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By F. O. Jones

The capabilities of small proportions of divalent cations, such as calcium or magnesium, for controlling clay blocking are reported. Potentially sensitive formations can be exposed to fresh water if at least one-tenth of the salts dissolved in both the native water and invading fresh water are calcium and magnesium salts. Often, even less suffices. The behavior evidently depends upon the cation exchange properties of the clays, which favor adsorption of calcium and magnesium over sodium. Clays having sufficient adsorbed calcium and magnesium resist dispersion by water and consequent blocking of permeability. An allied phenomenon, the dependency of clay blocking on salinity contrast, is also reported. Abrupt change from highly saline to fresh water can cause blocking which may not occur if salinity is lowered slowly. A process related to osmosis is thought responsible for this behavior. Applications of findings to drilling, fracturing and water flooding are discussed. INTRODUCTION Many formations, when exposed to fresh water, can lose permeability through clay effects.',' For example, drilling-mud filtrate can cause oil permeability decreases, which persist long enough to interfere with drill-stem testing and well completion.3 Ultimate productivity may suffer when clay damage is severe, especially if drawdown pressures are low.' The injection pressures and the time required for water flooding can increase if clay blocking occurs. Earlier work indicates that clay blocking is caused by obstruction of flow channels by clays or other mineral fines dispersed by fresh water.'!" It is well known that increasing salt concentrations in water tends to prevent clay blocking. Also it is well established, although perhaps not as widely known, that the nature of the dissolved solids is also important. If, for instance, formation clays are exposed to calcium chloride solution and then exposed to weaker solutions of calcium chloride or distilled water, considerably less permeability damage results than if the clays had been exposed instead to sodium chloride solutions. The reasons for this behavior are: (1) clays are cation-exchange, or base-exchange, materials similar in this respect to zeolites or exchange resins, and (2) clays in the calcium form do not disperse easily in fresh water, whereas clays in the sodium form do. The base-exchange form of a clay is easily altered by flowing a solution through it. For example, a sodium clay can be changed to a calcium clay simply by passing a calcium chloride solution through the clay bed. There is general agreement that the reason calcium and magnesium clays do not disperse easily in fresh water is because the calcium ions do not ionize easily from the clay surfaces.' Sodium clays, however, are believed to allow the sodium ions to ionize from the clay particle surfaces. In fresh water, this allows the particle to accumulate a net negative electrical charge great enough for the particles to repel one another and, therefore, disperse more easily. The foregoing suggests that, even in the presence of a large excess of sodium, a relatively small ratio of divalent cation, such as calcium or magnesium, might serve to prevent clay dispersion. The divalent ion probably adsorbs to a disproportionately large extent, because of being adsorbed more tightly, with the result that the proportion of divalent cation on the exchange positions of the clay might then be great enough for the clays to resist dispersion. Consequently, an investigation was conducted to find how mixtures of salts in solution influence clay blocking. APPARATUS AND PROCEDURE Water permeability tests were conducted using conventional techniques. The equipment is illustrated schematically in Fig. 1. Flow rates of solutions driven through small core samples at known temperatures and pressures were measured. Regulated compressed air, usually at 10 to 15 psig, was used to drive the solutions. Core samples 0.75 in. in diameter and 1 in. long were used for the most part. Cores were saturated by evacuating and then admitting a de-aerated solution. Tight core samples were first saturated with carbon dioxide gas and then evacuated and saturated with the test solution. After saturation, 140 psig pressure was imposed for several hours. Cores were tested to insure absence of gas saturation by a Boyle's

