in the cold in contact with fluorine, and
if the fluorine is led into the midst of the liquid a similar
production of flame occurs under the surface of the liquid, as in case
of nitric acid. No carbon is deposited, both the carbon and sulphur
being entirely converted into gaseous fluorides.

_Carbon tetrachloride_, as previously mentioned, reacts only very
slowly with fluorine. The liquid may be saturated with gaseous
fluorine at 15 deg., but on boiling this liquid a gaseous mixture is
evolved, one constituent of which is carbon tetrafluoride, CF_{4}, a
gas readily capable of absorption by alcoholic potash. The remainder
consists of another fluoride of carbon, incapable of absorption by
potash and chlorine. A mixture of the vapors of carbon tetrachloride
and fluorine inflames spontaneously with detonation, and chlorine is
liberated without deposition of carbon.

_Boric anhydride_ is raised to a most vivid incandescence by fluorine,
the experiment being rendered very beautiful by the abundant white
fumes of the trifluoride which are liberated.

_Silicon dioxide_, one of the most inert of substances at the ordinary
temperature, takes fire in the cold in contact with fluorine, becoming
instantly white-hot, and rapidly disappearing in the form of silicon
tetrafluoride. The _chlorides_ of both _boron_ and _silicon_ are
decomposed by fluorine, with formation of fluorides and liberation of
chlorine, the reaction being accompanied by the production of flame.

ACTION OF FLUORINE UPON METALLIC COMPOUNDS.

_Chlorides_ of the metals are instantly decomposed by fluorine,
generally at the ordinary temperature, and in certain cases, antimony
trichloride for instance, with the appearance of flame. Chlorine is in
each case liberated, and a fluoride of the metal formed. A few require
heating, when a similar decomposition occurs, often accompanied by
incandescence, as in case of chromium sesquichloride.

_Bromides_ and _iodides_ are decomposed with even greater energy, and
the liberated bromine and iodine burn in the fluorine with formation
of their respective fluorides.

_Cyanides_ react in a most beautiful manner with fluorine, the
displaced cyanogen burning with a purple flame. Potassium ferrocyanide
in particular affords a very pretty experiment, and reacts in the
cold. Ordinary potassium cyanide requires slightly warming in order to
start the combustion.

Fused _potash_ yields potassium fluoride and ozone. Aqueous potash