurus was a fairly large bipedal predator, but smaller than Tarbosaurus and Tyrannosaurus rex. Typical Albertosaurus adults measured up to long and weighed between in body mass.
Albertosaurus shared a similar body appearance with all other tyrannosaurids, Gorgosaurus in particular. Typical for a theropod, Albertosaurus was bipedal and balanced its large, heavy head and torso with a long, muscular tail. However, tyrannosaurid forelimbs were extremely small for their body size and retained only two functional fingers, the second being longer than the first. The legs were long and ended in a four-toed foot on which the first toe, the hallux, was very short and did not reach the ground. The third toe was longer than the rest. Albertosaurus may have been able to reach walking speeds of 14–21 km/hour (8–13 mi/hour). At least for the younger individuals, a high running speed is plausible.
Two skin impressions from Albertosaurus are known, and both show scales. One patch was found associated with some gastralic ribs and the impression of a long, unknown bone, indicating that the patch is from the belly. The scales are pebbly and gradually become larger and somewhat hexagonal in shape. Also preserved are two larger feature scales, placed 4.5 cm apart from each other, making Albertosaurus, along with Carnotaurus, the only known theropods with preserved feature scales. Another skin impression is from an unknown part of the body. These scales are small, diamond-shaped, and arranged in rows. |
Albertosaurus | Skull and teeth | Skull and teeth
thumb|left|Skull cast at the Geological Museum in Copenhagen
The massive skull of Albertosaurus, which was perched on a muscular, short, S-shaped neck, was about long in the largest adults. Wide openings in the skull, called fenestrae, provided space for muscle attachment sites and sensory organs that reduced its overall weight. Its long jaws contained, both sides combined, 58 or more banana-shaped teeth. Larger tyrannosaurids possessed fewer teeth, but Gorgosaurus had 62. Unlike most theropods, Albertosaurus and other tyrannosaurids were heterodont, with teeth of different forms depending on their position in the mouth. The premaxillary teeth at the tip of the upper jaw, four per side, were much smaller than the rest, more closely packed, and D-shaped in cross section. Like with Tyrannosaurus rex, the maxillary (cheek) teeth of Albertosaurus were adapted in general form to resist lateral forces exerted by a struggling prey animal. The bite force of Albertosaurus was less formidable, however, with the maximum force, by the back teeth, reaching 3,413 Newtons. Above the eyes were short bony crests that may have been brightly coloured in life and possibly used, by males in particular, in courtship to attract a mate."Albertosaurus." In: Dodson, Peter; Britt, Brooks; Carpenter, Kenneth; Forster, Catherine A.; Gillette, David D.; Norell, Mark A.; Olshevsky, George; Parrish, J. Michael; & Weishampel, David B. The Age of Dinosaurs. Lincolnwood, Illinois: Publications International, Ltd., 1993. pp. 106–107. .
thumb|Life restoration
In 2001, William Abler observed that Albertosaurus tooth serrations resemble a crack in the tooth ending in a round void called an ampulla.Abler, W.L. 2001. A kerf-and-drill model of tyrannosaur tooth serrations. p. 84–89. In: Mesozoic Vertebrate Life. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press. Tyrannosaurid teeth were used as holdfasts for pulling flesh off a body, so when a tyrannosaur pulled back on a piece of meat, the tension could cause a purely crack-like serration to spread through the tooth. However, the presence of the ampulla distributed these forces over a larger surface area and lessened the risk of damage to the tooth under strain. The presence of incisions ending in voids has parallels in human engineering. Guitar makers use incisions ending in voids to, as Abler describes, "impart alternating regions of flexibility and rigidity" to wood that they work on. The use of a drill to create an "ampulla" of sorts and prevent the propagation of cracks through material is also used to protect aircraft surfaces. Abler demonstrated that a plexiglass bar with incisions called "kerfs" and drilled holes was more than 25% stronger than one with only regularly placed incisions. Unlike tyrannosaurs, more ancient predators, like phytosaurs and Dimetrodon, had no adaptations to prevent the crack-like serrations of their teeth from spreading when subjected to the forces of feeding. |
Albertosaurus | Classification and systematics | Classification and systematics
Albertosaurus is a member of the theropod family Tyrannosauridae, specifically the subfamily Albertosaurinae. Its closest relative is the slightly older Gorgosaurus libratus (sometimes called Albertosaurus libratus; see below). These two species are the only described albertosaurines, but other undescribed species may exist. Thomas Holtz found Appalachiosaurus to be an albertosaurine in 2004, but his more recent unpublished work places it as a basal eotyrannosaurian just outside of Tyrannosauridae, in agreement with other authors.
