Why Is Milk White?: & 200 Other Curious Chemistry Questions (2013)
6. Things That Stink
Why do skunks smell bad?
Skunks use their odor to defend themselves and keep predators away. Skunks spray a mixture of chemicals from special glands under the tail. These chemicals mostly contain molecules with a thiol group (a sulfur attached to a hydrogen).
These chemicals are known as mercaptans.
These are molecules that humans can sense when even one molecule is present among 10 billion air molecules.
A modification of these molecules is also present, where the thiol group has reacted with acetic acid to form what is called a thioacetate. These molecules have no smell but break down into the mercaptans when they get wet. This is why a dog that has been sprayed by a skunk smells worse when the air is humid.
Knowing that altering the thiol group removes the smell allows us to find remedies for skunk spray. If you oxidize the molecules with bleach, they lose their aroma. This is fine for washing clothes, but to wash a pet, you need something milder than chlorine bleach.
Hydrogen peroxide will work, but only if it is in an alkaline solution. So if you wash the dog in a mixture of baking soda and peroxide, much of the odor goes away. Repeating the wash helps, as does a final wash with a scented shampoo.