Ammonia | Definition & Uses - Encyclopedia Britannica

Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos ammonia

• Introduction & Top Questions
• Uses
• Preparation
• Physical properties
• Chemical reactivity
• Derivatives
  • Hydrazine
  • Hydroxylamine

References & Edit History Related Topics Images & Videos For Students ammonia summary Science Chemistry

ammonia chemical compound Quick Summary Ask the Chatbot Print print Print Please select which sections you would like to print:

• Table Of Contents

Cite verifiedCite While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Select Citation Style MLA APA Chicago Manual of Style Copy Citation Share Share Share to social media Facebook X URL https://www.britannica.com/science/ammonia Feedback External Websites Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites

• Chemistry LibreTexts - NH3
• United States Enviromental Protection Agency - Ammonia
• New York State - Department of Health - The Facts About Ammonia
• American Chemical Society - Ammonia
• Cleveland Clinic - Ammonia Levels
• University of Bristol - Department of Chemistry - Ammonia
• Canadian Center for Occupational Health and Safety - Ammonia
• Science - Ammonia�a renewable fuel made from sun, air, and water�could power the globe without carbon
• The Essential Chemical Industry Online - Ammonia
• American Institute of Chemical Engineers - Introduction to Ammonia Production (PDF)
• National Center for Biotechnology Information - Ammonia Toxicity
• Frontiers - Frontiers in Mechanical Engineering - Ammonia as Green Fuel in Internal Combustion Engines: State-of-the-Art and Future Perspectives
• Chemical Safety Facts - Ammonia
• Centers for Disease Control and Prevention - Chemical Emergencies - Ammonia

Quick Summary Ask the Chatbot a Question Written by Steven S. Zumdahl Professor and Associate Head, Department of Chemistry, University of Illinois at Urbana-Champaign. Author of Chemical Principles and many others. Steven S. Zumdahl Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Nov. 28, 2025 •History Table of Contents Table of Contents Quick Summary Ask the Chatbot a Question Top Questions

What are the primary uses of ammonia?

Ammonia is primarily used as a fertilizer, in the manufacture of commercial explosives, synthetic fibers, and in various industrial processes such as petroleum refining and rubber production. It is also used in refrigeration and air-conditioning as a coolant.

How is ammonia produced commercially?

Ammonia is produced commercially using the Haber-Bosch process, which involves the reaction of hydrogen and nitrogen at high pressure and temperature, using a catalyst.

What are the physical properties of ammonia?

Ammonia is a colorless gas with a sharp odor, a boiling point of -33.35 °C, and a freezing point of -77.7 °C. It has a trigonal pyramidal shape and is a polar molecule with strong hydrogen bonding.

How does ammonia react with water?

Ammonia dissolves in water, releasing heat and forming a basic solution known as ammonium hydroxide. The equilibrium provides hydroxide ions, making the solution basic.

ammonia (NH3 ), colorless, pungent gas composed of nitrogen and hydrogen. It is the simplest stable compound of these elements and serves as a starting material for the production of many commercially important nitrogen compounds.

Uses

The major use of ammonia is as a fertilizer. In the United States, it is usually applied directly to the soil from tanks containing the liquefied gas. The ammonia can also be in the form of ammonium salts, such as ammonium nitrate, NH4NO3, ammonium sulfate, (NH4)2SO4, and various ammonium phosphates. Urea, (H2N)2C=O, is the most commonly used source of nitrogen for fertilizer worldwide. Ammonia is also used in the manufacture of commercial explosives (e.g., trinitrotoluene [TNT], nitroglycerin, and nitrocellulose).

In the textile industry, ammonia is used in the manufacture of synthetic fibers, such as nylon and rayon. In addition, it is employed in the dyeing and scouring of cotton, wool, and silk. Ammonia serves as a catalyst in the production of some synthetic resins. More important, it neutralizes acidic by-products of petroleum refining, and in the rubber industry it prevents the coagulation of raw latex during transportation from plantation to factory. Ammonia also finds application in both the ammonia-soda process (also called the Solvay process), a widely used method for producing soda ash, and the Ostwald process, a method for converting ammonia into nitric acid.

Ammonia is used in various metallurgical processes, including the nitriding of alloy sheets to harden their surfaces. Because ammonia can be decomposed easily to yield hydrogen, it is a convenient portable source of atomic hydrogen for welding. In addition, ammonia can absorb substantial amounts of heat from its surroundings (i.e., one gram of ammonia absorbs 327 calories of heat), which makes it useful as a coolant in refrigeration and air-conditioning equipment. Finally, among its minor uses is inclusion in certain household cleansing agents.

