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Why Does Iron Smell Metallic When You Touch It?

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Whenever you touch iron tools, railings or coins there is a characterstic metallic smell that we say smells of iron. However, recent research shows that it is not the iron that smells at all, the smell is something of an illusion.

When the skin touches iron, the skin and moisture on the surface of the skin causes the iron to start to corrode very slightly. A compound called 1-octen-2-one is produced, which has a very strong fungal metallic smell which persists even when it is very dilute. The precursors of this smelly compound are lipid peroxides, which are produced when oils on skin are oxidized by certain enzymes. The lipid peroxides are then decomposed by the doubly negative iron ions, which are consequently reduced to triply negative iron ions, which also give a strong metallic smell.

A third component of the smell is produced by organophosphines such as methylphosphine, which is intensively smelly and has a garlic and metallic odour. These form when acids in the skin react with iron compounds formed in minute quantities when iron is touched.

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