Improvements relating to the Production of Insulating Coatings or Linings in Electrolytic Apparatus:
Year: 1887

page_text: Date of Application, 14th July, 1887
Complete Left, 13th Apr., 1888
Complete Accepted, 18th May, 1888
Improvements relating to the Production of Insulating Coatings or
Linings in Electrolytic Apparatus:
I, LUDWIG GRABAU, of 41 Schiffgraben, Hanover, Civil Engineer do hereby declare
the nature of this invention to be as follows:-
My invention relates to the production of insulating coatings or linings in apparatus
for the electrolysis of substances which liquefy under the action of fire.
In the electrolysis of substances which liquefy under the action of fire, the manu-
facture of parts of apparatus such as for example pole cells, pole wire packings,
collecting vessels, and the like of refractory material which is a non-conductor of
electricity, has heretofore presented difficulties, because the refractory materials
employed have never, or only in a few cases, proved to be sufficiently resistive against
the destructive action of the molten masses to be decomposed, or their ingredients,
so that the electrolysis of substances which become liquid under the action of fire
has not heretofore led to satisfactory results.
The present invention has for its object to obviate the said defect, inasmuch as the
want hitherto experienced of resistive insulating materials suitable for pole cells, pole
wire packings and the like or their coatings is supplied successfully and in a satisfactory
manner.
For this purpose the parts of the electric decomposing apparatus which are to be
insulated or protected are provided with a coating which is not attacked either by the
molten mass to be decomposed or by their separated or single ingredients. This
is achieved by cooling the parts of the apparatus which are to be insulated so
thoroughly that on the cooled surfaces the liquid mass to be decomposed congeals and
forms an insulating or protecting crust.
This cooling is effected by making the parts to be cooled, with double walls, whereby
spaces are formed which are adapted to convey cooling liquids or cooling gases, for
example cold air.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.

page_text: Linings in Electrolytic Apparatus.
I, LUDWIG GRABAU, of 41 Schiffgraben, Hanover, Civil 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 production of insulating coatings or linings in
apparatus for the electrolysis of substances which liquefy under the action of heat.
In the electrolysis of substances which liquefy under the action of heat the manu-
facture of parts of apparatus such as for example pole cells, pole wire packings,
collecting vessels, and the like of refractory material which is a nonconductor of
electricity has heretofore presented difficulties, because the refractory materials employed
have never or only in a few cases proved to be sufficiently resistive against the
destructive action of the molton masses to be decomposed or their single ingredients,
so that the electrolysis of substances which become liquid under the action of heat
has not heretofore led to satisfactory results.
The present invention has for its object to obviate the said defect, inasmuch as the
want, hitherto experienced of resistive insulating materials suitable for pole cells,
pole wire packings and the like or their coatings is supplied successfully and in a
satisfactory manner.
For this purpose the parts of the electric decomposing apparatus which are to be
insulated or protected, are provided with a coating which is not attacked either by the
molten mass to be decomposed or by their separated or single ingredients. This is
achieved by cooling the parts of the apparatus which are to be insulated so thoroughly
that on the cooled surfaces the liquid mass to be decomposed congeals and forms an
insulating or protecting crust.
This cooling is effected by making the parts to be cooled with double walls, whereby
spaces are formed which are adapted to convey cooling liquids or cooling gases, for
example cold air.
The present invention can for example be used with great advantage in the manu-
facture of alkalies from the molten alkaline salts of the same that liquefy under the
action of fire by electrolysis, as by cooling the pole cells or the like, consisting of
refractory material containing silicon, they are protected against rapid destruction by
the liquid mass in immediate proximity to the respective parts of the apparatus being
congealed in consequence of the cooling and surrounds the said parts as a firm

page_text: protecting coating. In this manner the material of which the pole cells or other
parts of the apparatus are made is prevented from attack by the action of the molten
mass, or constituents separated from it, say by the electric current, inasmuch as, if
this material as hitherto, customary, contained silicon and was refractory, silicon is
reduced therefrom.
To better explain how this process is carried out, I will describe the application
of the same in the electric extraction of sodium.
If the present invention is to be used in the extraction of sodium an apparatus can
be employed such as that represented by way of example in the accompanying
drawing.
In the melting vessel A, which can be heated by any suitable heating apparatus, is
placed the molten mass of sodium into which the bell-shaped pole cell B having double
walls is immersed. From the upper thinner part of the pole cell B passes laterally a
pipe r beyond the edge of the melting vessel and serves for continuously leading off
the sodium formed during the decomposition by the electric current. The negative
electrode extending into the pole cell consists of an iron rod a, a¹ which, for the
purpose of enabling the same to be adjusted higher or lower, is guided by means of its
screw thread provided at a¹ and the female thread arranged in the thin part of the
pole cell. This adjustability of the negative electrode has the advantage that in order
to introduce the electric current, the end a of the electrode can be put within reach of
the liquid molten mass, even if all the said molten mass contained in the pole cell
should be congealed.
The negative electrode is at its upper end connected with the conducting
wire from the negative pole of a source of electricity, the positive pole of
which is connected by a conducting wire with the positive electrode, which may
consist of carbon, outside the pole cell and immersed in the molten mass. The pipe r
leads to a collecting vessel g filled with petroleum.
The sectional area of the electrode a, a¹ is preferably of such a size that the
electric current passing through it heats this electrode to a sufficient temperature to
obtain in its immediate vicinity the sodium salt to be decomposed.
As the specific gravity of sodium is lighter than that of its molten salts, it rises at
the electrode a, a¹, and finally flows through the piper into the vessel g.
For cooling purposes, a liquid, for example water or a gas such as air, is introduced
through the pipe into the space between the double walls of the pole cell B and
led from the same through the pipe . By the cooling action of the liquids or gases
passing through this space, a part of the molten mass contained in the vessel a congeals
and is deposited as a crust k on the walls of the pole cell and pipes.
By this means the walls of the pole cell receives an insulating coating, as the crust
of salt as a non-conductor of electricity, and at the same time a protecting coating,
so that firstly all the sodium must be formed and collected within the pole cell,
secondly the walls of the pole cell are preserved against destruction by the protecting
crust of salt as the latter cannot be destroyed by sodium thereby ensuring thirdly the
continual working and fourthly preventing the impurification of the sodium by any
decomposition of the pole cell, which with the employment of refractory pole cells
made for example of porcelain in the manner heretofore customary has always been
the case.
The described invention can also be employed in the electrolysis of other substances
which are liquefied under the action of heat, for example potassium salts for the
production of potassium.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-
First. In the electrolysis of substances that liquefy under the action of heat the
employment of pole cells and other parts of the apparatus, having cooled walls for the
purpose above described.

page_text: Second. In the electrolysis of substances that liquefy under the action of heat
the employment of pole cells and other parts of the apparatus, having a double
wall.
Third. In the electrolysis of substances that liquefy under the action of heat, the
employment of pole cells and other parts of the apparatus, having a double wall and
inlet and outlet pipes for cooling liquids or cooling gases.
Fourth. In the electrolysis of substances that liquefy under the action of heat the
employment of a cooled pole cell and an outflow pipe extending from the upper end
of the cell, for the substance separated by electrolysis.
+1 1009
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London,
Agents for the Applicant.