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By D. L. Martin, E. R. Parker

DURING the heat-treatment of silver specimens for tensile tests it was observed that the bars blistered and became brittle when heated in a hydrogen atmosphere. [ ] To check this unexpected result, a wide variety of commercial silvers were heated in hydrogen at 850°C, Only a few of the materials developed blisters, the most severe of which is the tube pictured in Fig. I. The microstructure of a cross section of the tube is shown in Fig, 2. The embrittlement is extremely severe at the edge; the blisters result from the severe deforma- [ ] tion of the surface material by large underlying gas pockets, The effects resulting from hydrogen embrittlement of silver have been observed by numerous investigators over a long time1,2,3 although it was only recently that a clear explanation was offered ,4 However, the damage resulting from hydrogen embrittlement has not been generally recognized; and it is of advantage to know more about this phe-

Jan 1, 1943

By E. E. Russell Tratman

The use of dynamite in cold weather is attended with some difficulty, owing to the freezing of the material and its consequeut liability to fail to explode when the fuse is fired. With proper methods and care the dynamite can be thawed with reasonable safety, but numerous accidents occur (more than get reported in the public press), due to carelessness in the operation and to the treacherous nature of the material, or a combination of both conditions. Dynamite will stand treatment at one time which at another time will result in explosion. An expert on explosives says that the most dangerous means of thawing cartridges are ingeniously devised by ignorant laborers; baking, boiling and toasting being favorite methods, while at a stone-quarry, in one instance, an apparatus was arranged for steaming the cartridges over a pot of boiling water. In this latter case the nitro-glycerine leaked through the canvas cover and settled on the bottom of the pot, with the result that an explosion occurred, the water acting as a tamping to the charge. The fact that small quantities of explosives containing nitroglycerine will burn quietly and without explosion if ignited by direct contact with a flame, has led to the dangerously mistaken reasoning that merely heating the explosive can produce no ill effect. If . a dynamite cartridge is ignited or placed in a fire it will probably burn harmlessly away, but if placed on a stove or in an oven and

Jan 1, 1893

By Jouko O. Kallioinen

The control of zinc flotation at Outokumpu Oy's Pyhasalmi and Vihanti mines is described. At Pyhäsalmi the zinc flotation circuit is partially open. Zinc and other metal assays of pulp flows are measured and direct assay control of concentrates in various flotation steps is adopted. Assay control is carried out by adjusting flotation air and pulp levels. Optimization with copper sulphate ensures high Zn- recovery and minimum copper sulphate consumption. A froth depth monitor is used to measure froth quality. At Vihanti the zinc flotation takes place in closed circuit. The most important control loop is the Zn-assay control of rougher concentrate by adjusting flotation air. The quality of froth is measured indirectly and thus copper sulphate consumption is altered. The circulating load is controlled also by flotation air in the three cleaning steps. The comparison of the control strategies shows that a more sophisticated control is adopted at Pyhäsalmi because the selective flotation of this massive sulphide ore is considered to be difficult. The control strategy includes numerous tests performed by the computer and control algorithms developed for the case. The control targets of the two zinc flotations described are also different: At Pyhäsalmi Zn-assay control of final concentrate including copper sulphate optimizing, at Vihanti the control of circulating load and Zn-assay of rougher concentrate.

Jan 1, 1984

By E. C. Wright, P. W. Mumma

This paper describes some properties of steels in the composition range 0.10 to 0.30 per cent carbon and 1 to 7 per cent chromium. It is well known that some steels of this type develop high tensile strengths upon receiving comparatively simple heat treatments, such as ordinary air cooling from appropriate temperatures, with or without subsequent tempering treatments. These high strengths are frequently associated with unusual toughness as measured by the Izod or Charpy impact test. The chromium content, in addition to imparting the above properties, enhances the resistance to corrosion and improves the strength and oxidation resistance at elevated temperatures. Moreover, these steels have good forging and fabricating properties, as evidenced by the fact that several thousand tons of seamless tubing have been made during the past five years from steels containing 0.10 to 0.25 per cent carbon and 5 per cent chromium. Composition and Properties of Materials Tested Twelve 15-lb. induction furnace heats of the compositions shown in Table 1 were prepared, using low-carbon open-hearth steel base melts

Jan 1, 1933

ECONOMICS In the preceding pages you will find an attempt to judge the direction of one phase of the mining industry in Drift, and following that a quick round up of what happened to production in 1958 in Trends. Next, Charles Merrill presents a comprehensive price history for the mineral products of greatest importance, complete with figures for the past 50 years. On the following pages Nathaniel Arbiter and Charles Will Wright take a look at price trend prospects and the cold war in mining, respectively. MINERALS BENEFICIATION Fifty years progress is reviewed as a springboard for a look ahead. In the past decade the art has moved forward, but the author fears that the science is not progressing as promisingly.

