436 
Sill B. C. BRODIE ON THE ACTION OE ELECTRICITY ON GASES. 
regarded this change of properties as due not to a special substance, but to a peculiar 
state or condition of oxygen caused by the electric action in which its “ affinities were 
exalted,” and proposed for this reason to discard the term ozone, and to term the gas in 
this condition simply electrized oxygen. Indeed they do not appear to have had any 
suspicion of the existence of ozone as an individual chemical entity distinct from oxygen 
itself. 
A further and most important contribution to our knowledge upon this subject was 
made by Andrews and Tait who, by means of a series of delicate and well-contrived 
experiments, arrived at the following conclusions : — (1) That under the influence of the 
electric action, which they employed in the form of what is termed the “ silent discharge,” 
oxygen undergoes a contraction of volume dependent upon the time for which the gas is 
thus acted upon, but not transcending a certain limit, the maximum contraction in their 
experiments being reached when the gas had diminished by one twelfth of its original 
volume. (2) That when the gas thus contracted was heated to 300° C., it expanded to 
its former bulk. (3) That when a solution of iodide of potassium was introduced into 
the contracted gas, an amount of iodine was formed equivalent to the amount of oxygen 
which disappeared in the contraction without the occurrence of any change in the volume 
of the gas. (4) That the gas which had been thus operated upon by iodide of potassium 
did not expand when heated to 300° C. 
Andrews and Tait do not offer any adequate interpretation of their remarkable 
experiments. “ To reconcile,” they say, “ the experimental results with the view that 
ozone is oxygen in an allotropic form, it is necessary to assume that its density im- 
mensely exceeds that of any known gas or vapour, being, as we have seen, according to 
the first and second series of experiments, from fifty to sixty times that of oxygen, and 
according to the third series absolutely infinite : even the former results would make it 
only six times less dense than the metal lithium, and would place it rather in the class of 
solid or liquid bodies than of gaseous”f ; and without absolutely rejecting the allotropic 
hypothesis, they proceed to seek for the origin of ozone in the decomposition of oxygen, 
and endeavour to explain the phenomena from this point of view. 
There is, however, an hypothesis as to the constitution of ozone which would naturally 
present itself to the mind of a chemist profoundly convinced of the dual nature of oxygen, 
and by which these results would be accounted for in a simple and probable way. This 
hypothesis appears to have been first publicly enunciated by Odling in his ‘ Manual of 
Chemistry,’ published in 1861, where the following passage occurs (p. 94): — “If we 
consider ozone to be a compound of oxygen with oxygen and the contraction to be con- 
sequent upon their combination, then if one portion of this combined or contracted oxygen 
were absorbed by the reagent, the other portion would be set free, and by its liberation 
might expand to the volume of the whole ; thus, if we suppose three volumes of oxygen 
to be condensed by their mutual combination into two volumes, then on absorbing 
one third of this combined oxygen by mercury the remaining two thirds would be set 
* Philosophical Transactions, 1860, p. 113. f Loc. cii. p. 128. 
