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By Welch B. J

Results obtained from linear sweep voltammetry at a graphite anode in cryolite-alumina melts are presented, together with those obtained from a chronopotentiometric investigation of the influence of dissolved metal. The results, consistent with both production information and other fundamental studies, showed that the following two reactions occur at the anode.Equation 1Al (dissolved) ? Al3+ + 3eThe latter accounted for some of the loss in currentefficiency.The rate of the former reaction is limited by the slow desorption of the CO from the electrode surface. Mass transfer conditions, and hence cell design, influence the importance of the second reaction.

Jan 1, 1976

By F. M. Van Tuyl

The oil industry had its inception in the United States in 1859 when the first oil well was drilled by Col. Drake at Titusville, Pennsylvania. From, a production of 2000 barrels for that year there was a slow but steady increase, with some fluctuations, up to 1901 for which year the output was approximately 69,389,194 barrels. Since that time the production has increased with leaps and bounds due to the rapid rise of the automotive industry, the widening use of oil as a fuel under boilers and the development of the. Diesel engine. The production for 1921 is estimated to have been 469,639,000 barrels. During the same year more than 125 millions of barrels were imported from Mexico. The oil industry, including the production, transportation, refining and distribution of petroleum and its products, is now the third largest in the country. Present Condition of the Industry During and immediately after the war the demand for petroleum exceeded the domestic production plus the imports from Mexico with the result that our storage oil was heavily drawn upon. Prices for crude exceeded all previous levels in the history of the industry. Pennsylvania crude sold for $6.10 per barrel and Mid-Continent crude for $3.50. Such prices stimulated wildcatting greatly with the result that several important new oil pools were discovered. Then as production increased the depression came which caused a large falling off in consumption. Pennsylvania crude fell to $2.25 per barrel and Mid-Continent to $1.00. Large oil companies such as the Standard, Sinclair and Empire took advantage of the situation, erected additional storage tanks and bought up millions of barrels to hold until better prices returned. Prices have already improved owing to a better market, but the domestic production coupled with the Mexican importations is still in excess of the demand with the result that the surplus is being stored. At the close of the year 1921, the U. S. Geological Survey estimates that there were 183,890,000 barrels of crude in storage in this country, the largest stocks in the history of the industry, yet an amount sufficient to supply the country for only 119 days at the present rate of consumption. Price reductions are again anticipated in some quarters but in view of the probable falling off in the Mexican output in the near, future due to the rapid rate of exhaustion of several of the most important pools and in view of the expected increase in consumption of gasoline and kerosene during the spring and summer months it is more likely that the present price level will be maintained. Present Sources of Domestic Supply Seven major oil fields are recognized by the U. S. Geological Survey in the United States. These are the Appalachian, Lima-Indiana, Illinois, Mid-Continent, Gulf Coast, Rocky Mountain and California. Two of these, Mid-Continent and California, supply about seventy-five per cent of the present total domestic output

Jan 1, 1922

By F I. Cox, D Peeler, T Bodisco

"Diesel particulate matter (DPM), in particular, has been likened in a somewhat inflammatory manner to be the ‘next asbestos’.From the business change perspective, there are three areas holding the industry back from fully engaging with the issue:There is no real feedback loop in any operational sense to assess the impact of investment or application of controls to manage diesel emissions.DPM are getting ever smaller and more numerous, but there is no practical way of measuring them to regulate them in the field. Mass, the current basis of regulation, is becoming less and less relevant.Diesel emissions management is generally wholly viewed as a cost, yet there are significant areas of benefit available from good management.This paper discusses a feedback approach to address these three areas to move the industry forward. The six main areas of benefit from providing a feedback loop by continuously monitoring diesel emissions have been identified: Condition-based maintenance. Emissions change instantaneously if engine condition changes. Operator performance. An operator can use a lot more fuel for little incremental work output through poor technique or discipline. Vehicle utilisation. Operating hours achieved and ratios of idling to under power affect the proportion of emissions produced with no economic value. Fuel efficiency. This allows visibility into other contributing configuration and environmental factors for the vehicle. Emission rates. This allows scope to directly address the required ratio of ventilation to diesel emissions. Total carbon emissions. For National Greenhouse Emissions Reporting (NGER)-type reporting requirements, calculating the emissions individually from each vehicle rather than just reporting on fuel delivered to a site.CITATION:Cox, F I, Bodisco, T and Peeler, D, 2014. Continuous remote emissions monitoring – the lynchpin for air quality management, in Proceedings 12th AusIMM Underground Operators’ Conference 2014, pp 137–142 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 24, 2014

