Improvements in Electrolytic Apparatus.
Year: 1899

page_text: Date of Application, 28th Nov., 1899-Accepted, 30th Dec., 1899
COMPLETE SPECIFICATION.
Improvements in Electrolytic Apparatus.
We, JAMES DOUGLAS DARLING, of 4826, Greenway Avenue, Electrical Chemist,
and CHARLES LELAND HARRISON, of 2028, Locust Street, Manufacturing Chemist,
both in the City of Philadelphia, State of Pennsylvania, United States of
America, 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; -
Our invention is adapted for use in connection with fused electrolytes
typical illustrations being hydroxides of alkaline metals, or alkaline earth metals
or the nitrates of such metals.
In our former Patent No. 22236, dated 28th September 1897, we have described
a porous diaphragm peculiarly adapted for use in an electrolytic apparatus of
this type.
It is found that where porous diaphragms are employed, the porous material
or body proper of the diaphragm being supported by metallic walls, the interpo-
sition of such metallic portions between the anode and cathode results in local
action, which tends to destroy the wall; Our present invention is intended to
obviate or minimise this difficulty and we have found that if one but preferably
both of the metallic walls are electrolytically connected with the positive pole
of the source of electricity the destructive effect upon the metallic portion of
the diaphragm can be almost entirely obviated.
Again in our former patent we have described a diaphragm consisting prin-
cipally of a vitrified oxide or oxides. Such diaphragms are permanent and effi-
cient to the highest extent, but somewhat costly.
It has generally been supposed that any material containing silica would be
of little value for such purpose, owing to the fact that in theory the fused elec-
trolyte would naturally attack the silica with great eagerness, and thus destroy
the integrity of the structure.
We have, however, ascertained that, contrary to natural expectation, a dia-
phragm composed of Portland cement in combination with a refractory oxide,
not in itself liable to combine with or be fluxed by the fused electrolyte, is
highly permanent and efficient, and has little or no tendency to crack under the
conditions of use.
We have found that a material well adapted for the purpose consists in burned
or calcined magnesite. When calcined at a red heat the magnesite, which is
a natural carbonate of magnesia, is reduced to magnesium oxide in the form of
hard dense lumps, which are then ground to a proper degree of fineness, for
instance, of such size as to pass through a 20 mesh sieve, but not through a
30 mesh. A mixture of equal parts, by measure, of Portland cement and such
ground burned magnesite, mixed with water and allowed to set in position
between the shells, gives a filling which is highly permanent, both as against
the attack of the electrolyte, and as against what otherwise would be the destruc-

