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Arizona Bureau of Mines and College of Mines and Engineering, University of Arizona, Tucson, Ariz. Lists of the maps and bulletins available will be sent upon request to G M Butler, Director, Arizona Bureau of Mines, Tucson, Ariz Bulletin 119, A resume of the geology of Arizona, by N. H Darton, is sold for $1, postpaid Fourteen other bulletins, any five of which may be had free of charge (additional numbers may be purchased for 10 cents each) are available as follows - 106, A geological reconnaissance of the Tucson and Amole Mountains, by Olaf P Jenkins and Eldred D Wilson, 114, Fluorspar, by M A Allen and G M Butler, 120, Gold and copper deposits near Payson, Arizona, by Carl Lausen and Eldred D Wilson, 122, Quicksilver resources of Arizona, by Carl Lausen and E D. Gardner, 123, Geology and ore deposits of the Courtland?Gleeson region, Arizona, by Eldred D Wilson; 125, The mineral industries of Arizona, by J B Tenney, 126, Asbestos deposits of

Jan 1, 1933

•Mineral Development Corp. of Salt Lake City, Utah purchased the Somerset and Oliver coal mines from the Kaiser Steel Corp. The mines are located at Somerset, Colo., about 75 miles east of Grand Junction, Colo. Somerset Town, with housing for 600 persons was included in the transaction. The mines employ 115 miners and have a combined capacity of 1750 tons per day. The Minerals Development Corp. is headed by Claude P. Heiner and is controlled by Godfrey L. Cabot, Inc. of New York and Boston. The Cabot Company is a major producer of carbon black. • The Dept. of Interior has announced that the name of the Defense Minerals Administration will be changed to Defense Minerals Exploration Administration. The new name of this defense agency more nearly describes its duties, since the mineral programming, procurement and claimant functions of the former DMA have been transferred to the Defense Minerals Procurement Agency. C. O. Mittendorf, formerly acting administrator of DMA, is serving as acting administrator of the new DMEA.

Jan 1, 1952

A HIGHLY successful joint conference on coal-mine transportation was held at Pittsburgh on Oct. 20 by the Pittsburgh Section of the American Insti-tute of Mining and Metallurgical Engineers and Mining Section of the Engineers' Society of Western Pennsyl-vania. C. E. Lesher, executive vice-president of the Pittsburgh Coal Co., presided over 215 members and others in the morning and Graham Bright, sales en-gineer with the Mine Safety Appliances Co., presided over about 180 in the afternoon. There were four prepared papers and much discussion, as well as a good luncheon between the sessions. Mechanical loading in the Pittsburgh district was discussed by L. E. Young, production vice-president of the Pittsburgh Coal Co. More companies in this district are using loading machines, more types of machines are being tried, and more coal is being mined by them than heretofore. The draw-slate above the Pittsburgh seam is the main problem; but devices for supporting and moving draw-slate are being tested. Except in two mines, the slate is being taken down. The fundamentals of the machines are similar, but the electrical drive and other parts have been improved. The problem is to recover or move as much coal as possible without hand labor. Methods of cleaning coal must be improved to meet the new methods of loading. The Pittsburgh Coal Co. has ten Joy machines and others are under order, a Myers-Whaley machine, Jeffrey conveyors, and Eichoff conveyors. The last mentioned are used in entries and other conveyors in rooms. At Montour No. 10 mine, one Joy machine is worked in rooms and one in entries.

Jan 12, 1927

By James E. Dunn

For several years, ground support at the Pitch uranium mine has been a serious headache to the management. The "moving" ground raised havoc with standard timber sets as well as steel sets. The author discusses this problem which has led to the adoption of heavy cribbing practices in drifts and raises.

Jan 6, 1961

By D. A. Hinckfuss

The large and compact but simple Bougainville Copper Limited flotation circuit has been in operation for 3-1/2 years. Discussion of problem areas encountered since start-up and remedies that have been implemented or proposed, form the main basis of this paper. Full current operational data is also provided.

