US2315830A - Production of alkali metals and their amides - Google Patents

Description

April 6, 1943. R. A. vlNGEE Erm. 2,315,330

PRODUCTION 0F ALKALI METALS AND THEIR AMIDES Filed Aug. l2, 1939 l (/rcentfaledlazzz af/f Ag .j

I (ncerztraefcd fall/50x af/f ((0 ayaeous /fl/ rely yl/MATTORNEY Patented Apr. 6, 1943 UNITED STATES PATENT OFFICE PRODUCTIN 0F ALKALI METALS AND THEIR AMIDES Application August 12, 1939, Serial No. 289,760

(ci. gt4-59)' `13 Claims.

This invention relates to the production of alkali metals, particularly potassium, and alkali metal amldes.

Metallic potassium is ordinarily produced by the electrolysis of fused potassium chloride or fused potassium hydroxide. 'I'he electrolysis of fused potassium chloride presents several serious difficulties, among which are severe corrosion of equipment and the necessity for employing an extremely high temperature to maintain the potassium chloride in fused condition. The electrolysis of fused potassium hydroxide also requires a relatively high temperature to maintain the potassium hydroxide in a. fused condition. Furthermore, the anode reaction in the electrolysis of potassium hydroxide Vresults in the formation of oxygen and Water; the water thus formed tends to diffuse through the electrolyte and react with the metallic potassium product, thus diminishing the yield of potassium and generating hy drogen. The evolution oi' hydrogen and oxygen from the cell causes frequent explosions which are obviously objectionable.

Ewan has described in United States Patents 1,538,389 and 1,538,390 a method for producing metallic potassium involving the electrolysis of a solution of potassium iodide in liquid ammonia in a cell having a potassium amalgam anode. In Ewans process, potassium is produced at the cathode in the form of a solution of potassium in liquid ammonia, which solution is continuously withdrawn and the potassium recovered therefrom. However, it has been found that the potassium reacts slowly with the liquid ammonia solvent, forming potassium amide and hydrogen.

The concentration of the potassium amide in the electrolyte thus gradually builds up, causing variations in the conductivity of the electrolyte which make cell operation diiiicult, and ulti mately resulting in the crystallization of potassium iodide, potassium amide. or a mixture thereof. 1f a mixture of potassium amide and potnssium iodide crystallizes from the solution it is necessary to separate these compounds, since the cost of potassium iodide is so high that it must be recovered and reused to permit an economical working of the process. Even if the cell is operated so that only potassium amide crystallizes from the solution, it is important to Wash carefully the crystallized amide to recover the expensive potassium iodide retained by the crystais. Moreover, the molal solubility of potassium iodide is such that the electrolyte has a comparatively low conductivity; the usual practice, therefore, has been to design the cells i'or operation at high pressures (thus permitting use 0f higher temperatures) to obtain more favorable cell operating characteristics. 'I'hese factors obviously render the electrolysis o! potassium iodide in liquid ammonia a highly expensive and complicated method of'obtaining metallic potassium.

Potassium amide has heretofore been prepared by either treating metallic potassium with gaseous ammonia at elevated temperatures or by reacting metallic potassium with liquid ammonia in the presence of catalysts. Obviously any process permitting a more simple and inexpensive production of metallic potassium would also be of advantage to the production 'of potassium amide therefrom and would therefore be highly desirable.

It is an object of this invention to provide simple and relatively inexpensive processes for the production of potassium and potassium amide and to combine these processes, if desired, with processes for production oi sodium and sodamlde.

In accordance with our invention, metallic potasslum is produced by electrolyzing a solution of potassium amide in liquid ammonia, whereby potassium is produced at the cathode of the cell and recovered therefrom. By operating in accordance with our invention the reaction oi the potassium product with the liquid ammonia solvent may be substantially diminished, thereby increasing the yield of potassium. Furthermore, the complicated and expensive treatments required in prior processes for recovery of electrolyte from potassium amide crystals formed in the cell are avoided since the small amounts of crystallized amide formed in the practice of our invention are uncontaminated with other potassium salts and may thus be reused without further treatment. The cell used in accordance with our invention preferably has a potassium amalgam anode, whereby the production o! metallic potassium is effected without substantial consumption or the relatively expensive potassium amide.

