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By Charles Barron McIntosh

BECAUSE of the well known relationship between a low atmospheric pressure and increased amounts of methane in coal mines, attempts have been made to find associations between low pressures and coal mine explosions. An early study by F. Able disclaimed this relationship. He found that half the explosions took place during a rising barometer when methane content in a ventilated mine would be decreasing. A more recent study by C. L. Hosler revealed a close relationship between anthracite mine explosions and low atmospheric pressure. Bituminous coal mine explosions, where coal dust as well as methane can be exploded, were found to be more closely associated with a rising pressure following a low barometer than with the falling or low pressure period. Emphasis on rising pressure periods led the present writer to investigate the effect of the post-frontal or post-cyclonic weather on coal dust. Dust samples of uniform mesh were exposed in an Illinois mine. Analyses of the dust taken before and after the passage of cold fronts and their accompanying low pressure troughs indicated an increase in coal dust moisture prior to a frontal passage and loss of moisture from coal dust following the time of lowest pressure. Thus the warm, moist air (Tropical Maritime)found over the mine during the falling pressure period was cooled in the mine and moisture added to the dust. Cold, dry air (Polar Continental) accompanies' the rising barometer following a frontal passage and the air, being heated in the mine, subtracted moisture from the coal dust. A similar but seasonal phenomenon occurs from summer to winter, the dry dust period in winter being recognized as the more dangerous period. The question arose as to how the short period or daily changes in moisture content of coal dust compared with the seasonal changes. Temperature and humidity statistics were obtained from the surface and mine entry for the months of July andJanuary. The gain and Ioss of mdisture. to the hine were calculated for these two morths as were the gain and loss associated with mT (Tropical Maritime) and cP (Polar Continental),air masses as observed in the investigatiynsl. Temperature and humidity statistics tigatiynsl.taken from [the two air masses represent atimp span of only 34 hr. The redultant changes as presented in the accompanying table verify the supposition that short period changes in coal mine moisture may attain the magnitude of recognized dangerous seasonal changes. Statistics for the mT air and the July air have been placed next each other and those for cP and January air together for easier comparison of the two warm and two cold air units. The last column readily reveals that there is little difference in the amount of moisture being deposited in the mine from the mT air and the July average air. A similar conclusion is reached regarding the loss of moisture from the mine when it is affected by the cP air mass or the average January air. This comparison would be particularly true from late fall through early spring when strongly contrasting air mass changes are a common occurrence. The invasion of cold, dry air following a cold front thus produces a drying period that could well receive more attention as a danger period for coal dust explosions. This drying period would compare with Able's explosion period during a rising barometer. The drying period is also perltinent in Hosler's findings, where it was noted that the average explosion day (for bituminous coal mines) followed the day of lowest atmospheric pressure. Moreover, the author's investigation of some 365 coal mine explosions also indicates that this post-frontal period should receive special attention in connection with mine safety measures. Two comparatively recent major explosions in Illinois (Centralia and West Frapkfort) occurred after the mines had been under the influence of cold-dry air for 25 to 30 hr-following a deep low pressure passage. Dust was the important explosive element in both these explosions.

Jan 1, 1958

By A. Phillips, D. H. Killpatrick, V. Kerlins

The tensile failure of two dispersion-strengthened Ni-20 Cr alloys was studied and compared to the fracture of a similar alloy with no dispersoid. The fracture characteristics were studied using electron fruc-tography and transmission electron microscopy. In all three cases, the mode of failure was found to be microvoid coalescence. The failure in the dispersion-strengthened alloys was found to have initiated at the particles. The size of the dimples in the fracto-graphs was found to be related to the spacing of the particles, but not to the total elongation before failure. The elongation before failure was found to be related only to the amount of dispersed phase. These results are compared to those predicted by a theoretical model of ductile failure. THE continually increasing strength requirements for creep-resistant materials capable of long life at service temperatures above 1600"F (875"C) have developed considerable interest in dispersion-strengthened nickel-base alloys. The high yield strength of these alloys results from the presence of a dispersion of fine particles of thoria which act to impede the normal motion of dislocations. Many theories have been presented to explain the role of the dispersion in the strengthening of these alloys. A good review of these theories is presented by Ansell.' The ultimate strength of such alloys is not only related to mechanisms raising the yield strength, but also to the amount of work-hardening which occurs. This work-hardening is determined by the work-hardening rate and the amount of plastic strain before failure. Since fracture limits the amount of plastic strain, a study was undertaken to gain a better understanding of the fracture mechanisms in these alloys. Electron fractography and transmission electron microscopy were used to study the fracture characteristics in two dispersion-strengthened alloys and one similar alloy containing no dispersoid. These results are related to the tensile properties of the dispersion-strengthened alloys at room temperature and at 2000°F (1095°C). The results are also related to a theory for ductile fracture. 1) PROCEDURE Standard tensile specimens were made from 0.020-in. (0.051-cm) sheets of three different Ni-Cr alloys. The alloys had nominal compositions of Ni-20Cr, Ni-20Cr-2Th0,, and Ni-2OCr-4Th0,. All alloys were supplied in an annealed condition. The specimens were fractured in tension at room temperature to determine the effect of the dispersed thoria on the fracture appearance. The tensile properties were determined from the average of a minimum of three ten- sile specimens for each condition tested. The fracture surface of all of the alloys was examined by electron microscopy using standard two-stage plastic-carbon replica techniques. Thin foils of the dispersion-strengthened alloys were used to investigate the size and spacings of the dispersion particles, and to investigate sections of the 2 pct thoria alloy taken from areas of the specimen adjacent to the fracture surface. The thin foils were mechanically ground to 0.010 in. (0.025 cm) and then chemically polished to approximately 0.001 in. (0.003 cm) in a solution of 29 g of ferric chloride and 10 ml hydrochloric acid in a liter of water. The polishing solution was maintained at 150"F (65°C) during the thinning operation. The final thinning of the foil was done electrolytically using a solution of 700 ml ethanol, 100 ml 2-butoxy eth-anol, 120 ml distilled water, and 78 ml perchloric acid (70 pct). The potential was maintained at 15 v and the bath temperature at -20°~ (-29°C) during the thinning operation. The final thickness of the foil was approximately l000A as determined from the width of twins boundaries observed in many of the foils. 2) RESULTS AND DISCUSSION The electron fractographs of the fracture surfaces of the alloys are shown in Figs. 1, 2, and 3. The normal interpretation of this type of fractographz is that, as a result of the difference between elastic and plastic properties of the matrix and the particles or other inhomogeneities in the alloy, microvoids are formed

