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By Glenn Allen

SAN FRANCISCO Mines of Mexico, Ltd. owns and operates an extensive group of claims in the San Francisco del Oro-Santa Barbara district, about 15 miles southwest of Parral, Chihuahua. The property comprises the mines, aerial tramways, flotation mill, power plant, shops, offices, assay and testing laboratories, modern hospital, water and sanitary system, quarters for miners, mechanics and operators, a well housed colony for Mexican staff employees and residences for foreigners. Each colony has a club house and mess and tennis courts. The employees have constructed a nine-hole golf course. In other words, the property is self-contained and completely integrated for production of lead and zinc concentrates from complex sulfide ores.

Jan 1, 1930

By J. H. Fletcher

AIR has been cooled, heated, washed; humidified and dehumidified for many purposes and in many industries. At a number of metal mines air is conditioned to reduce the high humidity and unbearable heat found in deep workings, and at some mines air is washed to allay siliceous dust. Steam is introduced into the intake air at many coal mines, particularly in winter, for the purpose of keeping loose coal dust so moistened that the hazard of an explosion is lessened. This paper will describe a further successful application of air conditioning in a coal mine, where, for over three years, all intake air has been cooled to a constant temperature for the sole purpose of preventing roof falls.

Jan 1, 1931

By L. O. Millard

Stockpiles in the minerals industries serve a wide variety of purposes. Usually they are for surge between stages of processing, for a dependable plant feed in anticipation of delays, or to provide for single or double shift mining in conjunction with round-the-clock milling. Often surge piles are necessary to insure a uniform feed to continuous process equipment where the material is received as an intermittent or variable flow. Extensive use is made of stockpiling for the primary purpose of blending. The significant fact about all stockpiling of bulk materials is that storing and reclaiming are two separate and distinct operations and they may present widely different problems in the selection of methods and tools.

Jan 10, 1959

By G. D. Monk, W. C. Krumbein

The relation between permeability and the size parameters of unconsolidated sand is approached by considering sands as logarithmic frequency distributions having the basic parameters mean size and standard deviation. Sieve separates were mixed in accordance with the normal logarithmic probability law, so that the mean and standard deviation could be varied at will. Experiments were conducted in which one parameter was kept fixed and the other varied; in this manner the dependence of permeability on the individual parameters was evaluated. It was found that permeability can he expressed as the product of a power function of the mean size and an exponential function of the standard deviation. Earlier studies of the effect of size of particles on the permeability of uncon-solidated sand have shown that the permeability varies with the square of some average diameter. This was first pointed out by Hazenl in 1892 and verified by Slichter2 in 1898. Hazen's mean size was defined as the 10 percentile of the cumulative curve (i.e., size that is smaller than 90 pel cent of the distribution and larger than 10 per cent). Slichter's effective size, on the other hand, was found by Wilsey3,4 to agree with the 31 percentile. Fair and Hatch6 found that the geometric mean size of sieve separates yielded the same power function; Hulbert and Feben6 found that the permeability of sieve separates varied as the 1.89 power of the median diameter (i.e., the size associated with the 50 percentile of the cumulative curve). Relatively few studies included the effect of the "sorting" of the sediment on the permeability. It was recognized that the nature of the size distribution, in terms of the spread of the particles about the mean, affects the permeability, but no systematic investigations of this effect are known to the writers. Cloud7 demonstrated that the effect of the grain-size distribution on permeability is definitely measurable. In the present paper the authors investigate this relation analytically, and show that the effects of the size parameters on permeability may be predicted for at least a restricted set of conditions. Properties OF Sediments Recent investigations have shown that essentially all the geologically important characteristics of sediments may be expressed in terms of six measurable quanti-tities possessed by each clastic sedimentary particle. These attributes are: (I) size, (2) shape (sphericity), (3) roundness (angularity) , (4) mineralogical composition (density), (5) surface texture, (6) orientation. Each of these characteristics may be defined in several manners. Size may be expressed in terms of sieve mesh, settling velocity, volume, etc. Sphericity is a shape concept introduced by Wadell;8 it is essentially a measure of the ratio of the surface area of an equivalent sphere to the surface area of the particle. The same

