366 PEOFESSOE BIJNSEIS' AXD DE. H. E. EOSCOE’S PHOTO-CHE:NnCAL EESEAECHES. 
through the apparatus before all the air is expelled, and the requisite equilibrium 
between the absorbed and free gases established. 
In order to answer these questions, we led a cuirrent of gas for several days through 
our instrument, freshly filled, observing from time to time the amount of action effected 
by the constant source of light. We obtained the following results, which were similarly 
observed each time the apparatus was refilled. 
Series of Experiments VI. 
Experiment 1, 
Experiment 2. 
Duration of 
the saturation. 
Action for each 
minute from 
twelve obser- 
vations. 
Duration of 
the saturation. 
Action for each 
minute from 
twelve obser- 
vations. 
Duration of 
the saturation. 
Action for one 
minute from 
twelve obser- 
vations. 
Duration of 
the saturation. 
Action for one 
minute from 
twelve obser- 
vations. 
First day. 
Fourth day. 
First day. 
Third day. 
h m 
h 
m 
h m 
m 
1 9 
0-00 
30 
9-65 
1 5 
0-00 
5 
9-90 
15 
2-49 
1 
1 
18-39 
1 35 
0-00 
10 
10-10 
15 
3-06 
15 
23-06 
33 
2-08 
30 
11-52 
Third day. 
5 
22-26 
5 
2-08 
15 
12-83 
18 
5-57 
27 
23-22 
Second day. 
20 
12-92 
16 
5*21 
10 
25-63 
30 
5-93 
15 
13-64 
25 
5-36 
1 
8 
19-66 
20 
6-41 
10 
13-60 
39 
5-01 
15 
17-28 
15 
7-40 
31 
4-86 . 
1 
8 
14-60 
1 0 
8-43 
39 
5-14 
Fifth day. 
10 
8-39 
1 19 
3-32 
15 
26-49 
35 
6-60 
19 
2-47 
2 
25-32 
29 
2-12 
2 
27-19 
20 
2-43 
2 
26-95 
2 
26-08 
2 
25-87 
2 
27-43 
From the first of these experiments, in which, as in all the later ones, hydrochloric 
acid of spec. grav. 1'148 was used, it is seen that after the gas had passed one hour 
through the apparatus the action was O’O ; after two hours’ saturation the action rose to 
5-57, at which amount it remained stationary after the gas had again passed through 
for 2^ hours; on further saturation the action diminished to about 2’43. Tlie difier- 
ence between the weight of the decomposing cell before and after the experiment, showed 
that 3755 cub. cent, of the chlorine and hydrogen mixture had passed tlirough the 
vessel i, of about 7 cub. cent, capacity and containing 1‘8 cub. cent, of water, and that 
the quantity of hydrochloric acid contained in the electrolyte had diminished from 30 
to 20 ’5 per cent. 
'Ihe experiment, which thus far had occupied two days, was extended o's er the follow- 
ing days, the diluted acid being replaced by concentrated acid. After the gas had passed 
through the instrument for half an hour the action increased to 9-65, and after satura- 
tion for another quarter of an hour the action amounted to 23-06, at Avhich number it 
remained constant for several successive hours. On further saturation the action dimi- 
nished to 14-6. The volume of gas which had passed through the insolation- vessel 
