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By Jay A. Carpenter

This paper deals with only one step in the treatment of ore at the West End mill; not because the other steps are repetitions of practice in other mills, but because in this particular step there is in use the Trent agitator: This device, although it has apparently failed in many mills, is here giving excellent service and has proved to be well adapted for making a thorough replacement of pregnant solution with a minimum amount of barren solution. The strong and weak points of this agitator, its present simple construction, and its use as a thickener for agitator or battery pulp are features of interest; but perhaps the point of greatest interest to the metallurgist in this day of continuous decantation is its use in a series of tanks for slime treatment by the replacement method. The agitating department of the West End mill consists of six redwood tanks, 24 ft. in diameter, 18 ft. high, each equipped with a Trent agitator, a centrifugal pump, and a motor. The pulp is transferred by a pump from the top of a flat-bottomed tank to a set of arms and nozzles in the bottom of the tank, at just sufficient pressure to cause the arms to revolve. The streams from the many nozzles keep the bottom of the tank clean, and these streams, coupled with the effect of the revolving mechanism and the ascending current, keep the pulp in constant motion and of constant gravity. These agitating tanks hold 90 tons of dry slime and 202 tons of solution with a 1.24 pulp, our ore having a specific gravity of 2.7. This capacity is about 10 per cent. in excess of the standard 15 by 45 ft. Pachuca tank. The tanks are connected in one series for continuous agitation, the pulp for each agitator being drawn by its pump through a branch suction from near the top of the preceding tank and delivered to the bottom of the tank by the agitator arms along with the regular pulp of that agitator. This method works automatically, since the flow through the branch suction varies directly with the difference in head of the two tanks. The chance for new pulp to pass out quickly is, therefore, much less than in many other systems of continuous agitation, since the new

Jan 1, 1916

By A. F. Melcher

THE present paper is a progress report. on an investigation of the physical factors of oil and gas and especially of their sands, I such as-pore space, size of pores or permeability, retentivity, viscosity of the oil, temperature, pressure, thickness and area of the pay sand, water relations, and capillarity. The purpose is to determine as many of these physical factors as possible, and to ascertain the relations existing, directly or indirectly, between these physical factors and the production of oil and gas. As yet only pore space2 and size of grains of pay sands have, been investigated, although an apparatus has been designed to determine the permeability of a sand to oil, water, or gas under definite drops of pressure between the entrance face and exit face of the sample. Messrs. E. W. Shaw, R. Van A. Mills, D. Dale Condit, G. B. Richardson, G. C. Matson, and C. H. Wegemann collected the samples upon which the physical determinations were made. Acknowledgment is made to my colleagues of the United States Geological Survey for many suggestions and criticisms; to Mr. Mills for the production data given of the oil wells from which some of the samples were collected; to Mr. A. W. McCoy of the Empire Gas and Fuel Co., Bartlesville, Okla., for many ideas.

Jan 4, 1920

By J. R. Low, M. B. Reynolds, L. O. Sullivan

The effect of neutron bombardment upon the stability of type 347 austenitic stainless steel has been investigated by a magnetic technique. The relation of the ferrite content of a stainless steel to its magnetic properties is given, and an apparatus suitable for the measurement of the ferromagnetic saturation induction of small specimens is described. Results of measurements on irradiated specimens are tabulated. Exposure to a neutron flux was found to cause a slight increase in the ferrite content of type 347 stainless steel, the change increasing with increasing length of exposure and with increasing initial ferrite content. The similarity of the effect of irradiation to the effect of annealing is pointed out. Possible effect of irradiation upon density of austenitic stainless steel is discussed. COMMERCIAL austenitic stainless steels are alloys of iron, chromium, and nickel, plus small quantities of other elements. Although these alloys are normally used in the austenitic condition, this state is thermodynamically metastable at ordinary temperatures and transformation to a more stable state takes place under favorable conditions. In the austenitic state, these stainless steels have the face-centered-cubic crystal structure characteristic of y iron, but the stable state at room temperature is a mixture of austenite and body-centered-cubic ferrite. The transformation from the pure austenitic condition may be brought about by cold working the alloy at a temperature below that at which the aus- tenite becomes thermodynamically unstable (about 400°C), the completeness of transformation increasing with increasing severity of cold work and decreasing temperature. The behavior of the austenitic stainless steels under ordinary conditions of use is rather well known. However, use of these alloys in a nuclear reactor introduces a new variable: the effect of neutron bombardment upon the transformation from the austenitic to the ferritic state. It was with this in mind that a study of the radiation stability of austenitic type 347 stainless steel was undertaken. Magnetic Technique for Ferrite Determination Commercial austenitic stainless steels such as type 347 undergo little transformation under normal conditions of fabrication and use. In view of this fact, it seemed likely that neutron irradiation would change the ferrite content of the alloy but little. The method chosen for measurement of the effect of neutron irradiation was thus limited to one which would be quite sensitive to small changes in the ferrite content of the alloy. Of the properties of the stainless steel which can be measured, the magnetic characteristics are most sensitive to the quantity of ferrite present.

