ON THE METHOD OP DISPLACEMENT. 
195 
liquid issues perfectly limpid. Assafoetida when thus treated 
gives a very fine tincture, and, at the same time, relieves us 
from the inconvenience of a protracted filtration, to which 
its viscous nature gives occasion. 
This class of tinctures, from the uniform character of the 
substances from which they are made, are more readily formed 
than the tinctures of roots or leaves. By these means our shop 
bottles would present a finer appearance, from having no sedi- 
ment, which, in the case of gum resins, is often very difficult 
to remove from the bottom of the bottle. We have found 
displacement an excellent auxiliary in the preparation of some 
of the tinctures from the vegetable extracts, such as Catechu 
and Kino. 
The Acetous Tincture of Squills, after a long maceration, 
becomes very difficult to filter. By resorting to immediate 
displacement, all the desired objects can be obtained at once. 
INFUSIONS. 
In making infusions it is a desideratum to obtain them trans- 
parent, and free from sediment, possessing the properties of 
the infused substance, and in as short a period as possible. 
These are not wholly accomplished in the ordinary method, 
especially in the case of bark, which resumes its opacity after 
filtration. But, by displacement, these three ends are com- 
pletely answered; and further, when thus made, the prepara- 
tions keep longer, being less liable to fermentation from the 
absence of starch in solution. 
The subjects of our essay were principally Bark, Rhu- 
barb, Digitalis, Belladonna, Chamomile, and Gentian. 
SYRUPS, 
The presence of starch in many syrups is a serious incon- 
venience,rendering them liable to the fermentative process ; not- 
withstanding they may be saturated solutions of sugar. When 
made by displacement, however, this is entirely obviated, at 
the same time that a preparation is obtained possessed of all 
the virtues of the plant. 
