10 
LECTURES ON THE BRITISH PHARMACOPOEIA. 
tion and subsequent displacement of adhering tincture by the spirit finally placed 
in the percolator. Thirdly, a substance having been partially exhausted of its 
valuable constituents by the forty-eight hours of maceration, and then placed in 
the percolator, the remainder of its active principles may be dissolved out by 
the percolation through it of the semi-formed tincture, the final addition of 
spirit displacing what tincture may be remaining adhering to the marc, subse¬ 
quent pressure recovering some of the spirit so added. This last case is doubt¬ 
less the model on which, theoretically, the processes for the thirty-nine tinctures 
are constructed. How far they actually conform to it can only be determined by 
experiment; and such experiments, though not by any means difficult to per¬ 
form,—that is, so far as ascertaining the proportions of solid matter in a tincture 
at various stages of its manufacture is concerned,—have not yet, so far as I am 
aware, been conducted on any extensive scale. If one or several pharmacolo¬ 
gists would take up this subject, the probable result would be the discovery of 
greatly improved processes for each tincture. Some would possibly be found 
to require only short maceration ; others long maceration, shortened probably 
in most instances by subsequent percolation; and many perhaps be most advan¬ 
tageously prepared by percolation alone. 
The only general series of experiments made with a view of improving the 
processes for the preparation of tinctures are those of Burton (Pharm. Journ. 
vol. v. p. 82). He examined the officinal tinctures of the London Pharmaco¬ 
poeia with the object of comparing the efficiency of the process of maceration, 
in which the ingredients after agitation subside to the bottom of the vessel, with 
that of maceration, in which the ingredients enclosed in a bag are suspended in 
the upper part of the menstruum. Burton’s method of examination consisted, 
first, in taking the specific gravity of the tinctures, it being assumed that a pro¬ 
cess was complete when a tincture ceased to acquire weight by further contact 
with the solid materials. Specific gravity alone could not, however, always be 
depended on, chiefly on account of the variation in the amount of moisture in 
the ingredients ; it was therefore considered together with the weight of hard 
extract obtained on evaporating a portion of the tincture in an oven, and ex¬ 
posing the residue to a temperature of 230°. In this way, operating upon dif¬ 
ferent portions of one sample of a drug, Burton ascertained the most desirable 
period of maceration for each tincture. By the light of his researches we may 
be able, to some extent, to judge of the efficiency of the new process given in 
the British Pharmacopoeia. 
Tinctura Aloes. This tincture, which cannot be easily prepared by percolation, 
is to be made by maceration for seven days. Now Burton found (Pharm. Journ. 
vol. v. p. 123) that so far as the aloes is concerned, exhaustion was complete in 
forty-eight hours if the ingredients were suspended in the upper portion of the 
spirit, but that the extract of liquorice was not perfectly dissolved at the end of 
that time. Probably, therefore, the period of seven days might be much short¬ 
ened, especially if the extract of liquorice were previously rubbed down with 
some of the water of the proof spirit. 
Tinctura Assafceticlce. In preparing this tincture, the Pharmacopoeia orders 
maceration of assafoetida in rectified spirit for seven days. According to Bur¬ 
ton, this period cannot be shortened. 
Tinctura Calumbce. The triple operation of maceration, percolation, and ex¬ 
pression, ordered by the Pharmacopoeia, is according to Burton’s results unne¬ 
cessary. By his method of macerating, less than forty-eight hours is sufficient 
to effectually exhaust calumba of everything soluble in proof spirit. 
Tinctura Cascarillcc. Burton’s results show that if cascarilla be suspended in 
proof spirit, two days’ maceration is ample time for perfect exhaustion. The 
triple process of the Pharmacopoeia is not therefore the best that could have 
been adopted. 
