the temperature of the reaction is sufficiently high to determine the
combination of platinum and fluorine (toward 500°), a tube of
fluorspar is substituted for the platinum tube. The fluorspar tubes
employed by M. Moissan for the study of the action of phosphorus were
about twelve to fourteen centimeters long, and were terminated by
platinum ends furnished with flanges and screw threads in order to be
able to connect them with the preparation apparatus. If it is required
to heat the fluorspar tubes, they are surrounded by a closely wound
copper spiral, which may be heated by a Bunsen flame.

In experimenting upon liquids, great care is necessary, as the
reaction frequently occurs with explosive violence. A preliminary
experiment is therefore always made, by allowing the fluorine delivery
tube to dip just beneath the surface of the liquid contained in a
small glass cylinder. When the liquid contains water, or when
hydrofluoric acid is a product of the reaction, cylinders of platinum
or of fluorspar are employed. If it is required to collect and examine
the product, the liquid is placed along the bottom of a horizontal
tube of platinum or fluorspar, as in case of solids, connected
directly with the preparation apparatus, and the product is collected
over water or mercury if a gas, or in a cooled platinum receiver if a
liquid.

During the examination of liquids a means has accidentally been
discovered by which a glass tube may be filled with fluorine gas. A
few liquids, one of which is carbon tetrachloride, react only very
slowly with fluorine at the ordinary temperature. By filling a glass
tube with such a liquid, and inverting it over a platinum capsule also
containing the liquid, it is possible to displace the liquid by
fluorine, which, as the walls are wet, does not attack the glass. Or