Improvements in Process and Apparatus for Electrolytical Decomposition of Alkali Salts.
Year: 1894

page_text: Date of Application (in United Kingdom), 12th July, 1894
Complete Specification Left, 12th July, 1894-Accepted, 27th Oct., 1894
No text detected.
GUNEMIMIPULA
Improvements in Process and Apparatus for Electrolytical
Decomposition of Alkali Salts.
I, ALF SINDING-LARSEN, of No. 49 Huitfeldt's Gade, Christiania, Norway,
Electrical Engineer, 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 art of electrolysis and particularly to the
electrolytical processes in which mercury is employed as a means of transporting
the metallic constituent, separated from the salt in solution under treatment, from
the field of electrolytic action into contact with a solvent being capable of
depriving the mercury of the metal amalgamated with it.
In this class of apparatus for treating electrolytically alkaline salts such as
chloride of sodium it has been found to be a drawback, that a very great quantity
of mercury has to be employed in comparison with the efficiency of the apparatus ;
this being due to the fact, that the surface of contact between the amalgamated
mercury and the said solvent must be very large in comparison with the surface of
mercury acted upon by the electric current.
My invention has for its object a method whereby the amalgam may be
transported in a very thin sheet or layer through the solvent agent, whereby the
amount of mercury exposed to the electric action may be a proportionally great one
and by far greater than the amount of mercury in contact with the solvent agent.
To this end my invention consists in introducing in the mercury acted upon by the
electrical current a metallic body having an amalgamated surface and having part
of the same also in contact with the solvent agent. This metallic body is rotated or
otherwise moved, so that the amalgamated mercury adhering to the part of the
body dipped in the mercury will be carried with the body or driven along the
surface of the same in a very thin layer up towards and through the solvent
agent.
In this way not only the quantity of mercury necessary for a certain efficiency
of the apparatus is reduced to a minimum, but the action of the solvent agent
upon the amalgam is greatly increased because of the amalgam being passed
through the liquid in a very thin sheet.
My improved method may be carried out by means of several kinds of apparatus,
the construction of which will vary according to the shape and arrangement of
the moving metallic body.
In annexed drawing I show as examples some convenient forms of the apparatus.
Figure 1 shows a vertical axial section through my improved apparatus and
Figure 2 front elevation and cross section of the same. Figure 5 is an enlarged
cross section of the electrode space. Figure 6 is a similar enlarged view of a
+

page_text: modified arrangement of the electrode space and parts connected therewith.
Figures 3 and 4 show details and Figure 7 illustrates a modification of the
apparatus.
A is a sheet metal cylinder (for instance tinned iron) the inner and outer
surface of which is coated with an amalgam (for instance tin and mercury) and
which is mounted on the shaft B by means of the disc C the boss D of which
may be keyed to the shaft. The shaft B has its bearings in the back wall of a
vessel E, which serves as holder for the solvent agent (for instance water) and inay
be made of iron or any other suitable material. F is the foot of the vessel.
The front wall of the vessel forms part of another vessel G, which serves as
holder for the electrolyte or salt solution to be treated by electrolysis (for instance
chloride of sodium) and this vessel, which is preferably made of a non-conductive
and non-porous material such as porcelain (or it may be made partly of such
material and partly of iron), has an inner cylindrical part G', which nearly fills
out the inner space of the sheet metal cylinder A and an outer compartment Gu
which is provided with a holder O for the salt, an opening L for charging purposes
and an escape pipe M for gas. The vessel G has a flange H by means of which
it is bolted to the vessel E.
The said inner cylindrical part G¹ of the vessel G is open at I and this opening
is surrounded by a flange or sidewalls J, and in the lower part of the outer vessel E
just below the said opening I is formed a cup K for the mercury Q. The sheet
metal amalgamated drum A will then pass through the mercury just below the
edges of flange J. PP are the anodes, which may be of any suitable construction
and the mercury in the cup K serves as cathode, N being the negative conductor.
