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By J. R. Finlay

THE other day, I fell into conversation with two gentlemen who desired to improve the condition of the people; so that the talk was semi-political. They seemed to agree that I was inclined to be "con-servative," "reactionary," perhaps an "evolutionist," looking upon "reform" with suspicion. Finally I rejoined somewhat in this manner: "You attach to me phrases that I have heard all my life but which convey no meaning to me. It is quite true that I do not make a fetish of terms like reform, liberty, democracy and so forth; neither do I worship the idea that `things are good enough as they are,' `leave well enough. alone' and so forth. There is more satisfaction in building something up than in tearing something down, or in just maintaining something that is already built. Progress is a popular word; but what is progress? In my opinion it is comprised, so far as public welfare is concerned, of two elements: Improvements in production of goods and knowledge; improvements in keeping order." This substitute for politics, economics, reform, pro-gress, conservatism, radicalism, democracy, socialism, monarchism and all the phrases of public welfare may seem over-simple; perhaps it is, but at least it defines something. It seems to me to be at least worth attention.

Jan 4, 1922

By H. A. Lequear, J. D. Lubahn

A sudden change from one constant strain rate to another during a tensile test causes an unusual transient in aluminum alloy 61ST. A sudden change from one constant stress to another during a creep test does not produce an unusual transient in this material. A specially devised test shows that the nature of the previous steady-state conditions, which the sudden change disturbs, is one of the factors affecting the transient behavior. Some of the observations may be explained in terms of strain aging. USUALLY a sudden change during a tensile test from one constant strain rate to another causes a small, abrupt vertical shift from one stress-strain curve to another, parallel one. This behavior is apparently characteristic of all metals at very low temperatures and of many metals for wide ranges of temperature. It is illustrated in Fig. 1 for some early data on 61ST tested at — 195oC, and in Fig. 2 for some recent data on copper at room temperature. The greater accuracy of the results of Fig. 2 over previous ones' is due to the equipment shown in Fig. 3. Three levers apply the bulk of the load, while the changes in the small remainder load are indicated sensitively by a low capacity load scale. Refs. 2 and 3 describe the recording equipment. A test like those in Figs. 1 and 2 provides the information necessary to determine the rate sensitizrity, n,4 of the metal. ( a log s ) ? log s n = ------------------------ ----------------------------= ( a logs e, ? log e logS2-logS1 log S2/S1 log i2 — log e1 log e2/e1 where S equals stress: e is logarithmic strain or natural logarithm of (final gage length/initial gage length);" i is strain rate or de/dt: and n is rate sensitivity, rate of change of log stress with log strain rate at a given strain, or (a log S/a log i),. Normally, the rate sensitivity, n, is positive, which means that an increase in stress causes an increase in rate. However, certain exceptions, attributed to strain aging,5 have been observed. Fig. 2 indicates how rate sensitivity values are derived from the measurements. Table I summarizes the rate sensitivity values derivable from Fig. 1. In contrast to the behavior of copper in Fig. 2, the aluminum alloy 61ST, which strain ages when tested near room temperature, exhibits an unusual transient when the strain rate is suddenly changed,' as shown in Fig. 4. Initially, there is a comparatively sudden vertical shift of the stress-strain curve in a direction corresponding to the rate change, but then the curve gradually shifts back again. The initial shift is not as sudden as might be expected, because the testing machine is unable to achieve the impressed rate change instantaneously, as illustrated in Fig. 2. The behavior shown in Fig. 4 will be referred to as a tensile transient, the word tensile implying that the behavior was observed in a tension type of test. The corresponding test, where the strain rate is maintained constant except for the sudden change, will be called a tensile transient test. A creep transient, by contrast, will be defined as a temporarily abnormal behavior in a creep transient test, where there is a sudden change from one constant load to another.' In Fig. 4, a naive look at the gradually decreasing and then increasing load after a sudden rate incre-

Jan 1, 1957

By Roswell Johnson

THE principle of sliding or graduation in royalties is accomplished either by the block, period, cumulative, or class method. The block method calls for a very low royalty rate on all oil produced up to. a certain amount. This amount would normally be that which is believed to suffice to repay the cost of the well. A higher rate would be charged after the well is making a profit. This method, common in many industries, is peculiarly inadaptable to any industry such as this where the productivity per day of the units gradually and inevitably decreases. This, for reasons given later, is because it forces an early abandonment of the well and so offends against conservation. In the period method, the royalty rate is changed by some definite amount when the well produces less than a specified quantity per day or other given unit of time. While simple to explain, it operates badly because a great deal is made to depend upon a small reduction in production, whereas the reduction as a matter of fact declines rather erratically owing to the exigency of lease management, connecting of tankage, and vagaries of the gaugers. These disadvantages are obviated by the cumulative method. In this method, all the production less than a certain amount per week has one rate of royalty, or none at all, and the oil produced in excess of that amount pays an additional rate of royalty. In the long run the calculation is probably no greater than with the period method, for simple tables will be published and printed in the oil papers that can be cut out, enabling quick readings to be made. Even without the table the calculation is easy with the few royalty rates, two or three, which would be used. In this method, the amount paid in royalty declines gradually, rather than suddenly as in the period method.