Jan 1, 1976

By C. S. Smith, L. Guttman

It is shown, from a study of geometric probabilities, that the average number of intercepts per unit length of a random line drawn through a three-dimensional structure is exactly half the true ratio of surface to volume. Since the surfaces can be internal or external, the area of grain boundary or of the interface between any two constituents in a micro-structure can be measured. Other metric relations are tabulated that may be of use in studies of the microstructure of polycrystalline, cellular, or particulate matter generally. IN many fields of scientific investigation the structure of cellular aggregates or random arrays of discrete particles imbedded in some matrix is observed on a two-dimensional section and inferences are drawn therefrom as to the real structure in three dimensions. The biologist's microtome slice, the petrologist's thin section, and the metallurgist's plane polished and etched sections are common examples, although the problem is a general one. Scientists have commonly limited their thinking to the same dimensionality as their structures, and the few attempts that have been strictly three-dimensional in character have been laborious and noteworthy. From a metallurgical standpoint it is often of considerable importance to know, in addition to the volume fraction of two or more components in an alloy, the amount of two-dimensional interface between crystals. Such grain boundaries (which may separate either two identical crystals differing only in orientation or two crystals differing in structure, and possibly also in orientation) have a determining factor upon the mechanical behavior. It is at these boundaries that melting commences, that stress-induced corrosion occurs, and that various precipitates (harmful or otherwise) first appear. The boundary is doubtless of equal importance in nonmetallic crystalline aggregates such as rocks, ceramics, and concrete, and the biologist is deeply concerned with the area of cellular membranes. Many synthetic cellular foams involve similar structural problems. The very term structure usually implies the presence of interfaces and a complete understanding of structure involves nothing but an analysis of the geometrical, metrical, and topological relations between the various interfaces (zero, one and two-dimensional) that exist in a three-dimensional structure. Even systems lacking sharp physical interfaces often have interrelated gradients of composition or velocity (as cored crystals or turbulence cells) in which a neutral surface can be treated as a two-dimensional interface. In an earlier paper by one of the authors' the question of cell shape was considered in terms of simple topological principles without regard to physical dimensions. The determination of the actual size of grains in two dimensions is carried out in a routine fashion in innumerable metallurgical laboratories (see, for example, the ASTM standard methods of grain size determination2), though this is done merely to check the uniformity of a product and has no relation to the actual three-dimensional shape or size of the grains. Some authors have discussed the three-dimensional problem but only on the basis of assumptions as to idealized grain shapes.:'-' Quantitative measurements of microstruc-tures to obtain the volumetric relations of various phases have been carried out by petrographers for many years and are of increasing popularity among metallurgists." The present paper will show how, on the basis of no assumptions other than randomness of sectioning (usually realizable in experiment), it is possible to learn a great deal about the three-dimensional structure. The relations to be derived will generally be used on random arrays of cells or other particles, although they are equally applicable to ordered arrays and even to isolated objects of complex shape provided that suitable random sections can be made. Total Area of Interfaces in a Sample Consider a typical microstructure of a single-phase polyerystalline metal, such as that shown pres- in Fig. 1. The plane cross section shown contains a network of lines which subdivides the area into two-dimensional cells. The lines, of course, represent merely the intersection of the two-dimensional plane of sectioning with the two-dimensional interfaces between adjacent three-dimensional cells. The structure also contains points at which two or more lines intersect: in three dimensions the points are, of course, lines. In the more general case there may be in three dimensions isolated particles surrounded by a single interface without contact with others, and both two and one-dimensional features which do not necessarily connect with others. On the two-dimensional section these will appear as areas delineated by a closed line (as at a and b, Fig. 2), as isolated lines

Jan 1, 1954

By R. H. Terhune

THE enormous production of pig-iron, together with the many difficult and interesting problems with which its manufacture is fraught, has secured to this industry the exclusive attention of scientists with reference to the chemistry of iron, while some of the minor departments of its metallurgy have suffered neglect. Particularly is

Jan 1, 1873

By F. D. Mahone

Much crude oil, as produced from the well, carries varying amounts of water, which may be present as free water in globules sufficiently large to settle out, in time, if the fluid is allowed to stand, or as an emulsion formed by myriads of minute water particles, each surrounded and entrapped by a film of oil through which it cannot break under the action of gravity alone. Such an emulsified mixture of oil and water is commonly termed "cut oil." When such an emulsion is subjected, under proper conditions, to the influence of a high-potential alternating-current field, the minute water particles rupture the enveloping oil films and coalesce into larger water droplets this procedure continuing until all the water is freed into drops of such size that they readily settle out. This action has been photographed by the micro-moving-picture camera; under the microscope, the breaking-up of the emulsion, as described, is seen to be accomplished in a few seconds. The low power requirements of the process, from records of commercial plants, substantiate the theory that the action is that of a multitude of electrical condensers in series, rather than that of a number of conducting paths. The minute water particles serve as the metallic elements, or plates, of the condensers and the separating oil acts as the dielectric. Such surface charges as the particles may have are removed, and the intervening oil is broken, probably electrically by the voltage and mechanically by the attractive force between adjacent oppositely electrified particles. The principle of breaking up an emulsion under the influence of an alternating electric field was discovered by F. G. Cottrell and Buckner Speed, through experiments conducted, at the University of California, which resulted in a plant being installed on the property of the Lucile Oil Co. in the Coalinga field, California, early in 1909. This plant was able to reduce 14-per cent. emulsion to less than Pper cent. with commercial success. Standard Cottrell Apparatus The present standard Cottrell apparatus consists essentially of the electric treater and a settling or trap tank. The treater is a galvanized-iron tank approximately 3 ft. in diameter and 10 ft. high, which con-

