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By E. G. King

Many of the rare-earth oxides are now commercially available in pure form and they have a variety of potential technical uses. Thermodynamic data for these oxides, however, are rather sparse. It is one of the functions of the Bureau of Mines to fill the need for this type of information. This report gives the results of low-temperature heat-capacity and high-temperature heat-content measurements by the Bureau of Mines of lanthanum sesquioxide. The entropy at 298.15° K. was evaluated and heat-content and entropy increments above 298.15° K. were obtained to 1,800° K. The results were combined with the known heat of formation at 298.15° K. to derive heats and free energies of formation at higher temperatures. Sufficient information is now available to permit reliable thermodynamic calculations involving lanthanum sesquioxide within the temperature range 298° to 2,000° K.

Jan 1, 1961

By Mah Alla D.

Previously existing heat-of-formation values for the oxides of vanadium were rudimentary. They were subject to uncertainties of 1 to 5 kilocalories per gram-atom of contained oxygen. This fact has been the only adverse influence on the accuracy of thermodynamic calculations involving these substances, as the requisite entropy and high-temperature heat-content data are known with reasonable accuracy. This report presents new heat-of-formation data for four oxides of vanadium (VO, V203, V02, and V205), obtained by combustion calorimetry. It is believed that the uncertainties have been reduced to 0.1 to 0.3 kilocalorie per gram-atom of contained oxygen. The new heat-of-formation data were combined with existing entropy and high-temperature heat-content values to obtain free energies of formation of the four oxides at temperatures up to 2,000° K.

Jan 1, 1961

By V. T. Dow

In April 1957 the Bureau of Mines instituted a reconnaissance of titanium-and zirconium-bearing heavy sandstone deposits in the Four-State area of Utah, Wyoming, New Mexico, and Colorado. This report summarizes the study. Eighty-two deposits or groups of deposits, containing an estimated 27,920,000 tons of titaniferous sandstone, were examined in the Four-State area; 16 in southern Utah, 19 in Wyoming, 33 in New Mexico, and 14 in southwestern Colorado. The 16 deposits examined in Utah contain an estimated 1,043,000 tons with an average grade of 17.98 percent TiO2, 5.67 percent ZrO2, 20.98 percent Fe, and 0.09 percent equivalent Th02. The 19 deposits investigated in Wyoming are estimated to contain 21,873,000 tons of titaniferous sandstone having a weighted grade of 5.22 percent 702, 0.55 percent ZrO2, 24.8 percent Fe, and 0.01 percent equivalent Th02.

Jan 1, 1961

By S. L. May

Procedures for separating columbium and tantalum have been developed by the Bureau of Mines as part of a broad research program on the utilization of low-grade ores of columbium and tantalum, Columbium and tantalum compounds of greater than 99 percent purity have been obtained by application of the solvent extraction separation system: Hydrofluoric acid-sulfuric acid-methyl iso-butyl ketone. This system is unique in that it not only separates columbium from tantalum, but also separates these two metals from other metallic impurities. The system is effective for separating the metals irrespective of the tantalum and columbium ratio of the starting materials. Investigations in which the spent feed obtained from the initial coextraction step was recycled to the system indicated that efficiency was increased, and cost was reduced without impairing product purity. Continuous tests demonstrated that this solvent extraction system could be used in large-scale equipment without loss in efficiency or in purity of products. The separation of columbium and tantalum has been difficult because of the similarity in their chemical bahavior. Many methods have been proposed for separating these two elements, but most methods either did not achieve satisfactory separation or were tedious and time consuming. The Marignac process (3, 4)4 developed in 1866 was the only method used commercially until recently. This separation procedure is based on the difference in solubility in aqueous solution of potassium tantalum fluoride and potassium columbium oxyfluoride. Current commercial practice appears to favor solvent extraction as a method for separating tantalum from columbium (1). Several efficient methods for separating columbium from tantalum by solvent extraction (2, 9, 8) were reported earlier from this laboratory.

