Nickel
D E V E L O P M E N T S IN NICKEL 0.B. J. FRASER lnternational Nickel Co., Inc., 67 W a l l St., N e w York,
T h e discovery of nickel, of developments in its technology and utilization, and of the history of the metallurgy b y which it has been won from its ores are reviewed. Some physical data, statistical information to aid in defining the position of nickel in the world’s affairs, and comments on the distribution of nickel minerals in the earth’s crust and the locations of ore bodies, past and present, are also included.
EFISRESCE to the early use of nickel alloys for swords or other weapons (beaten into shape by primitive craft,smen from pieces of iron-nickel alloys of meteoric origin), of the “paktong” articles made by the Chinese from cupronickel V d copper-nickel-zinc alloys in very early times, and of the Bactrian cupronickel coins which were of a composition quite close to that, of our own “nickels” has been made by others (1, 15). The first or a t least a very early use of nickel in ot,her than metallic form was made by Germans who used a heavy, reddish-brown ore for coloring glass green. This n-as long before there was any knoa ledge of the element nickel, and it was not unt,il after the discovery of the element that the reddish-brown ore was found t o contain its arsenide, niccolite (25). The reddish-brown German ore had a lot to do with the naniiiig of the featured element of this symposium. During the Middle Ages the chief source of copper for Europe Tvas the mines in the Erz Gebirge along the boundary between western Saxony and Bohemia. One of the superstit’ions of the day was that, the subterranean ore formations were inhabited by supernatural beings who had influence over the minerals. -4mong the more exasperating of these creatures \$-erethe nickels, so i t was only natural that when the reddish-brown ore which was expected to yield good copper m s quite unproductive of that metal the good miners gave it the opprobrious name “Irupfer-nickel,” by which name it was identified in 1694 in the writings of t’he Swedish metallurgist Urban Hiiirne (9, 23). iibout the mid-point of the eighteenth century Axel Fredrik Cronstedt, a young metallurgist in the Swedish Bureau of Mines whose likeness is shown in the title photo for the symposium, made a study of a new mineral from the cobalt mine at Los Halsingland, Sweden. The mineral was similar in appearance to the bewitched ore of the Saxons. He, too, expected to obtain copper from this Norwegian kupfer-nickel but instead produced oiily a white metal. H e described his work first in the memoirs of the Stockholm Academy (4).A few years later, 1754, he publicly stated, “The greatest quantity of the new previously described half-metal is contained in kupfer-nickel; therefore, I retain the same name for its regulus or call it nickel for short” ( 2 3 ) , and nickel it has been ever since. The identity of Cronstedt’s material as a new element was disputed for many years, until Bergman described, in 1775, his own preparation of nickel of rather high purity ( 2 ) . Nickel seems t o have been just another element for many years, for William Nicholson’s “First Principles of Chemistry,” published in 1796, contained t’he statement, (‘Thismet,allic substance has not been applied t’o any use.” I n the early years of the nineteenth century, Europeans began to make their own copper-nickel-zinc versions of the Chinese “paktong,” thus starting the first important use of the new element. Nickel plating became an important use about 1844, and on toward the end of the century nickel steels made their
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appearance, though alloys of the typc had been investigated by Michael Faraday as far back as 1820. Malleable nickel wa.s produced first in the 1870’s by Fleitmann in Germany. The great development of the stainless steels and the corrosion- and heatresistant nonferrous alloys of nickel, of great importance to our modern economy, especialIy in the chemical and d i e d industries, has taken place in the present century. OCCURRENCE AND SUPPLY
Kickel is distributed widely in nature, hut in only a few 10c:dities is nickel mineralization sufficiently concentrated as to constitute ore bodies. More than 60 nickel minerals are recorded in modern lit,erature (18, ZZ), but only four have had commercial iniportance. In order of abundance in the lithosphere nickel is the twenty-third element; it is a minor constituent of a great many igneous rocks, the average nickel content of all igneous rocks being of the order of 0.009% (20). Nickel ore bodies have been found in several countries, as slion-n in Table I, which lists the areas in which there has been some production of ore in recent years. As a matter of fact, only and h-ew Caledonia, have three of the areas, Canada, U.S.S.R., been producing important t’onnages. In addition t’o the list,cd areas, notable concentrations of nickeliferous minerals oc(’ur in tn-o or three other countries.