Jan 6, 1915

By Suresh P. Babu, Joseph W. Leonard

The ultimate objectives of comminution should be to reduce material to some specified size while producing a minimum of undersize or fines, with less power, higher throughputs, and with more compact machinery. Attempts to achieve these objectives have been only partially successful, since gains in some areas are achieved at the cost of concessions in other areas. An example of some of these trade-offs can be found in the closed circuit crushing operations of the anthracite and crushed stone industry where, in order to produce a minimum of unprofitable fines, unfavorable concessions must be made in the size of the crushing facility where 2 or more crushing stages are interphased by 2 or more screening operations. This paper discusses experiments with a new process which attempts to achieve some, if not all, of the comminution objectives in a single pass operation without undesirable concessions; or, at the very least, to achieve more than is possible with systems in use today. These objectives are sought by use of water-flushing to enhance comminution. The crushing of coal and other minerals is a mature technology that is long overdue for a careful re-examination. Crushing of coal is generally achieved through the use of rotary breakers and roll crushers. Water-flushing, as envisioned here, appears to have potential application in the following areas: 1) For primary raw coal crushing or for secondary crushing of rotary breaker products. 2) For use as a size reduction and/or concentrating step for crushing coal mine refuse from present production or from existing refuse dumps. 3) For possible future application in underground preparation interphased with continuous mining machinery. Size reduction with conventional methods is known to be an inefficient operation when the increase in surface energy of the material crushed is compared with the input energy. A simple breakdown of the energy consumption in size reduction, given by Orr, is shown in [Fig. 1]. It is believed that most of the energy supplied is lost in the form of interparticle friction.2 Hence, the removal of fines immediately after their formation or the implementation of steps to prevent their formation, based on reduced friction, will reduce the energy requirements of the communition operation.3 A detailed discussion of the mechanism of size reduction is available in other literature.3-5 Even though the closed circuit crushing operation is designed to carry the fines away from the crushing zone, it is still inadequate for instantaneous removal of fines. The present investigation advocates the use of a flowing liquid medium to remove the crushed product immediately after size reduction. Unlike the wet-grinding methods, no constraints are required for the liquid flow rate, and, also, the liquid medium can be used in primary crushers like jaw crushers, hammer mills,

Jan 1, 1978

By Desmond De Villiers Oxford, Peter H. Williams

Nchanga Consolidated Copper Mines, Ltd., is one of the four mines operated by the Anglo American Corp. in Northern Rhodesia, now the independent nation of Zambia. Today Nchanga is the second largest single producer of copper in the world, accounting for more than 200,000 long tons of copper annually at a monthly milling rate of 430,000 tons of ore. The average mill-head grade is about 5.20% total copper, of which approximately 60% is copper sulfide. The remainder, referred to as "acid soluble," is copper oxide. Nchanga mines three separate orebodies varying in grade and sulfide-to-oxide ratio. Ore is processed in two separate grinding circuits feeding into three separate flotation circuits. A fourth flotation circuit treats leach plant residue for additional recovery of sulfides.

Jan 1, 1965

By M. G. F. Söhnlein

IN THE metallurgical treatment of sulfide silver-tin ores mined at Oruro, Potosi, and Chocaya, the most important and difficult step is chloridizing-roasting. The ores are chiefly mined from veins in rhyolite, a detailed description of which can be found in most textbooks on ore deposits. The chief gangue minerals are Pyrite and quartz, and the silver content is derived from tetrahedrite, jamesonite, stibnite, and cylindrite. Most of the tin is present in the form of a rather impure cassiterite, which forms microcrystalline aggregates of varying richness with quartz and pyrite; occasionally, some tin is found as stannite, cylindrite, and other complex sulfantimonates. The silver content of the minerals that compose the ore is approximately as follows: Pyrite, 3 to 5 oz. per ton; jamesonite, 30 to 50 oz. per ton; stibnite, 30 to 150 oz. per ton; cylindrite, 200 to 300 oz. per-Jon; tetrahedrite, 500 to 3000 oz. per ton. Occasionally, some ruby silver ore is found, but it is very rare. In the mines of Oruro, which are the deepest in the sulfide zone, tetrahedrite has nearly disappeared, stibnite, jamesonite, and, in the deepest levels, cylindrite taking its place. At present, there are six mills treating this ore, two at Potosi, two at Chocaya, one at Poopo, and one at Machacamarca. The ore is crushed dry, given a chloridizing roast, leached with water and hyposulfite solution (or with brine) to extract gold, silver and copper, and concentrated for tin with or' without regrinding.

