US1285714.Pdf

UNITED STATES PATENT OFFICE. GEORGE P. HULST, OF HAMMOND, INDIANA PROCESS OF TREATING LEAD BUILLION. 1,285,714. Specification of Letters Patent, Patented Nov. 26, 1918. Application filed March 20, 1918, Serial No. 223,573. To all whom it may concern. copper. The removal of the copper from the Be it known that I, GEORGE P. Hu LST, a bullion in the liquating step to the extent citizen of the United States, residing at here indicated, leaves the softening furnace Hammond, in the county of Lake and State in which the oxidizing step is conducted, 60 of Indiana, have invented certain new and free to operate on a practically decopperized useful Improvements in Processes of Treat charge, or one from which the harmful per ing Lead Bullion, of which the following is centage of copper has been eliminated. By a full, clear, and exact description, reference Subjecting the liquated decopperized bullion being had to the accompanying drawings, to oxidation in the softening furnace, th 85 0 forming a part hereof. impurities such as arsenic, antimony al In the refining of lead bullion by what is the like are separated in the form of a skim known as the Parkes process, the bullion is or antimony slag composed principally of first charged either directly into a softening lead antimony arsenic oxid (with 1% to 3% furnace, or thrown into kettles and melted of silica coming from the furnace linings), 70 5 down and then pumped into the softening this slag being subsequently treated in the furnace. The softening operation comprises antimony blast furnace for the production two steps, to wit, liquation and oxidation, of antimonial lead. In the present embodi- . the metals held in solution by the red-hot ment of the invention, the liquated decop lead being in a measure separated out in the perized bullion is subjected to oxidation in 75 liquating step, and metals alloyed with lead the softening furnace, preferably in the and more easily oxidized than lead, being presence of suitable oxidizing agents such as separated out in the oxidizing step. The the skim from the refining furnace (a lead impurities removed by the softening process zinc oxid), molding skim (a lead oxid), or (liquation and oxidation) are in the form skim from the pattisonizing kettles, the said 8) 25 of copper dross, and a slag or skim contain oxidizing agents materially hastening the ing oxids of lead, arsenic, and antimony with softening operation, their use resulting not Small percentages of copper and other im only in a better cooked charge but in a purities when present, and metallic shot lead greater direct output of lead as will herein bullion which contains silver and gold. This later more fully appear. A further object 85 30 slag is cooled down or dumped directly into of the invention is to remove from the anti the residue furnace. Usually there are two mony slag above referred to, all the mechan skims of the slag taken from the softening ically suspended lead bullion by Subjecting furnace, these being treated in the residue the skims from the softening furnace before furnace with a proper complement of coal their treatment in the blast furnace, to a 90 35 and lead sulfid ore giving a resulting anti preliminary treatment in a preheating fur mony slag free from silver which is subse nace without reduction with lead sulfid or , quently smelted with refinery skim in the coal, the preheating action (in which the blast furnace to antimonial lead; a hard temperature is raised to make the slag very lead bullion which is retreated (in the liquid) causing the bullion to drop and set 95 40 liquating kettles and softening furnace); tle out of the slag and carry down the silver and a lead copper matte which is sent to the and gold, the bullion being returned to the smelter and bessemerized. softening furnace. A further object is to The primary object of the present inven treat (in a blast furnace) the antimony slag tion is to dispense with the residue opera aforesaid in conjunction with outside lead 00 45 tion or treatment of the skims or oxids drosses free from silver, thereby producing aforesaid in the residue furnace, thereby good, clean, marketable antimonial lead, and effecting a material saving in the cost of eliminating the use of the residue furnace treatment of the bullion. To effect this sav for the treatment of the first and second ing however, care must be taken to segregate skimmings from the softening furnace as is 105 50 and remove from the charge of bullion in the now done under the old process. A further liquating kettle as much of the copper as object is to effect a material saving of zinc possible, or to such an extent that it gives in the desilverizing kettles, to reduce the no trouble in the later stages of the process. cost of retorting and cupel operations by In practice the copper should be removed segregating and removing the copper from O 5 5 from the metal in the liquating kettle to the bullion before