ON THE RESINS. 
45 
The combinations of these oils with oxygen have not 
hitherto been studied with that attention their importance de- 
mands. M. Henry Rose has lately, however, undertaken 
this task; and being of opinion that it would be most advanta- 
geous to investigate the composition of resins furnished by the 
isomeric essential oils, he confined himself principally to this 
class; his researches on these were capable of great extension, 
for, as pointed out by Unverdorben, most of the resins derived 
from essential oils act like acids, and form saline combinations 
with inorganic bases; some again, of which several can be ob- 
tained in a crystalline form, are wholly destitute of acid pro- 
perties; the author has, therefore, also examined some of the 
crystalline resins of this latter character. 
RESINS HAVING THE PROPERTIES OP ACIDS. 
Resin of Copaiba. No one of the resins can be obtained 
in as fine crystals as the resin of copaiba; they are best pro- 
cured by the process first indicated by Schweitzer. They are 
of a pure white colour, the smaller being transparent, the larger 
are translucent; they are soft; concentrated alcohol, when 
aided by heat, dissolves them more readily than when cold. 
The alcoholic solution reddens litmus paper. This resin com- 
bines with the inorganic bases, and these combinations have 
all the properties of salts. 0.509 grammes of the crystallised 
resin were decomposed with oxide of copper in the apparatus 
of Liebig. They afforded 0.464 grammes of water, and 1.459 
grammes of carbonic acid; hence 100 parts are composed of — 
Carbon 79.26 
Hydrogen 10.15 
Oxygen 10.59 
100.00. 
Now, this composition is in accordance with that given by 
MM. Blanchet and Sell as the constituents of colophane, viz. : 
carbon 79.65, hydrogen 10.08, oxygen 10.27; colophane is 
an oxide of the oil of turpentine; as the composition of this 
latter, according to M. Blanchet, is the same as that of the oil 