Jan 8, 1920

By N. G. W. Cook

The conventional cyclic system of deep-level mining by drilling and blasting gives rise to an inadequate degree of stope sorting when mining thin reefs. This results in poor utilization of the capital facilities of a mine in the form of shafts, haulages, airways, and associated equipment. Continuous and controlled removal of the thin gold-bearing portion of the reefs would permit better stope sorting and hence greater utilization of capital facilities. Results of experiments to develop hard-rock cutting machines for mining are reported and the benefits which could be derived from their use are discussed. Mining, from exploration through refining, is essentially a process of sorting in which the payable mineral, or metal, is progressively separated from the other constituents of the earth's crust with which it was originally associated. This takes place more distinctly at each step of the operation. What is it that determines the degree to which sorting should be carried out at each of the several steps comprising a whole mining operation? The formal answer is that degree of sorting at each step which results in the lowest overall cost for the complete separation. In practice, individual steps are chosen from those available in current technology, each of which effects a degree of sorting such that the quantity of material which must be sorted in the succeeding step is economically acceptable. It follows that any new technological development has repercussions throughout the whole mining operation and, more important, that the solution to excessive costs in any one step of the operation may lie not in improving the costly operation itself so much as in increasing the degree of sorting preceeding that operation. This concept, particularly in relation to deep-level mining of thin, tabular gold-bearing reefs in South Africa, is discussed here, and the most recent results achieved in the development of hard-rock cutting machines for stoping more selectively than is possible with explosives are presented. Deep-Level Mining Deep-level mining involves operations which are either not encountered, or are of only trivial importance, in near-surface mining. Near-surface, the major operations are those of rock breaking, transport, and milling. In deep-level mining, hoisting, environmental control, and strata control assume major importance. Some idea of the relative magnitude of these operations may be gained by comparing the separate amounts of energy which are required, or which must be controlled, to effect the various operations when, say, mining a tabular deposit 40 in. thick at 8000 ft below surface, Table 1. It is true that the costs of handling a given quantity of energy are not the same for each operation. Nevertheless, Table 1 does emphasize the fact that the operations of hoisting, strata control, and environmental control are of unique and major significance in deep-level mining. In particular, hoisting and environmental control place a heavy load on the reticulation system of the mine—the shafts, haulages, and airways. Typically, a new, deep gold mine with an annual revenue of about $35 million requires a total capital expenditure of about $140 million of which some $100 million is invested in developing and equipping this reticulation system. The ratio between annual turnover and capital invested of about one-quarter is exceptionally low, and it typifies the poor utilization of capital by the current technology of mining hard rock at depth. The average thickness of the reefs in the new South African goldfields varies from 10 to 30 in.,l and even in the thicker reefs the gold is often confined within a small fraction of the nominal thickness. Nevertheless, it is universal practice to mine these reefs at a stope width of about 40 in. or more, so that the quantity of rock broken in the stopes and hoisted out of the mine is between two and ten times the quantity of rock actually carrying a significant amount of gold. The reason for the adoption of such excessive stope widths is to be found in the method of rock breaking by drilling and blasting. The only free surface to which a blast hole can break is the stope face. It follows2 that each hole cannot have a burden in excess of the height of the free face if it is to break satisfactorily. To

