Improvements in the Electrolytical Decomposition of Chlorides and Mixtures thereof, and in Apparatus for the purpose.
Year: 1893

page_text: he decision of the Comptroller-General, of the 12th day of July 1894,
allowed, under Section 18 of the Patents, &c. Act, 1883, an Amendment of
this Specification.
Date of Application, 13th Apr., 1893
Complete Specification Left, 15th Jan., 1894-Accepted, 3rd Mar., 1894
Improvements in the Electrolytical Decomposition of Chlorides and
Mixtures thereof, and in Apparatus for the purpose.
I FARNHAM MAXWELL LYTE of 60 Finborough Road, Redcliffe Square,
S.W. Analytical Chemist, do hereby declare the nature of this invention to be
as follows:-
This invention relates to cells and anodes for use in electrolytic processes,
and more especially for use in the electrolytic decomposition of fused lead
chlorides into metallic lead and chlorine in relation to which the invention will be
described.
The invention consists essentially in effecting the electrolysis of fused metallic
chlorides (or mixtures thereof) within a bell chamber which is sealed by dipping
into fused metal corresponding to the base of the chloride or resulting from the
decomposition thereof, so that the pan or vessel in which the bell-like cell is
contained will never be exposed to contact with the chloride or the chlorine evolved
therefrom. No precautions being necessary to protect the pan from attack, it may
be made of iron or any other material of sufficient strength to support the weight
and being sufficiently refractory and a good conductor of heat.
It may be heated
directly by gas or be embedded in broken pumice supported in a wire net and heated
by gas or otherwise. It may be provided with an overflow pipe which dips below
the level of the metallic lead and passes through the side of the pan at such a height
that the superincumbent pressure of the fused chloride contained in the cell will
just counterbalance the column of lead in the pipe and cause the lead to flow
out as the electrolysis proceeds, provided the fused chloride be maintained at the
normal level. For this purpose the bell is provided with a pipe sealed by dipping
into the fused chloride through which more chloride may be introduced as the
operation proceeds.
The bell-like cell must be made of, or protected by a material not attacked by
chlorine but as it has only to support the pressure due to the head of fused
salt, many materials are available for the purpose-e.g. plumbago, earthenware,
firestone, lava, or enamelled iron. If provided with a removable crown, it should
be tightly closed by a packing, say, of powdered asbestos cemented by sodic silicate
to prevent the escape of chlorine and the carbon anodes, which, in case the cell and
its cover are of plumbago, should be properly insulated, passing through it, plunge
into the fused chloride to within a short distance of the subjacent molten lead
forming the cathode.
The invention also consists in making carbon anodes hollow and providing them
with metallic core to increase their conductivity, this core being so made or of
such a nature that whilst it makes intimate contact with the carbon it exerts little
or no bursting strain thereon when heated. The core may be made of sheet metal,
not fusible at moderate redness, bent or coiled to form a longitudinally or spirally

page_text: split tube fitting spring-tight in the carbon but yielding when expanded by heat so
as not to exert sufficient pressure to burst the carbon. The core may also be of
lead or of some other suitable easily-fusible metal run into the carbon anode and
which will contract on solidification and cooling so that when it re-expands on
heating so far as to come in contact with the sides of the carbon it will be fused
and therfore exert no bursting strain on the carbon consequent on such expansion
of the metal. A rod of iron or other difficultly fusible metal would enter or
traverse the fusible core to convey the current thereto, this rod being entirely free
from the carbon. It may be coated with another metal to prevent its corrosion and
promote electrical contact with the fusible core. To support the bottom of the
hollow carbon under the weight of the column of fused metallic core, it would be
traversed by an earthenware rod sealed or burnt into the lower end of the carbon
rising through the same and secured to a support at the top. By the use of this
fusible metallic core,
the danger of bursting the carbons is entirely obviated and
the resistance of the anodes so greatly diminished that the current easily traverses
the carbons throughout their length, while the chlorine has no action on the
carbon. The anodes may thus be made of relatively great length, thereby
admitting of a corresponding depth of the cell, and height of the column of fused
chloride.
The space between the upper part of the bell and the sides of the pan should be
packed with asbestos or other suitable solid or fluid material which may rest on the
surface of the molten lead outside of the bell, or the space may be enclosed by a
cover and filled with an atmosphere of inert gas, so as to prevent both access of air
causing the oxidation of the lead and loss of heat.
If any oxygen be present or if the lead chloride contain any oxychloride, the
carbon of the anodes being liable to be corroded thereby at or near their line of
immersion, they should be coated at this part with a protective covering such as
enamelled clay burnt on or asbestos and sodic silicate for instance. Anodes in
which plumbago is substituted for the retort carbon usually employed will be
found to conduct better and to be rather more resistant to the corrosion above
mentioned than the others. The oxidation of the lead chloride during its fusion is
prevented by the introduction within the chamber of the cell containing the lead
chloride of a gas which has no action on carbon or on fused lead chloride such as
chlorine or nitrogen.
Dated this 13th day of April 1893.
F. MAXWELL LYTE,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION (AMENDED).
Improvements in the Electrolytical Decomposition of Chlorides and
Mixtures thereof, and in Apparatus for the purpose.
I, FARNHAM MAXWELL-LYTE of 60, Finborough Road, London, S.W.
Analytical Chemist, 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 :―
My invention relates to the electrolytical decomposition of metallic chlorides
severally or in admixture, whilst in a state of fusion, and it consists essentially in
effecting the decomposition within an open-mouthed bell-like chamber which is
sealed by dipping into molten metal corresponding to the base of the chloride
under treatment and resulting, for the most part, from the decomposition of the
said chloride.
The object of performing the operation in a vessel so sealed is to prevent the

