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By D. W. McGlashan, K. N. Mcleod

IN the use of free bubbles with precise temperature control and continuous pH measurement, the contact angle apparatus differs from all previous equipment. Experimental procedures differ sharply from the captive bubble method1,2 of introducing the gaseous phase in the three-phase system. When freed from the tube and captured by a solid surface, a bubble more closely conforms to the spherical ideal set up by the usual mathematical analysis of surface free energy or surface tensional relationships of the forces involved. The assembled equipment, Fig. 1, departs from the usual contact angle apparatus in providing: 1) water circulation for fixing temperature, 2) instruments to measure and record pH during testing, and 3) a system for producing and using free bubbles. The apparatus allows testing over a broad range of closely controlled conditions, and the use of free bubbles gives contact angles independent of operator manipulation, which was unavoidable in the older captive bubble method. A bubble released below the specimen rises through the liquid and contacts the mineral. If the mineral is gas-avid the bubble adheres, developing a finite contact angle. Reaction cells (1), 2x33/8x5 3/16 in. ID, are of pyrex glass 5 mm thick. To prevent optical distortion, the sides are optical flats and are planed parallel to within five wave lengths of light over the entire surface. Special cement is required to withstand chemical attack and thermal shock. The cell is placed in a thermal jacket (2) made of welded aluminum. A water seal for the optical ports is made by using O-rings tightened against the flats of the cell by fine-threaded and adjustable ports, Fig. 2. In-flow water is discharged downward from a manifold located near the bottom of the cell jacket. Water overflows the weirs at each end of the cell jacket, discharging from both sides to a collecting manifold (24). A hose (26) leads the overflow water to the thermal-conditioner well (4), which is recessed to accommodate a reaction cell and two beakers (150 ml). Both the thermal jacket and the thermal-conditioner well are insulated to minimize the effects of temperature differentials. Water, discharging from the thermal-conditioner well, returns to a thermostat bath and pump (3), from which it is pumped to the thermal jacket. The thermostat bath permits temperatures to be adjusted from 1" or 2°C to 80°C and will maintain the selected temperature within 0.2ºC. An electrode support (22) groups the four electrodes (8) so that they fit conveniently into the reaction cell, Fig. 2. This assembly holds the glass electrode, the calomel electrode, the temperature-

Jan 1, 1957

By Richard F. Miller, W. E. Milligan

Work was undertaken two years ago at the Hammond Laboratory for the purpose of determining the magnitude of the elastic range in single crystals of pure metals by means of creep tests, the assumption being made that if a true elastic range exists, the elastic limit represents the maximum stress for no creep. A sensitive extensometer was constructed, and creep tests were made on zinc single crystals at a variety of loads and temperatures1. It was soon discovered that there is no measurable elastic limit in ductile zinc single crystals at, or above, room temperature. The inference that pure metallic single crystals may not possess a definite elastic range was not justified, however, since zinc had been tested in creep only above its recrystallization temperature, and several investigator2,3,4 had already shown that above the recrystallization temperature polycrystalline metals will flow under very small stresses, while below that temperature stresses of a much larger magnitude are required. For that reason, it was decided to extend the study of the elastic limit to other metals having a higher recrystallization temperature than zinc. Aluminum and silver were selected, because of the ease of obtaining pure materials and of preparing large single crystals, and because the crystallo-graphic glide system of these metals is well known. Owing to the limited time available, the elastic range was investigated by slow tensile tests rather than by creep tests. Production of Specimens A luminum Recrystallized single crystals were prepared from 99.95 per cent aluminum supplied by the Aluminum Company of America. The ingots were melted in an Acheson graphite crucible in a gas furnace, and cast

