This explains why chemists discovered how to take rubber apart over sixty years before they could find out how to put it together.  The first is easy.  Just put some raw rubber into a retort and heat it.  If you can stand the odor you will observe the caoutchouc decomposing and a benzine-like liquid distilling over.  This is called “isoprene.”  Any Freshman chemist could write the reaction for this operation.  It is simply

  C_{10}H_{16} —­> 2C_{5}H_{8}
  caoutchouc isoprene

That is, one molecule of the gum splits up into two molecules of the liquid.  It is just as easy to write the reaction in the reverse directions, as 2 isoprene—­> 1 caoutchouc, but nobody could make it go in that direction.  Yet it could be done.  It had been done.  But the man who did it did not know how he did it and could not do it again.  Professor Tilden in May, 1892, read a paper before the Birmingham Philosophical Society in which he said: 

I was surprised a few weeks ago at finding the contents of the bottles containing isoprene from turpentine entirely changed in appearance.  In place of a limpid, colorless liquid the bottles contained a dense syrup in which were floating several large masses of a yellowish color.  Upon examination this turned out to be India rubber.

But neither Professor Tilden nor any one else could repeat this accidental metamorphosis.  It was tantalizing, for the world was willing to pay $2,000,000,000 a year for rubber and the forests of the Amazon and Congo were failing to meet the demand.  A large share of these millions would have gone to any chemist who could find out how to make synthetic rubber and make it cheaply enough.  With such a reward of fame and fortune the competition among chemists was intense.  It took the form of an international contest in which England and Germany were neck and neck.

[Illustration:  Courtesy of the “India Rubber World.”

What goes into rubber and what is made out of it]

The English, who had been beaten by the Germans in the dye business where they had the start, were determined not to lose in this.  Prof.  W.H.  Perkin, of Manchester University, was one of the most eager, for he was inspired by a personal grudge against the Germans as well as by patriotism and scientific zeal.  It was his father who had, fifty years before, discovered mauve, the first of the anilin dyes, but England could not hold the business and its rich rewards went over to Germany.  So in 1909 a corps of chemists set to work under Professor Perkin in the Manchester laboratories to solve the problem of synthetic rubber.  What reagent could be found that would reverse the reaction and convert the liquid isoprene into the solid rubber?  It was discovered, by accident, we may say, but it should be understood that such advantageous accidents happen only to those who are working for them and know how to utilize them.  In July, 1910, Dr. Matthews, who had charge of the research, set some isoprene to drying over metallic sodium, a common laboratory method of freeing a liquid from the last traces of water.  In September he found that the flask was filled with a solid mass of real rubber instead of the volatile colorless liquid he had put into it.