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By C. N. Stout

Square-sets go out and labor saving combination of top-slicing and sub-level caving raises tons per man hour 300 pct, cuts timber cost 50 pct to permit mining lower grade ores.

Jan 1, 1953

By W. A. Backofen, G. Y. Chin, W. F. Hosford

The ductile fracturing process was studied in single-crystal and poly cvystalline aluminum deformed in tension over a temperature range from 295° to 4.2°K. At temperatures as low as 77°K, the fracture of "inclusion-free" material, including zone-refined aluminum, was by rupture (-100 pct RA). At 4.2 OK, fracture was brought on by adia-batic shear. Metallographic examination did not disclose any voids or slip-band microcracks, thus negating for inherently ductile metals any mechanism of void nucleation by vacancy condensation or of cracking due to dislocation pile-ups. In Izigh-purity aluminum not treated to be inclusion-free, fracture at temperatures as low as 45°K was of the double-cup type and a result of void formation. The reduction-of-area decreased as temperature was lowered, corresponding to the earlier appearance of voids. Such behavior was rationalized in terms of a larger increase, with decreasing temperature, in the .flow stress relative to the strength of the inclusion-matrix interface. Evidence for low-temperature adiabatic shear was found in discontinuous flow at 4.2"K, in the transition to a localized shear fracture at low temperatures, and in the suppression of shear fracture with an elastically hard pulling device. A simple analysis for the initiation of adiabatic shew permitted a general correlation of the various contributing factors. It has been pointed out that the duration of shear depends upon effective mass and elastic stiffness of the deformation system. IT has long been recognized that fracture* may Throughout this paper, the term "fracture" is taken to mean any process that results in the separation of a material into two (or more) parts. Thus rupture as it may be encountered in a tension test leading to 100 pct reduction-of-area is included in this category. occur in a ductile mode, and that the process can be of great practical as well as general interest. Much information about ductile fracture has also been accumulated over this period, but only recently has an understanding of mechanism begun to appear. Ludwik,' in 1926, first reported fracture in a tensile specimen starting with a central crack in the necked section. Since then, other studies have disclosed that such cracks may form by the coalescence of voids nucleated in this region where hydrostatic tension is highest.2-4 Rogers and Crussard et al.' have emphasized void formation and reori-entation along localized shear bands as a mode of crack propagation. pines6 has considered the tensile rod as a bundle of fibers joined by weak interfaces, which subsequently separate to allow individual fiber contraction. The notion of cavity growth and coalescence by purely plastic processes was discussed by Cottrell: who added that the tensile reduction-of-area ought not to be sensitive to temperature. On the other hand, it has been observed that the reduction-of-area is greatly increased if tests are carried out at high temperaturesa or under high hydrostatic pressure.' Fracturing anisotropy in wrought products lends support to the idea of void formation from preexisting flaws strongly aligned by earlier processing.''-l2 There is evidence that many voids result from the fracturing of inclusions or separation at the inclusion-matrix interface Another possibility is that voids grow out of pore volume produced in the initial solidification and never fully removed in later working. In general, a structure 3f particles, pores, and weak interfaces can be expected, at least in materials of engineering interest. Vacancy condensation has been suggested as an alternative mechanism of void formation for materials considered to be inclusion-free.13 Yet experience has shown that tensile reduction-of-area increases with purity, to the extreme of rupture as so often observed in single crystals. Adiabatic shear has an important bearing on ductile fracture. It occurs when the decrease of flow stress, as a result of local temperature rise from heat generated during straining, becomes larger than the increase due to strain and strain-rate hardening. As demonstrated by experiments on punching of plates,14 a large temperature rise may be brought about by rapid straining. Adiabatic flow as a result of the high strain rate reached in an ordinary tensile specimen just prior to separation may account for the cone formation in cup-and-cone fracture;14 evidence of such local heating has been presented.15 For geometrical reasons, however, pure sliding along the conical surfaces is unlikely, and separation under tensile forces is probably an important accompanying feature of the shear.7 In deformation processing operations, a high shear-strain rate may exist at boundaries between plas-

