Improvements relating to the Extraction of Aluminum from Substances Containing the same.
Year: 1887

page_text: This Specification was, upon the 30th day of April 1889, Amended under
Sections 18 to 21 of the Patents, Designs, and Trade Marks Act, 1883.
PROVISIONAL SPECIFICATION.
Improvements relating to the Extraction of Aluminum from
Substances Containing the same.
I, Professor CURT NETTO, of 16 Lindenanstrasse, Dresden, Germany, Engineer
do hereby declare the nature of this invention to be as follows:-
My invention relates to the preparation of metallic aluminium. The process of
preparing aluminium from sodium and cryolite or aluminium chloride hitherto
known consists essentially in mixing the said bodies with a flux in a more or less
finely divided state and fusing the same together in a crucible or reverberatory
furnace.
This process has serious defects, that is to say, the yield of metallic aluminium is
small in comparison with the quantity of aluminium contained in the mixture, and
For example, instead of the
also relatively to the quantity of sodium employed.
13 per cent. of aluminium which cryolite contains, only from about 4 to 5 per cent. is
obtained, accordingly only from 30 to 40 per cent. of aluminium is extracted from
the mixture the rest remaining in the slag. When using 100 parts by weight of
sodium 40 parts by weight of aluminium can theoretically be extracted, whereas
actually only about 12.5 parts by weight of aluminium are obtained. Therefore
about 70 per cent. of the sodium employed is lost. The aluminium obtained is
moreover impure, containing iron, if the preparation has taken place in iron crucibles,
and silicon if argillaceous vessels have been used; so that the total of the impurities
After the decomposition is ter-
is not below 3 per cent. and as a rule far higher.
iminated, the aluminium is never united into a coalescent lump (regulus) but is in the
form of pellets which in part exceedingly small, are distributed through the whole
slag, and the union of these particles is effected only with great trouble whilst loss
cannot be obviated. Lastly, the vessels employed, especially argillaceous vessels, are
so strongly attacked in the process that they can only be used for a short time.
These defects can be easily explained by observing what takes place during the
treatment of the charge. If the latter consisting, for instance, of cryolite, metallic
sodium and a flux, such as a chloride of the light metals or alkaline earths, is sub-
jected in a crucible or reverberatory furnace to an elevated temperature, the sodium,

page_text: fusing at 95 degrees centigrade, passes into a liquid state at the commencement of
the process, percolates through the mass, and, despite its small specific gravity, collects
at the bottom of the crucible or reverberatory furnace. The fused sodium, however,
cannot on its way downwards, produce any effect upon the cryolite, as the tempera-
ture for such action is far too low at this stage of the process.
With the increase of
the temperature the aluminium fluoride is no doubt decomposed here and there by the
sodium vapours rising in the mass, but a large portion of the sodium will volatilize
before the necessary temperature sets in. Although the sodium vapours act upon the
cryolite at red-heat and prior to the fusion of the same, they do not completely mix
therewith but pass upwards through cracks in the charge, and especially, along the
walls of the crucible, that is to say, between the walls and the contracted mass, and
burn without being used, as soon as they reach the air on the surface.
When the charge has at last become fused, the greater part of the sodium has thus
escaped. It is therefore requisite to add to the mass considerably more sodium than
is theoretically needful in order to ensure the greatest possible yield of aluminium
from the crvolite.
The solubility of aluminium in molten cryolite is a further cause of considerable
losses of aluminium. "This phenomenon can be readily proved by throwing
a piece of
aluminium into molten cryolite, the aluminium disappearing after a short time. The
consequence of this property of aluminium is apparent. As above stated the action of
the sodium upon the cryolite partly takes place prior to the melting of the latter, so
that before the mixture passes into the liquid state innumerable pellets of metallic
aluminium are distributed in the mass. When the cryolite is fused these pellets
slowly sink, but in doing this they come into contact with fresh parts of the cryolite,
whereby they are, in a great measure, re-dissolved and disappear. Besides, the mass
owing to its pasty condition and whose specific gravity differs but little from that of
aluminium, offers an energetic resistance to the union of the aluminium pellets dis-
tributed therein.
If attempts are made to effect the union of the finely divided aluminium by a
stronger heat and longer fusion, the yield will still further be diminished because
of the re-dissolution of the aluminium.
