190 TESTS OF THE PURITY OF BALSAM OF COPAIBA. 
in alcohol, is therefore no proof that it contains nothing 
mixed with it which by itself would be insoluble, or but 
slightly soluble in that menstruum. 
B. A solution of one part of hydrate of potassa in two 
parts of water has been recommended as a good test. It is 
stated that such a solution, mixed with nine parts of genuine 
copaiba, will form a transparent mixture, which will con- 
tinue clear after moderate dilution with water or rectified 
spirit; but if there be from three to six per cent, of fixed oil 
present, the mixture will be opaque. 
This test, when applied to sample No. 1, formed a mix- 
ture which continued opaque for several days; it then sepa- 
rated into two strata, the upper stratum being oily or sapo- 
naceous and clear, and the lower stratum aqueous, clear 
and colourless, and forming about one-tenth of the mixture. 
On shaking the tube, the mixture became again opaque ; 
when diluted with water, it was rendered perfectly milky ; 
the addition of spirit rendered it rather more clear, but left 
it still slightly opaque. 
The same test, applied to specimen No. 2, formed an 
opaque mixture, which, after standing for some days, sepa- 
rated into three strata. The top stratum, constituting near- 
ly one-half of the whole, consisted of the volatile oil of copai- 
ba ; the middle stratum appeared to consist of the resin and 
potash in the form of a soap ; while the lowest stratum was 
aqueous, clear, and colourless. On shaking the tube, the 
mixture became again opaque, and this continued after dilu- 
tion with water or spirit. 
The same test, added to specimen No. 3, formed a mix- 
ture that was but very slightly opaque. No separation took 
place in it after standing for several days, but it still retained 
a slight degree of opacity. On adding a little more of the 
copaiba to the mixture, and shaking them together, it became 
perfectly clear, thus proving that the quantity of solution of 
potash first added was rather more than the copaiba was 
