C    C              C—–­C
||   ||             ||  |
C—­C    C           C—­C   C
|    |     -->      |   |
C    C—­C           C   C—­C
||   ||             |   ||
C    C              C—–­C

[Illustration:  isoprene turns into caoutchouc]

I have dropped the 16 H’s or hydrogen atoms of the formula for simplicity’s sake.  They simply hook on wherever they can.  You will see that the isoprene consists of a chain of four carbon atoms (represented by the C’s) with an extra carbon on the side.  In the transformation of this colorless liquid into soft rubber two of the double linkages break and so permit the two chains of 4 C’s to unite to form one ring of eight.  If you have ever played ring-around-a-rosy you will get the idea.  In Chapter IV I explained that the anilin dyes are built up upon the benzene ring of six carbon atoms.  The rubber ring consists of eight at least and probably more.  Any substance containing that peculiar carbon chain with two double links C=C-C=C can double up—­polymerize, the chemist calls it—­into a rubber-like substance.  So we may have many kinds of rubber, some of which may prove to be more useful than that which happens to be found in nature.

With the structural formula of Harries as a clue chemists all over the world plunged into the problem with renewed hope.  The famous Bayer dye works at Elberfeld took it up and there in August, 1909, Dr. Fritz Hofmann worked out a process for the converting of pure isoprene into rubber by heat.  Then in 1910 Harries happened upon the same sodium reaction as Matthews, but when he came to get it patented he found that the Englishman had beaten him to the patent office by a few weeks.

This Anglo-German rivalry came to a dramatic climax in 1912 at the great hall of the College of the City of New York when Dr. Carl Duisberg, of the Elberfeld factory, delivered an address on the latest achievements of the chemical industry before the Eighth—­and the last for a long time—­International Congress of Applied Chemistry.  Duisberg insisted upon talking in German, although more of his auditors would have understood him in English.  He laid full emphasis upon German achievements and cast doubt upon the claim of “the Englishman Tilden” to have prepared artificial rubber in the eighties.  Perkin, of Manchester, confronted him with his new process for making rubber from potatoes, but Duisberg countered by proudly displaying two automobile tires made of synthetic rubber with which he had made a thousand-mile run.

The intense antagonism between the British and German chemists at this congress was felt by all present, but we did not foresee that in two years from that date they would be engaged in manufacturing poison gas to fire at one another.  It was, however, realized that more was at stake than personal reputation and national prestige.  Under pressure of the new demand for automobiles the price of rubber jumped from $1.25 to $3 a pound in 1910, and millions had