Jan 1, 1937

By Henry F. Heblby

HOW often has the thoughtful observer pondered the apparent contradictions experienced in the weather? One can take records of two days, one in the winter and one in the summer. The "degree days1' indicate that space heating and domestic load were present in one case and not in the other. The Business Index may be about the same, indicating that the industrial activity of the area and its concomitant use of fuel were about the same. Thus the volume of the products of combustion released to the atmosphere varied only as related to the space heating demand. Yet on one day in winter the atmosphere may be clear and bracing, while on a summer's day the air is thick and murky and the visibility sharply reduced. The situation may be reversed. What are some of the factors that contribute to the creation of these conditions? These few notes have been prepared to indicate some of the influences that are exerted on the problem. The Sources of Atmospheric PolLution The industrial area of Pittsburgh, Pa., has been a dominant center for the production of iron and steel for over one hundred years. In fact, with the growth of the numerous auxiliary processes Allegheny County which contains Pittsburgh is prob- ably the most industrialized county in the world. In addition, the type of manufacture carried out in this area is predominantly dependent on thermal energy (heat). That energy is supplied from coke and coal produced in the vicinity of Pittsburgh Indicative of the stupendous quantities of fuel that are employed in this industrial area's economy, the following (Table I) taken from the U. S. Census (1940) may be of interest. In tonnage consumed in the area, the figures are equally impressive: Annual Tons oF Coal Metallurgical Industries.... 35,000,000 to 40,000,000 Commercial Installations (Pgh.)................. 1,500,000 Domestic hand-fired) (Pgh.)................. 750,000 An influence that has never been fully appreciated by many individuals is the fact that no matter what adventures the gases of combustion experience as they pass through the various processes, uti-mately the spent gases are discharged through chimneys to the atmosphere.

Jan 1, 1949

By F. R. Hensel

The present paper describes a number of experiments with fine silver, coin silver, silver-cadmium oxide and silver-nickei-copper compacts, prepared by powder metallurgical methods. The test data are of a preliminary nature, since most of the work was exploratory. Fine Silver Eject of Compacting Pressure on Hardness and Density during Cold and Hot Pressing The cold-welding properties of silver have received considerable attention and the welding characteristics are functions of such variables as: cleanliness of metal particles (impurities and adsorbed gases), chemical nobility of particles, plasticity and hardness, particle assortment, particle shape, particle porosity, apparent density, temperature, pressure, time, recrystalliza-tion characteristics. Chemical nobility, plasticity and low temperature of recrystallization after work-hardening are responsible for the excellent low-temperature bonding properties of silver. Several series of compacts were pressed at pressures of 5, 10, 20, 30, 40, 50, 60 70 and 80 tons per square inch, at temperatures of 32°C. (room temperature), l00°, 2000, 300°, 400°, and 450°C. Silver powder of minus 325-mesh, produced by displacing silver from a nitrate solution by means of copper, was used. The density was calcuiated from accurately measured and weighed compacts. The hardness was measured on the Rockwell F scale. The investigation shows that an increase in pressure promotes a higher density and hardness regardless of pressing temperature, up to a temperature of 400° C. The pressure-density curves at various pressing temperatures are shown in Fig. I, the pressure-hardness curves at various pressing temperatures, in Fig. z. The greatest increase in both hardness and density was obtained in the pressure range of 5 to 20 tons per square inch. A compact from each series was annealed at 300°C. in air, for various lengths of time. The hardness values after annealing are shown in Table I. A minimum hardness was obtained after one hour of annealing. No change in density occurred during annealing. The maximum density was obtained at 80 tons per sq. in., and at this pressure the hardness is equal to that of hard-drawn wrought

Jan 1, 1945

By John P. Bryant, Samuel Kincheloe

Plant nutrients are obtained by plants from both the air and the soil. Carbon dioxide, a gaseous form of carbon and oxygen, supplies the carbon which usually makes up 50% or more of plant structure. Plants are capable of absorbing carbon dioxide directly from the air. Most of this nutrient comes from the air, although some carbon dioxide is absorbed by soil water and taken into the plant as liquid. Growing plants use more water than any other substance. Plant nutrients in the soil dissolve in soil water; soil water entering the plant carries nutrients into the plant structure. Water is then given off into the air as the plant breathes or transpires. Inorganic or mineral nutrients essential to plants are supplied through the soil. Inorganic or mineral composition of plants usually is less than 5% of their weight. In most crop-growing areas, much of this nutrition is inadequately supplied from the soil and must be provided by fertilizers. Proper fertilization of a soil to improve its mineral level and productivity is the role of the fertilizer industry. The 13 essential plant nutrients which often must be added to soils or plants and are generally considered fertilizer minerals are categorized as primary minerals (nitrogen, phosphorus, and potassium); secondary minerals (calcium, magnesium, and sulfur); and micronutrients, or trace minerals (boron, iron, manganese, copper, zinc, molybdenum, and chlorine). These classifications are based on quantity of nutrients utilized by plants and have no implication as to function or degree of necessity. One point of major significance to the fertilizer industry is that not all nutrient carriers supply that nutrient in a chemical form which will be available to the plant. Thus, a product which may be considered a fertilizer mineral may require substantial processing or may require substantial processing or treatment before it becomes useful as a nutrient carrier. Fertilizer Industry Scope Until about 1900 demands for higher crop yields were met simply by bringing new agricultural lands into cultivation. Since that time great progress has been made in increasing yields through fertilization and improved varieties and cultural practices. The importance of the fertilizer industry to the economy and welfare of the US is widely recognized. Fig. 1 illustrates the relationship of lime and fertilizers to crop yields. In terms of tons of fertilizer products, the growth of the industry has been phenomenal, particularly between 1950 and 1980. Table 1 shows the increase in fertilizer usage. Primary Plant Nutrients in Fertilizers Primary minerals (nitrogen, phosphorus, and potassium) are designated as such because [ ]

