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By A. L. Engel

This report is a compilation of results of preliminary tests on scheelite (tungsten) ores and tailings. These investigations were made to assist in establishing satisfactory treatment methods for small-scale concentrator operations, or to indicate a. method for conserving previously lost mineral values in old tailings, if possible. A discussion of test procedures is included, as it was felt that this would add to understanding the results reported under the several projects. The treatment of scheelite ores has become more or less standardized. Important differences occur in textures of ores from various mining districts. However, and this must be considered when planning ore-dressing operations. In most of the present investigations, only a limited amount of work was done, usually just enough to answer a specific question in regard to a particular ore or concerning local conditions. Two methods of treatment included gravity concentration, magnetic separation, and flotation.

Jan 1, 1952

The paper outlines the philosophies and the methods applied to resource estimation by North Flinders Mines Limited at The Granites. These are based on recognition of the prime importance of quality data, accurate geological perception of the deposit, and the judgement of the estimator. With reference to one particular deposit, East Bullakitchie, the series of resources statements published over a 5 year period is compared with the corresponding history of discovery and development. The comparison Illustrates:

Jan 1, 1990

By Eugene H. Skinner

The 7-mile Flathead Tunnel, located in the central Salish Mountains of northwestern Montana, was constructed between 1966 and 1969, With the contract awarded April 19, 1966, drill and blast tunnel excavation began September 30, 1966, and was completed June 21, 1968, in 488 tunnel-driving days, Peak advance was 66 feet per day. On June 27, 1969, all tunnel concrete lining was completed. Average wall and arch concrete placing rates exceeded 1,700 cubic yards daily, with nearly half of the concrete placed during a severe winter season. Major cost savings in concrete tunnel lining were achieved through a value engineering clause in the contract. Achieving consistent results and high rates of placement in concrete lining ranked equal to ground control in overall tunnel problems. Ground control problems exceeded expectations and were of continual concern throughout excavation, One support collapse in the tunnel and one portal slide condition developed during construction. Critical surface geologic exposures were largely obscured; only a portion could be accurately projected underground, An instrumentation program to gather basic data on rock defamation near the heading face for support purposes was a pioneering effort. The Flathead Tunnel was placed in service on November 7, 1970.

Jan 1, 1974

By R. A. Friedel

THE IMPORTANCE of infrared and ultraviolet-visible spectrometry in studies of the structure of coal and similar substances is described. Special experimental techniques have been developed for these studies. Thin sections of coal are preferred, but halide pellets are easier to prepare. Information obtained from infrared spectra on chemical functional groups has been discussed; the importance of both intensities and wavelengths of absorption bands has been emphasized. Functional groups assigned include aliphatic and aromatic CH, methylene and methyl groups, hydrogen-bonded hydroxyls, hydrogen-bonded and chelated carbonyls, phenolic structures, minerals, and aromatic structures that are benzenoid or polynuclear. Infrared studies of structures of coal extracts, distillates, and reaction products of various processes, both chemical and physical, are discussed. Coallike infrared spectra of chars of model compounds have been utilized extensively in studies of coal structure. Ultraviolet-visible absorption spectra of coals show a lack of fine structure and low spectral intensities. These results have been applied to the questions of the chemical and physical structure of coal, particularly the question of polynuclear aromaticity of coals. The color of coal is also treated. The physical-chemical origin of the color of coal may be due to free radicals, as interesting correlations of ultraviolet-visible spectra with electron paramagnetic resonance have been obtained. The optical color of coal has been explained and simulation of the color changes observed in thin sections has been carried out, The spectra and structure of coal derivatives and other carbonaceous materials are also discussed. Possible sources of error in absorption spectral measurements are pointed out. Limited measurements of the ultraviolet-visible reflectance spectra of coal are described.

