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ammonia

ammonia, chemical compound, NH3, colorless gas that is about one half as dense as air at ordinary temperatures and pressures. It has a characteristic pungent, penetrating odor. Ammonia forms a minute proportion of the atmosphere; it is found in volcanic gases and as a product of decomposition of animal and vegetable matter. Because ammonia was formerly obtained by destructive distillation of horns and hooves of animals, its water solution was called spirits of hartshorn. Ammonia has also been called alkaline air and volatile alkali.

Properties

Anhydrous (water-free) ammonia gas is easily liquefied under pressure (at 20°C liquid ammonia has a vapor pressure of about 120 lb per sq in.) It is extremely soluble in water; one volume of water dissolves about 1,200 volumes of the gas at 0°C (90 grams of ammonia in 100 cc of water), but only about 700 volumes at room temperature and still less at higher temperatures. The solution is alkaline because much of the dissolved ammonia reacts with water, H2O, to form ammonium hydroxide, NH4OH, a weak base. Liquid ammonia is used in the chemical laboratory as a solvent. It is a better solvent for ionic and polar compounds than ethanol, but not as good as water; it is a better solvent for nonpolar covalent compounds than water, but not as good as ethanol. It dissolves alkali metals and barium, calcium, and strontium by forming an unstable blue solution containing the metal ion and free electrons that slowly decomposes, releasing hydrogen and forming the metal amide. Compared to water, liquid ammonia is less likely to release protons (H+ ions), is more likely to take up protons (to form NH4+ ions), and is a stronger reducing agent. Because strong acids react with it, it does not allow strongly acidic solutions, but it dissolves many alkalies to form strongly basic solutions.

Ammonia takes part in many chemical reactions. Ammonia reacts with strong acids to form stable ammonium salts: with hydrogen chloride it forms ammonium chloride; with nitric acid, ammonium nitrate; and with sulfuric acid, ammonium sulfate. Ammonium salts of weak acids are readily decomposed into the acid and ammonia. Ammonium carbonate, (NH3)2CO3·H2O, is a colorless-to-white crystalline solid commonly known as smelling salts; in water solution it is sometimes called aromatic spirits of ammonia. Ammonia reacts with certain metal ions to form complex ions called ammines. Ammonia also reacts with Lewis acids (electron acceptors), e.g., sulfur dioxide or trioxide or boron trifluoride.

Another kind of reaction, commonly called ammonolysis, occurs when one or more of the hydrogen atoms in the ammonia molecule is replaced by some other atom or radical. Chlorine gas, Cl2, reacts directly with ammonia to form monochloramine, NH2Cl, and hydrogen chloride, HCl. Products of such ammonolyses include amides, amines, imides, imines, and nitrides. Ammonia also takes part in oxidation and reduction reactions. It burns in oxygen to form nitrogen gas, N2, and water. In the presence of a catalyst (e.g., platinum) it is oxidized in air to form water and nitric oxide, NO. It reduces hot-metal oxides to the metal (e.g., cupric oxide to copper).

Production

Ammonia is prepared commercially in vast quantities. The major method of production is the Haber process, in which nitrogen is combined directly with hydrogen at high temperatures and pressures in the presence of a catalyst. It is obtained as a byproduct of the destructive distillation of coal. Ammonia is also prepared synthetically by the cyanamide process: nitrogen gas combines with calcium carbide, CaC2, at high temperatures to form calcium cyanamide, CaCN2, and carbon; the calcium cyanamide reacts with steam to form calcium carbonate, CaCO3, and ammonia. For use in the laboratory, ammonia is prepared by heating an ammonium salt with a strong base. It can also be prepared by reacting a metal nitride with water.

Uses

Ammonia solutions are used to clean, bleach, and deodorize; to etch aluminum; to saponify (hydolyze) oils and fats; and in chemical manufacture. The ammonia sold for household use is a dilute water solution of ammonia in which ammonium hydroxide is the active cleansing agent. It should be used with caution since it can attack the skin and eyes. The vapors are especially irritating—prolonged exposure and inhalation cause serious injury and may be fatal. Water solutions of ammonia are also called ammonium hydrate, aqua ammonia, or ammonia water; the solution may contain up to 30% ammonium hydroxide by weight at room temperature and pressure.