Jan 1, 1964

By C. E. Shoenfelt

There was a notable decrease in drilling operations in 1940 in all of the Rocky Mountain states except Montana, where the two large fields on the Canadian border, Cut Bank and Kevin-Sunburst, were espe-cially active. The expanding markets for Montana natural gas made necessary the more intensive development of such fields as Rowdoin, Cedar Creek and Devon. While there were no important oil and gas discoveries in 1940 in any of the Rocky Mountain states, a few small pools were opened, which may constitute separate areas but may prove with later development to be extensions of old fields. Some of the old fields were extended and deeper pay zones were discovered in others. These have given the areas greatly increased oil reserves and therefore are just as important as the discovery of new fields. The more important of the developments in 1940 are given, by states, in the following paragraphs. Colorado Hiawatha Field, Moffat County.—The Mountain Fuel Supply Co. began the development at Hiawatha of its oil reserves, which were discovered in about 1929, and late in the summer oil began moving from the field by truck to the shipping point at Rock Springs, Wyoming. The Hiawatha field of northwestern Moffat County was discovered in 1927 by the Sormir Petroleum Co., with the completion of No. r Florence Wilson for 4,5,000,000 cu. ft. of gas a day from a Wasatch sand lens at 2200 it. In later development of the field, oil showings were reported in several wells but no development of this resource was undertaken until 1940, when a test of the oil possibilities was started with the release in April of a location for No. 5-A Wilson on the S\W. SW. NW. of sec. 23-1zN-1ooW., on the east side of the field. The Well had an initial production of 327 bbl. of oil a day pumping from three Wasatch (Tertiary) sands between 2005 and 2540 ft. It was drilled to 2562 ft., where the 65/8-in. casing was cemented and gun-perforated at 2005 to 2125 ft., 2260 to 2335 ft. and 2513 to 2540 ft. At the end of the year, this well was averaging zoo bbl. of oil per day, pumping. Two other wells were drilled for oil on Hiawatha during the summer—one a small well of 60 bbl. per day and the other a small gas well. Powder Wash Field, Moffat County.—The development of the Powder Wash field in northwestern Colorado was resumed in 1940 by the Mountain Fuel Supply Co., with the release of a location for No. 2-A Musser in the CWL.NW.SE. of sec. 4-1rN-97W. The Powder Wash field was discovered in 1931 by the Mountain Fuel Supply Co. and the discovery well, No. I Musser, on C.NW. of sec. 5-IIN-97W., was completed at 2152 ft. in the Hiawatha member of the nonmarine Wasatch for-mation for an open flow of 34,000,000 cu. ft. of gas per day under a natural pressure of 685 lb. per sq. inch. Oil was discovered in the Powder Wash field on Nov. 26, 1936, in the company's No. I Carl Allen on the NE.SW.SE. of sec. 32-12N-97W. The oil production was

Jan 1, 1941

By C. E. Shoenfelt

There was a notable decrease in drilling operations in 1940 in all of the Rocky Mountain states except Montana, where the two large fields on the Canadian border, Cut Bank and Kevin-Sunburst, were espe-cially active. The expanding markets for Montana natural gas made necessary the more intensive development of such fields as Rowdoin, Cedar Creek and Devon. While there were no important oil and gas discoveries in 1940 in any of the Rocky Mountain states, a few small pools were opened, which may constitute separate areas but may prove with later development to be extensions of old fields. Some of the old fields were extended and deeper pay zones were discovered in others. These have given the areas greatly increased oil reserves and therefore are just as important as the discovery of new fields. The more important of the developments in 1940 are given, by states, in the following paragraphs. Colorado Hiawatha Field, Moffat County.—The Mountain Fuel Supply Co. began the development at Hiawatha of its oil reserves, which were discovered in about 1929, and late in the summer oil began moving from the field by truck to the shipping point at Rock Springs, Wyoming. The Hiawatha field of northwestern Moffat County was discovered in 1927 by the Sormir Petroleum Co., with the completion of No. r Florence Wilson for 4,5,000,000 cu. ft. of gas a day from a Wasatch sand lens at 2200 it. In later development of the field, oil showings were reported in several wells but no development of this resource was undertaken until 1940, when a test of the oil possibilities was started with the release in April of a location for No. 5-A Wilson on the S\W. SW. NW. of sec. 23-1zN-1ooW., on the east side of the field. The Well had an initial production of 327 bbl. of oil a day pumping from three Wasatch (Tertiary) sands between 2005 and 2540 ft. It was drilled to 2562 ft., where the 65/8-in. casing was cemented and gun-perforated at 2005 to 2125 ft., 2260 to 2335 ft. and 2513 to 2540 ft. At the end of the year, this well was averaging zoo bbl. of oil per day, pumping. Two other wells were drilled for oil on Hiawatha during the summer—one a small well of 60 bbl. per day and the other a small gas well. Powder Wash Field, Moffat County.—The development of the Powder Wash field in northwestern Colorado was resumed in 1940 by the Mountain Fuel Supply Co., with the release of a location for No. 2-A Musser in the CWL.NW.SE. of sec. 4-1rN-97W. The Powder Wash field was discovered in 1931 by the Mountain Fuel Supply Co. and the discovery well, No. I Musser, on C.NW. of sec. 5-IIN-97W., was completed at 2152 ft. in the Hiawatha member of the nonmarine Wasatch for-mation for an open flow of 34,000,000 cu. ft. of gas per day under a natural pressure of 685 lb. per sq. inch. Oil was discovered in the Powder Wash field on Nov. 26, 1936, in the company's No. I Carl Allen on the NE.SW.SE. of sec. 32-12N-97W. The oil production was

