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By R. C. Hickman

Manganiferous breccia formations on three properties were prospected by the Bureau of Mines from January to November 1954 in Johnson County, Tenn. The prospecting consisted of diamond drilling, trenching, shaft sinking, and crosscutting. The results of the exploratory work show the manganiferous material to be low-grade, with little vertical extension. The manuscript on this report was completed February 1955. LOCATION The prospects are in Johnson County, Tenn. (fig. 1), within a radius of 12 miles from Mountain City. The nearest railroad terminal is Damascus, Va., 14 miles from Mountain City.

Jan 1, 1956

By M. M. Fine

A preliminary mineral-dressing study of five samples of East Texas limonitic brown iron ores was conducted as part of the Bureau of Mines program to develop and extend domestic resources of iron ore. The samples were considered to be typical of ore currently being mined and beneficiated by the Lone Star Steel Co. and Sheffield Steel Co. The objective of the research was to investigate those mineral-dressing unit operations that might recover some of the fine iron lost in current industrial wastes or perhaps improve the recoveries when applied to the ores as well. Since current industrial beneficiation practice yields a washed limonite analyzing 41 to 45 percent iron, higher grade concentrates were not sought in this laboratory study. Laboratory investigation included washing and sizing, reduction roasting, and subsequent magnetic separation of the finely ground roasted materials. The results showed that laboratory recoveries of over 80 percent of the iron were possible, for the ores investigated, at concentrate grades comparable to those expected from cur-rent industrial beneficiation practice. ACKNOWLEDGMENTS Acknowledgment is made to the Lone Star Steel Co. and Sheffield Steel Co. for supplying the brown iron-ore samples on which this research was conducted.

Jan 1, 1956

By W. J. West, T. D. Mueller, J. E. Warren

Two methods are used to obtain the relatiorlship between ratio of gas to oil permeability and gas saturation. One method is to calculate a curve from field measurements of reservoir behavior: the other is to measure the relationship on a core .sample in the laboratory. The curves resulting from these TWO methods arc often comparer1 and seldom found to agree. The most important reason for the nonagreement is often overlooked. This reason is that the performance k9/k0 curve is calculated with the assumption of uniform pressure and saturution throughout the reservoir. To show the differerence between performance type kg/k0 curves and laboratory type kg/k0 curves. two performance type kg/k0 curves for two different production rates were calculaled from the production perforrnance of a hypothetical reservoir for which a laboratory type curve was assumed. Production performance of the hypothetical reservoir bras calcu- lated by use of international Business Machine's 701 Computer. The perfortnance type kg/k0 curves differed from the laboratory curve for the hypothetical reservoir. The performance type crrrve for the lowest production rate most nearly coincided with the laboratory curve. INTRODUCTION Predictions of oil reservoir performance are often made with the aid of complex numerical calculations. An important quantity required in these calculations is the ratio of gas permeability to oil permeability (kg/k0 )at a particular gas saturation. Two methods arc used to obtain a relationship between this ratio and gas saturation. The curves resulting from these two methods are called performance kg/k0 curves and laboratory kg/k0 curves. The performance curve is obtained from field measurements of reservoir behavior. Particular kg/k0 values are calculated from the producing gas-oil ratio, the cumulative reservoir withdrawals, the original oil in place, the average reservoir pressure, and the PVT properties of the reservoir fluids. The particular kg/k0 values are then plotted against the average rcservoir gas saturations for the entire history period. In order to use this derived kg/k0 relationship for performance predictions, a curve through these points is extrapolated to higher gas saturations. The laboratory kg/k0 curve is obtained from measurements made on core samples. Saturation is maintained uniform throughout the core during these measurements. The kg/k0 curves obtained with these two independent methods are often compared and seldom are found to be the same. Various reasons have been offered for the lack of correlation. One is that insufficient core? were obtained to derive a curve representative of the reservoir rock. Another is that laboratory methods have failed to reproduce reservoir conditions. The most important reason for the noncorrelation has been often overlooked because of the difficulty in evaluating its effect. This reason is that the performance or field kg/k0 curve is calculated with the assumption of uniform pressure and saturation throughout the reservoir. In any

