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By W. H. Basssett

THE amount of oxygen present in refined copper bears an important relation to the effects of various impurities on physical properties of copper, as well as the effects of reducing gases at higher temperatures. It seems fitting at this time, when the effects of reducing gases on copper are being discussed, to describe methods that have proved satisfactory for the determination of oxygen and sulfur, and to present some results obtained by investigation of these methods in the authors' laboratory. The procedure for the determination of sulfur is closely interrelated with that for oxygen and has, therefore, been included. It was first proposed by Hamper that oxides in copper could be accurately determined by the loss in weight sustained by finely divided copper when reduced at red heat in pure hydrogen, or by the weight of water produced. Hampe's method was later modified by Archbutt,2 who established the accuracy of the method and demonstrated that equally accurate results were obtained by noting the loss in weight or by weighing the water formed. The determination of oxygen by heating in carbon monoxide has been proposed by West.3 In our hands this method has given slightly lower results than obtained by heating in hydrogen.

Jan 2, 1926

By C. L. Shapiro, R. Schempp

DuRing the past few years, general interest in the steel-producing and steel-consuming industries has been centered on the so-called "inherent characteristics" of steels. While often vaguely described, these characteristics are known to influence the response to heat-treatment and the hardening characteristics of the material. Although most of the recent papers and discussions have associated the "inherent characteristics" with the austenitic grain size and emphasized the importance of it, comparatively little is known of the variables that may affect the size of the austenite grain. The work to be described in this paper was carried out during the course of a study on the inherent characteristics of tool steel containing one per cent carbon. The discrepancies encountered in the determination and classification of the austenitic grain size led to an investigation of some of the variants influencing the austenitic grain size as determined by standard methods. Methods of Determining Austenitic Grain Size The present methods used for the determination of the austenitic grain size may briefly be classified in two groups: 1. Etching at room temperature to reveal the austenite grain size prior to cooling. 2. Etching at elevated temperatures, cooling to room temperature, and observing the structural conditions that existed at the temperature from which cooling occurred. The outstanding methods of the first group are: (1) the McQuaid-Ehn test, (2) optimum rate of cooling, (3) quenching and etching. McQuaid-Ehn Test.—This established and accepted test does not need much elaboration. It consists of pack carburizing at a definite temperature for a standard period of time and slowly cooling in the furnace. The temperature is 1700" F. (925' C.) and the time is 8 hr. The interpretation and evaluation of this test are fairly well defined in the A.S.T.M.

Jan 1, 1937

By J. E. Lawver, J. L. Wright, H. R. Kokat

Mesabi semitaconite and oxidized taconite ores that cannot be concentrated by froth flotation can be rendered amenable to flotation through partial concentration in a high-in tensity wet magnetic separator. Since 1964, a method for accomplishing this precon-centration has been under development at the Minnesota Mines Experiment Station, where several hundred tons of ore have been successfully processed. This paper is an analysis of the performance of the separators used at the Station. At present the United States is producing about 85 million tons of iron ore a year, and nearly 55 million tons of this comes from Minnesota. Nearly half of Minnesota's production is in the form of magnetite taconite pellets —the remainder being wash ore and gravity concentrates. As the demands of the blast furnace operators become more stringent - and they are becoming more so yearly — these demands are met by improved iron ore beneficiation technology. Furthermore, there is no doubt that as magnetite taconite, gravity ores, and wash ores are exhausted, new processes will be developed to produce a product comparable to magnetite taconite pellets from Minnesota's vast reserves of oxidized taconite and semitaconite. The magnetite taconite ores are rather easily bene-ficiated by conventional, low-intensity (500- to 1400-gauss) magnetic separators, followed, in some plants, by froth flotation of the magnetic concentrates.

