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Etching solutions containing hexavalent chromium ions (e.g., chromic acid) are used in brass finishing, printed circuit board etching, preparation of plastic for plating, anodizing, and various other industrial surface treatment operations. As the solutions are used, hexavalent chromium ions are reduced to their trivalent state, contaminants accumulate in the solution, and the effective acid concentration is reduced. When the etching rate becomes unsatisfactory for the particular operation, the solutions are discarded. This is a problem because the discarded solutions are pollutants, and because replacing the etching solution is expensive. The Bureau of Mines has developed a process for regenerating these spent solutions and returning them to the surface treatment operation without interrupting the etching process. An electrolysis cell containing anode and cathode compartments that are separated by permeable membranes, is used for regenerating the spent solutions. The spent chromic acid solution is fed to the anode compartment and sui (uric acid is circulated in the cathode compartment. Application of a steady electrical potential of a few volts dc across the electrodes causes the copper ions and other contaminants in the spent solution to migrate through the membrane to the cathode compartment where copper is plated onto the cathode. Zinc and the other contaminants remain in the sulfuric acid. At the same time, the complex, trivalent chromium ions in the spent solution are attracted to the anode where they are oxidized to their original hexavalent state. The regenerated solution in the anode compartment is then recycled back to the plant?s etching operation for reuse.

Jan 1, 1980

By Robert T. Beckman

The results of a preliminary investigation of compressive strength versus length-diameter (L/D) ratios of potash specimens and the statistical treatment of the data are summarized in this report. The purpose of the study was to evaluate a laboratory method for obtaining estimates of the strength of potash pillars during robbing operations. The specific objectives of this preliminary investigation were to test the method and the reliability (confidence limits) of the data, and to determine the number of additional specimens necessary for given confidence limits. The specimens were taken from three sites at two mines in New Mexico. The statistical analyses included the determination of the confidence limits for the data and the number of additional specimens necessary to obtain confidence limits of ±500 and 100 psi. The testing method was found acceptable, and estimates of the comprehensive strength, within 1500 psi, could be obtained by testing about 110 additional specimens from the three sites. The compressive strength of the specimens tested fits an empirical equation of the type

Dec 1, 1963

By J. M. Singer

Flame propagation of lower limit hybrid coal dust-methane-air mixtures in vertical and horizontal flame ducts of 15.2 cm id and 1.8 m length has been investigated to provide information bearing on safety in mines. Fuel concentrations at lower limits of flame propagation and equivalences of coal dust and methane are much higher for continuing flame propagation than for short-span flame propagation in the vicinity of an "overdriving" ignition source. As the energy of the ignition source was increased, the flame speed and the distance of flame propagation from the ignition source increased, whereas the total fuel concentration at the lower limit decreased.

Jan 1, 1968

By Will H. Coghill, G. Dale Cole

"INTRODUCTION This paper describes a method for the rational sorting of particles by means of a laboratory batch jig. Its purpose is to show that a material can be reliably appraised for gravity concentration without the drudgery of sink-float fractionations.Development of the batch- jig method of testing was incidental to a study of the Birmingham, Ala., red-iron ores now being conducted by the Bureau of Mines in cooperation with the University of Alabama and the ore-producing companies.APPLICATIONOres and coal are commonly tested for their gravity-concentration characteristics by specific-gravity dissections in heavy liquids. The heavy liquid most commonly used for coal is zinc chloride and for ores they are benzene, carbon tetrachloride, acetylene tetrabromide, methylene iodide, and thallium malonate formate. The last is poisonous and corrosive to the skin but is essential for separations in the 3.3 to 4.4 specific gravity range. The last two of these liquids are expensive, and several of them are hard to obtain now.Although it is not suggested that heavy-liquid dissections be eliminated entirely, sometimes a more reliable evaluation of coal and ore can be obtained by other and more simple means. For example, sink-float data were unsatisfactory as a guide to commercial gravity concentration of a red-iron ore because they did not take into account the difference in particle shape of the hematite and gangue and the differences in true and apparent specific gravity of the hematite grains, some of which were porous. For this ore, the batch-jig method of testing herein discussed proved advantageous. Not Only did the batch-jig data give a truer picture of the concentration problem, but only about one-tenth the time of the conventional sink-float tests was required."