Jan 1, 1967

By Brenton Fletcher, Yongjun Peng, Wonder Chimonyo

As a cheap, renewable and non-toxic material, starch can contribute to the sustainability of the flotation process, albeit in a minor way as one type of reagent in systems involving materials with far greater impact. But the physical and chemical versatility of starch can help address another issue, namely, that of processing complex ores with decreasing grades of valuable minerals and increasing mixtures of gangue. This paper compares the results of two lab scale flotation studies where starches (native wheat starch (NWS), dextrin and two oxidised wheat starches) were used to depress two common gangue minerals, copper-activated pyrite and carbon (graphite), over a range of dosages. The oxidised starch with the larger molecular weight structures depressed copper-activated pyrite best, and the oxidised starch with lower molecular weight structures was better at depressing graphite. In both cases, the oxidised starches allowed greater recovery of chalcopyrite, pointing to selectivity potential. The extent to which the carbonyl and carboxyl moieties of the oxidised starches contribute to depressant performance is difficult to quantify, but it should not be discounted. Importantly, the results demonstrate relatively simple modifications of native starch by oxidation can yield structures suitable for depressing gangue minerals with diverse surface properties. The challenge remaining for greater application of modified starch depressants is being able to replicate the desired structures at scale in cold-water-soluble form.

Jan 18, 2021

By M E. Barley, A D. George, M Kneeshaw

Detailed pit and outcrop mapping of sedimentary rocks and their alteration is providing insights into fluvial processes that operated during deposition of the world-class Yandi channel iron deposit. Five prominent rock units are traceable along the strike of the Yandi deposit and permit correlation of open pits and mesas. These units are the Eastern Clay Horizon (ECH), granule-pebble conglomerate (GPC), Main Ore Zone (MOZ), Basal Denatured Zone (BDZ), and Basal Conglomerate (BCONG). The upper part of the deposit is characterised by a transition from spheroidal grains with well-defined rims and nuclei to larger, subangular grains with poorly developed rims. The distribution of rock types and sedimentary features such as lateral accretion surfaces, channel scours and fills, graded bedding, cross-bedding, reworked horizons, and slumped strata are common at Yandi and indicate deposition in a fluvial system. Bedding is well preserved despite modification of original grain shapes and textures and introduction of secondary silica and alumina in the upper part of the deposit. The high lithic and clay content of the GPC and ECH possibly reflect changes in source area or a hiatus in deposition of the Marillana Pisolite. The MOZ and the BDZ may be the same depositional unit with the latter recording alteration by groundwater and destruction of primary textures and other sedimentary features. The BCONG is a channel lag deposit reworked during deposition of the MOZ. This interpretation is supported by the dominance of basement-derived lithic clasts, the presence of BCONG clasts, the variable thickness of the unit along strike and the presence of BCONG clasts in the BDZ.

Jan 1, 2002

By J. W. Thompson

ESTATE IN MINERALS. Minerals beneath the surface may be made the subject of separate ownership either by a grant of the minerals by the owner of the land or by a grant of the land excepting the minerals, and thereby an estate in fee simple is created in the minerals, as corporeal things real. Colby, In re, Iowa, 169 Northwestern 443, p. 444. DEEDS EXCHANGING DIFFERENT MINERALS-RIGHTS OF PARTIES. The lands of two adjoining owners were underlaid with cement rock and clay at a depth of about 100 feet from the surface and with coal veins some 600 feet below the surface. By an exchange of deeds one of the land owners conveyed to the other the cement rock and clay with the right to mine and remove the same without entering upon the surface, but the deed contained no covenant not to injure the surface. The other deed conveyed the coal seam and so much of the rock and other minerals just above and below the coal as might be required in connection with the mining and removing of the coal, together with the right to mine and remove the same, and the adja- cent rock, clay, and other minerals, without entering upon or injuring the surface, with one immaterial exception. The deeds do not define the word "surface" and neither expressly nor by implication did they secure to the coal owner the right to subside the overlying cement rock; but the implication is to the contrary, as the deed gives the right to mine and remove coal without entering upon or injuring the surface. The provision that the coal owner should not enter upon or injure the surface amounts to a clause that the coal mine. shall not be worked so as to let down the surface and this does not create any inconsistency with the provision giving the right to mine and carry away the coal.

