Search Documents

PRESIDENTS DAVID THOMAS 1871 R W RAYMOND 1872-1874 A L HOLLEY1875 ABRAM S HEWITT 1876 T STERRY HUNT 1877 ECKLEY B COXE 1878 - 1879 WILLIAM P SHINN 1880 WILLIAM METCALF 1881 RICHARD P ROTHWELL 1882 RICHARD W HUNT 1883

Jan 1, 1917

By R. A. Meussner, C. T. Fujii

Chromium solution in wustite depresses the oxygen activity in a nonideal manner and expands the lattice slightly. Gravimetric measurements of the equilibrium compositions of wustite containing 0.00 to 1.38 wt pct Cr define the oxygen potential (CO2-CO atm) and the limits of the phase field at 1000°C. These data extrapolate to a maximum solubility of 2 wt pct Cr. The lattice parameter data, room-temperature measurements of quenched samples, differ significantly from those in the literature. Both pure and chromium wus-tites contract at uniform and equal rates as the oxygen content (metal deficit) increases. The a. US metal deficit relationships are straight lines showing none of the curvature previously reported. At constant metal deficit, the a. expands by 0.002? on alloying with 0.4 to 0.5 wt pct Cr but is insensitive to further chromium additions: a small expansion rather than a marked contraction. These results require a modification of the accepted alloying mechanism. IN the high-temperature oxidation of Fe-Cr alloys in Ha-H,and CO2-CO atmospheres the vapor transfer of oxygen from the continuous wustite outer scale to the porous inner scale/alloy interface sustains the high oxidation rates.1"3 The driving force for this transport is the difference in the oxygen activity of the outer wustite and that at the inner scale/alloy interface. In pure CO2, as well as in CO2-CO atmospheres, carburization of the alloy accompanies this oxidation. Current efforts to evaluate the parameters controlling this carburization have shown that the process is not simple; i.e., the carbon concentration in the alloy initially increases rapidly, reaches a maximum, and then decreases slowly as the oxidation time is extended. This is the same pattern reported by McCoy for the more complex oxidation-carburization of stainless steels and an Fe-Cr alloy in CO2 at lower temperatures.4 These changes in the carburization process occur while the overall oxidation rate and the lattice parameters of the scale layers remain constant. If this invariance of the lattice parameter is assumed to indicate a constant scale composition and thus a constant oxygen potential, the carburization results are not easily explained. Electron microprobe traces across the thickness of these outer scales, however, have revealed distinct chromium gradients penetrating 10 to 50 µ from the inner surface where the chromium concentrations were estimated at a few tenths percent. The variation of the chromium cmcentration on the inner surface of the scale, and the resulting change of the oxygen activity, during the oxidation process is considered to be important in defining the carburization process. Thus, to gain an understanding of the complex oxidation-carburization proc- ess, it was necessary to measure the properties of wustite containing known amounts of chromium (chromium wustite). Although the general features of the Fe-Cr-0 equilibrium diagram between 900° and 1300°C have been fairly well established by Richards and white: Wood-house and White,6 Seybolt,7 and Katsura and Muan,8 there have been no detailed studies of the limits of the chromium wustite phase field or the properties of these alloyed wustites. The recent results of a limited study of chromium wustite by Levin and wagner9 indicate that more than 0.67 wt pct Cr is soluble in wustite above 850°C and that this alloying is accompanied by a substantial lattice contraction. This change in the lattice parameter was not evident in the X-ray diffraction patterns of wustite layers from the oxidation experiments;1,3 the lines were sharp even though a chromium gradient existed in the scale. The present paper describes gravimetric equilibrium experiments which delineate the boundaries of the chromium wustite single-phase field at 1000°C and define the changes in the oxygen activity and the lattice parameter of wustite as functions of chromium and oxygen contents. The lattice parameter data of chromium wustite obtained from these equilibrium and special quenching experiments differ considerably from those reported.9 Those for pure wustite show significant differences from the widely accepted data of Jette and Foote.10 Since the causes of these differences are not easily assignable, and since the literature contains many sets of data on wustite which if not in conflict are at best not in harmony, the experimental procedures are discussed in the present paper. EXPERIMENTAL Oxide Preparation. The specimens used in these studies were porous pellets compacted from high-purity (Fe,Cr)2O3 or Fe2O3 powders. These powders were prepared from electrolytic chromium (99.8 pct purity) and electrolytic iron purified by consumable-electrode, vacuum arc-melting processing (299.9 pct purity).11 The oxides were produced by standard analytical procedures: solution of the metals in acids (HC1, then HNO3 added), coprecipitation of the hydroxides (NHaOH), and filtering and washing these precipitates. Initial dehydration of the coprecipitated hydroxides was done in a porcelain evaporating dish heated by a Meker-type burner, final dehydration by firing in a recrystallized alumina crucible at 1000" to 1050°C for 20 hr in an electrically heated furnace. Spectrographic analysis detected the following impurities: silicon, 0.01 pct or less; aluminum, 0.001 pct to trace; manganese and copper, 0.0001 pct to none. Each of these levels is at least one order of magnitude lower than in commercially available CP grade ferric and chromic oxides. Fluorescence analy-