O ur invention also contemplates an improved process for the production of potassium amide Yinvolving the electrolysis of a solution oi' potassium amide in ammonia in a cell employing a potasslum amalgam anode, whereby potassium goes into solution from the potassium amalgam anode to form potassium amide and potassium is formed as the primary product at the cathode, and treatment of the potassium thus produced with liquid ammonia in the presence of a catalyst capable of accelerating the reaction of potassium and liquid ammonia to produce potassium amide. amples of catalysts which may be used in accord= As exance with this phase of our invention there may be mentioned finely divided iron oxide. platinum black, aluminum, high carbon steel, asbestos iiber, and ilnely divided metals prepared by reduction of their salts by sodium, potassium or calcium in ammonia solution, e. g. nely divided silver prepared by reduction of silver cyanide by means of potassium or reduction oi silver nitrate by means of calcium, or finely divided iron prepared by reduction oi ferrie nitrate hexahydrate by means of sodium. The catalyst may be present in the cell in which the electrolysis is carried out, or a solution of potassium in liquid ammonia may be contacted with the catalyst in a separate vessel. In either case potassium amide is produced in a simple and efiicient manner.

In carrying out this invention a solution of potassium amide in liquid ammonia is formed and electrolyzed in a cell oi suitable design. 'I'l'ieI percentage oi' potassium amide in the liquid ammonia solution may vary between about 5 and about 60%. We prefer. however, to employ a. relatively concentrated solution oi' potassium amide, e. g. a solution containing about 50% potassium amide, or a saturated solution thereof. Ii a concentrated but unsaturated solution of potassium amide is used in accordance with this invention, a concentrated solution of potassium in ammonia is formed at the cathode. However, if a solution oi' potassium arnlde is employed, which is substantially saturated at the higher temperatures suitable for operation of our process as hereinafter indicated. solid potassium is produced at the cathode. We prefer to employ a concentrated solution of potassium amide in ammonia and to control conditions of concentration and temperature so as to form a solution of potassium in ammonia rather than solid potassium at the cathode. The bronze solution of potassium in ammonia thus formed thereafter serves as cathode in the cell. Since both the solution of potassium in ammonia and the solid potassium, which are formed at the cathode, are less dense than the potassium amide solution and hence rise to the top of the cell, the cell should be arranged so that the cathode is disposed above the anode. We prefer to employ a cell having a potassium amalgam anode, since in such a cell the potassium amide electrolyte is not substantially consumed as the -NI-Iz ion formed on electrolysis reacts at the anode with the potassium in the amalgam to regenerate potassium amide, thereby permitting more economic operation. The potassium amalgam may be produced by the electrolysis of an aqueous solution of potassium chloride in a cell employing a mercury cathode and may contain between about 0.1 and about 1.5% potassium.

The process oi' our invention is preferably carried out continuously, potassium amalgam being continuously introduced at the anode and potassium product being continuously withdrawn at the cathode. As above pointed out, the potassium product is withdrawn either in solid form or in the form of a solution thereof in ammonia; the solid potassium contains small amounts of ammonia and potassium amide, while the solution contains in addition to the potassium -small quantities o! potassium amide dissolved therein. In either case, the product withdrawn from the cathode is heated to evaporate the ammonia and the potassium metal then separated from the potassium amide by melting the potassium and withdrawing the molten metal. The metal thus obtained is nished as desired.

When operating in accordance' with this invention, it is desirable to maintain the potassium amide concentration of the electrolyte substantially constant. Ammonia, which in the absence of catalysts is slowly consumed by reaction with potassium product, should thus be continuously replenished. The maintenance of a substantially constant amount oi potassium amide in the cell depends chiefly upon two factors, namely, the rate` of potassium amide `formation in the cell due to reaction of the potassium product and liquid ammonia and the amount of potasslum amide withdrawn at the cathode along with the potassium product. These factors may vary widely depending somewhat upon the particular concentration of potassium amide used. When the rate of removal from the cell of potassium amide withdrawn with the potassium product is approximately equal to the rate at which it is formed in the cell, then the amount of potassium amide in the cell will automatically be maintained substantially constant. When the rate of removal of potassium amide from the cell is greater than the rate at which it is formed, some of the potassium amide removed from the cell and recovered as described above should be returned to the cell, preferably in the form of a solution thereof in liquid ammonia. 0n the other hand, when the rate of potassium amide formation is greater than the rate of removal thereof from the cell, an ammonia solution rich in potassium amide should be removed from the anode portion of the cell, cooled to precipitate some of the potassium amide, and the dilute solution of potassium amide thus formed returned to the cell. Hydrogen formed by the reaction of potassium and ammonia should be periodically removed from the top of the cell.

