the fluorspar tube, the resulting gaseous silicon tetrafluoride,
SiF_{4}, may be collected over mercury.

Amorphous silicon likewise burns with great energy in fluorine.


ACTION OF FLUORINE UPON METALS.

_Sodium_ and _potassium_ combine with fluorine with great vigor at
ordinary temperatures, becoming incandescent, and forming their
respective fluorides, which may be obtained crystallized from water in
cubes. Metallic _calcium_ also burns in fluorine gas, forming the
fused fluoride, and occasionally minute crystals of fluorspar.
_Thallium_ is rapidly converted to fluoride at ordinary temperatures,
the temperature rising until the metal melts and finally becomes red
hot. Powdered _magnesium_ burns with great brilliancy. _Iron_, reduced
by hydrogen, combines in the cold with immediate incandescence, and
formation of an anhydrous, readily soluble, white fluoride.
_Aluminum_, on heating to low redness, gives a very beautiful
luminosity, as do also _chromium_ and _manganese_. The combustion of
slightly warmed zinc in fluorine is particularly pretty as an
experiment, the flame being of a most dazzling whiteness. _Antimony_
takes fire at the ordinary temperature, and forms a solid white
fluoride. _Lead_ and _mercury_ are attacked in the cold, as previously
described, the latter with great rapidity. _Copper_ reacts at low
redness, but in a strangely feeble manner, and the white fumes formed
appear to combine with a further quantity of fluorine to form a
perfluoride. The main product is a volatile white fluoride. _Silver_
is only slowly attacked in the cold. When heated, however, to 100°,
the metal commences to be covered with a yellow coat of anhydrous