Jan 1, 1969

By Victor Formanek, Paul Chataignon, Maurice Rey

IT is found when floating oxidized lead ores by sulphidization, that the presence of calcium salts in the water, is usually detrimental and lowers the recovery. This effect is particularly marked in dry countries such as North Africa, where the waters often carry large amounts of calcium sulphate and where the ore may even contain gypsum. The effect of calcium salts is readily visible. Whereas in their absence cerussite is quickly stained brown and then black by sodium sulphide, in their presence the mineral remains very light in color. A similar effect is produced when barium sulphide is used as a sulphidizing agent instead of sodium sulphide. Magnesium salts have little or no effect and even tend to reduce the detrimental effect of calcium salts. A study of this phenomenon indicates that it is due to the precipitation of calcium or barium carbonate in contact with the mineral simultaneously with the formation of lead sulphide. The chemical reactions can be interpreted as: PbCO3 + Na2S = PbS + Na2CO3 CaSO4 + Na2CO3 = CaCO3 + Na2 SO4 They might also be written: PbCO3 + S = + Ca++ = PbS + CaCO3 The precipitation of calcium carbonate can be followed by the lowering of the pH with which it is accompanied. Magnesium carbonate is more soluble than calcium carbonate and usually does not precipitate under the conditions prevailing. It is interesting to note that calcium salts have no effect on anglesite (lead sulphate) because calcium sulphate is soluble, but barium salts hinder the sulphidization of anglesite because of the precipitation of barium sulphate. Remedies When calcium sulphate is present in large amounts, the softening of the water with soda ash is usually too expensive to be considered, but the precipitation of the objectionable calcium carbonate can be prevented in two different ways. One is the use of sodium hydrosulphide instead of sodium sulphide. This salt gives a lower pH than sodium sulphide and does not bring about the immediate precipitation of the calcium which remains in solution as calcium bicarbonate. The other procedure is to add ammonium salts such as the sulphate or chloride which have the property of increasing markedly the solubility of calcium carbonate. Ammonium salts have other effects such as cutting down conditioning time and accelerating flotation. They should be added to the flotation cells rather than to the ball mills. Table I. Effect of Sodium Hydrosulphide and/or Ammonium Sulphate on the Flotation of Two Oxidized Lead Ores Mibladen Ore4 La Plagne Ored Con- Tall- Con- Tail-centrate ing centrate ing Reagents Pb, Pct Pb, Pct Pb, Pct Pb, Pot Without addition of CaSO, NaS 56.0 0.68 43.4 0.65 NaSH 56.2 0.60 40.4 0.50 Na2S + (NH4)2SO4d 54.6 0.56 NaSH + (NH4)2SO4d 43.0 0.66 With addition of 40 lb/ton CaSO4 Na2S 39.4 3.85 34.0 3.21 NaSH 49.1 0.70 49.6 0.88 Na2S + (NH4)2SO4d 53.9 0.85 NaSH + (NH4)2SO4d 51.0 0.45 41.1 0.78 In table I are given the results of representative tests on two different oxidized ores. They show that the strongly detrimental effects of calcium sulphate can be offset by the two procedures outlined above. Sodium hydrosulphide is now used regularly on a mill scale on certain ores. Tests are being carried out with ammonium salts. It should be noted that malachite is subject to influences similar to cerussite. One final word of caution—when the ore is rich in primary slime, which is flocculated by the calcium salts, it may be indispensable to remove these by washing or precipitation with sodium carbonate instead of keeping them in solution by the above methods. Acknowledgment We wish to thank Socibtk Miniere & Metallurgique de Penarroya and Minerais et Metaux, for permission to publish these results.