page_text: tive effect of heat. The filling may be topped with a layer of cement alone, if
desired.
In the drawings Figure 1 represents a vertical central section through an
apparatus embodying our invention, and Figure 2 is a horizontal section on the
line 2, 2, Figure 1.
A represents the wall of a furnace, having burner pockets A', which communi-
cate by inwardly extending passages a, with a circular opening B, said open-
ing in turn communicating by a transverse flue 6 with a chimney C. Within
this opening is situated the electrolytic cell comprising the following elements:
An outer vessel D having an overhanging flange d, fits snugly within the top
of the opening B, and rests upon the bottom thereof. Adjacent to the inner sur-
face of the vessel is the downwardly depending annular metallic anode E,
which may be of cast iron, having an overhanging flange e whose exterior peri-
phery rests upon a cement ring d², supported upon the Hange d, of the vessel D.
The porous diaphragm is concentrically placed within the anode and consists
of inner and outer walls of metal, such as sheet iron, with an intermediate filling.
The outer wall comprises a solid upper portion F and base f¹ connected by
vertical rods f³, and supporting an intermediate shell of wire gauze f. A close
joint between the upper portion F and the flange e of the anode is formed by
means of a ring e of non-conducting material, such as cement. The inner
wall F, of the diaphragm, is preferably heavier than the outer one, and may be
composite, consisting of two layers of perforated metal, as indicated in the
sectional view. It is provided at its lower end with a solid bottom f. The
wall consists preferably of wrought iron pipe, throughout the greater portion
of whose length a number of radial holes fare drilled; in close contact there-
with is a covering of wire gauze f having interstices of very much less diameter
than the holes f. Intermediate between the two walls FF is the packing G
preferably of the material above described. The annular space between the
walls above the upper limit of the filling G is preferably closed by a solid ring
of cement g. The base f' of the diaphragm rests upon a mass of refractory,
non-conducting material such as Portland cement."
For convenience of renewal of the parts, we prefer to construct the upper
portion F and base f¹ of separable imperforate pieces as indicated. The base fl
is as shown in Figure 2 composed of two semicircular pieces fo, f, joined together
by means of bolts f8, passing through adjacent vertical flanges fo. The upper
portion F is similarly constructed.
Within the porous cup is the cathode H of the usual character, supported by
means of a rod h, which is arranged to slide vertically in an overhanging
frame I, I Said rod h passes through the cover h¹, which closes the cathode
compartment. At a convenient point an escape pipe J, is provided in com-
munication with the interior of the apparatus outside of the porous diaphragm
to permit the discharge of the gaseous products of electrolytic action. L and M
represent respectively the conductors leading to the cathode and anode. From
the conductor M however, we provide a shunt n which leads through an adjust-
able rheostat N, and thence to the wall or walls of the porous diaphragm. In
the illustration shown, we have indicated the inner wall F, as thus connected
by means of the wire n', but the outer wall F, of the diaphragm may, if desired,
also be connected by another wire n², indicated in dotted lines.
We have found that by shunting a very small percentage of the current
(say, 5%) directly through the wall of the diaphragm, destructive electrolytic
action is practically prevented, and the loss of current required for the purpose
is insignificant in comparison with the prolongation of the life of the walls.
We have found also that where the outer wall of the diaphragm is of wire
gauze, the perforations occupying relatively a large portion of its surface and
the actual quantity of metal per unit of area is small, it is not always necessary
to shunt any portion of the current to said wall, the main destructive action
occurring at the relatively heavy inner wall F¹.

page_text: Having now particularly described and ascertained the nature of our said in-
vention and in what manner the same is to be performed, we declare that what
we claim is ;-
1. In an electrolytic apparatus, the combination, with the anode and cathode,
of an intervening porous diaphragm having a metallic wall, said wall being
electrolytically connected with the positive pole of the source of electricity, sub-
stantially as described.
2. In an electrolytic apparatus, the combination of a furnace wall with an
exterior vessel mounted in said wall; a downwardly depending annular anode
having an overhanging flange and supported thereby upon the top of said vessel;
a porous diaphragm comprising inner and outer metallic walls with an inter-
mediate filling of porous material, the outer wall being indirectly supported by
the flange of the anode; an intervening packing of insulating material between
said flanges and said wall; a cathode arranged within said porous cup; and an
escape pipe leading from an opening in the flange of the anode, substantially as
and for the purposes described.
3. In apparatus in which there is a molten electrolyte interposing a diaphragm,
consisting of Portland cement and powdered oxide, between the electrodes, sub-
stantially as described.
4. In apparatus in which there is a molten electrolyte, interposing a diaphragm,
consisting of Portland cement and ground burned magnesite, between the elec-
trodes, substantially as described.
an
5. The combination of an enclosed shell, consisting of an inner perforated
tube; a cylindrical covering of wire gauze having smaller perforations;
exterior perforated shell; a porous filling arranged between said shells; and
removable top and bottom pieces provided with projecting flanges and with bolts
engaging said flanges, substantially as set forth.
6. Improvements in electrolytic apparatus substantially as described and illu-
strated in the drawings.
Dated this 28th day of November 1899.
CARPMAEL & Co.,
Agents for the Applicants.