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By Bunting S. Crocker

DISCUSSION Fred C. Bond (Allis-Chalmers Manufacturing Co., Milwaukee)—This is a very complete description of the screened ore fine grinding installation at Lake Shore. The only important data which might be desired are the operating screen analyses and power consumption in each stage. The statement that the energy consumption, or kw-hr per ton, remains constant for all mill diameters is of great interest, but the opinion is widely held that the kw-hr per ton decreases as the mill diameter increases. More definite test work is needed to establish this point. Screened ore fine minding has been successful on hard Lake Shore ore &d on about equally hard South African Rand ore. However, it is still not determined whether it would be successful on ores of average or less than average hardness. It is possible that with softer ores the consumption of ore pebbles might be exceedingly high, or might even exceed the available supply. Also, the softer feed might result in a rapid buildup of harmful intermediate sizes in the mill circuit. These factors can be determined only by a full scale or long pilot mill test. In any case the Lake Shore staff is to be congratulated for this pioneering work. Bunting. S. Crocker (author's reply)—As requested, the operating screen analyses and Bower consumption for each of the four stages of pebble milling are given, see Table XII. The fist three stages are in series circuit; the last stage is in closed circuit. The primary circuit had rock feed averaging 124 g per piece and the final stages rock feed weighing 63 g. The intermediate stages had mixtures of the two. Regarding Mr. Bond's statement that "the opinion is widely held that the kw-hr per ton decreases as the mill diameter increases," I would say that I have frequently been told this but have never yet been shown any evidence or seen any evidence published that would prove this statement. It may be true that some of the big mills recently installed have mechanical power savers such as micarta bearings and better lubrication, but as far as the power consumed inside the mill is concerned, we at Lake Shore think that it varies as D2 .", and that is all. We published extensive information on this point in our 1939 paper. Recently Mr. Banks at Consolidated published the figures on his 10 ft 8 in. x 12 ft 0 in. rod mill. As reported in this discussion by the writer: we calculated the power necessary to run this mill based on our 7x6-ft rod mill to within 1 pct of the actual power reported by Mr.

Jan 1, 1953

By G. R. Speich, S. A. Kulin

The isothermal formation of martensite at subzero temperatures has been studied in an austenitic stainless steel. The amount of martensite formed isothermally in a given time was found to follow a C-curve behavior with decreasing temperature. Since isothermal rnartensitic transformation occurs at temperatures above the true M. temperature of the olloy, the observed M. temperature is dependent on the cooling rate. It is believed that a general martensite theory must include the basic concepts of the strain embryo theory, and also the important role of thermal fluctuations. UNTIL recently the isothermal component of the martensitic transformation had been considered as a trivial effect in theoretical considerations of this type of transformation. One of the postulates used in defining a martensitic transformation was that the reaction was temperature dependent but not time dependent. Cohen and his associates1'2 were the first to report the isothermal formation of mar-tensite. They obsel-ved the time dependency of the martensite reaction at room temperature in plain carbon steels and certain tool steels. They found that a small amount of additional transformation occurred after the specimen reached the quenching temperature and that the rate of this isothermal transformation decreased rapidly with time. These authors considered this phenomenon to be a "tailing-off" of the main athermal reaction. Kurdjumov and MaksimovaL 5 studied the isothermal formation of martensite at subatmospheric temperatures in steels containing 0.6 pct C-6 pct Mn, 1.6 pct C, and in an iron-base alloy containing 23 pct Ni and 3.4 pct Mn. In each case it was found that both the initial rate and the total amount of isothermal transformation exhibited sharp maxima with decreasing temperature. They stated that it was possible to completely suppress the martensitic transformation in the 0.6 pct C-6 pct Mn steel by drastic quenching in liquid nitrogen. They interpreted their results in terms of a thermally activated process. The maximum in the rate of nucleation vs. temperature curve was assumed to be a result of the temperature dependence of the rate of growth of the martensite plates. It has been demonstrated," however, that martensite plates can form with great rapidity even at temperatures approaching absolute zero. In addition," attempts to confirm the reported suppression of the martensitic transformation by rapid cooling of a 0.6 pct C-6 pct Mn steel have proved unsuccessful. On this basis, and on other theoretical grounds, the validity of some of Kurd-jumov's results and conclusions is open to serious question. Cohen, Machlin, and Paranjpe' have proposed a theory of martensite formation based on the nucleation of strain embryos and a growth mechanism involving cooperative atomic displacements. According to this theory thermal fluctuations can make a strain embryo supercritical and thereby produce martensite isothermally. Das Gupta and Lement' have investigated the isothermal formation of martensite in a 17 pct Cr-0.7 pct C steel at temperatures below the ambient. They found that partial suppression of the martensitic reaction occurred on quenching into liquid nitrogen. That part of the reaction which can be suppressed is taken to correspond to the isothermal rather than the athermal part of the rnartensitic transformation. The initial rate of isothermal transformation for this steel was found to go through a maximum with decreasing temperature. This is in conformity with the findings of Kurdjumov and Maksimova for the steels used in their investigation. Das Gupta and Lement conclude that isothermal martensite formation occurs by the nucleation of new plates and is always preceded by some athermal transformation. An iron-base alloy containing 14 pct Cr-9 pct Ni was used in this investigation to study further the kinetics of the austenite to martensite transforma-