Jan 1, 1965

By J. B. Cohen, B. W. Howlett, M. B. Bever

The partial molar heats of solution at infinite dilution in tin of aluminum at 300° and 350°C and of gallium, indium, and thallium at 240°, 300°, and 350°C have been measured by tin solution calori-metry. Aluminum, gallium, and thallium are endo-thermic on solution; indium is exothermic. Any temperature dependence of the heats of solution lies within the experimental scatter. Over the dilute ranges investigated, only aluminum has a measurable change in its heat of solution with composition. HEATS of solution of one element in another reflect the interaction between them. The investigation of partial molar heats of solution in dilute alloys is of particular interest as the properties of the solvent are altered to only a limited extent by the presence of the solute and also as the interaction between solute atoms is small. When the heats of solution of a related series of elements in a solvent are known, a systematic comparison may be made. In the investigation reported here, the partial molar heats of solution of the Group III elements aluminum, gallium, indium, and thallium in dilute solution in tin were measured. This work follows an investigation of the heats of solution in tin of the Group IB elements.' EXPERIMENTAL PROCEDURES Materials. Samples of gallium, indium, and thallium were obtained from Johnson, Mathey and Co., Ltd. Indium and thallium were supplied as wire, 1.6 mm in diam; gallium was in the form of irregular pieces. The supplier reported the following minimum purities: gallium—99.95 pct; indium—99.99 pct; thallium—99.99 pct. The aluminum, obtained from Alcoa Research Laboratories, was reported to be 99.995 pct pure. The tin was supplied by Baker and Co., Inc.; the reported analysis indicated a tin content of at least 99.96 pct with lead as principal impurity. Calorimeter. this description will cover only the essential features of the calorimeter with special attention to modifications made since an earlier description was published.' A Dewar flask containing the tin bath was held in a constant-temperature bath of a near-eutectic mixture of lithium, sodium, and potassium nitrates. This bath, which was stirred vigorously, was heated by a primary resistance winding in the container wall and by a secondary winding immersed in the salt. The voltage supplied to both windings was stabilized. The temperature of the salt bath was controlled by means of a platinum resistance thermometer in one arm of a Wheatstone bridge. The light from a mirror galvanometer in the bridge circuit fell on a photocell which controlled the current in a saturable reactor in series with the secondary winding. In this manner, the temperature of the salt bath was controlled to ±0.003°C and that of the tin bath to at least ±0.002°C. Each of these temperatures was measured by two iron-constantan thermocouples in series, coiled in a helix to minimize heat loss and immersed in the salt and tin baths in protective sheaths. The temperature of the laboratory was kept constant to ± 1°C during a run. Specimens were dropped into the tin bath from an addition arm held at O°C which was part of the cal-orimetric system. The system was evacuated to about 0.02 1 to minimize oxidation and to reduce transfer of heat. The bath was stirred by a glass stirrer introduced through a double Wilson seal. The samples were scraped clean before weighing, which was carried out as rapidly as possible. Each sample was immediately placed in the evacuated addition arm to minimize contamination. These precautions were especially necessary with aluminum. After the runs with gallium and thallium at all temperatures and with indium at 240° and 350°C (Series I) were completed and before the runs with indium at 300°C and aluminum at 300° and 350°C (Series 11) were begun the following changes were made. The shape of the Dewar flask was changed so as to result in a lower surface to volume ratio of the bath and at the same time the amount of tin was reduced from 500 to 400 g. The paddle type stirrer was replaced by a helical screw and the rate of stirring was increased to about 150 to 200 rpm.

