124 
DE. AJS'DEEWS AND PEOEESSOE TAIT ON THE 
On comparing these experiments with the foregoing, it will be ohseired that they do 
not give exactly the same result. Interpreted as they stand, they indicate a density for 
ozone, if we may use the expression, more than infinite, inasmuch as the quantity of 
oxygen deduced from the analysis is less than that corresponding to the contraction 
observed. But, although every precaution was taken to avoid all sources of uncertainty, 
it is not improbable that this difierence between the amount of oxygen deduced from 
the contraction and from the analysis may arise from a slight defect in some of the data, 
particularly as it would only involve an error of the order of -i^ooth of the entire gas. 
Taking the mean result of the three series of experiments as they stand, it gives, on 
the allotropic hypothesis, almost exactly an infinite density for ozone. 
§ 5 . 
The commonly received statement, that the whole of a given volume of dry oxygen 
gas can be converted into ozone by the passage of electrical sparks, is erroneous. In 
repeated trials, with tubes of different forms and sizes, we found that not more than one- 
twelfth of the oxygen could, under the most favourable circumstances, be converted into 
ozone, even by the silent discharge, and a much smaller proportion by the action of sparks. 
But if the ozone is removed as fast as it is produced, the conversion may be caiiied on 
indefinitely. An apparatus was constructed of the form shown in fig. 7. At h two 
fine platinum wires were hermetically sealed into the glass ; at c there was a solution of 
iodide of potassium, and de was filled with fragments of fused chloride of calcium which 
allowed the ozone to pass freely, but arrested the vapour of the solution ; so that while 
the discharge always took place in pure and dry oxygen, the ozone was gradually 
absorbed. The volumetric change was measured by the readings of the sulphuric acid 
in the siphon tube fg sealed at g. The experiment was continued till five-twelfths of 
the oxygen (whose entire volume was about 12 cub. cent.) was absorbed, and the action 
was still going on. It was not considered necessary to persevere further, as the labom- 
of turning the machine was very great. To produce the efiect just mentioned, the 
discharge from the machine in excellent order had to be passed through the tube for 
twenty-four hours. 
When the electrical discharge is passed through rarefied oxygen, the phenomena are 
apparently the same as with the gas at the common pressui’e of the atmosphere. We 
filled a vessel with oxygen and exhausted it till the pressure was equal to 1 inch of 
mercury, in the hope that in this rarefied state a larger portion of the oxygen might be 
converted into ozone than under greater pressures, but this did not prove to be the 
case. We intend on a future occasion to pursue this part of the inquuy, and to 
examine particularly the efiects of the electrical discharge on oxygen m different states 
of rarefaction and condensation. 
Ozone, obtained by electrolysis, gave results nearly similar to those akeady described. 
As the volume of the oxygen gas from which the ozone was derived could not, m the 
case of electrolytic ozone, be observed directly, it was estimated indii’ectly by placing 