Jan 1, 1969

By Henry S. Washington

During the last twenty years or so the chemical investigation of rocks has made great advances, and it is now generally recognized that a knowledge of the chemical composition is as essential as that of the texture or mineral composition—if not more so—for the proper classification of rocks and study of their origin and relationships. Rock-analyses have vastly increased in number and, what is of greater importance, in quality. New and improved methods permit of greater accuracy than was possible in the early days, and the list of chemical constituents frequently determined has risen from the seven or eight of the greater part of the nineteenth century, to twenty or more. Indeed, rock-analyses with determinations of so many constituents are now commonly made by the chemists of the United States and Australia, while in Germany, Great Britain, France, and Italy the rarer constituents are determined more frequently than formerly. As a consequence of this modern, accurate work, it has been discovered that some elements which were formerly supposed to be rare are of wide-spread occurrence and are often present in considerable amount. The fact is further being developed that the elements tend to show certain relations of occurrence or abundance in connection with each other. This is a fact which is applicable to the rarer elements, and which also finds a broad geological and petrological expression in the recognition of petrographic provinces. We are beginning to obtain some definite, though as yet rudimentary, knowledge of the distribution of the elements among igneous rocks. Some of the results along these lines obtained by study of the vast accumulation of analytical data now available are well known to petrologists, while others do not seem to be so gener-

Jan 1, 1909

By Henry Carlisle

W. W. Mein: One of the most amusing things in Nevada City – I was born and was going to school there - was that my mother made overcoats for us, and because they were different from other boys’ overcoats, we’d hide them under a bridge and pick them up on the way home. I left Nevada City with my parents when I was about eleven years old, and moved to Oakland. This was caused by the closing down of the hydraulic mines and my father being send to the El Cayo mine in Venezuela, which was then one of the richest gold mines in the world. Hamilton Smith operated the hydraulic mines in California, and when they were closed down by the Sawyer decision, he was persuaded by the Rothschilds to go to London. There, together, they formed the London Exploration Co.

Jan 1, 1964

Jan 9, 1950

By W. M. Phillips

Processing kaolin clays from the sedimentary deposits of Georgia and South Carolina is described in this article. While the major processing steps are touched on briefly, emphasis is given to the dewater-ing of the clay-water slurries (slips) formed in the processing of kaolin clays. The dewatering steps discussed include gravity settling, centrifugal dewatering, vacuum filtration and thermal drying. Particular attention is given to vacuum filtration and the variables affecting filtration of these kaolin clays. Kaolin consists essentially of the mineral kaolinite, which is a hydrated aluminum silicate (Al2O3 . 2SiO,). Commercial deposits of kaolin occur in several areas of the U. S., but approximately 90% of the kaolin produced in this country comes from Georgia and South Carolina. These deposits are of sedimentary nature and occur in a geological fall line in the Tuscaloosa formation at elevations between 300 and 450 ft above sea level. Over two million tons of kaolin clays are used by industry in the U. S. each year. A big percentage of this tonnage is used in the paper industry for coatings in making glossy and high quality grades of printing papers. In addition, large tonnages are used as pigments; as fillers for rubber, plastic and fertilizers; and in ceramics. Properties of kaolin that make it widely used in the above applications are its particle size fineness, natural whiteness, chemical stability and non-abrasiveness. In addition to these desirable properties, it is relatively inexpensive. The finer coating grades of clays range in price from $15 to $28 per ton while the coarser filler grades sell within a range of $7 to $13.50 per ton. Pure kaolin particles are small hexagonal flat platelets. Above the 2-p size, the particles usually consist of stacks of plates, while below the 2-p particle size they occur as individual flat, hexagonal plates. Since these individual platelet particles provide the most desirable coating and flow characteristics, major importance is given to particle size fractions of 2 p and smaller. Generally, coating grade clays are those with all particles smaller than 15 p and at least 70% of the particles less than 2p. These coating grades also have 50% or more of the particles smaller than 1 µ in size. The extremely fine grades of coating clay currently being produced approach the range of 100% smaller than 2p. The filler grades of kaolin have 100% of the particles passing 325 mesh but have less than 70% of their particles below the 2-p range. Fig. 1 is a schematic representation of the major processing steps involved in preparing kaolin clays for marketing. MINING All kaolin mining is open pit. The ratio of overburden to clay will average 3:1, but this ratio can, of course, be much higher depending upon the grade of the clay and the size of the deposit. Most of the commercially mineable deposits occur from 20 to 120 ft below the ground surface. Both draglines and pans are used in removing the overburden and mining the clay deposit itself. After mining, the most common method of transporting the clay to the processing plant is by blunging or re pulp-