Jul 1, 1944

By F. R. McDonald

The compound ?-valerolactone has been identified in an acid fraction isolated from waste water collected from an in situ oil-shale retort. Infrared, nuclear magnetic resonance, and mass spectrometry were used by the Bureau of Mines to confirm the identification of a subfraction collected from a gas chromatograph.

Jan 1, 1974

Develop a simple and economical technique for determining the absolute stresses and the change of stress on the surface of roofs, floors, or walls in miners. Approach Use a commercially-available, permissible, Whittemore-type gage to determine the stress at the surface of a mine opening and to monitor any stress changes that might take place. How It Works The following equipment is used: ? One steel templet (for laying out a 60° rosette on the: rock surface). See first photograph. ? One 3/8-inch rock drill bit for drilling holes for the rosette pins. ? Six stainless-steel rosette pins. ? One Whittemore-type mechanical strain gage. ? One drill (not shown). ? Epoxy for cementing the rosette pins. ? Tape to hold the pins while the epoxy sets. The following procedure is used to determine the absolute stress on the rock surface. 1) Spot the location of the rosette pins with the templet. 2) Drill the pin holes and set the pins with epoxy cement. 3) Measure and record the distance between the pins across three diameters of the rosette with a 10-inch Whittemore-type gage. See diagram. 4) Drill a 1 1/2-inch diameter hole in the center of the

Jan 1, 1981

One of the major unknowns in the use of iron and copper is the quantity of various low level impurities, particularly hydrogen, that may be introduced during the deoxidizing process prior to casting. Introduction of hydrogen results in the embrittlement of components made from these metals. In addition, hydrogen bubbles in castings of copper result in the formation of blisters and swelling of the casting. During the last year, a significant effort has been made at the University of Missouri-Rolla to understand the permeation of hydrogen in galvanized automotive steel components and the hydrogen absorption during the electrodeposition of copper. The galvanized steel components consisted of automotive upholstery clips, seat belt holders and brake clips. Although the process of galvanization protects the steel from corrosion the process invariably causes the steel to pick up enough hydrogen to make it susceptible to brittle fracture.

Jan 1, 1992

By Steven J. Schatzel, Joseph Cervik, Gerald L. Finfinger

Gas drainage through surface bore¬holes has been the conventional means of methane control for U.S. longwall gobs. However, these vertical boreholes are becoming so costly, and the surface rights so difficult to obtain, that the Bureau of Mines is developing underground gob gas drainage as an alternate means of methane control for U.S. longwal..ls. Holes are drilled into the roof over the panel and on retreating longwalls, towards the working face from a location inby the face. As the longwall retreats, an increasing portion of the hole inter¬cepts the fracture system over the caved gob. A surface exhauster maintains a vacuum on a pipeline parelleling the panel and draws the methane mixture out of the mine. Auxiliary systems of gob gas drain¬age during longwall mining will be essen¬tial for an increasing number of coal mines. Deep and gassy mines often find ventilation insufficient for adequate dilution of methane in bleeder entries. Although this cross-measure method of degasification has been used successfully in Europe, some of the European tech¬niques cannot be directly applied to U.S. mines. This is the first study of its kind in this country.

Jan 1, 1982

By H. J. Heinen

The Bureau of Mines, investigated a cyanidation-carbon adsorption technique for extracting gold from arsenopyrite concentrates. Agitation leach experiments were conducted on 85-pct-minus-35-mesh gravity concentrates containing 21.8 oz gold and 6.4 oz silver per ton. Results obtained in leaching the concentrates showed that 96.9 pct gold and 90.7 pct silver extraction could be achieved in 96 hours of agitation. Gold and silver were recovered from the resulting pregnant solution by exposure to granular activated carbon in a countercurrent system. Carbon loadings of 2,556 oz of gold and 502 oz of silver per ton were achieved. These loadings are significantly higher than heretofore thought practical.

