518 
PHARMACEUTICAL MEETING. 
the various specific gravities of the solutions described, could only point to one 
conclusion, viz. that the Pharmacopoeia solution did not coincide in its described 
spec. grav. as compared with its percentage of acid ; for a solution of T040 in¬ 
dicated but 7'8 per cent, of real acid instead of 9*2 per cent., or in other words, 
if the spec. grav. was correct, the strength was an error, or vice versa. 
The Brit. Pharm. 1864 directed an acid of P040 spec, grav., but only indi¬ 
cated the numbers of measures of iodine solution required for its saturation as 
equivalent to 8*3 per cent. 
This, therefore, is an approximation to the result I have obtained. 
In an excellent review of the officinal acids by Mr. C. H. Wood, article “ Sul¬ 
phurous Acid,”* it is said, “ This acid is of the same strength, and is prepared 
in the same manner as before.” 
It is certainly of the same specific gravity, viz. 1*040, but I find by calcula¬ 
tion that 88 measures of iodine solution less in 1000 measures are indicated than 
by the B. P. 1867, an equivalent of nearly 1 per cent, real acid. The two solu¬ 
tions of the two pharmacopoeias, although of the same specific gravity, cannot, 
then, be of the same strength. 
The manufacture of the acid on the large scale, up to even the highest point 
to which I have arrived, is next to impossible. I will quote the remarks of a 
chemist, in a letter upon this subject to me, who is in the habit of making tons 
yearly. He says, “ I obtain a solution of 1,030 easily (comparatively) ; and in 
cold weather and a slow current of gas, ordinarily I get acid from 1*025-30.” 
Through the kindness of Messrs. May and Baker, Battersea, I have been 
favoured by their chemist, Mr. Tyrer, with the result of two experiments made 
on a very large scale, and under the most favourable circumstances. 
A charge of 200 lbs. charcoal and 140 lbs. oil of vitriol was placed in a still of 
120 gallons’ capacity ; the gas washed and passed through a series of Woulfe’s 
bottles, the exit pipe from the last bottle being weighted at 6 lbs. pressure. In 
temperate weather by this method an acid from 1*033 to 1*035 can be pro¬ 
duced, and by passing through a second charge of gas from a fresh supply of oil 
of vitriol, a solution of 1*036 to 1*038 can be produced,—but this only on cold 
nights and working very slowly ; if the gas is passed rapidly, more is lost than 
gained. 
The second experiment was but a modification of this, substituting at the last 
of the Wouife’s bottles a pressure produced by a column of water of 12 feet 
(G lbs. pressure), with plugs inserted at 3 feet intervals, so that by withdrawing 
them the pressure could be regulated. This means of producing pressure was 
adopted in preference to the valve, which invariably corroded, as it gave a ready 
means of allowing the carbonic acid and carbonic oxide to escape. The re¬ 
sult, however, was an acid of only 1*038 specific gravity, as in previous expe¬ 
riment. To work regularly at this amount of pressure would, be anything but 
des Table. 
The U. S. Pharm. orders a solution of 1*035 specific gravity ; no strength is 
however named, neither is a process given for its estimation ; it does, however, 
direct the solution to be put into half-pint bottles, well stopped, and kept in a 
cool place. In the 1837 edition of the French Codex, a solution of thirty-seven 
volumes is directed, the specific gravity described as 1*053. The gas, however, 
is made by the reduction of oil of vitriol with mercury, which gives a product 
nearly pure. This is almost identical with my result, taking into consideration 
the quantity of carbonic acid necessarily dissolved with the sulphurous acid 
under pressure. 
It cannot for one moment be doubted that a solution of much greater strength 
than any here indicated could, in the experimenting room, under certain cir- 
* Pharm. Journ. Vol. IX. page 64. 
