Improvements in and connected with the Electrolytic Decomposition of Alkaline Salts.
Year: 1895

page_text: Date of Application, 17th Sept., 1895-Accepted, 19th Oct., 1895
COMPLETE SPECIFICATION.
Improvements in and connected with the Electrolytic Decomposition
of Alkaline Salts.
I, WILLIAM ADOLPH ROSENBAUM, of 118 South Fullerton Avenue, Montclair,
in the County of Essex and State of New Jersey, United States of America,
Patent Agent, 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 :-
This invention pertains to the electrolytic decomposition of alkaline salts, the
object being the economical electrical decomposition of alkaline salts in solution
and is particularly applicable to the production of pure alkaline hydrates and
chlorine and hypochlorites from alkaline chlorides.
By my invention I am able to produce in a continuous operation from chloride of
sodium pure caustic soda and chlorine or hypochlorites.
In my apparatus 1 dispense entirely with the use of porous partitions or
diaphragms to separate the electrodes and consequent products of electrolysis.
Briefly stated, my invention consists in the employment of a body of mercury
which is subjected alternately to contact with the alkaline chloride undergoing
electrolytic decomposition to receive a deposit of metal, and to contact with an
electrolyte capable of dissolving the oxidised alkaline metal which is contained in
the mercury. While receiving its deposit of metal the body of mercury acts as the
cathode of an electric circuit, and for extracting the metal from the mercury by
oxidization, oxygen is produced by passing a current of electricity through the
electrolyte between an anode and a cathode immersed therein and separate and
distinct from the body of mercury er amalgam. The anode is located as close to
the surface of the amalgam as possible, in order that the oxygen which is liberated
at the anode may be brought into as intimate relations with the surface of the
amalgain as possible, thereby to readily combine with the metal which has been
deposited in the mercury. The invention comprehends a stationary elongated
structure in the form of a hood divided into a series of compartments by vertical
partitions. The bottom of the hood is constructed open, but is closed by dipping
into a tray, in the bottom of which is a layer of mercury and inasmuch as the
lower edges of the partitions and slides of the hood continuously project into and
are covered by the mercury, the compartments thereof will be effectually scaled
from one another, and the solutions contained within the compartments and resting
upon the surface of the mercury will be prevented from mixing. The invention
also comprehends suitable mechanism for moving the tray containing mercury, in
the direction of the range of compartments of the cell, thereby transferring a given
portion of the mercury from contact with the solution in one compartment of the
cell to contact with the solution in the next succeeding compartment, and so on
alternately exposing the given portion of mercury to action in the two kinds of
compartments of the cell. Suitable means are provided for mounting the
electrodes and establishing the electrical connections for the circuits employed and
suitable ducts or pipes are provided for supplying a saturated solution of chloride
to, and removing the spent portions thereof from, the chloride compartments, while
other suitable passages are provided for supplying liquid to and removing it from
the hydrate compartments. It will be observed therefore that the invention
provides for the continuous separation and production of materials combined in an

page_text: alkaline salt. In the passage of the mercury from one compartment to another it
alternately receives and gives off the metallic element of the chloride and as my
invention comprehends a circular form for the chamber or cell, the mercury in one
passage around the circle may receive and give off a number of charges of metal,
and for that reason, the time which the mercury remains in any one compartment
may be comparatively short, so that the amalgam produced in the chloride
compartment will not be so rich as to lessen the efficiency in the use of current and
cause the formation of by-products, which would be destructive to the electrodes.
The tray carrying the mercury is, in fact, given a continuous slow motion, although
if desired the tray may move intermittently a distance each time equal to the
length of a compartment, the interval between the movements giving time for the
deposit to be made into, and extracted from, the several portions or sections of
the body of mercury.
In the accompanying drawings I have illustrated one form of apparatus in.
which my invention may be embodied.
Figure 1 is a plan of the complete apparatus.
Figure 2 is a vertical section of the apparatus taken on line x of Figure 1, and
passing through only one side of the circular apparatus.
