Search Documents

By E. C. Truesdale, R. K. Waring

THE Research Division of The New Jersey Zinc Company (of Pa.) has conducted, over a period of years, numerous tests of the reducibility of various zinc ores and the reactivity of various kinds of coal, using a number of different experimental methods. Most of these tests have involved the reduction of mixtures of ore and coal. In such cases the following simultaneous reactions are believed to be mainly responsible for the production of zinc, as was shown by Bodenstein1 some years ago: ZnO + CO = Zn + CO2[I] C + CO2 = 2CO[2]. Each of these reactions is dependent upon the other for the supply of CO and C02, respectively, and the over-all rate of formation of zinc vapor will be determined by the slower of these two reactions. An analogous pair of reactions sometimes of importance is: ZnO + H2 = Zn + H2O[3] C+ H2O=CO+H2[4] While it is possible to obtain an indication of the relative reducibility of various ores, or of a fine versus a coarse ore, by testing them with a given coal, and while coal reactivities may be measured in a corresponding manner, a more direct determination of relative reaction rates is possible by carrying out the desired reactions, such as I and 2, separately and under reproducible conditions. It is one purpose of this paper to present some of the results that have been obtained by the latter method. C. G. Maier2 discusses the relative rates of reactions I and 2 and concludes that while at relatively low temperatures reaction I is faster than reaction 2, this difference becomes less with increasing temperatures, although at smelting temperatures reaction I is still the faster. He also says (p. 48), "At temperatures . . . between 1100° and 1300°C the zinc oxide reduction reaction is intrinsically more rapid than its physical limitations; that is, it is limited by gas diffusion rates." In the course of numerous reactivity tests involving the separate use of reactions and I and 2, we have obtained data that show by direct experiment, we believe for the first time, the correctness of Maier's statements concerning these reactions. We also include data on the relative rate of reaction 3, involving reduction by hydrogen. Finally, some interesting results obtained by carrying out the reduction of a zinc ore-coal briquet in streaming atmospheres of nitrogen, carbon monoxide and hydrogen, respectively, are presented.*

Jan 1, 1941

By Wilson D. Michell

The Magma copper vein trends east-west, dips 70" south, and cuts through a 6000-ft thickness of limestones, quartzites,. shale, diabase, and schist. The vein is itself a fault with a horizontal offset of 500 ft on the formation contacts in the two walls. There are two principal faults of large displacement and numerous smaller steep and flat faults that complicate the prediction of ore occurrence. A study of the geology, its systematic recording to facitliate ready reference, and graphic methods of interpretation of mineralization have aided the exploration, development, 2nd mining of the ore. In making predictions of the distribution of mineable ore bodies and their shape in critical areas, studies are made of "mineralization contours" and "mineralization trends," which are developed on a longitudinal section of the vein from variations in the concentration of the combined base metal content as shown by assays of available openings in the mine. Introduction This paper describes an example of geological work applied directly to mining and exploration problems in a deep vein deposit, and it is presented as being of interest especially to those engaged in working more or less similar veins. In 1944 to 1945 the writer spent a year as assistant to J. K. Gustafson in a thorough geological examination of the Magma mine. Much of the writer's subsequent independent work described in the present paper had its inception in ideas originated by Gustafson during that examination. Objectives of Geological Work at Magma Mine The objectives of geological work at Magma, as at operating vein mines of a similar nature, can be summarized as follows: 1. Direct assistance to the mining department by means of predictions as to the size, shape, grade, and location of ore bodies; by solution of fault problems and irregularities in the veins; by prepara-?ion of detailed ore-reserve estimates in specific areas; by keeping a complete record of the geology and assay results in the mine; and by guiding development work. In short, geology can aid in the realization of the prime purpose of the mining department, which is that of producing the greatest amount of ore in the most economical and expeditious manner possible. 2. Guidance for exploration, especially diamond drilling, in undeveloped areas of the mine. 3. Contributions to the understanding of the general geology of the deposit and its regional setting, including ore genesis, structure, and mineral relationships. Magma Ore Deposit The east-west trending Magma vein, dipping about 70" south, cuts through a 6000-ft thickness of concordant limestones, quartzites, shale, diabase, and schist, named in descending order. These

Jan 1, 1949

By E. S. Wheeler

THE conversion plant of the Climax Molybdenum Co. is at Langeloth, Washington County, Pennsylvania, approximately 30 miles west of Pittsburgh. The molybdenite concentrates converted originate in the company's mine and mill at Climax, Colorado.1 They are delivered to the Langeloth plant by rail packed in 175-lb. bags. War production of concentrates at the mill started in 1918 but it was not until about 1920 that any peacetime uses of the metal began to develop. Early conversion of Climax concentrates was mainly into ferromolybden um, produced for the company by a custom smelter. CHRONOLOGY OF PLANT DEVELOPMENT In 1924 a small hand-rabbled roaster was built at Langeloth, the roasted concentrates being used principally in the production of calcium molybdate by a conventional wet method. The size of the original plant is indicated by the fact that during 1925 about 400,000 lb. of molybdenum was converted. In 1925-1926, a multiple-hearth roaster was erected (12-ft. o.d. 8-hearth Nichols-Herreshoff); also the first experimental ferromolybdenum was produced at Langeloth. At this time calcium molybdate was produced in the furnace by a process to be described. With continued interest in and increased use of molybdenum, it was necessary to arrange for enlargement of plant facilities. Although only one 12-hearth 16-ft. o.d. roaster was erected at this time (1929), plans were prepared for a duplicate unit, which was completed in 1935, giving a potential roasting capacity of some 16,000 lb. Mo per day under the then prevailing roasting practice. Shortly after this second unit had gone into production, increased demand overtaxed the plant, and as a result two 12-hearth 18-ft. o.d. roasters were placed in operation in 1936 and 1937. This gave the plant a potential roasting capacity of 40,000 to 50,000 lb. Mo per day, and necessitated major changes in auxiliary handling equipment as well as improved facilities for producing ferromolybdenum. Following the introduction (1938) of a new product-molybdic oxide briquets and because of the constantly growing demand for molybdenum, plant facilities were again enlarged in 1940 and 1941 by the erection of two 16-hearth 18-ft. o.d. roasters. These two new units, along with a change in roasting practice, brought the potential roasting capacity to 150,000 to 190,000 lb. Mo per day, based on about 15 lb. per sq. ft. of hearth area. Other departments of the plant have necessarily grown, until today the plant is modern throughout and completely mechanized, with equipment geared to produce marketable products as follows:

Jan 1, 1944

By William J. Harris, Morris Cohen

INTRODUCTION THE recent application of lineal analysis1,2 to the austenite-martensite reaction has made possible a quantitative study of the kinetics of this transformation during rapid cooling. Martensite range curves can thus be constructed to portray the onset of the reaction at [M.] and its subsequent progress as a function of temperature down to and below the ambient. It now seems in order to investigate other aspects of the martensite transformation, using this quantitative method of approach. One of the least understood characteristics of the austenite-martensite reaction is that of stabilization which has been defined by Troiano and Greninger3 as "a lowering of [M.], resulting from aging, without change in chemical composition of the parent solid solution." In other words, if the hardening quench is arrested at a predetermined subcritical temperature (Th) for a sufficient period of time, more austenite may be retained at a given lower or reference temperature (Tr) than if the steel had been cooled directly and rapidly to Tr in the first place. For the purposes of the work at hand, the extent of stabilization produced by the isothermal treatment at Th, is measured explicitly in terms of the excess austenite [(S)] that exists in the steel at Tr, over and above the amount that is normally present after direct quenching to Tr. Tr is conveniently taken to be room temperature, but this choice is not essential and is sometimes undesirable. The holding temperature (Th) may be above or below [M], and still cause stabilization depending upon the chemistry of the austenite. Stabilization has been found to occur in the presence of bainite4 and of martensite5,6,7,8 as well as in the absence of either.9 The phenomenon of stabilization is not concerned with (and may even be obscured by) ferrite formation or any other type of phase change occurring at Th that alters the chemistry of the remaining austenite. Such a structural change would obviously influence the martensite transformation during subsequent cooling. Stabilization, however, is more subtle; it appears to manifest itself without detectable variation of the austenite composition, whether in the presence or absence of transformation products. There are relatively few direct references to stabilization in the literature. The stabilizing effect of room temperature aging and tempering on the subzero transformation of retained austenite has been clearly shown in plain carbon,6.8 low alloy 6.7.8 and high alloy tool steels.10,5 Starting with the as-hardened steel, the degree of stabilization increases with tempering time and temperature through

Jan 1, 1948

By J. Charles Miller

Natural carbon dioxide has recently been exploited in the United States in consequence of oil and gas developments in the Western States and the growing demand by transcontinental and transoceanic shippers for solid carbon dioxidc. The discovery by drilling of commercial deposits resulted in consideration of its geographic and geologic distribution and occurrence. Its wide distribution in nature is evidenced by its occurrence in the atmosphere, hydrosphere and lithosphere. The question of origin of carbon dioxide involves consideration of theories similar to those concerning natural hydrocarbons, although available evidence favors an inorganic rather than an organic source. Areas favorable to development of commercia1 production appear to be those in proximity to igneous rocks or in the vicinity of decadent volcanic activity, where, it has long been known, the gas is evolved either free or dissolved in the waters of fumaroles, geysers or mud pots. Structure contour maps are presented showing the Wagon Mound anticline in New Mexico and the Farnham anticline, Utah. A well drilled on the latter supplies gas to a 20-ton plant manufacturing solid carbon dioxide at Wellington, Utah, on the Denver and Rio Grande R.R., whence it is shipped to surrounding territory and to the West Coast. Before funds are invested in a plant for the manufacture of liquid or solid carbon dioxide, whether supplied by wells or springs, an effort to ascertain the volume of gas available is advisable. The use of present methods of estimation of gas reserves with modifications to account for the quantity absorbed by any water present in the producing formation is recommended. The Farnham anticline is used as an example and computations are made of the probable volume of gas originally present in the structure. No attempt was made to compute reserves in the Niland area, California, for the reason that in such areas it is believed the volume is indeterminate. Introduction Carbon dioxide, in liquid and solid form, has found a wide variety of uses other than its primary application in carbonating beverages. It is now used in more than 40 different ways, ranging from cooling or freezing to use in gas or liquid form for mechanical purposes, chemical industry, explosive, fire extinction, and tire manufacturing. Undoubtedly the chief supply of carbon dioxide is obtained from industrial plants or artificial sources and until recently natural deposits of the gas have received little consideration. Few will question the utility and perhaps dependability of artificial sources, which possess the advantage over

Jan 1, 1941

By J. Charles Miller

Natural carbon dioxide has recently been exploited in the United States in consequence of oil and gas developments in the Western States and the growing demand by transcontinental and transoceanic shippers for solid carbon dioxidc. The discovery by drilling of commercial deposits resulted in consideration of its geographic and geologic distribution and occurrence. Its wide distribution in nature is evidenced by its occurrence in the atmosphere, hydrosphere and lithosphere. The question of origin of carbon dioxide involves consideration of theories similar to those concerning natural hydrocarbons, although available evidence favors an inorganic rather than an organic source. Areas favorable to development of commercia1 production appear to be those in proximity to igneous rocks or in the vicinity of decadent volcanic activity, where, it has long been known, the gas is evolved either free or dissolved in the waters of fumaroles, geysers or mud pots. Structure contour maps are presented showing the Wagon Mound anticline in New Mexico and the Farnham anticline, Utah. A well drilled on the latter supplies gas to a 20-ton plant manufacturing solid carbon dioxide at Wellington, Utah, on the Denver and Rio Grande R.R., whence it is shipped to surrounding territory and to the West Coast. Before funds are invested in a plant for the manufacture of liquid or solid carbon dioxide, whether supplied by wells or springs, an effort to ascertain the volume of gas available is advisable. The use of present methods of estimation of gas reserves with modifications to account for the quantity absorbed by any water present in the producing formation is recommended. The Farnham anticline is used as an example and computations are made of the probable volume of gas originally present in the structure. No attempt was made to compute reserves in the Niland area, California, for the reason that in such areas it is believed the volume is indeterminate. Introduction Carbon dioxide, in liquid and solid form, has found a wide variety of uses other than its primary application in carbonating beverages. It is now used in more than 40 different ways, ranging from cooling or freezing to use in gas or liquid form for mechanical purposes, chemical industry, explosive, fire extinction, and tire manufacturing. Undoubtedly the chief supply of carbon dioxide is obtained from industrial plants or artificial sources and until recently natural deposits of the gas have received little consideration. Few will question the utility and perhaps dependability of artificial sources, which possess the advantage over