Jan 1, 1969

By H. L. Luo, W. Klement

By rapidly quenching Ag-Pt alloys from the melt, a continuous series of solid solutions has been obtained. At equilibrium''2 these fcc elements form a peritectic system, Fig. 1. Weighed amounts of silver and platinum powder (325 mesh, purity greater than 99.9 pct) were mixed for 24 to 120 hr, pressed into compacts, sintered at 1000°C in a hydrogen atmosphere for at least 16 hr, and then furnace-cooled. Because of the difficulty in achieving homogeneity in alloys containing more than about 40 at. pct Pt, the sintered compacts were induction-melted under hydrogen in alumina crucibles and then cold-rolled into wires. Small amounts ("30 mg) of alloys cut from various sections of the sintered compacts or rolled wires were heated to at least 50' ~ above the liquidus in an alumina insert held within an induction-heated graphite crucible; then the molten alloy was ejected by a blast of helium onto a lightly polished copper strip held on the inner periphery of a rotating wheel. The flakes thus obtained were typically 1 sq mm in area or often slightly larger for the silver-rich alloys. X-ray diffraction patterns were obtained with nickel-filtered copper K radiation in a 114.6-mm-diam Debye-Scherrer camera with rotated specimens. Lattice parameters and associated uncertainties were estimated from extrapolations against the Nelson-Riley function. High-angle lines were always resolved and spacings were computed relative to r(CuKa!,) = 1.540508 The details of these techniques have been discussed previously.s'6 Lattice parameters of the solid solutions are plotted in Fig. 2, together with the data of Schneider and Esch,' Johansson and Linde,' and Novikova and pudnitskii. Each of the present lattice spacings represents two or more independent determinations. The alloys were homogeneous within 2 at. pct of nominal composition as estimated from the uncertainties in the lattice spacings. Many of the mechanisms involved in the achievement of metastable solid solutions by rapidly quenching from the melt have been previously discussed. There is some evidence" that such solid solubility cannot be obtained when the liquid alloys are cooled

Jan 1, 1963

By L. W. Kemph, K. R. VanHorn

During the recent development of aluminum alloys for free-cutting screw-machine rod, it became desirable to know something of the solubility of lead and bismuth in liquid aluminum and in some aluminum alloys. The literature is not particularly helpful in supplying this information. These portions, therefore, of the constitutional relationships of aluminum-bismuth and aluminum-lead alloys were investigated by thermal analysis and by chemical analysis of samples taken from aluminum-rich melts in equilibrium with precipitated lead or bismuth. The solubility of lead and bismuth in some liquid aluminum-copper alloys was also investigated. Some consideration was also given to the solubility of these elements in solid aluminum. Among the earliest investigators of the aluminum-lead and alunlinum-bismuth systems was Wright,' who reported that melts of aluminum and lead formed two layers indicating limited liquid solubility. Under his conditions, the aluminum-rich layer was reported to contain 1.91 per cent Pb and the lead-rich layer, 0.07 per cent Al. Subsequently, Pecheau2 found that in aluminum-rich alloy melts with more than 10 per cent Pb three layers were distinguishable. He reported that the middle layer contained from 3 to 10 per cent Pb. He also found that the melting point of aluminum appeared to be lowered slightly by the addition of lead. Gwyer3 investigated these alloys and found evidence of a slight lowering of the freezing point of aluminum by the addition of either lead or bismuth. He found no evidence of solid solubility in either case and made no attempt to determine the liquidus curves. Hansen and Blumen-tha14 reported that the addition of lead distinctly lowered the solidification point of aluminum. They also found that bismuth lowered the melting point of aluminum. Guillet5 reported almost complete mutual immiscibility for the aluminum-bismuth alloys in the liquid state. Bohner6 examined the effect of various concentrations of lead and bismuth on the electrical conductivity of aluminum. He found decreases in conductivity on annealing at 500' C. as compared with the conductivity of the same alloys on annealing at 300' C.