Jan 1, 1961

By R. M. Becker

As part of the Bureau of Mines program for examining the Nation's iron and titanium resources, magnetic, gravity, and geologic surveys were made to permit an estimate of the extent and magnitude of the Iron Mountain, Colorado, titaniferous magnetite deposit. Gabbro is the dominant rock type of the area. Within the gabbro are lenses of titaniferous magnetite, 5 to 25 feet wide and as much as several hundred feet long. These lenses comprise a zone which has scattered occurrences of magnetite for 2,200 feet. To the west, the gabbro grades into a strip of pyroxenite that in turn borders a large monzonite mass. A wedgelike broadening of the pyroxenite with depth accompanied by little or no increase in the titaniferous magnetite is considered a reasonable interpretation of the field data. The iron deposits appear to be limited and discontinuous.

Jan 1, 1961

By A. N. Fried

With the growing importance of fluid injection in recent years, the petroleum industry has been investigating and field- testing a variety of new methods designed to modify the physical properties of reservoir oil to improve the efficiency of gas and water injection. These procedures include condensing-gas drive, LPG (liquefied petroleum gas) injection, alcohol-slug process, high-pressure-gas displacement, detergent-solution flooding, and in situ combustion (30, 37).3 A new and different method to increase the effectiveness of gas and water injection has been tested by the Bureau of Mines, Consideration of both fundamental and practical factors that operate to limit the oil recovery attain- able by conventional oil-displacement mechanisms led to the concept of a displacement mechanism called the foam-drive method. This report describes the experimental study that tested this concept in the laboratory.

Jan 1, 1961

By E. Morrice

This report of the Federal Bureau of Mines presents a laboratory procedure, with the requisite equipment, for electrowinning ingot (liquid) cerium metal from a fused-fluoride bath, the metal purity being about 99.9 percent. Physicochemical studies, including bath properties and electrochemistry, are included, with a speculative model of the mechanisms involved. An historical review of the methods used for electrowinning misch metals and yttrim-group metals, as well as individual rare-earth metals, is presented. The electrolytic preparation of metal from fused salt and nonaqueous media is summarized, along with the unsuccessful attempts at depositing the metals from aqueous solutions.

Jan 1, 1961

By K. C. Dean

The combination of flotation and chemical processing methods presented in this report of the Bureau of Mines enabled treatment of typical low-grade ferberite ores from the Boulder County, Colo. area, to produce specification-grade synthetic scheelite. The overall recovery from ore to synthetic scheelite was 87 percent, based on a flotation recovery of 93 percent and a similar recovery in chemical processing. Preliminary mineral dressing studies revealed that the physical and mineralogical nature of typical ferberite ores precluded high recovery of tungsten in plus 60-percent-W03-grade products by these methods. Therefore, the flotation research was focused on attaining plus 90-percent recovery in a concentrate containing 10 percent W03. Detailed studies were made (1) to establish optimum grinding conditions for obtaining adequate mineral liberation, (2) to develop collecting and modifying reagent combinations that would enable controllable selective flotation, and (3) to define the influence of different pulp solids, temperature, pH, and time for conditioning and for the rougher and cleaner flotation stages.

Jan 1, 1961

By J. H. Field

Synthesis of hydrocarbons by the Fischer-Tropsch reaction in a hot-gas- recycle system was demonstrated to be technically feasible. This project was undertaken, by the Bureau of Mines, to determine if the system was operable and to ascertain the optimum conditions for the production of gasoline. Carbon steel turnings packed with a void volume from 88 to 90 pct. were satisfactory catalysts, but steel catalysts with greater void volume, either turnings or steel wool, were not as active. Good temperature control with a pressure drop of less than 0.5 pounds per square inch (p.s,i,) per foot of catalyst bed of turnings was obtained by operating with a recycle to fresh feed ratio of 20 and by splitting the total gas flaw and injecting portions into the reactor at different entry ports.

