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By J. M. Stuve

Calorimetric determinations of the low-temperature heat capacities, standard enthalpy of formation, and high-temperature enthalpies were made of (Na20)4 ?Fe20,(c). The resulting values of entropy (S°), enthalpy of formation (?Hf°), and free energy of formation (?Gf°) at 298.15° K are 104.676 cal/deg mole, -656.2 ±.kcal/mole, and -603.4 A kcal/mole, respectively. Tabulations of Cp°, S°, - (G°-H°298)/T, H°-H°298, ?Hf°, ?Gf°, and log Kf are given to 1,200° K.

Jan 1, 1971

By W. L. Cooley, K. Y. Lee, M. M. Hassan

Because power system topographies for surface coal mines are significantly different from those for underground coal mines, the requirements for ground wire monitors for surface systems are somewhat different. This paper analyzes the problems faced by high-voltage ground wire monitors. Based on this analysis, some design requirements for monitors are suggested. Finally, results from laboratory evaluation of some of the commercially available monitors are presented.

Jan 1, 1979

By Alla D. Mah

Relatively pure aluminum nitride (AIN) recently has been prepared in sufficiently large amounts to permit a variety of experimental studies.4/ Several mechanical and chemical properties have been investigated, which show that this substance has good potentialities as a container for liquid aluminum, gallium, and boric oxide. The present work by the Bureau of Mines was undertaken to obtain thermo-dynamic data pertinent to the calculations regarding thermal stability and reactivity of aluminum nitride. The following measurements were made: (1) determination of the heat of formation from the elements at 298.15° K.; (2) determinations of the heat capacity over the temperature range 51° to 298.15° K. and the evaluation of the entropy at 298.15° K. therefrom; and (3) determinations of the heat content over the temperature range 298.15° to 1,800° K. These data are combined to obtain free energies of formation from the elements between 298.15° and 2,000° K.

Jan 1, 1961

By Martin Hertzberg

The concept of limit burning velocities is being used to formulate a quantitative theory of flammability limits. Competing and complicating processes dissipate power from a combustion wave and quench propagation at some characteristically low limit velocity. Two earlier reports dealt with process (a), natural convection (RI 8127); and with process (b), conductive-convective wall losses (RI 8469). This report considers process (c), radiative losses, and process (d), selective diffusional demixing. The limit burning velocity for radiative losses is [(SU)c ~ e cp] It is normally not a significant process for premixed gas flames; however, for laminar flame propagation in a gravity-free environment, it is the only loss process present. Accordingly, limit velocities at zero gravity should be much lower than on earth, and premixed gases should be flammable over wider composition ranges. For highly emissive dusts, soot, or ash-forming flames, radiative losses are significant even under normal gravity conditions. Selective diffusional demixing is a complication that manifests itself in the form of cellular flame structures and wide gaps in composition between upward and downward propagation limits. It induces a burning velocity shift (?Su)d, causing the flame to behave as though it were richer or leaner than its initial composition, depending on whether the fuel or the oxidizer mole¬cule has the higher diffusivity. A simple pertubation analysis shows that the process generates stable cellular flames whenever [dsu] > 0, where ci is the concentration of the reactant with the higher diffusivity. The same analysis indicates that at the opposite stoichiometry, where [dcu] < 0, laminar structures are stabilized. A simple formula for the diameter of cellular flames is derived, which predicts that dcell should vary inversely with the product of the diffusivity difference Di -DJ, and the burning velocity slope [dc ]. Those predictions are in good agreement with the available data. Buoyancy forces for upward propagation induce flame front curvature, and hence buoyancy and selective diffusion are mutually supportive in upward propagation. Thus large gaps in composition between upward and downward limits are present in those composition domains where cellular flames are stable.