Jan 1, 1980

By N. N. Moebs

The atmosphere in part of an air-sealed coal mine was monitored continuously through a drill hole for oxygen content to determine the effectiveness of sealing a mine against the entrance of air and the major force that caused the phenomenon of mine breathing through the overburden. The differential pressure across the seal and the barometric pressure on the outside also were recorded. A general correlation, obtained between the oxygen level, differential pressure, and barometric pressure, indicates that changes in air pressure are the cause for periodic replenishment of the oxygen in the mine. Mine effluent quality was determined by conditions in many sections of the mine and could not be related to the oxygen level at the drill hole.

Jan 1, 1972

By Harold L. Rhodes

The Bureau of Mines has developed a quantitative method to determine water vapor in helium in the range of 0.1 to 15 ppm by volume. This method uses the quantitative chemical reaction of H20 with CaH2, which produces 1 mole of hydrogen for each mole of H20 in the sample. A gas chromatograph is then used to determine the concentration of hydrogen in the product. The precision of the H20 analysis is ±0.05 ppm at a concentration of 1 ppm. This method is used to calibrate a commercial platinum-phosphorus pentoxide (Pt-P205) electrolytic water vapor analyzer that has an improved inlet system and digital voltmeter readout.

Jan 1, 1981

By R. R. Sayers

There is probably no industry , trade , or art in which mercury is used but what has produced some cases of mercury poisoning . This is true of the mining and smelting of mercury , where the hazard has long been recognized . When the ore contains free mercury or the more soluble salts , and when the workings are underground and are poorly ventilated , cases occur , but there are a far greater number of cases among the employees about the reduction works . 3 In 1863 William V. Wells visited the mines at Almaden , * Spain , which were worked by convicts . He reported that the men at the furnaces suffered severely , being able to work only about one week out of four , when it was necessary to transfer them to places where the exposure was less . He states that "pale cadaverous faces and leaden eyes are consequences of even these short periods . " Mercury , like lead , when absorbed in small amounts at intervals , as daily, over an extended period of time will result in symptoms of poisoning . This is due to the fact that the mercury is eliminated from the body more slowly than it is absorbed . The frequency and severity of cases of mercury poisoning are far less with modern methods of mining and recovery of the metal than formerly . However , further reduction is possible and much can be done by both the workmen and the operators by following the proper precautionary measures , some of which are described in this chapter .

May 1, 1922

By T. OnIin, F. F. ApIan

"A study has been made of the surface properties of coals of differing ranks, in their natural state and as modified by the addition of collectors. The evaluation of their surface properties has been done by captive bubble contact angles, water and methylene iodide sessile drop contact angles, zeta potential, point-of-zero charge (PZC) shift, and flotation. .changes in the hydrophobicity of coal is a function of both the rank of the coal and the collecting reagent.INTRODUCTIONThe chemical and physical properties of a raw coal will determine its response to a given beneficiation process. .For such processes as flotation, filtration, flocculation, dispersion, handling, dust supression and agglomeration, however, it is also necessary to consider the surface properties of the coal and mineral matter constitutents of the raw coal. In the case of a specific particle to be floated, it is also necessary to consider the properties of the coal as modified by the addition of some reagent designed to modify (usually increase) the hydrophobicity of the coal surface. General properties of the coal have been well summarized by Van Krevelen (1) and Elliott (2), while the data for the surface properties of coal are much more scattered in the literature (see, e.g.: Parekh and Aplan (3), Gutierrez-Rodrigues et al. (4), Aplan (5), Arnold and Aplan (6), Hogg and Chander (7) and Rosenbaum and Fuerstenau (8)). While a knowledge of the inherent surface properties of a sample are important, of much greater practical significance are the properties of the particle in the presence of a reagent, such as a collector, designed to enhance the hydrophobicity of the particle. This study will focus on the surface properties of coals of various ranks in the presence of a variety of collectors."

