C
|
H

Professor Kekulé saw at once that the demons of his subconscious self
had furnished him with a clue to the labyrinth, and so it proved. We
need not suppose that the benzene molecule if we could see it would look
anything like this diagram of it, but the theory works and that is all
the scientist asks of any theory. By its use thousands of new compounds
have been constructed which have proved of inestimable value to man. The
modern chemist is not a discoverer, he is an inventor. He sits down at
his desk and draws a "Kekulé ring" or rather hexagon. Then he rubs out
an H and hooks a nitro group (NO_{2}) on to the carbon in place of it;
next he rubs out the O_{2} of the nitro group and puts in H_{2}; then he
hitches on such other elements, or carbon chains and rings as he likes.
He works like an architect designing a house and when he gets a picture
of the proposed compounds to suit him he goes into the laboratory to
make it. First he takes down the bottle of benzene and boils up some of
this with nitric acid and sulfuric acid. This he puts in the nitro group
and makes nitro-benzene, C_{6}H_{5}NO_{2}. He treats this with hydrogen,
which displaces the oxygen and gives C_{6}H_{5}NH_{2} or aniline, which
is the basis of so many of these compounds that they are all commonly
called "the aniline dyes." But aniline itself is not a dye. It is a
colorless or brownish oil.

It is not necessary to follow our chemist any farther now that we have
seen how he works, but before we pass on we will just look at one of his
products, not one of the most complicated but still complicated enough.

[Illustration: A molecule of a coal-tar dye]