Devardas alloy (Copper/Aluminium/Zinc) is a reducing agent. When reacted with nitrate in sodium hydroxide solution, ammonia is liberated. The ammonia formed may be detected by its characteristic odor, and by damp red litmus papers turning blue, signalling that it is an alkali &mdash; very few gases other than ammonia evolved from wet chemistry are alkaline.
:3  + 8 Al + 5  + 18  → 3  + 8 
Aluminium is the reducing agent in this reaction that will occur.