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Camphor can
now be made directly from turpentine so we may be independent of Formosa
and Borneo.
When we have a six carbon ring without double linkings (cyclo-aliphatic)
or with one or two such, we get soft and delicate perfumes like the
violet (ionone and irone). But when these pass into the benzene ring
with its three double linkages the odor becomes more powerful and so
characteristic that the name "aromatic compound" has been extended to
the entire class of benzene derivatives, although many of them are
odorless. The essential oils of jasmine, orange blossoms, musk,
heliotrope, tuberose, ylang ylang, etc., consist mostly of this class
and can be made from the common source of aromatic compounds, coal tar.
The synthetic flavors and perfumes are made in the same way as the dyes
by starting with some coal-tar product or other crude material and
building up the molecule to the desired complexity. For instance, let us
start with phenol, the ill-smelling and poisonous carbolic acid of
disagreeable associations and evil fame.


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