US2419973A

US2419973A - Separation of copper and nickel sulfides

Info

Publication number: US2419973A
Application number: US527510A
Authority: US
Inventors: Sproule William Kelvin; Harcourt George Alan
Original assignee: International Nickel Co Inc
Current assignee: Huntington Alloys Corp
Priority date: 1944-02-02
Filing date: 1944-03-21
Publication date: 1947-05-06
Anticipated expiration: 1964-05-06

Description

y 1947. w. K. SPROULE ET AL 2,419,973

SEPARATION OF COPPER AND NICKEL SULFIDES I Filed March 21, 1944 2 Sheets-Sheet 1 FIG. 3 FIG. 4

I/VI/E/VTORS W/LL/AM KEL SPROULE GEORGE ALAN HARCOURT BY W Q Q- ATTORNEY y 1947. w. K. SPROULE ET-AL S EPARATIbN OF COPPER AND NICKEL SULFIDES Filed March 21, 1944 2 Sheets-Sheet 2 MOLTEN MASS CONTAINING COPPER, NICKEL AND SULPHUR REGULATEO SLOWCOOLING FROM TEMPERATURES AT WHICH PRIMARY CRYSTALS FORM TO BELOW ABOUT q60E 51.0w OR RAPID COOLING TO BELOW ABOUT 200 E COMMINUTION MECHANICAL SEPARATION OF NICKEL SULPHIDE AND COPPER SULPHIDE COPPER SULPHIDE NICKEL SULPHIDE SUBSTANTJALLY SUBSTANTIALLY FREE PROM NICKEL FREE FROM COPPER INVENTORS Wu. 1. /A M [(E/ vuv 5. 2001. E. GEORGE A LAN HARcOu/Pr BY Q gym- ATTORNEY.

Patented May 6, 1947 4 William Kelvin Sproule and George Alan Harcourt, Copper Clifl, Ontario, Canada, assignors to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware Application March 21, 1944, Serial No. 527,510 In Canada February 2, 1944 9 Claims. (Ci. 23-135) The present invention relates to a method for treating mixtures containing copper, nickel and sulfur to obtain each metal as a sulfide in crystalline form substantially chemically free from sulfides of the other metal preliminary to the separation of copper sulfide from nickel sulfide, and more particularly to a method for treating Bessemer matte to provide a product in which copper sulfide may be separated from nickel sulfide by physical means.

Heretofore, nickel and copper have usually been recovered from sulfide ores of copper and nickel, such as the Sudbury ores, by the Orford process. This process involves the treatment of 75% copper-nickel Bessemer matte containing very little iron and about 20% to about 24% sulfur.- The molten-75% copper-nickel matte is mixed in, a converter with second tops (see be- -low) until most of the copper sulfide present in 'the 75% copper-nickel matte has dissolved in sodium sulfide introduced by the second tops.

The mass is then cooled in pots, the pots stripped from the solidified melt, and the solidified melt broken at the line of demarcation between the sodium sulfide-copper sulfide area and the nickel sulfide area to provide first tops and first bottoms. The first tops contain about 40% copper, about 4% nickel and, the first bottoms contain about 9% copper and about 65% nickel. The first bottoms are mixed with coke, sodium sulfate and sometimes nitre cake and melted in a cupola furnace and the molten mass discharged into pots, the contents of the pots are allowed to cool, the pot stripped from the solidified melt, and the melt broken again at the line of demarcationbetween the nickel sulfide-rich bottom and the copper sulfide-rich top to provide second tops and second bottoms. The second tops, as mentioned hereinbefore, are mixed with a fresh charge of 75% copper-nickel matte while the second bottoms are further refined either to nickel oxide or electrolytically to metallic nickel. The processes in use for producing nickel fromthe Sudbury oreshave been described in many publications, notably the U. S. Bureau of Standards Circular No.- 100, Report of the Royal Ontario Nickel Commission of 1917 and in the November 1937 issue of the Canadian Mining Journal.

From the foregoing brief description, it will be appreciated that the Orford process for separating copper and nickel is a complicated process and although the most satisfactory process for the separation of copper-nickel as sulfides now known to the art, nevertheless it is not entirely satisfactory from either a technical or an economical viewpoint.

Other processes which have been-used on a commercial scale for separation of the copper and nickel found in Sudbury ores include the Mond and the Hybinette. The Mond and the Hybinette processes are approximately as tedious as the Orford process, and do not ofler greatly increased simplicity or efiiciency in the treatment 10 of copper-nickel Bessemer converter matte.