Jan 1, 1953

By H. F. Bishop, F. A. Brandt, W. S. Pellini

M. S. Fisher and D. R. F. West (Imperial College of Science and Technology, London, England)—It may be of value to compare certain features of the results recorded in this very interesting paper with those of an investigation11 involving determinations of temperature gradients and rates of solidification of steel blocks of 3 in. sq section, cast horizontally in sand molds, some of which contained chills. Castings in plain carbon steels containing up to 0.8 pct C were made and, throughout this range of compositions, both inverse-rate and direct cooling curves, obtained from thermocouples placed within the mold cavity, showed a major arrest, the temperature of which was taken as the "effective liquidus" for the particular steel in question, solidifying under the conditions of the investigation. At the completion of the arrest, the curves showed a comparatively rapid de- crease in temperature. Some of the steels investigated lay within the peritectic region, and a second arrest at 1485°C was detected. In Fig. 15, which shows the effective liquidus temperatures, the limit of the 8 + liquid field has been placed at approximately 0.5 pct C. In inverse-rate curves corresponding to the thermal center of each casting, there was always a discontinuity, viz: an abrupt change of slope, at a temperature about 10 to 20°C below the "liquidus arrest," after which there seemed to be no significant irregularity in the rate of cooling. Curves corresponding to other positions in the casting generally showed some irregularities below the main arrest, probably as a result of heat flow from the solidifying interior. Even the reproducible discontinuity in the curves for the central positions appeared to have no theoretical or practical significance, though it probably corresponded to a stage in the solidification process at which only a relatively small amount of interdendritic liquid remained. Its temperature, rela-

Jan 1, 1953

By Maurice J. Peterson

THE VISUAL-ARC spectroscopic method of rapid qualitative analysis of complex inorganic compounds has been popularized in the past few years and is being employed by an increasing number of laboratories. The mineralogy and chemistry departments of several universities recently have added visual spectroscopy to their laboratory curricula. This revival of interest in a somewhat dormant analytical method has been stimulated through the publication of three papers 4 by members of the College Park staff of the Bureau of Mines. These virtually are the only recent sources of information on visual-arc spectroscopic analysis. They include data on the spectroscopic assembly, the analytical procedure, and the practical application of the method to determinative mineralogy and related fields. Requests for reprints of these papers continue to be received; at present only a limited number of copies are available for distribution. In order that these requests may be adequately answered, material from the three papers has been combined and, with some additional data, is presented in this bulletin. Numerous specific inquiries have been received regarding types of equipment available, problems in instrumentation, and information on the approximate sensitivity limits of the elements that can be detected by this method. Some of this material was not included in the original papers. Accordingly, the table of wavelengths has been revised to include the approximate visual-arc spectroscopic sensitivities, and a section on commercially available equipment has been added.

Jan 1, 1953

By D. C. McDonald

"IntroductionTHE GIANT YELLOWKNIFE property is on the west side of Yellowknife bay, Great Slave lake, N.W.T., some 600 air miles north of Edmonton. This paper deals with the underground development and mining of the complex system of orebodies which have produced, in the first fifty-six months of operation (May, 1948, to December, 1952), 652,464 tons of ore with an average grade of 0.80 ounces of •gold per ton (1).The mine has been developed from three vertical shafts designated A, B, and C. Figure l shows the positions of these openings with respect to the known ore-bearing zones and the surface plant.A shaft was sunk to a depth of 522 feet in 1945-46, primarily as a prospect shaft for investigation and development of the East Zone orebody. Drifting was carried out on the 200-and 325-foot levels. Before this development had been completed it was clear that the funds immediately available made it imperative to get revenue from production as soon as possible. By the beginning of 1946, the remarkably high-grade character of the ore in the present B Shaft area had been established by surface drilling, and the decision was made to obtain initial production from this source. Since known orebodies at shallow horizons were to be developed quickly, the choice of a suitable rock outcrop for the shaft was something of a problem."

Jan 1, 1953

By R. W. Geehan

The Bureau of Mines has been investigating deposits of critical and essential minerals in the United States since 1939. Bureau engineers made a preliminary examination of the Morefield mine early in 1943 and recommended investigation by trenching and diamond drilling, The Bureau of Mines conducted work from August to December of 1943, which indicated that the Morefield mine was a favorable location for an experimental mining program. The Bureau of Mines carried on such a program from September 1947 to March 1949. The property investigated is 30 miles southwest of Richmond in Amelia County, Va. (fig. 1). During World War II mica and beryl were shipped from the Morefield mine, but after the high prices and premiums paid during the war years were not available the mine was closed.

