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By Glenn Keep

THIS paper is not an announcement of the successful conclusion of the Cerro de Pasco Copper Corporation's pacos-pyrite problems, but merely a description of the commercial-scale, intermittent-roasting operations conducted by the writer, J. H. Lucas and others of the staff. It was prepared by request, for presentation at the February meeting of the Institute. The results obtained in Peru confirm the 1-ton-a-day experiments completed about three years ago at Kearny, N. J. by C. C. Gordon and Mr. Lucas, where it was first demonstrated that a mixture of about 80 per cent. pacos ore with 10 per cent. pyrite ore and 10 per cent. salt could be roasted intermittently in a small 1-ton-a-day Holt-Dern furnace without extraneous fuel, producing porous calcine that could be leached rapidly. Mr. Keep and his staff, by successfully introducing improvements in the construction of the commercial furnace and in their handling of material, have established beyond doubt a low cost for roasting. The other steps in the process of treating pacos and pyrite ores have not as yet been demonstrated as sufficiently conclusive to warrant their acceptance for a permanent plant.

Jan 1, 1929

By M. J. Hordon

Measurements of the 103 yield stress of ordered and disordered poly crystalline Cu ,Au were related to the ordered antiphase domain size determined by resistivity measurements. For undeformed material, a yield stress maximum wa obtained at a critical domain diameter of about 40A. Plastic deformation resulted in a marked increase in the yield stress and electrical resistivity of the ordered alloy compared to the disordered, the strain hardening rate increasing regularly with initial antiphase domain size. Order hardening was accompanied by a sharp reduction in size of the initially large domains. It has been observed that the yield stress of ordered and partially ordered Cu3Au alloy varies sensitively with antiphase domain size aid degree of order.ly2 In addition, ordering of the lattice leads to a marked increase in the strain hardening rate (order hardening) as compared to the rate for the disordered alloy. In the present investigation, changes in the electrical resistivity and yield stress of ordered polycrystalline Cudu with varying initial domain diameters were measured after tensile plastic deformation in order to examine the effect of cold work on the antiphase domain size. EXPERIMENTAL PROCEDURE Au-Cu alloy of 99.99 pct purity analyzing 50.85 wt pct Au-balance copper was obtained from the Handy-Harmon Co., N. Y., in the form of 0.061 in. diam drawn wire. Wire specimens 3 in. in length were given the following annealing treatment in nitrogen: 500" for 72 hr, 820" for 15 hr, and 450" for 5 hr, followed by a water quench. The annealing sequence resulted in a completely disordered structure with a grain size of about 0.2 mm. The disordered specimens were then reannealed at 360' in nitrogen for periods varying from 10 min to 150 hr followed by quenching to produce ordered structures with varying domain sizes. The degree of ordering and variation of domain size was followed by electrical resistivity measurements made at room temperature using a low resistance precision Kelvin double bridge apparatus. The specimen resistance was determined over a length of 4.0 cm between two brass knife-edge contacts while the specimen was immersed in an oil bath to minimize temperature variations. In addition, the current flow in the circuit was minimized by a current pulse technique in balancing the bridge in order to avoid heating the specimen. Using a sensitive galvanometer to detect the bridge null, the accuracy of the resistance measurement Wire specimens were plastically strained in tension with an Instron tensile unit at strain rates in the range 5 x 10"5 sec-' to 2 x 10"4 sec-'. Stress and extension data were fed into the Instron chart drive amplifier to obtain the actual stress-elongation curve from which the yield stress at 10"3 strain was determined. The maximum resolution of the apparatus was approximately 50 psi stress and 3 x 104 strain. At various plastic strain levels, deformation was interrupted and the electrical resistivity determined after removing the stress. RESULTS AND DISCUSSION 1) Yield Strength of Ordered Cudu. In order to determine the effect of the ordered antiphase domains on the initial yield stress, specimens were prepared with varying domain sizes ranging from zero for 5 completely disordered structure to about lo5A for a completely ordered structure by suitable annealing treatment. Domain sizes were estimated by comparing room temperature electrical resistivity data with the original data of Jones and sykes3 as modified by rdle.' In agreement with previous work, the resistivity varied sensitively with domain diameter and degree of order, decreasing from approximately 11.6 x l0- ohm-cm for the disordered structure to about 5.9 x l0- ohm-cm for ordered domains above 10"3 cm in diameter. Fig. 1 shows the change of the 103 yield stress with ordered domain size. It is evident that the maximum

