Search Documents

By P. Breidt, E. S. Greiner

THIS note reports a determination of the melting point of germanium, and the liquidus of the Ge-Ga alloys; lattice constants of the a phase are given. The alloys were prepared by melting germanium (>20 ohm-cm resistivity) and gallium (99.6 pct) in evacuated silica tubes. The materials (50 to 70 g) were heated at 1000°C, held in the liquid state for about ¾ hr, and then cooled rapidly in the tubes. Points on the liquidus were obtained by thermal analysis which consisted of obtaining time-temperature data during heating and cooling the materials in high purity graphite crucibles and a helium at- mosphere. Temperatures were determined with a Pt—Pt-Rh thermocouple protected by a silica sheath. The couple was calibrated against a National Bureau of Standards calibrated couple and also against the freezing points of copper, silver, aluminum, and the 28.1 wt pct Cu, 71.9 wt pct Ag alloy eutectic. The samples for X-ray analysis were prepared by heating small pieces of the ingots in evacuated glass or quartz tubes at temperatures between 600" and 900°C for periods ranging from 2 hr to 22 days, periods deemed sufficient for equilibrium to be attained, followed by quenching in water. The heat-treated samples were ground to powder for X-ray analysis. The lattice constants of the germanium-rich phase (a) were determined with a baok-reflection focusing camera. The X-ray reflections (331 and 422 Cr Ka, 422 and 333 Cr KB) were corrected

Jan 1, 1956

By Frank T. Wheby

The cost of tunneling is highly sensitive to the rock characteristics through which the tunnel is to be driven. These characteristics affect in a major way the rates at which tunnels and shafts can be driven and the degree to which the openings must be supported to maintain them in a permanent stable condition. Tunnel and shaft design and cost criteria have been computerized, permitting estimates of tunnel-shaft systems to be made directly from inputs of rock mechanics characteristics and other data. Curves of quantities of steel, rock bolts, and other rock support items as related to tunnel size and rock quality designation are presented. An illustrative example of the use of the program in calculating the cost of a hypothetical tunnel system is included.

Jan 1, 1971

By Shiou-Chuan Sun

THIS paper presents the design and operation of a frothmeter capable of measuring the frothing characteristics of pine oils and other frothing reagents. The experimental data show that the froth-ability of pine oil is governed by: 1—rate of aeration, 2—time of aeration, 3—height of liquid column, 4—chemical composition of pine oil, 5—pH value of solution, 6—temperature of solution, and 7—concentration of pine oil in solution. The effect of mineral particles on the behavior of froth also was studied, and the results can be found in a separate paper.' The results also show that the relative froth-abilities of pine oils in the frothmeter generally correlate with those in actual flotation, provided that other factors are kept constant. In addition to pine oils, the other well-established flotation frothers were tested, and the results are included. In this paper, compressed air frothing is the frothing process performed by means of purified compressed air, whereas sucked air frothing is the frothing process accomplished by purified air sucked into the glass cylinder by a vacuum system. The term vacuum frothing denotes that froth was formed by degassing of the air-saturated liquid under a closed vacuum system. Apparatus The frothmeter, shown in Fig. 1, is capable of re-producibly measuring the volume and persistence of froth as well as the volume of air bubbles entrapped in the liquid and is capable of being used for compressed air frothing, sucked air frothing, and vacuum frothing. Fig. la shows that for compressed air frothing, the apparatus consists of an airflow regulating system, 1-3; a purifying and drying system, 4-8; a standardized flowmeter to measure the rate of airflow from zero to 500 cc per sec, 9; and a graduated glass cylinder, 13; equipped with an air regulating stopcock, 10; an air chamber, 11; and a fritted glass disk to produce froth, 12. The fritted glass disk, 5 cm in diam and 0.3 cm thick, has an average pore diameter of 85 to 145 microns. The pyrex glass cylinder has a uniform ID of 5.588 cm and an effective height of 63 cm. The inside cross-sectional area of the glass cylinder was calculated to be 24.53 sq cm, or 3.8 sq in. For sucked air frothing, Fig. lb shows that the apparatus for compressed air frothing is used again, with the following modifications: 1—compressed air and its regulating system, 1-3, are eliminated; and 2—a vacuum system, 16, equipped with a vapor trap, 15, and a vacuum manometer, 17, is added. The vacuum system can be either a water aspirator or a laboratory vacuum pump. Any desired rate of airflow can be drawn into the glass cylinder, 13, by adjusting the opening of the air regulating stopcock, 10. The sucked air stream is cleaned by the purifying and drying system, 4-8, before entering the glass cylinder, 13. When this setup is used for vacuum frothing, the air regulating stopcock is closed. The frothmeter has been used for almost 3 years and has proved to give reproducible results, as illustrated in Table I. With a magnifying glass and suitable illumination, the frothmeter also can be used to study the attachment of air bubbles to coarse mineral particles.' Experimental Procedures Except where otherwise stated, the data presented were established by means of the compressed air method. The volume and persistence of froth were recorded respectively at the end of 4 and 6 min of aeration at a constant rate of airflow of 29.3 cc per sec, which is equivalent to 71.6 cc per sq cm per min, or 462.6 cc per sq in. per min. The aqueous solution for each test, containing 1000 cc of distilled water and 19.2 ± 0.5 mg frothing reagent, was adjusted to a pH of 6.9 0.2. The volume of froth is expressed as cubic centimeter per square centimeter and is equivalent to the height of the froth column (the distance between the bottom and the meniscus of the froth). The volume of froth was obtained by multiplying the height of froth by the cross-sectional area of the glass cylinder, 24.53 sq cm. Before each test, the glass cylinder, 13, was cleaned thoroughly with jets of tap water, ethyl alcohol, tap water, cleaning solution, tap water, and finally distilled water. The cylinder with stopcock,