The other major subfamily of tyrannosaurids is Tyrannosaurinae, which includes members like Daspletosaurus, Tarbosaurus, and Tyrannosaurus. Compared with the more robust tyrannosaurines, albertosaurines had slender builds, with proportionately smaller skulls and longer bones of the lower legs (tibia) and feet (metatarsals and phalanges).
thumb|upright|Cast in the Rocky Mountain Dinosaur Resource Center in Woodland Park, Colorado
Below is the cladogram of Tyrannosauridae based on the phylogenetic analysis conducted by Loewen et al. in 2013. |
Albertosaurus | Palaeobiology | Palaeobiology |
Albertosaurus | Growth pattern | Growth pattern
thumb|300px|A graph showing the hypothesized growth curves (body mass versus age) of four tyrannosaurids, with Albertosaurus drawn in red
Most age categories of Albertosaurus are represented in the fossil record. Using bone histology, the age of an individual animal at the time of death can often be determined, allowing growth rates to be estimated and compared with other species. The youngest known Albertosaurus is a two-year-old discovered in the Dry Island bonebed, which would have weighed about 50 kilograms (110 lb) and measured slightly more than long. The specimen from the same quarry is 28 years old, the oldest and largest one known. When specimens of intermediate age and size are plotted on a graph, an S-shaped growth curve results, with the most rapid growth occurring in a four-year period ending around the sixteenth year of life, a pattern also seen in other tyrannosaurids. The growth rate during this phase was per year, based on an adult weighing 1.3 tonnes. Other studies have suggested higher adult weights, which would affect the magnitude of the growth rate, but not the overall pattern. Tyrannosaurids similar in size to Albertosaurus had similar growth rates, although the much larger Tyrannosaurus rex grew at almost five times this rate ( per year) at its peak. The end of the rapid growth phase suggests the onset of sexual maturity in Albertosaurus, although growth continued at a slower rate throughout the animals' lives. Sexual maturation while still actively growing appears to be a shared trait among small and large dinosaurs, as well as in large mammals like humans and elephants. This pattern of relatively early sexual maturation differs strikingly from the pattern in birds, which delay their sexual maturity until after they have finished growing.
During growth, thickening of the tooth morphology changed so much that, had the association of young and adult skeletons on the Dry Island bonebed not proven that they belonged to the same taxon, the teeth of juveniles would likely have been identified by statistical analysis as those of a different species. |
Albertosaurus | Life history | Life history
thumb|left|Restoration of Edmontosaurus fighting off Albertosaurus
Most known Albertosaurus individuals were aged 14 years or older at the time of death. Juvenile animals are rarely fossilized for several reasons, mainly preservation bias, where the smaller bones of younger animals were less likely to be preserved by fossilization than the larger bones of adults, and collection bias, where smaller fossils are less likely to be noticed by collectors in the field. Young Albertosaurus are relatively large for juvenile animals, but their remains are still rare in the fossil record when compared to adults. It has been suggested that this phenomenon is a consequence of life history, rather than bias, and that fossils of juvenile Albertosaurus are rare because they simply did not die as often as adults did.
