MEMOIR XX.] THE ALLOTROPISM OF CHLOKINE. 293 



X. When chlorine-water has been exposed to the sun, 

 the oxygen accumulated in it is readily expelled by rais- 

 ing the temperature. 



Having exposed one of the bulbs used in the last ex- 

 periment until it was actively evolving gas, I raised its 

 temperature with the spirit-lamp until the bulb was full 

 of gas. But on cooling this gas did not all condense as 

 in the last instance, a large quantity remained behind. 

 This was oxygen. 



These ninth and tenth facts are of further interest, as 

 bearing upon a question much discussed by chemists 

 the nature of the bleaching compounds of chlorine. The 

 chloride of lime, and other such substances, probably 

 have the same theoretical constitution as chlorine- water. 

 Berzelius and Balard suppose that in this solution chlo- 

 rous or hypochlorous acid exists. It might be inquired, 

 if this be the condition of things, why does not an ex- 

 posure to heat alone evolve oxygen, for chlorous acid is 

 exceedingly liable to decomposition by slight elevation 

 of temperature, and we should be justified in inferring 

 that if any of this acid is to be found in chlorine-water 

 it would be decomposed at the boiling-point. M. Mil- 

 Ion adopts the view that the bleaching compounds are 

 metallic chlorides analogous to the corresponding per- 

 oxides. But the ninth fact seems incompatible with this 

 view. If chlorine -water be analogous to peroxides of 

 hydrogen, and this last be what its name imports, and 

 not merely oxygenated water, it is difficult to understand 

 why, when chlorine-water is thus boiled, oxygen is not 

 given off. If the atom of chlorine and the atom of oxy- 

 gen in this body are placed under the same relations to 

 the atom of hydrogen, it seems necessary that the chlo- 

 rine atom at 212 Fahr. should expel the oxygen atom 

 and hydrochloric acid form. It is probable, indeed, that 

 the two oxygen atoms in peroxide of hydrogen are re- 