Jan 1, 1941

By J. W. King

URANIUM ore was first discovered in the Edge-mont district of the southern Black Hills in the summer of 1951. The discovery was not made known for some time, but after the news leaked out prospecting became intense, and several hundred claims were staked in the spring of 1952. The Hot Springs Sub Office of the Atomic Energy Commission was established at that time and airborne radiometric surveys were commenced by the Government and by private companies. During the succeeding summer another important discovery was made by private airborne surveys in the northern Black Hills, and the area favorable for uranium ore was expanded many times. Between that summer of 1952 and the present, many individuals and groups have explored, developed, and exploited their claims until now uranium ore is produced in significant quantities and substantial reserves have been developed. The Black Hills portion of the geologic map of the U. S. issued by the U. S. Geological Survey is shown in Fig. 1. Sedimentary formations are exposed as a series of cuestas and hogbacks in a roughly annular pattern with the older sediments resting on the pre-Cambrian core, which is exposed in the eastern and southern portions of the dome. The South Dakota-Wyoming state line bisects the area from north to south. The Cheyenne River crosses the southern tip of the Black Hills and the Little Missouri bounds them roughly on the north. Headquarters of the AEC in the Black Hills is the Sub Office at Hot Springs, S. D. An ore buying station is located in Edgemont, 28 miles to the southwest, where a mill is presently under construction. The area of original uranium ore discovery and of principal activity in the southern Hills is a few miles north of Edgemont. Several areas of anomalous radioactivity have been noted between Dewey, S. D., and Newcastle, Wyo. A limited amount of ore has come from the Dewey area and private exploration is active there. The Carlile deposit, largest producing mine in the northern Black Hills to date, lies northwest of the Belle Fourche River near the western extremity of the Hills. Two of the larger known orebodies of the area are located near the Little Missouri River where a small window exposes the favorable strati-graphic horizon of the Fall River sandstone. Small production has recently come from Barlow Canyon, near Devils Tower, Wyo., Fig. 2, and numerous areas of anomalous radioactivity are known in the vicinity. Three producing deposits and scattered radioactivity are found along the state line east of Aladdin, Wyo. Several areas of weakly anomalous radio-

Jan 1, 1957

I. PRESIDING OFFICER. At all business meetings of the Institute the President, or, in his absence, the First Vice-President, or, in the absence of both of them, any other Vice-President or Director, chosen by the meeting, shall preside. At all other meetings of the Institute the President, or, in his absence, one of the Vice-presidents, shall preside. If none of these be present the meeting shall elect a Chairman. The President shall do and perform such other duties as may from time to time be assigned to him by resolution of the Board of Directors of the Institute. II. ORDER OF BUSINESS. At each business meeting of the Institute the order of business shall be as follows: 1. Reading of minutes of preceding meeting. 2. Report of the President. 3. Report of the Treasurer. 4. Report of the Secretary. 5. Election of Directors. 6. Reports of Standing Committees. 7. Reports of Special Committees. 8. Special Orders. 9. Miscellaneous business. This order of business may be changed at any meeting, by a vote of a majority of the Members and Associates present. At all sessions of the Institute, other than business meetings, the order of proceedings and the time of adjournment shall rest in the discretion of the presiding officer. III. SECRETARY OF THE INSTITUTE. The Secretary shall keep a record of the proceedings of all the meetings of the Institute. He shall be custodian of the corporate seal, of the minute books and of all the legal documents belonging to the Institute. He shall have charge on behalf of the Institute of all correspondence. He shall notify all Officers and Directors and all members of committees of their election and appointment; shall issue notices of all meetings of the Board, and of the annual and other business meetings of the Institute; and shall, in calling special meetings of the Directors, specify the objects of such meetings. He shall act as clerk at all the meetings of the Board of Directors and at all meetings of the Institute. The Secretary shall be custodian of all technical or scientific papers submitted to the Institute for its consideration and shall have general charge and supervision of the editing and proof-reading of all material published by the Institute, and of the distribution thereof. The Secretary shall be the custodian of all back numbers of the Transactions and other publications of the Institute. There shall be kept under his direction an account

Jan 1, 1925

I. PRESIDING OFFICER. At all business meetings of the Institute the President, or, in his absence, the First Vice-President, or, in the absence of both of them, any other Vice-President or Director, chosen by the meeting, Shall preside. At all other meetings of the Institute the President, or, in his absence, one of the Vice-presidents, Shall preside. If none of these be present the meeting Shall elect a Chairman. The President Shall do and perform Such other duties as may from time to time be assigned to him by resolution of the Board of Directors of the Institute. IL ORDER OF BUSINESS. At each business meeting of the Institute the order of business Shall be as follows: 1. Reading of minutes of preceding meeting. 2. Report of the President. 3. Report of the Treasurer. 4. Report of the Secretary. 5. Election of Directors. 6. Reports of Standing Committees. 7. Reports of Special Committees. 8. Special Orders. 9. Miscellaneous business. This order of business may be changed at any meeting, by a vote of a majority of the Members and Associates present. At all sessions of the Institute, other than business meetings, the order of proceedings and the time of adjournment Shall rest in the discretion of the presiding officer. III. SECRETARY OF THE INSTITUTE. The Secretary Shall keep a record of the proceedings of all the meetings of the Institute. He Shall be custodian of the corporate Seal, of the minute books and of all the legal documents belonging to the Institute. He Shall have charge on behalf of the Institute of all correspondence. He Shall notify all Officers and Directors and all members of committees of their election and appointment; Shall issue notices of all meetings of the Board, and of the annual and other business meetings of the Institute; and Shall, in calling Special meetings of the Directors, Specify the objects of Such meetings. He Shall act as clerk at all the meetings of the Board of Directors and at all meetings of the Institute. The Secretary Shall be custodian of all technical or Scientific papers Submitted to the Institute for its consideration and Shall have general charge and supervision of the editing and proof-reading of all material published by the Institute, and. of the distribution thereof. The Secretary shall be the custodian of all back numbers of the Transactions and other publications of the Institute. There Shall be kept under his direction an account