Jan 1, 1971

By J. L. Huitt, S. R. Darin

The use of a partial monolayer of propping agent to obtain a high flow capacity for a hydraulically induced fracture is discussed. From the results of laboratory work it was shown that a modified form of the Kozeny-Carman relation could be used to describe the flow in the partial monolayer propped fracture. With equations presented in the paper, the density pattern of the propping agent (number of particles per unit of fracture surface) that results in the maximum flow capacity for the fracture can be determined. The maxitnum flow capacity obtained with a partial monolayer is often an order of magnitude greater than the flow capacity obtained in greater width fractures containing multilayers of the propping agent. INTRODUCTION One of the predominant factors controlling the success of a hydraulic fracturing operation is the propping of the fracture. The trend in hydraulic fracturing recently has been an increase in the ratio of propping agent-to-fluid. The primary purpose of this increased ratio is to sustain a propped fracture of greater width. It was shown in a recent study' that for some formations low concentrations of propping agent would result in "closing" or "healing" of the fracture. In some cases, in an effort to insure sufficient propping agent concentration, the fracturing operation is designed to obtain a pack of the propping agent in the fracture. The placing of a pack of propping agent in the fracture provides a fracture of maximum width; however, the width alone does not control the flow capacity of the fracture. The flow capacity is dependent on the permeability of the fracture, as well as the fracture width. Thus, increasing the permeability to obtain larger flow capacities is as important as obtaining a greater width fracture. By increasing the concentration and particle diameter of the propping agent, fractures of sufficient flow capacities are obtainable for effective well stimulation in a number of formations. However, in some of the recovery techniques, the fracture capacity obtained by commonly used practices in fracturing is inadequate. One such recovery technique is gravity drainage via a horizontal fracture placed near the base of the productive zone. For this recovery technique, the fracture capacity desired is usually one to two orders of magnitude greater than the fracture capacity normally obtained in fractures propped with the size of sand commonly used (20-40 mesh). By the use of particles of larger diameter, the permeability of a pack2 is increased; however, even a multilayer pack results in a fracture flow capacity lower than that desired for some formations. For example, a fracture of 1/4-in. width, packed with 8-12 mesh sand of about 2,000 darcies permeability, would result in a fracture flow capacity (permeability X fracture width) of only 40,000 md-ft. If the fracture flow capacity needed is an order of magnitude greater than that cited in the example, an approach different from the formation of a pack in the fracture is needed. One approach is a partial monolayer of large-diameter propping agent. In working with this type of fracture system, it was found that the flow problems were unique to the system; therefore, the study discussed in this paper was made. THEORY AND RELATED STUDIES Previous studies, although related to that described in this paper, have not pertained directly to the flow in a fracture propped with a partial monolayer of propping agent. However, studies such as flow between parallel plates,' flow in packed columns,' fracture flow capacity' and flow in simulated fractures reduce the scope of this flow problem considerably. A fracture propped with a partial monolayer of dropping agent may be considered to be between two extremes — between an open fracture and a bed of particles packed In a conduit of fracture geometry. Thus, it seems appropriate to review the extreme cases.

By L. G. Truby

DISCUSSION By Rhrt G. Nisle, Phillips Petroleum Co., Barthesville, Okla. The subject paper presents the results of a reservoir behavior analyzer study of the pressure-production performance of five Ellenburger pools in West Texas. These five pools are Wheeler, TXL, Andector, Embar, and Martin. This laboratory has also made reservoir behavior analyzer studies in this area and arrived at substantially the same conclusions. Although the principal results of the studies made in this laboratory are confirmed by the results in the subject paper, there are certain points of difference. The points of difference are (1) the subject paper includes the Martin pool in the common aquifer, whereas our studies indicate that it is not, and (2) the subject paper concludes that the effective aquifer is considerably smaller than that derived from studies made in this laboratory. In terms of reservoir analyzer data, our rejection of Martin is based on the inability to obtain a satisfactory match of the pressure curve when Martin is considered as lying within the common aquifer. A satisfactory match was possible, however, when Martin was run as an isolated pool. This indicates that the pressure disturbance resulting from production at Martin had not reached Embar, Andector, TXL, or Wheeler at the time of our study. A similar situation exists relative to Dollarhide. In tern of geological data, our rejection of Martin is based on the presence of a faulted zone between Martin and Embar. This condition is indicated in Fig. 4 and again in Fig. 10 of the subject report. If a permeable connection between Martin and the other fields does exist, it is probably by way of a detour around this fault. The second point of difference between the two studies is illustrated by a comparison of Fig. 4 of the subject paper with Eg. A. Fig. A is obtained from an internal report on one of the studies made by this laboratory. It will be noted that the area indicated in Fig. 4 is roughly that marked "Pool Unit" in Fig. A. The additional portion of the aquifer shown in Fig. A was simulated on the reservoir analyzer by means of the water drive network. A satisfactory pressure match could not be obtained without this additional network. The differences involved here stem from a more fundamental consideration concerning reservoir analyzer operating techniques. The true source of these differences in reported results cannot at this time be determined because of the incompleteness of the subject paper. It is not stated, for instance, whether the pressure match was induced by altering the field resistance or the field capacitance, or both. Changing analyzer