By S. J. Schatzel, W. P. Diamond

Longwall mining alters the fluid-flow-related reservoir properties of the rocks overlying and underlying an extracted panel due to fracturing and relaxation of the strata. These mining-related disturbances create new pressure depletion zones and new flow paths for gas migration and may cause unexpected or uncontrolled migration of gas into the underground workplace. One common technique to control methane emissions in longwall mines is to drill vertical gob gas vent holes into each longwall panel to capture the methane within the overlying fractured strata before it enters the work environment. Thus, it is important to optimize the well parameters, e.g., the borehole diameter, and the length and position of the slotted casing interval relative to the fractured gas-bearing zones. This paper presents the development and results of a comprehensive, "dynamic," three-dimensional reservoir model of a typical multipanel Pittsburgh coalbed longwall mine. The alteration of permeability fields in and above the panels as a result of the mining- induced disturbances has been estimated from mechanical modeling of the overlying rock mass. Model calibration was performed through history matching the gas production from gob gas ventholes in the study area. Results presented in this paper include a simulation of gas flow patterns from the gas-bearing zones in the overlying strata to the mine environment, as well as the influence of completion practices on optimizing gas production from gob gas ventholes.

By L. H. Reiss, J. Groult, L. Montadert

Many fields, where the reservoir is composed of sandy layers, show great complexity because of the lack of continuity which results from a particular type of seditnentation. This complexity may be a factor of prime importance in studying reservoir drainage, especially in the displacement of oil by water or gas. This paper describes work done to study this heterogeneity and its influence in the exploitation of the fields of the lower Devonian sandy shale in the Fort Polignac Basin in Algeria. Two lines of research were followed. 1. On the border of the hasin, a detailed sedimentological study established rules for the distribution of the sandy zones, which furnished hypotheses necessary for devising a geologic model of the reservoir. A certain number of sandy zones were recognized and characterized by their sedimentation. 2. In the interior of the basin, production logs deterrnined the productivity profile. Study of these point data led to a description of the distribution of oil and gas phases in the reservoir so that the continuity of different zones between the wells could be deduced. These techniques were applied to the study of the lower Devonian sandy shale reservoir of Zarzaitine. The sedimentological study guiding the correlation work, with the aid of the conventional static data (logs and cores), led to the establishment of a useful geologic model of the reservoir. Production logs, thanks to the contribution of dynamic elements, permitted corrobora-tion of the model. In particular, the logs confirmed separation, as proposed by the sedimenfological study, of two comparable sandy groups by revealing the continuity of a thin impermeable layer, invisible on conventional logs. INTRODUCTION The heterogeneity of sandstone reservoirs considerably influences the distribution of fluids, as well as their displacement in the reservoir. Rational development of a field and maximum recovery of hydrocarbons are closely tied to an exact and precise knowledge of the intern architecture. We will try to show how it is possible I refine the knowledge of the reservoir by seeking qui different and varied sources of information. Productic geology, the group of techniques which leads to idei concerning reservoir architecture and its geometric descris tion, furnishes the framework of this undertaking. Of these techniques. those used so far are qui varied. Descriptive as well as quantitative, the technique partake as much of classical geology as of reservo science. They include (1) geologic studies of the enti basin, especially a stratigraphic and sedimentologic study of the reservoir member at its outcrop, detail1 observations of cores taken from wells and, finall oriented cores; (2) interpretation of geophysical dat (3) interpretation of electric logs, nuclear and sonic lo and dipmeters: (4) petrophysical study of the reserve on samples taken from wells; (5) reservoir dynamics (stu of the production history and, in particular, interpretati of production logs); and (6) analysis of the fluids a thermodynamic studies. This incomplete list could also include (1) study the migration of the fluids, (2) geochemistry (chemi characterization of the oils), (3) regional hydrodynamii and (4) injection and detection of tracers. If most of these techniques are classic, attention i nevertheless be called to applying two of the techniql in conjunction: the study of the reservoir member its outcrop and the study of dynamic distribution fluid phases in the reservoir through use of product logs, used in the study of the sandy shale reservoirs the lower Devonian of the Fort Polignac Basin, Alge in particular, their application to the study of the 2 zaitine field where they have led to a new and satisfact model of the reservoir will be described. THE ZARZAITlNE FIELD Situated in the interior of the Fort Polignac 8 about 150 kilometers (km) north of the lower Devol outcrop, the Zarzaitine Devonian oil field was discovc On Ian. 28, 19'' (Figs. 1 and l8). It is in the fern a monocline truncated by two perpendicular fault: great throw, with a downthrown section to the north\: Erosion at the top of the structure has caused one of it to disappear. It is a reservoir with a gas cap an m coefficient on the order of 1:5, open to the aql On the northeast, with the oil zone covering an Of 106 sq km and with initial oil reserves of 222 mi