Jan 1, 1963

By H. N. Hall

Reservoir and producing characteristics can govern the decision to use either a one-, two- or three-dimensional model for making predictions for gravity-drainage reservoirs. Examples of conditions requiring one-, two- and three-dimensional calculations are given. In 1961 the author presented a method for predicting one-dimensional gravity-drainage performance. This work has been exrendcd to obtain a three-dimensional model, which is described and for which a sample problem is presented. Introduction Many papers on gravity drainage or gas-cap drive'-3 have been presented for conditions where the reservoir is treated as a single areal segment so that, in effect, only one-dimen-sional flow is considered. Other authors'-Q ave given evidence showing that the one-dimensional concept would be unsatisfactory to predict reservoir performance for certain types of reservoirs. Experience has indicated that specific reservoir and producing conditions govern whether one-, two- or three-dimensional concepts must be used as a basis for reliable reservoir performance predictioils. Previously the author presented a paper outlining a method for predicting the performance of gravity-drainage reservoirs.' That paper treated the reservoir as a single areal segment so that it was applicable for only one-dimensional flow. The work has been extended to obtain a three-dimensional model that can be used to predict performance of gravity-drainage reservoirs. Although capable of being three-dimensional, it can be used equally well for one- and two-dimensional predictions. This paper discusses those reservoir and producing conditions governing the choice of model, and also describes a three-dimensional model suitable for predicting reservoir performance in the more complex situations. Discussion The Choice of Model To predict reservoir performance, it is necessary to represent the reservoir by a physical model. A mathematical model, based on the assumed physical model, then is used to predict the movement of oil and gas within the reservoir. The word "model" is used here to connote the combination of both a physical model and a mathematical model based on the physical model. Certain types of reservoir situations may be predicted suitably with a one-dimensional model, whereas two- and three-dimensional models may be required for other situations. This section illustrates reservoir conditions associated with the use of a specific type of model. Many types of reservoir structures are such that gravity drainage possibly could be an important factor in oil production. Production practices, as well as the nature of the structure. can influence the type of model that should be used. obviously, it is impossible to discuss all combinations of reservoir structure and production practices that might be encountered in gravity-drainage reservoirs. The following are typical examples of conditions where a choice must be made among a one-, two- or three-dimensional model to predict reservoir performance satisfactorily. Conditions Requiring a One-Dimensional Model Fig. la shows contours for an asymmetrical anticline in which gravity drainage might be expected to be important. Fig. Ib depicts a cross-section along Line A-A in Fig. la. Existence of a gas cap is a good clue that gravity drainage will be an important factor in producing oil from this type of reservoir. However, it is not essential since a gas cap will form as oil is produced from the reservoir. If the proper combination of reservoir permeability and withdrawal rates is present, the reservoir will behave like a

Jan 1, 1969

By C. M. Tucker, K. R. Van Horn, W. P. Sykes

Recent investigations of the molybdenum-carbon alloys have been reported by Becker and Ebertl,‡ Westgren and Phragmén2, T. Takei3, and H. Tutiya4. Takei3 studied the Mo-C system by employing metal-lographic and X-ray methods, and the other publications described the determination of the crystal structure of the molybdenum carbides. In exploring this system by a technique previously applied to the tungsten-carbon series5, the results of Takei were confirmed with two definite exceptions; i.e., first the composition of the eutectic, and second the nature of the carbon-rich intermediate phase. Consequently, a more thorough examination of the molybdenum-carbon constitution was initiated in an effort to correlate the data supplied by the microstructures, diffraction patterns and chemical analyses. Metallographic Investigation A briquette of molybdenum powder when heated in a carburizing atmosphere at 1500" to 1600" C. for several hours develops the carbon-rich layer shown in Fig. 1. The carburization was accomplished by placing the briquette in a carbon tube, which was heated in the hydrogen atmosphere of an alundum muffle wound with tungsten resistor. While the macrostructure indicates two distinct shells, and suggests the possibility of two carbon-rich phases, no evidence of this condition could be detected by the microscope, which revealed but one high-carbon constituent. This carbide forms next to the molybdenum as a relatively dense, light-colored zone (Fig. 2) which passes abruptly into an outer layer of spongy texture. As will be noted later, only one intermediate phase was observed in the X-ray photograms prepared of different locations in the carburized zone. The metallographic structure at the inner border of the shell, reproduced in Fig. 3, shows a marked porosity accom-

