Improvements in Processes for the Manufacture of Certain Metals and Alloys, especially for the Manufacture of Magnesium and its Alloys.
Year: 1896

page_text: Date of Application, 3rd Oct., 1890
Complete Specification Left, 5th July, 1897-Accepted, 2nd Oct., 1897
Complete Specification Left, 5th July, 1897-Accepted, 2nd Oct., 1897
PROVISIONAL SPECIFICATION.
Improvements in Processes for the Manufacture of Certain Metals
and Alloys, especially for the Manufacture of Magnesium and its
Alloys.
I, ALFRED LE REDOTTE, of 12 Boulevard Bonne Nouvelle, Paris, in the Republic
of France, Chemist, do hereby declare the nature of this invention to be as
follows:-
This invention relates to the manufacture, by electrolysis only or by electrolysis
and dissociation together, of the following metals viz.:-magnesium, aluminium,
lithium, sodium, potassium, calcium, barium and strontium, either alone, com-
bined, or alloyed, in any proportion, with metals or metalloids susceptible of
forming alloys or combinations with the said metals consequent upon a reduction
of their fusible. salts or of their mixture by electricity.
The metal to which I have more particularly directed my attention is
magnesium.. I will therefore begin by describing the different phases of the
manufacture of this metal and its alloys.
The primary substances for the manufacture of magnesium are carnallite
(double chloride of potassium and magnesium); tachydrite (double chloride of
calcium and magnesium); double chloride of sodium and magnesium; kieserite;
fluoride of magnesium; the double fluorides of magnesium; and chloride of
magnesium obtained from salt-marshes or from any other source.
I extract the magnesium from infusible minerals in the form of a chloride or
of fluorides.
With reference to double chlorides, the preliminary treatment, for rendering
these products suitable for the manufacture of the metal, consists of a desiccation
in a stove or drying chamber at a temperature which is at first moderate, in order
to avoid the fusion of the products in their water of crystallization, and then
higher than 100° C. so as to hasten the drying. The desiccation is completed by
fusion in the crucible.
The fused product is run off, either directly into the apparatus in which it is
to be treated, or upon metallic or terra cotta plates and kept in hermetically
closed vessels.
When I employ simple chloride of magnesium, I find it necessary to have
recourse to a special process of fusion with a view to preventing the decomposition
of the salt by the water which it contains during the desiccation.
This process is carried out in the following manner:
The simple chloride of magnesium is intimately mixed with a proportion of
hydrochlorate of ammonia, such proportion varying according to the quantity of
water contained by the chloride it may even be as great as one half with very
moist chlorides. This mixture is then dried in a stove or drying chamber, care
being taken not to exceed 100° C. which is the temperature at which hydro-
chlorate of ammonia commences to volatilize. Care should also be taken, during

page_text: the drying process, to break up the agglomerated masses which form, as their
centres would only dry imperfectly.
The arrangement of the stove or drying chamber which I have found most
advantageous consists in a series of tablets superposed as baffle plates, between
which a current of hot air circulates.
**
The drying operation finished, I introduce the mixture into crucibles of
plumbago or of refractory earth which are placed in a blast or gas furnace which
is slowly raised to a bright red heat, which temperature I maintain until the
hydrochlorate of ammonia is completely driven off. This furnace is divided
horizontally into two compartments by an impermeable slab which is provided with
openings into which the crucibles fit, in this manner the liberated hydrochlorate
of ammonia is isolated from the furnace gases and proceeds to a series of cold
chambers which communicate with the upper portion of the furnace. When such
liberation is completed the opened crucible contains fused chloride of magnesium
which I run off in the manner already described with reference to double chlorides,
or in a continuous manner through an orifice provided for the purpose in the
lower portion of the crucible; in this latter case, after each tapping, the crucible
is recharged by means of a funnel provided with a stoppering device which is
arranged in the dome of the furnace.
The cold chambers may he common to several crucibles and the form and like-
wise the dimensions of the various appliances may be modified according to the
scale on which the manufacture is to take place.
The process for the manufacture of metallic magnesium consists in forming an
electric arc within the body of the magnesium salt in a refractory receptacle which
may or may not be provided with a metallic envelope and furnished with a luted
lid.
In this operation magnesium is formed both by simple electrolysis and by
dissociation produced by the high temperature of the electric arc.
