Why do metals have this typical smell?

Right / sense of smell: Does metal have a smell?

Everyone thinks they know this smell: if you've held a few coins in your hand or handled a tool for a while, your hands smell metallic. A piece of metal also develops a characteristic taste in the mouth. And blood tastes very similar - because there is iron in it, right?

We perceive smells (and most of the tastes) when volatile chemical compounds land on our nasal mucous membrane and dock onto receptors there. But metals are solids, their atoms are very tightly bound in a crystal structure. There is no cloud of iron atoms hanging over a piece of iron that could irritate our nose. So where does the characteristic metal aroma come from?

That secret was only revealed ten years ago. Researchers from the Leipzig-Halle Environmental Research Center and the Virginia Polytechnic Institute in the USA published a work in the journal at the time Applied Chemistry. Your explanation: What we smell there is ultimately chemically altered human sweat.

The oily sweat on our skin, or more precisely: the lipid peroxides in it, releases ions from a piece of iron when we touch it. They then split up and the so-called 1-octen-3-one is formed as a degradation product. It has a typical smell that we perceive as "metallic", although there is no iron atom in it.

Such compounds also occur when blood comes into contact with the skin. Therefore, the head of the research project, Dietmar Glindemann, suspected an evolutionary reason for our sensitivity: "The fact that humans can 'smell' iron is to be interpreted as a sense of blood smell. Early humans were thus probably able to track down wounded prey or members of their tribe."



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