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Skunk Chemistry

April 20, 2010

There is nothing like the fresh smell of a spring morning, unless during the night a skunk skulked about your neighborhood. The Striped Skunk (Mephitis mephitis) is armed with up to a teaspoon of the odoriferous oil in its two anal glands. A skunk can direct the spray for several feet. And little bit goes a long way. Our noses can detect a mere 10 parts per billion of the spray.

When I was in 8th grade I was unlucky enough to get a burst of spray from a skunk onto my pants at close range. I can attest that at high concentrations it definitely causes nausea and acts like tear gas causing watering eyes and a running nose. Oh, and your mother will make you take your clothes off outside and throw them out.

What makes this stuff so potent that it can chase a bear away? The secretion is a yellow oil and it is composed of seven major volatile components from two groups of compounds, thiols and acetate derivatives of thiols. A thiol is a compound that contains the functional group composed of a sulfur-hydrogen bond. Most of us immediately recognize the smell of another thiol, the odorizor that is added to natural gas, which is odorless, so that any gas leaks can be detected by our nose. Another is the “skunky smell” of beer after it is exposed to ultraviolet light.

The thioacetate derivatives are not as odoriferous as thiols, but are easily converted to the more potent thiols when they react with water. For weeks after I was sprayed I would give off the faint smell of skunk at basketball practice. Perhaps the thioacetate derivatives trapped in my hair reacted with the moisture from my sweat. I don’t remember, but I wonder if my defenders backed off a bit affording me more scoring opportunities.

Many people will tell you that tomato juice will neutralize the odor, but human olfactory fatigue is a better explanation for the apparent disappearance of the odor. I could hardly smell the odor on my body after a few hours, but when a new nose came into range, they squealed with disgust. I tired nose will smell the tomatoes rather than the skunk.

You can neutralize the odoriferous thiols in the spray through oxidation to sulfonic acids, which are found in organic acids that are used in detergents and dyes. Oxidizers such as hydrogen peroxide and baking soda are mild enough to be used on pets. For washing down your deck or trash can try liquid laundry bleach.

The smell is certainly memorable. Even decades later the thought of that moment when the skunk turned and sprayed my pants almost turns my stomach and brings tears to my eyes again.

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