Jan 1, 1963

By Oliver Bradley

THE utilization of casing-head gas in the manufacture of casing-head gasoline by both the absorption and the compression method is a most important factor in the conservation of our natural resources.. Any industry connected with the oil business, in general, possesses particular attraction for a large number of people not conversant with its basic principles, for the reason that the large fortunes made in the production and utilization of petroleum and its products have been given undue prominence. The general impression of the public that enormous profits are to be realized in the casing-head gas industry with minimum expenditures of both capital and effort has, in a large measure, accounted for the phenomenal expansion of the industry in recent years and, likewise, has resulted in many mistakes and loss of investment funds. It is true that many installations have been very profitable, but such instances are always the result of careful planning, experienced judgment and conservative estimates. The inception and subsequent activity in the manufacture of casing-head gasoline, enabling the business to assume an important position in the petroleum industry, are of, comparatively recent origin, as its greatest growth, particularly in Oklahoma, occurred during the years 1917 and 1918. Much information must yet be secured and systematized concerning the methods of manufacture of gascline from high-yield casing-head gas, and a large field is still open for the application of accumulated experience and good engineering practice in devising better methods of extracting gasoline from casing-head gas of the poorer grades. The absorption process is coming into general use as a most efficient system of treating casing-head gas, and even so-called dry gas. In fact, there is a decided tendency toward the universal adoption of the absorption process as against compression methods. However, a general discussion of the relative merits of these two systems is not within the scope of this article.

Jan 9, 1920

By A. W. Cochardt

THERE are a number of effects that can cause material damping or internal friction. Some of these are frequency dependent, such as the thermo-elastic effect' and the stress-induced ordering.' Others depend on the amplitude of vibration, i.e., the damping related to the motion of dislocations3 and that due to magneto-mechanical hysteresis.' While many of these effects have been studied, only the magneto-mechanical effect has found extensive practical application. It is the principal source of damping in the current blade material in steam turbines.A magneto-mechanical hysteresis loop is seen in Fig. 1. If an unmagnetized, polycrystalline wire of a material exhibiting magneto-mechanical hysteresis, such as an Fe-14 pct A1 alloy, is twisted in torsion, a relation between shear stress and shear strain y is observed as indicated. The stress-strain curve does not follow Hooke's law -dashed line. Instead, the strain y increases nonlinearly and partly irreversibly, due to the motion of ferromagnetic domain walls,* until a critical stress is reached, which in this case is about 3,500 psi. If the applied stress is raised further, the strain appears to increase linearly and reversibly in accordance with Hooke's law, since all domains are now aligned in easy directions of magnetization nearest to the direction of the applied stress, and plastic flow has not yet started noticeably. On removing the applied stress, a remanent shear strain y, is observed, which is related to the irreversible magnetostriction of the material.' The energy dissipated in the material during a stress-strain cycle is proportional to the critical stress t, and the remanent magnetostrictive shear strain 7,. The purpose of this investigation was to make a survey of the magneto-mechanical damping of ferro-

Jan 1, 1957

By W. A. Koehler, W. L. Eaton, Reynold Q. Shotts, M. E. Hinkle, M. R. Geer, Ralph M. Hunter, H. F. Yancey, Andrew B. Crichton, E. Zimmerman, S. H. Ash

R. Maize and H. P. Greenwald presiding) E. T. POWELL*-I would like to ask either Mr. Ash or Mr. Eaton if they know of any place where the Mine Inspectors' for¬mula has been used that water has flowed from one colliery to the other. W. L. EATON (authors' reply)-We have made considerable study but we have not gotten around to very many of the barrier pillars. I would not say that any or all of them have been designed to the strict figures of this formula. Most of those ex¬amined will not hold back the water that they are supposed to hold back. E. T. POWELL-If the pillar remains ac¬cording to the Mine Inspectors' formula? W. L. EATON-We have not found very many where the provisions were followed. E. T. POWELL-Where the Mine Inspec¬tors' formula has been fully complied with, have there been failures or not? W. L. EATON-I cannot say. Most of these barrier pillars probably were designed in accordance with this formula, but most of them, if they were so designed, are not in that shape now because a large number of them will not hold back the water; they have been reinforced, and they are punc¬tured in various places. Holes have been driven through them to relieve the hydro¬static pressure to avoid a failure. They do not dare to have a failure. In many instances, the barrier is punc¬tured to avoid a failure. In order to mine their coal safely, many companies must pump water from mines that were aban¬doned many years ago. R. MAIZE-That is true, Mr. Eaton, but do you know of any case where a barrier pillar actually failed and flooded an ad¬joining mine when the pillar had been left in accordance with the Mine Inspectors formula?