The major use of ammonia and its compounds is as fertilizers. Ammonia is also used in large amounts in the Ostwald process (see Ostwald, Wilhelm) for the synthesis of nitric acid; in the Solvay process for the synthesis of sodium carbonate; in the synthesis of numerous organic compounds used as dyes, drugs, and in plastics; and in various metallurgical processes.

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ammonia

ammonia A colourless gas, NH3, with a strong pungent odour. Ammonia is produced by the deamination of excess amino acids in the liver. Industrially it is made from its constituent elements by the Haber process for use in the manufacture of nitric acid, ammonium nitrate, ammonium phosphate, and urea (the last three as fertilizers), explosives, dyestuffs, and resins. The participation of ammonia in the nitrogen cycle is a most important natural process. By means of nitrogenase enzymes, nitrogen-fixing bacteria are able to achieve similar reactions to those of the Haber process, but under normal conditions of temperature and pressure. The reactions release ammonium ions, which are converted by nitrifying bacteria into nitrite and nitrate ions.

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ammonia

ammonia Colourless, nonflammable, pungent gas (NH3) manufactured by the Haber process. It is used to make nitrogenous fertilisers. Ammonia solutions are used in cleaning and bleaching. The gas is extremely soluble in water, forming an alkaline solution of ammonium hydroxide (NH4OH) that can give rise to ammonium salts containing the ion NH4+. Chief properties: r.d. 0.59; m.p. −77.7°C (−107.9°F); b.p. −33.4°C (−28.1°F).

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ammonia

ammonia XVIII. — modL. ammōnia, so named as being obtained from sal ammoniac. ammoniac XIV, earliest form armoniak — medL. armōniacus, -um, alt. of ammōniacus, -um — Gr. ammōniakós, -kón, applied to a salt and a gum obtained from a region in Libya near the temple of Jupiter Ammon.
So ammoniacal XVIII. ammonium XIX. — modL. ammōnium.

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ammonia

am·mo·nia / əˈmōnyə; -nēə/ • n. a colorless gas, NH3, with a characteristic pungent smell. It dissolves in water to give a strongly alkaline solution. ∎  a solution of this gas, used as a cleaning fluid.

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ammonia

ammonia (ă-moh-niă) n. a colourless gas with a pungent odour that can be cooled and compressed to form a liquid (formula: NH3). Ammonium chloride is occasionally used to acidify urine.

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ammonia

ammoniaCampania, Catania, pannier •apnoea •Oceania, Tanya, Titania •biennia, denier, quadrennia, quinquennia, septennia, triennia •Albania, balletomania, bibliomania, crania, dipsomania, egomania, erotomania, kleptomania, Lithuania, Lusitania, mania, Mauritania, megalomania, miscellanea, monomania, nymphomania, Pennsylvania, Pomerania, pyromania, Rainier, Romania, Ruritania, Tasmania, Transylvania, Urania •Armenia, bergenia, gardenia, neurasthenia, proscenia, schizophrenia, senior, SloveniaAbyssinia, Bithynia, curvilinear, Gdynia, gloxinia, interlinear, Lavinia, linear, rectilinear, Sardinia, triclinia, Virginia, zinnia •insignia • Sonia • insomnia • Bosnia •California, cornea •Amazonia, ammonia, Antonia, Babylonia, begonia, bonier, Catalonia, catatonia, Cephalonia, Estonia, Ionia, Laconia, Livonia, Macedonia, mahonia, Patagonia, pneumonia, Rondônia, sinfonia, Snowdonia, valonia, zirconia •junior, petunia •hernia, journeyer

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Ammonia

Ammonia

Ammonia in the past

Physical and chemical properties of ammonia

Sources and production of ammonia

Uses of ammonia

Future prospects

Resources

Ammonia, composed of three parts hydrogen and one part nitrogen, is a sharp-smelling, flammable, and toxic gas that is very soluble in water, where it acts as a base in its chemical reactions.

Ammonia in the past

Ammonia was present in the primordial atmosphere of Earth, and may have been the source of nitrogen for the earliest forms of life, although much controversy exists over the details. In ancient Egypt, ammonium compounds were used in rites honoring the god Ammon, from which came the name we still use for the gas and its compounds. Early chemists learned to generate ammonia from animal parts such as deerhorn, and obtained ammonial preparations (spirits of hartshorn, etc.), but Joseph Priestley (1733-1804) first collected and experimented with the pure substance. C. L. Berthollet (1748-1822) proved that ammonia is composed of nitrogen and hydrogen.

