ON THE CHEMICAL PROCESSES AND PREPARATIONS. 
411 
And now, having sketched out the general purport and extent of the changes 
made in the chemical preparations of the Pharmacopoeia, I must direct your 
attention to some points in connection with those preparations which appear to 
claim particular notice. 
Aciclum aceticum. —The acid ordered under this name is not quite so strong 
as that of the London Pharmacopoeia. It now contains 28 per cent, of anhy¬ 
drous acetic acid, while the acid of the London Pharmacopoeia contained 308 
per cent. There is no process given for its production, and I think it is much 
to be regretted that the example thus set was not more generally followed with 
other chemical preparations. Besides this form of acetic acid, however, there 
are three others ordered. 
Aciclum aceticum glaciate is described as monohyclrated acetic acid—that is, 
anhydrous acid with one atom of water. In this case, in addition to the de¬ 
scription, which is given pretty fully, there is also a process given, and from the 
manner in which this is described, it might be inferred that this glacial or mo- 
nohydrated acetic acid may be readily produced ; but any one who tries will 
soon discover that such is not the case. In fact, the monohydrated glacial ace¬ 
tic acid cannot be obtained at all by the process given. It may be said that this 
is not of much importance, as the glacial acid can be obtained in commerce 
without any difficulty, and cannot be successfully produced upon other than the 
large manufacturing scale. It this be so, as undoubtedly it is, why should the 
Committee have undertaken to give a process ? If they had rested satisfied 
with describing the preparation they wished to be used, as they have done in 
the case of Acidurn aceticum , they would have avoided the inconsistency of de¬ 
scribing the product in one part of the work as a body having certain characters, 
and answering to a chemical formula which very precisely defines its composi¬ 
tion, while in another part of the work they give a process which fails to yield 
the product they have described. 
Acidurn aceticum dilutum is weaker than the diluted acid of the London 
Pharmacopoeia ; in fact, it is only about three-fourths of the strength of that 
acid. One fluid ounce of it is neutralized by 9'6 grains of soda (NaO), while 
the same quantity of the London acid requires 12-6 grains of the same alkali. 
It may be remarked here that while the diluted mineral acids—that is, the 
hydrochloric, nitric, and sulphuric—have been equalized in strength, and made 
to contain as many grains of the acid in six fluid drachms as represents the 
atomic weight of the acid in each case, the diluted acetic acid is much weaker 
than this, and requires more than four times that quantity to represent the 
same strength. 
Acidurn hydrocliloricum. —This acid is to be rather stronger than that ordered 
in the London Pharmacopoeia, but the difference is slight, and I have therefore 
not represented it as a new or altered preparation. It is now to have a specific 
gravity of 1T7, instead of 1T6 as formerly. In the last London Pharmacopceia 
there was no process given for the preparation of hydrochloric acid, although a 
good process was contained in the Pharmacopoeia of 1836. A process is now 
again introduced, which, although in some respects a very good one, is in one 
respect defective. The process of the British Pharmacopoeia is practically that 
of the late Dr. Gregory, of Edinburgh ; and its peculiarity consists partly in the 
use of two atoms instead of one of sulphuric acid to every atom of chloride of 
sodium, so that bisulphate instead of sulphate of soda results from the decompo¬ 
sition ; and partly in the dilution of the sulphuric acid with water until it has a 
specific gravity of about 1*6. The result of thus diluting the sulphuric acid and 
using it in increased quantity is, that it is less likely to yield sulphurous acid 
when it comes into contact with organic impurities in the common salt, and that 
in other respects it facilitates the process and yields a purer product. The ap¬ 
paratus as described in the British Pharmacopoeia is here fitted up, and the 
