US1687188A - Refining of lead bullion containing other metals - Google Patents

Description

G. K. WILLIAMS REFINING oF LEAD BULLION CONTAINING OTHER METALS Oct. 9, 1928.

Filed Feb. 9, 1927 TIE Patented Oct. 9, 1928.

UNITED STATES GEORG .KENNETH WILLIAMS, 0F PORT PIRIE, SOUTH AUSTRALIA, AUSTRALIA.

REFINING OF LEAD BULLION CONTAINING OTHER METALS.

Application led February 9, 1927, Serial No. 166,988. and in Australia March 6, 1926.

zinc (With or without lead) and which beingf present in the initial bullion, it is desired to remove, both for their own values and for the -purpose of providing'lead sufficiently free therefrom for commercial purposes.

A Hoy-such alloys of zinc (with or without lead) and the said alloying metals.

Residual bullion-the bullion remaining after treatment which is relatively .low in one or more of the alloying metals.

@rustesuch alloys of the alloying metals with zinc and lead (with or without lead) which are formed by the cooling of the bullion as distinct from the alloys which are formed as conjugate solutions.

In the refining of lead bullion by the wellknown Parkes process, it is the practice to incorporate a certainamount of Zinc with the molten bullion sufficient for the formation of certain alloys with zinc and the said metals desired to be removed. The bullion is then cooled, whereby the alloys separate from the bullion, and as the temperatures obtaining during such cooling are below the melting points of the above alloys so liberated such alloys separate in the form of crusts. Such crusts, owing to theirspecific gravity being lower than that of the liquid bullionrise to the surface and are then removed, leaving residual bullion relatively low in such metals.

The crusts obtained by y the aforesaid Parkes process usually contain a considerable amount of entangled lead, the removal of which has been effected, either by subjecting the said crusts to liquation, or to presses.

In the operation of the Parkes process, as universally practised, the amount of zinc added to the bullion and the temperatures employed are insuicient for" the formation and maintenance of conjugate solutions in a liquid system enabling the separation of such solutions from each other.

Now, the object of this present invention is to provide means whereby lead bullion containing the said alloyingmetals may yberelined for the removal therefrom of the said alloying metals, providing on the one hand alloys relatively rich in such alloying metals and low in lead, and on the other hand residual bullion sufficiently low in such alloying metals as required for commercial purposes, in amore economical and efficient manner than heretofore.

According to this invention the refining of lead bullion may be effected either as a continuous or as an intermittent process, and the different alloying metals imay be preferentially removed from the bullion giving alloys rich in one or more of the said alloying'metals in specific order.

Now, I have found that if an amount of zinc beyond a certain quantity greater than that which is used in the Parkes process is incorporated with bullion containing the said alloying metals,l and a Asuiiiciently high temperature is maintained to liquefy the system layers of conjugate solutions are formed, the top solution comprising the said alloy,V and the bottom solution bullion, which, when cooled to about its eutectic temperature produces residual bullion. A

This invention therefore comprises cerv tain improvements in the refining of lead bullion containing alloying metals and -consists of incorporating zinc with the said bullion in sufficient quantities and maintaining the required temperature, whereby distinct molten layers of conjugate solutions are formed, the upper of which consists of the said alloy which may be separated, and the lower of which consists of bullion which, if desired, can be cooled to about its eutectic temperature, producing on the one hand residual bullion, and on the other hand alloys in the form of crusts relatively rich in zinc.

This invention-also comprises the preferential separation of the alloys of the alloying metals by the regulation of the amount of Zinc incorporated with the bullion, and the temperature. to which the mixture is submitted, whereby conjugate solutions are formed, the upper of which comprises an alloy rich in a certain alloying metal as distinct from the other alloying metals.

