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By E. G. King

Many of the existing thermodynamic values for the titanium halides are estimates, including all the entropies and high-temperature heat contents of their crystalline and liquid phases. This report contains the results of low-temperature heat capacity measurents (which lead to entropy values at 298.15° K,) and high-temperature heat-content measurements of four halides - trichloride, tribromide, tetrabromide, and tetraiodide. The new data are combined with selected heat-of-formation values at 298.15° K. to obtain improved values of the heats and free energies of formation of these halides at high temperatures, thus supplementing the previous data of Kelley and Mah.5/ ACKNOWLEDGEMENTS This investigation was conducted under a cooperative arrangement between the Federal Bureau of Mines and the Department of the Navy, Office of Naval Research. The work was done by Bureau of Mines personnel using Bureau of Mines calorimetric equipment. The Office-of Naval Research supplied the supporting funds and arranged for procuring the samples of the titanium halides. The samples were prepared and analyzed by the Inorganic Chemistry Section, Division of Chemistry, National Bureau of Standards.

Jan 1, 1961

By J. F. Shea, O. F. Tangel

Battelle Memorial Institute participated in a program for the General Services Administration aimed at developing a nickel-cobalt separation process that could be integrated in the Nicaro nickel plant. At the time the programwas being carried out, the Nicaro process was a straight-through operation, in which the ore was reduced and leached, after which the pregnant solution was boiled to produce a so-called "bulk precipitate" which contained virtually all of the nickel and cobalt which had been dissolved in the leaching step. The weight ratio of nickel to cobalt in Nicaro ore is approximately 15 to 20:l. The weight ratio of nickel to cobalt in the finished product had to be 100:l or higher to meet specifications. Because the Nicaro process embodied no nickel-cobalt separation step, the only way that a bulk precipitate of the specified nicke1:cobalt ratio could be produced was to so adjust roasting and leaching conditions that nickel would be selectively leached and most of the cobalt would be rejected with the tailings. The required selectivity, however, was achieved at the expense of nickel recovery, which was 5 or more per cent less than might have been obtained with the existing equipment, utilities, man power, etc., had selectivity been no object. The over-all purpose of the program was to develop a separation step that could be fitted into or onto the Nicaro facilities and which would permit the manufacture of a product that would meet the desired specifications and still permit the recovery of a maximum amount of nickel. Battelle suggested that this might be accomplished by reprocessing off-specification bulk precipitate and specifically suggested the process based on ammonium sulphate leaching followed by hydrogen reduction of the leach solution according to techniques developed commercially by Sherritt Gordon Mines Limited. Such a process would not only satisfy the objectives of the research but would present two additional advantages. (1) It would produce a separate cobalt product which could be further processed into metal, alloys, oxides, or salts. (2) It would yield nickel in metallic form which might be more generally marketable and command a slightly higher price per unit of nickel than the Nicaro oxide product. DESCRIPTION OF THE PROCESS Figure 1 is a flowsheet of the process. The essential features are: (1) Extraction of about 97 per cent of the nickel and about 85 per cent of the cobalt from bulk precipitate by a principal leach with ainmonium sulphate solution (Step A). Extraction of virtually all of

Jan 1, 1961

By Dale W. Richardson

Ductile hafnium was not obtained consistently by the conventional Kroll process. The bimetal reduction modification produced a more ductile hafnium by lowering the impurities, especially oxygen, in the sponge metal. Hafnium oxide was chlorinated in the presence of carbon to form anhydrous hafnium tetrachloride, which was reduced by sodium and magnesium in an inert atmosphere to produce sponge hafnium metal. After vacuum distillation to remove the byproducts, the sponge was arc-melted into ingot and rolled into strip. Metallic impurities were decreased by evaporating the hafnium tetrachloride from a fused salt. An excessive amount (over 1,200 parts per million (p.p.m.)) of aluminum was contained in some of the hafnium oxide, much of which remained as aluminum chloride in the hafnium tetrachloride during chlorination. Evaporation of the hafnium tetrachloride from a fused NaCI-KCI mixture during the Mg-Na reduction greatly lowered its aluminum content, as most of the aluminum and some of the other metallic impurities were retained by the fused salt.

