liquid fluoride of iodine attacks glass with great energy and
decomposes water when dropped into that liquid with a noise like that
produced by red-hot iron. Its properties agree with those of the
fluoride of iodine prepared by Gore by the action of iodine on silver
fluoride.

_Phosphorus._--Immediately phosphorus, either the ordinary yellow
variety or red phosphorus, comes in contact with fluorine, a most
lively action occurs, accompanied by vivid incandescence. If the
fluorine is in excess, a fuming gas is evolved, which gives up its
excess of fluorine on collecting over mercury, and is soluble in
water. This gas is phosphorus pentafluoride, PF_{5}, prepared some
years ago by Prof. Thorpe. If, on the contrary, the phosphorus is in
excess, a gaseous mixture of this pentafluoride with a new fluoride,
the trifluoride, PF_{3}, a gas insoluble in water, but which may be
absorbed by caustic potash, is obtained. The trifluoride, in turn,
combines with more fluorine to form the pentafluoride, the reaction
being accompanied by the appearance of a flame of comparatively low
temperature.

_Arsenic_ combines with fluorine at the ordinary temperature with
incandescence. If the current of fluorine is fairly rapid, a colorless
fuming liquid condenses in the receiver, which is mainly arsenic
trifluoride, AsF_{3}, but which appears also to contain a new
fluoride, the pentafluoride, AsF_{5}, inasmuch as the solution in
water yields the reactions of both arsenious and arsenic acids.

_Carbon._--Chlorine does not unite with carbon even at the high
temperature of the electric arc, but fluorine reacts even at the
ordinary temperature with finely divided carbon. Purified lampblack