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The reported values of the standard reduction potentials of the Au(NH3)2+/Au(0) and Au(S2O3)23-/Au(0) couples are reviewed to emphasise the experimental difficulties associated with the measurement of reliable values for these quantities. The standard reduction potential for Ag(I)/Ag(0) in ammonia and thiosulphate solutions measured at ionic strength 0.1 and 25oCis used to predict the following relevant stability constants () for gold complexes based on the linear free energy correlations: Au(NH3)2+2 = 1013, Au(S2O3)23-2 = 1024 and Au(NH3)43+4 = 1033. The equilibrium constant ( 10-11) for the reaction Au(S2O3)23- + 2NH3 = Au(NH3)2+ + 2S2O32- based on these stability constants is in reasonable agreement with the measured value (10-9) based on potentiometric and spectroscopic data when excess ammonia was added to a solution of Na3Au(S2O3)2. This also indicates that the stability constant of Au(NH3)2+ is 9 to11 orders of magnitude less than that of Au(S2O3)23-. Relevant species distribution and Eh-pH diagrams based on the revised data are presented.

Jan 1, 2003

With a total value to date of well over $200,000.000.00 for its ore production, the Tintic mining district, which is about 100 miles southwest of Salt Lake City, ranks as one of the three main ore producing areas of Utah. In it are located the biggest silver mines of the country, silver having been the chief metal produced in the camp since its start. Tintic's silver production to date has a total value of over $1 00,000,000, approximately half of the value of the camp's ore production, the balance being roughly divided among lead, gold and copper. Discovery of the camp was made in the late sixties. Lack of transportation and ore reduction facilities delayed extensive development of the area for nearly a decade. In recent years Tintic's ore production has ranged from 350,000 to 400,000 tons annually. In 1924 the camp produced one-eighth of the silver produced in the nation with an output of 7,729,700 ounces. Its lead production was 77,765,000 pounds and its gold production 26,285 ounces.

Jan 1, 1925

By Charles H. Fulton

Experimental work on the process was begun on a laboratory scale at Cleveland, Ohio, in 1914, and transferred to East St. Louis, Ill. in 1916, where a commercial sized furnace was in technical operation until January, 1918. The essential steps of the process are as follows: Oxidized zinc ore or roasted zinc concentrate is mixed with crushed coke and coal-tar pitch and formed into briquets 9.25 in. (23.5 cm.) in diameter and 21 in. (53 cm.) long in a manner similar to that used in the manufacture of graphite or carbon electrodes, except that much less care and time are required. The composition varies with the nature of the ore; in one case, the composition was 100 parts ore, 70 parts coke, and 18 to 20 parts pitch. These briquets maintain their form and volume during and after the distillation of the zinc. This object is gained by using coke as the matrix and coal-tar pitch as the binder; this pitch becomes coke on heating and unites the ore particle and the original coke particle into a continuous mass. The briquet is an electrical conductor but only to such a degree that it can be used as a resistor. The size of the ore, as in the present practice of zinc metallurgy, ranges from fine material, such as flotation concentrate, to coarse table and fine jig concentrate. The process is not restricted to any particular kind of ore, but is applicable to pure high-grade ores, ores high in iron, and complex zinc-lead ores, since the residue from the distillation IS held immovably in place within the briquet. In the case of complex zinc-lead ores, the distillation is conducted with a carefully regulated temperature so that a high percentage of lead is retained in the distilled briquet, which may then be smelted for its lead content. In present zinc smelting practice, the reduction fuel is from 40 to 50 per cent. of the weight of the ore. In the briquet, it is from 60 to 85 per cent. of the ore; but unless the ore is exceptionally high in residue, the distilled briquet may be used over again as coke, or as a high ash coke for fuel purposes in power production. Baked briquets are hard and tough and may be handled roughly

Jan 1, 1921

By Douglas N. Kendall

There are three definite steps in the making of a mining industry in any country. These are as follows: Step A - Geological Mapping This step covers the basic geological mapping of the country at scales of 1/250, 000 up to l/50, 000. This step eliminates territory and directs the exploration teams to the areas of potential interest. Step B Prospecting This step includes all phases from detailed geology through geophysics and drilling up to the point of proving that an economic ore body exists. Step C - Mine Development This is the expensive step, involving the creation of the mine, including shaft-sinking, ore treatment plant, etc.

