US2294053A

US2294053A - Refining of nonferrous metals

Info

Publication number: US2294053A
Application number: US393193A
Authority: US
Original assignee: ALVILDA L STACK; Nassau Smelting & Refining Com
Current assignee: ALVILDA L STACK; Nassau Smelting & Refining Com; Nassau Smelting & Refining Company Inc
Priority date: 1938-03-21
Filing date: 1941-05-13
Publication date: 1942-08-25
Anticipated expiration: 1959-08-25

Description

1942 J. R. STACK ET AL 2,294,053

REFINING OF NONFERROUS METALS Original Filed March 21, 1938 2 e s-Sheet 1 FIG. I

CRUDE COPPER ANODES ELECTROLYTIC DEPOSIT/ON OF COPPER FROM AN AROMA TIC SULPHONIC ACID ELECTROLYTE COPPER REMOVED RY ELECTROLYS/S AND PREC/ PI TA TION WITH T'IN OR LEAD COPPER c4 THODES PUMP, EL 56 may 75 PP TED COPPER 7'0 CRUDE ANODES STEP 2-- LEAD AND TIN REMOVED BY ELECTROLYS/S ZINC AND NICKEL REMOVED STEP 4 8V CRYSTAL /z,4 r/o/v AS SULPHONA TE ZINC AND NICKEL SULPHONA TES RECRKS'TALL IZED, PPTED WITH LIME STEP 3-- RECZJEIIQIZRA TED FREE Z/NC REMOVED R M CALCIUM SULPHONATE AC/ URNED 7'0 SOLUTION WORKED UP PPTED HYDROX/DES PREPARATION OF TO RECOVER ACID ELECTROLYTE WITH CAUSTIC SODA I SOD/UM ZINCATE SOLU TION ELEC TROLYZED TO RECOVER ZINC NICKEL HVDROX/DE DISSOLVED INVENTOR IN AMMONIA AND NICKEL JAMES RSMCK RECOVERED BY ELECTROLYS/S ALWLDA LSTACK V HIS EXECUTR/X A TTORN REFINING 0F NONFERROUS METALS Original Filed March 21, 1958 2 ee s-sheet 2 ANODE SL/MES (FROM FIGURE I.)

ROAS TED, PUL VE/P/ZED AND LEACHED WITH SuLPHON/C ACID L/QUORS RETURNED 7'0 ELEC TROLYTE OF FIG. I.

SMELTED 7'0 METAL AND CAST AS ANODES TIN AND LEAD REMOVED BY ELECTROLYS/S IN J'ULPHON/C AC/D ELEC TROLVTE TIN 0/? SOLDER CA THODES INVENTOR JAMES R. STACK ALV/LDA L.ST4C/( H/S EXECUTE/X Patented Aug. 25, 1942 REFINING OF NONFERROUS METALS James B. Stack, deceased, late of Montpelier, Vt., by Alvilda L. Stack, executrix, Pittsburgh, Pa., assignor to Nassau Smelting & Refining Company, Incorporated, New York, N. Y., a corporation of New York Original application March 21, 1938, Serial No. 197,209. Divided and this application May 13, 1941, Serial No. 393,193

Claims. (Cl. 204-106) This invention relates to the refining of nonferrous metals and more particularly to the refining of copper bearing materials.

Considerable quantities of scrap materials containing substantial amounts of copper and lesser amounts of tin, lead, zinc, iron and other metals are obtained from discarded materials, such as used telephone and other electrical equipment, machine shop tumlngs, refinery and foundry scraps and materials from various other sources. Eflorts have been made heretofore to refine these low grade materials to obtain the constituent metals therefrom in usable forms. Numerous processes for refining such material have been tried but usually they have presented disadvan tages which rendered them uneconomical.