Jan 1, 1953

By Shiou-Chuan Sun

THIS paper presents the design and operation of a frothmeter capable of measuring the frothing characteristics of pine oils and other frothing reagents. The experimental data show that the froth-ability of pine oil is governed by: 1—rate of aeration, 2—time of aeration, 3—height of liquid column, 4—chemical composition of pine oil, 5—pH value of solution, 6—temperature of solution, and 7—concentration of pine oil in solution. The effect of mineral particles on the behavior of froth also was studied, and the results can be found in a separate paper.' The results also show that the relative froth-abilities of pine oils in the frothmeter generally correlate with those in actual flotation, provided that other factors are kept constant. In addition to pine oils, the other well-established flotation frothers were tested, and the results are included. In this paper, compressed air frothing is the frothing process performed by means of purified compressed air, whereas sucked air frothing is the frothing process accomplished by purified air sucked into the glass cylinder by a vacuum system. The term vacuum frothing denotes that froth was formed by degassing of the air-saturated liquid under a closed vacuum system. Apparatus The frothmeter, shown in Fig. 1, is capable of re-producibly measuring the volume and persistence of froth as well as the volume of air bubbles entrapped in the liquid and is capable of being used for compressed air frothing, sucked air frothing, and vacuum frothing. Fig. la shows that for compressed air frothing, the apparatus consists of an airflow regulating system, 1-3; a purifying and drying system, 4-8; a standardized flowmeter to measure the rate of airflow from zero to 500 cc per sec, 9; and a graduated glass cylinder, 13; equipped with an air regulating stopcock, 10; an air chamber, 11; and a fritted glass disk to produce froth, 12. The fritted glass disk, 5 cm in diam and 0.3 cm thick, has an average pore diameter of 85 to 145 microns. The pyrex glass cylinder has a uniform ID of 5.588 cm and an effective height of 63 cm. The inside cross-sectional area of the glass cylinder was calculated to be 24.53 sq cm, or 3.8 sq in. For sucked air frothing, Fig. lb shows that the apparatus for compressed air frothing is used again, with the following modifications: 1—compressed air and its regulating system, 1-3, are eliminated; and 2—a vacuum system, 16, equipped with a vapor trap, 15, and a vacuum manometer, 17, is added. The vacuum system can be either a water aspirator or a laboratory vacuum pump. Any desired rate of airflow can be drawn into the glass cylinder, 13, by adjusting the opening of the air regulating stopcock, 10. The sucked air stream is cleaned by the purifying and drying system, 4-8, before entering the glass cylinder, 13. When this setup is used for vacuum frothing, the air regulating stopcock is closed. The frothmeter has been used for almost 3 years and has proved to give reproducible results, as illustrated in Table I. With a magnifying glass and suitable illumination, the frothmeter also can be used to study the attachment of air bubbles to coarse mineral particles.' Experimental Procedures Except where otherwise stated, the data presented were established by means of the compressed air method. The volume and persistence of froth were recorded respectively at the end of 4 and 6 min of aeration at a constant rate of airflow of 29.3 cc per sec, which is equivalent to 71.6 cc per sq cm per min, or 462.6 cc per sq in. per min. The aqueous solution for each test, containing 1000 cc of distilled water and 19.2 ± 0.5 mg frothing reagent, was adjusted to a pH of 6.9 0.2. The volume of froth is expressed as cubic centimeter per square centimeter and is equivalent to the height of the froth column (the distance between the bottom and the meniscus of the froth). The volume of froth was obtained by multiplying the height of froth by the cross-sectional area of the glass cylinder, 24.53 sq cm. Before each test, the glass cylinder, 13, was cleaned thoroughly with jets of tap water, ethyl alcohol, tap water, cleaning solution, tap water, and finally distilled water. The cylinder with stopcock,

