surface of 1,800 square meters, or 12 square meters per hectoliter of
impure spirits of 50° to 60° Gay-Lussac. The raw impure spirits enter
the apparatus through the upper pipe, E, and, after a sufficient stay
therein, are drawn off through the lower pipe, H, into a reservoir, R,
from whence, by means of a pump, they are forced to the rectifier.

The hydrogen engendered during the electrolysis is disengaged through an
aperture in the cover of the pile.

As a measure of precaution, the hydrogen saturated with alcoholic vapors
may be forced to traverse a small, cooled room. The liquefied alcohol
returns to the pile. At a mean temperature of 15°, the quantity of
alcohol carried along mechanically is insignificant. In order to secure
a uniformity of action in all parts of the spirits, during the period
devoted to the operation, the liquid is made to circulate from top to
bottom by means of a pump, O. The tube, N, indicates the level of the
liquid in the vessel. The zinc having been arranged, the first operation
consists in forming the couple. This is done by introducing into the
pile, by means of the pump, O, a solution of sulphate of copper so as to
completely fill it.

The adherence of the copper to the zinc is essential to a proper working
of the couple, and may be obtained by observing the following
conditions:

1. Impure spirits of 40° Gay-Lussac, and not water, should be used as a
menstruum for the salt of copper.

2. The sulphatization should be operated by five successive solutions of
½ per cent., representing 20 kilogrammes of sulphate of copper per 100