Jan 1, 1962

By William Y. Holland, Roger M. Cook

In view of the increasingly widespread deterioration of concrete structures as the result of the interaction of the alkalies sodium and potassium released by hydration of portland cement and susceptible rocks and minerals in aggregates, it is believed that a paper summarizing the geographic distribution of these aggregates will be of interest to producers and users of concrete, concrete products, and concrete-making materials. THIS paper reviews the problem of alkali-aggre-gate reaction in concrete and describes the geologic and geographic occurrence and distribution of alkali-reactive sand and gravel in western United States. It includes no discussion of crushed stone or synthetic aggregates. Most deposits of sand and gravel are accumulations of particles of rocks and minerals from a variety of sources, and it is not unusual for at least one or two varieties of the rocks to contain some form of reactive material. Examination by petro-graphic methods of many sands and gravels, as well as manufactured aggregates, has shown that a comparatively high proportion of the deposits does contain, in greater or lesser degree, rocks and minerals known to be deleteriously reactive with the alkalies of cement. Fortunately the amount of reactive materials is commonly less than that necessary to cause deleterious effects in concrete. As investigation of unsound concrete structures progresses, it becomes evident that the alkali-aggre-gate reaction is even more widespread than supposed, Figs. 1 and 2. Even though some parts of the country appear at present to be immune, further investigations will probably show that the effects of alkali-aggregate reaction can be seen in many structures in these areas, although only on a small scale in most of them. Many concrete structures will, of course, have lived their useful life before disintegration from this cause is serious, and in others the alkali-aggregate reaction may never become significant even though the microscopic evidence of reaction is present. The alkali-aggregate reaction first was reported to be a cause of deterioration of concrete in 1940 when Stanton1 described expansion of concrete pavements in California. Similar expansion and deterioration of concrete was recognized during succeeding years in concrete structures located in many parts of the country, but particularly in the western states. A number of concrete laboratories2 became interested in the problem. It was soon determined that only certain combinations of aggregate and cement caused the alkali-aggregate reaction to take place, and moreover that the reaction progresses only in the presence of water. Further research proved that cements containing more than 0.60 pct total alkalies (pct Na,O + 0.658 x pct K2O), when used with aggregates containing appreciable amounts of reactive ingredients, caused the reaction to take place, usually with subsequent deterioration of the concrete. During the last few years this limitation has been adhered to in both government and private construction as the maximum allowable alkali content of cement to be used with aggregates of known alkali reactivity. Because of this limitation, it appears that deleterious reaction either has been reduced or eliminated in many recently built structures in which it probably would otherwise have occurred. Recent tests have shown that the degree of expansion obtained with any particular cement-aggre-gate combination depends not only on the alkali content of the cement but also upon the relation of this alkali content to the amount and degree of reactivity of reactive constituents in the aggregate.' In laboratory mortar bars, opal and cements with alkali content of as low as 0.2 pct (as equivalent of Na2O) have produced deleterious expansion as the result of alkali-aggregate reaction. These experiments demonstrate that aggregates containing even 0.1 pct of opal are deleteriously reactive. It was soon determined that alkali-silica gels were formed by the interaction of the alkalies of the cement and the reactive aggregate, Figs. 3 and 4. Osmotic or swelling pressures produced by the continued hydration of these gels cause expansion of the concrete with resulting cracking, warping, and dislocation. Evidence of the alkali-aggregate reaction can be seen by a petrographic study of the deteriorated concrete. Among the first structures studied by this method was Parker Dam on the Colorado River, California-Arizona. In the concrete from this dam pebbles of rhyolite, andesite, siliceous limestone, and chalcedonic chert were found to be reactive.

Jan 1, 1954

By R. L. Perrine

A stability theory is developed for miscible liquid-liquid displacement within a porous medium. In the usual case considered, a high-density high-viscosity "oil" is displaced downdip by a low-density low-viscosity "solvent'! Perturbation methods are used to find the conditions under which the spreading mechanism changes from the stable dispersion process to unstable viscous fingering. We find that instability is conditional, that there is a dependence on the shape of a disturbance leading to a"diameter" effect and that very difficult experimental scaling problems may result. A useful consequence is the definition of a minimum "slug size" for stable miscible displacement. This should make possible optimum use of the solvent process for oil recovery. The results may apply to many situations in which one fluid displaces another of somewhat different fluid properties within a porous medium. INTRODUCTION The process of miscible liquid-liquid displacement looked very favorable when it first received serious consideration as a means to increase petroleum recovery. Some early laboratory results were interpreted to mean that only a small "slug" of solvent was needed, perhaps 2 to 3 per cent of a hydrocarbon pore volume. This "slug" could recover the oil in an entire reservoir provided the fluids remained miscible.1,2 Only a slow growth of the "mixing zone", or gradual transition from oil to solvent, should occur. This would follow naturally from mixing by a dispersion mechanism such as that described by Scheidegger.3 And, indeed, laboratory cores have shown this kind of behavior provided solvent viscosity was at least as great as that of the oi1.2,4-6 The same kind of behavior has also been observed with solvent viscosity lower than that of the oil after the distance traversed became large. Not all laboratory results have been this favorable, however.7-9 Mixing zone growth may become proportional to the distance traveled rather than the square root of this quantity. Such behavior accompanies high rates in short systems of large diameter, provided the viscosity ratio is adverse. If this more rapid spreading were to persist in a reservoir, the solvent requirement for miscible "slug" displacement could exceed 30 per cent of a pore volume. There is considerable economic importance in the difference between 3 and 30 per cent solvent. A 1ogical conclusion is that two different kinds of flow behavior are possible, with each kind leading to a different result. One kind gives efficient displacement, the other does not. In the efficient case, the solvent bank spreads out only by the mechanism we have termed dispersion. Under these conditions, displacement is as near piston-like as possible. In the second kind of flow, found only with adverse viscosity ratios, viscous fingering occurs. That is, permeability variations cause a small finger of low-viscosity solvent-rich fluid to move ahead of its average position within the mixing zone. This creates a path of low resistance to flow, and an even greater amount of solvent-rich fluid follows. Thus, the process is autocatalytic. Once started, the fingering mechanism rapidly becomes dominant. The question to be answered is this. Under what conditions will each of these two different kinds of flow occur? In particular, what conditions denote the transition from dispersion to viscous fingering as the solvent spreading mechanism? The answer may tell us whether or not the desirable, near piston-like miscible displacement process is practical. An answer to this problem can be obtained from theory by the use of perturbation methods. The procedure is as follows. We first formulate a mathematical representation of the system. Then a small disturbance (or perturbation) in solvent concentration profile is introduced and observed to see what happens. Unstable flow is indicated when a small disturbance will grow larger. This will lead to eventual viscous fingering. If on the other hand the disturbance dies out, the displacement is stable. In this latter case, with dispersion as the spreading mechanism, near piston-like displacement is possible. Thus, this paper presents the development of a stability theory for miscible liquid-liquid displace-

