US636234A

US636234A - Process of and apparatus for electrolytic decomposition of saline solutions.

Info

Publication number: US636234A
Application number: US63687397A
Authority: US
Inventors: Elbridge Baker
Original assignee: NASHOBA Co
Current assignee: NASHOBA Co
Priority date: 1897-05-17
Filing date: 1897-05-17
Publication date: 1899-11-07
Anticipated expiration: 1916-11-07

Description

atented Nov. 7, I899. E. BAKER.

PROCESS OF AND APPARATUS FOR ELECTROLYTIC DECOMPOSITION OF SALINE S O L U T l O N S.

(Application filed Kay 17, 1897.)

3 Sheets-Sheet I.

(No Model.)

[NW-1N TUR PxTTY' No. 636,284.- Patented Nov. 7, I899. E. BAKER.

PROCESS OF AND APPARATUS FOR ELECTROLYTIC DECOMPOSITION OF SALI'NE SOLUTIONS.

(Application filed May 17, 1897.)

(No Model.)

W ITNEEIEEE- No. 636,234. Patented Nov. 7, I899.

E. BAKER.

PROCESS OF AND APPARATUS FOR ELECTROLYTIC DECOMPOSITION OF SALINE SOLUTIONS.

(Application filed May 1'7, 1897.)

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UNITED STATES PATENT Erica.

ELBRIDGE BAKER, F TVINOHESTER, MASSACHUSETTS, ASSTGNOR TO THE NASHOBA COMPANY, OF PORTLAND, MAINE.

PROCESS OF AND APPARATUS FOR ELECTROLYTIC DECOMPOSITTON OF SALINE SOLUTIONS.

SPECIFICATION forming part of Letters Patent NO. 636,234, dated November 7, 1899.

Application filed May 17, 1897. Serial No. 636,873. (No model.)

To all whom, it may concern.-

Be it known that I, ELBRIDGE BAKER, of WVinchester, in the State of Massachusetts, have invented certain new and useful Improvements in Processes of and Apparatus for the Electrodecomposiiion of Saline Solutions, of which the following is a specification.

The invention relates to the mercury process; and its object is to increase the efficiency of that process as hitherto practiced by preventing reabsorption by the electrolytic solution of any part of the sodium of the amalgam formed during such process.

My improved process consists in flowing a film of mercury continuously from a higher to a lower level beneath a column of the saline solution, passing a current of electricity through said solution to said film during the flow of said mercury, thereby forming an amalgam of mercury and the metal of the saline solution and separating the amalgam as soon as formed from contact with said solution by continuing the flow of the mercury and amalgam by their own weight and mo- '25 mentum and the Weight of the column of saline solution in a substantially vertical direction until such column is counterbalanced by a column of mercury and amalgam.

The distinguishing feature of the improved o process from other mercury processes hitherto practiced consists more particularly in the separation of the amalgam from the saline solution or electrolyte as soon as formed and the creation and maintenance of a mercury 3 5 seal for both the separated amalgam and the "electrolyte as a result of the maintenance of a balance between the column of the eiectrolyte and a column made up of mercury and amalgam that have passed beneath the electrolyte, since in the last-mentioned column the amalgam rises above the mercury. The result is an efficiency far superior to any hitherto attained.

A further resulting feature of the invention is that not only is the reclaiming of the mercury from the amalgam rendered independent of the forming of the amalgam, so that the extent or time of either operation is not in any degree controlled by the extent or time of the other, but the process of forming the amalgam may be at any time stopped by design or accident without the reabsorption by the electrolyte of sodium or other metal from the amalgam.

Prior to this invention I am aware that a flowing film of mercury has been employed as the negative pole of the electrolytic cell to enable the metal of the alkali or alkaline earthas, for instance, sodium-to form an amalgam with it, which amalgam is employed to obtain one of the products sought for as, for instance, sodium hydrate.

The employment of mercury as the negative pole of the electrolytic cell, as heretofore practiced and known to me in the manufacture of sodium hydrate, is attended by the objectionable feature of the amalgam decomposing in the electrolytic cell in the presence of the saline solution, which results in the sodium uniting with the water of the said solution and generatinga counter electromotive force in the electrolytic cell, which opposes the decomposing current in the cell and also necessitates the sodium product formed being again decomposed, thereby decreasing the efficiency of the apparatus.

In the continuation of this specification sodium is frequently specifically mentioned as the metal of the saline solution for the reason that I have employed the invention in S the manufacture of sodium hydrate; but, as has alreadyappeared,the inventionis not confined. thereto.

