350 Prof. Draper on the Allotropism of Chlorine 
dark side raised its temperature. On measuring the quantity of 
gas collected, it was found, 
In the transparent bulb, - ~ - 3°46 
In the half blackened bulb, - - - 6°19 
IV. The decomposition of water, once begun in the sunbeams, 
goes on afterwards in the dark. 
1st. This very important fact may be established in a variety 
of ways. Thus, ifa bulb be removed from the sunshine whilst 
it is actively evolving gas, and be placed in the dark after all the 
gas has been turned out of it, a slow evolution continuously goes 
on; the gas collecting in the upper part of the bulb. 
2d. A bulb A, Fig. 2, having a neck 5, the end of which was 
bent at c upwards at an angle of about 45 degrees, was employed. 
After exposure to the sun, by inverting the bulb and with one 
finger closing the extremity c, the gas disengaged could be trans- 
ferred to a graduated vessel and measured. I satisfied myself by 
several variations of this arrangement that the small quantity of 
water, introduced from time to time when the gas bubble escaped 
from the end of the tube e, exerted no essential influence on the 
phenomenon. The following table shows the amount of gas 
evolved in the dark during the periods indicated. 
The bulb having been exposed to the sunshine, in ten minutes 
the evolution of gas commenced, and in an hour, *107 cubic inch 
having collected, this was thrown away, and the arrangement 
placed in the dark. 'T'o prevent the undue escape of the chlorine, 
the flat piece of glass d, was laid on the open end of the tube ec. 
In each successive hour the quantity of gas given in the following 
table was then evolved. 
First hour, - - - - 0162 
Second “ - - - - 0159 
hind aa - - - -  -0086 
Fourth “ - - - - ‘0060 
Pifth: 2S - - - - ‘0038 
Sixth.) - - - - 0031 
And for four days afterwards gas was collecting in the bulb in 
diminished quantities. 
VY. This evolution of gas in the dark is not merely a gradual 
escape of oxygen, originally formed whilst the solution was ex- 
posed to the sun, but is traceable to an influence continuously 
exerted by the chlorine, arising in properties it has acquired du- 
ring its exposure to the rays. 