It has been discovered that the separation of copper and nickel, when present as sulfides, can be accomplished in relatively simple and efiica- 'cious manner.

It is an object of the present invention to provide a means for separating copper and nickel as sulfides.

It is another object of the present invention to provide'a method for separating copper and nickel when present as sulfides which does not involve the relative solubility of copper sulfide in sodium sulfide and the relative insolubility of nickel sulfide in sodium sulfide.

It is a further object of the present invention 2 to provide a method for producing crystals of 4 a method for separating copper sulfide from nickel sulfide in the solid state, which includes the crystallization of a mass containing copper sulfide and nickel sulfide to produce crystals of copper sulfide and/or'nickel sulfide substantially chemically free from sulfides of the other metal, said crystals being large enough that crystals of each sulfide can be mechanically freed from crystals of the other sulfide by a grinding opera- 40 tion which is industrially, technically and economically practical;

Other objects and advantages will become apparent from the following description taken in conjunction with the drawings in which- Figure 1 is a photomicrograph taken at 30 diameters of the microstructure of bessemer matte containing about 20% sulfur and about two parts of nickel to one of copper after chilling from the molten state at 1600 F. (870 C.)

Figure 2 is a photomicrograph taken at 30 dir ameters of the microstructure of a sample of Bessemer matte containing about 20% sulfur and about two parts of nickel to one of copper slowly cooled from the molten state to 1435" F. (780 C.) 5 and quenched from 1485 F. (780 C.)

Figure 3 is a photomicrograph taken at 30 diameters of the microstructure of a sample of Bessemer mattecontaining about sulfur and about two parts of'nickel to one of copper slowly cooled from the molten state to 1100 1". (593 C.) and quenched from about 1100 1". (593' C.):

Figure 4 is a photomicrograph taken at diameters of the microstructure of a sample of Bessemer matte containing about 20% sulfur and about two parts of nickel to one of copper slowly. cooled to below about 980 1''. (515 C.); and

Figure 5 is a fiow sheet illustrative of the broader aspects of the present invention.

Broadly stated, the present method involves, cooling a molten mass containing copper, nicke and sulfur, e. g., Bessemer matte (for example, '10 to 80% copper-nickel matte), in a regulated manner to cause one of the metallic components of the mass to crystallize out of the mass as crystale of a sulfide and to continue the regulated slow cooling of the mass to provide a solidified product in which the primary crystals are substantially freed from the other metallic constituent and the ground-mass of the slowly solidified matte is substantially free from the component of the primary crystals. For example, a Bessemer matte containing about 25 to about copper, about 54% to about 39% nickel and about 20% sulfur is slowly cooled until primary crystals of cop er sulfide appear and the still molten portion of the mass comprises a solution of co per sulfide, beta nickel sulfide and metal. The regulated slow cooling of the mass is continued to below about 950 F. (510 C.) during which time the copper sulfide in solution crystallizes upon the primary copper sulfide already formed, and the beta-NUS: transforms to alpha-mas: which is left as a matrix relatively free from copper sulfide. i. e., containing 1% or less of copper. Thereafter the cooling may be slow or rapid until the mass has reached a conveniently low temperature at which it can be comminuted. The cooled mass is then ground to a sufilcient degree of fineness to provide crystals of copper sulfide (Cues) substantially devoid of mechanically attached crystals of sulfide of nickel, such as alpha- 13138:. The comminuted matte may then be treated in any suitable manner to separate the mechanically freed cop er sulfide from the nickel sulfide, as for example by flotation.

Those skilled in the art will readily appreciate that the temperature at which the primary crystals appear in any mass will be dependent upon the composition of the mass. Thus, for example, a mixture containing about 19% copper, about 57% nickel and about 22% sulfur starts to-solidify at about 1430 F. (777 C.). On the other hand, a mass containing about 22% sulfur and having a copper to nickel ratio of about 1:1 commences ,to freeze at about 1700'1". (927 0.). Furthermore, a mass approaching copper sulfide (ems) ferred not only during the mam formation of primary crystals to limit the number of crystals. but is particularly important during the final stages of crystallization and in that temperature interval in which beta-N118: is converted into alpha-Niasz, which range is about 1300' 1". (705 C.) to about 950 1". (510 0.). Slow cooling through this range favors diffusion of the cues and its deposition on the primary Cu'aS crystals already present. 1