Jan 1, 1953

By W. F. Hosford

A quantitative explanation is offered for the peculiar curled grain shapes found in the microstructures of drawn wires of bcc metals and compressed aluminum specimens. It is shown that once an [011] fiber texture is developed, the slip system are so oriented that further slip tends to produce plane strain rather than axially symmetric flow of individual grains. With plane -strain flow, however, compatibility of neighboring grains can be maintained only by a bending of grains about one another. PROBABLY the most obvious microstructural feature of heavily worked metals is the distorted shapes of grains. In the course of deformation, the shape change of each grain must be compatible with that of neighboring grains; otherwise holes would be formed at grain boundaries. In analyses of poly-crystalline deformation by Taylor and subsequent workers it was assumed that grain boundary compatability was maintained by each grain undergoing the same shape change as the polycrystalline aggregate in which it is imbedded. According to this assumption, when simple tension or compression is applied to a random polycrystal or to one with a fiber texture, each grain ought to deform with axially symmetric flow. Initially equiaxed grains should become cigar-shaped during wire drawing and pancake-shaped during compression. While microstructural observations of deformed metals are generally in accord with such a picture, certain striking exceptions may be noted. Peck and Thomas5'8 found that grains in heavily drawn tungsten, iron, and niobium (columbium) wires become shaped like ribbons curled about the wire axis, Fig. 1. At a suggestion from the author, they rationalized the development of these micro-structures by considering the orientation of the slip systems in the [011] texture formed by the wire drawing. It is shown in this paper that marked departure from axially symmetric flow of grains is also observed when polycrystalline aluminum is severely compressed. Again the explanation must lie in the orientation of the slip system in the [011] texture, which is formed in fcc metals by compression.' THEORY A simple quantitative argument will be presented to show that the development of these microstructures is a result of flow on the combination of slip systems for which the minimum amount of mechanical work is expended in producing a unit tensile (or compressive) strain. First it must be realized that the macroscopic strains of a crystal resulting from slip are given by: where d dy, and dc, are normal strain increments parallel to the x, y, and z reference axes; are crystallographic shear-strain increments on slip systems

Jan 1, 1964

By G. U. Greene

The various lead producers have given the subject of lead drosses much attention in recent years but the problem of their economical treatment is yet to be solved. Formerly the copper in the furnace feed was removed from the furnace in the form of matte. The speiss at that time consisted principally of the iron arsenide. The practice today is to roast off most of the sulphur and the copper in the feed forms a dross in the furnace, which is removed from the furnace with the lead. This material is poured into the drossing kettles and allowed to cool down to but slightly above the freezing point of lead. The copper dross, containing almost all of the arsenic and part of the antimony, is skimmed off and treated in a small reverberatory furnace at most plants. This is essentially a liquation process. The skimmed dross contains from 70 to 80 per cent lead, and much of this lead is liquated out. The products from this treatment are: (1) impure lead, (2) speiss and (3) matte. The speiss from the reverberatory furnace was studied in this research. The literature on the subject is of very little assistance, as almost no work has been done on the problem of establishing the exact identity of the various phases present. One author(1)† states that speiss consists of a series of isomorphous compounds of the general formula FexAsy in which the Fe may be replaced by Ni, Co, Cu, Pb, Ag, Au, Pt, Zn, Cd and the As replaced by Sb, S and Bi. Hofman(2) states that the iron arsenide present is Fe5As. Experimental Work In the present research, the author used for methods in an attempt to determine the composition of the various phases: (1) chemical, (2) microscopic, (3) roentgenographic and (4) thermal. Previous to this research, considerable time had been spent making analyses of different speisses, but unfortunately no very definite conclusions could be made as a result of these analyses.

Jan 1, 1937

By W. R. Strickler, P. Hazebroek, M. Prats

The pressure and production behavior of a homogeneous cylindrical reservoir producing a single fluid through a centrally located vertical fracture of limited lateral extent was determined by using mathematical methods to solve the appropriate differential equation. It is assumed that there is no pressure drop within the fracture — that is, that the fracture capacity is infinite. It was found that the production-rate decline of such a reservoir is constant (except for very early times) when the flowing bottom-hole pressure remains constant. The production-rate decline increases as the fracture length increases. Thus, the lateral extent of fractures can be determined from the production-rate declines before and after fracturing or from the decline rate after fracturing when the properties of the formation and fluids are known. The production behavior over most of the productive life of such a fractured reservoir can be represented by an equivalent radial-flow reservoir of equal volume. The effective well radius of this equivalent reservoir is equal to one-fourth the total fracture length (within 7 per cent); the outer radius of this equivalent reservoir is very nearly equal (within 3.5 per cent) to that of the drainage radius of the fractured well. The effective well radius of a reservoir producing at semisteady state is also very nearly equal to one-fourth the total fracture length. It thus appears that the behavior of vertically fractured reservoirs can be interpreted in terms of simple radial-flow reservoirs of large wellbore. INTRODUCTION An earlier report1 has considered the effect of a vertical fracture on a reservoir producing an incompressible fluid. That investigation of the fractured reservoir producing an incompressible fluid was started because of its simplicity. Thus, pertinent behavior of fractured reservoirs was obtained at an early date, while experience was being gained of value in the solution of more complicated fracture problems. One of these more complicated problems, and the one discussed in this report, considers the effect of a compressible fluid (instead of incompressible fluids) on the production behavior of a fractured reservoir. In the incompressible-fluid work mentioned, it was shown that the production rate after fracturing could be described exactly by an effective well radius equal to one-fourth the fracture length whenever the pressure drop in the fracture was negligible. Because of the simplification in interpretation, it is a matter of much interest to determine whether the production behavior of reservoirs producing a compressible liquid could be described in terms of an effective well radius which remains essentially constant over the producing life of the field. The details of the mathematical investigation are given in the Appendixes. IDEALIZATION AND DESCRIPTION OF THE FRACTURED SYSTEM It is assumed that a horizontal oil-producing layer of constant thickness and of uniform porosity and permeability is bounded above and below by impermeable strata. The reservoir has an impermeable circular cylindrical outer boundary of radius re. The fracture system is represented by a single, plane, vertical fracture of limited radial extent, bounded by the impermeable matrix above and below the producing layer (reservoir). It is assumed that there is no pressure drop in the fracture due to fluid flow. Fig. 1 indicates the general three-dimensional geometry of the fractured reservoir just described. When gravity effects are neglected, the flow behavior in the reservoir is independent of the vertical position in the oil sand. Thus, the flow behavior in the fractured reservoir is described by the two-dimensional flow behavior in a horizontal cross-section of the reservoir, such as the one shown in Fig. 2. Production is due to the expan-

