292 THE ALLOTROPISM OF CHLORINE. [MEMOIR XX. 



dark. A third exposure was followed by the same re- 

 sult. 



The form of this vessel renders it very convenient for 

 . these experiments ; because when sufficient gas has col- 

 lected for the purpose of observation, it is easily removed 

 by inclining the instrument, without the necessity of 

 introducing fresh quantities of liquid. 



Having found, as has been said, that the rapidity of 

 the decomposition depended to a certain extent on the 

 temperature, it seemed desirable to determine whether 

 heat alone could bring about the change. 



IX. The decomposition of water by chlorine is not 

 brought about by mere elevation of temperature when 

 the liquid is set in the sunbeam : although heat accel- 

 erates, it does not give rise to the phenomenon. 



1st. I raised by a spirit-lamp the temperature of one 

 of the bulbs nearly to its boiling-point, until so much 

 gas was given off that all the liquid was expelled from 

 the tube to the bottle beneath. If at this temperature, 

 which probably was higher than 200 Fahr., chlorine 

 had been able to decompose water, an equivalent quan- 

 tity of oxygen would have been produced ; but on al- 

 lowing the apparatus to cool, all the gas was reabsorbed 

 with the exception of a small bubble, amounting in vol- 

 ume to y^Vr of the water. This bubble, which was left 

 after the chlorine was recondensed, I found in three dif- 

 ferent experiments contained 32, 33, and 36 per cent, of 

 oxygen, the remainder being nitrogen ; but this being 

 nearly the constitution of the gas dissolved in ordinary 

 water, the source from which the small bubble came 

 was inferred to be the water used in these experiments. 



2d. One of the bulbs was painted black all over with 

 India-ink. Its temperature now rose much higher than 

 in former experiments when it was set in the sun, but 

 not a bubble of oxygen appeared. 