Among the objects of the present invention are the provision of an effective and economical method of refining low grade copper bearing materials to obtain the principal constituents thereof in usable forms and the provision of electrolytic processes for separation of metals such as In accordance with one embodiment of the invention, anodes consisting of low grade copper material containing relatively large amounts of lead and tin, together with smaller amounts of other metallic impurities including nickel, may be electrolyzed for the production of pure copper cathodes in a bath having an aromatic sulphonic acid, for example, benzene disulphonic acid, as the principal active electrolytic agent. Suflicient nickel is maintained in solution in the bath to cause the precipitation as anode slimes of a substantial quantity of tin which would otherwise be held in solution in the bath. The anode slimes produced may be smelted, the resulting metal cast into anodes and the anodes then refined in an electrolytic bath in which the principal active electrolytic agent is an aromatic sulphonic acid, such as phenol sulphonic acid.

The above described and other objects and features of the-invention will be more apparent from the following detailed description thereof taken in conjunction with the accompanying drawings, in which 1 Fig. 1 is a diagrammatic and skeleton flow sheet of a process embodying the invention, and

Fig. 2 is a similar flow sheet of another process embodying a feature of the invention.

In one specific embodiment of the invention,

impure copper bearing materials from any suitable sources are partially refined, if necessary, to remove the non-metallic and some of the metallic impurities therefrom and the resulting metal is cast into anodes which consist principally of copper, tin and lead, but which may contain minor quantities of such metals as zinc, antimony, nickel and iron. These anodes are then electrolyzed for the production of electrolytic copper cathodes in an electrolyte which will form soluble salts of 1 copper, lead and tin. Anodes produced by treating junked telephone equipment ht contain from 70% to-95% copper, 0.5% to l to 15% lead, and the remainder a mixture of small amounts of other metals. A typical anode obtained from materials of the type referred to above comprised substantially 90% copper, 3.5% tin, 5% lead, 0.5% zinc, and the remainder other metals, such as antimony, nickel and iron.

Among the materials which are particularly suitable for use as electrolytesin the refining of the anode metal are the aromatic sulphonic acids and very satisfactory results may be obtained by employing a sulphonic acid such as phenol sulphonic acid or benzene disulphonic acid inwhich copper, lead, tin, zinc, iron and nickel are all, soluble. The various chloro-sulphonic and nitrosulphonic acids may also be applied to this use. It is furthermore found that, especially when lead is present, an absence of any appreciable amount of sulphuric acid or of sulphates is preferable.

In carrying out one process embodying the present invention, an electrolytic bath is made up containing about 350 to 500 grams of benzene disulphonic acid per liter. Copper is then dissolved into this solution, preferably electrolytically, until 9 to 50 grams per liter of copper are present. The free acid in the bath will then range from 290 to 410 grams per liter. The above has been found to be a satisfactory and simple a tin, 0.5%

method of preparing a bath according to the present invention, but other methods which have substantially the'same resulting product may well be used, e. g., dissolving 290 to 410 grams per liter of the acid and a sufllcientquantity of previously prepared copper salt of the acid to provide 9 to 50 grams of copper per liter.

Anodes for use in such a bath may typically consist principally of copper containing tin and lead as primary impurities but which may also include smaller amounts of nickel, zinc, arsenic, antimony, iron, etc. L

Such anodes are electrolyzed in the bath described, preferably using copper starting sheets as cathodes. Preferably, the electrolyte is circulated during the electrolysis, although rotating anodes or cathodes or the like means, such as stirrers, may'also be used, and, also preferably, the-temperature of the bath will be maintained at from 60 C. to 82 0., although, the procedure operates satisfactorily under some conditions within the range of from 40 C. to 90 C. or even beyond this.

Depending somewhat upon the composition of the anodes actually used at any given time, as well as upon the composition of the bath, and

also conditions of temperature, the current density will preferably run from 8 to 25 amperes per square foot, and the cell voltage from 0.15 to 0.35 volt.

In a given illustrative instance in which the procedure shown in Fig. 1 may be followed, an electrolyte containing no oxidizing agents and nickel fre'e crude anodes may be used. The following is a typical anode composition, the weight 5 used being 2128 pounds Type I Per cent Copper 86.0 Lead v.0 4 Tin 5.0 Arsenic 0.1 Antimony 0.2 Iron 0.1 Nickel 0.0 Zinc 10 The copper cathodes produced are substantially pure metallic copper of the usual high grade Per cent Copper 43.0 Tin 17.4 Lead 6.5 Antimony 4.0

These slimes are disposed or substantially in a manner hereinafter described.

