316 
Selected Articles. 
of the products, the economy in the menstruum, and the sim- 
plicity of the operation. With the exception of a single sub- 
stance, in all cases when I used water, I obtained a larger 
quantity of extract by displacement than by maceration. But 
this result cannot be generalized ; that obtained with sarsapa- 
rilla leads to the supposition that other substances may be in 
the predicament. Different results were afforded when alcohol 
was used ; hemlock alone furnished a larger proportion of 
extract by displacement, than after a previous maceration, 
whilst in all the other cases, equal quantities were obtained, 
showing that previous maceration is useless. 
It results from these experiments : — 
1. That this process is generally advantageous with sub- 
stances containing but little mucilaginous matter, and not 
liable to swell when they imbibe water. 
2. That it is also preferable in a treatment with alcohol, 
first, because organic substances are acted on by this men- 
struum better than by water; and also because by this pro- 
cess there is less waste of the alcohol. 
3. Finally, that a previous maceration is useless, as has 
been shown by M. M. Boullay. 
Another deduction to be made from these details, is, that 
the process of displacement is not indifferently applicable to 
all substances : with certain articles it is very tedious and 
with others almost impossible. It fails with those substances 
which swell on imbibing water, and the number of these is 
very considerable. 
It must also be observed that the good results obtained in 
operating upon small quantities, may not be found when large 
masses are acted upon. In general, the operation depends for 
its success on the fineness of the powder and the manner in 
which this is placed in the funnel. 
If it is too tightly compressed, the passage of the fluid will 
be very slow, and during summer fermentation may ensue. 
If it be too loose, the liquid will pass through too rapidly. 
Much depends on the fineness of the powder, as one degree 
is better with one substance, but will not succeed with another. 
