476 



weighed, which contained on one side an acid solution of iodide of 

 potassium, and on the other sulphuric acid ; the former to decompose 

 the ozone, the latter to prevent the escape of moisture. The increase 

 in weight of this apparatus gave the entire weight of the ozone ; the 

 iodine set free, when reduced to its equivalent in oxygen, the weight 

 of the active oxygen. The precautions to be taken in conducting 

 this experiment are fully described in the communication. 



The following are the numerical results of five experiments per- 

 formed according to the above method : 



Volume of electrolytic Increase in weight of Active oxygen deduced 

 oxygen. compound apparatus. from iodine set free. 



litres. grm. grm. 



10-20 0-0379 0-0386 



2-72 0-0107 0-0100 



2-86 0-0154 0-0138 



6-45 0-0288 0'0281 



6-80 0-0251 0-0273 



Total 0-1179 0-1178 



The agreement in these numbers proves that the active oxygen is 

 exactly equal to the entire weight of the ozone, and is therefore iden- 

 tical with it. 



In the next series of experiments the author shows that no water 

 is produced in the decomposition of electrolytic ozone by heat. 

 Large quantities of electrolytic oxygen, containing from 38 to 27 

 milligrammes of ozone, were decomposed by heat, but no water was 

 obtained in a weighed absorption apparatus, in which the gas was 

 exposed, not only to the action of sulphuric acid, but was also passed 

 through a tube containing anhydrous phosphoric acid. 



Having confirmed by new experiments the fact that ozone is 

 formed by the action of the electrical spark on pure and dry oxygen, 

 the author proceeds to institute a comparison between the properties 

 of ozone derived from different sources. These he finds to be in 

 every respect the same. Thus ozone, however prepared, is de- 

 stroyed, or rather converted into ordinary oxygen, by exposure to a 

 temperature of about 237 C., and catalytically, by being passed over 

 peroxide of manganese, no water being formed in either case ; it is 

 not absorbed by water, but when sufficiently diluted with other 