Jan 1, 1956

By R. D. Russell, R. M. Farquhar

SOTOPIC tracers have become an important aid in following the progress of chemical processes in the laboratory. It has recently been found possible to utilize a system of naturally existing iso-topic tracers to obtain information about the geological history of lead ores. Common lead, such as is found in lead deposits, is a mixture of four stable isotopes having atomic weights 204, 206, 207, and 208. Of these, the last three are identical with the lead isotopes produced as stable end products of the radioactive decays of uranium and thorium: the first, lead-204, is not known to be produced on the surface of the earth by any process. Since uranium and thorium Occur in the surface regions of the earth in amounts comparable with lead, and since the half-lives of uranium and thorium isotopes are of the same order as the age of the earth, they produce the radiogenic lead isotopes in amounts comparable to the amount of nonradiogenic lead present. Every significant exposure of a sample of lead to uranium and thorium will therefore lead to the permanent alteration of the lead isotope ratios in that sample. It is this unique property of lead that serves as a means of tracing the history of a lead sample in terms of its contacts with the radioactive elements. If lead from a lead mineral has been analyzed with a mass spectrometer, the measured isotope ratios are determined entirely by the isotope ratios of primeval lead, which are identical for all minerals, and by the particular history of the sample. It follows that for samples from any particular geological area, observed differences in the isotopic composition are enough to distinguish different geological histories. An illustration of the qualitative application of this statement is given in Table I by analyses of some galenas from the western Cordillera. Samples from deposits in Pre-Cambrian sediments have very different lead isotope ratios from those of the ores in the Paleozoic sediments. Although the two types are associated closely geographically, it is apparent that they have had quite different histories and have probably been emplaced at quite different times, as the ideas outlined in the following section suggest. Even when applied quantitatively, a lead isotope analysis can never indicate a unique history of any lead sample. However, it greatly restricts the choices available and combined with other geological and geochemical data can lead to a much better understanding of the genesis of lead ores. General Character of Lead Isotope Variations: Early isotopic analyses of common leads by Nierl showed that geologically younger leads were generally richer in isotopes of masses 206, 207, and 208, with respect to that of mass 204. This regularity of measured lead isotope ratios can be easily observed by plotting each of the ratios Pb207/Pbm and Pb205/ Pb204 against the ratio Pb206/Pb204. In both graphs the points lie scattered closely about a well defined mean curve. It was immediately supposed that this regularity resulted from the growth of all leads from a common primeval lead present at some time, To, early in the earth's history. Lead in the outer part of the earth would become continually enriched in the radiogenic isotopes as a result of the uranium and thorium intimately associated with it. The subsequent extraction of some of this lead and formation of a lead mineral free of the radioactive parents provide samples of lead existing in the earth at the time of mineralization, T. Younger leads in general will be richer in the radiogenic isotopes because they have been associated with uranium and thorium for a longer time. Then lead ratios would be given by the formulae: (Pb206/Pb204)YTPb^/Pb204) +f "(u201) kdt T (Pb207Pb204)r = (Pb208/Pb204)T0 + J (U295/Pb204) k' dt T (Pb208/Pb204) t = (Pb208Pb204 + J (Th204) A." dt [1] where A, A', and A" are the decay constants of U238, U285 and Th232. Summaries of measurements of radioactivity of surface rocks, such as given by Faul,2 are of limited

Jan 1, 1958

By Earle C. Smith

The Chairman.—Mr. Earle Smith has kindly offered to make some remarks in connection with segregation in the product, Mr. Smith: E. C. Smith,* Cleveland, Ohio—I will start this Off by a story oF the code days of the American Iron and Steel Institute. In those days, Republic did not have a big strip mill, and the question came up of the check analysis of rimmed steel. I suggested that they let me be the chairman of the Committee on Accumulating the Information on the Variation of the Composition of the Ingots of Rimmed Steel. Somebody wanted to know why I wanted to be the chairman. I said, "we don't make any of the big ingots of rimmed steel, and no matter who makes them they are so bad that you don't dare publish the information. So if 1 collect it and hide it you can't charge me with having done anything that really disrupted the commercial situation." So, everybody furnished me with a rather complete story as to the horrible variations in big rimmed ingots. I took it out to my house and put it away, and it is still there. Now, segregation in the big ingot is no longer an "academic " matter as far as I am concerned. I am in a situation like that of the German who was told in 1956 about the coming war. He said: "until it is your throat that is going to be cut, you don't pay any attention to what is happening to the otherman." 'That is the way with the problem that we have in front of us. Recently I have been told that the 'Omptroller was questioning the payment for certain articles of stamped steel that had been made from rimmed steel, because upon check analysis of the rimmed steel it had been determined that these stamped articles were nut within the compositions that were included in the specification, and therefore he as the camptroller had no alternative. It was not meeting the specification; therefore, no payment. So I I say to all of you: You can very seriously consider this matter of segregation now and on into the future on the basis of the fact that it is actually going to cost your companies, which are making these products, money unless there is some new idea about the infallibility of quantitative , chemists who analyze some of these products or lawyers who read specifications, I don't know which man is going to be the major factor in the future. if the National Bureau of Standards could in some way show the specification writers the variation between good chemists analyzing for That they expect to be umpire eel. the writers would certainly realize that some of the to to which we have calmly signed our names as being O.K. are— well, as one man said to me, they might be filled by the devil, and they certainly could be filled by the Lord, but they could not he me by mankind. I would like to inject two or three things into a segregation study which I Want you to think about, because 1 would be a little surprised if there is very much discussion of them, In the first place, we generslly make steel in the United States in the basic open hearth, and I do not think there has bee,, nearly enough consideration given to segregation German the bath before it moves into the ladle. I am sure that any of the people who handled the 9400 series of the NE series when it contained the 0,60 per cent silicon have more respect than they had previously for the segregation that is within, the ladle; that is, before the metal reaches the ingot mold, the frozen ingots and the segregation in them. Another pint to which I think We ought to sis serious consideration is the segregation of iron oxide in the ingot-iron type of material, where the distinction between that and the steel segregation is that it is actually segregat. ing iron oxide, Normally we are segregating some form of carbon or sulphur, or something like that, with the stamping steel industry now coming down into the ranges of chemistry, where the segregation of iron oxide will be just