Jan 1, 1963

By C. L. Popp

The scope is to address issues confronted by parties in the mining industry such as: Mine planners, survey and engineering departments, field teams and subcontractors. Describing approaches and best practices for assembling a project team to identify and create modeling requirements and to implement beneficial results. 3D Machine Control and Guidance tools continue to reduce project risk and attract quality resources with skill sets new to the earthmoving industry. These tools increase production, reduce rework and help with government permitting.

May 1, 2013

By P K. Wong, D A. F Oliveira, F M. Azad

In situations where foundation piles are located in proximity to existing or future tunnels, it is typical for the tunnel owner to require that sleeving of the piles be carried out to at least the invert of the tunnels to minimise any load transfer to the tunnel lining. In competent rock, this practice may be sometimes unnecessary, thus uneconomical. This paper presents an assessment of the effect of pile loading from one of the multi-storey buildings at Barangaroo South in Sydney on the adjacent future Sydney Metro tunnels. It was originally required by Transport for NSW (TfNSW) that the piles be sleeved below the tunnel invert level; however, the building developer wanted to reduce the pile sleeving depth to achieve a more economical solution due to the large number of load transfer piles being required for the project. To assess this feasibility, a full 3D commercial numerical code, FLAC3D, was used to carry out this complex soil-structure interaction analyses. Based on these assessments, it was demonstrated successfully to the TfNSW that the pile sleeving may be terminated at 2 m above the tunnel invert level. For this arrangement, the investigations found that the loading on the piles should have negligible adverse impact on the tunnel lining design. As a result of such an assessment, the proposed pile sleeving level was approved by TfNSW, thus offering an economical foundation solution for the project.CITATION:Azad, F M, Oliveira, D A F and Wong, P K, 2014. The impact of pile loading on adjacent metro tunnels – Barangaroo South, Australia, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 355–360 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Rangaswamy. K, Naga Sivaji

A stone column is one of the most commonly employed methods of ground improvement techniques. This method used to increase the strength, decrease the compressibility of loose granular and finegrained soils. Also, it accelerates the consolidation in clays and reduces the liquefaction potential of sands and silt soils. In general, the stone column contains 15 to 75mm stone aggregates. In reality, it is not easy to avail the natural stone aggregates due to unavailability in locally nearby places. Present work aims to replace the stones partially or entirely by scrap tyre chips as an alternative material. The utilisation of recycled tyre chips in ground improvement is an environmentally friendly solution and avoid the disposal of tyre chip waste in large pits. Model tests conducted on marine clay with encased end bearing stone columns (ESC) constructed with a mixture of stone aggregate and tyre chips with sizes 4.75 to 10mm. The column diameter is 75 mm, L/d ratio maintained to 5.3. Non-woven geotextile wrapped encased stone column has introduced in the soft marine clay model. Encasement prevents the lateral squeezing of aggregates into the surrounding clay and protects the drainage function of the stone column. A set of load-settlement tests were conducted on both the clay model and clay model treated with the stones-tyre chips column. The model was loaded by the tri-axial loading frame. Shear strength parameters of stones and tyre chips were determined by large size direct shear tests. Model test results are concluding that the load-carrying capacity of the clay is improved significantly after installing the stone column in it. The encasement increases the load-carrying capacity and stiffness of the ordinary stone column. It is also proved that the stone aggregate could be replaced partially by tyre chips up to 60% without a significant reduction in its performance.

Nov 1, 2022

By Phil D. Newman, Robert J. Pine, Kevin Ross

The Stratoni Operations in northeastern Greece rely on a selective backfill method to exploit high-grade lead-zinc deposits. Underhand cut and fill often results in spans approaching 6-9 m (depending on the mining method employed) and a competent backfill is required to avoid dilution problems. Cement consumption represents a significant mining cost and through improving the control of the backfill batch preparation, the cement content could be greatly reduced without jeopardizing the grade control. A new distribution system was installed and a QAIQC system designed in cooperation with the operators to allow a wide range of backfill recipes, providing cost savings to the mine. A review of possible failure modes and the consequent strength required for the chosen mining method was also completed and indicated potentially significant cement content reductions. The calculations are supported by 12 years of experience at the mines which provides a valuable insight into the applicability of the approach developed.