Jan 1, 1948

By Bunting S. Crocker

In the summer of 1961, the Anaconda Research staff and Kilborn Engineering Ltd. began a study to investigate the possibilities of using some form of autogenous grinding in the new concentrator which Anaconda was planning to erect at Butte, adjacent to their Berkeley pit. The following criteria applied to the project: 1) The Butte mill was to be able to handle 36,000 to 42,000 tpd of copper ore, taken from the Berkeley pit and adjacent underground mines. 2) The plant was to be built in six units. 3) It would be started up two units at a time. 4) Equipment from the Anaconda mill was available for use in the new location. 5) Tonnage would be maintained at Butte and Anaconda, with equipment being moved down as required. 6) The ore from the Berkeley pit was known to vary widely from place to place in the pit and to be generally soft and friable.

Jan 5, 1964

By J. L. Meijering

Oxidation hardening of cylindrical and spherical specimens first decreases with depth below the surface, but then increases again as the center is approached. This is in agreement with the view that this change in hardness is mainly determined by the change in velocity of the oxidation boundary, which affects the dispersion of the oxide. WHEN a thick slab of silver containing 0.3 pct Mg by weight is internally oxidized, the hardness measured on a cross section is found to decrease considerably with distance from the surface.&apos; This phenomenon has been attributed to the diminution of the velocity of the oxidation boundary. The smaller this velocity is, the more slowly the free-oxygen concentration rises towards the concentration in equilibrium with the oxygen gas. And a small 0 concentration favors dissociation and thus conglomeration of the oxide. For instance, the hardness decreases more rapidly during long annealings in nitrogen than in air.&apos; Measurements by Gregory and Smith3 on sections through internally oxidized Al-silver wire showed a smaller variation in hardness, probably because the wire diameter was only 0.9 mm. Wood4 found a drop in hardness with depth in internally oxidized Al-copper strip, and also—by electron microscopy—the concomitant increase in Al2O3 particle size. Under certain circumstances internal oxidation leads to formation of rather irregular inner oxide films in the midst of dispersed oxide. This special sort of conglomeration—discussed in Ref. 5—is also favored by greater depth below the surface.3,5 In this paper hardness measurements in large diameter cylindrical and spherical specimens are described. Here the oxidation velocity* goes through ness initially decreases with depth but increases again towards the center. Normally, the diffusion coefficient D1 of oxygen is very large compared to D2, that of the dissolved metal. If, furthermore, the atomic fraction c2 of the latter is much larger than the O-solubility cl- but c2D2 << c1D1- the velocities in question are easily calculated2 to be: for the cylinder and for the sphere. Here p is the radial coordinate of the oxidation boundary and R the specimen radius, which in dilute silver alloys is constant, as no external oxidation occurs. These equations have been derived for a divalent solute; for nondivalent solutes c2 has to be multiplied by half the valency. The equations are not valid near the center. For which can be considered as a standard case,2 the Eqs [I] and [2] begin to yield U-values which are appreciably too high for p/R = 0.05 and 0.15, respectively. But at the v-minima they are still very good approximations. These minima lie at p = emlR= 0.37R in the cylinder and p = 1/2 R in the sphere. Other factors besides the velocity v will also influence the hardness. The oxide concentration cox is constant in a flat strip, apart from a narrow region in the middle,2 but in cylindrical and spherical specimens cox decreases steadily with depth. When C1 << c2 and c1D1 >> c2D2 one can calculate

Jan 1, 1961

MINING METHODS F A WARDLAW, JR, Chairman WILLIAM J COULTER, Past Chairman PHILIP B BUCKY, Past Chairman FRANCIS CAMERON, Vice-Chairman R D LONGYEAR, Vice-Chairman J MURRAY RIDDELL, Vice-Chairman LELAND A WALKER, Vice-Chairman E D GARDNER, Secretary