Jan 1, 1961

By M. J. Saarivirta, P. P. Taubenbla

This paper presents some high-temperature properties of copper-zirconium conductor alloy compared to copper-chromium alloy. Definite superiority of the copper -zirconium alloy over the copper-chromium alloy at high temperatures is shown. RECENT investigations have shown that cold-worked copper-zirconium alloy possesses good room-temperature strength, ductility, and conductivity and maintains most of its strength at temperatures up to 450°C (840°F). As a result, this alloy is now used for many applications, such as commutator segments, resistant welding wheels and tips, rectifier bases, electrical contacts, and so forth. Early investigations1-3 have shown that the maximum solid solubility of zirconium in copper is close to 0.15 pct and the alloy containing Cu-0.10-0.15 pct Zr exhibits the optimum mechanical and physical properties. Results2 have also shown that the alloy has better elevated temperature strength and ductility than copper-chromium and copper-silver alloys. The present investigation was undertaken to learn more about the elevated temperature properties of copper-zirconium alloy and to compare these properties with those of the copper-chromium alloy. WORK PROCEDURE The commercial copper-zirconium alloy, Amzirc was selected for this investigation. Because this alloy is composed of oxygen-free high-conductivity copper and 0.10-0.15 pct Zr, it was believed that possible disturbance from impurities would thus be negligible. Copper-chromium alloys used in this investigation contained 0.40 and 0.70 pct Cr and balance copper. The Cu-0.40 pct Cr alloy was a commercial brand, whereas the Cu-0.70 pct Cr alloy was made from OFHC copper and Cu-5 pct Cr master alloy. It was made in a graphite crucible under argon gas cover and cast. In the preparation of specimens, all three alloys were treated to give the optimum properties; thus the Cu-0.15 pct Zr alloy was solution annealed at different temperatures to determine the desirable solution annealing temperature. It was then cold worked and aged at 375" to 400°C (705" to 750" F). A solution annealing temperature of 1000°C (1830°F) was selected for the copper-chromium alloys because this temperature is widely used in commercial practice. The same alloy was aged at 450°C (840°F) after solution annealing and cold working. It was found that the maximum precipitation hardening of the copper-chromium alloy occurred at this temperature. When aged after solution annealing, the aging temperature was 500°C (930"F) for both alloys. The following properties were determined: 1) Tensile properties as a function of temperature. 2) Effect of solution annealing temperature on high-temperature tensile properties. 3) Stress to rupture strength at 350° and 400°C (660"to750°F). 4) Impact strength. 5) Electrical conductivity and resistivity as function of temperature. 6) Thermal expansion.

Jan 1, 1961

By R. H. Doremus, E. F. Koch

The first carbide phase that precipitates at 120°C from a iron containing about 0.02 wt pct, C was studied with the electron microscope. In both strained and unstrained material the carbide particles appeared to form on the dislocations in the iron, in agreement with the results of the kinetic study in part II. The structure of the carbide was tentatively identified as an expanded a-iron lattice (body-centered tetragonal) with about 0.7 wt pct C. This phase appeared to be metastable and apparently transformed into cementite or epsilon carbide when the iron was over-aged. WhEN a iron containing less than about 0.025 wt pct C is quenched from 700°C to room temperature the carbon is retained in solid solution and precipitates out slowly with time. The morphology and structure of the precipitating phase are still in doubt, two different carbide phases, epsilon carbide and cementite, have been identified, but there is considerable disagreement about the time and temperature at which they appear.1-4 Epsilon carbide seems to form at lower temperatures than cementite, although one group of investigators4 found only the latter phase over a wide range of aging temperatures. Usually these two phases have been identified after aging times much longer than needed to drain the carbon from supersaturated solution, at least for aging temperatures below 200oC. The precipitated carbides have been observed with the electron microscope,'-5 but again most results have come from samples aged much longer than necessary to reduce the carbon concentration in solution to a low value. In this study the carbide phases were observed in earlier stages of precipitation with the electron microscope, in order to learn more about the shape, size, and distribution of the carbide particles. Samples strained small amounts before aging, as well as unstrained samples, were studied, and the structure of the carbide phase was tentatively identified. EXPERIMENTAL "Ferrovac E" vacuum-melted iron, from which the wires for kinetic studies were also made (Refs. 6 and 7 and the following paper) was used for this work. An analysis of this material is given in Table I; it agrees well with the manufacturer's values. The number of inclusions in the iron was very small, as can be seen in the optical micrograph in the following paper. Pieces of iron about 1 mm thick and 5 to 10 mm in diam were used for all the studies except for those in which the sample was strained before aging; then the specimen was a rod 3 to 6 mm in diam and 20 cm long. The samples were held at about 700°C in wet hydrogen for at least an hour to remove residual carbon and nitrogen, after which they were heated to 950" (in the y region) and cooled to room temperature in the furnace. This treatment gave an average grain diam of more than 1 mm, so that the effect of grain boundaries on the precipitation process was negligible. The samples were carburized at 710°C for about 2 hr in hydrogen that had passed over toluene held at -30°C; then they were rapidly quenched into water. From chemical analysis this treatment gave a carbon concentration of from 0.012 to 0.016 wt pct, which is less than the solubility of carbon at this temperature. After quenching, the samples were aged at 120 "C in an oil bath for vari-

