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By V. H. Gottschalk

SEVERAL years ago a group in the metallurgical division of the U. S. Bureau of Mines began a study of the application of new developments in physics to metallurgical problems'. Among these developments were the extensions of what may be termed by analogy the "sound spectrum." Electromagnetic waves, from X-rays to radio waves, have been quite thoroughly explored for metallurgical use, but the sound spectrum, extending from low-frequency vibrations involved in certain types of metal failure by fatigue through the range of audible sound to inaudible vibrations having frequencies of many kilocycles, has had only meager consideration from metallurgists. Because of the general interest in the process recently demonstrated by St. Clair3 for flocculating smoke by means of sound waves, this article is written to point out possible applications of sound and supersonic (ultrasonic) waves in the metallurgical industry.

Jan 1, 1937

By Mark D. Tabak

Measurments of the transient photoconductivity in fillns of amorphous selenium with blocking- contacts haue been used in studying the transport properties. The results shozu that the transport of free carviers cannot be explained in terms of a model using bulk trapping. Measurments of the photocurrent-applied field characteristic as a unction of sample thickness do not pvoduce the scaling lau,s approps-iate lo a range-limited model. THE investigation described here was undertaken to explore the mechanisms of transport in amorphous selenium films. These films are used in xerography, where a photoconductor is charged electrostatically and then exposed to light to form a latent image. The sensitivity that one can expect when operating in this mode is directly related to the transport properties of the photoconductor material. The study of photoconductivity at high fields in insulating materials is often complicated by contact effects. Injection from the contacts can easily mask the fundamental transport processes that are being studied. A technique is described in this paper that allows a study of photoconductivity and transport processes in amorphous selenium films without the complicating effects introduced by contacts. Accordingly, the samples are prepared using insulating films between the sample and the metal electrodes, where the electrodes are capacitively coupled to the surfaces of the sample under study. A transient measurement is performed with pulsed light, and the photocurrent measured near the beginning of the pulse before the field is distorted by polarization at the blocking elec- trodes. A similar method has been described by Manyl using pulsed electric fields in studying the high field transport in insulating cadmium sulfide. EXPERIMENTAL It is possible to eliminate undesirable contact effects and maintain uniform high fields across the sample by using blocking electrodes and measuring the current-field characteristic under transient conditions. The sample configuration is shown schematically in Fig. 1. Each of the gold electrodes is separated from the amorphous selenium film by a layer of insulating plastic (Formvar) approximately 2000~ thick. The electrode on the front surface is semi-transparent to allow illumination of the sample. The whole configuration is mounted on a KEL-F substrate, which is a transparent insulating plastic having a thermal expansion coefficient that allows low-temperature measurements without cracking the selenium film. Fig. 2 shows a block diagram of the measurement apparatus. Light was obtained from a 450-w Xenon arc lamp, the intensity of which was controlled by stainless-steel screen filters and monitored by a pho-tomultiplier which was calibrated periodically against a thermopile. A camera shutter operated at 1/200 sec provided the light pulse and a synchronized signal to the oscilloscope. The photocurrent transient is ob-served with a high-speed picoammeter (response time of 1 msec) the output of which is displayed on an oscilloscope. The applied voltage is constant throughout the transient measurement. The selenium films were prepared by evaporation of four 9's pure selenium shot supplied by Canadian Copper Refiners. Spectrographic analysis showed about 1 ppm of Te and Fe, 5 ppm of C1, and 0.05 ppm

Jan 1, 1968

By D. A. Stevenson, T. Alden, J. Wulff

A portion of the liquidus curve has been determined for the binary alloy systems Ni-Pb and Cr-Pb. The solubility of nickel is 0.53 atomic pet at 372° and 18.63 atomic pet at 1200°C. Chromium shows low solubility, 0.634 atomic pet at 1210°C. Molybdenum and tungsten were also studied and found insoluble in lead, less than 0.005 atomic pet at 1200°C. INCREASED use of liquid metals of low melting X point for heat transfer, coating, joining, and other purposes has renewed interest in the solubility of structural metals in these liquids. A study of Hansen1 and current literature indicates that few liquidus curves at the low melting end of the binary diagrams have been accurately delineated. This statement applies particularly to the binaries of lead. The present paper is limited to nickel, chromium, tungsten, and molybdenum in lead. In early studies2, 3 of the lead end of the Pb-Ni system, a monotectic at 1340°C was established. Tammann and Oelsen' determined the solid solubility of nickel in lead at 20°C to be 0.023 wt pet. Recently Pelzel5 determined the liquidus curve from the eutectic temperature of 327° up to 727°C using a segregation method. In the present paper this part of the curve has been checked and extended to 1244°C. The Pb-Cr system was first studied by Hindrichs.6 He pointed out the existence of a monotectic at 1470°C and indicated a tentative liquidus. Recent corrosion studies of Fe-Cr alloys in lead suggest that chromium is more soluble than iron in lead.7-8 The solubility of tungsten in lead according to Inouye8 is about 30 wt pet at 1200°C. Appreciable solubility of molybdenum in lead might therefore be expected. Experimental Various experimental techniques have been employed in the determination of solubility in liquid metals. For low solubility, thermal analysis is unsatisfactory. A segregation method was used by Pelzel3 in his study of the Pb-Ni system. In this procedure separation of liquid and solid is possible due to difference in density. In the technique of Kleppa10 a single piece of material is maintained in contact with the liquid metal in evacuated Vycor vials. After equilibration, solid and liquid are separated by tilting. Keck and Broder" measured the weight of a piece of the solid solute before and after immersion in a pure solvent bath; the weight loss was a measure of the solubility. All of the above procedures are time-consuming since they permit only one determination per run. Numerous samples for analysis may be taken from the melt in the method described by Gurinsky and CO-workers.10 The rate of extraction of samples is limited only by the time required for equilibration. In the present work, a modification of this method was employed. A 150-g charge of analytical reagent grade lead and the added metal* were contained in an Alun- dum crucible. It rested on firiely divided silica at the closed end of a 45 mm Vycor tube, 500 mm long. The top of the tube was provided with an inlet and