Jan 1, 1925

By E. C. Hopkinson, A. H. Youmans, R. A. Bergan, H. I. Oshry

A new log has been developed for quantitative formation evaluation which is based on a measurement of the length of time slow neutrons survive before they are captured in the rocks and fluids. The logging instrument employs a cyclically pulsed neutron generator and a gated scintillation counter which is synchronized with the source. The source emits short, intense bursts of 14 mev neutrons once every 1,000 microsec and is quiescent between bursts. During the period the source is quiescent, the detector is electronically actuated for two independent preselected intervals. A comparison of the counting rates during these two intervals gives a measure of the rate of decay of the slow neutrons and of the associated gamma radiation. The average neutron lifetime in most earth formations is in the range from 50 to 500 microsec. It can be measured during a continuous logging operation at conventional logging speeds. The design of the logging instrument is described and the results of tests are compared with theoretical predictiom. Formulas are developed which give the relationship between log response and formation properties. It is shown that the method is particularly sensitive to formation fluid salinity, and that salt water saturation can be measured accurately in either cased or open hole. The measurement can be made independent of borehole size, fluid type, casing and tool position in the hole by properly selecting the intervals during which the measurements are made. The results of tests with a prototype logging tool are given. INTRODUCTION A new nuclear logging system has been developed which employs the Accelatron,* an accelerator-type neutron source, and accurately measures formation brine saturation in an entirely new way. It has produced a type of formation log with better sensitivity, greater sampling depth and simpler quantitative interpretation than any other nuclear log thus far suggested. The new Neutron Lifetime Log* employs a pulsed electromechanical neutron source and a synchronously gated radiation detector. A prototype instrument has been field tested during recent months to demonstrate the operability of the apparatus and the feasibility of the method. Tests in wells and simulated boreholes have confirmed theoretical predictions and have shown that formation param ters can be measured independent of casing and other borehole parameters. Preliminary results of field tests have indicated that the log may have important and widespread applications. BASIC PRINCIPLE OF NEUTRON LIFETIME LOG The Neutron Lifetime Log is based on the fact that neutrons emitted by a source in a well are rapidly but not instantly captured by the material around the source. Their capture is a matter of statistical probability; the greater the number of capturing nuclei and the greater the "capture cross section", the greater is the probability that a neutron will be captured quickly. The average life of a thermal neutron in vacuum is about 13 minutes, but in common earth materials, the average neutron life ranges between extremes of about 5 rnicrosec for rock salt and perhaps 900 microsec for quartzite. The Neutron Lifetime Log responds to variations in this average neutron life. The theoretical basis for a log of this general type has been well understood by nuclear logging experts in many laboratories both in America and in Russia, and develop mental work along these lines has been in progress for many years. The Russian literature has reported both theoretical and experimental work1,2 but in this country there have been no published reports of progress toward a practical logging instrument. The logging instrument is designed to measure radiation produced by slow neutrons during selected intervals when no neutrons are being emitted by the source. The source is arranged to emit neutrons in bursts or pulses. During the quiescent interval between the pulses, it is possible to observe the exponential "decay" of the neutrons and the neutron-induced radiation as the individual neutrons progressively disappear due to capture by atoms in the formation or the borehole. When a short pulse of 14 mev neutrons is emitted by a source in a borehole, the individual neutrons are slowed to thermal energy within a few microsec. Thus, a cloud of "slow" neutrons is formed around the source within 10 to 50 microsec after the pulse. This cloud is most dense within a few inches of the source, and is progressively less dense out to a radius of about 3 ft, where radiation from the source is practically undetectable.