Jan 1, 1952

By A. F. van Everdingen

The pressure drop in a well per unit rate of flow is conrolled by the resistance of the formation, the viscosity of the fluid. and the additional resistance concentrated around the well bore resulting from the drilling and completion technique employed and, perhaps, from the production practices used. The pressure drop caused by this additional resistance is defined in this paper as the skin effect. denoted by the symbol S. This skin effect considerably detracts from a well&apos;s capacity to produce. Methods are given to determine quantitatively (a) the value of S, (b) the final build-up pressure, and (c) the product of average permeability times the thickness of the producing formation. INTRODUCTION Equations which relate the pressure in a well producing from a homogeneous formation with pressures existing at various distances around the well are generally used within the industry. The relation ii quite simple when the fluid flowing is assumed to be incompressible. It becomes somewhat more complicated when the flowing fluid is considered compressible so that the duration of the flow can he considered. In each case the major portion of the pressure drop occurs close to the well bore. However analyses of pressure build-up curves indicate that the pressure drop in the vicinity of the well bore is greater than that computed from these equations using the known, physical characteristics of the formation and the fluids. In order to explain there excessive drops it is necessary to assume that permeability of the formation at and near the well bore is substantially reduced as a result of drilling. completion and, perhaps. production practice. This possibility has been recognized in the literature. A method to compute the pressure drop due to a reduction of the permeability of the formation near the well bore. which is designated as the skin effect. S, is given in the following paragraphs. To start, equations normally used to describe flow in the vicinity of a well are given without considering this effect. These equations then are modified to include the effect of a skin on the pressure behavior. Finally a method is given to estimate the effect of the skin on the pressure and production behavior of a well. PRESSURE EQUATIONS Incompressible Fluid Flow If p is defined as the flowing pressure in a well of radius the pressure at distance r from the well has been shown to be:" The total pressure drop between the drainage boundary, and the well bore is given by These equations are valid only if the flow towards the well occurs in a horizontal homogeneous medium and the fluids are incompressible. The assumptions imply that all fluid taken from the well enters the system at r a condition rarely encountered in practice. Compressible Fluid Flow, Steady State A more realistic equation is obtained if it is assumed that the compressibility, c, of the flowing fluids is small and has a constant value over the pressure range encountered. After the well has been producing for some time so that its rate has become constant and steady state is reached, the pressures throughout the drainage area are falling by the same amount per unit of time, and the pressure differences between a point in the drainage area and the well are constant. When these conditions are met. the rate of production, q, from a well is equal to where dp/dt is the pressure drop per unit time. The fluid flowing at a distance from the center of the well is equal to From the last equation and from Darcy&apos;s law it can be shown that The equation holds for a depletion-type reservoir of radius drained by a well located in its center, provided the compressibility of the fluid per unit pressure drop is small and constant, and no fluid moves across the boundary Compressible Fluid Flow — Nonsteady State Table 111 of reference (5) shows the relationship between the pressure at the well bore and the reduced time, The pressure-drop function, p represents the drop below the original reservoir pressure, p caused by unit rate of production for several values of R, the ratio of drainage boundary radius to well radius, r In most reservoirs the values of approach infinity. and under these conditions the values of p shown in Table I of reference (5) can be used where p then signifies the difference between the pressure in the well and the prevailing reservoir pressure per unit rate of flow. The total pressure drop below prevailing reservoir pressure amounts to where the factor converts the cumulative pressure drop per unit rate of production to cumulative pressure drop for actual rate. q. For values of T > 100 the P function may be written (equation VI-15 of reference 5) as Using the time conversion the difference in pressure between reservoir and well becomes If values for the physical constants of the formation and the fluids are inserted, it is found that T exceeds 100 after a few seconds of production (or closed-in time), so that the approximation becomes valid almost at once. A simple relation between the pressure in the well and in the reservoir can also be derived by considering the well as a point source"" &apos;" instead of a unit circle source, that is, by using Lord Kelvin&apos;s solution instead of the unit circle source

Jan 1, 1953

By Y. Wang, M. M. Singh, H. L. Hartman

Knowledge of the state of stress at the bottom of a drillhole is of practical importance in rock drilling, since the induced stresses must exceed the strength of the rock in order to cause fracture. This note reports on a numerical method to determine the stress distribution at the bottom of a borehole induced by a static bit load and overburden and fluid pressures. The procedure adopted is similar to that for the plane-strain, discrete model employed by Harper and Ang.1,2 The rock medium is considered to be homogeneous, isotropic, and elastic-perfectly-plastic. METHOD OF ANALYSIS AND PROGRAMMING The discrete model adopted consists of two types of points: mass points and stress points. The configuration and numbering notation are depicted in

Jan 1, 1967

By C. W. MacGregor

IN the testing of materials there exist various methods of recording graphically the behavior of a material subjected to tensile stress. Prob-ably the most common method is to plot the tensile stress So, obtained by dividing the load P by the original area of cross section AO at the start of the test, as a function of the strain ?o, which is obtained by dividing the ?Lo or the change in the gauge length by the original gauge length Lo. A list of the symbols used here is given in Table 1. This method, while it has proved useful in the routine testing and comparison of various materials, does not have a very sound physical basis, as was first pointed out by P. Ludwik1, and consequently does not afford a very deep insight into the true physical behavior of the material under stress. Among the objections to this method may be mentioned: (1) that by dividing the load P at any stage of the test by the original area Ao a fictitious stress is obtained, which does not actually exist; (2) that the strain ?o = ?Lo /Lo is not an exact expression for the true strain for large values of ?Lo in per cent of Lo; (3) that when necking starts the strain varies considerably along the gauge length and the above expression no longer gives the true strain existing at any point on the outside of the bar; and (4) that the axial strain varies over the cross section of the necked portion and ?o does not represent an average of these strains over the cross section. Stresses taken from such a diagram would be only approximate and, if used to compare results of a test on a given material under simple tension with results obtained under combined stresses, certain errors would he thus introduced. In order to overcome some of these objections, various methods have been suggested, both as to the quantities to be measured and as to their graphical representation. In some cases the so-called "true stress," obtained by dividing the load P by the actual area of cross section A existing when the load P was applied, is plotted as a function of the strain