Jan 1, 1961

By R. J. Leary

Iron and steel scrap has accounted for 45 to 50 percent of the metallics used by the steel industry. In an electric furnace which utilizes a 100-percent cold charge consisting of about 99 percent scrap and 1 percent pig iron, sensible heat from molten pig iron is not present as it is when hot metal is charged to open hearths and converters. A study of means for more efficient utilization of iron and steel scrap in steelmaking indicated that the time and fuel requirements to melt scrap were important cost factors, particularly in arc-furnace steelmaking. A process to preheat scrap economically prior to charging into the arc furnace has been developed, utilizing efficiently the heat from combustion of fossil fuels as a substitute for electric-arc heating in the initial stage of arc-furnace steelmaking. Scrap is loaded into a portable vertical cylindrical furnace body that is open at the top and has a perforated dropout door at the bottom. In the heating operation, the furnace body containing scrap is placed upon a hollow base connected to a flue, and then the burner and combustion-chamber unit is lowered on top of the furnace body. The stream of hot-combustion products flows down through the bed of scrap imparting heat to it, and the cooled gases exhaust through the flue. After the heating operation the furnace body containing hot scrap is transported to the arc furnace for charging. Thus, the furnace body serves as a charging bucket for top-charged arc furnaces, enabling this preheating process to be integrated into existing material-handling patterns in many arc-furnace plants.

Jan 1, 1961

By J. M. Kuchta

Concentrated hydrogen peroxide (H202) is a highly reactive oxidizing agent that liberates heat when it decomposes. The heat liberated may be sufficient to ignite combustibles with which the peroxide comes in contact. For this reason, concentrated hydrogen peroxide should be handled only by personnel familiar with its many unique properties.6 Hydrogen peroxide is used as a bleaching agent in the manufacture of textiles; this is its major single use in the United States. It is also employed as a reagent in chemical synthesis, as a source of free radicals to start polymerization, as a foaming agent in the manufacture of porous substances, and for its effect on biological processes. Moreover, highly concentrated hydrogen peroxide is a compact source of energy that can be utilized both as a monopropellant and as the oxidizer in a bipropellant system, During World War II, large quantities of highly concentrated hydro- gen peroxide were used as propellants, particularly in Germany. Since then, production of the peroxide has increased rapidly; in the United States alone it has more than doubled since 1950.7 Because of its widespread use, increasing interest has been shown in the hazards of handling the high- strength peroxide.

Jan 1, 1961

By Bernard Porter

The solubility of UO2 was determined at 1,250° C. in ternary melts of UF4 and BaF2 with CaF2, LiF, and SrF2. The solubility of Ce02 was measured at 800° and 850° C. in a solution of CeF3, BaF2, and LiF. The amount of La203 which dissolves at 950° C. in a binary mixture of LiF and LaF3 and a ternary of LiF, LaF3, and BaF2 was also measured. In each case, the amount of soluble oxide was mound to be less than 5 weight-percent. A procedure was developed for filtering fused, oxide-saturated fluoride melts in order to obtain a representative sample for chemical analysis. The oxide content of the samples was determined by an inert-gas fusion procedure.

Jan 1, 1961

By R. E. Lindstrom

Separation efficiency of a 4 percent divinylbenzene (DVB) resin is not altered over a wide range in temperature. A 12 percent DVB resin, however, exhibits a marked sensitivity to temperature. When flow rates are high at ordinary temperatures, 4 percent DVB resin exhibits higher efficiency, but at 200° F. both resins are equal in performance. Effective separation of rare-earth mixtures may be obtained with hydrogen as a retaining ion by maintaining column temperatures above the solubility of ethylenediaminetetraacetic acid (EDTA) in the free acid form. Slightly lower separation characteristics were obtained with this method as compared with copper as a retaining ion, Recovery of 99 percent of the EDTA from spent eluting solutions that contain copper has been accomplished by a calcium-copper displacement reaction followed by EDTA precipitation. Impurities in the product are correspondingly low. Recoveries of EDTA from holmium solutions with sulfuric acid are substantial; however, those from yttrium solutions are quite modest. Radiotracer experiments show the presence of approximately 0.1 percent yttrium contamina¬tion in the recovered material. The study presented is one phase of a broad research program designed to assist the technology of separating and purifying rare-earth elements.

