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By Herbert Clark Hoover, Lou Henry Hoover

THE third book has explained the various and manifold varieties of veins and stringers. This fourth book will deal with mining areas and the method of delimiting them, and will then pass on to the officials who are connected with mining affairs'. Now the miner, if the vein he has uncovered is to his liking, first of all goes to the Bergmeister to request to be granted a right to mine, this official's special function and office being to adjudicate in respect of the mines. And so to the first man who has discovered the vein the Bergmeister awards the head meer, and to others the remaining meers, in the order in which each makes his application. The size of a meer is measured by fathoms, which for miners are reckoned at six feet each. The length, in fact, is that of a man's extended arms and hands measured across his chest ; but different peoples assign to it different lengths,

Jan 1, 1950

[Murray and Renard: chondres on ocean floor, XLI, [155]. Musconetcong Iron Works, Stanhope, N. J., blnst furnace, XL, 467. MUSSEN, H. W.: Discussion on The Bogoslovsk Mining Estate, XXXIX, 897. death, XLIII, [Ixxvi]. Muzo, CoIombia: emerald deposits, LV, 910. emerald mine, XXXIX, 317. minerals, LV, 925.]

Jan 1, 1918

By D. C. Hilty, W. Crafts

J. Chipman—It has been my privilege to discuss this work with the authors on several occasions and to observe at first hand the experimental methods employed. I wish, therefore, to emphasize certain points which they have mentioned only briefly with regard to the experimental techniques. The rotating induction furnace as here employed interposes liquid metal between slag and refractory thus preventing the two nonmetallic parts of the system from reaching equilibrium with one another. It is therefore impossible for the metallic phase to be completely in equilibrium with both the slag and the crucible. The metal also acts as a partially permeable membrane allowing certain components, including oxygen, to diffuse from slag to crucible. This transfer results in building up on the face of the crucible a layer of material whose composition is in part dependent on that of the bath. Reactions between the layer and the solid refractory are slow, as evidenced by the rather good life of the crucible. Hence it seems probable that the layer is more nearly in equilibrium with the metal than with the underlying crucible material and that, once it is established under a bath of a given composition, its further reactions with that bath are slow. Additions to slag or bath may be followed by changes in the layer; and time must be allowed for virtual completion of such changes, before it can be assumed that slag and metal are in equilibrium. We may judge from the results reported that, in general, this was the case and that the data represent at least quite close approximations to slag-metal equilibrium. Data on deoxidation and on oxygen solubility are no better than the analytical methods employed. The vacuum fusion method as used by the authors seems entirely adequate for the samples analyzed. I have had frequent occasion to compare results with their laboratory, always with very satisfactory agreement. The determination of aluminum at very low concentrations is perhaps an even more difficult procedure. Here also the colorimetric method used has been worked out with great care and is undoubtedly the most dependable method available. The discrepancy between observed and calculated deoxidation or solubility lines is not to be explained as the result of experimental errors, either in the sampling or analysis of the metal. Nor is it to be blamed upon inaccuracies in the several kinds of indirect data upon which the calculated results were based. It is true that both the observed and the calculated lines admit of some uncertainty as to their exact locations, but the uncertainties are small compared to the wide gap which separates the two lines. The authors have pointed out the real cause of the discrepancy. In all of their experiments the solid phase was not Al2O3 but a mixed oxide containing iron and aluminum. This suggests an extension of the calculated values to include equilibrium with the spinel FeO . A12O3. The free energies of FeO and A12O3 are known, that of the spinel is not. However, it cannot differ greatly from that of its component oxides for even in the more stable spinel, chromite, the free energy of formation from the oxides is less than 10,000 cal. For purposes of calculation we shall call this free energy X and solve for values of X lying between zero and 10,000 cal. The other data required are taken from the forthcoming revision of "Basic Open Hearth Steelmaking" and are given in the following equations in which underlined symbols indicate elements dissolved in liquid steel and the standard concentrations are 1 pct. ?F° at 1600°C, cal ?LA = 2 Al + 3 O; + 107,200 FeO = Fe + 0; + 5,460 FeO + A12O3 = Fe + 2A1 + 4 0; + 112,660 — X The corresponding equilibrium concentrations are shown in fig. 21. The line marked A12O3 corresponds to the first equation, those marked FeO . AL2O3 correspond to the last, with X = 0, 5000 and 10,000 cal, respectively. The two upper lines represent the data of Hilty and Crafts and of Wentrup and Hieber. The points are the observations of Hilty and Crafts in the presence of 0.50 pct Mn.