Jan 1, 1959

By H. T. Clark

NO previous determinations of the deformation or recrystallization textures of titanium or of titanium-base alloys have been reported in the literature. The room-temperature structure of titanium is hexagonal close-packed with a c/a ratio less than 1.633. It would be expected, therefore, to have a rolling texture similar to that of other hexagonal close-packed metals, namely (0001) [1010]. Burgers and Jacobs1 have shown that zirconium, a metal isomorphous with titanium in its structure and similar in many of its properties, has such a texture with a scatter of the basal plane toward the transverse direction. This scatter is in the opposite direction from that found in magnesium by Bakarian2 but similar to that reported by Smigelskas and Barrett3 or beryllium. The rolling and annealing textures reported here for high-purity iodide titanium are significantly different from the . textures of any other hexagonal close-packed metal. All titanium used during this investigation was prepared by the iodode process." The annealed hardness of this material varied from 73 (material used for sample No. 2) to 97 Vickers hardness number. An estimate of the chemical composition of this grade of titanium has been reported by Finlay and Snyder.5 With one exception, shown in table I, the as-deposited titanium was cast into 10 to 20 g ingots in an electric arc furnace in purified argon before being rolled to sheet. The cast ingots were forged and ground until their cross-section was approximately rectangular, annealed 1 hr at 700°C in vacuum and cold rolled. Rolling was carried out in a two-high, 4 in. diam mill, using reductions no greater than 10 pct per pass. The direction of rolling was reversed after each pass, and, in order to avoid temperature effects, the sheet was allowed to cool after each pass. Unless the rolled sheet was sufficiently thin for X-ray penetration (about 0.004 in.), it was reduced to this thickness by pickling. Because of the possibility of introducing twinning or other deformation during grinding, no attempt was made to maintain uniform thickness of the sample during pickling by intermediate grinding or sanding operations. Those samples to be used for determining the annealed texture were recrystallized by vacuum annealing the cold-rolled sheet for 1 hr at 500°C. These thin samples were held between thick titanium sheets during annealing to prevent distortion. Table I outlines the rolling and annealing schedule of those samples for which photograms or texture patterns are shown. X-ray Techniques The usual techniques for determining textures were employed during this work. Molybdenum radiation was used for the transmission exposures and copper radiation for the glancing angle ones. Since titanium fluoresces under these conditions, it is necessary to employ a filter between the sample and the film. The Kß radiation filters are very satisfactory for this purpose. Sufficient grains having favorable orientation were present in both the cold-worked and in the cold-worked—500°C annealed samples to provide satisfactory patterns with the samples stationary. Because of the difficulties of comparing intensities of transmission photograms with those obtained

Jan 1, 1951

By H. M. St. John

THE melting department is the heart of the foundry. From it clean metal flows to the molding floor, in the right quantity, at the right time and at a sufficiently low cost-or, if not, the foundry fails to thrive. Since it is our purpose here to discuss present-day melting practice in the foundry, it may be well at the start to emphasize the wide differences in foundries and the conditions under which they must operate in order to reach the goal stated in the first paragraph. In every foundry, large or small, jobbing or captive, the same factors must be dealt with but they are of varying consequence and must be dealt with in varying ways in different foundries. Particularly in the nonferrous industry, there is so wide a variation in the composition of alloys used and in the character of castings made that no one type of furnace, nor any one method of operation, can be expected to produce the best results at all times. The present discussion will not attempt to include all nonferrous metals. It is intended to cover only the copper-base alloys in which copper is the dominant element, most of which are commonly known as brass or bronze. The discussion is further limited to the melting of these copper-base alloys for use in sand-casting foundries. Die-casting plants, the brass-rolling mills and certain other metal industries have melting problems peculiar to those industries, which will not be considered here. The following considerations are elemental in all foundries and are listed in what is believed to be the relative order of their present-day importance: I. The melting department must meet the foundry's requirement for dean, fluid metal, of specified composition and purity, at a temperature suitable for the work the foundry has in hand. This is the prime consideration in any foundry, at any time, anywhere. 2. Working conditions surrounding the melting furnaces and attending their use must be good. 3. The cost of molten metal at the mold must be as low as possible. 4. The operating characteristics of the furnaces must be sufficiently flexible, to meet normal variations in foundry requirements. 5. The operation and maintenance of the melting equipment must not require more skill and experience than is available in the particular foundry in question. METAL QUALITY It is not a function of the melting furnace to refine or improve the quality of the metal but simply to melt it without impairing its quality. Good practice requires, therefore, that care must be taken to supply the melting department with metal of inherently good quality, assured by specification or otherwise, having all the properties necessary to produce the castings desired. An alloy contains a number of primary elements, which must be present in definite proportions if the castings made from it are to have the desired properties. If the castings are made to a customer's specification, this will state the range within which these principal elements (for example, copper, tin, lead and zinc) are permitted to vary.

Jan 1, 1946

By C. A. Fothergill

An improved blotter model is described which makes use of a plastic sheet as base for the blotter field and pins to represent the input wells. The model is simple to construct and adapt and is particularly useful for demonstration purposes. Operational details are given. INTRODUCTION The blotter model was first applied to the investigation of oilfield problems by Wyckoff, Botset and Mus-kat,' primarily in order to demonstrate the flood patterns which could be expected from various arrangements of input and output wells in waterflooding projects. In recent years the model has been largely superseded for analog studies by the potentiometric and electric analog models which are more refined and versatile, since they can simulate the form, and, in certain cases, permeability variations which it is not possible to do with the blotter model. However, the latter is still used for analog studies where the reservoir can be represented as being uniform in thickness and permeability, and where a visual record of the flood advance is required. Ramey andNabor,2 for example, have applied the model to the investigation of areal sweeps in oil recovery by in-situ combustion. Because of its limitations, the blotter model can be used in general for only very simple arrangements of input and output wells, but within these limitations it has a definite advantage over all other types, in that it provides a picture of the advancing flood using the simplest and most easily constructed apparatus, by contrast with the gelatin model, for example, which requires more elaborate equipment. Moreover, the experiments can be quickly repeated and modified if necessary, whereas considerable time is required to prepare a gel field, compared with that required for the preparation of sheets of conducting blotting paper. For these reasons the blotter model can be very useful for demonstration and teaching purposes, enabling the student to experiment for himself with different arrangements of input and output wells. A model has been constructed for this purpose which is simple to operate and adapt. The model (Fig. 1) consists of a base platform or box, approximately 12-in. square, on top of which are screwed three lathes of 1/2 -in. square section to form three sides of a square 6 in. in length. This forms the support for a sheet of Cobex, transparent plastic, thickness .003 in., on which is carried the blotting paper representing the field. The plastic is flexible and relatively soft, and can be attached to the support by cellulose tape so that it can be easily removed when required. The input wells are represented by brass drawing pins pressed through the plastic sheet from the underside until the points are just projecting through the top; these are connected in the circuit as shown in Fig. 2. The sheet of blotting paper of required shape and size is saturated with a solution of 0.2 n-potassium sulfate to which has been added a saturated alcohol solution of phenol-phthalein at a strength of 10 cc/liter of stock solution. The surplus water is removed and the blotting paper placed in position on the plastic sheet making contact with the drawing pins and the sheet (which is an insulator). The anode consists of a second sheet of blotting paper cut as shown and saturated with the same solution. This is suspended from a laboratory stand, being connected to the conducting wire by means of a crocodile clip and making contact with the horizontal blotting paper at the projecting point. This is the method used by Ramey and Nabor and which permits the hydroxyl ions or colored front to reach the anode. As shown in Fig. 2, the electrical voltage used is 220-v DC and a shunt is placed across the terminals to step down the voltage as required. Further adjustment can be made as necessary using a lamp board in series with the shunt to obtain the

