TESTS OF THE PURITY OF BALSAM OF COPAIBA. 191 
capable of forming a clear mixture with. After obtaining 
the clear mixture in this way, it became quite opaque and 
milky on diluting it with water, and slightly opaque on add- 
ing spirit to it. 
Finding that specimen No. 3 formed a clear mixture when 
rather less than the quantity specified of the solution of pot- 
ash was added, I treated the other specimens with the solu- 
tion of potash in several different proportions. No. 2 form- 
ed a mixture very nearly transparent, when only one-third of 
the specified quantity of the solution of potash was used ; 
but a separation took place on letting it stand for some hours. 
No. 1, when mixed in this and several other proportions, 
still continued opaque. 
It is very evident, therefore, that no satisfactory inference 
can be drawn, with reference to the purity of copaiba, from 
the application of this test. 
C. ^ Solution of ammonia of sp. gr. .960, has been recom- 
mended as affording a good test of the purity of copaiba. 
It is stated, that if one part of such solution of ammonia be 
' added to three or five parts of genuine copaiba, the mixture 
will be clear, presenting a similar appearance to that of the 
copaiba before the admixture. If the mixture be opaque, 
it is said to be a sign of adulteration in the copaiba. 
I believe this test has been more used and relied on than 
any other ; but Dr. Christison has objected to it, on the 
ground that copaiba may be mixed with a sixth of its weight 
of castor oil without affecting the action of the test. I have 
found it liable to an objection of a different character, as the 
following experiments will show : 
Specimen No. 1, when treated with the ammonia as 
directed, formed an opaque mixture, which continued so 
after standing for several days. The ammonia was added 
in a great many different proportions to this specimen, but 
in all cases the mixture was opaque. 
Specimen No. 2, treated with the ammonia, formed at 