Jan 1, 1983

By S. M. Parmley

Experience has shown that there are some factors connected with the drying of fine washed coal that are not present in drying of slack coal as normally practiced at cement kilns or pulverized coal plants. It is the purpose of this paper to show some of these variations as they have been encountered under actual operation. The Champion No. 1 cleaning plant of the Pittsburgh Coal Co. uses the wet system of cleaning coal. The plant is equipped to produce commercial sizes or mixtures, the primary sizes being plus 6 in. and 4 by 6 in., which are hand-picked. Minus 4-in. sizes are all cleaned by the wet process. To produce a commercial product as free of moisture as possible, the washed coal is first passed over sizing and dewatering screens, then each size except the — ?-in. coal is conveyed to loading booms by slow-moving draining conveyors. As the +?-in. sizes are not heat-dried, no data will be given, as it is the purpose of this paper to describe the heat drying of — ?-in. coal as practiced at the Champion No. 1 plant of the Pittsburgh Coal Company. To fully appreciate the conditions, it must be remembered that the — ?-in. product is now shipped at a lower moisture content than when received from the mine. The incoming coal in the — ?-in. size will average 5 per cent. moisture and the shipped product 3 per cent. moisture. This is a case where a wet process gives a reduction of both ash and moisture in the fine sizes. The shipped product, therefore, is more uniform in all characteristics, and uniformity of product is the most important single factor in coal preparation. The 0 by ?-in. coal is first dewatered on slow-moving continuous bucket dewatering elevators, running at the rate of 40 ft. per minute, with 48-in. perforated buckets with ¼ by 1½-in. slots, spaced ? by 2?-in. centers staggered. The moisture in the coal discharged from the elevators runs 20 to 28 per cent., depending on the fineness of the product. The discharge from the dewatering elevator is further drained on a drag-type conveyor equipped with ½-mm. wedge wire screen. The conveyor discharges coal with an 18 to 25 per cent. moisture to three centrifugal dryers of the Carpenter type. The Carpenter dryers

Jan 1, 1931

The function of a preposition is to show the relation of one thing to another; it is necessary therefore for the writer to select the preposition that indicates the particular relation, otherwise he will fail to express himself clearly. Is it against common sense &o suggest that a Government is justified, morally as well as constitutionally, in preventing the decay of an industry by insisting upon the amalgamation of the prosperous with the needy? All these seven prepositions are used correctly. With the first dredge introduced in Russia, of Werf Conrad, Haarlem, make, this method of alluvial mining became important. Here the prepositions "with", "in", and "of" are used wrongly. He means: "This method of alluvial mining sprang into importance shortly after the first dredge, made at the Werf Conrad, Haarlem, was introduced into Russia." The statement itself is not true, but for that I am not responsible. Once, while I was serving with him, we were frozen in out of sight of land in the Gulf of Pichili in the North of China. Admiral Fisher wrote thus. He has used nine prepositions in making this brief statement. The sequence of three prepositions "in out of" is particularly awkward. Lounsbury says : One might fairly infer from the way in which it [newspaper English] is often spoken of that with the steadily increasing circulation of this sort of periodical literature there is no hope whatever for our speech. "Of that with" is lamentable. The construction is thoroughly bad, and it is bad mainly because the misplaced prepositions have tangled the meaning. I suggest:

