2 RUBBER AND 



1851 for the manufacture of vulcanite by more complete 

 combination of rubber with sulphur. 



Vulcanised Rubber. 



The method of vulcanisation, which ranks among 

 the most important of all industrial discoveries, was 

 first found out in America by Goodyear. In England, 

 Hancock shortly afterwards arrived at the same method 

 independently. The following facts will help the reader 

 to realise the far-reaching importance of vulcanisation. 



Raw rubber becomes soft and sticky when heated, 

 and when cooled beyond a certain point it becomes stiff 

 and almost horny in consistency. Vulcanised rubber 

 retains its physical properties almost unaltered over a 

 range of temperatures extending from the freezing point 

 to the boiling point of water. After prolonged immer- 

 sion in water, raw rubber absorbs as much as 25 per cent, 

 of its own weight of moisture. On the other hand, "The 

 water absorption of vulcanised rubber is extremely small 

 certainly not large enough to appreciably affect the 

 insulation of a rubber cable after five years' continuous 

 immersion" (Weber). From these facts the enormous 

 increase in the durability and general usefulness of 

 vulcanised rubber at once becomes apparent. Moreover, 

 according to the proportion of sulphur which has entered 

 into combination with the rubber, the physical properties 

 of the finished product can be made to vary from those 

 of the softest elastic up to those of the hardest vulcanite. 



