Improvements in the Electrolytic Production of Hypochlorite of Sodium.
Year: 1889

page_text: Improvements in the Electrolytic Production of Hypochlorite of
Sodium.
I, EMILE MARIE HIPPOLYTE ANDREOLI, of 62 Loughborough Park, Brixton, in the
County of Surrey, Journalist, 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 ;-
This invention has for its object improvements in the electrolytic production of
hypochlorite of sodium.
The production of hypochlorite of sodium by the electrolysis of chloride of sodium,
has been known for many years, but the yield of hypochlorite has been found to fall
far short of what on theortical grounds might be expected.
By my invention, I get a much better yield than has yet been obtained; this I do
by altering the relation of the Anodes and Cathodes and minimising the powerful
reducing action of the nascent hydrogen.
Hertofore the anodes and cathodes, immersed in the bath of salt solution, have been
of equal area, and sometimes a considerable number of electrodes have been employed,
so arranged that each anode is placed between two cathodes, the total number of anodes
being equal to the number of cathodes.
In my practice I provide a much smaller area of cathodes than of anodes; for
example, I may employ only two small cathodes offering a small surface, and twenty
large anodes.
A further improvement consists in having each cathode placed between two cages
charged with peroxide of manganese or other like oxidising agent.
In order that my said invention may be fully understood and readily carried into
effect, I will proceed to describe the drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a perspective view of the tank with anodes, cathodes and absorbing
filters.
Figure 2 represents a cathode between its two cages.
Figure 3 represents one of the anodes.
These figures show the arrangement of apparatus which I prefer, for carrying my
invention into practice.
In Figure 1 is a tank of a capacity to contain say 100 gallons; it is to be charged
with a solution of common salt having a density of about 12° Beaumé; the solution
is rendered alkaline by the addition of a small quantity of caustic soda. b b b are the
anodes; as here shown they are twenty in number. They consist of carbon rods,
fixed in wooden frames, or better enamelled copper or iron frames. c c are the
cathodes. As they are here shown, they consist of two short and narrow iron frames
to which is firmly applied an iron gauze or trellis. Each cathode is about 3rd the size
of the anodes, but being of open material it exposes very little surface. Each cathode
is hung between two cages dd dd; these are hydrogen absorbing filters consisting
of openwork boxes of paraffined wood or enamelled wire cages filled up with
small pieces of peroxide of manganese or peroxide of iron or other like oxidising
substance.
All the anodes are connected, as the drawings indicate, with the main conductor e
and the cathodes are connected as shown, with the main conductor f.
The conductors e and f lead to the poles of a continuous current dynamo capable,
under the conditions specified, of maintaining a current of 1000 Ampères and giving
a difference of potential of 5 volts.

page_text: The current is to be passed through the solution in the tank, until it contains
sufficient hypochlorite of sodium, for bleaching purposes. The liquid is then drawn
out of the tank and it is ready for use in bleaching by well-known processes.
The spent liquor from the bleaching operation may be returned to the bath to be
again treated, after it has been brought to the original strength.
Figure 3 represents a carbon anode.
g is a copper rod to which all the carbon rods are connected. This may be done by
depositing copper upon the end of the carbon rod and then making a metallic
connection with the rod g by the aid of solder. The rod g is bent at one end to enter
a hole in a copper bar fixed alongside the tank and to which all the anodes are
similarly connected. The bar is connected to the main conductor e in figure 1.
The cathodes are connected in the same way as the anodes to a copper bar
on the other side of the tank which is connected to the main conductor f in
figure 1.
It is not essential that the anode should be of carbon; I may employ anodes
consisting of small pieces of peroxide of manganese alone or mixed with pieces of
broken carbon or coke and which fill paraffined wooden cages. The best results are
obtained with pyrolusite of the best quality.
Contact with the pyrolusite is made by having in its midst a small carbon or peroxide
of manganese plate to which is soldered a copper rod which is connected to the main
conductor e as in the case of the carbon anodes.
1
It is not essential that the cathodes should be of iron wire gauze but this material
is preferred.
By the means above set forth, I prevent in great part, the hypochlorite produced at
the anodes from being destroyed in the neighbourhood of the cathodes by the nascent
hydrogen, which heretofore has been the cause of serious loss.
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 the production substantially as described of hypochlorite of sodium by
electrolysis of a solution of chloride of sodium solution the use of cathodes and anodes
in such numbers or dimensions that the total anode surface exposed to the liquid is
several times larger than the corresponding cathode surface.
2. In the production, substantially as described, of hypchlorite of sodium by
electrolysis, the use of cathodes which are separated from the anodes by absorbing
filters consisting of cages filled with peroxide of manganese or other such like solid
insoluble oxidising agent.
3. In the production of hypochlorite of sodium by electrolysis, the conduct of the
process substantially as herein set forth whereby I prevent to a large extent the
reduction by nascent hydrogen of the hypochlorite formed.
Dated this 3rd day of July 1889.