In the nineteenth century, ammonia was sometimes manufactured by the action of steam on calcium cyanamide, called the cyanamide process, which in turn was made by reacting calcium carbide with nitrogen at high temperatures. In the early twentieth century, German chemists Fritz Haber and Carl Bosch learned how to make ammonia in large quantities by high-pressure catalytic reactions of nitrogen (from air) with hydrogen. Both men were awarded Nobel prizesHaber in 1918 and Bosch in 1931. The Haber-Bosch process is the basis for modern ammonia production, although many improvements have been made in the details of the technology.

Physical and chemical properties of ammonia

Ammonia (boiling point °28.03°F [-33.35°C]) can be made in the laboratory by heating ammonium chloride with lime, and the gas collected by downward displacement of air, or displacement of mercury. Water solutions of ammonia, called ammonium hydroxides, having as much as 28% ammonia by weight, can be obtained by this method. Ammonium hydroxide exhibits the characteristics of a weak base, turning litmus paper blue, and neutralizing acids with the formation of ammonium salts. Transition metal ions are either precipitated as hydroxides (iron [II], iron [III]) or converted to ammonia complexes (copper [II], nickel [II], zinc [II], silver [I]). The copper (II) ammonia complex, in solution, is deep blue in color, and serves as a qualitative test for copper. It also has the ability to dissolve cellulose, and has been used in the process for making regenerated cellulose fibers, or rayon.

Ammonia molecules possess a pyramidal shape, with the nitrogen atom at the vertex. These molecules continually undergo a type of motion called inversion, in which the nitrogen atom passes through the plane of the three hydrogen atoms like an umbrella turning inside out in the wind. When ammonia acts as a base, the nitrogen atom bonds either to a proton (to form ammonium ion) or to a metal cation.

Ammonium salts such as ammonium chloride, called sal ammoniac, are water soluble and volatile when heated. It is often found that considerable heat is absorbed when ammonium salts dissolve in water, leading to dramatic reduction in temperature. Ammonium salts containing anions of weak acids (carbonate, sulfide) easily liberate ammonia owing to the tendency of a proton to break off the nitrogen atom and be bound by the weak acid anion.

In liquid or frozen ammonia, the molecules attract one another through sharing a hydrogen atom between one molecule and the next, called hydrogen bonding. In this attraction, called association, compounds apparently containing free electrons can be obtained by treating sodium/ammonia solutions with complexing agents.

Ammonia is a flammable gas and reacts with oxygen to form nitrogen and water, or nitrogen (II) oxide and water. Oxidation of ammonia in solution leads to hydrazine, a corrosive and volatile ingredient in fuels. Ammonium salts of oxidizing anionsnitrate, dichro-mate, and perchlorateare unstable and can explode or deflagrate when heated. Ammonium nitrate is used as a high explosive; ammonium perchlorate is a component of rocket fuels. Ammonium dichromate is used in a popular artificial volcano demonstration in which a conical pile of the salt is ignited and burns vigorously, throwing off quantities of green chromium (III) oxidethe lava.

When ammonium hydroxide is treated with iodine crystals, an explosive brown solid, nitrogen triiodide, is formed. When dry, this substance is so sensitive that the lightest touch will cause it to explode with a crackling sound and a puff of purple iodine vapor.

Sources and production of ammonia

Ammonia is manufactured by the reaction of hydrogen with nitrogen in the presence of an iron catalyst, which is known as the Haber-Bosch process. The reaction is exothermic and is accompanied by a concentration in volume. (The ammonia occupies less volume than the gases from which it is made.) High pressure conditions (150-250 bar) are used, and temperatures range from 752932°F (400500°C). The mixed gases circulate through the catalyst, ammonia is formed and removed, and the unconverted reactants are recirculated. Large ammonia plants can produce over 1, 000 tons per day. Each ton of ammonia requires 3, 100 cubic yards (2, 400 cu m) of hydrogen and 1, 050 cubic yards (800 cu m) of nitrogen, as well as 60 gigajoules of energy. Much of the energy is consumed in heating the reactants and in the compressors needed to attain the high pressure used in the synthesis. Further energy is needed to produce the hydrogen from hydrocarbon feedstocks and to separate nitrogen from air. The synthesis reaction itself produces some heat, and great attention is given to heat efficiency and use of waste heat. The gases that enter the catalytic converter must be highly purified and free of sulfur compounds, which adversely affect the catalyst. The catalyst is prepared in place by hydrogen treatment of magnetite, an iron oxide containing potassium hydroxide and other oxides in small amounts as promoters. A large ammonia plant might have as much as 100 tons of catalyst.