Moreover, the union of the aluminium particles is rendered even more difficult by
proceeding in this manner because the mass, when the fusion is continued and the
temperature is raised, becomes more and more pasty in consequence of volatilization.
To collect the pellets after the cooling of the slag, a wet dressing process cannot be
employed, because if water be added the slag has a dissolving effect upon the
aluminium even at the ordinary temperature.
The deleterious action of the vessels in which the decomposition of the cryolite
takes place can likewise be easily explained. If iron crucibles are made use of,
the aluminium obtained is comparatively free from silicon, but it contains iron.
Again if argillaceous crucibles are used the sodium vapours passing along between the
wall of the crucible and the contents thereof separate silicon from the red hot wall of
the crucible. The aluminium also, separated in the course of the process, acts in like
manner. These effects are the more marked as the action of the sodium upon the
aluminium salt in this process is slow.
This explains the rapid destruction of the crucibles, which is so very considerable
that fireclay crucibles can seldom be used for more than one operation.
If a reverberatory furnace is used, the aforesaid defects are less pronounced, but
owing to the large surface of the bath in comparison to the depth of the same
there is. on the one hand, a great loss of aluminium fluoride by valatilization;
and, on the other hand, the sodium, on account of the low column of liquid has
less occasion to act upon the aluminium fluoride. Neither is the prejudicial action
of the material of which the hearth is composed excluded in reverberatory furnaces,
These impurities are the more inconvenient because the subsequent purification
either would involve great loss, or, as for instance, as far as silicon is concerned,
could not be carried out at all.

page_text: All the above disadvantages exist, although in some cases in a less degree, it the
cryolite is wholly or partially replaced, for example, by aluminium chloride.
Although in presence of aluminium chloride the vessels are less powerfully attacked,
and the separated aluminium unites better, the aluminium chloride, by reason of
its volatility, escapes still more easily from the action of the sodium than
aluminium fluoride or the double fluoride of aluminium and sodium, so that also
here the yield, as compared with the theoretical quantity, is by far too low.
Moreover, the production of aluminium chloride is very expensive.
Extensive observations of the described circumstances occurring in the prepara-
tion of aluminium have led me to discern that in order to obviate the defects and
losses it is necessary.
a) To separately prepare the bodies which are to act upon each other for the
subsequent decomposition.
b) To effect the decomposition of the bodies which are properly prepared as rapidly
as possible.
c) To suddenly interrupt the process on the termination of the decomposition.
The process which I preferably employ, observing the conditions above stated, is
as follows: 100 parts by weight of cryolite and from 30 to 100 parts by weight of
decrepitated common salt are fused in a fire-clay crucible at red-heat, a cover being
put on to prevent volatilization. As soon as the mass has become completely liquid,
35 parts by weight of sodium are introduced in one or more pieces on to the bottom
of the bath by means of an instrument to be hereinafter described. The decomposition
commences at once and is completed in a few moments or minutes whereupon the
crucible is taken from the fire and its contents are poured into a crucible-shaped cast
iron mould to cause the rapid congelation of the mass. After the solidification of the
latter the mould is inverted, and the aluminium which is united into a single lump
near the hottom of the mould is separated from the slag by a few strokes of a
hammer.
For the process to perfectly succeed it is of the utmost importance that the mass
shall be quite liquid prior to the introduction of the sodium.
Also on the one hand, the smelting must not last too long, so that the dissolution
of silicon is limited; and, on the other hand, it must not take place at too high a
temperature by reason of the easy volatilization and the consequent stubbornness of
the bath.
To obviate explosions when introducing the sodium into the liquid mass, the
sodium must not have any hollow spaces within it, nor contain any humidity, oil,
asphaltum or other hydrocarbons. It is therefore preferable to remelt the sodium in
a closed iron crucible immediately before its employment, to pour it into suitablo
moulds, and protect it against moisture after the congelation. When performing
this remelting, further precautionary measures are not required, except that as low a
temperature as possible must be used. The sodium must be introduced into the bath
in such a manner that the metal does not fuse on the surface of the bath, as it would
be as hard to submerge the sodium, which is specifically lighter, as it would be for
instance to put oil under water. The sodium would in this case burn away for the
most part without being used.