The foul electrolyte after this step should show a metal content of about Grams per liter A portion 01 this liquor is removed and replaced with fresh solution, and this liquor is treated 7 metals would begin to deposit, thus producing a further relatively small amount (about 70 pounds) of copper. The liquor is then treated with tin to deposit out copper by replacement and to reduce stannic tin in the solution to the stannous form. This produces roughly 20 pounds of copper cement which could be returned to the production of crude anodes or roasted and used in the preparation of electrolytic solution for the first step.

The resultant liquor is substantially copper free and contains about Grams per liter Lead 28.0 Tin 34.0 Zinc 8.0

This is then electrolyzed with insoluble anodes to deposit the lead and tin together as electrolytic solder and produces some 310 pounds of solder showing about 45% lead and 55% tin.

The original crude anodes being thought of as substantially free from nickel, the liquor now to be considered is practically a solution only of zinc sulphonate and free sulphonic acid. This may be concentrated by evaporation to crystallize out the zinc sulphonate. The mother liquor may be returned to the preparation of electrolyte. The zinc salt may be re-crystallized if necessary, dissolved, and treated with lime, thus precipitating the zinc out as hydroxide.

The calcium sulphonate solution upon treatment.

with a quantitative amount of sulphuric acid to precipitate the calcium as calcium-sulphate yields free sulphonic acid to be returned to the cycle. The zinc is recovered from the hydroxide by leaching with caustic soda and electrolysis oi the sodium zincate solution.

The original electrolyte may well be charged with copper by using a relatively high grade copper scrap, clippings, turnings, punch scrap, scrap wire, or the like. i

Inthis particular example, the original electrolysis of step 1 is done in an open topped tank, with the surface of the electrolyte exposed to the atmosphere, and with the electrolyte circulated, thus exposing all of the solution to the oxygen of the air. In the case of nickel free crude anodes like type I, this exposure to the air is usually unimportant. If there is nickel present and the air is given free access to the circulated electrolyte in step 1, the procedure changes materially in the eifected results, as will appear from the following illustrative procedure, which also follows the general outline of Fig. 1.

In this instance the crude anodes may be thought of as generally like type I; but comprising also some nickel. For example, the following composition will be termed type II.

Per cent Copper 86.0 Lead 7.0 Tin 5.0 Arsenic 0.1 Antimony 0.2 Iron 0.1 Nickel 0.25

: Zinc Except as instanced below, the process and its results are substantially the same as those deelectrolytically with insoluble anodes to remove scribed above for the treatment of crude anodes of type I. In step 1, the first electrolysis of the crude anodes in the sulphonic acid electrolyte, it is found that by far the greater portion of the anodically dissolved tin precipitates out of solution and is to be found in the anode slimes. The foul electrolyte will show a metal content such as Grams per liter The anode slirnes of step 1, on the other hand, amount to about 12% of the weight of the anodes consumed, or twice as much as in the case of type I, and show a metal content such as the followmg:

Per cent Copper 20 Tin a Al lead 3 Antimony 2 Thus, with no nickel or oxygen containing oxidizing agent present (type I), the bulk of the tin remains dissolved in the electrolyte and accompanies the lead through step 3 to be recovered, without separation from the lead, as electrolytic solder, while with nickel present and the bath exposed to the air 90% or more of the anodically dissolved tin from the crude anodes goes into the anode slimes and the lead continues on as before. I

Hence in step 2, although tin, lead or solder may be used to cement out the residual copper, it may be preferred to use only lead with the result that at step 3, the cathodes produced are principally lead, running in some cases upward of 95% lead and the small balance tin. In fact, experimental work shows that in some cases at least, proper balancing of conditions in step 1 will result in driving practically all of the tin into the slimes, thus effecting a substantially clean separation in one step at this stage of the lead and tin from each other, tin into the slimes, and lead into the electrolyte.