Jan 1, 1956

By R. L. Grant

At the Eighth International Conference of the Directors of Safety in Mines Research, Sartorius and Thouzea5/ presented and discussed data obtained in explosives tests made under varying conditions of humidity. These tests showed that there was less probability of explosives failure when the humidity of the testing gallery atmosphere was high. As it is to be expected that the relative humidity of mine atmospheres where permissible explosives are used will not be identical with that of the test-gallery atmospheres, the influence of atmospheric moisture upon the incendivity of permissible explosives is of the utmost importance if decreasing humidity reduces the relative safety of an explosive. Because of this and because the question has recurred frequently in discussions of gallery testing at Bruceton, Pa., it was decided to investigate the effect of humidity and ambient temperature on the ignition of firedamp by explosives, applying the small-scale gallery methods developed at the Bureau of Mines and used earlier to study the fundamental causes of such ignitions.6 7 8/

Jan 1, 1956

By F. E. Block

The reaction between calcined dolomite and ferrosilicon has been studies with the aim of developing a continuous process for magnesium production. Small-scale tests were made in vacuum retorts similar to those used in the vacuum retort process as developed by Pidgeon (1)2/ and operated during the period of World War II in several Government-owned plants. Factors investigated with respect to the silicon efficiency were the reaction temperature, reaction time, amount of excess dolomite in the charge, and effect of adding sodium silicate to the charge to serve as a binder. Additional laboratory tests were made to study the reaction at elevated temperature but at atmospheric pressure. Silicon efficiencies exceeding 80 percent were found to result when operating in the temperature range from 1,750° to 1,800° C. for periods of 20 to 30 minutes.

Jan 1, 1956

By H. D. Kline

Manganese ores have been mined in the Batesville district since 1849. Although not continuous over the intervening years, production had totaled approximately 432,000 tons of manganese ore and ferruginous manganese ore to the end of 1953. The ores occur in deposits, essentially low in manganese content, distributed over an east-west belt 24 miles long and 4 to 8 miles wide, the core of which is about 6 miles north of Batesville, Independence County. Although the reserves of high-grade ores in the district are comparatively small, the large deposits of subgrade ores and low-grade manganiferous material comprise potential sources of supply of manganese that may have increasing future importance. The manganese occurs as primary oxide and carbonate minerals in relatively flat-lying limestone and shale formations in which they were originally deposited and as oxides in residual clays resulting from decomposition of the shale and lime-stone. Most of the deposits underlie from a few to over a hundred feet of sedimentary chert, but many occur in the residual clays on exposed slopes of chert-covered hills.

Jan 1, 1956

By E. W. Hart, W. R. Hibbard

The room temperature flow characteristics of a series of Cu-Cr alloys are found to be related to the amount and characteristics of the chromium-rich precipitate. The results are consistent with the theory of Fisher, Hart, and Pry, which considers the trapping to dislocation loops around precipitate particles. THE use of dispersed phases for hardening metals, particularly high temperature alloys, has been practiced for several years. Current theories describing the effects of dispersions on the basis of dislocation theory have been proposed by Mott and Nabarro.l-4 rowan," and Fisher, Hart, and Pry.8 These theories recently have been discussed by Hart,' who pointed out that the experimental data available for comparison with theoretical calculations for overaged alloys are confined to studies by Gensamer, Pearsall, Pellini, and Low,8 Shaw, Sher-by, Starr, and Dorn,9 and some hitherto unpublished data on Cu-Cr alloys which will be described herein. Certain difficulties were associated with the interpretation of the first two studies. Gensamer, Pearsall, Pellini, and Low were concerned principally with interparticle spacing and did not document particle sizes. Shaw, Sherby, Starr, and Dorn included all the data in their report which was necessary for the theoretical evaluation, but their study is subject to some question1" due to difference in prior history of various specimens and due to systematic differences in particle characteristics" which appeared to be associated with differences in the magnification of their microscopic examination. The current study was undertaken to obtain critical data in a manner which avoids some of these limitations. Specimens of eight Cu-Cr alloys remaining from a previous investigation'' were available in the form of 100 mil sheet of the compositions shown in Table I. At 200 mil this material had been previously an- nealed ½ hr at 1000°C, water quenched, and cold rolled 50 pct. Samples were further cold rolled to a thickness of 20 mil for a total reduction of 90 pct. Sheet tensile specimens of standard geometry with a gage length 2½ in. long and 0.20 in. wide were machined from this sheet. These specimens were then annealed in a dried N2-H2 atmosphere for the times and temperatures indicated in Table I. This anneal served two purposes: 1—to obtain a fairly uniform and nearly constant grain size of 0.015 to 0.022 mm average diameter, and 2—to precipitate a fairly uniform, nearly spherical over-aged dispersion of essentially pure chromium. A typical microstructure illustrating the grain size and the uniformity of the dispersion is shown in Fig. 1. A typical dispersion illustrating the range of sizes and shapes of the particles is shown in Fig. 2. The tensile specimens were tested in the Instron equipment described in ref. 11 at room temperature at a strain rate of 0.04 in. per in. per min. Three tests were run on each alloy with sufficient repro-ducibility that a single true stress-true plastic strain curve could be drawn through the three sets of data for each alloy. Typical curves are shown in Fig. 3.