Jan 11, 1951

By J. B. Hess, C. S. Barrett

Single crystal rods of cadmium collapse under uniaxial compression into peculiar kinks if the (0001) glide plane is nearly parallel to the axis of compression. In his report first describing this behavior, Orowan1 proposed that these "kink bands" do not develop entirely by ordinary gliding and twinning but by a special mechanism in which glide lamellae of uniform thickness snap abruptly to a tilted position that permits lattice continuity across the glide planes. He concluded that a portion of each boundary of a kink band consists of a plane (non-crystallo-graphic) which bisects the angle between the glide planes on the two sides of it, and along which the bending and the dislocations are concentrated. The data presented by Orowan seemed to us to be insuffcient to conclude that a wholly new mechanism of deformation was responsible for the kinks. Therefore, we have investigated zinc, which is hexagonal close-packed and has an axial ratio near to cadmium, to see whether similar bands are produced, and whether the ordinary mechanisms of glide, bend-gliding, twinning, and the formation of deformation bands can account for its mode of deformation. We find that kinks form profusely in zinc as shown in Fig 1. The structure of these kinks, reported below, seems to require no new mechanism for their explanation, but indicates that kink bands are a special form of deformation bands and develop gradually, solely from basal glide. A theory covering the formation and structure of the bands is presented in detail because it is seldom possible to study deformation bands under such simple conditions, yet many principles applying to these kinks should also apply to deformation bands in general. Experimental Procedures Single crystal rods of 2-3 mm diam and 10-15 cm length were grown by the Brideman technique from swaged wire of Horsehead Special zinc in un-coated pyrex tubes. Orientations of the rods were determined with an optical goniometer after cleaving the rods at liquid air temperature. Crystals of desired orientations were then selected and used as "seeds" to grow additional crystals approximately 4 ft in length from which all specimens were cut. The wires were compressed in two ways: in a simple hydraulic handpress —a "soft" machine—and in a Riehle hydraulic testing machine modified to produce very "stiff" action by the simple expedient of inserting lengths of steel bars at the sides of the zinc crystals between the compression plates. For metallographic examination, the specimens were mounted in sealing wax. Hand polishing was employed, with no grits coarser than No. 1 paper; following the abrasives about 0.025 in. was removed by an etch-polishing reagent.* Final etching to reveal ori-

