C 88 j 



13. Resin is very common in the vegetable king* 

 dom. One of the most usual species is that afforded 

 by the different kinds of fir. When a portion of the 

 bark is removed from a fir tree in spring, a matter 

 exudes, which is called turpentine ; by heating this 

 turpentine gently, a volatile oil rises from it, and a 

 more fixed substance remains ; this substance is 

 resin. 



The resin of the fir is the substance commonly 

 known by the name of rosin ; its properties are well 

 known. Its specific gravity is 1O72. It melts readily, 

 burns with a yellow light, throwing off much smoke. 

 Resin is insoluble in water either hot or cold ; but 

 very soluble in alcohol. When a solution of resin in 

 alcohol is mixed with water, the solution becomes 

 milky ; the resin is deposited by the stronger attrac- 

 tion of the water for the alcohol. 



Resins are obtained from many other species of 

 trees. Mastich, from the Plstada lentiscus, Elemi 

 from the Amyris elemifera^ Copal from the Rhus copal- 

 linum, Sandarach from the common juniper. Of these 

 resins copal is the most peculiar. It is the most diffi- 

 cultly dissolved in alcohol ; and for this purpose 

 must be exposed to that substance in vapour , or the 

 alcohol employed must hold camphor in solution. Ac- 

 cording to Gay Lpssac and Thenard, 

 100 parts of common resin contain 



Carbon - - - - - 75,944 

 Oxygene 13,337 



Hydrogene - 10,719 