Jan 1, 1958

By C. F. Baes, H. H. Kellogg

The effect of dissolved sulphur on the surface tension of liquid copper has been measured by a sessile-drop method at 1120°C. Sulphur is highly "surface active" in liquid copper; the surface tension lowering is about 650 dynes per cm for a sulphur content of 0.6 pct. The degree of adsorption of sulphur on the liquid copper surface has been calculated, and various models of the surface layer have been tested against the results. THE science and technology of surface chemistry and physics at room temperature are relatively advanced, and the engineer possesses a background of information that allows him to predict and control many phenomena—such as frothing, emulsifica-tion, wetting of solids by liquids, flow through capillaries, adsorption, mineral flotation, penetration of porous bodies by liquids—which are related to the behavior at interfaces. Surface phenomena in high temperature systems are probably of equal importance to the metallurgist and ceramist, but at present are incompletely understood. Frothing of liquid slags, penetration of refractories by liquid metals and slags, infiltration of powder metallurgy "skeletons" by liquid metals, bonding of metals to ceramic oxides in the manufacture of "cermets," wetting of one metal by another for purposes of soldering and welding, are but a few of the many phenomena of metallurgy that are controlled by surface behavior. Concerning the most elementary of surface properties—the gas-liquid surface tension—the existing data on liquid metals are inadequate. For the surface tension of "pure" metals the results of different investigators differ by 10 or 20 pct. The role of surface-active agents in liquid metals is relatively unknown, and it is not unlikely that the discrepancy in the values for the surface tension of pure metals is due to the presence of traces of surface-tension-lowering impurities in the samples. Based on analogy to room-temperature systems, the highly surface-active impurities in liquid metals should be elements or compounds of limited solubility in the liquid metal and possessing considerably weaker in-termolecular bonding forces than the metal itself. The nonmetals of the V, VI, and VII groups of the periodic table might be expected to act in this way. The experimental work in this paper represents a study of the surface tension of pure liquid copper in hydrogen at 1120°C, and the effect of dissolved sulphur (which is a strongly surface-active agent in liquid copper) on the surface tension of copper. The Gibbs equation has been applied to the results and an attempt made to correlate the surface tension behavior with two models of the interfacial layer. The sessile-drop method for surface-tension measurement at high temperatures which was used in this investigation has been described by several investigators.1,2 It involves the measurements of the dimensions of a stationary liquid drop on a horizontal surface. From these dimensions and the liquid density, the surface tension of the liquid may be calculated either by means of various approximate formulas, or more accurately by means of the Bash-forth and Adams tables.- or liquid drops which exhibit a contact angle greater than 90°, by far the simplest dimensions to measure are those indicated in Fig. 1, i.e., the diameter of the maximum horizontal cross section (2X) and the maximum height (Z) above this plane. In order to calculate the contact angle and the volume of the drop, the diameter at the base of the drop (2a) and the total height (h) also must be measured. Upon investigation of the literature, the authors failed to discover a concise statement of the accuracy of the method when used in conjunction with the Bashforth and Adams tables, hence a careful examination of the tables was made and the curve shown in Fig. 2 was constructed. The "error factor," plotted as the ordinate, is the factor by which the

Jan 1, 1954

By C. S. Smith, Chih-Chung Wang

TURNBULL and his collaborators1,2 have developed the theory of homogeneous nucleation as applied, inter alia, to solidification of liquid metals. Vonnegut³ and Turnbull4 have shown that if a liquid metal is subdivided into small droplets a vast majority of them will undercool very considerably before solidification, generally to as low as about 0.8 of the freezing temperature on the absolute scale. The nuclei effective at small degrees of supercooling in bulk metal seem to be internal or surface heterogeneities, relatively small in number. If the metal is subdivided, those droplets that happen to contain such nuclei will solidify at a temperature not greatly below the true freezing point, but only a small part of the whole volume will be affected and the majority of the drops will under-cool to the much lower temperature at which homo- geneous nucleation occurs as a result of fluctuations. It occurred to one of the authors that an appropriate subdivision to give effective freedom from random nuclei is produced during the solidification of many alloys that contain a minor amount of a phase of low melting point, and that one might then expect marked undercooling of the distributed phase. Experimental: The alloys selected for initial study were copper with minor amounts of lead and bismuth, and aluminum with tin. In all these alloys, the major component freezes at a temperature not much below that of the pure metal, and there is little further change in constitution on cooling until the lower melting point constituent freezes in an almost pure state. Cooling curves were taken using the controlled heat flow method permitting approximate specific heats to be obtained. Chromel-alumel thermocouples were used, with the standard emf tables, since extreme precision was not needed. The crucible (3/4 in. id, 5/16 in. wall) was made of B & W K-20 insulating brick. It held about 10 cc of the alloy being investigated. The cooling rate was 2.5" to 2.9°C per min under a controlled temperature difference of 20°. Approximate specific heats were computed from the inverse rate curves together with data from a blank run and from a standard run with a copper cylinder of known heat capacity. The alloys for investigation were made from high-purity metals (99.99+pct) and cast into graphite molds. The castings were machined to fit the crucible and to provide a hole for the inner thermocouple. Cooling curves were taken after heating to a temperature about 50" above the melting point of the minor, lower melting-point, constituent. Results The lead phase in an alloy of copper with 5 pct lead did not undercool more than 3" below the melting point of lead (327°C) either as cast or after annealing to produce a new dispersion of the liquid phase. A copper-zinc-lead alloy with 23.75 pct zinc and 5 pct lead undercooled more but showed no thermal effect below 319°C. A cast alloy of copper with 5 pct bismuth undercooled to 249°C (M.P. bismuth 27l °C), but once solidification started it was completed at the same temperature. This was anticipated, since the bismuth forms a nearly continuous phase between the grains of copper, and a solid crystal nucleated anywhere would rapidly* con- sume the entire network of liquid, unless the physical continuity of the liquid were broken through volume changes, inadequate fluidity, or gas evolution. Similar arguments apply in the case of copper-lead alloys, where the lead-rich liquid forms a network along grain edges, though not grain faces. In both cases there would be a few isolated particles

