BALSAM PERU. 257 
The free cinnamic acid can thus be employed qualitatively and 
quantitatively as a criterion of the purity of Peru balsam, but too 
much importance should not be attached thereto. This acid is not 
to be regarded like cinnamein as an active constituent, and, on the 
other hand, does not occur to such an amount in the balsam as to be 
regarded, like the black resin, as a peculiarly indicative portion of 
the mixture. As the free acid always amounts to but a few per 
cent., the percentage amount would be but little changed even by 
a large adulteration, except in so far as benzoin is concerned, in 
which case readily-perceptible large amounts of benzoic or cin- 
namic acids would be introduced. <A large admixture of storax, 
on the contrary, produced no correspondingly increased yield of 
cinnamic acid. In comparison with most materials which are 
adapted to its adulteration, the somewhat slighter tendency of 
Peru balsam to decomposition by the action of alkalies appears to 
be of service. This peculiarity was indicated by Dr. Grote, as he * 
recommended 3 to 6 drops of the balsam (about a quarter cubic 
centimetre) to be shaken with 2 to 3 cubic centimetres of ammonia, 
sp. gr. 0°960, or, according to the relations by weight, 2 parts of 
balsam with about 17 parts of ammonia. The free acid passes 
into solution, and of the remaining constituents only a small 
amount is emulsionized, while the chief portion is not at all further 
changed. From the pure balsam, after one day, a turbid liquid 
may be decanted, while the residue remains semi-liquid, or very 
soft. But little is here dependent upon the proportions, as it was 
found that the balsam shows still the same behaviour when it is 
shaken with only half its weight of ammonia. The action of 
ammonia upon adulterated balsams, however, is quite different ; 
they solidify after a short time, as Dr. Grote has shown, to a stiff 
jelly from which no liquid can be decanted, or they become perfectly 
hard. Dr. Grote has, however, already indicated that it is chiefly 
colophony which may be detected in this manner, and that other 
admixtures, on the contrary, such as benzoin, storax, copaiba, and 
“oardschan” balsam (“wood oil”’) cannot be recognized by means 
of ammonia. Thesame is applicable to the fatty oils. Ifa balsam 
containing fat is shaken with carbon disulphide the latter is taken 
up by the solvent, whereby an (apparent) increase of the cinnamein 
will appear. If this is saponified with alcoholic soda and carbonic 
* Pharm. Centralh. May, 1880, p. 179. 