Table
I.*
Geographical Distribution of Nickel O r e Production (U. S. Bureau of Mines “Minerals Yearbook”)
Country 1023-27 Australia (Tasmania) X Brazil Canada i;: Cuba ..
Egypt
Finland Germany Greece India (Burma) Iran Italy Japan Morocco, French Netherlands Indies New Caledonia Norway Southern Rhodesia Sweden Union of South Africa U.S.S.R. United States
.. # .
..
x
x ..
x
.. .. ,.
x x
..
.. .
.
x
1929
X
x
.. .. ..
..
1933 X
x x ..
.. .
I
..
x x .. .. ..
x x
.. x
..
..
.. .. .. ..
x
x x
..
..
.. ..
x
x
. .. ..
,.
1937-38
1941
1045
X
X
..
x x .. x .. x x x x .. x x x x x x x x
x x
.. x
x x x x x x x x
x x
x x x x x
x x x x x x : x x
x x x
x x x x x
x x
1949
..
x x
..
:: ._ :
..
,. ..
..
._ x x x .. x x x
Siclrel ranks ninth among the metallic elements in tonnage produced annually. Korld production of nickel from 1860 t o 1949, inclusive, is shown in Figure 1, which \vas constructed from statistical data in the Royal Ontario h-ickel Commission Report (1917); Mineral Industry; U. S. Mineral Resources; and Minerals Yearbook. For the period covered by Figure 1, Sorway was the chief source of nickel until 1875, when New Caledonia, a French island in the South Pacific, rapidly took over the lead and held it until Canada’s output took the lead in 1903. Canadian production has dominated the field by a wide margin in all succeeding years. The peak production of all time came in the war ye?r 1943, and the maximum peacetime production on the chart camp in 1948. The U. S. Bureau of &lines ‘World Review” figures for the last 10 years available (1940-49, inclusive) indicate that in t h a t
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period Canada has been the squrce of from 71 to nearly 82% of the world supply. Russia, for the accuracy of whose estimated figures there could be some doubt, has been the second largest source for about 6 t o IS%, and New Caledonia has been providing from 2 t o 751,. The largest Canadian producer has increased its capacity by approximately 57, in the current year (1951), and the second largest producer also is increasing capacity considerably. A third and new Canadian producer will be in the field within the next 2 or 3 years, and there will be sizable production again from Cuba in the near future. In addition, the complex ores of the Fredericktown area, in southeast Missouri, which were worked -SOURCES
R o Y 4 t ONTbRlO NICKEL COMMISSION REPORT, MINERAL INOUSTRY. -U 5
MINERAL RE90URCES AN0 MINERALS YEAR B O O K ‘
iao,ooo 160.000
140,000
120.000
if
iCO,QOO
f,
80,000
60,000
$
40,000
L
20,000
10,000
1.000 800
-
.
cination. Weeks’ account says further that, in 1751, he mixed some kupfer-nickel with “black flux,” placed the mixture in a crucible, and covered it with a layer of common salt. On roasting it, he not only reduced the oxide to the metallic state, but melted the metal. Cronstedt, according to another translation available to the author, mentioned removal of iron and cobalt by “slight roasting’’ followed by repeated fusions with borax. Arsenical ores, the type with which Cronstedt worked, have been and still are sources of minor quantities of nickel. They occur in Canada, Europe, and French Morocco. The usual initial procedure (8,10-1Q, 1 6 , l Y,21 ), even in the early days of the industry, was to smelt the ore in blast furnaces to form a speiss. Ores high in iron were first roasted to oxidize the iron and thus facilitate its conversion to slag in the smelting operation. The initial smelting was followed by roasting and resmelting in blast or reverberatory furnaces or by crucible smelting to arrive a t a sufficiently concentrated speiss for further treatment. When other elements were not present in complicating amounts, the nickel speiss was dead-roasted with additions of carbonaceous matter, sodium nitrate, and soda ash to ensure complete volatilization of arsenic or its conversion to water-soluble sodium arsenate, which was removed by leaching. The nickel monoxide thus produced was mixed with a carbonaceous binder, and reduced by wood charcoal either a t temperatures below the melting point of nickel to produce a spongy product or above the melting point to make a castable, molten product. According to Schnabel (21) mixed nickel-cobalt speisses also were dead roasted, and the calcined product was treated with sulfuric acid. Iron and copper were precipitated from the sulfate solution by boiling it with calcium carbonate. Cobalt sesquioxide was then thrown down by chloride of lime and separated
600
Figure 1.