'I'he temperature at which the electrolysis is carried out may vary Widely. We prefer to operate in the range between about 0 and about 30 C., since within this temperature range the solubility of potassium amide is distinctly greater than at lower temperatures, whereas the ammonia vapor pressure is not excessively high, so that sumcient potassium amide may be dissolved in the ammonia to greatly diminish the tendency o1' the potassium product to redissolve in the ammonia, whereby shorting" of the cell is avoided. The pressure under which the cell is maintained during electrolysis depends upon the temperature used and may vary between about 3 and about 8 atmospheres. The current density employed may vary Widely but generally will be between about 0.05 and about 0.5 ampere per sq. cm. The voltage applied to the cell mayvary depending somewhat upon the current density and somewhat upon the design oi' the cell, and thus may be between about 0.5 and about 6.

As pointed out above, our invention also contemplates the production of potassium amide from the metallic potassium produced in accordance with this invention. This may be accomplished by conducting the electrolysis in the presence oi a catalyst which accelerates the reaction of potassium and liquid ammonia to produce potassium amide. The catalyst meployed may be finely divided iron oxide, platinum black, aluminum, high carbon steel, asbestos fibers, or iinely divided metals prepared as hereinbefore described, by reduction of salts of the desired metal by sodium, potassium or calcium in ammonia solution. When operating in this manner the catalyst may be added to the electrolyte in an amount between about 0.01 and about 1.0% by weight of the electrolyte, or, if desired, the cathode or the cell walls may be constructed oi or coated with catalytic material. However, potassium amide may be prepared by withdrawing the potassium formed at the cathode and contacting the potassium with liquid ammonia in the presence of the catalyst in aI separatevessei or series of vessels. If desired, potassium may first be necovered from the potassium product formed at the cathode during electrolysis and then treated with gascous ammonia at elevated temperatures to yield potassium amide and hydrogen.

Sodium may also be produced from the potassium' obtained in Aaccordance with our invention by contacting the potassium product formed at the cathode with a solution of sodium chloride in liquid ammonia preferably at a temperature between about and 0 C. We have i'ound that under these conditions the potassium reacts with sodium chloride to forrn potassium chloride `and sodlum,.the potassium chloride being insoluble in ammonia and precipitating. Operating in this manner it will be seen. that the potassium chloride thusobtainedmay be electrolyzed'in an aqueous potassium chloride cell having a mercury cathode to produce lpotassium The potassium amalgam may then be used as the anode in a cell employed in accordance with our invention and the potassium product obtained from the cell may be treated as abovedescribed `to produce metallic Thet overall reaction oi such a process is therefore to prepare metallic sodium and chlorine (in the aqueous potassium chloride cell) while consuming only sodium chlorlde.- The potassium used for the Vabove reaction may be either substantially pure potassium or potassium accompanied by small amountsot potassium amide, as il:` is withdrawn from the cathode. Potassiumv amide reacts with sodium chloride in ammonia solution to precipitate potassium chloride and sodamide, and the latter may u be extracted from the combined precipitate by continued washingjwith ammonia. Potassium chloride is;thu.s made avaliable for electrolysis as indicated above, and sodamide may be recovered from the ammonia wash liquor.

Figures l; 2 and 3 illustrate embodiments of our invention, Figure 1 illustrating the embodiment in 'which a concentrated solution oi' potassium amideY in ammonia `is electrolyzed, Figure 2 illustrating the embodiment in which potassium amide is produced. and Figure 3 illustrating the embodiment in which metallic sodium' is produced.