The construction in detail of this part of the apparatus is shown on a larger scale
in Figure 5. The lower edge of the flange J is shown. lined with a metal frame J'
having an amalgamated surface and on one side of the same is journalled a
metallic roller J having also amalgamated surface.
When the apparatus is to be used for decomposition of common salt the cup K
is charged with mercury, so that the same cuts off the communication between the
inner and outer compartment. The inner compartment is charged with a solution
of sodium chloride the holder O being also charged with salt, serving to enrich the
solution as it is deprived of its salt, and the outer compartment is simultaneously
charged with water. Then the shaft B is put in rotation, whereby the metal
drum A will move through the mercury at Q, and when the electric current has
been closed the mercury will in a well known manner take up the metallic
constituent of the salt (sodium) in the inner cell and form the amalgam. As now
the amalgamated drum A passes through the mercury or amalgam in the cup K
the amalgam will adhere to the drum and be taken along with the latter through the
annular water space of the vessel E. During the passage through the water
the alkali metal will decompose the water, forming hydrogen and caustic soda,
while the mercury will remain on the drum or drop down in the cup K again.
The roller J (Figure 5) rotated by any suitable means serves to skim off the
amalgam floating on the mercury and bring it against the metal drum on the side,
where it is moving out of the mercury. The amalgamated metal lining J¹ on the
flange serves to keep a watertight joint between the two spaces containing
salt and soda, the mercury adhering to the edges, so that it prevents the
solution from being carried along with the mercury or amalgam on the roller.
The metal drum may be perforated in the manner shown in Figure 3 whereby
the mercury is stirred up in the cup K.
The construction of the electrode compartment may also be that shown in
Figure 6. In this case the inner vessel G¹ serves as holder for the solvent (water)
and the metal drum A is therefore placed inside of this vessel. P is the anode,
preferably of carbon or other suitable material, Q the mercury cathode and Oa
pipe of conductive material having lateral slots just above the top of the anode.
E is the outer vessel serving as holder for the salt solution, which in this case is
introduced between the anode and the mercury through the pipe O-the slots in the

page_text: pipe being so narrow and the pressure so high that the salt water will keep the
mercury out of contact with the carbon. There may be laid a piece of thin cloth
on top of the carbon covering the pipe, or put right through the slots of the same,
which cloth cover will serve to prevent the mercury from coming into contact with
the carbon. In this form of apparatus it will be seen that the alkali amalgam is
formed on the lower side of the mercury and rises up through the mercury and
is taken up by the metal drum, while in the first case it is to be taken down
through the mercury underneath the edges J.
In Figure 7 I show a modified arrangement of the amalgamated metal body
whereby the construction of the apparatus becomes another one; e is the outer
vessel containing the solvent (water) and g the inner vessel serving as holder for
the salt solution, this vessel being open at the bottom; it has a flange h, that
b is
serves as a cover for the outer vessel, while g¹ is the cover for the inner vessel.
a shaft being journalled in the cover g' and in the bottom of the vessel e; this
shaft carries a bowl shaped amalgamated metal disc a, provided with a flange cat
its periphery and perforated at d close to the hub; q is the mercury, p the anodes
and n denotes the electrical circuit connection of the mercury. When the bowl a
revolves with the shaft b the amalgam formed inside of the bowl will adhere to the
amalgamated surface of the rotating bowl and by the centrifugal force be driven
upwards along the conical face of the same which as will be seen is surrounded by
the solvent agent (water); the mercury deprived of its alkali metal will then fall
down on the outside of the flange c and gather in the bottom of the vessel from
where it enters the bowl again through the perforations at d. As will be seen the
result is exactly the same as in the former apparatus. The amalgamated metallic
body serving as a bearer for a thin layer of amalgam moving through the solvent
agent may also be given the form of a band or belt and the arrangement of the
apparatus may be varied accordingly; the characteristic feature of the process
being the use of an amalgamated metal body, having a greater part of its surface
exposed to the solvent agent and having also part of its surface in contact with the
mercury serving as a cathode and being moved in such a manner that the amalgam
in the cathode is passed through the solvent in the form of a thin layer adhering
to the surface of the moving body., Figure 4 shows an arrangement of a float
(areometer) in the compartment containing the solvent agent or in a pipe E¹
branched off from the same, by means of which the lye formed in the same may
be automatically emptied out when it has reached a certain degree of concentration.