Jan 1, 1953

By Shiou-Chuan Sun

THIS paper presents the design and operation of a frothmeter capable of measuring the frothing characteristics of pine oils and other frothing reagents. The experimental data show that the frothability of pine oil is governed by: 1-rate of aeration, 2-time of aeration, 3-height of liquid column, 4-chemical composition of pine oil, 5-pH value of solution, 6-temperature of, solution, and 7-concentration of pine oil in solution. The effect of mineral particles on the behavior of froth also was studied, and the results can be found in a separate paper.1 The results also show that the relative frothabilities of pine oils in the frothmeter generally correlate with those in actual flotation, provided that other factors are kept constant. In addition to pine oils, the other well-established flotation frothers were tested, and the results are included. In this paper, compressed air frothing is the frothing process performed by means of purified compressed air, whereas sucked air frothing is the frothing process accomplished by purified air sucked into the glass cylinder by a vacuum system. The term vacuum frothing denotes that froth was formed by degassing of the air-saturated liquid under a closed vacuum system. Apparatus The frothmeter, shown in Fig. 1, is capable of reproducibly measuring the volume and persistence of froth as well as the volume of air bubbles entrapped in the liquid and is capable of being used for compressed air frothing, sucked air frothing, and vacuum frothing. Fig. la shows that for compressed air frothing, the apparatus consists of an airflow regulating system, 1-3; a purifying and drying system, 4-8; a standardized flowmeter to measure the rate of airflow from zero to 500 cc per sec, 9; and a graduated glass cylinder, 13; equipped with an air regulating stopcock, 10; an air chamber, 11; and a fritted glass disk to produce froth, 12. The fritted glass disk, 5 cm in diam and 0.3 cm thick, has an average pore diameter of 85 to 145 microns. The pyrex glass cylinder has a uniform ID of 5.588 cm and an effective height of 63 cm. The inside cross-sectional area of the glass cylinder was calculated to be 24.53 sq cm, or 3.8 sq in. For sucked air frothing, Fig. lb shows that the apparatus for compressed air frothing is used again, with the following modifications: 1-compressed air and its regulating system, 1-3, are eliminated; and 2-a vacuum system, 16, equipped with a vapor trap, 15, and a vacuum manometer, 17, is added. The vacuum system can be .either a water aspirator or a laboratory vacuum pump. Any desired rate of airflow can be drawn into the glass cylinder, 13, by adjusting the opening of the air regulating stopcock, 10. The sucked air stream is cleaned by the purifing and drying system, 4-8, before entering the glass cylinder, 13. When this setup is used for vacuum frothing, the air regulating stopcock is closed. The frothmeter has been used for almost 3 years and has proved to give reproducible results, as illustrated in Table I. With a magnifying glass and suitable illumination, the frothmeter also can be used to study the attachment of air bubbles to coarse mineral particles.2 Experimental Procedures Except where otherwise stated, the data presented were established by means of the compressed air method. The volume and persistence of froth were recorded respectively at the end of 4 and 6 min of aeration at a constant rate of airflow of 29.3 cc per sec which is equivalent to 71.6 cc per sq cm per min, or 462.6 cc per sq in. per min. The aqueous solution for each test, containing 1000 cc of distilled water and 19.2 ± 0.5 mg frothing reagent, was adjusted to a pH of 6.9 ± 0.2. The volume of froth is expressed as cubic centimeter per square centimeter and is equivalent to the height of the froth column (the distance between the bottom and the meniscus of the froth). The volume of froth was obtained by multiplying the height of froth by the cross-sectional area of the glass cylinder, 24.53 sq cm. Before each test, the glass cylinder, 13, was cleaned thoroughly with jets of tap water, ethyl alcohol, tap water, cleaning solution, tap water, and finally distilled water. The cylinder with stopcock,

Jan 1, 1952

By W. F. Boericke

THE recent completion by the United States Aluminum Company of a $4,000,000 addition to its plant at Massena, N. Y., consisting of a large blooming mill and structural mill, gives this organization, a subsidiary of the Aluminum Company of America, the distinction of possessing the largest aluminum rolling mill in the world, as well as the first mil1 in this country to roll aluminum exclusively. The plant is located near the international boundary line between Canada and the United States, about 3 miles from the St. Lawrence River, to take advantage of the development of cheap hydroelectric power which is needed not only for the manufacture of structural shapes from the ingots, but in the reduction of alumina to the metal by the well-known Hall process as well. A power canal from the St. Lawrence River to the power house on the Grasse River at the plant provides for the waterflow, which, coupled with a drop of 47 ft. in 2% miles, generates 80,000 hp. through vertical turbines. An additional 60,000 hp. is purchased.

