An Improved Process and Means used therein for the Production of Caustic Alkali.
Year: 1893

page_text: Date of Application, 23th Oct., 1893-Accepted, 1st Sept., 1894
AAMIDELE SPECIFICATION.
An Improved Process and Means used therein for the Production
of Caustic Alkali.
I, CLAUDE THEODORE JAMES VAUTIN, of 42, Old Broad Street in the City of
London, 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 :-
My invention consists of an improved process, and means used therein, for the
production of caustic alkali, such as the hydrates of sodium and potassium from
salts of sodium and potassium, such as chlorides, by electrolysis; and from an alloy
of sodium or potassium and lead or other metal which will alloy and is not affected
by fused caustic alkali when molten, however produced.
And in order that my invention may be the better understood I now proceed to
describe the same in relation to the means illustrated herewith reference being had
to the letters and figures marked thereon.
Figure 1 is a longitudinal section of a furnace, showing auxiliary pot or vessel
for the production of caustic alkali, and means for the collection of chlorine.
Figure 2 is a transverse section of the said furnace, showing means for the
continual supply of the alkali salt.
-
Figure 3 shows an alternative arrangement for extracting the caustic alkali from
the metallic alloy.
To carry my improved process into effect, I place a charge of metal A which
will alloy with sodium or potassium and which will not be affected by a fused
caustic alkali when in a molten condition, such as metallic lead, in the bottom of
the furnace or vessel, in which the operation is to be carried out, and this charge
of metal or metallic lead constitutes the cathode D of an electric circuit.
Above this charge of metal or lead A, is added a sodium or potassium salt, such
as sodium or potassium chloride as an electrolyte and I may mix with the said salt,
other salts, such as chloride of calcium or strontium, to reduce the temperature at
which the electrolyte melts.
One or more anodes F of carbon or other suitable material, are inserted into the
sodium or potassium salt, and they are surrounded by a case G of refractory and
impervious material, such as fire-clay to protect them from the products of com-
bustion of the fuel used in the furnace, and also serve to collect the chlorine gas,
which is liberated and rises at the said anodes where chlorides are used, and is
led away by suitable pipes H to a chamber X containing calcic hydrate or
powdered slaked lime, for the purpose of producing bleaching powder.
The whole charge of the furnace is exposed to gentle heat, until the metallic or
lead charge A is melted, and the sodium or potassium salt or mixture of salts is
fused.
An electric current is then passed through the charge and electrolysis takes
place.
The chlorine is liberated at the anodes F where chlorides are used for the
electrolyte, and is collected by the surrounding tubes G, and pipes H, and carried
to a chamber containing calcium hydrate, or powdered slaked lime, to be converted
into chloride of lime, or to be utilized in any other convenient manner. The sodium
or potassium freed at the surface of the molten bath of metal or lead A, is entirely
absorbed, forming an alloy with the lead or other metal of which the bath or
cathode is composed.