After the molten mass has been slowly cooled through the aforesaid temperature range, rapid cooling may be employed. However, better results are obtained when the molten mass is sub- Jected to regulated slow cooling throughout the temperature range extending from that temperature at which primary crystals first solidify down to about 200 F. (93 C.)-.' Preferably the molten mass is subjected to slow regulated cooling of such character as to Produce primary'crystals having a short diameter of about .003 to .01 inch.

average about .005 inch. Nevertheless, satisfactory results can be obtained when a mass is subjected to regulated slow cooling of such character that the primary crystals are substantially smaller. 1. e., having a short diameter of about onethird to about one-fifth of the aforesaid values. However, a crystallized mass containing these finer crystals requires finer grinding. When the molten mass is completely solidified, it is then crushed and ground to liberate the constituents from each other. It has been found that grinding the crystallized mass which has been sub- Jected to regulated slow cooling to provide primary crystals having a short diameter of about .003 to .01 inch, average about .005 inch, to produce a product of which approximately 10% to 30% by weight remains on a 325-mesh screen, provides material in which the primary crystals are substantially free I from mechanically attached particles of the ground-mass or matrix.

.The comminuted material can then be separated in any suitable manner, such as by flotation, by.

electronic sorting, by magnetic separation, by sink and float, by solution of one component in a non-solvent for the other component, by classification, and the like.

in composition, 1. e., containing about to".

about copper, about 5% to about 10% nickel and about 18% to about 20% sulfur first shows some crystallization at about 2000 F. (1095 C.) whilea molten mass approaching N138: in composition and containing about 2% to about 5% of copper, about 65% to about 75% nickel and about.23% to about 27% sulfur begins to solidify at about 1400 to 1450 F}. (760 C. to 788 C.). In addition, a molten mass containing about 10% to about 12% copper, about 63% to about nickel and about 22% to about 23% sulfur will start to solidify and be .completely solidified at a temperature of about 1100 1'. (593 C.).

In order that those skilled in the art may have a better understanding of the present method for treating material containing copper and nickel as sulfides preparatory to separating the copper and nickel sulfides, the following example of the treatment of copper-nickel matte containing about 20% sulfur and about two parts of nickel to one of copper is described. A copper-nickel matte of such composition is cooled to about 1600' F., at which temperature crystals of copper sulfide begin to form in the liquid. Matte quickly cooled from this temperature, before slow crystallization has commenced, has the appearance of Figure 1. The matte consists of small crystals of copper sulfide, represented by the dark areas on the photomicrograph. in a copper-nickel matrix, represented by the light areas. The copper-nickel material is too impure for satisfactory results and the crystal size is too small for mechanical separation to be feasible.

If the aforesaid matte is slowly cooled to about 1435 F. and then quenched, coarse crystals of substantially pure copper sulfide appear, as shown by the dark areas of Figure 2. The fine grained matrix was liquid when the matte was cooled and contains fine crystals of copper sulfide together with substantially all the nickel. Here again, the matrix consists of nickel sulfide contaminated with a substantial proportion of copper sulfide, and the fine copper sulfide crystals are too small for separation from the nickel-rich matrix.

As slow cooling is continued from about 1435 F. to about 1100 F., a copper-nickel alloy containing approximately 20% copper and 80% nickel begins to separate concurrently with the copper sulfide. At about 1100 F., the liquid contains only about copper due to the crystalli-- zation of copper sulfide. The photomicrograph of Figure 3 represents matte which has been slowly cooled to about 1100 F. and then chilled. As before, the dark areas represent the large copper sulfide crystals while the light areas represent the nickel-rich material which, however, still contains about 15% copper.

With further regulated slow cooling below 1100 F., beta nickel sulfide containing about 2% cop per in solid solution crystallizes together with 8 obtainable in a period of time practical for industrial operation by re-heatlng is not as coarse as can be obtained by regulated slow cooling. The difference between regulated slow cooling and re-heating, in so far as duration of treatment required for a given grain size is'concerned, decreases as the temperature of reheating approaches the temperature at which the matte is completely liquid.