Jan 1, 1956

Jan 1, 1956

By L. M. Clarebrough, A. K. Head, G. W. West, M. E. Hargreaves

RECENTLY Welber and Webelerl reported that during the annealing of fatigued copper no energy was released, but that energy was absorbed in the range of temperature 250" to 400°C. In view of the fact that strain hardening occurs during the fatigue of copper, this result was surprising and it seemed desirable to check the measurements. This note describes measurements made by a different technique which indicates that energy is stored during the fatigue of copper. Two test bars with gage length ¾ in. in diameter and 6 in. long were machined from OFHC copper and annealed in vacuum for 1 hr at 600°C. These were fatigued to fracture in an Avery pulsator at a frequency of 2000 cycles per min. The first specimen fractured after 0.25x10 cycles under a push-pull

Jan 1, 1956

By J. M. Provost

1. Estimates have been made for eight coal beds in Marion County, but only the Pittsburgh is important from a production standpoint at this time. The Pittsburgh bed has the largest recoverable reserve, and the Sewickley is second in importance. 2. Known measured and indicated reserves thickness of 14 inches and on 1,800 short tons estimated at 3,141 million tons, as of January lion tons is in beds 28 inches and more thick in all beds, based on a minimum per acre-foot of coal in place, are 1, 1955. Of this total, 2,983 mil-Areas in each bed were omitted from the estimate because available data relative to the bed characteristics were too meager for making an estimate that conforms with the definitions of measured and indicated coal adopted for this study. Should future drilling or development prove reserves in these areas, such reserves should be added to the total estimated reserves.

Jan 1, 1956

By Floyd G. Anderson

Owing to the rapid growth of the perlite industry in recent years, the Bureau of Mines has received numerous requests for information relative to the possible harmful effects of breathing dust resulting from the processing and use of perlite. As published information on the composition of perlite is rather meager, consisting chiefly of conventional chemical analyses, samples of crude and expanded perlite from 9 deposits in 6 Western States were studied. Crude perlite ores were examined petrographically and analyzed by chemical, spectrographic, and X-ray-diffraction methods. Sized crude and expanded perlites were analyzed chemically for total free and combined silica content.

Jan 1, 1956

By H. W. Mead, C. E. Birchenall

SELF-DIFFUSION of cobalt has been investigated by Ruder and Birchenall,1, 2 Nix and Jaumot,3 and Gruzin.4 The results for a given tem- perature differ by a factor of about six in the extreme cases with no really close agreement between any two sets of data. The first two groups of investigators employed the decrease of surface activity method. Since Ruder and Birchenall have shown that the values obtained from this method are sensitive to the surface preparation, it seemed desirable to perform a few check experiments by a method not open to this objection.