In order to rapidly introduce the sodium in a solid state into the liquid mass and
on to the bottom of the crucible, the instrument hereinafter described is advantageously
employed.
This instrument consists of a simple iron rod to which the piece of sodium to be
introduced into the bath is applied, and of a plate-shaped disc, provided with holes
and a radial slit, which disc is attached to one end of a second rod.
To obviale cooling as much as possible, the disc is heated to red heat, and, prior to
the introduction of the sodium into the crucible, is placed over the sodium. The
whole is then suddenly immersed as far as the bottoin of the crucible before the
sodium has time to melt on the surface of the bath and to cominence burning.
The disc prevents the sodium, which is specifically lighter, from rising after the

page_text: mersion, whilst the perforations formed in the disc admit of the fused sodium
rising in a divided state.
The immediate occurrence of a decomposition is perceived by the violent ebullition
of the entire mass and also by the trembling of the two iron rods and is accompanied
by a flame. As soon as these phenomena have ceased, which takes place after a few
moments or minutes the decomposition may be considered complete and the contents
of the crucible can be discharged.
By reason of the exceedingly short duration of the decomposition the introduction
of the iron instrument into the bath has no disadvantageous effect upon the purity of
the aluminium.
The higher the stratum of the molten cryolite in the crucible the more completely
will the escape of sodium vapours be prevented. This height should accordingly not
be less than 30 centimetres.
By the described process a series of advantages are obtained, that is to say;
chiefly the sodium cannot escape without having been used, as in the processes
heretofore known. As the sodium is suddenly introduced into a medium which is
heated far beyond its degree of volatilization, the entire mass of the bath is furrowed
through by the sodium vapours, and the sudden decomposition occurring at all points
of the liquid will give rise to violent ebullitious of the bath, so that the molten and
evaporated sodium mixes as perfectly as possible with the molten cryolite. As the
sodium cannot moreover be burnt because it is completely shut off from air by the
bath itself, nearly all the sodium is rendered available for the decomposition. In
consequence of the sudden decomposition not only the thorough mixing of the
sodium with the bath is effected but a considerable increase of the temperature takes
place. The bath which previously presented a sirupy consistency, accordingly
becomes as fluid as water, so that the union of the aluminium distributed in the bath
is promoted to such a degree that, when the contents of the crucible are poured out,
only a single coalescent lump of aluminium is found in the congealed mass, whilst
the slag contains only exceedingly small aluminium pellets which are not perceptible
to the naked eye.
As the decomposition passes off very smoothly, and the mass is quickly poured
from the crucible, a redissolution of the aluminium will take place only in a very slight
degree, thus ensuring a high yield on the one hand, and a pure product on the other.
In this manner, when, for example, the weight of the sodium used is only 35 per
cent. of that of the cryolite, up to 77 per cent. of the aluminium contained therein
can be obtained, that is to say more than double the quantity heretofore obtainable.
In order to obtain the infinitely small particles of aluminium that are present after
the termination of the decomposition having escaped union with the lump, it is useful
to stir the bath with a copper rod. In this operation the said particles of aluminium
are deposited upon the copper rod, aluminium bronze being formed. In like manner
copper vessels or other articles of copper can be coated upon their surfaces with
layers of aluminium bronze by immersion into the bath immediately after the
termination of the decomposition. The same object can be attained by immersing
other metals, if such metals form alloys with aluminium.
A further very material advantage of the process consists in the production of
aluminium that is almost chemically pure, and especially free from silicon. This fact
can be explained on the one hand by the short duration of the action of the sodium
and the liquid aluminium, produced upon the walls of the vessels, as compared with
the known processes; and on the other hand from the circumstance that the fused
common salt forms a kind of glaze upon the walls of the crucible, thus preventing
the passage of the sodium and aluminium to the said walls.
Aluminium which was obtained by the described process contained for instance
only from 10 to 1.5 per cent. of impurities, whereas the usual aluminium of
commerce as already stated, contains about 3 per cent. of impurities, a difference
which enormously affects important physical qualities of the metal (strength,
ductibility, malleability, appearance, conductibility of electricity).