Jan 1, 1937

By H. Hance James

SOME of the outstanding features of petroleum production in Illinois during 1923 were: (1) Sustained production from the older wells, due to cleaning and deepening; (2) good results from new drilling in a few localities; (3) large percentage of dry holes, many of which were ill advised tests, with a resulting high cost of the new production; (4) decrease in the number of productive wells in the state; (5) low average price of crude petroleum, a serious factor over the entire country. FIG. 1.-ANNUAL TOTALS OF ILLINOIS PRODUCTION. The total production of Illinois for 1923 was 8,710,000 bbl.,1 a decrease of 7.2 per cent. from that of 1922. Of this amount, it is estimated that about 8,500,000 bbl. were produced by old wells, many of which had been cleaned and deepened somewhat, and approximately 210,000 bbl. were obtained from the new wells drilled during the year. About 95 per cent. of the oil comes from the southeastern field in Clark, Crawford, and Lawrence Counties, where production is almost entirely from Pennsylvanian and Mississippian rocks. Extensions of the productive area were made in Clark, Wabash, Marion, and Jackson Counties. Some important gas development has been accomplished near Jacksonville, in Morgan County, and at Gillespie, in Macoupin County.

Jan 3, 1924

By E. S. Machlin, C. W. Chen

THIS investigation is concerned with the origin of the intercrystalline voids and cracks formed in metals and alloys subjected to stress at elevated temperature. There have been many suggestions in the recent literature relating to this problem. Greenwood&apos; suggested that the voids may be produced by vacancy condensation. Zener has stated that shear-stress relaxation across grain boundaries could initiate high tensile stresses at the regions blocking grain boundary slip and thereby cause the formation of cracks. Chang and Grant3 have described the formation of cracks at grain boundary triple points and have experimentally verified Zener&apos;s mechanism for the grain boundary regions in the vicinity of a triple point. Subsequent to the completion of this investigation, Gifkins4 developed a model which made use of Stroh&apos;s5 mechanism of fracturing to produce sub-microscopic fractures that subsequently grow by grain boundary slip. Chen and Machlin,6 in answer to Gifkins, described a model deduced from the present investigation, in which grain boundary slip provides both the stress to fracture at grain boundary jogs and the deformation required to separate fractured jog surfaces. The possibility of gas condensation to form intercrystalline voids and cracks is eliminated as a basic mechanism because such voids and cracks are developed in vacuum melted material containing minute amounts, if any, of gaseous impurities. In a theoretical evaluation of this problem, Machlin7 concluded that void nucleation by vacancy condensation during creep-rupture is improbable but that vacancy condensation on supercritical sized voids to produce growth is probable. This investigation was begun to evaluate the suggested mechanisms for intercrystalline fracture. In particular, in order to correlate vacancy supersaturation ratios produced in creep with those determined by Bal-luffi and Seigle8 as critical for , the nucleation of voids, specimens were obtained from the same heat of brass as used by the latter authors, through the courtesy of Dr. Seigle. The experiments conducted in this investigation fall into the following categories: 1) Brass—observation of voids produced under a variety of conditions, including creep under compression, to evaluate the mechanisms of void nucleation and growth. 2) Bicrystal experiments to check the mechanism of void nucleation deduced in this investigation. 3) Morphology of intercrystalline voids produced in a variety of metals. Each set of experiments will be described and discussed separately. Experimental Techniques A special creep-rupture test rack was constructed which made it possible to apply the stress to the specimen in a controlled atmosphere of inert gas, reducing gas, or vacuum. All the creep-rupture tests on a-brass (30 pct Zn) were conducted in nitrogen under a pressure slightly above atmospheric. Either dead weight loading or constant elongation rate loading could be applied with the load measured by means of a strain gage dynamometer. In order to obtain a coarse-grained crystal structure stable at