Jan 1, 2001

By Callaghan T

The Henty Gold Mine is located approximately 30 km north of Queenstown, at the head waters of the Henty River on the west coast of Tasmania at 41¦50'S, 145¦40'E on the Queenstown (SK 55-5) 1:250 000 and Sophia (8014) 1:100 000 map sheets (Figure 1). The mine is accessed from Queenstown along the A10 Highway and Anthony's Road. The town of Queenstown is located 260 km north west of Hobart on the A10 Highway, and

Jan 1, 1997

By Rosiane Mary Rezende Faleiro

O GMC intensivo, apoiado na evolução da metodologia do GMC atual, é um grupo de trabalho no qual os desempenhos dos processos são analisados e melhorados expressivamente em um curto espaço de tempo. Surgiu na indústria automobilística japonesa e consiste na melhoria contínua dos processos com base no envolvimento das pessoas e o trabalho em pequenos grupos. As principais diferenças estão na velocidade de condução da análise e da implementação das ações, além da maior disponibilidade e dedicação dos integrantes do grupo e do gestor. Foi formado um grupo de 9 pessoas para reduzir a queda de carvão vegetal nas correias transportadoras e em seus entroncamentos, com integrantes da produção e da manutenção. Durante a “semana de execução”, o grupo ficou 100% disponível para planejar e executar ações levantadas para solução dos problemas de queda do carvão vegetal. Após essa semana, o grupo teve mais quatro meses para fechamento e sustentação das ações. O resultado do grupo foi uma redução da queda de carvão vegetal em 49%, para uma meta inicial de 20%, o qual representa cerca de 183t de carvão vegetal por mês.

Aug 1, 2018

By P Radulovic, V Lawson, M Muller, J Wallace

The Mount Isa Copper Concentrator was commissioned in 1973. Since commissioning some significant upgrades have been undertaken such as: • the replacement of the rod mill/ball mill circuit with AG mills and the subsequent conversion of the AG mills to SAG Mills. • the introduction of columns as retreat cleaners in 1987, then reallocated as prefloat cleaners in 1994 and rougher cleaners in 1996.• the repurposing of some rougher capacity to preflotation roughing to remove carbonaceous pyrite and talc in 1994.• the introduction of a Jameson Cell for preflotation cleaning in 2000. • the expansion of the rougher and cleaner circuits in 2002 with the inclusion of 6 x 100 m3 Wemco cells to replace the capacity lost to preflotation and to increase residence time and improve recovery. In 2013 work commenced to replace the cleaner circuit after 40 years of operation. The new cleaner circuit, consisting of 3 x B5400/18 Jameson Cells, replaced the rougher cleaner columns, cleaners, recleaners and retreat Agitair banks and was commissioned in Sep 2015. The new cleaner circuit was configured as two cells in series producing the final concentrate and a cleaner scavenger cell to supplement the existing Wemco cleaner scavenger cells. The performance of the new circuit is discussed.CITATION:Lawson, V, Muller, M, Radulovic, P and Wallace, J, 2017. Mt Isa copper concentrator cleaner circuit redesign, in Proceedings MetPlant 2017, pp 279–287 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 11, 2017