Jan 2, 1959

By H. L. Shergold, O. Mellgren

Concentration of fine quartz particles at the iso-octane/water interface has been investigated under different conditions of pH and dodecylamine concentration. The results obtained from the related studies on the effect of amine concentration and pH on the interfacial tension, adsorption density, electrokinetic potential, contact angle, and concentration of the various amine species in the system are presented. A good correlation was obtained between these different variables. It is well-known that very fine mineral particles are difficult to float in conventional flotation machines. Flotation rate studies have revealed that the rate of flotation of fine mineral particles is much smaller than that of coarser size fractions. The theories accounting for this behavior have been discussed by Arbiter and Harris1 and also Meloy.2 Theoretically, a hydrophobic fine particle might never make contact with a bubble because of the presence of an energy barrier in the vicinity of the air/water interface.' This energy barrier will have electrostatic, hydrodynamic, and Van der Waals force components. It was thought that by using an oil phase instead of air the energy barrier would be decreased so that fine particles could be concentrated at the oil/water interface more readily than at the air/water interface. The technique used involves dispersing the fine particles in water, containing the appropriate chemical reagents, and injecting a fine dispersion of iso-octane oil droplets into the pulp. After vigorous conditioning, the pulp is passed into a separating column where the oil droplets coated with a layer of mineral particles rise to the surface to form a separate layer. Air is introduced into the base of the separating column to ensure that heavy agglomerates of oil and particles report with the organic layer. This technique has been described previously4 and adopted by Lai and Fuerstenau5 who studied the alumina-dodecyl sulfonate system. The interfacial phenomena in the system composed of hematite, water, and iso-octane in the presence of sodium dodecyl sulfate have been studied and the results reported" earlier. This paper describes the results obtained from investigations into the interfacial phenomena in the quartz/water/iso-octane system in the presence of dodecylamine. The technique used in measuring the interfacial tension, electrokinetic potential, contact angle, and adsorption density were similar to those described previously? Materials Selected pieces of a high purity natural quartz, from the Isle of Man, were crushed in a laboratory jaw crusher and pulverizer. The — 52+72 mesh size fraction was retained and leached with successive washes of hot concentrated hydrochloric acid to remove iron impurities. When no iron was detected in the solution by ammonium thiocyanate, the quartz was washed thoroughly with distilled water until the conductivity of the wash water assumed that of the distilled water. Samples of 25 g of the —52+72 mesh quartz were ground for 5.25 min in an agate vibratory mill. The ground product was 100% —44 m and 57% —10 am, as determined by the Andreasen pipette. The specific surface area of the sample used for the adsorption and flotation tests was 0.94 sq m g-l. This corresponds to a mean particle diameter of 2.4 am. The —44 am quartz sample was stored under vacuum in the presence of silica gel crystals. For the contact angle determination between the three phases, quartz, iso-octane, and water, a piece of the natural quartz was ground into a block about 15 mm long, 15 mm wide, and 5 mm thick. One surface of the block was then polished by successively finer grades of silicon carbide "paper." The final polishing was conducted with alumina on a "hyprocel" paper. The polished quartz specimen was cleaned using nitric acid and ethyl alcohol followed by a wash with distilled water and then stored under distilled water. This pro-

Jan 1, 1971

By Charles White Merrill

Money is one of the most .pervasive elements in human life. The compensation for a workman's daily efforts is expressed as a wage and is measured in money. What an individual may consume depends largely on his income which also is expressed in terms of money. If he would start an enterprise its size would be determined in large part by the amount of money available for capitalization and its success would be measured in net income expressed in money. In short, the most widely used common denominator for comparing merchandise, real property, jobs, enterprises, gross national product, or personal success is money. Despite this use of money by almost everyone past infancy to express his appraisal of the in- numerable values he sees around himself, the complexity of the device called money makes its nature and workings a mystery to most users. Some of the difficulty in understanding money results from the fact that it has three distinct but interrelated functions: (1) a medium of exchange, (2) a unit of account, and (3) a store of value. In many statements about money the discussion moves from one function of money to another without the speaker or the listener recognizing the changes. For example, the housewife says "We took the money we had saved up to make the down payment and after twelve monthly payments the television will be ours." When this housewife spoke of "saving up the down payment" she referred to money in its function as a store of value; when she spoke of "the down payment" she was using money as a medium of exchange; and when she referred to the "monthly payments" she spoke of money as a unit of account. Another cause of confusion in understanding money is its paradoxical nature in that it represents both the power to produce and the power to consume. For example, when the rich uncle dies one nephew may regard his inheritance as an opportunity to buy a farm and leave the ranks of the wage earners to become an independent producer, whereas the other nephew may regard his portion as the means of living in complete leisure as a pure consumer.

Jan 1, 1959

By Bruce N. McIver, Leo Casagrande

Similarities are noted in the practices and problems of constructing dams to impound mine tailings, fly ash, and chemical wastes. The comparison of a typical tailings dam with a conventional water-retaining earth dam shows that the former is inherently less stable and can be susceptible to cracking, liquefaction, erosion, and frost action, as illustrated by examples. Several methods are presented for building safe tailings dams using either the coarse fraction of the tailings or local soils, the important factor in each method being proper compaction of the material. The safety of existing tailings dams can be improved by flattening the overall slope, preferably by adding berms, or by decreasing the height. Where neither remedy is possible, the installation of electro-osmotic tie-backs is suggested. Dumps of mine spoil can be stabilized economically by compacting the material in layers along the toe to form a dam.