Since the hydrogen is usually derived from a natural gas called methane, the price of ammonia is very sensitive to the availability or price of fuels. United States production of ammonia reached 17 million tons in 1991, and demand was even larger than U.S. production, leading to about two million tons of imports. World ammonia production is about 100 million tons per year, which amounts to about 40 pounds (18 kg) for each person on Earth.

Ammonia is formed from nitrogen in air by the action of nitrogen-fixing bacteria that exist in the soil on the roots of certain plants like alfalfa. Nitrogen fixation can also be accomplished by blue-green algae in the sea. These bacteria and algae possess an enzyme called nitrogenase that permits them to convert nitrogen to ammonia at 77°F (25°C) and 1 bar of pressure, much milder conditions than those of the Haber-Bosch process. Nitrogenase is known to be a complex protein containing metal atoms, such as iron and molybdenum and sulfide ions, but its structure and mode of action are imperfectly understood, even after decades of research. Recent research indicates that the nitrogen molecule may bind to iron atoms in the enzyme as a reaction step.

Ammonia can be formed in the human body and may build up abnormally during serious illnesses such as Reyes syndrome. Much nitrogen is normally excreted by humans (and other mammals) as urea, a water soluble solid, but fish can excrete ammonia directly.

Urea eventually reacts with water to form ammonia, which therefore is usually present to some extent in waste water. Low concentrations of ammonia in water can be detected and measured using a solution called Nesslers reagent, which develops a strong color in the presence of ammonia. A recent toxic substance inventory done by the United States government estimated that in 1989, 200, 000 tons of ammonia were released into the environment. This figure does not include fertilizer applications of ammonia.

Although Earths atmosphere is free of ammonia, liquid and solid ammonia exist on other planets, such as Jupiter, where it may have originally formed from metal nitrides reacting with water. Ammonia has also been detected in interstellar space by radioastronomy.

Uses of ammonia

The largest use of ammonia is in fertilizers, which are applied to the soil and help provide increased yields of crops such as corn, wheat, and soybeans. Liquid ammonia, ammonia/water solutions, and chemicals made from ammonia, such as ammonium salts and urea, are all used as sources of soluble nitrogen. Urea, which is made from ammonia and carbon dioxide, can also be used as a feed supplement for cattle, aiding in the rapid building of protein by the animals.

All other important nitrogen chemicals are now made from ammonia. In a reaction called the Ostwald process, nitric acid results from oxidation of ammonia in the presence of a platinum catalyst and is followed by treatment of the resulting nitrogen oxides with water. Nitric acid and nitrates are needed for the manufacture of explosives like TNT, nitroglycerin, gunpowder, and also for the propellants in cartridges for rifles and machine guns.

Two types of polymers needed for artificial fibers require the use of ammonia, polyamides (nylon), and acrylics (orlon). The original polyamide, named nylon, produced by DuPont Chemical Co., was made from two components, adipic acid and hexamethylenediamine. The nitrogen in the second named component is derived from ammonia. Acrylics are made from a three-carbon nitrogen compound, acrylonitrile. Acrylonitrile comes from the reaction of propene, ammonia, and oxygen in the presence of a catalyst.

Because of its basic properties, ammonia is able to react with acidic gases such as nitrogen oxides and sulfur oxides to form ammonium salts. Thus ammonia

KEY TERMS

Ammonia complexes Species, usually positively charged ions, formed by linking several ammonia molecules through their nitrogen atoms to a transition metal ion.

Gigajoule A billion joules. An amount of energy equal to 277 kilowatt-hours, or about the electrical energy used by an American family in a month.

Polyamide A polymer such as nylon, containing recurrent amide groups linking segments of the polymer chain.

is useful in scrubbers that remove acidic gases before they are released into the environment.

Future prospects

Ammonia will continue to be important for agriculture and for the whole nitrogen chemicals industry. As countries in Asia and Latin America develop higher standards of living and stronger economies, they will need their own ammonia plants. For this reason, capacity and production will continue to grow. New uses may develop, particularly for ammonia as a relatively inexpensive base with unique properties, for liquid ammonia as a solvent, and as a storage medium for hydrogen, as the nations evolve toward alternative fuels.

See also Amides.

Resources

BOOKS

Buechel, K. H., et al. Industrial Inorganic Chemistry. New York: VCH, 2000.

