Improvements in the Manufacture or Production of Chlorine and Caustic Soda, and in Apparatus therefor.
Year: 1890

page_text: Date of Application, 22nd Nov, 1890
Complete Specification Left, 14th Apr., 1891-Accepted, 23rd May, 1891
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture or Production of Chlorine and
Caustic Soda, and in Apparatus therefor.
I, JAMES GREENWOOD, of 774, Queen Victoria Street, in the City of London,
Electro-Chemist, do hereby declare the nature of this invention to be as follows:—
My invention relates to improvements in the manufacture or production of
chlorine gas and caustic soda.
In manufacturing chlorine and caustic soda according to my invention, I employ
a current of clectricity to decompose a saturated solution of sodium chloride or
common salt, and for this purpose I take a series of cylindrical or oblong vessels
of copper or other suitable conducting metal the interior of which is lined with
pure carbon soldered to the metal vessel by first coating the adhering surface with
an electrically deposited film of any suitable metal, thus forming a perfectly
homogeneous combination between the metal vessel and the carbon.
My metal-carbon vessel is advantageously utilised as both the containing or
electrolytic vessel, and also as the cathode, the terminal of which is connected with
the negative pole of a dynamo or other electrical generator.
In the centre of the said vessel, a metal-carbon cylinder or plate, is placed in a
vertical position, and which forms the anode, the terminal of which is carried
through the cover and connected with the positive pole of the dynamo or other
electrical generator.
The anode is perfectly insulated from the cathode by means of an insulating
plate placed at the bottom of my electrolytic vessel.
At a suitable distance between the anode and cathode a porous partition divides
the vessel into what may be described as the anode or chlorine section, and the
cathode or caustic soda section. This porous partition entirely dispenses with the
ordinary porous partitions of high resistance, and is formed by a number of
V shaped porcelain troughs filled with carded asbestos fibre, built up inside each
other in such a manner as to prevent the diffusion of the chlorine gas evolved in
the anode section into the cathode or caustic soda section of the electrolytic vessel.
Both the anode and cathode sections of the vessel are connected with a reservoir
containing a saturated solution of sodium chloride, which flows into, and enters each
section at the bottom, and in quickly circulating upwards, to reduce the polarization
to a minimum, the solution is decomposed by the current of electricity, chlorine
being evolved in the anode section and caustic soda being formed in the cathode
section, which may be further concentrated by passing the caustic soda solution
through a series of vessels until the required strength is obtained.
The flow of solution is regulated and maintained in a simple and automatic
nanner by placing the supply reservoir at a slight elevation, and also by arranging
he vessels so that the solution can flow through the entire series.
The electrolytic vessel is sealed by a porcelain, ebonite or other suitable cover,
with which tubes are connected to conduct the chlorine gas and caustic soda
olution to their respective receivers.

