M. Moissan now employs electrodes of pure
platinum instead of irido-platinum, and the interior end of each is
thickened into a club shape in order the longer to withstand
corrosion. The apparatus is immersed during the electrolysis in a bath
of liquid methyl chloride, maintained in tranquil ebullition at -23 deg..
In order to preserve the methyl chloride as long as possible, the
cylinder containing it is placed in an outer glass cylinder containing
fragments of calcium chloride; by this means it is surrounded with a
layer of dry air, a bad conductor of heat.
The purifying vessels are three in number. The first consists of a
platinum spiral worm-tube of about 40 c.c. capacity, immersed also in
a bath of liquid methyl chloride, maintained at as low a temperature
as possible, about -50 deg.. As hydrofluoric acid boils at 19.5 deg.
(Moissan), almost the whole of the vapor of this substance which is
carried away in the stream of issuing fluorine is condensed and
retained at the bottom of the worm.
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