Greenwood, N. N., and A. Earnshaw. Chemistry of the Elements. New York: Butterworth-Heinemann, 1997. Minerals Yearbook 2000. Washington, DC: Government Printing Office, 2001.

PERIODICALS

Seiler, N. Ammonia and Alzheimers Disease. Neurochemistry International 41, no. 2-3 (2002): 187-207.

OTHER

Ammonia (Anhydrous) Chemical Backgrounder National Safety Council: Crossroads <http://www.nsc.org/xroads/ChemicalTemplate.cfm?id=80&chempath=xroads > (accessed October 14, 2006).

John R. Phillips

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Ammonia

Ammonia

Ammonia, composed of three parts hydrogen and one part nitrogen , is a sharp-smelling, flammable, and toxic gas that is very soluble in water , where it acts as a base in its chemical reactions .


Ammonia in the past

Ammonia was present in the primordial atmosphere of Earth , and may have been the source of nitrogen for the earliest forms of life, although much controversy exists over the details. In ancient Egypt, ammonium compounds were used in rites honoring the god Ammon, from which came the name we still use for the gas and its compounds. Early chemists learned to generate ammonia from animal parts such as deerhorn, and obtained ammonial preparations (spirits of hartshorn, etc.), but Joseph Priestley (1733-1804) first collected and experimented with the pure substance. C. L. Berthollet (1748-1822) proved that ammonia is composed of nitrogen and hydrogen.

In the nineteenth century, ammonia was sometimes manufactured by the action of steam on calcium cyanamide, called the cyanamide process, which in turn was made by reacting calcium carbide with nitrogen at high temperatures. In the early twentieth century, German chemists Fritz Haber and Carl Bosch learned how to make ammonia in large quantities by high-pressure catalytic reactions of nitrogen (from air) with hydrogen. Both men were awarded Nobel prizes—Haber in 1918 and Bosch in 1931. The Haber-Bosch process is the basis for modern ammonia production, although many improvements have been made in the details of the technology.


Physical and chemical properties of ammonia

Ammonia (boiling point -28.03°F [-33.35°C]) can be made in the laboratory by heating ammonium chloride with lime, and the gas collected by downward displacement of air, or displacement of mercury. Water solutions of ammonia, called ammonium hydroxides, having as much as 28% ammonia by weight, can be obtained by this method. Ammonium hydroxide exhibits the characteristics of a weak base, turning litmus paper blue, and neutralizing acids with the formation of ammonium salts. Transition metal ions are either precipitated as hydroxides (iron [II], iron [III]) or converted to ammonia complexes (copper [II], nickel [II], zinc [II], silver [I]). The copper (II) ammonia complex , in solution , is deep blue in color , and serves as a qualitative test for copper. It also has the ability to dissolve cellulose , and has been used in the process for making regenerated cellulose fibers, or rayon.

Ammonia molecules possess a pyramidal shape, with the nitrogen atom at the vertex. These molecules continually undergo a type of motion called inversion, in which the nitrogen atom passes through the plane of the three hydrogen atoms like an umbrella turning inside out in the wind. When ammonia acts as a base, the nitrogen atom bonds either to a proton (to form ammonium ion) or to a metal cation . Ammonium salts such as ammonium chloride, called sal ammoniac, are water soluble and volatile when heated. It is often found that considerable heat is absorbed when ammonium salts dissolve in water, leading to dramatic reduction in temperature . Ammonium salts containing anions of weak acids (carbonate, sulfide) easily liberate ammonia owing to the tendency of a proton to break off the nitrogen atom and be bound by the weak acid anion .

In liquid or frozen ammonia, the molecules attract one another through sharing a hydrogen atom between one molecule and the next, called hydrogen bonding. In this attraction, called association, compounds apparently containing free electrons can be obtained by treating sodium/ammonia solutions with complexing agents.

Ammonia is a flammable gas, and reacts with oxygen to form nitrogen and water, or nitrogen (II) oxide and water. Oxidation of ammonia in solution leads to hydrazine, a corrosive and volatile ingredient in fuels. Ammonium salts of oxidizing anions—nitrate, dichromate, and perchlorate—are unstable and can explode or deflagrate when heated. Ammonium nitrate is used as a high explosive; ammonium perchlorate as a component of rocket fuels. Ammonium dichromate is used in a popular artificial volcano demonstration, in which a conical pile of the salt is ignited and burns vigorously, throwing off quantities of green chromium (III) oxide-the lava.

