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By S. R. B. Cooke, R. O. Huch, C. S. Chang

IN the flotation of iron ores laurylamine derivatives have been used for considerable time.1, 2' To effect satisfactory separation of the gangue, pre-dominantly silica, from the iron oxide minerals, the addition of specific depressants for the iron oxides has been found necessary. Starches and starch products have been used for this purpose.V here is, however, very little published information on the effects of these materials and other variables on this process. In some cases it has been found that prior acid scrubbing and desliming are essential," and depending upon the efficiency of the subsequent washing step, there will be accompanying changes in pH. It was the object of this investigation to test and observe the effects of the above factor as well as to examine and compare the action of various starches and starch products. Ore Preparation The ore used in this experiment was a wash-ore tailing obtained from the western Mesabi range. Microscopic examination and x-ray analysis of the ore showed it to consist of hematite, goethite, and quartz. Physical properties of the iron minerals ranged from hard and crystalline to earthy and ocherous. The quartz grains were discolored either because of iron-oxide inclusions or because of a sur-face coating of iron oxide. The ore assayed 27.52

Jan 1, 1954

By C. A. Heiland

The Eötvös torsion balance permits the measurement of certain second derivatives of the gravity-potential, which are known as the gradients of gravity and the curvature values for an equipotential plane of gravity. These quantities are influenced on level ground by the configuration of the masses underneath. Hence, the torsion balance has gained great importance for the location of geological structures and thus indirectly for the discovery of oil and other mineral deposits. If the ground is not level, however, the measurements become more difficult, because the superficial mass-irregularities also produce more or less considerable disturbances. It is necessary, therefore, to determine the shape of the surrounding topography by leveling as well as by consulting topographic maps and to compute its influence upon the torsion balance. The correction thus determined is called, in general, the topographic correction; it is composed of two constituents, the terrain correction and the cartographic correction. The terrain correction would be that part of the topographic correction as derived from the direct leveling of the area surrounding the station, whereas the data for the computation of the cartographic correction are obtained from a topographic map, usually beginning with a radius of LOO meters, as under most circumstances it is difficult to level along a arger concentric circle about the station. Principle of Topographic Correction The principle of all topographic corrections is to assume a homogene-ous compositon of the masses around the station in regard to specific gravity as well as a mathematical shape of the topography. The results become the more accurate the closer this mathematical shape is to the actual configuration of the terrain, but naturally the amount of necessary computation also increases. If a standard correction with fixed dis-ances is adopted, the middle error of this method will, therefore, increase as the irregularity of the terrain. Hence, the application of the torsion balance in mountainous areas may be successful only if the disturbances due to heavy masses underneath the surface are so large as to exceed onsiderably the increased middle error due to rugged topography, or,

Jan 1, 1929

By S. Razi

Injection luminescence of single crystals of rare-earth-activated CdS was investigated. Crystals of CdS:Nd, CdS:Er, and CdS:Yb, grown by the vapor transport technique, were suitably etched and hetero-junctions of Cu2S-CdS were fabricated on one side of the CdS substrate by chemical reaction. The device was then heated to 200°C in an inert atmosphere for 5 min. Static V-I measurements show that at low voltages (V < 1 v) the current is controlled by the junction, while at higher voltages the bulk Properties of the CdS substrate effectively control the current. Because of the large thicknesses no negative resistance was found. Reverse breakdown voltage varied from 5 v, for junctions that were not heat-treated, to 100 v, for diodes that received the proper heat treatment. The rectification ratio, measured in the range of 2 to 10 v, varied from 300 to 3000. Capacitance- voltage measurements indicate a weak dependence of the junction capacity on applied voltage. The capacity was found to increase appreciably with room light illumination. The variation of capacitance with frequency is indicative of a p+-i-n structure. An open-circuit voltage of 0.4 v was measured under an illumination of 100 mw per sq cm. Under forward bias, the bluish-green edge emission characteristic of CdS was observed. No sharp rare earth emission line was observed, which is in contrast to our results using ZnS:Tb, where, under high-voltage excitation, the rare earth emission was dominat over the lattice emission. The absence of rare earth emission implies that either the nature of the rare earth ion is different at the het-erojunction than in the bulk or the probability of energy transfer to the rare earth ion is small. RARE earth elements are playing an increasingly important role in the Synthesis of materials for a variety of purposes, e.g., solid-state lasers, color television screens, and so forth. Interesting systems result when wide-band-gap photoconducting lattices are activated with rare earths. A study of the lumines-