Jan 1, 1945

By E. C. Smith

THE CHAIRMAN.-Mr. Earle Smith- has kindly offered to make some remarks in connection with segregation in the product, Mr. Smith: E. C. SMITH,* Cleveland, Ohio-I will start this off by a story of the code days of the American Iron and Steel Institute. In those days, Republic did not have a big strip mill, and the question came up of the check analysis of rimmed steel. I suggested that they let me be the chairman of the Committee on Accumulating the Information on the Variation of the Composition of the Ingots of Rimmed Steel. Somebody wanted to know why I wanted to be the chairman. I said, "We don't make any of the big ingots of rimmed steel, and no matter who makes them they are so bad that you don't dare publish the information. So if I collect it and hide it you can't charge me with having done anything that really disrupted the commercial situation. So, everybody furnished me with a rather complete story as to the horrible variations in big rimmed ingots. I took it out to my house and put it away, and it is still there. Now, segregation in the big ingot is no longer an "-academic-matter-as far as II am concerned. ¬I am in a situation like that of the German who was told in 1936 about the coming war. He said: "Until it is your throat that is going to be cut, you don't pay any attention to what is happening to the other man." That is the way with the problem that we have in front of us. Recently I have been told that the comptroller was questioning the payment for certain articles of stamped steel that had been made from rimmed steel, because upon check analysis of the rimmed steel it had been determined that these stamped articles were not within the compositions that were included in the specification, and therefore he as the comptroller had no alternative. It was not meeting the specification; therefore, no payment. So I would say to all of you: You can very seriously consider this matter of segregation now and on into the future on the basis of the fact that it is actually going to cost your companies, which are making these products, money unless there is some new idea about the infallibility of quantitative chemists who analyze some of these products or lawyers who read specifications. I don't know which man is going to be the major factor in the future. If the National Bureau of Standards could in some way show the specification writers the variation between good chemists analyzing for what they expect to be umpire results, the writers would certainly realize that some of the specifications to which we have calmly signed our names as being O.K. are well, as one man said to me, they might be filled by the devil, and they, certainly could be filled by the Lord, but they could not be filled by mankind. I would like to inject two or three things into a segregation study which I want you to think about, because I would be a little surprised if there is very much discussion of them. In the first place, we generally make steel in the United States in the basic open hearth, and I do not think there has been nearly enough consideration given to segregation within the bath before it moves into the ladle. I am sure that any of the people who handled the 9400 series of the NE series when it contained the 0.60 per cent silicon have more respect than they had previously for the segregation that is within the ladle; that is, before the metal reaches the ingot mold, the frozen ingots and the segregation in them. Another point to which I think we ought to give serious consideration is the segregation of iron oxide in the ingot-iron type of material, where the distinction between that and the steel segregation is that it is actually segregating iron oxide. Normally we are segregating some form of carbon or sulphur, or something like. that, with the stamping steel industry now coming down into the ranges of chemistry, where the segregation of iron oxide will be just

Jan 1, 1944

By NORMA D. MACFADDEN

WHILE the library work of the Woman's Auxiliary to the A. I. M. E. was founded three years after the formation of the Auxiliary, its present policy of establishing permanent libraries in mining camps throughout the United States dates only from 1924. Since then sixteen libraries have been established and thousands of books have found their way to homes of far-away miners, bringing pleasure and knowledge to a multitude of Americans and future citizens. Library work was initiated under the presidency of Mrs. H. W. Hardinge in 1922 and firmly established with her aid as one of the main activities of the Auxiliary. The first chairman served but a short time and Mrs. A. O. Ihlseng then took over the work of chairman of the Library Committee. To place the surplus books of Auxiliary members and their friends in use in mining camps was the immediate work of the committee. This was accomplished by placing a traveling library in the Bureau of Mines' cars and also by sending books for distribution to section chair- men in our larger mining camps.

Jan 1, 1929

By M. J. Pool, P. J. Spencer

Using liquid tin as the solvent metal, the heats of solution of silver and gold in dilute Ag-Au-Sn alloys have been determined at 723°K by solution calorimetry. From the values obtained, the various enthalpy interaction coefficients in the liquid solutions have been calculated. The self-interaction coefficients Au and Ag values of 2413 and -6322 cal per g-atom in binary Au-Sn and Ag-Sn alloys, respectively. For an alloy containing 0.04 mole fraction Ag, Au is equal to 2443 cal per g-atom, and in an alloy containing 0.04 mole fraction Au, Ag has a value of —8883 cal per g-atom. Ag Au has been determined as —2650 cal per g-atom. ADDITION of a second solute to a dilute binary alloy may cause striking changes in the thermodynamic characteristics of the alloy. As yet, such influences cannot be reliably predicted and it is only by accumulation and critical assessment of data that definite patterns can be established. Solute interactions in dilute solutions were first treated mathematically by Wagner,1 who derived expressions for the Gibbs energy interaction coefficients. For an alloy consisting of. two dilute solutes, i and j, in a solvent s, these coefficients are given by: where yi is the activity coefficient of component i and x represents the mole fraction of solute or solvent. Other interaction coefficients have since been established in terms of the various partial molar thermodynamic properties of an alloy; the definitions of these are summarized in a recent paper by Lupis and Elliott.2 Mathematical and experimental studies of such coefficients have received much attention recently, providing a very useful theoretical background to an understanding of the nature of solute interactions taking place in dilute solutions. One of the definitions to arise from such work has been the extension of Wagner's treatment by Lupis and Elliott4 to include an enthalpy interaction coefficient, defined as. where ?Hi is the relative partial molar enthalpy of component i. ?Hi is related to the relative partial molar enthalpy at infinite dilution, ?Hio, and to the enthalpy interaction coefficients by the expression: Values of ?Hi can often be obtained with a high degree of accuracy by calorimetry, and, if the composition of the alloy is carefully controlled by making calculated solute additions throughout a series of measurements, application of Eq. [2] will enable reliable enthalpy interaction coefficients to be determined. Partial heats of solution must be investigated as a function of solute concentrations down to xi = 0, and, since ? values are obtained from the slope of mi plotted against x, great care must be taken to obtain precise data. The data for binary systems which are presently available often require extrapolation of ?Hi values from compositions as great as xi = 0.05 or even 0.1 to obtain limiting heats of solution. Reliable enthalpy interaction coefficients are thus impossible to obtain from published data for most of the alloy systems already investigated. The aim of the present work was to determine values of Au, Ag, Ag, and Au in the limit xsn -1 for the relatively simple Ag-Au-Sn system and from these results to gain some insight into the possible influence

