ntages. You may mold, you may color the stuff
as you will, the scent of the camphor will cling around it still. This
is not usually objectionable except where the celluloid is trying to
pass itself off for something else, in which case it deserves no
sympathy. It is attacked and dissolved by hot acids and alkalies. It
softens up when heated, which is handy in shaping it though not so
desirable afterward. But the worst of its failings is its
combustibility. It is not explosive, but it takes fire from a flame and
burns furiously with clouds of black smoke.

But celluloid is only one of many plastic substances that have been
introduced to the present generation. A new and important group of them
is now being opened up, the so-called "condensation products." If you
will take down any old volume of chemical research you will find
occasionally words to this effect: "The reaction resulted in nothing but
an insoluble resin which was not further investigated." Such a passage
would be marked with a tear if chemists were given to crying over their
failures. For it is the epitaph of a buried hope. It likely meant the
loss of months of labor. The reason the chemist did not do anything
further with the gummy stuff that stuck up his test tube was because he
did not know what to do with it. It could not be dissolved, it could not
be crystallized, it could not be distilled, therefore it could not be
purified, analyzed and identified.

What had happened was in most cases this. The molecule of the compound
that the chemist was trying to make had combined with others of its kind
to form a molecule too big to be managed by such means. Financiers call
the process a "merger." Chemists call it "polymerization." The resin was
a molecular trust, indissoluble, uncontrollable and contaminating
everything it touched.

But chemists--like governments--have learned wisdom in recent years.
They have not yet discovered in all cases how to undo the process of
polymerization, or, if you prefer the financial phrase, how to
unscramble the eggs. But they have found that these molecular mergers
are very useful things in their way. For instance there is a liquid
known as isoprene (C_{5}H_{8}). This on heating or standing turns into a
gum, that is nothing less than rubber, which is some multiple of
C_{5}H_{8}.

For another instance there is formaldehyde, an acrid smelling gas, used
as a disinfectant. This has the simplest possible formula for a
carbohydrat