Jan 1, 1931

By George Kunz

(Butte Meeting, August, 1913.) THE manifold inconveniences resulting from the absence of a uniform standard of mass for determining the weight of precious stones have long been obvious. This lack has been keenly felt in commercial transactions, and those who have devoted time and research to the study of historic diamonds and precious stones have had frequent occasion to deplore the absence of such a standard in the past. In a paper read in Chicago in 1893, before the International Congress of Weights and Measures, held in connection with the World's Columbian Exposition, the writer suggested dividing the carat into 100 parts, and constituting a standard international carat of 200 mg. ; that is, 5 diamond carats or 20 pearl grains to a French gram, making 5,000 carats or 20,000 pearl grains to a kilogram. He also called attention to the fact that while this would depreciate the present diamond carat or pearl grain only about 2.5 per cent., it would abolish the troublesome discrepancies between the various carat-weights now in use, and could be easily explained and understood everywhere.1 The subject of the various diamond carats, their incongruity, and the resulting confusion as to the correct weights of historic gems when definite records of them are searched for, has been fully treated by me in an extensive study of this subject in The Book of the Pearl.2 To the earnest and unremitting efforts of C. E. Guillaume, Director of the Bureau Internationale des Poids et Mesures at Sèvres, is largely clue the eventual success of this eminently desirable reform, which lie has constantly urged both by articles on the subject and by addresses delivered in Paris before the International Committee for Weights and Measures.3

Jan 7, 1913

By Arthur Tauber, Horst Kedesdy

FERRITES are sintered metallic oxides of the spinel structure type1 and belong to the class of soft ferromagnetic materials. Similar to a ceramic, they can be formed and fired to a dense body, exhibiting a high electrical volume resistivity ranging from 10 90 10' ohm-cm as compared with 10-6 hm-cm for some of the metallic magnetic materials. This high resistivity, with resulting low eddy current losses, finds special application at high frequencies. The dispersive susceptibility of ferrites at microwave frequencies has also led to many applications in this field. Where high resistivity with high permeability is desirable, ferrites are used in low frequency applications. During the last few years ferrites exhibiting rectangular hysteresis loops have been developed for computer and magnetic memory systems. The general formula for ferrites is MeFe2O4 where Me is a divalent metal ion such as Ni, Zn, Mg, Mn, Cu, Cd, and Fe. Only two of these ferrites are nonferromagnetic, namely, those with Zn and Cd. Solid solutions can be formed between different ferrites, and it is of interest to note that solid solutions of a ferromagnetic ferrite with a nonferromagnetic ferrite yield much better magnetic materials than the basic ferrite body. In general, it can be said that the solid solution formation between ferrites has widened the field of ferrite synthesis and has led to methods of preparing materials with a large variety of magnetic properties. During the last two decades the synthesis of ferromagnetic oxides has been the object of extensive research, but commercial production has been started only within the last ten years. Along with more fundamental studies, there remains the never- ending task of developing ways to realize the optimum characteristics of materials in large-scale production. Ordinarily, to produce a ferrite material it is necessary for the constituent oxides to be mixed intimately, pressed, and then fired at temperatures above 1000°C. Ferrite Synthesis: Formation of a basic ferrite by solid state reaction from Fe,O, and a monoxide such as NiO, under normal atmospheric conditions, is governed by a progressive diffusion of cations between adjacent particles of the constituents. Firing temperature, furnace atmosphere, and cooling can vary the magnetic properties, however. If, for example, a dioxide, a sesquioxide, or an oxide of the Me0 type is substituted for the monoxide, the reaction mechanism becomes more complex and extremely dependent on atmospheric conditions and firing cycles. For this reason reproduction often

Jan 1, 1958

By A. J. M. Ross

BACKFILLING of stopes and other underground openings in the Homestake mine with sand tailings was undertaken primarily to reduce surface subsidence, which was wrecking much of the surface plant and a substantial part of the town, and to make possible maintenance of openings into the top of pillar stopes as mining progressed. The progress of this type of filling has been rapid and the results very satisfactory. Sand is now used in filling timbered stopes, shrinkage stopes, and abandoned drifts and crosscuts. A permanent pipe-line system for transporting sand tailings into the mine by gravity has been installed. The close filling of all stopes has resulted in important benefits other than the two major ones. The ore bodies in the Homestake mine occur as replacements in one distinctive layer of the metamorphosed pre-Cambrian sediments along a group of minor folds that together form a complex anticline that pitches at 35º to 40º to the southeast. The ore bodies are extraordinary for their magnitude. Widths of over 300 ft. have been mined and continuous ore has been followed for over 1200 ft. along the strike on some of the upper levels. Mining has been by shrinkage stoping with square-set mining of crowns and pillars. In the standard plan, shrinkage stopes 60 ft. in the direction of strike and the full width of the ore have been taken up to within 25 ft. of the level above. After filling, the crown has been mined by square-set methods, as have also the 40-ft. pillars between shrinkage stopes. In former days, when the supply of ore seemed inexhaustible, the mining of pillars was allowed to lag far behind because of the high cost. Many pillars were rather badly fractured on the level and in some places between levels. Coarse waste was used for backfilling all stopes, but in pillars it became increasingly difficult to maintain haulageways for the transportation of this fill over the top of the stopes as mining progressed The cost of maintaining these crosscuts was excessive and in many pillars practically impossible. Therefore it became the practice to fill pillar stopes by tapping the back and sides of the stopes.