Jan 1, 1967

By Godofredo Torreblanca

El presente trabajo identifica, inventaria y estima los montos de inversión de los “peligros históricos” que conforman los “pasivos de seguridad” en la unidad de producción Morococha, -en tanto, representan las mayores causas ocultas de los incidentes /accidente, de forma que priorizan el nivel de riesgo que representan para tomar las medidas preventivas y crear un sistema de gestión de seguridad. De otro lado, los pasivos se han codificado para facilitar su administración y seguimiento, en aspectos relacionados con posibles fallas en el diseño de las instalaciones, peligros por antigüedad de equipos y herramientas, peligros por infraestructura minera defectuosa, y todo aquello que pueda representar un riesgo para los trabajadores (labores con secciones reducidas, tajeos sin chimeneas de ventilación, equipos defectuosos o inadecuados, instalaciones inadecuadas, instalaciones eléctricas sub estándares, etc.).

Sep 14, 2009

By J. C. Cawley

This National Institute for Occupational Safety and Health study was conducted to focus future research on the most significant electrical problems in the mining industry. Data from 1,926 mine electrical accidents (including 75 fatalities) that occurred between 1990 and 1999 were studied. Coal and metal-nonmetal operator- and contractor-reported data are presented. All data used in this analysis were MSHA closeout data, except 1999, which were preliminary data. Electricity was the 4th leading cause of death reported in mining despite being the 14th leading cause of injuries. Electrical shock, not electrical burns, caused 70 of the 75 electrical fatalities reported. About one-half of mine electrical accidents and fatalities occurred during electrical maintenance. Suggestions for mitigating electrical hazards are proposed.

Jan 1, 2002

By Gema Ribeiro Olivo

The hydrothermal Au-Pd deposits are hosted by the jacutinga in the Lake Superior-type iron-formation of the Itabira Group, Minas Supergroup. Jacutinga is a highly sheared, metamorphosed, hydrothermally altered iron-formation composed of hematite, magnetite, quartz, talc and phlogopite (Cauê) or muscovite (Conceição) and minor tourmaline, palladian gold, arsenopalladinite, mertierite II and palladeisite (hydrothermal) and native gold, native palladium Pd-Cu-oxides, and kaolinite (weathering products). The highest concentrations of Pd-Au occur in quartz and hematite veins parallel to the S1 foliation (Corpo Y, CorpoX, Aba Leste and Central orebodies, at Cauê and a single orebody at Conceição) or parallel to the S2 foliation (Aba Norte). The average ore grade is 30-40 g/t Au+Pd. The characteristics of the Au-Pd ore favor an epigenetic model for gold and palladium concentration in the iron-formation. During the D1 deformation and peak metamorphism, the oxiziding, acid and hot hydrothermal fluids transported Au and Pd preferentially as chloride complexes. The reaction of the fluid with the dolomitic carbonate (the probably protolith of the jacutinga) would have dissolved carbonate and K-feldspar to form muscovite or phlogopite and tourmaline, resulting in an increase in solution pH and a decrease of Cl concentration and subsequent deposition of gold and palladium minerals.

May 1, 2003

By L. C. Reese

? Good construction and inspection presumed. ? Capacity-computation factors are independent of construction method. ? To account for variable or uncertain site conditions, anticipated construction problems, and/or minimal inspection, increase factor of safety. ? Conduct load tests and/or develop easily implemented design alternates (e.g., straight shaft in case bell can't be formed) to reduce factor of safety.