Jan 1, 1971

By Elmars Ence, Harold Margolin

The partial isothermal section of the Ti-Cu-Zr system at 750°C has been studied. The crystal structure of Ti2Cu has been detevnlined as tetragonal and when expressed as face-centered tetragonal, a = 4.164, c = 3.611 A, and c/a = 0.867. TITANIUM systems in which ß-titanium decomposes eutectoidally into a and a compound rather readily are known as active eutectoid systems. Recently in active eutectoid alloys based on the Ti-Cu system, and containing additionally A1 and Zr, it has been found that zirconium may produce both moderate weakening and marked strengthening at elevated temperatures.' In order to obtain some insight into the behavior of zirconium, an attempt was made to determine whether compounds of the type Tix Zr and TixZryCu exist. Only results of the Ti-Zr-Cu studies are reported here since data on Ti-Zr alloys will be presented in a separate publication. EXPERIMENTAL PROCEDURE Alloys were nonconsumably arc melted in argon atmosphere as 15-g buttons, prepared from materials of the following purities: Bureau of Mines electrolytic Ti — Bhn 63 OFHC copper Reactor Grade Zirconium Bhn .C 150 Prior to alloy preparation the electrolytic titanium was premelted to avoid excessive spattering of the charges during melting. The weight losses during melting did not exceed 1 pct of the total weight of the charge. The alloys prepared are listed in Table I together with analyzed compositions. in cases where they were determined. Specimens for heat treatment were wrapped in molybdenum sheet, annealed in argon-filled quartz capsules, and quenched by breaking the capsules under iced brine. About 1 to 2 sec are required to remove the capsule from the furnace, drop it into the iced brine and break it. Because of the insulation effect of the quartz, this delay in quenching should not produce a large drop in temperature. In many instances, no difference or little difference has been detected between the same specimen quartz capsule quenched or directly quenched in vacuum by an impinging stream of water.' Ti-Cu-Zr alloys were homogenized for 48 hr at 825°C prior to annealing at 750°C. Annealing for 5 days at 750°C produced the same results as 11 days at temperature and it was therefore assumed that 5 days was sufficient to establish equilibrium. Titanium-copper alloys were homogenized for 40 hr at 900°C prior to heat treatment for 6 days at 750°C. Specimens for metallographic examination were electropolished and etched with the following solution:

Jan 1, 1962

By F. M. Perkins, R. H. Jamison

Publications concerning scaling laws for laboratory flow models of oil reservoirs indicate that the relative permeability and capillary pressure relations must be the same functions of saturation in the model and its prototype. In this paper, the relative permeabilities and saturations are redefined in a way which permits one to have diflerent relative permeability and capillary pressure relations in the model and prototype. The development of the new scaling criteria is demonstrated by deriving scaling laws for one simple flow problem. INTRODUCTION The successful application of information gathered through bench-scale model studies to the prediction of multi-phase fluid flow behavior in petroleum reservoirs requires careful consideration of the scaling criteria. The requirements which must be met for a small-scale model to duplicate the behavior of a much larger reservoir prototype have been discussed by Leverett, et al,' Rapoport,2 and Geertsma, et al.3 According to these authors, the relative permeabilities to water, oil and gas and the dimensionless capillary pressures must be the must have the same values in the model and prototype. Furthermore, they point out that the viscosity ratios must have the same values in the model and prototype. In addition to these requirements, other scaling criteria are given which, when considered, usually dictate a much higher permeability in the model than exists in the reservoir. Since the more permeable model sands may have connate-water and residual oil saturations quite different from those in the prototype, the scaling requirements pertaining to the dependence of relative permeabilities and dimension l ess capillary pressures on saturation usually are not met. Also, if the model fluids are selected to give equal viscosity ratios in the model and prototype, one may find greatly different mobility ratios* in the two cases and, therefore, may expect grossly different flow patterns. For this reason, Craig, et al,' correlated the results of their model studies with mo- bility ratio rather than with viscosity ratio. As yet, however, no satisfactory method has been advanced which permits use of anything other than the scaling requirements outlined in the previously mentioned papers. The purpose of this paper is to present a method of developing a set of scaling criteria which permits different relationships between saturation and relative permeability or capillary pressure in the model and prototype. Rather than attempt to report scaling criteria for a variety of practical situations, this paper demonstrates by use of one simple example how the modified scaling criteria are derived.