Jan 1, 1943

By G. D. Monk, W. C. Krumbein

The relation between permeability and the size parameters of unconsolidated sand is approached by considering sands as logarithmic frequency distributions having the basic parameters mean size and standard deviation. Sieve separates were mixed in accordance with the normal logarithmic probability law, so that the mean and standard deviation could be varied at will. Experiments were conducted in which one parameter was kept fixed and the other varied; in this manner the dependence of permeability on the individual parameters was evaluated. It was found that permeability can he expressed as the product of a power function of the mean size and an exponential function of the standard deviation. Earlier studies of the effect of size of particles on the permeability of uncon-solidated sand have shown that the permeability varies with the square of some average diameter. This was first pointed out by Hazenl in 1892 and verified by Slichter2 in 1898. Hazen's mean size was defined as the 10 percentile of the cumulative curve (i.e., size that is smaller than 90 pel cent of the distribution and larger than 10 per cent). Slichter's effective size, on the other hand, was found by Wilsey3,4 to agree with the 31 percentile. Fair and Hatch6 found that the geometric mean size of sieve separates yielded the same power function; Hulbert and Feben6 found that the permeability of sieve separates varied as the 1.89 power of the median diameter (i.e., the size associated with the 50 percentile of the cumulative curve). Relatively few studies included the effect of the "sorting" of the sediment on the permeability. It was recognized that the nature of the size distribution, in terms of the spread of the particles about the mean, affects the permeability, but no systematic investigations of this effect are known to the writers. Cloud7 demonstrated that the effect of the grain-size distribution on permeability is definitely measurable. In the present paper the authors investigate this relation analytically, and show that the effects of the size parameters on permeability may be predicted for at least a restricted set of conditions. Properties OF Sediments Recent investigations have shown that essentially all the geologically important characteristics of sediments may be expressed in terms of six measurable quanti-tities possessed by each clastic sedimentary particle. These attributes are: (I) size, (2) shape (sphericity), (3) roundness (angularity) , (4) mineralogical composition (density), (5) surface texture, (6) orientation. Each of these characteristics may be defined in several manners. Size may be expressed in terms of sieve mesh, settling velocity, volume, etc. Sphericity is a shape concept introduced by Wadell;8 it is essentially a measure of the ratio of the surface area of an equivalent sphere to the surface area of the particle. The same

Jan 1, 1943

By T. E. Leontis, J. P. Murphy

During the last few years, the trend in the aircraft and automotive industries has been toward higher and higher operating engine temperatures. This has created considerable interest in the effect of temperature on the properties of alloys. In the magnesium field, it has been recognized for many years that the addition of cerium imparts high strength and good resistance to creep at elevated temperatures. Beck,' in his treatise on magnesium, has summarized the work of German investigators. This includes the unpublished data of Menking, showing the increase in strength and hardness of extruded alloys containing 2 to 20 per cent Ce at temperatures from 20' to 300°C. (68" to 57z°F.) and the results of Vosskiihler, who demonstrated the improved resistance to creep of alloys containing 6 per cent Ce plus 2 per cent Mn and 0.5 per cent Ce plus 2 per cent Mn at 150°C. (302°F.). Wellinger and Kei12 have also reported the creep properties of a forged magnesium-cerium-man-ganese alloy at 200' and 250°C. (392' and 482°F.). Haughton and Prytherch have determined the tensile properties of various forged magnesium alloys containing cerium, cerium plus manganese, cerium plus calcium, cerium plus nickel, cerium plus nickel plus manganese, and cerium plus cobalt plus manganese at temperatures up to 290°C. (554OF.). Magnesium-cerium alloys have been used in some commercial applications. It is reported that an alloy containing 3 per cent Ce plus 0.5 per cent Mn plus 0.5 per cent Ca is being used on a forged impeller in Great Britain. Two forged parts made from an alloy with a nominal composition of 5 per cent Ce and 2 per cent Mn have been found on the German BMW-8o1D aircraft engine. These two forgings consist of a supercharger impeller and a rear cam-follower guide. In this country, several types of pistons have been made experimentally in both the cast and the forged conditions from an alloy containing 6 per cent Ce plus 2 per cent Mn and in the cast condition from an alloy of magnesium plus 10 per cent Ce. The cast pistons have been tested in various types of internal-combustion engines, with promising results. This paper presents the results of an extensive investigation on the properties of various cerium-containing magnesium alloys in both the cast and the forged conditions. Data are presented to show the beneficial effects of increasing amounts of cerium on the mechanical properties of magnesium at at temperatures' The effects of heat-treatment on the properties of these alloys and the attendant changes in the microstructure are discussed. The alloys investigated most extensively are

