REACTION OF THE ESSENTIAL OILS. 
157 
sassafras with the alcohol, in the manner described in the ac- 
count given of the first experiment with the oil of turpentine, 
I succeeded in obtaining in addition to a small quantity of the 
heavy liquid containing sulphuric acid, a minute quantity of 
a lighter one, devoid of that acid, which burned without 
smoke, was insoluble in water and very fluid. I am disposed 
to consider the liquid thus procured as a hydrate of sassafras 
oil, or sassafreine, as I would call it, being analogous to hydric 
ether. 
The oil of sassafras, whether isolated or in combination, 
possesses a remarkable property, which, I believe, has not at- 
tracted sufficient observation: I mean that of producing an 
intense crimson colour, when added, even in a very minute 
quantity, to concentrated sulphuric acid. 
One drop of oil of sassafras imparted a striking colour to 
forty-eight ounce measures of sulphuric acid, and appeared 
perceptible when it formed less than a five millionth part. 
This property was completely retained by the lighter liquid 
above described as procured from oil of sassafras. 
I subsequently observed, that when sulphurous acid, whe- 
ther in the form of sulphurous ether, in that of a gas, or when 
in union with water, was brought into contact with any of the 
essential oils, (including kreosote,) which were subjected to 
the experiment, they acquired a yellow colour, and a strong 
smell of this acid. 
In the case of the yellow compound thus obtained from any 
of the essential oils which I have tried, if the sulphurous acid 
be removed by heat, the oil, by analysis, will be found to 
yield sulphuric acid. That some acid of sulphur remains in 
union must be evident, since washing with ammonia will not 
entirely remove the power of yielding sulphuric acid; and 
the total absence of the sulphurous smell demonstrates that 
the sulphurous acid either enters into an intim.ate combination 
with the oil, or acquires oxygen sufficient to convert it into 
sulphuric or hyposulphuric acid. 
Those essential oils which contain oxygen, are most affect- 
ed by the action of sulphurous acid. 
