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By M. L. Hammond, G. M. Bowers

Silicon dioxide films have been prepared on silicon wafers by the oxidation of SiH, near 400°C. Results previously reported by Goldsmith and Kern7 have been qualitatively corrobovated using a system of different geometry, and significantly greater deposition rates have been achieved. The deposition rate is independent of thickness and nearly independent of the O2/SiH, ratio over a wide range; however, the rate is strongly temperature-dependent. The structure of the deposit depends upon the cleanliness of the substrate, and the electrical field strength of the deposited oxide depends upon the nature of the electrodes. MULTILEVEL interconnects in integrated circuits using aluminum metallization require an insulator that can be deposited at low temperature. Because the A1-Si eutectic is only 577°C, the maximum deposition temperature must be below about 500°C to prevent reaction of the aluminum with the silicon and with other materials in the integrated circuit. Many methods of depositing insulating films of SiO, and other dielectrics have been reported'-6 but the technique described by Goldsmith and Kern7 offers the simplest method of preparing SiO, films. The technique involves the reaction of SiH, and 0, to form SiO, films in the 300" to 500°C temperature range. Previous work using this gas system has been reported8 and the initial development work at Philco Microelectronics was done at the East Coast R&D Laboratories. 9 This paper corroborates some of the results of Goldsmith and Kern,7 shows that much higher deposition rates can be obtained than previously reported, and presents some observations on the structure of deposited SiO, films. EXPERIMENTAL CONDITIONS Fig. 1 is a schematic drawing of the apparatus used in this study. It differs from that of Goldsmith and Kern in that 1) the gases are mixed before they enter the reaction chamber, 2) there is no fritted glass diffuser, and 3) the wafers are stationary during deposition. The control thermocouple was in a well located 0.06-in. from the substrate, and three gas supplies were used: 1 pct SiH4 in N 2, O 2, and N 2. Water vapor must be excluded from the plumbing to prevent the formation of colloidal SiO, and the SiH4 must be diluted with an inert gas because SiH4-0, mixtures are extremely flammable above about 4 pct SiH The wafer temperature was determined by attaching a thermocouple to a test wafer and the temperature was maintained to +5 C. The conditions used in this investigation are listed in Table I. The temperature range was chosen for compatibility with the A1-Si system. The volume ratio of 0, to SiH4 is the actual volume of 0, delivered to that of SiH4, taking into account the initial dilution of the SiH4. This ratio, which was used by Goldsmith and Kern,7 is a useful indicator of the experimental conditions. The active/inactive ratio is the ratio of the volume of active gases, SiH4 and O2, delivered to the volume of dilution gas. The active/inactive ratio is an important parameter to specify for deposition rate determinations since it determines the amounts of reactants that arrive at the sample per unit time. Fairly high dilution ratios were necessary to achieve uniform deposits of SiO,. Most of the process characterizations were performed on the polished (111) face of 3 to 5 ohm-cm, n-type silicon wafers which were 0.009 in. thick; but the data approximately apply to deposition of SiO, on thin films of aluminum. It is difficult to obtain accurate deposition rate data over aluminum films because of coarsening the aluminum surface during exposure to 300" to 400°C. The deposited SiO, film fol-

Jan 1, 1969

By H. A. Tobelmann

age Introduction ............................. 22 Crushing............................... 25 Leaching............................... 28 .Reduction.............................. 47 Electrolytic Deposition..............a.......... 51 Discard for Purification of Electrolyte.................. 60 Recovery of Copper from Discard Solution .............. 62 Resolution of Cement Copper...................... 64 Summary............................... 64 Appendix............................... 66 Discussion............................... 69 Introduction The location, mode of occurrence of ore, and preliminary tests leading to the development of the present leaching process and the building of the present plant on the property of the New Cornelia Copper Co. at Ajo, have been described in previous papers presented to the Institute and in the discussions thereof.l It is sufficient to say that these tests began early in July, 1912, and were continued to the close of January, 1916; that small tests at Douglas were followed by the construction of a 1-ton plant at the mine; and this was followed by the operation of a 40-ton plant for 11 mo. In all about 15,000 T. of ore were treated experiment-