Jan 1, 1946

By J. P. Murphy, T. E. Leontis

During the last few years, the trend in the aircraft and automotive industries has been toward higher and higher operating engine temperatures. This has created considerable interest in the effect of temperature on the properties of alloys. In the magnesium field, it has been recognized for many years that the addition of cerium imparts high strength and good resistance to creep at elevated temperatures. Beck,' in his treatise on magnesium, has summarized the work of German investigators. This includes the unpublished data of Menking, showing the increase in strength and hardness of extruded alloys containing 2 to 20 per cent Ce at temperatures from 20' to 300°C. (68" to 57z°F.) and the results of Vosskiihler, who demonstrated the improved resistance to creep of alloys containing 6 per cent Ce plus 2 per cent Mn and 0.5 per cent Ce plus 2 per cent Mn at 150°C. (302°F.). Wellinger and Kei12 have also reported the creep properties of a forged magnesium-cerium-man-ganese alloy at 200' and 250°C. (392' and 482°F.). Haughton and Prytherch have determined the tensile properties of various forged magnesium alloys containing cerium, cerium plus manganese, cerium plus calcium, cerium plus nickel, cerium plus nickel plus manganese, and cerium plus cobalt plus manganese at temperatures up to 290°C. (554OF.). Magnesium-cerium alloys have been used in some commercial applications. It is reported that an alloy containing 3 per cent Ce plus 0.5 per cent Mn plus 0.5 per cent Ca is being used on a forged impeller in Great Britain. Two forged parts made from an alloy with a nominal composition of 5 per cent Ce and 2 per cent Mn have been found on the German BMW-8o1D aircraft engine. These two forgings consist of a supercharger impeller and a rear cam-follower guide. In this country, several types of pistons have been made experimentally in both the cast and the forged conditions from an alloy containing 6 per cent Ce plus 2 per cent Mn and in the cast condition from an alloy of magnesium plus 10 per cent Ce. The cast pistons have been tested in various types of internal-combustion engines, with promising results. This paper presents the results of an extensive investigation on the properties of various cerium-containing magnesium alloys in both the cast and the forged conditions. Data are presented to show the beneficial effects of increasing amounts of cerium on the mechanical properties of magnesium at at temperatures' The effects of heat-treatment on the properties of these alloys and the attendant changes in the microstructure are discussed. The alloys investigated most extensively are

Jan 1, 1946

By W. A. Backofen, F. de Kazinczy

FRACTURING under conditions of particular interest is identified with the junction of curves relating tensile yield and fracture stresses to test temperature; the intersection point gives the lowest stress, for brittle fracture (at the ductility transition temperature). An expression for is found in Cottrell's brittle-fracture analysis, Eq. [15],1 while measurements of this stress and temperature have been reported for a low-carbon steel heat treated to differ-

Jan 1, 1962

M. G. CORSON.'-I am not going to discuss any of the papers presented but merely the question of season cracking of brass in general. Alpha brass has been known for nearly 500 yr. and from the very beginning a number of articles were made from sheets of this alloy by the process of spinning. Metal turning lathes were not yet known but wood turning lathes already existed and the wood turners used to make the mandrils and do the brass spinning themselves. Cases of season cracking were known even then. In 1915 I was connected with a small company doing a certain amount of brass spinning. Before the war its products never gave cause for complaint but their war-time products were cracking too frequently. The reason was, that due to the exigencies of war an excessive speed-up was attempted and the material simply could not take it. Today corrosion cracking of brass is most important in the case of cartridges for small arms ammunition and shell cases for large guns. The cracking takes place in storage and too frequently it is explained by the hypothetical presence of vapors of ammonia. However, I had the experience of purchasing some 20,000 rounds for the old Vetterli rifle from the Swiss government in 1905. The rifle and the cartridges were obsolete for many years and those which I bought were stored for at least 10 yr. None of them was found to be cracked or to crack in use. And the reason again was in the amount of work used in manufacturing the cartridges between anneals. The machinery today is more powerful and the amount of

Jan 1, 1945

By F. W. Jessen, R. W. Durie

The development in the laboratory of mall salt cavities illustrated that the rate at which salt dissolved was affected by the rate at which fresh water was injected into the cavity. Experiments carried out with small salt cores indicated, however, that the rate of salt removal with forced convection was not significantly different from that with natural convection, provided the flow was in the laminar range. The rate of salt removal was apparently controlled by the water salinity, which was indirectly determined by the rate at which fresh water was injected. With turbulent flow at the salt surface, the rate of salt removal could be increased several-fold with the same salinity in the cavity. A quantitative evaluation of the rate of salt removal under natural convection was attempted by using techniques developed for the analogous heat convection system. The values of the rate of salt removal obtained experimentally were considerably greater than the calculated values due to surface irregularities. To determine the effect of these irregularities, the rate of salt removal was found for a smooth surface by experimentally determining the rate of salt removal as an irregular surface developed and then extrapolating this trend back to initial time. Excellent agreement between the experimental and calculated values then were obtained. INTRODUCTION Underground cavities leached from massive salt formations have been used extensively for many years for storing LPG products. The development techniques for storing methane gases in the liquid state at a low temperature leads to speculation that underground salt cavities of controlled geometry may be quite important in this field. In any case, the increasing number of salt cavities used for storage indicates an impending need for a better knowledge of the washing process to efficiently develop maximum storage volumes within specified regions. It is the purpose of this paper to discuss some aspects of -the mechanism of the dissolution of salt in the formation of cavities of controlled geometry. Although no attempt is made to resolve the problems that may be associated with the storage of methane in the liquid state in salt formations, the fact that salt cavities can be formed at reasonable cost would appear to justify investigation in this direction. Further, underground cavities have the advantage of allowing storage at higher pressures (and hence higher temperatures) than surface installations. Although the thermal conductivity of salt is somewhat higher than frozen earths, 0.017 cal/(sec) (cm)(c) for salt at 32F vs 0.005 cal/(sec) (cm) () for ice at this temperature, this disadvantage is offset by the higher storage temperature in underground cavities. For example, at atmospheric pressure, the temperature of liquid methane would be —258F. In a storage cavity at 2,000 ft, the pressure would be approximately 1,000 psia, which would allow a storage temperature of -9OF. The formation temperature would be roughly 110F at this depth, hence the total temperature differential would be 200F. Under surface storage conditions the corresponding temperature difference would be some 333 F (75 F + 258 F). The results of this difference can be compared more readily by substituting the appropriate values of thermal conductivity, temperature difference, heat capacity and density into the solution of the diffusion equation for the unsteady linear conduction of heat. For the underground salt storage, the heat flux is 15cal/(sec) (sq cm), where t is the time in seconds from the initiation of the cooling. For the surface system, and using the thermal properties of ice at the average temperature, the corresponding figure is 21cal/(sec) (sq cm). Hence, the heat losses through ice under surface conditions would be some 30 per cent higher than the underground salt storage. This ratio would vary, considerablv. Of course, for other conditions, but it indicates that an advantage over surface facilities may be obtained by storage in underground salt cavities.

