MEMOIR XX.] THE ALLOTROPISM OF CHLORINE. 291 



VII. The quantity of gas thus collecting in the dark 

 depends on the intensity of the original disturbance, 

 which in its turn depends on the time of exposure to 

 the rays, to their intensity, and other such conditions. 

 In other words, the rays are perfectly definite in their 

 action a long exposure giving a larger amount of sub- 

 sequent decomposition, and short exposure a less amount. 



On exposing a bulb filled with chlorine-water to the 

 rays until bubbles of gas began to appear, and a second 

 one until the decomposition had been actively going on 

 for a quarter of an hour, and then transferring both to 

 the dark and measuring the oxygen collected at the end 

 of a day, I found in the former one twelfth of what was 

 collected in the latter. 



VIII. In a given quantity of chlorine -water, the de- 

 composition in the dark corresponding to a given expos- 

 ure to the light having been performed, and the proper 

 quantity of oxygen evolved and the phenomenon ended, 

 it can be re-established from time to time, as long as 

 any chlorine is found in the liquid, by a renewed expos- 

 ure to the sun. 



In a glass vessel, like Fig. 46, which, indeed, was noth- 

 ing more than one of Liebig's dry- 

 ing apparatus, I placed a sufficient 

 quantity of chlorine -water to fill 

 the larger vessel, and the vertical 

 tubes half full. After exposing 

 this to the light for a certain time, Fi - 46 - 



until decomposition had fairly set in, I placed it in the 

 dark and found that for several days it gave off gas 

 the quantity continually diminishing. Finally, no more 

 gas was evolved. But the liquid still contained free 

 chlorine, as was shown by its color. I therefore again 

 exposed it to the sun, and, repeating the former observa- 

 tion, found that it evolved gas for several days in the 