Jan 1, 1951

By Maurice Rey, Victor Formanek, Paul Chataignon

IT is found when floating oxidized lead ores by sulphidization, that the presence of calcium salts in the water, is usually detrimental and lowers the recovery. This effect is particularly marked in dry countries such as North Africa, where the waters often carry large amounts of calcium sulphate and where the ore may even contain gypsum. The effect of calcium salts is readily visible. Whereas in their absence cerussite is quickly stained brown and then black by sodium sulphide, in their presence the mineral remains very light in color. A similar effect is produced when barium sulphide is used as a sulphidizing agent instead of sodium sulphide. Magnesium salts have little or no effect and even tend to reduce the detrimental effect of calcium salts. A study of this phenomenon indicates that it is due to the precipitation of calcium or barium carbonate in contact with the mineral simultaneously with the formation of lead sulphide. The chemical reactions can be interpreted as: PbCO3 + Na2S = PbS + Na2CO3 CaSO4 + Na2CO3 = CaCO3 + Na2 SO4 They might also be written: PbCO3 + S = + Ca++ = PbS + CaCO3 The precipitation of calcium carbonate can be followed by the lowering of the pH with which it is accompanied. Magnesium carbonate is more soluble than calcium carbonate and usually does not precipitate under the conditions prevailing. It is interesting to note that calcium salts have no effect on anglesite (lead sulphate) because calcium sulphate is soluble, but barium salts hinder the sulphidization of anglesite because of the precipitation of barium sulphate. Remedies When calcium sulphate is present in large amounts, the softening of the water with soda ash is usually too expensive to be considered, but the precipitation of the objectionable calcium carbonate can be prevented in two different ways. One is the use of sodium hydrosulphide instead of sodium sulphide. This salt gives a lower pH than sodium sulphide and does not bring about the immediate precipitation of the calcium which remains in solution as calcium bicarbonate. The other procedure is to add ammonium salts such as the sulphate or chloride which have the property of increasing markedly the solubility of calcium carbonate. Ammonium salts have other effects such as cutting down conditioning time and accelerating flotation. They should be added to the flotation cells rather than to the ball mills. Table I. Effect of Sodium Hydrosulphide and/or Ammonium Sulphate on the Flotation of Two Oxidized Lead Ores Mibladen Ore4 La Plagne Ored Con- Tall- Con- Tail-centrate ing centrate ing Reagents Pb, Pct Pb, Pct Pb, Pct Pb, Pot Without addition of CaSO, NaS 56.0 0.68 43.4 0.65 NaSH 56.2 0.60 40.4 0.50 Na2S + (NH4)2SO4d 54.6 0.56 NaSH + (NH4)2SO4d 43.0 0.66 With addition of 40 lb/ton CaSO4 Na2S 39.4 3.85 34.0 3.21 NaSH 49.1 0.70 49.6 0.88 Na2S + (NH4)2SO4d 53.9 0.85 NaSH + (NH4)2SO4d 51.0 0.45 41.1 0.78 In table I are given the results of representative tests on two different oxidized ores. They show that the strongly detrimental effects of calcium sulphate can be offset by the two procedures outlined above. Sodium hydrosulphide is now used regularly on a mill scale on certain ores. Tests are being carried out with ammonium salts. It should be noted that malachite is subject to influences similar to cerussite. One final word of caution—when the ore is rich in primary slime, which is flocculated by the calcium salts, it may be indispensable to remove these by washing or precipitation with sodium carbonate instead of keeping them in solution by the above methods. Acknowledgment We wish to thank Socibtk Miniere & Metallurgique de Penarroya and Minerais et Metaux, for permission to publish these results.