By Ralph Hultgren, Bernard York, David W. Mitchell

It is a well-known fact that magnesium-alloy castings are apt to be coarse grained if the melt is not superheated several hundred degrees above the melting point before casting. (The casting temperature varies according to the shape of the mold. A typical casting temperature is perhaps 1400°F.) British practice is to heat to 900°C. (1650°°F.) for 15 min., cool rapidly to casting temperature, and cast.1 In Germany superheating is carried out at 850° to 900°C. (1560° to 1650°F.) depending on the amount of scrap used. It is stated that further refinement will be obtained by prolonging the period of superheating or by increasing the superheat temperature to 950°C. (1740°F.).2 In the United States superheating is carried out at i600° to 1700°F. (871° to 927°C.), perhaps even higher in some places. It is stated that superheating effects are found as low as 1500°F. (816°C.), but several hours are required.3 These commercial treatments lead to grain sizes in sand castings that may vary from 4 to 8 grains per sq. mm.§ in heavy sections and from 60 to l00 in 3-in sections to perhaps 380 in thin sections. It is also generally known that the refining effect of superheating is lost if the melt is held for some time at lower temperatures before casting. Aside from these very qualitative statements, there is little to be found in the literature as to the effect of temperature and time of superheat on the final grain size. Because of the uncertainty of these factors, the Office of Production Research and Development of the War Production Board placed a research contract with the University of California, supervised by the War Metallurgy Committee. This research, which was done under the "Restricted" Project NRC-550, is the basis of this paper, which has been released for publication by the O.P.R.D. The material studied was an alloy prepared from carbothermic magnesium. The temperatures required for grain refinement proved to be widely different from those used in practice, as described in the statements in the first paragraph. This difference is attributed to the fact that the magnesium in the specimens was of carbothermic origin instead of the electrolytic magnesium in common use. MATERIALS AND METHODS The magnesium alloy studied was one of the most popular sand-casting alloys, with a nominal composition of 9 per cent aluminum, 2 per cent zinc, and 0.r per cent (minimum) manganese and the balance magnesium. This is designated

Jan 1, 1945

By Earl Ingerson

BORE surfaces of used guns commonly show a pattern of cracks in various degrees of development. It has been suggested that these cracks may aid erosion by providing channelways for the gases, eventually leading to the tearing out of blocks of metal. Under the general studies of gun erosion conducted at the Geophysical Laboratory it appeared desirable to consider this factor, and to determine the resistance to surface cracking offered by gun steel and by various other materials that might be used in the bores of guns. METHOD AND APPARATUS In order to make such a determination it is necessary to have (I) an arrangement in which the surface to be studied can be subjected to conditions similar to those in a gun with respect to temperature, pressure (developed by explosion gases), composition of the gases and length of time the surface is exposed to the gases; and (2) a specimen that can be examined readily after any number of shots, and then fired again, if necessary. The first of these conditions can be met by using an explosion vessel designed by H. S. Roberts of the Geophysical Laboratory. Fig I shows a cross section of the apparatus. The "gun" G from which the charge is fired is made from the receiver of a caliber 0.30 army rifle, M1903, and the charges are prepared in caliber 0.30 cartridge cases. The test specimen S is held in place by a cone-shaped plug P and by a steel ,bridge B which is bolted to the outside of the explosion vessel on either side of the section shown. The plug, in turn, is held in place by a screw collar C. Maximum pressure is controlled by a brass rupture disk R. Part of the explosion gases flow past the two flat areas on S. st the two flat areas on S. Temperature and composition of gases, and the time before the rupture disk breaks, can be controlled by amount and kind of powder used, and pressure can be controlled by using rupture disks of different thickness. While the explosion vessel used was not designed so that temperature and pressure could be measured, in other vessels of closely similar size and shape containing proportionate charges of the same kind of powder as that used for standard testing procedure, values of 2700°K and 5000 psi were obtained. Since the orifices past the flat areas on the plug are small compared to the rupture disk hole (1:16), most of the gas goes out through the rupture disk when it breaks. The amount that goes by the plug depends on (I) the pressure attained before the rupture disk breaks and (2) the time it takes for this pressure to be built UP. The second condition (examination at will after any firing) is met by using for specimens short rods that have flat areas ground on opposite sides. These flat

Jan 1, 1947

By C. E. Cottrell, G. W. Preckshot, N. D. Delisle, D. L. Katz

Most crude oils contain asphaltic substances that may be naturally or artificially precipitated. In the Greeley field, California, this asphaltic bitumen is precipitated during the flow of the oil from the reservoir to the stock tank The mechanism of such precipitation is not well understood. This paper presents the progress that has been made by using the electron microscope as a new tool and by observing the effects of the streaming potential on the formation of bitumen particles. Crude oils at atmospheric pressure viewed in the electron microscope in very thin films under a vacuum showed no asphaltic particles. A technique of preparing slides of thin films by dilution of the oil with benzene and washing in petroleum ether was used at first, and these observations showed that the solvents caused the formation of the particles, varying from 0.01 to 0.2 micron in diameter. The electrical effects of fluids flowing through porous solid were studied, with emphasis on the formation of colloidal particles by the streaming potential. The streaming potential of crude oil flowing through sand was measured and was shown to be responsible for the formation of bitumen particles. These results bring out a new phenomenon, which may occur when crude oil flows through the porous oil reservoir. mechanisms. Asphalt has been the subject of widespread investigation but, owing to the complexity of the substances being considered, progress has been slow. Investigators working primarily with the asphaltic substances have treated the subject from the colloidal standpoint and have developed theories that picture the asphaltic particles as surrounded by adsorbed materia1s.14,15,17,24 The deasphaltization of lubricating oil by the use of solvents treats the subject primarily from the standpoint of liquid-liquid equilibria.'' A complete understanding of asphaltic substances would make possible the following of the material from its initial state in the crude oil through precipitation processes to the final plastic stage, the most common form of which is used in asphaltic pavements. Since these asphaltic particles are very small, it appears 'hat the electron microscope4 might be a useful tool in studying the precipitation processes. Specimens are examined by the electron microscope in a vacuum and as very thin films, requiring special techniques in preparation of samples. A brief description of the electron microscope and its operation will bring out the difficulties and advantages of its use for this problem. The first work was done with crude oils that had been diluted with solvents for the preparation of the film to be examined. Later a technique was developed by which the undiluted oil film could be made thin enough for direct examination. These two techniques show vastly different results Asphaltic particles have been precipitated from crude oils by a variety of