This invention overcomes the objectionable features referred to, and thereby enables the electrolytic decomposition of saline solutions and the consequent formation of the sodium hydrate or other products desired to be carried on remuneratively and on a commercial scale with maximum efliciency.

In accordance with this invention the mercury forming the negative pole of the electrolytic cell is kept in continuous motion by gravity on its passage through the cell from a higher point, at which it enters, to a lower 5 point, at which it leaves the said cell, and is then carried up to a point higher than the point at which it leaves the cell, so as to form a mercury seal between the separated amalgam and the electrolyte. The mercury on its passage through the cell amalgainates with the sodium or other metal decomposed from the saline solution, and the amalgam thus formed is kept in continuous motion in its transit through the cell, and the said amalgam is passed through the said cell at a rate or velocity sufficient to prevent the sodium of the amalgam rising through the mercury, which latter appears to envelop or cover it as a protective film as long as the amalgam is kept in transit, thereby preventing the amalgam acting on the water of the alkaline solution and forming hydrate of sodium, which reaction in the cell acts to diminish its efficiency for the purpose desired. The sodium amalgam formed in the electrolytic cell is re ceived in a separate vessel or reclai II] or wherein the amalgam is permitted to come in contact with water, with which the sodium unites to form sodium hydrate, leavingthe mercury free to be withdrawn from the reclaimer and returned to the electrolytic cell to be again used in forming an amalgam with the sodium of the electrolyte.

The body of mercury in the reclaiming-vat should be of greater depth than the body of mercury in transit through the electrolytic cell, which results in an upper portion, layer, or stratum of amalgam in the reclaiming-vat substantially quiet and a lower portion or layer of mercury in gentle motion, which condition in the reclaiming-vat affords the sodium opportunity to rise to the top and unite with the water in the reclaiming-vat. In other words, the state of the amalgam in the reclaiming-vat is the reverse of that in the electrolytic cell. In one case-namely, that of the electrolytic cell-the amalgam is kept in motion at such a rate or velocity as will prevent the sodium rising through the mercury and uniting with the water of the electrolyte, Whereas in the other case-namely, in the reclaiming vat or vesselthe velocity or rate of motion is reduced, so as to permit the sodium to rise and unite with the water in the reclaiming-vat. the flow of the amalgam through the reclaimer, I employ one or more foraminous dams, as will be described. The variation in the depths of the body of mercury in the electrolytic cell and of the body of mercury in the reclaimer may be obtained by making the cell substantially long as compared with the reclaimer and providing one or more straight passages through the said cell for the mercury or by making the cell shorter and dividing its floor or bottom area into a continuous winding or tortuous passage, as will be described, which latter method I prefer. In practice a number of electrolytic cells may and preferably will be employed with a single reclaiming vat or vessel.

These and other features of this invention will be pointed out in the claims at the end of this specification.

Figure 1 represents in plan view a complete apparatus with which to practice my invention. Fig. 2 is a top or plan View, on an en larged scale, of the electrolytic cell preferred To still further retard by me, the top or cover of the cell being removed; Fig. 3, a longitudinal section of the electrolytic cell shown in Fig. 2, with the cover or top in place, the section being taken on the line 3 3; Fig. 4, a transverse section through the electrolytic cell, taken on the line 4 4, Fig. 2; Fig. 5, a longitudinal section through the reclaiming vat or vessel shown in Fig. 1, the section being taken on the line 5 5; and Fig. 6, a front elevation, on an enlarged scale, of the foraminous dam removed.

The complete apparatus preferred by me and as shown in Fig. 1 comprises a series of electrolytic cells A and a reclaiming vat or vessel A, communicating with the cells A, as. will be described, so that a continuous circulation of the mercury through the cells may be obtained. Each of the electrolytic cells A is preferably made as herein shown and is provided with a metallic or conducting bottom a, (see Figs. 2 and 3,) sides a a ends a a and a cover or top a. The sides and ends may be made of soapstone or other non-eonducting material and are preferably set into grooves c in the bottom a and cemented or otherwise secured therein. The bottom a, preferably a metallic plate, has erected upon it a series of partitions or walls a", preferably of glass, which are cemented or otherwise suitably secured to the bottom plate a and which are arranged with relation to each other so as to form one continuous passage 5 from one end of the cell to the other. In the present instance the partitions or walls a are arranged transversely of the cell, alternate walls or partitions extending from the same side of the cell toward but not to the other side of the cell, so as to form the continuous passage 7).