Jan 1, 1941

By S. R. Krogh, T. O. Olsen

Analytical expressions for the breakage rate as functions of mill charge, mill speed, particle size, ball diameter, and ball load are derived, using idealized models for probability of breakage (Gaudin and Meloy), energy distribution (Mempel), and arithmetic mean of effective ball energy (Langemanns). Computational results using the theoretical equations are compared to experiments. The equations enable simulation of ball mill grinding at different grinding conditions.

Jan 1, 1973

By E. Gregory, C. G. Goetzel

The outstanding elevated temperature properties of materials made from sintered aluminum powder have been well established in recent years.1,2 and considerable investigation has been carried out on the structures which appear to be responsible for this type of strengthening.2,3 The maximum operating temperature of such materials is severely limited, however, by the low melting point of the aluminum matrix; and, therefore, considerable interest was aroused in methods of introducing the

Jan 1, 1959

By Joseph E Pogue

Over a period of years the writer has presented a number of studies1 on various aspects of proration, in a progressive attempt to analyze critically and constructively the economic complexities of this interesting institution, which in a decade has revolutionized the economics of oil production in the United States. In the course of the investigations leading to these papers, the changing nature of proration and the principles underlying its evolution have gradually become clear, so that it is now possible to depart from the analytical method and to construct a synthesis of the steps that, if furthered by the industry, should carry proration past the economic hazards that still surround it to the goal of maximizing the value of the petroleum resource to the industry and the public alike. Nature of Proration Proration literally means the allocation of demand among competing producers on a pro rata basis, but the term now carries a much broader significance for it is employed to describe the entire process by which the production of crude oil in the United States is regulated. There is naturally much confusion of thought on the subject, for proration is an evolving system of control based upon principles of conservation and equity and embracing a body of practices that are tending to adjust themselves to the needs of the situation but are subjected to varying and divergent influences in the process. As it is now constituted, proration is a planned production measure designed to prevent waste, insure ratable takings, and balance supply and demand. The procedure is administered by State regulatory bodies through use of the police power of the States under authority of State conservation laws; the practice is supported by a considerable degree of voluntary conformance on the part of operators; and the Federal Government has accorded its cooperation by providing advisory quotas, circumscribing imports, checking movements of hot

Jan 1, 1939

By Joseph E. Pogue

Over a period of years the writer has presented a number of studies1 on various aspects of proration, in a progressive attempt to analyze critically and constructively the economic complexities of this interesting institution, which in a decade has revolutionized the economics of oil production in the United States. In the course of the investigations leading to these papers, the changing nature of proration and the principles underlying its evolution have gradually become clear, so that it is now possible to depart from the analytical method and to construct a synthesis of the steps that, if furthered by the industry, should carry proration past the economic hazards that still surround it to the goal of maximizing the value of the petroleum resource to the industry and the public alike. Nature of Proration Proration literally means the allocation of demand among competing producers on a pro rata basis, but the term now carries a much broader significance for it is employed to describe the entire process by which the production of crude oil in the United States is regulated. There is naturally much confusion of thought on the subject, for proration is an evolving system of control based upon principles of conservation and equity and embracing a body of practices that are tending to adjust themselves to the needs of the situation but are subjected to varying and divergent influences in the process. As it is now constituted, proration is a planned production measure designed to prevent waste, insure ratable takings, and balance supply and demand. The procedure is administered by State regulatory bodies through use of the police power of the States under authority of State conservation laws; the practice is supported by a considerable degree of voluntary conformance on the part of operators; and the Federal Government has accorded its cooperation by providing advisory quotas, circumscribing imports, checking movements of hot