For example: Lead bullion containing copper, gold and silverpmay be treated in accordance with this invention by inco-r.L porating a. certain quantity of zinc withthe bullion and maintaining the saine at such a temperature that an alloy relatively rich in copper and gold and low in silver, and a residual bullion relatively low in copper and gold and high in silver can be obtained. Or alternatively by incorporating larger amounts of zinc with the lead bullion an alloy relatively rich in copper and gold and silver an be obtained and a residual billion `relatively low in copper and gold and silver.

Consequently by this method oftreatment I am enabled to effect the removal from the bullion of the copper and gold and silver in one operation, or by successive operations in which the quantities. of Zinc present are co'ntrolled'to preferentially remove the copper and the gold, and thenthe silver. This preferential treatment is capable of many modifications owing to the different aiinities possessed by zinc for the different alloying metals. Zinc has a slirrhtly greater affinity for copperthan for go d so that by lincorporating a relatively small amount of zinc with f the bullion and heating the saine to therequired temperature' alloys relatively higher in copper than in gold can be obtained, but for practical purposes'owing tothe fact that such differences in the affinities of zinc for copper and gold are slight I prefer toform alloys as relatively rich as possible lin both gold and copper.I Inthe practical application of this invention regard should be had of the quantity of zinc present in the crusts formed during the coolingof the bottom solution td about its eutecticl temperature, and the zinc contents of such crusts are availed of to supply a proportion of the zinc required to be present in thevarious treatments carried out during the refining operation, whereby economies are effected in the consumption of zinc necessary for the carrying. out of the process.

Thus, in carr ing the invention Vinto practi' cal effect, it 1s preferred that a suitable amount of zinc beincorporated with the lead bullion and the vtemperature of the same f maintained at the required de ree for the liquefaction of the alloy, where y conjugate solutions are formed, the lupper of which consists of the alloy which is separate-d, and the lower of which consists of bullion which when cooled to about its eutectic temperature gives residual bullion on the one hand and alloys in the form of crusts on the otheringI metal or metals.I lI-Iovvever, to obtain thel highest eiiciency with .respect to the lzine con,- sumption and quantity ofcrusts formed during the cooling of the bottom solution, it is advisable that such bottom solution be cooled to about its e'utectic temperature.

This improved method of refining lead bullion\,may be carried outxeither as inter.

part of the treatment may be carried out in c a reverberatory -furnace or a suitable container, and the other part in a suitable kettle.

One method of applying` the invention to refining `in ordinaryl open kettles, the requisite quantity of zinc (in the form of sp-clter with or without crusts obtained from the cooling of the bottom solution of the corresponding treatment of the previous charge) is incorpo-rated with the charge o'f bullion in the kettle (which may be either the lead bullion to be refined containing the said alloying metals, or residual bullion from a preceding preferential treatment) and the mixture is heated to the requisite temperature for the formation of conjugate solutions, the top solution of which comprises the desired alloy, which is separated, and the bottom solution is either cooled in the kettle or else transferred to some other vessel of suitable-type l other suitable container wherein the desired,

temperatures may be -maintained and molten .layers of conjugate solutions formed. When operating in reverberatory furnaces precalition should be taken for avoiding oxidation of the bullion such as by a reduclng atmos- ,phere in thesaid furnace or by forming a surface liquid layer of a substance such as common salt.. Or such a reverberatory furnace may be used for preheating the bullion to the required temperature before being fed into the separating kettle. Instead of effecting the incorporation of the zinc with the lead inthe kettle itself, such incorporation'may be effected in a separate vessel such as by causing the liquid bullion to pass through a bath or layer of molten zinc previous to being fed to the kettle. Or instead of both' forming the conjugate solutions and separating the4 same in the ione kettle or other suitable container the process may be A'applied using one kettleor vessel for in- Icorporation of the requisite quantity of zinc with the bullion and maintaining the required temperature lfor the formation of conjugate solutions andthen discharging the same into a separate kettle o r suitable container when the bullion is cooled to the requisite temperature for theseparation of the alloy comprising the conjugate solution and also, if required, the crusts formed.

