You find an unused can of Zyklon B what do you do with it?

You thank God that you had never witnessed Shoah...

Call the fire dept. they will know how to dispose of it. My uncle called them one time after he found a bottle of gun blueing in his cabinet that he forgot about. They showed on the news that it gets unstable and becomes as volatile as nitro-glycerin when it gets old enough. The fire department send firefighters to collect it and told him he did the right thing.