Jan 1, 1939

By Stephen E. Merritt, John W. Straton, T. Carl Shelton

Surveying and mapping are used to locate and visually portray objects, lines, or areas in relation to a reference point or line. The actual making of the measurements to locate the objects and points falls under surveying while mapping is concerned with putting the survey information into a graphical form. Generally, the type or class of proposed survey depends on the precision required. Some surveys may need only approximate measurements which can be obtained by simply pacing or by using an ordinary measuring tape; others may require much accuracy, thus calling for the use of an engineer's transit or theodolite along with a graduated steel tape for horizontal measurements, or a level and a graduated rod for measuring vertical distances. Mapping is likewise dependent on accuracy requirements. For example, a general layout showing the relative position of surface facilities may not call for a large scale of dimension or great precision whereas for detailed work, a large scale plus care in plotting points and drawing lines and curves are important factors. SURVEYING METHODS There are many kinds or types of surveying methods. Some examples include : land surveying for determining boundaries of land areas; route surveying for locating roads, highways, right-of-way, and haulways; city surveying for laying out lots, streets, and alleys; and mining surveying for projecting mine openings and locating mining operations. See Fig. 1. There are other types of surveying than those named, but in general, the type of method to be used will depend on the purpose for which the survey is to be made.

Jan 1, 1981

By Ralph Hultgren, Bernard York, David W. Mitchell

It is a well-known fact that magnesium-alloy castings are apt to be coarse grained if the melt is not superheated several hundred degrees above the melting point before casting. (The casting temperature varies according to the shape of the mold. A typical casting temperature is perhaps 1400°F.) British practice is to heat to 900°C. (1650°°F.) for 15 min., cool rapidly to casting temperature, and cast.1 In Germany superheating is carried out at 850° to 900°C. (1560° to 1650°F.) depending on the amount of scrap used. It is stated that further refinement will be obtained by prolonging the period of superheating or by increasing the superheat temperature to 950°C. (1740°F.).2 In the United States superheating is carried out at i600° to 1700°F. (871° to 927°C.), perhaps even higher in some places. It is stated that superheating effects are found as low as 1500°F. (816°C.), but several hours are required.3 These commercial treatments lead to grain sizes in sand castings that may vary from 4 to 8 grains per sq. mm.§ in heavy sections and from 60 to l00 in 3-in sections to perhaps 380 in thin sections. It is also generally known that the refining effect of superheating is lost if the melt is held for some time at lower temperatures before casting. Aside from these very qualitative statements, there is little to be found in the literature as to the effect of temperature and time of superheat on the final grain size. Because of the uncertainty of these factors, the Office of Production Research and Development of the War Production Board placed a research contract with the University of California, supervised by the War Metallurgy Committee. This research, which was done under the "Restricted" Project NRC-550, is the basis of this paper, which has been released for publication by the O.P.R.D. The material studied was an alloy prepared from carbothermic magnesium. The temperatures required for grain refinement proved to be widely different from those used in practice, as described in the statements in the first paragraph. This difference is attributed to the fact that the magnesium in the specimens was of carbothermic origin instead of the electrolytic magnesium in common use. MATERIALS AND METHODS The magnesium alloy studied was one of the most popular sand-casting alloys, with a nominal composition of 9 per cent aluminum, 2 per cent zinc, and 0.r per cent (minimum) manganese and the balance magnesium. This is designated

