ON ALCOHOLIC TINCTURES. 
31 
feet, that the residue of the gray bark treated by alcohol at 
80° still remained bitter, while that which had been treated by 
alcohol at 56° was insipid. 
I should, therefore,, give the preference to alcohol at 56 Q , 
as the Codex does, and although four parts of this solvent 
are, as we see by the table, sufficient to dissolve all the solu- 
ble matters, I should adopt the proportion of five parts to get 
rid, as I said above, of these few objections. 
We are struck in the very onset with the difference of the 
results obtained with yellow bark and the two other varieties 
used ; we may ask ourselves the explanation of this anomaly. 
The most plausible explanation appears to me to be the fol- 
lowing : yellow bark, as we see by the last experiments made 
with it, is that which yields the smallest quantity of extract 
to alcohol of various degrees of strength — containing conse- 
quently fewer extractive or other matters, enveloping the ac- 
tive principle ; this last is found in immediate contact with 
the concentrated alcohol, which is its best solvent ; while in 
the case of the two other varieties of bark, these extractive 
matters, which are found in greater quantity, are coagulated 
by the concentrated alcohol, and thus shield the active prin- 
ciple from the action of the solvent. We see, in fact, that in 
the case of the red bark, which furnishes a smaller amount of 
extract than the gray bark, the difference between the quan- 
tity of the alkaloid dissolved by strong and weak alcohol is 
small, while it is considerable in the case of gray bark,, which 
furnishes the greatest quantity of extract. 
May we not, also, admit the existence of certain principles 
at present unknown or badly defined, more or less soluble ac- 
cording to the species of bark to which they belong, principles 
that will either hinder or assist the solution of the active prin- 
ciple ? Notwithstanding the progress of organic chemistry, 
this science is not at present sufficiently advanced to enable 
us to understand the composition of organic bodies, and con- 
sequently prevent our laying down this hypothesis. 
(To be continued.) 
