New or Improved Process for Electrolysing Chemical Combinations and Winning the Products of Decomposition Formed by the Electrolysis.
Year: 1894

page_text: This Print is in accordance with the Original Specification as it stands after
Amendment (under Section 18 of the Patents, &c. Act, 1883), as allowed by
the decision of the Comptroller General of the 6th day of December 1895.
Date of Application, 12th Nov., 1894-Accepted, 27th July, 1895
COMPLETE SPECIFICATION (AMENDED).
New or Improved Process for Electrolysing Chemical Combinations
and Winning the Products of Decomposition Formed by the
Electrolysis.
I, WILLY BEIN, Doctor of Philosophy, of 36 Schaper Strasse, Berlin, in the
Kingdom of Prussia, German Empire, 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 :-
If a solution of an electrolyte is electrolysed for a considerable time in a cell,
the products of decomposition will finally combine at the anode and cathode, and
after this has taken place, the electric energy conveyed to the solution is lost.
These products of decomposition have hitherto been separated out and gained
separately from the electrolyte in the case of standing electrolytes on the mechanical
principle by means of porous diaphragms or artificial or natural membranes. These
means do not however entirely obviate the disadvantages of a recombination of the
products formed since the endosmotic action as soon causes a mixture to take place,
as pointed out by Hittorf in his fundamental works in "Poggendorf's Annalen," a
fact which has however never been taken into account in the technical electrolysis.
The employment of diaphragms, furthermore has the effect of producing considerable
resistance and renders working with simple apparatus difficult, whilst working
generally is more difficult to control and more expensive. In addition to this, all
diaphragms are chemically or mechanically destroyed in time.
According to the process hereinafter described the employment of diaphragms is
entirely avoided. According to the same, the disadvantages above mentioned are
consequently obviated, whilst it more easily enables an increased concentration of
the products of decomposition and a more economical use of the electric energy.
The present process is based on the following principle:
:-
The products of decomposition formed in the electrolysis of a conductive solution
will remain near to the electrodes as long as the current is passing through the
solution, but no longer, if diaphragms are not employed and if suitable arrange-
ments are made at the electrodes to prevent purturbation in the solution through
the sinking or rising of the said products formed, owing to variations in the amount
of their specific gravity, or by rising gas bubbles, or owing to sudden local rises in
the temperature etc., the products of decomposition thus collecting at the electrodes
will be separated by the layer of unchanged liquid lying between them.
I have found by a number of experiments that whilst the current is passing
through the solution no practically observable intermingling of the products of

