The major use of ammonia is as a fertilizer. It is most commonly applied directly to the soil from tanks containing the liquefied gas. The ammonia can be applied directly or in the form of ammonium salts, such as ammonium nitrate, NH4NO3, ammonium sulfate, (NH4)2SO4, and various ammonium phosphates. Urea, (H2N)2C=O, is also used as a source of nitrogen for fertilizer. 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 fibres, 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 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.