SIR B. C. BRODIE ON THE ACTION OE ELECTRICITY ON OASES. 
85 
tube was transferred to a large gas-pipette and there measured, the pipette being filled 
with the gas at atmospheric pressure and a known temperature. The arrangement of the 
induction-tube was precisely as in my previous experiments with oxygen, the tube being 
in all cases placed between two sets of small bulbs permanently attached to it con- 
taining anhydrous phosphoric acid. The bulb also containing the solution of potassium 
iodide was of the form previously employed. A sketch 
is here annexed of the absorption-bulb, from which this \T 
part of the arrangement will be easily understood. 
The stopcock ( d ) was a three-way stopcock of steel 
similar to that attached to the aspirator. Before the 
experiment the bulb a was filled with mercury by means • i ^rcz FiT ^ 
of the tube b, the stopcock being open to the air; it 
was then closed, and a partial vacuum created in the 
bulb by running out a portion of mercury at c, where 
an india-rubber tube closed by a clamp was attached. 
The solution of caustic potash was introduced by pouring 
the solution into the absorption-bulb through the tube b. 
The upper part of the bulb and the capillary tube were 
filled with the solution to within about half an inch of 
the stopcock, which should not be allowed to come in 
contact with the alkali. 
At the commencement of the experiment the appa- 
ratus was thoroughly swept out with carbonic acid, the 
connexion with the absorption-bulb being shut off and 
a suitable channel provided for the gas by means of the 
three-way stopcock. The pipette having been filled 
with the gas and the requisite observations made for its 
measurement, the gas was drawn through the induction- 
tube, which may readily be effected at any required rate by opening the communica- 
tion with the interior of the bulb and running mercury from it. The absorption at 
first is very rapid, and some management is required not to expose at once too great a 
surface of the alkaline solution to the action of the gas. The connexion having been 
made with the coil, iodine speedily appears in the titre-bulb, and after a short time a 
sensible quantity of permanent gas is collected in the absorption-apparatus. After the 
first pipette of gas had thus been passed through the tube, the coil was temporarily 
disconnected, a second pipette filled and drawn over as before. The experiment was 
continued until in each case five pipettes of carbonic-acid gas had been thus acted on. 
This part of the experiment having been completed, the absorption-bulb was discon- 
nected, and having been attached to the aspirator described in my former memoir, the 
total gas was transferred to it and measured. A small quantity of an alkaline solu- 
tion of pyrogallic acid was now introduced into the absorption-bulb and the gas drawn 
