540 
PHARMACEUTICAL MEETING. 
lower half; and therefore, unless they be brought in a line, they will not com¬ 
municate, and there will be no passage for air. By turning the stopper the 
grooves may be connected or separated, and this may be done wholly or par¬ 
tially, so that the passage of air may be allowed to take place freely or slowly, 
or not at all, by adjusting the relative positions of these grooves, and the flow 
of the liquid is thus brought completely under control. 
Continuing the percolation of the ginger, or rather the displacement of the 
tincture already formed by the spirit that has been absorbed : if a pint of spirit 
has been used in the first part of the operation, the same quantity ought to 
suffice for its displacement, and this quantity of spirit being carefully intro¬ 
duced as before, the process may proceed until a pint of strong tincture has 
been recovered. This displacement of the tincture by the superincumbent 
spirit will take place without the occurrence of more than a slight admixture 
of the two liquids. The progress of this operation will be indicated by a line 
showing where the two liquids join, the liquid above this line being nearly 
pure spirit while that below it is a clark-coloured tincture. When this line 
has reached the bottom of the percolator, the tincture first formed will have 
been displaced as completely as the process will admit of its being done with¬ 
out dilution. It will be found, however, that the ginger has not been com¬ 
pletely exhausted by the passage of the first pint of tincture, for the spirit 
that passes afterwards will contain a little of the active matter of the ginger ; 
and this, I believe, arises, not from the inadequacy of the first portion of spirit 
for the exhaustion of the ginger, but from the incompleteness of the displace¬ 
ment. In fact, the displacing spirit passes more readily between the masses 
of ginger, minute as they are, than it does through them, and these masses do 
not therefore give up their liquid contents immediately under the influence of 
the displacing spirit, but gradually empty themselves into it. It will be ob¬ 
served on close examination during the process, that the line of demarcation 
between the two columns of liquid becomes less defined and distinct as it ap¬ 
proaches the bottom of the mass, a shading into the upper column being per¬ 
ceptible, which is occasioned by the diffusion of the contents of the little 
masses of ginger into the displacing liquid. In order to recover the whole of 
the soluble matter, therefore, it will be necessary to displace at least a part of 
the second portion of spirit, but the tincture thus procured will be much 
weaker than the preceding. 
In operating in this way, nearly the whole of the active and soluble 
constituents of the ginger are obtained in solution in the first portion of tinc¬ 
ture displaced, and by continuing the process until a quantity of tincture, 
rather less than double the weight of the ginger, has passed, the solid residue 
will be so completely exhausted as not to retain the slightest taste or smell. 
There are but few substances employed in the preparation of tinctures that 
admit of the application of the displacement process so readily and advanta¬ 
geously as ginger does ; and therefore, in studying the process and its results 
in this case, we at least see the full extent of the advantages it may possess. 
These may be briefly stated as follows:—• 
1. Economy of time. This is one of the most important advantages in 
this process, as a tincture may be prepared in a few hours, which by maceration 
would require a week or two. 
2. Excellence of product. Some tinctures are considered to be better 
when made by this process than by lengthened maceration, because in the 
latter case a change may be effected in some of the soluble constituents of the 
solution first formed when this is left in contact with the insoluble residue of 
the vegetable substance. 
3. Concentrated state of the product. The process is certainly well suited 
for getting highly-concentrated tinctures. 