Jan 1, 1969

Copper ores from small mines in the area south of Tucson, where the Twin Buttes mine is located, were first operated in the 1880's. Today this area is one of the great copper mining centers of the world. In 1963, Anaconda Company acquired the property from Banner Mining Company and in recent years joined with AMAX in a 50/50 partnership to work the Twin Buttes property. From the beginning, Anaconda had relied on conveyors to remove overburden, oxide material for eventual leaching, and ore from the open pit. In the large st preproduction stripping program in mining history, Anaconda in a four-year period (1965 to 1969) removed 266 million tons of overburden of an average depth of 500 ft (152 m) lying over the ore body. The alluvium overburden was stripped by scrapers carrying 70 to 80 tons and push-loaded by two D9 tractors operating in tandem. The scrapers delivered their loads to bins which fed a 60 in. (1.52 m) conveyor having a capacity of 8500 tph. The 25% slope belt conveyor, which was 2100 ft (640 m) long, transported the material to the brow of the pit, where it was transferred to an 8300 ft (2530 m) surface belt to a 1000 ton loadout bin. At this point, the overburden was trucked to the sites of the tailings ponds, where it was used for dam construction. During 1976, the one billionth ton of overburden was removed from the Twin Buttes mine. The Twin Buttes quartz monzonite porphyry contains only scattered mineralization of which chalcopyrite is the most abundant mineral, associated with chalcocite, covellite, minor bornite, and several oxide minerals. Oxidation has progressed to variable depths of up to several hundred feet below the base of the alluvium. Because of the depth of the sulfide and oxide ores and hard rock waste, two in-pit crushers and conveyor systems were also installed for their transport out of the pit; and in 1976 a third crusher and conveyor system was installed lower in the pit for waste rock only. The two initial crushing and conveying systems were designed to handle any of three functions: crushing waste to be disposed of by a rail-mounted stacker -conveyor, crushing oxide ore for conveyor and then truck transport to stockpiles for future leaching, and primary crushing of sulfide ore for conveyor transport to the two 30 in. by 70 in. (0.76 by 1.78 m) secondary crushers and the two 7 ft (2. 13 m) standards and four 7 ft shortheads in the third and fourth stage crushing plant. A third standard crusher has been in- stalled recently. Mining is done by 15 yd (11.5 cum) shovels which load 100- and 150-ton

Jan 1, 1978

By W. R. Foster, J. M. McMillen, A. S. Odeh

The complete equations of average linear momentum balance for a single-phase fluid in an incompreisible, homogeneous, porous medium are derived. The derivation begins with Euler's equation of motion for a continuum and uses an integral transform recently developed by Slattery. 7 For steady flow of a compressible, Newtonian fluid, the usual equations of motion result. For transient flow, the space-time description of the pressure is determined in the lowest approximation by the telegrapher's equation. From the analysis a new phenomenological coefficient results which connects the viscous traction to the deriv ative of the linear momentum density. The magnitude of this coefficient determines the velocity of sound through the pore structure in this approximation to the pressure field. INTRODUCTION The modification of Darcy's law of momentum balance for steady, single-phase flow through porous media has been discussed for many years. The first modification was suggested by Forcheimerl who added terms of higher order in the velocity. These can be expected to appear because the underlying microscopic equations of momentum balance are themselves nonlinear in the point velocity field. The Reynolds tensor pvv, which represents the convective flux of momentum density, appears in the momentum balance equation. Only in rectilinear flow (parallel stream lines) does the divergence of this tensor vanish. Since the steady flow stream lines in most porous media are not parallel, nonlinear dependence of the pressure gradient on the velocity should naturally appear. This nonlinearity has nothing to do with turbulence in the ordinary sense of random fluctuations in the pressure and velocity fields. It arises simply because the stream lines converge and diverge, even for steady flows. Klinkenberg2 demonstrated that the permeability coefficient in Darcy's law depends on the absolute pressure or, alternatively, on the density field. However, because he neglected inertial terms of the Forcheimer type, his correction coefficient could not be represented by a constant but tended toward a constant as the velocity decreased. Forcheimer's and Klinkenberg's modifications can be combined in a rigorous way to account for both inertia and slip during steady flow. This will be shown in a future paper. The transient change of pressure in porous media has been described by the diffusion equation.3 This form results from eliminating the velocity and density fields from a combination of the equations of motion in the form of Darcy's law, the continuity equation and an equation of state. Fatt4 suggested that the cause of deviations from the prediction of the diffusion equation for pressure transients lies not in the choice of Darcy's law as the equation of motion but on the existence of dead-end pores which might invalidate the averaged equation of continuity. On the other hand, Oroveanu and Pascal5 noted chat the time derivative of the momentum density must be included in the equations of motion since this measures the local rate of change of momentum density. Their differential equation for pressure is the telegrapher's equation (neglecting gravity). However, their form of this equation predicts that the speed of pressure propagation through the pore structure is the same as that through the bulk fluid. M. K. Hubbert6 attempted a derivation of Darcy's law by volume averaging the Navier-Stokes equations. Since these equations represent momentum balance at a point within an open set of points containing the fluid itself, Hubbert's volume averaging cannot lead to tenns involving transfer of momentum between the fluid and the walls of the pores. Once these viscous tractions are lost by choosing a control volume containing only fluid, they cannot