By R. G. Treuting

Germanium single crystals strained in tension at 600°C slip on the {Ill} plane and, macroscopically at least, in the <110> direction. Deformation is in homogeneous: various localized rotations are observed, as is a banding consistent with secondary slip banding. The structure after deformation is polygonized with a domain size of about 2x1O-3 cm. In relaxation tests, an incubation period prior to flow is observed, of duration inversely related to temperature and applied stress. Under continuous loading, there is a sharp first yield point. A critical resolved shear stress therefore must be cited with respect both to temperature and to rate of loading. At 600°C, when loading proceeds at 2900 psi per min, it is 1310 psi. The yield point phenomenon is suggestive of Cottrell&apos;s solute atom atmosphere theory and five points of qualitative agreement with this theory are found. PLASTICITY of germanium at elevated temperatures has been reported by Gallagher,&apos; who ascribed it to slip on {Ill) planes and described some associated effects. Preliminary experiments with single crystals of silicon and germanium loaded as simple beams confirmed {ill) as the slip plane of both materials.V his was demonstrated by the standard technique employing traces on two surfaces of known angle on a deformed crystal of known orientation.3 These experiments did not fix the slip direction, since more than one glide system operated. Uniaxial tensile straining is preferred for this purpose in order to restrict slip to one predominant system and to provide an unequivocal determination of the orientation change with respect to the stress axis. Experimental Method Specimens were diamond-sawed from germanium crystals containing about 5x10-5 wt pct Sb prepared by the zone-leveling process described by Pfann and Olsen;4 these specimens measured about 81/2 in. long, 0.20 in. wide, and were of various thicknesses from 0.035 to 0.060 in. Prior to testing, a specimen was coated over 1 in. or more of length at each end with Apiezon wax, chemically polished (in a solution of 15 ml HF, 25 ml HNO,, 15 ml CH3COOH, and 3 to 4 drops Br2), and dewaxed in warm xylene. A brief re-etching after scribing through a complete wax coating with vernier dividers provided gage marks at 0.200 in. intervals on the polished surface. A specimen with grips soft soldered to the ends was passed through the furnace tube and the grips pinned to the tensile machine in series with a stress gage. The Schopper testing machine is best described by reference to the illustration on p. 107 of Schmid and Boas5 and is operated with the pendulum arm locked, fixing the upper head. Load is applied through the screw-driven lower head, manually or by reduced speed motor. The furnace is 21/2 in. long surrounding a 4x7/16 in. ID quartz tube and was positioned about the specimen to permit free motion. The inert or reducing atmosphere required was sufficiently provided by a flow of helium introduced at the center of the furnace tube, with the tube ends loosely plugged with asbestos paper. Surface corrosion was slight. The stress gage employs a Be-Cu strip with SR-4 units incorporated in a simple bridge network with provision for balancing and calibrating. The bridge output on loading is fed through a Leeds and North-rup dc amplifier to a Speedomax 10 mv recorder, and calibration is obtained by dead loading. Experiments of two types have been conducted. Most have been in relaxation at constant elongation. One stress-strain curve has been taken with the machine continuously driven. Following extension of a specimen, Laue X-ray photographs were taken to obtain the orientation change between deformed and undeformed regions, recorded on a single film by translating the specimen in a plane normal to the beam between exposures. Sequences of such multiple exposures were made on some specimens to include the entire orientation range on one film. Slip Direction To obtain a maximum orientation change with a single slip system, crystals of very closely <110> axial orientation were used. The classic determination of slip direction rests on establishing that direc-

Jan 1, 1956

By V. Castranova, L. Wu, K. Van Dyke, J. Gutierrez, V. Vallayathan

Since it has been demonstrated that silica caused phagocytic cells to activate lipoxygenase metabolism of unsaturated fatty acids we thought selective inhibition of this metabolic pathway might be helpful in treatment of silicosis. It is known that lipoxygenase metabolism plays a role in the pathogenesis of a variety of inflammatory and hypersensitivity conditions. Further, it is believed that the alveolar phagocytic cells which engulf silica begin the inflammatory cycle which produces the metabolic products, cytokines and growth factors which causes fibrosis in the lung. There have been indications that drugs which inhibit lipoxygenase can inhibit fibrosis from other causes. Previously, we developed a method which detects the activity of lipoxygenase metabolism by measuring free radical oxidation via light production or chemiluminescence (CL). We decided to apply this method to phagocytic cells that would be found in the lung in the presence of silica with and without newly developed inhibitors of the lipoxygenase reaction. We used drugs which inhibit lipoxygenase directly including AA861 (TAKEDA), A63162 (Abbott), and an inhibitor that scavenges free radicals produced from the lipoxygenase reaction, nordihydroguairetic acid. In addition we used an indirect inhibitor, tetrandrine. We found drug inhibition of silica activated CL from alveolar macrophages, neutrophils and human leukemia (HL-60) cells differentiated with DMSO. Nordihydroguairetic acid 2x10-5M produced almost complete inhibition in all three cell types. In human leukemia cells (HL-60) A63162 and tetrandrine were equally inhibitory at 42% while in human neutrophils A63162 and tetrandrine were less active 22 and 10% respectively. In macrophages A63162 and AA861 were less than 50% inhibitory to cellular CL at 2xl0-5M. Direct assay of tetrandrine (2x10-5M) with sodium arachidonate and soybean lipoxygenase reveals no inhibition. All antilipoxygenase drugs regardless of mechanism were inhibitory to cellular chemiluminescence from all three types of phagocytic cells. These drugs alone or in mixtures could prove useful in treatment of silicosis.

