CHEMICAL SCIENCE. 275 



ON THE CONSTITUTION AND PROPERTIES OF OZONE, BY 

 THOMAS ANDREWS, F.R.S. 



The conflicting views which have so long existed as to the true constitu- 

 tion of ozone, induced the author to undertake a careful investigation of the 

 whole subject, particularly as he had reason to doubt the accuracy of the only 

 quantitative experiments which have yet been made to elucidate this difficult 

 question. According to the experiments before made, two substances have 

 been confounded under the name of ozone, one a compound body, having the 

 formula HO 3 , the other an allotropic variety of oxygen. To ascertain whether, 

 in conformity with this statement, ozone obtained hi the electrolysis of water 

 contains hydrogen as a constituent, the author made two series of experiments. 

 In the first series he followed nearly the same line of investigation by which 

 its compound nature is supposed to have been established, but modified so as 

 to avoid a source of error, which, if neglected, vitiates altogether the results. 

 Electrolytic oxygen, unless very great precautions are taken, is always accom- 

 panied with a small but appreciable quantity of carbonic acid, which is liable to 

 be partially absorbed by the potassa set free when a neutral solution of iodide 

 of potassium is decomposed by ozone. By adding a little hydrochloric acid to 

 the solution of iodide of potassium before the commencement of each experi- 

 ment, this error may be avoided. The method of performing the experiment 

 was to conduct a stream of electrolytic oxygen through a compound apparatus 

 previously 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, and the iodine, when set free 

 and reduced to its equivalent hi oxygen, the weight of the active oxygen. 



The result of five experiments performed hi this manner, proved that the 

 active oxygen is exactly equal to the weight of the ozone, and is therefore 

 identical with it. 



In the next series of experiments, the author shows that no water is pro- 

 duced by the decomposition of electrolytic ozone by heat. Large quantities 

 of electrolytic oxygen, containing from 38 to 27 milligrams of ozone, were 

 decomposed by heat, but no water was obtained in a weighed absorption ap- 

 paratus, 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 found to be in every respect the same. The ozone, however 

 prepared, is destroyed, or rather converted into ordinary oxygen, by exposure 

 to a temperature of about 237 Centigrade, and catalytically, by being passed 

 over peroxyd of manganese, no water being formed hi either case. It is not 

 absorbed by water, but when sufficiently diluted with other gases, is destroyed 

 by agitation with a large quantity of water ; it is also, contrary to the usual 

 statements, destroyed by being agitated with lime-water and baryta water, 