Jan 1, 1953

By H. N. Dunning

A comprehensive research program designed to aid development of new and improved methods for more complete production of petroleum from partly depleted reservoirs is being conducted at the Bureau of Mines Petroleum Experiment Station, Bartlesville, Okla. Water flooding has accounted for much of the petroleum produced by secondary-recovery methods; however, a considerable portion of the crude oil commonly remains in place after water flooding has been terminated. In recent years the possibility of increasing the efficiency of water flooding by using surface-active additives has received wide attention. In general, the results of laboratory research have shown that use of detergents as water-flooding additives will reduce the residual petroleum in porous media (1).3/ Some less extensive field tests have supported this conclusion but have not been entirely conclusive (2). Later studies (3, 4) have given conflicting evidence as to the relative worth of detergent additives for water floods in water-wet (hydrophilic) or oil-wet (hydrophobic or lipophilic) reservoir materials. The results of these studies emphasize the need for a more complete understanding of the fundamental principles involved in displacing petroleum from reservoir surfaces by injected fluids. Accordingly, a comprehensive research program was initiated to investigate the practical and fundamental aspects of detergency in petroleum production.

Jan 1, 1953

By S. Beatty

RECENT experimental results' on the superconductive properties of vanadium indicate that the magnetic behavior of the metal is greatly affected by internal strains caused by mechanical work, and particularly by oxygen and nitrogen impurities. These result in an increase in the hardness of the metal such that metallurgists' have used hardness as a measure of the impurities. An increase in the impurities should also be reflected in a change of lattice parameter with increasing impurity content. The lattice parameter of vanadium prepared by the thermal decomposition of the iodide has been determined by two workers. Neuburger3 obtained a value of a, =3.0338 ± 0.0003A for the body-centered cubic lattice by means of the powder method. The work of Katelaar is referred to by van Arkel4 in which a value of a0 = 3.025 is given. Four samples were used for this investigation. Sample A, the vanadium of the highest purity in the group, was obtained by means of the thermal decomposition of vanadium diiodide and deposited on a 3 mil diam tungsten filament in the form of crystals. The second sample, labeled B, was obtained by the calcium reduction of the pentaoxide at a sufficiently high temperature to give a melt. A third sample, C, was obtained in the same manner as B but remelted in a pure argon atmosphere. The last sample, D, was prepared by the calcium reduction method and the fine powdered vanadium was then sintered by means of applied heat and pressure. Samples A, B, and C were thus essentially free of mechanical strain in their preparation. Sample D was annealed in a high vacuum at 800°C. The samples were prepared for X-ray diffraction analysis such that all additional strain by cold work or by contamination with oxygen and nitrogen was kept at a minimum. Powder obtained from filings was deemed unsuitable since this would require annealing to get rid of the cold work. A heat treatment up to 1000°C at 10-6 m pressure might still increase the impurity content by means of adsorbed oxygen from residual gas in the vacuum chamber. The most satisfactory samples were prepared for back-reflection film techniques. Samples were cut to size, etched with hydrobromic acid, and mounted in Bakelite. They were then lightly polished on 3-0 paper and lightly etched. Chemical and Hardness Analysis of Samples Spectrographic analyses were made of the four samples and indicated similar metallic impurities for the group. The major metallic impurity in each sample was iron, which was less than 0.01 pct. The sum of the other metallic impurities was approximately 0.1 pct. The carbon content was assumed low by virtue of the methods of sample preparation. The principal impurity difference between the samples was in the oxygen and nitrogen content.