Jan 1, 1939

By M. Muskat

A theory has been developed describing the behavior of wells and reservoirs producing by the action of bottom water drives. It is assumed that the pressures are maintained above the bubble point, and that the permeability to viscosity ratio of the water in the flooded zone is the same as for the oil in the oil-saturated pay. Accordingly, the treatment is based on the homogeneous fluid potential theory. The effect of the difference in density between the oil and water is neglected. .4fter deriving the proper potential distrihutions, the nature of the rise of the water-oil interface below the producing wells is calculated. The primary clean-oil-production phase is expressed in terms of the displacement efficiency, defined as the fraction of the pay flooded out by the rising water table at tlle time of first water entry. The variation of this displacement efficiency is calculated as a function of the well spacing, pay thickness, the ratio of the horizontal to vertical permeability, and the well penetration. The important parameter, other than the well penetration, is found to be the ratio of the well separation to the thickness of the oil pay multiplied by the square root of the ratio of vertical to horizontal permeability. It was found that the displacement efficiency continually decreases as this parameter increases, and for values of the latter >3.5, the efficiency varies inversely as the square of the parameter. It also increases with decreasing well penetration. Perhaps the most striking result of this phase of the analysis is the conclusion that in order to explain the delay in entry of water in wells producing by bottom water drives for periods longer than a few days normal production, with drawdowns large compared with the differential density head between the oil and water, it is necessary to assume that the vertical permeability is a very low fraction of the horizontal permeability. An analysis is also given of the production history after the water has broken through, on the assumption that the production mechanism and details of the flow distribution continue to be the same as during the phase of clean-oil production. As is to be expected, it is found that the water cut will increase at an accelerated rate as production proceeds. However, the initial differences between systems of different well penetrations or well spacings with respect to the total clean-oil production gradually decrease in terms of the variation of the water-oil ratio with cumulative production. In particular, by the time the water-oil ratio has reached values of the order of 5 or greater the cumulative recoveries will generally differ much less among various producing systems than their corresponding clean-oil recoveries. Introduction On the basis of elementary geological principles, one may classify effective water-drive fields in two groups. In the first, the entry of water into the oil-producing formation may be characterized as an edge-water encroachment. This term is used to suggest that the motion of the water proceeds largely in a direction parallel to the planes of stratification. This type of water intrusion occurs usually in thin producing zones and in strata lying along structural flanks of appreciable dip. In the second group—"bottom water-drive" fields—the water-oil interface lies in a plane of zero or slight inclination to the

Jan 1, 1947

By M. Muskat

A theory has been developed describing the behavior of wells and reservoirs producing by the action of bottom water drives. It is assumed that the pressures are maintained above the bubble point, and that the permeability to viscosity ratio of the water in the flooded zone is the same as for the oil in the oil-saturated pay. Accordingly, the treatment is based on the homogeneous fluid potential theory. The effect of the difference in density between the oil and water is neglected. .4fter deriving the proper potential distrihutions, the nature of the rise of the water-oil interface below the producing wells is calculated. The primary clean-oil-production phase is expressed in terms of the displacement efficiency, defined as the fraction of the pay flooded out by the rising water table at tlle time of first water entry. The variation of this displacement efficiency is calculated as a function of the well spacing, pay thickness, the ratio of the horizontal to vertical permeability, and the well penetration. The important parameter, other than the well penetration, is found to be the ratio of the well separation to the thickness of the oil pay multiplied by the square root of the ratio of vertical to horizontal permeability. It was found that the displacement efficiency continually decreases as this parameter increases, and for values of the latter >3.5, the efficiency varies inversely as the square of the parameter. It also increases with decreasing well penetration. Perhaps the most striking result of this phase of the analysis is the conclusion that in order to explain the delay in entry of water in wells producing by bottom water drives for periods longer than a few days normal production, with drawdowns large compared with the differential density head between the oil and water, it is necessary to assume that the vertical permeability is a very low fraction of the horizontal permeability. An analysis is also given of the production history after the water has broken through, on the assumption that the production mechanism and details of the flow distribution continue to be the same as during the phase of clean-oil production. As is to be expected, it is found that the water cut will increase at an accelerated rate as production proceeds. However, the initial differences between systems of different well penetrations or well spacings with respect to the total clean-oil production gradually decrease in terms of the variation of the water-oil ratio with cumulative production. In particular, by the time the water-oil ratio has reached values of the order of 5 or greater the cumulative recoveries will generally differ much less among various producing systems than their corresponding clean-oil recoveries. Introduction On the basis of elementary geological principles, one may classify effective water-drive fields in two groups. In the first, the entry of water into the oil-producing formation may be characterized as an edge-water encroachment. This term is used to suggest that the motion of the water proceeds largely in a direction parallel to the planes of stratification. This type of water intrusion occurs usually in thin producing zones and in strata lying along structural flanks of appreciable dip. In the second group—"bottom water-drive" fields—the water-oil interface lies in a plane of zero or slight inclination to the