World Nickel Production, 1 850-1 949
during both world wars, will again be the source of a small, but appreciable, annual output of nickel. The excess of demand for nickel over available supply which exists today probably will not persist into the time t o which we all look forward hopefully, when the requirements for defense purposes will not be dominating the industrial picture and there will be more nickel available for use as a chemical raw material. EARLY METALLURGY
There have been quite a number of things of interest to chemists in the extractive metallurgy of nickel through the past two centuries. Only sketchy accounts are possible here, but sources of more copplete information are given in the bibliography (8, 10-14, 16, 21). There could be no better introduction to this part of the discussion than a few words on the procedure followed by Cronstedt in his discovery investigations. Quoting from Weeks ( 2 3 ) : “Upon calcining the green crystals which covered the surface of some weathered kupfer-nickel, and reducing the calx, or oxide, by heating it with charcoal, Cronstedt obtained a white metal bearing no resemblance whatever t o copper.”
Figure 2.
Frood-Stobie Open Pit, Sudbury District, Ontario, Can,
Cronstedt said (23): This salt or this vitriol, after having been calcined! gives a colcothar, or clear, gray residue which, when fused with three parts of black flux, gives a regulus of 50 pounds per quintal. H e described the regulus as being yellowish on the outside, silvery i n the fracture, laminar in structure, hard and brittle, feebly attracted by the magnet and convertible to a black powder by cal-
May 1952
from the solution. Nickel hydroxide was then precipitated by milk of lime. The nickel hydroxide was washed, dried, ground, and reduced to metallic nickel. Of course, there were differences in details in the practices of the different European smelters and refiners, but these cannot be dealt with here, except to note that in some plants the speiss itself, or the dead-roasted product, was
INDUSTRIAL AND ENGINEERING CHEMISTRY
9s 1
Figure 3.
The International Nickel Co. of Canada, Ltd., Smelter at Copper Cliff, Ontario
treated with hydrochloric rather than sulfuric acid, but the separation of cobalt and nickel was handled similarly. T R E A T M E N T O F A R S E N I C A L AND SILICATE ORES
The developments of later years are set forth in more modern texts (17, 86). The preliminary blast furnace smelting is still retained. The resulting speiss is still roasted but not to the same end point. In the case of Moroccan ores enough arsenic is left in the roasted material to provide for precipitation of iron as ferric arsenate. The oxidized material is ground and dissolved as in earlier times in either sulfuric or hydrochloric acids. Excess acid is neutralized and copper is precipitated on scrap iron. The iron is oxidized by aeration or with chlorine and precipitated by limestone. To the now purified solution fractional additions of sodium hydroxide and bleaching powder are made. Bt first fairly pure cobaltic hydroxide is precipitated and removed, then the rest of the cobalt comes out in a mixed cobalt-nickel precipitate which has to be reverted t o the dissolving stage. Finally, nickel is precipitated with sodium hydroxide, and the precipitate is either dissolved for electrolytic purification or reduced t o metallic nickel. Practice in Canada on northern Ontario cobalt ores is further illustrative of modern practice. According to Mutch ( 1 7 ) crushed ore is smelted in a blast furnace with coke, limestone, scrap iron, and revert speiss. There are several products of this operation, but what follows concerns only the speiss, which carries the nickel contents of the ore. The furnacing is conducted in such manner as to produce speiss containing cobalt, nickel, arsenic, and iron in proper balance t o ensure the success of later operations. It also contains some copper, antimony, and silver. The speiss is ground to 20 mesh and roasted to the elimination of about half its arsenic content. It is then mixed with common salt, roasted again with further substantial, but by no means complete, elimination of arsenic. This product is ground and leached with water to dissolve the water-soluble chlorides of cobalt, nickel, and copper. Insoluble chlorides are pugged with sulfuric acid and dumped into bins to “sulfate” over a period of four weeks. The soluble part of the sulfated material is then dissolved in water. The pregnant solution is treated with sodium chlorate or hypochlorite to oxidize iron; it is then neutralized with lime to p H 3.5, whereupon remaining arsenic comes out as ferric and calcium arsenates and the balance of the iron precipi-
952