Jan 1, 1953

By J. J. Gilman, T. A. Read

S URFACE effects in the cleavage of brittle crystals have been known for some oftime,1, 2 but our knowledge of surface effects in the plastic deformation of crystals is of relatively recent origin. In 1936, Roscoe9 eported his observations comparing oxidized and clean cadmium crystals. He found that cadmium crystals 1/2 mm in diam when covered by an oxide film less than 1200 atoms thick had critical shear stresses about twice those for clean crystals. This effect is anomalous in that it cannot be caused by the inherent shear strength of a normal oxide film. Either an interaction between the film and the crystal causes the large increase in strength, or the oxide film has an abnormal mechanical strength. Several authors since Roscoe have studied surface effects in crystal plasticity. A complete review of the literature will not be presented, but most of the results may be summarized as follows: 1—The critical shear stress for slip is increased markedly by very thin oxide films on zinc4 and cadmium crystals;" ' also, the entire stress-strain curve is raised by an oxide coating;3,4 both effects increase with decreasing specimen radius. 2—Surface active substances such as oleic acid destroy the hardening effect of oxide films.4, 6-8 The time required for the reduction of the hardening effect to begin increases with the viscosity of the solvent4~ 3—There has been dispute in recent years about the effects of surface active substances themselves on plastic deformation. Rehbinder, Lichtmann, and Maslenikov9 state that surface active substances reduce the strength of metal monocrystals markedly and increase the number of slip lines per unit length at a given strain. The effect varies with orientation for tin crystals being smallest for x, = 0, largest for x, = 45", and intermediate as x, + 90°.10 Several workers claim to have disproved the results of Rehbinder')"." but Rehbinder and Lichtmann9 have defended themselves and Masing with his collaborators" has confirmed some of Rehbinder's results. 4—Immersion of metal specimens in electrolytes such as sodium chloride reduces their strength12,13' and subsequent cathodic polarization increases the strength reduction. For noble metals, the strength reduction occurs for both anodic and cathodic polarization," increasing with increasing polarizing voltage. 5—Electroplated copper coatings effect the creep rates of zinc monocrystals. Poly crystals are not affected." 6—Immersion in dilute acid destroys the hardening effect of an hydroxide film. When an acid solution is applied to a steadily creeping crystal, the creep rate jumps to a very high value and then drops gradually to a steady value which is higher than the initial steady rate.*' " If the hydroxide film to be removed is very thin (about 100A thick), the creep rate does not change measurably, but a small rapid strain-increment is observed when dilute acid is applied." 7—Crystal plasticity depends on specimen dimensions. This was observed by Lichtmann and Ven-stroml" for monocrystalline tin and by Andrade and Kennedy" for polycrystalline lead. 8—Immerson of copper crystals in mercury has no effect on their stress-strain curves.'" 9—Bombardment of creeping cadmium crystals with a particles which penetrate the surface to only 0.005 mm may increase their creep rates as much as five times.''' The experiments which will be described in this paper pertain to: (a) the effect of a crystal's shape on its plastic deformation, and (b) the effect of metallic surface films on plastic deformation. For the work pertaining to (a), crystals of zinc, tin, and lead were grown which had various shapes. These were tested in simple tension. Macroscopic rotations about the tension axis which are unpredicted by the classical theory of slip were observed, and serrated edges were observed in tin crystals. For the work pertaining to (b), the effects of evaporated and electrodeposited films of copper, nickel, gold, and zinc on the mechanical properties of zinc, tin, and lead crystals were determined. The films influenced both slip and twinning of the crystals in creep and tensile tests. Experimental Details Chemically pure zinc, tin, and lead were used in this investigation. The zinc was 99.999t pct pure;

Jan 1, 1953

By J. L. Lummus, Frank O. Jones

A field procedure for determining graphite in drilling mud is presented which is sensitive to 0.25 lbs/bbl and accurate to 20 per cent. The method, utilizing oil flotation principles, is suitable for use in all oil-free water base muds except those containing ligno-sulfonates, lignites, or surface active agents. INTRODUCTION Graphite was proposed as a drilling lubricant as early as 1940, but has not been used extensively until recently.' Graphite has been substituted for oil in certain instances to avoid oil contamination of core samples since it has been found that graphite does not interfere with routine core analysis. A major difficulty in using graphite is the lack of a satisfactory field test for determining the concentration of graphite in mud. DISCUSSION OF METHOD Several possible methods of analysis were investigated, including chemical separation, density fractionation, radioactive tracers, and oil flotation.', ' The investigation indicated that a satisfactory method for field use could be devised using an oil flotation method. It was found that toluene shaken with a highly diluted mud sample would recover sufficient graphite to be apparent in the oil phase. Refinement and standardization of technique made it possible to detect as little as 0.25 lb/bbl graphite and to estimate graphite content to within 20 per cent by using a visual comparison method. The test is limited to oil-free water base muds. Quebracho, phosphates, or barytes in the mud do not interfere with the test but surface active agents, lignosulfonates' and lignites evidently render !he graphite water-wet so that none may be recovered by oil-flotation. PROCEDURE Instructions for determining graphite in mud: 1. Collect representative one gallon sample.- from mud stream. Transfer immediately 350 ml portions of this Sample into four mixing cans labeled A, B, C, and D. Measure out graphite (same as is used to treat mud) for addition to cans as indicated below, using either a specially designed scoop or a balance. Can: A B C D Grams Graphite to Add: none 2 4 6 Stir samples B, C, and D for 15 minutes with propeller type mixer. 2. Clean and rinse well with water four 250 ml volumetric flasks labeled I, 11, 111, and IV. Using a 5 ml hypodermic syringe, transfer the indicated volume of samples from cans A, B, C, and D into designated flasks as follows: From Can: A B C D To Flask: I II III IV Add This Volume of Mud: 4 ml 2 ml 2 ml 2 ml 3. Measure 100 ml fresh or distilled water to each flask and swirl gently to disperse mud. Add exactly 5 ml toluene to each flask. Stopper and shake each

Jan 1, 1953

By Ruddle R. W.

