ON THE PREPARATION OF TINCTURES. 
535 
advocates of the process of percolation as applied to the preparation of tinc¬ 
tures have contended that the solid ingredients should always be packed in 
the percolator in the dry state. This is much insisted upon by M. Buignet, 
in his paper, the most important perhaps that has appeared of late years on 
the subject, which was published in the ‘ Journal de Pharmacie ’ in 1857. M. 
Buignet states that he has succeeded in treating all the vegetable powders by 
percolation, using in all cases the fine powders, such as are ordinarily employed 
in medicine, without any admixture of sand or other similar substance; and 
he has accomplished this by having the powders carefully dried before putting 
them into the percolator, but he admits that the percolation has been so slow 
in some instances, that the process has occupied three or four days. At 
the same time he neglects to tell us how much he has operated upon at a 
time. 
In the last edition (1863) of the United States Pharmacopoeia, the process 
of percolation has been very generally adopted for the preparation of tinctures, 
and there the powders are directed to be moistened before being packed in the 
percolator. A conical percolator is directed to be used, and the percolation 
is to be carried on without allowing any time for the ingredients to macerate. 
This agrees also with the instructions given by others, including Buignet. It 
is a very general practice, however, to allow some time to elapse after adding 
the first portion of spirit to the solid ingredients, before commencing the per¬ 
colation, the time thus allowed varying from two to twelve hours. This is, no 
doubt, necessary when the solid substances are not in fine powder, but in all 
such cases the process ceases to be perfectly efficient percolation, and it is ren¬ 
dered efficient onty by superadding maceration. 
In the percolation of the liquid through the bed of solid ingredients, it is 
intended to cause a great number of successive particles of liquid to come into 
contact with each separate particle or molecule of solid matter, until all that 
is soluble of the solid matter has been imparted to the liquid. A compara¬ 
tively small quantity of liquid may in this way be made to exhaust the solid 
ingredients, if the mutual action of the two bodies be made as complete as 
possible. Not only must each solid particle have a great number of liquid 
particles brought into contact with it, and rubbed against it, but each liquid 
particle must be made to rub against a great number of solid particles, one 
after another, and this may be done until the liquid particles become saturated, 
and the solid particles are completely exhausted. But to effect this object it 
is not sufficient that the liquid should pass over the surface of masses of solid 
matter, it must permeate the masses, and come into contact with the proxi¬ 
mate molecules themselves ; and not only must the liquid permeate the masses, 
which it maj' - be made to do by capillary attraction, there must also to some ex¬ 
tent be a circulation through the masses, caused by hydrostatic pressure, and 
this can only be ensured by the masses being reduced to the smallest practi¬ 
cable size, and by their being packed so closely and tightly that the spaces be¬ 
tween the masses are not very sensibly greater than those within the masses. 
The differences of structure in the different vegetable substances operated 
upon, render it practically impossible to have the ingredients so packed that 
the required conditions shall be always equally fulfilled, and probably in few, 
if any instances, is it possible by the exercise of the greatest skill to fulfil the 
conditions perfectly. Thus, for instance, such substances as galls, ergot, dried 
opium, colchicum seeds, etc., are less porous than the cellular and vascular 
tissues of many woods, barks, and leaves, and if these two classes ot sub¬ 
stances be operated upon under similar circumstances with regard to disinte¬ 
gration, closeness of packing, and contact of the liquid, the exhaustion 
effected by mere percolation would necessarily differ to some extent, and the 
results could only be equalized by either extending the period of contact with 