Jan 1, 1969

By S. S. Shen, M. J. Pool, P. J. Spencer

Heats of solution of silver and copper in dilute Ag-Cu-Sn alloys at 720°K have been determined using a liquid metal-solution calorieter. Values of the se2f-interaction coefficient n AgAghave been calculated at constant copper concentrations and n Cu Cuhas been determined at constant silver contents. The reliability of the experimental data is shown by the very good agreement between nCujAg and ij &$; these interaction coefficients have experimental values of -9100 and - 9590 cal per g-atom, respectively. Certain solution models are shown to be inadequate for prediction of solute interaction coefficients in dilute Ag-Cu-Sn alloys. In a previous publication&apos; the results of a thermody-namic study of dilute Ag-Au-Sn alloys were presented. The present work represents the continuation of a program to investigate dilute alloys of the noble metals with tin and in particular is concerned with solute interactions in the Ag-Cu-Sn system. By determination of the magnitude and sign of the various interaction coefficients in dilute alloys it is possible to gain some understanding of the different types of solute-solute and so lute-solvent bonding changes that occur as the solute concentrations are varied. Hence systematic studies of alloys with similar physical characteristics as regards size, structure, electronegativity, and so forth, of their components can contribute a great deal to present theoretical knowledge of solutions. The recent definition of an enthalpy interaction coefficient, 11, by Lupis and Elliott2 is of particular value in calorimetric studies such as the present one: where j and i are solutes and s is the solvent; Si is the relative partial molar enthalpy of component i and x represents the mole fraction of solute or solvent. Values of ?Hi can be obtained directly by solution calorimetry and data for n are thus easily determined, often with a high degree of accuracy. ?Hi is related to the relative partial molar enthalpy at infinite dilution, ?Hi and to the enthalpy interaction coefficients by the expression: ?Hi?Hi + X;nz+ ... [2] The aim of the present work was to determine the self-interaction coefficients n AgAgand 178: in alloys of different compositions and also to establish values for n Agcg| and ncuAg. Since it is a thermodynamic requirement (resulting from the Maxwell-type relationships which can be applied to partial molar properties) that nAgcu and ncuAg should be equal, a further aim of this study was to demonstrate the agreement between experiment and theory. EXPERIMENTAL A description of the liquid metal-solution calorimeter used in this research has already been published,3 and no further details of its construction and operation will therefore be given here. Copper supplied by the American Smelting and Refining Co. was indicated by them as being 99.999 pct pure, and the silver obtained from A. D. Mackay, Inc., was also quoted as being 99.999 pct pure. A solvent bath consisting of between 70 and 80 g of 99.99 pct pure Sn was used for each series of experimental drops. Its weight was accurately determined and the appropriate amounts of copper or silver were added to give alloys of the desired composition. Approximately 0.00125 g-atom additions were used for determinations of the heat of solution of silver in the bath, while, for copper, specimens consisting of approximately 0.0015 g-atom were used. The heat capacity of the bath was determined at regular intervals during a series of drops using tin or tungsten calibration samples. The heats of solution of silver and copper in pure tin were first determined as a function of their concentration in order to establish the self-interaction coefficients 7AgAg and ncucu Alloys containing a constant 0.01, 0.02, 0.03, and 0.04 mole fraction of copper were then used to study 17:: in alloys of different copper content, while alloys of the same mole fractions of silver were used to determine equivalent data for 178: at constant silver concentrations. The composition of the bath was held at the desired copper or silver concentration by making calculated additions of the appropriate solute throughout the experiment. From the limiting values of ?HAg in the constant copper content alloys it was possible to study ?HAg as a function of xCu and hence to determine 42:. A similar analysis of the re, values permitted calculation of nAgcu. Heat content and heat capacity data from Hultgren et al* were used to calculate heat of solution values from the measured heat effects at the experimental temperature of 720°K. RESULTS AND DISCUSSION Determinations of ?HAg. A preliminary investigation of the heat of solution of silver in pure tin at 720°K was first made in order to establish the value of nAgAg before additions of copper were made and also to compare the value of ?HOAg(l) with that obtained in the previous study of Ag-Au-Sn alloys.&apos; Then the heat of solution of silver in Cu-Sn alloys was investigated as a func-

Jan 1, 1970

By J. J. Jakosky

THE fundamental hydrodynamic principles governing the production of oil from wells have been carefully studied and evaluated by many investigators. These prior studies are quite complete and cover virtually the entire field of oil production and recovery.1 One of the most impor-tant measurements in production studies is that of the bottom-hole pressure at various rates of production.2 It is the purpose of this paper to outline the technique and economics of fluid-level measurements as applied to pumping wells and to review briefly other methods for obtain-ing bottom-hole data. The applications of bottom-hole pressure or fluid-level measure-ments are based on simple hydrodynamic principles. Under equilib-rium conditions, pbh = hd + pg + pch [ l] when pbh = bottom-hole pressure, lb. per sq. in. absolute, h = height of fluid in well, ft., d = average fluid density, lb. per sq. in. per foot, pg = weight of section of gas column 1 in. square from fluid level to casing head, pch = casing-head pressure, lb. per sq. in. absolute. In words, equation 1 states that the bottom-hole pressure is equal to the weight hd of the column of fluid plus the weight of the column of gas between the fluid and the casing head plus the casing-head pressure. At moderate rates of flow, the rate of production is approximately proportional to the difference between the reservoir, or static bottom-hole, pressure and the flowing or producing pressure; i.e.: Q = c(pr - pbh) [2] pr = the reservoir pressure, c = the constant of proportionality. However, at production rates approaching zero and also at high rates the proportionality may break down. By combining equations 1 and 2 the