In order to avoid sharp corners in the passage Z), and thereby avoid the formation of eddies in the current of mercury flowing through the said passage, the end walls 19 0f the connected sections or parts of the passage Z) are rounded,as shown in Fig. 2, and the said end walls b may and preferably will be made of cement, which serves to firmly hold or sustain the partitions Q The partitionwalls a? may be of any desired height, and preferably sustain the positive electrode of the cell, which electrode may and preferably will be composed of a series or plurality of conducting bars or rods N, which may be platinum or carbon, inserted in the present instance through one end of the cellnamely, the end a The body of mercury in the cell (represented by the dotted line Fig. 3) is such that its surface is below the upper edge of the partition-walls a The conducting bars or rods b may be connected together outside the cell by a bar Z), to which the positive wire I) of a dynamo or other source of electric current is connected.

The cell A is provided at one end of the passage 1) with an inlet port or opening h for the mercury and at its opposite end with an outlet port or opening 19 (See Fig. 2.) The cell A contains the electrolyte to be decomposed, which is represented by the dotted line 19 (see Fig. 3) and which may, for example, be supposed to be a solution of sodium chlorid or common salt, and this solution b may and preferably will be maintained concentrated by means of a mass 19 of salt crystals, which may and preferably will be sustained by a trough or support, preferably V-shaped and composed of two inclined slabs b Z9 of soapstone or slate, resting upon cross bars or frames 19 of like material, secured to the sides of the cell A and provided with V-shaped recesses or openings for the reception of the trough, as clearly shown in Fig. 4. The trough may be provided with a suitable opening or openings, through which the concentrated solution may pass toward the electrodes, and a suitable opening may be obtained by having the lower ends of one side of the trough abut against the lower end of the other side of the said trough. The inletport Z9 for the passage 17 has connected to it the short leg of a substantially U -shaped pipe 0, (see Fig. 4,) having its longer leg, as 0, extended up above the level of mercury in the cell to obtain a column of mercury,with which the necessary head or pressure is obtained for moving the mercury through the passage 1) with the desired momentum or velocity. The outlet-port b for the passage 1) has connected to it the short leg of a substantially U -shaped discharge or outlet pipe 0 having its other leg 0 extended up above the level of the mercury in the cell. The leg c of the outlet-pipe has connected to it a branch pipe 0, which is adapted to discharge the amalgam in the cell into an upright pipe 0 secured to or forming part of the inlet-pipe c for the reclaiming vat or vessel A.

The branch pipe 0 is attached to the leg 0 of the discharge-pipe at such height above the bottom of the cell as will leave in the leg 0 a vertical column of mercury and amalgam su fficient to counterbalance the column of electrolyte in the cell.

The reclaiming vat or vessel A may be of any suitable or desired construction, and is herein shown as oblong in shape and provided with a series or plurality of inclined and preferably foraminous partitions or dams d, of soapstone or other non-conducting material, which offer a resistance to and retard the flow of the mercury through the vat or vessel A, and consequently afford opportunity for the column of the amalgam to rise and unite with Water in the reclaiming-vat, which water is represented by the dotted line (1 thereby setting free the mercury of the amalgam, which descends and flows from the reclaiming-vat through an outlet-pipe (1 having a branch pipe 61 which delivers it into the inlet-pipe d for a pump d having its dischargepipe d adapted to discharge the reclaimed mercury into the leg 0' of the inlet-pipe c for the cell A.

The foraminous dams d maybe made as shown in Fig. 6, wherein a single dam is shown in elevation, and by reference to Fig. 6 it will be seen that the lower part or half of the dam is provided with openings or perforations, while the upper half is imperforated, which construction offers an obstruction to the flow of amalgam through the reclaimer, and thereby keeps the upper surface of the amalgam in a quiet state, while the mercury, being heavier, falls to the bottom of the reclaimer and flows through the openings in the lower part of the dam.

In the present instance the discharge-pipe d of the pump is provided with a series of branch pipes (1 one for each electrolytic cell A, as shown in Fig. 1, and each of the branch discharge-pipes d" is extended over or above the mouth of the inlet-pipe for the cell A, with which it cooperates, as shown in Fig. 4. The branch discharge-pipe d is separated from the inlet-pipe with which it cooperates a suitable distance to prevent the mercury from electrically connecting the said pipes, and so, also, the branch outlet-pipe c for the electrolytic cell is separated from the branch inlet-pipe c for the reclaimer A a suitable distance to prevent electrical connection between the pipes c 0 The electrolytic cells A may be provided with salt-inlet pipes (1 extended up through the cover of the said cell, and with an outletpipeat for the gases liberated in the said cell. The decomposition of the sodium amalgam may be hastened in the reclaimer A, if desired, by means of a heating medium circulated through a coil (Z of pipes located in the reclaimer, or it maybe hastenedin other well-known ways, such as by admitting steam directly into the said reclaimer.