Jan 1, 1961

By H. S. Caldwell

Molten zinc, condensed from zinc vapor, was used by the Federal Bureau of Mines to leach aluminum from an aluminum-silicon alloy made by carbothermic reduction of silicious aluminum ores. Zinc requirements were minimized by re-fluxing condensed zinc in a low-pressure, Soxhlet-type distillation unit. The minimum ratio of zinc used to aluminum in the crude alloy was approximately 2:1. When the system pressure was reduced from atmospheric pressure to 100 microns or less, the rate of aluminum extraction increased by a factor of 20. Leaching rates were much higher when the zinc vapor was condensed directly on the crude alloy than when molten zinc was passed over the alloy in the absence of appreciable zinc vapors. Observations indicated higher extraction efficiencies from crude alloys containing greater amounts of iron. Complete extraction was obtained with negligible loss of zinc. Assuming complete removal of zinc, the aluminum products will contain 1 to 6 percent silicon and about 0.5 percent iron plus titanium. The leached crude-alloy residue is a highly friable spongelike material containing about 80 percent silicon, several percent iron and titanium, with the remainder aluminum. This extraction method has been patented (Patent 2,810,637) and assigned to the Government. Research and development investigations are continuing at the College Park Metallurgy Research Center.

Jan 1, 1961

By L. S. Castleman, R. Resnick

The self-diffusion coefficient of columbium has been measured over the temperature range 1535o to 2120°C, using the radioactive isotope Nb95 as the tracer. The data for the temperature dependence of the self-diffusion coefficient are best fitted by the equation D = (12.4 ± 0.8) exp [(-105,000 ± 3000)/RT] cm2/sec. THE increasing need for high-temperature structural materials has stimulated considerable interest in the properties of columbium, since it is a strong, ductile metal with a high melting point—in the vicin- ity of 2450oc.l One fundamental property which has not heretofore been measured is the self-diffusion coefficient. The self-diffusion coefficient plays an important role in theories of oxidatioq2 creep,' sintering4 and other phenomena. Accordingly, the investigation reported in this paper was undertaken to determine the value of the self-diffusion coefficient and its temperature dependence by the use of Mb95.

Jan 1, 1961

By A. E. Gorum, I. Cornet

Fatigrle of ionic crystals has been studied primarily in magnesinm oxide. under cyclic stress dislocations move irrreversibly; they multiply; slip bands form and grow; cracks mucleate and propagnte, and failure occurs. The use of ionic crystals such as MgO is advantageorus in such investigations because they are optically transparent. Individual dislocation Intersections with {100} surfaces may be observed with a standard microscope, using etch-pit techniques. Slip, deformation, crack .formation, and fracture in MgO crystals under cyclic stress are compared with cotrresponditzg processes in metals. ThE effect of cyclic loading in metals has been studied for many years. The appearance of slip lines is readily observed and the ensuing fracture may also be seen. From these observations it is possible to predict the behavior of a material and make an educated guess as to what is happening internally, but the actual changes taking place within the structure are not readily apparent. If one could obtain a material in which the individual glide components could be observed, it would be invaluable in determining the actual slip distribution resulting from cyclic loading as well as the distribution of slip in the neighborhood of a growing crack. Such a material is magnesium oxide. Dislocation arrays may be observed by means of etch pits