Jan 1, 1988

By Kelly E. G

New Zealand suffers the disadvantage of widely scattered ore bodies, none of which is large enough to economically support its own smelter. This leads to the concept of a centrally located smelter which must be flexible enough to cope with var

Jan 1, 1980

By Gerald Sherman

(San Francisco Meeting, September, 1915) THE ore deposits of the Warren district, in which the mines of the Copper Queen Consolidated Mining Co. are situated, have been described in a number of technical publications, and will not be-discussed here in detail. Certain of their characteristics, however, control -methods of underground transportation and hoisting of ore. In the Copper Queen mine, the majority of the ore has occurred in a zone encircling the west boundary of the porphyry intrusion of Sacramento Hill. It has a width varying from 800 to 1,200 ft., and a thickness of about 400 ft. It reaches the surface in the older part of the mine to the northwest, but dips to the southeast, where it is reached at 1,400 ft. below the Czar collar, in its farthest extension at present developed on Copper Queen ground. There is one major extension from the northwest end of the zone toward the west along the Czar fault, and others of minor importance. Individual orebodies are scattered through the zone in an eccentric manner, only matched by their own irregularities of form and size. Their most general characteristics are the softness of the ore and their great horizontal rather than vertical extent. It has been estimated that the average vertical thickness of ore in the Czar and Lowell divisions is between 30 and 35 ft. It is calculated by assuming it to be uniformly distributed over its horizontally projected area. In this zone, and for some distance above it, the ground has been .subjected to intense alteration and intense but irregular oxidation. It has resulted in an enormous quantity of earthy or clayey material, which may be either ore or waste, which when wet is both heavy and tenacious. Below alteration, the ground is fairly hard, and the limestones contain primary ores differing from those heretofore considered typical of the camp, and which have not yet been thoroughly exploited. The mine production has been drawn from many orebodies spread . over a great area. A diagram map (Fig. 1), of haulage drifts and loading stations, illustrates the situation in 1914.

Jan 9, 1915

By H. J. Stehli

Probably the earliest sinter from lead ore was made in the product sinter boxes attached to some hand reverberatory roasters. The ore was drawn from the roaster bed when dead roasted, and then by laborious effort fritted together by rabbling at a high temperature in the sinter box. This was not a true sinter, but was a great improvement over the dusty dead-roasted fine ores. The Huntington-Heberlein pots were the first real advance in the art, and produced some real sinter. They required that the sulphides be preroasted to 5 or 6 per cent sulphur, and the long cycle of operating and deep bed of material used in the pots fostered the formation of densely fused material and fines. This necessitated crushing of the densely fused cake and returning to the next charge large amounts of fines screened out. The Huntington-Heberlein pots made comparatively high lead losses because the deep bed and high internal temperature together favored the volatilization of lead. Lime (CaO) was added to the charges, and this addition constituted the patented feature of the Huntington-Heberlein process. Its sole function we now know was to act as an isolator of the sulphide particles, and any other substance—for instance, iron oxide—of equal fineness performed the same function. The Savelsberg process used limestone instead of burned lime, and in this there was a definite advantage. The converting of CaCO3, to CaO is a highly endothermic reaction, so the lime acted not only as an isolator of sulphide particles but absorbed excess heat and to some extent prevented premature fusion of the sulphides. The Carmichael-Bradford process used gypsum instead of limestone, and had the disadvantage of adding more sulphur to a charge from which it was desired to eliminate sulphur. Here again the gypsum served only as an infusible isolator of sulphide particles. The first Dwight-Lloyd apparatus to sinter lead ores commercially was installed at Perth Amboy in 1907. The fact that lime in any form was necessary to sintering was quickly disproved by making excellent sinter from Bunker Hill and Sullivan table concentrates, silica sand and iron oxide only.

Jan 1, 1937

By W. D. Maier, H. V. Eales

Paper presented at the IAGOD international symposium on mineralization related to mafic and ultramafic rocks held in Orleans, France, 1-3 September 1993. A lithological and geochemical study revealed significant lateral variation of the interval over 170 km of strike, from about 30 m at the Union Section to 220 m near Brits. The cumulates also become more evolved and leucocratic with distance from the Union Section both towards the NE (Amandelbult) and SE (Impala, Rustenburg and Brits). It is inferred that the persistent heat flux from a putative major feeder zone near the Union Section impaired deposition of felsic cumulates in the vicinity, delaying crystallisation of successive phases in parts of the chamber near the feeder. New influxes were therefore deposited on a footwall of varying thickness and lithology in response to different degrees of crystallisation and accumulation along strike. The development of cyclic units of chromitite, harzburgite, pyroxenite, norite and anorthosite was interrupted at different stages in different parts of the chamber