By Luis Toron, Salvador Cortes-Obregon

John D. Price (Colorado Fuel and Iron Corp., Pueblo, Colo)—The paper on the coal fields of the Oaxaca district as prepared by engineers Toron and Cortes-Obregon of the staff of the Bank of Mexico bears witness to the thorough and careful way in which the men associated with this organization perform their work. There is little to be added to their paper in way of discussion other than to confirm and amplify some of their statements. Since the only extensive and well-developed field of coking coal lies in the northeastern section of the country adjacent to Sabinas in the state of Coahuila, it follows that blast furnace plants would be located in that same region. Two such plants are now operating at Monterrey and Monclova, using coke produced at the Sabinas district mines. But the nearer of these two plants is 600 miles from Mexico City and even farther from the center of population. Transportation of products from these mills to the market area is therefore expensive, both because of the distance and the difficulty of the terrain over which it must be carried. The development of an integrated steel industry closer to the center of population has therefore long been a goal toward which the Mexican technicians have been striving. While the presence of coal of some grade has been reported in many of the states, and many ideas have been advanced regarding its possible uses in iron and steel production, deposits of anthracite in Sonora and the various coals of the Oaxaca district as reported on in this paper are the only ones that have been explored in a serious manner. The coking coal from the Mix-tepec zone appears to offer promise of producing a coke which could be used in a standard blast furnace. Several problems are indicated, however: 1—The ash in the coal is high as mined, but indications are that it can be washed to an ash content of 15 pct with a recovery of 70 pct of washed coal. 2—Such washing would increase the volatile content from 17.4 pct to about 20 pct, and in a byproduct oven this should give a coke yield of close to 80 pct with an ash content of coke under 20 pct. 3—A free swelling index of 5 appears low for a good coking coal, and below that of the coals from the Sabinas district, which show between 6 and 9. But washing of the coal should result in an improvement in this regard; in the United States coals from Utah with an index even lower than 5 have made a usable coke. 4—A coal with volatile as low as 17.4 in raw coal and 20 in washed coal would come close to being classed as a low-volatile rather than medium-volatile coal, and low-volatile coals are notorious for their high expansion properties. Several plants in the United States are making coke from straight medium-volatile coal of 26 to 28 volatile content, and one at Rosita,, Mexico, from coal of 25 volatile. But no plants to my knowledge are using coal as low as 20 volatile. Since the Rosita coal appears to be a borderline coal from the angle of its expansion properties the coking of one of the straight lower volatile must be approached with caution. 5—There are few coals possessing any degree of coking properties which cannot be used in coke production by careful attention to its preparation and blending. The fact that coals of other types are available in this same region make improvement through blending very possible. 6—There are other workable methods of reducing iron ore other than the conventional coke-blast-furnace method. These will not be discussed here but it is known that their use has been considered. The technicians of not only Mexico but also of the other Latin American countries are keenly aware of their natural resources and their national needs. This paper emphasizes the fact that the Mexican technicians are working on their problem and attempting to speed the day of self-sufficiency for their country. Salvatore Cortes-Obregon (author's reply)—I wish to thank Mr. Price for his kind remarks. The Mixtepec coal as shown in Table II has 30 pct ash and a free swelling index of 5, but when the same coal is washed to 15 pct ash it has a free swelling index of 8 to 9 and the volatiles increased from 17.4 to 20.7 pct. A satisfactory coke has been produced from blends made in the Mexican laboratory using at least 40 pct of the Mixtepec coking coals with the other Oaxaca non-coking coals. Koppers in Germany report good coke obtained from the Oaxaca coal with a blend of 80 pct Mixtepec coal. Consideration is being given the possibility of using methods other than the conventional blast furnace for the reduction of iron ore near the Oaxaca area; electric furnaces appear promising. The non-coking coals could be used to produce cheap electric energy and the coking coals to make metallurgical coke.

Jan 1, 1955

By Richard H. Olson

"Rarely in our technological society does the discovery of a new class of inorganic materials result in such a wide scientific interest and kaleidoscopic development of applications as has happened with the zeolite molecular sieves." The foregoing, the opening sentence in a landmark volume on zeolite molecular sieves by D. W. Breck (1974), is, if anything, an understatement. Zeolites were recognized as a new group of minerals in the 1750s, but it was not until 1930 that the first analysis of the crystal structure of a zeolite mineral was made. In the late 1940s research workers at Union Carbide Corp. began a program of zeolite synthesis and study which has resulted in one of the major research achievements of all time. Naturally, with the vast research and development efforts devoted to the synthetic molecular sieves, Union Carbide became concerned in the mid-1950s about its position should minable deposits of natural analogues be discovered. Zeolite minerals have diverse origins, and even a brief discussion of these is beyond the scope of this paper. The early work on zeolites was confined to igneous rock occurrences (e.g., amygdules and veins) which were formed by "space-filling;" these crystals tend to be euhedral, thereby rendering them appealing to both mineralogists and collectors. During the first year or so of Union Carbide's exploration (which began in mid-1957) attention was devoted solely to such igneous occurrences. A landmark paper by Bramlette and Posnjak (1933) heralded the potential significance of the occurrence of zeolite minerals as alteration products of vitric ash and similar materials. In the summer of 1958, full attention was directed by Union Carbide to the search for deposits of this type in the western United States. Since then, such exploration has been continu-

Jan 1, 1975

By S. J. CRAIGHEAD

IN 1912 the United States Smelting Refining and Mining Company made a large investment in a number of coal properties in Utah and in 1915 a subsidiary, the United States Fuel Co., was organized to take over these properties. Operations started in 1916 and the Company soon became, and remains, one of the major coal producers of the State. It now produces approximately one million tons of coal annually, which is about 22 per cent of Utah's output. The U. S. Fuel Co. owns large reserves of good coal and is in a position to expand operations with the industrial growth now taking place in the West. Traveling through the Western States, one is struck by numerous advertising signs portraying the picture of jovial Old King Cole of nursery rhyme fame. His rotund figure and beaming countenance are the symbols of Utah King Coal, the product of the King mine of U. S. Fuel Co. King Coal is a by-word of quality coal throughout all the Western States.