The areometer R is guided at S and its upper end rests against one end of the
lever T, pivoted at V and having its other end above a cup U containing mercury.
When the lye is getting concentrated the areometer rises and thereby tips the
lever T so that contact is formed at U. From U and V conductors lead to a
source of electricity and an electromagnet, which latter, when the circuit is being
closed opens a valve through which the lye may flow out. Simultaneously fresh
water is automatically supplied to the vessel by means of a ball-cock in a well-
known manner, which needs no further description.
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 process of electrolytically treating alkaline salts for the purpose of
decomposing the same and combining their metallic constituent with a dissolving
agent for the same consisting in exposing the solution of the salt to the action of
an electric current passing through a mercury cathode in contact with the salt
solution, and moving through the said mercury cathode a metallic body having
an amalgamated surface in contact with the mercury and partly in contact with a
solvent for the alkali metal in such a manner that the amalgam formed at the
cathode may adhere to the metallic body and be passed in a thin layer covering
the same through the solvent agent enclosed in a space outside of the electric
field.

page_text: 2. In an apparatus for electrolytically treating alkaline salts for the purpose of
decomposing the same and combining their metallic constituent with a dissolving
agent for the same the combination with a vessel serving as holder for the said
dissolving agent and having in its bottom a receptacle for mercury, of a vessel
serving as holder for the salt solution (electrolyte) the latter vessel being placed
inside of the former and being provided in its bottom with an opening the
surrounding edges of the same reaching into the mercury and of a moving metallic
body having part of its surface dipped into the mercury and part of the same
surrounded by the dissolving agent the said metallic body having an amalgamated
surface, and the said mercury serving as cathode while the anode or anodes are
placed in or above the said bottom opening of the inner vessel.
3. In an apparatus as secondly claimed the modification consisting in constructing
the inner vessel to hold the solvent agent and the outer vessel to hold the
electrolyte and placing the anode in the form of a receptacle for the mercury in
the bottom of the outer vessel just below the opening of the inner vessel, and
separating the mercury from the anode by means of salt solution.
4. In an apparatus as secondly and thirdly claimed the combination with the
holder for the electrolyte or salt solution, the holder for the solvent agent and the
mercury cathode closing the opening of communication between the two vessels of
an amalgamated sheet metal drum or cylinder (A) of less diameter than the
holder for the solvent agent being mounted on a rotable horizontal shaft in such a
manner that the lowermost part of its periphery is dipped in the mercury while
the greater part of the same is in contact with the solvent agent in order that the
amalgam formed in the electric field adhering to the amalgamated sheet metal
cylinder shall be taken along with the latter and carried through the solvent
agent.
.
5. In an apparatus for electrolytically treating alkaline salts for the purpose set
forth the combination with the holder (g) for the electrolyte or salt solution, the
holder (e) for the solvent agent and the mercury cathode q closing the opening of
communication between the 'two vessels of an amalgamated bowl shaped metal
disc a being mounted on a rotatable vertical shaft in such a manner that the
perforated central part of the disc is dipped into the mercury while the peripheral
greater part of the disc is in contact with the solvent agent in order that the
amalgam formed in the electric field shall adhere to the disc and be forced
outwardly and upwardly along the bowl shaped amalgamated disc by the action of
the centrifugal force.
6. Process and apparatus for electrolytically treating alkaline salts while using
mercury as a cathode substantially as described and shown.
Dated thin 11th den of 1.1 1001
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.