Jan 1, 1989

By G. R. Palmer

Using a fluidized, countercurrent multiple-compartment ion-exchange (MCIX) column previously developed by the Bureau of Mines, Bureau researchers have successfully extracted uranium from a simulated acidic in situ leach liquor that contained 150 ppm U30s? This successful demonstration of the MCIX system is reported, and the effects of varying the operating conditions on the performance of the system are also examined. Operating the MCIX system with a flow rate of 15 gpm/ft2 and an aqueous-to-resin flow ratio of 200:1, more than 90 percent of the uranium Has extracted, and a resin containing approximately 28 grams U308 per liter was produced. The absorption column used to investigate the operating variables was approximately 18 feet long with a 2-inch ID and was divided into compartments that were 1 foot long.

Jan 1, 1980

By J. B. Stephenson

The Bureau of Mines, under an interagency agreement with the Department of Energy (DOE), investigated the feasibility of hardfacing the critical surfaces of valves and similar devices by chemical vapor deposition. The purpose of this research was to increase the wear resistance of these components for use in the abrasive and erosive environment of coal gasification units. Tungsten and molybdenum coatings were produced on nickel-plated carbon steels and stain-less steels by hydrogen reduction of the metal hexafluoride at 325° to 600° C. Titanium nitride coatings were produced on low-carbon steels by the reaction of titanium tetrachloride, hydrogen, and nitrogen at 1,000° C. Titanium carbonitride coatings were produced on low-carbon steels by the reaction of nitrogen, hydrogen, and methane at 900° C. Tungsten, molybdenum and titanium nitride coatings were formed on 6-, 10-, and l2-inch (0.15-, 0.25-, and 0.30-meter) ball valve seats for evaluation in the low-Btu coal gasification pilot plant at the Morgantown Energy Research Center, Morgantown, W. Va.

Jan 1, 1979

By R. P. Beyer

[The Bureau of Mines has measured the low-temperature heat capacities and high-temperature enthalpies of crystalline K2Si2O5 as part of a program for advancing mineral resources technology with energy economy. High-temperature enthalpies of glassy and liquid K2Si2O5 and crystalline K2SiO3 were also mea¬sured. An adiabatic calorimeter operating over the range 5 to 308 K was used for the heat capacity measurements for K2Si2O5 from which the standard entropy at 298.15 K, S°298 = 45.55 ±0.05 cal/deg-mole, was calculated. Tabulated values of Cp°, S°, -(G° -HO°)/T, and H°-HO° from 5 to 300 K are given for K2Si2O5. A copper-block drop calorimeter was used in the enthalpy measurements, operating from 298.15 to 1,198 K for K2SiO3 and from 298.15 to 1,453.8 K for K2Si2O5. No transitions were found for K2SiO3. The KI2Si2O5 showed two reversible first order transitions, one at 510 K with a heat of transition of 0.29 kcal/mole and one at 867 K with a heat of transition of 0.38 kcal/mole. The heat of fusion for K2Si2O5 20 5 was calculated to be 8.42 kcal/mole. Relative enthalpies are given in equation form, and high-temperature values are tabulated for Cp°, S°, - (G°-H°298 )/T, and H°-H°298 . Also tabulated are ?H°, ?G°, and log K for formation of K2SiO3 and K2Si2O5 from both the elements and the oxides.]