Jan 1, 1948

CHARLES F: WILLIS,* Bisbee, Ariz. (written discussion?).-An employment department operated only with the object of relieving the foremen from hiring and for the purpose of centralizing record keeping is not likely to be entirely successful, and is doing but a small part of the good that practice has shown is possible; although it was .probably a desire to save time and to conduct the business more conveniently that led many mining companies to centralize their employment department. The ultimate object, however, is the reduction of labor turnover, by obtaining men better qualified to fill the positions to which they are assigned, by following up their work and providing for transfer to other departments or for promotion, if advisable, by reducing the number of quits for inconsequential reasons, and by supervising such laying-off as is necessary in such a way that the permanent force is not upset. It provides a stability 'of employment, free from favoritism and paternalism, probably the best form of employment insurance that we can have. The value of the employment department is in direct proportion to the breadth of its supervisor, his ability to estimate and place men, his sympathy in dealing with their petty troubles, and his analysis of quits and the reasons therefor. There is probably no better index of the soundness of the industrial relationship between the employee and the employer than the reasons why men quit; an intelligent, unbiased analysis of these reasons tells where corrective measures are necessary. In nine cases out of ten the reasons are small grievances, easily corrected, and are things usually overlooked by mine officials.

Jan 6, 1919

By K. J. Gill, P. Chiotti, J. T. Mason

Thermal, metallographic, and vapor pressure data were obtained to establish the pkase boundaries and the standard free energy, enthalpy, and entropy of formation for the compounds in the Y-Zn system. Three coinpounds with stoichiometric formulas of YZn, YZn2, and Y2Zn17 melt congruently at 1105", 1080°, and 890°C, respectively. Four compounds with stoiclziometric formulas of YZn3, YZn4, YZn5, and YZn,, undergo perztectic reactions at 905", 895", 870º, and 685ºC, respectively. Three eutec-tics exisl in this system with the .following eutectic temperatures and zinc contents in wtpct: 875ºC, 23.2 Zn; 1015ºC, 51 Zn; 865ºC, 82 Zn. The YZn, pkase undergoes an allotropic transformation. In the two phase YZn2 -YZn alloys the trans.formation gives a weak thermal arrest at 750°C, whereas in the two phase YZn2-YZn3 alloys no thermal arrest is observed and the transformation occurs over a temperature range below 750°C. At 500°C the free mzergies of formation per lnole vavy from —18,090 for YZn to —53,430 fov YZr11 and corresponding enthalpies vary from -24,050 to -92,080. The free energies and enthalpies per g atom as a function of composition show a maximum for the YZn2 phase; the 500°C values are -9580 and -13,180, vespectively. 1 HE only information found in the literature on Y-Zn alloys was the observation reported by Carlson, Schmidt. and speddingl that Y-20 wt pct Zn forms a low melting alloy. The alloy was produced by the bomb-reduction of YF3 and ZnF2 with calcium in an investigation of methods for producing yttrium metal. The solubility of yttrium in zinc has been determined by P. F. woerner2 and reported by Chiotti, Woerner, and Parry.3 In the temperature range 495" to 685°C the solubility may be represented by the relation In these equations N represents atom fraction of yttrium and T is the temperature in degrees Kelvin. The purpose of the present investigation was to establish the phase diagram for the Y-Zn system and to determine the standard free energy, enthalpy, and entropy of formation for the compounds formed. MATERIALS AND EXPERIMENTAL PROCEDURES The metals used in the preparation of alloys were Bunker Hill slab zinc, 99.99 pct pure, and Ames Laboratory yttrium sponge. Arc-melted yttrium buttons contained the following impurities in parts per million: C-129, N-12, 0-307, Fe-209, Ni-126, Mg-13, Ca < 10, F-105, and Ti < 50. Some of the alloys containing 70 wt pct or more of Zn were prepared from yttrium containing 5000 ppm Ti as a major impurity. Tantalum containers were found to be suitable for all alloys studied and were used throughout the investigation. The pure metals, total weight about 30 g, were sealed in 1 in. diam tantalum crucibles by welding on preformed tantalum covers. A 1/8 in. diam tantalum tube was welded in the base of each crucible for use as a thermocouple well. Welding was done with a heli-arc in a glove box which was initially evacuated and filled with argon. The sealed crucibles were enclosed in stainless steel jackets and heated in an oscillating furnace at temperatures up to 1150°C. Homogeneous liquid alloys were obtained within a half hr at these temperatures except for alloys containing less than 20 pct zinc. The latter alloys were held at 1000º to 1100°C for 2 to 3 days in order to obtain equilibrium. After the initial equilibrations the tantalum crucibles containing the alloys were removed from the steel containers and used directly for differential thermal analyses. Further annealing heat treatments for alloys in which peritectic reactions were involved were carried out in the thermal analyses furnace. After thermal analyses the tantalum crucibles were opened and the alloys sectioned and polished for metallographic examination. In the following discussion alloys referred to as "quenched" were obtained by quenching the sealed stainless steel jacket containing the tantalum crucible and alloy in water. The differential thermal analyses apparatus used was a modified version of the one described in an earlier paper., The graphite crucible was replaced by an inconel crucible, the nickel standard and sampie container were separated by a 1/8 in. MgO plate, no getter was used, and provisions were made to