Jan 1, 1958

Jan 1, 1954

By C. W. MacGregor

In the testing of materials there exist various methods of recording graphically the behavior of a material subjected to tensile stress. Probably the most common method is to plot the tensile stress So, obtained by dividing the load P by the original area of cross section A0 at the start of the test, as a function of the strain e0, which is obtained by dividing the ?Lo or the change in the gauge length by the original gauge length Lo. A list of the symbols used here is given in Table 1. This method, while it has proved useful in the routine testing and comparison of various materials, does not have a very sound physical basis, as was first pointed out by P. Ludwikl, and consequently does not afford a very deep insight into the true physical behavior of the material under stress. Among the objections to this method may be mentioned: (1) that by dividing the load P at any stage of the test by the original area A. a fictitious stress is obtained, which does not actually exist; (2) that the strain e0 = ?L0 is not an exact expression for the true strain for large values of ?LO in per cent of Lo; (3) that when necking starts the strain varies considerably along the gauge length and the above expression no longer gives the true strain existing at any point on the outside of the bar; and (4) that the axial strain varies over the cross section of the necked portion and e0 does not represent an average of these strains over the cross section. Stresses taken from such a diagram would be only approximate and, if used to compare results of a test on a given material under simple tension with results obtained under combined stresses, certain errors would be thus introduced. In order to overcome some of these objections, various methods have been suggested, both as to the quantities to be measured and as to their graphical representation. In some cases the so-called "true stress," obtained by dividing the load P by the actual area of cross section A existing when the load P was applied, is plotted as a function of the strain

Jan 1, 1937

By E. Mille, R. Geffken

The Mg-Si and Mg-Ge phase diagrams were rede-levtnined by thermal analysis, and the existence of a single congruent melting compound in each system was confirmed. The melting points of the two compounds Mg2Ge and ,Wg2Si were found to be 1117.4° and 1085.0°C respectively. The euteclics for the Mg-Ge system occur at 635.6°C (1.15 at. pcl Ge) and 696. 7°C (64.3 at. pct Ge); for the Mg-Si system the eutectics are at 6376°C (1.16 at. pct Si) and 945.6°C (53.0 al. pcl Si). The phase diagrams and known thermodynamic data were used to calculate activity values for both systems. The activities calculated for the Mg-Ge system agreed very well with those previously published. Partial molar enthalpy values for the Mg-Si systetn were calculated from the phase diagram for the composition region where no experimental values have been reported. THE phase diagram for any system is an important source of thermodynamic data. Steiner, Miller, and Komarek1 have derived equations which permit calculation of the activity in binary systems with an inter-metallic compound! if the liquidus and enthalpy data are known. The thermodynamic properties of the Mg-Ge and Mg-Si systems have recently been determined in this by by an isopiestic method, and it was considered that it would be interesting to compare these directly determined values with those computed from the phase diagram. The basic features of the Mg-Ge and Mg-Si systems are essentially similar. The one intermediate compound present in each system. Mg2X, crystallizes in the antifluorite structure and melts congruently. Raynor4 has accurately determined the temperature and composition of the magnesium-rich eutectic in both the Mg-Ge and Mg-Si systems. Klemm and West-linning5 investigated the entire Mg-Ge liquidus, employing sintered alumina crucibles; the purity of the magnesium and germanium starting materials was not reported. The melt was not stirred, and the temperature was automatically recorded to an accuracy of ±3°C. The authors reported large weight changes due to magnesium evaporation between 50 and 67 at. pct Mg. The Mg-Si system has been studied by a number of investigators, and the results have been compiled by Hansen and Anderko.6 Significant discrepancies exist between the two principle investigations of voge17 and Wohler and Schliephake.8 Two different grades of silicon were used by Vogel, one of 99.2 pct purity and the other quite impure, containing 6 pct Fe and 1.7 pct Al. The magnesium purity was not specified. The melts were contained in graphite crucibles with porcelain thermocouple protection tubes under an atmosphere of hydrogen. Samples weighing 10 g were rapidly heated to 50° to 100°C above the liquidus: held, and then rapidly cooled without stirring. Accuracy was ±1 at. pct which is equivalent to a maximum error in temperature of ±18°C. Wohler and Schliephake used 97.9 pct Mg and 99.48 pct Si. The graphite crucibles contained a stirrer and the 15-g samples were melted under an atmosphere of streaming hydrogen. The samples were chemically analyzed after each run. Because of the scarcity of the data, the impurity of the starting materials, and the resultant uncertainty and inconsistency in the published liquidus values, it was decided to undertake a reevaluation of the Mg-Ge and Mg-Si phase diagrams by thermal analysis. EXPERIMENTAL PROCEDURE Alloys were prepared from 99.99+ pct Mg (Dominion Magnesium Ltd.) with impurities in ppm: 20 Al, 30 Zn, 10 Si, <1 Ni, <1 Cu. <10 Fe; 99.999 pct Ge (United Mineral and Chemical Corp.), and 99.999 pct Si (Wacker Chemie Corp.). All graphite parts were machined from high-density (1.89 g per cu cm) G-grade graphite obtained from Basic Carbon Corp. with a total ash content of 0.04 pct. Boron nitride parts were machined from rods of National-grade H.B.N. boron nitride. All graphite and boron nitride pieces were baked out under running vacuum at 1100°C for 24 hr before us Cylindrical graphite crucibles (1; in. OD, 23/4 in. long, l3/8 in. ID) were tightly closed with threaded graphite covers which had 21/4-in.-long thermocouple wells and 1/4-in.-diam off-center holes for stirrers. The cover and thermocouple well were machined from a single piece of graphite. A stirrer was made from a flat cylindrical graphite plate perforated with five 3/16-in.-diam holes and a 1/2-in.-diam central hole, and was held parallel to the crucible bottom by a 1/4-in.-diam. 4-in.-long graphite rod which screwed into the plate and extended up through a tightly fitting hole in the crucible cover. An iron core enclosed in a glass capsule was attached to the stirrer with an 18-in.-long molybdenum wire, so that the stirrer could be magnetically raised and lowered from outside the system. One crucible and stirrer with essentially the same dimensions given above was made entirely of boron nitride. Chunks of magnesium were premelted, cast into 11/2-in.-diam. rods, and then cut into lengths varying from a to 1 in. A 5/16-in. hole was drilled through the center of each piece to accommodate the thermocouple well and the individual pieces were then cleaned and rinsed with acetone. The total weight of an alloy was 50 to 70 g in the Mg-Ge system and 40 to 60 g in the Mg-Si system. The pure components were weighed to an accuracy