Jan 1, 1919

By F. M. Goodwin, John Campbell, G. W. Jones

"INTRODUCTION In cooperation with the Boston Edison Co. and the Boston Consolidated Gas Co. of Boston, Mass., a survey has been conducted continuously since 1929 by the Bureau of Mines to determine the general hazards of combustible gases and vapors in manholes of the Boston Edison Co. The New England Telephone & Telegraph Co. also has cooperated in the investigation, and tests have been made in its manholes from May 1, 1933, to October 15, 1937. Yearly reports. 6/ on the results obtained since the beginning of the survey have been published.The methods and procedure of conducting the survey in 1937 were the same as heretofore."

Jan 1, 1939

By A. Landsberg

Kaolinitic clays are potentially a vast domestic resource for aluminum. Utilization of this resource could decrease or eliminate the nearly complete dependence of the United States on foreign raw materials for this important metal. Furthermore, processing of clay to aluminum through anhydrous chloride metallurgy could reduce the high electrical energy requirements of the conventional Hall-Heroult aluminum reduction process. Several anhydrous chloride processes have been proposed; however, unresolved technical problems have prevented their commercialization. In particular, an acceptable chemical means has not been found to extract aluminum from clay as a highly pure anhydrous aluminum chloride. This Bureau of Mines report identifies and discusses the important chemical problems involved in achieving an acceptably rapid, self-heating, selective chlorination reaction and the subsequent separation of iron chloride byproduct from the anhydrous aluminum chloride.

Jan 1, 1983

By G. S. Scott

Safety problems in the mining and allied industries have led the Bureau of Mines to investigate over a period of years; the flammability (explosibility) of many types of combustible atmospheres principally at ordinary pressure; the results of these investigations have been made available as a bulletin. However, more recently, the demand for information on the flammability of gaseous mixtures at high and low pressures has increased greatly. In particular, the rapid development of high-altitude aviation has brought demands for information on the flammable (or explosive) characteristics of certain gases and liquids at low pressures. The present report gives the results of about 900 tests made to determine the flammability of the lighter paraffin hydrocarbons mixed with air and nitrogen at pressures of 400 200, 100 and 70 ram. Hg. The gases tested include natural gas, methane, ethane, propane normal butane and isobutane. The minimum pressures at which these gases are capable of propagating flame whorl individually mixed with air also were investigated.

Jan 1, 1952

By Soumendra Basu, Uday Pal, Yang Yu, Srikanth Gopalan, Karl Ludwig, Deniz Cetin, Jacob Davis

"A limiting factor for Solid Oxide Fuel Cell (SOFC) performance is the oxygen reduction reaction (ORR) at the cathode surface. Changes in the surface composition and structure on annealing at 800°C has been studied, since these can influence the ORR. Idealized single crystals of cathode materials La0.8Sr0.2MnO3 (LSM) and La1-xSrxCoyFe1-yO3 (LSCF) were grown as heteroepitaxial thin films on lattice matched single crystal substrates. Changes upon heating the films to operating temperature and pressures were characterized using various synchrotron x-ray techniques. Total Reflection X-ray Fluorescence (TXRF) measurements, which probe compositional changes, were made at high temperature in real time. The LSM surfaces were found to develop manganese enrichment when heated. Highly strontium doped LSCF were found to develop strontium-rich surfaces. HArd X-ray PhotoElectron Spectroscopy (HAXPES) was used to investigate the electronic structure of the materials. Highly strontium doped LSCF precipitates a surface strontium phase that contains both oxide and carbonate contributions.IntroductionSolid oxide fuel cells (SOFCs) are chemical to electrical energy conversion devices that could potentially reshape how energy demands are fulfilled. SOFCs have a potential efficiency over 70%, fuel flexibility, low emissions, and low degradation over long time scales. Commonly, SOFCs are operated at high temperatures (above 800°C). At these temperatures expensive housing is needed to contain an operating stack as well as coatings to contain the oxidation of the metallic interconnects. Lowering the temperature of an operating device would allow for more conventional materials to be used, thus lowering overall cost. Understanding the reaction kinetics of the oxygen reduction reaction at the surface of the cathode is vital to designing a system that will perform well at lower temperatures. A commercialization goal is to reduce operating temperatures without sacrificing performance.In order to exploit the advantages of SOFCs, an understanding is needed of the surface chemical states of cations on the surface of the cathode and how this relates to the oxygen reduction reaction (ORR):"

