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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