Jan 1, 1924

By John W. Vanderwilt

THE unpredictable behavior of ground movement and subsidence has complicated the problems that attend the extraction of large quantities of ore. Special studies, particularly relating to coal mining, have yielded such a voluminous literature and so many involved controversial theories that a partial review would be difficult. Limited space makes any kind of a review impractical. The features to be considered cover only a relatively small part of the broad problems of ground movement and subsidence, but it is believed that this small part is critical. The practical aspects are important, since they bear directly on safety of mine workings, on recovery of ore and on dilution of ore in block caving and related systems for extracting large quantities of rock. The ground movement to be described occurs outside the vertical boundaries of a caved block in the area that is commonly referred to as being in the "zone of draw." "Draw" is a term that originated in the subsidence problems related to coal mining, and it is defined by a line drawn from the margin of the area caved underground to the most distant fracture at surface on the same side of the caved area as shown in Fig. I.1 " A line thus drawn is called the cave line, and its angle with respect to the horizontal is the cave angle or angle of draw. It is understood that the line is taken normal to the limit of mining, and in a vertical plane. The prevailing theories as to draw and angle of draw assume that appreciable movement occurred along the cave line, which has been described as a fracture resulting from the shearing action brought about by the weight of the overlying load. Fig. 2 shows diagrammatically the mechanics of ground movement adjacent to an area of subsidence according to the prevailing theory of draw (A, from Royce2) and, for comparison, ground movement observed in the Climax mine (B). The text in Peele's Handbook2 referring to Fig. 2 does not state the meaning of the "original position of top of workable ore" in the rectangular space above "ore in place," and the arrows are not explained. However, this presentation is most concerned with the zones outside the rectangle. According to the prevailing theory, as shown at the extreme left under A, Fig. 2, the vertical tension cracks at surface change at a shallow depth to shear fractures forming the cave line, and it is assumed that appreciable movement takes place along the cave line toward and into the subsiding caved block. The mechanics of ground movement observed in the Climax mine, as shown under B, Fig. 2, does not accord with the prevailing theory, particularly as regards the cave angle and draw. The vertical

Jan 1, 1946

By Oliver Bowles

WHILE vast quantities of limestone and dolomite. are used in metallurgy, the estimated production in 1926 being 23,860,000 tons, there are many problems connected with their use which have not received adequate study. The literature of metallurgy is notably lacking in comprehensive discussions of fluxing or furnace stone. Approximately 900 lb. of limestone is used for every long ton of pig iron produced in the blast furnace, but this important constituent of the charge receives little attention compared with the intensive study that has been applied to ores and fuels, the other important constituents of the charge. In an effort to elucidate some of the doubtful points, the writer has made a wide review of metallurgical literature, and has had the disappointing experience of finding not more than a paragraph or two on metallurgical stone' for each two or three thousand pages of literature reviewed. Furthermore, the limited information supplied is in some instances contradictory and even absurd. For example, a correspondent in a reputable metallurgical magazine classifies magnesia and silica together as impurities in flux "that must be melted and run off as slag." From the furnace operator's viewpoint it is desirable that as complete knowledge as possible be obtained concerning the effects of chemical composition and physical character of the stone on its action in the furnace and on the quality of the metal produced. A better knowledge of these features is advantageous also to the quarry operator in that it enables him to work more intelligently in producing stone that will best satisfy the metallurgists' requirements. The following pages comprise a brief compilation of data now available. Much of the information is well established and probably acceptable to most metallurgists. On some points there is room for debate, and the chief purpose in presenting a paper at this time is to arouse discussion which will throw more light on controversial points and thus assist the author in preparing a more comprehensive and accurate discussion of metallurgical limestone problems.