Jan 1, 1939

By R. E. Ogilvie, A. R. Kaufmann, S. H. Gelles

The solid-solubility limits of iron in beryllium were determined between 850o and 1200oC by analysis of differential type multiphase diffusion couples, using an X-ray absorption technique. The maximum value of the solubility limit was found to be 0.92 ± 0.02 at. pct (5.46 wt pet) at the eutectic temperature 1225°C. The solubilities of nickel and beryllium were determined between 900°and 1200°C by the same technique and the maximum solubility was found to be 4.93 + 0.01 at. pct (25.2 wt pet) at the eutectoid temperature, 1065°C. A previously unreported high-temperature phase which decomposes eutectoidally at 1065 °C was found to exist in the beryllium-nickel system at a composition of approximately 8 at. pct Ni (36 wt pet) by diffision-couple analysis. The presence of this phase was confirmed by thermal analysis and metallo-graphic analysis of the structure resulting from the eutectoid decomposition. G. V. Raynor1 has treated the solid solubilities of some of the elements in beryllium on the basis of the "Hume-Rothery" rules2 which have been modified to include ionic size and ionic distortion effects. It was predicted that the solubility of iron and nickel in beryllium should be slightly less than that of copper. The lowering of the solubility, according to Raynor, is due to a more unfavorable relative valency effect and an ionic size effect. Kaufmann and corzine3 have compiled data on the solubilities of elements in beryllium and have discussed them in the light of the Raynor paper. These authors feel that, because the elements having the greatest solubility in beryllium systematically fall in the Group VIII and IB Columns of the periodic table, the electronic structure greatly influences the maximum solid solubility of elements in beryllium. The solubility of iron in beryllium was determined by Teitel and cohen4 as part of the study of the beryllium-iron phase diagram. The determination was carried out by X-ray and thermal analysis and according to the phase diagram presented, the maximum solubility of iron in beryllium is 0.41 at. pct (2.5 wt pct) at 1225oC. However, it is estimated that the uncertainty in the position of the a-beryllium primary solid-solution boundary is about 0.5 at. pct (3wtpct). Losana and Goria3 in studying the beryllium-nickel phase diagram, determined the solid solubility of nickel in beryllium by thermal analysis. They found the maximum solubility to be between 1.65 and 2.65 at. pct (10 to 15 wt pct) at 1240°C. This value decreased rapidly with decreasing temperature. In determining approximate ranges of solubilities for different elements in beryllium, Kaufmann, et al,8 reported a value of between 1.3 and 1.7 at. pct (7.9 to 10.1 wt pct) for the solubility of nickel in beryllium. The value was obtained by metallographic examination of quenched alloys and lattice-parameter measurements. However, the authors also noted a single-phase structure for a 1.7 at. pct Ni alloy (10 wt pct) on cooling from the liquid. This would indicate a higher solubility range than was reported. ~isch,&apos; in his X-ray studies of beryllium-copper, beryllium-nickel, and beryllium-iron intermetallic compounds, reports the disappearance of a second phase (Ni,Be2) in the beryllium primary solid solution at approximately 4 at. pct (20 wt pct). THEORY The analysis of concentration gradients in diffusion couples has proven to be a useful tool in determining phase equilibria.8-14 In this particular study the diffusion couples were chosen to straddle the expected composition range of the phase boundary, then heat treated at a given temperature and the concentration gradient evaluated. The composition of the phase boundary for a given temperature appears at a point of discontinuity of the composition gradient. Examples of typical phase diagrams and the concentration gradients which should be found in such systems are shown in Fig. 1. In the present work, gradients of the form of Fig. l(c) were obtained in diffusion couples made of pure beryllium and two-phase alloys of beryllium with either iron or nickel. The composition at the point where the gradient becomes discontinuous, Cs, corresponds to the solubility limit of either iron or nickel in beryllium. The analysis of the concentration gradients was carried out by an X-ra absorption method developed and applied by Ogilvie and later used by Moll13 and Hilliard.l4 It depends on the fact that the absorption of X-rays by matter is determined by the concentration and type of the various atomic species present. The relationship for the intensity, I, of a monochro-

