214 THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [September 14,1872. 
off, [and the remainder submitted to the action of a 
powerful press. Filtration completes the process. 
Many persons still strongly advocate maceration, 
because it gives tolerably uniform results which they 
cannot so easily obtain by other means. The objections 
are the length of time required, the great waste from 
•evaporation, and from the marc left in the press being 
«till rich in active principles. It is in our opinion the last 
method that ought to be adopted by the careful and 
economically inclined pharmacist for the perfect extrac¬ 
tion of the soluble matters of any herb or plant. There 
have been many suggestions for improving the process 1 
and saving the time, such, for instance, as that recom¬ 
mended by Dr. B urton, where the ingredients were sus¬ 
pended in the upper part of the solvent. The spirit, as 
it becomes saturated, and therefore of greater density, 
falls to the bottom of the vessel, its place being taken by 
more spirit, to be in its turn saturated and deposited. 
By this means exhaustion is attained with considerable 
rapidity, and saving more than half the time. 
_ Preparation by percolation. —This method is compara- i 
tively a recent one, and was introduced some years ago, 
•and strongly recommended by our friend Mr. Deane. 
When properly conducted, there is no doubt that perco¬ 
lation is of all methods the most perfect, and accompanied 
by the least waste. The resulting tincture is ready for 
use, quite bright, and independent of the press and 
filtering paper. 
Probably why percolation is not more generally in use 
is on account of the difficulty attendant on “packing.” A 
satisfactory percolation can only be performed by an 
absolutely perfect and uniform arrangement of the in¬ 
gredients, and which is often an impossibility. It is 
imperative that the spirit should pass through equally 
and horizontally, or else one portion would permeate 
much faster than another. Each layer of the solvent as 
it passes downwards should be displaced by a fresh one, 
but a mixture of the two should not be allowed, which 
would entirely alter the modus operandi of the whole 
process. 
Tincture making is generally placed in the hands of 
the apprentice or junior assistant, and of course a want 
of experience only makes matters still worse. The 
consequence is, that the proprietor of the establishment 
is startled at the thin bodied laudanum, the washy 
tincture of gentian, or the tasteless Vin. Ipecac. 
It is surprising how constantly the meaning of the 
word percolation is misunderstood. It is so in the Phar¬ 
macopoeia itself; for instance, in the directions for 
making Tinct. Chiratae, Capsici, Colchici, Conii, Gen¬ 
tian®, etc., what is there by inference termed percolation 
is not percolation but simply washing, and a large waste 
of spirit unnecessarily entailed. To obviate this waste is 
the object of our experiments, and of the process which 
we now recommend, the adoption of which an experience 
of twenty years will fully justify. There are two essen¬ 
tials for success in the operation, namely, the proper 
form of percolator; and secondly (strange as it may 
seem), no direct packing. 
1 heform of percolator .—These are sold of every pos¬ 
sible variety, according to the fancy of the manufacturer, 
but all are referable to two kinds, cylindrical and conical. 
Repeated trials have proved that the perfect cylinder 
is the only one on which dependence can be placed. A 
little reflection will at once point out the error of recom¬ 
mending the conical form. The well-known laws of 
hydiod} namics show that the pressure of a column of 
fluid on the bottom of a containing vessel is invariably 
equal to the weight pressing on the area of the base. It 
will, therefore, be evident that a percolator, having the 
form of an inverted cone, must have an unequal pres¬ 
sure from the contained fluid, and, as a consequence, the 
materials being exposed to an unequal pressure, must be 
unequally exhausted. The fluid will pass most rapidly 
thiough those parts where the force from behind is the 
greatest. 
The diagram represents the form 
of percolator, ABCD, prepared 
by Mr. Deane (Pharm. Jourm. 
5.533) having the sides inclined to 
the base line at an angle of 82°. 
If the vertical height be 24 inches, 
a column of water at EF would 
exert a pressure on the base CD, 
equal to 12-384 ounces for every 
square inch. But at the point G 
the pressure would be only 6 - 192 
ounces, and at II only 3-096 ounces, 
or one-fourth of the whole. 
Lateral pressure also causes a diagonal current in the 
direction of the central column, and exercises a con¬ 
siderable mixing force, which is of the greatest con¬ 
sequence when water is employed to displace spirit. 
Instead of true displacement, a combination of the two 
fluids wall take place, and very much heighten the sp. 
grav. of the tincture. 
Professor Redwood alluded to this fact when he said, 
“ The conical form is most used, because the liquid 
aggregates towards the middle of the column, so that 
near the bottom more liquid runs than at the side * * * 
spirit not to be driven out with water because it mixes.” 
Our experiments, as detailed in the accompanying table 
prove, we think, that the Professor's warning may be ren¬ 
dered unnecessary. We also differ from the opinion of Dr. 
Burton (Pharm. Jourx. 5, 1845,) when he affirmed that 
percolation is more expensive, more difficult, and less 
generally applicable than maceration. Our investiga¬ 
tions and general practice prove just the contrary, and 
show that, with the exception of Tinct. Limonis (when 
fresh peel is ordered), percolation is by far the best and 
most economical method of preparing the tinctures and 
wines. 
The most satisfactory work was done when the perco¬ 
lator had a diameter about one-fourth the length, and 
when the ingredients occupied one-fourth the interior. 
Spontaneous packing. —As we before mentioned, any 
one who has worked much in the tincture department 
must be aware of the almost total impossibility of so 
regularly placing the ingredients with the requisite uni¬ 
formity. The method which we venture to recommend 
is to allow the ingredients to pack themselves , and we 
think that so great a simplicity and completeness are at¬ 
tained that the veriest tyro may be entrusted with the 
operation without the risk of failure. Our mode of pro¬ 
cedure is to powder the ingredients and pass them 
through a sieve having from 20 to 30 apertures to the 
inch, and put into the whole of the spirit and macerate 
for 48 hours, with occasional agitation. At the expira¬ 
tion of the time, the supernatant spirit is poured off, the 
dregs stirred up and poured into the cjdindrical perco¬ 
lator, and allowed to drop until the liquid passes away 
clear and bright. It is then placed in thejreceiver, and 
all the spirit gradually poured on and allowed to perco¬ 
late in the usual way. When all has passed through, an 
equivalent proportion of water is carefully poured on the 
residue to displace the spirit absorbed. If properly con¬ 
ducted, the water will not mix with the spirit, but by its 
gravitating force, will drive it forward. The process 
thus proceeds with great uniformity, and the materials 
are perfectly exhausted. No waste is incurred, and the 
tincture is made with a rapidity equal to the method of 
Dr. Burton, identical with that of the Pharmacopoeia, and 
without the necessity of using the extra quantity of 
spirit or the aid of pressure. We give two examples to 
explain more clearly our made of proceedure, one where 
there is an excess of the material to the spirit, and 
another where the quantity of spirit is greatly in excess 
of the materials. To exemplify the first we would in¬ 
stance Tinct. Zingib. fort. 
