284 INDUSTRIAL PLANTS 



with caoutchouc is called vulcanization. By using much 

 sulphur and a high degree of heat hard rubber or vulcanite 

 is produced. 



The discovery of vulcanization revolutionized the rubber 

 industry. Not only were the old uses greatly extended but 

 new uses for rubber have so multiplied that caoutchouc now 

 ranks among the most important products of the vegetable 

 kingdom. The elasticity of soft vulcanized rubber makes it 

 invaluable in various articles of dress, for many surgical 

 purposes, for elastic bands, solid or pneumatic tires, for 

 various parts of machines, and for rubber balls, toys, and in- 

 numerable other articles of minor use. Its imperviousness 

 to water and air, combined with its flexibility, render it of 

 greatest service for waterproof garments or coverings, sub- 

 marine diving-dresses, flexible tubes or hose, water-bottles, 

 air-cushions, life-preservers, portable boats, etc. Hard rub- 

 ber takes a high polish and is very resistant to the action 

 of acids and other corrosive fluids. Therefore it makes the 

 best possible material for photographer's developing trays, 

 certain parts of fountains pens, telephones, surgical instru- 

 ments, etc., while it is a most excellent and inexpensive sub- 

 stitute for horn or shell in such articles as combs and handles. 

 Both vulcanite and the softer vulcanized rubber are exten- 

 sively used for insulation in electric work. Pure rubber on 

 account of its remarkable adhesiveness is an indispensable 

 part of the best surgeon's plaster, and of the rubber tape 

 used in repairing bicycle tires and in electric wiring. The 

 curious erasing power of rubber, whether pure or vulcanized, 

 is possessed by no other substance to anything like the same 

 degree; hence one of its earliest uses still remains one of the 

 commonest and most important. 



Caoutchouc as a raw material bears, as we have seen, some- 

 what the same relation to the milky juice of plants that 

 cheese bears to the milk of animals. That is to say, it sepa- 

 rates from the fluid part as curd from whey, and becomes 

 solid by drying. Chemically, however, caoutchouc is quite 

 different from the proteid of which cheese mainly consists. 

 Pure caoutchouc is a hydrocarhon; in other words, it contains 

 only hydrogen and carbon in its composition. Commonly 