the latter is charged into bring the bullion down to .05% (or less) the softening furnace. A further object is 32 1285,734: to treat the copper drosses from the liquat liquating operation the drossing of the cop ing operation, the copper skims from the de per is carried to the point where the bullion silverizing kettle, the copper litharge from in the kettle drops to .05% copper (the cop the cupels, and lead slag from the reducing per in the liquating kettle may even be low hearth, in the residue furnace with a proper ered to .03%), the object sought being to re 70 complement of lead sulfid ore (galena) with duce the copper content of the lead bullion a view of producing a lead copper matte, charged into the softening furnace to the dross bullion, and a slag free from silver lowest possible degree so as not to interfere (and copper), said slag going to the blast with the desilverizing operation later on. The 0. furnace to be treated in conjunction with the antimony slag from the preheating fur lead in the liquating kettle, after thorough 75 nace, for the production of antimonial lead drossing or skimming off of the copper dross the dross bullion being liquated or returned is pumped into the softening furnace (rever to the liquating kettle, and retreated in the beratory) where the lead is subjected to softening furnace, and the matte subse oxidation (by air) preferably in the pres quently bessemerized. In the old process ence of suitable oxidizing agents added to the copper skims from the desilverizing ket the charge to hasten the softening operation. tles went to the softening furnace, an objec In the present embodiment of the invention tion avoided by the new process, the presence these oxidizing agents comprise (1) refiner 20 of copper in the softening furnace not being skim which is a lead zinc oxid, the oxygen E. constituting as it does an interfer of the oxid taking up arsenic and antimony 85 ing element in the later desilverizing opera and dropping lead to the extent that the tion. A further object of the invention is arsenic and antimony are taken up in the to effect by proper treatment on a reducing slag, the presence of the zinc which goes into 25 the slag materially reducing the lead content hearth, a partial reduction of the litharge of the slag and therebv increasing the direct 90 coming from the cupels and to return the output of lead; (2) molding skim which is high grade metal thus produced to the cupels a lead oxid; (3) Pattison skim (a lead oxid); for retreatment, the resulting lead slag be or (4) impure lead oxids derived from ing charged into the residue furnace for the other or outside sources may be used. Where 30 recovery of any copper in the form of lead refiner skims or equivalent oxidizing agents copper matte. The advantages of the new are employed in the softening furnace there process will be readily apparent from the is no occasion to blow air into or stir the following detailed description in connection mass, but merely bring the heat up to slag with the accompanying drawing in which ging temperature. The resulting slag is 35 The figure represents a flow sheet of the 100 several steps involved in the new process. principally a lead antimony arsenic oxid in The various instrumentalities employed in which a considerable portion of lead bullion carrying out the successive steps of the proc is held mechanically or in suspension, the ess are fully designated on the flow sheet bullion carrying silver and gold. To re 40 so that a reference thereto may be made lease this bullion the slag is skimmed from without the necessity of identification the metal in the softening furnace (there thereof by reference letters or numbers as are two skimmings) and charged into a pre will be clearly apparent from an examina heating furnace or settler in which the tion of the flow sheet. Some of the indi mechanically held lead bullion is dropped, vidual steps involved in the new process are the preheating of the slag causing it to be old per se, and to these I make no claim, the come very liquid thereby releasing the lead 10 novelty of the process residing in the se bullion which is returned to the softening quence of steps by which the several objects furnace. The preheating furnace is fired above enumerated are attained. The inven preferably with an oil burner. The anti 50 mony slag after all the metallic bullion has tion will now be described in connection settled out of it is conveyed either directly 15 with the flow sheet detailing the various to the blast furnace for the production of steps of the process. antimonial lead, cutting out the treatment The lead bullion is taken from the car and in the residue furnace under the old process; 55 charged into the liquating kettle (which or, it may be run into slag pots and taken also serves as a sampling kettle) where it is direct to the antimony slag pile after which 20 heated to the melting or liquating point, the it may be