Jan 1, 1951

By Gordon W. Hodgson, Edward Tipman

INT'RODUCTION An appreciable number of the oil fields in Western Canada are accumulations of heavy black oils in more or less unconsolidated sandstones. When the crude oils are produced by conventional means, they are frequently contaminated with both sand and oilfield water. The water is usually present as emulsified water, and the sand and other solid materials are suspended in the emulsions. The presence of the solid material in the crude oils is troublesome and, in general, little is known about the behavior of suspended solid particles in emulsions. The Stokes equation describes the behavior of suspended particles in homogeneous fluids in terms of particle size, density differential, and fluid viscosity. In the case of an emulsion, particle size and density differential introduce no difficulties, but considerable doubt centers around the viscosity term. It has been reported1 that the viscosity of an emulsion is related to the viscosity of the continuous phase by an expression of the type: n = a, (1 + a C) where n is the viscosity of the emulsion, n,, is the viscosity of the continuous phase, a is a constant, C' is the volume concentration of the disperse phase. The value of 17, the coefficient of the concentration term, has been determined for various systems, and has been found to vary from a value of 1 to 4.75. The value of 2.5 has been found to be applicable to a large number of systems, and this is the value that is widely used in the equation which then becomes the Einstein equation for the viscosity of emuls~ons. It is of considerable significance that neither the particle size nor the viscosity of the disperse phase enters the expression; the expression for the viscosity of the enlulsion is based solely upon the viscosity of the continuous phase and the concentration of the disperse phase. For crude oil emulsions the Simha equation and the data presented by Fukushima and lchimurai show a non-linear dependence of the viscosity ratio on the water concentration. While it is undoubtedly reasonable to use these data for predicting the viscosity of a specific emulsion, and while it is equally reasonable to expect the calculated viscosity to predict the settling rate of a solid spherical particle in the emulsion by means of Stokes equation, there seems to be no direct evidence that this calculation is indeed sound for describing the settling rates of solid particles in emulsions of water in crude oils. PROCEDURE A direct approach to the problem was thus indicated. Laboratory equipment was designed and built for the direct determination of the rate-of-fall characteristics of solid particles in emulsions of water in oil. Although the apparatus incorporated the basic design of conventional falling-ball viscometers, the study was concerned directly with the rate-of-fall characteristics of particles in emulsions, rather than with the viscosity of the emulsions as such. The crude oil used in this study was a very heavy black crude oil—the McMurray oil obtained from oil-soaked sands outcropping on the Athabasca River in northeastern Alberta. It was produced from the sands by strip mining followed by hot-water separation of the oil in the separation plant of the Alberta Government at Bitumount'. The primary plant product was a wet crude oil containing about 5 per cent solids and 35 per cent water. The final plant product was only slightly different from the native oil, having lost only about 4 per cent of its bulk as light ends during dehydration distillations. In the present investigation two kerosene dilutions of the McMurray oil were used in addition to the dry plant product. The McMurray oil contained 1.92 per cent solids. Analysis of the solids by X-ray diffraction showed the presence of kaolinite, pyrite, and illite as major constituents. with lesser amounts of quartz. Particle size of the pyrite and quartz was less than 10

Jan 1, 1957

By D. J. DeLazaro, W. Rostoker, R. E. Riley, M. Hansen

At very low concentrations, carbon dissolves interstitially in molybdenum resulting in a linear expansion of lattice parameter with increase of carbon in solid solution. Geometrical consideration of the relative size of carbon atom to size of interstice approximately predicts the observed volume expansion. THE element carbon, occurring in molybdenum, either as an unavoidable impurity, or purposely added, markedly affects the mechanical properties of molybdenum. Several investigators1-" have noted the occurrence of molybdenum carbide at the grain boundaries of cast molybdenum, and Fischer and Rengstorff' have shown that this intergranular constituent can induce intergranular brittleness. The appreciable change, with temperature, of the solid solubility of carbon in molybdenum, found by Few and Manning," suggests other important effects upon mechanical properties. Finally the relative atom diameters of carbon and molybdenum (the ratio of atom diameters is 0.59) are indicative, by analogy with iron (ratio of carbon atom diameter to iron atom diameter is 0.65), of a possible interstitial solid solution. If carbon dissolves intersti-tially in molybdenum, anelastic effects and age-hardening effects, similar to those observed in other body-centered cubic metals, could be expected. However, from the work of Sykes, Van Horn, and Tucker," it might be inferred that carbon forms only a substitutional solid solution with molybdenum. These considerations made it desirable to study the effect of carbon on the lattice parameter of molybdenum in greater detail than heretofore. All heat treating was done in a high temperature furnace7 built specifically for heat treatment of molybdenum. The temperatures and times of heat treatment were determined from the a solubility limit for the Mo-C system." These heat treatments were carried out in argon which was purified with respect to N, and H.!0." Purification of the argon was accomplished by passing the argon over hot (750°C) titanium and then through a magnesium perchlorate drying tower. As many as six samples were run concurrently and quenched at different times without interrupting the furnace cycle. Both the purity of the furnace atmosphere and ability to quench samples from any temperature up to 4000 °F were of prime importance in the successful heat treatment of samples for the lattice parameter investigation. Carbon Analysis The Leco Combustion apparatus was used for carbon analysis. This apparatus is capable of an accuracy of & 0.003 pct for a 1 g sample in the range below 0.10 pct. However, it is felt the degree of accuracy is somewhat better than this limit in view of the consistency evident by cross checking a number of determinations. The Battelle Analytical Laboratory consistently reported check results to within k 0.001 pct C. X-ray Measurements The molybdenum wire specimens (20 mils) were carefully filed down to about 12 mils and then etched with nitric acid to 8 mils. Carbon analyses were made on specimens before reduction in size; however, since there was no evidence of surface carburization, it is probable that the carbon was uniformly distributed throughout the sample. The resultant specimens were strain free and small enough to minimize the error in the lattice parameter determinations due to X-ray absorption. Diffraction patterns were obtained with a Debye-Scherrer powder camera 114.59 mm in diam utilizing the Straumanis type asymmetrical film mounting. Nickel-filtered copper. Ka radiation and zirconium-filtered molybdenum Ka radiation were used. Line positions on the film were measured with a traveling microscope equipped with a vernier scale permitting measurement to 0.001 cm. The average of five readings was used to determine the position of each line. The lattice parameter for each specimen was determined from the data by the extrapolation method of Bradley and Jay, Y.e., the intercept at 90" of the straight line obtained by plotting the apparent lat-