Jan 1, 1939

By Robert C. Mackenzie

EXAMINATION by the differential thermal analysis technique of a large number of samples of soil and other clays from various parts of the world has demonstrated that the occurrence of cold-precipitated hydrated ferric oxide (the identification of which in soil clays has previously been reported5) is not confined to any limited locality; e.g., it has been found in varying amounts in clays from Britain, France, South Africa, and Mexico. The conditions necessary for its formation have not yet been elucidated in spite of the number of samples examined, and, since this mineral is so easily prepared in the laboratory, it has been considered that a study of its constitu¬tion and of the conditions under which it could be prepared might. lead to a better understanding of the factors involved. These experiments form the subject of this short paper, and while they do not supply a definite answer to the mode of formation of this mineral in nature, they may, it is hoped, add something to our knowledge in this direction. EXPERIMENTAL WORK Materials Employed The a-Fe2O3.H2O (goethite) and B-Fe2O3.H2O (Weiser and Milligan") were obtained from the Department of Geology, University of Aberdeen, and Rothamsted Experimental Station, respectively. The beta material had been prepared by the method described by Fernelius.1 y-Fe2O3.H2O (lepidocrocite) was prepared at the Macaulay Institute for Soil Research by the method of van Schuylenborgh.6 The method employed for preparation of the cold-precipitated hydrated ferric oxide* was as follows: 1: 1 NH4OH was added (moderately fast with rapid stirring) to a solution of 5 grams FeC13.6H2O in 250 ml distilled water at room temperature (ca. 15°C) until red litmus turned blue, and then 2 to 3 drops in excess. The resultant precipitate was filtered off on a Buchner funnel and washed free from Cl- with distilled water. Previous experiments having shown that drying over P2O5 at room temperature or drying at 105°C in the oven did not significantly affect the thermogram,5 samples were nor-

Jan 1, 1952

By L. W. Kempf, K. R. Van Horn

DURING the recent development of aluminum alloys for free-cutting screw-machine rod, it became desirable to know something of the solubility of lead and bismuth in liquid aluminum and in some aluminum alloys. The literature is not particularly helpful in supplying this information. These portions, therefore, of the constitutional relationships of aluminum-bismuth and aluminum-lead alloys were investigated by thermal analysis and by chemical analysis of samples taken from aluminum-rich melts in equilibrium with precipitated lead or bismuth. The solubility of lead and bismuth in some liquid aluminum-copper alloys was also investigated. Some consideration was also given to the solubility of these elements in solid aluminum. Among the earliest investigators of the aluminum-lead and aluminum-bismuth systems was Wright,1 who reported that melts of aluminum and lead formed two layers indicating limited liquid solubility. Under his conditions, the aluminum-rich layer was reported to contain 1.91 per cent Pb and the lead-rich layer, 0.07 per. cent Al. Subsequently, Pecheau2 found that in aluminum-rich alloy melts with more than 10 per cent Pb three layers were distinguishable. He reported that the middle layer contained from 3 to 10 per cent Pb. He also found that the melting point of aluminum appeared to be lowered slightly by the addition of lead. Gwyer3 investigated these alloys and found evidence of a slight lowering of the freezing point of aluminum by the addition of either lead or bismuth. He found no evidence of solid solubility in either case and made no attempt to determine the liquidus curves. Hansen and Blumenthal4 reported that the addition of lead distinctly lowered the solidification point of aluminum. They also found that bismuth lowered the melting point of aluminum. Guillet5 reported almost complete mutual immiscibility for the aluminum-bismuth alloys in the liquid state. Bohner6 examined the effect of various concentrations of lead and bismuth on the electrical conductivity of aluminum. He found decreases in conductivity on annealing at 500° C. as compared with the conductivity of the same alloys on annealing at 300° C.

Jan 1, 1938

By L. W. Kemph, K. R. VanHorn

During the recent development of aluminum alloys for free-cutting screw-machine rod, it became desirable to know something of the solubility of lead and bismuth in liquid aluminum and in some aluminum alloys. The literature is not particularly helpful in supplying this information. These portions, therefore, of the constitutional relationships of aluminum-bismuth and aluminum-lead alloys were investigated by thermal analysis and by chemical analysis of samples taken from aluminum-rich melts in equilibrium with precipitated lead or bismuth. The solubility of lead and bismuth in some liquid aluminum-copper alloys was also investigated. Some consideration was also given to the solubility of these elements in solid aluminum. Among the earliest investigators of the aluminum-lead and alunlinum-bismuth systems was Wright,' who reported that melts of aluminum and lead formed two layers indicating limited liquid solubility. Under his conditions, the aluminum-rich layer was reported to contain 1.91 per cent Pb and the lead-rich layer, 0.07 per cent Al. Subsequently, Pecheau2 found that in aluminum-rich alloy melts with more than 10 per cent Pb three layers were distinguishable. He reported that the middle layer contained from 3 to 10 per cent Pb. He also found that the melting point of aluminum appeared to be lowered slightly by the addition of lead. Gwyer3 investigated these alloys and found evidence of a slight lowering of the freezing point of aluminum by the addition of either lead or bismuth. He found no evidence of solid solubility in either case and made no attempt to determine the liquidus curves. Hansen and Blumen-tha14 reported that the addition of lead distinctly lowered the solidification point of aluminum. They also found that bismuth lowered the melting point of aluminum. Guillet5 reported almost complete mutual immiscibility for the aluminum-bismuth alloys in the liquid state. Bohner6 examined the effect of various concentrations of lead and bismuth on the electrical conductivity of aluminum. He found decreases in conductivity on annealing at 500' C. as compared with the conductivity of the same alloys on annealing at 300' C.