Apr 1, 1994

By Takeo Fujino, Nobuaki Sato, Yarong Wang, Kohta Yamada

"Ternary mixed sulfides of some transition metals MTS3 (M=Ba, ·Pb, T=Ti, Zr) were synthesized by a relatively low temperature process using sulfur melt. The mixture of starting materials, such as, metals and/or binary sulfides and a large excess of sulfur was reacted in a vacuum-sealed Pyrex or quartz ampoule at 350- 600 °C for one to three weeks. After the reaction, the remaining sulfur was completely removed by a process composed of filtration of sulfur melt and followed dissolution in CS2• The binary sulfides impurities coexisted in the products were removed by rinsing the products in water and acetone. By using the above method, BaTiS3, PbTiS3 and BaZrS3 'Were obtained in pure form. The effect of addition of halides on the yields of these ternary sulfides were also discussed.IntroductionThere have been a vast number of studies on the preparation and physical and /or chemical properties of mixed metal oxides. As is well known, some of such compounds exhibit excellent materials properties, causing them for use in mechanical, electronic, magnetic and chemical devices. Not a few mixed metal sulfides show similar physico-chemical properties to those of the corresponding mixed metal oxides. However, the study of the mixed sulfide crystals is rather sparse mainly due to difficulties in preparing these compounds. In various methods which have been adopted for preparing mixed sulfides, the simplest method would be the solid-solid reaction of the component binary sulfides or elements. However, there are always diffusional constraints with regard to the reactions in solid phases causing it necessary to heat the reactants at sufficiently high temperatures, viz. 800-1200°C. On the other hand, some mixed sulfides are unstable at high temperatures or to change their materials properties due to sulfur nonstoichiometry and structural modification depending on temperature, i.e., synthesis of such compounds needs to be made at lower temperatures. Processing in alkali halide melts is hopeful to overcome the above problems but to obtain the halide melts the temperatures above ~ 600 °C is needed. Low temperature reaction has been carried out for the preparation of Hg1.24TiS4, which was formed by the ·combination of TiS2 and molten Hg metal at 320°C[l]. Reaction of WS2 with LiBH4 melt at 350°C yielded LixWS2[2]. These sophisticated methods, however, can be applied only to the vary special cases."

Jan 1, 2000

By Fred C. Bond

It sometimes happens that old knowledge is forgotten, or half-forgotten, and its rediscovery is hailed as a great new advance in technology. Autogenous grinding affords such an example. The oldest-or apparently the oldest-commercial application of continuous autogenous grinding on a large scale outside of South Africa occurred at San Juancito, Honduras, where a total of more than two million tons of silver ore were ground autogenously with complete success from 1918 to the early 1940's. The history of the San Juancito silver deposits begins in 1880 when- the New York and Honduras Rosario Mining Co. started mining silver at a rate which soon reached two million ounces of silver annually. In 1912 the Company's first mill, located in the village of San Juancito, was shut down and its equipment transferred to a new cyanide plant. This plant, constructed on a mountainside near the mine, was equipped with tube pebble mills in which Normandy or Danish pebbles were used initially.

Jan 5, 1963

By S. Frimpong, S. R. Dindarloo

Material handling in open pit mining accounts for about 50% of production costs. The selection and deployment of efficient, safe, and economic loading and haulage systems is thus critical to the production process. The problems of truck and shovel selection and sizing include determination of the optimal number and capacities of haulage and loading units, as well as their allocation and operational strategies. Critical survey and analysis of the literature has shown that deterministic, stochastic, and experimental approaches to these problems result in considerably different outputs. This paper presents a comprehensive simulation framework for the problem of truck and shovel selection and sizing based on the random processes underlying the network-continuous-discrete event nature of the mining operation. The framework builds on previous research in this field and attempts to address limitations of available methodologies in the form of a comprehensive algorithm. To test the validity of the framework a large open pit mine was evaluated. The stochastic processes governing the uncertainties underlying the material loading and haulage input variables were defined and built into the stochastic model. Discrete event simulation was used to simulate the stochastic model. The proposed model resulted in several modifications to the case study.