Jan 1, 1951

By Joseph B. Perry, G. M. Kirwan

MAGNESITE is found in 22 California counties, but many of the deposits are too small or too impure to be of commercial value. Several of substantial size and quality were entirely exhausted by wartime operation. At present, three properties comprise the only known workable deposits in the state. Of these, the Western mine and the Patterson mine have been known and worked for many years, and have been described in considerable detail in various publications, therefore need only brief mention here, because of their proximity to the Bald Eagle mine. The latter, recently developed, is unusual in type of ore deposit, plant design and operation, as well as products made, and very little has been written concerning it. WESTERN MINE The Western mine, 32 miles south of Livermore, Calif., was formerly operated by C. S. Maltby. It has been a consistent producer for many years.1 The ore is of amorphous variety, occurring along fracture zones in serpentine. The veins vary greatly in width, the average being perhaps 8 ft., with the maximum indicated in one early stope of 40 ft.; 2 ft. is considered the minimum for economical mining. The strike of the veins is predominantly north and south, with dip to the west varying from 40º to 75 º. Walls are well defined and as a rule firm and easily supported. Veins range in length from a few hundred feet to 1000 or more. Their maximum vertical extent is about 350 ft., but many run less. Early mining consisted of open-cut and glory-hole work on the larger outcrops. This was followed underground by a modified shrinkage system, the waste and low-grade horses being removed by hand sorting on the tramming levels and transported to surface dumps. Filled-stope mining is used now, in order to eliminate the handling of waste, which has

Jan 1, 1938

By M. R. Geer, J. D. Davis, H. F. Yancey

ALTHOUGH the mechanical cleaning of coal is carried out at plants on the surface, preparation is actually begun at the face in the mine. Here the character of the coal and the amount, character, and distribution of the impurities within the bed may be seen. Blasting methods, dust-allaying procedures, location of mining cut with respect to bands of impurity, and the practice of discarding segregated impurities underground, all have an important bearing on the successful operation of surface cleaning units. The most important single characteristic of both coal and its asso¬ciated impurities from the standpoint of cleaning is specific gravity. Other characteristics related in one way or another to the preparation of coal are rank, petrographic composition, structure and hardness, and friability. These and still other coal properties are discussed in the first section of this chapter and impurity characteristics in the second. COAL CHARACTERISTICS RELATED TO PREPARATION Rank As a result of work done over a period of several years by committees of the American Society for Testing Materials and the American Standards Association, standard specifications are now available showing the classification of coals according to rank and quality of grade.' The term "rank" expresses the degree to which the original coal-forming material has been changed by metamorphism through successive stages from peat to anthracite. Table 1 shows the classification of coals according to rank as devised by the committees of the organizations mentioned. The basic scheme of classification for the higher-rank coals is according to

Jan 1, 1943

By F. O. Blackwell

It is roughly estimated that some three hundred companies in the United States engaged in mining and the kindred arts now employ electricity in their operations. As all these plants have been installed within the last few years, it is evident that mining engineers have been quick to appreciate the great advantages of the use of electricity and adopt it for their many requirements. In