The arrangement for producing the, electric arc which I have found to afford
the best results, consists of a regulator, provided with a rheostat, of which only
one electrode--the anode is movable and subject to adjustment. The polarisation
of the electrolyte gives rise to a considerable heating of the anode,, which neces-
sitates a section of the latter larger than would otherwise be required; the second-
the cathode being connected to a kind of crucible stand placed at the bottom of
the crucible, the dimensions of the latter being suitable to the density, of the
current. I may also line the walls of the apparatus with carbon dust; such a
lining will then form the cathode.
In order to prevent the gases which are given off from the anode from coming
into contact with the metal formed, I have found that it is necessary to surround
this electrode with a sheath of some refractory substance, preferably carbon. I
arrange this envelope in such a manner as to leave between the said sheath and
the anode, a space sufficient to allow of the free escape of the gases; this space
communicates with the outlet pipe for the inert gas to which reference will be made
later. This sheath is provided with holes in its upper portion in order to allow
the inert gases which are introduced, to escape by the same pipe. Finally, in
order to prevent any loss of the liberated gases by way of the opening left between
the sheath and the anode, I effect as perfect a closing as possible with an asbestos
plug through which this electrode passes with slight friction. This plug is located
in a kind of head of some insulating and refractory substance, which is superposed
upon the sheath properly so called and inserted in the lid of the crucible.'
For the purpose of carrying along the liberated gases, and also, for preventing
the re-entry of air into the crucible, I establish through two openings provided in
the lid a current of some inert gas, such as nitrogen, carbonic acid, carbonic oxide
and the like.
When a sulphated mineral is to be treated, in order to avoid condensation of the
sulphuric acid, I employ one of the following processes;
I add a certain quantity of chloride of calcium (CaCl2) such quantity being

page_text: based upon the constituent amount of sulphate which transforms sulphate of
magnesium (MgSO) into sulphate of calcium (CaSO); or, preferably, I intro-
duce fragments of carbonate of calcium (CaCO3) into the apparatus; as soon as
sulphuric acid (SO3) is given off, it is saturated and forms sulphate of calcium
(CaSO) with liberation of carbonic acid, (CO). This gas may then be used as
an inert gas and carry along the chlorine in the same manner as the inert gases
above referred to.
In the case of chlorine I condense it under the form of hypochlorites, of
perchloride of iron, and chlorates, generally it may be utilised for the same purposes
as chlorine manufactured by any other process.
As regards the magnesium, which is lighter than the chlorides, it rises to the
surface of the bath where it forms a stratum which may be left to cool or may be
run off through an opening provided in the side of the apparatus. In the latter
case, the manufacture may be continuous, the metal being withdrawn as produced
and replaced by a corresponding quantity of the salt employed. An opening
specially provided in the lid for the purpose, allows of the introduction of such
salt..
I may, by the same process, electrolyse the fluorides, and double fluorides of
magnesium, the arrangement remaining the same..
When I employ double chlorides or fluorides, there remains in the crucible,
after decomposition of the magnesium salt, the salt of the other metal which may
constitute a useful residue. For example in the treatment of the fluorides and
chlorides of magnesium and potassium, the chloride of potassium passes out through
the lower outlet port when it may either be purified or used commercially as it is.
My process also admits of obtaining double chlorides or double fluorides such as
aluminium, calcium, barium, strontium, lithium, sodium, potassium and the like
by means of chlorides or fluorides.
This operation, which should preferably be carried out at a high intensity and
low voltage in order to economise motive power, may be effected with all types of
either continuous or alternating current machines.
Instead of producing the magnesium only it may be desired to produce alloys
of this metal and of the other metals above referred to. In order to obtain
these alloys direct, I proceed in one or other of the following ways;
I introduce into the electrolytic apparatus a mixture of fusible salts of the
metals intended to form the alloys, this mixture containing the metals in the
desired proportions.
I may likewise replace one or several of these fusible salts by a relatively infusible
combination of the same metals sufficiently small in quantity not to thicken the
bath.
In electrolysis the alloy is formed directly; it is thus that in effecting the
electrolysis of a mixture of fused chlorides of magnesium and of lithium, I have
been able to obtain a magnesium-lithium combination, the density of which is
lower than, or at most equal to, that of water.
The manufacture of this alloy constitutes one of the principal features of this
invention, another feature being the commercial use of lithium as an 'alloy with
other metals with a view to reducing their density.