Jan 1, 1945

By F. Kurata, P. C. Davis, T. L. Gore

An experimental method and apparatus for the study of the low-temperature phase and volumetric behavior of volatile mixtures are described. The phase diagrams, including the critical points, and the volumetric behavior of a natural gas and a mixture of the natural gas with methane at temperatures from -40°F to -200°F and pressures to 1.200 11si are givrn. INTRODUCTION Knowledge of the phase and volumetric behavior of mixtures of the light hydrocarbons at low temperatures is becoming increasingly important as interest in low-temperature separation processes increases. Distillation at low-lemperatures has been used for some time to recover ethane and ethylene from natural gas and refinery gas for petrochemical uses. Removal of excess nitrogen from natural gas by distillation has been proposed as a means of increasing the capacity of gas transmission lines and of improving the marketability of the gas.1,2 Evaluation of the latter process has been hampered, however, by the scarcity of data from which the phase behavior of natural gases at low temperatures might be predicted. While existing correlations of vaporization equilibrium constants may be used to predict the behavior of such mixtures at lower pressures, high-pressure computations often require knowledge of the location of the critical point of the system involved. Although correlations have been developed for the prediction of the critical temperature and pressure of certain types of hydrocar-bon systems, they do not apply to very volatile systems such as nitrogen-bear-ing natural gases. This paper describes the initial stages of an investigation of the low-temperature behavior of a numher of natural gases and other gases of commercial interest. The experimental method and apparatus are described. and the phase and volumetric behavior of a natural gas and a mixture of the natural gas with methane are presented. PREVIOUS WORK The published low-temperature vapor-liquid equilibrium data for hydrocarbons and mixtures of hydrocarbons with nitrogen and helium are listed in Table I. Most of these data are for binary systems, and the data of Stutz-man and Brown" at 100 psi are the only data on a natural gas. The data of Bloomer and Parent3 on the methafie-nitrogen system, which have been phblished since this study was completed, are a valuable addition to the knowledge in this field. Prior to the publication of these data the only published critical point data on systems having critical temperatures below the ice point were those of Ruhemann.1 on the methane-

Jan 1, 1952

By R. A. L. Black

Rock mechanics is a very new science. It has been accepted as a recognized discipline for some two decades, but it is only within the last five to ten years that it has been common to include the teaching of rock mechanics as a separate subject in undergraduate curricula at universities. Thus, few senior mining engineers practicing in industry, either men in charge of production or those engaged in mine planning and design, are familiar with the subject. That this unfamiliarity has continued so long is also due in part to the fact that the results of rock mechanics investigations have been published in a large number of different periodicals covering subjects ranging from experimental stress analysis to obscure branches of applied earth sciences. The first really useful textbook ' in the English language was published only in 1965, in Canada. It made available to students and to practicing engineers, for the first time in concise form, the essential body of accepted knowledge about rock mechanics and developed the theories on which it is based in a simple, clear and logical manner. Another factor which has resulted in rock mechanics science being slow to be accepted by the mining industry is that research work has often appeared to be esoteric and unpractical. Senior engineers have been reluctant to spend money on the application of new knowledge when the process of application seemed uncertain and ill-defined, and where the cost of field investigations (which is necessarily high) appeared to offer no certainty of economic reward. This is a reasonable attitude on the part of mining engineers; they are responsible to skeptical boards of directors whose chief concern is, very properly, the net return on capital invested. The application of rock mechanics science has not in the past,

Jan 1, 1968

By T. N. McVay, E. E. Creitz

Rather large amounts of titanium minerals and some zircon and monazite are being recovered from dune sands about I. miles west of Jacksonville Beach, Fla. The Mining Branch of the Bureau of Mines, Southern Experiment station, has been interested in developing additional large deposits of similar sands in other areas of Florida. The results of a field study have been published1 concerning the sands occurring on Trail Ridge which runs north and south about 30 miles southwest of Jacksonville. This investigation was undertaken in order to identify the opaque titanium minerals occurring in Trail Ridge and because of the economic importance of Florida titanium minerals. Nature of the Problem The minerals present in the heavy fractions (sp gr > 2.94) of the sands are principally opaque minerals; staurolite, zircon, sillimanite, tourmaline, kyanite, rutile, a small amount of corundum, traces of the zinc spinel gahnite and garnet. Epidote, monazite, hornblende and ti-tanite are present in other dune sands but these minerals were not noted in the samples collected on Trail Ridge. All of the minerals except those which are opaque can be readily identified by the usual petrographic methods. However, Opaque minerals cannot be examined satisfactorily by transmitted light. Polished sections of the opaque-mineral grains were examined but these sections did not furnish useful information. Consequently, it was necessary to use means other than the usual petrographic methods to identify them. Previous Investigations of Heavy Minerals in Florida Sands Martens2 has described the heavy minerals in the Florida beach sands and has classified the opaque minerals as ilmenite with minor amounts of leucoxene. Miller3 studied a number of sands collected by Ross and Mertie in Florida. He states that the material from the Florida beach and dune sands that commonly has been called ilmenite has essentially the chemical composition of the material that has been called arizonite.4 The x ray diffraction patterns of several samples indicated that the supposed ilmenite is essentially amorphous, with only weak lines corresponding to ilmenite, and hence the material is unlike the type of arizonite from Arizona. Opaque Titanium Minerals Rutile is essentially titanium dioxide. However, as pointed out by Dana,5 important amounts of Fe+2 and Fe+3 as well as Cb and Ta are reported in some analyses.