Jan 1, 1960

By D. G. Westlake

The electrical resistance of a series of V-H alloys (0 to 3.5 at. pct H) has been measured over the temperature range G° to 360°. Interstitial impurities made contributions to the residual resistivity, but not the ideal resistivity. The contribution of hydrogen in solid solution is expressed by Ap = 1.12 microhm-cm per at. pct H; but the contribution of precipitated hydride was negligible. A portion of the so1vu.s for the V-H phase diagram is presented. The solubility limit is given by In N (at. pct H) = (5.828 i 0.009) - (2933 i 44)/RT. Comparison of critical temperatures joy hydride precipitation and published critical temperatures for hydrogen embrittlement suggests the two are related. ThiS study was initiated as part of an investigation of the mechanism by which small concentrations of hydrogen embrittle the hydride-forming metals at low temperatures. It has already been shown that, in the case of hcp zirconium, a reduction in ductility accompanies the strengthening resulting from precipitation of a finely dispersed hydride phase.&apos;&apos;&apos; Our attempts to detect a similar precipitation of a second phase at low temperatures in V-H alloys by transmission electron microscopy have been thwarted because we have been unable to prepare thin foils that are representative of the bulk material with respect to hydrogen concentrati~n.~&apos;~ The present investigation establishes the solvus of the V-H system at subambient temperatures. Subsequently, we hope to be able to determine whether the embrittlement temperature is related to the critical temperature for precipitation of the hydride in a given V-H alloy. veleckis5 has proposed a partial phase diagram for the V-H system based on extrapolations of the pressure-composition relations he measured at higher temperatures. Kofstad and wallace&apos; conducted a similar study of single-phase alloys but did not attempt to establish the phase diagram. Zanowick and wallace&apos; and ~aeland&apos; have studied a portion of the phase diagram by X-ray diffraction, but they investigated no alloys in the hydrogen concentration range 0 to 3 at. pct, the range of interest to us. EXPERIMENTAL PROCEDURE The vanadium was obtained from the Bureau of Mines, Boulder City, Nev., in the form of electrolytic crystals. The analyses supplied with them listed 230 ppm by weight metallic impurities, 20 ppm C, 100 ppm N, and 290 ppm 0. The crystals were electron-beam-melted into an ingot that was rolled to 0.64 mm. Strips, 60 mm long and 4.2 mm wide, were cut from the sheet, and both rolled surfaces were ground on wet 600-grit Sic paper to produce specimens 0.4 mm thick. They were wrapped in molybdenum foil, vacuum-encapsulated in quartz, and annealed 4 hr at 1273°K. The specimens were annealed in a dynamic vacuum of 2X lo-&apos; Torr for 30 min at 1073°K for dehydrogenation, and charged with the desired quantity of hydrogen by allowing reaction with hydrogen gas at 1073°K for 2 hr and cooling at 100°K per hr. Purified hydrogen was obtained by thermal decomposition of UH3. Sixteen specimens were studied: two contained no hydrogen and the others had hydrogen concentrations between 0.5 and 3.5 at. pct (hydrogen analyses were done by vacuum extraction at 1073°K). Electrical resistances were measured by the four-terminal-resistor method on an apparatus similar to the one described by Horak.~ The specimen holder was designed so that both current and potential leads made spring-loaded mechanical contact with the specimen. The potential leads were 30 mm apart, and the current leads were 55 mm apart. The current was 0.10000 amp. We used the following baths for the indicated temperature ranges: liquid nitrogen, 77°K; Freon 12, 120" to 230°K; Freon 11, 230" to 290°K; and ethanol, 290" to 340°K. Temperatures lower than 77°K were achieved by allowing the specimen to warm up after removal from liquid helium. Temperatures above 77°K were measured by a calibrated copper-constantan thermocouple (soldered to the specimen holder) and below 77°K by a calibrated carbon resistor. The temperature of the bath changed less than 0.l0K between duplicate measurements of the resistance. RESULTS AND DISCUSSION Typical plots of resistivity p vs temperature T are shown in Fig. 1. In the interest of clarity, only five curves are presented and the data points have been

Jan 1, 1968

By Walter Mathesius

The use of high blast heats on furnaces melting Mesaba ores is still the exception, the average blast temperatures carried on Mesaba stacks seldom reaching 1,100" F. Some 15 years ago, when the use of fine Mesaba ores in larger proportions to the total burden first came into practice, it was found difficult to employ even those blast heats which it had been possible &apos; to carry with the Old Range ores. The furnaces refused to "take" high heats, and would persistently labor with irregular stock movement, which impaired the practice and increased the coke consumption. By lowering the blast temperature, the working of the furnace became smoother, and experience taught that with the softer and more easily reduced Mesaba ores, satisfactory practice could be obtained with comparatively low blast heats. Therefore a large number of Mesaba furnaces have ever since been operated on very low blast temperatures, ranging between 800" and 1,000" F. In the face of these difficulties, furnace men were slow to recognize that furnaces could be so designed as to permit a free movement of the charges in combination with the use of higher heats. Since higher blast temperatures did not seem to offer great advantages in the smelting of Mesaba ores, investments in hot-blast stoves were not as attractive to the furnace man as labor-saving devices and means of obtaining greater tonnages. The effect of this preference is keenly felt at the present time. It has brought about the peculiar situation, that the majority of our furnace plants (among them some of the most progressive) lack modern and efficient stove equipment. The result is that, even where the proper furnace lines have been adopted and conditions are now favorable to the successful employment of higher blast temperatures, the heats required for the greatest fuel economy are not available. In an endeavor to obtain results, even with inadequate equipment, we find that, at many plants, the stoves are worked far beyond their capacity. This leads, in many instances, to a situation in which the coke saving in the