Solid mattes are generally held to be either (a) eutectiferous mixtures of the component sulphides Cu2S and FeS or (b) mixtures of complex sulphides. This chapter shows that liquid mattes consist essentially of a homogeneous phase in which iron, copper and sulphur are present. The amount of sulphur is generally less than that required to account for all the metals as stoichiometric sulphides; mattes cannot therefore be regarded as mixtures of FeS and Cu2S. Some iron oxide may be dissolved in the sulphide phase and magnetite is often present as a second phase. If the sulphur content of the matte is reduced the composition enters the miscibility gap in the ternary system and either an iron- or copper-rich solution (depending upon the composition of the matte) separates as a new phase. On solidification any one of four phases (iron, copper, Cu2S and FeS solid solutions) may crystallize as primaries. The remainder of the matte solidifies as a ternary eutectic. It is possible that iron oxides enter into this eutectic. Knowledge of the ternary Cu-Fe-S system is far from complete and nothing is known of the quaternary system Cu-Fe-S-O

Jan 1, 1953

By S. H. Ash

THE MAGNITUDE of the anthracite industry's drainage problem in the Northern field of Pennsylvania is realized when it is known that, for the 8-year period 1944-51, all pumping plants in this region pumped an average volume of 112.5 billion gallons of water from the mines to the surface each year. This is over 214,000 gallons per minute pumped against an average hydrostatic head of 400 feet each year for that period (12).4 By comparison, Lake Wallenpaupack, the largest artificial body of water lying wholly in Pennsylvania, contains 71 billion gallons of water in its 24-square-mile area; the average volume of water pumped from the mines in the Northern field each year during the 8-year period was 58 percent more than the volume impounded in Lake Wallenpaupack. The natural configuration of the drainage area overlying the Northern field subdivides the total area into two major drainage areas-the Lackawanna River drainage area and the Susquehanna River drainage area overlying the Wyoming Basin. Although the 169-square-mile drainage area overlying the Wyoming Basin is slightly less than half that of the Lackawanna River drainage area (10), the total volume of water pumped to the surface from mines in the Wyoming Basin is 21 percent more than the total volume pumped to the surface from mines in the Lackawanna Basin. From this, it is apparent that the Susquehanna River and the pervious deposits in the buried valley over which it flows in its course across the coal measures of Wyoming Valley is the greatest single source of mine water affecting mines in this area. Because of its relatively flat terrain, the wide flood plain of Wyoming Valley does not facilitate rapid runoff; consequently, much of the surface water seeps directly into the buried-valley deposits and eventually into the mine workings.

Jan 1, 1953

By A. D. Mutch

IT has long been known that there are wide variations in the thermo-electric potential of pyrite. In the last few years a study of this variation and other properties of pyrite was carried out at the University of Toronto by F. G. Smith on specimens of pyrite from many loyalities. As a result of these studies the pyrite geothermometer was developed by Professor Smith. The calibration of the pyrite geothermometer is based on the assumption that "crystals of any one electronically conducting mineral species deposited at a high temperature have a more positive thermoelectric potential than crystals deposited at a low temperature, and the thermo-electric potential varies continuously between any given limits of the temperature of deposition." The cause of the variation was postulated to be crystal discontinuities, such as lineage boundaries. As yet this postulated relationship has not been established as fact. On theoretical grounds it is indicated that the thermo-electric potential of pyrite or any other partial conductor is dependent upon a number of factors as well as the temperature of formation. For this and other reasons there is ground for doubt as to the validity of the relationship postulated above. To date a large number of readings have been made with the pyrite geothermometer which have been recorded in terms of the calibration of the instrument in degrees centigrade. So far most of the pyrite tested by this technique has been in association with gold ore. The values for the temperature of formation obtained in these tests appear to be reasonable and, in relation to geological problems, to vary in the right sense. Determinations on some specimens not in association with gold ore have given readings that appear to be much too high, taking into account the probable maximum temperature of the host rock. To sum up, although many determinations made with the pyrite geothermometer appear to give reasonable values for the temperature of formation of the pyrite, there are at the same time other readings which seem anomalous. On the basis of an examination of available results of work with the pyrite geothermometer, two problems must be considered: 1—the validity of the calibration of the pyrite geothermometer; and 2— the nature of the distribution of the thermo-electric potentials of pyrite in relation to the specific problems that have been examined. In this paper the academic problem relating to the validity of the calibration of the pyrite geothermometer will not be discussed. Instead, the variations of thermo-electric potential of pyrite in association with gold veins will be discussed with regard to specific examinations. The first of these two examinations deals with the distribution of thermo-electric potentials of pyrite in association with a gold vein and was carried out in the McIntyre Porcupine Mine, Schumacher, Ont., in the summer of 1949 as part of a study with this technique. The second problem deals with variations of thermo-electric potential of pyrite in gold ore specimens from all over the world. The specimens used in this study were part of the private collection of Frank Ebbutt, geologist for Howe Sound Exploration Co. Results of Detailed and Reconnaissance Studies In discussion of the results of determinations made in these two studies the values of thermo-electric potential in millivolts will be used. It will be noted that in some of the diagrams the determinations are recorded in terms of pyrite geothermometer temperatures. Fig. 1 is a calibration chart relating pyrite geothermometer temperatures and thermoelectric potentials. A full discussion of the technique is given in the original paper by F. G. Smith.' Briefly, the determinations are made by placing two stainless steel probes, one hot and the other cold, against the surface of the pyrite crystal being tested. The thermoelectric potential that is developed is read with a null-point potentiometer that is calibrated in what

