370 CHEMICAL DISCOVERY AND INVENTION 



The cultivation of Hevea in the East is fully treated from the 

 scientific and practical points of view in Mr. Herbert Wright's 

 Hevea Brasiliensis or Para Rubber (MacLaren and Sons, London). 



HISTOEY OF SYNTHETIC RUBBER 



In the course of researches in connection with the hydro- 

 carbons called terpenes, which include turpentine oil, the author 

 obtained from turpentine by the action of heat a peculiar very 

 volatile liquid, called isoprene, which had previously been 

 produced only by the destructive distillation of india-rubber. 

 A peculiarity of this limpid liquid, which possesses a boiling 

 point close to that of common ether, is that in contact with 

 certain reagents, common hydrochloric acid among them, it is 

 converted partly into rubber. The liquid which remained over, 

 after the termination of this series of experiments, was pre- 

 served in well-closed bottles. Some few years later, in May, 

 1892, in a paper read by the author to the Philosophical Society 

 of Birmingham, the following passage occurs : "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 colourless liquid the bottles contained a dense 

 syrup in which were floating several large masses of solid, of a 

 yellowish colour. Upon examination this turned out to be india- 

 rubber. . . . The artificial, like natural, rubber appears to con- 

 sist of two substances, one of which is more soluble in benzene or 

 carbon bisulphide than the other. A solution of the artificial 

 rubber leaves on evaporation a residue which agrees in all 

 characters with a similar preparation from Para rubber. The 

 artificial rubber unites with sulphur in the same way as ordinary 

 rubber, forming a tough elastic compound." At the time 

 mentioned there was no means of further testing rubber chemically 

 so as to establish the relation of synthetic to natural rubber, but 

 the discovery many years later of ozonides of rubber by Professor 

 Harries of Berlin, and their decomposition products, has supplied 

 the means of testing the identity of rubbers from different 

 sources. This test has been applied by Professor Perkin of 

 Oxford to Tilden's original specimens and their true character 

 as rubber has thus been established. The remains of the original 

 specimens examined in 1892 and exhibited at the York meeting 

 of the British Association in 1906 have been deposited in the 

 Victoria and Albert Science Museum at South Kensington. As 