The second method consists in placing beforehand at the cathode, that is to say
at the bottom of the apparatus, the relative proportion of the heavy metals to be
added to the principal metal, and, after the fusible salts of the latter have been
introduced, in causing the amount of current to pass which I have found by
experiment to be necessary to liberate the quantity of the principal metal which I
require in order to complete my alloy.
It will of course be understood that as the greater part of these alloys become
heavier than the fused salt; they will fall to the bottom of the crucible. If then
the operation is being carried out by tapping at the side of the vessel an orifice for
running' off should be provided near the bottom.
Amongst the metals and metalloids which form alloys suitable for ordinary

page_text: purposes with light metals, I may mention tin, nickel, copper silver, gold,
platinum, boron, chromium, cobalt, tungsten, antimony, titanium, cadmium and the
like.
While running off the alloy should always be sheltered from the air, and I provide
for this by means of a current of inert gas, which travels with the metal and
remains with it until it has cooled.
I obtain excellent results by placing the moulds in a chamber filled with
carbonic acid.
My process permits of the use of magnesium and lithium for commercial
purposes and of the production of new alloys which hitherto have had a strictly
scientific application only.
It is obvious that I may modify the form, the dimensions and the accessory
arrangements of the different appliances which permit of the practical carrying
out of my process, according to the results desired.
I also employ the sub-products of such manufacture, whether they arise from
the decomposition of the salts employed in the manufacture of the metals or alloys
above referred to, or form that portion of a double salt which is not decomposed.
Dated this 3rd day of October 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.
Improvements in Processes for the Manufacture of Certain Metals
and Alloys, especially for the Manufacture of Magnesium and its
Alloys.
I, ALFRED LE REDOTTE, of 12 Boulevard Bonne Nouvelle, Paris, in the Republic
of France, Chemist, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described in and by the
following statement:-
This invention relates to the manufacture, by electrolysis only or by electrolysis
and dissociation together, of the following metals viz.:-magnesium, aluminium,
lithium, sodium, potassium, calcium, barium and strontium, either alone, com-
bined, or alloyed, in any proportion, with metals or metalloids susceptible of
forming alloys or combinations with the said metals consequent upon a reduction
of their fusible salts or of their mixtures by electricity.
The metal to which I have more particularly directed my attention is
magnesium. I will therefore begin by describing the different phases of the
manufacture of this metal and its alloys.
The primary substances for the manufacture of magnesium are-carnallite
(double chloride of potassium and magnesium); tachydrite (double chloride of
calcium and magnesium); double chloride of sodium and magnesium; kieserite;
fluoride of magnesium; the double fluorides of magnesium and chloride of
magnesium obtained from salt-marshes or from any other source.
I extract the magnesium from infusible minerals in the form of chloride or
of fluorides.
With reference to double chlorides, the preliminary treatment, for rendering
these products suitable for the manufacture of the metal, consists of a dehydration
in a stove or drying chamber at a temperature which is at first moderate, in order

page_text: to avoid the fusion of the products in their water of crystallization, and then
higher than 100° C. so as to hasten the drying. The dehydration is completed by
fusion in the crucible.
The fused product is run off, either directly into the apparatus in which it is
to be treated, or upon metallic or terra cotta plates and kept in hermetically
closed vessels.
When I employ simple chloride of magnesium, I find it necessary to have
recourse to a special process of fusion with a view to preventing the decomposition
of the salt by the water which it contains during the dehydration.
This process is carried out in the following manner:
The simple chloride of magnesium is intimately mixed with a proportion of
hydrochlorate of ammonia, such proportion varying according to the quantity of
water contained by the chloride it may even be as great as one half with very
moist chlorides. This mixture is then dried in a stove or drying chamber, care
being taken not to exceed 100° C. which is the temperature at which hydro-
chlorate of ammonia commences to volatilize. Care should also be taken, during
the drying process, to break up the agglomerated masses which form, as their
centres would dry imperfectly.
The accompanying drawings shews in principle and by way of example only
the apparatus by means of which my process may be carried out.
Figures 1 and 2 represent in vertical longitudinal and cross section respectively
the arrangement of the drying stove or chamber.
Figure 3 represents a longitudinal section through the furnace.
Figures 4 and 5 are a front elevation and a cross section of the same
respectively.
Figures 6 and 7 represent two vertical sections through the crucible, and
Figure 8 is a part sectional plan view of the same.
The arrangement of the stove or drying chamber which I have found most
advantageous consists in a series of tablets superposed as baffle plates, between
which a current of hot air circulates.
