Any salt or ester of nitric acid (HNO 3 ).
The salts are inorganic compounds with ion (NO 3 - ) and any cation . Many, particularly ammonium nitrate, are used as agricultural fertilizers (see {{link=saltpetre">saltpeter ). Their runoff in surface water and groundwater can cause serious illness in humans. The esters are organic compounds with covalent bonds , having the structure R―O―NO 2 , in which R represents an organic combining group such as methyl, ethyl, or phenyl.