Jan 1, 1965

By Irving Cadoff, Jack Medoff

THE linear thermal expansions of oriented single crystals of zinc were measured in the range from 20" to 416°C using a Leitz HTV optical lever differential dilatometer. The single crystals, supplied by Dr. J. J. Gilman, General Electric Research Laboratory, Schenectady, N.Y., were prepared from 99.999 pct-purity zinc, and were in the form of rods approximately 2 in. long by 0.15 in. in diameter having the following orientations: x = 1.5, 12, 20, 30, 37.5, 49, 60, 73, and 82 deg where x is the angle between the specimen axis and the (0001) plane of the crystal. From the family of expansion vs temperature curves, the instantaneous expansion coefficients were calculated at 100°C intervals, and Fig. 1 shows a plot of these derived coefficients for each orientation. Coefficients were obtained from the raw data using the chord-slope method. The curves in Fig. 1 indicate a positive temperature coefficient for low x, a negative temperature coefficient for high X, and an expansion coefficient invariant with temperature, amounting to about 43 x 106, for a crystal orientation of approximately 52 deg. From the available data, it is possible to arrive at the values for the axial thermal-expansion coef- ficients a, and a, by extrapolating the curve of the expansion coefficient vs orientation to zero and 90 deg orientations. More precise values for a, and a, are obtained if the instantaneous coefficients are plotted against the square of the cosine of the orientation angle, as shown in Fig. 2. The extrapolated terminal points of the best straight line through the data points of such a plot define the axial coefficients at that temperature. The theoretical justification for the linearity of this curve comes from inspection of a rearranged form of the general anisotropic equation for expansion: ax=a, + (a, -a,)cosZx [1I in which a, is the expansion coefficient in the "c" or [0001] direction and a, the expansion coefficient in the "a" or [ll50] direction. From Fig. 2, the axial coefficients at 100°C, for example, were found to be a, = 13.9 x 10'6 and a, = 62.4 x 10"6 per "C. In the same way, the coefficients were determined for 20", 200°, 300°, and 400°C. This data is summarized in Fig. 3. It is of interest to observe the common intersection of the curves in Fig. 3, which seems to bear out the earlier observation, from Fig. 1, of a

Jan 1, 1964

By Vaughn Moyer

A method for incorporating well drawdown effect into reservoir calculations is presented in detail, together with examples of its use for widely divergent conditions that could be normally encountered in oil reservoir sands. Tentative conclusions as to the effect such factors as permeability, producing interval, well spacing, or well damage caused by completion or repair practice could have upon economic ultimate recovery are reached. It is carefully pointed out that the conclusions reached are subject to limitations indicated in the text, and placed upon all calculations made in the paper. Introduction Papers have been presentedl-3 in which theoretical depletion histories for reservoirs under equilibrium conditions and no appreciable well-bore drawdown pressure are determined. However, except for a limited number of cases, appreciable drawdown Pressures in a well bore exist, and Pressure and saturation gradients consequently vary throughout a reservoir. This Paper is an attempt to incorporate well-pressure drawdown into reservoir history, and to analyze certain factors, such as those involving recovery, well spacing, and productivity index, from the standpoint of permeability and drainage radius. BY incorporation of drawdown into reservoir history, it is believed that theoretical considerations will more closely approxi- mate actual reservoir behavior experienced in an oil field. For purposes of simplification, a solution gas-drive type field1 without primary gas cap, has been selected. Basic Data and Assumptions Details of equilibrium saturation conditions for no drawdown production for various pressures in a reservoir are deter-minable by methods described by several are permitting the construction of a curve of oil saturation vs Pressure for any selected combination of initial interstitial water and hydrocarbon saturation (Fig I). This curve is then a description of equilibrium saturation conditions at any given pressure in a reservoir. Developing the above, details of saturation and flow permeability may thus be determined for any increment or portion of a well drainage area or reservoir. In this manner the effect of pressure differential (drawdown) may be incorporated into reservoir and well drainage considerations. It is pointed out that this method thus makes use of no-drawdown equilibrium production data, superimposing a draw-hwn effect upon them. It also assumes that net flow conditions in any considered increment of reservoir are not materially altered by the entrance of fluids from other increments into them, but approach equilibrium for the existing pressure and saturation (i.e., each increment behaves in more or less independent fashion, dependent largely upon the equilibrium considerations mentioned above)

