the glass tube may be filled with the liquid, and then the latter
poured out, leaving the walls wet; the tube may then be filled with
fluorine gas, which being slightly heavier than air, remains in the
tube for some time. In one experiment, in which a glass test tube had
been filled with fluorine over carbon tetrachloride, it was attempted
to transfer it to a graduated tube over mercury, but in inclining the
test tube for this purpose the mercury suddenly came in contact with
the fluorine, and absorbed it so instantaneously and with such a
violent detonation that both the test tube and the graduated tube were
shattered into fragments. Indeed, owing to the powerful affinity of
mercury for fluorine, it is a most dangerous experiment to transfer a
tube containing fluorine gas, filled according to either the first or
second method, to the mercury trough; the tube is always shattered if
the mercury comes in contact with the gas, and generally with a loud
detonation. Fluorine may, however, be preserved for some time in tubes
over mercury, provided a few drops of the non-reacting liquid are kept
above the mercury meniscus.

For studying the action of fluorine on gases, a special piece of
apparatus, shown in Fig. 3, has been constructed. It is composed of a
tube of platinum, fifteen centimeters long, closed by two plates of
clear, transparent, and colorless fluorspar, and carrying three
lateral narrower tubes also of platinum. Two of these tubes face each
other in the center of the apparatus, and serve one for the conveyance
of the fluorine and the other of the gas to be experimented upon. The
third, which is of somewhat greater diameter than the other two,
serves as exit tube for the product or products of the reaction, and
may be placed in connection with a trough containing either water or
mercury.