Jan 1, 2014

By Alisson Paulo de Oliveira, Altair Lucio de Souza, Jacson Morais Borges, Cleiton Arlindo Martins

A customized version of the Microsim-PM software for one Steckel rolling mill was built and adapted for specific mill parameters. The focus of this study is to use this model, which predicts the austenite grain size distribution evolution during rolling, to understand and quantify metallurgical issues happening during hot rolling. This will allow the steel mill to optimize the rolling process and chemical composition before the first industrial trial. Materials rolled for final thicknesses of 4.75, 6.30 and 12.5 mm of a carbon manganese steel and a microalloyed steel were selected to tailor the equations used by the model and to accurately reproduce the reality of the Steckel mill. This paper analyses the results from the customized model and compares them to mill data and final microstructure. Measured and predicted Mean Flow Stress (MFS) values are compared. After rolling, the material is subjected to accelerated cooling using laminar cooling. These cooling curves obtained from mill data are also considered to analyze the final microstructure characterized for all the cases using EBSD. The quantification of the microstructure allows for a better understanding of the relationship between chemical composition, process parameters and mechanical properties.

Oct 1, 2019

By F. M. Jenkins

Longwall mining systems are used to mine approximately 50 pet of the world's total underground coal production. Single entries are the predominant method of longwall development in Europe and Asia, where mining conditions are more severe than those encountered in the United States. During the 1970's and early 1980's, the U.S. Bureau of Mines and the U.S. mining industry invested nearly $20 million in single-entry and related research. This report reviews the accomplishments of single-entry research in the United States and describes two U.S. single-entry field projects: the Sunnyside single-entry project in central Utah and the tunnel-boring project in northern West Virginia. Also discussed are a single-entry study conducted by North American Mining Consultants (NAMCO) and a single-entry design study conducted by Ketron, Inc. This Bureau report compares the resulting technology with European counterparts to further assess the utility and efficiency of U.S. systems.