Jan 1, 1947

By F. Julius Fohs

CENTRALLY located with relation to the largest iron- and steel-producing districts of the United States, the fluorspar-deposits of Kentucky possess increasing interest and importance. As typical of the numerous fluorspar-mines of Kentucky and Illinois, I have selected for description the Memphis., because it and others of its immediate group exhibit the conditions characteristic of all. I. THE MEMPHIS MINE. This mine lies 5 miles NW. of Marion, in Crittenden county, Kentucky, a station on the Chicago and Nashville division of the Illinois Central R. R. For the first mile and a half out of Marion we see only Birdsville or Middle Chester sandstones of Mississippian age. Then we cross a fault of some 350 ft. displacement, and the Ste. Genevieve oolite sets in. Beyond the fault, oolite is the predominant rock, except that the bills to the north have a capping of Cypress or lowest Chester sandstone, 80 ft. below which is an outcrop of from 6 to 10 ft. of Ste. Genevieve (Rosiclare) sandstone. Occasional sink-holes are noticed, and as the mines are approached evidence of faulting is again seen.. A line of crude head-frames and open-cut dumps, extending for more than a quarter of a mile, marks the Klondike vein. The open-cuts are from 15 to 20 ft. deep, and in most of them, from the surface down, was found the reddish gravel which is really fluorspar-some of it white or purple and crystal-clear (if the red clay is washed off), and some carrying iron and silica, and stained by waters from the decaying limestone walls. In one of these cuts, at a depth of 20 ft., white and purplish honey-combed fluorspar was found, in which the larger cavities are due to limestone and calcite leaching, and the minute ones to the leaching of zinc-blende.

Apr 1, 1909

By G. D. Cody, D. S. Beers, B. Abeles

The thermal diffusivity (thermal conductivity divided by specific heat) of Armco iron has been measured over the temperature range 30º to 1025ºC. The results are in good agreement with the thermal diffusivity computed from published values of thermal conductivity and specific heat, except near the Curie point and at the a to y phase transition, where the measured diffusivity undergoes rabid variations. The differences observed are ascribed to a rapid variation in the electronic thermal conductivity near the Curie point, and a decrease in the lattice thermal conductivity, at the a to ? phase transition. A major difficulty in measuring the thermal conductivity of materials at high temperatures is the determination and elimination of radiation losses. It has been shown, however, that in measuring thermal diffusivity D (thermal conductivity/specific heat) radiation losses can be taken into account exactly.' In order to test the performance of a newly designed apparatus for measuring thermal diffusivity of solids,' we measured Armco iron to an accuracy of 2 pct in the temperature range 30" to 1025°C. This material was selected since both the thermal conductivity,3'4 k, and specific heat,5 C, are known accurately in this temperature range and thus the measured values of D could be compared with D computed from the pub-

Jan 1, 1962

By Ancel St. John

During a session on coal and coke at the February, 1926, meeting of the American Institute of Mining and Metallurgical Engineers, the writer called attention to the important work on the X-ray analysis of coal1,2 being carried on in England by C. Norman Kemp and his associates. This aroused so much interest that a paper on the subject was requested for the October meeting. It has seemed advisable to make this paper a preliminary survey of the present status in the application of X-ray methods to coal problems and to follow it from time to time with further articles as the art develops. A survey of this sort naturally divides itself into two parts, radio-scopic analysis of the distribution of constituents through the body of the coal, and diffraction analysis of the state of association of the elementary components. In this article the subject matter concerning radioscopic analysis has been drawn almost entirely from the writings of Kemp and his associates and the illustrations have been sptcially furnished by him. It is a pleasure to record here a great indebtedness for this courtesy and cooperation. The subject matter and illustrations concerning diffraction analysis are taken from the author's unpublished researches. Nature and Properties of X-rays Before proceeding it is well to recall the nature and some of the properties of X-rays, as well as our present conception of atomic structure According to the accepted theory atoms are composed of electrically-charged particles. A positively-charged center, called the nucleus,