Jan 1, 1965

By R. J. Reynik

A semiempirial small flunctation theory of diff- sion in liquids is presented, which employs a fluctuation energy assumed quadratic for a small atomic or molecular displacement and Einstein's random-iralh model. The resulting diffusion equation is given by In these equations. D is the diffusivity, is the average liquid shite coordination number (at interatomic distance d. cm. T is the absolute temperature, xu. em, is (the diffusive displacement. K, is the quadratic fluctuation energy force constant, and rg, cm, are the radii oj diffusing atoms A and B, respectively. The quantities Xn and K are calculated from the computer-filled values of the slope and intercept. respectively. The radius of self-diffusing atom or radii and of diffusing atoms A and B are eta United and compared with values reported in the literature.. The predicted linear variation of diffusivity with. It tempera lure htm been observed in approximately thirty-iire metallic liquid systems, and in over seventy-fiee other liquid systems, including the organic .alcohols, liquified inert gases, and the molten salts, ALTHOUGH the average density within a macroscopic volume element of liquid is constant for fixed total number of atoms. pressure. and temperature, there exist microscopic: density fluctuations within the respective volume element. As such the microscopic volume available to an atom and its Z first nearest neighbors at any instant of time fluctuates above and below the average volume available to these atoms. If one assumes that liquid state atoms vibrate as in a solid. and further postulates that the mean position of any atom in the liquid state is not stationary. but shifts during every .vibration a distance 0 5 j 5 xo. then every atom in the liquid state continuously undergoes diffusive displacements which vary in the range 0 5 j 5 ro. Mathematically. for a binary liquid system consisting of atcrms A and B. the maximum diffusive displacement. .YO, is defined by the equation: where d is the average liquid state interatomic distance at specified liquid state coordination number Z. and v~ \ and vg are the effective radii of diffusing atoms A and B: respectively. For self-diffusion. r^ equals rg , and Eq. [I.] reduces to: It is interesting to note that Eq. [l] or [2] can be used to compute the radii of the diffusing atoms, provided one had an experimental evaluation of xo. As such. the computed radii could be compared with metallic or crystallographic ionic radii to ascerlain the electronic character of the diffusing atoms. Thus it is proposed that in the liquid state the n~otion of an atom relative to its original equilibrium position of oscillation represents the thermal vibration of any atom and its Z first nearest neighbors. while the small and variable displacements. 0 5 1 5 xc,. of the centers of oscillation represent the complex diffusive motions of the atoms at constant temperature and pressure. This is consistent with data obtained from slow neutron scattering by liquids1 ' and resembles an itinerant oscillator model of the liquid state.'" It is further postulated that the atomic displacements characterizing the liquid state diffusion process are essentially a random-walk process. As such. it nlay be described by Einstein's equation:' where D is the diffusivity. sq cm sec-'. j2 is the mean square value of the diffusive displacement. and i> is the frequency of density fluctuations giving rise to diffusion. FORMULATION OF DIFFUSION EQUATION The effective spherical volume occupied by an atom, as a consequence of a microscopic density fluctuation which enlarges the volume available to any atom, exceeds its average liquid state atomic volume by an amount: where AV is the enlarged spherical volume, v is the radius of the diffusing atom. and j is the elementary displacement distance from the original center of oscillation of the vibrating atom to a new center of oscillation position. For small atomic displacements. where c is a constant whose value depends upon the assumed geometry of the enlarged volume. For a spherical increase in volume, c equals 4nr2. Following the treatment of Furthl' and ~walin." assuming the enlarged volu~nes AL7 for the diffusing atoms are distributed in a continuunl. the probability of finding a fluctuation in the size range 0 5 j 5 xo defined by Where c includes the geometric constant cl and Eij) is the fluctuation energy causing the volume change. But the proposed model assumes all the Z first nearest-neighbor atoms are centers of oscillation. and hence the probability that any of these atoms is adjacent to a fluctuation of magnitude 05j5xo is unity. Thus:

Jan 1, 1970

By A. Ghosh, T. B. King

The kinetics of the discharge reaction: 20'- (in silicate melt) = O,(g) + 4e- at a platinum anode in lithium silicate melts have been studied al 1350°C by galvanostatic methods. Plots of the sleady-state overpotential, q, as a function of the logarithm of the current density, i, showed injlections and were linear only at high current densities. The value of the overpotential was influenced by bubbling gas through the electrolyte. The ocer potential was also studied as a function of time. The rise and decay of overpotential were very slow processes. At low current densities transport is the likely rate-controlling process but at high current densities passivation of the electrode, Presumably by an oxide film on the surface, seems to be a contributory functor. IT is well-established that molten silicates behave as electrolytes'5 and, except in a few cases,6 conduction is entirely ionic. Moreover, it is supposed that a possible, and perhaps predominant, mechanism for phase boundary reactions between metals and slags is similar to that in corrosion whereby anodic and cathodic processes occur at unrelated sites, the metal serving to conduct electrons.1'8 Thus electrochemical studies of some slag-metal reactions would seem to be a useful way to diagnose the rate-controlling steps in the overall reaction. The electrochemical method is, in principle, a better diagnostic tool than the direct chemical method for the following reasons: 1) The partial electrochemical reactions, which are simpler than the overall reaction, may be studied individually. 2) The rate of reaction can be controlled at will and independently of the concentrations of reactants. 3) Fast reactions can be studied by relaxation methods.' Esin and his coworkers5'10"12 have pioneered such studies in silicates and have deviloped some ingenious techniques. Not all of their findings, however. can be accepted without a good deal of further work. In this investigation, the kinetics of the oxygen discharge reaction: 202- (in silicate melt) = Oz(g) + 4e- [I] at a platinum electrode were studied by both steady-state and transient galvanostatic techniques. Interest in this reaction was first developed as a result of the findings of Fulton and chipman13 that the reduction of silica, in a silicate slag, by carbon, dissolved in liquid iron, is a very slow reaction. Subsequent work, for example, by Rawling and ~lliott,'~ has demonstrated that the reaction under these conditions must be slow, because the rate is limited by diffusion of oxygen in the iron to the metal-crucible phase boundary at which a CO bubble may be nucleated. Further work by Tarassof,'~ in which the reduction of silica by aluminum dissolved in copper was studied, has shown that under these conditions, where carbon monoxide evolution is not involved, control of the reaction rate resides in diffusion of silica in the slag phase. However, there is no practical way of inducing sufficient convection in the system to make it clear that the phase boundary reaction is indeed fast. The overall reaction of silica reduction involves the discharge of silicon ions at cathodic sites and oxygen ions at anodic sites. In the examples cited, the discharged ions are dissolved in a liquid metal. In the present study of oxygen ion discharge, gaseous oxygen may be evolved at high current densities or oxygen may simply dissolve, possibly as oxygen molecules, in the silicate at very low current densities. The discharge of an oxygen ion at an anode must, in silicates less basic than the orthosilicate composition, be preceded by a reaction in the vicinity of the electrode, such as: which makes oxygen ions available. Platinum was chosen as the working electrode since it is comparatively inert to oxygen and is, therefore, expected to come rapidly into equilibrium with the electrolyte and with gaseous oxygen. Minenko, Petrov, and Ivanova16 have measured the electromotive force at a platinum electrode in molten silicates as a function of the partial pressure of oxygen in the atmosphere, the concentration of oxide ions in the melt, and the temperature. They found platinum to behave as a reversible oxygen electrode. At two different oxygen pressures, Po2 (I) and Pq (11). the electromotive force is given by: where F is the Faraday constant, equal to 23,060 cal per v equivalent, indicating that the electrode reaction is as written in Eq. [I.]. Platinum has been similarly used in molten silicates by other inve~ti~ators. "'~~ In this investigation platinum was used only as an anode, since a current deposits other elements on its surface and changes its characteristics.