page_text: An auxiliary pot or vessel N provided with a grate M and flues L L for heating
the same, is connected by a conduit P communicating with the lower part of the
metallic bath in the hearth.
The charge of alloyed metal or, lead and sodium or potassium (the cathode) is
thus in free communication with the auxiliary pot or vessel N, and it is found that
as the sodium or potassium is removed from the alloy in the pot N in the form of
an hydrate it will be continually replaced by fresh sodium or potassium in con-
sequence of the diffusion of further sodium or potassium from the hearth of the
furnace through the metal in the conduit P to the metal in the pot N.
The conversion of the sodium or potassium into the hydrate that is into caustic
alkali; may be effected by a jet of steam admitted by the pipe K to the surface of
the charge in the auxiliary pot or vessel N, without chilling the molten alloy.
The caustic alkali, so produced, may be removed in a fused condition by ladling
or by an exit pipe as may be desired. Or the temperature of the auxiliary pot or
vessel N may be increased until the caustic alkali is volatilized in the presence
of steam, and it is carried over through a suitable vent pipe Q from the closed
pot N, for condensation and collection.
The production of caustic alkali may thus be a continuous process; the removal
of the caustic alkali from the metal in the pot N being compensated for by the
continuous deposition of the sodium or potassium by electrolysis in the metallic
bath or cathode in the furnace; in consequence of the diffusion of alkaline metal
from the furnace to the outer pot.
The charge of sodium or potassium salts in the furnace may be maintained
through a suitable hopper or hoppers S; the lead bath remaining as a collector
and carrier of the sodium or potassium, and the chlorine (where chlorides are used
as the electrolyte) being collected simultaneously for the production of bleaching
powder, or otherwise.
Or, alternatively, the metallic sodium or potassium alloy may be led in a molten
condition by an exit pipe T into or preferably under a bath of water R, Figure 3,
where the alloy is granulated, and the sodium or potassium forms immediately a
hydrate with the water.
In such case the fresh charge of metal such as lead, to form the alloy with the
sodium or potassium, would be conveniently melted in an auxiliary pot or vessel L',
in communication with the hearth by the pipe O fitted with a valve so that a fresh
charge could be introduced as the molten alloy was removed.
Where an alloy of sodium or potassium with lead or other metal which is not
attacked when molten, by sodium or potassium hydrate is obtainable, I may employ
part of my process, as described above, by melting the said alloy and applying to
its surface a jet of steam to produce caustic alkali therefrom, which may be
removed as formed, by ladling or by a suitable vent; or I may increase the
temperature sufficiently to evaporate the caustic alkali in the presence of steam
from such closed vessel, by a suitable pipe and thereafter condense and collect the
same.
It is obvious that instead of an open hearth furnace the process as above
described could be conducted in a pair or series of conjoined crucibles, one
containing the electrolyte for electrolysis and the cathode, and the preparation of
the caustic alkali being effected in the other.
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 :-
1st. A process for the production of a caustic alkali, consisting of the treatment,
in a fused condition by electrolysis, of a salt of sodium or potassium forming the
electrolyte upon a molten bath of a metal alloying with sodium or potassium, and
not affected by a fuzed caustic alkali, such as lead; the latter forming the cathode
of an electric circuit; the conversion of the sodium or potassium, (when alloyed
in a molten condition with the metallic bath) by water, steam, or water vapour, in

page_text: an auxiliary pot or vessel into a caustic alkali and the removal of the latter
by evaporation, or in any way, for collection and utilization, substantially as
described.
2nd. In a process for the production of a caustic alkali from the chlorides of
potassium or sodium in a fuzed condition over a bath of molten metal by
electrolysis; the collection by suitable means of the chlorine evolved at the anodes
of an electric circuit, and the utilization thereof by conversion into the chloride of
lime or other product of chlorine, substantially as described.
3rd. In a process for the production of a caustic alkali from the electrolysis of
the fuzed salts of sodium or potassium over a bath of molten metal, the treatment
of the sodium or potassium, transfused as an alloy, through the metal bath, in a
separate heated pot or vessel by steam or water vapour to convert the sodium or
potassium, as it collects in the metal alloy, into a caustic alkali, for collection and
utilization, substantially as described.
4th. In a process for the production of a caustic alkali from the electrolysis of
fused salts of sodium or potassium over a bath of molten metal; the treatment of
the resulting alloy by discharging into, or under water, to form a caustic alkali, and
the further supply, by auxiliary heated pot, to the metal bath in the furnace, of
molten metal, as the alloy is removed, substantially as described.
5th. In a process for the production of a caustic alkali;-the treatment of a
molten alloy of sodium or potassium, and other metal not affected by water, steam
or caustic alkali such as lead, by steam or water vapour to produce the said caustic
alkali for collection and utilization substantially as described.
6th. In a process for the production of caustic alkali; the distillation or
evaporation by heat in the presence of steam of the caustic alkali, produced by
said steam or water from a molten alloy of sodium or potassium with another
metal, unaffected by caustic alkali, to remove the said caustic alkali for after
condensation and collection.
7th. In a process for the production of caustic alkali; the combination of
furnaces, and appliances used therewith, to carry the said process into effect,
substantially as described and illustrated herewith.
Dated this 28th day of October 1893.
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.