It is also possible to cool rapidly a Bessemer matte to a temperature of about 100 F. to about 200 F. above the temperature of final solidification and thenslowly to cool the matte from this temperature to about 100 F. to about 400 F. below the temperature at which beta-nickel sulfide is converted to alpha-nickel sulfide,i. e.,

about 1000 F. (535 C.) to about 950 F. (510 C.)

copper sulfide and copper-nickel alloy. At about 960 F., beta nickel sulfide transforms to alpha nickel sulfide in which copper sulfide is only slightly soluble, with resultant deposition of copper sulfide upon the copper sulfide crystals already present, leaving a ground mass or matrix of nickel sulfide containing about'1% or less of copper. Thus, as illustrated in Figure 4, when slow cooling is continued below about 960 F., the matte comprises crystals of copper sulfide containing about 1% or less nickel, represented by the dark areas, and crystals of nickel sulfide containing about 1% or less copper, as illustrated by the light areas.

From a study of Figures 1 to 4, inclusive, it is evident that regulated slow cooling from the temperature of first crystallization to below about 960 F., and especially from about 1200 F. to about 950 F., is an important characteristic of the present process for obtaining nickel sulfide substantially chemically free from copper and copper sulfide substantially chemically free from nickel. After the temperature of the matte has fallen below about 960 F., the matte may be rapidly cooled if desired. However, better results are obtained if the regulated slow cooling is continued until the temperature of the matte has fallen to about 200 F.

Satisfactory results have been obtained by subjecting Bessemer, i. e. 75% copper-nickel, matte to regulated slow cooling from the temperature at which first crystals appear to belowthe temperature at which the transformation of beta- NiaSz to alpha-NizSz occurs.

It has been found that a matte which has been treated in such a manner that the temperature of the matte falls to about 900 F. to 950 F. in about one day to about 15 days is in a condition in which the primary crystals may be separated from the crystals of the second component by crushing and grinding to provide a product ofwhich about 10% to about; is retained on a screen of about 325-mesh;

From the foregoing it will be understood by those skilled in the art that a coarse grain size for the primary crystals can be obtained by regulated slow solidification of the matte. A coarse grain size can also be obtained by re-heating quickly cooled matte. However, the grain size The structure of the matte which has been slowly cooled through the temperature of final solidification is illustrated by, the photomicrograph Fig. 4. Here the Cues last to crystallize has completely migrated and deposited on the large primary CuzS crystals (dark areas in photomicrograph), leaving a clean NiaSz (light area in Fig. 4). v

The present method of separating copper and nickel, when present as sulfides, may be utilized for mattes which contain as little as 4% sulfur and as much as 25% to 30% or even more sulfur. The present process is also applicable to mattes which contain copper and nickel in the ratio of 1:1 and copper and nickelin the so-called Monel ratio of about two parts nickel to one of copper.

Mattes containing about 15% to about 18% copper may also be treated. This is somewhat surprising, but it has been found that mattes of the aforesaid composition, when subjected to regulated slow cooling, cool in such a manner that there is a segregation of CuzS around the top and sides of the container, leaving a mass containing about 10-12% copper in the center and atfthe bottom which is the last to solidify. This material can be concentrated, for example by fiotation, to produce a large quantity of unusually good nickel concentrate and a relatively small quantity of a poor copper concentrate.

In addition to mattes having the composition set forth hereinbefore, a copper matte containing only a small amount of nickel can be treated toproduce a regulated slowly cooled product which, upon grinding and concentration, for example by flotation, produces copper concentrate essentially nickel-free. Similarly, a nickel-rich matte containing only a small amount of copper can be subjected to regulated slow cooling to produce a product which when comminuted and concentrated, for example by flotation, provides a nickel concentrate essentially copper-free. It is preferred, however, to treat mattes containing about 20% to 24% sulfur, about 15% to 50% copper and about 61% to about 30% nickel.

In the event that our novel process is to be used for the recovery of copper and nickel sulfides, from sulfide ores of copper and nickel, such as those mined at Sudbury, any suitable method may be used to establish a molten mass containing copper, nickel and sulfur from the untreated For example, the untreated ore may be smelted in a blast furnace and then Bessemerized to form a molten mass containing copper, nickel and sulfur, or the untreated ore may be charged directly into a Bessemer converter. Alternatively,

- 7 whereby a copper-nickel matte is obtained to which our novel process is applicable. If desired, the raw ore may be fed directly to the sintering machine and the flotation step eliminated. Another method of preparing copper-nickel matte which is suitable for use with our novel process involves flotation of .the ore to separate sulfides from gangue, separation of a nickel-rich concentrate from the sulfides by further flotation, roasting the nickel-rich concentrate, smelting in a reverberatory furnace and Bessemerizing'. Sudbury ore-may also bejtreated by magnetic separation of the valuable minerals from the ore, said minerals being smelted and Bessemerized to obtain Bessemer matte to which our novel process is applicable. The examples given are illustrative of methods of obtaining a molten mass containing copper, nickel and sulfur which is treated in accordance with the principles of the present invention, that is, by regulated slow cooling, comminution and separation of substantially pure.

copper sulfide from substantially pure nickel sulfide.