Jan 1, 1935

By I. W. Walling, F. B. Plummer

Bastin and others have demonstrated the presence of sulphate-reducing bacteria in oil wells producing salt water. Analyses show that at 125°F. bacteria alone reduce sulphates in East Texas salt water by only 3 per cent in 30 days, forming principally hydrogen sulphide and sodium or calcium hydroxide. The hydrogen sulphide reacts with soluble iron compounds to produce iron sulphide in the absence of oxygen, and ferric hydroxide where oxygen and air are present. Where iron or other metals and iron sulphide are already in the water containing bacteria, I00 per cent reduction of the sulphates is complete in 30 days or less; where magnesium is present, reduction is complete in 15 days. The effects of changes in temperature, of different bactericides, and of concentration of bactericides on sulphate reduction are described in detail and illustrated by tables and curves. The significance of sulphate reduction on corrosive properties of oil-field water is briefly discussed. Chemistry of East Texas Oil-field Water The chemical composition of the water in the East Texas field salt-water disposal pits is shown in Table I. This salt water corrodes pipes, pumps, and steel tanks excessively, principally because of its content of oxygen, hydrogen, sulphide, and carbonic acid. The carbonates in the water when exposed to air tend to give up carbon dioxide and to precipitate calcium carbonate in large quantities. This forms coatings in tanks, settling pits, and ditches, and soon, unless removed by acid treatment, will effectively clog an injection well and reduce the flow of water back into the ground. The iron compounds in the water, most of which are dissolved from tanks and pipes, are in the ferrous form, and when exposed to the air are oxidized from soluble ferrous carbonate to insoluble ferric hydroxide, resulting in the precipitation of a gelatinous precipitate that will clog oil-field sands effectively: 2Fe(HCO3)2 + O + H2O -> 2Fe(OH)3 + 4CO2 The sulphates in strong sulphate-bearing water may be attacked by swarms of sulphate-reducing bacteria and more hydrogen sulphide may be produced. The hydrogen sulphide reacts with soluble minerals in the water to form black sludges. A knowledge of the chemistry of each reaction in oil-field water is important to the oil-field engineer, since means must be devised to prevent the formation of harmful precipitates that clog injection wells and to prevent corrosion of tanks by harmful products of biochemical processes. Methods of Treating Water before Injection into Ground* The open system of handling the waste salt water in the East Texas field consists of aerating and chemically treating the water to precipitate the unstable iron,

Jan 1, 1946

By C. E. Sims

The carbon-oxygen reaction without doubt is the basic reaction in steelmaking. It is important on several counts: In the first place, carbon is the element that distinguishes steel from iron. It is the principal element controlling properties, and its control is of prime concern. Although the principal objective of the carbon-oxygen reaction is to oxidize excess carbon, the accompanying boil should not be underrated. The mechanical agitation, stirring, and mixing resulting from the boil are so useful in the distribution of heat and in promoting uniformity of composition in the bath that, were it not a natural accompaniment of the carbon-oxygen reaction, it is probable that something would have to be invented to replace it. The open-hearth operation, for example, with the bath heated from above by radiation, would be impracticable without the carbon boil. The electric-arc furnace is somewhat less dependent on it, but every melter knows how much easier it is to gain temperature with minimum damage to refractories during the boil than with a dead bath The motor action of the induced current of the induction furnace makes the carbon boil unnecessary but even there a severe oxidation has been found useful in giving greater freedom from porosity in certain steels. The quantitative aspects of the carbon-oxygen reaction have been given considerable attention by a large number of investigators, and the principles of physical chemistry have played an important part in these studies. Physical chemistry is the science of the mechanics and mathematics of chemical reactions. It is possible to study the mechanisms of reactions in a qualitative manner writhout reference to mathematics and thus obtain valuable concepts as to the manner in which the wheels go around. When it is desired to express quantitative relations in these reactions, however, resort to mathematics is not only convenient but necessary. Mathematics may also be regarded as the shorthand language of physical chemistry. A basic relation whose description requires numerous words may be expressed very simply by a mathematical formula or equation. A good example of this is the equilibrium constant for a chemical reaction. Expressed verbally, it is: When a chemical reaction has reached a condition of equilibrium, the Product of the concentration of the reacting substances on one side of the equation, divided by the product of the concentration of the reacting substances on the other side, gives a quotient that is a constant at constant temperature For the carbon-oxygen reaction C + O ^ CO this is expressed simply as % C X % O -%co where K (from the German Konstant) is the equilibrium constant for the reaction. Although mathematics is such a necessary and useful tool, it is also a potential pitfall. Mathematics in itself is an abstract science, which is not inhibited by consideration of mechanisms or materials.