In Fig. l the series of cells A are represented as connected in series-that is, the positive electrode of one cell is connected to the bottom plate and thereby to the mercury or negative pole of an adjacent cell. In operation the mercury enters each cellA through the inlet-pipe c and flows through the passage 1) in said cell in a shallow stream or film, the depth of which is in practice preferably about one sixteenth of an inch, and passes out from said cell into theinlet-pipe of the reclaimer, from which it is pumped back again into the electrolytic cell. The transit of the mercury through thepassageb of the electrolytic cellis substantially rapid and keeps the mercury in constant agitation and preventsthe sodium of the amalgam, formed in the cell by the decomposing current,from combining with the water of the saline solution in the cell, the rapid transit of the mercury and amalgam through the cell being such as to practically keep the amalgam protected by a film of mercury created by the agitation referred to, which prevents the sodium of the amalgam making contact with the saline solution. If the transit of the m ercury and amalgam is arrested or retarded sufficiently to afford opportunity for the sodiu m to rise through the film of mercury (by reason of its lighterspecific gravity) and unite with the saline solution in the electrolytic cell, the said sodium will create a counter electromotive force and effect a recombina- 5 tion with the electrolyte, which has to be again decomposed, and the counter electromotive force opposes the main or decomposing current, and consequently, if allowed to occur, diminishes the efficiency of the electrolytic action and output of the process.

The amalgam formed in the cell is removed as fast as formed by the gravitating flow of the mercury and amalgam under the pressure of the column of mercury in the supplypipe, its momentum, the incline of the floor of the cell, and the weight of the electrolytic column and is carried thereby out of contact with the electrolyte confined within the cell and up into the long leg of the outlet-pipe to a point sufficiently high to form in the leg 0 a column of mercury, which counterbalances the weight of the column or body of electrolyte in the cell and effectively seals the same within the cell at the outlet end thereof, while at the same time the column of mercury in the leg 0 of the inlet-pipe effectively seals the electrolyte at the inlet end of the cell. These seals are maintained while the process is in operation by the continued flow of the mercury and amalgam, as aforesaid, which results in the electrolyte being confined in the cell and prevented from running out thereof and mixing with the amalgam and solution in the reclaimer and also results in the removal of the amalgam from contact with the electrolyte in case of stoppage from accident or design, for it will be seen that in case the process is interrupted the mercury in the cell will run down into the pipe 0 and will carry with it all the amalgam in the cell, which by reason of its lighter specific gravity will rise in the leg 0 above the column of mercury therein, leaving the latter in contact with theelectrolyte in the short leg of said pipe. As a result all danger of recombination of the amalgam with the electrolyte in the cell in case of stoppage of the process is avoided, and the cell is thus always maintained in the best possible condition for carrying on the process with a maximum efficiency. Furthermore, it will be noticed that the sealing of the electrolyte in the cell renders the latter independent of the reclaimer and that the mercury seals are established and maintained by the gravitating flow of the mercury independent of the column of liquid in the reclaimer, so that the column of liquidin the reclaimer may be made of any desired height to obtain any desired concentration of sodium hydrate in a minimum time. So, also, it will be seen that the solution in the reclaimer may be drawn off at any time and replenished without disturbing or in any way affecting the decomposition going on in the electrolytic cell.

The amalgam formed in the electrolytic cell is discharged into the reclaimer A, and op portunity is afforded the sodium to unite with the water or othersolution in said reclaimer. This opportunity is obtained most favorably by retarding the flow of the amalgam through the reclaimer, which may be effected by pr0- viding for a body of amalgam of greater depth in the reclaimer than the body of mercury passing through the electrolytic cell. This increased depth of mercury and amalgain in the reclaimer may be obtained by using an excess of mercury over that necessary to obtain the desired depth in the cell; but to economize in the amount of mercury used the increased depth in the reclaimer may be obtained by making the length of the surface in the reclaimer over which the mercury flows less than that of the cells coupled to it or less than that of one cell, it only one cell is used, and providing the said reclaimer with an outlet restricted in area or so proportioned as to discharge the proper amount of mercury from the reclaimer as will give the proper or desired depth in the cell. The mercury and amalgam being of greater depth in the reclaimer than in the cell enables the desired amount of mercury to be drawn off from the reclaimer without causing the amalgam and mercury to flow or travel through the said reclaimer at a rapid rate, which affords op-- portunity for the sodium of the amalgam to rise to the top and unite with the water in the reclaimer. The flow or transit of the amalgam and mercury through the reclaimer may and preferably will be retarded by means of the perforated or foraminous dams or obstructions cl.