Jan 1, 1915

By C. F. Rust

Experimental evidence is presented showing that reproducible formation resistivity factor measurements and resistivity index determinations on reservoir core samples map be made utilizing either the two- or four-electrode methods. Equipment is described which permits the application of either technique to the core specimen without loss of time and with a minimum amount of effort. Since electrical resistivity measurements on reservoir rocks are important not only in electric log interpretations, but also in the study of fundamental rock parameters, it was considered desirable to compare the applicability of both techniques of resistivity measurement. INTRODUCTION The techniques employed in the measurement of electrical resistivity on reservoir rocks, as practiced in the petroleum industry, may be reduced to two fundamental methods: one utilizing two electrodes only, usually referred to as the two-electrode method; the other using two additional electrodes and commonly known as the four-electrode method. In the former, the core sample whose resistivity is to be measured is mounted between two electrodes, usually metal discs, which serve to pass a current of known magnitude through the saniple. The potential drop across the sample, measured between these same two electrodes, and the core dimensions furnish the necessary data to compute he resistivity of the sample. In the four-electrode technique the end plates, again usually ol metal, still serve as current electrodes. Additional probes or electrodes dispersed along the sample are utilized to measure the potential drop. Both methods are used in practice1,2 and it is the purpose of this paper to compare the two techniques as applied to the determination of formation reiistivity factors and the resistivity index exponent n, in Archie&apos;s empirical equation I = p/po = Sw 11. To evaluate the two techniques it is desirable to point out the experimental precautions which must be taken to insure reliable results. It is evident from the electrode arrangements of the two- and the four-electrode methods that, for a given sample, the volume of sample included by the four-electrode method is less than the volume included by the two-electrode method. One of the prime difficulties associated with the two-electrode method is the possible occurrence of an abnormally high resistance between the electrodes and the brine-saturated sample, which results in erroneous resistivity values for the core sample itself. Attempts to alleviate this difficulty meet varying degrees of success. Methods used in the past employ such absorbent materials as brine-saturated Kleenex: chamois, or felt. A technique described by Morgan, Wyllie, and Fulton,1 appears to be more satisfactory. Their method consists of spraying or painting the end areas of a core sample with conductive silver paint. This technique reduces contact resistances between the porous medium and the electrodes to a value which is generally negligible as compared to the resistance of the sample itself. In the four-electrode method these requirements are not as stringent since separate probes are used to measure the potential difference acrozs a portion of the sample. In this case, contact resistance occurring at the current electrode; are of no consequence. and those appearing at the potential

Jan 1, 1952

By S. F. Emmons

There is, in the southern part of the State of Illinois, a series of deposits of fluorspar and galena in which the former mineral occurs on a scale of magnitude unequalled, so far as I know, in any other part of the world. In June, 1891, 1 had an opportunity of visiting the region of their principal development, near Rosiclare, Hardin county, Ill., and examined such of the mines in the vicinity as were accessible at that time. A very large proportion of the mining shafts that had been sunk in this region were unfortunately abandoned for the time being, and full of water. Moreover, detailed maps of the region are unattainable, no surveys having been made there, apparently, since the original land-surveys&apos; of the early part of the century. In spite of these disadvantages I was enabled, in the few days at my disposal, to ascertain with sufficient accuracy certain facts not hitherto published with regard to these deposits, which seem worthy the attention of the members of the Institute. Before proceeding to a description of the deposits in question, I will give a brief abstract of the little historical and geological information hearing directly or indirectly upon them, which I have been able to find in existing publications. Historical. That the mineral was known to the Indians, is proved by the discovery, in some of the pre-historic mounds of the region,* of fluorspar, shaped into ornaments. The earliest scientific mention of its occurrence is found in the first volume of the American Journal of Science (1818+), which describes specimens obtained in the vicinity of Shawneetown by Mr. Joseph Baldwin. Similar notices appear in the same journal in 1820 and 1821, but without mention of the exact locality. They remark on the fetid odor which characterizes the mineral and its association with galena. Schoolcraft, as early as 1819, note: the occurrence of fluate of

Jan 1, 1893

By Otto C. Kopp, Thomas B. Crattie, Dennis R. Owen

Whole-rock analyses of limestones, fine-gralned dolostones and coarser-grained dolostones adjacent to mineralized breccias (Coy mine, Mascot-Jefferson City district) were compared with similar lithologies adjacent to apparently non-mineralized breccias at the new Thorn Hill section located approximately 39 km north of the Coy mine. Specimens were analyzed for Ca, Mg, Si, Al, K, Fe, Mn, Sr, Br, C1, S, Ti and P using X-ray fluorescence analysis. The concentrations of the major and most minor elements for Thorn Hill specimens fall within the range of concentrations for Coy mine specimens; however, significant differences (probability < 0.05) were noted for Fe, C1 and Br for fine-grained dolostones and for MgO, Fe and Mn for the coarser-grained dolostones. No significant differences were detected for the limestones.