Jan 1, 1956

By G. P. Conard, R. C. Hall, J. F. Libsch

The 50 pct Fe-50 pct Co alloy undergoes a transformation from disorder to an ordered structure of the CsCl type reportedly in the vicinity of 732OC. During this process, the coercive force goes through a maximum, apparently as a result of strains associated with the coherent nucleation and growth reaction. This magnetic alloy also shows a marked increase in the ratio of residual to saturation induction, which is associated with annealing to a high degree of order with the continuous application of a magnetic field. The increase in ratio can be explained on the basis of a decrease in 90' domain boundaries and, perhaps, by an increase in anisotropy resulting from lattice distortion. THE 50 pct Fe-50 pct Co alloy undergoes a disorder-order transformation which has been reported to occur in the vicinity of 732°C1,2 The ordered structure is the CsCl type.' This magnetic alloy also shows a marked increase in the ratio of residual to saturation induction as a result of heat treatment in a magnetic field, sometimes called a response to magnetic anneal.'-' The purpose of this investigation was to study the course of the ordering reaction, the nature of the response to .heat treatment in a magnetic field, and the relation, if any, between ordering and the response. Procedure The method of approach in this investigation was to produce an initial structure as completely disordered as possible and then gradually to order the alloy by isothermal anneals at various temperatures under different conditions of the applied magnetic field. Magnetic, magnetostriction, and X-ray analyses were of primary importance in determining the property and structural changes resulting from the isothermal anneals. Rings of the 50 pct Fe-50 pct Co alloy were prepared from the elemental powders by a powder metallurgy technique, further details of which may be found in ref. 7. The initial structure was produced by annealing the specimens for ½ hr at 1000°C, cooling to and holding for ½ hr at 900°C (in the a range above the ordering temperature), and water quenching. Isothermal anneals were performed at 600°, 675°, 720°, and 740°C. For example, rings were heated to 600°C, held for a predetermined period of time, and cooled by natural cooling at a rate slightly slower than an air cool (average of 20" to 25°C per min). The tests (magnetic, etc.) were made after each heat treatment. All high temperature treatments were performed in a purified hydrogen atmosphere. The treatments at the various temperatures were carried out under one or more conditions of an applied field including 1—no field, 2—field of 20 oersteds applied on cooling only, and 3—field of 20 oersteds applied continuously during heating, holding, and cooling. Magnetic measurements were made using the standard Rowland ring technique8 with a maximum field strength of 100 oersteds. The magnetization curve, induction at 100 oersteds (B.), residual induction (Bt), and coercive force (Hc) were determined. All magnetic analysis data were based on an average of the results from three rings. A strain gage technique9 as used for the measurement of magnetostriction. The X-ray determination of the relative amount of ordered phase present was made on the ring specimen used for magnetic measurement. This was done by the back-reflection method using a rotating specimen (because of the large grain size) with unfiltered CoKa radiation and a 7 hr exposure time. Intensity measurements of the ordered line (300) were made by comparing visually the films so obtained with standard films prepared by exposing for different lengths of time a specimen given a long time anneal (high degree of order). Results In all instances the saturation induction (induction at 100 oersteds) was found to increase slightly with annealing time. This effect was small and appears to be the increase in saturation induction to be expected on ordering.10-13 The residual induction behavior was markedly influenced by the field condition during annealing, Figs. 1, 2. For the condition of no applied field, the ratio of residual to saturation induction remained essentially constant for short annealing times but showed a significant increase at longer times. With increasing annealing temperature, less time was required to produce this increase in the ratio. In the case of the 600°C anneals, the increase did not occur until approximately 20 hr, Fig. I, while on annealing at 740°C the increase was immediate, Fig. 2. Slight decreases in the ratio may be observed at 100 hr for specimens treated at 720°C and at 1 hr for those treated at 740°C. Specimens annealed in a field of 20 oersteds showed a residual to saturation induction ratio consistently higher than that for the specimens annealed without the field. The first anneal with the field (¼ hr) caused an abrupt increase in the ratio at all temperatures; thereafter, the increase in the ratio was generally similar for specimens annealed