Jan 1, 1948

By Vaughn Moyer

A method for incorporating well drawdown effect into reservoir calculations is presented in detail, together with examples of its use for widely divergent conditions that could be normally encountered in oil reservoir sands. Tentative conclusions as to the effect such factors as permeability, producing interval, well spacing, or well damage caused by completion or repair practice could have upon economic ultimate recovery are reached. It is carefully pointed out that the conclusions reached are subject to limitations indicated in the text, and placed upon all calculations made in the paper. Introduction Papers have been presentedl-3 in which theoretical depletion histories for reservoirs under equilibrium conditions and no appreciable well-bore drawdown pressure are determined. However, except for a limited number of cases, appreciable drawdown Pressures in a well bore exist, and Pressure and saturation gradients consequently vary throughout a reservoir. This Paper is an attempt to incorporate well-pressure drawdown into reservoir history, and to analyze certain factors, such as those involving recovery, well spacing, and productivity index, from the standpoint of permeability and drainage radius. BY incorporation of drawdown into reservoir history, it is believed that theoretical considerations will more closely approxi- mate actual reservoir behavior experienced in an oil field. For purposes of simplification, a solution gas-drive type field1 without primary gas cap, has been selected. Basic Data and Assumptions Details of equilibrium saturation conditions for no drawdown production for various pressures in a reservoir are deter-minable by methods described by several are permitting the construction of a curve of oil saturation vs Pressure for any selected combination of initial interstitial water and hydrocarbon saturation (Fig I). This curve is then a description of equilibrium saturation conditions at any given pressure in a reservoir. Developing the above, details of saturation and flow permeability may thus be determined for any increment or portion of a well drainage area or reservoir. In this manner the effect of pressure differential (drawdown) may be incorporated into reservoir and well drainage considerations. It is pointed out that this method thus makes use of no-drawdown equilibrium production data, superimposing a draw-hwn effect upon them. It also assumes that net flow conditions in any considered increment of reservoir are not materially altered by the entrance of fluids from other increments into them, but approach equilibrium for the existing pressure and saturation (i.e., each increment behaves in more or less independent fashion, dependent largely upon the equilibrium considerations mentioned above)

Jan 1, 1948

By S. J. Aresco, George E. Keller, J. Visman

INTRODUCTION The accurate sampling of coal, as with most minerals, is a difficult task. Coal is a very heterogeneous material made up of different types of coal and varying amounts of mineral matter. The product as mined may contain all of the layers of coal and impurities found in the seam as well as portions of the strata above and below the coal seam. The preparation plant is the device to size, crush and/or remove impurities so that the coal may be shipped as a saleable product. Sampling may be needed at many stages in the preparation process. Although this chapter is mainly concerned with sampling in connection with preparation processes, the principles will apply to all coal sampling. The main reasons for sampling in connection with coal preparation are: 1. To determine the washability characteristics of the raw coal by means of float and sink tests. These may be used for the design of a preparation plant, prediction of results to be obtained or for monitoring raw coal delivered to the plant. 2. To check the performance of various operating units in the plant, either by float and sink tests or chemical analyses. 3. To determine the analytical characteristics of the products produced, such as moisture, ash, Btu, sulfur, etc. HISTORY The earliest accepted methods of sampling coal in the United States were given in U. S. Bureau of Mines publications by J. A. Holmes,1 G. S. Pope2 and A. C. Fieldner.3 The American Society for Testing and Materials more or less adopted the methods proposed by the U.S. Bureau of Mines in their Standard D-21-1916, and it remained a standard for many years. Briefly, the standard called for a 500 pound sample for coals less than. 3/4 -in. in size and a 1,000 pound sample for all coals over ?4 -in. in size. No mention was made of increments but there was an instruction that the sample should spread over the coal to be sampled. Sample preparation was by hand crushing with the alternate shovel method for reduction to 250 pounds followed by coning and quartering below 250 pounds. Obviously, with the amount of work involved, this method of sample preparation was rarely followed. This method of preparation resulted in samples that were practically air dried because of long exposure while crushing, shoveling and quartering. In the late nineteen twenties and early nineteen thirties, studies for more practical methods were begun. Dr. E. S. Grummell4, Imperial Chemical Industries, Ltd, London, summarized the work to date at the

