192 TESTS OF THE PURITY OF BALSAM OF COPAIBA. 
first an opaque mixture ; after standing for two or three days, 
it separated into three strata in the same manner as the mix- 
ture of the same specimen with the solution of potash. 
Specimen No. 3, when treated in the same way, formed 
a perfectly clear and homogeneous mixture, which retained 
this character after standing for a considerable length of 
time. 
This test, therefore, in addition to the objection stated by 
Dr. Christison, may indicate impurity where none exists. 
D. Pure copaiba is said to dissolve a fourth of its weight 
of carbonate of magnesia, with the aid of a gentle heat, and 
to continue translucent, the presence of a small proportion 
of any fixed oil being indicated by the product being opaque. 
This, again, is one of the tests given in the Edinburgh Phar- 
macopoeia, 
This test was tried on specimen 1, 2, and 3, and the re- 
sults were nearly the same in each case. After adding the 
magnesia, applying the heat of a water bath for about half 
an hour, *and stirring the mixture from time to time, on al- 
lowing them to stand for a few minutes, a portion of the 
magnesia settled to the bottom of each of the tubes in which 
the mixtures were made. The fluid, or semi-fluid, portion 
might probably be said to be translucent, but I presume the 
test would leave as many degrees of impurity undetected as 
there may be degrees of translucency, for, surely, a more in- 
definite indication could hardly be conceived. After stand- 
ing for several days, there was found at the bottom of each 
tube a saponaceous mass, constituting from one-third to one- 
half of the whole, and a clear oily fluid above. Specimen 
No. 3 gave the largest quantity of the saponaceous mass, 
and specimen No. 2 the smallest. 
This test is as valueless as those previously noticed. 
E. The last test to which I shall allude is probably the 
worst of all. It is stated,that if one part of oil of vitriol be 
triturated with three parts of pure copaiba, a plastic reddish 
