US2677656A - Liquid cathode electrolysis cell - Google Patents

Description

May 4, 1954 Filed June 2, 1950 R. C. OVERBECK LIQUID CATHODE ELECTROLYSIS CELL 3 Sheets-Sheet 1 FIGURE INVENTOR. Reynolds 0. Overbec W 5 M v m AGENTS.

y 4, 1954 R. c. OVERBECK LIQUID CATHODE ELECTROLYSIS CELL 5 Sheets-Sheet 2 Filed June 2, 1950 FIGURE 2 FIGURE 5 INVENTOR.

M 0 e W r w; 0 C m m y e R AGENTS.

y 4, 1954 R. c. OVERBECK 2,677,656

LIQUID CATHODE ELECTROLYSIS CELL Filed June 2, 1950 3 Sheets-Sheet 3 F/GURE 3 F lGUHE 4 INVEN TOR. Reynolds 0. Overbec BY M/ [f a AGENTS.

Patented May 4, 1954 LIQUID GATHODE ELECTROLYSIS CELL Reynolds 0. Overbeck, Columbus, Ohio, assignor, by mesne assignments, to Eberbach & Son Company, Ann Arbor, Mich., a corporation of Michigan Application June 2, 1950, Serial No. 165,670

7 Claims. 1 This invention relates to electrolysis cells, and more particularly to a method of electrolysis and a novel electrolysis cell.

Electrolysis with a liquid metallic electrode is frequently one of the most convenient, if not the only practical, means for the separation of certain elements. Such electrolysis is particularly useful where large amounts of interfering metals must be separated from small quantities of other elements which are not deposited upon the liquid metallic electrode and is used both in manufacturing processes as well as analytical techniques.

The disadvantages of usingan electrolysis cell, either for production purposes or for analytical testing, wherein one orbothof .the electrodes is a liquid metal are that it is difficult to keep the surface of the liquid metallic electrode clean and the solution stirred. These disadvantages result in low. rates of deposition .of-materials on the electrode, lack of completequantitative separation in certain systems, and difficulties in handling the electrolyte used, the liquid metallic electrode, and the deposited material, whether the material be in the form of an amalgam or other alloy, both duringand after electrolysis.

It is therefore one-object of this invention to provide a method of electrolysis wherein the surface of the liquid metallicelectrode is continuously renewed, and theisolution is effectively stirred.

It is another objectof this invention to provide an electrolysis'cell which :may be used'to effect a rapid and complete'separation of certain materials.

It is still another obiectof this invention to provide various componentsofsuch a-cell.

It is a still further-object of; this invention to provide a mercury cathode'cell wherein complete and rapid-separation of materials-in an electrolyte occurs.

Various additional objects-and advantageous features of this invention will become apparent .to those skilled in the art upon readingthefollowing description when taken inconjunction with the accompanying drawings in which:

Fig. l is a perspective view of an electrolysis cell, which constitutes a part of this invention,

with a portion broken awaymore readily to illus- Fig. i is a section of Fig. 8 in the plane 4-4; and

Fig. 5 Ba perspective view of a modification of a portion of the electrolysis cell.

While the followin description will be confined to a mercury cathode electrolysis cell, as used in analytical testingflt is to be understood that the invention is not limited thereto. For instance, intended to be' included within the scope of this invention is the :use of this cell and the application of the method which constitutes a portion of this invention for the purpose of cleaning pickle liquor for commercial applications, such as in the cleaning of spent pickleliquor from steel mills, and the purifying of' pl'ating electrolytes. Furthermorazit is'intendedinot to limit this particular cell to a mercury electrode, but it is intended to include other liquid metallic materials such as Woods -metal,. l 1ipowitz metal, Roses metal, and gallium.