Jan 1, 2015

By R. Karl Zipf

Use of Salamon's stability criterion in underground mine design can prevent the occurrence of catastrophic domino-type pillar failure. Evaluating the criterion requires computation of the local mine stiffness and knowledge of the post failure behavior of pillars. This paper summarizes the status of the practical use of this important criterion and suggests important research to improve our capabilities. Analytical and numerical methods are used to compute the local mine stiffness. Work to date in computing local mine stiffness relies mainly on elastic continuum models. Further work might investigate local mine stiffness in a discontinuous rock mass using alternative numerical methods. Existing post failure data for coal pillars are summarized, and a simple relationship for determining the postfailure modulus and stiffness of coal pillars is proposed. Little actual postfailure data for noncoal pillars are available; however, numerical models can provide an estimate of post failure stiffness. Important factors controlling postfailure stiffness of rock pillars include the postfailure modulus of the material, end conditions, and width-to-height ratio. Studies show that the nature of the failure process after strength is exceeded can be predicted with numerical models using Salamon's stability criterion; therefore, a method exists to decrease the risk of this type of catastrophic failure. However, the general lack of good data on the postfailure behavior of actual mine pillars is a major obstacle. Additional back-analyses of failed and stable case histories in conjunction with laboratory testing and numerical modeling are essential to improve our ability to apply the stability criterion.

Jan 5, 1999

By C. C. Huang

Rare earth compounds, such as samarium-cobalt compounds and neodymium-icon compounds, are being used more often for the manufacture of permanent magnets, because these materials permit the production of permanent magnets with higher magnetic energy potential than the conventional ferrite magnets. Especially, the recent rapid developments in the field of electronics and electro-technology have demanded an increased production of rare earth magnets. Unlike ferrite, which is typically produced by a wet process, rare earths can be ground and classified either in a wet or dry process. In the past, batch ball mills, through-pass ball mills in circuit with air classifiers, and conventional jet mills were primarily employed for the dry processing. These methods, however, have suffered from the problems, for example, wear and contamination, low product quality In particle size distribution, difficult to adopt inert-gas operation, and high specific energy consumption. In this report, dry processing of rare earth powders will be presented, especially ultrafine grinding with fluidized bed jet mill.

Jan 1, 1993

By Erdal Unal

In underground mining today, safety and economical aspects demand a better understanding of the rock-mass conditions, particularly for design of underground mine openings excavated in weak and stratified rock mass. The rock mass classification systems, in essence, are empirical approaches utilized during preliminary design stage. These systems have been developed for specific purposes and rock mass types, therefore, direct utilization of the classification systems in their original form, for characterization of complex rock-mass conditions is not always possible. This is probably one of the main reasons why designers continue to originate new systems, or modify and extend the ones already existing. RMR and Q systems, for example, although widely used in mining and tunnelling, can not fully describe the specifications of the weak, stratified and flay bearing rock mass. Consequently, the engineering applications that would be carried out based on original RMR and Q ratings could be inadequate for making design decisions even during the preliminary design stage.

Jan 1, 1990

By O. Jay Myers

The war effort has furnished the necessary impetus for better magnesium foundry practice. Four or five years ago, there were but a few formulas in general use for core-sand mixtures for magnesium castings. Certain sands, binders, and inhibitors were specified and the proportions of these materials in each mixture were maintained between very narrow limits. As more and more war industries entered the field, much research was carried out and methods and practices were improved. Magnesium founding is still in a state of flux; therefore it is not uncommon to find one foundry spraying inhibitors on its cores, and another foundry using sand mixtures with incorporated protective agents. The basic core or dry-sand mold mixture for magnesium in use today is compounded with sand, core oil or resin binder, cereal, and moisture. Core oil or resin binder are added for baked strength while the cereal binder and moisture are for green strength. The normal mixtures (based on the weight of the sand) contain from o.5 to 1.5 per cent of both cereal binder and core oil, and the moisture content variesbetween 1.5 and 5 per cent. The ratio of core oil to cereal binder varies from 60:40 to 40:60, while the correct amount of moisture depends upon the method of coremaking. Protective Agents In all magnesium practice, protective agents are used in conjunction with the core and molding sands to prevent oxidation of the metal. The use of these inhibitors is not novel, but publications covering this field are not entirely adequate. Beck1 says: Magnesium alloys decompose water to form magnesium oxide, hydrogen being liberated in the process (Mg + H2O ? H2 ?+ MgO). This reaction results in the blackening of the skin and the appearance of areas of porosity on the casting surface, the cavities of which are filled with a grey oxide powder (these are termed 'burns'). Although sand cores for magnesium castings are thoroughly dried during the baking cycle, burning will take place on the casting5 unless the metal is protected properly. This type of burning is more difficult to define than the "water-magnesium" reaction cited by Beckl A possible explanation may lie in the following equation: 2Mg + O2—> 2MgO Here, the source of the oxygen is not water, but the air in the mold cavity, together with the chemically combined oxygen in the core-binding media. Generally, two methods are used to prevent this reaction from taking place.

Jan 1, 1945