Jan 1, 1953

By J. A. Hafford, J. K. Kerver, J. G. Richardson, P. M. Blair, J. S. Osoba

This paper presents the results of laboratory measurements of relative permeabilities to oil and gas on small core samples of reservoir rock by five methods, and describes the influences of such factors as boundary effect, hysteresis, and rate upon these measurements. The five methods used were the "Penn State," the "single core dynamic," the "gas drive," the "stationary liquid," and the "Hassler" techniques. In those methods in which the results are subject to error hecause of the boundary effect, the error may be minimized hy the use of high rates of flow. In order to avoid complexities introduced by hysteresis, it is necessary to approach each saturation unidirectionally. Observed deviations of relative permeabilities with rate can be explained as a manifestation of the boundary effect, and disappear as the boundary effect vanishes. The results indicate that all five methods yield essentially the same relative permeabilities to gas. Of the four methods applicable to the determination of relative permeability to oil, three, the Penn State, single core dynamic, and gas drive, gave relative permeabilities to oil which were in close agreement. The Hassler method gave relative permeabilities to oil which were consistently lower than the results obtained by the other methods. INTRODUCTION The relationship between the effective permeability of a reservoir rock to each of the fluids flowing through it and the corresponding fluid saturation is an important characteristic of the reservoir rock. Knowledge of this characteristic is and gas reservoirs and of the ultimate recovery to be expected extremely important in the prediction of the behavior of oil under various operating conditions. These effective permeabilities are usually expressed as the "relative permeability" to a fluid phase, defined as the ratio of the effective permeability to the permeability of the rock to a single phase at 100 per cent saturation. Relative permeability-saturation relations are not the same for all kinds of reservoir rock, but may vary from formation to formation, and within the different portions of a heterogeneous formation. In studying the performance of a specific reservoir, it is necessary, then, that the relative permeability characteristics of the individual portions of the reservoir be measured. These measurements may be made in the laboratory on small core samples from the reservoir. Various techniques have been proposed for the measurement in the laboratory of relative permeability-saturation relations. In varying degree, difficulties attend the use of all of the methods which have been proposed. It is the purpose of this paper to discuss the factors which influence the measurement of relative permeability, the difficulties encountered in several methods, and to present comparative results obtained by the use of various techniques. FACTORS WHICH INFLUENCE THE MEASUREMENT OF RELATIVE PERMEABILITY It is necessary that the relative permeability data measured in the laboratory yield the same relative permeability-saturation relationships that would govern the flow of fluids through the sample if it were to occupy its original position in the reservoir. Since the core sample upon which the laboratory measurements are made is not surrounded by similar core material as it was in the reservoir, an error in measuring the relative permeabilities may arise from the "boundary effect" which results from a discontinuity in capillary properties of the system at the effluent end of the core. Again, the rates of

Jan 1, 1951

By C. R. Johnson, R. A. Greenkorn, L. K. Shallenbarger

This paper describes a study, based on core data, of the directional permeability of a sandstone reservoir. Directional air permeabilities are explained and correlated with lithology by the tensor theory of permeability, which is extended to the more general case of heterogeneous anisotzopic porous media. In this case, the permeability tensor is made up of two components: (I) anisotropy (variation around a point) which correlates with bedding, and (21 heterogeneity (variation from point-to-point) which correlates with grain size. INTRODUCTION Previous studies of directional permeabilityl.5-8 have concerned themselves only with anisotropy at a point, rather than with both point-to-point differences and local anisotropies. In this paper, we present the existing tensor theory of permeability for anisotropic porous media and then extend it to the more general case of heterogeneous anisotropic porous media. The laboratory measurements of directional permeability are explained in view of this extended theory and the data are discussed in terms of the lithologic factors that correlate with it. The results show what the heterogeneity and anisotropy of the reservoir element are, and that the directional permeability correlates with lithology. Data used in this paper are measurements of air permeability in eight directions, spaced at 45° intervals, on 142 2-in. vertical plugs from 30 cores. The core data are meaningful in terms of directional permeability because the cores were oriented to within 45O during drilling and coring.3 Although we initially thought that only 60 per cent of the core material was reliable, subsequent study showed that almost all of it was reliably oriented. After determining the air permeabilities, the data were reduced to three independent variables for each plug: the major and minor permeability axes, and the direction of the major axis. These were obtained by converting the permeability data to the reciprocal square root of permeability and fitting the transformed data with ellipses according to the tensor theory of permeability.8 The point-to-point areal variation of the minimum permeability axis is related to grain size. The direction of the permeability axes, where the major axis exceeds the minor axis by at least 5 per cent (measured variation is about 4 per cent), correlates with the bedding. The permeability tensor used in this study must be considered as the sum of a scalar and a tensor, with the scalar being the minor axis permeability as a function of position, and the tensor the directional effect, which is additive permeability over the minor axis. In this case, the point-to-point variation or heterogeneity (minor axis) is substantially larger than the variation at a point or anisotropy. It may be important that this separation of "directional permeabilities" be recognized when considering migration of fluids due to permeability variation. Local migration may be due to anisotropy and point-to-point migration may be due to heterogeneity, but the direction and magnitude of these may not be the same. Furthermore, in truly heterogeneous systems, one would expect that anisotropy would be the smaller of the two effects. THEORY TENSOR THEORY OF PERMEABILITY FOR ANISOTROPIC POROUS MEDIA8 Darcy's law for flow in porous media in its usual form is where qis the flow rate vector, k is the permeability, is the viscosity, is the vector differential operator, and P is the Pressure. Consider flow, q, through a unit area in the direction of the unit vector n from elementary flow tubes parallel

Jan 1, 1965

By J. K. Kerver, J. S. Osoba, J. G. Richardson, P. M. Blair, J. A. Hafford

This paper presents the results of laboratory measurements of relative permeabilities to oil and gas on small core samples of reservoir rock by five methods, and describes the influences of such factors as boundary effect, hysteresis, and rate upon these measurements. The five methods used were the "Penn State," the "single core dynamic," the "gas drive," the "stationary liquid," and the "Hassler" techniques. In those methods in which the results are subject to error hecause of the boundary effect, the error may be minimized hy the use of high rates of flow. In order to avoid complexities introduced by hysteresis, it is necessary to approach each saturation unidirectionally. Observed deviations of relative permeabilities with rate can be explained as a manifestation of the boundary effect, and disappear as the boundary effect vanishes. The results indicate that all five methods yield essentially the same relative permeabilities to gas. Of the four methods applicable to the determination of relative permeability to oil, three, the Penn State, single core dynamic, and gas drive, gave relative permeabilities to oil which were in close agreement. The Hassler method gave relative permeabilities to oil which were consistently lower than the results obtained by the other methods. INTRODUCTION The relationship between the effective permeability of a reservoir rock to each of the fluids flowing through it and the corresponding fluid saturation is an important characteristic of the reservoir rock. Knowledge of this characteristic is and gas reservoirs and of the ultimate recovery to be expected extremely important in the prediction of the behavior of oil under various operating conditions. These effective permeabilities are usually expressed as the "relative permeability" to a fluid phase, defined as the ratio of the effective permeability to the permeability of the rock to a single phase at 100 per cent saturation. Relative permeability-saturation relations are not the same for all kinds of reservoir rock, but may vary from formation to formation, and within the different portions of a heterogeneous formation. In studying the performance of a specific reservoir, it is necessary, then, that the relative permeability characteristics of the individual portions of the reservoir be measured. These measurements may be made in the laboratory on small core samples from the reservoir. Various techniques have been proposed for the measurement in the laboratory of relative permeability-saturation relations. In varying degree, difficulties attend the use of all of the methods which have been proposed. It is the purpose of this paper to discuss the factors which influence the measurement of relative permeability, the difficulties encountered in several methods, and to present comparative results obtained by the use of various techniques. FACTORS WHICH INFLUENCE THE MEASUREMENT OF RELATIVE PERMEABILITY It is necessary that the relative permeability data measured in the laboratory yield the same relative permeability-saturation relationships that would govern the flow of fluids through the sample if it were to occupy its original position in the reservoir. Since the core sample upon which the laboratory measurements are made is not surrounded by similar core material as it was in the reservoir, an error in measuring the relative permeabilities may arise from the "boundary effect" which results from a discontinuity in capillary properties of the system at the effluent end of the core. Again, the rates of