page_text: decomposition with the sharply defined separating layer takes place, and that this
is the case even in the presence of slight mechanical disturbances. The separating
layer or body of liquids gets smaller and smaller the longer the electrolysis is
continued, but in spite of this fact no intermingling takes place. If now the
electrolysis is continued until the separating layer which may be rendered noticeable
by suitable means is on the point of disappearing and the apparatus in which the
electrolysis is being performed, is at this moment divided into two parts either by
an impervious partition sunk into the liquid in place of the neutral layer or by other
suitable mechanical means, for instance by drawing off the liquid by cocks or the
like, and the products of decomposition may be obtained in a technically pure
state.
A separating layer of this description should, of course be formed when diaphragms
are employed, if the apparatuses are properly arranged, this does not however take
place because the diffusion or, more properly speaking endosmosis, caused by the
porous partition, gives rise to local currents which disturb the separating layer and
render it impossible to obtain a concentration of the products of decomposition
equal to that obtained by the present process.
One form of apparatus for carrying out the present process is shown in the
accompanying drawings in Fig. 1 in vertical cross section; Figs. 2 and 3 are
similar sections of modified forms of the apparatus.
The apparatus consists of a receptacle having two impervious partitions W
and Wextending across the same from about the top and reaching down to a short
distance above the bottom, and one partition W2 extending from the bottom
upwards and terminating some little distance below the top, said apparatus being
thus divided into four communicating compartments A, B, C, D, through which
the electric current may flow from the anode N to the cathode K, without hindrance.
The two interior compartments B and C may be entirely separated from each other
by a falling slide E, so that the whole apparatus may be divided into two compart-
ments A B and C D having no communication with each other.
If for instance bromide of sodium is subjected to the electrolysis in the apparatus
above described, the caustic soda formed at the cathode will be constantly
sinking to the bottom of the compartment D on account of its specific gravity.
As soon, however, as it gets into the compartment C, a separating layer begins to
form between it and the bromide of sodium not yet decomposed. At the same
time bromine separates out at the anode, first sinking and then entering and rising
in the compartment or chamber B, and allowing the formation of a separating layer
in this chamber. In this case the separating layer is visible exteriorly. As soon
as this separating layer has risen to the upper edge of the partition the slide E is
closed down.
Two openings O and O¹ are provided in the cover of the apparatus through which
syphons may be introduced by means of which the small quantities of bromide of
sodium standing above the separating layers in B and C and not yet decomposed
may be removed after which the pure products of decomposition may be obtained
by opening the cocks H and H¹.
The apparatus herein before described which is of a very simple nature, only
serves for carrying out one form of the process forming the object of the present
invention.
The process may be considerably simplified as shown in the following instances:-
In order to reduce the resistance of the solution to be electrolysed which is of the
greatest importance from a technical point of view.
In electrolysing bromide of sodium as in all cases, in which the products of
decomposition formed are both specifically heavier than the electrolyte, the
arrangement sketched in Fig. 2 may be employed. Here only two partitions W
and W₁ are employed. The anode is placed in the compartment or chamber 3 at
the bottom of the same, the cathode in chamber near the surface of the liquid.
The bromine collects in chamber 3 and rises very slowly in the same. The
soda lye formed in chamber I sinks gradually to the bottom, passes into the

page_text: chamber 2 and as soon as it has reached the top of the partition W, the products
must be separated.
The arrangement of the cathodes, allows the hydrogen to escape, without causing
disturbances in the current by mechanically agitating the solution and thus
intermingling the layers.
If the products of decomposition formed by the electrolysis are of different
specific gravity so that one part would rise and the other sink, as would for instance
be the case in electrolysing potassium chloride and cyanide of potassium in which
case chlorine and cyanogen would escape as gases and the potassium lye sink to the
bottom or in electrolysing rhodanide of potassium in which case the specifically
lighter sulphocyanic acid would rise and the potassium lye sink, the present process
may be carried.out in the manner shown in Fig. 3.
In this case only one partition W is employed. The potassium lye formed rises
gradually in chambers 1 and 2, the separating layer is formed by the layer of salt
not yet decomposed gradually rising in chamber 2, which is divided off by a laterally
operated slide V, corresponding to E as soon as it gets near the electrode, where a
disturbance would otherwise be occasioned.
The present process which has now been described in a few variations, may be
advantageously employed for working all kinds of artificial and natural brine, for
electrolysing Stassfurt saline deposits (the alkaline earths are precipitated as
hydroxydes,) and, generally for working almost all kinds of soluble salts. The
process further enables the production of acids, such as nitric acid by electrolysing
saltpetre, sulphuric acid from sulphates, hydrochloric acid from chloride and
sulphate.
If the anodes consist of ores they can be dissolved by means of the present
process. The present process is also suitable for purifying many substances, and
for separating out certain substances from mixtures, thus for instance for purifying
iron or copper salts, waste lyes containing sulphide, syrups, as also for electrolysing
organic substances, in which the reducing or oxidating powers of the electric current
are employed at one electrode.
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 :-
A process for electrolysing chemical combinations and for winning the products
of decomposition formed by the electrolysis, consisting in preserving the inter-
mediate layer or body of liquid formed during the electrolysis as a means of keeping
the products of decomposition formed at the anode and cathode separated
substantially as described.
Dated this 12th day of November 1894.
CASTLE SMITH,
"Invention" Office, 54 Fleet Street, London, E.C.,
Agent for the Applicant.