By Alan D. Randolph

INTRODUCTION The production of fines is an unwanted side-effect in most crystallization processes. The definition of “fines" is relative to the size of the desired product and varies from <30 mesh for coarse KC1 fertilizers to subsieve organic material produced by salting-out pro- cesses. Sometimes a well-developed fines distribution is necessary in the production of large crystals, e.g. the fines removal stream from a potash crystallizer. The production of fines is usually not desired in a crystallization separation step. However, product purity can either improve or degenerate with a decrease in crystal size depending on the relative importance of product washing vs mother liquor occlusions in determining over-all purity. Typically, both washing efficiency and mother liquor occlusions decrease with decreasing particle size. Fine crystal distributions have historically been difficult to measure and categorize; however this situation is changing rapidly with the use of electronic particle counters of the electrical zone- sensing or light scattering type. In fact, fine-crystal measurement is perhaps the key to better understanding and control of coarse- crystal crystallization processes. The fine-crystal distribution carries much useful information from which nucleation and growth rates can be inferred. The purpose of this paper is to briefly discuss a few crystallization processes in which production and/or measurement of fines is important and to categorize the process conditions which yield a fine- crystal product.

Jan 1, 1980

By James A. Beck

Phosphorus is essential to all life processes and therefore to the existence of man. In this role, there are no substitutes for phosphorus. In a commercial sense, phosphorus and its compounds are important to our entire economy, both in agricultural and in nonagricultural applications. The world&apos;s phosphate requirements are met by mining phosphate rock. Two general types of phosphate ore deposits are commercially important-igneous and sedimentary. Igneous deposits generally are more difficult and more expensive to mine than sedimentary deposits and are of importance mainly in the USSR, North Vietnam, and South Africa. Approximately 15% of current world production comes from these deposits. Over 80% of world production is from the pellet sedimentary deposits of Florida, North Africa, and elsewhere. Guano, the second type of sedimentary deposit, is produced in South America but is declining in world importance. Production Production of phosphate rock was reported in 31 countries during 1972. However, about 80% of world output is produced in three countries: the United States, the USSR, and Morocco (Table 15.2A.1). Throughout the past 20 years, between 75% and 80% of world output has been produced by these three leading countries. Between 1948 and 1972 world production increased at an average rate of 10% per year, from 21.5 to 103.9 million tons. Growth was quite steady at 6% per year through 1963, but in the 5 years from 1963 to 1968 production increased 11 1/2% per year. Since 1968 production has increased about 91/2 % annually. Since 1948 several new phosphate mining ventures have been developed in Senegal, Togo, Israel, and North Vietnam. In the same period, only one important phosphate deposit, on Makatea Island, has been mined out and closed. A number of other phosphate mining ventures are in various stages of planning and development. The most important new venture in phosphate mining is in the Spanish Sahara. New mining capacity is expected also in Syria, and serious investigation is in progress in Peru, India, Turkey, and Australia. Major expansion of existing operations is expected in Morocco, Russia, Tunisia, Israel, and Jordan. Consumption Historical data on world consumption of phosphate rock are not available in detail, but world consumption of phosphate has closely paralleled world production in the past two decades. The United States is the world&apos;s largest user of phosphate rock, accounting for 30%

Jan 1, 1976

By Glenn C. Waterman

THE diamond drill is a very important tool in exploration and development testing and its use is increasing. In almost all cases results of diamond drilling are analyzed on the basis of grade and tons. A proper evaluation of core and sludge assays is important if drilling results are to be acceptable as a basis for geologic and engineering appraisal. The relatively wide variation in assay averages as calculated by various well-known combining methods indicates that the engineering choice of a method may affect the outcome of the drilling in terms of ore and waste. The problem of combining assay results from core and sludge samples has been discussed many times in conference and in the literature.&apos;" Most writers agree that the field of disagreement in methods is large and that the engineer on the job must consider features unique to his drilling, pick one of several combining methods, and depart from the rules when abnormal results come in. All the discussion to date can be summed up by the admission that as yet there is no fairly simple, generally acceptable combining method that is practicable over a wide range of drilling conditions, ground conditions, and ore occurrence.