Although the present invention has been described in conjunction with certain preferred embodiments thereof, those skilled in the art will readily understand that variations and modifications thereof can be made. Such variations and modifications are to be considered within the purview of the specification and the scope of the appended claims. Thus, for example, while the present process has been described in conjunction with Bessemer matte produced from Sudbury ore,

fide substantially chemically free from copper. comminuting said mixture to obtain crystals of copper sulfide substantially chemically and mechanically free from nickel and nickel sulfide and crystals of nickel sulfide substantially chemically and mechanically free from copper and copper sulfide. and separating said copper sulfide and said nickel sulfide.

2. A process for treating mixtures containing sulfur and the metals copper and nickel to obtain each 'of said metals in crystalline sulfide form substantially chemically free from the other metal, which comprises maintaining a mass consisting essentially of copper, nickel and sulfur at a temperature above about 950 F. and in the neighborhood of the temperature at which said mass is completely liquid until primary crystals of a first metal sulfide having a short diameter of about 0.0006 inch to about 0.01 inch form in said it is to be understood that the present process can be utilized with equally satisfactory results in the separation of metallic nickel from metallic copper. In such an application of the present process copper-nickel scrap, for example, can be melted with sufiicient sulfur to provide a product having essentially the same composition as Bessemer matte and this synthetic Bessemer mattecan then be subjected to regulated slow cooling in the same manner as Bessemer matte produced in the treatment of Sudbury ores. Similarly, other materials containing copper and nickel, but devoid of or only containing small amounts of sulfur can be sulfidized to produce a product consisting essentially of copper, nickel and sulfur of substantially the same composition as a matte and the product so produced subjected to regulated slow cooling followed by comminution and separation of the comminuted material into a product consisting essentially of copper sulfide and a product consisting essentially of nickel sulfide. Furthermore, the terms substantially chemically free and substantially chemically uncontaminated from the other sulfide as used in the specification and the appended claims are to be understood as indicating that the crystallized copper sulfide does not contain more than about 1% nickel sulfide and the crystallized nickel sulfide does not contain more than about 1% copper sulfide.

We claim:

1. A process for treating mixtures containing sulfur and the metals copper and nickel to obtain each of said metals in crystalline sulfide form substantially chemically free from the other metal, which comprises establishing a molten mass consisting essentially of copper, nickel and sulfur, subjecting said molten mass to regulated slow cooling until the temperature thereof is reduced to below about 960 F. to obtain a mixture of crystals of copper sulfide substantially chemically free from nickel and crystals of nickel sulmass to obtain a mass containing primary crystals of a first metal sulfide, reducing the temperature of said mass containing primary crystals of a first metal sulfide to below about 950 F. in a period of time sufilcient to cause further amounts of said first metal sulfide to crystallize out of the mass and to diffuse to and become associated with said primary crystals of said first metal sulfide and to obtain crystals of a second metal sulfide substantially chemically free from the first metal sulfide, comminuting said mixture to obtain crystals of said first metal sulfide substantially chemically and mechanically free from said second metal sulfide and crystals of said second metal sulfide substantially chemically and mechanically free from said first metal sulfide, and separating said metal sulfides.

3. A process for treating mixtures contair ing sulfur and the metals copper and nickel to obtain each of said metals in crystalline sulfide form substantially free from the other metal, which comprises cooling a mass consisting essentially of copper, nickel and sulfur during about one day to about fifteen days until the temperature of the mass is reducedto within the range of about 900 'F. to about 960 F. to obtain a mass containing crystals of copper sulfide containing not more than about. 1% of nickel and crystals of nickel sulfide containing not more than about 1% of copper, comminuting said mass to obtain crystals of copper sulfide containing not more than about 1% of nickel and mechanically free from crystals of nickel sulfide and crystals of nickel sulfide containing not more than 1% copper and mechanically free from copper sulfide, and separating said crystals of copper sulfide from said crystals of nickel sulfide.