Jan 1, 1894

By Arthur G. Levy, Henry M. Howe

$1. Introduction.—Any given piece of metal is made up of a very great number of grains, usually microscopic, each of which is a perfect crystal save only in outward form, with cleavage planes of low cohesion, geometrically arranged quite as in fie familiar non-metallic crystals. The plastic deformation of such a mass occurs chiefly through the slipping of the crystalline blocks of which each grain is composed along these cleavage planes, causing steps called slip bands to form on a previously polished surface. In this slip, the metal immediately adjoining each of the cleavage planes along which the slip takes place is thought to pass extremely rapidly through a very mobile state into the amorphous state, in which it is harder than the remaining still crystalline metal between the amorphous layers thus formed along the slip planes. Whether the slip planes below the surface in ferrite can be detected by cutting, polishing, and etching sections is in dispute; but if this detection is possible at all, it is usually made impossible by heating the metal even gently. In short, the change along the slip planes does not persist through heating, and it is thought not to persist through time even at the room temperature, nearly all the amorphous metal recrystallizing. The network in Fig. 22 and the parallel N.-70-E. lines in Fig. 21 are slip bands in copper. When plastically deformed metal is heated, certain parts of certain grains may twin, that is, their component crystalline units may rotate into a position, or more exactly into an orientation, symmetrical with the initial orientation and hence with that of the remainder of that grain. As seen in a microsection of a metal the twinned areas usually have parallel sides. The existence of twinning is recognized in metallic sections either by the presence of such parallel-sided areas differing in brightness from the adjoining metal, especially when seen under oblique light after etching, or more surely by the zigzagging of the slip bands which form when twinned metal is itself deformed again. Hence the usual procedure in developing twins is to deform plastically so as to cause the twinning tendency; to heat so as to allow the tendency to assert

Jan 1, 1915

By B. H. Caudle, L. H. Silberberg

Reservoir depletion by natural water drive is typified by the movement of water from an aquifer into the adjacent oil-bearing formation. Prior studies of this type 01 water movement have generally neglected the resistance to flow in the aquifer and its effect on the movement of water into the oil bearing zone. A method for designing and operating scaled models of such reservoir systems is presented. Experimental data on a model of an edge-water-drive reservoir are shown and discussed. INTRODUCTION Most petroleum reservoirs derive at least a part of their productive capacity from water influx. This water may be injected from the surface or it may come from an aquifer adjacent to the oil zone. In either case, the reservoir engineer must be able to estimate the advance of the water as a function of either the elapsed time or the fluid produced. This paper describes a type of fluid flow model which includes the effect of viscous and gravitational forces in the reservoir and the surrounding aquifer. Natural water influx can be divided into three general (but widely overlapping) categories according to the direction of flow in the aquifer. These are shown schematically in Fig. 1. Fig. l(a) illustrates an edge-water-drive mechanism. In this case, water advances updip along the stratum but the movement of water is essentially horizontal and very little of the oil is actually underlain by water. The bottom-water drive (Fig. l(b)) is characterized by a thick aquifer underlying the oil zone. The water movement is generally vertical in the aquifer. The third category is illustrated in l(c). Referred to as the "thin oil column", this type of oil accumulation consists of oil over water in a relatively thin stratum. Fluid movement is horizontal in both the oil and water zones, except close to the producing well. One characteristic which all three of these types have in common is that part of the water flow takes place in the water invaded region of the oil reservoir while the remainder of the water flow occurs in the aquifer. The resistance to the flow of water usually will not be the same in these two regions. This occurs because the porous rock normally contains only water in the aquifer, while the water-invaded region always contains microscopic globules of bypassed oil (residual oil) which interfere with the flow of water through the rock. The production history of any type of a water-drive system is a function of two phenomena — where the water goes, and how it displaces the oil in the area invaded by the water. It is usually impractical to study these two phenomena at the same time. In most cases one type of analysis is used to predict the gross movement of water in the reservoir, while a different type of analysis is employed to determine the amount of oil to be recovered from the gross volume contacted by the water. The portion of the oil reservoir which is invaded by water is mainly a function of the resistances to fluid flow in the several parts of the flow system. This gross water influx in the three types of natural water drive typically results in water cusping to the production wells either from the side or from below (water coning). In 1747, Muskat described a greatly simplified mathematical model for predicting the area invaded by water in a bottom-water-drive reservoir.1 This model used the Laplace equation and suitable boundary conditions to describe the isopotentials and streamlines in the flow system. The use of this model assumes that (1) the reservoir rock is homogeneous in nature, (2) the oil and water mobilities are equal, (3) there is no oil flowing in the water invaded region, and (4) external forces — such as gravity — do not affect the flow. This method has been used for both natural water drives and water injection projects. In this, as in most models, the method of images is used to reduce the size of the model necessary to describe the reservoir. The assumption of equal viscosities and permea-

