Abstract Treatment of 3, 4-bis (formylamino) pyridine with a mixture of concentrated nitric and sulfuric acids unexpectedly afforded 4-nitro-1, 2, 3-triazolo [4, 5-c] pyridine 2-oxide. Reduction of the latter with iron in acetic acid gave previously known 4-amino-1, 2, 3-triazolo [4, 5-c] pyridine.