Also in the process now being considered, it may be preferable to prepare the original electrolyte for step 1 with a certain minimum content of nickel necessary to act from the begin ning of the electrolysis as a catalyte to efiect the oxidation and precipitation of the tin as soon as its anodic solution begins. To this end the electrolyte will be compounded to contain sulphonic acid and copper sulphonate as already described, and will also have enough nickel introduced, by anodic solution of metallic nickel or by solution oi nickel sulphonate or otherwise, to efiect in the electrolyte a content of enough nickel to give the desired effect, in the present instance about 2 grams per liter.

It is found that if access of air to the bath in cally, this may be accomplished by adding to the bath a direct oxidizing agent which will not effect the procedure lnjuriously in other respects. Thus hydrogen peroxide will give a substantially quantitative precipitation of the tin in the slimes, as will also barium peroxide, lead peroxide, and other suitable agents. The decomposition prodnot of hydrogen peroxide is water, which helps to offset evaporation from the bath. The lead from lead peroxide accompanies the anodic lead and is removed at step 3. Barium from barium peroxide will continue, inertly so far as the process is concerned, in the liquor, to mix with the calcium waste at the end.

In Patent 2,111,575 mentioned above, there is disclosed a variety of sulphonic, chloro-sulphonic and nitro-sulphonic acids and the like, which are suitable for use as electrolytes for the separation tive only and will require no. essential alteration or modification in case another of the electrolytes in question is used in place of benzene disul phonic acid.

In each of the above procedures, the first step of electrolyzing the crude copper anodes in the sulphonic acid electrolyte produced an amount of anode slimes which was merely set aside for future consideration. These are now to be taken up and the treatment of them described according to the procedure diagrammatically outlined in Fig. 2.

The anode slimes from step 1 of Fig. 1 are removed at suitable intervals from the electrolytic cells of step 1. The collective slimes are washed, dried, roasted to oxidize the copper content, and leached with benzene disulphonic acid to remove the copper. The leachings and washlogs are returned to the cells of step i of Figs. 1 or 2 or are used to make up fresh solutions.

The leached residues are smelted to metal in any approved manner and furnace and are cast into anodes, which in one illustrative instance showed the following composition upon analysis:

Per cent Tin 89 Lead 13 Antimony t Copper 2 Other admixtures l For the electrolysis of such material it is preferable to use phenol sulphonic acid free from sulphuric acid and sulphates although benzene disulphonic acid is also suitable. In practice the phenol sulphonic acid employed may be the'purified product of the direct sulphonation of phe nol, containing a mixture of mono and disulphonated phenol with perhaps small amounts of even higher sulphonation products, and in which may be present any one or two or'all three of the (ii-acids.

A preferred bath for this electrolysis will carry about to 350 grams per liter of the phenol sulphonic acid. The bath is improved for the production of good cathodes by the addition of such agents as glue, resorcinol or the like. In one instance an admixture in the bath of about used in the electrolyte in carrying out the electrolytic steps in the refining process embodying the invention for several reasons. In the first place, they dissolve not only the copper but also the lead and tin. In addition, they have a high conductivity, they are relatively non-volatile, and are not appreciably decomposed electrolytically. They, therefore, permit the electrolytic deposition of pure copper without the precipitation of substantial quantities of the lead and I tin as slimes. Their high conductivity lowers the power consumption and their stability makes them economical to use because they may be recovered and reused.

Among the aromatic sulphonic acids which may be employed are the mono and poly sulphonic acids of phenol, benzol (benzene), toluol (tuluene) the cresols, xylenes, the xylenols, naphthalene, the naphthols, the anthracene, phenanthrone, and related compounds. The related chloro and nitro sulphonic acids of aromatic hydrocarbons may, likewise, be used. In addition, satisfactory results may be obtained by using the sulphonic acids of aliphatic compounds like methane, ethane, propane, etc. Mixtures of these acids may, of course, be used if desired.

Since the acids mentioned above dissolve copper, lead and tin, it is obvious that the invention may be practiced to refine copper bearing metals that include either one or both of lead and tin. For example, scrap brasses may contain no tin, while bronzes may be free from lead. These materials may be carried through the refining steps described in the same manner that is employed for materials containing both lead and tin, the only difierence being that the products obtained would not include lead or tin, as the case may be.