Jan 1, 1966

By Alexander L. Field

This paper contains an account of experimental results obtained in an extensive investigation of steels containing zirconium. There recently appeared' an announcement by F. M. Becket, at whose suggestion and under whose general direction this investigation was made, a statement of the outstanding features of the work and a brief explanation of the factors that led to its inception. It is not possible, in a paper of this character, to record all of the operating and test data collected, which includes the production of more than 350 heats of steel. The difficulty of a complete presentation is increased by the fact that several lines of experimentation are too incomplete to warrant publication of the results at the present time. In addition to the methods of manufacture and test employed in the work, there is described experimental evidence on which are based certain definite conclusions regarding the remarkable effects brought about by the presence in steel of relatively small percentages of zirconium. When added to a molten steel bath, zirconium combines chemically with dissolved oxygen, nitrogen, and sulfur, in the order named, and is capable of neutralizing the embrittling effect of phosphorus in whole or in part; although in the case of phosphorus there is no evidence so far of actual chemical combination. These effects arc not in the nature of suppositions supported by theory, nor is their existence deduced merely on the basis of analytical evidence. In each phase of its relation to or reaction with the four impurities mentioned, zirconium affects beneficiauy the mechanical properties of the steel to which it is added, in a manner which it is one of the purposes of this paper to explain in terms of a tentative working theory.

Jan 1, 1923

By Alexander L. Field

This paper contains an account of experimental results obtained in an extensive investigation of steels containing zirconium. There recently appeared' an announcement by F. M. Becket, at whose suggestion and under whose general direction this investigation was made, a statement of the outstanding features of the work and a brief explanation of the factors that led to its inception. It is not possible, in a paper of this character, to record all of the operating and test data collected, which includes the production of more than 350 heats of steel. The difficulty of a complete presentation is increased by the fact that several lines of experimentation are too incomplete to warrant publication of the results at the present time. In addition to the methods of manufacture and test employed in the work, there is described experimental evidence on which are based certain definite conclusions regarding the remarkable effects brought about by the presence in steel of relatively small percentages of zirconium. When added to a molten steel bath, zirconium combines chemically with dissolved oxygen, nitrogen, and sulfur, in the order named, and is capable of neutralizing the embrittling effect of phosphorus in whole or in part; although in the case of phosphorus there is no evidence so far of actual chemical combination. These effects arc not in the nature of suppositions supported by theory, nor is their existence deduced merely on the basis of analytical evidence. In each phase of its relation to or reaction with the four impurities mentioned, zirconium affects beneficiauy the mechanical properties of the steel to which it is added, in a manner which it is one of the purposes of this paper to explain in terms of a tentative working theory.

Jan 1, 1923

By G. S. Cole, G. F. Bolling

Fluid flow strongly influences ingl structure and the columnar -to-equaaxed transition. Artificial flow patterns siwzilar to the nuturul ones act to induce this transition, while dampening forces act to suppress this transition. It is shown here how simple mechanical forces can be applied to a systerrz in order to induce or slipPvess relative fluid flow and the change both the structure transition and the exact structures obtained. The example used is the effect of slow rotations and oscillations 012 a cooling- ingot (of laboratory scale). The details of rotution and oscillation for various cooling rates, lenlperal~ire gradients, and sizes of ingot are related to other solidzfication variables. THE grain structure of a casting can be changed by altering the fluid motion during solidification. Just how important these changes are depends directly upon the degree to which the fluid motion can be controlled. An early step in understanding the nature and influences of fluid motion was taken by studying natural thermal convection; when a static mechanical device was used to suppress natural flow the result was opposite to that obtained when an electromagnetic device was used to augnlent flow in a pattern similar to the natural one. ''2 Suppression allowed more columnar growth to occur, but "augmented natural convection" brought about an earlier columnar-to-equiaxed transition (CET). Since the solidification of a free ingot must have characteristics somewhere between those displayed during suppression and augmentation, we know that natural convection must influence the CET. Further, since heat transfer in the liquid is always some time-dependent combination of convection and conduction, it can easily be guessed that the temperature gradient in the liquid is the vital factor affecting the CET.1,2 It is obvious that the structure arising from the unadulterated solidification of an ingot, without external influence, is rarely if ever the best possible one. Although the pattern of the natural fluid flow may be considered efficient, the magnitude of the flow and the heat transfer decrease freely from the outset. For a