Jan 1, 1919

By George J. Clark

One of the major problems of operation in the anthracite industry is the disposal and handling of refuse—not because of its complexity but because of the quantity and type of material involved. It is the purpose of this paper to describe the kinds of refuse, methods of disposal, quantities of material to be handled and equipment used, together with present day application at specific operations in the Northern, Eastern Middle, Western Middle and Southern anthracite fields. For the purpose of this paper, refuse is considered to be any material that has no present or foreseeable future value and that must be handled and disposed of in the process of mining and preparing anthracite for market. Included in this classification are tunnel rock, mine rock, cleaner plant refuse, breaker refuse, old timber, ashes and silt. Disposal Methods Old timber is disposed of either by burning or by depositing on the refuse bank. Burning is preferred because timber on the refuse bank is a potential fire hazard. Ashes are deposited on a separate bank, mixed with other refuse, or flushed into old mine workings. In many places, the latter practice has caused considerable difficulty in preparation of coal mined from these areas. In depositing ashes on the surface, it is wise to refrain from mixing them with material containing coal as such contamination may prevent reclamation of the coal in future years. Tunnel work, mine rock, cleaner plant and breaker refuse compose the bulk of the material to be disposed of and handled, and are referred to collectively as "refuse" in this paper. Waste material in or adjacent to the coal beds may be removed at the working face wherever possible. This can be done in flat or lightly pitching beds, and in the Northern field represents a sizable percentage of this type of refuse handled. In the other three coal fields, this method of disposal cannot often be used. Refuse not removed at the working face is taken to the surface and generally is deposited on banks; occasionally it is crushed and flushed into old mine workings. Breaker refuse often is used for constructing berms for silt-retention basins. Disposal Problems The problem of handling refuse is different for each operation, owing to topographical conditions, quantity of material to be handled, anticipated requirements and types of equipment in use elsewhere at the operation. Preparation plants with limited refuse-disposal areas, excessive grades to reach the required elevation and long hauls to disposal areas not readily accessible require the selection of equipment to best meet the conditions. The quantity of refuse to be handled from a given amount of raw material varies considerably throughout the four fields. In mine coal, this varies from a low

Jan 1, 1949

By T. L. Loucks, E. T. Guerrero

Pressure drop characteristics in a system composed of two adjacent concentric regions of different permeability were studied. The differential equations for continuity of mass flow in the two regions were solved using the Laplace transformation and the necessary boundary conditions to give the pressure distribution in the composite reservoir, the resulting equation for pressure drop at the inner boundary was evaluated for a variety of composite reservoirs and compared with the results for a uniform reservoir. From this study it was found that under certain conditions the permeability in both zones, as well as the size of the inner zone, can be determined from the pressure drop curve. INTRODUCTION The theory for the pressure distribution and pressure build-up behavior of a well producing a single, slightly compressible fluid from infinite and finite homogeneous reservoirs was presented by Hornerl and Miller, Dyes and Hutchinson.2 Extensions on this original work to provide improved and extended interpretations and better agreement between theory and observed results have been made by Matthews, et a1,3 van Everdingen,4 Gladfelter, et al5 Stegemeierand Matthews,6 Hurst and Guerrero,7 and Perrine.8 More recently Lefkovits, et al,9 studied pressure build-up behavior in bounded reservoirs composed of stratified layers. Houpeurtl0 has suggested various approaches to the general problem of variable permeability and porosity but presented no analytic solutions for particular permeability variations. Albert, Jaisson and Marionll studied the finite composite reservoir and presented numerical solutions to the unsteady-state case and an analytical solution valid only for large times. They also studied the so-called pseudo-steady state for several examples of radial permeability variations. Very similar examples have been treated in the unsteady state with application to pressure build-up by Loucks in an unpublished manuscript. More recently Hurst12 has presented the complete point-sink solution (valid for all times) for the infinite composite reservoir. He applied these solutions to interference between oil fields along with an even more elegant application of his explicit solution to the material-balance equation including water influx. Mortada 13 approaches the same application by avoiding the point-source limitation but gives the solution for the aquifer region which is valid only for large times. Hopkinson, Natanson and Temple14 have treated both the finite and infinite composite reservoir obtaining the pressure distribution for the inner zone valid for large times. This paper presents a theoretical study of the pressure distribution in an infinite composite reservoir composed of two adjacent concentric regions of different permeability. The object was to determine the manner in which pressure drop at the inner boundary of a composite reservoir depends upon time, the permeability of each zone and the size of the inner zone. Expressions for the pressure distribution in both zones are developed which take into account the radius of the sink and are valid for small times as well as large times. It was felt that an understanding of the pressure drop behavior in various composite reservoirs would be of assistance in the interpretation of some pressure build-up curves which do not behave according to the theory derived for uniform systems. Often the region surrounding the wellbore is either more permeable or less permeable than the reservoir because of the various drilling and completion practices. The effects of reduced permeability due to drilling-fluid invasion and of increased permeability due to fracturing or acidizing need to be more carefully defined. Therefore, an equation for the pressure drop in a composite reservoir was developed, and the effects of both the permeability in each zone and the size of the inner zone were studied. STATEMENT AND SOLUTION OF PROBLEM BOUNDARY CONDITIONS AND ASSUMPTIONS The physical system studied was a composite