Jan 1, 1939

By John W. Buch

NeaRly 25 years ago operating officials in the northern anthracite field were confronted with the problem of profitably mining virgin beds of thin coal (those 48 in. and under) or destroying them by mining underlying thick beds. To solve this problem costly hand-mining methods were replaced by cheaper mechanical methods, which eliminated the need for the lifting of bottom or the brushing of top in excessive quantities, which was essential if proper height for hand loading1 was to be provided. During this period long-face mining was an outstanding development. In its favor in comparison with any other method were the ease with which undercutting machines could be used, a differential in powder cost of about fifteen cents per ton in favor of this method over mining from a solid chamber or pillar face, and a greater production per day from a single working place, resulting in lower capital expenditures for a given total production, closer supervision and lower transportation cost. The long faces were drilled by jackhammer and undercut by machines. The coal from the cut was loaded into mine cars placed on the gangway road by means of a double-drum mechanical scraper engine and a mechanical V-type scoop. A tugger hoist was used to spot empty cars at the loading point from a supply placed at the operation by an electric mine locomotive. During loading the roof was supported by vertical wooden props paralleling the face. After the loading was completed the scraper engine and the ropes that had been used to propel the scoop in the loading of coal transferred the props to and along the face. A row of unfilled cogs was then built parallel to the new face and about 6 ft. from it. These cogs were usually made 6 by 3 ft., the longer dimension paralleling the face; they were placed on an average at 12-ft. centers. These wooden cogs were left in place and were buried later by falling roof. Attempts to remove them were never successful. When a new long face was started, the cog spacing would be increased to about 20-ft. centers. As successive cuts were made, weight would begin on the cogs, and they

Jan 1, 1940

By Ralph J. Schilthis

Several investigators1-8 have reported evidence of the existence of native or connate water in oil-and-gas-bearing strata. Both water and salt have been detected in cores of oil sands that yielded oil and gas exclusively when produced. Electrical logs often reveal unexpectedly low resistivity through oil and gas sands, indicating the presence of some material that is a considerably better conductor of current than oil and gas. Furthermore, calculationsg of the oil and gas content of reservoirs based upon production and reservoir-pressure decline data indicate appreciably lower values than are arrived at under the assumption that the pore space is occupied completely by oil and gas. Origin and Occurrence of Connate Water in Oil-and-gas-bearing Formations The view has been expressed, 10-15 and is generally agreed upon, that the expulsion of oil and gas material from source beds and the subsequent migration and accumulation occurred in the presence of salt water. As the strata that usually form reservoirs for oil and gas were laid down by, or in the presence of, ancient seas, the pore space within the strata must have been saturated with salt water before the entrance of the oil and/or gas. Thus, the accumulation of oil and/or gas in the upper regions of structures suitable for reservoirs must have required displacement of the connate water therefrom. In the absence of any forces other than gravitational, it would be expected that the displacement of the connate water out of the zones finally occupied by gas and oil would be complete, and that the vertical distribution of gas, oil, and water in a reservoir would be strictly in the order of their densities. Apparently, however, surface and interfacial forces that will not permit complete segregation of the fluids are active within the capillary spaces comprising a reservoir. The effects of these forces on both accumulation and production of oil and gas have been the subject of study by a number of investigators.16-37 In general, the view is held that the character of most materials that make up the reservoir rock leads to preferential wetting of the rock by

Jan 1, 1938

By John W. Buch

NeaRly 25 years ago operating officials in the northern anthracite field were confronted with the problem of profitably mining virgin beds of thin coal (those 48 in. and under) or destroying them by mining underlying thick beds. To solve this problem costly hand-mining methods were replaced by cheaper mechanical methods, which eliminated the need for the lifting of bottom or the brushing of top in excessive quantities, which was essential if proper height for hand loading1 was to be provided. During this period long-face mining was an outstanding development. In its favor in comparison with any other method were the ease with which undercutting machines could be used, a differential in powder cost of about fifteen cents per ton in favor of this method over mining from a solid chamber or pillar face, and a greater production per day from a single working place, resulting in lower capital expenditures for a given total production, closer supervision and lower transportation cost. The long faces were drilled by jackhammer and undercut by machines. The coal from the cut was loaded into mine cars placed on the gangway road by means of a double-drum mechanical scraper engine and a mechanical V-type scoop. A tugger hoist was used to spot empty cars at the loading point from a supply placed at the operation by an electric mine locomotive. During loading the roof was supported by vertical wooden props paralleling the face. After the loading was completed the scraper engine and the ropes that had been used to propel the scoop in the loading of coal transferred the props to and along the face. A row of unfilled cogs was then built parallel to the new face and about 6 ft. from it. These cogs were usually made 6 by 3 ft., the longer dimension paralleling the face; they were placed on an average at 12-ft. centers. These wooden cogs were left in place and were buried later by falling roof. Attempts to remove them were never successful. When a new long face was started, the cog spacing would be increased to about 20-ft. centers. As successive cuts were made, weight would begin on the cogs, and they

Jan 1, 1940

By Irving A. Palmer

During the past 15 years in this country there have been few additions to the literature of lead smelting. After the consolidation of the principal smelting companies at the beginning of this period it became the policy of the larger company not to permit the publication of details in regard to many of its metallurgical processes. This led to similar action on the part of some of its competitors. The result, of course, was a decided decrease in the number of papers written upon the practical side of the subject. Even upon the theoretical side the contributions have been few. It would seem that the industry as a whole has suffered from this general unwillingness to exchange information. While it is true that a given company is entitled to the reward that may come from its own development of a new process, it is also true that a still greater reward might be the result of a free exchange of ideas with other plants. This principle has been recognized for a long time in other metallurgical industries, notably those engaged in the smelting of iron and the manufacture of steel. It is pleasing to note that the leading lead-smelting company has very recently decided to modify its policy of secrecy, and to permit the publication of papers covering some details of its metallurgical methods. The statement has been made that there has been but little progress in lead smelting during the period just referred to. This impression is due in part, no doubt, to the scarcity of papers written on the subject. 'There has been, it is true, some discussion of the new sintering processes, but with little reference to detail, and to the effect that blast roasting has had upon the industry as a whole. In spite of the prevailing belief, it may be said that lead smelting, in common with other metallurgical industries, has made steady and substantial progress. It is the purpose of the present paper to discuss briefly some features of the industry as it is now conducted, with special reference to the blast-furnace practice in the larger silver-lead smelting plants of the United States and Mexico.

