Literature of Ozone. 371 



time to a temperature of 270° — 300°, it expands to its original 

 volume. That the increase in density is exactly proportional to 

 the amount of ozone formed, was proven by an analysis of the 

 contracted gas by means of potassium iodide. The amount of 

 iodine in every case set free,, was precisely equivalent to the 

 weight of a volume of oxygen equivalent to the volume of the 

 contraction, which the oxygen had experienced in the process of 

 ozonation. The same laws were demonstrated to hold good 

 with regard to electrolytic ozone, not only by these authors 

 (1860), but also by Von Babo and Clans, and by Soret (1863). 



Andrews and Tait found great difficulty in reconciling the 

 theory of the allotropism of ozone, with their experiments, inas- 

 much as the oxidation of a body like mercury, potassium iodide, 

 etc., was effected without any diminution in the volume of the 

 contracted gas. In other words, the density of the allotropic 

 oxygen concerned in this oxidation was apparently infinite. 

 They sought, therefore, to explain the origin of ozone by the 

 assumption of a decomposition of the oxygen. 



But in 1861, Odling put forth the interpretation, that ozone 

 was a compound of oxygen with oxygen, the combination being 

 attended by a contraction. Hence, if one portion of the com- 

 bined or contracted oxygen were absorbed by an oxidizable body, 

 the other portion would be set free, and by its liberation might 

 expand to the initial volume. He likewise suggested that this 

 contraction might consist in the condensation of three volumes 

 *of oxygen into two volumes, not because this ratio was the only 

 one which would explain the volume and density relations, so 

 far as then known, but because, on the hypothesis of the dual 

 nature of oxygen, this was their simplest possible explanation. 



Four years later, Soret discovered that a very remarkable re- 

 action occurs when electrolytic ozone is allowed to act upon 

 oil of turpentine. Its volume is diminished by a volume equi- 

 valent to twice that of the oxygen, corresponding to the iodine 

 set free on passing the ozonized oxygen into a solution of iodide 

 of potassium. The latter, it will be remembered, is the same as 

 the diminution in volume, which the oxygen undergoes in ozo- 

 nation, and may be called the contraction-volume. Hence the 

 two volumes of ozonized oxygen, absorbed in Soret's experi- 

 ments, contained not only their own volume of oxygen, but 