By GUY C. RIDDELL

ZINC, manganese, and aluminum received attention at the two nonferrous metallurgy sessions at the Annual Meeting. L.P. Davidson, general superintendent of the rebuilt Monsanto zinc plant, described its operation, which reflects Polish practice and is really a combination of electrolytic, Waelz, and retort procedure. Briefly, it embraces leaching of roasted concentrate with sulphuric acid, electrolysis of sulphate solution using Tainton lead-silver anodes with ?goulac? added to the electrolyte, treatment of tailing in Waelz kilns, and retorting of the recovered zinc oxide, casting furnace dross and residues. Recovery is good, equipment and maintenance costs low. Ferrate zinc that might be lost in the electrolytic process appears to be recovered as oxide in the Waelz treatment.

Jan 1, 1942

By Browne TJ

On 13 October 1993, a shallow earthquake registering 7.1 on the Richter Scale occurred near Tauta in the Finisterre Range of Papua New Guinea (PNG) killing 37 people. The aftershock series lasted three months and resulted in considerable landslide damage that destroyed villages, food gardens and airstrips, and blocked rivers causing catastrophic flooding. These effects have irrevocably altered the form of many of the valleys and rivers draining into the Markham and Ramu valleys.The earthquake occurred in a pilot study area for a landslide hazard mapping project being carried out by the PNG Geological Survey that commen-ced in April 1993. Comparisons made between areas identified as unstable during the study with those damaged by the earthquakes show good correlation.It is concluded that aerial photograph and Landsat TM imagery interpretation can be used with a high degree of confidence to identify potential landslide hazards in mount-ainous terrain. Landslide hazard maps are promoted as a tool for use in the route planning of roads and powerline corridors, as well as for identifying vulnerable communities.

Jan 1, 1994

By Frank Foote, Eric R. Jette

In a recent article,1 the authors reported the results of an X-ray investigation on the range of solid solutions that occurs in the iron-oxygen system in the vicinity of the compound FeO, which frequently is called "wüstite." The object of that investigation was primarily to study the unusual type of solid solution phenomena involved in this range. Briefly summarized the results were: 1. The NaCl type of lattice found by earlier workers was confirmed. 2. The lattice dimensions decrease rapidly with decrease in iron content. 3. No alloy that was a homogeneous single phase was ever found at compositions beyond 76.80 per cent Fe, while the theoretical iron content of FeO is 77.73 per cent Fe. 4. Measurements of the densities and lattice constants led to the conclusion that the form of substitution was complex, an FeO group being replaced by oxygen. Such a substitution, of course, is equivalent to removing an iron atom (or ion). The ideal unit cell of FeO can be considered as containing four groups of FeO and, thus, when this type of substitution takes place, there remain in the unit cell three FeO groups and an oxygen, or a total of seven atoms with a gross formula of Fe3O4 instead of the original Fe4O4. 5. This was the only interpretation that would fit the experimental results and at the same time be consistent with (a) the previously determined fact that the FeO lattice is ionic (i, e., consists of Fe++ and O? ions) and (b) the chemical fact that as the oxygen content of the substance increases, ferrous iron becomes oxidized to ferric iron. The experimental results of this investigation are included in Fig. 1. The purpose of the present investigation was to determine the limits of this homogeneity range by means of the X-ray structure analysis. This method has been applied frequently to the study of solid solutions by Westgren and his coworkers as well as by other investigators. The principle is simple: if the change in lattice constant with composition is