Jan 1, 1961

By T. T. Campbell

This report traces the development of techniques for the preparation of high-purity rare-earth metals. Rare-earth metals, excepting samarium, europium, and ytterbium, were prepared by converting their oxides to anhydrous chlorides or fluorides and reducing the rare-earth halides with active metals such as lithium or calcium. High-purity, anhydrous rare-earth chlorides were prepared by dissolving the rare-earth oxides in hydrochloric acid to form hydrated chlorides and by subsequently dehydrating the hydrated salts in the presence of ammonium chloride at temperatures ranging from 70° to 360° C. while under reduced pressure (50 microns to 1 inch Hg). The chlorides were also prepared by direct chlorination of rare-earth oxide-carbon mixtures. Reaction efficiencies in excess of 95 percent were obtained by either method; however, purer chlorides were prepared by the aqueous ammonium chloride conversion method. Purification of yttrium chloride by high-temperature vacuum distillation proved to be an effective method of separating, oxygen-bearing compounds from the chloride. Yttrium metal prepared from purified chloride contained significantly smaller amounts of oxygen (990 p.p.m. oxygen in yttrium metal prepared from raw chloride and 200 p.p.m. in that prepared from distilled chloride).

Jan 1, 1961

By K. E. Tame

A resume of the history and state of the art of physical beneficiation of uranium ores is presented along with a detailed description of research on concentration of uranium ores by attrition grinding. The information on flotation, gravity concentration, electronic sorting, and selective grinding was gathered to complement the study of attrition grinding methods. Both dry and wet grinding procedures were investigated as potential methods of upgrading a variety of ore types, ranging in grade from 0.02 to 0.42 percent U308. A Mardun4 disintegrator that employs high-speed rotating paddles in a cylindrical shell lined with interrupter bars was used in most of the dry grinding studies. Attrition scrubbing devices, which impart a violent mixing or attritioning action to ore pulps, and cylindrical mills, employing rods or punchings as grinding media, were used in the wet grinding tests.

Jan 1, 1961

By J. T. McCartney

Thin sections of coal have been prepared for many years either by cutting on a microtome (1,2)5 or by grinding and polishing (2,1). Specimens of most coals had to be demineralized in hydrofluoric acid and softened in caustic solutions before they could be successfully cut with a conventional microtome. Some lignites could be cut without pretreatment. Jeffrey (1) obtained sections from coals of all ranks, although long and tedious pretreatment was required for anthracite. His sections were less than 1 cm.2 in area (probably much less for high rank coals) and about 5 microns thick. Thiessen (2) also cut sections of softened coals, mostly of low rank. His sections were a few square millimeters in area and about 3 microns thick. However, Thiessen preferred ground and polished sections for detailed studies because they were larger and had not been chemically attacked by softening media. He prepared ground sections as large as 4 cm.2 in area and usually 5 to 10 microns thick. Thousands of such sections, covering complete column samples of many coal beds, were studied for a number of years (4). With the development of the electron microscope and increased interest in quantitative optical studies of coals, a need for much thinner sections arose. However, no suitable technique for preparing such sections was known until Fernández-Morán developed a diamond knife for cutting ultrathin sections of hard materials (5). Workers at the Centre d'Etudes et Recherches de Charbonnages de France applied this new tool to the cutting of coal sections and have recently described their technique to the Burg, of Mines. Using their methods, with some modifications, researchers of the Bureau of Mines have succeeded in cutting ultrathin sections of coals ranging in rank from lignite to