When such treatment is carried out in the ordinary open kettles which are at present in use, the thickness of the surfa-ce layer of top conjugate solution comprising the alloy is relatively small, owing to the large surface area, so that considerable diculty is experienced in effecting al separation of the same Without undue contamination by, and entanglement of, the lower layer. of solution. Moreover, such open kettles as at present in use are adapted only for intermittent treatment ofl bullion in accordance with this invention.

Consequently ythe treatment of the said bullion in accordance with this invention is 1preferably effected in such manner that thel ture, and this invention comprises the treati ment of the said lead bullion in avessel` oi kettle wherein the abovementioned conditions aie maintained. Kettles of this description are adapted for either intermittent -or continuous treatment of bullion.

A kettle of this description is illustrated in the accompanying drawings wherein Figure 1 is a view in sectional elevation; Figure 2 is a viewl in sectional plan of part of Figure 1 taken on the line 2 2; l'

Figure 3 is aiview in sectional plan of a part of Figure 1 taken on the line 3 3;

Figures 4 and 5 are vertical sections of portion of a ykettle showing the accommodation of means foi` ensuring tlieadmixture of the metal therein.

The kettle 10 consists of a deep narrow vessel having means suchas an upper circular flue 11`and a lower circular fiue 12 whereby the different portions thereof may be differentially heated and a higher temperature imparted to the upper portion than to the lower.

`The kettle is provided with au upwardly projecting spout 13 from its lower portion` the/discharge 14 of whichis at a lower level than'the top of the kettle, and means may be provided, such as by a surrounding flue 17 whereby the said spout may be also heated maintaining the same at the required temperature. Y

As the upper portion of the kettle 10 is subjected to considerably higher temperatures than the lower portion the saine is more liable to deterioration and cracking, so thatl the kettle 10 is preferably formed intwo parts having tlangeslQ` and 20 by which the said parts may be boltedor otherwise fastened together, whereby the upperpart may be renewed Without having to dismantle the lower part. The joint between the twoiflanges 19;

and 2O is made tight by forming a concentric groove 21 of circular cross section therebetween, tlie same being adapted to accommodate a pipe 22 through which a cooling medium (such as water) is caused to circulate,

thereby causing any metal entering the joint to freeze and leakage thereby avoided.

rllie upper flue 11- surrounding the u pper portion, of the kettle 10 is provided with a liquid fuel bu-riier 15 or other source of heat whereby the] same is'maintained at therequisite temperature.

The lower flueg12 surrounding the lower portion of the kettle 10 is also provided with a liquid fuel burner 16or other source of heat whereby thesame is maintained at its requisite temperature. j i

In some cases it may be necessary to maintain the lower portion of the kettle 10 at a lowerl teiiipei'ature than would ensue by the mere absence of heating means in the lower flue 12 and in such a case a cooling medium (such as cool air) may be passed through the i said flue 12. the same being for the time being cut off from the main combustion flue, orl if necessary-water circulating pipes may be disposed within the Said flue l2.

When adapting this invention for continu:

ous'treatment-the bullion is continuously fed into the'top of the kettle with the requisite i amount of zinc Iand the' residual bullion is likewise continuously discharged from the.

bottom of the kettle, the alloy comprising thev i "upper layer of conjugate solution being continuously or intermittently withdrawn.- In

'may be necessary,jthe alloys comprising the f upper layer of conjugate solutions formed in each kettle being separately withdrawn either continuously or intermittently.y .i

The following twofmethods of operating such treatment are mentioned by way of eX- ample. j

The bullion is continuously fed into the kettle-10 together with the desired quantity of zinc, the upper part of the kettle 10 being maintained above the point of liquefaction ofv i jugate solution'by means of the burner 15 in the flue 11, whilst the lower part of the kettle 10 is maintained at a gradually decreasing temperature towards the bottom by regulating the temperature in the flue 12,- thetemthe alloy comprising the upper layer of con` ,125.

perature at the entrance to the spout`13 being at approximately the eutectic temperature of the residual bullion.