Jan 1, 1956

By Leendert de Witte, Fred J. Radd

In many areas caring failures can be directly related to electrical currents observed in the casings. It is the thesis of this paper that the observed casing currents are mainly due to electrochemical potentials of the type in evidence on spontaneous potential curves of electrical logs. The general nature of these potentials are discussed and an equivalent circuit is given for current and potential distributions around open holes. The casing forms a short circuit to these potentials and tends to average the effects of local cells. The case of casing corrosion opposite the Dakota water sands in the salt-mud area of Kansas is discussed anil used us a qualitative, illustration of the relation between SP's and casing currents. A method of quantitative derivation of casing current distribution frorn electric log SP curves, using linear transform theory, is described and results are compared with a measured current profile. The effects of hydrogen over-potentials at the cathodic portions of the pipe are considered and some laboratory data are given in support of conclusions regarding the over-1.01tuge.s. INTRODUCTION To date an appreciable amount of work has been done on the measurement of oil well casing currents and on the correlation of the anodic portions of the current profiles with corrosive casing failures. Speculations on the origin of the casing currents have, however, remained rather vague; and although almost every plausible cause has been mentioned, there is to the writers' knowledge no clear-cut expose' on the details of the causes of the corrosive currents in the literature. A study of current surveys and casing failures in the N.W. Burnett field, Ellis County. Kan.. indicated the probability that concentration cell emf's between the Wellington salt section and the relatively fresh waters in the Dakota sands were a major cause of the corrosion currents. A more general concept evolved upon analysis of the severe corrosive conditions in the Pleistocene sands in the Ventura Avenue and San Miguelito fields in California. In this area no major variations in the salt content of the formation waters occur and yet large casing currents are observed. An explanation is found in the fact that the local spontaneous potentials which are set up due to concentration contrast between the drilling fluid and the connate water are short circuited when casing is set. The very conductive path through the casing increases the magnitude of the currents and has the tendency to average local sources over fairly large intervals. Current will flow between the sections that are predominently shaly and the sections that are mostly sandy. At the places where the current leaves the pipe, corrosive attack will occur. This same phenomenon will be present wherever unprotected pipe is set through sections that show large SP kicks on the electric logs over reasonably thick interval~. GENERAL- NATURE OF THE SPONTANEOUS POTENTIALS When a sequence of sedimentary rocks is penetrated by a drill hole filled with a mud which has a different salt concentration from that in the formation waters, various types of electrochemical potentials are established between the formations and different parts of the mud column. Opposite clean sand sections. a simple liquid-liquid junction potential will be observed; while opposite argillaccous formations, a membrane potential, often referred to as shale potential, will be established. The first quantitative analysis of these emf's in terms of liquid junction and membrane potentials is due to Wyllie.1

Jan 1, 1956

By J. J. Gilman

Examination showed that characteristic cleavage step patterns are observed on the cleavage surfaces of undeformed, slipped, bent, twinned, compressed, and indented zinc crystals; and the effect of temperature is discussed. Dimples were seen to produce cleavage steps in a treelike pattern in otherwise undeformed crystals. The steps seem to originate when cracks intersect screw dislocations. IT has been known for a long time that the path of fracture in polycrystals may be discontinuous (see Jaffe, Reed, and Mannl for review). Recently, Kies, Sullivan, and Irwin2 have proposed, and given evidence, that crack propagation is discontinuous within individual crystals as well. Other evidence has been given by Low.' When discontinuous cracks within a crystal join together to make a macrocrack, the lamellae between each set of two cracks are torn somewhere, forming small cliffs. These cliffs appear as lines when the cleavage surface is observed microscopically.4,5 The lines have been called vein, tree, and riverlike markings by various authors, and they have sometimes been mistaken for fissures. The descriptive term cleavage steps is used in this paper. Cleavage steps vary in height over a wide range of values, from molecular dimensionsG to lor. and larger. Kies, Sullivan, and Irwin,2 as well as George,' have shown that the gross cleavage step patterns for plastics, polycrystalline metals, and for mono-crystals are sometimes similar. Thus, they depend mostly on the mechanical variables that prevail during cleavage and are relatively insensitive to the structure of the material. For example, parabolic markings2,7,8 sometimes result when cracks open up ahead of, and not coplanar with, the main crack front. If the advance crack has the same velocity as the main crack, their intersection line is a parabola, otherwise it is a hyperbola or an ellipse. The patterns are strongly affected by differences in crack velocities. This results in chevron patterns which point to the place of origin of the main crack. It is the purpose of this paper to demonstrate the existence of a mechanism of cleavage step formation which is a continuous rather than a discontinuous process. Also, certain characteristic step patterns are described, and the strong effect of temperature is shown. The specimens were zinc monocrystals (grown from 99.999+ pct pure metal). These were cleaved at room temperature and at — 196°C. Results and Discussion Cleavage step patterns are highly variable from point to point on a given specimen, as well as from one specimen to another. Although the patterns shown in the photographs are typical, they have been selected for graphic illustration. Figs. la and lb compare undeformed crystals that were cleaved at —196 °C and room temperature, respectively. Cleavage at room temperature (Fig. lb) resulted in a higher density of high steps (dark black lines) and enhanced the visibility of the fine background markings. Deformation by simple slip caused no marked change in the step patterns until the glide strain reached about 1.0. But, as Fig. lc shows, the density of high cleavage steps was greatly increased by large glide strains. Corrugations lying perpendicular to the slip direction may also be seen in Fig. lc. These are caused by deformation bands. The cleavage resistance of the crystal of Fig. lc was very high compared to undeformed crystals (estimated by the force on a needle required for cleavage). Striking and varied cleavage step patterns were observed on bent crystals. Two characteristic patterns that were observed on crystals bent at 25°C, and cleaved by reverse bending at —196°C, are shown in Figs. 2a and 2b. The first, Fig. 2a, consists of V-shaped lines similar to the parabolas of other materials2,7 Fig. 2b shows a pattern that is the equivalent of Fig. la, consisting of faint background lines with a few higher step markings. Cleavage of bent crystals at room temperature resulted in Figs. 2c and 2d. Now, the cleavage step lines show a strong tendency to follow one of two perpendicular paths. In Fig. 2c (bent once), many of the cleavage step components that lie parallel to the bend axis are assembled into irregular lines. In Fig. 2d (bent twice), the cleavage steps again tend to consist of two perpendicular components, but neither of the components is assembled into lines. Also, the step density is higher.

