# Why does Devarda's alloy include copper?

Devarda's alloy is used in the detection of nitrates. However, judging by the reaction equation, only aluminium plays the role of reducer:

$$\ce{3NaNO3 + 8Al + 5NaOH + 18H2O -> 8Na[Al(OH)4] + 3NH3(g)}$$

Why does it contain copper? Is copper also capable of acting as a reducer here?

I know that zinc, the third component, is capable of that.

• Galvanic couple, I guess. – Ivan Neretin May 25 '16 at 15:23
• Catalyst, I guess. ;-) – aventurin May 25 '16 at 15:30
• Blessed be the guessers, for they lead us to understanding. – CowperKettle May 26 '16 at 6:13