Jan 1, 1933

By L. W. Bahney

Many methods for the determination of gold or silver, or both, in cyanide solutions have been published, which with care in manipulation, and modification in some cases, will give results that are satisfactory. It is possible to classify or group these methods as follows: 1. Evaporating the solution in a porcelain or agate-ware dish containing litharge,l or in a "boat" made of lead foil. 2. Forming a lead sponge containing the precious metals by means of zinc shavings,2 zinc dust,3 or a piece of aluminum.4 3. Decomposing the cyanide solution with an acid and precipitating the precious metals by the use of one or a combination of some of the following: Copper sulphate,5 sodium sulphite,6 hydrogen sulphide,' cement copper.ll 4. Precipitating the silver by zinc dust held in a Gooch crucible and determination with a standard solution of sulphocyanate.9 5. Electrolysis.l0 . 6. Colorimetry.ll

Jan 1, 1915

The Australian lead-zinc industry faces a future in which the world market is likely to show at best only minimal growth and in which there will be increasing competition. Its production facilities use mature technologies employing expensive labour and increasingly costly energy in a country which demands the highest standards of environmental performance. Returns on investment are already unsatisfactory.Technology for survival would appear to indicate a need not only for more efficient capital, labour and energy usage combined with improved environmental performance, but also flexibility to handle more complex materials than the traditional, virtually single metal concentrates. This offers the potential for improved overall economics from the mine onwards, but will demand efficient separation and by-product recovery processes.In the lead industry these problems are being addressed in several emerging technologies. With zinc, the situation is less clear.

Jan 1, 1985

By M. Jaramillo

The expanded west pit of the 15 Mta (13.6 stpy) El Cerrejon mine will eventually reach a maximum depth of 270 m (890 ft). Slope-stability evaluations indicated that this depth, combined with structural complexities, would create a serious risk of footwall instability. Stabilization calls for anchoring the footwall by the installation of 9- to 33-m- (30- to 108 ft-) long multistrand steel cable bolts. For each of the 15-m- (50-ft-) high mining benches, a row of bolts is installed with variable horizontal spacing, depending on the dip magnitude. Cable bolting is now standard operating practice, and an estimated 11,800 bolts will be installed during the life of the mine. Results to date have been satisfactory in terms of the stability condition of the bolted slopes.

Jan 1, 1997

By Juan José Retamozo Padilla

El presente texto señala los beneficios de la gestión en salud ocupacional a través de NATCLAR, empresa con estándares OIT (Organización Internacional del Trabajo) de Gestión de Salud Ocupacional y Competencias Laborales del Perú. En este sentido, el estudio de causalidad de los riesgos o accidentes de trabajo nos derivará a causas inmediatas y básicas, las cuales se dividen en factores personales y de trabajo, para así identificar peligros y evaluar los riesgos directamente relacionados a la salud de los trabajadores por grupo ocupacional. Asimismo, contribuir con la empresa para evitar problemas legales, laborales y en beneficio de la salud del trabajador a partir de una adecuada planificación de perfiles de evaluaciones médicas específicas y finalmente, contribuir a la maximización de la productividad de los trabajadores a través de un programa de recuperación física para las personas con alteraciones anatómicas.