The method, constituting a partof'this invention, comprises positioning a magnetic field in a liquid electrode, which is located in anelectrolysis cell. The positioningof thismagnetic field is important. If the magneticfieldis so positioned .that the two ends thereof adjacent the respective poles generating such field are merely spaced vertically below the'liquid metallic electrode, one advantageous result "is achieved. On the other hand, if this magnetic field is positioned so that one end thereof is in the approximate center of the liquid metallic electrode and the other end thereof-is approximately at'the periphery of such liquid metallic electrode, and the opposite electrode is vertically spaced above said liquid electrode and horizontally extends thereover, and if the electrical contact to the liquid electrode is approximately in theupper center thereof, an additional and totally unexpected advantageous result will be-achieved.

A great difficulty in the operation of-such-a cell in the past has beenthe formation of amalgams on the upper surface of the cathode at the interface of the cathode and the electrolyte positioned thereahove. The deposition of such amalgams at this interface pr sents two problems. If the overvoltage of the element forming the amalgam is small, there is a strong tendency for the floating amalgam to redissolve in the electrolyte. Even if this amalgam does not redissolve in the electrolyte, its presence on the surface of the mercury cathode slows down the rate of reaction and prevents clean mercury from contacting the electrolyte. Therefore, when the magnetic'field ispositioned as first described, any'ferromagnetic amalgam materials will be drawn down to the bottom of the container which holds the mercury, thereby continuously exposing a fresh mercury cathode surface to the electrolyte. In the analysis of steels, which happens to be one of the major uses of the mercury cathode cell for analytical purposes, the greater portion of the material dissolved in the electrolyte is iron, and consequently prompt removal of iron amalgam formed at the interface of the electrolyte and the mercury cathode cell results in a marked increase in the rate of deposition. Of course, other form-magnetic materials which form amalgams, such as nickel and cobalt, often are important constituents of the particular materials being separated, and consequently the removal of these is also an advantageous feature of this method. While prompt and continuous removal of ferro-magnetic amalgams formed at the interface greatly increases the rate of deposition, it will be obvious that stirring of the electrolyte and/or the liquid cathode will also result in a much higher rate of deposition. In the past, this has been accomplished by the use of mechanical stirring devices, such as motor driven agitators and the like. Attempts also exist in the prior art to circulate the mercury by means of convection currents.

For analytical testing purposes the introduction of a mechanical stirrer in the electrolyte may cause considerable inconvenience and does not always create effective agitation. Such mechanical agitation is also, often times, undesirable in commercial electrolysis systems. Various other attempts at agitation, such as the use of convection currents, create such a small amount of agitation as to be worthless, and consequently such methods have never been successfully adapted to commercial or analytical testing.

The second positioning of the magnetic field, described above, causes an extremely unusual effect. Since the current is passing up through the central portion of the mercury to the cathode connection, and the current is passing down through the electrolyte from the platinum anode, the mercury will rotate in one direction and the electrolyte in the opposite direction, while the ferro-magnetic materials are continuously and .simultaneously pulled down below the interface. This countercurrent rotation of the mercury and electrolyte thereby keeps a renewed mercury surface in eflicient contact with fresh portions of the electrolyte. Using 100 milliliters of electrolyte and current of amperes, a rotation of '70 or more turns per minute can be produced. Using 50 milliliters of electrolyte and a current of 14 amperes, 85 and more turns per minute are produced.

Using the above method in a mercury cathode cell, with either position of the magnetic field, an alloy dissolved in the electrolyte has separated therefrom in the form of amalgams, all metals except those in the mercury cathode group. Thereafter, the electrolyte is merely withdrawn from the cell, and standard analytical methods are utilized to determine the quantities of the various elements, including those metals in the mercury cathode group, that are still present.

Suitable acids which may be used to dissolve a particular sample of metal which it is desired to test are sulfuric, aqua regia, phosphoric, perchloric and nitric, as is well known to those skilled in the art.

To illustrate this invention, and to show the marked utility of this method, and also to enable one skilled in the art properly to perform this invention, the following examples are given. It is to be understood that these examples are merely illustrative in nature, and should in no way be construed as limitations on the scope of the disclosure.