Jan 1, 1951

By M. Guney, A. R. Bell

In Mindola mine on the Zambian Copperbelt, there is a plan to extend the current production level of 1.2- 1.5 km (3,900-4,900 ft) with five additional production levels. Research work indicated that the present total heat output of 38.6 MW will inevitably increase to 63.2 MW in 25 years. Estimated WE and DB temperatures, representing the total heat generation in stope faces and development headings during these same periods are predicted to increase to 33.8/40.2°C (93/104°F) and 35.3/42.1°C (95/108°F) respectively. It is assessed that the nominal refrigeration capacity needs to be progressively increased to 9,000 M W.

Jan 1, 1984

PRESIDENTS DAVID THOMAS 1871 R W RAYMOND 1872-1874 A L HOLLEY1875 ABRAM S HEWITT 1876 T STERRY HUNT 1877 ECKLEY B COXE 1878 - 1879 WILLIAM P SHINN 1880 WILLIAM METCALF 1881 RICHARD P ROTHWELL 1882 RICHARD W HUNT 1883

Jan 1, 1917

Jan 1, 1928

By Paul C. Merritt

The story now unfolding on the Mesabi Range is more than just another chapter in the continuing history of iron mining. It is an epic of foresight, research and pioneering instinct just now culminating in the rapid growth of a new industry hardly more than ten years old. And that growth has been impressive. In the decade that has passed since Reserve Mining Co. blazed a trail as the first successful large- scale commercial taconite operation, the number of plants now existing or soon to be operating has grown to six. From Reserve's initial capacity of 3 million tons of pellets per year, total production capacity on the Range has surged to 31.5 million tons while capital investment has leaped from $300 million in 1955 to almost $1 billion today. During the past year alone, more than $500 million has been committed to these projects, an amount probably greater than that going into any other single mining area in the world. There is more yet to come.

Jan 10, 1965

By C. E. Johnston

In December 1956, International Minerals & Chemical Corp. installed a rope-suspended belt haulage system in its Carlsbad, N. M., potash mine to complement the already existing rail transport arrangement. In this article the author describes when and where each system is used, the advantages and disadvantages of both, and future planning and proposed changes in haulage at IMC. The haulage system at the International Minerals & Chemical Corporation (IMC) potash mine near Carlsbad, N. M., reached a turning point in December 1956 with the introduction of rope-suspended belt haulage. In fact, IMC pioneered the use of this type of belt in the potash industry. Since that time belt conveyance has been employed as an extension of the rail system but not as a replacement of the main rail haulage. IMC's potash mine is located in the Permian Basin, approximately 20 miles east of Carlsbad in Eddy County, N. M. The 800, 850 and 900-ft levels have been exploited. From these levels over 60 million tons have been extracted. The two ore minerals are sylvite (KCl) and langbeinite (K2SO4. 2MgSO4). The principal gangue mineral is halite, with minor amounts of polyhalite, kainite and leonite. Langbeinite is mined on the 850-ft level and sylvite on the 900. The 800-ft level, with both langbeinite and sylvite mineralization, is idle. Mining heights vary from 54 in. to over 10 ft. A room and pillar mining system is used. Geologically, mining is done in the Salado salt formation. The U.S. Geological Survey has classified the 900-ft sylvite level as the first ore zone and the 850-ft langbeinite level as the fourth ore zone. Since the grade of sylvite is low, mineralization at the IMC mine is somewhat irregular and salt horses, are common. Selective mining and a flexible haulage