Jan 1, 1948

By C. E. Sims

The carbon-oxygen reaction without doubt is the basic reaction in steelmaking. It is important on several counts: In the first place, carbon is the element that distinguishes steel from iron. It is the principal element controlling properties, and its control is of prime concern. Although the principal objective of the carbon-oxygen reaction is to oxidize excess carbon, the accompanying boil should not be underrated. The mechanical agitation, stirring, and mixing resulting from the boil are so useful in the distribution of heat and in promoting uniformity of composition in the bath that, were it not a natural accompaniment of the carbon-oxygen reaction, it is probable that something would have to be invented to replace it. The open-hearth operation, for example, with the bath heated from above by radiation, would be impracticable without the carbon boil. The electric-arc furnace is somewhat less dependent on it, but every melter knows how much easier it is to gain temperature with minimum damage to refractories during the boil than with a dead bath The motor action of the induced current of the induction furnace makes the carbon boil unnecessary but even there a severe oxidation has been found useful in giving greater freedom from porosity in certain steels. The quantitative aspects of the carbon-oxygen reaction have been given considerable attention by a large number of investigators, and the principles of physical chemistry have played an important part in these studies. Physical chemistry is the science of the mechanics and mathematics of chemical reactions. It is possible to study the mechanisms of reactions in a qualitative manner writhout reference to mathematics and thus obtain valuable concepts as to the manner in which the wheels go around. When it is desired to express quantitative relations in these reactions, however, resort to mathematics is not only convenient but necessary. Mathematics may also be regarded as the shorthand language of physical chemistry. A basic relation whose description requires numerous words may be expressed very simply by a mathematical formula or equation. A good example of this is the equilibrium constant for a chemical reaction. Expressed verbally, it is: When a chemical reaction has reached a condition of equilibrium, the Product of the concentration of the reacting substances on one side of the equation, divided by the product of the concentration of the reacting substances on the other side, gives a quotient that is a constant at constant temperature For the carbon-oxygen reaction C + O ^ CO this is expressed simply as % C X % O -%co where K (from the German Konstant) is the equilibrium constant for the reaction. Although mathematics is such a necessary and useful tool, it is also a potential pitfall. Mathematics in itself is an abstract science, which is not inhibited by consideration of mechanisms or materials.

Jan 1, 1948

By F. B. Plummer, I. W. Walling

Bastin and others have demonstrated the presence of sulphate-reducing bacteria in oil wells producing salt water. Analyses show that at 125°F. bacteria alone reduce sulphates in East Texas salt water by only 3 per cent in 30 days, forming principally hydrogen sulphide and sodium or calcium hydroxide. The hydrogen sulphide reacts with soluble iron compounds to produce iron sulphide in the absence of oxygen, and ferric hydroxide where oxygen and air are present. Where iron or other metals and iron sulphide are already in the water containing bacteria, I00 per cent reduction of the sulphates is complete in 30 days or less; where magnesium is present, reduction is complete in 15 days. The effects of changes in temperature, of different bactericides, and of concentration of bactericides on sulphate reduction are described in detail and illustrated by tables and curves. The significance of sulphate reduction on corrosive properties of oil-field water is briefly discussed. Chemistry of East Texas Oil-field Water The chemical composition of the water in the East Texas field salt-water disposal pits is shown in Table I. This salt water corrodes pipes, pumps, and steel tanks excessively, principally because of its content of oxygen, hydrogen, sulphide, and carbonic acid. The carbonates in the water when exposed to air tend to give up carbon dioxide and to precipitate calcium carbonate in large quantities. This forms coatings in tanks, settling pits, and ditches, and soon, unless removed by acid treatment, will effectively clog an injection well and reduce the flow of water back into the ground. The iron compounds in the water, most of which are dissolved from tanks and pipes, are in the ferrous form, and when exposed to the air are oxidized from soluble ferrous carbonate to insoluble ferric hydroxide, resulting in the precipitation of a gelatinous precipitate that will clog oil-field sands effectively: 2Fe(HCO3)2 + O + H2O -> 2Fe(OH)3 + 4CO2 The sulphates in strong sulphate-bearing water may be attacked by swarms of sulphate-reducing bacteria and more hydrogen sulphide may be produced. The hydrogen sulphide reacts with soluble minerals in the water to form black sludges. A knowledge of the chemistry of each reaction in oil-field water is important to the oil-field engineer, since means must be devised to prevent the formation of harmful precipitates that clog injection wells and to prevent corrosion of tanks by harmful products of biochemical processes. Methods of Treating Water before Injection into Ground* The open system of handling the waste salt water in the East Texas field consists of aerating and chemically treating the water to precipitate the unstable iron,