Jan 1, 1953

By F. R. Zacher

Unmined blocks in the Sewickley seam, surrounded by worked out areas, have been found to transmit overburden oads through the interval strata to the Pittsburgh seam workings 90 ft below. Operating experiences under these conditions are described in this paper. IT has always been understood, in northern West Virginia where both the Pittsburgh and Sewickley seams are mined, that pillaring or splitting in the lower Pittsburgh seam could break the interval strata and make mining in the overlying Sewickley difficult or impossible. In some instances, however, mining methods practiced in the overlying Sewickley have reversed the problem, resulting in a shifting of the intermediate layer and destroying valuable acreages of the Pittsburgh seam below. The Pittsburgh seam in this area is, on the average, 102 in. thick. About 18 in. of low-quality head coal are left for roof protection as it is mined. Immediately over the coal are two draw slates, two rider seams, and a good hard black shale, locally called black rock, which serves as a permanent roof where draw slates and riders are taken down on certain main haulroads. In most areas mined in this seam in the past the bottom has been satisfactory but soft. However, in areas now being mined by the Christopher Coal Co. in Monongalia County the bottom is very hard and unyielding. The Sewickley seam, lying 85 ft above the Pittsburgh, will average nearly 70 in. in thickness and is overlain by massive shales and sandstones. Much of the seam is mined only down to the "sheep skin," a hard band about 4 in. above the bottom, which is composed of relatively hard shale. Fig. 1 shows a typical cross-section through the Pittsburgh and Sewickley seams in the area being discussed. The thin Redstone seam is not deep-mined but is stripped in some locations where it outcrops. Most of the Sewickley seam in the Morgantown areas has been mined out from 10 to 30 years. There are at present only two large mines and five or six others of small production operating in that seam. Mining systems in the past were generally of the room and pillar type with some full pillar extraction. This seam in the Scott's Run area was operated by as many as thirty or forty different companies at one time, during an era beset with strikes, market failures, and depressions. Most of the barrier pillars along the many main haulroads were abandoned, and blocks of Sewickley coal that would be fully recovered with today's machinery were left unmined when conditions became anything less than favorable. Consequently the mined-out Sewickley is spotted throughout with solid blocks varying in size from 100x100 ft to 200x400 ft and larger. It is these unmined Sewickley blocks surrounded by worked-out portions that have caused transmissions of roof stresses to underlying Pittsburgh mining areas, see Fig. 2, resulting in untold difficulty. As the Christopher Coal Co. operates both the Pittsburgh and Sewickley seams, accurate maps of workings in both seams are readily available and are regularly consulted. The first Pittsburgh squeeze attributed to overlying Sewickley blocks occurred in the Arkwright mine, where a shuttle car crew was developing a section consisting of seven panel headings. These entries were being driven in solid coal 3400 ft from the nearest worked-out Pittsburgh area. As mining advanced it was noticed that certain ribs began to slough and certain areas to show signs

Jan 1, 1953

By Andrew Allan

[Research conducted by the Bureau of Mines hrinq the last 5 years on the uce of machines for 7!naer:rolmrl ?.eve loym~nt in pi.t,c hlng anthracite beds l~a~ provide? data ?howin? that ?:;panrt of thc roof an9 str?eg of thes? oTen - jnqs requires almst half of' the PRS? workin? time. The possibilitie~ of i!rinz a mvable,. te1.ee*co@. c tpr? 3f ?tee1 ~h-!.oltl at the face in~tetcrl of conventional wood a*ti~yorts w?r? si:~q~eteil by engineers engaqad on the~ work If ~uch a shi~l8 COLI.~,~. be ~sve~.~yad, it tnillil man that face workera w~uld be provi8ed with mulrnu.m prot?ct+on from falls of' roof and ribs mi! the en- tire ehift could he I~W? Lo ~lro,J.~:ce cocl. Fermanent tim3er coald be p'l.acnA behind the shielR independently of the 'face work as the face advanced.]