A hypothesis of Albertosaurus life history postulates that hatchlings died in large numbers, but have not been preserved in the fossil record because of their small size and fragile construction. After just two years, juveniles were larger than any other predator in the region, aside from adult Albertosaurus, and more fleet-footed than most of their prey animals. This resulted in a dramatic decrease in their mortality rate and a corresponding rarity of fossil remains. Mortality rates doubled at age twelve, perhaps the result of the physiological demands of the rapid growth phase, and then doubled again with the onset of sexual maturity between the ages of fourteen and sixteen. This elevated mortality rate continued throughout adulthood, perhaps due to the high physiological demands of procreation, including stress and injuries received during intraspecific competition for mates and resources, and the eventual, ever-increasing effects of senescence. The higher mortality rate in adults may explain their more common preservation. Very large animals were rare because few individuals survived long enough to attain such size. High infant mortality rates, followed by reduced mortality among juveniles and a sudden increase in mortality after sexual maturity, with very few animals reaching maximum size, is a pattern observed in many modern large mammals, including elephants, African buffalo, and rhinoceros. The same pattern is also seen in other tyrannosaurids. The comparison with modern animals and other tyrannosaurids lends support to this life history hypothesis, but bias in the fossil record may still play a large role, especially since more than two-thirds of all Albertosaurus specimens are known from the exact same locality. |
Albertosaurus | Social behaviour | Social behaviour
thumb|Bronze sculptures of a pack, RTM, designed by Brian Cooley
The Dry Island bonebed discovered by Barnum Brown and his crew contains the remains of 26 Albertosaurus, the most individuals found in one locality of any large Cretaceous theropod and the second-most of any large theropod dinosaur behind the Allosaurus assemblage at the Cleveland-Lloyd Dinosaur Quarry in Utah. The group seems to be composed of one very old adult, eight adults between 17 and 23 years old, seven sub-adults undergoing their rapid growth phases at between 12 and 16 years old, and six juveniles between the ages of 2 and 11 years old that had not yet reached the growth phase.
The near-absence of herbivore remains and the similar state of preservation common to the many individuals at the Albertosaurus bonebed quarry led Currie to conclude that the locality was not a predator trap, such as the La Brea Tar Pits in California, and that all of the preserved animals died at the same time. Currie claims this as evidence of pack behavior. Other scientists are skeptical, observing that the animals may have been driven together by a drought, flood, or other reasons.(published abstract only)
thumb|left|Two Albertosaurus hunting Saurolophus
There is plentiful evidence for gregarious behaviour among herbivorous dinosaurs, including ceratopsians and hadrosaurs. However, only rarely are so many dinosaurian predators found at the same site. Small theropods, like Deinonychus and Coelophysis, have been found in aggregations, as have larger predators, such as Allosaurus and Mapusaurus. There is some evidence of gregarious behaviour in other tyrannosaurids as well, as fragmentary remains of smaller individuals were found alongside "Sue", the Tyrannosaurus mounted in the Field Museum of Natural History in Chicago, and a bonebed in the Two Medicine Formation of Montana contains at least three specimens of Daspletosaurus preserved alongside several hadrosaurs. These findings may corroborate the evidence for social behaviour in Albertosaurus, although some or all of the above localities may represent temporary or unnatural aggregations. Others have speculated that, instead of social groups, at least some of these finds represent Komodo dragon-like mobbing of carcasses, where aggressive competition leads to some of the predators being killed and even cannibalized. The evidence of cannibalism was later reported in 2024 by Coppock and Currie.
Currie has also speculated on the pack-hunting habits of Albertosaurus. The leg proportions of the smaller individuals were comparable to those of ornithomimids, which were probably among the fastest dinosaurs. Younger Albertosaurus were probably equally fleet-footed or at least faster than their prey. Currie hypothesized that the younger members of the pack may have been responsible for driving their prey towards the adults, who were larger and more powerful, but also slower. Juveniles may also have had different lifestyles than adults, filling predator niches between the enormous adults and the smaller contemporaneous theropods, the largest of which were two orders of magnitude smaller than adult Albertosaurus in mass. A similar situation is observed in modern Komodo dragons, with hatchlings beginning life as small insectivores before growing to become the dominant predators on their islands. However, as the preservation of behaviour in the fossil record is exceedingly rare, these ideas cannot readily be tested. In 2010, Currie, though still favouring the hunting pack hypothesis, admitted that the concentration could have been brought about by other causes, such as a slowly rising water level during an extended flood. |
Albertosaurus | Palaeopathology | Palaeopathology
thumb|Tyrannosaur jaw-bones with trichomonosis-type lesions; D (upper right) is Albertosaurus
In 2009, researchers hypothesized that smooth-edged holes found in the fossil jaws of tyrannosaurid dinosaurs, such as Albertosaurus, were caused by a parasite similar to Trichomonas gallinae, which infects birds. They suggested that tyrannosaurids transmitted the infection by biting each other and that the infection impaired their ability to eat.