Jan 1, 1951

By Robert B. Hall, Charles W. Bauer

Alunite, KA13(SO4)2(OH)6, was used from the 15th century until early in the present century as a source of potash alum and aluminum sulfate. Since early in this century its use for this purpose has declined to virtually nil with acid treatment of bauxite or clay replacing alunite as a source of alum. During the First World War alunite served as an emergency source of potassium sulfate fertilizer in the United States and Australia. More recently, alunite has been investigated as a nonbauxite ore of aluminum, with potassium sulfate and sulfuric acid as recoverable byproducts. The Soviet Union established a commercial-scale plant in the mid-1960s producing cell-grade alumina from alunitic ore and recovering byproduct potassium sulfate and sulfuric acid. Interest in nonbauxite ores, including alunite, is expected to continue in countries that presently are dependent on imports of bauxite or alumina to support their aluminum industries. The US has the largest aluminum producing and fabricating industry in the world but imports more than 90% of its aluminum-bearing raw materials. This chapter reviews the status of alunite as a potential source of aluminum with byproduct fertilizer, and the resources available to support this industry, whenever this becomes economically feasible. Historical Background Alunite has received little attention until recently, yet for centuries it held a higher place than many of the industrial minerals considered essential today. The deposits of alunite at Tolfa, northwest of Rome, were mined almost continuously from 1462 until about the middle of the present century (DeLaunay, 1907; Lombardi, 1977). The potash alum made from the alunite, called Roman alum, was a valued commodity in international trade, being used in the making of paper, in tanning leather, and as a mordant in textile dyeing. The industry at Tolfa is said to have been controlled by the Vatican and was a source of revenue for the Papal State until fairly recent times (Lombardi et al., 1977). Since early in the present century, the preferred method for making alum has been by acid treatment of bauxite, clay, or other aluminous material, so that alunite has fallen into near-total disuse as a source of alum chemicals. Appreciable quantities of mixed alunite-kaolin rock still are quarried in the Tolfa district for use by the Italian cement industry (Lombardi and Mattias, 1979), but the role of this material in the making of Italian cement is not clear. A large deposit of alunite-bearing rock in Chekiang province, mainland China, is said to have yielded a "great quantity" of alum over a period of several centuries (Yih, 1931). During the 19th century, alunite deposits in France, Spain, Australia, and other countries were exploited as raw material for making potash alum and aluminum sulfate. Interest in alunite was revived during the First World War, not for alum, but as an emergency source of potassium sulfate fertilizer. Large veins of nearly pure alunite had just been discovered on Alunite Ridge, 11 km southwest of Marysvale in Piute County, Utah (Butler and Gale, 1912), and these were quickly brought into production for making potash fertilizer to replace supplies cut off from the famous deposits at Stassfurt, Germany. An estimated 225 kt of Marysvale alunite was mined and processed at that time (Callaghan, 1973). Similarly, Australian alunite deposits were mined as a source of potash fertilizer during both world wars (Hall, 1978).

Jan 1, 1983

By N. Marusov, D. K. Lowe, J. C. Karp

This paper considers, from an engineering viewpoint, several factors involved in creating, designing and locating horizontal barriers for controlling water coning. This is an effort to consolidate new concepts with previous information so that a reasonable selection of barrier materials, dimensions and vertical position can be made. Coning theories previously developed are briefly reviewed and an effort i,s made to reduce the results of coning-theory calculations to a point where routine calculations can be made with a desk calculator. It is expected that these simplified calculations will give usable predictions of the amounts of improvement attainable with barriers of various dimensions. Apparatus and procedures used for testing the suitability of commercial cements are described and test results are presented. INTRODUCTION Just about as soon as the phenomenon of water coning was recognized as an oilfield problem, there were suggestions that the production of water coning could be controlled or completely suppressed by means of horizontal barriers. It was also suggested that natural barriers such as shale streaks were helpful in restricting bottom-water production. The implication was that wells not having the benefit of continuous shale streaks to suppress bottom waters should, in some way, be supplied with an artificial barrier. With regard to the selection of barrier materials, there are many references which give the merits of liquid barriers.',' These liquids include surface-active agents," recipitates' and emu1sions. There is no real need to review the merits of these materials again. This paper deals with the use of solid barriers which could be made from various cements. The two major restrictions placed on these barrier cements are that (1) they must be commercially available in large quantities, and (2) they must be applicable by means of standard tools and equipment with techniques that have been fully developed and are in general use at the present time. A schematic drawing of a horizontal barrier in a reservoir is shown in Fig. 1. Two maximum stable water cones are illustrated-—-one for the wellbore diameter and the other for a barrier. A maximum stable cone is one that has attained its maximum volume at the critical production rate and is on the threshold of producing water. The volume displaced by each water cone and the rise in water table are indications of the amount of water-free oil produced. Corrections for porosity, connate water and residual oil, of course, must be applied. The water-oil interface which defines a maximum stable cone is called a free surface. It is a surface over which the pressure is constant. This free surface has the shape of a limiting streamline at and below which there is no movement or transport. The shape of the water cone describes the pressure drop in the reservoir. The effect of a completely impermeable barrier on the cone shape is essentially the same as extending the wellbore out to the barrier radius. The placement of a horizontal barrier requires that a horizontal fracture be created using a single-point entry technique. Two methods may be employed for filling this fracture. One method consists of propping the fracture before filling with cement. The other consists of fracturing with fracture fluid, then immediately following with cement