The front wall of the stove is provided witu inspection apertures 6 glazed or
covered with crystal, and the rear wall is provided with removable plugs c
(Figures 1 and 2).
The stove rests upon a foundation of refractory bricks d providing a heating
floor or surface e.
The drying operation finished, I introduce the mixture into crucibles f of
plumbago or of refractory earth which are placed in a blast furnace 9 Figure 3
or gas furnace h which is slowly raised to a bright red heat, which temperature
I maintain until the hydrochlorate of ammonia is completely driven off. This
furnace is divided horizontally into two compartments by an impermeable slab i
which is provided with openings into which the crucibles f fi, in this manner the
liberated hydrochlorate of ammonia is isolated from the furnace gases and proceeds
to a series of cold chambers k which communicate with the upper portion
the furnace.
of
The drainage of the water of condensation, charged with hydrochloric acid, is
assured by means of an inclined plane L M, L M Figures 3 and 5 forming the
bed of the chambers. The gases which have not been condensed escape by way of
the chimney s beneath which is provided a dust chamber into which falls the
hydrochlorate carried along by the gases. When such liberation is completed the
crucible at m opened contains fused chloride of magnesium which I run off in
the manner already described with reference to double chlorides, or in a continuous
manner through an orifice n Figure 4 provided for the purpose in the lower
portion of the crucible; in this latter case, after each tapping, the crucible is
recharged by means of a funnel o provided with a stoppering device p which is
arranged in the dome g of the furnace, next to the stopping plug r of agglomerated
coals Figures 3 and 4.
The cold chambers may be common to several crucibles and the form and like

page_text: wise the dimensions of the various appliances may be modified according to the
scale on which the manufacture is to take place.
The process for the manufacture of metallic magnesium consists in forming an
electric arc u Figures 6 and 7 within the body of the magnesium salt v in the
refractory receptacle wo which may or may not be provided with a metallic envelope
and furnished with a lid luted at y and placed upon a refractory foundation z.
In this operation magnesium is formed both by simple electrolysis and by
dissociation produced by the high temperature of the electric arcu.
The arrangement for producing the electric arc which I have found to afford
the best results, consists of a regulator, provided with a rheostat, of which only
one electrode the anode-is movable and subject to adjustment. The polarisation
of the electrolyte gives rise to a considerable heating of the anode A, which
necessitates a section of the latter larger than would otherwise be required; the
second the cathode B-being connected to a kind of electrical agglomerate coal
cake or mass B placed at the bottom of the crucible, the dimensions of the
latter being suitable to the density of the current. I may also line the walls
of the apparatus with clectrical agglomerate coal, such a lining will then form
the cathode. By electrical agglomerate coal I mean a hard agglomerate coal
obtained in the "Street" electrical furnace.
In order to prevent the gases which are given off from the anode from coming
into contact with the metal formed, I have found that it is necessary to surround
this electrode with a sheath C of some refractory substance, preferably agglomerate
coal. I arrange this envelope in such a manner as to leave between the said sheath
and the anode, a space D sufficient to allow of the free escape of the gases; this
space communicates with the outlet pipe E for the inert gas to which reference
will be made later. This sheath is provided with holes F Fig. 7 in its upper
portion on order to allow the inert gases which are introduced at G Figs. 6, 7
and 8, to escape by the same pipe. Finally, in order to prevent any loss of the
liberated gases by way of the opening left between the sheath and the anode, I
effect as perfect a closing as possible with an asbestos plug H through which
this electrode passes with slight friction. This plug is located in a kind of head
or stuffing box I of some insulating and refractory substance, which is superposed
upon the sheath properly so called and inserted in the lid of the crucible.
For the purpose of carrying along the liberated gases, and also for preventing
the re-entry of air into the crucible, I establish through two openings G, E
provided in the lid of a current of some inert gas.
When a sulphated mineral is to be treated, in order to avoid condensation of
the sulphuric acid, I employ one of the following processes:-
I add a certain quantity of chloride of calcium (CaCl2), such quantity being
based upon the constituent amount of sulphate, which transform sulphate of
magnesium (MgSO), into sulphate of calcium (CaSO4), or, preferably, I introduce
fragments of carbonate of calcium (CaCO3) into the apparatus, as soon as
sulphuric acid (SO3) is given off, it is saturated and forms sulphate of
calcium (CaSO) with liberations of carbonic acid (CO3). This gas may then be
used as an inert gas and carry along the chlorine in the same manner as the
inert gases above referred to.