In Figure 1 potassium amalgam formed by the `electrolysis of an aqueous potassium chloride ysolution in a cell having a mercurycathode is introduced into cell I. forming a layer at the bottom thereof. Cell i4 is provided .with a` suitable metallic cathode disposed above the potasnslum amalgam layer which serves as the anode of the cell. A solution of potassium amide in ammonia is disposed in the cell and floats on top. oi the potassium yamalgam layer. Upon electrolysis, a concentrated solution of potassium in liquid ammonia containing some' potassium amide is formed atthe cathode and continuously withdrawn therefrom. This solution to rated; the ammonia is passed to condenser l,

wherein it is condensed and returned to cell I. The residue from evaporator 2 consisting oi metallic potassium containing some potassium amide passes to separator l, wherein the mixture is heated and molten potassium withdrawn therefrom, leaving a potassium amide residue. When the rate of potassium amide removal is substantially the same as its rate of formation. the potassium amide recovered in separator I may be withdrawn and reused in another cell in accordance with our invention. When the rate of potassium amide removal from the cell is greater than the rate of its formation therein.

all or a portion of the potassium amide .recovered in separator 4 may be dissolved in the liquid ammonia from condenser 3 in dissolver 5 and returned to cell I. When the rate of potassium amide removal in substantially less than its rate of formation, then a solution rich in potassium amide may be removed, as shown. 4from the anode Aportion of the cell to cooler 6. wherein it is cooled to precipitate some potassium amide which is removed and the dilute solution returned to the cell. Make-up ammonia to replenish the ammonia lost by reaction with potassium is in introduced to the cell along with ammonia from condenser 3. Depleted amalgam is continuously withdrawn from the anode and returned to the aqueous potassium chloride cell.

It is to be understood that in `the embodiment described in Figure l when the concentration of the potassium amide in the electrolyte is such that solid potassium is formed at the cathode. instead of withdrawing a concentrated solution of potassium in ammonia from the cathode portion, as shown in Figure l, solid potassium containing small amounts or liquid ammonia and potassium amide is withdrawn. The solid potasslum is then heated to remove any liquid ammonia and the potassium separated from the potassium amide contained therein in the manner hereinabove described ln connection with the disclosure of Figure 1.

In Figure 2, potassium amalgam produced by the electrolysis of anv aqueous potassium chloride solutionA in a cell having a mercury cathode is continuously introduced into cell 1 forming a layer at the bottom thereof. Cell l is provided with a suitable metallic cathode disposed above the potassium amalgam layer which serves as the anode. A concentrated solution of potassium amide in ammonia ls disposed in the cell and i'loats on top of the potassium amalgam anode. Upon electrolysis, a concentrated solution of potasslun in ammonia containing some potassium amide is formed at the cathode and continuously withdrawn therefrom This solution is then introduced into catalyst chamber 8, wherein it contacts a catalyst such as platinum black, ilnely divided iron oxide, aluminum. high carbon steel, asbestos rilbers, or iinely divided metal as hereinbefore described, so that the potassium reacts with the ammonia solvent to form a solution of potassium amide in ammonia. This solution is then passed to evaporator 9. the ammonia evaporated therefrom. passed through condenser I0. and returnedto cell 1. Solid potassium amide product is withdrawn from evaporator 9 as resi due. "Ihe concentration of potassium amide in the electrolyteln cell 1 may be controlled in a manner similar to that illustrated and described in connection with Figure 1. Depleted amalgam is continuously withdrawn from the anode and returned to the aqueous potassium chloride cell. In Figure 3, -pizvtassium\amalgani produced by the electrolysis of a potassium chloride solution in a cell having a mercury cathode is continuously introduced into cell Il, forming a layer at the bottom thereof. Cell Il is provided with a suitable metallic cathode disposed above the potassium amalgam layer which serves as the anode. A concentrated solutionof potassium amide in ammonia is disposed in the cell oating on top of the potassium amalgam anode. Upon electrolysis, a concentrated solution of potassium in ammonia containing some potassium amide is formed at the cathode and continuously withdrawn therefrom; the potassium amide concentration of the electrolyte may be controlled as described in connection with Figure 1. The solution withdrawn from the cathode is introduced into reactor i2. In saturator il sodium chloride and liquid ammonia are introduced and agitated to form a substantially saturated solution oi sodium chloride in ammonia. This solution is then passed to reactor l2, wherein lt contacts the solution of potassium in ammonia preferably maintained at a temperature of from 20 to C.; the sodium chloride reacts with the potassium to form metallic sodium and potassium chloride, and reacts with the potassium amide to form sodamide and potassium chloride. The potassium chloride and sodamide being relatively insoluble in liquid ammonia precipitate and are withdrawn to washer Il, where the precipitate is washed with liquid ammonia. to remove the dissolved sodium and sodium chloride adhering Y thereto, and to dissolve the sodamide contained therein. The washed potassium chloride is withdrawn from washer il and may be returned to the aqueous potassium chloride cell. The liquid ammonia containing small amounts of sodium, sodium chloride and sodamide, withdrawn from washer Il, and the solution of sodium in liquid ammonia containing sodium chloride formed in reactor I2 are both introduced into evaporator i5, wherein the ammonia is evaporated, passed to condenser I6, and reused in saturator I3. The residue from evaporator Il, consisting of sodium, sodium chloride and small amounts of sodamide. is withdrawn therefrom Vto separator l1. wherein the mixture is heated and molten sodium product withdrawn therefrom. The sodium chloride residue containing small amounts of sodamide may be returned directly to saturator I8, or sodamide may first be recovered therefrom by fractional crystallization from an ammonia solution; alternatively a part of the sodium chloride vresidue containing sodamide may be discarded as a bieed" to avoid building up a high concentration of sodamide in the system, or the sodamide contained in the sodium chloride residue may be neutralized with the required quantity of HC1 or NHaCl.