Jan 1, 1927

By R. E. Ogilvie, J. I. Goldstein, R. E. Hanneman

The interdiffusion coefficients for the Fe-Ni system were determined as a function of composition in both the a and y phases at 1 atm pressure. The inter diffusion coefficients were also determined in the y phase at 40 kbar pressure. The concentration gradients were measured with an electron probe, and the diffusion coefficients were calculated by the Matano analysis. At 1 atm, Ey increases with nickel content up to 65 at. pct Ni. The relationship of Dy with temperature and nickel concentration, up to 50 at. pct Ni, is given by the equation DY-l atm = exp(.0519 CN~ +1.15) MANY of the transformations that occur in the solid state are diffusion-controlled, especially those involving precipitate growth in most metallurgical systems. Multicomponent diffusion is usually expressed in terms of a chemical or an inter diffusion The activation energy Q at 1 atm decreases from pure iron to 60 to 70 at. pct Ni and decreases from pztre nickel to 60 to 70 at. pct Ni. The Kirkendall marker movement indicates that DFe is greater than DNi zcp to about 60 at. pct Ni. Above 60 at. pct Ni, however, DNi becomes peater than DFe The inter diffusion coefficients were also compared with those calculated from self-diffusion data. A comparison between calculated and measured coefficients shows only rough agreement. The effect of 40 kbar pressure is to decrease DyPl atm by an order of magnitude. The activation volumes for high-pressure diffusion are in favorable agreement with theoretical models developed for self-diffusion. coefficient which determines the rate at which material is transferred from the matrix phase to the precipitate and hence determines the growth rate of the precipitate. Since the numerical values of the diffusion coefficients differ widely as a function of the metallic system, temperature, and pressure, the diffusion coefficients must be determined for each particular environmental condition. Of long-standing interest is the growth of the classic Widmanstatten pattern in metallic (Fe-Ni) meteorites. The growth rate of the pattern is controlled by the diffusion coefficients in the Fe-Ni system. Since these coefficients are essential to calculating the growth rate of the pattern, we found it necessary to determine the diffusion coefficients

Jan 1, 1965

By T. G. Decker, A. F. Witt, A. M. Gaudin

The historical development of the concept of contact angle hysteresis is reviewed. The measurements of contact angles reported in literature have all been made under static conditions. For the measurement of dynamic advancing and receding contact angles, four methods are described together with an evaluation of their precision. Three of these methods were adapted from devices already used for the measurement of static contact angles. The fourth method uses a new principle and apparatus and is the most accurate. While the relationship between surface tensions and the contact angle was extablished as early as 1805 by T. Young,' it was only in 1890 that the existence of contact angle hysteresis was reported by Lord Rayleigh. His observations, however, remained almost unnoticed. With the invention of froth flotation, the contact angle and its behavior became the subject of investigation. In 1907, L. Sulman and collaborators investigated the cause of discrepancies between recorded values of contact angles. They found that certain variations existed in most cases, but that definite maximum and minimum values of contact angles are obtainable. The difference between the maximum and the minimum contact angle in a given system was termed "hysteresis" by Sulman. First attempts to explain hysteresis were made by E. Edser. In the following years extensive studies of contact angles in various three-phase systems

Jan 1, 1963

By Howard Reiss, C. S. Fuller

A theoretical and experimental study has been made of those interactions between holes and electrons which influence the solubilities of donors and acceptors in semiconductors. The major portion of the work concerns the solubility of lithium in silicon doped to varying degrees with boron. This solubility increases with increasing boron content in a manner predicted by theory and exhibits the expected temperature dependence. A qualitative experiment in germanium is described which demonstrates, in accordance with theory, that doping with a donor decreases the solubility of another donor. SEVERAL authors have discussed the possibility that holes and electrons behave like chemical entities and influence the solubilities of ionized impurities, Wagner was the first to invoke this concept in connection with his studies on nonstoichio-metric oxides. He used it again in explaining the solubility of hydrogen in molten binary alloys. In a theoretical paper,' Reiss drew attention to the fact that solutions of impurities in semiconductors