Jan 1, 1968

By C. W. George, Bruce Chalmers

The authors enumerate the factors which appear, from their observations and practical experience of failure of aircraft components in Great Britain, to be responsible for causing a metal or alloy to fail by stress corrosion. The essential conditions for promoting failure by stress corrosion are: (I) tensile stress at the surface of the component, (either residual or applied), and (2) an attacking medium that may be a solution or a liquid metal. Particular attacking agents are effective only on certain metals. In all instances of stress-corrosion failure experienced, cracking of an intercrystalline form has occurred and examples of such failure in aluminum alloy, steel and copper alloys are described and illustrated. The relation between microstructure and stress corrosion is mentioned and methods of investigating the susceptibility to stress-corrosion failure of metallic materials are described. The precautions to be taken in selecting materials for particular aircraft components and the importance of adequate protection against chemical attack are considered. The authors have given a factual survey of stress corrosion and have made no attempt to advance any scientific explanation of the phenomenon.

Jan 1, 1945

By William Alden

A GREAT landslide occurred on June 23, 1925, in the valley of Gros Ventre River, about 35 miles south of Yellowstone National Park (Fig. 1). The relations of the north-easterly dipping rock formations of the slide scarp and of the dam formed by the slide are shown in the diagrammatic cross-section of the valley (Fig. 2). This generalized section is based on unpublished maps and notes by Eliot Blackwelder, in the files of the U. S. Geological Survey. FIG. 1.-MAP SHOWING SCARP AND DAM (LARGE DOTS) AND LAKE (CROSS-LINED) FORMED BY LANDSLIDE BLOCKING GROS VENTRE RIVER. (Scale 1, in. = 1 mile; contour interval 100 ft. From Grand Teton and Mt. Leidy topographic maps). Heavy rains and melting snow in the Gros Ventre Mountains had saturated clay layers in the Carboniferous strata, which dip toward the valley at angles of 18° to 21°, consequently an enormous mass of rock at the end of the north spur of Sheep Mountain became loosened and, on the afternoon of June 23, slid suddenly down into the valley. Within a few minutes this mass of debris-estimated as 50,000,000 cu. yd.-carrying

Jan 1, 1928

By Nathaniel Arbiter, Chas. H. Behre

Two outstanding factors characterize most undertakings in the mineral industries: (1) mineral deposits are not equally distributed over the earth but are localized by natural processes, and (2) the mineral industries are largely based upon wasting assets. Neither of these factors is invariably true, for a few mineral materials, such as water, are essentially world-wide and others are replaced periodically by processes not unlike crop production. Indeed, with some, such as the salts in the sea, the supply is cyclic in short or long periods, whereas others, like water, though locally or periodically in short supply, are essentially inexhaustible. But to the extent that most minerals are limited to certain areas and are "permanently" consumed, any industry founded upon them, by implication, demands great care in planning for the most effective extraction-the essence of wise and conservative expenditure. Several less unusual yet also truly fundamental factors in the economics of the mineral industry are those involving (1) the various kinds and properties of mineral materials, which influence their use; (2) their geologic and geographic availability; and (3) the 'techniques unique to their discovery, exploration, and utilization. This chapter is designed primarily as a brief background for later ones and as a summary of the several unusual or at least special factors and of their effect upon the economics of the mineral industry. The social and political and especially the economic aspects of the industry are the main subjects of this volume and are dealt with in extended fashion in subsequent chapters. Fundamental Characteristics of Mineral Deposits DEFINITIONS Minerals are naturally occurring compounds of nonliving matter, each technically defined as having ( 1 ) a chemical composition that may vary