Jan 1, 1985

By R. C. Stevens

INTRODUCTION Idarado Mining Company, a subsidiary of Newrnont Mining Corporation, is situated high in the San Juan Mountains in southwestern Colorado. Portals, offices and surface plants are located near the towns of Ouray and Telluride at elevations ranging from 9,000 to 12,000 feet. The Ouray portion of the development was initiated in 1943. Upon completion in 1945 of a 250-ton mill, processing of development ores containing copper, lead and zinc was undertaken; thus, serving as a pilot testing unit for larger scale milling operations. These facilities were subsequently enlarged and utilized until 1956. Meanwhile, in 1953 Idarado had acquired The Telluride Mines Company, 62 miles distant by highway; however, only six miles via a network of tunnels which eventually linked the two workings. Extensive underground development and increased ore production necessitated reconstruction and expansion of the milling plant. The facility was designed to accomodate processing of 1700 tons of ore daily. This goal was achieved and it represents the current daily output. MINERALOGY The veins are a compound fissure which have undergone several stages of mineralization. The first stage is represented by complex ores of copper, lead and zinc in a quartz gangue. Precious

Jan 1, 1970

By A. Haas, L. Bubenicek

The Lorraine deposit of minette iron ore has been mined for more than a century. During this time, the economic conditions have changed frequently, and especially during the past decade. Thus, it has become economically prudent to proceed to new iron ore reserves with consideration of many and varied parameters. In the past, only traditional mining parameters were considered. Today, the quantity of information that must be taken into account is of such magnitude that the only practical means of data processing is by use of a digital computer and a mathematical model. One such model, based on geostatistics, was developed by G. Matheron. Much of the required input information, such as the petrology of ores, has been generated through IRSID investigations. This paper deals with several aspects of data processing in mining including information recording, reserves calculation, and stages of shrinking data in the calculation of mining iron beds, variograms, kriging, and tonnages.

Jan 1, 1969

By Edgar C. Bain

Of the important phenomenon of the hardening of steel, Professor Sauveurl says: It would seem as if the methods used to date for the elucidation of this complex problem have yielded all they are capable of yielding and that further straining of these methods will only serve to confuse the issue, the point having been reached when this juggling, no matter how skilfully done, with allotropy, solid solutions, and strains is causing weariness without advancing the solution of the problem. The tendency of late has been to abandon the safer road of experimental facts and to enter the maze of excessive speculations, in which there is great danger of some becoming hopelessly lost. The conclusion seems warranted that new avenues of approach must be found if we are to obtain a correct answer to this apparent enigma. With some degree of fitness we may say this of other problems. It seems likely that one of the new avenues of approach to many metallo-graphic problems is the study of crystal structure, or more accurately, the atomic arrangement, by means of the x-ray spectrometer. The crystal structure of some materials has been carefully worked out by the mineralogist, but his methods are, in general, unsuited to commercial metals and a method that yields even better information is at hand as the result of work on the diffraction of x-rays by Laue and the Braggs2 and later by HullI3 St. John, and others. It should be understood that the contour of free crystals, which is the subject of measurements by the crystallographer, is the result of the atomic structure and, in general, bears a simple and obvious relation to it. The use of the x-ray spectrometer4 has been described frequently, so the procedure will not be given here.

Jan 1, 1923

By Edgar C. Bain

Of the important phenomenon of the hardening of steel, Professor Sauveurl says: It would seem as if the methods used to date for the elucidation of this complex problem have yielded all they are capable of yielding and that further straining of these methods will only serve to confuse the issue, the point having been reached when this juggling, no matter how skilfully done, with allotropy, solid solutions, and strains is causing weariness without advancing the solution of the problem. The tendency of late has been to abandon the safer road of experimental facts and to enter the maze of excessive speculations, in which there is great danger of some becoming hopelessly lost. The conclusion seems warranted that new avenues of approach must be found if we are to obtain a correct answer to this apparent enigma. With some degree of fitness we may say this of other problems. It seems likely that one of the new avenues of approach to many metallo-graphic problems is the study of crystal structure, or more accurately, the atomic arrangement, by means of the x-ray spectrometer. The crystal structure of some materials has been carefully worked out by the mineralogist, but his methods are, in general, unsuited to commercial metals and a method that yields even better information is at hand as the result of work on the diffraction of x-rays by Laue and the Braggs2 and later by HullI3 St. John, and others. It should be understood that the contour of free crystals, which is the subject of measurements by the crystallographer, is the result of the atomic structure and, in general, bears a simple and obvious relation to it. The use of the x-ray spectrometer4 has been described frequently, so the procedure will not be given here.