Jan 1, 1957

By Michael J. Messel

W. P. MOULD*—Has consideration been given to the problem of retreating the 4,000,000 ton tailings pile to recover the very considerable amount of asbestos fiber that was lost over the years due to insufficient operation and poor recoveries? Also, what was known about the possible content of chromite and the sulphides of nickel and cobalt? M. J. MESSEL (author's reply)—Consideration was given to the problem but nothing concrete has been done up to this time. W. P. MOULD—I am certain the tail- ings contain a very considerable quantity of fiber, not all of which is in the shortest lengths, because in the milling of talc rock from a neighboring location having a common origin with the asbestos bearing serpentine source of the tailings pile, a concentrate carrying 15 pct Ni and Co in complex sulphides and constituting about 4/10 of 1 pct of the talc rock was recovered. In the belief that the tailings also contained an appreciable content of chromite (then in demand, 1937) it was suggested to the management of the asbestos company that a truck load of the current tailings be sent to the flotation plant of the talc company where it would be put over the concentrating tables in an effort to discover the presence and roughly the percentages of chromite, nickel, and cobalt. Preparations for the test were woefully inadequate and the test was completely snarled up by the surprisingly large quantity of asbestos fiber from 1 in. long down to very short fiber, all of which matted up and plugged launders and pumps with disastrous effects and practically the total loss of the sample. If anything was indicaded by the test, it was that a wet process for milling asbestos was worthy of very serious consideration. M. J. MESSEL—A wet milling process for tailings retreatment only, is at present under study at our plant. One asbestos mining company in Canada has constructed a fairly large test plant for this purpose, but as yet no definite results have been obtained other than in a small test unit plant which were in some respects quite encouraging.

Jan 1, 1950

By L. A. Panek

Using an approach based on the theory of similitude, the author develops a general equation and related concepts that provide new insights to an old problem. The load-bearing capacity (strength) of a square, rectangular, or cylindrical prism of a brittle material such as rock, coal, or concrete is expressed as the mathematical product of a size effect, a shape effect, and a function of the mechanical properties (deformability, cleat/joint spacing, and friction) of the pillar, roof, and floor materials. Through an application of multivariate statistical analysis, the results of assorted tests (laboratory and in situ) and observations of failed pillars can be combined into a fundamental scaling equation, which provides a unified, consistent approach to the estimation of mine pillar strength. The form of the equation is sufficiently general to be able to incorporate refinements in the characterization of the structural parameters, as they become available through future analysis and experimentation. Analysis of the published test data suggests that pillar compressive strength (per unit of area) is proportional to the cube root of the pillar width, and that the height effect can be described as the superimposing of a variable size effect (characteristic of the material) on the constant width effect.

Jan 1, 1981

By Y. L. Yao

The solubility limit of oxygeu in a titanionn at 850°C has been determined by magnetic measurements as 12.5 + 0.5 pct (29.0—30,9 at. pct). Also in the susceptibility-co~centmtion curve, there is n distinct but not sharp maximum at 19.0 * 0.5 z~t pet (40.5--42.1 at. pct), which indicates the presence of the 6 phase. The magnetic susceptibilities of the alloys of the titanium-oxygen system were determined byEhrlich in 1939.' is alloys were prepared by sintiring mixtures of titanium and its oxide at high temperatures. On the titanium-rich side, despite the fact that the alloy compositions he measured crossed two phase boundaries, the limited results obtained

Jan 1, 1960

By W. Rostoker, A. Siede

THE venerable problem of hydrogen embrittlement of ferritic iron lacks as yet a complete explanation. Possibly part of the difficulty has been the exclusive preoccupation with the total ductility prior to fracture. In the past few years it has been noted at least twice1,2 that hydrogen charged into iron has the ability to depress the upper yield point and, at room temperature, to eliminate completely the discontinuous yield phenomenon. Cracknell and Petchl rationalize that the depression of the yield stress is an example of the behavior of inhomogeneous stresses. Their explanation requires that microcracks exist in the annealed metal, and that hydrogen collect in these cavities under high hydrostatic pressure. The hydrostatic pressure of hydrogen generates localized tensile stresses in the iron which, with external loading, reach the critical stress for yield prematurely. The local plastic zones will spread across the specimen before the Lüders bands can be generated, and the yield-point elongation phenomenon is eliminated. This viewpoint will be discussed in succeeding paragraphs. Rogers,2 on the other hand, represents the depression of the initial flow stress as a result of the interaction of hydrogen with dislocations. He submits two alternative modes of interaction. In the

Jan 1, 1959