element, a considerable amount of additional information has been
acquired concerning the chemical behavior of fluorine, and important
additions and improvements have been introduced in the apparatus
employed for preparing and experimenting with the gas. M. Moissan now
gathers together the results of these subsequent researches--some of
which have been published by him from time to time as contributions to
various French scientific journals, while others have not hitherto
been made known--and publishes them in a long but most interesting
paper in the October number of the _Annales de Chimîe et de Physique._
Inasmuch as the experiments described are of so extraordinary a
nature, owing to the intense chemical activity of fluorine, and are so
important as filling a long existing vacancy in our chemical
literature, readers of _Nature_ will doubtless be interested in a
brief account of them.


IMPROVED APPARATUS FOR PREPARING FLUORINE.

In his paper of 1887, the main outlines of which were given in
_Nature_ at the time (1887, vol. xxxvii., p. 179), M. Moissan showed
that pure hydrofluoric acid readily dissolves the double fluoride of
potassium and hydrogen, and that the liquid thus obtained is a good
conductor of electricity, rendering electrolysis possible. It will be
remembered that, by passing a strong current of electricity through
this liquid contained in a platinum apparatus, free gaseous fluorine
was obtained at the positive pole and hydrogen at the negative pole.
The amount of hydrofluoric acid employed in these earlier experiments
was about fifteen grms., about six grms. of hydrogen potassium
fluoride, HF.KF, being added in order to render it a conductor. Since
the publication of that memoir a much larger apparatus has been