treated for antimonial lead. It metal being stirred by repeated blowing with may be stated in passing that under the new air or steam through a pipe inserted there process (which cuts out the treatment of the into and held in the hands of the operator, slag or skims from the softening furnace in 60 the pipe being connected to a suitable air the residue furnace) the slag, (or skim or steam line as well understood in the art. mings) from the softening furnace (before This operation raises the copper dross, the treatment in the preheating furnace) con latter floating on the surface of the molten tains substantially 20% arsenic and anti metal from which it is skimmed and then 65 timony, .55% lead, 6% to 8% zinc, .1% cop charged into the residue furnace. in the per, .8 to 1 ounce of silver, the copper being 30 1,285,714 considerably less than in the resulting slag The refined lead in the refining furnace from the subsequent treatment of the first after the refiner skim is removed, is tapped and second skims (from the softening fur into the molding furnace or reverberatory mace) in the residue furnace under the old receiver. In running the refined lead bullion process, where the copper content ranges into the molding furnace a certain amount of 70 form .3% to .5%, and the silver 1 to 1.5 lead oxidis formed; and while standing dur OCS. ing the molding operation this lead oxid Where the lead bullion already runs low along with some metallic lead is skimmed off in copper it is charged direct into the soften into a pan and subsequently, if needed, is ing furnace without preliminary treatment charged into the softening furnace and used 75 in the liquating kettle. This applies to bul as an oxidizing agent in the manner pre lion which has been liquated to .05% cop viously pointed out. In the flow sheet a part per at the smelter, thus cutting out the of the refined lead from the refining furnace liquating operation at the refinery. is shown as going into the pattisonizing ket After the bullion in the softening furnace tles where it is still further refined by the 80 has been thoroughly cooked, and the impuri well known Pattison process of melting and ties (arsenic, antimony and the like) have crystallization. In the pattisonizing oper been oxidized and driven into the slag and ation lead oxid will likewise be formed, this the latter skimmed off or removed, the bul being skimmed off and if needed, subse lion thus cooked is tapped into the desilver quently charged into the Softening furnace izing kettle which when full is drossed clean and used as an oxidizing agent. From the of the copper skim that forms in the kettle pattisonizing kettles the refined lead goes to on account of a little zinc left in the lead the molds as fully indicated on the flow or on the sides of the kettle alloying with sheet. '. 5 any copper that may be present, said alloy The zinc skim from the desilverizing kettle 90 as it forms being brought to the surface and is next retorted, the retort being of the skimmed off and charged into the residue Faber du Faur type and oil fired, about furnace together with copper dross from the 1250 pounds of the zinc skim forming a liquating kettle and slag from the reducing charge. In this connection it may be stated BO hearth (to be presently referred to) the idea that by the new process I produce cleaner 95 being to eliminate the copper from the Zinc skims and have less zinc to retort than softening furnace to the greatest possible ex under the old, the reason for this being that tent. Under the old process the copper skim the major portion of the copper has been from the desilverizing kettle went to the sof segregated from the lead bullion before the tening furnace. The lead bullion in the de latter reaches the desilverizing kettle in 100 silverizing kettle having been drossed clean which the presence of an excessive quantity . of its copper skim is now ready, for the zinc of copper would be a serious objection on which is added to the bullion and the desil account of the large amount of zinc. which verization carried on in the usual way well would necessarily be absorbed by it before 0 known in the art. Under the new process the zinc could take up the silver. The neces 05 however, by the time the lead bullion reaches sary segregation of the copper from the bul the desilverizing kettle the copper content lion in the early stages of the process is has been practically eliminated so low brought about, as shown by the flow sheet, as to be negligible) so that less zinc is re . (1) by liquation (in kettles) to the extent of quired to take up the silver (and gold) mak getting the bullion down to .05% copper, the O ing less zinc skim to go to the retorts; also resulting copper dross being charged into the desilverized lead if properly treated in the residue furnace; and (2) by segregation the desilverization, will have less zinc and of the copper from the metal in the desilver silver. From