4. A process for treating mixtures containing sulfur copper, nickel and sulfur to obtain each of said metals in crystalline sulfide form substantially chemically free from the other metal, which comprises cooling a mass consisting essentially of copper, nickel and sulfur to a temperature 01' about F. to about 200 F. above the temperature of final solidification to obtain a partially cooled mass, slowly cooling said partially cooled mass to a temperature of about 100 F. to about 400 F. below the temperature at which beta nickel sulfide is converted into alpha nickel sulfiide, comminuting said mass to obtain a mixture containing crystals of copper sulfide containing not more than 1% nickel and mechanically freed from nickel sulfide and crystals of nickel sulfide containing not more than 1% copper and mechanically freed from copper sulfide, and separating said crystals of nickel sulfide from said crystals of copper sulfide.

5. A process for treating mixtures containing sulfur and the metals copper and nickel to obtain each of said metals in crystalline-sulfide form, which comprises establishing a molten mass consisting essentially of from about 70% to about 80% copper, about to about nickel and about 18% to about 20% sulfur, cooling said mass to about 2000? F. to obtain a partially cooled mass, and subjecting said partially cooled mass to regulated slow cooling during a period of about one day to about fifteen days, until the temperature of said mass is reduced to below- 6. A process for treating mixtures containing sulfur and the metals copper and nickel-to obtain each of said metals in crystalline sulfide form, which comprises establishing a molten mass consisting essentially of from about 2% to about 5% copper, about 65% toabout 75% nickel and about 23% to about 27% sulfur, cooling said mass to a temperature of about 1450 F. to about 1400 F. to obtain a partially cooled mass, sub- Jecting said partially cooled mass to regulated cooling during a period of about one day to about fifteen days, until the temperature of said mass is reduced to below about 950 F., comminuting said mass to obtain crystals of copper sulfide mechanically freed from the major portion of the nickel sulfide and crystals of nickel sulfide mechanically freed from copper sulfide, and separating said crystals of copper sulfide.

7. A process for treatingmixtures containing sulfur and the metals copper and nickel to obtain each of said metals in crystalline sulfide form substantially free from the other metal, which comprises establishing a molten mass consisting essentially of from about to about 50% copper, about 61% to about 30% nickel, 24% to about sulfur, cooling said molten mass until primary crystals of a metal sulfide form in said mass to obtain a partially cooled mass, subjecting said partially cooled mass to regulated .l a The following references are of record in the slow cooling during a period of about one day to more than 1% of nickel and mechanically freed fromnickel sulfide and crystals of nickel sulfide containing not more than 1% of copper and me-- chanically freed from copper sulfide, and separating said crystals of copper sulfide from said crystals of-nickel sulfide.

8. A process for treating mixtures containing sulfur and the metals copper and nickel to obtain each of said metals in crystalline sulfide form substantially chemically free from the other metal which comprises establishing a molten mass consisting essentially of copper, nickel and sulfur and subjecting said mass to regulated slow cooling from the start of solidification thereof until said massis completely solidified and until beta nickel ,sulfide is converted to alpha nickel sulfide to obtain a solid mixture of crystals of copper sulfide substantially chemically free from nickel sulfide and crystals of nickel sulfide substantially chemically free from copper sulfide, said nickel sulfide and copper sulfide being amenable to subsequent separation.

9. A process for treating mixtures containing sulfur and the metals copper and nickel to obtain each of said metals in crystalline sulfide form substantially chemically free from'the other metal, which comprises establishing a molten mass consisting essentially of copper, nickel and sulfur, subjecting said mass to regulated slow cooling from the start of solidification thereof until the temperature of said mass is reduced to below about 950 F. to obtain a mixture of crystals of copper sulfide substantially chemically free from nickel sulfide and crystals of nickel sulfide substantially chemically free from coppersulfide,

comminuting said mixture to obtain crystals of copper sulfide substantially chemically and mechanically free from nickel sulfide and crystals of nickel sulfide substantially chemically and mechanica-lly free from copper sulfide, and separating said nickel sulfide and copper sulfide.

I WILLIAM KELVIN SPROUIE.

GEORGE ALAN HARCOURT.

REFERENCES CITED Country Date British June 21, 1939 Number 507,792

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