Jan 1, 1946

By E. A. Trager, A. W. McCoy, H. R. Shidel

Sampling of the fluid from oil wells for percentages of oil, emulsified oil, and water during the last two years has brought out some interesting facts concerning oil-water emulsion. This result led to a laboratory investigation of emulsion, which substantiated the conclusions made from the field observations. The purpose of this paper is to present the information collected, the laboratory experiments, and our interpretation of the same. In order to define emulsified .oil exactly, give its synthesis and origin, and to show how and when it is formed in the wells, the work was necessarily divided into two separate lines—laboratory work and field observations. It is hoped that this study may lead to a discussion of such points so that the petroleum engineer, geologist, or technologist may be benefited by its practical bearing on oil-field management. Special credit is due Mr. Everett Carpenter, chief geologist of the Empire Gas & Fuel Co., for his assistance and cooperation in this work. Labobatory Investigations on Emulsified Oil Laboratory investigations were conducted in an attempt to learn the composition and some of the properties of emulsified oil, or B. S., as it is more commonly called, also to demonstrate, by laboratory methods, how B. 5. may be formed under conditions similar to those existing at the time a well is being pumped, and how it may be broken down. Literature bearing on this subject is widely scattered and very limited in scope. Bacon and Hamor define B. S., or bottom settlings, as "earthy matter, inert organic matter, or, in the case of Pennsylvanian petroleum, an emulsion of paraffin wax and water, which accompanies crude oil." In this discussion we will limit the term B. S. to that heavy, dark-brown emulsion, composed of a physical mixture of water, oil, and air with some included inert matter, either organic or inorganic. Possibly the first step in a description of this product should be a description of its physical properties, but since most operators are quite

Jan 1, 1921

By C. M. Tucker, K. R. Van Horn, W. P. Sykes

Recent investigations of the molybdenum-carbon alloys have been reported by Becker and Ebertl,‡ Westgren and Phragmén2, T. Takei3, and H. Tutiya4. Takei3 studied the Mo-C system by employing metal-lographic and X-ray methods, and the other publications described the determination of the crystal structure of the molybdenum carbides. In exploring this system by a technique previously applied to the tungsten-carbon series5, the results of Takei were confirmed with two definite exceptions; i.e., first the composition of the eutectic, and second the nature of the carbon-rich intermediate phase. Consequently, a more thorough examination of the molybdenum-carbon constitution was initiated in an effort to correlate the data supplied by the microstructures, diffraction patterns and chemical analyses. Metallographic Investigation A briquette of molybdenum powder when heated in a carburizing atmosphere at 1500" to 1600" C. for several hours develops the carbon-rich layer shown in Fig. 1. The carburization was accomplished by placing the briquette in a carbon tube, which was heated in the hydrogen atmosphere of an alundum muffle wound with tungsten resistor. While the macrostructure indicates two distinct shells, and suggests the possibility of two carbon-rich phases, no evidence of this condition could be detected by the microscope, which revealed but one high-carbon constituent. This carbide forms next to the molybdenum as a relatively dense, light-colored zone (Fig. 2) which passes abruptly into an outer layer of spongy texture. As will be noted later, only one intermediate phase was observed in the X-ray photograms prepared of different locations in the carburized zone. The metallographic structure at the inner border of the shell, reproduced in Fig. 3, shows a marked porosity accom-

Jan 1, 1935

By R. W. Waterfill

MANY existing ore deposits of valuable metals have been worked out in their upper surface levels and the continued productivity of these mines is dependent on their extension to greater depths in the earth. The maximum depths at present reached are about 6000 to 8000 ft. below the surface, with no evidence of an impoverished ore vein. These mines are widely distributed; some of the best known are in South Africa, Brazil, India and in the western sections of the United States. Among the factors which increase the difficulty of working these mines at increasing depths are hoisting, rock pressure and temperature. The manner and effectiveness with which these problems are met will, no doubt, determine in a large measure the ultimate depths to which any mine can be profitably worked. The most critical of these three factors at present is the increase in temperature with depth. The high temperature and humidity in many of these mines at present is severely detrimental to the health of the workers and greatly hampers their efficiency. Some have almost reached a condition in which the human system cannot survive. The problems involved in the cooling and ventilation of mines have all been ably analyzed and presented in previous articles. For this reason, only a resume of conditions affecting the cooling and conditioning of deep and hot mines will be given in this paper before attention is directed to possible methods of improving atmospheric conditions in the working levels.

