TESTS OF THE PURITY OF BALSAM OF COPAIBA. 193 
mass will be formed ; but if the copaiba contains castor oil 
it will be scarcely or not at all coloured, and will acquire 
the consistence of turpentine. 
I need hardly say that this statement is erroneous, and the 
test of no manner of value. 
Having thus proved the worthlessness of these methods 
of detecting impurity in balsam of copaiba, it becomes an 
important question to determine whether there is any other 
less.exceptionable method. 
The consideration of this question involves a reference 
to the natural history and chemical composition of the dif- 
ferent varieties of copaiba met with in commerce. What 
is the substance to be tested? Is it always the same, or do 
different specimens of it differ in their physical and chemical 
characters ? The answers to these questions will be found 
to explain the discrepancies already noticed in the action of 
the foregoing tests on different samples of copaiba. 
The substance called balsam of copaiba, is an oleo-resi- 
nous exudation, obtained from several species of the genus 
Copaifera, by making incisions into the trunks of the trees. 
It possesses most of the chemical characters of common tur- 
pentine. By distillation, or saponification, it may be resolved 
into a volatile oil and a hard resin. These exist in very 
different proportions in different samples of copaiba, depend- 
ing, probably, upon the species of Copaifera from which 
it has been obtained, the soil and climate in which the trees 
have grown, and the lengthof time during which the copaiba 
has been kept. I have found the quantity of volatile oil to 
be twice as great in some samples as in others, and to this 
difference is chiefly to be ascribed the dissimilar action of 
the tests upon it. There is probably no simple test that 
could with any satisfaction be applied for the detection of 
impurities in a substance which is itself subject to such great 
varieties in composition. 
The only method that appears to me to be at all satisfac- 