Jan 1, 1991

By W. V. Green

Creep of tantalum was measured at temperatures from 0.6 to 0.89 of the absolute melting temperature. The creep curves include first, second, and third stages. Steady-state creep rate depends on the fourth power of stress. The activation energy for creep throughout this temperature range is approximately 114 kcal per mole, measured by the aT technique. Subgrain formation occurs as a result of creep strain, and pile-up dislocation arrays are observed in etch-pit patterns. BECAUSE of its high melting point-which is exceeded only by those of rhenium and tungsten—and its high room-temperature ductility compared to most of the other high-melting-point metals, tantalum will undoubtedly be utilized in an increasing number of high-temperature applications. Alloying studies directed toward increased high-temperature strength must use data on tantalum itself as a base line in order to evaluate the effectiveness of the alloying additions. However, to date, no systematic study of creep of tantalum at temperatures above one-half of its melting point has been reported in the literature. Conway, Salyards, McCullough, and Flagella1 have measured linear creep rate of tantalum sheet as a function of stress, but at only one temperature, 2600°C. This paper describes a relatively thorough study of the high-temperature creep of tantalum. METHOD Material Tested. The commercially supplied, l/2-innch-diameter tantalum rod used for this work was electron-beam-melted, cold-forged, rolled, swaged, cleaned chemically, and vacuum-annealed for 1 hr at 1000°C, all by its manufacturer. The vendor&apos;s analysis included 60 to 170 ppm C, 3.4 to 4.2 ppm H, 60 to 80 ppm 0, 15 ppm N, and a hardness ranging from 66 to 81 Bhn and averaging 76 Bhn. Creep eimens Used. Two creep-tested specimens are shown in Fig. 1. The 1/4 in.-diameter gage section was 3/4 to 1 in. long, and terminated either at shoulders 5 mils high or at 20-mil-diameter tantalum wires spot-welded to the circumference of the gage section. Both kinds of shoulders served equally well as fiducial marks for optical strain measurements. The spot welding did not alter the creep behavior in any detectable way; the 5-mil- high sharp shoulders did not result in any detectable localized effect on the strain. Before testing, each tensile bar was first mechanically polished -id then electrochemically polished according to the method referred to by Forgeng2 as the "Thompson Ramo Woolridge" method, which was suitable for tantalum after small adjustments of technique were made. Two tensile bars tested at low stresses had 1/8-in.-diameter gage sections and utilized only the weight of the bottom grip for the applied load. Although these diameters were smaller than were desired for other reasons, applied loads were known with high precision in the tests in which they were used. Testing Procedure. Two different constant-load creep-testing machines were employed, one of which has been described by Smith, Olson, and Brown.3 In both, the tensile bar is held vertically on the axis of a cylindrical tungsten tube or screen heater by threaded tungsten grips. The tensile bars and associated grips are heated by radiation from the incandescent heaters, which are heated by their own electrical resistance. Both testing machines use pins to hold the bottom grips in place. The load is applied to a tensile bar through hanging weights, a constant force-multiplication lever, a pull rod sealed to the chamber lid, and a top grip threaded to the pull rod at one end and to the tensile bar at the other. In one machine, the vacuum seal is a bellows with a low spring constant; in the other, the seal involves a rotating "0 ring". With the latter, rotation is converted to translation with a crank shaft, so that elongation of the tensile bar is accommodated with no change of tensile load. The incandescent tensile bar is viewed by an external optical system through slots in the radiation shields and heater, and an enlarged image is projected on a ground-glass screen. Gage-length measurements are made on this image with cathetometers on traveling microscopes. With regard to creep-test results, the two machines were identical. Thorium oxide coatings were applied to the threaded ends of the tensile bars, to prevent diffusion welding of the tensile bars to the grips during testing. Specimen temperatures were measured with an L. & N. optical pyrometer which had been calibrated against a standard carbon arc, and were corrected fir window absorption by calculation from the measured spectral transmittance of the quartz observation windows. Longitudinal temperature gradients in the tensile-bar gage length and temperature drifts during testing were detectable but small, and were estimated to be 10°C or less. Accuracy of temperature measurement was confirmed by comparing the temperature measured on the surface of a special