Jan 1, 1949

By Pedro G. Salom

I HAVE had an opportonity, within the last few months, of making a large number of physical and chemical tests of steel for boiler and ship-plate, which has been, and is now being, used principally for the United States Government cruisers, now building in Mr. John Roach's yard, at Chester, Pa. Through the courtesy of the Messrs. Houston, of the Chester Rolling Mills, I have the honor to lay before the members of the Institate the results of these tests. These results have developed some points in regard to the nature of steel, which are more or less new, and which, I hope, will prove interesting. The original specifications, as regards the manner of testing, were so inipracticable (when their severity mas taken into consideration), that the keel of the first vessel, which will be launched next month, would, had they been carried out, probably not have been laid until next year. At my suggestion, in order to simplify and expedite the immense amount of testing that had to be done, the Naval Advisory Board was induced, after considerable discussion, to alter the specifications, so as to test each heat, instead of each lot of twenty plates, but reserved the right of making the quenching-test on a piece from each ingot, after it had been rolled. This relieved us from the anxiety of having a lot of plates rejected, after they had beell rolled and sheared, by reason of the presence of one or two plates which might have been injured in heating or rolling, or which might not have been able to stand the tests; while it insured the Government in obtaining a uniform quality of steel, and prevented the temptation to introduce a half-dozen or more had plates in a lot, and run the risk of their being selected as the testplates. I give below a portion of the original specifications, as prescribed

Jan 1, 1884

By Research Staff ? Verde Copper Mines

FLOTATION is now commonly practiced in alkaline ore pulps, yet little is known regarding the action of the alkaline solutions on the ore particles beyond the fact that films of oxidized material form. We wish to chronicle our discovery of the presence of soluble reducing agents in alkaline ore pulps of the United Verde, and present some data on lime consumption. During the grinding and flotation of a pyritic ore containing small amounts of ferrous sulfate and other soluble salts, an excess of lime was added to precipitate the salts, and filtered samples of the solution were titrated with standard permanganate solution. Even in pulps of high causticity an appreciable permanganate titration was always obtained, in spite of the fact that the solutions were shown to contain little iron. Investigation of the cause brought about the discovery of several previously unsuspected compounds in flotation pulps made from pyritic ore. Not only the reducing agents present had to be identified, but also the amount of dissolved oxygen, and a survey was finally made of the free oxygen content and reducing agents of the mill pulp in the concentrating mill at Clarkdale. A great many. compounds might form, caused by oxidation of pyrite or other metal sulfides or by reaction between a lime solution and pyrite. The most probable compounds considered were calcium sulfides, polysulfides, thiosulfates, and polythionates. Later it was discovered in the literature that in alkaline pulp polythionates do not exist and if introduced are decomposed into sulfites and thiosulfates.1 Any precipitated sulfur is changed by alkali into thiosulfate and polysulfide. Sulfites and sulfides react to form thiosulfate, so that in the end it is possible to have in an alkaline solution only thiosulfate and an excess either of sulfide or sulfite. Confirmatory tests were made and it was finally established that the alkaline mill pulps made from the United Verde ore contained

Jan 1, 1929

A general discussion on the subject of Crushing and Grinding was held on August 24, 1927, during the meeting of the Institute at Salt, Lake City. G. H. Clevenger, Chairman of the Milling Methods Committee of the Institute, made the following introductory remarks "Several years ago, a number of us felt that the time was ripe for a fundamental investigation of crushing and grinding. At the outset, it appeared that the first thing we needed was a yardstick whereby grinding efficiency could be measured. "The U. S. Bureau of Mines has been most generous in cooperating with the Milling Methods Committee in getting this work well undrr way. John Gross, who served the committee for a year as secretary, was placed in charge of the investigation and has been ably assisted by S. R. Zimmerley. "Messrs. Gross and Zimmerley will now present the Progrcss Report covering their work to date." Progress Report J. Gross, Salt Lake City, Utah.—-This has not been a simple problem, and when I tell you that me can give you a verbal report of what we have done during three years in five or ten minutes you will realize that we have necessarily done a great deal of work that dors riot appear in the final results. We have been in a virtually new field. Therefore, we have had to feel our way at each step so as to be fairly sure we were correet. The first thing that was realized in this problem ass that unless we had some method of measuring what happened when we crushed an ore, we might as well quit and not go further. we realized that if we tried to measure the results of crushing or grinding by the ordiuary sizing test we would not get anywhere. We could sieve down to say 200 mesh fairly accurately; we could even go one sieve size further with a little less accuracy, and then we were absolutely lost, unless we went into microscopic measurement. Even this latter method would not have been satisfactory. The question was: what were we going to measure? If we were going to measure size, we might measure one particular dimension of a particle and be off 200 per cent. or more. If we tried to measure surfaee, we would have something tangible; the surface of a particle, no matter how irregular, is something definite, far more definite than any linear dimension would be. Moreover, if we could measure surface, we would immediately have a method of checking the Rittinger law as to whether it was or was not correct. So the first thing that we sought. was a method whereby we could measure surface on crushed particles or, we will sag., on particles; it would not make any difference whether crushed or not. It then became a question of what kind of particles we were going to use in obtaining a method for surface measurement. We realizcd that it would be rather a corn-