In the following three examples, 5 grams of iron sulfate were dissolved in 100 milliliters of N sulfuric acid to form the electrolyte. 35 milliliters of mercury were placed in a container which was of size whereby 40 square centimeters of mercury surface was obtained. The anode comprised centimeters of B it S gauge 1'? platinum wire. In Example I no magnetic field was provided. In Example II a magnetic field was provided merely through and below the cathode. In Example III a magnetic field was produced extending from the center of the cell to the periphery and was formed by a magnet positioned below the cell. The resultant cell efficiencies are tabulated below:

EX. I EX. III

Cell Efficiency (gms. Fe removcd/ ampere hour) It is obvious from the above examples that while the positioning of the magnetic field of Example II enables a cell efiiciency to be produced which was never before enjoyed, the positioning of the magnetic field of Example III results in an extremely high cell efliciency, due to the unexpected countercurrent stirring which results, as well as the removal of term-magnetic materials from surface of the cathode. This second positioning of the magnetic field results in a true synergistic effect.

The remaining portion of this particular invention comprises an electrolysis cell, which for purposes of illustration will be described in conjunction with a mercury cathode analytical testing cell.

Referring now to the drawings, and more especially to Figs. 1 and 2, a container I0 is provided. This container may merely be a glass beaker, but it is desirable to provide a glass beaker which is provided with a drain [2 having a valve l3 therein. Platinum anode l4, having a horizontally extending spiralled portion [5 at the lower end thereof, is positioned within the container H1. The quantity of mercury present will vary depending upon the size of the cell. For a container having a volume of about 500 milliliters, 35 milliliters of mercury, which produced about 40 square centimeters of cathode surface, were used.

The horizontally extending spiralled end l5 of the anode may be spaced at various distances from the surface of the cathode. However, for the above quantity of mercury an optimum spacing has been found to be between 5 and 8 millimeters.

It has been found that an electrolysis cell of this size operated with efiiciency using 15, 30, 35 and 50 milliliters of mercury as a cathode. Platinum wire was used for the anode and consisted generally of B & S gauge No. 17, 80 cm. in length. Positioned exterior of the container l0 and vertically spaced from it but in very close proximity thereto is a strong permanent magnet I8 having a north pole l9 and a south pole 20. In order to achieve both advantageous effects of using such a magnet, the magnet is of a size and so positioned that one pole, 20 in this case, is approximately directly belowthecenter of the container, while the other pole I9 is in the vicinity of the periphery of the container. It is, of course, immaterial which pole is the north pole and which pole is the south pole. Cathode probe 22, insulated from the electrolyte by means of glass jacket 23, but extending into the mercury as shown at 24, is positioned approximately in the center of the container. The lower portion of the cathode probe 22 is at approximately right angles to the remainder of the probe, as shown at it, to insure continuous contact with the mercury. It is desirable that the cathode probe be positioned approximately directly above the pole of the permanent magnet that is located below the center of the container.

Referring now more particularly to Figs. 3 and there is shown a component of the electrolysis cell. A stand 25, having an upwardly extending column 2? extending therefrom, is so positioned that the container it may be placed alongside thereof. A clamp 26, having associated therewith a tightening screw 25, and having extending therefrom a support member is shown fixedly secured to the column 27:. l he outer portion of member 3! is in the form of an annular tapered ring 23 which supports a member such as a rubber stopper 3d. Extending therethrough are the anode i i, the glass enclosed cathode probe 22, and a hollow glass tube comprising vertical 130T" tions 36% and a lower, horizontally extending, circular portionSll. This tube is preferably made of glass, and its purpose is to conduct cooling water down to the portion of the cell where heat is generated. The upper portions 3-36 of the tube may be fitted with flexible conduits (not shown).

Fig. 5 shows a particular type of magnet which is ideally suited to the electrolysis cell which is a part of the subject matter or this invention. outer periphery 39 of this magnet comprises one pole while the inner member dd comprises the other pole.

