Ammonia

Ammonia is a small molecule: one nitrogen atom with three hydrogen atoms (NH₃). It's a colorless gas with a sharp smell, familiar from some household cleaners. It's one of the most-produced chemicals on Earth, and most of it goes into fertilizer.

Nearly all of it is made by the Haber-Bosch process, worked out in Germany by Fritz Haber and Carl Bosch between 1909 and 1913. Nitrogen comes from the air, and hydrogen usually comes from natural gas reacted with steam. The two gases are squeezed to roughly 100 to 250 times normal air pressure, heated to about 400 to 500 °C and passed over an iron catalyst. Only part of the mix turns into ammonia on each pass, so the ammonia is cooled until it turns liquid and the rest is sent round again.

For electronics, ammonia is purified to an extreme degree. It supplies the nitrogen when silicon nitride films are deposited on display glass, and when gallium nitride crystals are grown for blue LEDs. It also supplies the nitrogen atom in acrylonitrile, one of the building blocks of ABS plastic.