Figure 3 is a similar section taken on line y y of Figure 1 the gearing being
omitted, and
Figure 4 is a section taken on the curved line of Figure 1.
Referring to the drawing by letter, A represents a circular tray having outer
and inner vertical sides a and a¹ respectively, and a bottom a. This is supported
and carried upon the extremities of rotating arms or spokes a³ attached to a hub a³
mounted loosely upon a vertical axle or stud a³. To the hub is attached a large
worm gear at which is engaged and driven by a worm a', the power being supplied
in any desired manner and taken from any suitable source. Obviously, when-
worn a is rotated, the tray A rotates around the centre stud a. The tray is
electrically insulated from the arms a³ by non-conducting material o.
B represents a stationary, circular hood having outer and inner vertical
walls respectively and a curved top b. The bottom is open and the lower part
projects downward into the tray A, but is supported at such an elevation as to
leave a short space between the bottom of the tray and the lower edge of the
vertical sides. This hood is supported by framework of any suitable character.
I have shown braces and brackets b³ which it will be understood are attached to
any fixed structure. The width of the tray is such that there will be an annular
space outside and inside between the vertical walls of the tray and hood as shown.
The hood is divided circumferentially into a series of compartments by vertical
transverse partitions b^. The partitions are preferably so located that every
alternate chamber or compartment will be somewhat larger than the intervening
compartiments, for a purpose which will hereinafter appear, although under some
conditions the compartments may all be of the same size. The partitions extend
downward nearly, if not quite, to the lower edges of the sides b. In the smaller
compartments, which I call the chloride compartments, will be mounted
horizontal row of carbon pencils attached in any suitable manner to the side of
the compartment, and forming a single electrode, (the anode) of an electrical
circuit, hereinafter referred to. In the larger or hydrate compartments will be
mounted two electrodes, an anode and a cathode, the former 6 being preferably a
row of carbon pencils similar to the pencils. These will be located below the
cathode and the latter may be of any material suitable for the purpose. The
anodes and cathodes of the larger compartments are electrodes of an entirely
separate circuit from that which included the electrodes in the smaller compart-
ments. represents outlets from the chloride compartments for gaseous products.
6 and 610 respectively represent the inlets and outlets for liquids to and from the
same compartments. 6 represents inlet pipes for liquids, extending downward to
the lower portion of each of the larger compartments, and 613 are outlets for liquids
'from the same compartments.
a

page_text: C is a stationary circular frame surrounding the tray A at its lower edge: it
supports an electrical conductor c in the form of a band attached to its inner
face. At points opposite the chloride compartments of the stationary hood the
conductor has attached to it a number of metallic contact brushes c' which
press against the bottom of the tray and drag along its surface when the tray
rotates. To this conductor c is attached a wire c³ leading from the negative
pole of a source of electricity G. The positive pole is connected by wire c
with the anodes in the chloride compartments of the stationary hood. "Anode 66.
is connected by wire c¹ with the positive pole of a separate source of electricity (
while the negative pole of this source of current is connected by wire c with
the electrode b7.
When the apparatus is equipped for work the tray contains a shallow layer
of mercury e of the same depth throughout the circle. This depth of mercury
will be sufficient to immerse or cover the lower edges of the side walls band!
the partitions of the stationary hood. The small or chloride compartiments
will contain a body of material such for instance as a solution of sodium chloride.
The larger or hydrate compartments will contain a body of water or weak caustic
solution. The partition being absolutely non-porous, it will be observed that the
mercury effectually seals the two solutions in the adjoining compartments from,
each other. In order to maintain the mercury at the same level both inside of the
stationary hood and outside of it in the tray, 1 place in the annular spaces between
the hood and the tray a quantity of heavy oil or other material the weight of
which will balance that of the liquids inside of the cell, and which may be kept
cool if desired, by any suitable means such as circulating it through a refrigerating
apparatus.