tates as ferric hydroxide. Antimony also is precipitated a t this point. After filtration, copper is precipitated on scrap iron and the dissolving iron is thrown don-n with additional lime. The purified solution is treated similarly to the practice for Moroccan ores, except that the precipitant for cobalt is sodium hypochlorite solution. From the cobalt-ire8 solution resulting, the nickel is precipitated by soda ash, and the operation is finished by adding a little bleach solution to bring the nickel precipitation more nearly to completion. The final precipitate, now black in color and largely hydrated nickel oxide, is filtered, washed, and calcined to the green oxide, xhich is either sold as such or reduced to metal. Silicate ores are of greater importance than arsenical ores as sources of nickel. Gamier, after whom was named the hydrated nickel-magnesium silicate mineral which is the important constituent of New Caledonia ores, was probably the first experimenter with those ores. His first attempt, which was not commercially successful, was to copy the ferrous metallurgical practice of the time (1876), but he was able to produce for the International Exposition in Paris in 1878 some nickel-iron ingots by reduction of the ore with wood charcoal in a cupola furnace. He was also able to refine the alloy to 98% nickel content. Greater success was achieved by a radically different process, vhich was first put into practice in 1889 and which is the process of today (6). In current practice (l’?), nhich is believed to be eubstantially unchanged since the time of this reference, a matte is produced by smelting the ore in blast furnaces with gypsum ahd an excess of coke to reduce the gypsum. Sulfide-containing alkali waste or even pyrites may be used as sulfur sources. The matte is Bessemerized, or blown with air, in small converters, in which the iron is oxidized and slagged off with silica. The converter product is a rich (80y0Ni) matte, nhich is ground and dead roasted to practically pure nickel oxide. The oxide and a reducing agent are ground together and briquetted into cylindrical “rondelles” or cubes, which are then reduced to metal by heating to bright redness. T R E A T M E N T O F SULFIDE ORES
Sulfide ores have been the outstanding source of nickel since the first days of Canadian production, about 1890. The nickel mineral in the Sudbury district of Ontario, which area is the world’s largest source today, is pentlandite, a mixed sulfide of
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Figure 4.
Nickel Refinery of The M o n d Nickel Co., Ltd., Clydach, Swansea, Wales
iron and nickel. It is associated with large amounts of pyrrhotite, the magnetic sulfide of iron, and smaller amounts of the copper-iron sulfide, chalcopyrite. Similar ores occur in other areas in Canada and in other parts of the world. Ores of the New Caledonia type and the somewhat different nickeliferous lateritic iron ores of Cuba which have been worked in recent years, in fact all nickel ores that have been formed by the weathering of peridotites or similar basic rocks, are amenable t o treatment, following preliminary reduction at elevated temperatures with reducing gas, by Caron’s ammonia leaching process (3). This process, perhaps slightly modified, was used during World War I1 in production of large tonnages of nickel and nickel oxide in Cuba (6). Active metallic nickel is readily soluble in solutions of ammonia and ammonium salts in the presence of oxygen. I n the Cuban operation the leaching solution contained ammonia and ammonium carbonate. Basic nickel carbonate
Figure 5.
May 1952
Rolling
Mills of The
was thrown out of the pregnant solution by heating t o drive off all ammonia. The basic carbonate was calcined to nickel oxide which was sold as such, although i t could well have been reduced to metal. Sulfide ores from t h e old Gap Mine in Pennsylvania were worked in the United States prior t o 1875, and, contemporaneously, such ores were being reduced to metal a t many points in Europe. Schnabel’s discussions ( 2 1 ) of the practices followed are very interesting. The first mining operations in the Copper Cliff area in the province of Ontario, Can., were begun in ignorance of the presence of nickel in the ore. It was thought to be a copper ore only and was shipped as such t o two copper smelters in the New York area-namely, the old Nichols Copper Co. on Long Island and the Orford Copper Co., a t Bayonne, N. J. At the latter plant, which was to become part of The International Nickel Co., the seemingly impossible economic separation of the nickel and copper in the ore was worked out by an ingenious process which was actually an application of solvent extraction t o a molten system a t high temperatures. This was the so-called Orford process, which was practiced until very recent years. It is described in the following discussion as part of a more extensive story. Shipping costs very early made it necessary to carry on some of the metallurgy a t the mines. The ore was roasted in heaps, out in the open, and the roasted ore was smelted in blast furnaces to matte containing nickel, copper, and iron. Some of the sulfur and all the iron were removed by Bessemerizing or blowing air through the matte in “converters.” This process had t o be stopped a t the iron removal stage, which was accomplished by slagging off the iron oxide, because beyond this point the nickel itself would be oxidized and slagged off, and because the converter reactions, which had been exothermic up t o this point now became endothermic, which would mean rapid chilling and even solidification of the matte. The matte was cast into slabs, which were broken up and shipped to the Orford Works in Bayonne. The matte was subjected to multiple smelting operations in cupola furnaces using niter cake as flux, which was reduced in the furnaces with excess of coke. The resulting molten sodium sulfide is a good solvent for copper and iron sulfides b u t not for nickel sulfide. The mixed sulfides from the second of two cupola smeltings were tapped into large cast-iron pots and allowed to
