Improvements in Electrolytic Apparatus.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in Electrolytic Apparatus.
EMILE ANDREOLI 18 Somerleyton Road, Brixton Journalist do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to further improvements in an electrolytic apparatus for
the decomposition of salts such as chlorates sulphates etc. for which I filed a
Complete Specification No. 18597 on the 28th October 1891. The apparatus is
also applicable to other purposes.
The invention refers to the employment of porous conducting diaphragms, the
control of the electric current passed through them and the protection of the
material of which they are composed.
The porous conducting diaphragms or septa are brought into electric contact
more or less complete with the negative pole of the generator of electricity or with
the principal cathode. Such diaphragms or septa will therefore act as additional
cathodes with more or less activity according to the amount of current supplied to
them and may be termed supplementary cathodes. I control the amount of current
by varying the size or section and the length of the wires employed to make
the connexions with the diaphragms or supplementary cathodes. This is shewn in
Figure 5.
By this arrangement the principal cathode becomes the centre of activity in its
compartment whilst the action of the diaphragms as supplementary cathodes may
be so reduced that there is very little activity on their surfaces and thus the
liberation of cathions in the anode compartments may be reduced to a minimum.
One of the results of placing the porous conducting diaphragms in contact with
the cathodes is that iron or other metal when used in their construction, is protected
from corrosion although the current through them may be relatively feeble. But
when a stoppage in the electrolytic operation takes place the metal is no longer
protected and in order to remedy this inconvenience, I may use what I will call an
exciting cell, ie. a primary or secondary battery or other convenient source of
electricity, the positive pole of which is connected with the anode, and the
negative with the cathode and thus maintain a constant though slight current.
In certain cases, as in the production of chlorine and caustic soda, I use the
following apparatus :-In the tank Figures 1 and 2 made of slate or other con-
venient material, I dispose, vertically a carbon anode A a porous conducting
diaphragn C, in convenient electric connection with a perforated iron cathode B on
the other side of which and similarly connected with it is another diaphragm C',
and then another anode A' and another diaphragm C" and so on. Figure 6 shows
a diaphragm constructed of gauze and granular conducting material.
Figure 2 shows a transverse section of the electrolytic tank.
The space D I will call the first anode compartment, and the space D' Figure 2
the second anode compartment. The space E the first cathode compartment and
so on.
The first anode compartment D I close with a cover formed of two pieces of
glass or thin slabs of slate or other suitable material fixed together at right angles,
Fig. 3.
The horizontal portion rests on the edge of the tank and is attached to it so as
to form an air-tight joint. The vertical portion dips below the surface of the
electrolyte and is brought into close opposition to the proximate side of the
diaphragm. C. The ends of this vertical piece rest in grooves in the sides of

page_text: the tank.
The joints may be packed so as to render them airtight with slag wool
or in any suitable manner.
Covers for the anode compartments, other than the two end ones, D¹ D" are
similarly constructed but with a descending vertical portion dipping into the fluid
on each side Figure 4. The anodes in these compartments may be attached along
the centre of these covers or lids.
The upper part of these anode compartments thus form closed chambers for the
reception of the gas liberated in the compartment and prevent mixture with the
gas evolved in the cathode compartments which may be allowed to escape or be
collected in a similar manner.
The vertical portions of the above described covers may be fixed at each end
to the tank and the horizontal portion used as a flat lid fastened down by a clamp.
When the cathode compartments are to be closed a vertical piece of slate, or
material similar to the rest of the tank, is fixed on the cathode side of the
diaphragms and the compartments are closed by flat lids as in the case of the
anode compartments.
Figure 4 shows a carbon anode fixed to a slate, glass or ebonite cover by means
of a metallic screw or terminal which is protected against corrosion by an insulating
material.
The gas evolved in such close compartments is either forced or drawn out by a
convenient apparatus, through the tubes G shown in Figure 1.
The electrolyte is made to flow continuously through a succession of electrolytic
tanks all the anode and all the cathode compartments in each of which communicate
by means of pipes of glass Figure 1 F and F¹ or other suitable material with the
corresponding compartments of the adjoining tanks, the liquid in the last tank
being caused to flow off at such a rate as insures the most suitable strength
obtainable for the purpose in view, by fresh solution being allowed to flow into the
first tank at the rate thus found to be best. Or the electrolyte may be made to
circulate by receiving the liquid from the anode and cathode compartments
separately and returning them by two pumps to two feeding tanks. Or in some
cases (as when a hypochlorite is to be formed) the liquids from the anode and
cathode compartments, may be united and returned to one feeding tank.
In either arrangement the solution can be renovated by a supply of salt in the
feeding tank, when that is the electrolyte.
In any arrangement it is important when chlorine is to be produced to keep the
electrolyte as cool as possible.
Cooling may be effected by separating the tanks a convenient distance say 3 feet
and causing the connecting pipes in each interval to pass through a tank containing
iced water or ice and salt, the solution being subsequently transferred to the feeding
tank when salt is in the electrolyte. If heat is required the water surrounding
these pipes is heated.
To separate the chlorine more effectually, I may decompose the hypochlorite
formed in the anode compartment either by hydro-chloric or other acid,
gradually added by a pipe passing nearly to the bottom of the tank or by a
convenient salt.
Having now particularly described, and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed I declare that what I
claim is
1. The connexion of a porous conducting diaphragm with the negative pole of
the generator of electricity or with the principal cathode by a relatively fine wire
by varying the size and length of which the current made to pass through the
diaphragm can be controlled substantially as and for the purposes described.
2. The protection of the material of the porous conducting diaphragm when
not working by connexion with the negative pole of an independent electric
generator substantially as described.

page_text: 3. The construction of an electrolytic tank and the arrangement of anodes,
cathodes, and of porous conducting diaphragms acting as supplementary cathodes,
substantially as described with reference to Figures 1 and 2.
Dated this 25th day of January 1893.
ERNEST SALAMAN,
61 & 62, Chancery Lane, London, W.C., Agent for Applicant.