Jan 1, 1928

By R. S. Sandhu, S. H. Advani, J. K. Lee, B. L. Aboustit

A comprehensive finite element formulation for thermo-elastic consolidation based on a general variational principle is presented Sample one dimensional problems associated with isothermal consolidation, heat conduct ion, and thermo-elastic consolidation are presented. In addition, evaluations of thermo-elastic consolidation for an underground coal conversion field site are conducted.

Jan 1, 1982

By M. A. Matzkin

The Problem: There are no roads and mapping has been inadequate. There isn't a clearing large enough to accommodate a conventional airplane. Entry would consume months, yet the area must be investigated. Sustained communication is impossible except by radio. Cost in time and money for exploration would be exorbitant. . . . . . . . .

Jan 9, 1953

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

TO reach equilibrium between different phases in cobalt-rich alloys requires prohibitively long annealing cobalt-richalloystimes when temperatures are below about 700°C. The fact that a transformation from face-centered cubic to close-packed hexagonal readily tered takes place at temperatures below this in the cobalt-rich solid solutions is not an indication that thermally activated processes occur at an appreciable rate, for the transformation is well established as martensitic in nature. Wide divergence between heating and cooling experiments and high sensitivity to prior heat treatment make it difficult to judge temperatures of equilibrium between the phases.&apos; One object of the present work was to see if the information object of on the relative stability of phases could be gained by substituting plastic deformation for thermal agitation. Procedures were worked out that led to the determination of a diffusionless type of phase diagram, which represents the temperature of of phase equal stability for phases of the same composition, and the technique was applied to the Co-Ni system. Another object of the work was to see whether or not deformation would generate frequent stacking faults when these were thin lamellae of quentstackingfaultsa phase having higher free energy than the parent phase. The alloys were prepared in 80 to 100 g melts from cobalt (with metallic impurities estimated spectrochemically as follows: Ni, 0.05 pct; Fe, 0.001 pct.; Mg, Si, Cu, Cr, Al, < 0.001 pct) and Mond Car-bony1 nickel (with Fe, 0.05 pct; Si, 0.003 pct; C, 0.61 pct.; Cu, 0.001 pct; Co, Cr not detected, < 0.01 pct). The metals were melted in pure Al2O3 crucibles. An atmosphere of argon, that had been purified by passing over hot magnesium chips, was used for the alloys that, by analysis of the portions of the ingots actually used, were found to contain 15.3, 25.7, and 35.0 pct Ni, and vacuum melting (after degassing) was used for those containing 29.4 and 31.5 pct Ni. After induction melting the alloys were allowed to solidify in the crucible, and slices % in. thick x ½ in. in diam were annealed 12 hr at 1350°C for homogenization. These same specimens were used throughout the series of experiments, with annealing treatments of 4 hr at 900°C in purified hydrogen followed by furnace cooling, alternating with the deformation and X-ray tests discussed below. Results Spontaneous transformation was observed on cooling to room temperature in all alloys containing 29.4 pct Ni or less and by cooling the 31.5 pct alloy to — 195°C but was not observed in the 35 pct alloys after cooling to —195°C. These results are in satisfactory agreement with the cooling experiments of Masimoto.4 From these data it is clear that the temperature of beginning transformation M,,, drops to 20°C with the addition of about 30 pct Ni. The test for spontaneous transformation was metallographic. Specimens were thermally polished by annealing 10 hr in hydrogen at 1350°C, then furnace cooled; if trans- formation had occurred there were relief effects visible on the thermally polished surfaces. These markings were narrow straight lines, usually resolvable at high magnification as clusters of fine lines that resembled slip lines. It was concluded that they resulted from displacements on (111) planes, for the number of directions in individual grains often reached but never exceeded four, and lines could always be found parallel to the thermally etched (111) boundaries of annealing twins. The markings were thus consistent with the idea that the transformation occurs by (111) plane displacements (Shockley partial dislocations moving on (111) planes). This was further confirmed by X-ray tests for stacking disorders. Using an oscillating crystal technique previously employed to detect strain-induced faulting in Cu-Si alloys," streaks indicative of the stacking faults were looked for and found on X-ray films of the spontaneously transformed 25.7 pct Ni alloys, as expected by analogy with Edwards and Lipson&apos;s results on pure cobalt." The streaks were much intensified after rolling at room temperature. Transformation induced by plastic strain was investigated as a function of alloy composition and temperature of deformation. A series of tests was made to determine suitable straining and X-raying techniques. Filing was found inferior to abrasion in converting cubic samples to hexagonal, and abrasion was less effective than peening in producing smooth unspotty Debye rings in the X-ray patterns. Because the diffraction lines were broad, Geiger-counter spectrometer records of filings were less sensitive in revealing small amounts of transformed material than X-ray patterns recorded on films in a small diameter camera. After these exploratory tests the following methods were adopted. Specimens that had been annealed at least 4 hr at 900°C and furnace cooled were mounted in a block of aluminum, brought to temperature, and peened thoroughly with a mullite pestle preheated to the same temperature. The specimens were then quenched to room temperature. In peening, a circular area of % in. diam was given 500 blows. A few control tests showed that an additional 1000 blows did not detectably change the proportions of the phases present. The amount of transformation was judged by X-ray reflection patterns from the peened surface, using the innermost four lines of the cubic and the hexagonal patterns with filtered CoKa radiation,