Jan 1, 1915

By E. N. Skinner, Arthur Philliops

During the course of an experimental program concerned with the hydrogen embrittlement of copper containing oxygen in concentrations within the solubility limits it became necessary to make a critical appraisal of the literature dealing with the solubility relationships of oxygen and solid copper. The latest determinations, and perhaps the only data obtained on "spectroscopically" pure copper, are those of Rhines and Mathewson' who reported that the solid solubility increases from 0.007 per cent oxygen at 600°C. to about 0.01; per cent at 1500ºC. Hanson, Marryat and Ford2 had previously placed the solubility limit at less than 0.009 per cent oxygen at 1000ºC. and Allen and Street3 had suggested, on the basis of an unpublished research by T. Hemitt, not over 0.005 per cent oxygen at 500°C. In the introductory stages of the investigation indirect evidence accumulated to suggest that the solubility limits were significantly lower than those previously reported. For this reason it was deemed essential to clarify this point before proceeding with a program intended to establish a quantitative relationship between hydrogen embrittlement and oxygen concentrations positively known to be within the solid solution range. Furthermore, the increasing production and the highly selective applications of the commercial "oxygen-free" coppers inevitably direct attention to the practical necessity for exact knowledge regarding the effects of mini-tie concentrations of the elements ordinarily found in the high-purity coppers now available. Of these elements oxygen occupies a unique position, not only by virtue of its specific effects on copper but more particularly in view of its important reactive tendencies toward the other impurities with which it is associated. Rhines and Mathewson considered several methods for measuring the solubility of oxygen and finally adopted the simple plan of saturating the specimens, obtained from redeposited cathode copper, by heating at the desired temperature in air. After the removal of surface oxide by mechanical and chemical means, the oxygen content was determined in the underlying metal. In general, this process of saturation, with a few modifications, was followed by the present writers. Although the procedure is direct and has obvious advantages, its effectiveness, unfortunately, is reduced by an excessive scaling of the copper, particularly at the higher temperatures. After saturation treatments above 900°C. the writers found that the specimens, necessarily rather thin in the original condition, consisted largely of scale and yielded too little metal for a satisfactory analytical sample. Furthermore, great difficulty was experienced in effecting complete removal of the scale. Needless to say, it is necessary to exercise extraordinary care in the preparation of the surface of the analytical sample in order to eliminate submicro-scopic fragments of cuprous oxide which ordinarily are lodged in the crevasses and

Jan 1, 1941

By E. N. Skinner, Arthur Philliops

During the course of an experimental program concerned with the hydrogen embrittlement of copper containing oxygen in concentrations within the solubility limits it became necessary to make a critical appraisal of the literature dealing with the solubility relationships of oxygen and solid copper. The latest determinations, and perhaps the only data obtained on "spectroscopically" pure copper, are those of Rhines and Mathewson' who reported that the solid solubility increases from 0.007 per cent oxygen at 600°C. to about 0.01; per cent at 1500ºC. Hanson, Marryat and Ford2 had previously placed the solubility limit at less than 0.009 per cent oxygen at 1000ºC. and Allen and Street3 had suggested, on the basis of an unpublished research by T. Hemitt, not over 0.005 per cent oxygen at 500°C. In the introductory stages of the investigation indirect evidence accumulated to suggest that the solubility limits were significantly lower than those previously reported. For this reason it was deemed essential to clarify this point before proceeding with a program intended to establish a quantitative relationship between hydrogen embrittlement and oxygen concentrations positively known to be within the solid solution range. Furthermore, the increasing production and the highly selective applications of the commercial "oxygen-free" coppers inevitably direct attention to the practical necessity for exact knowledge regarding the effects of mini-tie concentrations of the elements ordinarily found in the high-purity coppers now available. Of these elements oxygen occupies a unique position, not only by virtue of its specific effects on copper but more particularly in view of its important reactive tendencies toward the other impurities with which it is associated. Rhines and Mathewson considered several methods for measuring the solubility of oxygen and finally adopted the simple plan of saturating the specimens, obtained from redeposited cathode copper, by heating at the desired temperature in air. After the removal of surface oxide by mechanical and chemical means, the oxygen content was determined in the underlying metal. In general, this process of saturation, with a few modifications, was followed by the present writers. Although the procedure is direct and has obvious advantages, its effectiveness, unfortunately, is reduced by an excessive scaling of the copper, particularly at the higher temperatures. After saturation treatments above 900°C. the writers found that the specimens, necessarily rather thin in the original condition, consisted largely of scale and yielded too little metal for a satisfactory analytical sample. Furthermore, great difficulty was experienced in effecting complete removal of the scale. Needless to say, it is necessary to exercise extraordinary care in the preparation of the surface of the analytical sample in order to eliminate submicro-scopic fragments of cuprous oxide which ordinarily are lodged in the crevasses and