Jan 1, 1930

I HIT the ceiling when I opened my November MINING ENGINEERING and after waiting a week to cool off I' still find it necessary to express my resentment of the gross libel embodied in the editorial introduction to Norman Stines' legitimate criticism of my paper on "Russia's Mineral Potential" (p. 949). The underlying thesis of my article, and a point that I tried to make even more clearly in my oral presentation at the St. Louis meeting last February, is that we should not over estimate the present and near-future mineral production of the USSR. The words that I resent in your boxed introduction are: "Opinions range from those presented by Paul Tyler ... to those of Norman C. Stines . . ." This is not merely an understatement that can be defended by admitting that the range goes much farther to the left, beyond me. It represents the appraisal that 90 pct of your members will carry away, namely that I am not only an incompetent observer-which may be true-but always that my bias is to applaud the efficiency of the beasts in the Kremlin-which is not true. Notwithstanding my efforts to clarify the record I now find myself branded as being at the opposite pole from 'Mr. Stines among the red-eyed worshipers of Communism or at least among the timid souls that shake in their boots in the belief that the Soviet system has created an invincible as well as an evil menace to the decent peoples of the world. My ideas are somewhere in the middle ground between Mr. Stines' complaisance or contempt and the exaggerated fears of several other observers whose views have received wide acceptance. PAUL M. TYLER MINERAL TECHNOLOGIST & ECONOMIST 5005 EDGEMOOR LANE, BETHESDA, MD. The introductory paragraph to Mr. Stines' criticism of Mr. Tyler's article (Russia's Mineral Potential, June issue MINING ENGINEERING, page 494) is erroneous as pointed out in author Tyler's letter above. In his article he objectively presented an estimate of the mineral position of the Soviet based on the statistics available to him which sources are credited in the first paragraph of his article. We happen to know that, Mr. Tyler was reluctant to prepare the article for the Mineral Economics Division sessions at the 1951 Annual Meeting and did so only because of his loyalty to AIME. It was thought that this article would be a basis for discussion of this important subject at the Annual Meeting. We apologize to Mr. Tyler for any embarrassment our introduction, may have caused him. Editor

Jan 1, 1952

By H. I. Smith

THE technical and safety press have devoted much space in support of or in opposition to the use of booster and auxiliary fans in coal mines. The Mine Safety Board of the U. S. Bureau of Mines has given the matter consideration, and the Mine Ventilation Committee of the A. I. M. E. is now seeking a discussion of the merits and demerits of such fans to guide it in formulating recommendations. In this paper, I will set up some principles on which I believe most engineers will agree and from which we may work toward a decision, though as to what that decision shall be there may be a difference in opinion. Before stating the points on which I believe. there is accord, I will distinguish between booster and auxiliary fans.

Jan 1, 1927

By I. R. Kramer

The apparent activation energy, U, JOY plastic deformation of aluminium, copper, and gold single crystals and polycrystalline aluminum was found to he dependent upon surface condition. At low strains, the value for U for aluminum single crystals was 4200 cal per mole ; however, this value decreased to 920 cal per mole when the specimens were polished during the test at a rate of 50 X 10-5 win-1 The activated volume also was found to increase with the rate of metal removal. That the surface plays an important role in plastic-deformation processes has been adequately demonstrated.1-4 Of particular interest at this time are the observations4 that the creep rate of single crystals of fee metals is increased markedly when specimens are polished during the deformation process. These observations were interpreted in terms of a dislocation debris layer at the surface regions of the crystal. This layer, which appears to be a region containing a high concentration of dislocations or segments of dislocations, not only will impede the egress of dislocations on the primary slip system, but will also provide a barrier against which dislocations may pile up. By this means, a stress which opposes the motion of dislocations will be generated. It is considered that this stress must be taken into account in any theory which describes the plastic-deformation process. Although a detailed dislocation model cannot be given at this time, it may be stated that the stresses opposing the motion of dislocations arise from the dislocations in the debris layer, Ts, and ti due to the resistance to motion imposed by internal obstacles such as Lomer-Cottrell barriers, subgrain and grain boundaries, forest dislocations, and so forth, as well as the resistance due to the presence of jogs on dislocations and the interaction of the stress fields of dislocations, and so forth. In essence, we have added an additional term, ts, to the usual form of the equation T = Ta- Tb, where Tb is the back stress due to the various types of obstacles which impede the motion of dislocation. Accordingly, the net stress, t, acting on a dislocation may be written as where Ta is the applied shear stress. For deformation which occurs by a thermally activated process5,8 ?=Ae-u/kT = A e(u,-VT)/kT [2] and U = Uo- Vt PI where U = activation energy for plastic flow, y = shear strain rate, Uo = activated energy for plastic deformation in the absence of stress and depends upon the particular deformation process, V = activated volume, k = Boltzmann constant, T = temperature, OK, and A = frequency factor. From Eqs. [I] and [3], U = Uo- V(Ta - Ti - TS) [4] and it is seen that if Ts decreases, the activation energy, U, must decrease if V remains constant. However, as will be shown, V is a function of the surface conditions. In their work on aluminum, Lytton and coworkers7 reported that at low strains the activation energy was 3400 cal per mole and at high strains it was 28,000 cal per mole. The lower value was interpreted in terms of the energy necessary to overcome the Peierls force, while the higher value was associated with the energy necessary for dislocations to move by a cross-slip process. It will be shown that the lower activation energy is associated with the surface debris layer rather than with the Peierls force. EXPERIMENTAL PROCEDURE Single crystals having a nominal cross section of 1/8 in. and a 3-in. gage length were prepared by a modified Bridgman technique using a multiple-cavity graphite mold. The initial purity of the metals was 99.997, 99.999, and 99.999 pet for aluminum, copper, and gold, respectively. The orientation of the specimens is given in Fig. 1. The measurement of the activation energy as a