Jan 1, 1953

By J. P. Morris

PREVIOUS investigations1,2 have shown that alloying elements in liquid iron influence the thermodynamic activity of sulphur and thereby affect the partition of sulphur between metal and slag in the desulphurization process. For example, the greater efficiency of desulphurization in the blast furnace as compared to the open hearth can be attributed in part to a higher level of sulphur activity in blast-furnace metal due to the higher concentration of carbon and silicon. In the present investigation, a short study was made of the influence of manganese on the activity of sulphur in liquid iron and iron-carbon alloys. In contrast to carbon and silicon, manganese was found to decrease the activity coefficient of sulphur; and in iron-carbon alloys it counteracts to some extent the influence of carbon. However, at manganese concentrations normally present in the blast furnace or open hearth, the effect of manganese is small. Since manganese sulphide has a limited solubility in iron, manganese can act, under certain conditions as a desulphurizing agent. Considerable data on the manganese-sulphur product in carbon-saturated melts were obtained in the investigation and have been included in this report. The experimental procedure was the same as that used in the earlier investigations on the effect of silicon' and carbon' on sulphur activity. Briefly, the method was as follows: The molten alloy, contained in a graphite or sintered alumina crucible, was brought to equilibrium at a constant temperature with a mixture of hydrogen and hydrogen sulphide of constant composition by bubbling the gas through the metal. Samples of' the melt were taken for analysis at regular intervals by suction through a 2 to 3 mm bore silica tube dipped into the metal. The experiments were run in a graphite spiral resistance furnace with melts weighing 50 to 60 g. The gas bubbling tubes were made of sintered alumina and were 5/16 in. OD, 1/16 in. ID, and 24 in. long. Equilibrium was assumed to have been attained when the sulphur content of the liquid metal reached a constant value. During an experiment there was a rapid loss of manganese from the melt by volatilization. To offset this loss, small additions of manganese were made periodically. The rate of manganese addition needed to maintain a constant manganese concentration was determined in preliminary tests. In all of the experiments, deposits of manganese sulphide formed above the melts in a cooler region of the furnace. Apparently, these deposits resulted from a reaction between manganese vapor and hydrogen sulphide in the gas. To prove that manganese sulphide did not volatilize from the melts to a measurable extent, an experiment was run in which helium was bubbled through liquid iron containing both manganese and sulphur. Although manganese volatilized rapidly in this test, there was no appreciable loss of sulphur. Volatilization of manganese sulphide from a melt would have led to an apparent equilibrium condition in which the sulphur content of the metal was lower than the true equilibrium value. The experimental results are shown in the first seven columns of Table I. The data in the last two columns were obtained from the previous work on the effect of carbon' and show what the results would have been in the absence of manganese but with temperature, gas composition, and carbon content of the metal remaining the same. Comparison of the last four columns show that, in the presence of manganese, the sulphur content of the metal increased at equilibrium and the activity coefficient of sulphur decreased. However, the results show that, for manganese concentrations below 3 pct, the effect of manganese is small. The values for activity coefficient of sulphur given in Table I were calculated from the following relations: S (in liquid metal) + H2 (gas) = H2S (gas) [l] K ph2s/?s X %S X phg = 0.00251 [2] where K is the equilibrium constant for the reaction, PH2S and ph2 are the partial pressures of hydrogen sulphide and hydrogen, respectively, and ?s is the activity coefficient of sulphur. The standard state for sulphur was taken to be a 1 pct solution of sulphur in pure iron. The numerical value for K at 1600°C was determined in the earlier work. For the purpose of showing graphically the results of the tests run at 1600°C, the activity coefficients of sulphur were recalculated so as to correspond to a manganese concentration in the metal of 2 pct in each case. In the calculation it was assumed that the increase in sulphur content of the metal at equilibrium caused by the presence of manganese

Jan 1, 1953

By S. R. B. Cooke, W. Philippoff, Donald E. Cadwell

THE importance of contact angles in flotation has long been recognized, but little has been done to get quantitative relationships between the surface coverage of the mineral by the reagent, the length of the hydrocarbon chain, and the contact angle. It is well known that for a complete monolayer on the surface of a mineral the contact angle 8 is determined only by the reagent1 and principally by the chain length of the hydrocarbon radical. Although for flotation the monolayer usually is regarded as being complete, early experiments of Wark and Cox&apos; showed that at very small concentrations of potassium ethyl xanthate the contact angle on galena changed in a continuous way from 0&apos; to the equilibrium value of 60". Further, Gaudin and Vincenta showed a similar continuity using heptylic acid and sphalerite. This shows that with probably incomplete monolayers, 0 varies with the degree of surface coverage. At the time these experiments were made it was impossible to measure the actual amount of surface coverage, especially since the decrease of the collector concentration in the liquor could be influenced by chemical side reactions. Through the use of the radioactive tracer method for the measurement of the amount of collector adsorbed on the surface of the mineral, Gaudin and Bloecher&apos; were able to determine accurately the actual surface coverage of dodecylamine acetate on quartz, but they did not measure any contact angles. It is believed that the relationship between the surface coverage and the contact angle is extremely important in flotation, especially as Gaudin and Bloecher showed that a 95 pct recovery is possible with a coverage of only 5 pct. Theoretical Considerations The work of adhesion W is the energy bound (in ergs per sq cm) when an interface is formed. It is determined by the difference of the free surface energies (surface tensions) of the respective phases 7j and yZ before contact and the interfacial free surface energy y, after contact. The definition of the contact angle permits the elimination of the unknown surface energy of the solid and hence the calculation of W from the surface tension of the liquid y and the contact angle 8: W = y (1 + COS0) [1] Consider a surface consisting of two components, identified as 2 and 3, 1 being the liquid. The amount of 2 in the composite surface is x, where 0 < x < 1. The respective contact angles with 1 and air are 8, and 8.. The total work of adhesion of such a surface is the sum of the values of the components multiplied by their respective areas. A formal relation can be written: Wm = x-W2+ (l-x)-W, [2] in which W, is the work of adhesion of the composite surface. Eq 1 can be introduced into Wt and Wa, but in the case of W, some discussion is needed. If the two components are segregated, each component forming an integral part of the composite surface there is no physical meaning for a contact angle 8m calculated from W,, by using eq 1. If, on the other hand, the area of each patch of the components is small in comparison with, say, the diameter of the bubble used in measuring, it could be expected that 0m would have a physical significance, because of the action of the surface tension of the liquid-gas interface tending to smooth out sharp corners. How small these patches would have to be is difficult to predict, but by using composite surfaces with microscopically