Jan 1, 1923

By Stanley L. Arnot

The Mother Lode district in California is probably better known as the land of Bret Harte and Mark Twain than as a gold-producing district, although in this respect it holds an important place. The history of quartz mining on the Mother Lode dates back to the &apos;50s, when, after the first fever of the gold rush, men began to look for something more permanent, if not more lucrative, than the placers. Since that time, the discoveries, shutdowns, and reopenings of the many mines, together with the varying fortunes of their numerous operators, constitute an interesting chapter in California history, but one too long to include in a description of mining methods. The district is well situated, so far as physical conditions are concerned. The Mother Lode extends along the western slope of the Sierra Nevada Mountains, about half way between the crest and the Sacramento and San Joaquin Valleys, the country traversed consisting of low rolling hills—typical foot-hills. The elevation varies from 1000 to 1800 ft. and the climate is most desirable. There is an abundance of water, timber is easily obtained from the higher foot-hills a few miles east, and cheap hydro-electric power is generated practically on the Lode. These natural conditions are conducive to low costs in mining and have been the deciding factor in allowing profitable exploitation of the comparatively low-grade orebodies. Transportation facilities are not bad. Five branch railroads, from the main trunk lines in the valley, tap the district at intervals of from 10 to 30 miles, and the roads connecting these are fairly good for trucking purposes. Labor is made up of several nationalities, the principal ones being American, Spanish, Jugo-Slav, Italian, and Mexican. There were few Mexicans on the Lode prior to 1919, but the shortage of labor, experienced generally by the mining camps of the country in the years following the war, made necessary the hiring of some. The percentage of Mexican labor rapidly increased in 1920 and for a year or so thereafter, but it has now diminished until at most of the mines only a few Mexicans are working. Of the different nationalities, Americans are the most efficient and Mexicans the least.

Jan 1, 1925

By J. J. Gilman

THEORIES of fracture in metals have been based primarily on the dependence of fracture strength on grain size. This dependence was first observed by Masing and Polanyi.l These workers, as well as 0rowan12 and Davidenkov and Wittman,&apos; thought the grain size could be equated with the crack size in the Griffith condition for crack propagation.4 In this way they could account for the observed proportionality between fracture stress and the reciprocal square root of the grain size. The chief results of recent investigations of the fracture strength of polycrystals are summarized in Fig. 1. Low for iron,5 Petch for iron,&apos; Greenwood and Quarrel for zinc, Petch and Zein for zinc,&apos; and Hauser, Landon, and Dorn for magnesium&apos;&apos; have all found that the fracture stress of a polycrystal is proportional to the reciprocal square root of the grain size. Also, they find that, for large grain sizes, the fracture stress lies near the extrapolation of the yield-stress curve determined at small grain sizes; where measurable plastic strain precedes fracture. Low9 has gone a step further and shown that, in Range 1, the fracture stress in tension is almost identical to the yield stress in compression for a given grain size. Homes and Gouzou, 10 and Low also have shown that, in Range 2 of Fig. 1, microcracks form when the yield stress is reached, but they do not cause failure until the stress reaches a much higher value. The fact that yielding always precedes fracture suggests that fracture is induced by plastic flow. A mechanism by which this might occur was first proposed by Zener.11 He pointed out that blocked dislocations would cause stress concentrations which might cause fracture. The blocking would be caused by grain boundaries. This idea has been developed by Eshelby, Frank, and Nabarro,12 by Koehler,13 and by Stroh.14 By means of etchpits blocked dislocations have been observed in brass by Jacquet,15 in zinc by Gilman,16 and in lithium fluoride by Gilman and johnston. The blocked-dislocation theory and the experiments that bear on it have been summarized by Mott.18 One of the strong points of the blocked-dislocation theory is that it can explain the grain-size dependence of the fracture stress in a natural way. However, Low9 has pointed out that the theory is not satisfying when it is considered quantitatively. Gilman10 also has criticized the theory and presented an alternative interpretation of the relation between fracture stress and grain size. Since the blocked-dislocation theory is not the only theory that can explain in the grain-size effect, it is necessary to find other evidence either to support or deny it. In this investigation the following points were studied: 1) If blocked dislocations normally cause fracture, then the fracture stress ought to be very high in the absence of plastic glide. Is it? 2) If dislocations must be blocked in order for metals to fracture, then certain types of grain