the desilverizing kettle the de izing kettle in the form of copper skim O silverized lead goes to the refining furnace, which is likewise charged into the residue and the zinc skim goes to the retort as indi furnace. The products of the retort are re cated on the flow sheet. The refining furnace tort zinc, blue powder, retort metal or bul is a reverberatory furnace heated with out lion and dross from retort metal. The re side fire box, the desilverized lead in the fur tort zinc is conducted to the stock pile and 55 nace being brought to a good red heat and the used over again in the desilverizing opera 120 zinc and impurities such as arsenic and anti tion; the blue powder is sent to the zinc mony in small percentages are oxidized by smelter; and the retort metal or bullion is steam inserted in the furnace by steam charged into the cupel furnace which is pipes, the resulting agitation of the lead preferably of the Rhodes type. In practice 60 forming a refiner skim containing 75% to the retort metal is poured into a slag pot and 125 80% lead, 8% to 10% zinc, arsenic and anti first drossed, after which the metal free of mony in small percentages, and from 10% dross is poured direct into the cupel. As to 12% of oxygen. This skim is a good oxi well understood in the art this metal will dizing agent and, as previously pointed out, start to make litharge immediately on hit 65 is utilized as such in the softening furnace. ting the bath of the cupel. As soon as suffi 30 sé 1285,714. cient litharge is formed to cover the bath, grade lead) is returned to the cupel furnace the dross removed from the retort metal is the final refined product of which is doré charged into the cupel, the litharge being bullion as well understood in the art. The availed of to slag the dross. The retort test breakings from the cupel go to the metal dross is substantially a mixture of crusher and from the crusher to the residue 70 zinc oxid and alloys of copper, zinc, and furnace. A part of the crushed test break lead, the copper going in the metal which is ings and high grade crushed brick go to the being cupeled and coming of later as cop reducing hearth, and low grade crushed per litharge. The retort metal and dross brick from the crusher (together with O might be charged together into the cupel but since the dross can not be slagged until crushed retort breakings) go to the residue sufficient litharge is formed to effect the furnace. Under the old, process three resi slagging, the better practice is to first dross due operations were required, one of which the metal, then charge the metal into the was directly involved in the treatment of the cupel, and as soon thereafter as sufficient copper litharge and yellow litharge from the litharge is formed, feed in the dross. In cupel furnace, and another in the treatment 80 charging the dross on the litharge bath and of the skim from the refining furnace which slagging it, it does not appreciably change in the new process is utilized as an oxidiz the color of the litharge. The copper lith ing agent in the softening furnace. In the 20 arge resulting from the slagging of the re new process a single residue operation is tort metal dross as aforesaid, is a litharge sufficient; and since the yellow litharge from 85. slag which is removed in the last stages of the cupel furnace has its silver returned to the operation, said slag being liquid and of the cupel from the reducing hearth, the ma a dark red or reddish brown color, and jor portion of the silver in the litharge is 25 readily distinguishable and separable from prevented from going back through the the yellow litharge formed during the cupel process. The residue furnace is a reverbera 90 ing operation. The copper litharge or slag tory fired with coal, one of the products is charged into the residue furnace where, whereof is dross bullion, an impure lead with other copper drosses and skims it is bullion containing from 93% to 95% of 30 reduced to a lead copper matte. It may be lead, the balance being antimony, arsenic, stated in passing that the retort breakings copper, silver and gold in varying propor 95 are fed to the crusher, the crushed materials tions, said bullion being returned to the being charged into the residue furnace as in liquating kettle to get rid of the copper. dicated on the flow sheet. Under the old process this bullion was re 35 turned to the softening furnace. As previously stated, the moment cupella Reference to the flow sheet discloses three 00 tion begins, or as soon as the retort metal or sources of oxidizing agents that may be bullion strikes the bath of the cupel, yellow availed of for use in the softening furnace, litharge begins to form; and when liquid to wit, refiner skim, molding skim, and Pat 40 and before the copper litharge is removed tison skim, all these operating to hasten the (said copper litharge being the last slag softening operation and to increase the lead 105 that runs off