own
and sufficiently adherent; but the adherence becomes much greater after
a fortnight's operation.

Temperature has a marked influence upon the rapidity and continuity of
the reaction. Below +5 deg. the couple no longer works, and above +35 deg. the
reaction becomes vigorous and destroys the adherence of the copper to
such a degree that it becomes necessary to sulphatize the pile anew. The
battery is kept up by adding every eight days a few thousandths of
hydrochloric acid to a vatful of the spirits under treatment, say 5
kilos. of acid to 150 hectoliters of spirits. The object of adding this
acid is to dissolve the hydrate of oxide of zinc formed during the
electrolysis and deposited in a whitish stratum upon the surface of the
copper. The pile required no attention, and it is capable of operating
from 18 months to two years without being renewed or cleaned.

[Illustration: FIG. 2.--ELECTROLYZING APPARATUS.]

Passing them over, the zinc-copper couple does not suffice to deodorize
the impure spirits, so they must be sent directly to a rectifier. But,
in certain cases, it is necessary to follow up the treatment by the pile
with another one by electrolysis. The voltameters in which this second
operation is performed have likewise been modified. They consist now
(Fig. 2) of cylindrical glass vessels, AH, 125 mm. in diameter by 600 in
height, with polished edges. These are hermetically closed by an ebonite
cover through which pass the tubes, B' C' and B C, that allow the
liquid, E+E-E'+E', to circulate.

The current of spirits is regulated at the entrance by the cock, R,
which, through its division plate, gives the exact discharge per hour.
In addition, in order to secure great regularity in the flow, there is
placed between the voltameters and the reservoir that supplies them a
second and constant level reservoir regulated by an automatic cock.

In practice, Mr. Naudin employs 12 voltameters that discharge 12
hectoliters per hour, for a distillery that handles 300 hectoliters of
impure spirits every 24 hours. The electric current is furnished to the
voltameters by a Siemens machine (Fig. 3) having inductors in
derivation, the intensity being regulated by the aid of resistance wires
interposed in the circuit of the inductors.

The current is made to pass into the series of voltameters by means of a
commutator, and its intensity is shown by a Deprez galvanometer. The
voltameters, as shown in the diagram, are mounted