Jan 1, 1970

The Rio Tinto - Cerro Colorado operation was the first major cyanide plant built out of South Africa since the Carlin and Corte mills came on-stream in 1965 and 1969. Its flowsheet was presented in the original monograph, "Gold and Silver Cyanidation Plant Practice, " published in 1975, with a brief description of the plant but without the operating costs. The authors have recently received these data and it was believed worthwhile to present them in this volume along with the aforementioned flowsheet. The Cerro Colorado ore deposit is located at Minas de Rio Tinto in the province of Huelva, Spain, approximately 88 km (55 miles) north- west of Seville. The previously mined copper ore bodies lie on either side of the deposit which is mainly copper ore. The crest of the deposit is a capping of "gossan" containing hematite, limonite, gold, and silver. Separate facilities for primary crushing, concentration of copper ores and cyanidation of gold-silver ores are provided. Fine crushing is common to both ores. The run-of-mine open-pit ore is fed from a stockpile via a surge bin and apron feeder to a jaw crusher. After crushing to minus 150 mm (6 in. ), the ore is washed in a rotary scrubber to remove the clay material ahead of fine crushing. Minus 6 mm (1/4 in. ) screen undersize is pumped directly to the grinding circuit with the screen oversize being crushed to minus 19 mm (3/4 in. ) for feed to the primary ball mill; this is followed by two subsequent stages of ball mill grinding to 80% minus 43 microns (325 mesh). Grinding is with water only; no cyanide is used. After thickening, lime is added to the first two of seven Pachuca tanks for conditioning ahead of cyanide addition in each of the five remaining Pachuca tanks. This flowsheet indicates rapid cyanide consumption and the need to maintain a high strength cyanide solution for silver extraction. Agitation for dissolution of the gold and silver is followed by standard CCD practice employing four 67 m (220 ft) washing thickeners in series, with repulping between each thickener. A departure from American and Canadian practice is the use of Stellar filters developed in South Africa for pregnant solution clarification and recovery of zinc-gold-silver precipitates. The precipitate is treated with acid for zinc removal, the sludge filtered in presses, dried, calcined and smelted to produce dore bullion of 900 fineness containing 12% gold and 78% silver.

Jan 1, 1981

By C. W. Wark, Fred Wise

The Getchell mine, a comparatively recent gold discovery, is in the old Potosi mining district, Humboldt County, Nevada. All ore is mined from open pits using Diesel shovels and gasoline trucks. Two types of ore are mined, oxide and sulphide. Oxide ores are siliceous or shaly; sulphide ores either gougy, siliceous or shaly. In mining, the sulphide ore is segregated into hard and gougy ore, because the gouge must be dried before it can be crushed. The oxide ore is not segregated. General Metallurgy The oxide ore is the leached outcrop that overlies the sulphide ore body. All of the iron and arsenic sulphides found in the sulphide ores have been thoroughly oxidized. The sulphur and arsenic have been leached out while the iron is present as hematite and limonite. The oxide ore is amenable to direct cyanidation, and although no visible free gold is present it is released at a comparatively coarse grind. The sulphide ore is more refractory, since the gold is all of micron size and some of it is locked in fine sulphides. It has been established microscopically that the free gold is coated with an impervious shell, which is probably some form of iron compound. The sulphide ores contain from 1.5 to 2 per cent of arsenic, which is present as orpiment and realgar with minor amounts of arsenopyrite. The orpiment and realgar are of a later mineralization than the gold and are barren. Roasting and washing of the sulphide ore prior to cyanidation is necessary to eliminate , the arsenic, to alter the gold coating from an insoluble form to a soluble form, and to release the gold associated with the fine sulphides. Washing the ground calcine in weak sulphuric acid, trona, or hot water are beneficial in the order named, but to date the water is the best from an economic standpoint. Metallurgical tests as well as plant practice indicate that a certain amount of gold cannot be recovered even by going beyond economic practices. On this basis metallurgical results are viewed in the light of an optimum tailing rather than a percentage of extraction. Milling Practice Crushing (Fig. I).—There are three primary ore bins, one each for oxide ore, gougy sulphide ore, and hard sulphide ore. In front of each bin a substantial yard is maintained, which makes it possible to Stockpile 2500 tons of oxidized ore, 1000 tons of hard sulphide ore, and 1000 tons of gougy sulphide ore. The bins are fed by a 60-hp. caterpillar bulldozer from the stockpiles. Fig. I shows the method and

Jan 1, 1943

By Jim Douglas, H. H. Rachford, D. W. Peaceman

The problem of unsteady-state gas flow through porous media has been solved numerically only for the case of linear or radially symmetric reservoirs. A recently introduced numerical method for solving the unsteady-state heat flow equation in two dimensions is applied to the calculation of the depletion of a square region containing a perfect gas. Solutions are presented in graphical form for various values of dimensionless parameters. The solutions are compared with published .solutions for radial reservoirs. I NTR ODUCTION The problem of unsteady-state flow of gas through porous media gives rise to a second-order non-linear partial differential equation for which no analytical solution has been found. Numerical approximations to solutions of the gas flow problem have been obtained by the stepwise solution of an associated difference equation1,2. However, the methods so far developed have required that the reservoir be either linear or radially symmetric. This restriction in shape has been necessary so that only two independent variables be considered, namely, one distance variable and time. In order to deal with reservoirs having more realistic shapes, it is necessary to develop numerical procedures for the solution of the gas flow problem involving two distance variables. A numerical procedure, denoted as the alternating-direction implicit method, for the solution of the heat-flow problem in two dimensions has recently been introduced" By the use of this procedure, approximate solutions have been obtained for heat-flow problems in a square8, and in regions having various non-rectangular boundariesa. Because of the similarity between the equation for heat conduction in solids and the equation for gas flow in porous media, it is reasonable to expect that the alternating-direction implicit method should also be useful for solving the gas flow problem in various two-dimensional regions. Solutions have been calculated for the simplest two-dimensional region, a square reservoir with a single well in the center. While reservoirs of such simple geometry seldom, if ever, exist, the solution of this problem is of some practical importance because it is also the solution of another problem, that of determining the depletion history about an individual well in an infinite uniform reservoir containing wells spaced throughout on a square lattice and producing equally from each well. Finally, it is of interest to compare solutions for a square reservoir with those for a circular reservoir and to determine the effect of the shape of the boundary for that particular case. METHOD OF CALCULATION Basic Differential Equation By combining the equation of continuity, the perfect gas law,

