413 
LECTURES ON THE BRITISH PHARMACOPOEIA. 
materials are put together as directed ; hut in consequence of the unfortunate 
omission in the directions to which I have alluded, the process, when conducted 
strictly according to the book, yields no hydrochloric acid. The fact appears to 
have been overlooked by the writer of the article describing the process, that 
when the sulphuric acid is used in this state of dilution, the hydrochloric acid is 
not given off without the application of heat. On supplying that omission, how¬ 
ever, the process, as you will perceive, will proceed in a very satisfactory manner, 
and a perfectly good product will be obtained. I do not consider the increase 
of strength in this acid, as compared with that of the London Pharmacopoeia, to 
be an advantage, but rather the reverse, as it has a greater tendency, in conse¬ 
quence, to throw off vapours when exposed to the air, and there is no purpose 
that I am aware of to which it is applied where the weaker acid would not an¬ 
swer equally well. 
Acidum nitricum .—There are many present, no doubt, who will recollect the 
nitric acid of the London Pharmacopoeia of 1836, and the trouble and annoyance 
attending its use. We all rejoiced to find that in the Pharmacopoeia of 1851 a 
weaker acid was ordered—an acid easily obtained, easily preserved without un¬ 
dergoing deterioration, which answers every purpose required in medicine, and 
which can be used without the inconvenience attending the use of the other. 
The nitric acid of 1851 is admitted on all hands to be the most stable of the 
hydrates of nitric acid. It is easily produced as a colourless acid, which retains 
this condition when exposed to the light. It may even be distilled without 
change, which cannot be said of nitric acid in any other state of hydration. 
What better acid could be selected for use in medicine? Yet we are now r carried 
back again to the stronger acid of 1836. The nitric acid of the British Phar¬ 
macopoeia is an acid having the specific gravity of 1*5. It is not a commercial 
acid, but has to be made specially for our use. It is not obtained in a colourless 
condition; and although it may be rendered colourless by a troublesome and 
somewhat difficult process, it cannot be kept in that state, for it is constantly 
undergoing decomposition under the influence of light, and the result of this de¬ 
composition is that it loses strength, and becomes more and more contaminated 
with the red nitrous gases which are generated. The introduction of this strong 
fuming nitric acid again into the Pharmacopoeia is certainly a retrograde move¬ 
ment. There is no purpose to which nitric acid is directed in the Pharmacopoeia 
to be applied where the acid of the last Pharmacopoeia would not answer as well 
as or better than this. 
Acidum sulphuricum is described in the Materia Medica part of the work as 
monoliydrated sulphuric acid, for which a chemical formula (HO, SO s ) is given 
in accordance with that name. But what, it may be asked by some of our 
brethren who have not just issued from the chemical laboratory of this or some 
other institution,—what does monohydrated sulphuric acid mean, and what is the 
body represented by that chemical formula ? Does it mean oil of vitriol ? because 
if it does, we know what that is. Well, it must be admitted that it does not 
mean oil of vitriol, for oil of vitriol is commercial sulphuric acid, and this is 
something different from that. Then if the “ sulphuric acid ” of the British 
Pharmacopoeia is not oil of vitriol, and is not a commercial article, which it is 
not, how is it to be obtained ? The Pharmacopoeia tells us how to obtain it, for 
it gives a process for the purpose. This consists in distilling oil of vitriol with 
sulphate of ammonia, fractionizing the products of distillation, rejecting the first 
product, and saving the second, which is the acid in question. Now all this pre¬ 
sents a greater amount of difficulty than might appear at first sight. To carry 
the process out as directed is no easy matter. To begin at the beginning, w r e are 
told that the oil of vitriol to be thus treated, must give no evidence of the pre¬ 
sence of arsenic by that most delicate of tests called Marsh’s test; and it is 
doubtful if any oil of vitriol can be met with in this country that will stand this 