Jan 1, 1955

By B. Ladanyi, G. Archambault

It is generally recognized to date that a rational stability analysis of slopes and foundations in rock masses is a desirable but still rather remote goal of rock mechanics.1 In principle, a slope analysis is possible provided the original state of effective stress in the ground is known and the shear strength of the earth material can be clearly defined. In a macroscopically continuous earth medium such as soil, the two basic ingredients of the stability analysis in most cases can be assessed with sufficient approximation. A much less favorable situation exists when the slope is composed of a macroscopically discontinuous medium such as rock mass containing one or more sets of geological planar structures. In such a case, both the original effective stresses and the overall shear strength of the mass are much more difficult to determine. As for the former, it is only recently that certain calculation methods and solutions concerning the stress distribution2 and the seepage forces3 in a discontinuous medium have been proposed. As the strength behavior of the rock mass is concerned, much valuable effort has been made in recent years toward reaching a proper understanding of the phenomenon of rock mass failure under stress. Probably one of the most complete investigations of the problem to date has recently been made at the University of Illinois. The study resulted in establishing a first useful working hypothesis of the shear behavior of a regularly jointed rock mass, proposed by Patton in 1966.4 The main purpose of the work described in this chapter is to establish a more general framework for the shear behavior of rock mass, one that would be directly related to some basic rock parameters and would also

Jan 1, 1970

C. M. Bishop (Aircraft Div., A. V. Roe Cnnada Ltd., Toronto)—Reference is made to the coherency hardening of ß due to ß&apos; and also to the hardening of ß due to a coherent precipitation of the a phase. What is meant by the term "ß&apos;?" Would not the coherency hardening of ß during cooling be due to precipitation of a sub-microscopic dispersion of a, as is the case during reheating a ß-quenched alloy? I feel that these two phenomena are essentially the same mechanism, i.e., precipitation of a from unstable or supersaturated ß. From the text, it would appear that Tables III and IV are intended to show the effect of the martensite transformation on the properties of Ti-Mn alloys. Referring to Table 111, the ß-quenched alloys would contain a greater proportion of retained ß than would the equilibrated alloy. Could not the increase in properties be attributed to this, along with possible coherency hardening of the ß? In the same way, the structures referred to in Table IV contain ß from which they could derive their hardness. It would appear to be difficult, if not impossible, to assess the role of the martensite transformation from the data contained in these tables. F. C. Holden, H. R. Ogden, and R. I. Jaffee (authors&apos; reply)—In reply to the first question raised by Mr. Bishop, the term "ß"&apos; designates an apparent retained-p structure which is harder than it is after the most rapid cooling from the ß field. It is thought to be the result of a coherent precipitation of a. The mechanism by which hardening takes place is undoubtedly the same as that involved in the early stages of aging of a re-tained-p structure, and we are in agreement with Mr. Bishop on this point. The term "ß&apos;" to designate the anomalously hard retained-ß structure was agreed upon at a symposium in 1953." The authors do not agree that the quantity of retained ß and/or ß&apos; in the ß-quenched specimens of Table III is necessarily greater than that of the 600°C equilibrated specimens. The ß-quenched specimen has a structure which appears to be completely a&apos; formed by the martensite reaction. It is recognized that there could be some retained ß (or ß&apos;) between the a plates if the M, temperature is below room temperature. This is unlikely for the 3.4 pct Mn alloy where the M, is known to be at about 640°C. Therefore, the increase in strength cannot be attributed to the presence of a greater quantity of coherency-hardened ß, but, rather, the increase in strength must be attributed to the transformation products formed, e.g., a&apos; (martensiti-cally formed a). Concerning the data in Table IV, we agree that it is difficult to estimate the role of the martensite reaction, since the 6.4 pct Mn alloy was retained ß in the quenched condition.

Jan 1, 1955

By R. V. Wheeler, F. V. Tideswell

The suggestion, which appears to find increasing favor, that the elementary composition of coals should be used as the basis of their classification, makes it important that our methods of expressing this elementary composition should be refined. It is doubtful whether many published ultimate analyses of coals are accurate within 1 per cent. carbon. Many are probably as much as 3 or 2 per cent. in error in carbon. It is, perhaps, not always realized that the extreme variation in carbon content over the range of bituminous coals is but 16 per cent. An error of 1 per cent. in carbon on analysis corresponds therefore with one-sixteenth of the whole range, an amount which is unjustifiable even for the application to commercial needs of a system of classification based on ultimate analysis. For the purposes of scientific research such limited accuracy is of little value. The object of this paper is to examine one important source of error in ultimate analysis, that due to the occurrence in coal of inorganic material, and to emphasize the need for the quantitative measurements (of carbon more particularly) on coals to be rendered independent of their contents of such material. Adventitious Mineral Matter When a determination of calorific value, for example, is made upon a coal, it is customary to correct the measured value with respect to the ash left by the coal on incineration, recording the result as being on an "ash-free basis." It is desirable, before discussing the adequacy of the correction thus made, to demonstrate its validity, which turns on whether the ash is present as an adventitious impurity in the coal and forms no part of the coal substance itself. The inorganic matter associated with coal has originated in several ways1: 1. The "inherent" inorganic materials, occurring as constituents of the plants from which the coal-forming deposits were derived.