Jan 1, 1950

By M. S. Abrahams

Germanium has been rolled in the temperature range of 700o to 800°C. The thickness has been decreased by as much as a factor of four, from a thickness of 0.032 in. to a thickness of 0.008 in. For deformations below 60 pet, the true strain per pass is found to be a constant; from the temperature dependence of this slope, an activation energy of about 2.5 ev is obtained. This energy agrees with that for dislocation climb in germanium . For reductions greater than 60 pet, complete rings are seen in the Lave photographs, new grains are observed in the microstructure, considerable softening occurs, and the hole mobility is very low. This evidence indicates that the recrystallization of gertnanium has occurred. GERMANIUM has been deformed in many ways1 including tension, compression, torsion, and bending since Gallagher2 first described its plastic nature at elevated temperatures. All of these studies indicate that the glide plane in germanium is (111) and that the glide direction is (110). Rolled germanium specimens were used by Kolm, Warekois, and Kulin3 in their X-ray study of deformed semiconductors, but no information is given on the rolling itself. The present experiments deal with the rolling of germanium at various temperatures and for different orientations. In all previous deformation studies, the phenomenon of recrystallization (i.e., the transformation of a single crystal into a polycrystal) in germanium has not been observed4 despite relatively large deformations at elevated temperatures. The proposed reason4 for this was that sufficient energy could not be stored in the deformed germanium lattice. In contrast to the earlier studies this work will present evidence indicating that recrystallization occurs in germanium during rolling at an elevated temperature. I) EXPERIMENTAL PROCEDURE A) Test Specimens. The samples used for rolling were in the form of rectangular parallelepipeds measuring 0.3 in. long, 0.06 in. wide, and 0.035 in. high. They were cut from an undoped single-crystal ingot of p-type germanium with a resistivity of 24.4 ohm-cm, a Hall mobility of 2300 sq cm v-' sec-l, and a hole concentration of 1.1 x 1014 cm"3 at room temperature. The surfaces of the specimens were metallographically polished prior to rolling. The initial dislocation density of the samples was about 10' cm-' as determined by etching in CP4. Two different specimen orientations were used. In the first case, the direction of rolling was parallel to (251), the surfaces in contact with the rolls were of the form (1021, and the normal to the third face was parallel to (211). The corresponding di-

Jan 1, 1964

By S. F. Urban, G. Derge

At the time this investigation was initiated variations were observed in the quality of different heats of basic electric-furnace steels, although they had been made under purportedly similar conditions. This indicated that these variations were related to normally unobserved variations in the character of the bath, especially during the "refining" period. Although the slags used for this operation are commonly referred to as "reducing" slags, and are regarded as having a "deoxidizing" action on the bath, no reliable measurements of this action were available. It was decided, therefore, to study the behavior of oxygen in the metal for ' large enough number of heats to learn its normal variations and to relate these variations to regularly observed conditions of operation. The most important general conclusion reached was that the time a heat is held under a reducing 'lag should be reduced to a minimum, which was about an hour and a half under the conditions studied. Beyond this time no observable beneficial effects are obtained from the reducing slags, insofar as oxygen and sulphur content of the bath are concerned. It is likely that added time may increase hydrogen content as well as heat costs. The oxygen content of the bath is never reduced below the amount in equilibrium with the carbon. Concurrently with this work, J. S. Marsh1 presented data that supplement and support many of the results of this paper. Procedure The work was done in two different electric-furnace shops of the same plant. The selection of heats was made primarily with regard to the convenience of heat schedules. companion slag and metal samples were taken just prior to slag-ofi and throughout the refining period for an initial set of 17 heats, and before slag-off and near tap for an additional I3 heats. slag Sampling presented no particular problem; a spoonful of slag was poured onto a metal plate and when sufficiently cool was sealed in an airtight container. Sampling the metal for oxygen presented a more complex problem. Because of the lack of previous experience in sampling electric-furnace baths, a number of methods were compared. Chilled Wedge Samples2 An unkilled metal sample is removed from the furnace in a well-slagged car-bometer spoon and poured immediately into a heavy copper mold designed to provide rapid freezing. Three different types of molds were used to determine the optimum for electric-furnace hats. The Big wedge Mold (a) was a 4 by 4 by 4-in. split copper mold, yielding a wedge-shaped casting I in. wide, 1 1/2 in. long, and 34 in. maximum thickness, and was finally adopted as the most satisfactory design.