Where the phrase benzene disulphomc acid is used, it is thought of as standing for any one, two or all three of the several isomers, viz., the para-, meta-, and ortho-benzene disulphonic acids. In ordinary practise, however, a commercially obtainable acid is used which appears to have the meta-benzene disulphonic acid as its principal constituent with admixtures in varying total and relative proportions of the para and ortho forms.

The molecular or atomic mechanics of the actions of nickel in effecting increased precipitation of tin in the anode slimes of Fig. '1 is not as yet clearly understood. It behaves, however, as if it were a carrier or catalyte to eiiect oxidation of tin with oxygen from the air. In this application, the phrases catalytic agent," catalytic oxidation agent and the like are to be taken to mean substances which effect this oxidation in the manner that nickel does and which themselves contain no oxygen, whereas phrases like chemical agent, chemical oxidizing agent, direct oxidizing agent and the like are to be taken to mean oxygen-bearing oxydants such as hydrogen peroxide, barium peroxide, lead peroxide and the like. 7

In step 1 of Figs. 2 and-3, when nickel is present in the crude anodes and the process is started with a nickel free electrolyte, nickel will build up in the solution and begin an increasing catalytic eflect. If it be desired to throw out tin in the anode slimes, this may obviously be accomplished by adding diminishing amounts of direct oxidizing agent from the beginning (e. g., hydrogen peroxide) until the nickel is sufilciently built up to act alone.

It will be clear from the foregoing that a principal feature of the present invention is the discovery that in such electrolytic baths as are described hereinabove, the anodically dissolved tin may be caused to divided itself in substantially any desired ratio between dissolved tin remaining in the bathand tin-precipitated as anodic slimes, while the lead reamins in solution. This is accomplished by maintaining in the bath a predetermined degree of oxidizing effect which can be created and maintained by addition of the catalytic oxidizing agent nickel, by addition of chemical oxidizing agents such as peroxides, or by any convenient combination of these agencies.

From the foregoing description, it is apparent that the invention provides simple, effective and economical processes for refining non-ferrous metals. It also provides new and improved electrolytes and electrolytic processes for the separation of metals, including copper, lead and tin. Various modifications and changes may, of course be made to adapt the invention to varying conditions. Hence, the invention is not limited to the specific embodiments described herein, but embraces all modifications and equivalents falling within the scope of the annexed claims.

What is claimed is:

1. The method of separating metals from tin- .containing metallic materials consisting prinsulphonic acid as principal electrolytic agent to quantity of tin which would otherwise be held deposit substantially pure copper, and causing nickel to be in solution in the bath during the electrolysis in suiiicient amount to eiiect the precipitation as anode slimes of a material quantity of tin which would otherwise be held in solution.

2. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises electrolyzing anodes of such a material in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, and causing nickel to be in solution in the bath during the electrolysis in suilicient amount to effect the precipitation as anode slimes of a material quantity of tin which would otherwise be held in solution.

3. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises electrolyzing anodes of such a material in a bath having benzene disulphonic acid as principal electrolytic agent to deposit substantially pure copper, and causing nickel to be in solution in the bath during the electrolysis in sufiicient amount to effect the precipitation as anode slimes of a material in solution.

4. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises forming anodes of such a material, electrolyzing the anodes in a bath having from about 350 to about 500 grams per liter of the acid radical of benoneness zene disulphonic acid as principal electrolytic agent to deposit substantially pure copper, and causing nickel to be in solution in the bath duri'na the electrolysis in suficient amount to effect the precipitation as anode slimes of a material quantity of tin which would otherwise he held in solution.

5. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises forming anodes of such a material, electrolyzing the anodes in a bath having a sulphonic acid as principal electroiytic agent to deposit substantially pure copper, causing nickel to be in solution in the bath during the electrolysis to promote precipitation of tin as, anodeslimes, and regulating the concentration oi the nickel in the bath so as to maintain substantially throughout the electrolysis a predetermined ratio between tin precipitated as ani ode slimes and tin dissolved in the bath, the tin precipitated as anode slimes comprising a material quantity of tin which would otherwise be held in solution i d. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises forming anodes of such a material, electrolyzing the anodes in a hath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, causing nickel to be in solution in the bath during the electrolysis, and regulating the concentration of the nickel in the bath so as to maintain substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and the dissolved in the hath, the tin precipitated as anode slimes comprising a material quantity of tin which would otherwise be held in solution l. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises forming anodes of such a material, electrolyzin'g the anodes in a bath having from about 350 to about 500 grams per liter of the acid radical of benzene disulphonic acid as principal electrolytic agents to deposit substantially pure copper, causing nickel to be in solution in the bath during the e1ec= trolysis, and regulating the concentration of the nickel in the bath so as to maintain substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath, the tin precipitated as anode slimes comprising a material quantity of tin which would otherwise be held in solution.

8. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises forming anodes of such a material, electrolyzing the anodes in a loath having from about are to about no grams per liter 'of free benzene disulphonic acid and from about 9 to about 50 grams per liter of dissolved copper as principal electrolytic agents to deposit substantially pure copper, causing nickel to he 'ln'solution in the bath during the electrolysis, and regulating the concentration of the nickel in the bath so as to maintain substantially of such a material, electrolyzing the anodes in a 1 bath having an aromatic sulphonic acid as prinit. The method of separating metals from me-- tallic materials consisting principally of copper and containing metal of the group consisting of tin and alloys of lead and tin, which comprises forming anodes of such a material, electrolyzing' the anodes in a bath saving benzene disulphonic acid as principal electrolytic agent to deposit sub stantially pure copper, causing nickel to be in solution in the bath during the electrolysis in sufficient amount to efiect the precipitation as anode slimes of a material quantity of tin which mherwise would be held in solution, forming throughout the electrolysis a predetermined ratio I between tin precipitated as anode slimes and the dissolved in the bath, the tin precipitated as anode slimes comprising a material quantity of 'tin which would otherwise be held in solution.

pally of copper, which comprises forming anodes metallic anodes from the anode slimes, and electrolyzlne the last named anodes in a bath having phenol sulphonic acid as principal electrolytic agent to deposit tin substantially free from any admixture except lead.

, I ll. The method of separating metals from metallic materials consisting principally of copper tin and alloys of lead and tin, which comprises forming anodes of such a material, electrolyzing the anodes in a bath having benzene disulphonic acid as principal electrolytic agent to deposit substantially pure copper, causing nickel to be in solution in the bath during the electrolysis, regulating the concentration of the nickel in the bath so as to maintain substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath, the tin precipitated asanode slimes comprising a material quantity of tin which would otherwise be held in. solution, forming metallic anodes from the anode slimes, and electrolyzina the last named anodes in a bath havin phenol-sulphonic acid as principal electrolytic agent to deposit tin substantially free from any admixture except lead.

12. The method of separating metals from tincontaining mixtures of metals which consist principally of copper and are soluble in sulphonic acids, which comprises electrolyzing anodes of such a mixture in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, and causing at least 2 grams per liter of nickel to be in solution in the bath during the electrolysis to precipitate as anode slimes a material quantity of tin which would otherwise be held in solution.

13; The method of separating metals from mixtures consisting principally of copper with metal of the class consisting of tin and alloys of tin and lead present as a minor constituent, which method includes the steps of forming anodes of such a mixture, electrolyzing the anodes in a bath having from about 350 to about 500 grams per liter of the acid radical of benzene disulphonic acid as principal electrolytic agent to deposit substantially pure copper, and maintaining at least 2 grams per liter of nickel in solution in said bath during the electrolysis to precipitate as anode'slimes a material quantity of tin which would otherwise be held in solution.