Jan 1, 1956

By T. C. Atchison

This report describes a mobile laboratory designed and constructed by the Bureau of Mines in 1950 to meet the needs of an experimental blasting research program. The laboratory has facilities for making; film recordings of 16 simultaneous transient electrical signals over a broad range of amplitude, frequency, and duration. The signals are recorded with specially designed oscilloscopes and high-speed drum cameras. Each of the 16 channels records on a separate strip of 35-millimeter film by using interchangeable input units, transducers having different sensitivities and output impedances can be accommodated. The laboratory can be used to record both steady-state and transient phenomena originating as electrical voltages or capable of being converted to electrical voltages by appropriate transducers. Thus, the laboratory can, be used in studying various types of vibration problems or high-speed phenomena, such as ground and building vibrations, machinery vibrations, airborne vibrations, electrical-circuit switching phenomena, millisecond timing, and seismic phenomena occurring when rock is broken by explosives.

Jan 1, 1956

By J. M. McDowell

A study has been made to deter~r~irre how the behavior of a water drivee reservoir changes as a function of the permeability of the formation and as a function of the size of the aquifer. The effect of pressure maintenance programs on the rote of nat11rn1 water influx is also studied, (IS well as the influence on the influx of the position of water injection we1ls with reference to the oil-water contact. The results are determined by the use of an electrical reservoir analyzer and are plotted as families of curves of pressure, natural water influx, and water injection vs time or cumulalive production. Two size aquifers are studided. One is limited with a 36-inile radius, and the, other approximates an infinite reservoir. The field remains the same in all respects for the completed. study except that the permeability is changed to agree with that assumed for the aquifer. 1 N TR ODUCTI ON this study was undertaken in -dcr to determine how the pres- sure decline and water influx of a water drive field would change as a function of the rate of fluid withdrawals, as a function of the permeability of the formation, and as a function of the size of the aquifer. The effect of pressure maintenance programs on the rate of natural water influx was also studied as was the position of water injection wells with reference to the oil-water contact. The information has been determined by the use of an electrical reservoir analyzer1, sometimes referred to as a Carter type analyzer. This instrument is an analog type computer which can be set up to represent a water-drive oil field. It can reproduce the past performance of the field in terms of analogous electrical quantities when the proper circuit analog of resistors and condensers has been determined, also, it can determine the future behavior for any method of production which may be selected, or permit the comparison among several different methods. Although most applications of the reservoir analyzer"" have been to thc study of specific field performance, it is intended to use the analyzer here to help understand how various reservoir characteristics effect the final performance of the field and to sec under what conditions water injection will be of benefit and to what extent. Within the oil industry the performance of water-drive reservoirs was first described analytically by LV. Hurst' and M. Muskat2 for certain types of boundary conditions. The solutions of the equations developed involved products of exponential functions and Bessel functions. Later publications by Hurst4 and van Ever-clingen" and the hooks of Muskat6 gave further information on reservoirs with other boundary conditions. They also presented rather extensive curves and tables to help evaluate the analytical expressions involved. A rccent series of publications by Chatas. bascd on the work of Hurst and van Everdingen, gives quite complete charts and tables of data to evaluate the pressure decline or water influx in infinite or limited radial reservoirs. and in linear reservoirs. The curves in all of these publications are given in dimensionless form