Jan 1, 1981

By Shirley F. Colby

A continued rise in construction activity in 1941 forecasts further increases in the demand for building materials of mineral origin, Recent studies by the Bureau of Mines, United States Department of the Interior, reveal that sales of mine and quarry products and their derivatives as a class have followed the long-term trend of construction activity in the past and are benefiting now by the upswing in all types of building. At present most building materials of mineral origin are holding their own in the competitive arena. A few are slipping behind, but others have forged fax ahead. Prominent among those that have surpassed general construction activity since 1925 are sand, gravel, and crushed stone (used in concrete and road metal and railroad ballast) and cement. Both building stone and roofing slate have followed the building curve closely, although in the last few years sales of roofing slate have risen above the curve and sales of building stone have dropped below it. Clay products and building lime, on the other hand, have lagged behind the general procession. Gypsum sales likewise dropped behind, but during the last few years, this industry, thanks to the wider acceptance of its newer products, has staged a marked recovery so that it now stands in about the same relation to total construction activity as it did is 1927-25.

Jan 1, 1941

By E. C. Strycula

Solid-state equipment offers a number of potential advantages in the coal mining industry. These advantages can only be realized, however, through careful and judicious design of the control and protection circuitry. Problems relating to the interaction of solid-state equipment on the electrical system and the special design considerations which apply to solid-state circuitry are examined. Design guidelines are provided for solid-state applications in the areas of: (a) equipment operated from a DC trolley wire, (b) drive systems for surface mining equipment, (c) AC motor starters, and (d) electromagnetic interference.

Jan 1, 1981

By D. Harrington

An explosive may be defined as a substance (usually a mixture) that has the property of yielding, readily to combustion or oxidation upon application of flame or shock, the combustion or oxidation process being rapid and accompanied by formation of such relatively large quantities of gases that much violence and pressure are produced; these, in turn, react against their surroundings and cause what is termed an explosion. By their very nature their action is destructive and disruptive of adjunct materials; hence, all explosives axe potentially hazardous and every type of explosive, irrespective of its relative safety, should be handled, .stored, and used with utmost care at all times and under all conditions. It should always be remembered that any explosive can be rude safe only in certain of its features and under certain conditions and circumstance. If these facts (and they certainly are facts) are always kept in mind, most of the modern types of explosives can be utilized advantageously in our industrial life and with a considerable degree of safety. That commercial explosives can be handled. safely is borne out in part by the fact that in the past 15 years at least 3,000,000,000 pounds of the commercial explosive dynamite have been transported by railroads in the United State, without injury to any person, insofar as available records indicate.

Jan 1, 1939

By L. C. IlsLey, E. J. Gleim, F. CRAVEN

Electrical apparatus and circuits began to be used in mines about 50 years ago. A search of the literature on mining reveals that in 1882, umping was being done by electricity in some aines of England. One account tells of a small electric locomotive being used in 1882 "to drive eight corves loaded with coal" in a mine near Dresden. In an account of his visit to some English mines, en American in 1892 mentions that he saw underground electric signals, lights, pumps, hoists, and one revolving- cutter-bar 19wall mining machine,. Among the carl electrical installa- tions in the United States was an electric locomotive in the Lykens Valley Coal Co. mine at Lykens Valley, Pa., in 1887. In 1889 the Sperry electric coal digger was being tried out. Tarce mining machines were placed in the Prospect mine, East Palestine, Ohio, in 1890. An electrical pumping plant was put in oneration during 1892 in the Woodward mine of the Delaware, Lacka- rahma & Western Railroad Co. Thus we Almost coincident with the proposed use of this new servant in under- ground workings, came the thought of making it safe in gassy mines. find an account of a design for a protected stationary electric mine lamp proposed by Edison in 1831. Enclosed-type motors rere developed in the United States and shiped to English collieries about 1903. From those early beginnings there has been continuous progress until to-day one finds hundreds of pieces of specially designed electrical apparatus distributed in American coal mines and in mines of nearly all important coal-producing countries. Along with introduction of this equipment grew the idea of the necessi- ty of government aid, in standardization. In most coal-mining countries to- day the governments either directly or indirectly have a considerable in- fluence in guiding the design of electrical equipment intended for use in Pasay mine