Jan 1, 1943

By G. W. Preckshot, C. E. Cottrell, D. L. Katz, N. D. Delisle

Most crude oils contain asphaltic substances that may be naturally or artificially precipitated. In the Greeley field, California, this asphaltic bitumen is precipitated during the flow of the oil from the reservoir to the stock tank The mechanism of such precipitation is not well understood. This paper presents the progress that has been made by using the electron microscope as a new tool and by observing the effects of the streaming potential on the formation of bitumen particles. Crude oils at atmospheric pressure viewed in the electron microscope in very thin films under a vacuum showed no asphaltic particles. A technique of preparing slides of thin films by dilution of the oil with benzene and washing in petroleum ether was used at first, and these observations showed that the solvents caused the formation of the particles, varying from 0.01 to 0.2 micron in diameter. The electrical effects of fluids flowing through porous solid were studied, with emphasis on the formation of colloidal particles by the streaming potential. The streaming potential of crude oil flowing through sand was measured and was shown to be responsible for the formation of bitumen particles. These results bring out a new phenomenon, which may occur when crude oil flows through the porous oil reservoir. mechanisms. Asphalt has been the subject of widespread investigation but, owing to the complexity of the substances being considered, progress has been slow. Investigators working primarily with the asphaltic substances have treated the subject from the colloidal standpoint and have developed theories that picture the asphaltic particles as surrounded by adsorbed materia1s.14,15,17,24 The deasphaltization of lubricating oil by the use of solvents treats the subject primarily from the standpoint of liquid-liquid equilibria.'' A complete understanding of asphaltic substances would make possible the following of the material from its initial state in the crude oil through precipitation processes to the final plastic stage, the most common form of which is used in asphaltic pavements. Since these asphaltic particles are very small, it appears 'hat the electron microscope4 might be a useful tool in studying the precipitation processes. Specimens are examined by the electron microscope in a vacuum and as very thin films, requiring special techniques in preparation of samples. A brief description of the electron microscope and its operation will bring out the difficulties and advantages of its use for this problem. The first work was done with crude oils that had been diluted with solvents for the preparation of the film to be examined. Later a technique was developed by which the undiluted oil film could be made thin enough for direct examination. These two techniques show vastly different results Asphaltic particles have been precipitated from crude oils by a variety of