Jan 1, 1956

By Harris J. W

Mr. Gillie and Mr. Harris have given us a wealth of information and food for thought on the vital subject of information and food fo rthought on the vital subject of reducing costs and mention considerable saving in some of the larger items. There are a number of points on which I would like further information, but I will confine my remarks to a relatively small saving which is of particular interest in view of another paper to be presented this afternoon.Mention is made of a 50 per cent reduction in the amount of zinc used in the precipitation of gold slime from the pregnant solution. Would Mr. Harris enlarge on the methods by which they obtained this reduction; and could he give an actual figure of zinc consumption either by ton of ore treated or per ounce of bullion recovered.AuthorsWe consider the reduction of zinc is due to improved clarification of the pregnant solutions. The sand clarifiers used prior to the installation of the 50 ft. -thickener were not satisfactory due mainly to the blending of the hessian and matting under the sand. Under these conditions the leaf clarifiers were fed with overflow solution from the clarifiers and were overloaded in consequence. The addition of Calgon has also been beneficial.The present consumption of zinc per ton of solution treated is 088 lb. per ton.A. L. "Keats (No,rth Broken Hill Limited)In the operation of milling equipment there is a progressive increase in maintenance expenditure during the life of a machine, so that when comparing the cost of operating old equipment with the cost of operating new equip...

Jan 1, 1956

By R. S. Shoemaker, D. L. Harris

PST investigations into the possibility of concentrating the low-grade iron ores of the Gogebic Range in Wisconsin have been hampered by the complex association of the constituent minerals. In part the problem arises from the fact that the iron occurs essentially as two minerals, hematite and goethite, having nearly the same chemical composition but exhibiting different physical properties. Individual grains of these minerals are usually so small that the ore must be ground to a size finer than 325 mesh if substantial liberation of the minerals is to be secured. Appraisal of beneficiation tests on this iron ore requires, therefore, some method of determining quantitatively the contents of constituent minerals in the various products of the beneficiation. Because of the chemical similarity of the two iron minerals, chemical analyses do not provide a means of differentiation. Although the minerals are different physically, they are both opaque and friable, and as the ore must be ground to a very fine size for liberation to be secured, quantitative microscopic methods of analysis are extremely difficult at best. In an effort to overcome these analytical problems, a quantitative X-ray diffraction analysis method has been developed at the University of Wisconsin for the research program on iron ore beneficiation. The X-ray diffraction analysis of chemical compounds of crystalline form has proved of inestimable value for structure studies and rapid qualitative analytical purposes in a number of fields.' In some cases X-ray diffraction analysis has been found suitable for quantitative determinations. H. P. Klug2 found that quantitative procedures for quartz powders when mixed with calcium fluoride were reproducible within ±1.0 pct. Talvenheimo and White3 reported quantitative analyses of clay minerals to be accurate within 10 pct and also detected 1 pct of bentonite in 99 pct illite. In other investigations,'" powders of quartz and mica have been analyzed quantitatively with accuracies from 1 to 5 pct. A powder of tungsten carbide was analyzed similarly by Redmond7 and Rooksby8 reported the determination of small amounts (0.11 pct) of calcium oxide in magnesium oxide. In the most generally practiced use of X-ray diffraction, traces of the diffracted beam are recorded as lines on a film much as lines of elements are recorded on an optical spectrograph film. As with the spectrograph, the darkness of the lines denotes the amount of the constituent in the sample. If the film is replaced by a Geiger tube assembly and a graphic recorder or a scaling unit, the intensity of the diffracted beam can be registered as a peak on a chart or energy impulses per unit of time on the scaler. Several methods of quantitative measurement have been investigated and reported in literature. Klug2 used manual operation of the goniometer and a counting technique to determine the difference in counting rates at the diffracted angle and for the background. In another case3 the area under the recorded diffracted peak was the basis for the determination. In other instances the height of the recorded diffraction peak above background, measured while the goniometer was moving, has been the basis for the measurement. The sizes of particles most suitable for diffraction techniques are reported in the literature as follows: for tungsten carbide a maximum of 40 microns7 and for quartz a maximum of 5 microns.' Very fine sizes of crystals are known to cause a broadening of the diffused beams; hence some workers have set a lower limit of 0.1 micron for quantitative results. Guinier10 has indicated that broadening of the diffracted X-ray beam is not appreciable for crystallites larger than 0.02 to 0.03

Jan 1, 1956

Jan 1, 1956