from the cupel before the doré content in the softening furnace by passing is fine), the yellow litharge is run into the their oxygen over to the arsenic and anti reducing hearth operating in conjunction mony and dropping the lead. There may be 45 with the cupel, enough reducer being added still another source on which to draw for to the charge in the hearth to drop about 3% our oxidizing agent, and that is the yellow O of the metal, and heated up to form a fluid litharge from the cupels, provided it be free slag which is a lead copper oxid with 1% to of copper. This practice is not recommend 3% of silica, and 1% to 3% CaO. This slag ed however as the litharge usually contains 50 is charged into the residue furnace to be some copper (oxid); and as arsenic and an treated with copper dross, copper skim, cop timony have a greater affinity for oxygen 115 per litharge (from sources previously indi than has copper, the lead bullion takes up cated), materials from the crusher as indi the copper as fast as it is reduced by these cated on the flow sheet, and just enough lead metals. Under the new process the yellow sulfid ore or galena to reduce the copper to a litharge and its associated copper are re lead copper matte; the products of the resi duced on the reducing hearth to the extent 20 due furnace being dross bullion which is re previously indicated, the slag going to the turned to the liquating kettle for re-treat residue furnace wherein is produced a lead ment, lead copper matte, and a slag free of copper matte and a low grade antimony slag 60 copper and silver, this slag (a low grade free of copper and silver. In this way I antimony slag) going to the antimony blast prevent the copper in the litharge from re 25 furnace for the production of antimonial turning to the softening furnace. lead. The lead copper matte from the resi Features on the flow sheet to which no due furnace goes to the crusher, the crushed reference has been made are well under 65 matte being sold to the smelters. The metal stood in the art; and as the flow sheet is dropped in the reducing hearth (a high self-explanatory there will be no occasion to 30 1285,714 5. enter into any extended discussion of these present connection is to be understood as features. The chief innovations which the contemplating not necessarily the removal new process has wrought on the old may be of all the copper from the lead bullion said to consists (1) in the segregation and undergoing liquation, but a removal to an removal of the bulk of the copper from the extent where the copper no longer gives 70 liquating bullion whereby the copper is trouble in the desilverizing and subsequent kept out of the softening furnace; (2) in operations. In practice, if the bullion is the use of the oxidizing lead skims in the decopperized or reduced to a copper content softening furnace to hasten the softening of .05% or .03%, the new process herein gives O operation and increase the lead content; (3) excellent results. 75 in the specific treatment of the slag or skims Having described my invention what I from the softening furnace, in the preheat claim is: ing furnace to release the lead bullion held 1. In the treatment of lead bullion, the in mechanical suspension thereby; (4) in process of liquating a charge of the metal 15 the subsequent treatment of the aforesaid to segregate therefrom the bulk of the cop 80 slag or skims direct in the blast furnace per, removing the resulting copper dross, for the production of antimonial lead, thus subjecting the decopperized metal to the eliminating the residue furnace treatment action of oxidizing agents to effect the sepa of these skims as practised under the old ration of the impurities therefrom in the 20 process; (5) in the saving of zinc on de form of lead antimony slag, and recovering 85 silverizing kettles, reduced cost of retorting the antomonial lead from said slag. and cupel operations as a result of the seg 2. In the treatment of lead bullion, the regation and removal of the copper from process of liquating a charge of the metal the charge before said charge reaches the to segregate therefrom the bulk of the cop 25 softening furnace; (6) in the treatment of per, removing the resulting copper dross, 90 copper dross from the liquating kettles, subjecting the decopperized metal to oxida copper skim from the desilverizing kettles, tion in the presence of oxidizing agents and copper litharge from the cupels, in the carrying lead to effect the separation of the residue furnace with lead sulfid ore for the impurities therefrom in the form of slag, 30 production of lead copper matte, dross bul and recovering the antimonial lead from 95 lion, and a slag free from silver which goes said slag. to the blast furnace and is there treat 3. In the treatment of lead bullion, the ed with antimonial slag from the preheat process of liquating a charge of the metal ing furnace for the production of antimo to segregate