Jan 1, 1969

By S. C. Schaeker, A. W. Schlechten, A. H. Larson

PARRAVANO and Malquori&apos; studied the equilibrium of H2S-Hz with molybdenum and its lowest sulfide which they believed to be MoS2. Mc Cabe&apos; has shown that its composition is actually Mo2S3 and determined its dissociation pressure by means of Knud-sen effusion measurements. Stubbles and Richard- son3 have recently studied the equilibrium of gas mixtures of H2S-HZ with the two-phase solid mixtures of Mo-MozS3 and Mo2S3-MoS2. The latter investigators found that M02s3 deviated slightly from the stoichiometric composition, but they did not determine the homogeneous region of the disulfide phase. Morimoto and Kullerud, studied the Mo-S system by quenching, microscope, and X-ray methods and concluded that the disulfide is stoichiometric. The present investigation was concerned with the measurement of the sulfur vapor pressure variation with composition at 1100°C in the homogeneous region of "MoS2". These measurements were made by reacting: 1) molybdenum powder (99.97 pct Moj with sulfur vapor, and 2) MoS1.g9 (formed by reaction of Mo + H2S) with sulfur vapor in a quartz capsule. Conditions were controlled to form an equilibrated phase within the homogeneous region of the disulfide. The quartz capsule was sealed off initially under a vacuum and the residual gases were gettered by titanium powder contained in one end of the capsule. A mixture of Mo + S or MOS,., + S was in the other end. The section containing the titanium powder was heated for 24 hr at 700°C and then removed by flame sealing. The end of the capsule containing the charge was then heated to 1100°C. The other end of the capsule was maintained at a temperature which would produce the desired sulfur pressure in the capsule (liquid sulfur distilled from the charge mixture was retained in this end). After equilibration, the capsule was removed from the heating assembly and rapidly air-cooled. It is assumed that equality existed between the total sulfur pressures (PT) in the two ends of the capsule and not between the partial pressures of the different molecular species (S, SZ, Three separately controlled heating elements were used to maintain the proper temperature gradient over the length (approximately 12 in.) of the capsule. A thermocouple-Wheelco "Capacitrol" system was used for temperature control of the two end heating elements within 2"C. The center heating element was controlled directly by a " Power -stat". Separate controlling and measuring thermocouples were used for both end heating elements. Pt-Pt(l0 pct Rh) thermocouples were used for 1100°C and Chromel-Alumel thermocouples were used for lower-temperature control and measurement of the assembly. Silver foil was wrapped around the end of the capsule containing the liquid sulfur to insure a constant temperature zone. The thermal gradient over the entire length of the capsule was measured to: 1) ascertain that the length of the constant temperature zone of the liquid-sulfur end and the sulfide end was sufficient, and 2) ascertain that the liquid-sulfur zone was the zone of lowest temperature. The data obtained in this investigation are shown in Fig. 1 and Table I. The total sulfur pressure (PT) and p(S2) were calculated from the data of Braune et UZ.~ The compositions of the equilibrated disul-