International Nickel Co., Inc., at Huntington,
W. Va.
INDUSTRIAL AND ENGINEERING CHEMISTRY
953
NICKEL Table 11.
Physical Constants of Pure N i c k e l
Atomic KO. Atomic weight Radioisotopes Stable isotopes Cryital form Lattice constant Density (computed) Latent heat of fusion Vapor pressure Boiling
point
(approx .)
Table
111.
Thermal Properties of Pure Nickel
Average coe5cient. of linear thermal expansion at - 180 to 00 c. 10.22 X 10-6/’ C. 00 to 1000 1 3 . 3 X 1 0 - 6 / ’ C. no to 5000 c. 1 5 . 4 5 X 10-6/’C. 253 to 9000 c. 16.3 X 10-@/’C. True coefficient of linear thermal expansion at 200 c. 1 2 . 5 x 1 0 - a / o c. 13.5 X 10-6/’ C. 1000 c . 16.3 X l O - f l / O C. 300’ C. Thermal conductivity st ; o o o c. 0.198 cal./sq.cm./sec./ O C./cm. 5000 0 . 148 cai./sq.cm./sec. . / ” C./cm. Specific heat a t 0 . 1 1 2 3 cal./g./’ C. 1000 c. 0 . 1265 cal./g./’ C . 5000 c.
c.
level with water gas. The reduced nickel is then subjected a t about SO” C. to a gas stream composed in part of the same gas used in the reduction operation. The nickel reacts with the carbon monoxide in the gas stream to form volatile nickel carbonyl, which, in another vessel, is raised considerably in temperature; this causes decomposition of the carbonyl and deposition of its nickel content on grains of nickel, which are recirculated through the decomposers until large enough t o be withdrawn for market. The operations of The International Kickel Go. and the Mond Kickel Co. have been described in detail in the literature (8, 1014). It is interesting to note that the owners of the latest imporhnt nickel development in northern Manitoba, Can., proposed to treat ores that are quite similar to the Sudbury sulfide ores in a radically different way. The suggested process is t o roast copper-nickel sulfide concentrates to oxide, reduce the calcines with hydrogen to metallic nickel and copper, plus magnetite, and then subject the reduced material to a modification of Caron’s ammonia leaching process ( 3 ) .
c.
Table
IV. Electrical and Magnetic Properties of Pure Nickel
Electrical resistivity a t 00
c. c.
200
6 . I 4 1 microhm-cm. 6 . 844 microhm-om.