Jan 1, 1965

US 4,194,729 - Sintering of iron oxide ore on a straight sinter belt. The upper strand of the belt is divided into sintering and cooling sections with windboxes for removing their respective gases. The main for collecting cooling gas is located beneath the lower strand and is connected to opposite sides of the windboxes, while the main for collecting sinter exhaust gas is located beneath the lower strand and connected to sinter section windboxes. Both mains are exhausted via gas-evacuating fans and pipes to a flue. Space requirements are lessened and plant accessibility can be maintained at optimum conditions. K. Wacker and F. Feigk, assigned to Dravo Corp. Mar. 25, 1980. 8 pp. (266-144). Filed: 10-30-78 (956,058). Priority: West Germany, 12-16-77 (2,756,082).

Jan 1, 1982

By Steven A. Elmquist

INTRODUCTION R&D activities are needed, at a minimum, for a company&apos;s competitive survival followed in importance by the growth and diversification of the company. For most industrial companies, however, R&D is the business area that has been the most difficult relative to confident long-range financial commitments and effective control and relative to its value as a long-term investment. Investors look not only at the current profitability of the company but increasingly at the plans, actions, and quality of the personnel in position to improve the market position and profitability of an organization. "The strongest predictor of investment value is the degree of innovation of the &apos;company.&apos; I believe this is true of both strategic planning and R&D activities." R&D is the lifeblood of a company&apos;s future. If this basic premise-R&D for survival and growth-is believed to be true, why is it necessary to "Sell R&D in your organization? My personal experience, in a number of organizations, is that R&D budget is perceived as a business element area that could be delayed or reduced to improve the bottom line during difficult business conditions. I believe the following quote speaks volumes about this subject-"There is only one thing I know for certain about research, and that is it costs money-lots of it." -Unnamed, Hard- headed Financial Executive. A business must make money and be profitable in order to maintain and create jobs, pay taxes, cover working capital and costs of goods sold, and most importantly, create value for its shareholders. The foremost element of selling R&D, therefore, is to consistently demonstrate the R&D group&apos;s contribution to the bottom line.

Jan 1, 2004

By D. N. Hedges

This paper discusses the actual recovery and installation of a longwall in a bituminous coal mine in western Pennsylvania. The coal bed mined is in the Lower Freeport seam, which averaged 1.07 m (42 in.) in height locally. Drainage from the mine is about 13.25 ML/day (3.5 million gal per day) of water. This water deteriorates the mine&apos;s predominately fire clay bottom making it extremely difficult to move equipment. Support removal is accomplilshed by pulling the 5.44 t (6 st) shields out under their own hydraulic power and transporting them by track 8.05 km (5 miles) to the next longwall panel. This paper also discusses the changes that will be made to aid in the succeeding longwall recoveries and installations.

Jan 1, 1985

By L. B. Pankratz

Low-temperature heat capacities, high-temperature enthalpy increments, and the enthalpy of formation at 298° K were determined calorimetrically for vanadium subnitride (VN0.465). The low-temperature investigation gave S°298.15 = 6.379 ±0.005 cal/deg mole, and a combustion calorimeter investiga¬tion provided ?Hf°298.15 = -31.80 ±0.60 kcal/mole. The two quantities were combined with the high-temperature data to give standard values of enthalpies of formation and free energies of formation above 298° K. These and related thermodynamic functions were tabulated to 1,800° K. Similar data are included in the range of 298° to 1,600° K for the mononitride, VN.

Jan 1, 1971

By Donald G. Rogich

The concept of initiating a large action-oriented contract, directed toward inherently safe mining systems, was conceived by the U. S. Bureau of Mines in January 1970. At that time we were in the process of establishing research contracts and grants, about 100 of which were let in FY 71 to deal individually with fairly specific technological areas. These projects in the aggregate covered a wide spectrum of health and safety problems. What appeared to be necessary was the creation of a project or program that would provide a focal point for the demonstration of many of the results of this research and also in the action sense culminate with working hardware and systems that could be tested and demonstrated over a fairly long teen. The concept of working demonstrable systems, rather than just a conceptual study, was, felt to be necessary for two significant reasons. In the development of any new system, the translation from concept to working hardware is usually a costly and time consuming process which acts as a deterrent to implementation. Secondly, many decisions in the mining community to change equipment or systems ,are based on first hand observation of the new system, in operational practice, an attitude which is certainly understandable in view of the high capital costs of equipment. The decision was made to procure a single R&D contract which would be aimed at developing underground coal mining systems which

