This article is from the Chemistry FAQ, by Bruce Hamilton B.Hamilton@irl.cri.nz with numerous contributions by others.
Mothballs were originally made from camphor ( C10H16O, [76-22-2], MP 176C,
BP 204C ), or naphthalene ( C10H8, [91-20-3], MP 82C, BP 218C ),
but para-dichlorobenzene ( C6H4Cl2, [106-46-7], MP 55C, BP 173C ), became
cheaply available as an unwanted by-product of ortho-dichlorobenzene
production, and thus became the most common active ingredient. However
para-dichlorobenzene is also a suspected carcinogen, and naphthalene
has again become a common active ingredient. Consequently, the best
method of finding the active ingredient is to read the label on the packet,
Note that adding mothballs to modern gasolines will not increase the octane
rating of the fuel - refer to the Gasoline FAQ posted in rec.autos.tech for
more details.
 
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