244 ON THE VOLATILE OIL OP BETULA LENTA, ETC. 
gested the idea of an analogous chemical constitution of 
their volatile oils. 
Twenty-five pounds of the bark taken from the trunk and 
larger branches, deprived of its external layers, was coarse- 
ly bruised, macerated for several days in as much water as 
would cover it, and then submitted to distillation. By this 
treatment the bark yielded five drachms of volatile oil, 
besides that portion which remained in solution in the dis- 
tilled liquid. Several circumstances interfered with the 
success of the operation, and it is probable that the amount 
of oil indicated is less than it might have been under more 
favorable auspices. 
Volatile oil of Betula lenta, as obtained by careful distil- 
lation, is colorless, has the specific gravity 1.173, and in 
odor and taste closely resembles oil of Gaultheria. Like 
that oil, when exposed to the air, it gradually acquires a red 
color, of which it is easily deprived by distillation. It is 
also obtained colorless by decomposing its compound with 
potassa by a dilute acid. It is slightly soluble in water, to 
which it communicates taste and odor, and mixes in all 
proportions with alcohol and ether. Its aqueous solution is 
colored purple by persulphate of iron. Dropped into a 
concentrated solution of potassa, combination immediately 
ensues, with the production of a solid compound and the 
evolution of heat. This product, when pressed between 
bibulous paper to remove the excess of potassa, and then 
dissolved in hot alcohol, is obtained in rhombic, and six-sided 
tables by its evaporation. When one of these crystals is 
placed in contact with a drop of dilute sulphuric acid, it is 
at once decomposed, minute globules of oil float on the sur- 
face of the liquid, and the odor of the oil is developed. It 
reacts with caustic soda and baryta, and with oxide of lead 
and copper, in the same manner as the oil of Gaultheria. 
When heated with an excess of potassa, salicylic acid is 
produced; and when agitated with solution of ammonia, it 