Jan 1, 1964

By M. G. Benz

The superconducting performmce of diffusion-processed Nb3Sn is influenced by its micro structure. High isotropic transverse current density may be achieved in this material by a process which forms a precipitate of ZrO, within the Nb3Sn. FOR an ideal type-I1 superconductor, little or no transport current can be carried in the mixed state; i.e., little or no transport current can be carried above the lower critical field H,,, where the field penetrates abruptly in the form of current vortices or fluxoids, even though full transition to the normal state does not occur until the upper critical field H,,.' Fortunately, nonideal type-I1 superconductors can be readily obtained and these carry large transport currents up to the upper critical field H. Both theoretical and experimental investigations have attributed this current-carrying capability for nonideal type-I1 superconductors to pinning of the fluxoid lattice by heterogeneities in the microstructure of the superconducting material. These heterogeneities may take the form of dislocations or dislocation clusters,2"5 grain boundaries: structural imperfections introduced by phase transformations; radiation damage,8"10 or precipitates.11"15 Nb3Sn formed by diffusion processing is a type-I1 superconductor. Heterogeneities are needed for high superconducting critical currents above H,,. This paper will cover: a) what the microstructure of diffusion-processed NbSn looks like; b) what changes in the microstructure take place when the system is doped with precipitates, and c) how these changes in microstructure influence the superconducting critical currents. EXPERIMENTAL Preparation of Samples. Diffusion processing was used to form the Nb3Sn. The procedure used was as follows: a) coat the surface of a niobium tape with tin; b) heat-treat this tape at a temperature above 930°C to form a layer of Nb3Sn at the Sn-Nb interface. Such a layer of NbsSn is shown in Fig. 1 The thickness of the NbsSn layer formed was controlled by the time and temperature of the heat treatment. The same general procedure was used for preparation of both undoped samples and samples doped with a precipitate. An additional step was included in the preparation of the doped samples which consisted of internal oxidation of zirconium to form ZrOn. The details of the doping process will be reported in a later paper. Sample Testing. The Nb3Sn tape samples were soldered to a copper or brass shunt. Current and voltage leads were then attached to the sample in the usual four-probe resistance measurement configuration. The sample was cooled to 42°K. In some cases it was cooled in the presence of a high magnetic field and in other cases with the field turned off. The results were the same for both cases. The samples were oriented in a configuration with field transverse to current but could be rotated such that the angle between the field vector and the wide side of the tape sample could be changed. Measurements up to 100 kG were done in a superconducting solenoid and measurements above 100 kG in a water-cooled copper magnet at the MIT National Magnet Laboratory. Once the test field was reached, the current in the sample was increased until voltage was detected across the sample. The critical current was taken as the current at which voltage was first detected in excess of background noise. In most cases this was 1 to 2 x 10~6 v for a— in.-wide sample carrying several hundred amperes with a in. separation between voltage leads and with a 10 "-ohm shunt resistance. RESULTS AND DISCUSSION Microstructure. Examination of the microstructure of the undoped Nb3Sn shows rather large-diameter (1 to 2 columnar grains growing outward from the niobium surface toward the tin surface. As the layer is made thicker by longer diffusion times, these grains grow longer. Few new grains are started. Transmission electron microscopy shows little or no second-phase material within the bulk of the Nb3Sn layer. The microstructure of a diffusion-processed NbsSn layer changes quite drastically when the system is doped so as to form a precipitate within the NbsSn layer. Instead of large-diameter columnar grains of NbaSn forming, smaller-diameter (0.5 to 1 ) equiaxed grains of Nb3Sn decorated with the precipitate form. Fig. 2 shows a transmission electron micrograph of a Nb3Sn layer doped with zirconium oxide. This layer has been etched so that one may look between the grains

Jan 1, 1969

The following Nominating Committee having been already appointed and approved by the Executive Committee in accordance with authority vested in the Executive Committee by the Board of Directors, was approved by the Directors: John V. N. Dorr, Chairman, Percy G. Beckett, J. W. Hutchinson, Julian Kennedy, William H. Linney, Charles W. Merrill, and E. Gybbon Spilsbury. The question of the purchase of Liberty Bonds, as well as that of bringing to the attention of the members the advisability of the purchase of these bonds, was referred to the Finance Committee. Sixty Members, four Associates, and thirty-six Junior Members were elected. Two Members were reinstated. Eight resignations were accepted.