Jan 1, 1956

By Fred Wise, C. W. Wark

The Getchell mine, a comparatively recent gold discovery, is in the old Potosi mining district, Humboldt County, Nevada. All ore is mined from open pits using Diesel shovels and gasoline trucks. Two types of ore are mined, oxide and sulphide. Oxide ores are siliceous or shaly; sulphide ores either gougy, siliceous or shaly. In mining, the sulphide ore is segregated into hard and gougy ore, because the gouge must be dried before it can be crushed. The oxide ore is not segregated. General Metallurgy The oxide ore is the leached outcrop that overlies the sulphide ore body. All of the iron and arsenic sulphides found in the sulphide ores have been thoroughly oxidized. The sulphur and arsenic have been leached out while the iron is present as hematite and limonite. The oxide ore is amenable to direct cyanidation, and although no visible free gold is present it is released at a comparatively coarse grind. The sulphide ore is more refractory, since the gold is all of micron size and some of it is locked in fine sulphides. It has been established microscopically that the free gold is coated with an impervious shell, which is probably some form of iron compound. The sulphide ores contain from 1.5 to 2 per cent of arsenic, which is present as orpiment and realgar with minor amounts of arsenopyrite. The orpiment and realgar are of a later mineralization than the gold and are barren. Roasting and washing of the sulphide ore prior to cyanidation is necessary to eliminate , the arsenic, to alter the gold coating from an insoluble form to a soluble form, and to release the gold associated with the fine sulphides. Washing the ground calcine in weak sulphuric acid, trona, or hot water are beneficial in the order named, but to date the water is the best from an economic standpoint. Metallurgical tests as well as plant practice indicate that a certain amount of gold cannot be recovered even by going beyond economic practices. On this basis metallurgical results are viewed in the light of an optimum tailing rather than a percentage of extraction. Milling Practice Crushing (Fig. I).—There are three primary ore bins, one each for oxide ore, gougy sulphide ore, and hard sulphide ore. In front of each bin a substantial yard is maintained, which makes it possible to Stockpile 2500 tons of oxidized ore, 1000 tons of hard sulphide ore, and 1000 tons of gougy sulphide ore. The bins are fed by a 60-hp. caterpillar bulldozer from the stockpiles. Fig. I shows the method and

Jan 1, 1943

By Henry R. Joesting

DURING the past year and a half, the Territorial Department of Mines in Alaska has conducted a modest experimental program for the purpose of determining the extent to which magnetic and resistivity methods can be used in interior Alaska in connection with prospecting, mining and geological studies. Since little information is available concerning previous work,1,2 and since conditions differ considerably from those in most other regions, it was considered advisable to make a general study of the possibilities and limitations of the two methods, rather than a detailed study of any single problem. PROBLEMS One of the most serious handicaps to prospecting and geological study in interior Alaska, especially in the mature regions, is a cover of unconsolidated deposits ranging in thickness from a few feet to several hundred feet. These deposits, some of which are permanently frozen, consist of silt with varying proportions of vegetation and windblown material in the valleys and of residual deposits on the hills.3,4 The problems treated here are caused by the existence of this overburden: I. Location of buried placers. 2. Determination of depth and areal distribution of permanently frozen and of thawed unconsolidated deposits. 3. Location of water-bearing beds under unconsolidated deposits. INSTRUMENTS AND METHODS Magnetic and direct-current resistivity methods were used because they are relatively simple, rapid and inexpensive and because generally they are well suited to the study of the problems indicated. The instruments used were a vertical Schmidt-type magnetometer and a direct-current resistivity instrument similar to those used by the Geophysical Branch of the U. S. Geological Survey.5 For placer surveys with the magnetometer, a sensitivity of about 25 gammas per scale division was found suitable. For resistivity studies of frozen and thawed overburden and of underground water, the Lee partitioning method6 was found to be most generally suitable. In the Lee method a central potential electrode is placed midway between the two potential electrodes of the Wenner four-electrode configuration.7 Nonpolarizable electrodes were made from unglazed porcelain pots about 10 cm. high and 5 cm. in diameter. In order to retard evaporation of the electrolyte the sides of the pots were glazed, inside and out, with clear Duco lacquer. For resistivity work in cold weather, a nonfreezing electrolyte consisting of equal parts of ethylene glycol and a saturated water solution of copper sulphate proved satisfactory. Stainless steel rods of 3/4-in. diameter made excellent current electrodes because their bright finish enabled good ground contacts to be made.