14. The method of separating metals from tincontaining metallic materials consisting principally of copper, which comprises electrolyzing anodes of such a material in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper and the precipitation as anode slimes of a material 'quantity of tin which would otherwise be held in solution ,15. The method of separating metals from metallic materials consisting principally of copper and containing tin and a relatively small amount of nickel, which comprises electrolyzing anodes of such a material in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, causing an oxygen-bearing oxidizing agent tending to promote precipitation of tin as anode slimes to be present in the bath in suflicient amount to effect the precipitation as anode slimes of a material quantity of tin which would otherwise be held in solution until suilicient nickel has dissolved in the bath from the anodes to act alone to eiiect the desired precipitation of tin as anode slimes, and thereafter maintaining suflicient nickel in solution in the bath to eiiect the precipitation as anode slimes of a material quantity of tin which would otherwise be held in solution. p

16. The method of separating metals from metallic materials consisting principally of copper and containing tin and a relatively small amount of nickel, which comprises electrol'yzing anodes of'such a material in a bath having a sulphonic acid as principal electrolytic agent to deposit substantially pure copper, and maintaining substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath by adding to the bath successive amounts of an oxygenbearing oxidizing agent tending to precipitate tin as anode slimes until suflicient nickel has dissolved in the bath from the anodes to act alone to cause said ratio to exist, and thereafter regulating the concentration of the nickel in the bath so as to maintain said ratio, the tin precipitated as anode slimes comprising a material quantity of tin which would otherwise be held in solution.

17. The method of separating metals from metallic materials consisting principally of copper and containing tin and. a relatively small amount of nickel, which comprises electrolyzing anodes of such a material in a bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, and maintaining substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath by adding to the bath successive diminishing amounts of an oxygen-bearing oxidizing agent tending to precipitate tin as anode slimes until sufilcient nickel has dissolved in the bath from the anodes to act alone to cause said ratio to exist, and thereafter regulating the concentration of the nickel in the bath so as to maintain said ratio, the tin precipitated as anode slimes comprising a material quantity of tin which would otherwise be held in solution.

18. The method of separating metals from metallic materials consisting principally of copper and containing tin and a relatively small amount of nickel, which comprises electrolyzing anodes of such a material in a bath having benzene disulphonic acid as principal electrolytic agent to deposit substantially pure copper,'and maintaining substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath by adding to the bath successive diminishing amounts of an oxygen-bearing oxidizing agent tending to precipitate tin as anode slimes until suiiicient nickel has dissolved in the bath from the anodes to act alone to cause said ratio to exist, each successive addition of said oxidizing agent being proportionate to the nickel content of the bath at the time of addition and the combined contentof said oxidizing agent and nickel in the bath during the period 01 said additions being sufiicient to maintain said ratio, and thereafter regulating the concentration of the nickel in the bath so as to maintain said ratio, the tin precipitated'as anode slimes comprising a material quantity 0! tin which would otherwise be held in solution .19. The method of separating metals from megen-bearing oxidizing agent tending to promote precipitation of tin as anode slimes to be present in the bath in sumcient amount to efiect the precipitation as anode slimes or a material quantity of tin which would otherwise be held in solution until the dissolved nickel content 0! the bath has reached about 2 grams per-liter, at which concentration the nickel is present in solution in the bath in sufllcient amount to act alone to effect the precipitation as anode slimes oi. a material quantity of tin which would otherwise be held in solution, and thereafter maintaining at least 2 grams per liter of dissolved nickel in the bath.

20. The method of separating metals from metallic materials consisting principally of copper and containing tin and a relatively small amount of nickel, which comprises electrolyzing anodes of such a material in a. bath having an aromatic sulphonic acid as principal electrolytic agent to deposit substantially pure copper, and maintaining substantially throughout the electrolysis a predetermined ratio between tin precipitated as anode slimes and tin dissolved in the bath by adding to the bath diminishing amounts of an oxygen-bearing oxidizing agent tending to precipitate tin as anode slimes until the dissolved nickel content of the bath has reached about 2 grams per liter, at which concentration the nickel is present in solution in the bath in suiiloient amount to act alone to eflect the precipitation as anode slimes of a material quantity of tin which would otherwise be held in solution, and thereafter maintaining at least 2 grams per liter of dissolved nickel in the bath.

ALVILDA L. STACK. Executriz of the Estate of James R. Stack, De-

ceased.