Jan 1, 1933

Mining officials, as well as members of the Bureau of Mines staff, in their efforts to make mining safer are confronted from time to time pith complicated problems concerning solution of which there is a diversity of opinion. To reduce these differences of opinion as much as possible and to obtain a generally acceptable decision on any mine-safety question, the Director of the U.S. Bureau of Mines established the Mine Safety Board on June 1, 1924- *** to consider questions arising within any divisions of the Bureau that require a definition of tie Bureaus s collective opinion as to safety practices, safety devices, or safety methods for underground operations or open-pit mining. The approved2/decisions shall form the basis of teaching and policy for the Bureau.

Jan 1, 1935

By W. J. McConnell, C. P. Yaglaglou

"IntroductionThis paper on the kata thermometer is issued by the Bureau of Mines on account of the general interest in this instrument and the fact that it is frequently used in studies of mine ventilation conditions with regard to comfort and health of miners. It has been used in the studies being conducted along this line by the Bureau of Mines on the effects of high temperatures and humidities of air in mine working on the comfort conditions, as well as in studies of atmospheric conditions in mine, railway and vehicular tunnels.The study of the various physiological responses of the human body to different degrees of temperature combined with different percentages of relative humility in still and in moving air, now being conducted at the Pittsburgh experiment station of the bureau in the research laboratory of the American Society of Heating and Ventilating Engineers, cooperating with the Bureau of and the U. S. Public Health Service, presents an added opportunity of investigating the instruments that have been devised to measure atmospheric conditions as they affect the comfort and health of human beings.The ordinary mercury thermometer, as pointed out by Heberden3 almost hundred years ago is a very inadequate instrument for measuring the physiological effects of atmospheric conditions. It merely accounts for that part of the body heat lost by raliation and convection, while as a matter of fact greater part of the body heat resulting from the metabolic process within the body is eliminated by means of evaporation from the surface of the body."

Jan 1, 1924

By W. J. Boone, Will E. DeVaney, Lowell Stroud

This report is the fifth in a series presenting equilibrium vapor - liquid data for helium- bearing natural gases . It covers a 0.41 - mole - percent - helium natural gas that may be processed in the Department of the Interior's longrange helium conservation program . A Bureau of Mines phase equilibrium apparatus was used to obtain 139 samples of equilibrium vapor and liquid phases at 85 experimental conditions at temperatures from 0 ° to -299 ° F and at pressures from 100 to 500 psia . An appendix covers phase data at 100 , 200 , and 300 psia and at temperatures from -125 ° to -275 ° F for the dehydrated gas containing its original concentration ( 0.2 mole - percent ) of carbon dioxide , and the effect of a preliminary hydrocarbon trap upon subsequent vapor - liquid compositions .

Jan 1, 1964

By B. W. Jong

As part of the Bureau of Mines program to develop substitutes for critical and strategic materials for metallurgical applications, the Tuscaloosa Research Center has evaluated the effect of additives and starting materials on the sintering and strength properties of sialon (silicon-aluminum-oxynitride) compositions fabricated by conventional pressing and sintering techniques. Sintering and MOR (modulus of rupture) data were developed for sialon compositions produced from three components, Si3N4, A1203, and AIN. When doped with Y203 to aid in sintering, the highest MOR values were obtained with compositions containing between 20 and 30 mole-pet (A1203 + AIN). The effect of the crystalline phase of the Si3N4 and Al203 used in the three-component system on MOR also was investigated. Alpha-Si3N4 and ?-A1203 were found to be the best starting materials. A sialon composed of 67.4 mole-pct a-Si3N4 plus 32.6 mole-pct (?-AI203 + AIN), doped with 5 wt pct Y203, had MOR values at 25°, 1,200°, and 1,400° C of 40,300, 40,300, and 31,100 psi, respectively. Samples of this composition doped with Gd203, MgO, Zr02, and ZrSi04 also were evaluated. The ZrSi04-doped sialon had higher MOR values than Gd203-, MgO-, and Zr02-doped materials but lower MOR values than the Y203-doped sialon. The MOR values of ZrSi04-doped sialons were 25,000 and 25,900 psi, respectively, at 25° and 1,400° C.