Jan 7, 1917

By A. W. Fahrenwald

THE function of the classifier in modern fine-grinding practice is to remove a finished product from the grinding-mill discharge, leaving material that needs further comminution. The classifier, therefore, makes two products: (1) "finished" product, which overflows the rim of the classifier tank, sometimes referred to as "slimes" or as "classifier overflow," and (2) "unfinished" product, which settles to the sloping bottom of the classifier tank and is removed by dragging or raking. This product is generally referred tows "sands" or "oversize." One of the outstanding features of the closed-circuit classifier is its ability automatically to return the unfinished product of the ball-mill discharge to the feed end or scoop box of the ball mill. This is a distinct advantage because it avoids dilution of the ball-mill feed, and, furthermore, the particular method of removing the settled sand, by raking it up the inclined bottom of the classifier, gives a classifier discharge containing a minimum of water. This leads to maximum classifier efficiency, in this type of classifier, because the maximum volume of water is displaced upward by the settling sands. The closed-circuit classifier is required to deliver a finished pulp of closely specified density requirements, therefore added hydraulic water generally is not permitted.

Jan 1, 1930

By Charles White Merrill

A forecast of mineral demand during the remaining years of the 20th century can serve as an excellent starting point for student mining and mineral engineers in planning their professional careers. This approach of appraising demand before seeking supply is not new. of course, but, it is quite the opposite of the traditional attack on mineral resources in which adventurous prospectors, followed by practical miners and engineers, have in the past sought out and developed mineral supply with a faith that markets existed for the products they were preparing to offer. Such faith, even to this day remains fully justified if the product is gold, which still enjoys an unlimited market at $35 a fine ounce, but other mineral products must compete in markets of varying stability and capacity for adsorbing new supply. The world is in a period of rapid expansion. Most basic is the worldwide increase in the number of people which has reached proportions popularly termed "the population explosion." Conservative demographers, noting an increase from 1 ?h billion people at the beginning of the 20th century to 3 billion today, are predicting 5 billion by the year 2000; some predictions are much higher.

Jan 2, 1964

DR FRANK DAWSON ADAMS Montreal, Canada HENRY STURGIS DRINKER Bethlehem, Pa PROF HATON DE LA GOUPILLIERE Paris, France SIR ROBERT A. HADFEILD London, England HERBERT C. HOOVER Leoben, Austria ROBERT W. HUNT Chicago, ILL JAMES FURMAN KEMP New York, N.Y. PROF HENRI LOUIS LE CHATELIER Paris France EZEQUIEL ORDONEZ Mexico City, Mexico ALEXANDRE, POURCEL Paris, France RICHARD H, RICHARDS Boston Mass. JOHN E. STEAD Middlesborugh, England PROF DIMITRY CONSTANTIN TSCHERNOFF St Petersburg, Russia CHARLES D WALCOT Washington D.C.

Jan 1, 1923

By Arthur Coffinberry

EVE have studied the gold-aluminum system by X-ray diffraction and by the microscope over the entire range of composition for temperatures between 300° and 500° C. Results obtained are shown in Fig. 1, com-bined with the work of Heycock and Neville1 at higher temperatures. The diagram differs in important details from that given by Hansen2 in his critical compilation of the literature of binary alloy systems. This work was, undertaken both because of the intrinsic value of a knowledge of the phase diagram of this system and because of the need of theoretical metallurgy for precise and accurate data, particularly X-ray diffraction data. Systematic studies of equilibrium diagrams, particularly by Hume-Rothery,3 have shown regularities that yield a certain insight into the nature of alloying forces. It has been shown, for example, that solid solubility depends on the concentration of free electrons in the alloy, on the relative radii of solvent and solute atones, on the forces of attraction between atoms, and on the relative stability of intermediate phases. The well-known Hume-Rothery rule states that the crystal structures and compositions of many intermediate phases depend on the electron-to-atom ratio. This has been confirmed and extended by wave mechanical calculations.4 A knowledge of the forces between atoms in alloys, even an imperfectly developed empirical one, should be a valuable guide in the preparation of technological alloys of desirable properties. Furthermore, such informa-tion is basic in such problems as rate of diffusion, age-hardening, phase transformations, and others. The most valuable data for this purpose are furnished by X-ray diffraction studies. Unfortunately, work has been