Sep 14, 2009

By L. Eros, R. H. King

The US Bureau of Mines has funded several research and development projects in computerized mine monitoring and control. Hardware and software components have been sufficiently developed so that mine operators have been provided with an efficient means to comply with federal regulations and increase mine safety. Several cost benefits have been realized as well, particularly with increased conveyor belt haulage availability. Western Fuels-Utah Inc. approached the Bureau to assist in planning, installing, and evaluating a computerized mine monitoring and control system because of the agency's research experience in this area. The installation was planned for Western Fuel's Deserado mine, located in Rangely, CO. Since a large, complex, underground mine producing about 2.4 Mt/a (2.7 million stpy) of coal was projected, the company anticipated significant benefits in safety and efficiency through a computerized monitoring and control system. A major part of the cooperative program was to document and evaluate the system design, installation, and operation. This will assist others to adequately design, specify, install, and operate future systems. Mine description The Deserado mine plan and layout have important impacts on the monitoring system requirements. Long range plans are to produce 2.4 Mt (2.7 million st) of clean coal annually from two longwall sections and four continuous sections. Presently, two continuous miner sections operate under 213 m (700 ft) of overburden in the 2.3 to 2.5 m (7.5 to 8.5 ft) thick D seam to develop main, submain, and panel entries have developed for a longwall. These began operation in December 1986. Belt conveyors haul the coal from the mining sections to a 1.4-m (54-in.) belt located in the upper compartment of the slope. The lower compartment contains a hoist for men and material transport. From the slope, the coal moves to two 9 kt (10,000 st) raw coal storage silos, then to a 680-t/h (750-stph) preparation plant. After cleaning, a 5.5-km (3.5-mile) overland conveyor carries the coal to a clean coal slot storage and rail load-out facility. An electric locomotive then transports the coal to the Bonanza Power Plant in Utah. Allen-Bradley monitoring and control hardware and software controls the preparation plant, with two PLC-3 programmable controllers and a Process Control Industries D-1200 color graphics interface. The system operator uses three "smart" color video display units and an alarm printer for hard copy records. Originally, it also monitored and controlled the conveyors from the bottom of the slope to the top of the raw coal silos, the preparation plant, the overland conveyors, the main mine ventilation fan, and the hoist. Some of these features, though, were later transferred to the mine system.

Jan 2, 1988

By Etienne A. Ritter

The Evergreen mine, located at Apex, in the northern part of Gilpin county, Colorado, has opened a very peculiar and interesting copper-deposit, in which both bornite and chalcopyrite occur as rock-minerals. The country-rocks are crystalline schists cut by dikes of granu-lite and of pegmatite. At the Evergreen property they have been cut by a dike of a uew kind of eruptive rock, to which I have given the name " Evergreenite." The rock is composed of quartz, alkali feldspars, orthoclase and albite (often interlocked as microperthite), with augite of the ægirine variety and long needles of enstatite and diallage. For reasons stated below, I believe the dike to be of Tertiary age. It is easily traced on the surface of the ground, from a point in the bottom of Pine creek, about a mile below Apex, to the top of Nevada hill, 1,500 ft. beyond and 600 ft. above it. (See Fig. 1.) It varies from 3 to 12 ft. in width, and is bounded on both sides by contact-zones about 60 ft. wide, in which the crystalline schists have been changed into pseudo-quartzites or pseudo-gneisees, according to the injection of an excess of quartz or of feldspars through the special layer of the schists. The most interesting feature is the presence of the pyroxenes, which are always found, though in very variable proportions from place to place, in the layers of these metamorphosed crystalline schists. The dike has torn from its walls a large number of fragments of the wall-rock. It must have been in a viscous state when that happened, because these fragments of the wall-rock do not show any sign of resorption or of assimilation by the magma. In places they are so distinct and so numerous that the rock looks to the naked eye like a pseudo-breccia, of which, never-

Jan 1, 1908

By F. P. Schwarz, A. J. Erickson, S. M. Weber

The Mount Hope stockwork molybdenum exposit, Eureka County, Nevada, occurs in a small igneous cauldron complex 32 to 38 mybp in age. The deposit is characterized by alteration zones and mineralized shells symmetrically distributed around multiple intrusives. For samples from the 25 000 meters of 1981-82 drilling, an appraisal of error in in-house sample preparation and in commercial assaying has been made. After splitting, drill core is crushed and reduced in volume (8:1 at 10-mesh, 8:1 at 70-mesh, 6:1 at 200-mesh) to supply 25 grams of 200-mesh pulp for replicate analyses. A 0.5 g portion of the pulp is used for dissolution and atomic absorption analyses. Factors which initially generated unacceptable data variances have been minimized by planning, repeat analyses, introduction of standards, and routine monitoring. Assuming that error between replicate assays defines a Gaussian distribution with its average ideally equal to zero, precision (from preparation including core splitting and analysis of 8400 pairs of molybdenum samples) is on the order of + 25%. The error distribution is not biased. Accuracy is approximately 4% lower than absolute as determined by replicate assays of commercially prepared samples.