In practice the electrolytic cell and preferably the reclaimer are supported so as to incline from their mercury inlet to the outlet ports.

I claim- 1. The herein-described process in the electrodecomposition of saline solutions, consisting in flowing a film of mercury continuously from a higher to a lower level beneath a column of the saline solution, passing a current of electricity through said solution to said film during said flow of the mercury thereby forming an amalgam of mercury and the metal of the saline solution, and separating the amalgam from said solution as soon as formed, by continuing the ilowof the mercury and amalgam by their own weight and momentum and the weight of the column of saline solution, in a substantially vertical direction until such column is counterbalanced by a column of mercury and amalgam, substantially as described.

3. The herein-described improvement in the mercury process of decomposing saline solutions electrically, which consists in flowing the mercury in a thin film from a higher to a lower level across the bottom of the column of electrolytic solution from end to end of the latter, and then continuing the flow of mercury and amalgam in a substantially vertical direction, apart from the said column,

until said column is balanced by a column of mercury and amalgam, substantially as described.

3. In an apparatus for the electrolytic decomposition of electrolytes such as described by the mercury process, an electrolytic cell provided with an inclined metallic bottom having in it inlet and outlet openings at the opposite ends of the cell, substantially U- shaped inlet and outlet pipes for the mercury at one end and the mercury and amalgam at the other, the shorter legs of said pipes being extended beneath the said metallic bottom and connected to said openings therein, and the longer legs being extended up outside of said cell to a point sufficiently high to enable a column of mercury or mercury and amalgam in such long arms to balance the electro lytic solution in the cell, whereby the latter may be sealed, substantially as described.

4. In an apparatus for the electrolytic decomposition of electrolytes such as described, an electrolytic cell provided with an in clined metallic bottom having in it inlet and outlet openings at the opposite ends of the cell, substantially U-shaped inlet and outlet pipes for the mercury having legs of unequal length, the shorter legs of said pipes being extended beneath the metallic bottom and connected to said openings therein and the longer legs being extended up outside of said cell and to a point above or higher than the metallic bottom to enable mercury seals to be formed for the electrolytic solution contained in said cell, the arrangement of the metal seal being such that no residual pool of amalgam will remain in contact with the electrolyte when the operation of the apparatus is stopped, substantially as described.

5. In an apparatus for the electrolytic decomposition of electrolytes such as described, an electrolytic cell provided with an inclined metallic bottom having inlet and outlet openings in it for the mercury, a substantially U shaped mercury-inlet pipe having legs of unequal length with its shorter leg connected to the inlet-0pening in the metallic bottom and its longer leg extended above the metallic bottom outside of said cell, a substantially U- shaped mercury-outlet pipe havinglegs of unequal length with its shorterleg connected to the outlet-openin g in the metallic bottom and its longer leg extended above the metallic bottom outside of the said cell, and a plurality of positive electrodes extended through one wall of the cell substantially parallel to said metallic bottom and in close proximity thereto, the arrangement of the metal seal being such that no residual pool of amalgam will remain in contact with the electrolyte when the operation of the apparatus is stopped, substantially as described.

6. In an apparatus for the electrolytic decomposition of electrolytes such as described, an electrolytic cell provided with a metallic bottom, mercury inlet and outlet pipes communicating with the said cell near the said metallic bottom and extended above the said bottom, and a plurality of positive electrodes extended through one wall of the cell to near the opposite Wall thereof and substantially parallel to the metallic bottom and in close proximity thereto, the arrangement of the metal seal being such that no residual pool of amalgam will remain in contact with the electrolyte when the operation of the apparatus is stopped, substantially as described.

7. In an apparatus for the electrolytic decomposition of electrolytes such as described, a reclaiming vat or vessel for the amalgam formed in the electrolytic cell provided With a dam extended across the cell above the bottom thereof and constructed to leave an open= ing or openings near the bottom of the reclaimer and to offer a solid obstruction above the said opening or openings, whereby the flow of the amalgam is retarded and the upper layer or surface of the amalgam in contact with the liquid in the reclaimer is thereby rendered quiet and the flow of the re claimed mercury over the bottom of the said vessel and below the quiescent layer of amalgam is facilitated, substantially as described.

8. In an apparatus for the electrolytic decomposition of electrolytes such as described, an electrolytic cell provided with a metallic bottom having a series of alternately-arranged partitions or upright walls of non conducting material erected upon it and form ing a continuous passage for the flow over the metallic bottom of mercury constituting the negative electrode of the said cell, and a positive electrode extended into the cell above and in close proximity to the said upright walls or partitions,substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

ELBRIDGE BAKER.

Witnesses:

Jns. H. CHURCHILL, J. MURPHY.