Jan 1, 1964

West Virginia Geological Survey Morgantown, W. Va James D. Sisler, State Geologist. Of great importance among the publications of this Survey have been the volumes of Detailed Reports on the counties of the state These volumes take up in detail the geology, topography, soils and resources of the areas under consideration; they are profusely illustrated and each carries topographic and geologic maps Detailed Reports are available for areas as follows: Marshall, Wetzel and Tyler counties (1911) $3, Wirt, Roane and Calhoun counties (1911), $2 50, Jackson, Mason and Putnam counties (1911), $2, Cabell, Wayne and Lincoln counties (1912), $2 50, Doddridge and Harrison counties (1912), $2 50, Monongaha, Marion and Taylor counties (1913), $2 50, Kanawha County (1914), $2 50; Preston County (1914), $2, Logan and Mmgo counties (1915),12 50, Boone County (1915), $2, Wyoming and McDowell counties (1915), $2 50, Lewis and Gilmer counties (1916), $2 50; Raleigh County, Summers west of New River, and the coal area of Mercer County (1916), $2 50, Jefferson, Berkely and Morgan counties (1916), $2 50, Braxton and Clay counties (1917), $2 50; Barber and Upshur counties, and western Randolph County (1918), $3; Fayette County (1919), $3 25;

Jan 1, 1933

By C. M. Wayman, R. Bullough

The rediffraction of Bragg diffracted beams by differently oriented regions (such as twins) of a crystal may give rise to "extra" reflections or reciprocal lattice points. These two papers are concerned with predicting these additional reflections which result from twin related regions of a lattice. Analysis is made for {111}fcc twins, (112)bcc twins, and {hkil}hcp twins. It is first required, knowing the specific variant of the twinning plane in each case, to predict the positions of the twin reflections relative to the matrix reciprocal lattice. Once this is done, the positions of the "extra" multiply diffracted reflections may be deduced. Part I is devoted to establishing "selection ru1es" for twinning, i.e., the necessary and sufficient conditions for the existence of twinned reciprocal lattice points. 1. INTRODUCTION. Transmission electron diffraction patterns are frequently complicated by multiply diffracted beams. Pashley and stowell1 have recently demonstrated that certain extra reflections in evapo- rated films of gold result from the rediffraction of matrix Bragg diffracted beams by (111) microtwins in the gold. It was previously (and erroneously) suggested 2,3 that observed "irrational" reflections in fine-grained gold were due to the presence of some hcp gold. A similar situation exists, apparently, for some bcc materials; fine (112) twins in bcc martensite in Fe-Ni alloys4 give rise to extra reflections. There are many other examples. The number of transmission electron microscopic investigations is continually increasing, and because of the importance of double (and multiple) diffraction in the interpretation of diffraction patterns, it was judged that a detailed elaboration of the principles involved is desirable, as well as the extension of these principles in reasonably closed form to other crystal structures, particularly bcc and hcp. The present analysis considers double diffraction caused by (111) twins in fcc metals, (112) twins in bcc metals, and {hkil} = {hkl) twins in hcp metals. For each case of twinning, the various possible (variants of) twins give rise to a set of interpenetrating reciprocal lattices. The relative spatial arrangements of these reciprocal lattices can be deduced (Part I) and are expressed in terms of simple "selection rules". The resulting sets of interpenetrating reciprocal lattices are then analyzed for possible doubly diffracted reflections (Part II). The notation used, and some important formulas are given in Appendices I and 11.

Jan 1, 1967

By AIME AIME

THE luncheon of the Milling Methods Committee in the Engineers&apos; Club, on Feb. 16, was distinctly a social affair, although several matters of a non-milling nature were fruitfully discussed. The session* on Milling Methods, the same afternoon, attracted a gathering which overtaxed the capacity of the Board Room on the fifteenth floor. Galen H. Clevenger presided, with the moral reinforcement of Charles Butters. As all papers were available in printed form, and since synopses have appeared in MINING & METALLURGY, it is unnecessary to cover the contents of each in detail here. The first paper (T. P. 410), by Leaver and Woolf, on the "Flotation of Minor Gold in Large-scale Copper "Concentrators," was excellently summarized by R. S. Dean of the U. S. Bureau of Mines, who stressed the -very definite action of lime as a depressant of gold, and showed how the authors had worked out the best conditions of alkalinity, pH concentration and reagents for -optimum recovery of gold along with base metals, especially where lime had to be used to depress pyrite. No discussion was evoked.

Jan 1, 1931