the bulk of the copper, remov 35 nial lead, the dross bullion from this opera ing the resulting copper dross, subjecting 100 tion being liquated, and then re-treated in the decopperized metal to oxidation in the the softening furnace; (7) in the treatment presence of oxidizing agents carrying lead of the yellow litharge from the cupels, in and zinc to effect separation of the impuri the reducing hearth or furnace to prevent ties in the form of slag and to reduce the 40 the major portion of the silver in the lith lead content of the slag, and recovering the 05 arge from going back through the process, antimonial lead from said slag. the lead slag from the reducing hearth go 4. In the treatment of Ef bullion, the ing to the residue furnace for the recovery process of decopperizing a charge of the of copper as lead copper matte, and the metal, subjecting the decopperized metal in 45 high grade metal from the reducing hearth a molten condition to the action of oxidizing O being returned to the cupels. agents to slag off the impurities, removing The innovations aforesaid result in the said slag and subjecting the same to suffi following advantages over the old process, cient heat to render the same fluid and cause to wit, (1) a greater direct output of re the mechanically held bullion therein to be 50 fined lead by the use of refinery skim in the released therefrom and carry down any sil 5 softeners; (2) saving of rehandling of first ver and gold associated therewith. and second skimmings in residue furnace; 5. In the treatment of lead bullion, the (3) elimination of loss of silver, gold, lead, process of liquidating a charge of the metal and antimony in fume in residue furnace to segregate the copper therefrom, removing 55 operations; (4) elimination of the re-treat the resulting copper dross, subjecting the de 20 ment of residue bullion in the softeners; copperized molten metal to oxidation in the (5) saving smelting in the blast furnace of presence of metallic oxids for oxidizing the refinery skimmings; (6) a direct saving of antimony and arsenic and forming a slag, silver in the resulting slag from the sof removing the slag and heating it to render 60 teners, as this slag is lower in silver than the the same fluid to cause the release there 25 slag under the old process; (7) saving of from of the mechanically held bullion, re interest on money tied up on account of turning the released bullion to the main de stock on hand; (8) a material saving in the copperized charge undergoing oxidation, cost per ton of bullion treated. and recovering the antimonial lead from 65 The term “decopperized' as used in the the slag. 30 1285,724. 6. In the treatment of lead bullion, the charge, and treating the slag for the recov process of subjecting a charge of bullion to ery of antimonial lead. the softening action of suitable oxidizing 12. In the treatment of lead bullion, the agents to oxidize the impurities and form a process of liquating a charge of the metal slag or skim, removing said slag, subjecting to segregate the copper, removing the cop 70 the softened bullion to zinc treatment to de per dross thus formed, subjecting the de silverize tine lead, oxidizing the impurities copperized liquated lead bullion to the soft in the desilverized lead to form a refiner ening action of suitable oxidizing agents, skim, adding said skim to the charge Sub removing the resulting slag or skim, de O jected to the softening action aforesaid, silverizing the softened lead bullion by 75 drossing the desilverized lead of copper means of zinc, refining the desilverizing lead skim, and retorting the final zinc skim. by oxidation of the impurities, adding the 7. In the treatment of lead bullion, the refiner skim to the softening lead bullion, process of retorting the zinc skim from a retorting the zinc skim from the desilveriz 5 charge of desilverized bullion, cupeling the ing Operation, cupeling the retort bullion, 80 resulting retort bullion, reducing the yellow reducing the yellow litharge from the cupel litharge from the cupels, and returning the ing operation, returning the high grade high grade bullion from said reduction to metal from Said reduction to the cupels, the main charge of retort bullion in the charging the resulting slag from said reduc. 