Jan 1, 1963

By M. J. Duggin

Evidence is produced below to show that the carbide "Mn,C," reported by Kw,and ersson' is really a mixture of two carbides. One is an Fe-Mn carbide which is probably isomorphous with hexagonal Mn15C4, reported by Bouchand and Pruchart.' The othev is a tetragonul Fe-Mn carbide with cell dzmensions close to those reported previously by the author3 for an Fe0.1Mno. carbide. IN a recent investigation several Fe-Mn carbide specimens, each weighing about 5 g, were prepared in a manner previously reported.3 Debye-Scherrer X-ray photographs were taken of at least two samples from different parts of each specimen using a 114.6-mm-diam camera. The exposure time was 2 hr using filtered chromium radiation, a tube voltage of 35 kv and a tube current of 10 ma. In the case of one specimen, which contained nominal weight percentages of iron, manganese, and carbon of 9.40, 84. 6,, and 6.0, respectively, duplicate chemical analyses indicated f1.2 and 5.5 wt pct C to be present in the two samples taken of the specimen: no graphitic carbon was detected. One powder-diffraction pattern of this specimen indicated the presence of the tetragons: carbide reported earlier,3 (a = 6.772A, c = 9.427A), plus cementite (O), plus an unknown structure. The second powder-

Jan 1, 1970

PRESIDENTS DAVID THOMAS 1871 R W RAYMOND 1872-1874 A L HOLLEY1875 ABRAM S HEWITT 1876 T STERRY HUNT 1877 ECKLEY B COXE 1878 - 1879 WILLIAM P SHINN 1880 WILLIAM METCALF 1881 RICHARD P ROTHWELL 1882 RIVHARD W HUNT 1883

Jan 1, 1910

By E. Gybbon Spilsbury

In the course of the persistent and rapid advance of our country towards the goal she has set for herself, of commercial and manufacturing supremacy, there stand out certain periods or cycles of prosperity or depression, succeeding one another with a comparative regularity as to their ultimate trend, but of varying lengths and intensities. I might compare this course to that of a railroad between two points at different levels, with intervening mountain ranges and valleys, the up-grades climbing towards the final upper terminal of prosperity, while the down-grades retard the ascent, and tend to return to the valleys below. Just at the present time we are evidently at the bottom of one of these valleys, and, before starting to climb the next divide, it may be prudent for us to look into the condition of our rolling-stock, and especially into that of our brakes, and see what the experience of our downward journey has taught us, and whether we are properly equipped for the new upward advance which now lies before us. Probably no previous period of the same duration has produced in all branches of mining and metallurgy improvements SO many and so various as have the last ten or twelve years. Not that they have brought forth any such startling and revo-

Jan 1, 1898

PRESIDENTS DAVID THOMAS 1871 R W RAYMOND 1872-1874 A L HOLLEY1875 ABRAM S HEWITT 1876 T STERRY HUNT 1877 ECKLEY B COXE 1878 - 1879 WILLIAM P SHINN 1880 WILLIAM METCALF 1881 RICHARD P ROTHWELL 1882 RIVHARD W HUNT 1883