Jan 1, 1992

By Lockhart D. A, Gleeson P, Lang S. C

The Glenrock Group forms the uppermost part of the Early Devonian to Early Carboniferous Burdekin Basin sequence in the Townsville hinterland, north Queensland. As redefined, three formations make up the Glenrock Group. The Percy Creek Volcanics (base), the dominantly epiclastic Mount Douglas Formation, and the Horse Pocket Volcanics (top). The Ellenvale beds unconformably overlie the Mount Douglas Formation and Percy Creek Volcanics and have been excluded from the Glenrock Group as defined by Wyatt and Jell (1980). Three facies associations are recognised in the Mount Douglas Formation: Alluvial Plain facies, Alluvial Fan facies and Lacustrine facies.Deposition of the Glenrock Group, began with the eruption of massive basalt and basaltic andesite lavas, probably in a volcanic arc setting. With time, the volcanism evolved to become more dacitic to rhyolitic in composition. Waning of the volcanic activity appeared to coincide with uplift of source areas (probably to the west). Deposition on an alluvial plain during this waning volcanic cycle, gave way to alluvial fans at the margins of the uplifted terrain. As the uplift ceased and the system became more mature, the alluvial fans gave way to widespread lakes. Rhyolitic ignimbrite and airfall tuff, interbedded with the alluvial plain, alluvial fan and lacustrine facies, indicate that some volcanism continued, probably vented in the uplifted terrain to the west.

Jan 1, 1990

By Leon Dominian

(Wilkes-Barre Meeting, June, 1911.) I. INTRODUCTION. THE lack of Aryan roots for the names of metals commonly known among the Aryan settlers of Asia Minor, as well as the later colonizers of Europe, indicates that these races were generally ignorant of the use of metals until they came into contact with Semitic peoples. Practically all mining-terms in current use among the earliest Greeks resemble very strongly their distinctly Semitic equivalents, which can be traced all the way in a broad belt beginning in Lower Mesopotamia, and extending westwardly to the Syrian shores of the Mediterranean. The Greek word " "metallon," for instance, used indiscriminately to designate mine or ore, probably came from the earlier Semitic equivalent, " matal." Again, the Greek words " chrysos " (gold) and " chalkos " (copper) seem to be descended from the Semitic forms " throats " and a chalak." It is a natural inference that primitive mining-methods were evolved by the dwellers in the mineralized areas of Asia Minor, from whom later Greek, Roman, and even North European miners obtained their first notions of the reduction of metallic ores, by virtue of a general westward migration of mining and metallurgy. Some traces of its passage through Turkish territory will be noted in this paper. While European Turkey can boast of one ancient gold-field, the Asiatic dominions of the Sultan may lay claim to at least two well-defined and widely-separated gold-producing districts. These three regions may be distinguished as the Thracian, the Pontic, and the Anatolian gold-fields. II. TURKEY IN EUROPE. . The Thracian Gold-Field. The most conspicuous topographic feature of the lowland between Constantinople and Salonica is the uplifted Archaean

Nov 1, 1911

By P. K. Davis

The results of a previous basic study of the flow and design characteristics of the hydrocyclone has shown that a recovery as high as 99% with a product rating of 0.95 can be achieved on a "batch?2 basis with a single, water-only cyclone if it is configured properly. The next logical step was to demonstrate continuous processing of gob for the efficient recovery of coal by means of a laboratory-size demonstration system. A project to design and construct such a single-cyclone system was also sponsored by the U.S. Department of Energy. A recovery of 93% with a product rating of 0.89 was demonstrated. The system design and the data taken are discussed.

