Thursday, August 25, 2011

El "Olor metalico " es meramente olor corporal.

¿Por que el metal tiene olor ?

Probablemente la mayoría de las personas alguna vez en su vida hayan experimentado un olor al entrar en contacto con metales como el hierro o el cobre . Al agarrar un pasamanos de hierro o algún pedazo de metal aparentemente la mano queda impregnada de este olor metálico. Sin embargo Dietmar Glindermann y sus compañeros de la universidad alemana de Leipzig dicen que realmente el metal no es que tiene olor si no que mas bien este reacciona con algunos compuestos de la piel y genera este peculiar olor asociado al metal. Lean la nota completa(esta en inglés ) .

Why does metal smell? Chemists have found a surprising answer: it doesn't.

After you've grasped an iron railing, a door handle or a piece of steel cutlery, your hand often gives off what seems to be a metallic odour. But Dietmar Glindemann of the University of Leipzig, Germany, and his co-workers say that you're not smelling the metal at all.

They have found that the musty odour comes from chemical compounds in your skin, which are transformed in an instant by the touch of iron. They report the results in the international edition of Angewandte Chemie.

Copper has a similar effect, accounting for the metallic smell created by handling coins made of copper alloys. "When a shopkeeper hands you a coin," says Glindemann, "you're smelling his body odour."

The smelly reactions induced by these metals create "the sensory illusion that it is the 'metal in itself' that we smell right after touching it", the researchers say. In other words, a 'metallic' smell is only deemed to be so by association.

Sweaty palms

When a shopkeeper hands you a coin, you're smelling his body odour.
Dietmar Glindemann,

University of Leipzig
Glindemann began studying this question years ago when he became curious about the garlic-tinged metallic aroma of iron after it has been touched by a sweaty palm. He found that acids naturally present in sweat induce reactions between carbon and phosphorus impurities typically present in iron, generating smelly, volatile molecules called organophosphines.

But the 'metallic' smell left on your hands after you handle iron or copper was different from the scent of metals touched by acid in the lab. "This problem tortured me for five or six years," Glindemann says.

The breakthrough came when he teamed up with environmental chemist Andrea Dietrich at Virginia Polytechnic Institute and State University in Blacksburg. She was trying to understand why people often complain of a metallic taste in drinking water.

Exploring the issue of metallic taste led her to think about metallic smell. That took her to Glindemann, and they cracked the problem together.

The researchers captured the vapours emitted from the skin of people who had handled iron objects, and studied their chemical composition. The gases contained several compounds called aldehydes and ketones, which often have strong and distinctive smells. The odour of preserving fluid, or formaldehyde, makes for the characteristic reek of old anatomy labs, for example, while the ketone acetone makes the distinctive solvent whiff of nail-varnish remover.

These compounds are produced by rapid reactions between iron or copper and oils on our skin.

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The "Silver Song"

Este video es obra creativa de Armando Isaac, para el curso de Química Inorgánica I.