Jan 1, 1941

By Morgan Walker

Intermittent injection of gas in gas-lift pumping is a variation of the common practice in that the gas is delivered to the well for a short period, called the "on time," followed by a period during which none is admitted, called the "off time," instead of being admitted continuously at a constant rate or by intermittent flowing in which it is occasionally delivered to the well in just sufficient quantity to flow off the accumulated head of fluid. The term "gas" is used throughout this discussion but it should be remembered that in so far as the operation is concerned either air or natural gas may be used. The equipment at the well is the same as commonly used in gas-lift installations and gas may be admitted to either the tubing or the casing. It seldom occurs that all the wells on a lease can be pumped economically by intermittent injection from one header. Wells that have flow characteristics which permit their being handled together have their intake lines grouped at a central compressor station. Well groups may consist of two or more wells. The total volume of gas delivered by each group of compressors goes to one well at a time through a quick opening valve, each well connected to the header receiving its charge of gas in turn. Special cases may require a deviation from this arrangement. The distribution of the gas to the different wells is effected by an automatic timing device which operates quick-opening valves on the intake lines. The timing mechanism may be actuated by electricity, liquid or gas pressure, The essential factor in the operation of the timing mechanism is that as one intake valve is closed another must be opened. Water-operated Timing Device Timing devices operate the intake valves either directly, or indirectly by pilot valves. Of the former type one that is operated by water and has given satisfactory service is shown in Fig. 1 and can be made on the lease. The horizontal cylinder is a piece of 10-in. casing about 7 ft. long, closed at each end and free to oscillate about a fulcrum at the center.

Jan 1, 1929

By J. E. Howard

On Aug. 25, 1911, a rail failed on the Lehigh Valley Railroad, causing a disastrous wreck. The surface of the fracture was in a plane at right angles to the length of the rail. There was a dark-colored, oval spot on this surface, located on the gage side of the head, representing the part of the rail which was the first to fracture. The nucleus of this spot showed that the fracture had an interior origin. Other fractures of this kind, the peripheries of which had not reached the surface of the rail, presented surfaces having a (silvery luster. The darkened surface of the present fracture was caused, doubtless, by the air having had access to it. This fracture was recognized as a fatigue fracture, of a modified type, its interior origin having been due to a component in the rail which is not usually present in cases of fatigue fractures. The metal next the running surface of the head of the rail was in a state of internal compression, this being the component not commonly met with in other cases, and which caused the fracture to have its interior origin. For the purpose of giving this modified type of fatigue fracture a specific name, for identification, the term "transverse fissure" was applied. No mystery was thought to attach to its formation, or to its development. The explanation of its occurrence seemed obvious in the light of common knowledge upon the behavior of steel under repeated alternate stresses.' By reason of the state of internal compression at the running surface, the maximum tensile stresses in the head, ander bending loads, were along an interior element. Here the tensile strains were higher than in the fibers more remote from the neutral axis. Under such conditions the fracture of the rail would be expected to have an interior origin. A discussion of the subject of transverse fissures essentially becomes a discussion of fatigue fractures, since they are believed to be identical. The descriptive term employed, merely for the identification of this type of fatigue fracture, had the appearance of creating alarm. Apprehensions arose that a new phenomenon in the physical properties of steel had presented itself, the explanation of which was sought in every

Jan 1, 1918

By H. Q. Golder

With the development of open-pit mines of ever increasing depth, the stability of the pit slopes in soil and rock is of growing economic importance. How is it, considering the newness of the problem that we know anything at all about the stability of man-made slopes? How much do we know and how did it all begin? We can make a reasonable estimate of the stability of a slope in soil, but we know as yet woefully little about slopes in rock because the problem is much more complex. It is only with the development of the capacity of the computer to handle wearisome calculations that any but the simplest of stability problems in rock have become possible of solution. But what we do know is a guide of immense value in the design of slopes in rock. But remember that the computer is a great elevator; it takes everyone's feet off the ground! So our study began with soils and what is now known as "Soil Mechanics", which is a translation of the German term "Bodenmechanik". It is a pity that the title of Terzaghi's book "Erdbaumechanik" was not used instead. But here the task of the translator is difficult because English lacks the facility of German to string together several words and make a new one whose meaning is unequivocal. Thus, we have the three German words 'Erde' 'Bau' and 'Mechanik'. 'Erde' means "earth" in almost all the English senses including "soil". 'Bau' and 'bauen' convey the meaning of building and construction, and 'Mechanik' means "mechanics" which includes statics and dynamics and the 'mechanics of materials', etc. So that a correct translation of the German is a phrase like "the mechanics of construction with, in or on, earth or soil." However we are stuck with 'Soil Mechanics' and that is where it all began. Now this study or subject did not begin with 'Terzaghi' although his contribution to the subject is unquestionably greater than that of any other single person. Every scientific discipline has its 'classical problem' and that of soil mechanics is 'the earth pressure problem' and it began in the 17th century. In fact, it probably began before this with the introduction of gunpowder to Western Europe in about the 15th century, but the first known reference to the problem was by Vauban, a distinguished French military engineer who lived from 1633 to 1707 and who gave rules for the dimensions of retaining walls from 6 to 80 ft. in height. The soil properties were not mentioned by Vauban probably because the rules were intended to be applied to fortifications only, but Poncelet (1840) claimed that Vauban's rules were based on a theory, and not simply on military and practical