Jan 1, 1961

By Frank Parrish

THIS REPORT by the Federal Bureau of Mines presents data on water-supply wells used by waterflood operators in North Texas and shows the distribution of permeable source sediments. Averages of well characteristics, including static fluid levels, working fluid levels, net thicknesses, producing rates, and depths, are presented and discussed. Essentially all water used in waterflooding is mineralized water from consolidated sediments. This study is concerned with the geology and distribution of these mineralized source sediments, whereas previous work in this area was predominantly a study of shallow sources of potable water. Tables, isopachous maps, and electric-log cross sections are included to describe the several source aquifers. In general, water-producing capacity increases with depth of the sediments. Wells completed in Cretaceous sediments 82 to 600 feet deep yield 50 to 600 barrels of water daily, whereas those completed in Pennsylvanian sediments 360 to 4,110 feet deep yield 100 to 7,000 barrels daily. Although deeper formations are used where oil and water are produced conjunctively and where large withdrawal rates are required, insufficient well data prevented mapping of deeper formations.

Jan 1, 1961

By H. Kenworthy

The purpose of the study described in this publication is to develop methods for recovering simple master alloys or single metal components from discarded and scrapped S-816 alloy, The Bureau of Mines started this investigation late in 1955 after the need became apparent for a method of reclaiming high-temperature alloys from an ever-increasing accumulation of rejected and wornout jet engine turbine buckets. Laboratory studies showed the following: (1) Pyrometallurgical separations are not selective enough, (2) several methods can be used for effective chemical dissolution of the major constituents of the alloy, (3) a master alloy or complex salts of cobalt and nickel can be separated, (4) chromium, contaminated by several other metals, may be segregated, and (5) more time and effort need to be expended in separating the minor constituents and improving the purity of the major metals removed. Difficult and incomplete chemical separations were attributed to the complexity of alloy composition, as were the long tedious chemical analyses o' products. For determination of several of the metallic components, standard methods of separation and routine analytical procedures had to be considerably modified to achieve satisfactory results. The overall technical problems involved in separating S-816 components do not appear to be insurmountable; however, refinement of several of the methods used in this investigation is desirable.

Jan 1, 1961

Jan 1, 1961

[Officers and Committees of the Society of Petroleum Engineers 1 Officers and Staff of the AIME 2 Officers of AIME Sections Predominantly Petroleum in Membership 3 Society of Petroleum Engineers By-Laws 5 Alphabetical List of Members 9 Geographical List of Members 110 List of Members by Companies 127 Advertisers' Index 137]

Jan 1, 1961

By J. E. Elliott, K. O. Miller

Solubility studies were carried out to establish the phase distributions for various Fe-Ni-Pb-C alloys at temperatures where the metallic components exist as liquid solutions. Temperature us composition diagrams for the Ni-Pb, Fe-Pb, Fe-Ni-Pb, and Ni-Pb-C systems are derived by employing various approximations in conjunction with the data. Results are summarized for 1550°C in a quaternary phase diagram of the Fe-Ni-Pb-C system. BECAUSE surprisingly little information has been published on the phase diagrams of the Ni-Pb, Fe-Pb, Fe-Pb-Ni, and Fe-Ni-Pb-C systems, a study of these systems was undertaken to ascertain the important phase relationships in the temperature range of 1300" to 1550°C. Measurements were also made on the carbon-saturated systems in the hope that they would assist in the interpretation of the systems without carbon. This paper reports the results obtained from the simple equilibration of the various liquid and solid phases. EXPERIMENTAL PROCEDURE The experimental technique involved holding appropriati quantities of the metals in an alumina crucible, or in a graphite crucible when saturation of the melt with carbon was desired, for sufficient time at the desired temperature to ensure equilibrium. Then a sample of each liquid phase presen was drawn into a small-bore silica tube. This sample was withdrawn quickly from the furnace, cooled, and sent to the chemical laboratory for analysis. The cell assembly used is shown in Fig. 1. Durin the work on the Fe-Pb-Ni system, it was placed in a furnace wound with 20 pct Rh-80 pct Pt wire. This furnace eventually failed and subsequent studies were carried out between 1350" and 1475°C in a tube furnace heated by silicon-carbide resistance elements. A protective atmosphere of argon with approximately 10 pct hydrogen was supplied to the cell assembly at a gage pressure of 1 in. of water. Hydrogen was passed over palladized alumina and then anhydrous calcium chloride for purification. Argon was purified of oxygen and water vapor by passing it over copper gauze at 550°C and then through a calcium chloride drying column. The gases were mixed and redried before they entered the equilibration cell. Temperature was measured by calibrated Pt/Pt-10 pct Rh thermocouples and a Rubicon Type B potentiometer. The thermocouples were standardized against the melting points of pure nickel