Jan 1, 1929

By Maurice K. Seguin

It is a difficult task to find enriched soft iron ore deposits in the central part of the Labrador Trough, New Quebec, Canada, when the areas investigated are covered by glacial drift. A qualitative interpretation of either a combined gravity-magnetic-seismic-resistivity survey or gravity-magnetic-seismic or gravity-magnetic-resistivity survey permits (with a low probability level) the detection of iron formations and ore zones as well as their delineation from most of the country rocks. This is possible because most of the altered iron formation underwent a slight increase in density through enrichment and because the accompanying geochemical alteration changed their magnetic properties. In order to increase the chances of success in finding ore bodies when using geophysical methods, different types of correlation were done for many deposits. These are: I) A quantitative correlation of the residual gravity anomaly intensities with the specific gravity, the iron content, the silica content, the porosity factor, and the dimensions of the underlying ore bodies. 2) A quantitative correlation of the ground magnetic intensity relative to a reference lithologic unit with the percentage of Fe.,O, recovery and with the volume ferromagnetic susceptibility. A few discoveries already have been made with this method. The details of the location, the description of the geology, and the history of previous geophysical surveys and their qualitative interpretation have already been given.', ' A very brief paragraph describing the regional and local geology is necessary in order to facilitate the understanding of this paper. The sedimentary iron formations of the Labrador Trough consist of a 700-mile geosynclinal segment composed of tightly folded and faulted Proterozoic sediments, volcanics, and intrusives that are rich in mineral deposits. The complex sequence rests unconformably on the basement of Archean granitic gneisses. The direct-shipping iron deposits are scattered along a northwest-trending strip, 5 to 10 miles wide and some 60 miles long in the facies rich in iron oxides and preferentially in localities where the original sedimentary environment favorized the deposition of a large concentration of magnetite associated with chert by physicochemical processes, e.g., oxidation-reduction potential, pH, temperature, pressure. Once leached of its silica and/or iron carbonate content and enriched with secondary a-hematite (occasionally goethite), this original magnetite associated with some primary hematite makes the blue direct-shipping ore which constitutes the important ore reserves in this mining district.

Jan 1, 1971

By Harry V. Welch

This paper presents a brief discussion of numerous devices and processes which have been utilized for the recovery of values from gases in copper reduction works and describes in greater detail the development and application in recent years of electrical precipitation, more familiarly known as the Cottrell process, to the problems of dust losses with furnace gases in copper-smelting and refining plants. The field for collection of suspended particles in gases is widely extended in our modern complex, congested .and industrialized mode of living, and its satisfactory solution is required by our increasing appreciation of the extravagant waste, unhealthful effects and nuisance which such uncontrolled emission of solid suspensions represents. Much of the special dust-recovery equipment in use today has been developed in one industry and carried over to many others. The early work of Cottrell was with sulfuric acid mists, aimed at the purification problem in contact acid manufacture, but the present uses of Cottrell equipment cover a diversified field—carbon black, combustible gas, oil mists, iron blastfurnace fumes and dusts, cement-kiln gases, as well as the purification of gases in contact and chamber acid plants and its wide and extended use in the nonferrous metallurgical field of copper, zinc and lead, and their associated metals. Dust and fume collection from furnace gases became a problem only with the modern development of large and amply powered auxiliary furnace equipment, which in turn permitted large furnace units, fast driving and large outputs of finished product per unit of furnace capacity. The ancient metallurgist with his small clay pot and hand-operated bellows had too little gas velocity to cause a real dust loss. As furnaces grew in size, flues and stacks were added, and undoubtedly the first observable dust losses were indicated by the deposits in the flue and stack base. Large flues, it was noted, collected more than smaller ones, and the expansion of a portion of the flue into a chamber represented the first serious attempt at recovery of furnace dust losses. For a century or more the settling chamber represented the best of skilled metallurgical practice in recovery of furnace dust, and it may be said to have reached