In the case of chlorine I condense it under the form of hypochlorites, of per-
chloride of iron, and chlorates, generally it may be utilized for the same purpose
as chlorine manufactured by any other process.
As regards the magnesium, which is lighter than the chlorides, it rises to the
surface of the bath where it forms a stratum which may be left to cool or may
be run off through an opening K Fig. 7 provided in the side of the apparatus
and closed by means of a refractory plug K¹ Figs. 7 and 8. In the latter case
the manufacture may be continuous the metal being withdrawn as produced and
replaced by a corresponding quantity of the salt employed. An opening L
Fig. 8 specially provided in the lid for the purpose, allows of the introduction
of such salt.-
WIL
I I
1...

page_text: I may, by the same process, electrolyse the fluorides and double fluorides of
magnesium, the arrangement remaining the same.
When I employ double chlorides or fluorides, there remains in the crucible,
after decomposition of the magnesium salt, the salt of the other metal which
may constitute a useful residue. For example in the treatment of the fluorides
and chlorides of magnesium and potassium, the potassium salt passes out through
the lower outlet port Ms Fig. 7 when it may either be purified or used commercially
as it is.
My process also admits of obtaining aluminium, calcium, barium, strontium,
lithium, sodium, potassium and the like by means of chlorides fluorides, double
chlorides or double fluorides of these metals.
This operation, which should preferably be carried out at a high intensity and
low voltage in order to economise active power, may be effected with all types
of either continuous or alternating current machines.
Instead of producing the magnesium only it may be desired to produce alloys
of this metal and of the other metals above referred to. In order to obtain these
alloys direct,. I proceed in one or other of the following ways:
I introduce into the electrolytic apparatus a mixture of fusible salts of the
metals intended to form the alloy, this mixture containing the metals in the
desired proportions.
I may likewise replace one or several of these fusible salts by a relative infusible
combination of the same metals sufficiently small in quantity not to thicken
the bath.
In the electrolytic operation above specified the alloy is formed directly; it
is thus that in effecting the electrolysis of a mixture of fused chlorides of
magnesium and of lithium, I have been able to obtain a magnesium-lithium
combination, the density of which is lower than, or at most equal to, that of
water. I have likewise obtained a magnesium chromium combination which
possesses great resistance without increase of density.
The manufacture of this alloy constitutes one of the principal features of this
invention another feature being the commercial use of lithium as an alloy with
other metals with a view to reducing their density.
The second method consists in placing beforehand at the cathode, that is to
say at the bottom of the apparatus, the relative proportion of the heavy metals
to be added to the principal metal, and, after the fusible salt of the latter have been
introduced, in causing the amount of current to pass which I have found by
experiment to be necessary to liberate the quantity of the principal metal which
I require in order to complete my alloy.
It will of course be understood that as the greater part of these alloys become
heavier than the fused salt; they will fall to the bottom of the crucible. If then
the operation is being carried out by tapping at the side of the vessel, an orifice Ma
for running off should be provided near the bottom.
Amongst the metals and metalloids which form alloys suitable for ordinary
purposes with light metals, I may mention: tin, nickel, copper, silver, gold,
platinum, boron, chromium, cobalt, tungsten, antimony, titanium, cadmium and
the like.
While running off the metal or the alloy should always be sheltered from the
air, and I provide for this either by means of a current of inert gas, which travels
with the metal introduced through the pipes N Fig. 7 and remaining with it
until it has cooled, or by creating a vacuum.
I obtain excellent results by placing the moulds in a chamber filled in which
a vacuum has been created.
My process permits of the use of magnesium, magnesium chromate and lithium
for commercial purposes and of the production of new alloys which hitherto have
had a strictly scientific application only.
It is obvious that I may modify the form, the dimensions and the accessory

page_text: arrangements of the different appliances which permit of the practical carrying
out of my process, according to the results desired.
I also employ the sub products of such manufacture, whether they arise from
the decomposition of the salts employed in the manufacture of the metals or
alloys above referred to, or form that portion of a double salt which is not
decomposed.
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:
The process for the manufacture on a commercial scale of various metals or
alloys, the said process being specially applicable to the manufacture of magnesium,
lithium, chromium and their alloys, and is characterised by the employment of
the electric current and by combined electro-chemical and electro-thermic action,
substantially as above described and for the purpose specified.
Dated this 5th day of July 1897.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.