The continuous feed of the lead bullion into the kettle 10 causes a continuous formation of an upper layer of conjugate solution comprising an valloy of one or more of the alloying metals anda continuous discharge of residual bullion from the spout 13. In the passage of the bullion through the kettle vcruSts are formed in the lower portions thereof due to cooling. These crusts rise into .the

'upper portion of the kettle, where they augment the aforesaid layer of conjugate solution. If necessary, means may befprovided for ensuring the' more or less complete admixture and if desired the same mayh comprise a stirrer 23 fitted to a spindle`24 and disposed l alloy required, and thus the continuous feed ing, and by maintaining the delivery of .residof bullion containing alloying metals and zinc into the kettle 10 will cause the continuous formation of conjugate solutions, the upper layer ofwhieh comprises an alloy rich in one or more of the alloying metals.

Consequently the bullion is continuously subjected to treatment as it passes through the kettle 10 whereby the particular alloying metal or metals is or are separated therefrom so that when the said bullion reaches the lower portion of the kettle 10 which is maintained ,at about the eutectic temperature of the residual bullion, it is relatively free from the said alloying metal or metals.

By maintaining the upward projecting spout 13 at a temperature abovewthe eutectic temperature of the residual. bullion, this residual bullion is prevented "from freezing as it flows upwardly through the said spout 13. whereby la continuous delivery may be effected, through the discharge d14p so that by continuously or periodicallyremovin'g the upper layer of alloy by either tapping or bailual bullion through the spout 13,- a continuous feed may be maintained into the kettle 10 of the bullion containing the alloying metal.

As an illustration of the above modification of'thisinvent-ion I give the following example of certain work performed by me at Port Pirie, South Australia: j

Example I A bullion assayng'zu Silver 57. 702s. per tcn Gold 1 grain Copper .r 0.004 per cent Zinc 0.2per cent y was continuously fed into the top of a kettle similar to that illustrated in the accompanying drawings together with periodic additions of zinc (spelter) equivalent to 18-lbs per ton of bullion treated, the upper portion of the kettle was maintained at a temperature of approximately 700 C. and the bottom partV of the kettle was cooled to a temperature of approximately 335 C. and the-spout at a temperature of approximately 400 C. A layer of conjugate solution' was continuously formed in the upper part of the kettle and4 was periodically removed by hailing and was found to be 15.7-lbs. per ton of bullion treated whilstl the residual bullion discharged rfrom the spout of the kettle assayed-z 'Silver l 0.2-ozs.perton Zinc 0.56 per cent Gold Trace Copper Trace l The kettle used in the above'experiment was 2-feet in diameter and 9-feet deep and a rate of feed .was 4maintained for a considerable period of ver 100-tons per day, but'l it was found 4that a much greatenra'te of feed could be maintained, the operation being limited by -the supplies of bullion available and the'temporary nature of the plant. A y

The work done in the above mentioned experimentat Port Pirie was limited by the nature of the material of which the kettle used was composed, viz: cast iron, but indications have been obtained that if the upper part ofthe kettle were made of material which would withstand a tem erature of from 800 C. to 850 C. so that al oys of a higher melting point could be formed as conjugate solutions a differentialseparation can be effected of the alloying metals copper and gold and silver and the following is anexample of a method of treatment based upon the above mentioned indicationsz. l

4Enma/mph: [I: A bullion 'assaying:

of two kettles as shewn in Figure'l together with periodic additions of zinc equivalent to 9-lbs. per` ton, the top portion of the kettle b eing maintained at a temperature of about being fed continuously into the first of a series y 850 C. and the flower portion of ,the kettle i 4cooled to a'temperature of approximately 330 C. andthe spout maintained at a temj perature of abouti400o'C. conjugate solution formed at the top of the kettle equivalent to 7.7-lbs.- per ton ofvbullion treated could be periodically removed assaying:

'whilst the residual bullion assayed:

Silver 57. 7 ozs. per ton Gold V1 vgrain Copper O. 004 per cent Zinc 0.2. per cent could be continuously fed into Hthe second kettle givingthe same result as the above mentioned example. Y

According to another modification of this invention the zinc necessary for the formation of the conjugate solution may be fed yinto the kettle at the commencement of the operation so that a layer of zinc or conjugate solution high' in zinc is disposed in the upper part of the kettle through which the bullion is caused to continuously pass until the layer of conjugate solution becomes enriched to a sufficient extent with the alloying metals desired to be removed. By this method of treatment the bullion is fed in continuously and the residual bullion removed continuously and the alloy removedperiodically. If desired an amount of zinc as isrequired to make up for that with-4 drawn inthe residual bullion may be added to the feed of bullion. This methodof operation `dispenses with carefulfcalculation as to the amount of zinc lfed with the bullion.

As anillustrationof this modification of the' invention the rkettle 10` is first charged with bullion up to the level of the discharge 14 of the spout 1.3, and zinc, or alloy relatively high in zinc, is then added'thereto tothe upper level of the top of the kettle. g Bullion (either the lead bullion to be refined containing the said alloying metals, or residual bullion-from a preceding treatment) is then fed continuouslyinto the saidkettle 10, being caused to pass down through the surface layer of molten zinc or alloy, in such a way that it is brought in'to intimate contact with the same, and if necessary, for this purpose suitable trays or baffles or stirrers may be-provided for ensuring the more or less complete contact. Y*

The temperature around the upper part of the kettle 10 is maintained at the necessary degree for the ,liquefaction of the alloy by means of the burne-rs'l in the flue 11, whilst the lower part bf the kettle is maintained at a decreasing temperature by means of the lower flue 12 until the bottom thereof is at about'the eutectic temperature of the residual bullion. The spout 413 of the said kettle is also maintained at a temperature slightly above the said euteetic temperature by means of the iue 17, so that the said residual bullion is prevented from freezing, and is permitted of a continuous flow through the said spout 13.

'Ihecrusts which are formed by the cooling in the lower part of the kettle rise into the upper portion of the kettle, Where they come in contact. with the bullion feeding into the kettle and the conjugate solutions which exist in that portion of the kettle, the upper layer of which is relatively high in zinc. rl'he conm tinuousfeed ofv bullion into the kettle causes the gradual enrichment ofthe upper layer of 1 the conjugate solutions in alloying metals by incorporation of the same therein.' At the same time intermittent -additions of zinc (spelter) may be madein order to maintain the level of the solutions to compensate for the zincwithdrawn in the residual bullion. v The flow of bullion into the kettleis maintained until the content'of alloying metal or metals in the residual bullion vrisesvbeyond a certain. determining limit. When this limit is reached the upper layer of conjugate solution comprising the alloy rich in the said alloying metal or metals is removed by tapping or bailing and a further requisite quantity of zinc (spelter) or alloy rich in zinc is added.

By operating in this way no accurate determination of the amount of zinc (spelter) to be added is necessary, the continuous flow of the bullion functioning to increasingly enrich theI conjugate solutions formed until the desired i degree of enrichment is attained. Whilst the layer of conjugate solution in the upper portion of the kettle is of high zinc content and low in yalloying metals the residual bullion discharging from the lower portion of the kettle is correspondingly low in the said alloy-` ing metals and as the percentage of thesaid alloying metals in the said upper layer of'conjugate solution increases there is a corresponding increase in the percentage of alloying metals in the residual bullion. Consequently the content of the alloying metals in the residual bullion discharged affords alrelatively accurate determiningpoint at which the alloy' should be removed and a fresh charge of zinc fed into the kettle. l By way of an illustration df this modifica.- tionA of anapplicationof this invention the following is given by way of/example;

Example [Il: The ,bullion treated assayed as follows: f' f A kettle similar to that illustrated in the alccompanying-drawings 2-feet in diameter and 9-feet deep-*was charged with bullion up to the level of the discharge of thespout and 1600-lbs'. of zinc v(spelt-er) 'was fed on to the Vformation of conjugate solutions.