By S. J. Rothman, J. J. Hines, D. Rokop, R. Bastar

Self-diffusion has been measured along each principal axis of mosaic-structured and relatively perfect a uvaniuln single crystals. The anisotropy reported before,' D[loo] = D[001] » D[010 , has been confirmed. and is shown to represent volume diffusion. Diffusion along the dislocations in the imperfect crystals increases the measured value of D significantly without changingr either the shapes of the penetvation plots or the anisotropy. SINCE a uranium is orthorhombic, the diffusion coefficients along the principal crystallographic axes need not be equal. A previous measurement of self-diffusion in three mosaic-structured a uranium single crystals1 showed that Dil00| =D[001 >>D[010 This result was deduced from penetration plots similar to those in Fig. 1. That is, the plots for diffusion along [loo] and [001] were the straight lines expected from the solution of the diffusion equation for the boundary and initial conditions of the experiment, while the plot for diffusion along [010] was curved so that the part near X = 0 had a much steeper slope than the straight lines did. The observed anisotropy could have been due either to volume diffusion or to diffusion along the very large number of dislocations in such crystals, according to the model proposed by aart.' The authors of Ref. 1 argued that the latter possibility was unlikely, but did not exclude it. To settle the question, a simultaneous measurement of self-diffusion in mosaic-structured and mosaic-free crystals was carried out. This paper reports the results, as well as a measurement of the temperature dependence of self-diffusion in a uranium. EXPERIMENTAL The single crystals of a uranium used in this experiment are listed in Table I, together with other experimental details. '(Mosaic structured" here means crystals grown by solid-state phase change.3 The Laue spots from such crystals spread over about 6 deg of arc, which indicates that the density of dislocations is very large. "Perfect" crystals are ones grown by Fisher's grain-coarsening tehnique; the Laue spots from these are quite sharp,4 which shows that the dislocation density in these crystals is much lower. All of the crystals were made from high-purity uranium; a typical analysis is given in Ref. 1. The actual diffusion directions were within a few degrees of the nominal. The thin layer-sectioning method was used. The experimental techniques were similar to those described in Ref. 1, except the sectioning. Crystals Za, 2b, 2c, 4a, 4b, and 4c were sectioned on a lathe. Crystals 3a, 3b, and 3c were sectioned by grinding on glass plates, with 1 p diamond powder in butyl alcohol as the abrasive. The use of glass plates eliminated the crowning noted in Ref. 1, and the use of butyl alcohol as a lubricant simplified the chemical processing of the sections. Material from the sides of these three crystals was removed by spark machining before sectioning. The sectioning of crystals 4a and 4c was botched. A small cylinder of metal was extruded from the center of crystal 4a while turning off material from the side of the sample. Crystal 4c was misaligned by 2.1 x 10"3 cm because the dial gage jammed during the alignment. Notwithstanding these errors, useful data were still obtained from these crystals. The points

Jan 1, 1967

By C. H. Herty

AN earlier paper on absorption of sulfur by the slag in the basic open-hearth furnace included a brief discussion of the absorption of sulfur during the melting period. The data available at that time showed that the amount of sulfur absorbed by the melting scrap was proportional to the sulfur content of the furnace gases, and the following statement was made: "The conclusion may be drawn from these results that if a gas entirely free from sulfur were used during the melting, any iron in direct contact with the gases would be completely, or nearly completely, desulfurized before it reached the bath proper." The experimental work discussed herein deals with absorption of sulfur by the melting scrap when fuels with both high and low-sulfur content were used. Before taking up the experimental work let us consider the process as a whole as to the "flow" of sulfur. The input of sulfur occurs in: 1, the hot metal charged; 2, the scrap; 3, the stone or lime charged; 4, the ores charged; and 5, the gas. Sulfur goes out of the furnace in the steel, the slag and the gas. The distribution of sulfur in the furnace depends on the sulfur concentration in each of these materials and on the equilibrium conditions between them.

Jan 1, 1926

By M. F. COOLBAUGH

WHEN I was asked to speak on the subject of leaching, I did not realize that a complete summary of recent progress in leaching had been given by Stuart Croasdale. I shall try to give some other phases of the subject that were not touched by Mr. Croasdale. Not all metallurgists are in harmony as to their methods of treating metals. If they were it would probably mean lack of progress. They can be divided into two classes-the pyrometallurgists, using fire means, and the hydrometallurgists, or those using leaching methods. Conflict is always good for progress; we have it in politics, and in religion there are fundamentalists, and those who are not fundamentalists. As representing pyrometallurgy, may I hope not to be classed among the fundamentalists. The leaching of ores is not new. The leaching of ores for the recovery of metals, however, is quite new. The older leaching was simply to recover the salts. Agricola, back in 1555, I think it was, outlined a great many methods of leaching for the recovery of salts. They called them solid juices at that time. There was no real competition, however, between leaching meth-