When ammonium hydroxide is treated with iodine crystals, an explosive brown solid, nitrogen triiodide, is formed. When dry, this substance is so sensitive that the lightest touch will cause it to explode with a crackling sound and a puff of purple iodine vapor.

Sources and production of ammonia

Ammonia is manufactured by the reaction of hydrogen with nitrogen in the presence of an iron catalyst, which is known as the Haber-Bosch process. The reaction is exothermic and is accompanied by a concentration in volume . (The ammonia occupies less volume than the gases from which it is made.) High pressure conditions (150-250 bar) are used, and temperatures range from 752–932°F (400–500°C). The mixed gases circulate through the catalyst, ammonia is formed and removed, and the unconverted reactants are recirculated. Large ammonia plants can produce over 1,000 tons per day. Each ton of ammonia requires 3,100 cu yd (2,400 cu m) of hydrogen and 1,050 cu yd (800 cu m) of nitrogen, as well as 60 gigajoules of energy . Much of the energy is consumed in the compressors needed to attain the high pressure used in the synthesis, and in heating the reactants. Further energy is needed to produce the hydrogen from hydrocarbon feedstocks, and to separate nitrogen from air. The synthesis reaction itself produces some heat, and great attention is given to heat efficiency, and use of waste heat. The gases that enter the catalytic converter must be highly purified and free of sulfur compounds, which adversely affect the catalyst. The catalyst is prepared in place by hydrogen treatment of magnetite, an iron oxide containing potassium hydroxide and other oxides in small amounts as promoters. A large ammonia plant might have as much as 100 tons of catalyst.

Since the hydrogen is usually derived from a natural gas called methane, the price of ammonia is very sensitive to the availability or price of fuels. United States production of ammonia reached 17 million tons in 1991, and demand was even larger than U.S. production, leading to about two million tons of imports. World ammonia production is about 100 million tons per year, which amounts to about 40 lbs (18 kg) for each person on earth.

Ammonia is formed from nitrogen in air by the action of nitrogen-fixing bacteria that exist in the soil on the roots of certain plants like alfalfa. Nitrogen fixation can also be accomplished by blue-green algae in the sea. These bacteria and algae possess an enzyme called nitrogenase that permits them to convert nitrogen to ammonia at 77°F (25°C) and 1 bar of pressure, much milder conditions than those of the Haber-Bosch process. Nitrogenase is known to be a complex protein containing metal atoms, such as iron and molybdenum, and sulfide ions, but its structure and mode of action are imperfectly understood, even after decades of research. Recent research indicates that the nitrogen molecule may bind to iron atoms in the enzyme as a reaction step.

Ammonia can be formed in the human body, and may build up abnormally during serious illnesses such as Reye's syndrome . Much nitrogen is normally excreted by humans (and other mammals ) as urea , a water soluble solid, but fish can excrete ammonia directly.

Urea eventually reacts with water to form ammonia, which therefore is usually present to some extent in waste water. Low concentrations of ammonia in water can be detected and measured using a solution called Nessler's reagent, which develops a strong color in the presence of ammonia. A recent toxic substance inventory done by the United States government estimated that in 1989, 200,000 tons of ammonia were released into the environment. This figure does not include fertilizer applications of ammonia.

Although Earth's atmosphere is free of ammonia, liquid and solid ammonia exist on other planets, such as Jupiter , where it may have originally formed from metal nitrides reacting with water. Ammonia has also been detected in interstellar space by radioastronomy.


Uses of ammonia

The largest use of ammonia is in fertilizers , which are applied to the soil and help provide increased yields of crops such as corn, wheat , and soybeans. Liquid ammonia, ammonia/water solutions, and chemicals made from ammonia, such as ammonium salts and urea, are all used as sources of soluble nitrogen. Urea, which is made from ammonia and carbon dioxide , can also be used as a feed supplement for cattle, aiding in the rapid building of protein by the animals.

All other important nitrogen chemicals are now made from ammonia. Nitric acid results from oxidation of ammonia in the presence of a platinum catalyst, called the Ostwald process, followed by treatment of the resulting nitrogen oxides with water. Nitric acid and nitrates are needed for the manufacture of explosives like TNT, nitroglycerin, gunpowder, and also for the propellants in cartridges for rifles and machine guns.

