Nitrogen is a fairly common element in the minechem mod. Nitrogen behaves, and has the properties, of the standard gas.
By Chemically decomposing Feathers, or Most recipes that use Feathers, or through breaking down more complex molecules - will produce pure nitrogen gas alongside water. Many items in the game, including gunpowder, will produce a nitrate ion or nitrogen compound. Gunpowder, a fairly common product derived from the killing of Creepers, will produce potassium nitrate when decomposed. Poppies, abundantly occuring in the Plains biome, will decompose into cobalt (ii) nitrate. This can further be decomposed into cobalt metal and a nitrate ion (NO3).