Jan 1, 1972

By N. A. Gokcen

The construction and operation of a simple and accurate vacuum-fusion apparatus are described in detail. Absolute accuracy of the oxygen analysis has been determined by the reduction of oxides weighed to 20.01 mg. The Bureau of Standards steel samples have been analyzed repeatedly, and their inadequacy for the acceptable range of oxygen is presented. The limits of interference of manganese, aluminum, and titanium, and the effects of tin and water-cooling of the furnace tube have been investigated in detail. ANALYSIS by the vacuum-fusion method consists of melting a sample in a degassed graphite crucible under high vacuum and extracting oxygen as carbon monoxide, and nitrogen and hydrogen as gaseous elements. The resulting gas mixture is analyzed for its constituents, from which oxygen, nitrogen, and frequently hydrogen may be determined within 1/2 hr or less. The history and summary of methods1-4 and extensive reviews of literature&apos;.&apos; for the determination of gases in metals have been published in detail. The foundation of the modern vacuum-fusion method of analysis was laid by Jordan and Eckman,11 and Oberhoffer and his associates.1, 10 Diergarten,11, 12 Meyer,13 Thanheiser et al.,14, 15 Ericson and Benedicks,16 Ziegler,17, 18 Sloman,16-23 Thompson et al.,24 and later many others contributed to the improvement, accuracy, and limitations of the method. In some investigations, however, the limitations of the procedure and the errors involved in the analysis require further critical examination and evaluation. In many apparatuses, lunnecessarily complicated and cumbersome features and elaborate precautionary measures do not have conclusive advantages. The purpose of this invest:igation was, therefore, a) to construct a very simple and accurate apparatus, b) to determine the absolute accuracy of results, c) to establish the limits of interference of manganese. aluminum, and titanium, d) to reexamine critically the reduction and recovery of oxygen from oxide powders of various sizes, and e) to evaluate critically the eight steels of the Bureau of Standards."&apos; Apparatus The apparatus used in this investigation is shown in Fig. 1. It has been used for over three years, during which several modifications were made. A brief description of the apparatus is as follows. The transparent silica or Vycor tube, E, is joined to the Pyrex head, B, by mean of a face to face ground joint sealed with mercury. A similarly sealed ball and socket joint would also have been satisfactory. A standard tapered ground joint, successfully used by some investigators, was tried, but in the absence of grease or vacuum cement it was very difficult to disassemble the joint. The graphite crucible, G, 15/16 or l 1/8 in. OD, 2 1/2 or 3 in. high, 1/10 in. wall, shown enlarged in Fig. 3a, is made from the rods containing less than 0.08 pet ash. Two baffles, overlapping sufficiently to prevent spattering, are inserted in two opposite slots cut on a band saw. Two small holes in the baffles permit the temperature measurement of the melt. A second type of crucible, Fig. 2, G, shown enlarged in Fig. 3b, is also satisfactory, though not as convenient as the crucible shown in Fig. 3a. Somewhat similar but more elaborate crucibles with baffles were first tried by Ericson and Benedicks,&apos;" but were abandoned in favor of a crucible with a stopper and a peripheral graphite powder filter. Various versions of their crucible with a stopper have later been used by other analysts, 10-27, 27-30 The crucible is packed directly in E, Figs. 1 and 2, with —35 + 48 graphite powder for shielding and insulation. A minimum layer of 7 mm of powder is necessary for keeping E cool and minimizing the blank. The first use of graphite powder was made by Sloman,10-23 Who found that —200 mesh was the most satisfactory. The author tried various size powders from +20 to —100 mesh and found that a) particles of 28 mesh or larger were not sufficiently insulating and were heated by the induction current, b) the powder finer than 60 mesh packed too much and did not readily permit the escape of gases even when the crucible was heated very slowly; hence, the powder was occasionally blown out of the side in the crucible and in the mercury pump. The optimum size powder is, therefore, 35 to 48 mesh size or 0.4 mm in average diameter. The furnace is designed to eliminate excessive amounts of

Jan 1, 1959