Jan 1, 1979

By Jürgen F. Brune, R. Karl Zipf, Michael J. Sapko

Seals are barriers constructed in underground coal mines throughout the United States to isolate abandoned mining panels or groups of panels from the active workings. Historically, mining regulations required seals to withstand a 140-kPa (20-psig) explosion pressure. However, the Mine Improvement and New Emergency Response Act (“MINER Act”) requires the Mine Safety and Health Administration (MSHA) to increase this design standard by the end of 2007. This report provides a sound scientific and engineering justification to recommend a three-tiered explosion pressure design criterion for new seals in coal mines in response to the MINER Act. Much of the information contained in this report also applies to existing seals. Engineers from the National Institute for Occupational Safety and Health (NIOSH) examined seal design criteria and practices used in the United States, Europe, and Australia and then classified seals into their various applications. Next, the engineers considered various kinds of explosive atmospheres that can accumulate within sealed areas and used thermodynamic calculations and simple gas explosion models to estimate worst-case explosion pressures that could impact seals. Three design pressure-time curves were developed for the dynamic structural analysis of new seals under the conditions in which those seals may be used: unmonitored seals where there is a possibility of methane-air detonation or high-pressure nonreactive shock waves and their reflections behind the seal; unmonitored seals with little likelihood of detonation or high-pressure nonreactive shock waves and their reflections; and monitored seals where the amount of potentially explosive methane-air is strictly limited and controlled. Figure 1 is a simple flowchart that illustrates the key decisions in choosing between the monitored or unmonitored seal design approaches and the three design pressure-time curves. For the first condition, an unmonitored seal with an explosion run-up length of more than 50 m (165 ft), the possibility of detonation or high-pressure nonreactive shock waves and their reflections exists. The recommended design pressure-time curve rises to 4.4 MPa (640 psig) and then falls to the 800-kPa (120-psig) constant volume (CV) explosion overpressure. For unmonitored seals with an explosion run-up length of less than 50 m (165 ft), the possibility of detonation or high-pressure nonreactive shock waves and their reflections is less likely. A less severe design pressure-time curve that simply rises to the 800-kPa (120-psig) CV explosion overpressure may be employed. For monitored seals, engineers can use a 345-kPa (50-psig) design pressure-time curve if monitoring can ensure that (1) the maximum length of explosive mix behind a seal does not exceed 5 m (16 ft) and (2) the volume of explosive mix does not exceed 40% of the total sealed volume. Use of this 345-kPa (50-psig) design pressure-time curve requires monitoring and active management of the sealed area atmosphere. These design pressure-time curves apply to new seal design and construction.

Jan 7, 2007

By Ronald T. Mayerle

There are no producing or developing mines in the Rattlesnake RARE II area. Specific areas with mineral occurences are prospects for: 1) stratabound copper and silver in Belt sedimentary rocks on the northwest border of the study area; 2) base metal sulfides, in thin veins and shear zones in Belt sedimentary rock, and diabase dikes and adjacent metasedimentary rocks in the southern part of the study area; 3) barite in sedimentary rocks near Rattlesnake Creek and Sheep Mountain; 4) limestone near Rattlesnake Creek and Blue Point; and 5) silica in quartz veins near the headwaters of Rattlesnake Creek and Sanders Lake. Stone, sand and gravel suitable for construction material are in the study area; however, equal or better quality deposits are common throughout the region. The RARE II area has no known oil and gas, coal, or geothermal energy deposits.

Jan 1, 1983

By Causey J. Douglas

In 1988, at the request of the Bureau of land Management, the U.S. Bureau of Mines studied part of the 13,460-acre Owyhee Breaks Wilderness Study Area (OR-003-059) in order to evaluate its identified mineral resources. The study area is in Malheur County, OR, about 27 miles northwest of Jordan Valley. No mineral resources were identified in the study area during this investigation. There is an occurrence of jasper along Birch Creek and an associated occurrence of zeolite in some tuffs. In the northern part of the study area is an occurrence of bentonitic clay containing less than 40,000 tons. Much of the area is covered by landslide blocks, colluvium, earthflow deposits, and talus, composed of Tertiary-age volcanic rocks. The upper plateaus are capped by Tertiary-age basalt.

Jan 1, 1989

By Laxman S. Sundae

In the vast majority of American coal mines, roof bolt holes are drilled dry, mainly because of mine operator concern with the spent water creating adverse working conditions. Wet drilling, however, can increase drilling rates and the effective lifetime of the drill bits used. This study, carried out as part of an ongoing cooperative research program between the U.S. Bureau of Mines and the University of Missouri-Rolla, shows that the large volumes of water conventionally used in wet drilling are not necessary, and the performance benefits from wet drilling can be achieved with total volume flows on the order of 0.4 L per hole. This conclusion is validated based on the measured respirable dust generated in drilling Berea sandstone. The results are confirmed using a variety of bit shapes, which are also shown to have a significant effect on penetration rate.

Jan 1, 2010