page_text: escape of chlorine and permit of running off the metal as fast as it is reduced, and,
on the one hand, to relieve that part of the apparatus with which the fused chloride
and the chlorine generated come into contact from all strain due to the weight of
the fused chloride and molten metal and, on the other hand, to entirely isolate the
vessel which supports the weight of the whole contents of the cell from contact
with the chloride or chlorine generated, so that whilst the former vessel need only
be made of a material able to resist attack by chlorine and withstand heat without
regard to strength, the material of which the latter vessel is made need only possess
the necessary strength and conductivity for heat without regard to any effect
consequent on chemical action.
My invention also relates to the carbon electrodes used in the electrolytic
decomposition of metallic chlorides or other metallic haloids in a fused condition,
whether in the cell herein described or in any other. This part of my invention
has for its object to obtain the advantage, as regards conductivity, of a metal core
for the carbon, without the liability of defective electrical contact between the
carbon and the core or of bursting the carbon in consequence of the different ratios
of expansion of the metal and carbon when heated by immersion in the fused salt
to be decomposed.
To this end I employ a hollow carbon electrode closed at bottom and open at
top and a core of metal or alloy which is fusible at about the same or at a lower
temperature than the metallic salt to be decomposed or the metal to be produced,
so that the core will melt and in the fluid state will make intimate electrical contact
with the carbon of the electrode but will exert no bursting strain thereon, in
consequence of the expansion of the metal. The terminal of the electrode is put
in electrical communication with the fusible core by a conducting rod dipping into
the fusible core nearly to the bottom but entirely free from the carbon. By means
of this fusible metallic core, the thickness of the carbon to be traversed by the
current may be so much reduced and the electrical resistance so greatly diminished
that the current will easily traverse the carbon throughout its whole area, thereby
enabling electrodes of considerable length to be used.
The invention also consists in the combination, with a hollow carbon electrode,
of a core of non-fusible metal in the form of a split tube fitting spring-tight in the
carbon so as to obtain good contact therewith, but which is able to expand by heat
without exerting any bursting strain on the carbon, sufficient play being allowed to
avoid excessive bursting strain, by the longitudinal split in the tube.
I will describe the invention as applied to the decomposition of lead chloride,
when in a state of fusion, into metallic lead and chlorine, and with reference to the
accompanying drawings, forming part of this Specification, wherein
Figure 1 is a central vertical section and Figure 2 a plan of the apparatus
employed in carrying the process into effect.
Figure 3 is a vertical section and Figures 4 and 5 are cross-sections, on lines 1-1
and 2-2 of Figure 3, of one form of electrode embodying my invention, although
it must be understood that I do not limit myself to any particular external or
internal form of the electrode.
Figure 6 is a perspective sectional view of a carbon anode with split spring
tube core and Figure 7 is a cross section thereof.
Referring to Figures 1 and 2, A is the containing vessel or pan and B is the bell
chamber in which the electrolytic decomposition is effected, the open mouth of this
vessel being sealed by dipping into molten lead L. The vessel B is partly filled
with lead chloride C, leaving a space above for the collection of the chlorine
generated, the pressure due to the height of the column of chloride causing a
difference of level of the lead sufficient to raise the lead outside the bell chamber
to the bend of an overflow pipe D with which the pan or container A is furnished.
E are anodes of carbon passing through the crown of the bell chamber B and
immersed in the chloride Ĉ to within a short distance of the subjacent lead L which
forms the cathode of the electrolytic decomposition cell. F is an open pipe also
passing through the crown of the bell, for supplying chloride to the cell B, the said

