December 2i, 1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
501 
PRACTICAL NOTES 
Take of 
ON THE 
PREPARATIONS OF THE BRITISH PHARMACOPEIA. 
BY CHARLES R. C. TICHBORNE, F.C.S., M.R.I.A. 
Chemist to the Apothecaries' Hall of Ireland, etc. 
Acetum Cantharidis and the Vesicating Prepa¬ 
rations of Cantharides. 
Tlie vinegar of cantliarides calls for very few re¬ 
marks. If made strictly according to the Pharma¬ 
copoeia the result is a very pungent liquid, having a 
brown colour. The specitic gravity at 15° C. will 
range from l Of‘0 to 100-2. It should be miscible 
with water in all proportions. The heat employed 
in the maceration is, as will he seen, conducive to 
the solution of cantliaridine (vide remarks upon the 
solubility of cantliaridine). 
Taking the formula of the Pharmacopoeia, 12 fluid 
ounces are got by percolation, and 3£ ounces b}^ pres¬ 
sure, so that 2 ounces of glacial and 22f ounces of 
acetic acid are consumed. It directs that powdered 
cantharides should be used, but it will be found more 
convenient that the flies should be simply bruised, 
particularly when making large quantities. The 
substance of the flies is easily permeated by the acid, 
whilst the structure generally gets into such a pulpy 
state from its action, that it is difficult to manipulate 
with large quantities of powder. 
In the Pharmacopoeia no characteristics or tests 
are given for what used to be called the “ prepara¬ 
tions” in the edition published in 1804. These pre¬ 
parations are in the majority of cases more easily 
sophisticated than the materia medica, and are fre¬ 
quently the vent for inferior drugs. The point is 
worth consideration, and any specific or general cha¬ 
racter which can be applied to them must be of im¬ 
portance. It is for this reason that I have given the 
specific gravity. 
The relative strength of the present preparation 
to those formerly in use is given:— 
Total Crystal. Acetic Acid. Cantha- 
lizable Acid. 1-005) ' (sp. gr. T044). rides. 
Per cent. Per cent. Per cent. Per cent. 
B.P . . 39 7 . . 10 . . 90 . . 10 
L.P. . . 37-0 . . . . 100 . . 10 
Ed. P. . 43-75 . . 25 . . 75 . . 17*5 
Dub. P. . 40-4 . . 20 
(Sp. gr. (Eupborbium 
1-034.) 2-5 per cent.) 
80 . . 20 
The Pharmacopoeia has the following note in con¬ 
nection with the strength of these preparations:— 
“ This preparation is rather stronger than the acetum 
cantharidis of the London Pharmacopoeia; it is less 
active than the preparations ordered under the same 
name in the Edinburgh and Dublin Pharmacopoeias 
in fact, as will be seen in the first and fourth columns, 
these two preparations are almost identical. The 
percentage of flies could be increased with great ad¬ 
vantage. 
Liquor Epispasticus .—It is, perhaps, as well to 
consider the remainder of the vesicating preparations 
of cantharides in tliis place. The first of these is 
the liquor epispasticus; this term having been sub¬ 
stituted for the “ linimentum cantharidis ” of 1804. 
In the present formula for liquor epispasticus, there 
is evidently a mistake. Based upon a valuable idea, 
it is obvious that the wrong acid has been specified. 
The following is the formula :— 
Third Series, No. 20. 
Cantharides, in powder, 8 ounces 
Acetic Acid, 4 fluid ounces 
Ether, a sufficiency. 
“ Mix the cantharides and acetic acid, pack them 
in a percolator, and, at the expiration of twenty-four 
hours, pour ether over the contents of the percolator, 
and allow it to pass slowly through till twenty fluid 
ounces are obtained.” 
The acid directed in the above formula is the or¬ 
dinary acetic acid, having a specific gravity of 1*044, 
Now, independently of the want of solubility of can- 
tliaridine in cold acid of that gravity (vide remarks 
on solubility of cantliaridine, p. 502), two parts of 
acetic acid are not miscible with fourteen parts of 
ether of the gravity required by the Pharmacopoeia. 
(These are the proportions that would be used.) 
If we mix them in the above proportions we get a 
product presenting two layers; the lower one con¬ 
sists almost entirely of water, and is about one-half 
the bulk of the original acid employed; whilst the 
upper is ether, holding in solution about T V of a 
stronger acid than that originally used; however, 
these fluids act rather differently when employed for 
the exhaustion of the cantharides. Obeying strictly 
the Pharmacopoeia, we find that on passing the ether 
through the powdered flies, the ether extracts the 
green oil and other ingredients of the cantharides, 
the latter retaining the greater part of the water pre¬ 
sent in the acetic acid. The result is an ethereal 
tincture saturated with water, and having a specific 
gravity of about -770 at 15° C. About 14 ounces 
of ether are consumed to produce the half-pint of 
liniment. If the residue is squeezed a considerable 
quantity of water is the result, and on drying in the 
air until the whole of the ether lias evaporated, the 
flies will be found to weigh nearly one quarter more 
from the water absorbed, instead of being lighter from 
the loss of extractive. A process of separation seems 
instituted by which the aqueous portion is retained 
by virtue of the attraction of the animal matter. 
It is evident that glacial acetic acid should be 
used; if tliis is done, a rapidly vesicating and homo¬ 
geneous fluid is obtained. The following is the al¬ 
teration that we venture to suggest:— 
Take of 
Cantharides in powder 8 ounces. 
Glacial Acetic Acid . 2 fluid ounces. 
Ether.28 ounces, or a sufficiency. 
Piub the cantharides in a mortar with the glacial 
acetic acid, and proceed as directed in the Pharma¬ 
copoeia. The consumption of ether will be found to 
be about the same as in the previously mentioned 
formula, namely 28 ounces, the specific gravity at 
15° C. being ‘779; in this instance the cantharides 
will be found to have lost considerably hi weight, 
for on exposure to the air for a short time until the 
ether had evaporated, they were found to weigh only 
7 ounces. 
A formula for vesicating collodion might at the 
same time be introduced, that preparation being 
more extensively used than the vinegar or liniment. 
The collodion is a great favourite with the ophthal¬ 
mic surgeons; it is easily made in the following 
manner:— 
Take of— 
Blistering Liquid, 10 fluid ounces. 
(not made with ordinary acetic acid.) 
Gun Cotton, \ of an ounce or a sufficiency. 