The following examples are illustrative of our invention. Amounts are given in parts by Weight.

Example 1.-A 50% solution of potassium amide in anhydrous liquid ammonia was electrolyzed by the application of a potential of about 2 volts to a cell having a 1.0% potassium amalgam anode and a chrome iron cathode, the cathode being disposed above the anode. The cell was maintained at a temperature of about C. and a pressure of about 7.5 atmospheres. A solution of potassium in ammonia containing a small amount of potassium amide was continuously formed at the cathode and withdrawn therefrom. Pressure on this solution was released to allow NH: to vaporize. At the same time. heat was supplied to complete the vaporization'of the solvent and to melt the potassium. The liquid potassium was separated from the solid amide at a temperature of about 65 C. and the potassium allowed to cool and harden. The evaporated ammonia was condensed and returned to the cell. Depleted amalgam was continuously withdrawn from the anode. i Since the concentration of potassium amide in11 the electrolyte tended to increase, a portion of the electrolyte was continuously withdrawn and a part of the ammonia evaporated therefrom adiabaticallylby release of pressure to crystallize solid potassium amide. After separation ofthe solid. the depleted potassium amide solution was returned to the cell together with make-up ammonia.

Example 2.-A solution of potassium amide in anhydrous liquid ammonia containing about 59.2% potassium amide was electrolyzed by the application of a potential of about 2 volts to a cell having a 1.0% potassium amalgam anode and a chrome iron;V cathode, the cathode being y disposed above the anode. The cell was main- 1 tained at a temperature of about 25 C. and a pressure of about 7.5 atmospheres. Solid metallic potassium containing small amounts of liquid ammonia and potassium amide was continuously produced at the cathode. The mixture thus formed was continuously withdrawn and ammonia was evaporated therefrom by releasing the pressure and supplying hea'rl thereto. The residue was thenheated to about 65 C. and molten potassium metal was separated from residual potassium amide. Depleted amalgam was continuously withdrawn from the anode. Since the concentration of potassium amide in the electrolyte tended to increase, a portion of the elec trolyte was continuously withdrawn and a part of the ammonia evaporated therefrom adiabatically by release of pressure to crystallize solid potassium amide. After separation of the solici` the depleted potassium amide solution was returned to the cell together with make-up ammonia.