page_text: pipe being sealed by dipping into the chloride C so as to prevent the escape of
chlorine. G is a pipe leading through the crown of the bell, for the outlet of the
chlorine generated. The pan A is set in brickwork or otherwise supported so as to
be exposed at bottom and sides to the direct heat of a suitable gas or other
furnace M in connection with return flues N whereby the lead L and chloride C
are maintained in a state of fusion. The bell chamber is maintained in position in
the pan A by the cover A' of the said pan which has an aperture in which the
upper part B' of the bell B fits, as shewn, the cover being bolted or otherwise fixed
in place and provided with hand-holes S at which the space S' around the bell B at
the upper part of the pan is filled up with powdered charcoal, sand, or equivalent
material, which resting on the surface of the lead outside of the bell prevents
access of air to, and consequent oxidation of, the lead and which also prevents loss
of heat by radiation. As the bell chamber B has only to withstand the pressure
due to the head of fused chloride, no great strength is required and it may be made
of any sufficiently refractory material not liable to attack by chlorine, preferably
earthenware or of plumbago,-gas-tight joints being made between it and the anodes
and pipes passing through it by means of asbestos-string or ground asbestos and
silicate of soda, or other suitable cement, the anodes being insulated from it if it
be made of plumbago or other electrically-conductive material. The pan A needs
no protection from attack, since it is not exposed to contact by the chlorine.
may therefore be made of cast or wrought iron and electrical connection may be
made with the cathode of molten lead L either by a tinned iron rod H immersed in
the lead or by the pan A itself if it be tinned internally to ensure good electrical
contact with the lead. The overflow pipe D dips down within the pan, as shewn, to
avoid choking with sand.
It
The anodes EI employ are preferably tubular carbons, such as are hereafter
described, containing a core of metal or alloy fusible at or below the melting point
of the lead chloride or other chloride to be decomposed, or provided with split
or spring tubular cores, but although I prefer to use such carbons, my process
is by no means limited in this respect as any other suitable carbons may be used
for anodes.
'-
The operation is as follows
-The pan A being initially filled to a sufficient
height with molten lead, the bell B is secured in position, lead chloride, either in
crystals or in the fused state, is fed in through the pipe F until the exterior column
of lead reaches the normal height, and, the space around the bell at the upper
part having been packed with sand (or filled with a gas which has no action on
carbon or on fused lead chloride, such as chlorine or. nitrogen) the electrolytic
decomposition is proceeded with, the normal level of the fused chloride and molten
lead being maintained by feeding in more chloride at F as fast as the lead runs
off at D.
Referring now to Figures 3, 4, and 5, E is the carbon electrode in the form of a
hollow cylinder closed at the lower, and open at the upper, end but any other form
may be adopted provided it is hollow and closed at the lower end.
It may either
be moulded hollow or be made solid and bored out and may be made either of
retort carbon or of plumbago. E' is the fusible core of lead, tin, or any other
metal or alloy which fuses at about the same or a lower temperature than the
metallic salt to be decomposed or than the metal to be produced. The fusing
point of the metal or alloy of which the core is composed should, of course, not be
so far below the fusing point of the cult to be decomposed as to render the core
liable to be sublimed or volatilised by the heat necessary to fuse the salt. In the
case of decomposing fused plumbic chloride, for which the electrodes are principally
intended, I find that lead will answer the purpose. I is a rod of difficultly-fusible
metal, such as copper or iron, attached to the terminal J and which passes through
a plug or fits quite loosely in the upper end of the carbon, so as to exert no
bursting strain thereon, or is otherwise supported in position, the lower portion of
the rod, which is of considerably smaller section than the bore of the carbon,
plunging into the fusible core E¹. This rod, if of iron, may be coated with

page_text: another metal, lead for instance, to prevent corrosion and ensure good electrical
contact with the fusible core E'.
Referring to Figures 6 and 7, E is the hollow carbon, as before, and E' is a
longitudinally-split steel tube fitting spring-tight in the carbon and attached to the
terminal J, no fusible metal being employed. The splitting of the tube allows of
free expansion of the metal without materially affecting its diameter or increasing
the bursting strain on the carbon.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In the process of electrolytically decomposing fused metallic chlorides, the
method which consists in enclosing the metallic chloride and effecting the
electrolytic decomposition thereof wholly within a bell chamber whose mouth is
sealed by dipping into molten metal corresponding to the base of the chloride
treated and resulting, in part, from the decomposition of the said chloride,
substantially as specified.
2. In the process of electrolytically decomposing fused metallic chlorides wholly
within a bell chamber, the method which consists in sealing the mouth of the bell
chamber against the escape of chlorine whilst permitting the reduced metal to run
off as fast as it is produced, by causing the mouth of the vessel to dip into a bath of
molten metal corresponding to the base of the chloride treated and resulting, in
part, from the decomposition of the chloride, as specified.
3. The combination, with a hollow carbon electrode closed at bottom, of a core
of metal or alloy which is fusible at or below the temperature at which the
electrolytic decomposition of a fused metallic salt is to be performed, substantially
as specified.
4. The combination, with a hollow carbon electrode closed at bottom, of a core
of metal or alloy which is fusible at or below the temperature at which the
electrolytic decomposition of a fused metallic salt is to be performed, and of a
terminal conductor of metal, not fusible at that temperature, which is surrounded
by the fusible core and is free from the carbon so as to exert no bursting strain
whatever thereon, substantially as specified.
5. The combination, with a hollow carbon electrode closed at bottom, of a spring
tubular core fitting spring-tight therein, substantially as specified.
6. The herein described combined process of, and apparatus for, effecting the
electrolytical decomposition of fused chlorides and mixtures thereof, substantially
as specified.
Dated this 12th dor of Ton 1904
F. MAXWELL LYTE,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.