Process for the Production of Acetic Acid.
Year: 1898

page_text: Process for the Production of Acetic Acid.
I, COUNT HENRI PLATER-SYBERG, of 81, Rue de la Boëtie, Paris, France, do
hereby declare the nature of this invention to be as follows:
. The usual process hitherto for separating acetic acid from its saline combina-
tions consists in treating the latter with a mineral acid which displaces the
But this process
acetic acid while saturating the base wherewith it is united.
has the inconvenience of destroying almost entirely the value of the mineral
acid employed and that of the base while forming residuals that are difficult
to utilize.
In order to avoid these inconveniences, I first electrolytically separate the
acetic acid from the alkaline base, while contriving to obtain the latter in the
free state and the acetic acid in the form of a soluble salt.
For this purpose one has to operate cold in an electrolytical trough provided
with a positive iron electrode and divided in two by a porous partition which
prevents the mixing of the two liquids wherein the electrodes are immersed.
A last condition which has to be fulfilled is to add to the solution of alkaline
acetate to be decomposed a little acetic acid in order to provide around the
positive electrode an acid liquid at the beginning of the operation.
Under these conditions after the passage of the current the alkaline acetate is
decomposed and the acetic acid attacks the iron of the positive electrode to form
acetate of protoxide of iron, while the base flows around the negative electrode.
When collected there, said base can serve for any purpose and namely it can be
employed to treat substances which submitted to the action of an alkali by a
suitable process produces an alkaline acetate, so that if thus employed, the same
alkali may serve ad infinitum to prepare fresh quantities of acetic acid.
The acetate of protoxide of iron after being heated is pulverized in contact with
the air and forms itself into acetate of sesquioxide of iron. To this acetate of
sesquioxide of iron is added a suitable quantity of neutral acetate of potash and
I then heat till it boils; a little before this moment a double decomposition
takes place the neutral acetate of potash being transformed into biacetate of
potash, while the iron is all precipitated in the form of hydrate of sesquioxide of iron.
The bi-acetate of potash thus obtained is then submitted to the action of heat
and divides into acetic acid and neutral acetate of potash which serves to decom-
pose fresh quantities of acetate of sesquioxide of iron.
Thus while operating in this manner free alkali and free acetic acid áre
obtained, only a certain quantity of iron has to be spent which passes from the
metallic state into that of an iron hydrate and the necessary force for engendering
the necessary electric current for the electrolytic operation is a relatively small
matter.
I have stated above that an iron electrode has to be employed in this operation
but one might strictly speaking replace the iron by another metal forming with
acetic acid a soluble acetate (such as zinc or lead for instance), iron is however

page_text: preferable, not only because of its cheapness but also because the iron salt is
more suitable for the reactions named than the salts of zinc or lead.
Dated this Fourth day of January 1898.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.
I, COUNT HENRI PLATER-SYBERG, of 81, Rue de la Boëtie, Paris, France, 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:-
The usual process hitherto for separating acetic acid from its saline combina-
tions consists in treating the latter with a mineral acid which displaces the
acetic acid while saturating the base wherewith it is united. But this process
has the inconvenience of destroying almost entirely the value of the mineral
acid employed and that of the base while Torming residuals that are difficult
to utilize.
In order to avoid these inconveniences I first electrolytically separate the
acetic acid from the alkaline base, while contriving to obtain the latter in the
free state and the acetic acid in the form of a soluble salt.
For this purpose one has to operate cold in an electrolytical vat provided
with a positive iron electrode and divided in two by a porous partition which
prevents the mixing of the two liquids wherein the electrodes are immersed.
The negative electrode may be of iron but it is preferable to make it of copper
in order to diminish the resistance.
. A last condition which has to be fulfilled is to add to the solution of alkaline
acetate to be decomposed a little acetic acid in order to provide around the
positive electrode an acid liquid at the beginning of the operation. Instead of
acidified alkaline acetate I may place in the compartment surrounding the posi-
tive electrode some water slightly acidulated with acetic acid.
After the passage of the current the alkaline acetate is decomposed and the
acetic acid attacks the iron of the positive electrode to form acetate of protoxide
of iron, while the free base flows around the negative electrode. When collected
there, said base can serve for any purpose and specially it can be employed to
treat substances which submitted to the action of a base of this kind by a suitable
process produce an alkaline acetate, so that if thus employed, the same alkaline
may serve ad infinitum to prepare fresh quantities of acetic acid.
The solution of acetate of protoxide of iron after being heated is atomized in
contact with the air and forms itself into acetate of sesquioxide of iron. To
this acetate of sesquioxide of iron is added a suitable quantity of neutral acetate
of potash in the proportion of 754 parts by weight of the former to approximately
877 parts by weight of the latter and I then heat till it boils: a little before this
moment a double decomposition takes place the neutral acetate of potash being
transformed into bi acetate of potash, while the iron is all precipitated in the
form of hydrate of sesquioxide of iron.
The solution of bi-acetate of potash thus obtained is then submitted to the
action of heat and divides into acetic acid and neutral acetate of potash which
serves to decompose fresh quantities of acetate of sesquioxide of iron.
Thus while operating in this manner caustic alkali and free acetic acid
are obtained, only a certain quantity of iron has to be spent which passes from

page_text: the metallic state into that of an iron hydrate, and the necessary force for engen-
dering the necessary electric current for the electrolytic operation is a relatively
small matter.
I have stated above that an iron electrode has to be employed in this operation
but one might strictly speaking replace the iron by another metal forming with
acetic acid a soluble acetate (such as zinc or lead for instance), iron is however
very preferable, not only because of its cheapness but also because the iron salt is
more suitable for the reactions named than the salts of zinc or lead.
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:-
A process for extracting acetic acid from alkaline acetates consisting in firstly
separating the, acetic acid from the alkali by electrolysis, cold, in a vat provided
with positive electrode of iron or other equivalent metal and in which the two
electrodes are separated by a porous partition, then in transforming the acetate
of protoxide of iron thus produced into acetate of sesquioxide through oxydation
by means of air, then treating with neutral acetate of potash under the influence
of heat this acetate of sesquioxide for the purpose of obtaining bi-acetate of
potash, and finally in decomposing by heat this bi-acetate into neutral regenerated
acetate and into free acetic acid.
Dated this Third day of September 1898
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.