page_text: For the same reason the walls of the vessels are scarcely attacked at all, but appear
after their use perfectly smooth and as if glazed whereas they have heretofore always
had corroded surfaces. Even ordinary crucibles of fire-clay can therefore be used
several times.
For these reasons the cost of producing aluminium, quite apart from the great
purity of the product and the consequent suppression of the further purification of
the same, amounts to from about one-third to one-fourth the cost of the processes
hitherto employed.
The described process is susceptible of numerous modifications without the essential
nature of the same being departed from. Thus it can be made use of not only for
the decomposition of natural or artificial cryolite, but also of the compounds of
aluminium with chlorine, bromine, iodine, or fluorine, and mechanical mixtures of
these compounds, or double salts of the said compounds with the corresponding ones
of sodium or potassium.
Instead of common salt, which is designed to lower the fusing point of the cryolite,
to increase the fluidity of the mass and to protect the smelting vessels from injury,
other fluxes, especially compounds of chlorine or fluorine with the metals of the
alkalies or alkaline earths, or mixtures of the said bodies can be employed. The
quantitative proportions necessary in this case are substantially the same as those
above given for the use of cryolite. The decomposition of the molten aluminium
compound can moreover be effected, instead of by sodium, by other metals of the
alkalies or alkaline earths, for example by potassium or magnesium.
Instead of immersing the reducing metal in the liquid bath by itself as set forth, it
can previously be united with part of the aluminium compound to be decomposed or
with mercury (for the purpose of increasing the specific weight of the metal to be
introduced into the bath); or the molten aluminium compound to be decomposed can
be admitted to the molten decomposing metal. A mechanical mixture of the
aluminium compound to be decomposed and the decomposing metal can also be put
in a molten flux that may consist of one of the said compounds (or mixtures of the
sume) of chlorine or fluorine with the metals of the alkalies or alkaline earths.
In this case an immediate decomposition of the aluminium compound is likewise
caused on the introduction of this mixture into the liquid bath.
Lastly, the decomposition instead of being performed in crucibles can be effected
in reverberatory furnaces, in closed furnaces, or in receptacles which permit their
position to be changed, such as converters, revolving furnaces or the like to promote
the decomposition.
A
M. 1007
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION (AMENDED).
Improvements relating to the Extraction of Aluminium from
Substances Containing the same.
I, Professor CURT NETTO, of 16 Lindenaustrasse, Dresden, in the Empire of
Gormany, Engineer, 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 relates to the manufacture of metallic aluminium. Amongst the
processes of preparing aluminium from sodium and cryolite or aluminium chloride,
some thereof consist essentially in mixing the said bodies with a flux in a more or
less finely divided state and fusing the same together in a crucible or reverberatory
furnace.
These processes have serious defects, that is to say, the yield of metallic aluminium
is small in comparison with the quantity of aluminium contained in the mixture, and
also relatively to the quantity of sodium employed.
When using in the known sodium process 100 parts by weight of sodium, 40 parts
by weight of aluminium should theoretically be extracted, whereas, actually, in most
cases only about 12.5 parts by weight of aluminium would be obtained. Therefore about
70 per cent of the sodium employed is wasted. The aluminium obtained is moreover
impure, containing iron if the preparation has taken place in iron crucibles, and
silicon if argillaceous vessels have been used, so that the total of the impurities is not
below 3 per cent and as a rule far higher. After the decomposition is terminated, the
aluminium is never seldom united into a coalescent lump (regulus), but is in the form of
pellets which, in exceedingly small parts are distributed through the whole slag, and
the union of these particles is effected only with great trouble, whilst waste cannot be
obviated. Lastly, the vessels employed, especially argillaceous vessels, are so strongly
attacked in the process that they can only be used for a short time.
These defects can be easily explained by observing the changes which take place
during the treatment of the mixture. If the latter consisting, for instance, of
cryolite, metallic sodium and a flux, such as a chloride of the light metals or alkaline
earths, is subjected in a crucible or reverberatory furnace, to a high temperature, the
sodium. fusing at 95 degrees Centigrade, passes into a liquid state at the commence-
ment of the process, percolates through the mass, and notwithstanding its small
specific gravity, collects at the bottom of the crucible or reverberatory furnace. The
fused sodium, however, cannot, on its way downward produce any effect upon the
cryolite, as the temperature for such action on the cryolite is far too low at this
stage of the process. With the increase of temperature, the aluminium fluoride is no
doubt decomposed here and there by the sodium vapours rising in the mass, but a
large portion of the sodium will volatilize before the necessary temperature is attained.