Jan 1, 1953

By M. R. Daly

In a recent paper on Geologic Structure in the Cushing Oil and Gas Field, Oklahoma,l Carl H. Beal has pointed out some interesting peculiarities in the distribution of the hydrocarbons and the disposition of the "planes of separation" between the oil and the water (water surfaces). Mr. Beal&apos;s principal statements on this matter may be, summarized as follows: I. In every important dome in the Cushing field, which has not been complicated by folding along its sides, the oil area in each of the three oil and gas sands studied (Layton, Wheeler and Bartlesville) apparently extends farther down on the long axis of the dome than it does on the steeper sides. The result is that water is encountered at a lesser depth below datum plane (sea level) on the steep sides of the dome than along the ends where the beds are more gently tilted. II. In the Layton and Wheeler sands (to which the detailed study of water surfaces has been almost entirely confined), the water surface is not level, but dips at a gentle angle (maximum dip 100 ft. to the mile) away from the center of the structure. This inclination existed prior to development, and it has been rendered greater by the rapid extraction of oil and gas. To these statements, the following observations are added: The dominant structural feature in the Cushing field is a broad north and south anticlinal fold, along whose axis the domes are distributed (Fig. 1, p. 897), and the more important oil areas in each sand lie on the west side of the field. In many cases, gas has been forced to the east side of the structure, sometimes as far as the water line. From the distribution of the oil and gas bodies, Mr. Beal concludes that the hydrocarbons in this region probably migrated from the west or the northwest. It seems as if these different features would be susceptible of some

Jan 1, 1918

By E. D. Gardner

INTRODUCTION OIL shale deposits have been exploited in various countries throughout the world, but generally with government aid. The oil-shale industry of Scotland perhaps is the oldest and best-known; the largest was conducted in Manchuria by the Japanese during World War II as a source of liquid fuels for military uses. In general, foreign oil-shale deposits that have been exploited are much lower grade than those in the western United States. Considerable interest began to be shown in western oil shales in 1916; the peak of activities was in 1923. The Catlin operation, near Elko, Nevada, perhaps was the nearest approach in this country to an oil-shale enterprise on a commercial scale. Over 100 companies were formed, ostensibly for exploiting the oil shale; a large number of them, however, proved to be stock promotions only, which gave the embryo industry a black eye. The Bureau of Mines operated an experimental oil-shale retort plant near Rifle, Colorado, from September 1926 to June 1927 and again from April 1928 to July 1929, after which the plant was dismantled. By this time the East Texas oil fields had come in and the country lost interest in substitute liquid fuels. During World War II the Nation again became concerned about the magnitude of its petroleum reserves. Congress (April1944) directed the Bureau of Mines to build and operate demonstration plants to produce synthetic liquid fuels from coal, oil shales, and agricultural and other products; a five-year program was authorized. As a part of this program the Bureau of Mines has built, at Anvil Points near Rifle, Colorado, a retort plant and developed an experimental mine to supply the plant with oil shale. An important part of the mining work at Rifle is to devise methods and select practices for mining the oil shale on a commercial scale at the lowest practicable cost. The product to be mined has a relatively low value, a fact that must be kept continuously in mind. The combined aim of those in charge of the mining and those in charge of retorting is to demonstrate that the shale oil can be produced at a cost per barrel corresponding to the current quotation for crude petroleum -or at least very close to it. Plans call for an uninterrupted flow of broken oil shale from the face in the mine, through crushers, through the retorts and thence to the disposal dump. The disposal of the spent shale in the Rifle area should present no unusual problem. Mining research has consisted so far of paper studies of the general phases of the problem, determination of the widest span that the roof stone will stand safely unsupported, and drilling problems. Underground development has not proceeded far