Jan 1, 1941

By B. B. L. Seth, H. U. Ross

A generalized rate equation for the reduction of iron oxide was derived from which two particular equations were obtained: one for rate controlled by the transportation of gas, the other for rate controlled by the phase-boundary reaction. Pellets of pure ferric oxide having diameters of 8.5 to 17.5 mm and a density of 4.8 g per cm3 were prepared and reduced by hydrogen at 750° to 900°C. From the analysis of data obtairzed, it was observed that neither the phase-houndarv reaction nor the transportation of gas controlled entirely the rate of redziction. Rather, the mechanism of reduction can he divided into three stages. In the beginning, the process seems to depend predominantly on the surJrce reaction, hut after a layer of iron is formed the diffusion of gas becomes the controlling factor. Towards the end, however, the rate falls sharply due to a decrease in porosity. The times predicted by the generalized equation for a certain degree of reduction showed an excellent agreement with those obtained experinmentally for pellets of varying sizes. WIDE interest in iron oxide reduction has resulted in many valuable studies pertaining to thermody-namical properties, equilibrium diagrams, and chemical kinetics. Although the thermodynamical properties and equilibrium diagrams are now known with a fair degree of accuracy, the mechanism and rate-controlling step in the reduction of iron oxides presents a problem to research workers which is still unsolved. This is because the field of chemical kinetics is so highly complex. Besides the chemical reaction between oxide and reducing gas, several other processes are occurring simultaneously such as solid-state diffusion of iron through intermediate oxides (FeO and Fe3O4), the diffusion of reducing gas inwards and of product gas outwards, and the sintering of iron if reduction is carried out above the sintering temperature of iron. Furthermore, there is a large number of variables, including the nature and flow rate of the reducing gas, the chemical composition and physical properties of the ore, the temperature of reaction, particle size, and so forth, all of which can affect both the mechanism and the kinetics of reduction. Despite the controversy and diversity of opinion about the mechanism of iron oxide reduction, three main schools of thought have emerged. According to the first, the rate is controlled by the diffusion of gas through the boundary layer of stagnant gas; the second claims that the rate is proportional to the area of the metal-oxide interface, while the third believes the transportation of reducing gas from the main stream to the metal-oxide interface and of product gas from the metal-oxide interface to the main stream to be the rate-controlling step. 1) The boundary-layer theory is true mainly for packed beds where the flow of gas through the bed is important. For a single particle, the boundary layer may be prevented from being the rate-controlling step if a gas flow rate of reducing gas above the critical flow rate is used. 2) Several workers have reported a linear advance of the Fe/FeO interface which provides excellent support for the belief that reduction is controlled by the surface area. McKewanl has given formal shape to this concept with mathematical derivation and has shown it to be valid for reduction of several iron ores, hematite, and magnetite, both by H2 and H2, H2O, N2 mixtures. Some other investigators, however, do not find this theory to be entirely valid. Deviations have been observed2 and further confirmedS3 Hansen4 also agrees that deviations do occur, at least in the latter stages of reduction, while from the data of several investigators summarized by Themelis and Gauvin,5 it is clear that the theory is not always applicable and further that, when it is applicable, it does not hold in the final stages of reduction. 3) Among those who claim the transportation of gas to be the rate-controlling step are Udy and Lorig,6 Bogdandy and Janke,7 and Kawasaki el a1.8 The validity of the theory has also been acknowledged indirectly by other research workers who show that the sintering and recrystallization of iron cause a decrease in reduction rate, for it is only if the transportation of gas is important that this sintering has any bearing. However, the theory has been rejected by some because they have failed to obtain

Jan 1, 1965

Human engineering was the keynote of the thirty-ninth annual meeting of the American Society of Mechanical Engineers, which was held in New York, December 3-6. This note was sounded by President Charles T. Main in his address at the opening session and was carried through by all the speakers. In his survey of the year's work, he said that more than 6000 names of engineers were furnished the Government for filling a wide variety of positions. In addition to the 1400 members in service, two members of the council of the society are in uniform in France and one, as a distinct war service, is in charge of one of the largest shipyards. After giving other ways in which the Society has helped the Government, President Main called attention to the necessity for thoroughgoing efforts to increase production and the settlement of questions involving industrial relationships. At the following meeting, President Adams of the American Institute of Electrical Engineers called attention to the necessity of meeting labor in a progressive way, facing labor questions fairly and squarely, as the real interests of labor cannot be separated from those of the engineer. Charles E. Knoeppel, discussing "Industrial Organization as It Affects Executives and Workers," said the problem of the cost of living might be settled in two ways: 1, there must be more producers, and 2, there must be a greater amount supplied by those now producing. The first solution is practicable, he said, if labor is allowed shorter hours, better conditions, and a remuneration that will attract workers. The second can be employed by eliminating waste, standardizing conditions, setting fair tasks, and allowing men to earn an amount that will compensate them for' their skill and cooperation. Dudley R. Kennedy of Philadelphia, employment manager of the American International Shipbuilding Corporation, said the human-engineering phase of the country's industrial development had generally been overlooked. "We hardly yet know what competition means; we will learn it within a few years. Permit me to prophesy that the executive of the next decade will be the man who best knows men. He will be an originator, a handler of men as individuals, a handler of men in the mass, a leader not a driver, a very human man. The science of human engineering is here to stay. The study of human characteristics is the most enduring, as well as the most fascinating in the world, and still the most complex."

Jan 1, 1919

By F. M. Waring

produced when zinc is substituted for a certain amount of tin are decidedly unsatisfactory. The substitution of aluminum for tin is entirely impractical, and such castings are worthless. This does not, however, exhaust all the possibilities of substituting other metals for tin in the copper-tin-lead alloys, but it is my opinion that the substitution of any other metals, in those alloys, can be made only by sacrificing the quality of the alloy. The possibility of substituting alloys of an entirely different type presents an attractive field for research. The copper-tin-lead alloy has attained its position as the most desirable bronze bearing alloy, but this does not mean that some other alloy may not be found which may give equally good or better results. In the search for such a substitute alloy it should be borne in mind that a bearing metal should possess the following properties: (1) It should be sufficiently rigid to support the load or resist the impact, but yet not so brittle that it will easily crack. (2) It should have as great a yielding or plastic nature as is consistent with its ability to support the load or resist the impact without deformation of the bearing as a whole. (3) The ideal structure combines a hard matrix to support the load and a softer metal or alloy contained within such matrix, to permit the bearing surface to adjust itself to irregularities of service. (4) It should be easy to handle in the foundry and machine shop. (5) It should be capable of being remelted without deterioration. (6) For use in babbitt-lined bearings, it should be capable of being tinned, so that the babbitt can be applied thereto. (7) It should have good heat conductivity in order to dissipate the heat generated by friction. Pennsylvania Railroad Anti-friction and Bell Metals F. M. Waring," Altoona, Pa.—Thc necessity for conserving tin has recently been very forcibly brought to the attention of all consumers, and efforts are now being made to reduce the tin content in certain alloys or to substitute other alloys not containing tin. The approximate composition of the non-ferrous alloys in general use on the Pennsylvania Railroad are given in the accompanying table. Phosphor bronze is used principally for rod bushings, main-rod brasses, and crosshead shoes. Ex. B bronze is used to a small extent for backs of car and coach bearings, but the majority of these are now made of the car-journal bronze, which contains, on the average, about 5 per cent. tin.

Jan 1, 1919