Reduced iron powder
Reduced iron powder, gray, or black powder, also known as the "double agent", can absorb moisture from the air and oxygen, commonly used in food preservation.
Reduced iron powder from iron oxide under high heat conditions hydrogen gas or reduction in carbon monoxide gas, mainly composed of loose structure of iron. Because of reduced iron powder is a powder for themselves, along with its micro-structure is very loose, so the surface actively. Often used in chemical production and laboratory work as good reducing agents.