An Improved Process for the Electrolytic Separation of Aluminium, Aluminium Alloys, and Magnesium from Solutions of their Salts.
Year: 1889

page_text: Date of Application, 23rd May, 1889
Complete Specification Left, 28th June, 1889-Accepted, 3rd Aug., 1889
PROVISIONAL SPECIFICATION.
An Improved Process for the Electrolytic Separation of Aluminium,
Aluminium Alloys, and Magnesium from Solutions of their Salts.
I, GEORG NAHNSEN of Am Judenkirchhof, Hanover, in the German Empire,
Chemist, do hereby declare the nature of this invention to be as follows:-
This invention consists in electrolytically separating aluminium, aluminium alloys
and magnesium from solutions of their salts without bye decomposition, and as dis-
tinguished from the process hitherto employed the object is attained by cooling by
suitable means the electrolyte, and by preventing augmentation of the temperature of
the salt solutions during electrolysis.
The cooling of the solution may be effected in various ways. It may be accomplished
by passing refrigerated air into the solution to be electrolysed or the necessary low
temperature may be brought about and maintained by means of cooling worms
through which is caused to circulate brine or salt lye of low temperature, for instance,
chloride of calcium lye. The cooling is specially necessary at the negative electrode as
it is upon this that the metal is precipitated and as I have found in practice, with very
considerable generation of heat. It is therefore in many cases indispensable to place
the negative electrode in immediate contact with the cooling liquid. In the separation
of aluminium this course is however only necessary with great densities of current ;
for magnesium which gets heated at a lower temperature, the direct cooling of the
negative electrode is always the most suitable.
.
In order to carry out the process successfully, the salt solutions should be highly
and equably concentrated. This may be done in two ways. Either a retort carbon
saturated with the hydrated oxide of the respective metal is used as a positive electrode,
the saturation of the same being effected by suspending it in the salt solution and
afterwards in soda lye, or as a continuous movement of the electrolyte is very advan-
tageous this is allowed to flow through a series of cases and between these in which
the electrolysis takes place are disposed other cases provided with stirring mechanism
into which the respective metallic oxide hydrate is conducted and in which it is stirred
up. The electrodes should be of antisoluble material, namely for the negative, sheet
aluminium and for the positive retort carbon in the form above stated.
Dated this 02nd day of Max 1880
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
An Improved Process for the Electrolytic Separation of Aluminium,
Aluminium Alloys, and Magnesium from Solutions of their Salts.
I, GEORG NAHNSEN of Am Judenkirchhof Hanover, in the German Empire,
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 a process for the electrolytic separation of aluminium,
aluminium alloys and magnesium from solutions of their salts.
The practical production of aluminium and magnesium from the point of view of
pyro-chemical methods of production has for a long time been carried on only by
electrolysing the dissolving anhydrous salts of the same. On the other hand all
attempts to obtain these metals from bydrous or alcoholic solutions of their salts
have been unsuccessful, the resulting product being mainly hydrate of metallic oxide,
with at the best, hardly discernable traces of the metal. The various explanations

page_text: and hypotheses which have been put forward for the purpose of accounting for such
a result have made it appear impossible ever to obtain these metals from their solutions,
but as we have discovered the true cause of the said phenomena we are able to prevent
the formation of the hydrate of metallic oxide.
It is known that aluminium beaten out into thin sheets decomposes water at a
temperature of from 70 to 80 degrees Celsius accompanied by the formation of
hydrogen and separation of hydrated oxide, but upon the electrolytic reduction of
the aluminium salts the aluminium appears in statu nascendi and thus will be able to
act still more readily upon the water. The higher temperature produced in part by
the passage of the electric current and chemical reaction and in part by the application
of artificial heat for the purpose of increasing the conductibility of the electrolyte
must therefore cause the formation of hydrated oxide.
Our invention consists in electrolytically separating aluminiun. aluminium alloys
and magnesium from solutions of their salts without bye decomposition, and as dis-
tinguished from the process hitherto employed, we attain our object by cooling by
suitable means the electrolyte and by preventing augmentation of the temperature of
the salt solutions during electrolyis.
We have ascertained by experiments that at a temperature of the solutions of
+40 degrees Celsius the separation of the metals takes place to a considerable extent
in the form of bydrated oxide, but at a temperature under + 4 degrees Celsius all the
metal is obtained as such. Further in the latter case the secondary evolution of
hydrogen always occurring at the higher temperature, is prevented. Primary
evolution of hydrogen may be avoided by suitably proportioning the density of the
current,
The cooling of the solution may be effected in various ways. To this end either
refrigerated air may be passed into the solution to be electrolysed or the necessary low
temperature may be brought about and maintained by means of cooling worms
through which is caused to circulate suitable brine or salt lye of low temperature,
chloride of calcium lye for instance. The cooling is specially necessary at the
negative electrode as it is upon this that the metal is precipitated, and as our ex-
periments have shewn, with very considerable generation of heat. It is therefore in
many cases indispensable to place the negative electrode in immediate contact with
the cooling liquid. In the separation of aluminium this however is only necessary
with great densities of current; for magnesium which becomes heated at a lower
temperature the direct cooling of the negative electrode is always the most suitable.
In order to carry out the process successfully, the salt solutions should be highly
and equably concentrated. This may be done in two ways. Either a retort carbon
saturated with the hydrated oxide of the respective metal is used as a positive electrode,
the saturation of the same being effected by suspending it in the salt solution and
afterwards in soda lye, or as a continuous movement of the electrolyte is very advan-
tageous, this is allowed to flow through a series of cases and between these in which
the electrolysis takes place are disposed other cases provided with stirring mechanism
into which the respective metallic oxide hydrate is conducted and in which it is stirred
up. The electrodes should be of anti-soluble material, namely for the negative, sheet
aluminium and for the positive, retort carbon in the form previously stated.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, 1 declare that what I
claim is:
The process for the electrolytic separation of aluminium, aluminium alloys and
magnesium from the solutions of their salts, consisting in cooling the electrolytes and
during the electrolysis preventing by further cooling any increase in the temperature
of the salt solutions, substantially as described.
Dated this 28th dow of Trine 1980
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C., Agents for the Applicant.