A Process for the Electrolytic Separation of Metals.
Year: 1897

page_text: Date of Application, 30th Oct., 1897
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2000
Date of Application, 30th Oct., 1897
Complete Specification Left, 20th July, 1896-Accepted, 24th Sept.,
1898
A Process for the Electrolytic Separation of Metals.
I, Dr. HEINRICH VON DER LINDE, of 192, Uerdingerstrasse, Crefeld, in the
Empire of Germany, Chemist, do hereby declare the nature of this invention to be
as follows:-
The object of this invention is to separate metals, either from alloys or from ore,
by electrolysis. Where the electrolytic method has hitherto been applied to the
separation of metals at all, it was invariably carried out in the following
manner the metals to be subjected to electrolysis were either dealt with after
having previously been dissolved (as salt solutions); or they were dissolved in the
course of the electrolytic process. But few methods are known, in which it is
not necessary to convert all the metals to be separated into solutions. Taking,
for example, the process of removing the tin from tinned articles by electrolysis,
I find that it is mostly carried out as follows: the tinned scrap iron, say is sub-
mitted to electrolysis in a bath composed of soda lye, which will not affect the
iron itself but only the tin with which it is coated. The difficulty in the way of
extending this mode of operation to other metals, however, has, as a rule, resided
in the nature of the solvent, or the electrolyte, the agent employed for either or
both of these purposes having proved unserviceable, either on account
of its being a bad conductor, (or non-conductor), whilst at the same
time inducing decomposition,―or by reason of its being too expen-
sive. This is how the soda lye acts in the process above referred to: the soda
lye only dissolves the tin, and transfers it to the cathode, while, as before stated,
such soda lye has no effect whatever upon the iron. Now it is this principle that
I have endeavoured to apply to other metals, and, in the course of my enquiries,
I have discovered a solvent adapted for use in the electrolytic separation of a
number of metals, and more particularly in dissociating copper from iron. This
solvent could not be an acid, since in acid both metals would dissolve, nor could
it be a soda or potash solution, since neither of the said metals would dissolve in
these alkaline lyes. In short, of all the numerous solvents which might have been
considered in connection with this question, one only-viz.: ammonium carbonate
solution was found to answer the purpose stated and to be perfectly serviceable
in practice; nor did it prove so only in the separation of copper from iron, but
in that, likewise, of a wide range of other metals, such as cobalt, nickel, tin and
zinc, which had to be dis-united from either iron or manganese. The merits of
this solvent reside in this that it dissolves the metals named, even cold, and espec-
ially with air admitted freely; while at the same time it does not become decom-
posed in the process of electrolysis, and inasmuch as, in addition to this, it is
inexpensive, there is nothing, from an economical point of view to preclude it
from employment on a large scale.
Doted this 20th day of Octahat 1007

page_text: I, Dr. HEINRICH VON DER LINDE, of 192, Uerdingerstrasse, Crefeld, in the
Empire of Germany, 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:
This invention relates to an improved process of separating metals, existing in
the form of alloys, by employing electrolytical means.
In as much as in former methods of separating metals, electrolytical means
have been used, the process has been such, that all metals, to be treated by elec-
trolysis, are either from the first in a state of solution (salt solutions) or that the
said metals only enter into the state of solution during electrolysis.
Only a few processes are known, in which it is not necessary that all the metals
to be separated need be transformed into a state of solution. For instance, the
electrolytical process of detinning, which in most cases is carried out in such a
manner, that the tinned iron is placed in a bath of soda lye and subjected therein
to electrolysis, in which operation the iron does not undergo any change. Now
the difficulty in extending this process to other metals, as a rule was due to the
solvent or electrolyte, seing that this solvent or electrolyte was unsuitable for use,
either owing to its insufficient conducting capacity, while at the same time being
decomposed, or owing to its being too expensive. The action of soda lye, when
used as electrolyte in the detinning process, above mentioned,, is such, that the
said soda lye only dissolves the tin, transforming the same to the cathode,
whereas the iron, as has already been stated, is not attacked at all by said soda
lye. In endeavouring to also utilize this principle for separating other metals I
have found a solvent, which is suitable for the electrolytical separation of a
number of metals; as for example for the separation of copper from iron. This
solvent could not be an acid, because both said metals dissolve in acid; nor could .it
be soda lye or potash lye or soda, seeing that none of these chemicals are capable
of dissolving either of the two metals Now. the only suitable and utilizable
solvent out of all solvents to be taken into, consideration, has been found to be
the aqueous solution of carbonate of ammonium and this not only for the separa-
tion of copper and iron but also of a large number of other metals such as cobalt,
nickel, tin and zinc from iron and manganese. The advantages of this solvent
consist in the fact that it easily dissolves these metals, even cold, especially if air
is afforded access.; a further advantage of the said solvent being due to its great
conducting capacity and to the fact, that; it is not subject to being decomposed by
the electrolytical process. Moreover from an economical point of view there. is
nothing in the way of this solvent being utilized on a large scale, owing to its
'cheapness.
The process is especially intended for removing the plating from plated iron
articles. Such iron articles are mostly. covered with copper, with nickel or with
an alloy of copper and nickel. If articles of this kind are placed as anodes into a
solution of carbonate of ammonium and if the cathode be made of the metal to
be dissolved, which lies in form: of. a. plating, upon the, iron article, then, as the
electric current acts, the metal is separated from the iron article and deposited
upon the cathode. The iron article itself however, remains unattacked, so that
the iron freed from its plating may be further used in the manufacture of steel
or the like. The intensity of the current may be varied with the surface of the
material to be treated...
The degree of concentration of the solution of carbonate of ammónium may be
A

page_text: chosen by the operator according to circumstances and can be easily fixed by
assaying. The sand solution however is preferably a saturated one.
The essential feature of the process, is, that carbonate of ammonium is used as
solvent for the metal utilized as plating, under the action of the electric current,
without iron being attacked, and that out of the solvent the separated metal is
simultaneously precipitated. There is further point to be considered as new, viz;
that carbonate of ammonium under the action of the electric current will separate
the metals, existing in a pure, combined or worked condition.
The use of carbonate of ammonium has already been repeatedly suggested as a
solvent for oxides of various metals and for non-compact and unworked metals, as
reduced from the respective ore (see for example the English Patent No. 19934,
1895); According to the methods mentioned therein, however considerable quan-
tities of oxide were always present; thus with carbonate of ammonium, ammonia
has been nixed and the mixture used as the electrolyte and the metal was not
found compact and coherent, as in the case of the platings which latter prove
especially resistant against attacks. It has not heretofore been known, that car-
bonate of ammonium without an addition of ammonia when under the action of
the electric current was able to separate the pure, compact metals, which were
present in form of coherent platings, that the iron remained unattacked, but that
the said iron in this operation was so purified as to admit of its being further
treated in metallurgy, which was an impossibility in cases where ammonia was
simultaneously employed; moreover a process for removing platings from nickel,
copper and copper-nickel from iron, without the iron being dissolved, has likewise
not heretofore been known.
The tension of current to be applied is dependent on the metal to be treated and
can in each case be formed according to known methods.
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
1. A process of electrolytically separating metals; the characteristic feature
being the use of carbonate of ammonia as electrolyte; the object being to simul-
taneously dissolve by the electrolyte the one of the metals to be separated.
2. The application of the process described in the first claim, with the object
of separating nickel, copper or copper-nickel-alloys, provided in form of platings
upon iron articles, from such iron articles, while the iron remains unattacked.
Di. 06th dow of August 1898.
HASELTINE, LAKE & Co.
45, Southampton Buildings, London, W.C., Agents for the Applicant.