Jan 1, 1968

By W. A. Weimer

Australia, the land of the kangaroo, koala, and the platypus, is often referred to as "down under" by people of the Northern Hemisphere. It is a tropical land and has very little freezing and thawing; consequently the in-place rocks are near the surface, exposing some of the unaltered mineralization. This type of geology induces the prospector and miner to search for minerals which lie at his feet (or not far under them), and it is adapted to open cut surface mining. Some of the rules and regulations applicable to exploration and mining in Australia will be interesting and helpful towards understanding acquisitions and control of minerals. They are common and basic to the United Kingdom. Throughout Australia practically all minerals are the property of the Crown (government), and their exploration and exploitation are administered by the state Department of Mines. Surface owners, or land lessees, do not control the minerals. Their mining codes protect the prospector. If a prospector obtains a permit, "miner's right," it entitles him to search for minerals any place within the state, only holding him responsible for damages he may incur in his exploration. If he finds something of interest, he may then apply for an authority to prospect, which gives greater latitude and protection in his work to develop the find. However, he will be obligated to spend a minimum specified amount to exclusively hold an area. He will be required to furnish maps, analyses, and geological data to the Mines Department. Presuming that he has located something economically valuable for mining, he may then apply for a mining lease or be granted a franchise to produce a specific material. It will contain a quantity clause so that the area cannot be held indiscriminately without production of the mineral. The states have Bureaus of Mineral Resources, Geology, and Geophysics that keep constantly abreast of the search for minerals and often do much of the drilling and deep boring to promote geological study for the states.

Jan 1, 1969

By Benjamin C. Greene, H. Beecher Charmbury

Water is a most remarkable substance, essential for life of all kinds. As well as needing water to survive, man has always used it for agriculture, transportation, recreation, and many other things. When our country was young and inhabited by few people, the streams, rivers, and lakes were able to provide all the clean water needed by man and take away all the wastes created. However, with our growing population and an ever-increasing demand for goods and services, the public, industry, and government at all levels have become acutely aware of the need to manage the nation's water resources more efficiently. Abundant energy from many sources has helped this nation to become the greatest industrial nation in the world. Coal has contributed a major portion of this energy, generating electricity, running railroads, and maintaining national security during wartime. The result has been the highest standard of living in the world and a time of widespread economic prosperity. The use of water in coal mining is somewhat different from its use in most industries. With the exception of water used in cleaning plants, for underground dust control, and for fire protection, most of the water en- countered in coal mining operations serves no useful purpose. In other words, it is an undesirable element and must be removed, otherwise it will interfere with operations, cause potential water quality problems, and may even stop operations by flooding. In the past, removing water from working areas of most mines was usually a fairly simple matter. Pumps with piping were installed at sumps or low spots in the mine and the water was pumped to the surface or to drainage control facilities constructed for the operation. Ditches were often used to collect and drain the water by gravity to the outside or to main sumps for pump discharge. In either case, the water was allowed to flow into the nearest stream or river. The concept of "water is water" was generally accepted without too much concern for what was in

Jan 1, 1981

By Benjamin C. Greene, H. Beecher Charmbury

Water is a most remarkable substance, essential for life of all kinds. As well as needing water to survive, man has always used it for agriculture, transportation, recreation, and many other things. When our country was young and inhabited by few people, the streams, rivers, and lakes were able to provide all the clean water needed by man and take away all the wastes created. However, with our growing population and an ever-increasing demand for goods and services, the public, industry, and government at all levels have become acutely aware of the need to manage the nation's water resources more efficiently. Abundant energy from many sources has helped this nation to become the greatest industrial nation in the world. Coal has contributed a major portion of this energy, generating electricity, running railroads, and maintaining national security during wartime. The result has been the highest standard of living in the world and a time of widespread economic prosperity. The use of water in coal mining is somewhat different from its use in most industries. With the exception of water used in cleaning plants, for underground dust control, and for fire protection, most of the water en- countered in coal mining operations serves no useful purpose. In other words, it is an undesirable element and must be removed, otherwise it will interfere with operations, cause potential water quality problems, and may even stop operations by flooding. In the past, removing water from working areas of most mines was usually a fairly simple matter. Pumps with piping were installed at sumps or low spots in the mine and the water was pumped to the surface or to drainage control facilities constructed for the operation. Ditches were often used to collect and drain the water by gravity to the outside or to main sumps for pump discharge. In either case, the water was allowed to flow into the nearest stream or river. The concept of "water is water'' was generally accepted without too much concern for what was in

