December 21, 1872.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
483 
to a fine powder, the menstruum or solvent being 
usually strong or absolute alcohol, ether or chloro¬ 
form. 
Percolation. —Percolation, on the contrary, means 
simply the flowing through of your menstruum. It is 
a process specially adapted for large quantities. 
You usually work with proof spirit or more frequently 
with water; it is, moreover, a process where you 
usually have to use more fluid than absolutely neces¬ 
sary for the mere exhaustion of your ingredients. 
The Percolator. —After these preliminary remarks 
let us consider the best form of our percolator. I 
think it is now generally admitted that the cylindri¬ 
cal form is the best, while the cone, which found many 
advocates in the commencement, is rejected. The 
conical percolator was first of all selected, because 
the ingredients when packed in it can readily rise 
when moistened and swelling out; consequently 
there was no danger of blocking the percolator up or 
bursting it; but the same loose attachment of the 
species with the sides of the percolator which enabled 
the solid ingredients to rise, allowed also the fluid to 
pass without penetrating right through them. Be¬ 
sides this most serious objection, a conical per¬ 
colator is unnecessarily bulky, while the principal 
amount of the ingredients is of necessity in the upper 
and wider part where the fluid exerts the least pressure 
and has the least solvent action. But whatever perco¬ 
lator may be used, it will be found an additional ad¬ 
vantage to have a tap at the bottom for the check 
and regulation of the outflow of the fluid. 
The Species. —With regard to the condition of the 
ingredients, they must be in a uniform, more or less, 
finely divided state; the larger the quantities used 
and the more mucilaginous the nature of the in¬ 
gredients, the coarser the species may be; while 
the smaller the quantities worked with and the 
more insoluble and woody in fibre, the finer the in¬ 
gredients can be. These are, of course, only general 
rules, and those who have experience in the process 
will find no difficulty in percolating a cwt. of finely 
powdered opium or ergot of rye at one time. 
In such cases it is necessary to mix the powder 
with some inert, insoluble, and light material; in 
the above-mentioned instances I took the rumex 
fruit and residue, so abundantly obtained in the pre¬ 
paration of extract of opium, and ordinary rye- 
husks. In fact, I found husks or straw, either cut 
fine as chaff or in whole pieces, a most useful help 
to facilitate in many instances the process of perco¬ 
lation. The ingredients themselves must be of a 
uniform powder to allow the fluid to pass through 
every particle at an equal rate; the fineness, as I 
have stated before, may vary from a powder passed 
through a sieve of 3G to 144 meshes to the square 
inch. They ought, moreover, to be moistened with 
the menstruum used for percolation, and allowed to 
absorb as much of it as possible, taking care that 
the single particles retain their shape or individu- 
ality, and that the mass does not form a shapeless 
magma. During this absorption of moisture, some 
vegetable ingredients will increase very materially 
in bulk, and this swelling out ought to be allowed 
to go on to its full extent before packing them in 
the percolator. If you percolate with water you will 
find that some ingredients, such as poppj^-heads or 
orange-peel, absorb a great amount; in fact as much 
as they contained in their fresh condition. The dry 
vegetable cellular tissue retains the power to fill 
these cells and vessels with moisture again, and it is 
of great importance for the process of percolation 
that this is so; and pains ought to be taken to see 
that the ingredients are thoroughly impregnated and 
soaked by sprinkling them from time to time with 
the menstruum, and turning them over and over. 
The Packing. —After the ingredients are brought 
to the proper condition for packing, a little tow or 
cotton-wool is placed in the bottom of the percolator, 
over the tap, and on this the ingredients are packed. 
Where it is possible it is best to use the hand, to en¬ 
sure a uniform and close position without jamming 
or smashing the ingredients, the hand being the best 
guide for the amount of pressure required to effect 
this; a little tow or cotton-wool is again covered 
over the top and some weighty and not acted upon 
substance placed over it to prevent the floating up of 
the mass. I have found old glass stoppers very 
serviceable for this purpose. Sufficient fluid is now 
added to cover the species, and it is well before 
starting the process to allow the apparatus to stand 
quiet for a couple of hours, after which the tap may 
be turned on so as to enable the fluid to escape drop 
by drop in quick succession. 
The Percolating or Exhausting. —The exhaustion 
of the species is effected by the means of two agencies, 
the force of gravitation compels the fluid to descend, 
and the capillarity of each single particle absorbs 
the descending fluid and facilitates and enables it to 
pass right through the mass from particle to 
particle, carrying with it the soluble portion. The 
first portions which pass out of the percolator are 
those most highly charged with extractive matter, 
and are best kept separate from those obtained last, 
especially where water is used for percolating, and 
where the products have to be concentrated by eva¬ 
poration; in these cases the evaporation ought to 
commence with the more diluted portions obtained 
at the end of the process, adding the first products 
last. 
Conclusion. —I cannot leave this subject without 
throwing out some suggestions. Percolation enables 
us to separate the active, soluble and volatile aro¬ 
matic principles of plants in a highly concentrated 
and natural condition; and from my experiments I 
have but little hesitation in stating that all our proof 
tinctures, such as tincture of orange-peel, henbane, 
cinchona bark, etc. etc., could be made much more 
uniformly and economically by exhausting the re¬ 
spective drugs simply by water, concentrating the 
percolated products to such a degree that three parts 
of it added to five parts of rectified spirit would pro¬ 
duce eight parts of tincture of Pharmacopoeia strength. 
Such a plan, if once introduced, would naturally 
lead a step further; after ascertaining the best solvent 
for each drug, concentrated standard solutions of 
each would be made, and from these, by addition of 
spirit or wine, or by mixing one or more together, 
all our tinctures and wines, simple and compound, 
could readily be made at a moment’s notice, with the 
certainty that in each case they really possessed all 
the soluble active principles of the drugs. A chemist 
in thus preparing his stock preparations with the 
least amount of spirit, and in a concentrated form, 
would usually select the time of the year when 
orange-peel, henbane, conium and all our indigenous 
plants are in proper season; in many cases he would 
buy the fresh plants and dry them himself, instead 
of, as now, using them whenever wanted all the year 
round, immaterial whether in or out of season. He 
would find, moreover, that in many of the present 