Jan 1, 1963

By J. D. Verhoeven

In the past 15 years a considerable amount of experimental and theoretical work has been done concerning the onset of convection in liquids as a result of interm1 density gradients. This work, which has been doue in many different fields, is reviewed here and extended slightly to give a rrlore quantitative understanding to the probletrz of conzection in liquid metal dlffusion experinletzts. In liquid metal systems the capillary reservoir technique is currently used, almost exclusively, to measure diffusion coefficients. In this technique it is necessary that the liquid be stagnant in order to avoid mixing by means of convection currents. Convective mixing may result from: 1) convection produced as a result of the initial immersion of the capillary; 2) convection produced in the region of the capillary mouth as the result of the stirring frequency used to avoid solute buildup in the reservoir near the capillary mouth; 3) convection produced during solidification as a result of the volume change; and 4) convection produced as a result of local density differences within the liquid in the capillary. The first three types of convection have been discussed elsewhere1-a and are only mentioned for completeness here. This work is concerned only with the fourth type of convection. Local density differences will arise within the liquid as a result of either a temperature gradient or a concentration gradient. It is usually, but not always, recognized by those employing the capillary reservoir technique that the top of the capillary should be kept slightly hotter than the bottom and that the light element should be made to migrate downward in order to avoid convection. In the past 15 years a considerable amount of work, both theoretical and experimental, has been done in a number of different fields which bear on this problem. This work is reviewed here and extended slightly in an effort to give a more quantitative understanding of the convective motion produced in vertical capillaries by local density differences. The Stokes-Navier equations for an incompressible fluid of constant viscosity in a gravitational field may be written as: %L + (v?)v = - ?£ + Wv - g£ [1] where F is the velocity, t the time, P the pressure, p the density, v the kinematic viscosity, g the gravitational acceleration, and k a unit vector in the vertical direction. A successful diffusion experiment requires the liquid to be motionless, and under this condition Eq. [I] becomes: where a is the thermal expansion coefficient [a =-(l/po)(dp/d)], a&apos; is a solute expansion coefficient [a&apos; = -(l/po)(dp/d)], and the solute is taken as that component which makes a&apos; a positive number. Combining with Eq. [3] the following restriction is obtained: Since there is no fixed relation between VT and VC in a binary diffusion experiment, Eq. [5] shows that the condition of fluid motionlessness requires both the temperature gradient and the concentration gradient to be vertically directed. Given this condition of a density gradient in the vertical direction only, it is obvious that, as this vertical density gradient increases from negative to positive values, the motionless liquid will eventually become unstable and convective movement will begin. The classical treatment of this type of instability problem was given by aleih&apos; in 1916 for the case of a thin fluid film of infinite horizontal extent; and a very comprehensive text has recently been written on the subject by handrasekhar.&apos; It is found that convective motion does not begin until a dimensionless number involving the density gradient exceeds a certain critical value. This dimensionless number is generally referred to as the Rayleigh number, R, and it is equal to the product of the Prandtl and Grashof numbers. For the sake of clarity a distinction will be made between two types of free convection produced by internal density gradients. In the first case a density gradient is present in the vertical direction only, and, since the convection begins only after a critical gradient is attained, this case will be called threshold convection. In the second case a horizontal density gradient is present and in this case a finite convection velocity is produced by a finite density gradient so that it will be termed thresholdless convection. Some experimentalists have performed diffusion experiments using capillaries which were placed in a horizontal or inclined position in order to avoid convection. These positions do put the small capillary dimension in the vertical direction and, consequently, they would be less prone to threshold convection than the vertical position. However, if the diffusion process produced a density variation, as it usually does, it would not be theoretically possible to avoid thresh-

Jan 1, 1969

By John C. Gifford, Charles L. Thomas

A unique and reproducible method is presented for the determination of water vapor in tough pitch wire bar copper. The procedure involves reduction of the water vapor with molten aluminum to form hydrogen, which is subsequently measured by mass spectroscopy. Average water vapor pressures within the porosities of the wire bar samples are calculated. Correlation is to exist between the specific gravities of the samples and their measured water vapor contents. The method should find application as a very sensitive means of detecting hydrogen embrittlement in copper. The nature and quantity of gases evolved and retained during the horizontal casting of tough pitch wire bar copper have long been of interest to the metallurgist. Considerable work has been done at this laboratory on the determination of these gases. The work has involved not only qualitative but also quantitative analysis, so as to provide a basis for a total accounting of the porosity which is associated with the cast product. From a knowledge of the gas-forming elements within the copper, and the practice of melting and protecting it with a reducing flame followed by contact with a charcoal cover in the casting ladle, the gases which one might expect to find in the pores of the cast product are sulfur dioxide, carbon monoxide, carbon dioxide, hydrogen, and water vapor. Hydrogen sulfide, nitrogen, and hydrocarbons would be other possibilities; however vacuum fusion-mass spectroscopy techniques employed at this laboratory have shown that no hydrogen sulfide and only traces of nitrogen and methane are present. It is highly improbable according to phillipsl that any sulfur dioxide could be evolved in wire bar copper with 10 ppm or less sulfur under normal freezing conditions. Mackay and smith2 have noted that porosity due to sulfur dioxide only becomes noticeable at concentrations above 20 ppm S. Investigation of carbon monoxide and carbon dioxide by a variation in the method of Bever and Floe showed that these two gases could only account, at 760 mm and 1064°C (Cu-Cua eutectic temperature), for a maximum of about 25 pct of the total porosity in a wire bar having a specific gravity of 8.40 g per cu cm. phillips&apos; has noted that no normal furnace atmosphere is ever sufficiently rich in hydrogen to cause porosity in copper from hydrogen alone. In addition, using a hot vacuum extraction technique for hydrogen,4 values have never been observed in excess of 10 ppb in tough pitch wire bar. On the basis of the preceding considerations of gases in tough pitch wire bar, only water vapor is left to account for the major portion of the porosity. Direct determinations of water vapor are virtually impossible at low concentrations by any presently known technique, due to adsorption and desorption within the walls of the apparatus used.5 The present investigation deals with a method for the determination of water vapor by an indirect procedure, using molten aluminum as a reducing agent to form hydrogen according to the reaction: 2A1 + 3H2O — A12O3 + 3H2 The evolved hydrogen can then be measured quantitatively by mass spectroscopy. EXPERIMENTAL A 10-g piece of 99.9+ pct A1 was charged into a porous alumina crucible (Laboratory Equipment Co., No. 528-30). Fig. 1 shows the crucible in place at the bottom of an 8-in.-long quartz thimble. A funnel tube with two l1/8-in.-OD sidearms extending at a 90-deg angle from each other was attached to the top of the thimble. One of the sidearms was joined to the inlet system of the mass spectrometer (Consolidated Electrodynamics Corp. Model 21-620A) via a mercury diffusion pump situated between two dry-ice traps. The copper samples were placed in the other sidearm, followed by a glass-enclosed magnetic stirring bar for pushing the samples into the crucible. All ground joints were sealed with vacuum-grade wax. The entire system was evacuated and the aluminum was heated with a T-2.5 Lepel High Frequency Induction Furnace for 21/2 hr at a temperature visually estimated to be 900°C. The temperature was then lowered and the hydrogen was monitored on the mass spectrometer until it was given off at a constant rate of about 4 to 5 1 per hr. This rate corresponded to a slope of 2 to 3 divisions per min on the X3 attenuation of a 10-mv recorder at a hydrogen sensitivity of approximately 100 divisions per 1. A micromanometer (Consolidated Electrodynamics Corp. Model 23-105)