Jan 1, 1964

By Charles S. Barrett, Robert F. Mehl, Dana W. Smith

The Widmanstatten figures found in the steels have been long recognized and in some aspects carefully studied,' especially as they occur in cast hypoeutectoid alloys. Aside from the practical importance of the structures obtained in the steels by various heat treatments, a study of the characteristics of these figures is interesting because of the rich opportunity the system affords to obtain new data on the mechanism of segregation from solid solutions. This opportunity is twofold: first, by changing composition within the austenite range the proeutectoid precipitate may be changed from that of ferrite to that of cementite, thus offering the same opportunity for changing the type of precipitate while maintaining the same basic lattice as that afforded by the Cu-Zn alloys;2 and second, the eutectoid inversion leads upon drastic quenching to the formation of martensite, a Widman-statten figure of unique interest from the crystallographic viewpoint, particularly in comparison with those formed on slow cooling.3 We have, therefore, two types of structure to study: that formed on slow cooling of hypoeutectoid and hypereutectoid alloys, and that formed on quenching hypoeutectoid, eutectoid, and hypereutectoid alloys. For each of these types of structure we require the crystallographic plane in the mother austenite along which the precipitate forms (we shall see that the precipitates in these alloys are invariably platelike in form), and also the orientation of the precipitate upon this plane. Some of these

Jan 1, 1933

The regular activities of the Insti¬tute are financed mainly by income derived from members' dues, from advertising in MINING AND METALLURGY, and from the sale of publications to the public. In addition, collateral activities and special projects are financed each year by means of income from endowed funds controlled and administered by the Institute. In the aggregate, the principal sums of these endowments amount to more than $560,000. An active effort is being made to in¬crease the endowment funds of the Institute through a standing committee, of which H. T. Hamilton is chairman; Paul D. Merica, vice-chairman, and of which the other members are: W. H. Aldridge, George D. Barron, Cleveland E. Dodge, John V. M. Dorr, Howard N. Eavenson, D. C. Jackling, Henry Krumb John M. Lovejoy, Harvey D. Mudd and J. V. W. Reynders. This committee feels that there exists a tremendous opportunity for the Institute to be of ever-growing service to the public, to the mineral industries, and to the profession. It welcomes suggestions as to names of men of means who are vitally interested in the mineral industries, and to whom the opportunity to make a contribution or bequest might appeal favorably if presented in the proper light by the committee.

Jan 1, 1943

By W. P. Sykes

SEVEN years ago, Dr. S. L. Hoyt1 presented a masterful discussion of the hard metal carbides and cemented tungsten carbide. His lecture summarized most of the data then available in the field; many of the details relating to the production, properties and structure of cemented tungsten carbide had never been previously published, for, in fact, this information was only then being acquired. During the intervening years, the cemented carbides have assumed a place of real importance in the commercial field, with an ever widening variety of applications due to constant improvement in the control of production technique and the unremitting search for new compositions that might better the performance of the alloys in one or another type of service. The most recent summary of production methods, properties and guides for the successful application of the cemented carbides appears in the 1936 edition of the Metals Handbook. Of necessity, much detailed information relating to structures and physical properties is not included in such a summary, and it is with such details that the present discussion is concerned. STEPS IN PREPARATION While the past 25 years have contributed a valuable store of working knowledge in the field of powder metallurgy, many of the process controls are derived entirely from experience and are not as yet finally explained by a specific physical or chemical phenomenon. For most of the cemented carbides such difficulties are aggravated by our lack of knowledge not only of the complex alloy systems involved, but also by the possible changes in structure and even in composition which may accompany variations in temperature, heating time, and furnace atmospheres. The principal steps in the preparation of these cemented carbide alloys are fairly well known, but to supply a foundation for discussion these steps are briefly outlined as follows: 1. Formation of the metal carbide in the form of powder by heating a mixture of carbon and the metal powder or oxide for several

