RUBBER 453 



CH 2 = CH — CH — CH 2 , can be made in just the same way as isoprene 

 from isoamyl alcohol. Butadiene is the next lower homologue of iso- 

 prene, and when it is treated with sodium it produces a substance very 

 like rubber which is called nor-caoutchouc. It is said that its quality is 

 even superior to that of ordinary rubber. As there are a number of 

 alcohols homologous to butyl and isoamyl alcohol, a number of substances 

 similar to isoprene and butadiene can be made from them, and from these 

 by the action of sodium a series of rubbers. It is said that the rubber 

 produced by the action of acetic acid on isoprene is identical with 

 natural rubber, and that the rubber made by the action of sodium is 

 slightly different in its chemical reactions. It may be that all natural 

 rubbers are not identical and that the difference between Para rubber 

 and plantation rubber may depend upon some slight differences in the 

 caoutchouc itself and that what the chemist does with extreme difficulty 

 when he changes starch into rubber, nature does with ease, and, as the 

 chemist may get slightly different products by pursuing different meth- 

 ods, so nature may get different products under different circumstances. 

 It was said at the beginning of this paper that rubber has the empir- 

 ical formula C 5 H 8 . It seems that the formula is more correctly written 

 C 10 H lt3 and that the name 1.5 dimethyl cyclooctadiene 1.5 represents the 

 structure of Para rubber, while the rubber produced by the action of 

 sodium on isoprene is 



1.5 dimethyl cyclooctadiene 1.3 

 or 1.5 dimethyl cyclooctadiene 1.7 



Dr. Duisberg, of Elberfeld, stated in his address to the Congress of 

 Applied Chemistry at New York in 1912 that he had for some time used 

 tires of artificial rubber on an automobile. The German Emperor has 

 also received a present of similar tires. The rubber can be made, but it 

 is still far too expensive to compete with natural rubber. 



Closely connected with the history of the rubber industry are the 

 Congo atrocities. Congo rubber is not so good for most purposes and 

 commands a lower price, though, being softer, it is said to be better as 

 a filling for driving belts and for other uses. It is obtained from Land- 

 olphia vines, which are not usually tapped, but cut off, the latex being 

 extracted all at once. This fact may be partly responsible for the atro- 

 cities, since, the more accessible sources of supply having been depleted, 

 the natives have been obliged to go farther and farther in order to obtain 

 the rubber demanded of them. 



In the sixties and seventies of the last century, central Africa became 

 known to Europe, and the commercial interests of the various nations 

 led to what is termed the " Scramble for Africa." Stanley's discovery 

 of the Upper Congo induced King Leopold to form the " International 

 African Association" and he sent several investigating expeditions at 



