90 
13. Resin is very common in the vegetable 
kingdom. 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 turpen- 
tine ; by heating this turpentine gently, a volatile 
oil rises from it, and a more fixed substance re- 
mains : 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 1072. 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 attraction of the water 
for the alcohol. 
Resins are obtained from many other species of 
trees. Mastich from the Pistacia lentiscus, Elemi 
from the Amy r is elemifera, Copal from the Rhus 
copallinum , Sandarach from the common juniper. 
Of these resins copal is the most peculiar. It is 
the most difficullty dissolved in alcohol y and for 
this purpose must be exposed to that substance in 
vapour ; or the alcohol employed must hold cam- 
phor in solution. According to Gay Lussac and 
Thenard, 
100 parts of common resin contain 
Carbon - - 75*944 
Oxygene - - - 13*337 
Hydrogene - - 10*719 
or of 
Carbon 
75*944 