Jan 1, 1910

By Charles H. Jacoby, Stanley J. LeFond

Salt, or halite, has a long and most varied history. While we know the Chinese were producing salt as early as 3000 B.C., the first written reference to salt appears in the book of Job recorded about 2250 B.C., which reads: "Can nothing which is unsavory be eaten without salt?" We do not know when man first used or realized that he needed salt. Perhaps one of our early Eolithic ancestors noted a piece of salt shining along the shore of a salt lake or a bay. He may have been attracted by its shining luster and tasted it. He found that it had a tart, zesty, distinctive flavor and perhaps chewing a large piece, became ill. However, by experimentation he soon learned that taken in the proper proportions salt was a very pleasant additive to his food. He may have noticed, too, that it increased his feeling of well-being. Thus, when the curtain of recorded history rises, we find man using salt for his health's sake, seasoning his food with it, feeding it to his animals, and using it in many superstitious and religious ceremonies. These uses, however, are a far cry from the uses for salt today. The first attempts of white man to make salt in continental United States were reported in the year 1614, while the first commercial production was in 1753 from the Kanawha licks. Practically all this salt was for human consumption, preserving food, and curing hides. Prior to the coming of the white man, Indians are known to have made salt from salt springs such as those that existed at Avery Island, LA, Charleston, WV, Saltville, VA, and Onondaga, NY. In 1862 the first rock salt was mined in the US from the Avery Island salt dome. Almost immediately thereafter, rock salt was mined at Saltville, VA and then at Retsof, NY in 1885. Of the more than 39 million tons produced annually in the United States, about 58% or 23 million tons are consumed by the chemical industry in the production of chlorine, caustic soda, hydrochloric acid, sodium metal, and some 30 other basic chemicals. These basic chemicals, in turn, are used in the preparation of approximately 14,000 chemicals which range from soap and detergents, to such chlorinated hydrocarbons as DDT, BHC, carbon tetrachloride, etc. Utilization of cavities created in salt beds and domes has grown rapidly since 1947 until now the waste salt is creating an ecological problem. The uses for both dry- and solution-mined cavities range from the storage of liquid hydrocarbons to containerized storage of toxic wastes, from compressed air for the peak shaving of power to storage of nuclear wastes. Geology Mineralogy Properties: Because of its simple structure, halite, the mineralogical name for salt, was the first structure to be analyzed by X-rays. It has the following properties: Formula: NaCl (Na-39.34%. Cl2-60.66% ) Crystallography: isometric, hexoctahedral, 4/m 32/m Space group: Fm3m A0: 5.627 kX Cell contents: Na4CI4 Habit: usually cubic, rarely octahedral, massive, granular to compact Physical properties: Refractive index: 1.554 Twinning: observed on {111} Cleavage: {001} perfect Fracture: conchoidal, brittle

Jan 1, 1983

By R. S. Busk

TWO groups of binary alloys were prepared. The first group consisted of those elements relatively soluble in magnesium: Li, Al, Zn, Ga, Ag, Cd, In, Sn, Hg, T1, Pb, and Bi. These are predominately Group B elements. The second group consisted of most of the remaining metallic elements, all of which are relatively insoluble in magnesium: As, Au, Ba, Ca, Ce, Cu, Ir, La, Mn, Ni, Pd, Pt, Rh, Sb, Si, Te, Ti, W, and Zr. These are all Group A, transition, or rare earth elements. Alloys of the first group were prepared by melting sublimed magnesium and elements as pure as obtainable in a graphite crucible, using a standard flux1 for protection. The melts were poured into a small graphite mold to produce 3xY4 in. diam slugs. Spectroscopic analyses were made of each slug. In all cases, the total impurity content was less than 0.05 pct. The slugs were then heat treated 5°C below the eutectic temperature until complete solution, as judged metallographically, was obtained. Filings from the center of the slugs were compacted at room temperature into 1/2 in. long x 1/4 in. diam cylinders, sealed in pyrex under 1/2 atm of purified argon, annealed at the heat-treating temperature for 1 hr, and quenched in water. After the X-ray diffraction patterns were made, each compact was analyzed chemically for the solute. It was found that the Mg-Li alloys reacted during filing to reduce the Li in solid solution. For this series of alloys, the slug was cold worked, annealed in purified argon, the surface dissolved in dilute HC1 to a depth of about 0.005 in., and the X-ray exposure made on the fresh surface. This procedure resulted in sharp, continuous lines and in true values for the lattice parameters. The alloys in the second group were prepared in the same way except that about 1 wt pct of each solute was added. Since the solubility limit was exceeded, not all the solute dissolved. These alloys were analyzed spectroscopically only to confirm the presence of the solute. The diffraction patterns were of the back-reflec-tion type using the characteristic copper radiation* and a flat cassette. Both the film and the specimen were rotated. The specimen temperature was maintained at 25" ± 1°C. The films had sharp lines; their diameters were measured directly to 0.01 cm. The parameters were calculated from the line diameters using a modified version of Cohen's extrapolation method.2 his method effectively eliminates systematic errors such as film shrinkage, inaccurate alignment, and non-precise film-to-speci-men distance. The random errors were minimized