In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. They found that only one of the 319 Albertosaurus foot bones checked for stress fractures actually had them and none of the four hand bones did. The scientists found that stress fractures were "significantly" less common in Albertosaurus than in the carnosaur Allosaurus.Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331–336. ROM 807, the holotype of A. arctunguis (now referred to A. sarcophagus), had a deep hole in the iliac blade, although the describer of the species did not recognize this as pathological. The specimen also contains some exostosis on the fourth left metatarsal. In 1970, two of the five Albertosaurus sarcophagus specimens with humeri were reported by Dale Russel as having pathological damage to them.Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 337–363.
In 2010, the health of the Dry Island Albertosaurus assembly was reported upon. Most specimens showed no sign of disease. On three phalanges of the foot, strange bony spurs that consisted of abnormal ossifications of the tendons, so-called enthesophytes, were present, but their cause is unknown. Two ribs and a belly-rib showed signs of breaking and healing. One adult specimen had a left lower jaw showing a puncture wound and both healed and unhealed bite marks. The low number of abnormalities compares favourably with the health condition of a Majungasaurus population of which it was established, in 2007, that 19% of individuals showed bone pathologies. |
Albertosaurus | Palaeoecology | Palaeoecology
thumb|left|The Horseshoe Canyon Formation is exposed in its type section at Horseshoe Canyon, Alberta
Most fossils of Albertosaurus sarcophagus are known from the upper Horseshoe Canyon Formation in Alberta. These younger units of this geologic formation date to the early Maastrichtian age of the Late Cretaceous period, about 70 to 68 million years ago. Immediately below this formation is the Bearpaw Shale, a marine formation representing a section of the Western Interior Seaway. The Inland Sea was receding as the climate cooled and sea levels subsided towards the end of the Cretaceous, thus exposing land that had previously been underwater. It was not a smooth process, however, and the seaway would periodically rise to cover parts of the region throughout Horseshoe Canyon before finally receding altogether in the years after. Due to the changing sea levels, many different environments are represented in the Horseshoe Canyon Formation, including offshore and near-shore marine habitats and coastal habitats, such as lagoons, estuaries, and tidal flats. Numerous coal seams represent ancient peat swamps. Like most of the other vertebrate fossils from the formation, Albertosaurus remains are found in deposits laid down in the deltas and floodplains of large rivers during the later half of Horseshoe Canyon times.
The fauna of the Horseshoe Canyon Formation is well-known, as vertebrate fossils, including those of dinosaurs, are very common. Sharks, rays, sturgeons, bowfins, gars, and the gar-like Aspidorhynchus made up the fish fauna. Mammals included multituberculates and the marsupial Didelphodon. The saltwater plesiosaur Leurospondylus has been found in marine sediments in the Horseshoe Canyon, while freshwater environments were populated by turtles, Champsosaurus, and crocodilians like Leidyosuchus and Stangerochampsa. Dinosaurs dominate the fauna, especially hadrosaurs, which make up half of all dinosaurs known. These include the genera Edmontosaurus, Saurolophus, and Hypacrosaurus. Ceratopsians and ornithomimids were also very common, together making up another third of the known fauna. Along with much rarer ankylosaurians and pachycephalosaurs, all of these animals would have been prey for a diverse array of carnivorous theropods, including troodontids, dromaeosaurids, and caenagnathids. Intermingled with the Albertosaurus remains of the Dry Island bonebed, the bones of the small theropod Albertonykus were found. Adult Albertosaurus were the apex predators in their environment, with intermediate niches possibly filled by juvenile Albertosaurus. |
Albertosaurus | See also | See also
Timeline of tyrannosaur research |
Albertosaurus | References | References |
Albertosaurus | External links | External links
Category:Tyrannosauridae
Category:Dinosaur genera
Category:Maastrichtian dinosaurs
Category:Horseshoe Canyon Formation
Category:Dinosaurs of Canada
Category:Fossil taxa described in 1905
Category:Taxa named by Henry Fairfield Osborn |
Albertosaurus | Table of Content | Short description, History of discovery, Naming, Early discoveries, Dry Island bone bed, Other discoveries, ''Gorgosaurus libratus'', Other species, Description, Skull and teeth, Classification and systematics, Palaeobiology, Growth pattern, Life history, Social behaviour, Palaeopathology, Palaeoecology, See also, References, External links |
Assembly language | Short description | In computer programming, assembly language (alternatively assembler language or symbolic machine code), often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence between the instructions in the language and the architecture's machine code instructions. Assembly language usually has one statement per machine instruction (1:1), but constants, comments, assembler directives, symbolic labels of, e.g., memory locations, registers, and macros are generally also supported.
