YOLIBIETEIC EELATIONS OF OZONE, 
119 
Viewing ozone as an alio tropic form of oxygen, in the gaseous state, we expected that 
when mercury came into contact with it, a contraction would take place, equal to the 
volume of the ozone which entered into combination with the metal. This anticipation 
has not been realized. After the rupture of the capsule, the vessel was immediately 
replaced in the calorimeter and the levels read. Not the slightest diminution of volume 
was observed in any one of a large number of experiments ; on the contrary, an increase, 
corresponding to a change of 1 millim. in the levels, generally occurred. On allowing 
the vessels to remain in the calorimeter, and reading the position of the acid in the 
siphon tubes from time to time, the gas was found to expand steadily, but slowly, for 
some hours, till from two-thirds to five-sixths of the contraction produced by the dis- 
charge was recovered. If the vessel was opened at any time while this expansion was 
going on, the ozone reactions were always manifest ; but, when the expansion was at an 
end, the ozone reactions had also ceased. 
If the mercury, instead of being allowed tranquilly to act upon the gas, was violently 
agitated after breaking the capsule, a much smaller portion of the contraction was 
restored ; in some cases not more than one-sixth. 
Metallic silver, in the state both of leaf and of filings, gave similar results. The sur- 
face of the silver was partially blackened, about three-fourths of the original contraction 
was recovered, and the whole operation much more quickly terminated. 
As the above reactions were evidently complex, the mercury and silver partly entering 
into combination with the gas, while the compounds formed appeared to exercise a cata- 
lytic action, we endeavoui-ed to find an elementary body which would instantly destroy 
the ozone reactions, and at the same time be without action on dry oxygen. After some 
trials, we found iodine possessed the required properties. We first ascertained that 
its vapour, although nsible at common temperatures, has no appreciable tension. When 
a small capsule, containing pm’e and dry iodine, was broken in a vessel of the usual form 
filled -with ox}’gen, the levels of the acid in the siphon tube were not altered. So slight 
also is the afiinity of iodine for oxygen, that, on heating the reservoir so as to volatilize 
a considerable portion of the iodine, and afterwards allowing it to cool, the volume of 
the gas underwent no change. On the other hand, if ozone be present, the iodine is 
immediately attacked, a gre}ish-yellow compound is formed, and all ozone reactions are 
instantly destroyed. 
The experiment already described with mercury was now repeated, substituting iodine 
for that metal. On breaking the capsule, the levels of the acid scarcely changed 1 mil- 
lim., although the original contraction amounted to 50 millims. No subsequent expan- 
sion took place, and, on opening the vessel, the ozone reactions had entirely disappeared. 
On the allotropic hypothesis, these experiments, and particularly the last, lead to the 
conclusion that ozone must have a density at least fifty times as great as that of oxygen. 
This conclusion is indeed unavoidable from the experiments just described, unless it is 
assumed that at the same moment that one portion of the ozone combines with the 
iodine, another portion changes back into oxygen, and that these quantities are so 
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