The signature metallic smell of a handful of coins isn't the scent of pure metal. According to Virginia Tech organic chemist Dietmar Glindemann, most people wouldn't even recognize the acrid smell of a vat of copper. But in a recent experiment, Glindemann showed that when we handle metal objects like coins (most U.S. coins are about 75 percent copper), our sweat begins corroding them immediately, creating a film of unstable ions that behave like partially oxidized rust. Fatty acids from oils on the skin are decomposed by these loose ions and form the compounds that give coined money its distinctive smell—an aroma that bears an odd resemblance to blood's.
Glindemann and colleague Andrea Dietrich placed pure iron, copper, and other metals in the hands of volunteers, then added artificial sweat to speed up the corrosion. Using a funnel to capture the rising odor, they determined that the musty smell peaked at the highest concentrations of the carbonyl compound 1-octen-3-one. This compound also turned up when researchers rubbed their own iron-rich blood on their skin.
Being able to smell 1-octen-3-one, or blood and money, is an age-old survival mechanism, they suggest. Being hunters, we are evolutionarily programmed to track the blood trails of animals, a talent that developed well before metallurgy. "I think that the ability to smell blood is as old as Tyrannosaurus rex," Glindemann says. What about the scent of dollars? "I have analyzed paper vapor with the same method," he says, adding that he found carbonyl compounds there too. But the compounds are quite different. "Therefore, paper smells like paper and not metallic."