The first assembly code in which a language is used to represent machine code instructions is found in Kathleen and Andrew Donald Booth's 1947 work, Coding for A.R.C.. Assembly code is converted into executable machine code by a utility program referred to as an assembler. The term "assembler" is generally attributed to Wilkes, Wheeler and Gill in their 1951 book The Preparation of Programs for an Electronic Digital Computer, who, however, used the term to mean "a program that assembles another program consisting of several sections into a single program". The conversion process is referred to as assembly, as in assembling the source code. The computational step when an assembler is processing a program is called assembly time.
Because assembly depends on the machine code instructions, each assembly languageOther than meta-assemblers is specific to a particular computer architecture.
Sometimes there is more than one assembler for the same architecture, and sometimes an assembler is specific to an operating system or to particular operating systems. Most assembly languages do not provide specific syntax for operating system calls, and most assembly languages can be used universally with any operating system,However, that does not mean that the assembler programs implementing those languages are universal. as the language provides access to all the real capabilities of the processor, upon which all system call mechanisms ultimately rest. In contrast to assembly languages, most high-level programming languages are generally portable across multiple architectures but require interpreting or compiling, much more complicated tasks than assembling.
In the first decades of computing, it was commonplace for both systems programming and application programming to take place entirely in assembly language. While still irreplaceable for some purposes, the majority of programming is now conducted in higher-level interpreted and compiled languages. In "No Silver Bullet", Fred Brooks summarised the effects of the switch away from assembly language programming: "Surely the most powerful stroke for software productivity, reliability, and simplicity has been the progressive use of high-level languages for programming. Most observers credit that development with at least a factor of five in productivity, and with concomitant gains in reliability, simplicity, and comprehensibility."
Today, it is typical to use small amounts of assembly language code within larger systems implemented in a higher-level language, for performance reasons or to interact directly with hardware in ways unsupported by the higher-level language. For instance, just under 2% of version 4.9 of the Linux kernel source code is written in assembly; more than 97% is written in C. |
Assembly language | Assembly language syntax | Assembly language syntax
Assembly language uses a mnemonic to represent, e.g., each low-level machine instruction or opcode, each directive, typically also each architectural register, flag, etc. Some of the mnemonics may be built-in and some user-defined. Many operations require one or more operands in order to form a complete instruction. Most assemblers permit named constants, registers, and labels for program and memory locations, and can calculate expressions for operands. Thus, programmers are freed from tedious repetitive calculations and assembler programs are much more readable than machine code. Depending on the architecture, these elements may also be combined for specific instructions or addressing modes using offsets or other data as well as fixed addresses. Many assemblers offer additional mechanisms to facilitate program development, to control the assembly process, and to aid debugging.
Some are column oriented, with specific fields in specific columns; this was very common for machines using punched cards in the 1950s and early 1960s. Some assemblers have free-form syntax, with fields separated by delimiters, e.g., punctuation, white space. Some assemblers are hybrid, with, e.g., labels, in a specific column and other fields separated by delimiters; this became more common than column-oriented syntax in the 1960s. |
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