This product, obtained from several different parcels of virgin scammony, I have considered free from admixture with any of the substances with which scammony is said to be adulterated, and from the similarity of their behavior, and, as the circumstances under which the sample from Trieste above alluded to was obtained are such as to make its genuineness very certain, feel warranted in so doing.
Sulphuric acid does not immediately decompose it, but produces the effect described by M. Thorel.
Nitric acid produces no discoloration, nor does hydrochloric acid immediately.
If scammony should be adulterated with colophony, sulphuric acid would be a very ready method of detection, though it would seem that this substance would hardly be resorted to, unless an entirely new mode of sophisticating the article should be adopted abroad.
The introduction of farinaceous substances and chalk is effected while the scammony is in a soft condition, in which state it would be difficult to incorporate colophony completely with the mass.
An admixture of resin of guaiac is also detected by the same agent, a fact which seems to have escaped observation.
When brought in contact with sulphuric acid, resin of guaiac immediately assumes a deep crimson hue, and this reaction is so distinct that a proportion of not more than four or five per cent. is readily detected.
The deep red mixture of sulphuric acid with resin of guaiac becomes green when diluted with water, a remarkable change, which adds to the efficacy of the test. Scammony resin, on the contrary, suffers no alteration by dilution.
In addition, nitric acid affords a ready mode of ascertaining the presence of resin of guaiac. It is well known that nitric acid, when mixed with an alcoholic solution of guaiac, causes a deep green color, which soon passes into brown, or if the solution is dilute, into yellow.
This reaction is manifest when scammony resin is mixed with guaiac resin in the proportion above mentioned, though the greenish blue tinge is then very transient, and sometimes not readily perceived.