Jan 1, 1948

By S. F. Urban, G. Derge

At the time this investigation was initiated variations were observed in the quality of different heats of basic electric-furnace steels, although they had been made under purportedly similar conditions. This indicated that these variations were related to normally unobserved variations in the character of the bath, especially during the "refining" period. Although the slags used for this operation are commonly referred to as "reducing" slags, and are regarded as having a "deoxidizing" action on the bath, no reliable measurements of this action were available. It was decided, therefore, to study the behavior of oxygen in the metal for ' large enough number of heats to learn its normal variations and to relate these variations to regularly observed conditions of operation. The most important general conclusion reached was that the time a heat is held under a reducing 'lag should be reduced to a minimum, which was about an hour and a half under the conditions studied. Beyond this time no observable beneficial effects are obtained from the reducing slags, insofar as oxygen and sulphur content of the bath are concerned. It is likely that added time may increase hydrogen content as well as heat costs. The oxygen content of the bath is never reduced below the amount in equilibrium with the carbon. Concurrently with this work, J. S. Marsh1 presented data that supplement and support many of the results of this paper. Procedure The work was done in two different electric-furnace shops of the same plant. The selection of heats was made primarily with regard to the convenience of heat schedules. companion slag and metal samples were taken just prior to slag-ofi and throughout the refining period for an initial set of 17 heats, and before slag-off and near tap for an additional I3 heats. slag Sampling presented no particular problem; a spoonful of slag was poured onto a metal plate and when sufficiently cool was sealed in an airtight container. Sampling the metal for oxygen presented a more complex problem. Because of the lack of previous experience in sampling electric-furnace baths, a number of methods were compared. Chilled Wedge Samples2 An unkilled metal sample is removed from the furnace in a well-slagged car-bometer spoon and poured immediately into a heavy copper mold designed to provide rapid freezing. Three different types of molds were used to determine the optimum for electric-furnace hats. The Big wedge Mold (a) was a 4 by 4 by 4-in. split copper mold, yielding a wedge-shaped casting I in. wide, 1 1/2 in. long, and 34 in. maximum thickness, and was finally adopted as the most satisfactory design.

Jan 1, 1948

Discussion of the paper of John H. Hall, presented at the New York. Meeting, October, 1913, and printed in Bulletin No. 79, July, 1913, pp. 1247 to 1256. WILLIAM 'R. WEBSTER, Philadelphia, Pa.:-I would like to call ,attention to the fact that the results of the ordinary tension and bend tests do not always give us the information we want even if we figure out the amount of work done. You want a bending test of sufficient width and full thickness. In the case of eyebars, for instance, I have had experience with a 10- by 1-in. eyebar which gave perfectly good results in a full-size test of the finished bar. The 10- by 1.5-in. and 10- by 1.75-in. eyebars from the same heats-of steel were absolutely worthless in full-size tests. The narrow bending tests from all these bars gave good results. Bat after going into the matter fully, we found that if pieces about 3 in. wide and full thickness were used for the. cold bending tests, the heavier material would not stand this test, but failed. That is, in order to check the quality of the rolled bar you should have a wide piece of full thickness for cold bending, as the narrow pieces give misleading results. J. E. JOHNSON, JR., New York, N. Y. :-I would like to ask if there have been any tests made to compare the results of Charpy tests with the true dynamic test similar .to the Wohler test, except that the piece is subjected to a tensile or compressive stress and to alternating stresses in addition, at the same time. This seems to me to approach more nearly than any other test to the conditions of actual service. where the piece is under a fixed initial stress plus a highly variable and often alternating stress. Some tests were made on this plan in England within a year or two. The test piece was Subjected to either a tensile or compressive stress of known amount and simultaneously to alternating stresses in addition. Such a. test as this gives information which we cannot get by a tensile test or even from the tensile strength multiplied by an. elongation. Such tests, however, are exceedingly tedious and require long periods of time in order to obtain valuable results. If material could be subjected to these dynamic tests and the same material to the. Charpy shock test, and if some reasonable qualitative relation could be established between the results of the two tests, then we could assume that the shock test, which is so simple and easy to make, was a measurably accurate test of the dynamic qualities of the material. At present it does not seem