Jan 1, 1938

By F. Weinberg

Lead single crystals have been deformed in tension over the temperature range of 4.2°K to the melting point. Changes in flow stress resulting from temperature cycling and strain rate cycling have been measured as a function of temperature for crystals of different orientations and purity. It was found that the flow stress ratio, after correcting for the temperature dependence of the shear modulus, decreased progressively with temperature above approximately 0.5Tm. The activation energy calculated from the high-temperature portion of the curve was found to be markedly higher than that of self-diffusion. For single glide crystals, the corrected flow stress showed an increase above 0.5 Tm before decreasitzg with temperature. This increase is attributed to static recovery occurrittg during temperature cycling. THE temperature dependence of the flow stress, based on temperature cycling and strain rate cycling, has been extensively investigated,' and on the basis of these results dislocation models of the work-hardening process have been proposed. In general, the flow stress is divided into two parts, ts, the short-range interaction term, which is only effective at low temperatures and which decreases with increasing temperature, and TG, the long-range stress term, which is independent of temperature after allowing for the temperature dependence of the shear modulus. The observations demonstrating that tG/µ is independent of temperature were generally carried out at low temperatures to minimize recovery effects. Several investigations have been reported on flow stress measurements at high temperatures2"5 which demonstrate that TG/µ does not remain constant at temperatures above 0.5Tm (where Tm is the melting temperature of the material in OK). Specifically, Hirsch and warrington3 carried out temperature cycling tests at two strain rates on single and polycrystalline aluminum up to 0.8 Tm and on polycrystalline copper. For aluminum they found that the flow stress ratio (the flow stress at temperature T2, divided by the flow stress at the reference temperature T1 in one temperature cycle) dropped progressively with increasing temperature above 0.5Tm. From the slopes of the high-temperature portions of the curves, they determined an activation energy for the deformation process of 1.6 ev (at best) which they considered was in agreement with the activation energy of self-diffusion, 1.35 ev. Calculations of the activation volume demonstrated that the deformation was not controlled by dislocation climb. They proposed a mechanism in which the rate-controlling process at high temperatures was due to the rate of move- ment of vacancies away from jogs, i.e., that of self-diffusion. Results of Lucke and Buhler4 on single crystals of aluminum confirmed this conclusion. They measured the critical resolved shear stress of aluminum over a wide range of temperature and strain rates. They found that the temperature dependence of the critical resolved shear stress was similar to that of the flow stress ratio, as determined by Hirsch and Warrington, and from their data calculated an activation energy for high-temperature deformation of 1.35 ev identical to that of self-diffusion. More recently Gallagher5 has carried out a detailed investigation of the temperature dependence of the flow stress ratio of copper, silver, and gold. In all cases, he found that the flow stress ratio, after adjusting for the shear modulus temperature change, drops at high temperatures. The activation energies he determined were found to be appreciably higher than the activation energy of self-diffusion of the material being considered. The flow stress ratio was found to be dependent on the orientation of the material, and, in addition, an anomalous increase in the flow stress ratio for copper, oriented for single glide, was observed above 0.5Tm. The purpose of the present investigation was to measure the critical resolved shear stress, the flow stress ratio, and the strain rate sensitivity of lead, primarily as a function of temperature. The results should indicate whether, following Lucke and Buhler, the critical resolved shear stress of lead has the same temperature dependence as the flow stress, and, following Hirsch and Warrington, whether the activation energy for high-temperature deformation in lead is the same as that of self-diffusion. Lead deforms as a normal fee material,6'7 is available in high-purity form, can readily be grown as single crystals, and, for this investigation, has the very considerable advantage of having a low melting point, 327°C. The observations of the critical resolved shear stress of lead have been published elsewhere.' EXPERIMENTAL PROCEDURE The experimental procedure was essentially the same as that used in the critical resolved shear stress measurements.' Single crystals of 99.999 pct (59) and 99.9999 pct (69) lead were deformed in tension with a table-model Instron in a silicone oil bath above room temperatures and in a cooled methyl alcohol or liquid-nitrogen bath below room temperatures. The test specimens were rectangular in section, 0.65 by 0.33 cm, and had a 5-cm gage length. The specimens were grown as single crystals with tapered ends, which fitted into matched tapered grips for testing. To obtain the flow stress between two temperatures, specimens were first deformed approximately 1.0 pct at the higher temperature. The test was then stopped, the load relaxed, the oil bath removed without disturbing the specimen, the grips and specimen cooled with a fan and then immersed in liquid nitro-

