The element fluorine has at last been successfully isolated, and its
chief chemical and physical properties determined. Many chemists,
notably Faraday, Gore, Pflaunder, and Brauner, have endeavored to
prepare this element in the free state, but all attempts have hitherto
proved futile. M. Moissau, after a long series of researches with the
fluorides of phosphorus, and the highly poisonous arsenic trifluoride,
has finally been able to liberate fluorine in the gaseous state from
anhydrous hydrofluoric acid by electrolysis. This acid in the pure state
is not an electrolyte, but when potassium fluoride is dissolved in it, a
current from ninety Bunsen elements decomposes it, evolving hydrogen
from the negative and fluoride from the positive electrode.
[Illustration:
(+) (-)
| |
| |
__/_|_\_A __/_|_\_A
| | | | | |
|____|____| |____|____|
| | | | | |
_____| | | | | |_____
/ ---- | | | | -----\
// | | | | | | \\
|| F |===|===| |===|===| H ||
|| |- -|- -| |- -|- -| ||
|| | - | - | | - | - | ||
|| |- -|- - \_________/ - -|- -| ||
|| | - | - - - - - - - - - | - | ||
// \___________________________/ \\
]
The apparatus employed in this process is constructed of platinum, and
is made in the form of a U tube, as shown in the accompanying
illustration, with fluorspar stoppers, through which the battery
terminals, made of platinum iridium alloy, are led. The gas is liberated
at about the rate of two liters per hour, and has very powerful chemical
properties. It smells somewhat like hypochlorous acid, etches dry glass,
and decomposes water, liberating ozone, and forming hydrofluoric acid.
The non-metallic elements, with the exception of chlorine, oxygen,
nitrogen, and carbon, combine directly with it, evolving in most cases
both light and heat. It combines with hydrogen, even in the dark,
without the addition of any external energy, and converts most metals
into their fluorides. Gold and platinum are not attacked in the cold,
but when gently heated are easily corroded. Mercury readily dissolves
the gas, forming the protochloride; iron wire also completely absorbs
the gas, while powdered antimony and lead take fire in it. It is
necessary in the electrolysis of the liquid hydrofluoric acid to cool
the electrolytic cell by means of methyl chloride to -50° C. Fluorine
appears to thus fully confirm the predictions which have been made by
chemists concerning its properties. It is by far the, most energetic of
all the known elements, and its position in the halogen series is
established by its property of not liberating iodine from the iodides of
potassium, mercury, and lead, and also of setting free chlorine from
potassium chloride. With iodine it appears to form a fluoride. No
compound with oxygen has yet been obtained.--_Industries._
* * * * *
AN APPARATUS FOR PREPARING SULPHUROUS, CARBONIC, AND PHOSPHORIC
ANHYDRIDES.