Jan 1, 1938

Cycle, automatic, in mine hoists, LV, 17. Cylindrical furnaces, repairing partly collapsed, XXXVI, 215-222. Dacite-porphyry, San Jose, Tamaulipas, Mex., percentage composition, XXXVI, 186. DAGGETT, ELLSWORTH: The Extraordinary Faulting at the Berlin Mine, Nev., XXXVIII, [liii], 297. Daiquiri, Cuba: geology, LIII, 3, 43. iron deposits, LIII, 40. Magdalena mine, LIII, 9, 23, 24. mines, bibliography, LIII, 59. situation of mines, LIII, 42. [ ]

Jan 1, 1918

By William E. Ford, Edward Salisbury Dana

THIS Appendix contains a series of tables, more or leas complete, of minerals arranged according to chemical composition or to certain prominent crystallograhic or physical characters. These, it is believed, will be of service not only to the student, but ago to the skilled mineralogist. The type used in the printing of the mineral names indicates their relative importance. Table I is a complete list of the species named in this book arranged fist according to the prominent basic elements which they contain and secondly according to their acid radicals. Table II is of Minerals arranged according to their System of Crystallization The other tablets make no claim to completeness, being limited often to common ah important species. For an exhaustive system of Determinative Tables based particularly upon blowpipe and chemical characters, the student is referred to the work of Professors Brush and Pen- field, mentioned on p. 330.

Jan 1, 1922

By Thomas O. Ziebold, Robert E. Ogilvie

Experimental analysis of diffusion samples covering the entire Cu-Ag-Au system at 725°C has been carried out. Experimental coefficients are computed at twenty-eight points in the lermary system. It is found that the direct coefficienl for copper is nearly independent of the silver, content for 1ow-silver alloys and that the cross coefficient for silver correlates with the ther-nzodynatnic properlies. This lalter observalion leads to the conclusion that the mobililies of copper and gold are nearly equal. Thermodynarmic actiuilies for Cu-Ag-Au were computed from binary data and adjusted to be consistent with neasured tie lines across the two-phase region which extends into the ternary diagram at 725°C. Application of these therknodynarnic calculaliorls to the dijftcsion data terifies the Onsager reciprocal relations to the extent that experimental uncertainlies will allow. It is jound that diffusion neav the critical point of the 1200-phase field in the isothermal section at 725°C causes the composition gradients for copper and silver to approach infinity while the direct and cross coeficients become equal. From the standpoint of experimental Procedures, it has been shown that microanalysis of ternary samples may be carried out using a simple expression for the conversion of X-ray zntensily to composilion. The accuracy of' this method has been demonstrated by the analysis of standard alloys and by the reproducibility of composition determinations using differed X-ray lines. DIFFUSION in a ternary alloy system is basically and significantly different from diffusion in binary alloys. When only two elements are present there is just one independent composition variable, and the diffusion profile of composition vs distance across a sample must change monotonically through all solid solutions bracketed by the terminal alloys. If two-phase regions are stable for compositions between the terminal values, these must appear as planar interfaces in the diffused sample, with the composition profile exhibiting sharp discontinuities. Adding a third element may alter this picture completely. Because of the additional degree of freedom in the composition, we may see composition profiles which do not change monotonically through solid-solution ranges, and stable, nonplanar phase interfaces. Even though two-phase regions may lie between the terminal compositions of a diffusion sample on the constitution diagram, they will not necessarily appear in the diffusion profiles. In binary diffusion only one coefficient is needed to describe the interdiffusion process. From Fick's law this coefficient relates the diffusive flux of one component to its own composition gradient. In ternary diffusion we must allow for cross interaction between the two independent species. By a linear extension of Fick's law we introduce "cross" or "off-diagonal" diffusion coefficients which relate the flux of one component to the composition gradient of the other independent constituent. Thus, we require four interdiffusion coefficients to describe the transport process in a ternary system. In its most general form,1,2 the rate equation for mass transport by isothermal diffusion in a system of s components states that the diffusive flux of component i, Ji, is a linear summation of all driving forces, Xk, each force being multiplied by an appropriate compliance coefficient:

Jan 1, 1968