Jan 1, 1947

By Thomas H. Clagett

ThE Pocahontas coal field comprises the area in Tazewell County, Va. and Mcrcer and McDowell counties, W. Va., in which Nos. 3 and 4, Pocahontas seams of bituminous coal are mined. It is a mountainous region with ridges rising 300 to 1000 ft. (91 to 305 111.) above the very narrow valleys and, except for some poorly kept farms along the tops of the ridges and the area occupied by the mining and coking plants and villages, is wooded throughout. First shipments were made from Pocahontas in 1883. There are now about 100 mines, 95 per cent. of which are drift mines. At the end of 1920, approximately 298,000,000 gross tons of coal had been produced and 35,000 acres of coal mined. No. 3 seam is from 4 to 10 ft. (1.2 to 3 m.) thick, but the change is gradual and the thickness fairly uniform in any particular locality. It has a streak of bone, about 2 in. (5 cm.) thick, to which the coal adheres on both sides. In parts of the field this bone is replaced by hard slate, usually from 2 to 4 in. thick. The seam has a slate or fireclay bottom and a draw-slate top. No. 4 seam is from 65 to 80 ft. (19.8 to 24 m.) above No. 3 seam, and of minable section only in the western part of the field. It is from 3 to 8 ft. thick and has two streaks of bone, cach from 1 to 2 in. thick. It has a fireclay or slate bottom and is overlaid by from 4 to 24 in. of a laminated coal and slate, locally termed "black rash," which is separated from the coal seam by about 3 in. of slate. This "black rash" averages about 2.5 per cent. ash, but contains some clean coal. The coal in both seams is quite soft. Cleavage sufficieiltly well defined to exert an influence on the mining is rare. Overlying strata arc slates, shales, and sandstones, the sandstones predominating, extending from 30 to 1000 ft. above No. 3 seam. The strata directly above the draw slate of No. 3 seam, or "black rash" of No. 4 seam, and up to the first sandstone are usually slates or shales, about 10 ft. thick over the.

Jan 1, 1923

By Thomas H. Clagett

ThE Pocahontas coal field comprises the area in Tazewell County, Va. and Mcrcer and McDowell counties, W. Va., in which Nos. 3 and 4, Pocahontas seams of bituminous coal are mined. It is a mountainous region with ridges rising 300 to 1000 ft. (91 to 305 111.) above the very narrow valleys and, except for some poorly kept farms along the tops of the ridges and the area occupied by the mining and coking plants and villages, is wooded throughout. First shipments were made from Pocahontas in 1883. There are now about 100 mines, 95 per cent. of which are drift mines. At the end of 1920, approximately 298,000,000 gross tons of coal had been produced and 35,000 acres of coal mined. No. 3 seam is from 4 to 10 ft. (1.2 to 3 m.) thick, but the change is gradual and the thickness fairly uniform in any particular locality. It has a streak of bone, about 2 in. (5 cm.) thick, to which the coal adheres on both sides. In parts of the field this bone is replaced by hard slate, usually from 2 to 4 in. thick. The seam has a slate or fireclay bottom and a draw-slate top. No. 4 seam is from 65 to 80 ft. (19.8 to 24 m.) above No. 3 seam, and of minable section only in the western part of the field. It is from 3 to 8 ft. thick and has two streaks of bone, cach from 1 to 2 in. thick. It has a fireclay or slate bottom and is overlaid by from 4 to 24 in. of a laminated coal and slate, locally termed "black rash," which is separated from the coal seam by about 3 in. of slate. This "black rash" averages about 2.5 per cent. ash, but contains some clean coal. The coal in both seams is quite soft. Cleavage sufficieiltly well defined to exert an influence on the mining is rare. Overlying strata arc slates, shales, and sandstones, the sandstones predominating, extending from 30 to 1000 ft. above No. 3 seam. The strata directly above the draw slate of No. 3 seam, or "black rash" of No. 4 seam, and up to the first sandstone are usually slates or shales, about 10 ft. thick over the.