Preparation

Pure ammonia was first prepared by English physical scientist Joseph Priestley in 1774, and its exact composition was determined by French chemist Claude-Louis Berthollet in 1785. Ammonia is consistently among the top five chemicals produced in the United States. The chief commercial method of producing ammonia is by the Haber-Bosch process, which involves the direct reaction of elemental hydrogen and elemental nitrogen. N2 + 3H2 → 2NH3

This reaction requires the use of a catalyst, high pressure (100–1,000 atmospheres), and elevated temperature (400–550 °C [750–1020 °F]). Actually, the equilibrium between the elements and ammonia favors the formation of ammonia at low temperature, but high temperature is required to achieve a satisfactory rate of ammonia formation. Several different catalysts can be used. Normally the catalyst is iron containing iron oxide. However, both magnesium oxide on aluminum oxide that has been activated by alkali metal oxides and ruthenium on carbon have been employed as catalysts. In the laboratory, ammonia is best synthesized by the hydrolysis of a metal nitride. Mg3N2 + 6H2O → 2NH3 + 3Mg(OH)2

Physical properties

Ammonia is a colorless gas with a sharp, penetrating odour. Its boiling point is −33.35 °C (−28.03 °F), and its freezing point is −77.7 °C (−107.8 °F). It has a high heat of vaporization (23.3 kilojoules per mole at its boiling point) and can be handled as a liquid in thermally insulated containers in the laboratory. (The heat of vaporization of a substance is the number of kilojoules needed to vaporize one mole of the substance with no change in temperature.) The ammonia molecule has a trigonal pyramidal shape with the three hydrogen atoms and an unshared pair of electrons attached to the nitrogen atom. It is a polar molecule and is highly associated because of strong intermolecular hydrogen bonding. The dielectric constant of ammonia (22 at −34 °C [−29 °F]) is lower than that of water (81 at 25 °C [77 °F]), so it is a better solvent for organic materials. However, it is still high enough to allow ammonia to act as a moderately good ionizing solvent. Ammonia also self-ionizes, although less so than does water. 2NH3 ⇌ NH4+ + NH2−

Access for the whole family! Bundle Britannica Premium and Kids for the ultimate resource destination. Subscribe

Chemical reactivity

The combustion of ammonia proceeds with difficulty but yields nitrogen gas and water. 4NH3 + 3O2 + heat → 2N2 + 6H2O However, with the use of a catalyst and under the correct conditions of temperature, ammonia reacts with oxygen to produce nitric oxide, NO, which is oxidized to nitrogen dioxide, NO2, and is used in the industrial synthesis of nitric acid.

Ammonia readily dissolves in water with the liberation of heat. NH3 + H2O ⇌ NH4+ + OH− These aqueous solutions of ammonia are basic and are sometimes called solutions of ammonium hydroxide (NH4OH). The equilibrium, however, is such that a 1.0-molar solution of NH3 provides only 4.2 millimoles of hydroxide ion. The hydrates NH3 · H2O, 2NH3 · H2O, and NH3 · 2H2O exist and have been shown to consist of ammonia and water molecules linked by intermolecular hydrogen bonds.

Key People: Joseph Priestley Fritz Haber Gerhard Ertl (Show more) Related Topics: smelling salts ammonium sulfate anhydrous ammonia carbamoyl phosphate ammoxidation (Show more) See all related content

Liquid ammonia is used extensively as a nonaqueous solvent. The alkali metals as well as the heavier alkaline-earth metals and even some inner transition metals dissolve in liquid ammonia, producing blue solutions. Physical measurements, including electrical-conductivity studies, provide evidence that this blue colour and electrical current are due to the solvated electron. metal (dispersed) ⇌ metal(NH3)x ⇌ M+(NH3)x + e−(NH3)y These solutions are excellent sources of electrons for reducing other chemical species. As the concentration of dissolved metal increases, the solution becomes a deeper blue in color and finally changes to a copper-colored solution with a metallic lustre. The electrical conductivity decreases, and there is evidence that the solvated electrons associate to form electron pairs. 2e−(NH3)y ⇌ e2(NH3)y Most ammonium salts also readily dissolve in liquid ammonia.