AND CHLOKINE UNDER THE INFLUENCE OF LIGHT. 
95 
induction period may be prolonged indefinitely, so that an interval of some hours 
may occur between the beginning of insolation and the formation of hydrochloric acid 
in large enough quantities to be observed. 
In the following two experiments the time to the first visible contraction showing 
formation of hydrochloric acid was in the first 48 minutes, and in the second 178 
minutes. 
I. 
1 
IT 
1 
Time from 
Time from 
1 
HCl formed. 
illumination in 
minutes. 
HCl formed. 
illumination in 
minutes. 
48 
0 
177 
0 
50 
5 
178 
1 
51 
10 
180 
3 
53 
24 
184 
9 
! 55 
39 
188 
17 
60 
86 
190 
23 
70 
214 
194 
41 
201 
81 
— 
— 
205 
104 
The bulb used for these experiments was a large one, about 8 centims. in diameter, 
and the capillary tube was about 150 centims. long, so that the induction could be 
followed for a long time. 
§ 2. The Effect after Darkening. 
When feeble light is used for insolation the effect that remains after the light is 
cut off can be detected for a very considerable time. The effect is that after the gas 
has been illuminated and then darkened, on again illuminating the period of 
induction is shorter than in the first instance. That is, that all effect of the light 
does not cease when the light is removed. We have seen that the formation of 
hydrochloric acid stops almost immediately, hut the gases are in a condition when 
they can combine more readily under the influence of fresh light. The gas is in a 
condition of insolation. In Bunsen and Boscoe’s experiments this effect could not 
be detected after about 15 minutes in the dark, but it can be prolonged, and in one 
experiment was detected after the gas mixture had remained in the daik for ovei 
22 hours. With more intense light the visible effect passes off in a very much 
shorter time, giving results agreeing with those of Bunsen and Roscoe. (For 
example, in the experiment on p. 85, the effect as far as it affected the initial 
expansion passed off in about 6 minutes.) 
In figs. 10, 11, 12, 13 are represented experiments on this effect. The light 
