Caoutchouc

Caoutchouc, or Indiarubber, a tough elastic substance obtained by drying the milky sap of certain tropical trees, as Jatropha elastica, Siphonia catechu, etc. It is composed of carbon and hydrogen, consisting of a variable mixture of different hydrocarbons. It is soluble in oil of turpentine, benzene, and carbon disulphide. If cooled it becomes hard and loses its elasticity, but again becomes supple by warming. It is applied to a variety of purposes, as for the manufacture of elastic tubing, gas bags, etc., and to render fabrics impermeable and waterproof. When combined with two or three per cent. of sulphur it becomes more supple and elastic, and is known as vulcanised caoutchouc. If combined with more sulphur it becomes harder and capable of taking a polish. It is then known as Ebonite or Vulcanite, and is much used for electrical instruments and other purposes.