598 CONSIDERATION OF CARBON COMPOUNDS. 



into combination with from 7 to 10 per cent, of sulphur by heating 

 together the two substances to a temperature of 130-150 C. (266- 

 302 F.). Vulcanized rubber differs from the natural article by 

 possessing greater elasticity and flexibility, by resisting the action of 

 solvents, reagents and atmosphere to a higher degree, and by not 

 hardening when exposed to cold. 



Hard rubber, vulcanite, or ebonite, is vulcanized rubber, containing 

 from 20 to 35 per cent, of sulphur, and often also tar, white-lead, 

 chalk, or other substances. It is hard, tough, and susceptible of a 

 good polish. 



Preservation of rubber. Various substances have been recommended 

 for preserving articles of rubber. For undeteriorated rubber, it is said that a 

 3 per cent, solution of either phenol or aniline is the best, while for deterior- 

 ated rubber, or such as has been exposed many times to boiling water, a 1 per 

 cent, solution of potassium pentasulphide is best, the restorative properties of 

 the latter depending on the absorption of the sulphur from the pentasulphide. 

 The articles are immersed in the solutions in vessels of appropriate shape. It 

 has been observed that black rubber immersed in the aniline solution under- 

 goes an increase in volume. For example, rubber tubing shows a marked in- 

 crease in length. 



Gutta-percha is the concrete juice of a tree Isonaudra gutta. It 

 resembles india-rubber both in composition and properties. At ordi- 

 nary temperature it is a yellowish or brownish, hard, somewhat 

 flexible, but scarcely elastic substance ; when warmed it softens, and 

 is plastic above 60 C. (140 F.) ; at the temperature of boiling-water 

 it is very soft. It is insoluble in water, alcohol, dilute acids and 

 alkaline solutions ; soluble in oil of turpentine, carbon disulphide, 

 and chloroform. 



Oxygen derivatives of terpenes. 



Stearoptens or camphors are substances closely related to the 

 terpenes and to cymene both in physical and chemical properties; 

 while terpenes are liquid, camphors are crystalline solids. Borneo 

 camphor has the composition C 10 H 18 O, while the camphor found 

 in the camphor-trees of China and Japan has the composition 

 C 10 H 16 0. 



Camphor, Camphora, C ]0 H 16 O (LaurinoT), forms white, translucent 

 masses of a tough consistence and a crystalline structure ; it has a 

 characteristic, penetrating odor and poisonous properties ; in the pres- 

 ence of a little alcohol or ether it may be pulverized ; it is nearly 

 insoluble in water, but soluble in alcohol, ether, chloroform, etc. ; 

 boiled with bromine it forms the monobromated camphor, carnphora 