Jan 1, 1943

By S. Nakajima, H. Okazaki

Quantitatiue studies of the deformation texture in drawn tungsten wives were made by the X-vay dif-fractottletetr. Experimental results show that the diffraction Intensities are equal to tilose pvedicted from the (1 10). fiber lexlure but the angxla), spreads of. diffraction peaks in the pole distribution curres are different for different diffraction planes and directions. For this reason a modified (110) fiber lextuve model, in which a kind of anisotropy is assumed, is proposed to explain the results. According to this model the poles lying on a line directing front the (110) to the (110) poles in the (1 10) standard stereograpllic projection should show spreads which are different from those lyitlg on a line directing from the (001) to the (001) poles, which is confirmed by the experiments. The anisolvopy and the spveads of the pole positions are large at the outer part of the wires and decrease gradually lowards the inside of the wire. The possibilily of occurrence of such anisolropy in irrelals with fcc stvuctures is discltssed. THE deformation texture of drawn tungsten wires has been assumed by different investigators to be the simple ( 110) fiber texture.' Recently, however, Leber2,3 has shown that a swaged tungsten rod has a cylindrical texture. It changes gradually to the (110) fiber texture by drawing through dies. However, even after drawing to 0.25 mm in diam, the cylindrical texture can still be found in wires together with the (110) fiber texture. This was deduced from the pole figures obtained from the longitudinal section of these wires. Use was made also of quantitative measurements of the pole distribution curves. Leber stated that the angular spread of the pole distribution curves (henceforward called dispersions) are quite different for (400) 45 deg and (400) 90 deg: the former is always larger than the latter. This inequality is accompanied by deviations of the diffraction intensities from the theoretical values for the ( 110) fiber texture. Bhandary and cullity4 have reported similar results on iron wire and explained them by assuming a cylindrical texture. Both Leber3 and Bhandary4 used only the results of the (400) reflection for the determination of the dispersion. The pole figures found by Leber3 and by Rieck5 are largely different. The model given by Leber to explain the effects is in the authors' opinion in some respects unsatisfactory, especially if one looks at other than the (400) reflections. Intensities and dispersions of diffraction peaks are conclusive factors for the determination of the fine structure in wire textures. For this reason we studied them extensively to come to a model which is more suitable to fit the facts. In the following, after giving the experimental set-up, we report about measurements of X-ray diffraction on drawn tungsten wires. Different models to describe the experimental results will be discussed. EXPERIMENTAL GO-SiO2-A12O3 doped tungsten wires drawn to 0.18 mm in diam were used for the measurements. The wires were chemically etched to various diameters down to 0.03 mm. Measurements were carried out for the different wires in order to determine the dependence of the texture on the radius. The wires were cut to pieces of 10 mm length and fixed with paste closely against each other on a flat, polished glass plate. Parallelism of the wires with the surface of the glass plate should be adequate. For the diffraction studies three different X-ray sources were applied, respectively, giving the CuK,, FeK,, and FeKp emission. The measurements were carried out with a diffrac-tometer with a GM counter. The latter was fixed to a certain diffraction angle 20hkl and the diffraction intensity was recorded as a function of the angle of rotation of the specimen around the axis, lying in the specimen surface and perpendicular to the wire axis, as shown in Fig. 1. Measurements were also done with the detector at angles slightly deviating from the diffraction maxima The measured intensities in this case were taken to be equal to the background level. The deviations were chosen as small as possible but large enough to eliminate the influence of the diffraction maxima. The useful range of the rotation angle x of the specimen is generally limited by the wavelength of the X-rays. We have: where and cp is the angle between the wire axis and the normal of the diffraction plane. Intensity measurements were made to find the necessary corrections for counting loss of the GM counter and for distortion resulting from such effects as absorption of X-rays and from inclination of the reflection plane under study with respect to the surface of the specimen. The counting loss was esti-

Jan 1, 1968

By R. E. Schilson, F. H. Poettmann

The direct determination of the stabilized performance behavior of low capacity, slowly stabilizing gas wells is extremely time-consuming and wasteful of gas. From both field experience and theoretical considerations, a test procedure has been evolved by which the stabilized hack pressure behavior of such gas wells can he predicted without having to revert to long time flow tests. The method consists of using the isochrona1 test procedure to establish the slope of the back pressure curve, "n", and the short time variation of the performance coeficient, "C", with time. From this short time transient flow data and theoretical considerations, the value of C at large times can he established. By assuming the radius of drainage of a well to be half the distance between wells, one can calculate the stabilization time for various well spacing patterns. Once the stabilization time for a given .spacing has been determined, the value of C can be calculated and the stabilized back-pressure curve can he. establbrhed. The calculated perfortnance coefficient as a function of tinze was cotnpared to the experintentally measured values for a number of gas wel1.e. The deviation of the calc~*lated from the cxperimental res1tlt.s vary depending on the set of short time experimental points used to evabrate the parcrttzeters of the equation. The longer the tirne far the flow test data user1 in the calculations, the better was the agreement with the experimental results. The time necessary to obtain this data from well tests varies consitlerably, depending on the physical natrcre oj the rt3scrvoir under consideratiot~. INTRODUCTION For many years, the U. S. Bureau of Mines Monograph 7' has served as a guide for testing and evaluating the performance of gas wells by means of the back-pressure method. The back-pressure performance of a gas well is expressed by the following equation: Q~ CW-W.........(I) where the characteristics of the back-pressure equation are determined by C, the performance coefficient, and n, the exponent which corresponds to the slope of the straight line when Q and {P* - PN2) are plotted on logarithmic paper. Q is gas flow rate at standard conditions, and P, and P, are equalized and flowing bottom-hole pressures, respectively. Prior to the development of the back-pressure tcst, the "open flow" capacity method of testing a well was common. By this method, the wells were flowed wide open to the air and the flow rate measured. Such procedure was wasteful of gas and did not provide information on the deliverability of the gas to the pipe line. Monograph 7 Procedure The back-pressure method of testing wells was developed to overcome these shortcomings. Although much has been learned regarding the laws of the flow of gas through porous formations, the original development of the back-pressure relationship was based entirely on empirical methods. The back-pressure behavior provides the engineer with information essential in predicting the future development of a field. It permits him to calculate the deliverability of gas into a pipe line at predetermined line pressures, to design and analyze gas gathering lines, to determine the spacing and number of wells to he drilled during the development of a field to meet gas purchasers' requirements, and to solve many other technical and economic problems. As described in Monograph 7, the flow-after-flow method of back-pressure testing, when applied to fast stabilizing and usually high capacity wells, correctly characterized the behavior of the well. However, as the value of the gas at the wellhead increased, small capacity gas wells having slow rates of stabilization became economically operable. The flow-after-flow method of testing could not be used to describe the behavior of these slowly stabilizing wells. The procedure of Rawlins and Shellhardtl for establishing the back-pressure behavior of a gas well was based on the rcquirement that the data be obtained under stabilized flow conditions; that is, that C is constant and does not vary with time. C depends on the physical properties of the reservoir, the location, extent and geometry of the drainage radius, and the properties of the flowing fluid. In a highly permeable formation, only a very short period of time is required for the well to reach a stabilized condition, and, consequently, the requirements for the test procedure described in Monograph 7 are met. For a given well, n is also constant