Jan 1, 1969

By H. W. Paxton, C. C. Busby

IT has been shown previously' that strain aging can markedly improve the tensile properties of low carbon martensites, especially the yield-tensile ratio, without seriously affecting the ductility. In view of interest in high strength steels, an investigation has been made of the effect of strain aging following tension or rolling on the tensile properties of A1S1 4340 in an attempt to obtain a tensile

Jan 1, 1957

By George Bell

THE mine and milling plant of Demonstration Gold Mines, Ltd., is near the city limits of Baguio, Mt. Province, P. I. The mine road connects with the main highway to Manila. The nearest railway point is near sea level, approximately 40 miles distant. The Baguio district is very mountainous and has one of the heaviest rainfalls in the world. It is therefore difficult to maintain roads or to impound tailings and mine dumps. All supplies are trucked into the district direct from Manila or the nearest railway point, which means uncertain deliveries and high freight rates. Installation of equipment is difficult and costly. The average elevation at the mine is 4000 ft. and the climatic condi-tions.are ideal except for a three months rainy season. The company generates its own power for mining and milling opera-tions with three 400-hp. Ruston Diesel engines direct connected to 250-kw. General Electric alternating current generators. Labor conditions have been excellent, although at present social security laws are causing some unrest. Labor receives a higher average wage rate in this district than other labor in the Islands. The com-pany also furnishes free living quarters, hospitalization and work-men's compensation. Taxation has been reasonable up to the present time, but some of the new mining legislation may make it difficult to operate and pay dividends. The future depends largely upon the continuation of $35 gold and the political outcome in the Islands.

Jan 1, 1939

By Anthony Anable

THE definite trend to stricter specifications with respect to hydraulic concrete has become increasingly manifest in the last six years or so; but it remained for the vast reclamation projects of the Bureau of Recla-mation of the Department of the Interior of the last few years to focus attention on this trend, and to demonstrate how thousands of tons of concrete-making aggregates can be produced continuously and auto-matically with a control of fineness comparable with that obtained with small samples in well equipped private and governmental laboratories. Pioneer work in this direction was done, to be sure, by private com-panies, notably the Kaiser Paving Co. of San Francisco, prior to the present vast public works program. Then in 1931 came the first great aggregates-preparation plant of the Six Companies, Inc. to supply. construction materials for Boulder Dam' in Nevada, and now, in 1936, the aggregates plant of the Mason-Walsh-Atkinson-Kier Co., general con¬tractors on the Grand Coulee dam in Washington. At Boulder dam and to an even greater degree at Grand Coulee dam, sand production is recognized as probably the most important single element affecting the physical characteristics of the concrete. For in the construction of dams accurate grading of the fine aggregate has consider-able bearing on the attainment of a uniform and homogeneous concrete of a high degree of workability and placeability and, at the same time, combining high density and low cement content. Low cement content is of value not only from the standpoint of economy but also because the use of an unnecessarily rich concrete causes certain undesirable characteristics to develop. This paper will relate how at Grand Coulee dam methods that are more advanced than ever before are producing four sizes of gravel and a sand having a fineness modulus of 2.5-3.0. The design capacity is 1000 tons an hour. Significantly, the methods and equipment employed are broadly those that have been used for a generation in metallurgical mills for accurately sizing and grading both precious

Jan 1, 1936

By Quentin D. Singewald, B. S. Butler

Some of the broader relations between structure and ore deposition along the London fault, deduced from a thorough study of the geology of the eastern part of the Mosquito Range, should be of general interest to economic geologists. The first part of this paper is a generalized statement of the geology of the region in which the London fault is located; it may be supplemented by reference to several earlier publications by the writers and to the U. S. Geological Survey's Professional Paper 148, on the Leadville district. The second part deals with the structure of both the fault and the disturbed zone adjoining the fault. The third part discusses the salient features of the ore deposits, particularly emphasizing structural control. The two generalized maps are complementary to one another but contain too many data to show on a single small map. The London fault is between Leadville and Alma, and the ore deposits along it are said to lie in the Alma district. Field work in this district, during six summers since 1927, has been a part of the cooperative work of the U. S. Geological Survey, the State of Colorado, and the Colorado Metal Mining Board. The writers have made use of work by R. D. Butler, J. W. Vanderwilt and R. E. Landon. G. F. Loughlin and C. H. Behre, Jr., who have worked on the west side of the range, have contributed valuable suggestions. Mining men of the district have aided in many ways. General Geology Pre-Cambrian Rocks.—The oldest rocks in the district are schists, correlated with the Idaho Springs formation of the Front Range. Quartz-mica schist predominates, but other types occur locally; almost everywhere the rocks show considerable lit-par-lit injection. Intrusive into the schists are two varieties of granite, only one of which is widespread. It is a fine-grained, porphyritie, gray granite correlated with the Silver Plume granite of the Front Range. Near the head of Buckskin Gulch a

Jan 1, 1937