Ex'ample 3.-A 5% solution of potassium amide in anhydrous liquid ammonia was electrolyzed by the application of a potential of about 2 volts to a cell having a 1.0% potassium amalgam anode and a chrome iron cathode, the cathode being disposed above the anode. The cell was maintained at a temperature of about 25 C. and a pressure of about 7.5 atmospheres. A 30% solution of potassium in ammonia containing small amounts of potassium amide was continuously formed at the cathode. This solution was continuously withdrawn, diluted with liquid ammonla so as to form an approximately 10% solution of potassium in liquid ammonia, and then introduced into a.Y vessel containing nely divided iron maintained in suspension by agitation and maintained at a temperature of about -33 C., wherebyithe potassium reacted with the liquid ammoniaI solvent to produce potassium amide. Agitatlon of the solution was then s pped, the catalyst allowed to settle, and the lution decanted. 'I'he solvent was removed from the solution by release of pressure and moderate heat input. Solid potassium amide was thus obtained as the product. Since the concentration of potassium amide in the electrolyte tended to increase, a portion of the electrolyte was continuously withdrawn and a part of the ammonia evaporated therefrom adiabatically by release of pressure to crystallize solici potassium amide. Ai'ter separation of the solid, the depleted potassium amide solution was returned to the cell together with make-up ammonia.

Example 4.-A 30% solution or potassium in liquid ammonia (containing a small amount of potassium amide) obtained as 'described in Example 1 was treated with a 14% solution oi sodium chloride in liquid ammonia at a temperature of about -10 C., whereby potassium chloride, sodium'and a small amount oi sodamide were formed. The potassium chloride and sodamide precipitated from the solution and were removed: the sodium dissolved in the solution of sodium chloride in ammonia. The precipitated `potassium chloride and sodamide were washed with liquid ammonia to recover dissolved sodium retained therein and to dissolve the sodamide from theprecipitate. The wash liquor and the solution of sodium and sodium chloride in liquid ammonia were combined and the ammonia evaporatedtherefrom by releasing the pressure and heating. The residue of sodium, sodium chloride and sodamide was then heated to about 100 C. and molten sodium was withdrawn as product.

Example 5.-A 50% solution oi' potassium amide in anhydrous liquid ammonia is electrolyzed in a cell having an anodeconsisting oi a 1% potassium amalgam and a rough surfaced, mild steelcathode or relatively large area coated with iron oxide, therv cathode being `disposed in the upperpart of the cell. The cell is maintainedV at a temperature of about 25 C. and a pressure of about 7.5 atmospheres, and a. sufriciently low voltage -is supplied to the cell to maintain a cathode current density below about .15 ampere per sq. cm. Under these conditions no appreciable amount of bronze solution oi potassium in ammonia will be formed at the ca hode; potassium formed at the cathode will be converted, substantiallyasfast as it is formed, to potassium amide by reaction with ammonia, catalyzed by the iron oxide on the cathode surface. Hydrogen formed by the reaction between potassium and ammonia, is continuously vented from the cell; potassium amide formed at the cathode goes into solution in therelectrolyte. A portion of the electrolyte is continuously withdrawn from the cell, and a part or the ammonia evaporated therefrom adiabatically by release or pressure, to crystallize solid potassium amide. After separation of the solid, the depleted potasslum amide solution is returned to the cell together with make-up ammonia, the potassium amide concentration in the electrolyte thereby being maintained substantially constant.

It will be evident from the above description that our invention provides a simple and etlicient processV for the production or metallic potassim and potassium amide which may be operated more economically than processes heretotore used.

Since certain changes may be made in carrying out"the above process without departing yfrom the scope of the invention. it is intended that all matter contained in 'the above description shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. A process for the production o1 metallic potassium which comprises electrolytically decomposing the potassium amidey in a solution of potassium amideinliquid ammonia in a cell having a potassium amalgam anode.

2. A process for the production oi metallic potassium which comprises electrolytically decomposing the potassium amide in a solution of potassium amide in liquid ammonia in a cell having a potassium amalgam anode and recovering metallic potassium from the solution of potassium in ammonia formed at the cathode.

3. A substantially continuous process for the production oi metallic potassium which comprises electrolyticaily decomposing the potassium amide in a concentrated but not saturated solution d! potassium amide in liquid ammonia in a cell having a potassium amalgam anode maintained at a temperature between about 0 and about 30 C., continuously withdrawing a solution o! potassium in ammonia containing small amounts of potassium amide from the cathode portion of the cell, and recovering metallic potassium from said cathode solution.

4. A process for the production oi' metallic potassium which comprises electrclytically decomposing the potassium amide in a substantially saturated solution of potassium amide in liquid ammonia in a cell having a potassium amalgam anode and withdrawing solid potassium metal from the cathode portion of the cell.