Jan 1, 1990

By Winston A. Wong, John J. Jonas

Commercial purity aluminum was deformed by extrusion over the temperature range 320° to 616°C and the strain rate range 0.1 to 10 per sec. Flow stresses and strain rates were calculated from the experimenLa1 ram pressures and speeds. The stress-strain rate-lemperature relationship in extrusion was found to be similar to that in creep. Extrusion, torsion, compression, and creep data extending over ten orders of magnitude of strain rate and over two orders of magnitude of stress were correlated by a single creep equation. It was concluded that hot-working is a thermally activated process, in which the rate-controlling mechanism is either the climb of edge dislocations or [he motion of jogged screw dislocations. The microstructural changes observed during extrusion were consistent with the proposed deformation mechanisms. ALTHOUGH great progress has been made in understanding the technology of extrusion, very little is known about the actual deformation mechanisms operating during flow. Previous accounts describing extrusion have indicated that the relationship between ram speed (V), pressure (P), and temperature (T) can be given as follows:1 V = apb and P = A' exp(-AT). In these equations, a and b are constants which depend on temperature, A' is a constant which depends on ram speed, and A is a "coefficient" with a different value for each metal. Although these equations have fairly wide application, they do not contribute much to a fundamental understanding of the deformation. Furthermore, extrusion has not hitherto been considered as a thermally activated rate process. This lacuna is surprising because hot-working is similar to high-temperature creep in several respects. There is, in fact, a fair body of experimental evidence suggesting that the material response under hot-working conditions is similar to that occurring under creep conditions, in spite of the many orders of magnitude difference in strain rate.2"4 Since creep has been extensively analyzed in terms of dislocation mechanisms, the comparison of hot-working to creep is useful, for it can suggest the possible deformation mechanisms operating during hot-working. In this paper, the hot extrusion of aluminum will be examined from the point of view of thermally activated deformation mechanisms, such as operate during creep. EXPERIMENTAL PROCEDURE The experimental procedure consisted of extruding commercial purity aluminum* over a range of ram velocities and temperatures at constant die reduction by the direct method. Details of the experimental equipment have been published elsewhere.5 Extrusion was carried out at each of the following billet temperatures: 320°, 376°, 445°, 490°, 555°, and 616°C at the following constant ram speeds: 0.002, 0.008, 0.02, 0.1, and 0.2 in. per sec.* All results were obtained using a square-shouldered die with an extrusion ratio of 40:1, giving a reduction in area of 97.5 pct. The ram force was the dependent variable, and was measured by means of strain gages on the ram and was plotted as a function of ram travel. The sequence of events before making an extrusion was duplicated before each run so as to minimize as much as possible variations in experimental conditions. For example, after the equipment had been assembled, the billet was allowed to heat up to temperature inside the insulated container. Once the container attained the desired temperature, a period of 1/2 hr was allowed to elapse before the extrusion was made. This time was found to be required to allow the billet to reach a steady-state temperature, as determined from previous tests. When all was ready, extrusion was carried out without interruption; that is, the billet was upset and extruded in one operation. EXPERIMENTAL RESULTS AND DISCUSSION The two usual experimental approaches for investigating high-temperature deformation exhibit an important common feature. In the first approach, which corresponds to creep, a constant stress (or load) is applied to the material at constant temperature and the resultant strain is recorded against time. After an initial transient stage, a state of constant strain rate exists (secondary creep), in which a steady-state condition is established which is sensitive to variation in either applied stress or temperature. In the second approach, a constant strain rate is applied and the resultant flow stress is recorded. This corresponds to the situation in hot torsion or hot compression, where it is observed that, for a constant test temperature, there is an initial rise in stress to a steady value which is maintained up to very high strains. In tests of this type, a steady-state region is also established in which the stress is sensitive to variation in either the strain rate or the temperature.3,4,6-16 In both types of tests, therefore, a steady-state region is established after an initial transient. In the case of hot-working this region may be called steady-state hot-working, and it is analogous to steady-state creep with which it has many common features. Stress Dependence of the strain Rate in Extrusion. In order to assess the stress dependence of the strain rate under extrusion conditions, and to compare it to that of creep, as well as of hot torsion and hot compression, the extrusion data were analyzed according to power, exponential and hyperbolic sine creep equations.

Jan 1, 1969

By James J. Dowd

The investigation to evaluate the reserves of coking coal in the United States suitable for the manufacture of metallurgical coke is being made by the Bureau of Mines in three parts: (1) To estimate known measured and indicated recoverable reserves of all coking coal; (2) to upgrade marginal coals through effective preparation; and (3) to study the carbonizing properties of coals and coal blends not now widely used for metallurgical coke making. This is the eighth of a series of reports giving the results of studies by counties under part (1) of the investigation. (See appendix.) This report covers Jefferson County, Pa., which comprises parts of Marienville, Hallton, Ridgway, Brookville, DuBois, Penfield, Smicksburg, and Punxsutawney quadrangles. (See fig. 1.) A short resume of the chemical and carbonizing properties of the coals is included. Data on the coal beds in the county were obtained from mining companies, land companies, individual landowners, and other sources of authentic information. A base map for each bed in each quadrangle was made to the scale 1 inch equals 1,200 feet. Maps of mines, locations of drill holes, bed and total coal thicknesses, and the outcrop of the bed were plotted on the maps. With all available data plotted, isopach lines were drawn to limit areas of known unmined reserves in beds 0 to 14 inches thick, 14 to 28 inches thick, 28 to 42 inches thick, and over 42 inches thick, These areas of coal reserves also were divided into "measured" and "indicated" categories. All areas in each thickness range and in each category, mined-out areas, areas excluded from the estimate, and areas outside of the outcrop were measured by planimeter on the base maps. Estimates of total reserves 14 inches and more thick and maps for individual beds were prepared from these data.