Jan 1, 1972

By D. W. Fuerstenau

Recently R. J. Charles1 showed that comminution of brittle or semi-brittle materials in batch operations is described more appropriately by a variable energy relationship than by the specific relationships proposed by Rittinger,2 Kick,3 and Bond.' That is, the value of n in the empirical differential operation which applies to crushing and grinding (Eq. 1) is variable. Independently, Holmes' developed an identical generalized equaton for size reduction. The experimental data of Charles and Holmes show that the value of n is determined by the material and the comminuting machine and is constant for a given combination of these two conditions. The general objective of the present article is to extend the Charles-Holmes concepts to continuous ball milling. The specific objective is to analyze the operation of a vibratory ball mill dry-grinding chromite in a continuous open circuit and to develop an equation for the comminution of chromite in this mill. Basic Principles: In a batch mill the length of time during which the material is ground is a direct measure of the energy expended on the material, except possibly for exceedingly fine grinding. However, in a continuous operation, the fraction of the total expended energy which is useful for grinding will vary according to feed rate and amount of material in the mill. If the amount of material within a continuously operating vibratory mill is low enough so that only part of the expended energy is used for grinding, the extent of size reduction at constant power input must depend upon the length of time the material is retained within the mill, namely, upon retention time. The following analysis pertains to a continuous mill operating under these conditions. The empirical differential equation that applies to the comminution of brittle materials is:" dE = -Cdx/x" [1] where dE is an infinitesimal energy expenditure, C a constant, dx an infinitesimal size change, x the particle size, and n a constant. For continuous grinding in an open circuit at constant power input, P, Eq. 1 must be written as (dtr)P = -C dx/x" [la] where dt, is an infinitesimal time during which a particle of size x is in the mill, and C' is a constant. A ground product never consists of particles of single size but always comprises a distribution of sizes. In comminution, the expenditure of energy causes a lateral shift in the size distribution.', ' " The general objective of any engineering study of comminution is to correlate the magnitude of this size distribution shift with the energy expended, the ultimate aim being to cause the greatest shift with the least amount of expended energy. Although a number of criteria can be used to measure this shift, Schuhmann's size modulus has been found convenient.' Mathematically, the Schuhmann size distribution can be expressed as follows:" y = l00(x/k) [2] or in differential form: dy = [F- xa-' dx ] K, where y is percentage of material finer than size x, a is a constant that determines weight distribution among particles of various sizes, and k the size modulus that denotes the theoretically maximum-sized particle in any size distribution. By considering the energy required to reduce an element of weight of material, dy, from size x, to size x, the element of time during which the material must remain in the mill at at power will be (dt..).= J'-Cax!(dy) [3] Summing up all the elements of weight from zero to 100 for a product that conforms to the Schuhmann size distribution yields C C f Cdx,\( 100«x°-'dx\

Jan 1, 1960

By W. L. Worrell

R. C. Gifkins (CSIRO)—In this paper evidence is put forward to support the idea of grain boundary shearing in aluminum at 4.2°K and the phenomenon is explained in terms of a low-temperature "equicohesive temperature". It is stated that these findings show that grain boundary shear cannot be ruled out in any situation by temperature arguments alone. We believe, from our own recent study of "apparent grain boundary sliding'' at temperatures below 0.45 Tm, that it can be ruled out on temperature arguments alone.45 Our experiments were made principally with magnesium and a Ms-A1 alloy ("Magnox A12"). Careful examination of offsets of marker lines or steps at grain boundaries produced by deformation at room temperature (-0.3 Tm) showed many of these to result from curvature over narrow zones along the grain boundaries. A significant residuum did, however, appear as a sharp offset or step. It was found that the mean value of this step rose to a small value during the first 0.5 to 1 pct strain and then remained at this level with further strain. Moreover, exactly the same values were obtained (at the same stress) at 75°C instead of 21°C. That is, in this range of temperature the "apparent sliding" was not temperature-sensitive. At 125°C and above there was sliding which increased with strain and which was temperature-dependent. When this temperature-dependent sliding was used to calculate the sliding to be expected at room temperature, this underestimated the "apparent sliding" by a factor of 104. The conclusion drawn is that the "apparent sliding" consists of shear localized in a zone of a width measured perhaps in microns, whereas it seems that true sliding occurs on the boundary surface.46 A model for such localized shear has been developed in general terms, following a similar model of Urie and Wain.47 Other strong evidence for low-temper- ature sliding has been based on the offsets of marker lines consisting of a substructure seen using the electron microscope to resolve these.48 We have repeated this work and found that the effects can be accounted for in terms of cracks in an oxide film which is produced when the substructure is etched up; these cracks form over zones of shear rather than at actual interfaces. However, in aluminum at room temperature (-0.3 Tm) there is no "apparent sliding" which is optically detectable. We suggest that, when the temperature is much lower (and possibly the rate of strain higher, too), as in the experiments of Chin et al., then aluminum behaves like magnesium at room temperature, and a narrow zone of shear develops to accommodate differences in strain across the grain boundary. Such a zone could well give rise to triple-point cracks. It is hoped to investigate these suggestions further. B. Y. Chin, W. F. Hosford, Jr., and W. A. Backofen (authors' reply)—It is interesting to have Dr. Gif-kin's comments, although it is somewhat difficult to reply in detail without the reference containing the work that he describes. Apparently though, he does find a low-temperature temperature-independent sliding that would seem to be related to the observations reported here. Perhaps some of the difficulty has semantic origins, growing out of the distinction between ('true sliding" and "apparent sliding".