Jan 1, 1923

By Thomas Clagett

THE Pocahontas coal field comprises the area in Tazewell County, Va., and Mercer and McDowell Counties, W. Va., in which Nos. 3 and 4 Pocahontas seams of bituminous coal are mined. It is a mountainous region with ridges rising 300 to 1000 ft. (91 to 305m.) above the very narrow valleys and, except for some poorly kept farms along the tops of the ridges and the area occupied by the mining and coking plants and villages, is wooded throughout. First shipments were made from Pocahontas in 1883. There are now, about 100 mines, 95 per cent. of which are drift mines. At the end of 1920, approximately 298,000,000 gross tons of coal had been produced and 35,000 acres of coal mined. No. 3 seam is from 4 to 10 ft. (1.2 to 3 m.) thick, but the change is gradual and the thickness fairly uniform in any particular locality. It has a streak of bone, about 2 in. (5 cm.) thick, io which the coal adheres on both sides. In parts of the field this bone is replaced by hard slate, usually from 2 to 4 in. thick. The seam has a slate or fireclay bottom and a draw-slate top. No. 4 seam is from 65 to 80 ft. (19.8 to 24 m.) above No. 3 seam, and of minable section only in the western part of the field. It is from 3 to 8 ft. thick and has two streaks off bone, each from 1 to 2 in. thick. It has a fireclay or slate bottom and is overlaid by from 4 to 24 in. of a laminated coal and slate, locally termed "black rash," which is separated from the coal seam by about 3 in. of slate. This "black rash" averages about 25 per cent. ash, but contains some clean coal. The coal in both seams is quite soft. Cleavage sufficiently well defined to exert an influence on the mining is rare. Overlying strata are slates, shales, and sandstones, the sandstones predominating, extending from .30 to 1000 ft. above No. 3 seam. The strata directly above the. draw slate of No. 3 seam, or "black rash" of No., 4 seam, and up to the first sandstone are usually slates or shales, about 10 ft. thick over the

Jan 5, 1922

By Dale A. Vaughan, Oliver M. Stewart, Charles M. Schwartz

Solid-solubility limits at 1500°, l000q and 500°C for carbon, nitrogen, and oxygen in high-purity tantalum were determined by X-ray lattice-parameter methods. For carbon, the solubility was found to be 0.17 at. pct at 1500°C, and less than 0.07 at. pct at 1000°C. A nitrogen solubility of 3.70 at. pct at 1500° C decreases linearly with temperature to 2.75 at. pct at 1000°C, and 1.8 at. pct at 500°C. In the case of oxygen, the solubility was found to be 3.65 at. pct at 1500°C, 2.95 at. pct at 1000°C, and 2.5 at. pct at 500°C. The phases Ta2C, the low-temperature modification of Ta205, and Ta,N of unknown composition but which has a superlattice structure based upon the original bcc tantalum lattice have been identified as the initial precipitates in the respective systems. Metallographic methods were employed to verify the X-ray analyses. The etching behavior of Ta is discussed in terms of lattice i?rzperfections and precipitate phases. The excellent fabricability, high melting point, and nuclear properties of tantalum are responsible for interest in this refractory metal. Data on the solid solubility of the interstitial elements (oxygen, nitrogen, and carbon) in tantalum and on the precipitate phases are somewhat limited. The significant contributions are discussed below. Because the purity of electron-beam melted tantalum (only recently available) is considerably higher than that used in previous studies, the present investigation was initiated. Gebhardt et all-3 have investigated the tantalum-oxygen and tantalum-nitrogen systems with particular reference to the changes in physical properties and to the rates of reaction between these gases and the metal. The solubility of oxygen in tantalum was reported2 to be 3.7 at. pet at 1500°, 2.3 at. pet at 100O°C, and 1.4 at. pct at 750°C. Schonberg4 reported that several oxide phases (Ta40, Ta,O, TaO and Ta,05) exist while X-ray studies by Gebhardtl showed only two oxides, Ta,05 and an unidentified phase which was associated with a platelet-type precipitate. La-gergren and Magneli,&apos; however, questioned the existence of compounds other than the two allotropic modifications of Ta,05 for the tantalum-oxygen system. In the case of nitrogen, the solubility was estab- lished by Gebhardt3 to be of the order of 7 at. pct at 1800°c. The solubility was reported to decrease rapidly with temperature, and, although no limits were established, a precipitate phase was observed by Gebhardt except when the high-nitrogen specimens were cooled very rapidly from the reaction temperature of 1800c. He reported the initial precipitate phase to be a tetragonal distortion of the bcc tantalum lattice while Schonberg6 reported the phase lowest in nitrogen Jo be a cubic super-lattice with a cell size of 10.11 A. Two other nitride phases, Ta,N and TaN, were reported; these appear to be isomor-phous with the carbides of tantalum. The tantalum-carbon system was investigated by Ellinger7 and by Lesser and Braurer. Two compounds, Ta,C and TaC, were reported to exist, each with a range of composition. The solubility of carbon in tantalum was found to be practically nil at all temperatures. Thus, of the interstitial elements which are present in small amounts in high-purity tantalum, carbon might be expected to form precipitates. The present investigation was initiated to obtain additional data on the solid-solubility limits of these interstitials at 1500°, 1000°, and 500&apos; with particular emphasis on the distribution and the identification of the precipitate phases. EXPERIMENTAL WORK AND RESULTS In the present investigations of the solid solubility and of the precipitate phases in the systems tantalum-nitrogen, -oxygen, and -carbon, high-purity tantalum was reacted with high-purity gases, homogenized at 1800°c, and annealed at and quenched from 1500°, 1000,