This electrolysiscell is operated in the followmanner. Container it has added thereto the sired quantity of mercury. Preferably this is i -t enough to extend up to the lower Part of the discharge tube l2. Thereafter the electrolyte, which usually comprises the metal from which certain elements are to be separated, dissolved in I an acid, is placed in the container ill above the mercury cathode. Then the assembly comprising the anode, the cathode probe and the cooling coil is lowered into the solution and so positioned that the cathode probe extends down into the mercury and the horizontally extending anode portion to is spaced from the surface of the cathode. This, of course, is accomplished by backing oil the screw 29, and then tightening it when the desired position has been. reached. The current is then turned on. Preferably about 12 volts and 15 amps. of direct current are used. It is desir able to have a unit to supply this current which may be attached to any ordinary 115 volt A. C. outlet. Such a unit merely comprises a transformer, a rectifier, and a variable resistance in electrical circuit that is well known to those skilled in the art.

As form-magnetic materials are formed as alganis at the interface of the electrolyte and the cathode, the magnetic field created by the magnet will pull these form-magnetic materials down to the bottom of the container it. Furtherinore, by positioning the magnetic field in the second position described above, countercurrent stirring is accomplished. Thusly, there is realized a complete separation of all metals which will iorm amalgams in a much shorter period of time than would otherwise be theoase.

It should be obvious that an electromagnet, properly positioned, could be substituted for the permanent magnet and the same results would be obtained. Moreover, it is to be understood. that the term magnet when used in the appended claims includes electromagnets as well as other artificial magnets.

When all thematerialzhas; been deposited on the cathode, the cathode probe, the anode and the cooling coil may be raised from the solution as a unit and allowed to drip or may be washed in the conventional manner to remove any electrolyte containing dissolved material that it is desired further to test. Thereafter, the electro lyte is merely drained from the cell and the analysis of the electrolyte iscarried on in known fashion.

In the prior art cooling has generally been attempted by means of a water jacket surrounding the electrolysis cell, or other equally ineflicient means. Furthermore, quite often the electrical connection to the cathode has been at some portion of the cell below the normal level of the mercury, n cessitating an expensive and especially designed container therefore. Moreover, on completion or the deposition or the elements in solution, it has beennecessary in the pastto remove the anode, then the cathode and then the agitator, wash each of these elements separately, with the net result that a long period of time is involved in such operation.

It will be apparent that the novel positioning of the cathode probe, the anode, and the cooling coil results in a muchmore efiicient operation of the cell as far as cooling is concerned, and much speedier removalof the electrolyte, since the entne cooling system anode, and cathode probe may be removed from the cell simultaneously, as had not been previously considered possible.

From the foregoing, it should be apparent that there has been devised a novel method for effecting electrolysis, a novel electrolysis cell, and equally novel component parts of such a cell. The practice of this method, or the utilization of this cell, results in the rapid separation of metals in the electrolyte, provides unique countercurrent stirring, reduces to a minimum resolution of deposited metals, and eliminates changing mercury during electrolysis.

While this invention has been described in its preferred embodiment, it is to be understood that the words that have been used are words of description rather than of limitation and that changes within the purview of the above description and the appended claims may be made without departing from the true scope and spirit of the invention.

What is claimed is:

1. An electrolysis cell assembly comprising a container adapted to contain a liquid cathode and an electrolyte therein, a horizontally extending anode, a cathode probe electrically insulated generally and provided with an electrically conductive contact portion positioned centrally of and below said anode, and a magnet vertically spaced below said anode and said cathode probe contact portion for producing a magnetic field having lines of force substantially vertically extending adjacent said cathode probe contact portion and substantially horizontally extending adjacent said anode; said assembly being adapted to have said anode located in said electrolyte and vertically spaced above said liquid cathode, said cathode probe contact portion being immersed in said liquid cathode, and said magnet vertically spaced below said liquid cathode and exterior of said container.