Jan 1, 1928

By Paul T. Allsman

1.1-1. Current Status. The history of surface mining is essentially that of mining coal, copper, and iron ores, and the nonmetallic minerals--clays, gypsum, phosphate rock, sand, gravel, and stone. Table 1.1-1 is a comparison of the estimated world production of crude metallic and nonmetallic ores and coal with that of the United States for 1964, in short tons. It includes an estimate of the quantity produced by surface mining methods. Two-thirds of the 8.8 billion tons are mined from surface, ranging from a third of the coal, half the metallic ores, and nearly all clays, stone, sand, and gravel. In the United States, production by surface methods parallels that of the world with two major exceptions: 74% of copper ore and 90% of usable iron ore are mined from the surface, whereas outside the country less than 40% of copper ore and only 50% of usable iron ore are mined from the surface. In surface mining of both metallic ores and coal, much waste is stripped, but in mining nonmetallics the ratio between waste and ore is small. Assuming that the stripping ratio for surface mining in the United States will apply equally to world production, it is estimated on a weighted basis that over 21 billion tons of waste, or a total of nearly 27 billion short tons of material, are mined annually in the world by surface methods. Data are not available to confirm the assumption for waste stripping outside the U.S., but the estimate expresses an order of magnitude that is worth noting. Table 1.1-2 shows the materials-crude ore, coal, and waste-mined by surface methods and the relation to total mined by both surface and under- ground methods in the United States during 1964. Eighty-two percent of all crude metallic and nonmetallic ores and coal was mined from the sur- face, including 82% of metallic, 96% of nonmetallic ores, and 35% of coal. Copper and iron ore comprise 83% of the metallic ores mined from the surface, and clays, gypsum, phosphate rock, sand, gravel, and stone

Jan 1, 1968

By James M. Hodge

The Cumberland Gap extension of the Louisville and Nashville railroad, recently completed from Cumberland Gap to Norton, 71 miles, connects at the latter point with the Norfolk and Western, making a direct through line from Louisville to Norfolk. The whole of this connecting link skirts the southern boundary of the southwest Virginia coal region, but for the first 57 miles of its course it is separated from the coal by a mountain range (Cumberland mountain and its extension, Stone mountain), which bars entrance to the field from that direction, excepting at Pennington Gap, where access may he had to a small area only, which has not yet developed any very satisfactory coal. The railroad passes through the range at Big Stone Gap, and for the last 14 miles of its course to Norton is in direct contact with that part of the coal region known as the Big Stone Gap coal-field. By this road a western and southwestern outlet from the field is secured; the Clinch valley extension of the Norfolk and Western railroad gives exit eastward from Norton, and the South Atlantic and Ohio railroad, built through Big Stone Gap simultaneously with the L. & N. R. R., delivers the coal to points south and southeast. Besides these lines already built, an early connection with the East Tennessee, Virginia and Georgia railroad, via its Rogersville branch, is probable, and connections with the railroads of eastern Kentucky are projected. The Charleston, Cincinnati and Chicago railroad has already done some grading on one of the latter, but the rugged country intervening will prevent its construction till the demand for it becomes urgent. The coal-field embraces in Virginia about 120 square miles, to which should be added some 30 square miles in Kentucky, also tributary to Big Stone Gap, the whole of it underlaid by coal, probably of workable thickness, and much of it by two or more such beds. The determination of the boundaries of the field, however (except on the south, where Stone mountain forms a natural limit beyond which only a small, isolated tract of coal is found), is involved in much

Jan 1, 1893