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture or Production of Chlorine and
Caustic Soda, and in Apparatus therefor.
1, JAMES GREENWOOD, of 774, Queen Victoria Street, in the City of London,
Electro-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 improvements in the manufacture or production of
chlorine and caustic soda by means of electrolysis.
In manufacturing or producing caustic soda and chlorine according to my
invention I decompose a solution of sodium chloride or common salt by a current
of electricity in one or a series of cylindrical square or oblong vessels of iron or
combined metal and carbon having porous partitions or diaphragus, all as more
particularly hereinafter described by reference to the accompanying drawings, in
which
Figures 1 and 2 are respectively a vertical and a horizontal section of one of my
vessels of a circular form for producing caustic soda and chlorine gas according to
my invention :
Figure 3 is an elevation shewing three of the said vessels arranged in combination
with suitable tanks and pumps for carrying out the process :
Figures 4 and 5 are respectively an elevation (partly in section) and a plan with
the cover removed of one of my vessels of an oblong form.
Similar reference letters indicate similar or corresponding parts throughout the
drawings.
I will first describe my circular form of vessel shewn in Figures 1 to 3.
a indicates the wall of the electrolytic vessel, which wall, when of copper, or
other metal than iron, is coated inside with carbon in the manner hereinafter
described, the carbon being shewn at b; but if the wall is of iron I use it uncoated.
The wall of the vessel also serves as the cathode, the terminal c of which is
connected with the negative pole of a dynamo or other electrical generator. In
the centre of the said vessel a combined metal and carbon cylinder d is placed in a
vertical position which forms the anode, the terminal e of which is connected with
the positive pole of the said dynamo or other electrical generator. The carbon
coating referred to above, is formed by electrolytically depositing a film of copper
or other suitable metal upon the adhering surface of the carbon, and then soldering
the same to the copper or other metal required to be combined with it, thus forming
a perfectly homogeneous combination of the metal and carbon, which is well adapted
for electrodes in which metal is altogether unsuitable for the purpose.
The anode d is insulated from the cathode a by means of a slate or other
insulating plate placed at the bottom of the vessel.
At a suitable distance between the anode and the cathode a a porous partition
or diaphragm g divides the vessel into what may be described as the anode or
chlorine section and the cathode or caustic soda section i. The use of this
diaphragm g enables me to dispense entirely with the usual porous partition of high
resistance hitherto employed. My diaphragm is formed of a number of V-shaped
troughs of porcelain or other suitable substance, such as glass or slate which are
filled with carded asbestos fibre k or other suitable porous material such as a
quantity of powdered steatite. These troughs are built up inside each other, as
shewn clearly in Figure 1, so as to prevent the diffusion of the chlorine gas evolved
in the anode section into the cathode section and thus separates the products
obtained in each of the said sections in the most effectual manner.
Both the sections and i are filled at the commencement with a solution of
sodium chloride which is caused to flow into them at the bottom through the
pipes and m respectively from the supply-tanks o and p. The solution will

page_text: quickly circulate upwards (whereby the polarization will be reduced to a minimum)
and will be decomposed by means of a current of electricity which is caused to
pass through the same, whereby chlorine will be evolved in the anode section h and
caustic soda will be formed in the cathode section i.
The flow of the solution can be regulated and maintained in a known, simple and
automatic manner such for example, as by placing the supply-tanks o and p at a
suitable elevation, as shewn in Figure 3, and also by arranging the vessels so that
the two solutions can flow through their respective sections in the entire series into
delivery tanks y, r from whence the solutions are pumped by suitable pumps, such
as s, t, back to the supply-tanks o, p, the circulation being maintained until the
solutions are sufficiently decomposed and the caustic soda solution is of the strength
required for any particular purpose, the solution of sodium chloride in the tank p
being gradually changed to caustic soda. Each electrolytic vessel is sealed by a
porcelain or other suitable cover u, and pipes v are connected with the sections h, h
to conduct the chlorine gas away; w, w are cocks for drawing off the contents of
the tanks o and p as required.
I will now describe my oblong form of vessel shewn in Figures 4 and 5. In this
arrangement the electrolytic vessel is divided into a series of anode and cathode
sections by the anodes and cathodes in the form of plates marked d and a
respectively and extending, as also do the porous partitions g across the vessel
between the sides thereof. The cathodes which in this instance do not form the
walls of the vessel, I use in an uncoated state and have indicated them as not being
carbon covered. The pipes and m are arranged so as to allow the solutions to
flow through their respective chambers, chlorine and caustic soda being produced
and collected in a similar manner to that described with reference to Figure 3.
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. In apparatus for the manufacture or production of chlorine or caustic soda by
electrolysis the use of metal carbon electrodes constructed and used substantially as
hereinbefore described.
2. In apparatus for the manufacture or production of chlorine or caustic soda by
electrolysis the use of porous partitions formed of a number of V-shaped troughs
filled with asbestos fibre or other suitable material, substantially as hereinbefore
described and illustrated in Figures 1 and 4 of the accompanying drawings.
3. The manufacture or production of chlorine or caustic soda by the improved
apparatus herein before respectively described and respectively illustrated in
Figures 1, 2 and 3 and in 4 and 5 of the accompanying drawings.
Dated the 14th of Anni 1901
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.