Jan 1, 1961

By Thomas C. Atchison

The experimental work described in this report is part of a continuing study by the Federal Bureau of Mines of the fundamental physical processes involved in breaking rock with explosives. Six explosives were tested for their strain-producing abilities in a dolomitic marble. The explosives selected for testing had a tenfold variation in detonation pressure and a fivefold variation in characteristic impedance (product of loading density and rate of detonation). Strain pulses produced by the detonation of small charges of the explosives were recorded at distances of 5 to 130 feet. Peak strain, ?, was found to decrease with distance, R, in accordance with an exponential propagation law previously determined for other rock types, namely ? = (K/R)e ?aR The absorption constant, a, did not vary significantly with the explosive and was of the same order of magnitude as that for other rock types. The different explosives produced a fivefold variation in the value of the intercept constant, K.

Jan 1, 1961

By Maurice J. Peterson

The applications of optical spectrochemical methods of analysis for determining trace impurities in metals are described, and the need for developing analytical procedures capable of accurately determining fractional parts per million of impurity elements in metals is stressed. Factors which determine sensitivity of detection and means to extend sensitivity levels in spectrochemical methods are discussed. Examples from the current literature illustrate the diversity of spectrochemical techniques that have been applied to the analyses of varied sample types, Many of the methods use preconcentration procedures to increase sensitivity limits. A bibliography containing abstracts of recent methods in included. Optical spectrochemical analysis is based upon the measurement of radiant energy emitted by atoms of the elements to be determined when a sample is subjected to a suitable source of excitation. The behavior of the valence electrons during excitation, usually by an arc, spark, or flame, produces radiant energy of specific wavelengths. This is recorded as spectral line images on a photographic film or plate by the spectrograph; for direct-reading instruments, the spectral lines are detected with photomultiplier tubes. The spectral lines result from the excitation of atoms in the sample. Each variety of atom produces its own characteristic set of lines, thus serving to identify the elements in the sample. Increased concentrations of elements in the excited sample results in increased blackening of the spectral line images.

Jan 1, 1961

By M. I. Copeland

The investigation of the zirconium-gadolinium equilibrium diagram was part of a program to investigate rare:earth alloys for use as nuclear reactor control materials. Investigation of the zirconium-gadolinium equilibrium diagram revealed a eutectic system with limited terminal solubilities and one peritectoid reaction. The eutectic composition occurs at about 82 percent gadolinium, and the eutectic isotherm, which occurs at 1,220 ±5° C., extends from about 12 to 99+ percent gadolinium. A peritectoid isotherm occurs at 890 ±5° C. and extends from about 2 to 99+ percent gadolinium. The solubility of gadolinium in beta zirconium decreases from about 12 percent at 1,220 ±5° C. to about 2 percent at 890 ±5° C. The solubility of gadolinium in alpha zirconium decreases from approximately 5 percent at 890 ±5° C. to between 2 and 3 percent at 600° C. Vary little solubility of zirconium in gadolinium was indicated. An allotropic transformation of gadolinium was observed at 1,260 ±5° C. A change of the gadolinium transformation temperature on alloying with zirconium was not observed.

