constructed, in order to obtain the gas in greater quantity for the
study of its reactions, and important additions have been made, by
means of which the fluorine is delivered in a pure state, free from
admixed vapor of the very volatile hydrofluoric acid. As much as a
hundred cubic centimeters of hydrofluoric acid, together with twenty
grms. of the dissolved double fluoride, are submitted to electrolysis
in this new apparatus, and upward of four liters of pure fluorine is
delivered by it per hour.

This improved form of the apparatus is shown in the accompanying
figure (Fig. 1), which is reproduced from the memoir of M. Moissan. It
consists essentially of two parts--the electrolysis apparatus and the
purifying vessels. The electrolysis apparatus, a sectional view of
which is given in Fig. 2, is similar in form to that described in the
paper of 1887, but much larger.

The U-tube of platinum has a capacity of 160 c.c. It is fitted with
two lateral delivery tubes of platinum, as in the earlier form, and
with stoppers of fluorspar, F, inserted in cylinders of platinum, _p_,
carrying screw threads, which engage with similar threads upon the
interior surfaces of the limbs of the U-tube. A key of brass, E,
serves to screw or unscrew the stoppers, and between the flange of
each stopper and the top of each branch of the U-tube a ring of lead
is compressed, by which means hermetic closing is effected. These
fluorspar stoppers, which are covered with a coating of gum lac during
the electrolysis, carry the electrode rods, _t_, which are thus
perfectly insulated. 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