Ammonia

Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula NH₃. 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 pharmaceutical products and is used in many commercial cleaning products.

Ammonia is common in nature, both terrestrially and in the outer planets of the Solar System. It is widely used in dilute form, but is both caustic and hazardous in its concentrated form. In many countries it is classified as an extremely hazardous substance, and is subject to strict reporting requirements by facilities that produce, store, or use it in significant quantities.

The global industrial production of ammonia in 2021 was 235 million tonnes. Industrial ammonia is sold either as ammonia liquor (usually 28% ammonia in water) or as pressurised or refrigerated anhydrous liquid ammonia transported in tank cars or cylinders.

Because of the chemical inertness of nitrogen gas, production of ammonia from atmospheric nitrogen is difficult. Biological nitrogen fixation is only performed by a few families of microorganisms, the diazotrophs. The Haber process that enabled industrial production was invented at the beginning of the 20th century, revolutionizing agriculture.

NH₃ boils at −33.34 °C (−28.012 °F) at a pressure of one atmosphere, so the liquid must be stored under pressure or at low temperature. Household ammonia or ammonium hydroxide is a solution of NH₃ in water. The concentration of such solutions is measured in units of the Baumé scale (density), with 26 degrees Baumé (about 30% of ammonia by weight at 15.5 °C or 59.9 °F) being the typical high-concentration commercial product.