Ammonia is a colourless gas possessing a characteristic pungent smell and a strongly alkaline reaction. It does not support combustion; and it does not burn readily unless mixed with oxygen, when it burns with a pale yellowish-green flame. Ammonia gas has the power of combining with many substances, particularly with metallic halides; thus with calcium chloride it forms the compound CaCl2.8NH3,

The main process for manufacturing nitrates is from ammonia through the Haber process. Fritz Haber created the process in 1908. The reaction occurs at high pressure and with high temperature, and with iron acting as a catalyst.

N2 + 3H2 = 2NH3

The ammonia is mixed with air and compressed then passed over a Platinum/Rhodium catalyst heated to 900°c.

4NH3 + 5O2 = 4NO2 + 6H2O

The NO2 is mixed with air and passed up a tower where water is flowing down.

4NO2 + O2 = 4HNO3 + 2H2O

A solution of approximately 50% nitric acid flows out at the bottom of the tower. Nitric acid is used to manufacture ammonium nitrate fertiliser