20 cupel. tion and the copper litharge from the cu 85 8. In the treatment of lead bullion, the peling operation into a suitable residue fur process of subjecting a charge of decopper nace, charging the copper dross from the ized bullion to the softening action of suit liquating operation into said residue fur able oxidizing agents to oxidize the impuri nace, charging the copper skim from the 25 ties and form a slag or skim, removing said desilverizing operation into said residue 90 skim, treating the softened bullion with zinc furnace, adding a complement of sulfid ore to desilverize the lead, oxidizing the impuri to the materials charged into the residue ties in the desilverized lead to form refiner furnace, treating the combined charges to skim, adding said skim to the softening reduce the metals to a lead copper matte and 30 charge, drossing the desilverized lead of a slag free of copper and silver, and at the 95 copper skim, and retorting the final zinc same time form dross bullion, and return skim. ing said dross bullion to the liquating 9. In the treatment of lead bullion, the charge. process of subjecting a charge of decopper 18. In the treatment of lead bullion, the 35 ized bullion to the softening action of suit process of liquating a charge of the metal 00 able oxidizing agents to oxidize the impuri and segregating the copper therefrom, re ties and form a slag or skim, removing said moving the resulting copper dross, subject skim, treating the softened bullion with zinc ing the decopperized liquated metal to the to desilverize the lead, oxidizing the impuri Softening action of suitable oxidizing 40 ties in the desilverized lead to form refiner agents, removing the resulting slag or skim, O skim, molding the refined lead while hot and heating the slag to a degree of fluidity to forming molding skim, adding the refiner effect a release or precipitation of the me and molding skims to the softening charge, chanically held bullion, returning said bul drossing the desilverized lead of copper lion to the softening charge, removing the 45 skim, and retorting the final zinc skim. slag thus freed from its bullion, desilveriz O 10. In the treatment of lead bullion, the ing the softened lead bullion by means of process of subjecting a charge of liquated zinc, refining the desilverized lead by oxi bullion to the softening action of suitable dation of its impurities, adding the refiner oxidizing agents, removing the skim of in skim to the softening bath, retorting the 50 purities or slag thus formed, charging the Zinc skim from the desilverizing operation, 5 slag into a suitable settler maintained at Cupeling the retort bullion, reducing the proper temperature to keep the slag fluid yellow litharge from the cupeling operation, and thereby release the bullion held me returning the high grade lead from said re chanically by the slag, returning the re duction to the cupels, charging the resulting leased bullion to the softening charge, and slag from said reduction and the copper 20 removing the slag for further treatment. litharge from the cupeling operation into a 11. In the treatment of lead bullion, the Suitable residue furnace, charging the cop- . process of subjecting a charge of liquated per dross from the liquating operation into bullion to the softening action of suitable said residue furnace, charging the copper 60 oxidizing agents, removing the slag or skim skim from the desilverizing operation into 25 thus formed, charging the slag into a settler said residue furnace, adding a complement and maintaining the same at a temperature of sulfid ore to the materials charged into sufficient to bring about a release of the bull the residue furnace, treating the combined lion mechanically held by the slag, return charges to reduce the metals to a lead copper 65 ing the released bullion to the softening matte and a slag free of copper and silver, 30 1,285,714. 57 and at the same time form dross bullion, process of liquating a charge of the metal and returning said dross bullion to the li to segregate therefrom the bulk of the cop quating charge. per, removing the resulting copper dross, 14. In the purification of lead bullion, the subjecting the decopperized metal to oxida process of subjecting a charge of liquated tion in the presence of metallic oxids react decopperized metal to the softening action ing with the antimony and arsenic impuri of suitable oxidizing agents, removing the ties to form a slag, and removing said slag. resulting slag, heating the slag to make the 17. In the purification of lead bullion, the 30 same fluid and cause the lead bullion held process of cupeling a charge of retort bul 10 mechanically thereby to drop, whereby a lion, reducing the yellow litharge from the lead antimony slag is produced free of cop cupeling operation, heating the charge to per, silver and gold. fluidify the slag, charging said slag into a 15. In the purification of lead bullion, the residue furnace with a complement of mate 35 process of cupeling a charge of retort bul rial carrying lead sulfid, and reducing the 15 lion, reducing the yellow litharge from the residue furnace charge to form a matte, lead . cupeling operation, heating the charge to bullion, and a slag free of copper. fluidify the slag, charging said slag into a In testimony whereofI affix my signature, residue furnace with a complement of sulfid in presence of two witnesses. ore, and reducing the residue furnace charge GEORGE P. HULST. 20 to form a matte, and a slag free of copper Witnesses: and silver. F. E. STOLLE, 16. In the treatment of lead bullion, the JAMEs O. JoHNSTONE.