Although the sodium vapours act upon the cryolite at red heat and prior to the fusion
of the same, they do not completely mix therewith but pass upward through the

page_text: mixture and, especially along the walls of the crucible that is to say, between the walls
and the contracted mass, and burn without being used as soon as they reach the air at
the surface of the mass.
When the mechanical mixture has at last become fused, the greater part of the
sodium has thus escaped. It is therefore requisite to add to the mass considerably
more sodium than is theoretically needful, in order to ensure as far as possible the
greater proportion of the aluminium being obtained from the cryolite.
Now although this may actually have been effected the solubility of aluminium in
molten cryolite is a further cause of a considerable loss of aluminium. This
phenomenon can be readily proved by throwing a piece of aluminium into molten
cryolite, the aluminium disappearing after a short time. The consequence of this
property of aluminium is apparent. As above stated the action of the sodium upon
the cryolite partly takes place prior to the melting of the latter, so that before the
mechanical mixture passes into the liquid state innumerable pellets of metallic
aluminium are distributed in the mass. When the cryolite is fused the pellets slowly
sink to the bottom, but in doing this they come into contact with fresh parts of the
cryolite; whereby they are in a great measure re-dissolved and disappear, so that a
renewed decomposition becomes necessary.
The more or less stubborn part of the mass, however, whose specific gravity differs
but little from that of aluminium, offers an energetic resistance to the union of the
aluminium pellets distributed therein.
If the union of the finely divided aluminium is effected by a higher degree of heat
and longer fusion, the yield is still further diminished because of the redissolution of
the aluminium.
Moreover, the union of the aluminium particles is rendered even more difficult in
this process because the mass, when the fusion is continued and the temperature--is
high, becomes more and more stubborn in consequence of volatilization. To collect
the several pellets after the cooling of the slag, a wet dressing process cannot be
employed, because if water be added a dissolving effect is produced upon the
aluminium at the ordinary temperature.
The deleterious action of the vessels in which the decomposition of the cryolite
takes place can likewise be easily explained. If iron crucibles are made use of, the
aluminium obtained is comparatively free from silicon, but it contains iron. Again
if argillaceous crucibles are used, the sodium vapours passing along between the wall
of the crucible and the contents thereof separate silicon from the red-hot wall of the
crucible. The aluminium also separated in the course of the process acts injuriously
upon the vessels. Thus the longer the action of the sodium and aluminium lasts,
the more impure will the aluminium be rendered] by the silicon. This explains the
rapid destruction of the crucibles, which, is so very considerable that fire-clay crucibles
can seldom be used for more than one operation.
If a reverberatory furnace is used. the aforesaid defects are less pronounced, but
owing to the large surface of the bath in comparison with the depth of the same
there is on the one hand a great loss of aluminium fluoride by volatilization, and on
the other hand the sodium, on account of the low column of liquid, has less occasion
to act upon the aluminium fluoride, moreover the action of the material of which
the hearth is composed, upon the metal injuriously affects the purity of the latter.
These impurities are the more inconvenient because the subsequent purification
either involves great loss, or, as for instance, as far as the quantity of silicon is
concerned, cannot be carried out with advantage.
All the above disadvantages exist, although in some cases in a less degree, if the
cryolite is wholly or partially replaced for example by aluminium chloride. Although
in presence of aluminium chloride the vessels are less powerfully attacked, and the
separated aluminium unites better, yet the aluminium chloride, by reason of its
volatility, escapes still more easily from the action of the sodium than aluminium
fluoride or the double fluoride of aluminium and sodium so that also here the yield, as
compared with the theoretical quantity, is by far too low. Moreover, the production of
aluminium chloride is very expensive.

page_text: Extensive observations of the described changes occurring in the preparation of
aluminium have led me to the conclusion that in order to obviate the defects and losses
it is very advantageous.
First, to separately prepare the bodies which are to act upon each other for the
subsequent decomposition.