Temperature coefficient of electrical resistivity 0-1000 c . 0.00658-0.00692/0 C. Curie temperature (approx.) 3530 c. 6500 Magnetic saturation value (B.H) (rtpprox.) Coercive force (He)(from B = 5000) 2.73 oersteds
P H Y S I C A L CHARACTERISTICS OF NICKEL
Simply to round out, this discussion, Tables 11, 111, and IV are included to give an idea of the physical constank, thermal propcrt , i w and electrical and magnetic properties, respectively, of pure nickel (96). il compact discussion of nickel and its alloys has been published by the National Bureau of Standards (1.9);the circular contains a bibliography with 379 references. Figures 2 to 5, inclusive, show views of the mining, smelting, and refining plants of The International Nickel Co. of Cannda, I’td., and subsidiary companies. BIBLIOGRAPHY
solidify. The molten sulfides stratified in t,he pot,s to form a lower layer of nickel sulfide and an upper layer of copper and iron sulfides dissolved in sodium sulfide, iifter solidification of the whole contents, the pots were dumped, the nickel sulfide “bottoms” were separated, crushed, and ground. The ground sulfide was leached first with hot water to remove small residual amounts of sodium sulfide, then with dilute sulfuric acid to remove residual iron. After washing with hot water, the sulfide was subject,ed to a two-stage roasting, the first stage for sulfur removal only and the second, with added salt, t o convert the residual copper to the soluble chloride. ,4 water leaching removed the copper. The impure oxide thus produced was then roasted again u-itJhadded sodium nitrate and soda ash to convert the remaining sulfur to sodium sulfate, which was leached out with hot water. The oxide, now black though still NiO, was reduced with wood charcoal in oil-fired reverberatory furnaces to metallic nickel, which was cast into ingots or shot. Some of the oxide was sold as such. At a later date, some of the met,allic nickel was cast into anodes and subjected to further refining by electrolysis. This basic series of processes has gone through many changes and has practically disappeared. Today a large part of the separation of nickel and copper is done by flotation while still in the ore stage. All the roasting is done now in multiple-hearth mechanical furnaces. Reverberatory smelting to a large extent has eliminated blast furnace operations. The Orford process has disappeared entirely and has been replaced by a process in which the Cu-Ni matte is subjected to controlled cooling. After casting it is crushed and ground and subjected to flotation and magnetic separation. A nickel concentrate thus produced is subjected to a sintering operation to produce a dense, nodular “nickel oxide sinter,” for refining by both t.he electrolytic and Mond processes or for use in the manufacture of nickel alloys and alloy steels. The ingenious Mond process has undergone changes and refinements through the years, but essentially it is not greatly different today from earlier years. I n this process, suitably prepared oxidized nickel material is reduced at a preferred temperature
954
Baldwin, W. H., J . Chem. Education, 8 , 1749-50 (1931). Bergman, T., De niccolo, Stockholm (1775). Caron, M. H., J . Metals. 188, No. 1, Trans. 67-90 (1950). Cronstedt. A. F.. Vet. Acad. Handl.. 1751. 287-92. Dhavernas, J., “Histoire du Kickel,” Pa& Centre d’Information du Nickel, 1938. Dufour, M.F., and Hills, R. C., Chem. I d s . , 57, 621-7 (1945). Forward, F. A , Samis, C. S.,and Kaidrik, V., Can. Mining M e t . Bull., 434, 350-5 (1948).
Griffiths. W.T., Proc. 4th Empire Mining Met. Congr. (Grcat Britain), Part 11, 1950, 848-80 Hiarne, U., En kort Anledning Till, atsicillige Malmoch Bergarters, p. 21, Stockholm (1964). International Nickel Co. (staff paper), Can. Mining J.,58, 581748 (1937). Ibid., 67, 309-556 (1946). Ibid., 71, N134-43 (1950).
International Nickel Co. (staff paper), Can. Mining M e t . H t t l l . , 434, 356-67 (1948).
International Nickel Co. (staff paper), Eng. Mining J . , 130,42397 (1930).
International Nickel Co., Sew York, “The Romance of Nickel
”
1950.
Liddell, D. M., “Handbook of Sonferrous Metallurgy,” 1st ed., Vol. 11, pp. 1295-306, ?;en. York, McGraw-Hill Book Co., 1926. Ibid., 2nd ed., Vol. 11,pp. 585-97, 1279-87, 1945. Mellor, J. W., “A Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Vol. XV, pp. 5-6, London, Longmans, Green & Co., 1936. Natl. Bureau of Standards, Washington 25, D. C., Ciw. 485 (1950).
Rankama, K., and Sahama, Th. G., “Geochemistry, pp. 39, 52, Chicago, Univ. of Chicago Press, 1950. Schnabel, C., and Louis, H., “Handbook of Metallurgy,” pp. 5 5 6 9 6 , London, Macmillan & Co., Ltd., 1898. Smith, 0. C., “Mineral Identification Simpl!pd,” 1940. Weeks, M. E., “Discovery of the Elements, 5th ed., pp. 70-7, Easton, Pa., J. Chem. Education, 1945. Wise, E. M., and Schaefer, R. H., Metals 6: Alloys, 16, 424-8, 891-3 (1942).
Young, R. S., “Cobalt,” pp. 38-45, A.C.S. Monograph Series KO.108, New York, Reinhold Publishmg Corp., 1948. RECEIVED for review February 20, 1952.
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AUCEPTED Marah 17, 1952.
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