By R. D. Burlingame, T. L. Joseph, Gust Bitsianes

DESPITE almost fifty years of commercial practice, the sintering of iron ore has received little fundamental study. Much of the theoretical work1-'has dealt with the constitution of sinter produced under widely varying conditions. While these studies have broadened our knowledge of the changes that occur in the sintering zone and in the freshly formed sinter during the early stages of cooling, they provide little insight into the changes that precede the formation of sinter. These preliminary changes merit study as a part of the overall process. Hessle. working with beds of Swedish magnetite concentrates, was one of the first investigators to study the sintering process in its entirety. On the basis of temperatures observed at various levels of the bed during sintering, he postulated a number of distinct reaction zones to account for the chemical changes leading to the formation of sinter. A more direct method of attack is that of arresting the sintering zone after it has progressed part way through the bed. A study of a vertical cross section through such a quenched bed provides direct information on the changes taking place at various levels. This method was used by McBriar et al.' to show that several well-defined zones of chemical change existed within beds that were typical of British sintering practice. The same general method of attack was developed independently in the present investigation to study partially sintered beds typical of American practice. Experimental Sintering Equipment The sintering operation was carried out on an experimental scale with the equipment shown in Fig. 1. The refractory-walled sintering chamber A was 11 in. deep and averaged 9 in. in diameter. Air was introduced through a tapered flow section B, which contained the orifice C for accurate metering of the incoming air. This section was located directly above the square ignition housing D, which in turn rested upon the sintering chamber A. The bed was ignited with burner E. The required suction for the operation was furnished by a fan F, which had an air capacity of 500 cfm (stp). Hot exhaust gases from the sintering chamber were cleaned in the dustcatcher G before entering the exhaust fan. In the study of partially sintered beds, it was essential to find some technique for removing the entire charge from the sintering pot without disarranging the unsintered bottom portion. This problem was finally solved by sintering the charge in a removable basket, which snugly fitted the sintering chamber. This basket was constructed of two thicknesses of window screen and was lined with a 3/16-in. layer of asbestos paper. The bottom of the basket consisted of two thicknesses of wire screen, which were fastened to the basket wall. For high fuel mixtures, additional insulation was provided by a somewhat thicker layer of asbestos cement. Preparation of Partially Sintered Mixtures The moist feed was carefully placed in the sintering basket, to prevent segregation of the particles, which varied widely in size and composition. A thermocouple was placed in the center of the basket with the hot junction halfway down, and the mixture was evenly distributed around it. During ignition and throughout the sintering of the upper half of the bed, the hot junction temperature increased very little. When the sintering zone reached the halfway point, as indicated by the sudden increase in the hot junction temperature, the charge was quenched. During quenching the suction was turned off and the orifice was tightly stoppered to prevent further influx of air. At the same time, nitrogen was admitted to the sintering chamber through the orifice tap. As soon as the nitrogen had displaced the air and products of combustion, the charge was removed from the sintering pot for immediate dissection. It is impossible to preserve the exact zone structure of the bed at the instant that combustion is arrested unless the downward transmission of heat is also immediately stopped. Fortunately, heat transfer is very slow in beds containing a stationary fluid, especially if the particle size is small. It follows that the minimum quantity of nitrogen should be used to displace the air and that static conditions be established as soon as possible. A very steep temperature gradient across the combustion zone for some time after the quench was evidence of in-

Jan 1, 1957

By L. G. Sprague

THE fact that this latest and most modern of the Universal Atlas Cement Company's plants at Northampton, Pa., is the fifth to be built on these same properties, and their development has been coincidental with the development of the portland cement industry in the United States, makes it appropriate to sketch briefly the history of the successive steps. In 1889 the original Atlas Portland Cement Co. started its first plant at Coplay, Pa., which is just across the Lehigh River from the present operation. Here the first successful rotary kiln was operated. These kilns were 6 ft. in diameter and 60 ft. long; they used oil for fuel until 1895, when the company developed the first burner for pulverized coal. Shortly thereafter the Atlas company acquired property on the Northampton side of the river and built its plants Nos. 2, 3 and 4 within the following 10 years. During the same period the production of portland cement in the country was increasing rapidly; owing largely to the development of the rotary kiln and improved grinding machinery, which lowered the cost and improved the quality of cement. The general tendency has been to increase the length of the kiln and grind both raw material and finished product finer. In 1930 the Atlas Portland Cement Co. and the Universal Portland Cement Co. united to form the Universal Atlas Cement Co., and the same policy of improving the product has been continued. Because of the large amount of research carried on by manufacturers and consumers, including government agencies, there is a demand for cement of different chemical and physical characteristics for different kinds of structures. Hence many engineers in recent years have been asking for cements of certain definite chemical analyses, which they think are best for their particular jobs. This has compelled the manufacturer to make several different types of cement by variations of chemical composition. These are generally made by adding silica, iron and lime to the standard mixture, which necessarily increases the cost of the product. Therefore the Universal Atlas Cement Co., in planning the modernization of its Northampton plant, gave this particular phase of the problem considerable study. Research and experimentation have developed the practicability of making a wide variety of differently proportioned raw materials for cement by a process of subtraction rather than by addition. With such process, it is possible to discard the undesirable aluminates and silicates from the ample supply of impure limestone available from the company's property rather than by adding high-grade limestone obtained from distant sources. This procedure requires mineral separation by centrifugal sedimentation and froth flotation. Since the chemical and mineral constituents of Lehigh Valley "cement rock," together with the methods of separating them, have been thoroughly described in published