The operation is as follows:-Power is applied to worm a' at a speed to impart
a slow rotary motion to the tray. The circuits of both sources of current G G
are completed, and the separation of the elements of the chloride solution.
immediately commences. In the smaller compartments the current passes from the
anodes to the body of mercury e immediately beneath it, (which acts as a cathode),
thence through the bottom of the tray to the brushes c'. Electrolysis of the saline
solution takes place, chlorine gas is liberated in the compartment above the surface
of the liquid, whence it is drawn off through passages b³. The sodium is deposited
in the mercury, forming an amalgam, and as the tray rotates this amalgam is
carried into the hydrate compartments, where it comes into contact with the
electrolyte therein. The action of the current in these compartments in passing
from the anode to the cathode above decomposes the electrolyte and liberates the
oxygen at and around the anode. The anode being located as near to the surface.
of the amalgam as possible, the oxygen formed at that locality will immediately!
oxidize or combine with the sodium of the amalgam. The sodium oxide will then
immediately dissolve in the water and form sodium hydrate or caustic soda. The
mercury thus freed of its burden of sodium is then carried to the next compartments
(the chloride) where it will receive another deposit of sodium and thence to the
bydrate compartments, where the deposit will be given up and so on continuously
around the circle. The process will not be step by step, as perhaps indicated by
the above description, but will be continuous. The speed of the tray will be such
as to allow of a deposit of about two-tenths of one per cent. of sodium, and in the
event that this quantity of sodium cannot be oxidised I have made the hydrate
compartments longer to expose the amalgam therein for a longer period than it is
retained in the chloride compartiments.
The hydrate compartments are supplied with water through the pipes ; the
water on entering the chamber at the bottom forces the caustic solution to the top
whence it is drawn off through the pipes 61. A saturated solution of chloride of
sodium is supplied to the chloride compartiments through the inlet pipes and
being heavier than the spent liquids containing the hypochlorites, it immediately
goes to the lower portions of the chamber and forces the spent liquid to the top,
whence it flows out through pipes 610.

page_text: The lower edges of the partitions 6 projecting into the mercury will tend to
retard the mercury and prevent its moving at the same speed with the tray, but
such retardation will take place equally around the circle and will not materially
effect the process, but at any rate the partitions will cause a slight wave of mercury
to form which will tend to mix the sodium more intimately with the mercury, and
it will therefore be carried more readily into the hydrate compartment. If desired,
I may place small ridges as indicated at in Figure transversely along the
bottom of the tray. These will counteract any retarding movement which the
edges of the partition may create. Another way of overcoming any difficulty on
this point is to run the tray in one direction for a short length of time and then
reverse it. In case the tray is given a step by step movement each movement
being equal to the length of one compartment (the compartments then being all of
the same length) there will be no appreciable retardation of the mercury, with
respect to the tray, for at the end of each short movement the tray will come to a
rest and allow the mercury to settle.
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 :-
1. In the manufacture of hydrates of alkaline metals, electrolytically depositing
the metal upon a mercury cathode which is then exposed to an electrolyte con-
taining a separate anode and cathode, the anode being so arranged that the oxygen
liberated combines with the metal contained within the mercury, the resulting
oxide being soluble in the electrolyte, substantially as herein before described.
2. In apparatus for the production of the hydrates of alkaline metals, a cell or
cells each containing a separate anode and cathode and a suitable electrolyte which
is in contact with mercury charged with the alkaline metal, substantially as and
for the purpose hereinbefore described and as illustrated by the accompanying
drawings.
3. Apparatus for the production of the hydrates of alkaline metals, consisting of
a tray or receptacle containing mercury and a hood or the like divided into
compartments the mouths of which are sealed by the mercury, some of the com-
partments containing anodes and some containing anodes and cathodes, all
constructed arranged and operated substantially as and for the purpose herein-
before described and as illustrated by the accompanying drawings.
4. Apparatus for the production of hydrates of alkaline metals constructed
arranged and operated substantially as hereinbefore described and as illustrated by
the accompanying drawings.
Dated this 17th day of September A.D. 1895.
W. E. HEYS & SON,
Agents for the Applicant.