Jan 12, 1913

By L. Grånäs, B. Aronsson

In a recent study of Fe-Si alloys Walter and Koch' observed pairs of dislocations in Fe-6.25 pct Si crystals rolled to reductions of 10 pct and subsequently annealed for 1 hr at 650°C. They interpreted these pairs as being due to stacking faults. From the spacing of the dislocations a stacking-fault energy of 15 to 19 ergs per sq cm was calculated. These authors did not pay any attention to the order -disorder phenomena in Fe-Si alloys. It is the purpose of this communication to report some preliminary results from a study of ordering and its influence on the plastic deformation of Fe-6.0 pct Si alloys. Our results suggest that the dislocation pairs observed by Walter and Koch may have been due to long-range order rather than to stacking faults. The alloys used in this investigation were prepared from pure electrolytic iron and silicon and were melted in argon. After hot working, strip tensile specimens were machined to a gage length of 70 mm and a thickness of 1 mm. The specimens were heat- treated for 2 hr at 1000°C, furnace-cooled, and subsequently deformed 2 pct in tension at 400°C. The strain rate was 5.6 X lo-' sec-'. Thin foils of the deformed specimens were prepared by means of the Bollman technique and examined in a Siemens Elmis-kop I at an accelerating voltage of 100 kv. In the Fe-Si system long-range ordering occurs at a silicon content of about 6 pct Si. In our alloys evidence for ordering is given by selected-area diffraction patterns which show extra reflections consistent with a super lattice of the D0 9 type. In addition, the dislocation arrangement in deformed specimens indicates that long-range order is present. A typical mi-crophotograph of a thin foil is shown in Fig. l. The dislocations are usually straight and parallel and laying in distinct directions. In the commonly observed (111) zone the projections of the dislocations are close to (113) and (oil). Observation of the image position indicates that the two dislocations in a pair have the same Burgers vector and hence constitute a superlattice dislocation.~ According to theory3 a superlattice dislocation in the DO3 structure consists of four ordinary dislocations connected by two types of antiphase boundaries as shown in Fig. 2. In our specimens only two dislocations in each pair have been observed, Fig. 1. The problem is to decide whether the area between these is a NN or a NNN antiphase boundary. Dark-field images using the (200) reflexion (the indices are defined with respect to the DO3-type superlattice) can

Jan 1, 1968

Jan 1, 1952

By C. M. Brown

Selection criteria for the instrumentation employed in semi-autogenous grinding circuits are reviewed. Instruments in use for grinding mill and related process equipment start- up, shutdown, protection, monitoring, control, and performance reporting functions are discussed with examples given of current industry practice. The quantity and type of instrumentation used vary from operation to operation, but today many semi- autogenous circuits are highly instrumentated, and employ automatic process control for both circuit stabilization and optimization of economic performance. Examples of analog and digital based control systems exist, and are described.

Jan 1, 1982

By Donald M. D. Stuart

It gives me great pleasure to accept the invitation I had the honor of receiving through the Secretary of the Institute, to reply to the criticisms made in discussion of the theory advanced in my work entitled, Coal-Dust an Explosive Agent; and to lay before the Institute a further statement of the views which investigations have led me to form upon this subject,

Jan 1, 1897

COUNCIL OF SECTION DELEGATES Nicholas A D'Arcy, Jr, Chairman (Southern California Section) Charles Chapman, Vice-Chairman (Florida Section) Ben H Parker, Secretary (Colorado Section) Frontier Refining Co Boston Bldg Denver 2, Colorado

Jan 1, 1956

By George Norman

A NUMBER of methods have been developed for the determination of the dust concentration in air, some of which have been reported as very efficient and for research may be more satisfactory than the method about to be described. In practical mine use, however, the accurate research equipment is unwieldy and requires a high degree of technical skill to manipulate it. Also, it gives less general practical information to the operator in the same length of time than the method described here. Moreover, it is doubtful whether at the present stage of affairs the results obtained from the precise methods have any more practical significance than those obtained with simpler and more portable appara-tus, which can rapidly give a sufficiently reliable indication of the rela-tive dust hazard.

Jan 1, 1937

Jan 1, 1879

By AIME

[Fig. 1], at left, is a corrected version of the first figure of the paper. Please note corrections in labeling of deposits.

Jan 1, 1973

By H. G. Doll

THIS paper discusses a method and apparatus for determining the dip of formations traversed by a drill hole, by means of electrical measurements in the hole. The process consists in recording the Spontaneous Potentials present along three oriented generatrices in the hole. By comparison of the three curves thus obtained, after application of a correction factor to compensate for any deviations of the hole, the dip angle and the dip direction are determined. Excellent accuracy is obtained for dip angles over 10°. Because the method is simple and the apparatus rugged, the measurements are rapid and reliable; consequently, they can be made at all the levels that are of interest at any time after the well has been drilled. Mechanical cores are not needed to evaluate the dips. A convenient, timesaving procedure is to perform the dipmeter survey at the time the electrical log is taken, using for both operations the same cable and truck. Actual examples of results obtained in wells of the Gulf Coast area are given.

Jan 1, 1944

A-Metal Mining B-Minerals Beneficiation F-Coal H-Industrial Minerals

Jan 11, 1950