Jan 1, 1962

By H. M. Otte, A. L. Esquivel

A new leasl-squares method is Presented for determining lattice parameters of hexagonal or tetragonul structures. The method is adapted for use on electronic computers and involves a reiterative procedure. The correction factor employed raries linearly with the lattice parameter, a (determined from the Brag, angle). In contrast, Cohen&apos;s method and recent modifications of it use a correction factor that varies incersely as the squure of the lattice paramneter, a. While the recent modifications attempt to improve the precision of the extrapolated lattice parameter, a, (or-cu). by stressing the importance of the weighting factor. the present approach emphasizes the need for choosing the correct extrapolation function. A comparison between the present method (the Linear method) and Cohen&apos;s method indicates that the Linear method may be more appropriale in certain cases. through a priori no critertion appears to he available for making a chorce between the methods. The size of hexagonal and tetragonal crystal lattices is determined by two parameters, a, and c,. Although in principle the two lattice parameters can be determined independently from reflections for which h - k = 0 and 1 = 0, respectively, in practice this may be inconvenient (because of the angular positions at which these reflections may occur) or not easily possible (because of low intensity). Furthermore, if a high precision or accuracy is required, the limited number of reflections of this type available, particularly in the high-angle region, is not sufficient for the necessary corrections (mainly due to absorption) to be determined with accuracy. Several methods1-7,11-13 have been proposed employing all reflections, to obtain the optimum values, a. and co, either by a trial and error procedure or a least-squares fit. Of the latter method, cohen&apos;s5 is the best known one since it provides explicit expressions for the optimum a. and c,. However, Cohen&apos;s method is only strictly valid if an extrapolation function is used that varies linearly with l/a2 or lie2 (see Section 3), a requirement that does not appear to be generally appreciated. On the other hand, all the better known and more widely used A recent trial and error method was proposed by Massalski and King8,7 who computed extensive auxiliary tables of axial ratios vs the functions A = [(4/3)(h2 + hk +k2) + l2+(a/c)2] and C = A(c/a)2 used in computing a and c values from the observed Bragg angles. These values of a and c were then plotted against a function which permitted linear extrapolation. As a criteria; for the "optimum" values, Massalski and King rely upon a visual fitting of the line through points representing reflections of low 1-index points to compute the extrapolated value of ao and high 1-index reflections to obtain CO. The successive computations and graphical plotting required to reach the "optimum" value are quite lengthy and tedious even on a desk calculator and no quantitative assurance is obtained of having in fact selected the optimum value.* If the method of Massalski and King is used on an electronic computer, then their published tables become redundant and a least-squares fit becomes a natural selection for the choice of optimum values. Such an approach will be called the Linear method. For work now in progress on the effect of certain physical variables on the lattice parameters of hexagonal crystals, it has become essential to determine the confidence limits of small changes in the lattice parameters. Since extrapolation functions that varied linearly with a and c actually also appeared to vary linearly with l/a2 or l/c2 when tested against published as well as our data, a comparison of Cohen&apos;s method and the Linear method was considered desirable (Sections 3 and 4). For the latter method an electronic computer was required since a reiterative procedure to obtain the optimum ao and co values had to be employed. The purpose of this paper is to describe the principles of the Linear method, illustrate its application, and compare it with Cohen&apos;s method. 1) THE LINEAR METHOD The standard practice in obtaining the lattice parameters in the Debye-Scherrer method is to

Jan 1, 1965