A Process of Obtaining Aluminium from its Ores or from Aluminiferous Earths, or Earths containing Alumina, and of Combining Aluminium with other Metals.
Year: 1887

page_text: Date of Application, 17th May, 1887.
Specification Accepted, 19th July, 1887.
A Process of Obtaining Aluminium from its Ores or from
Aluminiferous Earths, or Earths containing Alumina, and of
Combining Aluminium with other Metals.
I, WILLIAM AUGUSTUS BALDWIN, residing at 195, La Salle Street, Chicago, County
of Cook, and State of Illinois, one of the United States of America, Metallurgist, 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 invention consists in a process of producing aluminium from aluminiferous
minerals, or minerals containing alumina and in a process of combining aluminium
with other metals.
The process is carried out as follows: the mineral such as clay, corundum or
beauxite is finely pulverized mixed with pulverized charcoal and sodium chloride
(common salt) in or about in the proportions by weight of one part clay, for instance,
part charcoal and three parts sodium chloride.
These proportions may be varied according to the nature of the mineral or according
to circumstances but I have found by experience that they will ordinarily accomplish
the purposes sought and produce invariably good results. The compound described is
now fused or smelted in a suitable crucible or pot, a top stratum consisting of a
combination of sodium and aluminium, being the result. This stratum is carefully
skimmed off or otherwise separated from the remaining portion of the charge and
transferred into a second crucible or pot previously heated to a red heat and charged
with a sufficient quantity of sodium or sodium chloride to cover the sodium and
aluminium compound and the whole is again fused and finally run into heated molds
to prevent the too rapid congealing and to permit the aluminium to subside therein by
reason of its greater specific gravity.
In some cases the complete separation of the aluminium may not take place at the
second fusion and a third or fourth or more fusions in the presence of sodium or
sodium chloride may then be resorted to, I have however found as a rule that but one
fusion with sodium or sodium chloride is usually necessary to completely separate
the aluminium.
The final separation of the aluminium may also be effected in other ways than that
desired above. For instance after the charge of clay charcoal and sodium chloride has
D

page_text: been well fused or smelted I introduce into the fused mass strips, sheets or bars of
metal known to have an affinity for aluminium. These are alternately and repeatedly
immersed or plunged into the molten compound and withdrawn therefrom at short
intervals care being taken to prevent the introduced metal from melting. This
operation is continued until all the aluminium has been taken up thereby and from
these the aluminium may be recovered by any ordinary and well known chemical
process. Or the aluminium may be separated from the remaining constituents of the
fluid mass by forming an alloy thereof with other metals by introducing iron scraps,
bars or pigs, copper, zinc tin etc. and smelting the same with or in the fused or smelted
clay and sodium chloride...In this case the quantity of metal introduced should be
approximately equal in weight to the charge of clay (or other mineral containing
alumina) employed.
When the alloy is completed I draw the whole charge off into heated molds in which
the alloy by reason of its greater specific gravity subsides and after cooling may
readily be separated from the remaining parts and the aluminium recovered therefrom
by ordinary chemical processes or the alloy may be used as such for any purpose.
Aluminium is readily volatilized at comparatively low temperatures as compared
with the temperatures required to volatilize other metals and I believe from observa-
tion that the sodium chloride not only acts as a flux but effectually prevents this
volatilization under such temperatures as are required to melt iron.
Finally instead of proceeding to recover the aluminium from a metal charged
therewith or from an alloy and instead of forming absolute alloys by fusion for use as
such I may utilize the properties of the aluminium by simply combining it in various
proportions with other metals by absorption.
I have discovered that aluminium may be combined in variable proportions with all
metals that have an affinity for aluminium without alloying the same by fusion. I have
found that those metals will absorb aluminium even to sursaturation if I may so term
it and that the aluminium may be recovered by ordinary chemical processes as described
above. I have also found that by combining the aluminium with other metals in
varying proportions by absorption, the texture, tensile strength, hardness and brittle-
ness may be varied in proportion to the quantity of aluminium absorbed thereby.
I have also discovered that the absorption of the aluminium by another metal having
an affinity therefor will take place whether the metal is brought in absolute contact
with the molten or fused aluminium or whether simply brought in close proximity
thereto. This may or may not be due to the magnetic properties of aluminium and
other metals, a fact which I have as yet not been able to determine.
In the treatment of metals such as iron, copper, zinc, tin or other metals having an
affinity for aluminium with a view to combining the latter metal therewith by
absorption to change the nature of such metal to a greater or less extent by the
combination, the article to be treated may be plunged or immersed in the fused
contents of the smelting pot or other vessel until it has absorbed the desired quantity
of aluminium.
The time of immersion and absorption will of course depend upon the amount of
aluminium to be combined with the article as well as upon the degree of affinity of
the metal of which such article is made for aluminium and upon the mass of metal in
such article.
Sheet iron for instance of the thickness ordinarily used for stove pipes may be
immersed for about five minutes and then withdrawn. This is repeated about three
times in succession without allowing the sheet iron to cool after each withdrawal from
the fused charge and allowing the said sheet iron to cool slowly after the last immersion.
The time or duration of immersion increases in proportion to the thickness of the
metal treated. For instance wrought or cast iron bars of about an inch in thickness
should remain in the fused charge about, 20, minutes at each immersion to fully charge
the same with aluminium. Articles of metal so treated are effectually protected
against atmospheric or other oxydizing influences and their quality greatly improved.
The combination of the aluminium with another metal may also be effected by bringing
the two in close proximity as above stated. The metal or metallic article being in this

page_text: case brought near the fused aluminium turning the article occasionally to present its
different faces to the aluminium to better effect the combination by absorption. In
this method the combination is effected more slowly than when the two metals are
brought in direct contact as above described.
In either case the metal or metallic article to be charged with aluminium should be
heated before immersion in or exposure to the aluminium, the combination taking
place more rapidly than when the metal or metallic article is cold.
Sheet metal may when so treated be employed for ship bottoms in lieu of copper,
and cast or wrought iron may be employed for the manufacture of tools, cutlery, &c.
in lieu of steel, the iron being susceptible of a high polish the same as the best steel.
In fact the range of use of metals combined with a greater or less quantity of
aluminium is almost illimited whether it be iron, copper, zinc, tin &c. &c.
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. The hereindescribed process of obtaining aluminium from its ores or from
aluminiferous earths or earths containing alumina which consists in smelting the same
with sodium chloride in the presence of carbon and resmelting the sodium and
aluminium compound obtained with sodium or sodium chloride and finally transferring
the charge to heated moulds and allowing the aluminium to subside as described.
2. The hereindescribed process of obtaining aluminium from its ores or from
aluminiferous earths or earths containing alumina which consists in smelting the same
with sodium chloride and another metal in the presence of carbon and recovering the
aluminium from the alloy by ordinary chemical processes as described.
3. The hereindescribed process of combining aluminium with other metals which
consists in smelting aluminium ore, or aluminiferous earths, or earths containing
alumina, with sodium chloride in the presence of carbon and immersing or plunging
the metal to be combined with aluminium into the molten mass or bringing said
metal into close proximity to the sodium and aluminium compound, substantially as
and for the purpose specified.