Jan 1, 1943

By C. Dean Starr

The physical basis of the equation correlating electrical conductizlity and temperature coefficient of resistance of solid solution alloys has been inzlestzgated and the nature of the constants evaluated. It is shaun that the same form of correlation is valid irrespective of the magnitude of the temperature coefficient. However, the effect of therma1 expansion and change in resistivity with temberature nust be considered when the magnitude of the temperature coefficient of resistance is near zero. In a comprehensive literature survey conducted at the Armour Research Foundation in 1950, it was found that a linear relationship exists between the electrical conductivity, K, and the temperature coefficient of resistance, a, for solid solution alloys. This was expressed by the equation where B, a constant, depends on the solvent metal but not the solute. A continuing investigation by Hansen, Johnston, and Parks showed this equation was generally appropriate for Cu, Ag, Au, Pd, Pt, and Co base binary solid solution alloys as well as for many ternary alloys of copper over a range of conductivities and temperature coefficient of resistances from 0.02 to 0.60 reciprocal pohm cm and-0.00015to0.004Q per 0 per "C respectively. Eq. [I] was not always valid for alloys that exhibited a change in state (magnetic to nonmagnetic) or for alloys that had a temperature coefficient of resistance near or below zero. For example, in nickel alloys, a simple linear curve as predicted by Eq. [l] was not obtained when the conductivity was plotted against the temperature coefficient of resistance. Hansen suggested that deviations observed were caused by transitions from a ferromagnetic to a nonmagnetic state. Subsequent and more extensive data by ronin on Ni-Mn alloys confirmed Hansen's postulate. While both states independently showed a linear relationship between K and a, the value of B was different for the two states. In some copper and gold base alloys, as well as the platinum and palladium alloys investigated by Hansen, the conductivity did not extrapolate to zero at zero a as demanded by Eq. [I]. This deviation can be readily corrected by simply adding a constant to Eq. [I.] whence Eq. [2] shows the K decreases as a decreases but that K has a positive value when a = 0 which is observed for commercial solid solution alloys as well as the experimental alloys tested by Hansen. While other methods of correlation of electrical properties have been made such as the one by Starr and Wang3 who found a linear relationship between resistivity and temperature coefficient of resistance for Ni-Cr-Al-Cu alloys, the data, in general, can also be correlated by a form of Eq. [2]. Thus, Hansen's empirical equation has considerable merit. The objective of this paper is to determine the physical basis for this equation and to examine the region near zero a in more detail. ELECTRICAL CONDUCTIVITY VS TEMPERATURE COEFFICIENT OF FU3SISTANCE The resistance of a metal or alloy is defined as

Jan 1, 1963

By Paul M. Tyler

Mineral raw materials, because they are essential to our industrial prosperity and military strength, must be made available in substantial quantities regardless of cost. Variations in the cost of procuring minerals, as compared with the cost of obtaining other commodities, and changes in the cost of production of different minerals relative to one another, will naturally influence the quantities of a given mineral item that can be marketed readily. However, in the last analysis, the cost of winning minerals from the ground usually constitutes only a small fraction of the value of the end-use products and services derived from them. The miner's share of the cost of a typewriter, telephone circuit, or even a modem office building, is almost insignificant. Far more important to the ultimate consumer, therefore, than any minor saving in cost is the assurance of ample supplies of the minerals needed to aliment our expanding economy. To create a successful metal mining operation involves (1 ) the discovery and systematic development of a mineral deposit, (2) extraction of the ore, (3) the mechanical and metallurgical processing to eliminate worthless or harmful impurities, and (4) the profitable disposal of the product. The fist step of the technological process belongs chiefly in the realm of the geologist, the second is a mining engineer's job, the third is mainly up to the millmen and extractive metallurgists; whereas the fourth and equally important step poses a commercial problem that has aspects in common with the marketing of other products. Ore finding is far from being an exact science. There is no mathematical criterion for evaluating the efficiency of prospecting and exploration. Lady Luck shares the honors or assumes part of the blame along with the prospector and geologist. Marketing like- wise involves factors that seemingly defy engineering analysis. Although the other steps can be measured with some degree of mathematical accuracy, even they tend to vary so widely in basic principle, as well as in

Jan 1, 1964