Two types of polymers needed for artificial fibers require the use of ammonia, polyamides (nylon) and acrylics (orlon). The original polyamide named nylon, brought out by DuPont Chemical Co., was made from two components, adipic acid and hexamethylenediamine. The nitrogen in the second named component is derived from ammonia. Acrylics are made from a three-carbon nitrogen compound, acrylonitrile. Acrylonitrile comes from the reaction of propene, ammonia, and oxygen in the presence of a catalyst.

Because of its basic properties, ammonia is able to react with acidic gases such as nitrogen oxides and sulfur oxides to form ammonium salts. Thus ammonia is useful in scrubbers that remove acidic gases before they can be released into the environment.

Future prospects

Ammonia will continue to be important for agriculture and for the whole nitrogen chemicals industry. As countries in Asia and Latin America develop high standards of living and stronger economies, they will begin to need their own ammonia plants. For this reason, capacity and production will continue to grow. New uses may develop, particularly for ammonia as a relatively inexpensive base with unique properties, for liquid ammonia as a solvent, and as a storage medium for hydrogen, as the nations evolve toward alternative fuels.

See also Amides.


Resources

books

Greenwood, N. N. and A. Earnshaw. Chemistry of the Elements. New York: Butterworth-Heinemann, 1997.

K.H. Buechel, et al. Industrial Inorganic Chemistry. New York: VCH, 2000.

Minerals Yearbook 2000. Washington, DC: Government Printing Office, 2001.


periodicals

Seiler, N. "Ammonia and Alzheimer's Disease." Neurochemistry International 41, no. 2-3 (2002): 187-207.


John R. Phillips

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ammonia complexes

—Species, usually positively charged ions, formed by linking several ammonia molecules through their nitrogen atoms to a transition metal ion.

Gigajoule

—A billion joules. An amount of energy equal to 277 kilowatt-hours, or about the electrical energy used by a family in a month.

Polyamide

—A polymer such as nylon, containing recurrent amide groups linking segments of the polymer chain.

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Ammonia

Ammonia

OVERVIEW

Ammonia (uh-MOH-nyah) is a colorless gas with a strong, suffocating odor. It was present in the primordial (original) atmosphere of the Earth. Scientists believe that it may have been the source of nitrogen for the earliest forms of life. Ammonia was the first chemical compound to be found in interstellar space, the space between stars. It is a major component of the atmosphere of many planets in our solar system.

Early chemists learned to produce ammonia from animal parts, such as the horns of deer. But it was the English chemist and physicist Joseph Priestley (1733–1804) who first collected and studied the pure gas. In 1785, the French chemist Claude-Louis Berthollet (1748–1822) determined the correct chemical formula for the gas, NH3.

KEY FACTS

OTHER NAMES:

None

FORMULA:

NH3

ELEMENTS:

Nitrogen, hydrogen

COMPOUND TYPE:

Inorganic base

STATE:

Gas

MOLECULAR WEIGHT:

17.03 g/mol

MELTING POINT:

−77.7°C (−108°F)

BOILING POINT:

−33.35°C (−28.03°F)

SOLUBILITY:

Very soluble in cold water; soluble in alcohol, ether, and many organic solvents

In 2004, American companies produced 10,762,000 metric tons (11,863,000 short tons) of ammonia, making it the tenth highest-volume chemical made in the United States. Only ten years earlier, it had ranked number 5 on the list of all chemicals produced by volume. About 90 percent of all the ammonia used in the United States goes to the production of fertilizers.

HOW IT IS MADE

Ammonia is produced naturally by the action of certain types of bacteria on nitrogen found in the atmosphere. It is also formed during the decay of dead organisms.

Until the end of the nineteenth century, ammonia was produced commercially by the cyanamide process. Calcium carbide (CaC2), nitrogen gas (N2), and steam were reacted with each other to produce ammonia.

In the early 1900s, the German chemist Fritz Haber (1868–1934) developed a method for making ammonia directly from its elements, nitrogen and hydrogen. The two gases are combined with each other at high temperature (400°C to 650°C; 750°F to 1200°F) and pressure (200 to 400 atmospheres; 3,000 to 6,000 pounds per square inch) over a catalyst made of finely-divided iron. Haber's process was later refined and improved by German chemical engineer Carl Bosch (1874–1940). Haber and Bosch both won Nobel Prizes in chemistry for their work on the production of ammonia. The Haber-Bosch process remains the most common form of ammonia production in many countries, including the United States. Small amounts of ammonia are also produced during the process by which soft coal is converted to coke.