Silver 0. 05 ozs. per ton Zinc 0. 6- per cent The bullion was continuously fed in to the top of the kettle together with periodic additions of zinc equivalent to 8.5-lbs. per ton, and this feed was continuously maintained until the silver content of the residual bullion discharging from the spoilt had increasedl to 0.2-oz. per ton. The operation was stopped and it was found that approximately 200 tons of bullion had been passed through the kettle.`

The alloy comprising the conjugate solution in the upper portion of the kettle Was hailed off and found to be 2680-lbs. equivalent toy 13A-lbs. per ton ofbullion treated, assaying:

Grold i 7-dwts.perton Y Silver 29.4 per cent= 9604 ozs. per ton Copper 0. 67 per cent Zinc 59. 3 per cent Lead 10. 0 per cent In the above description of this invention reference has only been made to the alloying metals present as governing the amount of zinc and the temperature required for the It will, however, be understood that other factors will govern these conditions, such as for example the presence of other metals' such as Antimony, Arsenic and Bismuth which are usually regarded and designated as Impurities.

Consequently in determining thev amount of4 zinc added and the temperature required for the purposes-of this invention regard will be had to the aforesaid impurities in the bullion.

The amount of zinc and the temperature required for the formation of conjugate solutions comprising' the desired alloying metal or metals may be determined by a simple test on a laboratory scale. For this purpose a small miniature kettle may be used comprising a narrow deep kettle similar in shape tothat illustrated in the accompanying drawings having also a similar spout and likewise-means for differentially heating the body of the said kettle and the said spout..

If such experimental work is required to be,4 carried out at temperatures-above that 'which :mamas casgtJ iron will withstand such a kettle may be constructed of any suitable material such as refractory vmaterial Ihe bullion lInay be heated in a separate vessel and a certain definite quantity of zinc added, such as an amount equivalent to say 8-lbs. per ton.

, This mixture is thencontinuously fed into the kettle which is maintained at a temperature of approximately 335 C. at the bottom,

and the spout at a temperature of about 400o C. and the upper portion of the kettle at such a temperature as is required to just maintain the conjugate solutions formed,

v that is to say, if there is any indication of crusts in the top 'of the kettle it may be assumed that the temperatureis too low. and should be increased. The feedis continued and the kettle maintained at thesetemperatures until equilibrium is established as indicated by periodic assays of the residual bullion discharged from the spout. In this Way indications may be obtained as to whetherl yor'not greater or lesserquantities of zinc are required and the experiment is continued with varying 'amounts of zinc until the correct amount of zine is determined as indicated by the condition of the residual bullion discharged from the spout after equilibrium of the system is established following each successive variation in the amount of Zinc added:

1. A process for the refining of lead 'bull l10n containing alloying metals consisting of incorporating zinc with the said bullion in such quantity a'nd Isubjecting the same to such differential temperatures that `molten `layers of conjugate solutions lare formed'the upper layer comprising an .alloy rich in a certain alloying metal or metals and separating such alloy in liquid system. w

2. A process for the refiningv of-lead bullion which consists offeeding thesaid bullion continuously through a suitable vessel together withrthe requisite quantity of zinc and subjecting the same to differential temperatures as it passes through the said vessel, the temperature at the top being such as to cause 4the formation of conjugate solu- -tions comprising an alloy relatively rich in one or more of the' alloying metals, the temperature at the bottom'being at or about the eutectic temperature of the residual bullion separating the said alloy and continuously discharging the said residual bullion.V