Second, to effect the decomposition of the bodies which are properly prepared as
rapidly as possible. Third to suddenly interrupt the process on the termination of the
decomposition.
The process which I preferably employ, observing the conditions above stated, is as
follows, 100 parts by weight of cryolite and from 30 to 10 parts by weight of
decrepitated common salt are fused in a fire-clay crucible at red-heat, a cover being
put on to prevent volatilization. As soon as the mass has become completely liquid,
35 parts by weight of metallic sodium are introduced in one or more pieces on to
the bottom of the bath by means of an instrument to be hereinafter described. The
decomposition commences at once, and is completed in a few moments, minutes where-
upon the crucible is taken from the fire and its contents are poured into a crucible-
shaped cast iron mould to cause the rapid congelation of the mass.
solidification of the latter the mould is inverted, and the aluminium, which is united
into a single lump near the bottom of the mould, is separated from the slag by a few
strokes of a hammer.
After the
For the process to perfectly succeed it is of the utmost importance that the mass
shall be quite liquid prior to the introduction of the sodium.
Also on the one hand, the smelting must not last too long so that the dissolution of
silicon is limited and on the other hand it must not take place at too high a
temperature by reason of the easy volatilization and the consequent stubbornness of
the bath.
To obviate explosions when introducing the sodium into the liquid mass, the sodium
must not have any hollow spaces within it nor contain any humidity or any oil,
asphaltum or other hydrocarbons. It is therefore preferable to remelt the sodium in
a closed iron crucible immediately before its employment; to pour it into suitable
moulds, and protect it against moisture after the congelation. When performing this
remelting, farther precautionary measures are not required except that as low a
temperature as possible must be used, and water must of course be excluded. The
sodium must be introduced into the bath in such a manner that the metal does not
fuse on the surface of the bath, as it would be difficult to submerge the sodium which
is of a lighter specific gravity. The sodium would in this case largely burn away
without being used.
In order to rapidly introduce the sodium in a solid state into the liquid mass and
on to the bottom of the crucible I may advantageously employ the instrument
represented in the accompanying drawings the figures of which are hereinafter
referred to.
of
This instrument consists of a simple iron rod & Figure 1, to which the piece
sodium to be introduced into the bath is applied, and of a plate-shaped disc a provided
with holes i Figures 2 and 3, which disc is secured to the end of a rod and has a
radial slit b. In Figure 4 the introduction of sodium into the bath is illustrated.
Figure 5 is a horizontal section on the line A, B Figure 4.
To obviate cooling as much as possible, the disc a is heated to red-heat, and prior
to the introduction of the sodium into the crucible T, is placed over the sodium in
the position shown in Figures 4 and 5. The whole is then suddenly immersed as far
as the bottom of the crucible T, hefore the sodium has time to melt on the surface of
the bath and to commence burning.
The disc a prevents the sodium, which is specifically lighter, from rising after the
immersion, whilst the perforations i formed in the disc admit of the fused sodium
rising in a divided state,
The immediate occurrence of a decomposition is perceived by the violent ebullition
of the entire mass and also by the trembling of the two iron rods s and t, and is
accompanied by a flame. As soon as these phenomena have ceased, which takes

page_text: place after a few minutes, the decomposition may be considered complete, and the
contents of the crucible can be discharged.
By reason of the exceedingly short duration of the decomposition the introduction
of the iron instrument into the bath has no d'sadvantageous effect upon the purity of
the aluminium.
The higher the stratum of the molten cyrolite in the crucible the more completely
will the escape of solium vapours be prevental.
By the described process many advantages are obtained that is to say ;—The sodium
cannot easily escape without having been used as is the case in the processes hereto-
fore known. As the sodium is suddenly introduced into an agent that is heated fur
beyond its degree of volatilization, the entire mass of the bath is penetrated by the
sodium vapours, and the decomposition suddenly occurring at all points of the liquid
gives rise to violent ebullitions of the bath so that the molten and evaporated sodium
mixes as perfectly as possible with the molten cryolite. Also As the sodium cannot
moreover be burnt so long as it is completely shut off from air by the bath itself,
nearly all the sodium is rendered available for the decomposition. In consequence of
the sudden decomposition not only the thorough mixing of the sodium with the bath
is effected but there is also a considerable increase of temperature. The bath which
previously was of a viscid consistency becomes very fluid so that the union of the
aluminium distributed in the bath is promoted to such a degree that, when the confents
of the crucible are poured out, a single coalescent lump of aluminium is found in the
congealed mass, whilst the slag contains only exceedingly small aluminium pellets
which in most cases are not perceptible to the naked eye.
