90 
SIR B. C. BRODIE ON THE ACTION OE ELECTRICITY ON GASES. 
methods ; and, taken in conjunction with the previous experiments referred to, we may 
confidently infer that the fundamental reaction is the same as in the case of the experi- 
ment with pure oxygen, but that the experiments are affected by the operation of a con- 
stant cause which depresses the mean value of the ratio R. 
Such a cause is to be found in the absorption of oxygen by the strongly alkaline 
solution employed in the absorption-bulb for the removal of the carbonic acid from the 
mixed gases. The gas passed through the hyposulphite of soda and the gas passed 
through iodide of potassium have, it is true, been subjected to a similar treatment in 
this respect ; and if the same quantity of oxygen were absorbed by the alkaline solution 
in the two cases, the value of the difference between the volumes of the gases, which is 
Y— y 
the numerator of the fraction — rp— 1 in the preceding calculation, would not be affected 
by this circumstance. But this cannot on the average be the case; for the relative 
volume of oxygen present in the latter gas being considerably greater than that present 
in the former, a larger quantity of it will be absorbed by the solution. Now we 
have (as has been explained) in the contraction which the unabsorbed gas undergoes on 
detonation with oxygen an independent measure of the total oxygen formed in the 
induction-tube ; and, in fact, if we compare the average values thus actually obtained 
for the total oxygen in the gas, it will be found that the sum of the “ titre ” and the 
oxygen absorbed by pyrogallate of potash is sensibly less than the contraction. This, 
however, only appears when we consider the mean result, as there are many causes of 
error which affect the individual experiments. The comparison of these values in the case 
of fourteen experiments is given below. In column I. is given the sum of the oxygen 
absorbed by pyrogallate of potash and the “titre” of the gas; in column II. the con- 
traction which the same gas underwent when detonated with oxygen — the results of the 
experiments being calculated on equal volumes of gas in the two experiments respectively. 
I. 
II. 
15-76 
16-17 
14-49 
14-62 
11-20 
10-78 
10-53 
10-84 
9-21 
9-75 
10-42 
10-49 
8-63 
8-89 
12-60 
13-47 
16-83 
17-62 
16-10 
17-68 
11-80 
12-05 
17*34 
18-42 
3-20 
3-61 
14-96 
15-42 
Sum =172-17 
Sum =179-81 
It hence appears that for every 100 volumes of oxygen found in the induction-tube 
as estimated by the contraction, only 95-8 volumes are found by the other method, 
