174 
MISCELLANY. 
upon the perusal of the paragraph quoted ; and I am induced at the same 
time to suggest a means hy which the efficacy may be tested, without 
exposing the patient to the risk of injury from the direct action of the 
strong mineral acids. 
It is essential that the gas employed for this purpose should be per- 
fectly free from the sulphuric or hydrochloric acids, by means of which 
it is liberated from its solid compound; and this degree of purity can 
only be accomplished by washing the gas in water. The employment of an 
apparatus for this purpose may be somewhat inconvenient in the country ; 
but it would be far better to abstain from the use of the gas altogether 
than to incur the risk of irritation, or even inflammation, which might ensue 
from its employment in an unwashed state. I shall endeavor to arrange 
some simple apparatus for this purpose, in which if I should be success- 
ful I will forward you a drawing and description of it. At present, the only 
means which suggests itself, is to employ for the purpose Woulfe's bottles, 
connected with each other by a bent tube. In the one, the carbonate of 
lime is to be placed ; in the other, water enough to cover the end of the 
bent tube which connects the bottles. The elastic tube should then be 
connected with the open mouth of the second bottle, in which the water 
is contained ; and the whole apparatus being prepared, the dilute acid 
may be poured into the first bottle containing the carbonate of lime ; the 
mouth of the bottle being immediately closed. Effervescence will imme- 
diately take place, and the gas proceeding through the bent tube will be 
compelled to pass through the water in the second bottle, be deprived of all 
contamination, and forced out of the elastic tube by the pressure from be- 
hind, arising from the constantly accumulating pressure in the bottle 
wherein it is disengaged. 
The chief difficulty attending the use of this would be obtaining the 
Woulfe's bottles; in all other respects no improvement or simplification 
would be required. The patient could readily perform all the manipula- 
tions herself, after having been once instructed in the proper proportions 
of the materials to be employed. 
A word or two as regards the acid to be used. Hydrochloric acid is 
decidedly preferable to sulphuric acid, on account of its yielding a soluble 
salt with lime, which may be removed from the generator with far greater 
ease than the heavy, adhesive, insoluble sulphate; and on this account it 
should always be employed. The quantity of carbonic acid yielded by 
limestone or chalk, if of tolerable purity, is always the same, whatever 
be the acid employed ; and I annex the quantity by weight which is re- 
quired to produce a gallon of carbonic acid gas at the average temperature 
of 60° F. ; should the temperature range above 60° F., the volume of gas 
will be somewhat increased. The paper from which I quote the above 
paragraphs, gives no idea of the quantity of gas required ; but it is de- 
cidedly an advantage to the correct observer to be acquainted with the 
