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 "Kekule 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]

The name of this is sodium ditolyl-disazo-beta-naphthylamine-
6-sulfonic-beta-naphthylamine-3.6-disulfonate.

These chemical names of organic compounds are discouraging to the
beginner and amusing to the layman, but that is because neither of them
realizes that they are not really words but formulas. They are
hyphenated because they come from Germany. The name given above is no
more of a mouthful than "a-square-plus-two-a-b-plus-b-square" or "Third
Assistant Secretary of War to the President of the United States of
America." The trade name of this dye is Brilliant Congo, but while that
is handier to say it does not mean anything. Nobody but an expert in
dyes would know what it was, while from the formula name any chemist
familiar with such compounds could draw its picture, tell how it would
behave and what it was made f