Jan 1, 1959

By E. F. Ketterer, D. B. Collyer, A. B. Wilder

The microstructural stability of 59 carbon and low alloy steels after 34,000 hr exposure at 900&apos; and 1050°F, including the weld heat-affected zone, is discussed. The tensile and creep rupture properties of the parent metal of many of the steels before and after 10,000 hr exposure are presented. SEAMLESS pipe has been used for many years at elevated temperatures. When seamless first began to be used, operating temperatures and pressures were relatively low and the steel produced adequately met the existing requirements. The need for knowledge of creep properties and graphitiza-tion was nonexistent. Today the requirements for tubular products have changed considerably. Operating temperatures and pressures are increasing continually and corrosion, particularly at high temperatures, presents a problem. Carbon steels have, under these conditions, certain economic advantages particularly in oil refinery use. However, the use of low alloy steels in the generation of steam power has increased appreciably due to the influence of molybdenum on creep strength and the control of graphitization with chromium. The behavior of carbon and certain low alloy steels after long periods of exposure at 900° and 1050°F (480° and 565°C) has been investigated. The steels were examined before and after 10,000 to 34,000 hr exposure. Results obtained with material exposed at 1200°F (650°C) are not presented due to the severe oxidation and resulting decarburiza-tion after long periods of exposure. The graphitization characteristics of carbon and low alloy steels are of fundamental concern to the users of these materials. This is particularly true where welded joints are employed. In order to evaluate properly the behavior of steels at elevated temperatures, it is desirable to employ not only long periods of exposure under controlled conditions, but to use material with known properties and steelmaking practices. The purpose of this investigation has been to study the microstructure of the weld and the tensile and creep rupture properties of the parent metal after long periods of exposure at elevated temperatures. In the report&apos;.&apos; of a previous investigation data were presented on the microstructure, impact strength, hardness, and oxidation characteristics after 10,000 hr exposure at elevated temperatures. When this investigation was planned, methods for controlling the graphitization characteristics of steel were not established and, therefore, a number of special alloy steels were included in the study. During the exposure of these steels, the influence of aluminum in accelerating the rate of graphitization and the inhibiting power of chromium were established by various investigators. Also, the vanadium-bearing steels, because of their outstanding creep properties, received attention. As a result of these developments, considerable progress has been made in the field of high temperature tubular products, and the necessity for special alloys to prevent graph-itization has been restricted largely to the use of chromium. Material Chemical analysis, deoxidation treatment, and austenitic grain size of the 59 steels discussed in this paper are shown in Table I. The steels were forged to 1x1 in. bars with the exception of steels 12B, 12DX, 12DY, 12DZ, 70, 70A, 72 to 78, 82, and 83 which were machined from heavy wall pipe. All bars were surface ground before exposure. Heat treatment before exposure is shown in Table 11. The majority of the steels included were melted in either a basic open hearth or basic electric furnace; how-

Jan 1, 1955

By E. O. Jones, E. Whitehead

During the heating of cold-worked nickel silver, the tendcncy of the material to crack is well known. The present research deals with this question, and may conveniently be divided into the following sections: Changes in these alloys during heating and cooling, determination of the temperature at which cracking occurs, effect of grain size, quenching cracks, methods of overcoming annealing cracking. The work is far from complete, in particular the influence of impurities on this tendency has not been investigated, but the results so far obtained lead to certain definite conclusions, which are of theoretical and practical importance. Changes in Alloys During Heating and Cooling During the annealing of many metals at a temperature just below that at which recrystallization sets in, there is evidence of some change, the effect of which is to harden and embrittle the material. This effect has been most clearly demonstrated in the cases of aluminum, copper, brass, and nickel silver, and appears to be a common property of cold-worked metals and alloys, or, at any rate, the non-ferrous ones. The effect would obviously offer an explanation for certain types of annealing cracking, but the trouble is so much more common in the nickel silvers than in the other alloys that some special cause should be looked for. There is, however, fairly good reason for believing that similar cracking may occur in some of the brasses; D. Bunting1 suggests that the a brasses toward the saturation limit are subject to a transformation closely allied in nature to that known to occur in the nickel silvers at around 320" C. Although the existence of this critical temperature range was known, it did not necessarily follow that this transformation was responsible for the trouble under investigation, so the first portion of this paper deals with the attempts made to determine whether other critical changes might not occur in these alloys. There were already reasons for the belief that such would prove to be the case, as the mechanical properties of the nickel

Jan 1, 1926

By J. J. Gilman

IT is well established that dislocations exist in crystals and account for crystal plasticity.&apos; However, the origins of the dislocations are not clear. Among the means by which dislocations might originate are: a) through crystal growth accidents, b) by the collapse of condensed sheets of vacancies, or c) by stress-induced nucleation. Theoretical calculations&apos; have indicated that the last means should require very high stresses in order to operate. The purpose of this paper is to show that the stresses around the tips of cracks are large enough to nucleate large numbers of dislocation loops. Specifically, it will be shown that (100) cleavage cracks in LiF crystals nucleate dislocations in regions of the crystals where dislocations did not exist previously. It is believed that the use of LiF for this investigation does not restrict the significance of the 1 results. In fact, it is believed that this complements and extends previous papers by the same author which dealt with metal crystals.10,14 The dislocations were detected by means of the etching techniques that were described in a previous paper by Gilman and Johnston.3 In that paper it

Jan 1, 1958