2. An electrolysis cell assembly comprising a container adapted to contain a liquid cathode and an electrolyte therein, a horizontally extending anode, a cathode probe electrically insulated generally and provided with an electrically conductive contact portion positioned centrally of and below said anode, and a magnet provided with two pole portions, one of said pole portions being positioned centrally of and below said anode and said cathode probe contact portion, while said other pole portion is positioned adjacent the periphery of said anode, whereby a magnetic field is produced having lines of force substantially vertically extending adjacent said cathode probe contact portion, and substantially horizontally extending adjacent said anode; said assembly being adapted to have said anode located in said electrolyte and vertically spaced above said liquid cathode, said cathode probe contact portion being immersed in said liquid cathode, and said magnet vertically spaced below said liquid cathode and exterior of said container.

3. The structure set forth to claim 2 wherein a conduit, vertically spaced above said anode and adapted to convey a cooling fluid, is also provided.

4. The structure set forth in claim 2, wherein said pole portion which is positioned adjacent the periphery of said anode is annularly shaped and substantially coaxial therewith.

5. In a liquid cathode electrolysis cell, comprising a container adapted to contain a liquid cathode in the bottom thereof, the improvement which comprises a horizontally extending anode adapted to be vertically spaced above said cathode, a cathode probe electrically insulated generally and provided with an electrically conductive contact portion positioned centrally of said anode and adapted to be immersed in said cathode, and a magnet exterior 'of said container and vertically spaced therebelow for producing a magnetic field having lines of force substantially vertically extending adjacent said cathode probe contact portion, and substantially horizontally extending adjacent said anode.

6. In a liquid cathode electrolysis cell, comprising a container adapted to contain a liquid cathode in the bottom thereof, the improvement which comprises a horizontally extending anode adapted to be vertically spaced above said cathode, a cathode probe electrically insulated generally and provided with an electrically conductive contact portion positioned centrally of said anode and adapted to be immersed in said cathode, and a magnet exterior of said container and provided with two pole portions, one of said pole portions being positioned centrally of the base of said container, and said other pole portion being positioned adjacent the periphery of said container, whereby a magnetic field is produced having lines of force substantially vertically extending adjacent said cathode probe contact portion, and substantially horizontally extending adjacent said anode.

7. The structure set forth in claim 5 wherein said pole portion adjacent the periphery of the base of said container is an annular member and substantially coaxial therewith.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 652,761 Entz July 3, 1 00 FOREIGN PATENTS Number Country Date 5,648 Great Britain of 1905 573,894 France Mar. 20, 1924 OTHER REFERENCES Journal of Industrial and Engineering Chemistry, vol. 4, 1912, pages 534 and 535.

Zeitschrift fur Electrochemie, v01. 13, (190 pages 308 and 309.

Claims (1)

1. AN ELECTROLYSIS CELL ASSEMBLY COMPRISING A CONTAINER ADAPTED TO CONTAIN A LIQUID CATHODE AND AN ELECTROLYTE THEREIN, A HORIZONTALLY EXTENDING ANODE, A CATHODE PROBE ELECTRICALLY INSULATED GENERALLY AND PROVIDED WITH AN ELECTRICALLY CONDUCTIVE CONTACT PORTION POSITIONED CENTRALLY OF AND BELOW SAID ANODE, AND A MAGNET VERTICALLY SPACED BELOW SAID ANODE AND SAID CATHODE PROBE CONTACT PORTION FOR PRODUCING A MAGNETIC FIELD HAVING LINES OF FORCE SUBSTANTIALLY VERTICALLY EXTENDING ADJACENT SAID CATHODE PROBE CONTACT PORTION AND SUBSTANTIALLY HORIZONTALLY EXTENDING ADJACENT SAID ANODE; SAID ASSEMBLY BEING ADAPTED TO HAVE SAID ANODE LOCATED IN SAID ELECTROLYTE AND VERTICALLY SPACED ABOVE SAID LIQUID CATHODE, SAID CATHODE PROBE CONTACT PORTION BEING IMMERSED IN SAID LIQUID CATHODE, AND SAID MAGNET VERTICALLY SPACED BELOW SIAD LIQUID CATHODE AND EXTERIOR OF SAID CONTAINER.

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