Jan 1, 1961

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

By A. Alonso, J. Daubenspeck

In the nickel extraction process at Nicaro, Cuba, dried and ground nickel bearing laterites are reduced at 1300-1400F in multiple-hearth furnaces. Nickel is leached from the reduced ore by aeration in an aqueous solution of ammonium carbonate. Nickel carbonate is precipitated from the liquor and calcined to yield nickel oxide. The following are the more important modifications of the Nicaro process since plant rehabilitation and expansion. Ten percent increase in tonnage was achieved without decreasing the fineness of the ore by minor mechanical modifications of the grinding plant. Another five percent increase in tonnage was attained by intentionally overloading the ore prepration and leaching circuits in an effort to control cobalt extraction. Modifications at the sintering plant allowed it to handle the entire output of the expanded plant. A fifty percent increase in leach liquor cooling facilities alone provided an increase in nickel production of five percent. Stronger fresh leach liquor for increased nickel washing efficiency was obtained through improved distribution of water to the ammonia absorption towers. Advantage was taken of the reduced calcine's capability to precipitate cobalt, and modifications in the leach liquor circulation provided controlled cobalt solubility with minimum harm to nickel extraction. Several process changes at the drying plant brought about a ten percent reduction in the fuel oil consumption at this pint. Controlled air addition to the reduction furnaces' upper hearths burned formerly wasted combustibles thereby reducing oil consumption by twenty percent. The nickel extraction process successfully emplayed on the extensive but lowgrade lateritic ores of Eastern Cuba at the U. S. Government owned Nicaro plant, has been previously described in various publications. The large mine and plant operated by the Nickel Processing Corporation, located on the northeastern shore of Oriente Province, have been recently expanded to a yearly capacity of about 50 million pounds of nickel. Essentially, the operation involves open pit mining of a limonite-serpentine ore mixture containing 1.3 to 1.4 percent nickel and 34 to 38 percent iron. The comparatively lumpy, wet (25 to 30 percent moisture) ore is first dried and ground prior to chemical treatment, to which the entire 7,000 tons per day feed must be subjected. In the initial chemical action the dried and ground ore is reduced with carbon manoxide and hydrogen at 1300-1400° in multiple-hearth furnaces. The resulting metallic nickel is selectively leached from the reduced calcine by aeration in an

Jan 1, 1961

By Oscar H. Lentz

During 1960, the controversy over percentage depletion reached the level of debate between presidential candidates. Nixon took the position that he would not tamper with the status quo in this matter. Kennedy took the position that he was willing to take a fresh look at the issues involved. Kennedy's position appears to have been based upon two premises: (1) new sources of federal revenue may be needed; and (2) current depletion rates, even if sound in principle, may be too high and, therefore, inequitable. The latter premise constitutes the basis for the claims that depletion allowances are simply "loopholes" of tax avoidance. Very probably the controversy over percentage depletion will remain in the political limelight during most of the coming decade. It is quite possible that the current depletion rates, at least those for oil and gas, will be reduced during this period. The aim of this paper is to isolate the complex causes of this mounting opposition to percentage depletion.

Jan 1, 1961

By S. H. Ward

Since the advent of the first airborne electromagnetic system, it has been evident that such systems were inherently limited to shallow depths of exploration of the orderof 100 to 200 feet. Hence in 1948 the author and his associates commenced a study of the feasibility of applying natural audio frequency magnetic fields to investigation of the electrical properties of the subsurface in order to provide a system capable of overcoming this limitation. This research culminated, in the summer of 1958, in the development of a new airborne prospecting device — AFMAG. This device has detected surface massive sulphide bodies while flown at heights as great as 3000 feet. Hence, by inference, it is deduced that it could find similar sulphide bodies if they were buried 2500 feet below surface and the aircraft flown at 500 feet. Thus a considerable improvement over conventional airborne electro-magnetic systems is obtainable with AFMAG. Airborne exploration in mountainous terrain involving deep valley fill now becomes possible. Examples are presented of the results of actual airborne AFMAG test surveys over known deposits of massive sulphide mineralization. Interpretation of the data is discussed with particular reference to the knowledge of size, dip, depth, depth extent, and conductivity of causative bodies as deduced from the flight records. The possibility of mapping major geologic structures, for both mining and oil exploration purposes, is discussed with the aid of examples of airborne AFMAG data. INTRODUCTION Electrical prospecting with natural audio frequency electromagnetic waves as a source has, within the last three years, become a practical reality. Both airborne and ground survey instruments under the trademark "AFMAG" (for audio frequency magnetics) have been used successfully in the search for conductive mineral deposits. It is the object of this paper to discuss the principles of airborne AFMAG and to illustrate its application by means of examples obtained over known geological situations. WHY AFMAG? In view of the large number of good airborne electromagnetic systems available for purchase or contract surveying, one may well ask, "Why another new system?". Primarily the answer lies in the fact that AFMAG does not suffer from the very limited depth of exploration available with, and inherent in, any conventional airborne electromagnetic system. AFMAG is not conventional insofar as an artificial transmitter is not required. Only a receiving and detecting device is employed. The electromagnetic fields measured are those from millions of electrical discharges in the atmosphere (e.g;..- lightning strokes). Their random distribution in time and space make these fields difficult to employ and it is only with recent advances in the electronics of geophysical instrumentation that this has become possible. A second reason for AFMAG and one of its

Jan 1, 1961