Year: 1896

page_text: I, PAUL EMILE PLACET, of 18 Rue Denfert-Rochereau, Paris, France, Engineer,
do hereby declare the nature of this invention to be as follows:-
The aluminium of commerce is never pure; it contains carbon, iron, silicon,
sodium, nitrogen and other impurities, which considerably alter its properties.
Up to the present time only nitrate of potash has been employed for purifying
aluminium; this salt does not give a satisfactory result; it attacks all the vessels
in which it is melted, and, in consequence of its decomposition it introduces into
the aluminium detrimental bodies, which render it more liable to change and
diminish its resisting power.
My invention relates to a process which offers a double advantage; not only does
it allow of the elimination of the impurities of aluminium, but at the same time
and by the same operation it allows of the introduction into the aluminium of
bodies which improve its properties and increase its resistance.
I obtain this result by treating aluminium by means of very oxygenised salts,
such for example as the bichromates, permanganates chromic acid, and other
analogous compounds, which not only disengage, by simple heat, the oxygen,
which burns, and consequently eliminates, the impurities of the aluminium, but
also, which cannot by their decomposition, introduce into the aluminium any other
bodies than such as improve its properties.
I operate in the following manner. In a crucible or furnace lined internally
with magnesia or other suitable material, I put molten aluminium in contact with,
for example, bichromate of potass, and I stir the mixture energetically.
The heat first melts the bichromate and then decomposes it; the disengaged
oxygen, in burning, oxidises the impurities contained in the aluminium. When
the reaction is completed I add, in cases where it is necessary, a solvent, such as
chlorides, chromates, fluorides, or the like, which collect and hold the slags formed.
If the operation is carried out rapidly, the aluminium thus purified only con-
tains a small quantity of chromium which, so far from being detrimental, actually
improves its qualities.
If the operation is-effected slowly, the aluminium contains larger or smaller
quantities of chromium, according as the operation has lasted a longer or shorter
time.
This purified aluminium containing chromium serves for forming alloys with

page_text: the other metals, or for refining wrought or cast iron, steel, nickel, copper and
other metals into which it is desired to introduce at the same time a certain
quantity of chromium.
Instead of: bichromate of potass, above described as example, I may employ
bichromates of soda, or of ammonia,. chromic acid, bichromates of magnesia, of
lime, of alumina, or mixtures of such Bichromates. Bichromates of manganese,
of nickel, of copper, of zinc, of molybdenium, &c. may also be employed, when the
aluminium purified with these salts is intended to form alloys containing nickel,
manganese, copper, zinc, molybdenium, &c.
Instead of the bichromates may also be used permanganates chlorates, nitrates,
and other analogous compounds, which disengage oxygen simply on being heated,
but care should be taken not to employ the nitrates of soda, potass, or ammonia,
as is at present done, because these salts leave, as residue of their decomposition,
sola, potass or ammonia which are detrimental.
The addition of solvent which I have indicated above, for eliminating the slags,
is of advantage in certain cases, but is not indispensable; for example, when
bichromate of potass is used as in the above example this salt is decomposed by
the heat into oxygen, sesquioxide of chromium, and neutral chromate of potass;
this neutral chromate of potass is undecomposable by the heat and is liquid at the
temperature employed; it may in this case itself serve as solvent for collecting
and retaining the slags which are formed.
Dated this 15th day of December 1896.
ABEL & IMRAY,
Agents for the Applicant.
I, PAUL EMILE PLACET, of 18 Rue Denfert-Rochereau, Paris, France, 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:-
The aluminium of commerce is never pure; it contains carbon, iron, silicon,
sodium, nitrogen and other impurities, which considerably alter its properties.
Up to the present time only nitrate of potash has been employed for purifying
aluminium; this salt does not give a satisfactory result; it attacks all the vessels
in which it is melted, and, in consequence of its decomposition it introduces into
the aluminium detrimental bodies, which render it more. liable to change and
diminish its resisting power.
My invention relates to a process which offers a double advantage; not only does
it allow of the elimination of the impurities of aluminium, but at the same time
and by the same operation it allows of the introduction into the aluminium of
bodies which improve its properties and inci case its resistance.
I obtain this result by treating aluminium by means of very oxygenised salts,
such for example as the bichromates, permanganates, chromic acid, and other
analogous compounds, which not only disengage, by simple heat, the oxygen,
which burns, and consequently eliminates, the impurities of the aluminium, but
also, which cannot by their decomposition, introduce into the aluminium any other
bodies than such as improve its properties.
I operate in the following manner. In a crucible or furnace lined internally
with magnesia or other suitable material, I put molten aluminium in contact with,
for example, bichromate of potass, and I stir the mixture energetically..

page_text: The heat first melts the bichromate and then decomposes it; the disengaged
oxygen, in burning, oxidises the impurities contained in the aluminium. When
the reaction is completed I add, in cases where it is necessary, a solvent, such as
chlorides, chromates, fluorides, or the like, which collect and hold the slags formed.
If the operation is carried out rapidly, the aluminium thus purified only con-
tains a small quantity of chromium which, so far from being detrimental, actually
improves its qualities.
If the operation is effected slowly, the aluminium contains larger or smaller
quantities of chromium, according as the operation has lasted a longer or shorter
time.
This purified aluminium containing chromium serves for forming alloys with
the other metals, or for refining wrought or cast iron, steel, nickel, copper and
other metals into which it is desired to introduce at the same time a certain
quantity of chromium.
Instead of bichromate of potass, above described as example, I may employ
bichromates of soda, or of ammonia, chromic acid, bichromates of magnesia, of
lime, of alumina, or mixtures of such bichromates. Bichromates of manganese,
of nickel, of copper, of zinc, of molybdenium, &c., may also be employed, when the
aluminium purified with these salts is intended to form alloys containing nickel,
inanganese, copper, zinc, molybdenium, &c.
Instead of the bichromates may also be used permanganates, chlorates, nitrates,
and other analogous compounds, which disengage oxygen simply on being heated,
but care should be taken not to employ the nitrates of soda, potass,, or ammonia,
as is at present done, because these salts leave, as residue of their decomposition,
soda, potass, or ammonia which are detrimental.
The addition of solvent which I have indicated above, for eliminating the slags,
is of advantage in certain cases, but is not indispensable; for example, when
bichromate of potass is used as in the above example this salt is decomposed by
the heat into oxygen, sesquioxide of chromium and neutral chromate of potass;
this neutral chromate of potass is undecomposable by the heat and is liquid at the
temperature employed; it may in this case itself serve as solvent for collecting
and retaining the slags which are formed.
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 [
claim is :-
1. The herein described process for the purification of aluminium consisting in
stirring energetically the molten aluminium in contact with one or more of the
following salts or compounds: chromic acid, all kinds of bichromates, perman-
ganates and chlorates; the nitrates with the exception of nitrates of soda, of potash
and of ammonia.
1907