essential oil
A naturally occurring volatile liquid, formed in
various parts of plant life, principally in the
leaves, flowers, or fruit. The main constituents
are the terpines, i.e., hydrocarbons which
generally have the empirical formula C
10 H 16 , and their
derivatives. They also contain alcohols,
aldehydes, esters, ketones, as well as compounds
containing nitrogen and sulfur. Essential oils are
volatile in steam, have characteristic odors, and
leave no oily marks on paper. They are virtually
insoluble in water but are soluble in alcohol and
ether. Many are susceptible to oxidation in the
presence of air or oxygen. They are obtained by
steam distillation or by extraction.
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