Ammonia is a natural product of metabolism in all animals. When proteins break down, the nitrogen they contain is converted, in part, to ammonia. The ammonia is then converted to urea, which is excreted in the urine.

Interesting Facts

  • Ammonia's name comes from an ancient Egyptian practice conducted at the temple of the sun god Amon (or Ammon) near Karnak. Camel dung burned at the temple gave off a strong odor (ammonia) and left behind a white crystalline substance on the ground. The white substance was given the name of sal ammoniac, or salt of Amon, and the gas itself later became known as ammonia.
  • The Haber-Bosch process was developed largely because of Germany's need for explosives in World War I. Ammonia gas is converted to nitric acid, which, in turn, is used in making sodium and potassium nitrate, major components of explosives. Fritz Haber believed that it was his patriotic duty to contribute to the German war effort in whatever way he could, which led to his development of a new method for making ammonia.

COMMON USES AND POTENTIAL HAZARDS

Ammonia is used in a variety of forms as a fertilizer. It can be liquified or dissolved in water and sprayed on land, or it can be converted into any one of a number of compounds, such as ammonium nitrate, ammonium phosphate, or ammonium sulfate. In these forms, it is spread as dry granules on the land. Urea, made from ammonia and carbon dioxide, is also used as a feed supplement for cattle. Plants and animals use the nitrogen in ammonia and its compounds to synthesize new proteins that contribute to their growth and development.

The next largest use of ammonia is in the synthesis of nitric acid (HNO3). In a process developed by the German chemist Wilhelm Ostwald (1853–1932), ammonia, oxygen, and water are reacted together in a series of steps that results in the formation of nitric acid. Nitric acid, the thirteenth most important chemical in the United States in terms of productions, has a number of important uses, including the manufacture of explosives. Like the Haber-Bosch process, the Ostwald process contributed to the success experienced by Germany during World War I.

In addition to its use in the manufacture of fertilizers and explosives, smaller amounts of ammonia are used:

  • As a refrigerant;
  • In the manufacture of plastics;
  • As a raw material in the manufacture of other nitrogen-containing chemicals;
  • In the production of dyes;
  • As a rocket fuel;
  • For the neutralization of acids during the refining of petroleum;
  • In order to produce specialized types of steel; and
  • As a nutrient in yeast cultures in food processing operations.

Both gaseous and liquid ammonia pose moderate health hazards to those who come into contact with them. For example, farmers who handle liquid ammonia risk the possibility of painful blistering of the skin or damage to the mucous membranes if they come into contact with the ferilizer. Ammonia fumes can irritate the mouth, nose, and throat, causing coughing and gagging responses. Higher levels of exposure may irritate the lungs, resulting in shortness of breath and producing headaches, nausea, and vomiting. Very high exposures can cause a buildup of fluid in the lungs that can result in death. Since ammonia is a common ingredient of many household products, everyone should be aware of its health risks, although the threat posed by such products is, in fact, very small.

Words to Know

CATALYST
A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure.
METABOLISM
The process including all of the chemical reactions that occur in cells by which fats, carbohydrates, and other compounds are broken down to produce energy and the compounds needed to build new cells and tissues.
MUCOUS MEMBRANES
Tissues that line the moist inner lining of the digestive, respiratory, urinary and reproductive systems.
SYNTHESIS
A chemical reaction in which some desired chemical product is made from simple beginning chemicals, or reactants.

FOR FURTHER INFORMATION

"Ammonia." Masterliness. http://www.masterliness.com/a/Ammonia.htm (accessed on September 19, 2005).

Buechel, K. H., et al. Industrial Inorganic Chemistry. New York: VCH, 2000, pp. 29-43.

"The Facts about Ammonia." New York State Department of Health. http://www.health.state.ny.us/nysdoh/bt/chemical_terrorism/docs/ammonia_general.pdf (accessed on September 19, 2005).

"Toxicological Profile for Ammonia." Agency for Toxic Substances and Disease Registry. http://www.atsdr.cdc.gov/toxprofiles/tp126.html (accessed on September 19, 2005).

"Uses and Production of Ammonia (Haber Process)." Ausetute. http://www.ausetute.com.au/haberpro.html (accessed on September 19, 2005).

See AlsoAmmonium Chloride; Ammonium Hydroxide; Ammonium Nitrate; Ammonium Sulfate; Nitric Acid; Potassium Nitrate; Urea

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