440 
SIR B. C. BRODIE ON THE ACTION OF ELECTRICITY ON GASES. 
thus filled with sulphuric acid. The stopcock in the siphon-tube is now closed, as also 
the stopcock w ; the stopcock v is opened, and the gas as delivered from the induction- 
tube at n is allowed to pass into the gas-holder. The sulphuric acid which is thus dis- 
placed is drawn back into the reservoir r, by creating in the reservoir a partial vacuum ; 
this is effected by means of an air-pump, connected with the glass tube u by a caout- 
chouc tube. Similarly, any required quantity of gas may be delivered from the gas- 
holder by closing the stopcock v and opening the stopcock w, the gas being expelled 
from the gas-holder by the column of sulphuric acid in the jar delivered from the 
siphon-tube. 
The drawing of the apparatus given in the figure is a quarter the actual height ; the 
capacity of this gas-holder is about 3000 cub. centims. The arrangement, although 
somewhat complicated in description, is easily worked. 
The volume of gas submitted to experiment was measured in a glass pipette, of which a 
drawing is given in Plate LII. fig. 5 to the same scale as the last. The capacity of the 
pipette between the two marks b and c was estimated by calibration with mercury, the 
quantity of mercury required to fill the pipette between the marks being weighed at an 
observed temperature ; its capacity as thus ascertained was 290*8 cub. centims. It was 
then welded to a glass tube of the form given in the figure : e is a reservoir of sulphuric 
acid with a siphon-tube attached, similar in principle to that previously described ; d is a 
cylinder containing water, in which the gas-pipette a is immersed, and of which the tem- 
perature is observed by means of a thermometer placed in it. The gas-pipette is placed 
in connexion with the gas-holder by means of a paraffine-joint at f; the arrangements for 
working this pipette are precisely similar to those previously described in the case of the 
gas-holder. At the commencement of the experiment the pipette is filled with sulphuric 
acid from the reservoir e by means of the siphon-tube, the stopcock g being closed and li 
open ; this having been effected, the pipette is filled with the electrized gas by closing the 
stopcock h and opening the stopcock g, a partial vacuum being made in the reservoir e as 
previously described, and a pressure of 2 or 3 inches of sulphuric acid being put upon the 
gas in the gas-holder. The pipette is thus filled with gas to some point below the mark c\ 
the stopcock g is then momentarily lifted so as to allow the sulphuric acid to rise to the 
mark c. The quantity of sulphuric acid in the reservoir was so adjusted that when the 
siphon-tube was empty the pipette was necessarily filled to this level. It is to be 
observed that the tubes connected with the apparatus were first filled with the electrized 
gas by drawing over, at the commencement of the experiment, a certain volume of the 
gas into the pipette and expelling it into the air. In this manner the pipette was filled 
to the mark c with the electrized gas at atmospheric pressure as observed by the baro- 
meter, and at the temperature indicated by the thermometer placed in the water in which 
the pipette was immersed ; the gas was delivered from the pipette at c. To effect this 
the stopcock in the siphon-tube was opened, and a pressure was thus put upon the gas, 
the stopcock h being also open and the stopcock g closed : the quantity of sulphuric acid 
was so arranged that the gas could readily be brought at atmospheric pressure to the 