Jan 1, 1989

By W. A. West

One who attempts to collect and classify equilibrium data from various iron-alloy systems is soon struck with the absence of any quantitative theory that can serve as a general background against which to compare and contrast results from different systems, at different temperatures, and with different concentrations. It is not necessary to wait for a perfect theory; investigation of divergences of theory from observation may prove of great value in acquiring understanding of the subject. For example, one has only to think of Raoult's law as applied to aqueous solutions. The equations developed by Zener1 represent an effort to provide such a quantitative theoretical background, and it is therefore desirable to subject this theory to such tests as can be applied. The present article is intended to be an application of available tests, and may thus be considered as a supplement to Zener's paper. It is assumed that this paper is available to the reader. The equations make it possible to calculate the effect on the equilibrium concentration of one alloying element due to the presence of one or more other elements. In particular. they are intended to give, for alloy steels, the carbon concentrations in alpha and gamma phases in equilibrium with each other, and in gamma in equilibrium with cementite. They may, however, be modified for use for carbon-free alloys. A summary is given later of the equations used in analyzing the data in this paper, and the symbols are there defined. About 125 papers have been examined for experimental data suitable for this investigation. An effort was made to look up all available reports of ternary systems including iron and carbon, as well as similar systems of higher order. Supplementary material was also obtained from a number of binary systems. A few noncarbon ternary systems were also found to which these methods could be applied. A comparatively small proportion oi the papers read provided usable material. In many systems the number of quantitative observations made in the iron-rich region is extremely small, and the smoothed curves to be found in most published phase diagrams are entirely useless for quantitative treatment. This opinion is confirmed by the authors of the series on Alloys of Iron Research, whose remarks show clearly that they have no illusions as to the accuracy of many diagrams that they present. A further difficulty arises from the fact that these equations apply only to rather low percentages of alloying elements. The result is that at the lowest concentrations, where the best agreement might be hoped for, the errors of observation become relatively very large. The experimental difficulties in measurements of this kind of equilibrium are, of course, an old story.

Jan 1, 1947

By W. A. West

One who attempts to collect and classify equilibrium data from various iron-alloy systems is soon struck with the absence of any quantitative theory that can serve as a general background against which to compare and contrast results from different systems, at different temperatures, and with different concentrations. It is not necessary to wait for a perfect theory; investigation of divergences of theory from observation may prove of great value in acquiring understanding of the subject. For example, one has only to think of Raoult's law as applied to aqueous solutions. The equations developed by Zener1 represent an effort to provide such a quantitative theoretical background, and it is therefore desirable to subject this theory to such tests as can be applied. The present article is intended to be an application of available tests, and may thus be considered as a supplement to Zener's paper. It is assumed that this paper is available to the reader. The equations make it possible to calculate the effect on the equilibrium concentration of one alloying element due to the presence of one or more other elements. In particular. they are intended to give, for alloy steels, the carbon concentrations in alpha and gamma phases in equilibrium with each other, and in gamma in equilibrium with cementite. They may, however, be modified for use for carbon-free alloys. A summary is given later of the equations used in analyzing the data in this paper, and the symbols are there defined. About 125 papers have been examined for experimental data suitable for this investigation. An effort was made to look up all available reports of ternary systems including iron and carbon, as well as similar systems of higher order. Supplementary material was also obtained from a number of binary systems. A few noncarbon ternary systems were also found to which these methods could be applied. A comparatively small proportion oi the papers read provided usable material. In many systems the number of quantitative observations made in the iron-rich region is extremely small, and the smoothed curves to be found in most published phase diagrams are entirely useless for quantitative treatment. This opinion is confirmed by the authors of the series on Alloys of Iron Research, whose remarks show clearly that they have no illusions as to the accuracy of many diagrams that they present. A further difficulty arises from the fact that these equations apply only to rather low percentages of alloying elements. The result is that at the lowest concentrations, where the best agreement might be hoped for, the errors of observation become relatively very large. The experimental difficulties in measurements of this kind of equilibrium are, of course, an old story.

