NOTE ON DISTILLED SULPHURIC ACID. 
G01 
denser than necessary. Then having ascertained by the balance the proportions 
required, quantities of the same materials, no matter how great, can at once be 
adapted for use without further trouble. 
My chief object in giving the details of this process is to enable prescribers 
to devise for themselves, if they think fit, a form, of the exact composition of 
which they are aware,—an all-important requirement, one would J imagine, 
where remedies of great potency are to be administered. 
Mr. Han bury said that when the subject was announced, it recalled to his 
mind a paper which appeared in tbe 1 Journal de Pharmacie ’ a few years ago, 
which gave a method for suspending chloroform in a mixture. The Societe de 
Pharmacie of Paris appointed a commission on the subject, which gave what 
was concluded to be the best method. He had brought some specimens made ac¬ 
cording to this method, and it would be seen they were good and perfect mixtures. 
The Chairman said there was no doubt that if chloroform was added to sub ¬ 
stances of the same specific gravity they could be made to mix readily. 
NOTE ON DISTILLED SULPHURIC ACID. 
BY PROFESSOR REDWOOD. 
The sulphuric acid of the British Pharmacopoeia differs from that hitherto 
used in medicine in this country. We have been accustomed under the name 
of sulphuric acid to use commercial oil of vitriol, and this, according to the last 
London Pharmacopoeia, was to have a specific gravity of 1-843. We are now 
directed in the British Pharmacopoeia to use, not commercial oil of vitriol, but 
distilled sulphuric acid, and this is described as monohydrated sulphuric acid 
(HO,SO a ), the specific gravity of which is represented as 1-846. 
Having had occasion in my lectures on the British Pharmacopoeia to remark, 
with reference to sulphuric acid, that in the processes and descriptions given in 
that work there are some inconsistencies and errors, I have been called to ac¬ 
count for making such a statement on what has been assumed to be insufficient 
grounds. 
The subject is one on which I had worked a good deal some years ago, and 
my remarks were partly founded on results then obtained, and partly on the 
published investigations of others. I have since repeated some of the experi¬ 
ments to which I referred, and wish on one or twoj points to lay the results 
before the meeting. 
Forty-eight fluid ounces of commercial oil of vitriol, of sp. gr. 1843, were put 
into a small platinum still with one ounce of sulphate of ammonia, and the mix¬ 
ture submitted to fractional distillation. The first distillate, consisting of seven 
fluid ounces, was rejected. The three subsequent distillates, consisting of three 
fluid ounces, five and a half fluid ounces, and six and a half fluid ounces, had 
all very nearly the same specific gravity, ranging from 1841-3 to 1841-5. The 
next distillate, consisting of seven and a half fluid ounces, had a sp. gr. 1842-3, 
and the next, consisting of six fluid ounces, had a sp. gr. 1842 - 5. I observed 
that all these products had a slight smell of sulphurous acid, the produc¬ 
tion of which I could only account for by assuming that a portion of the sul¬ 
phuric acid was decomposed in contact with the heated platinum vessel at the 
temperature required for the distillation. I ascribed to this decomposition the 
low specific gravity of the product as compared with what is indicated in the 
Pharmacopoeia, and I therefore relinquished the further use of the platinum still. 
Another operation was performed in a glass retort as described in the Phar¬ 
macopoeia. The specific gravity of the oil of vitriol operated upon in this case 
was 1844, this being the densest commercial oil of vitriol I was able to get. 
The process was conducted strictly according to the Pharmacopoeia, the first ten 