Jan 1, 1969

By W. R. Ingalls

ThE following chronology presents the history of lead-mining in the United States in a brief form and is a useful reference in connection with the statistics of production: 1621.. Lead was mined and smelted near Falling Creek, Va., to supply the local demand for bullets and shot. This was the first mining and .smelting of lead in what is now the United States. 1632. In a report made on the minerals of New England, lead-ore is mentioned. (Bishop, I., 470.) 1650. Supposed beginning of mining by Jesuits in Pima county, Ariz. 1651. Grant of lead-mine at Middletown, Conn., to Gov. John Winthrop. 1682. Lead-ore supposed to have been discovered in Wisconsin by Nicholas Perrot. (K. D. Irving, Mineral Resources of Wisconsin, Trans., viii., 498.) 1700 Discovery of lead in Missouri by Penicaut, one of Le Sueur&apos;s party. Tile same expedition discovered lead near the southern boundary of Wisconsin in August of the same year. 1712. Grant by Louis XIV. of the Crozat patents, with special privileges respecting the discovery and operation of mines in the then territory of Louisiana. Little or no mining was done under this patent until about 1720. 1717. Transfer of Crozat patents to the Mississippi Co., promoted by John Law, which prepared for active mining. 1719. First attempt to mine and smelt lead in Missouri, made by Sieur de Lochon, in behalf of the Mississippi Co., near Meramec river. Results unsuccessful.

Jan 1, 1908

By N. A. Gjostein

The formal descnption of the decay of an isolated scratch can be written in terms of an appropriate Fourier integral. With the application of certain approximations, this description leads to the second-moment analysis developed by King and Mullins. It is shown that the second-moment analysis does not adequately describe the behavior of a decaying, isolated scratch, and that it is difficult to obtain internally consistent values of the surface self-diffusion coefficient, D,,from this analysis. This inconsistency arises from contributions of higher-order moments to the decay process. Two new analytical methods, based on the Fourier integval representation of a scratch profile, have been developed for determining values of D, from the decay kinetics of isolated scratches. In the profile-matching method, a given initial profile is resolved into its Fourier components, the components are allowed to decay exponentially over an annealing time interval, At, and finally they are synthesized to form a decayed profile. The predicted profile is adjusted to fit the experimental profile by varying only the parameter, D,At; the contribution from volume diffusion is directly taken into account and the integrals involved in the Fourier analysis are evaluated by numerical integration on an electronic computer. In the kinetic method, the widths, W, of a series of predicted profiles are determined for various volume-diffusion contributions, and the results are plotted in the form W vs DSAt. For a fixed ratio of surface to volume diffusivities, R, these plots are linear; the slope of the lines increases as R decreases. A simi-lar analysis can be performed on the depths of the predicted profiles. In this case, plots of (l/df3 vs D,At are found to be nonlinear. The proper value of Ds is found by superimposing the data for the experimental widths and depths on Plots of this kind and adjusting Ds until a fit is obtained with the line having the appropriate value oj R. An analysis of the slopes of these plots for R —= (surface diffusion only) reveals that they do not give the correct value, 2276, for width tf second-moment standard profile. This finding allows one to modify the second-moment analysis in such a way as to obtain internally consistent values of Ds. ThERE are several processes, involving a flow of matter along a surface, due to gradients in curvature of the surface, that may be used to determine the surface self-diffusion coefficient, Ds. These processes are commonly known as 1) thermal grooving, 2) single and 3) multiple scratch decay, 4) blunting of field-emitter tips, and 5) sintering. In this series of papers, the first three of these processes are examined in detail in an attempt to subject the phenomenological theories governing these processes to a critical test and, furthermore, to make a critical comparison of the values of D, obtained from these techniques. Although the thermal grooving technique has been established&apos;&apos; as a reliable method for determining D, , this has not been the case for the process of scratch flattening. Mullins and coworkers374 have proposed phenomenological laws governing the growth of the width and the decay of the amplitude of an isolated scratch, but only in one study5 has the width-growth law been supported by experimental evidence. In paper I of this series detailed experimental evidence is presented that points up the deficiencies of the second-moment analysis; the origins of these deficiencies are also discussed. Following this development, some new analytical procedures, based on representing the scratch profile by Fourier integrals, are presented as a means of obtaining reliable values of D, from the kinetics of the scratch-flattening process. Further applications of the Fourier integral approach are reported in papers 11&apos; and 111,~ where the method has been useful in interpreting the anisotropy of flattening rates of isolated scratches (paper 11) and in describing the multiple scratch decay process (paper 111). THEORY OF SCRATCH DECAY Following ~ullins" approach we consider an arbitrarily shaped scratch profile, Fig. 6, at some time, t. The profile is designated by a function z(x,t) which can be expressed in terms of a Fourier integral as follows:

Jan 1, 1967

By Henry J. Sandri

The use of economic models for forecasting purposes is an inexact yet necessary tool for mineral decision making. One method not commonly used is cyclical analysis because of its "non-scientific approach". However, under certain circumstances a modified cyclical approach can provide useful insight to mining companies. The current paper discusses mineral modeling, the type of economic models and the use of cyclical forecasting for mining firms (not speculators) involved in precious metals.

Jan 1, 1984