Jan 1, 1981

By G. S. Coe, G. F. Bolling

The columnar-to-equiaxed transition (CET) has often been studied as a function of concentration, C, temperature gradient in the melt, G, and rate of solidification, R. Although it may not be immediately obvious it is sure that the CET, expressed as some ratio G/R necessary to suppress equiaxed nucleation for a given C,' cannot be a single-valued function of C. This restriction which is ignored in theoretical presentations is most trivially illustrated by the following simple reasoning. An ordinary casting is an unconstrained system where the thermal conditions change continuously with progressive solidification, and thus where the ratio G/R decreases from the outset. A CET occurring early in a casting (much equiaxed material) must then mean a higher value of G/R at transition, in comparison with the late CET which implies a more columnar ingot. Therefore, when we choose to experiment under constant superheat for all alloys across the simplest binary, and we find an inversion in the amount of equiaxed material, we shall find two values of C satisfying the G/R condition. However, in addition to this simple instance, the early experiments of ~orthcott' seem to show that the amount of equiaxed material in cast ingots may be a multivalued function of composition in a given binary system. In the present investigation, the CET has been examined in Pb-Sb, Pb-Ag, Pb-Sn, and Sn-Pb under several types of casting conditions. First, we have used the "bidirectional" ingot section Simulation;~ and we have used .'i~z situ" ingot solidification where a hot mold already filled with liquid is chilled so that there is no disturbance provoked by pouring. Differences in method are trivial to our purpose except for the fact that certain variations are more simply observed by one technique than by the other. Second, we have varied the mode of superheating from the simple extreme of casting all alloys from the same temperature regardless of composition to the careful casting at a standard superheat, calculated with respect to the alloy liquidus. Third, we have made provisions for decanting and interface observation, so that some "castings" were not completed. The results obtained with Pb-Sb are exemplary; some of these are shown in Fig. 1 along with explanatory captions. At 9 to 10 at. pct Sb, and thus above the solid-solubility limit Cs = 5.8 at. pct Sb and yet below the eutectic concentration Ceu = 17.5 at. pct Sb, there is a persistent anomaly in all the variations. Measurement was easy enough and standard enough so that we may forgo discussion of either method or possible error, in view of the forceful self-consistency shown by experiment. Solute distributions were measured along the bidirectional ingots in order to determine if a solute buildup had occurred at the CET. No anomalous changes in concentration were observed along the bars at either side of the solute anomaly of 10 at. pct Sb. The microstructures of the ingots were also examined across the range of composition investigated. At concentrations less than 9 at. pct Sb the micro- and macrostructures were typical of the cellular-dendritic growth usually reported for the columnar zone. Above the anomaly, both the columnar grain size and the amount of primary phase decreased. This microstruc-tural observation can be correlated with observations made of decanted interfaces. Below 9 at. pct Sb, the interface reveals the "normal" columnar dendritic structure; however above the anomalous concentration range, preferential growth of certain dendrites appears to form a "super dendrite" pattern. In Fig. 2 a microstructural view of the etched '(super dendrites'' shows their constitution both in terms of relative phase proportion and in terms of the ordinary smaller dendrites.