Jan 1, 1952

By S. P. Lucido, I. Iwasaki

The potential of controlling heavy metal ions in effluents from discontinued mining operations and waste rock piles has been investigated. A fresh water green alga, Cyanidium caldarium, was found to have the potential to remove Cut' from solutions while exhibiting high tolerance to acid conditions which are commonly encountered in copper-nickel mine drainage. The process has the potential for application as a low maintenance metal decontamination system. The growth requirements and copper removal characteristics of this microorganism are described.

Jan 1, 1991

By James S. Baker

LARGER than continental United States but with only about one third the population, Brazil is a land of enormous potential wealth, waiting to be developed. During a recent visit to that country I saw Brazil at war and learned about some of the recent mineral developments. Many engineers and geologists have been sent to Brazil by various U. S. Government agencies to assist the Brazilian producers and co-operate with the Brazilian Government in producing needed war minerals. The Foreign Economic Administration staff of engineers has been active and through their assistance to the Brazilian producers, steadily increasing quantities of strategic minerals were provided to aid the United Nations' war effort. Mineral wealth has been found in almost every state of Brazil. Many mineral deposits have been discovered during the war period. Examples are: barite near Bahia; the tungsten and molybdenum deposits in Rio Grande do Norte; and corundum, beryl, and tungsten ores in Ceara.

Jan 1, 1945

By D. Bahrami, W. K. Asante, G. L. Danko

It is prudent to interpret atmospheric monitoring signals in real time for checking the safe limits of the air conditions in underground mines. In gassy mines, real-time evaluation increases the safety of operations. In all mines, continuous monitoring and evaluation contributes to maintaining air conditions within healthy and safe limits. Signal interpretation for safety conditions in mines is difficult for many reasons. An increase in hazardous contaminant concentrations can be predicted by signal pattern recognition, root cause analysis of rapid changes toward deterioration, and forward prediction in time using algorithms and numerical models. The paper describes an early warning system for analyzing monitored signal patterns continuously in real time as well as forward predicting the various environmental and working conditions to recognize dangerous trends that may affect safety and health in underground mines. A dynamic, numerical ventilation model with heat and gas contaminant simulation components is used for the analysis of atmospheric data. Methods and test results are discussed with numerical examples for signal propagation prediction. Several mine examples are studied using controlled, synthetic data for malfunction simulations to evaluate time delays between the detection time of suspicious signal trends and the time of dangerous threshold crossing marking an accident scenario. Delay time is found in the order of 20 min in the examples, signifying the useful time period for preventive intervention between EWS warning and the likely breakout of a following accident.

By Robert W. Van Dolah

The prevention of fires and explosions involving the combustibles and oxidants likely to be found in flight vehicles requires a knowledge of the flammability and related characteristics of these materials. This circular is a compilation of the available charactersilics data for a series of combustibles and oxidants of current interest. Vapor pressure data are presented for fluorine, oxygen, chlorine trifluoride, nitrogen tetroxide, nitric acid, hydrogen peroxide, ethylene oxide, hydrogen, ammonia, pentaborane, unsymmetrical dimethylhydrazine, monomethylhydrazine, hydrazine, and a series of hydro-carbons including decalin, tetralin, bicyclohexyl and other high-density fuels. In addition, flammability characteristics diagrams are included for each of the fuels in contact with air and, where available, other oxidants (for example, oxygen and nitrogen tetroxide). To assist in understanding these data, sections on definitions and theory and applications have been included. Each section is complete in itself and can be used separately. For example, a reader who is familiar with the general theory of combustion and detonation may find the data sections more useful than the definitions and theory and the application sections. However, since pertinent data are included in these sections, they should also prove useful to the experienced engineer interested in preventing fires and explosions.