Jan 1, 1926

By R. I. Jaffee, H. R. Ogden, D. J. Maykuth

IN THE past year, Jaffee and Campbell&apos; and Finlay and Snyder2 reported on the mechanical properties of titanium-base alloys, some of which were in the same ranges of composition as are covered in this paper. In this paper, evidence confirming that given by Finlay and Snyder on the effects of carbon, oxygen, and nitrogen on titanium will be presented; and, in addition, new data will be given on the effects of these elements on the flow properties and phase transformation of titanium. Materials and Preparation of Alloys The preparation and general properties of iodide titanium have been adequately described elsewhere.&apos; , As-deposited iodide titanium rod, prepared at Battelle, of Vickers hardness less than 90 was employed as the base metal in the present work. This was the same material as that used by Finlay and Snyder.2 The probable analysis reported by them for standard quality metal holds here also: N 0.005 pct, 0 0.01 pct, C 0.03 pct, Fe <0.04 pct, A1 <0.05 pct, Si <0.03 pct, and Ti 99.85 pct. Carbon was added in the form of flake graphite supplied by the Joseph Dixon Crucible Co. Oxygen was added in the form of c.p. grade TiO, powder, produced by J. T. Baker Chemical Co. Nitrogen was added in Ti3N4 powder, supplied by the Remington Arms Co. Individual ingots weighed 7 or 8 g. Carbon, oxygen, or nitrogen was added by placing the corresponding powder in a capsule made from as-deposited iodide titanium rods and melting the capsule with the balance of the charge. The charge was are-melted with a tungsten electrode on a water-cooled copper hearth under a partial vacuum of very pure argon (99.92 pct minimum). Melting was practically contamination free. Vick-ers hardness increases of less than 10 points were normal for unalloyed iodide titanium control melts. Nitrogen analyses of are-melted iodide titanium showed a nitrogen content of 0.005 pct, about the same as is present in the as-deposited rod. No tungsten pickup was found in a melt of iodide titanium analyzed for tungsten. Weight losses in melting nitrogen-free alloys were very small and varied consistently from nil to 0.015 g (0 to 0.2 pct). This permitted the use of nominal composition for these alloys. Chemical analyses made for carbon, which can be analyzed conveniently by combustion methods, justified this procedure. Where nitrogen was added, considerable splattering took place. Here it was necessary to analyze for nitrogen by the Kjeldahl method. The ingots were hot rolled at 850°C to about 0.045 in. thick. After hot rolling, the strips were descaled by mechanical grinding, and then given a cold reduction of 5 to 10 pct to insure a uniform thickness throughout the length of the specimen. The edge strips and the tensile strips were annealed in a vacuum of 1x10-4 mm Hg pressure for 3 1/2 hr at 850°C and furnace cooled. Methods of Investigation Hardness Measurements: At least five Vickers hardness measurements were taken using a 10-kg load on each sample in the following conditions: (1) top and bottom of each ingot, (2) top and bottom surface of as-rolled and annealed sheet, and (3) on cross-section of annealed sheet and all quenched specimens. Tensile Tests: Tensile tests were conducted on Baldwin-Southwark testing machines having load ranges of 600 or 2000 lb. Tests were made on 1-in. gauge-length specimens, 3 1/4-in. overall length, 1/2 in. wide, 0.040 in. thick, with a reduced section 1 1/4 in. long and 0.250 in. wide. Two SR-4, A-7 strain gauges, one mounted on each side of the specimen, were used to measure the strain over a limited range to determine the modulus of elasticity. After the modulus of elasticity readings had been taken, load vs. strain readings were taken, using only one strain gauge, at increments of 0.0001 in. until the yield points were passed and then at 0.001-in. increments to the limit of the strain-gauge indicator (0.02 in.). Strain readings above 0.02 in. per in. were taken every 0.01 in., using dividers to measure the strain between the 1-in. gauge marks until the maximum load had been reached. Crosshead speed, when using the SR-4 gauges, was 0.005 in. per min, and, when using dividers, 0.01 in. per min. Flow Curves: Flow curves were determined using the true stress-true strain data obtained during the tension test. The usefulness of this type of information has been dealt with very adequately elsewhere by L. R. Jackson,&apos; J. H. Hollomon,6 and many others. Flow curves of true stress vs. true strain could be converted to the more conventional cold-work curve of 0.2 pct offset yield strength vs. percentage of cold reduction by means of the transformation, 1/1 = 1/1-R, where R is the fraction reduction in cold working. Thus, the true strains corresponding to percentage reduction can be calculated, and the 0.2 pct offset yield strengths scaled off the — 6 curve by taking the true stresses corresponding to the values of 6 + 0.002 strain. Heat Treatment: For the transformation studies, the alloys were heat treated in a horizontal-tube furnace using a dried 99.92 pct argon atmosphere, and quenched into water. Essentially no contamination was found after several hours of heat treatment at temperatures up to 1050°C. Metallography: Specimens were prepared in the

Jan 1, 1951

By Oscar Weiss

STILFONTEIN and surrounding areas gave nega-tive results in all prospecting attempts since about 1904 when Goerz and Co., a forerunner of Union Corporation Ltd., first drilled in the region and on the farm Stilfontein. Subsequent efforts by African and European Investments Co. and Anglo American Corp. from 1934-37 were completely unsuccessful. Holes drilled by these companies on the farms Riet-fontein, Hessie, and Palmietfontein were stopped in the Lower Witwatersrand system without finding payable reefs. The results of gravimeter, ground magnetometer, and aerial magnetometer surveys are presented in the area, in and around the new Stilfontein Gold Mine, in the Klerksdorp District of the Transvaal in the Union of South Africa. The gravimeter and ground magnetic surveys were completed in 1947—48. The gravity anomalies suggested a block of Upper Witwatersrand quartzites faulted-up between denser rocks of dolomite and Ventersdorp lava. Boreholes S.T. 1, 2, and 3 were drilled in 1948 and, after penetrating the dolomite and Ventersdorp lava, entered Upper Witwatersrand quartzites and intersected the Gold Estates Reef and Vaal Reef. Subsequent drilling delineated the suboutcrop of the Vaal Reef and determined the main structure of this horizon. The gold content of the Vaal Reef was highly payable and shaft sinking is now in progress. The Stilfontein Gold Mining Co. has been formed and, up to date, f5,000,000 capital has been raised for plant, shaft sinking, and development. The payable Vaal Reef horizon extends further south from Stilfontein, the reef occurring at increasing depths. It is possible that at least another mine may be established on these deeper horizons. The farm Stilfontein 39 is situated in the Klerksdorp District of the Transvaal. This farm and the surrounding areas have been subjected to repeated programs of prospecting dating back to about 1904, when Goerz and Co., the forerunner of Union Corporation, Ltd., first drilled on the farm and in the surrounding areas. From 1934-37, numerous boreholes were drilled on the neighboring farms, Riet-fontein. Hessie. and Palmietfontein, by African and European Investment Co. and Anglo American Corp. All these efforts were completely unsuccessful, and nobody suspected any possible gold-bearing area on Stilfontein until about 1947, when a gravity traverse run by B. D. Maree on the main road, showed a negative gravity anomaly. During 1947-48, the writer&apos;s organization completed gravimeter and magnetic surveys on Stilfontein and Rieffontein. An area of negative gravity anomalies was mapped, and it was suggested that this could be caused by blocks of Upper Witwatersrand quartzites, of the average density of 2.65, faulted up between dolomites and Ventersdorp lavas, the density of both of these rocks being 2.8. Fig. 1 shows the geology of the area as mapped by L. T. Nel of the Geological Survey of South Africa. The boreholes on Stilfontein, with the exception of a single hole of Goerz and Co., were drilled after the completion of the geophysical survey. The grouping of the first boreholes S.T. 1, 2, 3, 4, 5, and 6, clearly shows that these were located in the zone of negative gravity anomalies. Fig. 2 shows the gravity anomaly contours. Fig. 3 shows two sections across the gravity anomaly, together with the corresponding geological sections as obtained from boreholes. The close relation between gravity values and thickness of dolomite plus Ventersdorp lavas is striking. The two latter formations having the same density (2.8), act as one mass as far as gravity effects are concerned. Fig. 4 shows the magnetic anomalies observed on the ground by vertical magnetometers and at 500 ft abbve mean ground level by aerial magnetometer. The latter are anomalies of the total magnetic intensity. The magnetic results show that, on the farm Rietfontein and on the northern half of Stilfontein. Lower Witwatersrand magnetic shales were to be expected at relatively shallow depths. As the strongly

Jan 1, 1952