Jan 1, 1969

By D. Turnbull, R. E. Cech

THE supercooling behavior of pure liquid metal droplets has been described.' The solidification behavior of small droplets of Cu-Ni alloys as a function of composition is described herein. The Cu-Ni system is of interest for such an investigation because the components are miscible in all proportions in both the liquid and solid state and the phase diagram of the system, Fig. 1, is a type often encountered in metal systems. It was noted by Van Riemsdyk2 and others that the nature of the "blick" of gold droplets during assaying is not perceptibly affected by the content of the platinum group metals that are soluble in both liquid and solid gold. With the exception of these very qualitative observations there appear to have been no prior investigations of the supercooling of alloy droplets. A series of nine alloys varying in composition by 10 pct (nominal weight) steps was made using certified OFHC copper, 99.996 pct purity, obtained from the American Brass Co., and electrolytic nickel pellets, 99.92 pct purity, obtained from the International Nickel Co. The alloys were melted and cast in vacuo in a high frequency induction furnace. Segregation was minimized by chill casting into 1-in. diam steel molds. Each alloy rod was homogenized at a temperature 50°C lower than the solidus for 100 hr in dry hydrogen. Samples for solidification experiments and chemical analysis were machined from the same portion of each rod and at a depth of in. from the rod surface. A Car-boloy tool was used in taking turnings to minimize contamination of sample by the cutting tool. As a check, a number of samples for microscopic observation were chipped from the ingot with a fragment of pyrex glass. The resultant data in all cases agreed, within experimental error, with the data obtained from machined turnings. A number of small particles, 30 to 50 micron diam, of a Cu-Ni alloy were placed in a quartz vial 1/32 in. diam x % in. long. This was inserted into a platinum ribbon heater and mounted in a high temperature microscope stage. The general procedure followed in inserting samples into the stage and measuring the temperature of melting and solidification was the same as described in an earlier paper.' A chromel-alumel thermocouple was used to study alloys of 88.93 pct Cu, 80.62 pct Cu, and 72.27 pct Cu. A platinum-10 pct rhodium thermocouple was used for the remainder of the alloys. Procedure The assembled high temperature microscope stage was first evacuated and the sample given a 2 min in situ treatment at 900 °C in dry hydrogen to remove surface oxides which might otherwise catalyze crystal nucleation. After this treatment the atmosphere was changed to purified helium and melting and solidification were observed microscopically. It was not possible to determine the solidus with certainty. However, the liquidus temperature was measured very accurately since the surface of the particle changed in appearance from coarse and uneven to smooth, mirror-like within a few degrees. The visually determined liquidus temperature was checked by finding the highest temperature to which the particle could be heated such that it did not supercool upon lowering the temperature. This temperature which checked within experimental error with that found by observing surface change was assumed to be characteristic of the thermody-namic liquidus. In order to minimize the effect of selective evaporation of copper from the alloy, samples were changed frequently and the droplets were heated no more than 50 °C in excess of the liquidus temperature T,. When the latter conditions were fulfilled, T, values were reproducible. After melting, the temperature was decreased slowly until the particles solidified. The sudden release of heat of fusion on solidification caused the

Jan 1, 1952

By Y. Kondo, A. M. Gaudin

A combined method for sizing in the sub-micron range was developed using centrifugation and gamma emission. Its essential features are: 1) Centrifugation of suspended mineral in water carried out at 4°C where water has its maximal density and zero temperature gradient of density 2) Gamma activition of the sample suspension induced by irradiating it in a nuclear reactor prior to centrifugation 3) Measurement of the activity of a beam of suspension as it is sedimenting in the centrifuge, using a scintillation counter provided with a discriminator. Albite, the sodium feldspar, was used as feed to the comminution step, and the induced gamma activity of Na24 was measured. Dissolved sodium ion caused a a non-settling activity in the measurement. Other "noise" is due to scattered gamma radiation from albite particles in the centrifuge outside of the line of sight. These two activities were obtained sep arately and subtracted from the total activity counted. The relative solid concentration in the suspension under the collimating slit is proportional to this net activity. The cumulative weight per cent of undersize particles was calculated and plotted against size on logarithmic scales. The relationship was found to be linear down to about 30 mµ. The specific surfaces calculated from particle size distribution agree with those measured by krypton gas adsorption. The measurement of particle size distribution of comminution products has been of interest in clarifying the mechanism of the process. The Gaudin-Schuhmann equation1,2 relates the cumulative percentage undersize, y, to relative particle size x/k. The particle size, x, and the size modulus, k, together with the distribution modulus, m, characterize the particle size distribution, m is the slope of a plot of log (y) against log (x/k). This equation has been verified for ground particles down to 1 micron in size.3'4 For particle sizes smaller than a few microns, the precision and facility of sedimentation and microscope techniques become questionable. Use of a centrifuge which shortens settling time from weeks to hours is attractive. Many centrifugal methods have been proposed; however, determination of the solid concentration of the suspension at a reference level as a function of time is difficult, and sampling the suspension is likely to introduce errors. Measurement of particle size distribution by X-ray absorption in gravitational5 and in centrifugal6 sedimentation have also been tried. In these methods, the absorption coefficient for the solid is independent of size, since the wave lengths of the X-rays and gamma-rays are orders of magnitude smaller than the particles. Radiometric techniques7 in size distribution measurement have been developed within the last several years. They offer advantages over usual gravimetric and optical methods. PRINCIPLE OF METHOD The combined method of centrifugation and gamma emission for sizing in submicron range described in the present paper has the following essential features. 1) Centrifugation is carried out at 4 ± 0.1°C. Convection currents in the water phase due to density changes caused by temperature variation may disturb completely the settling system. To avoid this difficulty, the unique property of water having zero temperature gradient of density at 4°C is used. 2) Prior to size measurement the sample suspension is irradiated in a nuclear reactor and gamma activity induced. The gamma activity of the particles sedi-mented radially is measured by a scintillation counter provided with a discriminator. By this method, interruption of centrifugation by withdrawing samples is avoided and the counting rate at any time represents the solid concentration in the suspension at the level of the collimating slit of the centrifuge at the particular time at which the measurement is made. 3) By proper selection of the feed material and of the comminution device, gamma activities of foreign

Jan 1, 1964