Jan 1, 1963

By D. H. Shaffer, W. F. Harris, W. M. Hickam, M. H. Loeffler

Experiments have been performed on the quantitative addition to niobium of enriched isotopes 018 and 017 at the 0.1 - 40 micro-gram level and their subsequent recovery. A measured quantity of molecular oxygen of known isotopic concentration is added to niobium metal by oxidation. Recovery of the enriched isotopes as carbon monoxide is by the vacuum fusion technique. Quantitative determinations of the enriched isotopes are made in standard volumes at constant temperature using accurately calibrated micromanometers and the mass spectrometer as pressure measuring instruments. THE presence of low concentrations of nonmetallic impurities in metals can often adversely affect the physical properties of the metal. The increase in hardness and the embrittlement of refractory metals due to oxygen is well known. In metallurgical studies dealing with the diffusion rates or the effect of oxygen on the physical properties of refractory metals, it is often necessary to add small quantities of oxygen to the metal and later recover the total quantity present. It is desirable, therefore, to establish the accuracy with which microgram quantities of oxygen can be added to niobium and recovered by vacuum fusion. The successful addition of microgram quantities of oxygen to metals by the usual manometric techniques and the subsequent recovery by vacuum fusion is difficult because of the uncertainty in the accurate determination of the quantity of oxygen originally present in the metal and because of the chance of contamination by atmospheric oxygen. In order to minimize these uncertainties earlier workers have added quantities of O16 at levels much higher than the oxygen concentrations that are of interest.'-3 In order to eliminate the uncertainty associated with the O16 additions to metals at low microgram levels, experiments have been performed on the quantitative addition of oxygen highly enriched in O17 and O18 at the 0.1 to 40 pg level to niobium and the subsequent quantitative recovery of the isotopes by vacuum fusion. Since the natural abundance of O17 is 0.04 pct and of 0" is 0.2 pct this enriched oxygen provides a uniqueness from interference not achieved in earlier work.'-= A measured quantity of molecular oxygen of known isotopic concentration is diffused into the metal. Recovery of the isotopes in the form of carbon monoxide is by vacuum fusion. The total quantity of gas is determined in standard volumes at constant tempera- ture using accurately calibrated Consolidated Electrodynamics micromanometers and the mass spectrometer for pressure measurements. The molecular and isotopic composition is determined mass spectrometrically. APPARATUS A schematic of the oxygen addition apparatus is shown in Fig. 1. Take-offs are provided for the attachment of the isotope container and for sample bulbs which are used to transfer samples to the mass spectrometer. Metal valves are used throughout the system including the sample bulbs in order to achieve a vacuum of 10"6 mm Hg. Evacuation is accomplished with a 3-stage oil-diffusion pump backed by a mechanical pump. A liquid nitrogen trap is used to remove condensables and to prevent oil vapor from entering the system. A micromano-meter is used for pressure measurements. The furnace assembly is shown in Fig. 2. It consists of a quartz tube joined to the apparatus through a 40/W joint with Apiezon W low-pressure wax. The furnace cap, also a 40/W pyrex joint, is provided with a pyrex hook. The sample is suspended from this hook with a platinum wire. The total volume of the furnace section is 435 ml. All volumes were determined by expanding a known volume of gas at a known pressure into the evacuated system and re-measuring the pressure. Both the micromanometer used on the oxygen addition system and the micromanometer used on the mass spectrometer were compared to a precision

Jan 1, 1961