Jan 1, 1981

By J. B. Janus

In connection with the purchase of coal under specifications for Government use, the Bureau of Mines in this report has compiled data on 81 mines located in 15 States. This annual report lists analytical data on the composition and quality of tipple and delivered samples of coal collected during fiscal year 1973. Tipple samples were collected by Bureau of Mines engineers at tipples as coal was being loaded into railroad cars or trucks. Ultimate analyses are given for most of the coalbeds listed. The deliveries were sampled at destination in accordance with instructions issued by the Bureau of Mines. All samples were analyzed in the Bureau laboratory at Pittsburgh.

Jan 1, 1973

By David Schlain

This Bureau of Mines report describes a method for electrodepositing titanium diboride from a molten salt bath. Initially, the electrolyte is a mixture of LiBO2, NaB02, Na2 Ti03 , Li2Ti03, and Ti02? The cell is operated at 900° C in a dry, inert atmosphere with consumable anodes of titanium or hot-pressed titanium diboride (TiB2) powder. Agitation of the electrolyte is essential. Current densities may be 6 to 9 amperes per square decimeter (amp/dm2) with titanium anodes and 9 to 30 amp/dm2 with titanium diboride anodes. A current density of 6 amp/dm2 is equivalent to a plating rate of about 35 micrometers per hour. The adherence of the TiB2 deposit varies with the substrate material. It is most adherent on molybdenum and on 4130 steel that has been preplated with copper and nickel, less adherent on nickel, and still less adherent on Inconel and on 4130 steel without the preplate. Cathode and anode reactions are suggested.

Jan 1, 1976

By H. A. Doerner

For the past three or four years attention has been attracted to the deposits of lead vanadate in the Goodsprings , Nevada , district . Some ore running as high as 9 per cent 205 has been produced , but most of it runs from 0.5 to 3 per cent . Only a little ore , and that of the richer sort , has been shipped , since the low- grade ore will not stend the cost of shipment and no concentration mill has been available . Preliminary experiments indicate that chemical treatment of the low- grade ore without concentration is not feasible . Its treatment therefore involves two distinct problems ; first , mechanical concentration ; and second , a smelting or chemical treatment to obtain the lead and vanadium in marketable form . Upon this basis the work has been conducted . The writer wishes to acknowledge the excellent work done by J. T. Norton and Virgil Miller on table concentration and by J. E. Conley , who suggested and did preliminary work on the direct smelting method . Many helpful suggestions were received from Dr. S. C. Lind and John Gross of the Bureau of Mines . The ores were furnished by Mr. Frank Williams and Mr. James Ewing .

Jan 1, 1923

By N. H. Coates

The Bureau of Mines determined average film coefficients of heat transfer for helium flowing through smooth, water-cooled tubes at Reynolds numbers of 5,000 to 25,000, helium inlet temperatures of 1,600° to 2,600° F, average temperature difference across the helium film of 800° to 1,300° F, and heat flux to 215,000 Btu/(hr)(sq ft). Since helium was the only gas used, the ranges of values for physical properties of the fluid are limited--thermal conductivity from 0.15 to 0.20 Btu/(hr)(sq ft)(O F/ft), viscosity from 0.082 to 0.104 lb/(ft)(hr), and Prandtl number from 0.63 to 0.68. Four equations, three of them dimensionless, correlate these coefficients with other properties of the helium--bulk temperature, film temperature, dimensionless parameters based on temperature, and the ratio of wall temperature to bulk temperature.