5. A substantially continuous process for the production of metallic potassium which comprises electroiytically decomposing the potassium amide in a substantially saturated solution ot potassium amide in liquid ammonia in a cell having a potassium amalgam anode maintained at a 'temperature between about 0 and about 30 C., continuously withdrawing solid potassium metal containing small amounts of ammonia and potassium amide from the cathode portion o! the cell, and recovering metallic potassium from the cathode product thus Withdrawn.

6. A substantially continuous process for the production oi' metallic potassium which comprises .electrolytically decomposing the potassium amide in a solution of potassium amide in liquid ammonia ina cell having a potassium amalgam anode, continuously withdrawing potassium containing some potassium amide from the cathode portion of the cell, continuously recovering metallic potassium from the cathode product thus withdrawn, and maintaining the potassium amide concentration oi' the electrolyte substantially constant.

'7. A substantially continuous process lor the production ot metallic potassium which comprises electrolytically. decomposing the potassium amide in a solution of potassium amide in liquid ammonia in a cell having a potassium amalgam anode, continuously withdrawing potassium containing some potassinm amide from the cathode portion of the celi,-continuously recovering metallic potassium.from the cathode product thus withdrawn, and maintaining the' potassium amide concentration of the electrolyte substantially constant by continuously introducing additlonal quantities oi' potassium amide into 'the electrolyte.

il. A substantially continuous process for the production ci metallic potassium which comprises electroiyticai1y decomposing the potassium amide in a solution ot potassium amide in liquid a ina cellhaving a potassium l' anode, continuously withdruving` potassium am. taining some potassium amide from the cathode portion of the cell, continuouslyrecovc'ring metailic potassium from the cathndcmduct thus withdrawn, and the. potassium mlntinlnl amide concentration o! the electrolyte substantially constant by continuously removing potassium amide from the anode portion oi the celL 9. A substantially continuous process for the production o! metallic potassium which comprises electrolyzing ai. approximately 50% solution ot potassium amide in liquid ammonia in a cell having an approximately 1.0% potassium amalgam anode and maintained at a temperature of about 25 C., continuously withdrawing a solution oi' potassium in `iquid ammonia con-- taining about 30% potassium and small amounts of potassium amide, from the cathode portion of the cell, and recovering metallic potassium from said cathode solution.

l0. A substantially continuous process for the production o! metallic potassium which comprises electrolyzing an approximately 59% solution ot potassium amide in liquid ammonia in a cell having an approximately 1.0% potassium amalgam anode and maintained at a temperature of about 25 C., continuously withdrawing solid potassium metal containing small amounts of ammonia and potassium amide from the cathode portion ot the cell, and recovering metallio potassium from the cathode product thus withdrawn.

l1. A process for the production of potassium amide which comprises electrolytically decomposing the potassium amide in a solution ot potassium amide in liquid ammonia in a cell having a potassium amalgam anode and reacting the potassium produced in the cathode portion oi the cell with ammonia to obtain potassium amide, said reaction being carried out 'at the cathode, substantially simultaneously with the electrolysis, in the presence of a catalyst selected from the group consisting oi' iron oxide, platinum black, aluminum, high carbon steel, asbestos fibers, finely divided iron and nely divided siiver.

12. A process for the production of potassium amidewhich comprises electrolytically decomposing the potassium amide in a solution of potassium amide in liquid ammonia in a cell having a potassium amalgam anode and a rough-surfaced cathode coated with iron oxide, at a cathode current density below about 0.15 ampere per square centimeter, to form potassium at the cathode and to convert said potassium, substantially as fast as it is formed, to potassium amide, by reaction with ammonia, catalyzed by the iron oxide on the cathode surface, withdrawing a portion oi' the solution of potassium amide in liquid ammonia, separating potassium amide therefrom, and returning the depleted solution together with added ammonia to the cell.

i3. In an electrolytic process involving formation of potassium at the cathode, the improvement which comprises electrolytically decomposing potassium. amide in a solution of potassium amide in liquid ammonia, to form potassium, in a cell having a potassium amalgam anode.

RAYMOND A. VINGEE. CHARLES K. LAWRENCE.

Images