3. In the refining of lead bu`llioncontain-` 120 ing alloying etals incorporating zinc with the said bullion in such quantities and main` taining such atemperature that molten layers loo icav

ofconjugate solutions are formed comprising i an upper layer of an alloy 'rich in a certain alloying metal ormetals separating such alloy in liquid system, maintaining the remain-` ing bullion at progressively decreasing temperatures to` about the eutectic temperature v j residual bullion'in liquid system.

ofthe residual bullion and separating such 4. In the refining of lead bullion containing alloying metals the preferential separa- .tion of such alloying metals by incorporating a suliicient amount of zinc in the said bullion and maintaining the same at such temperature thatconj ugatesolutions are formed comprising an alloy rich in a certain alloying metal or metals separating such alloy, cooling the remaining bullion to a point above its eutectic temperature and reheating the same at such a temperature or temperatures that other conjugate solutions are formed coIn-. 4prising an alloy or alloys -rich in the remaining alloying metal or metals, separating such alloy or alloys and removing the residual bullion.

5. In the refining of lead bullion containing alloying metals continuously feeding the A said bullion vin a molten condition through a number of kettlesin series together with the requisite quantity of zinc and mlintaining a higher temperature at the top portion of the said kettles in the said series than at the bottom portion thereof whereby conjugate solutions are formed in-'theupper portions of the ket-tles rich in certain alloying metals,- removing the said alloys from the upper portions of the said kettles and maintaining `the temperaf ture of the 'lower portion of the last kettle at a point just above the eutecticv temperature of the residual bullion in each kettle and removing the residual bullion from the last kettle` in the series. i 6. In the reiningof .lead bullion containing alloying metals continuously feeding the said bullion in molten condition through a seriesof kettles lto ether with the requisite quantityof zinc an maintaining such a temperaturev at the vupper vportion of" the-first kettle that a molten layer of conjugate solution is formed comp-rising an alloy'rich in jugate solutions are Aformed comprisingl alyloys relatively high in other alloying metal Aor metals, :cooling the bullion in sthe' low-er ortion of the second kettle to a temperature just abovethe eutectic temperature of the residual bullionl periodically or continuously separating'th'e'alloy formed in theupper portion of the second kettle and continuously reing alloying metals continuously feeding the said bullion in molten condition through a layer of molten zinc in the upper portion of a suitable kettle, maintaining the said upper portion of the said kettle at such a temperature that molten layers of conjugate solutions are formed comprising an alloy of a certain alloying metal or metals maintaining t-he lower portion of the said kettle ata temperature just above he eutectic temperatureof the residual bu lion therein, continuously discharging the residual bullion from the bottom of the said kettle until its contents in the alloying metal which is associated with the alloy in the aforesaid conjugate solution rea/ches a predetermineddimit, removing the said conjugate solution eomprising the said alloy relatively rich in such alloying metal and adding a further quantity of zinc to' form a further layer of molten zinc in the upper portion of the kettle and repeating the ing at such a relativelyihigh temperature that molten layers of conjugate solutions are formed and maintainin the lower portion of l the said column at a re atively low temperature just,above the eutectic temperature of the residual bullion, continuously removing Nthe said bullion and removing the alloy com.-

prising thesa-id conjugate solution.

9. In the reliningof lead bulllon containing gold, silver and copper, ,incorporating zinc with the said bullionin such quantities and maintaining the same at such a temperature -that molten layers of conjugate solutions are'formed, the upper of which comprises an alloy relativelyrich in copper` and gold and low in silver, separating the said-A alloy, maintainin the temperature ofthe remaining bullion just above the eutectic temperature of the residual bullion relatively low 1n copperand gold and high in silver, subsequently treating the said residual bullion with the requisite quantity vof zinc and maintaining the same at such a temperature that conjugate solutions are formed comprising an alloy relatively rich insilver and low in copper. and gold, separating ysuch alloy and discharging the said residualbullion relatively. .j

'low in copper, old and silver.

In witness/.w ereof I hereunto aix my signature.

erronea-3 KNNETHVWILLIAMS. l

Images