Jan 1, 1928

By A. J. Langhammer

A. J. Langhammer.—That is rather asking a question of the wrong man. However, I will reply to the question from our point of view. There is a considerable amount of iron powder available but the properties vary over a wide range. Powder metallurgy has progressed to the stage where we recognize certain requirements in powdered iron, and what may be a good powdered iron for one application will not necessarily fit the picture for the next one. Further, I believe that there is room for great improvement in the properties of powdered iron. Also, that there is only a limited quantity of powdered iron available having certain specific properties in which we are at the moment interested. F. P. Peters.—May I have a word? With all possible respect to the contributions of the Chrysler Corporation (and they have been tremendous) to the war effort, I think it is easy to get from part of Mr. Langhammer&apos;s discussion a false impression of vaster possibilities than really exist. It would be well if in addition to Mr. Langhammer some other manufacturers of machine parts&apos; might tell us in the next few minutes some of the limitations they have found. For example, what is the maximum tensile strength that is being produced in a commercial part in production today? And what is the actual size limitation on bearings that are in operation and are standing up well? We should always bear in mind the fact—and I think Mr. Langhammer will agree with me— that quoting on a particular part does not necessarily mean placing it in production. In many cases it may be several months before the quotation is resolved and we know whether the part can be made. Let us open up this thing for a little free-for-all discussion of some of the ceilings that do exist in the design of machine parts made by powder metallurgy. The ceiling is not unlimited, and Mr. Langhsmmer will agree with that, 3 am sure. H. Hendriks.*—I do not think that there is so much limitation in the making of powder metallurgic manufactured parts as mentioned. Last year we had the problem of making dies for a special machine used in the manufacturing of slide fasteners. This part was wearing out very fast. It was very hard to make, it had to be hobbed out of a special steel and it was a difficult thing to manufacture in general. The tolerances were one half of one thousandth of one inch on all dimensions. We submitted this die to a manufacturer of powder-metal parts. He thought that it was impossible, but we were not as skeptical as he was and decided to try it anyway. The Canadian General Electric Carboloy Division, in Toronto, gave us then the design for the dies, which we made to their specifications. When the first part was delivered, we submitted it to our Inspection Department and its check showed that all the tolerances were right on the dot. They delivered I9 parts of exact specification, then they went off the beam; they could not keep to the tolerances. It took them a long time to get back again. We do not know what happened, but the main point I want to&apos; make is that if a problem is attacked in the right may, the dies are made right and corrected as to dimensions found out by experiment, I do not think that there is so much diffculty in making powder-metal parts to close tolerances.

Jan 1, 1945

By James O. Elton

This paper covers, besides laboratory work, a study of actual operation at the Washoe Smelter over a considerable period of time, together with the results of a visit to the Midvale plant of the United States Smelting & Refining Co., near Salt Lake. For the latter privilege, as well as permission to publish the resulting data herein given, I am indebted to George W. Heintz, General Manager of the Midvale plant, and here take pleasure in expressing my appreciation for the many courtesies extended to me by Mr. Heintz and members of the technical staff at the smelter. Almost all of the world&apos;s supply of arsenic is recovered as a byproduct in the smelting of other metals. It is seen &apos;on the market in various forms, the most common being arsenic trioxide, the " white arsenic " of commerce, which is sold as a heavy white powder, or in white, glassy, translucent masses. The trioxide is used in the manufacture of pigment, glass, and insecticides. About 50 per cent. of the domestic consumption is supplied by imports. Statistics of Arsenic Trioxide in United States.&apos; Production. Consumption. Price Per Pound. Year. Tons. Tons. Cents. 1907..........1.010 5.471 5 1908,.........1,302 6,098 33/4 1909,.........1,007 4,600 2 7/8 1910,.........1,526 5,428 2 1/2 1911,.........3,081 6,539 2 1912,2........ 2,926 Closed at 4 7/8 Arsenic occurs in combitlation with sulphur and the metals in a large number of minerals. It is present in small amounts in many ores. In the roasting and smelting furnaces many of its compounds break down, liberating arsenic trioxide, which is volatilized and carried by the gases into the flue system, where a part is condensed and settles with the flue dust.

Jan 1, 1914