Jan 1, 1934

By Ulick Evans

I SHOULD like to commence by saying how much I appreciate the honor which the American Institute of Mining and Metallurgical Engineers has done me in inviting me to visit your country, and to deliver this lecture before you. In choosing a subject, and in deciding what to include and what to omit, I have endeavored to discuss as far as possible work carried out recently in Europe with which you may not be unduly familiar. It would be poor return for your hospitality, and a mistaken sort of compliment indeed, if I were to load the lecture with accounts of researches 'carried out in your own country-researches with which you are probably better acquainted than I. Not that I have in any way excluded work done on, this side of the Atlantic from my survey; one would indeed find it difficult to write on this, or on any other branch of science, without mentioning American work. But I have endeavored as far as possible to concentrate on aspects of the case which will, I hope, be comparatively fresh to you, and I feel fairly certain that this will be in accordance with your own wishes. If a strip of iron is heated strongly at one end, the other end remaining cold, there is produced over the heated portion a layer of oxide scale, the thickness of which diminishes steadily with the distance from the hot end. Somewhere in the middle of the strip, the thickness of the oxidized layer will become comparable .to the wave length of light, and over this region the thin films give rise to a series of beautiful interference tints, commonly known as "temper colors." The colors are caused by the fact that two trains of light waves are reflected respectively from the outer and inner surfaces of the oxide film, .and the possibility arises that the "crests" of one series of waves may coincide with the "troughs" of the other, thus diminishing the intensity of the light of some particular wave length. The state of affairs in this part of the strip is shown diagrammatically in Fig. 1, in which the film thickness is enormously exaggerated, of course, in comparison with the length of the strip; the

Jan 1, 1929

By Richard H. Olson

"Rarely in our technological society does the discovery of a new class of inorganic materials result in such a wide scientific interest and kaleidoscopic development of applications as has happened with the zeolite molecular sieves." That opening sentence in a landmark volume on zeolite molecular sieves by D. W. Breck (1974), is, if anything, an understatement. Zeolites were recognized as a new group of minerals in the 1750s, but it was not until 1930 that the first analysis of the crystal structure of a zeolite mineral was made. In the late 1940s research workers at Union Carbide Corp. began a program of zeolite synthesis and study which has resulted in one of the major research achievements of all time. Naturally, with the vast research and development efforts devoted to the synthetic molecular sieves, Union Carbide became concerned in the mid-1950s about its position should minable deposits of natural analogues be discovered. Zeolite minerals have diverse origins, and even a brief discussion of these is beyond the scope of this paper. The early work on zeolites was confined to igneous rock occurrences (e.g., amygdules and veins) which were formed by "space-filling;" these crystals tend to be euhedral, thereby rendering them appealing to both mineralogists and collectors. During the first year or so of Union Carbide's exploration (which began in mid-1957) attention was devoted solely to such igneous, occurrences. A landmark paper by Bramlette and Posnjak (1933) heralded the potential significance of the occurrence of zeolite minerals as alteration products of vitric ash and similar materials. In the summer of 1958, full attention was directed by Union Carbide to the search for deposits of this type in the western United States. Since then, such exploration has been continuous by both commercial firms and private parties. The future economic potential for natural zeolite deposits seems to be restricted to those of the "open-and-closed system" types as described by Sheppard (this chapter). Therefore, this and the following discussions will concentrate upon these types; the other types of zeolites in sedimentary rocks (e.g., deep-sea sediments, burial metamorphic, and hydrothermal) will be, for the most part, ignored. Despite the relative cheapness of natural zeolite deposits as compared with the cost of synthetic molecular sieves, there has been minimal development of zeolite mining in the US over the past 25 years or so. Mumpton (this chapter) discusses the present commercial utilization of natural zeolites and their future potential in detail, but perhaps the following will serve as useful background. In the early days of synthetic molecular sieve research and production, the efforts were concentrated largely upon such high-value applications as physical separation of components in a stream (based upon molecular size and geometry) and in catalysis. Due to a number of reasons (some of which are difficult for an outsider to understand), natural zeolite ores (beneficiated or not) have not made substantial inroads upon the use of the higher-priced synthetic molecular sieves for the foregoing applications, but this is not to say that such a condition will exist forever. Furthermore, in view of the many other uses which are now known, or which loom in the future, the competitive position of the natural zeolites vs. the more expensive

Jan 1, 1983