Jan 1, 1947

To be held from the 9th to 14th April, 1972, in Johannesburg, South Africa. GENERAL INFORMATION The first symposium in the series was staged by the University of Arizona in 1961. Since then Stanford University, Colorado School of Mines, Pennsylvania State University and the Society of Mining Engineers of the American Institute of Mining, Metallurgical and Petroleum Engineers have acted together with the University of Arizona as co-sponsors of the series. The 9th Symposium in 1970 was sponsored by the Canadian Institute of Mining and Metallurgy together with McGill University and Ecole Poly technique in Montreal. The 10th Symposium, the first to be held outside the North American continent, is being organised by the South African Institute of Mining and Metallurgy (with the Council for Scientific and Industrial Research and the South African Council for Automation and Computation) in close collaboration with the previous co-sponsors. OBJECTIVES Mineral ventures increase in scale and complexity. The planning and control of these projects requires more and more sophisticated techniques. The intention of the symposium is to pool and exchange experience and knowledge and also to discuss new and potential developments. The papers presented in the main sessions, which will extend over one week, will together indicate progress which has been made in the successful application of operations research, mathematical, statistical and computer methods in each of the various aspects of operation in the mineral industry. A coherent account will be developed by consideration, in consecutive sessions, of the stages through which mineral prospects evolve in the course of their life. Primary aims are thus to stimulate discussion in depth of previous applications, to highlight current trends and to provide guidelines for future developments. PARTICIPATION The intention is to bring together persons responsible for managing the various operations in the mineral industry and the workers engaged in the development of mathematical and computer methods relevant thereto. SYMPOSIUM TOPICS 1. Market Analysis-demand and supply trends, models of mineral markets, price prediction. 2. Exploration and ore reserve estimation--exploration strategies, choice of drilling and sampling patterns, quantification of geological information, geo-statistical analysis, ore reserve assessment. Storage and retrieval of associated data. 3. Project design and analysis-influence on viability and risk of capitalisation, scale and method of operation, processing, uncertainties in design premises. 4. Planning of operation-planning and scheduling of construction, of development and of depletion of ore reserves. Logistics, rock mechanics and ventilation. 5. Control of operations-financial, production, cost and quality control as applied to both mining and processing. Flow and processing of relevant information. CALL FOR PAPERS An invitation is extended to intending authors to submit a synopsis, in 200 to 300 words, of papers which would develop the themes outlined above. The Programme Sub-Committee will choose, on the basis of these synopses, some 20 to 30 authors who will be invited to submit papers. Selection will be aimed at the provision of a coherent structure. Other authors may be invited to submit short papers either as contributions to the primary papers or for brief discussion in ancillary sessions which will be scheduled to follow on the main sessions. The official language of the symposium will be English. DEADLINES Prospective authors must submit synopses of papers by ............end April, 1971 Authors will be informed of results of selection of papers by . . . . . . . end June, 1971 Manuscripts will have to be in the hands of the Editors by . . . . . . . . . end October, 1971 PRE-PRINTS Papers selected for presentation in the main sessions will all be pre-printed and distributed prior to the symposium. As many as possible of the shorter papers and prepared contributions will also be pre-printed. PROCEEDINGS All of the main and ancillary papers together with edited discussion will be published shortly after the symposium in a single volume. TOURS AND VISITS A choice of visits to relevant local undertakings on a day during the course of the symposium will be available to participants. These will include a deep level gold mine. A tour which will include mineral projects of interest and the Kruger National Game Park will be arranged in the week following the symposium. LADIES' PROGRAMME Arrangements will be made for the reception and entertainment of ladies. ACCOMMODATION Accommodation will be available at hotels convenient to the symposium venue. The cost of reasonable hotel accommodation in Johannesburg is in the range R5 to RIO (7 to 14 U.S. dollars) per person per night. All reservations and associated arrangements may be made through agents to be appointed by the organisers in due course. FEES AND COSTS Symposium fees will not exceed R70 (100 U.S. dollars). These will include registration, one copy of the published proceedings, a set of pre-prints of the main papers, teas and lunches during the course of the symposium, and the various official social events as well as the mid-week visits. Accommodation, travel and post-symposium tour charges are not included in this figure. FURTHER INFORMATION All communications should be addressed to: The Secretary, South African Institute of Mining and Metallurgy, Kelvin House, Hollard Street, Johannesburg, South Africa.