Jan 1, 1965

By M. T. Halbouty

The Laredo oil district, South Texas, includes an area of approximately 200 miles long north and south and 75 miles wide, embracing the following counties: Starr, Zapata, Jim Hogg, Webb, Duval and McMullen. The area is relatively old in respect to the production of oil, as the first oil was discovered and produced in the Piedra Pintas field in Duval County on Sept. 10, 1905. Since that date, continuous new discoveries have contributed to the development of this district until, at the present time, it is one of the important oil-producing and gas-producing areas in the world. The year 1937 also had its share of new discoveries in the district, including not only new oil fields but also new sands in already producing pools and important extensions to existing sands and fields. Among the most important field discoveries, by counties, are: Duval County..... Benavides, Sweden, Thomas-Lockhart, Labbe and Lundell fields Jim Hogg County.. Las Animas field McMullen County. Ezzell field Starr County...... El Tanque field Webb County..... Killam and Oilton fields Of these, Benavides, Oilton, Killam and Ezzell have so far proved themselves most important; the Benavides field, Duval County, showing by far the most activity. For the year 1937, therc were 283 wildcat tests drilled in this district, of which 35 were oil producers, 20 completed as gas wells and 228 abandoned as dry holes. Duval County, as usual, received the greatest amount of wildcat drilling, having 21 oil wells, 5 gas wells and 63 dry holes completed during the year for a total of 89 tests. Next came Webb County with 4 oil wells, 4 gas wells and 53 dry holes for a total of 61 tests.The Laredo oil district, South Texas, includes an area of approximately 200 miles long north and south and 75 miles wide, embracing the following counties: Starr, Zapata, Jim Hogg, Webb, Duval and McMullen. The area is relatively old in respect to the production of oil, as the first oil was discovered and produced in the Piedra Pintas field in Duval County on Sept. 10, 1905. Since that date, continuous new discoveries have contributed to the development of this district until, at the present time, it is one of the important oil-producing and gas-producing areas in the world. The year 1937 also had its share of new discoveries in the district, including not only new oil fields but also new sands in already producing pools and important extensions to existing sands and fields. Among the most important field discoveries, by counties, are: Duval County..... Benavides, Sweden, Thomas-Lockhart, Labbe and Lundell fields Jim Hogg County.. Las Animas field McMullen County. Ezzell field Starr County...... El Tanque field Webb County..... Killam and Oilton fields Of these, Benavides, Oilton, Killam and Ezzell have so far proved themselves most important; the Benavides field, Duval County, showing by far the most activity. For the year 1937, therc were 283 wildcat tests drilled in this district, of which 35 were oil producers, 20 completed as gas wells and 228 abandoned as dry holes. Duval County, as usual, received the greatest amount of wildcat drilling, having 21 oil wells, 5 gas wells and 63 dry holes completed during the year for a total of 89 tests. Next came Webb County with 4 oil wells, 4 gas wells and 53 dry holes for a total of 61 tests.

Jan 1, 1938

By R. F. Jones, N. E. Truitt, M. Prats

In most published discussions and theories of in situ combustion, the combustion fronts are assumed to be vertical. However, evidence from field tests leaves no doubt that combustion fronts often advance more rapidly along the top than near the bottom of a formation as a result of difference in density between injected air and formation liquids. The approximation proposed in this paper to determine the movement of the resultant tilted combustion surfaces states that the vertical rate of movement of combustion surfaces is proportional to the horizontal oxygen flux. Where self-ignition is possible, the proposed method demands that a secondary combustion surface exist around production wells which produce some oxygen. These secondary combustion surfaces may be formed long before the primary combustion surface can advance from injection to production wells. Heat liberated near production wells at these secondary combustion surfaces can contribute to an early increase in production rate. Results indicate that significant oil recoveries cannot be obtained from the usual flood patterns (five-spots, seven-spots, etc.) without producing large volumes of unused oxygen. Ideally, to increase oxygen- consumption efficiency, well patterns should allow oil production from a first line of production wells and gas production from more distant lines of producers. However, it may be desirable to produce some gas at all wells to support (and benefit from) active secondary combustion surfaces. Results indicate that the well spacing through which combustion can be advanced is larger than that predicted by other methods. A large number of production wells may still be desirable to take quick advantage of gravity drainage. From a comparison with results at South Belridge field, California, it appears that this method adequately describes oxygen concentration and temperature histories and combustion-front shapes. However, this method does not accurately locate the most advanced point of the combustion surface. There is some field evidence to substantiate the actual presence of secondary combustion surfaces at South Belridge. Use of the proposed method appears warranted at this time when lay-over of the combustion surface can be anticipated. INTRODUCTION The assumption of vertical combustion fronts has been embodied in all previous publicationsl-6 which use the movement of combustion fronts away from injection wells to determine the temperature and fluid distributions in the reservoir. The only paper concerned with a mathematical model of the combustion process in which a nonvertical combustion front is used was written by Gottfried.11 Actually, nonvertical combustion fronts have been observed in most in situ combustion field tests for which adequate data are available.7, 8, 6 In practice, the typical vertical extent of the burned zone decreases with distance from the injection well, and this burned zone is at or near the top of the sand body. In some cases, such as at South Belridge field near Taft, Calif., the combustion surface is almost horizontal over a very large area.8 Thus, for some years an obvious and serious gap has existed between theory (vertical fronts) and practice (tilted fronts). This is indicated in Fig. 1. Tilted combustion fronts such as observed at South Belridge8 sometimes result from the natural tendency of injected gases to rise to the top of an oil sand. An initially present gas cap, even if thin, would make apparent the effect of gravity segregation from the first, particularly since formations considered for in situ combustion field operations are generally selected for their

Jan 1, 1969