Arguing from the fact that oxygen gas, when subjected to the silent
discharge, partially undergoes condensation into ozone, it seemed
possible, says Mr. H.M. Vernon, in the _Chemical News_, that other
elementary gases, as chlorine and bromine vapor, might undergo an
analogous change when subjected to the same treatment. A glass tube,
with a U-shaped index of fine bore glass tubing, was filled with
purified and dried chlorine. After passing a current of the gas
through the tube for some time, the end was sealed in the blowpipe
flame. The tube was then warmed slightly, and a few bubbles of gas
thus driven out. The end of the index tube dipped under strong
sulphuric acid saturated with chlorine gas, so that, on cooling, a
short column of the acid was drawn up. This served as an index for any
changes of volume which might take place in the chlorine in the tube.
A silent discharge of electricity was then passed. The volume of the
gas was observed to increase slightly, but afterward it remained quite
constant, even after the discharge had been passed for several hours.
We may therefore conclude that no allotropic change takes place when
chlorine gas is subjected to the silent discharge of electricity, the
initial increase of volume being merely due to the heating effect the
discharge has upon the gas. Into another similar tube, filled with
chlorine, was introduced a small quantity of liquid bromine.
The tube thus contained chlorine saturated with bromine vapor. The
silent discharge on being passed through this tube did not produce any
different effect than for chlorine alone. So we may conclude that
bromine vapor also does not undergo any allotropic condensation when
subjected to the influence of a silent discharge of electricity. The
fact that oxygen gas is capable of undergoing condensation while
chlorine and bromine are not is easily explained. The oxygen atom,
being divalent, is capable of uniting itself to two other atoms of
oxygen or other elements, and thus with oxygen forming ozone. The
atoms of chlorine and bromine, however, being only monovalent, have
all their affinity satisfied when they are united to a single other
atom of chlorine and bromine. It is not possible, therefore, that
condensation can take place if the atoms remain monovalent. Hydrogen
gas and iodine vapor are in a similar manner debarred from undergoing
condensation. Mr. Vernon, therefore, comes to the conclusion that it
is most improbable that any other element but oxygen will be found
capable of undergoing molecular condensation when in the gaseous state
and subjected to the silent discharge.
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