Jan 1, 1951

By D. de Fontaine

A convolution procedure is described for obtaining an analytical expression for the composition profiles of solute concentration:; in binary solid solutions. The free energy of solutions containing such compositional inhomogeneities can then be evaluated and the stability of spherically symmetric clusters (G.P. zones, for short) us a function of their radii and central compositions can be studied accordingly. Two characteristic zone radii are defined: the minimum radius (RM) corresponding to the smallest zone for which growth is energetically favored over dissolution, and the critical radius RK) corresponding to zones associated with the minimum work of formation. The values of RM and RK coincide at the two classical limits of nucleation and growth and spinodal decomposition. As the spinodal is approached, however, RM and RK diverge increasingly and it is proposed that the initial] decomposition morphology is governed more closely by the minimum, rather than by the critical radius since the former possesses no singularity within the m eta stable phase boundary. Reversion is briefly discussed in the light of the foregoing and it is shown that a set of reversion temperatures located between the coherent miscibility gap and the coherent spinodal must correspond to a given distribution of low temperature zones. SINCE the early works of Guinier1 and preston,2 the kinetics and morphology of GP zones have been studied extensively, see Ref. 3, for example, for a recent review. Nevertheless, a completely satisfying theoretical treatment of the decomposition of meta-stable or unstable binary solid solutions is still lacking due to the almost unsurmountable mathematical difficulties that one encounters in attempting to solve the pertinent diffusion equation which, in principle, describes the whole process. This equation, first derived by Cahn for the initial stages of spinodal decomposition,4 is a nonlinear partial differential equation of the fourth order in anisotropic space, a general analytical solution of which is completely out of the question. From this equation, some prediction can be made, however, concerning the later stages of spinodal decomposition5 and a recent numerical solution6 of the equation in the case of one- and two-dimensional composition modulations of a solid solution inside the spinodal has led to the following considerations: the sinusoidal morphology7 is to be expected only for solutions of average composition c, located near the center of the coherent miscibility gap.8 For solutions with co closer to the spinodal decomposition, depleted shell zones9 should constitute the first recognizable decomposition product, later evolving to iso- lated, enriched preprecipitates in a uniformly depleted matrix as this must, in all cases, constitute the final metastable morphology, barring, of course, loss of coherency and change in crystal structure. In agreement with the qualitative description of Bonfiglioli and Guinier,l0 it thus appears that the various models discussed by previous authors are, in fact, idealized successive stages of the general decomposition process. Unfortunately, corresponding calculations for a solid solution outside the spinodal are not yet available because of two additional difficulties: it is essential that the diffusion equation be solved in three-dimensional space, and furthermore, one must include in the equation an appropriate "source term" describing the statistics of the creation of composition fluctuations required to trigger the nucleation events. At present, a general treatment of this problem does not appear to be tractable. Nevertheless, by using a modelistic approach, i.e., by selecting a priori certain composition variation profiles and by evaluating their associated free energies, one can draw certain conclusions relative to the stability of these isolated composition modulations or "zones", both outside and inside the spinodal. This is the object of the present investigation. THEORY We shall now describe a standard four-parameter spherically symmetric GP zone, evaluate its free energy according to the Cahn and Hilliard11 formula (Eq. [5], below), and plot the corresponding energy surfaces as a function of zone amplitude and radius as