Jan 1, 1961

By Harry R. Nicholls

A simple economical method has been developed for determining the in situ longitudinal and shear velocities in rock from which its elastic constants can be calculated. By detonating small charges of high explosives in shallow drill holes near a free surface, both longitudinal and shear waves were generated simultaneously. Accelerometers and velocity gages mounted to the rock surface were used to record the arrival time for both waves over travel path lengths from 50 to 450 feet, Measurements were made in two rock types. From the arrival time measurements, the longitudinal and shear wave velocities were calculated. From these velocities and the density of the rock, the elastic constants were calculated. The dynamic elastic constants of drill core samples of the two rock types were determined in the laboratory by the resonant-frequency method, The lab- oratory and in situ elastic constants are compared and significant differences noted. In general, there is less spread in the in situ data than in the laboratory data, and Poisson's ratio does not fall outside the theoretical limits for the in situ data as is often the case for laboratory-determined elastic constants.

Jan 1, 1961

By T. N. McVay

The Bureau of Mines has developed a field test for detecting the presence of columbium in a variety of minerals containing the clement. The test consists of fusing the mineral or rock powder with potassium pyrosulfate in a porcelain crucible, digesting the melt with hot dilute hydrochloric acid to release the columbium oxide (Cb205), and subsequently reducing the columbium oxide to a lower oxide by adding tin, which gives a blue color to the contents of the crucible. The method will detect 1 percent of contained columbium oxide (Cb205) in a mineral sample provided no tungsten is present. If a mineral containing appreciable titanium is test,-!d in the same manner, the solution in the crucible becomes violet. In the presence of columbium, titanium at first causes a violet coloration of the solution, which after a few minutes is masked by the stronger blue of the reduced columbium oxide. Although tantalum oxide (Ta205) does not interfere with the columbium test, tungsten gives a blue color that is indistinguishable from the color obtained with columbium. A simple method is available to detect the presence of columbium in the absence of tungsten, but when the presence of tungsten is suspected, the sample must be subjected to somewhat more elaborate chemical tests to determine the presence or absence of columbium. Although these latter tests can be made in the field, several steps are involved that arc best performed in the laboratory with simple equipment.

Jan 1, 1962

By R. Barany

This report contains the results of experimental work conducted by the Bureau of Mines to obtain the heats of formation at 298.15° K. of analcite, dehydrated analcite, lawsonite, anorthite, hexagonal anorthite, and leonhardite. Thermodynamic data for these minerals have applications in ceramics, extractive metallurgy, and particularly in geochemistry. Except for data on anorthite, no previous similar data existed. The present results will be a substantial aid in deriving the temperature-pressure-equilibrium relationships among these minerals. The heats of formation were determined by solution calorimetry, with hydrofluoric acid as the reaction medium. The results were expressed both in terms of the constituent oxides and in terms of the constituent elements. The heat of formation data were combined with related entropy values to obtain the free energies of formation at 298.15° K.

Jan 1, 1962

By K. K. Kelley

Thermodynamics data for silicates have applications in the fields of extractive metallurgy, ceramics, and geochemistry. To facilitate these applications, up-to-date tables of heats and free energies of formation are needed. It is the purpose of this report to supply such tables for anhydrous silicates. During the last 15 years the heats of formation of a substantial number of anhydrous silicates have been reliably determined at or near room temperature. This resulted from the development (first by the Bureau of Mines and later by the Geophysical Laboratory of the Carnegie Institution of Washington, by the Institute of Geology of the University of Helsinki, Finland, and by the Department of Geology of the University of Chicago) of accurate solution calorimeters, employing hydrofluoric acid as the reaction medium. Specific references to work of these laboratories will be made in the next section of this report. Also, entropy data at 298.150 K. and high-temperature heat-content values are available for many of these silicates, mainly owing to work of the Bureau of Mines. Most of these entropy and heat-content data have been compiled in Bureau of Mines Bulletins (13, 15).3

Jan 1, 1962