Jan 1, 1953

By J. L. Wyatt

THE strain sensitivity, K, a property of metals defined as the unit change in electrical resistance per unit strain, was measured for commercial purity titanium wire to determine its usefulness as a strain gage material. A Kelvin double bridge, accurate to 0.000001 ohm, was used to make measurements from 0 to 1 pct total strain. A positive value of 0.17 for K was found. This compares with 2.15 for constantan and 3.5 for cold-worked invar, two of the more common strain gage materials. The effect of temperature also was determined. It was found that a change in temperature of 30°F caused the same resistance change as 1 pct strain. It is therefore concluded that titanium would have utility as a strain gage only if the thermal fluctuations in the specimen could be controlled to a high degree and in applications of very large total strain.

Jan 1, 1953

By G. H. Tausch, T. A. Huber

Very encouraging progress has been made ill the develop-ment of the permanent-type well completion which decreases considerable the cost of completions and workovers and aid-in the acquisition of reliable reservoir information at low cost. Completion and remedial operations are performed with tool,; which pass through the well tubing. Perforating and plug-hack operations can be done with the tubing in place and do not require pipe-handling equipment. Because of the many advantages afforded by this method, development work is going forward in anticipation of ultimately being able 10 use it to perform all usual well completion and workover operations. Effort is also being directed to the development of a more permanent type of lift equipment suitable for use with the permanent-type well completion. INTRODUCTION The permanent-type well completion in one in which the tubing and well-head are set in place only once in the life of the well and the completion or remedial work is performed through the tubing with a tubing-type perforator. a retrievable tubing extension. and other wire-line tools. This new type completion has made possible the saving of one to two days&apos; rig time in the completion of each of several hundred wells During the last two years, and use of equipment developed for this type of completion has resulted in a 75 per cent reduction in cost. of certain types of workovers. In addition. the more reliable indication of the commercial value of a reservoir and the more accurate general reservoir information made Possible promise to be of even greater value in oil recovery than the reduction of costs for completions and workovers Recently. several well.. were worked over by using the retrievable tubing extension suspended on a swab line to plug back with cement and then perforating a higher producing interval with the tubing-type perforator, thus opening the way for complete through-the-tubing workovers which may be performed without pipe-handling equipment or mud. Those items attendant to the use of pipe-handling equipment and mud. such as hoard matting rig substructure. and pits. were also eliminated. There are indications that the elimination of drilling mud during completion and workover operations will frequently give increased well productivity, as plugging of the perforation. will not occur. It ii now possible to perforate selectively small sections of the producing interval and to test a well through these sections prior to perforating more interval. The perforating of additional interval will not entail the costly operations of killing the well and pulling tubing, nor will the old or the new perforations be plugged. The productivity of .mall sections of a reservoir and the actual gas-oil or oil-water contacts may now be determined economically under flowing condition.. Selective completions can be made in this manner to delay gas and water problems and bring about maximum oil recovery. At the present time, gas lift appears to offer the greatest potentialities for artificial lift in the permanent-type well com"letion since it can provide full-open tubing to accommodate the through-the-tubing tools and it may be ultimately developed into a fairly permanent type of lift. With precent-day pas-lift equipment. valve or mandrel failure necessitates occacio11al removal of the tubing. thereby reducing to some extent the permanence of the completion. New gas-lift valves are now

Jan 1, 1953

By A. Ignatieff

"Demonstrations of Automatic Coal Burning EquipmentAT THE 1951 and 1952 Annual Coal Research Conferences sponsored by the Dominion Coal Board and attended by delegates from the Dominion and Provincial governments as well as industry, the importance ,of encouraging the co-operative interest of Canadian coal and equipment industries in •promoting the use of equipment types best suited to burn given Canadian coals was emphasized. It. was suggested that this idea •be enlarged upon at forthcoming C.I.M. meetings that would be .attended largely by coal mining engineers.With this in view, a Domestic Heating Forum (1) was featured in the Coal Division programme at the 1951 Annual Western Meeting of the Institute in Calgary, and a much more ambitious programme, highlighted by live demonstrations, was •staged at the combined Annual Western Meeting and Fourth Meeting of District 4 held in Winnipeg in October 1952.With the excellent co-operation of a number of equipment manufacturers and coal companies, and with facilities kindly provided •by the University •of Manitoba authorities, burning demonstrations were• arranged in the Agricultural Engineering Building, on October l 7th. These demonstrations were a fitting sequel to the Coal Division sessions held in the Royal Alexandra Hotel on October 16th, at which the combustion of coal was specially featured in a series of papers by prominent Canadian and United States specialists.The primary purpose of the demonstrations was to •show that all coal, regardless •of rank, can be satisfactorily used provided that proper application is made with equipment suited to its purpose."

Jan 1, 1953