Jan 1, 1966

Develop hydrometallurgical or pyrometallurgical recycling methods to recover valuable rare-earth compounds from various forms of NdFeB magnet scrap. Background The U.S. Bureau of Mines (USBM) has developed technology to treat and recycle a variety of wastes containing valuable and strategic metals. As part of this effort, the USBM developed a process to separate neodymium and other valuable rare earths from iron in NdFeB magnet scrap (fig. 1). Since this scrap typically contains nearly 30 weight percent neodymium and since the demand for neodymium is constantly increasing, cost-effective methods for scrap treatment could have a significant impact on industrial expenditure and materials supply in the expanding area of magnet manufacture. Approach A hydromctallurgical, H2SO4 dissolution-precipitation process provided the most effective treatment for separating rare earths from bulk NdFcB magnet scrap (fig. 2). Precipitation of neodymium-alkali sulfate double salt proved advantageous over direct precipitation of fluoride or oxalate products. This double salt is easily converted to a variety of useful rare-earth compounds, which eliminates many of the materials-handling and economic problems inherent with direct precipitation. Following rare-earth precipitation, dissolved iron was removed from the acid leach solution by precipitation as a jarosite.

Jan 1, 1993

By H. D. Baylor

This paper, describing the operations of the Louisville Cement Co. in quarrying limestone for the manufacture of quicklime, is one of a series being prepared for and published by the United States Bureau of Mines on stone quarries throughout the United States. Those papers are designed to disseminate technical information regarding the methods used. The cost tabulations represent operating only and not total costs. It is recognized that publication of total costs might in many instances cause embarrassment to individual operators as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations shall ensue. ACKNOWLEDGMENTS The author acknowledges the assistance of J. H. Lemmon, plant superintendent, Charles Taylor, plant engineer, and F. H. Compton, chief engineer, of the Louisville Cement Co. in the compilation and preparation of this paper.

Jan 1, 1932

By William D. Monaghan

The U.S. Bureau of Mines evaluated a teleoperated continuous mining machine for deep mining in thin-seam applications as low as 1 m. Teleoperation increases the safety of mining machine operators because it removes the operator from the face, an area of immediate hazards to safer outby locations. By using teleoperation, the miner can avoid many including unexpected roof falls that can maim or kill miners instantly, methane and coal dust explosions that can be ignited with just a small spark or flame, adverse health effects from miners breathing coal and silica dust, adverse long-term inner ear damage from loud noise pollution, and other hazards related to heavy mining equipment moving about in confined underground roadways. This report presents the surface evaluation results of a teleoperated control system.

Jan 1, 1994

By GLADYS G. HEFFNER, William H. Waggaman, Edwin A. Gee

Thallium is one of the rare and relatively neglected elements that has recently assumed conspicuous importance. This element is widely distributed in nature but occurs in such minute quantities in most rocks and minerals that its recovery at present is only commercially feasible as a byproduct of other industries. World War II, with its unprecedented demand for products having special or unusual properties, led to a study of a number of the rarer elements that previously had been given comparatively little attention for one or more of the following reasons: 1. 2. Limited knowledge of properties. Small quantitios present in available raw materials. 3. High cost of concentration and recovery. Some of those rare elements, either alone or in the form of compounds, have already proved of such value for certain military and industrial purposes that their extraction from ores and waste products, oven at high cost, is fully justified. On the othor hand, further investigation of their character- istics, discovery of more adequato sources, and improvement in methods of con- centration and recovery would greatly broaden their field of usefulness and establish new and expanded industries. The current market for some of these elements exceeds the available supply. One of the functions of the Bureau of Mines is to study the properties of such elements in greater detail, locate the most promising raw materials from which they can be derived, and work out methods of extraction that will render the recovery of such elements more economical. The purpose of a serios of information circulars on the raror elements is to present in condensed form the facts and data so far available. This information may serve as a basis in planning more complete investigations loading to a full utilization of such elements.

Mar 1, 1950