Jan 1, 1970

El Indio, eighty percent -owned by Compania Minera an Jose Inc., a subsidiary of St. Joe Minerals, and twenty percent-owned by private Chilean investors, will open their new flotation and Carbon -In -Pulp plant near La Serena, 480 km (300 miles) north of Santiago, Chile, in early 1981. The underground mine, at an altitude of 4,270 m (14,000 ft), will produce about 1,270 mt per day (1,400 st per day) of ore containing about 2. 2570 Cu, and gold and silver to the extent of 16 and 254 g per mt (0.47 and 7.4 oz per st) respectively. While construction of the plant was underway, development ore, containing some 1,400 kg (45,000 oz) of gold, was shipped to the United States for recovery in a copper smelter. At El Indio the underground ore is rail-hauled to the mill a short distance from the portal where it is crushed, ground, and floated to produce a copper concentrate containing both gold and silver. The crushing plant also crushes waste for use as mine backfill. Approximately 92% of the copper and 60% of the gold and silver are recovered in the flotation concentrate. Flotation tailings, at a grade of 19 g Au and 116 g Ag per mt (3.4 oz Au and 0.55 oz Ag per st), are cyanided for 72 hours in six Pachucas with auxiliary air lifts for pulp transfer. Lime, cyanide, lead nitrate, and a phosphate are also fed to the cyanidation Pachucas. After cyanidation, the pulp is treated in four air lift Carbon-In-Pulp tanks equipped with external vibrating screens for carbon advance. Loaded carbon is stripped in two pressure vessels in parallel. Pressure stripping must be used because of the high altitude. Stripped carbon is dewatered in a spiral classifier before being reactivated in a rotary kiln and returned to the C. I. P. circuit. Pregnant solution is then sent to four banks of four Zadra cells for gold and silver recovery on steel wool. Zadra cell cathodes.are washed with the slimes being captured in a plate and frame filter. The filter cake and the washed cathodes are then dried on an infrared dryer and smelted in two stages to bullion bars. Published reports indicate that the total investment for this unique operation was in the neighborhood of $80 million.

Jan 1, 1981

By A. D. Hughes

C. W. MERRILL*-Mr. Hughes' paper not only is very well presented but is most timely in that it covers a subject of vital interest to the United States. Tin is one of the strategic metals which has not been found here in appreciable quantities. The total United States tin output since the first recorded production over 100 years ago would not supply current consumption for a fortnight. On the consumption side, tin is extremely important in national defense because of its use in tin plate which, in the form of tin cans, makes it possible to feed properly the armies that the United States recruits from its civilian population in emergencies. Moreover, the internal combustion engines so important in powering tanks, planes, and other war machines, require large quantities of tin alloys for bearings and for soldering. These considerations, along with the fact that Malaya, historically, has been the leading source of tin to the United States, make the kind of information that Mr. Hughes has presented so ably, a matter of vital interest.

Jan 1, 1949

By J. J. Mike

During the past few years the combination of continuous billet casting with in-line reduction has been studied and several machines have been built with this capability included in the design parameters. (1,2,3,4,5) In-line reduction and continuous casting in combination are obvious and attractive. As pinch rolls are already in place for the continuous casting operation, it can be readily seen that a redesign of the mechanical and electrical equipment of the pinch rolls is all that is necessary to have in-line rolling. There have been numerous in-line reduction experiments conducted by simply increasing the pinch roll pressure on existing machines. (6,7,8,9) These generally failed to produce quality billets and often resulted in internal metallurgical defects (Figure 1).

Jan 1, 1972

AIME Committee on Local Section Affairs Joseph L Gillson, Chairman J C Kinnear, Jr Lloyd E Elkins AIME Committee on Student Chapter Affairs (Special Committee, pending Bylaw revision) R F Mehl, Chairman E H Crabtree, Jr John C Calhoun, Jr

Jan 1, 1958