TESTS Or THE PURITY OF BALSAM OF COPAIBA. 189 
the Edinburgh Pharmacopoeia; it is stated that genuine 
copaiba is perfectly soluble in the above quantity of alcohol. 
On applying this test to the specimens, a perfect solution 
was formed with No. 1, but not with either of the others- 
After adding the alcohol, which was of specific gravity 
.795, to No. 2 and No. 3, a white rloculent substance re- 
mained undissolved, and ultimately settled to the bottom. 
This substance was collected, and appeared on examination, 
to be the viscid resin of the copaiba, which, as met with in 
many specimens, is scarcely, if at all soluble, either in recti- 
fied spirit or in alcohol. I applied this test to several other 
samples of copaiba, which 1 believe to have been perfectly 
genuine, and obtained results similar to those afforded with 
Nos. 2 and 3. 
The use of this test in the manner described may there- 
fore lead to error, as it indicates the presence of impurity in 
cases where none exist. But this is not the only objection 
to this test. The evidence it affords of the presence or ab- 
sence of substances which are insoluble in alcohol, is very 
imperfect. It is an error to conclude that a substance inso- 
luble in alcohol, when added to that liquid alone, will there- 
fore be insoluble if it be added when mixed with other bodies. 
The balsam of copaiba itself affords an illustration of this 
statement. This oleo-resinous substance consists principally 
of volatile oil and resin, whicrnnay be easily separated. The 
volatile oil is but sparingly soluble in alcohol, yet when 
mixed with the resin it is freely soluble. The same may 
be said of oil of turpentine and some of the fixed oils, which 
by themselves are either slightly, or not at all soluble in 
spirit, but which, nevertheless, become freely soluble when 
mixed with other substances, such as camphor, resin, oil of 
lavender, and other volatile oils. Some of the resins, also, 
which, alone, are but little soluble in alcohol, may be 
readily dissolved when mixed with camphor, volatile oils, &c. 
The fact of an oleo-resinous substance being freely soluble 
17' 
