Improvements in the Production of Aluminium and Alloys of Aluminium.
Year: 1887

page_text: Date of Application, 16th Sept., 1887
Complete Left, 9th June, 1888
Complete Accepted, 13th July, 1888
Improvements in the Production of Aluminium and Alloys of
Aluminium.
I, ALEXANDER FELDMANN, chemist, residing at Linden near Hanover, in the
Kingdom of Prussia, do hereby declare the nature of this invention to be as
follows:-
My invention relates to the process of producing aluminium from compound
fluorides of aluminium and of alkali-metals, the said process consisting in melting
the compound fluoride together with the chloride of an alkali-metal, and in exposing
the molten mass to an electric current, or to the chemical action of an alkali-
metal.
This process is deficient, inasmuch as by means of the same only a portion of
the aluminium contained in the said compound fluoride is extracted, and the object
of my invention is to completely separate out the aluminium and to regenerate the
residue, in order to render it available for a renewed operation.
For this purpose I employ the compound fluorides of aluminium and of strontium,
baryum, calcium, magnesium or zinc instead of the aforesaid compound fluorides of
aluminium and alkali-metals, and a chloride of the metals of alkaline earths, preferably
strontium chloride, instead of a chloride of an alkali-metal.
For the decomposition by the electric current and by alkali-metals are adapted the
double fluorides of aluminium and of strontium, baryum, calcium and magnesium,
whereas by means of magnesium and zinc may be decomposed aluminium-magnesium
fluoride and aluminium-zinc fluoride.
In view of regenerating the residue obtained by the electric process, the same is
mixed with a watery solution of aluminium chloride and boiled, whereupon the water
is evaporated off. The double salt as originally employed, is thereby formed again.
If the residue obtained from the process in which alkali-metals are used for the decom-
position, is to be regenerated, the alkalic chloride contained therein must first be
washed out. The residues resulting from the treatment of the double fluorides of
aluminium and magnesium or zinc by means of metallic magnesium or zinc, and
which contain magnesium or zinc fluoride, have also to be washed for removing the

page_text: chloride of earth-alkali-metal, and thereupon they are boiled with one equivalent of
sulphate of aluminium and evaporated. The magnesium or zinc sulphate thereby
formed is then washed out and a new portion of chloride of earth-alkali-metal is
added.
By employing, in the electric process, negative electrodes of metal, for instance of
copper or iron, or by adding such metals to the molten mass if the reduction is
brought about by alkali-metals, zine or magnesium, alloys of aluminium with
copper, iron, &c., are obtained.

page_text: COMPLETE SPECIFICATION.
Improvements in the Production of Aluminium and Alloys of
Aluminium.
I, ALEXANDER FELDMANN, chemist, residing at Linden near Hanover in the
kingdom of Prussia, 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 :—
My invention is an improvement in the process of producing aluminium from com-
pound fluorides of aluminium and of alkali-metals, the said process consisting in
melting the compound fluoride together with the chloride of an alkali-metal or earth-
alkali metal, and in exposing the molten mass to an electric current or to the chemical
action of an alkali-metal.
This process is deficient inasmuch as by means of the same only a portion of the
aluminium contained in the said compound fluoride is extracted, and the object of my
invention is to completely separate out the aluminium and to regenerate the residue in
order to render it available for a renewed operation. The invention also comprises
the application of the improvement to the production of alloys of aluminium with
other metals.
For this purpose I employ the compound fluorides of aluminium and of the metals
of the alkaline earths (strontium, barium, calcium, magnesium), instead of the said
compound fluorides of aluminium and alkali-metals, the substance to be melted there-
with being the chloride of an earth-alkali-metal, preferably strontium chloride. For
the rest the process is carried out in the same manner as the former process. The
compound fluoride is melted together with the chloride, which has to be in excess, and
the molten mass is exposed to the action of an electric current, or of an alkali-metal
introduced thereinto.
In the first case the current disengages from a portion of the chloride of the earth-
alkali-metal the chlorine contained therein, which is conducted away; an equivalent
portion of the metal combines with the fluorine of the aluminium, the latter separates
out in metallic state, and a residue remains, consisting in fluoride and chloride of the
earth-alkali-metal.
Supposing the compound fluoride of aluminium and strontium and chloride of
strontium be employed, the process may be rendered by the equation:
(A), F. + 2 Sr F₂) + 6 Sr Cl₂ = 2 Al + 5 Sr F, + 3 Sr Cl, + 6 CI.
In the second case, in which an alkali-metal is added, this metal acts on the chloride
of the earth-alkali metal with the like effect as the electric current, inasmuch as it
disengages therefrom chlorine; but the chlorine, instead of being set free, combines
with the alkali-metal to form therewith alkalic chloride, as is shown by the following
equation:
(Al, F₁ + 2 Sr F₂) + 6 Sr Cl₂ + 6 Na = 2 Al + 5 Sr F₂ + 3 Sr Cl₂ + 6 Na Cl.

page_text: According to both equations the quantity of chloride of strontium supposed to be
employed, is such that three equivalents of the same are in excess, this amount having
been found advantageous in practice.
In view of rendering the molten mass more liquid, an alkalic chloride, preferably
chloride of potassium, may be added to the same; but, especially in this case, it is
requisite to have an ample excess of chloride of earth-alkali-metal, in order to prevent
the formation of the compound fluoride of aluminium and alkali-metal.
For the purpose of regenerating the solid residue obtained by the electric process, it
is mixed with a watery solution of aluminium-chloride in the proportion of about one
equivalent thereof to five equivalents of the fluoride; the mixture is boiled and the
water is evaporated off. The double salt as originally employed, is thereby reobtained
according to the following equation, in which the metal of the earth-alkilic chloride
used, is again supposed to be strontium :
5 Sr F. +3 Sr Cl₂ + AI, Cl₂ = (AL, F₁ + 2 Sr F₂) + 6 Sr Ch.
If the residue contains alkalic chloride, as is the case in the process carried out by
means of alkali-metals, or when alkalic chloride as such has been added to the molten
mass, the said residue is preferably first washed, all chlorides being thereby removed.
The fluoride of earth-alkali-metal then remaining is treated with aluminium chloride,
as in the first instance, and finally the requisite quantity of chloride of carth-alkali-metal
is added again.
If an alloy of aluminium with copper, iron, or other metal is to be produced
instead of pure aluminium, this may be attained in the electric process by employing
negative electrodes of the metal to be incorporated into the aluminium.
In the process in which the reduction is brought about by an alkali-metal, the
copper, iron, &c., is simply added to the molten mass.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The process of melting together a double fluoride of aluminium and of an earth-
alkali-metal (strontium, barium, calcium or magnesium) with a chloride of an earth-
alkali-metal and exposing the molten mass to an electric current or introducing
thereinto an alkali-metal, for the purpose of separating out aluminium, substantially as
described.
2. In the process claimed above, the introduction into the molten mass of a metal
adapted to combine with aluminium, the said metal being connected, when an
electric current is employed, to the electric circuit so as to form the negative
electrode, for the purpose of producing alloys of aluminium, substantially as
specified.
3. The process of regenerating the residue obtained by the processes claimed and
containing a fluoride of an earth-alkali-metal, by mixing the said residue, either in
its crude state or subsequent to a washing-operation, with a solution of aluminium
chloride, boiling the mixture and evaporating to dryness, substantially as set forth.
Dated the Sixth day of June 1888.
CARL PIEPER,
Agent.