As the decomposition, which passes off very smoothly and the pouring of the mass
from the crucible are rapidly effected a redissolution of the aluminium will hardly
take place, thus ensuring a high yield on the one hand, and a purer product than
heretofore on the other.
The described process is susceptible of numerous modifications without the essential
nature of the same being departed from. Thus it can be made use of not only for
the decomposition of natural or artificial cryolite, but also of the compounds of
aluminium with chlorine, bromine, iodine or fluorine, and mechanical mixtures of
these compounds, or double salts of the said compounds with the corresponding ones
of sodium or potassium.
Instead of common salt, which is designed to lower the fusing point of the cryolite,
to increase the fluidity of the mass, and to protect the smelting vessels from injury,
other fluxes, especially compounds of chlorine or fluorine with the metals of the
alkalies or alkaline earths, or mixtures of the said bodies can be employed. The
quantitative proportions necessary in this case are substantially the same as those
above given for the use of cryolite. The decomposition of the molten aluminium
compound can moreover be effected, instead of by sodium by other metals of the
alkalies or alkaline earths.
Instead of immersing the decomposing metal in the liquid bath by itself as set forth,
other means of obtaining the instantaneous reaction can be employed, for example, the
decomposing metal can previously be united with part of the aluminium compound to
be decomposed or with mercury (for the purpose of increasing the specific weight of
the metal to be introduced into the bath); or the molten aluminium compound to
be decomposed can be admitted to the molten decomposing metal. A mechanical
mixture of the aluminium compound to be decomposed and the decomposing metal
can also be put in a molten flux that may consist of one of the said compounds (or
mixtures of the same) of chlorine or fluorine with the metals of the alkalies or alkaline
earths.
In this case an immediate decomposition of the aluminium compound is likewise
cansed on the introduction of the mixture into the liquid bath.
In lieu of the apparatus herein before described and represented in Figures 1 to 5
of the accompanying drawing, other suitable devices by which the sodium is intro-
duced into the liquid bath can be used for carrying the present process into
effect.
•

page_text: This
Thus the device for immersing the solid sodium can be of various forms.
device which may be appropriately designated a "diver" can be of the shape of a
bell or consist of a hollow vessel of any shape such as a sphere, cylinder, ellipsoid. and
having perforated walls. Figure 6 shows a diver" constructed according to the
present invention.
"
e
The hollow vessel a made of thin wrought iron is provided with a number of holes i,
and is fixed to the iron rod t. This vessel is set into the divided mould h which
tightly encloses the same; liquid sodium is thereupon introduced through the funnel.
corresponding with the opening f; until a is full, the sodium is allowed to solidify,
and the mould is then removed from the vessel a. The diver thus produced is now
ready for use.
The decomposition instead of being performed in crucibles can be effected in
reverberatory furnaces, in close furnaces, or in receptacles which permit their position
being changed such as converters, revolving furnaces or the like, to promote the
decomposition.
Thus the present process can be variously modified without departing from the
nature of the present invention.
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
In the manufacture of aluminium from the compounds of the same with chlorine,
bromine, iodine, fluorine, or the double compounds of aluminium with the aforesaid
bodies and potassium or sodium by means of the metals of the alkalies or alkaline
earths.
First. The process of introducing the decomposing metal in a solid state by means
of a diver such as shown in Figures 1 to 6 into the molten aluminium compound to
be decomposed thereby effecting a practically instantaneous decomposition and there-
fore upon terminating the operation substantially as and for the purposes specified.
Second. Immersing the solid sodium or other decomposing metal into previously
molten cryolite or other aluminium compound substantially as described.
Third. The diver shown in Figures 1 to 6 substantially as described.
Fourth. The production of aluminium from the ores or compound substances con-
taining it by the improved process of treatment substantially as herein described.
Dated this 21st day of December 1887.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.